Title of Invention	"MOTOR-ASSISTED BICYCLE"
Abstract	To provide a motor-assisted bicycle having an electric motor for assisting a depression force applied to crank pedals wherein an assist power by the electric motor can be quickly obtained according to a push force applied to a vehicle body by a rider in walking the bicycle regardless of the strength of the rider and the manner of pushing the vehicle body. [Constitution] A push force applied to a vehicle body B by a rider in walking the bicycle is detected by push force detecting means 741, and an assist power by an electric motor 28 is controlled by a controller 42 according to a detected value from the push force detecting means 74a.

Title of Invention

"MOTOR-ASSISTED BICYCLE"

Abstract

To provide a motor-assisted bicycle having an electric motor for assisting a depression force applied to crank pedals wherein an assist power by the electric motor can be quickly obtained according to a push force applied to a vehicle body by a rider in walking the bicycle regardless of the strength of the rider and the manner of pushing the vehicle body. [Constitution] A push force applied to a vehicle body B by a rider in walking the bicycle is detected by push force detecting means 741, and an assist power by an electric motor 28 is controlled by a controller 42 according to a detected value from the push force detecting means 74a.

Full Text	[DETAILED DESCRIPTION OF THE INVENTION] [0001] [Field of the Invention] The present invention relates to a motor-assisted bicycle having a vehicle body and an electric motor mounted on the vehicle body for assisting a depression force applied to crank pedals, and more particularly to control of the electric motor in walking the bicycle. [0002] [Prior Art] Conventionally known from Japanese Patent Laid-open No. 4-358988 is a motor-assisted bicycle having an electric motor wherein an assist power exerted by the electric motor in walking the bicycle is controlled so that the vehicle speed becomes a speed slightly lower than a walking speed. [0003] [Problem to be Solved by the Invention] In the prior art mentioned above, however/ the assist power by the electric motor is obtained in walking the bicycle at a vehicle speed greater than or equal to a given value. Accordingly, in the case of ascending a slope with a large slope angle or in the case of carrying a heavy load to result in an increased weight of the vehicle body, for example, there is a possibility that the vehicle speed may not reach the above-mentioned given value until a push force applied to the vehicle body by a rider becomes a relatively large value. As a result, a weak rider requires much time to obtain the assist power in walking the bicycle. Further, in the case of passing over a bump or the like in walking the bicycle, the vehicle speed does not reach the above-mentioned given value, so that the assist power in walking the bicycle cannot be obtained. Further, there is a case that some riders may intend to push the vehicle body in walking the bicycle at a slowly running speed. In this case, however, the assist power cannot be obtained because it is controlled so that the vehicle speed becomes a speed slightly lower than a walking speed. [0004] It is accordingly an object of the present invention to provide a motor-assisted bicycle which can obtain an assist power quickly according to a push force applied to a vehicle body by a rider in walking the bicycle regardless of the strength of the rider and the manner of pushing the vehicle body. [0005] [Means of Solving the Problem] According to the invention as defined in claim I, there is provided in a motor-assisted bicycle having a vehicle body and an electric motor mounted on the vehicle body for assisting a depression force applied to crank pedals; the improvement comprising push force detecting means for continuously or stepwise detecting a push force applied to the vehicle body, and a controller for controlling an assist power by the electric motor according to a detected value from the push force detecting means. [0006] With this configuration, the assist power by the electric motor in walking the bicycle is controlled according to the push force applied to the vehicle body. Accordingly, even when a weak rider walks the bicycle in the case of ascending a slope with a large slope angle or in the case of carrying a heavy load to cause an increased weight of the vehicle body, the assist power corresponding to the push force applied can be quickly obtained. Further, when passing over a bump in walking the bicycle, a large assist power responsive to an increase in the push force can be obtained. Further, when pushing the vehicle body in walking the bicycle at a slowly running speed, the assist power corresponding to the push force applied can be obtained. [0007] According to the invention as defined in claim 2 including the configuration of the invention as defined in claim 1, the controller corrects to increase or decrease the assist power by the electric motor corresponding to the detected value from the push force detecting means, according to the degree of change in the detected value from the push force detecting means. With this configuration, the assist power can be changed well responsive to a transition state where the push force changes. [0008] According to the invention as defined in claim 3 including the configuration of the invention as defined in claim 1 or 2, the controller controls a duty ratio of the electric motor according to the detected value from the push force detecting means. With this configuration, an assist torque by the electric motor and a vehicle speed are determined according to a running resistance, thereby allowing simultaneous control of the assist torque and the vehicle speed. [0009] According to the invention as defined in claim 4 including the configuration of the invention as defined in claim 1 or 2, the controller controls an output torque of the electric motor according to the detected value from the push force detecting means. With this configuration, the output torque of the electric motor is reduced in ascending a gentle slope or the like because of a small push force. Accordingly, undue power consumption can be suppressed to thereby attain energy saving. [0010] According to the invention as defined in claim 5, there is provided in a motor-assisted bicycle having a vehicle body and an electric motor mounted on the vehicle body for assisting a depression force applied to crank pedals; the improvement comprising a walking switch to be operated by a rider in walking the bicycle, at least one of slope angle detecting means for detecting a slope angle of a road surface and load detecting means for detecting a load carried on the vehicle body, and a controller for controlling an assist power by the electric motor according to a detected value from at least one of the slope angle detecting means and the load detecting means in an operated condition of the walking switch. [0011] With the configuration of the invention as defined in claim 5, the assist power by the electric motor is controlled according to at least one of the slope angle of the road surface and the load carried on the vehicle body in the operated condition of the walking switch in walking the bicycle. Accordingly, even when a weak rider walks the bicycle in the case of ascending a slope with a large slope angle or in the case of carrying a heavy load to cause an increased weight of the vehicle body, the assist power required can be quickly obtained. Further, the assist power can be obtained regardless of the manner of pushing the vehicle body. [0012] According to the invention as defined in claim 6 including the configuration of the invention as defined in claim 1 or 5, the controller stops power assisting by the electric motor when a vehicle speed of the bicycle becomes greater than or equal to a set value. With this configuration, an undue increase in the vehicle speed in walking the bicycle can be prevented. [BRIEF DESCRIPTION OF THE DRAWINGS] [FIG. 1] FIG. 1 is a side view of a motor-assisted bicycle according to a first preferred embodiment. [FIG. 2] FIG. 2 is a schematic illustration of the structure of a power unit. [FIG. 3] FIG. 3 is a block diagram showing the configuration of a controller. [FIG. 4] FIG. 4 is an enlarged sectional view of an encircled portion 4 in FIG. 1, showing the configuration of push force detecting means. [FIG. 5] FIG. 5 is a flowchart showing processing in pedal operation decision means and on-riding motor drive control means. [FIG. 6] FIG. 6 is a flowchart showing processing in on-walking motor drive control means. [FIG. 7] FIG. 7 is a graph showing a coefficient corresponding to a battery deviation voltage. [FIG. 8] FIG. 8 is a graph showing a coefficient corresponding to the amount of change in push force detected value. [FIG. 9] FIG. 9 is a graph showing a duty ratio corresponding to a push force. [FIG. 10] FIG. 10 is a graph showing the relation among a vehicle speed, assist torque, duty ratio, and running resistance. [FIG. 11] FIG. 11 is a graph showing a target vehicle speed corresponding to a push force. [FIG. 12] FIG. 12 is a graph showing an output torque of the electric motor corresponding to a push force according to a second preferred embodiment. [FIG. 13] FIG. 13 is a graph showing the relation among an output torque, duty ratio, and vehicle speed. [FIG. 14] FIG. 14 is a graph showing the relation among a vehicle speed, assist torque, push force, and running resistance. [FIG. 15] FIG. 15 is a sectional view showing a first modification of the push force detecting means. [FIG. 16] FIG. 16 is a sectional view showing a second modification of the push force detecting means. [FIG. 17] FIG. 17 is a sectional view showing a third modification of the push force detecting means. [FIG. 18] FIG. 18 is a side view of a motor-assisted bicycle according to a third preferred embodiment. [FIG. 19] FIG. 19 is a vertical sectional view of slope angle detecting means. [FIG. 20] FIG. 20 is a cross section taken along the line 20-20 in FIG. 19. [FIG. 21] FIG. 21 is a block diagram showing the configuration of a controller. [FIG. 22] FIG. 22 is a flowchart showing processing in walking motor drive control means. [FIG. 23] FIG. 23 is a graph showing a duty ratio corresponding to a slope angle. [FIG. 24] FIG. 24 is a graph showing a duty ratio corresponding to a load. [FIG. 25] FIG. 25 is a graph showing a preset map of a duty ratio corresponding to a slope angle and a load. [0013] [Preferred Embodiment] Some preferred embodiments of the present invention will now be described with reference to the attached drawings. [0014] FIGS. 1 to 11 shows a first preferred embodiment of the present invention, wherein FIG. 1 is a side view of a motor-assisted bicycle; FIG. 2 is a schematic illustration of the structure of a power unit; FIG. 3 is a block diagram showing the configuration of a controller; FIG. 4 is an enlarged sectional view of an encircled portion 4 in FIG. 1, showing the configuration of push force detecting means; FIG. 5 is a flowchart showing processing in pedal operation decision means and on-riding motor drive control means; FIG. 6 is a flowchart showing processing in on-walking motor drive control means; FIG. 7 is a graph showing a coefficient corresponding to a battery deviation voltage; FIG. 8 is a graph showing a coefficient corresponding to the amount of change in push force detected value; FIG. 9 is a graph showing a duty ratio corresponding to a push force; FIG. 10 is a graph showing the relation among a vehicle speed, assist torque, duty ratio, and running resistance; and FIG. 11 is a graph showing a target vehicle speed corresponding to a push force. [0015] Referring first to FIG. 1, a vehicle body B of the motor-assisted bicycle includes a front frame 21 substantially U-shaped in side elevation and located between a front wheel WF and a rear wheel WR, and a rear frame 22 for supporting the rear wheel WR. The front frame 21 is composed integrally of a head pipe 2la for steerably supporting a front fork 23 which rotatably supports the front wheel WF/ a main frame portion 21b extending rearward and obliquely downward from the head pipe 21a, a curved portion 21c convexed downward and connected to the rear end of the main frame portion 21b, and a seat frame portion 2Id extending upward from the curved portion 21c. A bar handle 24 is provided at the upper end of the front fork 23. [0016] A seat post 26 having a seat 25 at the upper end is vertically movably mounted on the seat frame portion 2Id of the front frame 21 in such a manner as to allow the vertical position of the seat 25 to be adjusted. A power unit 29 having an electric motor 28 is supported to a lower portion of the front frame 21. [0017] The rear frame 22 includes a pair of right and left rear forks 30 extending rearward and obliquely downward from the upper end of the curved portion 21c of the front frame 21 at a position above a rear portion of the power unit 29 and further extending substantially horizontally at a position behind the power unit 29, and a pair of right and left stays 31 extending between the upper end of the seat frame portion 21d of the front frame 21 and the rear ends of the right and left rear forks 30. The rear wheel WR is supported between the right and left rear forks 30 at their rear ends. A rear carrier 34 is located behind the seat 25 and is fixedly supported by a pair of right and left support members 32 extending rearward from the upper ends of the right and left stays 31 and by a pair of right and left support members 33 extending upward from the lower ends of the right and left stays 31. [0018] A crankshaft 36 having a pair of right and left crank pedals 35 at the opposite ends is rotatably supported at a casing 37 of the power unit 29. An endless chain 40 is wrapped between a drive sprocket 38 and a driven sprocket 39 so as to be covered with a chain case 41. The drive sprocket 38 is capable of transmitting a pedaling power from the crankshaft 36 to the rear wheel WR and also applying an assist power from the electric motor 28 to the crankshaft 36. [0019] The operation of the electric motor 28 is controlled by a controller 42 fixedly supported to a lower portion of the front frame 21 at a position before the power unit 29. [0020] A front basket 44 is mounted through a bracket 43 on the head pipe 2la. A battery storage case 45 located at the back portion of the front basket 44 is also mounted on the bracket 43. A battery 46 for supplying electric power to the electric motor 28 is removably stored in the battery storage case 45. [0021] Most of the front frame 21 is covered with a cover 47, and a main switch 48 for supplying the electric power from the battery 46 to the controller 42 and the electric motor 28 is provided at an upper portion of the cover 47. The cover 47 is constructed by jointing an upper cover 47a for covering the front frame 21 from its upper side and a lower cover 47b for covering the front frame 21 from its lower side. An opening (not shown) for exposing the main switch 48 is formed at an upper portion of the upper cover 47a. [0022] As shown in FIG. 2, a rotating cylinder 50 is rotatably supported to the casing 37. A right end portion of the crankshaft 36 is rotatably supported to the inner circumference of the rotating cylinder 50, and a left end portion of the crankshaft 36 is rotatably supported to the casing 37. The drive sprocket 38 engaged with the chain 40 is connected to the rotating cylinder 50. [0023] A depression force input from the crank pedals 35 to the crankshaft 36 is transmitted through power transmitting means 51 to the drive sprocket 38. The electric motor 28 is mounted on the casing 37, and an output from the electric motor 28 is transmitted through a reduction gear train 52 to the drive sprocket 38 in order to assist the depression force from the crank pedals 35. [0024] The power transmitting means 51 is composed of a torsion bar 53 connected to the crankshaft 36 and a first one-way clutch 54 provided between the rotating cylinder 50 and the torsion bar 53. [0025] The crankshaft 36 is formed with an axially extending slit 55, and the torsion bar 53 is mounted in the slit 55 of the crankshaft 36 in such a manner that an arm portion 53a formed at one end of the torsion bar 53 is nonrotatably connected to the crankshaft 36. Another arm portion 53b is formed at the other end of the torsion bar 53, and is loosely engaged with the slit 55 with gaps defined between the arm portion 53b and the inner opposed wall surfaces of the slit 55. Accordingly, torsional deformation of the torsion bar 53 is allowed within a given range corresponding to the angular movement of the arm portion 53b within the gaps. [0026] The first one-way clutch 54 is provided between the arm portion 53b of the torsion bar 53 and the rotating cylinder 50. When the crank pedals 35 are depressed to normally rotate the crankshaft 36, the torque of the crankshaft 36 is transmitted through the torsion bar 53, the first one-way clutch 54, and the rotating cylinder 50 to the drive sprocket 38, whereas when the crank pedals 35 are depressed to reversely rotate the crankshaft 36, the first one-way clutch 54 slips to allow reverse rotation of the crankshaft 36. [0027] The torque input from the crank pedals 35 to the crankshaft 36 is detected by torque detecting means 56. The torque detecting means 56 includes a torque-displacement conversion mechanism 57 for converting the torsion of the torsion bar 53 according to the input torque into a displacement along the axis of the crankshaft 36, and a stroke sensor 58 for outputting an electrical signal according to the displacement. The torque-displacement conversion mechanism 57 includes a slider 59 supported to the outer circumference of the crankshaft 36 so as to be nonrotatable and axially movable relative to the crankshaft 36. The slider 59 has a projecting cam surface 59a engaged with a recessed cam surface 60 formed on a clutch inner ring of the first one-way clutch 54. [0028] Further, the outer circumference of the crankshaft 36 is formed with a toothed portion 61 to detect a rotating speed of the crankshaft 36, and a crankshaft rotation sensor 62 is fixedly provided in the casing 37 so as to be opposed to the toothed portion 61. The crankshaft rotation sensor 62 is configured so as to detect the teeth of the toothed portion 61 optically or magnetically and output detected pulses. [0029] The reduction gear train 52 for transmitting the power of the electric motor 28 to the drive sprocket 38 includes a drive gear 64 fixed to a motor shaft 63, a first idle shaft 65 rotatably supported to the casing 37, a first intermediate gear 66 fixed to one end of the first idle shaft 65 and meshing with the drive gear 64, a second intermediate gear 67 integral with the first idle shaft 65, a third intermediate gear 68 meshing with the second intermediate gear 67,a second idle shaft 69 arranged coaxially with the third intermediate gear 68 and rotatably supported to the casing 37, a second one-way clutch 70 provided between the third intermediate gear 68 and the second idle shaft 69, a fourth intermediate gear 71 integral with the second idle shaft 69, and a driven gear 72 integral with the rotating cylinder 50 to which the drive sprocket 38 is connected and meshing with the fourth intermediate gear 71. [0030] The electric motor 28 is mounted on the casing 37 in such a manner that the motor shaft 63 extends parallel to the crankshaft 36. The first and second idle shafts 65 and 69 are rotatably supported to the casing 37 so as to have axes parallel to the crankshaft 36 and the motor shaft 63. [0031] In the reduction gear train 52, the torque generated by the operation of the electric motor 28 is transmitted to the drive sprocket 38 with a rotating speed reduced. When the operation of the electric motor 28 is stopped, the second one-way clutch 70 operates to permit idling of the second idle shaft 69, thereby allowing rotation of the drive sprocket 38 by the depression force applied to the crank pedals 35. [0032] Referring to FIG. 3, the operation of the electric motor 28 is controlled by the controller 42. In this preferred embodiment, the controller 42 controls the operation of the electric motor 28 according to detected values output from the crankshaft rotation sensor 62, the torque detecting means 56, and push force detecting means 741. [0033] The push force detecting means 741 functions to continuously detect a push force applied to the vehicle body B by a rider in walking the bicycle. As shown in FIG. 1, the push force detecting means 741 is mounted on the seat post 26 immediately under the seat 25. [0034] Referring to FIG. 4, the push force detecting means 741 includes a lever 75 for receiving a push force from one of the right and left hands of the rider in walking the bicycle, a spring 76 for biasing the lever 75 in a direction opposite to the direction of the push force applied to the lever 75, and a stroke sensor 77 for detecting a stroke of the lever 75 pushed against a biasing force of the spring 76. A bracket 78 is provided on the seat post 26 immediately under the seat 25, and a support cylinder 79 having an axis extending in the longitudinal direction of the vehicle body B is fixed to the bracket 78. The lever 75 is integrally formed at its front end with a radially outward projecting flange 75a. The flange 75a is slidably engaged in the support cylinder 79. The spring 76 for rearwardly biasing the lever 75 is contained in the support cylinder 79 in such a condition where the spring 76 is normally compressed between the bracket 78 and the flange 75a. The support cylinder 79 is integrally formed at its rear end with a radially inward projecting flange 79a for engaging the flange 75a of the lever 75 to define a rear limit position of the lever 75, thereby setting the rear end of the lever 75 in its rear limit position before the rear end of the seat 25 by a distance L as shown in FIG. 4. The purpose of this setting is to prevent that the lever 75 may be undesirably pushed by a luggage carried on the rear carrier 34. [0035] The stroke sensor 77 is mounted on the bracket 78 in adjacent relationship with the support cylinder 79. The stroke sensor 77 has a sensing member 77a contacting a push member 75b extending downward from the lever 75. Examples of the stroke sensor 77 include a potentiometer using a resistor and any other sensors utilizing a resistance change due to deformation of conductive rubber. [0036] By using the push force detecting means 74i, the stroke of the lever 75 according to the push force applied to the lever 75 can be detected by the stroke sensor 77. A detected value from the stroke sensor 77 is input into the controller 42. [0037] Referring to FIG. 3, the controller 42 includes pedal operation decision means 80, on-riding motor drive control means 81, relay driving means 82, on-walking motor drive control means 83, motor drive limiting means 84, first switching means 85, second switching means 86, relay 87 having a relay switch 87a, and FET (field effect transistor) 88. [0038] The positive terminal of the battery 46 is connected through the main switch 48 and the relay switch 87a to the positive terminal of the electric motor 28, and the negative terminal of the electric motor 28 is grounded through the FET 88. Thus, the operation of the electric motor 28 is controlled by controlling the switching operation of the FET 88 in the closed states of the main switch 48 and the relay switch 87a. [0039] The first and second switching means 85 and 86 perform switching operations according to an output from the relay driving means 82. More specifically, the first switching means 85 can switch between a first condition (shown by a solid line in FIG. 3) where an output from the on-riding motor drive control means 81 is supplied to the relay 87 when the output from the relay driving means 82 is in a low level and a second condition (shown by a broken line in FIG. 3) where the output from the relay driving means 82 is supplied to the relay 87 when the output from the relay driving means 82 is in a high level. On the other hand, the second switching means 86 can switch between a first condition (shown by a solid line in FIG. 3) where an output from the motor drive limiting means 84 is supplied to the gate of the FET 88 when the output from the relay driving means 82 is in a low level and a second condition (shown by a broken line in FIG. 3) where an output from the on-walking motor drive control means 83 is supplied to the gate of the FET 88 when the output from the relay driving means 82 is in a high level. [0040] The relay driving means 82 functions to amplify the detected value from the push force detecting means 741 up to a level enough to drive the relay 87. During running of the bicycle on the seat 25 or at rest, no push force is detected by the push force detecting means 741 and accordingly the first and second switching means 85 and 86 are kept in the respective first conditions. When a push force is detected by the push force detecting means 741 during walking of the bicycle, the first and second switching means 85 and 86 are switched into the respective second conditions. [0041] The motor drive limiting means 84 functions to limit a motor drive signal output from the on-riding motor drive control means 81 according to the detected value from the torque detecting means 56, so as to control the switching operation of the FET 88. When the detected value from the torque detecting means 56 is less than or equal to a given value, the motor drive limiting means 84 generates a signal for cutting off the FET 88 irrespective of the motor drive signal output from the on-riding motor drive control means 81. [0042] The pedal operation decision means 80 functions to determine whether or not the crank pedals 35 have been depressed according to the detected value from the torque detecting means 56. When determining that the crank pedals 35 have been depressed, the pedal operation decision means 80 supplies an assist permission command signal to the on- riding motor drive control means 81. When receiving the assist permission command signal from the pedal operation decision means 80, the on-riding motor drive control means 81 generates a motor drive signal for controlling the operation of the electric motor 28 to obtain an assist power in riding the bicycle, according to the detected values from the crankshaft rotation sensor 62 and the torque detecting means 56 and the voltage of the battery 46, and further generates a relay drive signal for driving the relay 87 to close the relay switch 87a in obtaining the assist power. Further, the on-walking motor drive control means 83 generates a motor drive signal for controlling the operation of the electric motor 28 to obtain an assist power in walking the bicycle, according to the detected values from the crankshaft rotation sensor 62 and the push force detecting means 741. [0043] The pedal operation decision means 80, the on-riding motor drive control means 81, and the on-walking motor drive control means 83 are configured by a microcomputer, which performs processing according to the flowchart shown in FIGS. 5 and 6. Referring to FIGS. 5 and 6, steps S2, S4, S5, S9, and S10 show processing in the pedal operation decision means 80; steps S1, S6 to S8, Sll, and S12 show processing in the on-riding motor drive control means 81; and steps S13 to S21 show processing in the on-walking motor drive control means 83. [0044] Referring first to FIG. 5, step S1 is executed in the condition that the main switch 48 is on. In step S1, a crankshaft rotating speed is computed according to the detected value from the crankshaft rotation sensor 62. In step S2, a depression force increase AT is computed according to the detected value from the torque detecting means 56. [0045] In step S3, it is determined whether or not the bicycle is being walked. If the first and second switching means 85 and 86 are in the respective first conditions on the basis of the fact that no push force is detected by the push force detecting means 741, that is, if the bicycle is not being walked, the program proceeds to step S4 in which it is then determined whether or not the depression force increase AT is greater than or equal to a set value vTth. If ∆T > ∆Tth, it is determined that the crank pedals 35 are depressed to pedal the bicycle, and the program proceeds to step S5 in which an assist permission command signal is input from the pedal operation decision means 80 into the on-riding motor drive control means 81. Next in step S6, the on-riding motor drive control means 81 outputs a relay drive signal to operate the relay 87 to close the relay switch 87a. [0046] In step S7, a coefficient a corresponding to a battery deviation voltage ∆E as a difference between the voltage of the battery 46 and a reference voltage is generated according to a map preset as shown in FIG. 7. The coefficient a is set to avoid a change in current passing through the electric motor 28 due to variations in the voltage of the battery 46. The coefficient a is set in such a manner that when AE 0, the coefficient a gradually decreases in the range of 1 > a > 0 with an increase in ∆E. [0047] In step S8, an energization ratio (duty ratio) of the electric motor 28 per unit time is obtained by a preset map or arithmetic expression according to the detected values from the crankshaft rotation sensor 62 and the torque detecting means 56. Then, the duty ratio thus obtained is corrected by the above coefficient a , and a motor drive signal modulated by PWM according to the corrected duty ratio is output from the on-riding motor drive control means 81. [0048] The motor drive signal from the on-riding motor drive control means 81 is input into the motor drive limiting means 84. When the detected value from the torque detecting means 56 is greater than a given value, the switching operation of the FET 88 is controlled by the motor drive signal from the on-riding motor drive control means 81 to thereby duty-control the electric motor 28. [0049] If ∆T time has not elapsed in step S9, the program proceeds to step S5, whereas if the delay time has elapsed in step S9, the program proceeds to step S10 to stop the power assisting by the electric motor 28. [0050] In step S10, the output of the assist permission command signal from the pedal operation decision means 80 is stopped, and in step s11, a signal for stopping the operation of the relay 87 is output from the on-riding motor drive control means 81. Next in step S12, the output of the motor drive signal from the on-riding motor drive control means 81 is stopped. [0051] If it is determined in step S3 that the bicycle is being walked, that is, the first and second switching means 85 and 86 are switched into the respective second conditions (shown by the broken lines in FIG. 3), the program proceeds to step S13 shown in FIG. 6. [0052] Steps S13 to S21 shown in FIG. 6 show processing to be executed in the on-walking motor drive control means 83. In step S13, a detected value output from the push force detecting means 741 is read. In step S14, the amount of change in the detected value from the push force detecting means 741 is computed: In step S15, a coefficient ß corresponding to the amount of change in the detected value is computed. The coefficient ß is preset as shown in FIG. 8, for example. In this example, the coefficient ß is set to "1" for small amounts of the change; however, the coefficient ß is set to "0.5" when the change becomes large on the negative side, and the coefficient ß is set to "1.5" when the change becomes large on the positive side. [0053] In step S16, a motor drive signal for driving the electric motor 28 is generated according to the detected value from the push force detecting means 74i- A duty ratio of the electric motor 28 is preset as shown in FIG. 9, for example. In this example, the duty ratio increases with an increase in the push force up to a given value. When the push force becomes greater than or equal to the given value, the duty ratio is fixed to a constant maximum value, e.g., 30%. The vehicle speed and assist torque are defined according to the duty ratio increasing with an increase in the push force as shown in FIG. 10. For example, the maximum value (30%) of the duty ratio is set so that the maximum vehicle speed in walking the bicycle on the ascending slope with a slope angle of about 5 degrees becomes 4km/h, for example. [0054] In step S17 to be executed after deciding the duty ratio of the electric motor 28 according to the push force, the coefficient a corresponding to the battery deviation voltage AE is generated according to the map shown in FIG. 7. Next in step S18, the duty ratio decided in step S16 is corrected by the coefficients α and ß . [0055] In step S19, it is determined whether or not the current vehicle speed is greater than or equal to a target vehicle speed VO. The current vehicle speed is computed according to the crankshaft rotating speed, and the target vehicle speed VO is preset according to the push force as shown in FIG. 11, for example. In this example, the target vehicle speed VO gradually increases with an increase in the push force up to a given value. When the push force becomes greater than or equal to the given value, the target vehicle speed VO is fixed to a constant value, e.g., 5 km/h. [0056] If the current vehicle speed is less than the target vehicle speed VO in step S19, the program proceeds to step S20 in which the motor drive signal corrected in step S18 is output from the on-walking motor drive control means 83, whereas if the current vehicle speed is greater than or equal to the target vehicle speed VO in step S19, the program proceeds to step S21 in which the output of the motor drive signal from the on-walking motor drive control means 83 is stopped. That is, the assist power from the. electric motor 28 in walking the bicycle is controlled so that the vehicle speed does not become greater than or > equal to the target vehicle speed VO. [0057] The operation of the first preferred embodiment will now be described. In walking the bicycle by applying a push force to the vehicle body B, the push force is detected by the push force detecting means 741, and the assist power by the electric motor 28 is controlled according to a detected value from the push force detecting means 741. Accordingly, even when a weak rider walks the bicycle in the case of ascending a slope with a large slope angle or in the case of carrying a heavy load on the bicycle to result in an increased weight of the vehicle body B, an assist power corresponding to the push force can be quickly obtained. Furthermore, when passing over a bump in walking the bicycle, a large assist power corresponding to an increased push force can be obtained. Moreover, when walking the bicycle at a slowly running speed, a suitable assist power corresponding to the push force can be obtained. [0058] The controller 42 for controlling the assist power by the electric motor 28 controls the duty ratio of the electric motor 28 according to the detected value from the push force detecting means 741. Accordingly, the assist torque by the electric motor 28 and the vehicle speed are decided according to a running resistance as shown in FIG. 10, thus allowing simultaneous control of the assist torque and the vehicle speed. [0059] Further, the controller 42 corrects to increase or decrease the assist power by the electric motor 28 corresponding to the detected value from the push force detecting means 741, according to the degree of change in the detected value from the push force detecting means 74i. Accordingly, in a transition state where the push force changes, an assist power changing well in response to the transition state can be obtained. [0060] Further, the assist power from the electric motor 28 in walking the bicycle is controlled so that the vehicle speed does not become greater than or equal to the target vehicle speed. Accordingly, an undue increase in vehicle speed can be prevented during walking the bicycle. [0061] In the event that the vehicle speed detecting means, or the crankshaft rotation sensor 62 whose detected value is used to compute a vehicle speed comes into failure under the control of the assist power from the electric motor 28 during walking the bicycle where the vehicle speed is prevented from becoming greater than or equal to the target vehicle speed VO, there is a possibility that the increase in vehicle speed up to the target vehicle speed VO cannot be detected to cause an undue increase in output from the electric motor 28, increasing the vehicle speed beyond the target vehicle speed VO. However, since the duty ratio of the electric motor 28 is decided according to the push force, the assist torque decreases with an increase in vehicle speed as shown in FIG. 10, so that an undue increase in output from the electric motor 28 as inviting an excess vehicle speed can be prevented. As a modification, the failure of the vehicle speed detecting means may be determined to stop the power assisting by the electric motor 28 in walking the bicycle when a zero vehicle speed continues for a given period of time or more under the detection of the push force by the push force detecting means 741 or under the detection of the torque by the torque detecting means 56. [0062] FIGS. 12 to 14 show a second preferred embodiment of the present invention, in which FIG. 12 is a graph showing an output torque of the electric motor 28 corresponding to a push force; FIG. 13 is a graph showing > the relation among an output torque, duty ratio, and vehicle speed; and FIG. 14 is a graph showing the relation among a vehicle speed, assist torque, push force, and running resistance. [0063] In the first preferred embodiment, the duty ratio of the electric motor 28 is decided according to the push force in step S16 shown in FIG. 6. To the contrary, in the second preferred embodiment, the output torque of the electric motor 28 is decided according to the push force in step S16. That is, the output torque of the electric motor 28 corresponding to the push force is preset as shown in FIG. 12, for example. In this example, the output torque increases with an increase in the push force. The relation between the output torque and the duty ratio is preset as shown in FIG. 13, for example, wherein when the vehicle speed is fixed, the duty ratio increases with an increase in the output torque, whereas when the vehicle speed is increased, the duty ratio becomes large with a small output torque. Particularly, when the vehicle speed becomes a maximum speed, e.g., 4 km/h or more, the duty ratio becomes a maximum value, e.g., 30% with a relatively small output torque. [0064] Accordingly, the vehicle speed, the assist torque, and the push force are related as shown in FIG. 14. As apparent from FIG. 14 in comparison with FIG. 10 showing the first preferred embodiment wherein the duty ratio of the electric motor 28 is decided according to the push force, the duty ratio does not reach 30% in a range of small vehicle speeds as shown by a hatched area in FIG. 14, thereby attaining energy saving. That is, during walking the bicycle on a gentle ascending slope, the push force is small and the output torque of the electric motor is also small, so that undue power consumption can be suppressed. [0065] FIG. 15 shows a first modification of the push force detecting means. Reference numeral 742 denotes push force detecting means provided at a right end portion of the bar handle 24, for example. A support member 92 for pivotably supporting a brake lever 91 operable by a rider's right hand gripping a grip 90 is mounted on the bar handle 24 at its right end portion. The push force detecting means 742 includes a lever 93 supported to the support member 92 pivotably in opposite directions as moving toward and away from the bar handle 24 and located at the back of the bar handle 24, a spring 94 for biasing the lever 93 in such a direction as moving the lever 93 away from the bar handle 24, i.e., rearwardly of the bar handle 24, and a stroke sensor 77 mounted on the support member 92 and having a sensing member 77a adapted to be pushed by the lever 93 pivoted forward, i.e., toward the bar handle 24. The spring 94 is a torsion coil spring, for example, and it is provided between the lever 93 and the support member 92 in such a manner that a coiled portion of the spring 94 surrounds a support shaft 95 for pivotably supporting the lever 93 to the support member 92. [0066] Also according to the push force detecting means 742, the push force can be continuously detected by pushing the lever 93 with the rider's right hand, for example, in walking the bicycle. [0067] FIG. 16 shows a second modification of the push force detecting means. Reference numeral 743 denotes push force detecting means provided on the bar handle 24, for example, like the push force detecting means 742 shown in FIG. 15. The push force detecting means 743 includes a push button 96, a stroke sensor 77 having a sensing member 77a, and a spring 97. [0068] A cylindrical housing 98 extending in the longitudinal direction of the vehicle body B and having an opening 98a is mounted on the bar handle 24. The stroke sensor 77 is contained in the housing 98 at a front portion thereof, and the sensing member 77a projects from the rear end of the stroke sensor 77. The push button 96 has a flange portion 96a at the front end, which is normally engaged with the inner surface of the front end of the housing 98 in the periphery of the opening 98a. The push button 96 is inserted through the opening 98a in such a manner that the flange portion 96a is in contact with the sensing member 77a. The spring 97 is interposed under compression between the stroke sensor 77 and the flange portion 96a of the push button 96 to normally rearward bias the push button 96. [0069] Also according to the push force detecting means 743, the push force can be continuously detected by pushing the push button 96 in walking the bicycle. [0070] FIG. 17 shows a third modification of the push force detecting means. Reference numeral 744 denotes push force detecting means provided on the bar handle 24, for example, like the push force detecting means 742 shown in FIG. 15. The push force detecting means 744 includes a push button 100, a movable contact 101 operating with the push button 100, a common fixed contact 102 always kept in electrical connection with the movable contact 101, first and second individual fixed contacts 103 and 104 electrically connectable through the movable contact 101 to the common fixed contact 102, and a spring 105. With this configuration, the push force can be detected stepwise, e.g., two-stepwise in walking the bicycle. [0071] A cylindrical housing 106 extending in the longitudinal direction of the vehicle body B and having an opening 106a at the rear end. A circular guide plate 107 having a central guide hole 107a coaxial with the housing 106 is fixed in the housing 106. The push button 100 is inserted through the opening 106a of the housing 106, and is integrally formed with a flange portion lOOa normally engaged with the inner surface of the housing 106 in the periphery of the opening 106a and a stem portion lOOb slidably engaged with the guide hole 107a of the guide plate 107. The spring 105 is interposed under compression between the guide plate 107 and the flange portion lOOa of the push button 100 to normally rearward bias the push button 100. [0072] The movable contact 101 is fixed to the stem portion lOOb of the push button 100 and relatively long extends in the axial direction of the stem portion 10Ob. The movable contact 101 is integrally formed with first and second contact portions lOla and lOlb each semispherically projecting at two positions spaced in the longitudinal direction of the movable contact 101. [0073] The common fixed contact 102 is fixedly located in the housing 106 so as to be always kept in contact with the first contact portion lOla located nearer to the guide plate 107 than the second contact portion lOlb. The first individual fixed contact 103 is fixedly located in the housing 106 in such a manner as to come into contact with the second contact portion lOlb of the movable contact 101 when the push button 100 is depressed against the biasing force of the spring 105 from the condition where the push button 100 is in a normal or rearmost position (the condition shown in FIG. 17). On the other hand, the second individual fixed contact 104 is fixedly located in the housing 106 in such a manner as to come into contact with the second contact portion lOlb when the push button 100 is further depressed from the condition where the second contact portion lOlb is in contact with the first individual fixed contact 103. [0074] According to the push force detecting means 744/ by pushing the push button 100 in walking the bicycle, the push force can be stepwise detected in two steps, that is, a first step of electrically connecting the first individual fixed contact 103 through the movable contact 101 to the common contact 102 and a second step of electrically connecting the second individual fixed contact 104 through the movable contact 101 to the common contact 102. [0075] FIGS. 18 to 25 show a third preferred embodiment of the present invention, in which FIG. 18 is a side view of a motor-assisted bicycle; FIG. 19 is a vertical sectional view of slope angle detecting means; FIG. 20 is a cross section taken along the line 20-20 in FIG. 19; FIG. 21 is a block diagram showing the configuration of a controller; FIG. 22 is a flowchart showing processing in on-walking motor drive control means shown in FIG. 21; FIG. 23 is a graph showing a duty ratio corresponding to a slope angle; FIG. 24 is a graph showing a duty ratio corresponding to. a load; and FIG. 25 is a graph showing a preset map of a duty ratio corresponding to a slope angle and a load. [0076] Referring to FIG. 18, a push-button walking switch 110 to be operated by a rider in walking the bicycle is mounted on a left end portion of the bar handle 24, for example. Load detecting means lll1 for detecting the load of a luggage carried in the front basket 44 is mounted on the bottom of the front basket 44, Load detecting means 1112 for detecting the load of a luggage carried on the rear carrier 34 is mounted on the rear carrier 34. Slope angle detecting means 112 for detecting the slope angle of a road surface is mounted on a front portion of the vehicle body B of the bicycle, e.g., on the main frame portion 21b of the front frame 21. [0077] Referring to FIGS. 19 and 20, the slope angle detecting means 112 includes a sectionally circular housing 114 fixedly mounted oh the front frame 21, a support shaft 115 fixed to the housing 114 and having an axis extending in the lateral direction of the vehicle body B, a movable member 117 pivotably supported to the support shaft 115 and having an integral weight 116, a support plate 118 fixed in the housing 114 in opposed relationship with the movable, member 117, a conductor strip 119 provided on one surface of the support plate 118 opposed to the movable member 117 and having an arcuate shape about the axis of the support shaft 115, a resistor strip 120 provided on the one surface of the support plate 118 opposed to the movable member 117 and having an arcuate shape about the axis of the support shaft 115 with a radius larger than that of the conductor strip 119, and a brush 121 fixed to the movable member 117 so as to slidably contact the conductor strip 119 and the resistor strip 120. The opposite ends of the resistor strip 120 are connected to the opposite ends of the battery 46, and a voltage detector 122 is connected between one end of the conductor strip 119 and a ground. [0078] According to the slope angle detecting means 112, even when the vehicle body B is inclined on a slope or the like, the movable member 117 is rotated about the support shaft 115 by the action of the weight 116 so that the weight 116 integral with the movable member 117 keeps its fixed position just under the support shaft 115. On the other hand, the angular position of the support plate 118, i.e., the resistor strip 120 about the axis of the support shaft 115 relative to the movable member 117 changes according to the slope angle. Accordingly, the contact position of the brush 121 on the resistor strip 120 changes to result in a change in voltage detected by the voltage detector 122. Thus, the slope angle of a road surface in walking the bicycle can be detected by the slope angle detecting means 112. [0079] Referring to FIG. 21, detected values from crankshaft rotation sensor 62, torque detecting means 56, walking switch 110, load detecting means lll1 and 1112, and slope angle detecting means 112 are input into a controller 42 including pedal operation decision means 80, on-riding motor drive control means 81, relay driving means 82, on-walking motor drive control means 83, motor drive limiting means 84, first switching means 85, second switching means 86, relay 87 having a relay switch 87a, and FET 88. [0080] The relay driving means 82 functions to drive the relay 87 when the walking switch 110 is turned on. When the walking switch lib is not depressed during riding the bicycle on the seat 25 or at rest, the first and second switching means 85 and 86 are kept in the respective first conditions (shown by solid lines in FIG. 21), whereas when the walking switch 110 is depressed as in walking the bicycle, the first and second switching means 85 and 86 are switched into the respective second conditions (shown by broken lines in FIG. 21). [0081] The on-walking motor drive control means 83 functions to output a motor drive signal for controlling the operation of the electric motor 28 to obtain an assist power in walking the bicycle, according to the detected values from the crankshaft rotation sensor 62, the load detecting means lll1 and 11l2, and the slope angle detecting means 112. [0082] The pedal operation decision means 80 and the on-riding motor drive control means 81 perform the same processing as that described with reference to FIG. 5 in the first preferred embodiment. If the decision in step S3 shown in FIG. 5 is that the bicycle is being walked, that is, if the walking switch 110 has been depressed, the processing shown in FIG. 22 rather than the processing shown in FIG. 6 of the first preferred embodiment is executed by the on-walking motor drive control means 83. [0083] Referring to FIG. 22, in step S22 the detected value from the slope angle detecting means 112 is read. In step S23, the detected values from the load detecting means llli and Ilia are read and added up. In step S24, a motor drive signal is generated so as to decide the duty ratio of the electric motor 28 according to the slope angle and the load. [0084] The duty ratio of the electric motor 28 corresponding to the detected value from the slope angle detecting means 112 is preset as shown in FIG. 23. For example, the duty ratio corresponding to a slope angle of 12 degrees is preset to 30%. Further, the duty ratio of the electric motor 28 corresponding to the sum of the detected values from the load detecting means lll1 and 1112 is preset as shown in FIG. 24. For example, the duty ratio corresponding to a load of 15 kgf is preset to 30%. By combining FIGS. 23 and 24, the duty ratio corresponding to both the slope and the load is preset on a three-dimensional map as shown in FIG. 25. [0085] After generation of the motor drive signal in step S24, a coefficient a corresponding to a battery deviation voltage AE is generated in step S25, and the duty ratio decided in step S24 is then corrected by the coefficient a in step S26. [0086] In step S27, it is determined whether or not the current vehicle speed is greater than or equal to a target vehicle speed VO. If the current vehicle speed is less than the target vehicle speed VO, the motor drive signal corrected in step S26 is output from the on-walking motor drive control means 83 in step S28. If the current vehicle speed is greater than or equal to the target vehicle speed VO, the output of the motor drive signal from the on-walking motor drive control means 83 is stopped in step S29. [0087] According to the third preferred embodiment, the assist power by the electric motor 28 is controlled according to the slope angle of a road surface and the load on the vehicle body B when the walking switch 110 is depressed in walking the bicycle. Accordingly, even when a weak rider walks the bicycle in the case of ascending a slope with a large slope angle or in the case of carrying a heavy load on the bicycle to result in an increased weight of the vehicle body B, the assist power by the electric motor 28 can be quickly obtained. [0088] While the load detecting means lll1 and 1112 are provided on the front basket 44 and the rear carrier 34, respectively, in the third preferred embodiment, any one of the load detecting means lll1 and 1112 may be provided. Further, the assist power by the electric motor 28 may be controlled according to any one of the slope angle of a road surface and the load carried on the bicycle. [0089] Having thus described specific preferred embodiments of the present invention, it should be noted that the present invention is not limited to the above preferred embodiments, but various design changes may be made without departing from the scope of the present invention defined in the appended claims. [0090] [Effect of the Invention] According to the invention as defined in claim 1, the assist power by the electric power in walking the bicycle is controlled according to the push force applied to the vehicle body. Accordingly, even when a weak rider walks the bicycle in the case of ascending a slope with a large slope angle or in the case of carrying a heavy load to cause an increased weight of the vehicle body, the assist power corresponding to the push force applied can be quickly obtained. Further, when passing over a bump in walking the bicycle, a large assist power responsive to an increase in the push force can be obtained. Further, when pushing the vehicle body in walking the bicycle at a slowly running speed, the assist power corresponding to the push force applied can be obtained. [0091] According to the invention as defined in claim 2, the assist power can be changed well responsive to a transition state where the push force changes. [0092] According to the invention as defined in claim 3, an assist torque by the electric motor and a vehicle speed are determined according to a running resistance, thereby allowing simultaneous control of the assist torque and the vehicle speed. [0093] According to the invention as defined in claim 4, undue power consumption can be suppressed to thereby attain energy saving. [0094] According to the invention as defined in claim 5, the assist power by the electric motor is controlled according to at least one of the slope angle of the road surface and the load carried on the vehicle body in the operated condition of the walking switch in walking the . bicycle. Accordingly, even when a weak rider walks the bicycle in the case of ascending a slope with a large slope t angle or in the case of carrying a heavy load to cause an increased weight of the vehicle body, the assist power required can be quickly obtained. Further, the assist power can be obtained regardless of the manner of pushing the vehicle body. [0095] According to the invention as defined in claim 6, an undue increase in the vehicle speed in walking the bicycle can be prevented. [Explanation of Reference Numerals] 28: electric motor 35: crank pedal 142: controller 741, 74a, 74a, 744: push force detecting means 110: walking switch lll1, 1112: load detecting means 112: slope angle detecting means B: vehicle body [CLAIMS] [claim 1] In a motor-assisted bicycle having a vehicle body (B) and an electric motor (28) mounted on said vehicle body (B) for assisting a depression force applied to crank pedals (35); the improvement comprising push force detecting means (741, 742, 743, 744) for continuously or stepwise detecting a push force applied to said vehicle body (B) by a rider in walking said bicycle, and a controller (42) for controlling an assist power by said electric motor (28) according to a detected value from said push force detecting means (741, 742/ 743/ 744). [claim 2] A motor-assisted bicycle according to claim 1, wherein said controller (42) corrects to increase or decrease the assist power by said electric motor (28) corresponding to the detected value from said push force detecting means (74i, 742/ 743/ 744), according to the degree of change in the detected value from said push force detecting means (741, 742, 743, 744). [claim 3] A motor-assisted bicycle according to claim 1 or 2, wherein said controller (42) controls a duty ratio of said electric motor (28) according to the detected value from said push force detecting means (741, 742, 743/ 744). [claim 4] A motor-assisted bicycle according to claim 1 or 2, wherein said controller (42) controls an output torque of said electric motor (28) according to the detected value from said push force detecting means (741, 742, 743/ 744). [claim 5] In a motor-assisted bicycle having a vehicle body (B) and an electric motor (28) mounted on said vehicle body (B) for assisting a depression force applied to crank pedals (35); the improvement comprising a walking switch (110) to be operated by a rider in walking said bicycle, at least one of slope angle detecting means (112) for detecting a slope angle of a road surface and load detecting means (lll1,, 1112) for detecting a load carried on said vehicle body (B), and a controller (42) for controlling an assist power by said electric motor (28) according to a detected value from at least one of said slope angle detecting means (112) and said load detecting means (lll1, 1112) in an operated condition of said walking switch (110). [claim 6] A motor-assisted bicycle according to claim 1 or 5, wherein said controller (42) stops power assisting by said electric motor (28) when a vehicle speed 56 of said bicycle becomes greater than or equal to a set value. 7. A motor-assisted bicycle substantially as herein described with reference to the accompanying drawings.

Full Text

[DETAILED DESCRIPTION OF THE INVENTION] [0001]
[Field of the Invention]
The present invention relates to a motor-assisted bicycle having a vehicle body and an electric motor mounted on the vehicle body for assisting a depression force applied to crank pedals, and more particularly to control of the electric motor in walking the bicycle. [0002]
[Prior Art]
Conventionally known from Japanese Patent Laid-open No. 4-358988 is a motor-assisted bicycle having an electric motor wherein an assist power exerted by the electric motor in walking the bicycle is controlled so that the vehicle speed becomes a speed slightly lower than a walking speed. [0003]
[Problem to be Solved by the Invention]
In the prior art mentioned above, however/ the assist power by the electric motor is obtained in walking the bicycle at a vehicle speed greater than or equal to a given value. Accordingly, in the case of ascending a slope
with a large slope angle or in the case of carrying a heavy
load to result in an increased weight of the vehicle body, for example, there is a possibility that the vehicle speed may not reach the above-mentioned given value until a push force applied to the vehicle body by a rider becomes a relatively large value. As a result, a weak rider requires much time to obtain the assist power in walking the bicycle. Further, in the case of passing over a bump or the like in walking the bicycle, the vehicle speed does not reach the above-mentioned given value, so that the assist power in walking the bicycle cannot be obtained. Further, there is a case that some riders may intend to push the vehicle body in walking the bicycle at a slowly running speed. In this case, however, the assist power cannot be obtained because it is controlled so that the vehicle speed becomes a speed slightly lower than a walking speed. [0004]
It is accordingly an object of the present invention to provide a motor-assisted bicycle which can obtain an assist power quickly according to a push force applied to a vehicle body by a rider in walking the bicycle regardless of the strength of the rider and the manner of pushing the vehicle body. [0005]
[Means of Solving the Problem]
According to the invention as defined in claim I, there is provided in a motor-assisted bicycle having a vehicle body and an electric motor mounted on the vehicle body for assisting a depression force applied to crank pedals; the improvement comprising push force detecting means for continuously or stepwise detecting a push force applied to the vehicle body, and a controller for controlling an assist power by the electric motor according to a detected value from the push force detecting means. [0006]
With this configuration, the assist power by the electric motor in walking the bicycle is controlled according to the push force applied to the vehicle body. Accordingly, even when a weak rider walks the bicycle in the case of ascending a slope with a large slope angle or in the case of carrying a heavy load to cause an increased weight of the vehicle body, the assist power corresponding to the push force applied can be quickly obtained. Further, when passing over a bump in walking the bicycle, a large assist power responsive to an increase in the push force can be obtained. Further, when pushing the vehicle body in walking the bicycle at a slowly running speed, the assist power corresponding to the push force applied can be obtained.
[0007]
According to the invention as defined in claim 2 including the configuration of the invention as defined in claim 1, the controller corrects to increase or decrease the assist power by the electric motor corresponding to the detected value from the push force detecting means, according to the degree of change in the detected value from the push force detecting means. With this configuration, the assist power can be changed well responsive to a transition state where the push force changes. [0008]
According to the invention as defined in claim 3 including the configuration of the invention as defined in claim 1 or 2, the controller controls a duty ratio of the electric motor according to the detected value from the push force detecting means. With this configuration, an assist torque by the electric motor and a vehicle speed are determined according to a running resistance, thereby allowing simultaneous control of the assist torque and the vehicle speed. [0009]
According to the invention as defined in claim 4 including the configuration of the invention as defined in
claim 1 or 2, the controller controls an output torque of the electric motor according to the detected value from the push force detecting means. With this configuration, the output torque of the electric motor is reduced in ascending a gentle slope or the like because of a small push force. Accordingly, undue power consumption can be suppressed to thereby attain energy saving. [0010]
According to the invention as defined in claim 5, there is provided in a motor-assisted bicycle having a vehicle body and an electric motor mounted on the vehicle body for assisting a depression force applied to crank pedals; the improvement comprising a walking switch to be operated by a rider in walking the bicycle, at least one of slope angle detecting means for detecting a slope angle of a road surface and load detecting means for detecting a load carried on the vehicle body, and a controller for controlling an assist power by the electric motor according to a detected value from at least one of the slope angle detecting means and the load detecting means in an operated condition of the walking switch. [0011]
With the configuration of the invention as defined in claim 5, the assist power by the electric motor is
controlled according to at least one of the slope angle of the road surface and the load carried on the vehicle body in the operated condition of the walking switch in walking the bicycle. Accordingly, even when a weak rider walks the bicycle in the case of ascending a slope with a large slope angle or in the case of carrying a heavy load to cause an increased weight of the vehicle body, the assist power required can be quickly obtained. Further, the assist power can be obtained regardless of the manner of pushing the vehicle body. [0012]
According to the invention as defined in claim 6 including the configuration of the invention as defined in claim 1 or 5, the controller stops power assisting by the electric motor when a vehicle speed of the bicycle becomes greater than or equal to a set value. With this configuration, an undue increase in the vehicle speed in walking the bicycle can be prevented.

[BRIEF DESCRIPTION OF THE DRAWINGS]
[FIG. 1]
FIG. 1 is a side view of a motor-assisted bicycle according to a first preferred embodiment.
[FIG. 2]
FIG. 2 is a schematic illustration of the structure
of a power unit.
[FIG. 3]
FIG. 3 is a block diagram showing the configuration of a controller.
[FIG. 4]
FIG. 4 is an enlarged sectional view of an encircled portion 4 in FIG. 1, showing the configuration of push force detecting means.
[FIG. 5]
FIG. 5 is a flowchart showing processing in pedal operation decision means and on-riding motor drive control means.
[FIG. 6]
FIG. 6 is a flowchart showing processing in on-walking motor drive control means.
[FIG. 7]
FIG. 7 is a graph showing a coefficient corresponding to a battery deviation voltage.
[FIG. 8]
FIG. 8 is a graph showing a coefficient corresponding to the amount of change in push force detected value.
[FIG. 9]
FIG. 9 is a graph showing a duty ratio
corresponding to a push force.
[FIG. 10]
FIG. 10 is a graph showing the relation among a vehicle speed, assist torque, duty ratio, and running resistance.
[FIG. 11]
FIG. 11 is a graph showing a target vehicle speed corresponding to a push force.
[FIG. 12]
FIG. 12 is a graph showing an output torque of the electric motor corresponding to a push force according to a second preferred embodiment.
[FIG. 13]
FIG. 13 is a graph showing the relation among an output torque, duty ratio, and vehicle speed.
[FIG. 14]
FIG. 14 is a graph showing the relation among a vehicle speed, assist torque, push force, and running resistance.
[FIG. 15]
FIG. 15 is a sectional view showing a first modification of the push force detecting means.
[FIG. 16]
FIG. 16 is a sectional view showing a second
modification of the push force detecting means.
[FIG. 17]
FIG. 17 is a sectional view showing a third modification of the push force detecting means.
[FIG. 18]
FIG. 18 is a side view of a motor-assisted bicycle according to a third preferred embodiment.
[FIG. 19]
FIG. 19 is a vertical sectional view of slope angle detecting means.
[FIG. 20]
FIG. 20 is a cross section taken along the line 20-20 in FIG. 19.
[FIG. 21]
FIG. 21 is a block diagram showing the configuration of a controller.
[FIG. 22]
FIG. 22 is a flowchart showing processing in walking motor drive control means.
[FIG. 23]
FIG. 23 is a graph showing a duty ratio corresponding to a slope angle.
[FIG. 24]
FIG. 24 is a graph showing a duty ratio

corresponding to a load.
[FIG. 25]
FIG. 25 is a graph showing a preset map of a duty ratio corresponding to a slope angle and a load.
[0013]
[Preferred Embodiment]
Some preferred embodiments of the present invention will now be described with reference to the attached drawings. [0014]
FIGS. 1 to 11 shows a first preferred embodiment of the present invention, wherein FIG. 1 is a side view of a motor-assisted bicycle; FIG. 2 is a schematic illustration of the structure of a power unit; FIG. 3 is a block diagram showing the configuration of a controller; FIG. 4 is an enlarged sectional view of an encircled portion 4 in FIG. 1, showing the configuration of push force detecting means; FIG. 5 is a flowchart showing processing in pedal operation decision means and on-riding motor drive control means; FIG. 6 is a flowchart showing processing in on-walking motor drive control means; FIG. 7 is a graph showing a coefficient corresponding to a battery deviation voltage; FIG. 8 is a graph showing a coefficient corresponding to the amount of change in push force detected value; FIG. 9 is a graph showing a duty ratio corresponding to a push force; FIG. 10 is a graph showing the relation among a vehicle speed, assist torque, duty ratio, and running resistance; and FIG. 11 is a graph showing a target vehicle speed corresponding to a push force. [0015]
Referring first to FIG. 1, a vehicle body B of the motor-assisted bicycle includes a front frame 21 substantially U-shaped in side elevation and located between a front wheel WF and a rear wheel WR, and a rear
frame 22 for supporting the rear wheel WR. The front frame 21 is composed integrally of a head pipe 2la for steerably supporting a front fork 23 which rotatably supports the front wheel WF/ a main frame portion 21b extending rearward and obliquely downward from the head pipe 21a, a curved portion 21c convexed downward and connected to the rear end of the main frame portion 21b, and a seat frame portion 2Id extending upward from the curved portion 21c. A bar handle 24 is provided at the upper end of the front fork 23. [0016]
A seat post 26 having a seat 25 at the upper end is vertically movably mounted on the seat frame portion 2Id of the front frame 21 in such a manner as to allow the vertical position of the seat 25 to be adjusted. A power unit 29 having an electric motor 28 is supported to a lower portion of the front frame 21. [0017]
The rear frame 22 includes a pair of right and left rear forks 30 extending rearward and obliquely downward from the upper end of the curved portion 21c of the front frame 21 at a position above a rear portion of the power unit 29 and further extending substantially horizontally at a position behind the power unit 29, and a pair of right and left stays 31 extending between the upper end of the
seat frame portion 21d of the front frame 21 and the rear ends of the right and left rear forks 30. The rear wheel WR is supported between the right and left rear forks 30 at their rear ends. A rear carrier 34 is located behind the seat 25 and is fixedly supported by a pair of right and left support members 32 extending rearward from the upper ends of the right and left stays 31 and by a pair of right and left support members 33 extending upward from the lower ends of the right and left stays 31. [0018]
A crankshaft 36 having a pair of right and left crank pedals 35 at the opposite ends is rotatably supported at a casing 37 of the power unit 29. An endless chain 40 is wrapped between a drive sprocket 38 and a driven sprocket 39 so as to be covered with a chain case 41. The drive sprocket 38 is capable of transmitting a pedaling power from the crankshaft 36 to the rear wheel WR and also applying an assist power from the electric motor 28 to the crankshaft 36. [0019]
The operation of the electric motor 28 is
controlled by a controller 42 fixedly supported to a lower portion of the front frame 21 at a position before the power unit 29.
[0020]
A front basket 44 is mounted through a bracket 43 on the head pipe 2la. A battery storage case 45 located at the back portion of the front basket 44 is also mounted on the bracket 43. A battery 46 for supplying electric power to the electric motor 28 is removably stored in the battery storage case 45. [0021]
Most of the front frame 21 is covered with a cover 47, and a main switch 48 for supplying the electric power from the battery 46 to the controller 42 and the electric motor 28 is provided at an upper portion of the cover 47. The cover 47 is constructed by jointing an upper cover 47a for covering the front frame 21 from its upper side and a lower cover 47b for covering the front frame 21 from its lower side. An opening (not shown) for exposing the main switch 48 is formed at an upper portion of the upper cover 47a. [0022]
As shown in FIG. 2, a rotating cylinder 50 is rotatably supported to the casing 37. A right end portion of the crankshaft 36 is rotatably supported to the inner circumference of the rotating cylinder 50, and a left end portion of the crankshaft 36 is rotatably supported to the
casing 37. The drive sprocket 38 engaged with the chain 40
is connected to the rotating cylinder 50.
[0023]
A depression force input from the crank pedals 35 to the crankshaft 36 is transmitted through power transmitting means 51 to the drive sprocket 38. The electric motor 28 is mounted on the casing 37, and an output from the electric motor 28 is transmitted through a reduction gear train 52 to the drive sprocket 38 in order to assist the depression force from the crank pedals 35. [0024]
The power transmitting means 51 is composed of a torsion bar 53 connected to the crankshaft 36 and a first one-way clutch 54 provided between the rotating cylinder 50 and the torsion bar 53. [0025]
The crankshaft 36 is formed with an axially extending slit 55, and the torsion bar 53 is mounted in the slit 55 of the crankshaft 36 in such a manner that an arm portion 53a formed at one end of the torsion bar 53 is nonrotatably connected to the crankshaft 36. Another arm portion 53b is formed at the other end of the torsion bar 53, and is loosely engaged with the slit 55 with gaps defined between the arm portion 53b and the inner opposed
wall surfaces of the slit 55. Accordingly, torsional deformation of the torsion bar 53 is allowed within a given range corresponding to the angular movement of the arm portion 53b within the gaps. [0026]
The first one-way clutch 54 is provided between the arm portion 53b of the torsion bar 53 and the rotating cylinder 50. When the crank pedals 35 are depressed to normally rotate the crankshaft 36, the torque of the crankshaft 36 is transmitted through the torsion bar 53, the first one-way clutch 54, and the rotating cylinder 50 to the drive sprocket 38, whereas when the crank pedals 35 are depressed to reversely rotate the crankshaft 36, the first one-way clutch 54 slips to allow reverse rotation of the crankshaft 36. [0027]
The torque input from the crank pedals 35 to the crankshaft 36 is detected by torque detecting means 56. The torque detecting means 56 includes a torque-displacement conversion mechanism 57 for converting the torsion of the torsion bar 53 according to the input torque into a displacement along the axis of the crankshaft 36, and a stroke sensor 58 for outputting an electrical signal according to the displacement. The torque-displacement
conversion mechanism 57 includes a slider 59 supported to the outer circumference of the crankshaft 36 so as to be nonrotatable and axially movable relative to the crankshaft 36. The slider 59 has a projecting cam surface 59a engaged with a recessed cam surface 60 formed on a clutch inner ring of the first one-way clutch 54. [0028]
Further, the outer circumference of the crankshaft 36 is formed with a toothed portion 61 to detect a rotating speed of the crankshaft 36, and a crankshaft rotation sensor 62 is fixedly provided in the casing 37 so as to be opposed to the toothed portion 61. The crankshaft rotation sensor 62 is configured so as to detect the teeth of the toothed portion 61 optically or magnetically and output detected pulses. [0029]
The reduction gear train 52 for transmitting the power of the electric motor 28 to the drive sprocket 38 includes a drive gear 64 fixed to a motor shaft 63, a first idle shaft 65 rotatably supported to the casing 37, a first intermediate gear 66 fixed to one end of the first idle shaft 65 and meshing with the drive gear 64, a second intermediate gear 67 integral with the first idle shaft 65, a third intermediate gear 68 meshing with the second
intermediate gear 67,a second idle shaft 69 arranged coaxially with the third intermediate gear 68 and rotatably supported to the casing 37, a second one-way clutch 70 provided between the third intermediate gear 68 and the second idle shaft 69, a fourth intermediate gear 71 integral with the second idle shaft 69, and a driven gear 72 integral with the rotating cylinder 50 to which the drive sprocket 38 is connected and meshing with the fourth intermediate gear 71. [0030]
The electric motor 28 is mounted on the casing 37 in such a manner that the motor shaft 63 extends parallel to the crankshaft 36. The first and second idle shafts 65 and 69 are rotatably supported to the casing 37 so as to have axes parallel to the crankshaft 36 and the motor shaft 63. [0031]
In the reduction gear train 52, the torque generated by the operation of the electric motor 28 is transmitted to the drive sprocket 38 with a rotating speed reduced. When the operation of the electric motor 28 is stopped, the second one-way clutch 70 operates to permit idling of the second idle shaft 69, thereby allowing rotation of the drive sprocket 38 by the depression force
applied to the crank pedals 35. [0032]
Referring to FIG. 3, the operation of the electric motor 28 is controlled by the controller 42. In this preferred embodiment, the controller 42 controls the operation of the electric motor 28 according to detected values output from the crankshaft rotation sensor 62, the torque detecting means 56, and push force detecting means 741. [0033]
The push force detecting means 741 functions to continuously detect a push force applied to the vehicle body B by a rider in walking the bicycle. As shown in FIG. 1, the push force detecting means 741 is mounted on the seat post 26 immediately under the seat 25. [0034]
Referring to FIG. 4, the push force detecting means 741 includes a lever 75 for receiving a push force from one of the right and left hands of the rider in walking the bicycle, a spring 76 for biasing the lever 75 in a direction opposite to the direction of the push force applied to the lever 75, and a stroke sensor 77 for detecting a stroke of the lever 75 pushed against a biasing force of the spring 76. A bracket 78 is provided on the
seat post 26 immediately under the seat 25, and a support cylinder 79 having an axis extending in the longitudinal direction of the vehicle body B is fixed to the bracket 78. The lever 75 is integrally formed at its front end with a radially outward projecting flange 75a. The flange 75a is slidably engaged in the support cylinder 79. The spring 76 for rearwardly biasing the lever 75 is contained in the support cylinder 79 in such a condition where the spring 76 is normally compressed between the bracket 78 and the flange 75a. The support cylinder 79 is integrally formed at its rear end with a radially inward projecting flange 79a for engaging the flange 75a of the lever 75 to define a rear limit position of the lever 75, thereby setting the rear end of the lever 75 in its rear limit position before the rear end of the seat 25 by a distance L as shown in FIG. 4. The purpose of this setting is to prevent that the lever 75 may be undesirably pushed by a luggage carried on the rear carrier 34. [0035]
The stroke sensor 77 is mounted on the bracket 78 in adjacent relationship with the support cylinder 79. The stroke sensor 77 has a sensing member 77a contacting a push member 75b extending downward from the lever 75. Examples of the stroke sensor 77 include a potentiometer using a
resistor and any other sensors utilizing a resistance change due to deformation of conductive rubber. [0036]
By using the push force detecting means 74i, the stroke of the lever 75 according to the push force applied to the lever 75 can be detected by the stroke sensor 77. A detected value from the stroke sensor 77 is input into the controller 42. [0037]
Referring to FIG. 3, the controller 42 includes pedal operation decision means 80, on-riding motor drive control means 81, relay driving means 82, on-walking motor drive control means 83, motor drive limiting means 84, first switching means 85, second switching means 86, relay 87 having a relay switch 87a, and FET (field effect transistor) 88. [0038]
The positive terminal of the battery 46 is connected through the main switch 48 and the relay switch 87a to the positive terminal of the electric motor 28, and the negative terminal of the electric motor 28 is grounded through the FET 88. Thus, the operation of the electric motor 28 is controlled by controlling the switching operation of the FET 88 in the closed states of the main
switch 48 and the relay switch 87a. [0039]
The first and second switching means 85 and 86 perform switching operations according to an output from the relay driving means 82. More specifically, the first switching means 85 can switch between a first condition (shown by a solid line in FIG. 3) where an output from the on-riding motor drive control means 81 is supplied to the relay 87 when the output from the relay driving means 82 is in a low level and a second condition (shown by a broken line in FIG. 3) where the output from the relay driving means 82 is supplied to the relay 87 when the output from the relay driving means 82 is in a high level. On the other hand, the second switching means 86 can switch between a first condition (shown by a solid line in FIG. 3) where an output from the motor drive limiting means 84 is supplied to the gate of the FET 88 when the output from the relay driving means 82 is in a low level and a second condition (shown by a broken line in FIG. 3) where an output from the on-walking motor drive control means 83 is supplied to the gate of the FET 88 when the output from the relay driving means 82 is in a high level. [0040]
The relay driving means 82 functions to amplify the
detected value from the push force detecting means 741 up to a level enough to drive the relay 87. During running of the bicycle on the seat 25 or at rest, no push force is detected by the push force detecting means 741 and accordingly the first and second switching means 85 and 86 are kept in the respective first conditions. When a push force is detected by the push force detecting means 741 during walking of the bicycle, the first and second switching means 85 and 86 are switched into the respective second conditions. [0041]
The motor drive limiting means 84 functions to limit a motor drive signal output from the on-riding motor drive control means 81 according to the detected value from the torque detecting means 56, so as to control the switching operation of the FET 88. When the detected value from the torque detecting means 56 is less than or equal to a given value, the motor drive limiting means 84 generates a signal for cutting off the FET 88 irrespective of the motor drive signal output from the on-riding motor drive control means 81. [0042]
The pedal operation decision means 80 functions to determine whether or not the crank pedals 35 have been
depressed according to the detected value from the torque detecting means 56. When determining that the crank pedals 35 have been depressed, the pedal operation decision means
80 supplies an assist permission command signal to the on-
riding motor drive control means 81. When receiving the
assist permission command signal from the pedal operation
decision means 80, the on-riding motor drive control means
81 generates a motor drive signal for controlling the
operation of the electric motor 28 to obtain an assist
power in riding the bicycle, according to the detected
values from the crankshaft rotation sensor 62 and the
torque detecting means 56 and the voltage of the battery
46, and further generates a relay drive signal for driving
the relay 87 to close the relay switch 87a in obtaining the
assist power. Further, the on-walking motor drive control
means 83 generates a motor drive signal for controlling the
operation of the electric motor 28 to obtain an assist
power in walking the bicycle, according to the detected
values from the crankshaft rotation sensor 62 and the push
force detecting means 741.
[0043]
The pedal operation decision means 80, the on-riding motor drive control means 81, and the on-walking motor drive control means 83 are configured by a
microcomputer, which performs processing according to the flowchart shown in FIGS. 5 and 6. Referring to FIGS. 5 and 6, steps S2, S4, S5, S9, and S10 show processing in the pedal operation decision means 80; steps S1, S6 to S8, Sll, and S12 show processing in the on-riding motor drive control means 81; and steps S13 to S21 show processing in the on-walking motor drive control means 83. [0044]
Referring first to FIG. 5, step S1 is executed in the condition that the main switch 48 is on. In step S1, a crankshaft rotating speed is computed according to the detected value from the crankshaft rotation sensor 62. In step S2, a depression force increase AT is computed according to the detected value from the torque detecting means 56. [0045]
In step S3, it is determined whether or not the bicycle is being walked. If the first and second switching means 85 and 86 are in the respective first conditions on the basis of the fact that no push force is detected by the push force detecting means 741, that is, if the bicycle is not being walked, the program proceeds to step S4 in which it is then determined whether or not the depression force increase AT is greater than or equal to a set value vTth.
If ∆T > ∆Tth, it is determined that the crank pedals 35 are depressed to pedal the bicycle, and the program proceeds to step S5 in which an assist permission command signal is input from the pedal operation decision means 80 into the on-riding motor drive control means 81. Next in step S6, the on-riding motor drive control means 81 outputs a relay drive signal to operate the relay 87 to close the relay switch 87a. [0046]
In step S7, a coefficient a corresponding to a battery deviation voltage ∆E as a difference between the voltage of the battery 46 and a reference voltage is generated according to a map preset as shown in FIG. 7. The coefficient a is set to avoid a change in current passing through the electric motor 28 due to variations in the voltage of the battery 46. The coefficient a is set in such a manner that when AE 0, the coefficient a gradually decreases in the range of 1 > a > 0 with an increase in ∆E. [0047]
In step S8, an energization ratio (duty ratio) of the electric motor 28 per unit time is obtained by a preset
map or arithmetic expression according to the detected values from the crankshaft rotation sensor 62 and the torque detecting means 56. Then, the duty ratio thus obtained is corrected by the above coefficient a , and a motor drive signal modulated by PWM according to the corrected duty ratio is output from the on-riding motor drive control means 81. [0048]
The motor drive signal from the on-riding motor drive control means 81 is input into the motor drive limiting means 84. When the detected value from the torque detecting means 56 is greater than a given value, the switching operation of the FET 88 is controlled by the motor drive signal from the on-riding motor drive control means 81 to thereby duty-control the electric motor 28. [0049]
If ∆T time has not elapsed in step S9, the program proceeds to step S5, whereas if the delay time has elapsed in step S9, the program proceeds to step S10 to stop the power assisting by the electric motor 28. [0050]
In step S10, the output of the assist permission command signal from the pedal operation decision means 80 is stopped, and in step s11, a signal for stopping the operation of the relay 87 is output from the on-riding motor drive control means 81. Next in step S12, the output of the motor drive signal from the on-riding motor drive control means 81 is stopped. [0051]
If it is determined in step S3 that the bicycle is being walked, that is, the first and second switching means 85 and 86 are switched into the respective second conditions (shown by the broken lines in FIG. 3), the program proceeds to step S13 shown in FIG. 6. [0052]
Steps S13 to S21 shown in FIG. 6 show processing to be executed in the on-walking motor drive control means 83. In step S13, a detected value output from the push force detecting means 741 is read. In step S14, the amount of change in the detected value from the push force detecting
means 741 is computed: In step S15, a coefficient ß corresponding to the amount of change in the detected value is computed. The coefficient ß is preset as shown in FIG.
8, for example. In this example, the coefficient ß is set
to "1" for small amounts of the change; however, the
coefficient ß is set to "0.5" when the change becomes
large on the negative side, and the coefficient ß is set
to "1.5" when the change becomes large on the positive
side.
[0053]
In step S16, a motor drive signal for driving the electric motor 28 is generated according to the detected value from the push force detecting means 74i- A duty ratio of the electric motor 28 is preset as shown in FIG.
9, for example. In this example, the duty ratio increases
with an increase in the push force up to a given value.
When the push force becomes greater than or equal to the
given value, the duty ratio is fixed to a constant maximum
value, e.g., 30%. The vehicle speed and assist torque are
defined according to the duty ratio increasing with an
increase in the push force as shown in FIG. 10. For
example, the maximum value (30%) of the duty ratio is set
so that the maximum vehicle speed in walking the bicycle on
the ascending slope with a slope angle of about 5 degrees
becomes 4km/h, for example. [0054]
In step S17 to be executed after deciding the duty ratio of the electric motor 28 according to the push force, the coefficient a corresponding to the battery deviation voltage AE is generated according to the map shown in FIG. 7. Next in step S18, the duty ratio decided in step S16 is corrected by the coefficients α and ß . [0055]
In step S19, it is determined whether or not the current vehicle speed is greater than or equal to a target vehicle speed VO. The current vehicle speed is computed according to the crankshaft rotating speed, and the target vehicle speed VO is preset according to the push force as shown in FIG. 11, for example. In this example, the target vehicle speed VO gradually increases with an increase in the push force up to a given value. When the push force becomes greater than or equal to the given value, the target vehicle speed VO is fixed to a constant value, e.g., 5 km/h. [0056]
If the current vehicle speed is less than the target vehicle speed VO in step S19, the program proceeds to step S20 in which the motor drive signal corrected in
step S18 is output from the on-walking motor drive control means 83, whereas if the current vehicle speed is greater than or equal to the target vehicle speed VO in step S19, the program proceeds to step S21 in which the output of the motor drive signal from the on-walking motor drive control means 83 is stopped. That is, the assist power from the. electric motor 28 in walking the bicycle is controlled so that the vehicle speed does not become greater than or
>
equal to the target vehicle speed VO. [0057]
The operation of the first preferred embodiment will now be described. In walking the bicycle by applying a push force to the vehicle body B, the push force is detected by the push force detecting means 741, and the assist power by the electric motor 28 is controlled according to a detected value from the push force detecting means 741. Accordingly, even when a weak rider walks the bicycle in the case of ascending a slope with a large slope angle or in the case of carrying a heavy load on the bicycle to result in an increased weight of the vehicle body B, an assist power corresponding to the push force can be quickly obtained. Furthermore, when passing over a bump in walking the bicycle, a large assist power corresponding to an increased push force can be obtained. Moreover, when
walking the bicycle at a slowly running speed, a suitable assist power corresponding to the push force can be obtained. [0058]
The controller 42 for controlling the assist power by the electric motor 28 controls the duty ratio of the electric motor 28 according to the detected value from the push force detecting means 741. Accordingly, the assist torque by the electric motor 28 and the vehicle speed are decided according to a running resistance as shown in FIG. 10, thus allowing simultaneous control of the assist torque and the vehicle speed. [0059]
Further, the controller 42 corrects to increase or decrease the assist power by the electric motor 28 corresponding to the detected value from the push force detecting means 741, according to the degree of change in the detected value from the push force detecting means 74i. Accordingly, in a transition state where the push force changes, an assist power changing well in response to the transition state can be obtained. [0060]
Further, the assist power from the electric motor 28 in walking the bicycle is controlled so that the vehicle
speed does not become greater than or equal to the target vehicle speed. Accordingly, an undue increase in vehicle speed can be prevented during walking the bicycle. [0061]
In the event that the vehicle speed detecting means, or the crankshaft rotation sensor 62 whose detected value is used to compute a vehicle speed comes into failure under the control of the assist power from the electric motor 28 during walking the bicycle where the vehicle speed is prevented from becoming greater than or equal to the target vehicle speed VO, there is a possibility that the increase in vehicle speed up to the target vehicle speed VO cannot be detected to cause an undue increase in output from the electric motor 28, increasing the vehicle speed beyond the target vehicle speed VO. However, since the duty ratio of the electric motor 28 is decided according to the push force, the assist torque decreases with an increase in vehicle speed as shown in FIG. 10, so that an undue increase in output from the electric motor 28 as inviting an excess vehicle speed can be prevented. As a modification, the failure of the vehicle speed detecting means may be determined to stop the power assisting by the electric motor 28 in walking the bicycle when a zero vehicle speed continues for a given period of time or more
under the detection of the push force by the push force detecting means 741 or under the detection of the torque by the torque detecting means 56. [0062]
FIGS. 12 to 14 show a second preferred embodiment of the present invention, in which FIG. 12 is a graph showing an output torque of the electric motor 28 corresponding to a push force; FIG. 13 is a graph showing
>
the relation among an output torque, duty ratio, and vehicle speed; and FIG. 14 is a graph showing the relation among a vehicle speed, assist torque, push force, and running resistance. [0063]
In the first preferred embodiment, the duty ratio of the electric motor 28 is decided according to the push force in step S16 shown in FIG. 6. To the contrary, in the second preferred embodiment, the output torque of the electric motor 28 is decided according to the push force in step S16. That is, the output torque of the electric motor 28 corresponding to the push force is preset as shown in FIG. 12, for example. In this example, the output torque increases with an increase in the push force. The relation between the output torque and the duty ratio is preset as shown in FIG. 13, for example, wherein when the vehicle

speed is fixed, the duty ratio increases with an increase in the output torque, whereas when the vehicle speed is increased, the duty ratio becomes large with a small output torque. Particularly, when the vehicle speed becomes a maximum speed, e.g., 4 km/h or more, the duty ratio becomes a maximum value, e.g., 30% with a relatively small output torque. [0064]
Accordingly, the vehicle speed, the assist torque, and the push force are related as shown in FIG. 14. As apparent from FIG. 14 in comparison with FIG. 10 showing the first preferred embodiment wherein the duty ratio of the electric motor 28 is decided according to the push force, the duty ratio does not reach 30% in a range of small vehicle speeds as shown by a hatched area in FIG. 14, thereby attaining energy saving. That is, during walking the bicycle on a gentle ascending slope, the push force is small and the output torque of the electric motor is also small, so that undue power consumption can be suppressed. [0065]
FIG. 15 shows a first modification of the push force detecting means. Reference numeral 742 denotes push force detecting means provided at a right end portion of the bar handle 24, for example. A support member 92 for
pivotably supporting a brake lever 91 operable by a rider's right hand gripping a grip 90 is mounted on the bar handle 24 at its right end portion. The push force detecting means 742 includes a lever 93 supported to the support member 92 pivotably in opposite directions as moving toward and away from the bar handle 24 and located at the back of the bar handle 24, a spring 94 for biasing the lever 93 in such a direction as moving the lever 93 away from the bar handle 24, i.e., rearwardly of the bar handle 24, and a stroke sensor 77 mounted on the support member 92 and having a sensing member 77a adapted to be pushed by the lever 93 pivoted forward, i.e., toward the bar handle 24. The spring 94 is a torsion coil spring, for example, and it is provided between the lever 93 and the support member 92 in such a manner that a coiled portion of the spring 94 surrounds a support shaft 95 for pivotably supporting the lever 93 to the support member 92. [0066]
Also according to the push force detecting means 742, the push force can be continuously detected by pushing the lever 93 with the rider's right hand, for example, in walking the bicycle. [0067]
FIG. 16 shows a second modification of the push

force detecting means. Reference numeral 743 denotes push force detecting means provided on the bar handle 24, for example, like the push force detecting means 742 shown in FIG. 15. The push force detecting means 743 includes a push button 96, a stroke sensor 77 having a sensing member 77a, and a spring 97. [0068]
A cylindrical housing 98 extending in the
longitudinal direction of the vehicle body B and having an opening 98a is mounted on the bar handle 24. The stroke sensor 77 is contained in the housing 98 at a front portion thereof, and the sensing member 77a projects from the rear end of the stroke sensor 77. The push button 96 has a flange portion 96a at the front end, which is normally engaged with the inner surface of the front end of the housing 98 in the periphery of the opening 98a. The push button 96 is inserted through the opening 98a in such a manner that the flange portion 96a is in contact with the sensing member 77a. The spring 97 is interposed under compression between the stroke sensor 77 and the flange portion 96a of the push button 96 to normally rearward bias the push button 96. [0069]
Also according to the push force detecting means
743, the push force can be continuously detected by pushing
the push button 96 in walking the bicycle.
[0070]
FIG. 17 shows a third modification of the push force detecting means. Reference numeral 744 denotes push force detecting means provided on the bar handle 24, for example, like the push force detecting means 742 shown in FIG. 15. The push force detecting means 744 includes a push button 100, a movable contact 101 operating with the push button 100, a common fixed contact 102 always kept in electrical connection with the movable contact 101, first and second individual fixed contacts 103 and 104 electrically connectable through the movable contact 101 to the common fixed contact 102, and a spring 105. With this configuration, the push force can be detected stepwise, e.g., two-stepwise in walking the bicycle. [0071]
A cylindrical housing 106 extending in the longitudinal direction of the vehicle body B and having an opening 106a at the rear end. A circular guide plate 107 having a central guide hole 107a coaxial with the housing 106 is fixed in the housing 106. The push button 100 is inserted through the opening 106a of the housing 106, and is integrally formed with a flange portion lOOa normally
engaged with the inner surface of the housing 106 in the periphery of the opening 106a and a stem portion lOOb slidably engaged with the guide hole 107a of the guide plate 107. The spring 105 is interposed under compression between the guide plate 107 and the flange portion lOOa of the push button 100 to normally rearward bias the push button 100. [0072]
The movable contact 101 is fixed to the stem portion lOOb of the push button 100 and relatively long extends in the axial direction of the stem portion 10Ob. The movable contact 101 is integrally formed with first and second contact portions lOla and lOlb each semispherically projecting at two positions spaced in the longitudinal direction of the movable contact 101. [0073]
The common fixed contact 102 is fixedly located in the housing 106 so as to be always kept in contact with the first contact portion lOla located nearer to the guide plate 107 than the second contact portion lOlb. The first individual fixed contact 103 is fixedly located in the housing 106 in such a manner as to come into contact with the second contact portion lOlb of the movable contact 101 when the push button 100 is depressed against the biasing
force of the spring 105 from the condition where the push button 100 is in a normal or rearmost position (the condition shown in FIG. 17). On the other hand, the second individual fixed contact 104 is fixedly located in the housing 106 in such a manner as to come into contact with the second contact portion lOlb when the push button 100 is further depressed from the condition where the second contact portion lOlb is in contact with the first individual fixed contact 103. [0074]
According to the push force detecting means 744/ by pushing the push button 100 in walking the bicycle, the push force can be stepwise detected in two steps, that is, a first step of electrically connecting the first individual fixed contact 103 through the movable contact 101 to the common contact 102 and a second step of electrically connecting the second individual fixed contact 104 through the movable contact 101 to the common contact 102. [0075]
FIGS. 18 to 25 show a third preferred embodiment of the present invention, in which FIG. 18 is a side view of a motor-assisted bicycle; FIG. 19 is a vertical sectional view of slope angle detecting means; FIG. 20 is a cross
section taken along the line 20-20 in FIG. 19; FIG. 21 is a block diagram showing the configuration of a controller; FIG. 22 is a flowchart showing processing in on-walking motor drive control means shown in FIG. 21; FIG. 23 is a graph showing a duty ratio corresponding to a slope angle; FIG. 24 is a graph showing a duty ratio corresponding to. a load; and FIG. 25 is a graph showing a preset map of a duty ratio corresponding to a slope angle and a load. [0076]
Referring to FIG. 18, a push-button walking switch 110 to be operated by a rider in walking the bicycle is mounted on a left end portion of the bar handle 24, for example. Load detecting means lll1 for detecting the load of a luggage carried in the front basket 44 is mounted on the bottom of the front basket 44, Load detecting means 1112 for detecting the load of a luggage carried on the rear carrier 34 is mounted on the rear carrier 34. Slope angle detecting means 112 for detecting the slope angle of a road surface is mounted on a front portion of the vehicle body B of the bicycle, e.g., on the main frame portion 21b of the front frame 21. [0077]
Referring to FIGS. 19 and 20, the slope angle detecting means 112 includes a sectionally circular housing
114 fixedly mounted oh the front frame 21, a support shaft
115 fixed to the housing 114 and having an axis extending
in the lateral direction of the vehicle body B, a movable
member 117 pivotably supported to the support shaft 115 and
having an integral weight 116, a support plate 118 fixed in
the housing 114 in opposed relationship with the movable,
member 117, a conductor strip 119 provided on one surface
of the support plate 118 opposed to the movable member 117
and having an arcuate shape about the axis of the support
shaft 115, a resistor strip 120 provided on the one surface
of the support plate 118 opposed to the movable member 117
and having an arcuate shape about the axis of the support
shaft 115 with a radius larger than that of the conductor
strip 119, and a brush 121 fixed to the movable member 117
so as to slidably contact the conductor strip 119 and the
resistor strip 120. The opposite ends of the resistor
strip 120 are connected to the opposite ends of the battery
46, and a voltage detector 122 is connected between one end
of the conductor strip 119 and a ground.
[0078]
According to the slope angle detecting means 112, even when the vehicle body B is inclined on a slope or the like, the movable member 117 is rotated about the support shaft 115 by the action of the weight 116 so that the
weight 116 integral with the movable member 117 keeps its fixed position just under the support shaft 115. On the other hand, the angular position of the support plate 118, i.e., the resistor strip 120 about the axis of the support shaft 115 relative to the movable member 117 changes according to the slope angle. Accordingly, the contact position of the brush 121 on the resistor strip 120 changes to result in a change in voltage detected by the voltage detector 122. Thus, the slope angle of a road surface in walking the bicycle can be detected by the slope angle detecting means 112. [0079]
Referring to FIG. 21, detected values from crankshaft rotation sensor 62, torque detecting means 56, walking switch 110, load detecting means lll1 and 1112, and slope angle detecting means 112 are input into a controller 42 including pedal operation decision means 80, on-riding motor drive control means 81, relay driving means 82, on-walking motor drive control means 83, motor drive limiting means 84, first switching means 85, second switching means 86, relay 87 having a relay switch 87a, and FET 88. [0080]
The relay driving means 82 functions to drive the relay 87 when the walking switch 110 is turned on. When
the walking switch lib is not depressed during riding the bicycle on the seat 25 or at rest, the first and second switching means 85 and 86 are kept in the respective first conditions (shown by solid lines in FIG. 21), whereas when the walking switch 110 is depressed as in walking the bicycle, the first and second switching means 85 and 86 are switched into the respective second conditions (shown by broken lines in FIG. 21). [0081]
The on-walking motor drive control means 83 functions to output a motor drive signal for controlling the operation of the electric motor 28 to obtain an assist power in walking the bicycle, according to the detected values from the crankshaft rotation sensor 62, the load detecting means lll1 and 11l2, and the slope angle detecting means 112. [0082]
The pedal operation decision means 80 and the on-riding motor drive control means 81 perform the same processing as that described with reference to FIG. 5 in the first preferred embodiment. If the decision in step S3 shown in FIG. 5 is that the bicycle is being walked, that is, if the walking switch 110 has been depressed, the processing shown in FIG. 22 rather than the processing
shown in FIG. 6 of the first preferred embodiment is executed by the on-walking motor drive control means 83. [0083]
Referring to FIG. 22, in step S22 the detected value from the slope angle detecting means 112 is read. In step S23, the detected values from the load detecting means llli and Ilia are read and added up. In step S24, a motor drive signal is generated so as to decide the duty ratio of the electric motor 28 according to the slope angle and the load. [0084]
The duty ratio of the electric motor 28
corresponding to the detected value from the slope angle detecting means 112 is preset as shown in FIG. 23. For example, the duty ratio corresponding to a slope angle of 12 degrees is preset to 30%. Further, the duty ratio of the electric motor 28 corresponding to the sum of the detected values from the load detecting means lll1 and 1112 is preset as shown in FIG. 24. For example, the duty ratio corresponding to a load of 15 kgf is preset to 30%. By combining FIGS. 23 and 24, the duty ratio corresponding to both the slope and the load is preset on a three-dimensional map as shown in FIG. 25. [0085]
After generation of the motor drive signal in step S24, a coefficient a corresponding to a battery deviation voltage AE is generated in step S25, and the duty ratio decided in step S24 is then corrected by the coefficient a in step S26. [0086]
In step S27, it is determined whether or not the current vehicle speed is greater than or equal to a target vehicle speed VO. If the current vehicle speed is less than the target vehicle speed VO, the motor drive signal corrected in step S26 is output from the on-walking motor drive control means 83 in step S28. If the current vehicle speed is greater than or equal to the target vehicle speed VO, the output of the motor drive signal from the on-walking motor drive control means 83 is stopped in step S29. [0087]
According to the third preferred embodiment, the assist power by the electric motor 28 is controlled according to the slope angle of a road surface and the load on the vehicle body B when the walking switch 110 is depressed in walking the bicycle. Accordingly, even when a weak rider walks the bicycle in the case of ascending a slope with a large slope angle or in the case of carrying a
heavy load on the bicycle to result in an increased weight of the vehicle body B, the assist power by the electric motor 28 can be quickly obtained. [0088]
While the load detecting means lll1 and 1112 are provided on the front basket 44 and the rear carrier 34, respectively, in the third preferred embodiment, any one of the load detecting means lll1 and 1112 may be provided. Further, the assist power by the electric motor 28 may be controlled according to any one of the slope angle of a road surface and the load carried on the bicycle. [0089]
Having thus described specific preferred embodiments of the present invention, it should be noted that the present invention is not limited to the above preferred embodiments, but various design changes may be made without departing from the scope of the present invention defined in the appended claims. [0090]
[Effect of the Invention]
According to the invention as defined in claim 1, the assist power by the electric power in walking the bicycle is controlled according to the push force applied to the vehicle body. Accordingly, even when a weak rider
walks the bicycle in the case of ascending a slope with a large slope angle or in the case of carrying a heavy load to cause an increased weight of the vehicle body, the assist power corresponding to the push force applied can be quickly obtained. Further, when passing over a bump in walking the bicycle, a large assist power responsive to an increase in the push force can be obtained. Further, when pushing the vehicle body in walking the bicycle at a slowly running speed, the assist power corresponding to the push force applied can be obtained. [0091]
According to the invention as defined in claim 2, the assist power can be changed well responsive to a transition state where the push force changes. [0092]
According to the invention as defined in claim 3, an assist torque by the electric motor and a vehicle speed are determined according to a running resistance, thereby allowing simultaneous control of the assist torque and the vehicle speed. [0093]
According to the invention as defined in claim 4, undue power consumption can be suppressed to thereby attain energy saving.

[0094]
According to the invention as defined in claim 5, the assist power by the electric motor is controlled according to at least one of the slope angle of the road surface and the load carried on the vehicle body in the operated condition of the walking switch in walking the . bicycle. Accordingly, even when a weak rider walks the bicycle in the case of ascending a slope with a large slope
t
angle or in the case of carrying a heavy load to cause an increased weight of the vehicle body, the assist power required can be quickly obtained. Further, the assist power can be obtained regardless of the manner of pushing the vehicle body. [0095]
According to the invention as defined in claim 6, an undue increase in the vehicle speed in walking the bicycle can be prevented.
[Explanation of Reference Numerals]
28: electric motor
35: crank pedal
142: controller
741, 74a, 74a, 744: push force detecting means
110: walking switch
lll1, 1112: load detecting means
112: slope angle detecting means
B: vehicle body

[CLAIMS]
[claim 1] In a motor-assisted bicycle having a vehicle body (B) and an electric motor (28) mounted on said vehicle body (B) for assisting a depression force applied to crank pedals (35); the improvement comprising push force detecting means (741, 742, 743, 744) for continuously or stepwise detecting a push force applied to said vehicle body (B) by a rider in walking said bicycle, and a controller (42) for controlling an assist power by said electric motor (28) according to a detected value from said push force detecting means (741, 742/ 743/ 744).
[claim 2] A motor-assisted bicycle according to claim 1, wherein said controller (42) corrects to increase or decrease the assist power by said electric motor (28) corresponding to the detected value from said push force detecting means (74i, 742/ 743/ 744), according to the degree of change in the detected value from said push force detecting means (741, 742, 743, 744).
[claim 3] A motor-assisted bicycle according to claim 1 or 2, wherein said controller (42) controls a duty ratio of said electric motor (28) according to the detected
value from said push force detecting means (741, 742, 743/
744).
[claim 4] A motor-assisted bicycle according to claim 1 or 2, wherein said controller (42) controls an output torque of said electric motor (28) according to the
detected value from said push force detecting means (741, 742, 743/ 744).
[claim 5] In a motor-assisted bicycle having a vehicle body (B) and an electric motor (28) mounted on said vehicle body (B) for assisting a depression force applied to crank pedals (35); the improvement comprising a walking switch (110) to be operated by a rider in walking said bicycle, at least one of slope angle detecting means (112) for detecting a slope angle of a road surface and load detecting means (lll1,, 1112) for detecting a load carried on said vehicle body (B), and a controller (42) for controlling an assist power by said electric motor (28) according to a detected value from at least one of said slope angle detecting means (112) and said load detecting means (lll1, 1112) in an operated condition of said walking switch (110).
[claim 6] A motor-assisted bicycle according to claim 1 or 5, wherein said controller (42) stops power assisting by said electric motor (28) when a vehicle speed 56 of said bicycle becomes greater than or equal to a set value.
7. A motor-assisted bicycle substantially as herein described with reference to the accompanying drawings.

Documents:

2833-del-1998-abstract.pdf

2833-del-1998-claims.pdf

2833-del-1998-correspondence-others.pdf

2833-del-1998-correspondence-po.pdf

2833-del-1998-description (complete).pdf

2833-del-1998-drawings.pdf

2833-del-1998-form-1.pdf

2833-del-1998-form-19.pdf

2833-del-1998-form-2.pdf

2833-del-1998-form-3.pdf

2833-del-1998-form-4.pdf

2833-del-1998-gpa.pdf

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Patent Number

213463

Indian Patent Application Number

2833/DEL/1998

PG Journal Number

03/2008

Publication Date

18-Jan-2008

Grant Date

02-Jan-2008

Date of Filing

21-Sep-1998

Name of Patentee

HONDA GIKEN KOGYO KABUSHIKI KAISHA

Applicant Address

1-1, MINAMIAOYAMA 2-CHOME, MINATO-KU, TOKYO, JAPAN.

Inventors:

#	Inventor's Name	Inventor's Address
1	SATOSHI HONDA	C/O KABUSHIKI KAISHA HONDA GIJUTSU KENKYUSHO 4-1, CHUO 1-CHOME, WAKO-SHI, SAITAMA, JAPAN.
2	TOSHIYUKI CHO	C/O KABUSHIKI KAISHA HONDA GIJUTSU KENKYUSHO 4-1, CHUO 1-CHOME, WAKO-SHI, SAITAMA, JAPAN.

PCT International Classification Number

B62M 23/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	Hei-9-268415	1997-10-01	Japan