Title of Invention	ENGINE STARTING APPARATUS
Abstract	To ensure good engine startability with a small starter motor to satisfy both of the startability of the engine and the drivability.An engine starting apparatus which rotates a crankshaft reversely to a predetermined position after an engine stops to prepare for next strating of the engine, is configured such that maximum generated torque of a starter motor is equal to or lower than approximately 60% of maximum craking torque necessary for a piston to overcome a compression stroke upon strating of the engine but is equal to or higher than craking torque necessary for the piston to proceed in any other stroke than the compression stroke.

Title of Invention

ENGINE STARTING APPARATUS

Abstract

To ensure good engine startability with a small starter motor to satisfy both of the startability of the engine and the drivability.An engine starting apparatus which rotates a crankshaft reversely to a predetermined position after an engine stops to prepare for next strating of the engine, is configured such that maximum generated torque of a starter motor is equal to or lower than approximately 60% of maximum craking torque necessary for a piston to overcome a compression stroke upon strating of the engine but is equal to or higher than craking torque necessary for the piston to proceed in any other stroke than the compression stroke.

Full Text	Original THE PATENTS ACT 1970 [39 OF 1970] COMPLETE SPECIFICATION [See Section 10] "ENGINE STARTING APPARATUS" HONDA GIKEN KOGYO KABUSHIKI KAISHA, a corporation of Japan, having a place of business at 1-1, Minamiaoyarna 2-chome, Minato-ku, Tokyo, Japan, GRANTED 3-4-2007 The following specification particularly describes the nature of the invention and the manner in which it is to be performed:- The present invention relates to engine starting apparatus [DETAILED DESCRIPTION OF THE INVENTION] [0001] [Technical Field to Which the Invention Pertains] This invention relates to an engine starting apparatus for cranking an engine using a starter motor to start the, engine, and more particularly to an engine starting apparatus which uses both of inertial force of a rotating system including a crankshaft and driving torque of a starter motor to allow good starting of an engine even if the torque of the starter motor is low. [0002] [Prior Art] Cranking torque upon starting of an engine exhibits a maximum value (overcoming torque) immediately before a piston reaches the compression top dead center (TDC), and in order to overcome the TDC, conventionally a comparatively large starter motor wherein maximum generated torque (lock torque) which can be generated is equal to or higher than the maximum cranking torque mentioned above is adopted. [0003] [Problem to Be Solved by the Invention] The startability of an engine rises as the driving torque of a starter motor increases. However, in a structure wherein the starter motor is directly coupled to the crankshaft of the engine, since a rotational portion of the starter motor acts as an inertial mass, if a starter motor of a large size whose driving torque is high is adopted, then it cannot be avoided that the drivability is deteriorated particularly upon starting and acceleration. [0004] For example, in a four-cycle engine of 100 cc or less adopted by a general two-wheeled vehicle of a small SIze, the maximum cranking torque reaches 1.3 kgfm. However, if a starter motor whose maximum generated torque is 1.3 kgfm is directly coupled to the crankshaft, then the inertial mass thereof becomes 40 kgcm2 and is much higher than an optimum inertial mass of 28 to 33 kgcm2. In other words, the startability of an engine and the drivability have a relationship of antinomy to each other, and it is difficult to satisfy both of them. [0005] It is an object of the present invention to solve the object of the prior art described above and provide an engine starting apparatus wherein a good engine startability is ensured with a small starter motor to satisfy both of the startability of an engine and the drivability. [0006] [Means for Solving the Problem] In order to attain the object described above, according to the present invention, an engine starting apparatus which rotates a crankshaft reversely to a predetermined position after an engine stops to prepare for next starting of the engine is characterized by including: a starter motor for rotating the crankshaft forwardly and reversely; and reverse rotation controlling means.for causing the starter motor to rotate reversely after the engine stops, wherein maximum generated torque of the starter motor is equal to or lower than approximately 60% of maximum cranking torque necessary for a piston to overcome a compression stroke upon starting of the engine but is equal to or higher than cranking torque necessary for the piston to proceed in any other stroke than the compression stroke. [0007] With the characteristic described above, since the piston is accelerated sufficiently to obtain comparatively high inertial force before a compression stroke is reached, only if the resultant force of the inertial force and driving torque of the starter motor reaches the maximum cranking torque, even if the maximum generated torque of the starter motor itself is lower than the maximum cranking torque, the piston can overcome the compression stroke. [BRIEF DESCRIPTION OF THE DRAWINGS] [FIG. 1] FIG. 1 is a side elevational view of an entire motorcycle of the scooter type to which the present invention is applied. [FIG. 2] FIG. 2 is a sectional view taken along a crankshaft of a swing unit of FIG. 1. [FIG. 3] FIG. 3 is a partial enlarged view of FIG. 2. [FIG. 4] FIG. 4 is a block diagram of a control system for a starter-generator. [FIG. 5] FIG. 5 is a block diagram showing a configuration of a principal portion of an ECU of FIG. 4. [FIG. 6] FIG. 6 is a flow chart of swing back control. [FIGS. 7(a), 7(b) and 7(c)] FIGS. 7(a), 7(b) and 7(c) are explanatory views of operation of the swing back control. [FIG. 8] FIG. 8 is a view showing an example of transition of cranking torque. [FIG. 9] FIG. 9 is a flow chart illustrating operation of a decompression driving section. [FIG. 10] FIG. 10 is a flow chart of an ACG generation control process. [FIG. 11] FIG. 11 is a view illustrating timings of phase currents of stator coils and an output of a rotor angle sensor upon the ACG energization control. [FIG. 12] FIG. 12 is a table of an energization duty wherein an engine speed is used as a parameter. [FIG. 13] FIG. 13 is a view illustrating time variations of an engine speed Ne and a cranking torque Tcnk. [FIG. 14] FIG. 14 is a view illustrating time variations of driving torque Tdrv of a starter motor, inertial torque Tine of a rotating system including a crankshaft, and resultant torque Tadd of the driving torque Tdrv and the inertial torque Tine. motorcycle to which an engine starting apparatus of the present invention is applied. The vehicle further has an engine automatic stopping-starting function of automatically stopping the engine if the vehicle is stopped and then automatically driving the starter motor to re-start the engine if such a starting operation that a throttle grip is opened or a starter switch is operated into an on-state is performed thereafter. [0009] A vehicle body front portion and a vehicle body rear portion are connected to each other through a floor portion 4, and a body frame which forms a skeleton of the vehicle body is generally composed of a down tube 6 and a main pipe 7. A fuel tank and an accommodation box (both not shown) are supported by the main pipe 7, and a seat 8 is disposed above the main pipe 7. [0010] A handle bar 11 is supported for pivotal motion by a steering head 5 in the upper side of the vehicle body front portion. A front fork 12 extends in the lower side of the vehicle body front portion, and has a front wheel FW supported for rotation at lower ends of the front fork 12. An upper portion of the handle bar 11 is covered with a handle bar cover 13 which serves also as an instrument panel. A bracket 15 is provided in a projecting manner at a lower end of a rising portion of the main pipe 7, and a hanger bracket 18 of a swing unit 2 is connected to and supported for rocking motion on the bracket 15 through a link member 16. [0011] A single cylinder 50 cc four-cycle engine E is carried at a front portion of the swing unit 2. A belt type continuously variable transmission 10 is formed such that it extends rearwardly from the engine E, and a rear wheel RW is supported for rotation on a speed reducing mechanism 9 which is provided at a rear portion of the belt type continuously variable transmission 10 through a centrifugal clutch. A rear cushion 3 is interposed between an upper end of the speed reducing mechanism 9 and a bent portion of an upper portion of the main pipe 7. A carburetor 17 connected to an intake pipe 19 extending from the engine E and an air cleaner 14 connected to the carburetor 17 are disposed at a front portion of the swing unit 2. [0012] FIG. 2 is a sectional view of the swing unit 2 taken along a crankshaft 201, and FIG. 3 is a partial enlarged view of the same. Like reference characters to those appearing as above denote like or equivalent elements. [0013] The swing unit 2 is covered with a crankcase 202 which is formed from left and right crankcases 202L and 202R joined together, and the crankshaft 201 is supported for rotation by bearings 208 and 209 secured to the crankcase 202R. A connecting rod (not shown) is connected to the crankshaft 201 through a crank pin 213. [0014] The left crankcase 202L serves also as a belt type continuously variable transmission chamber case, and a belt driving pulley 210 is provided for rotation on the crankshaft 201 which extends to the left crankcase 202L. The belt driving pulley 210 is composed of a fixed side pulley half 210L and a movable side pulley half 210R. The fixed side pulley half 210L is fixed to a left end portion of the crankshaft 201 through a boss 211. The movable side pulley half 210R is spline fitted on the crankshaft 201 on the right side of the fixed side pulley half 210L such that the movable side pulley half 210R can be moved toward and away from the fixed side pulley half 210L. A V belt 212 is wound around the two pulley halves 210L and 210R. [0015] On the right side of the movable side pulley half 210R, a cam plate 215 is fixed to the crankshaft 201, and a slide piece 215a provided at an outer circumferential end of the cam plate 215 is held in engagement for sliding motion on a cam plate sliding boss portion 210Ra formed in an axial direction at an outer circumferential end of the movable side pulley half 210R. The cam plate 215 of the movable side pulley half 210R has a tapered face near an outer circumference thereof. The tapered face is inclined to the movable side pulley half 210R side. A dry weight ball 216 is accommodated in a free space between the tapered face and the movable side pulley half 210R. [0016] If the speed of rotation of the crankshaft 201 increases, then the dry weight ball 216 which is positioned between and rotates together with the movable side pulley half 210R and the cam plate 215 is moved in a centrifugal direction by centrifugal force, and the movable side pulley half 210R is pushed by the dry weight ball 216 to move leftwardly so that the movable side pulley half 210R approaches the fixed side pulley half 210L. As a result, the V belt 212 held between the two pulley halves 210L and 210R moves in the centrifugal direction and the winding diameter thereof increases. [0017] A driven pulley (not shown) corresponding to the belt driving pulley 210 described above is provided at a rear portion of the vehicle, and the V belt 212 is wound around the driven pulley. Through this belt transmission mechanism, power of the engine E is automatically adjusted and transmitted to the centrifugal clutch so that the power drives the rear wheel RW through the speed reducing mechanism 9 and so forth. [0018] A starter-generator (ACG starter) 1 which includes a starter motor and an AC generator in combination is disposed in the right crankcase 202R. In the ACG starter 1, an outer rotor 60 is secured to the tapered portion of the end of the crankshaft 201 by a screw 253. [0019] A stator 50 disposed on an inner circumference side of the outer rotor 60 is secured to the crankcase 202 by a bolt 279. A fan 280 secured by a bolt 246 is provided on the outer rotor 60. A radiator 282 is provided next to the fan 280, and the radiator 282 is covered with a fan cover 281. [0020] As shown in an enlarged scale in FIG. 3, a sensor case 28 is fitted in an inner circumference of the stator 50. Rotor angle sensors (magnetic pole sensors) 29 and a pulser sensor (ignition pulser) 30 are provided at equal distances along an outer circumference of a boss 60a of the outer rotor 60. The rotor angle sensors 29 are provided to perform energization control of stator coils of the ACG starter 1 and provided one by one corresponding to the U phase, V phase and W phase of the ACG starter 1. The ignition pulser 30 is provided for ignition control of the engine, and only one ignition pulser 30 is provided. The rotor angle sensors 29 and the ignition pulser 30 can each be formed from a Hall IC or a magnetic reluctance (MR) element. [0021] Leads of the rotor angle sensors 29 and the ignition pulser 30 are connected to a board 31, and further, a wire harness 32 is coupled to the board 31. A magnet ring 33 magnetized in two stages is fitted on an outer periphery of the boss 60a of the outer rotor 60 so that the magnet ring 33 may have a magnetic action on each of the rotor angle sensors 29 and the ignition pulser 30. [0022] N poles and S poles disposed alternately at distances of 30° width in a circumferential direction in a corresponding relationship to the magnetic poles of the stator 50 are formed on one of the magnetization zones of the magnet ring 33 which corresponds to the rotor angle sensors 29. On the other magnetization zone of the magnet ring 33 which corresponds to the ignition pulser 30, a magnetized portion is formed over a range from 15° to 40° at one location in a circumferential direction. [0023] The ACG starter 1 functions as a starter motor (synchronous motor) when the engine starts and is driven with electric current supplied from a battery to rotate the crankshaft 201 thereby to start the engine. After the engine is started, the ACG starter 1 functions as a synchronous generator and charges the battery with electric current generated thereby and besides supplies electric current to electric parts. [0024] Referring back to FIG. 2, a sprocket 231 is secured to the crankshaft 201 between the ACG starter 1 and a bearing 209, and a chain for driving a camshaft (not shown) from the crankshaft 2 01 is wound around the sprocket 231. It is to be noted that the sprocket 231 is formed integrally with a gear 232 for transmitting power to a pump for circulating lubricating oil. [0025] FIG. 4 is a block diagram of an electric system including the ACG starter 1. An ECU 3" includes a three-phase full-wave rectification bridge circuit 300 for full wave rectifying three-phase alternating current generated by the power generation function of the ACG starter 1, and a regulator 100 for limiting an output of the full-wave rectification bridge circuit 300 to a predetermined regulated voltage (regulator operation voltage: for example, 14.5 V). [0026] Further, the ECU 3" of the present embodiment includes a swing back control section 700 for rotating the crankshaft reversely to a predetermined position immediately after the engine stops to improve the startability in next starting of the engine, a starting control section 500 for lowering the cranking torque upon starting of the engine, and a power generation control section 400 for increasing the generated energy amount when the engine speed is within a predetermined low speed region. [0027] An ignition coil 21 is connected to the ECU 3", and an ignition plug 22 is connected to the secondary side of the ignition coil 21. Further, a throttle sensor 23, a fuel sensor 24, a seat switch 25, an idling switch 26, a cooling water temperature sensor 27, the rotor angle sensors 29 and the ignition pulser 30 are connected to the ECU 3", and detection signals are inputted from the elements to the ECU 3". [0028] Furthermore, a starter relay 34, a starter switch 35, stop switches 36 and 37, a standby indicator 38, a fuel indicator 39, a speed sensor 40, an auto by-starter 41 and a headlamp 42 are connected to the ECU 3". A dimmer switch 43 is provided for the headlamp 42. [0029] To the elements mentioned above, electric current is supplied from a battery 2" through a main fuse 44 and a main switch 45. It is to be noted that the battery 2" is connected directly to the ECU 3" by the starter relay 34 and has a circuit which is connected to the ECU 3" only through the main fuse 44 without through the main switch 45. [0030] Now, a configuration and operation of the swing back control section 700, starting control section 500 and power generation control section 400 of the ECU 3" described above are described with reference to a functional block diagram of FIG. 5. [0031] In the swing back control section 700, a stage discrimination section 73 divides one rotation of the crankshaft 201 into 36 stages of stages #0 to #35 based on output signals of the rotor angle sensors 29 and discriminates the present stage using the detection timing of a pulse signal generated by the ignition pulser 30 as a reference stage (the stage #0). [0032] A stage passing time detection section 74 detects, based on a period of time after the stage discrimination section 73 discriminates a new stage until the stage discrimination section 73 discriminates a next stage, passing time Atn of the present stage. A reverse rotation control section 75 generates a reverse driving instruction based on a result of the discrimination by the stage discrimination section 73 and the passing time Atn detected by the stage passing time detection section 74. [0033] A duty ratio setting section 72 dynamically controls the duty ratio of a gate voltage to be supplied to power FETs of the full-wave rectification bridge circuit 300 based on a result of the discrimination by the stage discrimination section 73. A driver 80 supplies a driving pulse of the duty ratio set as described above to the power FETs of the full-wave rectification bridge circuit 300. [0034] Now, operation of the swing back control section 700 described above is described with reference to a flow chart of FIG. 6 and an explanatory view of operation of FIG. 7. [0035] FIG. 7(a) illustrates a relationship between the cranking torque (reverse rotation load) required to rotate the crankshaft 201 reversely and the crank angle, and the cranking torque rises drastically immediately before the compression top dead center is reached (upon reverse rotation). FIG. 7(b) illustrates a relationship between the crank angle and the stage, and FIG. 7(c) illustrates a variation of the angular speed of the crankshaft upon reverse rotation. [0036] If stopping of the engine is detected at step S61, then the present stage discriminated already by the stage discrimination section 73 is referred to at steps S62 and S63. Here, if the present stage is one of the stages #0 to #11, then the processing advances to step S64, but if the present stage is one of the stages #12 to #32, then the processing advances to step S65. However, in any other case (that is, if the present stage is one of the stages #33 to #35), then the processing advances to step S66. At step S64 or S65, the duty ratio setting section 72 sets the duty ratio of a driving pulse to 70%, but at step S65, the duty ratio setting section 72 sets the duty ratio to 80%. [0037] Such dynamic control of the duty ratio as just described is performed in order to sufficiently lower, upon reverse rotation, the angular speed of the crankshaft 201 prior to an angle corresponding to the compression top dead center at which the cranking torque increases (upon reverse rotation) but allow quick reverse rotational driving at any other angle than the angle as hereinafter described in detail. [0038] At step S67, the driver 80 controls the power FETs of the full-wave rectification bridge circuit 300 with the duty ratio set as described above to start energization for reverse rotation. At step S68, the passing time Atn of the stages #n passed is measured by the stage passing time detection section 74. [0039] At step S69, the reverse rotation control section 75 discriminates whether or not the crankshaft 201 has passed a position in the proximity of the stage #0, that is, the top dead center. If the crankshaft 201 has not passed the stage #0, then a ratio [Atn/Atn-1] between the passing time Atn of the stage #n which the crankshaft 201 has passed last and the passing time Atn-1 of the stage #(n-l) which the crankshaft 201 has passed second last is compared with a reference value Rref (in the present embodiment, 4/3) at step S71. If the passing time ratio [Atn/Atn-1] is not higher than the reference value Rref, then the processing returns to step S62 described above to continue the reverse rotation driving, and the processing described above is repeated in parallel to the reverse rotation driving. [0040] Here, if the stopping position of the engine, that is, the reverse rotation starting position, is on the side nearer to the compression top dead center for the next time than a middle position between the compression top dead centers for the preceding and next times, or in other words, is in the process to the compression top dead center after the exhaust top dead center is passed (upon forward rotation) as indicated by a curve A in FIG. 7(c), then although the ACG starter 1 is being driven to rotate reversely with the duty ratio of 70%, the crankshaft can pass the stage #0 (exhaust top dead center). Accordingly, after this is detected at step S69, the processing advances to step S70, at which it is discriminated whether or not the crankshaft 201 reaches the stage #32. If it is discriminated that the crankshaft 201 reaches the stage #32, then since the energization for reverse rotation described above is stopped at step S72, the crankshaft thereafter stops after the crankshaft is further rotated reversely by the inertial force. [0041] On the other hand, if the reverse rotation starting position is on the side nearer to the compression top dead center for the preceding time than the middle position between the compression top dead centers for the preceding and next times, or in other words, is in the process to the exhaust top dead center after the compression top dead center is passed (upon forward rotation) as indicated by a curve B in FIG. 7(c), then since the ACG starter 1 is being driven to rotate reversely with the duty ratio of 7 0%, when the reverse rotation load increases before the stage #0 (upon reverse rotation) is reached, the angular speed of the crankshaft 201 drops drastically as shown in FIG. 7(a). Then, if it is discriminated at step S71 that the passing time ratio [Atn/Atn-1] is equal to or higher than 4/3 the reference value, then the energization for reverse rotation is stopped at step S72, and the reverse rotation of the crankshaft stops nearly simultaneously with stopping of the energization. [0042] In this manner, in the swing back control of the present embodiment, upon driving for reverse rotation after the engine stops, it is supervised whether or not the crankshaft has passed an angle corresponding to the top dead center and whether or not the angular speed of the crankshaft has dropped, and if the crankshaft passes the top dead center upon reverse rotation, then the energization for reverse rotation is ended immediately after that. Also when the angular speed of the crankshaft drops as a result of increase of the reverse rotation load, the energization for reverse rotation is ended. Accordingly, irrespective of the reverse rotation starting position, the crankshaft can be returned to a position prior to the compression dead center for the preceding time (upon reverse rotation) at which the compression reactive force is low. [0043] Further, in the swing back control of the present embodiment, since the angular speed of the crankshaft 201 is detected based on outputs of the rotor angle sensors 29 for detecting the rotor angle (that is, a stage) of the ACG starter, a sensor for detecting the angle of the crankshaft 201 need not be provided separately. [0044] Referring back to FIG. 5, the starting control section 500 compulsorily lifts the exhaust valve only immediately after starting of the engine to lower the internal pressure of the cylinder in a compression stroke in order to lower the cranking torque upon the starting of the engine. [0045] In the starting control section 500, an engine speed discrimination section 52 discriminates an engine speed based on a detection signal of the ignition pulser 30, a frequency signal of a generated voltage and so forth. A decompression driving section 51 detects depression of the starter switch 35 to drive the ACG starter 1 and excite a decompression solenoid 63, which compulsorily lifts the exhaust valve, at a predetermined timing. [0046] Since the cranking torque upon starting of the engine rises in a compression stoke to the TDC as shown in FIG. 8, it is demanded for the AGC starter to have maximum generated torque equal to or higher than maximum cranking torque Tmax in a compression stroke. Therefore, in the present embodiment, upon starting of the engine, the exhaust valve is opened to suppress a rise of the internal pressure of the cylinder in a compression stroke to suppress the maximum cranking torque Tmax low. [0047] FIG. 9 is a flow chart illustrating operation of the decompression driving section 51 described above. If depression of the starter switch 35 is detected at step S51, then the engine speed Ne is compared with a predetermined reference speed Nref at step S52. Here, the engine still remains in a stopping state and the engine speed Ne is lower than the reference speed Nref, and therefore, the processing advances to step S53. [0048] At step S53, fuel injection is inhibited, and at step S54, the decompression solenoid 63 is excited so that the exhaust valve is lifted compulsorily. At step S55, the ACG starter 1 is driven. [0049] Thereafter, the engine speed Ne rises until it exceeds the reference speed Nref, and when this is detected at step S52, fuel injection is started at step S56. At step S57, the excitation of the decompression solenoid 63 is stopped. [0050] It is to be noted that, if cancellation of the depression of the starter switch 35 is detected at step S51, then the decompression solenoid 63 is turned off at step S58, and the ACG starter 1 is turned off at step S59. [0051] In this manner, in the present embodiment, since, upon starting of the engine, the exhaust valve is opened compulsorily to suppress a rise of the internal pressure of the cylinder in a compression stroke to suppress the maximum cranking torque Tmax low, good startability can be ensured even if a starter of a small size whose maximum generated torque is low is adopted. [0052] Referring back to FIG. 5, the power generation control section 400 has, in addition to a function of controlling the generated power amount (voltage) normally, a function of delay angle energizing the stator coils of the different phases of the ACG starter 1 from the battery 2" to increase the generated power amount (hereinafter referred to as "ACG energization control"). [0053] Here, the delay angle energization signifies to energize a stator coil after a delay corresponding to a predetermined electrical angle from a detection signal upon a change between magnetic poles of magnetized zones of the magnet ring 33 detected by the rotor angle sensors 29. However, in order to prevent instability of rotation of the engine which arises from a sudden variation of the load to the engine which occurs when the regulator 100 operates in a low rotation region, the control is performed so that the output voltage (battery voltage) of the full-wave rectification bridge circuit 300 may remain within a predetermined voltage range equal to or lower than the regulated voltage. [0054] In the power generation control section 400, an engine speed discrimination section 48 detects an engine speed, for example, based on a detection signal of the ignition pulser 30 and supplies a delay angle instruction to the driver 80 if the engine speed is within a predetermined power generation control region. The driver 80 receiving the delay angle instruction reads out an energization delay angle amount set in advance from a delay angle amount setting section 49 and performs delay angle energization. An energization duty ratio is supplied from a duty ratio setting section 47 to the driver 80. [0055] The driver 80 detects a magnetic pole detection signal from the rotor angle sensors 29, that is, a signal which rises to an on state every time the rotor angle sensors 29 detect one of the magnetized zones of the magnet ring 33 formed in a corresponding relationship to the magnetic poles of the outer rotor 60. Then, the driver 80 outputs a PWM control signal to the FETs of the full-wave rectification bridge circuit 300 after a delay by an angle corresponding to an energization delay angle amount from a rising edge of the signal. [0056] A battery voltage discrimination section 46 compares a battery voltage Vb with a control voltage maximum value VMax and a control voltage minimum value VMin, which define a voltage control range, and adjusts the energization duty set by the duty ratio setting section 47 based on a result of the comparison so that the battery voltage Vb may remain within the control range described above. In particular, if the battery voltage Vb reaches the control voltage maximum value VMax, then the battery voltage discrimination section 46 decreases the energization duty by a predetermined small value (for example, 1%), but if the battery voltage Vb drops to the control voltage minimum value VMin, then the battery voltage discrimination section 46 increases the energization duty by the small value. [0057] FIG. 10 is a flow chart illustrating operation of the power generation control section 400 described above, which is activated after the engine starting control by the starting control section 500 is ended. [0058] At step S41, it is discriminated whether or not the engine speed is within the power generation control region. The power generation control region is set, for example, to a region not smaller than 1,000 rpm but not more than 3,500 rpm. If the engine speed is within the power generation control region, then the processing advances to step S41, at which it is discriminated whether or not a flag FACG indicating that the engine speed is within the power generation control region is in a set state (= 1) . If the flag FACG is not set, then the processing advances to step S43, at which the flag FACG is set. At step S44, a predetermined value ACGAGL is placed into an energization delay angle amount acgagl. While the predetermined value ACGAGL can be set suitably in advance, the predetermined value ACGAGL in the present embodiment is, for example, an electrical angle of 60*. [0059] At next step S45, an initial value ACDUTY is placed into an energization duty acduty. While also the initial value ACDUTY can be set suitably in advance, the initial value ACDUTY in the present embodiment is, for example, 40%. After the steps S43 to S45 are completed, the processing advances to step S47. If the discrimination at step S42 is affirmative, then the processing skips steps S43 to S45 and advances to step S47. On the other hand, if the engine speed is not within the generation control region, then the flag FACG is reset (= 0) at step S46, whereafter the processing advances to step S47. [0060] At step S47, it is discriminated whether or not the flag FACG is in a set state. If the flag FACG is set, then it is discriminated at step S48 whether or not the battery voltage Vb is equal to or higher than the control voltage maximum value VMax. The control voltage maximum value VMax is set to a value lower than the regulated voltage, for example, to 13.5 volt. If the battery voltage Vb is smaller than the control voltage maximum value VMax, the processing advances to step S49, at which it is discriminated whether or not the battery voltage Vb is equal to or lower than the control voltage minimum value VMin. The control voltage minimum value VMin is set, for example, to 13.0 volt. [0061] If the battery voltage Vb is higher than the control voltage minimum value VMin at step S49, then it is determined that the battery voltage Vb is within an ACG energization voltage range set to a value lower than the regulated voltage of the regulator, and the processing advances to step S50, at which ACG energization control is performed in accordance with the energization delay angle amount acgagl and the energization duty acduty described hereinabove. [0062] If it is discriminated at step S48 that the battery voltage Vb is equal to or higher than the control voltage maximum value VMax, then the processing advances to step S51, at which the energization duty acduty is decremented by a small value DDUTY. The small value DDUTY is, for example, 1%. On the other hand, if it is discriminated at step S49 that the battery voltage Vb is equal to or lower than the control voltage minimum value VMin, then the processing advances to step S52, at which the energization duty acduty is incremented by the small value DDUTY. After the processing at steps S51 and S52, the processing advances to step S50. [0063] It is to be noted that the small value DDUTY when the energization duty acduty is incremented need not necessarily be equal to the small value DDUTY when the energization duty acduty is decremented, or the small value DDUTY may be varied in proportion to the difference between the control voltage maximum value VMax or the control voltage minimum value VMin and the present value. [0064] On the other hand, if the flag FACG is not in a set state at step S47, then since the engine speed is not in the power generation control region, the processing advances to step S53, at which the ACG energization control is stopped. [0065] FIG. 11 is a view illustrating timings of electric currents (phase currents) flowing in the phases of the stator coils and an output of the rotor angle sensors 29 upon ACG energization control. In an ordinary case wherein the delay angle energization control is not performed, electric current is supplied to each of the U, V and W phases of the stator coils in response to a variation between the positive and the negative (N and S) of the detection output of the rotor angle sensors 29. On the other hand, if delay angle energization control is performed, electric current is supplied to each of the U, V and W phases of the stator coils after a delay by a predetermined delay angle amount d (= 60") from the time of the change between the positive and the negative (N and S) of the detection output of the rotor angle sensors 29. [0066] While, in FIG. 11, the energization angle T by duty chopping is 180", it can be determined within 180" depending upon the energization duty of energy supplied from the duty ratio setting section 47 to the driver 80. [0067] FIG. 12 is a table of the energization duty set using the engine speed Ne, that is, the speed of the ACG starter 1, as a parameter. An engine speed is detected, and an energization duty is determined in accordance with the engine speed. [0068] In this manner, with the generation control of the present embodiment, increase of the generated power amount can be achieved stably without rendering an ordinary voltage regulator operative in a low speed rotation region. Accordingly, upon idling or the like, the variation of the engine load can be reduced to minimize the variation of rotation of the engine thereby to stabilize the idling. [0069] Now, specifications of the ACG starter 1 in the present embodiment, particularly maximum generated torque which relates to the constitution of the ACG starter 1, is described. [0070] Torque necessary for cranking of the crankshaft 201 by external force upon starting of the engine, that is, cranking torque, exhibits its maximum value Tmax immediately before the piston reaches the compression top dead center (TDC) as described hereinabove with reference to FIG. 8. Accordingly, there is no necessity to generate torque equal to or higher than the maximum cranking torque Tmax on the crankshaft 201. [0071] However, the startability of an engine and the drivability have a relationship of antinomy to each other, and in a structure wherein the ACG starter 1 is directly coupled to the crankshaft 201 as in the present embodiment, since the ACG starter 1 acts as an inertial mass of the crankshaft 201, if a starter motor of a large size which provides high driving torque is adopted, then the acceleration performance and so forth are deteriorated. [0072] Here, in an engine starting apparatus wherein the crankshaft is rotated reversely to a predetermined position after the engine stops as in the present embodiment, since the approach running until the piston reaches a compression stroke upon next starting of the engine is long and the engine speed can be raised higher than ever during the approach running period, the rotating system including the crankshaft 201 can obtain comparatively high inertial force. [0073] FIG. 13 is a view illustrating time variations of the engine speed Ne (solid line) and cranking torque Tcnk (broken line), and FIG. 14 is a view illustrating time variations of driving torque Tdrv (solid line) of the starter motor itself, inertial torque Tine (alternate long and short dash line) of the rotating system including the crankshaft, and resultant torque Tadd (broken line) of the driving torque Tdrv and the inertial torque Tine. [0074] In the present embodiment, since the cranking torque Tcnk exhibits its maximum value of 1.3 kgfm at time tmax as shown in FIG. 13, in order for the piston to overcome the compression top dead center, driving torque of at least 1.3 kgfm or more is required. Accordingly, conventionally a motor of a large size having maximum generated torque equal to or higher than 1.3 kgcm is required as the ACG starter 1. [0075] However, in the present embodiment, since the crankshaft is rotated reversely to a predetermined position after the engine stops, upon next starting of the engine, the engine speed immediately before a compression stroke is reached reaches 700 to 900 rpm as shown in FIG. 13. Accordingly, since the inertial torque Tine of the rotating system including the crankshaft 201 is high as shown in FIG. 14, even if the ACG starter 1 can generate only driving torque Tdrv of such a magnitude that it is much smaller than the maximum cranking torque Tmax, the resultant torque Tadd of the inertial torque Tine and the driving torque Tdrv can exceed the maximum cranking torque Tmax described above (in the present embodiment, 1.3 kgfm). in other words, reduction in size and weight of the ACG starter 1 can be anticipated. [0076] However, it is necessary for the ACG starter 1 to generate cranking torque Tcnk at least necessary for the piston to proceed in the other strokes than a compression stroke, and according to a result of an examination by the inventors, it was confirmed that the value of the cranking torque Tcnk corresponds to approximately 2 0% of the maximum cranking torque Tmax necessary for the piston to overcome a compression stroke. Accordingly, the maximum generated value of the ACG starter 1 in the present embodiment is preferably higher than at least approximately 2 0% of the maximum cranking torque Tmax. [0077 1 Further, in a structure wherein the ACG starter 1 and the crankshaft 201 are coupled directly to each other as in the present embodiment, the ACG starter 1 acts as an inertial mass upon the engine. It is empirically recognized that, with an engine whose maximum cranking torque corresponds to 1.3 kgfm as in the present embodiment, an appropriate value of the inertial mass is 28 to 33 kgcm2 from the point of view of the drivability upon acceleration or the like. [0078] FIG. 15 is a view illustrating a relationship between the inertial mass and the maximum generated torque of the ACG starter I. In the ACG starter I of a constitution wherein the inertial mass is 28 to 33 kgcm2, the maximum generated torque is 0.5 to 0.8 kgfm. This corresponds to approximately 40 to 60 percent of the maximum cranking torque Tmax, and with the ACG starter 1 whose inertial mass is higher than this, although the startability of the engine is better, the drivability upon acceleration is deteriorated. [0079] From the point of view of the foregoing, in the present embodiment, a starter motor of a small size whose maximum generated torque is approximately 20 to 60% of the" maximum cranking torque Tmax is adopted as the ACG starter 1. In other words, the maximum generated torque of the ACG starter 1 is selected so that the inertial mass of the crankshaft 201 directly coupled to the starter 1 may be an upper limit of. an optimum range therefor. [0080] [Effect of the Invention] According to the present invention, since the piston is accelerated sufficiently until the piston acquires comparatively high inertial force before the piston reaches a compression stroke, only if the resultant force of the inertial force and driving torque of the starter motor reaches maximum cranking torque, then even if the maximum generated torque of the starter motor itself is smaller than the maximum cranking torque, the piston can overcome the compression stroke. Accordingly, since the starter motor can be reduced in size when compared with a conventional starter motor, the drivability can be improved without suffering from damage to the startability. We claim: 1. An engine starting apparatus which rotates a crankshaft (201) reversely to a predetermined position after an engine stops to prepare for next starting of said engine, characterized by comprising: a starter motor (1) for rotating said crankshaft (201) forwardly and reversely; and reverse rotation controlling means (700) for causing said starter motor (1) to rotate reversely after said engine stops, wherein maximum generated torque of said starter motor is equal to or lower than approximately 60% of maximum cranking torque necessary for a piston to overcome a compression stroke upon starting of said engine but is equal to or higher than cranking torque necessary for said piston to proceed in any other stroke than the compression stroke, and the maximum generated torque of said starter motor is selected so that an inertial mass of said crankshaft directly coupled to said starter motor may be equal to an upper limit of an optimum range therefor. 2. An engine starting apparatus as claimed in claim 1 wherein the maximum generated torque of said starter motor is equal to or higher than approximately 20% of the maximum cranking torque. 3. An engine starting apparatus as claimed in any one of the preceding claims comprising means for reducing, upon starting of said engine, the internal pressure of a cylinder in the compression stroke for a period for which the speed of said engine is equal to or lower than a predetermined reference speed. 4. An engine starting apparatus according to any one of claims 1 to 3, wherein the speed of said engine immediately before said piston enters the compression stroke ranges from 700 to 900 rpm. 5. An engine starting apparatus substantially as herein described with reference to the accompanying drawings. Dated this 22nd Day of March, 2002 [RITUSHKA NEGI] OF REMFRY & SAGAR ATTORNEY FOR THE APPLICANTS

Full Text

Original
THE PATENTS ACT 1970 [39 OF 1970]
COMPLETE SPECIFICATION [See Section 10] "ENGINE STARTING APPARATUS"
HONDA GIKEN KOGYO KABUSHIKI KAISHA, a corporation of Japan, having a place of business at 1-1, Minamiaoyarna 2-chome, Minato-ku, Tokyo, Japan,
GRANTED
3-4-2007
The following specification particularly describes the nature of the invention and the manner in which it is to be performed:-

The present invention relates to engine starting apparatus
[DETAILED DESCRIPTION OF THE INVENTION] [0001]
[Technical Field to Which the Invention Pertains] This invention relates to an engine starting apparatus for cranking an engine using a starter motor to start the, engine, and more particularly to an engine starting apparatus which uses both of inertial force of a rotating system including a crankshaft and driving torque of a starter motor to allow good starting of an engine

even if the torque of the starter motor is low.
[0002]
[Prior Art]
Cranking torque upon starting of an engine exhibits a maximum value (overcoming torque) immediately before a piston reaches the compression top dead center (TDC), and in order to overcome the TDC, conventionally a comparatively large starter motor wherein maximum generated torque (lock torque) which can be generated is equal to or higher than the maximum cranking torque mentioned above is adopted.
[0003]
[Problem to Be Solved by the Invention]
The startability of an engine rises as the driving torque of a starter motor increases. However, in a structure wherein the starter motor is directly coupled to the crankshaft of the engine, since a rotational portion of the starter motor acts as an inertial mass, if a starter motor of a large size whose driving torque is high is adopted, then it cannot be avoided that the drivability is deteriorated particularly upon starting and acceleration.
[0004]
For example, in a four-cycle engine of 100 cc or

less adopted by a general two-wheeled vehicle of a small SIze, the maximum cranking torque reaches 1.3 kgfm. However, if a starter motor whose maximum generated torque is 1.3 kgfm is directly coupled to the crankshaft, then the inertial mass thereof becomes 40 kgcm2 and is much higher than an optimum inertial mass of 28 to 33 kgcm2. In other words, the startability of an engine and the drivability have a relationship of antinomy to each other, and it is difficult to satisfy both of them.
[0005]
It is an object of the present invention to solve the object of the prior art described above and provide an engine starting apparatus wherein a good engine startability is ensured with a small starter motor to satisfy both of the startability of an engine and the drivability.
[0006]
[Means for Solving the Problem]
In order to attain the object described above, according to the present invention, an engine starting apparatus which rotates a crankshaft reversely to a predetermined position after an engine stops to prepare for next starting of the engine is characterized by including: a starter motor for rotating the crankshaft

forwardly and reversely; and reverse rotation controlling means.for causing the starter motor to rotate reversely after the engine stops, wherein maximum generated torque of the starter motor is equal to or lower than approximately 60% of maximum cranking torque necessary for a piston to overcome a compression stroke upon starting of the engine but is equal to or higher than cranking torque necessary for the piston to proceed in any other stroke than the compression stroke. [0007]
With the characteristic described above, since the piston is accelerated sufficiently to obtain comparatively high inertial force before a compression stroke is reached, only if the resultant force of the inertial force and driving torque of the starter motor reaches the maximum cranking torque, even if the maximum generated torque of the starter motor itself is lower than the maximum cranking torque, the piston can overcome the compression stroke.

[BRIEF DESCRIPTION OF THE DRAWINGS] [FIG. 1]
FIG. 1 is a side elevational view of an entire motorcycle of the scooter type to which the present invention is applied. [FIG. 2]
FIG. 2 is a sectional view taken along a crankshaft of a swing unit of FIG. 1. [FIG. 3]
FIG. 3 is a partial enlarged view of FIG. 2. [FIG. 4]
FIG. 4 is a block diagram of a control system for a starter-generator. [FIG. 5]
FIG. 5 is a block diagram showing a configuration of a principal portion of an ECU of FIG. 4. [FIG. 6]
FIG. 6 is a flow chart of swing back control. [FIGS. 7(a), 7(b) and 7(c)]
FIGS. 7(a), 7(b) and 7(c) are explanatory views of operation of the swing back control. [FIG. 8]

FIG. 8 is a view showing an example of transition of cranking torque. [FIG. 9]
FIG. 9 is a flow chart illustrating operation of a decompression driving section. [FIG. 10]
FIG. 10 is a flow chart of an ACG generation control process. [FIG. 11]
FIG. 11 is a view illustrating timings of phase currents of stator coils and an output of a rotor angle sensor upon the ACG energization control. [FIG. 12]
FIG. 12 is a table of an energization duty wherein an engine speed is used as a parameter. [FIG. 13]
FIG. 13 is a view illustrating time variations of an engine speed Ne and a cranking torque Tcnk. [FIG. 14]
FIG. 14 is a view illustrating time variations of driving torque Tdrv of a starter motor, inertial torque Tine of a rotating system including a crankshaft, and resultant torque Tadd of the driving torque Tdrv and the inertial torque Tine.

motorcycle to which an engine starting apparatus of the present invention is applied. The vehicle further has an engine automatic stopping-starting function of automatically stopping the engine if the vehicle is stopped and then automatically driving the starter motor to re-start the engine if such a starting operation that a throttle grip is opened or a starter switch is operated into an on-state is performed thereafter. [0009]
A vehicle body front portion and a vehicle body rear portion are connected to each other through a floor portion 4, and a body frame which forms a skeleton of the vehicle body is generally composed of a down tube 6 and a main pipe 7. A fuel tank and an accommodation box (both not shown) are supported by the main pipe 7, and a seat 8 is disposed above the main pipe 7. [0010]
A handle bar 11 is supported for pivotal motion by a steering head 5 in the upper side of the vehicle body front portion. A front fork 12 extends in the lower side of the vehicle body front portion, and has a front wheel FW supported for rotation at lower ends of the front fork 12. An upper portion of the handle bar 11 is covered with a handle bar cover 13 which serves also as an instrument

panel. A bracket 15 is provided in a projecting manner at a lower end of a rising portion of the main pipe 7, and a hanger bracket 18 of a swing unit 2 is connected to and supported for rocking motion on the bracket 15 through a link member 16. [0011]
A single cylinder 50 cc four-cycle engine E is carried at a front portion of the swing unit 2. A belt type continuously variable transmission 10 is formed such that it extends rearwardly from the engine E, and a rear wheel RW is supported for rotation on a speed reducing mechanism 9 which is provided at a rear portion of the belt type continuously variable transmission 10 through a centrifugal clutch. A rear cushion 3 is interposed between an upper end of the speed reducing mechanism 9 and a bent portion of an upper portion of the main pipe 7. A carburetor 17 connected to an intake pipe 19 extending from the engine E and an air cleaner 14 connected to the carburetor 17 are disposed at a front portion of the swing unit 2. [0012]
FIG. 2 is a sectional view of the swing unit 2 taken along a crankshaft 201, and FIG. 3 is a partial enlarged view of the same. Like reference characters to

those appearing as above denote like or equivalent elements.
[0013]
The swing unit 2 is covered with a crankcase 202 which is formed from left and right crankcases 202L and 202R joined together, and the crankshaft 201 is supported for rotation by bearings 208 and 209 secured to the crankcase 202R. A connecting rod (not shown) is connected to the crankshaft 201 through a crank pin 213.
[0014]
The left crankcase 202L serves also as a belt type continuously variable transmission chamber case, and a belt driving pulley 210 is provided for rotation on the crankshaft 201 which extends to the left crankcase 202L. The belt driving pulley 210 is composed of a fixed side pulley half 210L and a movable side pulley half 210R. The fixed side pulley half 210L is fixed to a left end portion of the crankshaft 201 through a boss 211. The movable side pulley half 210R is spline fitted on the crankshaft 201 on the right side of the fixed side pulley half 210L such that the movable side pulley half 210R can be moved toward and away from the fixed side pulley half 210L. A V belt 212 is wound around the two pulley halves 210L and 210R.

[0015]
On the right side of the movable side pulley half 210R, a cam plate 215 is fixed to the crankshaft 201, and a slide piece 215a provided at an outer circumferential end of the cam plate 215 is held in engagement for sliding motion on a cam plate sliding boss portion 210Ra formed in an axial direction at an outer circumferential end of the movable side pulley half 210R. The cam plate 215 of the movable side pulley half 210R has a tapered face near an outer circumference thereof. The tapered face is inclined to the movable side pulley half 210R side. A dry weight ball 216 is accommodated in a free space between the tapered face and the movable side pulley half 210R.
[0016]
If the speed of rotation of the crankshaft 201 increases, then the dry weight ball 216 which is positioned between and rotates together with the movable side pulley half 210R and the cam plate 215 is moved in a centrifugal direction by centrifugal force, and the movable side pulley half 210R is pushed by the dry weight ball 216 to move leftwardly so that the movable side pulley half 210R approaches the fixed side pulley half 210L. As a result, the V belt 212 held between the two

pulley halves 210L and 210R moves in the centrifugal direction and the winding diameter thereof increases.
[0017]
A driven pulley (not shown) corresponding to the belt driving pulley 210 described above is provided at a rear portion of the vehicle, and the V belt 212 is wound around the driven pulley. Through this belt transmission mechanism, power of the engine E is automatically adjusted and transmitted to the centrifugal clutch so that the power drives the rear wheel RW through the speed reducing mechanism 9 and so forth.
[0018]
A starter-generator (ACG starter) 1 which includes a starter motor and an AC generator in combination is disposed in the right crankcase 202R. In the ACG starter 1, an outer rotor 60 is secured to the tapered portion of the end of the crankshaft 201 by a screw 253.
[0019]
A stator 50 disposed on an inner circumference side of the outer rotor 60 is secured to the crankcase 202 by a bolt 279. A fan 280 secured by a bolt 246 is provided on the outer rotor 60. A radiator 282 is provided next to the fan 280, and the radiator 282 is covered with a fan cover 281.

[0020]
As shown in an enlarged scale in FIG. 3, a sensor case 28 is fitted in an inner circumference of the stator 50. Rotor angle sensors (magnetic pole sensors) 29 and a pulser sensor (ignition pulser) 30 are provided at equal distances along an outer circumference of a boss 60a of the outer rotor 60. The rotor angle sensors 29 are provided to perform energization control of stator coils of the ACG starter 1 and provided one by one corresponding to the U phase, V phase and W phase of the ACG starter 1. The ignition pulser 30 is provided for ignition control of the engine, and only one ignition pulser 30 is provided. The rotor angle sensors 29 and the ignition pulser 30 can each be formed from a Hall IC or a magnetic reluctance (MR) element.
[0021]
Leads of the rotor angle sensors 29 and the ignition pulser 30 are connected to a board 31, and further, a wire harness 32 is coupled to the board 31. A magnet ring 33 magnetized in two stages is fitted on an outer periphery of the boss 60a of the outer rotor 60 so that the magnet ring 33 may have a magnetic action on each of the rotor angle sensors 29 and the ignition pulser 30.

[0022]
N poles and S poles disposed alternately at distances of 30° width in a circumferential direction in a corresponding relationship to the magnetic poles of the stator 50 are formed on one of the magnetization zones of the magnet ring 33 which corresponds to the rotor angle sensors 29. On the other magnetization zone of the magnet ring 33 which corresponds to the ignition pulser 30, a magnetized portion is formed over a range from 15° to 40° at one location in a circumferential direction.
[0023]
The ACG starter 1 functions as a starter motor (synchronous motor) when the engine starts and is driven with electric current supplied from a battery to rotate the crankshaft 201 thereby to start the engine. After the engine is started, the ACG starter 1 functions as a synchronous generator and charges the battery with electric current generated thereby and besides supplies electric current to electric parts.
[0024]
Referring back to FIG. 2, a sprocket 231 is secured to the crankshaft 201 between the ACG starter 1 and a bearing 209, and a chain for driving a camshaft (not shown) from the crankshaft 2 01 is wound around the

sprocket 231. It is to be noted that the sprocket 231 is formed integrally with a gear 232 for transmitting power to a pump for circulating lubricating oil.
[0025]
FIG. 4 is a block diagram of an electric system including the ACG starter 1. An ECU 3" includes a three-phase full-wave rectification bridge circuit 300 for full wave rectifying three-phase alternating current generated by the power generation function of the ACG starter 1, and a regulator 100 for limiting an output of the full-wave rectification bridge circuit 300 to a predetermined regulated voltage (regulator operation voltage: for example, 14.5 V).
[0026]
Further, the ECU 3" of the present embodiment includes a swing back control section 700 for rotating the crankshaft reversely to a predetermined position immediately after the engine stops to improve the startability in next starting of the engine, a starting control section 500 for lowering the cranking torque upon starting of the engine, and a power generation control section 400 for increasing the generated energy amount when the engine speed is within a predetermined low speed region.

[0027]
An ignition coil 21 is connected to the ECU 3", and an ignition plug 22 is connected to the secondary side of the ignition coil 21. Further, a throttle sensor 23, a fuel sensor 24, a seat switch 25, an idling switch 26, a cooling water temperature sensor 27, the rotor angle sensors 29 and the ignition pulser 30 are connected to the ECU 3", and detection signals are inputted from the elements to the ECU 3".
[0028]
Furthermore, a starter relay 34, a starter switch 35, stop switches 36 and 37, a standby indicator 38, a fuel indicator 39, a speed sensor 40, an auto by-starter 41 and a headlamp 42 are connected to the ECU 3". A dimmer switch 43 is provided for the headlamp 42.
[0029]
To the elements mentioned above, electric current is supplied from a battery 2" through a main fuse 44 and a main switch 45. It is to be noted that the battery 2" is connected directly to the ECU 3" by the starter relay 34 and has a circuit which is connected to the ECU 3" only through the main fuse 44 without through the main switch 45.
[0030]

Now, a configuration and operation of the swing back control section 700, starting control section 500 and power generation control section 400 of the ECU 3" described above are described with reference to a functional block diagram of FIG. 5.
[0031]
In the swing back control section 700, a stage discrimination section 73 divides one rotation of the crankshaft 201 into 36 stages of stages #0 to #35 based on output signals of the rotor angle sensors 29 and discriminates the present stage using the detection timing of a pulse signal generated by the ignition pulser 30 as a reference stage (the stage #0).
[0032]
A stage passing time detection section 74 detects, based on a period of time after the stage discrimination section 73 discriminates a new stage until the stage discrimination section 73 discriminates a next stage, passing time Atn of the present stage. A reverse rotation control section 75 generates a reverse driving instruction based on a result of the discrimination by the stage discrimination section 73 and the passing time
Atn detected by the stage passing time detection section 74.

[0033]
A duty ratio setting section 72 dynamically controls the duty ratio of a gate voltage to be supplied to power FETs of the full-wave rectification bridge circuit 300 based on a result of the discrimination by the stage discrimination section 73. A driver 80 supplies a driving pulse of the duty ratio set as described above to the power FETs of the full-wave rectification bridge circuit 300.
[0034]
Now, operation of the swing back control section 700 described above is described with reference to a flow chart of FIG. 6 and an explanatory view of operation of FIG. 7.
[0035]
FIG. 7(a) illustrates a relationship between the cranking torque (reverse rotation load) required to rotate the crankshaft 201 reversely and the crank angle, and the cranking torque rises drastically immediately before the compression top dead center is reached (upon reverse rotation). FIG. 7(b) illustrates a relationship between the crank angle and the stage, and FIG. 7(c) illustrates a variation of the angular speed of the crankshaft upon reverse rotation.

[0036]
If stopping of the engine is detected at step S61, then the present stage discriminated already by the stage discrimination section 73 is referred to at steps S62 and S63. Here, if the present stage is one of the stages #0 to #11, then the processing advances to step S64, but if the present stage is one of the stages #12 to #32, then the processing advances to step S65. However, in any other case (that is, if the present stage is one of the stages #33 to #35), then the processing advances to step S66. At step S64 or S65, the duty ratio setting section 72 sets the duty ratio of a driving pulse to 70%, but at step S65, the duty ratio setting section 72 sets the duty ratio to 80%.
[0037]
Such dynamic control of the duty ratio as just described is performed in order to sufficiently lower, upon reverse rotation, the angular speed of the crankshaft 201 prior to an angle corresponding to the compression top dead center at which the cranking torque increases (upon reverse rotation) but allow quick reverse rotational driving at any other angle than the angle as hereinafter described in detail.
[0038]

At step S67, the driver 80 controls the power FETs of the full-wave rectification bridge circuit 300 with the duty ratio set as described above to start energization for reverse rotation. At step S68, the
passing time Atn of the stages #n passed is measured by the stage passing time detection section 74.
[0039]
At step S69, the reverse rotation control section 75 discriminates whether or not the crankshaft 201 has passed a position in the proximity of the stage #0, that is, the top dead center. If the crankshaft 201 has not passed the stage #0, then a ratio [Atn/Atn-1] between the passing time Atn of the stage #n which the crankshaft 201 has passed last and the passing time Atn-1 of the stage #(n-l) which the crankshaft 201 has passed second last is compared with a reference value Rref (in the present embodiment, 4/3) at step S71. If the passing time ratio [Atn/Atn-1] is not higher than the reference value Rref, then the processing returns to step S62 described above to continue the reverse rotation driving, and the processing described above is repeated in parallel to the reverse rotation driving.
[0040]
Here, if the stopping position of the engine, that

is, the reverse rotation starting position, is on the side nearer to the compression top dead center for the next time than a middle position between the compression top dead centers for the preceding and next times, or in other words, is in the process to the compression top dead center after the exhaust top dead center is passed (upon forward rotation) as indicated by a curve A in FIG. 7(c), then although the ACG starter 1 is being driven to rotate reversely with the duty ratio of 70%, the crankshaft can pass the stage #0 (exhaust top dead center). Accordingly, after this is detected at step S69, the processing advances to step S70, at which it is discriminated whether or not the crankshaft 201 reaches the stage #32. If it is discriminated that the crankshaft 201 reaches the stage #32, then since the energization for reverse rotation described above is stopped at step S72, the crankshaft thereafter stops after the crankshaft is further rotated reversely by the inertial force. [0041]
On the other hand, if the reverse rotation starting position is on the side nearer to the compression top dead center for the preceding time than the middle position between the compression top dead centers for the preceding and next times, or in other words, is in the

process to the exhaust top dead center after the compression top dead center is passed (upon forward rotation) as indicated by a curve B in FIG. 7(c), then since the ACG starter 1 is being driven to rotate reversely with the duty ratio of 7 0%, when the reverse rotation load increases before the stage #0 (upon reverse rotation) is reached, the angular speed of the crankshaft 201 drops drastically as shown in FIG. 7(a). Then, if it is discriminated at step S71 that the passing time ratio [Atn/Atn-1] is equal to or higher than 4/3 the reference value, then the energization for reverse rotation is stopped at step S72, and the reverse rotation of the crankshaft stops nearly simultaneously with stopping of the energization. [0042]
In this manner, in the swing back control of the present embodiment, upon driving for reverse rotation after the engine stops, it is supervised whether or not the crankshaft has passed an angle corresponding to the top dead center and whether or not the angular speed of the crankshaft has dropped, and if the crankshaft passes the top dead center upon reverse rotation, then the energization for reverse rotation is ended immediately after that. Also when the angular speed of the crankshaft

drops as a result of increase of the reverse rotation load, the energization for reverse rotation is ended. Accordingly, irrespective of the reverse rotation starting position, the crankshaft can be returned to a position prior to the compression dead center for the preceding time (upon reverse rotation) at which the compression reactive force is low. [0043]
Further, in the swing back control of the present embodiment, since the angular speed of the crankshaft 201 is detected based on outputs of the rotor angle sensors 29 for detecting the rotor angle (that is, a stage) of the ACG starter, a sensor for detecting the angle of the crankshaft 201 need not be provided separately. [0044]
Referring back to FIG. 5, the starting control section 500 compulsorily lifts the exhaust valve only immediately after starting of the engine to lower the internal pressure of the cylinder in a compression stroke in order to lower the cranking torque upon the starting of the engine. [0045]
In the starting control section 500, an engine speed discrimination section 52 discriminates an engine

speed based on a detection signal of the ignition pulser 30, a frequency signal of a generated voltage and so forth. A decompression driving section 51 detects depression of the starter switch 35 to drive the ACG starter 1 and excite a decompression solenoid 63, which compulsorily lifts the exhaust valve, at a predetermined timing.
[0046]
Since the cranking torque upon starting of the engine rises in a compression stoke to the TDC as shown in FIG. 8, it is demanded for the AGC starter to have maximum generated torque equal to or higher than maximum cranking torque Tmax in a compression stroke. Therefore, in the present embodiment, upon starting of the engine, the exhaust valve is opened to suppress a rise of the internal pressure of the cylinder in a compression stroke to suppress the maximum cranking torque Tmax low.
[0047]
FIG. 9 is a flow chart illustrating operation of the decompression driving section 51 described above. If depression of the starter switch 35 is detected at step S51, then the engine speed Ne is compared with a predetermined reference speed Nref at step S52. Here, the engine still remains in a stopping state and the engine

speed Ne is lower than the reference speed Nref, and therefore, the processing advances to step S53. [0048]
At step S53, fuel injection is inhibited, and at step S54, the decompression solenoid 63 is excited so that the exhaust valve is lifted compulsorily. At step
S55, the ACG starter 1 is driven.
[0049]
Thereafter, the engine speed Ne rises until it exceeds the reference speed Nref, and when this is detected at step S52, fuel injection is started at step
S56. At step S57, the excitation of the decompression
solenoid 63 is stopped.
[0050]
It is to be noted that, if cancellation of the depression of the starter switch 35 is detected at step S51, then the decompression solenoid 63 is turned off at step S58, and the ACG starter 1 is turned off at step S59.
[0051]
In this manner, in the present embodiment, since, upon starting of the engine, the exhaust valve is opened compulsorily to suppress a rise of the internal pressure of the cylinder in a compression stroke to suppress the maximum cranking torque Tmax low, good startability can

be ensured even if a starter of a small size whose maximum generated torque is low is adopted.
[0052]
Referring back to FIG. 5, the power generation control section 400 has, in addition to a function of controlling the generated power amount (voltage) normally, a function of delay angle energizing the stator coils of the different phases of the ACG starter 1 from the battery 2" to increase the generated power amount (hereinafter referred to as "ACG energization control").
[0053]
Here, the delay angle energization signifies to energize a stator coil after a delay corresponding to a predetermined electrical angle from a detection signal upon a change between magnetic poles of magnetized zones of the magnet ring 33 detected by the rotor angle sensors 29. However, in order to prevent instability of rotation of the engine which arises from a sudden variation of the load to the engine which occurs when the regulator 100 operates in a low rotation region, the control is performed so that the output voltage (battery voltage) of the full-wave rectification bridge circuit 300 may remain within a predetermined voltage range equal to or lower than the regulated voltage.

[0054]
In the power generation control section 400, an engine speed discrimination section 48 detects an engine speed, for example, based on a detection signal of the ignition pulser 30 and supplies a delay angle instruction to the driver 80 if the engine speed is within a predetermined power generation control region. The driver 80 receiving the delay angle instruction reads out an energization delay angle amount set in advance from a delay angle amount setting section 49 and performs delay angle energization. An energization duty ratio is supplied from a duty ratio setting section 47 to the driver 80.
[0055]
The driver 80 detects a magnetic pole detection signal from the rotor angle sensors 29, that is, a signal which rises to an on state every time the rotor angle sensors 29 detect one of the magnetized zones of the magnet ring 33 formed in a corresponding relationship to the magnetic poles of the outer rotor 60. Then, the driver 80 outputs a PWM control signal to the FETs of the full-wave rectification bridge circuit 300 after a delay by an angle corresponding to an energization delay angle amount from a rising edge of the signal.

[0056]
A battery voltage discrimination section 46 compares a battery voltage Vb with a control voltage maximum value VMax and a control voltage minimum value VMin, which define a voltage control range, and adjusts the energization duty set by the duty ratio setting section 47 based on a result of the comparison so that the battery voltage Vb may remain within the control range described above. In particular, if the battery voltage Vb reaches the control voltage maximum value VMax, then the battery voltage discrimination section 46 decreases the energization duty by a predetermined small value (for example, 1%), but if the battery voltage Vb drops to the control voltage minimum value VMin, then the battery voltage discrimination section 46 increases the energization duty by the small value.
[0057]
FIG. 10 is a flow chart illustrating operation of the power generation control section 400 described above, which is activated after the engine starting control by the starting control section 500 is ended.
[0058]
At step S41, it is discriminated whether or not the engine speed is within the power generation control

region. The power generation control region is set, for example, to a region not smaller than 1,000 rpm but not more than 3,500 rpm. If the engine speed is within the power generation control region, then the processing advances to step S41, at which it is discriminated whether or not a flag FACG indicating that the engine speed is within the power generation control region is in a set state (= 1) . If the flag FACG is not set, then the processing advances to step S43, at which the flag FACG is set. At step S44, a predetermined value ACGAGL is placed into an energization delay angle amount acgagl. While the predetermined value ACGAGL can be set suitably in advance, the predetermined value ACGAGL in the present embodiment is, for example, an electrical angle of 60*. [0059]
At next step S45, an initial value ACDUTY is placed into an energization duty acduty. While also the initial value ACDUTY can be set suitably in advance, the initial value ACDUTY in the present embodiment is, for example, 40%. After the steps S43 to S45 are completed, the processing advances to step S47. If the discrimination at step S42 is affirmative, then the processing skips steps S43 to S45 and advances to step S47. On the other hand, if the engine speed is not within the generation control

region, then the flag FACG is reset (= 0) at step S46, whereafter the processing advances to step S47.
[0060]
At step S47, it is discriminated whether or not the flag FACG is in a set state. If the flag FACG is set, then it is discriminated at step S48 whether or not the battery voltage Vb is equal to or higher than the control voltage maximum value VMax. The control voltage maximum value VMax is set to a value lower than the regulated voltage, for example, to 13.5 volt. If the battery voltage Vb is smaller than the control voltage maximum value VMax, the processing advances to step S49, at which it is discriminated whether or not the battery voltage Vb is equal to or lower than the control voltage minimum value VMin. The control voltage minimum value VMin is set, for example, to 13.0 volt.
[0061]
If the battery voltage Vb is higher than the control voltage minimum value VMin at step S49, then it is determined that the battery voltage Vb is within an ACG energization voltage range set to a value lower than the regulated voltage of the regulator, and the processing advances to step S50, at which ACG energization control is performed in accordance with the

energization delay angle amount acgagl and the energization duty acduty described hereinabove.
[0062]
If it is discriminated at step S48 that the battery voltage Vb is equal to or higher than the control voltage maximum value VMax, then the processing advances to step S51, at which the energization duty acduty is decremented by a small value DDUTY. The small value DDUTY is, for example, 1%. On the other hand, if it is discriminated at step S49 that the battery voltage Vb is equal to or lower than the control voltage minimum value VMin, then the processing advances to step S52, at which the energization duty acduty is incremented by the small value DDUTY. After the processing at steps S51 and S52, the processing advances to step S50.
[0063]
It is to be noted that the small value DDUTY when the energization duty acduty is incremented need not necessarily be equal to the small value DDUTY when the energization duty acduty is decremented, or the small value DDUTY may be varied in proportion to the difference between the control voltage maximum value VMax or the control voltage minimum value VMin and the present value.
[0064]

On the other hand, if the flag FACG is not in a set state at step S47, then since the engine speed is not in the power generation control region, the processing advances to step S53, at which the ACG energization control is stopped. [0065]
FIG. 11 is a view illustrating timings of electric currents (phase currents) flowing in the phases of the stator coils and an output of the rotor angle sensors 29 upon ACG energization control. In an ordinary case wherein the delay angle energization control is not performed, electric current is supplied to each of the U,
V and W phases of the stator coils in response to a variation between the positive and the negative (N and S) of the detection output of the rotor angle sensors 29. On the other hand, if delay angle energization control is performed, electric current is supplied to each of the U,
V and W phases of the stator coils after a delay by a predetermined delay angle amount d (= 60") from the time of the change between the positive and the negative (N and S) of the detection output of the rotor angle sensors 29.
[0066]
While, in FIG. 11, the energization angle T by duty

chopping is 180", it can be determined within 180" depending upon the energization duty of energy supplied from the duty ratio setting section 47 to the driver 80.
[0067]
FIG. 12 is a table of the energization duty set using the engine speed Ne, that is, the speed of the ACG starter 1, as a parameter. An engine speed is detected, and an energization duty is determined in accordance with the engine speed.
[0068]
In this manner, with the generation control of the present embodiment, increase of the generated power amount can be achieved stably without rendering an ordinary voltage regulator operative in a low speed rotation region. Accordingly, upon idling or the like, the variation of the engine load can be reduced to minimize the variation of rotation of the engine thereby to stabilize the idling.
[0069]
Now, specifications of the ACG starter 1 in the present embodiment, particularly maximum generated torque which relates to the constitution of the ACG starter 1, is described.
[0070]

Torque necessary for cranking of the crankshaft 201 by external force upon starting of the engine, that is, cranking torque, exhibits its maximum value Tmax immediately before the piston reaches the compression top dead center (TDC) as described hereinabove with reference to FIG. 8. Accordingly, there is no necessity to generate torque equal to or higher than the maximum cranking torque Tmax on the crankshaft 201. [0071]
However, the startability of an engine and the drivability have a relationship of antinomy to each other, and in a structure wherein the ACG starter 1 is directly coupled to the crankshaft 201 as in the present embodiment, since the ACG starter 1 acts as an inertial mass of the crankshaft 201, if a starter motor of a large size which provides high driving torque is adopted, then the acceleration performance and so forth are deteriorated. [0072]
Here, in an engine starting apparatus wherein the crankshaft is rotated reversely to a predetermined position after the engine stops as in the present embodiment, since the approach running until the piston reaches a compression stroke upon next starting of the

engine is long and the engine speed can be raised higher than ever during the approach running period, the rotating system including the crankshaft 201 can obtain comparatively high inertial force.
[0073]
FIG. 13 is a view illustrating time variations of the engine speed Ne (solid line) and cranking torque Tcnk (broken line), and FIG. 14 is a view illustrating time variations of driving torque Tdrv (solid line) of the starter motor itself, inertial torque Tine (alternate long and short dash line) of the rotating system including the crankshaft, and resultant torque Tadd (broken line) of the driving torque Tdrv and the inertial torque Tine.
[0074]
In the present embodiment, since the cranking torque Tcnk exhibits its maximum value of 1.3 kgfm at time tmax as shown in FIG. 13, in order for the piston to overcome the compression top dead center, driving torque of at least 1.3 kgfm or more is required. Accordingly, conventionally a motor of a large size having maximum generated torque equal to or higher than 1.3 kgcm is required as the ACG starter 1.
[0075]

However, in the present embodiment, since the crankshaft is rotated reversely to a predetermined position after the engine stops, upon next starting of the engine, the engine speed immediately before a compression stroke is reached reaches 700 to 900 rpm as shown in FIG. 13. Accordingly, since the inertial torque Tine of the rotating system including the crankshaft 201 is high as shown in FIG. 14, even if the ACG starter 1 can generate only driving torque Tdrv of such a magnitude that it is much smaller than the maximum cranking torque Tmax, the resultant torque Tadd of the inertial torque Tine and the driving torque Tdrv can exceed the maximum cranking torque Tmax described above (in the present embodiment, 1.3 kgfm). in other words, reduction in size and weight of the ACG starter 1 can be anticipated. [0076]
However, it is necessary for the ACG starter 1 to generate cranking torque Tcnk at least necessary for the piston to proceed in the other strokes than a compression stroke, and according to a result of an examination by the inventors, it was confirmed that the value of the cranking torque Tcnk corresponds to approximately 2 0% of the maximum cranking torque Tmax necessary for the piston to overcome a compression stroke. Accordingly, the

maximum generated value of the ACG starter 1 in the present embodiment is preferably higher than at least approximately 2 0% of the maximum cranking torque Tmax.
[0077 1
Further, in a structure wherein the ACG starter 1 and the crankshaft 201 are coupled directly to each other as in the present embodiment, the ACG starter 1 acts as an inertial mass upon the engine. It is empirically recognized that, with an engine whose maximum cranking torque corresponds to 1.3 kgfm as in the present embodiment, an appropriate value of the inertial mass is 28 to 33 kgcm2 from the point of view of the drivability upon acceleration or the like.
[0078]
FIG. 15 is a view illustrating a relationship between the inertial mass and the maximum generated torque of the ACG starter I. In the ACG starter I of a constitution wherein the inertial mass is 28 to 33 kgcm2, the maximum generated torque is 0.5 to 0.8 kgfm. This corresponds to approximately 40 to 60 percent of the maximum cranking torque Tmax, and with the ACG starter 1 whose inertial mass is higher than this, although the startability of the engine is better, the drivability upon acceleration is deteriorated.

[0079]
From the point of view of the foregoing, in the present embodiment, a starter motor of a small size whose maximum generated torque is approximately 20 to 60% of the" maximum cranking torque Tmax is adopted as the ACG starter 1. In other words, the maximum generated torque of the ACG starter 1 is selected so that the inertial mass of the crankshaft 201 directly coupled to the starter 1 may be an upper limit of. an optimum range therefor.
[0080]
[Effect of the Invention]
According to the present invention, since the piston is accelerated sufficiently until the piston acquires comparatively high inertial force before the piston reaches a compression stroke, only if the resultant force of the inertial force and driving torque of the starter motor reaches maximum cranking torque, then even if the maximum generated torque of the starter motor itself is smaller than the maximum cranking torque, the piston can overcome the compression stroke. Accordingly, since the starter motor can be reduced in size when compared with a conventional starter motor, the drivability can be improved without suffering from damage to the startability.

We claim:
1. An engine starting apparatus which rotates a crankshaft (201)
reversely to a predetermined position after an engine stops to
prepare for next starting of said engine, characterized by
comprising:
a starter motor (1) for rotating said crankshaft (201) forwardly and reversely; and
reverse rotation controlling means (700) for causing said starter motor (1) to rotate reversely after said engine stops,
wherein maximum generated torque of said starter motor is equal to or lower than approximately 60% of maximum cranking torque necessary for a piston to overcome a compression stroke upon starting of said engine but is equal to or higher than cranking torque necessary for said piston to proceed in any other stroke than the compression stroke, and the maximum generated torque of said starter motor is selected so that an inertial mass of said crankshaft directly coupled to said starter motor may be equal to an upper limit of an optimum range therefor.
2. An engine starting apparatus as claimed in claim 1 wherein the maximum generated torque of said starter motor is equal to or higher than approximately 20% of the maximum cranking torque.
3. An engine starting apparatus as claimed in any one of the preceding claims comprising means for reducing, upon starting of said engine, the internal pressure of a cylinder in the compression stroke for a period for which the speed of said engine is equal to or lower than a predetermined reference speed.
4. An engine starting apparatus according to any one of claims 1 to 3, wherein the speed of said engine immediately before said piston enters the compression stroke ranges from 700 to 900 rpm.
5. An engine starting apparatus substantially as herein described with reference to the accompanying drawings.
Dated this 22nd Day of March, 2002
[RITUSHKA NEGI]
OF REMFRY & SAGAR
ATTORNEY FOR THE APPLICANTS

Documents:

284-mum-2002-abstract(3-4-2007).doc

284-mum-2002-abstract(3-4-2007).pdf

284-mum-2002-cancelled pages(3-4-2007).pdf

284-mum-2002-claims(granted)-(3-4-2007).doc

284-mum-2002-claims(granted)-(3-4-2007).pdf

284-mum-2002-correspondence(30-3-2007).pdf

284-mum-2002-correspondence(ipo)-(21-12-2006).pdf

284-mum-2002-drawing(3-4-2007).pdf

284-mum-2002-form 1(22-3-2002).pdf

284-mum-2002-form 1(3-4-2007).pdf

284-mum-2002-form 18(10-2-2006).pdf

284-mum-2002-form 2(granted)-(3-4-2007).doc

284-mum-2002-form 2(granted)-(3-4-2007).pdf

284-mum-2002-form 3(22-3-2002).pdf

284-mum-2002-form 3(3-4-2007).pdf

284-mum-2002-form 5(22-3-2002).pdf

284-mum-2002-petition under rule137(3-4-2007).pdf

284-mum-2002-petition under rule138(21-3-2007).pdf

284-mum-2002-power of authority(1-7-2002).pdf

284-mum-2002-power of authority(3-4-2007).pdf

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Patent Number

215132

Indian Patent Application Number

284/MUM/2002

PG Journal Number

13/2008

Publication Date

28-Mar-2008

Grant Date

21-Feb-2008

Date of Filing

22-Mar-2002

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	MASAYUKI TORIYAMA	C/O KABUSHIKI KAISHA HONDA GIJUTSU KENKYUSHO, 4-1, CHUO 1-CHOME, WAKO-SHI, SAITAMA, JAPAN

PCT International Classification Number

F02D15/00,29/06

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2001-138537	2001-05-09	Japan