Title of Invention	ENGINE FOR BACKBONE TYPE MOTORCYCLE
Abstract	n a backbone type motorcycle, space between the cylinder head and the backbone will be enlarged to thereby reduce the bending of the air intake system as far as possible with the aim of reducing the intake air resistance. In a motorcycle in which an engine main unit 20 of an engine E to be suspended from a backbone 2 inclining downward toward the rear from a head pipe 1 is constructed by a crankcase 21 for supporting a crankshaft 28; a cylinder block 22 which is arranged such that an axis Ab of a cylinder bore 22a inclines at a small gradient [alpha] upwardly toward the front; and a cylinder head 23 to be connected to the front end of the cylinder block 22, and in which in space 66 between the cylinder head 23 and the backbone 2, there is disposed an air intake system 70, the cylinder block 22 is arranged such that the axis Ab of the cylinder bore 22a offsets S downward with respect to the axis Ac of the crankshaft 28.

Title of Invention

ENGINE FOR BACKBONE TYPE MOTORCYCLE

Abstract

n a backbone type motorcycle, space between the cylinder head and the backbone will be enlarged to thereby reduce the bending of the air intake system as far as possible with the aim of reducing the intake air resistance. In a motorcycle in which an engine main unit 20 of an engine E to be suspended from a backbone 2 inclining downward toward the rear from a head pipe 1 is constructed by a crankcase 21 for supporting a crankshaft 28; a cylinder block 22 which is arranged such that an axis Ab of a cylinder bore 22a inclines at a small gradient [alpha] upwardly toward the front; and a cylinder head 23 to be connected to the front end of the cylinder block 22, and in which in space 66 between the cylinder head 23 and the backbone 2, there is disposed an air intake system 70, the cylinder block 22 is arranged such that the axis Ab of the cylinder bore 22a offsets S downward with respect to the axis Ac of the crankshaft 28.

Full Text	FORM 2 THE PATENTS ACT 1970 [39 OF 1970] COMPLETE SPECIFICATION [See Section 10] "ENGINE FOR BACKBONE TYPE MOTORCYCLE" HONDA GIKEN KOGYO KABUSHIKI KAISHA, a corporation of Japan, having a place of business at 1-1, Minamiaoyama 2-chome, Minato-ku, Tokyo, Japan, The following specification particularly describes the nature of the invention and the manner in which it is to be performed:- [Detailed Description of the Invention] [0001] [Technical Field of the Invention] The present invention relates to a backbone type motorcycle in which an engine main unit of an engine to be suspended from a backbone extending obliquely downward toward the rear from a head pipe of a vehicle body frame is constructed by a crankcase for supporting a crankshaft; a cylinder block which protrudes forward from the crankcase and is arranged such that the axis of a cylinder bore inclines upwardly toward the front; and a cylinder head to be connected to a front end of the cylinder block, and in which in space between the cylinder head and the backbone, there is disposed an air intake system of the engine, and more particularly to an improvement of the motorcycle engine. [0002] [Prior Art] As disclosed in, for example, Unexamined Patent Publication No. 2000-249028, the motorcycle has already been known. [0003] [Problems to be solved by the Invention] In such a motorcycle, the backbone extending obliquely downward toward the rear from a head pipe of the vehicle body frame has the advantage of facilitating ingress and egress of a rider by avoiding any interference with the rider"s legs. Also, the cylinder block which protrudes forward from the crankcase is arranged such that the axis of the cylinder bore inclines upwardly toward the front. This is because installation space for the air intake system is secured between the cylinder head and the backbone while natural flow of the oil, which has completed the lubrication of a valve train within the cylinder head, to the crankcase side is being furthered. [0004] In the motorcycle, in order to reduce intake air resistance by reducing the bending of the air intake system as far as possible with the aim of improving the engine output and low fuel consumption, it is required to enlarge space between the cylinder head and the backbone. [0005] It is an object of the present invention to provide an engine for the backbone type motorcycle, capable of satisfying the above-described request even if a forward upward-pointing angle of the axis of the cylinder bore is not changed. [0006] [Means for solving the Problems] In order to achieve the above-described object, according to a first special feature of the present invention, there is provided a backbone type motorcycle in which an engine main unit of an engine to be suspended from a backbone extending obliquely downward toward the rear from a head pipe of the vehicle body frame is constructed by a crankcase for supporting a crankshaft; a cylinder block which protrudes forward from the crankcase and is arranged such that the axis of a cylinder bore inclines upwardly toward the front; and a cylinder head to be connected to the front end of the cylinder block, and in which in space between the cylinder head and the backbone, there is disposed an air intake system of the engine, characterized in that the cylinder block is arranged such that the axis of the cylinder bore offsets downward with respect to the axis of the crankshaft. [0007] According to this first special feature, the cylinder block and the cylinder head make a displacement downward with respect to the crankcase while maintaining an inclined state of the axis of the cylinder bore, and it is possible to enlarge the space between the cylinder head and the backbone. Accordingly, the bending of the air intake system to be disposed in the space is reduced to thereby reduce the intake air resistance, thus making it possible to improve the output performance and low fuel consumption of the engine. [0008] Also, the offset of the axis of the cylinder bore with respect to the axis of the crankshaft reduces the side thrust exerting on the piston at the maximum pressure in the expansion stroke of the engine, and the sliding frictional resistance of the piston is reduced, thus making it possible to further improve the low fuel consumption. [0009] Also, a second special feature according to the present invention is, in addition to the first special feature, that the cylinder head is arranged such that the axis of the camshaft for the valve to be supported by the cylinder head offsets downward with respect to the axis of the cylinder bore. [0010] According to this second special feature, the cylinder head makes a displacement downward by two stages with respect to the crankcase, and it is possible to further enlarge the space between the cylinder head and the backbone. The bending of the air intake system to be disposed in the space is further reduced, thus making it possible to effectively reduce the intake air resistance. [0011] Also, a third special feature according to the present invention is, in addition to the first or second special feature, that a starting motor is mounted onto the upper part of the crankcase at the front of the crankshaft, and immediately behind this starting motor and substantially right above the crankcase, a hanger boss to be suspended from the backbone is formed on the top surface of the crankcase. [0012] According to this third special feature, the starting motor can be set up on the crankcase while comparatively wide space between the crankcase and the backbone is being utilized. Moreover, since it is to be set up at a place near the center of gravity of the engine, the hanger boss is less affected by vibrations of the engine, and accordingly vibrations from the hanger boss are less transmitted to the backbone, thus making it possible to contribute to the improved ride quality. [0013] Further, a fourth special feature according to the present invention is, in addition to the third special feature, that an input shaft and an output shaft of a transmission to be installed in the crankcase are arranged in parallel with the crankshaft respectively and that the input shaft is arranged at a higher position than the crankshaft and the output shaft. [0014] According to this fourth special feature, the distance between the crankshaft and the output shaft is shortened, and it is possible to miniaturize the crankcase, and accordingly to miniaturize the engine. Moreover, since the hanger boss occupies a position substantially right above the crankshaft, even when it is necessary to upwardly bulge a part of an upper wall of the crankcase right above the input shaft along with an upper offset of the input shaft with respect to the crankshaft and the output shaft, it is possible to avoid any interference between the bulged portion and the hanger boss. [Brief Description of the Drawings], -Fig. 1 is a side view showing a bacKbone type motorcycle according to a first embodiment of the present invention; ---Fig-,-2 is a verrtica1 enlarged.plan.view showing-the engine along,line 2-2 of Fig. 1; Fig. 3 is a cross-sectional view taken on line 3-3 of Fig. 2; Fig. 4 is.a cross-sectional view.taken on line 4-4 of Fig. 2; and Fig. 5 is a cross-sectional view corresponding to Fig. 3, showing a second embodiment of the present invention. [Embodiments of the Invention] The description will be made of embodiments according to the present invention with reference to one embodiment" of the present invention shown in the accompanying drawings. [0016] Figs. 1 to 4 show a first embodiment according to the present invention, and Pig. 1 is a side view showing a backbone type motorcycle; Fig. 2 is a vertical enlarged plan view showing an engine along line 2-2 of Fig. 1; Fig. 3 is a cross-sectional view taken on line 3-3 of Fig. 2; Fig. 4 is a cross - sectional view taken on line 4-4 of Fig. 2; and Fig. 5 is a cross- sectional view corresponding to Pig. 3, showing the second embodiment according to the present invention. [0017] In this respect, in the following description, "before and behind", and "right and left" mean with reference to a motorcycle M, to which the present invention is applied. [0018] First, the first embodiment according to the present invention shown in Figs. 1 to 4 will be described. In Figs. 1 and 3, a vehicle body frame F of a motorcycle M is composed of a head pipe 1; a backbone 2 made of steel pipe welded to this head pipe 1, extending obliquely downward toward the rear; and a rear frame 3 made of steel pipe, welded to the rear end of the backbone 2. On the head pipe 1, a front fork 5 for supporting the front wheel 4f is pivotally supported so as to be able to be steered. [0019] At the rear end portion of the rear frame 3, there is welded a center bracket 7 extending downward, and a rear fork 6 for supporting the rear wheel 4r is pivotally supported by the center bracket 7 through a pivot shaft 8. Between this rear fork 6 and the rear frame 3, there is coupled a rear cushion 9 . Also, on the top surface of the rear frame 3, there are mounted a glove compartment 10 containing a helmet and the like and a fuel tank 11 before or behind, and on top of them, a seat 12 is provided so as to be able to be opened and closed. [0020] A single-cylinder engine E is suspended from the backbone 2. This engine E is covered together with the backbone 2 with a body cover 13 and at the front end portion of the body cover 13, there are coupled a pair of leg shields 23,23 which overhang toward the right and left outer sides. [0021] As shown in Figs. 2 to 4, in the single-cylinder engine E, the engine main unit 20 is composed of a crankcase 21; a cylinder block 22 coupled to the crankcase 21 for protruding forward; and a cylinder head 23 to be connected to the front end of the cylinder block 22. In the crankcase 21, there are integrally formed one upper hanger boss 24 on its top surface, and a pair of upper and lower rear hanger bosses 25, 25 on the rear surface. The upper hanger boss 24 is fixed to a front bracket 15 protruding downward in the intermediate portion of the backbone 2, and the rear hanger bosses 25, 25 are fixed to the center bracket 7 through the use of bolts 26 respectively. [0022] The crankcase 21 is composed of a left side case half 21a and a right side case half 21b, which are obtained by dividing into right and left by a vertical plane P including the axis of the backbone 2, the crankshaft 28 arranged from side to side in the horizontal direction is supported by both case halves 21a, 21b through a pair of right and left bearings 27, 27 " . To this crankshaft 2 8, a piston 29, which slides within a single cylinder bore 22a which the cylinder block 22 has, is connected through a connecting rod 30. [0023] The cylinder block 22 is arranged such that the axis Ab of its cylinder bore 22a is located on the vertical plane P and inclines at a small gradient a upward toward the front. [0024] The cylinder head 23 is formed with a combustion chamber 31 which the top face of the piston 29 faces; an intake port 32 connected to this combustion chamber 31, which is opened on the top surface of the cylinder head 23; and an exhaust port 33 connected to the same combustion chamber 31, which is opened on the underside of the cylinder head 23, and there are mounted an intake valve 34 and an exhaust valve 35 which open or close those intake and exhaust ports 32, 33. Thus, a valve train 36 for open-close driving the intake and exhaust valves 34, 35 is provided in a valve chamber 37 of the cylinder head 23. [0025] This valve train 36 is composed of a camshaft 38 to be supported by a cylinder head 23 in parallel with the crankshaft 28 in an intermediate portion between the intake and exhaust valves 34, 35 through a pair of left and right bearings 39, 39" ; an intake rocker arm 40 to be supported by a cylinder head 23 to perform an interlock between this camshaft 38 and the intake valve 34; an exhaust rocker arm 41 to be supported by the cylinder head 23 to perform an interlock between the camshaft 38 and the exhaust valve 35; and valve springs 42, 43 for biasing the intake and exhaust valves 34, 35 in a direction to close respectively. [0026] The camshaft 38 is coupled to the crankshaft 28 through a timing transmission device 61. This timing transmission device 61 is composed of: a drive sprocket 62 to be fixed to the crankshaft 28 adjacent to the outer side of a left-side bearing 27 for supporting the crankshaft 28; a driven sprocket 63 to be fixed to one end of the camshaft 38; and an endless timing chain 64 to be spanned between both sprockets 62, 63, and is capable of transmitting the rotation of the crankshaft 28 to the camshaft 38 at a speed reducing ratio of 1/2. The timing chain 64 is housed in a timing chain passage 65 formed on one side wall of the cylinder block 22. [0027] The cylinder block 22 is arranged such that an axis Ab of its cylinder bore 22a is offset by a distance S downward with respect to an axis Ac of the crankshaft 28, and the cylinder head 23 is arranged such that an axis Am of the camshaft 38 is offset by a distance S" below an axis Ab of the cylinder bore 22a. By such offset in two stages, the cylinder head 23 is to make a displacement by two stages below the crankcase 21 while maintaining the inclined state of the cylinder bore 22a, whereby space 66 between the cylinder head 23 and the backbone 2 can be effectively enlarged. [0028] Again in Figs. 1 and 3, an air intake system 70 of the engine E is disposed in the space 66. An intake pipe 71 constituting a part of the air intake system 70 is combined with the top surface of the cylinder head 23 so as to communicate to the intake port 32. This intake pipe 71 is bent forward along the underside of the backbone 2 after it rises upwardly from the cylinder head 23. A side draft type carburetor 72 is connected to the end portion, that is, an upstream end of the intake pipe 71, and an air cleaner 73 is connected to the intake port thereof. Thus, the air intake system 70 is constituted. [0029] Since the space 66 between the cylinder head 23 and the backbone 2, in which this air intake system 70 is disposed, is enlarged as described above, it becomes possible to set the radius of curvature of the bent portion of the intake pipe 71 to a high value, and as a result, intake air resistance within the intake pipe 71 decreases, thus making it possible to increase the engine output and improve the low fuel consumption. [0030] Moreover, since the axis Ab of the cylinder bore 22a inclines at a small gradient a upward toward the front as in the conventional case, the timing chain passage 65 also inclines similarly. Therefore, oil which has been supplied to the valve train 36 of the cylinder head 23 from an oil reservoir at the bottom within the crankcase 21 by an oil pump (not shown) is, after the lubrication, capable of flowing through the timing chain passage 65 in a natural state and returning to the oil reservoir. [0031] Also, according to the offset of the axis Ab of the cylinder bore 22a with respect to the axis Ac of the crankshaft 28, at the maximum pressure in the expansion stroke of the engine E, the side thrust exerting on the piston 29 decreases, and sliding frictional resistance of the piston 29 decreases to enable the low fuel consumption to be further improved. [0032] On the underside of the cylinder head 23, an exhaust pipe 81 communicating to the exhaust port 33 is combined, and this exhaust pipe 81 is bent backward for extending, and is connected to a muffler (not shown) to be arranged on one side of the rear wheel 4r. [0033] In Figs. 2 and 3, at one end portion of the crankshaft 28, a rotor 76 of the alternator 75 is key-combined, and this rotor 76 and a starting gear 77 to be rotatably supported by the crankshaft 28 are combined with each other through an one-way clutch 78. The one-way clutch 78 is adapted to be able to transmit a rotating force only in one direction from the starting gear 77 to the rotor 76, and a starting motor 80 for driving the starting gear 77 through the deceleration gear train 79 is mounted onto the upper part of the crankcase 21 on the front side of this crankshaft 28. Immediately behind this starting motor 80 and substantially right above the crankshaft 28, a front hanger boss 24 for hanging the engine is arranged. [0034] Thus, the starting motor 80 can be set up on the crankcase 21 while comparatively wide space 66 between the crankcase 21 and the backbone 2 is being utilized. Moreover, since it is to be set up at a place hear the center of gravity of the engine E, the upper hanger boss 24 is less affected by vibrations of the engine E, and accordingly vibrations from the upper hanger boss 24 are less transmitted to the backbone 2, thus making it possible to contribute to the improved ride quality. [0035] In Figs. 2 and 3, the crankcase 21 contains a transmission 85 having an input shaft 86 and an output shaft 87 which are arranged in parallel with the crankshaft 28. At this time, the input and output shafts 86 and 87 are supported by the crankcase 21 through a pair of l^ft and right bearings 94, 94"; 95, 95" respectively. Between these input and output shafts 86, 87, transmission gear trains 881 to 88n each having plural stages are constituted. Generated power from the crankshaft 28 is transmitted to the input shaft 86 through a centrifugal clutch 89, a primary deceleration gear train 90 and a transmission clutch 91, is transmitted from the input shaft 86 to the output shaft 87 through one transmission gear train selected, and further is transmitted to the rear wheel 4r through a chain transmission device 92 to be disposed outside the crankcase 21 to drive it. [0036] In the transmission 85, the output shaft 87 is arranged on a horizontal plane substantially flush with the crankshaft 28, and the input shaft 86 is arranged at an intermediate position between the crankshaft 28 and the output shaft 87 by offsetting above these shafts. Further, above the input shaft 86, there is arranged a shift drum 93 for selecting transmission gear trains 881 to 88n. [0037] When performed as described above, the distance between the crankshaft 28 and the output shaft 87 is shortened, and it is possible to miniaturize the crankcase 21, and accordingly to miniaturize the engine E. Moreover, since the front hanger boss 24 occupies a position substantially right above the crankshaft 28, even when it is necessary to upwardly bulge a part of an upper wall of the crankcase 21 right above the input shaft 86 along with the upper offset of the input shaft 86 with respect to the crankshaft 28 and the output shaft 87, it is possible to avoid any interference between the bulged portion and the front hanger boss 24. [0038] Next, the description will be made of a second embodiment according to the present invention shown in Fig. 5. [0039] In this second embodiment, the cylinder block 22 and the cylinder head 23 of the engine E are formed with a water jacket 96. Only the axis Ab of the cylinder bore 22a of the cylinder block 22 is offset by a distance S downward with respect to the axis Ac of the crankshaft 28. In other words, the axis Am of the camshaft 38 is arranged on the axis Ab of the cylinder bore 22a. The upper hanger boss 24 is integrally formed on the upper wall of the cylinder block 22. Also, in the air intake system 70, a throttle body 172 is provided in place of the carburetor 72 of the preceding embodiment, and accordingly to the intake pipe 71, there is mounted a fuel injection valve 74 capable of injecting fuel toward the outlet of the intake port 32. [0040] The input shaft 86 and output shaft 87 of the transmission 85 are arranged on a horizontal plane substantially flush with the crankshaft 28. [0041] Since substantially the same as in the preceding embodiment in other structure, portions corresponding to the preceding embodiment in Fig. 5 are designated by the identical reference numerals, and the description thereof will be omitted. [0042] The present invention is not limited to the above-described embodiments, but various changes in design can be performed without departing from the gist of the present invention. [0043] [Effect of the Invention] As described above, according to the first special feature of the present invention, in a backbone type motorcycle in which an engine main unit of an engine to be suspended from a backbone extending obliquely downward toward the rear from a head pipe of the vehicle body frame is constructed by a crankcase for supporting a crankshaft; a cylinder block which protrudes forward from the crankcase and is arranged such that the axis of a cylinder bore inclines upwardly toward the front; and a cylinder head to be connected to the front end of the cylinder block, and in which in space between the cylinder head and the backbone, there is disposed an air intake system of the engine, the cylinder block is arranged such that the axis of the cylinder bore offsets downward with respect to the axis of the crankshaft. Therefore, the cylinder block and the cylinder head make a displacement downward with respect to the crankcase while maintaining an inclined state of the axis of the cylinder bore, and it is possible to enlarge the space between the cylinder head and the backbone. Accordingly, the bending of the air intake system to be disposed in the space is reduced to thereby reduce the intake air resistance, thus making it possible to improve the output performance and low fuel consumption of the engine. Also, the offset of the axis of the cylinder bore with respect to the axis of the crankshaft reduces the side thrust exerting on the piston at the maximum pressure in the expansion stroke of the engine, and the sliding frictional resistance of the piston is reduced, thus making it possible to further improve the low fuel consumption. [0044] Also, according to the second special feature of the present invention, since the cylinder head is arranged such that the axis of the camshaft for the valve to be supported by the cylinder head offsets downward with respect to the axis of the cylinder bore in addition to the first special feature, the cylinder head makes a displacement downward by two stages with respect to the crankcase, and the space between the cylinder head and the backbone can be further enlarged, and the bending of the air intake system to be disposed in the space is further reduced, thus making it possible to effectively reduce the intake air resistance. [0045] Further according to the third special feature of the present invention, in addition to the first or second special feature, a starting motor is mounted onto the upper part of the crankcase at the front of the crankshaft, and immediately behind this starting motor and substantially right above the crankcase, a hanger boss to be suspended from the backbone is formed on the top surface of the crankcase. Therefore, the starting motor can be set up on the crankcase while comparatively wide space between the crankcase and the backbone is being utilized. Moreover, since it is to be set up at a place near the center of gravity of the engine, the hanger boss is less affected by vibrations of the engine, and accordingly vibrations from the hanger boss are less transmitted to the backbone, thus making it possible to contribute to the improved ride quality. [0046] Furthermore, according to the fourth special feature of the present invention, in addition to the third special feature, an input shaft and an output shaft of a transmission to be installed in the crankcase are arranged in parallel with the crankshaft respectively and the input shaft is arranged at a higher position than the crankshaft and the output shaft. Therefore, the distance between the crankshaft and the output shaft is shortened, and it is possible to miniaturize the crankcase^ an^accordingly to miniaturize the engine . Moreover, since the hanger boss occupies a position substantially right above the crankshaft, even when it is necessary to upwardly bulge a part of an upper wall of the crankcase right above the input shaft along with the upper offset of the input shaft with respect to the crankshaft and the output shaft, it is possible to avoid any interference between the bulged portion and the hanger boss. [Description of the Symbols] E. . . Engine F... Vehicle body frame M... Motorcycle S. . . Lower offset amount of the cylinder bore axis with respect to the crankshaft axis S"... Lower offset amount of the camshaft axis with respect to the cylinder bore axis 1. .. Head pipe 2 . . . Backbone 20... Engine main unit 21... Crankcase 22... Cylinder block 23... Cylinder head 24... Hanger boss (front hanger boss) 28... Crankshaft 38... Camshaft 66... Space 70... Air intake system 80... starting motor 85... Transmission 86... Input shaft 87... Output shaft We claim: 1. An engine in a backbone type motorcycle in which an engine main unit (20) of an engine (E) to be suspended from a backbone (2) extending obliquely downward toward the rear from a head pipe (1) of a vehicle body frame (F) is constructed by a crankcase (21) for supporting a crankshaft (28); a cylinder block (22) which protrudes forward from the crankcase (21) and is arranged such that an axis (Ab) of a cylinder bore (22a) inclines upwardly toward the front; and a cylinder head (23) to be connected to the front end of the cylinder block (22), and in which in space (66) between said cylinder head (23) and said backbone (2), there is disposed an air intake system (70) of said engine (E), characterized in that said cylinder block (22) is arranged such that the axis (Ab) of said cylinder bore (22a) offsets (S) downward with respect to the axis (Ac) of said crankshaft and said cylinder head (23) is arranged such that an axis (Am) of a camshaft (38) for the valve to be supported by said cylinder head (23) offsets (S") downward with respect to an axis (Ab) of said cylinder bore (22a). 2. The engine in a backbone type motorcycle as claimed in claim 1, wherein a starting motor (80) is mounted onto an upper part of said crankcase (21) at the front of said crankshaft (28), and immediately behind said starting motor (80) and substantially right above said crankcase (28), a hanger boss (24) to be suspended form said backbone (2) is formed on a top surface of said crankcase (21). 3. The engine in a backbone type motorcycle as claimed in claim 2, wherein an input shaft (86) and an output shaft (87) of a transmission (85) to be installed in said crankcase (21) are arranged in parallel with said crankshaft (28) respectively and that said input shaft (86) is arranged at a higher position than said crankshaft (28) and said output shaft (87). Dated this 27.11.2001 RITUSHKA NEGI OF REMFRY & SAGAR ATTORNEY FOR THE APPLICANT[S]

Full Text

FORM 2
THE PATENTS ACT 1970
[39 OF 1970]
COMPLETE SPECIFICATION
[See Section 10]
"ENGINE FOR BACKBONE TYPE MOTORCYCLE"
HONDA GIKEN KOGYO KABUSHIKI KAISHA, a corporation of Japan, having a place of business at 1-1, Minamiaoyama 2-chome, Minato-ku, Tokyo, Japan,
The following specification particularly describes the nature of the invention and the manner in which it is to be performed:-

[Detailed Description of the Invention] [0001]
[Technical Field of the Invention]
The present invention relates to a backbone type motorcycle in which an engine main unit of an engine to be suspended from a backbone extending obliquely downward toward the rear from a head pipe of a vehicle body frame is constructed by a crankcase for supporting a crankshaft; a cylinder block which protrudes forward from the crankcase and is arranged such that the axis of a cylinder bore inclines upwardly toward the front; and a cylinder head to be connected to a front end of the cylinder block, and in which in space between the cylinder head and the backbone, there is disposed an air intake system

of the engine, and more particularly to an improvement of the
motorcycle engine.
[0002]
[Prior Art]
As disclosed in, for example, Unexamined Patent Publication No. 2000-249028, the motorcycle has already been known. [0003]
[Problems to be solved by the Invention]
In such a motorcycle, the backbone extending obliquely downward toward the rear from a head pipe of the vehicle body frame has the advantage of facilitating ingress and egress of a rider by avoiding any interference with the rider"s legs. Also, the cylinder block which protrudes forward from the crankcase is arranged such that the axis of the cylinder bore inclines upwardly toward the front. This is because installation space for the air intake system is secured between the cylinder head and the backbone while natural flow of the oil, which has completed the lubrication of a valve train within the cylinder head, to the crankcase side is being furthered. [0004]
In the motorcycle, in order to reduce intake air resistance by reducing the bending of the air intake system as far as possible with the aim of improving the engine output and low fuel consumption, it is required to enlarge space between the cylinder head and the backbone. [0005]
It is an object of the present invention to provide an

engine for the backbone type motorcycle, capable of satisfying the above-described request even if a forward upward-pointing angle of the axis of the cylinder bore is not changed. [0006]
[Means for solving the Problems]
In order to achieve the above-described object, according to a first special feature of the present invention, there is provided a backbone type motorcycle in which an engine main unit of an engine to be suspended from a backbone extending obliquely downward toward the rear from a head pipe of the vehicle body frame is constructed by a crankcase for supporting a crankshaft; a cylinder block which protrudes forward from the crankcase and is arranged such that the axis of a cylinder bore inclines upwardly toward the front; and a cylinder head to be connected to the front end of the cylinder block, and in which in space between the cylinder head and the backbone, there is disposed an air intake system of the engine, characterized in that the cylinder block is arranged such that the axis of the cylinder bore offsets downward with respect to the axis of the crankshaft. [0007]
According to this first special feature, the cylinder block and the cylinder head make a displacement downward with respect to the crankcase while maintaining an inclined state of the axis of the cylinder bore, and it is possible to enlarge the space between the cylinder head and the backbone. Accordingly, the bending of the air intake system to be disposed in the space is reduced to thereby reduce the intake air

resistance, thus making it possible to improve the output performance and low fuel consumption of the engine. [0008]
Also, the offset of the axis of the cylinder bore with respect to the axis of the crankshaft reduces the side thrust exerting on the piston at the maximum pressure in the expansion stroke of the engine, and the sliding frictional resistance of the piston is reduced, thus making it possible to further improve the low fuel consumption. [0009]
Also, a second special feature according to the present invention is, in addition to the first special feature, that the cylinder head is arranged such that the axis of the camshaft for the valve to be supported by the cylinder head offsets downward with respect to the axis of the cylinder bore. [0010]
According to this second special feature, the cylinder head makes a displacement downward by two stages with respect to the crankcase, and it is possible to further enlarge the space between the cylinder head and the backbone. The bending of the air intake system to be disposed in the space is further reduced, thus making it possible to effectively reduce the intake air resistance. [0011]
Also, a third special feature according to the present invention is, in addition to the first or second special feature, that a starting motor is mounted onto the upper part of the crankcase at the front of the crankshaft, and immediately

behind this starting motor and substantially right above the crankcase, a hanger boss to be suspended from the backbone is formed on the top surface of the crankcase. [0012]
According to this third special feature, the starting motor can be set up on the crankcase while comparatively wide space between the crankcase and the backbone is being utilized. Moreover, since it is to be set up at a place near the center of gravity of the engine, the hanger boss is less affected by vibrations of the engine, and accordingly vibrations from the hanger boss are less transmitted to the backbone, thus making it possible to contribute to the improved ride quality. [0013]
Further, a fourth special feature according to the present invention is, in addition to the third special feature, that an input shaft and an output shaft of a transmission to be installed in the crankcase are arranged in parallel with the crankshaft respectively and that the input shaft is arranged at a higher position than the crankshaft and the output shaft. [0014]
According to this fourth special feature, the distance between the crankshaft and the output shaft is shortened, and it is possible to miniaturize the crankcase, and accordingly to miniaturize the engine. Moreover, since the hanger boss occupies a position substantially right above the crankshaft, even when it is necessary to upwardly bulge a part of an upper wall of the crankcase right above the input shaft along with

an upper offset of the input shaft with respect to the crankshaft and the output shaft, it is possible to avoid any interference between the bulged portion and the hanger boss.

[Brief Description of the Drawings],
-Fig. 1 is a side view showing a bacKbone type motorcycle according to a first embodiment of the present invention;
---Fig-,-2 is a verrtica1 enlarged.plan.view showing-the engine along,line 2-2 of Fig. 1;
Fig. 3 is a cross-sectional view taken on line 3-3 of
Fig. 2;
Fig. 4 is.a cross-sectional view.taken on line 4-4 of

Fig. 2; and
Fig. 5 is a cross-sectional view corresponding to Fig.
3, showing a second embodiment of the present invention.

[Embodiments of the Invention]
The description will be made of embodiments according to the present invention with reference to one embodiment" of the present invention shown in the accompanying drawings. [0016]
Figs. 1 to 4 show a first embodiment according to the present invention, and Pig. 1 is a side view showing a backbone type motorcycle; Fig. 2 is a vertical enlarged plan view showing an engine along line 2-2 of Fig. 1; Fig. 3 is a cross-sectional view taken on line 3-3 of Fig. 2; Fig. 4 is a cross - sectional view taken on line 4-4 of Fig. 2; and Fig. 5 is a cross- sectional view corresponding to Pig. 3, showing the second embodiment

according to the present invention. [0017]
In this respect, in the following description, "before and behind", and "right and left" mean with reference to a motorcycle M, to which the present invention is applied. [0018]
First, the first embodiment according to the present invention shown in Figs. 1 to 4 will be described. In Figs. 1 and 3, a vehicle body frame F of a motorcycle M is composed of a head pipe 1; a backbone 2 made of steel pipe welded to this head pipe 1, extending obliquely downward toward the rear; and a rear frame 3 made of steel pipe, welded to the rear end

of the backbone 2. On the head pipe 1, a front fork 5 for supporting the front wheel 4f is pivotally supported so as to be able to be steered. [0019]
At the rear end portion of the rear frame 3, there is welded a center bracket 7 extending downward, and a rear fork 6 for supporting the rear wheel 4r is pivotally supported by the center bracket 7 through a pivot shaft 8. Between this rear fork 6 and the rear frame 3, there is coupled a rear cushion 9 . Also, on the top surface of the rear frame 3, there are mounted a glove compartment 10 containing a helmet and the like and a fuel tank 11 before or behind, and on top of them, a seat 12 is provided so as to be able to be opened and closed. [0020]
A single-cylinder engine E is suspended from the backbone 2. This engine E is covered together with the backbone 2 with a body cover 13 and at the front end portion of the body cover 13, there are coupled a pair of leg shields 23,23 which overhang toward the right and left outer sides. [0021]
As shown in Figs. 2 to 4, in the single-cylinder engine E, the engine main unit 20 is composed of a crankcase 21; a cylinder block 22 coupled to the crankcase 21 for protruding forward; and a cylinder head 23 to be connected to the front end of the cylinder block 22. In the crankcase 21, there are integrally formed one upper hanger boss 24 on its top surface, and a pair of upper and lower rear hanger bosses 25, 25 on the rear surface. The upper hanger boss 24 is fixed to a front

bracket 15 protruding downward in the intermediate portion of the backbone 2, and the rear hanger bosses 25, 25 are fixed to the center bracket 7 through the use of bolts 26 respectively. [0022]
The crankcase 21 is composed of a left side case half 21a and a right side case half 21b, which are obtained by dividing into right and left by a vertical plane P including the axis of the backbone 2, the crankshaft 28 arranged from side to side in the horizontal direction is supported by both case halves 21a, 21b through a pair of right and left bearings 27, 27 " . To this crankshaft 2 8, a piston 29, which slides within a single cylinder bore 22a which the cylinder block 22 has, is connected through a connecting rod 30. [0023]
The cylinder block 22 is arranged such that the axis Ab of its cylinder bore 22a is located on the vertical plane P and inclines at a small gradient a upward toward the front. [0024]
The cylinder head 23 is formed with a combustion chamber
31 which the top face of the piston 29 faces; an intake port
32 connected to this combustion chamber 31, which is opened on the top surface of the cylinder head 23; and an exhaust port
33 connected to the same combustion chamber 31, which is opened on the underside of the cylinder head 23, and there are mounted an intake valve 34 and an exhaust valve 35 which open or close those intake and exhaust ports 32, 33. Thus, a valve train 36 for open-close driving the intake and exhaust valves 34, 35 is provided in a valve chamber 37 of the cylinder head 23.

[0025]
This valve train 36 is composed of a camshaft 38 to be supported by a cylinder head 23 in parallel with the crankshaft 28 in an intermediate portion between the intake and exhaust valves 34, 35 through a pair of left and right bearings 39, 39" ; an intake rocker arm 40 to be supported by a cylinder head 23 to perform an interlock between this camshaft 38 and the intake valve 34; an exhaust rocker arm 41 to be supported by the cylinder head 23 to perform an interlock between the camshaft 38 and the exhaust valve 35; and valve springs 42, 43 for biasing the intake and exhaust valves 34, 35 in a direction to close respectively. [0026]
The camshaft 38 is coupled to the crankshaft 28 through a timing transmission device 61. This timing transmission device 61 is composed of: a drive sprocket 62 to be fixed to the crankshaft 28 adjacent to the outer side of a left-side bearing 27 for supporting the crankshaft 28; a driven sprocket 63 to be fixed to one end of the camshaft 38; and an endless timing chain 64 to be spanned between both sprockets 62, 63, and is capable of transmitting the rotation of the crankshaft 28 to the camshaft 38 at a speed reducing ratio of 1/2. The timing chain 64 is housed in a timing chain passage 65 formed on one side wall of the cylinder block 22. [0027]
The cylinder block 22 is arranged such that an axis Ab of its cylinder bore 22a is offset by a distance S downward with respect to an axis Ac of the crankshaft 28, and the cylinder

head 23 is arranged such that an axis Am of the camshaft 38 is offset by a distance S" below an axis Ab of the cylinder bore 22a. By such offset in two stages, the cylinder head 23 is to make a displacement by two stages below the crankcase 21 while maintaining the inclined state of the cylinder bore 22a, whereby space 66 between the cylinder head 23 and the backbone 2 can be effectively enlarged. [0028]
Again in Figs. 1 and 3, an air intake system 70 of the engine E is disposed in the space 66. An intake pipe 71 constituting a part of the air intake system 70 is combined with the top surface of the cylinder head 23 so as to communicate to the intake port 32. This intake pipe 71 is bent forward along the underside of the backbone 2 after it rises upwardly from the cylinder head 23. A side draft type carburetor 72 is connected to the end portion, that is, an upstream end of the intake pipe 71, and an air cleaner 73 is connected to the intake port thereof. Thus, the air intake system 70 is constituted. [0029]
Since the space 66 between the cylinder head 23 and the backbone 2, in which this air intake system 70 is disposed, is enlarged as described above, it becomes possible to set the radius of curvature of the bent portion of the intake pipe 71 to a high value, and as a result, intake air resistance within the intake pipe 71 decreases, thus making it possible to increase the engine output and improve the low fuel consumption. [0030]

Moreover, since the axis Ab of the cylinder bore 22a inclines at a small gradient a upward toward the front as in the conventional case, the timing chain passage 65 also inclines similarly. Therefore, oil which has been supplied to the valve train 36 of the cylinder head 23 from an oil reservoir at the bottom within the crankcase 21 by an oil pump (not shown) is, after the lubrication, capable of flowing through the timing chain passage 65 in a natural state and returning to the oil reservoir. [0031]
Also, according to the offset of the axis Ab of the cylinder bore 22a with respect to the axis Ac of the crankshaft 28, at the maximum pressure in the expansion stroke of the engine E, the side thrust exerting on the piston 29 decreases, and sliding frictional resistance of the piston 29 decreases to enable the low fuel consumption to be further improved. [0032]
On the underside of the cylinder head 23, an exhaust pipe 81 communicating to the exhaust port 33 is combined, and this exhaust pipe 81 is bent backward for extending, and is connected to a muffler (not shown) to be arranged on one side of the rear wheel 4r. [0033]
In Figs. 2 and 3, at one end portion of the crankshaft 28, a rotor 76 of the alternator 75 is key-combined, and this rotor 76 and a starting gear 77 to be rotatably supported by the crankshaft 28 are combined with each other through an one-way clutch 78. The one-way clutch 78 is adapted to be able

to transmit a rotating force only in one direction from the starting gear 77 to the rotor 76, and a starting motor 80 for driving the starting gear 77 through the deceleration gear train 79 is mounted onto the upper part of the crankcase 21 on the front side of this crankshaft 28. Immediately behind this starting motor 80 and substantially right above the crankshaft 28, a front hanger boss 24 for hanging the engine is arranged. [0034]
Thus, the starting motor 80 can be set up on the crankcase 21 while comparatively wide space 66 between the crankcase 21 and the backbone 2 is being utilized. Moreover, since it is to be set up at a place hear the center of gravity of the engine E, the upper hanger boss 24 is less affected by vibrations of the engine E, and accordingly vibrations from the upper hanger boss 24 are less transmitted to the backbone 2, thus making it possible to contribute to the improved ride quality. [0035]
In Figs. 2 and 3, the crankcase 21 contains a transmission 85 having an input shaft 86 and an output shaft 87 which are arranged in parallel with the crankshaft 28. At this time, the input and output shafts 86 and 87 are supported by the crankcase 21 through a pair of l^ft and right bearings 94, 94"; 95, 95" respectively. Between these input and output shafts 86, 87, transmission gear trains 881 to 88n each having plural stages are constituted. Generated power from the crankshaft 28 is transmitted to the input shaft 86 through a centrifugal clutch 89, a primary deceleration gear train 90 and a transmission clutch 91, is transmitted from the input shaft 86 to the output

shaft 87 through one transmission gear train selected, and further is transmitted to the rear wheel 4r through a chain transmission device 92 to be disposed outside the crankcase 21 to drive it. [0036]
In the transmission 85, the output shaft 87 is arranged on a horizontal plane substantially flush with the crankshaft 28, and the input shaft 86 is arranged at an intermediate position between the crankshaft 28 and the output shaft 87 by offsetting above these shafts. Further, above the input shaft 86, there is arranged a shift drum 93 for selecting transmission gear trains 881 to 88n. [0037]
When performed as described above, the distance between the crankshaft 28 and the output shaft 87 is shortened, and it is possible to miniaturize the crankcase 21, and accordingly to miniaturize the engine E. Moreover, since the front hanger boss 24 occupies a position substantially right above the crankshaft 28, even when it is necessary to upwardly bulge a part of an upper wall of the crankcase 21 right above the input shaft 86 along with the upper offset of the input shaft 86 with respect to the crankshaft 28 and the output shaft 87, it is possible to avoid any interference between the bulged portion and the front hanger boss 24. [0038]
Next, the description will be made of a second embodiment according to the present invention shown in Fig. 5. [0039]

In this second embodiment, the cylinder block 22 and the cylinder head 23 of the engine E are formed with a water jacket 96. Only the axis Ab of the cylinder bore 22a of the cylinder block 22 is offset by a distance S downward with respect to the axis Ac of the crankshaft 28. In other words, the axis Am of the camshaft 38 is arranged on the axis Ab of the cylinder bore 22a. The upper hanger boss 24 is integrally formed on the upper wall of the cylinder block 22. Also, in the air intake system 70, a throttle body 172 is provided in place of the carburetor 72 of the preceding embodiment, and accordingly to the intake pipe 71, there is mounted a fuel injection valve 74 capable of injecting fuel toward the outlet of the intake port 32. [0040]
The input shaft 86 and output shaft 87 of the transmission 85 are arranged on a horizontal plane substantially flush with the crankshaft 28. [0041]
Since substantially the same as in the preceding embodiment in other structure, portions corresponding to the preceding embodiment in Fig. 5 are designated by the identical reference numerals, and the description thereof will be omitted. [0042]
The present invention is not limited to the above-described embodiments, but various changes in design can be performed without departing from the gist of the present invention.

[0043]
[Effect of the Invention]
As described above, according to the first special feature of the present invention, in a backbone type motorcycle in which an engine main unit of an engine to be suspended from a backbone extending obliquely downward toward the rear from a head pipe of the vehicle body frame is constructed by a crankcase for supporting a crankshaft; a cylinder block which protrudes forward from the crankcase and is arranged such that the axis of a cylinder bore inclines upwardly toward the front; and a cylinder head to be connected to the front end of the cylinder block, and in which in space between the cylinder head and the backbone, there is disposed an air intake system of the engine, the cylinder block is arranged such that the axis of the cylinder bore offsets downward with respect to the axis of the crankshaft. Therefore, the cylinder block and the cylinder head make a displacement downward with respect to the crankcase while maintaining an inclined state of the axis of the cylinder bore, and it is possible to enlarge the space between the cylinder head and the backbone. Accordingly, the bending of the air intake system to be disposed in the space is reduced to thereby reduce the intake air resistance, thus making it possible to improve the output performance and low fuel consumption of the engine. Also, the offset of the axis of the cylinder bore with respect to the axis of the crankshaft reduces the side thrust exerting on the piston at the maximum pressure in the expansion stroke of the engine, and the sliding frictional resistance of the piston is reduced, thus making

it possible to further improve the low fuel consumption. [0044]
Also, according to the second special feature of the present invention, since the cylinder head is arranged such that the axis of the camshaft for the valve to be supported by the cylinder head offsets downward with respect to the axis of the cylinder bore in addition to the first special feature, the cylinder head makes a displacement downward by two stages with respect to the crankcase, and the space between the cylinder head and the backbone can be further enlarged, and the bending of the air intake system to be disposed in the space is further reduced, thus making it possible to effectively reduce the intake air resistance. [0045]
Further according to the third special feature of the present invention, in addition to the first or second special feature, a starting motor is mounted onto the upper part of the crankcase at the front of the crankshaft, and immediately behind this starting motor and substantially right above the crankcase, a hanger boss to be suspended from the backbone is formed on the top surface of the crankcase. Therefore, the starting motor can be set up on the crankcase while comparatively wide space between the crankcase and the backbone is being utilized. Moreover, since it is to be set up at a place near the center of gravity of the engine, the hanger boss is less affected by vibrations of the engine, and accordingly vibrations from the hanger boss are less transmitted to the backbone, thus making it possible to contribute to the improved

ride quality. [0046]
Furthermore, according to the fourth special feature of the present invention, in addition to the third special feature, an input shaft and an output shaft of a transmission to be installed in the crankcase are arranged in parallel with the crankshaft respectively and the input shaft is arranged at a higher position than the crankshaft and the output shaft. Therefore, the distance between the crankshaft and the output shaft is shortened, and it is possible to miniaturize the crankcase^ an^accordingly to miniaturize the engine . Moreover, since the hanger boss occupies a position substantially right above the crankshaft, even when it is necessary to upwardly bulge a part of an upper wall of the crankcase right above the input shaft along with the upper offset of the input shaft with respect to the crankshaft and the output shaft, it is possible to avoid any interference between the bulged portion and the hanger boss.

[Description of the Symbols] E. . . Engine
F... Vehicle body frame
M... Motorcycle
S. . . Lower offset amount of the cylinder bore axis with respect
to the crankshaft axis
S"... Lower offset amount of the camshaft axis with respect
to the cylinder bore axis
1. .. Head pipe
2 . . . Backbone
20... Engine main unit
21... Crankcase
22... Cylinder block
23... Cylinder head
24... Hanger boss (front hanger boss)
28... Crankshaft
38... Camshaft
66... Space
70... Air intake system
80... starting motor
85... Transmission
86... Input shaft
87... Output shaft

We claim:
1. An engine in a backbone type motorcycle in which an engine
main unit (20) of an engine (E) to be suspended from a backbone
(2) extending obliquely downward toward the rear from a head pipe
(1) of a vehicle body frame (F) is constructed by a crankcase (21)
for supporting a crankshaft (28); a cylinder block (22) which
protrudes forward from the crankcase (21) and is arranged such
that an axis (Ab) of a cylinder bore (22a) inclines upwardly toward
the front; and a cylinder head (23) to be connected to the front end
of the cylinder block (22), and in which in space (66) between said
cylinder head (23) and said backbone (2), there is disposed an air
intake system (70) of said engine (E), characterized in that
said cylinder block (22) is arranged such that the axis (Ab) of said cylinder bore (22a) offsets (S) downward with respect to the axis (Ac) of said crankshaft and said cylinder head (23) is arranged such that an axis (Am) of a camshaft (38) for the valve to be supported by said cylinder head (23) offsets (S") downward with respect to an axis (Ab) of said cylinder bore (22a).
2. The engine in a backbone type motorcycle as claimed in
claim 1, wherein a starting motor (80) is mounted onto an upper
part of said crankcase (21) at the front of said crankshaft (28), and
immediately behind said starting motor (80) and substantially right
above said crankcase (28), a hanger boss (24) to be suspended
form said backbone (2) is formed on a top surface of said
crankcase (21).

3. The engine in a backbone type motorcycle as claimed in claim 2, wherein an input shaft (86) and an output shaft (87) of a transmission (85) to be installed in said crankcase (21) are arranged in parallel with said crankshaft (28) respectively and that said input shaft (86) is arranged at a higher position than said crankshaft (28) and said output shaft (87).
Dated this 27.11.2001

RITUSHKA NEGI
OF REMFRY & SAGAR
ATTORNEY FOR THE APPLICANT[S]

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Patent Number

214138

Indian Patent Application Number

1132/MUM/2001

PG Journal Number

13/2008

Publication Date

28-Mar-2008

Grant Date

04-Feb-2008

Date of Filing

27-Nov-2001

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	RYO KUBOTA	C/O KABUSHIKI KAISHA HONDA GIJUTSU KENKYUSHO, 4-1, CHUO 1-CHOME, WAKO-SHI, SAITAMA, JAPAN
2	KATSUNORI TAKAHASHI	C/O KABUSHIKI KAISHA HONDA GIJUTSU KENKYUSHO, 4-1, CHUO 1-CHOME, WAKO-SHI, SAITAMA

PCT International Classification Number

F02B 1/00 ; B62K 11/04 ; B62J 37/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2000-403154	2000-12-28	Japan