Vehicle with an internal combustion engine which has a crankshaft, a main shaft, a countershaft and an output shaft

Abstract

Vehicle with internal combustion engine, wherein in the internal combustion engine a crankshaft (2), a main shaft (41), a countershaft (42) and an output shaft (43) are arranged parallel in a crankcase (3) and transversely with respect to the vehicle, wherein the main shaft (41) is arranged rearward of the crankshaft (2) with respect to the vehicle, the countershaft (42) is arranged rearward of the main shaft (41) with respect to the vehicle, and the output shaft (43) is arranged below and in front of the countershaft (42) with respect to the vehicle, wherein the crankcase (3) of the internal combustion engine (1) has upper and lower housing elements (3U, 3L) which are vertically halved with respect to the vehicle, and wherein the crankshaft (2), the main shaft (41) and the countershaft (42) are arranged on a contact surface (3S) between the upper and lower housing elements (3U, 3L), characterized by that a shift drum (47A) adapted to shift a combination of gears on the main shaft (41) and the counter shaft (42) is arranged above and between the main shaft (41) and the counter shaft (42) with respect to the vehicle.

Description

[0001] The present invention relates to a vehicle having an internal combustion engine having a crankshaft, a main shaft, a countershaft and an output shaft arranged in parallel. There is an internal combustion engine in which a crankshaft, a main shaft, a countershaft, and an output shaft are arranged in parallel in a crankcase vertically bisected into an upper case member and a lower case member. In this internal combustion engine, the crankshaft is provided on a mating surface of the crankcase. The main shaft is arranged vehicle-rearward of the crankshaft and above the mating surface of the crankcase. Main-shaft-side driven gears adapted to receive the driving force transmitted thereto from the crankshaft are installed on the main shaft. The countershaft, adapted to receive the driving force transmitted thereto from the main shaft, is arranged vehicle-rearward of the crankshaft and on the mating surface of the crankcase. In this way, the anteroposterior length of the internal combustion engine is made short.Additionally, an output shaft adapted to receive the drive force transmitted thereto from the countershaft is arranged rearward of the countershaft (see JP 2000 - 343 968 A.).

[0002] US 2004 / 0 123 596 A1 discloses a drive unit for a vehicle with an internal combustion engine for transmitting the power of the internal combustion engine to the vehicle's wheels through a static, oil-hydraulic, non-stepped transmission. US 2007 / 0 221 160 A1 discloses an integrated drive unit for a vehicle with an engine, a transmission, and a crankcase divided into an upper and a lower section. It further comprises fastening projections that enable the fastening of an upper crankcase to a lower crankcase by means of fastening bolts.

[0003] JP S58 - 46 832 U discloses a drive unit for a motorcycle which is formed integrally with a transmission case and comprises: a crankshaft arranged between an upper case and an intermediate case, and a main shaft and a countershaft of a variable speed transmission arranged between the intermediate case and a lower case.

[0004] However, in the conventional configuration (e.g., JP 2000-343968 A) described above, the mainshaft-side driven gears attached to the mainshaft have very large diameters; therefore, the crankcase protrudes upward, causing a restriction on the arrangement of accessories, etc.

[0005] Accordingly, it is an object of the present invention to solve the problem of the conventional art described above and to provide an internal combustion engine in which the vertical length of a crankcase is made short in addition to making the anteroposterior length of the crankcase short.

[0006] In order to solve the above problem, the present invention is characterized in that in an internal combustion engine in which a crankshaft, a main shaft, a counter shaft and an output shaft are arranged in parallel in a crankcase and transversely with respect to the vehicle having the internal combustion engine, the main shaft is arranged rearward of the crankshaft with respect to the vehicle, the counter shaft is arranged rearward of the main shaft with respect to the vehicle, and the output shaft is arranged below and in front of the counter shaft with respect to the vehicle.

[0007] With the above configuration, the main shaft is arranged rearward of the crankshaft, and the counter shaft is arranged rearward of the main shaft. That is, the crankshaft, main shaft, and counter shaft are arranged in this order from the front to the rear. Therefore, the vertical length of the crankcase can be made short. In this case, for example, although the main shaft-side driven gear fixed to the main shaft has a large diameter, it does not protrude upward. Therefore, it is possible to suppress the upward protrusion of the crankcase. In addition, since the output shaft is arranged in front of and below the counter shaft, the anteroposterior length of the crankcase can be made short.

[0008] Furthermore, the crankcase of the internal combustion engine includes the upper and lower housing elements which are vertically halved with respect to the vehicle, and the crankshaft, the main shaft and the countershaft are arranged on the contact surface between the upper and lower housing elements.

[0009] With the above configuration, since the crankshaft, main shaft and counter shaft are arranged on the contact surface between the upper and lower case members, the bearing structure of the crankshaft, main shaft and counter shaft is simplified, so that the assembly of the crankshaft, main shaft and counter shaft is facilitated.

[0010] Furthermore, the shift drum is adapted to shift a combination of gears on the main shaft and the counter shaft, and the shift drum is arranged above and between the main shaft and the counter shaft with respect to the vehicle. With the above configuration, since the shift drum is arranged by efficiently utilizing the space between the main shaft and the counter shaft, the anteroposterior length and vertical length of the crankcase can be made short. In the above configuration, the internal combustion engine is a V-type internal combustion engine having cylinders arranged in a V shape.

[0011] Even in the above configuration, the main shaft is arranged rearward of the crankcase, and the counter shaft is arranged rearward of the main shaft, so that the crankshaft, main shaft, and counter shaft are arranged in this order from the front to the rear. Therefore, the vertical length of the crankcase can be made short. In this case, for example, although the main shaft-side driven gear fixed to the main shaft has a large diameter, it does not protrude upward. Therefore, it is possible to suppress the upward protrusion of the crankcase. In addition, since the output shaft is arranged in front of and below the counter shaft, the anteroposterior length of the crankcase can be made short.

[0012] According to the present invention, the main shaft is arranged rearward of the crankcase, and the counter shaft is arranged rearward of the main shaft, so that the crankshaft, the main shaft, and the counter shaft are arranged in this order from the front to the rear. Therefore, the vertical length of the crankcase can be made short. In addition, since the output shaft is arranged in front of and below the counter shaft, the anteroposterior length of the crankcase can be made short. Thus, the internal combustion engine can be downsized. Since the anteroposterior length of the crankcase is made short, for example, the wheelbase can be shortened. Thus, the vehicle can be made compact, and the vehicle's steerability performance can be improved.

[0013] The crankcase contains the vertically halved upper and lower case members, and the crankshaft, main shaft, and countershaft are arranged on the contact surface between the upper and lower case members. Therefore, the bearing structure of the crankshaft, main shaft, and countershaft can be simplified, thus simplifying the assembly of the crankshaft, main shaft, and countershaft.

[0014] The shift drum is designed to shift the combination of gears on the main shaft and the countershaft, and the shift drum is arranged above and between the main shaft and the countershaft. Therefore, because the shift drum is arranged by efficiently utilizing the space between the main shaft and the countershaft, the anteroposterior length and vertical length of the crankcase can be shortened. As a result, the distance between the shift drum and the main shaft and between the shift drum and the countershaft can be reduced, thereby reducing the size and weight of the internal combustion engine.

[0015] Furthermore, although the internal combustion engine is a V-type internal combustion engine, the main shaft is arranged rearward of the crankshaft, and the counter shaft is arranged rearward of the main shaft, so that the crankshaft, main shaft, and counter shaft are arranged in this order from the front to the rear. Therefore, the vertical length of the crankcase can be made short. Thus, it is possible to arrange accessories, for example, between the cylinders and the crankcase. In addition, since the output shaft is arranged in front of and below the counter shaft, the anteroposterior length of the crankcase can be made short, thereby reducing the internal combustion engine in size. Because the anteroposterior length of the crankcase is made short, for example, the wheelbase can be shortened. Thus, the vehicle can be made compact, and the vehicle's maneuverability performance is improved.

[0016] A preferred embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a side view of a motorcycle on which an internal combustion engine according to an embodiment of the invention is mounted. Fig. 2 is a cross-sectional view illustrating an internal combustion engine. Fig. 3 is a cross-sectional view taken along a line II-II of Fig. 1. Fig. 4 is a cross-sectional view illustrating the arrangement of the relationship between the crankshaft, a main shaft, a counter shaft, and an output shaft.

[0017] Fig. 1 is a side view of a motorcycle on which an internal combustion engine according to the embodiment of the present invention is mounted. In the following explanation, descriptions of directions such as front, rear, left, right, top, and bottom are based on a vehicle body.

[0018] A body frame 111 of a motorcycle 100 includes a head pipe 112 disposed in a front portion of a vehicle body; main frames 114 extend rearward from the head pipe 112 to the center of the vehicle body; and rear frames (not shown) extend from rear ends of the main frames 114 to a rear portion of the vehicle.

[0019] A front fork 124 is rotatably coupled to the head pipe 112. A front wheel 125 is rotatably supported by the lower end of the front fork 124. A handlebar 126 is mounted on the upper portion of the head pipe 112. In the figure, reference numeral 142 denotes a front wheel brake, and 143 denotes front master cylinders.

[0020] A four-cylinder front-rear V-type internal combustion engine 1 is arranged below the main frame 114. This internal combustion engine 1 is installed transversely so that a crankshaft 2 is oriented in a horizontal left-right direction. The engine 1 is of an OHC water-cooled type and includes a crankcase 3. A front bank (cylinder) Bf and a rear bank (cylinder) Br, each including two cylinders, are formed in a V shape so as to be inclined forward and rearward from the crankcase 3, respectively, and to have a bank angle of less than 90°.

[0021] A pair of left and right exhaust pipes 161L, 161R are connected at one end to exhaust ports of the front bank Bf. The exhaust pipes 161L, 161R extend downward from the exhaust ports, then extend toward the rear of the vehicle body, and are connected to a cylindrical catalyst device 163 disposed below the crankcase 3. A pair of left and right exhaust pipes 171L, 171R are connected at one end to exhaust ports of the rear bank Br. The exhaust pipe 171L is configured to include an upper exhaust pipe 172L extending downward from the exhaust port, and a lower exhaust pipe 173L extending downward from the upper exhaust pipe 172L, then further extending toward the front of the vehicle body, and connected to the catalyst device 163.Similarly, the exhaust pipe 171R is configured to include an upper exhaust pipe 172R extending downward from the exhaust port, and a lower exhaust pipe 173R extending downward from the upper exhaust pipe 172R, then further extending toward the front of the vehicle body, and connected to the catalyst device 163. The catalyst 163 is connected via a single exhaust pipe 176 to a muffler 181 located rearward of the internal combustion engine 1.

[0022] A propeller shaft 127 is provided rearward of the engine 1. A rear fork 128 is attached to the propeller shaft 127 so as to swing vertically therearound. A rear wheel 131 is rotatably supported by the rear end portion of the rear fork 128. A rear wheel brake 149 is attached to the rear wheel 131. The rear wheel 131 and the engine 1 are connected by a drive shaft 49 installed in the rear fork 128. The rotational power from the engine 1 is transmitted to the rear wheel 131 via the drive shaft 49. A rear damper (not shown) is interposed between the rear fork 128 and the body frame 111 to absorb shocks from the rear fork 128.

[0023] A stand 151 for parking the vehicle body is provided at the rear portion of the engine. A side stand 152 is provided at a lower portion and a left side surface of the engine 1.

[0024] A radiator 141 is arranged in front of the internal combustion engine 1. A fuel tank 144 is mounted on the upper portion of the main frame 114 to cover the internal combustion engine 1 from above. A seat 115 is arranged rearward of the fuel tank 144 and is supported by the rear frames. A taillight 118 is arranged behind the seat 115. A rear protective cover 117 is arranged below the taillight 118 to cover the rear wheel 131 from above.

[0025] The motorcycle 100 has a resin-made body cover 150 that covers the vehicle body. The body cover 150 includes a front cover 147 that continuously covers from the front of the body frame 111 to the front portion of the internal combustion engine 1. A mirror 148 is attached to the upper portion of the front cover 147. A front cowl 146 is attached to the front fork 124 to cover the front wheel 125 from above.

[0026] Fig. 2 is a cross-sectional view of the internal combustion engine 1. Incidentally, the description will be given with the top and bottom of the figure taken as the top and bottom of the internal combustion engine 1, respectively, and with the right side and left side of the figure as the front side and rear side of the engine 1, respectively.

[0027] A V-bank space K, which is a space formed in a V-shape as viewed from the side, is formed between the front bank Bf and the rear bank Br.

[0028] The crankcase 3 is configured to be vertically divided into an upper crankcase (an upper case member) 3U and a lower crankcase (a lower case member) 3L. A crankshaft 2 is rotatably supported so as to be interposed between the crankcases 3U, 3L. The upper crankcase 3U is integrally formed with a front cylinder block 3f and a rear cylinder block 3r, each of which has two cylinders arranged on the right and left sides and extending obliquely upward to form a V-shape when viewed from the side.

[0029] An oil pan 3G for storing oil (lubricating oil) of the internal combustion engine 1 is provided at a lower portion of the lower crankcase 3L so as to protrude downward. An oil pump 50 for circulating oil in the internal combustion engine 1 is arranged below the crankshaft 2 in the lower crankcase 3L.

[0030] A front cylinder head 4f is placed on the front cylinder block 3f from the slanted front side and is secured thereto by means of fastening bolts (not shown). Additionally, a front cylinder head cover 5f covers the front cylinder head 4f from above. Similarly, a rear cylinder head 4r is placed on the rear cylinder block 3r from the slanted back side and is secured thereto by means of fastening bolts (not shown). Additionally, a rear cylinder head cover 5r covers the rear cylinder head 4r from above.

[0031] The front cylinder block 3f and the rear cylinder block 3r are each formed with a cylinder bore 3a. A piston 6 is arranged to reciprocate within the cylinder bore 3a. The pistons 6 are connected to the single common crankshaft 2 via respective connecting rods 7f, 7r. The cylinder blocks 3f, 3r are provided with respective water jackets 8 surrounding the respective cylinder bores 3a, into which cooling water flows to cool the respective cylinder blocks 3f, 3r.

[0032] The front cylinder head 4f and the rear cylinder head 4r are provided with combustion chambers 20, intake ports 21, and exhaust ports 22 located above the respective cylinder bores 3a. A throttle body 23 is connected to each of the intake ports 21 to adjust the amount of mixture flowing to the intake port 21.

[0033] The cylinder heads 4f, 4r are provided with respective water jackets 9 which surround the intake ports 21 and the exhaust ports 22 and into which cooling water flows to cool the cylinder heads 4f, 4r.

[0034] A pair of intake valves 11 is arranged on each of the cylinder heads 4f, 4r in an openable and closable manner so as to be biased by respective valve springs 11a in a direction of closing the intake ports 21. A pair of exhaust valves 12 is arranged on each of the cylinder heads 4f, 4r in an openable and closable manner so as to be biased by respective valve springs 12a in a direction of closing the exhaust ports 22.

[0035] The intake valves 11 and the exhaust valves 12 are driven to be opened and closed by a single-cam type valve train 10 in which the intake valves 11 and the exhaust valves 12 are driven by a camshaft 25 arranged for each of the cylinder heads 4f, 4r.

[0036] The valve train 10 includes a camshaft 25 disposed above the intake valves 11 and rotatably supported by each of the cylinder heads 4f, 4r; a rocker shaft 26 having an axis parallel to the camshaft 25 and fixed to each of the cylinder heads 4f, 4r; and a rocker arm 27 swingably supported by the rocker shaft 26.

[0037] The camshaft 25 includes intake cams 30 and exhaust cams 31 projecting toward the outer peripheral side of the camshaft 25, and rotates in synchronization with the rotation of the crankshaft 2. The intake cam 30 and exhaust cam 31 each have a cam profile with an uneven distance (radius) from the center of the outer circumference. The radius variations, which are expected when the intake cam 30 and exhaust cam 31 are rotated, move the intake valves 11 and exhaust valves 12 upward and downward.

[0038] A valve lifter 13 is arranged between the camshaft 25 and the intake valve 11 so as to be slidably attached to each of the cylinder heads 4f, 4r at a position below the camshaft 25.

[0039] A roller 27a is provided at one end of the rocker arm 27, which is pivotally supported by the rocker arm shaft 26, so as to roll in contact with the exhaust cam 31. Additionally, a tappet screw 27b is screwed to the other end of the rocker arm 27 so as to abut against the upper end of the exhaust valve 12 and to be capable of adjusting advancing and retracting positions.

[0040] When the intake cams 30 and the exhaust cams 31 rotate together with the camshaft 25, the intake cams 30 push the intake valves 11 downward via the valve lifters 13, and the exhaust cams 31 push the exhaust valves 12 downward via the rocker arms 27. Thus, the intake ports 21 and the exhaust ports 22 are opened and closed at predetermined timings determined depending on the rotational phase of the intake cam 30 and the exhaust cam 31.

[0041] Fig. 3 is a cross-sectional view taken along a line II-II of Fig. 2. Fig. 4 is a cross-sectional view illustrating an arrangement relationship among the crankshaft, the main shaft, the counter shaft, and an output shaft. Fig. 3 shows the cross section of the front bench Bf. However, the inside of the rear bench Br is configured similarly to that of the front bench Bf; therefore, the explanation of the rear bench Br is omitted. In Fig. 4, the top and bottom of the figure are assumed to be the top and bottom of the internal combustion engine 1, respectively, and the right side and left side of the figure are assumed to be the front side and the rear side of the engine 1, respectively.

[0042] As in Fig. 3, each cylinder of the cylinder head 4f is formed with a plug insertion hole 15 on a cylinder axis C, which is a central axis of the cylinder bore 3a. A spark plug 16 (the spark plug of the right cylinder is not shown in the figure) is arranged in the plug insertion hole 15 to have a leading end facing the inside of the combustion chamber 20.

[0043] The crankshaft 2 is supported in the crankcase 3 by a plurality of journal bearings 2A provided at both end portions and an intermediate portion in the axial direction.

[0044] A camshaft drive sprocket 17 adapted to output the rotation of the crankshaft 2 is provided on one end side of the crankshaft 2. A cam chain chamber 35 extending vertically in each of the banks Bf, Br is provided on the camshaft drive sprocket 17 side of the internal combustion engine 1. A driven sprocket 36 is secured to one end of the camshaft 25 and is arranged in the cam chain chamber 35 so as to be rotated integrally with the camshaft 25. A cam chain 37 is wound around the driven sprocket 36 and the camshaft drive sprocket 17. The camshaft 25 is rotated at a rotational speed which is half that of the crankshaft 2, via the cam chain 37 and the driven sprocket 36. A generator 18, such as an electric dynamo, is mounted on the other end side of the crankshaft 12.

[0045] The main shaft 41, the counter shaft 42, and the output shaft 43 are installed in the crankcase 3 parallel to the crankcase 2. These shafts, including the crankshaft 2, construct a gear transmission mechanism adapted to transmit the rotation of the crankshaft 2 in order from the main shaft 41, the counter shaft 42, and the output shaft 43.

[0046] As in Fig. 4, the crankshaft 2 is arranged on a contact surface 3S between the upper crankcase 3U and the lower crankcase 3L. The main shaft 41 is arranged rearward of the crankshaft 2, and the counter shaft 42 is arranged rearward of the main shaft 41. The main shaft 41 and the counter shaft 42 are arranged on the contact surface 3S. The output shaft 43 is arranged in front of and below the counter shaft 42. In other words, respective axial centers O1, O2 of the main shaft 41 and the counter shaft 42 are arranged rearward and forward on the contact surface 3S. An axial center O3 of the output shaft 43 is arranged rearward of the axial center O1 of the main shaft 41 and in front of and below the axial center O2 of the counter shaft 42.

[0047] Fig. 3 is a cross-sectional view taken along a cross section connecting the front bank Bf, the crankshaft 2, the main shaft 41, the counter shaft 42 and the output shaft 43 with straight lines.

[0048] A crank-side drive gear 2B, adapted to rotate the main shaft 41, is fixed to one end of the crankshaft 2 near the cam chain chamber 35. The crank-side drive gear 2B engages a main shaft-side driven gear 41A of the main shaft 41. The main shaft 41 is supported by bearings 41C provided on both sides thereof.

[0049] The main shaft-side wear gear 41A is provided on the main shaft 41 so as to be rotatable relative thereto and is connected to a clutch mechanism 44. The operation of the clutch mechanism 44 can connect and release the transmission of drive power between the crankshaft 2 and the main shaft 41.

[0050] The main shaft side output gear 41A is provided with an oil pump drive gear 41B which is adapted to drive an oil pump 50 (see Fig. 2). The oil pump drive gear 41B is rotated integrally with the main shaft side driven gear 41A regardless of the engagement or disengagement of the clutch mechanism 44. Thus, as shown in Fig. 2, the rotation of the crankshaft 2 is transmitted via the drive chain 45 to the drive gear 50B which is fixed to the drive shaft 50A of the oil pump 50 for driving the oil pump 50.

[0051] As in Fig. As shown in Fig. 3, the counter shaft 42 is supported by bearings 42C provided at both ends thereof. Speed ​​change gear groups are arranged to extend between the counter shaft 42 and the main shaft 41, constructing a transmission 46. More specifically, drive gears m1 to m6 for six speeds are provided on the main shaft 41. Driven gears n1 to n6 for six speeds are provided on the counter shaft 42. The drive gears m1 to m6 mesh with a corresponding one of the driven gears m1 to m6 for each speed change stage to construct a speed change gear pair (a combination of gears). Incidentally, the speed change gear pairs are reduced in a reduction ratio in the order from a first speed to a sixth speed (to become higher speeds).A first gear pair m1, n1, which is largest in reduction ratio, is arranged on one end side of the main shaft 41, which supports the main shaft-side driven gear 41A, and a second speed gear pair m2, n2 is arranged on the other end side of the main shaft 41. A fifth speed gear pair m5, n5, a fourth speed gear pair m4, n4, a third speed gear pair m3, n3, and a sixth speed gear pair m6, n6 are arranged in order from one end side between the first speed gear pair m1, n1 and the second speed gear pair m2, n2.

[0052] The third speed drive gear m3 and the fourth speed drive gear m4 on the main shaft 41 are keyed to the main shaft 41, and are configured to be axially moved as a slider and to selectively engage or disengage from the fifth speed drive gear m5 or the sixth speed drive gear m6 adjacent to the fourth speed drive gear m4 and the third speed drive gear m3, respectively.The fifth-speed drive gear m5 and the sixth-speed drive gear m6 on the countershaft 42 are keyed to the countershaft 42 and are configured to be moved axially as a slider, and to engage or disengage from the fourth-speed driven gear n4 or the third-speed driven gear n3 adjacent to the fifth-speed driven gear n5 and the sixth-speed driven gear n6, respectively. The third-speed drive gear m3 and the fourth-speed drive gear m4, as a slider on the main shaft 41, and the fifth-speed driven gear n5 and the sixth-speed driven gear n6 on the countershaft 42 are shifted by a switching mechanism 47 (see FIG. Fig. 4) to switch.

[0053] As in Fig. 4, the switching mechanism 47 includes a shift drum 47A which is parallel to the shafts 41 to 43. The shift drum 47A is arranged above and between the main shaft 41 and the counter shaft 42 so as to have an axial center O4 rearward of the axial center O3 of the output shaft 43. Fork shafts 47B and 47C are arranged in front of and behind, respectively, and parallel to the shift drum 47A. The fork shaft 47B is arranged in front of the shift drum 47A so as to have an axial center O5 slightly below the axial center O4 of the shift drum 47A. The fork shaft 47C is arranged rearward of the shift drum 47A so as to have an axial center O6 which is at the same height as the axial center O4 of the shift drum 47A.

[0054] A shift fork 47B1, which engages with the slider of the main shaft 41, is supported by the fork shaft 47B. A shift fork 47C1, which engages with the slider of the counter shaft 42, is supported by the fork shaft 47C. The gear change gear pair is changed by moving the shift forks 47B1, 47C1 of the shift change mechanism 47. The rotation of the main shaft 41 is transmitted to the counter shaft 42 via the gear change gear pair thus changed. As shown in Fig. 3, the countershaft 42 has an intermediate drive gear 42A adapted to transmit the rotation from the countershaft 42 to the output shaft 43.

[0055] The output shaft 43 is supported by bearings 43C mounted at both ends of the output shaft 43 and includes an output gear 43A meshing with the intermediate drive gear 42A. A cam-type torque damper 51 is disposed on the output shaft 43 adjacent to the output gear 43A. The cam-type torque damper 51 is adapted to absorb torque variation applied thereto and includes a cylindrical member 52 axially movably splined to the output shaft 43. The cylindrical member 52 is formed on an end surface near the output gear 43A, with a protruding cam 52A meshing with a recessed cam 43B formed on the output gear 43A. A spring-receiving member 53 is fixed to a general center of the output shaft 43.A coil spring 54 is provided between the cylindrical member 52 and the spring-receiving member 53 so as to bias the cylindrical member 52 toward the output gear 43A. The cam-type torque damper 51 is configured to include the cylindrical member 52, the spring-receiving member 53, and the coil spring 54.

[0056] An input bevel gear 48 is provided integrally with the left end portion of the output shaft 43. The input bevel gear 48 meshes with an output bevel gear 49A, which is provided integrally with the front end of the drive shaft 49, which extends in the forward and backward direction of the vehicle body. In this way, the rotation of the output shaft 43 is transmitted to the drive shaft 49.

[0057] The operation of the internal combustion engine 1 will next be described with reference to the Fig. 4 described.

[0058] The internal combustion engine 1 is configured as described above, with the crankshaft 2, the main shaft 41, and the countershaft 42 arranged in this order from the front to the rear. Therefore, the vertical length of the crankcase 3 can be made short. In this configuration, although the diameter of the mainshaft-side drive gear 41A fixed to the main shaft 41 is large, it does not protrude upward compared to the case where the main shaft is arranged above the crankshaft and the countershaft. Therefore, it is possible to prevent the upward protrusion of the crankcase 3. Thus, it is possible to arrange accessories between the rear bank Br and the upper surface 3b of the crankcase 3.

[0059] Furthermore, the main shaft 41 and the counter shaft 42 are arranged on the contact surface 3S between the upper and lower crankcases 3U, 3L. Therefore, the respective bearings 41C and 42C of the main shaft 41 and the counter shaft 42 can be simplified in configuration. Thus, the main shaft 41 and the counter shaft 42 can be easily assembled.

[0060] Since the output shaft 43 can be arranged in front of the counter shaft 42, the anteroposterior length of the crankcase 3 can be made short compared to the case where the output shaft 43 is arranged rearward of the counter shaft 42. The output shaft 43 is arranged at one vertex of a triangle, while the main shaft 41 and the counter shaft 42 are arranged at the other respective vertices. The output shaft 43 is arranged by effectively utilizing the space between the main shaft 41 and the counter shaft 42. Therefore, the downward protrusion of the crankcase 3 resulting from the output shaft 43 being arranged in front of the counter shaft 42 can be suppressed. Thus, the vertical length of the crankcase 3 can be made short in addition to shortening the anteroposterior length of the crankcase 3, whereby the internal combustion engine 1 can be reduced in size and weight.

[0061] In this way, since the anteroposterior length of the crankcase 3 is made short to shorten the wheelbase, the motorcycle 100 (see Fig. 1) can be made compact and the steering performance of the motorcycle 100 can be improved.

[0062] The shift drum 47A is arranged above and between the main shaft 41 and the counter shaft 42; therefore, the anteroposterior length of the crankcase 3 can be made short compared to the case where the shift drum 47A is arranged rearward of the counter shaft 42. The shift drum 47A is arranged at one vertex of a triangle, while the main shaft 41 and the counter shaft 42 are arranged at other respective vertices. The shift drum 47A is arranged by effectively utilizing the space between the main shaft 41 and the counter shaft 42. Therefore, the upward protrusion of the crankcase 3 resulting from the shift drum 47A being arranged above the main shaft 41 and the counter shaft 42 can be suppressed to make the vertical length of the crankcase 3 short. Thus, accessories can be arranged between the rear bank Br and the upper surface 3b of the crankcase 3.In addition, since the distance between the shift drum 47A and the main shaft 41 and between the shift drum 47A and the counter shaft 42 can be reduced, shift forks 47B1, 47C1 supported by the respective fork shafts 47B, 47C can be shortened, whereby the internal combustion engine 1 can be reduced in size and weight.

[0063] The shift drum 47A is arranged to have an axial center O4 rearward of the axial center O3 of the output shaft 43. Therefore, the vertical length of the crankcase 3 can be made short compared to the case where the axial center of the shift drum and the axial center of the output shaft are arranged above each other. Thus, accessories can be arranged between the rear bank Br and the upper surface 3b of the crankcase 3. In addition, the fork shaft 47B is arranged at one vertex of a triangle, while the main shaft 41 and the shift drum 47A are arranged at the other respective vertices. The fork shaft 47B is arranged by efficiently utilizing the space between the main shaft 41 and the shift drum 47A. Therefore, the upward protrusion of the crankcase 3 resulting from the fork shaft 47B being arranged above the main shaft 41 can reduce the vertical length of the crankcase 3.Thus, it is possible to arrange accessories between the rear bank Br and the upper surface 3b of the crankcase 3. Since the distance between the fork shaft 47B and the main shaft 41 and between the fork shaft 47B and the shift drum 47A can be reduced, the shift fork 47B1 supported by the fork shaft 47B can be shortened, thereby reducing the size and weight of the internal combustion engine 1.

[0064] Similarly, the fork shaft 47C is arranged at one apex of a triangle, while the counter shaft 42 and the shift drum 47A are arranged at the other respective apex. The fork shaft 47C is arranged by efficiently utilizing the space between the counter shaft 42 and the shift drum 47A. Therefore, upward protrusion of the crankcase 3 resulting from the fork shaft 47C being arranged above the counter shaft 42 can be suppressed to make the vertical length of the crankcase 3 short. Thus, it is possible to arrange accessories between the rear bank Br and the upper surface 3b of the crankcase 3. In addition, since the distance between the front shaft 47B and counter shaft 42 and between the fork shaft 47C and the shift drum 47A can be reduced, the shift fork 47C1 supported by the fork shaft 47C can be shortened, whereby the internal combustion engine 1 can be reduced in size and weight.

[0065] According to the present embodiment, as described above, the main shaft 41 is arranged rearward of the crankshaft 2, and the countershaft 42 is arranged rearward of the main shaft 41. Therefore, the crankshaft 2, the main shaft 41, and the countershaft 42 are arranged in this order from rear to front. Thus, the vertical length of the crankcase 3 can be made short. Accordingly, although the mainshaft-side driven gear 41A attached to the main shaft 41 has a large diameter, it does not protrude upward. Therefore, it is possible to suppress the upward protrusion of the crankcase 3.

[0066] Since the output shaft 43 is arranged in front of and below the counter shaft 42, the anteroposterior length of the crankcase 3 can be made short, thereby making the internal combustion engine 1 smaller. Since the anteroposterior length of the crankcase 3 is made short to shorten the wheelbase, the motorcycle 100 can be made compact, and the steering performance of the motorcycle 100 can be improved.

[0067] According to the present embodiment, the upper crankcase 3U and the lower crankcase 3L are provided, which are vertically divided. In addition, the main shaft 41 and the counter shaft 42 are arranged on the contact surface 3S between the upper and lower crankcases 3U, 3L. Therefore, the respective bearings 41C and 42C of the main shaft 41 and the counter shaft 42 can be simplified in configuration. Thus, the main shaft 41 and the counter shaft 42 can be easily assembled.

[0068] According to the present embodiment, the shift drum 47A is adapted to shift the combination of gears on the main shaft 41, and the counter shaft 42 is arranged above and between the main shaft 41 and the counter shaft 42. Therefore, the shift drum 47A is arranged by efficiently utilizing the space between the main shaft 41 and the counter shaft 42. Thus, the anteroposterior and vertical lengths can be made short. As a result, the distance between the shift drum 47A and the main shaft 41 and between the shift drum 47A and the counter shaft 42 can be made short to shorten the shift forks 47B1, 47C1, whereby the internal combustion engine 1 can be reduced in size and weight.

[0069] Furthermore, according to the present embodiment, although the internal combustion engine 1 is a V-type internal combustion engine in which the banks Bf, Br are arranged in a V shape, the main shaft 41 is arranged rearward of the crankshaft 2, and the countershaft 42 is arranged rearward of the main shaft 41. That is, the crankshaft 2, the main shaft 41, and the countershaft 42 are arranged in this order from the front to the rear. Thus, the vertical length of the crankcase 3 can be made short. In this case, although the mainshaft-side driven gear 41A fixed to the main shaft 41 has a large diameter, it does not protrude upward. Therefore, it is possible to suppress the upward protrusion of the crankcase 3. Thus, it is possible to arrange accessories between the rear bank Br and the crankcase 3.

[0070] Since the output shaft 43 is arranged below and in front of the countershaft 42, the anteroposterior length of the crankcase 3 can be made short, thereby miniaturizing the internal combustion engine 1. Since the anteroposterior length of the crankcase 3 can be made short to shorten the wheelbase, the motorcycle 100 can be made compact, and the steering performance of the motorcycle 100 can be improved. List of reference symbols: 1 internal combustion engine (vehicle internal combustion engine) 2 crankshaft 3 crankcase 3U Upper Crankcase (Upper Housing Element) 3L Lower Crankcase (Lower Housing Element) 3S touch surface 41 Main shaft 42 Countershaft 43 Output shaft 47A shift drum 100 Motorcycle (Vehicle) Bf Vordere Bank (Cylinder) Br Rear Bank (Cylinder) m1 - m6 drive gears n1 - n6 output gears

Claims

[1] Vehicle with internal combustion engine, wherein in the internal combustion engine a crankshaft (2), a main shaft (41), a countershaft (42) and an output shaft (43) are arranged in parallel in a crankcase (3) and transversely with respect to the vehicle, wherein the main shaft (41) is arranged rearward of the crankshaft (2) with respect to the vehicle, the countershaft (42) is arranged rearward of the main shaft (41) with respect to the vehicle, and the output shaft (43) is arranged below and in front of the countershaft (42) with respect to the vehicle, wherein the crankcase (3) of the internal combustion engine (1) has upper and lower housing elements (3U, 3L) which are vertically halved with respect to the vehicle, and wherein the crankshaft (2), the main shaft (41) and the countershaft (42) are arranged on a contact surface (3S) between the upper and lower housing elements (3U, 3L), characterized by , that a shift drum (47A) adapted to shift a combination of gears on the main shaft (41) and the counter shaft (42) is arranged above and between the main shaft (41) and the counter shaft (42) with respect to the vehicle. [2] A vehicle internal combustion engine according to claim 1, wherein the internal combustion engine (1) is a V-type internal combustion engine having cylinders arranged in a V-shape.

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