V-shaped engine

Abstract

The invention provides a V-shaped engine, and the V-shaped engine is compact. The V-type engine is provided with a crankshaft (10), connecting rod large end parts (17a) of adjacent front and rear cylinders on a crank pin (10d) of the crankshaft (10) are adjacent with a crank arm (10c) of the crankshaft (10) therebetween, cam chains (67, 68) are respectively arranged on one side of the engine of the front and rear cylinders (12F, 12R), and cam chain driving sprockets (65, 66) for driving the cam chains (67, 68) are driven by a cam chain driving gear (64) coaxially arranged on the side of the engine. In the V-type engine, the cam chain driving gear (64) is driven by an idling driven gear (63), the idling driven gear (63) is driven by an idling driving gear (62) meshed with a timing gear (61) of a crankshaft (10), and at least one of the driving sprockets (65, 66) is arranged at a position overlapped with a crankshaft counterweight (10e) or a connecting rod large end part (17a) in the vertical direction of the engine.

Description

Technical Field

[0001] The present invention relates to a V-type engine. Background Art

[0002] A V-type engine having front and rear cylinders is known. In this V-type engine, a cam chain is provided on one side of the engine between the front and rear cylinders. The rotation of the crankshaft is transmitted to a cam drive sprocket via a gear set provided on an idler gear support shaft, and the cam drive sprocket drives the cam chain (for example, see Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-168818 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] When the crankpins of the front and rear cylinders are in phase, the connecting rod big ends are adjacent, resulting in a small amount of offset in the crankshaft direction of the cam chain drive sprocket. In contrast, when the front and rear cylinders are out of phase, that is, when the connecting rod big ends of the front and rear cylinders adjacent to each other on the crankpins are adjacent with the crank arm interposed therebetween, the offset between the front and rear cylinders in the crankshaft direction is expected to increase, causing the cam chain drive sprocket and cam chain to protrude outward from the engine, resulting in an increased cylinder head size.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to make a V-type engine more compact.

[0009] Means for solving problems

[0010] A V-type engine is provided, which has a crankshaft, wherein the large ends of the connecting rods of the adjacent front and rear cylinders on the crank pin of the crankshaft are adjacent to each other with the crank arm of the crankshaft in between, and a cam chain is respectively provided on one side of the engine side of the front and rear cylinders, and the cam chain drive sprockets that drive each cam chain are driven by a cam chain drive gear coaxially arranged on the side of the engine, and the cam chain drive gear is driven by an idle driven gear, and the idle driven gear is driven by an idle driving gear meshed with the timing gear of the crankshaft, wherein at least one of the cam chain drive sprockets is arranged at a position overlapping with the crankshaft balance weight or the large end of the connecting rod in the upper and lower directions of the engine.

[0011] Effects of the Invention

[0012] According to the present invention, a V-type engine can be made compact. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a perspective view of an engine according to an embodiment of the present invention.

[0014] Figure 2 This is a cross-sectional view of the engine cut through the crankshaft, main shaft and front cylinder.

[0015] Figure 3 It is a diagram showing the peripheral structure of the idler gear support shaft and the cam chain drive shaft.

[0016] Figure 4 This is a perspective view showing a cross section of the crankshaft together with an idler gear support shaft and the like.

[0017] Figure 5 This is a perspective view showing a cross section of the idler gear support shaft together with the crankshaft and the like.

[0018] Figure 6 This is a perspective view showing the idler gear support shaft together with the surrounding structure.

[0019] Figure 7 This figure shows the cam chain drive shaft together with the surrounding structure.

[0020] Label Description

[0021] 1: Engine (internal combustion engine);

[0022] 10: crankshaft;

[0023] 10c: crank arm;

[0024] 10d: crank pin;

[0025] 10e: crankshaft balance weight;

[0026] 11: crankcase;

[0027] 12F, 12R: cylinder;

[0028] 13: Valve transmission mechanism;

[0029] 17a: connecting rod big end;

[0030] 21: spindle;

[0031] 31: Idle gear support shaft;

[0032] 31h: oil supply hole;

[0033] 33, 34: bearings;

[0034] 41: primary drive gear;

[0035] 51: Clutch mechanism;

[0036] 61: Timing gear;

[0037] 62: Idle drive gear;

[0038] 62s: intermediate gear (backlash absorption mechanism);

[0039] 63: Idle driven gear;

[0040] 64: Cam chain drive gear;

[0041] 65: first cam chain drive sprocket;

[0042] 66: second cam chain drive sprocket;

[0043] 67: first cam chain;

[0044] 68: Second cam chain;

[0045] 71: Balancer drive gear;

[0046] 72: Balancer driven gear;

[0047] 80: Balancer. DETAILED DESCRIPTION

[0048] The following describes embodiments of the present invention with reference to the accompanying drawings. In the description, directions such as front, back, left, right, and up and down are used interchangeably with respect to the vehicle body unless otherwise specified. In the figures, the symbol "FR" indicates the front of the vehicle body, the symbol "UP" indicates the top of the vehicle body, and the symbol "LH" indicates the left of the vehicle body.

[0049] [Implementation Method]

[0050] Figure 1 It is a perspective view of the engine 1 according to the embodiment of the present invention. Figure 1 The engine 1 shown is shown in a state where the crankcase cover 2 covering the engine 1 from the right side is removed.

[0051] Engine 1 is a V-type engine mounted on a motorcycle, also referred to as an internal combustion engine or power unit. Engine 1 includes a crankcase 11 that rotatably supports a crankshaft 10; cylinders 12F of a front cylinder group (also referred to as a first cylinder group) extending forward and upward from the upper portion of crankcase 11; and cylinders 12R of a rear cylinder group (also referred to as a second cylinder group) extending rearward and upward from the upper portion of crankcase 11.

[0052] Each cylinder 12F, 12R includes a cylinder block 12a, a cylinder head 12b connected to the upper surface of the cylinder block 12a, and a head cover (not shown) covering the upper surface of the cylinder head 12b. A valve train 13 is arranged between the cylinder head 12b and the head cover.

[0053] The crankcase 11 is formed as a hollow housing that supports the crankshaft 10 and the surrounding structure, and is split into left and right parts. However, the shape and structure of the crankcase 11 may be appropriately changed according to the specifications of the engine 1 and the like.

[0054] The crankshaft 10 is rotatably supported in the crankcase 11 along the vehicle width direction. Furthermore, the crankcase 11 rotatably supports the main shaft 21 below and rearward of the crankshaft 10, and the countershaft 22 is rotatably supported below the crankshaft 10 and main shaft 21. Furthermore, the crankcase 11 rotatably supports an idler gear support shaft 31 above and rearward of the crankshaft 10 and on the right side of the crankcase 11, and a cam chain drive shaft 32 is rotatably supported above and to the right side of the crankcase 11. The crankshaft 10, main shaft 21, countershaft 22, idler gear support shaft 31, and cam chain drive shaft 32 are parallel to each other.

[0055] Figure 2 The engine 1 is cut along a plane passing through the crankshaft 10, the main shaft 21, and the front cylinder. The crankshaft 10 includes left and right journals 10a rotatably supported in the crankcase 11, and a crank 10b disposed between the left and right journals 10a and housed in the crank chamber 14. The crank 10b includes a crank arm 10c integral with the journal 10a and a crank pin 10d connecting the crank arms 10c.

[0056] A crank balance weight 10 e is integrally formed on the crank arm 10 c on the side opposite to the crank pin 10 d with respect to the axis of the crankshaft 10 .

[0057] A cylinder bore 15 is provided in the cylinder block 12a above the crank chamber 14 , and a piston 16 is provided in the cylinder bore 15 . The piston 16 is connected to the crankshaft 10 via a connecting rod 17 .

[0058] The engine 1 of this structure has a structure in which the front and rear cylinders have different phases, and the connecting rod big ends 17a of the front and rear cylinders adjacent to each other on the crankpin 10d are adjacent to each other via the crank arm 10c.

[0059] The right (one) end portion of the crankshaft 10 projects to the right of the crankcase 11 , and a primary drive gear 41 is provided at this end portion. The primary drive gear 41 meshes with a primary driven gear 42 provided on the main shaft 21 .

[0060] A transmission chamber 18 is provided at the rear portion of the crankcase 11. A constantly meshing gear transmission 19 is housed in the transmission chamber 18. The transmission chamber 18 and the crank chamber 14 are partitioned by a partition wall 11w.

[0061] The gear transmission 19 includes a main shaft 21 provided parallel to the crankshaft 10, a countershaft 22 provided parallel to the main shaft 21, and a gear train 19g provided on the main shaft 21 and the countershaft 22. The countershaft 22 functions as an output shaft of the engine 1 and drives the rear wheel as a drive wheel via a power transmission mechanism (e.g., a chain drive mechanism).

[0062] A clutch mechanism 51 is provided at the right end of the main shaft 21, capable of interrupting power transmission between the crankshaft 10 and the power transmission mechanism. The clutch mechanism 51 comprises a clutch outer race 53 connected to the primary driven gear 42 via a damper mechanism 52, a clutch inner race 54 fixed to the main shaft 21, and friction plates 55 disposed between the clutch outer race 53 and the clutch inner race 54. The clutch mechanism 51 is covered from the vehicle widthwise outer side by the crankcase cover 2, which is also referred to as a clutch cover.

[0063] like Figure 2 As shown, a primary drive gear 41, a timing gear 61, and a balancer drive gear 71 are disposed at the right end portion of the crankshaft 10. These gears 41, 61, 71 are disposed in a space between the crankcase 11 and the crankcase cover 2.

[0064] The crankcase cover 2 includes a cylindrical portion 2t that protrudes toward the engine interior to surround a pipe 3 connected to the crankshaft 10. A seal member 4 seals the space between the cylindrical portion 2t and the pipe 3, and a cover 5 closes the vehicle widthwise outer opening of the cylindrical portion 2t.

[0065] Figure 3 1 and 2 are diagrams showing the peripheral structures of the idler gear support shaft 31 and the cam chain drive shaft 32 .

[0066] This engine 1 adopts a half-cam gear system in which a gear and a cam chain are used together to drive the valve train 13 of the front and rear cylinders.

[0067] In this engine 1, the rotation of the crankshaft 10 is transmitted to the idler drive gear 62 provided on the idler gear support shaft 31 via the timing gear 61 fixed to the crankshaft 10. The rotation of the idler drive gear 62 is then transmitted to the cam chain drive gear 64 provided on the cam chain drive shaft 32 via the idler driven gear 63 provided on the idler gear support shaft 31.

[0068] like Figure 3As shown, a first cam chain drive sprocket 65 for the rear cylinder and a second cam chain drive sprocket 66 for the front cylinder are fixed to the cam chain drive shaft 32. The valve train 13 of the rear cylinder (the camshaft of the valve train 13) is driven by a first cam chain 67 wound around the first cam chain drive sprocket 65, and the valve train 13 of the front cylinder (the camshaft of the valve train 13) is driven by a second cam chain 68 wound around the second cam chain drive sprocket 66. Figure 1 and Figure 3 As shown, the structure for implementing the semi-cam gear system is concentrated on the right side of the engine.

[0069] Figure 4 It is a perspective view showing a cross section of the crankshaft 10 together with the idler gear support shaft 31 and the like. Figure 5 This is a perspective view showing a cross section of the idler gear support shaft 31 together with the crankshaft 10 and the like. Figure 6 This is a perspective view showing the idler gear support shaft 31 together with the surrounding structure.

[0070] like Figure 4 As shown, on the crankshaft 10, a balancer drive gear 71 is fixed on the rightmost side of the crankshaft 10 (outside the engine), a timing gear 61 is fixed on the inner side of the balancer drive gear 71 in the crankshaft direction (inside the engine), and a primary drive gear 41 is fixed on the inner side of the timing gear 61 in the crankshaft direction (inside the engine).

[0071] The number of teeth and diameter of these gears 71, 61, and 41 are appropriately set according to the specifications of the engine 1. In this embodiment, the primary drive gear 41 is formed as the gear with the largest diameter. The balancer drive gear 71 drives a balancer 80 (described later) to suppress primary vibrations of the engine 1. Therefore, the speed ratio between the balancer drive gear 71 and the crankshaft 10 is 1:1, and the balancer 80 is driven at the same rotational speed as the crankshaft 10.

[0072] The timing gear 61 is a gear that reduces the rotation of the crankshaft 10 to ½ and transmits the rotation to the valve mechanism 13 (the camshaft of the valve mechanism 13 ).

[0073] like Figure 5 As shown, the idler gear support shaft 31 is a hollow, bottomed structure that is separate from the crankcase 11. With its bottom portion in contact with the crankcase 11, the idler gear support shaft 31 is secured to the crankcase 11 by a fastening member 31k inserted from the outside in the vehicle width direction. In this embodiment, the fastening member 31k is a single bolt. The structure for securing the idler gear support shaft 31 to the crankcase 11 may be modified as appropriate.

[0074] Two needle roller bearings, 31a and 31b, are positioned adjacent to each other on the idler gear support shaft 31. Mounted on the outer circumference of the bearing 31a, located on the crankshaft inner side (corresponding to the engine's inner side), are an idler driven gear 63 and an idler driving gear 62, which mesh with the timing gear 61. Therefore, the idler driven gear 63 and the idler driving gear 62 are rotatable relative to the idler gear support shaft 31. These gears 63 and 62 are fixed to each other for synchronized rotation.

[0075] An intermediate gear 62s, having the same diameter as the idler drive gear 62, is rotatably engaged with the idler drive gear 62. The intermediate gear 62s meshes with the timing gear 61 and is biased by an elastic member in a direction opposite to the rotation direction of the timing gear 61, thereby absorbing the backlash between the timing gear 61 and the idler drive gear 62. The intermediate gear 62s, also known as a scissor gear, is an example of the "backlash absorbing mechanism" disclosed herein.

[0076] A balancer driven gear 72 that meshes with the balancer driving gear 71 is attached to the outer peripheral surface of the bearing 31 b on the crankshaft direction outer side (corresponding to the engine outer side) of the idler gear support shaft 31 .

[0077] The balancer driven gear 72 is integrally provided with a balancer 80. Figure 6 As shown, the balancer 80 is formed by forming a portion of the balancer driven gear 72 into a fan-shaped thick wall portion that bulges toward the right side of the engine (equivalent to the outside in the crankshaft direction). The balancer 80 rotates synchronously with the crankshaft 10 at the same speed (counter-rotating), thereby functioning as a primary balancer to suppress the primary vibration of the engine 1. By adjusting the shape and weight of the balancer 80, the vibration suppression effect can be appropriately adjusted.

[0078] The structure of the balancer 80 is not limited to the one described above. For example, the balancer 80 may be made of a separate component from the idler drive gear 62, and the balancer 80 and the idler drive gear 62 may be integrally connected. Furthermore, vibrations other than the primary vibration may be suppressed by adjusting the number of teeth on the gears of the balancer drive system or by adjusting the balancer 80.

[0079] like Figure 5 As shown, a plurality of oil supply holes 31h are provided in the idler gear support shaft 31. Lubricating oil is supplied into the idler gear support shaft 31 and supplied to the bearings 31a, 31b and the gears 62, 63 through the oil supply holes 31h.

[0080] like Figure 3As shown, a cam chain drive gear 64 is provided at the right end of the cam chain drive shaft 32. This cam chain drive gear 64 meshes with an idler driven gear 63 provided on the idler gear support shaft 31. A second cam chain drive sprocket 66 for the front cylinders is provided on the cam chain drive shaft 32 on the vehicle widthwise inner side of the cam chain drive gear 64 (equivalent to the inner side of the engine). A first cam chain drive sprocket 65 for the rear cylinders is provided on the vehicle widthwise inner side of the second cam chain drive sprocket 66 (equivalent to the inner side of the engine).

[0081] Figure 7 This is a diagram showing the cam chain drive shaft 32 together with the surrounding structure.

[0082] like Figure 7 As shown, the cam chain drive shaft 32 , the cam chain drive gear 64 , the first cam chain drive sprocket 65 , and the second cam chain drive sprocket 66 are made as one body.

[0083] Rolling bearings 33 and 34 are press-fitted into both ends of the cam chain drive shaft 32. A first cam chain drive sprocket 65 is integrally formed on the outer periphery of the portion of the cam chain drive shaft 32 on the crankcase 11 side into which the bearings 33 are press-fitted. Furthermore, a cam chain drive gear 64 is integrally formed on the outer periphery of the portion of the cam chain drive shaft 32 on the crankcase cover 2 side into which the bearings 34 are press-fitted. The first cam chain drive sprocket 65, the second cam chain drive sprocket 66, and the cam chain drive gear 64 are coaxially arranged.

[0084] In this configuration, the cam chain drive shaft 32, cam chain drive gear 64, first cam chain drive sprocket 65, and second cam chain drive sprocket 66 are integrally formed, thereby reducing the number of components. Furthermore, since the first cam chain drive sprocket 65 is provided using the portion of the press-fit bearing 33, it can be positioned closer to the vehicle width inner side (inside the engine).

[0085] In addition, in this structure, if Figure 3 and Figure 5 As shown in FIG. 1 , the first cam chain drive sprocket 65 is positioned so as to overlap the crankshaft counterweight 10e or the connecting rod big end 17a in a vertical direction perpendicular to the crankshaft direction. This allows the first cam chain drive sprocket 65 and the first cam chain 67 to be positioned closer to the left-right inner side of the engine 1. Consequently, the engine 1 can be made more compact in the left-right direction (crankshaft direction).

[0086] As described above, the engine 1 of this embodiment includes a crankshaft 10. The connecting rod big ends 17a of adjacent front and rear cylinders are positioned adjacent to each other on the crankpin 10d of the crankshaft 10, with the crank arm 10c interposed therebetween. Cam chains 67 and 68 are provided on either side of the engine for the front and rear cylinders 12F and 12R, respectively. The cam chain drive sprockets 65 and 66 that drive the cam chains 67 and 68 are driven by a cam chain drive gear 64 coaxially disposed on the side of the engine. Furthermore, the cam chain drive gear 64 is driven by an idler driven gear 63, which is driven by an idler drive gear 62 that meshes with the timing gear 61 of the crankshaft 10.

[0087] like Figure 3 and Figure 5 As shown in FIG. 1 and FIG. 2 , in the present embodiment, the first cam chain drive sprocket 65 among the cam chain drive sprockets 65 and 66 is arranged at a position overlapping with the crankshaft balance weight 10e or the connecting rod big end 17a in the vertical direction of the engine perpendicular to the crankshaft direction. Therefore, the first cam chain drive sprocket 65 and the first cam chain 67 can be arranged close to the left and right inner sides of the engine 1, which can make the engine 1 compact in the width direction.

[0088] In addition, if Figure 3 and Figure 5 As shown, the idler driving gear 62 and the idler driven gear 63 rotate synchronously, and the idler driving gear 62 and the idler driven gear 63 rotate relative to the idler gear support shaft 31 supporting these gears 62 and 63. The idler gear support shaft 31 is fixed to the crankcase 11 of the engine 1.

[0089] According to this structure, it is not necessary to provide a bearing between the idler gear support shaft 31 and the crankcase 11 , so that the area around the idler gear support shaft 31 can be reduced in size.

[0090] Furthermore, an intermediate gear 62s that functions as a backlash absorbing mechanism is provided on the idle drive gear 62. According to this configuration, the backlash absorbing mechanism can be provided compactly.

[0091] Furthermore, the idler gear support shaft 31 is hollow with a bottom. The idler gear support shaft 31 is fixed to the crankcase 11 with its bottom abutting against the crankcase 11. Furthermore, the idler gear support shaft 31 includes an oil supply hole 31h for supplying oil from the interior to the idler drive gear 62 and the idler driven gear 63. This configuration allows for a compact lubrication structure for the gears provided on the idler gear support shaft 31.

[0092] Alternatively, an oil supply hole 31 h for supplying oil to at least one of the idle driving gear 62 and the idle driven gear 63 may be provided.

[0093] In addition, if Figure 1As shown, the idler gear support shaft 31 is arranged between the crankshaft 10 and the main shaft 21 arranged parallel to the crankshaft 10 when the engine is viewed from the side. According to this structure, the space between the crankshaft 10 and the main shaft 21 can be effectively utilized, and the idler gear support shaft 31 can be arranged compactly.

[0094] In addition, if Figure 5 As shown, the primary drive gear 41 is provided for transmitting the rotation of the crankshaft 10 to the main shaft 21. The primary drive gear 41 is arranged closer to the inside of the engine than the idle driven gear 63. This configuration allows the primary drive gear 41 to be arranged closer to the inside of the engine, thereby reducing the torsional torque acting on the crankshaft 10 and making the area around the crankshaft 10 compact.

[0095] Furthermore, the first cam chain drive sprocket 65, the second cam chain drive sprocket 66, and the cam chain drive gear 64 are coaxially arranged as an integral component. Bearings 33 and 34 are press-fitted into both ends of this integral component. The first cam chain drive sprocket 65 is formed on the outer periphery of the portion of this integral component where the bearing 33 is press-fitted on the crankcase 11 side. This structure facilitates compact axial formation of the component including the cam chain drive sprockets 65 and 66 and the cam chain drive gear 64, contributing to a reduction in the width of the engine 1.

[0096] Moreover, if Figure 3 As shown, the engine 1 of this embodiment is provided with cam chains 67 and 68 on the side of the engine. The cam chain drive sprockets 65 and 66 that drive the cam chains 67 and 68 are driven by a cam chain drive gear 64 coaxially arranged on the side of the engine. The cam chain drive gear 64 is driven by an idler driven gear 63, which is driven by an idler drive gear 62 that meshes with a timing gear 61 (a predetermined gear) provided on the crankshaft 10. Furthermore, a balancer 80 is arranged coaxially with the idler drive gear 62.

[0097] According to this configuration, the balancer 80 can be compactly arranged even in a portion other than the portion with a high degree of freedom in front of the engine, and the engine 1 can be made more compact.

[0098] Furthermore, the idle driven gear 63 and the idle driving gear 62 rotate synchronously and rotate relative to the idle gear support shaft 31 that supports these gears. The balancer 80 rotates relative to the idle gear support shaft 31 and rotates at a different rotational speed from the idle driving gear 62. With this configuration, the balancer 80 can be arranged coaxially with the idle driving gear 62, and the rotational speeds of the cam chain drive system and the balancer drive system including the idle driving gear 62 can be independently set, thereby ensuring design freedom for each drive system.

[0099] Furthermore, a balancer driven gear 72 is provided, which is driven by a balancer drive gear 71 provided on the crankshaft 10. The balancer 80 is integrally provided on the balancer driven gear 72. This configuration, with the balancer drive gear 71 dedicated to the balancer, allows for variable tooth counts in both the balancer drive system and the cam chain drive system, increasing the flexibility of the speed ratios of each drive system. Furthermore, the integration of the balancer 80 and the balancer driven gear 72 contributes to a reduced number of components and miniaturization.

[0100] Furthermore, the balancer 80 is positioned outside the idler drive gear 62 in the crankshaft direction, i.e., outside the engine. This configuration allows the cam chain drive system, including the idler drive gear 62, to be positioned closer to the inside of the engine, thereby making the engine 1 more compact. Furthermore, when the specifications of the balancer 80 are changed, or when a specification is changed to one without the balancer 80, there is no need to significantly alter the internal layout of the engine 1, such as the layout of the cam chain drive system.

[0101] In addition, if Figure 3 and Figure 5 As shown, the clutch mechanism 51 is provided to cut off the power transmission from the crankshaft 10. In a cross-sectional view taken along a plane that cuts the axis of the crankshaft 10 and the axis of the clutch mechanism 51 (equivalent to the axis of the main shaft 21), the balancer 80 and the clutch mechanism 51 overlap in a direction perpendicular to the crankshaft direction. This structure allows the balancer 80 to be arranged in a space that is free in a direction perpendicular to the crankshaft direction relative to the clutch mechanism 51, enabling a compact arrangement of the balancer 80.

[0102] Furthermore, the idler driven gear 63 is arranged on the crankshaft 10, outward in the crankshaft direction, i.e., outward from the engine, relative to the primary drive gear 41. The balancer driven gear 72 is arranged on the crankshaft 10, outward in the crankshaft direction, i.e., outward from the engine, relative to the idler driven gear 63. With this configuration, when the specifications of the balancer 80 are changed, or when a specification is changed to one without the balancer 80, it is not necessary to significantly change the internal layout of the engine 1, for example, the layout of the drive system including the primary drive gear 41, or the layout of the drive system including the idler driven gear 63.

[0103] [Other embodiments]

[0104] The above-described embodiment merely shows one mode of the present invention, and can be arbitrarily modified and applied without departing from the spirit of the present invention.

[0105] For example, in the above embodiment, the first cam chain drive sprocket 65 is arranged so as to overlap with the crankshaft counterweight 10e or the connecting rod big end 17a in the engine vertical direction. However, the present invention is not limited thereto. The second cam chain drive sprocket 66 may be arranged so as to overlap with the crankshaft counterweight 10e or the connecting rod big end 17a in the engine vertical direction. Furthermore, both the first cam chain drive sprocket 65 and the second cam chain drive sprocket 66 may be arranged so as to overlap with the crankshaft counterweight 10e or the connecting rod big end 17a in the engine vertical direction.

[0106] In addition, in the above embodiment, it is described that Figure 1 Although the balancer 80 is disposed coaxially with the idler drive gear 62 in the V-type engine 1 shown in FIG. 1 and FIG. 2 , the present invention is not limited thereto, and the balancer 80 may be disposed coaxially with the idler drive gear 62 in engines other than the V-type.

[0107] Furthermore, although the present invention has been described as being applied to the engine 1 mounted on a motorcycle, the present invention is not limited thereto and may be applied to engines mounted on saddle-riding vehicles other than motorcycles, vehicles other than saddle-riding vehicles, and mobile objects other than vehicles.

[0108] [Structure supported by the above-mentioned embodiment]

[0109] The above-mentioned embodiment supports the following structure.

[0110] (Structure 1) A V-type engine, wherein the V-type engine has a crankshaft, and the large ends of the connecting rods of the adjacent front and rear cylinders on the crank pin of the crankshaft are adjacent to each other with the crank arm of the crankshaft in between, and a cam chain is provided on one side of the engine side of the front and rear cylinders, and the cam chain drive sprocket that drives each cam chain is driven by a cam chain drive gear coaxially arranged on the engine side, and the cam chain drive gear is driven by an idle driven gear, and the idle driven gear is driven by an idle driving gear meshing with the timing gear of the crankshaft, wherein at least one of the cam chain drive sprockets is arranged at a position overlapping with the crankshaft balance weight or the large end of the connecting rod in the vertical direction of the engine.

[0111] According to this configuration, the cam chain drive sprocket can be arranged close to the left and right inner sides of the engine, and the engine can be made more compact.

[0112] (Structure 2) In the V-type engine of Structure 1, the idle driving gear rotates synchronously with the idle driven gear, and the idle driving gear and the idle driven gear rotate relative to the idle gear support shaft supporting the idle driving gear and the idle driven gear, and the idle gear support shaft is fixed to the crankcase of the engine.

[0113] According to this configuration, it is not necessary to provide a bearing between the idler gear support shaft and the crankcase, and thus the area around the idler gear support shaft can be reduced in size.

[0114] (Structure 3) In the V-type engine of Structure 1 or 2, a backlash absorbing mechanism is provided on the idle drive gear.

[0115] According to this configuration, the backlash absorbing mechanism can be provided compactly.

[0116] (Structure 4) In the V-type engine of Structure 2 or 3, the idler gear support shaft has a hollow shape with a bottom, the idler gear support shaft has a bottom that abuts against the crankcase and is fixed to the crankcase, and the idler gear support shaft has an oil supply hole for supplying oil from the inside to at least one of the idler drive gear and the idler driven gear.

[0117] According to this configuration, the lubrication structure for the gear provided on the idler gear support shaft can be compactly provided.

[0118] (Structure 5) In the V-type engine of any one of Structures 2 to 4, the idler gear support shaft is arranged between the crankshaft and a main shaft provided parallel to the crankshaft when the engine is viewed from the side.

[0119] According to this configuration, the idler gear support shaft can be compactly arranged by effectively utilizing the space between the crankshaft and the main shaft.

[0120] (Structure 6) In the V-type engine of any one of Structures 1 to 5, the V-type engine has a primary drive gear that transmits the rotation of the crankshaft to the main shaft of the engine, and the primary drive gear is arranged at a position closer to the inside of the engine than the idle driven gear.

[0121] According to this configuration, the primary drive gear can be arranged closer to the inside of the engine, so that the torsional torque acting on the crankshaft can be reduced and the area around the crankshaft can be made compact.

[0122] (Structure 7) In the V-type engine of any one of Structures 1 to 6, the cam chain drive sprocket and the cam chain drive gear are coaxial and arranged as an integral component, bearings are pressed into both ends of the integral component, and the cam chain drive sprocket is formed on the outer periphery of the portion on the crankcase side of the integral component into which the bearings are pressed.

[0123] According to this structure, it is easy to form the components including the cam chain drive sprocket and the cam chain drive gear compactly in the axial direction, which contributes to shortening the width of the engine.

Claims

1. A V-type engine, wherein: The V-type engine has a crankshaft (10), and the connecting rod large ends (17a) of the adjacent front and rear cylinders on the crankpin (10d) of the crankshaft (10) are adjacent to each other via the crank arm (10c) of the crankshaft (10). Cam chains (67, 68) are provided on one side of the engine of the front and rear cylinders (12F, 12R), respectively. The cam chain drive sprockets (65, 66) that drive the cam chains (67, 68) are driven by the cam chain drive gear (64) coaxially arranged on the side of the engine. The cam chain driving gear (64) is driven by an idle driven gear (63), and the idle driven gear (63) is driven by an idle driving gear (62) meshing with a timing gear (61) of the crankshaft (10). in, At least one of the cam chain drive sprockets (65, 66) is arranged at a position overlapping with the crankshaft balance weight (10e) or the connecting rod large end (17a) in the vertical direction of the engine.

2. The V-type engine according to claim 1, wherein: The idle driving gear (62) and the idle driven gear (63) rotate synchronously, and the idle driving gear (62) and the idle driven gear (63) rotate relative to an idle gear support shaft (31) supporting the idle driving gear (62) and the idle driven gear (63). The idler gear support shaft (31) is fixed to the crankcase (11) of the engine.

3. The V-type engine according to claim 2, wherein: The idle driving gear (62) is provided with a backlash absorbing mechanism (62s).

4. The V-type engine according to claim 2, wherein: The idle gear support shaft (31) is a hollow shape with a bottom. The idle gear support shaft (31) has a bottom that abuts against the crankcase (11) and is fixed to the crankcase (11). The idle gear support shaft (31) has an oil supply hole (31h) for supplying oil from the inside to at least one of the idle driving gear (62) and the idle driven gear (63).

5. The V-type engine according to claim 2, wherein: When the engine is viewed from the side, the idler gear support shaft (31) is arranged between the crankshaft (10) and a main shaft (21) provided parallel to the crankshaft (10).

6. The V-type engine according to claim 1, wherein: The V-type engine has a primary drive gear (41) for transmitting the rotation of the crankshaft (10) to the main shaft (21) of the engine. The primary drive gear (41) is arranged at a position closer to the inside of the engine than the idle driven gear (63).

7. The V-type engine according to claim 1, wherein: The cam chain drive sprockets (65, 66) and the cam chain drive gear (64) are coaxial and are provided as an integral component, bearings (33, 34) are pressed into both ends of the integral component, and the cam chain drive sprocket (65) is formed on the outer periphery of the portion of the crankcase (11) side of the integral component where the bearing (33) is pressed.

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