JP5698100B2 - Vehicle power unit - Google Patents

Description

In the present invention, a V-belt automatic transmission is provided on the side of the internal combustion engine, and a drive wheel is rotatably supported behind the V-belt automatic transmission, and between the rear portion of the V-belt automatic transmission and the drive wheel. Further, the present invention relates to a vehicle power unit provided with a gear reducer that decelerates the rotation of a driven shaft of a V-belt automatic transmission and transmits it to drive wheels.

  Conventionally, the lubrication required part of the internal combustion engine close to the crank chamber is lubricated via an oil pump driven by a crankshaft. Is not provided (see, for example, Patent Document 1). Further, inside the gear reducer, a part of the gear is immersed in the lubricating oil, and the meshing portion of the gear is lubricated by the oil splashed with the rotation of the gear. In the splash-type lubrication with a gear, a part of the gear is immersed in the lubricating oil, so that power loss occurs due to the stirring of the lubricating oil by the gear, and in order to immerse a part of the gear in the lubricating oil, Optimization of the gear shaft layout and reduction of the amount of lubricating oil were issues.

Japanese Patent No. 4425646

  The present invention seeks to reduce power loss due to the agitation of lubricating oil by the gears in the gear reducer, increase the degree of freedom of arrangement of the gear shaft of the gear reducer, and reduce the amount of lubricating oil.

The present invention solves the above-mentioned problems. In the invention according to claim 1, a V-belt automatic transmission is provided on the side of the internal combustion engine, and a drive wheel rotates behind the V-belt automatic transmission. In the vehicular power unit supported in a possible manner, a gear reducer that reduces the rotation of the driven shaft of the V-belt automatic transmission and transmits it to the drive wheel between the V-belt automatic transmission and the drive wheel, A transmission case member on one side of the V-belt automatic transmission is formed as a partition, and is separated from the V-belt automatic transmission, and oil in the gear case is accommodated in the gear case that houses the gear reducer. An oil pump for lubrication for supplying to the meshing portion of the gear is provided, and the oil pump is disposed at the lowermost part in the gear case, and each gear shaft of the gear reducer is a driven shaft of the V-belt automatic transmission. Against the same height or A power unit, characterized in that arranged in even higher level.

According to a second aspect of the present invention, in the power unit according to the first aspect, the oil passage from the oil pump to the meshing portion has a groove shape on the mating surface of a pair of left and right gear case members forming the gear case. It is provided in.

According to a third aspect of the present invention, in the power unit according to the first or second aspect, the oil pump is attached to the opposite side wall surface of the drive wheel of the gear case member in the gear case, and the drive wheel is viewed in a side view. It arrange | positions so that it may overlap with a part of outer periphery of the brake drum provided in this.

According to a fourth aspect of the present invention, there is provided a vehicular power unit in which a V-belt automatic transmission is provided on a side of an internal combustion engine, and drive wheels are rotatably supported behind the V-belt automatic transmission. A gear reducer that decelerates the rotation of the driven shaft of the V-belt automatic transmission and transmits it to the drive wheel between the belt automatic transmission and the drive wheel is a transmission case member on one side of the V-belt automatic transmission. A lubricating oil pump that is formed separately from the V-belt automatic transmission with a wall as a partition wall and supplies oil inside the gear case housing the gear reducer to the meshing portion of the gear of the gear reducer. Provided, the bottom wall of the gear case member constituting the gear case is extended downward to form an oil pump arrangement space, and an oil suction port of the oil pump is provided to open to a lower portion of the space. Features It is a power unit that.

According to a fifth aspect of the present invention, in the power unit according to the fourth aspect, the oil passage from the oil pump to the meshing portion has a groove shape on a mating surface of a pair of left and right gear case members forming the gear case. It is provided in.

According to a sixth aspect of the present invention, in the power unit according to the fourth or fifth aspect, the oil pump is attached to the opposite side wall surface of the drive wheel of the gear case member in the gear case, and the drive wheel is viewed in a side view. It arrange | positions so that it may overlap with a part of outer periphery of the brake drum provided in this.

According to the invention described in claim 1 , since the oil pump dedicated to the gear reducer is provided in the gear case, lubrication is efficiently performed with a small amount of oil, and the required oil amount is reduced. Since the degree of freedom of the arrangement of the gear shaft of the gear reducer increases, it is possible to reduce the power loss accompanying the stirring of the lubricating oil by the gears in the gear reducer and to reduce the size of the gear reducer.
Further, since oil is accumulated in the lower part of the gear case, the distance from the oil suction port of the oil pump to the low-pressure pump chamber can be shortened, and the pump structure can be simplified.
And even if each gear shaft of the gear reducer is at a position higher than the driven shaft of the V-belt automatic transmission, the oil is supplied from above the desired lubricating portion, so that the lubricating performance is ensured. Therefore, since the gear wheel shaft is at a high position, the driving wheel of the vehicle can be enlarged, so that the riding comfort is improved while maintaining the low center of gravity of the power unit.

According to the invention described in claim 2, by utilizing the mating surfaces of the pair of gear case member, the formation of the oil passage from the gear case bottom of the oil pump to the upper gear case is facilitated, oil desired lubrication Since it can be supplied from above the section, lubrication is effectively performed.

According to the third aspect of the present invention , the brake drum receiving rib provided on the outer wall surface of the gear case member reinforces the oil pump mounting portion in the gear case member, and the stress concentration in the oil pump mounting portion is alleviated. Is done.

According to the invention of claim 4 , since the oil pump dedicated to the gear reducer is provided in the gear case, lubrication is efficiently performed with a small amount of oil, and the required oil amount is reduced. Since the degree of freedom of the arrangement of the gear shaft of the gear reducer increases, it is possible to reduce the power loss accompanying the stirring of the lubricating oil by the gears in the gear reducer and to reduce the size of the gear reducer.
Further, since the bottom wall of the gear case member constituting the gear case is extended downward to form an oil pump arrangement space, the oil pump has good oil collecting performance, and the lubricating oil is efficiently collected inside the gear case. Since the natural circulation is performed, the amount of oil required for lubrication is reduced.

According to the invention described in claim 5, by utilizing the mating surfaces of the pair of gear case member, the formation of the oil passage from the gear case bottom of the oil pump to the upper gear case is facilitated, oil desired lubrication Since it can be supplied from above the section, lubrication is effectively performed.

According to the sixth aspect of the present invention , the brake drum receiving rib provided on the outer wall surface of the gear case member reinforces the oil pump mounting portion in the gear case member, and the stress concentration in the oil pump mounting portion is reduced. Is done.

1 is a left side view of a motorcycle equipped with a power unit according to an embodiment of the present invention. It is a longitudinal cross-sectional left view of the said power unit. It is III-III sectional drawing of FIG. It is a longitudinal cross-sectional left view of the gear reducer which forms a part of said power unit. It is VVV sectional drawing of FIG. It is VI-VI-VI cross-section expanded view of FIG. It is VII-VII sectional drawing of FIG. It is a longitudinal cross-sectional left view of the conventional gear reducer.

  FIG. 1 is a left side view of a motorcycle 2 equipped with a power unit 1 according to an embodiment of the present invention. A synthetic resin body cover 3 made of a plurality of parts is attached to the motorcycle 2, and the body frame and equipment are covered by the body cover 3. The body frame of the motorcycle 2 includes a head pipe, a main frame extending downward from the head pipe, a pair of left and right rear frames connected to the rear portion of the main frame and extending rearward, and a plurality of other frames. It is composed of A front wheel 5 is pivotally supported at the lower end of the front fork 4 that is rotatably supported by the head pipe, and a steering handle 6 is connected to the upper portion of the front fork 4. An air cleaner 7 is provided above the power unit 1.

  FIG. 2 is a left side view of the vertical cross section of the power unit 1. “Front / Rear / Left / Right” used in the description of the power unit 1 corresponds to “Front / Rear / Left / Right” of the motorcycle 2 on which the power unit 1 is mounted. The power unit 1 is suspended by a bracket fixed to the front portion of the rear frame of the motorcycle 2 via a hanger 10 formed integrally with the power unit 1 and a support shaft 11. A rear cushion 13 (FIG. 1) is provided between a bracket 12 provided at the rear end portion of the power unit 1 and a bracket fixed to the rear portion of the rear frame. As a result, the power unit 1 is suspended so as to be able to swing with its cylinder axis slightly raised forward. A driving wheel 15 (FIG. 1) for driving the motorcycle 2 is attached to a right protruding portion of the rear axle 14 provided at the rear portion of the power unit 1, and is driven by the power unit 1.

  In FIG. 2, the power unit 1 includes a front internal combustion engine 16 and a transmission 17 that extends from the left side of the internal combustion engine 16 rearward to the rear axle 14. The transmission device 17 includes a V-belt automatic transmission 18 and a gear reducer 19.

  The internal combustion engine 16 is a rocker arm type overhead valve type 4-stroke cycle single cylinder water-cooled internal combustion engine. The shell of the internal combustion engine 16 includes a crankcase 20, a cylinder block 21, a cylinder head 22, and a cylinder head cover 23 that are sequentially coupled to the front of the crankcase 20. A throttle body 25 is attached to an inlet pipe 24 attached to an intake port on the upper side of the cylinder head 22, and an air cleaner 7 (FIG. 1) is connected to the rear thereof. A fuel injection valve 26 is attached to the inlet pipe 24.

  3 is a cross-sectional view taken along the line III-III in FIG. In the power unit 1 of FIG. 3, the crankcase 20 is a left-right halved type, and is composed of a right crankcase 20R and a left crankcase 20L. The crankshaft 30 is rotatably supported by ball bearings 31A and 31B supported by the crankcase 20. The piston 32 is slidably fitted in a cylinder hole 33 formed in the cylinder block 21. The piston 32 is connected to the crankpin 35 via a connecting rod 34, and when the piston 32 reciprocates, the crankshaft 30 is driven to rotate. A combustion chamber 36 is formed on the bottom surface of the cylinder head 22 so as to face the top surface of the piston 32. A spark plug 37 facing the combustion chamber 36 is attached to the cylinder head 22.

  In the right half of the power unit 1 shown in FIG. 3, the cam chain drive sprocket 38 formed adjacent to the ball bearing 31 B of the crankshaft 30 and the cam chain driven sprocket 40 provided on the camshaft 39. A cam chain 41 is wound around. As a result, the camshaft 39 is driven in accordance with the rotation of the crankshaft 30. A water pump 42 is formed at the end of the cam shaft 39. As the cam shaft 39 rotates, the cooling water delivered from the water pump 42 circulates in the water jacket of the cylinder block 21 and the cylinder head 22. And sent to the radiator 43.

  An AC generator 44 is provided on the right extension of the crankshaft 30. The AC generator stator 45 is fixedly attached to the right crankcase 20R. The AC generator rotor 46 is fixed to the right end of the crankshaft 30 and rotates together with the crankshaft 30. A centrifugal cooling fan 47 is attached to the end of the crankshaft 30 on the right side of the AC generator rotor 46. This draws outside air into the radiator 43 and promotes cooling of the cooling water in the radiator 43. The right side of the radiator 43 is covered with a radiator cover 48 that guides cooling air to the radiator 43.

  In the left half of the power unit 1 in FIG. 3, the V-belt automatic transmission 18 is accommodated in a transmission case 50. The transmission case 50 includes a transmission case right member 50R and a transmission case left member 50L. The transmission case right member 50R is formed integrally with the left crankcase 20L. That is, the front half of this integral member acts as the left crankcase 20L, and the rear half acts as the transmission case right member 50R. The transmission case left side member 50L is coupled to the transmission case right side member 50R by a bolt.

  The drive shaft of the V-belt automatic transmission 18 is a left extension 30E of the crankshaft 30 extending into the transmission case 50. A drive pulley 51 for the V-belt automatic transmission 18 is provided on the crankshaft left extension 30E. The inside of the crankcase 20 and the inside of the transmission case 50 are liquid-tightly blocked by a seal material 57. The drive pulley 51 includes a fixed half 51A, a movable half 51B, a weight roller 51C, and a ramp plate 51D.

  The driven shaft 52 of the V-belt automatic transmission 18 is pivotally supported by the transmission case left side member 50L and the transmission case right side member 50R via ball bearings 53A and 53B. A driven pulley 55 is provided on the driven shaft 52 via a centrifugal clutch 54. The driven pulley 55 includes a fixed half 55A, a movable half 55B, a rotating sleeve 55C, and a coil spring 55D. The centrifugal clutch 54 provided on the driven pulley 55 includes a clutch outer 54A and a clutch inner 54B. The clutch outer 54A is connected to the driven shaft 52, and the clutch inner 54B is connected to the rotating sleeve 55C. An endless V-belt 56 is stretched between the drive pulley 51 and the driven pulley 55.

  When the rotational speed of the crankshaft 30 increases, in the drive pulley 51, the weight roller 51C between the movable half 51B and the ramp plate 51D moves radially outward by centrifugal force, and the movable half 51B is pushed. As a result, the winding diameter of the V-belt 56 is increased. As a result, the tension of the V-belt 56 is increased, so that on the driven pulley 55 side, the movable half 55B moves against the biasing force of the coil spring 55D, and the winding diameter of the V-belt 56 is reduced. As a result, the rotational speed of the driven pulley 55 increases according to the dimensional ratio of the winding diameter of the V belt 56. When the driven pulley 55 rotates beyond a predetermined rotational speed, the centrifugal clutch 54 is connected and the driven shaft 52 is driven to rotate.

  In FIG. 3, a gear reducer 19 is provided on the right side of the rear portion of the V-belt automatic transmission 18. The gear reducer 19 is accommodated in the gear case 60. The gear case 60 is configured by combining the rear portion of the transmission case right member 50R and the gear case right member 60R. That is, the gear reducer 19 is formed separately from the V-belt automatic transmission 18 with the transmission case right member 50R on one side of the V-belt automatic transmission 18 as a partition. The gear reducer 19 is for reducing the speed of the driven shaft 52 of the V-belt automatic transmission 18 between the V-belt automatic transmission 18 and the drive wheel 15 and transmitting it to the drive wheel 15. The gear case right member 60R is coupled to the rear portion of the transmission case right member 50R by a bolt 58 or the like. A right extension 52E of the driven shaft 52 extends into the gear case 60.

  FIG. 4 is a left side view of the longitudinal section of the gear reducer 19 and shows the inside of the gear case 60 except for the rear portion of the V-belt automatic transmission 18. The input shaft of the gear reducer 19 is a driven shaft rightward extension 52E of the V-belt automatic transmission 18 that extends into the gear case 60. An intermediate shaft 63 is provided between the driven shaft right extension 52E and the rear axle 14.

FIG. 5 is a VV-V cross-sectional view of the gear reducer 19 of FIG. The right end of the driven shaft right extension 52E shown in FIG. 5 is rotatably supported by the gear case right member 60R by a ball bearing 53C. The inside of the transmission case 50 and the inside of the gear case 60 are liquid-tightly blocked by the seal material 61.

  4 and 5, the rear axle 14 with the drive wheel 15 integrally coupled is rotated to the transmission case right member 50R, the gear case right member 60R, and the right support arm 27 via ball bearings 62A, 62B, 62C. It is supported freely. The intermediate shaft 63 is rotatably supported by the transmission case right member 50R and the gear case right member 60R via ball bearings 64A and 64B. The torque of the driven shaft 52 is transmitted to the rear axle 14 via the driven shaft pinion 52a of the driven shaft rightward extension 52E, the intermediate shaft large diameter gear 65, the intermediate shaft 63, the intermediate shaft pinion 63a, and the rear axle large diameter gear 66. Is done. The rear axle 14 is greatly decelerated with respect to the driven shaft 52, and the drive wheels 15 coupled to the rear axle 14 are driven to decelerate.

  An oil pump 67 is provided below the intermediate shaft 63 in the gear case 60 shown in FIG. An oil pump gear 69 that meshes with the intermediate shaft large-diameter gear 65 is fixed to the oil pump shaft 68 of the oil pump 67. The oil pump 67 is driven by an intermediate shaft large diameter gear 65 via an oil pump gear 69. This oil pump is a lubricating oil pump that supplies oil in the gear case 60 to the gear meshing portion 82 of the gear reducer 19. Since the oil pump 67 dedicated to the gear reducer is provided in the gear case 60, lubrication is efficiently performed with a small amount of oil, and the required oil amount is reduced. In addition, since the degree of freedom of the arrangement of the gear shaft of the gear reducer 19 is increased, reduction of power loss due to the agitation of the lubricating oil in the gear reducer (19) and reduction of the size of the gear reducer (19) are achieved. It is done.

  FIG. 6 is a sectional development view taken along line VI-VI-VI in FIG. This drawing is a developed view of a cross section passing through the oil pump shaft 68. FIG. 4 and 6, the bottom walls of the gear case right member 60R and the transmission case right member 50R constituting the gear case 60 are extended downward to form an oil pump arrangement space 70. An oil pump 67 is disposed below the shaft 63 and at the lowest part in the gear case 60. Since the oil pump 67 is arranged at the lowermost part in the gear case 60, the distance from the oil accumulated in the lower part of the gear case 60 to the suction port of the oil pump 67 can be shortened, and the pump structure can be simplified. . Since the oil collecting property is improved by the arrangement of the oil pump 67, the lubricating oil is efficiently circulated inside the gear case 60, and the amount of oil necessary for lubrication is reduced.

  In FIG. 6, the oil pump 67 is attached to the inner wall surface of the gear case right side member 60R which is the gear case member on the side close to the drive wheel 15, that is, on the opposite side wall surface of the drive wheel 15 by bolts 71 or the like. In FIG. 4, the brake drum 72 is disposed so as to overlap a part of the outer periphery of the brake drum 72 provided on the drive wheel 15. Therefore, the brake drum receiving rib 73 provided on the outer wall surface of the gear case right side member 60R reinforces the oil pump mounting portion in the gear case right side member 60R, so that stress concentration in the oil pump mounting portion is alleviated.

  FIG. 7 is a cross-sectional view taken along the line VII-VII in FIG. 4 and 7, an oil suction port 74 is opened on the inner wall surface of the gear case right member 60R below the oil pump arrangement space 70. An oil suction passage 76 from the oil suction port 74 toward the low pressure pump chamber 75 of the oil pump 67 is provided in the wall of the gear case right side member 60R. An oil discharge port 78 of the oil pump 67 is opened at a mating surface 77 of the gear case right member 60R with respect to the transmission case right member 50R. An oil discharge passage 80 from the high-pressure pump chamber 79 of the oil pump 67 toward the oil discharge port 78 is provided in the wall of the gear case right side member 60R.

  Further, a groove-like oil passage 81 extending from the oil discharge port 78 to the upper portion of the mating surface 77 is provided in the groove shape on the mating surface 77 of the gear case right side member 60R. Two downward oil jetting holes 83 from the groove-like oil passage 81 toward the two gear meshing portions 82 of the gear reducer 19 are provided in the upper portion of the mating surface 77. The oil accumulated in the lower part of the gear case 60 is sucked into the oil pump 67, discharged to the oil discharge port 78 of the mating surface 77, and sent to the upper part of the gear reducer 19 through the groove-like oil passage 81, and the oil injection hole Injected downward from 83 toward the meshing portion 82 of the gear. The use of the mating surface 77 of the gear case 60 facilitates the formation of the oil passage 81 from the lower part to the upper part of the gear case 60, and the oil is supplied from above to the gear meshing part 82, so that lubrication is effective. To be done.

  In FIG. 4, in the gear reducer 19, the intermediate shaft 63 is arranged at the same height and the rear axle 14 is arranged at a higher height than the driven shaft rightward extension 52E of the V-belt automatic transmission 18. Yes. Even if the gear shaft of the gear reducer 19 is at a position higher than the driven shaft 52 of the V-belt automatic transmission 18, oil is supplied from above the gear meshing portion 82, so that the lubricating performance is ensured. Therefore, in particular, since the rear axle 14 is at a high position, the drive wheels 15 of the vehicle can be enlarged, so that the ride comfort can be improved while maintaining the low center of gravity of the power unit 1.

  In FIG. 4, a gear case breather hose 84 extends from the upper part of the gear case 60. This is connected to the intake chamber of the air cleaner 7. A vehicle speed sensor 85 is provided above the gear case 60. This is a device that detects the tooth tip speed of the rear axle large-diameter gear 66 provided on the rear axle 14 in order to calculate the vehicle speed.

  In FIG. 4, a broken line A is a line indicating an oil level when lubricating oil is injected into the gear reducer 19 of the above-described embodiment. The oil is filled to substantially the vicinity of the upper edge of the oil pump arrangement space 70. Since the intermediate shaft large-diameter gear 65 and the rear axle large-diameter gear 66 are not immersed in oil, power loss due to oil agitation is reduced.

  FIG. 8 is a vertical sectional left view of a conventional gear reducer 19x. The inside of the gear case 60x is shown. The arrangement of the reduction gears is substantially the same as in the above embodiment. The reference numerals of the conventional members corresponding to the members of the above embodiment are indicated by adding “x” to the reference numerals of the corresponding members in the above embodiments. In the conventional gear reducer 19x, the oil pump arrangement space 70 and the oil pump 67 provided in the above embodiment are not provided. A broken line B in FIG. 8 is a line showing an oil level when lubricating oil is injected into the conventional gear reducer 19x. The intermediate shaft large-diameter gear 65x and the rear axle large-diameter gear 66x are immersed in oil. Lubrication of the meshing portion of each gear is performed by oil splashed with the rotation of these gears. For this reason, there is an increase in power loss accompanying oil agitation. Further, comparing the oil filling amounts of FIG. 4 and FIG. 8, it is estimated that the required amount of oil is much smaller in the above embodiment than in the conventional gear reducer 19x.

  DESCRIPTION OF SYMBOLS 1 ... Power unit, 14 ... Rear axle, 15 ... Drive wheel, 16 ... Internal combustion engine, 18 ... V belt automatic transmission, 19 ... Gear reducer, 50R ... Transmission case right side member, 52 ... Driven shaft, 60 ... Gear case , 60R ... gear case right side member, 63 ... intermediate shaft, 67 ... oil pump, 72 ... brake drum, 73 ... brake drum receiving rib, 74 ... oil suction port, 77 ... mating surface, 81 ... groove oil passage, 82 ... Gear meshing part

Claims (6)

A V-belt automatic transmission (18) is provided on the side of the internal combustion engine (16),
In the vehicle power unit (1) in which the drive wheel (15) is rotatably supported behind the V-belt automatic transmission (18),
Gear speed reduction that reduces the rotation of the driven shaft (52) of the V-belt automatic transmission (18) between the V-belt automatic transmission (18) and the drive wheel (15) and transmits it to the drive wheel (15). A machine (19) is formed with the transmission case member (50R) on one side of the V-belt automatic transmission (18) as a partition, and is separated from the V-belt automatic transmission (18), and the gear reducer (19 ) In the gear case (60) that houses the oil oil (67) for lubrication that supplies the oil inside the gear case (82) of the gear reducer (19),
The oil pump (67) is disposed at the bottom of the gear case (60),
Each gear shaft (63) (14) of the gear reducer (19) is disposed at the same height or higher than the driven shaft (52) of the V-belt automatic transmission (18). <br/> A power unit characterized by this. The oil passage (81) from the oil pump (67) to the meshing portion (82) has a groove shape on the mating surface of a pair of left and right gear case members (50R) (60R) forming the gear case (60). The power unit according to claim 1 , wherein the power unit is provided on the power unit. The oil pump (67) is mounted on the opposite side wall surface of the drive wheel (15) of the gear case member (60R) in the gear case (60), and is provided on the drive wheel (15) in a side view. The power unit according to claim 1 or 2 , wherein the power unit is arranged so as to overlap a part of the outer periphery of the drum (72). A V-belt automatic transmission (18) is provided on the side of the internal combustion engine (16),
In the vehicle power unit (1) in which the drive wheel (15) is rotatably supported behind the V-belt automatic transmission (18),
Gear speed reduction that reduces the rotation of the driven shaft (52) of the V-belt automatic transmission (18) between the V-belt automatic transmission (18) and the drive wheel (15) and transmits it to the drive wheel (15). A machine (19) is formed with the transmission case member (50R) on one side of the V-belt automatic transmission (18) as a partition, and is separated from the V-belt automatic transmission (18), and the gear reducer (19 ) In the gear case (60) that houses the oil oil (67) for lubrication that supplies the oil inside the gear case (82) of the gear reducer (19),
The bottom wall of the gear case member (50R) (60R) constituting the gear case (60) extends downward to form an oil pump arrangement space, and the oil suction port (74) of the oil pump (67) A power unit, wherein the power unit is provided so as to open at a lower portion of the space. The oil passage (81) from the oil pump (67) to the meshing portion (82) has a groove shape on the mating surface of a pair of left and right gear case members (50R) (60R) forming the gear case (60). The power unit according to claim 4 , wherein the power unit is provided on the power unit. The oil pump (67) is mounted on the opposite side wall surface of the drive wheel (15) of the gear case member (60R) in the gear case (60), and is provided on the drive wheel (15) in a side view. The power unit according to claim 4 or 5 , wherein the power unit is disposed so as to overlap a part of the outer periphery of the drum (72).

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