JP2007015455A - Cooling structure of power unit for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power unit for a vehicle in which a cooling device for a small-sized vehicle equipped with a radiator is installed optimally. <P>SOLUTION: The power unit 6 is equipped with an engine 19 mounted on a motor tricycle 1 and emitting a rotational driving force from a crank shaft 26 installed parallel with a rear wheel shaft 33 where rear wheels 4L and 4R are connected and a transmission device 37 to transmit the rotational driving force of the crank shaft 26 to the rear wheel shaft 33 through a counter-shaft 34 installed parallel with the rear wheel shaft 33, and further with the radiator 63 to perform heat emission from the cooling water for cooling the engine 19, wherein the radiator 63 has a heat emitting surface directed to ahead of the motor tricycle 1 and is installed in front of the rear right wheel 4R. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cooling structure for a vehicle power unit that includes an internal combustion engine and a transmission and is mounted on a small vehicle such as a motor tricycle.

  In a small vehicle such as a conventional tricycle, a radiator is provided to dissipate the cooling water that has cooled the internal combustion engine. Generally, the heat radiation surface faces the side of the power unit. It is attached (for example, refer to Patent Document 1).

JP-A-9-249170

  However, if the radiator is disposed with the heat dissipation surface facing sideways in this way, the width of the power unit in the left-right direction can be reduced. However, it is possible to efficiently dissipate the cooling water by applying the running air to the heat dissipation surface. There was a problem that it was not possible. Further, when the radiator is disposed on the side portion of the power unit, there is a problem that the cooling water passage connecting the internal combustion engine and the radiator becomes long and the arrangement becomes complicated.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a cooling structure for a power unit for a vehicle that is disposed in front of a drive wheel while the heat dissipation surface of a radiator is directed forward.

  In order to solve the above-described problems, a cooling structure for a power unit for a vehicle according to the present invention is mounted on a vehicle (for example, the tricycle 1 in the embodiment), and driving wheels (for example, the rear wheels 4L and 4R in the embodiment). An internal combustion engine (for example, the engine 19 in the embodiment) that outputs a rotational driving force from a crankshaft arranged in parallel to the connected drive wheel shaft (for example, the rear wheel shaft 33 in the embodiment), and rotation of the crankshaft This is used in a vehicle power unit having a transmission that transmits a driving force to a driving wheel shaft via a counter shaft disposed in parallel to the driving wheel shaft, and dissipates heat from cooling water that cools the internal combustion engine. This radiator has a radiator to be operated, and the radiator is disposed in front of the driving wheel while directing the heat radiation surface toward the front of the vehicle.

  At this time, the internal combustion engine is positioned in front of the crankshaft, has a cylinder in which a piston that extends in the front-rear direction and rotates the crankshaft slides, and the radiator is disposed on the side of the cylinder of the internal combustion engine. Is preferred.

  In addition, the internal combustion engine has a cooling fan at the end of the crankshaft on the side where the radiator is disposed, and a cooling duct (for example, the ventilation passage 15c in the embodiment is formed to guide the running wind that has passed through the radiator to the cooling fan. It is preferable to have an engine cover 15).

  Furthermore, the driving wheel is composed of a left driving wheel and a right driving wheel, a crankshaft is disposed between the left driving wheel and the right driving wheel, and a radiator is disposed along the outer periphery of one of the left and right driving wheels. It is preferable.

  If the cooling structure for a vehicle power unit according to the present invention is configured as described above, the radiator can be arranged in a space located in front of the drive wheels, the power unit can be reduced in size, and the radiator heat-radiating surface faces forward. Therefore, the cooling water can be efficiently radiated using the traveling wind.

  Further, by disposing the radiator on the side of the cylinder, the piping of the cooling water that connects the radiator and the internal combustion engine can be shortened.

  Furthermore, a cooling fan is provided at the end of the crankshaft on the side where the radiator is disposed, and a cooling duct that connects the cooling fan and the radiator is provided, so that the running wind that has passed through the radiator can be used efficiently, and the radiator can be used. It can be cooled with a cooling fan.

  At this time, in the vehicle power unit in which the crankshaft is disposed between the left and right drive wheels, the radiator is disposed along the outer periphery of one of the drive wheels, thereby reducing the width in the left-right direction of the left and right drive wheels. Can be

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. First, a motor tricycle 1 on which a vehicle power unit according to the present invention (hereinafter simply referred to as “power unit”) is mounted will be described with reference to FIG. The tricycle 1 having one front wheel 3 and two rear wheels 4L and 4R has a body frame 2 formed in a U shape in a side view, and a steering mechanism 5 is provided at the front end of the body frame 2. The front wheel 3 is supported via the vehicle body, and a power unit 6 for driving the left and right rear wheels 4L and 4R is provided at the rear portion of the vehicle body frame 2. A seat 14 is attached to the upper part of the rear end of the vehicle body frame 2, and the power unit 6 is covered with an engine cover 15.

  The steering mechanism 5 has a head pipe 7 that is attached to the front portion of the vehicle body frame 2 and extends in the vertical direction. A steering shaft (not shown) is rotatably attached to the head pipe 7. A front fork 8 is attached to the lower end of the steering shaft, and the front wheel 3 is supported on the lower end of the front fork 8. On the other hand, a handle post 9 is attached to the upper end of the steering shaft. Further, a handle 10 is attached to the upper end of the handle post 9 and the front wheel 3 can be steered by operating the handle 10.

  A swinging member 11 extending downward is attached to a rear end portion of the lower part of the body frame 2 so as to be swingable with respect to the body frame 2 in a predetermined angle range in the front-rear direction. Further, a hanger member 12 extending rearward is attached to a lower end portion of the swing member 11 so as to be swingable in the vertical direction with respect to the swing member 11.

  The hanger member 12 is inserted into the other end side of the front end member 12a whose one end is pivotally connected to the swing member 11, and is rotatable relative to the front end member 12a around an axis extending rearward. The rear end member 12b is attached to the rear end member 12b, and the rear end member 12b is connected to the lower portion of the power unit 6. The hanger member 12 is supported by a shock absorber 13 having one end pivoted to the rear portion of the vehicle body frame 2 and the other end pivoted to the front end member 12 a of the hanger member 12.

  Now, the power unit 6 will be described with reference to FIGS. In this embodiment, the direction of the arrow F in FIG. 2 is assumed to be the front, and the direction of the arrow U is assumed to be the upper side. The power unit 6 includes an engine 19 including a cylinder head 20 and an engine case 21 and a transmission 37 stored in the transmission case 22.

  The engine case 21 is configured by combining a front case half 21a and a rear case half 21b. A cylinder chamber 23a is formed at a front portion of the front case half 21a surrounded by a cylinder sleeve 23 fitted to extend in the front-rear direction. The cylinder chamber 23a has a piston slidable in the front-rear direction. 24 is arranged. Further, the piston 24 is connected via a connecting rod 25 to a crankshaft 26 that is rotatably held by the engine case 21. An intake port and an exhaust port formed in the cylinder head 20 communicate with the combustion chamber 27 formed by the cylinder sleeve 23, the cylinder head 20 and the piston 24.

  The crankshaft 26 attached to the engine case 21 so as to extend in the left-right direction is composed of a left crankshaft half body 26L and a right crankshaft half body 26R, and the crankshaft halves 26L and 26R are connected to each other. The connecting rod 25 is connected via the provided crank pin 30. In addition, the crankshaft 26 is disposed at a coupling portion between the front case half 21a and the rear case half 21b, and the crankshaft halves 26L and 26R are front and rear via the left and right bearings 31 and 32, respectively. It is held by the case halves 21a and 21b.

  A transmission case 22 is attached to the left side portion of the engine case 21, and the journal portion of the left crankshaft half body 26 </ b> L is disposed so as to protrude into the transmission case 22. A rear wheel shaft 33 that is positioned behind the crankshaft 26 and extends parallel to the crankshaft 26 and is rotatably held by the transmission case 22 is attached to the transmission case 22. A countershaft 34 that extends parallel to the crankshaft 26 and is rotatably held by the transmission case 22 is attached.

  A left cover member 35 is attached to the left side surface of the transmission case 22, and a transmission 37 is housed in a transmission chamber 36 surrounded by the transmission case 22 and the left cover member 35. The transmission device 37 is attached to the journal portion of the left crankshaft half 26L extending into the transmission chamber 36, and is attached to the left end portion of the drive pulley 38 and the countershaft 34, which rotate integrally with the countershaft 34. A driven pulley 39 that rotates, is attached to the center of the counter shaft 34, is wound around a clutch 40 that engages and disengages the driven pulley 39 and the counter shaft 34, and is wound around the drive pulley 38 and the driven pulley 39. The transmission belt 41 is configured to transmit the rotation to the driven pulley 39.

  The drive pulley 38 is a fixed pulley half 38a attached to the journal portion of the left crankshaft half 26L so as to be integrally rotatable. The drive pulley 38 is relatively movable in the axial direction with respect to the fixed pulley half 38a, and the left crankshaft The transmission belt 41 is sandwiched between the fixed and movable pulley halves 38a and 38b. On the other hand, the driven pulley 39 is fixed to the countershaft 34 so as to be relatively rotatable with respect to the fixed pulley half 39a. The transmission belt 41 is sandwiched between the fixed and movable pulley halves 39a and 39b. Therefore, by variably setting the pulley widths of the drive pulley 38 and the driven pulley 39, the winding radius of the transmission belt 41 around the pulleys 38 and 39 is continuously changed to change the transmission ratio steplessly (continuously. ) Can be controlled.

  An idle shaft 42 is mounted between the counter shaft 34 and the rear wheel shaft 33 so as to extend substantially parallel to the shafts 34 and 33, and the drive pulley 38 is rotated by the rotation of the crankshaft 26. It is transmitted to the driven pulley 39 via the machine belt 41 and further transmitted from the clutch 40 to the counter shaft 34. The rotation of the countershaft 34 is transmitted to the rear wheel shaft 33 via the gear train disposed on the countershaft 34, the idle shaft 42, and the rear wheel shaft 33, and left and right attached to the rear wheel shaft 33. The rear wheels 4L and 4R are driven to rotate.

  The rear wheel shaft 33 includes a left shaft 33L whose left end is connected to the left rear wheel 4L and a right shaft 33R whose right end is connected to the right rear wheel 4R. These shafts 33L and 33R are The differential mechanism 43 is connected to the right side of the transmission case 22. The differential mechanism 43 includes a differential carrier 44 that is disposed coaxially with the rear wheel shaft 33 so as to be rotatable relative to the rear wheel shaft 33, and a pinion shaft that is supported through the differential carrier 44 in a direction perpendicular to the rear wheel shaft 33. 45, a pair of pinion gears 46 attached to both ends of the pinion shaft 45, and a pair of left and right side gears 47 meshing with both pinion gears 46. The left and right shafts 33L and 33R are connected to the left and right side gears 47, respectively. . Then, the rotation transmitted to the counter shaft 34 via the idle shaft 42 is input to the differential carrier 44 of the differential mechanism 43, and is transmitted to the side gear 47 via the pinion shaft 45 and both pinion gears 46, and the left and right shafts 33L. , 33R is divided and transmitted.

  A right cover member 48 is attached to the right side surface of the transmission case 22 so as to cover the right side surface. The counter shaft 34, the idle shaft 42, the right shaft 33R, and the differential mechanism 43 have bearings. The left shaft 33L is held by the transmission case 22 and the left cover member 35 via bearings.

  As described above, the rear wheel shaft 33 is positioned between the crankshaft 26 to which the transmission 37 is connected and the counter shaft 34, so that the crankshaft 26 and the transmission 37 are close to the rear wheel shaft 33. Since the crankshaft 26 is positioned inside the outer shape of the rear wheel 4 (4L, 4R) in a side view, the front and rear length of the power unit 6 is shortened to reduce the size of the power unit 6. Can do. Further, in plan view, the transmission 37 is disposed on the left side of the power unit 6 and the differential mechanism 43 is disposed on the right side with respect to the center line extending in the front-rear direction of the tricycle 1, whereby the crankshaft 26 and the countershaft are arranged. Even if 34 is brought close to the rear wheel shaft 33, the drive pulley 38 and the driven pulley 39 of the transmission 37 and the differential mechanism 43 do not interfere with each other, and the dead space in the transmission case 22 is reduced, thereby reducing the power unit 6. Can be miniaturized.

  As shown in FIG. 2, the power unit 6 can be further downsized by configuring the rear wheel shaft 33 to be positioned in the closed loop of the transmission belt 41 in a side view.

  A kick start mechanism 28 for starting the engine 19 is provided at the front portion of the transmission case 22. The kick starting mechanism 28 includes a kick shaft 49, a kick arm 50, a kick connecting shaft 52, and a kick idle shaft 53.

  At the front of the transmission case 22, in front of the crankshaft 26, the transmission case 22 and the left cover member 35 are rotatably held, and a kick shaft 49 is attached in parallel with the crankshaft 26. The left end of the kick shaft 49 protrudes from the left cover member 35, and a kick arm 50 is attached to the tip thereof. A spring 51 is wound around the kick shaft 49, and in a normal state, the kick arm 50 is held so as to be swung upward.

  A kick connecting shaft 52 is disposed on the left side of the crankshaft 26 and coaxially with the crankshaft 26. The left end portion of the kick connecting shaft 52 is screwed and held in the left cover member 35 and is configured to move to the right by rotating and engage with the left end portion of the left crankshaft 26L. Yes. Further, between the kick shaft 49 and the crank shaft 26 (kick coupling shaft 52), the transmission case 22 and the left cover member 35 are rotatably held, and the kick idle is parallel to the shafts 26 and 49. A shaft 53 is provided. The rotation of the kick shaft 49 is transmitted to the kick connecting shaft 87 via the kick idle shaft 53 by the gear train disposed between the kick shaft 49, the kick idle shaft 53, and the kick connecting shaft 52. It is configured.

  When the kick pedal 50a provided at the tip of the kick arm 50 is kicked downward, the kick shaft 49 rotates against the urging force of the spring 51, and the rotation is provided to the kick shaft 49 and the kick idle shaft 53. It is transmitted to the kick idle shaft 53 by the gear train. The rotation of the kick idle shaft 53 is transmitted to the kick connection shaft 52 by a gear train provided between the kick idle shaft 53 and the kick connection shaft 52, and the kick connection shaft 52 moves to the right along with the rotation. It moves, engages with the left crankshaft half 26L, and rotation is transmitted to the crankshaft 26. On the other hand, when the foot is released from the kick pedal 50a, the kick shaft 49 is rotated in the reverse direction by the spring 51, the kick arm 50 is returned to the upper position, and the kick connecting shaft 52 is rotated in the reverse direction. The engagement is released.

  That is, by kicking the kick pedal 50a downward, the crankshaft 26 can be rotated and the piston 64 can be slid back and forth, so that a mixture of fuel and air is supplied to the combustion chamber 27 by the piston 64. The power unit 6 (engine 19) can be started by compressing and igniting.

  A kick gear 54 attached to the kick shaft 49 and transmitting the rotation of the kick shaft 49 to the kick idle shaft 53 has a fan shape as shown in FIG. This is because the angle at which the kick shaft 49 rotates due to the kick of the kick pedal 50a is limited. By eliminating unnecessary portions of the kick gear 54, the front and rear length of the transmission case 22 is shortened, and this transmission. The case 22 can be reduced in size.

  In addition, when viewed from the side, the rotation shaft of the kick shaft 49 is disposed forward and downward from the rotation shaft of the crankshaft 26, and the rotation shaft of the kick idle shaft 53 is forward and upward from the rotation shaft of the crankshaft 26. Has been placed. By providing the kick idle shaft 53 and transmitting the rotation of the kick shaft 49 to the crankshaft 26, the kick ratio can be increased, the startability of the power unit 6 can be improved, and the crankshaft 26 can be improved. By arranging the kick shaft 49 and the kick idle shaft 53 so as to be vertically separated, the kick shaft 49 can be prevented from projecting forward, and the transmission case 22 can be reduced in size.

  If the kick shaft 49 is prevented from projecting forward in this way, a space is formed in the left side portion of the cylinder head 20 in front of the transmission case 22, so that the cylinder head is, for example, as shown in FIG. Since the exhaust pipe 55 extending from 20 can be disposed in this space, the power unit 6 can be downsized as a whole.

  Furthermore, since the kick arm 50 is positioned in front of the left rear wheel 4L by disposing the kick shaft 49 in front of the crankshaft 26, the kick arm 50 can be brought closer to the center of the vehicle body. That is, the passenger can operate the kick arm 50 (kick out the kick pedal 50a) in the vicinity of the seat 14 and without being aware of the left rear wheel 4L. Operability is improved.

  A water jacket is formed inside the cylinder head 20 so as to surround the combustion chamber 27 and is cooled by flowing cooling water therein (not shown). The water jacket is supplied to the water jacket. The cooling water is supplied from a cooling water supply port 56 formed in the engine case 21. The cooling water that has flowed through the water jacket and cooled the cylinder head 20 flows into the engine case 21 through the cooling water passage 57 and is discharged from the cooling water discharge port 58 to the outside.

  A cooling water pump 59 for supplying cooling water to the cylinder head 20 is provided on the left side portion of the cylinder head 20, and the cooling water discharged from the cooling water pump 59 passes through the first pipe 60 and the engine. It is supplied from the cooling water supply port 56 of the case 21. Then, the cooling water heated through the water jacket of the cylinder head 20 is discharged from the cooling water discharge port 58 of the engine case 21 and flows into the radiator 63 through the second pipe 61. The cooling water is radiated through the radiator 63, flows into the cooling water pump 59 through the third pipe 62, and circulates between the cylinder head 20 and the radiator 63.

  A cooling fan chamber 64 surrounded by a wall portion 21c that opens to the right is formed on the right side of the engine case 21. The journal portion of the right crankshaft half 26R extends into the cooling fan chamber 64. Yes. In the cooling fan chamber 64, an ACG 65 is disposed at the journal portion of the right crankshaft half 26R, and a cooling fan 66 is disposed at the tip thereof.

  The right opening of the wall 21c is covered with the engine cover 15. As shown in FIG. 3, the engine cover 15 includes a cooling cover portion 15a that covers the right opening and forms a cooling fan chamber 64, and a ventilation passage 15c that connects the front opening 15b formed in the front to the cooling cover portion 15a. And a through hole 15e is formed at a position facing the cooling fan 66 on the right side of the cooling cover portion 15a so that the ventilation passage 15 and the cooling fan chamber 64 communicate with each other. It is configured.

  Further, as shown in FIG. 5A, the above-mentioned radiator 63 faces the front end of the front portion of the engine case 21 (the heat dissipating surface through which air is passed to dissipate heat faces the front). And the rear surface of the radiator 63 is covered with the front opening 15b of the engine cover 15 in a state where the engine cover 15 is attached. Therefore, when the tricycle 1 is traveling, the traveling wind directly strikes the radiator 63 and heat can be efficiently radiated from the cooling water. Further, the air passing through the radiator 63 takes the ventilation passage 15c of the engine cover 15. The inside of the power unit 6 can be efficiently cooled by being guided to the cooling fan 66 from the through-hole 15e and sent in the front-rear and vertical directions by the cooling fan 66.

  Thus, by arranging the radiator 63 on the front side of the engine case 21 and on the right side, the space in front of the right rear wheel 4R can be used effectively, and the size of the tricycle 1 can be reduced. Can do. At this time, the crankshaft 26 is disposed between the left and right rear wheels 4L and 4R, and the radiator 63 is disposed along the outer periphery of the right rear wheel 4R. be able to. Further, since the radiator 63 can be disposed in the vicinity of the engine case 21 to which the cooling water is supplied and the cylinder head 20, the pipe lengths of the cooling pipes (first to third pipes 60 to 62) connecting them. Can be shortened. Further, by forming the ventilation passage 15c in the engine cover 15 covering the rear part of the radiator 63 and guiding it to the cooling fan 66, the traveling wind can be efficiently used without complicating the cooling structure, and the radiator. 63 can be cooled by a cooling fan 66.

  The front surface of the radiator 63 is also covered with the vehicle body cover 15, but a plurality of vent holes that extend from side to side and open in the left and right directions are formed in a portion facing the radiator 63 of the vehicle body cover 15. . This vent is formed so as to blow the traveling wind flowing from the front to the rear toward the radiator 63 from the obliquely downward to the obliquely upward, so that the cooling water flowing through the radiator 63 is efficiently cooled by the traveling wind. It is configured. As is clear from FIG. 4, the ventilation passage portion 15 d formed in the engine cover 15 is formed so as not to cover the upper portion (upper half portion) of the rear surface of the radiator 63. Therefore, after the engine is stopped, the cooling effect by heat radiation from the radiator fin of the radiator 63 can be ensured.

  Next, the attachment structure of the power unit 6 and the hanger member 12 configured as described above will be described with reference to FIG. As shown in FIG. 4 and the like, hanger attachment portions 67 to 68 projecting downward are formed at the lower portion of the power unit 60, and the two connecting members 12c sandwich the hanger attachment portions 67 to 68 from the left and right. It is attached. The connecting member 12c is fastened by a set of two bolts 70a, 71a and nuts 70b, 71b to a rear end member 12b positioned between the two connecting members 12c. The lower part of the power unit 6 is fastened with nuts 72b and 73b with two bolts 72a and 73a passing through the connecting member 12c and the hanger attachment portions 67 to 68.

  The first hanger mounting portion 67 located in the front is formed in the lower part of the front case half 21a as shown in FIG. Further, the second and third hanger mounting portions 68 and 69 located at the rear are such that the second hanger mounting portion 68 is formed in the lower part of the rear case half 21b as shown in FIG. 69 is formed in the lower part of the transmission case 22 as shown in FIGS. As described above, the transmission case 22 is attached to the left side portion of the engine case 21, and the second hanger attachment portion 68 and the third hanger attachment portion 69 are arranged side by side as a pair of bolts 73a and nuts 73b. It is fastened with the connecting member 12c in a set. As is apparent from FIGS. 6 to 9, in order to make the distance between the two connecting members 12 c in the left-right direction equal, the width in the left-right direction of the first mounting portion 67 is the second mounting portion 68 and the third mounting portion 69. The left end portion of the first mounting portion 67 is formed so as to protrude to the left from the left end portion of the second mounting portion 68 so as to be substantially the same as the combined width in the left-right direction.

  As described above, the power unit 6 can be fastened to the hanger member 12 and the engine case 21 and the transmission case 22 can be fastened by fastening the second and third attachment portions 68 and 69 to the connecting member 12c. Therefore, the mounting to the hanger member 12 and the fixing of the transmission case 22 to the engine case 21 can be performed with a set of bolts 73a and nuts 73b, so that the number of assembly steps and the number of parts can be reduced. it can. Further, by fastening the power unit 6 so as to be sandwiched from the left and right using the two connecting members 12c, the coupling force between the hanger member 12 and the power unit 6 can be increased, and the driving wheel (rear wheel) The reaction force from 4L, 4R) can be efficiently transmitted to the vehicle body side (vehicle body frame 2 side), so that the ride comfort of the passenger can be improved.

  In addition, an oil pan portion 74 for storing lubricating oil supplied to the cylinder head or the like is formed in the lower portion of the engine case 21, but as is apparent from FIG. Since the connecting member 12c arranged on the left and right and the rear end member 12b spirally fastened between them are located, the lower part of the engine case 21 can be protected by these hanger members 12.

It is a right view which shows the motor tricycle by which the power unit which concerns on this invention is mounted. It is a right view of the power unit which concerns on this invention. It is a top view of the rear part of the above-mentioned automatic tricycle, and a power unit. It is a right view of a power unit. It is a figure which shows the front case half which comprises an engine case, (a) is a front view, (b) is a left view. It is a figure which shows the rear case half which comprises an engine case, (a) is a front view, (b) is a left view. It is a left view of a transmission case. It is VIII-VIII sectional drawing of FIG. It is IX-IX sectional drawing of FIG.

Explanation of symbols

1 Auto tricycle (vehicle)
4L left rear wheel (drive wheel)
4R Right rear wheel (drive wheel)
6 Vehicle power unit 15 Engine cover (cooling duct)
15c Ventilation passage (cooling duct)
19 Engine (Internal combustion engine)
26 Crankshaft 33 Rear wheel shaft (drive wheel shaft)
34 Countershaft 37 Transmission 63 Radiator

Claims (4)

An internal combustion engine that outputs rotational driving force from a crankshaft that is mounted on a vehicle and is arranged in parallel to a driving wheel shaft to which driving wheels are connected, and the rotational driving force of the crankshaft is parallel to the driving wheel shaft. A vehicle power unit cooling structure having a transmission for transmitting to the drive wheel shaft via a countershaft disposed on the vehicle,
A radiator that radiates cooling water for cooling the internal combustion engine;
A cooling structure for a power unit for a vehicle, wherein the radiator has a heat radiating surface directed in front of the vehicle and is disposed in front of the drive wheel. The internal combustion engine is located in front of the crankshaft, has a cylinder in which a piston that extends in the front-rear direction and rotates the crankshaft slides;
2. The cooling structure for a vehicle power unit according to claim 1, wherein the radiator is disposed on a side of the cylinder of the internal combustion engine. The internal combustion engine has a cooling fan at an end of the crankshaft on the side where the radiator is disposed;
3. The cooling structure for a vehicle power unit according to claim 2, further comprising a cooling duct that guides the traveling wind that has passed through the radiator to the cooling fan. The drive wheel is composed of a left drive wheel and a right drive wheel,
The crankshaft is disposed between the left drive wheel and the right drive wheel;
The cooling structure for a vehicle power unit according to claim 3, wherein the radiator is disposed along an outer periphery of one of the left and right drive wheels.

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