CN102003263B - Cooling device of a power unit - Google Patents

Abstract

The invention provides a cooling device for a power unit. It can suppress protrusion of the oil cooler. An oil cooler (105) is provided. The oil cooler (105) has: an oil passage (108) through which the oil supplied to the engine (20) as a power unit passes; Cooling cooler cooling mechanism (109). The oil cooler (105) extends in the direction of the cylinder axis (L1) and is formed in the shape of a plate located on the side of the cylinder block (22A).

Description

Cooling device for power unit

technical field

The invention relates to a cooling device for a power unit.

Background technique

Patent Document 1 discloses a structure in which a cylindrical oil cooler (for example, Refer to Patent Document 1).

Patent Document 1: Japanese Patent Laid-Open No. 2003-314277

However, in the conventional structure, the cylindrical oil cooler is disposed around the cylinder side wall, so the oil cooler protrudes and is bulky, leading to an increase in the size of the power unit. In addition, since the oil cooler is arranged in the lower part of the crankcase, the distance between the oil pan and the oil cooler is shortened, and the temperature of the oil cooler rises due to the influence of the oil temperature in the oil pan.

Contents of the invention

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a cooling device for a power unit capable of suppressing protrusion of an oil cooler.

In order to solve the above-mentioned problems, the cooling device of the power unit of the present invention has a crankcase and a cylinder, and the cylinder has a cylinder sleeve that can slide freely and holds a piston, and a cylinder cooling mechanism that covers the outer periphery of the cylinder sleeve, It is characterized in that it has an oil cooler, the oil cooler has an oil passage through which the oil supplied to the power unit passes, and a cooler cooling mechanism for cooling the oil passing through the oil passage, and the oil cooler is installed in the cylinder. It extends in the axial direction and is formed in the shape of a plate located on the side of the cylinder.

In the above structure, the cylinder may be integrally fastened with the crankcase by three or more fastening bolts arranged at substantially equal intervals, and the cylinder cooling mechanism may be formed by connecting the fastening bolts along a substantially straight line. The oil coolers extend along the plane of the cylinder cooling mechanism at intervals.

In addition, in the above structure, the power unit has a cylinder in front of the crankshaft supported on the crankcase, a transmission case at the end of the crankshaft, an oil pan below the crankshaft, and the oil cooler is arranged on the oil cooler. top of the plate.

In the above structure, the transmission case may accommodate a V-belt type transmission, and the oil cooler may be provided at the upper front of the transmission case.

In addition, in the above structure, an oil pump may be provided for sucking up the oil in the oil pan and supplying the oil to each part including the crankshaft lubricating part, and the oil cooler may be arranged between the oil pump and the oil cooler. between the crankshaft lubricating parts downstream of it.

In the above structure, there may be a cylinder head lubricating oil passage branched from between the oil pump and the oil cooler via an orifice, and sending oil to the cylinder mounted on the cylinder. cover supply.

In addition, in the above structure, there may be a piston nozzle branching from between the oil pump and the oil cooler via an orifice, and injecting oil to the piston freely sliding in the cylinder. .

In addition, in the above structure, the cooling air is sucked and exhausted in the inner space of the transmission case, and the oil cooler is integrally formed on the transmission case.

In addition, in the above configuration, the cylinder may be arranged horizontally forward with respect to the crankshaft, a cover member may be provided on the side of the crankshaft, and the oil cooler may be arranged between the cylinder and the cover member. on the ladder.

In addition, in the above configuration, the oil cooler may be provided on the cover member, and cooling fans may be provided as cooling means for the cooler on the side surface on the cylinder side and the side surface opposite to the cylinder.

The effect of the invention

In the present invention, the oil cooler extends in the direction of the cylinder axis and is formed in a plate shape on the side of the cylinder. Therefore, the oil cooler can be arranged along the cylinder side wall, and protrusion of the oil cooler can be suppressed.

In addition, the cylinder is integrally fastened to the crankcase by three or more fastening bolts arranged at substantially equal intervals, and the cylinder cooling mechanism is formed in a substantially flat shape extending in the direction of the cylinder axis connecting the fastening bolts with substantially straight lines. As long as the cooler extends along the plane of the cylinder cooling mechanism at intervals, the oil cooler can be arranged close to the cylinder, and even a large oil cooler can be suppressed from protruding from the engine.

In addition, the power unit has a cylinder in front of the crankshaft supported on the crankcase; a transmission case at the end of the crankshaft; 1. In an engine with a transmission case at the end of the crankshaft and an oil pan below the crankshaft, the oil cooler can be arranged away from the oil pan, thereby improving the cooling efficiency of the oil cooler and reducing the size of the oil cooler.

In addition, the transmission case accommodates the V-belt type transmission, and as long as the oil cooler is arranged on the upper front of the transmission case, the oil cooler can be formed on the case parts whose interior is a dry space, and the oil cooler is far away from the oil pan. configuration, the cooling efficiency of the oil cooler can be further improved.

In addition, there is an oil pump that sucks up the oil in the oil pan and supplies oil to each part including the crankshaft lubricating part, and the oil cooler can be used as long as the oil cooler is arranged between the oil pump and the crankshaft lubricating part located downstream of it. The oil cooled by the cooler is supplied to the crankshaft lubricating part, and even in an engine in which the heat dissipation of the crankcase is not so good, the crankcase can be satisfactorily cooled.

In addition, as long as there is a cylinder head lubricating oil passage that branches from between the oil pump and the oil cooler through the orifice and supplies oil to the cylinder head mounted on the cylinder, there is no need to lengthen the supply to the cylinder head. The oil passage can satisfactorily perform lubrication of the cylinder head lubricating portion and the like and oil-based cooling, and can prevent oil cut-off of the cylinder head lubricating portion.

In addition, the oil pressure of the piston nozzle can be ensured as long as there is a piston nozzle branched from between the oil pump and the oil cooler through the orifice and injecting oil to the piston freely sliding in the cylinder.

In addition, in the internal space of the transmission case, the cooling air is sucked and exhausted. As long as the oil cooler is integrally formed on the transmission case, the cooling effect based on the internal cooling air can act on the oil cooler through the transmission case, improving the performance of the oil cooler. Cooling efficiency of the oil cooler.

In addition, the cylinder is arranged horizontally forward with respect to the crankshaft, and there is a cover member on the side of the crankshaft, and the oil cooler is arranged on the stepped portion between the cylinder and the cover member, so that it is possible to avoid an increase in the size of the engine, and at the same time realize oil cooling. Cooler upsizing and protection.

In addition, the oil cooler is provided on the above-mentioned cover member, and as a cooler cooling mechanism, cooling fans are provided on the side surface on the side of the cylinder and the side surface on the opposite side of the cylinder, so that the cooling efficiency can be increased by increasing the heat dissipation area.

Description of drawings

Fig. 1 is a side view of a motorcycle according to an embodiment of the present invention.

Fig. 2 is a diagram showing the internal structure of the engine from the right side of the vehicle body.

Fig. 3 is a diagram showing a section III-III in Fig. 2 .

Fig. 4 is a diagram showing peripheral structures, a crankcase, and a cylinder unit together from the right side of the vehicle body.

FIG. 5(A) is a diagram showing the upper structure of the engine, and FIG. 5(B) is a diagram showing the left and right cross-sectional structures.

Fig. 6 is a side view of the transmission case viewed from the right side of the vehicle body.

Fig. 7 is a side view of the transmission case viewed from the left side of the vehicle body.

Fig. 8(A) is a diagram showing the oil cooler cover from the right side (front side) of the vehicle body, Fig. 8(B) is a diagram seen from the rear side of the vehicle body, and Fig. 8(C) is a view from the left side (inner side) of the vehicle body As seen, FIG. 8(D) is a diagram showing the D-D cross section of FIG. 8(A).

Fig. 9 is a diagram showing an oil lubrication system.

Fig. 10 is a diagram showing a lubricating structure of a crankshaft lubricating portion.

Explanation of reference signs

1 two-wheel motorcycle

2 body frame

20 engine (power unit)

22 cylinder part

22A cylinder block

22F, 106A, 109 cooling fans

24 crankcase

51 crankshaft

51R drive pulley shaft (drive shaft)

60 V belt continuously variable transmission

61 Transmission Storage Department

61A Transmission case (cover part)

61B Transmission cover (cover parts)

64 Driven pulley shaft (driven shaft)

68 V belt

80 Start clutch (wet centrifugal clutch)

97 Torque damper

105 oil cooler

106 Oil cooler body

107 Oil cooler cover

120 oil pump

L1 cylinder axis

Detailed ways

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In addition, in the following description, the description about the front-back, left-right, and up-down directions is the same as the direction in a vehicle unless otherwise specified. In addition, in the figure, arrow F indicates the front of the vehicle body, arrow R indicates the right side of the vehicle body, and arrow U indicates the upper side of the vehicle body.

FIG. 1 is a side view showing a motorcycle 1 to which an embodiment of the present invention is applied.

The body frame 2 of the motorcycle 1 has: a head pipe 3 at the front of the vehicle body; a main frame 4 extending obliquely downward from the head pipe 3 to the rear; extending downward and fixed to the main frame. A pair of left and right pivot brackets 5 at the rear of the main frame 4; a pair of left and right seat rails 6, which extend obliquely upward from the front near the fixed position of the pivot bracket 5 at the rear of the main frame 4 and A pair of left and right reinforcement frames 7 that reinforce the center between the pivot bracket 5 and the above-mentioned seat rail 6 are bent halfway to the rear end.

A passenger seat 8 is provided above a pair of left and right seat rails 6 of the vehicle body frame 2 , and a storage portion (storage box) 9 is provided at a lower portion thereof. A handlebar 10 pivotally supported on the head pipe 3 is provided above the front part of the vehicle body, front forks 11 , 11 extend below it, and a front wheel 12 is pivotally supported at the lower end thereof. A rocker arm (also referred to as a rear fork) 14 is pivotally supported on a pivot bracket 5 in the center of the vehicle body via a pivot shaft 13 so that the front end can swing, and extends rearward. round 15. A pair of left and right rear shock absorbers 16 are interposed between the rear portion of the rocker arm 14 and the seat rail 6 .

Below the main frame 4 and in front of the pivot bracket 5, the suspension has an internal combustion engine, an engine (also called a power unit) 20 . The upper part of the engine 20 is suspended on the support bracket 17, and the support bracket 17 is vertically arranged at the central part of the main frame 4, and the rear part of the engine 20 is fixed on two positions on the pivot bracket 5. That is, the engine 20 is supported on the lower rear side of the main frame 4 in a suspended state. In addition, the vehicle body frame 2 is covered with a synthetic resin body cover 18 divided into individual parts.

The engine 20 is a single-cylinder four-stroke air-cooled engine, and is configured as a horizontal engine in which the cylinder portion 22 is largely tilted forward from the front surface of the crankcase 24 in a nearly horizontal state, and the cylinder portion 22 is pivotally supported on the crankcase 24 relative to the The crankshaft 51 is configured horizontally forward. Therefore, while the center of gravity of the vehicle body can be lowered, the main frame 4 can also be lowered as shown in the figure, thereby reducing the straddle portion M on which the rider straddles when riding the vehicle, thereby improving rideability. In addition, a generator cover 25 is attached to the front left side of the crankcase 24 . As shown in FIG. 1 , the vehicle body cover 18 has a cover shape that covers the vehicle body up to the vicinity of the outer edge of the crankcase 24 when viewed from the side of the vehicle body, and exposes the side surface of the crankcase 24 including the generator cover to the outside.

An intake pipe 26 is connected to the upper side of the cylinder portion 22 of the engine 20 . The intake pipe 26 extends upward and is connected to a throttle body 27 and an air cleaner 28 supported by the main frame 4 . Connected to the lower side of the cylinder portion 22 is an exhaust pipe 29 that extends downward, bends, and extends rearward, and is connected to a muffler 30 disposed on the right side of the rear wheel 15 .

In addition, the output shaft 31 of the engine 20 is pivotally supported on the rear left side of the crankcase 24 so that the front end thereof is exposed. An output sprocket (also referred to as a driving sprocket) 32 is mounted on the front end of the output shaft 31, and a transmission chain 34 ( With reference to Fig. 1) thus constitute chain transmission mechanism.

That is, the motorcycle 1 is configured as a chain-driven vehicle, and the rotation of the output shaft 31 of the engine 20 is transmitted to the rear wheel 15 via a chain transmission mechanism. In addition, this chain transmission mechanism functions as a secondary reduction mechanism for setting a reduction ratio (secondary reduction ratio) between the output shaft 31 and the rear axle according to the gear ratios of the sprockets 32 and 33 . In addition, in the drawings, reference numeral 35 denotes a cover covering the chain transmission mechanism.

A pedal bar 36 extending in the left-right direction of the vehicle body is attached to the lower part of the crankcase 24 , and a pair of pedals 36A, 36A for the driver's feet are attached to both ends of the pedal bar 36 . In addition, in FIG. 2 , reference numeral 36B is a boss provided on the bottom of the crankcase 24 and screwed to engage the pedal rod 36 .

In addition, in this motorcycle 1 , a kick member (starting system member) 37 constituting a part of a kick starter for starting the engine 20 is arranged on the left side of the crankcase 24 . That is, the pedal member 37 has: a pedal arm portion 39 mounted on the pedal shaft 38 on the crankcase 24 with its front end exposed; Pedal 40. The engine 20 can be started by turning the pedal shaft 38 when the driver steps on the pedal 40 .

In addition, the motorcycle 1 is provided with a starter motor 41 for starting the engine in addition to the kick starter controlled by the pedal member 37 described above. The starter motor 41 is attached to the front portion of the upper surface of the crankcase 24 , and the engine 20 can be started by operating the starter motor 41 . That is, in the motorcycle 1, the engine 20 can be started by any of the pedal type and the starter motor type.

FIG. 2 is a view showing the internal structure of the engine 20 from the right side of the vehicle body, and shows the positions of main rotation axes of the power transmission system and the starting system. In addition, the cylinder axis L1 is also shown. In addition, FIG. 3 is a diagram showing the III-III section of FIG. 2 , FIG. 4 is a diagram showing the crankcase 24 and the cylinder portion 22 from the right side of the vehicle body together with the surrounding structure, and FIGS. 5(A) and (B) are diagrams showing the engine Figure 20 superstructure and left and right cross-sectional structure.

As shown in FIGS. 2 to 5 , the cylinder portion 22 of the engine 20 has: a cylinder block 22A connected to the front surface of the crankcase 24; a cylinder head 22B connected to the front surface of the cylinder block 22A; and a head covering the front surface of the cylinder head 22B. Cover 22C. The cylinder block 22A is a part that constitutes the cylinder main body (cylinder main part), and includes: a cylinder sleeve 22S (see FIG. 3 ) that slidably holds the piston 21A; and a cooling fan that constitutes a cylinder cooling mechanism that covers the outer periphery of the cylinder sleeve 22S. (cooling fan) 22F.

The cylinder block 22A and the cylinder head 22B are provided with a through hole 42H (refer to FIG. 4 ) through which three or more (four in this example) stud bolts or fastening bolts are inserted in parallel to the cylinder axis L1. 42. Fastening bolts 42 are respectively inserted into each through hole 42H, and one end (cylinder block 22A side) of each fastening bolt 42 is fastened to the crankcase 24, and the other end (cylinder head 22B side) of each fastening bolt 42 is fastened. Since the fastening nut 43 is provided, the cylinder block 22A and the cylinder head 22B are integrally fastened to the crankcase 24 . Here, the cylinder block 22A and the cylinder head 22B have a rectangular cross-sectional shape, and the fastening bolts 42 are arranged along the cylinder axis L1 at each corner of the rectangular cross-section centered on the cylinder axis L1 (see FIGS. 4 and 5(A), (B)).

As shown in FIG. 2 , the cooling fan 22F is a cooling fan that is perpendicular to the cylinder axis L1, and more specifically, is provided on the right side and upper and lower surfaces of the cylinder liner 22S and extends in the vertical direction and the left-right direction of the cylinder. It is flat and forms multiple rows at intervals in the direction of the cylinder axis.

As shown in the figure, the outer peripheral surfaces of the plurality of cooling fans 22F are planes HL, HU, and HB extending in the direction of the cylinder axis L1 connecting the fastening bolts 42 in a straight line, respectively, when viewed from the side of the cylinder and viewed from a plan view. (Refer to Fig. 3, Fig. 2) form. Therefore, the cylinder cooling mechanism composed of a plurality of cooling fans 22F is formed in a substantially planar shape extending in the direction of the cylinder axis L1 connecting fastening bolts 42 in a straight line, and the cylinder side (side surface of the cylinder block 22A) is formed in a planar shape.

Here, as shown in FIG. 1, since the body cover 18 of the motorcycle 1 has a leg guard 18A extending rearward and downward from the front of the vehicle body, the running wind from the front of the vehicle flows downward along the leg guard 18A and Flows around the cylinder portion 22 . Since the above-mentioned cooling fan 22F is a fan extending in the vertical direction on the side of the cylinder, the flow of the downward running wind along the leg guard 18A is not hindered, and the running wind can easily flow around the cooling fan 22F. Sufficient heat dissipation efficiency is ensured.

The cylinder head 22B is formed with a combustion chamber 22D and an unillustrated intake port and an exhaust port connected to the combustion chamber 22D. An ignition spark plug 23 is arranged so that the front ends of the combustion chamber 22D face each other. The above-mentioned intake pipe 26 is connected to the inlet of the port, and the above-mentioned exhaust pipe 29 is connected to the outlet of the exhaust port.

As shown in FIG. 3 , the crankcase 24 of the engine 20 has a left and right two-part structure composed of a left crankcase 24A and a right crankcase 24B. The crankshaft 51 is laterally supported on the front of the crankcase 24 so that the axis C1 is perpendicular to the traveling direction of the vehicle via a pair of left and right bearings (rolling bearings) 45 supported on the left and right crankcases 24A, 24B.

The crankshaft 51 has: a crank journal 51A serving as a center of rotation; a crank arm 51B having a larger diameter than the crank journal 51A; and a crank pin (eccentric shaft) 51C supported via the crank arm 51B. The crank arm 51B and the crank pin 51C are located between the pair of left and right bearings 45 , 45 . In addition, a balance weight (hereinafter referred to as “counterweight”) 51D for achieving rotational balance is provided on the crank arm 51B. In addition, in FIG. 3 , reference numeral 46 denotes a bearing (rolling bearing) arranged between the crankshaft 51 and the generator cover 25 .

A piston 21A slidably arranged along a cylinder axis L1 in the cylinder portion 22 is connected to a crank pin 51C of a crankshaft 51 via a connecting rod 21B. In FIG. 3 , reference numeral 55A denotes a sprocket provided on the crankshaft 51, and reference numeral 55B denotes a sprocket provided on the camshaft 55C, wherein the camshaft 55C is provided in the head cover 22C of the cylinder portion 22, and the chain The wheels 55A and 55B are connected via a cam chain 55D. As a result, the camshaft 55C rotates in accordance with the rotation of the crankshaft 51 , thereby driving a valve mechanism for pressing intake and exhaust valves (not shown) provided in the cylinder head 22B.

A V-belt type continuously variable transmission 60 is provided on the right side (one side) of the crankshaft 51 , and a generator 180 is provided on the left side (the other side) of the crankshaft 51 .

Specifically, the left end of the crankshaft 51 extends leftward in the left crankcase 24A to the vicinity of the generator cover 25 attached to cover the left opening (outer opening) of the left crankcase 24A, and passes through the bearing ( Rolling bearings) 46 are rotatably supported by the generator cover 25 . That is, generator 180 is accommodated in a space surrounded by generator cover 25 and left crankcase 24A. The generator 180 has a rotor 181 fixed to the crankshaft 51 and a stator 182 arranged in the rotor 181 , and the stator 182 is fixed to the generator cover 25 .

The V-belt continuously variable transmission 60 is a dry type power transmission mechanism that does not perform lubrication with engine oil (hereinafter referred to as suitable oil (lubricating oil)), and is housed in the right side (one side) of the crankshaft 51. In the transmission housing portion (cover member) 61 . This transmission accommodating portion 61 is an oil-free chamber formed separately from the oil-lubricated crankcase 24, and is composed of a transmission case 61A constituting a main body portion of the transmission accommodating portion 61 and an outer opening (right side) of the transmission case 61A covering the transmission case 61A. The transmission cover 61B of the opening) is formed in a structure divided into two parts on the left and right.

Specifically, the right end of the crankshaft 51 passes through the right crankcase 24B and extends further to the right, and passes through the transmission case 61A connected to the right side of the right crankcase 24B by bolts until it is connected to the transmission case 61A. In the vicinity of the transmission cover 61B, the right end portion is used as a drive pulley shaft (drive shaft) 51R of the V-belt type continuously variable transmission 60, and a drive pulley 63 is attached to the drive pulley shaft 51R.

A driven pulley shaft (driven shaft) 64 of the V-belt continuously variable transmission 60 is laterally pivotally supported on the rear of the crankcase 24 such that the axis C2 is perpendicular to the vehicle traveling direction. The driven pulley shaft 64 is located parallel to the rear of the driving pulley shaft 51R, and is pivotally supported by a pair of left and right bearings (rolling bearings) 65, 65 supported on the right crankcase 24B and the transmission accommodating portion 61 (transmission case 61A).

A driven pulley 67 is attached to the driven pulley shaft 64 , a V-belt 68 is wound between the driving pulley 63 and the driven pulley 67 , and the rotation of the driving pulley 63 is transmitted to the driven pulley 67 . . In addition, seal members 69A, 69B for preventing the engine oil on the crankcase 24 side from entering the transmission accommodating portion 61 are interposed between the transmission accommodating portion 61 and the respective sprocket shafts 51R, 64, so that the transmission accommodating portion 61 and the crankshaft Boxes 24 are sealed between them.

The drive pulley 63 has a fixed half body 63A that rotates together with the drive pulley shaft 51R, and a movable half body 63B. The way is fixed on the left side of the fixed half body 63A. The movable half body 63B rotates together with the crankshaft 51 and slides in the axial direction by the action of the weight roller 70 which moves in the centrifugal direction due to the centrifugal force so as to approach or move away from the fixed half body 63A, thereby changing the clamping position between the two chains. The winding diameter of the V-belt 68 between the wheel halves 63A, 63B.

The driven pulley 67 of the V-belt type continuously variable transmission 60 has a fixed half body 67A which rotates together with the driven pulley shaft 64 and a movable half body 67B, and the fixed half body 67A is fixed to the left side of the movable half body 67B. The movable half body 67B is disposed on the right end of the driven pulley shaft 64 so as to be movable in the axial direction via the annular slider 71 , and is biased to the left (the fixed half body 67A side) by the biasing member 72 which is a coil spring. Therefore, if the winding diameter of the V-belt 68 sandwiched between the two halves 63A, 63B of the driving pulley 63 becomes larger, conversely, the distance between the two halves 67A, 67B of the driven pulley 67 resists the disk. The urging force of the spring 72 expands, and the winding diameter of the V-belt 68 is reduced to automatically perform stepless speed change.

The driven pulley shaft 64 transmits power to a power transmission mechanism 81 arranged in the crankcase 24 via a starting clutch 80 arranged in a space formed between the right crankcase 24B and the transmission case 61A (described later). Clutch chamber R1).

The starting clutch 80 is a wet centrifugal clutch in which various parts are lubricated and cooled by oil, and has a clutch inner member 83 spline-fitted on the driven pulley shaft 64 and a clutch outer member 85 with a large diameter. The clutch output gear 84 is connected to the clutch output gear 84. The clutch output gear 84 is provided on the left end of the driven pulley shaft 64 so as to be relatively free to rotate. Clutch weight 87. Therefore, when the rotation speed of the driven pulley shaft 64 exceeds a predetermined speed, the clutch weight 87 moving in the centrifugal direction by the centrifugal force engages with the clutch outer member 85, and the clutch outer member 85 and the driven pulley shaft 64 are integrally formed. Rotation rotates clutch output gear 84 .

In addition, in the drawings, reference numeral 88 denotes a clutch reinforcing plate for suppressing the expansion of the clutch outer member 85 in the centrifugal direction, and reference numeral 90 denotes a plate disposed between the clutch output gear 84 and the driven pulley shaft 64 . Spacer. The spacer ring 90 is a roller row having two rows of bearing rollers arranged at intervals in the circumferential direction in the axial direction, and the clutch output gear 84 is opposed to the driven pulley shaft 64 by the two rows of roller rows. rotate.

The power transmission mechanism 81 is a mechanism that transmits power between the V-belt type continuously variable transmission 60 and the output shaft 31 of the engine 20, and functions as a primary reduction mechanism. This power transmission mechanism 81 is provided between the driven pulley shaft 64 and the output shaft 31 , and has an intermediate gear shaft (reduction gear shaft) 91 that connects the above-mentioned clutch output gear 84 provided on the driven pulley shaft 64 to The rotation of the motor is decelerated at a predetermined reduction ratio and transmitted to the output shaft 31. In addition, in FIG. 2 , the axis center of the intermediate gear shaft 91 is indicated by a code C3, and the axis center of the output shaft 31 is indicated by a code C4.

That is, in this engine 20, the transmission (engine side transmission) on the side of the engine 20 is constituted from the V-belt type continuously variable transmission 60 to the power transmission mechanism 81 serving as a primary reduction mechanism, that is, the V-belt type continuously variable transmission 60 , the starting clutch 80 , and the power transmission mechanism 81 constitute an engine-side transmission for changing the power of the engine 20 . In addition, the chain transmission mechanism constituting the secondary reduction mechanism constitutes a transmission outside the engine 20 (external engine transmission mechanism).

The intermediate gear shaft 91 is rotatably supported by a pair of left and right bearings (rolling bearings) 92, 92 supported by the left and right crankcases 24A, 24B, and has a through-shaft portion 91A penetrating through the wall of the right crankcase 24B. A large-diameter counter driven gear (reduction gear) 93 that meshes with the clutch output gear 84 provided on the driven pulley shaft 64 is fixed to the through shaft portion 91A, and is located between the left and right crankcases 24A, 24B. A small-diameter counter drive gear 94 that meshes with a final gear 95 fixed to the output shaft 31 is fixed in the space. Accordingly, the rotation of the clutch output gear 84 located outside the crankcase 24 is transmitted to the final gear 95 of the output shaft 31 located inside the crankcase 24 via the intermediate gear shaft 91 at a predetermined reduction ratio. In addition, the countershaft drive gear 94 and the final gear 95 are made of helical gears, so that the noise generated by the meshing of the gears can be reduced.

The output shaft 31 is supported by a pair of left and right bearings (rolling bearings) 96, 96, and the pair of left and right bearings 96, 96 are supported by the left and right crankcases 24A, 24B. A final gear 95 is provided rotatably and axially movable on the output shaft 31 , and the rotation of the final gear 95 is transmitted to the output shaft 31 via a cam-type torque damper (gear damper) 97 .

The torque damper 97 is supported on the output shaft 31, and has a final gear having an unillustrated cam structure that is frictionally engaged and meshed with each other by the elastic force of an elastic member (in this example, a plurality of disk springs) 99. The (first transmission member) 95 and the damper holding member (second transmission member) 98 are constituted. The final gear 95 is rotatably held on the output shaft 31 , and is biased to the right by a disc spring 99 inserted on the left side of the final gear 95 , and a damper holding member 98 is press-fitted and fixed on the right side of the final gear 95 . on the output shaft 31. Therefore, when the drive torque is applied from the engine 20 side, and the torque (that is, the counter torque) in the direction opposite to the drive direction from the drive wheel side (rear wheel 15 side) is not applied, the drive torque from the engine 20 With the drive torque on the side, the output shaft 31 and the final gear 95 are rotationally driven integrally, and the rear wheel 15 as a drive wheel is driven. On the other hand, when a reaction torque acts from the drive wheel side (rear wheel 15 side), the frictional engagement between the final gear 95 and the damper holding member 98 is released by the reaction torque, and the damper holds the The not-shown convex cam of the member 98 slides in the circumferential direction with respect to the not-shown concave-cam of the final gear 95 , and the transmission of the reaction torque to the engine 20 side is eased. Thus, the cam type torque damper that absorbs the reaction torque from the drive wheel side is disposed between the clutch outer 85 and the transmission chain 34 in the crankcase 24 .

As described above, in the engine 20, a right crankcase 24B and a transmission case are formed adjacent to the right side of the space surrounded by the left and right crankcases 24A, 24B (hereinafter referred to as the crank chamber R0). The space surrounded by 61A (hereinafter referred to as clutch chamber R1). That is, the transmission case 61A is connected to the right crank case 24B, thereby also serving as a clutch case member constituting the clutch case.

The crank chamber R0 and the clutch chamber R1 are chambers for lubricating and cooling the engine oil, and an oil pool (corresponding to the oil pan 114 ) is formed in the lower part of the crankcase 24 and the lower part of the transmission case 61A.

In addition, a space surrounded by a transmission case 61A and a transmission cover 61B (hereinafter, referred to as a transmission chamber R2 ) is formed at a position adjacent to the right side of the clutch chamber R1 , and this transmission chamber R2 does not lubricate and cool the engine oil. room. That is, in this engine 20 , the chambers in which engine oil exists and the chambers in which there is no engine oil are clearly distinguished in the vehicle width direction. In addition, in FIG. 2, the code|symbol R2A is the bottom surface of transmission chamber R2.

As shown in FIG. 2 , the pedal shaft 38 is arranged at a position not to overlap the driven pulley 67 formed with a large diameter in front and below the driven pulley shaft 64 when viewed from the side. The rotation of the pedal shaft 38 is transmitted to the crankshaft 51 through a pedal intermediate shaft 150 composed of a first pedal intermediate shaft 151 and a second pedal intermediate shaft 155 .

The first pedal intermediate shaft 151 is below the intermediate position between the driven pulley shaft 64 and the crankshaft 51, and is arranged laterally at a position overlapping with the driven pulley 67 formed in a large diameter when viewed from the side. The shaft 155 is arranged on the rear and lower side of the crankshaft 51, and is arranged laterally at a position not to overlap with the driven pulley 67 formed with a large diameter when viewed from the side, and is configured to be able to cooperate with the kick-starting slave provided on the crankshaft 51. The driving gear 172 (see FIG. 3 ) meshes. Here, in FIG. 2 , the axis center of the pedal shaft 38 is represented by a reference symbol K1, the axis center of the first pedal intermediate shaft 151 is represented by a reference symbol K2, and the axis of the second pedal intermediate shaft 155 is represented by a symbol K2. The heart is indicated with reference K3.

Next, the wind guide structure of the V-belt type continuously variable transmission 60 will be described.

FIG. 6 is a side view of the transmission case 61A viewed from the vehicle body right side (engine outside), and FIG. 7 is a side view of the transmission case 61A viewed from the vehicle body left side (engine inside).

External air is introduced into the transmission chamber R2 , that is, the transmission accommodating portion 61 , and the V-belt type continuously variable transmission 60 is cooled by the introduced external air.

As shown in FIG. 6, an external air intake port 115 is provided on the front upper part of the transmission case 61A above the drive pulley 63, and on the rear upper part of the transmission case 61A above the driven pulley 67. An external air exhaust port 116 is provided. These external air intake ports 115 and external air exhaust ports 116 are provided at intervals front and rear, have duct portions 115A, 116A extending rearward and upward in parallel, and are integrally formed on the transmission case 61A. In addition, ducts (not shown) are connected to the upper ends of these outside air inlets 115 and outside air outlets 116 , and outside air can freely circulate through the ducts. In addition, in FIG. 6, reference numeral 62 is a drain part for draining the water in the transmission case 61A (transmission chamber R2).

As shown in FIG. 3 , on the fixed half body 63A of the drive pulley 63 disposed in the transmission accommodating portion 61, a blower fan 63C for making the drive pulley 63 function as a blower fan is provided. The rotation of the blower fan 63C rotates, and the outside air is sent into the transmission chamber R2 from the outside air inlet 115 .

Moreover, the fixed half body 67A of the driven pulley 67 in the transmission accommodating portion 61 is also provided with a blower fan 67C for causing the driven pulley 67 to function as a blower fan, and by the rotation of the blower fan 67C, The outside air sent from the outside air intake port 115 can be introduced into the driven pulley 67 side in the transmission chamber R2 and can be exhausted from the outside air exhaust port 116 . Thereby, an external airflow from the drive pulley 63 side to the driven pulley 67 side is generated in the transmission chamber R2, and the V-belt type continuously variable transmission 60 is forcibly air-cooled.

In addition, in FIG. 6 , the rotation directions of the driving pulley 63 and the driven pulley 67 are indicated by solid line arrows, and they both rotate clockwise when viewed from the right side, so that the outside air can be smoothly sucked in from the outside air inlet 115. , and the inhaled outside air (shown by a dotted arrow in FIG. 6 ) can be smoothly exhausted from the outside air outlet 116 . The above is the description of the wind guide structure. In addition, the positive rotation direction of the intermediate gear shaft 91 is to rotate left when viewed from the right side (in FIG. , indicated by the solid arrow).

Next, the oil lubrication structure will be described.

As shown in FIG. 4 , an oil pump 120 for supplying engine oil to each part of the engine 20 is provided in a crankcase 24 of the engine 20 . This oil pump 120 is provided obliquely below the front of the crankshaft 51, driven by a cam chain, and driven by the rotational force of the crankshaft 51 to discharge engine oil, and the engine oil is supplied to the bearings such as the bearings 45 and 45 supporting the crankshaft 51, and the cylinder unit 22. A moving valve mechanism (not shown), a starting clutch 80, and a power transmission mechanism 81 are supplied.

In addition, the engine 20 has an engine-integrated small oil cooler 105 that cools oil that lubricates various parts of the engine 20 . This oil cooler 105 has: a plate-shaped oil cooler main body (extension part) 106 formed integrally with the case 61A when the transmission case 61A is cast; and an oil cooler connected to the oil cooler main body 106 by bolts. Cover (oil cover) 107. Here, the oil cooler cover 107 is shown in FIGS. 8(A) to (D). In addition, FIG. 8(D) shows the D-D cross section of FIG. 8(A).

As shown in FIGS. 6 and 7 , the oil cooler main body 106 extends from the transmission case 61A in the direction of the cylinder axis L1, is formed in a plate shape located on the side of the cylinder portion 22 (cylinder block 22A), and constitutes a cylinder cooling system. The cooling fans 22F of the mechanism extend along the plane HL at intervals thereon. In addition, the oil cooler main body 106 has a shape extending substantially vertically along the front surface of the crankcase 24, and oil passages (hereinafter referred to as cooling channels) are formed so as to extend along the outer shape of the oil cooler main body 106. Oil circuit) 108A.

That is, the cooling oil passage 108A is formed in a skewed substantially annular shape that is substantially long in the vertical direction and short in the front-rear direction, and is connected to a pair of openings 110 and 111 constituting an oil inlet and an oil outlet. . In addition, on the outer surface of the oil cooler main body 106, that is, on the side surface on the cylinder side, a grid-shaped cooling fan 106A (see FIG. 7 ) is integrally formed, and the surface area of the oil cooler main body 106 is increased by the cooling fan 106A. , so that the oil passing through the cooling oil passage 108A can be cooled more effectively. In addition, since the cooling fan 106A is formed in a grid-like rib shape, the rigidity of the oil cooler main body 106 is enhanced.

The oil cooler cover 107 is a cover covering the cooling oil passage 108A of the oil cooler main body 106 . As shown in FIGS. 8(A) to (D), on the oil cooler cover 107, a cooling oil passage 108B ( Referring to FIG. 8(C)) and the seal groove 108C (see FIG. 8(C)) formed along the outer periphery of the cooling oil passage 108B and inserted into the oil seal, at the same time, on the outer surface (the surface opposite to the cylinder portion 22) A plurality of cooling fans 109 linearly extending in the vertical direction are integrally formed.

In this way, the cooling oil passages 108A, 108B and the cooling fans 106A, 109 constituting the cooler cooling mechanism are respectively provided on the oil cooler main body 106 and the oil cooler cover 107, so that the cooling oil passages 108A, 108B can be brought close to each other. The cooling fans 106A and 109 can improve the cooling efficiency of the engine oil passing through the cooling oil passage 108 .

In addition, since the cooling fan 109 is a fan extending in the vertical direction, the flow of traveling wind flowing downward along the leg shield 18A is not hindered, and the traveling wind easily flows around the cooling fan 109 to ensure high heat dissipation efficiency. In addition, the oil cooler cover 107 can be reinforced by the cooling fan 109 . In addition, in the drawings, reference numeral 107A is a bolt fastening portion having a through hole for fastening the oil cooler cover 107 to the oil cooler main body 106 by bolts.

As shown in FIG. 2 , the oil cooler 105 extends up and down on the basis of the cylinder axis L1 when viewed from the side, its lower end PA is located slightly lower than the crankshaft 51, and is located above the lower end of the base of the cylinder block 22A, and its upper end PB It is positioned higher than the crankshaft 51 and is positioned at the same height as the base upper end of the cylinder block 22A. Therefore, the oil cooler 105 overlaps the cylinder block 22A in a side view, and the oil cooler 105 can be suppressed from protruding from the engine 20 in a side view, that is, the protruding of the engine 20 in the front, rear, up and down directions can be suppressed.

In addition, since the engine 20 is a single-cylinder engine, the width of the cylinder portion 22 is narrower than the maximum width of the engine 20 in the left-right direction, and there is a gap between the cylinder portion 22 and the transmission case 61A constituting a cover member on the side of the engine 20. A step portion X is formed between them (see FIG. 2 ). As shown in FIG. 2, since the oil cooler 105 is provided on the stepped portion X between the cylinder portion 22 and the transmission case 61A, it is possible to suppress the protrusion of the oil cooler 105 from the engine 20 in a plan view, that is, Protrusion in the left-right direction of the engine 20 can be suppressed. Therefore, it is possible to completely suppress the protrusion of the oil cooler 105 from the engine 20 to avoid an increase in the size of the engine 20 , and it is possible to increase the size of the oil cooler 105 without protruding, and to protect the oil cooler 105 .

Moreover, the lower end PA of the oil cooler 105 is located above the oil pan 114 (refer FIG. 4) which stores the oil in the crankcase 24. As shown in FIG. That is to say, as shown in FIG. 4 , the oil pan 114 is arranged at a height communicating with the filter chamber 121 in the horizontal direction. And it is provided at a position lower than the cylinder part 22 so that the oil stagnated in the oil pan 114 will not flow back to the cylinder part 22 .

Therefore, the oil cooler 105 of this structure is provided in the position higher than the upper liquid level UL (refer FIG. 2) of the oil which stagnates in the oil pan 114 reliably, and is arrange|positioned apart from the oil pan 114. As shown in FIG. If the oil cooler 105 and the oil pan 114 are arranged apart from each other, after lubricating and cooling each part, the high temperature of the oil falling into the oil pan 114 by its own weight is difficult to transfer to the oil cooler 105, so that the oil cooling can be improved. Cooling efficiency of device 105.

In addition, as shown in FIG. 4 , oil pump 120 is provided above filter chamber 121 , and oil pump 120 communicates with filter chamber 121 via suction oil passage 122 extending up and down inside right crankcase 24B. In addition, an oil filter 123 is disposed between the filter chamber 121 and the suction oil passage 122 , and the oil sucked by the oil pump 120 is purified (filtered) by the oil filter 123 .

Fig. 9 is a diagram showing an oil lubrication system. Furthermore, the flow of oil is indicated by solid arrows in FIG. 9 .

As shown in FIG. 9 , the oil pump 120 is located downstream of the oil pan 114 via the oil filter 123 and the suction oil passage 122 , and the oil stagnated in the oil pan 114 is sucked up by the oil pump 120 . The oil pump 120 has a single oil discharge port 120A (see FIG. 5(B) ), and the main oil passage 131 is connected to the oil discharge port 120A, and oil is discharged to the main oil passage 131 .

As shown in FIG. 5(B), the main oil passage 131 has: a first oil passage 132 in the right crankcase 24B formed in the wall of the right crankcase 24B in a manner communicating with the oil ejection port 120A; The first oil passage 133 inside the transmission case is formed in the wall of the transmission case 61A so that the downstream ends of the first oil passage 132 in the case are connected. That is, the downstream end of the first oil passage 132 in the right crankcase is opened on the abutting surface of the right crankcase 24B with the transmission case 61A, and is connected with the abutment surface of the right crankcase 24B in the transmission case 61A. The first oil passage 133 in the upper open transmission case communicates with it.

The first oil passage 133 in the transmission case communicates with the opening 111 (see FIG. 7 ) serving as the oil passage inlet of the oil cooler 105 . Therefore, as shown in FIG. 9 , the oil in main oil passage 131 is supplied to oil cooler 105 and air-cooled.

To the opening 110 serving as the oil passage outlet of the oil cooler 105, as shown in FIG. The downstream end of the oil passage 134 is opened on the surface of the transmission case 61A that is in contact with the right crankcase 24B. On the other hand, on the abutting surface of the transmission case 61A in the right crank case 24B, a second oil passage 135 in the right crank case (refer to FIG. The two oil passages 134 are opened in such a manner as to communicate with each other.

As shown in FIG. 4 , the second oil passage 135 in the right crankcase is an oil passage extending in the right crankcase 24B from the oil cooler 105 to the crankshaft 51 disposed behind the oil cooler 105 . As shown in FIG. 9 , the oil that has passed through the oil cooler 105 lubricates the crankpin 51C through the oil passage 135A. In addition, the oil that has passed through the oil cooler 105 is branched to the oil passage 135B, and functions as a driven bearing/clutch lubricating oil passage that supplies oil in this order to the bearing (driven bearing) 65 of the driven pulley shaft 64 and the starting clutch 80 .

FIG. 10 shows the lubrication structure of the crankpin 51C.

As shown in the figure, the oil supplied to the oil passage 135 in the right crankcase 24B passes through the oil passage groove 51M formed in the crankshaft 51 and passes through the inner side of the bearing 45 supported on the right crankcase 24B. It is supplied to the crank pin 51C arranged between the left and right crankcases 24A, 24B. Then, this oil is supplied to the large end portion of the connecting rod 21B through a small-diameter oil passage 51N formed in the crankpin 51C.

That is, in this structure, the oil passing groove 51M for passing oil to the side of the crank pin 51C is formed by forming a gap between the outer peripheral surface of the crankshaft 51 and the bearing 45 on the right side. The oil passage can be configured to supply oil to the sliding surface of the connecting rod 21B and the like. In addition, several oil passage grooves 51M may be provided at intervals in the circumferential direction of the crankshaft 51, or one may be provided when sufficient lubrication is possible. In addition, a sealed bearing is used for the bearing 45 supported by the right crankcase 24B, so that oil does not enter the bearing 45 .

As shown in FIG. 9 , in this engine 20 , between the oil pump 120 and the oil cooler 105 , the main oil passage 131 is branched into a first sub oil passage 136A and a second sub oil passage 136B. The first sub-oil passage 136A is branched from the main oil passage 131 via an orifice (throttle) 137A, and supplies oil to the cylinder head 22B via the cylinder block 22A. The second sub oil passage 136B is branched from the main oil passage 131 via the orifice 137B, and supplies oil to the piston nozzle 138 .

In this case, the oil passage (cylinder head lubricating oil passage) 136A is configured to include a plurality of (four in this example) through-holes 42H as shown by the flow of oil indicated by arrows in FIGS. 4 and 5 . One through hole 42H, wherein a plurality of through holes 42H penetrate the cylinder block 22A and the cylinder head 22B, and fastening bolts 42 are inserted therethrough. Therefore, the oil passes through the gap between the through-hole 42H and the fastening bolt 42 inserted through the through-hole 42H with a gap, and flows to the cylinder head 22B side via the cylinder block 22A, and passes through the oil drain in the cylinder block 22A. The hole 139 (see FIG. 4 ) lubricates the valve mechanism and the like arranged in the cylinder head 22B. Thus, since the through-hole 42H through which the fastening bolt 42 penetrates can be used also as an oil passage, reduction of the rigidity of the cylinder part 22 can be avoided and size reduction can be achieved.

In addition, the second auxiliary oil passage 136B is formed to have a smaller cross-sectional area than other oil passages penetrating the cylinder sleeve 22S, and supplies oil to the piston nozzle 138 that injects oil toward the piston 21A to lubricate the piston lubricating portion. and piston cooling. In this case, since the oil is supplied to the piston nozzle 138 through the orifice 137B, the oil pressure of the piston nozzle 138 can be ensured.

As described above, since the engine 20 of the present embodiment includes the plate-shaped oil cooler 105 extending in the direction of the cylinder axis L1 and positioned laterally to the cylinder portion 22, the oil cooler 105 can be arranged along the cylinder side wall, thereby enabling Protrusion of the oil cooler 105 is suppressed.

Further, the cooling fan 22F constituting the cylinder cooling mechanism is formed in a planar shape along the plane HL extending in the direction of the cylinder axis L1 connecting the fastening bolts 42 in a straight line when viewed from the side of the cylinder. Since they extend at intervals, the oil cooler 105 can be disposed close to the cylinder portion 22 (cylinder block 22A), and even a large oil cooler 105 can be suppressed from protruding from the engine 20 .

In addition, in this configuration, the engine 20 is configured as a horizontal engine having the cylinder portion 22 (cylinder block 22A) in front of the crankshaft 51 supported on the crankcase 24, and is configured to have a transmission case 61A at the end of the crankshaft. The oil pan 114 is provided below the crankshaft 51. In this structure, since the oil cooler 105 is arranged above the oil pan 114, the protrusion of the oil cooler 105 can be suppressed in a horizontal engine having a transmission case 61A at the end of the crankshaft. By arranging the oil cooler 105 and separating the oil cooler 105 from the oil pan 114 , it is possible to prevent the oil cooler 105 from being affected by the temperature of the oil in the oil pan 114 from increasing its temperature. In this case, since the cooling efficiency of the oil cooler 105 is improved, the size of the oil cooler 105 can be reduced in proportion to the improvement in the cooling efficiency.

In addition, the V-belt type continuously variable transmission 60 that does not require lubricating oil for lubrication is accommodated in the transmission case 61A, and since the oil cooler 105 is formed on the front upper portion of the transmission case 61A, the inside is a case member of a dry space. The oil cooler 105 is formed on the top, and the oil cooler 105 is arranged away from the oil pan 114, so that the cooling efficiency of the oil cooler 105 can be further improved.

In addition, since the oil cooler 105 is arranged between the oil pump 120 and the crankshaft lubricating part (bearings 45, 45) located downstream thereof, the oil cooled by the oil cooler 105 can be supplied to the crankshaft lubricating part, even in the crank chamber. Engines with poor heat dissipation can also cool the crankcase well.

In addition, since the first sub-oil passage 136A (cylinder head lubricating oil passage) is provided, the first sub-oil passage 136A is branched from between the oil pump 120 and the oil cooler 105 via the orifice 137A, and supplies oil to the Since the cylinder head 22B on the cylinder block 22A does not need to lengthen the supply oil passage to the cylinder head 22B, the lubrication of the cylinder head lubricating part (moving valve mechanism) and the like can be well performed and the cooling by oil can be prevented, and the cylinder head lubrication can be prevented. Partial cut off oil.

In addition, since the piston nozzle 138 branches from between the oil pump 120 and the oil cooler 105 through the orifice 137B, and injects oil to the piston 21A freely sliding in the cylinder, the piston nozzle 138 can be ensured. 138 oil pressure.

In addition, since the cooling air is sucked and exhausted in the internal space of the transmission case 61A, and the oil cooler 105 is integrally formed on the transmission case 61A, the cooling effect based on the internal cooling air also acts on the oil cooling via the transmission case 61A. on the oil cooler 105, thereby improving the cooling efficiency of the oil cooler 105.

In addition, since the cylinder portion 22 (cylinder block 22A) is arranged horizontally forward with respect to the crankshaft 51, there is a transmission case (cover member) 61A on the side of the crankshaft, and the oil cooler 105 is arranged between the cylinder portion 22 (cylinder block 22A) and Since the step portion X between the transmission cases 61A can avoid enlargement of the engine 20, enlargement and protection of the oil cooler 105 can be realized.

In addition, since the oil cooler 105 has the cooling fans 109 and 106A functioning as cooler cooling means on the cylinder side and the side opposite to the cylinder, the heat radiation area can be enlarged and ensured, and the cooling efficiency can be improved.

As mentioned above, although this invention was demonstrated based on one embodiment, this invention is not limited to this. For example, in the above-mentioned embodiment, the case where the cooling mechanism of the oil cooler 105 is constituted by the air-cooled cooling fans 109 and 106A has been described, but the present invention is not limited thereto. For example, a water passage may be formed in the oil cooler 105, and the oil cooler 105 may be water-cooled by passing cooling water through the water passage. In this case, the water passage constituting the cooler cooling mechanism is formed in a planar shape extending in the direction of the cylinder axis L1 connecting the fastening bolts 42 in a straight line, and the oil cooler 105 is partitioned along the plane. By extending at intervals, the oil cooler 105 can be arranged close to the cylinder portion 22 (cylinder block 22A), and even a large oil cooler 105 can be prevented from protruding from the engine 20 .

In addition, in the above-mentioned embodiment, the case where the present invention is applied to a single-cylinder engine has been described, but it is not limited thereto. Furthermore, the present invention is not limited to the case where the present invention is applied to a power unit cooling device of a motorcycle, and the present invention can also be applied to a power unit cooling device of a saddle-ride vehicle. In addition, as a saddle-riding vehicle, it refers to all vehicles that straddle the vehicle body, not only two-wheeled motorcycles (including bicycles with prime movers), but also three-wheeled vehicles that are classified into ATVs (all-terrain vehicles) and four-wheeled vehicles, including small motorcycles with low-floor footrests.

Claims (6)

1. A cooling device for a power unit, the power unit having a crankcase and a cylinder, the cylinder having a cylinder sleeve capable of freely sliding a piston and a cylinder cooling mechanism covering the outer periphery of the cylinder sleeve, characterized in that , The power unit is an air-cooled engine in which the cylinder cooling mechanism is composed of a plurality of cooling fans. The air-cooled engine has cylinders arranged horizontally forward in front of the crankshaft supported on the crankcase, and a transmission case at the end of the crankshaft. , with an oil pan below the crankshaft, The transmission case accommodates a V-belt transmission, and the cooling air is sucked and exhausted in the internal space of the transmission case. The cylinder is integrally fastened with the crankcase by three or more fastening bolts arranged at approximately equal intervals, and the plurality of cooling fans are provided at least on the side of the cylinder sleeve in the vehicle width direction, The cooling device of the power unit has an oil cooler having an oil passage through which oil supplied to the air-cooled engine passes, a cooler cooling mechanism for cooling the oil passing through the oil passage, and in the The transmission case constituting a part of the cover member is provided on the side of the crankshaft, The oil cooler is disposed above the oil pan and above the front of the transmission case, from a stepped portion between the cylinder and the cover member toward the outside of the cooling fan in the vehicle width direction. The outer peripheral surface of the vehicle extends in the direction of the cylinder axis at intervals in the vehicle width direction, and the oil cooler is integrally formed on the transmission case so as to overlap the cylinder in a side view, The oil cooler has a cooling fan as cooling means for the cooler on the side surface on the cylinder side and the side surface on the opposite side of the cylinder. 2. The cooling device for a power unit according to claim 1, wherein: The cylinder cooling mechanism is formed in a substantially planar shape extending along a cylinder axis direction connecting the fastening bolts with substantially straight lines, and the oil coolers extend at intervals along the plane of the cylinder cooling mechanism. 3. The cooling device for a power unit according to claim 1, wherein: An oil pump is provided for sucking up the oil in the oil pan and supplying the oil to each part including the crankshaft lubricating part, The oil cooler is disposed between the oil pump and the crankshaft lubricating unit located downstream thereof. 4. The cooling device for a power unit according to claim 3, wherein: A cylinder head lubricating oil passage branches from between the oil pump and the oil cooler via an orifice, and supplies oil to a cylinder head attached to the cylinder. 5. The cooling device of the power unit as claimed in claim 3 or 4, characterized in that, A piston nozzle is provided, which is branched from between the oil pump and the oil cooler through an orifice, and injects oil to a piston freely sliding in the cylinder. 6. The cooling device for a power unit according to claim 1, wherein: The cylinder is arranged horizontally forward with respect to the crankshaft, a cover member is provided on the side of the crankshaft, and the oil cooler is arranged on a stepped portion between the cylinder and the cover member.