JP2513407Y2 - Motorcycle power transmission device - Google Patents

Description

[Detailed Description of the Invention] A. Purpose of the Invention (1) Industrial Application Field The present invention relates to a power transmission device for a motorcycle, and in particular,
The present invention relates to a power transmission device of a motorcycle including a gear reducer having three shafts of an input shaft, an intermediate shaft, and an output shaft at a rear stage of a belt type continuously variable transmission.

(2) Conventional Technology Conventionally, as a power transmission device for a motorcycle equipped with such a gear reducer, one disclosed in Japanese Utility Model Laid-Open No. 60-188690 is known.

In the above-mentioned motorcycle power transmission device, the crankshaft of the engine and the input shaft of the gear reducer are connected by a belt type continuously variable transmission, and the gear reducer is gear-coupled to each other. Although it has three shafts, the crankshaft and the input and output shafts of the gear reducer are arranged on a straight line extending in the front-rear direction of the vehicle body.
The front-rear length of the power transmission device was relatively long.

(3) Problems to be Solved by the Invention By the way, in a rear intake case reed valve type two-cycle engine in which an intake system having a reed valve is arranged on the rear surface side of a cylinder, the cylinder is placed in a vertical plane passing through the crankshaft axis. Also, by arranging it forward to the horizontal plane passing through the coaxial line, the space of the intake system can be increased correspondingly, which is advantageous in improving the output characteristics of the engine.

However, when such a forward tilt cylinder structure is simply applied to a power transmission device combining a belt type continuously variable transmission and a gear reducer as in the above-mentioned known example, the power unit becomes considerably long in the front-rear direction. There is. Further, in the two-cycle engine of the above method, if the starter motor is arranged just below the crankcase in order to avoid interference with the intake system, the starter motor of the exhaust pipe extending downward from the front side surface of the forward leaning cylinder can be used. When routing it to the lower side,
It is necessary to bend the exhaust pipe midway downward, which is not easy to handle and causes an increase in exhaust resistance.

Further, lowering the center of gravity of the power transmission device is desirable in order to improve the running performance of the motorcycle.

The present invention has been made in view of the above circumstances, and provides a power transmission device for a motorcycle capable of solving the above-mentioned problems while sufficiently inclining the cylinder forward to increase the space of the intake system. With the goal.

B. Configuration of the Invention (1) Means for Solving the Problems In order to achieve the above object, the invention of claim 1 is tilted forward by being closer to the horizontal plane passing through the coaxial line than the vertical plane passing through the crankshaft axis. A crankshaft of a two-cycle engine having a cylinder, a reducer input shaft of a gear reducer, an intermediate shaft and a reducer output shaft are sequentially arranged from the front to the rear of the vehicle body, and the crankcase of the engine is continuously connected to the front part. In the transmission case, the belt type continuously variable transmission connecting the crankshaft and the reduction gear input shaft and the gear reduction gear are housed, and the exhaust pipe is extended downward from the front side surface of the cylinder. ,
Between the rear side surface of the cylinder and the upper surface of the transmission case, an intake system having a downstream end opened in the crankcase inner upper part is provided, and a reed valve is provided in the intake system. A power transmission device, wherein the intermediate shaft is arranged on one side in the vertical direction of a straight line extending in the vehicle front-rear direction connecting the crankshaft and the input shaft of the reduction gear, and the reduction gear is arranged on the other side of the straight line in the vertical direction. A starter motor that is provided with an output shaft and can apply a starting torque to the crankshaft,
The exhaust pipe is attached to a lower portion of the transmission case while being displaced rearward from the crankshaft axis, and the upstream portion of the exhaust pipe extending downward from the cylinder is located at a lower portion of the front surface of the transmission case when viewed from the side of the vehicle body. The starter motor is arranged so as to extend substantially along the lower part of the starter motor, and the invention of claim 2 is characterized in that, in addition to the features, the driven pulley of the belt type continuously variable transmission and the speed reducer are provided. The input shaft is arranged on the same axis line, the intermediate shaft is arranged below a straight line extending in the vehicle longitudinal direction connecting the crank shaft and the reduction gear input shaft, and the reduction gear output is arranged above this straight line. With a shaft,
A clutch outer of a clutch interposed between the input shaft and the driven pulley is coupled to the speed reducer input shaft.

(2) Action According to the above features of the invention of each claim, since the cylinder is inclined forward enough so as to be closer to the horizontal plane side passing through the coaxial line than the vertical plane passing through the crankshaft axis, A sufficiently wide space for the intake system is secured between the rear side surface of the tilt cylinder and the upper surface of the transmission case.

In addition, since the gear reducer input shaft, the intermediate shaft, and the reducer output shaft of the gear reducer are vertically offset, the distance between the reducer input shaft and the intermediate shaft and the intermediate shaft and the reducer are reduced. The distance between the reducer input shaft and the reducer output shaft in the front-rear direction of the vehicle body is shorter than the sum of the distances between the output shafts of the machine, and the front-rear length of the gear reducer (and hence the power transmission device) is shortened accordingly. . For this reason, even if the cylinder is inclined forward as described above and the engine tends to be vertically long, it is possible to avoid lengthening the entire power unit including the engine and the power transmission device in the front-rear direction.

Furthermore, even if the starter motor is placed in the lower part of the transmission case to avoid interference with the intake system and the continuously variable transmission, the starter motor is biased rearward of the crankshaft axis and extends downward from the front side surface of the cylinder. The exhaust pipe is arranged so that the upstream part of the exhaust pipe extends to the lower part of the starter motor substantially along the lower part of the front surface of the transmission case when viewed from the side of the vehicle body.
Even if the intermediate portion is not bent greatly downward, the lower portion of the motor can be easily routed. Moreover, the intake system and the starter motor, which should be arranged around the crankcase, cannot be placed above and below a continuously variable transmission that is relatively long in the front-rear direction while avoiding mutual interference and minimizing the downward extension of the motor. It can be distributed without.

On the other hand, according to the above feature of the invention of claim 2, both the reduction gear input shaft and the intermediate shaft are located below the straight line extending in the vehicle body front-rear direction connecting the crank shaft and the reduction gear output shaft. Moreover, the clutch outer is coupled to the reduction gear input shaft that is coaxial with the driven pulley of the continuously variable transmission. For this reason, the clutch outer and the driven side of the belt type continuously variable transmission, which are large parts of the power transmission device, and further, the reduction gear input shaft and the intermediate shaft can all be placed as close as possible to the lower side of the power transmission device.

(3) Embodiment An embodiment of the present invention will be described below with reference to the drawings. 1 to 8 show an embodiment of the present invention, and FIG. 1 is an overall side view of a motorcycle to which the present power transmission device is applied,
2 is an enlarged cross-sectional view of the main part of FIG. 1, and FIG. 3 is II of FIG.
Sectional view taken along line I-III, FIG. 4 is sectional view taken along line IV-IV in FIG. 3, and FIG.
The drawing is a sectional view taken along the line VV of FIG. 3, and FIG. 6 is the VI-VI of FIG.
FIG. 7 is a side view of the movable pulley half of the driven pulley, and FIG. 8 is an enlarged view of the cam groove.

As shown in FIG. 1, this motorcycle is equipped with a power unit P having an engine E and a transmission case T in the center of a body frame F. A rear fork 1 is pivotally supported on a rear portion of the body frame F by a pivot pin 2 so as to be vertically swingable, and a rear cushion 3 is mounted between the rear fork 1 and the body frame F. A rear wheel Wr pivotally supported on the rear end of the rear fork 1 via an axle 4 is connected to the power unit P via a chain 6 wound around a driven sprocket 5 fixed to the axle 4.

As shown in FIGS. 2 and 3, the power unit P
The engine E is a two-cycle rear intake case reed valve type engine, and its crankcase 10 is connected to the front of the transmission case T. The cylinder 7 of the engine E has a crankshaft 15 as shown in Figs.
Is inclined toward the horizontal plane passing through the coaxial line rather than the vertical plane passing through the axis line of the cylinder (i.e., tilted forward), and the exhaust port 7e is opened on the front side surface of the cylinder 7, and the exhaust port 7e Is connected to the upstream end of an exhaust pipe 90 extending downward from the front side surface of the cylinder 7. Further, when the cylinder 7 is in the tilted state, the intake reed valve 8 has the valve body 8a protruding into the intake port 9 so that the cylinder 7 has the valve body 8a.
It is mounted on the upper wall surface of the crankcase 10, which corresponds to the back surface of the crankcase 10, and is configured so that the volume of the crank chamber is minimized by the arrangement of the valve body 8a of the reed valve 8. A carburetor 11 and an air cleaner 12 are disposed on the upstream side of the reed valve 8 so as to be located in the space between the upper surface of the transmission case T extending rearward and the rear side surface of the forward tilt cylinder 7. Thus, the carburetor 11, the air cleaner 12, the reed valve 8, and the exhaust pipe connecting them cooperate with each other to form an intake system In of the present invention in which the downstream end is opened to the upper inside of the crankcase 10. .

A crankshaft 15 connected to a piston 13 slidably fitted in a cylinder 7 of an engine E via a connecting rod 14.
Is supported by the transmission case T in the left-right direction of the vehicle body through a pair of ball bearings 16, 16.

A flywheel 18 is fixed by a nut 19 to the right end of a crankshaft 15 that projects rightward from the crankcase 10 into the engine cover 17. A fan 20 for cooling the engine E is integrally fixed to the outer surface of the flywheel 18, and a magnet 22 of a generator 21 is provided with a stator coil 23 on the inner surface of a flange 18a formed on the outer periphery of the flyhole 18. It is mounted so as to surround the outer periphery of the.

On the other hand, a crankshaft 15 protruding leftward from the crankcase 10 into the transmission case T is formed with a spline 15a, and the fixed end of the drive pulley 25 of the belt type continuously variable transmission B is formed at the right end of the spline 15a. The pulley half 26 is fitted and fixed, and the movable pulley half 29 of the drive pulley 25 is axially slidably fitted in the middle portion of the spline 15a. A ramp plate 28 is fixed to the left end of the crankshaft 15 by a tightening force of a nut 27 so as not to rotate relative to the crankshaft 15, and a slide piece 28a provided at the tip of the ramp plate 28 is attached to a movable side of the drive pulley 25. It is slidably engaged with a guide piece 29a formed in the axial direction of the pulley half body 29. Accordingly, the lamp plate 28
Rotates integrally with the movable pulley half body 29 while allowing the movable pulley half body 29 to slide in the axial direction. A centrifugal weight 30 is housed in a space formed between the movable pulley half 29 and the ramp plate 28 and tapering outward in the radial direction, and the rotational speed of the crankshaft 15 increases to increase the centrifugal weight.
When the centrifugal force acting on 30 increases, the movable pulley half body 29 pressed by the centrifugal weight 30 moving radially outward in the tapered space moves to the right side and the fixed pulley half body 26
The belt 31 having a V-shaped cross section sandwiched between the two pulley halves 26 and 29 is moved outward in the radial direction.

The left half of the speed reducer input shaft 33, whose right end and center are supported by a pair of ball bearings 32 at the rear of the transmission case T, has a needle pocket 35 and a ball bearing provided with a grease pocket 34 in between. An inner sleeve 37 is supported by 36 so as to be rotatable relative to the reduction gear input shaft 33. An outer sleeve 38 is supported on the outer periphery of the inner sleeve 37 so as to be relatively rotatable and axially movable. The inner sleeve 37 and the outer sleeve 38 have a fixed pulley of a driven pulley 39 of a belt type continuously variable transmission B. The half body 40 and the movable pulley half body 41 are fixed to each other.
A clutch inner 43 of an automatic centrifugal clutch 42 is fixed to a right end of the inner sleeve 37 with a nut 44, and a spring 45 mounted between the clutch inner 43 and the outer inner sleeve 38 and the movable pulley half body 41. Is urged in the direction toward the fixed pulley half body 40.

An outside air introduction passage 80 is provided on the left side of the transmission case T, and the cooling air introduced through the outside air introduction passage 80 by the fan 40a integrally formed on the outer surface of the stationary pulley half body 40 is introduced. After being guided and rectified by the wind rib 81, the inside of the transmission case T is cooled. Then, this cooling air is discharged to the outside through a discharge passage 82 that communicates the inside of the transmission case T with the outside air.

As shown in FIG. 7, a pin 46 is planted radially outward on the peripheral surface of the inner sleeve 37, and a roller 47 provided at the tip of the pin 46 is formed on the peripheral surface of the outer sleeve 38. It is engaged with the cam groove 48. As is apparent from FIG. 8, the cam groove 48 has a substantially triangular shape and is inclined between the first position P1 and the third position P3 (advancing side in the rotational direction) with respect to the circumferential direction of the outer sleeve 38. Starting cam surface
A running cam surface 48b that is inclined with respect to the circumferential direction of the outer sleeve 38 is formed between the second position P2 and the third position P3 (on the rotation direction delay side).

At the rear of the engine E, an automatic centrifugal clutch 42 is arranged in a space formed between the belt type continuously variable transmission B and a gear reducer described later. That is, the clutch outer 49 located outside the clutch inner 43 is spline-fitted to the intermediate portion of the speed reducer input shaft 33 by nuts.
It is fixed at 50. As is clear from FIG. 4, the three clutch weights 53 pivotally supported by the pin 51 on the side wall of the clutch inner 43 and urged radially inward by the springs 52 have the inner circumference of the flange 49a of the clutch outer 49. The starting clutch 54 is configured by mounting a friction member 53a facing the surface. On the other hand, as is apparent from FIG. 5, the two clutch weights 57 pivotally supported on the side wall of the clutch outer 49 by the pins 55 and urged radially inward by the springs 56 are provided inside the flange 43a of the clutch inner 43. A friction member 57a facing the circumferential surface is attached to form an engine braking clutch 58. Therefore, as is apparent from FIG. 3, the starting clutch 54 is disposed adjacent to the driven pulley 39 side of the speed reducer input shaft 33, and the engine braking clutch 58 is disposed adjacent to the opposite side thereof.

The input gear 60 formed integrally with the speed reducer input shaft 33 of the gear speed reducer 59 is a first intermediate gear that is spline-fitted to an intermediate shaft 61 axially supported below the speed reducer input shaft 33 of the transmission case T.
The second that meshes with 62 and is formed integrally with this intermediate shaft 61
The intermediate gear 63 meshes with an output gear 66 which is press-fitted into a reduction gear output shaft 65 which is axially supported by a pair of ball bearings 64 above the rear portion of the transmission case T. A drive sprocket 67 is fixed to an end portion of the speed reducer output shaft 65 protruding outside from the transmission case T. The drive sprocket 67 is connected to the driven sprocket 5 of the rear wheel Wr via the chain 6. . Second
As is clear from the figure, the reduction gear input shaft 3 of the gear reduction gear 59
3, the intermediate shaft 61 and the reduction gear output shaft 65 are sequentially arranged from the front to the rear of the vehicle body, and one side in the vertical direction of a straight line extending in the vehicle front-rear direction connecting the crankshaft 15 and the reduction gear input shaft 33 (see FIG. The intermediate shaft 61 is arranged on the lower side in the illustrated example, and the reducer output shaft 65 is arranged on the other side in the vertical direction of the straight line (the upper side in the illustrated example).
33 and the intermediate shaft 61 are both the crankshaft 15 and the reducer output shaft.
It is located below the straight line that extends in the front-rear direction of the vehicle and that connects with 65.

As shown in FIGS. 2 and 6, the lower part of the transmission case T is lower than the crankcase 10 and the crankshaft.
A starter motor 68 is attached to the rear side of the axis of 15 so that the reed valve 8 is located on the opposite side of the crankcase 10 with the starter motor 68 interposed therebetween. The starter motor 68 is connected to a well-known starter pinion dive mechanism 69 provided inside the transmission case T so as to apply a starting torque to the crankshaft 15 when the engine E is started. Then, a starter ring gear 26a is formed on the outer periphery of the fixed pulley half body 26 of the drive pulley 25 so as to be located on the moving path of the starter pinion 70 that is fixed to the output shaft of the jumping mechanism 69 and can project to the left. Has been done. Therefore, when the starter motor 68 is started, the starter pinion 70 of the jumping mechanism 69 projects leftward and meshes with the starter ring gear 26a, and the crankshaft 15 to which the fixed pulley half body 26 integral with the starter ring gear 26a is fixed is rotated. Then, the engine E is started.

As shown in FIG. 1, the exhaust pipe 90 has a starter motor 90 in which an upstream portion 90a extending downward from a front side surface of a cylinder 7 of the exhaust pipe 90 is substantially along the lower front portion of the transmission case T when viewed from the side of the vehicle body. It is arranged so as to extend to the lower part of 68.

As shown in FIG. 3, a kick starter 71 is provided on the rear left side of the transmission case T. That is, the pedal 73 is attached to the outer end of the kick shaft 72 pivotally supported on the left wall of the transmission case T.
The kick arm 74 having the above is fixed, and the drive helical gear 75 is fixed to the inner end thereof. A return spring is placed between the drive helical gear 75 and the transmission case T.
76 is attached, and the kick arm 74 is automatically returned to the original position. The drive helical gear 75 meshes with a driven helical gear 77 which is movably supported in the axial direction on the inner surface of the transmission case T. The ratchet wheel 78 fixed to the inner end of the driven helical gear 77 is used for the reduction gear input shaft 33.
The ratchet teeth 37a formed on the left end of the inner sleeve 37 attached to the inner surface of the inner sleeve 37 are mateably opposed to each other. A ring-shaped friction spring 79 is provided on the outer periphery of the ratchet wheel 78.
And the end of the friction spring 79 is locked to the air guide rib 81 formed on the inner wall of the transmission case T.

Next, the operation of the above-described embodiment of the present invention will be described.

When the starter motor 68 is started, a starter pinion 70 protruding via the jumping mechanism 69 is formed on the outer circumference of the fixed pulley half 26 of the drive pulley 25.
The crankshaft 15 to which the fixed pulley half 26 is fixedly engaged is engaged with the crankshaft 26a, and the engine E is started. On the other hand, when starting the engine E using the kick starter 71,
Kick arm 74 pedal extending from the transmission case T to the outside
This is done by kicking 73 from the front to the back of the paper. By the kick of the pedal 73, the driving helical gear 75
The driven helical gear 77 meshing with the driven helical gear 77 rotates, and at that time, the frictional force received from the friction spring 79 slidingly contacting the ratchet wheel 78 resists the rotation of the driven helical gear 77.
A thrust force in the axial direction is applied from 75. As a result, the driven helical gear 77 and the ratchet wheel 78 integrally move to the right, and the ratchet wheel 78 meshes with the ratchet teeth 37a formed on the end surface of the inner sleeve 37. Inner sleeve 3
When the 7 rotates, the pin 46 implanted in the inner sleeve 37
The outer sleeve 38 also rotates through the two sleeves 37, 38.
The belt 31 wound around the fixed-side pulley half 40 and the movable-side pulley half 41 of the driven pulley 39 fixedly attached to the driven pulley 39 is driven.
The rotation of the belt 31 is transmitted to the drive pulley 25, and the crankshaft 15 supporting the cono drive pulley 25 rotates to start the engine E. When the engine E starts and the driven pulley 39 starts to rotate, the ratchet wheel 78 is separated by the ratchet teeth 37a formed on the inner sleeve 37, and the kick arm 74 is returned to the original position by the return spring 76. .

When the engine E is started by the kick starter 71 described above, the driving force of the kick arm 74 is first transmitted to the inner sleeve 37, and as shown in FIG. Is driven in the direction of arrow a. As a result, the pin 46 forms the cam groove formed on the outer sleeve 38.
While contacting the starting cam surface 48a of 48 and pressing the outer sleeve 38 in the direction of the arrow b, the first sleeve moves toward the first position P1.
The rotation of the inner sleeve 37 is transmitted to the outer sleeve 38. In this manner, the movable pulley half body 41 is pressed in the direction of the arrow b so as to approach the fixed pulley half body 40, so that the belt 31 is pinched by both pulley half bodies 40 and 41 and slips. This is prevented, and the engine E can be started smoothly.

When the engine E is started, the rotation of the crankshaft 15 is transmitted from the drive pulley 25 of the belt type continuously variable transmission B to the driven pulley 39. At this time, the driving force of the belt 31 is first the movable pulley half of the driven pulley 39 with a small load.
It is transmitted to 41. For this reason, as shown in FIG. 8, the movable pulley half body 41 rotates in the direction of arrow a, and the pin 46 planted in the inner sleeve 37 abuts on the running cam surface 48b of the cam groove 48 and the outer side. The rotation of the outer sleeve 38 is transmitted to the inner sleeve 37 while moving toward the second position P2 while pressing the sleeve 38 in the direction of arrow b. Also in this case, similarly to the above, the movable pulley half 41 is pressed in the direction of the arrow b so as to approach the fixed pulley half 40, so that the belt 31
Is prevented from slipping due to being pinched by the two pulley halves 40, 41, and power transmission is smoothly performed when the vehicle starts with a large load or when climbing a hill. As is apparent from FIG. 8, the inclination angle of the starting cam surface 48a with respect to the rotation direction of the outer sleeve 38 (direction of arrow a) is set smaller than the inclination angle of the traveling cam surface 48b. As a result, the pinching force of the belt 31 at the time of starting, where the sleep of the belt 31 is most likely to occur, is sufficiently increased, and the movement of the pin 46 from the second position P2 to the third position P3 described later after starting is prevented. It has become.

When the inner sleeve 37 is rotated by the driving force transmitted to the driven pulley 39 as described above, the clutch inner 43 of the automatic centrifugal clutch 42 fixed to the inner sleeve 37 is rotated. Then, the clutch weight 53 pivotally supported by the clutch inner 43 expands against the spring 52 by the centrifugal force, and the friction member 53a contacts the inner surface of the flange 49a of the clutch outer 49, so that the driving force is applied to the clutch outer 49. Transmitted. The rotation of the clutch outer 49 is transmitted to the speed reducer input shaft 33 to which the clutch outer 49 is spline fitted,
The rotation of the input gear 60 is transmitted to the first and second intermediate gears 62 and 63 fixed to the intermediate shaft 61 and the output gear 66 fixed to the output shaft 65 of the speed reducer. The rotation of the speed reducer output shaft 65 is transmitted to the rear wheel Wr via the drive sprocket 67, the chain 6 and the driven sprocket 5. At this time, since the intermediate shaft 61 is arranged below and the reducer output shaft 65 is arranged above the straight line connecting the crankshaft 15 and the reduction gear input shaft 33 and extending in the vehicle front-rear direction, this The front-rear length of the gear reducer 59 is shortened.

When the rotation of the engine E gradually increases, the centrifugal weight 30 attached to the movable pulley half 29 on the drive pulley 25 side of the belt type continuously variable transmission B moves outward in the radial direction by centrifugal force, and the movable pulley is moved. The half body 29 is moved in a direction of approaching the fixed pulley half body 26. As the two pulley halves 26, 29 approach each other, the width of the V space formed between the two halves is narrowed and the V belt 31 moves to the outside of the drive pulley 25 in the radial direction. V
When the belt 31 moves outward, the movable pulley half body 41 of the driven pulley 39 is pressed by the V belt 31 and moves to the right against the spring 45 to be formed between the pulley half bodies 40, 41. The width of the V space is widened, and the V belt 31 moves radially inward of the driven pulley 39. As a result, the continuously variable transmission is performed such that the reduction ratio is large in the low speed rotation range of the engine E and is small in the high speed rotation range. When the belt type continuously variable transmission B travels at a high speed where the reduction ratio is minimized, the tension on the belt 31 causes the movable pulley half body 41 to be separated most from the fixed pulley half body 40.
The pin 46 is stably held at the third position P3 of the cam groove 48.

When the rotation of the engine E is decelerated during traveling, the clutch weight 53 pivotally supported by the clutch inner 43 is separated from the flange 49a of the clutch outer 49 by the elastic force of the spring 52, and the transmission of the driving force is interrupted. However, since the clutch outer 49 connected to the rear wheel Wr side is still rotating, the clutch weight 57 pivotally supported on the side wall of the clutch outer 49 expands against the spring 56, and the friction member 57a moves toward the clutch inner 43.
Abuts the flange 43a. As a result, the rotation of the rear wheel Wr is transmitted to the engine E side and the engine brake operates.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various small design changes can be made without departing from the present invention described in the claims for utility model registration. It is possible to do.

For example, in the invention of claim 1, instead of providing the intermediate shaft 61 at the lower part of the straight line connecting the crankshaft 15 and the reducer input shaft 33 and providing the reducer output shaft 65 at the upper part, the intermediate shaft 61 and the reducer output shaft are provided. The upper and lower positions of 65 can be reversed.

C. Effect of the Invention As described above, according to the invention of each claim, the belt type continuously variable transmission and the gear reducer are provided in the transmission case in which the crankcase of the reed valve intake type two-cycle engine is continuously provided in the front part. The exhaust port is opened on the front side of the cylinder, and the intake system with the downstream end opened on the upper inside of the crankcase is installed between the rear side of the cylinder and the upper surface of the transmission case. In the two-wheeled vehicle, the cylinder is tilted sufficiently so that it is closer to the horizontal plane that passes through the coaxial line than the vertical plane that passes through the crankshaft axis. In addition, it is possible to secure a sufficiently wide space for the intake system, and thus contribute to the reduction of intake resistance and the improvement of engine output.

In addition, a reduction gear intermediate shaft is arranged on one side in the vertical direction of a straight line extending in the longitudinal direction of the vehicle body connecting the crank shaft and the reduction gear input shaft, and a reduction gear output shaft is arranged on the other side of the straight line in the vertical direction. Since the three shafts of the reduction gear input shaft, the intermediate shaft, and the output shaft arranged in the front-rear direction of the vehicle body are arranged so as to be displaced in the vertical direction, the gear reduction gear is a shaft that is required for the three shafts. The front-rear length of the power transmission can be shortened while maintaining a sufficient distance in the front-rear direction, and as a result, by tilting the cylinder forward enough as described above, the engine tends to be vertically long. However, since it is possible to avoid increasing the length of the entire power unit including the engine and the power transmission device in the front-rear direction, it is possible to increase the degree of freedom in mounting the power unit on the vehicle body.

Further, even if the starter motor is arranged in the lower part of the transmission case in order to avoid interference with the intake system and the continuously variable transmission, the starter motor is displaced to the rear side from the crankshaft axis line and is directed downward from the front side surface of the cylinder. The extending exhaust pipe is arranged so that the upstream portion thereof extends to the lower portion of the starter motor substantially along the lower portion of the front surface of the transmission case when viewed from the side of the vehicle body. Even if the motor is not bent greatly downward, the lower part of the motor can be smoothly routed, and smooth exhaust can be performed. Moreover, the intake system and the starter motor, which should be arranged around the crankcase, cannot be placed above and below a continuously variable transmission that is relatively long in the front-rear direction while avoiding mutual interference and minimizing the downward extension of the motor. Since it is possible to disperse and arrange the power units, it is possible to contribute to downsizing of the power unit in the vertical direction.

Further, according to the invention of claim 2, in particular, both the reduction gear input shaft and the intermediate shaft are located below a straight line connecting the crank shaft and the reduction gear output shaft and extending in the vehicle front-rear direction. Since the clutch outer is connected to the speed reducer input shaft that is coaxial with the driven pulley of the continuously variable transmission,
The clutch outer and the driven side of the belt type continuously variable transmission, which are major components of the power transmission device, and the input shaft and the intermediate shaft of the speed reducer can all be placed as close as possible to the lower side of the power transmission device. Can significantly contribute to lowering the center of gravity of the.

[Brief description of drawings]

1 to 8 show an embodiment of the present invention.
The figure is an overall side view of a motorcycle to which the present power transmission device is applied, FIG. 2 is an enlarged cross-sectional view of an essential part of FIG. 1, FIG. 3 is a cross-sectional view taken along line III-III of FIG. 2, and FIG. IV-IV line sectional view of FIG.
FIG. 5 is a sectional view taken along line VV of FIG. 3, and FIG. 6 is VI of FIG.
-VI line sectional view, FIG. 7 is a side view of the movable pulley half of the driven pulley, and FIG. 8 is an enlarged view of the cam groove. B ... Belt type continuously variable transmission, E ... Engine, In ... Intake system, T ... Transmission case, 7 ... Cylinder, 7e ... Exhaust port, 8 ... Reed valve, 10 ... Crankcase,
15 …… Crank shaft, 33 …… Reducer input shaft, 39 …… Driven pulley, 42 …… Automatic centrifugal clutch as a clutch,
49 …… clutch outer, 59 …… gear reducer, 61 …… intermediate shaft, 65 …… reducer output shaft, 68 …… starter motor, 90…
… Exhaust pipe, 90a …… Upstream part of the exhaust pipe extending downward from the cylinder

Claims (2)

(57) [Scope of utility model registration request] 1. A crankshaft (15) for a two-cycle engine (E), a gear having a cylinder (7) tilted forward toward a horizontal plane passing through a coaxial line with respect to a vertical plane passing through the crankshaft (15) axis. The reduction gear input shaft (33), the intermediate shaft (61) and the reduction gear output shaft (65) of the reduction gear (59) are sequentially arranged from the front to the rear of the vehicle body, and the crankcase (10) of the engine (E) is provided. A belt type continuously variable transmission (B) in which the crankshaft (15) and the reduction gear input shaft (33) are connected to each other in a transmission case (T) continuously connected to the front portion, and the gear reduction gear (59). ) And an exhaust pipe (90) extending downward from the front side surface of the cylinder (7) between the rear side surface of the cylinder (7) and the upper surface of the transmission case (T). In this, an intake system (In) with a downstream end opened is provided in the upper part of the crankcase (10), and the intake system (In) is A power transmission device for a motorcycle, which is provided with a reed valve (8), wherein the straight line extending in the vehicle longitudinal direction connects the crankshaft (15) and the speed reducer input shaft (33) to one side in the vertical direction. The intermediate shaft (61) is arranged, and the speed reducer output shaft (65) is arranged on the other side of the straight line in the vertical direction.
Starter motor (68) that can give starting torque to 5)
Is attached to the lower portion of the transmission case (T) while being displaced to the rear side from the axis of the crankshaft (15), and the exhaust pipe (90)
The upstream portion (90a) extending downward from the cylinder (7) extends substantially along the lower portion of the front surface of the transmission case (T) to the lower portion of the starter motor (68) when viewed from the side of the vehicle body. A power transmission device for a motorcycle, wherein the power transmission device is arranged as described above. 2. The driven pulley (39) of the belt type continuously variable transmission (B) and the speed reducer input shaft (33) are arranged on the same axis, and the crankshaft (15) and the speed reducer input shaft are arranged. (33)
The intermediate shaft (61) is arranged below the straight line that extends in the vehicle body front-rear direction, and the reduction gear output shaft (65) is arranged above this straight line, and the reduction gear input shaft (33 ), The clutch outer (49) of the clutch (42) interposed between the input shaft (33) and the driven pulley (39) is coupled to the (). Power transmission device for motorcycles.