JP2007113653A - Saddle ride type vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of idle rotation of a rear wheel occurring due to sticking of a clutch plate and a friction plate of a centrifugal clutch in a saddle ride type vehicle. <P>SOLUTION: A helical gear 80b on the left side half of a gear 80 rotating interlockingly with a clutch boss 77 of the centrifugal clutch 44 in a motorcycle is meshed with a first shift shaft 103 which is a helical gear for transmitting driving force to a shift shaft 100. Frictional force generates to the gear 80 by a washer 143 being pressed by an energizing force of a disk spring 140, and the frictional force becomes a braking force of the rear wheel 26. The helical gear 80b is provided so that the thrusting force working by receiving the driving force works in a reverse direction from the energizing force of the disk spring 140. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a straddle-type vehicle such as a motorcycle or a four-wheel buggy.

  Conventionally, in a straddle-type vehicle such as a motorcycle, the clutch is completely disconnected due to the fact that the clutch plate and the friction plate stick to each other when the clutch is off (disengaged). There is a possibility that the power is transmitted to the rear wheel without being able to rotate and the rear wheel rotates when the main stand is set up, that is, the rear wheel is accompanied. Therefore, in order to prevent occurrence of sticking between the clutch plate and the friction plate, for example, techniques such as Patent Documents 1 and 2 below have been proposed.

  Patent Document 1 discloses a sticking prevention mechanism including a spring that biases a clutch plate and a friction plate in a direction in which they are separated from each other. In this sticking prevention mechanism, a leaf spring that biases the clutch plates in a direction to separate them from each other is provided between adjacent clutch plates, and a coil that biases the friction plates in a direction to separate the friction plates between the friction plates. A spring is provided. When the clutch is off, the clutch plates are separated from each other by the urging force of the leaf spring, and the friction plates are separated from each other by the urging force of the coil spring, thereby preventing the clutch plate and the friction plate from sticking to each other. The improvement of cutting is achieved.

Patent Document 2 discloses a centrifugal clutch device in which the shape of a cam surface that guides the movement of a centrifugal weight is devised. Also in this centrifugal clutch device, a leaf spring is provided between the clutch plates to urge the clutch plates in a direction to separate them. A pressing plate is disposed at the end of the clutch plate, a cam surface is formed inside the bottom wall of the clutch plate, and a centrifugal weight is disposed between the cam surface and the pressing plate. As the centrifugal force of the centrifugal weight increases, the cam surface releases the pressure contact as the centrifugal force decreases, and a drive surface that guides the centrifugal weight to a position where the clutch plate and the friction plate are pressed against each other. And a flank for guiding the centrifugal weight to a position. The flank has an inclination angle larger than that of the drive surface so that the movement allowance in the direction away from the pressing plate of the centrifugal weight is increased. Therefore, the centrifugal weight moves to the flank as the centrifugal force decreases, so that a sufficient interval between the clutch plate and the friction plate is secured, thereby improving the clutch disengagement.
JP 2003-301903 A JP 2002-021879 A

  However, the techniques described in Patent Documents 1 and 2 described above cannot sufficiently prevent the clutch plate and the friction plate from sticking to each other, and can completely prevent the rear wheel from being accompanied. It wasn't. Therefore, a straddle-type vehicle that can sufficiently prevent the rear wheel from being accompanied is strongly desired.

  The present invention has been made in view of the above points, and an object of the present invention is to prevent the accompanying rotation of the drive wheels caused by sticking between the clutch plate and the friction plate. It is to provide a saddle-ride type vehicle.

  A straddle-type vehicle according to the present invention includes a centrifugal clutch, a driving wheel, a power transmission mechanism that transmits a driving force to the driving wheel when the centrifugal clutch is in a connected state, and the power transmission mechanism. A straddle-type vehicle including a friction mechanism that applies a braking force to the driving wheel by applying a friction force to the driving wheel.

  The straddle-type vehicle is configured to apply a braking force to the driving wheel and stop the driving wheel by applying a frictional force to the power transmission mechanism that applies the driving force from the centrifugal clutch to the driving wheel. Therefore, it is possible to prevent the driving wheels from rotating even when the driving force is applied to the power transmission mechanism even though the clutch is disengaged.

  According to the present invention, in a saddle-ride type vehicle equipped with a centrifugal clutch, it is possible to reliably prevent the drive wheels from being accompanied.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<First Embodiment>
As shown in FIG. 1, the straddle-type vehicle according to the present embodiment is a motorcycle 10. The motorcycle 10 includes a body frame 11 that forms a skeleton, and a seat 16 on which an occupant sits. The motorcycle 10 is a so-called moped type motorcycle. That is, the motorcycle 10 is formed with a concave space 17 in a side view that is recessed downward in front of the seat 16, and an occupant seated on the seat 16 rides over the vehicle body frame 11. The “moped type” here simply represents the type of vehicle shape, and does not limit the maximum speed or displacement of the vehicle, but also the size of the vehicle. is not.

  However, the straddle-type vehicle according to the present invention is not limited to a moped type motorcycle, and may be another motorcycle such as a so-called motorcycle type in which a fuel tank is disposed in front of a seat.

  In the following description, the front, rear, left, and right directions are directions viewed from the occupant seated on the seat 16. The vehicle body frame 11 includes a steering head pipe 12, a single main frame 13 extending rearward and downward from the steering head pipe 12, left and right seat rails 14L and 14R extending rearward and obliquely upward from a middle portion of the main frame 13, Left and right seat pillar tubes 15L and 15R connected to a rear end portion of the main frame 13 and midway portions of the seat rails 14L and 14R are provided (see FIG. 2).

  The upper and left and right sides of the body frame 11 are covered with a body cover 21. On the upper side of the vehicle body cover 21 and in front of the seat 16, a side view concave space 17 that is recessed downward is defined. A center tunnel 11 a that is a passage for the main frame 13 is defined below the vehicle body cover 21.

  A front wheel 19 is supported on the steering head pipe 12 via a front fork 18. A handle (not shown) is provided on the upper side of the front fork 13, and an accelerator grip 8 is provided on the right side of the handle. The accelerator grip 8 is an accelerator operator whose opening degree can be adjusted, and the occupant adjusts the output of the engine 29 by operating the accelerator grip 8. A fuel tank 20 and a seat 16 are supported on the seat rails 14L and 14R. The seat 16 extends from above the fuel tank 20 toward the rear ends of the seat rails 14L, 14R. The fuel tank 20 is disposed above the front half of the seat rails 14 </ b> L and 14 </ b> R and is covered with the vehicle body cover 21 and the seat 16.

  A pair of left and right first engine brackets 22 </ b> L and 22 </ b> R projecting downward is provided in the middle portion of the main frame 13. A pair of left and right second engine brackets 23L and 23R and rear arm brackets 24L and 24R are provided at the rear end of the main frame 13, respectively. Here, the brackets provided on the main frame 13 and the like, specifically, the first engine brackets 22L and 22R, the second engine brackets 23L and 23R, the rear arm brackets 24L and 24R, and the like are part of the body frame 11. Shall be made.

  The rear arm brackets 24L and 24R protrude downward from the rear end portion of the main frame 13. These rear arm brackets 24L and 24R are provided with a pivot shaft 38, and a front end portion of the rear arm 25 is swingably supported by the pivot shaft 38. A rear wheel 26 is supported at the rear end portion of the rear arm 25. The rear half of the rear arm 25 is suspended from the vehicle body frame 11 via a cushion unit 27.

  As shown in FIG. 5, the second engine brackets 23 </ b> L and 23 </ b> R protrude downward from the rear end portion of the main frame 13. The left and right second engine brackets 23L and 23R face each other with a gap in the vehicle width direction.

  As shown in FIG. 1, an engine unit 28 that drives the rear wheel 26 is supported on the body frame 11. Specifically, as shown in FIG. 4, the engine unit 28 includes a crankcase 35, a cylinder 43, and a cylinder head 44. The crankcase 35 has first and second engine mount portions 36 and 37. The first engine mount portion 36 protrudes upward from the upper side of the front end portion of the crankcase 35 and is supported by the first engine brackets 22L and 22R. The second engine mount portion 37 protrudes rearward and upward from the upper side of the rear end portion of the crankcase 35 and is supported by the second engine brackets 23L and 23R (see also FIG. 5). For this reason, the crankcase 35 is supported in a state of being suspended from the main frame 13.

  Further, as shown in FIG. 1, a main stand 115 is attached to the lower rear portion of the crankcase 35. The main stand 115 is disposed at the rear end portion of the crankcase 35 and is attached to a bracket 116 fixed using a bolt (not shown). Further, the main stand 115 is rotatable about a pivot shaft 117. FIG. 1 shows a state in which the main stand 115 is set and the body of the motorcycle 10 is held, and the rear wheel 26 is lifted from the road surface R.

  As will be described in detail later, the engine unit 28 includes an engine 29 and a belt-type continuously variable transmission (hereinafter referred to as CVT) 30 (see FIG. 6). Although the type of the engine 29 is not limited at all, in the present embodiment, the engine 29 is configured by a four-cycle single cylinder engine.

  As shown in FIG. 1, the motorcycle 10 includes a front fender 31 that covers the upper side and the rear side of the front wheel 19, and a rear fender 32 that covers the upper rear side of the rear wheel 26.

  The motorcycle 10 includes a front cowl 33 and left and right leg shields 34L and 34R in addition to the vehicle body cover 21 described above. The leg shields 34L, 34R are cover members that cover the front of the driver's legs, and extend obliquely up and down when viewed from the side. The leg shields 34L and 34R may be integrated with the front cowl 33 or may be separate.

  As shown in FIG. 2, the horizontal cross-sectional shape of the leg shields 34L, 34R is formed in a concave shape that opens rearward. In other words, the cross-sectional shape of the leg shields 34L and 34R is formed in a substantially C-shaped curved shape that tapers forward. As a result, on the back side (inside of the concave shape) of the leg shields 34L and 34R, there is provided a space whose front and sides are covered with the leg shields 34L and 34R.

  In the present embodiment, the leg shields 34L and 34R are formed of a resin material. However, the material of the leg shields 34L and 34R is not limited at all.

  The lengths of the leg shields 34L and 34R in the longitudinal direction are not particularly limited, but the lower ends 34a (see FIG. 1) of the leg shields 34R and 34L are preferably positioned below the upper end 53t of the transmission case 53. Further, the lower ends 34a of the leg shields 34L, 34R are below the intermediate position in the vertical direction of the transmission case 53 (a line L1 connecting a center C1 of a primary sheave shaft 46c described later and a center C2 of a secondary sheave shaft 62). It is preferable to be located, and in this embodiment, it is located below the lower end 53 d of the transmission case 53.

  As shown in FIG. 2, footrests 85 </ b> L and 85 </ b> R made of rubber or the like are disposed on the left and right sides of the engine unit 28. The footrests 85L and 85R are footrest members that support the driver's feet. The left and right footrests 85L and 85R are supported by the crankcase 35 of the engine unit 28 via a metal connecting rod 87 and a mounting plate 88 (see FIGS. 3 and 4) fixed to the connecting rod 87. ing.

  The connecting rod 87 extends in the vehicle width direction through the lower half of the crankcase 35. The left end of the connecting rod 87 protrudes to the left side of the crankcase 35 and supports the left footrest 85L. The right end of the connecting rod 87 protrudes to the right side of the transmission case 53 and supports the right footrest 85R. As shown in FIG. 3, the attachment plate 88 is formed by press-molding a metal plate, and a concave portion 89 into which the connecting rod 87 is fitted is formed in the middle portion of the attachment plate 88 in the front-rear direction. The recess 89 is abutted against the connecting rod 87 from below and is welded to the outer peripheral surface of the connecting rod 87.

  The mounting plate 88 includes a flange-shaped first mounting portion 90 that projects to the front of the connecting rod 87 and a flange-shaped second mounting portion 91 that projects to the rear of the connecting rod 87. The first attachment portion 90 and the second attachment portion 91 extend in the axial direction (left-right direction) of the connecting rod 87 and face the lower surface 83 of the rear half portion of the crankcase 35.

  The lower surface 83 of the rear half of the crankcase 35 has four (only two are shown in FIG. 3) bosses 92. These boss portions 92 protrude downward from the lower surface 83 of the crankcase 35 and are formed integrally with the crankcase 35. Each boss portion 92 is formed with a bolt hole (not shown). Bolt holes (not shown) are also formed in the mounting plates 88 of the footrests 85L and 85R at positions corresponding to the boss portions 92. The attachment plate 88 and the boss portion 92 are fastened by a bolt 99. Thus, the footrests 85L and 85R are fixed to the crankcase 35 by the bolt 99 via the connecting rod 87 and the attachment plate 88.

  As shown in FIGS. 1 and 2, a brake pedal 84 is provided in front of the right footrest 85R. The brake pedal 84 protrudes diagonally right forward through the lower part of the transmission case 53 and extends obliquely upward and forward on the right side of the transmission case 53. As shown in FIG. 2, when the motorcycle 10 travels, the driver's right foot 62 a is adjacent to the transmission case 53 in the vehicle width direction.

  Next, the internal configuration of the engine unit 28 will be described. As shown in FIG. 6, the engine unit 28 includes an engine 29, a CVT 30, a centrifugal clutch 41, and a speed reduction mechanism 42.

  The engine 29 includes a crankcase 35, a cylinder 43 connected to the crankcase 35, and a cylinder head 44 connected to the cylinder 43. The crankcase 35 has two divided case blocks, that is, a first case block 35a located on the left side and a second case block 35b located on the right side. The first case block 35a and the second case block 35b are abutted against each other along the vehicle width direction.

  A crankshaft 46 is accommodated in the crankcase 35. The crankshaft 46 extends in the vehicle width direction and is disposed horizontally. The crankshaft 46 is supported by the first case block 35 a via a bearing 47 and is supported by the second case block 35 b via a bearing 48.

  A piston 50 is slidably inserted into the cylinder 43. One end of a connecting rod 51 is connected to the piston 50. A crank pin 59 is provided between the left crank arm 46a and the right crank arm 46b of the crankshaft 46. The other end of the connecting rod 51 is connected to the crank pin 59.

  The cylinder head 44 is formed with a recess 44a and an intake port and an exhaust port (not shown) communicating with the recess 44a. A spark plug 55 is inserted into the recess 44 a of the cylinder head 44. As shown in FIG. 3, an intake pipe 52a is connected to the intake port, and an exhaust pipe 52 is connected to the exhaust port. As shown in FIGS. 1 and 2, the exhaust pipe 52 extends rearward and obliquely downward to the right from the cylinder head 44, and further extends rearward under the transmission case 53 of the engine unit 28. It is connected to a muffler 54 arranged on the right side.

  As shown in FIG. 6, a cam chain chamber 56 that connects the inside of the crankcase 35 and the inside of the cylinder head 44 is formed on the left side in the cylinder 43. A timing chain 57 is disposed in the cam chain chamber 56. The timing chain 57 is wound around the crankshaft 46 and the camshaft 58. The cam shaft 58 rotates in accordance with the rotation of the crank shaft 46, and opens and closes an intake valve and an exhaust valve (not shown).

  A generator case 66 that houses the generator 63 is detachably attached to the left side of the front half of the first case block 35a. A transmission case 53 that houses the CVT 30 is attached to the right side of the second case block 35b.

  An opening is formed on the right side of the second half of the second case block 35 b, and this opening is closed by the clutch cover 60. The clutch cover 60 is detachably fixed to the second case block 35b by bolts 61 (see FIG. 7).

  The transmission case 53 is formed independently of the crankcase 35, and includes an inner case 53a that covers the inner side (left side) of the CVT 30 in the vehicle width direction and an outer case 53b that covers the outer side (right side) of the CVT 30 in the vehicle width direction. It is configured. The inner case 53a is attached to the right side of the crankcase 35, and the outer case 53b is attached to the right side of the inner case 53a. A belt chamber 67 that accommodates the CVT 30 is formed inside the inner case 53a and the outer case 53b.

  As shown in FIG. 6, the right end portion of the crankshaft 46 extends through the second case block 35 b and the inner case 53 a to the belt chamber 67. A primary sheave 71 of the CVT 30 is fitted into the right end portion of the crankshaft 46. Therefore, the primary sheave 71 rotates according to the rotation of the crankshaft 46. A right portion of the crankshaft 46 (strictly, a portion on the right side of the bearing 48) forms a primary sheave shaft 46c.

  On the other hand, the left end portion of the crankshaft 46 passes through the first case block 35 a and extends into the generator case 66. A generator 63 is attached to the left end portion of the crankshaft 46. The generator 63 includes a stator 64 and a rotor 65 that faces the stator 64. The rotor 65 is fixed to a sleeve 74 that rotates together with the crankshaft 46. The stator 64 is fixed to the generator case 66.

  A secondary sheave shaft 62 is disposed in the latter half of the crankcase 35 in parallel with the crankshaft 46. A right side portion of the center portion of the secondary sheave shaft 62 is supported by the clutch cover 60 via a bearing 75. The left side portion of the secondary sheave shaft 62 is supported by the left end portion of the second case block 35 b via a bearing 76. The right end portion of the secondary sheave shaft 62 passes through the second case block 35 b and the clutch cover 60 and extends to the belt chamber 67. A secondary sheave 72 of the CVT 30 is connected to the right end portion of the secondary sheave shaft 62.

  As shown in FIG. 6, the CVT 30 includes a primary sheave 71, a secondary sheave 72, and a V belt 73 wound around the primary sheave 71 and the secondary sheave 72. As described above, the primary sheave 71 is attached to the right side portion of the crankshaft 46. The secondary sheave 72 is connected to the right side portion of the secondary sheave shaft 62.

  The primary sheave 71 includes a fixed sheave half 71a located on the outer side in the vehicle width direction, and a movable sheave half 71b located on the inner side in the vehicle width direction and facing the fixed sheave half 71a. The fixed sheave half 71a is fixed to the right end of the primary sheave shaft 46c and rotates together with the primary sheave shaft 46c. The movable sheave half 71b is disposed on the left side of the fixed sheave half 71a, and is slidably attached to the primary sheave shaft 46c. Therefore, the movable sheave half 71b rotates with the primary sheave shaft 46c and is slidable in the axial direction of the primary sheave shaft 46c. A belt groove is formed between the fixed sheave half 71a and the movable sheave half 71b. A cam surface 111 is formed on the left side of the movable sheave half 71 b, and a cam plate 112 is disposed on the left side of the cam surface 111. A roller weight 113 is disposed between the cam surface 111 and the cam plate 112 of the movable sheave body 71b.

  The secondary sheave 72 includes a fixed sheave half 72a located on the inner side in the vehicle width direction and a movable sheave half 72b located on the outer side in the vehicle width direction and facing the fixed sheave half 72a. The movable sheave half 72 b is attached to the right end of the secondary sheave shaft 62. The movable sheave half 72 b rotates with the secondary sheave shaft 62 and is slidable in the axial direction of the secondary sheave shaft 62. A compression coil spring 114 is provided at the right end of the secondary sheave shaft 62, and the movable sheave half 72 b receives a leftward biasing force from the compression coil spring 114. The shaft center portion of the fixed sheave half 72 a is a cylindrical slide collar and is spline-fitted to the secondary sheave shaft 62.

  In the CVT 30, the reduction ratio is determined by the magnitude relationship between the force that the roller weight 113 pushes the movable sheave half 71b of the primary sheave 71 to the right and the force that the compression coil spring 114 pushes the movable sheave half 72b of the secondary sheave 72 to the left. Is determined.

  That is, when the rotational speed of the primary sheave shaft 46c increases, the roller weight 113 receives the centrifugal force and moves radially outward to push the movable sheave half 71b to the right. Then, the movable sheave half 71b moves to the right, and the belt winding diameter of the primary sheave 71 increases. Along with this, the belt winding diameter of the secondary sheave 72 is reduced, and the movable sheave half 72 b of the secondary sheave 72 moves to the right against the urging force of the compression coil spring 114. As a result, the winding diameter of the V belt 73 in the primary sheave 71 is increased, while the winding diameter in the secondary sheave 72 is decreased, and the reduction ratio is decreased.

  On the other hand, when the rotational speed of the primary sheave shaft 46c decreases, the centrifugal force of the roller weight 113 decreases, so that the roller weight 113 moves radially inward along the cam surface 111 and the cam plate 112 of the movable sheave half 71b. . Therefore, the force with which the roller weight 113 pushes the movable sheave half 71b to the right is reduced. Then, the urging force of the compression coil spring 114 relatively exceeds the above force, the movable sheave half 72b of the secondary sheave 72 moves to the left side, and the movable sheave half 71b of the primary sheave 71 also moves to the left accordingly. . As a result, the belt winding diameter of the primary sheave 71 is reduced, while the belt winding diameter of the secondary sheave 72 is increased and the reduction ratio is increased.

  As shown in FIG. 6, the outer case 53 b includes a first bulged portion 93 and a second bulged portion 94 that bulge outward (right side) in the vehicle width direction. The 1st bulging part 93 and the 2nd bulging part 94 are located in a line with the front-back direction. The first bulging portion 93 covers the primary sheave 71, and the second bulging portion 94 covers the secondary sheave 72.

  A seal groove 68a is formed on the left side of the peripheral edge of the inner case 53a, and the right peripheral edge of the second case block 35b is fitted into the seal groove 68a. An O-ring 68 is inserted between the inner case 53a and the second case block 35b in the seal groove 68a. A seal groove 69a is also formed on the right side of the peripheral edge of the inner case 53a, and the peripheral edge of the outer case 53b is fitted in the seal groove 69a. An O-ring 69 is inserted between the inner case 53a and the outer case 53b in the seal groove 69a. The outer case 53b and the second case block 35b are fastened by a bolt 70 with the inner case 53a sandwiched therebetween.

  As shown in FIG. 7, the centrifugal clutch 41 is attached to the left side portion of the secondary sheave shaft 62. The centrifugal clutch 41 is a wet multi-plate clutch, and includes a substantially cylindrical clutch housing 78 and a clutch boss 77. The clutch housing 78 is splined to the secondary sheave shaft 62 and rotates together with the secondary sheave shaft 62. A plurality of ring-shaped clutch plates 79 are attached to the clutch housing 78. These clutch plates 79 are arranged at intervals in the axial direction of the secondary sheave shaft 62.

  A cylindrical gear 80 is rotatably fitted around the left side portion of the secondary sheave shaft 62 via a bearing 81. The right half of the gear 80 is a spur gear 80a in which tooth traces are formed in parallel in the axial direction, and the left half is a helical gear 80b in which tooth traces are formed in a spiral shape. The gear 80 is formed integrally with a spur gear 80a and a helical gear 80b, and both rotate integrally. The “helical gear” referred to in the present invention only needs to include at least a portion of a helical gear. In this embodiment, the gear 80 corresponds to the “helical gear” of the present invention. Corresponds to "gear". The clutch boss 77 is disposed radially inward of the clutch plate 79 and radially outward of the gear 80, and meshes with the right half of the gear 80, that is, the spur gear 80a. Therefore, the gear 80 rotates together with the clutch boss 77. As will be described in detail later, the left half of the gear 80, that is, the helical gear 80 b meshes with the first transmission gear 103 that is a helical gear provided at the right end of the transmission shaft 100. A plurality of ring-shaped friction plates 82 are attached to the outer side of the clutch boss 77 in the radial direction. These friction plates 82 are arranged at intervals along the axial direction of the secondary sheave shaft 62, and each friction plate 82 is disposed between adjacent clutch plates 79, 79.

  On the left side of the clutch housing 78, a plurality of cam surfaces 83a are formed. A roller weight 84a is disposed between the cam surface 83a and the rightmost clutch plate 79 facing the cam surface 83a.

  In the centrifugal clutch 41, the clutch-in state (connected state) and the clutch-off state (disconnected state) are automatically switched depending on the magnitude of the centrifugal force acting on the roller weight 84a.

  That is, when the rotational speed of the clutch housing 78 becomes a predetermined speed or more, the roller weight 84a receives the centrifugal force and moves radially outward, and the clutch plate 79 is pushed leftward by the roller weight 84a. As a result, the clutch plate 79 and the friction plate 82 are pressure-bonded, and a clutch-in state is established in which the driving force of the secondary sheave shaft 62 is transmitted to the output shaft 85 (see FIG. 6) via the centrifugal clutch 41.

  On the other hand, when the rotational speed of the clutch housing 78 is less than a predetermined speed, the centrifugal force acting on the roller weight 84a decreases, and the roller weight 84a moves radially inward. As a result, the pressure-bonding between the clutch plate 79 and the friction plate 82 is released, and a clutch-off state is established in which the driving force of the secondary sheave shaft 62 is not transmitted to the output shaft 85. In FIG. 7, the front side (upper side in FIG. 7) of the centrifugal clutch 41 represents the clutch-off state, and the rear side (lower side in FIG. 7) represents the clutch-in state.

  As shown in FIG. 6, the speed reduction mechanism 42 is interposed between the centrifugal clutch 41 and the output shaft 85 (see FIG. 6). The speed reduction mechanism 42 has a speed change shaft 100 disposed in parallel with the secondary sheave shaft 62 and the output shaft 85. The transmission shaft 100 is rotatably supported by the first case block 35 a via the bearing 101 and is rotatably supported by the second case block 35 b via the bearing 102. As shown in FIG. 7, a first transmission gear 103 that meshes with a helical gear 80 b of the gear 80 is provided at the right end portion of the transmission shaft 100. As described above, the first transmission gear 103 is also a helical gear.

  When the helical gear 80b and the first transmission gear 103 are engaged with each other, that is, when the helical gear is rotated with the helical gears engaged with each other, both the helical gear 80b and the first transmission gear 103 are axially moved. The power of (thrust force) works. When a driving force is applied to the helical gear 80b in a direction in which the motorcycle 10 moves forward, a rightward thrust force acts on the helical gear 80b.

  A disc spring 140, a washer 141, and a thrust bearing 142 are disposed on the right side of the spur gear 80a. The right end of the thrust bearing 142 is in contact with the secondary sheave shaft 62. Further, a washer 143 is disposed on the left side of the helical gear 80b, and the left side of the washer 143 is in contact with the bearing 76 described above. The disc spring 140 biases the gear 80 to the left with a predetermined force in a state in which no axial force is applied to the gear 80 and contracts by a predetermined length from the normal length. Is pressed. At this time, the left end portion of the gear 80 presses the washer 143 leftward, and a frictional force (static frictional force) acts between the gear 80 and the washer 143.

  Here, when a driving force is applied to the gear 80, a rightward thrust force acts on the helical gear 80b. Since this thrust force is a force in a direction opposite to the biasing force in the left direction generated in the disc spring 140, when this thrust force is smaller than the biasing force of the disc spring 140, the gear 80 moves to the left side. The force that presses the washer 143 is weakened, and the frictional force between the gear 80 and the washer 143 is weakened. When a large driving force is applied to the gear 80 and a thrust force larger than the biasing force of the disc spring 140 is applied to the helical gear 80b, the gear 80 moves to the right, and the gear 80 and the washer 143 Are separated. As a result, the force with which the gear 80 presses the left washer 143 becomes zero, and the frictional force between the gear 80 and the washer 143 also becomes zero. That is, in the present embodiment, as the driving force applied to the gear 80 increases, the thrust force acting on the gear 80 increases, and accordingly, the frictional force generated between the gear 80 and the washer 143 decreases. In FIG. 7, the front side (upper side in FIG. 7) of the gear 80 shows a state where the gear 80 presses the washer 143, and the rear side (lower side in FIG. 7) This shows a state where the washer 143 is separated and the frictional force is zero.

  The frictional force generated between the gear 80 and the washer 143 becomes a braking force with respect to the rotational driving force of the gear 80 and consequently becomes a braking force with respect to the rear wheel 26 (see FIG. 1). Therefore, if the driving force applied to the gear 80 is small, the frictional force between the gear 80 and the washer 143 increases, so the braking force applied to the rear wheel 26 increases, and conversely, the driving force applied to the gear 80 is reduced. If it is large, the frictional force is small, so that the braking force on the rear wheel 26 is small. Further, when a thrust force larger than the urging force of the disc spring 140 is applied to the helical gear 80b, no frictional force is generated between the gear 80 and the washer 143, so that a braking force is applied to the rear wheel 26. Disappear. In other words, the driving force applied to the gear 80 when a thrust force of the same magnitude as the urging force of the disc spring 140 acts on the helical gear 80b is used as a threshold, and a driving force smaller than the threshold is applied to the gear 80. Only when given, the braking force for the rear wheel 26 is generated.

  As shown in FIG. 6, a second transmission gear 104 having a smaller diameter than the first transmission gear 103 is provided at the center of the transmission shaft 100. A third transmission gear 105 that meshes with the second transmission gear 104 is formed on the outer peripheral side of the right end portion of the output shaft 85. The inner peripheral side of the right end portion of the output shaft 85 is supported by the left end portion of the secondary sheave shaft 62 via a bearing 106. Therefore, the output shaft 85 is rotatably supported by the secondary sheave shaft 62 via the bearing 106 and is arranged coaxially (on a straight line) with the secondary sheave shaft 62. Further, the center portion of the output shaft 85 is rotatably supported by the left end portion of the second case block 35 b via the bearing 107.

  With such a configuration, the clutch boss 77 and the output shaft 85 are connected via the gear 80, the first transmission gear 103, the transmission shaft 100, the second transmission gear 104, and the third transmission gear 105. Therefore, the output shaft 85 rotates according to the rotation of the clutch boss 77.

  The left end portion of the output shaft 85 passes through the first case block 35 a and protrudes outside the crankcase 35. A drive sprocket 108 is fixed to the left end portion of the output shaft 85. A chain 109 that transmits the driving force of the output shaft 85 to the rear wheel 26 is wound around the drive sprocket 108. The mechanism for transmitting the driving force of the output shaft 85 to the rear wheel 26 is not limited to the chain 109, and other members such as a transmission belt, a gear mechanism formed by combining a plurality of gears, and a drive shaft may be used. Good.

  In the present invention, the “power transmission mechanism” refers to a power transmission mechanism between the clutch housing 78 of the centrifugal clutch 41 and the rear wheel 26, and the motorcycle shown in FIGS. 10, a member downstream of the clutch housing 78 and upstream of the rear wheel 26, that is, a clutch boss 77, a gear 80, a first transmission gear 103, a transmission shaft 100, a second transmission gear 104, A mechanism comprising the third transmission gear 105, the output shaft 85, the drive sprocket 108, and the chain 109. In the present embodiment, the motorcycle 10 is configured to apply a frictional force to the gear 80 among the constituent members of the power transmission mechanism.

  In the wet type clutch, the clutch plate 79 and the friction plate 82 are stuck to each other by the lubricating oil, so that the driving force is applied to the gear 80 via the clutch boss 77 even though the clutch is in the off state. May be transmitted. The driving force transmitted to the gear 80 is relatively small. In general, the stationary motorcycle 10 does not start due to the driving force. However, as shown in FIG. 1, if idling is performed when the main stand 115 is set and the vehicle body of the motorcycle 10 is kept floating from the road surface R, the driving force applied to the gear 80 is reduced. The rear wheel 26 may rotate due to transmission. Note that idling refers to a state in which the engine 29 is driven and the accelerator grip 8 is fully closed.

  The magnitude of the driving force transmitted to the gear 80 due to sticking between the clutch plate 79 and the friction plate 82 can be investigated and recognized in advance. Therefore, it is also possible to apply a braking force to the rear wheel 26 when a driving force smaller than the threshold value is applied to the gear 80 by setting a value slightly larger than this value as a threshold value. Further, as for the braking force applied to the rear wheel 26, if the driving force applied to the rear wheel 26 when the rear wheel 26 is accompanied is investigated and recognized in advance, the accompanying force is generated. A braking force capable of reliably stopping the rotation of the rear wheel 26 can be obtained. Based on this, the specifications of the helical gear 80b, the first transmission gear 103, the disc spring 140, and the like are determined. Is possible.

  In addition, the motorcycle 10 can obtain not only the effect of preventing the rear wheel 26 from being rotated, but also the following effects. First, as the driving force applied to the gear 80 downstream of the centrifugal clutch 41 becomes smaller, a larger braking force can be obtained. Therefore, when the driving force increases as in acceleration, it does not interfere with acceleration. While a small braking force can be achieved, when the driving force becomes small as in deceleration, a strong braking force can be applied by applying a large braking force. Further, when the driving force applied to the gear 80 becomes a predetermined value or more, the frictional force between the gear 80 and the washer 143 can be reduced to zero, so that the braking force can be reduced to zero. The applied braking force can be made zero, and the engine brake can be applied only when the engine is idling.

  As described above, according to the present embodiment, the braking force is applied to the rear wheel 26 when the driving force applied to the gear 80 becomes a predetermined value or less. The driving force applied to the gear 80 is configured to increase as the driving force decreases. Further, when the driving force applied to the gear 80 becomes equal to or less than a predetermined value, it is larger than a size necessary for stopping the rotation of the rear wheel 26. It is comprised so that the braking force of may be given. Therefore, even when idling with the main stand 115 set, even when the driving force is applied to the gear 80 due to sticking between the clutch plate 79 and the friction plate 82 or the like, It is possible to prevent the ring 26 from rotating. Further, the braking force applied during acceleration can be reduced or reduced to 0, while strong engine braking can be applied during deceleration.

  Further, according to the present embodiment, the friction mechanism including the gear 80, the disc spring 140, the washer 141, the thrust bearing 143, and the washer 143 is provided inside the crankcase 35 and is covered from the outside. Therefore, the friction mechanism can be protected. In addition, since the friction mechanism is housed in the crankcase 35, it is possible to prevent the motorcycle 10 from being enlarged due to the addition of the friction mechanism.

  Further, since the centrifugal clutch 41 is a wet clutch, originally, the clutch plate 79 and the friction plate 82 are stuck to each other by the lubricating oil, so that a driving force is applied to the gear 80 and the rear wheel. There is a risk that 26 will be accompanied. However, according to the present embodiment, since the friction mechanism that applies the braking force to the gear 80 in response to the driving force applied to the gear 80 is provided, the driving force is applied to the gear 80. Even if it exists, it becomes possible to prevent the rear wheel 26 from rotating.

  Further, according to the present embodiment, since the centrifugal clutch 41 is a multi-plate clutch, the area of the portion where the clutch plate 79 and the friction plate 82 face each other increases, and thus the clutch plate 79. And the friction plate 82 are likely to stick to each other. However, since a friction mechanism that applies a braking force to the gear 80 in response to the driving force applied to the gear 80 is provided, even if the driving force is applied to the gear 80, the rear wheel 26. Can be prevented from rotating.

  In this embodiment, the disc spring 140 is used as the “elastic body”, but the disc spring is not limited to this disc spring, and other types of springs may be used, and an elastic body other than the spring may be used. Also good.

Second Embodiment
In the second embodiment described below, a mechanism for generating a frictional force and applying a braking force to the rear wheel 26 is different from that in the first embodiment described above. A braking force is applied to the wheel 26. As shown in FIG. 8, in the second embodiment, a ring-shaped transmission shaft interlocking member 150 is provided in the middle of the left side portion of the transmission shaft 100. This variable shaft interlocking member 150 is fitted and fixed to the transmission shaft 100 and rotates integrally with the transmission shaft 100. In FIG. 8, the same members and devices as those of the motorcycle 10 shown in the first embodiment are denoted by the same reference numerals.

  A weight 151 is attached to the left side surface of the transmission shaft interlocking member 150 so as to be slidable in the radial direction. The weight 151 is urged toward the center of the transmission shaft interlocking member 150 by a spring (not shown). Although not shown, the transmission shaft interlocking member 150 is formed with a stop portion that stops the weight 151 so as not to be detached when the weight 151 slides to the peripheral edge of the side surface of the transmission shaft interlocking member 150. Yes. A cylindrical friction body 152 is fixed to the first case block 35a on the left side of the transmission shaft interlocking member 150. The transmission shaft 100 is disposed inside the friction body 152. Further, the weight 151 is disposed on the outer side in the radial direction of the friction body 152.

  In a state where no driving force is applied to the transmission shaft 100, the weight 151 presses the outer peripheral surface of the friction body 101 by the biasing force of the spring, and the friction between the weight 151 and the friction body 152 occurs. Force (static friction force) is working. Here, when a driving force is applied to the gear 80, the driving force is transmitted to the transmission shaft 100 via the gear 80 and the first transmission gear 103. That is, a driving force is applied to the transmission shaft 100. At this time, a centrifugal force is generated by the rotation of the transmission shaft 100, and the centrifugal force acts on the weight 151 outward in the radial direction of the transmission shaft interlocking member 150. This centrifugal force is a force in the direction opposite to the direction of the biasing force of the spring (the center direction of the transmission shaft interlocking member 150). Therefore, when the centrifugal force is smaller than the biasing force of the spring, the force with which the weight 151 presses the friction body 152 is weakened, and the friction force between the weight 151 and the friction body 152 is weakened. On the other hand, when a large driving force is applied to the transmission shaft 100 and a centrifugal force larger than the biasing force of the spring acts on the weight 151, the weight 151 is separated from the friction body 152. As a result, the force with which the weight 151 presses the friction body 152 becomes zero, and the friction force between the weight 151 and the friction body 152 also becomes zero. In FIG. 8, the front side (upper side in FIG. 8) of the weight 151 shows a state in which the weight 151 and the friction body 152 are separated from each other and the frictional force is 0, and the rear side (FIG. 8). The lower part in FIG. 2 shows a state in which the weight 151 presses the friction body 152.

  The frictional force generated between the weight 151 and the friction body 152 becomes a braking force against the rotational driving force of the transmission shaft 100, and as a result, becomes a braking force against the rear wheel 26 (see FIG. 1). Therefore, if the driving force applied to the gear 80 is small, the braking force applied to the rear wheel 26 is increased. Conversely, if the driving force applied to the gear 80 is large, the braking force applied to the rear wheel 26 is decreased. Further, when a centrifugal force larger than the biasing force of the spring acts on the weight 151, no friction force is generated between the weight 151 and the friction body 152. That is, the driving force applied to the transmission shaft 100 when a centrifugal force having the same magnitude as the biasing force of the spring is applied to the weight 151, and a driving force smaller than the threshold is applied to the transmission shaft 100. Only when the braking force is applied, the braking force for the rear wheel 26 is generated.

  As described above, according to the present embodiment, when the driving force applied to the transmission shaft 100 via the gear 80 becomes a predetermined value or less, the centrifugal force generated in the weight 151 causes the weight 151 to interlock with the variable axis. The force is smaller than the urging force of the spring urging in the center direction of the member 150. When the weight 151 presses the friction body 152, the friction force is applied to the transmission shaft 100, and the braking force is applied to the rear wheel 26. Is configured to give. Therefore, even when the driving force is applied to the gear 80 due to sticking between the clutch plate 79 and the friction plate 82 during idling with the main stand 115 set, the rear wheel It is possible to prevent 26 from rotating. Further, the braking force applied during acceleration can be reduced or reduced to 0, while strong engine braking can be applied during deceleration.

<Third Embodiment>
In a third embodiment described below, braking force is applied to the rear wheel 26 in conjunction with the setting of the main stand 115. That is, the motorcycle according to the third embodiment includes a friction mechanism that applies a braking force to the rear wheel 26 in conjunction with the main stand 115.

  FIG. 9 is a right side view showing the engine unit 28 and the main stand 115. In FIG. 9, the same members and apparatuses as those provided in the motorcycle 10 shown in the first embodiment are denoted by the same reference numerals. FIG. 9 shows a state in which a part of the engine unit 28 is cut away. The motorcycle according to the third embodiment includes a stand interlocking member 163 that applies a frictional force to the clutch boss 77 in conjunction with the setting of the main stand 115.

  The stand interlocking member 163 is connected to the main stand 115 via the first connecting member 160, the connecting rod 161, and the second connecting member 162. A pivot shaft 117 is fixed to one end of the first connecting member 160, and the first connecting member 160 is formed to rotate with the main stand 115 via the pivot shaft 117. The other end of the first connecting member 160 is rotatably connected to the rear end of the connecting rod 161. A second connecting member 162 is rotatably connected to the front end portion of the connecting rod 161. The first connecting member 160, the connecting rod 161, and the second connecting member 162 constitute the “interlocking portion” as used in the present invention. The end of the second connecting member 162 opposite to the portion to which the connecting rod 161 is connected (the lower end of FIG. 9) is a semi-cylindrical shape protruding to the right (front side in FIG. 9). The protrusion 162a is formed, and the protrusion 162a is in contact with the stand interlocking member 163.

  As shown in FIG. 11, the stand interlocking member 163 includes an abutting portion 163a formed at a rear side (left side in the drawing) end portion. As described above, the protrusion 162a (see FIG. 9) formed on the second connecting member 162 contacts the contact portion 163. Further, the stand interlocking member 163 has a friction portion 163b formed so as to protrude to the right side (the front side in the figure). The friction portion 163b is formed in a curved piece shape having the same curvature as that of the clutch boss 77 (see FIG. 9). In the present embodiment, the friction portion 163 b presses the clutch boss 77 to generate a frictional force and apply a braking force to the rear wheel 26. The stand interlocking member 163 is formed with a mounting hole 163e for attaching a spring 168 (see FIG. 9) described later. Furthermore, a long hole-like boss hole 163c and a circular hole-like boss hole 163d are formed on the rear side and the front side of the stand interlocking member 163, respectively.

  As shown in FIG. 12, a boss 170 and a bolt 166 are inserted through the boss hole 163c. Since the boss hole 163c is a long hole, the boss 170 is slidable within the boss hole 163c. A rear portion of the stand interlocking member 163 is fixed to the crankcase 35 by a boss 170, a bolt 166, a washer 172, a lock nut 164, and the like. As shown in FIG. 9, a bolt 167, a boss (not shown), and the like are similarly inserted through the front boss hole 163d. A front side portion of the stand interlocking member 163 is rotatably attached to the crankcase 35 by these bolts 167, lock nuts 165, and the like. Further, one end of a tension spring 168 is attached to the mounting hole 163e (see FIG. 11) formed in the stand interlocking member 163, and the other end of the tension spring 168 is fixed to the crankcase 35. It is fixed to the screw 169. Thereby, the stand interlocking member 163 is always urged counterclockwise around the bolt 167.

  Hereinafter, the operation of the friction mechanism according to the third embodiment will be described. FIG. 9 shows a state where the main stand 115 is not set. The stand interlocking member 163 is biased toward the screw 169 side by the biasing force of the tension spring 168. In this state, the curved surface portion of the peripheral surface of the protrusion 162a of the second connecting member 162 is linked to the stand. It is in contact with the contact portion 163a of the member 163. As a result, counterclockwise rotation of the stand interlocking member 163 is restricted, and a slight gap is formed between the friction portion 163 b of the stand interlocking member 163 and the clutch boss 77. That is, the friction part 163b and the clutch boss 77 are not in contact.

  On the other hand, when the main stand 115 is set and the vehicle body of the motorcycle 10 is held with the rear wheel 26 (see FIG. 1) floating from the road surface R, the operation described below is performed. That is, as shown in FIG. 10, when the main stand 115 rotates around the pivot shaft 117 (the counterclockwise direction shown in the drawing), the first stand is connected via the first connecting member 160 and the connecting rod 161. Two connecting members 162 interlock with the main stand 115. As a result, the protrusion 162a of the second connecting member 162 rotates about 90 ° counterclockwise about the center thereof. Then, the contact portion 163a and the planar portion of the peripheral surface of the protrusion 162a face each other, and the restriction on the rotation of the stand interlocking member 163 is released. As a result, the stand interlocking member 163 receiving the urging force of the tension spring 168 rotates counterclockwise, and the friction portion 163b and the clutch boss 77 come into contact with each other. Even after the friction portion 163b and the clutch boss 77 abut, the stand interlocking member 163 is biased by the tension spring 168. Therefore, the clutch boss 77 is pressed by the friction portion 163b (see also FIG. 12). As a result, a frictional force is applied to the clutch boss 77, and as a result, a braking force is applied to the rear wheel 26.

  As described above, according to the third embodiment, the substantially semi-cylindrical protrusion 162a rotates in conjunction with the setting operation of the main stand 115, and accordingly, is biased by the tension spring 168. The stand interlocking member 163 moves and presses the clutch boss 77. Therefore, it is possible to apply a braking force to the rear wheel 26 only when the main stand 115 is set and the rear wheel 26 is floating. In general, the driving force applied to the clutch boss 77 due to the sticking between the clutch plate 79 and the friction plate 82 is not so large. Therefore, when the main stand 115 is not set, that is, when the rear wheel 26 is in contact with the road surface, the vehicle body does not move forward by the driving force. Therefore, as in this embodiment, if the braking force can be applied to the rear wheel 26 only when the main stand 115 is set and the rear wheel 26 is floating, the rear wheel 26 is sufficiently prevented from being rotated. It becomes possible to do. In the present embodiment, the braking force is not applied to the rear wheel 26 during traveling when the main stand 115 is not set. Therefore, it is possible to prevent the acceleration characteristics and the deceleration characteristics from being deteriorated during traveling.

  In the present invention, various mechanisms other than the mechanism of the third embodiment described above can be adopted as a mechanism for applying a braking force to the rear wheel when the main stand is set. For example, a sensor that detects that the main stand is set may be provided, and a mechanism that applies a frictional force to the power transmission mechanism based on the detection result of the sensor may be employed.

  Further, the first embodiment described above is configured to apply a frictional force to the gear 80, the second embodiment is configured to apply a frictional force to the transmission shaft 100, and the third embodiment is The clutch boss 77 is configured to give a frictional force. However, in the present invention, which component member in the power transmission mechanism is given a frictional force is not limited. For example, in each of the above-described embodiments, the first transmission gear 103, the second transmission gear 104, A frictional force may be applied to the third transmission gear 105, the output shaft 85, the drive sprocket 108, or the chain 109. Moreover, it is good also as giving a frictional force with respect to two or more structural members of the structural members of a power transmission mechanism.

  In the third embodiment, the timing when the friction mechanism generates the frictional force is when the main stand 115 is raised. However, the timing at which the friction mechanism generates the frictional force can be set as appropriate. The friction mechanism may generate a frictional force during idling. For example, a detection device that directly or indirectly detects the opening degree (grip position) of the accelerator grip 8 may be provided, and a frictional force may be generated when the accelerator grip 8 is fully closed. Further, the friction mechanism may generate a frictional force when the motorcycle 10 stops traveling (when not traveling). For example, the vehicle speed may be detected by a vehicle speed sensor or the like, and the frictional force may be generated when the vehicle speed becomes zero.

  In the embodiment, the case where the driving wheel is the rear wheel 26 of the motorcycle 10 has been described. However, in the present invention, the driving wheel of the saddle riding type vehicle is not limited to the rear wheel, and may be a front wheel. In the embodiments, the case where the straddle-type vehicle of the present invention is applied to a motorcycle has been described. However, the straddle-type vehicle of the present invention is not limited to a motorcycle, for example, a four-wheel buggy or the like. It may be.

  As described above, the present invention is useful for straddle-type vehicles such as motorcycles.

1 is a right side view of a motorcycle according to a first embodiment. It is a top view which shows the positional relationship of a vehicle body frame, a leg shield, an engine unit, etc. It is a right view of an engine unit. It is a left view of an engine unit. It is sectional drawing which shows the attachment state of an engine unit. It is sectional drawing which shows the internal structure of an engine unit. It is sectional drawing which shows a part of internal structure of an engine unit. It is sectional drawing which shows a part of internal structure of the engine unit of the motorcycle which concerns on 2nd Embodiment. It is a right view which shows an engine unit and a main stand. It is a right view which shows an engine unit and a main stand. It is a perspective view which shows a stand interlocking member. It is the AO line sectional view of Drawing 10.

Explanation of symbols

10 Motorcycle 11 Body frame 16 Seat 26 Rear wheel (drive wheel)
28 Engine unit 30 V-belt continuously variable transmission 35 Crankcase (casing)
41 Centrifugal clutch 80 Gear 80a Spur gear 80b Helical gear 100 Transmission shaft (Rotating body)
115 Main stand 140 Disc spring (elastic body)
141 Washer 142 Thrust bearing 143 Washer (contact member)
151 Weight (centrifugal weight)
152 Friction body (contact member)
160 1st connection member 161 connection rod 162 2nd connection member 162a Protrusion part 163 Stand interlocking member (friction member)
163b Friction part 168 Spring (elastic body)

Claims (16)

A centrifugal clutch,
Driving wheels,
A power transmission mechanism that transmits driving force to the driving wheels when the centrifugal clutch is in a connected state;
A straddle-type vehicle comprising: a friction mechanism that applies a braking force to the drive wheels by applying a friction force to the power transmission mechanism.   The straddle-type vehicle according to claim 1, wherein the friction mechanism increases the friction force applied to the power transmission mechanism as the driving force applied to the power transmission mechanism decreases.   The straddle-type vehicle according to claim 1, wherein the friction mechanism applies a friction force to the power transmission mechanism when a driving force transmitted to the power transmission mechanism becomes a predetermined value or less.   The straddle-type vehicle according to claim 1, wherein the frictional force that the friction mechanism applies to the power transmission mechanism becomes equal to or greater than a predetermined value when a driving force transmitted to the power transmission mechanism becomes equal to or less than a predetermined value. An accelerator operator with adjustable opening is provided.
The straddle-type vehicle according to claim 1, wherein the friction mechanism generates the frictional force during idling when the accelerator operation element is fully closed.   The straddle-type vehicle according to claim 1, wherein the friction mechanism generates the frictional force when the vehicle is not traveling. A casing that houses the power transmission mechanism;
The straddle-type vehicle according to claim 1, wherein the friction mechanism is provided inside the casing. The power transmission mechanism includes a helical gear,
The friction mechanism includes an elastic body that generates a biasing force that opposes a thrust force generated in the helical gear, and a thrust force generated when a driving force is applied to the helical gear is The straddle-type vehicle according to any one of claims 2 to 6, wherein a frictional force is generated using the biasing force when the biasing force is smaller than a body biasing force. The power transmission mechanism includes a helical gear that is movable in the axial direction,
The friction mechanism includes an elastic body that urges the helical gear from one end side toward the other end side against a thrust force generated in the helical gear, and the other end side of the helical gear. A contact member that presses the other end of the helical gear to generate a frictional force when the helical gear moves to the other end side, and
The helical gear presses the contact member to generate a frictional force when the thrust force is smaller than the urging force of the elastic body, while the thrust force is larger than the urging force of the elastic body. The saddle riding type vehicle according to any one of claims 2 to 6, wherein the saddle type vehicle is separated from the contact member. The power transmission mechanism includes a rotating body that rotates together with the drive wheel,
The straddle-type vehicle according to any one of claims 2 to 6, wherein the friction mechanism generates a frictional force when a centrifugal force generated in the rotating body becomes a predetermined value or less. The power transmission mechanism includes a rotating body that rotates together with the drive wheel,
The friction mechanism rotates together with the rotating body, and a centrifugal weight that is movable in the radial direction of the rotating body, and generates a frictional force by pressing the centrifugal weight when the centrifugal weight moves inward in the radial direction, The straddle-type vehicle according to any one of claims 2 to 6, further comprising a contact member that moves away from the centrifugal weight when the centrifugal weight moves radially outward. A main stand for holding the vehicle body in a state where the driving wheel is floating;
The straddle-type vehicle according to claim 1, wherein the friction mechanism applies a friction force to the power transmission mechanism when the main stand is set. The friction mechanism is
A friction member that generates frictional force by pressing the power transmission mechanism;
An elastic body that biases the friction member so that the friction member presses the power transmission mechanism;
An interlocking portion for restricting the friction member so as to be separated from the power transmission mechanism when the main stand is not set, and for releasing the restriction of the friction member in conjunction with the setting operation of the main stand; The straddle-type vehicle according to claim 10 provided.   The straddle-type vehicle according to claim 1, wherein the centrifugal clutch is a wet clutch.   The straddle-type vehicle according to claim 1, wherein the centrifugal clutch is a multi-plate clutch. Engine,
The straddle-type vehicle according to claim 1, further comprising: a belt-type continuously variable transmission provided between the centrifugal clutch and the engine.