JP2019173960A - Speed change gear - Google Patents

Abstract

To provide a speed change gear capable of smoothly shifting a shift fork even when the shift fork is temporarily caught by a shift fork shaft.SOLUTION: In a speed change gear 10, an end part 31t of a shift fork shaft 31 is axially slidably engaged with an engagement part 28 provided in a crank case 21, a gap part S is provided between a shaft end face 31e and the bottom face 28b of the engagement part 28, and axial widths W5 and W6 of the gap part S are shorter than moving distances d4 and d5 in which a shift fork 51 moves in an axial direction during gear shifting. The shift fork shaft 31 is provided with position regulation parts 61 and 62 so as to be brought into contact with the shift fork 51, and distances W7 and W8 between a fork end surface 51e and position regulation parts 61 and 62 when the shift fork 51 is located at a reference position Np1 are shorter than the moving distances d4 and d5 in which the shift fork 51 moves in the axial direction during gear shifting.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a transmission.

  2. Description of the Related Art Conventionally, transmissions in straddle-type vehicles such as motorcycles are known in which a shift fork for shifting a transmission gear is displaced in the axial direction by rotation of a shift drum. For example, Patent Document 1 discloses a structure in which a shift fork is slidably supported on a shift fork shaft, and both ends of the shift fork shaft are supported by a crankcase.

  In this type of transmission, when the shift fork slides on the shift fork shaft, the shift fork may be tilted and temporarily caught on the shift fork shaft, and an improvement in the shift feeling has been demanded.

Japanese Utility Model Publication No.59-192729

  However, in the transmission of Patent Document 1, the shift fork shaft has an elastic body interposed between the shift fork shaft and one end side in the axial direction, and the other end abuts against a retainer provided on the other end side. Since it is held so that it cannot move in the axial direction, if the shift fork is tilted and temporarily caught on the shift fork shaft, the shift fork cannot move smoothly in the axial direction, and the speed change operation There was a problem that the smoothness of the hindered. Moreover, since an elastic body is interposed between the shift fork shaft and the cran case, there is a problem that the number of parts increases.

  The present invention provides a transmission that can move a shift fork smoothly even when the shift fork is temporarily caught on a shift fork shaft.

The present invention includes a main shaft connected to a drive source so that power can be transmitted,
A countershaft arranged in parallel with the main shaft and connected to drive wheels so as to be able to transmit power;
A fixed gear that is non-slidable on the main shaft and has first engagement means;
A movable gear having second engagement means which is slidably disposed on the main shaft and engages with the first engagement means;
A shift drum that rotates in response to a speed change operation and has a lead groove on the outer peripheral surface;
A shift fork shaft supported by the crankcase;
A shift fork that is axially slidably supported by the shift fork shaft, has one end engaged with the lead groove, and the other end connected to the movable gear.
A shift device in which the shift fork slides the movable gear by the rotation of the shift drum, and the gear position is switched by engaging or disengaging the first engagement means and the second engagement means. There,
The end of the shift fork shaft is slidably fitted in an axial direction with a fitting portion provided in the crankcase,
A gap is provided between the shaft end surface of the shift fork shaft and the bottom surface of the fitting portion,
The axial width of the gap portion is configured to be shorter than the moving distance in which the shift fork moves in the axial direction by the lead groove when shifting.
The shift fork shaft is provided with a position restricting portion so as to be in contact with a fork end surface of the shift fork,
When the shift fork is positioned at the reference position, the distance between the fork end surface and the position restricting portion is the lead groove at the time of shifting. Thus, the shift fork is configured to be shorter than the moving distance in which the shift fork moves in the axial direction.

According to the present invention, the end portion of the shift fork shaft is fitted to the fitting portion provided in the crankcase so as to be slidable in the axial direction, and between the shaft end surface of the shift fork shaft and the bottom surface of the fitting portion. Since there is a gap, even if the shift fork is tilted with respect to the shift fork shaft and temporarily caught, the shift fork moves with the shift fork shaft and the shift fork shaft slides. Smooth movement is possible.
Further, since the gap portion is configured to be shorter than the moving distance in which the shift fork moves in the axial direction due to the lead groove at the time of shifting, the shift fork shaft is always regulated by the bottom surface of the gap portion. After the shift fork shaft slide is regulated, the shift fork moves the shift fork shaft due to inertial force, so even if the shift fork is temporarily caught on the shift fork shaft, the shift fork moves smoothly. Is possible.

FIG. 3 is a cross-sectional view taken along a cutting line passing through the rotation axis of the shift drum from the main shaft via the first shift fork shaft in the engine including the transmission according to the first embodiment of the present invention. In the engine provided with the transmission according to the first embodiment of the present invention, it is a cross-sectional view cut along a cutting line passing through the rotation axis of the shift drum from the counter shaft via the second shift fork shaft. It is a principal part expanded sectional view which shows the position of the 1st shift fork and the 1st shift fork shaft in a neutral state. It is a principal part expanded sectional view which shows the position of the 2nd and 3rd shift fork in a neutral state, and a 2nd shift fork shaft. It is a principal part expanded sectional view which shows the position of the 2nd and 3rd shift fork in a 1st speed state, and a 2nd shift fork shaft. It is a principal part expanded sectional view which shows the position of the 2nd and 3rd shift fork in a 2nd speed state, and a 2nd shift fork shaft. It is a principal part expanded sectional view which shows the position of the 2nd and 3rd shift fork in a 3rd speed state, and a 2nd shift fork shaft. It is a principal part expanded sectional view which shows the position of the 1st shift fork and the 1st shift fork shaft at the time of gear shifting. It is a principal part expanded sectional view which shows the shift fork shaft and position control part in 2nd Embodiment of this invention.

  Hereinafter, each embodiment of the transmission of the present invention will be described with reference to the accompanying drawings.

[First Embodiment]
First, a transmission according to a first embodiment of the present invention will be described with reference to FIGS.
In the drawings, the left side is indicated by L and the right side is indicated by R, and in the description, the left and right are described with reference to the drawings.

<Transmission>
As shown in FIGS. 1 and 2, the transmission 10 according to the present embodiment is incorporated in a crankcase 21 of a motorcycle engine, and holds a drive gear train 41, the drive gear train 41, and one end. A main shaft 11 (see FIG. 1) to which power of a crankshaft (not shown) is transmitted via a clutch device attached to the side (right side in FIG. 1) and a driven gear arranged to be able to mesh with the drive gear train 41 It has a gear train 42 and a counter shaft 12 (see FIG. 2) that holds the driven gear train 42 and is connected to the drive wheels so as to be able to transmit power, and is arranged in parallel with the main shaft 11.

  Further, the transmission 10 includes a shift drum 45 disposed in parallel with the main shaft 11 and the counter shaft 12 in the vicinity of a portion where the driving gear train 41 and the driven gear train 42 are engaged, and a shift drum in the vicinity of the shift drum 45. 45, a first shift fork shaft 31 and a second shift fork shaft 32 arranged in parallel with the first shift fork shaft 31, and a first shift fork 51 is coupled to the first shift fork shaft 31 so as to be movable in the axial direction. The second shift fork 52 and the third shift fork 53 are both connected to the second shift fork shaft 32 so as to be movable in the axial direction.

  In the shift drum 45, three lead grooves 45g corresponding to the first shift fork 51, the second shift fork 52, and the third shift fork 53 are provided on the outer peripheral surface of the drum along the circumferential direction. In each lead groove 45g, guide pins 51p, 52p, and 53p projecting from bases 51b, 52b, and 53b of the first shift fork 51, the second shift fork 52, and the third shift fork 53 are fitted. Accordingly, the rotation of the shift drum 45 controls the movement of the first shift fork 51, the second shift fork 52, and the third shift fork 53 in the axial direction by guiding each lead groove 45g. The shift drum 45 is rotated via a drum drive mechanism 47 connected to a change spindle 46 (see FIG. 1) that is rotated by a speed change operation, for example.

  As shown in FIG. 1, the drive gear train 41 is in the axial direction from one end side (right side in the figure) of the main shaft 11, a first speed drive gear 41 a, a fourth speed drive gear 41 d, a third speed drive gear 41 c, and a fifth speed drive. The gear 41e and the second-speed drive gear 41b are arranged in this order.

  Here, the first speed drive gear 41 a and the second speed drive gear 41 b are not movable in the axial direction with respect to the main shaft 11, and rotate synchronously with the main shaft 11. The third speed drive gear 41 c is movable in the axial direction with respect to the main shaft 11 and rotates synchronously with the main shaft 11. The fourth speed drive gear 41d and the fifth speed drive gear 41e cannot move in the axial direction with respect to the main shaft 11, and can rotate relative to the main shaft 11.

  An annular groove 41cg in the gear circumferential direction is formed in the third speed drive gear 41c, and a fork portion 51f of the first shift fork 51 is engaged in the annular groove 41cg. Accordingly, as the first shift fork 51 moves in the axial direction (left-right direction), the third-speed drive gear 41c also moves in the axial direction.

  When the 4-speed drive gear 41d and the 5-speed drive gear 41e arranged on the left and right sides of the 3-speed drive gear 41c are engaged with the 3-speed drive gear 41c by the movement of the 3-speed drive gear 41c in the axial direction, the main shaft 11 Rotate synchronously.

  Specifically, first engaging means 41dp and 41ed for engaging with the third speed drive gear 41c are respectively provided on the side facing the third speed drive gear 41c in the fourth speed drive gear 41d and the fifth speed drive gear 41e. Is provided. On the other hand, the third-speed drive gear 41c is provided with second engagement means 41cp and 41cd that can engage with the first engagement means 41dp and 41ed, respectively.

  Therefore, the 4th speed drive gear 41d and the 5th speed drive gear 41e can rotate relative to the main shaft 11, but the first engagement means 41dp and the second engagement are caused by the movement of the 3rd speed drive gear 41c in the axial direction. When the means 41cp is engaged, the 4-speed drive gear 41d rotates synchronously with the main shaft 11, and when the first engagement means 41ed and the second engagement means 41cd are engaged, the 5-speed drive gear 41e is synchronized with the main shaft 11. Rotate.

  As shown in FIG. 2, the driven gear train 42 includes a first speed driven gear 42a, a fourth speed driven gear 42d, a third speed driven gear 42c, and a fifth speed driven from the one end side (right side in the figure) of the counter shaft 12 in the axial direction. The gear 42e and the second-speed driven gear 42b are arranged in mesh with the drive gear train 41 in this order.

  Here, the 4-speed driven gear 42d and the 5-speed driven gear 42e are movable in the axial direction with respect to the counter shaft 12, and rotate synchronously with the counter shaft 12. The first-speed driven gear 42a, the third-speed driven gear 42c, and the second-speed driven gear 42b cannot move in the axial direction with respect to the counter shaft 12, and can rotate relative to the counter shaft 12.

  An annular groove 42dg in the gear circumferential direction is formed in the fourth speed driven gear 42d, and the fork portion 52f of the second shift fork 52 is engaged in the annular groove 42dg. Accordingly, when the second shift fork 52 moves in the axial direction (left-right direction), the fourth-speed driven gear 42d also moves in the axial direction.

  When the first-speed driven gear 42a and the third-speed driven gear 42c arranged on the left and right sides of the fourth-speed driven gear 42e are engaged with the fourth-speed driven gear 42d by the movement of the fourth-speed driven gear 42d in the axial direction, the countershaft 12 Rotate synchronously.

  Specifically, the first-speed driven gear 42a and the third-speed driven gear 42c have first engaging means 42ad and 42cd for engaging with the fourth-speed driven gear 42d on the side facing the fourth-speed driven gear 42d, respectively. Is provided. On the other hand, the fourth-speed driven gear 42d is provided with second engaging means 42dp and 42dd that can be engaged with the first engaging means 42ad and 42cd, respectively.

  Accordingly, the first-speed driven gear 42a and the third-speed driven gear 42c can be rotated relative to the counter shaft 12, but the first-engagement means 42ad and the second-engagement are moved by the movement of the fourth-speed driven gear 42d in the axial direction. When the means 42dd is engaged, the first speed driven gear 42a rotates synchronously with the counter shaft 12, and when the first engagement means 42cd and the second engagement means 42dd are engaged, the third speed driven gear 42c is synchronized with the counter shaft 12. Rotate.

  An annular groove 42eg in the gear circumferential direction is formed in the fifth speed driven gear 42e, and a fork portion 53f of the third shift fork 53 is engaged in the annular groove 42eg. Therefore, as the third shift fork 53 moves in the axial direction (left-right direction), the fifth speed driven gear 42e also moves in the axial direction.

  The second-speed driven gear 42b disposed on the left side of the fifth-speed driven gear 42e rotates synchronously with the counter shaft 12 when engaged with the fifth-speed driven gear 42e by the movement of the fifth-speed driven gear 42e in the axial direction.

  Specifically, the second speed driven gear 42b is provided with first engaging means 42bd that engages with the fifth speed driven gear 42e on the side facing the fifth speed driven gear 42e. On the other hand, the fifth-speed driven gear 42e is provided with second engaging means 42ep that can be engaged with the first engaging means 42bd.

  Accordingly, the second-speed driven gear 42b can be rotated relative to the countershaft 12, but when the first engagement means 42bd and the second engagement means 42ep are engaged by the movement of the fifth-speed driven gear 42e in the axial direction. The second speed driven gear 42b rotates in synchronization with the counter shaft 12.

  As shown in FIG. 3, the first shift fork shaft 31 is supported by inserting an end 31 t of the first shift fork shaft 31 into a fitting portion 28 formed in the crankcase 21. The first shift fork 51 is connected to the first shift fork shaft 31 so as to be slidable in the axial direction (left-right direction) so that the base 51b of the first shift fork 51 surrounds the outer peripheral surface of the first shift fork shaft 31. ing.

  Here, the length W1 of the first shift fork shaft 31 is set shorter than the distance W2 between the pair of bottom surfaces 28b facing the fitting portion 28 by a predetermined dimension. Therefore, a gap S is formed between the left and right shaft end surfaces 31e of the first shift fork shaft 31 and the bottom surface 28b of the fitting portion 28 facing the shaft end surface 31e.

  The first shift fork shaft 31 is held so as to be slidable in the axial direction (left and right direction) in the gap S while being supported by the fitting portions 28 on both the left and right sides. Thus, when the first shift fork 51 slides in the axial direction, even if the first shift fork 51 is temporarily caught by being tilted with respect to the first shift fork shaft 31, the first shift fork 51 is attached to the first shift fork shaft 31. The first shift fork shaft 31 can slide in the gap S in the axial direction while being hooked, and the first shift fork 51 can move in the axial direction.

  The axial width W5 of the gap S on one end side (right side in the figure) and the axial width W6 of the gap S on the other end side (left side in the figure) are determined by the lead groove 45g in the first shift fork at the time of a shift described later. The moving distance 51 is shorter than the moving distances d4 and d5 (see FIG. 8).

  Therefore, even if the first shift fork 51 is temporarily caught on the first shift fork shaft 31 when sliding in the axial direction, and the first shift fork shaft 31 slides in the gap S in the axial direction, When the first shift fork shaft 31 slides in the axial widths W5 and W6, the shaft end surface 31e of the first shift fork shaft 31 collides with the bottom surface 28b of the fitting portion 28. Therefore, the first shift fork 51 does not move the moving distances d4 and d5 while the first shift fork shaft 31 is caught. When the shaft end surface 31e of the first shift fork shaft 31 collides with the bottom surface 28b of the fitting portion 28, the first shift fork 51 slides on the first shift fork shaft 31 by the inertial force, and finally the moving distance Move d4 and d5.

  Thus, even when the first shift fork 51 is temporarily caught on the first shift fork shaft 31 when sliding in the axial direction, the first shift fork 51 can be smoothly moved.

  Here, the axial width W3 of the fitting portion 28 on one end side (right side in the drawing) and the axial width W4 of the fitting portion 28 on the other end side (left side in the drawing) are both gap portions S on one end side. The axial width W5 is longer than the sum of the axial width W6 of the gap S on the other end side. Accordingly, the first shift fork shaft 31 is supported so as to be slidable in the axial direction without dropping from the fitting portion 28.

  The axial width W5 of the gap S on one end side (the right side in the figure) is the first engagement means 41ed provided on the fifth speed drive gear 41e and the second engagement provided on the third speed drive gear 41c. The moving distance r2 (see FIG. 1) of the first shift fork 51 required for the means 41cd to change from the engaged state to the disengaged state is configured.

  Similarly, the axial width W6 of the clearance S on the other end side (left side in the figure) is the first engaging means 41dp provided on the fourth speed drive gear 41d and the second width provided on the third speed drive gear 41c. The engaging means 41cp is configured to be longer than the moving distance r1 (see FIG. 1) of the first shift fork 51 necessary for the engaged state to be changed from the engaged state to the disengaged state.

  Therefore, the third-speed drive gear 41c is moved from the engaged state to the non-engaged state with the fifth-speed drive gear 41e or the fourth-speed drive gear 41d by movement in the axial direction, that is, the first engagement means 41ed, 41dp While the second engagement means 41cd, 41cp moves the moving distances r2, r1 from the engaged state to the disengaged state, the first shift fork shaft 31 always rotates along with the first shift fork 51. It becomes possible to slide in the direction.

  As a result, the first shift fork 51 is most easily caught by the first shift fork shaft 31 until the first engagement means 41ed, 41dp and the second engagement means 41cd, 41cp are changed from the engaged state to the disengaged state. The first shift fork 51 can be moved smoothly when moving the moving distances r2 and r1.

  The first shift fork shaft 31 is provided with two position restricting portions 61 and 62 at positions facing the fork end surfaces 51e on both the left and right sides of the base portion 51b of the first shift fork 51. The position restricting portions 61 and 62 are formed by circlips that form grooves along the axial circumferential direction on the outer peripheral surface of the first shift fork shaft 31 and fit into the grooves.

  The position restricting portions 61 and 62 are arranged as follows.

  Assuming that the position of the first shift fork 51 in the neutral state of the transmission 10 is the reference position Np1, when the first shift fork 51 is located at the reference position Np1, the fork end surface 51e of the first shift fork 51 and the position restricting portion 61 , 62 are set to be shorter than the moving distances d4 and d5 (see FIG. 8) in which the first shift fork 51 moves in the axial direction by the lead groove 45g at the time of shifting.

  Accordingly, even when the first shift fork 51 slides in the axial direction without sliding on the first shift fork shaft 31 when sliding in the axial direction, the position restricting portion 61, When sliding with distances W7 and W8 from 62, the fork end face 51e of the first shift fork 51 comes into contact with the position restricting portions 61 and 62. When the fork end surface 51e of the first shift fork 51 comes into contact with the position restricting portions 61 and 62, the first shift fork 51 moves with the first shift fork shaft 31, and the first shift fork shaft 31 is Slide the gap S in the axial direction. Then, the first shift fork 51 finally moves the moving distances d4 and d5.

  As a result, when the first shift fork 51 moves in the axial direction for the moving distances d4 and d5, the first shift fork shaft 31 slides in the gap portion S in the axial direction. It becomes easy to make the part S secure.

  Further, the movable distances k4 and k5 of the first shift fork 51 in the direction of the position restricting portions 61 and 62 are the distances W7 and W8 between the fork end surface 51e of the first shift fork 51 and the position restricting portions 61 and 62, and 1 shift fork 51 is shorter than the sum of axial widths W5 and W6 of gap S on the moving direction side. That is, k4 <(W7 + W5) and k5 <(W8 + W6) are established. Thereby, even when the first shift fork 51 moves the longest distance, the clearance S on the moving direction side of the first shift fork 51 is always secured.

  Further, even when the first shift fork shaft 31 slides through the gap S by the shifting operation and the gap S in the sliding direction is filled, when the first shift fork 51 moves in the reverse direction by the subsequent shifting operation, The 1 shift fork 51 abuts on the position restricting portions 61 and 62 and moves with the first shift fork shaft 31. Thereby, the 1st shift fork shaft 31 can cancel the state where gap part S was buried. Therefore, even when the gap portion S in the sliding direction of the first shift fork shaft 31 is filled by the speed change operation, the state where the gap portion S is filled can be eliminated by the subsequent speed change operation, and the first shift fork 51 can be smoothly moved. Is possible.

  As shown in FIG. 4, the second shift fork shaft 32 is supported by inserting an end portion 32 t of the second shift fork shaft 32 into a fitting portion 28 formed in the crankcase 21. Then, the second shift fork 52 is disposed on one end side (right side in the drawing) of the second shift fork shaft 32, the third shift fork 53 is disposed on the other end side (left side in the drawing), the base 52b of the second shift fork 52 and the second shift fork shaft 32. The base 53b of the 3 shift fork 53 is slidably connected in the axial direction (left and right direction) so as to surround the outer peripheral surface of the second shift fork shaft 32.

  Here, the length W1 of the second shift fork shaft 32 is set shorter than the distance W2 between the pair of bottom surfaces 28b facing the fitting portion 28 by a predetermined dimension. Therefore, a gap S is formed between the shaft end surface 32e of the second shift fork shaft 32 and the bottom surface 28b of the fitting portion 28 facing the shaft end surface 32e.

  The second shift fork shaft 32 is held so as to be slidable in the axial direction (left-right direction) in the gap S while being supported by the fitting portions 28 on both the left and right sides. Thereby, when the second shift fork 52 slides in the axial direction, even if the second shift fork 52 is inclined and temporarily caught with respect to the second shift fork shaft 32, the second shift fork 52 is attached to the second shift fork shaft 32. The second shift fork shaft 32 can slide in the gap S in the axial direction while being caught, and the second shift fork 52 can move in the axial direction. Similarly, when the third shift fork 53 slides in the axial direction, the third shift fork 53 is attached to the second shift fork shaft 32 even when the third shift fork 53 is temporarily caught by being inclined with respect to the second shift fork shaft 32. The second shift fork shaft 32 can slide in the gap S in the axial direction while being caught, and the third shift fork 53 can move in the axial direction.

  The axial width W5 of the gap portion S on one end side (right side in the figure) and the axial width W6 of the gap portion S on the other end side (left side in the figure) are determined by the second shift fork by a lead groove 45g at the time of shifting described later. 52 and the third shift fork 53 are configured to be shorter than movement distances d1, d2, and d3 (refer to FIGS. 5, 6, and 7 respectively) in which the shaft 52 and the third shift fork 53 move in the axial direction.

  Therefore, even if the second shift fork 52 slides in the axial direction, the second shift fork shaft 32 is temporarily caught in the second shift fork shaft 32, and the second shift fork shaft 32 slides in the gap S in the axial direction. When the second shift fork shaft 32 slides in the axial widths W5 and W6, the shaft end surface 32e of the second shift fork shaft 32 collides with the bottom surface 28b of the fitting portion 28. Therefore, the second shift fork 52 does not move the moving distances d1 and d3 while the second shift fork shaft 32 is caught. When the shaft end surface 32e of the second shift fork shaft 32 collides with the bottom surface 28b of the fitting portion 28, the second shift fork 52 slides on the second shift fork shaft 32 by the inertial force, and finally the moving distance. Move d1 and d3.

  Similarly, even if the third shift fork 53 is temporarily caught on the second shift fork shaft 32 when sliding in the axial direction, and the second shift fork shaft 32 slides in the gap S in the axial direction. When the second shift fork shaft 32 slides in the axial width W6, the shaft end surface 32e of the second shift fork shaft 32 collides with the bottom surface 28b of the fitting portion 28. Therefore, the third shift fork 53 does not move the moving distance d2 while the second shift fork shaft 32 is caught. When the shaft end surface 32e of the second shift fork shaft 32 collides with the bottom surface 28b of the fitting portion 28, the third shift fork 53 slides on the second shift fork shaft 32 by the inertial force, and finally the moving distance Move d2.

  As a result, even if the second shift fork 52 or the third shift fork 53 is temporarily caught on the second shift fork shaft 32 when sliding in the axial direction, the second shift fork 52 and the third shift fork 53 smooth movements are possible.

  Here, the axial width W3 of the fitting portion 28 on one end side (right side in the drawing) and the axial width W4 of the fitting portion 28 on the other end side (left side in the drawing) are both gap portions S on one end side. The axial width W5 is longer than the sum of the axial width W6 of the gap S on the other end side. Thus, the second shift fork shaft 32 is supported so as to be slidable in the axial direction without dropping from the fitting portion 28.

  The axial width W5 of the gap S on one end side (right side in the drawing) is the first engagement means 42cd provided on the third speed driven gear 42c and the second engagement provided on the fourth speed driven gear 42d. The moving distance r4 (see FIG. 2) of the second shift fork 52 required for the means 42dd to change from the engaged state to the disengaged state, and the first engaging means 42bd provided on the second-speed driven gear 42b The second engagement means 42ep provided on the fifth speed driven gear 42e is configured to be longer than the moving distance r5 (see FIG. 2) of the third shift fork 53 required for the engagement state to be disengaged. ing.

  Similarly, the axial width W6 of the clearance S on the other end side (the left side in the figure) is the first engagement means 42ad provided on the first speed driven gear 42a and the second width provided on the fourth speed driven gear 42d. The moving means 42dp is configured to be longer than the moving distance r3 (see FIG. 2) of the second shift fork 52 that is necessary for the engaged state to be disengaged.

  Therefore, the fourth-speed driven gear 42d is moved from the engaged state to the non-engaged state with the third-speed driven gear 42c or the first-speed driven gear 42a by the movement in the axial direction, that is, the first engaging means 42cd, 42ad and While the second engagement means 42dd and 42dp move the moving distances r4 and r3 from the engaged state to the disengaged state, the second shift fork shaft 32 always rotates along with the second shift fork 52. It becomes possible to slide in the direction.

  As a result, the second shift fork 52 is most easily caught by the second shift fork shaft 32 until the first engagement means 42cd, 42ad and the second engagement means 42dd, 42dp change from the engaged state to the disengaged state. The second shift fork 52 can be moved smoothly when moving the moving distances r4 and r3.

  Similarly, while the fifth-speed driven gear 42e is moved from the engaged state to the non-engaged state with the second-speed driven gear 42b by the movement in the axial direction, that is, the first engaging means 42bd and the second engaging means 42ep The second shift fork shaft 32 can always slide in the axial direction along with the third shift fork 53 while moving the moving distance r5 from the engaged state to the disengaged state.

  Thereby, the moving distance r5 until the first engagement means 42bd and the second engagement means 42ep are changed from the engaged state to the disengaged state where the third shift fork 53 is most easily caught by the second shift fork shaft 32 is set. When moving, the third shift fork 53 can be moved smoothly.

  The second shift fork shaft 32 has three position restrictions so as to face the left and right fork end surfaces 52e of the base portion 52b of the second shift fork 52 and the left and right fork end surfaces 53e of the base portion 53b of the third shift fork 53. Portions 63, 64, and 65 are provided. The position restricting portions 63, 64, 65 are formed by circlips that form grooves along the axial circumferential direction on the outer peripheral surface of the second shift fork shaft 32 and fit into the grooves.

  The position restricting parts 63, 64, 65 are arranged as follows.

  Assuming that the position of the second shift fork 52 in which the transmission 10 is in the neutral state is the reference position Np2, when the second shift fork 52 is located at the reference position Np2, the fork end surface 52e of the second shift fork 52 and the position restricting portion 63, The distances W9 and W11 with respect to 64 are set shorter than the movement distances d1 and d3 (see FIGS. 5 and 7) in which the second shift fork 52 moves in the axial direction by the lead groove 45g at the time of shifting.

  Therefore, when the second shift fork 52 slides in the axial direction, even if it slides in the axial direction on the second shift fork shaft 32 without being caught by the second shift fork shaft 32, the position restricting portion 63, When the distances W9 and W11 with respect to 64 are slid, the fork end surface 52e of the second shift fork 52 comes into contact with the position restricting portions 63 and 64. When the fork end surface 52e of the second shift fork 52 comes into contact with the position restricting portions 63 and 64, the second shift fork 52 moves with the second shift fork shaft 32, and the second shift fork shaft 32 is Slide the gap S in the axial direction. Then, the second shift fork 52 finally moves the moving distances d1 and d3.

  Similarly, assuming that the position of the third shift fork 53 in the neutral state of the transmission 10 is the reference position Np3, when the third shift fork 53 is positioned at the reference position Np2, the position restriction with the fork end surface 53e of the third shift fork 53 is performed. The distance W10 to the portion 65 is set to be shorter than the moving distance d2 (see FIG. 6) in which the third shift fork 53 moves in the axial direction by the lead groove 45g during gear shifting.

  Therefore, even if the third shift fork 53 slides in the axial direction without being caught by the second shift fork shaft 32 when the third shift fork 53 slides in the axial direction, When the distance W10 is slid, the fork end surface 53e of the third shift fork 53 comes into contact with the position restricting portion 65. When the fork end surface 53e of the third shift fork 53 comes into contact with the position restricting portion 65, the third shift fork 53 moves with the second shift fork shaft 32, and the second shift fork shaft 32 has a gap portion. Slide S in the axial direction. And the 3rd shift fork 53 finally moves the moving distance d2.

  As a result, when the second shift fork 52 and the third shift fork 53 move in the axial movement distances d1, d3, d2, the second shift fork shaft 32 slides in the gap S in the axial direction. It becomes easy to make the clearance S secure on both sides of the shift fork shaft 32.

  Further, the movable distances k1 and k2 in the direction of the position restricting portions 63 and 64 of the second shift fork 52 are the distances W9 and W11 between the fork end surface 52e of the second shift fork 52 and the position restricting portions 63 and 64, and It is shorter than the sum of the axial widths W5 and W6 of the clearance S on the moving direction side of the two-shift fork 52. That is, k1 <(W9 + W5) and k2 <(W11 + W6) are established. Thereby, even when the second shift fork 52 moves the longest distance, the clearance S on the moving direction side of the second shift fork 52 is always ensured.

  Similarly, the movable distance k3 of the third shift fork 53 in the direction of the position restricting portion 65 is the distance W10 between the fork end surface 53e of the third shift fork 53 and the position restricting portion 65, and the moving direction of the third shift fork 53. It is shorter than the sum with the axial width W6 of the clearance S on the side. That is, k3 <(W10 + W6) is established. Thereby, even when the third shift fork 53 moves the longest distance, the clearance S on the moving direction side of the third shift fork 53 is always ensured.

  Further, even if the second shift fork shaft 32 slides through the gap S by the shifting operation and the gap S in the sliding direction is filled, the second shift fork 52 or the third shift fork 53 is moved in the reverse direction by the subsequent shifting operation. When moving to the second position, the second shift fork 52 or the third shift fork 53 contacts the position restricting portions 63, 64, 65 and moves with the second shift fork shaft 32. Thereby, the 2nd shift fork shaft 32 can eliminate the state where gap part S was buried. Therefore, even when the gap portion S in the sliding direction of the second shift fork shaft 32 is filled by the speed change operation, the state where the gap portion S is filled by the subsequent speed change operation can be eliminated, and the second shift fork 52 and the third shift The fork 53 can be moved smoothly.

<Speed change operation>
Next, the shifting operation will be described.
(Neutral operation)
As shown in FIGS. 3 and 4, when the transmission 10 is neutral, the first shift fork 51, the second shift fork 52, and the third shift fork 53 are at the reference positions Np 1, Np 2, Np 3 in the axial direction. positioned. As a result, the first-speed drive gear 41a, the third-speed drive gear 41c, and the second-speed drive gear 41b that rotate synchronously with the main shaft 11 are all in a relatively rotatable state, the first-speed driven gear 42a, the third-speed driven gear 42c, Since it is meshed with the second speed driven gear 42b, power transmission between the main shaft 11 and the counter shaft 12 is not performed.

(First speed operation)
As shown in FIG. 5, when the transmission 10 is put in the first speed, the clutch device 22 is operated to temporarily turn off the driving force from the crankshaft side and the shift drum 45 is rotated to move the second shift fork 52 to the right. Move the moving distance d1 in the direction. As a result, the 4-speed driven gear 42d (see FIG. 2) moves to the right, and the second engaging means 42dp of the 4-speed driven gear 42d engages with the first engaging means 42ad of the 1-speed driven gear 42a. Accordingly, since the first speed driven gear 42a rotates synchronously with the counter shaft 12, the rotation of the first speed drive gear 41a rotating synchronously with the main shaft 11 is transmitted to the counter shaft 12 via the first speed driven gear 42a.

  At this time, when the second shift fork 52 slides rightward on the second shift fork shaft 32 without being caught by the second shift fork shaft 32 when moving in the right direction, The fork end surface 52e abuts against the position restricting portion 63. Thereafter, the second shift fork 52 moves with the second shift fork shaft 32 and finally moves the moving distance d1, and the shift to the first speed is completed. At that time, the second shift fork shaft 32 slides the gap S in the axial direction by a predetermined distance m1.

  On the other hand, if the second shift fork 52 is temporarily caught on the second shift fork shaft 32 when moving to the right, the second shift fork 52 moves with the second shift fork shaft 32. The second shift fork shaft 32 slides in the clearance S to the right. When the second shift fork shaft 32 slides to the right in the gap S and the hook with the second shift fork 52 is not eliminated, the shaft end surface 32e of the second shift fork shaft 32 is Collides with the bottom surface 28b. When the shaft end surface 32e of the second shift fork shaft 32 collides with the bottom surface 28b of the fitting portion 28, the second shift fork 52 slides on the second shift fork shaft 32 by the inertial force, and finally the moving distance. d1 moves and the shift to the first speed is completed.

(2nd speed operation)
As shown in FIG. 6, when shifting the transmission 10 from the first speed to the second speed, the second shift fork 52 is returned to the reference position Np2, and the third shift fork 53 is moved leftward by the moving distance d2. As a result, the 4-speed driven gear 42d (see FIG. 2) moves leftward, and the engagement of the second engaging means 42dp of the 4-speed driven gear 42d and the first engaging means 42ad of the 1-speed driven gear 42a is released. Then, the fifth speed driven gear 42e (see FIG. 2) moves leftward, and the second engagement means 42ep of the fifth speed driven gear 42e engages with the first engagement means 42bd of the second speed driven gear 42b. Accordingly, since the second speed driven gear 42b rotates synchronously with the counter shaft 12, the rotation of the second speed drive gear 41b rotating synchronously with the main shaft 11 is transmitted to the counter shaft 12 via the second speed driven gear 42b.

  At this time, when the second shift fork 52 and the third shift fork 53 slide leftward on the second shift fork shaft 32 without being hooked on the second shift fork shaft 32, The second shift fork 52 moves to the left, the third shift fork 53 moves to the left, and the fork end surface 53e of the third shift fork 53 contacts the position restricting portion 65. Thereafter, the third shift fork 53 moves with the second shift fork shaft 32, and finally moves the moving distance d2, and the shift to the second speed is completed. At that time, the second shift fork shaft 32 slides the gap S in the axial direction by a predetermined distance m2.

  On the other hand, when the second shift fork 52 is temporarily caught on the second shift fork shaft 32 when moving in the left direction, the second shift fork 52 moves with the second shift fork shaft 32. The second shift fork shaft 32 slides leftward in the gap S. When the second shift fork shaft 32 slides to the left in the gap S and the hook with the second shift fork 52 is not eliminated, the shaft end surface 32e of the second shift fork shaft 32 is Collides with the bottom surface 28b. When the shaft end surface 32e of the second shift fork shaft 32 collides with the bottom surface 28b of the fitting portion 28, the second shift fork 52 slides on the second shift fork shaft 32 by the inertial force, and finally the moving distance. Move d1 and return to the reference position Np1.

  In addition, when the third shift fork 53 is temporarily caught on the second shift fork shaft 32 when the third shift fork 53 slides to the left in the state where the left clearance S is secured, the third shift fork 53 is The second shift fork shaft 32 slides to the left in the gap S. When the second shift fork shaft 32 slides to the left in the gap S and the hook with the third shift fork 53 is not eliminated, the shaft end surface 32e of the second shift fork shaft 32 is Collides with the bottom surface 28b. When the shaft end surface 32e of the second shift fork shaft 32 collides with the bottom surface 28b of the fitting portion 28, the third shift fork 53 slides on the second shift fork shaft 32 by the inertial force, and finally the moving distance d2 moves and the shift to the second speed is completed.

(3-speed operation)
As shown in FIG. 7, when shifting the transmission 10 from the 2nd speed to the 3rd speed, the third shift fork 53 is returned to the reference position Np3, and the second shift fork 52 is moved leftward by the moving distance d3. As a result, the 5-speed driven gear 42e (see FIG. 2) moves to the right, and the engagement of the second engaging means 42ep of the 5-speed driven gear 42e and the first engaging means 42bd of the 2-speed driven gear 42b is released. Then, the 4-speed driven gear 42d (see FIG. 2) moves leftward, and the second engaging means 42dd of the 4-speed driven gear 42d engages with the first engaging means 42cd of the 3-speed driven gear 42c. Therefore, since the 3rd speed driven gear 42c rotates synchronously with the countershaft 12, the rotation of the 3rd speed drive gear 41c rotating synchronously with the main shaft 11 is transmitted to the countershaft 12 via the 3rd speed driven gear 42c.

  At this time, when the second shift fork 52 and the third shift fork 53 slide in the axial direction on the second shift fork shaft 32 without being caught by the second shift fork shaft 32, The third shift fork 53 moves to the right, the second shift fork 52 moves to the left, and the fork end surface 53e of the second shift fork 52 contacts the position restricting portion 64. Thereafter, the second shift fork 52 moves with the second shift fork shaft 32 and finally moves the moving distance d3, and the shift to the third speed is completed. At that time, the second shift fork shaft 32 slides the gap S in the axial direction by a predetermined distance m3.

  On the other hand, when the third shift fork 53 is temporarily caught on the second shift fork shaft 32 when moving in the right direction, the third shift fork 53 moves with the second shift fork shaft 32. The second shift fork shaft 32 slides rightward in the clearance S, moves the moving distance d2, and returns to the reference position Np3. When the second shift fork 52 is temporarily caught on the second shift fork shaft 32 when moving in the left direction, the second shift fork 52 moves with the second shift fork shaft 32. The second shift fork shaft 32 slides leftward in the gap S. When the second shift fork shaft 32 slides to the left in the gap S and the hook with the second shift fork 52 is not eliminated, the shaft end surface 32e of the second shift fork shaft 32 is Collides with the bottom surface 28b. When the shaft end surface 32e of the second shift fork shaft 32 collides with the bottom surface 28b of the fitting portion 28, the second shift fork 52 slides on the second shift fork shaft 32 by the inertial force, and finally the moving distance. d3 moves and the shift to the third speed is completed.

(4-speed operation)
When shifting the transmission 10 from the third speed to the fourth speed, the second shift fork 52 is returned to the reference position Np2, and the first shift fork 51 is moved rightward by the moving distance d4. As a result, the 4-speed driven gear 42d (see FIG. 2) moves to the right, and the engagement of the second engaging means 42dd of the 4-speed driven gear 42d and the first engaging means 42cd of the 3-speed driven gear 42c is released. Then, the third speed drive gear 41c (see FIG. 1) moves to the right, and the second engagement means 41cd of the third speed drive gear 41c engages with the first engagement means 41dp of the fourth speed drive gear 41d. Therefore, the 4-speed drive gear 41d rotates synchronously with the main shaft 11, and the rotation is transmitted to the countershaft 12 via the 4-speed driven gear 42d rotating synchronously with the countershaft 12.

  As shown in FIG. 8, when the first shift fork 51 slides rightward on the first shift fork shaft 31 without being caught by the first shift fork shaft 31, the first shift fork 51 Moves to the right, and the fork end surface 51 e of the first shift fork 51 comes into contact with the position restricting portion 61. Thereafter, the first shift fork 51 moves with the first shift fork shaft 31 and finally moves the moving distance d4, and the shift to the fourth speed is completed. At that time, the first shift fork shaft 31 slides the gap S in the axial direction by a predetermined distance m4.

  On the other hand, when the first shift fork 51 slides in the right direction and is temporarily caught on the first shift fork shaft 31, the first shift fork 51 moves with the first shift fork shaft 31. The first shift fork shaft 31 slides in the gap S to the right. When the first shift fork shaft 31 slides to the right in the gap S and the hook with the first shift fork 51 is not eliminated, the shaft end surface 31e of the first shift fork shaft 31 is Collides with the bottom surface 28b. When the shaft end surface 31e of the first shift fork shaft 31 collides with the bottom surface 28b of the fitting portion 28, the first shift fork 51 slides on the first shift fork shaft 31 by the inertial force, and finally the moving distance d4 moves and the shift to the fourth speed is completed.

(5-speed operation)
As shown in FIG. 8, when shifting the transmission 10 from the fourth speed to the fifth speed, the first shift fork 51 is moved leftward, returned to the reference position Np1, and further moved by a movement distance d5. As a result, the third speed drive gear 41c (see FIG. 1) moves to the left, and the engagement of the second engagement means 41cd of the third speed drive gear 41c and the first engagement means 41dp of the fourth speed drive gear 41d is released. The second engaging means 41cp of the third speed driving gear 41c is engaged with the first engaging means 41ed of the fifth speed driving gear 41e. Therefore, the 5-speed drive gear 41e rotates in synchronization with the main shaft 11, and the rotation is transmitted to the countershaft 12 via the 5-speed driven gear 42e that rotates in synchronization with the countershaft 12.

  At this time, when the first shift fork 51 slides to the left on the first shift fork shaft 31 without being caught by the first shift fork shaft 31, the first shift fork 51 moves to the left, A fork end surface 51 e of the first shift fork 51 comes into contact with the position restricting portion 62. Thereafter, the first shift fork 51 moves with the first shift fork shaft 31 and finally moves the moving distance d5, and the shift to the fifth speed is completed. At that time, the first shift fork shaft 31 slides the gap S in the axial direction by a predetermined distance m5.

  On the other hand, when the first shift fork 51 slides in the left direction and is temporarily caught on the first shift fork shaft 31, the first shift fork 51 moves with the first shift fork shaft 31. The first shift fork shaft 31 slides leftward in the gap S. When the first shift fork shaft 31 slides to the left in the gap S and the hook with the first shift fork 51 is not eliminated, the shaft end surface 31e of the first shift fork shaft 31 is Collides with the bottom surface 28b. When the shaft end surface 31e of the first shift fork shaft 31 collides with the bottom surface 28b of the fitting portion 28, the first shift fork 51 slides on the first shift fork shaft 31 by the inertial force, and finally the moving distance d5 moves and the shift to the fifth speed is completed.

  As described above, in the present embodiment, the first shift fork 51, the second shift fork 52, and the third shift fork 53 move in any one of the left and right directions, and then in the opposite direction at the time of the next shift. Therefore, the first shift fork 51, the second shift fork 52, and the third shift fork 53 reciprocate around the respective reference positions Np1, Np2, and Np3. Therefore, even if the first shift fork shaft 31 or the second shift fork shaft 32 moves to the bottom surface 28b of the fitting portion 28, the first shift fork 51, the second shift fork 52, the third shift fork at the next shift. Due to the movement of the shift fork 53, any one of the fork end surfaces 51e, 52e, 53e of the first shift fork 51, the second shift fork 52, and the third shift fork 53 is connected to the position restricting portions 61, 62, 63, 64, 65. Since the first shift fork shaft 31 and the second shift fork shaft 32 are moved, the gap S is always formed. Therefore, it is not necessary to provide the fitting portion 28 with an urging member for securing the gap portion S.

[Second Embodiment]
Next, a transmission according to a second embodiment of the present invention will be described with reference to FIG. In the following description, the same components as those of the transmission 10 of the first embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified. In the transmission 10 of the first embodiment, the position restricting portions 63, 64, and 65 are configured by circlips that form grooves along the circumferential direction on the outer peripheral surface of the second shift fork shaft 32 and fit into the grooves. However, the transmission of the second embodiment employs another structure. Hereinafter, differences between the position restricting portions 63, 64, and 65 in the transmission 10 according to the first embodiment and the position restricting portions 66 and 67 according to the second embodiment will be described in detail.

<Position control part>
In FIG. 9, the 2nd shift fork shaft 32A provided with the three position control parts 63, 66, and 67 is shown. In the second shift fork shaft 32A, the rightmost position restricting portion 63 in the drawing has the same structure as that of the first embodiment. However, the other two structures are different.

  The position restricting portion 66 provided between the second shift fork 52 and the third shift fork 53 is configured by a step structure in which the diameter of the second shift fork shaft 32A is changed. That is, in the second shift fork shaft 32A, a substantially half region on the right side supported by the second shift fork 52 is configured to have a small diameter, and a left side portion that supports the third shift fork 53 is configured to have a large diameter. Accordingly, the leftward shift of the second shift fork 52 can be restricted by the contact between the left fork end surface 52e of the second shift fork 52 and the position restricting portion 66.

  The leftmost position restricting portion 67 has a structure in which an O-ring is fitted in an annular groove formed on the outer peripheral surface of the second shift fork shaft 32A. That is, the second shift fork shaft 32A has a structure in which an O-ring fitted in an annular groove protrudes in the radial direction from the outer peripheral surface, and the position restricting portion 67 allows the third shift fork 53 to slide to the left. Can be regulated.

  Thus, as in the present embodiment, for example, when the position restricting portion 66 is configured by the step structure of the second shift fork shaft 32A itself, the simplification of parts and the number of parts can be reduced.

  It should be noted that the above-described embodiment can be modified, improved, etc. as appropriate. For example, in the first embodiment, the main shaft 11 can move in the axial direction thereof, and one gear (three-speed drive gear 41c) that rotates synchronously with the main shaft 11 is arranged with respect to the counter shaft 12. Two gears (four-speed driven gear 42d and five-speed driven gear 42e) that can move in the axial direction and rotate synchronously with the counter shaft 12 can be slid in the axial direction on the first shift fork shaft 31 accordingly. One shift fork to be connected (first shift fork 51) and two shift forks slidably connected to the second shift fork shaft 32 in the axial direction (second shift fork 52, third shift fork 53) However, two gears that can move in the axial direction with respect to the main shaft 11 and rotate synchronously with the main shaft 11, A shift fork that is movable in the axial direction with respect to the union shaft 12 and that rotates synchronously with the counter shaft 12 is connected to the first shift fork shaft 31 so as to be slidable in the axial direction. Two shift forks may be slidably connected to the second shift fork shaft 32 in the axial direction.

  In addition, at least the following matters are described in this specification. In addition, although the component etc. which respond | correspond in the above-mentioned embodiment are shown in a parenthesis, it is not limited to this.

(1) a main shaft (main shaft 11) connected to a drive source so that power can be transmitted;
A counter shaft (counter shaft 12) that is arranged in parallel with the main shaft and is connected to drive wheels so as to be capable of transmitting power;
A fixed gear (fourth speed drive gear 41d, fifth speed drive gear 41e), which is non-slidable on the main shaft and has first engagement means (first engagement means 41dp, 41ed);
A movable gear (third speed drive gear 41c) having second engagement means (second engagement means 41cd, 41cp) which is slidably disposed on the main shaft and engages with the first engagement means;
A shift drum (shift drum 45) that rotates in response to a speed change operation and has a lead groove (lead groove 45g) on the outer peripheral surface;
A shift fork shaft (first shift fork shaft 31) supported by the crank case (crank case 21);
A shift fork (first shift fork 51) that is axially slidably supported by the shift fork shaft, has one end engaged with the lead groove, and the other end connected to the movable gear;
A transmission (wherein the shift fork slides the movable gear by the rotation of the shift drum, and the gear position is switched by engaging or disengaging the first engaging means and the second engaging means. A transmission 10) comprising:
An end portion (end portion 31t) of the shift fork shaft is fitted to a fitting portion (fitting portion 28) provided in the crankcase so as to be slidable in the axial direction,
A gap portion (gap portion S) is provided between the shaft end surface (shaft end surface 31e) of the shift fork shaft and the bottom surface (bottom surface 28b) of the fitting portion.
The axial width (axial width W5, W6) of the gap is configured to be shorter than the moving distance (moving distance d4, d5) in which the shift fork moves in the axial direction by the lead groove when shifting.
The shift fork shaft is provided with position restricting portions (position restricting portions 61 and 62) so as to be able to contact the fork end surface (fork end surface 51e) of the shift fork,
The position of the shift fork when the transmission is neutral is set as a reference position (reference position Np1), and when the shift fork is positioned at the reference position, a distance (distance W7, W8) is a transmission that is configured to be shorter than the movement distance (movement distances d4 and d5) in which the shift fork moves in the axial direction by the lead groove during gear shifting.

According to (1), the end portion of the shift fork shaft is fitted to the fitting portion provided in the crankcase so as to be slidable in the axial direction, and between the shaft end surface of the shift fork shaft and the bottom surface of the fitting portion. Since there is a gap, the shift fork moves with the shift fork shaft and the shift fork shaft slides even when the shift fork is tilted and temporarily caught with respect to the shift fork shaft. Therefore, it is possible to move smoothly.
Further, since the gap portion is configured to be shorter than the moving distance in which the shift fork moves in the axial direction due to the lead groove at the time of shifting, the shift fork shaft is always regulated by the bottom surface of the gap portion. After the shift fork shaft slide is regulated, the shift fork moves the shift fork shaft due to inertial force, so even if the shift fork is temporarily caught on the shift fork shaft, the shift fork moves smoothly. Is possible.

(2) The transmission according to (1),
The axial width (axial width W3) of the fitting portion on one end side of the shift fork shaft and the axial width (axial width W4) of the fitting portion on the other end side of the shift fork shaft are either Also, the sum of the axial width (axial width W5) of the gap portion on one end side of the shift fork shaft and the axial width (axial width W6) of the gap portion on the other end side of the shift fork shaft. Longer transmission.

  According to (2), the axial width of the fitting portion on one end side of the shift fork shaft and the axial width of the fitting portion on the other end side of the shift fork shaft are both on the one end side of the shift fork shaft. Since it is longer than the sum of the axial width of the gap and the axial width of the gap on the other end of the shift fork shaft, both ends of the shift fork shaft are always fitted to the fitting parts even if they slide. It is possible to prevent the fitting part from coming off.

(3) The transmission according to (1) or (2),
The shift fork has two shift forks (a second shift fork 52 and a third shift fork 53) that are axially slidably supported on the shift fork shaft.
The position restricting portion (position restricting portions 64 and 66) is a transmission that is provided between the two shift forks.

  According to (3), the shift fork shaft has two shift forks that are slidably supported in the axial direction, and the position restricting portion is provided between the two shift forks. Even if a plurality of shift forks are provided, the shift forks can be prevented from interfering with each other, so that the shift fork shaft can be shared and the number of parts can be reduced.

(4) The transmission according to any one of (1) to (3),
The shift fork movement direction is greater than the shift fork movement distance (movement distances r2, r1) required for the first engagement means and the second engagement means to change from the engaged state to the disengaged state. A transmission having a long axial width (axial widths W5, W6) of the gap on the side.

  According to (4), the gap portion on the shift direction side of the shift fork beyond the shift distance of the shift fork necessary for the first engagement means and the second engagement means to change from the engaged state to the disengaged state. Since the axial direction width of the shift fork shaft is always long, the shift fork shaft always slides in the axial direction along with the shift fork while the first engagement means and the second engagement means change from the engaged state to the disengaged state. Is possible. Thus, the shift fork can be smoothly moved even when the first engagement means and the second engagement means are changed from the engaged state to the disengaged state, where the shift fork is most easily caught on the shift fork shaft.

(5) The transmission according to any one of (1) to (4),
The shiftable distance (movable distances k4 and k5) of the shift fork in the direction of the position restricting portion is the distance (distance W7, W8) between the fork end surface of the shift fork and the position restricting portion, and the shift fork. A transmission that is shorter than the sum of the axial widths (axial widths W5 and W6) of the gap portion on the moving direction side.

  According to (5), the shiftable distance of the shift fork in the direction of the position restricting portion is based on the sum of the distance between the shift fork end surface and the position restricting portion and the axial width of the gap portion on the shift fork moving direction side. Therefore, even when the shift fork has moved the longest, the axial width of the gap portion on the shift fork moving direction side can always be ensured, and the shift fork can be moved smoothly.

DESCRIPTION OF SYMBOLS 10 Transmission 11 Main shaft 12 Counter shaft 21 Crank case 28 Fitting part 31 1st shift fork shaft 31e Shaft end surface 31t End part 32 Second shift fork shaft 32e Shaft end face 32t End part 41a First speed drive gear 41b Second speed drive gear 41c 3-speed drive gear (movable gear)
41cd, 41cp Second engaging means 41d 4th speed drive gear (fixed gear)
41dp 1st engagement means 41e 5 speed drive gear (fixed gear)
41ed 1st engagement means 42a 1st speed driven gear (fixed gear)
42ad 1st engagement means 42b 2nd speed driven gear (fixed gear)
42bd 1st engagement means 42c 3rd speed driven gear (fixed gear)
42cd 1st engagement means 42d 4 speed driven gear (movable gear)
42dd, 42dp Second engaging means 42e 5-speed driven gear (movable gear)
42ep Second engaging means 45 Shift drum 45g Lead groove 51 First shift fork (shift fork)
51e Fork end face 52 Second shift fork (shift fork)
52e Fork end surface 53 Third shift fork 53e Fork end surfaces 61, 62, 63, 64, 65, 66, 67 Position restricting portions d1, d2, d3, d4, d5 Shift fork moving distances k1, k2, k3, k4, k5 shift Fork movable distances m1, m2, m3, m4, m5 Predetermined distances Np1, Np2, Np3 Reference positions r1, r2, r3, r4, r5 Moving distance S Clearance W3, W4 Fitting axial width W5, W6 Clearance Axial width W7, W8, W9, W10, W11 distance between fork end surface and position restricting portion

Claims (5)

A main shaft (11) connected to a drive source so as to be able to transmit power;
A countershaft (12) disposed in parallel with the main shaft and connected to drive wheels to transmit power;
Fixed gears (41d, 41e) which are arranged on the main shaft (11) in a non-slidable manner and have first engaging means (41dp, 41ed);
A movable gear (41c) that is slidably disposed on the main shaft (11) and has second engagement means (41cd, 41cp) engaged with the first engagement means (41dp, 41ed);
A shift drum (45) that rotates in response to a speed change operation and is provided with a lead groove (45g) on the outer peripheral surface;
A shift fork shaft (31) supported by the crankcase (21);
A shift fork (51) that is axially slidably supported by the shift fork shaft (31), has one end engaged with the lead groove (45g), and the other end connected to the movable gear (41c). And comprising
The shift fork (51) slides the movable gear (41c) by the rotation of the shift drum (45), and the first engagement means (41dp, 41ed) and the second engagement means (41cd, 41cp). A transmission (10) that switches a gear position by engaging or disengaging
An end portion (31t) of the shift fork shaft (31) is fitted to a fitting portion (28) provided in the crankcase (21) so as to be slidable in the axial direction,
A gap (S) is provided between the shaft end surface (31e) of the shift fork shaft (31) and the bottom surface (28b) of the fitting portion (28),
The axial width (W5, W6) of the clearance (S) is larger than the moving distance (d4, d5) in which the shift fork (51) moves in the axial direction by the lead groove (45g) at the time of shifting. Composed short and
The shift fork shaft (31) is provided with position restricting portions (61, 62) so as to come into contact with the fork end surface (51e) of the shift fork (51),
The position of the shift fork (51) when the transmission (10) is neutral is set as a reference position (Np1), and when the shift fork (51) is positioned at the reference position (Np1), the fork end face (51e ) And the position restricting portions (61, 62) are distances (d4, w8) in which the shift fork (51) moves in the axial direction by the lead groove (45g) at the time of shifting. A transmission (10) configured shorter than d5). Transmission (10) according to claim 1,
The axial width (W3) of the fitting portion (28) on one end side of the shift fork shaft (31) and the axial width of the fitting portion (28) on the other end side of the shift fork shaft (31). (W4) is the axial width (W5) of the gap (S) on one end side of the shift fork shaft (31) and the gap (S) on the other end side of the shift fork shaft (31). ) Is longer than the sum of the axial width (W6) and the transmission (10). Transmission (10) according to claim 1 or 2,
The shift fork has two shift forks (52, 53) that are axially slidably supported on the shift fork shaft (32),
The position restricting portion (64, 66) is a transmission (10) provided between the two shift forks (52, 53). A transmission (10) according to any one of claims 1-3,
The moving distance (r2, r2) of the shift fork (51) necessary for the first engaging means (41dp, 41ed) and the second engaging means (41cd, 41cp) to change from the engaged state to the disengaged state. A transmission (10) in which the axial width (W5, W6) of the gap (S) on the moving direction side of the shift fork (51) is longer than r1). A transmission (10) according to any one of claims 1-4,
The movable distance (k4, k5) of the shift fork (51) in the direction of the position restricting portion (61, 62) is determined by the fork end surface (51e) of the shift fork (51) and the position restricting portion (61, 62) is shorter than the sum of the distance (W7, W8) to the shift fork (51) and the axial width (W5, W6) of the gap (S) on the moving direction side of the shift fork (51). .