JPS6218779B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shift mechanism for a transmission using a cylindrical cam, which is widely used in motorcycles and the like.

A transmission that changes gears by intermittently rotating a shift drum consisting of a cylindrical cam at a predetermined angle and sliding a shift fork that engages with a cam groove on the outer circumferential surface of the shift drum is used in motorcycles, etc.
Widely used. Generally, in this type of transmission, a first shift lever is fixed to a shift shaft to which a shift pedal is fixed, and the shift drum is moved at a predetermined angle so that the first shift lever swings to change gears one gear at a time. It is equipped with a shift mechanism consisting of a forward and reverse ratchet mechanism for rotation. On the other hand, when used in vehicles such as motorcycles, it is desired to downsize the transmission.
The shift lever and ratchet mechanism occupy a fairly large space considering their movable range, which limits the arrangement of other components, making it difficult to downsize the transmission.

This invention was made in view of the above circumstances, and aims to provide a shift mechanism suitable for downsizing of transmissions, and in order to achieve this purpose,
a first shift lever that is fixed to the shift shaft and has a habit of returning to a neutral position; and a first shift lever that is pivotally connected to a swinging end of the first shift lever and has a habit of returning to a neutral position. a second shift lever;
A shift drum is provided with a shift pin on the end face thereof, and the shift drum is disposed such that the shift pin is located between the shift shaft and the second shift lever, and the pivot shaft of the second shift lever is located between the shift pin and the second shift lever. The second shift lever is located approximately directly above the rotation locus circle at an appropriate interval, and is provided with a folded portion folded back from the pivot shaft toward the shift drum, and formed at both ends of the folded portion. A pair of claws opening toward the shift shaft are configured to engage with a shift pin located between the pivot shaft and the shift drum. The present invention will be explained in detail below based on the drawings.

FIG. 1 is a side view of an embodiment of the present invention applied to a motorcycle, FIG. 2 is a cross-sectional view taken along the line ``--'', and FIG. 3 is a side view of the main parts similarly showing a gear shift operation state. In these figures, reference numeral 1 denotes a crankcase that is integrated with an engine (not shown), and a shift shaft 2, a shift drum 3, and two guide bars 4 and 5 are held in parallel to each other in this crankcase 1. . Note that the shift shaft 2 and shift drum 3 are rotatable. shift axis 2
project to both sides of the crankcase 1, a shift pedal (not shown) is fixed to one projecting end, and a first shift pedal (not shown) is fixed to the other projecting end via a boss 6 rotatably mounted here. A shift lever 7 is fixedly installed. A stopper arm 8 is fixed to the boss 6, and a rotatable disc-shaped cam follower 9 is attached to the swinging end of the stopper arm 8. An opening 10 is formed in the first shift lever 7, the protruding end of the guide bar 4 faces the opening 10, and the edge of the opening 10 on the shift shaft 2 side is bent toward the crankcase 1 side. A curved protrusion 11 is formed. The opening 10 is the guide bar 4
The protrusion 11 has a width that is substantially the same as the diameter of the guide bar 4. These protrusions 11 and the protruding end of the guide bar 4 are pressed together by a torsion spring 12 attached to the boss of the first shift lever 7.

Therefore, if the shift pedal (not shown) is operated to rotate the first shift lever 7 in the direction of arrow A in FIG. It is pushed and spread by. When the operating force on the shift pedal is removed, the elastic force of the torsion spring 12 causes the first shift lever 7 to return to its neutral position as shown in FIG.

A second shift lever 13 is rotatably attached to the swinging end 14 of the first shift lever 7 via a collar 15 by a pivot shaft 16. The pivot shaft 16 is located approximately directly above the rotation locus circle of the shift pin 25, which will be described later, at an appropriate interval. Further, the second shift lever 13 has a pair of pawls 13.
These pawls 13a, 13a are provided at both ends of a folded portion 13b that is folded back from the pivot shaft 16 toward the shift drum 3 side, and open toward the shift shaft 2 side. It is formed to surround the mounting shaft 16 from both sides. An opening 17 is formed in the swinging end portion 14 at a position on the shift shaft 2 side of the pivot shaft 16.
An extension piece 18 extending into the opening 17 is formed on the side. The tip of this extending piece 18 is bent toward the crankcase 1 side, and serves as a protrusion 19. On the other hand, the second shift lever 13 has an extending piece 1 between the protrusion 19 and the pivot shaft 16.
A protrusion 20 is formed which is bent toward the 8th side. These protrusions 19 and 20 are clamped by a torsion spring 21 attached to the collar 15.

Therefore, the second shift lever 13 is now connected to the pivot shaft 1.
6, each projection 19, 20 pushes open the torsion spring 21 (see FIG. 3), and this torsion spring 21 causes the second shift lever 13 to move to the neutral position shown in FIG. Provides a return habit.

As shown in FIG. 1, the shift drum 3 is attached to the crankcase 1 so as to be located between the shift shaft 2 and the pivot shaft 16 when the first shift lever 7 is in the neutral position. Retained. A flower-shaped cam 22 is fixed to the end surface of the shift drum 3 on the first shift lever 7 side.
That is, this flower-shaped cam 22 is fixed together with the presser plate 23 by countersunk screws 24. The flower-shaped cam 22 is formed into a substantially flower shape with six peaks, and one of the peaks has a concave portion 22a whose top is depressed in an arc shape.
It is becoming. Five shift pins 25 pass through this flower-shaped cam 22 on a concentric circle corresponding to each peak except for one peak, and one end of this shift pin 25 enters the shift drum 3, and the other end is attached to the presser foot. It is pressed by the plate 23. The pawls 13a, 13a of the second shift lever 13 engage with this shift pin 25 during a gear change operation. Further, a cam follower 9 attached to the stopper arm 8 is elastically pressed against the outer periphery of the flower-shaped cam 22 by a torsion spring 26 attached to the boss 6 of the stopper arm 8, and the shift drum 3 is intermittently pressed. will be stopped.

The reason why the shift pin 25 is removed from one of the six peaks of the star-shaped cam 22 is to stop the rotation of the shift drum 3 at the final position of the gear shifting operation.
This is to cause the shift pedal to be depressed. In addition, there is a concave portion 22 in one of the peaks of the flower-shaped cam 22.
The reason why ``a'' is formed is to stop the shift drum 3 in the state in which the cam floor 9 is engaged with this recess 22a (the state shown in FIG. 1), and to hold the transmission in the neutral position.

Numerals 27 and 27 are bosses formed on the crankcase 1, and these bosses 27 and 27 have the function of preventing so-called skipping caused by over-rotation of the shift drum 3 during sudden gear change operations. That is, for example, in FIG. 3, during a sudden gear change operation, the shift drum 3 rapidly rotates counterclockwise in the figure, and the shift pin 25a in this figure pushes up the pawl 13a, causing the second shift lever 13 to rotate counterclockwise. However, since the second shift lever 13 is restricted from excessive rotation in the counterclockwise direction by the boss 27, the shift pin 25a is moved by the claw 13a. This prevents the player from jumping over the ball.

28 and 29 are shift forks slidably held on the guide bar 4; 30 are shift forks slidably held on the guide bar 5; pins provided on these shift forks 28, 29, and 30; 28a, 29a, and 30a engage in respective cam grooves formed in the shift drum 3. These shift forks 28, 29, and 30 slide on the respective guide bars 4 and 5 as the shift drum 3 rotates, thereby changing the meshing of the speed change gears (not shown).

Next, the operation of this shift mechanism will be explained. If the transmission is now in the neutral state as shown in Fig. 1 and the shift pedal (not shown) is operated to rotate the shift shaft 2 and the first shift lever 7 in the direction of arrow A, the result will be as shown in Fig. 3. Become. That is, one pawl 13a of the second shift lever 13 engages with one of the shift pins 25 (25b in FIG. 3), and the shift drum 3
Rotate counterclockwise by a predetermined angle. At this time the second
The shift lever 13 rotates clockwise while being engaged with the shift pin 25, and the protrusions 19 and 20 push the torsion spring 21 open. Also stopper arm 8
Since the cam follower 9 is pressed against the cam surface of the flower-shaped cam 22, after the shift drum 3 has rotated by a predetermined angle, its rotation is restricted and it does not rotate easily.

Except for the operating force of the shift pedal, the first shift lever 7 is moved to the first shift lever 7 by the elastic force of the torsion spring 12.
Attempts to return to the neutral position shown in the figure. At this time, claw 13
Since the pressing force on the shift pin 25b is released, the second shift lever 13 is moved by the torsion spring 2.
It returns to its neutral position by an elastic force of 1. When the first shift lever 7 returns to the neutral position, the pawl 13a abuts the adjacent shift pin 25a, and the second shift lever 13 rotates once counterclockwise to overcome this shift pin 25a.

This completes one shift operation, and by repeating such an operation, the shift drum is intermittently rotated by a predetermined angle to perform a shift.

In this embodiment, the shift pin 2 of the shift drum 3
The shift drum 3 is arranged so that the protrusion 5 is located between the second shift lever 13 and the shift shaft 2, and the protrusion 1 returns the second shift lever 13 to the neutral position.
9 and 20 are the pivot shaft 1 of the second shift lever 13.
6 and the shift shaft 2, respectively, and each of these protrusions 19, 20 is configured to be clamped by a torsion spring 21. The torsion spring 21 and the protrusions 19, 20 do not extend outward in the radial direction of the first shift lever 7, and the range of movement of the first shift lever 7 is further reduced. Also, each pawl 13a, 13a of the second shift lever 13
protrudes toward the shift shaft 2, so the movable range of the second shift lever 13 almost overlaps with the movable range of the first shift lever 7, and in the end, the movable range of the first and second shift levers 7, 13 is the sum of the movable ranges of the first and second shift levers 7, 13. The area is smaller than that of the conventional one, and the transmission can be significantly downsized.

As described above, in this invention, the pivot shaft of the second shift lever is located almost directly above the rotation locus circle of the shift pin with an appropriate interval, and the second shift lever is connected from the pivot shaft to the shift drum. It has a folded part that is folded back to the side, and a pair of claws that open toward the shift shaft are formed at both ends of the folded part, and these claws engage with a shift pin located between the pivot shaft and the shift drum. Because of this, the swinging range of the second shift lever during a gear change operation is reduced, and as a result, the rotation angle of the first shift lever is also reduced. The first shift lever is also shortened. Therefore, the movable range of this shift mechanism becomes smaller, and the transmission becomes smaller.

[Brief explanation of the drawing]

FIG. 1 is a side view of an embodiment of the present invention applied to a motorcycle, and FIG. 2 is a sectional view taken along the same line.
FIG. 3 is a side view of the main parts similarly showing the gear change operation state. 2...Shift shaft, 3...Shift drum, 7...
First shift lever, 13... Second shift lever, 13a... Claw, 13b... Folded portion, 14
... Swinging end, 16 ... Pivoting shaft, 25 ... Shift pin.

Claims (1)

[Claims] 1 A first shift lever fixedly attached to a shift shaft and having a habit of returning to a neutral position;
A second shift lever is pivotally connected to the swinging end of the shift lever and has a tendency to return to a neutral position, and a shift pin is provided on the end face, and the shift pin is connected to the shift shaft and the second shift lever. The pivot shaft of the second shift lever is located approximately directly above the rotation locus circle of the shift pin at an appropriate interval, and The shift lever includes a folded part that is folded back from the pivot shaft toward the shift drum, and a pair of pawls formed at both ends of the folded part and opening toward the shift shaft are connected to the pivot shaft and the shift drum. A shift mechanism for a transmission, characterized in that the shift mechanism engages with a shift pin located between.