JPH0574515B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a drive sprocket device for a motorcycle.

(Prior art and its problems) In general, in order to reduce the size, weight, and cost of motorcycles, a so-called cantilever structure rear fork with a single fork member is adopted as a rear fork that holds the rear wheel. The rear wheel is attached to one end of the rear axle held by the axle holding portion of the rear fork, and the driven sprocket is attached to the other end. An endless chain is wound between the driven sprocket and a drive sprocket attached to the output shaft of the transmission, and the rotational power from the transmission is transmitted to the rear through the chain. transmitted to the wheels.

By the way, it is necessary to adjust the tension of the chain in order to maintain proper power transmission efficiency, and this tension adjustment is usually performed on the driven sprocket side. is attached to the rear fork so that its set position can be adjusted in the longitudinal direction of the rear fork. More specifically, an eccentric holder having a rear axle insertion hole that is eccentric with respect to the axis of the axle holding part is attached to the axle holding part of the rear fork so that it cannot normally be rotated, but can be rotated when adjusting the tension of the chain. The rear axle is rotatably mounted in the rear axle insertion hole of the eccentric holder via a bearing. Therefore, when the eccentric holder is rotated, the axis of the rear axle, that is, the axis of the driven sprocket, is displaced in the longitudinal direction of the rear fork because the axis of the rear axle is eccentric with respect to the axis of rotation. As a result, the tension in the chain is adjusted by changing the distance between the shafts of the driven sprocket and the drive sprocket. In order to rotate the eccentric holder when adjusting the tension of the chain, a special tool for rotating the eccentric holder is used. For this purpose, a plurality of engagement recesses in which the engagement protrusions of the rotation operation tool engage are formed at intervals in the circumferential direction on the end surface of the eccentric holder facing the driven sprocket. In order to cause the engagement protrusion of the rotation operation tool to engage the engagement recess of the eccentric holder and rotate the eccentric holder, the rotation operation tool is inserted between opposing surfaces of the driven sprocket and the eccentric holder. A gap is required to insert the operating tool,
In particular, since a conventional driven sprocket has a disk shape that is uniformly flat over its entire surface, the chain engaging tooth portion on the outer periphery of the driven sprocket is arranged at a considerable distance in the axial direction from the axle holding portion of the rear fork. Therefore, the length of the shaft between the driven sprocket and the rear wheel becomes long, which poses a problem in reducing size, weight, and cost.

(Object of the Invention) The present invention has been made in view of the above circumstances, and eliminates the need for a gap for inserting a rotating operation tool between the facing surfaces of the driven sprocket and the eccentric holder, thereby reducing the size and weight. Another object of the present invention is to provide a chain drive sprocket device for a motorcycle that can smoothly reduce costs.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides an axle retaining portion for the rear end side of the rear fork whose distal end side is rotatably attached to the vehicle body frame. The rear axle is held through an eccentric holder having a rear axle insertion hole eccentric to the center, and the tension of a chain wound around a driven sprocket fixed to one end of the rear axle is applied to the rotation of the eccentric holder. In the chain drive sprocket device for a motorcycle, the driven sprocket can be adjusted by:
A central wall portion facing the outer end surface of the eccentric holder and an outer peripheral wall portion having chain engaging teeth provided on the outer peripheral surface thereof are connected by a cylindrical wall so as to be offset from each other in the axial direction, and the central wall portion is offset from each other in the axial direction. a rotational operation tool for arranging the outer circumferential wall portion closer to the axle holding portion of the rear fork, and further rotating the eccentric holder at a predetermined location on the wall of the driven sprocket from outside the driven sprocket; It is characterized by having an insertion hole for inserting the.

(Function) In the driven sprocket, an outer circumferential wall portion having chain engagement teeth on the outer circumferential surface and a central wall portion facing the outer end surface of the eccentric holder are connected in the axial direction via a cylindrical wall connecting them. Because the outer peripheral wall is located closer to the axle holding part of the rear fork than the central wall, the central wall of the driven sprocket is offset to the outside of the chain engagement teeth. The eccentric holder can be rotated by inserting a rotation operating tool through an insertion hole provided in the wall of the driven sprocket. This eliminates the need to provide a space for inserting a rotating operation tool between the facing surfaces of the driven sprocket and the eccentric holder.
Since the distance between the driven sprocket and the rear wheel can be shortened, size reduction in the axial direction can be achieved smoothly.

(Example) Hereinafter, one example of the present invention will be described based on the drawings. FIG. 1 is a side view of a motorcycle to which the present invention is applied, in which reference numeral 1 indicates the entire motorcycle, and a rear fork bracket 3 provided on a body frame 2.
The tip of the rear fork 4 is the pivot bolt 5.
It is rotatably attached. As shown in FIG. 2, the rear fork 4 has a cylindrical attachment part 6 with a predetermined axial length on the distal end side, and a single fork part 7 whose distal ends are integrally connected to both ends of the outer surface of one side of the attachment part 6.
It has a so-called cantilevered structure consisting of a short-axis cylindrical axle holding part 8 whose one outer surface is integrally connected to the rear end part of the fork part 7. Then, the mounting portion 6
is attached to the left and right rear fork brackets 3 of the vehicle body frame 2 by pivot bolts 5. The fork portion 7 and the axle holding portion 8
passes through an approximately intermediate portion in the axial direction of the attachment portion 6 and is displaced to the left in the vehicle body traveling direction from an axis L that is orthogonal to the axis of the attachment portion 6, and the approximately intermediate portion 7a of the fork portion 7 will be described later. It is curved so as not to interfere with the rear wheel 15. Further, the rear end side of the fork portion 7 and the axle holding portion 8 are close to the axis L. An eccentric holder 9 is fitted into the axle holding portion 8 so as to be rotatable as required. That is, a part of the circumferential wall of the axle holding part 8 is cut out, and by loosening a bolt (not shown) provided at the cut part, the eccentric holder 9 can be rotated within the axle holding part 8. Furthermore, by tightening the bolt, the eccentric holder 9 becomes unable to rotate within the axle holding portion 8. The eccentric holder 9 has a rear axle insertion hole 10 that is eccentric with respect to the axis of the axle holding portion 8, and a bearing 1 is inserted into the insertion hole 10.
A rear axle 13 is rotatably fitted through 1 and 12. A driven sprocket 14 is fixed to one end of the rear axle 13, and a rear wheel 15 is fixed to the other end. The driven sprocket 14 has a central wall portion 16 facing the outer end surface of the eccentric holder 9 and an outer peripheral wall portion 18 having chain engaging teeth 17 on the outer peripheral surface, which are connected by a cylindrical wall 19. Wall portion 16 and outer peripheral wall portion 1
8 and are offset from each other in the axial direction. The driven sprocket 14 has its outer circumferential wall 18 closer to the axle holding part 8 of the rear fork 4 than its center wall 16, and the driven sprocket 14 is attached to the rear axle 13 with the center wall 16 closer to the outer end surface of the eccentric holder 9. It is fixed to one end using a nut 20. The driven sprocket 14 is connected to a drive sprocket 22 fixed to an output shaft 22a of a transmission (not shown) via an endless chain 21 that engages with chain engaging teeth 17 on its outer peripheral wall 18. ing. The rotational power of the engine 23, which is installed approximately at the lower center of the vehicle body frame 2, is transmitted to the rear axle 13 via the transmission, drive sprocket 22, chain 21, and driven sprocket 14, and the rear wheels 15 are rotated. Ru. The tension of the chain 21 is adjusted by rotating the eccentric holder 9. That is, as shown in FIG. 4, a plurality of engagement recesses 24 are provided at equal intervals in the circumferential direction on the outer end surface of the eccentric holder 9, and a rotation operation tool 25 as shown in FIG. to rotate the eccentric holder 9. The rotation operation tool 25 is provided with the engagement recess 2 of the eccentric holder 9 on one side of both ends of the approximately semi-annular main body 26.
The main body 26 is provided with engaging protrusions 27, 27 which are integrally protruded and releasably engaged with the main body 26, and a handle 28 is protruded from approximately the middle portion of the main body 26. Insertion holes 29 are formed in the center wall portion 16 of the driven sprocket 14 at equal intervals in the circumferential direction, and the engagement protrusions 27 of the rotation operation tool 25 are inserted through the insertion holes 29 into the center wall portion 16 of the driven sprocket 14 . It can be engaged with the engagement recess 24 of the holder 9 and rotated by a predetermined angle. Main body 2 of the rotation operation tool 25
The inner diameter of the driven sprocket 6 is set to a size that allows the driven sprocket 14 to be located on the outer periphery of the nut 20 that fixes the driven sprocket 14 to the rear axle 13 and to be able to rotate without interfering with the nut 20.

The rear wheel 15 is formed by mounting a tire 31 on a wheel 30, and the boss hole 30a of the wheel 30 is fitted into the other end of the rear axle 13, and the nut 3 is inserted into the rear wheel 15.
It is fixed by 2. In addition, the rear wheel 15
A part of the tire 31 is located within the space A of the curved portion of the fork portion 7. Further, the center of this tire 31 coincides with the axis L. In addition,
In FIG. 2, 33 is a chain slider provided on the upper surface of the fork portion 7 of the rear fork 4, 34 is a brake caliper fixed to the rear fork 4 side, and 36 is a brake disc fixed to the wheel 30 side. Further, in FIG. 1, 36 is a handle, 37 is a front wheel, 38 is a fuel tank, and 39 is a muffler.

The rotational power of the engine 23 is transmitted to the rear axle 13 via the transmission, drive sprocket 22, chain 21, and driven sprocket 14, and the rear wheels 15 are rotated together with the rear axle 13 to drive the vehicle. It is something to do. When adjusting the tension of the chain 21, loosen the bolt (not shown) at the cutout of the axle holding part 8 to make the eccentric holder 9 rotatable, and move the rotation operation tool 25 at the two points shown in FIG. As shown by the chain line, the center wall 16 of the driven sprocket 14
and engage the engagement protrusion 27 with the engagement recess 24 of the driven sprocket 14,
By holding the handle 28 of the rotation operation tool 25 and rotating it by a predetermined angle in either the forward or reverse direction, the center-to-center distance L ₁ between the driven sprocket 14 and the drive sprocket 22 can be determined (see Fig. 1). changes, which causes the tension in the chain 21 to change.
Once the tension is at a proper level, the bolts at the cut portions of the rear axle holding portion 8 may be tightened to fix the eccentric holder 9 to the rear axle holding portion 8 in a non-rotatable state. In this way, the engagement protrusion 27 of the rotation operation tool 25 is engaged with the engagement recess 24 of the eccentric holder 9 through the insertion hole 29 of the center wall 16 of the driven sprocket 14, and the eccentric holder 9 Since the driven sprocket 14 can be rotated, the center wall portion 16 of the driven sprocket 14 can be brought close to the outer end surface of the eccentric holder 9 to the point where it is on the verge of contacting the outer end surface of the eccentric holder 9. Therefore, the driven sprocket 14 and the rear wheel 15 can be The axial length between them can be shortened, making it possible to reduce the weight and size.

In addition, in the above embodiment, the driven sprocket 1
4, the insertion hole 29 for inserting the engagement protrusion 27 of the rotation operation tool 25 has been described, but the insertion hole 29 is not limited to this, and for example, the cylindrical wall 19 has a Insertion holes 29 are provided equidistantly on the cylindrical wall 19, and the rotation operation tool 25 is applied to the outer periphery of the cylindrical wall 19 in correspondence with the insertion holes 29, and the engagement protrusions 27
The eccentric holder 9 is inserted through the insertion hole 29 of the cylindrical wall 19.
The eccentric holder 9 may be rotated by being engaged with the engagement recess 24 of the eccentric holder 9.

Further, the present invention can be applied to a motorcycle having a double-supported rear arm by providing an eccentric holder at least on the chain sprocket side and pivoting the other side to follow the adjustment amount of the eccentric holder. .

(Effects of the Invention) As detailed above, according to the chain drive sprocket device for a motorcycle of the present invention, the driven sprocket has a central wall portion facing the outer end surface of the eccentric holder and a chain engaging tooth on the outer peripheral surface. The provided outer circumferential wall portions are connected by a cylindrical wall so that they are offset from each other in the axial direction, and the outer circumferential wall portion is disposed closer to the axle holding portion of the rear fork than the central wall portion, and moreover, the driven sprocket Since the eccentric holder can be rotated by inserting the rotational operation tool through the insertion hole in the wall, it is necessary to provide a space for insertion of the rotational operation tool between the facing surfaces of the driven sprocket and the eccentric holder. This makes it possible to bring the center wall of the driven sprocket and the outer end surface of the eccentric holder close to each other, almost touching each other, which shortens the axial length between the driven sprocket and the rear wheel, resulting in miniaturization. It can be done smoothly. Moreover, although the shaft length between the driven sprocket and the rear wheel can be shortened, the chain does not get in the way when inserting the turning operation tool, making it easy to insert the tool.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is a side view of a motorcycle to which the present invention is applied, FIG. 2 is a partially cutaway plan view of the same essential parts, and FIG. 3 is an enlarged view of the driven sprocket portion. The side view and FIG. 4 are perspective views of the eccentric holder and the rotating operation tool. 1...Motorcycle, 2...Body frame, 4...
...Rear fork, 8...Axle holding part, 9...
Eccentric holder, 10... Rear axle insertion hole, 13
... Rear axle, 14 ... Driven sprocket, 16 ... Center wall, 17 ... Chain engagement teeth,
18... Outer peripheral wall portion, 19... Cylindrical wall, 21... Chain, 25... Rotating operation tool, 29... Insertion hole.

Claims (1)

[Claims] 1 At the rear axle holding part of the rear fork, whose tip end is rotatably attached to the vehicle body frame,
The rear axle is held through an eccentric holder having a rear axle insertion hole eccentric to the axis of the axle holding part, and the tension of the chain wound around the driven sprocket fixed to one end of the rear axle is In the chain drive sprocket device for a motorcycle, which can be adjusted by rotation of the eccentric holder, the driven sprocket has a center wall portion facing an outer end surface of the eccentric holder and a chain engaging tooth on an outer circumferential surface. The outer peripheral wall portions are connected to each other by a cylindrical wall so as to be offset from each other in the axial direction, and the outer peripheral wall portion is disposed closer to the axle holding portion of the rear fork than the central wall portion, and A chain drive sprocket device for a motorcycle, characterized in that an insertion hole is provided at a predetermined location on a wall portion into which a rotation operation tool for rotation operation of the eccentric holder is inserted from the outside of the driven sprocket.