JPH08216967A - Swing arm for motorcycle - Google Patents

Abstract

PURPOSE: To prevent a chain from being struck on the inlet of a chain insertion part and in the chain insertion part and to prevent dislocation of the chain from a drive sprocket. CONSTITUTION: A swing arm 9 has a front end pivotally supported on the pivot shaft 8 of a car body frame, a rear end pivotally supported to a rear wheel, and an intermediate part having a chain uncertain part 35 in which a chain 18 for driving a rear wheel is inserted. In the swing arm, a chain guide 43A is provided to suppress longitudinal oscillation of the chain 18 between the driven sprocket 17 and the chain insertion part 35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a swing arm for a motorcycle having a chain insertion portion through which a chain for driving rear wheels is inserted.

[0002]

2. Description of the Related Art Generally, a rear wheel of a motorcycle is pivotally supported by a rear end of a swing arm extending rearward from a body frame. Since the front end of the swing arm is pivotally supported by the pivot shaft installed on the vehicle body frame, the rear end of the swing arm pivots up and down together with the rear wheel about the pivot shaft. Then, the vertical movement of the rear wheels absorbs the unevenness of the road surface during traveling.

On the other hand, an engine is mounted in front of the pivot shaft, and a chain is wound between a drive sprocket, which is an output portion of the engine, and a driven sprocket, which is provided integrally with the rear wheels so as to rotate. It Therefore, the power of the engine is transmitted to the rear wheels via the chain. This chain extends rearward along the longitudinal direction of the swing arm.

By the way, the side shape of the swing arm is curved to, for example, a substantially "V" shape due to the structure of the suspension mechanism for cushioning and restoring the swing shock of the swing arm and the securement of the minimum ground clearance of the vehicle body. May be formed as follows. In this case, since the upper chain line of the chain interferes with the swing arm, a tunnel-shaped chain insertion part is formed in the middle part of the swing arm, and the upper chain line is inserted into this chain insertion part. By doing so, interference between the chain and swing arm is prevented.

[0005]

However, as described above, since the swing arm rotates up and down about the pivot axis as a fulcrum, the upper and lower chain lines also violently pitch, causing the chain to move above the chain insertion portion. There is a possibility of being slammed hard into the entrance or inside of the chain insertion part. Originally, the swing arm is usually made of a light alloy for weight reduction. Since the light alloy is a soft material, there is a concern that the swing arm may be worn and damaged when the chain is hit in this way.

Further, the chain itself may be worn or damaged by the collision with the swing arm, and uncomfortable noise is generated when the chain and the swing arm collide. Further, if the chain pitches greatly, the chain may come off the drive sprocket and become unable to run.

The present invention has been made to solve such a problem, and prevents a chain from being struck at the entrance of the chain insertion portion or the chain insertion portion in a swing arm having a chain insertion portion, and An object of the present invention is to provide a swing arm for a motorcycle capable of preventing the chain from coming off the drive sprocket.

[0008]

In order to achieve the above object, a swing arm of a motorcycle according to the present invention has a front end pivotally supported by a pivot shaft of a vehicle body frame and a rear wheel pivotally supported by a rear end thereof. In a swing arm of a motorcycle having a chain insertion portion through which the rear-wheel drive chain is inserted, a chain guide that suppresses vertical swinging of the chain between the rear wheel driven sprocket and the chain insertion portion is provided. It was

[0009]

With this structure, the chain guide suppresses the vertical swinging of the chain that is about to enter the chain insertion portion, so that the chain is not struck at the entrance of the chain insertion portion or the chain insertion portion. In addition, the vertical swing of the chain is suppressed, so that the chain is less likely to come off the drive sprocket.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a left side view showing an example of a motorcycle to which a swing arm according to the present invention is applied. The motorcycle 1 is of a motocrosser type capable of traveling on rough terrain, and has a large suspension stroke of front wheels 2 and rear wheels 3.

A front fork 5 supporting the front wheel 2 is pivotally mounted on a front head of the vehicle body frame 4 together with a handlebar 6, a front fender 7 and the like so as to be rotatable left and right. On the other hand, a pivot shaft 8 extending in the vehicle width direction is provided under the center of the body frame 4, and a front end of a swing arm 9 extending rearward is rotatably supported by the pivot shaft 8 so that the swing arm 9 can be rotated. The rear wheel 3 is rotatably supported at the rear end.

A suspension mechanism 12 having a cushion unit 11 as a main component is constructed at the base end of the swing arm 9, and the suspension mechanism 12 causes the swing shock of the swing arm 9 which rotates about the pivot shaft 8 as a fulcrum. The posture of the swinging arm 9 which is buffered and rotated is restored.

On the other hand, an engine 14 is mounted on the lower front portion of the vehicle body frame 4. A drive shaft 15 projects from the left side surface of the engine 14, and a drive sprocket 16 is provided on the drive shaft 15 so as to rotate integrally therewith. A driven sprocket 17 is rotatably provided on the left side surface of the rear wheel 3, and a chain 18 is wound between the drive sprocket 16 and the driven sprocket 17. Therefore, the power of the engine 14 is
It is transmitted to the rear wheel 3 via 18 and the rear wheel 3 is driven.

A carburetor 21 is provided at the rear of the engine 14.
And an air cleaner 22 are sequentially connected, a fuel tank 23 is installed above the engine 14, a seat 24 is placed behind the fuel tank 23, and a rear fender 25 is provided behind the seat 24.
Is provided.

FIG. 2 is a left side view of the swing arm 9 showing an embodiment of the present invention, and FIG. 3 is a plan view of the swing arm 9. The swing arm 9 is constructed by welding arm members 28L and 28R having a square pipe cross-section on both sides of an arm base 27 located at the front, and the arm base 27 does not interfere with the cushion unit 11. A notch 29 is formed to avoid it.

A pivot portion 31 is provided at the tip of the arm base portion 27.
L and 31R are provided. This pivot part 31L, 31R
Is formed in the shape of a through hole penetrating in the vehicle width direction.
Is inserted therethrough, whereby the entire swing arm 9 is rotatably supported by the pivot shaft 8.

Rear wheel support portions 32L and 32R are provided at the rear ends of the arm members 28L and 28R. The rear wheel supporting portions 32L and 32R are, for example, arm members 28 as separate parts.
It is welded to L and 28R, and has an axle insertion hole 33 through which the axle of the rear wheel 3 is inserted and fastened.

By the way, the swing arm 9 is molded so that the side surface thereof has a substantially "V" shape due to the structure of the suspension mechanism 12 and the securing of the minimum ground clearance of the vehicle body.

A chain insertion portion 35 is provided at an intermediate portion of the swing arm 9. This chain insertion part
For example, 35 is formed in a tunnel shape having a rectangular cross section that penetrates the left side portion of the arm base 27 in the front-rear direction, and the upper chain line 18a of the chain 18 is inserted therein.

When the motorcycle 1 is running, the chain
18 enters the chain insertion portion 35 through an inlet 36 that is open on the rear side of the chain insertion portion 35, and exits through an outlet 37 that is open on the front side. Therefore, the chain 18 does not interfere with the swing arm 9 even if the swing arm 9 is formed in a substantially "V" shape.

As shown in FIG. 2, roller chain chain tensioners 38, 3 are provided in the vicinity of the drive sprocket 16.
9 is installed, and a chain slider 42 is installed on the lower front portion of the left rear wheel support portion 32L via a bracket 41. The chain sliders 38, 39, 42 are located at the positions of the chains.
18 pitches, rolls, slacks, etc. are absorbed.

In the present invention, the chain guide 43A is provided between the chain insertion portion 35 and the driven sprocket 17 of the rear wheel 3. FIG. 4 shows the chain guide 43A.
The detailed structure of the chain guide is shown in (A) above.
A perspective view of 43A as seen from the rear diagonal right, (B) is IVB-IVB of (A)
It is a longitudinal cross-sectional view of the chain guide 43A along the line.

The chain guide 43A is, for example, a guide bracket 44 formed by bending a steel plate into a substantially "S" shape.
And a guide piece fixed to this guide bracket 44
It consists of 45 and.

The guide bracket 44 includes a fixing portion 44a fixed to the upper surface of the left arm member 28L and the fixing portion 44a.
A standing portion 44b that rises vertically from the inner edge of 44a,
The upright portion 44b is provided with a projecting portion 44c that extends horizontally from the upper edge toward the inside of the vehicle body and covers the upper chain line 18a in an eaves-like shape.
The individual bolt holes 46 are bored, and the front and rear screw holes 47 are formed in the projecting portion 44c.

The fixing portion 44a is fixed to the upper surface of the left arm member 28L with two bolts 48.
May be directly welded and fixed to the upper surface of the arm member 28L.

On the other hand, the guide piece 45 is made of an elastic material such as rubber or synthetic resin, and the guide bracket 44
It has a bolt insertion hole 50 which is aligned with the position of the two screw holes 47 provided in the overhanging portion 44c. This bolt insertion hole
Two bolts 51 are inserted from below into 50, and the guide pieces 45 are fixed to the lower surface of the overhanging portion 44c by fastening the two bolts 51 into the screw holes 47 of the overhanging portion 44c.

Since the tubular spacer 52 made of steel is press-fitted into the bolt insertion hole 50, the fastening force of the bolt 51 does not deform the guide piece 45. The bolt insertion hole 50 is formed in a stepped shape so that the head of the bolt 51 does not protrude from the lower surface of the guide piece 45. Further, an inclined surface 45a that obliquely rises rearward is formed on the lower surface of the guide piece 45.

If such a chain guide 43A is provided on the swing arm 9, the chain 18 abuts the guide piece 45 of the chain guide 43 from below when the upper chain line 18a is vertically swung, so that the vertical movement of the chain 18 is prevented. Amplitude is significantly limited. Therefore, the vertical swing of the chain 18 between the driven sprocket 17 and the chain insertion portion 35 is effectively suppressed.

Since the guide piece 45 is made of an elastic material, the shock due to the collision of the chain 18 is effectively absorbed by its elasticity. Therefore, no unpleasant noise is generated.

Therefore, even if the swing arm 9 pivots up and down about the pivot shaft 8 as a fulcrum, the chain 18 will not be hit into the inlet 36 of the chain insertion portion 35 or the chain insertion portion 35, and the swing arm 9 And chains
18 wear and damage are prevented. Further, since the vertical vibration of the chain 18 is suppressed, there is no concern that the chain 18 will come off the drive sprocket 16.

FIG. 5 shows a chain guide 43B which is a second embodiment of the present invention, in which (A) is the chain guide.
FIG. 43B is a perspective view of the chain guide 43B as seen from the rear oblique right side, and FIG. The chain guide 43B includes a guide bracket 54 and a guide roller 55 pivotally supported by the guide bracket 54.

The guide bracket 54 includes a fixed portion 54a fixed to the upper surface of the left arm member 28L and the fixed portion 54a.
It has a standing portion 54b which rises vertically from the inner edge of 54a, and the fixed portion 54a has two bolt holes at the front and rear.
56 is bored, and this fixing portion 54a is fixed to the upper surface of the left arm member 28L with two bolts 57. The fixed part 54
The a may be directly welded and fixed to the upper surface of the arm member 28L.

On the other hand, the guide roller 55 is made of an elastic material such as rubber or synthetic resin, and has a bolt 58 and a nut.
59 is rotatably supported on the upper end of the upright portion 54b of the guide bracket 54, and the central axis of the guide roller 55 crosses the upper chain line 18a at a right angle.

Even when this chain guide 43B is provided,
When the upper chain line 18a is pitched, the chain 18 comes into contact with the guide roller 55 of the chain guide 43B, whereby the amplitude of the chain 18 is significantly limited and the pitching is suppressed. Therefore, the chain 18 is prevented from being hit into the inlet 36 of the chain insertion portion 35 and the inside of the chain insertion portion 35, the swing arm 9 and the chain 18 are prevented from being worn or damaged, and the chain 18 is removed from the drive sprocket 16. It gets harder.

Since the guide roller 55 of the chain guide 43B is rotatable with respect to the guide bracket 54, when the chain 18 comes in contact with the guide roller 55 from below, the guide roller 55 is free.
Rotates. Therefore, the running resistance of the chain 18 does not increase due to contact with the guide roller 55, and the guide roller 55 is also less likely to wear.

FIG. 6 shows a chain guide 43C which is a third embodiment of the present invention, in which (A) is the chain guide.
Perspective view of 43C as seen from the rear diagonal right, (B) is VIB-VIB of (A)
It is a longitudinal cross-sectional view of the chain guide 43C along the line.

In this chain guide 43C, a rectangular sleeve portion 61 inserted into the inlet 36 of the chain insertion portion 35 and a frame-shaped flange portion 62 connected to the rear portion of the sleeve portion 61 are made of rubber, synthetic resin or the like. The elastic material is integrally formed. A tubular spacer 63 made of steel is provided above and below the flange portion 62, and a bolt 64 inserted into the tubular spacer 63 from the rear side is provided with an inlet 36 of the chain insertion portion 35.
And the chain guide 43C is fixed to the inlet 36.

The height H1 of the upper wall 61a of the sleeve portion 61
Is lower than the height H2 of the inlet 36 of the chain insertion portion 35 by a dimension h, and the upper wall 61a is connected to the flange portion 62 by a smooth curved surface 65.

According to the chain guide 43C, when the upper chain line 18a is vertically pitched, the chain 18
Comes into contact with the upper wall 61a of the sleeve portion 61, which limits the amplitude of the chain line 18a and suppresses pitching. The shock caused by the collision of the chain 18 at this time is absorbed by the bending of the upper wall 61a of the sleeve portion 61.

For this reason, the chain 18 will not be struck by the inlet 36 of the chain insertion portion 35 or the inside of the chain insertion portion 35. Even if the chain 18 swings sideward or downward as well as upward, the swing is damped by the lower wall 61b and both side walls 61c of the sleeve portion 61, so that the chain 18 is inserted into the chain insertion portion 35. There is no direct collision.

Incidentally, this chain guide 43C and the chain guides 43A and 43B shown in the first or second embodiment.
If this is installed, the vertical vibration of the chain line 18a can be suppressed more effectively.

[0042]

As described above, in the swing arm of the motorcycle according to the present invention, the front end is pivotally supported by the pivot shaft of the body frame, the rear wheel is pivotally supported by the rear end, and the rear wheel is intermediately supported. In a swing arm of a motorcycle having a chain insertion part through which a driving chain is inserted, a chain guide is provided between the driven sprocket of the rear wheel and the chain insertion part for suppressing vertical swinging of the chain. To do.

For this reason, the pitching of the chain that attempts to enter the chain insertion portion is suppressed by the above-mentioned chain guide, and the chain cannot be struck at the entrance of the chain insertion portion or the chain insertion portion. Damage is prevented and no unpleasant noise is generated. Further, since the vertical swing of the chain is suppressed, there is no concern that the chain will come off the drive sprocket.

[Brief description of drawings]

FIG. 1 is a left side view showing an example of a motorcycle to which a swing arm according to the present invention is applied.

FIG. 2 is a left side view of a swing arm showing an embodiment of the present invention.

FIG. 3 is a plan view of a swing arm.

4A is a perspective view of the chain guide shown in FIG. 2 as viewed from the rear oblique right side, and FIG. 4B is a vertical cross-sectional view of the chain guide taken along line IVB-IVB in FIG. 4A.

FIG. 5 shows a second embodiment of the present invention, (A) is a perspective view of the chain guide as seen from the rear obliquely right side, and (B) is a VB of (A).
The side view of the chain guide seen from the arrow.

6A and 6B show a third embodiment of the present invention, in which FIG. 6A is a perspective view of the chain guide as seen from the rear oblique right side, and FIG. 6B is a VI of FIG.
A vertical cross-sectional view of the chain guide taken along the line B-VIB.

[Explanation of symbols] 1 Motorcycle 2 Body frame 3 Rear wheel 8 Pivot shaft 9 Swing arm 17 Driven sprocket 18 Chain 35 Chain insertion part 43A, 43B, 43C Chain guide

Claims (1)

[Claims] 1. A swing of a motorcycle having a front end pivotally supported by a pivot shaft of a vehicle body frame, a rear end pivotally supported by a rear wheel, and an intermediate portion having a chain insertion portion through which the rear-wheel drive chain is inserted. A swing arm for a motorcycle, characterized in that a chain guide is provided in the arm for suppressing vertical swinging of the chain between the driven sprocket of the rear wheel and the chain insertion portion.