Rear wheel damping device for a motorcycle

Field of Invention

The present invention relates to a "Rear wheel damping device for a motorcycle" and more particularly to the cush drive means provided in the rear wheel of a motorcycle which provides necessary damping for smooth transmission of the drive from the engine to the driven wheel.

Background of the Invention:

Typically in any two wheeler such as a motorcycle, the drive torque is transmitted from the engine to the driven wheel sprocket mounted on the rear wheel assembly.

The cush drive rubber held between driven wheel sprocket and the wheel hub deforms elastically in the circumferential direction and provides required damping to allow smooth transmission of drive torque from the driven sprocket to the wheel. In the known prior arts the cush drive means are solid elastomer blocks or elastomer with metal inserts. The current known cush drive means have a higher stiffness with less increase in compression value as the rubber gets compressed during torque transmission and will not effectively dampen out variations in the drive torque. Even though stiffness of the cush drive means can be reduced by reducing the hardness of the cush drive means to solve the problem, the said cush drive will tend to deform elastically causing bulging in the axial direction deteriorating the cush drive means.

Hence the objective of the invention to provide a cush drive means overcoming the above problems associated with the prior art.

Summary of the Invention:

Accordingly, it is an object of the present invention to provide a rear wheel damping device for a motorcycle with a improved cushioning means.

Another objective of the present invention is to provide a cush drive means which will provide a differential stiffness in the required direction.

Yet another objective of the present invention is to provide a cush drive means to elastically deform without bulging in the axial direction.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Brief Description of the Drawings:

The invention in its preferred embodiments will be more particularly described by reference to the accompanying drawings, in which like parts are designated by the same numerals in the various figures and in which:

Fig. 1 illustrates a motorcycle;

Fig. 2 is exploded view of the wheel.

Fig. 3 shows the rear damping device.

Fig.4 shows one of the embodiments of the present invention.

Fig. 5 shows second embodiment according to the present invention.

Fig. 6 shows third embodiment according to the present invention.

Fig. 7 shows fourth embodiment according to the present invention.

Detailed Description of the Drawings:

A preferred embodiment of the present invention will be described hereunder with reference to the accompanying drawings.

First, with reference to Figure 1 a motorcycle comprises of a frame (101), front fork (102) attached to a pivot tube (201) of the vehicle frame, a front wheel (103) attached to these front forks (102), a handle bar (104) connected to the front forks (102), a fuel tank (105) attached so as to straddle an upper part of the vehicle frame, a seat (106) attached to the upper rear portion of the vehicle frame, an engine unit (107) attached to the lower front section of the vehicle frame, a swing arm (108) attached to a lower rear section of the vehicle frame, suspended by a rear shock absorber (not shown) from the vehicle frame and a rear wheel attached to a rear end of swing arm (108). The intake system of the engine comprises of a fuel air metering device such as a carburettor (109), intake duct and an air cleaner. The exhaust system of the engine comprises of exhaust pipe and a muffler. The motorcycle is also provided with a side cover for covering a side section of the vehicle frame, a seat cover for covering a rear section of the vehicle frame below the seat, a front fender (110) for covering an upper part of the front wheel (103), and a rear fender (111) for covering an upper part of the rear wheel (112). The drive from the engine (107) is transmitted from the engine to the driven wheel sprocket mounted on the rear wheel hub mounted on the rear wheel assembly.

Referring to figure 2 the rear wheel damping device (201) body is preferably made up of rubber like elastic material. The damping device or cosh drive (201) is held between the driven wheel sprocket (202) and the wheel hub (203) with the help of the teeth (or driving lug) (204) located on the sprocket carrier (205) and the teeth, wall or separator (206) on wheel hub (203). The said separator (206) goes into the gap between the damping devices

The rubber like damping device (201) deforms elastically in the circumferential direction and provides the necessary damping to allow smooth transmission of drive torque from the driven sprocket to the wheel.

Referring to figure 3, the damping device body (201) is having a cavity (301), to house the projected tooth (or lug) (204) which is attached to driven sprocket carrier (205). The said cavity is substantially placed in the middle portion of the damping device body, dividing the whole body into two segments or parts. One segment or part is referred to as compression side (302) and the other as non compression side (303).

The motorcycle when viewed from the left, the rear wheel being on rear side and the anti clockwise rotation (marked as direction A) of the damper device (201) by the wheel hub is herein understood as the compression side of the damper body. The clockwise rotation direction of the said damper device is referred to as non compression side (303).

A few numbers of holes or slots (which are preferably see thru holes) are provided in the damper device (201) on its compression side (302). When the load input from the teeth of the driven sprocket is transmitted to the said cavity (301) on the damper device body (201) in the anticlockwise direction, the change in the shape of the holes reduce the stiffness and allow the damping device to elastically deform without bulging in the axial direction. The axial bulging is avoided as the said holes or slots will change its shape during the load transmission.

A low stiffness persists till the said holes or slots change it's shape due to compression which results in more or less closure of the holes in the circumferential direction and then a higher stiffness after that. The values of the stiffness and the point after which the stiffness changes can be controlled by varying the shape and size of the holes or slots, thereby some of the said holes/slots can be closed earlier than the others. Similar effects can be achieved also by positioning the holes or slots in different manner.

According to the first embodiment of the present invention (as shown in figure 4) few holes are located in the compression side (or drive face) (302) of the damper device body (201). The said holes are preferably placed on the perpendicular line drawn to the edge of the compression side (302). According to the second embodiment of the present invention (as shown in figure 5) a slot (501) is made at the centre of the compression side. Few holes are formed on top and bottom of the said slot (501), formed on a pitch circle drawn radially inward.

According to the third embodiment of the present invention (as shown in figure 6) holes are arranged in a staggered fashion in the compression side (or drive face) of the damper device body.

According to the fourth embodiment (as shown in figure 7) of the present invention the holes are arranged in a two straight vertical line, one being just along the side of the cavity on the compression side ( or drive face) and the other being on the extreme outer edge on the compression side of the damper device body.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the claims.

We claim:
1. A motorcycle with a rear wheel damping device held between the driven wheel sprocket carrier and the wheel hub with the help of the teeth on driven sprocket carrier and the separator on wheel hub comprising:

a cavity to house the projected teeth located on driven sprocket carrier; and

at least one hole to prevent the rubber from bulging axially;

wherein the said damping device achieves a variable stiffness.

2. The rear wheel damping device as claimed in claim 1, wherein the said damping device is preferably made up of rubber.

3. The rear wheel damping device as claimed in claim 1, wherein the said cavity is preferably in rectangular cut out section.

4. The rear wheel damping device as claimed in claim 1, wherein the said hole is number of holes.

5. The rear wheel damping device as claimed in claim 1and claim 4, wherein the said holes are located in the compression side of the said cavity.

6. The rear wheel damping device as claimed in claim 1, wherein the said holes are arranged vertically.

7. The rear wheel damping device as claimed in claim 1, wherein the said holes are arranged diagonally.

8. The rear wheel damping device as claimed in claim 1, wherein the said holes are arranged along with a slot at the centre in the compression side.

9. The rear wheel damping device as claimed in claim 1, wherein the said holes are formed on a pitch circle drawn in a radially inward circumferential position.