Bump-stopper for a scooter type motorcycle

Field of the invention:

The present invention relates to a "Bump-stopper for a scooter type motorcycle" and particularly to a bump stopper used in the toggle link of scooter type motorcycles having swingably mounted engines.

Background of the invention:

A bump-stopper typically made of rubber or any other elastomer, is part of the toggle link, which is used in scooter type motorcycles to connect the engine and the frame. A bump-stopper has many functional requirements. In two- wheelers with swingably mounted engines, where the rear wheel is attached to the engine, a bump-stopper is used to isolate and damp the engine vibrations and road undulations. The bump-stopper is also used to stop the to and fro angular movement of the toggle link beyond a specified limit, an illustration of the above can be given in the following way.

When the rear wheel of the scooter passes over a bump, the engine is lifted up, at the same time the engine mount axle pivot which is the point that connects the front of the engine to the toggle link, will move downwards. When the engine mount axle goes down with respect to the frame mount pivot where the toggle link is attached to the frame, the top portion of the bump- stopper mounted on the toggle link bracket will get compressed over the main tube of the frame.

Similarly, when the wheel passes over a pothole the engine mount axle will come down with respect to the frame mount pivot due to the engine mass.

This will lead to the top portion of the bump-stopper to get compressed over the main tube of the frame.

In the known prior art, bump-stopper with corrugations on its surface is used as a cushioning member to limit the to and fro angular movement of the toggle link. Slight variable stiffness can be achieved using this corrugation. However the stiffness of this bump-stopper can be used to contain only small undulations. In case of large undulations, when it has to act like a solid, there is metal-to-metal contact (i.e., contact between toggle link bracket and main tube of the frame), which will increase the impact for high wheel loads. This might also lead to failure of the bracket, and also the arrangement necessarily makes the bracket design complex.

Furthermore, certain other prior arts use two bump-stoppers of variable height that are placed along the toggle link bracket. In such a case, one bump- stopper is used to contain certain to and fro angular movement, and the second stopper comes in contact for high loads, thereby providing high stiffness to stop the toggle link's further motion and avoid metal-to-metal contact. However in this design, the number of parts is more, which increases the cost of the parts and is not fool proof since the both the parts can be interchanged in assembly time. In the event of such a situation the ride comfort will deteriorate and also the possibility of engine fouling with the nearby parts.

Hence the objective of the present invention is to provide a bump-stopper for a swingably mounted engine in a scooter type motorcycle overcoming the problems associated with the prior arts and which can be fabricated as a single piece, is simple to design and manufacture and can be assembled at ease.

Brief description of the invention

The basic profile of the bump stopper is curved at top and bottom surface so as to make area contact with the main tube, which is cylindrical. This area contact helps in uniform loading of bump stopper and bump stopper-mounting bracket thereby reducing the stress on bracket. The bracket is slotted to hold the bump stopper. The top portion of bump stopper is stepped to achieve high variable stiffness ratio. The top step comes into contact for small rotation of toggle link, provide low stiffness to results in better vibration isolation and reduce road shocks. After certain rotation, entire area comes in contact with the main tube exerting very high stiffness when the toggle link motion has to be stopped. Thus a high differential stiffness ratio is achieved using a single bump stopper with this design.

Similar to other designs, apart from providing step, the top step and bottom portion of bump stopper is corrugated to have less stiffness ratio initially.

Also holes can be kept in both top and bottom portion of the bump stopper. These holes are the tuning parameters whose dimension and size can be adjusted based on the requirement. Also there is a possibility of inserting other materials in some of the holes to increase the stiffness that cannot be obtained by only rubber or any other elastomer.

Brief description of drawings

Figure 1 illustrates side view of a scooter type motorcycle according to the present invention

Figure 2 illustrates the bump stopper and its arrangement in the scooter type motorcycle according to the present invention

Figure 3 illustrates the mounting of bump stopper according to the present invention

Figure 4 illustrates the bump stopper according to the present invention

Detailed description of the invention:

A selected illustrative embodiment of the present invention will be now described with respect to the accompanying figures 1,2,3 and 4. Figure 1 illustrates the side view of a concerned scooter type motorcycle wherein all the embodiments. Scooter-type vehicles, or scooters, include a frame assembly, which usually supports the body of a scooter, along with front and rear wheels. A frame assembly for a scooter-type vehicle comprises of at least one front wheel, at least one rear wheel and a vehicle body.

Typically, a frame structure 501 for a scooter type motorcycle comprises a main frame and may also have a sub-frame. The sub-frame is attached to the mainframe using appropriate fastening members. All the other components such as the body panels 509, the engine 502, and the electrical units are mounted on the main frame and the sub frame either directly or by means of brackets and fastening members.

The frame assembly includes a head tube, which supports a front wheel suspension assembly 503 of the vehicle. An upper frame extends from the head tube to a rearward end of the vehicle body. A swing arm 504 is pivotally supported by the upper frame and supports a rear wheel of the vehicle. The frame assembly may include a lower frame removeably coupled to the upper frame and defining a space there between.

Typically, front 503 and rear 504 suspension assemblies are operatively positioned between the front and rear wheels and the frame assembly. The front suspension assembly commonly is a telescopic fork arrangement, while the rear suspension assembly is a swing type arrangement. In a scooter, the rear suspension swing arm typically supports a power unit 502, which is configured to drive the rear wheel of the scooter.

The power unit 502, is coupled along with a transmission assembly 508, such as a drive shaft, drive belt, or chain and sprocket assembly.

The frame assembly 501 of a scooter-type vehicle is an elongated structure, which typically extends from a forward end to a reanward end of the scooter. A scooter frame assembly generally is convex in shape, as viewed from a side elevational view. A handlebar assembly 505 and a seat assembly 506 are supported at opposing ends of the frame assembly and a generally open area is defined there between.

Accordingly, the open area 507 between the handlebar assembly and the seat assembly allows the scooter to be easily straddled, or mounted, as opposed to a typical motorcycle, wherein a motorcycle fuel tank occupies the space between the handlebar assembly and the seat assembly. Such an arrangement may be referred to as a "step-through" frame assembly. The scooter type motorcycle has a main frame 501 extending along the center of the body and is made of a metallic pipe. The swing type power unit is coupled to the rear end of the main frame with the help of a link 201. This link is called the toggle link 201. The front portion of the power unit 502 is attached to the rear part of the toggle link 201. A rear wheel 202 is supported on one side of the rear end of the swing type power unit 502. The rear part of the power unit 502 is suspended using a spring to the rear end of the frame 501 of the scooter.

The front portion of the toggle link 201, called the frame mount tube, is attached to the frame 501 of the scooter.

An elongated bracket 203, which extends from the frame mount tube, is called the toggle link bracket 203. A keyhole shaped slot (not shown in the drawing) is provided on the front end of the toggle link bracket 203 to house the bump- stopper 205. The toggle link bracket 203 is adapted to be housed inside the rear end of the main tube of the frame 501.

The bump-stopper 205 is mounted between the main tube of the frame and on the toggle link bracket 203, and on both sides of the said bracket 203. The area of contact helps in uniform loading of the bump-stopper 205 and the toggle link bracket 203 thereby reducing stress on the bracket 203. This bump-stopper 205 is used to isolate and damp the engine 502 vibrations and the road undulations.

The said bump-stopper 205 is of two cuboids shaped rubber or any other elastomer member, split in the middle portion and connected through a keyhole shaped bridge 207 thereby making a single integrated unit. The top 208 and bottom 209 portion is curved so that it enables area contact with the main tube of the frame 501, which is cylindrical in shape. The top 208 and bottom surface 209 of the bump stop rubber 205 are corrugated externally.

The continuous peripheral landscape forming part of the external corrugations in cross section present a ridged external surface. The intervening grooves 210 are suitably of trough or U shape. One side 209 of the cuboids shaped bump-stopper (bottom surface) is parallel to the split wall made in the middle portion of the stopper and is provided with corrugations. The other side 208 (top surface) of the said stopper is a stepped surface, half of which is corrugated and the other half made plain.

Thus, the top portion of the said bump-stopper 205 is stepped to achieve high variable stiffness ratio. When the wheel 202 travels over small undulations the engine oscillations will be less. These small oscillations can be dampened out by the corrugated step 212 provided, which offers low stiffness that results in better vibration isolation and helps to reduce road shocks.

On the other hand when a big bump or a pothole is to be traversed, the wheel 202 travel will be more and the engine 502 tends to oscillate more, which is undesirable. To stop the engine oscillation and thereby the toggle link motion the stepped portion 212 compresses completely and the entire area of the top portion 208 of the bump-stopper 205 comes in contact with the main tube exerting very high stiffness. Thus a high differential stiffness ratio is achieved using a single bump-stopper 205 with this design.

When the vehicle is in motion the bottom portion 209 of the bump-stopper 205 may or may not touch the main tube of the frame 501. However, when it touches, the corrugations 211 provided on the bottom portion 209 isolates the engine vibration from the frame 501.
Also holes 213 are provided in both top and bottom portion of the said stopper 205. These holes 213 are the tuning parameters whose dimensions and orientations are adjusted based on the requirements. There is a possibility of inserting other materials in the holes 213 to vary the stiffness of the bump- stopper 205.

The present invention also takes care of the assembly of the bump-stopper 205 so as to avoid wrong mounting of the member 205. Wrong mounting of the said stopper 205 in the bracket 203 would lead to ride discomfort and various other problems such as fouling of the engine 502 or toggle link 201 with other nearby parts.

In order to ensure that the bump-stopper 205 is assembled with the corrugated stepped surface 211 on the top 208, a small cylindrical pip 214 is provided on one of the sides in the top portion 208 of the bump-stopper 205. When the bump-stopper 205 is mounted upside down this projection 214 will hit against the mounting bracket and prevent the same from being mounted wrongly.

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 scooter type motorcycle comprising an engine, a frame connected to the said engine through a toggle link assembly, the said toggle link assembly comprising a bump stopper on a bracket wherein the said bump stopper comprises at least a cuboid shaped elastomer.

2. The bump stopper as claimed in claim 1, wherein the said cuboid shaped elastomer is split in middle portion and connected through a keyhole shaped connecting bridge.

3. The bump stopper as claimed in claim 1, wherein the top and bottom surfaces of the said cuboid shaped elastomer is curved.

4. The bump stopper as claimed in claim 1, wherein the top and bottom surfaces have external corrugations.

5. The bump stopper as claimed in claim 1, wherein one side of the said bump stopper is parallel to split wall and provided with corrugations and the other side is a stepped surface having a portion of plain surface.

6. The bump stopper as claimed in claim 1, wherein holes are provided on the peripheral surface of said bump stopper.

7. The bump stopper as claimed in claim 1, wherein a pip is provided on one of the sides of either top or bottom portion of the said bump stopper.