GB2322909A

GB2322909A - Reduction mechanism for throttle linkages, eg for motorcycles

Info

Publication number: GB2322909A
Application number: GB9704736A
Authority: GB
Inventors: Jan Piotr Tchorzewski
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-03-07
Filing date: 1997-03-07
Publication date: 1998-09-09
Also published as: GB9704736D0

Abstract

The throttle linkage of a vehicle, eg a motorcycle, may be modified to give a greater movement of the throttle for a given movement of the throttle handle by installing a reduction mechanism between the throttle and the handle. The reduction mechanism may take the form of a pair of cable guides 16,18 which are fixed together and have different radii, eg in the ratio 2:1. To modify the linkage, the ferrule 6 of the Bowden cable is removed from the control handle and located in the smaller cable guide 18; an extension cable 34 is connected between the control handle and the larger cable guide 16.

Description

DEVICE AND METHOD This invention relates to a device for a motor vehicle, notably to a device for use with a throttle cable of a motorcycle or a motor car, and to a motor vehicle which is fitted with the device. The invention also provides a method of modifying a motor vehicle by fitting the device to it.

To open the throttle of a motorcycle, the rider typically turns a throttle control handle which is rotatably mounted around one of the handlebars. Turning the throttle control handle causes movement of a Bowden cable which is attached to a throttle control lever which opens or closes one or more throttle control valves in the carburettors.

The further the throttle control handle is turned, the more the throttle control valves are opened.

To improve the performance of a motorcycle, it has been proposed to modify the throttle control handle so that a given amount of turn produces greater opening of the throttle control valves. A problem with such modification is that the throttle control handle is typically combined with electronic controls for other functions of the motorcycle, for example lights and ignition. In order to modify the throttle control handle it has been found necessary to move the clutch reservoir and re-route the electric circuits in the combined throttle and electronics control. This procedure is expensive and time-consuming.

According to a first aspect of the present invention there is provided a motor vehicle which has a throttle control handle operatively connected to a throttle control valve in a carburettor of the vehicle engine, characterised in that a reduction mechanism is provided between the throttle control handle and the throttle control valve, whereby a given movement of the throttle control handle produces a larger movement of the throttle control valve.

By providing a reduction mechanism externally of the throttle control handle, no modification of the throttle control handle or the vehicle's electronics is required.

The reduction mechanism may comprise any suitable gearing means for effecting a greater movement in response to a smaller movement. The reduction mechanism may, for example, comprise a lever which has arms of different lengths or a gear arrangement comprising pulleys or arcuate cable guides of different radius which are yoked together, the smaller arcuate cable guide being connected to the throttle control handle and the larger arcuate cable guide being connected to the throttle control valve, for example via a throttle control lever. For convenience hereinafter, the invention will be described with reference to such a gear arrangement. However it is to be understood that the invention is not limited to this embodiment.

In a preferred embodiment, the gear arrangement is mounted on or adjacent to one or more of the carburettors. This allows a conventional motor vehicle to be subsequently modified by fitting of the gear arrangement, which may be achieved by disconnecting the throttle cable from the throttle control lever and connecting the throttle cable to the small arcuate cable guide of the gear arrangement.

An extension throttle cable is then connected between the large arcuate cable guide of the gear arrangement and the throttle control lever.

The invention is suitable for use with any motor vehicle which has a throttle, but it is particularly suitable for use with a motorcycle, and the invention will be described hereinafter with reference to this embodiment. However it is to be understood that the invention is not limited to this embodiment.

The reduction mechanism may be sold separately, for use in modifying a motor vehicle.

In accordance with another aspect of the present invention there is therefore provided a reduction mechanism for modifying the throttle operation of a motor vehicle which has a throttle control handle operatively connected to a throttle control lever by a throttle cable, the mechanism comprising: a) a housing for mounting in relation to at least one carburettor of the vehicle engine; b) gearing means mounted on the housing, for connection to the throttle cable; and c) means for operatively connecting the gearing means and the throttle control lever whereby when the handle is connected to the lever via the mechanism, a given movement of the handle produces a greater movement of the lever than when the handle is directly connected to the lever.

The connecting means preferably comprises an extension cable.

According to a further aspect of the present invention there is provided a method of modifying a motor vehicle as defined in Claim 12.

The invention will now be further described, by way of example, with reference to the following drawing in which: Figure 1 is a perspective view of a motorcycle engine carburettors in accordance with the prior art; Figure 2 is a perspective view of a reduction mechanism in accordance with one aspect of the present invention, for use with the motorcycle engine carburettors of Figure 1; Figure 3 shows the throttle cable of the engine of Figure 1 on which has been mounted a spacer; Figure 4 shows the connection of the throttle cable shown in Figure 3 to the housing of the mechanism shown in Figure 2; Figure 5 is a perspective view of a reduction mechanism in accordance with the present invention mounted on a motorcycle engine carburettor; Figure 6 is a front elevation view of the mechanism of Figure 5; Figure 7 is a plan view of the mechanism of Figure 5; and Figure 8 is a side elevation view of the mechanism of Figure 5.

The known motorcycle engine carburettors 8 shown in Figure 1 each have a throttle control valve (not shown) which is operated by a common throttle control lever 2. The throttle control lever 2 is connected to the throttle cable 4 by a ferrule 6 on the end of the cable 4 which is adapted to be located in and retained by a recess in the adapted to be located in and retained by a recess in the lever 2. The cable 4 is disposed through a screw-threaded shank 44 (best seen in Figure 3) and secured in position between the carburettors 8 by locating the shank 44 in a hole in a lug 12 on a carburettor 8. A nut 46 is used to secure the shank 44 in the lug 12.

The other end of the cable 4 is connected to a throttle control handle (not shown) on the motorcycle. By twisting the handle, the cable 4 is pulled upwardly and the lever 2 is operated to open up the throttle. When the handle is released, a spring bias restores the handle and the cable 4 to an equilibrium position.

The reduction mechanism shown in Figure 2 comprises a housing 14 on which is rotatably mounted by means of a pin 24 a pair of arcuate cable guides 16, 18 which are fixed together. The arcuate cable guides are of different radius, the larger arcuate cable guide 16 having twice the radius of the smaller arcuate cable guide 18. Each arcuate cable guide has a recess 20, 22 for receiving a ferrule of similar dimension to the ferrule 6 on the cable 4. Apertured lugs 26 are provided on the housing 14 which are dimensioned and located so that the apertures may be brought into registration with apertures on corresponding lugs 10 on the carburettors 8. The housing 14 has a guide hole 28 for receiving a throttle cable 4.

The reduction mechanism also includes an extension cable 34 which is disposed through a threaded shank 36 with a bolt head 40 and a locking nut 38. The extension cable 34 has a ferrule 32 at the top end for fitting into the recess 20 in the large arcuate cable guide 18, and a ferrule 32 at the bottom end for fitting into the recess in the throttle control lever 2.

An optional spacer 30 is provided, for holding the sheath 42 of the cable 4 at a preset distance from the housing 14 when the reduction mechanism is in operation, as will be discussed below.

To modify the throttle arrangement of the engine carburettors shown in Figure 1, the ferrule 6 is removed from the throttle control lever 2, and the nut 46 is unscrewed from the shank 44. The throttle cable 4 is lifted and removed through a slot in the lug 12. The spacer 30 is placed around the shank 44 of the throttle cable 4, as shown in Figure 3. Screws are removed from the lugs 10 of the carburettor top cap on the adjacent carburettors 8. The shank 44 is passed through the hole 28 in the housing 14 of the reduction mechanism and the ferrule 6 is secured in the recess in the small arcuate cable guide 18.

The ferrule 32 on the bottom of the extension cable 34 is secured in the recess in the throttle control lever 2, and the extension cable 34 is passed through the slot in the lug 12 on the carburettor 8. The shank 36 on the extension cable 34 is then located in the hole in the lug 12 and the nut 38 is tightened to secure the shank 36 relative to the carburettors. The upper ferrule 32 on the extension cable 34 is then secured in the recess 20 on the large arcuate cable guide 16.

The lugs 26 on the housing are located over the lugs 10 on the top caps of the carburettors 8 so that both sets of holes are in register, and the housing 14 is secured between the carburettors 8 by means of the screws which were previously removed from the lugs 10 of the carburettor top caps. The modified throttle arrangement is shown in Figures 5 to 8.

If necessary, the throttle control handle may be adjusted to take up any slack in the throttle cable. This is a simple procedure which requires adjustment of a screw.

With the modified throttle arrangement, turning of the throttle control handle produces a greater opening of the throttle. The extension cable 34 moves twice the distance of the throttle cable 4. Although a 2:1 gearing ratio is preferred, it will be appreciated that other gearing ratios may be employed.

Claims

1. A motor vehicle which has a throttle control handle operatively connected to a throttle control valve in a carburettor of the vehicle engine, characterised in that a reduction mechanism is provided between the throttle control handle and the throttle control valve, whereby a given movement of the throttle control handle produces a larger movement of the throttle control valve.

2. A motor vehicle as claimed in claim 1, wherein the reduction mechanism comprises a gear arrangement mounted on or adjacent to a carburettor of the vehicle engine.

3. A motor vehicle as claimed in claim 1 or claim 2, wherein the reduction mechanism comprises a housing which is mounted on or adjacent to a carburettor of the vehicle engine, the housing having a pair of arcuate cable guides which are yoked together and rotatably mounted on the housing, the arcuate cable guides having different radii, wherein the smaller arcuate cable guide is connected to the throttle control handle and the larger arcuate cable guide is connected to the throttle control valve.

4. A motor vehicle as claimed in any one of the preceding claims, wherein the reduction mechanism is connected to the throttle control valve via a throttle control lever.

5. A motor vehicle as claimed in any one of the preceding claims, wherein the vehicle is a motorcycle.

6. A motor vehicle as claimed in any one of the preceding claims, wherein the reduction mechanism has a gear ratio of about 2:1.

7. A reduction mechanism for modifying the throttle operation of a motor vehicle which has a throttle control handle connected to a throttle control lever by a throttle cable, the mechanism comprising: a) a housing for mounting in relation to at least one carburettor of the vehicle engine; b) gearing means mounted on the housing, for connection to the throttle cable; and c) means for operatively connecting the gearing means and the throttle control lever whereby when the handle is connected to the throttle lever via the mechanism, a given movement of the handle produces a greater movement of the throttle lever than when the handle is directly connected to the throttle control lever.

8. A reduction mechanism as claimed in claim 7, wherein the gearing means comprises a pair of arcuate cable guides which are yoked together and rotatably mounted on the housing, the arcuate cable guides having different radii and the smaller arcuate cable guide being adapted to be secured to one end of the throttle cable, and wherein the means for connecting the gearing means to the throttle control lever comprises an extension cable adapted at one end to be secured to the larger arcuate cable guide and at the other end to be secured to the throttle control lever.

9. A reduction mechanism as claimed in claim 7 or claim 8, wherein the housing has a hole for receiving a screwthreaded shank on the throttle cable, further including a spacer arranged to be secured around the screw-threaded shank to limit the distance the shank can protrude into the housing.

10. A reduction mechanism for modifying the throttle operation of a motor vehicle which has a throttle control handle operatively connected to a throttle control lever by a throttle cable, substantially as herein described with reference to Figures 2 to 8 of the drawing.

11. A motor vehicle as claimed in Claim 1, substantially as herein described with reference to Figures 2 to 8 of the drawing.

12. A method of modifying a motor vehicle which has a throttle control handle operatively connected to a throttle control lever to give improved throttle response, the method comprising the steps of disconnecting the throttle cable from the throttle control lever, securing a reduction mechanism in relation to at least one of the carburettors of the vehicle engine, connecting the throttle cable to the reduction mechanism and connecting the reduction mechanism to the throttle control lever so that a given movement of the throttle cable produces a greater movement of the throttle control lever than when the throttle cable is directly connected to the throttle control lever.