GB2092532A

GB2092532A - Motorcycle wheel suspension

Info

Publication number: GB2092532A
Application number: GB8100667A
Authority: GB
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1979-02-13
Filing date: 1980-02-12
Publication date: 1982-08-18
Also published as: DE3005167A1; GB2067144A; GB2067144B; GB2045178B; GB2092532B; GB2045178A

Abstract

A motorcycle includes a main frame (1), a rear wheel support (3) pivotally mounted on the main frame for upward and downward movement relative thereto, and a shock absorber (7) pivoted (at 8) to the frame (1) and (at 9) to a plate (5), the latter being pivoted (at 6) to the support (3) and (at 11) to a rod (10) in turn pivoted to the frame (1) (at 12). As the support (3) swings upwardly in use the plate (5) turns anti-clockwise as viewed in Fig. 1 so causing additional compression of the shock absorber over and above that imparted by the support (3) and producing a progressive rise in the spring rate of the shock absorber. <IMAGE>

Description

1

SPECIFICATION

Motorcycle rear wheel suspension This invention relates to a motorcycle rear 70 wheel suspension.

In the past, there has been known a motor cycle rear wheel suspension in which a rear wheel support such as a rear fork, supporting a rear wheel is mounted on the main frame of the motorcycle at the rear thereof for up and down swinging movement, and in which a rear shock absorber is connected between the main frame and the rear wheel support. How ever, such a rear wheel suspension is disad vantageous in that the greater the load carried by the motorcycle, the worse becomes the riding comfort.

According to the present invention there is provided a motorcycle rear wheel suspension comprising a main frame of the motorcycle, a rear wheel support pivotally mounted on the main frame for upward and downward move ment relative thereto and rotatably supporting a rear wheel, rear shock absorber means dis posed between the main frame and the rear wheel support for damping the relative move ment between the main frame and the rear wheel; lever plate means pivotally mounted on the rear wheel support which is of triangu lar configuration with the lever plate means mounted at an upper apex, the rear shock absorber means being pivotally connected at one end to a rear upper portion of the main frame and at the other end to a first arm of the lever plate means; and pull rod means pivoted at one end to a second arm of the lever plate means and at the other end to a rear lower portion of the main frame; the co operation between the lever plate means, the pull rod means and the shock absorber means being such that the damping force of the shock absorber means varies in a manner such that the rate of increase in the compres sion stroke of the shock absorber means is increased in proportion to increasing upward displacement of the rear wheel relative to the main frame. Upward displacement of the rear wheel relative to the main frame increases with increasing load on the motorcycle. By increasing the rate of increase in compression stroke of the rear wheel shock absorber in proportion to increasing upward displacement of the rear wheel relative to the main frame, the rear shock absorber is able to absorb in an effective manner the greater amount of shock occurring under increased load, whereby rid ing comfort, and running performance of the motorcycle, is improved. The present rear wheel suspension can be small in size and adapted for installation in a limited available space, light in weight, excellent in durability and can perform its intended functions over long periods of use.

For a better understanding of the invention, 130 GB2092532A 1 and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:- Figure 1 is a schematic side view of a motorcycle main frame and rear wheel suspension; Figure 2 is a partial view of the suspension of Fig. 1 taken on line 1111 of Fig. 1; and Figure 3 is a graphic representation showing the relationship between displacement of the rear wheel and the compression stroke of a rear shock absorber.

Referring first to Figs. 1 and 2, reference numeral 1 indicates the main frame of the motorcycle, to the rear of which is pivotally connected at 2 a rear wheel support in the form of a rear fork 3 that is connected at its forward end to the main frame 1 for relative upward and downward swinging motion. The rear fork 3 has a pair of side fork members between which a rear wheel 4 is rotatably supported and each of which is in the form of a triangle. A single belicrank lever 5 rotatably mounted, at 6, on the pair of triangular side fork members at their upper apices, has a forwardly directed arm pivoted, at 11, to a single pull rod 10 which is pivotally connected, at 12, to the main frame 1. A rear- wardly directed arm of the lever 5 is pivoted, at 9, to the rear end of a single shock absorber 7 which lies in a vertical plane passing through the central longitudinal axis of the main frame 1. At its front end this shock absorber 7 is pivotally connected, at 8, to the rear upper part of the main frame 1.

Turnably mounted in the main frame 1 at its forward end is a front fork 13 which rotatably supports a front wheel 14.

In operation when the rear wheel 4 is caused to move up and down relative to the main frame 1 during travel of the motorcycle, the rear fork 3 is swung upwardly and downwardly around the pivot point 2 so that the shock absorber 7 contracts and expands to absorb impactive loads transmitted to the main frame 1. As the rear fork 3 swings upwardly around the pivot connection 2, the lever 5 is caused to rotate in an anti- clockwise direction (Fig. 1) relative to the rear fork 3 under the action of the pull rod 10 whereby the amount of movement of the pivot connection 9 is equal to the sum of the upward displacement of the rear fork 3 and the amount of rotation of the lever 5. As a result, as the shock absorber 7 is forced to contract, the amount of this contraction of the rear shock absorber 7, pivoted at 9 to the rearwardly directed arm of the lever 5, is equal to the sum of the amount of movement of its pivot connection 9 due to the upward movement of the rear fork 3, and the amount of rotation of its pivot connection 9 due to the anticlockwise rotation of its lever 5. Therefore, because the rate of displacement of the pivot 2 GB 2 092 532A 2 connection 9 in the direction of the axis of contraction and expansion of the shock ab sorber 7 due to the rotation of the [ever 5 increases in proportion to the upward move ment of the rear fork 3, the rate of increase in contraction of the shock absorber 7 is in creased in accordance with the upward move ment of the rear wheel 4. This is graphically illustrated in Fig. 3 in which reference charac ters L and 8 represent the upward displace ment of the rear wheel 4 and the amount of contraction of the shock absorber 7, respec tively. As apparent from this Figure, the con traction characteristic of the rear shock ab sorber 7 is shown by a parabolic curve. This means that as the amount of the upward movement of the rear wheel 4 is made greater due to increase in load imposed on the main frame 1 and/or due to the increase of exter nal forces acting from the road surface on the rear wheel 4, the amount of contraction of the rear shock absorber 7 is accordingly increased to render its damping characteristic harder so that the greater quantity of impactive forces exerted on the rear wheel 4 can be absorbed effectively thereby to improve the riding com fort and running performance to a substantial extent irrespective of variations in load on the main frame 1. In this case, during contracting movement of the rear shock absorber 7, the pull rod 10 is subjected only to tensile forces and not to twisting or bending forces and therefore it can have a relatively small cross section and yet be strong enought to with stand the tensile forces acting thereon. 100 In the foregoing the rear fork 3 is used as the rear wheel support but instead a swing arm of cantilever type could be used, support ing the rear wheel only at one side of the main frame.

To summarize, in the suspension described [ever plate means (the bellcrank lever 5) is arranged such that it is rotated relative to a rear wheel support (the rear fork 3 or a swing arm) in accordance with upward swing of this support to impart a compressive force to rear shock absorber means (the shock absorber 7) disposed between the main frame and the rear wheel support thereby to vary the damp ing force of the shock absorber means, as a consequence of which it becomes possible to set the rate of increase in the compression stroke of the shock absorber means at any desired value in a simple and easy way, thus improving the riding comfort and running performance of the motorcycle irrespective of the variation of loads carried thereon.

Further, since pull rod means (the rod 10) serving to impart torque to the lever plate means and subjected only to a tensile force but not to twisting, bending or like other undersirable forces and hence formed of rela tively small rod having a limited cross sec tional area, is used in conjunction with lever plate means of minimum size, it is possible to fabricate the entire assembly in a very compact and light-weighted manner adapted for installation in a limited space without increasing the total weight of the motorcycle.

Claims

1. A motorcycle rear wheel suspension comprising a main frame of the motorcycle, a rear wheel support pivotally mounted on the main frame for upward and downward movement relative thereto and rotatably supporting a rear wheel, rear shock absorber means disposed between the main frame and the rear wheel support for damping the relative move- ment between the main frame and the rear wheel; lever plate means pivotally mounted on the rear wheel support which is of triangular configuration with the lever plate means mounted at an upper apex, the rear shock absorber means being pivotally connected at one end to a rear upper portion of the main frame and at the other end to a first arm of the lever plate means; and pull rod means pivoted at one end to a second arm of the lever plate means and at the other end to a rear lower portion of the main frame; the cooperation between the lever plate means, the pull rod means and the shock absorber means being such that the damping force of the shock absorber means varies in a manner such that the rate of increase in the compression stroke of the shock absorber means is increased in proportion to increasing upward displacement of the rear wheel relative to the main frame.

2. A motorcycle rear wheel suspension as claimed in claim 1, wherein said first arm of the lever plate means extends rearwardly from the pivot connection of the lever plate means with the rear wheel support, and wherein said second arm extends forwardly from this pivot connection.

3. A motorcycle rear wheel suspension as claimed in claim 1 or 2, wherein said first arm of the lever plate means extends upwardly from the pivot connection of the lever plate means with the rear wheel support.

4. A motorcycle rear wheel suspension as claimed in any one of the preceding claims, wherein the lever plate means comprises a oellcrank lever.

5. A motorcycle rear wheel suspension substantially as hereinbefore described with reference to Figs. 1 and 2 and 3 of the accompanying drawings.

Printed for Her Majesty's Stationery Office by Burgess F Son (Abingdon) Lid-1982. Published at The Patent Office, 25 Southampton Buildings, London, WC2A 1AY, from which copies may be obtained.

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