GB2067144A

GB2067144A - Motorcycle wheel suspension

Info

Publication number: GB2067144A
Application number: GB8100668A
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: 1981-07-22
Also published as: GB2067144B; GB2092532B; GB2092532A; DE3005167A1; GB2045178B; GB2045178A

Abstract

A motorcycle includes a main frame (1), a rear wheel support (3) pivotally mounted (at 2) on the main frame for upward and downward movement relative thereto and a shock absorber (7) pivoted (at 108) to the support (3) and (at 109) to a plate (5), the latter being pivoted (at 110), at its rear end, to the frame (1) and at its forward end (at 11) to a rod (10) in turn pivoted to an extension (3') of the support (3) (at 111). As the support (3) swings upwardly in use the plate (5) turns as shown in chain-dotted lines in Fig. 2 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 1 GB2067144A 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 a rear upper portion of the main frame, the rear shock absorber means being pivotally connected at one end to the lever plate means and at the other end to the rear wheel support at an intermediate portion of the support; and pull rod means pivoted at one end to the lever 100 plate means and at the other end to an extension of the rear wheel support projecting forwardly beyond the pivot connection of the support with 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 compression 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 rela tive to the main frame increases with increas ing load on the motorcycle. By increasing the 115 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 effec tive 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 and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying draw ings, in which:- Figure 1 is a schematic side view of a motorcycle main frame and rear wheel suspension; Figure 2 shows a part of Fig. 1 drawn to a larger scale and illustrating operation of the rear wheel suspension; 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 sections between which a rear wheel 4 is rotatably supported. A forward extension 3' of the fork 3 projects forwardly beyond the pivot connection at 2. Two shock absorbers 7 are pivotally connected, at 108, at their lower ends with the opposite side sections of the rear fork 3 intermediate the front and rear ends of these sections. The shock absorbers extend forwardly and upwardly to be pivotally connected at their upper ends, at 109, with a single lever plate 5 mid-way along this plate. The plate 5 is pivotally mounted, at 110, on the rear upper portion of the main frame 1 and extends forwardly and downwardly from this mounting point to a pivot connection, at 11, with a single pull rod 10 which in turn is pivoted, at 111, to the extension 3' of the rear fork 3.

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

Fig. 2 illustrates the operating relationship between the rear fork 3, the shock absorbers 7, the lever plate 5 and the pull rod 10, when the rear wheel 4 swings up and down relative to the main frame 1. When the rear wheel 4 is caused to move upwardly and downwardly relative to the main frame 1 during travel of the motorcycle, the rear fork 3 is swung up and down around the pivot point 2 to absorb impactive forces transmitted to the main frame 1 by expansion and contraction of the rear shock absorbers 7. When the rear fork 3 swings upwardly from the full line position (lower position) to the chain-dotted line position (upper position), the rear shock absorbers 7, pivotally connected to the opposite side sections of the rear fork 3, are compressed and at the same time the extension 3' of the rear fork 3 is rotated anti-clockwise as viewed in Fig. 2 about the pivot point 2 to a lower position so that the pull rod 10, pivoted, at 111, to the extension 3' of the rear fork 3, is 2 GB2067144A pulled downwardly to swing the lever plate 5 in an anticlockwise direction about the pivot connection 110 further to compress the shock absorbers 7. As a result, the amount of compression or contraction of the rear shock absorbers 7 becomes equal to the sum of the amount of displacement of the pivot connection 108 due to the upward swing of the rear fork 3 and the amount of displacement of the pivot connection 109 due to the downward swing of the lever plate 5, whereby the amount of contraction of the rear shock absorbers 7 is increased in proportion to the upward movement of the rear wheel 4 while at the same time the rate of increase in contraction of the shock absorbers 7 is increased -in accordance with the increasing upward displacement of the rear fork 3.

The relationship between the amount of contraction of the shock absorbers 7 and the upward displacement L of the rear wheel 4 is as shown in Fig. 3 in which reference characters L and 8 represent the upward displacement of the rear wheel 4 and the amount of contraction of the shock absorbers 7, respectively. As apparent from this Figure, the contraction characteristic of the rear shock absorbers 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 external forces acting from the road surface on the rear wheel 4, the amount of contraction of the rear shock absorbers 7 is accordingly increased to render their 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 comfort 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 absorbers 7, the pull rods 10 are subjected only to tensile forces and not to twisting or bending forces and therefore they can have a relatively small cross section and yet be strong enough to withstand the tensile forces acting thereon.

It is to be noted that the shock absorbers 7 may be pivotally connected at 11 instead of at 109 to the lever plate 5, the pull rod 10 then being pivoted at 109 instead of at 11 to the lever plate 5. Such an arrangement operates substantially in the same manner as does the arrangement shown in Figs. 1 and 3.

In the suspension as illustrated in Figs. 1 and 2, pairs of shock absorbers are employed but a single shock absorber could be used satisfactorily. Furthermore, although the rear fork 3 is used as the rear wheel support, a swing arm of cantilever type could be used instead, supporting the rear wheel only at one side of the main frame.

To summarize, in the suspension described 2 lever plate means (the plates 5) is arranged such that it is rotated relative to a rear wheel support (the rearfork 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(s) 7) disposed between the main frame and the rear wheel support thereby to vary the dampin ' g 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 rods 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 undesirable forces and hence formed of relatively small rod having a limited cross sectional area, is used in combinaton 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 move- ment 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 movement between the main frame and the rear wheel; lever plate means pivotally mounted on a rear upper portion of the main frame, the rear shock absorber means being pivotally connected at one end to the lever plate means and at the other end to the rear wheel support at an intermediate portion of the support; and pull rod means pivoted at one end to the lever plate means and at the other end to an extension of the rear wheel support projecting forwardly beyond the pivot connection of the support with 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 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 the lever plate means is pivotally mounted at its rear end on the rear upper portion of the main frame and extends forwardly therefrom to a pivot connection at its forward end with the pull rod means; and wherein the shock absorber 1 Z 3 GB2067144A 3 means is pivotally connected to an intermediate portion of the lever plate means lying between the forward and rear ends of the lever plate means.

3. A motorcycle rear wheel suspension as claimed in claim 1, wherein the lever plate means is pivotally mounted at its rear end on the rear upper portion of the main frame and extends forwardly therefrom to a pivot connection at its forward end with the shock absorber means; and wherein the pull rod means is pivotally connected to an intermediate portion of the lever plate means lying between the forward and rear ends of the lever plate means.

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

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon) Ltd-1 981. Published at The Patent Office, 25 Southampton Buildings, London, WC2A 1 AY, from which copies may be obtained.

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