GB2139719A - Suspension struts for motor cycles having load-dependent braking - Google Patents

Description

SPECIFICATION Suspension struts This invention relates to suspension struts suitable for motor cycles.

In our application number 8118128 (G. B. 2 077 871 A), from which the present application is divided out, we describe a motor cycle braking system which incorporates a control valveforcontrolling the brake pressure applied to a wheel ofthe motorcycle.

In accordancewith the present invention, there is provided a manually adjustable suspension strut having an adjustable support for a suspension spring, said support comprising means for attachment of a control spring of a pressure control valve arrangementto a point on said support, and adjusting means forvarying the position of said point of attachment relative to the axis of the strut.

Preferably, the adjusting means comprises an eccentric collarfixed to the periphery of the strut and an annular member mounted on said collar, said annular member having said means for attachment of the control spring, wherein rotation of the annular member alters the position of the point of attachment ofthe control spring relative to the strut axis.

However, other adjusting means are possible, as described in more detail below.

The preferred embodiment of the present invention provides a motor cycle suspension strut particu larly useful for a motor cycle having a braking system as described on our application referred to above.

Three embodiments of suspension struts in accordance with the invention will now be described, byway of example, with reference to the accompanying drawings, in which :- Figure 1 is a diagrammatic elevational view of the arrangement of the rear of a motor cycle ; Figure 2 is a schematic view of the arrangement of Figure 1 illustrating the components in different conditions of loading of the motor cycle ; Figure3 is a schematic view of the arrangement of Figure 1 illustrating the components in different conditions of adjustment; Figure 4 is a view of part of an embodiment of adjustable suspension strut suitable for use in the arrangement of Figure 1, shown partly in section; Figure 5 is a viewsimilarto that of Figure 4 of another, differentstrut ; Figure 6 is a detail plan view of a suspension spring support of the strut of Figure 5, and Figure 7 shows a side view of a further embodiment of the invention.

Referring to Figure 1, there is shown part of a motor cycle having a fluid-operated braking circuit incorporating a control valve 1. The control valve 1 has a valve stem 3 subjected to a force which is dependent upon vehicle loading, as will be described. A suitable form of control valve is described and illustrated in British Patent Specification 1425147. The control valve 1 is connected inthe circuitfrom a fluid pressure sourceto the rearwheel brakes and modifiesthe pressure applied to the rearwheel brakes, as compared to full braking pressure applied to the front wheel brakes, the pressure being modified after a"cut-in"pressure, which is dependent upon the force applied to stem 3, is attained.

The control valve l is attached to the frame 2 of the motocycle by a racket4, and the valve stem 3, which is movable axiallyto control operation ofthevalve, is subjected to the variable force by a control tension spring 5 one end of which is connected to the valve stem 3. The other end of the control spring 5 is connected ata pointZto a support 6 for the suspension spring 7 of a combined coil spring and damper suspension strut8. The spring support 6 is adjustable byan adjuster9aswill be described below.

The suspension strut 8 is mounted at points A and B respectively between theframe 2 and the hub 2Aof the rearwheel 10. Thus, one end of control spring 5 is connected through the valve 1 to the frame 2 which constitutesthe sprung part of the motor cycle, and the otherend ofthe control spring 5 is connected to the spring support6which is part of the unsprung part of the motor cycle.

The wheel 10 is also supported by an arm 11 which is rotatably connected at point X to the frame 2 and is connected at pointYtothe hub 2A of wheel 10.

Referring to Figure 2, the positions of the components relative to the frame 2 in the laden condition of the motocycle are iflustrated in chain link lines and the positions in the unladen condition are illustrated in fulllines.

When thevehicle is laden the suspension spring 6 is compressed and the points B, Y moveto positions B', Y'relative to the frame 2. The length of the control spring 5 isthus increased to increase the force onthe valve stem 3. This increase in force on the valve stem 3 hasthe effectof increasing the"cut-in"pressure of the control valve 1. Thus, when the motocycle is laden, e. g. by a particularly heavy riderora pillion passen- ger, the braking effect of the rearwheel brake is increased.

If the rearwheel load is decreased, dueto removal of static load or dueto weight transfer to the front wheel during braking, the suspension spring 7 increases in length and the length of the control spring 5 is decreased and the"cut-in"pressure is decreased to effectively reducethe rearwheel braking pressure.

The amount of extension of the control spring 5 is lessthanthe change in length of the suspension spring 7 and lessthan the deflection of the sprung part 2 relativeto the axle of wheel 10.

The control valve 1 may be a pressure limiting valve, which limitsthe rearwheel brake pressure to a value dependent upon the loading of the rearwheel, or a pressure reducing valve which reduces the rearwheel brake pressure as compared to the full pressure applied to the frontwheel brakes.

As described, the control valve 1 is self-adjusting in dependence upon changes in both static loading, due for example to a pillion passenger getting on or off the motor cycle, and dynamic loading, caused by braking.

In both casesthe rearwheel braking is adjusted to provide a good rear wheel/frontwheel brake ratio.

As is described in more particulardetail below, the length of the strut 8 is manually adjustable to assist in coping with static load changes, forexample preparatoryto a pillion passengergetting on the cycle, by adjusting the position of the spring support 6 relative to the connecting point B. Since for any given load the length of the suspension spring 7, i. e. the distance AZ is constant, adjusting the spring support 6 without changing the loading on the suspension strut8, e. g. withoutadding a pillion passenger, leavesthe distance AZ unaltered but changes the distance ZB in orderto changethe overall length AB of the strut8.

Onlywhen the strut load changes, for example when the pillion passengergets on oroffthe cycle, doesthe distance AZ change.

As best seen in Figures 3, the adjustment of the suspension strut8 without altering the load on the suspensionstrutcausesthe pointBto moveto B"and thusthe pointYto moveto Y". Although the distance AZ is unchanged, there is a slight change ex in the angle between strut and the frame 2 of the motor cycle. Hence, adjusting the spring support 6 without altering the loading on the strut 8 causes the load of the control spring 5 ofthevalveto changeslightly.

This is undesirable.

In orderthat onlythe changes in the length AZ of the suspension spring 7 i. e. changes in strut loading, should alterthe characteristics of the valve 1 the suspension struts of the invention include means wherebytheforce of control spring 5 is not changed during manual adjustment of the strut. Several forms of strutfor achieving that end will now be described.

Referring to Figure 4, the spring support 6 comprises an eccentric collar 12 around which is rotatably mounted an annular connecting member 13 having a projection 14. The projection 14 has an aperture 15 through which passes an upstanding spigot 16 of a locating member 17 secured to the strut8, the member 17 preventing rotation of the connecting member 13. The aperture 15 also receives one end of the control spring 5.

The collar 6 has a lower cam surface 18 which co-operates with a stop 19 fixed to the strut 8. The cam surface 18 is preferably so shaped thatseveral stable positions of adjustment can be obtained by rotation of the collar 12.

To adjustthestrutlength, thecollar 12 is rotated to engage the stop 19 in a different portion of the cam surface 18, thus altering the distance ZB. During rotation ofthe collar 12, the eccentricity of the collar causes movement of the projection 14 radually relativeto the axis ofthe strut 8. The amount of eccentricity is chosen such thatthe radial movement compensatesforthe small change a in the angle of the strut and thusthere is no change in thetension of control spring 5.

In Figures 5 and 6 there is shown a strut8 having a suspension spring support 30 which is adjustable to perform afunction similartothatofthe strutof Figure 4. In the Figure 5 and 6, the support 30 comprises a plate31 having a projection 31Awhich hasan upstanding portion 32. The upstanding portion 32 has a screw-threaded bore 33 which receives a com plimentary screw-threaded shaft 34 of an adjuster mechanism. Connected to one end ofthe shaft 34 is a yoke 35 to which is secured the control spring 5. The other end of the shaft34 carries a gear 36 which co-operates with a gear 37formed on a rotatable collar 38 mounted on the strut8. Attached to the collar 38 is a pin 39 which engages with a cam surface 40 of a cam 41 secured to the lower part of strut 8. A downwardly depending guide member 42 fixed to the plate 31 hasa spigot43 engaged in slot44formed in an attachment 45 secured to the strut 8 in orderto preventthe plate 31 from rotating as the collar38 is adjusted.

In operation, asthe collar 38 is adjusted to adjustthe strut length, the gears 36,37 rotate relatively to effect rotation of the shaft 34 and compensate for changes in tension of control spring 5 which would otherwise be caused bythe change a in the angle of the strut.

The above-described valve arrangements have the advantages that sincethe valve is separate from the suspension strut, the control spring 5 may be tension spring, which needs no guide or casing to prevent kinking, and the deflection of the control spring 5 need not be the same as the change in length of the suspension spring. Furthermore, no direct mechanical connection is required between thetwo ends of the suspension spring and the valve. Sincethe valve is not directlyfixed to the strut, it does not need to be subjected to the angular movements of the strut and rigid fluid pipes and couplings can be used forthe valve.

Referring nowto Figure 7 a further embodiment of the invention isshown. In this embodimentwhere applicable like reference characters have been used to those used in the previously described embodiments.

In the embodiment of Figure7 the suspension strut 8 includes an adjustable spring support 6 similarto that shown in Figure 4. The spring support 6 is provided with an eccentric portion 12A which engages an upstanding portion 45 of a racket46. The bracket 46 includes an elongate slot in which is received the body47 of the damper of the suspension strut8. The bracket46 is biased against a flange 48 secured to the body 47 by a spring 49 so that rotation of the eccentric 12A during adjustment of the spring support 6 causes lateral sliding movement of the bracket 46 along the supportflange 48. An adjustable connecting rod 50 connects the bracket 46 to an arm 51 which is pivotally mounted onthetrailing arm 11 ofthe motorcycle suspension. A control spring 5A connectsthe arm 51 to the stem 3 of a control valve 1 mounted on the motorcycleframe.

In use, if the spring support 6 is adjusted and the load on the rearsuspension strut is not changed, lateral sliding movement of the bracket 46 caused by the eccentric 12A compensates for small changes in angle of the suspension strut and accordinglythe braking characteristics of the rear brake are unaltered.

However, changes in static or dynamic loading on the rear suspension strut cause changes in the angle of the suspension strutto the trailing arm, and changes in the angle of the trailing arm relative to thefixed frame. Thesechanges are applied by way of connect- ing rod 50, arm 51, andspring 5Atothestem3 of valve 1 in orderto providesuitable modification of the rear brake characteristics.

Claims (3)

1. CLAIMS 1. A manually adjustable suspension strut having an adjustable supportfor a suspension spring, said support comprising means for attachment of a control spring of a pressure control valve arrangementto a point on said support, and adjusting meansfor varying the position of said pointof attachment relative to the axis of the strut.
2. 2. A manually adjustable suspension strut according to claim 1 wherein the adjusting means comprises an eccentric collar located on the strut and an annular member mounted on said collar, said annular mem- ber having said means for attachment of the control spring, wherein rotation of the annular member alters the position of the point of attachment of the control spring relativeto the strut axis.
3. 3. A manually adjustable suspension strut accordingtoctaim 1 wherein said connection means is coupledtothe remainder of the strut by a screw threaded member, and said adjusting meanscompris- es meansfor rotating the screwthreaded member as the adjustable support is adjusted.

   3. A manually adjustable suspension strut sub- stantially as hereinbefore described with reference to and asshown intheaccompanying drawings.

   Newclaims or amendments to claims filed on 27 June 1984.

   Superseded claims 1, 2.

   1. A manually adjustable suspension strut com- prising: asuspensionspring ; an adjustable support forthesuspension spring ; connection meansfor connecting a brake pressure control valve arrangementto the strut; and adjusting meansforvarying the distance between said connection means and the axis of the strut in accordance with the setting of the adjustable support.

   2. A manually adjustable suspension strut accord- ing to claim 1 wherein the adjusting means comprises an eccentric collarforming part of the adjustable support, and an annular member mounted on said collar, said annular member having said connection meansthereon.