GB2423566A

GB2423566A - A variable ratio brake pedal assembly

Info

Publication number: GB2423566A
Application number: GB0503866A
Authority: GB
Inventors: Thomas Peter Randles
Original assignee: JC Bamford Excavators Ltd
Current assignee: JC Bamford Excavators Ltd
Priority date: 2005-02-25
Filing date: 2005-02-25
Publication date: 2006-08-30
Also published as: GB0503866D0; WO2006090173A1

Abstract

A pedal control assembly 10 for moving an operating member 22 of a system 10, includes an actuating part 14 which is pivoted to a pedal support structure 12, and a linkage mechanism 20 between the actuating part 14 and the operating member 22, the linkage mechanism 20 including a pivot member 28 which is pivotal about a second pivot axis B generally parallel to a first pivot axis A about which the actuating part 14 pivots, the pivot member 28 including first and second formations 29, 30 which extend radially outwardly of the second pivot axis B, the first formation 29 being pivotally connected to the operating member 22 and the second formation 30 being pivotally connected to a link 35 which extends to and is pivotally connected to a lever member 18 which extends radially outwardly of the first pivot axis A about which the actuating part 14 pivots, and moves with the actuating member 14, whereby upon an initial actuating part 14 movement from a rest condition, the operating member 22 is moved a greater amount than for a corresponding subsequent actuating part 14 movement.

Description

Title: Pedal Control Assembly DescriDtion of Invention This invention

related to a pedal control assembly and more specifically but not exclusively to a pedal control assembly for operating a brake system of a vehicle or machine.

Braking on an industrial vehicle such as a tractor or on a working machine such as an excavating or loading machine, typically is provided by a brake system including for each wheel hub, or more usually each axle, a plurality of discs. In such an arrangement, a plurality of interposed discs are provided with, typically, alternate discs, which are circumferentially fixed relative to the machine, and the interposed alternate discs are rotatable with a wheel hub/axle to be braked. The discs are immersed in hydraulic oil and prior to braking, are spaced apart from one another.

The circumferentially fixed discs are carried on a member which is moveable axially by a pressurised hydraulic fluid e.g. fluid displaced from a master cylinder, in response to movement of an operating member under driver/operator control.

It will be appreciated by those skilled in the art that the spacing apart of the interposed discs requires a compromise as on the one hand, it is desirable prior to braking, for the discs to be widely spaced apart to minimise drag losses occurring due to churning hydraulic oil between the plates, and on the other hand, desirably prior to braking the discs are closely spaced, so that on application of the brake by the operator/driver, minimal axial movement of the axially moveable circumferentially fixed discs provides braking.

In any event, the foot operated brake needs to have for the operator/driver, the correct "feel" i.e. it is desirable that there is plenty of pedal movement in which a braking effect is achieved, and no large foot pedal movements at the beginning of pedal movement to close the spacing between the interposed discs, before any braking effect is realised.

In our previous patent application EP-A-1182108 there is disclosed a variable ratio brake pedal in which a brake actuating lever is coupled to a piston rod of a brake master cylinder by cam and cam follower arrangement.

According to first aspect of the invention we provide a pedal control assembly for moving an operating member of a system, the pedal control assembly including an actuating part which is pivoted to a pedal support structure, and a linkage mechanism between the actuating part and the operating member, the linkage mechanism including a pivot member which is pivotal about a second pivot axis generally parallel to a first pivot axis about which the actuating part pivots, the pivot member including first and second formations which extend radially outwardly of the second pivot axis, the first formation being pivotally connected to the operating member and the second formation being pivotally connected to a link which extends to and is pivotally connected to a lever member which extends radially outwardly of the first pivot axis about which the actuating part pivots, and moves with the actuating part, whereby upon an initial actuating part movement from a rest condition, the operating member is moved a greater amount than for a corresponding subsequent actuating part movement.

Thus where the invention is applied to a multi-disc hydraulically operated brake, as the invention enables an initial pedal actuating part movement to move the operating member a greater amount than a corresponding subsequent movement, spaces between the discs of the brake system may be closed as the pedal actuating part is initially moved, leaving more available actuating part movement to control application of the braking effect.

The geometry of the pedal control enables the initial actuating part movement to be achieved by the driver or operator applying a low force to the actuating part, the required force to apply the brake, increasing as the actuating part is further moved.

Thus the invention enables a brake operator to have good braking control and brake "feel".

The link of the linkage mechanism is preferably non-linear over at least a portion of its length, so that pivotal movements of the actuating part and lever member about the first pivot axis result in asynchronous pivotal movements of the pivot member about the second pivot axis.

For example, in a first embodiment, the lever member may extend radially outwardly of the first pivot axis in a first direction along, or preferably to one side of a plane which passes through the first and second pivot axes, and the first and second formations of the pivot member extend to an opposite side of the plane to provide an "over- centre" configuration.

In this case, the link may have a first generally linear portion which extends from a first end which is pivotally connected to the lever member, a second portion which extends from a second end of the link which is connected to the second formation of the pivot member, and a portion intermediate the first and second portions which is non-linear.

The first and intermediate portions may lie substantially to the one side of the plane, whilst the second portion may lie substantially to the second opposite side of the plane. The second formation of the pivot member may extend radially outwardly of the second pivot axis in a direction away from the first pivot axis, and the link may extend around the second pivot axis to its pivotal connection to the second formation.

Thus when the actuating part is moved, and for example the first pivot axis is below the second pivot axis, pivotal movement of the actuating part, for example as the actuating part is depressed, will result in an opposite pivotal movement of the pivot member, which will result in the first formation, and hence the operating member, moving in the same direction as the brake actuating part e.g. downwardly.

In a second embodiment of the invention, the lever member may extend radially outwardly of the first pivot axis to an opposite side of a plane which passes through the first and second pivot axes and may for example, be an extension of the actuating part. The first and second pivot member formations may also extend radially outwardly of the second pivot axis to the one side of the plane. The link may include a first non-linear portion which extends from a first end which is pivotally connected to the lever member, a second non-linear portion which extends from a second end of the link which is pivotally connected to the second formation of the pivot member, and a linear portion intermediate the first and second portions.

The first and second non-linear portions may extend from the linear intermediate portion towards the respective lever member and second formation of the pivot member, and thus each extend at least partially around the respective first and second pivot axes to their pivotal connections to the respective lever member and second formation of the pivot member.

Thus when the actuating part is moved, and for example the first pivot axis is above the second pivot axis, pivotal movement of the actuating part, for example as the actuating part is depressed, will result in a pivotal movement of the pivot member in the same sense of rotation, which will result in the first formation and hence the operating member, moving in the opposite direction to the brake actuating part i.e. upwardly.

In each embodiment, if desired, the link may include an abutment surface which may abut a bush provided around at least one of the first and second pivot axes, to restrict pivoting of the pivot member and thus of the actuating part, e.g. to a limit governed by the system construction.

The invention is particularly useful where applied to a pedal control assembly for operating a brake system of a vehicle or machine, in which case the operating member may be a piston or a part secured to a piston, which piston is moveable in a cylinder to effect braking, when the actuating part is moved by an operator/driver, by the piston displacing hydraulic fluid from the cylinder.

The displaced hydraulic fluid may be provided to a brake cylinder relatively to move a piston to move a brake member which effects braking. The brake member may include a plurality of discs which are circumferentially fixed, the discs being interposed with discs which are rotatable with a wheel or axle to be braked.

According to a second aspect of the invention, we provide a vehicle or working machine including a pedal control assembly of the first aspect of the invention.

The system which the pedal control assembly operates, maybe a multi-disc brake system which may be provided to brake an axle or wheel of the vehicle/machine.

Embodiments of the invention will now be described with reference to the accompanying drawings in which:- FIGURE 1 is an illustrative perspective view of a first embodiment of a pedal control assembly in accordance with the invention, in a rest condition; FIGURE 2 is a side view of the control assembly of figure 1 but in an operated condition; FIGURE 3 is an illustrative perspective view of a second embodiment of a pedal control assembly in accordance with the invention, in a rest condition.

Referring to figure 1, a pedal control assembly 10 includes a pedal support structure 12 which may be a part of a vehicle or machine for which the pedal control assembly 10 is provided. For example, the pedal support structure 12 may be a chassis part, or a bracket or brackets secured relative to the chassis.

In the example, the pedal control assembly 10 is provided for operating a brake system of the vehicle/machine, in use an operator depressing a brake actuating part 14 with his/her foot, to pivot the actuating part 14 from the rest condition, about a first pivot axis A. In the example, the actuating part 14 includes a pedal plate 15, and an actuating part plate 16 secured together substantially at right angles at or adjacent one end 17 of the actuating part plate 16, and the actuating part plate 16 having an opening towards a second end thereof, through which a first pivot 19 passes. The actuating part 14 further includes a lever member 18 which extends radially outwardly of the first pivot axis A, and is pivotable with the remainder of the actuating part 14 about the first pivot axis A. In this example, the lever member 18 extends alongside the actuating part plate 16.

Pivotal movement of the actuating part 14 is transmitted via a linkage mechanism 20 which will be described in more detail below, to an operating member 22, which in this example is a piston rod which is fast with a piston (not seen) within a cylinder 24 of a master cylinder 25 of the brake system.

The master cylinder 25 is in this example mounted in a generally upright orientation, by a mounting 26 which may be fixed relative to the brake support structure 12 or otherwise relative to the vehicle/machine.

The brake system may be of the kind in which hydraulic fluid displaced from the master cylinder 25 as the operating member 22 and thus piston is moved, downwardly in the example shown and described, is transmitted to a brake cylinder to move a piston to bring a braking member into braking engagement with a surface to be braked. For example, the braking member may include a plurality of discs which are circumferentially fixed and interposed between alternate discs which are rotatable with a wheel or axle to be braked. In such multi-disc brake systems, the fixed and rotatable discs are immersed in oil, and when the brake is applied, residual spacing between the interposed discs is reduced to bring brake surfaces of the fixed and rotatable discs into contact to effect braking.

The operating member 22 has at an end distal from the master cylinder piston, a mounting 23 for pivotally mounting the operating member 22 to a formation of a pivot member 28 which is pivotal relative to the brake supporting structure 12 about a second pivot axis B generally parallel to the first pivot axis A about which the actuating part 14 pivots.

The pivot member 28 has first and second formations 29, 30, each of which extends radially outwardly of the second pivot axis B, the first formation 29 being pivotally connected to the mounting 23 of the operating member 22, and the second formation 30 of the pivot member 28 being pivotally connected as shown at 31, to a link 35 which extends to and is pivotally connected to the lever member 18 as indicated at 36.

The first and second formations 29, 30 of the pivot member 28 are circumferentially spaced, forming an acute angle between their extension directions. However, both of the first and second pivot member formations 29, lie to a side of a plane P which passes through the first and second pivot axes A, B, whilst the lever member 18 extends to the other side of the plane P. In the example, the second formation 30 of the pivot member 28 extends generally upwardly and to the side of the plane P when the pedal control assembly 10 is in the rest condition as shown.

The link 35 includes a first portion 38 which is generally linear and extends from one end where there is the pivotal connection 36 to the lever member 18, upwardly in the example shown, and a second portion 39 which also is generally linear and extends from the other link end where there is the pivotal connection 31 to the second formation 30 of the pivot member 28, and a portion 40 intermediate the first and second portions 38, 39. The intermediate portion 40 is curved so that overall, the link 35 is non-linear. In the example, the link 35 is provided by a pair of parallel closely coupled link elements 35a, 35b and the second formation 30 of the pivot member 28 and the lever member 18 of the actuating part 14, are each received between the link elements 35a, 35b although other link constructions may be employed as desired.

It can be seen that by virtue of the geometry described, the link 35 extends upwardly from the lever member 18, above and around the second pivot axis B to its pivotal connection 31 with the second pivot member formation 30. The first linear link portion 38 lies to the same side of the plane P as the lever member 18, whilst the second link portion 39 lies mainly to the same side of the plane P as the first and second formations 29, 30, at least when the pedal control assembly 10 is in the rest condition shown in figure 1. The curved intermediate portion 40 is also substantially at the same side of the plane P as the first link portion 38, but crosses the plane P and extends around the second pivot axis B to the second link portion 39.

Operation of the pedal control assembly 10 will now be described, including with reference to figure 2.

When the pedal plate 15 is downwardly depressed by a driver's or operator's foot from the rest condition shown in figure 1, the actuating part 14 pivots about the first pivot axis A. From the side of the assembly 10 shown in figure 1, the actuating part 14 pivots anti-clockwise whereas in figure 2, which views the other side of the assembly 10, the actuating part 14 pivots clockwise.

In each case, pivoting movement of the actuating part 14 when the pedal plate 15 is depressed will result in the link 35 being pulled downwardly.

Because of the geometry of the linkage mechanism 20 and particular the pivotal connection 31 of the second link portion 39 to the second formation 30 at the other side of the plane P to its pivotal connection 36 to the lever member 18 to provide an over-centre configuration, the pivot member 18 will be constrained to pivot about the second pivot axis B in a sense of rotation opposite to the actuating part 14 i.e. clockwise as seen in figure 1 or anticlockwise as seen in figure 2. As a result, the operating member 22 will be moved downwardly to cause the brake to be applied, as hydraulic fluid is forced from the master cylinder 25 by piston movement therein.

In accordance with the invention, the operating member 22 does not respond linearly to the brake actuating part 14 movement. Rather, an initial actuating part 14 movement will result in a greater movement of the operating member 22 than a corresponding amount of actuating part 14 movement subsequently. Thus where the invention is applied to a multi-disc type brake system as described, the initial actuating part 14 movement from the rest condition, will close the spaces between the interposed discs with minimal actuating part 14 pivotal movement and foot force, leaving more actuating part 14 pivotal movement actually to apply the brake, although of course, as the brake disc surfaces are moved into contact with one another, an increasing driver/operator foot force will be required to apply the brake.

This non-linear response of the operating member 22 to brake actuating part 14 movement, is achieved by virtue of the provision of the pivot member 28, the non-linear configuration of the link 35, and the general geometry of the linkage mechanism 20, although may be achieved with other linkage mechanism 20 geometries. For example in an arrangement in which the master cylinder 25 is not mounted in the generally upright orientation as seen in the drawings, an alternative linkage mechanism 20 geometry may be used, such as described below with reference to figure 3 in which the master cylinder 25 is inverted compared to that shown in figures 1 and 2.

It can be seen in the example of figures 1 and 2 of the drawings, and in particular in figure 2, that when the actuating part 14 has been pivoted downwardly to a maximum depressed position, an abutment surface 45 of the link 35 provided by an underside of the curved intermediate portion 40 of the link 35, may engage a bush 48 provided about the second pivot axis B, which engagement position may coincide with engagement of another abutment surface 50 (see figure 1) of the first link portion 38, with a bush 51 about the first pivot axis A. Referring to figure 3, a second embodiment of the invention is illustrated.

Similar parts to those described with reference to figures 1 and 2 are labelled with the same references.

In this embodiment, the operating member 22 of the master cylinder 25 is indicated by dotted lines only, but in contrast to the arrangement of the figures 1 and 2 embodiment, the master cylinder 25 is inverted so that the operating member 22 is moved upwardly as seen in the drawing, to effect braking.

In this embodiment, the lever member 18 is provided as an extension of the brake actuating part 14 but in any case, so that the lever member 18 extends to an opposite side of plane P which passes through the respective pivot axes A and B, to that on which the actuating part plate 16 is provided. The link 35 of the linkage mechanism 20 lies entirely to the side of the plane P opposite to the brake actuating part plate 16 too.

The link 35 has a first non-linear portion 38 which extends from the first end where the pivotal connection 36 to the lever member 18 is provided, and a second non-linear portion 39 which extends from the second link end where the pivotal connection 31 to the second formation 30 of the pivot member 28 is provided, and a generally linear portion 40 intermediate the first and second portions 38, 39, so that overall the link 35 is non-linear. The first link portion 38 extends slightly around the first pivot axis A to where it is connected to the lever member 18, whilst the second link portion 39 extends around the second pivot axis B to where it is pivotally connected to the second formation 29 of the pivot member 28.

Like the link 35 of the figures 1 and 2 embodiment, the link 35 is provided by a pair of parallel closely coupled link elements 35a, 35b and the second formation 30 of the pivot member 28 and the lever member 18 of the actuating part 14, are each received between the link elements 35a, 35b.

Although not seen in figure 3, the pivot member 28 and actuating part 14 are pivotally mounted with respect to a brake mounting structure which may also mount the master cylinder 25.

Operation of the pedal control assembly 10 of figure 3 will now be described.

When the pedal plate 15 is depressed to apply the brake, the lever member 18 will pivot about the first pivot axis A, clockwise as seen in figure 3. The link will thus be pulled upwardly, and by virtue of its connection to the second formation 30 of the pivot member 28, the pivot member 28 will pivot about the second pivot axis B, in this case, in the same sense of rotation that the actuating part 14 pivots. Thus the first formation 29 of the pivot member 29 will be pivoted in the same sense of rotation as the brake actuating part 14, about the first pivot axis A, and the operating part 22 pivotally connected to the first formation 29, will be moved upwardly to effect braking.

In this embodiment, the operating member 22 response to brake actuating part 14 movement will be non-linear again by virtue of the pivot member 28, and also the non-linear configuration link 35, which extends at least partially around each of the pivot axes A, B to the respective pivotal connections 31, 36, and by virtue of the general linkage mechanism 20 geometry. Thus the initial movement of the brake actuating part 14 from the rest condition shown, will effect a greater movement of the operating part 22 of the brake master cylinder 25 to close spaces between interposed discs of the brake system, than a subsequent corresponding movement, leaving more actuating part 14 pivotal movement actually to apply and control the braking effect.

In the figure 3 arrangement, there is shown a stop 60 to restrict return movement of the brake actuating part 14 towards the rest position, by a spring 61 or springs or other resilient return devices. In this embodiment, and in the figures 1 and 2 embodiment, the brake system may include other resilient return devices. For example, one or more springs may be provided to return the member on which the circumferentially fixed discs are mounted to provide the spaces between the interposed discs, when the brake is released, and/or the master cylinder 25 may too have some resilient return device to return the piston therein to the rest condition, when the brake is released.

By providing for a non-linear operating member 22 response to actuating part 14 movement as described, the spacing of the interposed plates of the brake system, may be made sufficiently wide when the brake is not being applied i.e. the pedal control assembly 10 is in the rest condition, so as to provide minimal drag due to churning fluid between the immersed interposed discs. However by virtue of the invention the spacing is efficiently reduced by an initial movement of the actuating part 14 with minimal driver/operator foot force, whilst efficient braking may be achieved whilst giving good brake control and brake feel to a driver/operator.

Although the invention has been described in relation to a pedal control assembly 10 for operating a brake system, the invention may be employed to any other system in which is it desirable for operating member response to movement of a foot operated actuating part to be non-linear.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A pedal control assembly for moving an operating member of a system, the pedal control assembly including an actuating part which is pivoted to a pedal support structure, and a linkage mechanism between the actuating part and the operating member, the linkage mechanism including a pivot member which is pivotal about a second pivot axis generally parallel to a first pivot axis about which the actuating part pivots, the pivot member including first and second formations which extend radially outwardly of the second pivot axis, the first formation being pivotally connected to the operating member and the second formation being pivotally connected to a link which extends to and is pivotally connected to a lever member which extends radially outwardly of the first pivot axis about which the actuating part pivots, and moves with the actuating member, whereby upon an initial actuating part movement from a rest condition, the operating member is moved a greater amount than for a corresponding subsequent actuating part movement.

2. An assembly according to claim I wherein the first and second formations of the pivot member are circumferentially spaced from one another.

3. An assembly according to claim I or claim 2 wherein the pivot member is pivoted relative to the pedal support structure.

4. An assembly according to any one of claims 1 to 3 wherein the link is non-linear over at least a portion of its length.

5. An assembly according to claim 4 wherein the lever member extends radially outwardly of the first pivot axis in a first direction along or to one side of a plane which passes through the first and second pivot axes, and the first and second formations of the pivot member extend to an opposite side of the plane.

6. An assembly according to claim 4 or claim 5 wherein the link has a first generally linear portion which extends from a first end which is pivotally connected to the lever member, a second portion which extends from a second end of the link which is connected to the second formation of the pivot member, and a portion intermediate the first and second portions which is non-linear.

7. An assembly according to claim 6 wherein the first and intermediate portions lie substantially to the one side of the plane, whilst the second portion lies substantially to the second opposite side of the plane.

8. An assembly according to claim 7 wherein the second formation of the pivot member extends radially outwardly of the second pivot axis in a direction away from the first pivot axis, and the link extends around the second pivot axis to its pivotal connection to the second formation of the pivot member.

9. An assembly according to claim 8 wherein when the actuating part is moved, the actuating part pivots in an opposite sense of rotation and the operating member moves in the same direction as the brake actuating part.

10. An assembly according to any one of claims I to 4 wherein the lever member extends radially outwardly of the first pivot axis to an opposite side of a plane which passes through the first and second pivot axes.

11. An assembly according to claim 10 wherein the lever member is an extension of the actuating part.

12. An assembly according to claim 10 or claim 11 wherein the first and second pivot member formations extend radially outwardly of the second pivot axis to the one side of the plane.

13. An assembly according to claim 12 wherein the link includes a first non- linear portion which extends from a first end which is pivotally connected to the lever member, a second non-linear portion which extends from a second end of the link which is pivotally connected to the second formation of the pivot member, and a linear portion intermediate the first and second portions.

14. An assembly according to claim 13 wherein the first and second nonlinear portions extend from the linear intermediate portion towards the respective lever member and second formation of the pivot member, and thus each extend at least partially around the respective first and second pivot axes to their pivotal connections to the respective lever member and second formation of the pivot member.

15. An assembly according to claim 14 wherein when the actuating part is moved, pivotal movement of the actuating part results in a pivotal movement of the pivot member in the same sense of direction, and the first formation and moves in the opposite direction as the brake actuating part.

16. An assembly according to any one of the preceding claims wherein the link includes an abutment surface which abuts a bush provided around at least one of the first and second pivot axes, to restrict pivoting of the pivot member and thus of the actuating part.

17. An assembly according to any one of the preceding claims which is for operating a braking system of a vehicle or machine, the operating member being a piston or a part secured to a piston, which piston is moveable in a cylinder to effect braking, when the actuating part is moved by an operator/driver, by the piston displacing hydraulic fluid from the cylinder.

18. An assembly according to claim 17 wherein the displaced hydraulic fluid is provided to a brake cylinder relatively to move a piston to move a brake member which effects braking.

19. An assembly according to claim 18 wherein the brake member includes a plurality of discs which are circumferentially fixed, the discs being interposed with discs which are rotatable with a wheel or axle to be braked.

20. A pedal control assembly substantially as hereinbefore described with reference to and/or as shown in figures 1 and 2 or figure 3 of the accompanying drawings.

21. A vehicle or working machine including a pedal control assembly according to any one of the preceding claims.

22. A vehicle or machine according to claim 21 wherein the system which the pedal control assembly operates, is a multi-disc brake system which is provided to brake an axle or wheel of the vehicle/machine.

23. Any novel feature or novel combination of features herein described and/or as shown in any of the accompanying drawings.