GB2338774A

GB2338774A - Vehicle control pedal assemblies eg for drive-by-wire systems

Info

Publication number: GB2338774A
Application number: GB9813999A
Authority: GB
Inventors: Michael Neil Basnett
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1998-06-27
Filing date: 1998-06-27
Publication date: 1999-12-29
Anticipated expiration: 2018-06-27
Also published as: GB9813999D0; GB2338774B

Abstract

A pedal assembly suitable for any vehicle control pedal, eg accelerator, clutch or brake especially in drive-by-wire systems, comprises a rigid pedal arm 10 pivotably mounted in a bracket 14. A friction element 22 slidably mounted in the bracket 14 is biased into contact with the pedal arm 10 by means of a spring 26 and lever 24 so as to provide frictional resistance to rotation of the pedal. The force on the friction element 22 from the spring 26 also serves to keep the pedal in its normal position at the rear end of channels 28 in the bracket under normal pedal loads. Under higher loads, e.g. in frontal impact, the spring 26 allows the friction element 22, and hence the pedal pivot. to move forwards giving extended pedal travel. The spring 26 also acts on the top end of the pedal arm 10 to provide the return force for the pedal. The shape of the friction element 22 may be shaped (fig.3) such that the frictional resistance to rotation of the pedal is greater when the pedal is moving downwards and forwards than when it is moving upwards and rearwards.

Description

2338774 Vehicle Pedal Assemblies The present invention relates to pedal

assemblies for vehicles. It is suitable for any control pedal such as an accelerator, brake or clutch pedal, but is particularly useful in 'drive by - wire' systems in which the pedal provides an input to an electrical control system rather than applying an 5 actuating load mechanically.

It is generally desirable in drive - by - wire pedal assemblies to add some hysteresis into the system so that the pedal does not vibrate or move too much as a result of vibration and movement of the driver's foot induced by movement of the vehicle, and so that the pedal can be controlled accurately. There is also a need to ensure that the sensor or potentiometer which converts pedal travel into an electrical signal, and the linkage from the pedal to that sensor or potentiometer is not damaged as a result of abusively high loads exerted on the pedal by the driver during normal driving. There is also an increasing demand for pedal assemblies that are not overly rigid in the event of a crash, so that injury to the driver's leg 11,1 minimised.

The present invention accordingly provides a pedal assembly for a vehicle comprising a rigid pedal rotatably supported by support means, a friction element biased into contact with the pedal so as to provide frictional resistance to rotation of the pedal in the support means and so as to retain -2 the pedal with its pivot axis in a fixed position under normal operating pedal loads, the biasing force of the biasing means being such that, under higher pedal loads, the friction element can move against the biasing force so as to allow movement of the pivot axis of the pedal.

Preferably the support means includes guide means arranged to guide the pedal so that its pivot axis moves in a forward direction of the vehicle under said higher pedal loads.

Preferably the friction element retains the pedal at one end of the guide means, most preferably towards the rear of the vehicle. under normal pedal loads. This can reduce or eliminate clearance in the pedal pivot, and therefore free play in the pedal.

Conveniently pivoting means, which may be of circular cross section, is provided, rigidly connected to an arm of the pedal, and is supported by the support means.

Preferably the pedal includes an actuating part arranged to transmit movement of the pedal about the pivoting means into movement of an actuating element, the assembly further comprising stop means arranged to limit movement of the actuating part to a predetermined distance from a rest position in which the pedal is released. Where the actuating element is, for example, an input to an electrical sensor, such as a linear or rotary potentiometer, this prevents damage to the sensor as a result of excessive travel.

Conveniently the stop means may comprise an abutment on the opposite side of the pivoting means from the foot-supporting part of the pedal.

Preferably the assembly further comprises a lever arranged to amplify the force from the biasing means when transmitting it to the friction element.

Preferred embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a side view of a pedal assembly according to the invention, Figure 2 is a section through part of the assembly of Figure 1, and Figure 3 is a section, simikr to Figure 2, through a pedal assembly 15 according to a second embodiment of the invention.

Referring to Figures 1 and 2, a brake pedal assembly comprises a pedal 8, having a pedal arm 10 with a foot supporting plate 12 at its lower end, pivotably mounted in a bracket 14 which in turn is mounted on the vehicle body. The pedal arm 10 has a pair of pivot bosses 16 extending horizontally from opposite sides which are captured in a pair of horizontal channels 18 on the inner faces of the side plates 20 of the bracket between which the D pedal arm is held. A friction block 22 is also supported in the bracket 14 with each end held in one of the channels 18 such that it can slide along them horizontally. The friction block 22 has on its rear side a concave., part cylindrical, friction surface 22a which fits against a correspondingly shaped convex surface 23 on the front of the brake pedal 8. Under normal operation, the pedal 8 is situated at the rear end of the channels 18. closest to the driver's seat and furthest from the front of the vehicle, the friction block 22 is in front of it, and is held against the pedal 8 by a pair of biasing arms 24 each acted on by a spring 26. The biasing arms 24 each extend vertically down one side of the bracket 14 and they are joined at their bottom ends by a cross bar 28 held in a locating channel 30 on the under side of the bracket 14. They each have a boss 32, about a third of the way up on the inside, extending horizontally inwards through a slot in the bracket and received in a hole in the end of the friction block 22, and a hook 34 at the top which captures one end of a biasing spring 26.

The springs 26, of which there is one on each side of the assembly, have a coil 38 wrapped around a raised annulus 40 on the outside of the bracket 14, and two straight arms 42, 44, one of which engages the top of one of the biasing arms 24 and the other of which engages the pedal arm 10 at a point near its upper end 46, above the pivoting bosses 16. These springs 26 serve two functions. Firstly they act as the pedal return springs, urging the top of the pedal 8 forwards away from the driver, and therefore the foot plate 12 and the lower end of the pedal arm 10 towards the driver. Secondly, they urge the top ends of the biasing arms 24 backwards, towards the driver which causes the biasing arms to rotate about the cross bar 28 urging the friction element 22 rearwards against the pedal arm 10 to create friction resisting movement of the pedal, and to retain the pedal at the rear end of the channels 18 closest to the driver. It will be appreciated that., as the force of the springs 26 is magnified by the lever action of the biasing arms 24 when it is applied to the friction element 22, the springs 26 can be made to hold the pedal in its normal position under normal pedal loads without the need for very high rated springs.

The top end 46 of the pedal arm 10 is connected to a linear potentiometer by means of a link 48 so that movement of the pedal varies the signal produced by the potentiometer, which can be used as an input to a control unit which controls the fuelling and air supply to a vehicle engine.

Under normal operation, normal operating loads on the pedal foot plate 12 cause the pedal 8 to rotate about the pivot bosses 16 against the force of the springs 26, and against the friction of the friction element 22 rubbing on the curved surface 23 on the front of the pedal arm. The friction element 22 under the influence of the springs 26 also acts to clamp the pivot bosses 16 at the rear end of the channels 18 thereby eliminating free play in the pivot arrangement. This rotation continues until the force on the pedal is 5 sufficient to being the top end of the pedal arm into contact with the stop 50. Under higher loads, such as might occur on frontal impact or simply due to the driver applying excessive force to the pedal, the pedal rotates about the stop 50 and the forward force at the pivot causes the friction element 22 to move forwards rotating the biasing arms 24 about the cross bar 28 against the force of the spring 26. Because the top end 46 of the pedal is limited in its rearward movement by the stop 50, higher loads do not get transmitted into the link 48 and potentiometer. This prevents them from being damaged by excessive loads.

In the event of one of the springs 26 failing, the return force on the pedal will be approximately halved. However, the force on the friction element 22 will also be halved. This means that return of the pedal will not be hampered by the friction element 22 to a much greater extent than when both springs 26 are working.

Referring to Figure 3, in a second embodiment of the invention, the shape of the friction element 22 is modified so that, instead of a smooth face of semi-circular section contacting the pedal over an arc centred on, and 1 symmetrical about, the horizontal plane through the pivot axis 52 at the centre of the bosses 16, it has a smaller raised contact area 54 above that centre line. The effect of this is that the frictional resistance to rotation of the pedal is greater when the pedal is moving downwards and forwards than when it is returning rearwards and upwards. This is because parts of the friction face 22a of the friction element which contact the pedal., if they are above the axis 52 are pulled rearwards by clockwise rotation of the pedal as shown in Figures 2 and 3, i.e. during depression of the pedal. This increases the contact force between the friction element 22 and the curved pedal surface 23. Parts of the friction surface 22a below the pivot axis 52 are pulled rearwards increasing friction when the pedal is rising, and forwards decreasing friction when it is being depressed. Therefore by tuning the relative sizes of the friction contact areas above and below the axis 52 and selecting the material of the friction element, and in particular by making the contact areas non-symmetrical about the horizontal plane through the pivot axis 52 and parallel to the direction of movement of the friction element 22, the frictional resistance to depression and return of the pedal 8 can be controlled.

Claims

1. A pedal assembly for a vehicle comprising a rigid pedal rotatably supported by support means. a friction element biased into contact with the pedal so as to provide frictional resistance to rotation of the pedal in the support means and so as to retain the pedal with its pivot axis in a fixed position under normal operating pedal loads, the biasing force of the biasing means being such that, under higher pedal loads, the friction element can move against the biasing force so as to allow movement of the pivot axis of the pedal.

2. An assembly according to claim 1 wherein the support means includes guide means arranged to guide the pedal so that its pivot axis moves in a forward direction of the vehicle under said higher pedal loads.

3. An assembly according to claim 2 wherein the friction element retains the pedal at one end of the guide means under normal pedal loads.

4. An assembly according to claim 3 wherein when the assembly is mounted in a vehicle, said end is towards the rear of the vehicle.

5. An assembly according to any of claims 2 to 4 wherein the guiding means comprises a channel in the supporting means in which the pedal is supported.

1

6. An assembly according to any foregoing claim wherein the pedal includes pivoting means which is rigidly connected to an arm of the pedal and which is supported by the support means.

7. An assembly according to claim 6 wherein the pivoting means has a circular cross section.

8. An assembly according to any foregoing claim wherein the pedal includes an actuating part arranged to convert rotation of the pedal into movement of an actuating element, the assembly further comprising stop means arranged to limit movement of the actuating part to a predetermined distance from a rest position in which the pedal is released.

9. An assembly according to claim 8 wherein the stop means comprises an abutment on the opposite side of the pivoting means from the footsupporting part of the pedal.

10. An assembly according to any foregoing claim further comprising a lever arranged to amplify the force from the biasing means when transmitting it to the friction element.

11. An assembly according to any foregoing claim wherein the biasing means also acts to bias the pedal towards a rest position.

12. An assembly according to any foregoing claim wherein the blaSI111-11 means comprises at least two springs operating in parallel so that, in the event of failure of one of them, the assembly will operate using the other.

13. An assembly according to any foregoing claim wherein the friction element is arranged so as to produce greater frictional resistance to rotation of the pedal in one direction that in the other.

14. A pedal assembly for a vehicle comprising a rigid pedal rotatably supported by support means, a friction element biased into contact with the pedal so as to provide frictional resistance to rotation of the pedal in the support means, wherein the friction element is arranged so as to produce greater frictional resistance to rotation of the pedal in one direction that in the other.

15. An assembly according to claim 15 wherein the friction element comprises a friction block biased into contact with a surface which rotates with the pedal.

16. An assembly according to claim 14 or claim 15 wherein the friction element has a curved surface arranged to contact a corresponding curved surface on the pedal.

17. An assembly according to any one of claims 14 to 16 wherein the contact areas between the friction element and the pedal are arranged nonsymmetrically about a plane passing through the pivot axis of the pedal and parallel to the direction of movement of the friction element.

18. An assembly according to any one of claims 13 to 17 wherein said one direction corresponds to depression of the pedal.

19. A pedal assembly for a vehicle substantially as hereinbefore described with reference to the accompanying drawings.