GB2382115A

GB2382115A - A spring device for use in clutch release mechanisms

Info

Publication number: GB2382115A
Application number: GB0220674A
Authority: GB
Inventors: Thomas Riess
Original assignee: ZF Sachs AG
Current assignee: ZF Friedrichshafen AG
Priority date: 2001-11-16
Filing date: 2002-09-05
Publication date: 2003-05-21
Also published as: DE10156480B4; DE10156480A1; FR2832473A1; GB0220674D0

Abstract

A spring device (1) is connected between a pedal (18) used to operate a hydraulic master cylinder (19) for actuating a vehicle clutch. The spring device (1) is composed of a telescopic guide means (14) with respective guide elements connected to first and second stop plates (12, 13). A helical compression spring (15) surrounds the guide elements and biases the stop plates (12, 13) apart. The stop plates (12, 13) are provided with ball heads (4, 5) at the ends of the device. Socket-forming bearing shells (6) made of plastics material receive the ball heads (4, 5) and are detachably connected. The shells (6) define bearing surfaces (20) extending around practically the whole of the ball heads (4, 5). The bearing surfaces of the ball head and shell are lubricated or self-lubricated. The advantage of this arrangement is the ball heads can be lubricated for life, so operation of the pedal is not adversely affected by friction which increases over time.

Description

A SPRING DEVICE FOR USE IN CLUTCH RELEASE MECHANISMS The invention relates in general to a primary release mechanism, in particular for a motor vehicle clutch, consisting of a hydraulic unit with a master cylinder which can be operated by a pedal. More particularly the invention is concerned with a spring device usable with such a mechanism to absorb energy on engagement and release the energy again on release, the device being articulated to the pedal or a lever connected to the pedal.

A spring device for a hydraulically operated motor vehicle clutch is known from the German patent application DE 100 31 711.1. This device absorbs energy on depression of the pedal and releases the energy again once a dead centre has been exceeded. This known device consists of a spring mounted between two stop plates. One of the stop plates has a ball head which engages in a shallow depression forming a socket and acting as part of a piston and a cylinder capable of executing pump movements when the spring is actuated. The most important function of the spring device is to keep the wear-induced increase in the energy level in the hydraulic unit, and therefore the pedal forces, constant by means of a throttle and a return valve. The spring device pivots with its ball head in the socket relative to a fixed frame or chassis. At the other end the spring device has another ball-and-socket joint connecting it to the pedal. These pivotal movements occur under high contact pressure forces. As the spring device is articulated to the pedal at a certain angle, on actuation of the pedal this angle will approach zero and pass beyond zero, resulting in a pivoting range of the order of up to 90 .

Frictional losses can consequently occur which perceptibly increase the pedal forces.

An object of the invention is to develop improved forms of spring device of this known type.

According to the invention there is provided a spring device which has a first ball head at a first end, a second ball head at a second end, a spring interposed between the first and second ball heads and at least one detachable bearing shell with a curved bearing surface snugly receiving one of the ball heads and encompassing substantially the whole of the bearing surface defined by the ball head, the bearing shell serving to mount the spring device to the pedal or an abutment in a pivotal and lowfriction manner to co-operate with the master cylinder.

A similar ball-and-socket low-friction bearing can also be adopted for the connection between the pedal and the master cylinder. It is unimportant whether the spring device consists of a simple spring alone or of a combination of a spring with a pump device with piston and cylinder. Preferably the spring between the two ball heads is held between two stop plates which, in the relaxed state, are held with a defined spacing by guide means. In this position the spring, which has a high spring characteristic, is already biased and exerts a high force on the stop plates biasing these apart. The force can be limited so during its assembly the spring can be mounted as a unit in the motor vehicle like any other component. The guide means can take the form of relatively movable guide elements for example, telescopic guide elements are fixed to one stop plate and the other fixed to the other stop plate.

As already mentioned friction is produced on the ball heads during the pivotal movements. In accordance with the invention the ball heads no longer move openly in ball sockets but in precise raceways or bearing surfaces of the bearing shells preacsembled on the spring device and substantially surrounding the ball heads. The bearing shells are lubricated or selflubricated and can be deformable or snap-fitted plastics components. To facilitate assembly of the spring device a latching projection can be provided on one or both bearing shells which can latch into a hole.

A variation of the above-described bearing shell is used if holes with relatively large diameters can be provided for the fastening thereof to a fixed vehicle body part, to the pedal or to the lever, and constructional circumstances prevent fastening of the bearing shell with a latching projection. In this case bearing shells with a peripheral fastening groove which does not become detached on assembly of a ball head, may be latched in place.

As already mentioned, both variations of the bearing shells surround the ball heads and form ball contact bearing surfaces or raceways. It has proven to be of particular advantage to guide these ball raceways somewhat further around the ball head in order to be able to detachably latch the bearing shell on the ball head. The bearing shells could thus be reassembled on the ball heads and the unit obtained then finally assembled in the motor vehicle. The advantage here would be in simplified delivery to customers.

The bearing shells preferably consist of plastics material whereby inexpensive production is ensured. This plastics

material can have self-lubricating properties which are obtained in that the plastics material of the bearing shell contains additives providing for self-lubrication for the entire working life of the bearing shell. It has also proven to be advantageous to provide the ball raceway of the bearing shell with recesses which are filled with a lubricant prior to assembly of the ball head to thus allow prolonged lubrication. In certain cases, namely where the above-mentioned proposals of working life lubrication fail, it is expedient to provide the bearing shell with an additional seal which covers the aperture to the ball raceway or bearing surface and the ball head in the bearing shell in that it is fastened to the bearing shell as a ring made of flexible plastics material and is attached to the stop plate or to the neck of the ball head with a lip and in this manner forms a space for a lubricant deposit. This lubricant is always sufficient to guarantee working life lubrication even if the spring element is arranged in an unconventional position and/or with large pivotal angles between the pedal and the master cylinder.

The invention may be understood more readily and various other features of the invention may become apparent from consideration of the following description.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein Figure 1 is a part-sectional view of part of a spring device constructed in accordance with the invention;

Figure 2 depicts part of another device in accordance with the invention which employs a modified bearing shell and Figure 3 is a schematic representation of the spring device as installed with a clutch-operating pedal and a master cylinder.

Referring initially to Figure 3, there is shown a primary clutch release mechanism composed of a foot pedal 18 which can be depressed by a driver to disengage the clutch. A hydraulic master cylinder 19 has its piston rod pivotally coupled to the pedal 18. A spring device 1 constructed in accordance with the invention is also interposed between the pedal 18 and a fixed abutment such as a frame or chassis of a motor vehicle. The device 1 is articulated with ball-and-socket joints to the abutment and the pedal 18. The device 1 can be directly connected to the pedal 18 or as shown a lever can be interposed between the pedal 18 and the device 1. The pedal 18 is shown in its normal rest position. K represents the force vector acting on the pedal 18 when the pedal 18 is depressed by the driver.

An angle W is established between the vector K and the central axis M of the device 1. When the pedal 18 is depressed the angle W tends to decrease.

Turning now to Figure 1, the spring device 1 is composed of a first stop plate 12 and a second stop plate 13. Guide means 14 between the stop plates 12,13 serve to guide the relative displacement of the stop plates 12,13 towards and away from one another. A helical compression spring 15 is arranged with residual spring biasing force concentrically around the guide means 14 and is connected between the two stop plates 12,13.

The guide means 14 preferably consists of two tubular elements which can be moved telescopically one inside the other, the

first of which is connected to the first stop plate 12 and the second of which to the second stop plate 13. The tubular elements are equipped with a mutual stop which fixes the maximum spacing of the stop plates 12,13 relative to one another. This maximum spacing is simultaneously the maximum extension of the spring 15 in its rest position, in which it still develops a high force owing to its assembly with bias.

At a first end 2 of the device 1 there is a first ball head 4 connected to the first stop plate 12. Likewise, at a second end 3 of the device 1 there is a second ball head 5 connected to the second stop plate 13. The device 1 thus described has the longest extension in its rest position, which extension can only be reduced if the two ball heads 4,5 are moved together against the restoring force of the spring 15.

In practice the spring device 1 acts as a top dead centre spring. On actuation of the pedal 18 as the angle W approaches zero, the spring 15 is compressed to its minimum extension. If the pedal 18 is actuated beyond the dead centre at the angle W = 0, the spring 15 can expand again and release energy.

The ball heads 4,5 are received by socket-forming detachable bearing shells. As shown in Figure 1, a first bearing shell 6 is connected to the first ball head 4. The bearing shell 6 has a curvilinear bearing surface 20 which surrounds substantially the entire ball head 4. The shell 6 is detachably fitted to the ball head 4 and the bearing surface 20 leads into an opening 21 via a lead-in bevel 16 which allows the shell 6 made of resilient plastics to be pressed onto the ball head 4. The first bearing shell 6 can arculate about the first ball head 4 as far as the lead-in bevel 16 allows or as far as the angle W

requires. The bearing shell 6 is connected via an outwardly directed latching projection 8 directly to the pedal 18 or to the lever connected to the pedal 18. The shell 6 has an outer flange with an annular face 9 determining the position of the bearing shell 4.

A resilient seal 11 is arranged between the bearing shell 4 and the first stop plate 12. The seal 11 contains a deposit 17 of lubricant to ensure friction-reducing lubrication and to keep away dirt and abraded clutch particles from the bearing surface 20 and the first ball head 4 for the entire working life of the release device.

The other ball head 5 at the other end 3 of the device 1 can also be received in a similar bearing shell to that shown at the upper part of Figure 1.

Figure 2 depicts an alternative bearing shell 7 as a variation of the first bearing shell 6 differing only in the manner of its fixing to the pedal 18 or the lever or the abutment. Like reference numerals denote like parts to Figure 1. If a relatively large hole can be provided for locating the shell 7 and the latching projection 8 is not suitable, the second bearing shell 7 with a peripheral fastening groove 10 can be arranged in a hole of this type. The shell 7 may also be connected to the ball head 4,5 by resilient deformation and lubrication of the bearing surface can also be brought about by a deposit lubricant 17 and a seal 11 as in Figure 1 or by other methods.

The bearing shells 6,7 can be made entirely or at least partly from plastics material and the socket-forming bearing surfaces

20 contacting the ball head 4,5 are made from low-friction plastics, e. g. a plastics material with additives for selflubrication. It is also possible to provide recesses in the bearing surfaces 19 acting as lubricant reservoirs.

A similar ball-and-socket joint composed of the ball head 4,5 and the shell 6,7 can be used to couple the piston rod of the master cylinder 19 to the pedal 18.

List of reference numerals 1 spring 2 first end 3 second end 4 first ball head 5 second ball head 6 bearing shell 7 bearing shell 8 latching projection 9 bearing face (annular) 10 fastening groove (peripheral) 11 seal 12 first stop plate 13 second stop plate 14 guide means 15 spring 16 lead-in bevel 17 lubricant deposit 18 pedal 19 master cylinder 20 bearing surface 21 opening M centre line W angle K force vector

Claims

Claims 1. In or for a release mechanism, in particular for a motor vehicle clutch, consisting of a hydraulic unit with a master cylinder which can be operated by a pedal, a spring device for absorbing energy on operation of the pedal and releasing the energy again on release, the spring device being articulated to the pedal directly or indirectly during use, wherein the spring device has a first ball head (4) at a first end (2), a second ball head (5) at a second end (3), a spring (15) interposed between the first and second ball heads (4,5) and at least one detachable bearing shell (6,7) with a curved bearing surface (20) snugly receiving one of the ball heads (4,5) and serving to mount the spring device to the pedal (18) or an abutment in an articulated and low-friction manner to co-operate with the master cylinder (19).
2. A spring device according to claim 1, wherein the bearing shell (6) has a latching projection (8) and a bearing face (9) for its positional fixing as a detachable connection for the device.
3. A spring device according to claim 1, wherein the bearing shell (7) has a fastening groove (10) for its positional fixing as a detachable connection for the device.
4. A spring device according to any one of claims 1 to 3, wherein the bearing shell (6,7) is made of plastics material and is detachably connected as a press fit to the associated ball head (4,5).
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J. A spring device according to claim 4, wherein the plastics material contains additives for self-lubrication.
6. A spring device according to any one of the preceding claims and further comprising a seal (1) surrounding the space between the ball head (4, 5) and the bearing shell (6,7) and containing lubricant.
7. A spring device according to any one of claims 1 to 5, wherein recesses for receiving lubricant are arranged on the ball contacting surface of the bearing shell (6, 7).
8. A spring device according to any one or more of the preceding claims, wherein the ball heads (4,5) are mounted to stop plates (12,13) interconnected by a telescopic guide means (14) and the spring (15) acts to urge the stop plates apart and surrounds the guide means.
9. A spring device for a clutch release mechanism substantially as described with reference to, and as illustrated in, Figure 1 of the accompanying drawings or Figure 1 as modified by Figure 2 of the accompanying drawings.
10. A clutch release mechanism composed of a hydraulic master cylinder operable with a pedal and a spring device constructed in accordance with any one or more of the preceding claims.
11. A mechanism according to claim 10, wherein there are two bearing shells and both ball heads of the spring device are connected via the bearing shell to the pedal and to the abutment.
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j. 2. A mechanism according to claim 10 or 11, wherein a further ball-and-socket joint composed of a ball head and a bearing shell serves to connect the pedal to a piston rod of the master cylinder.
13. A clutch release mechanism according to any one or more of claims 1 to 12 and substantially as described and illustrated in Figure 3 of the accompanying drawings.