GB2100389A - Friction clutch driven plate - Google Patents

Abstract

In a friction clutch driven plate having a driven plate with low rate torsion damping springs (16) for damping out gearbox idle rattle and stiffer springs (25) for damping out drive oscillations the driven plate has a facing carrier plate (12) flanked by two side plates (14) and (15) which are capable of limited rotation relative to each other and the springs (16) act to resist such rotation. A bob weight (28) is housed in aligned apertures (29) and (31) in the carrier plate (12), and side plates (14) and (15), respectively and can be moved by centrifugal force from an inoperable position in which the carrier plate (12) is rotationally free relative to the other plates (14) and (15), to an operable position in which the three plates are locked rotationally fast together. A spring (34) biases the weight to its inoperable position. <IMAGE>

Description

SPECIFICATION Friction clutch driven plate This invention relates to friction clutch driven plates and particularly, but not exclusively to automobile friction clutches.

In friction clutch driven plates it is common for the friction facings to be rotatably mounted on a hub and for springs to operate between the hub and friction facing carrier to resist such rotation.

Further it is known in British Patent No.

1,167,749 to provide a driven plate with low rate torsion damping springs for damping out low load oscillations to eliminate gearbox idle rattle, and stiffer springs for damping out drive oscillations.

A disadvantage of this type of clutch driven plate is that when a vehicle is "on drive" ie. the driver has his foot on the accelerator, and then the accelerator is released the torque transmission between the friction facing and the hub suddenly changes direction, ie. it reverses, and the driven plate goes into overrun. This causes "knocking" because the low torque springs for damping out gearbox rattle cannot cope with the sudden change in direction, of high torque ioads and the clutch centre knocks as it comes up against the reverse stop. Therefore, there are two conflicting requirements (a) low torque springs to damp out gearbox idle rattle, and (b) the desirability not to have a "loose" clutch centre on overrun conditions.

In British Patent Applications Nos 2,044,397 (French Application No. 79.04719) and 2,050,568 (French Application No. 79.11968) there is described a locking mechanism responsive to centrifugal force and which shorts out the low torque damping springs during overrun conditions.

The clutch plates described in these two applications are of a very complicated construction. The present invention seeks to provide a driven plate which operates to short out the low torque springs on overrun conditions but which is of a simple construction.

Accordingly there is provided friction clutch driven plate having two co-axial parts capable of limited angular relative rotation and circumferentially aligned springs acting to resist the rotation between said parts, and a locking means acting between said parts and operable to make them rotationally fast, said locking means being spring biased into an inoperable position and being movable against the spring bias to lock said two parts rotationally fast above a predetermined speed of rotation of the clutch plate, characterised in that said locking means is a bob weight housed in aligned apertures in the two parts so as to allow for said angular rotation and is movable radially outwards in said apertures against the spring bias to lock said parts rotationally fast.

The invention will be described by way of example and with reference to the accompanying drawings in which: Fig. 1 is an elevation taken in the direction of arrow A in Fig. 2 of a clutch plate according to this invention and also showing in one quadrant the driven plate with a side plate removed; Fig. 2 is a section on the line A-A of Fig. 1; Fig. 3 is a section on the line B-B of Fig. 2; and Fig. 4 is a graph of torque vs rotation of the friction facing around the hub.

With reference to Figs. 1 to 3 a friction clutch driven plate for an automobile has a pair of annular friction facings 11 mounted on a co-axial annular friction facing carrier plate 12. The carrier plate 12 is mounted on a co-axial hub 10 and is free to rotate about the hub 10 on a bush 13. One each side of the carrier plate 12 is located a coaxial side plate 14 and 1 5, both of which are capable of rotational movement relative to the hub 10 and the carrier plate 12.

A pair of auxiliary damping springs 1 6 are located in aligned spring windows 1 7 in the carrier plate 1 2 and side plates 14 and 1 5 to resist relative rotation therebetween. The springs 1 6 are on diametrically opposite sides of the driven plate.

Two co-axial annular retaining plates 18 and 1 9 are located one on each outer side of the side plates 14 and 15, respectively (outer with respect to the carrier plate 12). The two retaining plates are rotationally fast with the hub 10 and are held axially in position by circlips 21. Friction washers 22 are located between the two side plates 14, 1 5 and their respective adjacent retainer plates 1 8 and 19. A washer 23 is located between the retainer plate 1 9 at its circlip 21'.

Four main damping springs 25 are located in equiangularly sets of aligned spring windows 26 in the plates 12, 14, 15, 18 and 19, to resist relative rotation between the retainer plate and the other plates 12, 14 and 1 5 for at least part of the range of rotation. The torsion springs 25 are held snugly by the windows 26' in the retainer plates 18 and 19, and are held snugly by the windows 26A in the side plates 14 and 15, and with some slight circumferential clearance by the other windows 26B in the side plates 1 4 and 1 5.

The spring 25 are all held with circumferential play by the carrier plate windows 26". The play P in the forward direction on two of the springs 26 is 120 and on the other two springs 26 the forward play P2 is 142 . The play P3 in the reverse direction is 80.

Four bob weights 28 are each held in equiangularly spaced apertures 29 in the carrier plate 1 2. The apertures 29 are located circumferentially between the windows 26" in the carrier plate and radially outside the springs 1 6 and are radially elongated so that the bob weights 28 are free to move radially in the apertures 29.

The apertures 29 each align with apertures 31 in the side plates 14 and 15. The apertures 31 are substantially 'L' shaped with the base of 'L' being radially inwards, so that each aperture has a circumferential portion 32 and a radial portion 33.

Each radial portion 33 is located in the same radial position as each of the apertures 29 and has a spring wire 34 affixed thereto, to resist entry of the respective bob weight 28 into said radial portion 33. The spring wire 34 is fixed at one end 36 and located in a clearance slot 37 at its other end to allow it to bend in the centre. With the clutch driven plate in the "at-rest" position shown in Fig. 1 and 3, the radial aperture 29 in the carrier 12 partially overlaps the apertures 31 in the plate 14 and 1 5 and is located to align with the base of the 'L' so that forward rotation of the carrier plate 12 relative to the hub 10 brings the aperture 29 into total alignment with the radial portion 33 of aperture 31.This will allow the weight 28 to move against the bias of the spring 34 into the radial portion and lock the plates 12, 14 and 1 5 rotationally fast.

The bob weights are held in the apertures 29 and 31 by the retainer plates 28 and 19.

With reference to Fig. 4, when the hub 10 is held stationary and the friction facings 11 rotated in the direction of arrow B the clutch operates in the following manner (i) The two side plates 14 and 1 5 are held stationary relative to the retainer plates 1 8 and 1 9 by the springs 25 which fit snugly in the side plate windows 26A. The facing carrier plate carrier 12 therefore moves clockwise against the resistance of the two auxiliary springs 1 6. Whilst the carrier plate 12 is moving clockwise the bob weights 28 at the radially inner end of the apertures 29 are also moved clockwise along the circumferential portion 33 of the apertures 31. In this particular case there is a slight ramp built into the aperture 31 but this is not necessary.

(ii) After 120 of clockwise movement the clearance 'P' between the carrier plate windows 26" and the springs 25 is taken up and the bob weights 28 are moved by the aperture 29 into the radial portion 33 of the apertures in the side plates 14 and 15. This is point Ton the curve.

(iii) Continued anticlockwise movement of the friction carrier plate 12 will result in the springs 25 being compressed to resist the relative rotation. If the speed of rotation of the clutch plate at this point is sufficient for the centrifugal load on each bob weight 28 to overcome the bias of the springs 34 then the weights will move into the radially outer end portion of the apertures 29 and 31 locking the plates 12, 14, and 1 5 rotationally fast.

Continued clockwise movement results in all the springs 25 being brought into operation to resist rotation. The total movement is limited by the coils of springs 25 binding up, (line Y on the curve).

(iv) If the load on the clutch facings is suddenly reversed, (line Y on curve), then because of the high rotation speed of the clutch, the side plates 14 and 1 5 are locked relative to the carrier 12, and the springs 1 6 are shorted out and the springs 25 are compressed in the return movement at +120. This is because the springs 25 are now compressed by movement between the side plates 14 and 1 5 and the retainer plates 1 8 and 19. (See Fig. 4, line X).

(v) If the load on the clutch plate is slowly reversed then the springs 25 are slowly relieved, and the rotational speed of the clutch drops until the bob weights 28 are returned to their inoperative positions by the spring 34. The clutch plate then follows the reverse of the above against the springs 17 until on the overdrive in an anticlockwise direction the clearance P3 has been taken up (Point T2 on curve). The clearance P3 can be made any size depending upon the curve required. After this the spring 25 comes into operation as before (line Y2).

The friction washers 22 only operate when the side plates 14 and 1 5 move relative to the retainer plates 18 and 19, ie. during the latter part of the rotation. Hence there is no friction damping when the low torque springs 1 6 are in operation.

Whilst the driven plate has been described with the 'L' shaped aperture in the side plates 14 and 15 and the radial aperture in the facing carrier plate 12, the reverse situation (not shown) could be utilised ie. L shaped aperture in the carrier plate etc.

Further it would be possible to place the auxiliary damping springs 16, within the main damping springs 25 so that spring 1 6 and 25 are concentric.

Claims (6)

1. A friction clutch driven plate having two coaxial parts capable of limited angular relative rotation and circumferentially aligned springs acting to resist the rotation between said parts, and a locking means acting between said parts and operable to make them rotationally fast, said locking means being spring biased into an inoperable position and being movable against the spring bias to lock said two parts rotationally fast above a predetermined speed of rotation of the clutch plate, characterised in that said locking means is a bob weight housed in aligned apertures in the two parts so as to allow for said angular rotation and is movable radially outwards in said apertures against the spring bias to lock said parts rotationally fast.

2. A friction clutch driven plate as claimed in Claim 1, wherein each bob weight is housed in a radially elongated aperture in one of said parts and the aligned aperture in said other part comprises, a substantially 'L' shaped aperture having a radially elongated portion, and a circumferentially elongated portion, the locking means being operative when the radially elongated portion in the other part, aligns with the radial aperture of the one part.

3. A friction clutch driven plate as claimed in Claim 2, wherein the radially elongate aperture is in a friction facing carrier which constitute one of said parts, and the 'L' shaped aperture formed in side plates located one on each side of the facing carrier.

4. A friction clutch driven plate as claimed in any preceding claim, wherein there are four bob weights equiangularly spaced around the driven plate.

5. A friction clutch driven plate as claimed in any preceding claim, wherein the bob weight is returned to its inoperative position by a spring wire fixed to one of said parts, such that one end of the wire is fixed to said part and the other end of the wire floats in a slot in said parts, so that the other end is free to move when the wire spring is bent in the centre.

6. A friction clutch driven plate as claimed in any preceding claim, wherein the circumferentially aligned springs acting to resist rotation between the parts are located radially inside the locking means.