GB2242254A

GB2242254A - Coupling for friction clutch driven plate

Info

Publication number: GB2242254A
Application number: GB9021321A
Authority: GB
Inventors: Luigi Cucinotta; Pietro Caracini
Original assignee: Automotive Products PLC; Automotive Products USA Inc
Current assignee: Automotive Products PLC; Automotive Products USA Inc
Priority date: 1990-03-23
Filing date: 1990-10-01
Publication date: 1991-09-25
Anticipated expiration: 2010-10-01
Also published as: IT9019785A0; IT1239415B; GB9021321D0; IT9019785A1; GB2242254B

Abstract

A rotary coupling having a friction damper 50 in which the friction load is generated by a spring washer (52) which also acts as a friction plate. The spring washer (52) is in frictional engagement with a relatively rotational component (43) and this frictional engagement resists the relative rotation therebetween. The rotary coupling may form part of a friction clutch driven plate and in particular a driven plate having two stages of torsion damping. <IMAGE>

Description

FRICTION CLUTCH DRTVEN PLATES This invention relates to rotary coupling and friction clutch driven plates, and in particular, but not exclusivelyt to friction clutch driven plates for use on vehicles.

In a typical motor vehicle the engine is connected to the vehicle gearbox via a friction clutch which includes a fly wheel and pressure plate connected to the engine, and between which is sandwiched a driven plate which is connected to the gearbox.

A friction clutch driven plate typically comprises a hub which is splined onto the gearbox input shaftr a co-axial friction facing carrier plate mounted on the hub and capable of limited angular rotation about the hub, and springs housed in aligned apertures in a flange connected to the hub and the carrier plate, to act between the hub and carrier plate to restrain said angular rotation. The facing carrier plate is connected to the vehicle flywheel through the friction facings.

In some vehicles when the engine is idling and there is no torque load passing through the clutch driven plate the irregular impulses from the vehicle engine can be transmitted to the gearbox and cause gearbox idle chatter.

Solutions to overcome this problem have involved the use of multi-stage spring damping in which the movement between the friction facing carrier plate and the hub flange is dampened by main or second stage damping springs and the hub flange is free to rotate through a limited angular movement relative to the hub drive and is restrained in this movement by a very low rate first stage torsional damping spring or springs. The hub flange can oscillate around the hub when the vehicle is idling with only the first stage damping springs operating to suppress any transmission of vibrations to the gearbox.

These very low load impulses passing through the driven plate can also be dampened by use of a low rate friction damping means which is operated sometimes in conjunction with the first stage damping.

The present invention provides a low rate friction damping means for use in a friction clutch driven plate.

Accordingly there is provided a rotary coupling comprising a pair of side plates secured rotationally fast with each other, a coaxial central annular flange means located between the side plates and capable of axial movement relative to the side plates, said flange means also being capable of limited angular rotation relative to the side plates, and a spring washer that is in frictional engagement with the flange means and acts to bias the flange means into frictional engagement with a side plate so that said relative rotation between the side plates and the flange means is resisted by frictional engagement between the spring and the flange means and between the side plate and flange means.

Conveniently the two side plates are secured rotationally fast with each other by pins which pass through co-operating apertures in both the spring washer and the flange means, the pin apertures in the spring washer having a smaller circumferential length than the flange means pin apertures, so that after any circumferential play between the pins and the spring washer apertures has been taken up the side plates become rotationally fast with the spring washer which is caused to rotate relative to the flange means.

The above coupling forms part of a friction clutch driven plate comprising a hub, a friction facing carrier mounted on the hub for limited angular rotation about the hub, and said rotary coupling is operable between the facing carrier and hub to resist said angular rotation.

The invention will now be described by way of example and with reference to the accompanying drawings in which: FIG 1 is an elevation of a clutch driven plate according to the invention, FIG 1A is a sectional view showing the hub flange meshing with the hub splines, FIG 2 is a section on the line II-II showing the central portion only Fig. 1, FIG 3 shows a flange plate from the friction damping means viewed from one side, FIG 4 is the spring washer from the friction damping means viewed from one side, FIG 5 an assembly of the side plate, spring washer and flange plate on the driven plate hub showing the relative pin clearance, FIG 6 is a graph of torsion load versus angular displacement for a driven plate according to this invention.

With reference to Figs 1 1A and Fig. 2 there is illustrated a friction clutch driven for a motor vehicle and which comprises a hub 11 having internal splines 13 for connection with a gearbox input shaft and an annular array of circumferantially spaced teeth 20 extending radially outwards on the outer surface of the hub 11. A coaxially annular flange 12 having spaced teeth 30 in its inner peripheral margin is mounted on the hub 11 concentrically so that the teeth 20 loosely engage teeth 30 allowing the flange 12 limited angular movement about the hub 11. A coaxial friction facing carrier 14 is also mounted on the hub 11 and is capable of limited angular movement relative to both the flange 12 and the hub 11.

A set of main torsion damping springs 15 are housed in aligned apertures 16 and 17 in the hub flange 12 and facing carrier 14 respectively, and act to restrain the angular movement therebetween. Although the number of springs illustrated is a preferred six springs, there is no reason why other number of springs cannot be used, for example between four springs and eight springs.

The annular facing carrier 14 comprises an annular carrier plate 18 located to one axial side of the flange 12, and an annular retainer plate 19 disposed on the other axial side of the flange 12. The two annular plates 18 and 19 are secured together by three stop pins 21 which pass through co-operating apertures 22 in the outer peripheral margin of the flange 12. The stop pins 21 limit the rotational movement of the facing carrier 14 about the hub 11 and flange 12 by abutment against the radial ends of the apertures 22.

A plurality of segments 23 are arranged in a circular array and are attached to the outer peripheral margin of the carrier plate 18 by any suitable means such as rivets, and a pair of opposed annular friction facings 24 are secured one on each side of the segments 23 by suitable means such as rivets. The segments 23 typically are of spring steel and are shaped to provide resilient axial cushioning between the two friction facings.

A flanged bush 25 preferably a nylon bush, is located on the hub 11 so that the centre portion 31 extends through the centre of the carrier plate and the flange 32 is located between the carrier plate 18 and the hub flange 12. The bush 25 is usually rotationally fast with the carrier plate so that the bush 25 supports the facing carrier 14 for rotation around the hub 11.

A friction damping washer 26 is located axially between the hub flange 12 and the carrier plate 18 and the carrier plate 18 is biased towards the hub flange 12 by a first spring washer 27, which acts between the other side of the hub flange 12 and the side plate 41 of a first stage damping means 50 to be described later.

The main damping springs 15 are housed in the aligned apertures (sometimes referred to as spring windows) 16, in the hub flange 12, and apertures 17 in the carrier plate 18 and retainer plate 19. The spring windows 16 and 17 have circumferential ends that are contactable with the ends of the springs 15 during the rotational movement of the carrier 14 around the hub 11 to compress the springs 15. The main damping springs may all act simultanously or can be brought into operation after different angular phases of rotation, as is well known in the trade.

The teeth 20 on the hub 11 are engaged in the notches 30 on the inner peripheral margin of flange 12 so that the flange 12 is capable of limited angular rotation around the hub 11. The angular rotation of the flange 12 around the hub 11 being limited in both directions of rotation by abutment of teeth 20 with the circumferential ends of the notches 30.

The rotational movement between the flange 12 and the hub 11 is resisted by a first stage damper means 50.

The first stage damping means 50 is of a similar construction to the main damping unit of the driven plate and comprises a pair of flange plates 43 and a pair of side plates 41, and 42. Each flange plate 43 (see Fig.

3) has lugs 44 on its inner periphery for engagement with splines or slots 45 on the outer surface of the hub 11 so that the flange plate is rotationally fast with the hub 11 and is free to move axially. The side plates 41 and 42 are fastened together by pins 46, preferably four pins which pass through elongated apertures 51 in the flange plates 43 so that the side plates 41 and 42 are free to rotate relative to the flange plate 43. The side plates 41 and 42 are made rotationally fast to the hub flange 12 by three axial tabs 47 on the plate 41 that engage in slots on the radially inner edge of the hub flange spring windows 16.

An annular combined spring washer and friction plate 52 is located axially between the two flange plates 43. The spring washer/friction plate 52 is shown in Fig 4 and is free to rotate around the outer surface of the hub 11.

The spring washer/friction plate 52 is a wavy washer having undulatations normal to the plane of the washer and which extend circumferentially around the washer.

The spring washer/friction plate 52 has apertures 49 therein to accommodate the pins 46.

As can be best seen in Fig. 5 the pins 46 have circumferential play in the respective spring washer apertures 49, and in the flange plate apertures 51. the pin apertures 51 in the flange plates having a greater circumferential length than the pin apertures 49 in the spring washer friction plate 52.

Four first stage torsion damping springs 48 are housed in spring apertures or windows 54, 55, 56, in the flange plates 43 , side plates 41 and 42 respectively , and spring washer/friction plate 52 (see Figs 3 and 4).

These low rate springs 48 provide a resistance to rotation that is much less than for the main torsion damping springs.

The springs 48 may all have the same spring rating or not as is desired and can all be brought into operation simultaneously or may be phased in at different dwell angles, again as is desired. In this case at least two springs 48 are an exact fit in the flange plate spring windows 54A, side plate windows 55A, to return the hub 11 to an at-rest position relative to the hub flange under no-load conditions (no torque loads on the friction facings) and also to give the required torque versus angular displacement characteristics for the crutch The other two springs 48 are arranged to come on in stages by having circumferentialy elongated spring windows 54B in the flange plate 43. In this case the second pair of springs come into operation after about 2 degrees of rotational movement.Furthermore but not shown when the side plates 41, '42r hub flang 43, and friction plate 52 are assembled, the assembly can be arranged so that the pins 46 are off set relative to the apertures 49, and 51 in the flange plate and spring washer/friction plate 52 respectively so that the damping characteristics are different in the drive and overun conditions.

A reference mark 57 is present on each flange plate 43 to aid correct assembly of the components.

A second friction washer 58, is located radially outwardly and concentric with the flange plates 43 to act between the side plate 41 and the retainer plate 19.

The operation of the driven plate will now be explained also with reference to Fig. 1 and Fig . 6 . In Fig. 6 the central portion of the graph has an enlarged scale to more clearly show the friction damping effect in the first stage damper 50. With the hub 11 held stationary and a drive load applied to the friction facings 24, the facing carrier 14 is moved anti-clockwise as shown by arrow X in Fig. 1. Since carrier 14 and flange 12 are held rotationaly fast by the main torsion damping springs 15, the flange 12 will initially move with the carrier 14 relative to the hub 11 to take up the clearance 'L' between the teeth 20 and notches 30.The plates 41 and 42 are held fast in the hub flange 12, by the tab 47, the friction damper flange plates 43 are held fast to the hub 11, and the spring washer friction plate 52 is held stationary relative to the flange plates 43 by frictional engagement. Therefore the initial resistance to rotational movement is due to the friction damping generated by the nylon bush and between the side plates 41 and 42 and the respective flange plate 43, and by the first stage damping springs 48. In the initial phase only two springs 48 are compressed between the ends of the side plate spring windows 55 and flange plate spring windows 54A.

This is represented by the dotted line in stage A of the graph in Fig. 6, which lasts for aproximately 3 degrees of rotation. After the lost motion clearance 'M' between the pins 46 and apertures 49 in the spring washertfriction plate 52 has been taken up (see Fig. 5), the plate 52 now moves with the side plates 41 and 42 being now rotationally fast therewith relative to the flange plate 43. The friction damping is now also generated between the spring washer/friction plate 52 and the engaging flange plate 43. The second pair of first stage damping springs 48 in the flange plate apertures 54B also begin to operate being compresed between the ends of the side plate windows 55 and the flange plate windows 54B. This is the dotted line in stage B in Fig 8.

This stage B continues until the lost-motion clearance 'L' between the teeth 30 on the hub flange 12, and the teeth 20 on the hub 11, is taken up (see Fig lA.) and should be for about 5 degrees of relative rotation. This effectively this ends the operation of the first stage damper.

When the lost motion movement between the teeth 20 the teeth 30 have been taken up, further anti-clockwise movement causes the compression of the main torsion springs 15 between the end of the respective flange spring windows 16 and the opposed friction carried spring windows 17. As the carrier 14 rotates around the hub 11 and flange 12 some friction hysterises will now be generated by the friction washers 26 and 58 under the bias of the second spring washer 27.

The friction facing continues its relative anti-clockwise movement until the stop pins 21 abut the ends of the stop pins apertures as is well known in the trade. This is stage C. During this stage it can be the main torsion springs 15 may come into operation in stages. It should be apreciated that the stages A and B are shown with a different torque load scale from the stage C. The difference is approximately a factor of ten.

If the load on the facings 24 is now relieved the facing carrier now moves clockwise and the torsion loads return back down the stage D, allowing for the effects of hysteresis. The initial return movement of side plates 41 and 42 and the pin 46 is accommodated by the clearance in the apertures 49 in the spring washer/friction plate 52, and then the pins 42 abut the ends of the apertures 49 and move the spring washer 52 relative to the flange means 43. This is stage , and the springs 48 in the apertures 54A then return the side plates 41, to their central at rest position, stage F. against a friction load between the flange plates 43 and the side plates 41 and 42. The spring washer 52 remains in an off-set condition.

When the driven plate goes into the over-run :node, the friction facing carrier 14 now moves clockwise relative to the hub, the lost motion clearances in the clockwise direction are the same as for the other direction of rotation and therefore the same sequences of events takes place as for the drive mode of operation. However, when going from drive to over-run the hysteresis follow the solid line G of Fig. 6 because the clearances between the pins 46 and the apertires 49 have already been taken up.

In the dynamic state in use in a vehicle when returning from over-run to the drive mode, the hysteresis does not follow the dotted line in Fig. 6 where the operation begins from a standing start but does in fact follow the outer solid line of H of the graph in Fig. 6.

It can therefore be seen, that in the dynamic state frictional hysteresis is greater around the equilibrium position for the driven plate than on either side of that position.

Claims

1. A rotary coupling comprising a pair of side plates secured rotationally fast with each otherr a coaxial central annular flange means located between the side plates and capable of axial movement relative to the side plates, said flange means also being capable of limited angular rotation relative to the side plates, and a spring washer that is in frictional engagement with the flange means and acts to bias the flange means into frictional engagement with a side plate so that said relative rotation between the side plates and the flange means is resisted by frictional engagement between the spring and the flange means and between the side plate and flange means.

2. A rotary coupling as claimed in Claim 1, characterised in that said flange means comprise two flange plates and said spring washer is located between the two flange plates and is in frictional engagement with both.

3. A rotary coupling as claimed in Claim 2, characterised in that both flange plates are rotationally fast with each other.

4. A rotary coupling as claimed in any one of Claims 1 to 3 characterised in that the two side plates are secured rotationally fast with each other by pins which pass through co-operating apertures in both the spring washer and the flange means, the pin apertures in the spring washer having a smaller circumferential length than the flange means pin apertures, so that after any circumferential play between the pins and the spring washer apertures has been taken up the side plates become rotationally fast with the spring washer which is caused to rotate relative to the flange means.

5. A rotary coupling as claimed in any one of Claims 1 to 4 characterised in that the rotary coupling includes torsion spring means acting between the side plates and the flange means to also resist the angular movement of said side plates relative to the flange means.

6. A friction clutch driven plate comprising a hub, a friction facing carrier mounted on the hub and capable of limited rotational movement about the hub, the driven plate including a rotary coupling as claimed in any one of Claims 1 to 5 and which is operably located between the facing carrier and the hub to resist the rotational movement therebetween.

7. A friction clutch driven plate as claimed in Claim 6 wherein the flange means are rotationally fast with the hub, and the side plates are connected to the facing carrier and rotational movement of the side plates causes the spring washer to rotate relative to the flange means.

8. A friction clutch driven plate as claimed in Claim 7 wherein the hub has an annular array of teeth on its outer periphery which mesh with teeth on the inner periphery of an annular hub flange such that the hub flange is capable of limited rotational movement relative to the hub, and the facing carrier is mounted on the hub for limited rotational movement relative to both the hub flange and the hub, said side plates being rotationally fast with the hub flange for movement of the side plates relative to the flang means during the limited rotational movement of hub flange around the hub.

9. A friction clutch driven plate according to Claim 8 wherein the friction facing carrier comprises a carrier plate arranged on one side of the hub flange and a retainer plate arranged on the other side of the hub flange and which is rotationally fast with the carrier plate and the rotary coupling is located axially between the hub flange and the retainer plate.

10. A friction clutch driven plate as claimed in Claim 9 wherein at least one of said side plates is connected to the hub flange by axially extending tabs at its outer periphery, said tabs being engaged in apertures in the hub flange.

11. A friction clutch as claimed in Claim 9 wherein a further second spring washer is located between said one side plate and hub flange to bias said one side plate into frictional engagement with frictional washer located between the retainer plate and said one side plate.