GB2242253A

GB2242253A - Friction clutch driven plates

Info

Publication number: GB2242253A
Application number: GB9019240A
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: 1990-09-04
Publication date: 1991-09-25
Anticipated expiration: 2010-09-04
Also published as: IT9019786A0; GB2242253B; GB9019240D0; IT1239416B; IT9019786A1

Abstract

A clutch driven plate comprising a hub (11), a hub flange (12) mounted on the hub (11) and capable of limited angular movement about the hub, and a friction facing carrier (14) also mounted on the hub and capable of limited angular movement relative to both the hub (11) and flange (12). A first stage damping means (48) acts between the hub flange and the hub during a first period of relative rotation of the carrier (14) around the hub. The first stage clamping springs are housed in a pre-built first stage damping unit (40) which is an independent rotary coupling which can be built and tested independantly of the remainder of the driven plate. <IMAGE>

Description

FRICTION CLUTCH DRIVEN PLATES This invention relates to friction clutch driven plates and in particular tut not exclusively, to to friction clutch driven plates for use on vehicles In a typical motor vehicle the engine is connected to the vehicle searbox via a friction clutch which includes a fly wheel and pressure plate connected to the engine, ar, between which is sandwiched a driven plate which is connected to the gearbox A friction clutch driven plate typically comprises a hub which is spy ine onto the searbox ir,vut shatt, d co-axial friction facing carrier plate mounted on the hub and capable of limited angular rotation abljut the hub, aid 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 idlins 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 @@volvedth@ use of multi-stage spring damping in which the movement between the friction facing carrier plate and tre hub flange is dampened by main or second stage damping springs and the hub flange is free to rotate thorough 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 dl ivet- plate can also be dampened by use of a low rate friction damping means which is operated only iri conjunction with the first stage damping.

Clutch driven plates which include idling dampers tend to have very complicated structures and are difficult to assemble. Further these driven Plates are typically bulky around the hub so that the driven plate is difficult to incorporate into a particular envelope According to the present invention there is provided a clutch driven plate comprising a hub, an annular hub flange mounted on the hub and capable of limited angular movement about the hub, aid a fricticl-l facing -r also mounted on the hub and capable of limited angular movement relative to both the hub and hub flange, a main torsion damping means acting between the facing carrier and the hub flange to restrain relative rotational movement therebetween, and an initial damping means which acts between the hub flange and the hub to restrain angular movement therebetween during a first period ot relative rotation of the carrier relative to the hub, characterised i that the initial damping means is housed in a pre-built first stage damping unit in which said initial damping means acts between a fir-st coaxial annular means adapted to engage rotationally fast with the hub flange, and a second coaxial annular means adapted to engage rotationallY fast with the hub, said unit forming an independent rotary coupling which can be built and tested independently of the remainder of the driven plate.

Also according to the invention there is provided a method of manufacture of friction clutch driven plate having a friction facing carrier cover rotatably mounted on a hub and having an initial dmaping device operative for a first period of angular rotation of the carrier around the hub, and a second damping device operative over a further second period of angular rotation, characterised in that the second damping device is assembled as a @re-built unit whirr @orms a &commat; -ot cj coupling in its own right, and can be tested and adjusted prior to assembling the driven plate Further there is also provided a driven plate capable of variably friction hystet-esis and which is of a simple construction.

Accordingly there is provided a friction clutch drive plate comprisins a hub, a friction facing carrier mounted on the hub and capable of limited angular rotation aroul Id the hub, and a friction damping means operating between the carrier and the hub for an initial period of arigulai- rotation of the carrier around the hub, said friction damping means comprising a flange means rotatiorially fast with one of the carrier or hub, and a pair of side plates rotationally fast with the other of said carrier or hub, said flange being biased into frictional engagement with one of the side plates and wherein said one side plate has raised areas thereon which make frictional contact with raised areas on t}-.e adjacent slltface of the flange means, the hysteresis effect of the frictional contact varying as the raised areas on said one side plate move across the raised areas on the flange means.

The invention will be described by war of example and with reference to the accompanying drawings in which: FIG 1 is an elevation of a clutch driven plate according to the inventions FIG 2 is a section on the line II-II of Fig. 1, FIG 3 is a pre-built first stage damping unit as used in Fig. 1, FIG 4 is a section on the line IV-IV of Fis.

FIG 5 is a centre flange from the first stage damping unit viewed from one side FIG 6 is the centre flange of Fis. 5 viewed frorn the other side showing the low spots in dark shading, FIG 7 is a graph of torque versus angular displacement for the driven plate, FIG 8 is an elevation of a side Plate from the first stage damper unit showing the raised radial ribs, FIG 9 is a section on the line IX-IX of Fig. 8 and FIG 10 is a graph of hysteresis versus angular displacement for the first stage damper unit only.

With reference to Fig. 1 and Fig. 2 there is illustratged a friction clutch driven plate 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 circumferentially- spaced teeth 20 extendillg radially outwards on the outer surface of the hub 11. A coaxial annular flange 12 having spaced annular notches 30 in its inner peripheral margin is mounted on the hub 11 concentrically with tt-ie teeth SO so ttat tr teet, 2(.

loosely engage with the notches 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 16 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 main torsion damping spring provide a resistance to relative rotation of into 25 da Nm.

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 tt-iree stop ruins 21 which pass through co-operating apertures 22 in the outer peripheral margin of the flange 12. The stop pin 21 limit the rotational movement of the facing carrier 14 about the hub 11 arid flange 12 by abutrnerlt against title radial ends of the apertures 22.

A plurality of seymerltss 23 are arrangd ii 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.

The carrier plate 18 and consequently the flange 12 are supported for rotational movement about tie hub 11 bv a flanged bush 25, preferably of nylon, which is rotationally fast with the carrier plate. A friction damping washer 26 is located axially between the hub flange 12 and the carrier plate 19 and is biased against the hub flange br a spring washer 27, which acts between the hub flange 12 and the side plate 41 of a first stage torsion damping unit to be described in greater detail later. The bush 25 is made rotationally fast to the facing carrier 14.

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 contact able with the ends of the springs 15 during the rotational movement of the carrier 14 around the hub 11 to compress the sprinss 15.

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 1.2 arc3url..i 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 tub il is resisted by an initial damping spring sometimes called a first stage damping unit 40 more clearly illustrated in Figs 3 and L.

The first stage damping unit 40 is pre-built Sub-assembly which is an independant rotary coupling in its own right and which is added to the remainder of the driven plate as a pre -tuned and pre-tested unit.

The first stage damping unit is of a similar construction to the main damping unit of the driven plate and comprises a central flange means 43 having lugs 44 on its inner periphery for engagement with splines or slots 5 on the outer surface of the hub 11 so tra-t flange is rotationally fast with the hub 11 and is freU to move axially . A pair of side plates 41 and 42 are fastened together by pins 46, preferablly four Pit'05, and are free to rotate relative to the flange means 43.The side plates 41 and 42 are made rotationally fast to the 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.

Four low rates first stase damping springs 48 dre housed in spring apertures or windows 49, 51, in the flange means 43 and side plate 41 and 42 respectively (see Figs 5, 6, 8, and 9). These low rate sprinss 48 provide a resistance to rotation of up to 1 da NM.

The springs 48 may all have the same springs ratins 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 spring an under a pre load condition 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 facias ) The side plate 41 which engages the hub flange 12 is shown in greater detail in Figs 8 and 9. The plate 41 on its surface adjacent the flange means 12 has eight raised surface portions in the form of radial ribs 52.

These radial ribs 52 are angular spaced so as to engage raised co-operatins surfaces on the adjacent surface of the flange means 43.

Now with reference to Figs 5 and 6 te flange means 43 is shown in Fig 5, viewing the side adjacent the side plate 42. There are four angularly spaced spring windows 49 and stop pin apertures 54 to allow for the limited angle rotation of the side plates 41, 42 relative to the flange means 43 against the resistance of the springs 48.

As viewed from its side adjacent the side plate 61 as shown in Fig 6, the flange means 43 has a surface comprising raised surface portions and low surface portions. The low Portions are shown as shaded areas.

The raised surface portions comprise a radially inner- set of eight raised surface portion 62 which are annularly spaced to be in alignment with the eight raised ribs 52 on the plate 41 in the 'at rest condition, and a set of eight radially outer raised surface portions 63 which are circumferentially offset from the inner r-aised portions 62, and are located outwardly of trite spring windows 49, and stop pin apertures 54. The flange means L3 is formed from nylon, preferably nylon 66 and all these raised areas can be formed in a single moulding operation.

In the first stage damping unit the Plate 41 is biased towards the flange means 43 by a wavy washer 64 located between the flange means 43 and the side plate 42 at the outer peripheral margin thereof.

The pre-built first stage damper unit is arranged i, the driven plate in annular space around the hub 11 between the hub flange 12 and the retainer plate 19.

The side plate 42 is arranged to fit concentrically within the centre of the retainer plate and is in axial alignment therewith.

When the pre-built unit is placed into position, the wavr washer 17 is first located on the hub flange 12 and the three tabs 47 on the Plate 41 are each located in their respective slot in the radially inner edges of hub flange spring windown 16. Washers or sPaces 66 are theti placed over the plate 42 and are located between the side plate 41 and the retainer plate 19 and act to transmit the loading from the wavy washer spring 27 via the retainer plate 19 onto the friction washers 26.

The operation of the driven plate will now be explained and for the sake of simplicity the operation of the hysterises control for first stage damper unit will be explained separately.

Now also with reference to Fig. 1 and Fig 7 with the hub 11 held stationary and drive load applied to the friction facing 24 the facing carrier 14 is moved anti-clockwise as shown by arrow A in Fig. 1. Since carrier 14 and flange 12 are held rotationaly fast by the main tension damping springes 15, the flange 12 will move initially relative to the hub 11 to take up the lost motion linkages between the teeth 20 and notches 30.Since the plates 41 and 42 are held fast in the flange 12, and the flange means 43 is held fast to the hub Il, the initial resistance to rotational movement is due to the friction damping generated by the bush 25 on the hub 11 and flange 12, and by the first stage damping unit 40. In the first period of rotation the springs 48 are compressed between the ends of tic spring windows 49 and 51 and come orl ir-i phased stages A and B as the side plates 41 & 42 rotate relative to the flange means 43.

When the lost motion movement between the teeth 20 on the hub 11 and the notches in the flange has been taker up.

point C on Fig. 7, further anit-clockwise movement causes the compression of the main torsion springs 15 betweeri the end of the resPective flange spring windows 16 and the opposed friction carried spring windows 17. The movement will contine until the stop pins 21 abut the ends of the hub flange apertures 22 and the torsion drive becomes solid, this shown in portion D of the graph.

As the carrier 14 rotates around the hub 11 and flange 12 some friction hysterises will be generated bw the friction washers 26 and the spaces 66.

If the torque drive load is now decreased the facing carrier 14 rotates clockwise releiving the torque springs 15, which are still held in compression. The frictioi damping generated by the friction washer 26 and spaces 66 still operates, and a reverse movement down the graph takes place. As the driven plate returns to the at rest state the springs 15 become relaxed. However ttlelee is some pre-load on the first stage damper springs 48 so as to return the hub 11 to a predetermined position relative to the hub flange. The drive load passes through te origin of the graph as the driven plate goes into ar-i overdrive or overrun condition.

In the overdrive condition, the hub 11 is still held stationary and the friction facing continues its relative clockwise movement. Since the teeth 20 are slightly offset relative to the notches 30, the first period of rotation , during which the only resistance to rotation of the carrier 14 around the hub 11 is due to the first stage damping springs 48 and the friction damping caused by rotation of the bush 25 on the hub 11,is of a lesser angular period than for the drive condition - This is shown by the portion E of the graph.

When the teeth 20 abut the ends of the notches 20, at Point F the flange 12 is now held stationary relative to the hub 11 and the main torsion spring 15 and friction washer 26 and sPacers 66 come into operation. This is the portion G of the graph. This clockwise movement will continue until the stop pin 21 abut the ends of the hub flange apertures 22 and the torque drives sloes solid.

If the overdrive torque load is now decreased, the facing carrier 14 moves anti-clockwise relative to the hub relieving the main torque springs 15 and then the first stage damping sprinss.

It will be appreciated that because the first stave spring damping has a so much smaller resistance load than the main torsion damping that the hyster-ises generated in first stage damper is insignificant in comparision Lorque capacity of the driven plate The generation of the friction hysteresis in the first stage damping unit will now be explained.

As the plate 41 rotates relative to the flange means 43 the raised ribs 52 on one plate 41 each move across their respective radially inner raised portion 62 which is shaped so that the ribs encounter increasing resistarlce to the rotational movement. This may also result ir son. resilient distortion of the nylon flange means 43. This is position S of the sraph in Fig. 1O.

At the end of a predetermined relative angular movement, the load exerted by the ribs 52 is transfered from the inner raised portions 62, to the outer raised portions 63. At this movement of transfer at point T there is a slight fall off in hysterises but this builds up again as further rotation takes place Since the friction contact is now radially further out than before the maximum value is increased due to effect of an increased moment ot force. This is shown at 'U' in Fig. 10.

It is thought possible that the iritierent elastic resilience in the flange means 43 also adds to te hysterises effect , as does the relative tarawential movement of the ribs 52 across the raised surfaces 62 and 63.

Claims

1. A clutch driven plate comprising a hub, an annular hub flange mounted in the hub and capable of limited angular movement about the hub, and a friction facing carrier also mounted on the hub and capable of limited angular movement relative to both the hub and hub flange a main torsion damping means acting between the facing carrier and the hub flange to restrain relative rotational movement there between, and an initial damping means which acts between the hub flange and the hub lull to restrain angular movement there between during a first period or relative rotation of the carrier elative to the hub, characterised in that the initial damping means is housed in a pre-built first stage damping unit in which said initial damping means acts between a first coaxial annular means adapted to engage rotationally fast with the hub flange, and a second coaxial annular means adapted to engage rotationally fast with the hub, said unit forming an independant rotory coupling which can be built and tested independantly of the remainder of the driven plate.

2 A clutch driver plate as claimed in Claims 1 characterised in that said second annular meal-is is a flange means having teeth on its inner periphery to engage splines on the radially outer surface of the hub, and said first annular means comprises a pair of annular side plates located one on each side of the flange means and secured together by pins which extend tE-,rougt, cooperating apertures in the flange means, - one of said plates having tab means for engagement in a slot in hub flange

3.A clutch driven plate as claimed in Claim 2 wher-ein the initial damping means comprises four compression springs housed in alisned spring windows in the flange means and annular side plates.

4. A clutch driven plate as claimed in Claim 2 or Claim 3 in which the friction clutch facing carrier comprises a carrier plate arranged on one side of the hub flange ard a retainer plate located on the other side of the hub flange, and characterised in that the first stage damperunit is housed in an annular space between the hub flange and the retainer plate so that a side plate of the first stage unit is concentric with the retainer plate.

5. A friction clutch driven plate as claimed in any one of Claims 1 to L characterised in that the pre-built unit includes a friction damping device to provide hysteresis during first period rotation.

6. A friction clutch driven plate as cla:Lrlled in Claim 5 when dependent upon Claims 2, 3, or o. characterised ir-l that in the pre-built unfit one of said side plates on z ts face adjacent the flange means has raised surface portions that are contactable with co-operating sus face portions on the adjacent surface of the flange means, and the flange means is biased towards said one side plate by a spring washer acting between flange means and the other side plate, such that rotation movement between the side plates and the flange means will be resisted by frictional contact between said surface portions.

7. A clutch driven plate as claimed in Claim 6 characterised in that in the pre-built unit the flange means is formed of flexible resilient material that allows the flange means to deform as the sidle plate moves relative thereto.

8. A clutch driven plate as claimed in Claim 6 or Claim 7 characterised in that the surface of the flange means adjacent said one side plate comprises a plurality of raised portions and low portions arranged so that the raised portions of said one side plate move across said raised portions on the flange means to generate the frictional resistance.

9. A clutch driven Plate as claimed in Claim 8 characterised in that , the raised Portions on the flange means ar-e arranged as radially inner raised portions adjacent the inner periphery of the flange means, and radially outer raised portions adjacent the outer periphery of the flange means and circumferentially offset from said radiallY inner raised portions, and the raised portions on said one side Plate are in the form of angular spaced radial ribs which are in alignment with, the radially inner raised Portion in the at rest condition, and as the side plates rotate relative to the flange means the friction contact between the radial ribs and the raised portion changes from contact with the inner raised portion to contact with the outer raised portions to give two distinct stages of hysteresis.

10. A clutch driven plate comprising a hub, a friction facing carrier mounted on the hub and capable of limited angular rotation around the hub, and a friction damping means operating between the carrier and the hub for ar initial period of angular rotation of the carrier around the hub, said friction vamping means comprising a flange means rotationally fast with one of the carrier or hub, and a pair of side plates rotationally fast with the other of said carrier or hub, said flange means being biased into frictional engagement with the side slates and wherein said one side plate has raised areaa thereon which make frictional contact with raised areas on the adjacent surface of the flange means, the hyster-esis effect of the frictional contact varyins as the raised areas on said one side plate move across the raised areas on the flange means.

11. A clutch driven plate as claimed in Claim 9 characterised in that the raised areas on the flange means are divided into radially inner raised areas and radially outer raised aresa which are circumferentially off set from the inner raised areas, and t?ic-' frletior,al contact changes from the inner areas to the outer areas after a predetermined angular rotation of the carrier to the hub to give two distinct stages of hYsteresis.

12. A method of manufacture of friction clutch driven plate having a friction facing carrier rotatably mounted on a hub and having an initial damping device operable over a first period of rotation of the carrier around the hub , and a second damping device operable over' a further second period of angular rotation, characterised in that the first damping device is asembled as a pre-built unit which forms a rotary coupling in its right, and can be tested and adjusted prior to assembly the driven plate.