GB2191831A

GB2191831A - Friction material and carrier plate assembly

Info

Publication number: GB2191831A
Application number: GB08708589A
Authority: GB
Inventors: John Stephen Bolton
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1986-06-21
Filing date: 1987-04-10
Publication date: 1987-12-23
Anticipated expiration: 2007-04-10
Also published as: GB8615230D0; GB8708589D0; GB2191831B

Abstract

A friction material and carrier plate assembly 2, which may be used in the construction of a driven plate for a friction clutch, comprises a carrier plate 4 having radial spokes or paddles 14A, 14B which are resiliently pliable axially of the carrier plate. The paddles 14A alternate with the paddles 14B and constitute a set splayed apart from the set formed by the paddles 14B. An annular resilient friction facing 20 is bonded by inelastic adhesive to the set of paddles 14A and another annular resilient friction facing 22 is bounded by inelastic adhesive to the set of paddles 14B. Rubber cushioning 24 formed by strips of silicone rubber 24P, 24Q is bonded between the paddles 14A and the friction facing 22 and between the paddles 14B and the friction facing 20. Rotary motion can be transmitted from the friction facings to the carrier plate and vice-versa through the inelastic bonds thus avoiding the application of shearing stress to the silicone rubber 24. <IMAGE>

Description

SPECIFICATION Friction material and carrier plate assembly This invention relates to a friction material and carrier plate assembly.

Such an assembly is used in the construction of a friction clutch driven plate particularly, though not exclusively, for the clutch of a motor vehicle.

The driven plate is intended and arranged for connection with an output shaft to transmit driving torque to the shaft, when the clutch is in use, to rotate the shaft with the driven plate about the axis of the shaft. To this end the driven plate can comprise said assembly of friction material and carrier plate, and a driving member may be connected to the carrier plate to receive driving torque from the latter, and said driving member may be arranged and intended for connection to a said output shaft.

The driving member may have a passage or opening lined internally with axial splines to engage with axial splines on an exterior of the output shaft. For example the driving member may be a disc provided with the passage or opening or may be a disc fast with a hub formed with the passage or opening.

The driven plate may be arranged to allow some limited relative arcuate movement between the carrier plate and driving member and therefore the transmission of driving torque to the driving member from the carrier plate may be through torsion damping resilient means, for example, helical springs known per se, constrained between the carrier plate and driving member.

In use in a clutch the driven plate may be releasably clampable between a flywheel or driving plate and a pressure plate under the action of spring means, for example, a diaphragm spring.

(A) Clutch driven plates are known in which facings of friction material are rivetted directly against a solid disc-like carrier plate. During clutch re-engagements undesired judder, vibration and noise is experienced. Furthermore since the driving member or fly-wheel and the pressure plate are seldom formed with absolutely flat pressure faces against which the friction facings are pressed but instead these pressure faces have high spots, relative rotation between a said pressure face and the adjacent friction facing causes rubbing on the high spots during clutch re-engagements and undesired heat spotting develops on the driving plate and the pressure plate and increases the rate of wear of the friction facings which again is undesirable.

(B) Other clutch driven plates are known in which facings of friction material are rivetted to spring plate-like steel cushioning segments attached to the outer periphery of a metal carrier plate. This construction generally avoids the aforesaid judder, vibration and noise, but the metal segments, the rivets, and the extra thickness of friction material required under the rivet heads to attach the rivets provide a mass adjacent to the periphery of the driven plate causing the latter to have a greater moment of inertia than desired.

(C) To reduce the inertia referred to at (B) above it has been proposed to bond friction facings to a carrier plate. But this gives rise to the undesired phenomena referred to at (A) above. An object of the invention is to provide a friction material and carrier plate assembly which may be so constructed for use in a clutch driven plate that the inertia of the latter can be reduced and the aforementioned undesirable phenomena may be avoided or at least reduced.

According to the invention a friction material and carrier plate assembly comprises a carrier plate for rotation about a central axis, said carrier plate being provided with a plurality of spokes comprising at least first and second sets of said spokes, first and second annular arrays of friction material each respectively disposed on first and second opposite sides of the carrier plate, the first annular array being connected to the first set for the transmission of rotary motion from the first array to the carrier plate and vice-versa, the second annular array being connected to the second set for the transmission of rotary motion from the second array to the carrier plate and viceversa, and resiliently deformable elastomeric material being disposed between the first and second arrays to provide axial cushioning.

The elastomeric material may be disposed between spokes of the first set and the second array of the friction material and may be disposed between spokes of the second set and the first array of friction material.

The first set of spokes may, axially of the assembly, be spaced from said second set.

Spokes of the first set may alternate with spokes of the second set.

The first array of friction material may be bonded to the first set of spokes and the second array may be bonded to the second set. The bonding may be substantially inelastic.

There may be a dog connection between at least one said spoke and the corresponding array of friction material.

The elastomeric material can be bonded to spokes of the first and second sets.

Preferably the elastomeric material is a heat resistant rubber, for example, a silicone rubber.

Preferably the arrays of friction material are flexible.

Preferably the spokes can flex resiliently along directions substantially parallel to the axis.

In a modification, the assembly may be arranged so that when the assembly is not in an axially compressed state the elastomeric material does not extend across the whole axial distance between at least one paddle in the first set and the second aray nor across the whole axial distance between at lease one paddle in the second set and the first array.

According to a second aspect of the invention there is provided a friction material carrier for a clutch driven plate comprising a central web and axially flexible radial spokes in at least two sets, at least one set of spokes being axiallW-ffset from the web towards one side thereof, friction facing material at each side of the carrier bonded to a respective set of spokes so as to be capable of transmitting torque from the friction material to the spokes, and elastomeric material interposed between the spokes of each set and the friction facing material at the opposite side of the carrier.

In a friction material carrier according to said second aspect at least two sets of spokes may axially offset from the web towards opoosite sides of the web.

The invention will now be further described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a plan view of a fragment of a friction material and carrier plate assembly formed according to the invention and intended to form part of a friction clutch driven plate; Figure 2 is a section on line ll-ll in Fig. 1; Figure 3 is a diagrammatic section, on an enlarged scale, on line Ill-Ill in Fig. 1; Figure 4 is a section, similar to Fig. 3, of a modification of the assembly: Figure 5 is a fragment of a carrier plate used in another modification of the assembly; and Figure 6 is a section similar to Fig. 2, of a further modification of the assembly.

Referring to Figs. 1 to 3, a friction material and carrier plate assembly is shown at 2 intended to form part of a friction clutch driven plate which can be used in a clutch, for example, a diaphragm spring clutch which may be used, for example, in a motor vehicle.

The assembly comprises a mainly flat steel carrier plate 4 of disc form centrally apertured at 6 to fit, for example, on an internally splined hub (not shown) known per se when the assembly is incorporated in a said driven plate. Aperture 6 is surrounded by a flared or Belleville marginal portion 8. Also the carrier plate is formed with windows 10 for torsional vibration damping springs (not shown) known per se and holes 12 for stop rivets (not shown) known per se. If desired the carrier plate may be of a more annular form and may comprise arcuate sections secured together.

At its periphery the carrier plate 4 has a plurality of radially outwardly projecting platelike paddles or spokes shown generally at 14 (Fig. 1) and integral with the main body of the carrier plate. The spokes 14 are each substantially flat and are substantially equi-angularly spaced about a central axis X about which the assembly is intended to rotate in use. Slots 16 space the spokes which have substantially radial opposite edges 18. If desired the spokes may be rivetted or otherwise attached to a carrier plate of annular or disc form.

Ajacent to the main body of the carrier plate, the spokes 14 are bent or cranked axially so as to be divided into one set of spokes 14A and another set of spokes 14B.

All the spokes 14A lie in a substantially common plane which is, axially, to one side of the plane in which the main body of the carrier plate lies. Similarly all the spokes 14B lie in a substantially common plane which, is axially to the other side of the plane of the main body.

Thus the set of spokes 1 4A is axially spaced from the set of spokes 14B. The spokes 1 4A alternate with the spokes 14B. If desired one of the sets of spokes may substantially lie in the plane of the main body of the carrier plate.

In the example shown there are thirty spokes 14 and thirty slots 16. Circumferentially each spoke 14 extends over about 7" of arc and each slot 16 over about 5". If desired the number, size, shape and spacing of the spokes can be varied.

The spokes 14 are axially pliable in the sense of being leaf springs capable of flexing resiliently along directions substantially paralled to the axis X.

The assembly 2 further comprises two substantially coincident and co-axial annular friction facings 20 and 22 which are bonded, preferably strongly, to the paddles 1 4A and 1 4B respectively. The bonds may be formed by axially thin amounts or layers 34 of adhesive which, prerferably, can be substantially inelastic so that circumferentially there is a substantially rigid connection between material forming the friction facings 20 and 22 and the paddles 14. The bonds enable rotary motion about axis X to be transmitted from any friction facing 20 or 22 to its corresponding paddles 14A or 14B and vice-versa.

Each friction facing 20, 22 can be formed of any friction material known per se and may be of a non-asbestos type but the facings are somewhat resilient such that each facing can flex or deform at least axiallly, but preferably also radially and circumferentially.

Resiliently, deformable elastomeric material 24 is disposed between the paddles 14A and the fricton facing 22 and between the paddles 14B and the friction facing 20.

The layer of elastomer 24 provides resilient cushioning between the friction facings 20, 22 and the paddles 14 and an overall axial cushioning between the friction facings. The layer of elastomer 24 can be of an appreciable axial thickness so that coupled with the flexibility of the friction facings will allow an appreciable local compression or axial compliance of the sandwich comprising both friction facings and elastomeric layer under an axial pressure applied to a relatively small area of friction facing at any region of the whole area of the facing. It is believed that by virtue of this that the object of avoiding or at least reducing undesired heat spotting and undesired judder, vibration and noise is attained.

However when the assembly 2 forms part of a clutch driven plate in use in a motor vehicle clutch such as a diaphragm spring clutch, the subjective feel and quality of clutch re-engagements may be further enhanced by provisions of further cushioning such as between the pressure plate and diaphragm spring and/or between the diaphragm spring and a clutch cover. That further cushioning may be a wavy wire fulcrum ring as in British Patent No.1583404.

The elastomeric material 24 is directly bonded to the paddles 14A, 14B and is not /or need not be bonded to the friction facings 20, 22. Alternatively the elastomeric material 24 may be directly bonded to the friction facings and not bonded to the paddles against which the elastomer presses. In a further variation the elastomeric material can be positioned in the slots 16 and extend between the friction facings.

Because the adhesive bonds 34 transmit torque between the paddles and the friction facings, the elastomeric material 24 is subject to little or no shearing force especially when it is only bonded to either the paddles or to the friction facings.

The elastomeric material 24 is preferably a heat resistant synthetic rubber, for example a silicone rubber.

The rubber can be a room temperature vulcanising (called RTV) rubber. An example of such a silicone rubber is RTV 7057 produced by Dow Corning. Another example is ELAS TOSIL (Trade Mark) E14 produced by Wacker Chemie GmbH, and a further example is RTV 159 produced by General Electric Company of the U.S.A. However a silicone rubber of the fluoro-silicone kind may also be used.

Desirably this rubber is of a kind which can withstand temperatures experienced by friction facings in use without the rubber degrading to loose its necessary bond strength or resilience. It is believed that the rubber should be able to withstand temperatures up to about 250"C, but an ability to withstand higher temperatures is thought desirable, for example up to about 300"C or higher.

In Fig. 1 to 3 the elastomer 24 is bonded to each paddle in the form of discrete, spaced, substantially radial beads or stripes 24P and 24Q. However the elastomer may be any other desired form, for example dots or larger blobs or as a continuous layer over each paddle.

During manufacture of the assembly 2 the elastomeric material 24 is applied to the paddles 14A and 14B as a paste in the form of stripes or beads 24P and 240, (for example by a combing method) of desired axial depth. Then the elastomeric material 24 is cured or vulcanised. After that the friction facings 20 and 22 are bonded to the paddles 14A and 14B using adhesive 34 so that the friction facings are held against the vulcanised material 24.

In the case of an RTV rubber, vulcanising is merely by subjecting the paste to appropriate room temperature and humidity for sufficient time. For example RTV 7057 vulcanises in about forty-eight hours at a temperature of about 25"C and about 50% humidity.

In the modification in Fig. 4, the paddles 14A and 14B are bonded at 34 to bases 30 of radial recesses 26 in the friction facings 20 and 22. The sides of the paddles are in juxtaposition with sides 32 of the recesses 26 so that there is dog-type connection between the paddles and friction facings to assist in the transmission of torque between the friction facings and the paddles.

In the modification in Fig. 5, each paddle 14A and 14B has a radial rib formation 36 which increases the area of the paddle to which elastomer beads 24P and 240 bond.

In the modification illustrated in Fig. 6 the elastomeric material 24 is axially thinner leaving a gap 38 between the friction facing 22 and the elastomeric material adhered to the paddles 14A and between the friction facing 20 and the elastomeric material adhered to the paddles 14B. When the assembly in Fig. 6 is used in a friction clutch driven plate, during clutch re-engagements a first stage of axial cushioning comprises pressing the sets of resiliant paddles 14A and 14B closer together to close the gap 38 after which a second stage of cushioning comprises compressing the elastomeric material 24.

Claims

1. A friction material and carrier plate assembly comprising a carrier plate for rotation about a central axis, said carrier plate being provided with a plurality of spokes comprising at least first and second sets of said spokes, first and second annular arrays of friction material each respectively disposed on first and second opposite sides of the carrier plate, the first annular array being connected to the first set for the transmission of rotary motion from the first array to the carrier plate and viceversa, the second annular array being connected to the second set for the transmission of rotary motion from the second array to the carrier plate and vice-versa, and resiliently deformable elastomeric material being disposed between the first and second arrays to provide axial cushioning.

2. An assembly as claimed in Claim 1, in which said elastomeric material is disposed between spokes of the first set and the second array of friction material and is disposed between spokes of the second set and the first array of friction material.

3. An assembly as claimed in Claim 1 or Claim 2, in which the first set of spokes is, axially of the assembly, spaced from said second set.

4. An assembly as claimed in any one preceding claim, in which spokes of the first set alternate with spokes of the second set.

5. An assembly as claimed in any one preceding claim, in which the first array is bonded to the first set of spokes and the second array is bonded to the second set.

6. An assembly as claimed in Claim 5, in which the first array is substantially inelastically bonded to the first set of spokes and the second array is substantially inelastically bonded to the second set.

7. An assembly as claimed in any one preceding claim in which there is a dog connection between at least one said spoke and the corresponding array of friction material.

8. An assembly as claimed in Claim 7, in which said spoke is disposed in a recess in said corresponding array of the friction material.

9. An assembly as claimed in Claim 2, in which the elastomeric material is bonded to spokes of the first and second sets.

10. An assembly as claimed in Claim 2, in which the elastomeric material is bonded to the first and second arrays of friction material.

11. An assembly as claimed in any one preceding claim, in which the elastomeric material is a heat resistant rubber.

12. An assemly as claimed in Claim 11, in which the heat resistant rubber is a silicone rubber.

13. An assembly as claimed in any one preceding Claim in which the arrays of friction material are flexible.

14. An assembly as claimed in Claim 13, in which at least one of said arrays of friction material is a continuous integral annulus of friction material.

15. An assembly as claimed in any one preceding claim, in which the spokes can flex resiliently along directions substantially parallel to the axis.

16. An assembly as claimed in Claim 15 and Claim 2 or as claimed Claim 15 and in any one of Claim 3 to 6 when appended to Claim 2, in which when the assembly is not in an axially compressed state the elastomeric material does not extend across the whole axial distance between at least one paddle in the first set and the second array nor across the whole axial distance between at least one paddle in the second set and the first array.

17. An assembly as claimed in any one preceding claim in which the spokes are integral with the carrier plate.

18. An assembly as claimed in any one preceding claim in which the spokes have the form of plate-like paddles.

19. An assembly as claimed in Claim 18, in which the paddles comprise ribs.

20. A friction material carrier comprising a central web and axially flexible radial spokes in at least two sets, at least one set of spokes being axially offset from the web towards one side thereof, friction facing material at each side of the carrier bonded to a respective set of spokes so as to be capable of transmitting torque from the friction material to the spokes, and elastomeric material interposed between the spokes of each set and the friction facing material at the opposite side of the carrier.

21. A friction material carrier according to Claim 20, in which at least two sets of spokes are axially offset from the web towards opposite sides of the web.

22. A friction material and carrier plate assembly substantially as hereinbefore described with reference to Figs. 1 to 3, or Fig. 4, or Fig. 5, or Fig. 6 of the accompanying drawings.

23. A clutch driven plate having a friction material and carrier plate assembly as claimed in any one of Claims 1 to 19 or in Claim 22, or having a friction material carrier as claimed in Claim 20 or in Claim 21.

24. A motor vehicle provided with a clutch including a driven plate as claimed in Claim 23.