GB2247725A - Friction facing and carrier assembly - Google Patents

Abstract

A friction material facing and carrier assembly (10) for a clutch driven plate, and which comprises at least one annular friction facing (20) secured to the carrier plate (11) by a single continuous stripe (24A) of adhesive elastomeric material. The stripe (24A) extends circumferentially around the facing (20) in a sinuous path having a wave form in which the height of the wave is substantially equal to the radial width of the facing. The wave form is arranged with cirumferential portions (25, 26) adjacent the edges of the facing (27, 28) and transverse portions (29) that are substantially radially aligned.

Description

A Friction Facings and Carrier Assembly This invention relates to friction material facing and carrier assemblies particularly for friction clutch driven plates, and to a method of manufacture thereof.

It is known to manufacture a friction clutch driven plate by the use of adhesive to secure an annular friction facing to a support or carrier plate. In conventional driven plates an epoxy resin based adhesive may be used for this purpose.

It is desirable for the friction facing of a driven plate to have a certain degree of flexibility and axial cushioning.

The epoxy resin adhesive film generally provides little or no compliance or cushioning.

The axial cushioning is desired to ameliorate a phenomenon known in the trade as "heat spotting", which leads to localised overheating of high spots on the friction faces of the driven plate, flywheel, or pressure plate. The cushioning also helps to prevent clutch judder on take-up of the drive.

The necessary axial cushioning is generally provided between the opposed back faces of a pair of annular friction facings. This is conventionally achieved by mounting the facings on spring steel cushioning segments.

EP252583A, describes the use of a silicone rubber adhesive for mounting a friction facing onto a carrier or support.

The silicone rubber adhesive serves to secure the facing to its support and also provides the necessary axial cushioning, thus allowing a simplification of the driven plate construction. In PCT/GB88/953 there is disclosed a construction in which the silicone rubber adhesive is formed in discrete concentrically spaced circles. Each circle of adhesive is described as being formed by a respective adhesive nozzle.

In a further development, disclosed in EP32336, the silicone adhesive is applied to the reverse side of the friction facing as a continuous spiral of substantially three turns, the spiral starting radially inwardly of the facing and moving outwards.

This latter system has the advantage that only a single application nozzle is needed and that there are less problems associated with starting and finishing of the adhesive application process.

The adhesive when laid in substantially circumferential bands does not have a large component of radial strength.

The present invention provides a driven plate in which the adhesive is applied as a single strip and therefore requires only a single application nozzle, and which has an improved radial strength.

According to the invention there is provided a friction material facing and carrier assembly for a clutch driven plate, and which comprises at least one annular friction facing secured to the carrier by a stripe of adhesive elastomeric material which extends circumferentially around the facings in a sinuous path having a wave form in which the height of the wave is substantially equal to the radial width of the facing.

Preferably the sinuous path is formed so that the portions extending between the peaks. and troughs thereof are substantially radially aligned.

Also according to this invention there is further provided a method of making a friction material facings and carrier assembly having at least one annular friction facing secured to a carrier by adhesive applied to the back face of the facing, said method comprising the steps of extruding elastomeric adhesive material from a nozzle, causing simultaneous rotational movement between the nozzle and the facing and relatively reciprocating the nozzle radially to form a desired sinuous path of elastomeric adhesive around the facing.

The invention will be described by way of example and with reference to the accompanying drawings in which: Fig 1. is a view of the reverse side of the friction facing showing the adhesive laid in a sinuous path according to the invention Fig 2. is an illustration of a friction material facings and carrier according to the invention.

Fig 3. is a section on the line III-III of Fig 2, With reference to Figs 1-3, there is illustrated a friction material facing and carrier assembly l which is intended to form part of a friction clutch driven plate for a motor vehicle, preferably a motor car. The assembly 18 comprises a steel annular carrier plate 11 having a centre hole 12 for mounting of the plate 11 onto a driven plate hub (not shown). The carrier plate 11 is formed with windows 13 for receiving torsional damping springs (not shown) and holes 14 for stop rivets (also not shown) in a manner well known in the trade.

The carrier plate 11 has a plurality of radially outwardly extending fingers 15 equiangularly spaced around its outer periphery. These fingers 15 are spaced by gaps 16.

Preferably there are thirty fingers 15 but other numbers could be used if desired. The fingers 15 are capable of flexing resiliently to allow axial movement of a friction facing 2 mounted thereon, the friction facing 2 being somewhat flexible to allow small amounts of axial deformation.

The carrier plate 11 preferably has two coaxial friction facings 2 mounted thereon one facing 2 on each axial side of the carrier plate 11 with the friction surfaces 17 oppositely directed.

The facings 2 are mounted on the fingers 15 by use of an adhesive material which is laid onto the back face 18 of each facing 2 to adhere the respective facing to the fingers 15.

At least one of the facings 2 is secured to the carrier plate 11 by use of an elastomeric adhesive material 24, preferably a silicone rubber such as RTV7057 sold by Dow Corning, or Elastosil E14 produced by Waker-Chemie Gmbh, or RTV159 produce by the General Electric Company of the USA.

Alternatively, a two pack cure silicone rubber can be used.

The silicone rubber can withstand temperature of up to 25o - - 300 C and is sufficiently flexible to provide cushioning between the friction facings 2.

For better understanding of the relationship between the resilience of the silicone rubber, the clutch driven plate clamp loads, and the flexibility of the friction facings the reader is directed to the present applicants published European Patent application 0252583A1.

On said one facing 2, the elastomeric adhesive 24 is laid in a continuous sinuous or zig-zag stripe or bead 24A which is best seen in Fig 1.

As illustrated in Fig 2. the adhesive is laid in a sinuous path comprising substantially circumferential portions 25, 26 adjacent the radially inner and outer edges 27, 28 of the facing respectively, and transverse portions 29 extending across the facing interconnecting the circumferential 27 and 28.

The path illustrated is a sine wave form but it could be castellated in order than the transverse portions 29 are more radially aligned. The greater the degree of radial alignment the better the radial strength of the adhesive bond between the facing 2 and its carrier plate 14. This is advantageous for the burst strength of the clutch driven plate when rotating at high speeds.

The sinuous path is preferably arranged so that each discrete wave 26 is aligned with a finger 15 with the carrier plate 14 such that the transverse portions 29 are aligned with a finger 15 and the circumferential portions 25 or 26 are aligned with a gap 16 between adjacent fingers as is best seen in Fig 1. The waves can be evenly radially spaced to align with the fingers 15 as is shown in chain dot in Fig 2 so that each finger has two radial portions of a wave thereon. Preferably the circumferential portion 25 adjacent the inner edge 27 coincides with the gaps.

The spaces 16 between the fingers 15 allow the facing 2 to flex and the beads of adhesive 24C on one facing 2 can be arranged so that the adhesive bead on the inner edge 27 of one facing unites with the adhesive bead on the inner edge 27 of the other facing in said spaces so that some adhesive is provided between the facings at the spaces 16. This particularly useful with the two pack silicone rubber.

The sinuous path of the adhesive exposes all the stripe of adhesive to air allowing for the removal of gases emitted by single pack silicone rubbers during their curing processes.

The elastomeric adhesive can be applied to the respective friction facing by extruding the elastomeric adhesive through a nozzle and by simultaneously causing relative rotation between the nozzle and the facings, and relatively displacing the nozzle radially inwardly and outwardly during the rotation until the circle has been completed with the desired number of waves of adhesive around the facing.

Preferably the facing is held stationary and the nozzle is moved relative to the facing to lay the adhesive material stripe onto the facing. The nozzle is moved at a substantially constant linear ' speed to lay a stripe of substantially constant cross-section. However, the cross-sectional area of the extrudate adhesive can be altered as desired by varying the extrusion speed of the adhesive or the linear speed of the nozzle.

Once the desired pattern of elastomeric adhesive materials has been laid on the back face 18 of the facing 2, the facing can be mounted onto the fingers 15 of the carrier plate 11. The facing 2 must be held flat as the carrier plate 11 is pressed into contact with the adhesive, and spacer means must be provided between the carrier plate and facing to prevent the, adhesive from being squeezed out of shape.

A suitable method and apparatus is described in British Patent application 88174933.

An appropriate passage of time must be allowed for full cure of the adhesive. For example, a single pack silicone rubber will take about 24-48 hours to cure at room temperature with a humidity of 5%.

Claims (9)

Claims

1. A friction material facing and carrier assembly for a clutch driven plate, and which comprises at least one annular friction facing secured to the carrier by a stripe of adhesive elastomeric material which extends circumferentially around the facing in a sinuous path having a wave form in which the height of the wave is substantially equal to the radial width of the facing.

2. An assembly as claimed in Claiml wherein the sinuous path is formed with substantially radially extending transverse portions extending between substantially circumferentially extending portions adjacent the edges of the facing.

3. An assembly as claimed in Claim 1 or Claim 2 wherein the adhesive is a silicone rubber adhesive.

4. An assembly as claimed in any one of Claims 1 to 3 wherein the carrier is a disc having its outer peripheral margin formed as a plurality of circumferentially spaced fingers, and the friction facing is adhered to said fingers.

5. An assembly as claimed in Claim 4 when dependent on Claim 2 wherein the adhesive path is arranged so that radial transverse portions of the adhesive stripe align with the fingers of the carrier.

6. An assembly as claimed in any one of Claims 1 to 5 and further comprising a second friction facing arranged coaxially with the first facing and adhered to the carrier to face in the opposite direction to the first facing.

7. An assembly as claimed in Claim 6 wherein said second facing is secured to the carrier as aforesaid in Claims 1 to 5 with regard to the first facing.

8. An assembly as claimed in Claim 7 wherein the radially extending portions of adhesive stripe on one facing are in alignment with the radially extending portion of stripe on the other facing.

9. A friction clutch driven plate including a friction material facing and carrier assembly as claimed in any one of Claims 1 to 8.

1B.A method of making a friction material facings and carrier assembly having at least one annular friction facing secured to a carrier by adhesive applied to the back face of the facing, said method comprising the steps of extruding elastomeric adhesive material from a nozzle, causing simultaneous relative rotational movement between the nozzle and the facing and relatively reciprocating the nozzle radially to form a desired sinuous path of elastomeric adhesive around the facing.

ll.A method as claimed in Claim 1B wherein the nozzle is reciprocated radially so as to cover the full radial width of the facing during the radial displacement.