GB2092684A

GB2092684A - Clutch release bearing

Info

Publication number: GB2092684A
Application number: GB8203634A
Authority: GB
Original assignee: Valeo SE
Current assignee: Valeo SE
Priority date: 1981-02-11
Filing date: 1982-02-09
Publication date: 1982-08-18
Also published as: DE3204491A1; ES8306840A1; IT1157623B; IT8212430A0; ES509471A0; FR2499646A1; JPS57149627A; FR2499646B1

Abstract

A clutch release bearing (B) comprises a thrust ring (A) adapted to exert an axial thrust on a rotatable clutch disengaging device, such as the fingers (15) of a diaphragm (D) of a diaphragm spring clutch. This ring (A) consists of a composite of one or more thermosetting resins such as polyester resin, epoxide resin, phenolic resin, and heat-stable resin such as polyimide, polyamide-imide, polybenzoxazole and polybenzothiazole, one or more lubricating fillers such as graphite molybdenum sulphide, polytetrafluoroethylene and hexagonal boron nitride, and infusible synthetic fibres such as aramides, polyimides, phenolics and carbon. The thrust ring (A) made from this composite has a low coefficient of friction and high wear resistance. The composite may further comprise glass fibres or mineral oil. <IMAGE>

Description

SPECIFICATION Clutch release bearing The present invention relates to a clutch release bearing comprising a ring, referred to as a thrust ring, which is adapted to exert a force, in a generally axial direction, for example under the control of a fork, on a disengaging device of the clutch, said device being rotatable about the axis of the clutch.

In operation, the thrust rings of clutch release bearings are subjected to difficult working conditions, and the materials of which these rings have hitherto been made only resist these working conditions provided that the latter are alleviated by various mechanical arrangements, which, however, complicate the construction.

The present invention relates to a clutch release bearing of which the thrust ring is made of a material which has an excellent resistance to the most difficult working conditions.

According to the invention there is provided, a clutch release bearing comprising a thrust ring adapted to exert a thrust on a clutch disengaging device, wherein said ring comprises a mixture of thermosetting resin, a lubricating filler and infusible synthetic fibres.

By virtue of this composition, the performance characteristics of the ring are excellent as regards both its low coefficient of friction with the counter-material of which the disengaging device is made, for example of the order of 0.05 to 0.1 5, and its very high wear resistance.

The thermosetting resin may include at least one resin chosen from the group of resins comprising polyester resins, epoxide resins, phenolic resins, and heat-stable resins such as polyimides, polyamideimides, polybenzoxazoles and polybenzothiazoles.

The lubricating filler may include at least one filler chosen from the group of fillers comprising graphite, molybdenum sulphide,polytetrafluoroethylene and hexagonal boron nitride.

Preferably, the lubricating filler further includes at least one filler chosen from the group of fillers comprising the sulphides, selenides and tullurides of molybdenum, tantalum and tungsten.

The infusible synthetic fibres suitably include at least one fibre chosen from the group of fibres comprising aramides, polyimides, phenolics and carbon.

Moreover, the ring can comprise glass fibres such as silionne and verranne, and also mineral oil.

Suitably, the proportion by weight of the various constituents of the mixture forming the ring is between 7 and 45% for the thermosetting resin, between 1 0 and 80% for the lubricating filler and between 2 and 60% for the infusible synthetic fibres.

The infusible synthetic fibres can be provided either in discontinuous form or in the form of filaments.

If the infusible synthetic fibres are discontinuous, the proportion by weight is advantageously between 1 5 and 45% for the thermosetting resin, between 30 and 80% for the lubricating filler and between 2 and 20% for the infusible synthetic fibres.

If the infusible synthetic fibres are provided in the form of filaments, the proportion by weight is advantageously between 7 and 25% for the thermosetting resin, between 10 and 30% for the lubricating filler and between 30 and 60% for the infusible synthetic fibres.

Embodiments of the invention will now be described, by way of example only and with reference to the single Figure, which shows a view in lonyitudinal section of a clutch equipped with a clutch release bearing according to the invention.

The embodiment shown in the single Figure relates, by way of example, to an application of the invention to a clutch of the type with a diaphragm D making direct or indirect contact with the thrust ring A of the clutch release bearing B.

This clutch comprises a mechanism M, a friction disc F and the clutch release bearing B.

The mechanism M comprises a cover 10 designed to be fixed at 11 to a driving flywheel plate 12, a pressure plate 1 3 which can be displaced axially and is integral in rotation with the cover 10 by any suitable means, and the diaphragm D. On its periphery, the latter has a continuous ring 14 acting as a cup spring, whilst its central part is in the shape of spaced-out radial fingers 1 5. The diaphragm D is coupled to the cover 10 by means of short columns 1 6 and acts on the pressure plate 1 3. The fingers 1 5 constitute the disengaging device of the clutch.

The friction disc F is designed to be clamped between the plates 1 2 and 1 3 and is coupled to a driven shaft 1 7.

The clutch bearing B comprises the thrust ring A cooperating with the fingers 1 5 and is controlled by a fork 18.

In the example shown, the clutch release bearing B is mounted to slide along a fixed tubular guide 19, which is coaxial with the axis of the clutch and surrounds the driven shaft 1 7.

When the bearing B is not acting on the fingers 1 5 of the diaphragm D, the collar 14 of the diaphragm D pushes the plate 1 3 elastically towards the flywheel 12, clamping the disc F. Engagement takes place.

When the bearing B thrusts against the fingers 1 5 of the diaphragm D via the ring A, the collar 14 tilts and no longer exerts a clamping force on the disc F. Disengagement takes place.

The thrust ring A of the clutch bearing B is subjected to difficult working conditions and is made, according to the invention, of a material which enables it to have an excellent resistance to these working conditions, as regards both its lower coefficient of friction with the fingers 1 5 of the diaphragm D, and its very high wear resistance.

According to the invention, the thrust ring A of the bearing B consists of a mixture of thermosetting resin, in particular a resin chosen from the group of resins comprising polyester resins, epoxide resins, phenolic resins, and heat-stable resins such as polyimides, polyamide-imides, polybenzoxazoles and prlybenzothiazoles, with a proportion by weight of between 7 and 45%, lubricating fillers chosen from the group of fillers comprising graphite, molybdenum sulphide, polytetrafluoroethylene and hexagonal boron nitride, with a proportion by weight of between 10 and 80%, and infusible synthetic fibres inciuding fibres chosen from the group of fibres comprising aramides such as "KELVAR" and "NOMEX", polyimides such as "KERMEL", phenolics such as "KYNOL", and carbon, with a proportion by weight of between 2 and 60%.

Example of the thrust ring are given below without implying a limitation.

EXAMPLE I To make the thrust ring, a mixture of thermosetting resin, lubricating fillers and infusible synthetic fibres is formed with the following constituents and in the following proportions by weight:

Constituents Proportion by weight Thermosetting resin Phenolic resin 30 % Lubricating fillers Molybdenum sulphide 68 % Infusible synthetic fibres J "KYNOL" fibres 2 % This mixture is compressed at a temperature of 900C and baked in a mould for 10 minutes, at a temperature of 1400 C, under a pressure of 50 bars. It is then stabilised in an oven for 3 hours at a temperature of 2000C.

A test is carried out on the counter-material at a speed of 12 m/second under a normal force of 54 DaN, which corresponds to a pressure of 4 bars, and at a temperature of 1 000C.

The coefficient of friction is 0.15 and the wear is 30 microns per hour.

EXAMPLE II To make the thrust ring, a mixture of thermosetting resin, lubricating fillers and infusible synthetic fibres is formed with the following constituents and in the following proportions by weight:

Constituents Proportion by weight Thermosetting resin | Polyimide resin 45 % Polytetrafluoro ethylene powder 8 % Lubricating fillers Graphite 8 X

Constituents Proportion by weight I Polytetraf luoroa ethylene fibres 17 % Infusible synthetic fibres cut to 3 mm Carbon fibres cut to 1 mm 17 % Other Mineral oil 5 % The solid constituents and the mineral oil are mixed in a powder mixer and the mixture is baked in a mould for 20 minutes, at a temperature of 1 500C, under a pressure of 200 bars. It is stabilised in an oven for 7 hours at a temperature of 25O0C.

The ring made in this way is tested by rubbing it on the counter-material at a speed of 9 m/second, under a normal force of 101 DaN, corresponding to a pressure of 7.5 bars, and at a temperature of 900C.

The coefficient of friction is 0.08 and the wear is 5 microns/hour.

EXAMPLE Ill To make the thrust ring, the following constituents are mixed in the following proportions:

| Constituents Proportion by weight Thermosetting resin Epoxide resin 17 % Molybdenum sulphid 55 % Lubricating fillers Graphite 21 % Hexagonal boron nitride 2 % Infusible synthetic fibres "KERMEL" fibres cut to 6 mm 5 % The liquid components of the epoxide resin and the various solid constituents are mixed in a blade mixer. The mixture is baked in a mould for 10 minutes, at a temperature of 1 400C, under a pressure of 100 bars.It is stabilised in an oven for 5 hours at a temperature of 1 700C.

The thrust ring made in this way is tested by rubbing it on the counter-material at a speed of 6 m/second, under a normal force of 54 DaN, which corresponds to a pressure of 4 bars. This test is carried out at a temperature of 800C.

The coefficient of friction is 0.10 and the wear is 2 microns per hour.

EXAMPLE IV To produce the thrust ring, the following constituents are mixed in the following proportions:

Constituents Proportion by weight Thermosetting resin Phenolic resin 35 96 Graphite 35 % Lubricating fillers Polytetrafluoro ethylene powder 25 % Infusible synthetic fibres "NOMEX" fibres 5 % The constituents are mixed at a temperature of 1 000C and the mixture is injection-moulded under a pressure of 1,200 bars at a temperature of 1 700C. It is stabilised in an oven for 2 hours at a temperature of 2500C.

The thrust ring made in this way is tested by rubbing it on the counter-material at a speed of 6 m/second, under a normal force of 81 DaN, corresponding to a pressure of 6 bars. This test is carried out at a temperature of 1 00 C.

The coefficient of friction is 0.10 and the wear is 4 microns per hour.

EXAMPLE V To make the thrust ring, the following constituents are mixed in the following proportions:

Constituents Proportion by weight Thermosetting resin Phenolic resin in alcoholic solution 8 % Polytetrafluoro ethylene 21.5 % Lubricating fillers Molybdenum selenide 095 % Infusible synthetic fibres "KEVLAR"- 45 % Other Verranne 25 % Firstly, a mixed fabric is made with filaments formed by polytetrafluoroethylene fibres, filaments formed by verranne fibres and also filaments formed by "KEVLAR" fibres.

This mixed fabric is impregnated, under alternating vacuum and pressure effects, with a solution of resin in alcohol, with a solids content of 35%, containing molybdenum selenide in suspension. The whole is dried at a temperature of 800C and cut. A certain number of folds are made in order to form a cake, which is baked in a mould for 1 5 minutes, at a temperature of 1 350C, under a pressure of 250 bars, so that the cake has a final thickness of 8 mm. It is stabilised in an oven for 5 hours at a temperature of 1 700C.

The thrusting made in this way is tested on the counter-material at a speed of 6 m/second, under a normal force of 135 DaN, corresponding to a pressure of 10 bars. This test is carried out at a temperature of 1200C.

The coefficient of friction is 0.12 and the wear is 5 microns per hour.

Claims

1. A clutch release bearing comprising a thrust ring adapted to exert a thrust on a clutch disengaging device, wherein said ring comprises a mixture of thermosetting resin, a lubricating filler and infusible synthetic fibres.

2. A clutch release bearing according to Claim 1, in which the proportion by weight is from 7 to 45% for the thermosetting resin, from 10 to 80% for the lubricating filler and from 2 to 60% for the infusible synthetic fibres.

3. A clutch release bearing according to Claim 2, in which the proportion by weight is from 1 5 to 45% for the thermosetting resin, from 30 to 80% for the lubricating filler and from 2 to 20% for the infusible synthetic fibres, which are discontinuous.

4. A clutch release bearing according to Claim 2, in which the proportion by weight is from 7 to 25% for the thermosetting resin, from 10 to 30% for the lubricating filler and from 30 to 60% for the infusible synthetic fibres, which form filaments.

5. A clutch bearing according to any preceding claim, in which the thermosetting resin includes one or more of polyester resins, epoxide resins, phenolic resins, and heat-stable resins.

6. A clutch release bearing as claimed in Claim 5, in which the heat-stable resin include one or more of polyimides, polyamide-imides, polybenzoxazoles and polybenzothiazoles.

7. A clutch release bearing according to any preceding claim, in which the lubricating filler includes at least one of graphite, molybdenum sulphide, polytetrafluoroethylene and hexagonal boron nitride.

8. A clutch release bearing according to Claim 7, in which the lubricating filler further includes at least one of the sulphides selenides and tellurides of molybdenum, tantalum and tungsten.

9. A clutch release bearing according to any preceding claim, in which the infusible synthetic fibres include one or more of aramide fibres, polyimide fibres, phenolics fibres and carbon fibres.

10. A clutch release bearing according to any preceding claim, in which the ring further includes glass fibres.

11. A clutch release bearing according to Claim 10, in which the glass fibres include one or both of silionne and verranne.

12. A clutch release bearing according to any preceding claim, in which the ring further includes mineral oil.

13. A clutch release bearing according to Claim 1, in which the ring comprises, as the thermosetting resin, a phenolic resin with a proportion by weight of about 30%, as the lubricating filler, molybdenum sulphide with a proportion by weight of about 68%, and as the infusible synthetic fibrins, phenolics fibres with a proportion by weight of about 2%.

14. A clutch release bearing according to Claim 1, in which the ring comprises, as the thermosetting resin, a polyimide resin with a proportion by weight of about 45%, as the lubricating filler, polytetrafluoroethylene with a proportion by weight of about 8%, graphite with a proportion by weight of about 8% and mineral oil with a proportion by weight of about 5%, and as the infusible synthetic fibres, polytetrafluoroethylene fibres with a proportion by weight of about 17% and carbon fibres with a proportion by weight of about 1 7%.

1 5. A clutch release bearing according to Claim 1, in which the ring comprises, as the thermosetting resin, an epoxide resin with a proportion by weight of about 17%, as the lubricating filler molybdenum sulphide with a proportion by weight of about 55%, graphite with a proportion by weight of about 21% and hexagonal boron nitride with a proportion by weight of about 2%, and as the infusible synthetic fibres, polyimide fibres with a proportion by weight of about 5%.

1 6. A clutch release bearing according to Claim 1, in which the ring comprises, as the thermosetting resin, a phenolic resin with a proportion by weight of about 35%, as the lubricating filler, graphite with a proportion by weight of about 35% and polytetrafluoroethylene with a proportion by weight of about 25%, and as the infusible synthetic fibres, aramide fibres with a proportion by weight of about 5%.

1 7. A clutch release bearing according to Claim 1, in which the ring comprises, as the thermosetting resin, a phenolic resin with a proportion by weight of about 8%, as the lubricating filler polytetrafluoroethylene with a proportion by weight of about 21.5% and molybdenum selenide with a proportion by weight of about 0.5%, and as the infusible synthetic fibres, aramide with a proportion by weight of about 45%, the ring also comprising verranne fibres with a proportion by weight of about 25%.

18. A clutch release bearing according to Claim 1, substantially as described in any one of the foregoing Examples.

1 9. A clutch release bearing substantially as hereinbefore described, with reference to and as illustrated in the Figure shown in the accompanying drawing.