GB2137640A

GB2137640A - Composite friction facing

Info

Publication number: GB2137640A
Application number: GB08404786A
Authority: GB
Inventors: Hiroshi Ban; Shozo Kuno; Masami Ishii
Original assignee: Aisin Seiki Co Ltd
Current assignee: Aisin Corp
Priority date: 1983-02-28
Filing date: 1984-02-23
Publication date: 1984-10-10
Also published as: JPS59159432A; GB2137640B; GB8404786D0

Abstract

A composite friction facing for a clutch or brake, wherein the or each frictional contact surface of the friction facing is provided by at least one first friction member comprising a friction material made from a synthetic resin or asbestos, glass, silicon carbide or a ceramic material bound in an organic matrix, and a plurality of second friction members each comprising a metal bound in an organic matrix.

Description

SPECIFICATION Composite friction facing The invention relates to composite friction facings for clutch discs, brake pads and brake shoes, and to clutch discs, brake pads and brake shoes utilizing such composite friction facings.

The parameters constraining the creation of suitable friction facings for clutches and brakes are very similar, so that for brevity the following general description will refer to clutch design only, it being understood that entirely analogous considerations apply in the field of brake design.

Clutch discs for use in automobile clutches enable the engine and the gear box in an automobile to be connected or disconnected as required when the gear ratio is changed. Clutch discs are also generally connected to the input shafts of synchromesh type gear boxes, so that the synchromism is affected by the weight of the clutch disc itself.

When it is desired to obtain a durable clutch disc capable of transmitting a high torque, the use of sintered alloy as the friction facing has been suggested. Such alloys have excellent wear resistance, but are heavy because their main ingredient is a metal. The resulting high moment of inertia prolongs the synchronism operation, thereby deteriorating the ability of the synchromesh type gear reducer to change the gear ratio. That the main ingredient is a metal also accelerates the abrasion of the members against which the friction facings are pressed into frictional contact, and tends to encourage wear of those members.

To improve the speed change performance of synchromesh type gear boxes it has been proposed to be used organic resins as friction facing materials. These resins generally form a matrix binding together an antislip agent which may be asbestos, glass, silicon carbide or ceramic. The antislip agent may be used in the form of powder, particles or fibres. The resulting friction facings have a high coefficient of friction coupled with a small unit mass. They therefore overcome the problems associated with the relatively heavy frictional materials made from sintered alloy, but their resistance to wear is not sufficiently high.

Various constructions have been proposed in which the aforementioned two kinds of friction members are disposed on substantially the same frictional contact surface so as to constitute a friction facing. A typical example of such a construction is disclosed in Japanese Patent Publication No. 13807/1972, wherein a first friction member of a sintered alloy is held at a certain distance from a metal lining and is surrounded by a second friction member made from organic resin. Another example is disclosed in Japanese Patent Publication No. 6780/1980, where a friction facing made from organic resin is provided with recesses in which sintered alloy is introduced.A further example is disclosed in Japanese Patent Publication No. 22651/1980, where pieces of sintered alloy are firmly fixed to the heads of rivets or similar means which firmly secure a friction member made from organic resin to a backing plate. Still another example is proposed in Japanese Patent Laid-Open No. 134960/1977, where annular members of the same structure are mounted on both sides of a shock-absorbing backing plate and have first and second friction members respectively made from organic resin and sintered alloy, the first and second friction members being alternately disposed on the annular members together to present an annular friction surface.A yet further example is proposed in Japanese Utility Model Laid-Open No. 142645/1978, where friction members respectively made from organic resin and sintered alloy are disposed on opposite sides of a backing plate, and friction members of the same material are firmly secured at the almost corresponding positions on the opposite sides of the backing plate. Also, various friction members for braking systems have been proposed as exemplified in Japanese Patent Publication No. 6579/1970 and Japanese Patent Laid-Open No. 113675/1975.

The present invention provides a composite friction facing for a clutch or brake, wherein the or each frictional contact surface of the friction facing is provided by at least one first friction member comprising a friction material made from a synthetic resin or asbestos, glass, silicon carbide or a ceramic material bound in an organic matrix, and a plurality of second friction members each comprising a metal bound in an organic matrix.

A clutch disc having a composite friction facing or facings according to the invention has a smaller inertial mass, wears away the surfaces against which the disc is pressed into contact to a much lesser extent, and exhibits a much better durability than the prior art clutch disc described above.

Preferred aspects of composite friction facings according to the invention are as follows: (a) if the antislip agent in the first friction member is asbestos, the or each first friction member preferably comprises from 45% to 65% by weight of asbestos fibres.

(b) if the antislip agent in the first friction member is glass or ceramic and or each first friction member preferably comprises from 20% to 45% by weight of glass or ceramic.

(c) if the antislip agent in the first friction member is ceramic, the or each first friction member comprises from 20% to 45% by weight of the ceramic material.

(d) each of the second friction members preferably comprises metal fibres, metal powder, metal particles and/or metal scales in an amount of from 20% to 40% more preferably 22% to 32%, and advantageously 25% to 30%, by volume of the second friction member.

(e) each of the second friction members preferably has a specific gravity of from 3.0 to 3.5.

(f) the metal of the second friction members is advantageously iron, for example cast iron, an iron alloy, copper or a copper alloy.

(g) over the or each friction contact surface the total frictional contact area of the second friction members is preferably from 5% to 40%, advantageouslsy 5% to 25%, of that of the first friction member or members.

DRAWINGS: Figure 1 is a cross-section through a clutch disc according to the invention; Figure 2 is an enlarged view of the facings of the disc shown in Fig. 1; Figure 3 is a side elevation of the facings shown in Fig. 2; Figure 4 is a cross-section through another clutch disc according to the invention; and Figure 5 is a graph showing a comparison between the results of tests made on prior art clutch discs and the results of tests made on clutch discs according to the invention.

Referring first to Figs. 1-3, there is shown a clutch disc according to the invention. The disc comprises a driven member consisting of a boss 1 with an annular flange 2 which is interposed between a main clutch plate 3 and an auxiliary plate 4. The main clutch plate 3 has a resilient annular plate 5 that is firmly fixed thereto by rivets 6. Friction facings 10 are secured fast to opposed sides of the resilient annular plate 5 and form the outer periphery of the clutch disc.

The auxiliary plate 4 is secured to the main clutch plate 3 by rivets 7 and is rotatable with the main clutch plate 3. The main and auxiliary clutch plates constitute a driving plate assembly which is angularly movable relative to the boss 1, in known manner. Resilient members 9 are disposed between the driving plate assembly and the flange 2 of the boss 1 to absorb mechanical shock, and are inserted into openings 2a, 3a and 4a that are formed in the flange 2, the main clutch plate 3 and the auxiliary plate 4, respectively. A small amount of relative motion is thus permitted between the driving plate assembly and the boss 1 by causing the resilient members 9 to extend or contract.

Friction rings 8 are held respectively between the flange 2 of the hub 1 and the main clutch plate 3 and between the flange 2 and the auxiliary plate 4. When the need arises, resilient members, pressure plates or other similar means may be added to keep the pressure applied to these rings 8 at an appropriate value.

Each of the friction facings 10 is formed by a first friction member 11 and second friction members 21, these members 11 and 21 having their working friction faces in substantially the same plane. The first friction member 11 comprises an antislip agent made from an inorganic material such as asbestos, glass or silicon carbide or a synthetic resin or other material. The ingredients of the first member are bound together in an organic medium. Each of the sand friction members 21 consists principally of a metal, and the ingredients of the members 21 are also bound together in an organic medium. The second members 21 are recessed at 12 into the first member 11 at intervals so that their working friction faces 21 a are exposed and lie in the same plane as that of the first member 11.Preferably, the total area of the working friction faces 21 a of the second friction members 21 is from 5% to 25% of the area of the working friction face 11 a of the first member 11. The second members 21 are firmly fixed by rivets 15 or similar means to anchor members 16, by means of which the first friction member 11 is securely affixed to the resilient annular plate 5. A hole 1 3 is formed in the first member 11 immediately at the back of each rivet 1 5 to prevent the rear head portions 1 7 of the rivets 1 5 from distorting the first friction members.

Referring next to Fig. 4 there is shown another clutch disc according to the invention. This disc is similar to the disc shown in Figs. 1-3 except for the construction of the friction facings 10, and the same reference numerals are used where appropriate. Each of the friction facings 10 comprises first and second friction members 11 and 21 mounted alternately around the resilient annular plate 5 on opposite sides thereof. Each friction facing 10 comprises an array of the first friction members 11 and the second friction members 21 alternately disposed.

Preferably, the total area of the frictional contact surfaces of the second members 21 is 20% to 40% of that of the first members 11, although the respective areas may be substantially equal if desired. The first friction members 11 and the second friction members 21 are firmly fixed to the resilient annular plate 5 by their rivets 1 8 and 28 respectively. Stepped recesses 1 2 and 22 are formed in the friction members 11 and 21 to receive the heads of the rivets 18 and 28, respectively. To prevent the rear head portions of the rivets 18 and 28 from contacting and distorting the opposite friction facings 10, each rivet rear head portion is received in a recess 1 3 or 23 of the respective friction member 11 or 21.

If the first friction members 11 contain asbestos as their main ingredient, the asbestos content is preferably from 45% to 65% by weight. Examples of suitable)bmpositions are as follows: Friction material AS-1 asbestos 50% by weight resin 10% by weight rayon 10% by weight barium sulphate 14% by weight other additives 16% by weight Friction material AS-2 asbestos 50% by weight phenol resin 20% by weight cashew resin 10% by weight barium sulphate 20% by weight Other examples of friction material containing asbestos as its main ingredient have been proposed in Japanese Patent Laid-Open Nos. 056249/1978, 107487/1979, and 063123/1981, and Japanese Patent Application No. 174956/1981.

If the first friction members 11 contain glass as their main ingredient, the glass content is preferably from 20% to 45% by weight. An example of a suitable composition is as follows: Friction material GL-1 glass 35% by weight resin 10% by weight rubber 17% by weight barium sulphate 17% by weight other additives 21 % by weight Another usable friction material containing glass as its main ingredient is proposed in Japanese Patent Application No. 1 71 632/1 981.

If the first friction members 11 contain a ceramic material as their main ingredient, the ceramic content is preferably from 20% 45% by weight. One such composition is proposed Japanese Patent Laid-Open No. 080351/1979 and has the following composition: Friction material CE-1 ceramic 35% by weight resin 15% by weight cashew resin 6% by weight rubber 6% by weight graphite 8% by weight barium sulphate 18% by weight copper powder 21 % by weight The second friction members 21 preferably contain from 20% to 40% by volume of metal Examples of suitable compositions are as follows:: Friction material ME-O metal material 22-32% by volume resin 16-28% by volume organic dust 10-22% by volume inorganic filler 7-17% by volume graphite 17-29% by volume This friction material exhibits a specific gravity ranging from 3.0 to 3.5 and a hardness ranging from 50 to 80.

Friction material ME-1 ferrous metal fibres 55-63% by weight resin 5-9% by weight organic dust 3-9% by weight other additives 13-22% by weight This material exhibits a specific gravity of 3.2 and a hardness of 65.

Other examples of suitable friction materials containing metal as their main ingredient are proposed in Japanese Patent Laid-Open Nos. 080352/1979, 161429/1981, and 040134/1982 and Japanese Patent Application Nos. 171630/1981 and 174957/1981.

Examples of clutch discs according to the invention using the above friction materials are as follows: EXAMPLE 1 In a clutch disc as shown in Figs. 1 to 3, each of the friction facings 10 had an inside diameter of 145 mm and an outside diameter of 225 mm (9 inches), and was annular in shape.

The first friction members 11 consisted of the aforementioned material AS-1, and the second friction members 21 consisted of the aforementioned material ME-1. The total area of the frictional contact surfaces 218 of the second members 21 on each facing 10 was approximately 10% of the area of the frictional contact surface 11 a of the first member 11.

EXAMPLE 2 In a clutch disc as shown in Fig. 4, the outside diameter of each friction facing 10 was more than 260 mm (10 inches) as specified by Japanese Industrial Standard D 4311-1975. The first friction members 11 and the second friction members 21 consisted of the aforementioned materials AS-1 and ME-1, respectively. The total area of the frictional contact surfaces 21 a of the second friction members 21 was roughly 30% of that of the frictional surfaces 11 a of the first members 11.

The wear characteristics of the clutch discs of Examples 1 and 2 are shown in Table 1 and in Fig. 5 in comparison with the characteristics of three comparative clutch discs according to the comparative Examples below.

COMPARATIVE EXAMPLE 1 A clutch disc was constructed of the same size as the disc in Example 1 but with friction facings which consisted entirely of the aforementioned material AS-1.

COMPARATIVE EXAMPLE 2 In a clutch disc having the same structure and size as that of Example 1, the first friction members were made from the aforementioned material AS-1, while the second friction members were made from a sintered copper alloy material Sl-1 (described below). The total area of the frictional contact surface of the second friction members was approximately 10% of that of the first friction members.

Friction material Sl- 1 copper 62% by weight iron 8% by weight tin 7% by weight lead 12% by weight graphite 7% by weight quartz sand 4% by weight In a clutch disc having the same dimensions as that of Example 1, for each annular friction lining, there was provided a friction lining whose area was about 40% of that of the annular surface of the resilient annular plate 5. The friction lining consisted of members of the above sintered copper alloy material Sl-1 or material Sl-2 (described below).

Friction material SI-2 copper 65% by weight tin 10% by weight lead 5% by weight graphite 10% by weight quartz sand 5% by weight alumina 5% by weight Table 1 shows the results of tests to evaluate the coefficient of friction and the amount of abrasion of each clutch at a temperature of 150"C using an inertia dynamometer. Clutches made as described in the Examples and comparative Examples were mounted in a vehicle and tests were made. The resistance to judder was evaluated in five grades from 1 (bad juddering) to 5 (little or no juddering). Fig. 5 shows the results of measurements, i.e., the quantity of abrasion against the number of contacts made by each clutch.

The clutch of Example 2 gave substantially the same performance as that of Example 1, so the results of its measurements are not shown herein.

TABLE 1 amount of coefficient amount of abrasion of resistance sample of friction abrasion member engaged to judder Example 1 0.35 0.57 0.02 5 Comparative 0.35 1.75 0.05 5 Example 1 Comparative 0.35 1.08 0.08 3 Example 2 Comparative 0.39 0.45 0.15 2 Example 3

Claims

1. A composite friction facing for a clutch or brake, wherein the or each frictional contact surface of the friction facing is provided by at least one first friction member comprising a friction material made from a synthetic resin or asbestos, glass, silicon carbide or a ceramic material bound in an organic matrix, and a plurality of second friction members each comprising a metal bound in an organic matrix.

2. A composite friction facing according to claim 1, wherein the or each first friction member comprises from 45% to 65% by weight of asbestos fibres.

3. A composite friction facing according to claim 1, wherein the or each first member comprises from 20% to 45% by weight of glass.

4. A composite friction facing according to claim 1, wherein the or each first friction member comprises from 20% to 45% by weight of a ceramic material.

5. A composite friction facing according to any preceding claim, wherein each of the second friction members comprises metal fibres, metal powder, metal particles and/or metal scales in an amount of from 20% to 40% by volume of the second friction member.

6. A composite friction facing according to claim 5, wherein each of the second friction members comprises metal fibres in an amount of from 22% to 32% by volume of the second friction member.

7. A composite friction facing according to claim 6, wherein each of the second friction members comprises metal fibres in an amount of from 25% to 30% by volume of the second friction member.

8. A composite friction facing according to any preceding claim, wherein each of the second friction members has a specific gravity of from 3.0 to 3.5.

9. A composite friction facing according to any preceding claim, wherein the metal of the second friction members is iron, an iron alloy, copper or a copper alloy.

10. A composite friction facing according to any preceding claim, wherein over the or each frictional contact surface the total frictional contact area of the second friction members is from 5% to 40% of that of the first friction member or members.

11. A composite friction facing according to claim 10, wherein over the or each frictional contact surface the total frictional contact area of the second friction members is from 5% to 25% of that of the first friction member or members.

1 2. A composite friction facing according to any preceding claim, wherein the second friction members are inset at spaced intervals in recesses or cut-out portions of the or each first friction member, to present a common frictional contact surface.

1 3. A composite friction facing according to any of claims to 11, wherein the second friction members are mounted on a support member alternately with a plurality of the first friction members, to present a common frictional contact surface.

14. A composite friction facing for a clutch, substantially as described in either of the Examples herein and as illustrated in the drawings.

1 5. A clutch disc having a composite friction facing according to any preceding claim.

1 6. A brake pad or brake shoe having a composite friction facing according to any of claims 1 to 13.