GB2228053A

GB2228053A - Brake disc

Info

Publication number: GB2228053A
Application number: GB8902786A
Authority: GB
Inventors: Jonathan Paul Tait; Richard Arnold Bass
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1989-02-08
Filing date: 1989-02-08
Publication date: 1990-08-15
Anticipated expiration: 2009-02-08
Also published as: GB2228053B; GB8902786D0

Abstract

A brake disc (11) comprising an annular support member (14) with a pair of annular carbon-carbon friction facings (12, 13) arranged on opposite sides of the support member (14). The facings (12, 13) are supported over their whole radial width and are secured to the support members (14) by releasable fasteners (15). The support member is made up of two annular side plates (21, 22) spaced apart by ribs (25) to form cooling channels (24) between the side plates and which are connected to the back surfaces of the facings by holes (25) in the side plates (21, 22). <IMAGE>

Description

Brake Disc This invention relates to brake discs for use in disc brakes for vehicles and in particular for use on racing cars.

Vehicles which have disc brakes operating in extreme conditions have recently adopted use of carbon-carbon materials for the manufacture of the brake disc. However these materials are extremely expensive and tend to wear faster than traditional cast iron brake discs.

Various ways have been proposed to overcome this problem.

In British Patent 1317880 there is disclosed a brake disc comprising a carbon core with, replaceable carbon friction facings on either axial side of the core. The disc appears to be fixed rotational relative to the rotary member to be braked by cut outs in the outer periphery of the disc and the friction rings are secured to the core by rivets, which makes replacement of the facings difficult since the heads of the rivets must be machined away.

Such a construction is not suitable for use with conventional disc brakes for vehicles in which a single disc is fixed by its inner periphery to a wheel hub, and the disc brake pads act on the outer periphery of disc.

In British Patent application 2151729, there is disclosed a brake disc comprising a metallic core hub with radial spokes thereon, and removeable carbon-carbon segments mounted on the spokes. The whole assembly is extremely complicated.

The present invention provides a brake disc comprising a pair of annular carbon-carbon friction facings mounted on opposite axial sides of an annular metallic support member which supports said facings across substantially the whole radial width thereof, the facings being secured to the support member by readily releasable fastener means to facilitate replacement of the facings in the event of wear or damage.

Preferably the annular support member comprises a pair of annular side plates held in axially spaced relationship by circumferentially spaced vanes which form radially extending cooling channels between the side plates.

Conveniently the readily realeasable fastener means are bolts which pass through aligned holes in the radially inner peripheral margins of the facings and the support member to clamp together an assembly of said facings and support member, and the bolts are each located in a bush which is flanged at one axial and thereof, said bush having an axial length which is less than the overall axial thickness of the assembled facings and support member so that when the bolt is fully engaged with its co-operating member the assembled facings and support member are nipped between the flange on the bush and the head of the bolt.

The invention also comprises the replaceable annular carbon-carbon friction facings having holes on the inner peripheral margin thereof for attachment to a support member forming part of a brake disc.

The invention will be described by way of example and with reference to the accompanying drawing in which: FIG 1 is an elevation of a brake disc according to this invention and showing in one sector a portion of the friction facing removed, and in another sector a portion of both friction facing and the support member side plate removed, and FIG 2 is a section on the line II - II of FIG 1.

Now with reference to FIG 1 and FIG 2, there is illustrated a brake disc for use primarily on racing cars but which can be used on other brakes which operate in extreme conditions.

The brake disc 11 comprises a pair of carbon-carbon annular friction facing 12, 13, mounted on opposite axial sides of an annular support member 14. The support member 14 is metallic, and whilst various materials such as heat resistant aluminuim and cuprous alloys could be used, the prefered material is ferrous metal, and in particular cast iron.

The support member 14 and the two friction facings 12 and 13, are held in assemblage by fastener means 15, in the form of bolts, which in this case co-operate with the threaded holes 16 in the rim 17 of a bell shaped housing 18 whereby the disc is mounted on the wheel hub of a vehicle.

In other embodiments the bolts may co-operate with nuts, or some other device which allows the bolt to be readily released so that the facings 12 and 13 can be easily replaced when worn or damaged.

The support member 14 comprises a pair of annular side plates 21 and 22 and support the facings 12 and 13 across substantially their whole radial width and around substantially the whole circumference of the facing. The side plates 21 and 22 are held in axially spaced relationship by vanes 23 which form circumferentially spaced cooling channels 24 which extend radially through the disc from the inner to the outer peripheries thereof.

Whilst the vanes are illustrated as having a helical form, they could have other forms, for example radial vanes.

The side plates 21 and 22 each have holes 25 therein that are arranged in groups between adjacent vanes 23 so that the holes 25 connect the back faces of the carbon-carbon friction facings 11 and 12 with the cooling channels 24.

The groups of cooling holes 25 are arranged so that the diameter of the readily outer cooling holes is largest, and the diameters decrease radially inwardly.

The bolts 15 pass through aligned holes 26 in the radially inner peripheral margins of the facings 12 and 13 and the support member 14. The holes 26 each accommodate a bush 27 which has a flange 28 at one end thereof adjacent the housing 18, and an axial length which is just less than the overall axial thickness of the assembled facings and support member.

There is a washer 29 located between the head of the bolt and the facing 12 so that assembly is nipped together when bolt is tightened and the washer 29 is pulled into abuttment with the bush 27.

Other similar constructions could be used, for example, the washer 29 could be formed integrally with the bolt head, or the bush could comprise, two parts each having a flange on the axially outer end thereof and which are pulled together by the bolt, so that the assembly is nipped between the two flanges.

The support member holes 26A for the bushes 27 are radially elongated to allow for differential thermal expansion between the carbon-carbon facings 12 and 13 and the cast iron support member 14.

The radially inner peripheral margins of the support member 14, in those marginal portions located circumferentially between the bolt holes 26, has a series of scallop shaped cut outs 30 which reduce the mass of the support member 14.

It will be appreciated that if it is necessary to change the facings 12 and 13 due to wear, or damage, the procedure is extremely fast and simple. The bolts 16 are simply released from the bell housing 18, and the composite sandwich can be dissembled and the new facings substituted and the sandwich re-assembled.

The replacement friction facings for such a brake disc will comprise an annular facings of carbon-carbon material having a series of spaced holes only through the inner peripheral margin thereof, and radially inwardly of the friction pad engaging area, for attachment to a support member 14 as previously described.

Claims

1. A brake disc comprising a pair of annular carbon-carbon friction facings mounted on opposite axial sides of an annular metallic support member which supports said facings across substantially the whole radial width thereof, the facings being secured to the support member by readily releasable fastener means to facilitate replacement of the facings in the event of wear or damage.

2. A brake disc as claimed in Claim 1 wherein the annular support member comprises a pair of annular side plates held in axially spaced relationship by circumferentially spaced vanes which form radially extending cooling channels between the side plates.

3. A brake disc as claimed in Claim 2 wherein the side plates have holes therein which connect the cooling channels with the back surface oflthe carbon-carbon facings.

4. A brake disc as claimed in any one of Claims 1 to 3 wherein the support member is a ferrous metal casting.

5. A brake as claimed in any one of claims 1 to 4 wherein the readily releasable fastener means are bolts which pass through aligned holes in the radially inner peripheral margins of the facings and support member to clamp them together.

6. A brake disc as claimed in Claim 5 wherein the bolts are each located in a bush which is flanged at one axial end thereof, said bush having an axial length which is less than the overall axial thickness of the assembled facings and support member so that when the bolt is fully engaged with its cooperating member the assembled facings and support member are nipped between the flange on the bush and the head of the bolt.

7. A brake disc as claimed in Claim 6 wherein each bush is a single piece bush extending from said flange for almost the whole thickness of the assembly , and there is a washer between the head of the bolt and the adjacent facing so that the assembly is clamped between said flange and the washer.

8. A brake disc as claimed in Claim 6 or Claim 7 wherein the bushes are titanium bushes.

9. A brake disc as claimed in any one of Claims 1 to 8 and having the fastener means located at the inner peripheral margin of the disc, wherein the radially inner peripheral margins of the support member are cut away in those marginal portions located circumferentially between adjacent fastener sites.

10 A brake disc as claimed in any one of Claims 5 to 9 wherein the fastener holes in the support member are radially elongated to allow for differential expansion between the support member and the facings.

11. A brake disc as claimed in any one of Claims 5 to 10 wherein the fastening bolts co-operate with aligned threaded holes in the rim of a bell shaped housing, whereby the disc is assembled to a rotatable hub.

12. A brake disc which is substantially as described herein with reference to the accompanying drawings.

13. A motor vehicle disc brake assembly having a brake disc as claimed in any one of Claims 1 to 12.

14. An annular carbon-carbon friction facing having circumferentially spaced holes only through the inner peripheral margin thereof for attachment to a support member to form part of a brake disc.