GB2334225A

GB2334225A - Disc brake manufacture

Info

Publication number: GB2334225A
Application number: GB9900902A
Authority: GB
Inventors: Edward Stephen Pine
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1998-02-12
Filing date: 1999-01-16
Publication date: 1999-08-18
Anticipated expiration: 2019-01-16
Also published as: GB2334225B

Abstract

Brake discs are generally made initially to an approximate of that required for use within a braking system of a motor vehicle. The final skimming of the braking surfaces constituted by a radial flange 2 is conducted by a machine tool, while the disc is attached to a drive member 3, to achieve as accurate a perpendicularity to rotational axis X-X of the brake disc as possible in order to ensure good run through of a brake calliper of the braking system. In order to achieve good machining tolerances, an additional locating surface 8 for the machine tool is formed on the drive member 3 which is radially outside the bearing surface 9 usually used for the purpose.

Description

DISC BRAKE MANUFACTURE The present invention relates to disc brake manufacture and more particularly to improved tolerance definition for such brake discs.

A brake disc for use in a disc brake system generally has a flanged bell cross-section with the flange providing the braking surfaces upon which a brake calliper operates. The central dome or bell provides location on the hub.

It will be appreciated that the brake disc needs to be produced to a reasonable degree of accuracy in order to achieve good run out with respect to the calliper assembly through which its braking flange will rotate. Any tilt or twisting of the disc will tend to create an inconsistent application of the brake pads to the braking flange during use with the result of inconsistent wear of the brake pads and brake judder.

Traditionally, brake discs have been made from cast iron with subsequent machining to achieve the desired perpendicularity for the flange as required to give good run out through the calliper. This machining has been performed by attaching a cast disc to a hub member and then, while rotating the hub and disc assembly, machining both sides of the braking flange of the brake disc to an acceptable perpendicularity. The usual way of locating the machine tool during machining of the disc is to use the bearing surface on the hub member which is arranged to bear against a bearing ultimately attached to the vehicle body when the brake disc is in use.

However, this bearing surface is quite close to the axis of the brake disc and so does not provide very accurate location for the machine tool, especially when it is operating at the outer edge of the disc.

It is an object of the present invention to provide a method of manufacturing a brake disc which improves the accuracy of such manufacture and so run out of the brake disc through a brake calliper in use.

In accordance with the present invention there is provided a method of making a brake disc including the steps of producing a disc shell having a bell configuration with a nat centre section and a radial flange orientated in respective parallel planes with a band section therebetween, attaching the shell to a drive member having a surface thereon arranged to act as a bearing surface when in use, and machining the braking surfaces of the disc using a machine tool, wherein the drive member also has a locating surface formed thereon, radially outside the bearing surface, and the locating surface is used to locate the machine tool during machining of the disc.

The present invention further provides a drive member and brake disc assembly wherein the drive member has a surface thereon arranged to act as a bearing surface when in use, a locating surface, radially outside the bearing surface, arranged to locate a machine tool during machining of the disc.

Preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a schematic cross-section of a brake disc shell and drive member mounted for final machining, Figure 2 is a detailed section through the drive member of Figure 1, and Figure 3 is a section through a drive member used in a second embodiment of the invention.

Referring to Figures 1 and 2 a brake disc shell 1 is cast and machined to approximate that required of an operational brake disc. Thus, the shell wall includes the appropriate orifices and apertures for assembly upon a motor vehicle hub, etc. However, a final stage of machining of the friction surfaces on the disc flange is still required, and it is this final stage of brake disc manufacture from the shell 1 that is the subject of the present invention.

The shell 1 is attached to a drive member 3 in the form of a hub flange by means of studs 3a attached to the drive member 3 and passing through holes in the shell. These studs and holes are the same as, or at least equivalent to, those that are used to hold the drive member and disc and a wheel together in final use. The assembly of the drive member 3 and shell 2 is then rotated such that milling or cutting tools 4 engage the flange 2 in order to machine the two opposite braking surfaces of flange 2 into a perpendicular orientation to the axis of rotation X-X of the brake disc. The two friction faces are machined at the same time by a pair of tools which are aligned with each other on opposite sides of the disc so that the net force they produce on the disc is negligible and does not produce distortion of the disc.

The drive member 3 has a shoulder 7 with an annular locating surface 8 on top. This is at the radially outer edge of the drive member 3 and therefore outside the bearing face 9 which is provided on the drive member which is conventionally used for location as described above, and also radially outside the studs 3a. During the machining of the braking faces on the shell 1, the machine tool 4 is located using the locating surface 8.

Typically, the drive member 3 is made for a specific size of brake disc.

Thus, the drive member 3 is a snug fit within the bell of the brake disc with the result that it is easy to locate. Greater accuracy is achieved by the increased diameter of the locating surface as a result of using the shoulder 7 compared to using the bearing surface 9 as in the prior art.

Referring to Figure 3 in a second embodiment of the invention the locating surface 8 is situated radially outside the bearing surface 9, but inside the studs 3a. This gives better accuracy than using the bearing surfaces for location, but less than using the embodiment shown in Figures 1 and 2.

Claims

CLAIMS 1. A method of making a brake disc including the steps of producing a disc shell having a bell configuration with a flat centre section and a radial flange orientated in respective parallel planes with a band section therebetween, attaching the shell to a drive member having a surface thereon arranged to act as a bearing surface when in use, and machining the braking surfaces of the disc using a machine tool, wherein the drive member also has a locating surface formed thereon, radially outside the bearing surface, and the locating surface is used to locate the machine tool during machining of the disc.
2. A method according to claim 1 wherein the shell is attached to the drive member using attachment means and the locating surface is positioned radially outside the attachment means.
3. A method according to claim 2 wherein the attachment means are those arranged to attach the drive member and the disc to a wheel when in final use.
4. A drive member and brake disc assembly wherein the drive member has a surface thereon arranged to act as a bearing surface when in use, a locating surface, radially outside the bearing surface, arranged to locate a machine tool during machining of the disc.
5. An assembly according to claim 4 wherein the disc is attached to the drive member using attachment means and the locating surface is positioned radially outside the attachment means.
6. An assembly according to claim 5 wherein the attachment means are those arranged to attach the drive member and the disc to a wheel when in final use.
7. A method of making a brake disc substantially as hereinbefore described with reference to the accompanying drawings.
8. A drive member and brake disc assembly substantially as hereinbefore described with reference to the accompanying drawings.