Brakes – Wheel – Axially movable brake element or housing therefor
Patent
1994-05-05
1995-12-26
Mitchell, David M.
Brakes
Wheel
Axially movable brake element or housing therefor
188250B, 188250G, F16D 55228
Patent
active
054779448
DESCRIPTION:
BRIEF SUMMARY
This invention relates to disc brakes for motor vehicles and in particular but not exclusively to disc brakes for high performance cars or motor cycles.
In a typical disc brake, a brake caliper straddles the outer peripheral margin of a brake disc, the caliper having at least one hydraulic cylinder therein for applying friction pads to each side of the disc. The calipers are of two basic types, fixed calipers which have hydraulic cylinders on both sides of the disc, and moving calipers in which typically the hydraulic cylinder(s) is on one side of the disc for direct application of friction pad(s) on that side of the disc, and the friction pads on the other side of the disc are applied by the reaction movement of the caliper.
With disc brakes of tile type fitted to high performance vehicles particularly racing cars or motor cycles the friction pads are extended over a relatively long arc to maximise the area of friction material in contact with the disc. When the brakes are applied, the leading edge of the pads tends to "grab" onto the disc and in the extreme conditions which these brakes operate, the leading edges and areas of the pads wear faster than the trailing areas.
Also due to the arcuate length of the pads, as the pads heat up during braking they tend to buckle due to internal expansion causing heat spotting of the friction material followed by material fade.
One way of compensating for the uneven wear has been to provide a plurality of hydraulic cylinders in the caliper, with the cylinders at the leading areas of the pad being of a smaller diameter than the cylinders at the trailing areas of the pad so that the leading edge area of the pad is applied to the disc by a smaller load than the trailing edge areas.
It is an object of the present invention to provide a disc brake caliper which mitigates the above problems.
Thus according to the present invention there is provided a disc brake caliper having two limbs which in use straddle an outer periphery of a brake disc to support friction pads on each side of the disc, characterised in that each caliper limb supports at least two friction pads arranged side by side in a circumferentially sequential array with the trailing edge of each pad abutting the leading edge of any circumferentially adjacent pad in the array to transmit torque loads from one pad to the adjacent pad.
Preferably the adjacent abutting trailing and leading edges of the pads have interlocking portions which prevent circumferentially adjacent pads from relative radial movement.
The invention will be described by way of example and with reference to the accompanying drawings in which:
FIG. 1 is a cross-section through a disc brake calliper according to the present invention, taken on the line I--I of FIG. 2, and
FIG. 2 is a section on the II--II of FIG. 1.
With reference to FIG. 1 and FIG. 2 there is illustrated a disc brake caliper 10 for a racing car and which comprises two limbs 11, 12 interconnected by three spaced bridge portions 14A,14B,14C. In use the caliper straddles the outer periphery of a brake disc 15 (shown in dotted outline) with a limb located on each side of the disc. One limb 12 is connected in use to the torque reaction member e.g. a stub axle to which the braking loads are transferred.
The two limbs 11 and 12 each have three hydraulic cylinder assemblies 16,17,18, circumferentially spaced across the caliper body (that is circumferentially with respect to the disc) so that the cylinder assemblies 16, 17, 18 in one limb 11 oppose the cylinder assemblies in the other limb 12. The cylinders each contain pistons 20 which thrust friction pads 22A, 22B and 22C against the opposed surfaces of the disc.
In the example shown each pad 22A, 22B, 22C is of a one piece so-called carbon/carbon construction (i.e. carbon fibre in a carbon matrix) machined to provide a braking or friction material portion 23A, 23B, 23C and a larger backing plate portion 24A, 24B, 24C. It will be appreciated that each pad may alternatively comprise friction material bonded to a separate backing plat
REFERENCES:
patent: 3602328 (1971-08-01), Fannin et al.
patent: 3923128 (1975-12-01), Lucien et al.
patent: 4090591 (1978-05-01), Pollinger et al.
patent: 4093043 (1978-06-01), Smith
patent: 4535874 (1985-08-01), Pollinger et al.
Bryan Stephen
Tyler Robert
Automotive Products plc
Germain Lee A.
Milliken Paul E.
Mitchell David M.
Young Lee W.
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