Brakes – Wheel – Axially movable brake element or housing therefor
Patent
1988-06-30
1989-08-29
Reger, Duane A.
Brakes
Wheel
Axially movable brake element or housing therefor
188196P, F16D 6554
Patent
active
048608580
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a spot-type disc brake, in particular for motor vehicles, comprising
a floating caliper which is displaceably guided on a brake support by means of sliding pins,
an inner and an outer brake pad which are displaceable parallel to the sliding pins with respect to the brake support,
an actuator with which the inner brake pad is operable directly and the outer brake pad by displacement of the floating caliper and
a resetting means on at least one of the sliding pins including a spring which is arranged around the sliding pin as part of a frictional connection between said pin and a bore guiding said pin and is resiliently yieldable to a limited extent in the axial direction.
In a known disc brake of this type (DE-PS 2,211,429) the sliding pins are detachably secured on the floating caliper and each displaceably guided in a bore of the brake support. In disc brakes of the type according to the preamble it is however also fundamentally possible for the sliding pins to be mounted on the brake support and each guided in a bore of the floating caliper. In both cases, on actuation of the brake the floating caliper is displaceable in such a manner that the outer brake pad, with respect to the associated vehicle, is pressed by the floating caliper against a brake disc when the actuator presses the inner brake pad directly against the brake disc. After actuation of the brake it is necessary for the two brake pads to be moved away from the brake disc by a predetermined distance, the so called release clearance. The release clearance should on the one hand be large enough to prevent under all circumstances, for example when the brake disc is deformed by heat or when travelling round a curve, the brake pads rubbing on the brake discs. On the other hand, the release clearance should be as small as possible to avoid making the pedal travel required on the next actuation of the brake unnecessarily large.
The release clearance of the brake pad operated directly by the actuator, the inner pad with respect to the vehicle, is generally governed by an actuating piston which is associated therewith and which is reset by a piston seal resilient in the axial direction. However, in disc brakes according to the preamble the resetting means mentioned at the beginning on at least one of the sliding pins is responsible for maintaining a predetermined release clearance of the outer brake pad actuable by displacement of the floating caliper.
In the known disc brake described the sliding pins each comprise at their end received in the associated bore an annular groove in which a spring element in the form of a resilient ring is accommodated in such a manner that its outer peripheral face bears in frictionally locking manner on the cylindrical wall of the bore. The spring element opposes a displacement in the axial direction with a frictional resistance such that its cross-section deforms resiliently under a normal brake actuation and thereby builds up an axial resetting force which suffices to return the floating caliper to its original position after the brake actuation. The frictional resistance between spring element and bore is however overcome on actuation of the brake when the release clearance due to wear of the brake pad has exceeded a predetermined amount; in this case the spring element in the bore is displaced into a new position from whence the spring element effects the resetting of the floating caliper after release of the brake.
With the known arrangement it has proved to be difficult and expensive to maintain with adequately narrow tolerances the dimensions, decisive for the magnitude of the frictional resistance, of the annular spring element, the sliding pin and the associated bore. The frictional resistance after overcoming which the spring element can be moved in the bore is thus subject to considerable fluctuations. If the frictional resistance is too small the spring element is unable to build up a resilient resetting force adequate for the return of the floating caliper; if however the frictio
REFERENCES:
patent: 2747694 (1956-05-01), Helvern
patent: 2830680 (1958-04-01), Hawley
patent: 3085663 (1963-04-01), Jakeways
patent: 3339683 (1967-09-01), Burnett
Erben Ralf
Langert Albert
Madzgalla Frank-Wilhelm
Madzgalla Hans-Georg
Lucas Industries Public Limited Company
Reger Duane A.
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