Disk brake assembly with piston retraction seal

摘要

A disk brake assembly has a piston retraction structure which can keep the space between the pad and the disk constant while the brake is not being applied by varying the distance the piston is retracted with the fluid pressure applied to the disk brake. The piston retraction structure has a piston seal fitted in a seal groove formed in the inner surface of a cylinder of a caliper. When a piston is advanced under fluid pressure, the piston seal is pulled by the piston and deformed until it fills up the gap defined by a chamfer formed along the edge of the seal groove. When the fluid pressure is removed thereafter, the piston is retracted by the resilient restoring force of the deformed piston seal. The piston seal is made of a rubber having a hardness of 80 IRH or more. In another arrangement, the piston seal has its outer-diameter portion fitted in the seal groove with a zero gap or with an interference. By further adjusting the size of the chamfer, it is possible to vary the distance the piston is retracted with the fluid pressure in an ideal manner.