Disk brake assembly with piston retraction seal

• US 5,826,681 A
• Filed: 08/28/1996
• Issued: 10/27/1998
• Est. Priority Date: 09/01/1995
• Status: Expired due to Term

• Current Assignee: Advics Company Limited (Aisin Corp.)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Kubo, Atsushi, Matsumoto, Atsuo
• Primary Examiner(s): Poon, Peter M.
• Application Number:
  US08/704,246
• Time in Patent Office: 790 Days
• Field of Search: 188/71.8, 188/72.3, 188/72.4, 188/73.1, 188/196 P, 188/322.18, 277/165, 277/177, 277/227, 277/180, 277/207 R
• US Class Current: 188/71.8
• CPC Class Codes: F16D 2121/02 Fluid pressure
• CPC Class Codes: F16D 2127/02 Release mechanisms
• CPC Class Codes: F16D 65/18 adapted for drawing members together , e.g. for disc brakes

Abstract

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.

Claims

1. A disk brake assembly, comprising:

a caliper formed with a cylinder, said cylinder having an inner surface;

a brake piston mounted in said cylinder, said brake piston having an outer periphery and an end on which fluid pressure can act; and

a piston retracting means for retracting said piston in said cylinder, said piston retracting means comprising a seal groove in said inner surface of said cylinder, said seal groove comprising an edge remote from the end of said brake piston on which fluid pressure can act, said edge having a chamfer, and a rubber piston seal fitted in said seal groove so as to be pressed against the outer periphery of said brake piston, forming a liquid tight seal of the space between said cylinder and said brake piston, said piston seal having an inner diameter portion having an inner peripheral surface and an outer diameter portion, and said seal groove having a depth;

wherein said piston seal is deformable from an original shape and is adapted to be pulled at said inner diameter portion thereof by said brake piston and resiliently deformed until said piston seal fills a gap defined by said chamfer when said brake piston is advanced to press a brake pad against a brake disk, and to resiliently move back to return to the original shape while retracting said piston when fluid pressure is released, and wherein said piston seal has said outer diameter portion thereof fitted in said seal groove such that 25-70% of the depth of said seal groove has said piston seal fitted therein with substantially no axial gap between said seal groove and said seal.

2. The disk brake assembly of claim 1, wherein 25-70% of the depth of said seal groove has said piston fitted therein with interference.

3. The disk brake assembly of claim 1, wherein said piston seal comprises an air vent passage extending from an inner periphery of said piston seal to an outer periphery of said seal in order to prevent axial movement of said piston seal.

4. A disk brake assembly, comprising:

a caliper formed with a cylinder, said cylinder having an inner surface;

a brake piston mounted in said cylinder, said brake piston having an outer periphery and an end on which fluid pressure can act; and

a seal groove in said inner surface of said cylinder, said seal groove comprising an edge remote from the end of said brake piston on which fluid pressure can act, said edge having a chamfer; and

a rubber piston seal fitted in said seal groove so as to be pressed against the outer periphery of said brake piston, forming a liquid tight seal of the space between said cylinder and said brake piston, said piston seal having an inner diameter portion having an inner peripheral surface and an outer diameter portion having an outer peripheral surface;

wherein said piston seal and said piston groove define a means for retracting said piston in said cylinder when fluid pressure is removed from acting on said piston in said cylinder after said piston has been advanced to press a brake pad against a brake disk by having said piston seal resiliently deform from its original shape by being pulled at said inner diameter portion thereof by said brake piston until said piston seal fills a gap defined by said chamfer between said chamfer and said piston seal when said piston seal has its original shape and by having said piston seal resiliently move back to return to the original shape while retracting said piston when the fluid pressure is removed; and

wherein said piston seal has a structural arrangement selected from the group consisting of a) said piston seal being at least partially made of a rubber having a hardness not less than 80 IRH, and b) said piston seal having the outer diameter portion thereof fitted in said seal groove such that 25-70% of the depth of said seal groove has said piston seal fitted therein with substantially no axial gap between said seal groove and said piston seal.

5. A disk brake assembly, comprising:

a caliper formed with a cylinder, said cylinder having an inner surface;

a brake piston mounted in said cylinder, said brake piston having an outer periphery and an end on which fluid pressure can act; and

a piston retracting means for retracting said piston in said cylinder, said piston retracting means comprising a seal groove in said inner surface of said cylinder, said seal groove comprising an edge remote from the end of said brake piston on which fluid pressure can act, said edge having a chamfer and a rubber piston seal fitted in said seal groove so as to be pressed against the outer periphery of said brake piston, forming a liquid tight seal of the space between said cylinder and said brake piston, said piston seal having an inner diameter portion having an inner peripheral surface and an outer peripheral surface;

wherein said piston seal is deformable from an original shade and is adapted to be pulled at said inner diameter portion thereof by said brake piston and resiliently deformed until said piston seal fills a gap defined by said chamfer when said brake piston is advanced to press a brake pad against a brake disk, and to resiliently move back to return to the original shape while retracting said piston when fluid pressure is released, and wherein said piston seal is at least partially made of a rubber having a hardness not less than 80 IRH; and

wherein said piston seal has an axial direction and comprises two soft portions and one hard portion, said hard portion being sandwiched between said two soft portions.