Patent ID: 7866763
Filing Date: 2011-01-11
Classification: B60T,F16D

Abstract:
1. An automatic parking brake system, comprising: a casing having a slide bore formed therein, said slide bore including an enlarged diameter portion, a reduced diameter portion, and a ramped annular latching step interconnecting the enlarged diameter portion with the reduced diameter portion; a parking piston which is slidably fitted into the slide bore of the casing, wherein the casing has a parking control fluid pressure chamber defined therein between a rear face of the parking piston and the casing, said parking piston configured and arranged such that a parking brake state is obtained by forward movement thereof in response to a parking control fluid pressure acting on the parking control fluid pressure chamber; a lock mechanism having a lock piston which is slidably fitted into the casing, said lock piston being operable to advance or retreat relative to the parking piston, wherein said lock mechanism has a parking release control fluid pressure chamber defined therein between a front face of the lock piston and the casing, and said lock piston is urged forward by a spring, said lock mechanism further comprising: a fluid pressure source; and a fluid pressure control mechanism for controlling a fluid pressure generated by the fluid pressure source such that the parking control fluid pressure and the parking release control fluid pressure are obtained and separately controlled; wherein the insertion shaft is formed by coaxially and integrally connecting a front small diameter shaft portion and a rear large diameter shaft portion via a tapered step, which is operable to change the position of contact of each of the spheres between the small diameter shaft portion and the large diameter shaft portion; the small diameter shaft portion being in contact with each of the spheres for putting each of the spheres in rolling contact with an inner face of the small diameter hole portion in a state in which the parking piston is at a retreat limit, and the large diameter shaft portion being connected coaxially to the small diameter shaft portion for pushing each of the spheres outward along the radial direction of the retaining tube in order to make the spheres contact the large diameter hole portion in response to the parking piston moving forward from the retreat limit and the lock piston moving forward.