Patent ID: 7779972

Claim:
A parking brake system comprising: a brake mechanism for releasably locking a wheel during parking in response to an input into an input member; a casing; a parking piston slidably fitted into the casing and configured so as to move forward in response to a parking control fluid pressure acting on a rear face side of the parking piston; a coupling linkage providing a linking connection between the input member and the parking piston so as to make the brake mechanism operate for parking in response to forward movement of the parking piston; a lock mechanism provided within the casing so as to automatically lock in response to forward movement of the parking piston in order to mechanically lock the parking piston at a forward position thereof, and unlock in response to a parking release control fluid pressure acting on the lock mechanism; a fluid pressure source and a fluid pressure control member for controlling a fluid pressure generated by the fluid pressure source so that the parking control fluid pressure and the parking release control fluid pressure can be obtained; the lock mechanism comprising a lock piston that is slidably fitted into the casing while having an axis that is orthogonal to the axis of the parking piston so that at least when the parking piston moves forward an urging force toward one side in the axial direction acts on the lock piston and that is arranged such that a parking release control pressure can act on the lock piston toward the other side in the axial direction; a retaining part that is provided on a middle section of the coupling linkage; and a locking part that is provided at one end, in the axial direction, of the lock piston in order to mechanically lock a forward operating state of the parking piston by engaging with the retaining part from the rear, the locking part being formed so as to engage with the retaining part while straddling the middle section of the coupling linkage only when the parking piston is at the forward position thereof; wherein the retaining part is provided on a stopper at the middle section of the coupling linkage, the stopper comprising a block body having a substantially rectangular cross-section, and wherein the retaining part comprises projections which extend outwardly on opposite sides of the block body.