Patent attributes
An automatic parking brake system is provided in which a parking piston that enables a parking brake state to be obtained by forward movement in response to a parking control fluid pressure acting on a rear face of the parking piston is slidably fitted into a casing, and a lock mechanism is provided within the casing in back of the parking piston to automatically lock in response to forward movement of the parking piston in order to mechanically lock the parking piston at a forward position and unlock in response to a parking release control fluid pressure acting on the lock mechanism, the parking control fluid pressure and the parking release control fluid pressure being obtained by a fluid pressure control mechanism for controlling a fluid pressure generated by a fluid pressure source. This enables an automatic parking brake state to be obtained by a simple structure without consuming power.