Vehicle brake system

A vehicle brake system comprising:

• a hydraulic pressure generating unit applying hydraulic pressure to a wheel brake side hydraulic path connected to a wheel brake in accordance with an operation of a brake operation member;
• a hydraulic pressure supply operated independently of the hydraulic pressure generating unit;
• a parking brake piston for achieving a parking brake applied state of a wheel mounted on the wheel brake through a forward movement thereof according to an increase of hydraulic pressure in a parking brake application control hydraulic chamber to which a back side of the parking brake piston faces;
• a lock piston operated to automatically lock the parking brake piston at a front position and also operated to a lock releasing side according to an increase of hydraulic pressure in a parking brake release control hydraulic chamber;
• a hydraulic pressure control unit which is electrically controllable to effect a changeover between:
• the application of hydraulic pressure from the hydraulic pressure supply to the parking brake application control hydraulic chamber and the parking brake release control hydraulic chamber and
• the release of hydraulic pressure applied from the parking brake application control hydraulic chamber and the parking brake release control hydraulic chamber;
• and
• a manual change-over unit provided among the wheel brake side hydraulic path, the parking brake application control hydraulic chamber and the parking brake release control hydraulic chamber, said manual change-over unit operable to selectively bypass the hydraulic pressure control unit, the manual change-over unit operated according to a manual operation of an operating member,
• wherein when the manual operation of an operating member is activated, the manual change-over unit establishes a communication between the wheel brake side hydraulic path and the parking brake application control hydraulic chamber and holds the hydraulic pressure of the parking brake release control hydraulic chamber to hydraulic pressure of the lock release side;
• a disc brake;
• and
• a drum brake for the parking brake,
• wherein the manual change-over unit includes:
• a first hydraulic path which connects between a disc brake side hydraulic path to which the output hydraulic pressure from the master cylinder is led and the parking brake application control hydraulic chamber to thereby bypass the hydraulic pressure control unit;
• a normally closed valve interposed in the first hydraulic path, the normally closed valve is opened by a manual operation;
• a second hydraulic path one end of which is connected to the first hydraulic path at a position between the normally closed valve and the parking brake application control hydraulic chamber, and the other end of which communicates with the parking brake release control hydraulic chamber in such a manner to bypass the hydraulic pressure control unit;
• and
• a one-way valve interposed in the second hydraulic path in such a manner as to permit only a flow to the parking brake release control hydraulic chamber side.