BRAKE ACTUATOR

PROBLEM TO BE SOLVED: To keep oil pressure from unnecessarily rising and restrain weight of a driving means by increasing wheel cylinder pressure by means of closing a connection opening on the master cylinder side with a first valve and closing a communication passage between a first and a second chambers with a second valve when a piston is displaced to the second chamber side on the wheel cylinder side. SOLUTION: The interior of a cylinder 23A equipped with a first and a second connection openings 29, 30 connected to a master cylinder and a wheel cylinder is partitioned into a first and a second chambers 24A, 24B by a piston 25. With the first and the second chambers communicating with each other through a communication passage 142, the first connection opening 29 is opened when the piston is in its initial position and closed when the piston 25 makes displacement to the second chamber 24B side by a first valve 34 energized by a return spring 34B toward the closing direction of the first connection opening 29 from the master cylinder side. The communication passage 142 is also closed by a second valve 32 by virtue of the energizing force of a return spring 141. Thus oil pressure in the wheel cylinder side does not rise more than that in the second chamber 24B and a powerful driving force is not required.