Anti-lock brake circuit with a piezo hydraulic pump and changeover valve

Abstract

A brake control device for vehicles includes a master cylinder, a plurality of wheel cylinders, and an anti-lock control apparatus disposed between the master cylinder and the wheel cylinders of at least one hydraulic circuit. The anti-lock control apparatus includes a hydraulic pump, a reservoir and a changeover device which is selectively changed over at least between a first condition which permits an increase in the hydraulic pressure of the wheel cylinders of at least one hydraulic circuit and a second condition which permits an decrease in the hydraulic pressure of the wheel cylinders of at least one hydraulic circuit in response to the locking condition of the road wheels. The hydraulic pump includes a housing, a slidable piston device for defining a pump chamber which is communicated with the reservoir and the changeover device at a side of one end thereof in the housing, an inlet check valve disposed between the pump chamber and the reservoir for permitting fluid communication from the reservoir to the pump chamber and for interrupting fluid communication from the pump chamber to the reservoir, an outlet check valve disposed between the pump chamber and the changeover device for permitting fluid communication from the pump chamber to the changeover device and for interrupting fluid communication from the changeover device to the pump chamber, and a piezo element for reciprocating the piston device disposed at the other end of the piston device.