Piston assembly and hydraulic brake pressure generating device including said piston assembly

摘要

A piston assembly is provided which detects and prevents binding of a piston which is always fixed in a normal state and required to move only in case of a failure of a hydraulic or pneumatic system. One end of a second piston (2) has a tubular extension. A first piston (1) is inserted in the tubular extension. The first piston (1) is acted upon by the hydraulic pressure introduced from a controlled pressure generating unit (9) into a first fluid chamber (3) and is kept in its initial position against a brake operating force transmitted from a brake pedal (7) through a first spring (5). The second piston (2) moves until the hydraulic pressure in the second fluid chamber (4) becomes substantially equal to the hydraulic pressure in the first fluid chamber (3). By the movement of the second piston (2), the sliding portions between the first and second pistons are frequently slid. This makes it possible to detect and prevent binding by comparing the hydraulic pressures in the first and second fluid chambers. <IMAGE>