Image Number 6 for United States Patent #7651175.
A parking brake system is provided in which a parking brake state for a wheel brake (2A) is obtained by forward movement of a parking piston (44) slidably fitted into a casing (23) with the rear side of the parking piston (44) facing a parking control fluid pressure chamber (47), and the forwardly moved state of the parking piston (44) is mechanically locked by spheres (58) pushed up as a result of forward movement of a lock piston (56) of a lock mechanism (31). Moreover, a plurality of guide grooves (126), into which parts of the spheres (58) are rollably fitted, are provided on the inner face of a large diameter hole (38), the inner face of a restricting step (42), and the inner face of a small diameter hole (39), the guide grooves (126) having a concavely curved cross-sectional shape and extending in the axial direction of an insertion shaft (59). This enables an automatic parking brake state to be obtained by a simple structure without consuming power.
|
