Abstract: 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.

Abstract: A parking brake system having a lock mechanism provided within a casing to the rear of a parking piston that provides a parking brake mode by forward movement of a lock mechanism in response to the action of a parking control fluid pressure. The lock mechanism responds to forward movement of the parking piston to mechanically lock the parking piston at a forward position and unlocking in response to the action of a parking release control fluid pressure. The lock mechanism includes a lock piston that is to the rear of the parking piston having an axis orthogonal to the axis of the parking piston. This enables an automatic parking brake mode to be obtained by a simple structure without consuming power.

Abstract: A parking brake system is provided in which, a lock mechanism (25) is provided within a casing (23) to the rear of a parking piston (24) that can give a parking brake state by forward movement in response to the action of a parking control fluid pressure, the lock mechanism (25) operating in response to forward movement of the parking piston (24) in order to mechanically lock the parking piston (24) at a forward position and unlocking in response to the action of a parking release control fluid pressure. The lock mechanism (25) includes a lock piston (30) that is disposed to the rear of the parking piston (24) while having an axis orthogonal to the axis of the parking piston (24) and that makes a forward urging force act on the parking piston (24) at least when the parking piston (24) moves forward, and opposite end parts of the lock piston (30) are slidably fitted into and supported on the casing (23). This enables an automatic parking brake state to be obtained by a simple structure without consuming power.

Abstract: 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 (12)6, 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 (12)6 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.

Abstract: A fluid pressure control device has a sliding member fitted in a housing for switching over the connection and the disconnection between an input port connected to a fluid pressure supply source, an output port connected to a fluid pressure operated device and a release port connected to a reservoir; a reaction chamber for generating a fluid pressure urging the sliding member in a retracting direction; an urging piston operatively connected to the rear end of the sliding member; an input piston operatively connected to an operation member; and a pressure chamber formed between a back surface of the urging piston and a front surface of the input piston; wherein a first pressure receiving area of the sliding member exposed to the reaction chamber is set smaller than a second pressure receiving area of the urging piston exposed to the pressure chamber, and the second pressure receiving area is set smaller than a third pressure receiving area of the input piston exposed to the pressure chamber.

Abstract: In a hydraulic braking pressure control system comprising a brake device (B.sub.FL, B.sub.FR, B.sub.RL, B.sub.

Abstract: An anti-lock control system includes wheel speed detecting device, wheel acceleration/deceleration detecting device, vehicle pseudo-speed calculating device for calculating a vehicle pseudo-speed on the basis of a wheel speed detected by the wheel speed detecting device, storing device for storing a wheel speed or vehicle pseudo-speed at a sampling time at which the wheel acceleration/deceleration has become equal to or less than preset acceleration set at a value near "0" (zero), including "0" (zero), after passing a peak in the course of increasing of the wheel speed, speed difference calculating device for calculating a speed difference between wheel speeds or vehicle pseudo-speeds stored currently and last time in the storing device, lapsed-time counting device for counting the time lapsed from the last sampling time to the current sampling time, and division device for dividing the speed difference by the lapsed time to provide a value corresponding to a friction coefficient of a road surface.

Abstract: A pressure supply system for a vehicle according to the invention incorporates a pump and an accumulator in which an output pressure of the pump is maintained within a prescribed range by controlling the on-off operation of the pump according to the inner pressure of the accumulator. By changing the prescribed range of pressure according to the actual pressure requirement, for instance according to the change in the travelling speed of the vehicle, the burden on the system is reduced. The prescribed range can be changed either by simply changing the upper and/or lower pressure limits at which the pump is deactivated and activated, respectively, or by operating the pump for a prescribed time period which is dependent on the pressure requirement after a certain reference pressure value is reached. Thus, the structure of the fluid pressure system is simplified, and the generation of unnecessary high pressure can be avoided.

Abstract: A hydraulic pressure control system has a hydraulic pressure control valve which includes a spool slidably received in a housing for axial sliding movement between a rear position in which it permits the communication between an output port and a release port and a front position in which it permits communication between an input port and the output port. The hydraulic pressure control system also has a reaction chamber connected to the output port for providing a hydraulic pressure for biasing the spool rearwardly, and an input pressure working chamber for providing a hydraulic pressure for biasing the spool forwardly, a differential pressure regulating valve is interposed between the output port and the reaction chamber and adapted to be opened in response to the hydraulic pressure from the output port becoming higher than the hydraulic pressure in the reaction chamber by a predetermined value therefor.