A brake system having a master cylinder including main pistons, a brake booster for displacing the main pistons a brake valve for controlling the brake booster and a pressure supply device. The brake booster has a booster cylinder and a booster piston which is displaceable into the booster cylinder. The booster piston divides a booster chamber from an auxiliary chamber, which is located between the booster piston and the master cylinder. A first valve assembly and a second valve assembly are provided. The second valve assembly is located between the pressure supply device and the brake valve as well as a connection associated with the booster chamber. The first valve assembly is intended for relieving pressure in the booster chamber in favor of a return line or to join it with the pressure supply device. In the anti-skid mode, pressure in the booster chamber is initially reduced by means of the second valve assembly. This is effected by blocking the inflow of pressure medium to the brake valve and by relieving pressure in the booster chamber. If the drop in brake pressure attainable thereby should be inadequate, then by means of the first valve assembly, pressure medium is directed out of the pressure supply device into the auxiliary chamber. This pressure displaces the booster piston toward its initial position. As a result, a pressure drop down to zero is possible, no matter how severely a brake pedal coupled with the brake valve is depressed.
A vehicle brake control unit includes a cylinder body (2); a spool member (18) which is slidably provided in the cylinder body (2), and has one end portion confronted with a pressure chamber (10) and the other end portion confronted with a regulator pressure chamber (24) in the cylinder body, the spool member being axially moved by both the pressure in the pressure chamber and the pressure in the regulator pressure chamber, thus adjusting the pressure of a pressure source (26) which is applied to a regulator port (2a) formed in the cylinder body. The pressure provided at the regulator port is led into the regulator pressure chamber and supplied to the wheel cylinders (33, 34, 35 and 36). The vehicle brake control unit further includes emergency-braking-operation detecting unit (65) for detecting an emergency braking operation, and brake pressure change-over unit (62, or 66 and 68) for communicating the pressure source with the wheel cylinders when the emergency-braking-operation detecting unit detects an emergency braking operation.
A brake system for automotive vehicles, comprising a tandem master cylinder (1) and a vacuum brake force booster (2). A pump (34) is connected to the supply chambers (10, 11) of the tandem master cylinder (1), which pump is actuated by an electromotor (35) started by a brake slip control device to replenish, in the brake slip control, the pressure fluid volume discharged from the working chambers (4, 5) of the tandem master brake cylinder (1), by way of the supply chambers (10, 11) and the sleeves of the master cylinder pistons (6, 7). To control the pump pressure, a pressure control valve (36) is provided to the control chamber (37) of which a control pressure is applied, which is generated in a control chamber (23) by a control piston (24) coupled ahead of the tandem master brake cylinder (1). The control chamber (23), by way of a magnetic valve (39), is pressure-relieved when the brake slip control device is turned off.
An hydraulic brake booster for an automobile hydraulic system comprising of a boost cylinder, a boost piston and a boost chamber defined by a boost piston working in a bore in a body and being adapted to apply an output force to an output rod in response to a pressure applied to a boost chamber under a control valve, in turn responsive to an input force from input rod, wherein the input rod move in a forward operating direction up to a prescribed point so as to prevent fluid from a radial high pressure supply port from entering the boost chamber when the booster is in an inoperative position, any added movement of the input rod in a forward operating direction lifts the boost piston ball and uncovers the supply port so as to allow pressurized fluid into the boost chamber from the accumulator.
In a combined booster and hydraulic master cylinder assembly the reservoir connection is adapted to serve as an inlet for high pressure fluid and by way of which the assembly can be operated independently of the pedal. High pressure fluid is supplied to the connection under the control of auxiliary control valve responsive to signals for a sensor. The sensor may be arranged to enable the assembly to be used in a variety of modes, for example for traction control, as a `hill holder`, and for remote control of the speed of the vehicle.
A normally closed secondary solenoid opening/closing valve 36 is provided along a secondary branched fluid pipe 35 establishing a communication between an accumulator 11 and a reservoir 8 through a fluid pressure input side to a fluid pressure output side of a regulator valve 3, and in the event that a fluid pressure supplied to the regulator valve 3 decreases down to or lower than a predetermined range due to something abnormal occurring in the accumulator 11, the state of the secondary solenoid opening/closing valve 36 is changed over from a closed state to an opened state, whereby a residual pressure in the accumulator 11 and a residual pressure in the output fluid pressure chamber 15 can be released through the reservoir 8 which is in communication therewith through an output fluid pipe 31 and the secondary branched fluid pipe 35 along which the secondary opening/closing valve 36 is provided.
