Abstract: A vacuum system used with an automotive vehicle such that an appropriate negative pressure is maintained within the vacuum system in order to assure the function of the vacuum brake booster even when the vacuum clutch booster is defective in airtightness. A vacuum system according to the present invention comprises a novel second check valve having an orifice therewithin, being connected between the intake manifold and the vacuum clutch booster. The second check valve operates as an ordinary check valve in a normal condition but as an orifice in an abnormal condition to prevent the vacuum pressure in the system from being decreased quickly, without use of any conventional vacuum tank.

Abstract: A hydraulic power booster in a hydraulic brake system for an automatic vehicle includes a booster housing having inlet and outlet ports respectively connected to a fluid reservoir. A piston is slidably received within the booster housing and is connected with a master cylinder of the brake system. The piston is operated by the motion of a spool valve slidably disposed within the piston responsive to depression and release of the brake pedal. The spool valve is operated by a plunger interpositioned between the spool valve and the brake pedal. The plunger slidably extends through an outer cylindrical member which is received within the booster housing. The outer cylindrical member is cooperatively connected with the piston so that it can move in accordance with the movement of the piston. The plunger and outer cylindrical member are exchangeable to vary the ratio of the reaction force with respect to the boost force built up in the booster.

Abstract: A hydraulic system is disclosed for use in an automotive vehicle including an engine, a power steering gear, and a brake booster. The system includes a single engine driven pump in fluid communication with first and second fluid flow control means. The first fluid flow control means responsive to fluid inputs for discharging a small or large predetermined amount of hydraulic fluid to control the operation of the power steering gear. The second fluid flow control means supplies a constant amount of hydraulic fluid to control the operation of the brake booster.

Abstract: A hydraulic booster for a brake system or the like, of a vehicle includes a throttle valve which produces hydraulic pressure corresponding to the depression force applied to a brake pedal. Relative axial displacement of an operating rod and a power piston produces relative rotation of a power piston. The throttle valve is formed between the power piston and the booster body, and responds to the relative rotation of the power piston.