The present invention relates to a vehicular hydraulic brake system with an anti-locking arrangement wherein first valve means are interposed between a master cylinder and brake-actuating members. The valve means allow interruption of a supply of pressure fluid to the brake-actuating members and removal of pressure fluid from the brake-actuating members. The first valve means is controllable by a slip-monitoring electronics in dependence upon the wheel rotational behavior, and a device for safeguarding availability of a minimum stroke as a reserve is provided.
A vehicular hydraulic brake system having these features is known from German printed and published patent application No. 30 40 562.0. A component of the known vehicular brake system is a hydraulic power booster with a tandem master cylinder connected downstream thereof. As a function of the force exerted on the brake pedal, hydraulic pressure is built up in the pressure chamber of the hydraulic power booster which, after having overcome the friction caused by the seals, provides that the booster piston displaces in the actuating direction. As a result thereof, the working chambers of the tandem master cylinder also will be pressurized. Wheel brakes are connected to the working chambers of the tandem master cylinder. Arranged between the working chambers of the tandem master cylinder and the wheel brakes are electromagnetically actuatable valves, which shut off the connection between the working chamber and the respective wheel brake and which permit removal of pressure fluid from the wheel brakes for the purpose of a pressure decrease in the wheel brakes and to return the fluid to an unpressurized supply reservoir.
The hydraulic power booster of the brake system described further comprises a so-called resetting sleeve which by way of corresponding valve means, can be acted upon during control in the direction of brake release by the presure that is in each case prevailing in the pressure chamber of the hydraulic power booster. The dimensions of the resetting sleeve and of the booster piston are conformed to one another in a fashion so as to allow the resetting sleeve to move into abutment on the booster piston under specific conditions. Thus, when pressurized appropriately, the resetting sleeve generates a force in the direction of brake release which confines the travel of the booster piston to a predefinable extent and which, in case of need, ensures that the booster piston is displaced in the direction of brake release. Thus, the necessary reserve volume is preserved in the working chambers of the tandem master cylinder also during brake slip control.
The brake system described affords very reliable operation, but--as explained--there is need for separate component (resetting sleeve), by means of which a minimum stroke as a reserve of the pistons of the tandem master cylinder is safeguarded.
An anti-lock vehicular brake system (German patent specification No. 23 44 969) is also known, wherein a hydraulic brake power booster is provided. In the booster chamber controlled pressure prevails which, in case of slip control, can be delivered to the brake circuits by way of valve means. However, this known brake system nevertheless requires a hydraulic brake power booster.
Therefore, it is an object of the present invention to provide upon a vehicular hydraulic brake system with an anti-locking arrangement of the type initially referred to such as to reduce manufacturing efforts and to attain a solution which is more favorable in terms of cost. In addition, the system is to be compatible with units comprising a braking pressure generator with a vacuum brake power booster.