The present invention relates to a hydraulic booster for slip-controlled brake systems having a booster piston in a booster chamber wherein the hydraulic booster accommodates boosting factors of any desired size both in construction and to minimize strength requirements.
German Published Patent Application (DE-OS) No. 37 01 018 describes a hydraulic booster in combination with a slip-controlled brake system of the type to which the present invention is directed. The hydraulic booster described therein receives a fastening element screwed into the booster housing and communicating with the lever mechanism so that, upon actuation of the push rod, the lever mechanism first end piece is guided in the actuating piston and features a ball-head design which performs a swivelling motion that is synchronous in respect of the stroke of the actuating piston. This is performed around the rigid point of support in the lever-receiving part of the screw-thread-design fastening element. The lever segment hinged to the shaft part of the lever mechanism is guided with its end faces in the opening of the prolonged, sleeve-like extension of the booster piston and in an opening of the actuating piston. Upon actuation of the push rod, the lever mechanism carries out a swivelling motion which results in a defined stroke of the braking pressure control valve displaceably supported in the booster housing. Accumulator pressure thereby is supplied into the booster chamber by way of the braking pressure control valve so that a hydraulic booster of the braking pressure is effective under the action of the accumulator pressure acting on the front face of the booster piston. At the same time, the actuating piston also is acted upon by the boosting pressure so that, as a function of the constructional dimensioning of the pressure-applied front face, a hydraulic force of a corresponding value acts on the actuating piston in the direction of the push rod.
Because of the construction and strength requirements with regard to the cross-section of the lever-receiving part in the opening of the actuating piston, it essentially is impossible to realize hydraulic boosting operations of any desired extent in the described booster so that, in the hydraulic boosters used at present, for example, a boosting factor of i=6.4 is achievable at the maximum with a one-inch tandem master cylinder connected downstream.
Further, in the known hydraulic boosters of this type which are in use today, because of the dynamic flow-in principle preferably used in the rear wheel brakes, the booster piston surface which by way of the booster chamber acts in the direction of the tandem master cylinder is coordinated with the effective surface of the tandem master cylinder and, consequently, does not permit any variations in the dimensioning of the components without resulting disadvantageous effects on the braking force distribution.
Accordingly, it is an object of the present invention to improve a hydraulic booster of the type referred to while avoiding the aforementioned disadvantages and while maintaining the operational reliability, so that boosting factors of any size may be realized without having to tolerate the abovementioned disadvantageous strength-minimizing influences on the actuating device of the booster.