The invention is based on a solenoid valve in a hydraulic brake system for motor vehicles.
A solenoid valve of this kind is disclosed in the technical manual Bremsanlagen fur Kraftfahrzeuge/Bosch [Brake Systems for Motor Vehicles/Bosch] 1st edition, Dusseldorf: VDI-Verlag, 1994, pp. 69, 70 (FIG. 8c). It is used in a slip regulated hydraulic brake system (FIG. 10) for motor vehicles, in actuality as an intake valve in a suction line of a regenerative high pressure pump which produces the braking pressure in the case of a drive slip regulation. This known solenoid valve is distinguished by a relatively large opening cross section, so that even at low temperatures, the high pressure pump can draw off pressure fluid fast enough from the master cylinder.
In the future, modern motor vehicles will be equipped with brake systems (for example according to German Patent Application P 44 41 791.8, FIG. 4) also for automatic braking with which, for example depending upon vehicle behavior, the traffic situation, or obstacles appearing in the path of the vehicle, the brake system activates--even independent of the driver--and brake pressure is built up and modulated in the above-mentioned manner. If the vehicle is already in a braking operation tripped by the driver, then the solenoid valve in the suction line has to open counter to the pressure produced by the master cylinder. The magnetic circuit of the valve could be correspondingly dimensioned in order to produce the opening forces required. This is undesirable, though, because it makes the solenoid valve larger, heavier, and more expensive.