Electronically controlled motor vehicle braking force distributor

Electronically controlled brake system, comprising:

• a pedal-operated braking pressure generator to which wheel brakes are connected by way of pressure fluid lines,
• at least one valve inserted into the pressure fluid lines, which switches from a first position into a second position as a function of the vehicle deceleration and is arranged in the pressure fluid conduit to the rear-wheel brakes, wherein a stroke piston acted upon by a compression spring is provided to actuate the valve,
• sensors to measure the individual wheel rotational behavior and/or corresponding average values and a controlling and evaluating electronic unit to combine and process the sensor signals and to generate control signals which are used to actuate the valve and permit controlling the braking pressure in the rear-wheel brakes, wherein the valve is maintained open in the initial position by the stroke piston,
• means for blocking the stroke piston in a position in which the valve adopts its open initial position to adapt the rear-wheel braking pressure to the level of the front-wheel braking pressure,
• and in that upon actuation of the braking pressure generator the valve is switched from its open initial position to a position in which the rear-wheel brake is separated hydraulically from the braking pressure generator, in which separating position the rear-wheel brake for braking pressure reduction is hydraulically connected exclusively to an accumulator chamber, expanded in volume, as soon as the rotational acceleration of one of the rear wheels exceeds the admissible limit value, wherein the rear-wheel brakes are arranged in a diagonal brake circuit and include an actuator with two parallel arranged stroke pistons, which actuator reduces inadmissibly high braking pressures in the rear-wheel brakes to the respective preloading pressure of the compression springs that are supported on the two stroke pistons, wherein the preloading pressure of the compression spring is lower than a rear-axle braking pressure which results from the ideal braking pressure distributor characteristic curve of an unloaded automotive vehicle.