Road vehicle electrohydraulic brake system

Electrohydraulic brake system for a road vehicle, having wheel brakes in which each wheel brake is assigned a brake-pressure regulating element arranged to be actuatable by supplying drive signals to an electric motor and, together with the respective wheel brake comprises a wheel-brake circuit and, at least one electronic or electromechanical signal transmitter is configured to be actuatable by a vehicle driver to specify a required desired value of the retardation of the road vehicle and produces an electrical output signal correlated monotonically with at least one of the force and the stroke with which the vehicle driver actuates the transmitter, and an electronic control unit is provided which, from comparison of the desired-value input signals with actual-value signals characteristic of the vehicle retardation, produces actuating signals required for rapid matching of the actual value to the target desired value for the brake-pressure regulating elements wherein the brake-pressure regulating elements each comprise a piston pump configured as a reciprocating positive-displacement machine, with at least one piston, which executes filling and delivery strokes in a fixed phase relationship to a driving part of the pump which can be rotationally driven by the electric motor;

• an output of the pump per pump cycle is controllable in opposed monotonic correlation with pressure prevailing in the respective wheel brake such that the output decreases when the pressure increases;
• a maximum delivery volume per pump cycle which occurs within one revolution of the driving part is small relative to an output required to couple a maximum value of the brake pressure into the connected wheel brake and amounts to between 1/20 and 1/100 of the maximum output;
• each wheel brake is assigned a brake-fluid holding space into which brake fluid can be released in a metered manner via an electrically drivable valve arrangement;
• and the electrically drivable valve arrangement is configured to shut off the brakes from the associated brake-fluid holding spaces when the vehicle is stationary and the desired-value transmitter is actuated, and, when the desired-value input is reduced, to allow the metered outflow of brake fluid from the wheel brakes into the brake-fluid holding spaces.