Vehicle brake system

A vehicle brake system comprising a main cylinder for supplying wheel brake cylinders with brake pressure, a hydraulic brake booster which is assigned to the main cylinder for activating fluid pressure and which has a booster piston (14) which can be displaced in a booster pressure chamber (15) in a direction of the main cylinder, a reservoir, a hydraulic energy source connected with said reservoir, a pump (19a) and a relief valve means (19b) and a pressure line (31) for producing boosting pressure for the booster chamber for hydraulically displacing the booster piston, a brake pedal for emergency displacement of the booster piston when the energy source fails, a travel simulator (4) which is arranged between the brake pedal and the booster piston which has a simulator spring which can be compressed during a brake boosting mode, an electrically controllable throttle valve (17, 48, 49, 63) arrangement which is connected to the pressure line and from which a return line (16.1) leads to the reservoir for adjusting boosting pressure in the booster chamber, at least one first sensor in the form of at least one pressure sensor (34, 34a) which can be adjusted by means of the brake pedal in order to output an electric reference signal variable as a function of the activation of the brake pedal and an electronic control unit which is connected to the at least one first sensor in order to control the throttle valve arrangement electrically dependent upon said electric reference signal variable when the brake pedal is activated, wherein the throttle valve arrangement normally has a wide flow area and the booster chamber (15) is permanently connected to the pressure line (31).