Traction control braking system with a piston storage unit connected to a reservoir and pump

A hydraulic dual-circuit brake system for motor vehicles having vehicle wheels with wheel brake cylinders comprising an antilock system and anti-spin control system, comprising a brake pedal and a main master brake cylinder for regulating brake pressure through brake pedal activation;

• said main master brake cylinder comprising two separate brake circuit outputs and being connected to a brake fluid supply container;
• a four-duct hydro unit (20) including two brake circuits connected to the two brake circuit outputs;
• said four-duct hydro-unit comprising four outlet ducts (21-24) distributed in the two brake circuits and connected with the wheel brake cylinders of the vehicle wheels, at least one control valve provided for each outlet duct to regulate a wheel-spin-dependent brake pressure to the wheel brake cylinders which are connected both to an individual outlet duct and also in pars via individual connection liens to a brake circuit output of the main brake cylinder, a return pump with two separate pump elements, each of said two separate pump elements operating in one particular brake circuit to return brake fluid from the wheel brake cylinders during brake pressure reduction;
• an input side of each of said two pump elements being connected with said wheel brake cylinders and the outlet ducts belonging to one particular brake circuit via the control valves and connected to an output side of each of said two separate pump elements with said output side connected via one of the connection lines with the main master brake cylinder brake circuit output associated with that brake circuit, at least one device for providing a brake supply pressure during a spin control;
• said at least one device comprising a stop valve (35) in at least one connection line between one brake circuit output and the output of one of said two separate pump elements associated with a brake circuit with at least one drive wheel;
• said stop valve separating the at least one brake circuit from the main master brake cylinder during anti-spin control operation;
• at lest one piston storage unit (40) for supply brake fluid to said one of said two separate pump elements, said at least one piston storage unit comprising a storage piston displaceable in a storage cylinder, a drive for driving the storage piston (44) in axial displacement contrary to a force of a spring (43) and a storage chamber (46) defined by the storage piston;
• said storage chamber being directly connected to a brake fluid supply container (18) via a one-way relief valve (50), and the storage chamber (46) of the at least one piston storage unit (40) is permanently connected to the input of said one of said two separate pump elements (28) and that at the beginning of the anti-spin control operation, the storage piston drive (47) is activated to produce a storage piston stroke to fill the storage chamber (46) with fluid form said brake fluid supply container (18) whereby the force of the spring (43) of the piston (44) is moved to charge said one of said two storage pump elements (28) so that said one of said two pump elements generates a necessary brake pressure required for compensating for spinning of the wheel.