Externally controllable electrohydraulic vehicle brake system

1. An externally actuable electrohydraulic vehicle brake system comprising:

an electrohydraulic vehicle system with slip control,

means for expressing a brake activation request in the form of a man/machine interface,

friction brakes for converting kinetic energy, wherein the friction brakes are organized into at least two independent brake circuits, and

an electronically controlled hydraulic unit for operating the friction brakes, said hydraulic unit having at least one hydraulic pump as a pressure source in order to permit distribution and/or control of friction braking portions as a function of either a brake activation request or an externally actuated braking intervention,

wherein the man/machine interface is configured to be decoupled mechanically from the friction brakes,

wherein the hydraulic pump is assigned means which permit the hydraulic pump to drive a hydraulic charging device which is connected to an inlet of the hydraulic pump for the purpose of pre-charging, and

wherein the hydraulic charging device comprises i) a control chamber having an inlet that is in constant fluid communication with the hydraulic pump and ii) a supply chamber having an outlet that is in constant fluid communication with the hydraulic pump.

2. The brake system as claimed in claim 1 , wherein the hydraulic pump drives the charging device in that an initial feed current is divided, and a separate part is fed to the charging device.

3. The brake system as claimed in claim 1 , wherein the electronically controlled hydraulic unit includes at least one branch, which is arranged downstream of an outlet of the hydraulic pump and a control valve for regulating a charging function.

4. The brake system as claimed in claim 1 , wherein the charging device is embodied as a piston/cylinder unit with an inlet and an outlet.

5. The brake system as claimed in claim 4 , wherein a piston of the piston/cylinder unit is displaceably arranged in a housing and separates the control chamber from the supply chamber, and in that the supply chamber is connected to the inlet of the hydraulic pump.

6. The brake system as claimed in claim 5 , wherein the electronically controlled hydraulic unit includes at least one branch, which is arranged downstream of an outlet of the hydraulic pump and a control valve for regulating a charging function, and

wherein an additional branch is provided and is configured for connecting the supply chamber of the piston/cylinder unit to wheel brakes or a master cylinder by bypassing the hydraulic pump, and the additional branch is located between the outlet of the piston/cylinder unit and the inlet of the hydraulic pump.

7. The brake system as claimed in claim 5 , wherein the supply chamber forms a variable pressure medium reservoir for supplying the hydraulic pump, and in that a suction path of the hydraulic pump ends in the supply chamber.

8. The brake system as claimed in claim 5 further comprising a connection provided between the outlet of the hydraulic pump and the control chamber.

9. The brake system as claimed in claim 5 , wherein the piston is embodied as a stepped piston with two piston faces such that a pressure medium which is fed into the control chamber by the hydraulic pump acts on a first piston face.

10. The brake system as claimed in claim 9 , wherein a second piston face acts on the pressure medium in the supply chamber, and wherein the second piston face is larger than the first piston face.

11. The brake system as claimed in claim 5 further comprising an elastically prestressed compression spring that continuously acts on the piston so that the piston is continuously forced elastically in a direction of the control chamber.

12. The brake system as claimed in claim 1 , wherein the hydraulic pump acts with the charging device on the friction brakes of a circuit, which friction brakes are associated with a non-driven axle of a motor vehicle with a hybrid drive.

13. The brake system as claimed in claim 12 , wherein each circuit has a pump with a charging device and in that the means for expressing a braking request include a simulator.

14. The brake system as claimed in claim 13 , wherein each circuit also has a low pressure accumulator in addition to the charging device.

15. The brake system as claimed in claim 12 , wherein each friction brake of an axle has, respectively separated from one another, a pump and a charging device.

16. The brake system as claimed in claim 15 , wherein each charging device has an integrated low pressure accumulator volume, and in that a piston of each charging device is provided in a tied fashion.