| 摘要 |
A “brake-by wire” brake system for motor vehicles, with a brake master cylinder which can be actuated by a brake pedal and has a housing and a piston, which is arranged displaceably in the housing and, together with the housing, delimits a pressure space. The piston of the brake master cylinder is designed as a stepped piston with at least two hydraulic active surfaces A1, A2 of differing size, wherein a first, small active surface A1 is assigned to the pressure space, and a second, large active surface A2 is assigned to a filling space, and, after a closing travel has been overcome, the second, large hydraulic active surface A2 is effective and the active surface A2, A1 are switched over in dependence on a hydraulic pressure in the pressure space and on the pedal force, respectively. |
| 主权项 |
1. A brake-by-wire brake system for motor vehicles, with a brake master cylinder which can be activated by a brake pedal, with a housing having a stepped bore and a piston arranged displaceably in the stepped bore of the housing, which together with the housing delimits a pressure chamber to which wheel brakes are connected, a pressureless medium storage reservoir, a hydraulically activatable travel simulator which cooperates with the brake master cylinder and comprises at least one elastic element, which, in a brake-by-wire operating mode, gives the vehicle driver a pre-determined pedal feel, an electrically controllable, pneumatic, electric or electrohydraulic actuator unit for pressurizing the wheel brakes, a pressure regulator valve assembly for regulation and/or control of a wheel brake pressure set at a wheel brake, and an electronic control and regulating unit which controls or regulates the actuator unit and/or the pressure regulator valve assembly,
wherein the piston of the brake master cylinder is formed as a stepped piston with at least two hydraulic active surfaces (A1, A2) of different sizes for delivering hydraulic fluid to the wheel brakes, wherein a first, small active surface (A1) of the piston is positioned in a small diameter portion of the stepped bore and is allocated to the pressure chamber and a second, large active surface (A2) of the piston is positioned in a large diameter portion of the stepped bore and is allocated to a filling chamber, and the second, large, hydraulic active surface (A2) is active after overcoming a closing travel, and switching of the active surfaces (A2, A1) takes place depending on a hydraulic pressure in the pressure chamber or the pedal force, and a valve assembly including a central valve arranged within a bore of the piston that is exposed to the pressure chamber, the central valve being moveable between an open position and a closed position with respect to a valve seat, wherein a pressure buildup in the pressure chamber causes the central valve to move away from the valve seat to the open position such that a fluid passageway is formed across the open central valve connecting the filling chamber with the pressureless medium storage reservoir. |
