Brake system for motor vehicles

摘要

A motor vehicle “brake-by-wire” system having an actuating unit, including a brake master cylinder, actuatable by a brake pedal, has a housing and a piston, arranged displaceably in the housing and, with the housing, delimits a pressure space. The brake master cylinder piston is a stepped piston with two differing size hydraulic active surfaces; a first, small active surface assigned to the pressure space, and a second, large active surface assigned to a filling space. In the “brake-by-wire” operating mode, the filling space is connected to the travel simulator via a pressure medium line such that, in the “brake-by-wire” operating mode, the first small active surface is effective, and, in the recoil plane after a closing travel has been overcome, the second, large hydraulic active surface is effective and the active surfaces are switched over depending on a hydraulic pressure in the pressure space and on the pedal force, respectively.

主权项

1. A brake-by-wire system for motor vehicles with an actuator unit comprising:
a brake master cylinder which can be activated by a brake pedal, with a housing and a piston arranged displaceably in the housing, which together with the housing delimits a pressure chamber to which wheel brakes are connected, a pressureless pressurized medium storage reservoir, a hydraulically activatable travel simulator which cooperates with the brake master cylinder and comprises a simulator piston which is positioned by means of a spring and delimits firstly a simulator chamber receiving the spring and secondly a simulator chamber connected with the pressure chamber of the brake master cylinder, wherein the travel simulator, in a “brake-by-wire” operating mode, gives the vehicle driver a pleasant pedal feel, wherein the brake master cylinder is activated purely by muscle power of the vehicle driver in a fall-back level, with an electrically controllable, pneumatic, electric or electrohydraulic pressure provision 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 with 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 of different sizes, wherein a first, small active surface is allocated to the pressure chamber and a second, large active surface is allocated to a filling chamber, and wherein the filling chamber in the “brake-by-wire” operating mode is connected with the pressureless pressurized medium reservoir via a pressurized medium line so that the first, small active surface is active in the “brake-by-wire” operating mode, and the second, large, hydraulic active surface is active in the fall-back level after overcoming a closing travel, and switching of the active surfaces takes place depending on a hydraulic pressure in the pressure chamber or the pedal force.