Brake system

Abstract

A brake system may include an actuation device, in particular a brake pedal; a first piston-cylinder unit with two pistons, in particular an auxiliary piston and a second piston, in order to supply brake circuits with a pressure medium via a valve device, wherein one of the pistons, in particular the auxiliary piston, can be actuated by means of the actuation device; a second piston-cylinder unit comprising an electric motor-powered drive, a transmission, and at least one piston in order to supply pressure medium to at least one of the brake circuits via a valve device; and a motor pump unit with a valve device in order to supply pressure medium to the brake circuits. The brake system may further include a hydraulic travel simulator which is connected to a pressure or working chamber of the first piston-cylinder unit.

What is claimed is: 
     
         1 . A brake system, comprising:
 an actuating device,   a first piston-cylinder unit having a first piston and a second piston, arranged to supply at least one first brake circuit and at least one second brake circuit with pressure medium via a valve device, wherein the first piston is enabled to be actuated by means of the actuating device, wherein the first piston-cylinder unit comprises a first pressure chamber or a first working chamber in which the first piston is arranged and to which at least the second brake circuit is connected, and wherein the first piston-cylinder unit comprises a second pressure chamber or a second working chamber, to which at least the first brake circuit is connected,   a second piston-cylinder unit with an electromotive drive, a transmission and at least one piston to supply pressure medium to at least one of the brake circuits via a valve device,   a motor-pump unit, with valve device, arranged to supply pressure medium to the brake circuits,   a hydraulic travel simulator connected to one of the pressure chambers or working chambers of the first piston-cylinder unit,   wherein the pressure or working chamber of the second piston-cylinder unit is connected to the first brake circuit via a hydraulic line and is supplied with pressure via the first piston,   wherein the second piston-cylinder unit is aligned parallel to an axis of the first piston-cylinder unit,   wherein the second piston-cylinder unit is only effective in a specific pressure range and the motor-pump unit is used for pressure generation for a further, higher pressure range than the specific pressure range,   wherein the motor-pump unit is arranged in separate housing, and   wherein the first piston-cylinder unit has a partition wall with a seal for a penetrating plunger, to form a third pressure chamber or a third working chamber, in which a piston is arranged, which is connected via a valve device to the second working chamber and to the first brake circuit.   
     
     
         2 . The brake system according to  claim 1 , wherein the brake system is designed for a subsequent conveying of volumes from a storage container during a piston return stroke of the second piston-cylinder unit via a suction valve, wherein the suction valve and a breather hole of the second piston-cylinder unit are connected to the storage container via a return line. 
     
     
         3 . The brake system according to  claim 2 , wherein, in an event of failure of the first brake circuit, the plunger transmits a force of a brake pedal to the second piston and thus generates pressure in the second brake circuit. 
     
     
         4 . The brake system according to  claim 3 , wherein the plunger has a smaller cross-sectional area, by a factor of five, than the pistons of the first piston-cylinder unit, and contributes insignificantly to the pressure build-up and serves for pressure sensing in the brake circuit, and wherein the plunger transmits a force to the brake pedal and thus generates a haptic feedback to the brake pedal during anti-lock braking system (ABS) operation and/or fading. 
     
     
         5 . The brake system according to  claim 1 , further comprising a control device to enable a motor of the electromotive drive of the second piston-cylinder unit and a motor of the motor-pump unit to be used together or independently of one another. 
     
     
         6 . The brake system according to  claim 1 , wherein, in an event of failure of the motor-pump unit, an ABS function is carried out by a piston control of the second piston-cylinder unit together with pressure regulating valves of the motor-pump unit. 
     
     
         7 . The brake system according to  claim 1 , wherein control of the second piston-cylinder unit is carried out via brake pedal travel and pressure by means of a corresponding brake booster characteristic, wherein instead of the pressure, a motor current is used for regulating the second piston-cylinder unit. 
     
     
         8 . The brake system according to  claim 1 , wherein a pressure-volume characteristic is used for controlling the second piston-cylinder unit and for diagnosis, wherein the brake system is designed to detect a failure of one of the brake circuits by comparing pressure-volume characteristics, wherein a respective pressure-volume characteristic is stored in a characteristic map at intervals as part of a diagnostic cycle. 
     
     
         9 . The brake system according to  claim 1 , wherein the first piston and the second piston of the first piston-cylinder unit have different diameters. 
     
     
         10 . The brake system according to  claim 1 , wherein a first module of a two-box is connected to a 12V battery or 12V voltage network and a second module of the two-box is connected to a DC/DC converter or 48V on-board network or other on-board network with a higher voltage, wherein a brake booster is supplied by the DC/DC converter or by the 48V on-board network. 
     
     
         11 . The brake system according to  claim 10 , wherein both modules are each connected redundantly to both the 12V battery and the DC/DC converter. 
     
     
         12 . The brake system according to  claim 1 , wherein four-wheel blending takes place for a recuperation control, wherein a pressure control takes place via a pressure supply piston with open valves of the valve device of the motor-pump unit and/or the transmission comprises a trapezoidal spindle with self-locking, with a self-locking action in an event of failure of the electromotive drive. 
     
     
         13 . The brake system according to  claim 2 , wherein a plug connection for the brake system is arranged below the storage container and is directed inwards towards a center of the system in order to enable a lateral removal of an associated plug. 
     
     
         14 . The brake system according to  claim 2 , wherein the second piston of the first piston-cylinder unit has, in addition to an associated passage comprising the breather hole, which is provided with two seals, a further associated passage which is provided with a further seal, and which is connected via a throttle to the return line leading to the storage container.