Brake device, in particular for electrically driven motor vehicles

Abstract

A brake apparatus, for electrically driven motor vehicles, includes a traction motor at an axle of a vehicle, which traction motor is used both as drive motor and as brake system with recuperation of brake energy, a first piston-cylinder unit, which is actuatable by means of an actuating device, in particular brake pedal, a second piston-cylinder unit, which is actuatable by means of an electromotive drive and a non-hydraulic gearing apparatus, in particular spindle drive. The piston-cylinder units are connected via hydraulic connecting lines to wheel brakes of the motor vehicle. A pressure chamber of the first piston-cylinder unit is connected to two wheel brakes of a vehicle axle, and a pressure chamber of the second piston-cylinder unit is connected to a vehicle axle for active brake force feedback control and recuperation control in interaction with the traction motor.

What is claimed is: 
     
         1 . A brake apparatus for electrically driven motor vehicles having a first and a second axle, each having two wheel brakes, the brake apparatus including:
 a. a traction motor at the first axle, wherein the traction motor is used both as a drive motor and as a brake system with recuperation of brake energy,   b. a first piston-cylinder unit, which is actuatable by means of an actuating device, the first piston-cylinder unit either having a first piston separating a first pressure chamber, or having a first piston separating a first pressure chamber and a second piston separating a second pressure chamber, wherein the first pressure chamber, or at least one of the first pressure chamber or the second pressure chamber, of the first piston-cylinder unit is connected to the two wheel brakes of one of the first axle or the second axle via a first hydraulic connecting line,   c. a second piston-cylinder unit, which is actuatable by means of an electromotive drive and a non-hydraulic gearing apparatus, wherein the second piston-cylinder unit has exactly one piston and one working chamber, and   d. at least one electronic control and feedback control unit,   wherein the working chamber of the second piston-cylinder unit is connected to the wheel brakes of the first vehicle axle, via a second hydraulic connecting line, enabling active brake force feedback control and recuperation control in interaction with the traction motor, and   wherein the at least one electronic control and feedback control unit is adapted to perform a distribution of braking torques at the wheel brakes or the corresponding axles between the traction motor and the second piston-cylinder unit, wherein a vehicle model is taken into consideration for performing the distribution, the vehicle model replicating a weight distribution and a friction coefficient between a roadway and tires of the vehicle.   
     
     
         2 . The brake apparatus as claimed in  claim 1 , wherein the brake apparatus is adapted to perform pressure metering in accordance with demand by means of the second piston-cylinder unit, wherein the control is performed via travel control or combined travel and pressure control of the piston of the second piston-cylinder unit through utilization of a pressure-volume characteristic curve. 
     
     
         3 . The brake apparatus as claimed in  claim 2 , wherein the pressure-volume characteristic curve is configured to be adaptively adjusted after every braking operation. 
     
     
         4 . The brake apparatus as claimed in  claim 2 , wherein the brake apparatus is adapted to utilize a characteristic map for refined brake force feedback control, the characteristic map providing a relationship between brake pressure and deceleration depending on temperatures of the wheel brakes. 
     
     
         5 . The brake apparatus as claimed in  claim 4 , wherein the brake apparatus is adapted to perform pilot control using an isolating valve and feedback control of the pressure change, to enable attainment of a target pressure or to enable adjustment to the traction motor braking feedback control. 
     
     
         6 . The brake apparatus as claimed in  claim 1 , wherein the brake apparatus is adapted to maximize the recuperation of the vehicle by means of intermittent braking only by means of the traction motor. 
     
     
         7 . The brake apparatus as claimed in  claim 2 , wherein the brake apparatus is adapted to replicate a pedal feel by means of the pressure-volume characteristic of a wheel brake or multiple wheel brakes of one of the first or second axles. 
     
     
         8 . A method for braking a motor vehicle having an electric traction motor and having an electrohydraulic brake system with a piston-cylinder unit, the method including:
 controlling, in a first operating strategy, an electric motor of the piston-cylinder unit and the electric traction motor to maximize a total deceleration of the motor vehicle, wherein the total deceleration is a sum of a deceleration established by the traction motor and a deceleration established using the electrohydraulic brake system, and   controlling, in the first operating strategy, the electric motor of the piston-cylinder unit and the traction motor to minimize a time-to-lock,   wherein a vehicle model is taken into consideration to distribute the total deceleration between the deceleration established by the traction motor and the deceleration established using the electrohydraulic brake system, the vehicle model replicating a weight distribution and a friction coefficient between a roadway and tires of the vehicle.   
     
     
         9 . The method as claimed in  claim 8 , further including controlling, in the first operating strategy, the traction motor such that up to at least the total deceleration of 1 g the deceleration established by the traction motor is maximized. 
     
     
         10 . The method as claimed in  claim 8 , further controlling, in the first operating strategy, the traction motor in a first phase such that the deceleration established by the traction motor is maximized to approach a maximum total deceleration. 
     
     
         11 . The method as claimed in  claim 10 , further include controlling, in the first operating strategy, the total deceleration in a second phase after the first phase such that the total deceleration is increased. 
     
     
         12 . The method as claimed in  claim 8 , further including controlling, in the first operating strategy, the traction motor such that the deceleration established by the traction motor is increased in at least a first interval of 50 ms and maintained as the total deceleration approaches a maximum total deceleration and/or at least until at least a total deceleration of 1 g is established. 
     
     
         13 . The method as claimed in  claim 8 , further including decelerating the vehicle, in a second operating strategy, with the total deceleration lower than a setpoint deceleration, whereby the deceleration established by the traction motor is kept constant. 
     
     
         14 . The method as claimed in  claim 8 , wherein for controlling the deceleration established by the traction motor a maximum torque of the traction motor is taking into consideration, wherein the maximum torque depends on vehicle speed or rotational speed of the traction motor. 
     
     
         15 . The method as claimed in  claim 8 , wherein the deceleration established using the electrohydraulic brake system is controlled using a set pressure, wherein for determining the set pressure a temperature is taken into consideration to compensate a fading effect. 
     
     
         16 . A method for managing a brake apparatus of a motor vehicle having an electric traction motor and having an electrohydraulic brake system with a piston-cylinder unit, the method comprising:
 determining an objective of a braking operation,   dividing a setpoint deceleration between the traction motor and the electrohydraulic brake system in accordance with the determined objective of the braking operation, and transmitting setpoint values to a first control and feedback control unit, which performs control and feedback control of the traction motor, and to a second control and feedback control unit, which performs control and feedback control of the electrohydraulic brake system, wherein at least one of a traction motor deceleration setpoint value and/or a traction motor torque setpoint value is determined for the traction motor, wherein at least one of an electrohydraulic brake system deceleration setpoint value, an electrohydraulic brake system pressure setpoint value, or an electrohydraulic brake system torque setpoint value is transmitted to the electrohydraulic brake system simultaneously with the setpoint value(s) transmitted to the traction motor, and   braking using the traction motor and the electrohydraulic brake system in accordance with the divided setpoint deceleration.   
     
     
         17 . The method as claimed in  claim 16 , further comprising:
 determining the setpoint deceleration at the traction motor and the electrohydraulic brake system in accordance with an objective of maximum recuperation, maximum deceleration or controlled deceleration, and   maximizing recuperation of the motor vehicle by means of intermittent braking only by means of the traction motor.   
     
     
         18 . The method as claimed in  claim 16 , further comprising:
 maximizing pressure build-up dynamics in a pressure range up to 10 bar by assistance of a further electric motor of the piston-cylinder unit.   
     
     
         19 . The method as claimed in  claim 16 , further comprising:
 evaluating a pressure-volume characteristic curve of a wheel brake and a pressure at an associated axle or a pressure of the electrohydraulic brake system for travel control of a piston of the electrohydraulic brake system.   
     
     
         20 . The method as claimed in  claim 16 , further comprising:
 taking a temperature into consideration for detecting a change in the electrohydraulic brake system.