Method for operating a brake system for motor vehicles and a brake system in which the method is carried out

Patent metadata

Field	Value
Publication number	US-9873416-B2
Application number	US-201414779499-A
Country	US
Kind code	B2
Filing date	Mar 4, 2014
Priority date	Mar 25, 2013
Publication date	Jan 23, 2018
Grant date	Jan 23, 2018

Abstract

An electrohydraulic brake system method for motor vehicles having a wheel-specific brake control function (ABS, ESC, TCS) and hydraulically actuable wheel brakes ( 43, 44, 45, 46 ), communicating with an electrically controllable pressure supply device. The pressure supply device ( 40 ) having a cylinder-based piston arrangement with a pressure space driven by an electromechanical actuator ( 2, 4 ). To set a brake system pressure (Psys) wherein a wheel-specific wheel setpoint pressure (Pi) is predefined for each wheel brake, and a pressure regulating process ( 301 ) is carried out, wherein at certain times a control process ( 303 ) of the pressure medium volume which is output by the pressure supply device is carried out instead of the pressure regulating process ( 301 ) of the brake system pressure, switching over ( 302 ) from the pressure regulating process to the control of the pressure medium volume is carried out as a function of the wheel setpoint pressures (Pi).

First claim

The invention claimed is:

1. A method for operating an electrohydraulic brake system for motor vehicles of the type having a wheel-specific closed-loop brake control function and hydraulically actuable wheel brakes, which are each disconnectably connected to an electrically controllable pressure supply device via an inlet valve, the pressure supply device having a cylinder-piston arrangement with a hydraulic pressure space, and a piston which can be moved by an electromechanical actuator in order to set a brake system pressure, and which wheel brakes are each connected or can be connected to a pressure medium reservoir via an outlet valve, wherein a wheel-specific setpoint wheel pressure is specified for each wheel brake, comprising the steps of:
determining and setting a setpoint value for the brake system pressure;
carrying out a closed-loop pressure control of the brake system pressure of the pressure supply device, wherein a measured actual brake system pressure is adjusted to the setpoint value of the brake system pressure;
determining that a wheel-specific brake pressure increase is to be carried out for at least one wheel brake and, in response thereto, carrying out a switchover from closed-loop pressure control of the brake system pressure to an open-loop control of the pressure medium volume which is output by the pressure supply device in accordance with the setpoint wheel pressures which are specified for the each of the wheel brakes; and
carrying out the open-loop control of the pressure medium volume instead of the closed-loop control of the brake system pressure.

2. The method as claimed in claim 1 , further comprising, in the closed-loop pressure control of the brake system pressure, adjusting the brake system pressure to a highest setpoint wheel pressure of the wheel specific setpoint wheel pressures or to a setpoint pressure that is higher than the highest setpoint wheel pressure by a specified amount.

3. A method for operating an electrohydraulic brake system for motor vehicles of the type having a wheel-specific closed-loop brake control function and hydraulically actuable wheel brakes, which are each disconnectably connected to an electrically controllable pressure supply device via an inlet valve, the pressure supply device having a cylinder-piston arrangement with a hydraulic pressure space, and a piston which can be moved by an electromechanical actuator in order to set a brake system pressure, and which wheel brakes are each connected or can be connected to a pressure medium reservoir via an outlet valve, wherein a wheel-specific setpoint wheel pressure is specified for each wheel brake, comprising the steps of:
carrying out a closed-loop pressure control of the brake system pressure of the pressure supply device;
carrying out at certain times an open-loop control of the pressure medium volume which is output by the pressure supply device instead of the closed-loop pressure control of the brake system pressure;
carrying out a switchover from closed-loop pressure control of the brake system pressure to the open-loop control of the pressure medium volume in accordance with the setpoint wheel pressures which are specified for the wheel brakes;
carrying out the switchover to the open-loop control of the pressure medium volume in response to determining that a wheel-specific brake pressure increase is to be carried out for at least one wheel brake.

4. The method as claimed in claim 1 , further comprising, during the open-loop control of the pressure medium volume, moving the piston by a position value, with the result that a pressure medium volume determined by means of the specified setpoint wheel pressures is displaced into at least one wheel brake.

5. The method as claimed in claim 4 , further comprising determining the position value by using at least one pressure/volume characteristic specified for the wheel brake or the wheel brakes.

6. The method as claimed in claim 4 , wherein, in the case of a brake pressure increase at two or more wheel brakes simultaneously, determining the position value by a sum of pressure medium volumes of the wheel brakes that is required for the brake pressure increase at the two or more wheel brakes.

7. The method as claimed in claim 6 , wherein a wheel-specific brake pressure increase at the two or more wheel brakes is provided through wheel-specific opening durations for the corresponding inlet valves.

8. The method as claimed in claim 1 , further comprising carrying out, after the completion of a phase of the open-loop control of the pressure medium volume, a phase of the closed-loop pressure control of the brake system pressure.

9. The method as claimed in claim 8 , further comprising switching the system from the open-loop control of the pressure medium volume to the closed-loop pressure control of the brake system pressure when either holding or reduction of the brake pressure is to be carried out for each of the wheel brakes.

10. The method as claimed in claim 8 , further comprising determining, at the beginning of the closed-loop pressure control phase, a deviation between the measured brake system pressure and the brake system pressure specified by the closed-loop brake control function, and carrying out a correction of a model for open-loop control of the pressure medium volume using the deviation.

11. The method as claimed in claim 10 , further comprising determining a wheel-specific correction factor, using the deviation and a pressure/volume characteristic, and determining the factor in accordance with the wheel brake pressure.

12. The method as claimed in claim 11 , further comprising determining a corrected pressure medium volume for a wheel brake in a subsequent phase of the open-loop control of the pressure medium volume using the correction factor.

13. A brake system for motor vehicles comprising:
a wheel-specific closed-loop brake control function,
a plurality of hydraulically actuable wheel brakes,
an electrically controllable pressure supply device, having a cylinder-piston arrangement with a hydraulic pressure space, and a piston which can be moved by an electromechanical actuator, wherein each of the wheel brakes is disconnectably connected to the pressure supply device via an inlet valve and is connected or can be connected to a pressure medium reservoir via an outlet valve,
a first detection device for determining a brake system pressure of the pressure supply device,
a second detection device for determining a position of the pressure supply device or the actuator,
an electronic open-loop and closed-loop control unit for controlling the electromechanical actuator, and
wherein the control unit is configured to carry out the steps of at certain times providing an open-loop control of the pressure medium volume which is output by the pressure supply device instead of a closed-loop pressure control of the brake system pressure, and carrying out, in response to a determination that a wheel-specific brake pressure increase is to be carried out for at least one wheel brake, a switchover from the closed-loop pressure control of the brake system pressure to the open-loop control of the pressure medium volume in accordance with setpoint wheel pressures which are specified for the wheel brakes.

14. The method of claim 1 , wherein the open-loop control is carried out when a wheel specific brake pressure increase is to be carried out in a wheel brake where the previous pressure level of said wheel brake was below the brake system pressure of the pressure supply device.

Assignees

• Continental Teves Ag & Co Ohg

Inventors

• Roll Georg
• Böhm Jürgen
• Besier Marco

Classifications

• B60T8/326 Primary

  Hydraulic systems · CPC title

• B60T8/4081

  Systems with stroke simulating devices for driver input (B60T8/4077 takes precedence) · CPC title