Vehicle brake system

Patent metadata

Field	Value
Publication number	US-9610930-B2
Application number	US-201214367653-A
Country	US
Kind code	B2
Filing date	Dec 11, 2012
Priority date	Dec 20, 2011
Publication date	Apr 4, 2017
Grant date	Apr 4, 2017

Abstract

A vehicle brake system comprises an electronic control unit (ECU) for controlling a vehicle brake arrangement, and an electric machine operating as a motor and a generator. The ECU controls valves and the electric machine so that, when a brake pedal is actuated, hydraulic fluid is supplied to a wheel brake from a master cylinder to generate a brake pressure. After a corresponding brake pressure is attained, the supply of hydraulic fluid is disabled, wherein the brake pressure effected by the hydraulic fluid is gradually dissipated, and, correspondingly, the electric machine is operated increasingly as a generator. Upon an increase of driver braking demand, hydraulic fluid is additionally supplied from the master cylinder to the wheel brake, and with decreasing vehicle speed, the electric machine is operated decreasingly as a generator, and, correspondingly, hydraulic fluid is supplied to the wheel brake from an intermediate accumulator and/or from the master cylinder.

First claim

The invention claimed is:

1. Vehicle brake system having an electronic control unit (ECU) for controlling a vehicle brake arrangement and an electric machine operable as a motor and a generator, wherein the ECU communicates with the vehicle brake arrangement and the electric machine and is designed to operate the electric machine as the generator to achieve a vehicle braking effect, and wherein the vehicle brake arrangement comprises at least one wheel brake, a master cylinder for generating a brake pressure at the wheel brake by means of a hydraulic fluid, a feed line and a return line, a plurality of valves for controlling the supply and removal of the hydraulic fluid, and an intermediate accumulator, wherein the ECU is further designed to control the valves and the electric machine in such a way that
upon a driver braking request through actuation of a brake pedal hydraulic fluid is fed to the wheel brake from the master cylinder through the feed line in order to generate the brake pressure at the wheel brake,
upon attainment at the wheel brake of the brake pressure corresponding to the driver braking request the feed of hydraulic fluid from the master cylinder to the wheel brake is interrupted, wherein the brake pressure created by means of hydraulic fluid is gradually reduced and to a corresponding extent at the same time the electric machine is operated increasingly as the generator in order to achieve a braking of at least one wheel of the vehicle corresponding to the driver braking request,
upon an increase of the driver braking request hydraulic fluid is additionally fed from the master cylinder to the at least one wheel brake, and,
as the vehicle velocity drops, the electric machine is operated decreasingly as the generator and to a corresponding extent at the same time hydraulic fluid is fed from at least one of the intermediate accumulator and the master cylinder to the wheel brake in order to achieve at the wheel brake the brake pressure corresponding to the driver braking request, wherein the ECU controls the electric machine and the valves in such a way that upon each further increase of the driver braking request through actuation of the brake pedal a quantity of hydraulic fluid corresponding to the increase is fed to the wheel brake in order to increase the brake pressure at the wheel brake, and that after each increase of the brake pressure at the wheel brake by means of hydraulic fluid, the hydraulic fluid is fed gradually to the intermediate accumulator, and to a corresponding extent at the same time the electric machine is operated increasingly as the generator in order to achieve at the wheel the braking corresponding to the driver braking request.

2. Vehicle brake system according to claim 1 , wherein the ECU controls the electric machine in such a way that upon an increase of the driver braking request the electric machine during the increase of the brake pressure at the wheel brake continues to be operated as a generator to the extent corresponding to the braking by the electric machine prior to the increase of the driver braking request.

3. Vehicle brake system according to claim 1 , wherein the ECU controls the electric machine in such a way that the braking provided by the electric machine is reduced when the driver braking request decreases as a result of a change of the position of the brake pedal.

4. Vehicle brake system according to claim 1 , wherein the brake pressure provided at the wheel brake and corresponding to the additionally fed hydraulic fluid corresponds to the difference of the varied driver braking request and the driver braking request prior to the increase.

5. Vehicle brake system according to claim 1 , wherein the sum of the brake pressure provided by means of the hydraulic fluid at the wheel brake and the braking provided by the regeneratively operated electric machine always corresponds to the driver braking request.

6. Vehicle brake system according to claim 1 , wherein the vehicle brake system comprises a pump for feeding the hydraulic fluid from the intermediate accumulator.

7. Vehicle brake system according to claim 6 , wherein the intermediate accumulator is connected to the feed line and, as the vehicle velocity drops, the pressure build-up in the feed line is controlled in that the ECU varies the rotational speed of the pump.

8. Vehicle brake system according to claim 7 , wherein disruptive influences affecting the pump and the regulation of the flow rate of hydraulic fluid are corrected by means of previously determined characteristics maps in the ECU.

9. Vehicle brake system according to claim 1 , wherein the ECU is implemented in a vehicle-braking controller.

10. Vehicle brake system according to claim 1 , wherein the ECU in order to generate a brake pressure at the wheel brake opens valves in the feed line.

11. Vehicle brake system according to claim 1 , wherein the ECU after attainment at the wheel brake of the brake pressure corresponding to the driver braking request interrupts the feed of hydraulic fluid from the master cylinder to the wheel brake in the feed line by closing at least one of the valves in the feed line.

12. Vehicle brake system according to claim 1 , wherein during the reduction of the brake pressure created by means of the hydraulic fluid the hydraulic fluid is fed to the intermediate accumulator.

13. Vehicle brake system according to claim 1 , wherein the ECU in order to reduce the brake pressure created at the wheel brake by means of the hydraulic fluid opens a valve between the wheel brake and the intermediate accumulator in the return line.

14. Vehicle brake system according to claim 1 , wherein the ECU closes the valve between the wheel brake and the intermediate accumulator in the return line after the reduction at the wheel brake of the brake pressure created by means of the hydraulic fluid.

15. Vehicle brake system according to claim 1 , wherein, as the vehicle velocity drops, the ECU opens the valve between the wheel brake and at least one of the intermediate accumulator and at least one of the valves in the feed line.

Assignees

• Lucas Automotive Gmbh

Inventors

• Marx Andreas

Classifications

• B60L7/18

  Controlling the braking effect (B60L7/12, B60L7/14, B60L7/16 take precedence) · CPC title

• B60T8/4872 Primary

  pump-back systems · CPC title

• B60T13/686

  in hydraulic systems or parts thereof · CPC title

• B60T13/142

  Systems with master cylinder · CPC title

• B60T2270/604

  Merging friction therewith; Adjusting their repartition · CPC title