Vehicle braking system and method

• US 10,099,670 B2
• Filed: 12/14/2016
• Issued: 10/16/2018
• Est. Priority Date: 12/14/2016
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Ngomssu, Emmanuel Kouemo, Maier, Bernhard, Flinner, Marko
• Primary Examiner(s): Schwartz, Christopher P
• Application Number:
  US15/378,908
• Publication Number:
  US 20180162336A1
• Time in Patent Office: 671 Days
• Field of Search: 3031141, 60545, 605471, 60593, 701 70- 72
• CPC Class Codes: B60T 13/143 Master cylinder mechanically coupled with booster
• CPC Class Codes: B60T 13/162 Master cylinder mechanically coupled with booster
• CPC Class Codes: B60T 13/662 characterised by specified functions of the control system components
• CPC Class Codes: B60T 13/686 in hydraulic systems or parts thereof
• CPC Class Codes: B60T 7/042 by electrical means, e.g. using travel or force sensors
• CPC Class Codes: B60T 8/3275 Systems with a braking assistant function, i.e. automatic full braking initiation in dependence of brake pedal velocity
• CPC Class Codes: B60T 8/4081 Systems with stroke simulating devices for driver input B60T8/4077 takes precedence
• CPC Class Codes: B60T 8/442 the booster being a fluid return pump, e.g. in combination with a brake pedal force booster
• CPC Class Codes: B60T 8/4872 pump-back systems

Abstract

A vehicle braking system includes a brake pedal, a master cylinder, and an electronically-controlled booster having an input member and an output member adapted to provide an input force to the master cylinder that combines a driver-supplied input force and a boost force provided by the electronically-controlled booster. A wheel cylinder is fluidly coupled to an outlet of the master cylinder and operable to provide a wheel braking force proportional to the input force to the master cylinder. A pump is operable to pump fluid toward the wheel cylinder to provide an assisting wheel braking force. A controller is programmed to trigger a hydraulic braking assist routine in which the pump is activated to provide the assisting wheel braking force. The controller is programmed to reduce the boost force provided by the electronically-controlled booster during the hydraulic braking assist routine.

Claims

1. A vehicle braking system comprising:

a brake pedal;

a master cylinder;

an electronically-controlled booster having an input member coupled to the brake pedal and having an output member coupled to the master cylinder and adapted to provide an input force to the master cylinder that combines a driver-supplied input force provided by the input member and a boost force provided by the electronically-controlled booster;

a wheel cylinder fluidly coupled to an outlet of the master cylinder and operable to provide a wheel braking force proportional to the input force to the master cylinder;

a pump having a suction side coupled to the outlet of the master cylinder, the pump operable to pump fluid in a direction from the master cylinder outlet toward the wheel cylinder to provide an assisting wheel braking force; and

a controller programmed to trigger a hydraulic braking assist routine in which the pump is activated to provide the assisting wheel braking force while in fluid communication between the master cylinder outlet and the wheel cylinder,

wherein the controller is programmed to reduce the boost force provided by the electronically-controlled booster during the hydraulic braking assist routine.

2. The vehicle braking system of claim 1, wherein the controller is programmed to trigger the braking assist routine when identifying that:

based on one or both of the speed and amount of actuation of the brake pedal, emergency braking is being requested, and

the input force to the master cylinder is not sufficient to maximize deceleration.

3. The vehicle braking system of claim 1, wherein the output member of the electronically-controlled booster is coupled to a boost body drivable by an electric motor for receiving the boost force.

4. The vehicle braking system of claim 3, wherein the boost body is arranged concentrically about a valve body in which the input member is slidably received.

5. The vehicle braking system of claim 1, wherein the electronically-controlled booster includes an elastomeric reaction disc through which both the boost force and the driver-supplied input force are applied to the output member.

6. The vehicle braking system of claim 1, wherein the wheel cylinder is coupled to a first chamber of the master cylinder by a first fluid circuit, the vehicle braking system further comprising at least one additional wheel cylinder coupled to a second chamber of the master cylinder by a second fluid circuit.

7. The vehicle braking system of claim 6, wherein the pump is a first pump, and wherein the second fluid circuit includes a second pump having a suction side coupled to a fluid reservoir.

8. The vehicle braking system of claim 1, wherein the controller is programmed to initiate the reduction in boost force simultaneously with initiation of the hydraulic braking assist routine.

9. The vehicle braking system of claim 1, wherein the controller is programmed to reduce the boost force proportional to a reduction in fluid pressure resulting from actuation of the pump during the hydraulic braking assist routine.

10. The vehicle braking system of claim 1, wherein the input member of the electronically-controlled booster is directly coupled to the brake pedal without any intermediate booster.

11. A method of operating a vehicle braking system, the method comprising:

providing an electronically-controlled booster having an input rod coupled to a brake pedal and having an output rod coupled to a master cylinder;

sensing a driver input supplied by the brake pedal to the booster input rod;

providing a boost force from the electronically-controlled booster to supplement a force supplied by the driver input so that the force supplied by the driver input and the boost force combine to produce a total output force applied by the booster output rod to the master cylinder;

conveying the total output force through hydraulic fluid from the master cylinder to at least one wheel cylinder to providing a vehicle braking force;

identifying the driver input to the brake pedal as an emergency braking demand;

actuating a pump to provide an assisting wheel braking force to the at least one wheel cylinder in response to identifying the emergency braking demand, wherein the pump has a suction side coupled to an outlet of the master cylinder, the pump operating to deliver brake fluid in a direction from the master cylinder outlet toward the at least one wheel cylinder; and

actuating the electronically-controlled booster to reduce the boost force during actuation of the pump to provide the assisting wheel braking force.

12. The method of claim 11, wherein the driver input is supplied by the brake pedal to the booster input rod without any intermediate booster.

13. The method of claim 11, wherein the driver input to the brake pedal is identified as an emergency braking demand by one or both of amount of brake pedal depression and speed of brake pedal application.

14. The method of claim 11, further comprising maintaining a consistent pedal reaction force at the booster input rod equal to the force supplied by the driver input throughout the actuation of the pump despite a drop in fluid pressure within the master cylinder.

15. The method of claim 14, wherein the boost force is reduced by an amount proportional to the drop in fluid pressure within the master cylinder.

16. The method of claim 11, wherein the reduction in the boost force is initiated simultaneously with an initiation of the pump actuation.

17. The method of claim 11, wherein the total braking force at the at least one wheel cylinder is increased during the simultaneous pump actuation and boost force reduction.

18. The method of claim 11, further comprising limiting the reduction in the boost force to a predetermined maximum amount to guarantee that the electronically-controlled booster does not actuate against the driver input.