Brake system with actuation assist

Patent metadata

Field	Value
Publication number	US-2016123418-A1
Application number	US-201414527053-A
Country	US
Kind code	A1
Filing date	Oct 29, 2014
Priority date	Oct 29, 2014
Publication date	May 5, 2016
Grant date	—

Abstract

A wheel braking system includes a fluid source connected to an actuator that applies a force to a friction element for retarding rotation of the wheel. The braking system also includes a hydraulic circuit that has a first fluid passage providing direct communication between the fluid source and the actuator and a second fluid passage in communication with the first passage. The second fluid passage has a first portion and a second portion and includes a reciprocating piston assembly with a first piston fixed to a second piston for selectively amplifying a volume of the pressurized fluid received by the actuator. The first portion of the second passage is in fluid communication with the first piston and the second portion is in fluid communication with the second piston. The first piston has a first diameter and the second piston has a second diameter that is greater than the first diameter.

First claim

1 . A braking system for retarding rotation of a wheel, the system comprising:
a rotor configured to rotate synchronously with the wheel; a fluid source configured to supply a pressurized fluid; an actuator configured to receive the pressurized fluid from the fluid source and generate an actuator force; a friction element configured to be selectively engaged with the rotor by the actuator force to thereby retard rotation of the wheel; and a hydraulic circuit configured to provide fluid communication between the fluid source and the actuator, the hydraulic circuit having:
a first fluid passage providing direct fluid communication between the fluid source and the actuator; and
a second fluid passage having a first portion and a second portion, wherein each of the first and second portions is in fluid communication with the first fluid passage; and
a reciprocating piston assembly arranged inside the second fluid passage and including a first piston fixed to a second piston and configured to selectively amplify a volume of the pressurized fluid received by the actuator to thereby generate rapid engagement of the friction element with the rotor;
wherein:
the first portion of the second fluid passage is in fluid communication with the first piston and the second portion of the second fluid passage is in fluid communication with the second piston; and
the first piston is defined by a first diameter and the second piston is defined by a second diameter that is greater than the first diameter.

2 . The braking system according to claim 1 , wherein a ratio of the second diameter to the first diameter defines an amplification factor that amplifies the volume of the pressurized fluid received by the actuator.

3 . The braking system according to claim 1 , further comprising a spring element configured to store energy when the pressurized fluid is supplied by the fluid source in a first mode of operation of the braking system and release the stored energy to assist disengagement of the friction element from the rotor when the actuator ceases to generate the actuator force in a second mode of operation of the braking system.

4 . The braking system according to claim 3 , wherein the spring element is arranged in direct contact with the second piston.

5 . The braking system according to claim 3 , further comprising a flow control valve arranged at a junction between the first fluid passage and the second portion of the second fluid passage, wherein the flow control valve is configured to selectively block fluid communication between the second portion of the second fluid passage and the first fluid passage via a closed position in a third mode of operation of the braking system and facilitate fluid communication between the second portion of the second fluid passage and the first fluid passage via an opened position in each of the first and second modes of operation of the braking system.

6 . The braking system according to claim 5 , wherein the flow control valve has a default closed position and is also configured to be at least partially opened for bleeding the hydraulic circuit to purge air therefrom.

7 . The braking system according to claim 5 , wherein the second piston is configured to accumulate a portion of the pressurized fluid when the actuator ceases to generate the actuator force in the second mode of system operation and release the portion of the fluid when the pressurized fluid is supplied by the fluid source in the first mode of system operation.

8 . The braking system according to claim 5 , further comprising a limit switch arranged in electrical communication with the flow control valve and configured to detect a position of the piston assembly inside the second fluid passage and select a position for the flow control valve in response to the detected position of the piston assembly.

9 . The braking system according to claim 8 , wherein the limit switch is configured to:
open the flow control valve in each of the first and second modes of system operation; and close the flow control valve in the third mode of system operation.

10 . The braking system according to claim 8 , wherein the first piston and the second piston are maintained in a spaced relationship via a connecting element, and wherein the connecting element includes a feature configured to communicate the position of the piston assembly to the limit switch.

11 . A motor vehicle comprising:
a road wheel; an actuator; and a braking system operatively connected to the road wheel for decelerating the vehicle, the braking system including:
a rotor configured to rotate synchronously with the road wheel;
a fluid source configured to supply a pressurized fluid;
an actuator configured to receive the pressurized fluid from the fluid source and generate an actuator force;
a friction element configured to be selectively engaged with the rotor by the actuator force to thereby retard rotation of the road wheel; and
a hydraulic circuit configured to provide fluid communication between the fluid source and the actuator, the hydraulic circuit having:
a first fluid passage providing direct fluid communication between the fluid source and the actuator; and
a second fluid passage having a first portion and a second portion, wherein each of the first and second portions is in fluid communication with the first fluid passage; and
a reciprocating piston assembly arranged inside the second fluid passage and including a first piston fixed to a second piston and configured to selectively amplify a volume of the pressurized fluid received by the actuator to thereby generate rapid engagement of the friction element with the rotor;

wherein:
the first portion of the second fluid passage is in fluid communication with the first piston and the second portion of the second fluid passage is in fluid communication with the second piston; and
the first piston is defined by a first diameter and the second piston is defined by a second diameter that is greater than the first diameter.

12 . The motor vehicle according to claim 11 , wherein a ratio of the second diameter to the first diameter defines an amplification factor that amplifies the volume of the pressurized fluid received by the actuator.

13 . The motor vehicle according to claim 11 , further comprising a spring element configured to store energy when the pressurized fluid is supplied by the fluid source in a first mode of operation of the braking system and release the stored energy to assist disengagement of the friction element from the rotor when the actuator ceases to generate the actuator force in a second mode of operation of the braking system.

14 . The motor vehicle according to claim 13 , wherein the spring element is arranged in direct contact with the second piston.

15 . The motor vehicle according to claim 13 , further comprising a flow control valve arranged at a junction between the first fluid passage and the second portion of the second fluid passage, wherein the flow control valve is configured to selectively block fluid communication between the second portion of the second fluid passage and the first fluid passage via a closed position in a third mode of operation of the braking system and facilitate fluid communication between the second portion of the second fluid passage and the first fluid passage via an opened position in each of the first and second modes of operation of the braking system.

16 . The motor vehicle according to claim 15 , wherein the flow control valve has a default closed position and is also configured to be at least partial

Assignees

• Gm Global Tech Operations Inc

Inventors

• Moore Joseph K
• Begleiter David
• Held Veit

Classifications

• F16D55/226

  in which the common actuating member is moved axially {, e.g. floating caliper disc brakes} · CPC title

• F16D2121/04

  acting on a piston-type actuator, e.g. for liquid pressure · CPC title

• F16D65/18 Primary

  adapted for drawing members together {, e.g. for disc brakes} · CPC title

• B60T13/12 Primary

  the fluid being liquid · CPC title

• B60T13/686 Primary

  in hydraulic systems or parts thereof · CPC title