GB2367868A - Delayed rear brake application in electro-hydraulic (EHB) braking systems - Google Patents

Delayed rear brake application in electro-hydraulic (EHB) braking systems Download PDF

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Publication number
GB2367868A
GB2367868A GB0025237A GB0025237A GB2367868A GB 2367868 A GB2367868 A GB 2367868A GB 0025237 A GB0025237 A GB 0025237A GB 0025237 A GB0025237 A GB 0025237A GB 2367868 A GB2367868 A GB 2367868A
Authority
GB
United Kingdom
Prior art keywords
brake
pressure
hydraulic
brakes
demand
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB0025237A
Other versions
GB0025237D0 (en
Inventor
Alan Leslie Harris
Mark Ian Philipps
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
TRW Ltd
Original Assignee
TRW Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by TRW Ltd filed Critical TRW Ltd
Priority to GB0025237A priority Critical patent/GB2367868A/en
Publication of GB0025237D0 publication Critical patent/GB0025237D0/en
Priority to EP01974523A priority patent/EP1324905A1/en
Priority to AU2001294038A priority patent/AU2001294038A1/en
Priority to PCT/GB2001/004577 priority patent/WO2002032734A1/en
Publication of GB2367868A publication Critical patent/GB2367868A/en
Priority to US10/412,635 priority patent/US20030205928A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
    • B60T8/34—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition
    • B60T8/40—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition comprising an additional fluid circuit including fluid pressurising means for modifying the pressure of the braking fluid, e.g. including wheel driven pumps for detecting a speed condition, or pumps which are controlled by means independent of the braking system
    • B60T8/4072—Systems in which a driver input signal is used as a control signal for the additional fluid circuit which is normally used for braking
    • B60T8/4081—Systems with stroke simulating devices for driver input
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
    • B60T13/10—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release
    • B60T13/66—Electrical control in fluid-pressure brake systems
    • B60T13/68—Electrical control in fluid-pressure brake systems by electrically-controlled valves
    • B60T13/686—Electrical control in fluid-pressure brake systems by electrically-controlled valves in hydraulic systems or parts thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
    • B60T13/74—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with electrical assistance or drive
    • B60T13/745—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with electrical assistance or drive acting on a hydraulic system, e.g. a master cylinder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/26—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force characterised by producing differential braking between front and rear wheels
    • B60T8/266—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force characterised by producing differential braking between front and rear wheels using valves or actuators with external control means

Abstract

A vehicle electro-hydraulic braking system of the type which can operate in a brake-by-wire mode wherein hydraulic pressure from an electric pump is applied to wheel brake actuators in proportion to the driver's braking demand DD as sensed electronically at a brake pedal (12, fig 1), wherein the pressure demand RBD for rear brake actuators (16b, fig 1) is arranged to be delayed until at least one of two conditions has been fulfilled, namely (a) the pressure FBD of at least one front brake actuator (16a, fig 1) has reached a predetermined pressure P<SB>min</SB>, (eg. 2 bar) and/or (b) a predetermined time delay threshold T<SB>max</SB> has been exceeded (eg. 100-300ms) and/or wherein delivery to the fluid brakes is limited to a predetermined value that is relatively low with respect to that for the front brakes (eg. 10% of front brake delivery). In emergency, a master cylinder mechanically coupled to the brake pedal can supply fluid directly to front brake actuators in a push-through mode via digital valves (30a, 30b, fig 1).

Description

DESCRIPTION OPTIMISED BRAKE-APPLY SEQUENCE IN ELECTRO-HYDRAULIC (EHB) BRAKING SYSTEMS The present invention is concerned with improving efficiency of braking performance in vehicle braking systems, in particular within the context of vehicle braking systems having electro-hydraulic (EHB) braking.
A typical EHB system for a vehicle comprises a brake pedal, respective braking devices which are connected to the vehicle wheels and which are capable of being brought into communication with electronically controlled control valves in order to apply hydraulic fluid under pressure to the braking devices, a hydraulic pump driven by an electric motor, and a high pressure hydraulic pressure accumulator fed by said pump for the provision of hydraulic fluid under pressure which can be passed to the braking devices and the electrically controlled control valves in order, in so called"brake-by-wire"mode, to apply hydraulic fluid under pressure to the braking devices in proportion to the driver's demand as sensed at the brake pedal. The EHB system is controlled by an electronic controller (ECU). In the case of typical four-wheeled vehicles, there are four said braking devices at the two front wheels and two rear wheels of the vehicle, respectively.
Where the high pressure accumulator is fed by the pump via an accumulator valve, it is found in practice that the accumulator valve can restrict infill flow to the braking devices because the brake stiffness is low and total flow is high. A bigger valve to reduce this problem is impractical because of packaging and thermal problems.
Furthermore, it is a feature of conventional systems that the braking devices at the rear wheels have a lower consumption of brake fluid than those at the front wheels because the calipers at the rear brakes are usually of smaller size than the calipers at the front brakes. It is therefore possible that the rear brakes pressure will increase faster than the front brakes pressure.
As a result of these characteristics, the effect is that front-brake pressure rise from zero can be delayed, leading to poor deceleration response, and rear-brake pressure often rises before front-brake pressure, leading to concern about vehicle stability.
There is therefore a requirement for these deleterious effects to be reduced.
In accordance with the present invention, the pressure demand for the rear brake actuators is arranged to be delayed until at least one of two conditions has been fulfilled, namely (a) the pressure of at least one front brake actuator has reached a predetermined pressure, and/or (b) a delay threshold of a predetermined level has been exceeded and/or wherein delivery of fluid to the rear brakes is limited to a predetermined value that is relatively low with respect to that for the front brakes.
A typical value for the predetermined pressure might, for example, be 2bar (=Pmin) and a typical value for the predetermined level might, for example, be 100300ms. (= Tmax). A typical value of the predetermined value might for example be 10% of the front brake level.
The aforegoing strategy would apply only to base-brake scenarios, including those triggered from an external system such as autonomous cruise control (ACC).
It would therefore not apply to traction control (TC) or VSC, or during ABS.
Prioritising the front brakes in this way allows them to be filled more quickly without increasing the size of the accumulator valve, and avoids the premature application of the rear brakes.
Responding to the first front brake to reach, say, 2bar is safe in the event of a failure at the one front brake.
Setting a maximum delay of, say, 300ms is safe in the event that the front brakes respond too slowly due to e. g. air/knockback/taper wear of the linings.
The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is an illustration of one embodiment of an electro-hydraulic (EHB) braking system to which the present invention is applicable; and Fig. 2,2a-2c illustrate graphically the three conditions mentioned above.
Fig. 1 illustrates an electro hydraulic braking system where braking demand signals are generated electronically at a travel sensor 10 in response to operations of a foot pedal 12, the signals being processed in an electronic control unit (ECU) 14 for controlling the operation of brake actuators 16a, 16b at the front and back wheels respectively of a vehicle via pairs of valves 18a, 18b and 18c, 18d. The latter valves are operated in opposition to provide proportional control of actuating fluid to the brake actuators 16 from a pressurised fluid supply accumulator 20, maintained from a reservoir 22 by means of a motor-driven pump 24 via a solenoid controlled accumulator valve 26. For use, for example, in emergency conditions when the electronic control of the brake actuators is not operational for some reason, the system includes a master cylinder 28 coupled mechanically to the foot pedal 12 and by which fluid can be supplied directly to the front brake actuators 16a in a"push through"condition. In the push-through condition, a fluid connection between the front brake actuators 16a and the cylinder 28 is established by means of digitally operating, solenoid operated valves, 30a, 30b. Also included in the system are further digitally operating valves which respectively connect the two pairs of valves 36a, 36b, and the two pairs of valves 18c, 18d.
Referring to Figs 2a-2c, for the purposes of the present invention as applied to the system illustrated in the figure, the ECU 14 is programmed to enable the pressure demand at the rear brake actuators 16b to be delayed until at least one of the two prescribed conditions has been fulfilled, namely that the pressure at at least one front brake actuator 16a has reached a predetermined pressure, such as 2bar (see Fig.
2a), and/or a delay threshold of a predetermined level, such as 300ms, has been exceeded (see Fig 2b) and/or delivery of fluid to the rear brakes is limited to a predetermined valve that is relatively lower compared to that for the front brakes.
The figures of 2bar and 300ms are given purely by way of illustration and are not intended to limit the invention to these figures.
In Figs 2a to 2c: DD = Driver Demand FBD = Front Brake Demand RBD = Rear Brake Demand

Claims (5)

1. A vehicle electro-hydraulic braking system of the type which can operate in a brake-by-wire mode wherein hydraulic pressure is applied to brake actuators at the vehicle wheels in proportion to the driver's braking demand as sensed electronically at a brake pedal, wherein the pressure demand for the rear brake actuators is arranged to be delayed until at least one of two conditions has been fulfilled, namely (a) the pressure of at least one front brake actuator has reached a predetermined pressure, and/or (b) a delay threshold of a predetermined level has been exceeded and/or wherein delivery to the fluid brakes is limited to a predetermined value that is relatively low with respect to that for the front brakes.
2. A braking system as claimed in claim 1, wherein said predetermined pressure is approximately 2bar.
3. A braking system as claimed in claim 1 or 2, wherein the delay threshold is between 100-300 ms.
4. A braking system as claimed in claim 1,2 or 3 wherein said typical value is approximately 10% of the delivery of fluid to the front brakes.
5. A vehicle electro-hydraulic brake system, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.
GB0025237A 2000-10-14 2000-10-14 Delayed rear brake application in electro-hydraulic (EHB) braking systems Withdrawn GB2367868A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
GB0025237A GB2367868A (en) 2000-10-14 2000-10-14 Delayed rear brake application in electro-hydraulic (EHB) braking systems
EP01974523A EP1324905A1 (en) 2000-10-14 2001-10-15 Optimised brake-apply sequence in electro-hydraulic (ehb) braking systems
AU2001294038A AU2001294038A1 (en) 2000-10-14 2001-10-15 Optimised brake-apply sequence in electro-hydraulic (ehb) braking systems
PCT/GB2001/004577 WO2002032734A1 (en) 2000-10-14 2001-10-15 Optimised brake-apply sequence in electro-hydraulic (ehb) braking systems
US10/412,635 US20030205928A1 (en) 2000-10-14 2003-04-10 Optimised brake-apply sequence in electro-hydraulic (EHB) braking systems

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB0025237A GB2367868A (en) 2000-10-14 2000-10-14 Delayed rear brake application in electro-hydraulic (EHB) braking systems

Publications (2)

Publication Number Publication Date
GB0025237D0 GB0025237D0 (en) 2000-11-29
GB2367868A true GB2367868A (en) 2002-04-17

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB0025237A Withdrawn GB2367868A (en) 2000-10-14 2000-10-14 Delayed rear brake application in electro-hydraulic (EHB) braking systems

Country Status (5)

Country Link
US (1) US20030205928A1 (en)
EP (1) EP1324905A1 (en)
AU (1) AU2001294038A1 (en)
GB (1) GB2367868A (en)
WO (1) WO2002032734A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2543890B1 (en) * 2011-07-04 2018-09-05 Valmet Technologies, Inc. Safety component

Families Citing this family (4)

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Publication number Priority date Publication date Assignee Title
JP4222382B2 (en) 2006-04-28 2009-02-12 トヨタ自動車株式会社 Vehicle braking device
JP5012820B2 (en) * 2009-01-23 2012-08-29 トヨタ自動車株式会社 Brake control device
US10576946B2 (en) 2017-02-22 2020-03-03 Arnaldo C. Gomes Collision avoidance braking system and method
US10124777B2 (en) 2017-02-22 2018-11-13 Arnaldo C. Gomes Multiple-stage collision avoidance braking system and method

Citations (3)

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Publication number Priority date Publication date Assignee Title
GB2136519A (en) * 1983-01-21 1984-09-19 Teves Gmbh Alfred Method of and device for controlling the distribution of brake force
GB2321684A (en) * 1995-10-07 1998-08-05 Bosch Gmbh Robert A vehicle brake system with electric-motor driven brake actuators
GB2345322A (en) * 1998-12-31 2000-07-05 Lucas Ind Plc Malfunction in an electro-hydraulic braking system

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GB2136519A (en) * 1983-01-21 1984-09-19 Teves Gmbh Alfred Method of and device for controlling the distribution of brake force
GB2321684A (en) * 1995-10-07 1998-08-05 Bosch Gmbh Robert A vehicle brake system with electric-motor driven brake actuators
GB2345322A (en) * 1998-12-31 2000-07-05 Lucas Ind Plc Malfunction in an electro-hydraulic braking system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2543890B1 (en) * 2011-07-04 2018-09-05 Valmet Technologies, Inc. Safety component

Also Published As

Publication number Publication date
GB0025237D0 (en) 2000-11-29
AU2001294038A1 (en) 2002-04-29
WO2002032734A1 (en) 2002-04-25
US20030205928A1 (en) 2003-11-06
EP1324905A1 (en) 2003-07-09

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Date Code Title Description
732E Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977)
WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)