GB2344861A - A brake-by-wire system for a motor vehicle - Google Patents
A brake-by-wire system for a motor vehicle Download PDFInfo
- Publication number
- GB2344861A GB2344861A GB9827681A GB9827681A GB2344861A GB 2344861 A GB2344861 A GB 2344861A GB 9827681 A GB9827681 A GB 9827681A GB 9827681 A GB9827681 A GB 9827681A GB 2344861 A GB2344861 A GB 2344861A
- Authority
- GB
- United Kingdom
- Prior art keywords
- motor vehicle
- electronic control
- brake
- control means
- braking system
- 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- Withdrawn
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
- B60T8/321—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 deceleration
- B60T8/3255—Systems in which the braking action is dependent on brake pedal data
- B60T8/326—Hydraulic systems
-
- 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
- B60T7/00—Brake-action initiating means
- B60T7/02—Brake-action initiating means for personal initiation
- B60T7/04—Brake-action initiating means for personal initiation foot actuated
- B60T7/042—Brake-action initiating means for personal initiation foot actuated by electrical means, e.g. using travel or force sensors
-
- 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
- B60T8/321—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 deceleration
- B60T8/3255—Systems in which the braking action is dependent on brake pedal data
- B60T8/3275—Systems with a braking assistant function, i.e. automatic full braking initiation in dependence of brake pedal velocity
-
- 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
- B60T8/88—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 with failure responsive means, i.e. means for detecting and indicating faulty operation of the speed responsive control means
Landscapes
- Engineering & Computer Science (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Braking Elements And Transmission Devices (AREA)
- Regulating Braking Force (AREA)
Abstract
A brake-by-wire system for a motor vehicle comprises a gas spring 10 which provides both feel for the driver and a pressure signal from sensor 8 to an electronic control unit 11. The control unit 11 also receives signals from a pedal position sensor 13 via an optic fibre 14 and a wheel speed sensor 24. A brake force generating means 12, including a hydraulic pump and valve assembly, is controlled by signals from the control unit e.g.for anti-lock braking. Failure of one of the sensors 8 and 13 may be indicated by comparing the signals from those sensors, and, if both sensors fail, the pedal actuates a switch 15 to ensure that braking is available. Sensor 13 may also measure pedal speed, a high speed, emergency application resulting in a greater ratio of braking effort to applied pedal force. A driver operable switch may be provided for selecting one of several pre-determined ratios.
Description
A Motor Vehicle and a Brakmg System Therefor
This invention relates to a motor vehicle and in particular to a braking system for a motor vehicle.
It is well known to provide a motor vehicle with a driver operable brake lever to apply a braking effort to a motor vehicle by means of a number of hydraulic or air actuated brake means. In such a system the braking effort produced is related to the load applied by the driver to the brake lever and this load is used as a feedback to the driver to indicate the amount of braking being applied.
It is becoming increasingly desirable to provide a motor vehicle with a full power braking system in which there is no direct mechanical connection between the brake lever and the brake means. Such systems are often referred to as brake by wire.
It is an object of this invention to provide an improved brake by wire braking system for a motor vehicle.
According to the invention there is provided a motor vehicle braking system having one or rnore brake means to selectively provide a braking effort to the motor vehicle, a driver input lever to provide an input demand indicative of the desired braking effort required by a driver of the motor vehicle, a gas spring operatively connected to the driver input lever, an electronic control means operatively connected to a brake force generating means and a pressure sensor to provide a signal indicative of the pressure of the gas within the gas spring to the electronic control means wherein movement of the driver input lever in a brake applying direction causes the pressure in the gas spring to be increased.
The level of braking effort generated may be proportional to the increase in pressure of the gas in the gas spring.
The electronic control means may be programme tc provide more than one relationship between the pressure of the gas in the gas spring and the level of braking effort generated.
The electronic control means may send a control signal to the brake force generating means in response to the signal received from the pressure sensor.
The driver input lever may have a position sensor associated therewith to provide a signal to the electronic control means indicative of the position of the input lever.
The signal from the position sensor may be used by the electronic control means to verify that the pressure sensor is operating correctly.
The signal from the position sensor may be used by the electronic control means to determine the speed of movement of the driver input lever.
The electronic control means may be operable when the rate of movement of the input lever is high to increase the ratio of braking effort to gas pressure.
Advantageously, a fail-safe sensor may be arranged to supply a signal to the electronic control means when the input lever moves to the end of its normal range of travel.
The invention will now be described by way of example with reference to the accompanying drawing of which:
Fig. 1 is a schematic representation of a braking system according to the invention;
and
Fig. 2 is a graph showing the relationship between gas pressure'N'and percentage
braking effort B%.
With reference to Fig. 1 there is shown in schematic form a motor vehicle braking system.
The braking system having a driver input lever in the form of a brake pedal 5 pivotally supported by part of the structure of the motor vehicle, a gas spring 10 operatively connected to the brake pedal 5, an electronic control means in the form of an electronic control unit 11, a brake force generating means 12 operatively connected to the electronic control unit 11 and a brake means 20 operatively connected to the brake force generating means 12.
The brake pedal 5 is connected to the gas spring 10 by means of an arm 6 which acts against an input pushrod 7 forming part of the gas spring 10. The pushrod 7 is arranged at its opposite end to move a piston or diaphragm (not shown) located within a working cylinder ( not shown) so as to vary the volume of the working cylinder. As the volume of the working cylinder is decreased the pressure of the gas trapped therein is increased thereby producing a resistance which is transferred back to the brake pedal 5 via the pushrod 7 and the arm 6.
This resistance to movement produces a feedback to the driver indicating how much load is being supplied, this feedback is often referred to as brake pedal feel.
A pressure sensor 8 is arranged to measure the pressure of the gas in the working cylinder and sends a signal indicative of the perceived pressure to the electronic control unit via a signal link in the form of the optic fibre 9.
A position sensor 13 is attached to the brake pedal 5 to provide a signal indicative of brake pedal position to the electronic control unit 11 via a signal link in the form of an optic fibre 14.
A fail-safe sensor in the form of an electric switch 15 is provided to ensure that braking is available even if the pressure and position sensors 8 and 13 fail.
The switch 15 is operated by an upturned end 4 of the arm 6 and is arranged to close the switch 15 when the brake pedal 5 has moved beyond its normally expected range of travel.
When the switch is closed a signal wire 16 connecting the switch 15 to the electronic control unit 11 is connected to earth via a body member of the gas spring 10.
The brake force generating means is controlled by the electronic control unit 11 to which it is connected by means of an electric cable 17. The brake force generating means comprises of a hydraulic pump (not shown) and a control valve assembly (not shown) to control the flow of hydraulic fluid from the pump to the brake means 20 via a brake pipe 18.
The brake force generating means could alternatively be arranged to be incorporated as part of the brake means as shown in DE-A-4229042.
The brake means 20 comprises of a brake calliper 21 arranged to be supplied with fluid via the brake pipe 18, and a brake disc 22 against which brake pads (not shown) are urged by the calliper 21 to provide a frictional braking effort.
A castigated ring 23 is attached to the brake disc 22 for co-operation with a speed sensor 24 used to measure the rotational speed of the brake disc.
Operation is as follows, when an operator or driver of the motor vehicle applies pressure to the brake pedal 5 it rotates in the direction of the arrow'P'on Fig. 1. This rotation causes the arm 6 to move the pushrod 7 into the gas spring 10 thereby increasing the pressure of the trapped gas. The increase in pressure of the trapped gas is sensed by the pressure sensor 8 and the signal received from the pressure sensor 8 by the electronic control unit 11 indicates that the pressure of the gas is rising.
The electronic control unit then sends a control signal to the brake force generating means 12 which is proportional to the signal it has received from the pressure sensor 8.
Therefore the greater the effort applied to the brake pedal 5 the greater the braking effort generated by the brake means 20 will be.
However to prevent locking of the wheel associated with the brake means the electronic control unit 11 is arranged to receive a signal from the speed sensor 24 that is used to control the signal sent to the brake force generating means 12 so as reduce the braking effort when the onset of wheel locking is sensed.
As an added safety precaution the electronic control unit 11 compares the signals it is receiving from the pressure sensor 8 and the position sensor 13. If there is a considerable difference between these signals the electronic control unit 11 alerts the driver to a possible system failure and controls the brake force generating means 12 to produce the maximum braking effort demanded by either of the signals.
In the event that the pressure sensor 8 and the position sensor 13 both fail, the fail-safe sensor 15 will be operated by the upturned end 4 of the arm 6 when the brake lever 5 moves to the end of its normal range of travel.
Upon receiving a signal from the fail-safe sensor 15 the electronic control unit 11 automatically sends a signal to the brake force generating means 12 to cause the brake means to be applied to bring the vehicle to a halt. The braking effort produced will ramp up so as the brake pedal 5 remains in contact with the switch 15 until-the maximum safe braking effort is being generated.
In a first modification to the invention the output signal from the position sensor is used by the electronic control unit 11 to not only monitor the position of the brake pedal 5 but also to measure the speed of movement of the brake lever 5.
If the brake lever 5 is sensed to be moving relatively slowly towards a brake applying position then the electronic control unit increase the signal to the brake force generating means at a relatively low ratio so that a large pedal force is required to produce a rapid deceleration of the motor vehicle but if the brake pedal 5 is sensed to be moving rapidly then the ratio to the brake generating means is increased so that the same rapid deceleration of the motor vehicle will be produced with a lower pedal force.
In effect the ratio between the gas pressure and the braking effort has been increased this can be seen in Fig. 2 where the line (i) represents normal application of the brake pedal 5 and the line (ii) represents an emergency application of the brake pedal 5.
In this way the electronic control unit is able to discriminate between a normal braking manoeuvre and an emergency braking manoeuvre.
By using a gas spring in the manner described above a brake by wire system is produced that provides good driver feedback or feel and is safe should the gas spring or one of the sensors fail.
The term brake by wire is intended to include all systems in which there is no direct mechanical linkage between a driver operable brake lever and the means used to produce a braking effort. The actual linkage may be made by means of conductive wire or could be some other form of signal transmission means such as an optic fibre.
It will be appreciated that the system could include a driver operable selector switch connected to the electronic control unit to change the ratio of braking effort to applied force between several pre-determined ratios.
Claims (10)
1. A motor vehicle braking system having one or more brake means to selectively provide a braking effort to the motor vehicle, a driver input lever to provide an input demand indicative of the desired braking effort required by a driver of the motor vehicle, a gas spring operatively connected to the driver input lever, an electronic control means operatively connected to a brake force generating means and a pressure sensor to provide a signal indicative of the pressure of the gas within the gas spring to the electronic control means wherein movement of the driver input lever in a brake applying direction causes the pressure in the gas spring to be increased.
2.-A motor vehicle braking system as Claimed in Claim 1 in which the level of braking effort generated is proportional to the increase in pressure of the gas in the gas spring.
3. A motor vehicle braking system as Claimed in Claim 1 in which the electronic control means is programmed to provide more than one relationship between the pressure of the gas in the gas spring and the level of braking effort generated.
4. A motor vehicle braking system as Claimed in Claim 2 or in Claim 3 in which the electronic control means sends a control signal to the brake force generating means in response to the signal received from the pressure transducer.
5. A motor vehicle braking system as Claimed in any of Claims 1 to 4 in which the driver input lever has a position sensor associated therewith to provide a signal to the electronic control means indicative of the position of the input lever.
6. A motor vehicle braking system as Claimed in Claim 5 in which the signal from the position sensor is used by the electronic control means to verify that the pressure sensor is operating correctly.
7. A motor vehicle braking system as Claimed in Claim 5 in which the signal from the position sensor is used by the electronic control means to determine the speed of movement of the driver input lever.
8. A motor vehicle braking system as Claimed in Claim 7 when Claim 5 is dependant upon Claim 3 in which the electronic control means may be operable when the rate of movement of the input lever is high to increase the ratio of braking effort to gas pressure.
9. A motor vehicle braking system as Claimed in any preceding Claim in which a failsafe sensor is arranged to supply a signal to the electronic control means when the input lever moves to the end of its normal range of travel.
10. A motor vehicle braking system substantially as described herein with reference to the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9827681A GB2344861A (en) | 1998-12-16 | 1998-12-16 | A brake-by-wire system for a motor vehicle |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9827681A GB2344861A (en) | 1998-12-16 | 1998-12-16 | A brake-by-wire system for a motor vehicle |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9827681D0 GB9827681D0 (en) | 1999-02-10 |
| GB2344861A true GB2344861A (en) | 2000-06-21 |
Family
ID=10844320
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9827681A Withdrawn GB2344861A (en) | 1998-12-16 | 1998-12-16 | A brake-by-wire system for a motor vehicle |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2344861A (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH10203349A (en) * | 1997-01-17 | 1998-08-04 | Jidosha Kiki Co Ltd | Electric control brake system |
| WO1998046461A2 (en) * | 1997-04-16 | 1998-10-22 | Siemens Aktiengesellschaft | Brake power detector for an electrically controlled and actuated braking system |
-
1998
- 1998-12-16 GB GB9827681A patent/GB2344861A/en not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH10203349A (en) * | 1997-01-17 | 1998-08-04 | Jidosha Kiki Co Ltd | Electric control brake system |
| WO1998046461A2 (en) * | 1997-04-16 | 1998-10-22 | Siemens Aktiengesellschaft | Brake power detector for an electrically controlled and actuated braking system |
Non-Patent Citations (1)
| Title |
|---|
| WPI Abstract Accession No.98-476143 [41] * |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9827681D0 (en) | 1999-02-10 |
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Legal Events
| 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) |