GB2212572A - Rail brake air regulator - Google Patents

Rail brake air regulator Download PDF

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Publication number
GB2212572A
GB2212572A GB8726734A GB8726734A GB2212572A GB 2212572 A GB2212572 A GB 2212572A GB 8726734 A GB8726734 A GB 8726734A GB 8726734 A GB8726734 A GB 8726734A GB 2212572 A GB2212572 A GB 2212572A
Authority
GB
United Kingdom
Prior art keywords
brake
speed
air pressure
friction
air
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Withdrawn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
GB8726734A
Other versions
GB8726734D0 (en
Inventor
George Keith Vale
Colin John Frederick Tickle
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.)
ZF International UK Ltd
Original Assignee
Lucas Industries 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 Lucas Industries Ltd filed Critical Lucas Industries Ltd
Priority to GB8726734A priority Critical patent/GB2212572A/en
Publication of GB8726734D0 publication Critical patent/GB8726734D0/en
Publication of GB2212572A publication Critical patent/GB2212572A/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Withdrawn legal-status Critical Current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
    • B60T8/321—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
    • B60T8/3235—Systems specially adapted for rail vehicles
    • 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
    • B60T13/665—Electrical control in fluid-pressure brake systems the systems being specially adapted for transferring two or more command signals, e.g. railway 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
    • 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
    • B60T8/17—Using electrical or electronic regulation means to control braking
    • B60T8/1701—Braking or traction control means specially adapted for particular types of vehicles
    • B60T8/1705—Braking or traction control means specially adapted for particular types of vehicles for rail vehicles

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  • Engineering & Computer Science (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Regulating Braking Force (AREA)

Abstract

An air pressure regulator for a rail vehicle has a source of air pressure (10) which is connectible to a brake actuator (22) either directly by means of a line (16) or alternatively via a pressure reduction device (18), the selection being made by means of a solenoid-operated valve (12). A control means (30) is fed with a signal representative of the brake speed v and compares the speed with the brake lining friction/speed characteristic which is stored in the control means. If the control means decides that the coefficient of friction of the brake lining at that brake speed is below a threshold valve, the source of air pressure (10) is connected directly to the brake actuator (22) instead of via the pressure reduction device (18). The invention compensates for the reduction in the coefficient of friction ( mu ) which occurs with increasing speed with relatively soft brake lining materials. <IMAGE>

Description

DESCRIPTION RAIL BRAKE AIR REGULATOR The present invention relates to air actuated brakes for rail vehicles, and in particular, but not exclusively to air actuated transmission brakes of rail vehicles.
The brakes used in rail vehicles are usually fairly massive devices using large, heavy brake discs and associated air actuated friction pads.
For smaller rail vehicles, such as the type of railcars found in local inner-city systems, there is a requirement for much lighter, smaller brake units, particularly for units which can be utilised as a transmission brake. The lower torque associated with transmission brakes means that lower air pressures can be utilised, since the load on the brake discs is relatively small. This means that relatively soft friction pads may be used, which is an advantage since soft disc pads tend to conform to the shape of the disc more than hard ones, thus reducing the likelihood of damage to the discs and the pads through localised heat spots caused by the rubbing of pads on the uneven surface of the discs.
However, the use of soft disc pads has a disadvantage, in that their coefficient of friction decreases with increasing speed of the disc to be braked. This property is illustrated in Fig. 3 of the accompanying drawings. The phenomenon is not the same as "fade" of brakes which is normally due to 3n increase in temperature of the brake and pad materials, but rather is a property of the pad itself, and is reversible.
Therefore, when using softer friction pads the stopping distance is greater than that calculated from the nominal coefficient of friction of the friction pads.
It is an object of the present invention to provide an air actuated brake for use in particular, but not exclusively, with relatively soft brake lining materials, which overcomes the above-mentioned disadvantages.
In accordance with the present invention in its broadest aspect, there is provided an air regulator for a brake of a rail vehicle, in which the energising air pressure supplied to a brake actuator for applying the brakes is arranged to be increased to a higher value above a predetermined vehicle speed.
In a preferred arrangement, the air regulator comprises means for producing a first air pressure, means for producing a second, higher air pressure, valve means for connecting one of the first and second air pressures to a brake actuator, a speed sensor for sensing the speed of the brake of the vehicle, and valve control means adapted to connect the second, higher air pressure to the brake actuator when the sensed speed- is such that the coefficient of friction of the brake lining at that speed is below a threshold value.
In this way, if the vehicle is being braked from a relatively high speed, a higher brake actuation air pressure will be applied to compensate for the reduction in the coefficient of friction, whereas if the vehicle is travelling relatively slowly, the lower pressure will be applied since the reduction in the coefficient of friction will be less.
In one embodiment of the present invention, the switchover control means is adapted to connect the second, higher air pressure, when on comparison of the brake lining friction characteristic stored in the control means and the sensed brake or vehicle speed, the control means calculates that the coefficient of friction of the brake lining is below a threshold value.
Preferably, when the second, higher air pressure is applied, it is applied for a pre-set period.
Preferably, the length of the period is calculated on the basis of the length of time required for the brakes to be applied in order to bring the vehicle to a halt on the assumption that the coefficient of friction of the brake lining has a value equal to that when the brake was applied.
By way of example, a specific embodiment of the present invention will now be described, with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic representation of an embodiment of air regulator for a brake of a rail vehicle in accordance with the present invention; Fig. 2 is a flow diagram illustrating the operation of the embodiment of Fig. 1; and Fig. 3 is a schematic representation showing the characteristic of a relatively soft brake lining material, i.e. the variation of coefficient of friction (u) with the speed of the braked wheel.
Referring firstly to Fig. 3, the graph shows, schematically, the variation of the coefficient of friction of a relatively soft brake lining with the speed of the brake. It will be appreciated that the speed of the brake is related directly to the speed of the vehicle. As the speed increases, the coefficient of friction decreases. The decrease with increasing speed is relatively small at lower speeds, but becomes significant at higher speeds.
Referring now to Fig. 1 of the accompanying drawings, an air regulator in accordance with the present invention comprises a supply 10 of air at a fixed pressure. The pressurised air is fed into a solenoid actuated valve 12. The valve 12 has two outlets, connected to air pressure lines 14, lo respectively. The first air pressure line 14 is connected to a pressure reduction device 18, such as a twin diaphragm valve. This device produces in its output line 20 an air pressure of about 85% that in the inlet line 14. The pressure reduction device is a conventional, known device, and will not be further described. The other line 16 bypasses the pressure reduction device 18 and is connected to the output line 20 of the device.The lines 16 and 20 are both connected to a brake actuation cylinder 22, whose piston 24 is pivotally connected to a brake linkage 26, illustrated schematically.
As seen in Fig. 1, the switchover valve 12 is movable from the illustrated position in which the source of pressure 10 is connected via the line 16, by-passing the pressure reduction device 18, and in which the source 10 is therefore connected directly to the brake actuation cylinder 22 to an alternative position in which the source of pressure 10 is connected via the pressure reduction device 18 to the brake actuation cylinder 22 (thereby applying a fixed percentage (e.g. 85%) of the pressure of source 10 to the cylinder 22). The solenoid valve 12 is biassed towards the former position by means of a spring 28 and is held in the latter position by energising the solenoid valve. The biassing towards the former position ensures that if the solenoid valve 12 fails to operate, the full pressure of the source 10 is applied to the brake actuation cylinder 22, in a failsafe manner.
The solenoid valve 12 is under the control of an electronic control unit 30 which feeds a signal E to the solenoid valve 12 to energise the valve. A signal representing the brake speed (or alternatively the vehicle speed which is directly proportional to the brake speed) v is fed into the control unit 30. The characteristic of the brake lining is stored in the control unit 30, such that at any given speed v, the control unit calculates the coefficient of friction P of the brake lining if the brake were to be applied at that instant. This can be done either by storing the value ofyu at different values of v, or by storing an equation representing the variation of)i with v.
The operation of the embodiment is illustrated in Fig.
2. After commencing the sequence at step 36, the control unit 30 periodically scans the signal v representing the speed of the brake at step 38. If the speed of the brake is below a certain threshold vT, the control unit proceeds to step 40 and sends a signal E to the solenoid valve 12, which, if the brake is applied, connects the source of air pressure 10 to the brake actuator 22 via the pressure reduction device 18, so that if the brake is applied a relatively low actuation pressure is applied to the brake actuator 22.
Alternatively, if at step 38 the control unit detects that the speed of the brake is greater than vT, the unit then determines, by comparison with previously-stored values of v, whether the speed of the brake is decreasing, i.e., whether the brake is being applied. Alternatively, if the brake is not being applied, then the sequence returns to step 38, as before. If at step 42 the control unit 30 determines that the speed of the brake is decreasing, i.e.
that braking is occurring, the control unit starts a timing period at step 44, the length of the period being equal to the period for which the brake must be applied to bring it to a stop assuming that the coefficient of friction T is constant at the value at the time the brake was first applied. The control unit then stops sending the electrical signal E to the solenoid valve 12, which then moves into the alternative position, in which the pressure reduction device 18 is by-passed by means of the air pressure line 16. The solenoid valve 12 moves into the alternative position by virtue of the helical spring 28, and the full air pressure of the source 10 is applied to the brake.
The control unit 30 periodically determines whetner the pre-calculated period has elapsed, at step 48. If the period has not elapsed, the unit returns to step 46. After the pre-set period has elapsed, the unit returns to step 38 once again and the process is repeated continuously.
It should be noted that, although the brake may not be applied for the full pre-set period, the higher pressure will be applied if the brake is re-applied at any time during that pre-set period.
The invention is not restricted to the details of the foregoing embodiment.

Claims (7)

1. An air regulator for a brake of a rail vehicle, in which the energising air pressure supplied to a brake actuator for applying the brakes is arranged to be increased to a higher value above a predetermined vehicle speed.
2. An air regulator for a brake of a rail vehicle, comprising means for producing a first air pressure, means for producing a second, higher air pressure, valve means for connecting one of the first and second air pressures to a brake actuator, a speed sensor for sensing the speed of the brake of the vehicle, and valve control means adapted to connect the second, higher air pressure to the brake actuator when the sensed speed is such that the coefficient of friction of the brake lining at that speed is below a threshold value.
3. An air regulator as claimed in claim 2, wherein the control means are adapted to switch over to the second, higher air pressure when, on comparison of the brake lining friction characteristic stored in the control means and the sensed speed, the control means calculates that coefficient of friction of the brake lining is below a threshold value.
4. An air regulator as claimed in claim 2 or claim 3, wherein the second, higher air pressure is available for connection to the brake actuation means for a pre set period of time.
5. An air regulator as claimed in claim 4, wherein the period is calculated on the basis of the length of time which would be necessary to bring the brake to a halt if the coefficient of friction of the lining had a constant the value equal to that at the prevailing speed at which the brakes were applied.
6. An air regulator as claimed in any of claims 2 to 5, comprising a common source of air pressure, and pressure-reduction means for producing the first air pressure.
7. An air regulator substantially as herein descriDed, with reference to, and as illustrated in, Fig.s 1 and 2 of the accompanying drawings.
GB8726734A 1987-11-14 1987-11-14 Rail brake air regulator Withdrawn GB2212572A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8726734A GB2212572A (en) 1987-11-14 1987-11-14 Rail brake air regulator

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8726734A GB2212572A (en) 1987-11-14 1987-11-14 Rail brake air regulator

Publications (2)

Publication Number Publication Date
GB8726734D0 GB8726734D0 (en) 1987-12-16
GB2212572A true GB2212572A (en) 1989-07-26

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB8726734A Withdrawn GB2212572A (en) 1987-11-14 1987-11-14 Rail brake air regulator

Country Status (1)

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GB (1) GB2212572A (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0410145A2 (en) * 1989-07-24 1991-01-30 Knorr-Bremse Ag Pneumatic brake device for railway vehicles
EP0741065A2 (en) * 1995-05-05 1996-11-06 The B.F. Goodrich Company Braking device and method for providing a more constant braking force
EP0928729A1 (en) * 1998-01-13 1999-07-14 SLM Schweizerische Lokomotiv- und Maschinenfabrik AG Operating method for a rail vehicle brake device and brake device therefor
WO2010003609A1 (en) * 2008-07-11 2010-01-14 Knorr-Bremse Systeme für Schienenfahrzeuge GmbH Brake device for controlling the pressure applied to a brake cylinder in a pneumatic braking system
US9296399B2 (en) 2012-05-25 2016-03-29 Knorr-Bremse Systeme Fur Schienenfahrzeuge Gmbh Method for controlling a compressed-air braking device of a rail vehicle in the case of automatic, quick, or emergency braking
WO2016079014A1 (en) * 2014-11-17 2016-05-26 Knorr-Bremse Systeme für Schienenfahrzeuge GmbH Braking device and method for even braking

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1118540A (en) * 1965-12-07 1968-07-03 Knorr Bremse Gmbh Improvements in or relating to speed-controlled switching apparatus

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1118540A (en) * 1965-12-07 1968-07-03 Knorr Bremse Gmbh Improvements in or relating to speed-controlled switching apparatus

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0410145A2 (en) * 1989-07-24 1991-01-30 Knorr-Bremse Ag Pneumatic brake device for railway vehicles
EP0410145A3 (en) * 1989-07-24 1992-07-08 Knorr-Bremse Ag Pneumatic brake device for railway vehicles
EP0741065A2 (en) * 1995-05-05 1996-11-06 The B.F. Goodrich Company Braking device and method for providing a more constant braking force
EP0741065A3 (en) * 1995-05-05 1998-08-19 The B.F. Goodrich Company Braking device and method for providing a more constant braking force
EP0928729A1 (en) * 1998-01-13 1999-07-14 SLM Schweizerische Lokomotiv- und Maschinenfabrik AG Operating method for a rail vehicle brake device and brake device therefor
WO2010003609A1 (en) * 2008-07-11 2010-01-14 Knorr-Bremse Systeme für Schienenfahrzeuge GmbH Brake device for controlling the pressure applied to a brake cylinder in a pneumatic braking system
US9296399B2 (en) 2012-05-25 2016-03-29 Knorr-Bremse Systeme Fur Schienenfahrzeuge Gmbh Method for controlling a compressed-air braking device of a rail vehicle in the case of automatic, quick, or emergency braking
EP2855223B1 (en) 2012-05-25 2016-04-06 KNORR-BREMSE Systeme für Schienenfahrzeuge GmbH Method for controlling a compressed-air braking device of a rail vehicle in the case of automatic, quick, or emergency braking
DE102012010519C5 (en) * 2012-05-25 2016-10-20 Knorr-Bremse Systeme für Schienenfahrzeuge GmbH Method for controlling a compressed air brake device of a rail vehicle in the case of forced, emergency or emergency braking
WO2016079014A1 (en) * 2014-11-17 2016-05-26 Knorr-Bremse Systeme für Schienenfahrzeuge GmbH Braking device and method for even braking
CN107107889A (en) * 2014-11-17 2017-08-29 克诺尔轨道车辆系统有限公司 Brake apparatus and the method for uniformly braking
CN107107889B (en) * 2014-11-17 2020-03-06 克诺尔轨道车辆系统有限公司 Braking device and method for uniform braking

Also Published As

Publication number Publication date
GB8726734D0 (en) 1987-12-16

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)