CA2053224A1 - Vehicle braking systems - Google Patents
Vehicle braking systemsInfo
- Publication number
- CA2053224A1 CA2053224A1 CA 2053224 CA2053224A CA2053224A1 CA 2053224 A1 CA2053224 A1 CA 2053224A1 CA 2053224 CA2053224 CA 2053224 CA 2053224 A CA2053224 A CA 2053224A CA 2053224 A1 CA2053224 A1 CA 2053224A1
- Authority
- CA
- Canada
- Prior art keywords
- braking
- braking system
- vehicle
- signal generating
- control signal
- 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.)
- Abandoned
Links
Classifications
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- 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
-
- 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
- B60T13/58—Combined or convertible 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
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- 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
-
- 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
- B60T15/00—Construction arrangement, or operation of valves incorporated in power brake systems and not covered by groups B60T11/00 or B60T13/00
- B60T15/02—Application and release valves
- B60T15/04—Driver's valves
- B60T15/14—Driver's valves influencing electric control means
Landscapes
- Engineering & Computer Science (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Regulating Braking Force (AREA)
- Braking Systems And Boosters (AREA)
- Valves And Accessory Devices For Braking Systems (AREA)
Abstract
The invention relates to a vehicle braking system comprising a braking element (15) operable by a driver of the vehicle, control signal generating means responsive to the operation of the braking element, means braking at least one wheel of the vehicle in response to the control signals generated by the control signal generating means and reaction means responsive to the control signals to provide a force on the braking element (15) so as provide a variable artificial feel to the driver through the braking element.
Description
WO90~12717 2 ~ 5 3 2 2 ~ PCT/GB90/00640 ,'~' - 1 VEHICLE BRAKI~G SY~
The invention relates to vehicle braking systems. ', Almost all moder~ vehicles, particularly motor cars, ~' have hydraulically operated fioot brakes operating on all wheels. The systems generally comprise either d mm or disc brakes with a brake pedal connected to a piston in a master cylinder whence the hydraulic operating pressure originates.
Depression of the brake pedal forces the hydraulic brake fluid along a network of pipes and hoses to wheel cylinders which urge brake calipers or shoes into contact with a brake disc or drum to provide the ~raking action.
Hydraulic systems' have many advantages, such as heing self-lubricating (reducing the chance of seizure), having a low `rate of wear and low fri'~tion,"'and enabling et~ual pressures to be eserted on all '~the~ br~ake''~shoes` or 'calipers, even compensating ~' for '~unequal: wear~'or adjustment. 'Further, installation ~-is generally''' eaæier-than ~or mechanical s~stems because of the~fle~ibility of'the~hoseæ ~`'':' ''` ' - -:~ .
'The" principal~disa~vantage`'~of''hydraulic brakingisystems ;is ;~:that ~a~:leakage~'`in''':the'lsystem'i or''-!''contamination of the hydraulic fluld used can r0nder the hrakes ine~fective or in-opera~ive. '~
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'''One':solution to ~'th'is proble'm is~prov~ide'd''by having a tandem master-tcylinder, and: splitting'~'he'system"into"two`parts 2~ 2 -so that if one part fails the other part can still function.
Obviously, in the event of failure of one part braking efficiency is reduced, and there are situations when this can be dangerous.
Sometimes it would be preferable to control the separate brakes individually for e~amyle if one tyre has been worn more than its a~ial counterpart. In standard systems both a~ial brakes would be operated identically. It would also be useful in braking systems to be able to control the f~.el at the braking, as some drivers prefer sharp braking and others prefer to have to move the brake pedal some distance before ma~imum braking is achieved.
Advances in braking technology have been restricted '.
because of the problems in distribution of the fluid in the brake mechanisms.
7'',, '~ Accord,ing to the invention there is provided a vehicle ..., braking system comprising a braking element operable by a : .driver of-~ the vehicle; control signal generating . means responsive to.operat1on of the,.braking.element; means braking at least one wheel of,,the: vehicle in re~ponse to control ,...... ...... ... ........ -,sign,als,generated.by,the control.signal generating maans; and ,reaction means ,responsive~,.to,,ithe.control~signals.to, provide a force .on the braking ,element to~provide a variable, artifical s feel to the driver through the braking element.
~3,; ~re~erably ~the control, signals are ,proportional to a ; forcejapplied to the.braking element by the driver.
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W~90/12717 2 ~ ~ 3 2 2 ~ PCT/~90/006~0 ' ` ' :. . ~
In a preferred embodiment the system comprises means for sensing the force appiied to the braking element and providing input signals proportional thereto to the control signal generating means, the sensing means preferably comprising an electrical load cell.
Preferably the system comprises means for sensing the position and~or movement of the braking element and providing input signals to the control -signal generating means proportionaI thereto, said sensing means preferably comprising one or more linear vari'able displacement transducers.
Preferably the reaction means comprises a hydraulic actuator coupled to the braking element, the actuator preferably being a double acting hydraulic actuator having a pair of opposed piston faces.
The actuator is preferably controlled by a servo-valve responsive to the control signals to control the application of hydraulic fluid pressure to the opposed piston faces to operate the actuator. ' '' ' "' '~
' ''' The braking element can be a brake pedal.
Another preferred 'embodiment includes error detection means operative to check whether 1the;artiical ~eel is being provided to the braking element and to provide input'signals to ~'the contr~l signal generatin~msans in'dependence thereon. On ~'detection -or~an error`~by''~the~error dete'ction means outside a ;I' pre-set ~limit~`l t'he -control signal~generating- means-,preferably 'gen'erates con~rol signals to operate a sa~e~y system.
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WOgo/12717 '~ PCTtGB90/00640 3~
The control signal generating means is preferably acomputer which can be programmable to generate control signals dependent on requirements of the driver or the condition of the vehicle .
A vehicle braking system according to the invention will now be described by way of e~ample with reference to the drawings, in which:- , Figure l is a schsmatic representation of the layout of the system;
Figure 2 is a part sectional front elevation of a brake reelN actuator assembly ~which is a part of the system of Figure l;
Figure 3 is a sectional view of Figure 2 on III-III;
Figure 4 is a part sectional front elevation of a distribution valve which is a part of the system of Fi~ure 1;
and . . .
:~ ,- -.. Figure -S~,is a:-front elevation of the distribution valve : of Figure 3 with parts omitted for clarity.
;~ Referring first .to Figure l there is shown a braking ~ system lO~.,for~use -,iin a:-motor vehicle .such as a ~motor car, !,: having ~ steerable.wheels.(not~shown). ~ ", :,. :.:,,'..The .~otor,,vehicle,~has ,~our wheels each itted ; with .,.~ standard hydraulically operated diæc or drum brakes., Althou~h ~.
. the .brakes., hemQel~es are not~,~shown "in the ,drawings,~,.the : ~ operable ~calipers,;or~,shoes..or each.~,wheel (hereinafter brake ~, mechanism).are attached to a,respective servo,valve ll,, 12, l~, ,... . . . . .. . . . . . . .
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14, which independently controls the pressure to the brake mechanism at the associated wheel.
The system 10 combines a primary active brake system and a secondary brake override system that provides the braking effort in the event of a system failure or when the active system is turned off.
The Prima,ry,Active Bra~ina System The active system is a fully active "feel" system including a braking element in the form of a brake pedal 15 which is physically decoupled frorn the braking mechanisms. The brake pedal 15 is mounted to the vehicle body to be pivotal about its polnt of attachment. Attached to the brake pedal 15 is a "feel" actuator 16.
Referring now to Figure 2 also, the feel actuator 16 is a double acting,;,hydraulic actuator comprising a moveable piston 17 ha~ing a pair of opposed ,piston faces and contained.in a , cylinder 18.: Mounted on the piston :17 is a piston head 17a which provides-the piston faces. One end of the piston ~17 is - coupled, to~ the brake pedal 15 by means of a linkage element 20 " ,which ~includes 'a-~load cell~.21 (or other ,sui~able;~device) ~which .~is pre~erably~,a duple~,.,sensor,~,for sensing,,the force,applied by a driver,o~,the,,vehicle,,to:the ,-brake :pedal 15. The,load cell 21 is,electrically connected~to a control ,unit 25, such as a mir,~opracessor,;and.sends, input signals_thereto-,relating-to the force.applîsd to the brake,pedal' 15.. -~`m~ a."~
:~ , Also attached to, the.linkage~lement~20 is a rod.22 ,: :
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woso~l27~ PCT/GB90/00640 6 ,.
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which enters a hol~er 23 of a linear variable differential transformer (LVDT) 24. The LVDT holder 23 is fi~ed adjacent to the cylinder 18 on a manifold block 75 housing the feel actuator 16. The LVDT 24 converts the mechanical displacement of the linkage element 20 (and therefore the displacement of the brake pedal 15) into an electrical signal which is transmitted to the microprocessor 25 to which the LVDT 24 is Plectrically connected. Other suitable devises may of course be used for converting the displacement into an electrical signal.
; The feel actuator 16 is hydraulically connected to servo valve 28. Hydraulic transfer tu~es 9 are provided in the manifold block 75 linking the hydraulic fluid lines ~rom the servo valve ~ to each end of cylinder 18 so that the servo valve 28 may be used to control the movement of the piStOTI 17 by hydraulic pressure to either side o~ the piston head 17a.
; As will be seen in Figure l a~non-return valYe ~9a is . 'included in the hydraulic fluid line between the servo valve 2a and feel actuator~. 16, for reasons described below. The -non-return valve~ 29a:is also connected'ito the pressure supply l~ ~ line~33 via an isolating valve 31"~describ~d below.' The non-... . returnlvalve!29a opens on'application of pressurè thereto.`
` The servo valve 28 is colnected to' h~draulic fluid.. suppl~ ,pressure and~:~return lines 33,:34 via an isolating valve ~: 31 which is pre~erably ^a solenoid val~e. When' the solenoid valve:31 is energised the pressure supply line 33 is connected , : , , ~ ~ ' , :
WO90/~2717 PCT/GB9~/00640 - 72~3224 to the servo valve 28 and when it is de-energised the return line 34 is connected to the servo valve 28. A prPssure reducing valve 30 is incorporated in the pressure supply line 33 leading to the isolating val~e 31 so that the servo valve 28 uses a pressure lower than the system pressure.
An anti-cavitation valve 27 is also included.
The microprocessor 25 is connected to control the brake servo valves 11, 12, 13, 14 ana signals g2nerated by the micro-processor 25 control the pressure applied to the four brake '' mechanisms independently. The servo valves 11, 12, 13, 14 are connected to brake lines 56 which are connected to the brake mechanisms of the front left, rear left, rear right and front brakes respectively, via a distribution valve 35, as shown in Figures 4 and 5. - -The servo valves 11, 12, 13, 14 are connected to the hydraulic pressure and retur~ lines 33, 34 via connectors 32.
One connector 32`connects a branch-o the pressure and return lines to one pair of servo~ valves- 11, 14 and the other ' connector 32 to the seco~d pair of servo valYes 1~, 13. ` ' The distribution'~'val've 35~'comprises a' valvè manifold 36 ha~ing ~our separate "chambers` 46; 47, 48, 49 'therein. ' Each chambe'r 46,;' 47,'48, 49"is connecte~ via a fluid pàssage 50 to a respective s~rvo'~-valvè 11,"12, 13,'` 14;~;;The manifold 36 has eight ports 37-44'therein such that~each chamber 46, 4i,'148, 49 has a pair of po'rts ~37', 41), '(~8, 42), ~3g; ~3j, (40,';44j`;' ~; ' , : .
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WO90/12717 2 ~ ~ 3 2 2 ~ PCT/GB90/00~0 ~ - B ~
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thPrein. One port 37, 38, 39, 40 of each pair is hydraulically connected to a master cylinder 45 via a pair of fluid lines 58, 59. The master cylinder 45 is preferably a tandem master cylinder and has a hydraulic booster 45a attached thereto, the function of which will be e~plained later.
As shown in Figure 1, one pair of ports 37, 38 feeds from one fluid line 58 from the master cylinder whilst the second pair of ports 39, 40 feeds from the second fluid line 59. A balancing valve 60 may be provided in one of the fluid lines 58, 59.
The other ports 41, 42, 43, 44 are connected to a brake line 56 leading to a brake mechanism. -.
Within each chamber 46, 47, 48, 49 is a spool 51 comprising a concave~first part 52 which is located in one end of a concave second part 53, the two parts 52 and 53 being . .
secured together by a screw 55. As shown the two parts 52 and 53 are of different materials in view of the possibly differant fluids acting on the.~.two..parts. The r spool 51 is slidable within the chamber 46,.47, 48, 49....
A compression spring 54 is also~iocated in each chamber ,46,~47, 48,;.49, with one.end located against~an inside face 55 .of the second spool part 53 so.as to bias the spool 51 outwards to seal o~ the 1uid passage..50 between~the chamber 46, ~7, ~8, .49 .and .~ the,a5sociated servo valvejll, .1~, 13, 14. The length of .the;.;spool.j51 .jis such .that.;when it is biased as mentioned a~ove ~rake fluid from the master cylinder 45 is free ! ~ :
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WO 90/12717 2 ~ 5 3 2 2 ~ P~T/GB90/00640 to enter/leave the chambers 46, 47, 98, 49 via the ports 37-44.
When hydraulic pressure is applied via pressure line 33 to the end face 57 of the spool part 53 the bias of the spring 54 is overcome and the spool 51 moves to compress the spring 54 and seals off the chambers.46, 47, 48, 49 from the ports 37-40.
S~con~ary Brakinq,SYs~em A secondary braking system is also incorporated, the secondary system being isolated when the primary active system is operating and thus providing no braking effort. However, when the primary active system is turned off or fails the secondary system is selectively activated, for e~ample by a pQSitive decision from the driver who operates a manual switeh, or by automatic decision from the system in the event of a failure.
The second system utilises a secondary hydraulic actuator 65 to operate the hooster 45a which in turn operates the master cylinder 45 in a known manner to:supply pressurised .
- 1uid to fluid lines 5B, 59.
: ~The actuator 65 comprises a.piston 66 having a single head 67 within a cylinder. 68. The ;secondary-actuator.65 is .:~. hydraulically .linked to .the,feel..actuator..).~6..as ~ollows. A
:.hydraulic flu1d.linei69iis connected to the cylinder:68..on.one - ~ 8ide o the plston.h~ad 67. After the.~luid :line 6g leaves the : cylinderI68 it~:divides into two, one ~ranch.69a.connecting to ;~ ~ the hydraulic:fluid ~eturn line.,34~via ~a non-return.;valve.:29b~
and the~s~cond branch ~9b leading to a switching valve~i70.i:.The ,: ~ .~, :
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switching ~alve 70 has a fluid line 71 which splits into two branches 71a, 71b; branch 71a leads to the non-return valYe 29a and branch 71b to the cylinder l8 of the feel actuator 16.
The non-return valves 29a, 29b and the switching ~alve are connected to the pressure supply line 33 via the isolating valve 31.
The Mechanical O~errid~
In the event of a~ undetected failure in the primary actiYe braking system an override mechanism comes into automatic operation. Under normal braking conditions the hrake pedal 15 may be depressed over distance A shown in Figure 2.
When the braking pedal 15 is subjected to a "panic~ force in the event of a failure undetected by the system lO so that no braking occurs during the normal travel A of the pedal lS, the pedal 15 moves through distance B and operates the override mechanism.
. :The override mechanism comprises a sha~t 76 mounted on the piston 66 of the actuator 65 and located within a cylinder 77, e~tending between.the actuators 16 and 65. Under normal ?~ conditions-the shaft 76 does not contact-.the cylinder 77. ~.
~ ..An override:compression spring:.79..is..located between the ..e manifold~lock 75~ which:houses the ~actuator l6 and a fi~ed support 78 on which the cylinder 77 `is ~ounted on a pivotal arm 79;; see ~Figures 2..and ~3. The mani~old block 75 is mounted in the system~;lO-;to be moveable, but ~:is..held, during normal braking, stationary by the spring 74 acting between the block 75 :, : .
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WO90/12717 2 ~ 5 ~ 2 2 ~ PCT/&BgO/00640 and the support 78.
Figure 2 shows the system in the condition when the override is operating, although the pedal 15 is shown in solid line in its normal position.
Primarv Ac~ive Brakina During primary active braking brake p~dal 15 travels through distance A (see Figure 2). The .load applied by the driver to the pedal 15 is measured by load.cell ~l which sends input sig~als relating to the load to the microprocessor 25.
A reaction to the driver's demand on the brake pedal 15 is provided by the ~eel actuator 16. To do this the microprocessor 25 sends control signals to the servo valve 28 which is connected to the feel actuator 1'6 to apply pressure to either side of the piston head 17a. This is used to provide resistance to movement of the brake pedal 15 and to generally simulate the ~feel~ of braking. This ~feel" may.be altered by .programming the microprocessor 25 to provide light or heavy braking or whatever the'driver prefers.~
: . During primary active braking -the lisolating valve 31 is energlsed to connect the servo valve ~8 with.the pressure line : .33.: When the isolating valve 31 is:energised pressure is`'also ~ .. -applied ~to :the ;non-return`valves 29a, 29b~-This causes the : non~return valves 29a, 29b to open and the switching valve 70 to close which allows the feel actuator ..16.i~ta be.'driven . directly ~by the servo valve .28 via~:the :fluid.lines to either side of the:!piston head -17a.: Any residual~fluid~;pressure 'in . .
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WO90/12717 '; ~'~ PCT/GB90/00640 2~32~ - 12 - ,;
the master cylinder 45 is ve~ted via fluid line 69 through the open non-return valve 29b to the fluid return line 34.
The feel actuator 16 is capable of simulating a wide range of characteristics depending on the 'feel' re~uired.
The actual braking is carried out by fluid pressure supplied by, the four servo valves 11, 12, 13, 14. The microprocessor 25 sends independent co ~ rol signals to each of the servo valves 11, 12, 13, 14, according to input siynals from the load cell 21.
Since the isolating valve 31 is energised the servo valves 11, 12, 13, 14 are connected to the pressure supply line via the connectors 32. The fluid pressure is controlled by each servo valve 11, 12, 13, 14 to operate each brake mechanism independently. The fluid pressure transmitted from the servo valves 11, 12, 13, 14 via fluid passages 50 is ~u~ficient to ,o~ercome the preload on the springs.54 causing the spools 51 to move in the ~hambers 46, .47, 48, 49 to seal them off from the ., :ports ,37-40 from the ma~ter,cylinder 45. The fluid remaining ~ ..the chambers 46.~49 is ,forced out of,the chambers 46-49 via : the:ports ~,41-~4 by~mo,vement of the spools 51 to,the individual " , brake,~,mechanisms to operate.:the brakes ~independently.o~ each ,. other.. .~ }
The secondar~braking ,.,s~stem ma~ be activated ,.in two ways;,either by means..o~:a~manual switch .~not ,shown) operated .
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WO 90/127~7 2 ~ ~ 3 2 2 ~ PCI/GB90101)640 . : .
by the driver to de-energise the isolating valve 31, or as a result of a failure detected in the primary active braking system.
The main failures may be in the form of loss of electrical power to the system of a drop in the system pressure below a pre-set safety limit.
Various safety control loops may be incorporated in the overall braking system which are monitored ~y the microprocessor 25. An e~ample described earlier in the provision of the LVDT 24 which checks whether the feel actuator 16 is in fact operating according to the control signals sent to the servo valve 28 by the microprocessor 2S. The LVDT,'load cell 21 and other sensors in the system are preferably duple~
sensors. Their-signals are duplicated and the signals'combined to give a demand and an error~detection signal. Failures in the control loops can be detected :by' comparing the actual . . .
output' from the system~with a~ real time model of the system ' running in''parallel. Any deteeted failures ':will result in ::
: de-èner~isation of the isolating valve 31. ' ^' Loss of the electrical~'supply will automatically result ' in de-engerisation.of the isolating'valve' 31. ~he efect of '' 'loss of 'pressure has`a 'similar e~ect 'which-will' be described : later'. ' ''"' ' ~'`~' ' " ''' Wh~n the isolating valve' 31:is'~dë-energisëd it conné~ts :: to: the'~fluid return~ line '34 This ;'resu'lt's ~in a drop in pressure to'the non-return valves'29a, 29b which ciose and the :
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and switching valve 70 which opens. This hydraulically disconnects the servo valve 28 from the feel actuator 16 and hydraulically connects the feel actuator 16 to the secondary hydraulic actuator 65 via switching valve 70 which operates the booster 45a and master cylinder 45.
Thus pressure applied to the pedal 15 will be transmittPd by movement of the p'ston 17 with piston head 17a forcing the fluid out of cylinder 18, via the switching valve 70, into the cylinder 68 of the secondary actuator 68 to act on the piston head 66 of the secondary actuator 68. Thus, braking in this mode feels and performs similar to a standard unmodified hydraulic braking system.
Referring to the distribu~ion valve 35, in secondary ~raking the servo valves 11-14 are connected to the fluid return line 34 and the pressure applied to the spools 51 drops. The force of springs 54 is sufficient to overcome any residual pressure and force the spools 51 outwards towards the servo valves 11-14 to seal off fluid passages 50 from the ..
: chambers 46-49 and the ports 37-40 which communicate with the : . master cylinder 45 are uncovered.
Thus, as the ~oot pedal..l5.is depressed brake ~luid is .,forced along the fluid lines 58, 59 from the~master cylinder 45, into chambers 4fi-49 and out of ports 41-44 to the brake . mechanismi.vla theJbrake ~lines,56. ~ :
Since ports 37, 40 are connected ~to the,fluid li~e 58 and ports 38, 39 are connected to line 59 equal pressures are :
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WO90/lZ717 2 ~ ~ 3 2 ~ ~ PCT/GB90/00640 : - 15 ~
transferred across each a~le pair of brakes.
~ oss of sys~em pressure below a certain limit will also allow the springs 54 to recover and return to their original state and thus has the same ef~ect as if the isolating valve 31 had been de-energised.
Overrid~ Brakinq In the event of an undetected ~ailure in the feel system the override mechanism comes into operation. If no braking occurs when the driver depresses pedal 15 through distance A, he will use a panic ~orce and the pedal will move through distance B. The length of the feel actuator cylinder 18 is such that when the brake pedal 15 has reached the end of travel distance A, the piston head 17a reaches the end of the cylinder 18. Further movement of the pedal 15, i.e. through travel distance B on applicaton of a panic force, will cause the piston head 17a to bear on the end face 80 of the cylinder 18, which lS attached to the manifold block 75 and thus causes the manifold block 75~to move aqainst and overcome the pre-load of spring 74 so that the whole manifold block 7S moves (to the position shown as Figure 2~. As the manifold block 75 moves toward the support 78 cylinder 77 moves into contact with shaft 76. Further movement of the block 75 cau~ed ~he shaft 76 to move the piston 66, which activates the brake booster 45a and ~aster cylinder 45 to operate the brakes.
The system is;thus very versatile, self-monitoring, fail-safe and may per~orm to a variety o~ control laws, such as anti-WO90/12717 - i`: PCT/GB90100640 2 ~ ~ 3 - 16 ~
lock braking, variable balance, deceleration demand and brake performance feed back to pedal.
Although the system described above operates primarily in dependence upon the load applied to the brake pedal, with appropriate modifications to the system it may be made responsive to the position or movement of the brake pedal or any other param~ter measurable in the system.
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The invention relates to vehicle braking systems. ', Almost all moder~ vehicles, particularly motor cars, ~' have hydraulically operated fioot brakes operating on all wheels. The systems generally comprise either d mm or disc brakes with a brake pedal connected to a piston in a master cylinder whence the hydraulic operating pressure originates.
Depression of the brake pedal forces the hydraulic brake fluid along a network of pipes and hoses to wheel cylinders which urge brake calipers or shoes into contact with a brake disc or drum to provide the ~raking action.
Hydraulic systems' have many advantages, such as heing self-lubricating (reducing the chance of seizure), having a low `rate of wear and low fri'~tion,"'and enabling et~ual pressures to be eserted on all '~the~ br~ake''~shoes` or 'calipers, even compensating ~' for '~unequal: wear~'or adjustment. 'Further, installation ~-is generally''' eaæier-than ~or mechanical s~stems because of the~fle~ibility of'the~hoseæ ~`'':' ''` ' - -:~ .
'The" principal~disa~vantage`'~of''hydraulic brakingisystems ;is ;~:that ~a~:leakage~'`in''':the'lsystem'i or''-!''contamination of the hydraulic fluld used can r0nder the hrakes ine~fective or in-opera~ive. '~
~, ; : , '~ : ~ :
'''One':solution to ~'th'is proble'm is~prov~ide'd''by having a tandem master-tcylinder, and: splitting'~'he'system"into"two`parts 2~ 2 -so that if one part fails the other part can still function.
Obviously, in the event of failure of one part braking efficiency is reduced, and there are situations when this can be dangerous.
Sometimes it would be preferable to control the separate brakes individually for e~amyle if one tyre has been worn more than its a~ial counterpart. In standard systems both a~ial brakes would be operated identically. It would also be useful in braking systems to be able to control the f~.el at the braking, as some drivers prefer sharp braking and others prefer to have to move the brake pedal some distance before ma~imum braking is achieved.
Advances in braking technology have been restricted '.
because of the problems in distribution of the fluid in the brake mechanisms.
7'',, '~ Accord,ing to the invention there is provided a vehicle ..., braking system comprising a braking element operable by a : .driver of-~ the vehicle; control signal generating . means responsive to.operat1on of the,.braking.element; means braking at least one wheel of,,the: vehicle in re~ponse to control ,...... ...... ... ........ -,sign,als,generated.by,the control.signal generating maans; and ,reaction means ,responsive~,.to,,ithe.control~signals.to, provide a force .on the braking ,element to~provide a variable, artifical s feel to the driver through the braking element.
~3,; ~re~erably ~the control, signals are ,proportional to a ; forcejapplied to the.braking element by the driver.
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W~90/12717 2 ~ ~ 3 2 2 ~ PCT/~90/006~0 ' ` ' :. . ~
In a preferred embodiment the system comprises means for sensing the force appiied to the braking element and providing input signals proportional thereto to the control signal generating means, the sensing means preferably comprising an electrical load cell.
Preferably the system comprises means for sensing the position and~or movement of the braking element and providing input signals to the control -signal generating means proportionaI thereto, said sensing means preferably comprising one or more linear vari'able displacement transducers.
Preferably the reaction means comprises a hydraulic actuator coupled to the braking element, the actuator preferably being a double acting hydraulic actuator having a pair of opposed piston faces.
The actuator is preferably controlled by a servo-valve responsive to the control signals to control the application of hydraulic fluid pressure to the opposed piston faces to operate the actuator. ' '' ' "' '~
' ''' The braking element can be a brake pedal.
Another preferred 'embodiment includes error detection means operative to check whether 1the;artiical ~eel is being provided to the braking element and to provide input'signals to ~'the contr~l signal generatin~msans in'dependence thereon. On ~'detection -or~an error`~by''~the~error dete'ction means outside a ;I' pre-set ~limit~`l t'he -control signal~generating- means-,preferably 'gen'erates con~rol signals to operate a sa~e~y system.
., , , . . , . , ~ . . :: . . ,., : :................. -:, ., :.: .
::.. ... .- .. ~ . . . :. . . , . ~ . .... .. :. . .. . .... . : . . .
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WOgo/12717 '~ PCTtGB90/00640 3~
The control signal generating means is preferably acomputer which can be programmable to generate control signals dependent on requirements of the driver or the condition of the vehicle .
A vehicle braking system according to the invention will now be described by way of e~ample with reference to the drawings, in which:- , Figure l is a schsmatic representation of the layout of the system;
Figure 2 is a part sectional front elevation of a brake reelN actuator assembly ~which is a part of the system of Figure l;
Figure 3 is a sectional view of Figure 2 on III-III;
Figure 4 is a part sectional front elevation of a distribution valve which is a part of the system of Fi~ure 1;
and . . .
:~ ,- -.. Figure -S~,is a:-front elevation of the distribution valve : of Figure 3 with parts omitted for clarity.
;~ Referring first .to Figure l there is shown a braking ~ system lO~.,for~use -,iin a:-motor vehicle .such as a ~motor car, !,: having ~ steerable.wheels.(not~shown). ~ ", :,. :.:,,'..The .~otor,,vehicle,~has ,~our wheels each itted ; with .,.~ standard hydraulically operated diæc or drum brakes., Althou~h ~.
. the .brakes., hemQel~es are not~,~shown "in the ,drawings,~,.the : ~ operable ~calipers,;or~,shoes..or each.~,wheel (hereinafter brake ~, mechanism).are attached to a,respective servo,valve ll,, 12, l~, ,... . . . . .. . . . . . . .
,:
f : ~ 5 - ,~
14, which independently controls the pressure to the brake mechanism at the associated wheel.
The system 10 combines a primary active brake system and a secondary brake override system that provides the braking effort in the event of a system failure or when the active system is turned off.
The Prima,ry,Active Bra~ina System The active system is a fully active "feel" system including a braking element in the form of a brake pedal 15 which is physically decoupled frorn the braking mechanisms. The brake pedal 15 is mounted to the vehicle body to be pivotal about its polnt of attachment. Attached to the brake pedal 15 is a "feel" actuator 16.
Referring now to Figure 2 also, the feel actuator 16 is a double acting,;,hydraulic actuator comprising a moveable piston 17 ha~ing a pair of opposed ,piston faces and contained.in a , cylinder 18.: Mounted on the piston :17 is a piston head 17a which provides-the piston faces. One end of the piston ~17 is - coupled, to~ the brake pedal 15 by means of a linkage element 20 " ,which ~includes 'a-~load cell~.21 (or other ,sui~able;~device) ~which .~is pre~erably~,a duple~,.,sensor,~,for sensing,,the force,applied by a driver,o~,the,,vehicle,,to:the ,-brake :pedal 15. The,load cell 21 is,electrically connected~to a control ,unit 25, such as a mir,~opracessor,;and.sends, input signals_thereto-,relating-to the force.applîsd to the brake,pedal' 15.. -~`m~ a."~
:~ , Also attached to, the.linkage~lement~20 is a rod.22 ,: :
.
woso~l27~ PCT/GB90/00640 6 ,.
2~22~
which enters a hol~er 23 of a linear variable differential transformer (LVDT) 24. The LVDT holder 23 is fi~ed adjacent to the cylinder 18 on a manifold block 75 housing the feel actuator 16. The LVDT 24 converts the mechanical displacement of the linkage element 20 (and therefore the displacement of the brake pedal 15) into an electrical signal which is transmitted to the microprocessor 25 to which the LVDT 24 is Plectrically connected. Other suitable devises may of course be used for converting the displacement into an electrical signal.
; The feel actuator 16 is hydraulically connected to servo valve 28. Hydraulic transfer tu~es 9 are provided in the manifold block 75 linking the hydraulic fluid lines ~rom the servo valve ~ to each end of cylinder 18 so that the servo valve 28 may be used to control the movement of the piStOTI 17 by hydraulic pressure to either side o~ the piston head 17a.
; As will be seen in Figure l a~non-return valYe ~9a is . 'included in the hydraulic fluid line between the servo valve 2a and feel actuator~. 16, for reasons described below. The -non-return valve~ 29a:is also connected'ito the pressure supply l~ ~ line~33 via an isolating valve 31"~describ~d below.' The non-... . returnlvalve!29a opens on'application of pressurè thereto.`
` The servo valve 28 is colnected to' h~draulic fluid.. suppl~ ,pressure and~:~return lines 33,:34 via an isolating valve ~: 31 which is pre~erably ^a solenoid val~e. When' the solenoid valve:31 is energised the pressure supply line 33 is connected , : , , ~ ~ ' , :
WO90/~2717 PCT/GB9~/00640 - 72~3224 to the servo valve 28 and when it is de-energised the return line 34 is connected to the servo valve 28. A prPssure reducing valve 30 is incorporated in the pressure supply line 33 leading to the isolating val~e 31 so that the servo valve 28 uses a pressure lower than the system pressure.
An anti-cavitation valve 27 is also included.
The microprocessor 25 is connected to control the brake servo valves 11, 12, 13, 14 ana signals g2nerated by the micro-processor 25 control the pressure applied to the four brake '' mechanisms independently. The servo valves 11, 12, 13, 14 are connected to brake lines 56 which are connected to the brake mechanisms of the front left, rear left, rear right and front brakes respectively, via a distribution valve 35, as shown in Figures 4 and 5. - -The servo valves 11, 12, 13, 14 are connected to the hydraulic pressure and retur~ lines 33, 34 via connectors 32.
One connector 32`connects a branch-o the pressure and return lines to one pair of servo~ valves- 11, 14 and the other ' connector 32 to the seco~d pair of servo valYes 1~, 13. ` ' The distribution'~'val've 35~'comprises a' valvè manifold 36 ha~ing ~our separate "chambers` 46; 47, 48, 49 'therein. ' Each chambe'r 46,;' 47,'48, 49"is connecte~ via a fluid pàssage 50 to a respective s~rvo'~-valvè 11,"12, 13,'` 14;~;;The manifold 36 has eight ports 37-44'therein such that~each chamber 46, 4i,'148, 49 has a pair of po'rts ~37', 41), '(~8, 42), ~3g; ~3j, (40,';44j`;' ~; ' , : .
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WO90/12717 2 ~ ~ 3 2 2 ~ PCT/GB90/00~0 ~ - B ~
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thPrein. One port 37, 38, 39, 40 of each pair is hydraulically connected to a master cylinder 45 via a pair of fluid lines 58, 59. The master cylinder 45 is preferably a tandem master cylinder and has a hydraulic booster 45a attached thereto, the function of which will be e~plained later.
As shown in Figure 1, one pair of ports 37, 38 feeds from one fluid line 58 from the master cylinder whilst the second pair of ports 39, 40 feeds from the second fluid line 59. A balancing valve 60 may be provided in one of the fluid lines 58, 59.
The other ports 41, 42, 43, 44 are connected to a brake line 56 leading to a brake mechanism. -.
Within each chamber 46, 47, 48, 49 is a spool 51 comprising a concave~first part 52 which is located in one end of a concave second part 53, the two parts 52 and 53 being . .
secured together by a screw 55. As shown the two parts 52 and 53 are of different materials in view of the possibly differant fluids acting on the.~.two..parts. The r spool 51 is slidable within the chamber 46,.47, 48, 49....
A compression spring 54 is also~iocated in each chamber ,46,~47, 48,;.49, with one.end located against~an inside face 55 .of the second spool part 53 so.as to bias the spool 51 outwards to seal o~ the 1uid passage..50 between~the chamber 46, ~7, ~8, .49 .and .~ the,a5sociated servo valvejll, .1~, 13, 14. The length of .the;.;spool.j51 .jis such .that.;when it is biased as mentioned a~ove ~rake fluid from the master cylinder 45 is free ! ~ :
. .
WO 90/12717 2 ~ 5 3 2 2 ~ P~T/GB90/00640 to enter/leave the chambers 46, 47, 98, 49 via the ports 37-44.
When hydraulic pressure is applied via pressure line 33 to the end face 57 of the spool part 53 the bias of the spring 54 is overcome and the spool 51 moves to compress the spring 54 and seals off the chambers.46, 47, 48, 49 from the ports 37-40.
S~con~ary Brakinq,SYs~em A secondary braking system is also incorporated, the secondary system being isolated when the primary active system is operating and thus providing no braking effort. However, when the primary active system is turned off or fails the secondary system is selectively activated, for e~ample by a pQSitive decision from the driver who operates a manual switeh, or by automatic decision from the system in the event of a failure.
The second system utilises a secondary hydraulic actuator 65 to operate the hooster 45a which in turn operates the master cylinder 45 in a known manner to:supply pressurised .
- 1uid to fluid lines 5B, 59.
: ~The actuator 65 comprises a.piston 66 having a single head 67 within a cylinder. 68. The ;secondary-actuator.65 is .:~. hydraulically .linked to .the,feel..actuator..).~6..as ~ollows. A
:.hydraulic flu1d.linei69iis connected to the cylinder:68..on.one - ~ 8ide o the plston.h~ad 67. After the.~luid :line 6g leaves the : cylinderI68 it~:divides into two, one ~ranch.69a.connecting to ;~ ~ the hydraulic:fluid ~eturn line.,34~via ~a non-return.;valve.:29b~
and the~s~cond branch ~9b leading to a switching valve~i70.i:.The ,: ~ .~, :
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WO90/12717 . . PCT/GB90/00640 -- 10 -- (' ' -':
~322~
switching ~alve 70 has a fluid line 71 which splits into two branches 71a, 71b; branch 71a leads to the non-return valYe 29a and branch 71b to the cylinder l8 of the feel actuator 16.
The non-return valves 29a, 29b and the switching ~alve are connected to the pressure supply line 33 via the isolating valve 31.
The Mechanical O~errid~
In the event of a~ undetected failure in the primary actiYe braking system an override mechanism comes into automatic operation. Under normal braking conditions the hrake pedal 15 may be depressed over distance A shown in Figure 2.
When the braking pedal 15 is subjected to a "panic~ force in the event of a failure undetected by the system lO so that no braking occurs during the normal travel A of the pedal lS, the pedal 15 moves through distance B and operates the override mechanism.
. :The override mechanism comprises a sha~t 76 mounted on the piston 66 of the actuator 65 and located within a cylinder 77, e~tending between.the actuators 16 and 65. Under normal ?~ conditions-the shaft 76 does not contact-.the cylinder 77. ~.
~ ..An override:compression spring:.79..is..located between the ..e manifold~lock 75~ which:houses the ~actuator l6 and a fi~ed support 78 on which the cylinder 77 `is ~ounted on a pivotal arm 79;; see ~Figures 2..and ~3. The mani~old block 75 is mounted in the system~;lO-;to be moveable, but ~:is..held, during normal braking, stationary by the spring 74 acting between the block 75 :, : .
~ ' ~
.
WO90/12717 2 ~ 5 ~ 2 2 ~ PCT/&BgO/00640 and the support 78.
Figure 2 shows the system in the condition when the override is operating, although the pedal 15 is shown in solid line in its normal position.
Primarv Ac~ive Brakina During primary active braking brake p~dal 15 travels through distance A (see Figure 2). The .load applied by the driver to the pedal 15 is measured by load.cell ~l which sends input sig~als relating to the load to the microprocessor 25.
A reaction to the driver's demand on the brake pedal 15 is provided by the ~eel actuator 16. To do this the microprocessor 25 sends control signals to the servo valve 28 which is connected to the feel actuator 1'6 to apply pressure to either side of the piston head 17a. This is used to provide resistance to movement of the brake pedal 15 and to generally simulate the ~feel~ of braking. This ~feel" may.be altered by .programming the microprocessor 25 to provide light or heavy braking or whatever the'driver prefers.~
: . During primary active braking -the lisolating valve 31 is energlsed to connect the servo valve ~8 with.the pressure line : .33.: When the isolating valve 31 is:energised pressure is`'also ~ .. -applied ~to :the ;non-return`valves 29a, 29b~-This causes the : non~return valves 29a, 29b to open and the switching valve 70 to close which allows the feel actuator ..16.i~ta be.'driven . directly ~by the servo valve .28 via~:the :fluid.lines to either side of the:!piston head -17a.: Any residual~fluid~;pressure 'in . .
,.: :.,~ .,, . . . . : . .. ,~: .. , ~ . : .
WO90/12717 '; ~'~ PCT/GB90/00640 2~32~ - 12 - ,;
the master cylinder 45 is ve~ted via fluid line 69 through the open non-return valve 29b to the fluid return line 34.
The feel actuator 16 is capable of simulating a wide range of characteristics depending on the 'feel' re~uired.
The actual braking is carried out by fluid pressure supplied by, the four servo valves 11, 12, 13, 14. The microprocessor 25 sends independent co ~ rol signals to each of the servo valves 11, 12, 13, 14, according to input siynals from the load cell 21.
Since the isolating valve 31 is energised the servo valves 11, 12, 13, 14 are connected to the pressure supply line via the connectors 32. The fluid pressure is controlled by each servo valve 11, 12, 13, 14 to operate each brake mechanism independently. The fluid pressure transmitted from the servo valves 11, 12, 13, 14 via fluid passages 50 is ~u~ficient to ,o~ercome the preload on the springs.54 causing the spools 51 to move in the ~hambers 46, .47, 48, 49 to seal them off from the ., :ports ,37-40 from the ma~ter,cylinder 45. The fluid remaining ~ ..the chambers 46.~49 is ,forced out of,the chambers 46-49 via : the:ports ~,41-~4 by~mo,vement of the spools 51 to,the individual " , brake,~,mechanisms to operate.:the brakes ~independently.o~ each ,. other.. .~ }
The secondar~braking ,.,s~stem ma~ be activated ,.in two ways;,either by means..o~:a~manual switch .~not ,shown) operated .
:
WO 90/127~7 2 ~ ~ 3 2 2 ~ PCI/GB90101)640 . : .
by the driver to de-energise the isolating valve 31, or as a result of a failure detected in the primary active braking system.
The main failures may be in the form of loss of electrical power to the system of a drop in the system pressure below a pre-set safety limit.
Various safety control loops may be incorporated in the overall braking system which are monitored ~y the microprocessor 25. An e~ample described earlier in the provision of the LVDT 24 which checks whether the feel actuator 16 is in fact operating according to the control signals sent to the servo valve 28 by the microprocessor 2S. The LVDT,'load cell 21 and other sensors in the system are preferably duple~
sensors. Their-signals are duplicated and the signals'combined to give a demand and an error~detection signal. Failures in the control loops can be detected :by' comparing the actual . . .
output' from the system~with a~ real time model of the system ' running in''parallel. Any deteeted failures ':will result in ::
: de-èner~isation of the isolating valve 31. ' ^' Loss of the electrical~'supply will automatically result ' in de-engerisation.of the isolating'valve' 31. ~he efect of '' 'loss of 'pressure has`a 'similar e~ect 'which-will' be described : later'. ' ''"' ' ~'`~' ' " ''' Wh~n the isolating valve' 31:is'~dë-energisëd it conné~ts :: to: the'~fluid return~ line '34 This ;'resu'lt's ~in a drop in pressure to'the non-return valves'29a, 29b which ciose and the :
.
~:
;~::;:
WO90/12717 pcT/GBso/oo~o - 14 - ! ;
2~3~
and switching valve 70 which opens. This hydraulically disconnects the servo valve 28 from the feel actuator 16 and hydraulically connects the feel actuator 16 to the secondary hydraulic actuator 65 via switching valve 70 which operates the booster 45a and master cylinder 45.
Thus pressure applied to the pedal 15 will be transmittPd by movement of the p'ston 17 with piston head 17a forcing the fluid out of cylinder 18, via the switching valve 70, into the cylinder 68 of the secondary actuator 68 to act on the piston head 66 of the secondary actuator 68. Thus, braking in this mode feels and performs similar to a standard unmodified hydraulic braking system.
Referring to the distribu~ion valve 35, in secondary ~raking the servo valves 11-14 are connected to the fluid return line 34 and the pressure applied to the spools 51 drops. The force of springs 54 is sufficient to overcome any residual pressure and force the spools 51 outwards towards the servo valves 11-14 to seal off fluid passages 50 from the ..
: chambers 46-49 and the ports 37-40 which communicate with the : . master cylinder 45 are uncovered.
Thus, as the ~oot pedal..l5.is depressed brake ~luid is .,forced along the fluid lines 58, 59 from the~master cylinder 45, into chambers 4fi-49 and out of ports 41-44 to the brake . mechanismi.vla theJbrake ~lines,56. ~ :
Since ports 37, 40 are connected ~to the,fluid li~e 58 and ports 38, 39 are connected to line 59 equal pressures are :
; .
:~ .
~: : : :
.. ... .. . . , ..... .,....... . , .. ...... .. . : ~ . ...
. . . .. : . ; . . ~ . . . : : ..
WO90/lZ717 2 ~ ~ 3 2 ~ ~ PCT/GB90/00640 : - 15 ~
transferred across each a~le pair of brakes.
~ oss of sys~em pressure below a certain limit will also allow the springs 54 to recover and return to their original state and thus has the same ef~ect as if the isolating valve 31 had been de-energised.
Overrid~ Brakinq In the event of an undetected ~ailure in the feel system the override mechanism comes into operation. If no braking occurs when the driver depresses pedal 15 through distance A, he will use a panic ~orce and the pedal will move through distance B. The length of the feel actuator cylinder 18 is such that when the brake pedal 15 has reached the end of travel distance A, the piston head 17a reaches the end of the cylinder 18. Further movement of the pedal 15, i.e. through travel distance B on applicaton of a panic force, will cause the piston head 17a to bear on the end face 80 of the cylinder 18, which lS attached to the manifold block 75 and thus causes the manifold block 75~to move aqainst and overcome the pre-load of spring 74 so that the whole manifold block 7S moves (to the position shown as Figure 2~. As the manifold block 75 moves toward the support 78 cylinder 77 moves into contact with shaft 76. Further movement of the block 75 cau~ed ~he shaft 76 to move the piston 66, which activates the brake booster 45a and ~aster cylinder 45 to operate the brakes.
The system is;thus very versatile, self-monitoring, fail-safe and may per~orm to a variety o~ control laws, such as anti-WO90/12717 - i`: PCT/GB90100640 2 ~ ~ 3 - 16 ~
lock braking, variable balance, deceleration demand and brake performance feed back to pedal.
Although the system described above operates primarily in dependence upon the load applied to the brake pedal, with appropriate modifications to the system it may be made responsive to the position or movement of the brake pedal or any other param~ter measurable in the system.
'' ' ' '" ' , :
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.
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' ;
'
Claims (16)
1. A vehicle braking system comprising a braking element operable by a driver of the vehicle; control signal generating means responsive to operation of the braking element; means braking at least one wheel of the vehicle in response to control signals generated by the control signal generating means; and reaction means responsive to the control signals to provide a force on the braking element to provide a variable artifical feel to the driver through the braking element.
2. A braking system as claimed in Claim 1, in which the control signals are proportional to a force applied to the braking element by the driver.
3. A braking system as claimed in Claim 2, comprising means for sensing the force applied to the braking element and providing input signals proportional thereto to the control signal generating means.
4. A braking system as claimed in claim 3, in which said sensing means comprises an electrical load cell.
5. A braking system as claimed in any preceding claim, comprising means for sensing the position and/or movement of the braking element and providing input signals to the control signal generating means proportional thereto.
6. A braking system as claimed in Claim 5, in which the position and/or movement sensing means comprises one or more linear variable displacement transducers.
7. A braking system as claimed in any preceding claim, in which the reaction means comprises a hydraulic actuator coupled to the braking element.
8. A braking system as claimed in Claim 7, in which the actuator is a double acting hydraulic actuator having a pair of opposed piston faces.
9. A braking system as claimed in Claim 8, in which the actuator is controlled by a servo valve responsive to the control signals to control the application of hydraulic fluid pressure to the opposed piston faces to operate the actuator.
10. A braking system as claimed in any preceding claim, in which the braking element is a brake pedal.
11. A braking system as claimed in any preceding claim, including error detection means operative to check whether the artificial feel is being provided to the braking element and to provide input signals to the control signal generating means in dependence thereon.
12. A braking system as claimed in Claim 11, in which on detection of an error by the error detection means outside a pre-set limit, the control signal generating means generates control signals to operate a safety system.
13. A braking system as claimed in any preceding claim, in which the control signal generating means is a computer.
14. A system as claimed in Claim 13, in which the computer is programmable to generate control signals dependent on requirements of the driver and/or the condition of the vehicle.
15. A vehicle braking system substantially as hereinbefore described with reference to the drawings.
16. A vehicle having a braking system as claimed in any one of Claims 1 to 15.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8909472.6 | 1989-04-26 | ||
| GB898909472A GB8909472D0 (en) | 1989-04-26 | 1989-04-26 | Vehicle braking system |
| GB898910275A GB8910275D0 (en) | 1989-05-04 | 1989-05-04 | Vehicle braking system |
| GB8910275.0 | 1989-05-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2053224A1 true CA2053224A1 (en) | 1990-10-27 |
Family
ID=26295272
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2053223 Abandoned CA2053223A1 (en) | 1989-04-26 | 1990-04-26 | Vehicle braking systems |
| CA 2053224 Abandoned CA2053224A1 (en) | 1989-04-26 | 1990-04-26 | Vehicle braking systems |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2053223 Abandoned CA2053223A1 (en) | 1989-04-26 | 1990-04-26 | Vehicle braking systems |
Country Status (4)
| Country | Link |
|---|---|
| EP (2) | EP0469052A1 (en) |
| JP (2) | JPH04504698A (en) |
| CA (2) | CA2053223A1 (en) |
| WO (2) | WO1990012717A1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2762160B2 (en) * | 1990-08-10 | 1998-06-04 | 本田技研工業株式会社 | Hydraulic braking control system for vehicles |
| JP2762161B2 (en) * | 1990-08-10 | 1998-06-04 | 本田技研工業株式会社 | Hydraulic braking control system for vehicles |
| GB9420957D0 (en) * | 1994-10-18 | 1994-12-07 | Lucas Ind Plc | Improvements in pedal assemblies for vehicle braking systems |
| DE29921027U1 (en) † | 1999-11-30 | 2001-06-28 | Kober Ag | Simulator for a non-hydraulic actuation system |
| JP2013174767A (en) | 2012-02-27 | 2013-09-05 | Sony Corp | Lens barrel and imaging apparatus |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2932620A1 (en) * | 1979-08-11 | 1981-02-26 | Bosch Gmbh Robert | HYDRAULIC FORCE BRAKE SYSTEM FOR A TRAIN VEHICLE WITH TRAILER |
| DE3027747A1 (en) * | 1980-07-22 | 1982-02-18 | Alfred Teves Gmbh, 6000 Frankfurt | CONTROL SYSTEM FOR A VEHICLE BRAKE SYSTEM WITH FLOW AND FRICTION BRAKE |
| DE3342552A1 (en) * | 1983-11-25 | 1985-06-05 | Volkswagenwerk Ag, 3180 Wolfsburg | Hydraulic brake system for motor vehicles provided with a servo device |
| DE3410006A1 (en) * | 1984-03-19 | 1985-09-19 | Alfred Teves Gmbh, 6000 Frankfurt | METHOD FOR CONTROLLING A BRAKE SYSTEM FOR MOTOR VEHICLES, AND DEVICE FOR IMPLEMENTING THE METHOD |
| DE3626751A1 (en) * | 1986-03-22 | 1987-09-24 | Bosch Gmbh Robert | Electro-hydraulic brake system |
-
1990
- 1990-04-26 CA CA 2053223 patent/CA2053223A1/en not_active Abandoned
- 1990-04-26 JP JP50666190A patent/JPH04504698A/en active Pending
- 1990-04-26 WO PCT/GB1990/000640 patent/WO1990012717A1/en not_active Application Discontinuation
- 1990-04-26 CA CA 2053224 patent/CA2053224A1/en not_active Abandoned
- 1990-04-26 JP JP50666090A patent/JPH04504697A/en active Pending
- 1990-04-26 EP EP19900907210 patent/EP0469052A1/en not_active Withdrawn
- 1990-04-26 WO PCT/GB1990/000641 patent/WO1990012718A1/en not_active Application Discontinuation
- 1990-04-26 EP EP19900907240 patent/EP0469056A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| CA2053223A1 (en) | 1990-10-27 |
| JPH04504698A (en) | 1992-08-20 |
| EP0469056A1 (en) | 1992-02-05 |
| JPH04504697A (en) | 1992-08-20 |
| WO1990012718A1 (en) | 1990-11-01 |
| EP0469052A1 (en) | 1992-02-05 |
| WO1990012717A1 (en) | 1990-11-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |