CA1285590C - Simplified anti-lock braking system - Google Patents
Simplified anti-lock braking systemInfo
- Publication number
- CA1285590C CA1285590C CA000549780A CA549780A CA1285590C CA 1285590 C CA1285590 C CA 1285590C CA 000549780 A CA000549780 A CA 000549780A CA 549780 A CA549780 A CA 549780A CA 1285590 C CA1285590 C CA 1285590C
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- Prior art keywords
- master cylinder
- pressure
- port
- fluid
- valve
- Prior art date
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Abstract
ABSTRACT OF THE DISCLOSURE
An anti-lock braking system which incorporates a pressure modulator disposed between a master cylinder and one or more wheel cylinders of the vehicle. The pressure modulator includes an electrically operated pump for pum-ping fluid from the rear cylinders back to the master cyl-inder and a pressure responsive isolating valve for iso-lating the wheel cylinders from the master cylinder in response to operation of the pump. The system is parti-cularly well suited for application to the rear wheels of the vehicle.
An anti-lock braking system which incorporates a pressure modulator disposed between a master cylinder and one or more wheel cylinders of the vehicle. The pressure modulator includes an electrically operated pump for pum-ping fluid from the rear cylinders back to the master cyl-inder and a pressure responsive isolating valve for iso-lating the wheel cylinders from the master cylinder in response to operation of the pump. The system is parti-cularly well suited for application to the rear wheels of the vehicle.
Description
s~o sIMpLIFIF~n ~NTI-LOCK ~RAKING SY~r~'E'M
_C _ OUWD ~ T~IE INVENI'ION
The present invention relates to antt-lock hrak-ing systems and in partlcular to an anti-lock brakinq system which incorporates an integrated modulatiny valve and brake pressure reducing pump, actuated by an elec-tronic control system responsive to rotational behaviorof a vehicle's wheels, the system being particularly applicable to anti-lock control of the rear wheels of a vehicle.
Anti-lock braking systems are well known.
Typically, prior art anti-lock brak~ng ~ys,tems have _~o~ r , ~;~ G6:1' evolved from mechanical to s~s~i~l~e~ electronically-controlled devices which sense the rotational behavior of a vehicle's wheels during braking and assume control of braking of the vehicle upon sensing an ~ r-~e~ skid con-dition to automatically modulate the application of brak-ing pressure to avoid wheel-lock. Typically, these sys-tems incorporate a power boosted master cylinder or a full power hydraulic system to produce the required pres-surized braking fluid. The systems are normally divided into a plurality of hydraulic circuits with braking of the front wheels of the vehicle heing individually con-trolled and the rear wheels of the vehicle being con-trolled either individually or as a pair. Such systems can be highly effective. Such systems are, however, complex and expensive, a factor which reduces their availability and widespread implementation.
There exist numerous applications for anti-lock braking systems in which substantial~improvements in the braking performance of the vehicle can be enhanced with-out the requirement of controlling three or more wheelsof the vehicle. Such applications typically include pick-up trucks and vans. In these applications, due to the substantial variation in loading of the rear wheels of the vehicle, it is possible to have a vehicle that is lightly loaded be very subject to locking of the rear 3~
~2~i5~V
wheels. Various brake pressllre proportlonlng dev1ce~
have been proposed to alleviate this prohlem hut sllch devices have been less than fuliy efectlve, due to sub-stantial variations in friction materials and other variable parameters of the braking system.
There therefore exists a need for a simple, low cost anti-lock braking system which is adaptable for ap-plications such as pick-up trucks and vans which can sub-stantially reduce the potential of rear wheel lock with a minimum of cost and complexity.
There also exists a need for such a system which can be used with braking systems incorporating vac~um boosted modulators, and any of various hydraulically boosted systems.
Broadly, the present invention is an anti-lock braking system which comprises a master cylinder means for generating pressurized braking fluid in a hydraualic circuit which includes at least one wheel cylinder. Means are provided for sensing the rotational behavior of a ve-hicle wheel and generating a signal corresponding thereto.
A control circuit is connected to the sensor means for receiving these signals and generating control signals in response to an incipient wheel-lock condition. A hrake pressure modulator is operatively connected to the hy-draulic circuit between the master cylinder and the wheelcylinder. The pressure modulator includes a pump for pumping fluid from the wheel cylinder to the master cyl-inder, and a pressure reducing means connected between the pump means and the master cylinder for producing a pressure drop thereacross in response to the flow of fluid therethrough. An isolating valve is provided, the valve having an inlet port, wheel cylinder outlet port, a pump outlet port, and a control port. The ports are connected to the master cylinder, wheel cylinder, the inlet of the pump means, and the input of the pressure reducing means, respectively. The isolating valve normally establishes fluid communication between the inlet, wheel cyllnder, and pump inlet ports and lnclude~
an element oper~ble in response to a pressure drop across the pressure reducing means to isolate the inlet port from the wheel cylinder and pump inlet ports. The pump means is responsive to the signa:Ls from the control means to pump fluid from the wheel cylinder to the master cylinder to thereby reduce the pressure of hLaking fluid therein.
It is therefore an object of the invention to provide an improved anti-lock braking system.
Another object of the invention is to provide an anti-lock braking system of reduced cost and compiexity.
Still another object of the invention is to pro-duce an anti-lock braking system particularly well suited for use in preventing lock of the rear wheels of a vehicle.
Another object of the invention is to provide an anti-lock braking system which includes a self-contained electrically operated pump and an isolating valve operable in response to signals from a control circuit and fluid flow from the pumpj-respectively, to pump fluid from a wheel cylinder and reduce the pressure therein.
These and other objects and purposes of the invention and the invention itself will he best under-stood in view of the following detailed descriptionthereof taken in conjunction with the appended drawings wherein:
Figure 1 shows an anti-lock braking system in accordance with the present invention, portions thereof being shown in schematic format; and Figure 2 is a fragmentary drawing of an alterna-tive pump for use in the invention.
DESCRIPTION OF PREFERRED EMBODIMENT
Referring now to the drawing there is shown an anti-lock braking system which comprises generally a master cylinder 12, typically a dual cylinder displace-ment type of master cylinder including a reservoir 14 and actuated by a Eoot pedaL 16. ~laster cylln(ler 12 h~lg two ou~ptll: cLr-cuits, I, [I. As illustratecl, hy~lrauLlc cLrcuLt I Ls cotlnec~e(l ~o a palr oE Eront wllee1 brake cyllnders l8, 20 nnd llyclrn~lLIe cLrcllLt II is connected throllgll n pUIllp ancl moduLator assemhly 22 to a pnir oE rear wheel cylinders 24, 26. ~laster cyLLnder 12 may be man~laL
or power boosted by means of sueh as a vacuum booster or a hydrallllc booster (not shown). Ilydraulic circuits I, II are fully hydraulically isolated, such systems and components being now well known in the art.
Pump modulator assembly 22 includes a body 28 of irregular configuration. Body 28 is provided with a generally cylindrical, stepped diameter valve chamber 30 having a closed end 32 and provided at its opposite end or master cylinder inlet 34 with a tapered valve seat 36.
An inlet passage or master cylinder port 38 communicates axially with valve chamber 30 via the valve seat 36 and is connected at its opposite end 40 to the hydraulic circuit II of master cylinder 12.
A wheel cylinder outlet passage or wheel cylinder port 42 and a pump inlet passage 44 communicate with chamber 30 adjacent valve seat 36. Wheel cylinder outlet passage 42 is connected via fluid conduit 46 to the wheel cylinders 24, 26 associated with the rear wheels of a vehicle (not shown).
Also formed fluidly in series in body 28 are a pump mani-fold chamber or pressure fluid inlet port 48, pump cylinder 50, stop valve chamber 52, connecting passage or pressure reducing means inlet port 54, pressure relief or reducing valve chamber 56, and a fluid passage 58 communicating between reducing valve chamber 56 and inlet passage 38. A solenoid 60 includes a coil 62 electrically connected to an electronic anti-lock control unit 64, a plunger 66 connected to a pump piston 68 which extends through a fluid tight bore 70 and "O" ring seal 72. Alternatively, pressurized fluid can be admitted to the coil chamber to provide a fluid balanced system, that is, a system wherein fluid pressure on the opposite ends of piston 68 are balanced. A spring 74 maintains the plunger 66 in its illus-trated position. Upon energization of the solenoid coil 62, plunger 66 moves upwardly (as viewed in the drawings) causing the piston 68 to move into the pump cylinder 50.
~. ' ~2~ ;3~
Stop valve chamber 52 has dispose(l there:Lrl an anl~ lr stop valve e:lement 76 res:L:L:Lent:ly ma:LIlta:Llle(l aga:L[Ist a slloll.l.(lor 7 oE chatllber 52 by a col:L spr:lng 80.
S:Lm:llarly, a ball valve 82 :ls rece:lvecl:ln red-lc:LIlg va:Lve chamber 56, ball valve 82 being ma:Lntalned agalnst a valve seat 84 in chamber 56 by a co:Ll spring 86.
~ fluid passage 54 connects stop valve chamber 52 and the pressure reducing valve chamber 56 to fluid passage 88 and to the end 90 of valve chamber 30 axially opposite inlet passage 38. Inlet passage 44 communicates chamber 30 with the pump inlet chamber 48.
~ valve element 92 is reciprocally received in valve chamber 30. Valve element 92 is provided with a valve closure portion 94 movable into engagement with the valve seat 36 to close the inlet passage 38. Preferably, an "0" ring seal 96 is fitted to the valve element 92 to provide fluid tight isolation thereacross. The end 98 of the valve element 92 is of reduced diameter to provide a fluid receiving space between the valve element 92 and the end 90 of chamber 30.
Lastly, a speed sensing device 95, typically a magnetic sensor associated with rotating tone wheel or the like is operatively connected to the drive shaEt of the rear wheels of the vehicle (not shown). This sensor, as is now well known to those skilled in the art, provides a signal proportional to the speed of the wheels associated with wheel cylinders 24, 26. This signal is applied to the electronic control unit 64. The control unit itself includes a computing circuit which will analyze the rotational behavior of the wheels of the vehicle to determine the occurence of an incipient skid condition. Based on this information, control signals are generated by the electronic control unit 64 to apply an operating signal to the solenoid coil 62 to effect reduction in pressure of fluid applied to the wheel cylinders 24, 26.
Under normal braking conditions, valve element 92 remains in its rightmost position as is shown in the drawing. Pressurized braking fluid in hydraulic circuit II passes through the passage 38, valve chamber 30, and to wheel cylinders 24, 26 via passage 42 and fluid conduit 46. This same pressure is also provided to pump 12~53~
inlet chamber 48 via fluid passage 44. When the electronic control unit 64 determines that the wheels are being braked excessively and an incipient lock condition exists, a control signal is generated to energize solenoid coil 62. This moves the plunger 66 vertically (as shown in the drawing) moving the piston 68 into the piston cylin-der 50. This forces a quantity of brake fluid from the cylinder 50 past the stop valve 76 and pressure reducing valve element 82.
Action of the pressure reducing valve 82 creates pressure drop in the fluid as it passes from passage 54 to the inlet passage 38. The highér pressure in passage 54 is conveyed via passage 88 to the end 98 of valve element 92. Because this pressure is higher than pressure at the inlet passage 38, valve element 92 moves to the left (as viewed in the drawings). With repetitive solenoid action, valve element 92 fully travels so that valve closure portion 94 seals against seat 36. This isolates master cylinder 12 from the wheel cylinders 24, 26. Simultaneously, fluid pumped from the cylinder 50 forces a simi-lar quantity of fluid backwardly through the inlet passage 38 thereby withdrawing a small quantity of fluid from the wheel cylinders 24, 26 via wheel cylinder outlet passage 42, valve chamber 30, and pump inlet passage 44. This, accordingly, reduces the pressure in the wheel cylinders 24, 26. Continued existence of the incipient skid condition will cause further repetitious operation of the solenoid plunger 66 thereby further reducing pressure in the wheel cylinders 24, 26O This will continue until the incipient skid condition has been alleviated.
When the driver lowers pressure in master cylinder 12, the pressue in passage 38 lowers. If the pressure in the brakes is greater (less the pressure drop across the regulator valve) fluid will return to the master cylinder via passages 42 to 44 to 48 past valve 76 to passage 54, past valve 82 to passage 58 to master cylinder inlet passage 38. When the pressure in chamber 90 is less than in chamber 30, piston 92 moves to its rest position reopening full com-munication from master cylinder to the brakes.
In the illustrated embodiment, the pump has been illustrated as a solenoid. This configuration provides the least expensive struc-ture. However, in severe spike applications of brakes, it is possible `~
. . .
7 1 2c~5~
that the solenoid actu.ltecl pump wLll have insuEficlent capncLl:y to reduce brake pressure rapicl:ly enough to EuLLy avoLcl 1 skLcl or loc:k cond:itlon oE the vehLcles wheeLs. ~ccorclLng1y, th:Ls l.:l.lll.l.t~lt:LOII (:all be alLeviatecl by replacLng tlle soleno:Ld p(llllp witll an cLectr1c nlotor pUIllp as sllown in FLgure 2. The motor pUIllp lO5 Lncorporates a Illotor (llOt shown) clrivLng an eccentrLc 102 wh1ch Ln turn rec-Lprocates the plston 68. ~ stop vaLve L04 may be provided. Because oE Lts Illgher capacity, the pump 105 wilL be able to eliminate locking oE the vehi-cles rear wheels even under severe spike applications but with an attendant increase in cost of the system. The system, nonetheless, represents a substantial reduction in the complexity of anti-lock braking systems. Because of its configuration, this system is excep-tionally well adapted for applications such as vans and light trucks with ~he system being applied to the rear wheels only.
In the operation of the system, it should be observed that the stop valve element 76 prevents the passage of fluid from the inlet passage 38 backwardly through pump cylinder 50, chamber 48, and the wheel cylinders 24, 26 during the brief period when the pres-sure reducing valve 82 remains open and the solenoid pump begins to retract. It should also be observed that a pressure build orifice lO0 may be provided in the valve seat 36 to allow for gradual controlled building of pressure in the wheel cylinders 24, 26 when the incipient lock condition has been alleviated and/or the brake pressure in the wheel cylinders 24, 26 has been reduced by an amount greater than necessary.
~ lthough the present invention has been illustrated and described in connection with example embodiments, it will be under-stood that this is illustrative of the invention, and is by no means restrictive, thereoE. It is reasonable to be expected that those skilled in the art can make numerous revisions and additions to the invention and it is intended that such revisions and additions will be included in the scope of the following claims as equivalents of the invention.
_C _ OUWD ~ T~IE INVENI'ION
The present invention relates to antt-lock hrak-ing systems and in partlcular to an anti-lock brakinq system which incorporates an integrated modulatiny valve and brake pressure reducing pump, actuated by an elec-tronic control system responsive to rotational behaviorof a vehicle's wheels, the system being particularly applicable to anti-lock control of the rear wheels of a vehicle.
Anti-lock braking systems are well known.
Typically, prior art anti-lock brak~ng ~ys,tems have _~o~ r , ~;~ G6:1' evolved from mechanical to s~s~i~l~e~ electronically-controlled devices which sense the rotational behavior of a vehicle's wheels during braking and assume control of braking of the vehicle upon sensing an ~ r-~e~ skid con-dition to automatically modulate the application of brak-ing pressure to avoid wheel-lock. Typically, these sys-tems incorporate a power boosted master cylinder or a full power hydraulic system to produce the required pres-surized braking fluid. The systems are normally divided into a plurality of hydraulic circuits with braking of the front wheels of the vehicle heing individually con-trolled and the rear wheels of the vehicle being con-trolled either individually or as a pair. Such systems can be highly effective. Such systems are, however, complex and expensive, a factor which reduces their availability and widespread implementation.
There exist numerous applications for anti-lock braking systems in which substantial~improvements in the braking performance of the vehicle can be enhanced with-out the requirement of controlling three or more wheelsof the vehicle. Such applications typically include pick-up trucks and vans. In these applications, due to the substantial variation in loading of the rear wheels of the vehicle, it is possible to have a vehicle that is lightly loaded be very subject to locking of the rear 3~
~2~i5~V
wheels. Various brake pressllre proportlonlng dev1ce~
have been proposed to alleviate this prohlem hut sllch devices have been less than fuliy efectlve, due to sub-stantial variations in friction materials and other variable parameters of the braking system.
There therefore exists a need for a simple, low cost anti-lock braking system which is adaptable for ap-plications such as pick-up trucks and vans which can sub-stantially reduce the potential of rear wheel lock with a minimum of cost and complexity.
There also exists a need for such a system which can be used with braking systems incorporating vac~um boosted modulators, and any of various hydraulically boosted systems.
Broadly, the present invention is an anti-lock braking system which comprises a master cylinder means for generating pressurized braking fluid in a hydraualic circuit which includes at least one wheel cylinder. Means are provided for sensing the rotational behavior of a ve-hicle wheel and generating a signal corresponding thereto.
A control circuit is connected to the sensor means for receiving these signals and generating control signals in response to an incipient wheel-lock condition. A hrake pressure modulator is operatively connected to the hy-draulic circuit between the master cylinder and the wheelcylinder. The pressure modulator includes a pump for pumping fluid from the wheel cylinder to the master cyl-inder, and a pressure reducing means connected between the pump means and the master cylinder for producing a pressure drop thereacross in response to the flow of fluid therethrough. An isolating valve is provided, the valve having an inlet port, wheel cylinder outlet port, a pump outlet port, and a control port. The ports are connected to the master cylinder, wheel cylinder, the inlet of the pump means, and the input of the pressure reducing means, respectively. The isolating valve normally establishes fluid communication between the inlet, wheel cyllnder, and pump inlet ports and lnclude~
an element oper~ble in response to a pressure drop across the pressure reducing means to isolate the inlet port from the wheel cylinder and pump inlet ports. The pump means is responsive to the signa:Ls from the control means to pump fluid from the wheel cylinder to the master cylinder to thereby reduce the pressure of hLaking fluid therein.
It is therefore an object of the invention to provide an improved anti-lock braking system.
Another object of the invention is to provide an anti-lock braking system of reduced cost and compiexity.
Still another object of the invention is to pro-duce an anti-lock braking system particularly well suited for use in preventing lock of the rear wheels of a vehicle.
Another object of the invention is to provide an anti-lock braking system which includes a self-contained electrically operated pump and an isolating valve operable in response to signals from a control circuit and fluid flow from the pumpj-respectively, to pump fluid from a wheel cylinder and reduce the pressure therein.
These and other objects and purposes of the invention and the invention itself will he best under-stood in view of the following detailed descriptionthereof taken in conjunction with the appended drawings wherein:
Figure 1 shows an anti-lock braking system in accordance with the present invention, portions thereof being shown in schematic format; and Figure 2 is a fragmentary drawing of an alterna-tive pump for use in the invention.
DESCRIPTION OF PREFERRED EMBODIMENT
Referring now to the drawing there is shown an anti-lock braking system which comprises generally a master cylinder 12, typically a dual cylinder displace-ment type of master cylinder including a reservoir 14 and actuated by a Eoot pedaL 16. ~laster cylln(ler 12 h~lg two ou~ptll: cLr-cuits, I, [I. As illustratecl, hy~lrauLlc cLrcuLt I Ls cotlnec~e(l ~o a palr oE Eront wllee1 brake cyllnders l8, 20 nnd llyclrn~lLIe cLrcllLt II is connected throllgll n pUIllp ancl moduLator assemhly 22 to a pnir oE rear wheel cylinders 24, 26. ~laster cyLLnder 12 may be man~laL
or power boosted by means of sueh as a vacuum booster or a hydrallllc booster (not shown). Ilydraulic circuits I, II are fully hydraulically isolated, such systems and components being now well known in the art.
Pump modulator assembly 22 includes a body 28 of irregular configuration. Body 28 is provided with a generally cylindrical, stepped diameter valve chamber 30 having a closed end 32 and provided at its opposite end or master cylinder inlet 34 with a tapered valve seat 36.
An inlet passage or master cylinder port 38 communicates axially with valve chamber 30 via the valve seat 36 and is connected at its opposite end 40 to the hydraulic circuit II of master cylinder 12.
A wheel cylinder outlet passage or wheel cylinder port 42 and a pump inlet passage 44 communicate with chamber 30 adjacent valve seat 36. Wheel cylinder outlet passage 42 is connected via fluid conduit 46 to the wheel cylinders 24, 26 associated with the rear wheels of a vehicle (not shown).
Also formed fluidly in series in body 28 are a pump mani-fold chamber or pressure fluid inlet port 48, pump cylinder 50, stop valve chamber 52, connecting passage or pressure reducing means inlet port 54, pressure relief or reducing valve chamber 56, and a fluid passage 58 communicating between reducing valve chamber 56 and inlet passage 38. A solenoid 60 includes a coil 62 electrically connected to an electronic anti-lock control unit 64, a plunger 66 connected to a pump piston 68 which extends through a fluid tight bore 70 and "O" ring seal 72. Alternatively, pressurized fluid can be admitted to the coil chamber to provide a fluid balanced system, that is, a system wherein fluid pressure on the opposite ends of piston 68 are balanced. A spring 74 maintains the plunger 66 in its illus-trated position. Upon energization of the solenoid coil 62, plunger 66 moves upwardly (as viewed in the drawings) causing the piston 68 to move into the pump cylinder 50.
~. ' ~2~ ;3~
Stop valve chamber 52 has dispose(l there:Lrl an anl~ lr stop valve e:lement 76 res:L:L:Lent:ly ma:LIlta:Llle(l aga:L[Ist a slloll.l.(lor 7 oE chatllber 52 by a col:L spr:lng 80.
S:Lm:llarly, a ball valve 82 :ls rece:lvecl:ln red-lc:LIlg va:Lve chamber 56, ball valve 82 being ma:Lntalned agalnst a valve seat 84 in chamber 56 by a co:Ll spring 86.
~ fluid passage 54 connects stop valve chamber 52 and the pressure reducing valve chamber 56 to fluid passage 88 and to the end 90 of valve chamber 30 axially opposite inlet passage 38. Inlet passage 44 communicates chamber 30 with the pump inlet chamber 48.
~ valve element 92 is reciprocally received in valve chamber 30. Valve element 92 is provided with a valve closure portion 94 movable into engagement with the valve seat 36 to close the inlet passage 38. Preferably, an "0" ring seal 96 is fitted to the valve element 92 to provide fluid tight isolation thereacross. The end 98 of the valve element 92 is of reduced diameter to provide a fluid receiving space between the valve element 92 and the end 90 of chamber 30.
Lastly, a speed sensing device 95, typically a magnetic sensor associated with rotating tone wheel or the like is operatively connected to the drive shaEt of the rear wheels of the vehicle (not shown). This sensor, as is now well known to those skilled in the art, provides a signal proportional to the speed of the wheels associated with wheel cylinders 24, 26. This signal is applied to the electronic control unit 64. The control unit itself includes a computing circuit which will analyze the rotational behavior of the wheels of the vehicle to determine the occurence of an incipient skid condition. Based on this information, control signals are generated by the electronic control unit 64 to apply an operating signal to the solenoid coil 62 to effect reduction in pressure of fluid applied to the wheel cylinders 24, 26.
Under normal braking conditions, valve element 92 remains in its rightmost position as is shown in the drawing. Pressurized braking fluid in hydraulic circuit II passes through the passage 38, valve chamber 30, and to wheel cylinders 24, 26 via passage 42 and fluid conduit 46. This same pressure is also provided to pump 12~53~
inlet chamber 48 via fluid passage 44. When the electronic control unit 64 determines that the wheels are being braked excessively and an incipient lock condition exists, a control signal is generated to energize solenoid coil 62. This moves the plunger 66 vertically (as shown in the drawing) moving the piston 68 into the piston cylin-der 50. This forces a quantity of brake fluid from the cylinder 50 past the stop valve 76 and pressure reducing valve element 82.
Action of the pressure reducing valve 82 creates pressure drop in the fluid as it passes from passage 54 to the inlet passage 38. The highér pressure in passage 54 is conveyed via passage 88 to the end 98 of valve element 92. Because this pressure is higher than pressure at the inlet passage 38, valve element 92 moves to the left (as viewed in the drawings). With repetitive solenoid action, valve element 92 fully travels so that valve closure portion 94 seals against seat 36. This isolates master cylinder 12 from the wheel cylinders 24, 26. Simultaneously, fluid pumped from the cylinder 50 forces a simi-lar quantity of fluid backwardly through the inlet passage 38 thereby withdrawing a small quantity of fluid from the wheel cylinders 24, 26 via wheel cylinder outlet passage 42, valve chamber 30, and pump inlet passage 44. This, accordingly, reduces the pressure in the wheel cylinders 24, 26. Continued existence of the incipient skid condition will cause further repetitious operation of the solenoid plunger 66 thereby further reducing pressure in the wheel cylinders 24, 26O This will continue until the incipient skid condition has been alleviated.
When the driver lowers pressure in master cylinder 12, the pressue in passage 38 lowers. If the pressure in the brakes is greater (less the pressure drop across the regulator valve) fluid will return to the master cylinder via passages 42 to 44 to 48 past valve 76 to passage 54, past valve 82 to passage 58 to master cylinder inlet passage 38. When the pressure in chamber 90 is less than in chamber 30, piston 92 moves to its rest position reopening full com-munication from master cylinder to the brakes.
In the illustrated embodiment, the pump has been illustrated as a solenoid. This configuration provides the least expensive struc-ture. However, in severe spike applications of brakes, it is possible `~
. . .
7 1 2c~5~
that the solenoid actu.ltecl pump wLll have insuEficlent capncLl:y to reduce brake pressure rapicl:ly enough to EuLLy avoLcl 1 skLcl or loc:k cond:itlon oE the vehLcles wheeLs. ~ccorclLng1y, th:Ls l.:l.lll.l.t~lt:LOII (:all be alLeviatecl by replacLng tlle soleno:Ld p(llllp witll an cLectr1c nlotor pUIllp as sllown in FLgure 2. The motor pUIllp lO5 Lncorporates a Illotor (llOt shown) clrivLng an eccentrLc 102 wh1ch Ln turn rec-Lprocates the plston 68. ~ stop vaLve L04 may be provided. Because oE Lts Illgher capacity, the pump 105 wilL be able to eliminate locking oE the vehi-cles rear wheels even under severe spike applications but with an attendant increase in cost of the system. The system, nonetheless, represents a substantial reduction in the complexity of anti-lock braking systems. Because of its configuration, this system is excep-tionally well adapted for applications such as vans and light trucks with ~he system being applied to the rear wheels only.
In the operation of the system, it should be observed that the stop valve element 76 prevents the passage of fluid from the inlet passage 38 backwardly through pump cylinder 50, chamber 48, and the wheel cylinders 24, 26 during the brief period when the pres-sure reducing valve 82 remains open and the solenoid pump begins to retract. It should also be observed that a pressure build orifice lO0 may be provided in the valve seat 36 to allow for gradual controlled building of pressure in the wheel cylinders 24, 26 when the incipient lock condition has been alleviated and/or the brake pressure in the wheel cylinders 24, 26 has been reduced by an amount greater than necessary.
~ lthough the present invention has been illustrated and described in connection with example embodiments, it will be under-stood that this is illustrative of the invention, and is by no means restrictive, thereoE. It is reasonable to be expected that those skilled in the art can make numerous revisions and additions to the invention and it is intended that such revisions and additions will be included in the scope of the following claims as equivalents of the invention.
Claims (8)
1. An anti-lock braking system comprising:
master cylinder means (1.2) for generating pressurized brak-ing fluid in a hydraulic circuit (II) which includes at least one wheel cylinder (24, 26), control means (64) for generating control signals in response to an incipient wheel skid condition, and a brake pressure modulator (22) operatively connected to said hydraulic circuit (II) between said master cylinder means (12) and said wheel cylinder (24, 26), characterized in that said brake pressure modula-tor (22) includes a housing (22) with pump means (60, 105) responsive to signals from said control means (64) for pumping fluid from said wheel cylinder (24, 26) to said master cylinder (12), pressure reducing means (82, 84, 86) connected between said pump means (60, 105) and said master cylinder (12) for producing a pressure drop thereacross in response to flow of fluid from said pump means (60, 105), an isolating valve (92) having a master cylinder inlet (34), a wheel cylinder outlet (42), a pressure fluid inlet (44) of the pump means (60, 105), and a pressure reducing means input (88), and ports (38, 42, 48, 54) connected to said master cylinder (12), said wheel cylinder (24, 26), the inlet (44) of said pump means (60, 105), and the input (88) of said pressure reducing means (82, 84, 86), respec-tively, said isolating valve (92) normally establishing fluid communication between the master cylinder inlet port (38), wheel cylinder outlet port (42) and pressure fluid inlet port (48) and including means (94, 36) connected to said pressure reducing means (82, 84, 86) and operable in response to a pressure drop thereacross for isolating said master cylinder inlet port (38) from said wheel cylinder port (42) and pump means inlet port (48), the housing (22) containing therein the pump means (60, 105), pressure redu-cing means (82, 84, 86), isolating valve (92), inlets (34, 44), outlet (42), input (88), ports (38, 42, 48, 54), and isolating means (94, 36).
master cylinder means (1.2) for generating pressurized brak-ing fluid in a hydraulic circuit (II) which includes at least one wheel cylinder (24, 26), control means (64) for generating control signals in response to an incipient wheel skid condition, and a brake pressure modulator (22) operatively connected to said hydraulic circuit (II) between said master cylinder means (12) and said wheel cylinder (24, 26), characterized in that said brake pressure modula-tor (22) includes a housing (22) with pump means (60, 105) responsive to signals from said control means (64) for pumping fluid from said wheel cylinder (24, 26) to said master cylinder (12), pressure reducing means (82, 84, 86) connected between said pump means (60, 105) and said master cylinder (12) for producing a pressure drop thereacross in response to flow of fluid from said pump means (60, 105), an isolating valve (92) having a master cylinder inlet (34), a wheel cylinder outlet (42), a pressure fluid inlet (44) of the pump means (60, 105), and a pressure reducing means input (88), and ports (38, 42, 48, 54) connected to said master cylinder (12), said wheel cylinder (24, 26), the inlet (44) of said pump means (60, 105), and the input (88) of said pressure reducing means (82, 84, 86), respec-tively, said isolating valve (92) normally establishing fluid communication between the master cylinder inlet port (38), wheel cylinder outlet port (42) and pressure fluid inlet port (48) and including means (94, 36) connected to said pressure reducing means (82, 84, 86) and operable in response to a pressure drop thereacross for isolating said master cylinder inlet port (38) from said wheel cylinder port (42) and pump means inlet port (48), the housing (22) containing therein the pump means (60, 105), pressure redu-cing means (82, 84, 86), isolating valve (92), inlets (34, 44), outlet (42), input (88), ports (38, 42, 48, 54), and isolating means (94, 36).
2. The system of claim 1, characterized in that said isolating valve includes a single valve chamber (30) communicating with said master cylinder inlet (34), wheel cylinder outlet (42), and pressure fluid inlet (44), and a valve element (92) disposed between said master cylinder inlet (34) and said wheel cylinder port (42), pressure fluid inlet port (48), and input port (54), and slideable in said chamber (30) between an open position displaced from said master cylinder port (38) and a closed position closing said master cylinder port (38).
3. The system of claim 2, characterized in that said chamber (30) is generally cylindrical, said valve element (92) being axially slideable therein and forming a fluid tight seal between said master cylinder inlet (34) and the wheel cylinder, fluid inlet, and input ports (42, 48, 54).
4. The system of claim 3, characterized in that said wheel cylinder port (42) and pump means inlet port (48) communicate through said chamber (30) in all positions of said valve element (92).
5. The system of claim 1, characterized in that said pressure reducing means (82, 84, 86) includes a ball valve (82) and a valve seat (84) and spring means (86) for maintaining said ball valve (82) against said seat (84) in a direction opposite the flow of fluid therethrough.
6. The system of claim 5, characterized in that said pump means (60, 105) includes a solenoid (60) having a plunger (66), a pump piston (68) operatively connected to said plunger (66), and a piston cylinder (50) formed in said body (28).
7. The system of claim 6, characterized in that the system further includes a stop valve (76) connected fluidly in series between said pump means (60, 105) and said pressure reducing means (82, 84, 86).
8. The system of claim 2, characterized in that the system further includes an orifice (100) communicating between said master cylinder inlet port (38) and said wheel cylinder port (42) when said valve element (92) is in said closed position.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000549780A CA1285590C (en) | 1987-10-20 | 1987-10-20 | Simplified anti-lock braking system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000549780A CA1285590C (en) | 1987-10-20 | 1987-10-20 | Simplified anti-lock braking system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1285590C true CA1285590C (en) | 1991-07-02 |
Family
ID=4136688
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000549780A Expired - Lifetime CA1285590C (en) | 1987-10-20 | 1987-10-20 | Simplified anti-lock braking system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1285590C (en) |
-
1987
- 1987-10-20 CA CA000549780A patent/CA1285590C/en not_active Expired - Lifetime
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| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |