CA1052421A - Braking fluid pressure device - Google Patents
Braking fluid pressure deviceInfo
- Publication number
- CA1052421A CA1052421A CA249,277A CA249277A CA1052421A CA 1052421 A CA1052421 A CA 1052421A CA 249277 A CA249277 A CA 249277A CA 1052421 A CA1052421 A CA 1052421A
- Authority
- CA
- Canada
- Prior art keywords
- chamber
- fluid
- pressure
- ball valve
- master cylinder
- 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.)
- Expired
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
- B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
- B60T8/26—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force characterised by producing differential braking between front and rear wheels
- B60T8/28—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force characterised by producing differential braking between front and rear wheels responsive to deceleration
- B60T8/282—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force characterised by producing differential braking between front and rear wheels responsive to deceleration using ball and ramp
Abstract
Abstract of the Disclosure A braking fluid pressure control device comprises control means for controlling a critical fluid pressure of the pressure control device in accordance with the various weights of a motor vehicle to predetermined various values corresponding to the various vehicle weights in which means passage means for feeding a master cylinder fluid pressure to a fluid chamber of the control means is provided therein with delay means for causing variation in the master cylinder fluid pressure is transmit to the fluid chamber with a time lag to prevent the pressure of fluid confined in the fluid chamber from being varied in accordance with the rate of increase in the master cylinder fluid pres-sure to have the pressure control device perform its desired function accurately.
Description
Tlle present invention relates generally to a i)rnking fluid pressure control device WtliCh COlllpriSe9 `' va:Lve means ~erves a3 a proportioning or limiting valve, and control means for varying a critical fluid prPssure of the valve means in accordance with v~rT~i~n the vehicle weight and particularly to a braking fluid pressure control device of this type improved to prevent the pressure of fluid confined in a fluid chamber of the control means from being varied in .-~
accordance with the rate of increa~e in a fluid ' press~re from the master cylinder when a ball valve of the control means move~ to a valve seat to close an inlet port of the fluîd chamber in response to a pre- ;. :
;' ' determined deceleration rate by providing delay means such as an orlfice in pas~age means leading to the inlet por~ from the ma3ter cylinder. ;:
As is well known in the art, usuAl motor vehicle ``:~
hydraulic braking systems are such that the brakes are ~:
applied to the front and rear wheels concurrently... In -this instance, if an excess a~ount Or braking force is applied to -the front wheels, the front wheels are ~
locked earlier than the rear wheels to make it im-possible for the driver to handle the motor vehicle.
On the contrary, if th~ rear wheels are braked excessively, they are locked prior to the front wh~els :~
accordance with the rate of increa~e in a fluid ' press~re from the master cylinder when a ball valve of the control means move~ to a valve seat to close an inlet port of the fluîd chamber in response to a pre- ;. :
;' ' determined deceleration rate by providing delay means such as an orlfice in pas~age means leading to the inlet por~ from the ma3ter cylinder. ;:
As is well known in the art, usuAl motor vehicle ``:~
hydraulic braking systems are such that the brakes are ~:
applied to the front and rear wheels concurrently... In -this instance, if an excess a~ount Or braking force is applied to -the front wheels, the front wheels are ~
locked earlier than the rear wheels to make it im-possible for the driver to handle the motor vehicle.
On the contrary, if th~ rear wheels are braked excessively, they are locked prior to the front wh~els :~
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to cause the rear portion of the motor vehicle to swing tran~versely to the longitudinal direction thereof.
Accordingly, in order to assure and increase the safety arld st~ll)i]ity of the vehicle during its braking oper-atiorl, it is neceffsary to effect the di~tribution ofthe braking forces to lock the front and rear wheels concurrently.
When the vehicle i~ braked, the so-called nose-dive phenomenon takes place in which the vehicle weight app]ied on the front wheels increases and the vehicle weight applied on the rear wheels decreases. According-ly, it i8 necessary for concurrently locking the front and rear wheel3 to distribute to the front wheel~ a braking force greater than a braking force distributed L5 to the rear wheel~. It i9 also nece~ary that the distribution of the braking force~ to the front and rear wheel~ i9 varied in accordance with variations in the vehicle weight. Thu~, ideal characteri~tics of ~`
the distribution of the braking force~ to the front and rear wheels, when are lllustrated on oblique coordinates having the axe~ of abscis.~a and ordinate indicating respectively thereon the ratios (deceleration rate ratios) Bf/W and Br/W of the braking forces Bf and Br on the front and rear wheels versus the vehicle z5 weight W, are e~pre~sed by a curve having tangents the :
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ar~gles of inclination of which are relatively large wi.thin a range of the origin to a certain value and are relatively small outside the range. I`urthermore, ~he ideal charac-teristics of the braking force dis- ~ :
~rihllt:ion are expre~sed by different curves in accordance with the vehicle weight and th~ heavier the vehJ.cle weight is, the higher the ideal charac-teristic~ curve i8 located on the coordinates. .:
It is accordin$1y nece~sary for providing the distribution of the braking forces which is clo.se to the ideal characteri~tios curve to feed to the rear wheel cylinders a fluid pres~ure increasing at a rate . :~
sma:l.l.er than that of increa~e in a fluid pre~sure fed .
to the front wheel cylinders or at a rate of zero when ~
the fluid pre~sure fed to the front wheel cylinders exceeds a predetermlned fluid presqure. As an expedient for solving the problem, a limiting valve, proportioning valve or G valve was employed to di~pose ~-as a braking pressure control valve in a rear braking .
circuit leading to the rear wheel cylinder~. The limiting valve generate~ an output fluid pres~ure increa~ing at a rate of zero when an input fluid pre~sure exceeds a critical fluid pre~qure. The proportioning valve generate~ an output fluid pr~ssure increa~ing at a rate lower than that of increase in an - 4 - `
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, input fluid pressure when the input fluid pressure exceeds a critical fluid pressure, The G valve emits an output fluid pressure increasing at a rate less than an input fluid pressure when a predetermined rate of deceleration is attained. ~lowever, the output fluid pressure emitted by these valves merely carried out the distribu-tion of the braking forces approximating to a single ideal characteristics curve which accordingly, corresponds to a predetermined vehicle weight and, when the vehicle weight is varied, effected a distribution of the braking forces which largely deviated from an ideal characteristics curve correspond-ing to the vehicle weight varied.
On the other hand, most motor vehicles are in recent years provided with a hydraulic braking system of the tandem type which comprises front and rear braking circuits leading from a master cylinder to the front and rear wheel cylinders, _~
respectively separately. However, the above-mentioned braking pressure control valve, when disposed in the rear braking circuit, emits in the event of the failure of the fluid pressure in the ~ f front braking circuit the same output fluid pressure as in the event of no such failure. This resulted in the deficiency of the braking force.
Thus, a braking ~' :
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fluid pressure control device has been proposed which comprises, in addition to valve means serving as a proportioning or limiting valve, an lnertia responsive type valve or "G" valve for controlling the valve means to vary the critical fluid pressure in accordance with variation in the vehicle weight to generate an ;
output fluid pressure which provides the distributions of the ~: :
braking forces to the front and rear wheels which approximate to the ideal charac-teristics curves corresponding to the vehicle weight varied. The control means comprises a piston biased to urge the valve means by a master cylinder fluid pressure fed into i :
a power or fluid chamber and a ball valve responsive to a prede- : -termined deceleration to move to a valve seat to close an inlet port to the fluid chamber to maintain the pressure of fluid there-in at a predetermined value. The valve means is also biased by the fluid pressure in the front braking circuit so that in the event of the failure of the fluid pressure the critical fluid pressure is increased to generate the output fluid pressure ~`
sufficiently high to compensate ~he deficiency of the braking . force.
~owever, this braking fluid pressure control device has suffered from the drawback that the pressure of fluid in the fluid chamber is varied in accordance with ~-~': ' '' ' .
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the rate of increase in the master cylinder fluid pressure to make it impossible to control -the critical fluid pressure to a predetermined value in accordance with variation in the vehicle weight as the ball moves to the valve sea-t and closes the inlet por-t of the fluid chamber in response to the predetermined deceleration notwithstanding that at this time it is necessary for controlling the critical fluid pressure to the predetermined value in accordance with variation in the vehicle weight that the :~.
pressure of fluid in the fluid chamber be at a predetermined 10 value independently of the rate of increase in the master cylinder .
fluid pressure if the vehicle weight remains unvaried. This is because, as the ball moves to the valve seat in response to the predetermined deceleration, variation in the master cylinder fluid pressure is transmitted to the fluid chamber until the ball : reaches the valve seat to close the inlet port.
It is, therefore, an object of the invention to provide an improved braking fluid pressure control device in which the `
pressure, or the rate of increase in the pressure, of fluid in the fluid chamber is maintained at a predetermined value indepen-dently of the rate of :
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increase in the master cylinder fluid pressure when the bal~ valve moves to the valve seat and closes the inlet port to the fluid :
chamber in response to a predetermined deceleration by providing ~ .
in passage means leading to the inlet port for passing the master cylinder fluid pressure thereto delay means for transmitting variation in the master cylinder fluid pressure to the fluid chamber with a suitable time lag to prevent or reduce the pressure ~ -of a fluid in the fluid chamber being varied in accordance with the rate of increase in the master cylinder fluid pressure until the ball abuts against the valve seat.
Accordingly the present invention provides a braking system for a wheeled vehicle having at least one front wheel and at least one rear wheel, said system comprising manually operable :~
master cylinder means for generating first and second variable hydraulic pressures; a front brake for the at least one front wheel; a rear brake for the at least one rear wheel; first fluid conduit means fluidly interconnecting said master cylinder and said.front brake for transmitting said first variable hydraulic pressure to said front brake; a fluid pressure control device which has an inlet chamber, an outlet chamber; a passage providing .
communication between said inlet and outlet chambers; a valve seat in the form of an annular sealing member arranged within said :
passage; a pressure-responsive plunger having a valve member in the form of an annular projection, said annular projection being -cooperative with said annular sealing member; chamber means for biasing said pressure responsive plunger in a direction tending to ~ .
move said annular projection toward said annular sealing member in response to said first variable hydraulic pressure; means for biasing said pres~sure responsive plunger in a direction tending to move said annular projection away from said annular sealing member;
means having a power chamber for increasing the preload of said biasing means in response to hydraulic pressure in said power .:
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~ chamber; means defining a ball valve chamber~`and a ball valv~e .. . ..
passage providing communication between said ball valve chamber and said power chamber; and an inertia ball valve disposed in said ' ball valve chamber to close said ball valve passage in response to a predetermined magnitude of deceleration of the vehicle; second conduit means fluidly interconnecting said master cylinder means and said inlet chamber for transmitting said second variable hydraulic pressure to said inlet chamber; third conduit means fluidly interconnecting said outlet chamber to said rear brake for transmitting the hydraulic pressure prevailing in said outlet chamber to said rear brake; and delay means fluidly interconnecting said master cylinder means and said ball valve chamber for restric-ting hydraulic fluid flow transmission from said master cylinder means to said ball valve chamber so that transmission of said second hydraulic variable pressure to said ball valve chamber is delayed.
The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:
Fig. 1 i9 a graphic representation of the ideal charac-teristics curves of the distribution of the braking forces to the front and rear wheels;
Fig. 2 is a schematic view of a motor vehicle hydraulic braking system incorporating thereinto a braking fluld pressure control device according to the invention;
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F`ig. 3 is a schematic cross sectional view of a pro.(`erred embodiment of a braking fluid pressure contro:L device according to the invention;
~ ig. 4 is a graphic representation of the re.Lationship between the pressure of fluid in a fluid chamber closed by a ball valve and the rate of increase in a master cylinder fluid pre~ure;
Fig. 5 is a graphic repre~entation of the relation-ship between the input fluid pre~sure and the output i`l.uid pressure of the braking fluid pressure control device shown in Fig. 3; and ~ ig. 6 i8 a graphic representation of the relation-~hip between the critical fluid pressure of the brakins f:luid pressure control device shown in Fig. 3 and the vehicle weight.
Referring to Fig. 1 of the drawings, the ideal characteristics curves al and a2 as per the introduction of the specification of the di~tibution3 of the braking force~ to thc front and rear wheels are illustrated on oblique coordin~te~ having the axes of absci~sa and ordinate indicating respectively thereon the ratios (deceleration rate ratios~ Bf/W and Br~W of the braking f`orces Bf and Br on the front and rear wheels versus tlle vehicle weight W. The curves al and a2 indicate the ideal characteristics at the time when the weight : .
_ 9 _ ~
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of tl-e vehicle iq Wl (no load) and W2 (the vehicle e.lrrio~ a load), re~pective]y. The general relation-911ip between the ideal characterlstics curve~ and the vehlcle weight is such that the heavier the vehicle weigllt is, the higher or the more the ideal charac-teri~tic~ curve is po~itioned or extends upwardly qteeply from the origin O in the graph of F`ig. -L.
As is apparent from the graph, the angle of in-clinatlon of a tangent of each of the curves al and a2 i~ relatively large within a range of the origin O to a certain value and i~ relatively small out~ide the range. In the graph of Fig. 1, there is also illustrated the characteriqtics line3 bl and b2 of the distributionq of the braking forceq to the front and rear wheels wllich distributions are pro~ided to approximate re3pectively ~to the ideal characteristics cur~es al and a2 by a motor vehicle hydraulic braking ~ystem incorporating therein a braking fluid pre3~ure control device according to the invention.
- Referring to Fig. 2 of the drawing~, there i.q -~hown a motor vehicle hydraulic braking ~y~tem incor-porating therein a braking fluid pre~sure control device or valve according to the invention. The hydraulic -braking ~qystem, generally de~ignated by the referenc~
~ D~LLy ~
numeral 10, include~ a ma3ter cylinder 12topera~ed ~P~m -- 10 _ ~5;~
a brake pedal 1/1. First and ~econd hydraulic f`luid circllits lf~ nnd 18 lead from the master cylinder 12 to receive fluid pres~ures Pml and Pm2 therefrom, re~pectively. The fluid pre3~ures Pml and Pm2 are equal to each other and are often referred to a~q the fluid pressure Pm hereinafter. The front f]uid line 16 is connected to front wheel cylinders 20 to feed th~ f`luid press~lre Pml thereinto, which cooperate with brakes (not ~hown) of front wheels 22 of a motor vehicle, ;
while the rear fluid line 18 i~ connected to the control device, generally deRignated by the reference numeral -24, to feed the fluid pres~ure Pm2 thereinto and is conllected from the control device 24 through a fluid line 26 to rear wheel cylinders 28 coop~rating with brakeY (not shown) of rear wheels 30 of the vehicle.
The front and rear braking circuit~. 16 and 18 are further connected through branch lines 34 and 36 to the conirol device 24 to feed the fluid pre~sures Pml and Pm2 thereinto~ respectively. The control valve 24 is mo~nted on the body (not shown) of the vehicle to have its axi~ 38 inclined at an angle of e from the hori-zontal plane 40 so that the forward end portion of the ~
control valve 24 i.~ positioned above the rearward end ~ ;
portion thereof.
Referring to Fig. 3 of the drawings, a detailed 5~
construction of the braking pressure control valve 24 according to the invention is shown. The control valve 24 comprises a housing 42 formed in its front portion 43 with a fi.rst cavity 44 and inletand outletports46and 48.The inletand outletports46and48 .;
are connected respectively to the second fluid line 18 and the . ~.
fluid line 26. An annular sealing member or valve seat 50 such as a lip type seal is fixedly attached to a wall defining the ;
cavity 44 and divides the cavity 44 into an inlet or first ~ .
chamber 52 and a second or outlet chamber 54 into which the inlet .:
and outlet ports 46 and 48 open, respectively. The annular .
sealing member or valve seat 50 has formed therethrough an aperture 56. A plunger 58 extends through the aper-ture 56 and is axially movable in the first and second chambers 52 and 54. The ~.
aperture 56 provides an annular clearance between the annular sealing member 50 and the plunger 58 to provide fluid communica~
tion between the first and second chambers 52 and 54. A plug . .~ .
member 60 is fi.rmly fitted in a bore 61 formed in the forward end portion 62 of the housing 42 and closes the forward end .
portion 62. The plug member 60 has formed therein an inlet port 64 connected to the branch line 34 of the front braking circuit 16, and a bore 65 communicating witll the inlet port 64. The plunger 58 has a stem portion 66 located in the first .;
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chamber 52, an annular projection or land 68 having a cxoss sectional area of Al, and forward and rearward end portions 70 and 72 having effective surface areas of A2 and A3, respectively, both of which can be smaller than Al as shown in Fig. 3. The annular projection 63 is located in the second chamber 54 and is engageable with the annular sealing member or valve seat 50 to obstruct fluid communication between the first and second chambers 52 and 54. The forward end portion 70 is connected to the annular projection 68 and is slidably supported in an aperture 74 formed through a front end wall 76 of the cavity 44 and extends into the bore 65 of the closure member 60 from the aperture 74. The bore 65 is sealed from the second chamber 54 by a seal member 78. The -rearward end portion 72 is connected to the s-tem portion 66 and is slidably supported in an aperture 80 formed through a rear end wall 82 of the cavity 44. The rear end portion 72 is formed therein with a blind bore 84 in which a push rod 86 is received.
The housing 42 further has a second cavity 88 formed in its mid portion 89, and two opposite bores 90 and 92 formed in opposite end walls 94 and 96 of the cavity 88 and both opening into the cavity 88. Two pistons 98 and 100 are slidably fitted in the bores 90 and 92, respectively. The push rod 86 extends from ., ~' '.
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the bore 84 of the plunger 58 into the bore 90 and engages the plllnger seat 98. A spring seat 102 is slidably fitted in the cavity 88 arld i3 in abutting engagement with the end wall 96 and/or the pi.ston 100.
An inner compression spring 104 is located between the p].utlger seat 98 and the spring ~eat 102 -to urge these memhers in opposite directions. An outer compres3ion ~: :
spring 106 is located between the end wall 94 and the ~
spring seat 102 to urge the latter against the piston : :
]0 100 and/or the snd wall 96. The piston 100 has a cross sectional area of A4. The bore 90 i9 sealed from the first chamber 52 by a seal member 107. A fluid chamber 108 ls defined in the bore 92 between the piston 100 and an end wall 110 of the bore 92.
The housing 42 further ha~ a third cavity 112 and a bore 114 which are formed in it~ rear end portion 116, and a bore 118 formed in an end wall 120 of the cavity 112. A ball member 122 is rotatably or rollably fitted in the cavity 112. A valve seat member 124 is ~20 firmly fitted in the bore 118 and has formed there- ' through an aperture 126 opening into -the cavity 112 4 p ~ U~6Q ~ Q
;~ and communicating with the~fluid chamber 108 through :
a passage 128. The ball member 122 serves as a valve which is responsive to a predetermined deceleration ~
or inertia force to move to the valve seat 124 and to ~ :
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engage the same to close the inlet poxt 126 to the power or fluid chamber 108. A plurality of gxooVes 130 are formed in a wall defining the cavity 112 and surrounding -the ball member 122 and extends axially of the housing 42. ~ plug member 132 is threaded in the bore 114 to close the rear end portion 116 of the housing 42 and is formed therein with a bore 13~ opening lnto the cavity 112 and an inlet port 136 communicating with the bore 134 through an orifice 137 and connected to the branch line 36 of the rear ~.
braking circuit 18. A member 138 for supporting the ball member 122 i5 press fitted in the bore 134 and is formed in its circumferential surface 139 with a plurality of axial grooves 140 which communicate with the grooves 130 and with the inlet port 136.
The ball support member 138 is not formed with an ~-aperture penetrating from its outer end surface 142 to its inner ~:
end surface 144 so that the flow of the fluid pressure Pm2 from the inlet port 136 is prevented from stri~ing the ball member 122 and from exerting thereon a thrust which moves the ball member 122 toward the valve seat 124 to have a bad influence upon the admission of the fluid pressure Pm2 into the fluid chamber 108 and to speed the ball ~ember 122 moving to the valve seat 124 in response to a predetermined deceleration r~n~ ~ The ~upport member 138 serve~ as barrier or bafrle ~
wllich causes the flow of the fluid pressure Pm2 from the inlet port 136 to diverge toward the peripheral edge of the support member 138 or the internal circumferential wall of the bore 134 alon$ the outer end surface 142 and to pass through the grooves 140 and 130 to the inlet port 126.
The orifice 137 serves as delay means which callses variation in the fluid pre~sure Pm2 to transmit to the fluid chamber 108 with a suitable time lag to cause the pressure of fluid in the fluid chamber lOo to increase at a predetermined rate irrespective of ~he rate of increase ~n the fluid pressure Pm2. This is to prevent the pressure of fluid in the fluid chamber 108 from being varied in accordance with the rate of increase in the fluid pressure Pm2 when the ball member 122 moves to the valve seat 124 to close ~;
the inlet port 126 in response to the predetermined deceleration ~.
~ig. 4 is a graph illustratins on orthogonal coordinates the relationship bstween the pressure of flllid in the fluid chamber 108 and the rate of increa~e in the fluid pressure Pm2 under several conditions wl~en the ball valve 122 clo~es the inlet port 126, ' ~ .
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wllich relationship re~ults from an experiment effecte~
on the control device 24 shown in Fig. 3 without vary-ing the vehicle weight. In the graph of ~ig. 4, the nxis o~` ordillate irldicates the pres~ure of fl.uid in 5 the fluid chamber 108, while the axi~ of abscissa indicates the rate of increase in the fluid pre~ure Pm2, that i~, the rate of depression of the brake :~
pedal 14. As is apparent from the graph of ~ig. 4, the pressure of fluid in the fluid chamber lOo recti-linearly increaqes mos~ greatly with increase in the rate of lncrea~e in the fluid presqure Pm2 as compared with the cases of other conditions when no re~triction is provided in pas~age means of the fluid pressure Pm2 to the fluid chamber 108, as shown by the refer-ence numeral h in Fig. 4. The pressure of fluid in .thetfluld chamber 108, when a re~triction such as the -~
orifice 137 is provided in the pass~ge means, reduce~
with increase in the rate of increa~e in the fluid pressure Pm2 and with decrea~e in the cross sectional - 20 area or diameter of the restriction since the rate of il~crease in the pressure of fluid in the fluid chamber :l0~3 is reduced by the restriction w ~ the ball valve ~-~ 6~C~63 12~ =4~ ~ the valve seat 124. The rates of in-creases in the fluid pre~ure Pm2 are divided into three ran~e4 of ordinary, rapid and impo~sibly rapid .. '~ .
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braking oper~tions as ~hown in Fig. 4. AltholJgh it i~ best to u~e 0.4 millimeter as the diameter of the ori~`ice 137 among the diameters within the range of 0.4 to ().~ mill~meter as shown in Fig. l~, it i8 desirable to u.Ye A ~iameter within the range of o.6 to o.8 milli-meter. This i8 becauYe, when the diameter of the restriction i~ less than o.6 millimeter, the clogging or choking_up of the restriction is apt to occur and a hole cannot be formed by a drill and is compelled to be formed by mean~ ~uch as an electrospark machinery which re~ults in reduction in productivity. It is per~itted to select an ori~ice of a diameter within the range of o.6 to o.8 millimeter ~ince the pressure of I`luid confirmed in the fluid chamber 108 is not largely varied by the rate of ~ncrea~e in the fluid pressure Pm2 within the range of ordin~ry braking opera-tiGn, a~ shown by the hatching in Fig. 4. Also, since the pre~Yure of fluid confined in the fluid chamber 108 tends to reduce at the rate o~ increaYe in the fluid pressure Pmz within the range of rapid braking oper-ation, the output fluld pressure fed for the rear wl~eels is reduced to make it impo3sible to lock the rear wheels.
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The braking pressure control device 24 thus far described is operated as follows;
When the brake pedal 14 is depressed, the master cyllnder 12 delivers hydraulic fluid pressures Pml and Pm2 into , the front and rear braking circuits 16 and 18. The fluid pressure Pml is fed into the front wheel cylinders 20 and through the inlet port 64 into the bore 65 of the pressure control valve 24.
The fluld pressure Pm2 is fed as an input fluid pressure into the first chamber 52 of the pressure control valve 24 through the inlet port 46 and is then delivered into the second chamber 54 through the aperture 56 of the annular sealing member 50 as an output hydraulic fluid pressure Pr. The outlet fluid pressure Pr in the second chamber 54 is fed into the rear wheel cylinders 28 through the outlet port 48. The fluid pressure Pm2 is also fed into the flUid chamber 108 of the pressure control valve 24 through the inlet port 136. The grooves 140 and 130, and the aperture 126 of the seat member 124.
When the input fluid pressure Pm is less than a critical fluid pressure Ps, the output fluid pressure Pr in the second chamber 54 is equal to the input fluid pressure Pm, that is, Pr = Pm Eq. 1 - ''~
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In this condition, the fluid pressure Pm in the bore 65 exerts on the forward end portion 70 of the plunger 58 a force Pm x A3 exceeds the force Fl of the inner spring 104 to move the plunger 58 into a closed position in which the land or annular projection 68 engages or is pressed against the annular sealing member 50 to obstruct fluid communication between the first and second chambers 52 and 54. At this time, the following relation is obtained:
; Ps x A3 = Fl Accordingly, the critical fluid pressure Ps is expressed as 1/ 3 Eq. 2 In this instance, since the displacement of the plunger 58 is extremely small, an increase in the force of the spring 104 is so little as to be neglected.
When the input fluid pressure Pm subsequently further Y
increases, the fluid pressure Pm in the first chamber 52 urges the plunger 58 into an open position to unseat the annular pro- -jection 68 from the annular . ~
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sea.ling member 50. When the ~nnular projection 68 is un3eated from the annular se~ling member 50, the fluid pressure Pm in the firqt chamber 52 i~ allowed to flow into the ~econd chamber 54 to cause an increa~e in the output f`luid pre~ure Pr. At this time, i.e., when `
Pm ~ PB, the following equilibrium equation i~
establi~hed:
PmA2 + Pr(A1 - A~) = Pm (A1 A3) Eq. 3 Accordingly, the output fluid pre~3ure Pr iq expres~ed a3 Pr = 1 3 a Pm ~ I Eq. 4 The output fluid pres~ure Pr delivered from the outlet port 48 under the control of the pres~ure control valve 24 is given by either of the Equation~
:l and 4 in accordance with the input fluid pres~ure Pm. Thus, when the input fluid pre3sure P~ increaYe~
from ~ero, the output fluid pre~ure Pr increa~eq at t~le ~ame rate a9 the input fluid presYure Pm until the input fluid pressure Pm reache3 the criticRl fluid pressure Ps, a~ shown in Fig. 5 of the drawing~. ;
:- ;
Whetl the input fluid pre3sure Pm increases above the critical fluid pressure Ps, the output fluid pressure .`
I'r increases at the rate of Cwi~erein m = (A1 - A3 - ~2)/ (Al ~ A2) ~ which i8 ~al.l.er than the rate of increa~e in the input fluid pressure Pm, a~ ~hown in ~ig. 5.
On the other hand, when the braking force B on the wheel~ increa~es with increase in the fluid pres-~ure Pm from the master cylinder 12~ the ratio of therot~-n-o~ deceleration ~ ersu~ ~ gravitational acceler~tion g al~o increases. This deceleration ~$~ ratio a/g 19 equal to the ratio of the braking force B ver~u~ the overall weight W of the motor vehicle as follow~:
g = W Eq~ 5 The brakin~ force B is proportional to the master cylinder fluid pressure Pm a~ follow~:
`, ., ~ .
B - CPm (wherein C i~ a con~tant) Eq. 6 ''"
When the deceleratlon ~eatæ ratio a/g reache3 .
a predetermlned value of (a/g)~ which is a functlon ` ~ .
f(~) of the angle ~ of inclination o~ the pres~ure A ~7 6n~
control valve 24, the ball valve~l22 rolls f~rwardly ~S~4'~
in re~ponse to the predetermined decelerat.ion ~e to ~e~t on the v~lve seat 124 to clo~e the inlet port 126 to i~olAte the fluid chamber 108 from the inlet port 136. 'rhus~ even if the fluid pre~ure Pm ~ubseguently lncrea~es, the fluid pres~ure in the fluid chAmber 108 i~ maintained at a fluid pre~sure Pg which is equal to the fluid pres~ure Pm at the moment when the inlet ~ 6~3 6 i2 port 126 h~s been clo~ed by the b~ll valve~l22. The fluid pres~ure Pg is expres~ed from the E4s. 5 and 6 and the Eq. 7 [(a/g)0 = f(Q)] a~
g C f(o) Eq. 8 At thi~ time, from the condition of equilibriu~ of the piston 100 and the Eq. 8, the following equation i~ obtained:
1 2 g A4 = C A~W Eq. 9 where Ez i~ the force of the outer spring 106.
rhe force~ ~1 and F2 of the inner ~nd outer ~pring~
104 ~nd 106 ~re expre~sed re~pectiv~ly ~9 the ~ums of the pre~et or initi~l loads f1 and f2 of the ~prings 104 ~nd 106 and the products of the amount~ of de-flection or shrinkage of the spring~ 104 and 106 . - 23 _ 4~
by a compressive force from the piston 100 and the spring constant~ Kl and K2 of the springs 104 and 106.
In this instance, ~ince the fimounts of deflection of the ~pring~ 104 and 106 are equal to each oth~r, the following equation i~ obtalned:
K :
F f + 2 (F ) Eq. 10 From the Eqs. 9 and 10, the force Fl of the spring~ 104 is obtained as C A4W ~ (f2 ~ K fl) 1 ~ Eq. 11 1 + ~
Substitution of the Eq. 11 into the Eq~D 2 and 4 result~
in . .
C A4W ~ (f2 - 2 f ) 1 Eq. 12 A3 (1 + K ) When Pm ~ Ps . : : , . .
. . : : :
. . . . : , . :
, - , `:
F
= mPm +
(A1 A2) K~
It i9 apparent from the Eq. 12 th~t by selecting the variable~ in the Eq. 12 in A mAnner to make the value of (f2 ~ f1~K2/K~) positive, the critical fluid pres*ure Ps increase~ at a rate greater than that of increase in the vehicle weight W ~hen the vehicle weight increaYes, aY shown in Fi~. 6 of the drawing~, As a re~ult, the characteristics of the di~tribution of` the braking forceY to the front and rear wheel~
approximate to the ideal characteri~tic~ curves a1, ; a2, ...... of Fig. 1 in accordance with increa~e~
the vehicle weight W.
, ~ ~ Since the fluid pres~ure Pm2 is fed into the ~fluid chamber 108 through the oriflce 137, the pres-sllre of fluid confined in the fluld chamber 108 i8 maintained at a predetermined value irre~pective of or i~ sllghtly varled in accordance with the rate of : increase in the fluid pres~ure Pm2 when the ball valve W~6h~6n ~122 closes the inlet port 126. AY a re~ult, the pre~- ;
sure control device 24 can control the crirical fluid .
5'~
pre~sure P~ to a predetermined value in ~ccordance with var:i.ation in the vehicle weight to perform its de~ired funct.ion accurately.
I.n the event of the failure of the fluid pres~ure l'ml in the fir~t fluid circuit 16, since PmA2 = O in the Eq. 3, the following equation iq obtained: :
Pr(A1 A2) = Pm(A1 - A3) Accordingly, the output fluid pressure Pr is obtained a~
,1 3 Pr Al-A2 Al-A2 :
A~_A 2 = m '>m In thi~ in~tance, between the braking force B on the wheels and the inp~t fluid pres~ure P~ the followin$
relation is pro~ided: ~:
B = C'P~
where C'< C. Ilence, the force Fl, of the spring 101~
iq expre9se~ a~ :
- 26 _ .
. .
, ~sf~
C ~ W ~ ( f 2 ~ K 1 f 1 ) 1 + K
When the i nput fluid pressure Pm i9 at a critical fluid pressure Ps', the following equation i~ obtained:
`,'' , ps ' (A3 - A2) =
Accord:ingly, the critical fluid pressure Ps' i~
obtalned as Cl A4W ~ (f2 ~ ~ f1) ~
( ~!\3 ~ A2 ) ( 1 ~ K2 ~ `
where Ps.' > I's.
Accordi.tlgly, it i~ apparent that the critical fluid pressure l)s~ is increased to a con~iderably high value which provides a braking force so great a~ to com- ~ :
pellsate the rai:L~Jre of the i`luid pres~ure Pml in the first f`Luid circuit 16. ~:
_ 27 -,. ~ "
, ,: . ' ' ~, . . . . . .
.. . . . ..
a~
to cause the rear portion of the motor vehicle to swing tran~versely to the longitudinal direction thereof.
Accordingly, in order to assure and increase the safety arld st~ll)i]ity of the vehicle during its braking oper-atiorl, it is neceffsary to effect the di~tribution ofthe braking forces to lock the front and rear wheels concurrently.
When the vehicle i~ braked, the so-called nose-dive phenomenon takes place in which the vehicle weight app]ied on the front wheels increases and the vehicle weight applied on the rear wheels decreases. According-ly, it i8 necessary for concurrently locking the front and rear wheel3 to distribute to the front wheel~ a braking force greater than a braking force distributed L5 to the rear wheel~. It i9 also nece~ary that the distribution of the braking force~ to the front and rear wheel~ i9 varied in accordance with variations in the vehicle weight. Thu~, ideal characteri~tics of ~`
the distribution of the braking force~ to the front and rear wheels, when are lllustrated on oblique coordinates having the axe~ of abscis.~a and ordinate indicating respectively thereon the ratios (deceleration rate ratios) Bf/W and Br/W of the braking forces Bf and Br on the front and rear wheels versus the vehicle z5 weight W, are e~pre~sed by a curve having tangents the :
' , :, ' -'' ' ' . '': ' . '" ' . ' - , . ~; . ' ' ,'.' . .
~5~
ar~gles of inclination of which are relatively large wi.thin a range of the origin to a certain value and are relatively small outside the range. I`urthermore, ~he ideal charac-teristics of the braking force dis- ~ :
~rihllt:ion are expre~sed by different curves in accordance with the vehicle weight and th~ heavier the vehJ.cle weight is, the higher the ideal charac-teristic~ curve i8 located on the coordinates. .:
It is accordin$1y nece~sary for providing the distribution of the braking forces which is clo.se to the ideal characteri~tios curve to feed to the rear wheel cylinders a fluid pres~ure increasing at a rate . :~
sma:l.l.er than that of increa~e in a fluid pre~sure fed .
to the front wheel cylinders or at a rate of zero when ~
the fluid pre~sure fed to the front wheel cylinders exceeds a predetermlned fluid presqure. As an expedient for solving the problem, a limiting valve, proportioning valve or G valve was employed to di~pose ~-as a braking pressure control valve in a rear braking .
circuit leading to the rear wheel cylinder~. The limiting valve generate~ an output fluid pres~ure increa~ing at a rate of zero when an input fluid pre~sure exceeds a critical fluid pre~qure. The proportioning valve generate~ an output fluid pr~ssure increa~ing at a rate lower than that of increase in an - 4 - `
., j., .: '':, . . . . . .
, input fluid pressure when the input fluid pressure exceeds a critical fluid pressure, The G valve emits an output fluid pressure increasing at a rate less than an input fluid pressure when a predetermined rate of deceleration is attained. ~lowever, the output fluid pressure emitted by these valves merely carried out the distribu-tion of the braking forces approximating to a single ideal characteristics curve which accordingly, corresponds to a predetermined vehicle weight and, when the vehicle weight is varied, effected a distribution of the braking forces which largely deviated from an ideal characteristics curve correspond-ing to the vehicle weight varied.
On the other hand, most motor vehicles are in recent years provided with a hydraulic braking system of the tandem type which comprises front and rear braking circuits leading from a master cylinder to the front and rear wheel cylinders, _~
respectively separately. However, the above-mentioned braking pressure control valve, when disposed in the rear braking circuit, emits in the event of the failure of the fluid pressure in the ~ f front braking circuit the same output fluid pressure as in the event of no such failure. This resulted in the deficiency of the braking force.
Thus, a braking ~' :
" ' ' ...
'~
, . . . . ,, , . ' .
.. . : , : .: ' ::'., ~
.. , .
.
.
. ~ . . .
~5~
fluid pressure control device has been proposed which comprises, in addition to valve means serving as a proportioning or limiting valve, an lnertia responsive type valve or "G" valve for controlling the valve means to vary the critical fluid pressure in accordance with variation in the vehicle weight to generate an ;
output fluid pressure which provides the distributions of the ~: :
braking forces to the front and rear wheels which approximate to the ideal charac-teristics curves corresponding to the vehicle weight varied. The control means comprises a piston biased to urge the valve means by a master cylinder fluid pressure fed into i :
a power or fluid chamber and a ball valve responsive to a prede- : -termined deceleration to move to a valve seat to close an inlet port to the fluid chamber to maintain the pressure of fluid there-in at a predetermined value. The valve means is also biased by the fluid pressure in the front braking circuit so that in the event of the failure of the fluid pressure the critical fluid pressure is increased to generate the output fluid pressure ~`
sufficiently high to compensate ~he deficiency of the braking . force.
~owever, this braking fluid pressure control device has suffered from the drawback that the pressure of fluid in the fluid chamber is varied in accordance with ~-~': ' '' ' .
' ~S'~2~
the rate of increase in the master cylinder fluid pressure to make it impossible to control -the critical fluid pressure to a predetermined value in accordance with variation in the vehicle weight as the ball moves to the valve sea-t and closes the inlet por-t of the fluid chamber in response to the predetermined deceleration notwithstanding that at this time it is necessary for controlling the critical fluid pressure to the predetermined value in accordance with variation in the vehicle weight that the :~.
pressure of fluid in the fluid chamber be at a predetermined 10 value independently of the rate of increase in the master cylinder .
fluid pressure if the vehicle weight remains unvaried. This is because, as the ball moves to the valve seat in response to the predetermined deceleration, variation in the master cylinder fluid pressure is transmitted to the fluid chamber until the ball : reaches the valve seat to close the inlet port.
It is, therefore, an object of the invention to provide an improved braking fluid pressure control device in which the `
pressure, or the rate of increase in the pressure, of fluid in the fluid chamber is maintained at a predetermined value indepen-dently of the rate of :
.;
' , - :; ' . , : .
increase in the master cylinder fluid pressure when the bal~ valve moves to the valve seat and closes the inlet port to the fluid :
chamber in response to a predetermined deceleration by providing ~ .
in passage means leading to the inlet port for passing the master cylinder fluid pressure thereto delay means for transmitting variation in the master cylinder fluid pressure to the fluid chamber with a suitable time lag to prevent or reduce the pressure ~ -of a fluid in the fluid chamber being varied in accordance with the rate of increase in the master cylinder fluid pressure until the ball abuts against the valve seat.
Accordingly the present invention provides a braking system for a wheeled vehicle having at least one front wheel and at least one rear wheel, said system comprising manually operable :~
master cylinder means for generating first and second variable hydraulic pressures; a front brake for the at least one front wheel; a rear brake for the at least one rear wheel; first fluid conduit means fluidly interconnecting said master cylinder and said.front brake for transmitting said first variable hydraulic pressure to said front brake; a fluid pressure control device which has an inlet chamber, an outlet chamber; a passage providing .
communication between said inlet and outlet chambers; a valve seat in the form of an annular sealing member arranged within said :
passage; a pressure-responsive plunger having a valve member in the form of an annular projection, said annular projection being -cooperative with said annular sealing member; chamber means for biasing said pressure responsive plunger in a direction tending to ~ .
move said annular projection toward said annular sealing member in response to said first variable hydraulic pressure; means for biasing said pres~sure responsive plunger in a direction tending to move said annular projection away from said annular sealing member;
means having a power chamber for increasing the preload of said biasing means in response to hydraulic pressure in said power .:
, . . , :, . ~ , ~. .
.
~ chamber; means defining a ball valve chamber~`and a ball valv~e .. . ..
passage providing communication between said ball valve chamber and said power chamber; and an inertia ball valve disposed in said ' ball valve chamber to close said ball valve passage in response to a predetermined magnitude of deceleration of the vehicle; second conduit means fluidly interconnecting said master cylinder means and said inlet chamber for transmitting said second variable hydraulic pressure to said inlet chamber; third conduit means fluidly interconnecting said outlet chamber to said rear brake for transmitting the hydraulic pressure prevailing in said outlet chamber to said rear brake; and delay means fluidly interconnecting said master cylinder means and said ball valve chamber for restric-ting hydraulic fluid flow transmission from said master cylinder means to said ball valve chamber so that transmission of said second hydraulic variable pressure to said ball valve chamber is delayed.
The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:
Fig. 1 i9 a graphic representation of the ideal charac-teristics curves of the distribution of the braking forces to the front and rear wheels;
Fig. 2 is a schematic view of a motor vehicle hydraulic braking system incorporating thereinto a braking fluld pressure control device according to the invention;
.
' Y - 8a -(95~
F`ig. 3 is a schematic cross sectional view of a pro.(`erred embodiment of a braking fluid pressure contro:L device according to the invention;
~ ig. 4 is a graphic representation of the re.Lationship between the pressure of fluid in a fluid chamber closed by a ball valve and the rate of increase in a master cylinder fluid pre~ure;
Fig. 5 is a graphic repre~entation of the relation-ship between the input fluid pre~sure and the output i`l.uid pressure of the braking fluid pressure control device shown in Fig. 3; and ~ ig. 6 i8 a graphic representation of the relation-~hip between the critical fluid pressure of the brakins f:luid pressure control device shown in Fig. 3 and the vehicle weight.
Referring to Fig. 1 of the drawings, the ideal characteristics curves al and a2 as per the introduction of the specification of the di~tibution3 of the braking force~ to thc front and rear wheels are illustrated on oblique coordin~te~ having the axes of absci~sa and ordinate indicating respectively thereon the ratios (deceleration rate ratios~ Bf/W and Br~W of the braking f`orces Bf and Br on the front and rear wheels versus tlle vehicle weight W. The curves al and a2 indicate the ideal characteristics at the time when the weight : .
_ 9 _ ~
. . , , .
of tl-e vehicle iq Wl (no load) and W2 (the vehicle e.lrrio~ a load), re~pective]y. The general relation-911ip between the ideal characterlstics curve~ and the vehlcle weight is such that the heavier the vehicle weigllt is, the higher or the more the ideal charac-teri~tic~ curve is po~itioned or extends upwardly qteeply from the origin O in the graph of F`ig. -L.
As is apparent from the graph, the angle of in-clinatlon of a tangent of each of the curves al and a2 i~ relatively large within a range of the origin O to a certain value and i~ relatively small out~ide the range. In the graph of Fig. 1, there is also illustrated the characteriqtics line3 bl and b2 of the distributionq of the braking forceq to the front and rear wheels wllich distributions are pro~ided to approximate re3pectively ~to the ideal characteristics cur~es al and a2 by a motor vehicle hydraulic braking ~ystem incorporating therein a braking fluid pre3~ure control device according to the invention.
- Referring to Fig. 2 of the drawing~, there i.q -~hown a motor vehicle hydraulic braking ~y~tem incor-porating therein a braking fluid pre~sure control device or valve according to the invention. The hydraulic -braking ~qystem, generally de~ignated by the referenc~
~ D~LLy ~
numeral 10, include~ a ma3ter cylinder 12topera~ed ~P~m -- 10 _ ~5;~
a brake pedal 1/1. First and ~econd hydraulic f`luid circllits lf~ nnd 18 lead from the master cylinder 12 to receive fluid pres~ures Pml and Pm2 therefrom, re~pectively. The fluid pre3~ures Pml and Pm2 are equal to each other and are often referred to a~q the fluid pressure Pm hereinafter. The front f]uid line 16 is connected to front wheel cylinders 20 to feed th~ f`luid press~lre Pml thereinto, which cooperate with brakes (not ~hown) of front wheels 22 of a motor vehicle, ;
while the rear fluid line 18 i~ connected to the control device, generally deRignated by the reference numeral -24, to feed the fluid pres~ure Pm2 thereinto and is conllected from the control device 24 through a fluid line 26 to rear wheel cylinders 28 coop~rating with brakeY (not shown) of rear wheels 30 of the vehicle.
The front and rear braking circuit~. 16 and 18 are further connected through branch lines 34 and 36 to the conirol device 24 to feed the fluid pre~sures Pml and Pm2 thereinto~ respectively. The control valve 24 is mo~nted on the body (not shown) of the vehicle to have its axi~ 38 inclined at an angle of e from the hori-zontal plane 40 so that the forward end portion of the ~
control valve 24 i.~ positioned above the rearward end ~ ;
portion thereof.
Referring to Fig. 3 of the drawings, a detailed 5~
construction of the braking pressure control valve 24 according to the invention is shown. The control valve 24 comprises a housing 42 formed in its front portion 43 with a fi.rst cavity 44 and inletand outletports46and 48.The inletand outletports46and48 .;
are connected respectively to the second fluid line 18 and the . ~.
fluid line 26. An annular sealing member or valve seat 50 such as a lip type seal is fixedly attached to a wall defining the ;
cavity 44 and divides the cavity 44 into an inlet or first ~ .
chamber 52 and a second or outlet chamber 54 into which the inlet .:
and outlet ports 46 and 48 open, respectively. The annular .
sealing member or valve seat 50 has formed therethrough an aperture 56. A plunger 58 extends through the aper-ture 56 and is axially movable in the first and second chambers 52 and 54. The ~.
aperture 56 provides an annular clearance between the annular sealing member 50 and the plunger 58 to provide fluid communica~
tion between the first and second chambers 52 and 54. A plug . .~ .
member 60 is fi.rmly fitted in a bore 61 formed in the forward end portion 62 of the housing 42 and closes the forward end .
portion 62. The plug member 60 has formed therein an inlet port 64 connected to the branch line 34 of the front braking circuit 16, and a bore 65 communicating witll the inlet port 64. The plunger 58 has a stem portion 66 located in the first .;
: . ' . . --12- ~
chamber 52, an annular projection or land 68 having a cxoss sectional area of Al, and forward and rearward end portions 70 and 72 having effective surface areas of A2 and A3, respectively, both of which can be smaller than Al as shown in Fig. 3. The annular projection 63 is located in the second chamber 54 and is engageable with the annular sealing member or valve seat 50 to obstruct fluid communication between the first and second chambers 52 and 54. The forward end portion 70 is connected to the annular projection 68 and is slidably supported in an aperture 74 formed through a front end wall 76 of the cavity 44 and extends into the bore 65 of the closure member 60 from the aperture 74. The bore 65 is sealed from the second chamber 54 by a seal member 78. The -rearward end portion 72 is connected to the s-tem portion 66 and is slidably supported in an aperture 80 formed through a rear end wall 82 of the cavity 44. The rear end portion 72 is formed therein with a blind bore 84 in which a push rod 86 is received.
The housing 42 further has a second cavity 88 formed in its mid portion 89, and two opposite bores 90 and 92 formed in opposite end walls 94 and 96 of the cavity 88 and both opening into the cavity 88. Two pistons 98 and 100 are slidably fitted in the bores 90 and 92, respectively. The push rod 86 extends from ., ~' '.
'~ J~
'' ';~ ' ` ~:
the bore 84 of the plunger 58 into the bore 90 and engages the plllnger seat 98. A spring seat 102 is slidably fitted in the cavity 88 arld i3 in abutting engagement with the end wall 96 and/or the pi.ston 100.
An inner compression spring 104 is located between the p].utlger seat 98 and the spring ~eat 102 -to urge these memhers in opposite directions. An outer compres3ion ~: :
spring 106 is located between the end wall 94 and the ~
spring seat 102 to urge the latter against the piston : :
]0 100 and/or the snd wall 96. The piston 100 has a cross sectional area of A4. The bore 90 i9 sealed from the first chamber 52 by a seal member 107. A fluid chamber 108 ls defined in the bore 92 between the piston 100 and an end wall 110 of the bore 92.
The housing 42 further ha~ a third cavity 112 and a bore 114 which are formed in it~ rear end portion 116, and a bore 118 formed in an end wall 120 of the cavity 112. A ball member 122 is rotatably or rollably fitted in the cavity 112. A valve seat member 124 is ~20 firmly fitted in the bore 118 and has formed there- ' through an aperture 126 opening into -the cavity 112 4 p ~ U~6Q ~ Q
;~ and communicating with the~fluid chamber 108 through :
a passage 128. The ball member 122 serves as a valve which is responsive to a predetermined deceleration ~
or inertia force to move to the valve seat 124 and to ~ :
'.
.
engage the same to close the inlet poxt 126 to the power or fluid chamber 108. A plurality of gxooVes 130 are formed in a wall defining the cavity 112 and surrounding -the ball member 122 and extends axially of the housing 42. ~ plug member 132 is threaded in the bore 114 to close the rear end portion 116 of the housing 42 and is formed therein with a bore 13~ opening lnto the cavity 112 and an inlet port 136 communicating with the bore 134 through an orifice 137 and connected to the branch line 36 of the rear ~.
braking circuit 18. A member 138 for supporting the ball member 122 i5 press fitted in the bore 134 and is formed in its circumferential surface 139 with a plurality of axial grooves 140 which communicate with the grooves 130 and with the inlet port 136.
The ball support member 138 is not formed with an ~-aperture penetrating from its outer end surface 142 to its inner ~:
end surface 144 so that the flow of the fluid pressure Pm2 from the inlet port 136 is prevented from stri~ing the ball member 122 and from exerting thereon a thrust which moves the ball member 122 toward the valve seat 124 to have a bad influence upon the admission of the fluid pressure Pm2 into the fluid chamber 108 and to speed the ball ~ember 122 moving to the valve seat 124 in response to a predetermined deceleration r~n~ ~ The ~upport member 138 serve~ as barrier or bafrle ~
wllich causes the flow of the fluid pressure Pm2 from the inlet port 136 to diverge toward the peripheral edge of the support member 138 or the internal circumferential wall of the bore 134 alon$ the outer end surface 142 and to pass through the grooves 140 and 130 to the inlet port 126.
The orifice 137 serves as delay means which callses variation in the fluid pre~sure Pm2 to transmit to the fluid chamber 108 with a suitable time lag to cause the pressure of fluid in the fluid chamber lOo to increase at a predetermined rate irrespective of ~he rate of increase ~n the fluid pressure Pm2. This is to prevent the pressure of fluid in the fluid chamber 108 from being varied in accordance with the rate of increase in the fluid pressure Pm2 when the ball member 122 moves to the valve seat 124 to close ~;
the inlet port 126 in response to the predetermined deceleration ~.
~ig. 4 is a graph illustratins on orthogonal coordinates the relationship bstween the pressure of flllid in the fluid chamber 108 and the rate of increa~e in the fluid pressure Pm2 under several conditions wl~en the ball valve 122 clo~es the inlet port 126, ' ~ .
.
'' : ; .. : , . :
wllich relationship re~ults from an experiment effecte~
on the control device 24 shown in Fig. 3 without vary-ing the vehicle weight. In the graph of ~ig. 4, the nxis o~` ordillate irldicates the pres~ure of fl.uid in 5 the fluid chamber 108, while the axi~ of abscissa indicates the rate of increase in the fluid pre~ure Pm2, that i~, the rate of depression of the brake :~
pedal 14. As is apparent from the graph of ~ig. 4, the pressure of fluid in the fluid chamber lOo recti-linearly increaqes mos~ greatly with increase in the rate of lncrea~e in the fluid presqure Pm2 as compared with the cases of other conditions when no re~triction is provided in pas~age means of the fluid pressure Pm2 to the fluid chamber 108, as shown by the refer-ence numeral h in Fig. 4. The pressure of fluid in .thetfluld chamber 108, when a re~triction such as the -~
orifice 137 is provided in the pass~ge means, reduce~
with increase in the rate of increa~e in the fluid pressure Pm2 and with decrea~e in the cross sectional - 20 area or diameter of the restriction since the rate of il~crease in the pressure of fluid in the fluid chamber :l0~3 is reduced by the restriction w ~ the ball valve ~-~ 6~C~63 12~ =4~ ~ the valve seat 124. The rates of in-creases in the fluid pre~ure Pm2 are divided into three ran~e4 of ordinary, rapid and impo~sibly rapid .. '~ .
~5~4;~
braking oper~tions as ~hown in Fig. 4. AltholJgh it i~ best to u~e 0.4 millimeter as the diameter of the ori~`ice 137 among the diameters within the range of 0.4 to ().~ mill~meter as shown in Fig. l~, it i8 desirable to u.Ye A ~iameter within the range of o.6 to o.8 milli-meter. This i8 becauYe, when the diameter of the restriction i~ less than o.6 millimeter, the clogging or choking_up of the restriction is apt to occur and a hole cannot be formed by a drill and is compelled to be formed by mean~ ~uch as an electrospark machinery which re~ults in reduction in productivity. It is per~itted to select an ori~ice of a diameter within the range of o.6 to o.8 millimeter ~ince the pressure of I`luid confirmed in the fluid chamber 108 is not largely varied by the rate of ~ncrea~e in the fluid pressure Pm2 within the range of ordin~ry braking opera-tiGn, a~ shown by the hatching in Fig. 4. Also, since the pre~Yure of fluid confined in the fluid chamber 108 tends to reduce at the rate o~ increaYe in the fluid pressure Pmz within the range of rapid braking oper-ation, the output fluld pressure fed for the rear wl~eels is reduced to make it impo3sible to lock the rear wheels.
.
. :, . . . . . . . ..
. . .
, ', . .: . . , ~5~
.
The braking pressure control device 24 thus far described is operated as follows;
When the brake pedal 14 is depressed, the master cyllnder 12 delivers hydraulic fluid pressures Pml and Pm2 into , the front and rear braking circuits 16 and 18. The fluid pressure Pml is fed into the front wheel cylinders 20 and through the inlet port 64 into the bore 65 of the pressure control valve 24.
The fluld pressure Pm2 is fed as an input fluid pressure into the first chamber 52 of the pressure control valve 24 through the inlet port 46 and is then delivered into the second chamber 54 through the aperture 56 of the annular sealing member 50 as an output hydraulic fluid pressure Pr. The outlet fluid pressure Pr in the second chamber 54 is fed into the rear wheel cylinders 28 through the outlet port 48. The fluid pressure Pm2 is also fed into the flUid chamber 108 of the pressure control valve 24 through the inlet port 136. The grooves 140 and 130, and the aperture 126 of the seat member 124.
When the input fluid pressure Pm is less than a critical fluid pressure Ps, the output fluid pressure Pr in the second chamber 54 is equal to the input fluid pressure Pm, that is, Pr = Pm Eq. 1 - ''~
~ ~5'~
In this condition, the fluid pressure Pm in the bore 65 exerts on the forward end portion 70 of the plunger 58 a force Pm x A3 exceeds the force Fl of the inner spring 104 to move the plunger 58 into a closed position in which the land or annular projection 68 engages or is pressed against the annular sealing member 50 to obstruct fluid communication between the first and second chambers 52 and 54. At this time, the following relation is obtained:
; Ps x A3 = Fl Accordingly, the critical fluid pressure Ps is expressed as 1/ 3 Eq. 2 In this instance, since the displacement of the plunger 58 is extremely small, an increase in the force of the spring 104 is so little as to be neglected.
When the input fluid pressure Pm subsequently further Y
increases, the fluid pressure Pm in the first chamber 52 urges the plunger 58 into an open position to unseat the annular pro- -jection 68 from the annular . ~
.
.:
. .
-20- ::
sea.ling member 50. When the ~nnular projection 68 is un3eated from the annular se~ling member 50, the fluid pressure Pm in the firqt chamber 52 i~ allowed to flow into the ~econd chamber 54 to cause an increa~e in the output f`luid pre~ure Pr. At this time, i.e., when `
Pm ~ PB, the following equilibrium equation i~
establi~hed:
PmA2 + Pr(A1 - A~) = Pm (A1 A3) Eq. 3 Accordingly, the output fluid pre~3ure Pr iq expres~ed a3 Pr = 1 3 a Pm ~ I Eq. 4 The output fluid pres~ure Pr delivered from the outlet port 48 under the control of the pres~ure control valve 24 is given by either of the Equation~
:l and 4 in accordance with the input fluid pres~ure Pm. Thus, when the input fluid pre3sure P~ increaYe~
from ~ero, the output fluid pre~ure Pr increa~eq at t~le ~ame rate a9 the input fluid presYure Pm until the input fluid pressure Pm reache3 the criticRl fluid pressure Ps, a~ shown in Fig. 5 of the drawing~. ;
:- ;
Whetl the input fluid pre3sure Pm increases above the critical fluid pressure Ps, the output fluid pressure .`
I'r increases at the rate of Cwi~erein m = (A1 - A3 - ~2)/ (Al ~ A2) ~ which i8 ~al.l.er than the rate of increa~e in the input fluid pressure Pm, a~ ~hown in ~ig. 5.
On the other hand, when the braking force B on the wheel~ increa~es with increase in the fluid pres-~ure Pm from the master cylinder 12~ the ratio of therot~-n-o~ deceleration ~ ersu~ ~ gravitational acceler~tion g al~o increases. This deceleration ~$~ ratio a/g 19 equal to the ratio of the braking force B ver~u~ the overall weight W of the motor vehicle as follow~:
g = W Eq~ 5 The brakin~ force B is proportional to the master cylinder fluid pressure Pm a~ follow~:
`, ., ~ .
B - CPm (wherein C i~ a con~tant) Eq. 6 ''"
When the deceleratlon ~eatæ ratio a/g reache3 .
a predetermlned value of (a/g)~ which is a functlon ` ~ .
f(~) of the angle ~ of inclination o~ the pres~ure A ~7 6n~
control valve 24, the ball valve~l22 rolls f~rwardly ~S~4'~
in re~ponse to the predetermined decelerat.ion ~e to ~e~t on the v~lve seat 124 to clo~e the inlet port 126 to i~olAte the fluid chamber 108 from the inlet port 136. 'rhus~ even if the fluid pre~ure Pm ~ubseguently lncrea~es, the fluid pres~ure in the fluid chAmber 108 i~ maintained at a fluid pre~sure Pg which is equal to the fluid pres~ure Pm at the moment when the inlet ~ 6~3 6 i2 port 126 h~s been clo~ed by the b~ll valve~l22. The fluid pres~ure Pg is expres~ed from the E4s. 5 and 6 and the Eq. 7 [(a/g)0 = f(Q)] a~
g C f(o) Eq. 8 At thi~ time, from the condition of equilibriu~ of the piston 100 and the Eq. 8, the following equation i~ obtained:
1 2 g A4 = C A~W Eq. 9 where Ez i~ the force of the outer spring 106.
rhe force~ ~1 and F2 of the inner ~nd outer ~pring~
104 ~nd 106 ~re expre~sed re~pectiv~ly ~9 the ~ums of the pre~et or initi~l loads f1 and f2 of the ~prings 104 ~nd 106 and the products of the amount~ of de-flection or shrinkage of the spring~ 104 and 106 . - 23 _ 4~
by a compressive force from the piston 100 and the spring constant~ Kl and K2 of the springs 104 and 106.
In this instance, ~ince the fimounts of deflection of the ~pring~ 104 and 106 are equal to each oth~r, the following equation i~ obtalned:
K :
F f + 2 (F ) Eq. 10 From the Eqs. 9 and 10, the force Fl of the spring~ 104 is obtained as C A4W ~ (f2 ~ K fl) 1 ~ Eq. 11 1 + ~
Substitution of the Eq. 11 into the Eq~D 2 and 4 result~
in . .
C A4W ~ (f2 - 2 f ) 1 Eq. 12 A3 (1 + K ) When Pm ~ Ps . : : , . .
. . : : :
. . . . : , . :
, - , `:
F
= mPm +
(A1 A2) K~
It i9 apparent from the Eq. 12 th~t by selecting the variable~ in the Eq. 12 in A mAnner to make the value of (f2 ~ f1~K2/K~) positive, the critical fluid pres*ure Ps increase~ at a rate greater than that of increase in the vehicle weight W ~hen the vehicle weight increaYes, aY shown in Fi~. 6 of the drawing~, As a re~ult, the characteristics of the di~tribution of` the braking forceY to the front and rear wheel~
approximate to the ideal characteri~tic~ curves a1, ; a2, ...... of Fig. 1 in accordance with increa~e~
the vehicle weight W.
, ~ ~ Since the fluid pres~ure Pm2 is fed into the ~fluid chamber 108 through the oriflce 137, the pres-sllre of fluid confined in the fluld chamber 108 i8 maintained at a predetermined value irre~pective of or i~ sllghtly varled in accordance with the rate of : increase in the fluid pres~ure Pm2 when the ball valve W~6h~6n ~122 closes the inlet port 126. AY a re~ult, the pre~- ;
sure control device 24 can control the crirical fluid .
5'~
pre~sure P~ to a predetermined value in ~ccordance with var:i.ation in the vehicle weight to perform its de~ired funct.ion accurately.
I.n the event of the failure of the fluid pres~ure l'ml in the fir~t fluid circuit 16, since PmA2 = O in the Eq. 3, the following equation iq obtained: :
Pr(A1 A2) = Pm(A1 - A3) Accordingly, the output fluid pressure Pr is obtained a~
,1 3 Pr Al-A2 Al-A2 :
A~_A 2 = m '>m In thi~ in~tance, between the braking force B on the wheels and the inp~t fluid pres~ure P~ the followin$
relation is pro~ided: ~:
B = C'P~
where C'< C. Ilence, the force Fl, of the spring 101~
iq expre9se~ a~ :
- 26 _ .
. .
, ~sf~
C ~ W ~ ( f 2 ~ K 1 f 1 ) 1 + K
When the i nput fluid pressure Pm i9 at a critical fluid pressure Ps', the following equation i~ obtained:
`,'' , ps ' (A3 - A2) =
Accord:ingly, the critical fluid pressure Ps' i~
obtalned as Cl A4W ~ (f2 ~ ~ f1) ~
( ~!\3 ~ A2 ) ( 1 ~ K2 ~ `
where Ps.' > I's.
Accordi.tlgly, it i~ apparent that the critical fluid pressure l)s~ is increased to a con~iderably high value which provides a braking force so great a~ to com- ~ :
pellsate the rai:L~Jre of the i`luid pres~ure Pml in the first f`Luid circuit 16. ~:
_ 27 -,. ~ "
, ,: . ' ' ~, . . . . . .
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A braking system for a wheeled vehicle having at least one front wheel and at least one rear wheel, said system comprising manually operable master cylinder means for generating first and second variable hydraulic pressures; a front brake for the at least one front wheel; a rear brake for the at least one rear wheel; first fluid conduit means fluidly interconnecting said master cylinder and said front brake for transmitting said first variable hydraulic pressure to said front brake; a fluid pressure control device which has an inlet chamber; an outlet chamber; a passage providing communication between said inlet and outlet chambers; a valve seat in the form of an annular sealing member arranged within said passage; a pressure-responsive plunger having a valve member in the form of an annular projection, said annular projection being cooperative with said annular sealing member;
chamber means for biasing said pressure responsive plunger in a direction tending to move said annular projection toward said annular sealing member in response to said first variable hydraulic pressure; means for biasing said pressure responsive plunger in a direction tending to move said annular projection away from said annular sealing member; means having a power chamber for increasing the preload of said biasing means in response to hydraulic pressure in said power chamber; means defining a ball valve chamber and a ball valve passage providing communication between said ball valve chamber and said power chamber; and an inertia ball valve disposed in said ball valve chamber to close said ball valve passage in response to a predetermined magnitude of deceleration of the vehicle; second conduit means fluidly interconnecting said master cylinder means and said inlet chamber for transmitting said second variable hydraulic pressure to said inlet chamber; third conduit means fluidly interconnecting said outlet chamber to said rear brake for transmitting the hydraulic pressure prevailing in said outlet chamber to said rear brake; and delay means fluidly inter-connecting said master cylinder means and said ball valve chamber for restricting hydraulic fluid flow transmission from said master cylinder means to said ball valve chamber so that transmission of said second hydraulic variable pressure to said ball valve chamber is delayed.
chamber means for biasing said pressure responsive plunger in a direction tending to move said annular projection toward said annular sealing member in response to said first variable hydraulic pressure; means for biasing said pressure responsive plunger in a direction tending to move said annular projection away from said annular sealing member; means having a power chamber for increasing the preload of said biasing means in response to hydraulic pressure in said power chamber; means defining a ball valve chamber and a ball valve passage providing communication between said ball valve chamber and said power chamber; and an inertia ball valve disposed in said ball valve chamber to close said ball valve passage in response to a predetermined magnitude of deceleration of the vehicle; second conduit means fluidly interconnecting said master cylinder means and said inlet chamber for transmitting said second variable hydraulic pressure to said inlet chamber; third conduit means fluidly interconnecting said outlet chamber to said rear brake for transmitting the hydraulic pressure prevailing in said outlet chamber to said rear brake; and delay means fluidly inter-connecting said master cylinder means and said ball valve chamber for restricting hydraulic fluid flow transmission from said master cylinder means to said ball valve chamber so that transmission of said second hydraulic variable pressure to said ball valve chamber is delayed.
2. A braking system as claimed in claim 1, in which said delay means comprises an orifice provided at a port in commun-ication with said ball valve chamber.
3. A braking system as claimed in claim 2, in which said orifice has a diameter within the range of 0.6 to 0.8 millimeter.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3860375A JPS51114565A (en) | 1975-04-01 | 1975-04-01 | Control valve for brake hydraulic pressure |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1052421A true CA1052421A (en) | 1979-04-10 |
Family
ID=12529839
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA249,277A Expired CA1052421A (en) | 1975-04-01 | 1976-03-31 | Braking fluid pressure device |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS51114565A (en) |
| CA (1) | CA1052421A (en) |
| DE (1) | DE2613886A1 (en) |
| FI (1) | FI62642C (en) |
| FR (1) | FR2306106A1 (en) |
| GB (1) | GB1540644A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5719328Y2 (en) * | 1977-02-04 | 1982-04-22 | ||
| JPS582860B2 (en) * | 1978-05-12 | 1983-01-19 | 日産自動車株式会社 | Hydraulic control valve for two-line piping |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4929551A (en) * | 1972-07-14 | 1974-03-16 |
-
1975
- 1975-04-01 JP JP3860375A patent/JPS51114565A/en active Pending
-
1976
- 1976-03-30 GB GB1269976A patent/GB1540644A/en not_active Expired
- 1976-03-31 DE DE19762613886 patent/DE2613886A1/en not_active Withdrawn
- 1976-03-31 CA CA249,277A patent/CA1052421A/en not_active Expired
- 1976-03-31 FI FI760858A patent/FI62642C/en not_active IP Right Cessation
- 1976-03-31 FR FR7609367A patent/FR2306106A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| FI62642C (en) | 1983-02-10 |
| DE2613886A1 (en) | 1976-12-16 |
| FR2306106A1 (en) | 1976-10-29 |
| FR2306106B1 (en) | 1980-06-20 |
| FI760858A (en) | 1976-10-02 |
| JPS51114565A (en) | 1976-10-08 |
| FI62642B (en) | 1982-10-29 |
| GB1540644A (en) | 1979-02-14 |
| AU1250876A (en) | 1978-03-23 |
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