CA1082262A - Load-responsive pressure reducing valve device for use in a vehicle brake system - Google Patents
Load-responsive pressure reducing valve device for use in a vehicle brake systemInfo
- Publication number
- CA1082262A CA1082262A CA278,388A CA278388A CA1082262A CA 1082262 A CA1082262 A CA 1082262A CA 278388 A CA278388 A CA 278388A CA 1082262 A CA1082262 A CA 1082262A
- Authority
- CA
- Canada
- Prior art keywords
- pressure
- fluid
- responsive
- valve
- inertia
- 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
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
- B60T8/26—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
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- Engineering & Computer Science (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Hydraulic Control Valves For Brake Systems (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A load-responsive pressure reducing valve assembly for hydraulic brake systems to be interposed between a brake master cylinder and the rear wheel brake cylinders of a wheeled vehicle and includes a fluid pressure proportioning valve which restricts the flow of fluid from the master cylinder to the brake slave cylinder during a predetermined range of increasing fluid pressure supplied therefrom to the brake slave cylinder. The assembly also incorporates an inertia-responsive valve which includes a valve member usually in the form of a ball which is responsive to a predetermined rate of deceleration so as to vary fluid pressure acting on the aforesaid proportioning valve to thereby correspondingly vary or set the reduction starting pressure of the fluid pressure proportioning valve. A preloaded piston is dis-placeable with the application thereto of a predetermined range of increasing fluid pressure from the master cylinder to correspondingly increase the distance which the ball valve member must travel up an incline to close the inertia-responsive valve and thereby regulate the reduction starting pressure of the reducing valve in correspondence with the distance which the inertia ball, which detects deceleration, travels and the master cylinder hydraulic pressure.
1.
A load-responsive pressure reducing valve assembly for hydraulic brake systems to be interposed between a brake master cylinder and the rear wheel brake cylinders of a wheeled vehicle and includes a fluid pressure proportioning valve which restricts the flow of fluid from the master cylinder to the brake slave cylinder during a predetermined range of increasing fluid pressure supplied therefrom to the brake slave cylinder. The assembly also incorporates an inertia-responsive valve which includes a valve member usually in the form of a ball which is responsive to a predetermined rate of deceleration so as to vary fluid pressure acting on the aforesaid proportioning valve to thereby correspondingly vary or set the reduction starting pressure of the fluid pressure proportioning valve. A preloaded piston is dis-placeable with the application thereto of a predetermined range of increasing fluid pressure from the master cylinder to correspondingly increase the distance which the ball valve member must travel up an incline to close the inertia-responsive valve and thereby regulate the reduction starting pressure of the reducing valve in correspondence with the distance which the inertia ball, which detects deceleration, travels and the master cylinder hydraulic pressure.
1.
Description
2~
~ . `--" . . .
The present invention relates generally to hydraulic braking systems of motor vehicles and, more particularly, to fluid pre~sure regulating devices to be incorporated in such braking systems.
More particularly, this invention relates to a load-responsive pressure reducing valve assembly which is so constructed that a starting pressure for the pressure reducing operation thereof whereby an input hydraulic brake pressure from a master cylinder is changed to an output hydraulic brake pres~ure in a prede~ermined ratio, is . , - .
controlled by means of a pressure proportioning valve which restricts the flow of fluid from the master cylinder to a ~ brake wheel cylinder during a predetermined range of ;', increasing fluid pre~sure supplied to the wheel brake ,, cylinder. The device is capable of distrib-~ting the hydraulic brake pressure, corresponding to a transient weight transfer from rear wheels of the vehicle to the front .,.;'j - . :, wheels caused by the braking operation, to front and rear . '1 . .
,; braki~g means by varying the star~ing pressure for brake .'.1 ' 1 ~ 20 fluid pres ure reduction to the rear braking m~ans in .".. ~ .- . .
~ response to load and deceleration of the vehicle.
, ~ .
It is a well known fact that when a wheeled ~-1 vehicle such as an automobile or truck having a brake system on the ~ront and rear wheels is brakedO the braking causes a forward transfer of the load which occurs due to the deceleration iner~ia of the vehicle and thereby reduces the ~ load on the vehicle rear wheels and consequently reduces ; the contact of the rear wheels with the ground surface~
Thus, the road holding ability of the rear wheels decreases, causing the rear wheels to lock under braking application .,~, ~ .
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z ~ which, in turn, causes dangerous skidding and possible ',~ loss of control of the vehicle. It is also known ~hat this tendency is even more likely to be observed in small siæed truc~s which have a large ratio of load variation and which also ha~e a shor~ wheel base or distance between the front and rear wheel axles.
A number of attempts have been proposed for ,' ~' accomplishing the above-described pre~sure reduction operation ,: .
wherein the fluid pressure supplied to the rear wheel brake~ is reduced to prevent such skidding and provide maximum brake efficiency under varying vehicle load ;. conditions. One such apparatus is illustrated in U.S.
'- Patent No. 3,802,750, wherein ~he starting point of pressure reduction in a reducing valve is delayed under conditionq , o a heavy vehicle load by utiliæing the characteristic ,;j that the vertical distance between the rear wheel axle '', and the loading platform of the vehicle is shortened with ~' the application of the load. Another apparatus of the ',~,.~ prior art is disclosed in U.S. Patent No. 3,317,251, wherein ~he operation of the reducing valve is initiated only when the hydraulic pressure from the master cylinder prevented from being tran~mitted to the rear wheel brake cylinders by mean,~ of an inertia ball valve member which moves in response to the deceleration of the vehicle.
, Another known method is illustrated in U.S. Patent No. 3,944,292, wherein the pressure reducing operation at the time o~ a heavy load condition is delayed by controlling the starting presqure of the pressure reduction operation of the ''' reducing valve in response to or in accordance with the hydraulic presoure of the master cylinder at the time the
~ . `--" . . .
The present invention relates generally to hydraulic braking systems of motor vehicles and, more particularly, to fluid pre~sure regulating devices to be incorporated in such braking systems.
More particularly, this invention relates to a load-responsive pressure reducing valve assembly which is so constructed that a starting pressure for the pressure reducing operation thereof whereby an input hydraulic brake pressure from a master cylinder is changed to an output hydraulic brake pres~ure in a prede~ermined ratio, is . , - .
controlled by means of a pressure proportioning valve which restricts the flow of fluid from the master cylinder to a ~ brake wheel cylinder during a predetermined range of ;', increasing fluid pre~sure supplied to the wheel brake ,, cylinder. The device is capable of distrib-~ting the hydraulic brake pressure, corresponding to a transient weight transfer from rear wheels of the vehicle to the front .,.;'j - . :, wheels caused by the braking operation, to front and rear . '1 . .
,; braki~g means by varying the star~ing pressure for brake .'.1 ' 1 ~ 20 fluid pres ure reduction to the rear braking m~ans in .".. ~ .- . .
~ response to load and deceleration of the vehicle.
, ~ .
It is a well known fact that when a wheeled ~-1 vehicle such as an automobile or truck having a brake system on the ~ront and rear wheels is brakedO the braking causes a forward transfer of the load which occurs due to the deceleration iner~ia of the vehicle and thereby reduces the ~ load on the vehicle rear wheels and consequently reduces ; the contact of the rear wheels with the ground surface~
Thus, the road holding ability of the rear wheels decreases, causing the rear wheels to lock under braking application .,~, ~ .
.. , :
'; ~,.. ~ .. ' ' "
2.
. .: :.
.; . .
:
z ~ which, in turn, causes dangerous skidding and possible ',~ loss of control of the vehicle. It is also known ~hat this tendency is even more likely to be observed in small siæed truc~s which have a large ratio of load variation and which also ha~e a shor~ wheel base or distance between the front and rear wheel axles.
A number of attempts have been proposed for ,' ~' accomplishing the above-described pre~sure reduction operation ,: .
wherein the fluid pressure supplied to the rear wheel brake~ is reduced to prevent such skidding and provide maximum brake efficiency under varying vehicle load ;. conditions. One such apparatus is illustrated in U.S.
'- Patent No. 3,802,750, wherein ~he starting point of pressure reduction in a reducing valve is delayed under conditionq , o a heavy vehicle load by utiliæing the characteristic ,;j that the vertical distance between the rear wheel axle '', and the loading platform of the vehicle is shortened with ~' the application of the load. Another apparatus of the ',~,.~ prior art is disclosed in U.S. Patent No. 3,317,251, wherein ~he operation of the reducing valve is initiated only when the hydraulic pressure from the master cylinder prevented from being tran~mitted to the rear wheel brake cylinders by mean,~ of an inertia ball valve member which moves in response to the deceleration of the vehicle.
, Another known method is illustrated in U.S. Patent No. 3,944,292, wherein the pressure reducing operation at the time o~ a heavy load condition is delayed by controlling the starting presqure of the pressure reduction operation of the ''' reducing valve in response to or in accordance with the hydraulic presoure of the master cylinder at the time the
3.
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inertia sensor senses the braking deceleration and moves.
Another example of this type of sensor is also illustrated in U.S. Patent No. 3,825,303. However, in load-responsive pressure reducing valves of this type, a shortcoming is . , observed when used in vehicles which display a tendency of not exhibiting any signiicant or definite difference in the relationship between braking hydraulic pres~ure and braking deceleration when it has a light load condition and when it has a heavy load condition. In this situation, the pressure reducing valve is thus apt ~o display the pres~ure reducing characteristic or a light load when, in fact, the vehicle is under a heavy load condition. This type o~ pressure reducing valve thus has the shortcoming that the braking .
~ force applied to the rear wheels tends to be insufficient ,,' undex heavy load conditions notwithstanding its relatively sophisticated and complicated construction.
, It is a principal object of the present invention ,.
;;~,,, to provide a load-responsive pressure reducing valve assembly which i~ devoid of the aforementioned disadvantages and to provide such a reducing valve assembly wherein the starting point of pressure reduction is controlled by detecting ~he i deceleration of the vehicle and further aims at providing an inexpen~ive load-responsive reducing valve of simpler construction and which further allows variation~ in the ; starting point of pressure reduction in response to deceleration.
One characteristic of the load-responsive ~-pressure reducing valve assembly of the present invention is ... ,. ,; .
-~ that it adopts the type o deceleration detector in which .
~ 30 the entire reducing valve body is installed on the vehicle .... .
. .
, . .
i 4.
. .
' ' ' ' ' ' ' at a predetermined angle of inclination to provide an incline for movement thereon of the inertia ball or inertia-responsive valve member, and dispenses with complicated mechanisms of the prior ar~ wherein the angle o~ inclination of the reducing va~ve body or housing is varied for light load conditions and heavy load conditions. The pressure reducing valve of the present invention also does away with complicated mechanisms which restrict the movement of the inertia ball or inertia-responsive valve member.
Another characteristic of the load-responsive pressure reducing valve assembly of the present invention is that the starting point or reduction starting pressuxe of the pressure reduction operation varies first of all in correspondence to the distance which the inertia ball or ,.
inertia-responsive valve member, which is detecting decleration c o~ the vehicle, must travel, and secondly in correspondence to `~ the master cylinder hydraulic pres~ure at hat time. The distance over which the inertia ball or inertia responsive valve member rolls or moves and the propagation velocity of the hydraulic pressure filling the space surrounding the inertia-responsive valve member are controlled~
Another characteris~ic of the pressure reducing valve assembly of the present invention is tha~ when a predetenmined hydraulic pressure from the master cylinder ; is exceeded, a piston within the valve assembly housing is depressed by th~ pressure ~hereby increasing the distance ; ov~r which the iner~ia ball or inertia-responsive valve member must travel as the inertia ball is always in contact with the piston until such time that a preset or predetermined deceleration i~ exceeded.
5.
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. Yet another characteristic of the reducing valve .. assembly of the present invention is that the operating hydraulic pressure of the master cylinder itself is utilized as the press-. ing or bias means to control the starting point of the pressure ~: reduction operation. Accordingly, it is thus made possible to . .:.. : .
control this hydraulic pressure over a very broad range with the use of small or limited mechanical space, whereas many of the conventional reducing valve assemblies require the use of a coil spring for this function which creates problems of increased required space for installation and manufacturing error.
.~ .
,. . .
Broadly speaking, therefore, the present invention provides, in a brake system provided with a reducing valve having .
a brake fluid inlet and a brake fluid outlet respectively connected to a brake fluid motor and a wheel brake cylinder in the rear wheel.s of a vehicle: a deceleration-responsive reducing valve including therein; a plunger which has one end exposed to the brake fluid inlet and the other end exposed to the brake fluid outlet of the reducing valve for restricting fluid pressure .
applied to the wheel cylinder when an operation-starting pressure at the outlet is attained; means to determine the operation-starting pressure of the plunger in relation to the weight of the vehicle and any load carried thereby and including an inertia :
ball resting on an incline for rolling up the incline upon vehicle deceleration to seal braking fluid from the brake system ::
. . .
, ....
under a then existing pressure in a cavity, which sealed flui~ ~.
communicates with the plunger to determine the operation-start- ~ .
.~ ing pressure thereof; and means to vary this then existing sealed ;~. pressure of the sealed fluid in the cavity and including a ,.. .
. piston provided downward on the incline and against which the ..
. ':
inertia ball normally rests when not rolling up the incline, the piston displaceable against a bias by brake. fluid under pressure from the brake system to displace the piston in a direction to increase the roll travel of the inertia ball when a predetermined ~,' . ~ 6 r . ~ `dap/ !
.
''.''' ` ' ' '' ~'` '' ' , ' ' ' : , .:; fluid pressure at the inlet of the reducing valve is exceeded to ,- .
` ; thereby increase the operation-starting pressure of the plunger : in proportion to an increase of load on the vehicle.
,~ If it is desired to make the inertia-responsive valve ~ member a variable deceleration detection type, then the afore-,... .
mentioned incline upon which the valve member must travel is provided with a curved convex surface to thereby increase the predetermined magnitude of detected vehicle deceleration with . an increase of travel surface.
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The following description and the accompanying drawings will serve as an illustration but not as a limita-, tion of this invention.
FIG. 1 is a schematic diagram of a vehicle braking ,~ system utilizing a load-responsive pressure reducing ~alve assembly according to the teachings of the present invention.
FIG. 2 i~ a cross~sectional view ~howing the load-~ responsive pressure reducing valve assembly of the present `~ invention.
FIG. 3 is a graph showing the relationship between .: . , pre~sure input to the pressure reducing valve apparatus of the present invention from the master cylinder to pressure output to the wheel cylinders for light and heavy vehicle load conditions.
FIG. 4 is a cross-sectional view showing an .. . .
embodiment variation of the inertia-responsive valve por~ion .,~, ; of the apparatus illustrated in Fig. 1 wherein the incline -~
ovex which the inertia ball tra~ls is a curved convex surface.
Referring to ~he drawings~ Fig. 1 diagrammatically illu~trates a vehicle braking sy~tem for a wheeled vehicle ~; utilizing the load-responsive pressure reducing valve ` assembly of the present invention and schematically illustrates the flcw diagram of the system.
Hydraulic braking pressure is generated in the conventional tandem master cylinder 1 by means o the brake ".
' pedal and linkage illustrated and the hydraulic fluid i~
directed through conduit 2 and di~tributed through triple connec~or 3 to the left and right front wheel brake cylinders
:'.
.,-,' , ,, l~ f~
inertia sensor senses the braking deceleration and moves.
Another example of this type of sensor is also illustrated in U.S. Patent No. 3,825,303. However, in load-responsive pressure reducing valves of this type, a shortcoming is . , observed when used in vehicles which display a tendency of not exhibiting any signiicant or definite difference in the relationship between braking hydraulic pres~ure and braking deceleration when it has a light load condition and when it has a heavy load condition. In this situation, the pressure reducing valve is thus apt ~o display the pres~ure reducing characteristic or a light load when, in fact, the vehicle is under a heavy load condition. This type o~ pressure reducing valve thus has the shortcoming that the braking .
~ force applied to the rear wheels tends to be insufficient ,,' undex heavy load conditions notwithstanding its relatively sophisticated and complicated construction.
, It is a principal object of the present invention ,.
;;~,,, to provide a load-responsive pressure reducing valve assembly which i~ devoid of the aforementioned disadvantages and to provide such a reducing valve assembly wherein the starting point of pressure reduction is controlled by detecting ~he i deceleration of the vehicle and further aims at providing an inexpen~ive load-responsive reducing valve of simpler construction and which further allows variation~ in the ; starting point of pressure reduction in response to deceleration.
One characteristic of the load-responsive ~-pressure reducing valve assembly of the present invention is ... ,. ,; .
-~ that it adopts the type o deceleration detector in which .
~ 30 the entire reducing valve body is installed on the vehicle .... .
. .
, . .
i 4.
. .
' ' ' ' ' ' ' at a predetermined angle of inclination to provide an incline for movement thereon of the inertia ball or inertia-responsive valve member, and dispenses with complicated mechanisms of the prior ar~ wherein the angle o~ inclination of the reducing va~ve body or housing is varied for light load conditions and heavy load conditions. The pressure reducing valve of the present invention also does away with complicated mechanisms which restrict the movement of the inertia ball or inertia-responsive valve member.
Another characteristic of the load-responsive pressure reducing valve assembly of the present invention is that the starting point or reduction starting pressuxe of the pressure reduction operation varies first of all in correspondence to the distance which the inertia ball or ,.
inertia-responsive valve member, which is detecting decleration c o~ the vehicle, must travel, and secondly in correspondence to `~ the master cylinder hydraulic pres~ure at hat time. The distance over which the inertia ball or inertia responsive valve member rolls or moves and the propagation velocity of the hydraulic pressure filling the space surrounding the inertia-responsive valve member are controlled~
Another characteris~ic of the pressure reducing valve assembly of the present invention is tha~ when a predetenmined hydraulic pressure from the master cylinder ; is exceeded, a piston within the valve assembly housing is depressed by th~ pressure ~hereby increasing the distance ; ov~r which the iner~ia ball or inertia-responsive valve member must travel as the inertia ball is always in contact with the piston until such time that a preset or predetermined deceleration i~ exceeded.
5.
''`' ' ' .
gL~ i2 . .
. Yet another characteristic of the reducing valve .. assembly of the present invention is that the operating hydraulic pressure of the master cylinder itself is utilized as the press-. ing or bias means to control the starting point of the pressure ~: reduction operation. Accordingly, it is thus made possible to . .:.. : .
control this hydraulic pressure over a very broad range with the use of small or limited mechanical space, whereas many of the conventional reducing valve assemblies require the use of a coil spring for this function which creates problems of increased required space for installation and manufacturing error.
.~ .
,. . .
Broadly speaking, therefore, the present invention provides, in a brake system provided with a reducing valve having .
a brake fluid inlet and a brake fluid outlet respectively connected to a brake fluid motor and a wheel brake cylinder in the rear wheel.s of a vehicle: a deceleration-responsive reducing valve including therein; a plunger which has one end exposed to the brake fluid inlet and the other end exposed to the brake fluid outlet of the reducing valve for restricting fluid pressure .
applied to the wheel cylinder when an operation-starting pressure at the outlet is attained; means to determine the operation-starting pressure of the plunger in relation to the weight of the vehicle and any load carried thereby and including an inertia :
ball resting on an incline for rolling up the incline upon vehicle deceleration to seal braking fluid from the brake system ::
. . .
, ....
under a then existing pressure in a cavity, which sealed flui~ ~.
communicates with the plunger to determine the operation-start- ~ .
.~ ing pressure thereof; and means to vary this then existing sealed ;~. pressure of the sealed fluid in the cavity and including a ,.. .
. piston provided downward on the incline and against which the ..
. ':
inertia ball normally rests when not rolling up the incline, the piston displaceable against a bias by brake. fluid under pressure from the brake system to displace the piston in a direction to increase the roll travel of the inertia ball when a predetermined ~,' . ~ 6 r . ~ `dap/ !
.
''.''' ` ' ' '' ~'` '' ' , ' ' ' : , .:; fluid pressure at the inlet of the reducing valve is exceeded to ,- .
` ; thereby increase the operation-starting pressure of the plunger : in proportion to an increase of load on the vehicle.
,~ If it is desired to make the inertia-responsive valve ~ member a variable deceleration detection type, then the afore-,... .
mentioned incline upon which the valve member must travel is provided with a curved convex surface to thereby increase the predetermined magnitude of detected vehicle deceleration with . an increase of travel surface.
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.",~, ~
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;
." , '; ' ., . .
:, .. ~
`:' ' ~ ~ dap/~
;~
'- -' . ~ . ' .
,:, .. ~ . . .
: " . , . : ' . . .
The following description and the accompanying drawings will serve as an illustration but not as a limita-, tion of this invention.
FIG. 1 is a schematic diagram of a vehicle braking ,~ system utilizing a load-responsive pressure reducing ~alve assembly according to the teachings of the present invention.
FIG. 2 i~ a cross~sectional view ~howing the load-~ responsive pressure reducing valve assembly of the present `~ invention.
FIG. 3 is a graph showing the relationship between .: . , pre~sure input to the pressure reducing valve apparatus of the present invention from the master cylinder to pressure output to the wheel cylinders for light and heavy vehicle load conditions.
FIG. 4 is a cross-sectional view showing an .. . .
embodiment variation of the inertia-responsive valve por~ion .,~, ; of the apparatus illustrated in Fig. 1 wherein the incline -~
ovex which the inertia ball tra~ls is a curved convex surface.
Referring to ~he drawings~ Fig. 1 diagrammatically illu~trates a vehicle braking sy~tem for a wheeled vehicle ~; utilizing the load-responsive pressure reducing valve ` assembly of the present invention and schematically illustrates the flcw diagram of the system.
Hydraulic braking pressure is generated in the conventional tandem master cylinder 1 by means o the brake ".
' pedal and linkage illustrated and the hydraulic fluid i~
directed through conduit 2 and di~tributed through triple connec~or 3 to the left and right front wheel brake cylinders
4 and 4' respectively. Fluid pressure is distributed to the rear wheel brake cylinders 9 and 9' from the tandem ~, ;~`
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.~ master cylinder 1 through conduit 5 via the reducing valve ~ body or assembly 6 of the present invention and conduit 7.
. The reducing valve assembly housing 6 i~ installed on a .. portion of the motor vehicle at an angle of inclination corresponding to the deceleration of the vehicle to be `' detected. The brake fluid exits the pressure reducing ~ valve assembly 6 via conduit 7 and is then dis~ributed ; through triple connector 8 to the right and left rear wheel brake cylinders 9 and 9' respectively.
Referring next to Fig. 2, the interior construction :: of the reducing valve assembly shown in Fig. 1 is disclosed.
.
The body or hou~ing 6 of the reducing valve assembly is divided into thxee major portions or sections, namely, the pxoportional pressure reduction section PR, the hydraulic pressure controlling section PC and the pressure buffer section BF.
: The proportional pressure reduction section PR
incorporates a fluid pressure proportioning valve for restricting the flow of fluid fed to the fluid inlet 19 . 20 from master cylinder 1 to the fluid ou~let 20 duri~g a ~i pr~determined range of increasing fluid pressure at the outlet 20~ This fluid pressure proportioning valve consists of a plunger 18 which is axially moveable in a first cavity or chamber 22 within the housing 6. The plunger 18 also .~ extends to the left toward a second cavity 55 within the housing 6.
The plunger 18 is provided with a valve head 35 which is cooperable with valve seat 33 to selectively : establish an interrupt communication between the first fluid , 30 inlet port 19 and the fluid outlet port 20 as the plunger 18 is axially moved.
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Valve head 35 is received within chambex 21 which in ~urn is connected to output port 20 which leads to the rear wheel brake cylinders. The o~her end or stem end of plunger 18 is exposed to second cavity or chamber ~5 through a slide fluid seal from ~he first cavity 22 ~or biasing plunger 18 to a position establishing communication between fir~t inlet port l9 and outl~t port 20 by ~luid under pressure in second cavity or chamber 55. Fluid under pressure -' in chamber 55 will bias plunger 18 to the right so that the plunger head in chamber 21 does not engage valve seat 32 thereby establishing communication between first inlet port 19 and outlet port 20.
The stem portion of plunger 18 i~ slidably received in the central bore 25 of seal holder 24 whioh in turn is seated in bore 23. Spring re~ainer 28 is also held in po~itio~ within bore 23 in buttlng engagement against annular shoulder 29 by pressure applied by seal holder 24 which, in tur~, is retained in ~sition by means of end cap 60 which is threadably received in housing 6 ac indicatedO
Seal holder 24 is constructed to block the direct passage of hydraulic fluid under pressure from the first cavity or chamber 22 directly into the second cavity or ~hamber 55 by mea~ of the cup seal 26 and O-ring 27.
Preload compression spring 31 is held under .:..................................................................... .
compres~ion between ~pring retainer 28 and the flange portion 30 of plunger 18 as illustrated.
;: ~he annular 3eal valve or ~alve seat 33 is ~ illustrated and described in detail in United States Patent No. 3,423,936. This Patent may be referred to to explain ` 30 the basic cooperative pressure reducing ~unction or operation `, that occurs between valve plunger 18 and valve seat 33.
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Seal valve or valve seat 33 is made of an ela~tic material and i5 sandwiched between the annular shoulder 32 and the righ~ æide or end of plunger 18. Hydraulic fluid under pressure PM from the master cylinder enters through the first inlet port 19 into the first cavity or chamber 22 and passes through the crescent shaped passages 34 formed between plunger 18 and the wall of cavity 22 and then continues to flow between valve seat 33 and pl~nger 18 on into chamber 21 and out outlet p~rt 20. This fluid passage or communication between inlet p~rt l9 and outlet por~ 20 is interrupted when plunger 18 moves to the left so that the head 35 of the plunger in chamber 21 engages valve seat 33.
This pressure reducing valve thus proportionally reduce~ the hydraulic fluid pressure fed to the output 20 and sub~equently the rear wheel brake cylinders by opening and clo~ing CDmmunication of valve head 35 with valve seat 33. A more detailed explanation of the oper,ation of this portion o~
the reducing valve may be obtain~ed by reference to lines 16 through 47 of U.SO Patent No. 3,736,031 issued May 29, 1973.
The ~hird cavity or chamber 37 in the hydraulic pre~sure controlling seal-in 3ection PC is connected by second inlet port 36 to the hydraulic fluid under pressure PM from the master cylinder via the first chamber or cavity 22. Inertia ball 38 is positioned in the center of third cavity 37. The right side or end of the third chamber or ball chamber 37 is closed by means of plug 39 that is threadably received in reducing valve body or hou~ing 6. An airtight seal is maintained between third cavity 37 a~d the exterior by msans of O-ring 40.
In the bore 41 of this plug 39 t a piston 42 is ~lidably received suoh ~hat the left end o the piston 42 . . :
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contacts the inertia bal:L 38 at rest. Hydraulic pressure within the third chamber 37 will ac~ on the piston cup seal 43 via the crescent groove 44 to urge piston 42 to the right against the compression of preload spring 47 for the maximum possible displacement of As indicated by the double-headed arrow. ~his displacement of piston 42 increases the distance - -of travel for inertia ball 38 over incline 37a.
. . .
Preload spring 47 is sandwiched in position between the annular shoulder 45 of pis~on 42 and the annular shoulder or end wall 46 of ~he fourth cavity or chamber 41 within ; housing 6 ox plug 39.
;,:", The installation length of preload spring 47 is .; .
determined by snap ring 49 inserted in the ring groove 48 ~` provided o~ the stem or spindle portion of the piston which , .,~: " .
extends through plug 39 to the exterior. This snap ring arrangement provides a stop to limit the extent to which ; piston 42 will be permitted to slide or extend toward third cavity 37 due to the bias of preload spring 47. The movement ~' of piston 42 on the other hand, is restricted to the right , , 20 side by the contact o~ annular ~houlder 50 on the stem portion of the piston with the annular shoulder 46 of the fourth cavity or chamber 41. Elastic dust boo~ 51 is provided ,~ with an annular snap fit to plug end plug 39 and slidably `~ receive the outer circumference of the exposed spindle ,;: . . .
,'~ portion of piston 42 in a sealed manner to prevent the entry of dust and water into the slide contact between the piston spindle and end plug 39 and consequently into the fourth ., ; , ; cavity or chamber 41.
An operating fluid channel 52 is provided in the 30 top of the third or ball cavity 37 and is of a semi-., .
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, . . ..
cylindrical cross con~iguration and is provided to assist the rolling of inertia ball 38 to the left on incline 37a, as this channel 52 permits the free flow of fluid around inertia ball 38 when it is in motion to reduce pressure build up as much as possible in front of the ball as it is rolling to the left.
- Check valve seat 53 of the inertia-responsive valve is constructed of a plastic tubing or material and has a central penetrating channel or bore. Check valve seat 53 is retained in the reducing valve housing 6 by means of retainer 54 at a position to preset or predetermine the small travel distance 8 which the inertia ball 38 must travel from ~- its engagement with pis~on 42 in order to press the mouth `~ portion of check valve seat 53 and thereby close the passage of fluid from third chamber 37 to the central bore of check valve seat 53.
...:
-; The pressure buffer section BF provides two functions~ First of all it is the chamber which provides ;~- fluid under pressure to bias the fluid pre~sure proportioning valve consisting of piston 18 and valve seat 33 in order to detexmine the pressure reduction starting pressure and in addition, it also improves the liquid seal function of check valve 53 when inertia valve 38 seats therewith. More ; definitely, the oil pocket of cavity or chamber 55 is utili~ed ~ as the control cha~ber to apply fluid pressures from there-" within against the exposed st~m end of plunger 18 in order to control the starting pressure for the reducing operation.
The hydraulic fluid is transmitted under pressure to the oil pocket or ~econd cavity 55 from the third cavity or chamber 37 through the central bore of check valve seat : i~ . . .: , : ~ 53 and thence through pa~sage 56 ~o the annular groove 57 to the radial communication pa~isage or opening 58 provided at the left end of seal holder 24.
The pressure bufer means within the s2cond cavity : or chamber 55 provides a means wherein the second chamber 55 . is enabled to expand its capacity elastically to compen-~ate -: for an incremental fluid pressure increase created therein : due to the closure of the iner~ia-responsive check valve, ....
i~e., engagem~nt of inertia ball 38 with inertia check valve seat 53, thereby improving the cloæure seal of the check ... valve in section PC of the load-responsive pressure reducing valve assembly.
This pressure buffer consists of an ela-~tic wall portion 59 in the ~econd chamber or cavity 55 which is ou~wardly expandable into a sealed air chamber 63. The expandable wall portion 59 may be designated as an oil ; pocket which is made of an elastic material and which is centrally held within end plug 60 by annular shoulder 61 and . the inside bottom 62 of end plug 60 to thus orm the annular ,'. 20 air chamber 63.
: "
::;,, The end plug 60 is threadably secured in the reducing valve body or housing 6 a~ indicated and thus `, maintains an air tight seal of both oil pocket or the second . cavity 55 and air chamber 63 from the exterior. This ~ealed relationship is insured by the use of O-ring 64 and as formerly pointed out, end plug 60 also restricts the movement ,.~
~ of seal holder 24 to the left, or as previously indicated, :...................................................................... .
.~' plug 60 holds ~eal holder 24 in its prescrib~d fixed position.
.. . .
~: Reference numeral 65 generally indicates an air ,` 3C bleeder which is provided for the purpose o~ expelling air ... ..
,,~., , .
14.
~' : ', which migh~ be entrapped in ch~ber or cavity 55, third ~- cavity 37, and second inlet port 36 or the first cavity or chamber 22. In other words, it is designed to purge the entire reducing valve assembly of air which is accidentally mixed in with the hydraulic braking fluid.
Fig. 3 illus~rates ideal hydraulic braking pressure curves for a given vehicle with two different load conditions.
The one-dot broken curve E indicates the ideal curve for a light load condition for master cylinder hydraulic fluid pressure Pm versus the output pressure Pr of the pressure reducing valve assembly of the present invention which is supplied to the rear wheel brake cylinders. The one-dot broken line F indicates an ideal curve for heavy load vehicle conditions. Curves O-Pse-E~ and O-Ps~-F' represent actual operating curves of the pressure reducing valve assembly of the present inv~ntion which attempt to closely correæpond to the ideal curves for light load and heavy load oDnditions.
In order to automatically force the hydra~lic i 20 pressure of th~ rear wheel cylinders, as shown by the - polygonal line O-Pse-E', at the time of liyht load conditions, ..... .
and the polygonal line O-Psf-F' at heavy load conditions, to correspond to these ideal hydraulic pressure curves i respectively. Inertia ball 38 is utilized to set the starting pressure of the fluid pressure reduction operation.
~, Inertia ball 38 controls both of the curves of actual operation by moving to the left on incline 37a for the predetermined distance 8 to contact the check valve seat 53 in order to make the actual straight line curves conform as closely as possible to the ideal curves illustrated in ':
':
15.
. : ~ .
:' , : . : ,' ' ' , ,: ....... . , . . : . ' : .
Fig. 3. Inertia ball 38 thus controls the starting point of the pressure reduction opera~ion by sealing off the master cylinder hydraulic pressure Pm from the control chamber or :.
second cavity 55 at the point in time that inertia ball 38 : oontacts the check valve seat 53 by traveling or rolling up . incline 37a and ~eals the check val~e bore within check valve seat 53~
If i~ is assumed that Po represents the hydraulic braking pressure of ~he vehicle brakes and tha~ C represents the brake fac~or, then the braking force B of the vehicle may be represented as shown by the following formula:
B = C Pc (1) In addition, the ratio between the deceleration ~ ~ of the vehicle and the acceleration of gravity g is ..
equal to the ratio between the braking ~orce B and the weight . W of the vehicle. This relationship may be expre~sed as ' follows:
~, B .
g W (2) ; When a deceleration occurs in a vehicle due to ., :
:1 20 braking, the following equilibrium will then occur or be .
, established around or in relation to the inertia ball 38, , ., if the weight o~ the inertia ball in the hydraulic braking liquid is designated as W: .
: W a cos ~ _ W sin ~ :
> tan ~ ~3) ~ .
.. . The inertia ball 38 will begin to move to the left as seen in Fig. 2 when the deceleration as shown by the inequality sign of Formula (3) is exceededO Expressing this mathematically, the operation of the inertia ball 38 may be expressed as a function of the angle of installation as follows:
'' .'. . .
., .
16.
, ;' , ': :
.-, .
.' ~
AS a re~ult, the hydraulic pressu_e Pa which is sealed within the second chamber or oil pocket 55 may ~hus be expressed from Fonmulae (l), (2) and (4) and mathematically reduced and placed in order as shown in :~ the following eql7ationO
:~ f (~) :~: pO ~ W (5) : C
~ On ~he other hand, if inertia ball 38 has traveled the distance 6 Up the incline 37a in time T at a velocity V, then, VT (63 In addition, if the hydraulic pressure of the master cylinder 1 is designated Pm2 at a givan time and the -velocity of pressure rise per unit tLme is designated as :
Vp, then Vp may be expressed by the following formula~
~ = Pmi (7) r',' Thus~ from Formulae 16) and (7), Pm2 ~ay be .`. designated as followss ~
~., Pm~ = 2 Vp ~ 8 ~8~ :
`"'' V , :, Furthermore, if the installation load of the preload spring 47 is F, the spring constant hereof is R
:: . .:
1 and the distance which ~he piston 42 is pe7~tted to slide ~ .
;. within its bore or chamber 41 is designated as ~8 due to the applied hydraulic pressure Pm o the master cylinder, which acts on the cross-sectional area A3 of piston 42 to move the same to the right, then the equilibrium of force about . the piston 42 can be expressed by the followi~g ~ormulae: .
, .'' .
.:, '':' : ,' :. 17 .~
:
~ : - . . . .
Pml A3 = F ~ Q~ K
: F + Q8 ~ K
Pml = __________ (9) To m~thematically state this relationship in a more meaningful manner, the hydraulic pre~sure Pc sealed in .. , the oil po~ket or sQcond chamber 55 may be expressed from ; Formulae (8) and (9) and mathematically reduced and placed i in oxder as indicated in the following formula:
Pc = Pml + Pm2 `:
;:: F + ~8 K 2Vp Pc - - + _ (8 ~ ~s) (10) i,.:
Formula ~10) indicates the hydraulic pressure which is sealed in the oil pocket or ~econd chamber 55 in the ~"~ situation wherein ~he floor surfaca of the third cavity or chamber 37 i8 flat as shown in Fig. 2, thus illustxating a ~ constant deceleration detecting type pressure reducing valve :~ assembly. However, the floor or surface upon which inertia ball 38 rolls in chamber 37 may be provided in the form of a ,., ; . .
.' convex curved surface as illustrated in Fig. 4 to thus make the apparatus a variable deceleration detection type wherein . .
~:1 the detected deceleration increases with the angle o~ tangent ~, which indicates the increments of angle increase of the incline 37b of Fig. 4.
- ~ With reference again to Fig. 3, the operation of the reducing valve assembly illustrated in Fig. 2 will be explained with regard to the polygonal line O-Pse-E~, which represents the pressure reduction characteristics o~ the apparatu~ or a light load condition.
Re~erring to Fi~. 2 for thi~ example, the input hydraulic pressure Pm supplied from the master cylinder to port 19 is tran~mitted directly to the output port 20 via . .
',.' ' l~o .
' .
' :
the annular gap between plungex 18 and the seal valve or valve seat 33 as plunger 18 i~ urged under the bi~s of compression spring 31 to the far right as indicated in the Figure. Protru~ions on the left side of valve seat 33 permit the fluid to pass the valve seat to the outle~ port 20.
Accordingly, if the hydraulic pressure Pc within second chamber or cavity 55 at the tLme inertia ball 38 contacts check valve seat 53 under the influence o~ an applied deceleration ~e as shown in Formula (10) is designated as - 10 P¢e, the equilibrium of plunger 18 may he mathematically illustrated by the following formula:
Pce A2 + f < P~
wherein A2 ie the cross-sectional area of the ~: stem portion of plunger 18 as indicated .; ., ,:
in the Figure, and f i3 the installation load of preload spring 31.
`~1' .
The principal object of preload spring 31 is to :~
restoxe plunger 18 to its original or normal position after ;~
: each time the fluid pressure proportioning valve has made a :
j 20 closure by plunger 18 moving to the left to thereby engage ~ :
'`J' the annular valve head 35 with the inner diameter of valve seat or seal 33 to reduce or re~rict fluid pressure flow : from the ma~ter cylinder to the rear wheel brake cylinders~
Another object of preload spring 31 i8 to guarantee minimal necessary braking force applied to the brake pedal indicated .
.~. in Fig. 1 even if the installation angle ~ shown in Fig. 2 ;~. may become nearly equal to zero when the vehicle is descending a s~eep slope and the inertia ball 38 thus moves to the left ~ :
a~ seen in Fig. 2 at a deceleration which is les~ than the .` 30 set or predetermined deceleration rate, wherein a hydraulic 'i . "
`' :, ,....................................... .. ~ :
.. 19. '.' . . , . :- - :
322~i~
~: ;
., pressure will be sealed in the oil pocket or second cavity -~ 55 which may eve~ be near to zero.
From the foregoing, one can derive from Formula (11) the following formula in regard to the master cylinder ..,~
.~ pressure Pm:
: f Pm ~ Pce ~ A ~12~
~hus, the hydraulic pressure Pm from the master cylinder at the moment wherein the condition~ of Form~la `: ll2) are caused to have an equality sign, the pressure Pm becom2s the pressure Pse required to start the pressure .~ reducing operation.
When the ma.~ter cylinder pressure Pm increases , .
a sufficient am~unt to at~ain the equality sign of Formula . (12) and thereafter increases to attain the inequality sign .:
'. thereof~ the plunger 18 will move to the left due to the ~, . . .
~i partial pressures which act against the larger area Al sf .. . .
,`, pi8ton head 35 in chamber 21 opp3sed to the smaller areas exposed to chamber 22~ such that the outer circumference of :., .` valve head 35 seats in the inner circumference of the valve seat 33 thereby temporarily bloclking the passage of hydraulic .: fluid from fir~t input port 19 to output port 20. The equilibrium of hydraulic pressure around or on opposite sides ~ of plunger 18 at this ~oint in time may be expressed as :~
: follows:
Pr Al = (Al - Az) Pm ~ f + Pce A2 (13) .. where Pr is the output hydraulic pre~sure supplied to the .' rear wheel brake cylinder through output 20, `~, Al is the cross-sectional area of valve head 35.
;~ From Formula (13), the output hydraulic pre~sure .-, 30 may be further reduced and expressed as follows: :
: ,~
... ~
. . .
.
:.' ,;~ 20.
. . ~
~:`
- . .
.,, .,'`'' ` .
Al - A2 f A2 Pr = ~ Pm ~ Pce (14) ~ Al Al A~
The relationship expressed in this Formula between the input and the output hydraulic pressures may be seen to satisfy the polygonal line O-PseoE~ illustrat2d in Fig. 4 for light load conditions.
(Al - A2)/AI in Formula (14) represent~ the ratio of pressure reduction after commencement of the pressure , ~ reducing operation.
In a like manner, when piston 42 has moved to the .
right in Fig. 2 under the influence of Pm for vehicle ; deceleration on the heavy load side9 and the hydraulic pre~sure Pc shown in Formula (10) has thus become or attained level Paf, an equilibrium of Formula (14) with P¢e ; substituted by Pcf, will be established and, at the ~ame time as Pse moves to the level of P~f, E~ makes a parallel translation to F' as seen in Fig. 3 and thereby effects load~responsive proportionating pressure reduction for heavy load ccnditions.
` In either load condition, when Pm reduces from a value on the line E' or ~' in Fig. 3, Pm does not follow Formula ~14). Stated in a different man~er, and with '` reference to Formula (133, the Aydraulic pressure Pm applied ,t, to the difference in area of plunger 18 (A~ - A2) reduces, the equilibrium of the plunger 18 in accordance with Formula `;. (13) is broken, and the valve head 35 moves even further to the le~t while retaining its sealed relationship of closure - with valve ~eat 33 and the hydraulic fluid or liquid of higher , pressure in output port 20 flows into the first cavity 22 on ,.~., the input port 19 side of the valve seat via the outer circumference of the seal valve or seat 33 and, thereafter, : . ,.
21. ~
.
` P~ reduces as Pm reducesO The extreme leftward movement .. ~ of plunger 18 at this point in time is restricted by means of the annular shoulder 66 within seal holder 24.
: Even if the hydraulic pressure applied from the master cylinder to the rear wheel brake cylinders is reduced ~rom high braking pressure by removal of brake application to the mas~er cylinder such that the vehicle gradually decelerates ,' below the prese~ deceleration at which check valve 53 will i close, inertia ball 38 will still remain in contact with check valve 53 as long as the equilibrium o the following ' ' formula holds true, A4 being the cross sectional area of the central hole o~ the check valve seat 53:
W u sin ~ _ Pm A4 (15) ~owever, if the master cylinder pressure Pm . reduces~ such that the left side of Formula ~15) becomes greater than the right side as indicated by the inequality : sign, the inertia ball then moves to the right as viewed in ~`~ Fig. 2 down incline 37a and the hydraulic pressure within :~ the third chamber or ball chamber 37 becomes equal to that ;~ 20 of second chamber or control chamber 55.
One of the major section.~ of the pressure reducing valve assembly, as previously explained, is the pres~ure ~-~ buffer section BF which includes the ~econd cavity or chamber :: 55~ ~n elastic wall portion in the form o~ an elastic oil ,;
... pocket 59 is provided for chamber 55. The first function of oil pocket 59 is explained as follows: when i~ertia ball 38 .~ presses against check valve 53, it compresses the elastic .:
material of the check valve seat such ~hat the hydraulic pressure Pa which is sealed in the chamber 55 of pressure ;, 30 buffer section BF at that moment becomes slightly higher :.
... .
22.
' ' .
:~ due to this compression e~fect. Alth~ugh the pressing force Pm o A4 of inertia ball 38 against the check valve ~eat 53 ,. is restricted due to the fact that the outer circumference , of the inertia ball contac~s ~he end surface 67 of retainer 54, nevertheless, this increase in pressure of ~Pc would have the effect of pushing the inertia ball 38 back off its check valve seat 53. To prevent this displacement of the inertia `;~ ball from its valve seat, oil pocket 59 elastically protrudes on air chamber 63 in end cap 60 ~o absorb this small pressure increase QP¢ and thereby cancels the possible undesirable effect~ of ~Po on the fluid pressure proportionin~ valve, : while at the same time improving ~he liquid sealing capabilities of the check valve consi~ting of inertia ball 38 and check valve seat 53.
The qecond function of the pres~ure buffer section i~ to ¢ompensate for the event that plunger 18 moves to the left a~ viewed in the figure to initiate the pressure reduction :-:
operation by having valv~ head 3~ press against seal valve seat 33 when the condition P~ > ~Pc + f has been attained.
When this occur~, the hydraulic pressure Pc in the chanlber 55 of pressure buffer section BF will increase by ~Pc , due :. to the leftward displacement of plunger 18 into the chamber.
In order to cancel this effect, oil pocket 59 will elastically ,:
:, protrude into air chamber 63 to the extent nececsary to . . . .
:: absorb ~Po and thereby stabilize the pressure level of Pc~
By ~irtue of the above-described valve assembly construction, the load-responsive reducing valve assembly of the present invention initiates pressure reduction by ~ean~
of the action of inertia ball 38 ~uch that the behavior of inertia ball 38 determines the pressure reduction starting '.
.
' ., ~' .
: . . : : ' ; . . .
`:
: point at the same detected dec~eleration for both light and :: heavy load conditions as do the inertia detecting reducing valves of the prior art. ~lowever, due to the displacement ; of piston 42, the point of deceleration at which pressure , ! .
' reduction will initiate will move in effect to the high ~` side or the situation wherein the vehicle carries a heavy . load and in addition, thi~ construction further makes it ,;.
possible to control the starting point of pressure reduction ln accordance with the rate of pressure application to the .~ 10 vehicle brake pedal.
.... .
:' ' ., . .
,, `,, '' ':
. ,,. ., ,~ , "',' :;: ~ :
~"'~,.
i'` ';
: .....
,,' ''"',;
.""~, , . ~ , ...
''`'~, .~" ,'` '~
'.',''~ ;
'``'' `: .
~`` '~ '.
''''~ :
~',', .
' '`-''-~;
~' 24.
' `
:
: `
" , : ' .~. ,
~,, : 8.
. . .
,~ . . .. . . . .
~ . . , .. . .
.. ~ .
. . , : j."~
.~ master cylinder 1 through conduit 5 via the reducing valve ~ body or assembly 6 of the present invention and conduit 7.
. The reducing valve assembly housing 6 i~ installed on a .. portion of the motor vehicle at an angle of inclination corresponding to the deceleration of the vehicle to be `' detected. The brake fluid exits the pressure reducing ~ valve assembly 6 via conduit 7 and is then dis~ributed ; through triple connector 8 to the right and left rear wheel brake cylinders 9 and 9' respectively.
Referring next to Fig. 2, the interior construction :: of the reducing valve assembly shown in Fig. 1 is disclosed.
.
The body or hou~ing 6 of the reducing valve assembly is divided into thxee major portions or sections, namely, the pxoportional pressure reduction section PR, the hydraulic pressure controlling section PC and the pressure buffer section BF.
: The proportional pressure reduction section PR
incorporates a fluid pressure proportioning valve for restricting the flow of fluid fed to the fluid inlet 19 . 20 from master cylinder 1 to the fluid ou~let 20 duri~g a ~i pr~determined range of increasing fluid pressure at the outlet 20~ This fluid pressure proportioning valve consists of a plunger 18 which is axially moveable in a first cavity or chamber 22 within the housing 6. The plunger 18 also .~ extends to the left toward a second cavity 55 within the housing 6.
The plunger 18 is provided with a valve head 35 which is cooperable with valve seat 33 to selectively : establish an interrupt communication between the first fluid , 30 inlet port 19 and the fluid outlet port 20 as the plunger 18 is axially moved.
... .
.' 9. : .
~ . , ~ , .. , . :
Valve head 35 is received within chambex 21 which in ~urn is connected to output port 20 which leads to the rear wheel brake cylinders. The o~her end or stem end of plunger 18 is exposed to second cavity or chamber ~5 through a slide fluid seal from ~he first cavity 22 ~or biasing plunger 18 to a position establishing communication between fir~t inlet port l9 and outl~t port 20 by ~luid under pressure in second cavity or chamber 55. Fluid under pressure -' in chamber 55 will bias plunger 18 to the right so that the plunger head in chamber 21 does not engage valve seat 32 thereby establishing communication between first inlet port 19 and outlet port 20.
The stem portion of plunger 18 i~ slidably received in the central bore 25 of seal holder 24 whioh in turn is seated in bore 23. Spring re~ainer 28 is also held in po~itio~ within bore 23 in buttlng engagement against annular shoulder 29 by pressure applied by seal holder 24 which, in tur~, is retained in ~sition by means of end cap 60 which is threadably received in housing 6 ac indicatedO
Seal holder 24 is constructed to block the direct passage of hydraulic fluid under pressure from the first cavity or chamber 22 directly into the second cavity or ~hamber 55 by mea~ of the cup seal 26 and O-ring 27.
Preload compression spring 31 is held under .:..................................................................... .
compres~ion between ~pring retainer 28 and the flange portion 30 of plunger 18 as illustrated.
;: ~he annular 3eal valve or ~alve seat 33 is ~ illustrated and described in detail in United States Patent No. 3,423,936. This Patent may be referred to to explain ` 30 the basic cooperative pressure reducing ~unction or operation `, that occurs between valve plunger 18 and valve seat 33.
,. ,~
10.
' ~' . : : ' , .
Seal valve or valve seat 33 is made of an ela~tic material and i5 sandwiched between the annular shoulder 32 and the righ~ æide or end of plunger 18. Hydraulic fluid under pressure PM from the master cylinder enters through the first inlet port 19 into the first cavity or chamber 22 and passes through the crescent shaped passages 34 formed between plunger 18 and the wall of cavity 22 and then continues to flow between valve seat 33 and pl~nger 18 on into chamber 21 and out outlet p~rt 20. This fluid passage or communication between inlet p~rt l9 and outlet por~ 20 is interrupted when plunger 18 moves to the left so that the head 35 of the plunger in chamber 21 engages valve seat 33.
This pressure reducing valve thus proportionally reduce~ the hydraulic fluid pressure fed to the output 20 and sub~equently the rear wheel brake cylinders by opening and clo~ing CDmmunication of valve head 35 with valve seat 33. A more detailed explanation of the oper,ation of this portion o~
the reducing valve may be obtain~ed by reference to lines 16 through 47 of U.SO Patent No. 3,736,031 issued May 29, 1973.
The ~hird cavity or chamber 37 in the hydraulic pre~sure controlling seal-in 3ection PC is connected by second inlet port 36 to the hydraulic fluid under pressure PM from the master cylinder via the first chamber or cavity 22. Inertia ball 38 is positioned in the center of third cavity 37. The right side or end of the third chamber or ball chamber 37 is closed by means of plug 39 that is threadably received in reducing valve body or hou~ing 6. An airtight seal is maintained between third cavity 37 a~d the exterior by msans of O-ring 40.
In the bore 41 of this plug 39 t a piston 42 is ~lidably received suoh ~hat the left end o the piston 42 . . :
,, 111.
; ' ':
..
. ' , ~- : ' 2~;Z
contacts the inertia bal:L 38 at rest. Hydraulic pressure within the third chamber 37 will ac~ on the piston cup seal 43 via the crescent groove 44 to urge piston 42 to the right against the compression of preload spring 47 for the maximum possible displacement of As indicated by the double-headed arrow. ~his displacement of piston 42 increases the distance - -of travel for inertia ball 38 over incline 37a.
. . .
Preload spring 47 is sandwiched in position between the annular shoulder 45 of pis~on 42 and the annular shoulder or end wall 46 of ~he fourth cavity or chamber 41 within ; housing 6 ox plug 39.
;,:", The installation length of preload spring 47 is .; .
determined by snap ring 49 inserted in the ring groove 48 ~` provided o~ the stem or spindle portion of the piston which , .,~: " .
extends through plug 39 to the exterior. This snap ring arrangement provides a stop to limit the extent to which ; piston 42 will be permitted to slide or extend toward third cavity 37 due to the bias of preload spring 47. The movement ~' of piston 42 on the other hand, is restricted to the right , , 20 side by the contact o~ annular ~houlder 50 on the stem portion of the piston with the annular shoulder 46 of the fourth cavity or chamber 41. Elastic dust boo~ 51 is provided ,~ with an annular snap fit to plug end plug 39 and slidably `~ receive the outer circumference of the exposed spindle ,;: . . .
,'~ portion of piston 42 in a sealed manner to prevent the entry of dust and water into the slide contact between the piston spindle and end plug 39 and consequently into the fourth ., ; , ; cavity or chamber 41.
An operating fluid channel 52 is provided in the 30 top of the third or ball cavity 37 and is of a semi-., .
:',, ' , .
,~ ' `',''~ ' .. :' ,i :;
,:: , , :, . . : .
. -. . .
.:................. .
.. . . . .
, . . ..
cylindrical cross con~iguration and is provided to assist the rolling of inertia ball 38 to the left on incline 37a, as this channel 52 permits the free flow of fluid around inertia ball 38 when it is in motion to reduce pressure build up as much as possible in front of the ball as it is rolling to the left.
- Check valve seat 53 of the inertia-responsive valve is constructed of a plastic tubing or material and has a central penetrating channel or bore. Check valve seat 53 is retained in the reducing valve housing 6 by means of retainer 54 at a position to preset or predetermine the small travel distance 8 which the inertia ball 38 must travel from ~- its engagement with pis~on 42 in order to press the mouth `~ portion of check valve seat 53 and thereby close the passage of fluid from third chamber 37 to the central bore of check valve seat 53.
...:
-; The pressure buffer section BF provides two functions~ First of all it is the chamber which provides ;~- fluid under pressure to bias the fluid pre~sure proportioning valve consisting of piston 18 and valve seat 33 in order to detexmine the pressure reduction starting pressure and in addition, it also improves the liquid seal function of check valve 53 when inertia valve 38 seats therewith. More ; definitely, the oil pocket of cavity or chamber 55 is utili~ed ~ as the control cha~ber to apply fluid pressures from there-" within against the exposed st~m end of plunger 18 in order to control the starting pressure for the reducing operation.
The hydraulic fluid is transmitted under pressure to the oil pocket or ~econd cavity 55 from the third cavity or chamber 37 through the central bore of check valve seat : i~ . . .: , : ~ 53 and thence through pa~sage 56 ~o the annular groove 57 to the radial communication pa~isage or opening 58 provided at the left end of seal holder 24.
The pressure bufer means within the s2cond cavity : or chamber 55 provides a means wherein the second chamber 55 . is enabled to expand its capacity elastically to compen-~ate -: for an incremental fluid pressure increase created therein : due to the closure of the iner~ia-responsive check valve, ....
i~e., engagem~nt of inertia ball 38 with inertia check valve seat 53, thereby improving the cloæure seal of the check ... valve in section PC of the load-responsive pressure reducing valve assembly.
This pressure buffer consists of an ela-~tic wall portion 59 in the ~econd chamber or cavity 55 which is ou~wardly expandable into a sealed air chamber 63. The expandable wall portion 59 may be designated as an oil ; pocket which is made of an elastic material and which is centrally held within end plug 60 by annular shoulder 61 and . the inside bottom 62 of end plug 60 to thus orm the annular ,'. 20 air chamber 63.
: "
::;,, The end plug 60 is threadably secured in the reducing valve body or housing 6 a~ indicated and thus `, maintains an air tight seal of both oil pocket or the second . cavity 55 and air chamber 63 from the exterior. This ~ealed relationship is insured by the use of O-ring 64 and as formerly pointed out, end plug 60 also restricts the movement ,.~
~ of seal holder 24 to the left, or as previously indicated, :...................................................................... .
.~' plug 60 holds ~eal holder 24 in its prescrib~d fixed position.
.. . .
~: Reference numeral 65 generally indicates an air ,` 3C bleeder which is provided for the purpose o~ expelling air ... ..
,,~., , .
14.
~' : ', which migh~ be entrapped in ch~ber or cavity 55, third ~- cavity 37, and second inlet port 36 or the first cavity or chamber 22. In other words, it is designed to purge the entire reducing valve assembly of air which is accidentally mixed in with the hydraulic braking fluid.
Fig. 3 illus~rates ideal hydraulic braking pressure curves for a given vehicle with two different load conditions.
The one-dot broken curve E indicates the ideal curve for a light load condition for master cylinder hydraulic fluid pressure Pm versus the output pressure Pr of the pressure reducing valve assembly of the present invention which is supplied to the rear wheel brake cylinders. The one-dot broken line F indicates an ideal curve for heavy load vehicle conditions. Curves O-Pse-E~ and O-Ps~-F' represent actual operating curves of the pressure reducing valve assembly of the present inv~ntion which attempt to closely correæpond to the ideal curves for light load and heavy load oDnditions.
In order to automatically force the hydra~lic i 20 pressure of th~ rear wheel cylinders, as shown by the - polygonal line O-Pse-E', at the time of liyht load conditions, ..... .
and the polygonal line O-Psf-F' at heavy load conditions, to correspond to these ideal hydraulic pressure curves i respectively. Inertia ball 38 is utilized to set the starting pressure of the fluid pressure reduction operation.
~, Inertia ball 38 controls both of the curves of actual operation by moving to the left on incline 37a for the predetermined distance 8 to contact the check valve seat 53 in order to make the actual straight line curves conform as closely as possible to the ideal curves illustrated in ':
':
15.
. : ~ .
:' , : . : ,' ' ' , ,: ....... . , . . : . ' : .
Fig. 3. Inertia ball 38 thus controls the starting point of the pressure reduction opera~ion by sealing off the master cylinder hydraulic pressure Pm from the control chamber or :.
second cavity 55 at the point in time that inertia ball 38 : oontacts the check valve seat 53 by traveling or rolling up . incline 37a and ~eals the check val~e bore within check valve seat 53~
If i~ is assumed that Po represents the hydraulic braking pressure of ~he vehicle brakes and tha~ C represents the brake fac~or, then the braking force B of the vehicle may be represented as shown by the following formula:
B = C Pc (1) In addition, the ratio between the deceleration ~ ~ of the vehicle and the acceleration of gravity g is ..
equal to the ratio between the braking ~orce B and the weight . W of the vehicle. This relationship may be expre~sed as ' follows:
~, B .
g W (2) ; When a deceleration occurs in a vehicle due to ., :
:1 20 braking, the following equilibrium will then occur or be .
, established around or in relation to the inertia ball 38, , ., if the weight o~ the inertia ball in the hydraulic braking liquid is designated as W: .
: W a cos ~ _ W sin ~ :
> tan ~ ~3) ~ .
.. . The inertia ball 38 will begin to move to the left as seen in Fig. 2 when the deceleration as shown by the inequality sign of Formula (3) is exceededO Expressing this mathematically, the operation of the inertia ball 38 may be expressed as a function of the angle of installation as follows:
'' .'. . .
., .
16.
, ;' , ': :
.-, .
.' ~
AS a re~ult, the hydraulic pressu_e Pa which is sealed within the second chamber or oil pocket 55 may ~hus be expressed from Fonmulae (l), (2) and (4) and mathematically reduced and placed in order as shown in :~ the following eql7ationO
:~ f (~) :~: pO ~ W (5) : C
~ On ~he other hand, if inertia ball 38 has traveled the distance 6 Up the incline 37a in time T at a velocity V, then, VT (63 In addition, if the hydraulic pressure of the master cylinder 1 is designated Pm2 at a givan time and the -velocity of pressure rise per unit tLme is designated as :
Vp, then Vp may be expressed by the following formula~
~ = Pmi (7) r',' Thus~ from Formulae 16) and (7), Pm2 ~ay be .`. designated as followss ~
~., Pm~ = 2 Vp ~ 8 ~8~ :
`"'' V , :, Furthermore, if the installation load of the preload spring 47 is F, the spring constant hereof is R
:: . .:
1 and the distance which ~he piston 42 is pe7~tted to slide ~ .
;. within its bore or chamber 41 is designated as ~8 due to the applied hydraulic pressure Pm o the master cylinder, which acts on the cross-sectional area A3 of piston 42 to move the same to the right, then the equilibrium of force about . the piston 42 can be expressed by the followi~g ~ormulae: .
, .'' .
.:, '':' : ,' :. 17 .~
:
~ : - . . . .
Pml A3 = F ~ Q~ K
: F + Q8 ~ K
Pml = __________ (9) To m~thematically state this relationship in a more meaningful manner, the hydraulic pre~sure Pc sealed in .. , the oil po~ket or sQcond chamber 55 may be expressed from ; Formulae (8) and (9) and mathematically reduced and placed i in oxder as indicated in the following formula:
Pc = Pml + Pm2 `:
;:: F + ~8 K 2Vp Pc - - + _ (8 ~ ~s) (10) i,.:
Formula ~10) indicates the hydraulic pressure which is sealed in the oil pocket or ~econd chamber 55 in the ~"~ situation wherein ~he floor surfaca of the third cavity or chamber 37 i8 flat as shown in Fig. 2, thus illustxating a ~ constant deceleration detecting type pressure reducing valve :~ assembly. However, the floor or surface upon which inertia ball 38 rolls in chamber 37 may be provided in the form of a ,., ; . .
.' convex curved surface as illustrated in Fig. 4 to thus make the apparatus a variable deceleration detection type wherein . .
~:1 the detected deceleration increases with the angle o~ tangent ~, which indicates the increments of angle increase of the incline 37b of Fig. 4.
- ~ With reference again to Fig. 3, the operation of the reducing valve assembly illustrated in Fig. 2 will be explained with regard to the polygonal line O-Pse-E~, which represents the pressure reduction characteristics o~ the apparatu~ or a light load condition.
Re~erring to Fi~. 2 for thi~ example, the input hydraulic pressure Pm supplied from the master cylinder to port 19 is tran~mitted directly to the output port 20 via . .
',.' ' l~o .
' .
' :
the annular gap between plungex 18 and the seal valve or valve seat 33 as plunger 18 i~ urged under the bi~s of compression spring 31 to the far right as indicated in the Figure. Protru~ions on the left side of valve seat 33 permit the fluid to pass the valve seat to the outle~ port 20.
Accordingly, if the hydraulic pressure Pc within second chamber or cavity 55 at the tLme inertia ball 38 contacts check valve seat 53 under the influence o~ an applied deceleration ~e as shown in Formula (10) is designated as - 10 P¢e, the equilibrium of plunger 18 may he mathematically illustrated by the following formula:
Pce A2 + f < P~
wherein A2 ie the cross-sectional area of the ~: stem portion of plunger 18 as indicated .; ., ,:
in the Figure, and f i3 the installation load of preload spring 31.
`~1' .
The principal object of preload spring 31 is to :~
restoxe plunger 18 to its original or normal position after ;~
: each time the fluid pressure proportioning valve has made a :
j 20 closure by plunger 18 moving to the left to thereby engage ~ :
'`J' the annular valve head 35 with the inner diameter of valve seat or seal 33 to reduce or re~rict fluid pressure flow : from the ma~ter cylinder to the rear wheel brake cylinders~
Another object of preload spring 31 i8 to guarantee minimal necessary braking force applied to the brake pedal indicated .
.~. in Fig. 1 even if the installation angle ~ shown in Fig. 2 ;~. may become nearly equal to zero when the vehicle is descending a s~eep slope and the inertia ball 38 thus moves to the left ~ :
a~ seen in Fig. 2 at a deceleration which is les~ than the .` 30 set or predetermined deceleration rate, wherein a hydraulic 'i . "
`' :, ,....................................... .. ~ :
.. 19. '.' . . , . :- - :
322~i~
~: ;
., pressure will be sealed in the oil pocket or second cavity -~ 55 which may eve~ be near to zero.
From the foregoing, one can derive from Formula (11) the following formula in regard to the master cylinder ..,~
.~ pressure Pm:
: f Pm ~ Pce ~ A ~12~
~hus, the hydraulic pressure Pm from the master cylinder at the moment wherein the condition~ of Form~la `: ll2) are caused to have an equality sign, the pressure Pm becom2s the pressure Pse required to start the pressure .~ reducing operation.
When the ma.~ter cylinder pressure Pm increases , .
a sufficient am~unt to at~ain the equality sign of Formula . (12) and thereafter increases to attain the inequality sign .:
'. thereof~ the plunger 18 will move to the left due to the ~, . . .
~i partial pressures which act against the larger area Al sf .. . .
,`, pi8ton head 35 in chamber 21 opp3sed to the smaller areas exposed to chamber 22~ such that the outer circumference of :., .` valve head 35 seats in the inner circumference of the valve seat 33 thereby temporarily bloclking the passage of hydraulic .: fluid from fir~t input port 19 to output port 20. The equilibrium of hydraulic pressure around or on opposite sides ~ of plunger 18 at this ~oint in time may be expressed as :~
: follows:
Pr Al = (Al - Az) Pm ~ f + Pce A2 (13) .. where Pr is the output hydraulic pre~sure supplied to the .' rear wheel brake cylinder through output 20, `~, Al is the cross-sectional area of valve head 35.
;~ From Formula (13), the output hydraulic pre~sure .-, 30 may be further reduced and expressed as follows: :
: ,~
... ~
. . .
.
:.' ,;~ 20.
. . ~
~:`
- . .
.,, .,'`'' ` .
Al - A2 f A2 Pr = ~ Pm ~ Pce (14) ~ Al Al A~
The relationship expressed in this Formula between the input and the output hydraulic pressures may be seen to satisfy the polygonal line O-PseoE~ illustrat2d in Fig. 4 for light load conditions.
(Al - A2)/AI in Formula (14) represent~ the ratio of pressure reduction after commencement of the pressure , ~ reducing operation.
In a like manner, when piston 42 has moved to the .
right in Fig. 2 under the influence of Pm for vehicle ; deceleration on the heavy load side9 and the hydraulic pre~sure Pc shown in Formula (10) has thus become or attained level Paf, an equilibrium of Formula (14) with P¢e ; substituted by Pcf, will be established and, at the ~ame time as Pse moves to the level of P~f, E~ makes a parallel translation to F' as seen in Fig. 3 and thereby effects load~responsive proportionating pressure reduction for heavy load ccnditions.
` In either load condition, when Pm reduces from a value on the line E' or ~' in Fig. 3, Pm does not follow Formula ~14). Stated in a different man~er, and with '` reference to Formula (133, the Aydraulic pressure Pm applied ,t, to the difference in area of plunger 18 (A~ - A2) reduces, the equilibrium of the plunger 18 in accordance with Formula `;. (13) is broken, and the valve head 35 moves even further to the le~t while retaining its sealed relationship of closure - with valve ~eat 33 and the hydraulic fluid or liquid of higher , pressure in output port 20 flows into the first cavity 22 on ,.~., the input port 19 side of the valve seat via the outer circumference of the seal valve or seat 33 and, thereafter, : . ,.
21. ~
.
` P~ reduces as Pm reducesO The extreme leftward movement .. ~ of plunger 18 at this point in time is restricted by means of the annular shoulder 66 within seal holder 24.
: Even if the hydraulic pressure applied from the master cylinder to the rear wheel brake cylinders is reduced ~rom high braking pressure by removal of brake application to the mas~er cylinder such that the vehicle gradually decelerates ,' below the prese~ deceleration at which check valve 53 will i close, inertia ball 38 will still remain in contact with check valve 53 as long as the equilibrium o the following ' ' formula holds true, A4 being the cross sectional area of the central hole o~ the check valve seat 53:
W u sin ~ _ Pm A4 (15) ~owever, if the master cylinder pressure Pm . reduces~ such that the left side of Formula ~15) becomes greater than the right side as indicated by the inequality : sign, the inertia ball then moves to the right as viewed in ~`~ Fig. 2 down incline 37a and the hydraulic pressure within :~ the third chamber or ball chamber 37 becomes equal to that ;~ 20 of second chamber or control chamber 55.
One of the major section.~ of the pressure reducing valve assembly, as previously explained, is the pres~ure ~-~ buffer section BF which includes the ~econd cavity or chamber :: 55~ ~n elastic wall portion in the form o~ an elastic oil ,;
... pocket 59 is provided for chamber 55. The first function of oil pocket 59 is explained as follows: when i~ertia ball 38 .~ presses against check valve 53, it compresses the elastic .:
material of the check valve seat such ~hat the hydraulic pressure Pa which is sealed in the chamber 55 of pressure ;, 30 buffer section BF at that moment becomes slightly higher :.
... .
22.
' ' .
:~ due to this compression e~fect. Alth~ugh the pressing force Pm o A4 of inertia ball 38 against the check valve ~eat 53 ,. is restricted due to the fact that the outer circumference , of the inertia ball contac~s ~he end surface 67 of retainer 54, nevertheless, this increase in pressure of ~Pc would have the effect of pushing the inertia ball 38 back off its check valve seat 53. To prevent this displacement of the inertia `;~ ball from its valve seat, oil pocket 59 elastically protrudes on air chamber 63 in end cap 60 ~o absorb this small pressure increase QP¢ and thereby cancels the possible undesirable effect~ of ~Po on the fluid pressure proportionin~ valve, : while at the same time improving ~he liquid sealing capabilities of the check valve consi~ting of inertia ball 38 and check valve seat 53.
The qecond function of the pres~ure buffer section i~ to ¢ompensate for the event that plunger 18 moves to the left a~ viewed in the figure to initiate the pressure reduction :-:
operation by having valv~ head 3~ press against seal valve seat 33 when the condition P~ > ~Pc + f has been attained.
When this occur~, the hydraulic pressure Pc in the chanlber 55 of pressure buffer section BF will increase by ~Pc , due :. to the leftward displacement of plunger 18 into the chamber.
In order to cancel this effect, oil pocket 59 will elastically ,:
:, protrude into air chamber 63 to the extent nececsary to . . . .
:: absorb ~Po and thereby stabilize the pressure level of Pc~
By ~irtue of the above-described valve assembly construction, the load-responsive reducing valve assembly of the present invention initiates pressure reduction by ~ean~
of the action of inertia ball 38 ~uch that the behavior of inertia ball 38 determines the pressure reduction starting '.
.
' ., ~' .
: . . : : ' ; . . .
`:
: point at the same detected dec~eleration for both light and :: heavy load conditions as do the inertia detecting reducing valves of the prior art. ~lowever, due to the displacement ; of piston 42, the point of deceleration at which pressure , ! .
' reduction will initiate will move in effect to the high ~` side or the situation wherein the vehicle carries a heavy . load and in addition, thi~ construction further makes it ,;.
possible to control the starting point of pressure reduction ln accordance with the rate of pressure application to the .~ 10 vehicle brake pedal.
.... .
:' ' ., . .
,, `,, '' ':
. ,,. ., ,~ , "',' :;: ~ :
~"'~,.
i'` ';
: .....
,,' ''"',;
.""~, , . ~ , ...
''`'~, .~" ,'` '~
'.',''~ ;
'``'' `: .
~`` '~ '.
''''~ :
~',', .
' '`-''-~;
~' 24.
' `
:
: `
" , : ' .~. ,
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a brake system provided with a reducing valve having a brake fluid inlet and a brake fluid outlet respectively connected to a brake fluid motor and a wheel brake cylinder in the rear wheels of a vehicle: a deceleration-responsive reducing valve including therein; a plunger which has one end exposed to the brake fluid inlet and the other end exposed to the brake fluid outlet of the reducing valve for restricting fluid pressure applied to the wheel cylinder when an operation-starting pressure at said outlet is attained; means to determine said operation-starting pressure of said plunger in relation to the weight of the vehicle and any load carried thereby and including an inertia ball resting on an incline for rolling up said incline upon vehicle deceleration to seal braking fluid from the brake system under a then existing pressure in a cavity, which sealed fluid communicates with said plunger to determine the operation-start-ing pressure thereof; and means to vary this then existing sealed pressure of said sealed fluid in said cavity and including a piston provided downward on said incline and against which said inertia ball normally rests when not rolling up said incline, said piston displaceable against a bias by brake fluid under pressure from the brake system to displace the piston in a direction to increase the roll travel of said inertia ball when a predetermined fluid pressure at the inlet of said reducing valve is exceeded to thereby increase the operation-starting pressure of said plunger in proportion to an increase of load on the vehicle.
2. A load-responsive pressure reducing valve assembly for hydraulic brake systems adapted to be interposed between a fluid motor and at least one brake cylinder of a wheeled vehicle, comprising: a fluid pressure proportioning valve including a housing having an inlet, an outlet, and a first chamber providing communication between said inlet and said outlet, and a pressure-responsive member disposed in said chamber and having a valve head cooperable with a valve member for restricting the flow of fluid from said inlet to said outlet through said valve member;
said pressure-responsive member having a portion thereof exposed to a second chamber in said housing through a fluid seal from said first chamber for biasing said member to a position establishing said communication between said inlet and said outlet by fluid under pressure in said second chamber and thereby controlling restricting starting pressure of said pressure-responsive member; an inertia-responsive valve including an inertia-responsive valve member responsive to a predetermined rate of deceleration of the assembly to roll a predetermined distance up an incline to close a normally open passage of fluid from said inlet to said second chamber; said inertia-responsive member in butting contact with a piston which recedes with an increase of fluid pressure from said inlet beyond a predetermined pressure limit to increase said predetermined distance of roll by virtue of the gravitational forces of said inertia-responsive member against said piston thereby increasing the distance said member must roll up said incline before closing said normally open passage; and pressure buffer means in said second chamber to expand elastically to compensate for an incremental fluid pressure increase created therein due to the closure of said inertia-responsive valve thereby improving the closure seal thereof.
said pressure-responsive member having a portion thereof exposed to a second chamber in said housing through a fluid seal from said first chamber for biasing said member to a position establishing said communication between said inlet and said outlet by fluid under pressure in said second chamber and thereby controlling restricting starting pressure of said pressure-responsive member; an inertia-responsive valve including an inertia-responsive valve member responsive to a predetermined rate of deceleration of the assembly to roll a predetermined distance up an incline to close a normally open passage of fluid from said inlet to said second chamber; said inertia-responsive member in butting contact with a piston which recedes with an increase of fluid pressure from said inlet beyond a predetermined pressure limit to increase said predetermined distance of roll by virtue of the gravitational forces of said inertia-responsive member against said piston thereby increasing the distance said member must roll up said incline before closing said normally open passage; and pressure buffer means in said second chamber to expand elastically to compensate for an incremental fluid pressure increase created therein due to the closure of said inertia-responsive valve thereby improving the closure seal thereof.
3. The load-responsive pressure reducing valve assembly as claimed in claim 2, wherein said incline is a curved convex surface.
4. The load-responsive pressure reducing valve assembly as claimed in claim 2, wherein said piston is baised toward said inertia-responsive valve member to a stop for engaging said valve member at rest on the down side of said incline, said piston displaceable against its bias by said fluid pressure from said inlet to thereby increase said predetermined distance of roll.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7754576A JPS534167A (en) | 1976-06-29 | 1976-06-29 | Load response type regulating valve |
| JP77545/76 | 1976-06-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1082262A true CA1082262A (en) | 1980-07-22 |
Family
ID=13636965
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA278,388A Expired CA1082262A (en) | 1976-06-29 | 1977-05-13 | Load-responsive pressure reducing valve device for use in a vehicle brake system |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS534167A (en) |
| AU (1) | AU509108B2 (en) |
| CA (1) | CA1082262A (en) |
| DE (1) | DE2727893C3 (en) |
| DK (1) | DK287577A (en) |
| FR (1) | FR2356543A1 (en) |
| GB (1) | GB1545349A (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS54144558A (en) * | 1978-04-28 | 1979-11-10 | Nippon Air Brake Co | Deceleration responsive hydraulic control valve |
| JPS5838341B2 (en) * | 1978-06-29 | 1983-08-22 | 株式会社ナブコ | Deceleration responsive hydraulic control valve |
| FR2437962A1 (en) * | 1978-10-05 | 1980-04-30 | Dba | BRAKE COMPENSATOR SERVED ON DECELERATION |
| FR2456014A1 (en) * | 1979-05-09 | 1980-12-05 | Dba | BRAKING CORRECTIVE ASSIGNED TO DECELERATION |
| GB2065251B (en) * | 1979-12-14 | 1983-07-13 | Automotive Prod Co Ltd | Brake pressure proportioning valves |
| GB2183007B (en) * | 1985-11-13 | 1989-10-11 | Automotive Products Plc | Inertia valves |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3168351A (en) * | 1961-05-05 | 1965-02-02 | Kelsey Hayes Co | Motor vehicle hydraulic brake system |
| FR89462E (en) * | 1963-06-21 | 1967-06-30 | Brake regulator | |
| FR1431765A (en) * | 1964-01-30 | 1966-03-18 | Kelsey Hayes Co | Hydraulic brake systems compensate for weight transfer during rapid braking |
| US3455609A (en) * | 1968-08-05 | 1969-07-15 | Gen Motors Corp | Inertia sensing proportioner |
-
1976
- 1976-06-29 JP JP7754576A patent/JPS534167A/en active Granted
-
1977
- 1977-04-12 GB GB1512877A patent/GB1545349A/en not_active Expired
- 1977-05-13 CA CA278,388A patent/CA1082262A/en not_active Expired
- 1977-06-21 DE DE19772727893 patent/DE2727893C3/en not_active Expired
- 1977-06-27 FR FR7719561A patent/FR2356543A1/en active Granted
- 1977-06-28 AU AU26518/77A patent/AU509108B2/en not_active Expired
- 1977-06-28 DK DK287577A patent/DK287577A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| DE2727893B2 (en) | 1979-08-30 |
| JPS534167A (en) | 1978-01-14 |
| DE2727893C3 (en) | 1980-05-14 |
| DK287577A (en) | 1977-12-30 |
| DE2727893A1 (en) | 1978-01-05 |
| AU509108B2 (en) | 1980-04-17 |
| FR2356543B1 (en) | 1982-06-18 |
| AU2651877A (en) | 1979-01-04 |
| GB1545349A (en) | 1979-05-10 |
| JPS6222820B2 (en) | 1987-05-20 |
| FR2356543A1 (en) | 1978-01-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |