GB2253664A - Load sensitive proportioning valve - Google Patents
Load sensitive proportioning valve Download PDFInfo
- Publication number
- GB2253664A GB2253664A GB9105125A GB9105125A GB2253664A GB 2253664 A GB2253664 A GB 2253664A GB 9105125 A GB9105125 A GB 9105125A GB 9105125 A GB9105125 A GB 9105125A GB 2253664 A GB2253664 A GB 2253664A
- Authority
- GB
- United Kingdom
- Prior art keywords
- fluid chamber
- load sensitive
- cup seal
- proportioning valve
- valve
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
- B60T8/18—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to vehicle weight or load, e.g. load distribution
- B60T8/1812—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to vehicle weight or load, e.g. load distribution characterised by the means for pressure reduction
- B60T8/1831—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to vehicle weight or load, e.g. load distribution characterised by the means for pressure reduction pressure reducing or limiting valves
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- Engineering & Computer Science (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Hydraulic Control Valves For Brake Systems (AREA)
Abstract
A load sensitive proportioning valve comprises housing means (12, 14); a fluid chamber (18) having an input (24) and an output (28); a valve member (54) having a plunger (58) axially slidable in a bore (20) and a valve head (56 positioned in the fluid chamber; an annular cup seal (32) positioned in the fluid chamber between the input and the output and having an outer edge (88) directed towards the input, the plunger passing through a central opening (36) in the seal, the valve head being axially movable into sealing engagement with the seal; and an annular collar (34) fixed in the fluid chamber between the end wall thereof and the seal and having a central aperture (38) within which the valve head is positioned and axially movable. <IMAGE>
Description
LOAD SENSITIVE PROPORTIONING VALVE
This invention relates to load sensitive proportioning valves of the type used for regulating the pressure of the hydraulic fluid in the braking systems of motor vehicles.
A load sensitive proportioning valve is positioned between a source of fluid pressure (typically a master cylinder) of the braking system and a brake cylinder at a wheel of the motor vehicle.
The load sensitive proportioning valve acts to limit or restrict the fluid pressure applied to the brake cylinder to reduce the risk of wheel lock on braking.
Various designs of load sensitive proportioning valves are known, as, for example, disclosed in GB 2071224A, GB 2046384A and GB 1557006.
These known arrangements include a valve head engageable with a valve seat to restrict the flow of hydraulic fluid between the input and output of the load sensitive proportioning valve. Typically, the housing of the load sensitive proportioning valve is secured to a sprung portion (such as, the chassis) of the motor vehicle, and the valve head or the valve seat is connected to an unsprung portion, such as a suspension member or wheel axle such that it is subjected to a force dependent on the load on the motor vehicle. Movement of the valve head relative to the valve seat takes place when the fluid pressure at the input reaches and rises above a level generally known as the cut-in pressure. The value of the cut-in pressure varies dependent on the load on the motor vehicle. For input pressures below the cut-in pressure, fluid flow between the input and output is unrestricted.
These known arrangements are complicated, and involve the use of a large number of components.
It is the object of the present invention to overcome this disadvantage.
To this end, a load sensitive proportioning valve in accordance with the preset invention connectable between a sprung portion and an unsprung portion of a motor vehicle, comprises housing means securable to one of the sprung or unsprung portions; a fluid chamber within the housing means and having side walls and an end wall; a bore extending through the housing means and into the fluid chamber; an input through a side wall of the fluid chamber; an output from the fluid chamber; a valve member axially slidable in the bore and including a valve head positioned in the fluid chamber and a plunger sealed in the bore and extending out of the housing means for engagement with the other of the sprung or unsprung portions; an annular cup seal positioned in the fluid chamber between the input and the output and having an outer edge directed towards the input which normally sealingly engages the side walls of the fluid chamber, the plunger passing through a central opening in the annular cup seal, the valve head being positioned adjacent the output side of the annular cup seal and being axially movable into sealing engagement therewith; and an annular collar fixed in the fluid chamber between the end wall thereof and the annular cup seal, the annular collar having a central aperture within which the valve head is positioned and axially movable relative thereto.
The bore and the valve member have longitudinal axes which are aligned, and which are also aligned with the axes of the central opening of the annular cup seal and the central aperture in the annular collar. Axial movement of the valve member is along its longitudinal axis.
The engagement of the plunger with the other of the sprung or unsprung portions generates a force on the valve member which acts to move the valve head away from the annular cup seal to allow flow of hydraulic fluid between the input and output.
The level of this force is dependent on the load on the motor vehicle. This is the normal or rest position of the load sensitive proportioning valve.
Fluid flow between the input and output through the fluid chamber is by way of the central opening in the annular cup seal and the central aperture in the annular collar. In this normal or rest position, the outer edge of the annular cup seal sealingly engages the side walls of the fluid chamber. This position prevails while the input pressure remains below a certain level, the cut-in pressure, which is dependent on the force on the valve member, and the cross-sectional area of the plunger, as will be described in greater detail below.
When the fluid pressure at the input reaches and passes the cut-in pressure, the fluid pressure acting on the valve head is such as to move the valve head, against the action of the force, into sealing engagement with the annular cup seal, thereby isolating the input from the output. This is the closed or cut-off position of the load sensitive proportioning valve. If the input pressure continues to rise, a pressure differential is generated across the valve head between its input side and its output side. This pressure differential acts to move the valve head away from the annular cup seal to allow fluid flow from the input to the output. This action dissipates the pressure differential, thereby causing the valve head to move back into engagement with the annular cup seal.Therefore, as the input pressure continues to rise above the cut-in pressure, the valve member is continually moving into and out of engagement with the annular cup seal. That is, the load sensitive proportioning valve moves back and forth between its normal or rest position and its closed or cut-off position.
When the input pressure is released, the pressure differential across the valve member is such as to move or retain the valve head in engagement with the annular cup seal and the outer edge of the annular cup seal moves away from the side walls of the fluid chamber to allow fluid flow from the output to the input. This is the release position of the load sensitive proportioning valve. This situation remains until the fluid pressure at the input drops below the cut-in pressure, at which stage the load sensitive proportioning valve returns to its normal or rest position.
Preferably, the annular cup seal is made from elastomeric material and has a metallic insert to substantially prevent warping thereof The annular cup seal preferably has one or more radially extending grooves in its surface on the input side thereof to allow passage of hydraulic fluid.
Preferably, the valve head has a circumferentially extending ridge directed towards the output side of the annular cup seal for sealing engagement therewith.
The annular collar preferably has at least one radially extending groove and a corresponding circumferentially extending groove therein to allow passage of hydraulic fluid.
Preferably, the housing means is securable to the sprung portion of the motor vehicle and the plunger is engageable with the unsprung portion of the vehicle. In this case, the load sensitive proportioning valve preferably comprises a lever pivotally mounted at one end on the housing means and engaging the plunger, with the other end of the lever being resiliently engageable with the unsprung portion of the motor vehicle by way of a spring.
The housing means preferably comprises a housing having an opening therein, and a cap threadingly and sealingly secured in the opening, the bore extending through the cap, the annular cup seal being secured in place against the annular collar by the cap.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a cross-sectional view of a load sensitive proportioning valve in accordance with the present invention;
Figure 2 is a partial cross-sectional view of the load sensitive proportioning valve of Figure 1 in its normal or rest position;
Figure 3 is a similar view to that of
Figure 2 with the load sensitive proportioning valve in its closed or cut-off position;
Figure 4 is a similar view to that of
Figure 2 with the load sensitive proportioning valve in its release position; and
Figure 5 is a plot of input pressure against output pressure for the load sensitive proportioning valve of Figure 1.
Referring to Figure 1, the load sensitive proportioning valve 10 comprises a housing 12 having a cap 14 threadingly secured in an opening 16 in the housing to define a fluid chamber 18. The housing 12 and the cap 14 define housing means for the load sensitive proportioning valve 10. A bore 20 extends through the cap 14 from an outer surface 22 thereof and into the fluid chamber 18. An input passage 24 passes through the housing 12 and opens through one of the side walls 26 of the fluid chamber 18 to define an input for the load sensitive proportioning valve 10. Similarly, an output passage 28 passes through the housing 12 and opens through an end wall 30 of fluid chamber 18 to define an output for the load sensitive proportioning valve 10.
Fixedly secured in the fluid chamber 18 between the cap 14 and the end wall 30 is an annular cup seal 32 and an annular collar 34, the annular collar being adjacent the end wall. The annular cup seal 32 has a central opening 36, and the annular collar 34 has a central aperture 38, the axes of the central opening and the central aperture being aligned with each other and with the longitudinal axis of the bore 20.
The annular cup seal 32 is made from elastomeric material and has a metallic insert 40 to substantially prevent warping thereof. The outer edge 88 of the annular cup seal 32 is directed towards the input passage 24 and sealingly engages the side walls 26 of the fluid chamber 18 when hydraulic fluid is flowing from the input passage to the output passage 28, or when the fluid pressure at the input is greater than the fluid pressure at the output (as shown in Figures 2 and 3). The annular cup seal 32 also has one or more (and preferably four) radially extending grooves 42 in its input side 44 adjacent the cap 14.
The annular collar 34 is substantially rigid and has at least one radially extending groove 46 in its surface 48 adjacent the end wall 30, and a corresponding circumferentially extending groove 50 in its outer edge 52.
The load sensitive proportioning valve 10 also comprises a valve member 54 which includes a valve head 56 and a plunger 58. The valve head 56 is positioned in the central aperture 38 in the annular collar 34. The plunger 58 extends through the bore 20 and the central opening 36 in the annular cup seal 32, and has one end 60 connected to the valve head 56, and the other end 62 extending out of the cap 14.
The valve member 54 can move axially along its longitudinal axis relative to the cap 14, the annular cup seal 32 and the annular collar 34. The dimensions of the components are such that small clearance gaps 64, 66 exist between the plunger 58 and the edge of the central opening 36 in the annular cup seal 32, and between the valve head 56 and the edge of the central aperture 38 in the annular collar 34, respectively. The valve head 56 has an output side 68 directed towards the end wall 30 of the fluid chamber 18, and an input side 70 facing the annular cup seal 32. The input side 70 has a ridge 72 extending around its circumference and directed towards the annular cup seal 32.The plunger 58 has a cross-sectional area S1, and the output side 68 has a cross-sectional area
Seals 74, 76 between the cap 14 and the housing 12, and between the plunger 58 and the cap respectively substantially prevent the egress of hydraulic fluid from the fluid chamber 18.
The input passage 24 is connected to a source of fluid pressure (for example, a master cylinder), not shown, and the output passage 28 is connected to a brake cylinder, not shown, of a wheel of a motor vehicle.
A lever 78 is pivotally mounted at one end 80 on the housing 12 and engages the other end 62 of the plunger 58. The other, free, end 82 of the lever 78 is connected to an unsprung portion (for example, a suspension member) of the motor vehicle by way of a spring 84. The housing 12 of the load sensitive proportioning valve 10 is secure to a sprung portion (for example, the chassis) of the motor vehicle. This arrangement generates a force F which acts on the valve member 54 in the direction shown and which is dependent on the load.on the motor vehicle. As the load increases, then the value of force F also increases, and vice versa.
In the normal or rest position of the load sensitive proportioning valve 10 (Figure 2), this force F acts on the valve member 54 to push the output side 68 of the valve head 56 into engagement with the end wall 30 of the fluid chamber 18. The input side 70 of the valve head 56 is spaced from the output side 86 of the annular cup seal 32. Hydraulic fluid can flow through the fluid chamber 18 between the input passage 24 and the output passage 28 by way of the radially extending grooves 42 in the annular cup seal 32 and by way of the clearance gaps 64,66.
the outer edge 88 of the annular cup seal 32 sealingly engages the side walls 26 of the fluid chamber 18. The load sensitive proportioning valve 10 remains in this position whilst the input pressure remains below the cut-in pressure (between A and B of
Figure 5). That is, the pressure on the input side 70 is equal to the pressure applied to the output side 68.
When the input pressure exceeds the cut-in pressure (point B of Figure 5), the force F equals, and then becomes less than, the force applied by the fluid pressure acting on the valve head 56. As a consequence, the valve head 56 moves into sealing engagement with the output side 86 of the annular cup seal 32, and the outer edge 88 of the annular cup seal 32 remains in sealing engagement with the side walls 26, so that fluid flow from the input passage 24 to the output passage 28 is prevented. At this stage, the load sensitive proportioning valve 10 is in its closed or cut-off position as shown in Figure 3. The ridge 72 on the valve head 56 helps to provide an improved sealing action.
The value Pc of the cut-in pressure is dependent on the cross-sectional area Sl of the plunger 58, and the force F. The cut-in pressure can be derived from the formula
c = F + ath S1 where Path is atmopspheric pressure. As can be seen, changes in the value of force F, due to changes in the loading on the motor vehicle, change the value P c of the cut-in pressure.
If the input pressure continues to rise (B to C of Figure 5), a pressure differential is generated across the valve head 56 and the valve head will move back to the rest or normal position (Figure 2). However, this action immediately dissipated the pressure differential, and whilst the input pressure continues to rise and remains above the cut-in pressure, the valve head 56 will then move back to the closed or cut-off position. This cycling of the valve head 56 between the Figure 2 and Figure 3 positions continues whilst the input pressure continues to rise and remains above the cut-in pressure. The consequence of this action is that the output pressure is restricted or limited with respect to the input pressure.
When the input pressure is released (C to D of Figure 5), the valve head 56 moves into or remains in sealing engagement with the annular cup seal 32, and the higher fluid pressure on the output side 86 of the annular cup seal forces the outer edge 88 thereof away from the side walls 26 of the fluid chamber 18 (see Figure 4). This allows hydraulic fluid to flow from the output passage 28 to the input passage 24 by way of the radially and circumferentially extending grooves 46,50 in the annular collar 34. When the fluid pressure at the input passage 24 falls below the cut-in pressure (D of Figure 5), the valve head 56 moves back to its
Figure 2 position allowing hydraulic fluid to flow by way of the radially extending grooves 42 in the annular cup seal 32 and the clearance gaps 64,66 as before. Also, at this time, the outer edge 88 of the annular cup seal 32 moves back into sealing engagement with the side walls 26.
The load sensitive proportioning valve of the present invention has the advantages of being of simple construction using a minimal number of components when compared with the prior art arrangements, and with limited relative movement, thereby providing increased reliability.
Claims (9)
1. A load sensitive proportioning valve connectable between a sprung portion and an unsprung portion of a motor vehicle, comprising housing means securable to one of the sprung or unsprung portions; a fluid chamber within the housing means and having side walls and an end wall; a bore extending through the housing means and into the fluid chamber; an input through a side wall of the fluid chamber; an output from the fluid chamber; a valve member axially slidable in the bore and including a valve head positioned in the fluid chamber and a plunger sealed in the bore and extending out of the housing means for engagement with the other of the sprung or unsprung portions; an annular cup seal positioned in the fluid chamber between the input and the output and having an outer edge directed towards the input which normally sealingly engages the side walls of the fluid chamber, the plunger passing through a central opening in the annular cup seal, the valve head being positioned adjacent the output side of the annular cup seal and being axially movable into sealing engagement therewith; and an annular collar fixed in the fluid chamber between the end wall thereof and the annular cup seal, the annular collar having a central aperture within which the valve head is positioned and axially movable relative thereto.
2. A load sensitive proportioning valve as claimed in Claim 1, wherein the annular cup seal is made from elastomeric material and has a metallic insert.
3. A load sensitive proportioning valve as claimed in Claim 1 or Claim 2, wherein the annular cup seal has one or more radially extending grooves in its surface on the input side thereof.
4. A load sensitive proportioning valve as claimed in any one of Claims 1 to 3, wherein the valve head has a circumferentially extending ridge directed towards the output side of the annular cup seal for sealing engagement therewith.
5. A load sensitive proportioning valve as claimed in any one of Claims 1 to 4, wherein the annular collar has at least one radially extending groove and a corresponding circumferentially extending groove therein.
6. A load sensitive proportioning valve as claimed in any one of Claims 1 to 5, wherein the housing means is securable to the sprung portion of the motor vehicle and the plunger is engageable with the unsprung portion of the vehicle.
7. A load sensitive proportioning valve as claimed in Claim 6, comprising a lever pivotally mounted at one end on the housing means and engaging the plunger, the other end of the lever being resiliently engageable with the unsprung portion of the motor vehicle by way of a spring.
8. A load sensitive proportioning valve as claimed in any one of Claims 1 to 7, wherein the housing means comprises a housing having an opening therein, and a cap threadingly and sealingly secured in the opening, the bore extending through the cap, the annular cup seal being secured in place against the annular collar by the cap..
9. A load sensitive proportioning valve substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9105125A GB2253664A (en) | 1991-03-12 | 1991-03-12 | Load sensitive proportioning valve |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9105125A GB2253664A (en) | 1991-03-12 | 1991-03-12 | Load sensitive proportioning valve |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9105125D0 GB9105125D0 (en) | 1991-04-24 |
| GB2253664A true GB2253664A (en) | 1992-09-16 |
Family
ID=10691363
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9105125A Withdrawn GB2253664A (en) | 1991-03-12 | 1991-03-12 | Load sensitive proportioning valve |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2253664A (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1161829A (en) * | 1965-12-07 | 1969-08-20 | Fiat Spa | Pressure Reducer Device for Hydraulic Brake Mechanisms on Vehicles. |
| GB1183523A (en) * | 1966-07-11 | 1970-03-11 | Girling Ltd | Improvements in or relating to hydraulic brake pressure control devices |
-
1991
- 1991-03-12 GB GB9105125A patent/GB2253664A/en not_active Withdrawn
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1161829A (en) * | 1965-12-07 | 1969-08-20 | Fiat Spa | Pressure Reducer Device for Hydraulic Brake Mechanisms on Vehicles. |
| GB1222492A (en) * | 1965-12-07 | 1971-02-17 | Fiat Spa | Improvements in or relating to pressure reducer devices |
| GB1183523A (en) * | 1966-07-11 | 1970-03-11 | Girling Ltd | Improvements in or relating to hydraulic brake pressure control devices |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9105125D0 (en) | 1991-04-24 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |