GB2393494A

GB2393494A - Pressure control valve

Info

Publication number: GB2393494A
Application number: GB0222566A
Authority: GB
Inventors: John Leslie Leng; Michael Stanley Barnes
Original assignee: Ultronics Ltd
Current assignee: Ultronics Ltd
Priority date: 2002-09-28
Filing date: 2002-09-28
Publication date: 2004-03-31
Anticipated expiration: 2022-09-28
Also published as: GB2393494B; GB0222566D0

Abstract

A pressure control valve 10 for controlling fluid pressure in a fluid pressure actuated circuit, the valve 10 having a fluid inlet 14 and a fluid outlet 16 and comprising a spool 18, a sleeve 20 having a bore 22 in which the spool 18 is slidably received, and actuator means for positioning the sleeve 20 relative to the spool 18. The spool 18 having an internal chamber 26 in fluid communication with the fluid inlet 14, a channel 28 which is formed in the outer surface 30 of the spool 18 and which is in fluid communication with the spool chamber 26 and the fluid outlet 16. A shoulder 32 is formed adjacent to the spool channel 28, and the sleeve bore 22 has a flared portion 44 at the end 46 adjacent to the spool shoulder 32. In use, when the flared portion 44 of the sleeve 20 is positioned adjacent to the channel 28 by an urging force of the actuator means to define a fluid metering area, the fluid passing through the fluid metering area to the fluid outlet 16 is directed by the spool channel 28 and the flared portion 44 of the sleeve 20 to impinge on the spool shoulder 32, resulting in a reaction force being generated to counteract the flow force of the fluid to thereby decrease the tendency for the fluid force to reduce the fluid metering area by closing the spool channel 28 and to decrease the urging force required to be exerted on the sleeve or the spool by the actuator means, which may be electromagnetic.

Description

PRESSURE CONTROL VALVE

This invention relates to a pressure control valve for controlling fluid pressure in a fluid pressure actuated circuit, such as a hydraulic or pneumatic circuit.

s Pressure control valves are known. These typically take the form of direct-

acting poppet-seat or nozzle-flapper type pressure relief valves. However the nominal force required by actuators on direct acting pressure relief valves is typically and approximately determined by multiplying the total seat area upon which the poppet or 10 flapper acts by the pressure drop across the seat-poppet or seat/nozzle-flapper opening. The seat areas of known typical direct acting valves need to be of a reasonable size to ensure that the minimum pressure drop through the valve is sufficiently low at the rated fluid flow, and thus the required actuator force and therefore electrical power consumption is high for controlling the maximum pressure 15 drop through the valve.

The present invention seeks to provide a solution to this problem.

According to the present invention, there is provided a pressure control valve 20 for controlling fluid pressure in a fluid pressure actuated circuit, the valve having a fluid inlet and a fluid outlet and comprising a spool, a sleeve having a bore in which the spool is slidably received, and actuator means for positioning the sleeve relative to the spool, the spool having an internal chamber in fluid communication with the fluid inlet, a channel which is formed in the outer surface of the spool and which is in fluid

communication with the spool chamber and the fluid outlet, and a shoulder which is formed adjacent to the spool channel, the sleeve bore having a flared portion at the end adjacent to the spool shoulder, so that, in use, when the flared portion of the sleeve is positioned adjacent to the channel by an urging force of the actuator means to 5 define a fluid metering area, the fluid passing through the fluid metering area to the fluid outlet is directed by the spool channel and the flared portion of the sleeve to impinge on the spool shoulder, resulting in a reaction force being generated to counteract the flow force of the fluid to thereby decrease the tendency for the fluid force to reduce the fluid metering area by closing the spool channel and to decrease 10 the urging force required to be exerted on the sleeve or the spool by the actuator means. Preferable and/or optional features of the present invention are set forth in claims 2 to 20, inclusive.

The present invention will now be described, by way of example, with reference to the accompanying drawings, wherein: Figure I is a longitudinal cross-sectional view of a first embodiment of a 20 pressure control valve, in accordance with the present invention; Figure 2 is an enlarged view of part of a spool and sleeve of the pressure control valve shown in Figure l;

Figure 3 is a perspective view of the spool and sectioned sleeve shown in Figure 1 and 2; Figure 4 is a longitudinal cross-sectional view of a second embodiment of a 5 pressure control valve, in accordance with the present invention; Figure 5 is an enlarged view, similar to that of Figure 2, showing a third embodiment of part of a pressure control valve, in accordance with the present invention; and Figure 6 is an enlarged view, similar to that of Figure 2, showing a fourth embodiment of part of a pressure control valve, in accordance with the present invention. 15 Referring firstly to Figures 1 to 3, there is shown a pressure control valve 10 having a housing 12 in which a fluid inlet 14 and a fluid outlet 16 are formed, and which comprises a spool 18, a sleeve 20 having a through-bore 22 in which the spool 18 is slidably received, and actuator means for positioning the spool 18 relative to the sleeve 20. There is a small diametral clearance between the sleeve 20 and spool 18 to 20 provide a sliding fit.

The valve housing 12 supports the spool 18 in a housing bore 24 which is in fluid communication with the fluid inlet 14.

The spool 18 has a blind axial bore 26, the open end of which is in fluid communication with the housing bore 24, and two skewed channels 28 which are formed in the outer surface 30 of the spool 18 and which are in fluid communication with the blind axial bore 26 and the fluid outlet 16.

s The spool 18 includes a radially extending continuous flange 32 which is formed adjacent to the skewed channels 28 and which has a circumferentially extending stepped portion 34 positioned facing the skewed channels 28. The spool 18 also includes a plurality of circumferentially extending grooves 36 formed adjacent to 10 one end of the spool 18 so that the skewed channels 28 are interposed between the grooves 36 and the flange 32.

Each skewed channel 28 includes an opening 38 at one end 40 which breaks out into the blind axial bore 26. The openings 38 of the skewed channels 28 are 15 formed diametrically opposite each other. The width and depth of each spool channel 28 tapers along the longitudinal extent of the channel in a direction away from the respective channel openings 38 and towards the spool flange 32, but skewed at an angle to the longitudinal axis of the spool 18. One or more of the longitudinal edges 42 of the skewed channels 28 are arcuate.

The through-bore 22 of the sleeve 20 has a flared portion 44 at the end 46 adjacent to the spool flange 32. This flared portion 44 is typically of frusto-conical or substantially frusto-conical shape, and, as can be seen in Figure 2, has a surface 48 comprising a plurality of distinct frusto-conical or substantially frusto-conical portions

48a, 48b, 48c. The external free edge 50 of the end 46 adjacent to the flared portion 44 is also chamfered.

The sleeve 20 also includes a radially extending continuous stepped flange 52.

The actuator means comprises an electromagnetic actuator 54, an energising circuit 56 arranged adjacent to the housing bore 24 and in electrical communication with the electromagnetic actuator 54, and two spring elements 58a, 58b for applying an urging force Fs (shown by an arrow in Figure 1) to urge apart the respective 10 flanges 32 and 52 of the spool 18 and the sleeve 20. Wires of the energising circuit 56 pass into the valve housing 12 through a fluid-tight sealing plug 57.

The electromagnetic actuator 54 has a fixed electromagnetic part 60 housing permanent magnets 60a, 60b and a pole piece 55, and a movable former part 62 which 15 is coaxial with, and fixedly received on, the sleeve 20 and which supports an electromagnetic coil 64. The spring elements 58a, 58b exhibit an increasing compressive resistance characteristic.

The fixed electromagnetic part 60 of the electromagnetic actuator 54 is 20 attached to the valve housing 12 adjacent to the end 66 opposite the housing bore 24.

The fluid outlet 16 is interposed between the fluid inlet 14 and the electromagnetic part 60.

The sleeve 20 is slidably received on the grooved end of the spool 18, and the

lands 68 between the grooves 36 thus act as bearing surfaces. A retaining element 70 may be used to retain the sleeve 20 on the spool 18.

The movable part 62 of the electromagnetic actuator 54 abuts the sleeve flange 5 52, so that the electromagnetic coil can move in an axial direction in channel 72 of the fixed electromagnetic part 60.

One of the two spring elements 58_ abuts the flanges 32 and 52 of the spool 18 and sleeve 20, and the remaining spring element 58b abuts the sleeve flange 52 and 10 the housing 12.

The electromagnetic actuator 54 is energised, via an electrical control current supplied to the coil 64 by the energising circuit 56, so that an electromagnetic force PA (shown in Figure 1) is generated to move the movable part 62. The resultant 15 magnitude of the actuator force FA and the urging force Fs of the two spring elements 58_, 58_ causes the sleeve 20 to be displaced and positioned along the longitudinal extent of the spool 18. This results in the two skewed channels 28 of the spool 18 being either opened to varying degrees or closed, and consequently a fluid metering area being adjusted.

In use, fluid enters the valve housing 12 through the fluid inlet 14, passes along the housing bore 24 and spool blind bore 26, through the channel openings 38 and into the skewed channels 28. The fluid exiting the skewed channels 28 generates a fluid flow force in the direction marked by arrow FF. The tapered shape of the

skewed channels 28 and the flared portion 44 of the sleeve 20 act to direct the fluid exiting the skewed channels 28 to impinge on the spool flange 32 and, depending on its flow rate, at least in part on the stepped portion 34. The impingement on the spool flange 32 generates a flow-dependent reaction force, in the direction marked by arrow 5 FR, which counterbalances or offsets the flow force FF.

The external chamfered edge 50 of the sleeve 20 in conjunction with the profile of the flange 32 helps determine the exit angle of the flow path of the fluid from the end 46 of the flared portion 44 and towards the fluid outlet 16.

The position that the sleeve moves to when the electrical actuator applies a force FF is determined by the force balance. The forces acting on the sleeve are: Electrical actuator force FA direction 15 Spring Force FS direction Flow force FF direction Reaction force FR direction The flow force FF is mainly dependent on the flow and pressure drop across 20 the fluid metering area provided by the opening between skewed channels 28 and sleeve intersection between sleeve flared portion 48a and bore 22.

The reaction force FR acts on the sleeve in the opposite direction to that of flow force FF and hence acts as a full or partial counterbalance force. In other words,

as the flow increases, the fluid flow force FF increases tending to close the spool /sleeve opening but the reaction force FR also increases and counterbalances or partially counterbalances the increase in FF.

5 The counterbalancing characteristic consequently provides partial pressure compensation. In other words, it reduces the change in port pressure at the fluid inlet 14 for a change in flow through the valve.

By at least partially counterbalancing or offsetting the fluid flow force FF by 10 the generated reaction force FR, the spring force FS required to be exerted by the spring elements 58_, 58_ is reduced and, as a consequence, the actuation force FA required by the actuator 54 to move the sleeve 20 is reduced.

Figure 1 depicts a pressure relief valve 10 which is part of an 'open loop' 15 system which could be used as, for example, a pilot stage to a larger pressure control valve, such as a mainstage pressure control valve (not shown).). The valve 10 is thus designed to regulate pressure in a hydraulic or pneumatic system in proportion to an applied electrical input.

20 This pressure relief valve 10, by the at least partial counterbalancing or offsetting of the fluid flow force FF, provides at least partial pressure compensation.

In other words, for a given actuator force FA, the change in fluid inlet pressure for a change in flow through the relief valve 10 is reduced. By adjusting the position of the sleeve 20 along the spool 18, and thereby changing the fluid metering area, a new

force balance, which arises from the change in flow, is obtained.

Figure 4 depicts a second embodiment of the pressure control valve 10 which is incorporated as part of a 'closed loop' system.

In the second embodiment, parts similar to those of the first embodiment have the same references. As can be seen, the valve 10 of the second embodiment is provided with feedback control from a pressure transducer 74 incorporated as part of the valve housing 12 to sense the fluid pressure at the fluid inlet 14. In this case, a 10 feedback controller 80 electronically regulates the energisation of the electromagnetic actuator, so that the actuation force FA applied to the sleeve 20 can be continually adjusted to obtain the required pressure.

By operating the control valve 10 using closed loop control, full pressure 15 compensation can be attained.

Although the skewed channels 28 are angled relative to the longitudinal axis of the spool 18, they could extend parallel to the longitudinal axis of the spool 18, as shown by way of a third embodiment of the pressure control valve 10 in Figure 5.

20 Similarly to the second embodiment, parts similar to the first embodiment have the same references.

Unlike the skewed spool channels 28 of the first and second embodiments, however, the parallel spool channels 28' of the third embodiment do not reduce as

much the axial component of the flow force, particularly under control at high pressures. A fourth embodiment is shown in figure 6. In this embodiment, as an 5 alternative to the flared portion 44 having frusto conical or substantially frusto conical portions 48_, 48_, 48_ and chamfered free-edge 50, the flared portion 44' has curved portions 78a, 78_, 78c and a curved external free-edge 79.

Obviously, the flared portion could have a combination of frusto-conical or 10 substantially frusto-conical portions and curved portions.

The fluid pressure at the fluid inlet 14 is thus controlled by passing fluid through the valve and adjusting the energisation of the electromagnetic actuator and hence the force applied to the sleeve. By increasing the actuation force PA acting on 15 the sleeve, the fluid metering area defined by the spool channel and the sleeve is reduced and, for a given flow, the pressure drop between the fluid inlet and the fluid outlet will increase. The fluid metering area versus sleeve stroke is mainly determined by the variation of cross-sectional area of the spool channels versus position along spool. Although the pressure control valve described is in the form of a pressure relief valve, the arrangement described could be incorporated into any type of pressure control valve. For example, it could be incorporated as part of a refrigeration circuit to regulate the pressure drop of refrigerant between two points in

the circuit.

Furthermore, the electromagnetic actuator could equally be a hydraulic, pneumatic, or steam actuator.

Although the spool has been described as having an axial blind bore, it could be any suitable chamber.

Also, the through-bore of the sleeve could be a blind bore if the sleeve is 10 provided with a suitable radial vent passage to allow movement of displaced fluid arising from movement of sleeve along spool.

The circumferential grooves could be dispensed with. However, these help balance the pressure around the circumference of the spool in the sleeve and promote 15 sliding. One or more grooves could be provided.

It should also be understood that the spool flange need not necessarily be continuous, and may be any suitable protruding shoulder. The stepped portion of the spool flange could also be omitted.

Although the embodiments have been described with reference to two spool channels, one spool channel or more than two spool channels could be used. In the latter case, the spool channels are preferably equi-angularly spaced around the spool and, consequently, the channel openings may not be diametrically opposed.

One or more spring elements may be provided.

The valve arrangement described above may be used as a single stage valve or as a pilot stage valve for controlling a two-stage pressure control valve.

s Also, even though the pressure control valve is intended to be operated as a proportional control valve, it may be used as simply an ON / OFF type valve.

It is thus possible to provide a pressure control valve which requires a lower 10 actuating force for controlling a given pressure of fluid, and therefore has a significantly reduced electrical power consumption.

The embodiments described above are given by way of example only and modifications will be apparent to persons skilled in the art without departing from the 15 scope of the invention as defined by the appended claims. For example, the spool could be movable and the sleeve could be fixed.

Claims

1. A pressure control valve for controlling fluid pressure in a fluid pressure actuated circuit, the valve having a fluid inlet and a fluid outlet and comprising a 5 spool, a sleeve having a bore in which the spool is slidably received, and actuator means for positioning the sleeve relative to the spool, the spool having an internal chamber in fluid communication with the fluid inlet, a channel which is formed in the outer surface of the spool and which is in fluid communication with the spool chamber and the fluid outlet, and a shoulder which is formed adjacent to the spool channel, the 10 sleeve bore having a flared portion at the end adjacent to the spool shoulder, so that, in use, when the flared portion of the sleeve is positioned adjacent to the channel by an urging force of the actuator means to define a fluid metering area, the fluid passing through the fluid metering area to the fluid outlet is directed by the spool channel and the flared portion of the sleeve to impinge on the spool shoulder, resulting in a 15 reaction force being generated to counteract the flow force of the fluid to thereby decrease the tendency for the fluid force to reduce the fluid metering area by closing the spool channel and to decrease the urging force required to be exerted on the sleeve or the spool by the actuator means.

20

2. A pressure control valve as claimed in claim l, wherein the spool includes a stepped portion which is positioned between the shoulder and the spool channel and on which, in use, at least part of the fluid exiting the spool channel can impinge.

3. A pressure control valve as claimed in claim 1 or claim 2, wherein the flared

portion of the sleeve bore is frusto-conical.

4. A pressure control valve as claimed in claim 3, wherein the flared portion of the sleeve bore comprises a plurality of distinct frustoconical or substantially frusto-

5 conical portions.

5. A pressure control valve as claimed in claim 3, wherein the flared portion of the sleeve bore comprises a plurality of distinct curved portions.

10

6. A pressure control valve as claimed in claim 3, wherein the flared portion of the sleeve bore comprises a combination of distinct frustoconical or substantially frusto-conical portions and curved portions.

7. A pressure control valve as claimed in any one of the preceding claims, 15 wherein the spool channel has an opening at one end, by which fluid communication with the spool chamber is achieved, and the spool channel tapers in the direction away from the opening.

8. A pressure control valve as claimed in any one of the preceding claims, 20 wherein the longitudinal extent of the spool channel extends at an angle to the shoulder and at an angle to the longitudinal axis of the spool.

9. A pressure control valve as claimed in any one of the preceding claims, wherein the spool channel is skewed at an angle to the longitudinal axis of the spool.

10. A pressure control valve as claimed in any one of claims 1 to 7, wherein the longitudinal extent of the spool channel extends parallel to the longitudinal axis of the spool. 5

11. A pressure control valve as claimed in any one of the preceding claims, wherein an external free-edge of the sleeve adjacent to the flared portion is chamfered to aid direction of the fluid flow.

12. A pressure control valve as claimed in any one of the claims 1 to 10, wherein 10 an external free-edge of the sleeve adjacent to the flared portion is curved to aid direction of the fluid flow.

13. A pressure control valve as claimed in any one of the preceding claims, wherein the internal chamber of the spool is a blind bore which is open at one end to 15 enable fluid communication with the fluid inlet.

14. A pressure control valve as claimed in any one of the preceding claims, wherein the spool further includes at least one circumferential groove which, in use, generates a bearing surface to aid sliding of the spool in the sleeve.

15. A pressure control valve as claimed in any one of the preceding claims, wherein the actuator means includes an electromagnetic actuator which, when energised, generates an electro-magnetic field to move or position the sleeve.

16. A pressure control valve as claimed in claim 15, wherein the actuator means also includes one or more spring elements which have an increasing compressive resistance characteristic, the or each spring element being arranged to oppose the urging force generated by the in use electromagnetic actuator.

17. A pressure control valve as claimed in any one of the preceding claims, wherein the valve is incorporated as part of an open loop system.

18. A pressure control valve as claimed in any one of claims I to 16, wherein the 10 valve is incorporated as part of a closed loop system.

19. A pressure control valve as claimed in claim 18, further comprising a pressure transducer which senses the fluid pressure at the fluid inlet and which supplies a feedback signal to adjust the energisation of the actuator means.

20. A pressure control valve as claimed in any one of the preceding claims, wherein the valve is a pressure relief valve.

21. A pressure control valve substantially as hereinbefore described with reference 20 to Figures 1 to 3, Figure 4, Figure 5, or Figure 6 of the accompanying drawings.