GB2338050A

GB2338050A - Pressure balanced solenoid valve

Info

Publication number: GB2338050A
Application number: GB9811704A
Authority: GB
Inventors: Colm Michael Patrick Keegan
Original assignee: Wabco Automotive UK Ltd
Current assignee: Wabco Automotive UK Ltd
Priority date: 1998-06-02
Filing date: 1998-06-02
Publication date: 1999-12-08
Also published as: GB9811704D0

Abstract

A valve comprises a valve member 16 movable between a closed position in which it seals against a first seat 28 to prevent communication between an inlet and an outlet, and an open position in which it is clear of the seat to permit communication between the inlet and the outlet. A fluid passageway 64 allows pressures on each side of the valve member to equalise and so balance the forces acting on the valve member. The valve member seals against a further seat 58 in the closed position to prevent communication between the inlet and outlet via the passageway. The valve member moves clear of the further seat in the open position.

Description

2338050 1 A SOLENOID VALVE The invention relates to a solenoid valve for

controlling fluid flow between inlet and outlet ports.

Hitherto, it has been known to produce solenoid valves for controlling the flow of air from an inlet to an outlet, but some conventional valves are unbalanced which limits them to small flow areas in relation to the size of the solenoid. In such a case, it is usual to use air relay valves as amplifiers if a large flow area is required.

It is possible to use a spool valve in which the press ure forces on either side of the spool are balanced. The spool travel required in such a valve may increase the required solenoid size. Spool valves also require very accurate manufacture to prevent leaks, or they must incorporate a complex sealing system.

The present invention is concerned with a poppet type valve member which is moved clear of a seat to permit fluid communication between the inlet and outlet ports.

The valve is of a kind where a fluid passageway is provided which enables equal fluid pressures to be applied to opposite ends of the valve member to provide substantially balanced end loadings. Hitherto, such a 2 valve has incorporated a sliding seal between the valve member and an adjacent surface of the valve body to prevent fluid communication between the inlet and outlet ports via the passageway. However, in order for the solenoid to move the valve member, it is necessary to overcome the frictional resistance of the sliding seal, which can be significant even with balanced end loading of the valve member.

An object of the invention is to provide an. improved solenoid valve member which helps to minimize the foregoing problem.

According to the invention there is provided a solenoid valve for controlling fluid flow between inlet and outlet ports and comprising a body, a valve member in the body movable between a closed position in which it seals against a seat on the body to prevent fluid communication between the ports and an open position. in which it moves clear of the seat to permit fluid communication between the ports, a solenoid for moving the valve member, a fluid passageway which enables equal fluid pressures to be applied to the ends of the valve member to provide substantially balanced end loading, and a further seat on the body, the valve member being arranged to seal against the further seat in the closed position to prevent fluid communication between the inlet and outlet 3 ports via the passageway and to move clear of the further seat in the open position.

With such an arrangement, no sliding seal is necessary making the valve member easier to move in response to operation of the solenoid because frictional forces from conventional fluid seals are eliminated.

Another problem with prior arrangements is that the valve member actually constitutes the armature of the valve, which necessarily places some design limitations on the armature and/or valve member. In a preferred embodiment of the present invention, the valve member preferably carries a separate armature. In that way there is less restriction on the size, configuration and material of the armature, which is particularly advantageous. Preferably, the armature is mounted at one end of the valve member. In such an embodiment the armature can be arranged to have no sealing function within the valve. Accordingly the armature can be made larger than the. sealing diameter and thus improve the magnetic circuit.

The fluid seals of the prior art valves are typically carried by a component of the magnetic circuit, usually within a recess in the armature of the solenoid valve. Provision of the recess reduces the effectiveness of the magnetic circuit.

4 The first said seat which cooperates with the valve member may either comprise a seal on the body which is contacted by a cooperable part of the valve member or may comprise a part on the body which is contacted by a seal on the valve member.

is The further said seat which cooperates with the valve member may either comprise a seal on the body which is contacted by a cooperable part of the valve member or may comprise a part on the body which is contacted by a seal on the valve member.

The seal of a valve seat may be made of an elastomeric or synthetic material. In order to prevent the cooperable part on the body or the valve member depressing the seal excessively or sinking too deeply therein when making sealing contact, a stop member may be provided on one of the body and valve member, and arranged to contact the other of the body and valve member. The stop member may be in the form of a projection or a series of projections arranged around the seat.

In a preferred embodiment, the valve member has an annular flange at one end cooperable with the first said seat, and a second annular flange spaced axially from the first annular flange and which is cooperable with the further seat. The first annular flange may have thereon an annular sealing member which projects towards the first seat for contact therewith in the closed position of the valve member. The second annular flange may have thereon an annular sealing member which projects towards the further seat which may be arranged on an annular shoulder on the body. Preferably the annular shoulder extends from the body into the space between the two annular flanges. In the preferred embodiment, the annular sealing member on the second annular flange projects towards the further seat for contact therewith in the closed position of the valve.

The valve member is arranged to make sealing contact with the both seats substantially simultaneously, and is is preferably assembled in situ by, for example, the use of adhesive, welding, or the use of interference fits between components. The valve member may be of a resin or plastic based material, and may be assembled by for example ultrasonic welding.

Preferably, the fluid passageway comprises a passage extending through the valve member from one end to the other and, in the preferred embodiment transmits inlet port pressure between the ends of the valve member for balanced end loading.

In one embodiment the valve member is biased towards its 6 closed position, for example by a spring which may be arranged between the valve member and the body, and as such is commonly referred to as "normally closed". The operation of the solenoid may move the valve member against the bias in such a case to move the valve member to an open position. In an alternative embodiment the valve member and spring are configured such that the valve member is biased towards its open position. The solenoid in this embodiment is operable to move the valve member against the spring bias to a closed position.

A solenoid valve in accordance with the invention will now be described by way of example only, with reference to the accompanying drawings in which:

Figure 1 is an axial cross-section through a known type of solenoid valve using a sliding seal; Figure 2 is a cross-section through a solenoid valve in accordance with a first embodiment of the invention; Figure 3 is a view to a larger scale of part of the solenoid valve shown in Figure 2 and illustrating a stop arrangement; and Figure 4 is a cross-section through a solenoid valve 7 in accordance with a second embodiment of the present invention.

In Figure 1, the solenoid valve comprises a body 10 having an inlet port 12, an outlet port 14 and a valve member 16 for controlling fluid flow between the inlet and outlet ports.

is The valve member 16 is of annular cross-section defining an upper bore 18 as viewed in the drawings and a reduced diameter lower bore 20. The bores 18,20 allows communication of fluid pressure in the inlet 12 from one end of the valve member 16 to the other so that inlet fluid pressure is applied to both ends of the valve member.

The lower end face 22 of the valve member 16 is bounded by a downwardly projecting sealing member 26. The sealing member 26 is a rigid annular projection and is arranged to cooperate with a seat 28 in the form of an annular seal of elastomeric or synthetic material. A further seal 30 in the form of a 0-ring is located in an annular groove 32 in the valve member 16 and makes sliding and sealing contact with an internal bore 34 in the body 10 in which the valve member is axially moveable. The mean seating diameter of the sealing member 26 is equal to the diameter of the internal bore is 8 34. Thus, when the valve member 16 is in the closed position, the pressure forces acting on the valve member are substantially balanced with the exception of the effective seat area. The upper part of the valve member above the seal 30 incorporates a magnetic material so as to form an armature for the solenoid valve. The body 10 has windings thereon to form a solenoid 36 arranged in a space between an outer wall 40 of the body 10 and inner wall 42 defining the bore 34. The wall 42 includes a non- magnetic portion 44. It will be understood that the present invention is equally suitable for use with valves having other known solenoid designs and configurations. The solenoid 36 is suitably connected to a source of electrical power (not shown) The valve member 16 is normally biased into a closed position as shown in Figure 1 by a light spring 46 arranged between the upper end of the body 10 and the bottom end of the bore 18 in the valve member. In use, the spring 46 holds the valve member closed. As the pressure in the inlet port 12 causes balanced end-loading on the valve member 16, the biased upper light spring 18 is sufficient to hold the sealing member 26 in sealing contact with the seat 28 to prevent fluid from flowing through the inlet port 12 to the outlet port 14. The seal 30 prevents fluid in the upper part of the bore 42 escaping through the outlet 14.

9 To open the valve, the solenoid 36 is energized thereby causing the valve member 16 to be lifted clear of the seat 28 to allow fluid to flow to the outlet port 14. An annular stop 48 on the body 10 limits the upward movement of the valve member 16. When the valve is to be closed, the solenoid 36 is switched off and the light spring 18 moves the valve member 16 into a closed position.

One of the problems with the valve as shown in Figure 1 is the fact that the friction of the seal 30 against the wall 42 must be overcome by the action of a solenoid 36 to move the valve member 16 towards an open position and must be overcome by the spring 48 to move the valve member 16 to its closed position. From that point of view, it is difficult to select a seal 30 which will keep is friction to a minimum to ensure proper opening and closing and which will, at the same time, provide adequate sealing. Also, sliding seals such as seal 30 take up radial space and tend to increase the overall size of the valve.

Moveover, as the valve member 16 incorporates the armature, there are certain undesirable design restrictions on the armature, particularly the diameter thereof.

Reference is now made to Figure 2 which shows a valve in accordance with the invention. Parts in Figure 2 which correspond to those parts in Figure 1 carry the same reference numerals and will not be described again in detail.

It should be noted that in Figure 2 that the valve member 16 is formed with upper and lower spaced-apart coaxial annular flanges 50,52. The lower annular flange 52 defines the lower end face 22 which is substantially the same as that shown in Figure 1. As in Figure 1, the lower end face has an annular sealing member 26 which makes sealing contact with the seal 28. However in order to control the extent to which the sealing member 26 sinks into the seal 28, a plurality of upwardly projecting stops 54 are provided on the body which limits the downward movement of the valve member 16 against the seat 28. As shown in Figure 3, the upper ends of the stops 54 contact the lower end face 22 to limit downward movement of the valve member 16. If desired, stops could be provided on the valve member 16 for engagement with the body 10.

The body 10 has an annular shoulder 56 thereon which projects inwardly into the space between the upper and lower flanges 50,52 of the valve member 16. The shoulder 56 carries seat 58 in the form of a seal of elastomeric 11 or synthetic material and the upper flange 50 has a sealing member 60 thereon which, like the sealing member 26 is in the form of an annular projection. As the sealing member 26 makes contact with the seat 28 in the closed position of the valve member 16, so the sealing member 60 of the upper flange 50 makes contact with the seat 58 in the closed position of the valve member. There is some resilience in the seats 28, 58 allowing them to be contacted sealingly by the sealing members 26,60 at the same time. Stops 54 could be provided on the upper rather than the lower flange.

It will be noted that the upper end of the valve member 16 is connected to a hollow cylindrical armature 62. In the embodiment shown a spigot of the valve member 16 locates within a central recess of the armature 62. With such an arrangement, the armature 62 can be made of a material which is different from the material required for the valve member 16. The valve member 16 is formed with an axial through bore 64 and is normally held in the closed position shown in Figure 3 by a light spring 46.

The valve member 16 and armature 62 are designed such that fluid pressure from the inlet port 12 passing through the bore 64 in the valve member 16 creates substantially balanced end forces on the valve member. Pressure applied to the lower face 22 generates an upward is 12 force whilst pressure applied to the upper part of the valve member 16 and the armature 62 generates a downwards force. It will be noted that pressure is applied to th3 inner wall of sealing member 26 and to the outer wall of sealing member 50, and that the valve member 16 is pressure balanced with the exception of the faces of the sealing members 26,50 in contact with the seats 28,58. The sealing action of the sealing member 60 against the seat 58 prevents passage of fluid from the inlet port 12 to the outlet port 14 via the bore 64 in the valve member 16 and bore 34 in the body 10.

In order to open the valve, the solenoid 36 is energized and the valve member 16 is lifted against the bias of the spring 46 into contact with the stop 48 to allow fluid communication between the inlet and outlet ports 12,14. As the valve member is in the form of a poppet valve, there is no sliding friction generated between the wall of bore 34 and a seal as in Fig 1 making the valve member easier to move into an open position.

To close the valve, the solenoid 36 is switched off and the spring 46 moves the valve member 16 downwards to seal against the seats 28,58. Again, the absence of sliding friction as in Fig 1 ensures easy closing of the valve by the spring 46. In order to reduce the possibility of the valve being held open by pressure forces acting across 13 the contact area between the armature 62 and the stop 48, the upper face of the armature 62 has a rounded profile. The rounded profile ensures that the contact area between the armature 62 and the stop 48 is minimised.

The body 10 and valve member 16 are shown as being made as one piece items whereas, in practice, they will be made as a number of parts assembled together as appropriate to construct the valve as shown. The valve member may for example be manufactured in two parts, and assembled in situ by e.g. adhesive. The body may also be manufactured in several parts and assembled in any convenient manner. Where the parts are of plastic material, ultrasonic bonding may be especially suitable.

Referring now to Figure 4 there is shown an alternative embodiment of a solenoid valve according to the present invention. The valve member 16 is configured to be held open by the action of the spring 46 and to close when the solenoid 36 is energised. The spring 46 is provided between a seat 66 surrounding the inlet port 12 and the lower end face 22 of the valve member 16. The solenoid 36 is surrounded by an annular non-magnetic ring 68 which ensures that the magnetic circuit, indicated diagrammatically by arrows 70, acts to close the valve.

The armature 62 is provided with a flange 72 which 14 projects into an annular cavity 74 within the body 10. The flange 72 and cavity 74 co-operate to provide a gap 76 in the magnetic circuit which, in use, generates the force to move the valve member 16 and armature 62. This embodiment further shows that the armature can be made larger than the sealing diameter of the sealing members 26,60.

is

Claims

CLAIMS:

1. A solenoid valve for controlling fluid flow between inlet and outlet ports and comprising a body, a valve member in the body movable between a closed position in which it seals against a first seat on the body to prevent fluid communication between the ports, and an open position in which it moves clear of the seat to permit fluid communication between the ports, a solenoid for moving the valve member, a fluid passageway adapted to equalise fluid pressures on opposite ends of the valve member to provide substantially balanced end loading, and a further seat on the body, the valve member being arranged to seal against the further seat in the closed position to prevent fluid communication between the inlet and outlet ports via the passageway and to move clear of the further seat in the open position.

2. A valve according to claim 1 wherein the valve member has a separate armature.

3. A valve according to claim 2 wherein the armature is mounted at one end of the valve member.

4. A valve according to any preceding claim wherein said first seat comprises a seal on one of the body and valve member which is contactable by a cooperable part of the other of the seal and the valve member.

5. A valve according to any preceding claim wherein said further seat comprises a seal on one of the body and valve member which is contactable by a cooperable part of the other of the seal and valve member.

6. A valve according to claim 4 or claim 5 wherein the seal is of an elastomenic or synthetic material.

7. A valve accordin. to claim 7 and further including a stop member on one of the body and valve member, and arranged to contact the other of the body and valve member to avoid excessive load on said seal.

8. A valve accordinc, to claim 7 wherein said stop member comprises a projection.

IG

9. A valve according to any preceding claim wherein said valve member has an annular flange at one end cooperable with the said first scat, and a second annular flange spaced axially from the first annular flange and which is cooperable with said further seat.

10. A solenoid valve substantially as described herein with reference to the accompanying drawings.