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Title:
ELECTROMAGNETIC VALVE WITH MAGNETICALLY ACTUATED MAIN AND PILOT VALVE ELEMENTS
Document Type and Number:
WIPO Patent Application WO/2016/180737
Kind Code:
A1
Abstract:
The invention is directed to an electromagnetic valve (2) comprising a main valve member (16) cooperating with a seat (12), a pilot valve member (20), a core (18) linked to the pilot valve member (20) and a counter-core (22) cooperating with the main valve member (16), said core (18) and counter-core (22) forming a first air- gap (30), and a solenoid (28) configured for producing a magnetic field in the first air-gap (30) for moving the core (18) towards the counter-core (22). The counter- core (22) forms with the bottom (144) of the armature (14) a second air-gap (32) where, in the presence of the magnetic field and after movement of the core (18) towards the counter-core (22), said counter-core (22) is magnetically attracted towards said bottom (144) so as to open the valve.

Inventors:
SELLEN, Stephan (Zum Sägewerk 1, Wehingen, 66693, DE)
SCHMITZ, Philippe (51 rue de la Forêt Verte, 7340 Heisdorf, 7340 Heisdorf, 7340, LU)
Application Number:
EP2016/060235
Publication Date:
November 17, 2016
Filing Date:
May 06, 2016
Export Citation:
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Assignee:
LUXEMBOURG PATENT COMPANY S.A. (24 route de Diekirch, 7440 Lintgen, 7440 Lintgen, 7440, LU)
International Classes:
F02M21/02; F16K27/02; F16K39/02
Domestic Patent References:
WO2015031633A12015-03-05
Foreign References:
EP2573438A12013-03-27
EP2653763A22013-10-23
US20140145101A12014-05-29
US5735582A1998-04-07
US20130277587A12013-10-24
Attorney, Agent or Firm:
LECOMTE & PARTNERS SÀRL (P.O. Box 1623, 1016 Luxembourg, 1016, LU)
Download PDF:
Claims:
Claims

1. Electromagnetic valve (2; 102) for a fluid like pressurized gas, comprising:

- a body (4; 104) with an inlet (8; 108), an outlet (10; 1 10), a main passage (6; 106) communicating said inlet (8; 108) with said outlet (10; 1 10), and a seat (12; 1 12) in said passage (6; 106);

- an armature (14; 1 14) with a bore (145; 1 145) and a bore bottom (144;

1 144), said bore (145; 1 145) housing:

o a main valve member (16; 1 16) cooperating with the seat (12; 1 12) and comprising a pilot passage (24; 124) for the fluid;

o a pilot valve member (20; 120) configured for opening the pilot passage (24; 124) in the main valve member (16; 1 16);

o a core (18; 1 18) linked to the pilot valve member (20; 120) and a counter-core (22; 122) cooperating with the main valve member (16;

1 16), said core (18, 1 18) and counter-core (22; 122) forming a first air-gap (30);

- a solenoid (28; 128) around the armature (14; 1 14) and configured for producing a magnetic field in the first air-gap (30; 130) that moves the core (18; 1 18) towards the counter-core (22; 122) and opens the pilot passage (24; 124);

characterized in that

the counter-core (22; 122) forms with the bottom (144; 1 144) of the armature (14; 1 14) a second air-gap (32; 132) where, in the presence of the magnetic field and after movement of the core (18; 1 18) towards the counter-core (22; 122), said counter-core (22; 122) is magnetically attracted towards said bottom (144; 1 144) so as to move the main valve member (16; 1 16) and open the main passage (6; 106).

2. Electromagnetic valve (2; 102) according to claim 1 , wherein the first air-gap (30; 130) has a stroke comprised between 0.3 and 0.7 mm and/or the second air-gap (32; 132) has a stroke comprised between 1 and 2 mm.

3. Electromagnetic valve (2; 102) according to any one of claims 1 and 2, wherein the main valve element (16; 1 16) comprises a front face cooperating with the seat (12; 1 12) and a back face forming a pilot seat (161; 1 161) extending from said back face.

4. Electromagnetic valve (2; 102) according to claim 3, wherein the pilot valve member comprises a seal element (20; 120) fluid-tightly cooperating with the pilot seat (161; 1 161), and a carrier (18; 121) carrying said element.

5. Electromagnetic valve (2; 102) according to claim 4, wherein the carrier (18;

121 ) comprises a bore (181; 1201) with a shoulder (182; 1202), the seal element (20; 120) being housed in said bore against said shoulder, the carrier bore (181; 1201) being essentially aligned with the armature bore (145; 1 145), and said shoulder (182; 1202) being in in front of the back face of the main valve element (16; 1 16).

6. Electromagnetic valve (2; 102) according to one of claims 4 and 5, further comprising a compression spring (26; 126) that abuts against the seal element (20; 120) and the bottom (144; 1 144) of the armature (14; 1 14).

7. Electromagnetic (2; 102) valve according to any one of claims 1 to 6, wherein the armature (14; 1 14) comprises a wall (142, 143; 1 142, 1 143) around the bore (145; 1 145) of the armature (14; 1 14) that comprises an intermediate ring portion (143; 1 143) made of non-magnetic material around the counter-core (22; 122) so as to force the magnetic field inside the bore (145; 1 145) of the armature (14; 1 14) through the core (18; 1 18) and the counter-core (22, 122).

8. Electromagnetic valve (2; 102) according to claim 7, wherein in the closed state of said valve, the counter-core (22; 122) does not extend axially beyond the intermediate ring portion (143; 1 143) towards the bottom (144; 1 144) of the armature (14; 1 14) of more than 50%, preferably 30%, more preferably 20%, of a mean thickness of the wall around the bore.

9. Electromagnetic valve (2; 102) according to one of claims 7 and 8, wherein the counter-core (22; 122) does not extend axially beyond the intermediate ring portion (143; 1 143) towards the core (18; 1 18).

10. Electromagnetic (2) valve according to any one of claims 1 to 9, wherein the main valve member (16) comprises a ring portion (164) in which the counter- core (22) is press fitted, said ring portion (164) preferably being in contact with the bore (145) of the armature (14).

1 1. Electromagnetic valve (2) according to claim 10, wherein the counter-core (22) comprises a shoulder that abuts the ring portion (164) of the main valve member (16).

12. Electromagnetic (2) valve according to one of claims 10 and 1 1 , wherein the main valve member (16) comprises a front portion (162) that cooperates with the seat (12) and that is in contact with the bore (145) of the armature (14), and arms (163) extending from said front portion (162) towards the ring portion (164), the core (18) and pilot valve member (20) being located between said front portion (162) and said ring portion (164).

13. Electromagnetic (102) valve according to any one of claims 1 to 9, wherein the main valve member (1 16) is screwed to the counter-core (122).

14. Electromagnetic valve (102) according to claim 13, wherein the main valve member (1 16) comprises a bore housing the pilot valve member (120).

15. Electromagnetic (102) valve according to one of claims 13 and 14, wherein the core (1 18) contacts the bore (145) of the armature (14) and comprises a bore housing the main valve element (1 16).

16. Electromagnetic valve (102) according to claims 14 and 15, wherein the core (1 18) is attached to the pilot valve member (120) by means of at least one pin (123) extending diametrically with regard to the longitudinal axis of the bore (1 145) of the armature (1 14).

17. Electromagnetic valve (102) according to claim 16, wherein the main valve element (1 16) comprises oblong holes (1 163) through which the at least one pin (123) extends.

18. Electromagnetic valve (102) according to one of claims 16 and 17, further comprising a carrier (121 ), which is preferably tubular shaped, which carries the pilot valve element (120) and which is attached to the at least one pin (123).

19. Electromagnetic valve (102) according to any one of claims 16 to 18, wherein the core (1 18) is generally cylindrically shaped with a front face (1 181) towards the seat (1 12) and a back face forming the first air-gap (130) with the counter- core (122), the front face (1 181) preferably comprising a profile that extends in the direction of the seat (1 12) at its outer portion.

Description:
Description

ELECTROMAGNETIC VALVE WITH MAGNETICALLY ACTUATED MAIN AND PILOT VALVE ELEMENTS

Technical field

[0001] The invention is directed to an electromagnetic valve for fluid, more particularly for pressurized gas. More particularly, the invention is directed to a pilot operated electromagnetic valve for high pressure gases, e.g. compressed natural gas (CNG) and compressed hydrogen gas at pressures of up to 70 M Pa.

Background art

[0002] Prior art patent document published US 2013/0277587 A1 discloses a pilot operated electromagnetic valve for a pressurized fuel tank of a vehicle. The fuel can be compressed natural gas, biogas or hydrogen. Such gases can be stored in a compressed form in pressure cylinders at nominal pressures of up to 700 bar. A first embodiment of the valve of this teaching (in figure 2 of that document) comprises a seat formed in passage in a body with a gas inlet and a gas outlet. The valve comprises also a main valve element cooperating with the seat for, selectively, shutting-off and opening the passage. This main valve element is slidingly received in a cylindrical cavity of a magnetic armature. It comprises an internal bore receiving a pilot valve element configured for opening a pilot passage in the front portion that cooperates with the seat. This pilot valve member is made of magnetic material so as to form a core. It forms also an air-gap with a counter-core that is free to slide in the cylindrical cavity and to abut against the main valve element. Upon energization of a solenoid disposed around the armature, the magnetic field thereby generated goes through the core, the air-gap and the counter-core. Attractive forces between the core and the counter-core are then generated so that these get close to each other so as to bring the air-gap to zero. Since the counter-core abuts against arms of the main valve element that extend along the pilot valve element, this latter, being attracted towards the counter-core, leaves its position of contact with the main valve element that shuts-off the pilot passage. This latter becomes then open and the gas under potentially high pressure at the inlet can flow at a reduced flow towards the outlet. This flow generates a pressure differential between the portion of the front surface of the main valve element that is outside of the seat and the inner surface of said main valve element. This pressure difference results in a force that causes an opening movement of the main and pilot valve elements, thereby opening the passage. This means that special constraints with regard to the design of the main valve element are to be observed for achieving this pressure differential. These constraints can be limiting and expensive. In addition, the opening of the main valve element by the pressure of the gas is dependent of the pressure in the tank. This can also provide limitations in the function of the valve. Also, with reference to figure 2 of this document it is not clear how the counter-core position is ensured. This teaching discloses also (in figure 6 of that document) another embodiment of the valve where the counter-core is mechanically engaged, with play, with the main valve element. It is however not clear how this mechanical engagement is supposed to assist the opening movement of the main valve element.

Summary of invention

Technical Problem

[0003] The invention has for technical problem to provide a pilot valve for fluids, more particularly for high pressure fluids, like fuel gases, that is more reliable and cheaper.

Technical solution

[0004] The invention is directed to an electromagnetic valve for a fluid like pressurized gas, comprising: a body with an inlet, an outlet, a main passage communicating said inlet with said outlet, and a seat in said passage; an armature with a bore and a bore bottom, said bore housing: a main valve member cooperating with the seat and comprising a pilot passage for the fluid; a pilot valve member configured for opening the pilot passage in the main valve member; a core linked to the pilot valve member and a counter-core cooperating with the main valve member, said core and counter-core forming a first air-gap; the valve further comprising a solenoid around the armature and configured for producing a magnetic field in the first air-gap that moves the core towards the counter-core and opens the pilot passage; wherein the counter-core forms with the bottom of the armature a second air-gap where, in the presence of the magnetic field and after movement of the core towards the counter-core, said counter-core is magnetically attracted towards said bottom so as to move the main valve member and open the main passage.

[0005] According to a preferred embodiment, the first air-gap has a stroke comprised between 0.3 mm and 0.7 mm and/or the second air-gap has a stroke comprised between 1 mm and 2 mm.

[0006] According to a preferred embodiment, the first air-gap is smaller than the second air-gap.

[0007] The core and the counter-core are advantageously made of ferromagnetic material.

[0008] The armature is advantageously made of ferromagnetic material.

[0009] The main valve element is advantageously made of non- or at least poor- ferromagnetic material.

[0010] Advantageously, the fluid at the inlet can flow into the bore of the armature and contact the core, the counter-core, the main valve element and the pilot valve element.

[001 1] According to a preferred embodiment, the main valve element comprises a front face cooperating with the seat and a back face forming a pilot seat extending from said back face.

[0012] According to a preferred embodiment, the pilot valve member comprises a seal element fluid-tightly cooperating with the pilot seat, and a carrier carrying said element.

[0013] According to a preferred embodiment, the carrier comprises a bore with a shoulder, the seal element being housed in said bore against said shoulder, the carrier bore being essentially aligned with the armature bore, and said shoulder being in front of the back face of the main valve element. [0014] According to a preferred embodiment, the valve further comprises a compression spring that abuts against the seal element and the bottom of the armature.

[0015] According to a preferred embodiment, the armature comprises a wall around the bore of the armature that comprises an intermediate ring portion made of non-magnetic material around the counter-core so as to force the magnetic field inside the bore of the armature through the core and the counter-core.

[0016] According to a preferred embodiment, in the closed state of said valve, the counter-core does not extend axially beyond the intermediate ring portion towards the bottom of the armature of more than 50%, preferably 30%, more preferably 20%, of a mean thickness of the wall around the bore.

[0017] According to a preferred embodiment, the counter-core does not extend axially beyond the intermediate ring portion towards the core, irrespective of the opened or closed state of the valve.

[0018] According to a preferred embodiment, the main valve member comprises a ring portion in which the counter-core is press fitted, said ring portion preferably being in contact with the bore.

[0019] According to a preferred embodiment, the counter-bore comprises a shoulder that abuts the ring portion of the main valve member.

[0020] According to a preferred embodiment, the main valve member comprises a front portion that cooperates with the seat and that is in contact with the bore of the armature, and arms extending from said front portion towards the ring portion, the core and pilot valve member being located between said front portion and said ring portion.

[0021] According to a preferred embodiment, the main valve member is screwed to the counter-core.

[0022] According to a preferred embodiment, the main valve member comprises a bore housing the pilot valve member.

[0023] According to a preferred embodiment, the core contacts the bore of the armature and comprises a bore housing the main valve element. [0024] According to a preferred embodiment, the core is attached to the pilot valve member by means of at least one pin extending diametrically with regard to the longitudinal axis of the bore of the armature.

[0025] According to a preferred embodiment, the main valve element comprises oblong holes through which the at least one pin extends.

[0026] According to a preferred embodiment, the valve further comprises a carrier, which is preferably tubular shaped, which carries the pilot valve element and which is attached to the at least one pin.

[0027] According to a preferred embodiment, the core is generally cylindrically shaped with a front face towards the seat and a back face forming the first air gap with the counter-core, the front face preferably comprising a profile that extends in the direction of the seat at its outer portion. This profile is advantageously curved so as to guide and deviate a counter-flow, this deviate transmitting an effort to the core.

Advantages of the invention

[0028] The invention is particularly interesting in that it provides an electromagnetic pilot valve with two air-gaps that are successively reduced for opening the valve upon energization of the solenoid. An advantage is that the core and the counter-core form a unique magnetic core after the first air-gap is closed, which leads to higher magnetic flux and forces to open the main valve member. The valve of the invention provides a simple, compact and cheap construction.

Brief description of the drawings

[0029] Figure 1 is a sectional view of a valve according to a first embodiment of the invention, the valve being in a shut-off state.

[0030] Figure 2 is a perspective view of the main valve element and the counter- core of the valve of figure 1.

[0031] Figure 3 corresponds to figure 1 where the pilot valve is in the open position.

[0032] Figure 4 corresponds to figure 3 where the main valve is in the open position.

[0033] Figure 5 is a sectional view of a valve according to a second embodiment of the invention, the valve being in a shut-off state. [0034] Figure 6 corresponds to figure 5 where the pilot valve is in the open position.

[0035] Figure 7 corresponds to figure 6 where the main valve is in the open position.

Description of an embodiment

[0036] Figure 1 is a sectional view of the relevant portion of an electromagnetic valve 2 according to a first embodiment of the invention.

[0037] The valve 2 comprises a body 4 preferably made of metal like steel, stainless steel, brass or any other suitable material. Only a portion of the body 4 is represented, being understood that the body can comprise other functions. The body 4 comprises a passage 6 connecting an inlet 8 with an outlet 10. The passage 6 comprises a seat 12 that can be integrally formed with the body 4. The valve comprises also an armature made essentially of ferromagnetic material, like soft iron. The armature 14 can comprise a head or front portion 14 1 that is mounted on the body 4, for example by screwing. It comprises essentially a cylindrical wall 14 2 extending axially from the front portion 14 1 . It comprises also a ring portion

14 3 of non-ferromagnetic material or at least with poor ferromagnetic properties. This portion can be made for example of brass alloy or stainless steel. It can be welded to the cylindrical portion 14 2 so as to be integral with that portion. The armature 14 comprises also a bottom portion

14 4 made of ferromagnetic material, ideally the same material as the other ferromagnetic portions 14 1 and 14 2 . As is visible in figure 1 , the contact surfaces between these portions 14 2 , 14 3 and 14 4 can be inclined with regard to the longitudinal axis of the armature, thereby permitting an adequate guiding of the magnetic flux. The armature 14 forms a bore 14 5 that receives a main valve element 16 that cooperates with the seat 12. The bore 14 5 slidingly receives also a core 18 and a counter-core 22. This latter is rigidly attached to the main valve element 16 by means of arms that extend from the front portion 16 2 to a ring 16 4 in which the counter- core 22 can be press fitted. The arms are not visible in the sectional view of figure 1 but are well visible in figure 2 illustrating the main valve element 16 and the counter-core 22. [0038] The front portion 16 2 of the main valve element 16 comprises a pilot passage 24 for the fluid. This passage provides a communication between the outlet 10 and the inlet 8 provided that the pilot valve element 20 is distant from the pilot seat 16 1 on the front portion 16 2 of the main valve element 16. This front portion 16 2 comprises indeed a front face fluid- tightly cooperating with the seat 12, for instance by means of a seal 16 5 , and a rear face, opposed to the front face, and comprising the pilot seat 16 1 that surrounds the pilot passage 24 and forms a circular rib extending from that rear face.

[0039] The pilot valve element 20 is in the presence case a seat element made of a material that is able to cooperate in a fluid-tight manner with the pilot seat 16 1 . It can be metallic or non-metallic, in any case preferably made of a material that is softer than the material forming the pilot seat 16 1 . The element 20 is housed in a bore 18 1 of the core 18 and abuts a shoulder 18 2 on the end of the bore 18 1 that is in front of the rear face of the front portion 16 2 of the main valve element 16. A compression spring 26 extends longitudinally through the bore 18 1 of the core 18 and through the counter-core 22. The spring 26 exerts a resilient effort on the pilot valve element 20 towards the pilot seat 16 1 .

[0040] The valve 2 comprises also a solenoid or coil 28 arranged around the armature 14. For instance, the solenoid 28 is slid axially over the external surface of the armature 14 and is retained in position by a cap 34 fastened to the bottom 14 4 of the armature 14. For instance, the cap is secured to the bottom 14 4 by a threaded engagement.

[0041] In the closed position of the valve as illustrated in figure 1 , a first air-gap 30 is present between the core 18 and the counter-core 22, and a second air-gap 32 is present between the counter-core 22 and the bottom 14 4 of the armature 14. The first air-gap 30 is smaller than the second one 32. The spring 26 presses the pilot valve element 20 against the pilot seat 16 1 , thereby shutting-off the pilot passage 24. Also the main valve element 16 is pressed against the seat 12, thereby shutting-off the passage 6. The fluid pressure present at the inlet exerts a closing force on the pilot valve element 20 and the main valve element 16. [0042] When the solenoid 28 is energized, it produces magnetic field in the wall 14 2 and in the bottom 14 4 of the armature 14. The non-ferromagnetic or poor ferromagnetic ring portion 14 3 of the armature forces the magnetic field towards the core 18 and counter-core 22. The magnetic field that is present in the core 18, the counter-core 22 and in the first air gap produces attractive force between the core and the counter-core. The counter-core 22 is rigidly attached to the main valve element 16, the attractive force moves therefore the core 18 and the pilot valve element 20 towards the counter-core 22, preferably until the core 18 contacts the counter-core 22.

[0043] Figure 3 illustrates the valve in this first opening stage when the solenoid 28 is energized. The pilot passage 24 is then opened and the fluid can flow at a limited flow rate from the inlet to the outlet via the pilot passage 24. We can observe the initial first air gap 30 present in figure 1 is now reduced to zero or at least nearly zero. The close contact between core 18 and counter-core 22 leads to an increased magnetic flux trough the parts 14 2 , 18, 22 and 14 4 by means of increased magnetic forces to open the main valve member. It therefore produces attractive forces between the counter-core 22 and the bottom 14 4 .

[0044] Figure 4 illustrates the valve of figures 1 and 2 in the second opening stage when the solenoid 28 is energized, this second stage corresponding to a fully opened stage. Indeed, the above mentioned attractive forces between the counter-core 22 and the bottom14 4 of the armature move the counter-core 22 and thereby also the main valve element 16 towards the bottom 14 4 until the counter-core 22 comes into contact with said bottom so as to reduce the initial second air gap 32 to zero or at least close to zero.

[0045] In the stage of figure 4, both initial air gaps 30 and 32 are reduced to zero or at least close to zero, thereby providing an increased magnetic flux through the assembly of the core 18, the counter-core 22 and the bottom 14 4 . The magnetic field is then maximum and the attractive forces between the core 18 and the counter-core 22 and also between the counter-core 22 and the bottom 14 4 are also maximum, thereby providing a stable opened position. [0046] As visible in figure 4, the front face of the front portion 16 1 of the main valve element 16 is now distant from the seat 12 and opens the passage 6.

[0047] When the solenoid 28 is not energized anymore, the attractive forces between the core 18 and the counter-core 22 and also between the counter-core 22 and the bottom 14 4 disappear. The spring 26 urging the pilot valve element 20 moves first the element 20 against the pilot seat 16 1 and second the main valve element 16 against the seat 12, thereby totally closing the passage 6.

[0048] Figures 5 to 7 illustrate an electromagnetic valve according to a second embodiment of the invention. In these figures the reference numbers used for the first embodiment are used for the same elements or for corresponding elements, these numbers being however increased by 100 to differentiate both embodiments. Reference is thereby made to the description of the first embodiment. Specific reference numbers, comprised between 100 and 200 are used for specific elements.

[0049] Figure 5 illustrates the valve 102 of the second embodiment in a closed state, similarly to figure 1. The valve 102 differs from the valve 2 of the first embodiment essentially in the construction of the main valve element 1 16, its attachment to the counter-core 122 and the construction of the pilot valve element 120.

[0050] Indeed, the main valve element 1 16 does not contact the bore 1 14 5 of the armature 1 14 but is rather housed in the core 1 18. This latter comprises indeed a through-bore slidingly receiving the main valve element 1 16. This latter comprises a rear portion 1 16 4 that extends out of the core 1 18 and engages with the counter-core 122. For instance, this engagement is a threaded engagement, being understood that other types of engagement are possible. The main valve element comprises also a bore slidingly receiving the pilot valve element 120, more particularly slidingly receiving a carrier 121 with a bore 121 1 housing the pilot valve element 120. This carrier is generally tubular with a shoulder 121 2 at its end in vis-a-vis of the pilot seat 1 16 1 formed around the pilot passage 124 and extending from the rear face of the front portion 1 16 2 of the main valve element 1 16. The carrier 121 is attached to the core 1 18 by means of a pin 123 that extends radially with regard to the longitudinal axis of the armature 1 14 and its bore 1 14 5 . To that end, the main valve element 1 16 comprises oblong holes 1 16 3 that permit movement of the pin 123 and thereby of the pilot valve element 120 relative to said main valve element 1 16. The pin 123 fixes the pilot valve element 120 in the carrier 121.

[0051] The functioning of the valve 102 is a follows. With reference to figure 5, in the absence of energization of the solenoid 128, the compressive spring 126 urges the pilot valve element 120 against the pilot seat 1 16 1 , thereby shutting-off the pilot passage 124, and also urges the main valve element 1 16 against the seat 1 12, thereby totally shutting-off the passage 106. The pressure of the fluid at the inlet 108 that is substantially higher than at the outlet 1 10 urges also both the pilot valve element 120 and the main valve element 1 16 towards their respective seats 1 16 1 and 124.

[0052] Still with reference to figure 5, in the shut-off state without energization of the solenoid, a first air-gap 130 is present between the core 1 18 and the counter-core 122, and a second air-gap 132 is present between the counter-core 122 and the bottom 1 14 4 . Similarly to the first embodiment, the first air-gap 130 is smaller than the second one 132.

[0053] With reference to figure 6, when the solenoid 128 is energized, the magnetic field generated by the solenoid is deviated towards the core 1 18 and the counter-core 122 due to the non- or poor-ferromagnetic ring portion 1 14 3 of the armature 1 14. This field generates attractive forces in the air-gap 130 between the core 1 18 and the counter-core 122. In the present case, high attractive forces are only present at the annular face of the core 1 18 facing the counter-core 122. These forces move the core 1 18 towards the counter-core 122. This moves the pilot valve element 120 away from the pilot seat 1 16 1 by means of the attachment pin 123 and the carrier 121 holding said element 120. The fluid under pressure at the inlet 108 can then flow at a reduced flow rate towards the outlet 1 10 through the pilot passage 124. This limited flow can create a counter-pressure at the outlet which reduces the effort necessary for moving the main valve element 1 16. [0054] With reference to figure 7, when the solenoid 128 is still energized, further to the reduction of the first air-gap 130 to zero or nearly zero, the magnetic field in the counter-core 122, the second air-gap 132 and the bottom 1 14 4 is increased due to the lower magnetic resistance. Attractive forces in the second air-gap 132 are increased and the counter-core 122 and thereby also the main valve element 1 16 are moved towards the bottom 1 14 4 . The valve 102 is then fully opened.

[0055] When the solenoid 128 is not energized anymore, the attractive forces between the core 1 18 and the counter-core 122 and also between the counter-core 122 and the bottom 1 14 4 disappears. The spring 126 urges first the pilot valve element 120 against the pilot seat 1 16 1 and second the main valve element 1 16 against the seat 1 12, thereby totally closing the passage 106.

[0056] With reference back to figure 5, the cylindrically shaped core 1 18 can comprise a profiled front face 1 18 1 with an increasing height towards its external contour. The purpose of this profiled front face 1 18 1 is to facilitate the refilling of a tank on which the valve 102 would be mounted. Indeed, refilling means generating a counter-flow from the outlet 1 10 towards the inlet 108. Such an operation is in principle possible by applying a pressure at the outlet 1 10 that, when acting on the surface of the main valve element 1 16 in the outlet, counteracts the urging force of the spring 126 so as to move the main valve element 1 16 away from the seat 1 12. As soon as this happens, a refill flow through the passage 106 is generated. This can cause a pressure drop on the front face of the main valve element 1 16. In order to keep the valve sufficiently opened during refilling, the profiled front face 1 18 1 of the core 1 18 has for effect that the refill flow exerts a dynamic effort on said core 1 18 which participates in counteracting the closing force of the spring 126.