Solenoid-operated cutoff valve for use with fuel cells

A solenoid-operated cutoff valve for use with fuel cells has a movable member disposed in a guide housing for displacement upon energization of a solenoid. When the movable member is displaced, a pilot valve is unseated from a pilot valve seat. A fluid in a communication chamber flows through a pilot passage into an output port. The communication chamber is divided into a first communication chamber and a second communication chamber by a diaphragm. Under a pressure difference developed between the first communication chamber and the second communication chamber, a main valve of a valve head is unseated from a valve seat of a valve housing, opening the solenoid-operated cutoff valve.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a solenoid-operated cutoff valve for selectively passing a reaction gas through a communication chamber upon energization of a solenoid in a fuel cell system.

2. Description of the Related Art

The KEIHIN CORPORATION has proposed a regulator unit for use with fuel cells which is connected to a fluid passage and includes a cutoff valve for selectively passing a fluid such as a fuel gas or the like through the fluid passage upon energization of a solenoid (see Japanese Laid-Open Patent Publication No. 2004-185831).

The cutoff valve has a stationary iron core fixed to a housing and a plunger disposed coaxially with the stationary iron core for displacement toward the stationary iron core in response to energization of the solenoid. A valve head is coupled to an end of the plunger, and is seated on a valve seat in the housing under the resiliency of a spring, thereby closing the cutoff valve. The valve head comprises a first valve seatable on a first valve seat in the housing and a second valve displaceably supported on the lower end of the plunger. The second valve is crimped on the plunger by a substantially c-shaped clip, thereby holding the valve head on the lower end of the plunger.

When the second valve is unseated from a second valve seat disposed in the plunger, a fluid flows through the second valve into a port, reducing the pressure of the fluid in a valve chamber in which the second valve is disposed. The reduction in the pressure of the fluid causes the first valve to be unseated from the first valve seat, allowing a larger amount of fluid to flow through the valve seat into the port.

SUMMARY OF THE INVENTION

It is a general object of the present invention to provide a solenoid-operated cutoff valve for use with fuel cells which is capable of displacing a valve head with an improved response.

The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiment of the present inventions are shown by way of illustrative example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a block diagram of a fuel cell system200which incorporates a solenoid-operated cutoff valve for use with fuel cells according to an embodiment of the present invention. The fuel cell system200is mounted on a vehicle such as an automobile or the like.

As shown inFIG. 1, the fuel cell system200includes a fuel cell stack202having a stack of cells each comprising a solid polymer electrolyte membrane, such as a polymer ion exchange membrane or the like, sandwiched between an anode and a cathode that are disposed one on each side of the polymer electrolyte membrane. The fuel cell stack202has anodes for being supplied with hydrogen, for example, as a fuel and cathodes for being supplied with air containing oxygen, for example, as an oxidizing agent. A reaction gas used in the present embodiment collectively refers to hydrogen, air, and excessive gas.

The cathode has an air supply port206for being supplied with air from an oxidizing agent supply204and an air discharge port210connected to an air discharger208for discharging air in the cathode. The anode has a hydrogen supply port214for being supplied with hydrogen from a fuel supply212and a hydrogen discharge port218connected to a hydrogen discharger216.

In the fuel cell stack202, hydrogen ions that are generated at the anode by a catalytic reaction move through the solid polymer electrolyte membrane to the cathode where the hydrogen ions and oxygen cause an electrochemical reaction to generate electric power.

To the air supply port206, there are connected the oxidizing agent supply204, a heat radiator220, and a cathode humidifier222through an air supply passage. The air discharger208is connected to the air discharge port210through an air discharge passage.

To the hydrogen supply port214, there are connected the fuel supply212, a pressure controller224, an ejector226, and an anode humidifier228by a hydrogen supply passage. The hydrogen discharger216is connected to the hydrogen discharge port218by a circulation passage230.

The oxidizing agent supply204comprises, for example, an air compressor and a motor for actuating the air compressor (not shown). The oxidizing agent supply204adiabatically compresses air, which is to be used as an oxidizing gas in the fuel cell stack202, and delivers the compressed air to the fuel cell stack202. When the air is adiabatically compressed, it is heated. The heated air is effective to warm the fuel cell stack202.

The air supplied from the oxidizing agent supply204is introduced into the fuel cell stack202under a preset pressure depending on a load on the fuel cell stack202, a degree of an accelerator pedal (not shown) pressed, or the like. After the air supplied from the oxidizing agent supply204is cooled by the heat radiator220, a portion of the air is supplied as a pilot pressure through a bypass passage232to the pressure controller224.

The heat radiator220comprises an intercooler or the like (not shown), for example. The air supplied from the oxidizing agent supply204is cooled by a heat exchange with cooling water which flows through a flow passage while the fuel cell stack202is in normal operation. Therefore, the air is cooled to a predetermined temperature and then introduced into the cathode humidifier222.

The cathode humidifier222has a water-permeable membrane, for example. The cathode humidifier222humidifies the air, which has been cooled to the predetermined temperature by the heat radiator220, to a certain humidity by passing water from one side of the water-permeable membrane to the other, and supplies the humidified air to the air supply port206of the fuel cell stack202. The humidified air is supplied to the fuel cell stack202to keep the ion conductivity of the solid polymer electrolyte membranes in the fuel cell stack202at a certain level. The air discharger208is connected to the air discharge port210of the fuel cells stack202.

The fuel supply212comprises a hydrogen gas container (not shown) for supplying hydrogen as a fuel to the fuel cells, for example. The fuel supply212stores hydrogen that is to be supplied to the anode of the fuel cell stack202.

The pressure controller224comprises a pneumatic proportional pressure control valve, for example. Using the pressure of air from the bypass passage232as a pilot pressure (pilot signal pressure), the pressure controller224sets a secondary pressure as its outlet pressure to a pressure in a predetermined range corresponding to the pilot pressure.

The ejector226comprises a nozzle and a diffuser (not shown). The fuel (hydrogen) supplied from the pressure controller224is accelerated when it passes through the nozzle, and ejected toward the diffuser. When the fuel flows at a high speed from the nozzle to the diffuser, a negative pressure is developed in an auxiliary chamber disposed between the nozzle and the diffuser, attracting the fuel discharged from the anode through the circulation passage230. The fuel and the discharged fuel that are mixed together by the ejector226are supplied to the anode humidifier228. The fuel discharged from the fuel cell stack202circulates through the ejector226.

Therefore, the unreacted gas discharged from the hydrogen discharge port218of the fuel cell stack202is introduced through the circulation passage230into the ejector226. The hydrogen supplied from the pressure controller224and the gas discharged from the fuel cell stack202are mixed with each other and supplied again to the fuel cell stack202.

The anode humidifier228has a water-permeable membrane, for example. The anode humidifier228humidifies the fuel, which has been delivered from the ejector226, to a certain humidity by passing water from one side of the water-permeable membrane to the other, and supplies the humidified fuel to the hydrogen supply port214of the fuel cell stack202. The humidified hydrogen is supplied to the fuel cell stack202to keep the ion conductivity of the solid polymer electrolyte membranes of the fuel cell stack202at a certain level.

The hydrogen discharger216which has a discharge control valve, not shown, is connected to the hydrogen discharge port218of the fuel cell stack202by the circulation passage230. The discharge control valve can be opened and closed depending on an operating state of the fuel cell stack202for discharging, out of the vehicle, excessive water (mainly liquid water) in a discharged gas which has been separated by a reservoir tank, not shown.

FIGS. 2 through 6show the solenoid-operated cutoff valve, denoted by10, for use with fuel cells according to the embodiment of the present invention. The solenoid-operated cutoff valve10is disposed between the fuel supply212and the pressure controller224of the fuel cell system200.

As shown inFIGS. 2 and 3, the solenoid-operated cutoff valve10(hereinafter referred to as “cutoff valve10”) has a valve housing (first housing)16for being supplied with and discharging supplied hydrogen (hereinafter referred to as “fluid”) through an inlet port12and an outlet port14. The cutoff valve10also has an auxiliary housing (second housing)18mounted on an upper surface of the valve housing16. A guide housing22having a displaceable movable member20disposed therein is mounted on an upper surface of the auxiliary housing18.

The cutoff valve10further includes a solenoid housing26mounted on an upper surface of the guide housing22with an end plate24interposed therebetween, a solenoid28disposed in the solenoid housing26, a cover member30mounted to cover external surfaces of the solenoid housing26, and a valve head34for selectively passing the fluid by being seated on and unseated from a valve seat (second valve seat)32of the valve housing16.

The valve housing16is made of a metallic material, e.g., aluminum, and has the inlet port12which is open at a side surface thereof and the outlet port14which is open at an opposite side surface thereof remotely from the inlet port12. The valve housing16also has a communication chamber36defined therein which extends into the auxiliary housing18. The valve head34is axially displaceably disposed in the communication chamber36. The valve housing16has a first passage38defined therein which extends between the communication chamber36and the inlet port12, and a second passage40defined therein which extends between the communication chamber36and the outlet port14. The valve seat32for seating the valve head34thereon is in the form of an annular seat projecting upwardly from an upper surface of the valve housing16toward the valve head34. The valve seat32defines an inner space therein which communicates with the second passage40.

A joint (not shown) connected to a pipe or the like is joined to the inlet port12. The pipe or the like is held in communication with the inlet port12through a passage in the joint.

The first passage38extends by a predetermined distance substantially horizontally from the inlet port12toward the center of the valve housing16, and then extends obliquely upwardly at a predetermined angle and is connected to a lower end of the communication chamber36. A filter (removing member)42having a substantially U-shaped cross section which is open toward the inlet port12is mounted in the first passage38. The filter42has its bottomed end directed toward the communication chamber36.

When the fluid is introduced from the inlet port12, dust particles and foreign matter contained in the fluid are removed by the filter42having a plurality of fine pores and prevented from entering the communication chamber36.

Specifically, the fine pores of the filter42have a pore size smaller than the diameter of the passage defined in an orifice (restriction)66(seeFIGS. 3 through 6), to be described later, defined in the auxiliary housing18. Since the filter42removes dust particles and foreign matter that are greater in size than the diameter of the passage defined in the orifice66, the orifice66is prevented from being clogged by those dust particles and foreign matter. Consequently, the fluid introduced from the inlet port12can reliably and stably flow through the orifice66into the communication chamber36.

The second passage40extends a predetermined distance vertically downwardly from the valve seat32into the valve housing16, and then extends radially outwardly into communication with the outlet port14. The vertically downwardly extending portion of the second passage40has a mount hole44in its lower portion which is smaller in diameter than the second passage40. A tubular guide sleeve46is lightly press-fitted or fitted in the mount hole44. The guide sleeve46is made of fluorine resin, e.g., Teflon®.

A ring-shaped flat washer (engaging member)50is mounted on a step48in the boundary between the second passage40and the mount hole44. The guide sleeve46has an end engaging in a hole52defined centrally in the flat washer50and engaging a portion of a lower end face of the flat washer50. The guide sleeve46is prevented from being axially displaced in the mount hole44by the flat washer50, and hence from being dislodged out of the mount hole44. The flat washer50serves as a seat for a valve spring (first spring)158, to be described later, and a stop for preventing the guide sleeve46from being dislodged out of the mount hole44.

The valve housing16has a first communication passage54defined therein near the outlet port14and providing fluid communication with the communication chamber36. The first communication passage54extends obliquely downwardly from an inner side surface of the communication chamber36, and then extends vertically upwardly. Specifically, the communication chamber36comprises a first communication chamber36adefined in the valve housing16and a second communication chamber36bdefined in the auxiliary housing18. The first communication passage54has an end connected to the first communication chamber36aand an opposite end connected to a second communication passage64that is defined in the auxiliary housing18in communication with the second communication chamber36b. The first communication passage54is positioned near the outlet port14remotely from the inlet port12in the valve housing16.

The valve housing16has an annular groove defined in an upper end face thereof which faces the auxiliary housing18, and an O-ring (seal)56ais mounted in the annular groove. The O-ring56akeeps the communication chamber36hermetically sealed when the valve housing16and the auxiliary housing18are connected to each other.

The valve housing16also has an annular recess58defined in the upper end face thereof at a position that is spaced radially inwardly from the annular groove which receives the O-ring56atherein. A diaphragm (flexible member)60, to be described later, has an enlarged outer peripheral edge62mounted in the annular recess58and clamped between the annular recess58and a lower end face of the auxiliary housing18which faces the valve housing16.

Since the O-ring56ais positioned radially outwardly of the recess58which receives the enlarged outer peripheral edge62of the diaphragm60, both the O-ring56aand the enlarged outer peripheral edge62of the diaphragm60are effective to keep the communication chamber36hermetically sealed. Accordingly, the fluid is reliably prevented from leaking out from between the valve housing16and the auxiliary housing18.

Specifically, when the enlarged outer peripheral edge62of the diaphragm60is mounted in the recess58, the upper surface of the enlarged outer peripheral edge62lies substantially flush with the end face of the valve housing16. The enlarged outer peripheral edge62and the O-ring56athat is positioned radially outwardly of the enlarged outer peripheral edge62provide a double-seal structure for a greater sealing capability than if only the enlarged outer peripheral edge62is provided in abutment against the lower end face of the auxiliary housing18. Consequently, the communication chamber36is reliably hermetically sealed.

The first communication passage54includes a substantially vertical portion extending from the valve housing16upwardly into the auxiliary housing18in a region between the recess58and the O-ring56a(seeFIG. 2). Even if the fluid flowing through the first communication passage54leaks into the boundary between the valve housing16and the auxiliary housing18, the fluid is prevented from leaking further outwardly by the enlarged outer peripheral edge62fitted in the recess58and the O-ring56a.

The auxiliary housing18is of a substantially hollow cylindrical shape and is integrally fastened to the upper end face of the valve housing16by bolts (not shown).

The second communication passage64is defined in the auxiliary housing18in communication with the communication chamber36and extends radially outwardly. The second communication passage64communicates with the first communication passage54in the valve housing16. An orifice66having a diameter smaller than the first and second communication passages54,64is defined in the auxiliary housing18between the first and second communication passages54,64. Therefore, the first and second communication passages54,64communicate with each other through the orifice66.

The diameter of the passage in the orifice66may be changed to control highly accurately the rate of the fluid that flows from the first communication chamber36athrough the orifice66into the second communication chamber36b.

The first and second communication passages54,64and the orifice66should preferably be positioned remotely from the inlet port12. It is the most suitable to position the first and second communication passages54,64and the orifice66in a region that is spaced most widely from the inlet port12. For example, the first and second communication passages54,64and the orifice66should preferably be positioned in the valve housing16and the auxiliary housing18closely to the outlet port14. With the first and second communication passages54,64and the orifice66being thus positioned, the rate of the fluid flowing therethrough does not become unstable due to the speed of the fluid that is introduced from the inlet port12, and the fluid can be supplied through the first and second communication passages54,64and the orifice66to the second communication chamber36bstably at a desired rate, making the fluid pressure stable in the second communication chamber36b.

The guide housing22is made of a metallic material such as stainless steel or the like, and is mounted on the upper surface of the auxiliary housing18. The guide housing22includes a relatively long guide sleeve68axially extending upwardly from an upper surface of the guide housing22, a flange70extending radially outwardly from the lower end of the guide sleeve68and mounted on an upper end face of the auxiliary housing18, and an insert72extending downwardly from the flange70and inserted into the auxiliary housing18.

The guide sleeve68comprises a thin-walled hollow cylinder having a support hole74defined therein. The movable member20is axially displaceably supported in the support hole74. The guide sleeve68is inserted in an insertion hole defined in a bobbin76, to be described later, and a through hole86, to be described later, defined in the end plate24. The guide sleeve68has an upper end secured to a fixing member104, to be described later, by laser beam welding or the like, for example.

An annular seal82is mounted in a space surrounded by an outer circumferential surface of the guide sleeve68, an insertion hole80defined in the solenoid housing26in which the guide sleeve68is inserted, and an upper surface of the end plate24. The annular seal82hermetically seals the interior of the solenoid28.

The insert72is slightly greater in diameter than the guide sleeve68and is fixedly inserted in an insertion hole84defined in the auxiliary housing18. The insert72has an annular groove defined in an outer circumferential surface thereof and receiving an O-ring56bmounted therein. The O-ring56bis held against an inner wall surface of the auxiliary housing18to keep the boundary between the guide housing22and the auxiliary housing18hermetically sealed.

The end plate24is made of a magnetic metallic material and has an annular shape. The end plate24is joined to an upper surface of the flange70of the guide housing22. The through hole86is defined substantially centrally in the end plate24, and the guide sleeve68of the guide housing22is inserted through the through hole86.

The solenoid housing26is integrally molded of a resin material, and is joined to the upper surface of the end plate24. A connector88for being electrically connected to a power supply, not shown, for supplying an electric current to the solenoid28is mounted on a side surface of the solenoid housing26. The connector88has a terminal90of metal disposed therein and having an exposed end portion. The terminal90is electrically connected to the bobbin76of the solenoid28through the solenoid housing26. The terminal90is electrically connected to the power supply through leads, not shown.

The solenoid housing26includes a flange92projecting radially inwardly from an upper end thereof. The flange92has an annular groove defined in an upper end face thereof and accommodating an O-ring56ctherein. The O-ring56cis held between the solenoid housing26and a cover member30, to be described later, and hermetically seals the gap between the solenoid housing26and the cover member30.

The cover member30is made of a magnetic metallic material and has a substantially inverted u-shaped cross section. The cover member30is mounted in covering relation to the solenoid housing26and the end plate24. The end plate24is prevented by the cover member30from being dislodged from between the guide housing22and the solenoid housing26. The cover member30has a hole96defined substantially centrally in an upper end thereof. The fixing member104has an externally threaded knob98projecting upwardly from its upper end face and inserted through the hole96.

The solenoid28comprises a bobbin76disposed in and surrounded by the solenoid housing26, a coil100wound around the bobbin76, the movable member20axially displaceably disposed in the bobbin76, and the fixing member104coupled to the upper end of the solenoid housing26by a cap nut102threaded over the externally threaded knob98and disposed in axially confronting relation to the movable member20.

The bobbin76is disposed in abutment against the inner circumferential surface of the solenoid housing26. The bobbin76has a first large-diameter flange106and a second large-diameter flange108disposed respectively on upper and lower ends thereof and extending radially outwardly. The coil100is wound around the bobbin76axially between the first large-diameter flange106and the second large-diameter flange108. The bobbin76is integrally molded with the solenoid housing26.

The first large-diameter flange106is held against a lower surface of the flange92of the solenoid housing26, and the second large-diameter flange108has an annular groove110defined in a lower surface thereof and receiving an annular protrusion112disposed on an upper end face of the solenoid housing26. Therefore, the bobbin76with the coil100wound thereon engages in the solenoid housing26, and is surrounded in its entirety by the solenoid housing26.

The fixing member104, which is made of a magnetic metallic material, is inserted in the bobbin76. The movable member20is disposed axially beneath the fixing member104within the guide sleeve68of the guide housing22.

For assembling the cover member30, the externally threaded knob98of the fixing member104is inserted into the hole96in the cover member30, a washer114is placed around the externally threaded knob98, and then the cap nut102is threaded over the externally threaded knob98to fasten the fixing member104to the solenoid housing26.

The fixing member104has a recess116defined in a lower end face thereof and having a predetermined depth in a direction away from the movable member20.

The movable member20is made of a magnetic metallic material. The movable member20includes a substantially cylindrical main body118that is displaceable axially in the guide sleeve68and a land120projecting from an upper end of the main body118toward the fixing member104.

The main body118has a spring retainer122projecting radially outwardly from the lower end thereof. A return spring (second spring)124is interposed between the spring retainer122and the guide housing22. The return spring124biases the movable member20to be displaced toward the valve seat32of the valve housing16, i.e., in the direction indicated by the arrow b (seeFIG. 3).

A pilot valve seat (first valve seat)128is mounted in a cavity126having a predetermined depth which is defined substantially centrally in a lower end portion of the main body118in facing relation to the valve seat32. The pilot valve seat128is made of an elastic material such as rubber or the like, and is disposed in a position that is spaced upwardly from a lower end face of the movable member20toward the fixing member104, i.e., in the direction indicated by the arrow a. The elastic pilot valve seat128has a seating function to close a pilot port (passage)140when a pilot valve (first valve)132is seated on the pilot valve seat128and a silencing function to prevent contact noise from being produced when pilot valve132, which is made of a metallic material, is seated on the pilot valve seat128.

The land120of the movable member20is radially inwardly smaller in diameter than the main body118. When the movable member20is displaced upwardly, the land120is inserted into the recess116in the fixing member104. A resilient member (first resilient member)130having a predetermined thickness is mounted on an upper end face of the land120which faces the recess116. The resilient member130is made of an elastic material such as rubber or the like, and serves to dampen shocks and eliminate contact noise when the land120is inserted into the recess116and hits the bottom of the recess116upon upward displacement of the movable member20.

The valve head34is made of a metallic material such as stainless steel or the like, and has a substantially crisscross shape. As shown inFIG. 3, the valve head34is includes the pilot valve132disposed closer to the movable member20for being seated on the pilot valve seat128on the movable member20, a main valve (first valve)134radially outwardly larger in diameter than the pilot valve132, for being seated on the valve seat32of the valve housing16, and a guide shaft (guide)136displaceably guided by the guide sleeve46mounted in the valve housing16.

The valve head34has a pilot passage138defined axially therethrough. The pilot valve132has the pilot port140held in communication with the pilot passage138. The pilot port140has a diameter smaller than the diameter of the pilot passage138. The diameter of the pilot port140is greater than the diameter of the orifice66in the auxiliary housing18.

The pilot valve132can be seated on and unseated from the pilot valve seat128mounted on the movable member20. The pilot valve132has an upper surface facing the pilot valve seat128, the upper surface being gradually inclined downwardly in a radially outward direction from its substantially central area.

The valve head34has an externally threaded outer circumferential surface142between the pilot valve132and the main valve134. The diaphragm60, which is in the form of a thin membrane, is mounted on the valve head34. With the diaphragm60held against an upper surface of the main valve134, a nut146is threaded over the externally threaded outer circumferential surface142with a retainer144and a washer114, fastening a substantially central area of the diaphragm60to the valve head34. The retainer144is in the form of a thin plate of a metallic material and has a peripheral edge portion curved upwardly away from the main valve134.

The diaphragm60is made of a resin material. The diaphragm60has a skirt148flexibly extending radially outwardly from the substantially central area thereof which is fixed to the valve head34, and the enlarged outer peripheral edge62disposed on an outer circumferential portion of the skirt148. The enlarged outer peripheral edge62is placed in the annular recess58and clamped between the valve housing16and the auxiliary housing18. The communication chamber36is divided by the diaphragm60into the first communication chamber36adefined in the valve housing16and the second communication chamber36bdefined in the auxiliary housing18.

The main valve134, which is radially outwardly larger in diameter than the pilot valve132, is disposed in the first communication chamber36ain the valve housing16. The main valve134has a diameter greater than the outside diameter of the valve seat32of the valve housing16.

The main valve134has a lower surface serving as a seating surface150that faces the valve seat32. The seating surface150has an annular mount groove152of a predetermined depth defined therein. A seat (second resilient member)154made of an elastic material such as rubber or the like is mounted in the annular mount groove152. The main valve134also has an annular groove156defined therein which extends upwardly from the mount groove152. The annular groove156is filled up with an elastic material joined to the seat154.

The seat154is mounted in a position to contact the valve seat32when the main valve134is displaced toward the valve seat32, i.e., in the direction indicated by the arrow b. The seat154is mounted in the main valve134by filling the mount groove152with the elastic material and then curing the elastic material. Since the elastic material introduced into the mount groove152flows from the mount groove152into the annular groove156, the seat154can easily be integrally molded in the mount groove152and the annular groove156, and hence can be mounted in place easily and efficiently.

The elastic seat154has a seating function to close the valve seat32when the main valve134is seated on the valve seat32and a silencing function to prevent contact noise from being produced when the main valve134is seated on the valve seat32which is made of a metallic material.

A valve spring158is interposed between the flat washer50mounted in the mount hole44in the valve housing16and the main valve134. The valve spring158is of a tapered shape which is progressively greater in diameter from an end thereof engaging the main valve134toward an opposite end thereof engaging the flat washer50. The valve spring158biases the valve head34including the main valve134to move in a direction away from the valve seat32, i.e., in the direction indicated by the arrow a. Specifically, the valve spring158has an upper end engaging a corner of the valve head34which is defined between the seating surface150and the guide shaft136and a lower end engaging a corner which is defined between an upper surface of the flat washer50and an inner wall surface of the step48in the valve housing16.

The tapered valve spring158is effective to radially keep the main valve134in axial alignment with the valve seat32under the resiliency of the tapered valve spring158.

The tapered valve spring158is spaced a predetermined radial distance from the guide shaft136of the valve head34. Therefore, the guide shaft136is kept out of contact with the valve spring158when the guide shaft136is axially displaced.

The flat washer50has an outer circumferential area pressed against the step48under the bias of the valve spring158. Therefore, the flat washer50is retained on the step48against removal therefrom.

The guide shaft136extends by a predetermined length downwardly from the main valve134. The pilot passage138extends axially substantially centrally in the guide shaft136. The guide shaft136has a communication hole160defined diametrically therein substantially perpendicularly to the pilot passage138. The communication hole160extends through the outer circumferential surface of the guide shaft136and communicates with the pilot passage138. The guide shaft136is inserted through a resin guide hole162which is defined axially in the guide sleeve46, and is axially displaceably guided therein.

FIG. 4shows a modified guide sleeve166in the form of a hollow cylinder having a flange164projecting radially outwardly. The modified guide sleeve166is used in place of the guide sleeve46and the flat washer50which are mounted in the valve housing16shown inFIG. 3. The guide sleeve166is made of a resin material, and can be lightly press-fitted or fitted in the mount hole44. The flange164engages the step48in the mount hole44.

The lower end of the valve spring158is held by the flange164of the guide sleeve166, which is retained in the mount hole44under the resilient force of the valve spring158. With the modified guide sleeve166, the flat washer50shown inFIG. 3is dispensed with. Therefore, the solenoid-operated cutoff valve with the modified guide sleeve166is made up of a reduced number of parts, can be manufactured at a reduced cost, and can be assembled efficiently.

Since the guide sleeve46is made of a metallic material, e.g., as a DU bushing, the guide sleeve46can be press-fitted into the valve housing16. Therefore, the guide sleeve46thus installed is prevented from being dislodged from the mount hole44. If the guide sleeve46is press-fitted into the valve housing16, the flat washer50and the flange164may be dispensed with, and hence the number of parts of the solenoid-operated cutoff valve may be reduced.

The solenoid-operated cutoff valve10for use with fuel cells according to the embodiment of the present invention is basically constructed as described above. Operation and advantages of the solenoid-operated cutoff valve10will be described below. InFIGS. 2 and 3, the solenoid-operated cutoff valve10is in an off state wherein the pilot valve132of the valve head34is seated on the pilot valve seat128and the main valve134is seated on the valve seat32, blocking the fluid flow between the inlet port12and the outlet port14.

In the off state, the fluid is introduced from the inlet port12through the first passage38into the first communication chamber36a. At this time, since the fluid flows through the filter42mounted in the first passage38, dust particles and foreign matter contained in the fluid are removed by the filter42and prevented from entering the first communication chamber36a.

A portion of the fluid introduced into the first communication chamber36ais introduced from the first communication passage54through the orifice66and the second communication passage64into the second communication chamber36b. Therefore, the fluid introduced from the inlet port12into the valve housing16is supplied through the first and second communication passages54,64respectively to the first communication chamber36aand the second communication chamber36b. The fluid pressure in the first communication chamber36aand the fluid pressure in the second communication chamber36bare substantially equal to each other across the diaphragm60.

When the non-illustrated power supply is turned on to supply an electric current to the coil100through the terminal90of the connector88, the coil100is energized to generate magnetic fluxes which flow from the coil100to the main body118of the movable member20and then back to the coil100.

As shown inFIG. 5, under the magnetic force, the movable member20is now displaced axially upwardly toward the fixing member104, i.e., in the direction indicated by the arrow a, against the resilient force from the return spring124, displacing the pilot valve seat128off the pilot valve132. At this time, the main valve134of the valve head34is seated on the valve seat32.

The fluid in the second communication chamber36bflows through the pilot port140in the pilot valve132, the pilot passage138, and the communication hole160into the second passage40, from which the fluid is discharged out of the solenoid-operated cutoff valve10through the outlet port14. At this time, the fluid pressure in the second communication chamber36bbecomes lower than the fluid pressure in the first communication chamber36a, developing a pressure difference between the fluid pressure in the second communication chamber36band the fluid pressure in the first communication chamber36a.

Specifically, because the fluid is introduced through the orifice66into the second communication chamber36b, the rate of the fluid flowing out of the second communication chamber36bthrough the pilot port140, which is greater in diameter than the orifice66, is higher than the rate of the fluid flowing into the second communication chamber36bthrough the orifice66. Therefore, the orifice66is effective to progressively lower the fluid pressure in the second communication chamber36b.

As a result, as shown inFIG. 6, a pressing force generated due to the pressure difference between the first communication chamber36aand the second communication chamber36bis applied upwardly to the diaphragm60, i.e., in the direction indicated by the arrow a. In addition the resilient force from the valve spring158is applied upwardly to the valve head34. Consequently, the valve head34is displaced toward the movable member20, unseating the seating surface150of the main valve134off the valve seat32.

As a result, the first communication chamber36aand the outlet port14are brought into fluid communication with each other, allowing the fluid introduced from the inlet port12into the first communication chamber36ato flow through the valve seat32and the second passage40into the outlet port14.

At this time, a value (W×Gmax) representing the product of the weight w of the movable member20and a maximum value Gmax of the vibratory acceleration G on the cutoff valve10, and the resilient force Pr of the return spring124are canceled by the electromagnetic force generated by the solenoid28. The sum of the pressing force Pd applied to the diaphragm60under the pressure difference between the first communication chamber36aand the second communication chamber36band the resilient force Ps of the valve spring158is set to a value greater than the product of the weight w and the maximum value Gmax of the vibratory acceleration G on the main valve134((W×Gmax)<Pd+Ps).

When the main valve134is unseated from the valve seat32, the sum of the pressing force pd applied to the diaphragm60under the pressure difference between the first communication chamber36aand the second communication chamber36band the resilient force Ps of the valve spring158overcomes the value (W×Gmax), keeping the main valve134open.

Conversely, when the main valve134is seated on the valve seat32, the resilient force Pr of the return spring124overcomes the pressing force pd applied to the diaphragm60under the pressure difference between the first communication chamber36aand the second communication chamber36band the resilient force Ps of the valve spring158, keeping the main valve134desirably closed. In addition, the value (W×Gmax) representing the product of the weight W of the movable member20and the main valve134and the maximum value Gmax of the vibratory acceleration G on the cutoff valve10is applied to keep the valve head34reliably open or closed even when the cutoff valve10is vibrated with the maximum value Gmax of the vibratory acceleration g, and also to allow the valve head34to be displaced freely.

For preventing the fluid from flowing through the solenoid-operated cutoff valve10in this on state, the electric current supplied from the non-illustrated power supply to the coil100is interrupted to de-energize the coil100, eliminating the force tending to displace the main body118of the movable member20toward the fixing member104. Therefore, the movable member20is pressed toward the valve seat32, i.e., in the direction indicated by the arrow b, under the resilient force of the return spring124, until the pilot valve seat128on the movable member20is seated on the pilot valve132of the valve head34.

The fluid flowing through the pilot passage138from the second communication chamber36binto the outlet port14is now blocked, whereupon the pressure difference between the first communication chamber36aand the second communication chamber36bis eliminated. The seating surface150of the main valve134of the valve head34is now seated on the valve seat32of the valve housing16. The solenoid-operated cutoff valve10is brought into the off state wherein the communication chamber36and the outlet port14are held out of fluid communication with each other. The fluid introduced from the inlet port12now stops being discharged out from the outlet port14.

With the cutoff valve10according to the present embodiment, as described above, the flexible diaphragm60is mounted in place between the main valve134of the valve head34and the pilot valve132, and the enlarged outer peripheral edge62of the diaphragm60is clamped between the valve housing16and the auxiliary housing18. The communication chamber36defined in the valve housing16and the auxiliary housing18is divided by the diaphragm60into the first communication chamber36adefined in the valve housing16and the second communication chamber36bdefined in the auxiliary housing18.

When the movable member20is displaced upwardly upon energization of the solenoid28, the fluid introduced into the first communication chamber36aflows through the first and second communication passages54,64into the second communication chamber36b. As the pilot valve132is unseated from the pilot valve seat128, the fluid flows through the pilot passage138into the outlet port14. As a result, the fluid pressure in the second communication chamber36bbecomes lower than the fluid pressure in the first communication chamber36a, applying an upward pressing force to the diaphragm60under the pressure difference between the first communication chamber36aand the second communication chamber36b, causing the diaphragm60to lift the valve head34off the valve seat32.

Therefore, the valve head34can reliably and quickly be displaced under the pressure difference between the first communication chamber36aand the second communication chamber36bwithout being affected by the fluid pressures in upstream and downstream regions of the fluid passage (not shown) to which the cutoff valve10is connected. The response of the cutoff valve10for seating the valve head34on the valve seat32and unseating the valve head34from the valve seat32is thus made higher than the response of conventional cutoff valves.

The diameter of the pilot port140in the pilot valve132is greater than the diameter of the orifice66in the auxiliary housing18, so that the rate of the fluid flowing from the pilot port140into the outlet port14is greater than the rate of the fluid flowing through the orifice66into the second communication chamber36b. The fluid pressure in the second communication chamber36bis thus made lower than the fluid pressure in the first communication chamber36a, making it possible to increase the pressure difference between the first communication chamber36aand the second communication chamber36b.

Furthermore, since the valve spring158is disposed between the seating surface150of the main valve134and the flat washer50mounted on the valve housing16in facing relation to the outlet port14, the communication chamber36may be smaller in size than if the spring is disposed in the communication chamber36. As the resilient force of the valve spring158is applied in a direction to press the valve head34toward the movable member20, the valve head34can follow the displacement of the movable member20. As a result, the communication chamber36may be reduced in size, allowing the fluid to be quickly introduced into and discharged from the communication chamber36, and the valve head34can be displaced axially with an increased response.

The guide sleeve46in the form of a hollow cylinder is disposed in the mount hole44in the valve housing16, and the guide shaft136of the valve head34extends through the guide hole162in the guide sleeve46. The valve head34is axially displaceably guided by the guide shaft136, so that the main valve134of the valve head34is prevented from being tilted and shifted radially. Therefore, the main valve134can stably and accurately be seated on the valve seat32, and the pilot valve132can stably and accurately be seated on the pilot valve seat128.

Inasmuch as the guide sleeve46is made of fluorine resin, e.g., Teflon®, the guide shaft136can displaceably be guided along the guide hole162in the guide sleeve46smoothly.

The flat washer50is mounted on the upper end of the guide sleeve46and the step48in the valve housing16. The flat washer50is effective to prevent the guide sleeve46lightly press-fitted or fitted in the mount hole44from being dislodged out of the mount hole44.