Valve mechanism for high pressure tank and valve device for high pressure tank

A valve mechanism includes a first plunger, a second plunger, a seal member, and a valve element. The first plunger has a thread engaging with a threaded portion provided on an inner wall of the flow passage. The first plunger is movable along the axis by rotating around the axis. The second plunger has a first end and a second end. The first end engages with the first plunger such that the first plunger is relatively rotatable with respect to the second plunger. The second plunger is movable along the axis by rotating the first plunger. The seal member is provided to surround the second plunger. The valve element has a back end engaging with the second end such that the valve element is movable along the axis according to movement of the second plunger so as to be seated on and separated from a valve seat.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U. S. C. § 119 to Japanese Patent Application No. 2016-035569, filed Feb. 26, 2016. The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND

Field of the Invention

The present invention relates to a valve mechanism for a high pressure tank and a valve device for a high pressure tank.

Discussion of the Background

In a high pressure tank to be used for a fuel cell powered vehicle and a stationary fuel cell, high pressure hydrogen of several dozens of MPa is stored. Therefore, the high pressure is applied also to a piping system connecting to the high pressure tank. When assembling the fuel cell powered vehicle or at the time of maintenance, the so-called airtightness inspection is carried out in order for confirming whether or not there is any leakage in the piping system. Concretely, high pressure fluid is filled into the piping system, and presence or absence of the leakage of the fluid from the piping system is inspected.

At the time of inspection, the hydrogen and the like as fuel is not used, inert gas such as helium and the like is used. In the airtightness inspection, a valve device (manual valve) for airtightness inspection is required to be fitted in the high pressure tank so as not to allow the inert gas to enter the high pressure tank. As the valve device for the airtightness inspection there is a manual safety restraint valve as disclosed in a Japanese Patent Application Laid-Open Publication No. H07-301359. This manual safety restraint valve is arranged in a gas flow passage. A threaded stem is rotated so as to tighten a resilient gasket against a second valve seat.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a valve mechanism for a high pressure tank, which is accommodated in a valve accommodating hole communicating with a flow passage through which prescribed fluid flows, includes a first plunger, a second plunger, a seal member, and a valve element. The first plunger is configured to be engaged with a threaded portion formed on at least a part of an inner wall of the valve mechanism accommodating hole and to be moved by rotation in the valve mechanism accommodating hole. The second plunger is configured to be engaged at one end thereof with the first plunger in a relatively rotatable manner. The seal member is in contact with a periphery of the second plunger. The valve element is configured to be engaged with the other end of the second plunder and to be seated on and separated from a valve seat which is formed in the flow passage.

According to another aspect of the present invention, a valve mechanism includes a first plunger, a second plunger, a seal member, and a valve element. The first plunger is provided in a flow passage and has a thread around an axis of the first plunger. The thread is engaging with a threaded portion provided on an inner wall of the flow passage. The first plunger is movable along the axis by rotating around the axis. The second plunger is provided in the flow passage and has a first end and a second end opposite to the first end along the axis. The first end engages with the first plunger such that the first plunger is relatively rotatable with respect to the second plunger. The second plunger is movable along the axis by rotating the first plunger. The seal member is provided to surround the second plunger around the axis so as to contact a circumferential outer surface of the second plunger. The valve element is provided in the flow passage and has a forward end and a back end opposite to the forward end along the axis. The back end engages with the second end of the second plunger such that the valve element is movable along the axis according to movement of the second plunger so as to be seated on and separated from a valve seat which is provided in the flow passage.

DESCRIPTION OF THE EMBODIMENTS

Hereunder, an embodiment of the present invention will be explained with reference to accompanying drawings. In the following explanation, while the term “axial direction” is used appropriately, it means the direction extending along a center axis in the longitudinal direction of a valve mechanism1or a valve mechanism accommodating hole90. Similarly, while the term “high pressure tank” is used, a tank in which fluid of higher pressure than at least atmospheric pressure is stored, is included within the high pressure tank of the present embodiment.

FIG. 1is a schematic diagram showing a valve device in accordance with an embodiment of the present invention, a high pressure tank101, a piping system111and a fuel cell stack121. The high pressure tank101is a high pressure tank for storing high pressure hydrogen, although not limited to this. In the case of the high pressure tank101used for a fuel cell powered vehicle, it is required to endure the pressure of about 70 Mpa. Moreover, it is required to have resistance to hydrogen. Therefore, the high pressure tank is made of resin material or aluminum. A body80is screwed with a mouthpiece potion103of the high pressure tank101so as to seal the mouthpiece portion103. In the interior of the body80, there is provided an electromagnetic type in-tank electromagnetic valve105which communicates with an internal space102of the high pressure tank101. In addition, a valve device8of this embodiment is provided on a downstream side of the in-tank electromagnetic valve105through a first flow passage85a. The valve device8of this embodiment is a manual valve which is manually operable from the outside of the body80. A second flow passage85bis formed on a downstream side of the valve device8. Herein, in the following explanation, the first flow passage85aand the second flow passage85bmay be referred to as a flow passage85, in combination of both.

A filling flow passage107for filling fluid from the outside is provided in the second flow passage85b. A check valve is provided in an intermediate position of the filling flow passage107so as to prevent the fluid from leaking out through the filling flow passage107from the second flow passage85b. From the filling flow passage107, hydrogen to be stored in the high pressure tank101is filled and further high pressure fluid (normally, inert gas) for an airtight inspection is filled. Moreover, main piping113for supplying hydrogen to a fuel cell stack121is connected to the second flow passage85b. To the main piping113there are connected a regulator115, pressure gauges116and117and a control valve119in the order named from the side of the body80. The regulator115is configured to adjust (decompress) the pressure of hydrogen supplied from the high pressure tank101. The pressure gauge116is configured to measure the pressure of hydrogen before adjustment, while the pressure gauge117is configured to measure the pressure of hydrogen after adjustment. The control valve119is configured to control (or shut off) the supply of hydrogen to the fuel cell stack121.

In a normal use mode, the opening and closing of the in-tank electromagnetic valve105is controlled by a control signal from a control section not shown in the drawing. Further, the valve device8of this embodiment is always in a closed condition. On the other hand, in the case of assembling and maintaining the piping system111and in the case of carrying out the airtight inspection, the valve device8is manually operated, and the first flow passage85aand the second flow passage85bare shut off. This is because the high pressure fluid for the airtight inspection enters the interior of the high pressure tank101through the first flow passage85awhen the first flow passage85aand the second flow passage85bare not shut off.

[Overall Configuration of Valve System]

Next, the overall configuration of the valve device8will be explained with reference toFIGS. 2 and 3. In the following explanation, while the term “engagement” is used, it shall not be interpreted narrowly. In other words, the term “engagement” is not limited to such an engaging configuration between a flange portion35of a first plunger3and one end engaging part52or such an engaging configuration between the other end engaging part54and a valve element head portion77as referred to with respect to the following embodiment. For example, such a configuration that the first plunger3is simply contacted with one end of a second plunger so as to apply thrust (force in the valve closing direction) to the second plunger5or such a configuration that the other end of the second plunger5is simply contacted with the valve element7so as to apply thrust to the valve element7may be included. Further, such a configuration that the first plunger3and the valve element7are connected by a wire is included in the “engagement”. In addition, the engagement between the first plunger3and the second plunger5, and the engagement between the second plunger5and the valve element7do not rest on the premise that they are always in contact with each other. According to the conditions, there may be cases where the first plunger3and the second plunger5are not in a direct contact relation, and there may be cases where the second plunger5and the valve element7are not in a direct contact relation.

The valve device8includes the valve mechanism1and the body80which holds the valve mechanism1. The body80includes a valve holder81which holds the first plunger3in the interior thereof, and a valve body83to which the valve holder81is fitted. In addition, the flow passage85through which the prescribed fluid flows is formed in the interior of the body80. Then, the valve mechanism1is configured to switch between the communication and the shut off of the flow passage85.

The valve holder81is a member of substantially cylindrical shape, of which a small diameter part81aon the upper side of the drawing and a large diameter part81bon the lower side are integrally formed with each other (inFIG. 2, represented while partitioning it up and down by a phantom line, for convenience of explanation). A valve holder male threaded portion81cis formed on an outer peripheral surface of the large diameter part81b. The valve holder male threaded portion81cis not formed on the whole surface of the outer peripheral surface of the large diameter part81bbut formed in an upper half region of the large diameter part81b. However, the valve holder male threaded portion81cmay be formed on the whole surface of the outer peripheral surface of the large diameter part81b. Herein, since a threaded portion is not formed in a lower half region of the large diameter part81b, the lower half region is slightly smaller in diameter than the valve holder male threaded portion81cby a height of the screw thread.

The interior of the valve holder81is hollow and is composed of a valve holder female threaded portion81d, a large diameter hole81eand a first seal member hole81fin the order named from the upper side of the valve holder81. These valve holder female portion81d, large diameter hole81eand first seal member hole81fconstitute a part of the valve mechanism accommodating hole90. With respect to diameter of each portion, the diameter of the valve holder female threaded portion81dis smallest, and the diameter of the first seal member hole81fis largest. The inner diameter of the valve holder female threaded portion81dcorresponds to the diameter of the male threaded portion31bformed in the first plunger3of the valve mechanism1. Therefore, the first plunger3is screwed with the valve holder female threaded portion81d. The valve holder female threaded portion81dis formed in the range from an upper end portion of the valve holder81to about a half position in the height direction thereof. Accordingly, the first plunger3is allowed to move, while rotating, in the axial direction in the range of the valve holder female threaded portion81d.

The large diameter hole81eis a hole of a columnar shape, and the second plunger5of the valve mechanism1is accommodated within the large diameter hole81e. Therefore, the diameter of the large diameter hole81eis formed slightly larger than the diameter of the second plunger5. The second plunger5within the large diameter hole81eis engaged at its one end (upper end) with the first plunger3. Therefore, the second plunger5is configured to move along with the first plunger3within the large diameter hole81e. However, when the one end (upper end) of the second plunger5comes into contact with the upper end portion of the large diameter hole81, it is not able to move further upward.

The first seal member hole81fis a hole for arranging a seal member (for example, an O-ring and a back up ring)87. In this embodiment, when the second plunger5is arranged in the large diameter hole81e, a ring shaped space is formed on the outside of the second plunger5. When the seal member87is arranged within the ring shape space, the seal member87is configured to come into contact with the periphery of the second plunger5. However, in this embodiment, as referred to later, the seal member87is arranged on the side of the valve body83.

Next, the valve body83will be explained.FIG. 2shows a part of the valve body83, namely, a part in which the valve mechanism3is provided. A valve body female threaded portion83ais formed in the valve body83. This valve body female threaded portion83ais provided for mounting the valve holder81. More precisely, the inner diameter of the valve body female threaded portion83acorresponds to the diameter of the valve holder male threaded portion81c. Therefore, when the valve holder81is screwed into the valve body female threaded portion83a, the valve holder81is secured to the valve body83. In addition, a valve holder accommodating hole for accommodating a lower part of the valve holder81is formed below the valve body female threaded portion83.

Further, a space constituting a part of the valve mechanism accommodating hole90is formed below the valve holder81. The valve mechanism accommodating hole90formed in the valve body83includes a second seal member hole83band a columnar space83c. The second seal member hole83bhas an inner diameter equal to that of the first seal member hole81f. Therefore, a prescribed ring shaped clearance is formed between the second seal member hole and an outer peripheral surface of the second plunger5. The seal member87is arranged around the periphery of the second plunger5within this clearance. When the seal member87is arranged, a space formed by the second seal member hole83band the second plunger5is blocked between the first plunder3side and the valve element7side. Therefore, it is possible to maintain an upper space which is open to atmosphere and a lower space which has a prescribed higher pressure than an atmospheric pressure, on either side of the seal member87.

Further, the flow passage85of the valve body83includes the first flow passage85awhich communicates with the internal space102of the high pressure tank101and the second flow passage85bwhich communicates with the exterior (for example, the piping system111for supplying hydrogen) of the high pressure tank101. The first flow passage85bis arranged coaxially with the valve mechanism accommodating hole90so as to face toward the valve element7. The diameter of the first flow passage85ais set so as to correspond to an inverted truncated cone shape of the valve element7. More precisely, the diameter of the first flow passage85ais larger than the diameter of a small diameter portion71aof an inverted truncated cone shaped valve portion71of the valve element7and smaller than the diameter of a large diameter portion71bthereof. In addition, since a taper surface of the valve portion71of the valve element7is configured to come into contact with an end portion (an upper end portion in the drawing) of the first flow passage85a(seeFIG. 3), the valve seat85cis provided on the boundary between the first flow passage85aand the second flow passage85.

By the way, the diameter of the first flow passage85ais not required to satisfy the above described conditions over the entire length thereof. At least the end of the first flow passage85aserving as the valve seat85cneeds to satisfy the above conditions, and other portions of the first flow passage85amay be formed in the different diameter. Further, in this embodiment, although the valve mechanism accommodating hole90and the first flow passage85aare formed coaxially, this is not essential. That is to say, it is sufficient that the valve seat85cis located in a position opposed to the valve element7, and the first flow passage85amay be formed in any shape and at any position.

The second flow passage85bextends in the orthogonal direction to the valve mechanism accommodating hole90and the first flow passage85a. InFIG. 2, the second flow passage85bis configured to extend in the right direction. Herein, a condition as shown inFIG. 2is a condition where the valve mechanism1provides communication between the first flow passage85aand the second flow passage85b. Therefore, the high pressure hydrogen stored in the internal space102of the high pressure tank101is supplied through the first flow passage85ato the second flow passage85b.

Next, the valve mechanism1of this embodiment will be explained with reference toFIG. 5. The valve mechanism1of this embodiment includes mainly four component parts. That is to say, the valve mechanism1includes the first plunger3, the second plunder5to be engaged with the first plunger3, the valve element7to be engaged with the second plunger5, and an elastic body6which is arranged between the second plunger5and the valve element.

The first plunger3includes a cylindrical head portion31formed with a hexagonal hole31ain the interior thereof, a columnar barrel portion33which is smaller in diameter than the head portion31, and the flange portion35formed below the barrel portion33. The hexagonal hole31ais a part into which a tool such as a hexagonal wrench or the like is inserted. However, the hole of the head portion31is not limited to the hexagonal hole, and a hole of triangular shape, square shape or star shape for example may be employed. Moreover, a male threaded portion31bis formed on at least a part of an outer peripheral surface of the head portion31. Further, the flange portion35is of a disc shape and has a diameter which is larger than the diameter of the barrel portion33. In the first plunger3of this embodiment, the barrel portion33is smallest in diameter, and the diameters of the head portion31and the flange portion35are substantially the same size.

The valve element7is configured to be seated on and separated from the valve seat85c(seeFIG. 2) formed in the flow passage85to be referred to later, so as to switch between the communication and the shut off of the flow passage85. The valve element7includes the inverted truncated cone shaped valve portion71having one side (lower side) of smaller diameter and the other side (upper side) of larger diameter, a disc portion73located above the valve portion71, a valve element neck portion75located above the disc portion73, and a valve element head portion77located above the valve element neck portion75. With respect to dimensions of the respective portions, the disc portion73has the largest diameter. In addition, the diameter of an upper end of the valve portion71is close to the diameter of the disc portion73. The valve element head portion77has the next largest diameter. The diameter of the valve element head portion77is about a half of the disc portion73. However, the diameter of the valve element head portion77will not be especially limited. Further, the valve element neck portion75has the smallest diameter.

In the interior of the valve element head portion77, there is formed a bottomed spring receiving part77awhich opens toward the second plunger5. This spring receiving part77ais provided for allowing an end of the elastic body (compressed coil spring)6to be referred to later, to be inserted thereinto. Therefore, the inner diameter of the spring receiving part77ais slightly larger than the diameter of the elastic body6. Preferably, material of the valve element7is required to have such strength as not to be deformed large by contact with the valve seat85c. In this embodiment, the material of the valve element is polyimide, polyamide-imide, etc.

The second plunger5is member of substantially columnar shape which has the diameter larger than the diameter of the flange portion35of the first plunger3. Then, at one end (upper end) and the other end (lower end) of the second plunger5, there are formed a notch51for the first plunger and a notch53for the valve element. The first plunger notch51is composed of a first notch section51ainto which the barrel portion33of the first plunger3is fitted and a second notch section51binto which the flange portion35of the first plunger3is fitted. The first notch section51aand the second notch section51beach have opening portions whose widths W1, W2are slightly larger than the diameters of the barrel portion33and the flange portion35of the first plunger3so as to allow the barrel portion33and the flange portion35to be inserted from the lateral side of the second plunger5. Moreover, the width W1of the first notch portion is narrower than the diameter of the flange portion35. Thus, inFIG. 5, a first engaging portion52ais formed above the second notch section51b, and a second engaging portion52bis formed below the second notch section51b. One end engaging part52is formed by these first engaging portion52aand second engaging portion52b. Therefore, when the flange portion35of the first plunger3is engaged with the one end engaging part52, the first plunger3and the second plunger5are not disengaged in the axial direction of the valve mechanism1.

Further, the position and size of the first plunger notch51are configured such that, when the first plunger3is engaged with the one end engaging part52of the second plunger5, center axes in the longitudinal direction of the two plungers are substantially coaxial with each other. However, the inner diameters of the first notch section51aand the second notch section51bmay be formed larger than the diameters of the barrel portion33and the flange portion35of the first plunger3in the range not disturbing the valve movement. This is because the first plunger3and the second plunger5become in coaxial relation when these plungers are accommodated in the valve mechanism accommodating hole90to be referred to later. Moreover, the height H2of the second notch section51bis larger than the thickness of the flange portion35of the first plunger3, and an axial clearance is formed between the one end engaging part52and the flange portion35. In addition, the inner diameter of the second notch section51band the width W2of the opening portion are configured to be larger in such an extent that a clearance is formed around an outer peripheral surface of the flange portion35of the first plunger3. Therefore, when the first plunger3is rotated, the rotation of the flange portion35is not transmitted to the second plunger5. In other words, the first plunger3and the second plunger5are engaged with each other in a relatively rotatable manner.

Further, the valve element notch53is composed of a third notch section53ainto which the valve element neck portion75fitted and a fourth notch section53binto which the valve element head potion77is fitted. The third notch section53aand the fourth notch section53beach have opening portions whose widths W3, W4are larger than the diameters of the valve element neck portion75and the valve element head portion77so as to allow the valve element neck portion75and the valve element head portion77to be inserted from the lateral side of the second plunger5. Moreover, the width W3of the third notch portion53ais narrower than the diameter of the valve element head portion77. Thus, a third engaging portion54ais formed above the fourth notch section53b, and a fourth engaging portion54bis formed below the fourth notch section53b. The other end engaging part54is formed by these third engaging portion54aand fourth engaging portion54b. Therefore, when the valve element7is engaged with the other end engaging part54, the second plunger5and the valve element7are not disengaged in the axial direction of the valve mechanism1. In addition, the height H4of the forth notch section53bis larger than the thickness of the valve element head portion77. Therefore, a clearance in the axial direction is formed between the other end engaging part54and the valve element head portion77. The second plunger5and the valve element7are configured in a relatively movable relation by this axial clearance.

As shown inFIG. 2, a spring accommodating hole55is formed in the interior of the second plunger5above the valve element notch53. This spring accommodating hole55is provided for accommodating a compressed coil spring constituting the elastic body6. In other words, when the valve element7is engaged with the second plunger5, a columnar space is formed by the spring receiving part77aof the valve element7and the spring accommodating hole55. The elastic body6is arranged in the columnar space. Since the elastic body6is constituted of the compressed coil spring, the elastic force is applied to the second plunger5and the valve element7in the direction to be separated from each other when the spring is arranged between the second plunger5and the valve element7. Herein, in this embodiment, the inner diameter of an upper end portion of the spring accommodating hole55is smaller than other portions. The inner diameter of this upper end is substantially the same as the diameter of the elastic body6. Therefore, when the elastic body6has been arranged, the elastic body6is retained by the upper end of the spring accommodating hole55. Herein, the elastic body6is not limited to the coil spring, and any member may be employed when it has elasticity and resistance against the fluid (for example, hydrogen, etc.) to be used.

Next, the operation of the valve mechanism1and the valve device8will be explained with reference toFIGS. 2 and 3.FIG. 2, as referred to hereinabove, shows a state in which the valve mechanism1allows the flow passage85to be communicated (between the first flow passage85aand the second flow passage). When the flow passage85is communicated, the interior of the first flow passage85and the interior of the second flow passage85bhave a pressure P1of the internal space102of the high pressure tank101.

Next, a process to be changed from a state ofFIG. 2to a state ofFIG. 3will be explained. In the state ofFIG. 2, the tool such as the hexagonal wrench and the like is fitted into the hexagonal hole31aof the first plunger3, the hexagonal wrench is rotated clockwise through the operation of the operator. Then, the first plunger3is screwed inwardly in the axial direction (in the downward direction of the drawing) of the valve mechanism accommodating hole90while being rotated by the valve holder female threaded portion81d. Accordingly, the second plunger5which is engaged with the flange portion35of the first plunger3is also moved downward in the axial direction of the valve mechanism accommodating hole90. At that time, the upper side, across the seal member87, of the second plunger5is the atmospheric pressure. On the other hand, the pressure P1of the fluid within the flow passage85is applied to the lower side of the second plunger5. Herein, the pressure P1is a pressure which is higher than the atmospheric pressure. Therefore, the force in the valve opening direction is added to the second plunger5, so that the lower surface of the flange portion35and the second engaging portion52bare brought into contact with each other.

Then, the first plunger3and the second plunger5are engaged in the relatively movable relation. Therefore, the rotational movement of the first plunger3is not transmitted to the second plunger5. Since the second plunger5is not rotated, the rotational movement is not transmitted also to the seal member87which is arranged around the outer peripheral part of the second plunger5. Accordingly, the surface of the seal member87is effectively prevented from being damaged. In addition, since the second plunger5is not caused the relative rotation, it is sufficient that the rotational force which is applied to the first plunger3by the operator is a smaller force in comparison with the conventional valve mechanism.

Further, the elastic body6is provided between the second plunger5and the valve element7. Therefore, the lower surface of the valve element head portion77makes contact with the fourth engaging portion54b. In addition, the first plunger3is rotated until the valve element7is seated on the valve seat85c. At that time, after the valve element7is seated on the valve seat85c, there may be cases where the first plunger3is further screwed inwardly. In this case, the valve element head portion77is separated apart from the fourth engaging portion54band the elastic body6is compressed, so that the movement in the axial direction of the second plunger5is transmitted to the valve element7without being suddenly increased. On the other hand, the operator can recognize that the rotational torque has been increased at the time the elastic body6starts to be compressed. Thus, since the operator can recognize indirectly that the valve element7is seated on the valve seat85c, he stops screwing operation of the first plunger3. Therefore, it is possible to prevent the excessive contact force from being caused between the valve element7and the valve seat85c.

Further, since the valve element7is not rotated at the time the valve body7is seated on the valve seat85c, the relative rotation is not caused between the valve element7and the valve seat85c. Accordingly, the valve portion71of the valve element7is moved in the axial direction of the valve mechanism accommodating hole90and merely comes into contact with the valve seat85c. Like this, since the relative rotation is not caused between the valve element7and the valve seat85c, the surface of the valve portion71of the valve element7is effectively prevented from being damaged. Particularly, the valve seat85cformed in the flow passage85may be formed with a taper surface of narrow width so as to maintain the high airtightness. In such a case, when the valve element7is rotated relatively to the valve seat85c, the valve portion71has a high possibility of being damaged. Accordingly, the valve device8of this embodiment not causing the relative rotation is effective particularly when being used for the high pressure tank101to which the high pressure is applied.

When the valve element7is seated on the valve seat85c, the first flow passage85aand the second flow passage85bare shut off. The first flow passage85aand the second flow passage85bare shut off in order to fill high pressure gas from the filling flow passage107(seeFIG. 1) into the second flow passage85bthereby to carry out the airtight inspection of the piping system connected to the second flow passage85b. In this case, the first flow passage85ais the pressure P1of the internal space102of the high pressure tank101, and the second flow passage85bis a pressure P2of the fluid for the airtight inspection. The pressure P2which is used for the airtight inspection is set to be higher than the pressure P1of the internal space102of the high pressure tank101. This is because the leakage of the piping system111can be surely inspected by applying a higher pressure than the pressure applied in the normal use condition, to the piping system111.

In the valve device8of this embodiment, since the valve element7is provided separately relative to the second plunger5, the following peculiar effects are obtained. When focusing on the valve element7only, the pressures P1, P2as shown by arrows inFIG. 4are applied to the surface of the valve element7through the fluid by the second plunger5and the seam member87. The force by which the fluid of the pressure P2of the second flow passage85bpresses the valve element7in the valve closing direction (downward in the drawing) is S2×P2. Herein, S2is a projected area when viewing the valve element7from the side of the valve element head portion77or the valve portion71. The force by which the fluid of the pressure P2of the second flow passage85bpresses the valve element7in the valve opening direction is (S2−S1)×P2, since the force is applied to a part removing an area S1from an area S2. Herein, S1is a projected area of a part of the valve element7surrounded by the valve seat85cwhen viewing the valve element7from the side of the valve portion71. Moreover, the force by which the fluid of the pressure P1of the first flow passage85apresses the valve element7in the valve opening direction is S1×P1. Herein, the force applied to the valve element7in the downward direction (in the direction facing toward the valve seat) is referred to as valve closing force, while the force applied to the valve element7in the upward direction is referred to as valve opening force. Then, the force F deducting the valve opening force from the valve closing force is F=(S2×P2)−((S2−S1)×P2)−(S1×P1). When simplifying this, F=S1(P2−P1). At that time, assuming that P1=P2, F=0. Therefore, the force applied to the valve element7is balanced with respect to the axial direction.

On the other hand, when carrying out the airtight inspection of the piping system111, the fluid of the pressure P2which is higher than the pressure P1of the internal space102of the high pressure tank101is filled into the second flow passage85b. At that time, the force F by which the fluid presses the valve element7in the valve closing direction is F=S1(P2−P1). Herein, since P2>P1, F is always a positive value. In other words, as far as the condition of P2>P1is satisfied, the valve closing force always acts on the valve element7.

As described hereinbefore, at the time of the airtight inspection, the valve closing force always acts on the valve element7. Therefore, without depending upon the valve closing force by screwing-in of the first plunger3, the first flow passage85aand the second flow passage85bcan be surely shut off. This is the peculiar effect by separating the valve element7from the second plunger5. In addition, when the second flow passage85bis filled with the fluid of the pressure P2, the pressure P2is applied to the second plunger5. By this pressure P2, the force in the valve opening direction is applied to the second plunger5. Therefore, the second plunger5is moved slightly upwards in the valve mechanism accommodating hole90. Then, the prescribed clearance is formed in the axial direction between the second plunger5and the valve element7. This clearance is larger than a distance that the second plunger5is moved in the valve opening direction by increasing the pressure within the second flow passage85bfrom P1to P2. Therefore, the upward movement of the second plunger5is not transmitted to the valve element7. The valve closing force caused by the pressure difference between the pressure P1and the pressure P2is maintained.

When terminating the airtight inspection, the fluid for airtight inspection is discharged from the second flow passage85b. In the case of having discharged the fluid into the air, the pressure of the second flow passage85bbecomes the atmospheric pressure. Then, the force in the vale opening direction is applied to the valve element7by the fluid of the pressure P1within the first flow passage85a. However, the movement of the valve element7is prevented by the elastic force of the elastic body6and the axial force through the screw-in of the plunger3. Thereafter, when the first plunger3is rotated in the counter clockwise direction, the first plunger3is moved in the valve opening direction. The valve element7is separated from the valve seat85cby the movement of the first plunger3. Consequently, the fluid (hydrogen) of the pressure P1within the second flow passage85bflows in thereby to allow the interior of the second flow passage85bto become the same pressure while decreasing the pressure P1. Then, the valve element7is moved in the valve opening direction along with the second plunger5while being supported by the fourth engaging portion54b. By the way, it is conceivable that all the fluid within the high pressure tank101is discharged thereby to allow the interior of the high pressure tank101to become the atmospheric pressure. In this case, the force in the valve opening direction is not applied to the second plunger5. Also in this case, the first engaging portion52acomes into contact with the flange portion35of the first plunger3, so that the second plunger5is moved in the valve opening direction.

Further, as described above, at the time of the airtight inspection, the pressure P2of the fluid within the second flow passage85bis configured to become higher than the pressure P1of the fluid within the first flow passage85a. However, there is a possibility that the heights of the pressures P1and P2are reversed due to unintended cause. In this case, the force pressing the valve element7upwardly is produced. Also in this case, since the axial force by the screw-in of the plunger3is set properly, the valve element7can be prevented from being suddenly moved upwardly.

Modified Example

By the way, in the above embodiment, the valve holder81and the valve body83are formed separately. However, without separating the valve holder81and the valve body83, the body may be formed as an integral component part, and the valve mechanism accommodating hole90may be formed directly in this body80. In this case, a female threaded portion for being screwed with the first plunger3is required to be formed in an inner surface of the valve mechanism accommodating hole90provided in the body80. Further, the valve device is not necessarily required to be provided in the body80. In other words, the valve device8′ (shown by a phantom line) may be provided in the piping system111on the further downstream side of the second flow passage85b. However, in this case, the filling flow passage107also is required to be provided on the further downstream side of the valve device8′.

Description of Reference Characters

1: Valve mechanism,3: First plunger,5: Second plunger,52: One end engaging part,54: The other end engaging part,6: Elastic body (Compressed coil spring),7: Valve element,8: Valve device,80: Body,81: Valve holder,83: Valve body,85: Flow passage,85a: First flow passage,85b: Second flow passage,90: Valve mechanism accommodating hole,101: High pressure tank,102: Internal space

According to a first mode, there is provided a valve mechanism for a high pressure tank, which is accommodated in a valve accommodating hole communicating with a flow passage through which prescribed fluid flows, comprising a first plunger configured to be engaged with a threaded portion formed on at least a part of an inner wall of the valve mechanism accommodating hole and to be moved by rotation in the valve mechanism accommodating hole, a second plunger configured to be engaged at one end thereof with the first plunger in a relatively rotatable manner, a seal member being in contact with a periphery of the second plunger, and a valve element configured to be engaged with the other end of the second plunder and to be seated on and separated from a valve seat which is formed in the flow passage. With this configuration, even if the first plunger is rotated, the rotation is not transmitted to the second plunger.

According to a second mode, in addition to the configuration of the first mode, the second plunger and the valve element are provided in a relatively movable relation, and an elastic body which applies elastic force in such a direction as to separate the second plunger and the valve element is provided between the second plunger and the valve element. With this configuration, even if the first plunger is further screwed in after the valve element is seated on the valve seat, the movement in the axial direction of the second plunger5is not directly transmitted to the valve element since the elastic body6is compressed. Therefore, strong contact pressure is prevented from being generated between the valve element and the valve seat. In addition, even if force by which the valve element is pushed upwardly is caused due to sudden movement, etc. of internal fluid when the valve is opened, the valve element is prevented from being suddenly moved upward and causing irregular movement.

According to a third mode, a valve device for the high pressure tank comprises the valve mechanism of the first mode or the second mode, a body being formed with the vale mechanism accommodating hole, the flow passage through which the fluid flows being formed in the interior of the body, and the valve seat being formed in the flow passage so as to carry out communication and shut off of the flow passage in cooperation with the valve element. Although the seal member is located between the outer periphery of the second plunger and the body, since the second plunger is not rotated, the force in the rotational direction is not applied to the seal member arranged on the periphery of the second plunger. Therefore, the seal member is effectively prevented from being damaged. Moreover, since the force for rotating the second plunger which is in contact with the seal member is not required, the force for rotating the first plunger can be reduced.

According to a fourth mode, in addition to the configuration of the third mode, the flow passage includes a first flow passage configured to communicate with an internal space of the high pressure tank and a second flow passage configured to communicate with the exterior of the high pressure tank. The valve seat is provided in the boundary between the first flow passage and the second flow passage. In the airtight inspection of a piping system connected to the second flow passage, the pressure of the fluid within the second passage is higher than the pressure of the fluid within the first flow passage. With this configuration, although the pressure of the fluid within the first flow passage and the pressure of the fluid within the second flow passage are applied to a surface of the valve element, since the pressure of the fluid within the second flow passage is higher, the force (valve closing force) which presses the valve element against the valve seat is larger than the force (valve opening force) which separates the valve element from the valve seat. Therefore, in the airtight inspection, the valve element is seated on the valve seat without relying on the contact pressure caused between the valve body and the valve seat by screwing in the first plunger, whereby it is possible to maintain an airtight condition.

According to the present embodiments, the force by rotation is not applied to the seal member and the valve member. Therefore, the seal member and the valve element can be prevented from being damaged. Further, since the force in the valve closing direction is applied to the valve element, the large contact pressure is not required to be applied by the first plunger.