JP6580458B2 - Pressure reducing valve - Google Patents

Description

  The present invention relates to a pressure reducing valve.

  As shown in FIG. 3, the pressure reducing valve housing 200 described in Patent Document 1 and Patent Document 2 includes a fluid or gas flow path 202 extending from an input port to an output port (not shown). A piston 206 is disposed in a cylinder 204 formed in the housing 200 so as to be able to reciprocate. The flow path 202 includes a flow path on the on-off valve side and a flow path on the cylinder side with the valve seat 211 as a boundary, and the open / close valve 209 includes the valve seat 211 in the flow path on the open / close valve side. It is arranged to be movable so as to open and close. A piston spring 208 is disposed in the piston 206, and an opening / closing valve spring 213 is disposed in the opening / closing valve 209.

  When the gas on the cylinder 204 side flows to the output port side and the pressure of the gas in the inner bottom side chamber (hereinafter referred to as a decompression chamber) of the cylinder 204 decreases, the pressure on the inner bottom side chamber (pressure adjusting chamber) depends on the atmospheric pressure. The piston 206 pushed by the pressure and the piston spring 208 moves downward in FIG. Then, when the on-off valve 209 is opened via the valve stem 212, gas is supplied into the cylinder 204 from between the variable throttle portion 210 provided on the on-off valve 209 and the valve seat 211, and more than necessary. Prevents gas pressure drop.

  Further, when the pressure of the gas in the decompression chamber rises and the sum of the pressure of the gas and the on-off valve spring 213 exceeds the sum of the pressure by the pressing force of the piston spring 208 and the pressure in the pressure adjustment chamber, the piston 206 In 3, move up. In conjunction with this, the valve stem 212 and the open / close valve 209 are pushed up by the open / close valve spring 213, and the flow path between the variable restrictor 210 and the valve seat 211 is closed (valve closed). Prevents gas pressure from rising.

JP2013-206360A JP 2014-115820 A

  Incidentally, the valve stem 212 is arranged so as to reciprocate in the valve stem chamber 214, and slides with the inner peripheral surface of the valve stem chamber 214 during the reciprocating movement. The valve stem is formed in a columnar shape and may be inclined when the valve stem reciprocates. When sliding in a state where this inclination is maintained, the end of the inclined valve stem causes a wear scratch on the sliding contact surface of the valve stem chamber 214. If sliding is repeated in a state where the abrasion scratches are generated, the sliding resistance of the valve stem 212 increases, and the reciprocating movement of the valve stem 212 is hindered, which may cause a transient pressure regulation failure. is there.

  An object of the present invention is to provide a pressure reducing valve that can reduce the generated stress on the valve stem and the inner peripheral surface of the valve stem chamber that is in sliding contact with the valve stem, and can suppress the occurrence of wear scratches on both.

  In order to solve the above problems, a pressure reducing valve according to the present invention includes a housing having an on-off valve chamber, a valve seat, a valve stem chamber, and a housing chamber in order from upstream to downstream on a fluid flow path provided inside. And an open / close valve arranged in the open / close valve chamber to adjust the opening degree with the valve seat, and the housing chamber can be divided into a decompression chamber and a pressure regulation chamber, and the volume of the decompression chamber can be increased or decreased. A pressure receiving member that is displaced or deformed to the valve stem chamber, and a valve stem that is provided so as to be slidable in an opening / closing direction with respect to the valve stem chamber so as to be positioned between the pressure receiving member and the opening / closing valve. A valve stem that allows adjustment of the opening degree of the on-off valve by interlocking movements of the on-off valve and the pressure-receiving member in the same direction when the volume of the decompression chamber is increased and decreased by the member; The bal The outer peripheral surface of the stem is one that is a barrel shape.

  With the above configuration, the reciprocating valve stem has a barrel-shaped outer peripheral surface that is in sliding contact with the inner peripheral surface of the valve stem chamber, thereby suppressing the stress generated at the parts that are in contact with each other and generating wear scratches at the parts. Suppress.

The outer peripheral surface of the valve stem may be crowned in the axial direction of the valve stem.
With the above configuration, the outer peripheral surface of the valve stem is barrel-shaped by crowning, and when the valve stem reciprocates, the generated stress on the outer peripheral surface of the valve stem and the inner peripheral surface of the valve stem chamber that is in sliding contact with the valve stem is suppressed. , The occurrence of abrasion scratches at the site is suppressed.

The on-off valve may have an outer peripheral surface that is in sliding contact with an inner peripheral surface of the on-off valve chamber, and the outer peripheral surface may have a barrel shape.
With the above-described configuration, the reciprocating on-off valve has a barrel-shaped outer peripheral surface that is in sliding contact with the inner peripheral surface of the on-off valve chamber, thereby suppressing the stress generated at the parts that are in contact with each other and generating wear scratches at the parts. Suppress.

  According to the present invention, it is possible to reduce the stress generated on the valve stem chamber and the inner peripheral surface of the valve stem chamber that is in sliding contact with the valve stem, and it is possible to suppress the occurrence of wear scratches on both.

Sectional drawing of the pressure-reduction valve of one Embodiment. Sectional drawing of a valve stem and its peripheral member. Sectional drawing of the conventional pressure-reduction valve.

Hereinafter, an embodiment in which the present invention is embodied as a pressure reducing valve that decompresses high-pressure hydrogen gas will be described with reference to FIGS. 1 and 2.
The pressure reducing valve 10 is mounted on a fuel cell system such as a fuel cell vehicle. The pressure reducing valve 10 decompresses a high-pressure (for example, about 3.70 MPa) fluid, that is, hydrogen gas supplied from a fuel tank (not shown) to a low pressure (for example, 1 MPa).

(Composition of pressure reducing valve)
The configuration of the pressure reducing valve 10 will be described.
As shown in FIG. 1, a pressure reducing valve 10 includes a housing 11 that connects between a primary port and a secondary port, a valve body 12 that is accommodated in the housing 11, a valve seat 13, a valve seat fixing member 14, a valve A stem 15 and a piston 16 are provided. The valve body 12 corresponds to an on-off valve, and the piston 16 corresponds to a pressure receiving member.

  A flow path 18 is formed inside the housing 11, and first to third cylindrical portions 111 to 113 and a cylinder 114 are coaxially formed on the flow path 18 in order from the lower side. The cylinder 114 corresponds to a housing chamber.

  The inner diameters of the first to third cylindrical portions 111 to 113 and the cylinder 114 are set to increase in this order. In addition, although illustration is abbreviate | omitted, the 1st cylindrical part 111 is connected with the primary port which is a high pressure gas supply source (for example, hydrogen tank) through the valve which is not illustrated. Further, a thread groove 113 a is cut in the inner wall of the third cylindrical portion 113. A metal valve body 12 having an outer diameter slightly smaller than the inner diameter of the first cylindrical portion 111 is accommodated in the first cylindrical portion 111. The first cylindrical portion 111 corresponds to an on-off valve chamber.

  The valve body 12 can be moved in the first cylindrical portion 111 in the opening direction (downward in FIG. 1; the same applies hereinafter) and in the closing direction (upward in FIG. 1; the same applies hereinafter). When referring to both the opening direction and the closing direction, hereinafter referred to as the opening and closing direction. The valve body 12 is always urged by the valve spring 71 in the closing direction. The valve body 12 includes a columnar valve body main body 21 and a valve body front end 22 having an outer diameter smaller than that of the valve body main body 21 continuously from the upper part of the valve body main body 21. Between the valve body main body portion 21 and the valve body tip portion 22, a valve body taper portion 23 whose outer diameter gradually decreases toward the valve body tip portion 22 side. Note that the valve body distal end portion 22 passes through the second cylindrical portion 112 and enters the third cylindrical portion 113.

  A ring-shaped valve seat 13 made of synthetic resin is accommodated in the second cylindrical portion 112. The hole 31 of the valve seat 13 has an inner diameter that is slightly larger than the outer diameter of the valve body tip 22. A lower portion of the hole portion 31 of the valve seat 13 is a valve seat taper portion 33 whose inner diameter gradually increases downward. The thickness of the valve seat 13 (vertical length in FIG. 1) is slightly thicker (longer) than the depth of the second cylindrical portion 112 (vertical length in FIG. 1).

  As shown in FIG. 1, a cylindrical valve seat fixing member 14 having a thread 14 a cut on the outer surface is screwed to the third cylindrical portion 113. The valve seat fixing member 14 is made of a metal material. The bottom surface of the valve seat fixing member 14 screwed to the third cylindrical portion 113 is in contact with the top surface of the valve seat 13. As the valve seat fixing member 14 is screwed into the third cylindrical portion 113, the valve seat 13 is pressed downward, and therefore, the valve seat 13 includes the valve seat fixing member 14 and the second cylinder. The portion 112 is sandwiched between the bottom portion (that is, the step portion). Thereby, the airtightness between the bottom part of the 2nd cylindrical part 112 and the valve seat 13 is ensured.

  Further, as shown by a two-dot chain line in FIG. 1, the valve seat 13 may be sandwiched between the valve body 12 biased by the valve spring 71 and the valve seat fixing member 14. In this case, the valve seat taper portion 33 and the valve body taper portion 23 come into contact with each other, and airtightness between them is ensured. Further, the through hole 41 penetrating the inside of the valve seat fixing member 14, that is, in the axial direction (vertical direction in FIG. 1) communicates with the hole portion 31 of the valve seat 13. As a result, the valve body distal end portion 22 penetrates into the valve seat fixing member 14. The valve seat fixing member 14 corresponds to a plug. As shown in FIG. 2, the valve seat fixing member 14 is screwed to the third cylindrical portion 113.

  As shown in FIG. 1, the through hole 41 and the cylinder 114 are connected by a flow path hole 43. As shown in FIG. 1, the thickness of the valve seat fixing member 14 (vertical length in FIG. 1) is thicker than the depth (vertical length) of the third cylindrical portion 113. The upper portion 42 of the seat fixing member 14 is disposed so as to be located in the cylinder 114.

As shown in FIG. 1, a metal valve stem 15 is accommodated in the through hole 41 and corresponds to a valve stem chamber.
As shown in FIGS. 1 and 2, the valve stem 15 includes a truncated cone-shaped valve stem lower end portion 51, a valve stem main body portion 52 continuous on the upper side thereof, and a cylindrical valve stem upper end continuous on the upper side thereof. Part 53. The valve stem lower end 51 and the valve stem upper end 53 are formed with a diameter smaller than that of the valve stem main body 52, and the valve stem main body 52 has both end faces in the axial direction.

  The valve stem 15 is in contact with the valve body distal end portion 22 in which the valve stem lower end portion 51 enters the through hole 41. As shown in FIG. 2, the valve stem main body 52 has a barrel shape so that the outer peripheral surface bulges in the center in the axial direction. In the present embodiment, crowning is applied to form a barrel shape.

  The barrel shape is formed by crowning or end relief. The crowning has a curved surface with R, and may be any of full crowning, partial crowning, logarithmic arc crowning, and complex arc crowning. In full crowning, the axial direction (that is, the longitudinal direction) has a constant curvature. In the partial crowning, both ends in the axial direction are crowned, and there is a straight portion between both ends. The logarithmic arc crowning is formed with an arc on the central side in the axial direction so that the outer diameter decreases logarithmically toward the end. The composite arc crowning is formed such that arcs with different curvatures are joined together so that the radius of curvature decreases toward the end.

The end relief is such that the diameter decreases as the outer peripheral surfaces on both ends in the axial direction go to the end, and the central part in the axial direction is formed linearly.
In the valve stem main body 52, a plurality of flow passage holes 54 penetrating between both end faces of the valve stem main body 52 are formed in the axial direction at a predetermined equal pitch. The channel hole 54 functions as a channel.

  As shown by a two-dot chain line in FIG. 1, when the valve body taper portion 23 of the valve body 12 is in contact with the valve seat taper portion 33, the valve stem upper end portion 53 extends from the upper portion of the valve seat fixing member 14. It protrudes and enters the cylinder 114.

  As shown in FIG. 1, the cylinder 114 accommodates a piston 16 that moves in the same direction as the opening / closing direction of the valve body 12 (vertical direction in FIG. 1). The piston 16 is formed in a cylindrical shape from a metal material. A seal member 80 is interposed between the inner wall of the cylinder 114 and the piston 16 to ensure airtightness between the inner wall of the cylinder 114 and the piston 16.

  The inside of the cylinder 114 is partitioned by the piston 16 with a pressure adjusting chamber 91 that is a space provided above the piston 16 and a space between the lower end surface of the piston 16 and the cylinder 114 as a decompression chamber 92. The decompression chamber 92 is connected to the secondary port.

  The piston 16 is always urged toward the opening direction (downward in FIG. 1) by a piston spring 72 housed inside the pressure regulating chamber 91. The biasing force of the piston spring 72 is set to be stronger than the biasing force of the valve spring 71 (that is, the biasing force of the valve spring 71 is smaller than the biasing force of the piston spring 72). The piston spring 72 corresponds to a first elastic member, and the valve spring 71 corresponds to a second elastic member. As a result, the lower end surface 61 of the piston 16 is always in contact with the upper end portion 53 of the valve stem. In addition, the lower end surface 61 of the piston 16 is a flat surface without unevenness.

  The outer diameter of the lower end surface 61 of the piston 16 is set larger than the outer diameter of the upper end surface 45 of the valve seat fixing member 14 (that is, the diameter of the circumscribed circle of the corner portion 42a). Accordingly, the lower end surface 61 of the piston 16 can be brought into contact with the upper end surface 45 of the valve seat fixing member 14. For this reason, the displacement of the piston 16 in the opening direction (downward) is restricted by the lower end surface 61 coming into contact with the upper end surface 45 of the valve seat fixing member 14.

  The piston 16 moves up and down under the influence of the fluid pressure in the decompression chamber 92 (in this embodiment, gas pressure). That is, when the fluid pressure in the decompression chamber 92 rises and the sum of the pressing force due to the fluid pressure and the urging force of the valve spring 71 exceeds the sum of the urging force of the piston spring 72 and the pressure due to the pressure in the pressure adjustment chamber 91, The piston 16 moves in the closing direction (upward direction).

  When the piston 16 moves in the closing direction (upward) and the lower end surface 61 of the piston 16 moves away from the upper end surface 45 of the valve seat fixing member 14, the valve body 12 and the valve stem 15 are moved by the biasing force of the valve spring 71. Following the piston 16, it moves in the closing direction, and the valve body taper portion 23 approaches the valve seat taper portion 33. As shown by a two-dot chain line in FIG. 1, the valve body taper portion 23 and the valve seat taper portion 33 come into contact with each other to close the valve.

In this case, the volume of the decompression chamber 92 increases as the piston 16 moves in the closing direction (upward).
In this state, the fluid pressure in the decompression chamber 92 decreases, and the sum of the pressing force due to the fluid pressure and the urging force of the valve spring 71 is the sum of the urging force of the piston spring 72 and the pressure due to the pressure in the pressure adjusting chamber 91. If it falls below, the piston 16 moves in the opening direction (downward). By this movement, the valve stem 15 pressed against the piston 16 against the biasing force of the valve spring 71 presses and moves the valve body 12 in the opening direction. In this case, the volume of the decompression chamber 92 decreases as the piston 16 moves in the opening direction (downward).

  1, when the lower end surface 61 of the piston 16 and the upper end surface 45 of the valve seat fixing member 14 come into contact with each other, the valve body taper portion 23 and the valve seat taper portion 33 of the valve body 12 are brought into contact with each other. Fully open apart. As described above, when the valve body 12 is separated from or approaches the valve seat 13, the opening degree of the valve body 12 with respect to the valve seat 13 is adjusted.

(Operation of the embodiment)
The operation of the pressure reducing valve 10 configured as described above will be described from the state in which the valve body 12 is fully opened.

  The high-pressure gas supplied to the pressure reducing valve 10 through the primary port passes through the fully open valve body 12, the through hole 41 of the valve seat fixing member 14, the flow path hole 54 of the valve stem 15, and the plurality of flow path holes 43. The pressure is reduced in the process of being introduced into the decompression chamber 92 and supplied to the secondary port.

  As a result, the pressure of the gas introduced into the decompression chamber 92 rises and the piston 16 is pressed in the direction from the decompression chamber 92 toward the pressure adjustment chamber 91. In other words, the piston 16 has a total sum of the pressing force due to the gas pressure (fluid pressure) in the decompression chamber 92 and the urging force of the valve spring 71, and the sum of the pressure due to the urging force of the piston spring 72 and the pressure in the pressure adjusting chamber 91. It is displaced by the relationship.

  Specifically, when the sum of the pressing force due to the gas pressure in the decompression chamber 92 and the biasing force of the valve spring 71 exceeds the sum of the pressure due to the biasing force of the piston spring 72 and the pressure of the pressure adjustment chamber 91 due to the increase in gas pressure, The piston 16 is displaced in the closing direction (pressure adjustment chamber 91 side). Thereby, the valve stem 15 and the valve body 12 are displaced upward, and the valve body 12 is closed.

  On the other hand, if the sum of the pressing force due to the gas pressure in the decompression chamber 92 and the urging force of the valve spring 71 is less than the sum of the pressure due to the urging force of the piston spring 72 and the pressure in the pressure adjusting chamber 91 due to the gas pressure decrease. The piston 16 is displaced in the opening direction (the decompression chamber 92 side). Thereby, the valve stem 15 and the valve body 12 are displaced in the opening direction, and the valve body 12 is opened.

  Further, the valve stem 15 has a barrel shape so that the outer peripheral surface bulges in the center in the axial direction. When the valve stem 15 reciprocates in the opening and closing direction, the barrel-shaped outer peripheral surface having an R has a through hole 41 (valve. The generated stress of the part which contacts mutually is suppressed by sliding-contacting with the internal peripheral surface of a stem chamber. As a result, the generation of wear scratches at the contacting parts is suppressed.

  That is, the higher the gas pressure, the greater the stress generated at the contacted portion, but the portion where the barrel-shaped curved surface of the valve stem 15 contacts the inner peripheral surface of the through hole 41 is microscopic. In the case of surface contact, the stress is dispersed. As a result, stress concentration is avoided and the generation of wear scratches at the contacting parts is suppressed.

  When the supply of the gas to the pressure reducing valve 10 is stopped, the gas escapes from the pressure reducing chamber 92 to the secondary port, and the piston spring is larger than the sum of the pressing force due to the gas pressure in the pressure reducing chamber 92 and the urging force of the valve spring 71. Since the sum of the pressure due to the urging force 72 and the pressure in the pressure adjusting chamber 91 becomes larger, the piston 16 is displaced in the opening direction (the decompression chamber 92 side).

  Finally, the lower end surface 61 of the piston 16 and the upper end surface 45 of the valve seat fixing member 14 come into contact with each other. Since both the lower end surface 61 of the piston 16 and the upper end surface 45 of the valve seat fixing member 14 are flat surfaces, this contact is so-called surface contact in which the surfaces collide with each other.

According to this embodiment, the following effects can be obtained.
(1) The pressure reducing valve 10 of the present embodiment includes a first cylindrical portion 111 (open / close valve chamber), a valve seat 13, a through hole 41 (valve) on the fluid flow path provided inside from the upstream to the downstream. A housing 11 having a stem chamber and a cylinder 114 (housing chamber) in this order. Further, the pressure reducing valve 10 is disposed in the first cylindrical portion 111 (open / close valve chamber), and includes a valve body 12 (open / close valve) for adjusting an opening degree with the valve seat 13 and a cylinder 114 (housing chamber). A piston 16 (pressure receiving member) is provided which is divided into a decompression chamber 92 and a pressure adjustment chamber 91 and which displaces the volume of the decompression chamber 92 so as to increase and decrease. The pressure reducing valve 10 is provided so as to be slidable in the opening / closing direction with respect to the through hole 41 (valve stem chamber) and is positioned between the piston 16 (pressure receiving member) and the valve body 12 (opening / closing valve). A valve stem 15. The valve stem 15 interlocks the movements of the valve body 12 (open / close valve) and the piston 16 (pressure receiving member) in the same direction when the volume of the decompression chamber 92 is increased or decreased by the piston 16 (pressure receiving member). The opening of the valve body 12 (open / close valve) is allowed to be adjusted. The outer peripheral surface of the valve stem 15 has a barrel shape. As a result, according to the present embodiment, it is possible to reduce the stress generated on the valve stem chamber and the inner peripheral surface of the valve stem chamber that is in sliding contact with the valve stem, and to suppress the occurrence of wear scratches on both.

  (2) In the pressure reducing valve 10 of this embodiment, the outer peripheral surface of the valve stem 15 is crowned in the axial direction of the valve stem. As a result, according to this embodiment, the outer peripheral surface of the valve stem is barrel-shaped by crowning, and when the valve stem reciprocates, the outer peripheral surface of the valve stem and the inner peripheral surface of the valve stem chamber that is in sliding contact with the valve stem The generation | occurrence | production stress of this can be suppressed and generation | occurrence | production of the abrasion crack of this part can be suppressed.

In addition, you may change the said embodiment as follows.
-In the said embodiment, although the valve body main-body part 21 of the valve body 12 was formed in the column shape, the barrel shape is comprised so that the center may bulge in the axial direction of the valve body 12 in the axial direction. May be. This barrel shape is formed, for example, by applying crowning or end relief.

  As a result, when the valve body 12 reciprocates in the opening and closing direction, the barrel-shaped outer peripheral surface with R is in sliding contact with the inner peripheral surface of the cylindrical portion 111, thereby suppressing the generated stress at the parts that are in contact with each other. It is possible to suppress the occurrence of abrasion scratches at the contacting parts.

  In the above-described embodiment, the piston 16 is the pressure receiving member. However, instead of the piston 16, a diaphragm that partitions the pressure adjusting chamber 91 and the decompression chamber 92 may be provided, and this diaphragm may be used as the pressure receiving member. When the diaphragm is deformed, the volume of the decompression chamber 92 is increased or decreased.

  In the above embodiment, the valve seat fixing member 14 is provided with the through hole 41 as the valve stem chamber. However, the valve seat fixing member 14 is formed integrally with the housing 11, and the housing itself is provided with the through hole 41. Also good. In this case, the housing 11 in FIG. 1 divided into two along the surface corresponding to the lower surface of the valve seat fixing member 14 is integrally connected to each other in an airtight, watertight, or oiltight manner, What is necessary is just to comprise a housing.

  In the embodiment, the flow path hole 54 is formed in the valve stem main body 52 of the valve stem 15. Instead of the flow path hole 54, a plurality of flow path grooves extending in the opening / closing direction of the valve stem 15 are recessed in a barrel-shaped outer peripheral surface formed so that the center of the valve stem main body 52 swells. May be. A single channel groove or a plurality of channel grooves may be provided so as to be appropriately spaced.

If the flow path is secured between the valve stem 15 and the valve seat fixing member 14, the flow path hole 54 may be omitted.
A plurality of flow path holes 54 may be arranged at unequal angular intervals.

The channel hole 43 may be changed to a channel groove that is recessed in the upper end surface 45.
In the embodiment, the piston 16 and the valve stem 15 may be integrated.
In the embodiment, the valve body 12 and the valve stem 15 may be integrated.

  The gas that the pressure reducing valve of the above embodiment depressurizes was hydrogen, but it may be a gas other than hydrogen, such as oxygen or nitrogen, and is not limited to a single composition, and may be a mixed gas in which a plurality of gases are mixed Good.

  -Moreover, it is good also as fluids other than gas, for example, liquids, such as vapor | steam or water, oil.

DESCRIPTION OF SYMBOLS 10 ... Pressure reducing valve, 11 ... Housing, 12 ... Valve body (open / close valve), 13 ... Valve seat,
14 ... Valve seat fixing member, 15 ... Valve stem, 16 ... Piston (pressure receiving member),
19 ... Open / close valve, 21 ... Valve body main body, 22 ... Valve body tip,
23 ... Valve body taper part, 31 ... Hole part, 33 ... Valve seat taper part,
41 ... Through-hole (valve stem chamber), 42 ... Upper part, 42a ... Corner part,
43 ... channel hole, 45 ... upper end surface, 51 ... valve stem lower end,
52 ... Valve stem body, 53 ... Valve stem upper end, 54 ... Channel hole,
61 ... lower end surface, 71 ... valve spring (second elastic member),
72 ... Piston spring (first elastic member) 80 ... Seal member,
91 ... Pressure adjusting chamber, 92 ... Depressurizing chamber, 111 ... First cylindrical portion (open / close valve chamber),
112 ... 2nd cylindrical part, 113 ... 3rd cylindrical part,
114: Cylinder (housing chamber).

Claims (1)

A pressure reducing valve for depressurizing high pressure fluid,
A housing having an on-off valve chamber, a valve seat, a valve stem chamber, and a housing chamber in order from upstream to downstream on the flow path of the high-pressure fluid provided inside,
An on-off valve disposed in the on-off valve chamber for adjusting an opening with the valve seat;
Said housing chamber, together with partitioning the decompression chamber and the pressure adjusting chamber, wherein that vacuum chamber volume increase may be decreased strange the Kreis, a pressure receiving member formed in a cylindrical shape,
A valve stem provided to be slidable in the opening / closing direction with respect to the valve stem chamber and located between the pressure receiving member and the opening / closing valve, and increasing the volume of the decompression chamber by the pressure receiving member A valve stem that allows adjustment of the opening degree of the on-off valve by interlocking movements of the on-off valve and the pressure receiving member in the same direction at the time and at the time of reduction,
The outer peripheral surface of the valve stem is crowned in the axial direction of the valve stem and has a barrel shape .
The on-off valve has an outer peripheral surface that is in sliding contact with an inner peripheral surface of the on-off valve chamber, and the outer peripheral surface is a cylindrical pressure reducing valve.

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