JP2009185924A - Constant flow valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a constant flow valve by which degree of freedom of designing flow-rate-setting is increased, and a change in setting the flow rate can be performed by simple work. <P>SOLUTION: In a sperical valve 30 provided with a valve hole 34 and a valve seat 35, a valve box 31 is partitioned by a parting wall 33 into a primary valve-chest a and a secondary valve-chest b. A valve shaft 36 is passed through the valve box 31, and a valve element 32 is brought into contact/separated with/from the valve seat 35 with advance/retreat of the valve shaft 36. In the valve box 31, a cylinder chamber 40 is provided, and the piston part 43 provided in the valve stem 36 can be advanced/retracted in the cylinder chamber 40. A diameter contracted-part 46 is provided on the primary side in the valve box 31. A pipe 46a drawn from the diameter-contracted part 46 is allowed to communicate with one side of the cylinder chamber 40, and a pipe 45a drawn from the upstream of the diameter contracted-part 46 is allowed to communicate with the other side thereof. The valve element 32 is urged by an elastic member 50 in the outside of the valve box 31 to the direction of opening the valve. With increase of the pressure differentials between the diameter-contracted part 46 and the upstream, the valve element 32 approaches the valve seat 35, and with decrease of the pressure differentials, both the valve elements separate from each other, and thus the opening in the duct is regulated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a constant flow valve provided in the middle of a fluid conduit for transferring various fluids such as a water feed pipe and an oil feed pipe.

  In some cases, a constant flow valve is provided in the middle of a fluid conduit for transferring various fluids. An example of the constant flow valve is a ball valve type shown in FIG.

  This constant flow valve 10 is arranged at the center of a partition wall 3 that partitions the flow path 2 in the valve box 1 into a primary side and a secondary side, and vertically between the valve chambers a and b on the primary side and the secondary side. A valve hole 4 to be connected is formed. A valve seat 5 is provided around the valve hole 4.

The valve box 1 is provided with an upper lid 1a that closes the upper surface of the secondary (downstream) valve chamber b, and a valve shaft 6 is inserted in the valve box 1 in the vertical direction through the upper lid 1a. ing. The male screw portion 6 a of the valve shaft 6 is screwed into the female screw portion 5 a of the valve seat 5.
By rotating the handle 8 fixed to the upper end portion of the valve shaft 6, the valve shaft 6 moves up and down in the axial direction with respect to the valve hole 4, and the valve shaft 6 moves up and down to the lower end portion of the valve shaft 6. The provided valve body 7 contacts and separates from the valve seat 5 to adjust the opening degree of the flow path.

Further, a pressure chamber 9 is provided above the secondary valve chamber b of the valve box 1. The pressure chamber 9 is located inside the upper lid 1 a and is separated from the secondary valve chamber b via a diaphragm 14.
A pipe 11 is drawn from the primary (upstream) valve chamber a in the valve box 1, and the pipe 11 communicates with the pressure chamber 9.

A movable valve body 12 is fixed to the diaphragm 14. A pressure adjustment spring 13 that presses the diaphragm 14 toward the pressure chamber 9 is provided between the diaphragm 14 and the valve seat 5.
The movable valve body 12 moves up and down by the deformation of the diaphragm 14 based on the pressure difference between the pressure in the pressure chamber 9 and the pressure in the secondary side valve chamber b and the pressing force by the pressure adjusting spring 13. The opening degree of the flow path can be adjusted by movement.

When the pressure in the primary valve chamber a in the valve box 1 increases, the pressure in the pressure chamber 9 increases due to the change in the water pressure, and the diaphragm 14 is deformed downward as indicated by the chain line in the figure. The movable valve body 12 is lowered and the opening of the flow path is reduced.
Further, when the pressure in the primary valve chamber a in the valve box 1 is lowered, the pressure in the pressure chamber 9 is also lowered due to the change in water pressure, and the diaphragm 14 is deformed upward as shown by the solid line in the figure, Due to the deformation, the movable valve body 12 is raised and the opening of the flow path is increased.

  Thus, the opening degree of the valve hole 4 is automatically adjusted by the pressure of the primary side valve chamber a, and the flow volume supplied to the secondary side is maintained constant (for example, refer patent document 1). .

Further, as shown in FIG. 4, an in-line type constant flow valve 20 may be employed. In this constant flow valve, a cylindrical valve element 22 can be moved forward and backward in the pipe axis direction in a valve box 21 that extends linearly from a primary valve chamber a to a secondary valve chamber b across a valve hole 24. It is arranged.
A pressure adjustment spring (elastic member) 25 is provided on the outer periphery of the valve body 22, and the valve body 22 is moved away from the valve hole 24 upstream by the pressure adjustment spring 25 fitted on the outer periphery thereof. It is energized.

The inside of the cylindrical valve body 22 is a part of the flow path of the primary valve chamber a, and the flow path in the valve body 22 is provided with a reduced diameter portion 26 in the middle.
The reduced diameter portion 26 functions as a venturi, and the flow velocity u1 in the slightly larger diameter general portion 23 located on the upstream side of the reduced diameter portion 26 and the flow velocity u2 in the reduced diameter portion 26 are: flow velocity = flow rate / cross-sectional area. From the relationship
u2> u1
Is supposed to hold.

Due to the difference in flow velocity, a pressure difference is generated between the reduced diameter portion 26 and the general portion 23. Between the pressure p1 in the general portion 23 and the pressure p2 in the reduced diameter portion 26,
p2 <p1
Is supposed to hold. This pressure difference becomes more prominent as the flow rate increases.

  The pressure p1 in the general portion 23 is introduced into the first pressure chamber 23b of the cylinder chamber provided on the outer periphery of the valve body 22 through the first conduction hole 23a, and the pressure p2 in the reduced diameter portion 26 is transmitted through the second conduction hole 26a. It is introduced into a second pressure chamber 26 b of a cylinder chamber provided on the outer periphery of the valve body 22.

  A pressure p1 in the first pressure chamber 23b, a pressure p2 in the second pressure chamber 26b, and a pressing force by the pressure adjustment spring 25 act on the piston portion 22a provided on the outer periphery of the valve body 22, and the flow rate When the pressure difference increases due to the increase in the valve body, the valve body 22 moves in the valve closing direction, and when the pressure difference decreases due to the decrease in the flow rate, the valve body 22 moves in the valve opening direction. The opening degree of the flow path can be adjusted by the movement of the valve body 22 based on the pressure difference (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 6-331056 (page 3, FIG. 2) JP 64-58886 (5th page, Fig. 1)

  The constant flow valve 10 shown in FIG. 3 deforms the diaphragm based on the pressure difference between the primary valve chamber a and the secondary valve chamber b in the valve box 1, and opens and closes the movable valve body 12 by the deformation. It is a configuration. For this reason, the movable valve body 12 may move due to slight pressure fluctuations in the valve box 1, and a constant flow rate may not be maintained. In addition, since the pressure adjustment spring 13 is disposed in the flow path in the valve box 1, a malfunction may be caused when a foreign matter is entangled with the pressure adjustment spring 13.

  Further, according to the constant flow valve 20 shown in FIG. 4, the valve body 22 opens and closes based on the pressure difference between the reduced diameter portion 26 and the general portion 23 on the upstream side thereof, so that a constant flow rate can be easily maintained. is there. In addition, since the pressure adjustment spring 25 is disposed in a portion outside the flow path in the valve box 21, the problem of malfunction due to foreign matter is reduced.

However, in the constant flow valve 20, a pressure adjustment spring 25 is fitted on the outer periphery of a cylindrical valve body 22, and the valve body 22 and the pressure adjustment spring 25 are housed in the valve box 21. For this reason, the space which accommodates the pressure adjustment spring 25 is narrow.
Since the flow rate of the constant flow valve 20 is set by a combination of the venturi diameter, the pressure adjustment spring 25 diameter, the spring constant, and the like, the flow rate is set when the accommodation space of the pressure adjustment spring 25 is small. There is a problem that the degree of freedom in design is reduced.

Further, each time the setting of the flow rate of the constant flow valve 20 is changed, it is necessary to replace the pressure adjusting spring 25 with one having a different spring coefficient.
At this time, since the pressure adjustment spring 25 is fitted on the outer periphery of the valve body 22 in the valve box 21, the valve box 21 fixed to the pipe of the replacement flow path is removed from the pipe. . Such work is a large-scale work. It is desirable that the setting of the flow rate can be changed with the simplest possible work.

  Therefore, an object of the present invention is to increase the degree of design freedom for setting the flow rate, and to enable the flow rate setting to be changed with a simple operation.

  In order to solve the above problems, the present invention connects the primary valve chamber and the secondary valve chamber to a partition wall that partitions the flow path in the valve box into a primary valve chamber and a secondary valve chamber. A valve shaft is inserted into the valve box of a ball valve in which a valve hole is formed and a valve seat is provided around the valve hole so as to be movable back and forth in the axial direction, and the valve body provided on the valve shaft is The valve shaft can be moved toward and away from the valve seat, a cylinder chamber is provided in the valve box, and a piston portion provided on the valve shaft can be moved forward and backward in the cylinder chamber as the valve shaft moves forward and backward. The cylinder chamber is provided with a first pressure chamber on one side and a second pressure chamber on the other side of the piston, and a reduced diameter portion is provided in the flow path on the primary side in the valve box. The pipe drawn from the flow path of the pipe is drawn to the first pressure chamber from the flow path upstream of the reduced diameter portion to the second pressure chamber. Accordingly, the valve shaft is provided through a lid that closes an opening provided on the secondary valve chamber side of the valve box, and the valve body is opened by an elastic member provided outside the lid. When the pressure difference between the flow path in the reduced diameter portion and the flow path upstream of the reduced diameter portion increases, the valve body approaches the valve seat, and the pressure difference A constant flow valve configuration is adopted in which the valve body is separated from the valve seat and the opening degree of the flow path is adjusted when the valve becomes smaller.

By adopting the ball valve as the constant flow valve, a piston portion that moves in the cylinder chamber based on the fluid pressure from the venturi can be provided in the valve shaft. Further, if a ball valve is employed as the constant flow valve and the valve shaft protrudes outside the valve box, an elastic member for urging the valve body can be provided outside the valve box.
For this reason, it becomes possible to ensure a large space for arranging the cylinder chamber and the piston portion that are operated by the fluid pressure. Further, a large space for accommodating the elastic member for urging the valve body can be secured.
Therefore, the degree of freedom in design for setting the flow rate of the constant flow valve can be increased. Further, since the elastic member is arranged outside the valve box, the flow rate setting can be changed with a simple operation.

  In this configuration, a guide cylinder is inserted into the valve box through the opening, the valve shaft is provided through a partition that partitions the guide cylinder in the cylinder axis direction, and the valve body is more than the partition. It is possible to adopt a configuration in which the valve chamber side is guided by the inner surface of the guide cylinder, and the cylinder chamber and the secondary valve chamber are partitioned by the partition wall.

According to this configuration, the guide cylinder guides the advancement / retraction of the valve body with respect to the valve seat and the axial advance / retreat of the valve shaft, and the guide cylinder includes the partition wall, so that the secondary valve chamber and the cylinder chamber are separated. Also demonstrates the function of partitioning.
For this reason, when changing the set flow rate of the constant flow valve, for example, when replacing the valve body with a different pressure receiving area, the diameter of the valve body can be easily changed by replacing the guide cylinder with a different inner diameter. become.

In addition, it can also be set as the structure by which the piston part is guided by the inner surface of the said guide cylinder in the said lid | cover side rather than the said partition.
According to this configuration, it is easy to change the diameter of the piston by replacing the guide cylinder with one having a different inner diameter.

Moreover, the structure which provided the three-way valve in the said piping pulled out from the flow path of the said diameter reduction part is employable.
According to this configuration, the three-way valve is normally in a state where the flow path of the reduced diameter portion and the second pressure chamber of the cylinder chamber communicate with each other, and the flow from the primary side to the secondary side is completely stopped during inspection or the like. If necessary, the valve body can be easily closed by switching the three-way valve so that the pressure in the second pressure chamber of the cylinder chamber is released to the outside.

  In addition, as a configuration of the venturi, for example, the reduced diameter portion is provided on the upstream side of the nodal point located on the most upstream side of the connection portion between the inner wall of the valve box of the ball valve and the partition wall. Can be adopted.

In the valve box of a ball-shaped valve, the upstream side of the partition wall that partitions the primary valve chamber and the secondary valve chamber is usually formed in a cylindrical shape protruding outward, and a flange or the like is formed at the protruding end. Is provided and can be connected to other pipes located on the upstream side.
Since the protruding portion is cylindrical, it is easy to arbitrarily change the diameter of the flow path as compared with the portion where the partition wall of the valve box is interposed. Therefore, it is easy to change the diameter of the venturi according to the application. For this reason, if the position of the venturi is on the upstream side of the partition wall, the degree of freedom in design can be increased.

  In the present invention, a ball valve is used as the constant flow valve, so that a piston portion that moves in the cylinder chamber based on the fluid pressure from the venturi can be provided in the valve shaft. Further, by adopting a ball valve as a constant flow valve and projecting the valve shaft out of the valve box, an elastic member for urging the valve body can be provided outside the valve box.

For this reason, it is possible to secure a wide space for accommodating the cylinder chamber and the piston portion operated by the fluid pressure and a space for accommodating the elastic member for biasing the valve body, so the flow rate of the constant flow valve is set. The degree of freedom in design can be increased.
Further, since the elastic member is arranged outside the valve box, the flow rate setting can be changed with a simple operation.

  Embodiments of the present invention will be described with reference to the drawings. This constant flow valve 30 is provided in the middle of the water distribution pipe, and at the center of the partition wall 33 that partitions the flow path in the valve box 31 of the ball-shaped valve into the primary side and the secondary side, A valve hole 34 that vertically connects the valve chambers a and b on the secondary side is formed. A valve seat 35 is provided around the valve hole 34.

The valve box 31 is provided with a lid 31a that closes an opening provided on the upper surface of the secondary (downstream) valve chamber b. A valve shaft 36 is inserted vertically in and out of the valve box 31 through the hole 31c penetrating the lid 31a. The valve shaft 36 has an upper end protruding upward from the lid 31a and a lower end screwed to the valve body 32 so that the valve shaft 36 and the valve body 32 move up and down together.
That is, the valve shaft 36 and the valve body 32 advance and retreat in the axial direction with respect to the valve hole 34, and the valve body 32 contacts and separates from the valve seat 35 by the advance and retreat, so that the primary (upstream) valve chamber a And the opening degree of the flow path to the secondary side valve chamber b is adjusted.

  A cylindrical guide cylinder 37 is inserted into the valve box 31 through the opening on the upper surface of the valve box 31.

  The valve shaft 36 is provided through a partition wall 38 that partitions the guide cylinder 37 in the cylinder axis direction. The partition wall 38 is provided so that the surface direction of the wall surface is perpendicular to the cylinder axis direction of the guide cylinder 37, and the valve shaft 36 can be moved forward and backward in a through hole 38 a provided in the center of the partition wall 38. It is inserted.

The valve body 32 has a circular cross section, and is guided by the inner surface of the guide cylinder 37 on the valve seat 35 side of the partition wall 38. That is, the outer periphery of the valve body 32 slides on the inner surface of the guide cylinder 37 over the entire circumference, so that the movement in the contact / separation direction is guided.
In the valve open state, the water that has passed through the valve hole 34 passes between the serrated partition plates 32 b provided at the lower part of the valve body 32, and then passes through the circulation hole 37 a provided at the lower end of the guide cylinder 37. Flows to the side. The serrated partition plate 32b has a function of suppressing a sudden increase in water pressure in the secondary valve chamber b when the valve is opened.

  Further, since the liquid tightness is always maintained between the inner peripheral surface of the through hole 38 a and the outer peripheral surface of the valve shaft 36, the space S closer to the lid 31 a than the partition wall 38 and the valve 38 than the partition wall 38. The space 39 on the seat 35 side (the secondary valve chamber b) is liquid-tightly partitioned by the partition wall 38. A space S closer to the lid 31 a than the partition wall 38 functions as a part of the cylinder chamber 40.

  A piston 43 having a circular cross section is provided in the middle of the valve shaft 36. The piston portion 43 is accommodated in the space S closer to the lid 31 a than the partition wall 38 in the guide cylinder 37, and moves in the axial direction integrally with the valve shaft 36. The movement of the outer periphery of the piston portion 43 is guided by sliding on the inner surface of the guide cylinder 37 over the entire circumference.

A connecting member 51 is fixed to the upper surface of the lid 31a so as to close the hole 31c of the lid 31a.
The connecting member 51 has a hollow space R inside, and the hollow space R passes through the hole 31c of the lid 31a and forms a space above the piston portion 43 in the space S between the partition wall 38 and the lid 31a. Communicate. The space R and the space S (including an upper space and a lower space across the piston portion 43) form a cylinder chamber 40.

  The valve shaft 36 passes through the hole 31c of the lid 31a, passes through the space R, and protrudes upward through a hole 51a provided at the upper end of the connection member 51. The valve shaft 36 can advance and retract in the axial direction with respect to the connection member 51, and liquid tightness is always maintained between the inner peripheral surface of the hole 51 a and the outer peripheral surface of the valve shaft 36.

  A spring bearing member 53 is fixed to the upper end of the valve shaft 36 with a nut 54. Since the coil spring (elastic member) 50 is provided between the spring receiving member 53 and the spring receiving portion 52 of the connecting member 51, the valve shaft 36 is urged upward by the elastic force. For this reason, the valve body 32 is biased in the valve opening direction (direction away from the valve seat 35).

  The piston portion 43 can move back and forth in the space S of the cylinder chamber 40 along with the axial movement of the valve shaft 36, and the inside of the cylinder chamber 40 is one side (upward) across the piston portion 43. Is the first pressure chamber 41, and the other (downward) is the second pressure chamber 42.

  In addition, a reduced diameter portion 46 is provided in the flow path on the primary side in the valve box 31 of the ball valve. The reduced diameter portion 46 is formed so as to reduce the outer diameter of the valve box 31, and the inner diameter D1 of the reduced diameter portion 46 is smaller than the inner diameter D2 of the general portion 45 on the upstream side. Yes.

The reduced diameter portion 46 is provided on the upstream side of the node 33 a located on the most upstream side of the connection portion between the inner wall of the valve box 31 and the partition wall 33.
Moreover, as shown in FIG. 1, the upstream part rather than the partition wall 33 which partitions the primary side valve chamber a and the secondary side valve chamber b comprises the cylindrical part 31b which protrudes outward. A flange f is provided at the projecting end of the cylindrical portion 31b so that it can be connected to another pipe located upstream.

  For this reason, in the manufacturing process of the valve box 31, for example, when changing the diameter of the venturi, if the shape of the protruding cylindrical part 31b is changed, the body part of the valve box 31 where the partition wall 33 is interposed is changed. The valve box 31 having a different venturi shape can be manufactured relatively easily without changing the shape.

  The pipe 46a drawn out from the flow path of the reduced diameter part 46 passes through the opening 42a to the second pressure chamber 42, and the pipe 45a drawn out from the general part 45 that is the flow path upstream of the reduced diameter part 46. Are communicated with the first pressure chamber 41 through the opening 41a.

If the pressure difference between the flow path in the reduced diameter portion 46 and the flow path upstream of the reduced diameter portion 46 increases, the pressure difference between the first pressure chamber 41 and the second pressure chamber 42 increases. The piston portion 43 moves downward against the elastic force of the coil spring 50, that is, the valve body 32 approaches the valve seat 35.
When the pressure difference becomes small, the pressure difference between the first pressure chamber 41 and the second pressure chamber 42 becomes small, and the piston portion 43 moves upward, that is, the valve body 32 moves away from the valve seat 35. .
The movement of the valve body 32 automatically adjusts the opening of the flow path.

A three-way valve 47 is provided in the pipe 46 a drawn out from the flow path of the reduced diameter portion 46.
The three-way valve 47 is normally in a state where the flow path of the reduced diameter portion 46 and the second pressure chamber 42 of the cylinder chamber 40 are in communication with each other, and at the time of inspection or the like, from the primary side to the secondary side in the valve box 31. When it is necessary to completely stop the flow, the valve body 32 can be easily closed by switching the three-way valve 47 so that the pressure in the second pressure chamber 42 of the cylinder chamber 40 is released to the outside. .

The operation of the constant flow valve 30 will be described. The reduced diameter portion 46 functions as a venturi, and the flow velocity u1 in the general portion 45 located on the upstream side of the reduced diameter portion 46 and the flow velocity u2 in the reduced diameter portion 46 Then, from the relationship of flow velocity = flow rate / cross-sectional area,
u2> u1
Is the same as the conventional example.

Due to the difference in flow velocity, a pressure difference is generated between the reduced diameter portion 46 and the general portion 45, and between the pressure p1 in the general portion 45 and the pressure p2 in the reduced diameter portion 46,
p2 <p1
Is supposed to hold. This pressure difference becomes more prominent as the flow rate increases.

  For this reason, when the flow velocity in the pipe is slow, the relationship between the pressure p1 in the general portion 45 and the pressure p2 in the reduced diameter portion 46 is slightly smaller than p1, and as shown in FIG. Is pushed up by the slight pressure difference and the elastic force of the coil spring 50, and the valve body 32 is maintained in the valve open state.

When the valve body 32 moves in a direction away from the valve seat 35, water flows in the directions of arrows A and B shown in FIG. 1 occur in the pipes 45a and 46a.
Further, in the space 39 in the guide cylinder 37, the valve body 32 approaches the partition wall 38, so that the water in the space 39 moves downward through the hole 32 a provided in the valve body 32, and the valve body The movement of 32 is not obstructed.

  When the flow velocity in the pipe is increased, the relationship between the pressure p1 in the general portion 45 and the pressure p2 in the reduced diameter portion 46 is such that p2 is much lower than p1, and as shown in FIG. It is pushed down against the elastic force. For this reason, the valve body 32 approaches the valve seat 35, and the flow rate from the primary side to the secondary side is kept constant.

When the valve body 32 moves in a direction approaching the valve seat 35, water flows in the directions of arrows C and D shown in FIG. 2 in the pipes 45a and 46a.
Further, in the space 39 in the guide cylinder 37, the valve body 32 is separated from the partition wall 38, so that the water in the space 39 moves upward through the hole 32 a provided in the valve body 32, and the valve body The movement of 32 is not obstructed.

Sectional drawing which shows the valve opening state of one Embodiment Sectional drawing which shows the state from which the flow rate increased from the state shown in FIG. 1, and the valve body approached the valve seat a little Cross section of conventional example Cross section of conventional example

Explanation of symbols

1, 2, 31 Valve box 2 Flow path 3, 33 Partition wall 4, 24, 34 Valve hole 5, 35 Valve seat 6, 36 Valve shaft 9 Pressure chamber 10, 20, 30 Constant flow valve
11, 45a, 46a Pipe 12 Movable valve body 13, 25, 50 Pressure adjustment spring (elastic member)
22, 32 Valve body 23, 45 General portion 26, 46 Reduced diameter portion 31a Lid 31c, 32a, 51a Hole 37 Guide cylinder 38 Partition 38a Through hole 39, S, R space 40 Cylinder chamber 41 First pressure chamber 42 Second pressure Chamber 43 Piston 47 Three-way valve 51 Connection member 52 Spring receiving portion 53 Spring receiving member a Primary side valve chamber b Secondary side valve chamber f Flange

Claims (4)

  A valve wall 34 that connects the primary valve chamber a and the secondary valve chamber b is formed in the partition wall 33 that partitions the flow path in the valve box 31 into the primary valve chamber a and the secondary valve chamber b. A valve shaft 36 is inserted into the valve box 31 of the ball valve 30 provided with a valve seat 35 around the valve hole 34 so as to advance and retreat in the axial direction, and a valve body 32 provided on the valve shaft 36 is provided. The valve shaft 36 can be moved toward and away from the valve seat 35, the cylinder housing 40 is provided in the valve box 31, and the piston portion 43 provided on the valve shaft 36 moves in the axial direction of the valve shaft 36. The cylinder chamber 40 is capable of moving forward and backward, and the cylinder chamber 40 is provided with a first pressure chamber 41 on one side and a second pressure chamber 42 on the other side with the piston 43 interposed therebetween. A reduced diameter portion 46 is provided in the flow path on the side, and the pipe drawn from the flow path of the reduced diameter portion 46 is the second pressure. Pipes drawn from the flow path upstream of the reduced diameter portion 46 to the chamber 42 are respectively connected to the first pressure chamber 41, and the valve shaft 36 is provided on the secondary valve chamber b side of the valve box 31. The valve body 32 is urged in the valve opening direction by an elastic member 50 provided outside the lid 31a, and the inside of the flow path in the reduced diameter portion 46 is provided. And the valve body 32 approaches the valve seat 35 when the pressure difference between the flow path and the upstream side of the reduced diameter portion 46 increases, and the valve body 32 moves toward the valve seat 35 when the pressure difference decreases. A constant flow valve in which the opening of the flow path is adjusted away from the valve.   A guide cylinder 37 is inserted into the valve box 31 through the opening, the valve shaft 36 is provided through a partition wall 38 that partitions the guide cylinder 37 in the cylinder axis direction, and the valve body 32 is provided with the partition wall 38. 2, further, is guided by the inner surface of the guide cylinder 37 on the valve seat 35 side, and the cylinder chamber 40 and the secondary valve chamber b are partitioned by the partition wall 38. The constant flow valve described in 1.   The constant flow valve according to claim 1, wherein the piston portion (43) is guided by the inner surface of the guide tube (37) closer to the lid (31a) than the partition wall (38).   4. The constant flow valve according to claim 1, wherein a three-way valve 47 is provided in the pipe drawn from the flow path of the reduced diameter portion 46.

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