阅读说明：本技术 流量控制阀 (Flow control valve ) 是由 菱谷康平 于 2020-01-27 设计创作，主要内容包括：提供一种能够有效地减小施加于阀芯的差压的流量控制阀。流量控制阀(1)具有：设有阀室(13)的有底圆筒状的基体部件(10)；以及阀芯(6),该阀芯与设置于基体部件(10)的底壁部(12)的阀口(15)相对配置。在基体部件(10)的外侧设有与阀室(13)划分开的背压室(23)。在基体部件(10)的基体主体部(11)设有向阀室(13)开口的流入口(19)。在基体部件(10)的底壁部(12)设有与阀口(15)相连的流路(16)和将流路(16)与基体部件(10)的外侧连接的均压孔(17)。而且,均压孔(17)配置为在从阀芯(6)与阀口(15)的相对方向观察时从流入口(19)的中心线M上的位置且与流入口(19)相对的位置错开。(Provided is a flow rate control valve capable of effectively reducing a differential pressure applied to a valve body. A flow control valve (1) is provided with: a bottomed cylindrical base member (10) provided with a valve chamber (13); and a valve element (6) that is disposed so as to face a valve port (15) provided in the bottom wall portion (12) of the base member (10). A back pressure chamber (23) is provided on the outside of the base member (10) so as to be separated from the valve chamber (13). An inlet (19) that opens into the valve chamber (13) is provided in the base body section (11) of the base member (10). A flow channel (16) connected to the valve port (15) and a pressure equalizing hole (17) connecting the flow channel (16) to the outside of the base member (10) are provided in the bottom wall portion (12) of the base member (10). The pressure equalizing hole (17) is disposed so as to be offset from the position on the center line M of the inlet (19) and from the position facing the inlet (19) when viewed from the direction in which the valve element (6) and the valve port (15) face each other.)

1. A flow control valve, comprising:

a bottomed cylindrical base member provided with a valve chamber; and

a valve element disposed to face a valve port provided in a bottom wall portion of the base member and movable forward and backward with respect to the valve port,

a back pressure chamber separated from the valve chamber is provided outside the base member,

an inlet port that opens into the valve chamber is provided in the peripheral wall portion of the base member,

a flow passage connected to the valve port and one or more pressure equalizing holes connecting the flow passage to the outside of the base member are provided in a bottom wall portion of the base member,

at least one of the pressure equalizing holes is arranged so as to be shifted from a position on a center line of the inflow port and a position facing the inflow port when viewed in a direction in which the valve body faces the valve port.

2. The flow control valve of claim 1,

at least one of the pressure equalizing holes is arranged to be shifted by 30 degrees or more from a center line of the inflow port when viewed from the opposing direction.

3. The flow control valve according to claim 1 or 2,

further comprising an outer cylinder member disposed outside the base member,

a connection passage connecting the pressure equalizing hole and the back pressure chamber is provided between the base member and the outer cylinder member.

4. The flow control valve according to any one of claims 1 to 3,

the valve body has a linear characteristic portion formed such that a rate of change of the valve opening degree is proportional to the flow rate.

5. The flow control valve of claim 4,

the valve body has an equal percentage characteristic portion formed such that a rate of change of the flow rate with respect to a change of the valve opening degree is constant.

6. The flow control valve according to any one of claims 1 to 5,

the base body part is provided with one of the pressure equalizing holes,

when the cross-sectional area of the pressure equalizing hole is a0 and the cross-sectional area of the valve port is a1, the following formula (1) is satisfied:

0.10≤A0/A1≤0.50···(1)。

7. the flow control valve according to any one of claims 1 to 6,

the base body part is provided with one of the pressure equalizing holes,

when the distance from the valve seat of the base member to the pressure equalizing hole is H and the diameter of the valve port is D1, the following formula (2) is satisfied:

0.25≤H/D1≤0.75···(2)。

8. the flow control valve according to any one of claims 1 to 7,

further comprises a drive shaft provided with the valve body at a tip end portion thereof,

the valve body or the drive shaft is disposed across the valve chamber and the back pressure chamber,

the valve chamber and the back pressure chamber are sealed by a sealing member formed in an annular shape,

the diameter of the sealing portion by the sealing member is the same as the diameter of the valve port.

9. The flow control valve according to any one of claims 1 to 8, characterized by further having:

a drive shaft having the valve element provided at a distal end thereof; and

a support member that supports the drive shaft so as to be movable in the opposite direction,

a protrusion is provided on one of the base member and the support member, and a hole into which the protrusion is inserted to restrict the movement of the protrusion in a direction orthogonal to the opposing direction is provided on the other of the base member and the support member.

10. The flow control valve of claim 9,

the base member is provided with a circular hole disposed coaxially with the valve port as the hole,

the support member is provided with a cylindrical portion disposed coaxially with the drive shaft as the projection.

11. The flow control valve of claim 10,

the cylindrical portion is pressed into the circular hole.

Technical Field

The present invention relates to a flow rate control valve incorporated in, for example, a refrigeration cycle and used for controlling the flow rate of a fluid such as a refrigerant.

Background

Fig. 14 shows a conventional pressure-balanced flow control valve. The flow rate control valve 901 includes a base member 910 and an outer tube member 920 disposed outside the base member 910. The base member 910 includes a valve chamber 913 and a valve port 915 opening to the valve chamber 913. A valve body 906 that opens and closes a valve port 915 is disposed in the valve chamber 913. The flow control valve 901 has a back pressure chamber 923 provided on the back surface of the valve body 906.

The base member 910 has a pressure equalizing hole 917 and an inflow port 919. The inlet 919 opens into the valve chamber 913. The pressure equalizing hole 917 extends from the flow path 916 connected to the valve port 915 to the outside of the base member 910. The pressure equalizing hole 917 is connected to the back pressure chamber 923 via a connection passage 924 provided between the base member 910 and the outer tube member 920.

The flow rate control valve 901 connects the flow path 916 connected to the valve port 915 and the back pressure chamber 923 via the pressure equalizing hole 917 and the connection passage 924. Thereby, a difference (differential pressure) between the fluid pressure applied to the valve body 906 from the valve port 915 side and the fluid pressure applied to the valve body 906 from the back pressure chamber 923 side is reduced. The present applicant discloses, for example, a pressure-balanced flow control valve having a structure similar to that of the flow control valve 901 described above in patent document 1.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 6515164

Fig. 15 shows the base member 910 of the flow control valve 901 described above. Fig. 15(a) is a perspective view, and fig. 15(b) is a sectional view taken along the line D-D of fig. 15 (a). In the base member 910, the pressure equalizing hole 917 is disposed at a position on a line (center line M) passing through the center of the inflow port 919 and at a position facing the inflow port 919 when viewed from the facing direction (axis L direction) of the valve core 906 and the valve port 915. In other words, the pressure equalizing hole 917 is disposed at a position sandwiching the valve body 906 between the pressure equalizing hole and the inlet 919.

The inventors of the present invention analyzed the flow of the fluid and the distribution of the fluid pressure in the valve-open state of the flow control valve 901. As a result, when the fluid flows from the inlet 919 into the valve port 915 through the valve chamber 913, the fluid flows from the inlet 919 side around the valve body 906 to the pressure equalizing hole 917 side, and it is found that, in the flow path 916 connected to the valve port 915, the fluid pressure in the vicinity of the pressure equalizing hole 917 located opposite to the inlet 919 is higher than the fluid pressure in the vicinity of the inlet 919. Therefore, the fluid pressure in the back pressure chamber 923 increases, the balance of forces applied to the valve body 906 is broken, and the differential pressure increases.

Disclosure of Invention

Accordingly, an object of the present invention is to provide a flow rate control valve capable of effectively reducing a differential pressure applied to a valve body.

In order to achieve the above object, a flow rate control valve according to the present invention includes: a bottomed cylindrical base member provided with a valve chamber; and a valve body that is disposed so as to face a valve port provided in a bottom wall portion of the base member and advances and retreats with respect to the valve port, wherein a back pressure chamber that is partitioned from the valve chamber is provided outside the base member, an inlet port that opens into the valve chamber is provided in a peripheral wall portion of the base member, a flow path that connects to the valve port and one or more pressure equalizing holes that connect the flow path to the outside of the base member are provided in the bottom wall portion of the base member, and at least one of the pressure equalizing holes is disposed so as to be shifted from a position on a center line of the inlet port and a position that faces the inlet port when viewed in a direction in which the valve body and the valve port face each other.

According to the present invention, one or more pressure equalizing holes are provided to connect the flow path connected to the valve port and the outside of the base member. The at least one pressure equalizing hole is disposed at a position on the center line of the inlet port and at a position facing the inlet port, when viewed in the direction in which the valve body faces the valve port. Thus, the pressure equalizing hole is disposed in the flow path connected to the valve port so as to avoid a portion where the fluid pressure is relatively high. Therefore, the differential pressure applied to the valve element can be effectively reduced while suppressing the increase in the fluid pressure in the back pressure chamber.

In the present invention, it is preferable that at least one of the pressure equalizing holes is arranged to be shifted by 30 degrees or more from a center line of the inflow port when viewed from the opposing direction. In this way, the pressure equalizing hole is disposed in the flow path connected to the valve port at a position close to the inlet port, and therefore, the fluid pressure in the back pressure chamber can be further suppressed from increasing, and the differential pressure applied to the valve body can be more effectively reduced.

In the present invention, it is preferable that the flow rate control valve further includes an outer tube member disposed outside the base member, and a connection passage connecting the pressure equalizing hole and the back pressure chamber is provided between the base member and the outer tube member. Thus, the valve port and the back pressure chamber can be connected with a simple structure.

In the present invention, it is preferable that the valve body has a linear characteristic portion formed such that a rate of change of the valve opening degree is proportional to the flow rate. In addition, the valve body may have an equal percentage characteristic portion in which a rate of change of the flow rate with respect to a change of the valve opening degree is constant, in addition to the linear characteristic portion. A flow rate control valve having a linear characteristic portion in a valve body tends to have a relatively high fluid pressure at a portion facing an inlet in a flow path connected to a valve port. Therefore, the pressure equalizing hole is disposed in the flow path connected to the valve port so as to avoid a portion where the fluid pressure is relatively high, whereby the differential pressure applied to the valve body can be more effectively reduced.

In the present invention, it is preferable that the base member is provided with one pressure equalizing hole, and when a cross-sectional area of the pressure equalizing hole is a0 and a cross-sectional area of the valve port is a1, the following formula (1) is satisfied:

0.10≤A0/A1≤0.50···(1)。

this can effectively reduce the differential pressure applied to the valve body while suppressing an increase in size of the flow rate control valve.

In the present invention, it is preferable that the base member is provided with one pressure equalizing hole, and when a distance from a valve seat of the base member to the pressure equalizing hole is H and a diameter of the valve port is D1, the following formula (2) is satisfied:

0.25≤H/D1≤0.75···(2)。

this can effectively reduce the differential pressure applied to the valve body while suppressing an increase in size of the flow rate control valve.

In the present invention, it is preferable that the flow rate control valve further includes a drive shaft, the valve body is provided at a distal end portion of the drive shaft, the valve body or the drive shaft is disposed across the valve chamber and the back pressure chamber, the valve chamber and the back pressure chamber are sealed by a seal member formed in an annular shape, and a diameter of a portion sealed by the seal member is the same as a diameter of the valve port. Thus, in the valve-closed state, the difference between the fluid pressure applied to the valve body from the valve port side and the fluid pressure applied to the valve body from the back pressure chamber side can be made zero (including substantially zero). Therefore, the differential pressure applied to the valve element can be reduced more effectively without being restricted in shape.

In the present invention, it is preferable that the flow control valve further includes: a drive shaft having the valve element provided at a distal end thereof; and a support member that supports the drive shaft so as to be movable in the opposing direction, wherein one of the base member and the support member is provided with a projection, and the other of the base member and the support member is provided with a hole into which the projection is inserted to restrict movement of the projection in a direction orthogonal to the opposing direction. Thus, by providing the positioning protrusion on one of the base member and the support member and the positioning hole on the other of the base member and the support member, the base member and the support member can be directly assembled, and the axial displacement of the valve port and the valve element can be effectively suppressed.

In the present invention, it is preferable that the base member is provided with a circular hole as the hole, the circular hole being disposed coaxially with the valve port, and the support member is provided with a cylindrical portion as the projection, the cylindrical portion being disposed coaxially with the drive shaft. Thus, the axial displacement of the valve port and the valve element can be effectively suppressed with a relatively simple structure.

In the present invention, it is preferable that the cylindrical portion is press-fitted into the circular hole. This enables the base member and the support member to be more reliably assembled.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the differential pressure applied to the valve element can be effectively reduced.

Drawings

Fig. 1 is a longitudinal sectional view of a flow rate control valve according to a first embodiment of the present invention.

Fig. 2 is another longitudinal sectional view of the flow control valve of fig. 1.

Fig. 3 is an enlarged sectional view of a valve body of the flow control valve of fig. 1 and its vicinity.

Fig. 4 is a view showing a base member included in the flow rate control valve of fig. 1.

Fig. 5 is a diagram showing a structure of a modification of the base member of fig. 4.

Fig. 6 is a diagram schematically showing the distribution of fluid pressure in the flow control valve of fig. 1.

Fig. 7 is a diagram schematically showing the distribution of fluid pressure in the flow rate control valve of the comparative example.

Fig. 8 is a graph showing a relationship between a valve opening degree and a load applied to a valve body in the flow rate control valve of fig. 1 and the flow rate control valve of the comparative example.

Fig. 9 is a longitudinal sectional view of a flow rate control valve according to a second embodiment of the present invention.

Fig. 10 is a view showing a valve body of the flow rate control valve of fig. 9.

Fig. 11 is a graph showing a relationship between a valve opening degree and a load applied to a valve body in the flow rate control valve of fig. 9 and the flow rate control valve of the comparative example.

Fig. 12 is a diagram illustrating a relationship between a ratio of a cross-sectional area of the pressure equalizing hole to a cross-sectional area of the valve port and a load applied to the valve body in the flow rate control valve.

Fig. 13 is a diagram illustrating the relationship between the ratio of the distance from the valve seat of the base member to the pressure equalizing hole and the diameter of the valve port and the load applied to the valve body in the flow rate control valve.

Fig. 14 is a sectional view of a conventional flow control valve.

Fig. 15 is a view showing a base member included in the flow rate control valve of fig. 14.

Detailed Description

(first embodiment)

A flow rate control valve according to a first embodiment of the present invention will be described below with reference to fig. 1 to 8.

Fig. 1 and 2 are cross-sectional views (vertical sectional views) of a flow control valve according to a first embodiment of the present invention along an axis. Fig. 1 is a cross-sectional view taken along a plane including an axis and perpendicular to a center line of an inflow port of a base member.

Fig. 2 is a cross-sectional view taken along a plane including the axis and the center line of the inflow port of the base member. Fig. 3 is an enlarged sectional view of a valve body of the flow control valve of fig. 1 and its vicinity. Fig. 4 is a view showing a base member included in the flow rate control valve of fig. 1. Fig. 4(a) is a perspective view, and fig. 4(b) is a sectional view taken along the line a-a of fig. 4 (a). Fig. 5(a) to (c) are perspective views showing the structure of a modification of the base member shown in fig. 4. Fig. 6 is a diagram schematically showing the distribution of fluid pressure in the flow control valve of fig. 1. Fig. 6(a) is a sectional view of the valve chamber and its vicinity, and fig. 6(B) is a sectional view taken along the line B-B of fig. 6 (a). Fig. 7 is a diagram schematically showing the distribution of fluid pressure in the flow rate control valve of the comparative example. Fig. 7(a) is a sectional view of the valve chamber and its vicinity, and fig. 7(b) is a sectional view taken along the line C-C of fig. 7 (a). Fig. 8 is a graph showing a relationship between a valve opening degree and a load applied to a valve body in the flow rate control valve of fig. 1 and the flow rate control valve of the comparative example.

The flow rate control valve 1 of the present embodiment is an electrically operated valve used for adjusting the flow rate of refrigerant in a refrigeration cycle or the like, for example.

As shown in fig. 1 to 3, the flow rate control valve 1 includes a valve main body 5, a valve body 6, and a valve body driving unit 8.

The valve main body 5 has a base member 10 and an outer cylinder member 20.

The base member 10 is made of, for example, a stainless steel material. The base member 10 is formed in a bottomed cylindrical shape. The outer diameter of the base member 10 is the same as the inner diameter of the outer cylindrical member 20. Fig. 4 shows the base member 10. The base member 10 integrally includes a base body 11 as a peripheral wall portion and a bottom wall portion 12 connected to a lower end of the base body 11.

The base body 11 is provided with a valve chamber 13 as a cylindrical space. The base body 11 is provided with a circular hole 14 as a positioning hole opened upward. The circular hole 14 is connected to the valve chamber 13. In the present embodiment, the diameter of the valve chamber 13 is the same as the diameter of the circular hole 14.

The base body 11 is provided with a circular inlet 19 opening to the valve chamber 13. The inlet 19 faces a direction orthogonal to the opposing direction (the direction of the axis L) of the valve element 6 and the valve port 15. A center line M as a line passing through the center of the inflow port 19 is orthogonal to the axis L.

The bottom wall portion 12 is provided with: a circular valve port 15 opening to the valve chamber 13; a flow path 16 connected to the valve port 15 and extending downward; a pressure equalizing hole 17 extending in the lateral direction from the flow path 16; and a valve seat 18 surrounding the valve port 15. The valve port 15 and the flow passage 16 have the same diameter. The valve port 15 and the flow passage 16 are provided coaxially with the valve chamber 13 and have a smaller diameter than the valve chamber 13. The pressure equalizing hole 17 penetrates from the flow passage 16 to the outside of the base member 10. The valve element 6 is seated on the valve seat 18.

In the base member 10, the pressure equalizing hole 17 is disposed at a position shifted from the position on the center line M of the inlet 19 and facing the inlet 19 when viewed from the direction of the axis L. Specifically, the pressure equalizing hole 17 is arranged to be shifted by 90 degrees (α is 90 degrees) in the clockwise direction from the center line M. The pressure equalizing holes 17 may be arranged to be shifted by 90 degrees in the counterclockwise direction from the center line M. The pressure equalizing hole 17 may be arranged 180 degrees apart from the center line M (i.e., aligned with the inlet 19 in the direction of the axis L). The pressure equalizing hole 17 is preferably shifted by 30 degrees or more from the center line M of the inlet 19 when viewed from the axis L direction.

A linear groove 22 extending from the vicinity of the pressure equalizing hole 17 to the upper end of the base member 10 is provided on the outer peripheral surface of the base member 10. By providing the linear groove 22, a connection passage 24 connecting the pressure equalizing hole 17 and the back pressure chamber 23 is formed between the base member 10 and the outer cylindrical member 20. Instead of the linear groove 22, for example, a connection passage connecting the pressure equalizing hole 17 and the back pressure chamber 23 may be formed by cutting a part of the outer peripheral surface of the bottomed cylindrical base member 10 along a chord in a planar manner. Alternatively, an annular connection passage may be formed to connect the pressure equalizing hole 17 and the back pressure chamber 23 by making the outer diameter of a part of the base member 10 smaller than the inner diameter of the outer tube member 20.

In the present embodiment, one pressure equalizing hole 17 and one linear groove 22 corresponding to the pressure equalizing hole 17 are provided, but the present invention is not limited to this configuration. For example, the base members 10A to 10C shown in fig. 5(a) to (C) may be used.

As shown in fig. 5(a), the base member 10A is provided with two pressure equalizing holes 17, one pressure equalizing hole 17 is disposed at a position shifted by 90 degrees from the center line M when viewed from the direction of the axis L, and the other pressure equalizing hole 17 is disposed at a position on the center line M and facing the inlet 19. Two linear grooves 22 corresponding to these pressure equalizing holes 17 are provided.

As shown in fig. 5(B), the base member 10B is provided with two pressure equalizing holes 17, and one pressure equalizing hole 17 is arranged so as to be shifted by 90 degrees in the clockwise direction from the center line M when viewed from the direction of the axis L, and the other pressure equalizing hole 17 is arranged so as to be shifted by 90 degrees in the counterclockwise direction from the center line M. Two linear grooves 22 corresponding to these pressure equalizing holes 17 are provided.

As shown in fig. 5(c), the base member 10B is provided with three pressure equalizing holes 17, one pressure equalizing hole 17 is arranged so as to be shifted by 90 degrees in the clockwise direction from the center line M when viewed from the direction of the axis L, the other pressure equalizing hole 17 is arranged so as to be shifted by 90 degrees in the counterclockwise direction from the center line M, and the remaining one pressure equalizing hole 17 is arranged at a position on the center line M and at a position facing the inflow port 19. Three linear grooves 22 corresponding to these pressure equalizing holes 17 are provided.

The outer cylinder member 20 is made of, for example, a stainless steel material. The outer cylinder member 20 is formed in a cylindrical shape. The outer tube member 20 is disposed outside the base member 10, and accommodates the base member 10 inside. The base member 10 is fitted into a lower end 20a, which is one end of the outer cylindrical member 20, and the lower end 20a is closed by the base member 10. The lower end 20a of the outer cylindrical member 20 is brazed to the bottom wall 12.

The valve body 5 has a first conduit 26 and a second conduit 27. The first duct 26 penetrates the outer tube member 20 in the lateral direction and is connected to the inlet 19 of the base body 11. The first duct 26 is brazed to the outer cylindrical member 20. The second duct 27 is connected to the flow path 16 of the bottom wall portion 12. The second conduit 27 is brazed to the bottom wall portion 12.

The valve body 6 is made of, for example, a stainless steel material. The valve body 6 is formed in a solid (i.e., not hollow) cylindrical shape as a whole, and has a downward conical shape at a lower end. The valve body 6 integrally includes a cylindrical body portion 31, a conical tip portion 32 provided at the lower end of the body portion 31 and directed downward, and an annular protrusion 33 protruding in the lateral direction from the lower end of the body portion 31. The distal end portion 32 is a linear characteristic portion formed in a conical shape so that the rate of change in the valve opening degree is proportional to the flow rate. The upper end surface 31a of the body portion 31 is provided with a mounting hole 31 b. A distal end protrusion 64e of a distal end portion 64c of the drive shaft 64 described later is fitted into the mounting hole 31 b. Thereby, the valve body 6 is provided at the distal end portion 64c of the drive shaft 64. The body portion 31 is provided with a lateral hole 31c that penetrates in the lateral direction from the attachment hole 31 b. The fluid pressure in the mounting hole 31b is made equal to the fluid pressure outside the valve body 6 by the lateral hole 31c, and the tip end projection 64e is prevented from coming out of the mounting hole 31 b.

The valve body 6 is disposed in the valve chamber 13 so as to face the valve port 15 in the vertical direction (the direction of the axis L). The valve element 6 moves in the vertical direction by the valve element driving unit 8 to move forward and backward with respect to the valve port 15, thereby opening and closing the valve port 15. The vertical direction is a direction in which the valve body 6 faces the valve port 15, and is a moving direction of the valve body 6. When the valve element 6 is separated from the valve seat 18, the valve port 15 is opened to be in an open state. In the valve-open state, the first conduit 26 and the second conduit 27 are connected via the valve chamber 13. When the valve element 6 contacts the valve seat 18 (is seated on the valve seat 18), the valve port 15 is closed and a valve-closed state is achieved. In the valve-closed state, the first conduit 26 and the second conduit 27 are cut off.

The tip portion 32 of the valve body 6 has a solid structure, and thus there is no limitation on the shape of the tip portion 32. In the present embodiment, the shape of the distal end portion 32 of the valve element 6 is a conical shape that can obtain linear characteristics as flow rate characteristics, but other shapes may be employed that are designed to obtain equal percentage characteristics or characteristics close thereto. As such a shape, for example, there is a shape having an elliptical surface or a multi-stage conical tapered surface portion. The tapered surface portion of the multistage cone shape is a pseudo-elliptical surface, and the taper angle gradually increases as the valve port 15 side approaches.

The valve body drive portion 8 is attached to the upper portion of the valve main body 5. The valve body driving unit 8 moves the valve body 6 in the vertical direction to bring the valve body 6 into contact with and away from the valve seat 18, thereby closing or opening the valve port 15. The valve body driving unit 8 includes a housing 40 as a casing, a motor unit 50, a driving mechanism unit 60, and a holder 70.

The housing 40 is made of, for example, a stainless steel material. The housing 40 is formed in a cylindrical shape with the upper end closed. A holder 70 (specifically, a holder body 71) described later is fitted into the lower end 40a of the housing 40, and the lower end 40a is closed by the holder 70. The lower end 40a of the outer shell 40 is welded to the holder 70.

The motor unit 50 includes: a rotor 51, the rotor 51 being rotatably housed inside the housing 40; and a stator 52, the stator 52 being disposed outside the housing 40. The stator 52 is constituted by a yoke 53, a bobbin 54, a stator coil 55, a resin mold cover 56, and the like. The rotor 51 and the stator 52 constitute a stepping motor.

The drive mechanism section 60 includes a guide bush 61, a valve shaft holder 62, a stopper mechanism 63, a drive shaft 64, and a seal member 65.

The guide bush 61 integrally has a cylindrical small diameter portion 61a and a cylindrical large diameter portion 61b coaxially connected to a lower end of the small diameter portion 61 a. The inner diameter of the small diameter portion 61a is the same as that of the large diameter portion 61 b. A male screw 61c is provided on the outer peripheral surface of the small diameter portion 61 a. The small-diameter portion 61a is provided with a transverse hole 61d penetrating in the transverse direction.

The valve shaft holder 62 is formed in a cylindrical shape with the upper end closed. The valve shaft holder 62 integrally has a cylindrical peripheral wall portion 62a and an upper wall portion 62b that closes the upper end of the peripheral wall portion 62 a. An internal thread 62c that is screwed into the external thread 61c of the guide bush 61 is provided on the inner peripheral surface of the peripheral wall portion 62 a. The upper wall 62b is integrally connected to the rotor 51 via a support ring 66 that is fixed to the upper wall 62b by caulking. Therefore, when the rotor 51 rotates, the valve shaft holder 62 also rotates. When the valve shaft holder 62 is rotated, the valve shaft holder 62 moves in the axial direction (vertical direction) of the guide bush 61 by the feed screw action of the male screw 61c and the female screw 62 c. A return spring 67 formed of a coil spring is provided above the valve shaft holder 62, and the return spring 67 is used to facilitate the re-screwing of the external thread 61c and the internal thread 62c when they are disengaged from each other.

The stopper mechanism 63 has a lower stopper body 63a fixed to the guide bush 61 and an upper stopper body 63b fixed to the valve shaft holder 62. When the valve shaft holder 62 reaches the lower limit position, the lower stopper body 63a and the upper stopper body 63b of the stopper mechanism 63 abut against each other, and the movement of the valve shaft holder 62 with respect to the guide bush 61 is restricted.

The drive shaft 64 is formed in an elongated cylindrical shape as a whole. The drive shaft 64 is inserted through the guide bush 61 and is disposed coaxially with the guide bush 61. The drive shaft 64 is integrally provided with an upper end portion 64a, a body portion 64b, and a distal end portion 64c in this order from the top downward. The upper end portion 64a is formed to have a diameter smaller than that of the body portion 64b, and is inserted into a through hole of the upper wall portion 62b of the valve shaft holder 62. A pushing nut 64d is fixed to the upper end portion 64 a. The body portion 64b is supported by the guide bush 61 so as to be slidable in the vertical direction. A compression coil spring 68 that presses the drive shaft 64 downward is provided between the stepped portion of the upper end portion 64a and the body portion 64b and the upper wall portion 62b of the valve shaft holder 62. By providing the urging nut 64d and the compression coil spring 68, the drive shaft 64 moves in the up-down direction in accordance with the movement of the valve shaft holder 62. The distal end portion 64c is provided with a slender distal end protrusion 64e that fits into the attachment hole 31b of the body portion 31 of the valve body 6. The drive shaft 64 is integrally provided with a flange portion 64f projecting in the lateral direction at the lower end of the body portion 64 b. The diameter of the flange portion 64f is the same as the diameter of the body portion 31 of the valve body 6.

The seal member 65 is formed in an annular shape. The seal member 65 has a distal end portion 64c of the drive shaft 64 fitted inside. That is, the distal end portion 64c of the drive shaft 64 penetrates the seal member 65. The seal member 65 is disposed between the flange portion 64f and the upper end surface 31a of the body portion 31 of the valve body 6. In the present embodiment, the seal member 65 is provided with an annular packing 65b made of Polytetrafluoroethylene (PTFE) on the outer side of an O-ring 65a made of a rubber material.

The holder 70 is made of, for example, a stainless steel material. The holder 70 integrally includes a substantially disc-shaped holder main body 71 and a cylindrical portion 72 serving as a positioning protrusion. The cylindrical portion 72 protrudes downward from the lower surface 71a of the holder main body 71.

The upper end 20b of the outer tubular member 20 is welded to the holder main body 71 in a state where the end face 20c of the upper end 20b is in contact with the lower surface 71a of the holder main body 71. The upper end 20b of the outer cylindrical member 20 is closed by the holder body 71. Thereby, the back pressure chamber 23 partitioned from the valve chamber 13 is formed by the base member 10, the outer tube member 20, and the holder body 71. In addition, the lower end 40a of the outer shell 40 is welded to the holder main body 71.

A circular press-fitting hole 71b is provided in the center of the upper surface of the holder main body 71, coaxially with the cylindrical portion 72. The large diameter portion 61b of the guide bush 61 is press-fitted into the press-fitting hole 71 b. Thus, the holder main body 71 and the guide bush 61 are integrated with each other in a state where the guide bush 61 and the cylindrical portion 72 are coaxially arranged. The holder 70 and the guide bush 61 constitute a support member 73 that supports the drive shaft 64 so as to be movable in the direction opposite to the valve element 6 and the valve port 15. A shaft hole 71c through which the body portion 64b of the drive shaft 64 is inserted is provided in the center of the bottom surface of the press-fitting hole 71 b. A vertical hole 71d penetrating in the vertical direction is provided in the peripheral edge portion of the holder main body 71.

The cylindrical portion 72 is press-fitted into the circular hole 14 of the base member 10. Thus, the holder 70 is directly assembled to the base member 10, and the cylindrical portion 72 and the circular hole 14 are coaxially arranged. The cylindrical portion 72 and the valve port 15 are also coaxially arranged. Further, by inserting the cylindrical portion 72 into the circular hole 14, the circular hole 14 restricts the movement of the cylindrical portion 72 in a direction orthogonal to the vertical direction (the opposing direction). The axes of the cylindrical portion 72, the valve body 6, the valve chamber 13, the valve port 15, and the drive shaft 64 coincide on the axis L.

Inside the cylindrical portion 72, the body portion 31 of the valve body 6, the distal end portion 64c and the flange portion 64f of the drive shaft 64, and the seal member 65 are disposed so as to be movable in the vertical direction. The gasket 65b disposed on the outer periphery of the seal member 65 is pressed against the inner surface of the cylindrical portion 72. Thereby, the seal member 65 seals between the valve chamber 13 and the back pressure chamber 23. The seal member 65 slides on the inner circumferential surface of the cylindrical portion 72 in accordance with the vertical movement of the drive shaft 64. A transverse hole 72a penetrating in the transverse direction is provided at the upper end of the cylindrical portion 72. In the present embodiment, the inner diameter of the cylindrical portion 72 (i.e., the diameter of the seal portion sealed by the seal member 65) is the same as the diameter of the valve port 15. The inner diameter of the cylindrical portion 72 may be different from the diameter of the valve port 15, but the difference is preferably reduced.

In the flow rate control valve 1, the valve chamber 13 and the back pressure chamber 23 are sealed by the seal member 65 fitted into the distal end portion 64c of the drive shaft 64, and therefore the drive shaft 64 is disposed across the valve chamber 13 and the back pressure chamber 23. The flow passage 16 and the back pressure chamber 23 of the base member 10 are connected to each other through the pressure equalizing hole 17 and the connecting passage 24 of the base member 10. The back pressure chamber 23 and the inner space 41 of the housing 40 are connected by a vertical hole 71d of the holder body 71. Therefore, in the valve-closed state, the fluid pressure in the flow path 16 is the same as the fluid pressure in the back pressure chamber 23, and the difference (differential pressure) between the fluid pressure applied to the valve body 6 from the valve port 15 side and the fluid pressure applied to the valve body 6 from the back pressure chamber 23 side becomes small. In the present embodiment, the diameter of the valve port 15 (indicated by a double arrow E1 in fig. 3) is made equal to the inner diameter of the cylindrical portion 72 of the holder 70 (indicated by a double arrow E2 in fig. 3). Therefore, the differential pressure is zero (including substantially zero), and it is possible to effectively prevent the movement of the valve element 6 from being hindered by the differential pressure.

A space 72b inside the cylindrical portion 72 and above the flange portion 64f is connected to the back pressure chamber 23 through a lateral hole 72 a. The space 72b is connected to the back pressure chamber 23 through the shaft hole 71c of the holder 70, the gap between the guide bush 61 and the drive shaft 64, the lateral hole 61d of the guide bush 61, the inner space 41 of the housing 40, and the vertical hole 71d of the holder 70 in this order. Thus, even when the fluid pressure in the space 72b changes due to the movement of the flange portion 64f, the fluid pressure in the space 72b is quickly equal to the fluid pressure in the back pressure chamber 23.

Next, a method of assembling the flow rate control valve 1 will be described.

(1) The valve body 5 is assembled. Specifically, the base member 10 is fitted into the lower end 20a of the outer tube member 20, and the lower end 20a is closed. The first guide pipe 26 is fitted into the outer tube member 20 and the base body portion 11 of the base member 10. The second conduit 27 is embedded in the bottom wall portion 12 of the base member 10. Then, brazing is performed by providing a brazing material at each brazing portion and charging the brazing material into a furnace.

(2) The valve body driving portion 8 is assembled. Specifically, the large diameter portion 61b of the guide bush 61 is press-fitted into the press-fitting hole 71b of the holder body 71, and the holder 70 is integrated with the guide bush 61. The internal thread 62c of the valve shaft holder 62 is screwed with the external thread 61c of the guide bush 61. The lower stopper 63a is mounted in advance on the guide bush 61. The upper stop body 63b is mounted in advance on the valve shaft holder 62. The rotor 51 is coupled to the valve shaft holder 62 in advance via a support ring 66. The tip end portion 64c of the drive shaft 64 is fitted into the seal member 65, and the tip end protrusion 64e of the tip end portion 64c is fitted into the mounting hole 31b of the valve body 6, whereby the valve body 6 is mounted on the drive shaft 64. The drive shaft 64 is inserted from below into the cylindrical portion 72 of the holder 70, the shaft hole 71c of the holder 70, and the guide bush 61. A compression coil spring 68 is provided at the upper end portion 64a of the drive shaft 64, and the upper end portion 64a is inserted into the through hole of the upper wall portion 62b of the valve shaft holder 62. A jack nut 64d is fixed to the upper end 64a of the drive shaft 64, and a return spring 67 is disposed. Then, an assembly in which the rotor 51, the guide bush 61, the valve shaft holder 62, the stopper mechanism 63, and the like are assembled is inserted into the housing 40. A holder body 71 is fitted into the lower end 40a of the housing 40, and the lower end 40a is closed by the holder body 71. The lower end 40a of the outer shell 40 is welded to the holder main body 71. The stator 52 is mounted to the housing 40. In this state, the drive shaft 64 and the valve body 6 are arranged coaxially with the cylindrical portion 72 on the axis L.

(3) Then, the valve main body 5 and the valve element driving portion 8 are assembled. Specifically, the cylindrical portion 72 is press-fitted into the circular hole 14 of the base member 10. The push cylinder portion 72 is pushed until the end surface 20c of the upper end 20b of the outer tube member 20 abuts against the holder main body 71, and the holder main body 71 closes the upper end 20b, thereby forming the back pressure chamber 23 outside the base member 10, which is partitioned from the valve chamber 13. Meanwhile, the drive shaft 64 is disposed so as to straddle the valve chamber 13 and the back pressure chamber 23. Finally, the upper end 20b of the outer cylindrical member 20 is welded to the holder main body 71. Thus, the flow control valve 1 is completed.

The inventors of the present invention analyzed the distribution of the fluid pressure in the open state and the relationship between the valve opening degree and the load (differential pressure) generated on the valve body with respect to the flow rate control valve 1 (example 1) and the conventional flow rate control valve 901 (comparative example 1). Fig. 6 schematically shows the distribution of fluid pressure in example 1. Fig. 7 schematically shows the distribution of fluid pressure in comparative example 1. Fig. 8 shows a graph showing a relationship between a valve opening (the number of pulses input to the stepping motor) and a load (differential pressure) generated on the valve element in example 1 and comparative example 1. In fig. 6 and 7, the fluid pressure is represented by three levels (high pressure PH, medium pressure PM, low pressure PL), and the higher the density of the dots, the higher the fluid pressure.

In example 1, the pressure equalizing holes 17 are arranged so as to be shifted by 90 degrees in the clockwise direction from the center line M when viewed from the axis L direction. In comparative example 1, the pressure equalizing hole 917 is disposed at a position on the center line M of the inflow port 919 and at a position facing the inflow port 919 when viewed from the axis L direction. Comparative example 1 has the same structure as example 1 except for the positions of the pressure equalizing hole 917 and the linear groove 922.

As shown in fig. 6 and 7, in both of example 1 and comparative example 1, the fluid pressures in the inlet and the valve chamber were high pressures PH. In addition, in any of example 1 and comparative example 1, the fluid pressure at a position on the center line M of the inlet and at a position facing the inlet in the flow path connected to the valve port becomes the intermediate pressure PM when viewed from the direction of the axis L. Further, in the flow path connected to the valve port, when viewed from the axis L direction, the range of the medium pressure PM extends to a position shifted by 30 degrees (β is 30 degrees) in the clockwise direction and the counterclockwise direction from the center line M, and when the range is shifted, the fluid pressure becomes the low pressure PL.

Therefore, in example 1, since the pressure equalizing hole 17 is provided in the passage 16 at a position where the fluid pressure becomes the low pressure PL, the back pressure chamber 23 connected to the passage 16 through the pressure equalizing hole 17 also becomes the low pressure PL. Thereby, a difference (differential pressure) between the fluid pressure applied to the valve body 6 from the valve port 15 side and the fluid pressure applied to the valve body 6 from the back pressure chamber 23 side becomes small.

On the other hand, in comparative example 1, since the pressure equalizing hole 917 is provided at a position where the fluid pressure in the flow passage 916 becomes the intermediate pressure PM, the back pressure chamber 923 connected to the flow passage 916 through the pressure equalizing hole 917 also becomes the intermediate pressure PM. Thereby, a difference (differential pressure) between the fluid pressure applied to the valve body 906 from the valve port 915 side and the fluid pressure applied to the valve body 906 from the back pressure chamber 923 side becomes large, and a load is applied to the valve body 906 in the valve closing direction.

As is apparent from the graph of fig. 8, when the valve opening degree is small, the load applied to the valve body is relatively small in either of example 1 and comparative example 1. When the valve opening degree is small, the flow rate flowing into the valve port is small, so that the difference in fluid pressure in the flow path connected to the valve port is small, and the flow path is at a low pressure PL and does not have a portion that becomes the intermediate pressure PM. Therefore, in example 1 and comparative example 1, a large difference in load applied to the valve body does not occur.

As is clear from the graph of fig. 8, when the valve opening degree is large, the load applied to the valve body is significantly large in comparative example 1, but the load applied to the valve body is still small in example 1. When the valve opening degree is large, the flow rate flowing into the valve port increases, and therefore, a portion where the fluid easily flows and a portion where the fluid hardly flows are generated, and a difference in fluid pressure in a flow passage connected to the valve port increases. Therefore, although a portion that becomes the low pressure PL and a portion that becomes the intermediate pressure PM are generated in the flow passage, the pressure equalizing hole is disposed so as to avoid the portion that becomes the intermediate pressure PM in example 1, and therefore, a difference occurs in the load applied to the valve body in example 1 and comparative example 1.

From these analysis results, it was confirmed that the flow rate control valve 1 of the present embodiment can effectively reduce the differential pressure applied to the valve body as compared with the conventional flow rate control valve 901.

As described above, according to the flow rate control valve 1 of the present embodiment, the single pressure equalizing hole 17 is provided to connect the flow channel 16 connected to the valve port 15 to the outside of the base member 10. The pressure equalizing hole 17 is disposed so as to be shifted from a position on the center line M of the inlet 19 and a position facing the inlet 19 when viewed from a facing direction (axis L direction) of the valve element 6 and the valve port 15. Thus, the pressure equalizing hole 17 is disposed in the flow passage 16 connected to the valve port 15 so as to avoid a portion where the fluid pressure is relatively high. Therefore, the differential pressure applied to the valve element 6 can be effectively reduced while suppressing an increase in the fluid pressure in the back pressure chamber 23.

The pressure equalizing hole 17 is disposed at a position shifted by 90 degrees from the center line M of the inlet 19 when viewed from the direction of the axis L. Accordingly, the pressure equalizing hole 17 is disposed in the flow path 16 connected to the valve port 15 at a position close to the inlet 19, and therefore, the fluid pressure in the back pressure chamber 23 can be further suppressed from increasing, and the differential pressure applied to the valve element 6 can be more effectively reduced.

The flow rate control valve 1 has an outer tube member 20 disposed outside the base member 10, and a connection passage 24 for connecting the pressure equalizing hole 17 and the back pressure chamber 23 is provided between the base member 10 and the outer tube member 20. This allows the valve port 15 and the back pressure chamber 23 to be connected with a simple configuration.

The valve body 6 has a tip portion 32 as a linear characteristic portion formed such that a rate of change of the valve opening degree is proportional to the flow rate. The flow rate control valve 1 having a linear characteristic portion in the valve body 6 tends to have a relatively high fluid pressure at a portion facing the inlet 19 in the flow path 16 connected to the valve port 15. Therefore, by disposing the pressure equalizing hole 17 in the flow passage 16 connected to the valve port 15 so as to avoid a portion where the fluid pressure is relatively high, the differential pressure applied to the valve element 6 can be more effectively reduced.

The flow rate control valve 1 further includes a drive shaft 64 provided with a valve body 6 at a tip end portion 64 c. The drive shaft 64 is disposed across the valve chamber 13 and the back pressure chamber 23. The valve chamber 13 and the back pressure chamber 23 are sealed by a ring-shaped seal member 65, and the diameter of the portion sealed by the seal member 65 is the same as the diameter of the valve port 15. Thus, in the valve-closed state, the difference between the fluid pressure applied to the valve body 6 from the valve port 15 side and the fluid pressure applied to the valve body 6 from the back pressure chamber 23 side can be made zero (including substantially zero). Therefore, the differential pressure applied to the valve element 6 can be reduced more effectively without being restricted in the shape of the valve element 6.

Further, the flow rate control valve 1 includes: a drive shaft 64 provided with a valve body 6 at a tip end portion 64c of the drive shaft 64; and a support member 73, the support member 73 supporting the drive shaft 64 movably in the direction of the axis L. The support member 73 is provided with a cylindrical portion 72 serving as a positioning protrusion, and the base member 10 is provided with a circular hole 14 serving as a positioning hole into which the cylindrical portion 72 is inserted. This allows the base member 10 and the support member 73 to be directly assembled, and thus axial displacement between the valve port 15 and the valve body 6 can be effectively suppressed.

Further, the cylindrical portion 72 is press-fitted into the circular hole 14. This enables the base member 10 and the support member 73 to be more reliably assembled.

In the above-described embodiment, the cylindrical portion 72 of the holder 70 is press-fitted into the circular hole 14 of the base member 10, but other configurations may be employed. For example, the following structure may be adopted: the cylindrical portion 72 is inserted into the circular hole 14, and a sealing member such as an O-ring is provided between the outer peripheral surface of the cylindrical portion 72 and the inner peripheral surface of the circular hole 14.

In the above-described embodiment, the valve body 6 and the drive shaft 64 are configured separately, but the valve body 6 and the drive shaft 64 may be configured integrally, for example. In this configuration, the spool 6 includes the drive shaft 64, and the spool 6 is disposed across the valve chamber 13 and the back pressure chamber 23. The seal member 65 is formed in an annular shape through which the valve body 6 passes, and seals between the valve chamber 13 and the back pressure chamber 23.

In the above-described embodiment, the circular hole 14 as the positioning hole is provided in the base member 10, and the cylindrical portion 72 as the positioning protrusion is provided in the holder 70, but the positioning protrusion may be provided in the base member 10 and the positioning hole may be provided in the holder 70, in contrast to this.

(second embodiment)

A flow rate control valve according to a second embodiment of the present invention will be described below with reference to fig. 9 to 11.

Fig. 9 is a longitudinal sectional view of a flow rate control valve according to a second embodiment of the present invention. Fig. 10 is a front view of a valve body of the flow control valve of fig. 9. Fig. 11 is a graph showing a relationship between a valve opening degree and a load applied to a valve body in the flow rate control valve of fig. 9 and the flow rate control valve of the comparative example.

The flow rate control valve 2 has the same configuration as the flow rate control valve 1 except that the flow rate control valve 1 of the first embodiment includes a valve body 6A having an equal percentage characteristic portion instead of the valve body 6. In the following description, the same components as those of the flow rate control valve 1 are denoted by the same reference numerals, and description thereof is omitted.

The valve body 6A is made of, for example, a stainless steel material. The valve body 6A is formed in a solid (i.e., not hollow) cylindrical shape as a whole, and has a substantially conical shape facing downward at a lower end. The valve body 6A integrally includes a cylindrical body portion 31, a substantially conical distal end portion 32A provided at the lower end of the body portion 31 and directed downward, and an annular protrusion 33 protruding in the lateral direction from the lower end of the body portion 31. The distal end portion 32A has a linear characteristic portion 34 formed in a conical shape so that a rate of change in the valve opening degree is proportional to the flow rate, and an equal percentage characteristic portion 35 formed in a ring-like curved surface shape so that a rate of change in the flow rate with respect to a change in the valve opening degree is constant. The linear characteristic portion 34 and the equal percentage characteristic portion 35 are arranged in this order from the lower side to the upper side. The equal percentage characteristic portion 35 has a shape designed to be able to obtain the equal percentage characteristic or a characteristic close thereto. As such a shape, for example, there is a shape having an elliptical surface or a multi-stage conical tapered surface portion. The tapered surface portion of the multistage cone shape is a pseudo-elliptical surface, and the taper angle gradually increases as the valve port 15 side approaches.

The inventors of the present invention analyzed the relationship between the valve opening degree and the load (differential pressure) generated on the valve body, with respect to the flow rate control valve 2 (example 2) described above and the flow rate control valve (comparative example 2) using the valve body 6A of fig. 10 in the conventional flow rate control valve 901. Fig. 11 shows a graph showing a relationship between a valve opening (the number of pulses input to the stepping motor) and a load (differential pressure) generated in the valve body in example 2 and comparative example 2.

As is clear from the graph of fig. 11, when the valve opening degree is small, the flow rate characteristic is an equal percentage characteristic, and the load applied to the spool is small in either of example 2 and comparative example 2. When the valve opening degree is small, the increase in the opening area with respect to the valve opening degree is small, and the flow rate flowing into the valve port is small compared to the linear characteristic, so that the difference in the fluid pressure in the flow path connected to the valve port is small, and the flow path has a low pressure PL and does not have a portion that becomes the intermediate pressure PM. Thus, in example 2 and comparative example 2, a large difference in load applied to the valve body does not occur.

As is clear from the graph of fig. 11, when the valve opening degree is large, the flow rate characteristic becomes linear, and the load applied to the valve body becomes significantly large in comparative example 2, but the load applied to the valve body is still small in example 2. When the valve opening is large, the flow rate flowing into the valve port increases, and therefore, a portion where the fluid flows easily and a portion where the fluid does not flow easily occur, and a difference in fluid pressure becomes large in the flow path connected to the valve port. Therefore, although a portion that becomes the low pressure PL and a portion that becomes the intermediate pressure PM are generated in the flow passage, the pressure equalizing hole is disposed so as to avoid the portion that becomes the intermediate pressure PM in example 2, and therefore, a difference occurs in the load applied to the valve body in example 2 and comparative example 2.

From these analysis results, it was confirmed that the flow rate control valve 2 of the present embodiment can effectively reduce the differential pressure applied to the valve body as compared with the flow rate control valve using the valve body 6A in the conventional flow rate control valve 901.

The flow rate control valve 2 according to the present embodiment also has the same operational advantages as those of the flow rate control valve according to the first embodiment 1 described above.

The inventors of the present invention measured the relationship between the ratio a0/a1 (the ratio of the cross-sectional area a0 of the pressure equalizing hole 917 to the cross-sectional area a1 of the valve port 915 (flow path 916)) and the load (differential pressure) applied to the valve body 906 when the valve port 915 is fully opened in the conventional flow rate control valve 901 shown in fig. 12 (a). Fig. 12(b) shows the measurement results. The cross-sectional area is an area of a cross-section (flow path area) perpendicular to the flow direction of the fluid.

Fig. 12(b) is a graph showing the relationship between the ratio a0/a1 (the ratio of the cross-sectional area a0 of the pressure equalizing hole 917 to the cross-sectional area a1 of the valve port 915) in the flow rate control valve 901 and the load applied to the valve body 906. As is apparent from this graph, the load applied to the spool 906 can be reduced as the ratio a0/a1 is larger than 0.10. However, since the flow rate control valve 901 is increased in size when the cross-sectional area a0 of the pressure equalizing hole 917 is increased, the ratio a0/a1 is preferably 0.50 or less.

Thus, in the flow rate control valve 901, when one pressure equalizing hole 917 is provided in the base member 910, and the sectional area of the pressure equalizing hole 917 is a0 and the sectional area of the valve port 915 is a1, the following equation (1) is satisfied, whereby the differential pressure applied to the valve body can be effectively reduced while suppressing an increase in size of the flow rate control valve.

0.10≤A0/A1≤0.50···(1)

In the conventional flow rate control valve 901 shown in fig. 13(a), the inventors of the present invention measured the relationship between H/D1 (the ratio of the distance H from the valve seat 918 of the base member 910 to the pressure equalizing hole 917 to the diameter D1 of the valve port 915) and the load (differential pressure) applied to the valve body 906 when the valve port 915 is fully opened. Fig. 13(b) shows the measurement results.

Fig. 13(b) is a graph showing the relationship between the ratio H/D1 (the ratio of the distance H from the valve seat 918 of the base member 910 to the pressure equalizing hole 917 to the diameter D1 of the valve port 915) in the flow rate control valve 901 and the load applied to the valve body 906. As is apparent from the graph, the smaller the ratio H/D1 is, the greater the load applied to the spool 906 is, the greater the load is. Therefore, by setting the distance H to 0.25 or more, the load applied to the spool 906 can be reduced. However, if the distance H is increased, the flow rate control valve 901 is increased in size, and therefore the ratio H/D1 is preferably 0.75 or less.

Thus, in the flow rate control valve 901, one pressure equalizing hole 917 is provided in the base member 910, and when the distance from the valve seat 918 of the base member 910 to the pressure equalizing hole 917 is H and the diameter of the valve port 915 is D1, the following expression (2) is satisfied, so that the differential pressure applied to the valve body can be effectively reduced while suppressing an increase in size of the flow rate control valve.

0.25≤H/D1≤0.75···(2)

It is considered that these equations (1) and (2) can provide similar operational effects even when applied to the flow rate control valve 1 of the first embodiment and the flow rate control valve 2 of the second embodiment.

The embodiments of the present invention have been described above, but the present invention is not limited to these embodiments. Those skilled in the art can appropriately add, delete, and modify the components of the above-described embodiments, and appropriately combine the features of the embodiments, without departing from the spirit of the present invention, and the scope of the present invention is also encompassed.

Description of the symbols

1. 2 … flow control valve, 5 … valve body, 6a … valve body, 8 … valve body driving portion, 10A, 10B, 10C … base member, 11 … base body portion, 12 … bottom wall portion, 13 … valve chamber, 14 … circular hole, 15 … valve port, 16 … flow path, 17 … pressure equalizing hole, 18 … valve seat, 19 … inlet, 20 … outer cylinder member, 20A … lower end, 20B … upper end, 22 … linear groove, 23 … back pressure chamber, 24 … connecting passage, 26 … first conduit, 27 coil former 27 … second conduit, 31 … trunk portion, 31a … upper end face, 31B … mounting hole, 31C … transverse hole, 32a … top end portion, 33 … annular protrusion, 34 … linear characteristic portion, 35 … percentage characteristic portion, 40 … housing, 40A … lower end, 41C … inner side space, …, electrical yoke 72, …, rotor …, 3653, …, 3653 stator 3653, …, 3653, and the like percentage characteristic portion, 55 … stator coil, 56 … resin mold cover, 60 … drive mechanism portion, 61 … guide bush, 61a … small diameter portion, 61b … large diameter portion, 61c … external screw thread, 61d … transverse hole, 62 … valve shaft holder, 62a … peripheral wall portion, 62b … upper wall portion, 62c … internal screw thread, 63 … stopper mechanism, 63a … lower stopper body, 63b … upper stopper body, 64 … drive shaft, 64a … upper end portion, 64b … trunk portion, 64c … top end portion, 64d … push nut, 64e … top end protrusion, 64f … flange portion, 65 … sealing member, 65a … O ring, 65b … gasket, 66 …, … return spring, 68 … compression coil spring, 70 … holder, … holder body, 3671 a … lower surface, 3671 b … press-in hole, 56 c …, … longitudinal hole, … hole 72, … a … hole 72, … support …, … transverse hole 72, … bearing part transverse hole, … support part transverse part, Axis of L …, center line of M …, cross-sectional area of A0 … pressure equalizing hole, cross-sectional area of A1 … valve port, distance from H … to pressure equalizing hole, diameter of D1 … valve port.