Valve device

Abstract

To provide a valve device that can reliably perform the reciprocating motion of the needle valve body, as in a connected and fixed type, without causing problems due to misalignment of the central axis between the shaft and the needle valve body, as in a separated and pressed type. [Solution] A needle valve 1 comprises a linear stepping motor 31 equipped with a shaft 33 that performs linear motion of the shaft 33, an annular valve seat 24 having an axial direction parallel to the direction of linear motion of the shaft 33, and a needle valve body 41 that moves forward and backward in the same direction as the linear motion of the shaft 33 relative to the annular valve seat 24 in response to the linear motion of the shaft 33, wherein the shaft 33 and the needle valve body 41 are connected by a male threaded portion 331 provided on the shaft 33 and a female threaded portion 413 provided on the needle valve body 41 engaging with the axis of the male threaded portion 331 with a radial degree of freedom.

Description

Technical Field

[0001] The present invention relates to a valve device including a shaft, a drive source that linearly moves the shaft, an annular valve seat having an axial direction in a direction parallel to the direction of the linear movement, and a valve body that moves forward and backward in the same direction as the linear movement with respect to the annular valve seat in response to the linear movement.

Background Art

[0002] Conventionally, an electric flow control valve has been used for controlling the flow rate of fluids (such as compressed air and water) in general industrial machines. As the flow control valve, for example, a needle valve 100 shown in FIG. 6 and a needle valve 200 shown in FIG. 7 are known.

[0003] The needle valve 100 shown in FIG. 6 is formed such that a valve body 101 and a drive unit 102 are stacked vertically. This vertical direction is parallel to the direction in which the needle valve body moves forward and backward with respect to the annular valve seat.

[0004] The valve body 101 includes an input side flow path 103 for allowing a control fluid to flow into the valve body 101 and an output side flow path 104 for allowing the control fluid to flow out of the valve body 101. Further, the valve body 101 includes a valve chamber 105 inside thereof for connecting the input side flow path 103 and the output side flow path 104. Furthermore, the valve body 101 includes an annular valve seat 106 at a connection portion between the input side flow path 103 and the valve chamber 105.

[0005] A needle valve body 107 is installed in the valve chamber 105. The needle valve body 107 has a cylindrical main body portion 107a. The axial direction of the main body portion coincides with the direction of movement. The main body portion 107a is inserted through a guide portion 108 provided on the valve body 101, and the movement of the needle valve body 107 is guided by the guide portion 108. The space between the main body portion and the guide portion is sealed by an O-ring 115. The end of the main body portion 107a on the annular valve seat 106 side has a reduced diameter portion 107b that is narrowed toward the annular valve seat 106 side, and as the needle valve body 107 moves forward and backward in the vertical direction, the clearance between the outer circumferential surface of the reduced diameter portion 107b and the annular valve seat 106 (i.e., the opening degree of the needle valve 100) is increased or decreased.

[0006] The drive unit 102 comprises a cylinder housing 109 and a linear stepping motor 110 (hereinafter simply referred to as motor 110) fixed to the cylinder housing 109. The motor 110 has a shaft 111 that performs linear motion along the vertical direction. The shaft 111 is inserted into the cylinder housing 109. The tip of the shaft 111 is rigidly connected to the needle valve body 107 within the cylinder housing 109. Adhesive or nuts are used for this connection. Because the shaft 111 and the needle valve body 107 are connected as described above, when the shaft 111 is moved in the direction of protrusion (downward), the needle valve body 107 moves together with the shaft 111 in the direction of approaching the annular valve seat 106 (valve closing direction). On the other hand, when the shaft 111 is moved in the direction of retraction (upward), the needle valve body 107 is pulled up by the shaft 111 and moves in the direction of moving away from the annular valve seat 106 (valve opening direction). Since the shaft 111 and the needle valve body 107 are rigidly fixed, the needle valve body 107 reliably follows the movement of the shaft 111 and moves forward and backward.

[0007] Next, we will explain only the differences between the needle valve 200 shown in Figure 7 and the needle valve 100. In the needle valve 200, the shaft 112 of the motor 110 and the needle valve body 113 are not rigidly connected. The needle valve body 113 is biased toward the shaft 112 by a compression coil spring 114, maintaining contact between the upper end surface 113a of the needle valve body 113 and the tip surface 112a of the shaft 112. Therefore, when the shaft 112 is moved in the direction of protrusion (downward), the needle valve body 113 is pressed by the shaft 112 and moves in the valve closing direction against the elastic force of the compression coil spring 114. On the other hand, when the shaft 112 is moved in the direction of retraction (upward), the needle valve body 113 moves in the valve opening direction, following the shaft 112 due to the elastic force of the compression coil spring 114.

[0008] As described above, in the needle valves 100 and 200, the needle valve bodies 107 and 113 move forward and backward in response to the linear motion of the shafts 111 and 112. This forward and backward movement allows the clearance between the needle valve bodies 107 and 113 and the annular valve seat 106 to be adjusted (i.e., the opening degree of the needle valve can be adjusted), thereby making it possible to adjust the flow rate of the controlled fluid. In the following description, among the connection methods between the shafts 111 and 112 and the needle valve bodies 107 and 113, the type in which the shaft 111 and the needle valve body 107 are rigidly connected, as in the needle valve 100, is called the "fixed connection type," and the type in which the shaft 112 and the needle valve body 113 are not rigidly connected, but the contact state between the shaft 112 and the needle valve body 113 is maintained by a compression coil spring 114, as in the needle valve 200, is called the "separated contact type." As an example of a separate-press type needle valve, the needle valve disclosed in Patent Document 1 is known. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2006-153204 [Overview of the project] [Problems that the invention aims to solve]

[0010] The conventional method of connecting shafts 111 and 112 with needle valve bodies 107 and 113 described above had the following problems.

[0011] First, let's explain the problems with the fixed-connection type. In the needle valve 100 with the above configuration, it is desirable that the central axis of the needle valve body 107, which is inserted through the guide portion 108, and the central axis of the shaft 111 of the motor 110, which is fixed to the cylinder housing 109, be located coaxially. However, due to manufacturing tolerances, for example, it is possible that there is a misalignment between the central axis of the needle valve body 107 and the central axis of the shaft 111, and they are not located coaxially. When such a misalignment of the central axes occurs, if the shaft 111 and the needle valve body 107 are rigidly connected and the needle valve body 107 moves back and forth, the sliding resistance between the needle valve body 107 and the guide portion 108 increases, thus increasing the load on the motor 110. For this reason, a motor with more power, i.e., a larger motor, may be required. Furthermore, when such a misalignment of the central axes occurs, the entire circumference of the O-ring 115 will not be compressed uniformly, which raises concerns about reduced sealing performance and uneven wear.

[0012] Next, let's discuss the problems with the separate-press type. In the separate-press type, the problem caused by the misalignment of the central axis described above does not occur. However, since the movement of the needle valve body 113 in the opening direction relies on the elastic force of the compression coil spring 114, if the O-ring 115 becomes fixed to the inner circumferential surface of the guide portion 108, even if the shaft 112 moves in the pull-back direction, the elastic force of the compression coil spring 114 may not be able to move the needle valve body 113 in the opening direction. In other words, this may lead to a decrease in the accuracy of adjusting the opening degree of the needle valve 200, that is, a decrease in the accuracy of adjusting the flow rate of the control fluid. In order to reliably move the needle valve body 113 in the opening direction, it is conceivable to use a compression coil spring 114 with stronger elastic force, but this would require a motor 110 with stronger force to move the needle valve body 113 in the closing direction. This would lead to a larger motor 110, which is undesirable.

[0013] The present invention has been made in view of the above problems, and aims to provide a valve device that can reliably perform the reciprocating movement of the needle valve body, as in a connected and fixed type, without causing problems due to misalignment of the central axis between the shaft and the needle valve body, as in a separated and pressed type. [Means for solving the problem]

[0014] To solve the above problems, the valve device of the present invention has the following configuration.

[0015] (1) A valve device comprising a drive source having a shaft and performing linear motion of the shaft, an annular valve seat having an axial direction parallel to the direction of the linear motion, and a valve body that moves forward and backward in the same direction as the linear motion relative to the annular valve seat in response to the linear motion, wherein the shaft and the valve body are connected by a first engaging portion provided on the shaft and a second engaging portion provided on the valve body engaging with at least a degree of freedom perpendicular to the direction of the linear motion.

[0016] (2) In the valve device described in (1), it is preferable that the first engaging portion is either a male thread or a female thread, the second engaging portion is either a male thread or a female thread, the first engaging portion and the second engaging portion are screwed together with play, and the degree of freedom is ensured by the play.

[0017] (3) In the valve device described in (1) or (2), it is preferable that the first engaging portion and the second engaging portion are engaged with a degree of freedom in a direction parallel to the direction of the linear motion, and that a biasing member is provided for biasing the valve body toward the shaft.

[0018] (4) In the valve device according to any one of (1) to (3), it is preferable that a positioning groove is provided for positioning the drive source, the positioning groove is a cylindrical space formed coaxially with the annular valve seat, the drive source is located on the inner circumference side of the positioning groove and has a cylindrical positioning part formed coaxially with the shaft, and an annular elastic member is provided in the clearance between the inner circumferential surface of the positioning groove and the outer circumferential surface of the positioning part.

[0019] (5) In a valve device according to any one of (1) to (4), it is preferable that a guide portion is provided to guide the forward and backward movement, the guide portion is a cylindrical space formed coaxially with the annular valve seat, the valve body is provided with a cylindrical insertion portion that can be inserted into the guide portion, and an annular first elastic seal member and a second elastic seal member are positioned coaxially and in the same direction as the forward and backward movement in the clearance between the guide portion and the insertion portion.

[0020] In the valve device described in (6)(5), it is preferable that the first elastic seal member and the second elastic seal member are aligned in the same direction as the forward and backward movement at a distance greater than the stroke amount of the forward and backward movement.

[0021] (7)(2) In the valve device described above, it is preferable that the valve element includes a rotation prevention pin that protrudes in the radial direction from the axis of rotation to prevent rotation in the loosening direction of the screwing or the opposite direction.

[0022] (8)(7) In the valve device described above, it is preferable that the rotation prevention pin is an indicator that is exposed outside the valve device and allows visual recognition of the position of the valve element in the direction of the advancing and retreating movement.

Advantages of the Invention

[0023] According to the valve device of the present invention, it is possible to reliably perform the advancing and retreating movement of the needle valve element, like the connection fixed type, without causing problems due to misalignment between the shaft and the central axis of the needle valve element, such as in the separation pressing type.

Brief Description of the Drawings

[0024] [Figure 1] It is a cross-sectional view of the needle valve according to this embodiment, showing the state where the needle valve is in the maximum valve open state. [Figure 2] It is a cross-sectional view of the needle valve according to this embodiment, showing the state where the needle valve is in the valve closed state. [Figure 3] It is a plan view of the needle valve according to this embodiment. [Figure 4] It is a graph showing the flow rate characteristics of the needle valve according to this embodiment. [Figure 5] It is a graph showing the flow rate characteristics of the needle valve according to this embodiment when a compression coil spring is not used. [Figure 6] It is a cross-sectional view of a needle valve (connection fixed type) according to the prior art. [Figure 7] It is a cross-sectional view of a needle valve (separation pressing type) according to the prior art.

Modes for Carrying Out the Invention

[0025] A needle valve 1, which is an embodiment of the valve device according to the present invention, will be described in detail with reference to the drawings. Figure 1 is a cross-sectional view of the needle valve 1 according to this embodiment, showing the needle valve 1 in the fully open state. Figure 2 is a cross-sectional view of the needle valve 1 according to this embodiment, showing the needle valve 1 in the closed state. Figure 3 is a plan view of the needle valve 1 according to this embodiment (a view of the needle valve 1 in Figure 1 or Figure 2 from above). Note that the drawings used in this explanation are simplified for illustrative purposes and do not accurately represent the shape, dimensions, etc.

[0026] The needle valve 1 according to this embodiment is a valve device that adjusts the flow rate of a control fluid, such as compressed air or water.

[0027] (Regarding the structure of the needle valve) The needle valve 1 is configured such that the valve body 20 and the drive unit 30 are stacked vertically in the direction shown in Figures 1 and 2. This vertical direction is parallel to the direction in which the needle valve body 41 (an example of a valve body; details will be described later) moves back and forth relative to the annular valve seat 24 (details will be described later).

[0028] The drive unit 30 mainly consists of a linear stepping motor 31 (an example of a drive source) and a cylinder housing 32.

[0029] The cylinder housing 32 is formed into a roughly rectangular parallelepiped shape by machining using a metal material (e.g., aluminum, stainless steel, etc.) or a resin material. A protrusion 323 is provided on the outer peripheral edge of the end face (lower end face) of the cylinder housing 32 on the valve body 20 side, projecting toward the valve body 20 and engaging with the positioning recess 27 of the valve body 20. Alternatively, the cylinder housing 32 and the valve body 20 may be engaged by providing a recess in the cylinder housing 32 and a protrusion in the valve body 20.

[0030] The cylinder housing 32 has a cylindrical space called a housing portion 321, which extends from the lower end surface on the valve body 20 side to the opposite end surface (the upper end surface in the figure). The cylinder housing 32 also has a cylindrical space called a positioning groove 322, which extends from the upper end surface to the lower end surface, for positioning the motor 31. This positioning groove 322 is positioned coaxially with the annular valve seat 24 when the cylinder housing 32 is engaged with the valve body 20 by a protrusion 323. The housing portion 321 and the positioning groove 322 are connected by a through hole 324.

[0031] A linear stepping motor 31 (hereinafter simply referred to as motor 31) is fixed to the upper end surface of the cylinder housing 32 by a mounting bracket 34.

[0032] The motor 31 mainly consists of a cylindrical body 311, a shaft 33, a positioning unit 314, and a drive circuit 312 (see Figure 3).

[0033] The shaft 33 protrudes from the main body 311 towards the cylinder housing 32 and is inserted into the housing 55 of the cylinder housing 32. The shaft 33 moves linearly in the vertical direction by the drive circuit 312. The drive circuit 312 is provided on the outer circumferential surface of the main body 311, as shown in Figure 3. The drive circuit 312 receives the amount of movement (number of steps) of the shaft 33 from a higher-level control device (not shown) via a signal line 313. The drive circuit 312 then controls the linear motion of the shaft 33 based on the input number of steps.

[0034] Furthermore, a male threaded portion 331 (an example of a first engaging portion) is provided at the tip of the shaft 33, and the female threaded portion 413 of the needle valve body 41, which will be described later, is screwed onto the male threaded portion 331 with some play.

[0035] The positioning portion 314 is provided on the end face (lower end face) of the main body portion 311 on the cylinder housing 32 side. The positioning portion 314 is formed in a cylindrical shape and is located coaxially with the shaft 33. The positioning portion 314 is located on the inner circumference side of the positioning groove 322 of the cylinder housing 32, and an O-ring 76 (an example of an elastic member) with a wire diameter thicker than the size of the clearance between the inner circumference surface of the positioning groove 322 and the outer circumference surface of the positioning portion 314 is provided.

[0036] The valve body 20 is formed into a roughly rectangular parallelepiped shape by machining using a metal material (e.g., aluminum, stainless steel, etc.) or a resin material. A positioning recess 27 is provided on the outer circumferential edge of the end face (upper end face) of the valve body 20 on the drive unit 30 side, which engages with a protrusion 323 of the cylinder housing 32.

[0037] The valve body 20 includes an input-side passage 21 for the control fluid to flow into the valve body 20 and an output-side passage 23 for the control fluid to be output from the valve body 20. A valve chamber 22 is drilled on the upper end surface of the valve body 20, extending toward the lower end surface, along the central axis of the valve body 20. A valve hole 25 is provided at the bottom surface of the valve chamber 22, connecting the valve chamber 22 to the input-side passage 21, and an annular valve seat 24 is provided surrounding the valve hole 25. The valve chamber 22 communicates with the output-side passage 23 on the side. Therefore, the control fluid that flows in from the input-side passage 21 passes through the valve chamber 22 and is output from the output-side passage 23.

[0038] A needle valve body 41 is installed in the valve chamber 22. The needle valve body 41 is formed into a roughly cylindrical shape by injection molding or machining, and its material is, for example, a metal material (e.g., aluminum, stainless steel, etc.) or a resin material.

[0039] The needle valve body 41 includes a cylindrical main body portion 411 (an example of an insertion portion). The axial direction of the main body portion 411 coincides with the direction of advancement and retraction.

[0040] Of the axial ends of the main body 411 of the needle valve body 41, the end on the drive unit 30 side (the upper end in the figure) is located inside the drive unit 30. Furthermore, a female threaded portion 413 (an example of a second engaging portion) is drilled coaxially with the end face of the main body 411 on the drive unit 30 side (the upper end face in the figure). The male threaded portion 331 of the shaft 33 is screwed into the female threaded portion 413 with some play. This screwing connects the needle valve body 41 and the shaft 33, allowing the needle valve body 41 to move forward and backward in accordance with the linear motion of the shaft 33.

[0041] Furthermore, the aforementioned play includes backlash in the direction of linear motion and forward / backward motion (up and down direction), and play in the direction perpendicular to the vertical direction (i.e., radially relative to the axis of the male screw portion 331). Due to this play, the needle valve body 41 is connected to the shaft 33 with degrees of freedom in the vertical direction and the aforementioned vertical direction.

[0042] Of the axial ends of the main body 411 of the needle valve body 41, the end on the annular valve seat 24 side (lower end) is provided with a reduced diameter portion 412 that is narrowed toward the annular valve seat 24. The main body 411 is inserted through a guide portion 26 provided on the valve body 20, and the reciprocating movement of the needle valve body 41 is guided by the guide portion 26.

[0043] Since the guide portion 26 is provided coaxially with the annular valve seat 24 and the valve bore 25, when the needle valve body 41 moves back and forth along the guide portion 26, the reduced diameter portion 412 of the needle valve body 41 can move in and out of the valve bore 25. As the reduced diameter portion 412 moves in and out of the valve bore 25, the clearance between the outer surface of the reduced diameter portion 412 and the annular valve seat 24 (i.e., the opening degree of the needle valve 1) is increased or decreased.

[0044] Furthermore, an O-ring 65A (an example of a first elastic sealing member) and an O-ring 65B (an example of a second elastic sealing member) are provided between the guide portion 26 and the main body portion 411. This maintains a seal between the guide portion 26 and the main body portion 411.

[0045] O-rings 65A and 65B are made of the same material, and are arranged coaxially and in the same direction as the reciprocating movement of the needle valve body 41. Furthermore, grease is filled between O-rings 65A and 65B. This allows the needle valve body 41 to slide smoothly against the guide portion 26. In addition, the distance between O-rings 65A and 65B is set to be greater than the stroke amount of the reciprocating movement of the needle valve body 41. This prevents grease from leaking to the outside of O-rings 65A and 65B (i.e., above O-ring 65A or below O-ring 65B) when the needle valve body 41 moves back and forth.

[0046] The needle valve body 41 has an enlarged diameter portion 414 in the part that is inserted into the housing portion 55 of the cylinder housing 32, which has a larger diameter than the rest of the body. A compression coil spring 35 is compressed between the end face (lower end face) of the enlarged diameter portion 414 on the valve body 20 side and the upper end face of the valve body 20, and the compression coil spring 35 constantly biases the needle valve body 41 in the direction of the shaft 33 (upward in the figure).

[0047] Furthermore, a rotation prevention pin 36 and an origin detection pin 37 are provided protruding radially outward from the outer circumferential surface of the enlarged diameter portion 414.

[0048] The anti-rotation pin 36 is inserted into the groove 325 of the cylinder housing 32. This prevents the needle valve body 41 from rotating in the direction of loosening the threads between the male thread portion 331 and the female thread portion 413, or in the opposite direction. This prevents fluctuations in the vertical position of the needle valve body 41 relative to the shaft 33, thereby improving the reliability of the opening degree control of the needle valve 1.

[0049] Furthermore, the tip of the anti-rotation pin 36 protrudes outward from the groove 325 to the needle valve 1 and is visible from outside the needle valve 1 through the opening 326 of the cylinder housing 32. Therefore, the anti-rotation pin 36 functions as an indicator that allows the position of the needle valve body 41 in the direction of forward and backward movement to be visually confirmed.

[0050] The origin detection pin 37 is used to set the origin position of the needle valve body 41 in the forward and backward direction. Specifically, it works as follows: A photosensor 38 fixed to the side of the cylinder housing 32 includes a detection unit 381 inserted inside the cylinder housing 32. When the vertical position of the origin detection pin 37 coincides with the position of the detection unit 381, the detection unit 381 detects the origin detection pin 37. The position of the needle valve body 41 at this time is set as the origin position. The position of the needle valve body 41 in the forward and backward direction is then controlled by its relative position from the origin position.

[0051] Conventionally, it was common for a single pin to be provided on the needle valve body, and this pin would have both the functions of an anti-rotation pin 36 and an origin detection pin 37. However, the anti-rotation pin 36 slides against the groove 325 as the needle valve body 41 moves back and forth, and there is a risk of generating wear particles. If both functions are given to a single pin, there is a problem that the wear particles may cause false detection by the photosensor. On the other hand, the needle valve 1 according to this embodiment has a separate anti-rotation pin 36 for preventing rotation and an origin detection pin 37 for detecting the origin, thus resolving the above problem.

[0052] Furthermore, the anti-rotation pin 36 and the origin detection pin 37 are made of the same material and are arranged at a 180-degree interval in the circumferential direction of the enlarged diameter portion 414. Therefore, both pins 36 and 37 can be used as either an anti-rotation pin or an origin detection pin. Consequently, there is no need to consider the direction of the needle valve body 41 when assembling the needle valve 1.

[0053] (Regarding the connection between the shaft and the needle valve body) The needle valve 1, having the configuration described above, can connect the shaft 33 and the needle valve body 41 while minimizing the misalignment between the central axis of the shaft 33 and the central axis of the needle valve body 41. This is because, during the assembly of the needle valve 1, the motor 31 is positioned so that the shaft 33 is coaxial with the annular valve seat 24, and the needle valve body 41 (main body 411) is positioned so that it is coaxial with the annular valve seat 24. Specifically, this is as follows.

[0054] First, let's explain the positioning of the motor 31. When the motor 31 is installed on the upper end surface of the cylinder housing 32 (before fixing with the mounting bracket 34), the positioning portion 314 of the motor 31 is positioned concentrically with respect to the positioning groove 322 of the cylinder housing 32 by the elastic force of the O-ring 76. Since the positioning portion 314 is located coaxially with the shaft 33, the positioning portion 314 being concentric with respect to the positioning groove 322 means that the positioning groove 322 and the shaft 33 are located coaxially. Furthermore, since the positioning groove 322 is located coaxially with the annular valve seat 24 when the convex portion 323 of the cylinder housing 32 is engaged with the valve body 20, the shaft 33, which is located coaxially with the positioning groove 322, is also located coaxially with the annular valve seat 24. As described above, the motor 31 is positioned so that the shaft 33 is coaxial with the annular valve seat 24 by the elastic force of the O-ring 76, and then fixed to the upper end surface of the cylinder housing 32 by the mounting bracket 34.

[0055] Next, the positioning of the needle valve body 41 will be described. When the needle valve body 41 is inserted into the guide portion 26, the elastic force of the O-rings 65A and 65B positions the needle valve body 41 (main body portion 411) concentrically with respect to the guide portion 26. Since the guide portion 26 is located coaxially with the annular valve seat 24, the concentric positioning of the needle valve body 41 (main body portion 411) with respect to the guide portion 26 results in the needle valve body 41 (main body portion 411) being located coaxially with the annular valve seat 24. As described above, the elastic force of the O-rings 65A and 65B positions the needle valve body 41 (main body portion 411) so that it is located coaxially with the annular valve seat 24. Furthermore, since the O-rings 65A and 65B, which are identical components, are arranged coaxially and in the same direction as the reciprocating movement of the needle valve body 41, the needle valve body 41 can be positioned without its central axis tilting in the vertical direction.

[0056] In this way, the motor 31 is positioned so that the shaft 33 is coaxial with the annular valve seat 24, and the needle valve body 41 (main body 411) is positioned so that it is coaxial with the annular valve seat 24. Therefore, it is possible to connect the shaft 33 and the needle valve body 41 while minimizing the misalignment between the central axis of the shaft 33 and the central axis of the needle valve body 41.

[0057] However, due to manufacturing tolerances, there may be a misalignment between the central axis of the shaft 33 and the central axis of the needle valve body 41, and they may not be positioned coaxially. However, since the needle valve body 41 has a degree of freedom relative to the shaft 33 in the direction perpendicular to the vertical direction in Figures 1 and 2 (i.e., radially relative to the central axis of the male screw portion 331), this degree of freedom can absorb the misalignment of the central axis.

[0058] As described above, it is possible to connect the shaft 33 and the needle valve body 41 while minimizing the misalignment between the central axis of the shaft 33 and the central axis of the needle valve body 41. Furthermore, the degree of freedom that the needle valve body 41 has relative to the shaft 33 allows it to absorb the misalignment of the central axis, thus preventing problems caused by the misalignment of the central axis. Problems caused by the misalignment of the central axis include increased load on the motor 31 due to increased sliding resistance between the needle valve body 41 and the guide portion 26, and reduced sealing performance and uneven wear due to the O-rings 65A and 65B not being compressed uniformly around their entire circumference.

[0059] (Regarding the operation of the needle valve) The needle valve 1 operates as follows. First, the operation to reduce the opening of the needle valve 1 will be explained. As described above, the shaft 33 of the motor 31 is controlled based on the number of steps input to the drive circuit 312. When the shaft 33 is moved in the direction of protrusion (downward in Figure 1), the needle valve body 41 moves together with the shaft 33 in the direction of approaching the annular valve seat 24 (closed direction). As a result, the clearance between the reduced diameter portion 412 of the needle valve body 41 and the annular valve seat 24 (opening of the needle valve 1) is reduced, and the flow rate of the control fluid flowing out to the output side flow path 23 decreases.

[0060] Next, the operation to increase the opening degree of the needle valve 1 will be described. The shaft 33 of the motor 31 is controlled based on the number of steps input to the drive circuit 312, similar to the case when decreasing the opening degree. When the shaft 33 is moved in the pull-back direction (upward in Figures 1 and 2), the needle valve body 41 is pulled up by the shaft 33 and moves in a direction away from the annular valve seat 24 (opening direction). At this time, even if the O-rings 65A and 65B are fixed to the inner circumferential surface of the guide portion 26, the shaft 33 and the needle valve body 41 are connected by the screwing of the male thread portion 331 and the female thread portion 413, so the shaft 33 can reliably pull up the needle valve body 41. When the needle valve body 41 moves in the opening direction, the clearance between the reduced diameter portion 412 of the needle valve body 41 and the annular valve seat 24 (opening degree of the needle valve 1) increases, and the flow rate of the control fluid flowing out to the output side flow path 23 increases.

[0061] The connection between the shaft 33 and the needle valve body 41 is made by screwing together a male threaded portion 331 and a female threaded portion 413. As a result, there is play (backlash) in the direction of the needle valve body 41's forward and backward movement (up and down direction) relative to the shaft 33. Therefore, there is a concern that the forward and backward movement of the needle valve body 41 will lag behind the linear movement of the shaft 33 by the amount of backlash. However, the needle valve 1 according to this embodiment is equipped with a compression coil spring 35, and the needle valve body 41 is constantly biased in the direction of the shaft 33 by the compression coil spring 35 (it should also be noted that it is also biased in the direction of the shaft 33 by the fluid pressure of the control fluid flowing in from the input side passage 21). Therefore, the forward and backward movement of the needle valve body 41 is performed without lag behind the linear movement of the shaft 33, just as in the fixed-connection type needle valve 100 (see Figure 6). Therefore, it is possible to prevent a decrease in the accuracy of flow rate adjustment of the control fluid due to a delay in the reciprocating movement of the needle valve body 41.

[0062] The prevention of a decrease in the accuracy of this flow rate adjustment will be further explained using the graphs shown in Figures 4 and 5. Figure 4 is a graph showing the flow rate characteristics of the needle valve 1 according to this embodiment. Figure 5 is a graph showing the flow rate characteristics of the needle valve 1 according to this embodiment when the compression coil spring 35 is not used. In both graphs, the vertical axis "flow rate" represents the flow rate of the control fluid output from the needle valve 1, and the horizontal axis "valve opening degree" is the command value (number of steps) of the opening degree input to the drive circuit 312. Note that the plots labeled "during valve closing operation" in the graphs show the fluctuation in the flow rate of the control fluid when the needle valve 1 is operated from the maximum valve open state (opening degree 100%) to the valve closed state (opening degree 0%), and the plots labeled "during valve opening operation" show the fluctuation in the flow rate of the control fluid when the needle valve 1 is operated from the valve closed state (opening degree 0%) to the maximum valve open state (opening degree 100%).

[0063] In the needle valve 1 according to this embodiment, as shown in Figure 4, the plots for the valve closing operation and the plots for the valve opening operation almost overlap, and hysteresis is reduced. Therefore, regardless of whether the valve is opening or closing, the flow rate corresponding to the specified opening degree can be accurately obtained. Specifically, for example, if an opening degree of 40% is specified, regardless of whether that opening degree is obtained by opening or closing the valve, a flow rate of approximately 15 L / min corresponding to a 40% opening degree can be accurately obtained. In other words, the accuracy of flow rate adjustment of the control fluid is ensured.

[0064] On the other hand, when the compression coil spring 35 is not used, as shown in Figure 5, the flow rate characteristics during valve closing are almost the same as those of the needle valve 1 according to this embodiment, but the flow rate during valve opening is less than that during valve opening. This is thought to be because, due to backlash, the needle valve body 41 cannot keep up with the movement of the shaft 33 in the pull-back direction, and the actual opening is smaller than the commanded opening. When such hysteresis occurs, the resulting flow rate changes depending on whether the needle valve 1 operates to the opening specified by the valve opening operation or to the opening specified by the valve closing operation. In other words, this leads to a decrease in the accuracy of flow rate adjustment of the controlled fluid, which is undesirable.

[0065] (Regarding the effects and benefits) As explained above, according to the needle valve 1 of this embodiment, (1) A valve device (needle valve 1) comprising a shaft 33 and a drive source (e.g., a linear stepping motor 31) that performs linear motion of the shaft 33, an annular valve seat 24 having an axial direction parallel to the direction of linear motion of the shaft 33, and a valve body (e.g., a needle valve body 41) that moves forward and backward in the same direction as the linear motion of the shaft 33 relative to the annular valve seat 24 in response to the linear motion of the shaft 33, characterized in that the shaft 33 and the valve body (needle valve body 41) are connected by a first engaging portion (e.g., a male screw portion 331) provided on the shaft 33 and a second engaging portion (e.g., a female screw portion 413) provided on the valve body (needle valve body 41) engaging with a degree of freedom at least perpendicular to the direction of linear motion of the shaft 33 (e.g., radially with respect to the axis of the male screw portion 331).

[0066] (2) In the valve device (needle valve 1) described in (1), it is preferable that the first engaging portion is either a male thread or a female thread (male thread portion 331), the second engaging portion is the other of the male thread or a female thread (female thread portion 413), the first engaging portion (male thread portion 331) and the second engaging portion (female thread portion 413) are screwed together with some play, and the degree of freedom is ensured by the play.

[0067] It is desirable that the central axis of the shaft 33 and the central axis of the needle valve body 41 be coaxially positioned. However, due to manufacturing tolerances and other factors, a misalignment may occur between the central axis of the shaft 33 and the central axis of the needle valve body 41, resulting in them not being coaxially positioned. However, with the above-described valve device (needle valve 1), the first engaging portion (male threaded portion 331) and the second engaging portion (female threaded portion 413) have degrees of freedom at least perpendicular to the direction of linear motion of the shaft 33 (radial direction with respect to the axis of the male threaded portion 331). This degree of freedom allows for the absorption of the misalignment of the central axis. In this embodiment, the first engaging portion is a male thread (male threaded portion 331) and the second engaging portion is a female thread (female threaded portion 413). However, the first engaging portion may be a female thread and the second engaging portion may be a male thread, with the first and second engaging portions being engaged.

[0068] (3) In the valve device (needle valve 1) described in (1) or (2), it is preferable that the first engaging portion (male thread portion 331) and the second engaging portion (female thread portion 413) are engaged with a degree of freedom (e.g., backlash) in a direction parallel to the direction of linear motion of the shaft 33, and that a biasing member (e.g., compression coil spring 35) is provided for biasing the valve body (needle valve body 41) toward the shaft 33.

[0069] According to the valve device (needle valve 1) described above, hysteresis due to degrees of freedom (backlash) can be reduced in a direction parallel to the direction of linear motion of the shaft 33, thereby preventing a decrease in the accuracy of flow rate adjustment of the controlled fluid.

[0070] (4) In the valve device (needle valve 1) described in any one of (1) to (3), it is preferable that a positioning groove 322 is provided for positioning the drive source (linear stepping motor 31), the positioning groove 322 is a cylindrical space formed coaxially with the annular valve seat 24, the drive source (linear stepping motor 31) is located on the inner circumference side of the positioning groove 322 and has a cylindrical positioning part 314 formed coaxially with the shaft 33, and an annular elastic member (O-ring 76) is provided in the clearance between the inner circumferential surface of the positioning groove 322 and the outer circumferential surface of the positioning part 314.

[0071] Since the valve body (needle valve body 41) moves back and forth relative to the annular valve seat 24, it is desirable that the central axis of the valve body (needle valve body 41) and the central axis of the shaft 33 be located coaxially with the annular valve seat 24. With the above valve device (needle valve 1), it is possible to position the central axis of the shaft 33 coaxially with the annular valve seat 24. Specifically, the positioning part 314 is positioned concentrically with respect to the positioning groove 322 by the elastic force of the elastic member (O-ring 76). Since the positioning part 314 is located coaxially with the shaft 33, the positioning part 314 being positioned concentrically with respect to the positioning groove 322 results in the positioning groove 322 and the shaft 33 being located coaxially. Furthermore, since the positioning groove 322 is located coaxially with the annular valve seat 24, the shaft 33, which is located coaxially with the positioning groove 322, is also located coaxially with the annular valve seat 24.

[0072] (5) In a valve device (needle valve 1) described in any one of (1) to (4), it is preferable that the valve device (needle valve 1) is provided with a guide portion 26 that guides the reciprocating movement of the valve body (needle valve body 41), the guide portion 26 is a cylindrical space formed coaxially with the annular valve seat 24, the valve body (needle valve body 41) is provided with a cylindrical insertion portion (e.g., main body portion 411) that can be inserted into the guide portion 26, and that an annular first elastic seal member (e.g., O-ring 65A) and a second elastic seal member (e.g., O-ring 65B) are positioned coaxially and in the same direction as the reciprocating movement of the valve body (needle valve body 41) in the clearance between the guide portion 26 and the insertion portion (main body portion 411).

[0073] Since the valve body (needle valve body 41) moves back and forth relative to the annular valve seat 24, it is desirable that the central axis of the valve body (needle valve body 41) and the central axis of the shaft 33 be located coaxially with the annular valve seat 24. With the above valve device (needle valve 1), it is possible to position the central axis of the valve body (needle valve body 41) coaxially with the annular valve seat 24. Specifically, when the needle valve body 41 (main body 411) is inserted into the guide portion 26, the insertion portion (main body 411) is positioned concentrically with respect to the guide portion 26 due to the elastic force of the first elastic sealing member (O-ring 65A) and the second elastic sealing member (O-ring 65B). Since the guide portion 26 is located coaxially with the annular valve seat 24, the needle valve body 41 (main body 411) is positioned concentrically with respect to the guide portion 26, which means that the needle valve body 41 (main body 411) is located coaxially with the annular valve seat 24. Furthermore, since the first elastic sealing member (O-ring 65A) and the second elastic sealing member (O-ring 65B) are arranged coaxially and in the same direction as the reciprocating movement of the needle valve body 41, the needle valve body 41 can be positioned without its central axis tilting with respect to the direction of its reciprocating movement.

[0074] In the valve device (needle valve 1) described in (6)(5), it is preferable that the first elastic sealing member (O-ring 65B) and the second elastic sealing member (O-ring 65B) are aligned in the same direction as the reciprocating movement of the valve body (needle valve body 41) at a distance greater than the stroke amount of the reciprocating movement of the valve body (needle valve body 41).

[0075] In order to ensure the sliding properties of the valve body (needle valve body 41) during its forward and backward movement, when a lubricant (e.g., grease) is filled between the first elastic seal member (O-ring 65B) and the second elastic seal member (O-ring 65B), the above-described valve device (needle valve 1) can prevent the lubricant from leaking out of the first elastic seal member (O-ring 65B) and the second elastic seal member (O-ring 65B) due to the forward and backward movement of the needle valve body 41.

[0076] In the valve device (needle valve 1) described in (7)(2), it is preferable that the valve body (needle valve body 41) is provided with a rotation prevention pin 36 that protrudes radially from the axis of rotation (central axis of the needle valve body 41) to prevent it from rotating in the direction of loosening of the screw or in the opposite direction.

[0077] In the valve device (needle valve 1) described in (8)(7), it is preferable that the rotation prevention pin 36 is exposed to the outside of the valve device (needle valve 1) and serves as an indicator that allows the position of the valve body (needle valve body 41) in the direction of the reciprocating movement of the valve body (needle valve body 41) to be visually confirmed.

[0078] According to the valve device (needle valve 1) described above, the rotation prevention pin 36 prevents the needle valve body 41 from rotating in the direction of loosening the threads between the male thread portion 331 and the female thread portion 413 or in the opposite direction, thereby preventing fluctuations in the vertical position of the needle valve body 41 relative to the shaft 33. Therefore, the reliability of the opening degree control of the needle valve 1 is improved.

[0079] The above embodiments are merely illustrative and do not limit the present invention in any way. Therefore, the present invention can naturally be improved and modified in various ways without departing from its essence. For example, in this embodiment, a male threaded portion 331 is exemplified as the first engaging portion and a female threaded portion 413 is exemplified as the second engaging portion, but the invention is not limited to these. For example, a cylindrical protrusion projecting from the shaft 33 toward the needle valve body 41 may be provided as the first engaging portion, and a recess into which the protrusion can be inserted may be provided as the second engaging portion, and the shaft 33 and the needle valve body 41 may be connected by inserting a retaining pin from a direction perpendicular to the axial direction of the shaft 33 with the protrusion inserted into the recess.

[0080] In this embodiment, an O-ring 76 is exemplified as the elastic member, an O-ring 65A as the first elastic sealing member, and an O-ring 65B as the second elastic sealing member, but a sealing member such as a square packing may also be used. [Explanation of Symbols]

[0081] 1. Needle valve (an example of a valve device) 24 Annular valve seat 31. Linear stepping motor (an example of a drive source) 33 shafts 41 Needle valve body (an example of a valve body) 331 Male threaded portion (an example of the first engaging portion) 413 Female thread portion (an example of the second engagement portion)

Claims

1. A drive source comprising a shaft and performing linear motion of the shaft, An annular valve seat having an axial direction parallel to the direction of the aforementioned linear motion, In response to the aforementioned linear motion, a valve body moves back and forth in the same direction as the linear motion relative to the annular valve seat, In a valve device equipped with, The shaft and the valve body are connected by a first engaging portion provided on the shaft and a second engaging portion provided on the valve body, which engage with each other with a degree of freedom perpendicular to the direction of the linear motion. A valve device characterized by the following.

2. In the valve device according to claim 1, The first engaging portion is either a male thread or a female thread. The second engaging portion is either a male thread or a female thread. The first engaging portion and the second engaging portion are screwed together with some play, and the degree of freedom is ensured by this play. A valve device characterized by the following.

3. In the valve device according to claim 1 or 2, The first engaging portion and the second engaging portion are engaged with a degree of freedom in a direction parallel to the direction of the linear motion. The valve body is provided with a biasing member for biasing it toward the shaft. A valve device characterized by the following.

4. In the valve device according to claim 1 or 2, The drive source is provided with a positioning groove for positioning the drive source. The positioning groove is a cylindrical space formed coaxially with the annular valve seat. The drive source is located on the inner circumference side of the positioning groove and includes a cylindrical positioning part formed coaxially with the shaft. The clearance between the inner circumferential surface of the positioning groove and the outer circumferential surface of the positioning portion is provided with an annular elastic member. A valve device characterized by the following.

5. In the valve device according to claim 1 or 2, It is equipped with a guide section that guides the aforementioned forward and backward movement. The guide portion is a cylindrical space formed coaxially with the annular valve seat. The valve body is provided with a cylindrical insertion portion that can be inserted into the guide portion. The clearance between the guide portion and the insertion portion is provided by an annular first elastic sealing member and a second elastic sealing member, positioned coaxially and aligned in the same direction as the forward and backward movement. A valve device characterized by the following.

6. In the valve device according to claim 5, The first elastic sealing member and the second elastic sealing member are aligned in the same direction as the forward and backward movement, with a distance greater than the stroke amount of the forward and backward movement. A valve device characterized by the following.

7. In the valve device according to claim 2, The valve body is equipped with an anti-rotation pin that protrudes radially from the axis of rotation to prevent rotation in the direction of loosening of the screw or in the opposite direction. A valve device characterized by the following.

8. In the valve device according to claim 7, The anti-rotation pin is exposed to the outside of the valve device and serves as an indicator that allows the position of the valve body in the direction of the forward and backward movement to be visually confirmed. A valve device characterized by the following.

Images