valve body and valve stem connection structure

Abstract

This invention provides a valve body and valve stem connection structure that allows for preventing loosening of the threaded portion with a simple structure, and allows for loosening of the threaded portion as needed. [Solution] The valve comprises a threaded portion 4 connecting the plug 2 (valve body) and the stem 3 (valve shaft), and a pin 5 that crosses the plug 2 and the stem 3. The plug 2, which has a female thread 7, has an annular groove 12. The stem 3, which has a male thread 8, has a pin hole 24 that extends in a direction perpendicular to the axial direction of the female thread 7 and into which the pin 5 fits. The pin hole 24 extends tangentially to the annular groove 12 through the annular groove 12 with the male thread 8 screwed into the female thread 7. The groove wall surface 12a of the annular groove 12 has a semicircular cross-section and is formed in a shape into which the outer circumferential surface of the pin 5 fits.

Description

Technical Field

[0001] The present invention relates to a connection structure between a valve body and a valve shaft having a locking mechanism in a screw portion for fixing the valve body and the valve shaft.

Background Art

[0002] Conventionally, as a control valve, there is one in which a stem as a valve shaft is screwed into a plug as a valve body and fastened, and the stem is connected to an actuator to drive the plug. When the stem and the plug are fastened by a screw, in order to prevent the screw portion from loosening due to vibration or heat during use, a locking mechanism is provided. As a method of locking, there are a method of driving a taper pin after screwing the stem into the plug to restrict the rotation of both, and a method of welding both after screwing the plug into the stem.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the above-described locking mechanism is provided at the fastening portion between the stem and the plug, if the stem or the plug is damaged, only one of them cannot be replaced, and both of them must be remanufactured. In the case of a bellows valve in which a bellows is welded to the stem, since the bellows is an expensive part, the problem is that only the plug cannot be replaced. Although it is possible to remove the plug from the stem by using a spring pin instead of a taper pin, there is a risk that the spring pin will come out and loosen due to vibration during use.

[0005] One example of a control valve that uses a loosening prevention mechanism while allowing only the plug to be replaced is described in Patent Document 1. In this control valve, a pin is passed through a notch formed on the outer circumference of the plug so as to extend axially, and a through hole that penetrates the stem radially, thereby preventing the threaded portion from loosening. The notch and through hole are formed at multiple positions arranged at predetermined intervals in the circumferential direction of the plug.

[0006] In the control valve shown in Patent Document 1, the plug can be replaced by removing the pin, rotating the stem relative to the plug, and loosening the threaded portion. However, in this control valve, it is necessary to align the notch and the through hole when assembling the stem to the plug, and it is necessary to provide the notch and through hole at multiple positions in the circumferential direction to facilitate alignment.

[0007] The object of the present invention is to provide a connection structure between a valve body and a valve stem that can prevent loosening of the threaded portion with a simple structure and can loosen the threaded portion as needed. [Means for solving the problem]

[0008] To achieve this objective, the valve body and valve stem connecting structure according to the present invention comprises a threaded portion provided on the valve body and valve stem of the valve to connect the valve body and the valve stem, and a cylindrical pin that crosses the valve body and the valve stem. The member of the valve body and valve stem on which the male thread of the threaded portion is formed has an annular groove, and the member of the valve body and valve stem on which the female thread of the threaded portion is formed has a pin hole that extends in a direction perpendicular to the axial direction of the female thread and into which the pin fits. The pin hole is formed to extend through the annular groove in the tangential direction of the annular groove when the male thread is screwed into the female thread, and the groove wall surface of the annular groove is semicircular in cross-section when viewed from a direction perpendicular to the circumferential direction of the annular groove, and is formed in a shape into which the outer surface of the pin fits.

[0009] In the present invention, in a connecting structure between the valve body and the valve stem, the member on which the male thread is formed has a stopper that, when the male thread is screwed into the female thread, comes into contact with the member on which the female thread is formed, thereby restricting further screwing, and the state in which the male thread is screwed into the female thread may be the state in which the stopper comes into contact with the member on which the female thread is formed.

[0010] The present invention relates to a connection structure between a valve body and a valve stem, wherein the female screw is formed in a threaded hole consisting of a non-through hole opening at one end of the member on which the female screw is formed, a female screw portion on which the female screw is formed is provided on the opening side of the threaded hole, a circular recess is provided on the side of the threaded hole beyond the female screw portion, the pin hole is formed so as to cross the circular recess of the threaded hole, the member on which the male screw is formed has the male screw and a columnar portion formed on the tip side of the male screw, the columnar portion is formed in a shape that fits into the circular recess, and the annular groove may be formed in the columnar portion of the member on which the male screw is formed.

[0011] The present invention relates to a connection structure between a valve body and a valve stem, wherein the female thread is formed in a threaded hole consisting of a non-through hole opening at one end of the member on which the female thread is formed, a hole portion consisting of a circular hole with a constant diameter is provided on the opening side of the threaded hole, the female thread portion on the inner side of the threaded hole is provided, the pin hole is formed so as to cross the hole portion of the threaded hole, the member on which the male thread is formed has the male thread located at the tip and a columnar portion located on the base side of the male thread, the columnar portion is formed in a shape that fits into the hole, and the annular groove may be formed in the columnar portion of the member on which the male thread is formed.

[0012] In the present invention, in the connection structure between the valve body and the valve stem, the pin may have knurling on its outer circumference. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a connection structure between a valve body and a valve stem that can prevent loosening of the threaded portion with a simple structure and allows the threaded portion to be loosened as needed. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a front view showing the connection structure between the valve body and the valve stem according to the first embodiment. [Figure 2] Figure 2 is a front view of the plug and stem, showing a portion of the plug broken away. [Figure 3] Figure 3 is a cross-sectional view showing an enlarged view of the main part. [Figure 4] Figure 4 is a cross-sectional view taken along line IV-IV in Figure 1. [Figure 5] Figure 5 shows the front and side views of the pin. [Figure 6] Figure 6 is a cross-sectional view showing the connection structure between the valve body and the valve stem according to the second embodiment. [Figure 7] Figure 7 is a cross-sectional view showing the connection structure between the valve body and the valve stem according to the third embodiment. [Figure 8] Figure 8 is a cross-sectional view showing the connection structure between the valve body and the valve stem according to the fourth embodiment. [Modes for carrying out the invention]

[0015] (First Embodiment) Hereinafter, one embodiment of the valve body and valve stem connection structure according to the present invention will be described in detail with reference to Figures 1 to 5. In this embodiment, an example of applying the valve body and valve stem connection structure according to the present invention to a control valve will be described. The valve body and valve stem connecting structure 1 shown in Figure 1 (hereinafter simply referred to as connecting structure 1) is a structure that connects the plug 2, which is the valve body depicted in the lower half of Figure 1, and the stem 3, which is the valve stem depicted in the upper half of Figure 1. The connecting structure 1 according to this embodiment includes a threaded portion 4 provided on the plug 2 and the stem 3 to connect the plug 2 and the stem 3, and a cylindrical pin 5 that crosses the plug 2 and the stem 3. The plug 2 and the stem 3 constitute the valve part of the control valve 6, and are connected to each other by the screw part 4 and used in an integrated state. The materials forming the plug 2 and the stem 3 are metals.

[0016] As shown in FIG. 2, the screw part 4 according to this embodiment is composed of an internal thread 7 formed on the plug 2 and an external thread 8 formed on the stem 3. Among the plug 2 and the stem 3, the stem 3 on which the external thread 8 is formed is formed in a shape that is entirely columnar, and includes a columnar part 11 that is columnar and formed on the tip side of the external thread 8, and an annular groove 12 formed at a part of the columnar part close to the external thread 8, and a shaft part 13 formed on the side opposite to the annular groove 12 from the external thread 8. The shaft part 13 is formed such that its outer diameter is larger than that of the external thread 8, penetrates through the ring 14 as shown in FIG. 1, passes through the inside of the bellows 15, extends to the side opposite to the external thread 8, and is connected to the actuator 16 of the control valve 6. The ring 14 is formed in an annular shape into which the shaft part 13 fits and is welded to the shaft part 13, and one end part of the bellows 15 is welded thereto. The other end part of the bellows 15 is detachably fixed to a shaft seal part (not shown) of the control valve 6 via a seal member.

[0017] The annular groove 12 is a groove that extends without interruption in the circumferential direction of the stem 3. As shown in FIG. 3, the groove wall surface 12a of the annular groove 12 is formed in a semi-circular cross-section when viewed from a direction orthogonal to the circumferential direction of the annular groove 12. The radius of curvature of the arc of the semi-circular cross-section forming the groove wall surface 12a is formed to coincide with the radius of curvature of the outer peripheral surface of the pin 5. The groove wall surface 12a of the annular groove 12 according to this embodiment is formed in a shape in which the outer peripheral surface of the pin 5 fits in a press-fitted state. As shown in Fig. 3, the shaft portion 13 of the stem 3 is formed so as to abut against the end face 2a of the plug 2 in a state where the male screw 8 is screwed into the female screw 7 of the plug 2 by a specified amount. For this reason, the shaft portion 13 constitutes a stopper 18 that abuts against the plug 2 when the male screw 8 is screwed into the female screw 7 and restricts further screwing. In this embodiment, when the shaft portion 13 abuts against the end face 2a of the plug 2, the male screw 8 is screwed into the female screw 7.

[0018] The plug 2 has a disk-shaped main body portion 21 drawn at the bottom in Fig. 2 and a cylindrical connecting portion 22 protruding from the main body portion 21. The main body portion 21 comes into contact with and separates from a valve seat (not shown) by reciprocating in the axial direction. A threaded hole 23 having the above-described female screw 7 is formed at the end of the connecting portion 22 of the plug 2 on the side opposite to the main body portion 21. The threaded hole 23 is a non-through hole that opens at the end face 2a, which is one end of the plug 2, and extends in the axial direction of the plug 2. A female screw portion 23a having the female screw 7 is provided on the opening side of the threaded hole. A circular recess 23b is provided on the back side of the female screw portion 23a in the threaded hole.

[0019] The columnar portion 11 located at the tip of the stem 3 is formed in a shape that fits into the circular recess 23b. A pin hole 24 formed of a through hole is formed at the boundary portion of the circular recess 23b with the female screw portion 23a. The opening shape of the pin hole 24 is circular. The diameter of the pin hole 24 is the diameter into which the pin 5 fits in a press-fitted state. That is, the radius of curvature of the circle forming the cross-sectional shape of the hole wall of the pin hole 24 coincides with the radius of curvature of the arc forming the cross-sectional shape of the groove wall of the annular groove 12.

[0020] The pin hole 24 is formed so as to cross the circular recess 23b and extends in a direction orthogonal to the axial direction of the female screw 7 (the axial direction of the plug 2) as shown in Fig. 4. The pin hole 24 according to this embodiment penetrates the plug 2 in a direction orthogonal to the axial direction of the female screw 7. As shown in Figure 3, the position of the pin hole 24 in the axial direction (up and down direction in Figure 3) of the plug 2 is such that, when the male thread 8 of the stem 3 is screwed into the female thread 7 of the plug 2 (with the shaft portion 13 in contact with the plug 2), the pin hole 24 extends tangentially through the annular groove 12 of the stem 3. More specifically, when the portion of the pin hole 24 that crosses the annular groove 12 is viewed from a direction perpendicular to the longitudinal direction of the pin hole 24, the groove wall surface 12a of the annular groove 12 and the hole wall surface 24a of the pin hole 24 face each other, forming a circular opening. This circular opening is continuous with the pin hole 24 without any steps.

[0021] As shown in Figures 5(A) and (B), the pin 5 is formed in a cylindrical shape of a predetermined length. Figure 5(A) is a front view of the pin 5, and Figure 5(B) is a side view of the pin 5. The pin 5 in this embodiment has knurling on its outer surface. The knurling is performed to create irregularities on the outer surface of the pin 5, preventing it from coming loose due to frictional resistance when inserted into the pin hole 24. Figures 5(A) and (B) show an example of a knurled pin 5, in which numerous protrusions 25 are formed on the outer surface. The protrusions 25 extend from one end to the other in the longitudinal direction of the pin 5 and are formed at multiple positions arranged at equal intervals in the circumferential direction on the outer surface of the pin 5. Note that the irregularities formed by the knurling are not limited to the numerous protrusions 25 shown in Figures 5(A) and (B), and can be changed as appropriate. The annular groove 12 and the pin hole 24 are formed such that the pin 5 fits into them in a press-fit state where the protruding end of the convex part formed by knurling is slightly elastically or plastically deformed.

[0022] To connect the stem 3 to the plug 2 using the connecting structure 1 configured as described above, the tip portion (columnar portion 11) of the stem 3 is inserted into the threaded hole 23 of the plug 2, and the male thread 8 is screwed into the female thread 7. As the male thread 8 is screwed into the female thread 7, the columnar portion 11 of the stem 3 fits into the circular recess 23b of the threaded hole 23. Furthermore, as the male thread 8 is screwed into the female thread 7, the shaft portion 13 (stopper 18) of the stem 3 comes into contact with the end face 2a of the plug 2, preventing further screwing.

[0023] As the male thread 8 is screwed into the female thread 7 in this manner, the annular groove 12 of the stem 3 and the pin hole 24 of the plug 2 are positioned at the same location in the axial direction of the female thread 7. In this state, the pin 5 is press-fitted into the pin hole 24 of the plug 2. This press-fitting is performed by aligning one end of the pin 5 with one end of the pin hole 24 and tapping the other end of the pin 5 toward the other end with a tool (not shown). This press-fitting operation causes the pin 5 to enter the plug 2 from one end of the pin hole 24, cross the annular groove 12, and reach the other end of the pin hole 24. In other words, the pin 5 is press-fitted into the pin hole 24 and housed in a fitted state. When pin 5 is inserted into pin hole 24, the relative axial movement of stem 3 and plug 2 is restricted by pin 5, so the threaded portion 4 will not loosen.

[0024] When replacing either the plug 2 or the stem 3, the pin 5 is removed from the plug 2, and the threaded portion 4 is loosened to separate the plug 2 and the stem 3. The pin 5 can be removed by, for example, tapping one end of the pin 5 toward the other end to push the pin 5 out of the pin hole 24, or by drilling a hole in the axial center of the pin 5 and cutting the pin 5 within the pin hole 24. In this way, the plug 2 and the stem 3 can be separated without damaging the pin hole 24 or the annular groove 12, so that the part that does not need to be replaced can be reused. Therefore, according to this embodiment, it is possible to provide a connection structure between a valve body and a valve stem that prevents loosening of the threaded portion with a simple structure and allows the threaded portion to be loosened as needed.

[0025] In this embodiment, the member (stem 3) on which the male thread 8 is formed has a stopper 18 that, when the male thread 8 is screwed into the female thread 7, comes into contact with the member (plug 2) on which the female thread 7 is formed, thereby restricting further screwing. The state in which the male thread 8 is screwed into the female thread 7 is the state in which the stopper 18 is in contact with the stem 3. Therefore, since the annular groove 12 and the pin hole 24 can be aligned accurately and easily, a valve body and valve stem connection structure that allows for easy connection can be provided.

[0026] In this embodiment, the female thread 7 is formed in a threaded hole 23 which is a non-through hole opening at one end of the member (plug 2) on which the female thread 7 is formed. On the opening side of the threaded hole 23, there is a female threaded portion 23a on which the female thread 7 is formed. A circular recess 23b is provided further inside the female threaded portion 23a in the threaded hole 23. The pin hole 24 is formed to cross the circular recess 23b of the threaded hole 23. The member (stem 3) on which the male thread 8 is formed has the male thread 8 and a columnar portion 11 formed on the tip side of the male thread 8. The columnar portion 11 is formed in a shape that fits into the circular recess 23b. The annular groove 12 is formed in the columnar portion 11 of the stem 3. Therefore, since the pin 5 does not cross the threaded portion 4, it is held more firmly by the plug 2 and stem 3 compared to when the pin 5 crosses the threaded portion 4, and the reliability of the pin 5 in preventing the threaded portion 4 from loosening is increased.

[0027] Furthermore, in the connecting structure 1 according to this embodiment, the female thread 7 of the screw hole 23 is formed on the opening side of the screw hole 23. Therefore, the female thread 7 can be threaded near the end face 2a of the plug 2, making threading easier. Because the female thread 7 is formed on the opening side of the screw hole 23, the pin hole 24 is formed at a distance of at least 7 units of the female thread from the end face 2a of the plug 2. The operation of driving in the pin 5 and the operation of pulling out the pin 5 are performed with both ends of the plug 2 supported by support members (not shown). According to this embodiment, because the pin hole 24 is formed away from the end face 2a of the plug 2, a wide support space can be provided between the pin hole 24 and both ends of the plug 2 when performing these operations, and the support of the plug 2 is stable, so the operation of driving in or pulling out the pin hole 24 can be performed easily.

[0028] In this embodiment, the pin 5 has knurling on its outer circumference. Therefore, the frictional resistance generated at the contact point between the pin 5 and the groove wall surface 12a of the annular groove 12 and the hole wall surface 24a of the pin hole 24 can be used to prevent the pin 5 from coming loose.

[0029] (Second Embodiment) The position where the pin crosses the plug and stem can be changed to the back of the screw hole, as shown in Figure 6. In Figure 6, the same or equivalent components as those described in Figures 1 to 5 are denoted by the same reference numerals, and detailed explanations are omitted as appropriate. The annular groove 12 shown in Figure 6 is formed on the tip side of the columnar portion 11. The pin hole 24 shown in Figure 6 is formed in a position close to the bottom of the circular recess 23b. The positions where these annular grooves 12 and pin holes 24 are formed can be appropriately changed within the range indicated by the dashed line A in Figure 6. Even with this configuration where the pin 5 crosses the bottom side of the screw hole 23 (the tip side of the stem 13), a simple structure can be used to prevent the screw portion from loosening, just as in the first embodiment, and a valve body and valve stem connection structure can be provided that allows the screw portion to be loosened as needed.

[0030] In the connecting structure 1 shown in Figure 6, the female thread 7 of the screw hole 23 is formed on the opening side of the screw hole 23. Therefore, the female thread 7 can be threaded near the end face 2a of the plug 2, making threading easier. Because the female thread 7 is formed on the opening side of the screw hole 23, the pin hole 24 is formed at a distance of at least 7 units of the female thread from the end face 2a of the plug 2. The operation of driving in the pin 5 and the operation of pulling out the pin 5 are performed with both ends of the plug 2 supported by support members (not shown). According to this embodiment, because the pin hole 24 is formed away from the end face 2a of the plug 2, a wide support space can be provided between the pin hole 24 and both ends of the plug 2 when performing these operations, and the support of the plug 2 is stable, so the operation of driving in or pulling out the pin hole 24 can be performed easily.

[0031] (Third embodiment) The position where the pin crosses the plug and stem can be changed to the side of the screw hole opening, as shown in Figure 7. In Figure 7, components that are the same as or equivalent to those described in Figures 1 to 5 are denoted by the same reference numerals, and detailed explanations are omitted as appropriate. The opening side of the screw hole 23 shown in Figure 7 is provided with a hole portion 23c, which is a circular hole with a constant diameter. Furthermore, a female thread portion 23a, on the inner side of the screw hole 23 beyond the hole portion 23c, is provided, on which the female thread 7 is formed.

[0032] The pin hole 24 shown in Figure 7 is formed to cross the hole portion 23c of the screw hole 23. The stem 13 shown in Figure 7 has a male thread 8 located at its tip and a columnar portion 11 located on the base side of the male thread 8 (opposite the tip of the stem 13 and on the upper side in Figure 7). The columnar portion 11 is shaped to fit into the hole 23c of the screw hole 23. In this embodiment as well, the annular groove 12 is formed in the columnar portion 11 of the stem 13. The positions in which these annular grooves 12 and pin holes 24 are formed can be changed as appropriate within the range indicated by the dashed line B in Figure 7. Even with this configuration where the pin 5 crosses the opening side of the screw hole 23 (the base end side of the stem 13), it is possible to provide a valve body and valve stem connection structure that prevents loosening of the screw portion with a simple structure, similar to the first embodiment, and allows the screw portion to be loosened as needed.

[0033] In the connecting structure 1 shown in Figure 7, the female thread 7 of the screw hole 23 is formed on the inner side of the screw hole 23. Therefore, a hole portion 23c with a constant diameter can be formed on the opening side of the screw hole 23, and the columnar portion 11 of the stem 3 can be fitted into this hole portion 23c to align the cores of the plug 2 and the stem 3. In order to improve the accuracy of this alignment, it is necessary to improve the accuracy of the cylindrical surface which is the hole wall surface of the hole portion 23c and the cylindrical surface which is the outer circumference surface of the columnar portion 11. Because the female thread 7 is formed on the inner side of the screw hole 23, the cylindrical surface on the plug 2 side (the hole wall surface of the hole portion 23c) is close to the end face 2a of the plug 2, and this cylindrical surface can be machined easily and accurately. Furthermore, because the female thread 7 is formed on the inner side of the screw hole 23, the pin hole 24 is positioned close to the end face 2a of the plug 2. Therefore, when drilling the pin hole 24 by machining, it is easy to achieve high accuracy in the distance from the end face 2a to the pin hole 24.

[0034] As shown in the first to third embodiments, it is rational for the product to form an annular groove 12 in the columnar portion 11 of the stem 3, and a pin hole 24 in the circular recess 23b or hole 23c of the screw hole 23 where the female thread 7 is not formed, and to drive a pin 5 into the annular groove 12 and the pin hole 24. However, if a configuration is adopted in which the female thread 7 is formed on the inner side of the screw hole 23, although not shown in the figures, another hole with a constant diameter can be formed further inside the screw hole 23 than the female thread 7, and the pin hole 24 can be formed so as to cross this hole. In this case, a cylindrical portion that fits into the above-mentioned other hole is provided on the tip side of the male thread 8 at the tip of the stem 3, and the annular groove 12 is formed on this cylindrical portion.

[0035] (Fourth embodiment) A stopper that prevents a male screw from being screwed into a female screw can be configured as shown in Figure 8. In Figure 8, components that are the same as or equivalent to those described in Figures 1 to 5 are denoted by the same reference numerals, and detailed explanations are omitted as appropriate. The screw hole 23 of the plug 2 shown in Figure 8 has a flat bottom surface 31 at its innermost part. The bottom surface 31 is a circular surface that extends in a direction perpendicular to the axial direction of the female screw 7.

[0036] Furthermore, the tip of the stem 3 shown in Figure 8 has a flat tip surface 32 that can be in close contact with the flat surface 31. When this tip surface 32 is in close contact with the bottom surface 31 of the screw hole 23, the male screw 8 cannot be screwed into the female screw 7 any further. For this reason, in this embodiment, the tip surface 32 of the stem 3 constitutes the stopper 18 according to this embodiment. Even in this configuration where the tip of the stem 3 constitutes the stopper 18, the stopper 18 can be used to accurately and easily align the annular groove 12 with the pin hole 24, thus providing a valve body and valve stem connection structure that allows for easy connection.

[0037] The screw-in restricting structure in which the tip of the stem 3 acts as a stopper 18 can be applied regardless of the position in which the annular groove 12 and the pin hole 24 are formed. That is, the screw-in restricting structure in which the tip of the stem 3 acts as a stopper 18 can be applied in either the form in which the female thread 7 is formed on the opening side of the screw hole 23, as shown in Figures 1 to 3, 6 and 8, or the form in which the female thread 7 is formed on the inner side of the screw hole 23, as shown in Figure 7.

[0038] In the embodiments described above, an example was shown in which the present invention is applied to a control valve 6, which is a bellows valve in which a bellows 15 is welded to a stem 3. However, the present invention is not limited to such limitations and can also be used for fastening the plug and stem of a general valve.

[0039] In the above-described embodiment, an example was explained in which the male thread 8 of the stem 3 is screwed into the female thread 7 formed in the plug 2. However, the valve body and valve stem connection structure according to the present invention is also applicable when the male thread 8 is formed in the plug 2 and the female thread 7 is formed in the stem 3. Even in this configuration, the loosening of the threaded portion can be prevented with a simple structure, and the threaded portion can be loosened as needed. [Explanation of symbols]

[0040] 1...Connecting structure, 2...Plug (valve body), 3...Stem (valve shaft), 4...Threaded part, 5...Pin, 6...Control valve, 7...Female thread, 8...Male thread, 11...Columnar part, 12...Annular groove, 18...Stopper, 23...Threaded hole, 23a...Female thread part, 23b...Circular recess, 23c...Hole, 24...Pin hole, 25...Protrusion.

Claims

1. A threaded portion is provided on the valve body and the valve stem of the valve to connect the valve body and the valve stem, The valve body and the valve stem are provided with a cylindrical pin that crosses them, Of the valve body and the valve stem, the member on which the male thread of the threaded portion is formed has an annular groove, The valve body and the valve stem, of which the female thread of the threaded portion is formed, have a pin hole into which the pin is fitted, extending in a direction perpendicular to the axial direction of the female thread. The pin hole is formed to extend through the annular groove in the tangential direction of the annular groove when the male screw is screwed into the female screw, The valve body and valve stem connection structure is characterized in that the groove wall surface of the annular groove has a semicircular cross-section when viewed from a direction perpendicular to the circumferential direction of the annular groove, and is formed in a shape that allows the outer circumferential surface of the pin to fit.

2. In the valve body and valve stem connection structure according to claim 1, The member on which the male thread is formed has a stopper that, when the male thread is screwed into the female thread, comes into contact with the member on which the female thread is formed, thereby restricting further screwing. A valve body and valve stem connection structure characterized in that the state in which the male thread is screwed into the female thread is a state in which the stopper is in contact with the member on which the female thread is formed.

3. In the valve body and valve stem connection structure according to claim 1 or claim 2, The female thread is formed in a threaded hole consisting of a non-through hole that opens at one end of the member on which the female thread is formed. The opening side of the screw hole is provided with a female screw portion on which the female thread is formed. A circular recess is provided in the screw hole on the side of the female thread portion that is further inside. The pin hole is formed so as to cross the circular recess of the screw hole, The member on which the male screw is formed has the male screw and a columnar portion formed on the tip side of the male screw, The columnar portion is formed in a shape that fits into the circular recess, The valve body and valve stem connection structure is characterized in that the annular groove is formed in the columnar portion of the member on which the male screw is formed.

4. In the valve body and valve stem connection structure according to claim 1 or claim 2, The female thread is formed in a threaded hole consisting of a non-through hole that opens at one end of the member on which the female thread is formed. The opening side of the screw hole is provided with a hole portion consisting of a circular hole with a constant diameter. In the screw hole, a female screw portion is provided on the side of the hole portion where the female thread is formed. The pin hole is formed so as to cross the hole portion of the screw hole, The member on which the male screw is formed has the male screw located at the tip and a columnar portion located on the base end side of the male screw. The columnar portion is formed in a shape that fits into the hole, The valve body and valve stem connection structure is characterized in that the annular groove is formed in the columnar portion of the member on which the male screw is formed.

5. In the valve body and valve stem connection structure according to claim 1, The aforementioned pin is characterized by having knurling on its outer circumference, forming a connection structure between the valve body and the valve stem.

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