Rotary valve

Abstract

To reduce a possibility that a fluid leaks to a downstream side when a passage is fully closed.SOLUTION: A rotary valve 10 includes: a valve body 20 through which a flow passage R passes; a plug 50 which is disposed in the flow passage R and rotates to adjust a flow rate of the fluid; and a cylindrical seat part 60 which forms a part of the flow passage R and adheres to a seat surface 51 of the plug 50 to close the flow passage R fully. The seat part 60 has: a cylindrical seat member 62 which adheres to the seat surface 51; a cylindrical positioning member 61 which has an overlapping part 61B partially overlapping with the seat member 62 in a direction orthogonal to a flow direction of the flow passage R, is fixed to the valve body 20, and positions the seat member 62; and a ring-shaped seal member 64 which seals a space between the seat member 62 and the overlapping portion 61B. The seat part 60 has a structure which presses the seat member 62 to the seat surface 51 with a force which increases as a differential pressure between a pressure PA of the fluid in the part of the flow passage R and a pressure PB of a fluid at the outside of the seat part 60 becomes larger when the flow passage R is fully closed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rotary valve. [Background technology]

[0002] Patent Document 1 discloses a rotary valve (36a) including a valve body (40) through which a fluid flow path passes, a plug (50) disposed in the flow path and rotating to adjust the flow rate of the fluid, the plug having a seat surface for fully closing the flow path, and a cylindrical seat portion (72, 74, 80) that forms part of the flow path and fully closes the flow path by coming into close contact with the seat surface. The seat portion includes a cylindrical seat member (74) that comes into close contact with the seat surface, a cylindrical positioning member (72) that has an overlapping portion that partially overlaps with the seat member in a direction perpendicular to the flow direction of the flow path and is fixed to the valve body to position the seat member, and a ring-shaped seal member (80) that seals the gap between the seat member and the overlapping portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5806871 Summary of the Invention [Problem to be solved by the invention]

[0004] In the valve body described in Patent Document 1, for example, when the flow path is fully closed, the differential pressure of the fluid between the primary and secondary sides applies a force to the seat member in a direction separating it from the plug, which may result in fluid leakage when the flow path is fully closed.In addition, for example, the seat member may be deformed by the differential pressure between the inside and outside of the seat member or the heat of the fluid, which may also result in fluid leakage downstream when the flow path is fully closed.

[0005] An object of the present invention is to reduce the possibility of fluid leaking downstream when a flow path is fully closed. [Means for solving the problem]

[0006] (1) A rotary valve according to the present invention comprises a valve body through which a fluid flow path passes, a plug disposed in the flow path and rotating to adjust the flow rate of the fluid, the plug having a seat surface for fully closing the flow path, and a cylindrical seat portion which forms a part of the flow path and fully closes the flow path by coming into close contact with the seat surface, the seat portion comprising: a cylindrical seat member which comes into close contact with the seat surface, a cylindrical positioning member which has an overlapping portion which overlaps with the seat member in a direction perpendicular to the flow direction of the flow path and is fixed to the valve body to position the seat member, and a ring-shaped sealing member which seals between the seat member and the overlapping portion, the seat portion having a structure such that when the flow path is fully closed, the greater the pressure difference between the pressure PA of the fluid in the part of the flow path and the pressure PB of the fluid outside the seat portion, the greater the force with which the seat member is pressed against the seat surface.

[0007] (2) A rotary valve according to the present invention comprises a valve body through which a fluid flow path passes, a plug disposed in the flow path and rotating to adjust the flow rate of the fluid, the plug having a seat surface for fully closing the flow path, and a cylindrical seat portion which forms part of the flow path and fully closes the flow path by coming into close contact with the seat surface, the seat portion comprising: a cylindrical seat member which comes into close contact with the seat surface; a cylindrical positioning member which has an overlapping portion which overlaps with the seat member in a direction perpendicular to the flow direction of the flow path and is fixed to the valve body to position the seat member; and a ring-shaped sealing member which seals between the seat member and the overlapping portion, the seat member surrounding the outer periphery of the overlapping portion of the positioning member, and the seat portion further comprising a cylindrical reinforcing member which has an inner circumferential surface which comes into contact with the outer circumferential surface of the seat member and is harder than the seat member. [Effects of the Invention]

[0008] According to the invention of (1) above, the greater the pressure difference between the pressures PA and PB, the greater the force with which the seat member is pressed against the seat surface, thereby reducing the possibility of fluid leaking downstream when the flow path is fully closed.

[0009] According to the invention of (2) above, the reinforcing member makes it difficult for the sheet member to deform, and reduces the possibility of fluid leaking downstream when the flow path is fully closed. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of a rotary valve according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged end view of the cross section of the portion X surrounded by the dashed line in FIG. [Figure 3] FIG. 3 is an enlarged end view showing a cross section of a rotary valve according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0011] A rotary valve 10 according to an embodiment of the present invention will be described below with reference to the drawings. Hereinafter, the flow direction of a fluid flowing through a flow path R in the rotary valve 10 will be referred to as the left-right direction. In particular, the upstream side (also referred to as the primary side) will be referred to as the left, and the downstream side (also referred to as the secondary side) will be referred to as the right. Furthermore, the direction perpendicular to the left-right direction will be referred to as the up-down direction. These directions are set for the convenience of explanation and do not limit the installation orientation of the rotary valve 10. In other words, the rotary valve 10 may be installed with the up-down direction in a direction different from the top-to-bottom direction.

[0012] The rotary valve 10 comprises a valve body 20, an upper cover member 31, a valve stem 35, a support portion 40, a plug 50, and a seat portion 60.

[0013] The valve body 20 is formed into a hollow cylindrical shape. A plug 50 is disposed in this hollow portion, and a flow path R consisting of an upstream (primary) flow path R1 and a downstream (secondary) flow path R2 separated by the plug 50 passes through it. The valve body 20 is provided with flanges 21 and 22 at both left and right ends for connection to piping. The valve body 20 is provided with through holes 23 and 24 at the top and bottom of the center in the left-right direction.

[0014] The lower part of the upper cover member 31 is inserted into the through-hole 23 to cover the through-hole 23. The upper cover member 31 and the valve body 20 are fitted, screwed, glued, or welded together to prevent leakage of the fluid flowing through the flow path R from between them. The upper cover member 31 is formed in a cylindrical shape and has a through-hole 31A that passes through in the vertical direction. A valve stem 35 is inserted into this through-hole 31A. A sealing member (not shown), such as an O-ring, is provided between the upper cover member 31 and the valve stem 35 to seal the gap so that the valve stem 35 can rotate relative to the upper cover member 31.

[0015] A plug 50 is connected to the lower end of the valve stem 35, and an electric or pneumatic operating device (not shown) is connected to the upper end of the valve stem 35. The operating device rotates the plug 50 via the valve stem 35. The rotation axis C of the valve stem 35 and the plug 50 is perpendicular to the axis A of the valve body 20 and the flow path R.

[0016] The support part 40 supports the plug 50. The support part 40 includes a lower cover member 41 and a shaft member 42. The upper part of the lower cover member 41 is inserted into the through-hole 24, covering the through-hole 24 from below. The lower cover member 41 and the valve body 20 are fitted, screwed, glued, or welded to prevent leakage of fluid flowing through the flow path R. A recess 41A is formed in the upper part of the lower cover member 41, and the shaft member 42 is rotatably inserted into this recess 41A. As a result, the lower cover member 41 rotatably supports the shaft member 42. The shaft member 42 supports the plug 50 by connecting its upper part to the plug 50. The shaft member 42 is arranged coaxially with the valve shaft 35. The plug 50, which rotates due to the valve shaft 35, rotates together with the shaft member 42. At this time, the lower cover member 41 does not rotate. The shaft member 42 may be fixed to the lower cover member 41 and the plug 50 may rotate relative to the shaft member 42 .

[0017] The plug 50 is formed in a shape where a portion of a spherical shell is cut out, with a cross section that is roughly C-shaped. The plug 50 changes the opening degree of the flow path R by rotating, thereby adjusting the flow rate of the fluid. The plug 50 has a spherical outer surface. The outer surface includes a seat surface 51 that comes into close contact with the seat portion 60 when the flow path R is fully closed. The plug 50 may be formed in a spherical shape with a through hole that extends in the upstream / downstream direction (left / right direction) when the flow path R is fully opened.

[0018] The seat portion 60 is formed into a cylindrical shape as a whole, forms an upstream flow path R1 of the flow path R, and is slidably attached to the outer surface of the plug 50. In particular, the seat portion 60 fully closes the flow path R by being attached to the seat surface 51 of the plug 50 (the seat surface 51 is seated on the seat portion 60). By being attached to the seat surface 51, the seat portion 60 seals the flow path R so that the fluid in the upstream flow path R1 does not leak into the downstream flow path R2 when the flow path R is fully closed.

[0019] As shown in FIG. 2, the seat portion 60 includes a positioning member 61, a seat member 62, a reinforcing member 63, a sealing member 64, and an elastic body 65 (shown simply in FIGS. 1 and 2).

[0020] The positioning member 61 is fixed to the valve body 20 and positions the seat member 62 and other components. The positioning member 61 is formed in a cylindrical shape. The outer peripheral surface of the upstream end of the positioning member 61 is fixed to the inner peripheral surface of the valve body 20. The two are fixed by fitting, screwing, bonding, or welding to prevent fluid leakage from the two.

[0021] The positioning member 61 has an annular recess 61A formed on its outer circumferential surface, which is open to the downstream side (right side). An elastic body 65 made of a spring is housed in this recess 61A. The elastic body 65 may be a ring-shaped rubber or the like. The elastic body 65 is disposed between the positioning member 61 (more specifically, the bottom surface of the recess 61A) and the sheet member 62, and biases the sheet member 62. The positioning member 61 has a cylindrical overlapping portion 61B at its downstream position, which partially overlaps with the sheet member 62 in a direction (the direction in which the rotation axis C extends) perpendicular to the upstream-downstream direction (the direction in which the axis A in FIG. 1 extends).

[0022] The seat member 62 is a member that actually comes into close contact with the outer surface (particularly the seat surface 51) of the plug 50 when the seat portion 60 comes into close contact with the outer surface. The seat member 62 is formed in a cylindrical shape that surrounds the outer periphery of the overlapping portion 61B. The seat member 62 includes a first portion 62A located downstream and not overlapping with the overlapping portion 61B, and a second portion 62B located upstream and surrounding the overlapping portion 61B. The first portion 62A is thicker than the second portion 62B.

[0023] The inner peripheral end of the downstream end face of the first portion 62A is a chamfered ring, forming a bank-shaped slope 62C that is inclined relative to a plane perpendicular to the left-right direction. This slope 62C comes into close contact with the outer surface of the plug 50, particularly the seat surface 51. There is line contact between the slope 62C and the outer surface of the plug 50, particularly the seat surface 51. The shape of the line contact is circular. Such a circular contact line is also called an osculating circle.

[0024] The second portion 62B of the seat member 62 has an annular groove 62D that opens to its inner circumferential surface. A ring-shaped seal member 64, such as an O-ring, is housed in the groove 62D. The seal member 64 is sandwiched between the bottom surface of the groove 62D and the outer circumferential surface of the overlapping portion 61B of the positioning member 61, thereby providing a seal between the inner circumferential surface of the seal member 64 and the outer circumferential surface of the overlapping portion 61B. The seal member 64 is in line contact with the positioning member 61 or the seat member 62, and this line contact forms an osculating circle.

[0025] The reinforcing member 63 is cylindrical and configured so that its inner peripheral surface comes into contact with the outer peripheral surface of the sheet member 62, thereby reinforcing the sheet member 62. The sheet member 62 is made of, for example, resin, and may be deformed as described below. The reinforcing member 63 is provided to suppress this deformation. The reinforcing member 63 is made of, for example, a metal that is harder than the sheet member 62.

[0026] The reinforcing member 63 includes a cylindrical main body 63A and a donut-shaped protruding portion 63B that protrudes inward from the upstream end of the main body 63A. The reinforcing member 63 covers the sheet member 62 from the upstream side. Specifically, the main body 63A covers the outer periphery of the sheet member 62, and the protruding portion 63B covers the upstream end face (left face) of the sheet member 62. The main body 63A extends toward the plug 50 side (right side) beyond the plug 50 side end, i.e., the right end, of the sheet member 62 (see portion 63AA to the right of the dashed line).

[0027] The reinforcing member 63 is biased together with the sheet member 62 in the downstream direction, i.e., toward the plug 50, by the elastic body 65. More specifically, the elastic body 65 is sandwiched between the bottom surface of the recess 61A of the positioning member 61 and the upstream side surface (left surface) of the protruding portion 63B of the reinforcing member 63, and biases the reinforcing member 63 and the sheet member 62 toward the plug 50. As a result, the elastic body 65 presses the sheet member 62 against the plug 50 by pressing it via the reinforcing member 63 (protruding portion 63B).

[0028] In the rotary valve 10 structure described above, the fluid flowing into the flow path R shown in Fig. 1 from upstream flows into the downstream flow path R2 when the flow path is opened or closed. At this time, the fluid also flows into the space Z outside the seat portion 60. For this reason, this space is also included in the downstream flow path R2.

[0029] The seat portion 60 is configured such that, when the flow path R is fully closed, the greater the pressure difference between the fluid pressure PA in the upstream flow path R1 within the seat portion 60 and the fluid pressure PB outside the seat portion 60 (space Z of the downstream flow path R2), the greater the force with which the seat member 62 is pressed against the seat surface 51 of the plug 50. This point will be explained below with reference to FIG. 2. Note that point D1 in FIG. 2 indicates the contact position between the seal member 64 and the overlapping portion 61B of the positioning member 61, and point D2 indicates the contact position between the inclined surface 62C of the seat member 62 and the seat surface 51 of the plug 50. The surfaces of the inclined surface 62C above and below point D2 are slightly separated from the seat surface 51, and pressure from the fluid is also applied to these surfaces.

[0030] Pressures PA and PB are applied to the combination of the seat member 62 and the seal member 64. These pressures include pressure applied to the seat member 62 via the reinforcing member 63. Pressures PA and PB along the direction toward the plug 50 (i.e., the left-right direction) are applied to surfaces of the combination of the seat member 62 and the seal member 64 facing in opposite directions, so they are canceled out. However, some of the pressures are not canceled out. For example, the same pressure PA is applied to the right surface of the seal member 64 and the two surfaces of the seat member 62 facing the right surface (surfaces located above point D1 of the seal member 64 and below the upper end of the seal member 64), and the two pressures are canceled out. The portions of the inclined surface 62C that are not canceled out are the surface V, shown by the bold line in FIG. 2, between points D1 and D2 in the vertical direction, and the surface W, shown by the bold line in FIG. 2, opposite the surface V. Pressure PB is applied to surface V (more precisely, a surface projected onto an orthogonal plane perpendicular to the left-right direction), and pressure PA is applied to surface W. Therefore, a force F in the left-right direction is applied to the seat member 62 as shown in the following formula (1) (for details of this concept, see also Patent Document 1). In formula (1), S1 is the area of ​​the osculating circle (the circle passing through point D1) between the sealing member 64 and the overlapping portion 61B of the positioning member 61, and S2 is the area of ​​the osculating circle (the circle passing through point D2) between the inclined surface 62C of the seat member 62 and the seat surface 51 of the plug 50. Furthermore, the force F has a positive value in the downstream direction, i.e., toward the plug 50. F = (PA - PB) * (S1 - S2) (1)

[0031] When the flow path R is fully closed, the pressure PA in the upstream flow path R1 increases, so that PA > PB. As is clear from FIGS. 1 and 2, the seat member 62 has a first portion 62A and a second portion 62B that is thinner than the first portion 62A. Therefore, the diameter of the osculating circle passing through point D1 is greater than the diameter of the osculating circle passing through point D2, and so S1 > S2. Therefore, the force F always acts in a direction that presses the seat member 62 against the seat surface 51 of the plug 50. While (S1 - S2) does not change, the pressure difference (PA - PB) varies depending on changes in the pressure PA and other factors. As the pressure difference (PA - PB) increases, the force F also increases.

[0032] As described above, in this embodiment, when the flow path R is fully closed, the seat portion 60 can press the seat member 62 against the seat surface 51 of the plug 50 with a greater force as the pressure difference between the pressures PA and PB increases. This reduces the possibility of fluid leaking downstream when the flow path R is fully closed.

[0033] Note that the structure of the sheet portion 60 is not limited to such a configuration. The sheet portion 60 may have, for example, a structure in which a force including the force F of the above formula (1) is applied to the sheet member 62. The sheet portion 60 may be arranged on the downstream side of the plug 50, and may be configured such that PA < PB and S1 < S2. For example, the structure shown in FIG. 3 may be adopted (in FIG. 3, the same reference numerals are used for the same or similar elements as those described above). FIG. 3 is an enlarged cross-sectional view showing the structure on the downstream side of the plug 50. In the structure of FIG. 3, the sheet portion 60 seals the plug 50 from the downstream side. The pressure PA is the pressure of a part of the fluid in the downstream channel R2 formed by the inner wall of the sheet portion 60, and the pressure PB is the pressure of the fluid that flows into the channel space outside the sheet portion 60 in the upstream channel R1. In the sheet member 62, the first portion 62A is not thicker than the second portion 62B, and the diameter of the contact circle passing through point D1 is smaller than the diameter of the contact circle passing through point D2, resulting in S1 < S2. The surface related to the above formula (1) is the surface drawn with a thick line in FIG. 3. As another modification, the reinforcing member 63 may be omitted. Also, the overlapping portion 61B of the positioning member 61 may be arranged on the outer peripheral side of the sheet member 62. Further, the structure of the sheet portion 60 may be such that the sheet member 62 is pressed against the sheet surface 51 of the plug 50 with a greater force as the differential pressure between the pressure PA and the pressure PB increases. The above-mentioned force may be a force other than the force obtained by the above formula (1).

[0034] In addition, by providing the elastic body 65 that presses the sheet member 62 against the plug 50, the possibility of fluid leakage to the downstream side when the flow path is fully closed is further reduced. According to the above structure, the effect that the elastic force of the elastic body 65 does not need to be increased can also be obtained.

[0035] When the pressure PA exceeds the pressure PB, the seat member 62 is deformed by a radial force, which reduces the adhesion of the plug 50 and may result in fluid leakage. This deformation increases as the pressure difference between the pressure PA and the pressure PB increases. Furthermore, when a resin material is used for the seat member 62 to ensure adhesion with the plug 50 while reducing sliding resistance with the plug 50, and when the fluid is hot, the deformation also increases. This increases the likelihood of seat leakage. In this embodiment, the reinforcing member 63 has an inner circumferential surface that contacts the outer circumferential surface of the seat member 62 and is harder than the seat member 62. This suppresses the deformation, thereby reducing the possibility of fluid leaking downstream when the flow path R is fully closed. In light of this effect, the seat portion 60 does not necessarily have to be configured to press the seat member 62 against the seat surface 51 of the plug 50 with a greater force as the pressure difference between the pressure PA and the pressure PB increases when the flow path R is fully closed (for example, the elastic force of the elastic body 64 may be increased).

[0036] The shape of the reinforcing member 63 is arbitrary, but as described above, by having the reinforcing member 63 extend further toward the plug 50 than the end of the sheet member 62 on the plug 50 side, the sheet member 62 becomes less likely to deform than if it did not extend, and the possibility of fluid leaking downstream when the flow path is fully closed is further reduced. In addition, the elastic body 65 presses the sheet member 62 via the overhanging portion 63B of the reinforcing member 63, so that the reinforcing member 63 can be easily positioned.

[0037] Although the present invention has been described above with reference to the embodiments and modifications, the present invention is not limited to the above embodiments and modifications. For example, the present invention includes various modifications to the above embodiments and modifications that can be understood by a person skilled in the art within the scope of the technical concept of the present invention. The configurations listed in the above embodiments and modifications can be combined as appropriate within a range that does not contradict. Furthermore, the omission of each configuration is optional.

[0038] The configuration of the above embodiment and its modified example will be described as an example.

[0039] (Appendix 1) A valve body through which a fluid flow path passes, A plug disposed in the flow path and configured to adjust the flow rate of the fluid by rotating, the plug having a seat surface for fully closing the flow path, A cylindrical shape forming a part of the flow path, and a seat portion that fully closes the flow path by adhering to the seat surface, and is provided with: The seat portion is, A cylindrical seat member that adheres to the seat surface, A cylindrical positioning member that has an overlapping portion that partially overlaps with the seat member in a direction orthogonal to the flow direction of the flow path and is fixed to the valve body to position the seat member, A ring-shaped seal member that seals between the seat member and the overlapping portion, and is provided with: The seat portion has a structure that presses the seat member against the seat surface with a greater force as the differential pressure between the pressure PA of the fluid in the part of the flow path and the pressure PB of the fluid outside the seat portion increases when the flow path is fully closed. Rotary valve. (Appendix 2) The force includes a force F represented by the following formula (A) when the direction toward the seat surface is taken as positive, The seat portion is formed in a structure that satisfies PA > PB and S1 > S2, or PA < PB and S1 < S2. The rotary valve according to Appendix 1. F = (PA - PB) * (S1 - S2) ··· (A) However, S1 is the area of the contact circle between the overlapping portion and the seal member, and S2 is the area of the contact circle between the seat member and the seat surface. (Appendix 3) The seat portion is disposed on the upstream side of the plug. The rotary valve according to Appendix 1 or 2. (Appendix 4) The seat portion is disposed between the seat member and the positioning member, and further includes an elastic body that presses the seat member against the seat surface. The rotary valve according to any one of Appendices 1 to 3. (Appendix 5) the sheet member surrounds the outer periphery of the overlapping portion of the positioning member, the seat portion is a cylindrical reinforcing member having an inner circumferential surface that contacts an outer circumferential surface of the seat member, and further including a reinforcing member that is harder than the seat member. 5. A rotary valve according to any one of appendices 1 to 4. (Appendix 6) a valve body through which a fluid flow path passes; a plug that is disposed in the flow path and that adjusts the flow rate of the fluid by rotating, the plug having a seat surface for fully closing the flow path; a cylindrical seat portion that forms a part of the flow path and that fully closes the flow path by being in close contact with the seat surface; The seat portion is a cylindrical sheet member that is in close contact with the sheet surface; a cylindrical positioning member that has an overlapping portion that partially overlaps with the seat member in a direction perpendicular to the flow direction of the flow channel, the positioning member being fixed to the valve body and positioning the seat member; a ring-shaped seal member that seals between the sheet member and the overlapping portion, the sheet member surrounds the outer periphery of the overlapping portion of the positioning member, the seat portion is a cylindrical reinforcing member having an inner circumferential surface that contacts an outer circumferential surface of the seat member, and further including a reinforcing member that is harder than the seat member. Rotary valve. (Appendix 7) The reinforcing member extends toward the plug side beyond the end of the sheet member on the plug side. 7. A rotary valve according to claim 5 or 6. (Appendix 8) the sheet portion further includes an elastic body disposed between the sheet member and the positioning member and pressing the sheet member against the sheet surface; the reinforcing member includes a cylindrical main body and a protruding portion protruding inward from an end of the main body opposite to the plug side, The elastic body presses the sheet member via the protruding portion. 8. A rotary valve according to any one of appendices 5 to 7. [Explanation of symbols]

[0040] 10...rotary valve, 20...valve body, 21...flange, 22...flange, 23...through hole, 24...through hole, 31...upper cover member, 31A...through hole, 35...valve stem, 36a...rotary valve, 40...support portion, 40...valve body, 41...lower cover member, 41A...recess, 42...shaft member, 50...plug, 51...seat surface, 60...seat portion, 61...positioning member, 61A...recess, 61B...overlapping portion, 62...sheet member, 62A...first portion, 62B...second portion, 62C...inclined surface, 62D...groove, 63...reinforcing member, 63A...main body, 63B...extending portion, 64...sealing member, 65...elastic body, C...rotation axis, D1...point, D2...point, PA...pressure, PB...pressure, R...flow path, R1...upstream flow path, R2...downstream flow path, V...surface, W...surface, Z...space.

Claims

1. a valve body through which a fluid flow path passes; a plug that is disposed in the flow path and that adjusts the flow rate of the fluid by rotating, the plug having a seat surface for fully closing the flow path; a cylindrical seat portion that forms a part of the flow path and that fully closes the flow path by being in close contact with the seat surface; The seat portion is a cylindrical sheet member that is in close contact with the sheet surface; a cylindrical positioning member that has an overlapping portion that partially overlaps with the seat member in a direction perpendicular to the flow direction of the flow channel, the positioning member being fixed to the valve body and positioning the seat member; a ring-shaped seal member that seals between the sheet member and the overlapping portion, The seat portion has a structure in which, when the flow path is fully closed, the greater the pressure difference between the pressure PA of the fluid in the portion of the flow path and the pressure PB of the fluid outside the seat portion, the greater the force with which the seat member is pressed against the seat surface. Rotary valve.

2. The force includes a force F expressed by the following formula (A) when the direction toward the sheet surface is defined as positive, the seat portion is formed in a structure that satisfies PA>PB and S1>S2, or PA<PB and S1<S2; The rotary valve of claim 1 . F=(PA-PB)*(S1-S2)... (A) Here, S1 is the area of ​​the contact circle between the overlapping portion and the seal member, and S2 is the area of ​​the contact circle between the sheet member and the sheet surface.

3. The seat portion is disposed upstream of the plug. The rotary valve of claim 1 .

4. The sheet portion further includes an elastic body disposed between the sheet member and the positioning member and pressing the sheet member against the sheet surface. The rotary valve of claim 1 .

5. the sheet member surrounds the outer periphery of the overlapping portion of the positioning member, the seat portion is a cylindrical reinforcing member having an inner circumferential surface that contacts an outer circumferential surface of the seat member, and further including a reinforcing member that is harder than the seat member. The rotary valve of claim 1 .

6. The reinforcing member extends toward the plug side beyond the end of the sheet member on the plug side.

6. The rotary valve of claim 5.

7. the sheet portion further includes an elastic body disposed between the sheet member and the positioning member and pressing the sheet member against the sheet surface; the reinforcing member includes a cylindrical main body and a protruding portion protruding inward from an end of the main body opposite to the plug side, The elastic body presses the sheet member via the protruding portion.

7. A rotary valve according to claim 5 or 6.

8. a valve body through which a fluid flow path passes; a plug that is disposed in the flow path and that adjusts the flow rate of the fluid by rotating, the plug having a seat surface for fully closing the flow path; a cylindrical seat portion that forms a part of the flow path and that fully closes the flow path by being in close contact with the seat surface; The seat portion is a cylindrical sheet member that is in close contact with the sheet surface; a cylindrical positioning member that has an overlapping portion that partially overlaps with the seat member in a direction perpendicular to the flow direction of the flow channel, the positioning member being fixed to the valve body and positioning the seat member; a ring-shaped seal member that seals between the sheet member and the overlapping portion, the sheet member surrounds the outer periphery of the overlapping portion of the positioning member, the seat portion is a cylindrical reinforcing member having an inner circumferential surface that contacts an outer circumferential surface of the seat member, and further including a reinforcing member that is harder than the seat member. Rotary valve.

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