Non-sealed butterfly valve

Abstract

The goal is to reduce conductance in the valve closed state or at a small opening while avoiding a decrease in conductance in the valve open state. [Solution] The butterfly valve body 9 is provided with a maximum outer diameter portion 91A, 91B that is point-symmetrically arranged with respect to the axis XL and faces the inner circumferential surface of the flow path 30 in the valve closed position, and a first chamfer 92A, 92B that reduces the diameter of the butterfly valve body 9 in the opposite direction to the rotational direction (K direction) from the valve closed position to the valve open position, starting from the maximum outer diameter portion 91A.

Description

Technical Field

[0001] The present invention relates to an unsealed butterfly valve provided with a flow path, a rotating shaft arranged in a direction orthogonal to the flow path, a disc-shaped butterfly valve body rotatable between a closed position where the flow path area of the flow path is minimized and an open position where the flow path area is maximized around the axis of the rotating shaft, and is disposed on a pipe connecting a vacuum vessel and a vacuum pump to control the pressure of the vacuum vessel.

Background Art

[0002] Conventionally, in the semiconductor manufacturing process, a process of introducing gas into a vacuum vessel after bringing the vacuum vessel into a vacuum state by pressure control has been performed.

[0003] As a device for controlling the pressure of a vacuum vessel, a butterfly valve is used. More specifically, it is as follows. The butterfly valve is disposed between the vacuum vessel and the vacuum pump. When the butterfly valve is opened, the vacuum vessel is depressurized by the vacuum pump. Then, a certain amount of gas is introduced into the vacuum vessel, and when the desired pressure state (vacuum state) is reached, the opening degree of the valve body is maintained.

[0004] As the butterfly valve, for example, the butterfly valve disclosed in Patent Document 1 is known. The butterfly valve disclosed in Patent Document 1 is an unsealed butterfly valve having a gap between the inner peripheral surface of the flow path and the outer peripheral surface of the butterfly valve body even in the valve-closed state. As a butterfly valve, a type that can completely block the flow path when the valve is closed by using a seal member is generally used, but when a seal member is used during pressure control, there is a concern about a decrease in product life due to wear or the like. Therefore, an unsealed type is preferable.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, the above-mentioned prior art had the following problems. The butterfly valve disclosed in Patent Document 1, even when closed, is not airtight, so gas is drawn into the vacuum pump through the gap between the butterfly valve body and the flow path. As a result, there is a risk that the pressure in the vacuum container 32 when gas is supplied cannot be maintained at the desired pressure. In particular, to widen the pressure control range, there is a need for an airtight butterfly valve with lower conductance (i.e., less gas flowing through the gap between the butterfly valve body and the flow path) when the valve is closed or at a small opening (e.g., an opening of 10 degrees or less).

[0007] In the butterfly valve disclosed in Patent Document 1, increasing the thickness of the butterfly valve body can reduce the conductance in the closed state or at a small opening. However, when the valve is open, the flow area of ​​the flow path decreases by the amount of the increased thickness of the butterfly valve body, resulting in a decrease in conductance. A decrease in conductance in the open state is undesirable because it leads to a decrease in the efficiency of pressure control. In other words, it is desirable to reduce the conductance in the closed state or at a small opening while avoiding a decrease in conductance in the open state.

[0008] The present invention aims to solve the above problems and to provide an open butterfly valve that can widen the pressure control range by reducing the conductance in the closed state or at a small opening while avoiding a decrease in conductance in the open state. [Means for solving the problem]

[0009] To solve the above problems, the non-sealed butterfly valve of the present invention has the following configuration. (1) An open butterfly valve for controlling the pressure of a vacuum vessel, comprising a flow path, a rotating shaft arranged in a direction perpendicular to the flow path, and a disc-shaped butterfly valve body rotatable between a valve closed position that minimizes the flow path area of ​​the flow path and a valve open position that maximizes the flow path area, disposed on piping connecting a vacuum vessel and a vacuum pump, wherein the butterfly valve body is provided with a maximum outer diameter portion facing the inner circumferential surface of the flow path at the valve closed position, and is provided point-symmetrically with respect to the axis in an axial view of the rotating shaft, and is provided with a chamfer that reduces the diameter of the butterfly valve body in the opposite direction to the rotation direction from the valve closed position to the valve open position, from the maximum outer diameter portion.

[0010] (2) In the non-sealed butterfly valve described in (1), it is preferable that the size of the maximum outer diameter portion in the thickness direction of the butterfly valve body is greater than 0.5% and 10% or less of the inner diameter of the flow path.

[0011] (3) In the non-sealed butterfly valve described in (1) or (2), it is preferable that the angle of the chamfer with respect to the thickness direction of the butterfly valve body is 30 degrees or less.

[0012] (4) In the non-sealed butterfly valve described in any one of (1) to (3), it is preferable that the butterfly valve body is provided with a second chamfer that reduces the diameter of the butterfly valve body toward the rotational direction from the maximum outer diameter portion, which is provided point-symmetrically with respect to the axis in an axial view of the rotational axis.

[0013] (5) In the non-sealed butterfly valve described in any one of (1) to (4), it is preferable that the axis of the chamfer is at an angle with respect to the axis of the maximum outer diameter portion.

[0014] (6) In the non-sealed butterfly valve described in any one of (1) to (5), it is preferable that the butterfly valve body is provided with a rotation restricting part that restricts the rotation of the butterfly valve body in the opposite direction to the rotation direction. (7) In the non-sealed butterfly valve according to (1) or (2), it is preferable to include a rotation restricting portion that restricts the further rotation of the butterfly valve body in the rotation direction from the valve open position.

Advantages of the Invention

[0015] Due to having the above configuration, the non-sealed butterfly valve of the present invention can reduce the conductance in the valve closed state or at a minute opening degree while avoiding a decrease in conductance in the valve open state.

Brief Description of the Drawings

[0016] [Figure 1] It is a schematic diagram of a vacuum pressure control system using the non-sealed butterfly valve according to the present embodiment. [Figure 2] It is a cross-sectional view of the non-sealed butterfly valve according to the present embodiment, cut in a direction parallel to the axis of the rotation axis and parallel to the flow path. [Figure 3] It is a cross-sectional view of the non-sealed butterfly valve according to the present embodiment, cut in a direction parallel to the axis of the rotation axis and perpendicular to the flow path. [Figure 4] It is a cross-sectional view of the non-sealed butterfly valve according to the present embodiment, cut in a direction perpendicular to the axis of the rotation axis and parallel to the flow path, showing the state where the butterfly valve body is in the valve closed position. [Figure 5] [[ID=​​​​​​​​​​​​​​​​​It is a cross-sectional view corresponding to FIG. 4 and shows a state in which a butterfly valve body according to a modified example is used.

Embodiments for Carrying Out the Invention

[0017] Embodiments of the non-sealed butterfly valve of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram of a vacuum pressure control system using the non-sealed butterfly valve 1 according to this embodiment. FIG. 2 is a cross-sectional view of the non-sealed butterfly valve 1 according to this embodiment, cut in a direction parallel to the axis RA of the output shaft 11a and parallel to the flow path 30. Further, FIG. 3 is a cross-sectional view of the non-sealed butterfly valve 1 according to this embodiment, cut in a direction parallel to the axis RA of the output shaft 11a and perpendicular to the flow path 30. Note that both FIGS. 2 and 3 represent the valve closed state. FIG. 4 is a cross-sectional view of the non-sealed butterfly valve 1 according to this embodiment, cut in a direction perpendicular to the axis XL of the rotary shaft rod 10 and parallel to the flow path, and shows a state in which the butterfly valve body 9 is in the valve closed position. Note that the butterfly valve body 9 in FIG. 4 shows the shape of the outer peripheral edge, not the cross-section. FIG. 5 is a partial enlarged view of part A in FIG. 4. The fluid flowing through the flow path 30 flows from right to left in FIGS. 2, 4 - 5. That is, the right side in FIGS. 2, 4 - 5 is the upstream side, and the left side is the downstream side. In FIG. 3, the back side in the figure is the upstream side, and the front side is the downstream side. Also, the dots on the butterfly valve body 9 in FIGS. 4 - 5 are provided to make the shape of the outer peripheral edge of the butterfly valve body 9 easier to understand, and do not represent the shape, surface state, etc.

[0018] The non-sealed butterfly valve 1 (hereinafter simply referred to as butterfly valve 1) according to this embodiment is used, for example, as a vacuum pressure control device to control the pressure of a vacuum vessel 32 in a semiconductor manufacturing process. As shown in Figure 1, the butterfly valve 1 is installed on a pipe 34 connecting the vacuum vessel 32 and a vacuum pump 33. Gas can be supplied to the vacuum vessel 32 from a gas supply source 37. The vacuum pump 33 is used to evacuate the vacuum vessel 32 via the pipe 34. The butterfly valve 1 controls the pressure of the vacuum vessel 32 by adjusting the opening degree of the butterfly valve body 9, which will be described later, thereby adjusting the amount of exhaust by the vacuum pump 33.

[0019] (Regarding the structure of the butterfly valve) As shown in Figures 2 and 3, the butterfly valve 1 consists of a drive unit 2 and a valve unit 3. The drive unit 2 has a direct drive motor (hereinafter referred to as DD motor) 11, and as shown in Figure 1, the DD motor 11 is connected to a motor driver 12 and an encoder 14. The motor driver 12 is connected to a control board 13. Since the DD motor 11 does not require an intermediate mechanism such as a reduction gear, the drive unit 2 can be made smaller, noise can be reduced, and response performance, speed stability performance and positioning accuracy can be improved. Therefore, the accuracy of vacuum pressure control by the butterfly valve 1 is improved. Also, as shown in Figure 2, the DD motor 11 has an output shaft 11a. This output shaft 11a rotates about the axis RA.

[0020] As shown in Figure 1, the control board 13 is connected to a motor driver 12 and a pressure gauge 35 for detecting the pressure in the vacuum vessel 32. The control board 13 has a storage means 131, which stores, for example, the closed and open positions of the butterfly valve body 9, and the rotation angle of the output shaft 11a corresponding to an arbitrary target pressure in the vacuum vessel 32 (i.e., the rotation angle of the butterfly valve body 9, which will be described later). Based on the rotation angle read from the storage means 131, the motor driver 12 controls the rotation of the DD motor 11 (output shaft 11a).

[0021] As shown in Figure 2, one end (the upper end in Figure 2) of a rod 10 (an example of a rotating shaft) inserted into the valve section 3 is connected to the output shaft 11a via a metal leaf spring type coupling 17. The axis XL of the rod 10 (see Figure 4) is coaxial with the axis RA of the output shaft 11a. As a result, the rod 10 rotates around axis XL as the output shaft 11a rotates. The output shaft 11a and the rod 10 are connected via the coupling 17. In addition, the drive unit 2 is connected to the valve section 3 via a motor base 15 and a shaft block 16.

[0022] The valve section 3, which is connected to the drive unit 2, has a valve body 8 and a butterfly valve body 9. The valve body 8 is made of corrosion-resistant stainless steel.

[0023] The valve body 8 is equipped with a joint 5 at its upstream end (right end in Figures 2 and 4) and a joint 6 at its downstream end (left end in Figures 2 and 4). An input-side flow path 8b is formed on the inner circumferential surface of joint 5, and an output-side flow path 8c is formed on the inner circumferential surface of joint 6. Between the input-side flow path 8b and the output-side flow path 8c, a valve hole 8a is formed, which has an inner circumferential surface with a circular arc cross-section as shown in Figure 3. Furthermore, as shown in Figure 2, the input-side flow path 8b, the valve hole 8a, and the output-side flow path 8c are arranged coaxially and communicate with each other, forming a series of flow paths 30. In the semiconductor manufacturing process, as shown in Figure 1, joint 5 is connected to the vacuum vessel 32 and joint 6 is connected to the vacuum pump 33 via piping 34. As a result, the butterfly valve 1 evacuates the vacuum vessel 32 through the flow path 30.

[0024] Furthermore, as shown in Figures 2 and 3, the valve body 8 has an end face (upper end face) 8e that connects to the drive unit 2 and an insertion hole 8d that penetrates the valve hole 8a, and the rod 10 is inserted through the insertion hole 8d. The rod 10 inserted through the insertion hole 8d is positioned in the valve hole 8a in a direction perpendicular to the flow path 30.

[0025] The rod 10 is formed into a cylindrical shape by machining corrosion-resistant stainless steel. The portion of the rod 10 inserted into the flow path 30 is equipped with a valve body mounting portion 101, and its cross-section in the direction perpendicular to the axis RA is approximately D-shaped.

[0026] An O-ring 18 is placed between the rod 10 and the inner surface of the insertion hole 8d for sealing. The O-ring 18 is compressed between the outer surface of the rod 10 and the inner surface of the insertion hole 8d, preventing the fluid flowing through the passage 30 from leaking through the insertion hole 8d to the drive unit 2 side.

[0027] Furthermore, one end of the rod 10 that is inserted into the flow path 30 (the lower end in Figures 2 and 3) is rotatably supported by a bush 22. The bush 22 is made of a resin that has high corrosion resistance and good sliding properties. In addition, the rod 10 is rotatably supported in the portion between the upper end surface 8e of the valve body 8 and the motor base 15 by two ball bearings 21A and 21B that are adjacent to each other in the axial direction of the rod 10. The rod 10 is supported in a double-supported manner by the ball bearings 21A and 21B and the bush 22, which stabilizes the rotational axis (axis XL) and makes it less prone to wobbling.

[0028] Each of the ball bearings 21A and 21B is pre-pressurized from above and below by the collar 23, the protrusion 241 of the bearing retainer 24, and the flange portion 102 of the rod 10. This makes it difficult for internal clearances to occur in the ball bearings 21A and 21B. In addition, the rigidity of the ball bearings 21A and 21B is increased by the pre-pressurization, which suppresses vibrations when the rod 10 rotates and reduces the wobble of the rotational axis (axis XL) of the rod 10.

[0029] The butterfly valve body 9 is connected to the rod 10 by screws 25A, 25B, and 25C and washers 26A, 26B, and 26C, as shown in Figure 2. Note that screws 25A, 25B, and 25C are all of the same type, and washers 26A, 26B, and 26C are also all of the same type.

[0030] Since the butterfly valve body 9 is coupled to the rod 10, when the output shaft 11a of the DD motor 11 rotates in the K direction or -K direction around the axis RA, the rod 10 connected to the output shaft 11a via the coupling 17 rotates in the same direction around the axis XL (see Figure 4), and consequently the butterfly valve body 9 rotates in the same direction.

[0031] More specifically, when the butterfly valve body 9 is in the closed position, and the output shaft 11a rotates in the K direction around the axis RA, the butterfly valve body 9 rotates in the same direction. The position where the rotation angle of the butterfly valve body 9 is 90 degrees (a position rotated 90 degrees in the K direction from the position shown in Figure 4) is the valve open position where the flow area of ​​the flow path 30 (valve hole 8a) is maximized. This enables a large volume of exhaust from the vacuum vessel 32.

[0032] On the other hand, when the butterfly valve body 9 is in the valve open position, if the output shaft 11a of the DD motor 11 rotates 90 degrees in the -K direction around the axis RA, the rod 10 rotates in the -K direction, and as shown in Figure 4, the butterfly valve body 9 moves to the valve closed position, blocking the valve hole 8a. However, since there is a gap between the butterfly valve body 9 and the flow path 30 (valve hole 8a) (details will be described later), the valve closed position does not mean that the butterfly valve body 9 completely blocks the valve hole 8a, but rather that the flow path area of ​​the flow path 30 (valve hole 8a) is minimized.

[0033] To restrict the butterfly valve body 9 from rotating in the -K direction from the valve closed position, or from rotating further in the K direction from the valve open position, the butterfly valve 1 is equipped with a rotation restricting section. As shown in Figure 3, the rotation restricting section mainly consists of a pin 39 and stoppers 38A and 38B provided between the valve body 8 and the motor base 15.

[0034] As shown in Figures 6 and 7, pin 39 is fixed to rod 10 so as to extend radially outward from rod 10. Therefore, pin 39 rotates around axis XL as rod 10 rotates in the K direction or -K direction. Stoppers 38A and 38B are pin-shaped members that extend parallel to rod 10 (in the vertical direction in Figure 3). As shown in Figures 6 and 7, stoppers 38A and 38B are positioned symmetrically with respect to the center line CL11 perpendicular to axis XL. Therefore, in Figure 3, only stopper 38A is visible externally, while stopper 38B is hidden behind stopper 38A.

[0035] Here, the positional relationship between pin 39 and stoppers 38A and 38B will be explained using Figures 6 and 7. Figures 6 and 7 are diagrams illustrating the positional relationship between the rotation restricting section (pin 39 and stoppers 38A and 38B) and the butterfly valve body 9.

[0036] When the butterfly valve body 9 is in the closed position, the pin 39 is positioned close to the downstream stopper 38A, as shown in Figure 6. At this time, there is a small gap between the pin 39 and the stopper 38A, and the pin 39 and the stopper 38A are not in contact. However, if the butterfly valve body 9 attempts to rotate further in the -K direction from the closed position due to a malfunction of the DD motor 11 or the like, the pin 39 will come into contact with the stopper 38A, restricting the rotation of the butterfly valve body 9. The small gap between the pin 39 and the stopper 38A when the butterfly valve body 9 is in the closed position is to prevent the pin 39 from coming into contact with the stopper 38A before the butterfly valve body 9 reaches the closed position due to manufacturing tolerances.

[0037] On the other hand, when the butterfly valve body 9 is in the valve open position, the pin 39 is positioned close to the upstream stopper 38B, as shown in Figure 7. At this time, there is a small gap between the pin 39 and the stopper 38B, and the pin 39 and the stopper 38B are not in contact. However, if the butterfly valve body 9 attempts to rotate further in the K direction from the valve open position due to a malfunction of the DD motor 11 or the like, the pin 39 will come into contact with the stopper 38B, restricting the rotation of the butterfly valve body 9. The small gap between the pin 39 and the stopper 38B when the butterfly valve body 9 is in the valve open position is to prevent the pin 39 from coming into contact with the stopper 38B before the butterfly valve body 9 reaches the valve open position due to manufacturing tolerances.

[0038] The butterfly valve body 9 is formed into a disc shape by machining corrosion-resistant stainless steel. Furthermore, the shape of the outer edge of the butterfly valve body 9 is point-symmetrical with respect to the axis XL of the rod 10 when viewed in the axial direction of the rod 10, with the left half in the flow direction in the valve closed position (the lower half portion 9A in Figure 4) and the right half in the flow direction in the valve closed position (the upper half portion 9B in Figure 4) being point-symmetric. Specifically, it is as follows:

[0039] As shown in Figure 4, the outer periphery of portion 9A of the butterfly valve body 9 is provided with a maximum outer diameter portion 91A, a first chamfer 92A, and a second chamfer 93A.

[0040] The largest outer diameter portion 91A is the part of the outer edge with the largest diameter. However, since the diameter of the largest outer diameter portion 91A is set to be smaller than the diameter of the flow path 30 (valve opening 8a), when the butterfly valve body 9 is in the valve closed position, the largest outer diameter portion 91A faces the inner surface of the flow path 30 (valve opening 8a) parallel to it, forming a gap of several tens to several hundreds of micrometers between the flow path 30 (valve opening 8a) and the largest outer diameter portion 91A. In other words, the flow path 30 (valve opening 8a) is not completely sealed even when the butterfly valve body 9 is in the valve closed position. Therefore, the vacuum vessel 32 is constantly being evacuated by the suction force of the vacuum pump 33 without the evacuating being stopped.

[0041] The dimension t11 in the thickness direction of the butterfly valve body 9 at the maximum outer diameter portion 91A is preferably more than 0.5% and 10% or less of the inner diameter of the flow path 30 (valve hole 8a). In this embodiment, the inner diameter of the flow path 30 (valve hole 8a) is 100 mm, and the dimension t11 is approximately more than 0.5 mm and 10 mm or less.

[0042] The first chamfer 92A reduces the diameter of the butterfly valve body 9 from the maximum outer diameter portion 91A toward the opposite side of the K direction (i.e., the downstream side). The angle A11 of the first chamfer 92A with respect to the thickness direction of the butterfly valve body 9 is preferably 30 degrees or less. However, when the butterfly valve body 9 rotates in the K direction, the angle must be such that the ridge line RL1 where the first chamfer 92A and the downstream end face 94 of the butterfly valve body 9 intersect does not interfere with the inner circumferential surface of the flow path 30 (valve hole 8a).

[0043] The second chamfer 93A reduces the diameter of the butterfly valve body 9 from the maximum outer diameter portion 91A toward the K direction side (i.e., the upstream side). It is desirable to make the angle A12 of the second chamfer 93A with respect to the thickness direction of the butterfly valve body 9 as small as possible. However, the angle must be such that when the butterfly valve body 9 rotates in the -K direction from the valve closed position and the pin 39 contacts the stopper 38A, the ridge line RL2 where the second chamfer 93A and the upstream end face 95 of the butterfly valve body 9 intersect does not interfere with the inner circumferential surface of the flow path 30 (valve hole 8a).

[0044] As shown in Figure 4, the outer periphery of portion 9B of the butterfly valve body 9 is provided with a maximum outer diameter portion 91B, a first chamfer 92B, and a second chamfer 93B. These maximum outer diameter portion 91B, the first chamfer 92B, and the second chamfer 93B are point-symmetric with respect to the maximum outer diameter portion 91A, the first chamfer 92A, and the second chamfer 93A formed on the outer periphery of portion 9A, with respect to the axis XL.

[0045] Therefore, unlike the first chamfer 92A of section 9A, the first chamfer 92B reduces the diameter of the butterfly valve body 9 from the maximum outer diameter section 91B toward the upstream side. However, it is the same as the first chamfer 92A in that it reduces the diameter of the butterfly valve body 9 toward the opposite side of the K direction. Also, the angle of the first chamfer 92B with respect to the thickness direction of the butterfly valve body 9 is set in the same way as angle A11 described above.

[0046] Furthermore, the second chamfer 93B, unlike the second chamfer 93A of section 9A, reduces the diameter of the butterfly valve body 9 downstream from the maximum outer diameter section 91B. However, it is the same as the second chamfer 93A in that it reduces the diameter of the butterfly valve body 9 toward the K direction. Also, the angle of the second chamfer 93B with respect to the thickness direction of the butterfly valve body 9 is set in the same way as angle A12 described above.

[0047] (Regarding the effects of butterfly valves) The butterfly valve 1 having the above configuration operates as follows.

[0048] Even when the butterfly valve body 9 is in the closed position shown in Figure 4, it has a gap of several tens of micrometers to several hundred micrometers between the inner surface of the flow path 30 (valve opening 8a), so the non-sealed butterfly valve 1 is always evacuating the vacuum vessel 32. Figure 4 shows the closed position of the butterfly valve body 9, and the butterfly valve body 9 rotates at any angle between the closed position (rotation angle 0°) and the open position (rotation angle 90°) to adjust the flow area of ​​the flow path 30 (valve opening 8a) so that the vacuum vessel 32 reaches the target pressure.

[0049] To widen the pressure control range, the conductance needs to be reduced when the valve is closed or at a small opening (e.g., opening of 10 degrees or less) (i.e., gas needs to be less likely to flow through the gap between the butterfly valve body 9 and the flow path 30 (valve hole 8a)).

[0050] The butterfly valve body 9 of the butterfly valve 1 according to this embodiment is characterized by having, in an axial view of the rod 10, a maximum outer diameter portion 91A, 91B provided point-symmetrically with respect to the axis XL, facing the inner circumferential surface of the flow path 30 (valve hole 8a) in the valve closed position, and a chamfer (first chamfer 92A, 92B) that reduces the diameter of the butterfly valve body 9 in the opposite direction from the rotation direction (K direction) from the valve closed position to the valve open position, extending from the maximum outer diameter portion 91A. Therefore, while keeping the thickness of the butterfly valve body 9 the same as in the conventional design, the size (dimension t11) of the maximum outer diameter portion 91A, 91B in the thickness direction of the butterfly valve body 9 can be increased. Thus, it is possible to reduce the conductance in the valve closed state or at small openings (for example, openings of 10 degrees or less) while avoiding a decrease in conductance in the valve open state.

[0051] Furthermore, it is preferable that the thickness of the butterfly valve body 9 at its maximum outer diameter portions 91A and 91B (dimension t11) is greater than 0.5% and less than or equal to 10% of the inner diameter of the flow path 30 (valve opening 8a). If dimension t11 is less than or equal to 0.5% of the inner diameter of the flow path 30 (valve opening 8a), the above-mentioned effect of reducing conductance cannot be sufficiently obtained. If it exceeds 10% of the inner diameter of the flow path 30 (valve opening 8a), when the valve is open, the flow area of ​​the flow path becomes smaller, reducing conductance and leading to a decrease in the efficiency of pressure control. In addition, it becomes impossible to create first chamfers 92A and 92B of sufficient size, and interference between the butterfly valve body 9 (ridge line RL1) and the flow path 30 (valve opening 8a) occurs when rotating in the K direction.

[0052] Furthermore, the butterfly valve 1 according to this embodiment is characterized in that the angle A11 of the chamfer (first chamfers 92A, 92B) with respect to the thickness direction of the butterfly valve body 9 is 30 degrees or less. Therefore, it is possible to reduce the conductance in the valve closed state or at a small opening (for example, an opening of 10 degrees or less) as much as possible.

[0053] Note that the shape of the butterfly valve body 9 described above is just one example, and a butterfly valve body 51 as shown in Figures 8 and 9 may also be used. Figure 8 is a cross-sectional view corresponding to Figure 4, and shows a state using the modified butterfly valve body 51. Figure 9 is a perspective view of the modified butterfly valve body 51.

[0054] The axes of the first chamfers 92A and 92B of the butterfly valve body 9 are coaxial with the axis of the butterfly valve body 9. However, as shown in Figures 8 and 9 for the butterfly valve body 51, the axis AL of the first chamfers 512A and 512B may have an angle A21 with respect to the axis BL of the butterfly valve body 51. The axis BL of the butterfly valve body 51 is the axis of the maximum outer diameter portions 511A and 511B, and is located coaxial with the flow path 30. The axis AL of the first chamfers 512A and 512B is the axis when the first chamfers 512A and 512B are viewed as a single cylinder with a diameter D11.

[0055] In the butterfly valve body 9, the process of machining the first chamfer 92A of part 9A and the process of machining the shape of the first chamfer 92B of part 9B are separate processes. However, if the axis AL of the first chamfers 512A and 512B is set at an angle with respect to the axis BL of the butterfly valve body 51, as in the butterfly valve body 51, then it becomes unnecessary to separate the processes for machining the first chamfer 512A of part 51A and the first chamfer 512B of part 51B.

[0056] Next, the effect of the butterfly valve bodies 9 and 51 on reducing conductance will be explained using Figure 10. Figure 10 is a graph summarizing the relationship between the rotation angle of the butterfly valve body and the pressure in the vacuum vessel.

[0057] The horizontal axis of the graph, "Rotation Angle," represents the rotation angle of the butterfly valve body 9,51. For example, 10deg means that the butterfly valve body has rotated 10 degrees in the K direction from the valve closed position. The vertical axis of the graph, "Pressure Inside Vacuum Vessel," represents the pressure inside the vacuum vessel 32 when gas is supplied to the vacuum vessel 32 from the gas supply source 37. Note that the values ​​on the vertical axis do not represent specific pressure values. Rather, with the pressure inside the vacuum vessel 32 at a rotation angle of 10deg in the conventional technology set as the baseline value "1," "2" on the vertical axis means twice the baseline pressure, "3" means three times the baseline pressure, "4" means four times the baseline pressure, "5" means five times the baseline pressure, and "6" means six times the baseline pressure. The higher the value on the vertical axis, the higher the pressure inside the vacuum vessel is maintained, which means that the conductance of the butterfly valve is small.

[0058] Furthermore, in the legend, "Prior Art" means that the square-shaped plots in the graph represent data when using the butterfly valve body disclosed in Patent Document 1; "Valve Body 51" means that the circular-shaped plots in the graph represent data when using the valve body 51; "Valve Body 9 (3mm)" means that the cross-shaped plots in the graph represent data when using the valve body 9 with a dimension t11 of 3mm; and "Valve Body 9 (5mm)" means that the triangular-shaped plots in the graph represent data when using the butterfly valve body 9 with a dimension t11 of 5mm.

[0059] As shown in Figure 10, in all the data for "Conventional Technology," "Valve Body 51," "Valve Body 9 (3 mm)," and "Valve Body 9 (5 mm)," it can be seen that the pressure in the vacuum vessel increases as the rotation angle decreases. This is because as the rotation angle decreases, the flow area of ​​the flow path 30 (valve hole 8a) is narrowed, and the conductance is reduced.

[0060] The valve body 51 maintains a generally higher pressure in the vacuum vessel 32 than in the "conventional technology" between rotation angles of 0 and 10 degrees (i.e., conductance is reduced). In particular, at a rotation angle of 2 degrees, the pressure rises to approximately 3 compared to approximately 2.8 in the conventional technology (i.e., the pressure in the vacuum vessel 32 is about 1.1 times higher), and at a rotation angle of 0 degrees (i.e., the valve closed position), the pressure in the vacuum vessel 32 rises to approximately 4.2 compared to approximately 3 in the conventional technology (i.e., the pressure in the vacuum vessel 32 is about 1.4 times higher).

[0061] With the "valve body 9 (3 mm)," the pressure in the vacuum vessel 32 is generally maintained higher than in the "conventional technology" between rotation angles of 0 and 10 degrees (i.e., conductance is reduced). In particular, the pressure in the vacuum vessel 32 at a rotation angle of 2 degrees rises to approximately 4.2 compared to approximately 2.8 in the conventional technology (i.e., the pressure in the vacuum vessel is about 1.5 times higher), and the pressure in the vacuum vessel 32 at a rotation angle of 0 degrees (i.e., the valve closed position) rises to approximately 4.7 compared to 3 in the conventional technology (i.e., the pressure in the vacuum vessel 32 is about 1.6 times higher).

[0062] With the "valve body 9 (5 mm)," at rotation angles of 3-10 degrees, the pressure in the vacuum vessel 32 is maintained at a level equivalent to that of the "valve body 9 (3 mm)" and higher than that of the "conventional technology" (i.e., conductance is reduced). At rotation angles of 0-2 degrees, the pressure in the vacuum vessel 32 is maintained at a higher level than that of the "valve body 9 (3 mm)," and in particular, at a rotation angle of 0 degrees (i.e., the valve closed position), the pressure in the vacuum vessel 32 rises to about 5.3 compared to about 3 in the conventional technology (i.e., the pressure in the vacuum vessel 32 is about 1.8 times higher).

[0063] As described above, the butterfly valve bodies 9 and 51 can maintain a higher pressure inside the vacuum container 32 when gas is supplied to the vacuum container 32 from the gas supply source 37 compared to butterfly valve bodies of the prior art.

[0064] As shown in the data for "valve body 9 (3 mm)" and "valve body 9 (5 mm)" above, it can be seen that the larger the dimension t11 of the maximum outer diameter portions 91A and 91B, the smaller the conductance can be and the higher the pressure inside the vacuum vessel 32 can be maintained. Therefore, in order to reduce the conductance, the butterfly valve body may be made without the second chamfers 93A and 93B. This will be explained in detail using Figure 11. Figure 11 is a cross-sectional view corresponding to Figure 4 and shows the state using the modified butterfly valve body 50.

[0065] The butterfly valve body 50 has a point-symmetric shape with respect to the axis XL of the rod 10, when viewed in the axial direction of the rod 10, with the left half in the flow direction in the valve closed position (the lower half portion 50A in Figure 11) and the right half in the flow direction in the valve closed position (the upper half portion 50B in Figure 11). The outer edges of portions 50A and 50B are provided with maximum outer diameter portions 501A and 501B and first chamfers 502A and 502B, but there are no second chamfers 93A and 93B. As a result, the thickness of the butterfly valve body 50 in the maximum outer diameter portions 501A and 501B (dimension t21) is larger than the above dimension t11. In this way, by adopting a shape without the second chamfers 93A and 93B, the size of the butterfly valve body 50 in the thickness direction of the maximum outer diameter portions 501A and 501B can be increased without changing the thickness of the butterfly valve body, and the conductance can be reduced.

[0066] However, if the butterfly valve body 50 rotates in the -K direction, or during the assembly of the butterfly valve, the ridge RL3 where the upstream end face 503 of the butterfly valve body 50 intersects with the maximum outer diameter portion 501A, and the ridge RL4 where the downstream end face 504 of the butterfly valve body 50 intersects with the maximum outer diameter portion 501B, may damage the inner circumferential surface of the flow path 30. In this regard, it is preferable that the butterfly valve body 9, as shown above, has second chamfers 93A and 93B that reduce the diameter of the butterfly valve body 9 toward the rotation direction (K direction) from the maximum outer diameter portions 91A and 91B, which are provided point-symmetrically with respect to the axis XL in an axial view of the rod 10. The butterfly valve body 9, which has second chamfers 93A and 93B, reduces the risk of damaging the inner surface of the flow path 30 when the butterfly valve body 50 rotates in the -K direction or when assembling the butterfly valve.

[0067] It should be noted that this embodiment is merely illustrative and does 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 the above description, for the sake of simplicity, there is only one gas supply source 37, but it is also possible to connect multiple gas supply sources to the vacuum container 32 and switch the gas supplied to the vacuum container 32 using a switching valve or the like provided between the vacuum container 32 and the gas supply sources. [Explanation of Symbols]

[0068] 1. Non-sealed butterfly valve 9. Butterfly valve body 10. Rod (an example of a rotating shaft) 30 flow channels 32 Vacuum container 33 Vacuum pump 91A Maximum outer diameter 91B Maximum outer diameter 92A First chamfer (an example of chamfering) 92B First chamfer (an example of chamfering)

Claims

1. Flow channels and A rotating shaft positioned perpendicular to the flow path, A disc-shaped butterfly valve body that is rotatable around the axis of the aforementioned rotating shaft between a valve-closed position that minimizes the flow area of ​​the flow path and a valve-open position that maximizes the flow area, Equipped with, In an open butterfly valve used for pressure control of a vacuum vessel, The butterfly valve body is In the axial view of the aforementioned rotation axis, the following are provided: At the valve closed position, the maximum outer diameter portion facing the inner circumferential surface of the flow path, From the maximum outer diameter portion, a chamfer is made to reduce the diameter of the butterfly valve body in the direction opposite to the rotational direction from the valve closed position to the valve open position, To be equipped, A non-sealed butterfly valve characterized by the following features.

2. In the non-sealed butterfly valve according to claim 1, The size of the maximum outer diameter portion of the butterfly valve body in the thickness direction is greater than 0.5% and less than or equal to 10% of the inner diameter of the flow path. A non-sealed butterfly valve characterized by the following features.

3. In the non-sealed butterfly valve according to claim 1 or 2, The angle of the chamfer with respect to the thickness direction of the butterfly valve body shall be 30 degrees or less. A non-sealed butterfly valve characterized by the following features.

4. In the non-sealed butterfly valve according to claim 1 or 2, The butterfly valve body is In an axial view of the rotation axis, a second chamfer is provided, which is point-symmetrically arranged with respect to the axis, and reduces the diameter of the butterfly valve body toward the rotational direction from the maximum outer diameter portion. A non-sealed butterfly valve characterized by the following features.

5. In the non-sealed butterfly valve according to claim 1 or 2, the axis of the chamfer is at an angle with respect to the axis of the maximum outer diameter portion. A non-sealed butterfly valve characterized by the following features.

6. In the non-sealed butterfly valve according to claim 1 or 2, The butterfly valve body is provided with a rotation restricting part that restricts it from rotating in the opposite direction to the rotation direction. A non-sealed butterfly valve characterized by the following features.

7. In the non-sealed butterfly valve according to claim 1 or 2, The butterfly valve body is provided with a rotation restricting part that restricts further rotation in the rotational direction from the valve open position. A non-sealed butterfly valve characterized by the following features.

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