butterfly valve

Abstract

To supply purge gas to the butterfly valve 1 to prevent control fluid from flowing into the magnetic fluid seal 19 from the flow path 30 through the through-hole 8d, a purge gas flow path 60 is included. A switching valve 62 for switching the purge gas flow path 60 and a pressure gauge 64 for measuring the pressure value of the purge gas flow path 60 are provided on the upstream side of the purge gas flow path 60. Downstream of the pressure gauge 64, the purge gas flow path 60 is connected between the magnetic fluid seal 19 of the butterfly valve 1 and the flow path 30, and is connected to the flow path 30 through the through-hole 8d. A control device 70 is included, at least for controlling the switching valve 62. The control device 70 includes a monitoring program for monitoring the pressure value P.

Description

Technical Field

[0001] The present invention relates to a butterfly valve, comprising a motor, a flow path for controlling the flow of fluid, a rod with one end connected to the motor and the other end inserted into the flow path, and a butterfly valve body connected to the rod within the flow path. Background Technology

[0002] In semiconductor manufacturing processes, butterfly valves with high flow conduction are often used as vacuum pressure control devices between a vacuum chamber and a vacuum pump to control the vacuum pressure in the vacuum chamber. As disclosed in Patent Document 1, butterfly valves are used in applications where a drive unit including a motor is combined with a valve part containing a flow path and a butterfly valve body. A rod connected to the motor extends from the drive unit, inserts into the flow path through a through-hole in the valve part, and is then connected to the butterfly valve body. [Previous Technical Documents] [Patent Literature]

[0003] Patent Document 1: Japanese Patent Application Publication No. 2019-19851 Summary of the Invention The technical problem that the invention aims to solve

[0004] In recent years, the widespread adoption of atomic layer deposition (ALD) has led to faster semiconductor manufacturing cycles. Consequently, butterfly valve stems require high durability, withstanding tens of millions of rotations. In the butterfly valve disclosed in Patent Document 1, an O-ring is provided on the outer circumferential surface of the stem to prevent control fluid (e.g., process gas) from flowing out of the butterfly valve through the through-hole in the stem insertion path. Although the through-hole is sealed, the O-ring lacks sufficient durability to withstand tens of millions of rotations.

[0005] Therefore, the applicant of this application has filed a butterfly valve in Japanese Patent Application No. 2020-009768. This butterfly valve has a magnetic fluid seal formed on the outer periphery of the rod between the motor and the valve section, thereby blocking gas flowing out of the flow channel through the through-hole to the outside of the butterfly valve. The magnetic fluid seal is characterized by its resistance to degradation even after tens of millions of rotations of the rod, and its superior sealing durability relative to rod rotation compared to O-rings.

[0006] Furthermore, the butterfly valve disclosed in Japanese Patent Application No. 2020-009768 includes a purge gas flow path connected to the flow path via a through-hole. By allowing the purge gas to flow from this purge gas flow path through the through-hole to the flow path, the processing gas that is about to enter the drive unit side from the flow path through the through-hole can be pushed back into the flow path.

[0007] The aforementioned magnetic fluid seal is formed by holding the magnetic fluid in place using magnetic force. Therefore, if the load on the magnetic fluid seal exceeds the pressure required to hold it in place by magnetic force, the magnetic fluid seal may be damaged.

[0008] The following situations can be considered as excessive pressure loads on the magnetic fluid seal. For example, if purge gas is supplied to the butterfly valve when the vacuum pump is not operating (i.e., when the flow path of the butterfly valve is not under negative pressure), the purge gas will accumulate in the flow path, causing the pressure inside the butterfly valve to rise. Conversely, if purge gas is not supplied for an extended period while the vacuum pump is operating (i.e., when the flow path of the butterfly valve is under negative pressure), the pressure inside the flow path will drop, resulting in a high vacuum state inside the butterfly valve. Consequently, if the pressure inside the butterfly valve rises or falls into a negative pressure state, the magnetic fluid seal will be subjected to excessive pressure, and the magnetic fluid seal may be damaged. Therefore, to protect the magnetic fluid seal, it is necessary to manage the start and stop of the purge gas supply.

[0009] The present invention is proposed to solve the above-mentioned problems, and its purpose is to provide a butterfly valve that can prevent the magnetic fluid seal from being damaged by preventing excessive pressure on the magnetic fluid seal. Means for solving technical problems

[0010] To solve the above problems, a butterfly valve according to an embodiment of the present invention has the following structure.

[0011] The butterfly valve includes a motor, a flow path through which a control fluid flows, a rod with one end connected to the motor and the other end inserted into the flow path, and a butterfly valve body connected to the rod within the flow path. A magnetic fluid seal is included between the motor and the flow path to prevent the control fluid from leaking from the flow path through the insertion portion of the rod into the motor. To supply purge gas to the butterfly valve to prevent the control fluid from flowing from the flow path through the insertion portion into the magnetic fluid seal, a purge gas flow path is included. An upstream switch valve for opening and closing the purge gas flow path and a pressure gauge for measuring the pressure value of the purge gas flow path are provided in the purge gas flow path. Downstream of the pressure gauge, the purge gas flow path connects the magnetic fluid seal of the butterfly valve to the flow path and communicates with the flow path through the insertion portion. The valve includes at least a control device for controlling the switch valve, and the control device includes a monitoring program for monitoring the pressure value. The effects of the invention

[0012] The butterfly valve of the present invention includes a control device that controls at least the switching valve of the purge gas flow path and measures the pressure value of the purge gas flow path, and monitors this pressure value through a monitoring program. Since the purge gas flow path is connected between the magnetic fluid seal and the flow path of the butterfly valve on the downstream side of the pressure gauge, the measurement and monitoring of the pressure value of the purge gas flow path is the same as the measurement and monitoring of the pressure under load on the magnetic fluid seal.

[0013] While the control device measures and monitors the pressure value of the purge gas flow path (that is, while measuring and monitoring the pressure load on the magnetic fluid seal), the start or stop of the purge gas can be managed via the control valve. This prevents excessive pressure on the magnetic fluid seal and protects it from damage. Furthermore, since the purge gas flow path is connected to the flow path via the insertion part of the insertion rod, abnormal conditions in the flow path can be detected by measuring and monitoring the pressure value of the purge gas flow path. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a vacuum pressure control system using a butterfly valve according to this embodiment. Figure 2 This is a cross-sectional view of the butterfly valve according to this embodiment, cut in a direction parallel to the axis of rotation and parallel to the flow path. Figure 3 This is a cross-sectional view of the butterfly valve according to this embodiment, cut in a direction parallel to the axis of rotation and perpendicular to the flow path. Figure 4 yes Figure 3 A magnified view of part X2. Figure 5 yes Figure 2 A magnified view of part X1. Figure 6 It is a flowchart representing the action flow of the monitoring program. Detailed Implementation

[0015] Embodiments of the butterfly valve of the present invention will be described in detail with reference to the accompanying drawings. Figure 1 This is a schematic diagram of a vacuum pressure control system using the butterfly valve 1 according to this embodiment.

[0016] The butterfly valve 1 in this embodiment is used in semiconductor manufacturing processes. For example, such as... Figure 1 As shown, a piping 34 is provided connecting a vacuum chamber 32 for wafer deposition and a vacuum pump 33 for venting the vacuum chamber 32. The vacuum chamber 32 is used as a vacuum pressure control device to control the pressure of the processing gas (an example of a control fluid) supplied by the processing gas supply source 37.

[0017] Figure 2 This is a cross-sectional view of the butterfly valve 1 according to this embodiment, taken along the axis RA parallel to the rotation axis 11a and parallel to the flow path 30. Furthermore, Figure 3 This is a cross-sectional view of the butterfly valve 1 according to this embodiment, taken along the axis RA parallel to the rotation axis 11a and perpendicular to the flow path 30. Furthermore, Figure 2 as well as Figure 3 Both indicate that the valve is closed. Also, Figure 4 yes Figure 3 A magnified view of part X2. Figure 5 yes Figure 2 A magnified view of part X1.

[0018] like Figure 2 as well as Figure 3 As shown, the butterfly valve 1 includes a drive unit 2 and a valve unit 3. The drive unit 2 has a durable direct drive motor 11 (an example of a motor, hereinafter referred to as a DD motor). Since the DD motor 11 does not require intermediate mechanisms such as a reducer, the drive unit 2 is miniaturized, noise is reduced, and response performance, speed stability, and positioning accuracy are improved. Therefore, the accuracy of vacuum pressure control of the butterfly valve 1 is improved. Furthermore, as... Figure 2 as well as Figure 3 As shown, the DD motor 11 has a rotating shaft 11a, and the rotation center of the rotating shaft 11a is the axis RA.

[0019] like Figure 2 as well as Figure 3 As shown, one end of rod 10 ( Figure 2 as well as Figure 3 The upper end of the rod is connected to the rotating shaft 11a by a metal leaf spring coupling 17. With the coupling 17, even if the rod 10 is heated by the processing gas (e.g., gas at about 200 degrees Celsius) flowing through the flow path 30 described later, this heat is difficult to transfer to the DD motor 11.

[0020] Furthermore, the drive unit 2 is constructed by stacking and combining the housing 16, the heat insulation member 7, the heat sink 15, and the DD motor 11. Since the drive unit 2 has the heat sink 15 and the heat insulation member 7 between the DD motor 11 and the valve unit 3, even if the valve unit 3 is heated by the processing gas or the heaters 27A and 27B described later, this heat is difficult to transfer to the DD motor 11.

[0021] The outer casing 16 is formed as a hollow cylinder, through which the rod 10 is inserted. A cylindrical magnetic member 18, covering the outer circumferential surface of the rod 10, is coaxially arranged with the rod 10. The inner diameter of the magnetic member 18 is larger than the outer diameter of the rod 10, and a gap 16e is provided between the inner circumferential surface 181 of the magnetic member 18 and the outer circumferential surface 101 of the rod 10. Within the gap 16e, a plurality of films 191 are formed along the axis RA by the magnetic force of the magnetic member 18, thereby forming a magnetic fluid sealing portion 19.

[0022] An O-ring 31 is provided between the housing 16 and the valve part 3 to maintain the airtightness of the flow path 30 and the buffer volume 51 described later.

[0023] Two ball bearings 21A and 21B are arranged adjacent to each other in the axial direction of the rod 10 on the DD motor 11 side of the magnetic fluid seal 19. These ball bearings 21A and 21B pivotally support the rod 10 in a rotatable manner. The ball bearings 21A and 21B are supported by the bearing cap 24 and the magnetic component 18. Figure 2 as well as Figure 3 It is clamped and fixed from the top and bottom.

[0024] Furthermore, the end 16c of the outer casing 16 on the valve section 3 side has a through hole 16b with an inner diameter larger than the outer diameter of the rod 10, and the rod 10 inserted into the outer casing 16 is inserted into the valve section 3 through the through hole 16b.

[0025] The valve section 3, which is connected to the drive section 2, has a valve body 8 and a butterfly valve body 9. The valve body 8 is made of stainless steel, which is corrosion-resistant and heat-resistant.

[0026] Valve body 8 in Figure 2 The left end has a connector 5, in Figure 2 The right end has a connector 6, and an input-side flow path 8b is formed on the inner wall of the connector 5, and an output-side flow path 8c is formed on the inner wall of the connector 6. Then, between the input-side flow path 8b and the output-side flow path 8c, a... Figure 3 The valve hole 8a is formed by the arc-shaped inner wall in the mid-section. (Example) Figure 2 As shown, the input-side flow path 8b, valve port 8a, and output-side flow path 8c are coaxially arranged and connected, forming a series of flow paths 30. Then, for example, in semiconductor manufacturing processes, the connector 5 and the vacuum chamber 32 (see reference...) Figure 1 ), connector 6 and vacuum pump 33 (refer to) Figure 1 ), respectively via piping 34 (refer to Figure 1 The vacuum chamber 32 is connected and vented through the flow path 30.

[0027] Also, such as Figure 3As shown, the valve body 8 includes a thermocouple 28, which serves as a temperature sensor, to measure the temperature of the valve body 8. Additionally, the valve body 8 includes a pair of heaters 27A and 27B to clamp the valve orifice 8a in the diametrical direction, thereby maintaining the temperature of the fluid flowing through the flow path 30. The heaters 27A and 27B are cartridge heaters and are connected to an external control device (not shown) of the butterfly valve 1. The control device then controls the heaters 27A and 27B to open or close based on the measurements from the thermocouple 28, thus adjusting the temperature of the valve body 8. Furthermore, the valve body 8 includes a thermostat 29. When the heaters 27A and 27B malfunction and the valve body 8 is overheated, the thermostat 29 activates. When the thermostat 29 activates, the control device stops the heaters 27A and 27B.

[0028] In addition, such as Figure 2 as well as Figure 3 As shown, the valve body 8 has a through hole 8d (an example of an insertion part) extending from the end face (hereinafter referred to as the upper end face 8e) that is coupled to the drive part 2 to the valve hole 8a. This through hole 8d and the through hole 16b of the housing 16 are located coaxially and communicate with each other. That is, the gap 16e formed in the magnetic fluid sealing part 19 and the flow path 30 are connected through the through hole 16b and the through hole 8d. Furthermore, in Figure 1 In the diagram, the magnetic fluid sealing part 19 is connected to the flow path 30 through the through hole 16b and the insertion hole 8d. This schematically shows that the gap 16e formed by the magnetic fluid sealing part 19 through the through hole 16b and the insertion hole 8d is connected to the flow path 30.

[0029] Because the gap 16e formed in the magnetic fluid seal 19 communicates with the flow path 30, the processing gas discharged from the vacuum chamber 32 flows through the flow path 30 and enters the drive unit 2 through the insertion hole 8d. However, because the magnetic fluid seal 19 is formed in the gap 16e of the housing 16, the processing gas is blocked by the magnetic fluid seal 19 and cannot reach the DD motor 11. This prevents the processing gas from flowing out of the butterfly valve 1, contaminating the outside air, shortening the life of the butterfly valve 1, and ultimately reducing semiconductor manufacturing efficiency. Furthermore, the sealing performance of the magnetic fluid seal 19 does not easily deteriorate even if the rod 10 rotates tens of millions of times, so its durability is very high relative to the increase in the number of rotations.

[0030] Furthermore, the rod 10, which passes through the through hole 16b and the insertion hole 8d, can be further inserted into the insertion hole 8d via the through hole 16b. Then, the rod 10, which passes through the insertion hole 8d, is positioned perpendicular to the flow path 30 and mounted on the valve hole 8a. The insertion hole 8d includes a bushing 20, the inner circumferential surface 20a of which forms a portion of the inner circumferential surface of the insertion hole 8d. Because the bushing 20 is made of a resin with high corrosion resistance and good sliding properties, smooth rotation of the rod 10 is ensured.

[0031] The diameter of the upper end of the through hole 8d (the portion opening on the upper end face 8e) is larger than the portion including the bushing 20, and as... Figure 4 As shown, a first space 511 is formed between the rod 10 and its outer peripheral surface. Additionally, a second space 512 is formed between the inner peripheral surface of the through hole 16b in the housing 16 and the outer peripheral surface of the rod 10, forming a buffer volume 51. By providing the buffer volume 51, even if a sharp pressure drop occurs in the flow path 30, the amount of gas drawn from the drive unit 2 into the flow path 30 is increased compared to the case without the buffer volume 51. Therefore, the pressure shock applied to the magnetic fluid seal 19 is mitigated, and damage to the magnetic fluid seal 19 can be prevented.

[0032] Rod 10 is formed into a cylindrical shape by machining a non-magnetic, corrosion-resistant stainless steel alloy (e.g., SUS316L). For example... Figure 5 As shown, on the outer peripheral surface of the inserted portion of the insertion hole 8d of the rod 10, a plurality of recesses 10a to 10e are arranged side by side in the axial direction of the rod 10. A labyrinth seal 50 is formed by the inner peripheral surface of the insertion hole 8d (the inner peripheral surface 20a of the bushing 20) and the plurality of recesses 10a to 10e. Since the labyrinth seal 50 limits the amount of gas drawn from the drive unit 2 into the flow path 30 even if a sharp pressure drop occurs, it can prevent a sharp pressure drop in the drive unit 2. As a result, the pressure shock applied to the magnetic fluid seal 19 is mitigated, and damage to the magnetic fluid seal 19 can be prevented.

[0033] Also, such as Figure 2 as well as Figure 3 As shown, one end of rod 10 is inserted into one side of flow path 30. Figure 2 as well as Figure 3 The lower end of the rod (in the middle) is pivotally supported by bushing 22. Bushing 22 is made of resin with high corrosion resistance and good sliding properties. As described above, since the rod 10 is also pivotally supported by ball bearings 21A and 21B, the rod 10 is pivotally supported in a double-held state by ball bearings 21A and 21B and bushing 22. With the rod 10 pivotally supported in a double-held state, the rotation center axis is stable and not easily shaken.

[0034] The insertion flow path 30 of the rod 10 includes a valve body mounting portion 10f, to which the butterfly valve body 9 is coupled. The butterfly valve body 9 is, for example, formed into a circular plate shape by cutting stainless steel with corrosion resistance and heat resistance. Its outer diameter is approximately the same as the inner diameter of the valve hole 8a, and the gap between the outer periphery of the butterfly valve body 9 and the inner wall of the valve hole 8a is extremely small.

[0035] like Figure 2 As shown, the butterfly valve body 9 is attached to the rod 10 by means of, for example, screws 25A, 25B, 25C and washers 26A, 26B, 26C. Furthermore, screws 25A, 25B, and 25C are all of the same type, and washers 26A, 26B, and 26C are all of the same type.

[0036] Since the butterfly valve body 9 is connected to the rod 10, as the rotating shaft 11a of the DD motor 11 rotates around the axis RA, the rod 10, connected to the coupling 17 via the rotating shaft 11a, is rotated, and thus the butterfly valve body 9 also rotates. For example, Figure 2 as well as Figure 3 The butterfly valve 1 shown is in the fully closed position with the valve body 9 closed by the valve port 8a. From this position, when the rotating shaft 11a of the DD motor 11 rotates 90 degrees in the positive direction K around the axis RA, the rod 10 rotates in the positive direction K, and the butterfly valve body 9 also rotates 90 degrees in the same direction. Thus, the butterfly valve body 9 becomes fully open. When the butterfly valve body 9 is fully open, the flow path 30 is open, and a large amount of processing gas can be discharged from the vacuum chamber 32 by the vacuum pump 33.

[0037] On the other hand, when the butterfly valve body 9 is in the fully open position, when the rotating shaft 11a of the DD motor 11 rotates 90 degrees in the negative direction -K, opposite to the direction when the valve is open, with the axis RA as the center, the rod 10 rotates in the negative direction -K, and simultaneously, the butterfly valve body 9 becomes fully closed. Furthermore, when the butterfly valve body 9 is fully closed, because a very small gap is provided between the outer circumferential surface of the butterfly valve body 9 and the inner wall of the valve hole 8a, the flow path 30 is not completely sealed. In other words, the butterfly valve body 9 acts as a restrictor. Therefore, even when the butterfly valve body 9 is fully closed, the vacuum chamber 32 does not completely stop exhausting; it remains in a state where exhausting continues. This is because the ALD only needs to control the pressure of the vacuum chamber 32, and does not need to completely seal the flow path 30.

[0038] Next, the protection of the magnetic fluid seal 19 will be explained from the viewpoints of corrosion resistance and pressure resistance.

[0039] First, the protection of the magnetic fluid seal 19 will be explained from the viewpoint of corrosion resistance. Since the magnetic fluid constituting the magnetic fluid seal 19 has low corrosion resistance, it may corrode upon contact with the process gas. Therefore, a purging gas (e.g., nitrogen) is supplied to the butterfly valve 1 to prevent the process gas from reaching the magnetic fluid seal 19. Figure 1 As shown, the purge gas is supplied to the butterfly valve 1 via a purge gas flow path 60 extending from the purge gas supply source 61 and connected between the magnetic fluid seal 19 and the flow path 30. The flow rate is, for example, 500cc to 1000cc / minute, and the pressure value is approximately kPa.

[0040] The purging gas flow path 60 is connected by piping 65 and an internal flow path 44 formed inside the valve section 3 of the butterfly valve 1 (see reference). Figure 4 The piping 65 is constructed as follows: The purge gas supply source 61 is upstream, and from the upstream side, a switching valve 62, a flow controller 63, and a pressure gauge 64 are sequentially included. The switching valve 62, when closed, cuts off the supply of purge gas to the butterfly valve 1. On the other hand, when open, purge gas can be supplied to the butterfly valve 1. The flow controller 63 can control the flow rate of the purge gas supplied to the butterfly valve 1 based on the flow command value F11 output from the control device 70. The pressure gauge 64, for example, is a strain gauge pressure sensor that measures the pressure value of the purge gas flow path 60. The switching valve 62, pressure gauge 64, and flow controller 63 are connected to the control device 70.

[0041] The control device 70 incorporates a central processing unit 701, a storage device 702, and a communication device 703. The storage device 702 stores a monitoring program for monitoring the pressure values ​​of the purge gas flow path 60 measured by the pressure gauge 64. It can also store the measured values ​​from the pressure gauge 64 and the flow rate values ​​measured by the flow controller 63. The switching valve 62, pressure gauge 64, and flow controller 63 are connected to the control device 70 wirelessly or wiredly via the communication device 703.

[0042] The central processing unit 701 is electrically connected to the storage device 702 and the communication device 703. Based on the monitoring program stored in the storage device 702, it performs actions such as opening or closing the switching valve 62, measuring the pressure value via the pressure gauge 64, storing the measured pressure value in the storage device 702, controlling the flow controller 63, measuring the flow value, or storing the measured flow value in the storage device 702. Furthermore, it notifies external devices of alarms via the communication device 703. The pressure value measured by the pressure gauge 64 is sampled at fixed time intervals (e.g., every few milliseconds). Regarding alarm notifications, the control device 70 includes a display device, where alarms can be displayed.

[0043] Piping 65 is connected to valve section 3 downstream of pressure gauge 64. More specifically, as... Figure 3 As shown, the inlet 41 for supplying purge gas is connected to the valve body 8 via the purge gas pipe 42, and the piping 65 is connected to this inlet 41. Thus, the piping 65 is connected to the internal flow path 44.

[0044] like Figure 4 As shown, the internal flow path 44 is composed of a flow path 42a formed inside the purge gas pipe 42, a connecting hole 8g, an insertion hole 8f (space 81) for inserting the heat exchanger 43 (described later), a hollow portion 43a of the heat exchanger 43, and connecting holes 8h and 8i.

[0045] The purge gas pipe 42 extends from the inlet 41 to the valve body 8. Thus, the purge gas supplied to the inlet 41 flows into the interior of the valve body 8 through the flow path 42a of the purge gas pipe 42.

[0046] The insertion hole 8f is disposed at an angle relative to the axis RA, passing through from the upper end face 8e of the valve body 8 to the vicinity of the heater 27A. This insertion hole 8f is connected to the flow path 42a of the purge gas pipe 42 via the connecting hole 8g, and is also connected to the insertion hole 8d of the valve body 8 via the connecting holes 8h and 8i.

[0047] A cylindrical heat exchanger 43, having an outer diameter slightly smaller than the inner diameter of the insertion hole 8f and a hollow portion 43a inside, is inserted into the insertion hole 8f. Because the heat exchanger 43 has an outer diameter slightly smaller than the inner diameter of the insertion hole 8f, a space 81 is formed between the outer circumferential surface of the heat exchanger 43 and the insertion hole 8f. Then, an O-ring 45 is installed at the end of the valve body 8 on the upper end face 8e side of the heat exchanger 43, and the O-ring 45, compressed by the insertion hole 8f, seals the space 81. Then, the internal flow path 44 is connected to the flow path 30 via the through hole 8d of the valve body 8.

[0048] As described below, the purge gas flows into the aforementioned purge gas flow path 60. The purge gas supplied from the purge gas supply source 61 and passing through the piping 65 is introduced into the purge gas pipe 42a from the inlet 41. Then, the purge gas passes through the connecting hole 8g and reaches the insertion hole 8f. At this time, the O-ring 45 prevents the purge gas from flowing towards the upper end face 8e of the valve body 8. Therefore, the purge gas flows through the insertion hole 8f (space 81) to the lowest end of the heater 27A side. Then, the purge gas reaching the lowest end of the insertion hole 8f (space 81) flows through the hollow portion 43a of the heat exchanger 43 to the upper end face 8e side of the valve body 8. Since the heat exchanger 43 is heated to approximately 200 degrees Celsius by the heater 27A, the purge gas is heated as it passes through the insertion hole 8f (space 81) and the hollow portion 43a. Then, the purge gas that reaches the upper end face 8e of the valve body 8 through the hollow part 43a flows further through the connecting holes 8h and 8i to the insertion hole 8d. Since a magnetic fluid sealing part 19 is formed above the insertion hole 8d, the purge gas does not flow into the DD motor 11 side, and the purge gas that reaches the insertion hole 8d is output to the flow path 30.

[0049] Since the purging gas is output to the flow path 30 through the through hole 8d, the processing gas that is about to flow out of the flow path 30 to the outside of the butterfly valve 1 through the through hole 8d is pushed back into the flow path 30. Therefore, the processing gas can be prevented from reaching the magnetic fluid seal 19, and the magnetic fluid can be prevented from being corroded due to contact with the processing gas.

[0050] Furthermore, since the processing gas is solid or liquid at room temperature, it is used after being heated to, for example, about 200 degrees Celsius. Therefore, if the temperature of the purge gas is low, the processing gas may solidify or liquefy when it comes into contact with the processing gas, and products such as solidified processing gas may accumulate in the flow path 30 or piping 34. However, in this embodiment, since the purge gas is heated to, for example, about 160 degrees Celsius by the heat exchanger 43 when it flows through the internal flow path 44, it is impossible for the purge gas to solidify or liquefy even when it comes into contact with the processing gas.

[0051] Next, the protection of the magnetic fluid seal 19 will be explained from the viewpoint of pressure resistance. The magnetic fluid forming the magnetic fluid seal 19 is held by the magnetic force of the magnetic member 18. Therefore, if the load on the magnetic fluid seal 19 exceeds the pressure of the force held by the magnetic force, the magnetic member 18 may be unable to hold the magnetic fluid, and the magnetic fluid seal 19 may be damaged.

[0052] The following situation can be considered a case of excessive pressure on the magnetic fluid seal 19. For example, if purge gas is supplied to the butterfly valve 1 when the vacuum pump 33 is not operating, that is, when the flow path 30 is not under negative pressure, the purge gas will accumulate in the flow path 30. If the purge gas accumulates in the flow path 30, the pressure in the buffer volume 51 will rise through the through hole 8d. If the pressure in the buffer volume 51 rises, the magnetic fluid seal 19 will be subjected to excessive pressure and may be damaged.

[0053] On the other hand, if the vacuum pump 33 is operating, meaning the flow path 30 is under negative pressure, and no purge gas is supplied for an extended period, the pressure within the flow path 30 will further decrease, resulting in a high vacuum state. When the flow path 30 is in a high vacuum state, the gas within the drive unit 2 is drawn into the flow path 30, also creating a high vacuum state within the drive unit 2. This can cause the base oil of the magnetic fluid constituting the magnetic fluid seal 19 to evaporate, potentially damaging the magnetic fluid seal 19. Therefore, to protect the magnetic fluid seal 19, it is necessary to monitor the pressure value of the purge gas flow path 60 and manage the start and stop of the purge gas supply.

[0054] Furthermore, when excessive pressure is applied to the butterfly valve 1 due to rapid pressure changes in the vacuum chamber 32, the holding force of the magnetic component 18 cannot withstand the pressure impact, and the magnetic fluid seal 19 may be damaged.

[0055] For example, if the pressure in the vacuum chamber 32 drops sharply due to operator error in operating the vacuum pump 33, a sharp pressure drop occurs in the flow path 30. Although purge gas is supplied to the drive unit 2 from the inlet 41, if a sharp pressure drop occurs in the flow path 30, the supply of purge gas cannot keep up, and gas in the drive unit 2 is rapidly drawn out into the flow path 30, causing a sharp pressure drop within the drive unit 2. This sharp pressure drop in the drive unit 2 may result in excessive pressure impacting the magnetic fluid seal 19, damaging it and rendering it inoperable.

[0056] Furthermore, for example, if the pressure in the vacuum chamber 32 rises sharply due to operator error in operating the vacuum pump 33, the pressure within the flow path 30 will also rise sharply. If the pressure within the flow path 30 rises sharply, the process gas will flow rapidly from the flow path 30 into the buffer volume 51, causing the pressure within the buffer volume 51 to rise sharply as well. This could potentially apply excessive pressure to the magnetic fluid seal 19, damaging it and rendering it inoperable.

[0057] Furthermore, if the magnetic fluid seal 19 is subjected to pressure exceeding its withstand pressure value, the magnetic fluid seal 19 may also be damaged, thus damaging the butterfly valve 1 itself. Therefore, in order to protect the magnetic fluid seal 19, it is necessary to monitor whether the pressure value of the flow path 30 is abnormal (that is, whether pressure shock or pressure exceeding the withstand pressure value occurs).

[0058] Therefore, according to this embodiment, the butterfly valve 1 manages the start or stop of the purge gas supply and monitors whether the pressure value of the flow path 30 is abnormal through the above-described monitoring procedure. The following uses... Figure 6 Explain the actions of the monitoring program. Figure 6 It is a flowchart representing the action flow of the monitoring program.

[0059] First, the pressure value of the purge gas flow path 60 is measured using pressure gauge 64 (step S11). Since the purge gas flow path 60 is connected between the magnetic fluid seal 19 of the butterfly valve 1 and the flow path 30, the measurement and monitoring of the pressure value of the purge gas flow path 60 is the same as the measurement and monitoring of the pressure under load on the magnetic fluid seal 19. Furthermore, since the purge gas flow path 60 is connected to the flow path 30 through the through hole 8d, abnormal conditions of the flow path 30 can be detected by measuring and monitoring the pressure value of the purge gas flow path 60.

[0060] Next, it is determined whether the measured pressure value P is less than a first threshold A (step 12). This first threshold A is, for example, atmospheric pressure. By determining whether the pressure value P is less than atmospheric pressure, it is monitored whether the vacuum pump 33 is activated (that is, whether the flow path 30 is under negative pressure).

[0061] If the vacuum pump 33 is not activated, the pressure values ​​of the flow path 30 and the purge gas flow path 60 are equivalent to atmospheric pressure. If purge gas is supplied in this state, as described above, the purge gas accumulates and the pressure rises in the buffer volume 51, and the magnetic fluid seal may be damaged. Therefore, if it is determined that the pressure value P is above the first threshold A (atmospheric pressure) (step 12: no), the switch valve 62 is closed (step S21). That is, if the switch valve 62 is in the closed state, this state is maintained, and purge gas is not supplied to the butterfly valve 1. On the other hand, if the switch valve 62 is in the open state, it is closed, and the supply of purge gas is stopped.

[0062] If the vacuum pump 33 operates, the flow path 30 and the purge gas flow path 60 are under negative pressure. In this state, if purge gas is not supplied for an extended period, as described above, the base oil of the magnetic fluid constituting the magnetic fluid seal 19 will evaporate, potentially damaging the magnetic fluid seal 19. Therefore, if the pressure value P is determined to be less than the first threshold A (atmospheric pressure) (step 12: Yes), the switch valve 62 is opened (step S13). That is, if the switch valve 62 is in the open state, this state is maintained, and purge gas is continuously supplied to the butterfly valve 1. On the other hand, if the switch valve 62 is in the closed state, it is opened, and the supply of purge gas begins. As described above, to protect the magnetic fluid seal 19, the monitoring program can prevent damage to the magnetic fluid seal 19 by managing the start or stop of the purge gas supply.

[0063] Next, when the pressure of the purge gas flow path 60 is in a stable state by the control device 70 (step S14: Yes), the monitoring program stores the pressure P of the purge gas flow path 60 at this time in the storage device 702 as a stable pressure value P0 (step S22).

[0064] Next, the monitoring program determines whether a pressure shock has been applied to the magnetic fluid seal 19 (step S15). Specifically, the control device 70 obtains pressure values ​​every predetermined unit of time (e.g., every few milliseconds) using the pressure gauge 64, and calculates the absolute value of the difference between the current pressure value P (the pressure value obtained n times) and the previously obtained pressure value Pb (the pressure value obtained n-1 times). The greater the instantaneous pressure change in the purge gas flow path 60, the greater the absolute value of the difference between the pressure value P and the pressure value Pb, and the magnitude of this absolute value corresponds to the magnitude of the pressure shock. Therefore, whether a pressure shock has occurred is determined by whether this absolute value is greater than or equal to a predetermined second threshold B. This second threshold B is, for example, the specification value of the pressure shock resistance per unit time of the magnetic fluid seal 19. If the absolute value of the difference between the pressure value P and the pressure value Pb is greater than or equal to the second threshold B, it is determined that the pressure value of the flow path 30 (purge gas flow path 60) is abnormal. That is, it is determined that a pressure shock has occurred (step S15: Yes). At this time, the control device 70 sends an alarm notification via the communication device 703 (step S23). On the other hand, if the absolute value of the difference between the pressure value P and the pressure value Pb is less than the second threshold B, it is determined that the pressure value of the flow path 30 (purge gas flow path 60) is normal. That is, it is determined that no pressure impact was applied to the magnetic fluid seal 19 (step S15: No).

[0065] Next, the monitoring program determines whether the magnetic fluid seal 19 is subjected to pressure exceeding its withstand pressure value (step S16). Specifically, the control device 70 monitors whether the pressure value P measured at predetermined unit times (e.g., every few milliseconds) is above the withstand pressure value C. If the pressure value P is above the withstand pressure value C, the pressure value of the flow path 30 (purge gas flow path 60) is determined to be abnormal (step S16: Yes). At this time, the control device 70 sends an alarm notification via the communication device 703 (step S24). On the other hand, if the pressure value P is less than the withstand pressure value C, the pressure value of the flow path 30 (purge gas flow path 60) is determined to be normal (step S16: No). As described above, the monitoring program can monitor whether the pressure value of the flow path 30 (purge gas flow path 60) is abnormal (that is, whether a pressure surge or pressure exceeding the withstand pressure value occurs).

[0066] Next, the monitoring program determines whether the flow rate of the purge gas in the purge gas flow path 60 is abnormal (step S17). Specifically, the flow controller 63 continuously monitors the flow rate value (control flow rate value F21) of the purge gas in the purge gas flow path 60, and compares this control flow rate value F21 with the flow command value F11 output from the control device. The determination is made by checking whether the control flow rate value F21 and the flow command value F11 are different. If the control flow rate value F21 and the flow command value F11 are different, it is determined that the flow rate of the purge gas is abnormal (step S17: Yes). At this time, the control device 70 sends an alarm notification via the communication device 703 (step S25). On the other hand, if the control flow rate value F21 and the flow command value F11 are the same, it is determined that the flow rate of the purge gas is normal (step S17: No). Furthermore, the determination of whether the control flow rate value F21 and the flow command value F11 are different is based on error consideration. For example, if the error between the controlled flow rate value F21 and the flow command value F11 is considered to be within the specified accuracy of the flow controller 63, then even if the controlled flow rate value F21 is different from the flow command value F11, if it is within this error range, then the controlled flow rate value F21 and the flow command value F11 are the same, and the flow rate of the purge gas is determined to be normal. Furthermore, the above error is one example; the flow rate of the purge gas also varies due to factors such as the flow rate of the processing gas flowing through the flow path 30. If the controlled flow rate value F21 is different from the flow command value F11, then the pressure within the purge gas flow path 60 cannot be maintained at a stable pressure value P0. Therefore, as described above, by determining whether the flow rate value of the purge gas in the purge gas flow path 60 is abnormal, monitoring can be performed to maintain the pressure within the purge gas flow path 60 at a stable pressure value P0.

[0067] Next, the monitoring program determines whether the pressure values ​​in flow path 30 and purge gas flow path 60 are unstable (step S18). Assume that the pressure value in flow path 30 becomes unstable due to malfunctions in vacuum chamber 32, vacuum pump 33, or other equipment. Although pressure instability may not have a direct adverse effect on the magnetic fluid seal 19, it may cause problems in the film formation process in vacuum chamber 32, therefore the monitoring program monitors it.

[0068] Specifically, the control device 70 calculates the pressure value P measured at each predetermined unit time (e.g., every few milliseconds) and the stable pressure value P0 stored in the storage device 702 (reference). Figure 6 The absolute value of the difference between the pressure value P and the stable pressure value P0 is used to determine whether this absolute value is above a predetermined third threshold D. This third threshold D is, for example, the fluctuation range of the operating pressure in a semiconductor manufacturing process. If the absolute value of the difference between the pressure value P and the stable pressure value P0 is above the third threshold D, the pressure value of the flow path 30 (purge gas flow path 60) is determined to be unstable (step S18: Yes). At this time, the control device 70 sends an alarm notification via the communication device 703 (step S26). On the other hand, if the absolute value of the difference between the pressure value P and the stable pressure value P0 is less than the third threshold D, the pressure value of the flow path 30 (purge gas flow path 60) is determined to be normal (step S18: No).

[0069] Next, the monitoring program confirms the presence or absence of an alarm (step S19). Figure 6 If any of the alarm notifications in steps S23, S24, S25, and S26 are not triggered (step S19: Yes), the butterfly valve body 9 of butterfly valve 1 is placed in the fully closed position (step S20). This shuts off the processing gas flowing through piping 34 to ensure safety. The monitoring procedure then ends. Conversely, if no alarm notification occurs (step S19: No), the process returns to... Figure 6 In step S11, continue monitoring the pressure value of flow path 30 (purge gas flow path 60) according to the flowchart.

[0070] As explained above, the butterfly valve 1 system of this embodiment includes (1) a motor (e.g., a DD motor 11), a flow path 30 through which a control fluid (e.g., a process gas) flows, a rod 10 with one end connected to the motor (DD motor 11) and the other end inserted into the flow path 30, and a butterfly valve body 9 connected to the rod 10 within the flow path 30. A magnetic fluid seal 19 is included between the motor (DD motor 11) and the flow path 30. The magnetic fluid seal 19 prevents the control fluid (process gas) from leaking from the flow path 30 through the insertion portion (e.g., through-hole 8d) of the rod 10 inserted into the flow path 30 to the motor (DD motor 11). This is to prevent the control fluid (process gas) from leaking into the motor (DD motor 11). The purge gas (processing gas) flows from the flow path 30 through the insertion part (through hole 8d) and into the magnetic fluid seal 19 to be supplied to the butterfly valve 1. The purge gas flow path 60 includes a purge gas flow path 60. The purge gas flow path 60 is provided with a switch valve 62 for switching the purge gas flow path 60 on the upstream side, and a pressure gauge 64 for measuring the pressure value of the purge gas flow path 60. The purge gas flow path 60 is connected between the magnetic fluid seal 19 of the butterfly valve 1 and the flow path 30 on the downstream side of the pressure gauge 64, and is connected to the flow path 30 through the insertion part (through hole 8d). The device includes at least a control device 70 for controlling the switch valve 62. The control device 70 includes a monitoring program for monitoring the pressure value P.

[0071] The aforementioned butterfly valve 1 includes a control device 70, which controls at least the switching valve 62 of the purge gas flow path 60 and measures the pressure value of the purge gas flow path 60, monitoring this pressure value through a monitoring program. Since the purge gas flow path 60 is downstream of the pressure gauge 64 and connected between the magnetic fluid seal 19 and the flow path 30 of the butterfly valve 1, the measurement and monitoring of the pressure value of the purge gas flow path 60 is the same as the measurement and monitoring of the pressure under the load of the magnetic fluid seal 19.

[0072] The control device 70 can simultaneously measure and monitor the pressure value of the purge gas flow path 60 (that is, simultaneously measure and monitor the pressure of the magnetic fluid seal 19) and manage the start or stop of the purge gas supply via the control switch valve 62. This prevents excessive pressure on the magnetic fluid seal 19 and prevents damage to the magnetic fluid seal 19. Furthermore, since the purge gas flow path 60 is connected to the flow path 30 via the insertion part (through hole 8d) into which the rod 10 is inserted, abnormal conditions in the flow path 30 can be detected by measuring and monitoring the pressure value of the purge gas flow path 60.

[0073] (2) In the above butterfly valve 1, the monitoring program (e.g.) Figure 6 In steps S11 to S26), it is preferable to output a command to open the switch valve 62 when the pressure value P is less than the predetermined first threshold A (e.g., atmospheric pressure).

[0074] When the vacuum pump 33 is not operating, that is, when the flow path 30 of the butterfly valve 1 is not under negative pressure, if purge gas is supplied to the butterfly valve 1, the purge gas accumulates in the flow path 30, and the pressure inside the butterfly valve 1 rises. Conversely, when the vacuum pump 33 is operating, that is, when the flow path 30 of the butterfly valve 1 is under negative pressure, if purge gas is not supplied for an extended period, the pressure inside the flow path 30 drops, and the butterfly valve 1 enters a high vacuum state. As a result, the pressure inside the butterfly valve 1 rises and becomes negative, placing an excessive pressure load on the magnetic fluid seal 19, which may damage the magnetic fluid seal 19.

[0075] According to the butterfly valve 1 described in (2), if the pressure value P is less than a predetermined first threshold A (e.g., atmospheric pressure), it can be determined that the vacuum pump 33 is in an operating state. If the pressure value P is greater than or equal to the predetermined first threshold A (e.g., atmospheric pressure), it can be determined that the vacuum pump 33 is not in an operating state. Therefore, the switching valve 62 can be controlled based on whether the pressure value P is less than the predetermined first threshold A (e.g., atmospheric pressure), and the start or stop of the purge gas supply can be managed. This prevents the magnetic fluid seal 19 from being damaged due to excessive pressure.

[0076] (3) In the above butterfly valve 1, the monitoring program ( Figure 6 In steps S11 to S26), pressure values ​​are obtained at predetermined unit times (e.g., every few milliseconds), and when the absolute value of the difference between the pressure value P obtained n and the pressure value Pb obtained n-1 is above the predetermined second threshold B, it is better to determine that the pressure value P is abnormal.

[0077] For example, if the operator mistakenly operates the vacuum pump 33, and the pressure in the vacuum chamber 32 drops or rises sharply, the pressure in the flow path 30 of the butterfly valve 1 will also drop or rise sharply. This pressure shock will apply excessive pressure to the magnetic fluid seal 19 through the through-hole 8d of the butterfly valve 1, potentially damaging the magnetic fluid seal 19.

[0078] In the butterfly valve 1 described in (3), a pressure value is acquired every predetermined unit time (e.g., every few milliseconds), and the absolute value of the difference between the pressure value P acquired in the nth time and the pressure value Pb acquired in the (n-1)th time is calculated. The greater the instantaneous pressure change, the greater the absolute value of the difference between the pressure value P and the pressure value Pb, and the magnitude of this absolute value corresponds to the magnitude of the pressure shock. Therefore, whether a pressure shock has occurred is determined by whether this absolute value is greater than or equal to a predetermined second threshold B. The second threshold B is, for example, the specification value of the magnetic fluid seal 19's resistance to pressure shock per unit time. If the absolute value of the difference between the pressure value P and the pressure value Pb is greater than or equal to the second threshold B, it is determined that the pressure value of the purge gas flow path 60 is abnormal. In other words, it can be determined that a pressure shock has occurred. Based on this, for example, if the butterfly valve 1 is closed, the possibility of applying excessive pressure shock to the magnetic fluid seal 19 and damaging the magnetic fluid seal 19 can be reduced.

[0079] (4) In the above-mentioned butterfly valve 1, when the pressure value P is higher than or equal to the pressure resistance value C of the magnetic fluid seal 19, the monitoring program ( Figure 6 Steps S11 to S26 in the process are preferred to determine if the pressure value P is abnormal.

[0080] For example, if the operator mistakenly operates the vacuum pump 33, and the magnetic fluid seal 19 is subjected to pressure exceeding its withstand pressure value, the magnetic fluid seal 19 may be damaged, and thus the butterfly valve 1 itself may also be damaged. When the pressure value P of the purge gas flow path 60 is greater than or equal to the withstand pressure value C of the magnetic fluid seal 19, it can be said that the magnetic fluid seal 19 is subjected to pressure exceeding the withstand pressure value C. Therefore, according to the butterfly valve 1 described in (4), the pressure value of the flow path 30 can be monitored for abnormalities by checking whether the withstand pressure value C of the magnetic fluid seal 19 is greater than or equal to that of the magnetic fluid seal 19. Based on this, for example, closing the butterfly valve 1 can reduce the possibility of the magnetic fluid seal 19 being damaged due to excessive pressure.

[0081] (5) In the above-mentioned butterfly valve 1, the control device 70 includes a storage device 702. When the pressure value P of the purge gas flow path 60 is in a stable state by the control device 70, the storage device 702 stores the pressure P at this time as a stable pressure value P0. When the absolute value of the difference between the pressure value P and the stable pressure value P0 is above a predetermined third threshold D, the monitoring program ( Figure 6 Steps S11 to S26 in the process are preferred to determine if the pressure value P is abnormal.

[0082] Suppose that due to malfunctions in the vacuum chamber 32, vacuum pump 33, or other machinery, the pressure value in the flow path 30 of butterfly valve 1 becomes unstable. Although the unstable pressure value may not have a direct adverse effect on the magnetic fluid seal 19, it may cause problems in the film formation process in the vacuum chamber 32.

[0083] Therefore, as described in (5) with butterfly valve 1, if the absolute value of the difference between the pressure value P and the stable pressure value P0 is calculated and it is above the third threshold D, it is determined that the pressure value P is abnormal, thus preventing problems in the film deposition process. Here, the third threshold D is, for example, the fluctuation range of the operating pressure in the semiconductor manufacturing process. Furthermore, although it is possible to immediately determine that the pressure value P is abnormal when the absolute value is above the third threshold D only once, it is also possible to determine that the pressure value P is abnormal only when the absolute value is above the third threshold a predetermined number of times.

[0084] (6) In the above-mentioned butterfly valve 1, in the purge gas flow path 60, based on the flow command value F11 output from the control device 70, the flow rate of the purge gas between the switching valve 62 and the pressure gauge 64 is controlled, and a flow controller 63 is provided to detect the flow rate value of the purge gas (control flow rate value F21), and a monitoring program ( Figure 6 In steps S11 to S26, when the flow value (control flow value F21) is in a different state relative to the flow command value F11, it is better to determine that the flow value (control flow value F21) is abnormal.

[0085] If the flow rate of the purge gas (control flow rate value F21) differs from the flow command value F11, the pressure within the purge gas flow path 60 cannot be maintained at a stable pressure value P0. Therefore, by determining whether the flow rate of the purge gas in the purge gas flow path 60 is abnormal, monitoring can be performed to maintain the pressure within the purge gas flow path 60 at a stable pressure value P0.

[0086] Furthermore, this embodiment is merely an example and is not intended to limit the invention. Therefore, various modifications and variations can be made to the invention without departing from its spirit. For example, in this embodiment, although the flow path 30 is not completely sealed even when the butterfly valve body 9 is in the fully closed position, a valve seat can be provided in the valve hole 8a, and the butterfly valve body 9 can be completely sealed by abutting against the valve seat. Explanation of reference numerals in the attached figures

[0087] 1: Butterfly valve 2: Drive Unit 3: Valve part 8d: Through hole (an example of an insertion part) 9: Butterfly valve body 10: pole 11: DD motor (an example of a motor) 18: Magnetic components 19: Magnetic fluid sealing section 30:Flow path 32: Vacuum chamber 33: Vacuum pump 34:Piping

Claims

1. A butterfly valve, comprising a motor, a flow path for controlling fluid flow, a rod with one end connected to the motor and the other end inserted into the flow path, and a butterfly valve body connected to the rod within the flow path, wherein: A magnetic fluid seal is included between the motor and the flow path; The magnetic fluid seal prevents the control fluid from leaking into the motor from the flow path, through the insertion part of the rod inserted into the flow path; In order to supply purge gas to the butterfly valve to prevent the control fluid from flowing from the flow path through the insertion part into the magnetic fluid seal, a purge gas flow path is included; The purge gas flow path is equipped with a switch valve for switching the purge gas flow path and a pressure gauge for measuring the pressure value of the purge gas flow path from the upstream side; The purge gas flow path is located downstream of the pressure gauge, connected between the magnetic fluid sealing part of the butterfly valve and the flow path, and communicates with the flow path through the insertion part. The purge gas supplied to the butterfly valve is output to the flow path through the insertion part. It includes at least a control device for controlling the switching valve; The control device includes a monitoring program that monitors the pressure value. The monitoring program monitors whether the flow path is under negative pressure by determining whether the pressure value is less than a predetermined first threshold. When the pressure value is less than the predetermined first threshold, the monitoring program outputs a command to open the switch valve and supplies the purging gas to the butterfly valve.

2. The butterfly valve as described in claim 1, wherein, The monitoring program acquires the pressure value at predetermined unit times. When the absolute value of the difference between the pressure value acquired n times and the pressure value acquired (n-1 times) is above a predetermined second threshold, the pressure value is determined to be abnormal.

3. The butterfly valve as described in claim 1 or 2, wherein, The monitoring program determines that the pressure value is abnormal when the pressure value is higher than the pressure resistance value of the magnetic fluid seal.

4. The butterfly valve as described in claim 1 or 2, wherein, The control device includes a storage device that stores the pressure value in the purge gas flow path when the pressure value is in a stable state by means of the control device as a stable pressure value. When the absolute value of the difference between the pressure value and the stable pressure value is above a predetermined third threshold, the pressure value is determined to be abnormal.

5. The butterfly valve as described in claim 1 or 2, wherein, In the purge gas flow path, the flow rate of the purge gas is controlled between the switching valve and the pressure gauge based on the flow command value output from the control device, and a flow controller is provided to detect the flow rate value of the purge gas. When the traffic value is in a different state relative to the traffic command value, the monitoring program determines that the traffic value is abnormal.

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