Fluid control valve

Abstract

A fluid control valve is provided with a spring (52) that applies a biasing force to a valve element (32) in a closing direction, and a servo motor (6) is provided with a drive shaft (62) that actuates the valve element (32), and is provided with a position control mode for controlling the drive shaft (62) so that the drive shaft (62) moves to a target position, and a thrust control mode for controlling the drive shaft (62) so that the drive shaft (62) can obtain a target thrust. When the valve body (32) is operated from the open valve position to the closed valve position, the servo motor (6) is controlled by a position control mode from the open valve position to a predetermined position before the valve body (32) reaches the closed valve position. The control of the servo motor 6 is switched from the position control mode to the thrust control mode in which the target thrust is zero from the predetermined position, and the valve body 32 is brought to the valve closing position only by the biasing force.

Description

Technical Field

[0001] The present invention relates to a fluid control valve, which includes a motor, a valve core, a valve seat and a flow path. The motor is used to move the valve core between an open valve position away from the valve seat and a closed valve position abutting the valve seat, thereby controlling the control fluid flowing in the flow path. Background Art

[0002] Film formation in semiconductor manufacturing processes uses a variety of process gases. A fluid control valve is used to control the flow rate of the process gas. As a fluid control valve, for example, the fluid control valve disclosed in Patent Document 1 is known. The fluid control valve disclosed in Patent Document 1 is a pneumatic on-off valve, which controls the flow rate of the process gas by controlling the contact and separation of the valve core (diaphragm) and the valve seat by a cylinder.

[0003] In addition, the fluid control valve disclosed in Patent Document 1 is a pneumatic on-off valve using a cylinder as a driving device, but sometimes an electric drive method using a linear servo motor as a driving device is adopted. When a linear servo motor is used as a driving source, for example, the position where the valve core contacts the valve seat is set as the origin position of the servo motor, and the valve opening is adjusted by the relative position from the origin position. And when closing the valve, the valve core contacts the valve seat by returning to the origin.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent document 1: Japanese Patent Application Publication No. 2017-223318. Summary of the invention

[0007] Problem that the invention aims to solve

[0008] However, the above-mentioned fluid control valve using the linear servo motor has the following problems.

[0009] Generally speaking, the setting of the origin position is usually performed by the user of the fluid control valve under normal temperature. However, the process gas to be controlled is at an extremely high temperature such as 200°C. The valve seat is usually made of resin such as PFA, and will be heated by the control fluid and expand. There is a risk that the size (thickness dimension) of the valve seat in the opening and closing direction of the valve core will become larger than the size at normal temperature due to this expansion. If the thickness dimension of the valve seat becomes larger, when the valve is closed from the open state, the servo motor will abut against the valve core and the valve seat before reaching the origin position. However, after the valve core and the valve seat abut, the servo motor still wants to return to the origin, so the valve core and the valve seat interfere strongly, causing the servo motor to bear a high load. Fluid control valves that control the flow rate of process gas in the semiconductor manufacturing process must control the valve opening with high precision, so servo motors with high resolution are used. Therefore, even if the valve seat expands by only a few μm, the servo motor will be subjected to an extremely high load. If the state of the servo motor being subjected to high load continues, it will cause servo motor failures such as motor coil burnout.

[0010] In addition, if the valve core and the valve seat are repeatedly in contact and separated, causing the valve seat to wear, there is a risk that the thickness of the valve seat will become smaller than the initial state. If the thickness of the valve seat becomes smaller, when the valve is closed from the open state, there is a risk that the valve core and the valve seat will not contact each other even if the servo motor has reached the origin position. If the valve core and the valve seat do not contact each other, there is a risk of fluid leakage due to poor sealing.

[0011] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a fluid control valve capable of coping with a dimensional variation of a valve seat in the opening and closing direction of a valve element.

[0012] Technical means of solving problems

[0013] In order to solve the above-mentioned problems, a fluid control valve according to one aspect of the present invention has the following structure.

[0014] (1) A fluid control valve comprising a motor, a valve core, a valve seat, and a flow path, wherein the motor is used to move the valve core between an open valve position away from the valve seat and a closed valve position abutting against the valve seat, thereby controlling a control fluid flowing in the flow path. The fluid control valve is characterized in that an elastic member is provided to apply a force to the valve core in a closing direction, the motor is provided with a drive shaft for moving the valve core, and the motor has a position control mode for controlling the drive shaft so that the drive shaft moves to a target position and a thrust control mode for controlling the drive shaft so that the drive shaft can obtain a target thrust, and the valve core has the following control program: when the valve core moves from the open valve position to the closed valve position, the motor is controlled by the position control mode from the open valve position to the predetermined position before the valve core reaches the closed valve position, and from the predetermined position, the control of the motor is switched from the position control mode to the thrust control mode in which the target thrust is zero, so that the valve core reaches the closed valve position only by the force.

[0015] The fluid control valve according to (1) is controlled in the following manner: when the valve core moves from the open valve position to the closed valve position, the motor is controlled by the position control mode from the open valve position to the specified position before the valve core reaches the closed valve position, and the control of the motor is switched from the position control mode to the thrust control mode with a target thrust of zero from the specified position, so that the valve core reaches the closed valve position only by the force of the elastic member. In other words, the valve core is driven from the specified position to the closed valve position only by the force of the elastic member, so even if the valve core and the valve seat abut before the motor reaches the origin position due to the expansion of the valve seat, the motor will not return to the origin afterwards. Therefore, the motor will not be subjected to high load, thereby preventing motor failures such as motor coil burnout.

[0016] In addition, in the case where the valve seat is worn and reduced so that the valve core does not contact the valve seat even when the motor reaches the origin position, the valve core is driven only by the force of the elastic member from the specified position, so it can be reliably driven to the closed valve position contacting the valve seat and does not stop at the origin position. Therefore, it is possible to prevent fluid leakage caused by poor sealing.

[0017] (2) In the fluid control valve described in (1), preferably, after the valve element reaches the valve closing position, the control program maintains the valve element in the valve closing position by the thrust control mode in which the target thrust is zero.

[0018] According to the fluid control valve described in (2), the valve closing state is maintained, that is, the state in which the valve core is in the valve closing position is maintained by a thrust control mode in which the target thrust is zero. In other words, the motor is not subjected to a load, and the valve closing state is maintained only by the force of the elastic member. In this way, the load borne by the motor can be reduced to achieve a longer life. In addition, for example, in the event that the fluid control valve fails or the power supply to the fluid control valve is cut off due to a power outage, the valve closing state is maintained only by the force of the elastic member, so it is highly safe from the perspective of fail-safe.

[0019] (3) In the fluid control valve described in (1) or (2), it is preferable that the predetermined position is determined based on the amount of thermal expansion of the valve seat in the opening and closing direction of the valve element.

[0020] To improve the responsiveness when the valve core is driven from the open valve position to the closed valve position, it is ideal to make the specified position as close to the valve seat as possible, so that the range between the open valve position and the closed valve position that only relies on the force of the elastic member is as narrow as possible. Therefore, the specified position is determined based on the thermal expansion of the valve seat in the opening and closing direction of the valve core. Specifically, for example, if the thermal expansion of the valve seat is set to Δt, the specified position is set to a position that is Δt+several μm forward from the origin position of the motor. This position is the position where the valve core moves 90-95% from the open valve position to the closed valve position in the stroke of the valve core from the open valve position to the closed valve position. By setting the specified position in this way, the valve core is driven by the position control mode of the motor before it is about to abut against the expanded valve seat, so the responsiveness of the closed valve can be high.

[0021] Effects of the Invention

[0022] According to the fluid control valve of the present invention, it is possible to cope with the dimensional variation of the valve seat in the opening and closing direction of the valve element. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic cross-sectional view of a fluid control valve.

[0024] Figure 2 for Figure 1 A partial enlarged view of part X.

[0025] Figure 3 A block diagram of a control system for a fluid control valve.

[0026] Figure 4 Flow chart of the initial setting procedure for the fluid control valve.

[0027] Figure 5 The flow chart of the control procedure for the fluid control valve.

[0028] Figure 6(a) is a diagram showing the state of the control mode of the servo motor when the valve element moves from the valve open position to the valve closed position. Figure 6 (b) is a graph showing the position of the valve element when the valve element moves from the open valve position to the closed valve position. Figure 6 (c) is a graph showing the thrust value of the drive shaft when the valve element moves from the valve open position to the valve closed position. DETAILED DESCRIPTION

[0029] Embodiments of a fluid control valve according to the present invention will be described in detail with reference to the accompanying drawings.

[0030] (About the structure of the fluid control valve)

[0031] use Figure 1 , the structure of the fluid control valve 1 according to the present embodiment will be described. Figure 1 2 is a schematic cross-sectional view of a fluid control valve 1. The fluid control valve 1 is an electric gas valve provided in a gas supply system of a semiconductor manufacturing device, and is composed of a drive unit 2 and a valve unit 3. The drive unit 2 is further composed of an actuator unit 4 and a spring unit 5.

[0032] First, the actuator unit 4 will be described. The actuator unit 4 includes a direct-acting servomotor 6 (an example of a motor) and a connecting frame 7 for connecting the servomotor 6 and the spring unit 5 .

[0033] The servo motor 6 includes a rectangular parallelepiped housing 61 and a cylindrical drive shaft 62 inserted into the center of the housing 61. The housing 61 is provided with linear bearings 63 at the end on the connecting frame 7 side (the lower end in the figure) and the end on the opposite side of the connecting frame 7 side (the upper end in the figure). The linear bearing 63 supports the drive shaft 62 in a manner that allows it to move forward and backward along the axial direction of the drive shaft 62. The axial direction of the drive shaft 62 is Figure 1 The up-down direction in the figure is consistent with the opening and closing direction of the valve core 32 described later. In addition, the upper side in the figure is the opening direction, and the lower side is the closing direction.

[0034] The drive shaft 62 is provided with a magnet 621 on the outer periphery of the portion inserted into the housing 61. In addition, the housing 61 includes a coil 64 placed so as to surround the magnet 621 of the drive shaft 62. The magnet 621 moves in the opening and closing direction according to the magnitude of the voltage and current energized to the coil 64. Thus, the drive shaft 62 combined with the magnet 621 can be driven in the opening and closing direction.

[0035] The drive shaft 62 is provided with a linear scale 622 at the end portion (upper end portion in the figure) on the opposite side to the connecting frame 7. In addition, the servo motor 6 is provided with a linear encoder 65 for detecting the displacement of the upper and lower positions of the linear scale 622 at the upper end portion of the housing 61. By detecting the displacement of the upper and lower positions of the linear scale 622 by the linear encoder 65, the position of the drive shaft 62 in the opening and closing direction can be detected.

[0036] The end of the drive shaft 62 on the connecting frame 7 side (the lower end in the figure) protrudes from the housing 61 and is connected to the cylindrical valve stem 9 by the coupling 8 in the connecting frame 7. The valve stem 9 is inserted into the spring portion 5 and extends from the connecting frame 7 to the valve portion 3.

[0037] Next, the spring portion 5 is described. The spring portion 5 includes a housing 51 and a spring 52 (an example of an elastic member). The housing 51 is hollow, and the valve stem 9 is inserted through the center. In addition, the spring 52 is located coaxially with the valve stem 9. The spring 52 is a compression coil spring, and the end portion on the valve portion 3 side (the lower end portion in the figure) abuts against the end surface (the upper end surface in the figure) on the spring portion 5 side of the valve core 32 described later, thereby always applying force to the valve core 32 in the closing direction (the lower direction in the figure).

[0038] Next, the valve portion 3 will be described. The valve portion 3 includes a valve body 31 and a valve element 32. The valve body 31 includes a cylindrical portion 315 connected to the spring portion 5. In addition, a valve chamber 311 is formed inside the cylindrical portion 315 of the valve body 31.

[0039] The valve chamber 311 is connected to an input flow path 313 via a valve port 312 at the center. The input flow path 313 is used to input process gas into the valve chamber 311. In addition, a circular valve seat 33 is provided on the bottom surface of the valve chamber 311 at the outer periphery of the valve port 312 in a coaxial manner with the valve port 312. Furthermore, the valve chamber 311 is connected to an output flow path 314 at the radial outer side of the valve seat 33. The output flow path 314 is used to output process gas from the valve chamber 311. That is, a series of flow paths for the process gas to flow are formed by the input flow path 313, the valve chamber 311, and the output flow path 314.

[0040] The valve seat 33 is made of, for example, PI (polyimide) or PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) having excellent heat resistance. The end surface of the valve seat 33 facing the valve core 32 is a contact surface 331 (see Figure 2 ).

[0041] Figure 2The position Y11 of the abutment surface 331 in the opening and closing direction is a position at room temperature. The process gas flowing in the fluid control valve 1 is at an extremely high temperature such as 200°C, so the valve seat 33 is heated by the process gas and expands. The position of the abutment surface 331 in the opening and closing direction after the expansion is the position shown in the position Y12. For example, if the material of the valve seat 33 is set to PFA and the dimension (thickness dimension) of the valve seat 33 in the opening and closing direction is set to about 1.5 mm, the expansion amount Δt11 is approximately 20 to 30 μm.

[0042] On the other hand, there is a risk that the valve seat 33 may be worn or deformed due to creep etc. due to repeated contact and separation between the valve core 32 and the valve seat 33. The position of the contact surface 331 formed by the wear or creep in the opening and closing direction is the position shown by the position Y13. The difference between the position Y11 and the position Y13 at this time is recorded as the shrinkage amount Δt12.

[0043] The valve core 32 includes a main body 321 and a diaphragm 322. The main body 321 is made of, for example, stainless steel. The main body 321 is connected to the valve stem 9 at the upper end, and moves in the opening and closing direction (the up and down direction in the figure) as the drive shaft 62 moves forward and backward. In addition, the lower end surface of the main body 321 is a contact surface with the valve seat 33.

[0044] The diaphragm 322 is a disc-shaped thin film member made of, for example, Ni alloy. The main body 321 and the diaphragm 322 are joined together, for example, by laser welding. Furthermore, the outer peripheral edge of the diaphragm 322 is fixed to the housing 51. Thus, the diaphragm 322 divides the interior of the cylindrical portion 315 of the valve body 31 into the valve chamber 311 and its upper portion, and repeatedly elastically deforms in coordination with the movement of the main body 321 in the opening and closing direction (the up and down direction in the figure).

[0045] (Regarding the control system of the fluid control valve)

[0046] use Figure 3 , the control system of the fluid control valve 1 is explained. Figure 3 1 is a block diagram of a control system of a fluid control valve 1. A driver 10 for controlling a servo motor 6 includes a position control controller 101, a thrust control controller 102, a position loop controller 103, a speed loop controller 104, a current loop controller 105, converters 106, 107, 108, and a control switching switch 109. The servo motor 6 includes a position control mode for controlling the drive shaft 62 so that the drive shaft 62 moves to a target position and a thrust control mode for controlling the drive shaft 62 so that the drive shaft 62 can obtain a target thrust. The position control mode and the thrust control mode can be switched by means of the control switching switch 109.

[0047] The control in the position control mode is performed as follows: First, the position control controller 101 outputs a position command to the position loop controller 103 according to the target position of the drive shaft 62 .

[0048] Then, the position loop controller 103 performs PD control, for example, to calculate a speed command based on the position command and the current position of the drive shaft 62 fed back from the linear encoder 65. The current position of the drive shaft 62 fed back from the linear encoder 65 is a signal output by the converter 107 based on the number of pulses output by the linear encoder 65.

[0049] Then, the speed loop controller 104 performs PID control, for example, to calculate a torque command based on the speed command calculated by the position loop controller 103 and the current speed of the drive shaft 62 fed back from the linear encoder 65. The current speed of the drive shaft 62 fed back from the linear encoder 65 is a signal output by the converter 108 based on the number of pulses output by the linear encoder 65.

[0050] Then, the current loop controller 105 outputs a current command according to the torque command calculated by the speed loop controller 104. The converter 106 supplies a required current to the servo motor 6 according to the current command, thereby controlling the position of the drive shaft 62 of the servo motor 6.

[0051] The control in the thrust control mode is performed as follows. First, the thrust control controller 102 outputs a thrust command to the current loop controller 105 according to the target thrust of the drive shaft 62. Then, the current loop controller 105 outputs a current command according to the thrust command output from the thrust control controller 102. The converter 106 supplies the required current to the servo motor 6 according to the current command, thereby controlling the thrust of the drive shaft 62 of the motor 2.

[0052] (About the operation of the fluid control valve)

[0053] In the control system described above, the fluid control valve 1 operates as follows. Figure 4 This is the flow of the initial setting procedure of the fluid control valve 1. Figure 5 This is the flow of the control program of the fluid control valve 1. Figure 6 (a) is a diagram showing a state of a control pattern of the servo motor 6 when the valve body 32 moves from the valve opening position to the valve closing position. Figure 6 (b) is a graph showing the position of the valve body 32 when the valve body 32 moves from the valve opening position to the valve closing position. Figure 6 (c) is a graph showing the thrust value of the drive shaft 62 when the valve element 32 moves from the valve opening position to the valve closing position.

[0054] Before starting to use the fluid control valve 1, set the parameters required for controlling the fluid control valve 1 according to the initial setting procedure ( Figure 4 The following is a detailed description of the initial settings.

[0055] First, the origin position of the servo motor 6 is set ( Figure 4 Specifically, the valve core 32 is brought into contact with the valve seat 33 at room temperature. That is, the valve core 32 is brought into the valve closing position. Then, the position of the drive shaft 62 in this state is set as the origin position. Furthermore, at this time, the position of the contact surface 331 of the valve core 32, with which the valve core 32 contacts, in the opening and closing direction is position Y11.

[0056] Next, set the target location ( Figure 4 The target position is the amount of movement of the drive shaft 62 from the origin position toward the opening direction. In the position control mode, the position control controller 101 (refer to Figure 3 ) outputs a position command based on the target position. The drive shaft 62 moves from the origin position to the opening direction, and accordingly, the valve core 32 moves from the closed valve position to the opening direction, so the setting of the target position is equivalent to the setting of the stroke from the closed valve position to the open valve position of the valve core 32. The target position is determined according to the flow rate of the process gas required in the film forming process of the semiconductor manufacturing process. For example, in this embodiment, it is about 1 mm.

[0057] Next, the switching position (an example of a predetermined position) of the control of the servo motor 6 is set ( Figure 4 Specifically, it is set at which position between the open valve position and the closed valve position the control of the servo motor 6 is switched from the position control mode to the thrust control mode when the valve core 32 is moved from the open valve position to the closed valve position.

[0058] The switching position is determined based on the thermal expansion amount Δt11 of the valve seat 33 in the opening and closing direction of the valve core 32. Specifically, for example, if the thermal expansion amount of the valve seat 33 is set to Δt11, the switching position is set to a position that is moved forward by the thermal expansion amount Δt11+several μm from the origin position of the servo motor 6. This position is a position where the valve core 32 moves 90-95% from the open valve position to the closed valve position in the stroke (for example, 1 mm) of the valve core 32 from the open valve position to the closed valve position.

[0059] Next, set the acceleration and deceleration time of the servo motor 6 ( Figure 4 This is the time taken to set the drive shaft 62 to move from the origin position to the target position. It is synonymous with the time taken to set the valve core 32 to move between the valve opening position and the valve closing position.

[0060] Next, set the stop time of the servo motor 6 at the valve opening position ( Figure 4 This is the time for setting the valve core 32 to maintain the valve open state after being in the valve open position.

[0061] Next, set the stop time of the servo motor 6 at the valve closing position ( Figure 4 This is the time for setting the valve core 32 to maintain the closed valve state after it is in the closed valve position. Figure 4 The time set in S14-S16 is set as appropriate according to the cycle time of the opening and closing action required in the film forming process of the semiconductor manufacturing process.

[0062] Next, set the target thrust ( Figure 4 This is to set the thrust for driving the drive shaft 62 when the servo motor 6 is controlled by the thrust control mode. Here, the target thrust is set to zero. When the setting of the target thrust is completed, the initial setting of the parameters is completed. In addition, each parameter ( Figure 4 The order of S11-17) in is not limited to the above order. In addition, the target thrust may be set to zero in advance and omitted. Figure 4 S17 in.

[0063] The opening and closing operations of the fluid control valve 1 are performed by a control program described below.

[0064] First, when the fluid control valve 1 starts to operate, the linear encoder 65 detects the current position of the drive shaft 62 ( Figure 5 The current position of the drive shaft 62 is also the current position of the valve core 32. The valve core 32 is always urged in the closing direction by the spring 52, so it is in the closed valve position when the fluid control valve 1 starts to operate. Therefore, it is detected here that it is in the origin position.

[0065] Next, the valve opening action is performed ( Figure 5 In other words, the valve core 32 is driven toward the valve opening position. This action is performed in the position control mode according to the target position set in the initial setting (refer to Figure 4 In this embodiment, the stroke is set to 1 mm, so the valve core 32 moves 1 mm from the origin position toward the opening direction. The moving speed at this time is based on the acceleration and deceleration time of the servo motor 6 set in the initial setting (refer to Figure 4 in S14).

[0066] Furthermore, Figure 6 The time point t0 in FIG. 1 is the time point when the valve core 32 reaches the valve opening position. Figure 6 As shown in (a), at time point t0, the control mode of the servo motor 6 is the position control mode. Figure 6As shown in (b), the position of the valve core 32 is at the valve opening position. In addition, the thrust of the drive shaft 62 shows a value greater than zero (F11). The reason why the drive shaft 62 generates thrust is to resist the force of the spring 52 and maintain the position of the drive shaft 62 at the valve opening position. Furthermore, whether the valve core 32 has reached the valve opening position is monitored by whether the change in the current position of the drive shaft 62 falls within the range of any deviation pulse. When it falls within the range, it is determined that the valve core 32 has reached the valve opening position.

[0067] Then, the valve core 32 moves to the valve opening position and remains at the valve opening position ( Figure 5 The holding time is based on the stop time of the servo motor 6 at the valve opening position set in the initial setting (refer to Figure 4 S15 in ).

[0068] Furthermore, Figure 6 The time point t0 to the time point t1 in the figure corresponds to the stop time. Between the time point t0 and the time point t1, the valve core 32 is maintained at the valve opening position by the position control mode (refer to Figure 6 (a), (b)). The thrust generated on the drive shaft 62 is also constant between time point t0 and time point t1 (refer to Figure 6 (c)).

[0069] When the above stop time has passed, the valve closing action is then performed ( Figure 5 This action is performed in the position control mode, and the drive shaft 62 of the servo motor 6 is controlled to move to the origin position, thereby driving the valve core 32 to the closed valve position. The moving speed at this time is based on the acceleration and deceleration time of the servo motor 6 set in the initial setting (refer to Figure 4 in S14).

[0070] Furthermore, Figure 6 The time point t1 in the figure is the time point when the valve closing action starts. From the time point t1, the valve core 32 starts to move toward the valve closing position while maintaining the position control mode (refer to Figure 6 (a), (b)). Moreover, the thrust of the drive shaft 62 shows a maximum value (F12) immediately after the valve closing action begins. This is because the drive shaft 62 is accelerated rapidly in the closing direction at the beginning of the action. Then, as the valve core 32 approaches the valve closing position, a thrust is generated in the opening direction to brake the drive shaft 62. Therefore, Figure 6 In (c), the thrust is reduced to a negative value (F13).

[0071] Next, when the valve closing operation is started, monitoring is performed to determine whether the drive shaft 62 has reached the switching position of the control of the servo motor 6 ( Figure 5The switching position of the control of the servo motor 6 is the position set in the initial setting to switch the control of the servo motor 6 from the position control mode to the thrust control mode (refer to S25 in FIG. 1 ). Figure 4 Before reaching the switching position, the drive shaft 62 of the servo motor 6 is continuously controlled to move to the origin position by the position control mode (S25: No). Then, when the drive shaft 62 reaches the switching position (S25: Yes), the thrust control mode is switched ( Figure 5 This action is achieved by controlling the switching switch 109 (refer to S26 in FIG. Figure 3 ) to switch.

[0072] When the thrust control mode is switched, the servo motor 6 is controlled according to the target thrust. The target thrust is a parameter set in the initial setting (refer to Figure 4 Thus, when switching to the thrust control mode, the target thrust is no longer transferred from the converter 106 (reference Figure 3 ) supplies electric current to the servomotor 6. Then, the valve element 32 moves to a position (valve closing position) in contact with the valve seat 33 only by the urging force of the spring 52.

[0073] At room temperature, the origin position of the servo motor 6 is the valve closing position. However, if the valve seat 33 has expanded, the valve closing position will expand from the origin position toward the opening direction by the amount of thermal expansion Δt11 (refer to Figure 2 ) degree of deviation. That is, the valve seat 33 abuts against the valve core 32 before the servo motor 6 reaches the origin position. However, the valve core 32 is driven only by the force of the spring 52 from the switching position. Therefore, even if the valve seat 33 expands and causes the valve core 32 to abut against the valve seat 33 before the servo motor 6 reaches the origin position, the servo motor 6 will not return to the origin afterwards. Therefore, the servo motor 6 will not be subjected to a high load, thereby preventing the servo motor 6 from malfunctioning, such as the burning of the coil 64.

[0074] In addition, since the switching position from the position control mode to the thrust control mode is set at a position where the valve core 32 advances 90-95% from the open valve position to the closed valve position in the stroke from the open valve position of the valve core 32 to the closed valve position, the responsiveness when the valve core 32 is driven from the open valve position to the closed valve position is improved. The fluid control valve 1 provided in the gas supply system of the semiconductor manufacturing device is small in size, so the force of the spring 52 is lower than that of a conventional pneumatic valve. Therefore, in order to improve the responsiveness, it is ideal to make the switching position as close to the valve seat 33 as possible so that the range between the open valve position and the closed valve position that depends only on the force of the spring 52 is as narrow as possible. By setting the switching position as described above, the valve core 32 is driven by the position control mode of the servo motor 6 until the position immediately before it abuts against the expanded valve seat 33, so the responsiveness of the closed valve can be improved.

[0075] On the other hand, if the valve seat 33 is worn or creeps and the position of the contact surface 331 is lowered, the closed valve position shrinks from the original position toward the closing direction by the amount Δt12 (refer to Figure 2 ) degree of deviation. That is, even if the servo motor 6 has reached the origin position, the valve core 32 will not abut against the valve seat 33. However, the valve core 32 is driven only by the force of the spring 52 from the switching position, so even if the servo motor 6 reaches the origin position, it will not stop at the origin position, but will be reliably driven to the closed valve position abutting against the valve seat 33. Therefore, the occurrence of fluid leakage caused by poor sealing can be prevented.

[0076] Furthermore, Figure 6 The time point t2 in the figure is the time point when the valve core 32 reaches the switching position, and is the time point when the control of the servo motor 6 is switched from the position control mode to the thrust control mode. When the thrust control mode is switched, the thrust of the drive shaft 62 becomes zero according to the set target thrust. Therefore, the moving speed of the valve core 32 decreases from the time point t2 when the thrust control mode is switched. Figure 6 (b) The slope of the graph becomes gentler). This is because the valve core 32 moves only by the force of the spring 52. Figure 6 The time point t3 in the figure is the time point when the valve core 32 reaches the valve closing position. Furthermore, whether the valve core 32 has reached the valve closing position is monitored based on whether the change in the current position of the drive shaft 62 falls within the range of any deviation pulse, and when it falls within the range, it is determined that the valve core 32 has reached the valve closing position.

[0077] Then, when reaching the valve closing position, the valve core 32 is kept at the valve closing position ( Figure 5 The holding time is based on the stop time of the servo motor 6 at the closed valve position set in the initial setting (refer to S27 in FIG. 11 ). Figure 4S16 in the figure). During the period of maintaining the closed valve position, the servo motor 6 is controlled by the thrust control mode in which the target thrust is zero. In other words, the servo motor 6 is not subjected to load and the closed valve state is maintained only by the force of the spring 52. As a result, the load borne by the servo motor 6 can be reduced to extend the service life. In addition, for example, when the fluid control valve 1 fails or the power supply to the fluid control valve 1 is cut off due to a power outage, the closed valve state is maintained only by the force of the spring 52, so it is highly safe from the perspective of fail-safe.

[0078] When the above stop time has passed, it switches to position control mode ( Figure 5 S28 in the process), and then the valve closing action is performed in the position control mode ( Figure 5 As described above, by repeating Figure 5 The processing of S22-S28 enables the opening and closing of the fluid control valve 1 to be performed.

[0079] As described above, the fluid control valve 1 of the present embodiment comprises (1) a motor (e.g., a servomotor 6), a valve core 32, a valve seat 33, and a flow path (a series of flow paths formed by an input flow path 313, a valve chamber 311, and an output flow path 314), wherein the valve core 32 is moved between an open valve position away from the valve seat 33 and a closed valve position abutting against the valve seat 33 by means of the motor (servomotor 6), thereby controlling a control fluid (e.g., a process gas) flowing in the flow path. The fluid control valve 1 is characterized in that it comprises an elastic member (e.g., a spring 52) for applying a force to the valve core 32 in a closing direction, the motor (servomotor 6) comprises a drive shaft 62 for moving the valve core 32, and comprises a position control mode for controlling the drive shaft 62 so that the drive shaft 62 moves to a target position and a thrust control mode for controlling the drive shaft 62 so that the drive shaft 62 can obtain a target thrust, and comprises the following control program ( Figure 5 S21-S28): When the valve core 32 moves from the valve opening position to the valve closing position, the motor (servo motor 6) is controlled by the position control mode from the valve opening position to the specified position (switching position) before the valve core 32 reaches the valve closing position, and from the specified position (switching position), the control of the motor (servo motor 6) is switched from the position control mode to the thrust control mode with a target thrust of zero, so that the valve core 32 reaches the valve closing position only by the action force.

[0080] According to the fluid control valve 1 described in (1), control is performed in the following manner: when the valve core 32 moves from the valve opening position to the valve closing position, the motor (servo motor 6) is controlled by the position control mode from the valve opening position to the predetermined position before the valve core 32 reaches the valve closing position, and the control of the motor (servo motor 6) is switched from the position control mode to the thrust control mode with a target thrust of zero from the predetermined position, so that the valve core reaches the valve closing position only by the force of the elastic member. In other words, the valve core 32 is driven from the predetermined position (switching position) to the valve closing position only by the force of the elastic member (spring 52), so even if the valve core 32 and the valve seat 33 are abutted before the motor (servo motor 6) reaches the origin position due to the expansion of the valve seat 33, the motor (servo motor 6) will not return to the origin thereafter. Therefore, the motor (servo motor 6) will not be subjected to a high load, thereby preventing motor (servo motor 6) failures such as burning of the motor coil 64.

[0081] Furthermore, in the case where the valve core 32 does not contact the valve seat 33 even when the motor (servo motor 6) has reached the origin position due to the wear of the valve seat 33, the valve core 32 is driven only by the force of the elastic member (spring 52) from the predetermined position (switching position), so it is reliably driven to the closed valve position contacting the valve seat 33 and does not stop at the origin position. Therefore, the occurrence of fluid leakage caused by poor sealing can be prevented.

[0082] (2) In the fluid control valve 1 described in (1), it is desirable that after the valve element 32 reaches the valve closing position, the control program ( Figure 5 S21-S28 in the flow chart) maintains the valve core 32 in the closed valve position through the thrust control mode with the target thrust being zero.

[0083] According to the fluid control valve 1 described in (2), the valve closing state is maintained, that is, the state in which the valve core 32 is in the valve closing position is maintained by a thrust control mode in which the target thrust is zero. That is, the motor (servo motor 6) is not subjected to a load, and the valve closing state is maintained only by the force of the elastic member (spring 52). As a result, the load borne by the motor (servo motor 6) can be reduced to achieve a longer life. In addition, for example, in the event that the fluid control valve 1 fails or the power supply to the fluid control valve 1 is cut off due to a power outage, the valve closing state is maintained only by the force of the elastic member (spring 52), so it is highly safe from the perspective of fail-safe.

[0084] (3) In the fluid control valve 1 described in (1) or (2), the predetermined position (switching position) is preferably determined based on the amount of thermal expansion Δt11 of the valve seat 33 in the opening and closing direction of the valve element 32 .

[0085] In order to improve the responsiveness when the valve core 32 is driven from the valve opening position to the valve closing position, it is ideal to make the specified position (switching position) as close to the valve seat 33 as possible, thereby making the range of the force of the elastic member (spring 52) between the valve opening position and the valve closing position as narrow as possible. Therefore, the specified position (switching position) is determined based on the thermal expansion amount Δt11 of the valve seat 33 in the opening and closing direction of the valve core 32. Specifically, for example, the specified position is set to a position that is Δt11+several μm forward from the origin position of the motor (servo motor 6). This position is a position where the valve core 32 advances 90-95% from the valve opening position to the valve closing position in the stroke from the valve opening position to the valve closing position of the valve core 32. By setting the specified position (switching position) in this way, the valve core 32 is driven by the position control mode of the motor (servo motor 6) until the position immediately before it abuts against the expanded valve seat 33, so the responsiveness of the valve closing can be improved.

[0086] Furthermore, the above-mentioned embodiments are merely examples and do not limit the present invention in any way. Therefore, the present invention can of course be improved and deformed in various ways without departing from the main purpose thereof. For example, the opening and closing action of the fluid control valve 1 of the present embodiment is performed by the lower end surface of the main body 321 of the valve core 32 abutting and separating from the valve seat 33, but the opening and closing action can also be performed by the abutting and separating of the diaphragm and the valve seat as in the fluid control valve disclosed in Japanese Patent Publication No. 2017-223318.

[0087] Explanation of symbols

[0088] 1…Fluid control valve;

[0089] 6…Servo motor (an example of a motor);

[0090] 32…valve core;

[0091] 33…valve seat;

[0092] 52…spring (an example of an elastic member);

[0093] 62…Drive shaft.

Claims

1. A fluid control valve comprising a motor, a valve core, a valve seat and a flow path, The motor is used to move the valve element between an open valve position away from the valve seat and a closed valve position abutting against the valve seat, thereby controlling the control fluid flowing in the flow path. The fluid control valve is characterized in that: An elastic member is provided to apply a force to the valve core in a closing direction, The motor includes a drive shaft for moving the valve element. and having a position control mode for controlling the drive shaft so that the drive shaft moves to a target position and a thrust control mode for controlling the drive shaft so that the drive shaft can obtain a target thrust, And it has the following control program: when the valve core moves from the open valve position to the closed valve position, the motor is controlled by the position control mode from the open valve position to the specified position before the valve core reaches the closed valve position, and the control of the motor is switched from the position control mode to the thrust control mode in which the target thrust is zero from the specified position, so that the valve core reaches the closed valve position only by the action force.

2. The fluid control valve according to claim 1, characterized in that: After the valve body reaches the valve closing position, the control program maintains the valve body in the valve closing position by the thrust control mode in which the target thrust is zero.

3. The fluid control valve according to claim 1 or 2, characterized in that: The predetermined position is determined according to the amount of thermal expansion of the valve seat in the opening and closing direction of the valve element.

Images