Gate valve drive unit

Abstract

To achieve a fine adjustment of a pressure and reduction of oscillation with a gate valve by generating a large thrust and securing a smooth and correct supply of the thrust.SOLUTION: A driving device 10 for a gate valve controls a flow amount of a fluid passing through an open of a valve seat by making a valve plate advance and retreat with respect to the open of the valve seat. The driving device 10 comprises: a shaft 14 connected to the valve plate; a linear motor 16 driving the shaft 14; and driving control means 18 of controlling a driving of the linear motor 16. The linear motor 16 includes: a plurality of coils 20 generating a magnetic field by current; and a magnet 22 that is reacted to the magnetic field generated by the plurality of coils 20. The plurality of coils 20 becomes a stator, and the magnet 22 becomes a movable element that makes the valve plate advance and retreat so as to be connected to the shaft 14. Each of the coils 20 is connected to an individual control circuit. The driving control means 18 individually controls the current flowing in each of the coils 20 via the control circuit.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an improvement in a gate valve drive device used, for example, in a processing chamber of a semiconductor device to create a vacuum inside various processing chambers, and in particular to an improvement in a gate valve drive device that adjusts the flow of processing gas by appropriately controlling the elevation of a valve plate (movement toward and away from the opening of the valve seat), and reduces the generation of particles and the effort and time required for maintenance and inspection by reducing mechanical contact between parts. [Background technology]

[0002] In the manufacturing process of semiconductor devices, gate valves are used between the processing chamber and the suction pump to create a vacuum inside the various processing chambers where etching equipment, thin film processing by CVD (chemical vapor deposition), PVD, etc. These gate valves have a poppet valve in which the valve plate moves back and forth (up and down) relative to the opening of the valve seat.

[0003] Typically, a rotary motor is used as the power source for the drive device to raise and lower the valve plate in this poppet valve. However, when using a rotary motor, mechanical elements that transmit power to the poppet valve, such as belts, ball screws, and bearings, are required, which require mechanical contact (metal contact). This mechanical contact generates particles, and if these particles are dispersed within the processing chamber, they can affect the performance of the semiconductor device being manufactured or damage various measuring instruments such as pressure sensors, resulting in malfunctions. Furthermore, this mechanical contact can shorten the lifespan due to wear, and maintenance to prevent this requires grease, which requires time and effort. Furthermore, the large number of components increases manufacturing time and effort, and there is a limit to the speed at which the valve plate can be raised and lowered, making it difficult to properly control its raising and lowering.

[0004] To avoid these problems, it is conceivable to use a linear motor as the power source for the gate valve drive device, which can raise and lower the valve plate by using the thrust generated between a coil and a magnet without requiring mechanical contact (see, for example, Patent Document 1). In many cases, a linear shaft motor is used as a gate valve drive device using this linear motor, and in this linear shaft motor, a magnet is used as the stator and a coil is used as the mover, and a magnetic field is generated by passing current through this coil, which displaces the coil, thereby raising and lowering the valve plate connected to the mover equipped with this coil.

[0005] However, when a coil that requires current is used as the mover, a cable (power line) is required to supply current to the coil, and this power line is dragged along with the coil, which is the mover, which can cause problems such as wire breakage, making it impossible to ensure a long lifespan and high maintainability, and the following movement of the power line limits the high-speed and high-precision control of the mover's movement.In addition, space must be secured for the movement of the power line, which places a limit on miniaturization.

[0006] For this reason, it has been proposed to use a magnet as the mover and a coil as the stator in a linear motor (see, for example, Patent Document 2 and Patent Document 3). However, even in these linear motors, it is common to use three-phase coils (see, for example, Figure 11 of Patent Document 3), and in these three-phase linear motors, in order to energize the coils to generate a magnetic field, current flows through all of the coil parts, and current continues to flow through the coil parts that are not located in front of the magnet, which is the mover, and which do not actually need to be energized (see Figure 9).

[0007] In this way, if current is passed through unnecessary coil parts, heat generation increases Joule loss, iron loss in the core, and copper loss in the coil, which reduces conversion efficiency (causing output loss) and may prevent the generation of greater thrust. Also, if current is passed through all parts of the coil, current also flows through the coil located at the end of the mover equipped with the magnet, which creates the problem of magnetic field loss due to magnetic field leakage from the end of the mover.

[0008] Furthermore, as the individual coils in a three-phase coil become larger, the inductance also increases, which causes a corresponding decrease in the time constant and dynamic response. This makes it difficult for conventional three-phase linear motors to precisely control the speed of the magnet (moving element) or achieve highly accurate positioning, which ultimately makes it difficult to raise and lower the valve plate at high speed and more appropriately control the gas flow. Another issue with linear motors in general is the need to suppress cogging and ensure smooth and accurate supply of thrust. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-337618 [Patent Document 2] Japanese Patent Application Publication No. 11-125356 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-129921 Summary of the Invention [Problem to be solved by the invention]

[0010] In view of the above problems, the object of the present invention is to provide a gate valve driver that generates a larger thrust to increase the acceleration of the valve plate, thereby realizing high-speed advance and retreat, and that ensures smooth and accurate supply of the required thrust, thereby enabling more appropriate fine adjustment of the pressure exerted by the gate valve and reducing vibration. [Means for solving the problem]

[0011] As a first means for solving the above problems, the present invention provides a drive device for a gate valve that controls the flow rate of a fluid passing through an opening in a valve seat by moving a valve plate back and forth relative to an opening in the valve seat, the drive device comprising a shaft connected to the valve plate, a linear motor that drives the shaft, and drive control means that controls the drive of the linear motor, the linear motor having a plurality of coils that generate a magnetic field in response to an electric current and a magnet that reacts to the magnetic field generated by the plurality of coils, the plurality of coils acting as a stator, while the magnet is connected to the shaft and displaces together with the shaft to act as a mover that moves the valve plate back and forth, the plurality of coils are each connected to an independent control circuit, and the drive control means controls the current flowing through each of the plurality of coils individually through these control circuits. The control circuit is a switching circuit, and the plurality of coils are each connected to an independent switching circuit. The linear motor is provided with a printed circuit board that is a multi-phase circuit on which a plurality of switching circuits are set. The plurality of coils are each individually connected to each switching circuit set on the printed circuit board, and current is passed through the plurality of coils. The present invention provides a gate valve driving device characterized by the above-mentioned.

[0012] The present invention provides, as a second means for solving the above-mentioned problems, the first means for solving the above-mentioned problems, wherein the drive control means applies current only to coils necessary to displace the magnet to a desired position among the plurality of coils. and passing a current of an appropriate magnitude through the necessary coil. The present invention provides a gate valve drive device characterized by:

[0013] As a third means for solving the above problems, the present invention provides a drive device for a gate valve, characterized in that in either the first or second solving means, the drive control means is equipped with a linear encoder that detects the current position of the magnet, and determines the coils that need to have current flow through them in order to displace the magnet to a desired position and the current that should be flowed through the coils according to the current position of the magnet detected by this linear encoder, thereby controlling the current flowing through the multiple coils.

[0014] As a fourth means for solving the above problems, the present invention provides a drive device for a gate valve, characterized in that in any of the first to third solving means, the drive control means controls the current flowing through the multiple coils so that the phase of the current flowing through the multiple coils leads the magnetic field of the magnet by 90° in the direction in which the magnet should move.

[0015] As a fifth means for solving the above problems, the present invention provides a drive device for a gate valve (a drive device in which the coils are located on the outside and the magnets are located on the inside) characterized in that, in any of the first to fourth solutions above, the multiple coils are divided into a set of coil units and arranged opposite each other with a gap between them, while the magnet is formed by arranging multiple individual magnets side by side on both sides of the plate portion of the slider and is installed so that it fits into the gap between the set of coil units.

[0016] As a sixth means for solving the above problems, the present invention provides a gate valve drive device according to the fifth means, characterized in that a slider having a plurality of single magnets attached to a plate portion thereof is provided with a plurality of guide shafts passing through it, and the slider is displaced along the plurality of guide shafts.

[0017] As a seventh means for solving the above problems, the present invention provides a drive device for a gate valve, characterized in that in either the fifth or sixth means, the linear motor comprises a set of motor units arranged on either side of a shaft, and each of the set of motor units has a plurality of coils and magnets, and is driven synchronously.

[0018] As an eighth means for solving the above problems, the present invention provides a drive device for a gate valve, characterized in that in the seventh means, a set of motor units share a slider, the slider has a bearing that supports the lower end of the shaft and two plate portions extending from the bearing, and a magnet is attached to each of the two plate portions and assigned to one set of motor units.

[0019] As a ninth means for solving the above-mentioned problems, the present invention provides a driving device for a gate valve, characterized in that in any one of the fifth to eighth solving means, the linear motor comprises seven or more single magnets and eighteen or more coils.

[0020] As a tenth means for solving the above problems, the present invention provides a drive device for a gate valve, characterized in that, in any of the first to ninth means above, it has an opening for allowing the shaft to move back and forth, and also has a bellows that is installed between the shaft and the magnet and expands and contracts in accordance with the displacement of the magnet, and this bellows blocks the inflow of outside air into the drive device from the opening, thereby keeping the inside of the drive device airtight except for the passageway of the shaft.

[0021] As an eleventh means for solving the above-mentioned problems, the present invention provides a drive device for a gate valve, characterized in that in any of the first to tenth means, the valve plate is supported by a plurality of drive devices, and the plurality of drive devices synchronously move the valve plate forward and backward relative to the opening of the valve seat. [Effects of the Invention]

[0022] According to the present invention, as described above, the multiple coils that form the stators are each connected to an independent control circuit, and the drive control means controls the current that flows through each of the multiple coils individually through these control circuits. This makes it possible to control each of the multiple coils individually, and to select from the multiple coils the coil that is necessary to displace the magnet that forms the mover from its current position to a desired position, and to pass a current of an appropriate magnitude through the required coil. This allows the magnet to be appropriately displaced, enabling precise control of the advancement and retreat of the valve plate relative to the opening of the valve seat, and ultimately the flow rate of fluid through the valve plate, and by adjusting the speed, it is possible to avoid unexpected collisions between the valve plate and the valve seat, etc. Furthermore, as described above, the coils are energized through the printed circuit board, so there is no need to use cables to energize the coils, and a compact design can be achieved. There is practical benefit.

[0023] In this case, particularly according to the present invention, as described above, the drive control means applies current only to those coils necessary for displacing the magnet to the desired position, and therefore current does not flow unnecessarily to coils that are not necessary for displacing the magnet (moving element) from its current position to the desired position, such as coils that are not currently facing the magnet (moving element) or that are not located at the displacement destination. This reduces Joule loss, core iron loss, coil copper loss, magnetic saturation, and magnetic field loss from the end of the magnet (moving element) that occur in the coils due to current, thereby efficiently ensuring sufficient thrust. This has the practical benefit of moving the magnet (moving element) and, ultimately, the valve plate at high speed with an appropriate thrust, thereby accurately controlling the pressure in the chamber. More specifically, according to the present invention, power can be saved by applying current only to the necessary coils, which reduces heat generation in the coils and allows the coils as a whole to receive more power, thereby more efficiently converting current into thrust and displacing the magnet with sufficient thrust.

[0024] According to the present invention, as described above, the drive control means is equipped with a linear encoder that detects the current position of the magnet, and determines the coils that need to have current flow through them and the currents that should be flowed through them in order to displace the magnet to the desired position according to the current position of the magnet detected by this linear encoder, and controls the currents that flow through the multiple coils, which has the practical benefit of enabling more accurate and precise control of the position of the magnet, which is the mover, and ultimately the valve plate.

[0025] According to the present invention, as described above, the drive control means controls the current flowing through the multiple coils so that the phase of the current flowing through the multiple coils leads the magnetic field of the magnet by 90 degrees (+ or -) in the direction in which the magnet should move. Generally, the phase of the current flowing through a coil lags behind the voltage by 90 degrees, so by leading the magnet by 90 degrees in the direction in which it should move, it is possible to obtain the maximum thrust per ampere, and there is the practical benefit of being able to displace the magnet, which is the moving element, at high speed with a greater thrust.

[0026] According to the present invention, as described above, the multiple coils are divided into a set of coil units and arranged opposite each other with a gap between them, while the magnet is formed by arranging multiple individual magnets side by side on both sides of the plate portion of the slider and is installed so as to fit into the gap between the set of coil units. This makes it possible to install a large number of individual coils and magnets, and the number of poles and slots can be appropriately adjusted to ensure sufficient thrust and smooth displacement of the mover. In addition, the coils are positioned on the outside so as to face both sides of the magnets located on the inside, and this coil forms a fixedly positioned stator. Therefore, when arranging the circuit for supplying current to the coils, it is not necessary to install cables for supplying current, which has the practical benefit of improving durability and maintainability.

[0027] Furthermore, in this case, according to the present invention, as described above, the slider having a plurality of individual magnets attached to the plate portion has a plurality of guide shafts passing through it, and the slider is displaced along the plurality of guide shafts, so that the slider can be displaced stably without tilting, etc., and has the practical benefit of being able to move the valve plate appropriately.

[0028] Furthermore, according to the present invention, as described above, the linear motor has a pair of motor units sandwiching the shaft, and each of the motor units has a plurality of coils and magnets, and drives synchronously, which has the practical advantage of allowing smooth displacement without tilting the shaft.

[0029] According to the present invention, as described above, a set of motor units share a slider, which has a bearing that supports the lower end of the shaft and two plate portions extending from the bearing, with magnets attached to each of the two plate portions and assigned to a set of motor units.This has the practical benefit of properly supporting the valve plate while reducing the number of parts, thereby reducing the effort and cost of manufacturing and maintenance.

[0030] According to the present invention, as described above, the linear motor is equipped with seven or more individual magnets and eighteen or more multiple coils, and therefore, by making each individual coil smaller and reducing inductance, it is possible to improve the time constant and dynamic response and speed up the movement of the magnet that is the mover, and as a result, these coils can be controlled individually, so that a large number of poles and slots can be set finely, for example, six slots and seven poles. Unlike a three-phase motor with a limited slot-pole configuration, this produces a large torque and allows for precise and accurate control of the movement of the mover, while at the same time reducing torque pulsation and cogging, thereby ensuring smooth displacement of the magnet that is the mover (displacement with little noise and vibration).

[0031] According to the present invention, as described above, the drive unit has an opening for allowing the shaft to move back and forth, and a bellows disposed between the shaft and the magnet that expands and contracts in response to the displacement of the magnet. The bellows blocks the inflow of outside air into the drive unit through the opening, keeping the inside of the drive unit airtight except for the passage of the shaft. This effectively maintains a vacuum inside the drive unit, suppresses external influences, and realizes smooth displacement of the magnet, which is the mover. In particular, if the bellows is made of a non-magnetic material such as stainless steel, it expands and contracts in response to the movement of the mover regardless of the magnetic force of the magnet, thereby effectively providing guidance and cushioning for the mover.

[0032] According to the present invention, as described above, the valve plate is supported by a plurality of drive devices that move the valve plate forward and backward relative to the opening of the valve seat in synchronization. This allows the valve plate to be stably supported at at least two points, and at the same time, since the drive devices are driven in synchronization, there is no tilt of the valve plate, and the valve plate can be moved smoothly to appropriately control the flow rate of the fluid, which is a practical advantage. [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a perspective view of a gate valve equipped with a drive device of the present invention. [Figure 2] 1 is a front view of a gate valve equipped with a drive device of the present invention. [Figure 3] FIG. 2 is a partially exploded perspective view of the driving device of the present invention with the cover removed. [Figure 4] FIG. 2 is a partially exploded perspective view of the driving device of the present invention with a cover and a coil unit removed. [Figure 5] 1 is a cross-sectional view of the driving device of the present invention in a state where a magnet, which is a mover, is positioned at the lowest position. [Figure 6] 1 is a cross-sectional view of the driving device of the present invention, in which the magnet, which is the mover, is positioned at the top. [Figure 7] FIG. 2 is a perspective view of a coil unit used in the driving device of the present invention. [Figure 8] 3A and 3B are diagrams showing the positional relationship between a coil and a magnet and the phase of a current in the present invention. [Figure 9] 10 is a graph showing the phases of three phases of current flowing through a coil and current flowing through a magnet in a conventional driving device. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0034] (1. Gate valve) A detailed description of an embodiment of the present invention will be given with reference to the drawings. FIGS. 1 and 2 show a gate valve 1 equipped with a drive device 10 of the present invention. As shown in FIGS. 1 and 2, this gate valve 1 is installed above a suction pump 2 for adjusting the pressure inside a processing chamber used in a manufacturing process of a semiconductor device (not shown), and is used to control the flow of fluid by the suction pump 2.

[0035] 1 and 2, the gate valve 1 has a valve seat 1A with an opening 1a, and a valve plate 1B that moves forward and backward relative to the opening 1a of the valve seat 1A. The drive unit 10 of the present invention controls the flow rate of fluid passing through the opening 1a of the valve seat 1A by moving the valve plate 1B forward and backward relative to the opening 1a of the valve seat 1A. The valve seat 1A is made of a non-magnetic material, for example, aluminum.

[0036] (2. Drive unit) In the illustrated embodiment, as shown in FIGS. 1 and 2 , the valve plate 1B is supported by a plurality of, specifically, two, drive units 10. Specifically, the two drive units 10 are connected to flanges on both ends of the substantially disc-shaped valve plate 1B, supporting the valve plate 1B at two points and moving the valve plate 1B toward and away from the opening 1a of the valve seat 1A. This allows the valve plate to be stably supported at two points. Furthermore, in this case, the plurality (two) drive units 10 synchronously move the valve plate 1B toward and away from the opening 1a of the valve seat 1A. This prevents tilting of the valve plate 1B, allowing the valve plate 1B to move smoothly and appropriately control the flow rate of the fluid. While the illustrated embodiment uses two drive units 10 to support the valve plate 1B, three or four drive units 10 may also be installed at equal intervals. In either case, it is desirable for the multiple drive units 10 to synchronously move the valve plate 1B toward and away from the opening 1a of the valve seat 1A using a common control circuit.

[0037] 3 to 6, each of the plurality of drive devices 10 includes a casing 12, a shaft 14 that partially protrudes from above the casing 12 and is connected to the valve plate 1B, a linear motor 16 that drives the shaft 14, and drive control means 18 that controls the drive of the linear motor 16. As shown in FIGS. 3 to 6, an opening 12a that allows the shaft 14 to move back and forth is formed in the top surface of the casing 12.

[0038] (3. Linear motor) 5 and 6, the linear motor 16 is composed of a pair of motor units 16A and 16B arranged on either side of the shaft 14, and each of the pair of motor units 16A and 16B is equipped with a plurality of coils 20 and magnets 22. The pair of motor units 16A and 16B are driven synchronously. Therefore, the pair of motor units 16A and 16B can smoothly displace the shaft 14 without tilting it.

[0039] 3 to 8, each of the motor units 16A, 16B has a plurality of coils 20 that generate a magnetic field when an electric current flows through them, and a magnet 22 that reacts to the magnetic field generated by these plurality of coils 20. In this case, in the present invention, as shown in Figures 3 to 8, these plurality of coils 20 serve as stators, while the magnet 22 is connected to the shaft 14 and serves as a mover that moves together with the shaft 14 to move the valve plate 1B back and forth.

[0040] Specifically, in each motor unit 16A, 16B, as shown in Figures 3 to 8, the multiple coils 20 are divided into a pair of (two) coil units 20A, 20B and are fixedly arranged opposite each other with a gap between them, while the magnet 22 is made up of multiple individual magnets 22a to 22g, which are arranged side by side on both sides of the plate portion 24b of the slider 24 and are installed so as to fit into the gap between the pair of coil units 20A, 20B.

[0041] For this reason, in the present invention, as shown in Figures 3 to 8, it is possible to install a large number of individual coils 20 and magnets 22, and as will be described later, the number of poles and the number of slots can be appropriately adjusted to ensure sufficient thrust and smooth displacement of the mover. In addition, the coils 20 are positioned on the outside so as to face both sides of the magnets 22 positioned on the inside, and since this coil 20 forms a fixedly positioned stator, there is no need to install cables for current flow in the arrangement of the circuit for supplying current to the coils 20, thereby improving durability and maintainability.

[0042] In this case, as shown particularly in Figures 5 and 6, a pair of motor units 16A, 16B share a slider 24, and this slider 24 has a bearing 24a located in the center of the slider 24 and supporting the lower end of the shaft 14, and two plate portions 24b extending from this bearing 24a, and a plurality of individual magnets 22a to 22g are attached to each of the two plate portions 24b and are allocated to the pair of motor units 16A, 16B.

[0043] Therefore, when the slider 24 to which the magnet 22 is attached is displaced in response to the magnetic field generated by energizing the coil units 16A, 16B, the shaft 14, whose lower end is supported by this bearing 24a, is also displaced, thereby allowing the valve plate 1B, which is connected to the shaft 14, to move forward and backward (raise and lower) relative to the opening 1a of the valve seat 1A. In this way, the pair of motor units 16A, 16B share the slider 24, and the lower end of the shaft 14 is supported by the bearing 24a of this slider 24, so that the valve plate 1B is appropriately supported while the number of parts is reduced, thereby reducing the effort and cost of manufacturing and maintenance.

[0044] 4 to 6, a plurality of guide shafts 26 (two as shown in Fig. 4 in the illustrated embodiment) are installed to pass through the slider 24 for each motor unit 16A, 16B, and the slider 24 can be displaced along these two guide shafts 26. Therefore, particularly for one set of motor units 16A, 16B, the slider 24 is guided by the guide shafts 26 at four locations, so there is no positional deviation, especially in the lateral direction, and these multiple guide shafts 26 allow the slider 24 to be displaced stably without tilting, and the valve plate 1B can be moved appropriately.

[0045] 5 and 6, the driving device 10 of the present invention has a bellows 28 that is installed between the shaft 14 and the magnet 22 and expands and contracts in response to the displacement of the magnet 22. The bellows 28 blocks the inflow of outside air into the driving device 10 from the opening 12a of the casing 12, keeping the inside of the driving device 10 airtight except for the passage of the shaft 14. Therefore, the bellows 28 maintains a vacuum inside the driving device 10 without interfering with the displacement of the magnet 22, suppressing external influences and realizing smooth displacement of the magnet 22, which is the mover.

[0046] In this case, as shown in Figures 5 and 6, the bellows 28 is formed into a cylindrical shape with a bellows-like outer circumferential surface, and the shaft 14 is disposed so as to pass through the interior thereof. The lower end of the bellows 28 is attached to the bearing 24a of the slider 24, and the upper end is attached to the opening 12a of the casing 12, so that the bellows 28 can expand and contract in response to the displacement of the slider 24 having the magnet 22 serving as the mover. Furthermore, the bellows 28 is preferably formed from a non-magnetic material such as stainless steel (e.g., SUS304 or SUS316). By forming the bellows 28 from a non-magnetic material, the bellows 28 can expand and contract in response to the movement of the slider 24 having the magnet 22 serving as the mover, regardless of the magnetic force of the magnet 22, and can appropriately provide guidance and cushioning for the slider 24 having the magnet 22 serving as the mover.

[0047] (4. Linear motor control) In the linear motor 16 having the above mechanical configuration, according to the present invention, the multiple coils 20 are each connected to their own control circuit (switching circuit). Specifically, as shown in FIG. 7, each of the coil units 16A and 16B is provided with a printed circuit board 30, which is a multiphase circuit on which multiple control circuits (switching circuits) are set, and the multiple coils 20 are individually connected to each control circuit (switching circuit) set on the printed circuit board 30. Furthermore, a control device (not shown) is used as the drive control means 18, and software included in the control device can individually control the current flowing through each of the multiple coils 20 via each control circuit set on the printed circuit board 30. Because the multiple coils 22 are energized through the printed circuit board 30, no cables are required to energize the coils 22, allowing for a compact design.

[0048] In the present invention, because the current flowing through each of the multiple coils 20 is controlled individually, the multiple coils 20 can be controlled individually. As shown in Figure 8, the coils 20 necessary to displace the slider 24 equipped with the magnet 22 as a mover from its current position to a desired position can be selected from the multiple coils 20, and an appropriate amount of current can be passed through the required coils 20. This allows the slider 24 equipped with the magnet 22 as a mover to be appropriately displaced, thereby precisely controlling the movement of the valve plate 1B relative to the opening 1a of the valve seat 1A, and ultimately the flow rate of fluid through the valve plate 1B. Furthermore, by adjusting the speed, unexpected collisions between the valve plate 1B and the valve seat 1A can be avoided. In each of the motor units 16A, 16B, the currents of the individual coils 20 facing each other across the magnet 22 are controlled in synchronization with the individual coils 20 facing each other. As shown in particular in FIGS. 7 and 8, each unit coil 20 is made up of a core (iron core) 20a and a copper plate 20b arranged around this core (iron core) 20a.

[0049] Specifically, in the present invention, as shown in Fig. 8, the drive control means 16 applies current only to those coils 20 among the plurality of coils 20 that are necessary for displacing a slider 24 having a magnet 22 as a mover to a desired position. In other words, as can be seen by comparing the current phases shown in Fig. 8 for the present invention with the current phases shown in Fig. 9 for a conventional three-phase linear motor, this means that in the present invention, current is not applied unnecessarily to coils 20 that are not necessary for displacing a slider 24 having a magnet 22 as a mover.

[0050] Therefore, in the present invention, as shown in FIG. 8, for example, no current flows unnecessarily through coil 20 that is not currently facing magnet 22 (the movable element) or is not positioned at the displacement destination. This reduces Joule loss, iron loss in core 20a, copper loss in copper plate 20b, magnetic saturation, and magnetic field loss from the end of magnet 22 (slider 24) (the movable element) that occurs in coil 20 due to the current, and it is possible to efficiently ensure sufficient thrust, and it is possible to move magnet 22 (the movable element), and ultimately valve plate 1B, at high speed with an appropriate thrust, thereby accurately controlling the pressure within the processing chamber.

[0051] This also allows power saving by passing current only through the necessary coils 20, thereby suppressing heat generation in the coils 20. As a result, the entire coil 20 (the entire coil units 16A, 16B) can receive more power, so that the current can be converted into thrust with higher efficiency and the slider 24 equipped with the magnet 22, which is the moving part, can be displaced with sufficient thrust.

[0052] In this case, in the present invention, the linear motor 16, i.e., each of the motor units 16A and 16B, is provided with seven individual magnets 22a-22g and eighteen individual coils 20, as shown in FIGS. 3, 4, 7, and 8. That is, in the present invention, as can be particularly seen from FIG. 8, the number of coils 20 is greater than the number of magnets 22, and the drive control means 16 generates a magnetic field by passing current through only those coils 20 necessary to displace the slider 24, which includes the magnets 22 serving as the mover, to a desired position, thereby displacing the slider 24, which includes the magnets 22 serving as the mover. As shown in FIGS. 3 to 8, by setting the widths of the individual magnets 22 and the widths of the coils 20 (cores 20a) to be approximately the same, the number of poles and slots can be appropriately set. Furthermore, the multiple magnets 22 are arranged so that the south and north poles of each of the individual magnets 22a-22g are alternately oriented, thereby allowing the magnetic field generated by the coils 20 to apply a thrust to the slider 24.

[0053] Specifically, for example, when the slider 24 equipped with the magnet 22 as a movable element is moved from the lowest position (where the valve plate 1B is in close contact with the opening 1a of the valve seat 1A) as shown in FIG. 5 to the upper position in FIG. 5, the slider 24 is displaced by passing a current only through the coils 20 of the multiple coils 20 that are located at the destination position of the slider 24, for example, the coils 20 located second to seventh from the bottom. By repeating this process, the slider 24 equipped with the magnet 22 as a movable element can be displaced to the uppermost position (where the valve plate 1B is retracted the furthest from the opening 1a of the valve seat 1A) as shown in FIG. 6.

[0054] Conversely, for example, when moving the slider 24 from a state in which the slider 24 equipped with the magnet 22 serving as the movable element is at the uppermost position (a state in which the valve plate 1B is retracted the furthest from the opening 1a of the valve seat 1A) as shown in FIG. 6 downward in FIG. 6, the slider 24 is displaced by passing a current only through those of the multiple coils 20 that are located at the destination position, for example, the fifth through tenth coils 20 from the top. By repeating this process, the slider 24 equipped with the magnet 22 serving as the movable element can be displaced to a state in which the slider 24 is at the lowermost position (a state in which the valve plate 1B is in close contact with the opening 1a of the valve seat 1A) as shown in FIG.

[0055] Of course, the slider 24 can be moved not only between the lowest and highest positions, but also at any intermediate position by appropriately selecting the coil 20 to which current should be passed using the drive control means 16, thereby enabling the slider 24 to move back and forth as needed to adjust the flow rate of fluid through the valve plate 1B. Furthermore, the speed of the slider 24 can be finely adjusted by controlling the magnitude of the current to be passed through each coil 20.

[0056] 8, it is desirable that the drive control means 16 controls the current flowing through the plurality of coils 20 so that the phase of the current flowing through the plurality of coils 20 leads the magnetic field of the magnet 22 by 90° in the direction in which the magnet 22 should move (for example, set to the + direction when raising the shaft 14 and the - direction when lowering it). This is because, generally, the phase of the current flowing through the coils 20 lags behind the voltage by 90°, so by leading the magnet 22 in the direction in which it should move by +-90°, the maximum thrust per ampere can be obtained, and the slider 24 equipped with the magnet 22, which is the mover, can be displaced at high speed with a larger thrust.

[0057] In this case, each of the 18 individual coils 20 is connected to one control circuit (switching circuit), and therefore, in the illustrated embodiment, a multiphase circuit with a total of 18 phases is formed on the printed circuit board 30. In this way, since a large number of phases are set in the present invention, as shown in Figures 3 to 8, it is possible to reduce the size of each individual individual coil 20, thereby reducing inductance and improving the time constant and dynamic response, thereby speeding up the movement of the slider 24 equipped with the magnet 22, which is the mover. Also, the induced electromotive force (V L ) is V L = L(di / dt) (L: inductance, di: change in current, dt: time), so by controlling the magnitude and time of the current change, the inductance of coil 20 can be increased and decreased more quickly to correct irregularities in thrust.

[0058] Furthermore, as a result of being able to individually control these multiple coils 20 in this way, it is possible to set a large number of poles and slots in detail, and unlike the case of a three-phase motor with a limited slot-pole configuration, it is possible to obtain a large torque and precisely and accurately control the movement of the slider 24 equipped with the magnet 22 as the moving part, while at the same time reducing torque pulsation and reducing cogging, thereby ensuring smooth displacement (displacement with little noise and vibration) of the slider 24 equipped with the magnet 22 as the moving part.

[0059] Specifically, in the illustrated embodiment, as shown in Fig. 8, seven poles are provided by seven magnets 22 and six slots are provided by six energized coils 20, so that a greater number of poles and slots can be provided than in a typical three-phase motor, which has two poles and three slots, thereby improving torque and reducing torque pulsation. Therefore, in order to be able to provide a greater number of poles and slots, it is desirable for the linear motor 16 to have seven or more individual magnets 22 and 18 or more coils 20.

[0060] Furthermore, in the present invention, the drive control means 16 is equipped with a linear encoder (not shown) that detects the current position of the magnet 22 (or the slider 24 equipped with the magnet 22). Based on the current position of the magnet 22 detected by this linear encoder, it is possible to determine the coils 20 to which current needs to flow in order to displace the magnet 22 to a desired position and the current to be passed through those coils 20, and to control the currents flowing through the multiple coils 20. This makes it possible to more accurately and precisely control the position of the slider 24 equipped with the magnet 22, which is the mover, and ultimately the valve plate 1B. [Industrial Applicability]

[0061] The present invention can be widely applied to etching devices for semiconductor devices, thin film processing by CVD, PVD, and further to processing chambers used in the manufacture of flat panel displays. [Explanation of symbols]

[0062] 1. Gate valve 1A Valve seat 1a Valve seat opening 1B Valve Plate 2. Suction pump 10 Drive unit 12 Casing 12a Casing opening 14 shaft 16 Linear motor 16A, 16B 1 motor unit 18 Drive control means 20 coils 20A, 20B 1 set of coil unit 20a Core 20b copper plate 22 Magnet 22a~22g Single magnet 24 Slider 24a bearing 24b Plate part 26 Guide shaft 28 Bellows 30 Printed Circuit Board

Claims

1. a drive device for a gate valve that moves a valve plate back and forth relative to an opening in a valve seat to control a flow rate of a fluid passing through the opening, the drive device comprising: a shaft connected to the valve plate; a linear motor that drives the shaft; and drive control means that controls the drive of the linear motor, the linear motor having a plurality of coils that generate a magnetic field when an electric current flows through it and a magnet that reacts to the magnetic field generated by the plurality of coils, the plurality of coils serving as a stator, while the magnet is connected to the shaft and displaces together with the shaft to move the valve plate back and forth, the plurality of coils being connected to an independent control circuit, the drive control means individually controlling the current flowing through each of the plurality of coils through the control circuit, the control circuit being a switching circuit, and the plurality of coils being connected to their own independent switching circuits, the linear motor is provided with a printed circuit board that is a multiphase circuit on which a plurality of the switching circuits are set, the plurality of coils being individually connected to each of the switching circuits set on the printed circuit board, and current is supplied to the plurality of coils through the printed circuit board.

2. 2. A gate valve drive device according to claim 1, wherein the drive control means passes current only through those coils of the plurality of coils that are necessary for displacing the magnet to a desired position, and passes current of an appropriate magnitude through the necessary coils.

3. 3. A gate valve drive device according to claim 1, wherein the drive control means includes a linear encoder that detects the current position of the magnet, and determines the coils through which current needs to be passed in order to displace the magnet to a desired position and the currents that should be passed through the coils in accordance with the current position of the magnet detected by the linear encoder, and controls the currents that flow through the coils.

4. 4. A gate valve drive device according to claim 1, wherein the drive control means controls the currents flowing through the plurality of coils so that the phase of the currents flowing through the plurality of coils leads the magnetic field of the magnet by 90 degrees in the direction in which the magnet should move.

5. 5. A gate valve drive device according to claim 1, wherein the plurality of coils are divided into a set of coil units and arranged opposite each other with a gap between them, while the magnet is formed by arranging a plurality of individual magnets side by side on both sides of the plate portion of the slider and is installed so as to fit into the gap between the set of coil units.

6. 6. The gate valve drive device according to claim 5, wherein the slider having the plurality of single magnets attached to the plate portion has a plurality of guide shafts passing therethrough, and the slider is displaced along the plurality of guide shafts.

7. 7. A gate valve drive device according to claim 5 or claim 6, wherein the linear motor is made up of a set of motor units arranged on either side of the shaft, each of the set of motor units having the plurality of coils and the magnet, and driven synchronously.

8. 8. A gate valve drive device according to claim 7, wherein the set of motor units share the slider, the slider has a bearing that supports the lower end of the shaft and two plate portions extending from the bearing, and the magnet is attached to each of the two plate portions and assigned to the set of motor units.

9. 9. A gate valve driving device according to claim 5, wherein the linear motor comprises seven or more of the single magnets and eighteen or more of the plurality of coils.

10. 10. A gate valve drive device according to claim 1, further comprising an opening for allowing the shaft to move back and forth, and a bellows disposed between the shaft and the magnet that expands and contracts in accordance with the displacement of the magnet, the bellows blocking the inflow of outside air into the drive device from the opening and maintaining an airtight seal inside the drive device except for the passage of the shaft.

11. 11. The gate valve drive device according to claim 1, wherein the valve plate is supported by a plurality of the drive devices, and the plurality of drive devices synchronously move the valve plate forward and backward relative to the opening of the valve seat.

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