JP2011243217A - Vacuum control valve and vacuum control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for increasing a degree of freedom of design of a vacuum control valve having a shutoff function.SOLUTION: This invention provides the vacuum control valve 30 which is connected between a vacuum vessel and a vacuum pump and controls a vacuum pressure inside the vacuum vessel by operating a valve opening degree by working fluid. The vacuum control valve 30 includes: an operation part provided with a valve body 33 and a piston for performing the operation of the valve opening degree and shutoff by adjusting a lift amount; a cylinder 31 for housing the piston; an energizing part for energizing the operation part in a direction of reducing the lift amount; a bellofram 34 for tightly closing a gap between an outer peripheral surface of the piston and an inner peripheral surface of the cylinder 31 while following movement of the piston; a valve opening degree operation chamber tightly closed by the bellofram 34, for generating a load in the direction of increasing the lift amount corresponding to a working pressure of the working fluid; and a shutoff load generation chamber for generating the load in the direction of reducing the lift amount to the operation part corresponding to supply of the working fluid.

Description

  The present invention relates to a vacuum control valve for discharging a gas in a vacuum vessel used in various vacuum apparatuses such as a semiconductor manufacturing apparatus and a liquid crystal manufacturing apparatus.

  A vacuum control valve is realized which is provided in a flow path for discharging gas in the vacuum vessel and controls the vacuum pressure in the vacuum vessel by operating the valve opening degree of the flow path. As the vacuum control valve, a valve having a blocking function for completely blocking the flow path as well as controlling the vacuum pressure has been proposed. Specifically, a vacuum control valve that achieves low hysteresis valve opening operation with a single-acting bellowram cylinder that uses a biasing spring and shuts off the flow path with a blocking function by the biasing spring is also from the present inventors. It has been proposed (Patent Document 1). The reason why low hysteresis valve opening operation can be realized with a single-acting bellophram cylinder is that hysteresis caused by the sliding resistance of the piston packing can be avoided.

Japanese Patent Laid-Open No. 09-72458 JP 09-89126 A JP 2003-56512 A JP 2003-322111 A

  However, the present inventor has found that the vacuum control valve of a single-acting Bellofram cylinder having a shut-off function has a design limit in increasing the diameter. This is because the shut-off function shuts off with a load according to the aperture area in order to ensure the pressure resistance at the time of shut-off. It has been found by the present inventor that a biasing spring that generates a large load makes the assembly of the valve extremely difficult, and thus the manufacturability is significantly deteriorated. On the other hand, the present inventor has also studied a double-acting bellowram cylinder without using an urging spring. However, in order to double-acting a bellowram cylinder, two bellophrams must be symmetrically equipped. Rather, it has been found by the present inventor that the vacuum control valve becomes large. This is because the belofram operates normally only in one direction of pressure.

  The present invention was created in order to solve at least a part of the above-described conventional problems, and an object thereof is to provide a technique for increasing the degree of design freedom of a vacuum control valve having a blocking function.

  Hereinafter, effective means for solving the above-described problems will be described while showing effects and the like as necessary.

  Means 1. A vacuum control valve connected between a vacuum vessel and a vacuum pump and operating a valve opening degree with a working fluid to control a vacuum pressure in the vacuum vessel, and connects the vacuum vessel and the vacuum pump. A control valve body having a flow path and a valve seat formed in the flow path; an operation of the valve opening by adjusting a lift amount which is a distance from the valve seat; and contact with the valve seat A valve body that shuts off the flow path according to the above, a piston, a rod that couples the valve body and the piston, and a cylinder that is connected to the control valve body and accommodates the piston. The gap between the urging portion that urges the operating portion in a direction in which the lift amount decreases and the outer peripheral surface of the piston and the inner peripheral surface of the cylinder is sealed while following the operation of the piston. Bellofram, comprising The working portion and the cylinder are sealed by the bellophram and have a cylindrical shape surrounding the rod, and increase the lift amount relative to the piston in accordance with the working pressure of the working fluid. A valve opening operation chamber for generating a load and a central axis line with the valve opening operation chamber are shared, and the load is generated in the direction of reducing the lift amount with respect to the operating portion in response to the supply of the working fluid. A vacuum control valve forming a shut-off load generation chamber.

  Means 1 is a vacuum control valve that is connected between the vacuum vessel and the vacuum pump and controls the vacuum pressure in the vacuum vessel by operating the valve opening degree with the working fluid. Since this vacuum control valve has a cutoff load generation chamber that applies a cutoff load to the piston by the pressure of the working fluid, it is possible to relax the required specifications for the urging unit due to the cutoff function. Thereby, the design freedom of the vacuum control valve which has a cutoff function can be raised.

  The required specifications for the urging unit due to the shut-off function assume, for example, the worst case assumed when the connection port on the vacuum pump side is open to the atmosphere and the connection port on the vacuum vessel side is in a vacuum state. Is set. In this setting, a larger biasing force is required as the vacuum pump side connection port has a larger diameter. The provision of such an urging portion (for example, a spring) that generates the urging force is one of the factors for increasing the size of the vacuum control valve, and the assembly burden during manufacturing is excessive. This vacuum control valve can solve such a problem by providing an interrupting load generating chamber for applying an interrupting load, and can suppress an increase in size and secure a manufacturability and an increase in diameter.

  The sealing (sealing) by the bellophram having followability has low sliding resistance between the inner peripheral surface of the cylinder and the outer peripheral surface of the piston, and can realize a highly responsive operation with low hysteresis. Such a sealed structure can achieve both the above-described high-performance operation and suppression of enlargement if it is a single-acting type using an urging portion. As a result, the vacuum control valve can control the valve opening with low hysteresis and high responsiveness by adjusting the lift amount, and can precisely control the vacuum pressure in the vacuum vessel.

On the other hand, since the breaking load generation chamber is formed inside the valve opening operation chamber with respect to the center line extending in the operation direction of the operation portion, the following effects can be obtained.
(1) Since a sliding radius can be made small, generation | occurrence | production of the sliding resistance resulting from the installation of the interruption | blocking load generation | occurrence | production chamber can be suppressed.
(2) Since the breaking load generation chamber can be arranged at a position overlapping with the valve opening operation chamber in the direction of the center line extending in the direction of operation of the piston, the large size of the vacuum control valve due to the equipment of the breaking load generation chamber Can be suppressed.

  Thus, the vacuum control valve of the means 1 realizes a low hysteresis control function while suppressing an increase in the size of the vacuum control valve, and relaxes the restriction on the degree of freedom of design of the urging unit due to the shut-off function. Can do. Accordingly, it is possible to achieve both a reduction in size and an improvement in manufacturability while realizing an improvement in the control performance of the low hysteresis of the vacuum control valve.

  Mean 2. The cylinder includes a head cover having a sliding convex portion housed in the shut-off load generating chamber, and the vacuum control valve is a seal that seals between the shut-off load generating chamber and the sliding convex portion. The vacuum control valve according to claim 1, further comprising a sealing portion having a surface and having a surface pressure of the sealing surface increased in response to the supply of the working fluid to the blocking load generation chamber.

  In the vacuum control valve of the means 2, a sealing portion in which the surface pressure of the sealing surface is increased in accordance with the supply of the working fluid to the breaking load generation chamber is used for the breaking load generation chamber. As a result, when the valve opening is manipulated, that is, when the valve is not cut off, the pressure of the sealing surface of the breaking load generating chamber can be suppressed and the sliding can be performed with low friction. As a result, for example, the operation of the valve opening with low hysteresis can be realized with a simple configuration without performing a bellophram.

  Means 3. The sliding convex portion shares a central axis with the valve opening operation chamber, has a cylindrical shape with an outer diameter smaller than an inner diameter of the valve opening operation chamber, and the operating portion has the sliding A guide portion extending in a direction of the operation in a space surrounded by an inner peripheral surface of the convex portion, wherein the vacuum control valve is disposed between the guide portion and the sliding convex portion, and the direction of the operation The vacuum control valve of means 2 comprising a bearing that enables the sliding movement of the guide portion and the sliding convex portion to mutually restrain the positional relationship in the direction perpendicular to the direction of the operation.

  In the vacuum control valve of the means 3, since the operating portion is provided with a guide portion extending in the direction of operation in the space surrounded by the inner peripheral surface of the cylindrical sliding convex portion, the bearing is more than the sliding surface of the bellophram. The sliding surface of the sliding convex portion is arranged at a position close to. Thereby, the precision of the clearance of the sliding surface between the interruption | blocking load generation | occurrence | production chamber and a sliding convex part which has a severe request | requirement of precision than a belofram can be improved easily.

  Means 4. 4. The vacuum control valve according to any one of means 1 to 3, wherein the breaking load generation chamber is formed inside the rod.

  In the vacuum control valve of means 4, since the breaking load generating chamber is formed inside the operating part, the breaking load applying part can be equipped by effectively utilizing the space occupied by the operating part. Thereby, the enlargement of the vacuum control valve resulting from the formation of the blocking load generation chamber can be suppressed. Furthermore, by forming the breaking load generation chamber inside the operating portion, it is possible to provide a large degree of design freedom in the direction of reducing the diameter of the breaking load generation chamber.

  Means 5. The vacuum control valve according to any one of means 1 to 4, a pressure sensor for measuring a vacuum pressure in the vacuum vessel, a working fluid supply unit for supplying a working fluid, and exhausting the working fluid A pneumatic circuit connected to a working fluid exhaust unit for supplying the working fluid to the vacuum control valve, and operating the working fluid supplied from the pneumatic circuit to the vacuum control valve, And a control unit that controls the vacuum pressure.

  The present invention can also be embodied as a vacuum control system.

  Means 6. The control unit connects a flow path between the valve opening operation chamber and the working fluid exhaust unit in response to reception of a vacuum pump stop signal including information indicating the stop of the vacuum pump, and the interrupting load The vacuum control system according to claim 5, wherein a flow path between the generation chamber and the working fluid supply unit is connected.

  The vacuum control system of means 6 is in an operation mode in which a shut-off load is applied in response to reception of a vacuum pump stop signal, so a shut-off state is secured even if the pressure on the vacuum pump rises due to an unexpected stop of the vacuum pump. Has the advantage of being able to. Note that “reception of the vacuum pump stop signal” has a broad meaning including, for example, confirmation of the state of the internal contact on the vacuum pump side indicating the operating state of the vacuum pump and failure of the normal signal of the vacuum pump.

  Mean 7 The pneumatic circuit includes a first electromagnetic valve that connects a flow path between the valve opening operation chamber and the working fluid exhaust part in a non-energized state, and the shut-off load generation chamber and the working fluid in a non-energized state. The vacuum control system according to claim 5 or 6, comprising a second solenoid valve for connecting a flow path to the supply unit.

  The vacuum control system of the means 7 includes a first electromagnetic valve that connects a flow path between the valve opening operation chamber and the working fluid exhaust part in a non-energized state, and the shut-off load generation chamber in a non-energized state. Since it has the 2nd electromagnetic valve which connects the flow path between the said working fluid supply parts, it will be in an emergency interruption state by all means at the time of power-off or a power failure. This makes it possible to easily realize a system design that considers ensuring safety during an emergency stop or power failure.

  The present invention can be embodied not only in a vacuum control valve and a vacuum control system but also in the form of, for example, a vacuum control method, a computer program that embodies the method, and a program medium.

Sectional drawing which shows the structure of the vacuum control valve 30 at the time of non-energization (valve full closure). The expanded sectional view which shows the structure of the rod cover 81 which the vacuum control valve 30 has at the time of non-energization. Sectional drawing which shows the structure of the vacuum control valve 30 at the time of valve full open. Sectional drawing which shows the operation state at the time of control of the vacuum pressure of the vacuum control valve 30. FIG. FIG. 3 is an enlarged cross-sectional view showing a friction surface between a packing 70 and an inner peripheral surface 63. The schematic diagram which shows the mounting state of the packing 70, and demonstrates the sealing principle. The schematic diagram which shows the state at the time of non-pressurization of the interruption | blocking load generation chamber 39, and demonstrates a sealing principle. The schematic diagram which shows the time of pressurization to the interruption | blocking load generation | occurrence | production chamber 39, and demonstrates a sealing principle. The schematic diagram which shows the structure of the vacuum control system 20 of embodiment. The schematic diagram which shows the structure and action | operation content of the pneumatic circuit 22 of embodiment. The control block diagram of the vacuum control system 20 of embodiment.

(Embodiment of the present invention)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The present embodiment embodies a novel vacuum control valve and a vacuum control system used in an etching process manufacturing line as a semiconductor manufacturing apparatus using the vacuum control valve.

  First, the configuration of the vacuum control valve will be described with reference to FIGS.

  FIG. 1 is a cross-sectional view showing the configuration of the vacuum control valve 30 when not energized (valve fully closed). FIG. 2 is an enlarged cross-sectional view showing the configuration of the rod cover 81 included in the vacuum control valve 30 when not energized. FIG. 3 is a cross-sectional view showing the configuration of the vacuum control valve 30 when the valve is fully opened. The vacuum control valve 30 includes a control valve main body 43, a cylinder tube 31, and an operation member 32. The control valve main body 43 has a cylindrical shape extending in the moving direction (axial direction) of the operation member 32. The control valve main body 43 is formed with a valve box 45 that is a substantially cylindrical recess that opens toward the cylinder tube 31 in the axial direction. The opening of the valve box 45 is closed by a rod cover 81 having a through hole 82 through which the operating member 32 is slidably penetrated.

  The operating member 32 includes a valve body 33 that operates the valve opening degree of the vacuum control valve 30 in the valve box 45, a rod 32r that passes through the through hole 82, and a piston 51 that is connected to an end of the rod 32r. ing. The valve body 33 is connected to the rod 32r, and the lift amount La can be changed by moving the operation member 32 in the axial direction. In this embodiment, the lift amount La corresponds to the valve opening. The operation member 32 corresponds to an operation unit.

  The valve body 33 has a function of blocking the flow path by contacting the valve seat 42 formed in the control valve main body 43. The flow path is blocked by bringing the valve body 33 into contact with the valve seat 42 inside the valve box 45 to isolate the secondary port 44 from the valve box 45. Sealing at the time of blocking is realized by bringing an O-ring 75 partially protruding from the valve body 33 into contact with the valve seat 42 and crushing. The valve seat 42 is, for example, an annular region facing the valve element 33 in the axial direction, and is a region having a small surface roughness formed around the connection port with the secondary port 44. The O-ring 75 has an annular shape at a position facing the valve seat 42 in the axial direction.

  The piston 51 has an annular shape extending in the radial direction toward the inner peripheral surface 53 of the cylinder tube 31, and the valve opening operation chamber 36 (see FIG. 3) sealed on the inner peripheral surface 53 of the cylinder tube 31. Forming. A cylindrical member 51v having a cylindrical shape extending to the opposite side of the valve opening operation chamber 36 in the axial direction is connected to the outer peripheral end portion of the piston 51. The piston 51 is connected to a bellophram 34 that seals the valve opening operation chamber 36.

  The valve opening operation chamber 36 is formed as a donut-shaped sealed space with a variable volume surrounded by the bellophram 34, the rod cover 81, the rod 32r, and the piston 51 (bellowram retainer 52). . The inner end of the bellophram 34 is fastened by a screw 54 between the piston 51 and the bellophram retainer 52. On the other hand, the outer end 34 a of the belofram 34 is sandwiched between the cylinder tube 31 and the rod cover 81. Thereby, the space between the bellophram 34 and the rod cover 81 and the space between the bellophram 34 and the cylinder tube 31 are sealed (sealed). The valve opening operation chamber 36 is formed by partitioning an internal space formed by the inner peripheral surface 53 by the bellophram 34. Operating air can be supplied to the valve opening operation chamber 36 via the valve opening air flow path 37 and the connection flow path 87. A method for supplying the operating air will be described later. Operating air corresponds to the working fluid.

  The belofram 34 is a flexible space partition member having a top hat shape and capable of following or rolling (moving the folded portion) in a long stroke (stroke). The bellophram 34 is a bellophram that seals the gap between the outer peripheral surface 51 s (see FIG. 3) of the piston 51 and the inner peripheral surface 53 of the cylinder tube 31 while following the operation of the piston 51. The bellophram 34 is also referred to as a rolling diaphragm, and does not form a surface contact that causes friction between the operating member 32 and the valve opening operation chamber 36. Therefore, the sliding resistance is extremely small, and low hysteresis characteristics and a small pressure are provided. It has unique characteristics such as responsiveness and high sealing performance. The belofram 34 is configured to ensure a gap between the outer peripheral surface 51s and the inner peripheral surface 53 by the linear bearing 65 so that rolling can be performed smoothly. Details of the linear bearing 65 will be described later.

  Since the bellophram 34 seals the sliding portion between the inner peripheral surface 53 of the cylinder tube 31 having the largest diameter in the vacuum control valve 30 and the piston 51, the friction surface is eliminated and the operation member 32 is remarkably removed. The sliding frictional resistance can be reduced. Thereby, adjustment of the lift amount La with high responsiveness in the low hysteresis characteristic is realized by the pressure operation of the operation air supplied from the electropneumatic control valve 26 to the valve opening air flow path 37. The operating member 32 may be configured to move using an electric motor.

  On the other hand, as shown in FIG. 2, the seal between the rod 32r and the rod cover 81 is configured as follows. In the through hole 82 of the rod cover 81, a mounting recess 83 is formed at a position close to the valve box 45 side, and a mounting groove 84 is formed at a position closer to the cylinder tube 31 side than the mounting recess 83. The mounting recess 83 is equipped with a first-stage light load seal 76 and a second-stage light load seal 77 that have relatively low pressure resistance and low dynamic friction resistance. The mounting groove 84 is provided with a packing 74 having a relatively high pressure resistance. On the other hand, the rod cover 81 is formed with a leak detection port 85 communicating with the mounting recess 83 between the packing 74 and the first-stage light load seal 76 and penetrating to the outside.

  The leak detection port 85 can detect leakage in the packing 74 and leakage in the first-stage light load seal 76 and the second-stage light load seal 77. Leakage in the packing 74 can be detected as leakage of operating air. Leakage in the first-stage light load seal 76 and the second-stage light load seal 77 injects helium gas into the leak detection port 85, while the valve box 45 connected to the helium leak detector (not shown) is in a vacuum state. Can be detected.

  The piston 51 is biased by a biasing spring 55. The biasing spring 55 applies a biasing force to the piston 51 of the operating member 32 in a direction in which both the lift amount La and the volume of the valve opening operation chamber 36 are reduced. The urging spring 55 is accommodated in a space surrounded by the inner peripheral surface 53 of the cylinder tube 31 and the head cover 61 having an annular shape. One of the urging springs 55 is in contact with the piston 51 on the side opposite to the valve opening operation chamber 36 in the axial direction (back side). The other side of the urging spring 55 is in contact with the head cover 61.

  The head cover 61 includes a cylindrical portion 61b having a cylindrical shape and a sliding convex portion 61a having a cylindrical shape having a smaller diameter than the cylindrical portion 61b. The head cover 61 shares the central axis with the sliding convex portion 61a and the cylindrical portion 61b. The difference in diameter between the sliding convex portion 61a and the cylindrical portion 61b forms a stroke limiting surface 61e. The stroke restricting surface 61e is a contact surface that restricts the rising amount of the piston 51 by contacting the stroke restricting end portion 51e formed on the piston 51. As a result, the stroke of the piston 51 is restricted in the ascending direction (lift amount La increasing direction) by the stroke restricting surface 61e, while the descending direction (lift amount La decreasing direction) is restricted by the valve seat 42. .

  The sliding protrusion 61 a is accommodated in a breaking load generation chamber 39 formed inside the operation member 32. The breaking load generation chamber 39 is formed inside the valve opening operation chamber 36 with respect to a center line extending in the operation direction of the operation member 32. As a result, the breaking load generation chamber 39 is provided at a position overlapping the valve opening operation chamber 36 in the operation direction of the operation member 32. As a result, an increase in the size of the vacuum control valve 30 (particularly an increase in the operation direction of the operation member 32) due to the equipment of the breaking load generation chamber 39 can be suppressed. Furthermore, since the sliding radius of the head cover 61 can be reduced, the generation of sliding resistance due to the equipment of the blocking load generation chamber 39 can also be suppressed.

  The application of the breaking load by the breaking load generation chamber 39 can also improve the manufacturability of the vacuum control valve 30. This is because the load when the urging spring 55 is set (load when the valve is closed) at the time of manufacture can be reduced to facilitate manufacture. In other words, the biasing spring 55 is equipped with a spring coefficient that generates a requested breaking load at the time of breaking (when the lift amount La is zero) and an initial deflection amount that generates an initial load (preload) in the prior art. It is requested to do.

  As a result, both the spring coefficient and the initial deflection amount become excessive as the diameter of the vacuum control valve 30 increases, and it is difficult for the vacuum control valve 30 to be manufactured as well as to increase the size of the vacuum control valve 30. It was found by. However, in this configuration, the initial load of the urging spring 55 can be reduced by generating a blocking load between the head cover 61 and the blocking load generation chamber 39.

  The linear bearing 65 restrains the positional relationship in the radial direction (direction perpendicular to the axial direction) between the head cover 61 and the guide rod 56, and relative to the axial direction (moving direction of the operating member 32) with small friction. It is a bearing that can reciprocate. The linear bearing 65 is a space inside the inner peripheral surface of the sliding convex portion 61 a having a cylindrical shape, and is disposed outside the outer peripheral surface of the guide rod 56.

  Since the guide rod 56 is connected to the operation member 32, the linear bearing 65 can maintain (restrain) the positional relationship (gap) between the piston 51 and the inner peripheral surface 53. Thereby, the belofram 34 can move the operating member 32 with respect to the cylinder tube 31 with almost no friction by smoothly moving the folded portion.

  The guide rod 56 is equipped with a valve body position sensor 35 for measuring the operation amount of the guide rod 56 with respect to the head cover 61. An insertion pipe 35b into which the probe 35a of the valve body position sensor is inserted is connected to the guide rod 56 via an adapter 35c. The valve body position sensor 35 can generate an electrical signal corresponding to the insertion length of the probe 35a into the insertion tube 35b. Since the movement amount of the guide rod 56 relative to the head cover 61 can be set as a variation amount of the insertion length, the lift amount La can be measured according to the variation amount. For the valve body position sensor 35, for example, a linear pulse coder (registered trademark) or the like can be used.

  The head cover 61 has two cylindrical sliding surfaces that share a central axis. The first sliding surface is a sliding surface between the outer peripheral surface 61as and the inner peripheral surface 63 of the sliding convex portion 61a. The second sliding surface is a sliding surface between the inner peripheral surface 62as of the sliding convex portion 61a and the guide rod 56. The clearance (gap) between the first sliding surface and the second sliding surface is accurately maintained by the linear bearing 65.

  The linear bearing 65 is disposed between the sliding convex portion 61a and the guide rod 56 as described above, and the mutual positional relationship between the sliding convex portion 61a and the linear bearing 65 is also the same as that of the operation member 32. Maintained regardless of operation. Thereby, the precision of the clearance gap between the interruption | blocking load generation | occurrence | production chamber 39 and the sliding convex part 61a can be improved easily. On the other hand, the linear bearing 65 is maintained with respect to the packing 74 provided in the through hole 82 regardless of the operation of the operation member 32, and the piston 51 and the inner peripheral surface 53 sealed by the bellophram 34 are maintained. It is maintained nearer than the sliding surface in between. As a result, the sliding surface, which requires strict accuracy of the clearance of the sliding surface, is arranged in the vicinity of the linear bearing 65, so that both improvement in sealing performance and reduction in sliding resistance can be easily achieved. Can do.

  In the first sliding surface, a mounting groove 78 (see FIG. 2) having a concave shape is formed on the outer peripheral surface 61as on the entire outer periphery, and a V-shaped packing 70b is formed in the mounting groove 78. It is installed. In the second sliding surface, a mounting groove 79 having a concave shape is formed in the inner peripheral surface 62as over the inner periphery, and a V-shaped packing 70a is mounted in the mounting groove 79. The V-shaped packings 70a and 70b are also called V packings.

  Next, a method for operating the lift amount La of the vacuum control valve 30 will be described with reference to FIG. FIG. 4 is a cross-sectional view showing an operating state when the vacuum pressure of the vacuum control valve 30 is controlled. As described above, the vacuum control valve 30 adjusts the lift amount La, which is the distance between the valve element 33 and the valve seat 42, as the valve opening, so that the vacuum control valve 30 is located between the primary side port 41 and the secondary side port 44. The conductance can be manipulated. The lift amount La is adjusted by moving the position of the operation member 32 relative to the valve seat 42. Conductance means the ease of fluid flow in the flow path.

  The lift amount La is manipulated by a balance between the driving force to the operating member 32 and the biasing force of the biasing spring 55 that is opposite to the driving force. The driving force to the operating member 32 is generated by the action of the operating air pressure inside the valve opening operation chamber 36. In the control of the lift amount La, it is desired to reduce the frictional force resulting from the relative movement between the operation member 32 and the cylinder tube 31. This is because the frictional force is a major factor that causes hysteresis and hinders precise control.

  As shown in FIG. 2, the operating member 32 has three friction surfaces between the operating member 32 and the cylinder tube 31. The first friction surface is a friction surface between the packing 70 b mounted in the mounting groove 78 and the inner peripheral surface 63. The second friction surface is a friction surface between the packing 70 a mounted in the mounting groove 79 and the guide rod 56. The third friction surface is a friction surface between the packing 74 attached to the through hole 82 of the rod cover 81 and the outer peripheral surface of the rod 32r.

  The third friction surface has reduced sliding resistance mainly by reducing the operating pressure in the valve opening operation chamber 36. In the present embodiment, the operation pressure in the valve opening operation chamber 36 can be reduced by reducing the load when the biasing spring 55 is set (the load when the valve is closed) as described above. Further, according to the experiment by the present inventor, it was confirmed that the reduction in sliding resistance and the necessary vacuum leak characteristics can be ensured by setting the surface roughness Ra of the outer peripheral surface of the rod 32r to about 0.2. ing. Note that the third friction surface may be configured to be sealed by covering the operation member 32 with a bellows.

  FIG. 5 is an enlarged cross-sectional view showing the first friction surface, that is, the friction surface between the packing 70 mounted in the mounting groove 78 and the inner peripheral surface 63. The packing 70 is a V-shaped packing having a heel portion 71 and a pair of lip portions 72a and 72b divided into two forks. The packing 70b is configured such that the pair of lip portions 72b are directed to the breaking load generating chamber 39 and the surface pressure is increased by receiving pressure from the breaking load generating chamber 39. The second friction surface is sealed in the same manner as the first friction surface.

  In the design of the sliding portion, the design parameter is the relationship between the clearance S2 of the sliding portion, the depth S1 of the mounting groove 78 and the size difference in the width direction of the pair of lip portions 72a and 72b of the packing 70b. Become. In the present embodiment, since the airtightness of the shutoff load generation chamber 39 is required only when the valve body 33 abuts against the valve seat 42 to generate the shutoff load, the crushing amount of the packing 70b is reduced as will be described later. be able to. Thereby, the amount of friction between packing 70b and inner skin 63 can be reduced, and hysteresis can be reduced.

  Next, the sealing mechanism by the packing 70b will be described in detail with reference to FIGS. FIG. 6 is a schematic diagram for explaining the sealing principle by showing the mounting state of the packing 70b. FIG. 7 is a schematic diagram illustrating the sealing principle by showing a state when the breaking load generation chamber 39 is not pressurized. FIG. 8 is a schematic diagram illustrating the sealing principle by showing the pressure applied to the breaking load generation chamber 39. 6 and 8, the surface pressure distributions Pd1 and Pd2 of the packing 70b are shown. Since the vacuum control valve 30 pressurizes the interrupting load generation chamber 39 only at the time of disconnection, pressurization to the interrupting load generation chamber 39 is not performed in a state where the lift amount La is controlled.

  As shown in FIG. 7, the packing 70 b is mounted in the mounting groove 78 in a state in which it is elastically deformed with a crushing amount Q. At the time of non-pressurization, the contact surface pressure and the surface pressure region of the packing 70b are extremely small as indicated by the surface pressure distribution Pd1. This is because the surface pressure distribution Pd1 is a surface pressure distribution generated due to the rigidity and crushing amount Q of the pair of lip portions 72a and 72b. As a result, in a state where the vacuum control is performed by the electropneumatic control valve 26 (when the breaking load generation chamber 39 is not pressurized), there is very little dynamic friction between the breaking load generation chamber 39 and the head cover 61. Will occur.

  On the other hand, as shown in FIG. 8, the breaking load generation chamber 39 can realize sufficient sealing performance as indicated by the surface pressure distribution Pd2 when the breaking load is applied. Further, since the valve body 33 is in the shut-off state in which the shut-off load is in contact with the valve seat 42, there is no need for relative movement between the shut-off load generating chamber 39 and the head cover 61, and there is no control state. It can be seen that the occurrence does not cause any problems. Further, the present inventor has also found that the surface pressure distribution Pd1 can be reduced because leakage during sliding is allowable. Thereby, even if the breaking load generating chamber 39 and the sliding protrusion 61a are provided in order to provide the breaking load generation function, it is possible to realize a design in which the sliding does not newly cause hysteresis. It was found.

  Next, the vacuum control system 20 using the vacuum control valve 30 will be described with reference to FIGS.

  FIG. 9 is a schematic diagram illustrating a configuration of the vacuum control system 20 of the embodiment. The vacuum control system 20 is connected in series to a vacuum vessel 90 for performing an etching process, a vacuum control valve 30, a controller 21, a pneumatic circuit 22, a turbo molecular pump 300, and a turbo molecular pump 300. A dry pump for evacuation. While the reactive gas G is supplied to the vacuum vessel 90 at a constant supply amount, it is exhausted by the turbo molecular pump 300 through the vacuum control valve 30. The vacuum pressure in the vacuum vessel 90 is controlled by manipulating the conductance of the vacuum control valve 30. The turbo molecular pump 300 corresponds to a vacuum pump.

  The vacuum container 90 includes a reactive gas supply hole 91 to which a reactive gas G is supplied, an exhaust hole 93, and a vacuum pressure sensor 92. A certain amount of reactive gas G measured by a mass flow sensor (not shown) is supplied to the reactive gas supply hole 91. The primary port 41 of the vacuum control valve 30 is connected to the exhaust hole 93. The vacuum pressure sensor 92 measures the vacuum pressure inside the vacuum vessel 90 and transmits an electrical signal to the controller 21. The vacuum pressure is used for operation of the vacuum control valve 30 by the controller 21.

  The internal pressure of the valve opening operation chamber 36 is operated by supplying or exhausting operating air from the pneumatic circuit 22 via the valve opening air flow path 37. The pneumatic circuit 22 is connected to a high-pressure side working fluid supply unit 95 for supplying operation air and a low-pressure side working fluid exhaust unit 96 for exhausting operation air.

  The shut-off load is a load that moves the valve body 33 to the valve seat 42 by operating air supplied from the pneumatic circuit 22 to the shut-off air flow path 38 and presses the valve body 33 against the valve seat 42 after the movement. Function. The blocking load acts as a resultant force with the urging load by the urging spring 55.

  In this embodiment, the blocking load is applied when the controller 21 receives a vacuum pump stop signal from the turbo molecular pump 300 and urgently stops the vacuum control system 20, for example. Below, the operation | movement content in each operation mode including an emergency stop is demonstrated. The controller 21 corresponds to a control unit. The vacuum pump stop signal is a signal that is transmitted, for example, when the vacuum pump stop signal is stopped or when the rotational speed of the turbo molecular pump 300 is abnormally reduced.

  Next, the operation contents of the pneumatic circuit 22 and the vacuum control valve 30 will be described with reference to FIG. FIG. 10 is a schematic diagram showing the configuration and operation contents of the pneumatic circuit 22 of the embodiment. The pneumatic circuit 22 is a circuit that supplies operation air in accordance with a command from the controller 21 and operates the vacuum control valve 30 by this. The pneumatic circuit 22 includes an electropneumatic control valve 26 and three electromagnetic valves SV1, SV2, and SV3. The electropneumatic control valve 26 has an air supply valve 26a connected to the high pressure side of the operating air, and an exhaust valve 26b connected to the exhaust side of the operating air.

  In this embodiment, the controller 21 is configured as a programmable logic controller (PLC) including two PID control circuits 24a and 24b. The programmable logic controller 21 is a logic circuit that can realize highly reliable control using, for example, ladder logic. The two PID control circuits 24a and 24b are used for feedback control of the vacuum pressure of the vacuum vessel 90, details of which will be described later. The controller 21 transmits to the pneumatic circuit 22 an on / off command to each of the three electromagnetic valves SV1, SV2, and SV3 and a pulse width modulation signal to the electropneumatic control valve 26. The solenoid valve SV2 and the solenoid valve SV3 are also called a first solenoid valve and a second solenoid valve, respectively.

  The electropneumatic control valve 26 operates, for example, a valve opening air passage for compressed air supplied from the outside by operating the valve opening time (duty) of the air supply valve 26a and the exhaust valve 26b by a known pulse width modulation method. The supply pressure to 37 can be manipulated. The electropneumatic control valve 26 increases air pressure acting on the operation member 32 in the valve opening operation chamber 36 by increasing the valve opening time (duty) of the air supply valve 26a and decreasing the valve opening time of the exhaust valve 26b. Can be high. Thereby, the lift amount La of the valve body 33 can be increased.

  On the other hand, the electropneumatic control valve 26 reduces the valve opening time (duty) of the air supply valve 26a and increases the valve opening time of the exhaust valve 26b, thereby acting on the operating member 32 in the valve opening operation chamber 36. The pressure can be lowered, whereby the lift amount La of the valve element 33 can be reduced by the load from the biasing spring 55.

  The electromagnetic valve SV1 is an electromagnetic valve that switches the flow path connected to the electromagnetic valve SV2 to either the electropneumatic control valve 26 or the working fluid supply unit 95, and is connected to the electropneumatic control valve 26 when not energized. . The electromagnetic valve SV2 is an electromagnetic valve that switches the flow path connected to the valve opening air flow path 37 to either the electromagnetic valve SV1 or the working fluid exhaust part 96. Connected. The electromagnetic valve SV3 is an electromagnetic valve that switches the flow path connected to the shut-off air flow path 38 to either the working fluid supply section 95 or the working fluid exhaust section 96, and the working fluid supply section 95 is not energized. Connected to.

  Next, the contents of each operation mode of the pneumatic circuit 22 will be described with reference to Table T. Table T is a table showing energization states of the three solenoid valves SV1, SV2, and SV3 in each operation mode. In Table T, ON and OFF are indicated by “ON” and “OFF”, respectively.

  In the operation mode at the time of emergency stop of the vacuum control system 20, the electropneumatic control valve 26 and the three electromagnetic valves SV1, SV2, SV3 are all turned off. The emergency stop is an operation mode as a worst case defined in the system design of the vacuum control system 20, and is an operation mode when the controller 21 receives a vacuum pump stop signal from a dry pump (not shown), for example. The dry pump is a pump that is connected in series to the turbo molecular pump 300 and used for evacuation. In this operation mode, all of the atmospheric pressure is applied as a differential pressure between the secondary side port 44 in the atmosphere open state and the primary side port 41 of the vacuum side. This differential pressure load is applied to the valve body 33 in a direction to increase the lift amount La, and the valve body 33 is moved away from the valve seat 42 and acts in a direction to allow the air to flow back to the vacuum vessel 90. In the emergency stop according to the present embodiment, backflow can be prevented against the above-described differential pressure by the blocking load.

  Thus, the high-pressure side working fluid supply unit 95 is connected to the shut-off air flow path 38, and the exhaust-side working fluid exhaust part 96 is connected to the valve opening air flow path 37. As a result, the air pressure in the breaking load generating chamber 39 to which the breaking load is applied increases, and the interior of the valve opening operation chamber 36 to which the load on the valve opening side (lift amount La increases) is lowered to the atmospheric pressure. . As a result, the valve element 33 connected to the operation member 32 moves rapidly in the direction of the valve seat 42, and the vacuum control valve 30 is closed (blocked) and the application of the blocking load is continued.

  Note that the solenoid valve SV3 may be configured such that a flow path connected to the shut-off air flow path 38 is connected to the working fluid exhaust section 96 when not energized. However, as described above, the power supply to the pneumatic circuit 22 is stopped at the time of a power failure if it is configured to be connected to the working fluid supply unit 95 at the time of non-energization. Thus, it can be set as the operation mode of the operation content same as the time of an emergency stop.

  As described above, in a power failure or emergency stop of the vacuum control system 20, the vacuum control valve 30 can be closed and a blocking load can be applied in any operation mode. As a result, in the vacuum control system 20 of the present embodiment, when the power supply to the pneumatic circuit 22 is stopped, the valve element 33 is moved by the urging force of the urging spring 55 and the pressurization of the breaking load generating chamber 39. The air circuit is configured to move to the valve seat 42 and apply a blocking load.

  In such a configuration, it is ensured that the shut-off state is always ensured even when the power is turned off or during a power failure, and thus there is an advantage that a system design that takes safety into consideration in an emergency stop or power failure can be realized easily. is there. Furthermore, in the present embodiment, the controller 21 enters the emergency stop operation mode in response to the reception of the vacuum pump stop signal, so that the pressure of the secondary side port 44 temporarily increases due to the unexpected stop of the turbo molecular pump 300. However, it also has an advantage that a shut-off state can be secured.

  Next, in the operation mode in which the vacuum control valve 30 is closed, the two solenoid valves SV1, SV2, SV3 are turned on, while the solenoid valve SV3 is turned off. In this operation mode, the vacuum control valve 30 is closed when the turbo molecular pump 300 is operating normally. In this operation mode, the biasing spring 55 is set so as to apply a load to the extent that the O-ring 75 is crushed with an appropriate crushing amount in order to close the vacuum control valve 30 in a normal operation state. Thereby, the durability of the O-ring 75 can be enhanced.

  Thus, since this embodiment is provided with the mechanism which generates the interception load for responding to an emergency, the urging force of the urging spring 55 to such an extent that the O-ring 75 is crushed with a crushed amount suitable for normal operation. It is also possible to provide a degree of design freedom that can be set.

  On the other hand, in the operation mode in which the vacuum control valve 30 is opened, all the three solenoid valves SV1, SV2, SV3 are turned on. As a result, the working fluid supply unit 95 on the high pressure side is connected to the valve opening air passage 37 via the two electromagnetic valves SV1 and SV2 in the on state. On the other hand, the exhaust-side working fluid exhaust part 96 is connected to the shut-off air flow path 38 via the electromagnetic valve SV3 in the on state. On the other hand, the electropneumatic control valve 26 is in a state where the flow path is separated from the valve opening air flow path 37 by the electromagnetic valve SV1 in the on state. Thereby, regardless of the operating state of the electropneumatic control valve 26, the vacuum control valve 30 can be rapidly opened (the lift amount La is maximum).

  Finally, in the operation mode in which the vacuum pressure is controlled by the vacuum control valve 30, the electromagnetic valve SV1 is turned off, while the two electromagnetic valves SV2 and SV3 are both turned on. Thereby, the working fluid supply unit 95 on the high pressure side is connected to the valve opening air passage 37 through the electropneumatic control valve 26, the off-state electromagnetic valve SV1, and the on-state electromagnetic valve SV2 in order. Is done. On the other hand, the working fluid exhaust part 96 on the exhaust side passes through the electromagnetic valve SV3 in the on state, and the flow path is connected to the shut-off air flow path 38. Thereby, the electropneumatic control valve 26 can adjust the lift amount La by supplying the operation air from the valve opening air flow path 37 to operate the internal pressure of the valve opening operation chamber 36.

  Next, the control content of the vacuum control system 20 will be described with reference to FIG. FIG. 11 is a control block diagram of the vacuum control system 20 of the embodiment. This control system is configured as a cascade control of a double loop structure having a slave loop SL that controls the lift amount La of the valve element 33 of the vacuum control valve 30 and a master loop ML that controls the internal pressure of the vacuum vessel 90. ing. Each control loop of slave loop SL and master loop ML can be configured as, for example, a well-known PID control system.

  The slave loop SL is a control loop for operating the internal pressure of the valve opening operation chamber 36 by the electropneumatic control valve 26 to bring the lift amount La of the valve element 33 close to the valve opening command value Vp. . In the slave loop SL, the PID control circuit 24b generates a control signal according to the deviation δm between the valve opening command value Vp (target value) and the lift amount La (measured value), and sends the pulse width modulation signal to the electropneumatic control valve. 26. The electropneumatic control valve 26 operates the internal pressure of the valve opening operation chamber 36 in accordance with the pulse width modulation signal to adjust the driving force to the operating member 32 to which the valve element 33 is attached.

  The lift amount La is measured by the valve body position sensor 35 and used as a feedback amount by the PID control circuit 24b. Thereby, the vacuum control valve 30 can feedback-control the lift amount La. Thereby, the conductance of the flow path between the vacuum vessel 90 and the turbo molecular pump 300 can be adjusted.

  In the master loop ML, the PID control circuit 24a determines the valve opening command value Vp according to a preset deviation δp between the target pressure value Pt and the measured pressure value Pm, and transmits it to the PID control circuit 24b. The measured pressure value Pm is the pressure inside the vacuum container 90 measured by the vacuum pressure sensor 92. The PID control circuit 24a adjusts the valve opening command value Vp so that the measured pressure value Pm approaches the target pressure value Pt.

  Note that the feedback loop of the lift amount La may be deleted, and simple single loop control in which the internal pressure of the valve opening operation chamber 36 is operated so that the deviation δp approaches zero may be configured. However, if a double loop configuration is used to feed back the lift amount La, it is possible to suppress a decrease in accuracy due to nonlinearity between the command value (control input) from the master loop ML and the lift amount (opening). This decrease in accuracy occurs when the opening ranges of the vacuum control valves are mutually shifted by the offset value. This configuration is configured such that the characteristics of the vacuum control valve are flat in any opening range by ensuring the linearity of the opening and the control input by actually measuring the opening.

  The vacuum control system 20 further has an open loop AL that applies a blocking load to the valve body 33 via the operation member 32. The programmable logic controller 21 generates a breaking load by applying air pressure to the breaking load generating chamber 39 (see FIG. 2) by turning off the two electromagnetic valves SV2 and SV3. The magnitude of the breaking load can be set in advance by appropriately setting the inner diameter of the breaking load generating chamber 39 and the outer shape of the head cover 61 regardless of whether the electromagnetic valve SV1 is on or off.

  The embodiment described above has the following advantages.

  In the vacuum control valve 30 of the present embodiment, since the space between the inner peripheral surface of the main cylinder having the largest diameter and the outer peripheral surface of the main piston is sealed by the bellophram, the sliding resistance is reduced and the hysteresis is alleviated. be able to.

  Furthermore, in the vacuum control valve 30 of the present embodiment, since the interrupting load generation chamber 39 that generates an interrupting load by supplying the working fluid is formed in the operating portion, the interrupting load is effectively utilized by utilizing the space occupied by the operation member 32. A generation chamber 39 can be equipped. Furthermore, by forming the breaking load generation chamber inside the operating portion, it is possible to provide a degree of freedom in design in the direction of reducing the diameter of the breaking load generation chamber 39. As a result, an increase in the size of the vacuum control valve caused by the equipment of the breaking load generation chamber 39 is suppressed, and the sliding area of the breaking load generation chamber 39 is reduced to reduce the hysteresis caused by the friction of the breaking load generation chamber 39. Can be made.

  In the vacuum control system 20 of the present embodiment, the air circuit is configured so that the valve element 33 immediately moves to the valve seat 42 and the cutoff load is applied in a state where the power supply to all the solenoid valves is stopped. Has been. This makes it possible to easily realize a system design that considers ensuring safety during an emergency stop or power failure.

(Other embodiments)
The present invention is not limited to the above embodiment, and may be implemented as follows, for example.

  (1) In the above embodiment, the gap between the breaking load generating chamber 39 and the head cover 61 is sealed with packing, but the gap between the breaking load generating chamber 39 and the head cover 61 is sealed with bellowram. May be. However, if the space between the breaking load generation chamber 39 and the head cover 61 is sealed with packing, the configuration of the vacuum control valve can be simplified and the size can be reduced.

  (2) In the above embodiment, a V-shaped packing is used for the sealing surface that seals between the breaking load generation chamber 39 and the head cover 61, but an O-ring may be used, for example. This is because the O-ring also has a property that the contact surface pressure increases in accordance with the supply of the working fluid to the breaking load generation chamber 39. For sealing between the breaking load generation chamber 39 and the head cover 61, generally, if a sealing portion whose surface pressure is increased according to the supply of the working fluid to the breaking load generation chamber 39 is vacuumed. Hysteresis of the control valve can be reduced. However, if a V-shaped packing is used, the dynamic friction force at the time of non-pressurization can be reduced.

  (3) In the above embodiment, the breaking load generating chamber 39 is formed inside the operation member 32 and the head cover 61 is arranged inside the biasing spring. However, the breaking load generating chamber 39 and the head cover 61 are reversed. It is good also as arrangement. However, if the breaking load generation chamber 39 is formed inside the operation member 32 head cover 61, the breaking load generation chamber 39 can be formed using the internal space of the operation member 32. Miniaturization can be achieved.

  (4) In the above embodiment, the present invention has been described by exemplifying a vacuum control system for a semiconductor manufacturing apparatus (for etching or CVD apparatus). However, the present invention is not limited to this, and a liquid crystal manufacturing apparatus, a vacuum drying furnace, The present invention can be used for controlling the vacuum pressure in a vacuum vessel used in various vacuum devices such as a binding device.

  (5) In the above embodiment, the vacuum control valve is connected with the primary side port (vacuum vessel side connection port) as the low pressure side and the secondary side port (vacuum pump side connection port) as the high pressure side to counter the differential pressure load. It is comprised as a form which maintains the interruption | blocking state with the interruption | blocking load to perform. However, the high pressure side and the low pressure side may be reversed. If it carries out like this, it can open to oppose the differential pressure load of the direction which maintains the interruption | blocking state. Furthermore, it can be used not only for vacuum vessels but also for pressure control of high-pressure vessels.

  DESCRIPTION OF SYMBOLS 20 ... Vacuum control system, 21 ... Controller, 22 ... Pneumatic circuit, 24 ... PID control circuit, 26 ... Electropneumatic control valve, 30 ... Vacuum control valve, 31 ... Cylinder, 32 ... Operating member, 33 ... Valve body, 34 ... Bellofram, 35 ... valve body position sensor, 55 ... biasing spring, 56 ... guide member, 92 ... vacuum pressure sensor, 300 ... turbo molecular pump.

Claims (7)

A vacuum control valve connected between a vacuum vessel and a vacuum pump, and controlling a vacuum pressure in the vacuum vessel by operating a valve opening by a working fluid;
A control valve body having a flow path connecting the vacuum vessel and the vacuum pump, and a valve seat formed in the flow path;
A valve body for operating the valve opening by adjusting a lift amount, which is a distance to the valve seat, and blocking the flow path by contact with the valve seat; a piston; the valve body and the piston A rod that couples to
A cylinder connected to the control valve body and containing the piston;
A biasing portion that biases the operating portion in a direction in which the lift amount decreases;
Bellofram that seals the gap between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder while following the operation of the piston;
With
The operating part and the cylinder are
A valve opening that is sealed by the bellophram and has a cylindrical shape surrounding the rod, and generates a load in the direction of increasing the lift amount with respect to the piston in accordance with the working pressure of the working fluid. An operation room,
A shut-off load generation chamber that shares a central axis with the valve opening operation chamber and generates a load in a direction to reduce the lift amount with respect to the operating portion according to the supply of the working fluid,
Forming a vacuum control valve. The cylinder includes a head cover having a sliding protrusion accommodated in the breaking load generation chamber,
The vacuum control valve has a sealing surface that seals between the blocking load generation chamber and the sliding protrusion, and the sealing surface according to the supply of the working fluid to the blocking load generation chamber The vacuum control valve according to claim 1, further comprising a sealing portion that increases a surface pressure of the vacuum. The sliding convex portion shares a central axis with the valve opening operation chamber, and has a cylindrical shape with an outer diameter smaller than the inner diameter of the valve opening operation chamber,
The operating portion has a guide portion extending in the direction of the operation in a space surrounded by an inner peripheral surface of the sliding convex portion,
The vacuum control valve is disposed between the guide portion and the sliding convex portion, enables sliding in the direction of the operation, and is perpendicular to the direction of the operation of the guide portion and the sliding convex portion. The vacuum control valve according to claim 2, further comprising a bearing that mutually restrains the positional relationship of directions.   The vacuum control valve according to any one of claims 1 to 3, wherein the breaking load generation chamber is formed inside the rod. A vacuum control valve according to any one of claims 1 to 4,
A pressure sensor for measuring a vacuum pressure in the vacuum vessel;
A pneumatic circuit connected to a working fluid supply unit for supplying the working fluid and a working fluid exhaust unit for exhausting the working fluid, and supplying the working fluid to the vacuum control valve;
A controller that controls a vacuum pressure in the vacuum vessel by operating a working fluid supplied from the pneumatic circuit to the vacuum control valve;
With a vacuum control system.   The control unit connects a flow path between the valve opening operation chamber and the working fluid exhaust unit in response to reception of a vacuum pump stop signal including information indicating the stop of the vacuum pump, and the interrupting load The vacuum control system according to claim 5, wherein a flow path between the generation chamber and the working fluid supply unit is connected.   The pneumatic circuit includes a first electromagnetic valve that connects a flow path between the valve opening operation chamber and the working fluid exhaust part in a non-energized state, and the shut-off load generation chamber and the working fluid in a non-energized state. The vacuum control system according to claim 5, further comprising a second electromagnetic valve that connects a flow path to the supply unit.

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