Foreign matter deposition amount estimation device and vacuum pump

Abstract

] Provided is a foreign matter deposition amount estimation device capable of estimating a deposition amount of foreign matter. A foreign matter deposition amount estimation device 210 used in a turbo molecular pump 100 including an inlet port and an outlet port includes: an exhaust member 212 connectable to the outlet port 133; a conductor member 214 which is disposed at an inner side of the exhaust member 212, at least a part of the conductor being provided with a gap t with respect to an inner peripheral surface 213 of the exhaust member 212, and to which a voltage for detecting electrostatic capacitance is applied between the conductor member and the exhaust member 212; a measurement device 216 that measures electrostatic capacitance between the exhaust member 212 and the conductor member 214; and an arithmetic device 218 that estimates from a change in electrostatic capacitance a deposition amount of foreign matter inside the turbo molecular pump 100.

Description

FOREIGN MATTER DEPOSITION AMOUNT ESTIMATION DEVICE AND VACUUM PUMP[Technical Field]

[0001] The present invention relates to, for example, a foreign matter deposition amount estimation device that can be used for a vacuum pump, and a vacuum pump including the foreign matter deposition amount estimation device.[Background Art]

[0002] In general, a turbo molecular pump is known as a kind of vacuum ump. This turbo molecular pump is used, for example, for exhaust in a device for manufacturing such as a semiconductor or a flat panel. In the turbo molecular pump, a rotor blade is rotated by energization to a motor in a pump main body, and gaseous molecules (gas molecules) of gas (process gas) sucked into the pump main body are flicked off to discharge the gas. In addition, such a turbo molecular pump may be a pump of a type provided with a heater and a cooling pipe in order to appropriately manage the temperature in the ump.

[0003] In a vacuum pump used for exhaust of a device for a semiconductor, a flat panel, or the like, a reaction product (foreign matter) generated in the manufacturing process of the semiconductor or the flat panel may be deposited in the vacuum pump. When a large amount of foreign matter is deposited, the flow of gas in the vacuum pump may be disturbed by the foreign matter, or the foreign matter may collide with the rotating portion. For this reason, a technigue of detecting a deposition amount of the foreign matter on the basis of a change in electrostatic capacitance has been devised so that a timing related to maintenance in a vacuum pump can be determined in advance.

[0004] In the invention disclosed in PTL 1 (paragraphs 0035 to 0039, Fig. 2, etc. ) described later, a change in electrostatic capacitance due to deposits deposited between parallel plate electrodes is measured. In the invention disclosed in PTL 2 (paragraphs 0073 and 0074, Fig. 7, etc. ) , a change in electrostatic capacitance due to deposits on the surface of the comb-shaped electrode is measured.[Citation List][Patent Literature]

[0005] [PTL 1] Japanese Patent Application Publication No. 2018-159632 [PTL 2] Japanese Patent Application Publication No. 2021-195893 [Summary of Invention] [Technical Problem]

[0006] The invention disclosed in PTL 1 has the following problems.(1) Since there is no sufficient installation space, only a small sensor can be installed, and sufficient detection sensitivity cannot be obtained .(2) The sensor blocks the gas flow path, which adversely affects the exhaust performance.(3) It is not easy to extract a sensor signal from the inside of the pump to the outside.

[0007] On the other hand, in the invention disclosed in PTL 2, since the thickness of the sensor is small and the sensor can be installed on the surface of the gas flow path, the gas flow path is not blocked as in the invention disclosed in PTL 1. However, although detection is possible in a situation where the thickness of the deposit is small (thin) , there is a problem in that the sensitivity decreases and detection becomes difficult as the thickness increases.

[0008] An object of the present invention is to provide a foreign matter deposition amount estimation device and a vacuum pump capable of estimating a deposition amount of foreign matter.[Solution to Problem]

[0009] In order to achieve the above object, a foreign matter deposition amount estimation device according to the present invention is used in a vacuum pump including an inlet port and an outlet port, the foreign matter deposition amount estimation device including: an exhaust member connectable to the outlet port; a conductor disposed inside the exhaust member, at least a part of the conductor having a predetermined distance from an inner surface of the exhaust member, and to which a voltage for detecting electrostatic capacitance is applied between the conductor and the exhaust member; a measurement device that measures the electrostatic capacitance between the exhaust member and the conductor; and an arithmetic device that estimates a deposition amount of foreign matter inside the vacuum pump from a change in the electrostatic capacitance .The vacuum pump according to the present invention includes the foreign matter deposition amount estimation device. [Advantageous Effects of Invention]

[0010] According to the above invention, it is possible to provide a foreign matter deposition amount estimation device and a vacuum pump capable of estimating the deposition amount of foreign matter. [Brief Description of Drawings]

[0011] [Fig. 1] Fig. 1 is an explanatory diagram schematically illustrating a configuration of a foreign matter deposition amount estimation device and a turbo molecular pump according to a first embodiment of the present invention . [Fig. 2] Fig. 2 is a circuit diagram of an amplifier circuit. [Fig. 3] Fig. 3 is a time chart illustrating control in a case where a current command value is larger than a detection value. [Fig. 4] Fig. 4 is a time chart illustrating control in a case where a current command value is smaller than a detection value. [Fig. 5] Fig. 5 is an enlarged explanatory diagram illustrating the foreign matter deposition amount estimation device according to the first embodiment. [Fig. 6] Fig. 6 is an explanatory diagram illustrating a foreign matter deposition amount estimation device according to a modification in which temperature control is performed. [Fig. 7] Fig. 7 is a perspective view illustrating a foreign matter deposition amount estimation device according to a modification in which one communication port of a conductor member is provided. [ Fig . 8 ] Fig. 8 is a cross-sectional view illustrating a foreign matter deposition amount estimation device according to a modification in which one communication port of a conductor member is provided. [Fig. 9]Fig. 9 is an explanatory diagram schematically illustrating a configuration of a foreign matter deposition device and a turbo molecular pump according to a second embodiment of the present invention. [ Fig . 10] Fig. 10 is an enlarged explanatory diagram illustrating the foreign matter deposition amount estimation device according to the second embodiment . [Description of Embodiments]

[0012] <Outline of First Embodiment>Fig. 1 illustrates a vacuum pump (here, a turbo molecular pump 100) according to a first embodiment of the present invention and a foreign matter deposition amount estimation device 210 attached to the turbo molecular pump 100. The turbo molecular pump 100 is connected to, for example, a vacuum chamber (not illustrated) of a target device such as a semiconductor manufacturing device.

[0013] Here, the turbo molecular pump 100 and the foreign matter deposition amount estimation device 210 can be combined and regarded as, for example, a vacuum exhaust system. In the following description, the turbo molecular pump 100 and the foreign matter deposition amount estimation device 210 will be described as separate devices, but the present invention is not limited thereto, and for example, the foreign matter deposition amount estimation device 210 can be regarded as a part of the turbo molecular pump 100.

[0014] The red portions are considered to be modified. <<Turbo Molecular Pump 100»A longitudinal sectional view of the turbo molecular pump 100 is illustrated in Fig. 1. In Fig. 1, in the turbo molecular pump 100, an inlet port 101 is formed at an upper end of a cylindrical outer cylinder 127. Inside the outer cylinder 127, a rotating body 103 in which a plurality of rotor blades 102 (102a, 102b, 102c, ... ) , which are turbine blades for sucking and exhausting gas, are radially formed in multiple stages in a peripheral portion is provided. A rotor shaft 113 is attached to the center of the rotating body 103, and the rotor shaft 113 is floated in the air, supported, and positionally controlled by, for example, a five-axis control magnetic bearing.

[0015] In an upper radial electromagnet 104, four electromagnets are arranged in pairs on the X axis and the Y axis. Four upper radial sensors107 are provided in proximity to the upper radial electromagnet 104 and corresponding to the upper radial electromagnets 104, respectively. As the upper radial sensor 107, for example, an inductance sensor having a conductive winding, an eddy current sensor, or the like is used, and the position of the rotor shaft 113 is detected on the basis of a change in inductance of the conductive winding that changes according to the position of the rotor shaft 113. This upper radial sensor 107 is configured to detect the radial displacement of the rotor shaft 113, i.e. the rotating body 103 fixed thereto, and to send it to a control device 200.

[0016] In the control device 200, for example, a compensation circuit having a PID adjustment function generates an excitation control command signal of the upper radial electromagnet 104 on the basis of a position signal detected by the upper radial sensor 107, and an amplifier circuit 150 (described later) illustrated in Fig. 2 performs excitation control of the upper radial electromagnet 104 on the basis of the excitation control command signal, whereby the upper radial position of the rotor shaft 113 is adjusted.

[0017] The rotor shaft 113 is formed of a high-permeability material (Iron, stainless steel, etc. ) or the like, and is attracted by the magnetic force of the upper radial electromagnet 104. Such adjustment is performed independently in the X axis direction and the Y axis direction. A lower radial electromagnet 105 and a lower radial sensor 108 are disposed similarly to the upper radial electromagnet 104 and the upper radial sensor 107, and the lower radial position of the rotor shaft 113 is adjusted similarly to the upper radial position.

[0018] Further, axial electromagnets 106A and 106B are arranged with a disc-shaped metal disc (also referred to as an "armature disc") 111 provided in the lower part of the rotor shaft 113 interposed therebetween in a vertical direction. The metal disc 111 is made of a high- permeability material such as iron. An axial sensor 109 is provided to detect the axial displacement of the rotor shaft 113, and its axial position signal is configured to be sent to the control device 200.

[0019] Then, in the control device 200, for example, a compensation circuit having a PID adjustment function generates an excitation control command signal of each of the axial electromagnet 106A and the axial electromagnet 106B on the basis of the axial position signal detected bythe axial sensor 109, and the amplifier circuit 150 performs excitation control on each of the axial electromagnet 106A and the axial electromagnet 106B on the basis of these excitation control command signals, so that the axial electromagnet 106A attracts the metal disc 111 upward by magnetic force, the axial electromagnet 106B attracts the metal disc 111 downward, and the axial position of the rotor shaft 113 is adj usted .

[0020] In this manner, the control device 200 appropriately adjusts the magnetic force exerted by the axial electromagnets 106A and 106B on the metal disc 111, magnetically floats the rotor shaft 113 in the axial direction, and holds the rotor shaft in the space in a non-contact manner. The amplifier circuit 150 that performs excitation control on the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B will be described later.

[0021] On the other hand, a motor 121 includes a plurality of magnetic poles arranged circumferentially so as to surround the rotor shaft 113. Each magnetic pole is controlled by the control device 200 to rotationally drive the rotor shaft 113 via an electromagnetic force acting between the magnetic pole and the rotor shaft 113. A rotational speed sensor (not illustrated) such as a Hall element, a resolver, or an encoder is incorporated in the motor 121, and the rotational speed of the rotor shaft 113 is detected by a detection signal of the rotational speed sensor .

[0022] Further, for example, a phase sensor (not illustrated) is attached in the vicinity of the lower radial sensor 108 to detect the phase of rotation of the rotor shaft 113. The control device 200 detects the position of the magnetic pole by using both the detection signals of the phase sensor and the rotational speed sensor.

[0023] A plurality of stator blades 123 (123a, 123b, 123c, ... ) is disposed with a slight gap (predetermined interval) from the rotor blades 102 (102a, 102b, 102c, ... ) . The rotor blades 102 (102a, 102b, 102c, ... ) are each formed to be inclined by a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transfer molecules of the exhaust gas downward by collision.

[0024] Similarly, the stator blades 123 are formed to be inclined by a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are alternately arranged with the steps of the rotorblades 102 toward the inside of the outer cylinder 127. The outer peripheral end of the stator blade 123 is supported in a state of being fitted between a plurality of stacked stator blade spacers 125 (125a, 125b, 125c, . . . ) .

[0025] The stator blade spacer 125 is a ring-shaped member, and is made of, for example, a metal such as aluminum, iron, stainless steel, or copper, or a metal such as an alloy containing these metals as a component. The outer cylinder 127 is fixed to the outer periphery of the stator blade spacer 125 with a slight gap. A base portion 129 is disposed at a bottom portion of the outer cylinder 127. An outlet port 133 is formed in the base portion 129 and communicates with the outside. The exhaust gas having entered the inlet port 101 from the chamber (vacuum chamber) side and transferred to the base portion 129 is sent to the outlet port 133.

[0026] Furthermore, depending on the application of the turbo molecular pump 100, a screw stator 131 is disposed inside the base portion 129. The screw stator 131 is a cylindrical member made of metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals as a component, and a plurality of spiral thread grooves 131a are engraved on an inner peripheral surface thereof. The direction of the spiral of the thread groove 131a is a direction in which molecules of the exhaust gas are transferred toward the outlet port 133 when the molecules move in the rotation direction of the rotating body 103. A rotating body lower cylindrical portion 103b is suspended from a lower portion of a rotor main body 103a in which the rotor blades 102 (102a, 102b, 102c, ... ) of the rotating body 103 are formed. The outer peripheral surface of the rotating body lower cylindrical portion 103b has a cylindrical shape and protrudes toward the inner peripheral surface of the screw stator 131, and is close to the inner peripheral surface of the screw stator 131 with a predetermined gap. The exhaust gas transferred to the thread groove 131a by the rotor blade 102 and the stator blade 123 is guided by the thread groove 131a and sent to the base portion 129. In this manner, the screw stator 131 and the rotating body lower cylindrical portion 103b facing the screw stator constitute a Holweck exhaust mechanism portion 204. The Holweck exhaust mechanism portion 204 imparts directionality to the exhaust gas by the rotation of the rotating body lower cylindrical portion 103b with respect to the screw stator 131, andimproves the exhaust characteristics of the turbo molecular pump 100.

[0027] The base portion 129 is a disc-shaped member constituting a base portion of the turbo molecular pump 100, and is generally made of metal such as iron, aluminum, or stainless steel. Since the base portion 129 physically holds the turbo molecular pump 100 and also has a function of a heat conduction path, it is desirable to use a rigid metal having high thermal conductivity such as iron, aluminum, or copper.

[0028] In the configuration of the turbo molecular pump 100, when the rotor blades 102 are rotationally driven together with the rotor shaft 113 by the motor 121, the exhaust gas is sucked from the chamber through the inlet port 101 by the action of the rotor blades 102 and the stator blades 123. The exhaust gas sucked from the inlet port 101 passes between the rotor blades 102 and the stator blades 123 and is transferred to the base portion 129. At this time, the temperature of the rotor blade 102 increases due to frictional heat generated when the exhaust gas comes into contact with the rotor blade 102, conduction of heat generated by the motor 121, and the like, but this heat is transmitted to the stator blade 123 side by radiation, conduction by gas molecules (gas molecules) of the exhaust gas, or the like.

[0029] The stator blade spacers 125 are joined to each other at the outer peripheral portion, and transmit heat received by the stator blades 123 from the rotor blades 102, frictional heat generated when the exhaust gas comes into contact with the stator blades 123, and the like to the outside .

[0030] In the above description, the screw stator 131 is disposed on the outer periphery of the rotating body lower cylindrical portion 103b of the rotating body 103, and the thread groove 131a is engraved on the inner peripheral surface of the screw stator 131. However, conversely, a thread groove may be engraved on the outer peripheral surface of the rotating body lower cylindrical portion 103b, and a spacer having a cylindrical inner peripheral surface may be disposed around the thread groove .

[0031] In addition, depending on the application of the turbo molecular pump 100, the periphery of the electric unit is covered with a stator column 122 so that the gas sucked from the inlet port 101 does not enter the electric unit including the upper radial electromagnet 104, the upper radial sensor 107, the motor 121, the lower radial electromagnet105, the lower radial sensor 108, the axial electromagnets 106A and 106B, the axial sensor 109, and the like, and the inside of the stator column 122 may be kept at a predetermined pressure by the purge gas .

[0032] In this case, a purge gas port (not illustrated) is disposed in the base portion 129, and the purge gas is introduced through the pipe. The introduced purge gas is delivered to the outlet port 133 through a gap between a protection bearing 120 and the rotor shaft 113, between the rotor and the stator of the motor 121, and between the cylindrical portion on the inner circumferential side (rotating body lower cylindrical portion 103b) of the rotor blade 102 and the stator column 122 and the base portion 129.

[0033] Here, the turbo molecular pump 100 requires identification of a model and control on the basis of individual adjusted unique parameter (for example, various characteristics corresponding to the model) . In order to store this control parameter, the turbo molecular pump 100 includes an electronic circuit unit 141 in its main body. The electronic circuit unit 141 includes a semiconductor memory such as an EEP-ROM, electronic components such as a semiconductor element for accessing the semiconductor memory, a substrate 143 for mounting the semiconductor memory, and the like. The electronic circuit unit 141 is accommodated in a lower portion of a rotational speed sensor (not illustrated) , for example, in the vicinity of the center of the base portion 129 constituting the lower portion of the turbo molecular pump 100, and is closed by an airtight bottom lid 145.

[0034] Incidentally, in the process of manufacturing a semiconductor, some process gases introduced into the chamber have a property of becoming solid when the pressure thereof becomes higher than a predetermined value or the temperature thereof becomes lower than a predetermined value. Inside the turbo molecular pump 100, the pressure of the exhaust gas is the lowest at the inlet port 101 and the highest at the outlet port 133. When the pressure of the process gas becomes higher than a predetermined value or the temperature of the process gas becomes lower than a predetermined value while the process gas is being transferred from the inlet port 101 to the outlet port 133, the process gas becomes solid and adheres and accumulates inside the turbo molecular pump 100.

[0035] For example, in a case where SiC14 is used as a process gas inan Al etching apparatus, it can be seen from the vapor pressure curve that a solid product (e.g., A1C13; also referred to as a "reaction product") is precipitated at low vacuum (760 [torr] to 10-2 [torr] ) and low temperature (about 20 [°C] ) , adheres inside the turbo molecular pump 100. As a result, when a precipitate of the process gas is deposited inside the turbo molecular pump 100, the deposit narrows the pump flow path and causes a decrease in performance of the turbo molecular pump 100. Then, the product described above is likely to solidify and adhere in the vicinity of the outlet port 133 or in the vicinity of the screw stator 131 at a portion where the pressure is high.

[0036] Therefore, in order to solve this problem, conventionally, a heater (not illustrated) or an annular water cooling tube 149 is wound around the outer periphery of the base portion 129 or the like, and a temperature sensor (for example, a thermistor) (not illustrated) is embedded in the base portion 129, and control of heating of the heater or cooling by the water cooling tube 149 (hereinafter referred to as temperature management system (TMS) ) is performed so as to keep the temperature of the base portion 129 at a constant high temperature (set temperature) on the basis of a signal of the temperature sensor. In the present embodiment, the screw stator 131 is heated by a heater (not illustrated) embedded in the screw stator 131, and the base portion 129 is cooled by the water cooling tube 149 embedded in the bottom lid 145.

[0037] Next, with regard to the turbo molecular pump 100 configured as described above, the amplifier circuit 150 for performing excitation control on the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B will be described. A circuit diagram of the amplifier circuit is illustrated in Fig . 2.

[0038] In Fig. 2, one end of an electromagnet winding 151 constituting the upper radial electromagnet 104 and the like is connected to a positive electrode 171a of a power supply 171 via a transistor 161, and the other end thereof is connected to a negative electrode 171b of the power supply 171 via a current detection circuit 181 and a transistor 162. The transistors 161 and 162 are so-called power MOSFETs, and have a structure in which a diode is connected between the source and the drain.

[0039] At this time, in the transistor 161, a cathode terminal 161a of the diode is connected to the positive electrode 171a, and an anodeterminal 161b is connected to one end of the electromagnet winding 151. In the transistor 162, a cathode terminal 162a of the diode is connected to the current detection circuit 181, and an anode terminal 162b is connected to the negative electrode 171b.

[0040] On the other hand, a current regeneration diode 165 has a cathode terminal 165a connected to one end of the electromagnet winding 151 and an anode terminal 165b connected to the negative electrode 171b. Similarly, a cathode terminal 166a of a current regeneration diode 166 is connected to the positive electrode 171a, and an anode terminal 166b thereof is connected to the other end of the electromagnet winding 151 via the current detection circuit 181. The current detection circuit 181 includes, for example, a current sensor of a Hall sensor type or an electric resistance element.

[0041] The amplifier circuit 150 configured as described above corresponds to one electromagnet. Therefore, in a case where the magnetic bearings are controlled by five axes and the total number of the electromagnets 104, 105, 106A, and 106B is 10, a similar amplifier circuit 150 is configured for each of the electromagnets, and ten amplifier circuits 150 are connected in parallel to the power supply 171.

[0042] Furthermore, an amplifier control circuit 191 includes, for example, a digital signal processor unit (hereinafter, referred to as a DSP unit) not illustrated in the drawing of the control device 200, and the amplifier control circuit 191 switches on / off of the transistors 161 and 162.

[0043] The amplifier control circuit 191 compares a current value detected by the current detection circuit 181 (a signal reflecting the current value is referred to as a current detection signal 191c) with a predetermined current command value. The magnitude (pulse width times Tpl and Tp2) of the pulse width generated in a control cycle Ts that is one cycle of the PWM control is determined on the basis of the comparison result. As a result, gate drive signals 191a and 191b having the pulse widths are output from the amplifier control circuit 191 to the gate terminals of the transistors 161 and 162.

[0044] Note that it is necessary to control the position of the rotating body 103 at a high speed and with a strong force when the rotating body 103 passes through the resonance point during acceleration operation of the rotational speed of the rotating body, when adisturbance occurs during constant speed operation, or the like.Therefore, a high voltage of, for example, about 50 V is used as the power supply 171 so that the current flowing through the electromagnet winding 151 can be rapidly increased (or decreased) . In addition, a capacitor is usually connected between the positive electrode 171a and the negative electrode 171b of the power supply 171 in order to stabilize the power supply 171 (not illustrated) .

[0045] In such a configuration, when both the transistors 161 and 162 are turned on, the current (hereinafter, referred to as electromagnet current iL) flowing through the electromagnet winding 151 increases, and when both are turned off, the electromagnet current iL decreases.

[0046] In addition, when one of the transistors 161 and 162 is turned on and the other is turned off, a so-called flywheel current is held. Then, by causing the flywheel current to flow through the amplifier circuit 150 in this manner, the hysteresis loss in the amplifier circuit 150 can be reduced, and the power consumption of the entire circuit can be suppressed low. By controlling the transistors 161 and 162 in this manner, high-frequency noise such as harmonics generated in the turbo molecular pump 100 can be reduced. Furthermore, the electromagnet current iL flowing through the electromagnet winding 151 can be detected by measuring the flywheel current with the current detection circuit 181.

[0047] That is, in a case where the detected current value is smaller than the current command value, as illustrated in Fig. 3, only once in the control cycle Ts (for example, 100 ps) , both the transistors 161 and 162 are turned on by the time corresponding to the pulse width time Tpl. Therefore, the electromagnetic current iL during this period increases toward a current value iLmax (not illustrated) that can flow from the positive electrode 171a to the negative electrode 171b via the transistors 161 and 162.

[0048] On the other hand, in a case where the detected current value is larger than the current command value, as illustrated in Fig. 4, both the transistors 161 and 162 are turned off only once in the control cycle Ts for the time corresponding to the pulse width time Tp2. Therefore, the electromagnet current iL during this period decreases toward a current value iLmin (not illustrated) that can be regenerated from the negative electrode 171b to the positive electrode 171a via the diodes 165 and 166.

[0049] In either case, either one of the transistors 161 and 162 isturned on after the pulse width times Tpl and Tp2 elapse. Therefore, during this period, the flywheel current is held in the amplifier circuit 150.

[0050] In the turbo molecular pump 100 having such a basic configuration, the upper side (the side of the inlet port 101) in Fig. 1 is an inlet portion connected to the target device side, and the lower side (the side of the base portion 129 on which the outlet port 133 is provided) is an outlet portion connected to an auxiliary pump (back pump) or the like (not illustrated) . The turbo molecular pump 100 can be used in an inverted posture, a horizontal posture, or an inclined posture in addition to the vertical posture in the vertical direction as illustrated in Fig . 1.

[0051] In the turbo molecular pump 100, the outer cylinder 127 and the base portion 129 described above are combined to form one case. Hereinafter, both the outer cylinder 127 and the base portion 129 may be collectively referred to as a "casing", a "main body casing", or the like. Further, only the outer cylinder 127 or only the base portion 129 may be referred to as a "casing". The turbo molecular pump 100 is electrically (and structurally) connected to a box-shaped electric case (not illustrated) , and the control device 200 described above is incorporated in the electric case.

[0052] The internal configuration of the main body casing (here, a combination of the outer cylinder 127 and the base portion 129) of the turbo molecular pump 100 can be divided into a rotation mechanism portion 136 that rotates the rotor shaft 113 and the like by the motor 121 and an exhaust mechanism portion 137 that is rotationally driven by the rotation mechanism portion 136. In addition, the exhaust mechanism portion 137 can be considered to be divided into a turbo molecular pump mechanism portion 138 constituted by the rotor blades 102, the stator blades 123, and the like, and a thread groove pump mechanism portion (Holweck exhaust mechanism portion 204) constituted by the rotating body lower cylindrical portion 103b, the screw stator 131, and the like.

[0053] In addition, the purge gas (protection gas) described above is used for protecting the bearing portion, the rotor blades 102, and the like, and performs prevention of corrosion due to the exhaust gas (process gas) , cooling of the rotor blades 102, and the like. The purge gas can be supplied by a general method.

[0054] For example, the purge gas port (not illustrated) linearly extending in the radial direction is provided in a predetermined portion of the base portion 129 (a position away from the outlet port 133 by 90 degrees, 120 degrees, or the like) . Then, the purge gas is supplied to the purge gas port (not illustrated) from the outside of the base portion 129 via a purge gas bombe (N2 gas bombe or the like) , a flow rate regulator (valve device) , or the like.

[0055] The protection bearings 120 described above may also be referred to as "Touch-down (T / D) bearings," "Back-up bearings," etc. With these protection bearings 120, for example, even in a case where a trouble such as a trouble in an electrical system or a trouble such as atmosphere entry occurs, the position and posture of the rotor shaft 113 are not greatly changed, and the rotor blade 102 and its peripheral portion are not damaged.

[0056] In Fig. 1 illustrating the structures of the turbo molecular pump 100 and the rotating body 103, hatching showing a cross section of a component is omitted to avoid complication of the drawing.

[0057] <Foreign Matter Deposition Amount Estimation Device 210>As described above, reaction products (foreign matters) may be deposited inside the turbo molecular pump 100. In the present embodiment, using the foreign matter deposition amount estimation device 210 as illustrated in Figs. 1 and 5, the deposition amount of foreign matters generated inside is estimated outside the turbo molecular pump 100. Hereinafter, the configuration and function of the foreign matter deposition amount estimation device 210 will be described.

[0058] Fig. 5 is an enlarged view of the foreign matter deposition amount estimation device 210 of Fig. 1. As illustrated in Fig. 5, the foreign matter deposition amount estimation device 210 includes an exhaust member 212 and a conductor member 214. Further, the foreign matter deposition amount estimation device 210 includes a measurement device 216 and an arithmetic device 218.

[0059] Although details will be described later, the exhaust member 212 and the conductor member 214 constitute a foreign matter detection device (foreign matter detection unit) 220. The foreign matter detection device 220 is electrically connected to the measurement device 216, and the generation status of the foreign matter in the foreign matter detection device 220 is measured by the measurement device 216. Themeasurement result of the measurement device 216 is transmitted to the arithmetic device 218, and the generation status of the foreign matter is determined on the basis of the calculation result of the arithmetic device 218.

[0060] The foreign matter detection device 220 has a double pipe structure including an exhaust member 212 and a conductor member 214, similarly to a foreign matter detection device 260 of a modification illustrated in Figs. 7 and 8. The foreign matter detection device 260 of Figs. 7 and 8 and the foreign matter detection device 220 of Figs. 1 and 5 are different from each other in the number of communication ports 236 to be described later, the magnitude relationship between the exhaust member 212 and the conductor member 214 in the axial direction, and the like .

[0061] However, here, with respect to the foreign matter detection device 220 illustrated in Figs. 1 and 5, points in common with the foreign matter detection device 260 in Figs. 7 and 8 will be described with reference to Figs. 7 and 8. Note that the foreign matter detection device 220 of Figs. 1 and 5 and the foreign matter detection device 260 of Fig. 8 to be referenced are illustrated in opposite directions with respect to the axial direction. In Fig. 7 referenced, the exhaust member 212 and the conductor member 214 are shown with different concentrations of shading.

[0062] In the foreign matter detection device 220 illustrated in Figs. 1 and 5, the exhaust member 212 and the conductor member 214 are formed into a cylindrical shape by, for example, processing a conductive material such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components. Among these members, the exhaust member 212 is a single tubular member including a cylindrical portion 222, a distal end flange portion 224, and an intermediate flange portion 226. One end (an end portion on the side where the distal end flange portion 224 is not provided) of the cylindrical portion 222 of the exhaust member 212 is connected to the outlet port 133 (described later) of the turbo molecular pump 100.

[0063] The exhaust member 212 is connected to the outlet port 133 by bolting using a bolt (hexagon socket set bolt) 225 in a state where one end is inserted into the outlet port 133. The bolt 225 is screwed into an attachment seat portion (reference numeral is omitted) of the baseportion 129 with the intermediate flange portion 226 interposed therebetween. The exhaust member 212 (foreign matter detection device 220) is detachably attached to the turbo molecular pump 100 via the bolt 225.

[0064] A method of connecting the exhaust member 212 to the outlet port 133 is not limited thereto, and may be a method using a clamp (vacuum pipe clamp) . The connection of the exhaust member 212 (foreign matter detection device 220) to the turbo molecular pump 100 may be performed, for example, by welding. Welding can be classified into a connection method in which the exhaust member 212 (foreign matter detection device 220) cannot be attached and detached.

[0065] The conductor member 214 is also formed in a single tube shape, and the outer diameter of the conductor member 214 is set to be smaller than the inner diameter of the exhaust member 212. The thickness of the conductor member 214 is thinner than the thickness of the exhaust member 212. The conductor member 214 is disposed concentrically (coaxially) inside the exhaust member 212. A gap t (Fig. 5) is interposed between an outer peripheral surface 215 of the conductor member 214 and an inner peripheral surface 213 of the exhaust member 212. This "gap" is also referred to as, for example, "interval", "distance", "inter-electrode distance", or the like. The size of the gap t is, for example, 2 mm.

[0066] The conductor member 214 is supported inside the exhaust member 212 in a state of being suspended by a conductive pin 230. The fixing between the conductive pin 230 and the conductor member 214 can be performed, for example, by screwing a distal end portion of the conductive pin 230 into a coupling hole 232 of the conductor member 214. In the modification of Fig. 8, a portion of the conductor member 214 into which the conductive pin 230 is screwed is partially formed thick so as to obtain a sufficient contact area (fastening force) . Such a structure may be adopted for the conductor member 214 of the foreign matter detection device 220 illustrated in Fig. 5.

[0067] In any of the foreign matter detection devices 220 and 260, the fixing between the conductive pin 230 and the conductor member 214 is not limited to the screwing as long as the conduction between the conductive pin 230 and the conductor member 214 is possible, and can be performed by various methods including press-fitting, for example.

[0068] The conductive pin 230 is formed in a stepped cylindrical shapeby, for example, processing a conductive material such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components. The conductive pin 230 is inserted into a through hole 228 formed in the intermediate flange portion 226. The through hole 228 extends in the radial direction of the exhaust member 212 (and the intermediate flange portion 226) .

[0069] 0-rings 227 and 227 are attached to portions of the conductive pin 230 having a relatively small diameter. The O-rings 227 and 227 are disposed away from each other in the axial direction of the conductive pin 230. In the through hole 228, the conductive pin 230 and the exhaust member 212 are airtightly sealed by the O-rings 227 and 227. Therefore, the O-rings 227 and 227 exhibit a vacuum sealing function. Further, the conductive pin 230 is fixed to the exhaust member 212 via a fastening force of a fixing nut 229 disposed outside the intermediate flange portion 226.

[0070] The fixing nut 229 is formed using, for example, a conductive material such as stainless steel. A rectangular plate-shaped insulating plate 233 made of an electrically insulating material and a round terminal (crimp terminal) 234 are sandwiched between the fixing nut 229 and the intermediate flange portion 226. The insulating plate 233 is in contact with the seat surface of the intermediate flange portion 226 processed to be flat. Electric wiring (not illustrated) is led out from the round terminal 234, and the round terminal 234 is used to connect the electric wiring (not illustrated) to the conductive pin 230.

[0071] As illustrated with reference to Fig. 7, two fixing screws 238a and 238b are used to fix the insulating plate 233, and the round terminal 234 is also sandwiched between the head of one fixing screw 238a and the insulating plate 233. Electric wiring (not illustrated) is also led out from the round terminal 234 connected to the fixing screw 238a. The two round terminals 234 are used to apply a voltage for foreign matter detection to the conductive pin 230 and the one fixing screw 238a. A method of foreign matter detection will be described later.

[0072] As illustrated in Figs. 1 and 5, the conductor member 214 is provided with a plurality of (seven in the example of Fig. 5) communication ports 236. The communication ports 236 penetrate the exhaust member 212 in the thickness direction (radial direction) , and are arranged in a line and at equal intervals along the axial direction ofthe conductor member 214. Further, the opening dimensions of the communication port 236 are common. Here, in the foreign matter detection device 260 according to the modification of Figs. 7 and 8, only one communication port 236 is provided, which is different from the foreign matter detection device 220 of Figs. 1 and 5 and the foreign matter detection device 260 of Figs. 7 and 8.

[0073] In the example of Figs. 1 and 5, a spacer 240 is inserted into the rightmost communication port 236 among the plurality of communication ports 236 arranged in a line. In Fig. 5, the spacer 240 is hatched for emphasis. An example of this spacer 240 is shown in Fig. 7 incorporated by reference. In the example of Fig. 7, only one spacer 240 is used, and is inserted into only one communication port 236. In the example of Fig. 7, the communication port (communication port 236) into which the spacer 240 is not inserted is not provided. Also in these respects, the foreign matter detection device 220 of Figs. 1 and 5 is different from the foreign matter detection device 260 of the modification according to Figs . 7 and 8.

[0074] As illustrated with reference to Fig. 7, the spacer 240 is formed in a stepped pin shape by, for example, processing an electrically insulating material such as rubber (including other synthetic resins) or ceramics. One end portion of the spacer 240 in the axial direction is formed to be relatively thin and is inserted into the communication port 236.

[0075] The other end portion of the spacer 240 in the axial direction (the end portion on the outer side of the conductor member 214) faces the inner peripheral surface 213 of the exhaust member 212. One end portion of the spacer 240 is interposed between the conductor member 214 and the exhaust member 212 in a state of being in contact with the inner peripheral surface 213 of the exhaust member 212. The spacer 240 prevents the conductor member 214 from rotating (swinging) about the conductive pin 230 as the central axis while ensuring the interval between the conductor member 214 and the exhaust member 212.

[0076] In Fig. 7, two spacers 240 are disposed at positions separated by 180 degrees in phase in the circumferential direction of the conductor member 214. Furthermore, three or more spacers 240 (and communication ports 236) may be disposed at intervals of 120 degrees, intervals of 90 degrees, or the like in the circumferential direction. The spacer 240 maybe attached to the communication port 236 located at the end portion closest to the turbo molecular pump 100. Furthermore, the spacer 240 may be attached to the communication port 236 disposed at a portion in the middle of one line. Further, the spacer 240 may be mounted on the plurality of communication ports 236 in one line.

[0077] <Main Configuration for Estimation of Foreign Matter Deposition Amount in Turbo Molecular Pump 100>As described above, the foreign matter detection device 220 is connected to the outlet port 133 of the turbo molecular pump 100 (Figs. 1 and 5) . The outlet port 133 is an opening formed on a side surface of the base portion 129 constituting the turbo molecular pump 100. The outlet port 133 constitutes one end portion (radially outer portion) of an inbase exhaust flow path 272 formed inside the base portion 129. The inbase exhaust flow path 272 is spatially connected to the outside of the turbo molecular pump 100 via the outlet port 133.

[0078] The other end portion of the in-base exhaust flow path 272 extends in parallel with the axial direction of the turbo molecular pump 100. Further, the other end portion of the in-base exhaust flow path 272 is opened toward the thread groove pump mechanism portion (Holweck exhaust mechanism portion 204) . A thread groove pump exhaust flow path 274 faces the thread groove pump mechanism portion (Holweck exhaust mechanism portion 204) , and the in-base exhaust flow path 272 is spatially connected to the thread groove pump exhaust flow path 274.

[0079] In the present embodiment, the thread groove pump exhaust flow path 274 is an exhaust flow path connected to the downstream side of the thread groove 131a in the thread groove pump mechanism portion (Holweck exhaust mechanism portion 204) . The thread groove pump exhaust flow path 274 is an exhaust flow path different from the thread groove 131a. The gas pressure-fed by the thread groove 131a flows into the thread groove pump exhaust flow path 274. The gas flowing into the thread groove pump exhaust flow path 274 flows in the in-base exhaust flow path 272 and flows into the foreign matter detection device 220.

[0080] A wiring passage 276 for electrical connection is also formed in the base portion 129. In the example of Fig. 1, the wiring passage 276 is formed at a position away by 180 degrees in the circumferential direction (of the base portion 129) with respect to the in-base exhaust flow path 272. Although not illustrated, wiring led out from an electriccomponent such as the substrate 143 passes through the wiring passage 276, and is electrically connected to a male connector member 280 on which an electrode 278 is formed. A female connector member 284 of an electrical cable 282 is connected to the male connector member 280.

[0081] As described above, a voltage (high-frequency voltage) for foreign matter detection is supplied to the foreign matter detection device 220. The value of the high-frequency voltage can be, for example, about 3 V (a peak value or an effective value) . Wiring and electrodes for supplying the voltage can be provided in the electrical cable 282, the male connector member 280, and the female connector member 284. The female connector member 284 can be electrically connected to the fixing screw 238a of the foreign matter detection device 220 and the conductive pin 230. In addition, the electrical cable 282, the male connector member 280, and the female connector member 284 may be provided in different systems .

[0082] <Detection of Electrostatic Capacitance C>The fixing screw 238a is connected to the exhaust member 212 in an energizable state, and the conductive pin 230 is connected to the conductor member 214 in an energizable state. When a voltage is applied to the exhaust member 212 and the conductor member 214 via the fixing screw 238a and the conductive pin 230, a potential difference is generated between the exhaust member 212 and the conductor member 214. Since the gap t is interposed between the exhaust member 212 and the conductor member 214, the electric charge Q (= CV) corresponding to the potential difference and the electrostatic capacitance is charged between the exhaust member 212 and the conductor member 214.

[0083] C in the above-described Q = CV equation (hereinafter, referred to as "Expression (1)") is an electrostatic capacitance, and V is a potential difference. Then, since the potential difference V is known, the electrostatic capacitance C can be obtained by detecting (measuring) the electric charge Q and performing calculation (C = Q / V) . Furthermore, by obtaining a difference in electrostatic capacitance calculated at different timings, a change (AC) in electrostatic capacitance C within the time can be obtained.

[0084] In addition, the electrostatic capacitance in the case of the parallel plate conductor is obtained by an equation of C = sS / d (hereinafter, referred to as "Expression (2)") . The meanings of thesymbols in Expression (2) are as follows.C: Electrostatic Capacitance s: Dielectric Constant of Substance between Conductors (Relative Dielectric Constant)S: Area of Opposed surface of Conductor d: Distance between Conductors

[0085] In the examples of Figs. 1 and 5, the exhaust member 212 and the conductor member 214 have a cylindrical shape arranged concentrically. The electrostatic capacitance between the exhaust member 212 and the conductor member 214 can be expressed by an equation of C = (2ns ) / (In (b / a) ) (hereinafter, referred to as "Expression (3)") , which is an equation of the electrostatic capacitance related to the coaxial cylindrical conductor.Here, the meaning of each symbol is as follows. C: Electrostatic Capacitance n: Circumference s: Dielectric Constant of Substance between Conductors (Relative Dielectric Constant) a: Outer Diameter of Conductor Member 214 b: Inner Diameter of Exhaust Member 212 In addition, in is a natural logarithm.

[0086] As described above, the exhaust member 212 and the conductor member 214 are connected to the measurement device 216, and the measurement device 216 is connected to the arithmetic device 218. The exhaust member 212 and the conductor member 214 serve as electrodes and constitute an electrostatic capacitance sensor. In the measurement device 216, the electric charges of the exhaust member 212 and the conductor member 214 are measured, and in the arithmetic device 218, the electrostatic capacitance and the change in electrostatic capacitance related to different timing are calculated on the basis of the measurement result of the measurement device 216. Note that the roles of the measurement device 216 and the arithmetic device 218 are not limited thereto. For example, some calculations may be performed in the measurement device 216, or all calculations may be performed in the arithmetic device 218. In addition, the measurement device 216 and the arithmetic device 218 may be integrated. Furthermore, the arithmetic device 218 may be integrated with the control device 200 (Fig. 1) .

[0087] The gas from the turbo molecular pump 100 flows into the foreign matter detection device 220, and the flowing gas flows between the exhaust member 212 and the conductor member 214 and inside the conductor member 214. The gas is in contact with both the inner peripheral surface 213 of the exhaust member 212 and the outer peripheral surface 215 of the conductor member 214. Therefore, foreign matters (reaction products) are generated and deposited on both the inner peripheral surface 213 of the exhaust member 212 and the outer peripheral surface 215 of the conductor member 214. As the operation time of the turbo molecular pump 100 is cumulatively increased, the amount of foreign matter deposited on the exhaust member 212 and the amount of foreign matter deposited on the conductor member 214 gradually increase.

[0088] As the thickness of the foreign matter increases, the gap t between the exhaust member 212 and the conductor member 214 is gradually filled, and the electrostatic capacitance between the exhaust member 212 and the conductor member 214 increases as the gap t narrows. Then, in the measurement device 216, the electrostatic capacitance is measured, and in the arithmetic device 218, the amount of change or the like related to the electrostatic capacitance is calculated.

[0089] Since the gas from the turbo molecular pump 100 is introduced into the foreign matter detection device 220, it can be considered that the change in electrostatic capacitance in the foreign matter detection device 220 is interlocked with the deposition of the foreign matter inside the turbo molecular pump 100 and reflects the deposition situation of the foreign matter. Therefore, by monitoring the change in electrostatic capacitance in the foreign matter detection device 220, the foreign matter deposition amount inside the turbo molecular pump 100 can be estimated.

[0090] In order to estimate the foreign matter deposition amount, a mathematical expression (relational expression) representing the relationship between the deposition amount of foreign matter in the foreign matter detection device 220 and the deposition amount inside the turbo molecular pump 100 is created in advance by an experiment. As this relational expression, for example, an expression such as TB = uTA (hereinafter, referred to as "Expression (4)") in which the product of a deposition amount TA of the foreign matter in the foreign matter detection device 220 and a conversion coefficient a is a depositionamount TB inside the turbo molecular pump 100 can be exemplified.

[0091] The relational expression is not limited to the above Expression (4) , and various relational expressions can be created and used. Then, using such a relational expression, it is possible to estimate the deposition amount of foreign matter by, for example, (Method 1) or (Method 2) described below.

[0092] (Method 1) The deposition amount inside the turbo molecular pump 100 is calculated and estimated from the deposition amount inside the foreign matter detection device 220 using the relational expression. This calculation and estimation are performed by causing a computer (conversion device) to execute a software program (deposition amount estimation software and deposition amount estimation application) created for estimating the deposition amount.

[0093] According to Method 1, various relational expressions can be described in the software program on the basis of the experimental result. Then, after the software program is installed in the computer, it is possible to easily cope with many types of deposits by applying the relational expression matching the condition. However, Method 1 requires a computer (conversion device) for performing estimation based on the relational expression.

[0094] (Method 2) Based on the relational expression, the gap (interval) t between the exhaust member 212 and the conductor member 214 is set to be smaller than the interval of the predetermined portion inside the turbo molecular pump 100 in advance. According to Method 2, a computer (conversion device) for performing estimation based on a relational expression is not required. Since the conversion device is not required, the cost can be reduced. Furthermore, the component configuration can be simplified.

[0095] As described above, according to the foreign matter deposition amount estimation device 210 of the present embodiment, it is possible to estimate the deposition amount by a plurality of methods using the relational expression. Any one of these methods may be selected in advance and adopted in the foreign matter deposition amount estimation device 210, or a plurality of methods may be adopted so that the user can select as necessary. In addition, a method combining a plurality of methods may be constructed. For example, in a case where the above Method1 and the above Method 2 are combined, it is conceivable to performestimation using the computer (conversion device) of the above Method 1 after setting the gap (interval) t in the above Method 2.

[0096] Note that the computer (conversion device) of the above Method 1 may be integrated with the arithmetic device 218. Alternatively, the function of the computer (conversion device) of the above Method 1 may be incorporated in the arithmetic device 218. The computer (conversion device) of the above Method 1 may be integrated with the arithmetic device 218 and the measurement device 216. Further, the computer (conversion device) of the above Method 1 may be integrated with the control device 200 (Fig. 1) .

[0097] <Utilization of Temperature Management>The above relational expression can also be created on the basis of the relationship between the internal temperature of the turbo molecular pump 100 and the temperature of the foreign matter detection device 220. That is, the deposition amount of the foreign matters varies depending on the pressure and temperature of the surrounding environment and the composition of the gas (type of gas) . Among these parameters, the pressure is not significantly different between the inside of the turbo molecular pump 100 and the inside of the exhaust member 212 in the foreign matter detection device 220. In addition, the composition of gas (type of gas) is usually known in advance after the user or application is determined. Therefore, the conversion coefficient a can be determined by experimentally clarifying the relationship between the internal temperature of the turbo molecular pump 100 and the internal temperature of the exhaust member 212 in advance.

[0098] For example, if it is known in advance that the internal temperature of the exhaust member 212 is 1 / 2 of the internal temperature of the turbo molecular pump 100, foreign matter is deposited at twice the speed inside the exhaust member 212. Therefore, in this case, a relational expression such as TB = TA / 2 can be created.

[0099] In a case where the relationship between the internal temperature of the turbo molecular pump 100 and the internal temperature of the exhaust member 212 is determined, it is also possible to estimate a value obtained by simply doubling the deposition amount TA of the foreign matter in the foreign matter detection device 220, for example, as the deposition amount TB inside the turbo molecular pump 100 without creating the above-described relational expression. In this case, it ispossible to input a multiple (sometimes a decimal point) to a computer (conversion device) in advance and perform conversion of multiplying a result of measurement and calculation of the deposition amount TA of the foreign matter in the foreign matter detection device 220 by the multiple .

[0100] As described above, since the relationship between the internal temperature of the turbo molecular pump 100 and the internal temperature of the exhaust member 212 is greatly related to the estimation of the foreign matter deposition amount, it is conceivable to control the internal temperature of the foreign matter detection device 220 to be the same as the internal temperature of the turbo molecular pump 100. In order to do so, for example, as illustrated in Fig. 6, it is possible to mount, for example, an annular heater 290 on the outer periphery of the exhaust member 212 and control the heater 290 by a temperature control device 292 to adjust the temperature in the foreign matter detection device 220.

[0101] In a case where the internal temperature of the turbo molecular pump 100 during operation (for example, during rated operation) is known and constant, the temperature of the heater 290 can be adjusted by the temperature control device 292 according to the determined internal temperature of the turbo molecular pump 100.

[0102] In addition, in a case where the internal temperature of the turbo molecular pump 100 changes or is not known, although the illustration of the configuration is omitted, it is also possible to measure the internal temperature of the turbo molecular pump 100 and control the temperature of the heater 290 by the temperature control device 292 on the basis of the measurement result.

[0103] In addition, in a case where the temperature of the foreign matter detection device 220 is adjusted to be the same as the internal temperature of the turbo molecular pump 100, the temperature condition of the foreign matter detection device 220 can be made the same as the state of the gas flow path inside the turbo molecular pump 100, so that the foreign matter deposition amount inside the turbo molecular pump 100 can be accurately estimated without requiring the conversion coefficient a described above.

[0104] Note that the internal temperature of the exhaust member 212 is not limited to be adjusted to be the same as the internal temperature ofthe turbo molecular pump 100, and may be adjusted to a temperature that maintains a certain relationship (for example, 1 / 2 times, 3 / 5 times, 1.5 times, 2 times, and the like) other than the same temperature. Furthermore, the temperature control device 292 may be integrated with the arithmetic device 218 or integrated with the control device 200 (Fig. 1) •

[0105] <Typical Merits of Foreign Matter Deposition Amount Estimation Device 210 and Turbo Molecular Pump 100 according to First Embodiment> According to the foreign matter deposition amount estimation device 210 of the first embodiment described above and the turbo molecular pump 100 including the foreign matter deposition amount estimation device 210, the foreign matter detection device 220 is connected to the outlet port 133 of the turbo molecular pump 100. Therefore, the deposition amount of foreign matter inside the turbo molecular pump 100 can be estimated on the basis of the amount of foreign matter deposited outside the turbo molecular pump 100 (outside the outer cylinder 127 or the base portion 129) .

[0106] Further, for example, as compared with the invention disclosed in PTL 1 described above, it is not necessary to dispose an electrostatic capacitance sensor inside the pump, and there are few restrictions on the installation space of the sensor (high degree of freedom) . Furthermore, the electrostatic capacitance can be detected using a relatively large space, and it is easy to increase the size of the electrostatic capacitance sensor. Then, it is easy to secure a large area (charged area) of the electrode in the electrostatic capacitance sensor, and it is easy to increase the detection sensitivity. Furthermore, the exhaust member 212 and the conductor member 214 serving as electrodes have a cylindrical shape, and it is easy to secure a large area as compared with a case where the electrodes have a flat plate shape. In addition, since the electrode can be arranged following the pipe shape (or along) , the detection direction of the electrode can be matched with the deposition direction of the foreign matters (for example, the radial direction of the pipe, the direction orthogonal to the axis of the pipe, and the like) , and the deposition amount of the foreign matters deposited in the pipe can be more accurately grasped.

[0107] In addition, since the conductor member 214 has a cylindrical shape and is disposed concentrically in the exhaust member 212, it ispossible to suppress the ratio of the electrostatic capacitance sensor to the cross-sectional area of the gas flow path to be small. Therefore, it is possible to prevent the electrostatic capacitance sensor from blocking the gas flow path inside the pump and adversely affecting the exhaust performance. Furthermore, it is not necessary to route the wiring connected to the electrostatic capacitance sensor to, for example, a narrow space inside the pump such as the thread groove pump exhaust flow path 274 (Fig. 5) or a space in which a plurality of components are closely overlapped, and the wiring can be easily routed.

[0108] As a result, it is possible to satisfactorily grasp the operation state of the pump inside the turbo molecular pump 100, determine the timing of cleaning, and make a maintenance plan. By appropriately performing the maintenance, it is possible to prevent the rotor blades 102 (102a, 102b, 102c, ... ) from coming into contact with deposits inside the turbo molecular pump 100.

[0109] The cleaning time may be determined by a person based on the calculation result of the arithmetic device 218. Alternatively, the cleaning time may be determined in a predetermined computer device on the basis of a command described in a predetermined software program. Examples of the predetermined computer device include a control device 200 of the turbo molecular pump 100, an integrated control device owned by a user of the turbo molecular pump 100, and an inspection terminal device carried by a maintenance worker such as the turbo molecular pump 100.

[0110] In addition, the arithmetic device 218 can estimate the deposition amount of the foreign matter in the turbo molecular pump 100 on the basis of the relationship among the change in the electrostatic capacitance C, the dielectric constant of the foreign matter, and the ratio, measured in advance by an experiment or the like, between the deposition amount of the foreign matter inside the turbo molecular pump 10 and the deposition amount of the foreign matter in the exhaust member 212. This is effective when the type of the foreign matter is known in advance .

[0111] The "ratio, measured in advance by an experiment or the like, between the deposition amount of the foreign matter inside the turbo molecular pump 100 and the deposition amount of the foreign matter in the exhaust member 212" can be, for example, "a ratio, measured in advance byan experiment or the like, between a deposition rate of the foreign matter inside the turbo molecular pump 100 and a deposition rate of the foreign matter in the exhaust member 212". The "deposition rate" mentioned here can be, for example, a "deposition amount per predetermined time", a "time required for a predetermined amount of foreign matter to be deposited", or the like.

[0112] In addition, the "deposition amount of foreign matter in the exhaust member 212" can be replaced with, for example, "the deposition amount of foreign matter in the conductor member 214", "the sum of the deposition amount of foreign matter in the exhaust member 212 and the deposition amount of foreign matter in the conductor member 214", or "the deposition amount of foreign matter in the foreign matter detection device 220". Furthermore, the "deposition amount of foreign matter in the foreign matter detection device 220" may be the "deposition amount of foreign matter in the exhaust member 212", the "deposition amount of foreign matter in the conductor member 214", or the "sum of the deposition amount of foreign matter in the exhaust member 212 and the deposition amount of foreign matter in the conductor member 214".

[0113] In addition, the distance (the size of the gap t) between the exhaust member 212 and the conductor member 214 can be equal (within ±20%) or less with respect to the flow path width of the narrowest portion of the gas flow path inside the turbo molecular pump 100. This is effective when the situation of the deposition of the foreign matter is the same (not greatly different) between the inside of the turbo molecular pump 100 and the inside of the exhaust member 212 (the inside of the foreign matter detection device 220) .

[0114] Specifically, examples of the "gas flow path inside the turbo molecular pump 100" herein include the following.(1) A gas flow path between the rotor blade 102 and the stator blade 123 in the turbo molecular pump mechanism portion 138 (Fig. 1) .(2) The thread groove 131a in the thread groove pump mechanism portion (Holweck exhaust mechanism portion 204) .(3) The thread groove pump exhaust flow path 274 connected to the downstream side of the thread groove 131a.(4) Each part of the in-base exhaust flow path 272 formed inside the base portion 129.

[0115] As the "narrowest portion" referred to herein, a narrowerportion can be fitted by comparison between the "narrowest portion" of the gas flow path between the rotor blade 102 and the stator blade 123 according to (1) above and the "narrowest portion" of the thread groove 131a according to (2) above. These portions are also portions where foreign matter is likely to be generated and accumulated as compared with other portions inside the turbo molecular pump 100.

[0116] The distance between the exhaust member 212 and the conductor member 214 (the size of the gap t) is preferably equal to or less than the flow path width (interval, distance) of the "narrowest portion". In this case, the gap t is smaller than the flow path width of the "narrowest portion". Then, for example, in a case where the gap t and the "narrowest portion" have the same deposition rate, the gap t and the "narrowest portion" are filled with a deposit at the same time or faster in the gap t, and the electrostatic capacitance is saturated in the gap t first. Therefore, even in a case where the dielectric constant of the deposit is unknown, it can be detected that the "narrowest portion" is likely to be filled with the deposit by the saturation of the electrostatic capacitance as a trigger.

[0117] According to the foreign matter detection device 220 (Figs. 1 and 5) of the foreign matter deposition amount estimation device 210, the conductor member 214 has the communication port 236 penetrating the conductor member 214 in the thickness direction. Therefore, the gas flowing into the conductor member 214 can be guided to the gap t via the communication port 236. Therefore, the gas can easily enter the gap t, and the fluidity of the gas is good. Furthermore, since the plurality of communication ports 236 are provided along the axial direction of the conductor member 214, the gas can be easily flowed over the entire gap t.

[0118] More specifically, in a case where the communication port 236 is not provided in the conductor member 214, the gas flowing into the conductor member 214 flows to the side of the distal end flange portion 224 located on the opposite side of the exhaust member 212 with respect to the turbo molecular pump 100. Since the conductor member 214 is formed in a cylindrical shape, the inlet of the gas into the gap t is limited to the end portion of the exhaust member 212 on the turbo molecular pump 100 side .

[0119] As a result, foreign matter is intensively generated in the vicinity of the inlet to the gap t, and is likely to be unevenlyaccumulated in the vicinity of the inlet to the gap t. As a result, the vicinity of the inlet to the gap t is filled with the deposit, and the gas hardly flows into the deep portion of the gap t. Further inflow of the gas into the gap t is prevented, and it becomes difficult to spread the gas throughout the gap t.

[0120] However, by providing the communication port 236 in the conductor member 214, it is possible to guide the gas from the inside of the conductor member 214 to the deep portion of the gap t via the communication port 236. Then, the gas can easily enter the entire gap t, and the fluidity of the gas can be improved. As a result, it is possible to prevent the foreign matter from being unevenly accumulated in the vicinity of the inlet of the gap t. Then, the electrostatic capacitance between the exhaust member 212 and the conductor member 214 can be measured more accurately.

[0121] In addition, since the plurality of communication ports 236 are provided along the axial direction of the conductor member 214, the gas can be easily flowed over the entire gap t. This also makes it possible to more accurately measure the electrostatic capacitance between the exhaust member 212 and the conductor member 214. Here, the arrangement of the plurality of communication ports 236 is not limited to one row, and may be a plurality of rows, staggered arrangement, or the like. In addition, the conductor member 214 may be formed using a punching metal or the like having a large number of holes.

[0122] In order to enhance the fluidity of the gas, for example, the conductor member 214 may be formed to have a semicircular (semi- cylindrical shape, arcuate shape) cross section to open a part of the side surface (peripheral surface) of the conductor member 214. However, also in this case, there is a possibility that foreign matter is unevenly deposited in the vicinity of the inlet of the gap t between the conductor member 214 having a semicircular (semi-cylindrical shape, arcuate shape) cross section and the exhaust member 212. Therefore, providing the plurality of communication ports 236 in the conductor member 214 along the axial direction makes it easier to guide the gas to the entire gap t. In a case where the conductor member 214 has a semicircular shape (semi- cylindrical shape, arcuate shape) or another shape, the conductor member 214 may be formed using a punching metal or the like having a large number of holes.

[0123] <Second Embodiment>Next, a foreign matter deposition amount estimation device 310 according to a second embodiment of the present invention will be described with reference to Figs. 9 and 10. Note that parts similar to those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

[0124] Fig. 9 illustrates the turbo molecular pump 100 to which a foreign matter detection device 320 of the foreign matter deposition amount estimation device 310 is attached, and Fig. 10 illustrates the foreign matter detection device 320 of Fig. 9 in an enlarged manner together with the measurement device 216 and the arithmetic device 218. In the examples of Figs. 9 and 10, the foreign matter detection device 320 includes two conductor members (a main conductor member 314A and a sub-conductor member 314B) . Although details will be described later, the sub-conductor member 314B functions as an auxiliary conductor.

[0125] The main conductor member 314A and the sub-conductor member 314B are both formed in a cylindrical shape, and are arranged inside the exhaust member 312 in a row along the axial direction of an exhaust member 312. The sub-conductor member 314B is disposed closer to the turbo molecular pump 100 than the main conductor member 314A. Further, the main conductor member 314A and the sub-conductor member 314B are disposed concentrically with the exhaust member 312.

[0126] The end portions 372 and 374 of the main conductor member 314A and the sub-conductor member 314B facing each other are processed obliquely with respect to the axial direction. In addition, the end portion 372 of the main conductor member 314A and the end portion 374 of the sub-conductor member 314B face each other obliquely and in parallel.

[0127] In the end portion 372 of the main conductor member 314A, a relatively largely protruding portion (a portion protruding in the axial direction) reaches the inner side (inner side in the radial direction) of an intermediate flange portion 326 in the exhaust member 312. Further, the distal end portion of a conductive pin 330A inserted into the intermediate flange portion 326 reaches the main conductor member 314A.

[0128] The main conductor member 314A is fixed to the conductive pin 330A, and is supported inside the exhaust member 312 in a state of being supported by the conductive pin 330A. Here, as the conductive pin 330A, one similar to the conductive pin 230 in the first embodiment can beadopted. In addition, the main conductor member 314A can be fixed to the conductive pin 330A in a similar manner to the fixing of the conductor member 214 to the conductive pin 230 in the first embodiment by a method such as screwing. Then, the main conductor member 314A may be fixed to the conductive pin 330A in a similar manner to any of the examples of Figs. 1 and 5 and the examples of Figs. 7 and 8.

[0129] In the end portion 372 of the sub-conductor member 314B, a relatively largely protruding portion (a portion protruding in the axial direction) reaches the inner side (inner side in the radial direction) of an intermediate flange portion 326 in the exhaust member 312. Further, the distal end portion of a conductive pin 330B inserted into the intermediate flange portion 326 reaches the sub-conductor member 314B.

[0130] The sub-conductor member 314B is fixed to the conductive pin 330B, and is supported inside the exhaust member 312 in a state of being suspended by the conductive pin 330B. Here, as the conductive pin 330B, one similar to the conductive pin 230 in the first embodiment can be adopted. In addition, the sub-conductor member 314B can be fixed to the conductive pin 330B in a similar manner to the fixing of the conductor member 214 to the conductive pin 230 in the first embodiment by a method such as screwing. Then, the conductor member 214 may be fixed to the conductive pin 330B in a similar manner to any of the examples of Figs. 1 and 5 and the examples of Figs. 7 and 8.

[0131] A gap tA (inter-electrode distance, Fig. 5) is interposed between an outer peripheral surface 315A of the main conductor member 314A and an inner peripheral surface 313 of the exhaust member 312. The size of the gap tA is a similar value (for example, 2 mm) to the gap t of the first embodiment.

[0132] A gap tB (inter-electrode distance, Fig. 5) is interposed between an outer peripheral surface 315B of the sub-conductor member 314B and the inner peripheral surface 313 of the exhaust member 312. The outer diameter of the sub-conductor member 314B is set to be larger than the outer diameter of the main conductor member 314A. Therefore, the size of the gap tB is smaller than the gap tA related to the main conductor member 314A (tA > tB) . The size of the gap tB can be, for example, less than 2 mm (0.5 to 1.9 mm, preferably 0.8 to 1.6 mm, more preferably 1 mm to 1.4 mm) .

[0133] As described above, by providing the sub-conductor member 314Bhaving a different inter-electrode distance from the main conductor member 314A in the exhaust member 312, it is possible to arrange, in a common environment, two (a plurality of) electrostatic capacitance sensors having different timings at which the electrostatic capacitance saturates first in one (a part) . The electrostatic capacitance sensor is formed by a combination of the main conductor member 314A and the exhaust member 312 and a combination of the sub-conductor member 314B and the exhaust member 312. Further, the combination of the main conductor member 314A and the exhaust member 312 functions as a main electrode, and the combination of the sub-conductor member 314B and the exhaust member 312 functions as a sub-electrode.

[0134] Then, by forming the gaps tA and tB having different sizes under a common environment, the gap tB on the small side is filled with foreign matter earlier than the gap tA on the large side, and the electrostatic capacitance C is saturated. For this reason, it is possible to form an electrostatic capacitance sensor with slow saturation (the main conductor member 314A side) and an electrostatic capacitance sensor with fast saturation (the sub-conductor member 314B side) . Then, by using the output signal related to the main conductor member 314A and the output signal related to the sub-conductor member 314B, the type (component) of the foreign matter can be grasped using one electrode (here, the sub-conductor member 314B) , and then the deposition amount of the foreign matter can be estimated using the other electrode (here, the main conductor member 314A) .

[0135] More specifically, in the electrostatic capacitance sensor on the side where the gap tB is narrow (the sub-conductor member 314B side) , the gap tB is filled with the foreign matter earlier than the electrostatic capacitance sensor on the side where the gap tA is wide (the main conductor member 314A side) , and the electrostatic capacitance is saturated. At this time, even in the gap tA on the wide side, it is considered that foreign matter is deposited with a thickness similar to that of the gap tB on the narrow side, and the size of the gap tB on the narrow side is known, so that the thickness of the deposit in the gap tA on the wide side can be estimated.

[0136] Further, thereafter, the dielectric constant (relative dielectric constant) s of the foreign matter can be calculated from the above-described Expression (2) related to the electrostatic capacitanceof the parallel plate conductor and Expression (3) related to the electrostatic capacitance of the coaxial cylindrical conductor. In addition, it is also possible to estimate the type of the foreign matter on the basis of the calculated value of the dielectric constant. In addition, the amount of foreign matter inside the turbo molecular pump 100 can be estimated using an electrostatic capacitance sensor (the main conductor member 314A side) on the side where the gap tA is wide.

[0137] Here, similarly to the gap t of the first embodiment, the distance (the size of the gap tA) between the exhaust member 312 and the main conductor member 314A can be equal to or less than the flow path width of the narrowest portion of the gas flow path inside the turbo molecular pump 100.

[0138] In the second embodiment, the main conductor member 314A is disposed on the distal end flange portion 224 side located on the downstream side, and the sub-conductor member 314B is located on the turbo molecular pump 100 side on the upstream side, but the present invention is not limited thereto. For example, the main conductor member 314A may be disposed on the upstream side (the turbo molecular pump 100 side) , and the sub-conductor member 314B may be disposed on the downstream side (the tip flange portion 22A side) .

[0139] In the second embodiment, the end portions 372 and 374 of the main conductor member 314A and the sub-conductor member 314B facing each other are processed obliquely, but the present invention is not limited thereto. Although not illustrated, for example, the end portions 372 and 374 of the main conductor member 314A and the sub-conductor member 314B facing each other may be processed at a right angle (perpendicular) with respect to the axial direction. In this case, for example, the thickness of the intermediate flange portion 226 may be increased, and the positions of the conductive pins 330A and 330B may be shifted (offset) in the axial direction of the exhaust member 312 to be connected to the main conductor member 314A and the sub-conductor member 314B. In addition, the main conductor member 314A and the sub-conductor member 314B may be processed into semicircular shapes so as to face each other in the vertical direction of Fig. 10. In Fig. 10, the spacer 240 is hatched for emphasis .

[0140] <Invention Extractable from Embodiments>The following inventions can be extracted from the embodimentsdescribed above.(1) A foreign matter deposition amount estimation device (foreign matter deposition amount estimation device 210, etc.) used in a vacuum pump (turbo molecular pump 100, etc. ) including an inlet port (inlet port 101, etc. ) and an outlet port (outlet port 133, etc.) , the foreign matter deposition amount estimation device including: an exhaust member (exhaust member 212, etc. ) connectable to the outlet port; a conductor (conductor member 214, main conductor member 314A, etc. ) disposed at an inner side the exhaust member, at least a part of the conductor having a predetermined distance (sizes of gaps t, tA, etc. ) from an inner surface (inner peripheral surface 213, etc. ) of the exhaust member, and to which a voltage for detecting electrostatic capacitance is applied between the conductor and the exhaust member; a measurement device (measurement device 216, etc. ) that measures the electrostatic capacitance between the exhaust member and the conductor; and an arithmetic device (arithmetic device 218, etc. ) that estimates, from a change in the electrostatic capacitance, a deposition amount of foreign matter inside the vacuum pump.(2) The foreign matter deposition amount estimation device according to ( 1 ) , in which the arithmetic device is configured to estimate the deposition amount of the foreign matter inside the vacuum pump on a basis of a relationship among: a change in the electrostatic capacitance (electrostatic capacitance C etc . ) ; a dielectric constant (dielectric constant s etc. ) of the foreign matter; and a ratio, which is measured in advance, between the deposition amount of the foreign matter inside the vacuum pump and a deposition amount of a foreign matter in the exhaust member.(3) The foreign matter deposition amount estimation device according to ( 1 ) , in which the predetermined distance is equal to or smaller than a flow path width of a narrowest portion (narrower portion between "narrowest portion" of the gas flow path between the rotor blade 102 and the statorblade 123 and "narrowest portion" of thread groove 131a, etc. ) of a gas flow path inside the vacuum pump.(4) The foreign matter deposition amount estimation device (foreign matter deposition amount estimation device 310 of Figs. 9 and 10, etc. ) according to (3) , in which an auxiliary conductor (sub-conductor member 314B, etc. ) is disposed at a distance (size of gap tB, etc. ) different from the predetermined distance, and presence or absence of saturation (saturation of electrostatic capacitance, filling of gap t with foreign matter, etc. ) related to an output of electrostatic capacitance is determined on a basis of a difference between a change in output of electrostatic capacitance measured by the conductor and a change in output of electrostatic capacitance measured by the auxiliary conductor.(5) The foreign matter deposition amount estimation device according to ( 1 ) , in which the exhaust member and the conductor are both cylindrical, and the exhaust member and the conductor are coaxially disposed.(6) The foreign matter deposition amount estimation device according to ( 1 ) , in which at least one of the exhaust member and the conductor is separable from the vacuum pump.(7) The foreign matter deposition amount estimation device according to ( 1 ) , in which the conductor has a communication port (communication port 236 etc. ) penetrating the conductor in a thickness direction.(8) The foreign matter deposition amount estimation device according to (1) , including: an exhaust member temperature control device (temperature control device 292 etc. ) that controls a temperature of the exhaust member.(9) A vacuum pump (turbo molecular pump 100 to which foreign matter deposition amount estimation devices 210 and 310 are connected, etc. ) including the foreign matter deposition amount estimation device according to any one of (1) to (8) .

[0141] <Others>Note that the present invention is not limited to the abovedescribed embodiments, and various modifications and combinations of theembodiments can be made without departing from the gist .[ Reference S igns List ]

[0142] 100 Turbo molecular pump101 Inlet port102 Rotor blade123 Stator blade129 , 429 Base portion131 Screw stator131a Thread groove133 Outlet port210 , 310 Foreign matter depos ition amount estimation device212 Exhaust member213 Inner peripheral surface214 Conductor member215 Outer peripheral surface21 6 Measurement device218 Arithmetic device220 , 2 60 Foreign matter detection device236 Communication port240 Spacer290 Heater292 Temperature control device310 Foreign matter deposition amount estimation device312 Exhaust member313 Inner peripheral surface314A Main conductor member314B Sub-conductor member315A Outer peripheral surface315B Outer peripheral surf ace320 Foreign matter detection device t Gap tA Gap tB Gap

Claims

[CLAIMS]

1. A foreign matter deposition amount estimation device used in a vacuum pump including an inlet port and an outlet port, the foreign matter deposition amount estimation device comprising: an exhaust member connectable to the outlet port; a conductor which is disposed at an inner side the exhaust member, at least a part of the conductor having a predetermined distance from an inner surface of the exhaust member, and to which a voltage for detecting electrostatic capacitance is applied between the conductor and the exhaust member; a measurement device that measures the electrostatic capacitance between the exhaust member and the conductor; and an arithmetic device that estimates, from a change in the electrostatic capacitance, a deposition amount of foreign matter inside the vacuum pump.

2. The foreign matter deposition amount estimation device according to claim 1, wherein the arithmetic device is configured to estimate the deposition amount of the foreign matter inside the vacuum pump on a basis of a relationship among: a change in the electrostatic capacitance; a dielectric constant of the foreign matter; and a ratio, which is measured in advance, between the deposition amount of the foreign matter inside the vacuum pump and a deposition amount of a foreign matter in the exhaust member.

3. The foreign matter deposition amount estimation device according to claim 1, wherein the predetermined distance is equal to or smaller than a flow path width of a narrowest portion of a gas flow path inside the vacuum pump.

4. The foreign matter deposition amount estimation device according to claim 3, wherein an auxiliary conductor is disposed at a distance different from the predetermined distance, andpresence or absence of saturation related to an output of electrostatic capacitance is determined on a basis of a difference between a change in output of electrostatic capacitance measured by the conductor and a change in output of electrostatic capacitance measured by the auxiliary conductor.

5. The foreign matter deposition amount estimation device according to claim 1, wherein the exhaust member and the conductor are both cylindrical, and the exhaust member and the conductor are coaxially disposed.

6. The foreign matter deposition amount estimation device according to claim 1, wherein at least one of the exhaust member and the conductor is separable from the vacuum pump.

7. The foreign matter deposition amount estimation device according to claim 1, wherein the conductor has a communication port penetrating the conductor in a thickness direction.

8. The foreign matter deposition amount estimation device according to claim 1, comprising: an exhaust member temperature control device that controls a temperature of the exhaust member.

9. A vacuum pump comprising the foreign matter deposition amount estimation device according to any one of claims 1 to 8.

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