Foreign matter accumulation sensor and vacuum pump

Abstract

This invention provides a foreign matter accumulation sensor and a vacuum pump that can effectively detect the amount of foreign matter accumulated in a small space. [Solution] The turbomolecular pump comprises a fixed disc 219 and an electrode 252 capable of forming a gas flow path 227 in a non-rotating state, a rotating disc 229 facing the fixed disc 219 and electrode 252 and capable of forming a gas flow path 227 in a rotating state, a first conductor 254 connected to the electrode 252, and a second conductor 256 connected to the fixed disc 219, making it possible to estimate the amount of foreign matter deposited from the change in capacitance between the fixed disc 219, the rotating disc 229, and the electrode 252.

Description

[Technical Field]

[0001] The present invention relates, for example, to a foreign matter accumulation sensor capable of detecting the amount of foreign matter accumulated, and to a vacuum pump. [Background technology]

[0002] Turbomolecular pumps are generally known as a type of vacuum pump. These turbomolecular pumps are used, for example, for exhaust in manufacturing equipment for semiconductors and flat panels. In a turbomolecular pump, power is supplied to a motor inside the pump body to rotate a rotor, which then ejects the gas molecules (process gases) drawn into the pump body, thereby exhausting the gas. Some types of turbomolecular pumps are also equipped with heaters and cooling tubes to properly control the temperature inside the pump.

[0003] In vacuum pumps used for exhausting the air from manufacturing equipment for semiconductors and flat panels, reaction products (foreign matter) generated during the semiconductor and flat panel manufacturing process can accumulate inside the vacuum pump. If a large amount of foreign matter accumulates, it can disrupt the gas flow inside the vacuum pump or cause problems such as collisions with rotating parts. Therefore, a technology has been devised to detect the amount of foreign matter accumulated based on changes in capacitance, so that the timing of maintenance inside the vacuum pump can be determined in advance.

[0004] In the invention disclosed in Patent Document 1 (paragraphs 0035-0039, Figure 2, etc.), the change in capacitance due to deposits accumulated between parallel plate electrodes is measured. In addition, in the invention disclosed in Patent Document 2 (paragraphs 0073, 0074, Figure 7, etc.), the change in capacitance due to deposits on the surface of a comb-shaped electrode is measured. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-159632 [Patent Document 2] Japanese Patent Application Laid-Open No. 2021-195893 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] In the invention disclosed in Patent Document 1, it is premised that it is installed in a narrow gas flow path inside the pump, and there are the following problems. (1) Since there is not enough 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 has an adverse effect on the exhaust performance.

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

[0008] An object of the present invention is to provide a foreign matter deposition amount sensor and a vacuum pump that can effectively detect the deposition amount of foreign matter in a small space. [Means for Solving the Problems]

[0009] In order to achieve the above object, the foreign matter deposition amount sensor according to the present invention includes a first conductive part that can form a gas flow path in the vacuum pump in a non-rotating state, and an electrode, a second conductive part that faces the first conductive part and the electrode and can form the gas flow path in a rotating state, a first wire connected to the electrode, a second wire connected to the first conductive part, and is configured to estimate the deposition amount of foreign matter from the change in the capacitance among the first conductive part, the second conductive part, and the electrode. In addition, the vacuum pump according to the present invention includes the foreign matter deposition amount sensor described above.

Advantages of the Invention

[0010] According to the above invention, it is possible to provide a foreign matter deposition amount sensor that can effectively detect the deposition amount of foreign matter in a small space, and a vacuum pump.

Brief Description of the Drawings

[0011] [Figure 1] It is an explanatory diagram schematically showing the configuration of the foreign matter deposition amount sensor and the turbo molecular pump according to the first embodiment of the present invention. [Figure 2] It is a circuit diagram of an amplifier circuit. [Figure 3] It is a time chart showing control when the current command value is larger than the detected value. [Figure 4] It is a time chart showing control when the current command value is smaller than the detected value. [Figure 5] It is a plan view schematically showing the fixed disk of the Sigma Bern type exhaust mechanism section. [Figure 6] It is an explanatory diagram showing an enlarged view of the foreign matter deposition amount sensor according to the first embodiment. [Figure 7] (a) is an explanatory diagram showing the theoretical model of the foreign matter deposition amount sensor according to the first embodiment, and (b) is a circuit diagram showing the equivalent circuit related to the theoretical model of (a). <​​​​​​​​​​​​​​​[Modes for carrying out the invention]

[0012] <Basic configuration of the turbomolecular pump 100 according to this embodiment> The following describes the foreign matter accumulation sensor 250 according to this embodiment and the turbomolecular pump 100 equipped with this foreign matter accumulation sensor 250. First, the basic configuration of the turbomolecular pump 100 will be described, followed by a description of the foreign matter accumulation sensor 250.

[0013] Figure 1 shows a turbomolecular pump 100 as a vacuum pump according to the first embodiment of the present invention. This turbomolecular pump 100 is connected to a vacuum chamber (not shown) of a target device, such as a semiconductor manufacturing apparatus.

[0014] Figure 1 shows a longitudinal cross-sectional view of the turbomolecular pump 100. In Figure 1, the turbomolecular pump 100 has an intake port 101 formed at the upper end of a cylindrical outer cylinder 127. Inside the outer cylinder 127 is a rotating body 103, which has multiple rotating blades 102 (102a, 102b, 102c...) formed radially and in multiple stages around its circumference, serving as turbine blades for drawing in and exhausting gas. A rotor shaft 113 is attached to the center of this rotating body 103, and this rotor shaft 113 is suspended in the air and its position is controlled, for example, by a 5-axis controlled magnetic bearing.

[0015] The upper radial electromagnet 104 consists of four electromagnets arranged in pairs along the X and Y axes. Four upper radial sensors 107 are provided in close proximity to the upper radial electromagnet 104, each corresponding to one of the upper radial electromagnets 104. The upper radial sensors 107 are, for example, inductance sensors or eddy current sensors with conduction windings, and detect the position of the rotor shaft 113 based on the change in the inductance of these conduction windings, which changes according to the position of the rotor shaft 113. These upper radial sensors 107 are configured to detect the radial displacement of the rotor shaft 113, i.e., the rotating body 103 fixed to it, and send the data to the control device 200.

[0016] In this control device 200, for example, a compensation circuit having a PID adjustment function generates an excitation control command signal for the upper radial electromagnet 104 based on the position signal detected by the upper radial sensor 107, and the amplifier circuit 150 (described later) shown in Figure 2 controls the excitation of the upper radial electromagnet 104 based on this excitation control command signal, thereby adjusting the upper radial position of the rotor shaft 113.

[0017] The rotor shaft 113 is made of a high-permeability material (such as iron or stainless steel) and is attracted by the magnetic force of the upper radial electromagnet 104. This adjustment is performed independently in the X-axis and Y-axis directions. The lower radial electromagnet 105 and lower radial sensor 108 are arranged in the same way as the upper radial electromagnet 104 and upper radial sensor 107, and adjust the lower radial position of the rotor shaft 113 in the same way as the upper radial position.

[0018] Furthermore, axial electromagnets 106A and 106B are positioned above and below a disc-shaped metal disk (also called an "armature disk") 111 located at the bottom of the rotor shaft 113. The metal disk 111 is made of a highly permeable 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 sent to the control device 200.

[0019] Then, in the control device 200, for example, a compensation circuit having a PID adjustment function generates excitation control command signals for the axial electromagnets 106A and 106B based on the axial position signal detected by the axial sensor 109, and the amplifier circuit 150 excites the axial electromagnets 106A and 106B based on these excitation control command signals, so that the axial electromagnet 106A attracts the metal disk 111 upward with magnetic force, and the axial electromagnet 106B attracts the metal disk 111 downward, thereby adjusting the axial position of the rotor shaft 113.

[0020] Thus, the control device 200 appropriately adjusts the magnetic force exerted by the axial electromagnets 106A and 106B on the metal disk 111, causing the rotor shaft 113 to levitate axially and be held in contact with space. The amplifier circuit 150 that excites and controls 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, the motor 121 is equipped with multiple magnetic poles arranged circumferentially around the rotor shaft 113. Each magnetic pole is controlled by the control device 200 to rotate the rotor shaft 113 via the electromagnetic force acting between it and the rotor shaft 113. The motor 121 also incorporates a rotational speed sensor, such as a Hall element, resolver, or encoder (not shown), and the rotational speed of the rotor shaft 113 is detected by the detection signal from this rotational speed sensor.

[0022] Furthermore, for example, a phase sensor (not shown) is attached near the lower radial sensor 108 to detect the phase of rotation of the rotor shaft 113. The control device 200 uses both the detection signals from this phase sensor and the rotational speed sensor to detect the position of the magnetic pole.

[0023] Multiple fixed blades 123 (123a, 123b, 123c...) are arranged with a small gap (a predetermined interval) between them and the rotating blades 102 (102a, 102b, 102c...). Each of the rotating blades 102 (102a, 102b, 102c...) is formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transport exhaust gas molecules downward by collision.

[0024] Similarly, the fixed wing 123 is formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and is arranged alternately with the stages of the rotor blade 102 toward the inside of the outer cylinder 127. The outer edge of the fixed wing 123 is supported by being fitted between a plurality of stacked fixed wing spacers 125 (125a, 125b, 125c, etc.).

[0025] The fixed-wing spacer 125 is a ring-shaped member and is made of a metal such as aluminum, iron, stainless steel, or copper, or an alloy containing these metals as components. An outer cylinder 127 is fixed to the outer circumference of the fixed-wing spacer 125 with a small gap in between. A base portion 129 is provided at the bottom of the outer cylinder 127. An exhaust port 133 is formed in the base portion 129 and communicates with the outside. Exhaust gas that enters the intake port 101 from the chamber (vacuum chamber) side and is transferred to the base portion 129 is sent to the exhaust port 133.

[0026] Furthermore, depending on the application of the turbomolecular pump 100, a fixed disc 219 is provided between the lower part of the fixed-blade spacer 125 and the base portion 129. The fixed disc 219 is a disc-shaped member, and multiple Sigburn spiral groove portions 229 (Figure 5) are formed on its upper surface (the surface facing the rotating disc 220, which will be described later). The fixed disc 219 and the rotating disc 220 (described later) constitute the Sigburn-type exhaust mechanism 201, the details of which will be described later.

[0027] The base portion 129 is a disc-shaped component that forms the base of the turbomolecular pump 100, and is generally made of a metal such as iron, aluminum, or stainless steel. The base portion 129 not only physically holds the turbomolecular pump 100 but also functions as a heat conduction path, so it is desirable to use a metal that is rigid and has high thermal conductivity, such as iron, aluminum, or copper.

[0028] In this configuration, when the rotor blade 102 is rotated by the motor 121 together with the rotor shaft 113, exhaust gas is drawn in from the chamber through the intake port 101 due to the action of the rotor blade 102 and the fixed blade 123. The exhaust gas drawn in from the intake port 101 passes between the rotor blade 102 and the fixed blade 123 and is transferred to the base section 129. At this time, the temperature of the rotor blade 102 rises due to frictional heat generated when the exhaust gas comes into contact with the rotor blade 102 and heat conduction generated by the motor 121, but this heat is transferred to the fixed blade 123 side by radiation or conduction by gas molecules of the exhaust gas.

[0029] The fixed-wing spacers 125 are joined to each other at their outer circumference, and they transmit heat received by the fixed wing 123 from the rotor blade 102, as well as frictional heat generated when exhaust gases come into contact with the fixed wing 123, to the outside.

[0030] Furthermore, depending on the application of the turbomolecular pump 100, the gas drawn in from the intake port 101 may be directed to the upper radial electromagnet 104, upper radial sensor 107, motor 121, and lower radial electromagnet 1 05. To prevent intrusion into the electrical components, which consist of a lower radial sensor 108, axial electromagnets 106A and 106B, and an axial sensor 109, the electrical components are surrounded by a stator column 122, and the inside of this stator column 122 may be maintained at a predetermined pressure with purge gas.

[0031] In this case, a purge gas port (not shown) is provided in the base section 129, and purge gas is introduced through this piping. The introduced purge gas is sent to the exhaust port 133 through the gap 134 between the protective bearing 120 and the rotor shaft 113, between the rotor and stator of the motor 121, and between the inner cylindrical part of the rotor blade 102 (lower cylindrical part 103b of the rotating body) and the stator column 122 or base section 129.

[0032] Here, the turbomolecular pump 100 requires model identification and control based on individually adjusted unique parameters (e.g., characteristics corresponding to the model). To store these control parameters, the turbomolecular pump 100 is equipped with an electronic circuit section 141 within its body. The electronic circuit section 141 consists of electronic components such as semiconductor memory such as EEP-ROM and semiconductor elements for accessing it, and a substrate 143 for mounting them. This electronic circuit section 141 is housed, for example, below a rotational speed sensor (not shown) near the center of the base section 129 that constitutes the lower part of the turbomolecular pump 100, and is closed by an airtight bottom cover 145.

[0033] Incidentally, in the semiconductor manufacturing process, some process gases introduced into the chamber have the property of becoming solid when their pressure exceeds a predetermined value or their temperature falls below a predetermined value. Inside the turbomolecular pump 100, the exhaust gas pressure is lowest at the intake port 101 and highest at the exhaust port 133. If the process gas pressure exceeds a predetermined value or its temperature falls below a predetermined value while it is being transferred from the intake port 101 to the exhaust port 133, the process gas becomes solid and adheres to and accumulates inside the turbomolecular pump 100.

[0034] For example, if SiCl4 is used as the process gas in an Al etching apparatus, the low vacuum (760 [torr] ~ 10 -2 The vapor pressure curve shows that when the pressure is low (torr) and the temperature is low (approximately 20°C), solid products (e.g., AlCl3) precipitate and adhere to the inside of the turbomolecular pump 100. As a result, when precipitates of process gas accumulate inside the turbomolecular pump 100, these deposits narrow the pump flow path, causing a decrease in the performance of the turbomolecular pump 100. Furthermore, the aforementioned products were prone to solidifying and adhering in areas of high pressure, such as near the exhaust port 133 and near the fixed disc 219.

[0035] Therefore, in order to solve this problem, conventionally, a heater (not shown) or an annular water cooling pipe 149 is wrapped around the outer circumference of the base portion 129, and a temperature sensor (e.g., a thermistor) (not shown) is embedded in the base portion 129, and the heating of the heater and the cooling of the water cooling pipe 149 are controlled (hereinafter referred to as TMS; Temperature Management System) based on the signal from this temperature sensor to maintain the temperature of the base portion 129 at a constant high temperature (set temperature). In this embodiment, the fixed disc 219 is heated by a heater (not shown) embedded in the fixed disc 219, and the base portion 129 is cooled by a water cooling pipe 149 embedded in the bottom cover 145.

[0036] Next, we will describe an amplifier circuit 150 that energizes and controls the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B of the turbomolecular pump 100 configured in this way. The circuit diagram of this amplifier circuit is shown in Figure 2.

[0037] In Figure 2, the electromagnet winding 151 that constitutes the upper radial electromagnet 104, etc., has one end Transistor 161 is connected to the positive terminal 171a of power supply 171, and the other end is connected to the negative terminal 171b of power supply 171 via current detection circuit 181 and transistor 162. Transistors 161 and 162 are so-called power MOSFETs, and have a structure in which a diode is connected between their source and drain.

[0038] In this configuration, transistor 161 has its diode cathode terminal 161a connected to the positive terminal 171a, and its anode terminal 161b connected to one end of the electromagnet winding 151. Transistor 162 has its diode cathode terminal 162a connected to the current detection circuit 181, and its anode terminal 162b connected to the negative terminal 171b.

[0039] On the other hand, the diode 165 for current regeneration has its cathode terminal 165a connected to one end of the electromagnet winding 151, and its anode terminal 165b connected to the negative terminal 171b. Similarly, the diode 166 for current regeneration has its cathode terminal 166a connected to the positive terminal 171a, and its anode terminal 166b connected to the other end of the electromagnet winding 151 via the current detection circuit 181. The current detection circuit 181 is composed of, for example, a Hall sensor type current sensor or an electrical resistance element.

[0040] The amplifier circuit 150 configured as described above corresponds to one electromagnet. Therefore, if the magnetic bearing is 5-axis controlled and there are a total of 10 electromagnets 104, 105, 106A, and 106B, a similar amplifier circuit 150 is configured for each electromagnet, and the 10 amplifier circuits 150 are connected in parallel to the power supply 171.

[0041] Furthermore, the amplifier control circuit 191 is configured, for example, by a digital signal processor (hereinafter referred to as the DSP section) of the control device 200 (not shown), and this amplifier control circuit 191 is configured to switch transistors 161 and 162 on and off.

[0042] The amplifier control circuit 191 compares the current value detected by the current detection circuit 181 (the signal reflecting this current value is called the current detection signal 191c) with a predetermined current command value. Based on this comparison, it determines the magnitude of the pulse width (pulse width time Tp1, Tp2) to be generated within the control cycle Ts, which is one period of PWM control. As a result, gate drive signals 191a and 191b with this pulse width are output from the amplifier control circuit 191 to the gate terminals of transistors 161 and 162.

[0043] Furthermore, when the rotating body 103 passes a resonance point during accelerated rotational speed operation, or when disturbances occur during constant-speed operation, it is necessary to control the position of the rotating body 103 with high speed and strong force. For this reason, a high voltage of, for example, 50V 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 to stabilize the power supply 171 (not shown).

[0044] In this configuration, when both transistors 161 and 162 are turned on, the current flowing through the electromagnet winding 151 (hereinafter referred to as the electromagnet current iL) increases, and when both are turned off, the electromagnet current iL decreases.

[0045] Furthermore, by turning one of transistors 161 and 162 on and the other off, a so-called flywheel current is maintained. By allowing this flywheel current to flow through the amplifier circuit 150, the hysteresis loss in the amplifier circuit 150 is reduced, and the overall circuit... This allows for lower power consumption. Furthermore, by controlling transistors 161 and 162 in this way, high-frequency noise such as harmonics generated in the turbomolecular pump 100 can be reduced. In addition, by measuring this flywheel current with the current detection circuit 181, the electromagnet current iL flowing through the electromagnet winding 151 can be detected.

[0046] In other words, if the detected current value is smaller than the current command value, both transistors 161 and 162 are turned on only once during the control cycle Ts (e.g., 100 μs) for a duration corresponding to the pulse width time Tp1, as shown in Figure 3. Therefore, the electromagnet current iL during this period increases from the positive electrode 171a to the negative electrode 171b, towards the current value iLmax (not shown) that can flow through transistors 161 and 162.

[0047] On the other hand, if the detected current value is greater than the current command value, both transistors 161 and 162 are turned off only once during the control cycle Ts for a duration corresponding to the pulse width time Tp2, as shown in Figure 4. Therefore, during this period, the electromagnet current iL decreases from the negative electrode 171b towards the positive electrode 171a, towards a regenerative current value iLmin (not shown) via diodes 165 and 166.

[0048] In either case, after the pulse width time Tp1 and Tp2 have elapsed, one of transistors 161 or 162 is turned on. Therefore, during this period, the flywheel current is maintained in the amplifier circuit 150.

[0049] The turbomolecular pump 100, having this basic configuration, has an intake section on the upper side (the side with the intake port 101) in Figure 1 that connects to the target equipment, and an exhaust section on the lower side (the side where the exhaust port 15, which constitutes the exhaust port 133, is provided on the base portion 129 so that it protrudes to the right in the figure) that connects to an auxiliary pump (back pump), etc., which is not shown. Furthermore, the turbomolecular pump 100 can be used not only in the vertical position shown in Figure 1, but also in an inverted position, a horizontal position, and an inclined position.

[0050] Furthermore, in the turbomolecular pump 100, the aforementioned outer cylinder 127 and base portion 129 are combined to form a single case. In the following, both the outer cylinder 127 and base portion 129 may be collectively referred to as the "casing" or "main casing." Alternatively, the outer cylinder 127 or the base portion 129 may be referred to as the "casing" alone. The turbomolecular pump 100 is electrically (and structurally) connected to a box-shaped electrical case (not shown), and the aforementioned control device 200 is incorporated into the electrical case.

[0051] The internal structure of the main casing of the turbomolecular pump 100 (here, a combination of the outer cylinder 127 and the base part 129) can be divided into a rotating mechanism 136 that rotates the rotor shaft 113 etc. by the motor 121, and an exhaust mechanism 137 that is rotationally driven by the rotating mechanism 136. Furthermore, the exhaust mechanism 137 can be considered as being divided into a turbomolecular pump mechanism 138 composed of rotating blades 102 and fixed blades 123 etc., and a screw groove pump mechanism (Sigburn type exhaust mechanism 201) composed of a fixed disc 219 and a rotating disc 220 etc.

[0052] Furthermore, the aforementioned purge gas (protective gas) is used to protect the bearing parts and the rotor blades 102, preventing corrosion caused by exhaust gas (process gas) and cooling the rotor blades 102. This purge gas can be supplied using conventional methods.

[0053] For example, the aforementioned purge gas port (not shown) extending linearly in the radial direction is provided at a predetermined location on the base portion 129 (such as at a position 90 or 120 degrees away from the exhaust port 133). Then, purge gas is supplied to this purge gas port (not shown) from the outside of the base portion 129 via a purge gas cylinder (such as an N2 gas cylinder) or a flow regulator (valve device). do.

[0054] The aforementioned protective bearing 120 is also called a "touchdown (T / D) bearing" or "backup bearing." These protective bearings 120 prevent the rotor shaft 113 from changing position or attitude significantly, and protect the rotor blades 102 and their surrounding parts from damage, even in the event of an electrical system malfunction or atmospheric re-entry.

[0055] Note that in Figure 1, which shows the structure of the turbomolecular pump 100 and the rotating body 103, the hatching indicating the cross-section of the parts has been omitted to avoid making the drawing too complex.

[0056] <Foreign Matter Accumulation Sensor 250> The turbomolecular pump 100 shown in Figure 1 is equipped with a foreign matter accumulation sensor 250. In the example shown in Figure 1, the foreign matter accumulation sensor 250 is located in the Sigburn-type exhaust mechanism 201. Below, we will first describe the basic configuration of the Sigburn-type exhaust mechanism 201, and then describe the foreign matter accumulation sensor 250.

[0057] <<Sigburn-type exhaust mechanism section 201>> The Sigburn-type exhaust mechanism 201 is a Sigburn-type exhaust mechanism and is formed to be spatially continuous with the turbomolecular pump mechanism 138, immediately following (downstream). In the Sigburn-type exhaust mechanism 201 shown in the example in Figure 1, gas is transported radially with respect to the axis of the rotor shaft 113.

[0058] The Sigburn-type exhaust mechanism 201 includes a fixed disc 219 and a rotating disc 220. The rotating disc 220 is integrally formed with the rotating body 103 and is flat in shape. Furthermore, the rotating disc 220 protrudes radially from the rotating body 103. In this embodiment, the material of the rotating disc 220 is the same as the material of the rotating body 103, for example, a metal such as aluminum, iron, stainless steel, or copper, or an alloy containing these metals as components.

[0059] The rotating disk 220 rotates in the same direction as the rotor shaft 113 and the rotating body 103 as the rotating body 103 rotates. The rotating disk 220 then rotates integrally with the rotor blades 102 (102a, 102b, 102c, etc.).

[0060] The fixed disc 219 is integrally assembled to the main casing (a combination of the outer cylinder 127 and the base portion 129). The fixed disc 219 is fixed in place, sandwiched between an annular spacer 225 and an annularly protruding portion of the base portion 129. The fixed disc 219 has a through hole 226 (Figure 5) in its center, through which the aforementioned stator column 122 passes. As shown in Figure 1, the fixed disc 219 and the rotating disc 220 face each other in parallel. As shown in an enlarged view in Figure 6, a gas passage 227 is formed between the fixed disc 219 and the rotating disc 220.

[0061] The material of the fixed disk 219 can be the same as that of the rotating disk 220, for example, metals such as aluminum, iron, stainless steel, copper, or alloys containing these metals as components.

[0062] As shown in Figures 1, 5, and 6, numerous rectangular ridges 228 are formed between the fixed disc 219 and the rotating disc 220. In this embodiment, the ridges 228 are integrally formed with the fixed disc 219. Between adjacent ridges 228, Sigburn spiral grooves 229, which are spiral groove channels, are formed, as schematically shown in Figure 5.

[0063] Multiple Sigburn spiral grooves 229 are formed on the fixed disc 219 in a curved, radial pattern. Furthermore, the Sigburn spiral grooves 229 are formed such that the flow path gradually narrows from the radially outer side (outer circumference) to the inner side (inner circumference) of the fixed disc 219. The gas introduced into the gas flow path 227 is then transported from the outer circumference to the inner circumference while being compressed as the rotor shaft 113 and rotor blades 102 rotate.

[0064] The gas transferred to the inner circumference passes through the through-holes 226 from each Sigburn spiral groove 229. The gas is then discharged from the through-holes 226 into the base internal exhaust passage 260 formed inside the base portion 129 (Figure 1). The base internal exhaust passage 260 is spatially connected to the outside of the turbomolecular pump 100 via the exhaust port 133.

[0065] In this embodiment, as described above, the protruding portion 228 is formed on the fixed disc 219. However, it is not limited to this, and the protruding portion 228 may be formed on the rotating disc 220, and the opposing surface of the fixed disc 219 that faces the rotating disc 220 may be formed flat. Also, in this embodiment, there is one set of fixed disc 219 and rotating disc 220, but the Sigburn-type exhaust mechanism 201 may be composed of multiple sets of fixed discs 219 and rotating discs 220.

[0066] <<Configuration and Function of Foreign Matter Accumulation Sensor 250>> Next, the configuration and function of the foreign matter accumulation sensor 250 will be described. In the example foreign matter accumulation sensor 250 shown in Figure 1, the fixed disc 219 and the rotating disc 220 facing the gas flow path 227 are part of the components of the foreign matter accumulation sensor 250.

[0067] Figure 6 shows a magnified view of the foreign matter accumulation sensor 250 enclosed by the dotted rectangular frame in Figure 1. The foreign matter accumulation sensor 250 includes a fixed disc 219 (first conductive component), an electrode 252, a first conductor 254, a rotating disc 220 (second conductive component), and a second conductor 256.

[0068] As mentioned above, the fixed disk 219 and the rotating disk 220 are made of a metal such as aluminum, or an alloy containing such a metal as a component. Furthermore, the fixed disk 219 and the rotating disk 220 are electrically conductive components.

[0069] The electrode 252 is formed, for example, in the shape of a rectangular plate. Various shapes can be used for the electrode 252, such as a parallelogram, trapezoid, triangular, or circular shape. In the example shown in Figure 5, the electrode 252 is formed in a perfect circle. The thickness t0 of the electrode 252 is, for example, about 1 mm. The electrode material can be, for example, metals such as aluminum, iron, stainless steel, or copper, or alloys containing these metals as components. Furthermore, other materials can be used as electrode materials, as long as they have sufficient conductivity.

[0070] The electrode 252 is positioned in a portion of the bottom 232 of the Sigburn spiral groove 229 on the fixed disc 219. A recess 234 is formed in a portion of the bottom 232 of the Sigburn spiral groove 229, and the electrode 252 is housed in the recess 234.

[0071] The electrode 252 is positioned such that its surface 262 is flush with the bottom 232 of the Sigburn spiral groove 229. Furthermore, a predetermined gap (air gap) t1 is interposed between the electrode 252 and the rotating disk 220. The surface 262 of the electrode 252 and the rotating disk 220 are parallel to each other and form a gas flow path 227.

[0072] As mentioned above, a gap t2 is interposed between the fixed disk 219 and the rotating disk 220. This gap t2 is the gap between the bottom 232 of the Sigburn spiral groove 229 in the fixed disk 219 and the rotating disk 220. In the example in Figure 6, the size of gap t2 is the same as gap t1. Also, since the fixed disk 219 and the rotating disk 220 are facing each other in parallel, the size of gap t2 is constant.

[0073] The recess 234 formed at the bottom 232 of the Sigburn spiral groove 229 is formed in a stepped shape that narrows towards the back. The recess 234 houses a first insulating collar 266 made of an electrically insulating material (insulating material). The first insulating collar 266 is formed in a cylindrical shape (for example, a cylindrical shape).

[0074] One axial end of the first insulating collar 266 (the upper end in Figure 6) protrudes slightly from the bottom 232 of the Sigburn spiral groove 229 and is in contact with the back surface 264 of the electrode 252. The other axial end of the first insulating collar 266 (the lower end in Figure 6) is in contact with the fixed disc 219. The electrode 252 is floating parallel to the bottom 232 of the Sigburn spiral groove 229.

[0075] A gap (air gap) t3 of a predetermined interval is interposed between the electrode 252 and the bottom 235 (fixed disc 219) of the recess 234. Furthermore, the back surface 264 of the electrode 252 and the bottom 235 of the recess 234 constitute a gas passage 227. In addition, the electrode 252 is provided with multiple gas passage holes 267 that penetrate in the thickness direction and spatially connect the gas passage 227 and the gap t3. Note that the symbols "t1" to "t3" related to the gaps t1 to t3 may be used not only to mean the symbols of the gaps but also to indicate the size of the gaps.

[0076] The shaft portion 268b of the fixing bolt 268 passes through the electrode 252 and the first insulating collar 266. The shaft portion 268b of the fixing bolt 268 passes through the fixing disc 219 in the thickness direction of the fixing disc 219 and protrudes from the back surface (the surface on the exhaust port 133 side) 270 of the fixing disc 219.

[0077] On the back surface 270 of the fixed disc 219, a second insulating collar 272, a crimp terminal 274, and a nut 276 are arranged. The shaft portion 268b of the fixed bolt 268 passes through the second insulating collar 272 and the crimp terminal 274.

[0078] The second insulating collar 272 is made of an electrically insulating material (insulating material). One axial end of the second insulating collar 272 (the upper end in Figure 6) is in contact with the back surface 270 of the fixed disc 219. The other axial end of the second insulating collar 272 (the lower end in Figure 6) is in contact with the crimp terminal 274.

[0079] The tip of the shaft portion 268b of the fixing bolt 268 is screwed into the nut 276. The electrode 252, the first insulating collar 266, the second insulating collar 272, and the crimp terminal 274 are fixed to the fixing disc 219, sandwiched between the head 268a of the fixing bolt 268 and the nut 276.

[0080] A first conductor 254 is electrically connected to a crimp terminal 274. The first conductor 254 is electrically connected to a predetermined conductive pin 278 of a male connector member 280 shown in Figure 1. The male connector member 280 is mounted on a base portion 129. A female connector member 284 of an electrical cable 282 is connected to the male connector member 280.

[0081] The electrode 252, the fixing bolt 268, and the crimp terminal 274 are electrically connected to the male connector member 280 via the first conductor 254. Furthermore, these electrodes 252, the fixing bolt 268, and the crimp terminal 274 are electrically insulated from the fixing disc 219 by the first insulating collar 266 and the second insulating collar 272.

[0082] As shown in Figure 1, a crimp terminal 281 is fixed to the base portion 129, and a second conductor 256 is electrically connected to the crimp terminal 281. The second conductor 256 is electrically connected to a predetermined conductive pin 279 of the male connector member 280 described above.

[0083] A voltage is applied to electrode 252 via the first conductor 254. As mentioned above, a gap t1 is formed between electrode 252 and the rotating disk 220, so electrode 252 and the rotating disk 220 constitute a capacitor C1, as schematically shown in Figure 7.

[0084] Furthermore, a voltage is applied to the fixed disk 219 via the second conductor 256. As mentioned above, a gap t2 is formed between the fixed disk 219 and the rotating disk 220, so the fixed disk 219 and the rotating disk 220 constitute a capacitor C2, as shown in Figure 7.

[0085] Furthermore, as mentioned above, a gap t3 is formed between the electrode 252 and the fixed disc 219, so the electrode 252 and the fixed disc 219 constitute a capacitor C3, as shown in Figure 7.

[0086] Here, Figure 7 shows a model in which the second conductor 256 is connected to the fixed disc 219. In contrast, in Figures 1 and 6, the second conductor 256 is connected to the base portion 129, and the base portion 129 is in electrically conductive contact with the fixed disc 219. In other words, with respect to the connection of the second conductor 256, the model in the example in Figure 7 and the embodiments in the examples in Figures 1 and 6 are electrically equivalent. Therefore, in the following explanations, unless there are special circumstances, we will not distinguish between the embodiments in the examples in Figures 1 and 6 and the model in the example in Figure 7 with respect to the connection of the second conductor 256.

[0087] Furthermore, the second conductor 256 may be directly connected to a conductive component (such as a fixed disc 219) to which the electrode 252 is attached. However, if this conductive component is electrically connected to the casing (such as the outer cylinder 127 or the base portion 129) or is electrically connected to the casing, the second conductor 256 may be attached to the outside of the casing (towards the atmosphere).

[0088] <<Theoretical model of capacitors C1-C3>> Figure 7(b) shows the theoretical model of capacitors C1 to C3 in Figure 7(a). When a voltage is applied to each capacitor C1 to C3, gaps t1 to t3 are formed between each capacitor C1 to C3, and a charge corresponding to the potential difference and capacitance is accumulated on each capacitor C1 to C3. The charge is expressed by the following equation (1). Q(=CV) (1) C: Capacitance V: Potential difference

[0089] The potential difference V is known. Therefore, by detecting (measuring) the charge Q and performing the calculation (C = Q / V), the capacitance C can be determined. Furthermore, by calculating the difference between the capacitances calculated at different time points, the change in capacitance C (ΔC) within that time period and the slope of the line representing the change in capacitance C can be determined.

[0090] As shown in Figure 7(b), capacitor C1 (the capacitor between electrode 252 and rotating disk 220) and capacitor C2 (the capacitor between fixed disk 219 and rotating disk 220) are connected in series. Capacitor C3 (the capacitor between electrode 252 and fixed disk 219) is connected in parallel with capacitors C1 and C2.

[0091] Combined capacitance C of capacitors C1 to C3 all This can be expressed as shown in equation (2) below. C all ={1 / ((1 / C1)+(1 / C2))}+C3 ={C1 / (1+C1 / C2)}+C3(2) In this case, if C2 >> C1, C all ≒C 1+ C3(3) This is the result.

[0092] In general, the capacitance of a capacitor can be expressed using the area of ​​the opposing conductors and the distance between them, as shown in equation (4) below. C n =ε×ε r ×A / d (4) The meanings of the symbols in this formula (4) are as follows. C n : Capacitance ε: Permittivity of free space ε r : Permittivity of the substance between conductors (relative permittivity) A: Opposing area of the conductors d: Distance between the conductors

[0093] In this embodiment, the substance between the conductors corresponds to the foreign matter to be deposited. Also, the distance d between the conductors corresponds to the gaps (sizes) t1 to t3 in the capacitors C1 to C3.

[0094] The opposing area A of the conductors corresponds to the area of the surface 262 of the electrode 252 (hereinafter referred to as "area A1") in the capacitor C1. Also, in the capacitor C2, it corresponds to the opposing area of the fixed disk 219 and the rotating disk 220 (hereinafter referred to as "area A2").

[0095] Here, regarding the area of the fixed disk 219, it is conceivable to use the total area of the bottom 232 of the sigmaburn spiral groove portion 229, etc. However, as in the above-mentioned formula (3), when C2 >> C1, the combined capacitance C all ≈ C 1+ becomes C3 、 The area of the fixed disk 219 has all little influence on the combined capacitance C. Therefore, it is possible to omit precisely defining the area of the fixed disk 219.

[0096] Also, in the capacitor C3, the opposing area A of the conductors (hereinafter referred to as "area A3") corresponds to the area of the portion of the back surface 264 of the electrode 252 that protrudes outward from the first insulating collar 266 and is exposed and faces the bottom 235 of the recess 234.

[0097] The magnitude relationship of the opposing areas A1 to A3 of the conductors related to the capacitors C1 to C3 is A2 >> A1, A2 >> A3, and A1 > A3.

[0098] <<Estimation of foreign matter deposition amount>> Figure 8 shows, from top to bottom, the state in which foreign matter accumulates in the foreign matter accumulation sensor of this embodiment. As shown in the upper figure, the gas flowing through the gas channel 227 (indicated by arrow D) passes through the gap t1 between the electrode 252 and the rotating disk 220, the gap t2 between the fixed disk 219 and the rotating disk 220, and the gap t3 between the electrode 252 and the fixed disk 219.

[0099] As shown in the middle diagram, the foreign material, sediment E, gradually accumulates on the surface of the fixed disk 219, the surface 262 of the electrode 252, and the back surface 264 of the electrode 252. As the thickness (amount) of sediment E increases, the narrowest gap among the gaps t1 to t3, the gap t3 between the electrode 252 and the fixed disk 219 (below the electrode), is filled with sediment E. The middle diagram schematically shows the state where the gap t3 between the electrode 252 and the fixed disk 219 is filled, and spaces remain in the other gaps t1 and t2 that are not yet filled with sediment E. Furthermore, the accumulation As it progresses, electrode 252 becomes completely embedded in sediment E, as shown in the lower diagram.

[0100] Here, sediment (sediment E) also accumulates on the tip surface 228a of the ridge 228 in the fixed disc 219 in Figure 6. The size of the gap (not shown) between the tip surface 228a of the ridge 228 and the rotating disc 220 is set to be larger than the gap t3.

[0101] The size of the gap (symbol omitted) between the tip surface 228a of the protruding portion 228 and the rotating disk 220 can be calculated simply by subtracting the amount of protrusion of the protruding portion 228 from the gap t2 between the fixed disk 219 and the rotating disk 220.

[0102] Figure 9 is an example of a graph showing the relationship between sediment thickness and capacitance. The horizontal axis represents the thickness of the sediment E (sediment thickness), and the vertical axis represents the equivalent capacitance C. all This indicates the equivalent capacitance C. all As the deposition thickness increases, d (distance between conductors) in equation (4) above decreases, and therefore increases.

[0103] Furthermore, as the deposition thickness increases and the gap t3 between the electrode 252 and the fixed disc 219 is filled, as shown in the middle and lower diagrams of Figure 8, C3 in equation (3) above saturates and becomes a constant value. The value at that time is C 3S Therefore, the equivalent capacitance C all This can be expressed as shown in equation (5) below. C all ≒C 1+ C 3S (5)

[0104] Therefore, as shown in Figure 9, the equivalent capacitance C all The increasing trend related to changes, the slope of the curve changes, and an inflection point F appears. In other words, as in this embodiment, one of the gaps t1 to t3 (here, gap t3) is changed to the other gaps (here, gap t 1、 By setting it smaller than t2) and allowing it to be filled with sediment E before other gaps, the capacitance of gap t3 can be selectively saturated. Then the combined capacitance C all It becomes possible to make an inflection point F appear on the curve.

[0105] Furthermore, since the size of the gap t3 between the electrode 252 and the fixed disk 219 is known, it is possible to estimate that the amount of sediment E deposited at the time the inflection point F appears is the same as the size of the gap t3.

[0106] Here, inflection point F in Figure 9 represents an inflection point related to a certain type of sediment (here referred to as sediment E1), and the other inflection point G represents an inflection point related to another type of sediment (here referred to as sediment E2). Inflection points F and G appear when the same sediment thickness is used with a foreign matter sediment amount sensor 250 of the same configuration and dimensions. However, the rate of change (slope, gradient) of the part other than the inflection point differs depending on the type (composition) of the sediment, and the combined capacitance C at the inflection point all They are also different.

[0107] Assuming that the amount of sediment E at the inflection point is the same as the size of the gap t3, the equivalent capacitance C at the inflection point is allUsing the dielectric constant ε of the sediment, r It is possible to estimate this.

[0108] At the inflection point, it is possible to estimate that deposits with a thickness t3 have accumulated inside capacitor C1. Therefore, the capacitance of capacitor C1 is equal to the capacitance of capacitor C1 with a gap t3 filled with deposits inside. 1a And, in the gap t1-t3, C is not filled with sediment inside. 1b Assuming they are connected in series, they can be expressed as shown in equations (6) to (8) below. C 1a =ε×ε r ×A1 / t3(6) C 1b =ε × 1 × A1 / (t1-t3) (7) C1 = {1 / ((1 / C 1a )+(1 / C 1b ))}(8)

[0109] On the other hand, at the inflection point, the capacitor C3 can be expressed as shown in equation (9) below. C 3S =ε×ε r ×A3 / t3(9) Using equations (5) to (9) above, the dielectric constant ε of the sediment is r Because it is possible to estimate this, the amount of sediment E can be estimated even when the dielectric constant of the sediment is not known in advance.

[0110] The various calculations related to the estimation of the amount of foreign matter accumulation described above can be performed in the control device 200 (Figure 1) by connecting the foreign matter accumulation sensor 250 to the control device 200. The various calculations include calculations using calculation formulas that include conversion factors. The control device 200 calculates the equivalent capacitance C before and after the appearance of inflection points F and G. all Based on this, the changes are monitored, and if inflection points F and G appear, it is determined that the gap t3 is filled with foreign matter (sediment).

[0111] The control device 200 estimates the dielectric constant of foreign matter (deposits) from the capacitance when the gap t3 is filled with foreign matter (e.g., the equivalent capacitance when inflection points F and G appear), based on the trend of capacitance change (e.g., the slope of the straight line).

[0112] Furthermore, it is possible to use computer equipment other than the control device 200 (not shown) to perform various calculations related to the estimation of foreign matter accumulation. The computer equipment may also output the results of the various calculations related to the estimation of foreign matter accumulation to the control device 200.

[0113] Furthermore, the aforementioned computer equipment can also include inspection terminals carried by maintenance workers. Maintenance workers can include those who maintain the turbomolecular pump 100, and those who maintain the vacuum exhaust system including these. Computer equipment can be considered as part of the turbomolecular pump 100 or the control device 200, regardless of whether it communicates via wired or wireless connections.

[0114] <Typical advantages of the foreign matter accumulation sensor 250 and turbomolecular pump 100 according to the first embodiment> According to the foreign matter accumulation sensor 250 of the first embodiment described above, and the turbomolecular pump 100 (vacuum pump) equipped with the foreign matter accumulation sensor 250, it is possible to form the foreign matter accumulation sensor 250 between the rotating disc 220, which is a rotating part, and the fixed disc 219, which is a non-rotating part (fixed part). Therefore, it becomes possible to effectively detect the amount of foreign matter accumulation in a small space. Furthermore, by performing calculations using the detection results of the foreign matter accumulation sensor 250, it becomes possible to estimate the amount of foreign matter accumulation.

[0115] Furthermore, a foreign matter accumulation sensor 250 can be formed using a rotating component (in this case, a rotating disc 220), which increases the degree of flexibility regarding the installation location of the foreign matter accumulation sensor 250.

[0116] Furthermore, since the amount of foreign matter accumulated inside the turbomolecular pump 100 can be estimated, the operating status of the pump can be understood, making it easier to plan maintenance for the turbomolecular pump 100. In addition, it is possible to prevent situations such as the turbomolecular pump 100 suddenly stopping due to contact between the rotor blades 102 (102a, 102b, 102c, etc.) and the accumulated matter (foreign matter).

[0117] Furthermore, a gap t3 is provided between the electrode 252 and the component on which the electrode 252 is installed (for example, the fixed disc 219), and since this gap t3 is smaller than the other gaps t1 and t2, it is possible to fill the gap t3 with sediment (foreign matter) first. In addition, the electrode 252 Since a gas passage hole 267 is provided, it is easy to guide gas from the gas passage 227 into the gap t3.

[0118] Furthermore, from the relationship between deposition thickness and equivalent capacitance shown in Figure 9, it is possible to derive the dielectric constant of the sediment based on the inflection points (e.g., inflection points F and G) in the curve of equivalent capacitance. Based on the dielectric constant, the type of sediment (type of gas) can then be estimated. Generally, the dielectric constant of sediment varies depending on the type and properties of the sediment, but if the type and properties of the sediment are not known in advance, the type and properties of the sediment can be estimated from the relationship between deposition thickness and equivalent capacitance at the inflection points (e.g., inflection points F and G).

[0119] Furthermore, it is possible to correct the conversion factor (for example, from 1.0 to 0.5) based on the trend (e.g., slope) of the equivalent capacitance after the inflection point (e.g., inflection point F, G).

[0120] Furthermore, by sufficiently separating the first conductor 254 and the second conductor 256, parasitic capacitance between the conductors can be reduced. And the combined capacitance C due to the accumulation of foreign matter (sediment E) all This makes it easier to detect increases.

[0121] <Principle model of the foreign matter accumulation sensor 250 of the first embodiment> Here, the principle of the foreign matter accumulation sensor 250 of this embodiment will be explained based on Figure 10. The four figures in Figure 10, from the top to the bottom, show the evolution of the principle model related to the foreign matter accumulation sensor 250. In Figure 10, parts that functionally correspond to the configuration of the foreign matter accumulation sensor 250 are given the same reference numerals, even if they have different names.

[0122] The top diagram in Figure 10 simply shows the first electrode 252 and the second electrode 253 facing each other with a gap between them. The first electrode 252 is electrically connected to the first conductor 254, and the second conductor 256 is electrically connected to the second electrode 253. In the model shown in the top diagram of Figure 10, there are no rotating parts yet, so it has not yet reached the same configuration as the foreign matter accumulation sensor 250 according to the first embodiment.

[0123] In the second diagram from the top in Figure 10, the first electrode 252 and the second electrode 253 are installed on the first conductive component 219 via electrically insulating insulators 266 and 272. The first electrode 252 and the second electrode 253 face the second conductive component 220 with a gap t1 (=t2) of the same size between them. The second conductive component 220 is a component (rotating component) that can rotate (horizontal rotation in the figure) because the conductors 254 and 256 are not connected in a way that allows current to flow.

[0124] The gap t1 (=t2) between the first electrode 252 and the second conductive component 220 serves as a gas flow path 227. The first conductor 254 is electrically connected to the first electrode 252, and the second conductor 256 is electrically connected to the second electrode 253.

[0125] As indicated by the same reference numerals as the foreign matter accumulation sensor 250, the first conductive component 219 corresponds to the fixed disk 219, and the second conductive component 220 corresponds to the rotating disk 220. The first electrode 252 corresponds to electrode 252, and the second electrode 253 corresponds to the portion of the fixed disk 219 facing the rotating disk 220. They are installed via electrically insulating insulators 266 and 272. The first electrode 252 and the second electrode 253 face the second conductive component 220 with a gap t1 (=t2) of the same size between them.

[0126] From this principle model, it is possible to extract the following inventions. It is possible to configure the gas flow path (gas flow path 227, etc.) inside the vacuum pump in a non-rotating state. A first conductive part (such as the first conductive component 219), and an electrode (such as the first electrode 252), The first conductive part and a second conductive part (such as a second conductive component 220) facing the electrode and capable of forming the gas flow path in a rotating state, A first conductor (such as the first conductor 254) connected to the electrode, The device comprises a second conductor (such as a second conductor 256) connected to the first conductive part, A foreign matter deposit sensor (such as a foreign matter deposit sensor 250) that enables estimation of the amount of foreign matter deposited from the change in capacitance between the first conductive part, the second conductive part, and the electrode.

[0127] More precisely, it is desirable to remove the outer periphery of the insulator 266 to form the aforementioned gap t3 between the first electrode 252 and the first conductive component 219.

[0128] In the third diagram from the top in Figure 10, the second electrode 253 in the second diagram is integrated with the first conductive component 219. The second conductor 256 is connected to the first conductive component 219.

[0129] In the fourth diagram from the top (the bottom diagram) in Figure 10, a gap t3 is formed between the first electrode 252 and the bottom 235 of the recess 234 formed in the first conductive component 219. In addition, multiple gas passage holes 267 are formed in the first electrode 252.

[0130] The second to fourth rows of figures in Figure 10 represent the broader conceptual invention of the foreign matter accumulation sensor 250 according to the first embodiment, as well as embodiments of that invention. The second to fourth rows of figures in Figure 9 approach the foreign matter accumulation sensor 250 according to the first embodiment in ascending order, but the example in the fourth row of figures shows the principle model that is closest to the foreign matter accumulation sensor 250 according to the first embodiment.

[0131] <Second Embodiment> Next, the foreign matter accumulation sensor 450 and the turbomolecular pump 300 according to the second embodiment of the present invention will be described with reference to Figure 11. Note that parts similar to those in the first embodiment are denoted by the same reference numerals, and their descriptions are omitted as appropriate.

[0132] <<Holbeck-type exhaust mechanism 401>> Figure 11 shows the foreign matter accumulation sensor 450 and the turbomolecular pump 300 according to the second embodiment. In the example of Figure 9, the foreign matter accumulation sensor 450 is provided in the Holbeck-type exhaust mechanism 401. Below, the basic configuration of the Holbeck-type exhaust mechanism 401 will be described first, followed by a description of the foreign matter accumulation sensor 450.

[0133] <<Holbeck-type exhaust mechanism 401>> The Holbeck-type exhaust mechanism 401 is a Holbeck-type exhaust mechanism and is formed to be spatially continuous with the turbomolecular pump mechanism 138, immediately following (downstream). In the Holbeck-type exhaust mechanism 401 example shown in Figure 11, gas is transported axially with respect to the axis of the rotor shaft 113.

[0134] The Holbeck-type exhaust mechanism 401 in the example shown in Figure 11 has a threaded spacer 131 and a lower cylindrical part 103b of the rotating body. The threaded spacer 131 is positioned between the lower part of the fixed-wing spacer 125 and the base part 129. The threaded spacer 131 is a cylindrical member made of a metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals, and has multiple helical screw grooves 131a engraved on its inner circumferential surface. The direction of the helix of the screw grooves 131a is such that when exhaust gas molecules move in the direction of rotation of the rotating body 103, these molecules are transported toward the exhaust port 133.

[0135] A lower cylindrical portion 103b of the rotating body hangs down from the lower part of the rotating body body 103a, on which the rotor blades 102 (102a, 102b, 102c...) of the rotating body 103 are formed. The outer circumferential surface of this lower cylindrical portion 103b is cylindrical and protrudes toward the inner circumferential surface of the threaded spacer 131, and is in close proximity to the inner circumferential surface of the threaded spacer 131 with a predetermined gap between them. In this embodiment, the material of the lower cylindrical portion 103b of the rotating body is the same as the material of the rotating body 103, for example, a metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components. The exhaust gas that has been transported to the screw groove 131a by the rotor blades 102 and the fixed blades 123 is guided by the screw groove 131a and sent to the base portion 129.

[0136] In the above description, the threaded spacer 131 was described as being positioned on the outer circumference of the lower cylindrical portion 103b of the rotating body 103, with a threaded groove 131a engraved on the inner surface of the threaded spacer 131. However, conversely, there are also cases where a threaded groove is engraved on the outer circumference of the lower cylindrical portion 103b of the rotating body, and a spacer having a cylindrical inner surface is positioned around it.

[0137] <<Configuration and Function of Foreign Matter Accumulation Sensor 450>> Next, the configuration and function of the foreign matter accumulation sensor 450 will be described. In the example foreign matter accumulation sensor 450 shown in Figure 11, the threaded spacer 131 and the lower cylindrical part 103b of the rotating body are part of the components of the foreign matter accumulation sensor 450.

[0138] Figure 12 shows a magnified view of the foreign matter accumulation sensor 450 enclosed by a dotted rectangular frame in Figure 11. The foreign matter accumulation sensor 450 includes a screwed spacer 131 (first conductive component), an electrode 252, a first conductor 254, a lower cylindrical part 103b of a rotating body (second conductive component), and a second conductor 256.

[0139] The foreign matter accumulation sensor 450 according to the second embodiment differs significantly from the foreign matter accumulation sensor 250 according to the first embodiment (Figures 1 and 6) in that the fixed disc 219 and rotating disc 220 of the first embodiment are replaced with a threaded spacer 131 and the lower cylindrical part 103b of the rotating body, and the axial directions of the electrode 252, first insulating collar 266, fixing bolt 268, second insulating collar 272, crimp terminal 274, and nut 276 are directed radially toward the rotating body 103, etc.

[0140] Furthermore, in the foreign matter accumulation sensor 450 according to the second embodiment, an electrode holder 452 is partially attached to the screwed spacer 131, and an electrode 252, a first insulating collar 266, a fixing bolt 268, a second insulating collar 272, and a crimp terminal 274 are mounted on this electrode holder 452. The fixing bolt 268 penetrates the electrode holder 452 in the thickness direction. The electrode holder 452 can be made of a metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals.

[0141] In the foreign matter accumulation sensor 450 according to the second embodiment, the electrode 252 and the lower cylindrical portion 103b of the rotating body constitute a capacitor C1, the threaded spacer 131 and the lower cylindrical portion 103b of the rotating body constitute a capacitor C2, and the electrode 252 and the threaded spacer 131 constitute a capacitor C3.

[0142] In the example shown in Figure 12, the gap t2 is not constant because the bottom of the screw groove 131a in the threaded spacer 131 is inclined with respect to the axis of rotation. For this reason, it is possible to use the average value of the gap t2 from one end (the lower end in Figures 11 and 12) to the other end (the upper end in Figure 11) of the threaded spacer 131 as the value of the gap t2. However, as in equation (3) above, when C2 >> C1, the equivalent capacitance C all ≒C 1+ It becomes C3. 、 The area of ​​the screw-type spacer 131 is equal to the equivalent capacitance C. all It does not have much effect. Therefore, the area of ​​the screw-type spacer 131 can be omitted from being strictly defined.

[0143] The combined capacitance of capacitors C1 to C3 can be determined in the same way as in the first embodiment. Then, by applying the same calculations as in the invention according to the first embodiment, it is possible to estimate the amount of foreign matter (deposits) deposited.

[0144] Furthermore, the principle model of the first embodiment shown in Figure 10 can be used as the principle model of the foreign matter accumulation sensor 450 according to the second embodiment by rotating the orientation of the figure 90 degrees to the right.

[0145] <Inventions that can be extracted from the embodiments> From the embodiments described above, the following inventions can be extracted. (1) A first conductive part (fixed disc (first conductive part) 219, screw spacer 131, etc.) and an electrode (electrode (first electrode) 252, etc.) that can constitute a gas flow path (gas flow path 227, etc.) in a non-rotating state within a vacuum pump (turbomolecular pump 100, 300, etc.), The first conductive part and a second conductive part (rotating disc (second conductive component) 229, lower cylindrical part 103b of the rotating body, etc.) facing the electrode and capable of forming the gas flow path in a rotating state, A first conductor (such as the first conductor 254) connected to the electrode, The device comprises a second conductor (such as a second conductor 256) connected to the first conductive part, A foreign matter deposit amount sensor that enables estimation of the amount of foreign matter (deposits E, E1, E2, etc.) deposited from the change in capacitance between the first conductive part, the second conductive part, and the electrode. (2) The area of ​​contact between the electrode and the second conductive part is smaller than the area of ​​contact between the first conductive part and the second conductive part. The electrode is held in the first conductive portion via an insulating material (such as the first insulating collar (insulator) 266). A foreign matter accumulation sensor as described in (1) above, characterized by the above. (3) At least one of the first conductive part and the second conductive part It is a disc-shaped component (such as a fixed disc (first conductive component) 219, a rotating disc (second conductive component) 220, etc.) that constitutes a Sigburn-type screw groove pump (such as a Sigburn-type exhaust mechanism 201). A foreign matter accumulation sensor as described in (1) above, characterized by the above. (4) At least one of the first conductive part and the second conductive part These are cylindrical components (such as the threaded spacer 131 and the lower cylindrical part 103b of the rotating body) that make up a Holbeck-type screw-groove pump (such as the Holbeck-type exhaust mechanism 401). A foreign matter accumulation sensor as described in (1) above, characterized by the above. (5) At least a portion of the opposing surface between the electrode and the first conductive portion is They are facing each other without the aforementioned insulating material in between, Furthermore, it is in communication with the aforementioned gas flow path. A foreign matter accumulation sensor as described in (2) above, characterized by the above. (6) The electrode is The space between the electrode and the first conductive part (such as the space of gap t3), It has a communication port (such as a gas passage hole 267) that connects the space between the electrode and the second conductive part (such as the space of gap t2). A foreign matter accumulation sensor as described in (5) above, characterized by the above. (7) The system includes a calculation unit (control device 200, other computer equipment, etc.) that performs calculations to estimate the amount of foreign matter deposited, The aforementioned calculation unit, Using the calculation formula for determining the change in capacitance, The above calculation formula includes a conversion factor, Based on the aforementioned change in capacitance, It is determined that the space between the electrode and the first conductive part is filled with foreign matter (e.g., the appearance of inflection points F and G), Based on the trend of the change in capacitance, To estimate the dielectric constant of a foreign substance from the capacitance when the space between the electrode and the first conductive part is filled with the foreign substance. A foreign matter accumulation sensor as described in (5) above, characterized by the above. (8) Correcting the conversion coefficient based on the change in capacitance after determining that the space between the electrode and the first conductive part is filled with foreign matter. A foreign matter accumulation sensor as described in (7) above, characterized by the above. (9) A vacuum pump equipped with a foreign matter accumulation sensor as described in any one of items (1) to (7) above (e.g., turbomolecular pump 100, 300).

[0146] <Other> It should be noted that the present invention is not limited to the embodiments described above, and various modifications and combinations of the embodiments are possible without departing from the spirit of the invention.

[0147] For example, the conductive portions of the electrode 252, fixed disc 219, and rotating disc 220 according to the first embodiment, and the conductive portions of the electrode 252, screw spacer 131, and lower cylindrical portion 103b of the rotating body according to the second embodiment, may be formed from a thin film (they may be made into thin films).

[0148] Alternatively, as shown in the second diagram from the top of Figure 10, a second electrode 253 may be installed, and this second electrode 253 may be used as the first conductive part to constitute the foreign matter accumulation sensors 250 and 450. [Explanation of Symbols]

[0149] 100, 300: Turbomolecular pumps 102: Rotary blade 103: Solid of revolution 103a: Rotating body 103b: Lower cylindrical part of the rotating body 113: Rotor shaft 121: Motor 122: Status Column 123:Fixed wing 125: Fixed-wing spacer 127: Outer cylinder 129: Base section 131: Screw-on spacer 131a: Screw groove 133: Exhaust vent 136: Rotating mechanism 137: Exhaust mechanism 138: Turbomolecular pump mechanism 200: Control device 201: Sigburn-type exhaust mechanism 219: Fixed disc (first conductive component) 220: Rotating disk (second conductive component) 227: Gas flow path 228: Projection 229: Sigburn spiral groove section 232: Bottom (Bottom of the Sigburn spiral groove) 234: Recess 235: Bottom (bottom of the recess) 250, 450: Foreign matter accumulation sensor 252: Electrode (First electrode) 253: Second electrode 254: First conductor 256: The second conductor 266: First insulating color 267: Gas passage hole 272: Second insulating color 274: Crimp terminals 276: Nut 401: Holbeck-type exhaust mechanism 452: Electrode holder C1~C3: Capacitors t1~t3: Gap

Claims

1. A first conductive part and an electrode capable of forming a gas flow path within a vacuum pump in a non-rotating state, The first conductive part and the second conductive part facing the electrode and capable of forming the gas flow path in a rotating state, A first conductor connected to the electrode, The device comprises a second conductor connected to the first conductive part, A foreign matter deposit sensor that enables estimation of the amount of foreign matter deposited from the change in capacitance between the first conductive part, the second conductive part, and the electrode.

2. The area of ​​contact between the electrode and the second conductive portion is smaller than the area of ​​contact between the first conductive portion and the second conductive portion. The electrode is held in the first conductive portion via an insulating material. A foreign matter accumulation sensor according to claim 1, characterized by the above.

3. At least one of the first conductive portion and the second conductive portion, It is a disc-shaped component that makes up a Sigburn-type screw-groove pump. A foreign matter accumulation sensor according to claim 1, characterized by the above.

4. At least one of the first conductive portion and the second conductive portion, It is a cylindrical component that makes up a Holbeck-type screw-groove pump. A foreign matter accumulation sensor according to claim 1, characterized by the above.

5. At least a portion of the opposing surfaces between the electrode and the first conductive portion is They are facing each other without the aforementioned insulating material in between, Furthermore, it is in communication with the aforementioned gas flow path. A foreign matter accumulation sensor according to claim 2, characterized by the above.

6. The electrode is The space between the electrode and the first conductive portion, It has a communication port connecting the electrode and the space between the electrode and the second conductive part. A foreign matter accumulation sensor according to claim 5, characterized by the above.

7. The system includes a calculation unit that performs calculations to estimate the amount of foreign matter deposited, The aforementioned calculation unit, Using the calculation formula for determining the change in capacitance, The above calculation formula includes a conversion factor, Based on the aforementioned change in capacitance, It is determined that the space between the electrode and the first conductive part is filled with foreign matter. Based on the trend of the change in capacitance, To estimate the dielectric constant of a foreign substance from the capacitance when the space between the electrode and the first conductive part is filled with the foreign substance. A foreign matter accumulation sensor according to claim 5, characterized by the above.

8. The conversion coefficient is corrected based on the change in capacitance after it is determined that the space between the electrode and the first conductive part is filled with foreign matter. A foreign matter accumulation sensor according to claim 7, characterized by the above.

9. A vacuum pump equipped with a foreign matter accumulation sensor according to any one of claims 1 to 8.

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