Vacuum pump and foreign object sensor

Abstract

To provide a vacuum pump that can accurately detect a change in capacitance.SOLUTION: A vacuum pump comprises an outer cylinder 127, etc. comprising an exhaust path through which exhaust gas flows, a spacer 131 with a screw to be heated by a heater 148, a base part 129 to be cooled by a water cooling pipe 149, and a foreign matter sensor 210 for detecting foreign matter. The foreign matter sensor 210 comprises a pair of electrodes in which capacitance can be changed by accumulation of the foreign matter, and a capacitance measurement part for measuring the capacitance between the electrodes. The electrodes are arranged in the spacer 131 with the screw. The capacitance measurement part is arranged in the base part 129.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vacuum pump, such as a turbomolecular pump, and a foreign object sensor used in the vacuum pump. [Background technology]

[0002] Generally, turbomolecular pumps are known as a type of vacuum pump. These turbomolecular pumps are used, for example, for exhausting gas in manufacturing equipment for semiconductors, flat panels, and the like. In turbomolecular pumps, a motor in the pump body is energized to rotate rotors, which ejects gas molecules (gas molecules) of a gas (process gas) sucked into the pump body, thereby exhausting the gas. Some turbomolecular pumps are equipped with a heater and a cooling tube to appropriately manage the temperature inside the pump.

[0003] In vacuum pumps such as turbomolecular pumps, reaction products generated during the manufacturing process of semiconductors and the like can accumulate inside the vacuum pump. A technology has been devised to detect the amount of accumulation by utilizing changes in electrostatic capacitance.

[0004] Patent Document 1, which will be described later, discloses a technique for detecting a change in capacitance caused by deposits between parallel plate electrodes. Patent Document 2, which will be described later, discloses a technique for detecting a change in capacitance caused by deposits on the surface of an interdigital electrode. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-159632 A [Patent Document 2] Patent Publication No. 2021-195893 Summary of the Invention [Problem to be solved by the invention]

[0006] If the electrodes for detecting deposits are made smaller, the change in capacitance caused by deposits will also become smaller (for example, to about 1 to 2 pF (picofarads)). As a result, the effects of parasitic capacitance generated by the cables and connectors connecting the electrodes and the detection circuit cannot be ignored.

[0007] The effect of parasitic capacitance becomes greater in the following cases (A) and (B). (A) When the distance between the positive and negative cables connecting the sensor and detection circuit, or the distance between the cables and the wall (metal wall) is short. (B) When the cable is long.

[0008] In order to solve the above problems (A) and (B), it is advisable to integrate the electrodes and the detection circuit and minimize the cable length. For example, sensors in which the electrodes and the detection circuit are integrated are widely used in proximity sensors and liquid level sensors. However, the gas flow path in which the sensor is installed is heated to a high temperature, and integrating the electrodes and the detection circuit causes the following problems (1) and (2). (1) If both (the electrode and the detection circuit) are installed in a high-temperature gas flow path, the temperature of the electrode is kept high and the amount of deposition can be detected properly, but the detection circuit becomes prone to overheating. (2) If both (the electrode and the detection circuit) are installed in a low-temperature area, the detection circuit is less likely to overheat, but the temperature of the electrode will drop and the amount of deposition will not be detected properly.

[0009] Due to the problems (1) and (2) above, the idea of ​​integrating the electrodes and the detection circuit and installing them inside the pump is not realistic. Therefore, in the past, the electrodes were installed inside the pump, and the detection circuit was installed in a control circuit outside the pump, and the two were connected by a cable. This is shown in Figures 1 and 2 of Patent Document 1 and Figure 6 of Patent Document 2.

[0010] However, if the electrodes are installed inside the pump and the detection circuit is installed outside the pump, the distance between the pump and the detection circuit may be several meters, and the effect of parasitic capacitance may be strong due to the long cable.

[0011] Also, moving the cable can change the parasitic capacitance, and in this case it may be difficult to distinguish between the change in capacitance due to cable movement and the change in capacitance due to deposits.

[0012] An object of the present invention is to provide a vacuum pump and a foreign object sensor capable of accurately detecting a change in capacitance. [Means for solving the problem]

[0013] (1) In order to achieve the above object, the vacuum pump according to the present invention comprises: A vacuum pump having a vacuum vessel having an exhaust path through which exhaust gas flows, a high-temperature part to be heated by a heating means, a low-temperature part to be cooled by a cooling means, and a foreign object sensor for detecting foreign objects, The foreign object sensor, A pair of electrodes whose capacitance can change due to the accumulation of foreign matter, and a capacitance measuring means for measuring the capacitance between the electrodes, The electrode is disposed in the high temperature portion, The capacitance measuring means is disposed in the low temperature portion. (2) In order to achieve the above object, the foreign object sensor according to the present invention comprises: A foreign object sensor for detecting foreign objects, which is used in a vacuum pump having a vacuum vessel having an exhaust path through which exhaust gas flows, a high-temperature portion to be heated by a heating means, and a low-temperature portion to be cooled by a cooling means, comprising: A pair of electrodes whose capacitance can change due to the accumulation of foreign matter, and a capacitance measuring means for measuring the capacitance between the electrodes, The electrode is disposed in the high temperature portion, The capacitance measuring means is disposed in the low temperature portion. Effect of the Invention

[0014] According to the above invention, it is possible to provide a vacuum pump capable of accurately detecting a change in capacitance. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is an explanatory diagram illustrating a schematic configuration of a turbomolecular pump according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a circuit diagram of an amplifier circuit. [Diagram 3] 6 is a time chart showing control when a current command value is larger than a detection value. [Figure 4] 6 is a time chart showing control when a current command value is smaller than a detection value. [Diagram 5] FIG. 2 is an explanatory diagram showing an enlarged view of a part of the turbomolecular pump according to the first embodiment. [Figure 6] FIG. 2 is a block diagram illustrating a schematic configuration of a foreign object sensor. [Figure 7] FIG. 4 is an explanatory diagram showing an example of an electrode in an electrode portion. [Figure 8] 6 is an explanatory diagram showing the measurement conversion board as viewed from below in FIG. 5. [Figure 9] FIG. 4 is an explanatory diagram illustrating a schematic configuration of a turbomolecular pump according to a second embodiment of the present invention. [Figure 10] FIG. 6 is an explanatory diagram showing an enlarged view of a part of a turbomolecular pump according to a second embodiment. [Figure 11] 11 is an explanatory diagram showing the measurement conversion board as viewed from below in FIG. 10. [Figure 12] FIG. 11 is an explanatory diagram that illustrates a schematic configuration of a turbo molecular pump according to a third embodiment of the present invention. [Figure 13] FIG. 11 is an explanatory diagram showing an enlarged view of a part of a turbomolecular pump according to a third embodiment. [Figure 14] FIG. 1 is an explanatory diagram showing an example of a conventional technique. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] <Basic Configuration of the Turbomolecular Pump 100 According to the First Embodiment> 1 shows a turbomolecular pump 100 as a vacuum pump according to a first embodiment of the present invention. This turbomolecular pump 100 is adapted to be connected to a vacuum chamber (not shown) of a target device such as a semiconductor manufacturing device.

[0017] A longitudinal cross-sectional view of this turbomolecular pump 100 is shown in Fig. 1. In Fig. 1, the turbomolecular pump 100 has an intake port 101 formed at the upper end of a cylindrical outer tube 127. Inside the outer tube 127, a rotor 103 is provided, the rotor 103 having a plurality of rotors 102 (102a, 102b, 102c, ...) which are turbine blades for sucking in and exhausting gas, formed radially and in multiple stages on its periphery. A rotor shaft 113 is attached to the center of the rotor 103, and the rotor shaft 113 is supported in the air and its position is controlled by, for example, a five-axis controlled magnetic bearing.

[0018] The upper radial electromagnets 104 are arranged in pairs on the X-axis and the Y-axis. Four upper radial sensors 107 are provided adjacent to the upper radial electromagnets 104 and corresponding to each of the upper radial electromagnets 104. The upper radial sensors 107 are, for example, inductance sensors or eddy current sensors having conductive windings, and detect the position of the rotor shaft 113 based on the change in inductance of the conductive windings that changes according to the position of the rotor shaft 113. The upper radial sensors 107 are configured to detect the radial displacement of the rotor shaft 113, i.e., the rotating body 103 fixed thereto, and send the detected displacement to the control device 200.

[0019] 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 a position signal detected by the upper radial sensor 107, and an 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.

[0020] The rotor shaft 113 is made of a material with high magnetic permeability (iron, stainless steel, etc.) 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. The lower radial electromagnet 105 and the lower radial sensor 108 are arranged in the same manner as the upper radial electromagnet 104 and the upper radial sensor 107, and adjust the lower radial position of the rotor shaft 113 in the same manner as the upper radial position.

[0021] Furthermore, axial electromagnets 106A and 106B are arranged above and below a circular metal disk (also called an "armature disk") 111 provided at the bottom of rotor shaft 113. Metal disk 111 is made of a high magnetic permeability material such as iron. An axial sensor 109 is provided to detect the axial displacement of rotor shaft 113, and an axial position signal is sent to control device 200.

[0022] In the control device 200, a compensation circuit having, for example, a PID adjustment function generates an excitation control command signal for each of the axial electromagnets 106A and 106B based on the axial position signal detected by the axial sensor 109, and the amplifier circuit 150 controls the excitation of 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 by magnetic force and the axial electromagnet 106B attracts the metal disk 111 downward, thereby adjusting the axial position of the rotor shaft 113.

[0023] In this way, the control device 200 appropriately adjusts the magnetic force that the axial electromagnets 106A, 106B exert on the metal disk 111, magnetically levitating the rotor shaft 113 in the axial direction and holding it in a non-contact manner in space. The amplifier circuit 150 that controls the excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A, 106B will be described later.

[0024] Meanwhile, motor 121 has a plurality of magnetic poles arranged circumferentially so as to surround rotor shaft 113. Each magnetic pole is controlled by control device 200 so as to rotate rotor shaft 113 via electromagnetic force acting between the magnetic pole and rotor shaft 113. Also, motor 121 incorporates a rotation speed sensor such as a Hall element, resolver, or encoder (not shown), and the rotation speed of rotor shaft 113 is detected by a detection signal from this rotation speed sensor.

[0025] 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 detects the position of the magnetic poles using the detection signals of both this phase sensor and the rotation speed sensor.

[0026] A plurality of fixed blades 123 (123a, 123b, 123c...) are disposed at small gaps (predetermined intervals) from the rotor blades 102 (102a, 102b, 102c...). The rotor blades 102 (102a, 102b, 102c...) are 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 with them.

[0027] Similarly, the fixed blades 123 are formed at an inclination at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged alternately with the stages of the rotor blades 102 toward the inside of the outer cylinder 127. The outer peripheral ends of the fixed blades 123 are supported in a state where they are inserted between a plurality of stacked stages of fixed blade spacers 125 (125a, 125b, 125c, etc.).

[0028] The fixed wing spacer 125 is a ring-shaped member and is made of metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components. An outer cylinder 127 is fixed to the outer periphery of the fixed wing spacer 125 with a small gap therebetween. A base portion 129 is disposed 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.

[0029] Furthermore, depending on the application of the turbo molecular pump 100, a threaded spacer 131 is disposed between the lower part of the fixed vane spacer 125 and the base part 129. The threaded spacer 131 is a cylindrical member made of metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals, and has a plurality of helical thread grooves 131a engraved on its inner peripheral surface. The helical direction of the thread groove 131a is the direction in which, when exhaust gas molecules move in the rotation direction of the rotor 103, the molecules are transported toward the exhaust port 133. A rotor lower cylindrical part 103b is suspended from the lower part of the rotor main body 103a on which the rotor vanes 102 (102a, 102b, 102c,...) of the rotor 103 are formed. The outer peripheral surface of the rotor lower cylindrical portion 103b is cylindrical and protrudes toward the inner peripheral surface of the threaded spacer 131, and is adjacent to the inner peripheral surface of the threaded spacer 131 with a specified gap therebetween. The exhaust gas transferred to the thread groove 131a by the rotor 102 and the fixed blades 123 is guided by the thread groove 131a and sent to the base portion 129. In this manner, the threaded spacer 131 and the rotor lower cylindrical portion 103b facing it constitute a Holweck type exhaust mechanism 204. The Holweck type exhaust mechanism 204 gives directionality to the exhaust gas by the rotation of the rotor lower cylindrical portion 103b relative to the threaded spacer 131, thereby improving the exhaust characteristics of the turbo molecular pump 100.

[0030] The base portion 129 is a disk-shaped member that constitutes the base of the turbomolecular pump 100, and is generally made of metal such as iron, aluminum, stainless steel, etc. The base portion 129 physically holds the turbomolecular pump 100 and also functions as a heat conduction path, so it is desirable to use a metal that has rigidity and high thermal conductivity, such as iron, aluminum, or copper.

[0031] In this configuration, when the rotor 102 is rotated together with the rotor shaft 113 by the motor 121, the exhaust gas is sucked from the chamber through the intake port 101 by the action of the rotor 102 and the fixed blades 123. The exhaust gas sucked in from the intake port 101 passes between the rotor 102 and the fixed blades 123 and is transferred to the base portion 129. At this time, the temperature of the rotor 102 rises due to frictional heat generated when the exhaust gas comes into contact with the rotor 102 and the conduction of heat generated by the motor 121, and the like, but this heat is transferred to the fixed blades 123 side by radiation or conduction by gas molecules (gas molecules) of the exhaust gas, and the like.

[0032] The fixed blade spacers 125 are joined to each other at their outer peripheries, and transmit heat received by the fixed blades 123 from the rotor blades 102, frictional heat generated when exhaust gas comes into contact with the fixed blades 123, and the like to the outside.

[0033] In the above description, the threaded spacer 131 is disposed on the outer periphery of the rotor lower cylindrical portion 103b of the rotor 103, and the thread groove 131a is engraved on the inner periphery of the threaded spacer 131. However, conversely, there are also cases where a thread groove is engraved on the outer periphery of the rotor lower cylindrical portion 103b, and a spacer having a cylindrical inner periphery is disposed around it.

[0034] Depending on the application of the turbomolecular pump 100, in order to prevent the gas sucked in from the intake port 101 from entering the electrical equipment section, which is composed of the upper radial electromagnet 104, the upper radial sensor 107, the motor 121, the lower radial electromagnet 105, the lower radial sensor 108, the axial electromagnets 106A and 106B, the axial sensor 109, etc., the electrical equipment section may be covered all around with a stator column 122, and the inside of this stator column 122 may be kept at a predetermined pressure by a purge gas.

[0035] In this case, a purge gas port (not shown) is provided in the base portion 129, and purge gas is introduced through this piping. The introduced purge gas is sent to the exhaust port 133 through gaps 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 portion of the rotor blades 102 (lower cylindrical portion 103b of the rotor) and the stator column 122 or between the base portion 129 and the protective bearing 120 and the rotor shaft 113.

[0036] Here, the turbomolecular pump 100 requires control based on specific parameters (e.g., various characteristics corresponding to the model) that are individually adjusted and identified as a model. In order to store these control parameters, the turbomolecular pump 100 has an electronic circuit section 141 in its main body. The electronic circuit section 141 is composed of a semiconductor memory such as an EEPROM, electronic components such as semiconductor elements for accessing the memory, and a substrate 143 for mounting these components. The electronic circuit section 141 is housed below a rotational speed sensor (not shown) near the center of a base section 129 that constitutes the lower part of the turbomolecular pump 100, and is closed by an airtight bottom cover 145.

[0037] 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 turbo molecular pump 100, the pressure of the exhaust gas is lowest at the intake port 101 and highest at the exhaust port 133. If the pressure of the process gas becomes higher than a predetermined value or the temperature falls below a predetermined value while the process gas 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 turbo molecular pump 100.

[0038] For example, when SiCl4 is used as the process gas in an Al etching device, low vacuum (760[torr]~10 -2 It can be seen from the vapor pressure curve that at a vapor pressure of 100 MPa (100 [torr]) and low temperature (approximately 20 [°C]), solid products (e.g., AlCl3) precipitate and adhere to and accumulate inside the turbomolecular pump 100. As a result, when precipitates of the process gas accumulate inside the turbomolecular pump 100, the deposits narrow the pump flow path, causing a decrease in the performance of the turbomolecular pump 100. The aforementioned products are prone to solidification and adhesion in high pressure areas near the exhaust port 133 and near the threaded spacer 131.

[0039] Therefore, in order to solve this problem, conventionally, a heater (not shown) or a circular water-cooled tube 149 is wound around the outer periphery of the base part 129, and, for example, a temperature sensor (e.g., a thermistor) (not shown) is embedded in the base part 129, and heating by the heater and cooling by the water-cooled tube 149 are controlled based on a signal from the temperature sensor to keep the temperature of the base part 129 at a constant high temperature (set temperature) (hereinafter referred to as TMS; Temperature Management System). In this embodiment, the threaded spacer 131 is heated by a heater 148 embedded in the threaded spacer 131, and the base part 129 is cooled by a water-cooled tube 149 embedded in the bottom cover 145; these points will be described later.

[0040] Next, regarding the turbo molecular pump 100 configured as above, an amplifier circuit 150 that controls excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B will be described. A circuit diagram of this amplifier circuit is shown in FIG.

[0041] 2, one end of an electromagnet winding 151 constituting the upper radial electromagnet 104 etc. is connected to a positive electrode 171a of a power source 171 via a transistor 161, and the other end is connected to a negative electrode 171b of the power source 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 drain.

[0042] At this time, the transistor 161 has a cathode terminal 161a of the diode connected to the positive electrode 171a, and an anode terminal 161b connected to one end of the electromagnet winding 151. The transistor 162 has a cathode terminal 162a of the diode connected to the current detection circuit 181, and an anode terminal 162b connected to the negative electrode 171b.

[0043] On the other hand, the current regeneration diode 165 has its cathode terminal 165a connected to one end of the electromagnet winding 151 and its anode terminal 165b connected to the negative electrode 171b. Similarly, the current regeneration diode 166 has its cathode terminal 166a connected to the positive electrode 171a and its anode terminal 166b connected to the other end of the electromagnet winding 151 via a current detection circuit 181. The current detection circuit 181 is composed of, for example, a Hall sensor type current sensor or an electric resistance element.

[0044] The amplifier circuit 150 configured as above corresponds to one electromagnet. Therefore, when the magnetic bearing is controlled by five axes and there are a total of ten electromagnets 104, 105, 106A, and 106B, a similar amplifier circuit 150 is configured for each electromagnet, and the ten amplifier circuits 150 are connected in parallel to the power supply 171.

[0045] Furthermore, the amplifier control circuit 191 is configured, for example, by a digital signal processor section (hereinafter referred to as a DSP section) (not shown) of the control device 200, and this amplifier control circuit 191 switches the transistors 161 and 162 on / off.

[0046] The amplifier control circuit 191 is adapted to compare the current value detected by the current detection circuit 181 (a signal reflecting this current value is called a current detection signal 191c) with a predetermined current command value. Then, based on the result of this comparison, the magnitude of the pulse width (pulse width times Tp1, Tp2) to be generated within a control cycle Ts, which is one period of PWM control, is determined. As a result, gate drive signals 191a, 191b having this pulse width are output from the amplifier control circuit 191 to the gate terminals of the transistors 161, 162.

[0047] In addition, when the rotor 103 passes through a resonance point during an accelerating operation of the rotation speed, or when a disturbance occurs during a constant speed operation, it is necessary to control the position of the rotor 103 at high speed and with a strong force. For this reason, 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 (not shown) is usually connected between the positive pole 171a and the negative pole 171b of the power supply 171 to stabilize the power supply 171.

[0048] In this configuration, when both transistors 161, 162 are turned on, the current flowing through the electromagnet winding 151 (hereinafter referred to as electromagnet current iL) increases, and when both are turned off, the electromagnet current iL decreases.

[0049] Moreover, when one of the transistors 161, 162 is turned on and the other is turned off, a so-called flywheel current is maintained. By passing a flywheel current 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 kept low. Furthermore, by controlling the transistors 161, 162 in this manner, high-frequency noise such as harmonics generated in the turbo molecular pump 100 can be reduced. Furthermore, by measuring this flywheel current with the current detection circuit 181, the electromagnet current iL flowing through the electromagnet winding 151 can be detected.

[0050] That is, when the detected current value is smaller than the current command value, both of the transistors 161 and 162 are turned on for a time period corresponding to the pulse width time Tp1 only once in a control cycle Ts (e.g., 100 μs) as shown in Fig. 3. Therefore, the electromagnet current iL during this period increases toward a current value iLmax (not shown) that can flow from the positive electrode 171a to the negative electrode 171b via the transistors 161 and 162.

[0051] On the other hand, when the detected current value is larger than the current command value, both of the transistors 161 and 162 are turned off for a time period corresponding to the pulse width time Tp2 only once during the control cycle Ts, as shown in Fig. 4. Therefore, the electromagnet current iL during this period decreases toward a current value iLmin (not shown) that can be regenerated from the negative pole 171b to the positive pole 171a via the diodes 165 and 166.

[0052] In either case, after the pulse width times Tp1 and Tp2 have elapsed, one of the transistors 161 and 162 is turned on. Therefore, a flywheel current is maintained in the amplifier circuit 150 during this period.

[0053] 1 (the side of the intake port 101) of the turbomolecular pump 100 having such a basic configuration is an intake section connected to the target device, and the lower side (the side of the base part 129 on which the exhaust port 133 connected to the exhaust port 135 is provided so as to protrude to the left side in the figure) is an exhaust section connected to an auxiliary pump (back pump) or the like (not shown). The turbomolecular pump 100 can be used in an inverted, horizontal or inclined position in addition to the vertical position shown in FIG. 1.

[0054] In the turbomolecular pump 100, the outer cylinder 127 and the base portion 129 are combined to form one case (hereinafter, both may be collectively referred to as the "main casing"). The turbomolecular pump 100 is electrically (and structurally) connected to a box-shaped electrical equipment case (not shown), and the above-mentioned control device 200 is incorporated in the electrical equipment case.

[0055] The internal configuration of the main body casing of the turbomolecular pump 100 (a combination of an outer cylinder 127 and a base portion 129) can be divided into a rotation mechanism portion that rotates the rotor shaft 113 and the like by the motor 121, and an exhaust mechanism portion that is rotationally driven by the rotation mechanism portion. The exhaust mechanism portion can be considered to be divided into a turbomolecular pump mechanism portion composed of the rotor 102, fixed blades 123, etc., and a threaded pump mechanism portion (Holbeck type exhaust mechanism portion) composed of the rotor lower cylindrical portion 103b, threaded spacer 131, etc.

[0056] The above-mentioned purge gas (protective gas) is used to protect the bearing parts and the rotor 102, etc., to prevent corrosion caused by the exhaust gas (process gas), and to cool the rotor 102. This purge gas can be supplied by a general method.

[0057] For example, the above-mentioned purge gas port (not shown) extending linearly in the radial direction is provided at a predetermined position (such as a position 90 degrees or 120 degrees away from the exhaust port 133) of the base portion 129. Then, purge gas is supplied to this purge gas port from the outside of the base portion 129 via a purge gas cylinder (such as an N2 gas cylinder) or a flow rate regulator (valve device).

[0058] The aforementioned protective bearings 120 are also called "touch-down (T / D) bearings" or "back-up bearings." These protective bearings 120 prevent the position and attitude of the rotor shaft 113 from changing significantly, and prevent damage to the rotor blades 102 and their surroundings, even in the unlikely event that a problem occurs with the electrical system or atmospheric inrush.

[0059] In FIG. 1 showing the structures of the turbo molecular pump 100 and the rotor 103, hatching showing cross sections of components is omitted to avoid complicating the drawing.

[0060] <Foreign object detection in the turbomolecular pump 100 according to the first embodiment> <<Outline of the Foreign Object Sensor 210>> As mentioned above, products may accumulate inside the turbo molecular pump 100. In this embodiment, the deposits are detected using a foreign matter sensor 210 as shown in an enlarged view in Fig. 5. The foreign matter sensor 210 may also be called a "deposition sensor" or a "deposit sensor".

[0061] 6, the foreign object sensor 210 includes an electrode unit 212, a capacitance measuring unit 214, and a signal converting unit 216. The electrode unit 212 changes a physical quantity (here, capacitance) due to the adhesion of deposits. The capacitance measuring unit 214 receives a signal corresponding to the capacitance of the electrode unit 212.

[0062] The signal conversion unit 216 converts the signal output from the capacitance measurement unit 214 into a digital signal and outputs it to a control unit (here, the control device 200). The control device 200 determines the state of the electrode unit 212 based on the information from the signal conversion unit 216. The combination of the capacitance measurement unit 214 and the signal conversion unit 216 constitutes a measurement conversion unit 217. Note that the "conversion" referred to here may be any of analog-to-digital conversion, digital-to-digital conversion, and digital-to-analog conversion.

[0063] <<Electrode section 212>> 7, the electrode unit 212 is of a type that detects deposits based on a change in electrostatic capacitance between a pair of electrodes A and B. The electrodes A and B are formed on a sensor substrate 218. The sensor substrate 218 is included in the electrode unit 212 and constitutes at least a part of the electrode unit 212.

[0064] The sensor substrate 218 is, for example, a rectangular insulating substrate (ceramic substrate in this case) on one plate surface 219 of which a pair of comb-tooth shaped electrodes (flat electrodes) A ​​and B are formed.

[0065] The electrodes A and B are formed so that they face each other without touching or crossing each other, and their comb teeth are interdigitated with a predetermined gap between them without touching. A high-frequency voltage is applied between the electrodes A and B from the capacitance measuring unit 214 to generate an electric field. The capacitance between the electrodes A and B is minimum in a clean state with no deposits attached. When deposits attach and the amount of deposits increases, the capacitance between the electrodes A and B increases.

[0066] 1 and 5, the sensor board 218 is disposed at a position approximately 180 degrees away from the exhaust port 133. In the threaded spacer 131, a protrusion 131b is located at a position approximately 180 degrees away from the exhaust port 133. The protrusion 131b is provided at an end of the threaded spacer 131 (the lower end in FIGS. 1 and 5). This protrusion 131b protrudes from the outer side of the threaded spacer 131 in the radial direction toward the center.

[0067] Sensor substrate 218 is placed on protruding portion 131b and fixed to protruding portion 131b. Sensor substrate 218 can be fixed to protruding portion 131b with screws (not shown). Exhaust gas (process gas) flows and comes into contact with plate surface 219 of sensor substrate 218 fixed to protruding portion 131b. Therefore, electrodes A and B come into contact with the flowing exhaust gas (process gas).

[0068] As described above, in this embodiment, the threaded spacer 131 is heated by the heater 148 shown by the two-dot chain line in Fig. 1. The sensor substrate 218 (Figs. 1 and 5) and the electrodes A and B (Fig. 7) formed on the sensor substrate 218 are also heated via the threaded spacer 131.

[0069] That is, the threaded spacer 131 constitutes a high-temperature part that becomes relatively hot when heated, and the electrodes A and B are disposed on the threaded spacer 131 which is the high-temperature part. The electrodes A and B are fixed in contact with the threaded spacer 131 so as to enable heat transfer. As the threaded spacer 131 is heated by the heater 148, the heat of the threaded spacer 131 is transferred to the electrodes A and B, and the electrodes A and B are heated.

[0070] Here, the heater 148 may be disposed closer to the sensor substrate 218 than shown in Fig. 1. Also, in Fig. 1, the sensor substrate 218 is disposed at a position spaced apart from the exhaust port 133 by approximately 180 degrees, but the distance between the sensor substrate 218 and the exhaust port 133 is not limited to 180 degrees. For example, the sensor substrate 218 may be disposed at a position spaced apart from the exhaust port 133 by 240 degrees, 270 degrees, or the like.

[0071] As shown in Fig. 5, a cylindrical insulating collar 221 protrudes vertically from the other plate surface 220 of the sensor board 218. The insulating collar 221 is formed using an electrically insulating material. An electrode pin 222 passes through the insulating collar 221. Although only one electrode pin 222 is shown in Figs. 1 and 5, there are actually two electrode pins 222, which are electrically connected to electrodes A and B formed on the sensor board 218.

[0072] The electrode pin 222 may be structurally integrated (including soldering, connector connection, etc.) with a portion of the electrodes A and B. Alternatively, the electrode pin 222 and the electrodes A and B may be electrically connected via pattern wiring inside the sensor substrate 218.

[0073] The electrode pin 222 further protrudes in the thickness direction of the protruding portion 131b from the insulating collar 221. The protruding portion 131b is provided with a through hole 131c penetrating in the thickness direction. The insulating collar 221 and the electrode pin 222 pass through this through hole 131c to reach the base portion 129.

[0074] The base portion 129 is provided with a receiving hole 129a that faces the transmission hole 131c of the protruding portion 131b. The receiving hole 129a is spatially connected to a wiring hole (also called a "connector port") 129b formed in the base portion 129. The wiring hole 129b extends in the radial direction of the base portion 129, and the receiving hole 129a extends in a direction perpendicular to the wiring hole 129b.

[0075] The electrode pin 222 passes through the transmission hole 131c and the receiving hole 129a, and reaches the measurement conversion board 226 in the wiring hole 129b.

[0076] <<Capacitance measuring unit 214>> The measurement conversion board 226 has the above-mentioned capacitance measurement section 214 (FIG. 6) formed thereon. FIG. 8 shows the measurement conversion board 226 in FIGS. 1 and 5 as viewed in plan from below the base section 129 (from below in FIGS. 1 and 5). The measurement conversion board 226 is accommodated in a measurement board accommodating recess 228 of the base section 129 and fixed to the base section 129. The measurement conversion board 226 can be fixed to the base section 129 via screws (not shown).

[0077] The measurement conversion board 226 is fixed to the base part 129 via a heat transfer promotion means. As the heat transfer promotion means, heat transfer grease (not shown) or the like can be adopted. In this case, the heat transfer grease is applied to at least one of the measurement conversion board 226 and a portion of the base part 129 that contacts the measurement conversion board 226.

[0078] 8, a measurement conversion package 230 is mounted on the measurement conversion board 226. The measurement conversion package 230 is an IC (integrated circuit) package having a measurement circuit section 231 built in mold resin 230a. The measurement circuit section 231 performs amplification, noise removal, etc. on the signal from the sensor board 218. The measurement circuit section 231 corresponds to the capacitance measurement section 214 in FIG.

[0079] As shown in FIG. 8, the measurement conversion board 226 is provided with power input terminals 232a, 232b used for power input (power supply) to the measurement conversion package 230, and sensor board input terminals 234a, 234b used for signal input (signal supply) to the sensor board 218 of the electrode portion 212.

[0080] 8 shows the state of the measurement conversion board 226 before the two electrode pins 222 of the sensor board 218 are connected. Two through holes 236a, 236b into which the electrode pins 222 are inserted are formed in the measurement conversion board 226. The electrode pins 222 of the sensor board 218 are inserted into these through holes 236a, 236b and soldered.

[0081] Here, the connection between the electrode pins 222 and the measurement conversion board 226 is not limited to soldering. For example, the measurement conversion board 226 may be provided with a connector (not shown) for receiving the electrode pins 222, and the electrode pins 222 may be inserted into this connector. Alternatively, the electrode pins 222 may be formed into a connector, and this connector may be mounted on the sensor board 218. In this case, it is possible to connect the connector of the sensor board 218 and the connector of the measurement conversion board 226.

[0082] A current flows through the electrode pin 222 at intervals according to the capacitance between the electrodes A and B. As the product accumulates and the capacitance between the electrodes A and B increases, a current flows through the electrode pin 222 at shorter time intervals.

[0083] As described above, in this embodiment, the base portion 129 is cooled by the water cooling pipe 149 (FIGS. 1 and 5). The measurement conversion board 226 is also cooled via the base portion 129. In other words, the base portion 129 constitutes a low-temperature part that is cooled to a relatively low temperature. The measurement conversion board 226 is also disposed on the base portion 129, which is a low-temperature part.

[0084] 5, an annular heat insulating material 238 is interposed between the base portion 129 and the threaded spacer 131. The heat insulating material 238 is formed using a material having thermal insulation properties. The outer diameter of the heat insulating material 238 is approximately equal to the inner diameter of the outer tube 127, and the outer peripheral surface of the heat insulating material 238 is in contact with the inner peripheral surface of the outer tube 127. A gap 240 is formed between the inner peripheral surface of the heat insulating material 238 and the threaded spacer 131.

[0085] The threaded spacer 131 constituting the high temperature portion and the base portion 129 constituting the low temperature portion are thermally insulated (separated) by the heat insulating material 238. The heat insulating material 238 prevents heat transfer from the threaded spacer 131 to the base portion 129.

[0086] <<Signal Conversion Unit 216 and Derivation of Converted Signal>> In this embodiment, the above-mentioned signal conversion section 216 (FIG. 6) is formed on the measurement conversion board 226. The signal conversion section 216 corresponds to a signal conversion circuit section 242 built into the measurement conversion package 230 as shown in FIG. 8. Although not shown, the signal conversion circuit section 242 includes circuit elements such as a signal conversion circuit and an input / output circuit, and is electrically connected to a vacuum connector 246 via a conductive wiring (lead line) 244 shown generally in FIGS. 1 and 5.

[0087] The signal output from the signal conversion circuit unit 242 may be any signal that can be used for information processing in the control device 200. The signal output from the signal conversion circuit unit 242 may be, for example, a signal that conforms to a standardized specification for voltage and current conditions (a signal that conforms to a standardized format), but it is preferable to select a method that is less susceptible to noise and parasitic capacitance.

[0088] In this way, by combining the signal from the measurement circuit section 231 with the signal conversion circuit section 242 and unitizing it into the measurement conversion package 230 rather than outputting the signal as is, it becomes less susceptible to the effects of noise and parasitic capacitance and makes it easier to place it in a location separate from the electrode section 212.

[0089] In addition, the embodiment of the capacitance measurement unit 214 and the signal conversion unit 216 is not limited to the measurement conversion package 230, but may be arranged in a manner such that the respective electrical circuits and circuit elements of the measurement circuit unit 231 and the signal conversion circuit unit 242 are implemented on the measurement conversion board 226.

[0090] The vacuum connector 246 is provided in the wiring hole 129b of the base portion 129 in a state in which airtightness can be ensured. The vacuum connector 246 is used for electrical connection between the inside and outside of the turbo molecular pump 100.

[0091] A control device cable 250 electrically connected to the control device 200 is connected to the vacuum connector 246. Electrical signals related to the above-mentioned various devices such as the sensors, electromagnets, and motors in the turbo molecular pump 100 are input and output via the vacuum connector 246. Figures 1 and 5 show a state in which the connector 250a of the control device cable 250 is separated from the wiring hole 129b.

[0092] <Advantages of the turbomolecular pump 100 according to the first embodiment> According to the turbo molecular pump 100 as described above, the electrode section 212 is disposed in the high temperature section (here, the threaded spacer 131), and the capacitance measuring section 214 and the signal converting section 216 are disposed in the low temperature section (here, the base section 129). Therefore, it is possible to simultaneously detect (sense) the deposition amount accurately and prevent the capacitance measuring section 214 and the signal converting section 216 from overheating.

[0093] Furthermore, the capacitance measuring unit 214 and the signal converting unit 216 of the foreign object sensor 210 are disposed inside the base portion 129 and are built into the turbo molecular pump 100. Therefore, it is possible to minimize the length (wiring distance) of the wiring between the electrode portion 212 and the capacitance measuring unit 214 and between the electrode portion 212 and the signal converting unit 216.

[0094] Therefore, compared to a case where, for example, the electrode portion 212 is arranged inside the turbomolecular pump 100 (inside the outer tube 127 or the base portion 129) and the capacitance measuring portion 214 and the signal conversion portion 216 are arranged outside the turbomolecular pump 100, it is less susceptible to the influence of parasitic capacitance and it is possible to detect changes in capacitance more accurately and easily.

[0095] Furthermore, according to the turbo molecular pump 100 of this embodiment, the sensor substrate 218 having the electrodes A and B is disposed on the threaded spacer 131 constituting the high temperature portion. Therefore, it becomes easier to bring the temperatures of the electrodes A and B closer to the temperatures of the threaded spacer 131 and the process gas (exhaust gas).

[0096] Furthermore, the portion located downstream of the exhaust gas and in contact with the exhaust gas is generally a portion where deposits are likely to occur. Therefore, in the portion where deposits are likely to occur, electrodes A and B can be used in an environment with a temperature similar to that of the surroundings.

[0097] In addition, since the electrodes A and B are provided so as to be in contact with the flowing exhaust gas (process gas), the electrodes A and B are disposed facing the exhaust path, and therefore the state of deposits can be detected more accurately.

[0098] In addition, since the measurement circuit section 231 and the signal conversion circuit section 242 are molded in the measurement conversion package 230, heat generated in the measurement circuit section 231 and the signal conversion circuit section 242 is diffused into the mold resin 230a. The heat diffused into the mold resin 230a is transferred to the base section 129 via the measurement conversion board 226. Therefore, the heat of the measurement circuit section 231 and the signal conversion circuit section 242 can be efficiently dissipated to the base section 129, which is a cooling section. Also, it is possible to prevent a local temperature rise in the portion where the measurement circuit section 231 and the signal conversion circuit section 242 are arranged.

[0099] Here, in this embodiment, the measurement circuit section 231 and the signal conversion circuit section 242 are packaged by a common molding resin 230a, but the measurement circuit section 231 and the signal conversion circuit section 242 may be packaged separately.

[0100] Furthermore, of the measurement circuit section 231 and the signal conversion circuit section 242, at least the signal conversion circuit section 242 may be disposed at a location outside the vacuum vessel (here, the combination of the outer cylinder 127 and the base section 129) of the turbo molecular pump 100. Examples of the location outside the vacuum vessel include the outer wall surfaces of the outer cylinder 127 and the base section 129, inside the control device 200, or a location between the vacuum vessel and the control device 200.

[0101] Furthermore, since the measurement conversion board 226 is in contact with the base portion 129 via a heat transfer promotion means such as thermal grease, heat can be dissipated from the measurement circuit portion 231 and the signal conversion circuit portion 242 to the base portion 129 more efficiently.

[0102] Furthermore, according to the turbo molecular pump 100 of this embodiment, the electrode pin 222 of the sensor substrate 218 is inserted and connected directly to the measurement conversion substrate 226 without the use of a cable (wiring cord). Therefore, the electrodes A and B can be connected to the measurement conversion substrate 226 over the shortest possible distance without the need for a cable. This prevents the parasitic capacitance from changing due to cable movement, and makes it possible to accurately detect the occurrence of deposits.

[0103] For these reasons, it is possible to accurately detect the occurrence of deposits through changes in capacitance detected by electrodes A and B. Furthermore, it is possible to detect foreign matter more accurately than in the turbomolecular pump 10 shown in FIG. 14, for example. In the turbomolecular pump 10 of FIG. 14, a common substrate 260 is disposed on the base portion 129, and the electrode portion 212, capacitance measurement portion 214, and signal conversion portion 216 as shown in FIG. 6 are disposed together on the common substrate 260. Various wirings 262 are connected to the common substrate 260.

[0104] In the turbo molecular pump 100 of the first embodiment, the exhaust port 133 and the wiring hole 129b (connector port) are arranged at positions separated by 180 degrees, but this is not limited to this. The positional relationship between the exhaust port 133 and the wiring hole 129b (connector port) can be changed in various ways depending on the circumstances of the purge port and other ports. For example, it is also possible to arrange the exhaust port 133 and the purge port at positions separated by 180 degrees, and arrange the wiring hole 129b (connector port) at another position.

[0105] <Foreign object detection in turbo molecular pump 300 according to the second embodiment> Next, a turbo molecular pump 300 according to a second embodiment of the present invention will be described with reference to Figures 9 to 11. Note that the same parts as those in the first embodiment are given the same reference numerals, and the description will be omitted as appropriate.

[0106] In the second embodiment, the electrical connection between the sensor board 218 and the measurement conversion board 326 is made via a cable 302, not the electrode pin 222 as in the first embodiment. One end of the cable 302 is connected to the sensor board 218 by a method such as soldering or connector connection.

[0107] 9 and 10, only one cable 302 is shown, but the number of cables 302 is two, corresponding to electrodes A and B formed on sensor substrate 218. Cable 302 and electrodes A and B may be electrically connected via pattern wiring inside sensor substrate 218. Note that what is indicated by reference numeral 310 in FIGS. 9 and 10 is a foreign object sensor according to the second embodiment.

[0108] Fig. 11 shows the measurement conversion board 326 in Fig. 9 and Fig. 10 as viewed from below the base portion 129 (from below Fig. 9 and Fig. 10) in plan view. The measurement conversion board 326 is provided with power input terminals 232a, 232b and sensor board input terminals 234a, 234b as well as sensor board output terminals 334a, 334b. The cable 302 extending from the sensor board 218 is electrically connected to the sensor board output terminals 334a, 334b.

[0109] <Advantages of the turbomolecular pump 300 according to the second embodiment> According to the turbomolecular pump 300 as described above, compared to the first embodiment, parasitic capacitance may occur due to the cable 302, but in other respects, it has the same advantages as the turbomolecular pump 100 according to the first embodiment.

[0110] <Foreign object detection in turbo molecular pump 400 according to the third embodiment> Next, a turbo molecular pump 400 according to a third embodiment of the present invention will be described with reference to Figures 12 and 13. Note that the same parts as those in the first embodiment (or the second embodiment) are given the same reference numerals, and the description will be omitted as appropriate.

[0111] 12 and 13, the measurement conversion package 230 is mounted on an electronic circuit section 441. The electronic circuit section 441 is enlarged compared to the first and second embodiments, and a space 429c for accommodating the electronic circuit section 441 is secured in the base section 429 with a larger diameter than the space 129c formed in the base section 129 in the first and second embodiments.

[0112] The electronic circuit section 441 is fixed to the axial direction sensor 109. Although not shown, the electronic circuit section 441 is equipped with a memory circuit section (IC package) that stores the ID (individual identification information for each unit) of the turbo molecular pump 400. This point is similar to the electronic circuit section 141 of the first and second embodiments. The measurement conversion package 230 may be integrated into the IC package that stores the ID of the turbo molecular pump 400, and the measurement circuit section 231 and the signal conversion circuit section 242 may be built in.

[0113] The electronic circuit section 441 and the sensor board 218 are electrically connected via a cable 402. Each end of the cable 402 is connected to the sensor board 218 and the electronic circuit section 441 in the same manner as in the second embodiment (FIGS. 9 to 11).

[0114] The electronic circuit section 441 and the vacuum connector 246 are electrically connected via a conductive wiring (lead wire) 444. The conductive wiring 444 is connected to the electronic circuit section 441 in the same manner as the conductive wiring 244 is connected to the electronic circuit section 141 in the first and second embodiments. The conductive wiring 444 is also connected to the vacuum connector 246 in the same manner as the conductive wiring 244 is connected to the vacuum connector 246 in the first and second embodiments.

[0115] The electronic circuit unit 441 may be fixed to the axial direction sensor 109 via a heat transfer promoting means such as heat transfer grease unless this causes any particular problem. In addition, what is indicated by the reference numeral 410 in Fig. 12 and Fig. 13 is a foreign object sensor according to the third embodiment.

[0116] <Advantages of the turbo molecular pump 400 according to the third embodiment> According to the turbo molecular pump 400 as described above, the electronic circuit section 441 is disposed inside the base section 429, and the base section 429 is thermally insulated (separated) from the threaded spacer 131 via the heat insulating material 238. Therefore, the electronic circuit section 441 can be cooled, and a rise in temperature of the electronic circuit section 441 can be prevented.

[0117] Furthermore, similarly to the first and second embodiments, heat from the measurement circuit section 231 and the signal conversion circuit section 242 can be dissipated to the electronic circuit section 441 via the mold resin 230a of the measurement conversion package 230. Then, the heat can be dissipated to the base section 429 via the mold resin 230a of the measurement conversion package 230 and the electronic circuit section 441.

[0118] <Inventions that can be extracted from each embodiment> From the above-described embodiments, the following inventions can be extracted. (1) A vacuum pump (such as turbo molecular pump 100, 300, 400) having a vacuum vessel (such as a combination of an outer cylinder 127 and a base portion 129) having an exhaust path through which exhaust gas flows, a high-temperature portion (such as a threaded spacer 131) to be heated by a heating means (such as a heater 148), a low-temperature portion (such as the base portion 129) to be cooled by a cooling means (such as a water-cooled tube 149), and a foreign object sensor (such as foreign object sensor 210, 310, 410) for detecting foreign objects, The foreign object sensor, A pair of electrodes (electrodes A, B, etc.) whose capacitance can change due to the accumulation of foreign matter, and a capacitance measurement means (a capacitance measurement unit 214, a combination of the capacitance measurement unit 214 and a signal conversion unit 216, etc.) that measures the capacitance between the electrodes, The electrode is disposed in the high temperature portion, The capacitance measuring means is disposed in the low temperature portion. (2) The vacuum pump according to (1) above, wherein the electrode is disposed facing the exhaust path. (3) The capacitance measuring means The vacuum pump according to (1) or (2) above, characterized in that it is disposed within the vacuum vessel. (4) The capacitance measuring means The vacuum pump according to (1) or (2) above, characterized in that it is resin molded (eg, molded with molding resin 230a). (5) The capacitance measuring means The vacuum pump according to (1) or (2) above, characterized in that the low-temperature section is disposed so as to be capable of exchanging heat. (6) The vacuum pump according to (1) or (2) above, wherein the capacitance measuring means is directly connected to a pin (such as electrode pin 222) extending from the electrode. (7) A foreign object sensor (e.g., foreign object sensor 210, 310, 410) for detecting foreign objects used in a vacuum pump having a vacuum vessel (e.g., a combination of an outer cylinder 127 and a base portion 129) having an exhaust path through which exhaust gas flows, a high-temperature portion (e.g., a threaded spacer 131) to be heated by a heating means (e.g., a heater 148), and a low-temperature portion (e.g., the base portion 129) to be cooled by a cooling means (e.g., a water-cooled tube 149), A pair of electrodes (electrodes A, B, etc.) whose capacitance can change due to the accumulation of foreign matter, and a capacitance measurement means (capacitance measurement unit 214, etc.) that measures the capacitance between the electrodes, The electrode is disposed in the high temperature portion, 4. A foreign object sensor according to claim 3, wherein the capacitance measuring means is disposed in the low temperature portion.

[0119] <Other> The present invention is not limited to the above-described embodiments, and various modifications and combinations of the embodiments are possible without departing from the scope of the present invention. [Explanation of symbols]

[0120] 100, 300, 400: Turbo molecular pump 127: Outer cylinder 129, 429: Base section 131: Threaded spacer 148: Heater 149:Water cooled pipe 210, 310, 410: Foreign object sensor 212: Electrode part 214: Capacitance measurement unit 216: Signal conversion unit 218: Sensor board 222: Electrode pin 226: Measurement conversion board 230: Measurement conversion package 231: Measurement circuit section 242: Signal conversion circuit section 244, 444: Conductive wiring 302, 402: Cable 326: Measurement conversion board A: Electrode B: Electrode

Claims

1. A vacuum pump having a vacuum vessel having an exhaust path through which exhaust gas flows, a high-temperature part to be heated by a heating means, a low-temperature part to be cooled by a cooling means, and a foreign object sensor for detecting foreign objects, The foreign object sensor, A pair of electrodes whose capacitance can change due to the accumulation of foreign matter, and a capacitance measuring means for measuring the capacitance between the electrodes, The electrode is disposed in the high temperature portion, A vacuum pump characterized in that the capacitance measuring means is disposed in the low temperature section.

2. 2. The vacuum pump according to claim 1, wherein the electrode is disposed facing the exhaust path.

3. The capacitance measuring means is 3. The vacuum pump according to claim 1, wherein the vacuum pump is disposed inside the vacuum vessel.

4. The capacitance measuring means is 3. The vacuum pump according to claim 1, wherein the vacuum pump is resin molded.

5. The capacitance measuring means is 3. A vacuum pump according to claim 1, wherein the low-temperature section is disposed so as to be capable of exchanging heat.

6. 3. The vacuum pump according to claim 1, wherein the capacitance measuring means is directly connected to a pin extending from the electrode.

7. A foreign object sensor for detecting foreign objects, which is used in a vacuum pump having a vacuum vessel having an exhaust path through which exhaust gas flows, a high-temperature portion to be heated by a heating means, and a low-temperature portion to be cooled by a cooling means, comprising: A pair of electrodes whose capacitance can change due to the accumulation of foreign matter, and a capacitance measuring means for measuring the capacitance between the electrodes, The electrode is disposed in the high temperature portion, 4. A foreign object sensor according to claim 3, wherein the capacitance measuring means is disposed in the low temperature portion.

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