Vacuum pump abnormality detection device, vacuum pump system, and vacuum pump abnormality detection method

Abstract

To provide a vacuum pump abnormality detection device, a vacuum pump system and a vacuum pump abnormality detection method capable of easily and accurately detecting an abnormality of a gap between a rotor and a stator or a casing without dismantling a vacuum pump.SOLUTION: An abnormality detection device 320 is for a vacuum pump 100 which comprises a casing 311, a rotor shaft 113, a magnetic bearing unit 312, a plurality of rotors 102, and a plurality of stators 123. The abnormality detection device has: vibration detection means 321 which acquires vibration generated on the vacuum pump 100; and contact determination means 323 which controls the magnetic bearing unit 312 to adjust a position of the rotor shaft 113 to a predetermined reference position, puts the rotor shaft 113 into a preset and predetermined operation state, offsets the position of the rotor shaft 113 a certain distance from the reference position by controlling the magnetic bearing unit 312 while putting the rotor shaft 113 into the predetermined operation state, and determines presence of contact of the plurality of rotors 102 on the basis of a change in vibration data acquired through the vibration detection means 321 before and after offsetting.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a vacuum pump abnormality detection device, a vacuum pump system, and a vacuum pump abnormality detection method. [Background technology]

[0002] Semiconductor manufacturing equipment, liquid crystal manufacturing equipment, electron microscopes, surface analysis equipment, microfabrication equipment, and the like require the environment within the equipment to be maintained at a high vacuum. Vacuum pumps are used to maintain the interior of these devices at a high vacuum. Vacuum pumps often use magnetic bearing devices that support a rotating body without contact as the bearing device (see, for example, Patent Document 1). The rotating body rotates while being levitated at a predetermined position by the magnetic bearing device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-120157 Summary of the Invention [Problem to be solved by the invention]

[0004] In vacuum pumps, the clearances between the rotor and stator blades and between the rotor and casing must be maintained within an appropriate range. If the clearances are out of the appropriate range, the rotor may come into contact with the stator or casing, potentially causing a malfunction of the vacuum pump. Abnormalities in the clearances between the rotor and stator or casing can be caused by, for example, incorrect assembly of parts such as the rotor or stator blades, improper part dimensions, part deformation, or deposition of process gas deposits on parts.

[0005] The present invention has been made to solve the above-mentioned problems, and aims to provide a vacuum pump abnormality detection device, a vacuum pump system, and a vacuum pump abnormality detection method that can easily and accurately detect abnormalities in the gap between the rotor and the stator or the casing without disassembling the vacuum pump. [Means for solving the problem]

[0006] The above object can be achieved by the invention described in (1) below.

[0007] (1) The abnormality detection device for a vacuum pump according to the present invention is an abnormality detection device for a vacuum pump comprising a casing, a rotor shaft arranged within the casing, a magnetic bearing device that magnetically levitates the rotor shaft to support it so that it can rotate without contact, a plurality of rotating blades that can rotate together with the rotor shaft, and a plurality of fixed blades that face the plurality of rotating blades, characterized in that it comprises at least one vibration detection means that acquires vibrations occurring in the vacuum pump, and a contact determination means that controls the magnetic bearing device to position the rotor shaft at a predetermined reference position and to set the rotor shaft to a predetermined operating state that is set in advance, controls the magnetic bearing device to offset the position of the rotor shaft by a predetermined amount from the reference position while the rotor shaft is in the predetermined operating state, and determines whether or not the plurality of rotating blades are in contact based on changes in vibration data acquired by the vibration detection means before and after the offset. [Effects of the Invention]

[0008] The anomaly detection device described in (1) above can detect abnormalities in the gap between the rotor and the stator or casing, which may be caused by incorrect assembly of parts, dimensional defects or deformation of parts, or accumulation of products, from changes in vibration data before and after offsetting the rotor shaft, so that it can detect abnormalities easily and with high accuracy without disassembling the vacuum pump.

[0009] (2) In the anomaly detection device described in (1) above, the position of the rotor shaft controlled by the magnetic bearing device and the reference position may be positions in the axial direction of the rotor shaft, thereby enabling the anomaly detection device to detect an anomaly in the axial gap between the rotor blades and the stator blades or the casing with high accuracy without disassembling the vacuum pump.

[0010] (3) In the anomaly detection device described in (1) above, the position of the rotor shaft controlled by the magnetic bearing device and the reference position may be a radial position of the rotor shaft, thereby enabling the anomaly detection device to detect an abnormality in the radial gap between the rotor blades and the stator blades or the casing with high accuracy without disassembling the vacuum pump.

[0011] (4) In the abnormality detection device described in any one of (1) to (3) above, the contact determination means may determine whether or not the plurality of rotor blades are in contact with each other for each offset amount obtained by changing the offset amount of the position of the rotor shaft relative to the reference position. This allows the abnormality detection device to detect the degree and position of the clearance abnormality from the determination result of whether or not there is contact with each other for each offset amount, without disassembling the vacuum pump.

[0012] (5) In the anomaly detection device described in any one of (1) to (4) above, the contact determination means may include a plurality of the vibration detection means, and may compare changes in the vibration data obtained for each of the plurality of vibration detection means before and after the offset to identify the vibration detection means with the largest change. This allows the anomaly detection device to easily identify the location of an abnormality in the gap between the rotor and the stator or the casing without disassembling the vacuum pump.

[0013] (6) In the anomaly detection device described in any one of (1) to (5) above, the predetermined operating state may be an operating state at a rotation speed lower than a rotation speed at rated rotation, thereby enabling the anomaly detection device to safely detect an abnormality in the gap between the rotor and the stator or the casing.

[0014] (7) In the vacuum pump described in any one of (1) to (6) above, the vibration detection means may be an acceleration sensor. This allows the anomaly detection device to stably acquire minute vibrations with low noise using the acceleration sensor, thereby enabling highly accurate detection of anomalies in the gap between the rotor and the fixed blades or the casing.

[0015] (8) In the vacuum pump described in any one of (1) to (6) above, the vibration detection means may be a sound sensor that detects vibrations caused by sound. This allows the abnormality detection device to detect abnormalities in the gap between the rotor and the stator or the casing in a non-contact manner.

[0016] (9) A vacuum pump system according to the present invention includes the vacuum pump and the anomaly detection device for the vacuum pump according to any one of (1) to (8) above, whereby the vacuum pump system can detect with high accuracy, by the anomaly detection device, an anomaly in the gap between the rotor and the stator or the casing that may occur due to incorrect assembly of parts, deformation of parts, deposition of products, etc., without disassembling the vacuum pump.

[0017] (10) A method for detecting an abnormality in a vacuum pump according to the present invention includes a casing, a rotor shaft disposed within the casing, a plurality of rotor blades rotatable together with the rotor shaft, and a plurality of stator blades facing the plurality of rotor blades, the method comprising the steps of: rotating the rotor shaft and the plurality of rotor blades at a predetermined rotational speed; acquiring vibration data of the vacuum pump when the rotor shaft is at a reference position using a vibration detection means while the vacuum pump is operating at the predetermined rotational speed; offsetting the rotor shaft by a predetermined amount from the reference position; acquiring vibration data of the vacuum pump at the predetermined rotational speed after the offset; calculating the difference in the vibration data before and after the offset; and comparing the difference in the vibration data with a predetermined reference value to determine whether the plurality of rotor blades are in contact with each other. This method for detecting an abnormality in a gap between the rotor blades and the stator blades, which may be caused by incorrect assembly of parts, deformation of parts, or deposition of products, without disassembling the vacuum pump, is thus capable of detecting with high accuracy an abnormality in a gap between the rotor blades and the stator blades, which may be caused by incorrect assembly of parts, deformation of parts, or deposition of products, without disassembling the vacuum pump. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 2 is a vertical cross-sectional view of a vacuum pump. [Figure 2] FIG. 2 is a circuit diagram of an amplifier circuit. [Figure 3] 10 is a time chart showing control when a current command value is larger than a detection value. [Figure 4] 10 is a time chart showing control when a current command value is smaller than a detection value. [Figure 5] 1 is a schematic plan view of a vacuum pump system according to an embodiment of the present invention. [Figure 6] FIG. 2 is a block diagram of a vacuum pump system. [Figure 7] 1A and 1B are schematic cross-sectional views illustrating the gap between the rotor and stator blades. (A) shows a state where there is no abnormality in the gap, (B) shows a state where the stator blade is installed at an angle, and (C) shows a state where products have accumulated on the stator blade. [Figure 8] 10 is a flowchart showing a control flow in a collision determination means. [Figure 9] 4 is a graph showing an example of a frequency spectrum of vibration detected by a vibration detection unit. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that dimensions in the drawings may be exaggerated for convenience of explanation and may differ from actual dimensions. Furthermore, in this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant explanations will be omitted.

[0020] The vacuum pump 100 is a turbomolecular pump that exhausts gas by ejecting gas molecules with rotating blades of a rotor that rotates at high speed. The turbomolecular pump 100 is used to suck and exhaust gas from a chamber of, for example, a semiconductor manufacturing device. First, the basic configuration of the turbomolecular pump 100 will be described.

[0021] 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 is provided a rotor 103, which has a plurality of rotors 102 (102a, 102b, 102c, etc.) that are turbine blades for sucking in and exhausting gas and are formed radially and in multiple stages around its periphery. A rotor shaft 113 is attached to the center of this rotor 103, and this rotor shaft 113 is levitated and supported in the air and its position is controlled by, for example, a five-axis controlled magnetic bearing. The rotor 103 is generally made of metal such as aluminum or an aluminum alloy.

[0022] 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 upper radial electromagnet 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 changes in the inductance of the conductive windings, which change 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 rotor 103 fixed thereto, and send the detected radial displacement to the control device 200.

[0023] 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.

[0024] The rotor shaft 113 is made of a high magnetic permeability material (iron, stainless steel, etc.) and is attracted by the magnetic force of the upper radial electromagnets 104. Such adjustment is performed independently in the X-axis direction and the Y-axis direction. The lower radial electromagnets 105 and the lower radial sensors 108 are arranged in the same manner as the upper radial electromagnets 104 and the upper radial sensors 107, and adjust the radial position of the lower side of the rotor shaft 113 in the same manner as the radial position of the upper side.

[0025] Furthermore, axial electromagnets 106A and 106B are arranged above and below a circular metal disk 111 provided at the bottom of rotor shaft 113. Metal disk 111 is made of a highly magnetic permeable 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.

[0026] In the control device 200, a compensation circuit having, for example, a PID adjustment function generates excitation control command signals for the axial electromagnet 106A and the axial electromagnet 106B based on the axial position signal detected by the axial sensor 109, and the amplifier circuit 150 controls the excitation of the axial electromagnet 106A and the axial electromagnet 106B based on these excitation control command signals, so that the axial electromagnet 106A attracts the metal disc 111 upward by magnetic force, and the axial electromagnet 106B attracts the metal disc 111 downward, thereby adjusting the axial position of the rotor shaft 113.

[0027] In this way, the control device 200 appropriately adjusts the magnetic forces that the axial electromagnets 106A and 106B exert on the metal disk 111, magnetically levitating the rotor shaft 113 in the axial direction and holding it in space without contact. The amplifier circuit 150 that controls the excitation of the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B will be described later.

[0028] 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. Motor 121 also incorporates a rotational speed sensor (not shown), such as a Hall element, resolver, or encoder, and the rotational speed of rotor shaft 113 is detected by the detection signal of this rotational speed sensor.

[0029] Furthermore, a phase sensor (not shown) is attached, for example, near the lower radial sensor 108, to detect the phase of rotation of the rotor shaft 113. The control device 200 uses the detection signals of both this phase sensor and the rotational speed sensor to detect the position of the magnetic pole.

[0030] A plurality of fixed blades 123 (123a, 123b, 123c...) are arranged at small gaps from the rotating blades 102 (102a, 102b, 102c...). Each of the rotating blades 102 (102a, 102b, 102c...) is formed at an angle of a predetermined degree from a plane perpendicular to the axis of the rotor shaft 113 in order to transport exhaust gas molecules downward through collision. The fixed blades 123 (123a, 123b, 123c...) are made of metal such as aluminum, iron, stainless steel, copper, or an alloy containing any of these metals as an ingredient.

[0031] Similarly, the fixed blades 123 are formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged in a staggered manner with the rows of rotor blades 102 toward the inside of the outer cylinder 127. The outer peripheral ends of the fixed blades 123 are supported by being inserted between a plurality of stacked rows of fixed blade spacers 125 (125a, 125b, 125c, etc.).

[0032] The fixed vane spacer 125 is a ring-shaped member made of a metal such as aluminum, iron, stainless steel, or copper, or an alloy containing any of these metals. An outer cylinder 127 is fixed to the outer periphery of the fixed vane spacer 125 with a small gap between them. 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.

[0033] Furthermore, depending on the application of the turbomolecular pump 100, a threaded spacer 131 (fixed member) is disposed between the lower part of the fixed vane spacer 125 and the base portion 129. The threaded spacer 131 is a cylindrical member made of metal such as aluminum, copper, stainless steel, iron, or an alloy containing any of these metals, and has a plurality of spiral thread grooves 131a engraved on its inner peripheral surface. The spiral direction of the thread grooves 131a is the direction in which, when exhaust gas molecules move in the rotation direction of the rotor 103, these molecules are transported toward the exhaust port 133. A cylindrical portion 102d hangs down from the lowest part of the rotor 103, next to the rotating vanes 102 (102a, 102b, 102c, etc.). The outer peripheral surface of cylindrical portion 102d is cylindrical and projects toward the inner peripheral surface of thread groove spacer 131, and is located close to the inner peripheral surface of thread groove spacer 131 with a predetermined gap between them. The exhaust gas transferred to thread groove 131a by rotor 102 and fixed blade 123 is sent to base portion 129 while being guided by thread groove 131a.

[0034] The base portion 129 is a disk-shaped member that forms the base of the turbomolecular pump 100, and is generally made of metal such as iron, aluminum, stainless steel, etc. 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.

[0035] In this configuration, when the rotor 102 is rotated together with the rotor shaft 113 by the motor 121, the action of the rotor 102 and the stator 123 draws exhaust gas from the chamber through the intake port 101. The rotational speed of the rotor 102 is typically 20,000 rpm to 90,000 rpm, and the peripheral speed at the tip of the rotor 102 reaches 200 m / s to 400 m / s. The exhaust gas drawn in through the intake port 101 passes between the rotor 102 and the stator 123 and is transported to the base 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 conduction of heat generated by the motor 121, but this heat is transferred to the stator 123 side by radiation or conduction through gas molecules of the exhaust gas.

[0036] The stator spacers 125 are joined together at their outer peripheries and transmit to the outside heat received by the stator 123 from the rotor 102 and frictional heat generated when exhaust gas comes into contact with the stator 123.

[0037] In the above description, the thread groove spacer 131 is disposed on the outer periphery of the cylindrical portion 102d of the rotor 103, and the thread groove 131a is formed on the inner circumferential surface of the thread groove spacer 131. However, conversely, there are also cases where a thread is formed on the outer circumferential surface of the cylindrical portion 102d, and a spacer having a cylindrical inner circumferential surface is disposed around the thread groove spacer 131.

[0038] Depending on the application of the turbomolecular pump 100, the electrical equipment section may be surrounded by a stator column 122 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., and the interior of this stator column 122 may be kept at a predetermined pressure by purge gas.

[0039] In this case, piping (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 between the protective bearing 120 and the rotor shaft 113, between the rotor and stator of the motor 121, and between the stator column 122 and the inner cylindrical portion of the rotor blades 102.

[0040] Here, the turbomolecular pump 100 requires control based on specific parameters (e.g., various characteristics corresponding to the model) that have been individually adjusted and identified for the model. To store these control parameters, the turbomolecular pump 100 is provided with an electronic circuit section 141 within its 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 lid 145.

[0041] In the semiconductor manufacturing process, some process gases introduced into a chamber have the property of solidifying when their pressure exceeds a predetermined value or their temperature falls below a predetermined value. Inside the turbomolecular pump 100, the pressure of the exhaust gas is lowest at the inlet port 101 and highest at the outlet port 133. If the pressure of the process gas exceeds a predetermined value or the temperature falls below a predetermined value while the process gas is being transferred from the inlet port 101 to the outlet port 133, the process gas solidifies and adheres to and accumulates inside the turbomolecular pump 100.

[0042] For example, when SiCl4 is used as the process gas in an Al etching system, the low vacuum (760 [torr] to 10 -2The vapor pressure curve shows that at high pressures (approximately 20°C) and low temperatures (approximately 20°C), solid products (e.g., AlCl3) precipitate and adhere to and accumulate inside the turbomolecular pump 100. When process gas deposits accumulate inside the turbomolecular pump 100, these deposits narrow the pump flow path, causing a decrease in the performance of the turbomolecular pump 100. The aforementioned products tend to solidify and adhere to high-pressure areas near the exhaust port 133 and the thread groove spacer 131.

[0043] Therefore, in order to solve this problem, conventionally, a heater (not shown) or a circular water-cooled pipe 149 is wrapped around the outer periphery of the base portion 129, etc., 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 by the water-cooled pipe 149 are controlled based on the signal from this temperature sensor to maintain the temperature of the base portion 129 at a constant high temperature (set temperature) (hereinafter referred to as TMS; Temperature Management System).

[0044] Next, a description will be given of the amplifier circuit 150 that controls excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B in the turbomolecular pump 100. A circuit diagram of this amplifier circuit 150 is shown in FIG.

[0045] 2, one end of the electromagnet winding 151 constituting the upper radial electromagnet 104 etc. is connected to a positive electrode 171a of a power supply 171 via a transistor 161, and the other end is connected to a negative electrode 171b of the power supply 171 via a current detection circuit 181 and a transistor 162. The transistors 161 and 162 are so-called power MOSFETs, and have a structure in which a diode is connected between the source and drain.

[0046] At this time, the transistor 161 has a diode cathode terminal 161a 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 diode cathode terminal 162a connected to the current detection circuit 181 and an anode terminal 162b connected to the negative electrode 171b.

[0047] Meanwhile, current regeneration diode 165 has its cathode terminal 165a connected to one end of electromagnet winding 151 and its anode terminal 165b connected to negative electrode 171b. Similarly, current regeneration diode 166 has its cathode terminal 166a connected to positive electrode 171a and its anode terminal 166b connected to the other end of electromagnet winding 151 via current detection circuit 181. Current detection circuit 181 is configured, for example, with a Hall sensor type current sensor or an electrical resistance element.

[0048] The amplifier circuit 150 configured as above corresponds to one electromagnet. Therefore, if the magnetic bearing is controlled in 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.

[0049] 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 in the figure of the control device 200, and this amplifier control circuit 191 is configured to switch the transistors 161 and 162 on / off.

[0050] The amplifier control circuit 191 compares 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. Based on the comparison result, the amplifier control circuit 191 determines the size of the pulse width (pulse width times Tp1 and Tp2) to be generated within a control cycle Ts, which is one period under PWM control. As a result, gate drive signals 191a and 191b having these pulse widths are output from the amplifier control circuit 191 to the gate terminals of the transistors 161 and 162.

[0051] It is necessary to control the position of rotor 103 at high speed and with strong force when, for example, the rotor 103 passes through a resonance point during acceleration of its rotational speed or when a disturbance occurs during constant-speed operation. For this reason, a voltage of, for example, about 50 V is used as power supply 171 so that the current flowing through electromagnet winding 151 can be rapidly increased (or decreased). In addition, a capacitor (not shown) is usually connected between positive electrode 171a and negative electrode 171b of power supply 171 to stabilize power supply 171.

[0052] In this configuration, when both transistors 161 and 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.

[0053] Furthermore, when one of the transistors 161 and 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, 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 and 162 in this manner, high-frequency noise such as harmonics generated in the turbomolecular 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.

[0054] That is, when the detected current value is smaller than the current command value, both transistors 161 and 162 are turned on for a time period corresponding to pulse width time Tp1 only once in a control cycle Ts (for example, 100 μs), as shown in Fig. 3. Therefore, during this period, the electromagnet current iL 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.

[0055] On the other hand, if the detected current value is greater than the current command value, both transistors 161 and 162 are turned off for a time period corresponding to 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 diodes 165 and 166.

[0056] 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.

[0057] <Present Embodiment> Next, a description will be given of a vacuum pump system 300 according to this embodiment. The vacuum pump system 300 includes a vacuum pump 100 and an abnormality detection device 320, as shown in FIGS.

[0058] As shown in Figures 1, 5 and 6, the vacuum pump 100 has a casing 311, a rotor shaft 113 rotatably arranged inside the casing 311, a magnetic bearing device 312 supporting the rotor shaft 113, a motor 121 that rotates the rotor shaft 113, multiple stages of rotor blades 102 fixed to the rotor shaft 113 and rotatable together with the rotor shaft 113, multiple stages of fixed blades 123 fixed to the casing 311 and arranged between the rotor blades 102, and a control device 200 that controls the operation of the motor 121 and magnetic bearing device 312 of the vacuum pump 100.

[0059] Anomaly detection device 320 is a device that detects an abnormality in gap G between rotor 102 and stator 123 or casing 311. As shown in Fig. 7(A), rotor 102 is disposed at an appropriate position in the radial and axial directions and rotates together with rotor shaft 113 that is levitated and supported by magnetic bearing device 312. For example, gap G between rotor 102 and stator 123 or casing 311 is maintained within an appropriate range.

[0060] As shown in Fig. 7(B), the gap G changes when there is an incorrect assembly of parts such as the rotor 102 and the stator 123, or when there is a dimensional defect or deformation of the parts. In addition, as shown in Fig. 7(C), the gap G also changes when deposits P of the process gas accumulate on the parts.

[0061] As shown in FIGS. 5 and 6, the abnormality detection device 320 includes at least one vibration detection means 321, an analog-digital converter 322 (AD converter), and a contact determination means 323.

[0062] The vibration detection means 321 is a device that detects vibrations of the vacuum pump 100, and is, for example, an acceleration sensor. The vibration detection means 321 is not particularly limited as long as it can detect vibrations, and may be a speed sensor, a displacement sensor, or a sound sensor such as a microphone that detects vibrations caused by sound. The sensor may be of either a contact type or a non-contact type. The attachment position of the vibration detection means 321 to the vacuum pump 100 is not particularly limited as long as it can detect vibrations of the vacuum pump 100. However, in consideration of ease of attachment, maintainability, detection sensitivity, etc., it is preferable that the attachment position be the outer surface of a thin portion of the casing 311. The direction of vibration detected by the vibration detection means 321 is not particularly limited.

[0063] The analog-to-digital converter 322 converts the analog signal from the vibration sensing means 321 into a digital signal.

[0064] The contact determination means 323 receives vibration data from the vibration detection means 321 that has been converted into a digital signal by the analog-to-digital converter 322, and determines whether or not there is contact between the rotor 102 and the fixed blade 123, or between the rotor 102 and the casing 311.

[0065] The contact determination means 323 is a device equipped with a memory circuit and an arithmetic circuit, and is, for example, a computer, a microcontroller, or a microprocessor. The contact determination means 323 can be connected to the control device 200 and can control the operation of the vacuum pump 100 via the control device 200. Therefore, the contact determination means 323 can control the magnetic bearing device 312 to adjust the axial (vertical) position and radial (horizontal) position of the rotor shaft 113, and can control the motor 121 to rotate the rotor shaft 113 at any rotational speed. The contact determination means 323 is a device separate from the control device 200, but may be a part of the control device 200.

[0066] Next, an abnormality detection method for the vacuum pump system 300 according to this embodiment will be described with reference to a flow chart of control in the contact determination means 323 shown in FIG.

[0067] 5, the inspector fixes at least one vibration detection means 321 to the vacuum pump 100. When using multiple vibration detection means 321, the inspector can install them at different circumferential positions or different axial positions of the vacuum pump 100.

[0068] Next, the inspector starts operation of the vacuum pump 100 for anomaly detection using the control device 200 via the contact determination means 323 or directly using the control device 200. The control device 200 controls and rotates the motor 121 to rotate the rotor shaft 113 at a predetermined rotational speed. The predetermined rotational speed is the rotational speed at which vibration measurement for anomaly detection is performed. The predetermined rotational speed is not particularly limited as long as it allows safe operation and allows features for anomaly detection to appear stably in the vibration data. For example, the predetermined rotational speed is equal to or lower than the rated rotational speed (20,000 to 90,000 rpm) to allow safe operation, but is not too low so that features for anomaly detection appear stably in the vibration data, such as 3,000 rpm. However, as long as safety during inspection can be ensured, inspection can also be performed at the rated rotational speed.

[0069] When the rotation speed of the rotor shaft 113 reaches a predetermined rotation speed, the control device 200 fixes the rotation speed at the predetermined rotation speed. Next, the inspector starts control by the contact determination means 323 shown in Fig. 8. Note that the control by the contact determination means 323 may be started automatically by the control device 200.

[0070] When control by the contact determination means 323 is initiated, the contact determination means 323 controls the magnetic bearing device 312 to set the axial position (floating position) of the rotor shaft 113 to a reference position, which is the center of the axial movable range (the range in which offsetting can be performed) (step S1). Note that the reference position does not necessarily have to be the center of the movable range. If the axial position of the rotor shaft 113 is the reference position from the start of operation of the vacuum pump 100, it is not necessary to move the rotor shaft 113 in step S1. Furthermore, if the contact determination means 323 is provided by a device separate from the control device 200, the position of the rotor shaft 113 may be set by the control device 200, not by the contact determination means 323.

[0071] Next, the contact determination means 323 acquires the vibration data output from each vibration detection means 321 via the analog-to-digital converter 322 (step S2). The contact determination means 323 converts the time waveform obtained from each vibration detection means 321 into a frequency spectrum by fast Fourier transform (discrete Fourier transform), and stores the data as data when the rotor shaft 113 is in the reference position, as shown by the solid line in the graph of Fig. 9.

[0072] Next, the contact determination means 323 controls the magnetic bearing device 312 to offset the axial position (floating position) of the rotor shaft 113 by a predetermined amount set in advance from the reference position (step S3). The value of the predetermined offset is, for example, +0.10 mm. Note that the positive offset direction here means an upward direction from the reference position, and the negative offset direction means a downward direction from the reference position. The predetermined offset may be in either the positive or negative direction. The value of the predetermined offset is, for example, a value obtained by subtracting a safety play from the value at which rotation is possible without contact if no problems occur. The value of the predetermined offset is set appropriately.

[0073] Next, the contact determination means 323 acquires the vibration data output from each vibration detection means 321 after the predetermined amount of offset has been applied via the analog-to-digital converter 322 (step S4). The contact determination means 323 converts the time waveform of the vibration obtained from each vibration detection means 321 into a frequency spectrum by fast Fourier transform (discrete Fourier transform), and stores the data as data when the predetermined amount of offset has been applied to the rotor shaft 113, as shown by the dotted line in the graph of Fig. 9.

[0074] Next, the contact determination means 323 compares the frequency spectrum when the rotor shaft 113 is at a position where the predetermined offset has been applied with the frequency spectrum when the rotor shaft 113 is at a reference position, and calculates a vibration evaluation value V by adding up the differences in vibration intensity (dB value) for each frequency in a predetermined frequency band B (step S5). That is, the vibration evaluation value V is calculated by adding up all the values ​​obtained by dividing the vibration intensity at the reference position shown by the solid line in Fig. 9 from the vibration intensity after the predetermined offset has been applied shown by the dotted line in Fig. 9 at each frequency in the predetermined frequency band B.

[0075] The predetermined frequency band B is not particularly limited as long as it is a frequency band in which characteristics appear in the vibration data when contact occurs between the rotor 102 and the stator 123 or the casing 311, and is, for example, 1300 Hz to 3000 Hz. Vibration data at frequencies below 1000 Hz is likely to vary depending on the installation conditions of the vacuum pump 100. Furthermore, the frequency band desired for measurement by the vibration detection means 321 is determined based on its product characteristics, and measurement accuracy usually decreases at high frequencies approaching the natural frequency of the vibration detection means 321 itself. It is preferable to determine the predetermined frequency band B by taking these factors into consideration comprehensively.

[0076] Furthermore, in this method, since the vibration strength is evaluated using dB values ​​expressed in common logarithms, it becomes easy to compare the vibration strength of each frequency in a frequency band having a width on the same scale, and by adding the dB values ​​for each frequency, it becomes possible to collectively detect changes in vibration strength across the entire frequency band B having a width. Furthermore, by being able to collectively detect changes in vibration strength across the entire frequency band B having a width, it becomes possible to make the determination of contact less susceptible to the influence of the vibration characteristics (e.g., natural frequency) of the casing 311 to which the vibration detection means 321 is attached.

[0077] The method for calculating the vibration evaluation value V is not limited to the above-mentioned method. For example, when calculating the vibration evaluation value V, the vibration intensity may be evaluated not in dB but in logarithms other than common logarithms, or amplitude values ​​of acceleration, velocity, or displacement. Furthermore, when calculating the vibration evaluation value V, the vibration intensity may be evaluated not in the entire frequency band B having a width but in amplitude values ​​of only a specific frequency, or amplitude values ​​of the time waveform of the vibration.

[0078] Next, the contact determination means 323 compares the vibration evaluation value V calculated from each vibration detection means 321 with a preset reference value (step S6).

[0079] If the vibration evaluation value V in all of the vibration detection means 321 is less than (or equal to or less than) the reference value, the contact determination means 323 determines that there is no contact because there is no significant change in vibration even when a predetermined amount of offset is applied to the rotor shaft 113 (step S7). Thereafter, the contact determination means 323 outputs the result (step S11) and ends the calculation for contact determination. The result is output, for example, to a display device such as a monitor provided in the contact determination means 323 or the control device 200, or to a display device with a separate configuration, but the output method is not particularly limited.

[0080] If the vibration evaluation value V in at least one vibration detection means 321 is equal to or greater than the reference value (or exceeds it), the contact determination means 323 determines that contact has occurred because a change in vibration has occurred by offsetting the rotor shaft 113 by a predetermined amount (step S8). When the rotor 102 comes into contact with the stator 123 or the casing 311, the contacting portion of the stator 123 or the casing 311 is vibrated each time contact occurs as the rotor 102 rotates, and this vibration is detected by the vibration detection means 321. Because the vibration frequency caused by contact is a wide range of frequencies, the increase in vibration intensity caused by contact occurs over a wide frequency range. Therefore, by adding up the changes in vibration intensity at each frequency in the predetermined frequency band B to determine whether or not contact has occurred, contact can be detected with high accuracy without being overlooked.

[0081] Next, the contact determination means 323 determines whether there are multiple vibration detection means 321 (step S9), and if there is only one vibration detection means 321, outputs a result indicating that there is contact (step S11), and ends the calculation for contact determination.

[0082] If the contact determination means 323 determines in step S9 that there are multiple vibration detection means 321, it identifies the vibration detection means 321 with the largest vibration evaluation value V (step S10). This is because the contact position is likely to be near the vibration detection means 321 with the largest vibration evaluation value V. Next, the contact determination means 323 outputs information on the identified contact position (the vibration detection means 321 that calculated the largest vibration evaluation value V) along with the result that there is contact (step S11), and ends the calculation of contact determination.

[0083] When there are multiple vibration detection means 321 in the axial direction, the contact determination means 323 can identify the vibration detection means 321 with the largest vibration evaluation value V, and determine to some extent the axial position where contact is occurring. When there are multiple vibration detection means 321 in the circumferential direction, the contact determination means 323 can identify the vibration detection means 321 with the largest vibration evaluation value V, and determine to some extent the circumferential position where contact is occurring.

[0084] If it is assumed that there is only one vibration detection means 321, steps S9 to S10 do not need to be provided.

[0085] As described above, the abnormality detection device 320 for a vacuum pump 100 according to this embodiment is an abnormality detection device 320 for a vacuum pump 100 comprising a casing 311, a rotor shaft 113 arranged within the casing 311, a magnetic bearing device 312 that supports the rotor shaft 113 so that it can rotate without contact by magnetically levitating it, a plurality of rotor blades 102 that can rotate together with the rotor shaft 113, and a plurality of stator blades 123 that face the plurality of rotor blades 102, and is equipped with at least one vibration detection means 321 that acquires vibrations occurring in the vacuum pump 100, and contact determination means 323 that controls the magnetic bearing device 312 to position the rotor shaft 113 at a predetermined reference position and to set the rotor shaft 113 to a predetermined operating state, and while the rotor shaft 113 is set to the predetermined operating state, controls the magnetic bearing device 312 to offset the position of the rotor shaft 113 by a predetermined amount from the reference position, and determines whether or not the plurality of rotor blades 102 are in contact based on changes in vibration data before and after the offset acquired by the vibration detection means 321. As a result, the anomaly detection device 320 can detect abnormalities in the gap between the rotor blades 102 and the stator blades 123 or the casing 311, which may be caused by incorrect component assembly, dimensional defects or deformation of components, or the accumulation of products, from changes in vibration data before and after the rotor shaft 113 is offset. This allows for easy and highly accurate detection without disassembling the vacuum pump 100. However, a simple method using a multimeter (circuit meter) to determine whether or not there is contact between the rotor shaft 113 and the casing 311 based on whether or not there is current flowing between them cannot determine whether or not there is contact while the vacuum pump 100 is operating due to the difficulty of installing the multimeter. In contrast, the anomaly detection device 320 can detect contact with high accuracy even when the vacuum pump 100 is operating at a high vacuum inside. Therefore, it is easy to periodically determine whether or not there is contact, as part of the normal operation of the vacuum pump 100.

[0086] The position of the rotor shaft 113 controlled by the magnetic bearing device 312 and the reference position are the axial positions of the rotor shaft 113. This allows the abnormality detection device 320 to detect with high accuracy an abnormality in the axial gap G between the rotor blades 102 and the stator blades 123 or the casing 311 without disassembling the vacuum pump 100.

[0087] The contact determination means 323 includes a plurality of vibration detection means 321, and compares the changes in vibration data before and after the offset obtained for each of the plurality of vibration detection means 321 to identify the vibration detection means 321 with the greatest change. This allows the abnormality detection device 320 to identify the position where an abnormality has occurred in the gap G between the rotor 102 and the stator 123 or the casing 311 without disassembling the vacuum pump 100.

[0088] The predetermined operating state for detecting an abnormality is an operating state at a rotation speed lower than the rated rotation speed, which allows the abnormality detection device 320 to safely detect an abnormality in the gap G between the rotor 102 and the stator 123 or the casing 311.

[0089] The vibration detection means 321 is an acceleration sensor. As a result, the abnormality detection device 320 can stably acquire minute vibrations with low noise using the acceleration sensor, and can therefore detect abnormalities in the gap G between the rotor 102 and the stator 123 or the casing 311 with high accuracy.

[0090] The vacuum pump system 300 includes an abnormality detection device 320 for the vacuum pump 100 and the vacuum pump 100. As a result, the vacuum pump system 300 can use the abnormality detection device 320 to detect with high accuracy an abnormality in the gap G between the rotor 102 and the stator 123 or the casing 311 that may occur due to incorrect assembly of parts, deformation of parts, deposition of products, or the like, without disassembling the vacuum pump 100.

[0091] Furthermore, the method for detecting an abnormality in a vacuum pump 100 in this embodiment is a method for detecting an abnormality in a vacuum pump 100 that includes a casing 311, a rotor shaft 113 arranged within the casing 311, a plurality of rotor blades 102 that can rotate together with the rotor shaft 113, and a plurality of stator blades 123 that face the plurality of rotor blades 102, and includes the steps of: rotating the rotor shaft 113 and the plurality of rotor blades 102 at a predetermined rotational speed; acquiring vibration data of the vacuum pump 100 when the rotor shaft 113 is in a reference position by a vibration detection means 321 during operation at the predetermined rotational speed; setting the position of the rotor shaft 113 to a position that has been offset by a predetermined amount from the reference position; acquiring vibration data of the vacuum pump 100 at the predetermined rotational speed after the predetermined offset has been implemented; calculating the difference in vibration data before and after the predetermined offset; and comparing the difference in vibration data with a predetermined reference value to determine whether or not the plurality of rotor blades 102 are in contact. As a result, the method for detecting an abnormality in the vacuum pump 100 can detect with high accuracy any abnormality in the gap G between the rotor 102 and the fixed blade 123 that may occur due to incorrect assembly of parts, deformation of parts, or deposition of products, without disassembling the vacuum pump 100.

[0092] The present invention is not limited to the above-described embodiment. Various modifications and combinations are possible within the technical spirit of the present invention. For example, the offset may be radial rather than axial. Therefore, the position and reference position of the rotor shaft 113 controlled by the magnetic bearing device 312 may be the radial position of the rotor shaft 113. The contact determination means 323 controls the magnetic bearing device 312 to offset the radial position of the rotor shaft 113 by a predetermined amount from the reference radial position. Note that the radial direction can be changed within a 360-degree angle range on a plane perpendicular to the axial direction, so the angle must also be set when offsetting. This allows the anomaly detection device 320 to accurately detect an abnormality in the radial gap G between the rotor blades 102 and the stator blades 123 or the casing 311 without disassembling the vacuum pump 100.

[0093] 8 may be repeated while changing the offset by a predetermined amount. That is, the contact determination means 323 may determine whether or not the rotor blades 102 are in contact with each other for each offset amount obtained by changing the offset amount of the rotor shaft 113 relative to the reference position. In this case, the contact determination means 323 can determine whether or not the rotor blades 102 are in contact with each other for each different offset amount (e.g., 0 mm, +0.1 mm, −0.1 mm). Therefore, for example, the contact determination means 323 can determine the value to which the offset amount must be increased to cause contact, and can detect the degree of abnormality in the gap. Furthermore, the contact determination means 323 can determine in which direction the abnormality in the gap exists based on the results of determining whether or not the rotor blades 102 are in contact with each other for each different offset amount (e.g., + and − axial directions, or directions at different angles in the radial direction).

[0094] Furthermore, the vibration detection means 321 may be a sound sensor that detects vibrations caused by sound, thereby enabling the abnormality detection device 320 to detect abnormalities in the gap G between the rotor 102 and the stator 123 or the casing 311 in a non-contact manner. [Explanation of symbols]

[0095] 102 Rotor 100 Vacuum Pump 113 Rotor shaft 121 Motor 123 Fixed wing 200 control device 300 Vacuum Pump System 311 Casing 312 Magnetic bearing device 320 Anomaly Detection Device 321 Vibration detection means 323 Contact determination means B. Prescribed frequency band G Gap

Claims

1. An abnormality detection device for a vacuum pump comprising: a casing; a rotor shaft arranged in the casing; a magnetic bearing device that supports the rotor shaft rotatably in a non-contact manner by magnetically levitating the rotor shaft; a plurality of rotor blades that are rotatable together with the rotor shaft; and a plurality of fixed blades that face the plurality of rotor blades, at least one vibration detection means for detecting vibrations occurring in the vacuum pump; a contact determination means for controlling the magnetic bearing device to set the position of the rotor shaft to a predetermined reference position and to set the rotor shaft to a predetermined operating state, and while the rotor shaft is in the predetermined operating state, controlling the magnetic bearing device to offset the position of the rotor shaft from the reference position by a predetermined amount, and determining whether or not the plurality of rotor blades are in contact with each other based on changes in vibration data before and after the offset obtained by the vibration detection means; A vacuum pump abnormality detection device comprising:

2. 2. The vacuum pump abnormality detection device according to claim 1, wherein the position of the rotor shaft controlled by the magnetic bearing device and the reference position are axial positions of the rotor shaft.

3. 2. The vacuum pump abnormality detection device according to claim 1, wherein the position of the rotor shaft controlled by the magnetic bearing device and the reference position are radial positions of the rotor shaft.

4. 2. The vacuum pump abnormality detection device according to claim 1, wherein the contact determination means determines whether or not the plurality of rotor blades are in contact with each other for each offset amount obtained by changing the offset amount of the position of the rotor shaft relative to the reference position.

5. 2. The vacuum pump abnormality detection device according to claim 1, wherein the contact determination means comprises a plurality of the vibration detection means, and compares changes in the vibration data before and after the offset obtained for each of the plurality of vibration detection means to identify the vibration detection means with the largest change.

6. 2. The vacuum pump abnormality detection device according to claim 1, wherein the predetermined operating state is an operating state at a rotation speed lower than a rotation speed at a rated rotation speed.

7. 2. The vacuum pump abnormality detection device according to claim 1, wherein the vibration detection means is an acceleration sensor.

8. 2. The vacuum pump abnormality detection device according to claim 1, wherein the vibration detection means is a sound sensor that detects vibrations caused by sound.

9. A vacuum pump system comprising: the vacuum pump abnormality detection device according to claim 1; and the vacuum pump.

10. A method for detecting an abnormality in a vacuum pump including a casing, a rotor shaft disposed within the casing, a plurality of rotor blades rotatable together with the rotor shaft, and a plurality of fixed blades facing the plurality of rotor blades, the method comprising: rotating the rotor shaft and the plurality of rotor blades at a predetermined rotation speed; acquiring vibration data of the vacuum pump when the rotor shaft is at a reference position by a vibration detection means during operation at the predetermined rotation speed; setting the position of the rotor shaft to a position offset by a predetermined amount from the reference position; acquiring vibration data of the vacuum pump at the predetermined rotation speed after the predetermined amount of offset is applied; calculating a difference between the vibration data before and after the predetermined amount offset; comparing the difference in the vibration data with a preset reference value to determine whether or not the plurality of rotor blades are in contact with each other; A method for detecting an abnormality in a vacuum pump, comprising:

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