Magnetic bearing device and vacuum pump

Abstract

The magnetic poles of the electromagnet unit and displacement sensor unit are appropriately positioned to achieve miniaturization. [Solution] A magnetic bearing device (110) comprising a rotating body (103), an electromagnet unit (104) that non-contactually supports the rotating body (103), and a displacement sensor unit (107) that detects the displacement of the rotating body (103), wherein the electromagnet unit (104) comprises a stator core (11) and electromagnet poles (17), the displacement sensor unit (107) comprises a displacement sensor core (21) and displacement sensor poles (23, 24), the displacement sensor poles (23, 24) are arranged between adjacent electromagnet poles (17), the electromagnet poles (17) include a first insulating member (16), the displacement sensor poles (23, 24) include a second insulating member (27), and the innermost end (16e) of the first insulating member (16) is located inside the innermost end (27e) of the second insulating member (27).

Description

Technical Field

[0001] The present invention relates to a magnetic bearing device and a vacuum pump.

Background Art

[0002] Generally, in a vacuum pump typified by a turbo molecular pump or the like, a magnetic bearing device that supports a rotating body in a non-contact manner is often used as a bearing device. Patent Document 1 discloses a magnetic bearing device including an electromagnet unit that supports a rotating body in a non-contact manner with a magnetic force in the radial direction and a displacement sensor unit that detects a displacement of the rotating body in the radial direction. In this magnetic bearing device, a magnet wire (conductive wire) is wound around the same stator core to form magnetic poles (coils) of the electromagnet unit and the displacement sensor unit, and the magnetic poles of the displacement sensor unit are arranged between the magnetic poles of the adjacent electromagnet units in the radial direction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the magnetic bearing device as described above, since a magnet wire (conductive wire) is wound around the same stator core to form magnetic poles (coils) of the electromagnet unit and the displacement sensor unit, there is no room in the circumferential direction, and particularly inside in the radial direction, the distance between the magnetic poles becomes narrow. Therefore, when trying to arrange the magnetic poles of the electromagnet unit and the displacement sensor unit with a certain margin in the radial direction, there is a problem that it hinders miniaturization of the magnetic bearing device.

[0005] [[ID=******]] Therefore, the main objective of the present invention is to provide a magnetic bearing device and a vacuum pump that can be miniaturized by properly arranging the magnetic poles of the electromagnet unit and the displacement sensor unit. [Means for solving the problem]

[0006] To achieve the above objective, one aspect of the present invention provides a magnetic bearing device comprising a rotating body, an electromagnet unit that non-contactly supports the rotating body radially by magnetic force, and a displacement sensor unit that detects the radial displacement of the rotating body, wherein the electromagnet unit comprises a stator core formed from a magnetic material and having a plurality of first teeth provided at predetermined intervals in the circumferential direction, and an electromagnet pole including a first magnet wire wound around the first teeth, and the displacement sensor unit comprises a displacement sensor core formed from a magnetic material and having second teeth, and a second tooth The device comprises a displacement sensor magnetic pole including a second magnet wire wound around a tooth, wherein the displacement sensor magnetic pole is positioned within the dimensional range of the electromagnet magnetic pole in the axial direction of the rotating body and between adjacent electromagnet magnetic poles in the circumferential direction, the electromagnet magnetic pole includes a first insulating member interposed between the first tooth and the first magnet wire, and the displacement sensor magnetic pole includes a second insulating member interposed between the second tooth and the second magnet wire, wherein the innermost end of the first insulating member in the radial direction is located inward of the innermost end of the second insulating member in the radial direction.

[0007] Furthermore, in the above configuration, it is preferable that the innermost end of the second tooth in the radial direction is located inward from the innermost end of the first tooth in the radial direction.

[0008] Furthermore, in the above configuration, it is preferable that the second teeth are perpendicular to the radial direction of the rotating body, and the cross-sectional area of ​​the first cross-section located inside the displacement sensor magnetic pole is larger than the cross-sectional area of ​​the second cross-section located radially inward from the first cross-section.

[0009] Furthermore, in the above configuration, it is preferable that the displacement sensor core is made of a separate component from the stator core.

[0010] To achieve the above objective, the vacuum pump of the present invention is equipped with the above-described magnetic bearing device. It is characterized by the following: [Effects of the Invention]

[0011] According to the present invention, the magnetic poles of the electromagnet unit and the displacement sensor unit can be appropriately arranged, and miniaturization can be achieved. Other problems, configurations, and effects will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0012] [Figure 1] This is a longitudinal cross-sectional view of a turbomolecular pump according to an embodiment of the present invention. [Figure 2] Figure 1 is a circuit diagram of the amplifier circuit for the turbomolecular pump shown. [Figure 3] This is a time chart showing the control of the amplifier control circuit when the current command value is greater than the detected value. [Figure 4] This is a time chart showing the control of the amplifier control circuit when the current command value is smaller than the detected value. [Figure 5] This is a perspective view showing the upper radial electromagnet and upper radial sensor that constitute the magnetic bearing device of the present invention. [Figure 6] Figure 5 shows a horizontal cross-sectional view of the upper radial electromagnet and upper radial sensor. [Figure 7] Figure 5 is an exploded perspective view showing a portion of the upper radial electromagnet. [Figure 8] Figure 6 shows an enlarged view of the main parts of the upper radial electromagnet and upper radial sensor, with hatching omitted for ease of understanding. [Figure 9] Figure 5 is a perspective view showing the state before the upper radial electromagnet and upper radial sensor are coupled. [Figure 10] Figure 5 shows a vertical cross-sectional view of the upper radial electromagnet and upper radial sensor. [Figure 11] This is a magnified view of a key part of Figure 10. [Figure 12] It is an enlarged view of the main part obtained by enlarging a part of FIG. 8. [Figure 13] It is a functional block diagram showing the configuration of a control device that controls an upper radial electromagnet and an upper radial sensor. [Figure 14] It is an enlarged view of the main part showing an upper radial electromagnet and an upper radial sensor that constitute the magnetic bearing device of Modification 1. [Figure 15] It is an exploded perspective view of the upper radial sensor shown in FIG. 14. [Figure 16] It is a horizontal cross-sectional view (A) of a displacement sensor core that constitutes the upper radial sensor shown in FIG. 15, a cross-sectional view (B) along line B-B of (A), and a cross-sectional view (C) along line C-C of (A). [Figure 17] It is a perspective view showing an upper radial electromagnet and an upper radial sensor that constitute the magnetic bearing device of Modification 2. [Figure 18] It is a horizontal cross-sectional view of the upper radial electromagnet and the upper radial sensor of Modification 2 shown in FIG. 17.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of a vacuum pump according to the present invention will be described with reference to the drawings, taking a turbo molecular pump as an example.

[0014] A longitudinal sectional view of this turbo molecular pump is shown in FIG. 1. In FIG. 1, in the turbo molecular pump 100, an intake port 101 is formed at the upper end of a cylindrical outer cylinder 127. And inside the outer cylinder 127, a rotating body 103 is provided with a plurality of rotating blades 102 (102a, 102b, 102c ···), which are turbine blades for sucking and exhausting gas, formed radially and in multiple stages on the circumferential part. A rotor shaft 113 is attached to the center of this rotating body 103, and this rotor shaft 113 is levitated and position-controlled in the air by, for example, a magnetic bearing with five-axis control. The rotating body 103 is generally made of a metal such as aluminum or an aluminum alloy.

[0015] The upper radial electromagnet 104 (electromagnet unit) consists of four electromagnets arranged in pairs along the X and Y axes. Inside the upper radial electromagnet 104 (within the dimensional range in the axial direction Z of the rotor shaft 113), and corresponding to each of the upper radial electromagnets 104, are four upper radial sensors 107 (displacement sensor units). The upper radial sensors 107 use, for example, inductance sensors or eddy current sensors with conduction windings, and detect the position of the rotor shaft 113 based on the change in the inductance of these conduction windings, which changes according to the position of the rotor shaft 113. These upper radial sensors 107 are configured to detect the radial displacement of the rotor shaft 113, i.e., the rotating body 103 fixed to it, and send the data to the control device 200.

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

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

[0018] Furthermore, axial electromagnets 106A and 106B are positioned above and below a disc-shaped metal disk 111 located at the bottom of the rotor shaft 113. The metal disk 111 is made of a high-permeability material such as iron. An axial sensor 109 is provided to detect the axial displacement of the rotor shaft 113, and its axial position signal is sent to the control device.

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

[0020] Thus, the control device 200 appropriately adjusts the magnetic force exerted by the axial electromagnets 106A and 106B on the metal disk 111, causing the rotor shaft 113 to levitate axially and be held in contact with space. The amplifier circuit 150 that excites and controls the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B will be described later.

[0021] On the other hand, the motor 121 is equipped with multiple magnetic poles arranged circumferentially around the rotor shaft 113. Each magnetic pole is controlled by the control device 200 to rotate the rotor shaft 113 via the electromagnetic force acting between it and the rotor shaft 113. The motor 121 also incorporates a rotational speed sensor, such as a Hall element, resolver, or encoder (not shown), and the rotational speed of the rotor shaft 113 is detected by the detection signal from this rotational speed sensor.

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

[0023] Multiple fixed blades 123 (123a, 123b, 123c...) are arranged with a small gap between them and the rotating blades 102 (102a, 102b, 102c...). The rotating blades 102a, 102b, 102c... are each 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. The fixed blades 123 (123a, 123b, 123c...) are made of metals such as aluminum, iron, stainless steel, copper, or alloys containing these metals as components.

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

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

[0026] Furthermore, depending on the application of the turbomolecular pump 100, a threaded spacer 131 is provided between the lower part of the fixed-blade spacer 125 and the base portion 129. The threaded spacer 131 is a cylindrical member made of a metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals, and has multiple helical screw grooves 131a engraved on its inner circumferential surface. The direction of the helix of the screw grooves 131a is such that when exhaust gas molecules move in the direction of rotation of the rotating body 103, these molecules are transported toward the exhaust port 133. A cylindrical portion 102d hangs down from the lowest part of the rotating body 103, following the rotor blades 102a, 102b, 102c, etc. The outer circumferential surface of this cylindrical portion 102d is cylindrical and protrudes toward the inner circumferential surface of the threaded spacer 131, and is in close proximity to the inner circumferential surface of the threaded spacer 131 with a predetermined gap between them. The exhaust gas, which has been transferred to the screw groove 131a by the rotor blade 102 and the fixed blade 123, is guided through the screw groove 131a and sent to the base section 129.

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

[0028] In this configuration, when the rotor blade 102 is rotated by the motor 121 together with the rotor shaft 113, exhaust gas is drawn in from the chamber through the intake port 101 due to the action of the rotor blade 102 and the fixed blade 123. The rotational speed of the rotor blade 102 is usually 20,000 rpm to 90,000 rpm, and the peripheral speed at the tip of the rotor blade 102 reaches 200 m / s to 400 m / s. The exhaust gas drawn in from the intake port 101 passes between the rotor blade 102 and the fixed blade 123 and is transferred to the base section 129. At this time, the temperature of the rotor blade 102 rises due to frictional heat generated when the exhaust gas comes into contact with the rotor blade 102 and heat conduction generated by the motor 121, but this heat is transferred to the fixed blade 123 side by radiation or conduction by gas molecules of the exhaust gas.

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

[0030] In the above description, the threaded spacer 131 is positioned on the outer circumference of the cylindrical portion 102d of the rotating body 103, and the threaded groove 131a is engraved on the inner surface of the threaded spacer 131. However, conversely, the threaded groove may be engraved on the outer surface of the cylindrical portion 102d, and a spacer having a cylindrical inner surface may be positioned around it.

[0031] Furthermore, depending on the application of the turbomolecular pump 100, the electrical components, which consist of an upper radial electromagnet 104, an upper radial sensor 107, a motor 121, a lower radial electromagnet 105, a lower radial sensor 108, axial electromagnets 106A, 106B, and an axial sensor 109, may be covered by a stator column 122 to prevent the gas drawn in from the intake port 101 from entering the electrical components, and the inside of this stator column 122 may be maintained at a predetermined pressure with purge gas.

[0032] In this case, piping (not shown) is provided in the base section 129, and purge gas is introduced through this piping. The introduced purge gas is sent to the exhaust port 133 through the 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 part of the rotor blade 102.

[0033] Here, the turbomolecular pump 100 requires model identification and control based on individually adjusted unique parameters (e.g., characteristics corresponding to the model). To store these control parameters, the turbomolecular pump 100 is equipped with an electronic circuit section 141 within its body. The electronic circuit section 141 consists of electronic components such as semiconductor memory such as EEP-ROM and semiconductor elements for accessing it, and a substrate 143 for mounting them. This electronic circuit section 141 is housed, for example, below a rotational speed sensor (not shown) near the center of the base section 129 that constitutes the lower part of the turbomolecular pump 100, and is closed by an airtight bottom cover 145.

[0034] Incidentally, in the semiconductor manufacturing process, some process gases introduced into the chamber have the property of becoming solid when their pressure exceeds a predetermined value or their temperature falls below a predetermined value. Inside the turbomolecular pump 100, the exhaust gas pressure is lowest at the intake port 101 and highest at the exhaust port 133. If the process gas pressure exceeds a predetermined value or its temperature falls below a predetermined value while it is being transferred from the intake port 101 to the exhaust port 133, the process gas becomes solid and adheres to and accumulates inside the turbomolecular pump 100.

[0035] For example, if SiCl4 is used as the process gas in an Al etching apparatus, the low vacuum (760 [torr] ~ 10 -2The vapor pressure curve shows that when the pressure is low (torr) and the temperature is low (approximately 20°C), solid products (e.g., AlCl3) precipitate and adhere to the inside of the turbomolecular pump 100. As a result, when process gas precipitates accumulate inside the turbomolecular pump 100, these deposits narrow the pump flow path, causing a decrease in the performance of the turbomolecular pump 100. Furthermore, the aforementioned products were prone to solidifying and adhering in areas of high pressure, such as near the exhaust port 133 and near the threaded spacer 131.

[0036] Therefore, in order to solve this problem, conventional methods involve wrapping a heater (not shown) or an annular water-cooling pipe 149 around the outer circumference of the base portion 129, and embedding a temperature sensor (e.g., a thermistor) (not shown) in the base portion 129. Based on the signal from this temperature sensor, heating by the heater and cooling by the water-cooling pipe 149 are controlled (hereinafter referred to as TMS; Temperature Management System) to maintain the temperature of the base portion 129 at a constant high temperature (set temperature).

[0037] Next, we will describe an amplifier circuit 150 that energizes and controls the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B of the turbomolecular pump 100 configured in this way. The circuit diagram of this amplifier circuit is shown in Figure 2.

[0038] In Figure 2, the electromagnet winding 151, which constitutes the upper radial electromagnet 104, has one end connected to the positive terminal 171a of the power supply 171 via transistor 161, and the other end connected to the negative terminal 171b of the power supply 171 via current detection circuit 181 and transistor 162. Transistors 161 and 162 are so-called power MOSFETs, and have a structure in which a diode is connected between their source and drain.

[0039] In this configuration, transistor 161 has its diode cathode terminal 161a connected to the positive terminal 171a, and its anode terminal 161b connected to one end of the electromagnet winding 151. Transistor 162 has its diode cathode terminal 162a connected to the current detection circuit 181, and its anode terminal 162b connected to the negative terminal 171b.

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

[0041] The amplifier circuit 150 configured as described above corresponds to one electromagnet. Therefore, if the magnetic bearing is 5-axis controlled and there are a total of 10 electromagnets 104, 105, 106A, and 106B, a similar amplifier circuit 150 is configured for each electromagnet, and the 10 amplifier circuits 150 are connected in parallel to the power supply 171.

[0042] Furthermore, the amplifier control circuit 191 is configured, for example, by a digital signal processor (hereinafter referred to as the DSP section) of the control device 200 (not shown), and this amplifier control circuit 191 is configured to switch transistors 161 and 162 on and off.

[0043] The amplifier control circuit 191 compares the current value detected by the current detection circuit 181 (the signal reflecting this current value is called the current detection signal 191c) with a predetermined current command value. Based on this comparison, it determines the magnitude of the pulse width (pulse width time Tp1, Tp2) to be generated within the control cycle Ts, which is one period of PWM control. As a result, gate drive signals 191a and 191b with this pulse width are output from the amplifier control circuit 191 to the gate terminals of transistors 161 and 162.

[0044] Furthermore, when the rotating body 103 passes a resonance point during accelerated rotational speed operation, or when disturbances occur during constant-speed operation, it is necessary to control the position of the rotating body 103 with high speed and strong force. For this reason, a high voltage of, for example, 50V is used as the power supply 171 so that the current flowing through the electromagnet winding 151 can be rapidly increased (or decreased). In addition, a capacitor is usually connected between the positive electrode 171a and the negative electrode 171b of the power supply 171 to stabilize the power supply 171 (not shown).

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

[0046] Furthermore, by turning one of transistors 161 and 162 on and the other off, a so-called flywheel current is maintained. By allowing this flywheel current to flow through the amplifier circuit 150, hysteresis loss in the amplifier circuit 150 can be reduced, and the overall power consumption of the circuit can be kept low. In addition, by controlling transistors 161 and 162 in this way, high-frequency noise such as harmonics generated in the turbomolecular pump 100 can be reduced. Moreover, by measuring this flywheel current with the current detection circuit 181, the electromagnet current iL flowing through the electromagnet winding 151 can be detected.

[0047] In other words, if the detected current value is smaller than the current command value, both transistors 161 and 162 are turned on only once during the control cycle Ts (e.g., 100 μs) for a duration corresponding to the pulse width time Tp1, as shown in Figure 3. Therefore, the electromagnet current iL during this period increases from the positive electrode 171a to the negative electrode 171b, towards the current value iLmax (not shown) that can flow through transistors 161 and 162.

[0048] On the other hand, if the detected current value is greater than the current command value, both transistors 161 and 162 are turned off only once during the control cycle Ts for a duration corresponding to the pulse width time Tp2, as shown in Figure 4. Therefore, during this period, the electromagnet current iL decreases from the negative electrode 171b towards the positive electrode 171a, towards a regenerative current value iLmin (not shown) via diodes 165 and 166.

[0049] In either case, after the pulse width time Tp1 and Tp2 have elapsed, one of transistors 161 or 162 is turned on. Therefore, during this period, the flywheel current is maintained in the amplifier circuit 150.

[0050] [Configuration of radial magnetic bearing 110 (magnetic bearing device)] Next, the specific configuration of the radial magnetic bearing 110 (magnetic bearing device) will be explained based on the drawings. Figure 5 is a perspective view showing the upper radial electromagnet 104 and the upper radial sensor 107, and Figure 6 is a horizontal cross-sectional view of the upper radial electromagnet 104 and the upper radial sensor 107. Figure 7 is an exploded perspective view showing a part of the upper radial electromagnet 104 disassembled. Figure 8 is an enlarged view of the main parts showing the upper radial electromagnet 104 and the upper radial sensor 107, with hatching omitted to avoid complexity. Figure 9 is a perspective view showing the state before the upper radial electromagnet 104 and the upper radial sensor 107 are coupled, and Figure 10 is a vertical cross-sectional view of the upper radial electromagnet 104 and the upper radial sensor 107. Figure 11 is an enlarged view of the main parts, showing a part of Figure 10.

[0051] Furthermore, in the following, the radial direction R, axial direction Z, and circumferential direction C of the rotor shaft 113 (rotating body 103) will simply be referred to as the radial direction R, axial direction Z, and circumferential direction C.

[0052] As shown in Figure 1, the radial magnetic bearing 110 comprises a rotating body 103, an upper radial electromagnet 104 (electromagnet unit), an upper radial sensor 107 (displacement sensor unit), a lower radial electromagnet 105, and a lower radial sensor 108. The upper radial electromagnet 104 and the lower radial electromagnet 105 have similar structures, and the upper radial sensor 107 and the lower radial sensor 108 have similar structures. Therefore, the structure of the upper radial electromagnet 104 and the upper radial sensor 107 will be described below as an example, and the description of the structure of the lower radial electromagnet 105 and the lower radial sensor 108 will be omitted.

[0053] As shown in Figure 5, the upper radial electromagnet 104 and the upper radial sensor 107 are coupled to each other, as will be described later, but the upper radial sensor 107 is made of a separate component from the upper radial electromagnet 104. The upper radial electromagnet 104 comprises a stator core 11 and a plurality of electromagnet poles 13 and 14.

[0054] [Configuration of Stator Core 11] As shown in Figure 6, the stator core 11 has a cylindrical first back yoke 11a and a plurality of first teeth 11b. The stator core 11 is formed from a magnetic material. More specifically, the stator core 11 is formed by laminating a plurality of steel plates (e.g., silicon steel plates) of the same shape in the axial direction Z. The first teeth 11b are provided at predetermined intervals in the circumferential direction C. The first teeth 11b protrude from the inner circumferential surface of the first back yoke 11a toward the center O of the stator core 11. The first teeth 11b are formed in a rectangular columnar shape extending along the radial direction R.

[0055] [Configuration of electromagnet poles 13 and 14] The electromagnet poles 13 and 14 include the first teeth 11b of the stator core 11 and a coil 15. The coil 15 is formed by winding a first magnet wire around the first teeth 11b. More specifically, the electromagnet poles 13 and 14 comprise the first teeth 11b, the coil 15, and a first bobbin 16 (first insulating member; see Figures 7 and 8) interposed between the first teeth 11b and the coil 15.

[0056] A pair of electromagnet poles 13 and 14 constitute a radial electromagnet 17 (17X, 17Y). In this embodiment, the upper radial electromagnet 104 has eight electromagnet poles 13. In other words, the upper radial electromagnet 104 has four radial electromagnets 17 (17X, 17Y). The four radial electromagnets 17 (17X, 17Y) provide non-contact magnetic support to the rotor shaft 113 in the radial direction R. Each radial electromagnet 17 (17X, 17Y) is spaced 90 degrees apart along the circumferential direction C and is positioned on the X-axis or Y-axis. The electromagnet poles 13 and 14 have different polarities by winding the first magnet wire of the coil 15 in opposite directions.

[0057] In this specification, the X-axis and Y-axis are perpendicular to the center O of the stator core 11, and the X-axis and Y-axis are perpendicular to each other. The X-axis direction and Y-axis direction are directions along the X-axis and Y-axis. In this embodiment, when distinguishing between radial electromagnets 17 according to the direction in which they support the rotor shaft 113, those that non-contact support the rotor shaft 113 in the X-axis direction are designated as radial electromagnets 17X by adding an X to the end of the number, and those that non-contact support the rotor shaft 113 in the Y-axis direction are designated as radial electromagnets 17Y by adding a Y to the end of the number, and when referring to them collectively, they are simply designated as radial electromagnets 17 with only a number.

[0058] [Configuration of coil 15] As shown in Figures 7 and 8, the coil 15 is mounted on the first tooth 11b with the coil wound around the first bobbin 16. The first bobbin 16 has a bobbin body a, a first flange 16b, and a second flange 16c. The first bobbin 16 is made of an insulating material such as resin.

[0059] The bobbin cylinder portion 16a is a cylindrical body having a through hole 16d into which the first teeth 11b can be inserted. The cross-sectional shape of the bobbin cylinder portion 16a perpendicular to the direction of penetration of the through hole 16d is rectangular, corresponding to the cross-sectional shape of the first teeth 11b. In other words, the bobbin cylinder portion 16a is a rectangular cylindrical body. The first magnet wire is wound around the outer circumferential surface of the bobbin cylinder portion 16a to form a coil 15.

[0060] The first flange portion 16b is formed in a flat plate shape, protruding from the outer circumferential surface of the bobbin cylinder portion 16a at approximately a right angle outward (away from the through hole 16d) at the end of the bobbin cylinder portion 16a located on the side of the center O of the stator core 11. The second flange portion 16c is formed in a flat plate shape, protruding from the outer circumferential surface of the bobbin cylinder portion 16a at approximately a right angle outward (away from the through hole 16d) at the end of the bobbin cylinder portion 16a located on the side of the center O of the stator core 11. The first flange portion 16b and the second flange portion 16c hold the first magnet wire wound around the bobbin cylinder portion 16a. In other words, the first flange portion 16b and the second flange portion 16c prevent the first magnet wire wound around the bobbin cylinder portion 16a from moving in the radial direction R.

[0061] In the radial electromagnet 17 (17X, 17Y), the pair of electromagnet poles 13 and 14 are adjacent to each other in the circumferential direction C, with a gap D1 between the side end faces of the first flange portion 16b of the first bobbin 16. On the other hand, in the circumferential direction C, adjacent electromagnet poles 13 and 14 (in other words, the electromagnet pole 13 constituting radial electromagnet 17X and the electromagnet pole 14 constituting radial electromagnet 17Y, and the electromagnet pole 14 constituting radial electromagnet 17X and the electromagnet pole 13 constituting radial electromagnet 17Y) have a gap D2 between the side end faces of the first flange portion 16b of the first bobbin 16 in the circumferential direction C. The gap D2 is larger than the gap D1.

[0062] [Configuration of the upper radial sensor 107 (107A, 107B)] The four upper radial sensors 107 (107A, 107B) detect the displacement of the rotor shaft 113 in the radial direction R. As shown in Figure 6, the four upper radial sensors 107 (107A, 107B) are positioned between adjacent radial electromagnets 17X, 17Y in the circumferential direction C.

[0063] As shown in Figure 6, each displacement sensor core 21 of the upper radial sensor 107 (107A, 107B) is positioned on the A-axis, which is tilted by a predetermined angle θ1 with respect to the X-axis, or on the B-axis, which is tilted by a predetermined angle θ2 with respect to the Y-axis. In this embodiment, the predetermined angles θ1 and θ2 are set to 45 degrees. The upper radial sensor 107 (107A, 107B) is a displacement sensor, such as an inductance type displacement sensor.

[0064] In this embodiment, when distinguishing the upper radial sensors 107 according to the direction of displacement detection, those located on the A-axis are designated as upper radial sensors 107A by adding "A" to the end of the number, and those located on the B-axis are designated as upper radial sensors 107B by adding "B" to the end of the number. When referring to these collectively, they are simply designated as upper radial sensors 107 with only the number added.

[0065] As shown in Figures 9 and 10, the upper radial sensors 107 (107A, 107B) comprise a displacement sensor core 21, a pair of displacement sensor magnetic poles 23 and 24, and a positioning section 25. The positioning section 25 is integrally formed from the same material as the displacement sensor core 21. The displacement sensor core 21 has a second back yoke 21a and a pair of second teeth 21b. The second back yoke 21a is positioned on the center O side of the stator core 11 relative to the first back yoke 11a. The second back yoke 21a is formed in a rectangular columnar shape extending along the axial direction Z.

[0066] A pair of second teeth 21b protrude inward from the second back yoke 21a (towards the center O of the stator core 11). In this embodiment, the pair of second teeth 21b are arranged side by side in the axial direction Z. The second teeth 21b are formed in a rectangular column shape extending along the radial direction R. In other words, the second teeth 21b have a uniform width W2 (see Figure 12) in the circumferential direction C.

[0067] [Configuration of displacement sensor magnetic poles 23 and 24] A pair of displacement sensor poles 23 and 24 are arranged side by side in the axial direction Z. The pair of displacement sensor poles 23 and 24 include a second tooth 21b of a displacement sensor core 21 and a coil 26. The coil 26 is formed by winding a second magnet wire around the second tooth 21b. More specifically, the displacement sensor poles 23 and 24 comprise a second tooth 21b, a coil 26, and a second bobbin 27 (second insulating member) interposed between the second tooth 21b and the coil 26.

[0068] [Configuration of coil 26] As shown in Figures 10 and 11, the coil 26 is mounted on the second tooth 21b with the coil wound around the second bobbin 27. The second bobbin 27 has a bobbin cylinder portion 27a, a first flange portion 27b, and a second flange portion 27c. The second bobbin 27 is made of an insulating material such as resin.

[0069] The bobbin cylinder portion 27a is a cylindrical body having a through hole 27d into which the second teeth 21b can be inserted. The cross-sectional shape of the bobbin cylinder portion 27a perpendicular to the direction of penetration of the through hole 27d is rectangular, corresponding to the cross-sectional shape of the second teeth 21b. In other words, the bobbin cylinder portion 27a is a rectangular cylindrical body. The second magnet wire is wound around the outer circumferential surface of the bobbin cylinder portion 27a to form a coil 26.

[0070] The first flange portion 27b is formed in a flat plate shape, protruding from the outer circumferential surface of the bobbin cylinder portion 27a at approximately a right angle outward (away from the through hole 27d) at the end of the bobbin cylinder portion 27a located on the side of the center O of the stator core 11. The second flange portion 27c is formed in a flat plate shape, protruding from the outer circumferential surface of the bobbin cylinder portion 27a at approximately a right angle outward (away from the through hole 27d) at the end of the bobbin cylinder portion 27a located on the side of the center O of the displacement sensor core 21. As a result, the first flange portion 27b and the second flange portion 27c hold the second magnet wire wound around the bobbin cylinder portion 27a. In other words, the first flange portion 27b and the second flange portion 27c prevent the second magnet wire wound around the bobbin cylinder portion 27a from moving in the radial direction R.

[0071] In this embodiment, the first flange portion 27b and the second flange portion 27c have the same width W1 in the circumferential direction C (see Figure 12), and are the largest parts of the second bobbin 27 in the circumferential direction C. The coil 26 has dimensions smaller than or the same as the second bobbin 27 in the circumferential direction C. In other words, the first flange portion 27b and the second flange portion 27c are the largest parts of the displacement sensor magnetic poles 23 and 24 in the circumferential direction C.

[0072] Displacement sensor poles 23 and 24 have different polarities because the second magnet wire of the coil 26 is wound in opposite directions. As described above, the upper radial electromagnet 104 has displacement sensor poles 23 and 24 arranged in the axial direction Z, whereas the radial electromagnet 17 (17X, 17Y) has electromagnet poles 13 and 14 arranged in the radial direction R. Therefore, in this embodiment, the magnetic flux flow MF2 (shown by the dashed line in Figure 11) of the upper radial sensor 107 (107A, 107B) is approximately perpendicular to the magnetic flux flow MF1 (shown by the dashed line in Figure 7) of the radial electromagnet 17 (17X, 17Y). As a result, magnetic interference caused by magnetic flux leaking from the radial electromagnet 17 (17X, 17Y) to the upper radial sensor 107 (107A, 107B) is suppressed.

[0073] Furthermore, the displacement sensor core 21 is formed from a magnetic material. More specifically, the displacement sensor core 21 is integrally formed from soft ferrite. If the displacement sensor core 21 is formed from laminated steel plates stacked in the Z-axis direction, the laminated steel plates will be arranged perpendicular to the magnetic flux flow MF2 of the upper radial sensor 107 (including the magnetic flux flow along the Z-axis direction), making it easy for induced currents (called eddy currents) to occur within the steel plates. When such eddy currents occur, the sensitivity of the upper radial sensor 107 (107A, 107B) decreases, or the phase of the signal output by the upper radial sensor 107 (107A, 107B) is delayed. However, in this embodiment, since the displacement sensor core 21 is integrally formed from soft ferrite, the eddy currents described above can be suppressed.

[0074] As shown in Figures 10 and 11, the positioning unit 25 is connected to one end of the displacement sensor core 21 in the axial direction Z and extends outward in the radial direction R. In other words, the positioning unit 25 is located on the outside of the stator core 11 in the axial direction Z.

[0075] The positioning unit 25 can perform relative positioning between the upper radial sensors 107 (107A, 107B) and the stator core 11. More specifically, the positioning unit 25 can position the upper radial sensors 107 (107A, 107B) in the axial direction Z by contacting the end face 11c of the stator core 11 in the axial direction Z.

[0076] The positioning portion 25 is connected to the stator core 11 at the end face 11c of the stator core 11. More specifically, the positioning portion 25 and the stator core 11 are fastened together, for example, by screws 30 (see Figure 9). However, the connection between the positioning portion 25 and the stator core 11 is not limited to this; for example, the positioning portion 25 and the stator core 11 may be welded together, or the positioning portion 25 and the stator core 11 may be bonded together with an adhesive.

[0077] [Arrangement of displacement sensor magnetic poles 23 and 24] As shown in Figures 6 and 8, the displacement sensor poles 23 and 24 are positioned between adjacent electromagnet poles 13 and 14 in the circumferential direction C, more specifically between the electromagnet pole 13 constituting radial electromagnet 17X and the electromagnet pole 14 constituting radial electromagnet 17Y, and between the electromagnet pole 14 constituting radial electromagnet 17X and the electromagnet pole 13 constituting radial electromagnet 17Y. As shown in Figures 10 and 11, the displacement sensor poles 23 and 24 are positioned within the range of dimension H of the electromagnet poles 13 and 14 in the axial direction Z (inside the dimension H in the height direction).

[0078] As shown in Figure 12, the width W1 of the second bobbin 27 (first flange portion 27b and second flange portion 27c) in the circumferential direction C is larger than the gap D2 described above. Therefore, the second bobbin 27 cannot be positioned at the location of the gap D2. Accordingly, in this embodiment, the innermost end 16e of the first bobbin 16 in the radial direction R (the inner end face of the first flange portion 16b) is located inward from the innermost end 27e of the second bobbin 27 in the radial direction R (the inner end face of the first flange portion 27b). This allows the displacement sensor magnetic poles 23 and 24 to be positioned between adjacent electromagnet magnetic poles 13 and 14 in the circumferential direction C.

[0079] Furthermore, the width W2 of the second tooth 21b in the circumferential direction C is smaller than the gap D2. Therefore, the innermost end 21c of the second tooth 21b can be positioned inward in the radial direction R than the innermost end 11d of the first tooth 11b (the inner end face of the first tooth 11b). In other words, the gap D3 (see Figure 11) between the rotor shaft 113 and the second tooth 21b in the radial direction R can be reduced.

[0080] [Functional configuration of the control device 200] Next, the control device 200 will be described. Figure 13 is a functional block diagram of the control device 200 that controls the upper radial electromagnet 104, the lower radial electromagnet 105, and the upper radial sensor 107.

[0081] As shown in Figure 13, the upper radial sensor 107A detects the A-axis displacement of the upper part of the rotor shaft 113 and sends a raw displacement signal PAh corresponding to this displacement to the control device 200. Similarly, the upper radial sensor 107B detects the B-axis displacement of the rotor shaft 113 and sends a raw displacement signal PBh corresponding to this displacement to the control device 200. In the same manner, the lower radial sensor 108A sends a raw displacement signal PAb corresponding to the A-axis displacement of the lower part of the rotor shaft 113, and the lower radial sensor 108B sends a raw displacement signal PBb corresponding to the B-axis displacement of the lower part of the rotor shaft 113 to the control device 200.

[0082] The control device 200 generates electromagnet drive signals to control the radial electromagnets 17 (17X, 17Y) based on the original displacement signals PAh, PAb, PBh, and PBb. The control device 200 comprises an axis conversion unit 201 and a control unit 202. The axis conversion unit 201 calculates the displacement of the rotor shaft 113 in the X-axis and Y-axis directions by adding an internal displacement signal PXh (PXh=PAh*cosθ1-PBh*sinθ2) to the original displacement signal PAh, an internal displacement signal PYh (PYh=PAh*sinθ1+PBh*cosθ2) to the original displacement signal PBh, an internal displacement signal PXb (PXb=PAb*cosθ1-PBb*sinθ2) to the original displacement signal PAb, and an internal displacement signal PYB (PYb=PAb*sinθ1+PBb*cosθ2) to the original displacement signal PBb.

[0083] The control unit 202 generates electromagnet drive signals CXh+ and CXh- to drive the radial electromagnet 17X of the upper radial electromagnet 104 based on the displacement of the rotor shaft 113 in the X-axis and Y-axis directions calculated by the axis conversion unit 201, and controls the radial electromagnet 17X. Similarly, the control unit 202 generates electromagnet drive signals CYh+ and CYh- to drive the radial electromagnet 17Y of the upper radial electromagnet 104, electromagnet drive signals CXb+ and CXb- to drive the radial electromagnet 17X of the lower radial electromagnet 105, and electromagnet drive signals CYb+ and CYb- to drive the radial electromagnet 17Y of the lower radial electromagnet 105, and controls each radial electromagnet 17 (17X, 17Y). Furthermore, a "+" at the end of the reference code for the electromagnet drive signal indicates that it is a signal that controls a radial electromagnet 17 (17X, 17Y) positioned in the positive direction of the X or Y axis, while a "-" indicates that it is a signal that controls a radial electromagnet 17 (17X, 17Y) positioned in the negative direction of the X or Y axis.

[0084] [Assembly process for the upper radial electromagnet 104 and the upper radial sensor 107] The assembly process for assembling the upper radial electromagnet 104 and upper radial sensor 107 of the above configuration will now be described. First, the worker winds the first magnet wire around the first teeth 11b of the stator core 11 to form a coil 15. In this process, the first teeth 11b may be inserted into the through hole 16d of the first bobbin 16 first, and then the first magnet wire may be wound around it, or the first teeth 11b may be inserted into the through hole 16d of the first bobbin 16 with the first magnet wire already wound around it.

[0085] Next, the worker winds the second magnet wire around the second teeth 21b of the displacement sensor core 21 to form the coil 26. In this step, the second teeth 21b may be inserted into the through hole 27d of the second bobbin 27 first, and then the second magnet wire may be wound around it, or the second teeth 21b may be inserted into the through hole 27d of the second bobbin 27 with the second magnet wire already wound around it. In this way, the steps of winding the first magnet wire around the first teeth 11b and winding the second magnet wire around the second teeth 21b can be performed separately.

[0086] As described above, after assembling the upper radial electromagnet 104 and the upper radial sensor 107, relative positioning is performed between the upper radial sensor 107 (107A, 107B) and the stator core 11. Specifically, the positioning portion 25 of the upper radial sensor 107 (107A, 107B) is brought into contact with the end face 11c of the stator core 11 for positioning. This positions the upper radial sensor 107 (107A, 107B) and the upper radial electromagnet 104 in the axial direction Z. Alternatively, the second back yoke 21a of the upper radial sensor 107 (107A, 107B) may be brought into contact with the inner circumferential surface of the first back yoke 11a for positioning. This positions the upper radial sensor 107 (107A, 107B) and the upper radial electromagnet 104 in the radial direction R.

[0087] By positioning the upper radial sensors 107 (107A, 107B) relative to the stator core 11, the displacement sensor magnetic poles 23 and 24 of the upper radial sensors 107 are positioned within the range of the dimension H of the electromagnet magnetic poles 13 and 14 in the axial direction Z, and between adjacent electromagnet magnetic poles 13 and 14 in the circumferential direction C, so that the innermost end 16e of the first bobbin 16 in the radial direction R is located inward from the innermost end 27e of the second bobbin 27 in the radial direction R.

[0088] After performing the positioning process as described above, with the relative positioning of the upper radial sensors 107 (107A, 107B) and the upper radial electromagnet 104 maintained, the operator connects the positioning unit 25 and the stator core 11. This connects the upper radial electromagnet 104 and the upper radial sensors 107 to each other.

[0089] [Operation and Effects of this Embodiment] The turbomolecular pump 100 configured as described above will produce the following actions and effects.

[0090] According to this embodiment, the displacement sensor poles 23 and 24 of the upper radial sensor 107 are positioned within the range of the dimension H of the electromagnet poles 13 and 14 in the axial direction Z, and between adjacent electromagnet poles 13 and 14 in the circumferential direction C, and the innermost end 16e of the first bobbin 16 in the radial direction R is located inward from the innermost end 27e of the second bobbin 27 in the radial direction R. Therefore, the displacement sensor poles 23 and 24 can be properly positioned between the electromagnet poles 13 and 14, and the upper radial electromagnet 104 (radial magnetic bearing 110) can be miniaturized. If the innermost end 16e of the first bobbin 16 in the radial direction R were located further out than the innermost end 27e of the second bobbin 27 in the radial direction R, the gap D2 between the first bobbins 16 (the gap between the side end faces of the first flange portion 16b) would have to be widened, which would increase the outer diameter of the upper radial electromagnet 104. However, in this embodiment, the innermost end 16e of the first bobbin 16 in the radial direction R is located further inward than the innermost end 27e of the second bobbin 27 in the radial direction R, so the outer diameter of the upper radial electromagnet 104 does not increase. Here, the electromagnet poles 13 and 14 need to generate a larger magnetic force than the displacement sensor poles 23 and 24 in order to non-contact support the rotor shaft 113 in the radial direction R. Therefore, generally, the dimensions of the electromagnet poles 13 and 14 in the circumferential direction C are larger than the dimensions of the displacement sensor poles 23 and 24 in the circumferential direction C. Thus, in order to achieve miniaturization of the upper radial electromagnet 104 while ensuring the dimensions of the electromagnet poles 13 and 14 in the circumferential direction C, it is effective to minimize the spacing between the electromagnet poles 13 and 14, specifically, the gap D2 between the first bobbins 16. In contrast, in this embodiment, the innermost end 16e of the first bobbin 16 in the radial direction R is located inward from the innermost end 27e of the second bobbin 27 in the radial direction R, so it is not necessary to widen the gap D2 between the first bobbins 16. Therefore, it is possible to ensure the dimensions of the electromagnet poles 13 and 14 in the circumferential direction C and to achieve miniaturization of the radial magnetic bearing 110 (magnetic bearing device).

[0091] Furthermore, since the innermost end 21c of the second tooth 21b in the radial direction R is located inside the innermost end 11d of the first tooth 11b in the radial direction R, the electromagnet poles 13 and 14 and the displacement sensor poles 23 and 24 can be positioned more appropriately. In addition, the gap D3 (see Figure 11) between the rotor shaft 113 and the second tooth 21b in the radial direction R can be reduced, thereby suppressing the amount of magnetic flux leakage between the upper radial sensor 107 and the rotor shaft 113. As a result, the upper radial sensor 107 can accurately detect the position of the rotor shaft 113.

[0092] Furthermore, since the displacement sensor core 21 and the stator core 11 are made of separate components, after assembling the upper radial electromagnet 104 and the upper radial sensor 107, the displacement sensor magnetic poles 23 and 24 of the upper radial sensor 107 can be positioned between adjacent electromagnet magnetic poles 13 and 14 in the circumferential direction C. If the displacement sensor core 21 and the stator core 11 were integrated, after winding the first magnet wire around the first tooth 11b to form the coils 15 of the electromagnet magnetic poles 13 and 14, the gap D2 would be small, making the winding process of winding the second magnet wire around the second tooth 21b to form the coils 26 of the displacement sensor magnetic poles 23 and 24, or the process of attaching the second bobbin 27 with the coil 26 (second magnet wire) wound around it to the second tooth 21b difficult. However, in this embodiment, since the displacement sensor core 21 and the stator core 11 are made of separate components, they can be easily assembled.

[0093] [Example 1] In the above embodiment, the second teeth 21b of the upper radial sensor 107 are rectangular columnar in shape with a uniform width W2 in the circumferential direction C, but are not limited to this. As shown in Figures 14 to 16, in this modified example 1, the second teeth 21b have a first cross-section CS1 and a second cross-section CS2 located inward in the radial direction R from the first cross-section CS1, and the cross-sectional area of ​​the first cross-section CS1 is formed to be larger than the cross-sectional area of ​​the second cross-section CS2.

[0094] As shown in Figures 14 and 15, in this modified example 1, the second teeth 21b of the upper radial sensor 107 have a wide portion 21d and a narrow portion 21e located inward in the radial direction R from the wide portion 21d. The wide portion 21d is located inside the coil 26 and the second bobbin 27. The width W22 of the narrow portion 21e in the circumferential direction C is smaller than the width W21 of the wide portion 21d in the circumferential direction C.

[0095] Figure 16(A) is a horizontal cross-sectional view of the displacement sensor core 21 of the upper radial sensor 107, Figure 16(B) is a cross-sectional view of the first cross-section CS1 along line BB in Figure 16(A) (perpendicular to the radial direction R), and Figure 16(C) is a cross-sectional view of the second cross-section CS2 along line CC in Figure 16(C) (perpendicular to the radial direction R). The first cross-section CS1 in the wide portion 21d is larger than the second cross-section CS2 in the narrow portion 21e. In other words, the second teeth 21b is smaller in the second cross-section CS2, which is located inside the radial direction R, than in the first cross-section CS1.

[0096] When forming a displacement sensor core 21 having a wide portion 21d and a narrow portion 21e as described above, first, a basic shape of the displacement sensor core 21 may be formed from soft ferrite or the like. Then, the narrow portion 21e may be formed by processing the inner portion of the second teeth 21b in the radial direction R to narrow its width by polishing or the like.

[0097] According to this modified example 1, the second tooth 21b has a first cross-section CS1 and a second cross-section CS2 located radially inward from the first cross-section CS1 in the radial direction R, and the cross-sectional area of ​​the first cross-section CS1 is formed to be larger than the cross-sectional area of ​​the second cross-section CS2. Therefore, even when the gap D2 between the first bobbins 16 (the gap between the side end faces of the first flange portion 16b) is very small, the second tooth 21b can be placed in the gap D2. Thus, the displacement sensor magnetic poles 23 and 24 can be properly positioned between the electromagnet magnetic poles 13 and 14, and the upper radial electromagnet 104 (radial magnetic bearing 110) can be miniaturized.

[0098] Furthermore, according to this modified example 1, in the first cross section CS1 (wide section 21d), which is located outside the radial direction R and has a larger cross-sectional area than the second cross section CS2, magnetic flux flows more easily (magnetic resistance is lower). Therefore, the upper radial sensor 107 can improve sensitivity because the flow of magnetic flux MF2 is not obstructed. Also, similar to the above embodiment, the gap D3 between the rotor shaft 113 and the second teeth 21b in the radial direction R can be reduced, so the amount of magnetic flux leakage from the upper radial sensor 107 is suppressed. As a result, the upper radial sensor 107 can accurately detect the position of the rotor shaft 113.

[0099] Furthermore, according to this modified example 1, similar to the embodiment described above, the innermost end of the first bobbin 16 in the radial direction R is located further inward than the innermost end of the second bobbin 27 in the radial direction R. Therefore, the electromagnet poles 13 and 14 and the displacement sensor poles 23 and 24 can be properly positioned, and the upper radial electromagnet 104 (radial magnetic bearing 110) can be miniaturized.

[0100] [Differentiation 2] In the above embodiment, the upper radial sensor 107 and the upper radial electromagnet 104 are composed of separate components, and their relative positioning is performed by coupling the positioning unit 25 with the stator core 11, but this is not the only possible configuration. As shown in Figures 17 and 18, in this modified example 2, the displacement sensor core 21 constituting the upper radial sensor 107 and the stator core 11 constituting the upper radial electromagnet 104 are integrally constructed from laminated steel plates stacked in the Z-axis direction, and the positioning unit 25 is not provided.

[0101] In this modified example 2, the stator core 11 and the displacement sensor core 21 are integrally configured, so even without the positioning unit 25, they are positioned in the same way as in the above embodiment. That is, in this modified example 2, the displacement sensor magnetic poles 23 and 24 of the upper radial sensor 107 are positioned within the range of the dimension H of the electromagnet magnetic poles 13 and 14 in the axial direction Z, and between adjacent electromagnet magnetic poles 13 and 14 in the circumferential direction C, so that the innermost end 16e of the first bobbin 16 in the radial direction R is located inward from the innermost end 27e of the second bobbin 27 in the radial direction R. As a result, similar to the above embodiment, the displacement sensor magnetic poles 23 and 24 can be properly positioned between the electromagnet magnetic poles 13 and 14, and the upper radial electromagnet 104 (radial magnetic bearing 110) can be miniaturized.

[0102] Furthermore, in this modified example 2, similar to the embodiment described above, the innermost end 21c of the second tooth 21b in the radial direction R is located inside the innermost end 11d of the first tooth 11b in the radial direction R. Also, in this modified example 2, similar to the modified example 1, the second tooth 21b has a first cross-section CS1 and a second cross-section CS2 located inside the first cross-section CS1 in the radial direction R, and the cross-sectional area of ​​the first cross-section CS1 may be larger than the cross-sectional area of ​​the second cross-section CS2. This allows the second tooth 21b to be placed in the gap D2, so that the displacement sensor magnetic poles 23 and 24 can be properly positioned between the electromagnet magnetic poles 13 and 14, and the upper radial electromagnet 104 (radial magnetic bearing 110) can be miniaturized.

[0103] The assembly process for assembling the upper radial electromagnet 104 and the upper radial sensor 107 in this modified example 2 will now be described. First, the worker winds the second magnet wire around the second teeth 21b of the displacement sensor core 21 to form the coil 26. In this process, the second teeth 21b may be inserted into the through hole 27d of the second bobbin 27 first, and then the second magnet wire may be wound around it, or the second teeth 21b may be inserted into the through hole 27d of the second bobbin 27 with the second magnet wire already wound around it.

[0104] Next, the worker winds the first magnet wire around the first teeth 11b of the stator core 11 to form a coil 15. In this step, the first teeth 11b may be inserted into the through hole 16d of the first bobbin 16 first and then the first magnet wire may be wound around it, or the first teeth 11b may be inserted into the through hole 16d of the first bobbin 16 with the first magnet wire already wound around it.

[0105] In this way, by performing the steps of winding the second magnet wire around the second tooth 21b and inserting the second tooth 21b into the through hole 27d of the second bobbin 27 before the steps of winding the first magnet wire around the first tooth 11b and inserting the first tooth 11b into the through hole 16d of the first bobbin 16, the displacement sensor magnetic poles 23 and 24 of the upper radial sensor 107 can be properly positioned between adjacent electromagnet magnetic poles 13 and 14 in the circumferential direction C, thereby enabling miniaturization of the upper radial electromagnet 104 (radial magnetic bearing 110).

[0106] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. All technical matters included in the technical concept described in the claims are subject to the present invention. The embodiments described above are preferred examples, but those skilled in the art can realize various alternative examples, modifications, variations, combinations, or improvements from the contents disclosed herein, and these are included in the technical scope described in the appended claims.

[0107] For example, in the above embodiment and modified examples, the upper radial sensor 107 (displacement sensor unit) is shown as having a pair of displacement sensor magnetic poles 23 and 24 arranged side by side in the axial direction Z. However, the displacement sensor unit may also be configured in which the pair of displacement sensor magnetic poles 23 and 24 are arranged side by side in the circumferential direction C.

[0108] Furthermore, in the above embodiments and modified examples, the first bobbin 16 is used as the insulating material for the electromagnet poles 13 and 14, and the second bobbin 27 is used for the displacement sensor poles 23 and 24. However, the materials are not limited to these, and insulating paper may be used, or the materials may consist only of the insulating coating of the magnet wire. [Explanation of Symbols]

[0109] 11 Stator Core 11a First back yoke 11b First Teeth 11d Innermost end 13, 14 Electromagnet magnetic pole 15, 26 coils 16. First bobbin (first insulating member) 16a Bobbin section 16b First flange 16th century Second guard 16d through hole 16e Innermost 17(17X, 17Y) Radial electromagnet 21 Displacement Sensor Core 21a Second back yoke 21b Second Teeth 21c innermost end 21d Wide section 21e Narrow section 23, 24 Displacement sensor magnetic poles 25 Positioning section 27. Second bobbin (second insulating member) 27a Bobbin section 27b First flange 27c Second guard 27d through hole 27e Innermost 100 Turbomolecular Pumps (Vacuum Pumps) 101 Air intake 102 (102a, 102b, 102c...) Rotary blade 102d Cylindrical section 103 Solids of revolution 104 Upper radial electromagnet (magnetic bearing) 105 Lower radial electromagnet (magnetic bearing) 106A, 106B Axial electromagnet (magnetic bearing) 107 (107A, 107B) Upper radial sensor 108 (108A, 108B) Lower radial sensor 109 Axial Sensor 110 Radial Direction Magnetic Bearing 111 Metal disc 113 Rotor shaft 122 Status Column 123(123a, 123b, 123c...) Fixed wing 125 (125a, 125b, 125c...) Fixed-wing spacers 127 Outer cylinder 129 Base section 131 Screw-on spacer 131a Screw groove 133 Exhaust vent 200 Control device C circumferential direction R Radial direction Z axis direction

Claims

1. A magnetic bearing device comprising a rotating body, an electromagnet unit that non-contactly supports the rotating body in the radial direction by magnetic force, and a displacement sensor unit that detects the displacement of the rotating body in the radial direction, The aforementioned electromagnet unit is A stator core formed from a magnetic material, with a plurality of first teeth provided at predetermined intervals in the circumferential direction, The device comprises an electromagnet pole including a first magnet wire wound around the first teeth, The displacement sensor unit is A displacement sensor core made of a magnetic material and provided with a second tooth, The displacement sensor comprises a magnetic pole including a second magnet wire wound around the second teeth, The displacement sensor magnetic pole is positioned within the dimensional range of the electromagnet magnetic pole in the axial direction of the rotating body, and between adjacent electromagnet magnetic poles in the circumferential direction. The electromagnet pole includes a first insulating member interposed between the first teeth and the first magnet wire. The displacement sensor magnetic pole includes a second insulating member interposed between the second teeth and the second magnet wire. The innermost end of the first insulating member in the radial direction is located inward from the innermost end of the second insulating member in the radial direction. A magnetic bearing device characterized by the following features.

2. The magnetic bearing device according to claim 1, characterized in that the innermost end of the second tooth in the radial direction is located inward from the innermost end of the first tooth in the radial direction.

3. The magnetic bearing device according to claim 1, characterized in that the second teeth are perpendicular to the radial direction of the rotating body, and the cross-sectional area of ​​the first cross-section located inside the displacement sensor magnetic pole is larger than the cross-sectional area of ​​the second cross-section located inward in the radial direction from the first cross-section.

4. The magnetic bearing device according to claim 1, characterized in that the displacement sensor core is made of a separate component from the stator core.

5. A vacuum pump characterized by comprising a magnetic bearing device according to any one of claims 1 to 4.

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