Vacuum pump and radial magnetic bearing device

Abstract

To provide a vacuum pump and a radial magnetic bearing device that can restrain a part closer to a rotor shaft than flanges of bobbins arranged in an annular electromagnet from falling off.SOLUTION: A vacuum pump comprises a radial magnetic bearing device 210, and a mold part 300 in close contact with the radial magnetic bearing device 210. The radial magnetic bearing device 210 comprises an annular electromagnet 230 comprising a plurality of bobbins fitted to a plurality of respective teeth. The bobbins comprise first flange parts. At least one of side end surfaces of the first flange parts adjacent to each other comprises a communication part for increasing a gap in a circumferential direction between the first flange parts. The mold part 300 comprises a penetrating mold penetrating the communication part in a radial direction, an outside mold arranged closer to the outside in the radial direction than the penetrating mold, and an inside mold arranged closer to the inside in the radial direction than the penetrating mold.SELECTED DRAWING: Figure 5

Description

Technical Field

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

Background Art

[0002] Semiconductor manufacturing equipment, liquid crystal manufacturing equipment, electron microscopes, surface analysis equipment, or microfabrication equipment, etc. need to make the environment inside the equipment in a high vacuum state. In order to make the inside of these devices in a high vacuum state, a vacuum pump is used. In a vacuum pump, a magnetic bearing device that supports a rotating body in a non-contact manner is often used as a bearing device (for example, refer to Patent Document 1). The magnetic bearing device includes a radial magnetic bearing device that supports the radial load of the rotating body and an axial magnetic bearing device that supports the axial load of the rotating body.

[0003] Patent Document 1 describes a radial magnetic bearing device in which each of a plurality of teeth protruding from the inner peripheral wall of an annular stator core is covered with a coil portion in which a coil wire is wound around a bobbin. Each tooth and the coil portion covering the tooth form an electromagnet that attracts the rotor shaft by magnetic force. That is, the radial magnetic bearing device includes a plurality of electromagnets arranged in the circumferential direction so as to surround the rotor shaft.

[0004] The bobbin has a cylindrical bobbin body around which a coil wire is wound, a first flange portion on the side of the bobbin body close to the rotor shaft, and a second flange portion on the side of the bobbin body far from the rotating body.

[0005] By the way, Patent Document 2 describes a vacuum pump in which a resin is molded to cover a radial magnetic bearing device, a displacement sensor, etc. to form a molded portion.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] A plurality of bobbins forming a radial magnetic bearing device described in Patent Document 1 are arranged in the circumferential direction so as to surround the rotor shaft, and thus, first flange portions on the side closer to the rotor shaft are close to each other. For this reason, when the radial magnetic bearing device is covered with a mold part, a portion closer to the rotor shaft than the first flange portion of the mold part is formed thinly, and there are few portions connecting to the mold part on the side far from the rotor shaft, so that it is likely to peel off. When a part of the mold part peels off, electronic devices and electrical devices such as a radial magnetic bearing device may be corroded by corrosive gases contained in the exhaust gas. Further, when a part of the mold part peels off, the peeled mold part may fall and narrow the gap with the rotor shaft or contact the rotor shaft, causing a failure of the vacuum pump.

[0008] The present invention has been made to solve the above-described problems, and an object thereof is to provide a vacuum pump and a radial magnetic bearing device that can suppress peeling of a portion closer to the rotor shaft than a flange of a bobbin disposed in an annular electromagnet of the radial magnetic bearing device. MEANS FOR SOLVING THE PROBLEM

[0009] The above object is achieved by the invention described in the following (1).

[0010] (1) The vacuum pump according to the present invention includes a radial magnetic bearing device disposed outside the rotor shaft in the radial direction and rotatably holding the rotor shaft, and a mold portion at least partially disposed inside the radial direction of the radial magnetic bearing device and in close contact with the radial magnetic bearing device. The radial magnetic bearing device includes an annular stator core having a plurality of teeth provided on an inner peripheral wall at a predetermined interval in the circumferential direction of the rotor shaft, and a coil portion including a plurality of bobbins each mounted on the plurality of teeth and a plurality of coil wires wound around the plurality of bobbins. The plurality of bobbins include a rectangular cylindrical bobbin body having the coil wire wound around an outer periphery and covering the plurality of teeth from the inner peripheral side of the annular stator core, and a flange portion rising from an outer peripheral surface of an end portion of the bobbin body facing the rotor shaft and formed in a rectangular hollow shape in a front view from the rotor shaft side. At least one of side end surfaces of the flange portions adjacent to each other in the circumferential direction of the plurality of bobbins mounted on the plurality of teeth adjacent to each other in the circumferential direction has a communication portion that increases a circumferential gap between the flange portions in the front view. The mold portion includes a through mold penetrating the communication portion in the radial direction, an outer mold disposed outside the radial direction of the through mold and integrally formed with the through mold, and an inner mold disposed inside the radial direction of the through mold and integrally formed with the through mold.

Advantages of the Invention

[0011] In the vacuum pump described in the above (1), the inner mold of the mold portion is firmly connected to the outer mold by a through mold passing through a communication portion formed in the flange portion. Therefore, in this vacuum pump, it is possible to suppress the inner mold, which is a portion closer to the rotor shaft than the flange of the bobbin disposed in the annular electromagnet of the radial magnetic bearing device, from peeling off.

[0012] (2) In the vacuum pump according to (1) above, the annular electromagnet is formed by a pair of the teeth adjacent to each other in the circumferential direction and the coil portion covering the teeth, and has a plurality of electromagnets arranged such that the magnetic poles of the pair of teeth are different. A radial displacement detection unit for detecting the displacement in the radial direction of the rotor shaft is arranged between the electromagnets adjacent to each other in the circumferential direction. The communication portion is formed on at least one of the adjacent side end faces of the two flange portions forming the same electromagnet. The two teeth forming different electromagnets adjacent to each other in the circumferential direction with the radial displacement detection unit interposed therebetween are arranged to have the same magnetic pole. The communication portion is not formed on the side end faces of the flange portions adjacent to each other in the circumferential direction with the radial displacement detection unit interposed therebetween, and may be formed on at least one of the adjacent side end faces of the two flange portions forming the same electromagnet. Thereby, between the two flange portions that form the same electromagnet and are arranged adjacent to each other, a through mold is formed by the communication portion that suppresses the peeling of the inner mold that is likely to peel off. However, between the two flange portions that are arranged apart with the radial displacement detection unit interposed therebetween, the peeling of the inner mold hardly occurs, so the communication portion is not formed, and a decrease in the strength of the bobbin can be suppressed as compared with the case where the communication portion is formed on both side end faces of the flange portion.

[0013] (3) In the vacuum pump according to (1) or (2) above, the length of the communication portion in the axial direction of the rotor shaft may be longer than the minimum width of the gap in the circumferential direction between the flange portions. Thereby, the strength of the through mold penetrating the communication portion becomes higher than that in the case where the communication portion is not provided. Therefore, this vacuum pump can effectively suppress the peeling of the inner mold.

[0014] (4) In the vacuum pump according to (1) or (2) above, the length of the communication portion in the axial direction of the rotor shaft may be longer than the width of the gap in the circumferential direction between the two flange portions at the position where the communication portion is formed. Thereby, the strength of the through mold penetrating the communication portion becomes higher. Therefore, this vacuum pump can effectively suppress the peeling of the inner mold.

[0015] (5) In the vacuum pump according to any one of (1) to (4) above, a plurality of the communication portions may be arranged in the axial direction of the rotor shaft on the side end surface of the flange portion. As a result, since the inner mold is connected to the outer mold by a plurality of through molds, peeling can be effectively suppressed.

[0016] (6) The radial magnetic bearing device according to the present invention is a radial magnetic bearing device that is arranged outside the rotor shaft in the radial direction while being in close contact with the mold part and rotatably holds the rotor shaft, and includes an annular stator core provided with a plurality of teeth at predetermined intervals in the circumferential direction of the rotor shaft on the inner peripheral wall, a plurality of bobbins each mounted on the plurality of teeth, and a coil portion including a plurality of coil wires wound around the plurality of bobbins. The annular electromagnet includes a rectangular cylindrical bobbin body having a coil wire wound around an outer periphery thereof and covering the plurality of teeth from the inner peripheral side of the annular stator core, and a flange portion that rises from an outer peripheral surface of an end portion of the bobbin body on a side facing the rotor shaft and is formed in a rectangular hollow shape when viewed from the front in the rotor shaft direction. At least one of side end surfaces of the flange portions adjacent to each other in the circumferential direction of the plurality of bobbins mounted on the plurality of teeth adjacent to each other in the circumferential direction has a communication portion that increases a gap in the circumferential direction between the flange portions when viewed from the front. and being in close contact with the mold part so as to form, in the mold part, a through mold that penetrates the communication part in the radial direction, an outer mold that is disposed outside the through mold in the radial direction and is integrally formed with the through mold, and an inner mold that is disposed inside the through mold in the radial direction and is integrally formed with the through mold It is characterized by this. As a result, when the inside of the annular stator core is covered by the mold portion, the inner mold inside the flange portion is firmly connected to the outer mold outside the flange portion by a through mold that passes through the communication portion formed in the flange portion. For this reason, the radial magnetic bearing device can suppress peeling of the inner mold covered closer to the rotor shaft than the flange of the bobbin disposed in the annular electromagnet.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the dimensions in the drawings may be exaggerated for convenience of explanation and may be different from the actual dimensions. Also, in this specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant explanations are omitted.

[0019] The vacuum pump 100 according to an embodiment of the present invention is a turbo molecular pump 100 that exhausts gas by the rotating blades of a rotating body rotating at high speed hitting and ejecting gas molecules. The turbo molecular pump 100 is used, for example, to suck and exhaust gas from a chamber such as a semiconductor manufacturing apparatus. First, the basic configuration of the turbo molecular pump 100 will be described.

[0020] A longitudinal sectional view of this turbo molecular pump 100 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 rotor 103 is provided with a plurality of rotating blades 102 (102a, 102b, 102c ···), which are turbine blades for sucking and exhausting gas, radially and in multiple stages on the circumferential part. A rotor shaft 113 is attached to the center of this rotor 103, and this rotor shaft 113 is levitated and position-controlled in the air by, for example, a magnetic bearing with 5-axis control. The rotor 103 is generally made of a metal such as aluminum or an aluminum alloy.

[0021] The upper radial electromagnet 104 has four electromagnets arranged in pairs with respect to the X-axis and the Y-axis. Four upper radial sensors 107 are provided in proximity to the upper radial electromagnet 104 and corresponding to each of the upper radial electromagnets 104. As the upper radial sensor 107, for example, an inductance sensor having a conductive winding or an eddy current sensor is used, and the position of the rotor shaft 113 is detected based on the change in the inductance of this conductive winding that changes according to the position of the rotor shaft 113. This upper radial sensor 107 is configured to detect the radial displacement of the rotor shaft 113, that is, the rotor 103 fixed thereto, and send it to the control device 200.

[0022] In this control device 200, for example, a compensation circuit having a PID control 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. The amplifier circuit 150 (described later) shown in FIG. 2 controls the excitation of the upper radial electromagnet 104 based on this excitation control command signal, thereby adjusting the radial position above the rotor shaft 113.

[0023] The rotor shaft 113 is formed of a high magnetic permeability material (such as iron or stainless steel) and is attracted by the magnetic force of the upper radial electromagnet 104. Such adjustment is performed independently in the X-axis direction and the Y-axis direction. Further, the lower radial electromagnet 105 and the lower radial sensor 108 are arranged in the same manner as the upper radial electromagnet 104 and the upper radial sensor 107, and the radial position below the rotor shaft 113 is adjusted in the same manner as the radial position above.

[0024] Furthermore, the axial electromagnets 106A and 106B are arranged to sandwich the disk-shaped metal disk 111 provided at the lower part of the rotor shaft 113 from above and below. The metal disk 111 is made of a high magnetic permeability material such as iron. An axial sensor 109 is provided to detect the axial displacement of the rotor shaft 113, and its axial position signal is configured to be sent to the control device 200.

[0025] In the control device 200, for example, a compensation circuit having a PID control function generates respective 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. The amplifier circuit 150 controls the excitation of the axial electromagnet 106A and the axial electromagnet 106B respectively based on these excitation control command signals. As a result, the axial electromagnet 106A attracts the metal disk 111 upward by magnetic force, the axial electromagnet 106B attracts the metal disk 111 downward, and the axial position of the rotor shaft 113 is adjusted.

[0026] In this way, the control device 200 appropriately adjusts the magnetic forces exerted by the axial electromagnets 106A and 106B on the metal disk 111, magnetically levitates the rotor shaft 113 in the axial direction, and holds it in a non-contact manner in space. Note that the amplifier circuit 150 for controlling the excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B will be described later.

[0027] On the other hand, the motor 121 includes a plurality of magnetic poles arranged circumferentially so as to surround the rotor shaft 113. Each magnetic pole is controlled by the control device 200 so as to rotationally drive the rotor shaft 113 via the electromagnetic force acting between the magnetic pole and the rotor shaft 113. Further, the motor 121 incorporates a rotational speed sensor such as a hall element, a resolver, or an encoder (not shown), and the rotational speed of the rotor shaft 113 is detected by the detection signal of this rotational speed sensor.

[0028] Furthermore, for example, a phase sensor (not shown) is attached near the lower radial sensor 108 to detect the rotation phase of the rotor shaft 113. In the control device 200, the detection signals of this phase sensor and the rotational speed sensor are used together to detect the position of the magnetic pole.

[0029] A plurality of fixed wings 123 (123a, 123b, 123c ···) are arranged with a slight gap from the rotating wings 102 (102a, 102b, 102c ···). The rotating wings 102 (102a, 102b, 102c ···) are each inclined by a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transfer the molecules of the exhaust gas downward by collision. The fixed wings 123 (123a, 123b, 123c ···) are made of a metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components.

[0030] In addition, the fixed wing 123 is also formed by being inclined by a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and is alternately arranged with the stages of the rotary wing 102 toward the inside of the outer cylinder 127. The outer peripheral end of the fixed wing 123 is supported in a state of being inserted between a plurality of stacked fixed wing spacers 125 (125a, 125b, 125c ···).

[0031] The fixed wing spacer 125 is a ring-shaped member and is made of, for example, a metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components. The outer cylinder 127 is fixed to the outer periphery of the fixed wing spacer 125 with a slight gap. 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. The exhaust gas that has entered the intake port 101 from the chamber (vacuum chamber) side and has been transferred to the base portion 129 is sent to the exhaust port 133.

[0032] Furthermore, depending on the use of the turbo molecular pump 100, a screw groove spacer 131 (fixing member) is disposed between the lower part of the fixed wing spacer 125 and the base portion 129. The screw groove spacer 131 is a cylindrical member made of a metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals as components, and a plurality of spiral screw grooves 131a are engraved on its inner peripheral surface. The direction of the spiral of the screw groove 131a is the direction in which the molecules of the exhaust gas are transferred toward the exhaust port 133 when the molecules of the exhaust gas move in the rotation direction of the rotor 103. A cylindrical portion 102d hangs down at the lowermost part following the rotary wings 102 (102a, 102b, 102c ···) of the rotor 103. The outer peripheral surface of this cylindrical portion 102d is cylindrical and protrudes toward the inner peripheral surface of the screw groove spacer 131, and is close to the inner peripheral surface of the screw groove spacer 131 with a predetermined gap amount. The exhaust gas transferred to the screw groove 131a by the rotary wing 102 and the fixed wing 123 is sent to the base portion 129 while being guided by the screw groove 131a.

[0033] The base portion 129 is a disk-shaped member that constitutes the base of the turbo molecular pump 100 and is generally made of a metal such as iron, aluminum, or stainless steel. The base portion 129 physically holds the turbo molecular pump 100 and also serves as a heat conduction path. Therefore, it is desirable to use a metal with high rigidity and high thermal conductivity, such as iron, aluminum, or copper.

[0034] In such a configuration, when the rotary blades 102 are rotationally driven by the motor 121 together with the rotor shaft 113, the exhaust gas is sucked from the chamber through the intake port 101 due to the action of the rotary blades 102 and the stationary blades 123. The rotational speed of the rotary blades 102 is usually 20,000 rpm to 90,000 rpm, and the peripheral speed at the tip of the rotary blades 102 reaches 200 m / s to 400 m / s. The exhaust gas sucked from the intake port 101 passes between the rotary blades 102 and the stationary blades 123 and is transferred to the base portion 129. At this time, the temperature of the rotary blades 102 rises due to the frictional heat generated when the exhaust gas contacts the rotary blades 102 and the conduction of the heat generated by the motor 121. This heat is transferred to the stationary blade 123 side by radiation or conduction by the gas molecules of the exhaust gas.

[0035] The stationary blade spacer 125 is joined to each other at the outer peripheral portion and transfers heat received by the stationary blade 123 from the rotary blades 102 and frictional heat generated when the exhaust gas contacts the stationary blade 123 to the outside.

[0036] 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 engraved on the inner peripheral surface of the thread groove spacer 131. However, conversely, there may be a case where a thread groove is engraved on the outer peripheral surface of the cylindrical portion 102d and a spacer having a cylindrical inner peripheral surface is disposed around it.

[0037] Depending on the application of the turbo molecular pump 100, in order to prevent the gas sucked from the intake port 101 from entering the electrical components composed of the upper radial electromagnet 104, the upper radial sensor 107, the motor 121, the lower radial electromagnet 105, the lower radial sensor 108, the axial electromagnets 106A and 106B, the axial sensor 109, etc., the electrical components are covered by the stator column 122 around them, and the inside of this stator column 122 may be maintained at a predetermined pressure with purge gas.

[0038] In this case, a pipe (not shown) is arranged in the base portion 129, and purge gas is introduced through this pipe. 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 the stator of the motor 121, and between the stator column 122 and the inner peripheral cylindrical portion of the rotating blade 102.

[0039] Here, the turbo molecular pump 100 requires control based on the identification of the model and specific parameters adjusted individually (for example, various characteristics corresponding to the model). In order to store this control parameter, the above-mentioned turbo molecular pump 100 is provided with an electronic circuit unit 141 inside its main body. The electronic circuit unit 141 is composed of electronic components such as a semiconductor memory such as an EEP-ROM and semiconductor elements for accessing it, a substrate 143 for mounting them, etc. This electronic circuit unit 141 is housed below, for example, near the center of a rotation speed sensor (not shown) that constitutes the lower part of the base portion 129 of the turbo molecular pump 100, and is closed by an airtight bottom cover 145.

[0040] By the way, in the semiconductor manufacturing process, among the process gases introduced into the chamber, there are some that have the property of becoming solid when their pressure becomes higher than a predetermined value or their temperature becomes lower than a predetermined value. Inside the turbo molecular pump 100, the pressure of the exhaust gas is the lowest at the intake port 101 and the highest at the exhaust port 133. When the process gas is transferred from the intake port 101 to the exhaust port 133, if its pressure becomes higher than a predetermined value or its temperature becomes lower than a predetermined value, the process gas will become solid and adhere and deposit inside the turbo molecular pump 100.

[0041] For example, when SiCl4 is used as a process gas in an Al etching apparatus, at low vacuum (760 [torr] to 10 -2 [torr]) and low temperature (about 20 [°C]), it can be seen from the vapor pressure curve that solid products (such as AlCl3) precipitate and adhere and deposit inside the turbo molecular pump 100. As a result, when deposits of the process gas accumulate inside the turbo molecular pump 100, these deposits narrow the pump flow path, causing a decrease in the performance of the turbo molecular pump 100. And the above-mentioned products were in a situation where they were likely to solidify and adhere at high-pressure parts near the exhaust port 133 and near the screw groove spacer 131.

[0042] Therefore, in order to solve this problem, conventionally, a heater (not shown) or an annular water-cooling pipe 149 is wound around the outer periphery of the base portion 129, etc., and for example, a temperature sensor (such as a thermistor, not shown) is embedded in the base portion 129, and based on the signal of this temperature sensor, the temperature of the base portion 129 is controlled to be kept at a certain high temperature (set temperature) by heating the heater and cooling by the water-cooling pipe 149 (hereinafter referred to as TMS. TMS; Temperature Management System).

[0043] Next, regarding the turbo molecular pump 100 configured as described above, an amplifier circuit 150 for exciting and controlling the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A, 106B will be described. The circuit diagram of this amplifier circuit 150 is shown in FIG. 2.

[0044] In FIG. 2, one end of the electromagnet winding 151 constituting the upper radial electromagnet 104 etc. is connected to the positive electrode 171a of the power supply 171 via the transistor 161, and the other end is connected to the negative electrode 171b of the power supply 171 via the current detection circuit 181 and the transistor 162. And the transistors 161, 162 are so-called power MOSFETs and have a structure in which a diode is connected between their source and drain.

[0045] At this time, for transistor 161, the cathode terminal 161a of its diode is connected to the positive electrode 171a, and the anode terminal 161b is connected to one end of the electromagnet winding 151. Also, for transistor 162, the cathode terminal 162a of its diode is connected to the current detection circuit 181, and the anode terminal 162b is connected to the negative electrode 171b.

[0046] On the other hand, for the current regeneration diode 165, its cathode terminal 165a is connected to one end of the electromagnet winding 151, and its anode terminal 165b is connected to the negative electrode 171b. Similarly, for the current regeneration diode 166, its cathode terminal 166a is connected to the positive electrode 171a, and its anode terminal 166b is connected to the other end of the electromagnet winding 151 via the current detection circuit 181. And the current detection circuit 181 is composed of, for example, a Hall sensor type current sensor or an electric resistance element.

[0047] The amplifier circuit 150 configured as described above corresponds to one electromagnet. Therefore, when the magnetic bearing is under five-axis control and there are a total of 10 electromagnets 104, 105, 106A, and 106B, similar amplifier circuits 150 are configured for each of the electromagnets, and 10 amplifier circuits 150 are connected in parallel to the power supply 171.

[0048] Furthermore, the amplifier control circuit 191 is composed of, for example, a digital signal processor section (hereinafter referred to as the DSP section) not shown in the control device 200, and this amplifier control circuit 191 is configured to switch the on / off states of transistors 161 and 162.

[0049] The amplifier control circuit 191 is configured to compare the current value detected by the current detection circuit 181 (a signal reflecting this current value is referred to as the current detection signal 191c) with a predetermined current command value. Then, based on this comparison result, it determines the magnitudes of the pulse widths (pulse width times Tp1, Tp2) to be generated within the control cycle Ts, which is one cycle of PWM control. As a result, gate drive signals 191a, 191b having these pulse widths are output from the amplifier control circuit 191 to the gate terminals of the transistors 161, 162.

[0050] Note that when passing through the resonance point during the acceleration operation of the rotational speed of the rotor 103 or when a disturbance occurs during the constant speed operation, etc., it is necessary to control the position of the rotor 103 with high speed and strong force. Therefore, as the power supply 171, for example, a voltage of about 50 V is used so that a rapid increase (or decrease) in the current flowing through the electromagnet winding 151 can occur. Also, a normal capacitor is connected between the positive electrode 171a and the negative electrode 171b of the power supply 171 for the stabilization of the power supply 171 (not shown in the figure).

[0051] In such a configuration, when both of the transistors 161, 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.

[0052] Also, when one of the transistors 161, 162 is turned on and the other is turned off, a so-called flywheel current is maintained. And by flowing the flywheel current through the amplifier circuit 150 in this way, the hysteresis loss in the amplifier circuit 150 can be reduced, and the power consumption of the entire circuit can be kept low. Also, by controlling the transistors 161, 162 in this way, high-frequency noise such as harmonics generated in the turbo molecular pump 100 can be reduced. Furthermore, by measuring this flywheel current with the current detection circuit 181, the electromagnet current iL flowing through the electromagnet winding 151 can be detected.

[0053] That is, when the detected current value is smaller than the current command value, as shown in FIG. 3, both transistors 161 and 162 are turned on only once during the control cycle Ts (for example, 100 μs) for a time corresponding to the pulse width time Tp1. Therefore, during this period, the electromagnet current iL increases toward the maximum current value iLmax (not shown) that can flow from the positive electrode 171a to the negative electrode 171b through the transistors 161 and 162.

[0054] On the other hand, when the detected current value is larger than the current command value, as shown in FIG. 4, both transistors 161 and 162 are turned off only once during the control cycle Ts for a time corresponding to the pulse width time Tp2. Therefore, during this period, the electromagnet current iL decreases toward the minimum current value iLmin (not shown) that can be regenerated from the negative electrode 171b to the positive electrode 171a through the diodes 165 and 166.

[0055] And in any case, after the elapse of the pulse width times Tp1 and Tp2, one of the transistors 161 and 162 is turned on. Therefore, during this period, a flywheel current is held in the amplifier circuit 150.

[0056] <This Embodiment> Next, the vacuum pump 100 according to this embodiment will be described. As shown in FIGS. 1 and 5, the vacuum pump 100 has two radial magnetic bearing devices 210 that are arranged outside the rotor shaft 113 in the radial direction and rotatably hold the rotor shaft 113. The vacuum pump 100 has, inside the stator column 122, an electrical equipment unit 220 including electrical and electronic devices, and a mold unit 300 that protects the electrical equipment unit 220 from corrosive gases contained in the exhaust gas.

[0057] One of the radial magnetic bearing devices 210 has an upper radial electromagnet 104 which is an annular electromagnet 230 and rotatably supports the upper part of the rotor shaft 113, and the other one of the radial magnetic bearing devices 210 has a lower radial electromagnet 105 which is an annular electromagnet 230 and rotatably supports the lower part of the rotor shaft 113. Note that only one radial magnetic bearing device 210 provided in the vacuum pump 100 may be provided.

[0058] As shown in FIGS. 6 to 10, each of the annular electromagnets 230 includes an annular stator core 240 and a plurality of coil portions 250 attached to the annular stator core 240.

[0059] The annular stator core 240 is formed by laminating a plurality of electromagnetic steel plates 241 (for example, silicon steel plates) having the same shape in the axial direction Z. The annular stator core 240 has an annular ring portion 242 and a plurality of teeth 244 protruding from the inner peripheral wall 243 of the ring portion 242 toward the center O of the annular stator core 240 (which is also the center O of the rotor shaft 113). The plurality of teeth 244 are arranged side by side in the circumferential direction C of the annular stator core 240 (which is also the circumferential direction C of the rotor shaft 113) at a predetermined interval. The shape of the cross section perpendicular to the protruding direction of the teeth 244 is rectangular. Each of the teeth 244 has a coil portion 250 attached thereto.

[0060] Each of the coil portions 250 has a bobbin 251 and a coil wire 252 wound around the outer periphery of the bobbin 251 a plurality of times.

[0061] As shown in FIGS. 7 to 11, the bobbin 251 has a bobbin body 253 around which the coil wire 252 is wound, a first flange portion 254, and a second flange portion 255. The bobbin 251 is formed of an insulating material such as resin.

[0062] The bobbin body 253 is a cylindrical body in which a through hole 256 into which the teeth 244 can be inserted is formed. The cross-sectional shape of the bobbin body 253 orthogonal to the through direction of the through hole 256 is rectangular corresponding to the cross-sectional shape of the teeth 244. That is, the bobbin body 253 is a rectangular cylindrical body (square tube). A plurality of turns of the coil wire 252 are wound around the outer peripheral surface of the bobbin body 253.

[0063] The first flange portion (flange portion) 254 protrudes from the end portion of the bobbin body 253 located on the center O side of the annular stator core 240 so as to project substantially at a right angle outward from the outer peripheral surface of the bobbin body 253 (in a direction away from the axis of the through hole 256), and is formed in a flat plate shape. The first flange portion 254 is formed in a rectangular hollow shape in which the through hole 256 opens at the center when viewed from the front from the center O side (rotor shaft 113 side) of the annular stator core 240. In order for the first flange portion 254 and the second flange portion 255 to serve to hold the wound coil wire 252, increasing the size of the protruding portion formed in a flat plate shape can increase the amount of winding of the coil wire 252.

[0064] The first flange portion 254 has side end faces 257 formed at both ends in the circumferential direction C. Each of the side end faces 257 has a proximity portion 258 extending along the axial direction Z of the rotor shaft 113 and two notched communication portions 259. Note that only one communication portion 259 may be formed on one side end face 257, or three or more may be formed. The communication portion 259 is formed by being notched from the proximity portion 258 at a predetermined depth. In any two bobbins 251 arranged in the circumferential direction C of the rotor shaft 113, the side end faces 257 of the respective first flange portions 254 are adjacent to each other with a gap in the circumferential direction C. In a front view seen from the center O side of the annular stator core 240, as shown in FIG. 10, two adjacent side end faces 257 form a first gap 260 at the proximity portion 258 and a second gap 261 at the communication portion 259. Each annular electromagnet 230 is covered on the teeth 244 from the inner peripheral wall 243 side of the annular stator core 240, and all the teeth 244 protrude toward the center O of the annular stator core 240. Therefore, in order to cover the coil portions 250 on each of the adjacent plurality of teeth 244, it is necessary to arrange the plurality of coil portions 250 so as not to interfere with each other. And in order to prevent the plurality of coil portions 250 from interfering with each other, it is preferable that the plurality of bobbins 251 adjacent to each other in the circumferential direction C are separated without the first flange portion 254 coming into contact. However, if the dimension of the first flange portion 254 in the circumferential direction C is reduced in order to increase the interval between the first flange portions 254 of the plurality of bobbins 251 adjacent to each other in the circumferential direction C, the amount of winding of the coil wire 252 will decrease, and the performance (attractive force) as the electromagnet 270 may deteriorate.

[0065] Therefore, in order not to deteriorate the performance as the electromagnet 270, it is preferable that the first flange portions 254 of the plurality of bobbins 251 adjacent to each other in the circumferential direction C are set to have as large a dimension as possible within a non-interfering range.

[0066] On the other hand, when the distance between the first flange portions 254 of a plurality of bobbins 251 adjacent to each other in the circumferential direction C is reduced, when covering the coil portion 250 with the mold portion 300, the strength of the through mold 301 penetrating the gap between the first flange portions 254 cannot be sufficiently ensured, and the connection between the inner mold 303 inside the first flange portion 254 and the outer mold 302 outside the first flange portion 254 becomes insufficient, and there is a risk that the inner mold 303 will peel off. To solve this problem, the communication portion 259 exists.

[0067] The first gap 260 is formed with the narrowest width W1 between two first flange portions 254 adjacent to each other in the circumferential direction C. The width W1 of each of the first gaps 260 arranged at different positions in the axial direction Z is the same in this embodiment, but may be different.

[0068] The second gap 261 is formed with a width W2 wider than the width W1 of the first gap 260 in the circumferential direction C between two first flange portions 254 adjacent to each other in the circumferential direction C. Each of the second gaps 261 is formed to be sandwiched between two first gaps 260 in the axial direction Z. That is, the plurality of first flange portions 254 adjacent to each other in the circumferential direction C have portions formed with a width W1 narrower than the second gap 261 on both the upstream side and the downstream side of the communication portion 259. The width W2 of each of the second gaps 261 arranged at different positions in the axial direction Z is the same in this embodiment, but may be different.

[0069] The axial Z length L2 of the second gap 261 is longer than the circumferential C width W1 of the first gap 260, and further, is longer than the circumferential C width W2 of the second gap 261. If the axial Z length L2 of the second gap 261 is too small, it is difficult to sufficiently secure the communication portion 259 through which the resin mold portion 300 described later penetrates in the radial direction. On the other hand, since the axial Z length L2 of the second gap 261 is longer than the circumferential C width W1 of the first gap 260 and further longer than the circumferential C width W2 of the second gap 261, a sufficiently wide communication portion 259 through which the mold portion 300 penetrates can be secured. As a result, the strength of the mold portion 300 penetrating the communication portion 259 in the radial direction can be improved, and the permeability of the molten resin to the communication portion 259 before molding the mold portion 300 can be improved. In the present embodiment, the two side end faces 257 of the first flange portion 254 are formed to be plane-symmetrical, but they do not have to be formed to be plane-symmetrical.

[0070] The sum of the axial Z lengths L2 of all the second gaps 261 formed on one side end face 257 may be equal to or more than half of the axial Z length L1 of this side end face 257, or may be less than half. If it is equal to or more than half, the strength of the mold portion 300 penetrating the communication portion 259 in the radial direction can be improved, and the permeability of the molten resin to the communication portion 259 before molding the mold portion 300 can be improved. Further, the communication portion 259 is preferably disposed near the center of the side end face 257 in the axial Z direction.

[0071] Then, as shown in FIGS. 6 to 10, the annular electromagnet 230 has four electromagnets 270 arranged at equal intervals in the circumferential direction C at 90-degree intervals. As shown in FIG. 6, the four electromagnets 270 are arranged so as to be paired with respect to the X-axis and the Y-axis that are perpendicular to each other in a plane perpendicular to the axial direction Z. That is, the two paired electromagnets 270 are arranged on both sides with the center O of the annular electromagnet 230 on the X-axis interposed therebetween. Then, the other two paired electromagnets 270 are arranged on both sides with the center O of the annular electromagnet 230 on the Y-axis interposed therebetween. Note that the number of electromagnets 270 does not have to be four.

[0072] Each electromagnet 270 has the same structure. Each electromagnet 270 has a first electromagnet 271 and a second electromagnet 272 adjacent to each other in the circumferential direction C. The first electromagnet 271 and the second electromagnet 272 are uniaxial electromagnets 270 formed symmetrically at an angle α. As shown in FIGS. 6 to 10, each of the first electromagnet 271 and the second electromagnet 272 is formed by one tooth 244 and one coil portion 250 covering the tooth 244. The paired first electromagnet 271 and second electromagnet 272 have different polarities. In order to have such a configuration, the coil wires 252 of each of the adjacent first electromagnet 271 and second electromagnet 272 constituting one electromagnet 270 are wound in opposite directions with respect to the tooth 244.

[0073] The adjacent first electromagnet 271 and second electromagnet 272 between different electromagnets 270 adjacent to each other in the circumferential direction C have the same polarity. That is, the first electromagnet 271 and the second electromagnet 272 adjacent to the boundary of different electromagnets 270 adjacent to each other in the circumferential direction C have the same polarity. In order to have such a configuration, the coil wires 252 of the adjacent first electromagnet 271 and second electromagnet 272 having the same polarity are wound in the same direction with respect to the tooth 244. As a result, the magnetic fluxes generated from the adjacent electromagnets 270 are canceled out, and the magnetic flux decreases between different electromagnets 270 adjacent to each other in the circumferential direction C.

[0074] As shown in FIGS. 5 to 8, the mold part 300 is formed by molding inside the stator column 122 to improve the corrosion resistance of the electrical equipment part 220 against corrosive gases. The mold part 300 covers the electrical equipment part 220 and is filled in the gaps of the electrical equipment part 220. The electrical equipment part 220 is a part including electrical and electronic equipment. In this embodiment, it includes an upper radial sensor 107 (radial displacement detection part 280), an upper radial electromagnet 104 (annular electromagnet 230), a motor 121, a lower radial electromagnet 105 (annular electromagnet 230), and a lower radial sensor 108 (radial displacement detection part 280). When molding the mold part 300, before filling the mold part 300, a cylindrical insert (not shown) is inserted into the stator column 122 from the opening side below the stator column 122. Next, for example, a thermosetting epoxy resin material is filled to cover the electrical equipment part 220 and form a cylindrical inner peripheral surface of the resin mold inside the stator column 122. After the mold forming operation is completed, the cylindrical inner peripheral surface of the formed resin mold is machined to expose the magnetic poles of the upper radial sensor 107, the upper radial electromagnet 104, the motor 121, the lower radial electromagnet 105, and the lower radial sensor 108. Note that the material of the mold part 300 is not particularly limited as long as it can be mold-formed.

[0075] The mold part 300 has a through mold 301 and a narrow mold 304 that penetrate in the radial direction between two first flange parts 254 adjacent in the circumferential direction C near each of the upper radial electromagnet 104 and the lower radial electromagnet 105, which are annular electromagnets 230, an outer mold 302 arranged on the outer side in the radial direction of the through mold 301 and the narrow mold 304, and an inner mold 303 arranged on the inner side in the radial direction of the through mold 301 and the narrow mold 304.

[0076] The narrow mold 304 has a proximity part 258 that forms a narrow first gap 260 and penetrates in the radial direction of the rotor shaft 113. The through mold 301 has a communication part 259 that forms a wide second gap 261 and penetrates in the radial direction of the rotor shaft 113.

[0077] As shown in FIGS. 6 to 8, the inner mold 303 is integrally formed with the through mold 301 and the narrow mold 304, and is in close contact with the surface of the first flange portion 254 facing the rotor shaft 113 (the surface facing the center O of the annular electromagnet 230) and the outer peripheral surface of the portion of the teeth 244 protruding radially inward of the first flange portion 254.

[0078] The outer mold 302 is integrally formed with the through mold 301 and the narrow mold 304, and is in close contact with the radially outer surface of the first flange portion 254, the coil wire 252, the second flange portion 255, and the inner peripheral wall 243 of the annular portion 242.

[0079] Next, the operation of the vacuum pump 100 according to the present embodiment will be described.

[0080] In the present embodiment, the outer mold 302 and the inner mold 303 are integrally formed by the narrow mold 304 passing through the narrow first gap 260 and the through mold 301 passing through the wide second gap 261. Therefore, the inner mold 303 is firmly connected to the outer mold 302 by the through mold 301 and is difficult to be peeled off from the outer mold 302. Further, when forming the mold portion 300, since a wide second gap 261 is formed between the first flange portions 254 adjacent to each other in the circumferential direction C, even if a narrow first gap 260 is formed between the first flange portions 254, the resin is likely to be uniformly filled up to the narrow region. Therefore, filling defects are less likely to occur in the mold portion 300. Thus, the present vacuum pump 100 can suppress a decrease in the strength of the mold portion 300 and can suppress a decrease in the corrosion resistance of the electrical component portion 220.

[0081] As described above, the vacuum pump 100 according to the present embodiment includes a radial magnetic bearing device 210 that is disposed outside the radial direction of the rotor shaft 113 and rotatably holds the rotor shaft 113, and a mold portion 300 at least a part of which is disposed inside the radial direction of the radial magnetic bearing device 210 and is in close contact with the radial magnetic bearing device 210. The radial magnetic bearing device 210 includes an annular stator core 240 provided with a plurality of teeth 244 at a predetermined interval in the circumferential direction C of the rotor shaft 113 on the inner peripheral wall 243, and a coil portion 250 including a plurality of bobbins 251 each attached to the plurality of teeth 244 and a plurality of coil wires 252 wound around the bobbins 251. The annular electromagnet 230 is provided. The plurality of bobbins 251 include a rectangular cylindrical bobbin body 253 wound with a coil wire 252 on the outer periphery and covering the plurality of teeth 244 from the inner peripheral side of the annular stator core 240, and a first flange portion 254 that rises from the outer peripheral surface of the end portion of the bobbin body 253 facing the rotor shaft 113 and is formed in a rectangular hollow shape when viewed from the front in the rotor shaft 113 side. At least one of the side end surfaces 257 of the first flange portions 254 adjacent to each other in the circumferential direction C of the plurality of bobbins 251 attached to the plurality of teeth 244 adjacent to each other in the circumferential direction C has a communication portion 259 that increases the gap in the circumferential direction C between the first flange portions 254 when viewed from the front. The mold portion 300 includes a through mold 301 that penetrates the communication portion 259 in the radial direction, an outer mold 302 that is disposed outside the radial direction of the through mold 301 and is integrally formed with the through mold 301, and an inner mold 303 that is disposed inside the radial direction of the through mold 301 and is integrally formed with the through mold 301. Thereby, in the vacuum pump 100 according to the present embodiment, the inner mold 303 of the mold portion 300 is firmly connected to the outer mold 302 by the through mold 301 that passes through the communication portion 259 formed in the first flange portion 254. For this reason, the present vacuum pump 100 can suppress the inner mold 303, which is a portion closer to the rotor shaft 113 than the first flange 254 of the bobbin 251 disposed in the annular electromagnet 230 of the radial magnetic bearing device 210, from peeling off.

[0082] The length L2 of the communication part 259 in the axial direction Z of the rotor shaft 113 is longer than the minimum width W1 of the gap in the circumferential direction C between the first flange parts 254. Thereby, the strength of the through mold 301 penetrating the communication part 259 becomes higher compared to the case where the communication part 259 is not provided. For this reason, this vacuum pump 100 can effectively suppress the inner mold 303 from peeling off.

[0083] The length L2 of the communication part 259 in the axial direction Z of the rotor shaft 113 is longer than the width W2 of the gap in the circumferential direction C between the two first flange parts 254 at the position where the communication part 259 is formed. Thereby, the strength of the through mold 301 penetrating the communication part 259 becomes higher. For this reason, this vacuum pump 100 can effectively suppress the inner mold 303 from peeling off.

[0084] A plurality of communication parts 259 are arranged in the axial direction Z of the rotor shaft 113 on the side end surface 257 of the first flange part 254. Thereby, since the inner mold 303 is connected to the outer mold 302 by a plurality of through molds 301, it can be effectively suppressed from peeling off.

[0085] Further, the radial magnetic bearing device 210 in the present embodiment is a radial magnetic bearing device that is disposed outside the rotor shaft 113 in the radial direction and rotatably holds the rotor shaft 113. The radial magnetic bearing device 210 includes an annular stator core 240 provided with a plurality of teeth 244 at a predetermined interval in the circumferential direction C of the rotor shaft 113 on the inner peripheral wall 243, and a coil portion 250 including a plurality of bobbins 251 each attached to the plurality of teeth 244 and a plurality of coil wires 252 wound around the bobbins 251. The annular stator core 240 is provided with an annular electromagnet 230. The plurality of bobbins 251 include a rectangular cylindrical bobbin body 253 wound with a coil wire 252 on the outer periphery and covering the plurality of teeth 244 from the inner peripheral side of the annular stator core 240, and a first flange portion 254 that rises from the outer peripheral surface of the end portion of the bobbin body 253 on the side facing the rotor shaft 113 and is formed in a rectangular hollow shape when viewed from the front in the rotor shaft 113 side. At least one of the side end surfaces 257 of the first flange portions 254 adjacent to each other in the circumferential direction C of the plurality of bobbins 251 attached to the plurality of teeth 244 adjacent to each other in the circumferential direction C has a communication portion 259 that increases the gap in the circumferential direction C between the first flange portions 254 when viewed from the front. Thereby, when the inside of the annular stator core 240 is covered by the mold portion 300, the inner mold 303 inside the first flange portion 254 is firmly connected to the outer mold 302 outside the first flange portion 254 by the through mold 301 passing through the communication portion 259 formed in the first flange portion 254. For this reason, the radial magnetic bearing device 210 can suppress the inner mold 303 covered on the side closer to the rotor shaft 113 than the first flange 254 of the bobbin 251 disposed in the annular electromagnet 230 from peeling off.

[0086] Note that the present invention is not limited to the above-described embodiments, and various modifications and combinations can be made by those skilled in the art within the technical idea of the present invention. For example, as in the first modification example shown in FIGS. 12 and 13, a radial displacement detection unit 280 for detecting the radial displacement of the rotor shaft 113 may be arranged between the electromagnets 270 adjacent in the circumferential direction C. In the first modification example, since the radial displacement detection unit 280 can be arranged at the same position as the electromagnet 270 in the axial direction Z, the dimension of the vacuum pump 100 in the axial direction Z can be reduced. The radial displacement detection unit 280 is a known displacement sensor, for example, an inductance type displacement sensor or the like. Each of the radial displacement detection units 280 includes a pair of magnetic poles 283, 283 formed by winding a sensor coil 282 around two claw portions 281 protruding from the inner peripheral wall 243 of the annular stator core 240. The pair of magnetic poles 283, 283 have different polarities by winding the sensor coil 282 in opposite directions.

[0087] The adjacent first electromagnet 271 and second electromagnet 272 between the electromagnets 270 adjacent in the circumferential direction C have the same polarity on the rotor shaft 113 side. Therefore, each of the radial displacement detection units 280 is arranged between the first electromagnet 271 and the second electromagnet 272 having the same polarity adjacent in the circumferential direction C. As a result, in the region where the radial displacement detection unit 280 is arranged, the magnetic fluxes generated from the adjacent electromagnets 270 cancel each other out, so that the influence of the magnetic flux of the electromagnet 270 on the radial displacement detection unit 280 is reduced.

[0088] In the first modification, since the radial displacement detection unit 280 is arranged at the same position as the electromagnet 270 in the axial direction Z, it is difficult to ensure a wide gap between two first flange portions 254 adjacent to each other in the circumferential direction C of the first electromagnet 271 and the second electromagnet 272 that form the same electromagnet 270. However, in the first modification, since the communication portion 259 is formed on at least one side end face 257 of two first flange portions 254 adjacent to each other in the circumferential direction C where it is difficult to ensure a wide gap, the inner mold 303 can be firmly connected to the outer mold 302 by the through mold 301, and peeling of the inner mold 303 can be suppressed. Further, when molding the mold portion 300, a wide flow path can be ensured between two adjacent first flange portions 254 where it is difficult to ensure a wide gap, and the resin can be easily filled evenly to a desired range. Also, since a sufficient gap can be ensured between two first flange portions 254 arranged apart with the radial displacement detection unit 280 interposed therebetween, peeling of the inner mold 303 is less likely to occur. For this reason, it is not necessary to form the communication portion 259 in two first flange portions 254 sandwiching the radial displacement detection unit 280, and a decrease in the strength of the bobbin 251 due to forming the communication portion 259 in the first flange portion 254 can be prevented.

[0089] Also, the configuration of the communication portion 259 of the first flange portion 254 is not limited as long as the first gap 260 can be widened. Therefore, for example, as in the second modification shown in FIG. 14(A), the communication portion 259 of the first flange portion 254 may have an arc-shaped body instead of a linear body when viewed from the center O side of the annular stator core 240. That is, the width in the circumferential direction C of the second gap 261 formed by the communication portion 259 may change along the axial direction Z. Also, as in the third modification shown in FIG. 14(B), the communication portion 259 may be formed by a step instead of a recess.

Explanation of Reference Numerals

[0090] 100 Vacuum pump 104 Upper radial electromagnet (annular electromagnet) 105 Lower radial electromagnet (annular electromagnet) 113 Rotor shaft 122 Stator Column 210 Radial Magnetic Bearing Device 220 Electrical Equipment Section 230 Annular Electromagnet 240 Annular Stator Core 241 Electromagnetic Steel Sheet 242 Annular Portion 243 Inner Peripheral Wall 244 Teeth 250 Coil Section 251 Bobbin 252 Coil Wire 253 Bobbin Body 254 First Flange Portion (Flange Portion) 255 Second Flange Portion 256 Through-Hole 257 Side End Face 258 Proximity Portion 259 Communication Portion 260 First Gap 261 Second Gap 270 Electromagnet 271 First Electromagnet 272 Second Electromagnet 280 Radial Direction Displacement Detection Section 300 Molded Portion 301 Through Mold 302 Outer Mold 303 Inner Mold 304 Narrow Mold C Circumferential Direction Z-Axis Direction

Claims

1. A vacuum pump having a radial magnetic bearing device disposed on the outer side in the radial direction of a rotor shaft and rotatably holding the rotor shaft, and a mold portion at least partially disposed on the inner side in the radial direction of the radial magnetic bearing device and in close contact with the radial magnetic bearing device, wherein the radial magnetic bearing device includes an annular stator core having a plurality of teeth provided on an inner peripheral wall at a predetermined interval in the circumferential direction of the rotor shaft, and a coil portion including a plurality of bobbins each mounted on the plurality of teeth and a plurality of coil wires wound around the plurality of bobbins, and includes an annular electromagnet, the plurality of bobbins include a rectangular cylindrical bobbin body having the coil wire wound around an outer periphery and covering the plurality of teeth from the inner peripheral side of the annular stator core, and a flange portion rising from an outer peripheral surface of an end portion of the bobbin body facing the rotor shaft and formed in a rectangular hollow shape in a front view from the rotor shaft side, at least one of side end surfaces of the flange portions adjacent to each other in the circumferential direction of the plurality of bobbins mounted on the plurality of teeth adjacent to each other in the circumferential direction has a communication portion that increases a gap in the circumferential direction between the flange portions in the front view, the mold portion includes a through mold penetrating the communication portion in the radial direction, an outer mold disposed on the outer side in the radial direction of the through mold and integrally formed with the through mold, and an inner mold disposed on the inner side in the radial direction of the through mold and integrally formed with the through mold.

2. The annular electromagnet has a plurality of electromagnets formed by a pair of teeth adjacent to each other in the circumferential direction and the coil portion covering the teeth, and the magnetic poles of the pair of teeth are arranged to be different. A radial displacement detection unit for detecting displacement in the radial direction of the rotor shaft is disposed between the electromagnets adjacent to each other in the circumferential direction. Two of the teeth that form different electromagnets adjacent to each other in the circumferential direction with the radial displacement detection unit interposed therebetween are arranged so as to have the same magnetic pole. The communication part is not formed on the side end surfaces of the flange parts adjacent to each other in the circumferential direction with the radial displacement detection unit interposed therebetween, but is formed on at least one of the adjacent side end surfaces of the two flange parts that form the same electromagnet. The vacuum pump according to claim 1, characterized in that.

3. The length of the communication part in the axial direction of the rotor shaft is longer than the minimum width of the gap in the circumferential direction between the flange parts. The vacuum pump according to claim 1 or 2, characterized in that.

4. The length of the communication part in the axial direction of the rotor shaft is longer than the width of the gap in the circumferential direction between the two flange parts at the position where the communication part is formed. The vacuum pump according to claim 1 or 2, characterized in that.

5. The communication part is arranged in a plurality in the axial direction of the rotor shaft on the side end surface of the flange part. The vacuum pump according to claim 1 or 2, characterized in that.

6. A radial magnetic bearing device that is disposed outside the rotor shaft in the radial direction and is in close contact with the mold part to rotatably hold the rotor shaft, An annular stator core provided with a plurality of teeth at a predetermined interval in the circumferential direction of the rotor shaft on the inner peripheral wall, An annular electromagnet having a coil part including a plurality of bobbins each mounted on the plurality of teeth and a plurality of coil wires wound around the plurality of bobbins, The plurality of bobbins, A rectangular cylindrical bobbin body having the coil wire wound around the outer periphery and covering and mounted on the plurality of teeth from the inner peripheral side of the annular stator core, A flange portion that rises from the outer peripheral surface of the end portion of the bobbin body on the side facing the rotor shaft and is formed in a rectangular hollow shape when viewed from the front in the direction of the rotor shaft side; At least one of the side end surfaces of the flanges adjacent in the circumferential direction of the plurality of bobbins attached to the plurality of teeth adjacent in the circumferential direction has a communication portion that increases the circumferential gap between the flanges when viewed from the front; The mold portion is in close contact with the mold portion so as to form a through mold that penetrates the communication portion in the radial direction, an outer mold that is disposed outside the through mold in the radial direction and is integrally formed with the through mold, and an inner mold that is disposed inside the through mold in the radial direction and is integrally formed with the through mold. A radial magnetic bearing device characterized by this.

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