vacuum pump

Abstract

To provide a vacuum pump that can restrain the deposition of a by-product in the pump.SOLUTION: A vacuum pump 300 comprises a casing 310, a rotor shaft 113 arranged in the casing 310, and rotary blades 102 capable of rotating together with the rotor shaft 113, exhausts gas by rotating the rotary blades 102, and comprises heating means 340 for heating a gas flow passage in the vacuum pump 300. The heating means 340 comprises a coil 342, a heated part 343 that is a magnetic body to be heated by electromagnetic induction caused by passing an alternating current through the coil 342, and a high-permeability magnetic body 341 covering the coil 342 on the side opposite to the side of a front surface 344 on which the heated part 343 is arranged.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a vacuum pump.

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. A vacuum pump is used to make the inside of these devices in a high-vacuum state. As an example of the vacuum pump used, for example, a composite pump combining a turbo molecular pump and a screw groove pump can be mentioned.

[0003] A vacuum pump combining a turbo molecular pump and a screw groove pump has a screw groove pump arranged on the downstream side of a turbo pump having rotating blades and fixed blades arranged alternately in the axial direction. The exhaust gas taken in from the intake port is compressed by the turbo molecular pump and the screw groove pump and discharged to the outside of the vacuum pump from the exhaust port.

[0004] The exhaust gas shows behavior like viscous flow especially because the pressure is relatively high in the downstream flow path. For this reason, by-products are likely to precipitate at locations where the flow of the exhaust gas stagnates in the flow path of the vacuum pump. When by-products precipitate in the flow path, an event occurs where locations that do not normally come into contact come into contact, which may cause damage to the vacuum pump and variations in the temperature distribution due to changes in the heat transfer performance of the internal structure, thus impairing safety and productivity.

[0005] For this reason, in order to suppress the precipitation of by-products in the gas flow path, the vacuum pump may have heating means for heating the components forming the gas flow path. For example, Patent Document 1 discloses a structure in which a heating part for heating the stator part on the fixed blade side by electromagnetic induction heating is arranged.

[0006] The heating section comprises a yoke fixed to the stator component, a coil positioned on the yoke, and a heating plate connected to the stator component. The heating plate and yoke are made of magnetic materials such as iron-based materials or stainless steel. When a high-frequency alternating current is passed through the coil, the coil, heating plate, and yoke are electromagnetically coupled, generating eddy currents inside the heating plate and yoke. Because the heating plate and yoke have their own inherent electrical resistance, they generate Joule heat. In addition, iron loss heat is generated in the heating plate and yoke, and copper loss heat is generated in the coil, and the stator component is also heated by this heat. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2014 / 119191 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] In the vacuum pump described in Patent Document 1, because metal components are present around the coil, areas other than the part to be heated are heated simultaneously, making it impossible to efficiently heat the heating plate. As a result, by-products may precipitate inside the pump.

[0009] This invention was made to solve the above-mentioned problems and aims to provide a vacuum pump that can suppress the precipitation of by-products in the pump. [Means for solving the problem]

[0010] The above objective is achieved by the invention described in (1) below.

[0011] (1) The vacuum pump according to the present invention comprises a casing, a rotor shaft disposed within the casing, and a rotor blade rotatable together with the rotor shaft, A magnetic bearing that supports the rotor shaft by magnetic levitation,A vacuum pump comprising a rotor that exhausts gas by the rotation of the rotor blades, the vacuum pump having a heating means for heating the gas passage within the vacuum pump, the heating means comprising a coil, a heated portion which is a magnetic material heated by electromagnetic induction by passing an alternating current through the coil, and a covering on the opposite side of the front of the coil from where the heated portion is located. Magnetic ceramics and, have Furthermore, the frequency of the current applied to the coil is equal to or a multiple of the control frequency of the magnetic bearing. It is characterized by the following. [Effects of the Invention]

[0012] The vacuum pump described in (1) above is located on the opposite side of the front side where the heated part of the coil is positioned. Magnetic ceramics Because a magnetic path can be formed so that the magnetic flux passes through it, the part to be heated by electromagnetic induction can be heated efficiently. Therefore, the vacuum pump can efficiently heat the gas flow path and suppress the deposition of by-products inside the pump. Furthermore, the vacuum pump has a magnetic bearing that magnetically levitates and supports the rotor shaft. This allows for efficient heating of the gas passage in the vacuum pump having a magnetic bearing. When the part to be heated is connected to a rotor blade, the rotor blade, which is difficult to energize, can be effectively heated. In addition, the frequency of the current applied to the coil is equal to or a multiple of the control frequency of the magnetic bearing. This suppresses the generation of noise caused by the difference between the frequency of the current applied to the coil and the control frequency of the magnetic bearing.

[0013] (2) In the vacuum pump described in (1) above, the heated part may be connected to the stator component that forms the gas flow path, or may be part of the stator component. This allows the vacuum pump to effectively heat the fixed blades.

[0014] (3) In the vacuum pump described in (1) above, the heated part may be connected to the rotor blade or be a part of the rotor blade. This allows the vacuum pump to effectively heat the rotor blade, which is difficult to heat from the outside.

[0017] ( 4 ) Above (1)~( 3 In a vacuum pump described in any one of the above, Magnetic ceramics A portion of the coil may be positioned on the side perpendicular to the direction from the coil to the heated part in a cross-section perpendicular to the direction of current flow of the coil. As a result, the vacuum pump is positioned on the side opposite to the front side where the heated part of the coil is located and on the side Magnetic ceramics By forming a magnetic path through which the magnetic flux passes, the part to be heated can be heated efficiently.

[0018] (5 ) In the vacuum pump according to any one of the above (1) to 4 ), the coil may be disposed in the gas flow path. Thereby, since the coil forms a magnetic path in the high-vacuum flow path, the heated portion can be efficiently heated.

[0019] ( 6 ) In the vacuum pump according to any one of the above (1) to 5 ), the Magnetic ceramics may be a soft magnetic ferrite containing manganese and zinc. Thereby, Magnetic ceramics has a high specific resistance, so it is difficult to generate eddy currents and has little loss at high frequencies. Therefore, Magnetic ceramics suppresses heat generation in the

Brief Description of the Drawings

[0020] [Figure 1] It is a longitudinal sectional view of a vacuum pump. [Figure 2] It is a circuit diagram of an amplifier circuit. [Figure 3] It is a time chart showing control when the current command value is larger than the detected value. [Figure 4] It is a time chart showing control when the current command value is smaller than the detected value. [Figure 5] It is a longitudinal sectional view of a vacuum pump according to the first embodiment. [Figure 6] It is a perspective view showing heating means. [Figure 7] It is an enlarged sectional view of the vicinity of the heating means of the vacuum pump according to the first embodiment. [Figure 8] It is a longitudinal sectional view of a vacuum pump according to the second embodiment. [Figure 9] It is an enlarged sectional view of the vicinity of the heating means of the vacuum pump according to the second embodiment. [Figure 10] It is a partially enlarged sectional view showing a modification of the vacuum pump according to the first embodiment.

Modes for Carrying Out the Invention

[0021] Embodiments of the present invention will be described below with reference to the drawings. Note that the dimensions in the drawings may be exaggerated for illustrative purposes and may differ from the actual dimensions. Furthermore, in this specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals to avoid redundant explanations.

[0022] The vacuum pump 100 is a turbomolecular pump that exhausts gas by using rotating blades of a high-speed rotating body to blast away gas molecules. The turbomolecular pump 100 is used, for example, to draw in and exhaust gas from a chamber in semiconductor manufacturing equipment. First, the basic configuration of the turbomolecular pump 100 will be explained.

[0023] Figure 1 shows a longitudinal cross-sectional view of the turbomolecular pump 100. In Figure 1, the turbomolecular pump 100 has an intake port 101 formed at the upper end of a cylindrical outer cylinder 127. Inside the outer cylinder 127 is a rotor 103, which has multiple rotating blades 102 (102a, 102b, 102c...) that are turbine blades for drawing in and exhausting gas, formed radially and in multiple stages around its circumference. A rotor shaft 113 is attached to the center of the rotor 103, and this rotor shaft 113 is levitated and supported in the air and its position is controlled by, for example, a 5-axis controlled magnetic bearing. The rotor 103 is generally made of a metal such as aluminum or an aluminum alloy.

[0024] The upper radial electromagnet 104 consists of four electromagnets arranged in pairs along the X and Y axes. Four upper radial sensors 107 are provided in close proximity to the upper radial electromagnet 104, and each sensor corresponds to one of the upper radial electromagnets 104. The upper radial sensors 107 are, for example, inductance sensors or eddy current sensors with conduction windings, and detect the position of the rotor shaft 113 based on the change in the inductance of these conduction windings, which changes according to the position of the rotor shaft 113. These upper radial sensors 107 are configured to detect the radial displacement of the rotor shaft 113, i.e., the rotor 103 fixed to it, and send the data to the control device 200.

[0025] 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.

[0026] 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.

[0027] 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 200.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] Furthermore, for example, a phase sensor (not shown) is attached near the lower radial sensor 108 to detect the phase of rotation of the rotor shaft 113. The control device 200 uses both the detection signals from this phase sensor and the rotational speed sensor to detect the position of the magnetic pole.

[0032] Multiple fixed blades 123 (123a, 123b, 123c...) are arranged with a small gap between them and the rotating blades 102 (102a, 102b, 102c...). Each of the rotating blades 102 (102a, 102b, 102c...) is formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transport exhaust gas molecules downward by collision. 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.

[0033] 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.).

[0034] The fixed-wing spacer 125 is a ring-shaped member and is made of a metal such as aluminum, iron, stainless steel, or copper, or an alloy containing these metals as components. An outer cylinder 127 is fixed to the outer circumference of the fixed-wing spacer 125 with a small gap in between. A base portion 129 is provided at the bottom of the outer cylinder 127. An exhaust port 133 is formed in the base portion 129 and communicates with the outside. Exhaust gas that enters the intake port 101 from the chamber (vacuum chamber) side and is transferred to the base portion 129 is sent to the exhaust port 133.

[0035] Furthermore, depending on the application of the turbomolecular pump 100, a screw groove spacer 131 (fixing member) is provided between the lower part of the fixed-blade spacer 125 and the base part 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, 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 rotor 103, these molecules are transported toward the exhaust port 133. A cylindrical part 102d hangs down from the lowest part following the rotor 103's rotating blades 102 (102a, 102b, 102c...). The outer circumferential surface of this cylindrical part 102d is cylindrical and protrudes toward the inner circumferential surface of the screw groove spacer 131, and is in close proximity to the inner circumferential surface of the screw groove spacer 131 with a predetermined gap amount 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] In the above description, the screw groove spacer 131 is positioned on the outer circumference of the cylindrical portion 102d of the rotor 103, and the screw groove 131a is engraved on the inner surface of the screw groove spacer 131. However, conversely, there are also cases where the screw groove is engraved on the outer circumference of the cylindrical portion 102d, and a spacer having a cylindrical inner surface is positioned around it.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] For example, if SiCl4 is used as the process gas in an Al etching apparatus, the low vacuum (760 [torr] ~ 10 -2 The vapor pressure curve shows that when the pressure is low (torr) and the temperature is low (approximately 20°C), solid products (e.g., AlCl3) precipitate and adhere to the inside of the turbomolecular pump 100. As a result, when 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 with high pressure, such as near the exhaust port 133 and near the screw groove spacer 131.

[0045] 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).

[0046] 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 150 is shown in Figure 2.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] Furthermore, the amplifier control circuit 191 is configured, for example, by a digital signal processor unit (hereinafter referred to as the DSP unit) of the control device 200 (not shown), and this amplifier control circuit 191 is configured to switch transistors 161 and 162 on and off.

[0052] 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.

[0053] Furthermore, when the rotor 103 passes a resonance point during acceleration operation or when disturbances occur during constant-speed operation, it is necessary to control the position of the rotor 103 with high speed and strong force. For this reason, a voltage of approximately 50V is used for 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).

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] <First Embodiment> Next, the vacuum pump 300 according to the first embodiment will be described.

[0060] As shown in Figures 5 to 7, the vacuum pump 300 comprises a casing 310 that forms the outer shell of the vacuum pump 300, a rotor shaft 113 rotatably disposed inside the casing 310, a magnetic bearing 320 that supports the rotor shaft 113, a motor 121 that rotates the rotor shaft 113, a multi-stage rotor blade 102 fixed to the rotor shaft 113 and rotatable together with the rotor shaft 113, a multi-stage fixed blade 123 fixed to the casing 310 and positioned between the rotor blades 102, and a heating means 340 that heats the gas flow path inside the vacuum pump 300.

[0061] The casing 310 is formed from multiple stator components. Specifically, the casing 310 comprises an upper case 311, a lower case 312, a fixed wing spacer 125, and a base portion 129. Furthermore, the casing 310 includes a heater spacer 330 and a screw groove spacer 131 inside the lower case 312. The casing 310 has a substantially cylindrical shape with the base portion 129 as its bottom, and various interior components are installed in its internal space. These components are arranged coaxially and are integrally connected by fastening members such as bolts. In this embodiment, the stator component heated by the heating means 340 is the screw groove spacer 131, but it is not limited to the screw groove spacer 131 and may be other stator components. Also, the fixed wing 123 can be a stator component heated by the heating means 340.

[0062] An intake port 101 is located on the upstream side (intake side) of the upper case 311, and an exhaust port 133 is located on the heater spacer 330, which is on the upstream side of the base portion 129.

[0063] The lower case 312 is formed in a cylindrical shape and is provided away from the heater spacer 330 so as to cover the outer surface of the heater spacer 330.

[0064] The heater spacer 330 is positioned to heat the threaded spacer 131. The heater spacer 330 is formed in a substantially cylindrical shape and is positioned inside the lower case 312. In the axial direction, the heater spacer 330 is positioned between the fixed wing spacer 125 and the base portion 129.

[0065] The heater spacer 330 is substantially cylindrical and has a ring-shaped first recess 331 on the upstream side (intake side) facing the screw groove spacer 131 for positioning the heating means 340.

[0066] The heating means 340 includes a high-permeability magnetic material 341 disposed in the first recess 331, a coil 342 disposed adjacent to the high-permeability magnetic material 341, and a heated portion 343 connected to a screw groove spacer 131, which is one of the stator components.

[0067] The high-permeability magnetic material 341 is a ring-shaped member positioned in the first recess 331, and has a circumferentially extending concave housing portion 345 on its front surface 344, which is the side where the heated portion 343 is positioned. The housing portion 345 is capable of housing the coil 342. The housing portion 345 comprises a first wall surface 346 located on the inner circumference side of the coil 342 to be housed, a second wall surface 347 located on the outer circumference side of the coil 342, and a housing surface 348 between the first wall surface 346 and the second wall surface 347 that faces the heated portion 343. Holes and grooves for introducing the metal wires of the coil 342 from the outside are formed on the outer surface of the housing portion 345. The high-permeability magnetic material 341 covers the side of the coil 342 opposite to the front surface 344 where the heated portion 343 is positioned. The thickness of the high-permeability magnetic material 341 is not particularly limited, and is, for example, about 1 mm to 2 mm, but may be less than 1 mm or 2 mm or more.

[0068] The high-permeability magnetic material 341 is a soft magnetic material with high permeability and is a magnetic ceramic that conducts electricity less easily than metallic magnetic materials. The high-permeability magnetic material 341 is, for example, a ferrite, which is a magnetic oxide mainly composed of ferric oxide, and is preferably Mn-Zn ferrite, which is a soft magnetic ferrite containing manganese and zinc, or Ni-Zn ferrite, which is a soft magnetic ferrite containing nickel and zinc. The high-permeability magnetic material 341 is more preferably Mn-Zn ferrite.

[0069] The coil 342 is formed by winding a wire made of a good conductor (e.g., copper) multiple times and is made up of at least one layer (multiple layers in this embodiment). The coil 342 is housed in the housing section 345 from the outside of the casing 310 through a passage (not shown) and positioned in contact with the housing surface 348. The coil 342 may be configured by arranging multiple coils in parallel. The number of turns of the wire in the coil 342 is not particularly limited, but is for example 15 to 20 turns.

[0070] The heated portion 343 is connected to the screw groove spacer 131 that forms the gas flow path and is positioned to cover the housing portion 345 of the high-permeability magnetic material 341. That is, the heated portion 343 faces the front surface 344 of the housing portion 345 and is positioned to cover the front surface 344 side of the coil 342. The heated portion 343 is housed in a ring-shaped second recess 350 formed on the downstream (intake side) surface of the screw groove spacer 131 that is in contact with the heater spacer 330. The position in which the heated portion 343 contacts the screw groove spacer 131 is not particularly limited. If the screw groove spacer 131 (stator component) is made of a magnetic metal material such as stainless steel, the heated portion 343 may be part of the screw groove spacer 131.

[0071] The heated portion 343 is formed as a ring-shaped flat plate with a substantially constant thickness, corresponding to the shape of the housing portion 345 of the high-permeability magnetic material 341. The heated portion 343 is located at a minute distance from the front surface 344 of the housing portion 345. The heated portion 343 is formed from a magnetic metal material such as an iron-based material (e.g., pure iron, S15C, S25C) or a magnetic stainless steel material (e.g., ferritic stainless steel, SUS430, SUS420J2).

[0072] Next, the operation of the vacuum pump 300 according to the first embodiment will be described.

[0073] When a high-frequency alternating current flows through the coil 342, the coil 342, the high-permeability magnetic material 341, and the heated part 343 are electromagnetically coupled, generating eddy currents inside the heated part 343. The frequency of the applied alternating current is, for example, 20kHz to 60kHz, but may be a different frequency. The voltage is, for example, 100V to 300V, but is not limited to this. Because the heated part 343 has its own electrical resistance, Joule heat is generated by the eddy currents. The heated part 343 also generates heat due to iron loss. As a result, the heated part 343 becomes hot and can heat the screw groove spacer 131 in contact with it. The high-permeability magnetic material 341 does not conduct electricity well, so it does not generate Joule heat due to eddy currents. Furthermore, since the coil 342 is positioned in the housing portion 345 of the high-permeability magnetic material 341, the high-permeability magnetic material 341 covers the opposite side (downstream side in this embodiment) and the lateral side (inner and outer radial sides in this embodiment) of the direction in which the front surface 344 faces. As a result, as shown in Figure 7, magnetic flux leakage from the coil 342 is suppressed. Therefore, it is possible to suppress the generation of heat due to Joule heating and losses in the metal material located outside the high-permeability magnetic material 341 (heater spacer 330 in this embodiment). Consequently, the heating means 340 can efficiently heat the part to be heated 343.

[0074] The frequency of the current applied to the coil 342 is preferably equal to or a multiple of the control frequency of the magnetic bearing 320. If the frequency of the current applied to the coil 342 differs from the control frequency of the magnetic bearing 320 or a multiple thereof, noise at the frequency of that difference may be generated. In contrast, if the frequency of the current applied to the coil 342 is equal to or a multiple of the control frequency of the magnetic bearing 320, the generation of noise caused by the above-mentioned difference can be suppressed.

[0075] Furthermore, the high-permeability magnetic material 341 only needs to cover the side opposite to the front surface 344 where the heated portion 343 of the coil 342 is located, and does not need to be located on the side perpendicular to the direction from the coil 342 to the heated portion 343 in a cross section perpendicular to the current flow direction of the coil 342 (the inner and outer sides in the radial direction in this embodiment). In other words, the high-permeability magnetic material 341 does not need to have the first wall surface 346 and / or the second wall surface 347, as long as it has a housing surface 348. However, in that case, the magnetic flux will be more susceptible to influence from surrounding metal parts (e.g., heater spacer 330), so it is preferable to maintain a sufficient distance between the coil 342 and the heater spacer 330 on the side where the high-permeability magnetic material 341 is not located.

[0076] As described above, the vacuum pump 300 according to the first embodiment comprises a casing 310, a rotor shaft 113 disposed within the casing 310, and a rotor blade 102 rotatable together with the rotor shaft 113, and is a vacuum pump 300 that exhausts gas by the rotation of the rotor blade 102, and has a heating means 340 for heating the gas passage in the vacuum pump 300, the heating means 340 comprising a coil 342, a heated portion 343 which is a magnetic material heated by electromagnetic induction by passing an alternating current through the coil 342, and a high-permeability magnetic material 341 that covers the opposite side of the front 344 side of the coil 342 where the heated portion 343 is located. As a result, the vacuum pump 300 can form a magnetic path so that the magnetic flux passes through the high-permeability magnetic material 341 on the opposite side of the front 344 side where the heated portion 343 of the coil 342 is located, and thus can efficiently heat the heated portion 343 which is heated by electromagnetic induction. Therefore, the vacuum pump 300 can efficiently heat the gas flow path and suppress the precipitation of by-products within the pump.

[0077] Furthermore, the heated portion 343 is connected to or is part of the stator component (screw groove spacer 131) that forms the gas flow path. This allows the vacuum pump 300 to effectively heat the fixed blade 123.

[0078] Furthermore, the vacuum pump 300 has a magnetic bearing 320 that magnetically levitates and supports the rotor shaft 113. This allows the gas passage of the vacuum pump 300 with the magnetic bearing 320 to be heated efficiently. When the part to be heated 343 is connected to the rotor blade 102, the rotor blade 102, which is difficult to energize, can be heated effectively.

[0079] Furthermore, the frequency of the current applied to the coil 342 is equal to or a multiple of the control frequency of the magnetic bearing 320. This suppresses the generation of noise caused by the difference between the frequency of the current applied to the coil 342 and the control frequency of the magnetic bearing 320.

[0080] Furthermore, a portion of the high-permeability magnetic material 341 is positioned on the side perpendicular to the direction from the coil 342 to the heated section 343 in a cross section perpendicular to the direction of current flow of the coil 342. As a result, the vacuum pump 300 can efficiently heat the heated section 343 by forming a magnetic path through the high-permeability magnetic material 341 on the opposite side of the front 344 of the coil 342 where the heated section 343 is located, as well as on the side.

[0081] In the first embodiment, the coil 342 was installed on the vacuum side, but it may also be installed on the atmospheric side. Considering that a discharge countermeasure for the coil 342 is necessary when it is installed on the vacuum side, the atmospheric side is preferable.

[0082] Furthermore, the high-permeability magnetic material 341 is a soft magnetic ferrite containing manganese and zinc. As a result, the high-permeability magnetic material 341 has high resistivity, making it less likely to generate eddy currents and resulting in low losses at high frequencies. Therefore, heat generation in the high-permeability magnetic material 341 is suppressed, and the heated part 343 can be heated efficiently.

[0083] <Second Embodiment> Next, the vacuum pump 400 according to the second embodiment will be described. The second embodiment differs from the first embodiment in that the heated portion 443 of the heating means 440 is connected to the rotor blade 102.

[0084] As shown in Figures 8 and 9, the heating means 440 includes a cylindrical high-permeability magnetic material 441 that covers the outer surface of the stator column 122 (stator component) surrounding the electrical equipment, a coil 442 arranged to wind around the outer surface of the high-permeability magnetic material 441, and a cylindrical heated part 443 connected to the rotor blade 102.

[0085] The high-permeability magnetic material 441 is a cylindrical member, and a coil 442 is wound around the front surface 444, which is the outer circumferential surface, on the side where the heated portion 443 is located. From the viewpoint of suppressing magnetic flux leakage from the coil 442, it is preferable that the upstream end of the high-permeability magnetic material 441 be located upstream of the upstream end of the coil 442. Also, it is preferable that the downstream end of the high-permeability magnetic material 441 be located downstream of the downstream end of the coil 442. In the second embodiment, the high-permeability magnetic material 441 does not have a concave housing portion, but it may have a concave housing portion 445, similar to the first embodiment. That is, a part of the high-permeability magnetic material 441 may be located on the side perpendicular to the direction from the coil 442 to the heated portion 443 in a cross section perpendicular to the current flow direction of the coil 442 (the upstream side and / or downstream side in the second embodiment). The coil 442 is located in the gas flow path. In other words, coil 442 is placed under high vacuum in the gas flow path.

[0086] The heated portion 443 is, for example, a cylindrical member fixed to the inner circumferential surface of the rotor blade 102. The heated portion 443 may also be a member fixed to the inner circumferential surface of the rotor blade 102 by plating or the like. The heated portion 443 is formed of a magnetic metal material such as stainless steel. If the rotor blade 102 is formed of a magnetic metal material such as stainless steel, the heated portion 443 may be a part of the rotor blade 102.

[0087] Next, the operation of the vacuum pump 400 according to the second embodiment will be explained.

[0088] In the vacuum pump 400 according to the second embodiment, when the rotor blade 102 rotates, the heated portion 443 connected to the rotor blade 102, or the heated portion 443 which is a part of the rotor blade 102, also rotates. In this state, when a high-frequency alternating current flows through the stationary coil 442, the coil 442, the high-permeability magnetic material 441, and the heated portion 443 are electromagnetically coupled, and eddy currents are generated inside the heated portion 443. The heated portion 443 generates Joule heat due to the eddy currents, as well as iron loss heat. As a result, the heated portion 443 becomes hot and can heat the rotor blade 102 connected to the heated portion 443, or the rotor blade 102 having the heated portion 443. Therefore, the heating means 440 can efficiently heat the rotor blade 102 with the coil 442 located on the stationary side. Note that the high-permeability magnetic material 441 does not conduct electricity well and therefore does not generate Joule heat due to eddy currents. Furthermore, since the coil 442 is positioned on the outer circumferential surface of the high-permeability magnetic material 441, magnetic flux leakage from the coil 442 is suppressed, as shown in Figure 9. This suppresses the generation of heat due to Joule heating and losses in the metal material (stator column 122 in this embodiment) located radially inside the high-permeability magnetic material 441. Consequently, the heating means 440 can efficiently heat the part to be heated 443.

[0089] Furthermore, the heated part 443 is connected to the rotor blade 102 or is part of the rotor blade 102. This allows the vacuum pump 400 to effectively heat the rotor blade 102, which is difficult to heat from the outside.

[0090] Furthermore, the coil 442 is positioned within a high-vacuum gas flow path. This allows the coil 442 to form a magnetic path near the heated section 443, enabling efficient heating.

[0091] In the second embodiment, the coil 442 was installed on the vacuum side, but it may also be installed on the atmospheric side. While the atmospheric side is preferable considering the need for discharge prevention measures when the coil 442 is placed on the vacuum side, it is not limited to this.

[0092] It should be noted that the present invention is not limited to the embodiments described above, and various modifications and combinations are possible within the technical concept of the present invention by those skilled in the art. For example, the first and second embodiments described above may be combined.

[0093] Furthermore, as shown in the modified example of the first embodiment in Figure 10, the coil 542 may be located radially inward of the high-permeability magnetic material 541, and the heated portion 543 may be located radially inward of both the high-permeability magnetic material 541 and the coil 542.

[0094] Furthermore, the vacuum pump 300 may consist only of a turbomolecular pump without a screw groove pump section. Also, although the screw groove pump in each of the above embodiments is a Holbeck-type screw groove pump with axial helical grooves, it may also be a Sigburn-type screw groove pump with radial spiral grooves, or a configuration having both. [Explanation of symbols]

[0095] 102 Rotary blades 113 Rotor shaft 123 Fixed wing 131 Threaded groove spacer (stator component) 300, 400 vacuum pumps 310 Casing 320 Magnetic Bearing 330 Heater Spacer 340, 440, 540 Heating means 341, 441, 541 High permeability magnetic material 342, 442, 542 coils 343, 443, 543 Heated part 344, 444, 544 front

Claims

1. Casing and, The rotor shaft is located inside the casing, A rotor blade that can rotate together with the rotor shaft, A magnetic bearing that supports the rotor shaft by magnetic levitation, A vacuum pump comprising the rotation of the rotor blades which exhausts gas, The vacuum pump has a heating means for heating the gas flow path within the vacuum pump, The heating means is Coil and, The heated part is a magnetic material that is heated by electromagnetic induction caused by passing an alternating current through the coil, The coil comprises a magnetic ceramic covering the side opposite to the front side where the heated portion is located, A vacuum pump characterized in that the frequency of the current applied to the coil is equal to or a multiple of the control frequency of the magnetic bearing.

2. The vacuum pump according to claim 1, characterized in that the heated portion is connected to or is part of the stator component that forms the gas flow path.

3. The vacuum pump according to claim 1, characterized in that the heated portion is connected to or is part of the rotor blade.

4. The vacuum pump according to claim 1, characterized in that a portion of the magnetic ceramics is arranged on the side perpendicular to the direction from the coil to the heated part in a cross section perpendicular to the direction of current flow of the coil.

5. The vacuum pump according to claim 1, characterized in that the coil is arranged within the gas flow path.

6. The vacuum pump according to claim 1, characterized in that the magnetic ceramic is a soft magnetic ferrite containing manganese and zinc.

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