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 technology]

[0002] Semiconductor manufacturing equipment, liquid crystal manufacturing equipment, electron microscopes, surface analysis equipment, microfabrication equipment, and the like require the environment within the equipment to be kept at a high vacuum. Vacuum pumps are used to create a high vacuum within these devices. Examples of the vacuum pumps used include a composite pump that combines a turbomolecular pump and a thread groove pump.

[0003] In a vacuum pump that combines a turbomolecular pump and a screw groove pump, the screw groove pump is placed downstream of a turbopump that has rotating and fixed blades arranged alternately in the axial direction. Exhaust gas taken in through an intake port is compressed by the turbomolecular pump and the screw groove pump and then discharged outside the vacuum pump through an exhaust port.

[0004] Exhaust gas behaves like a viscous flow due to the relatively high pressure, especially in the downstream flow path. For this reason, by-products are likely to precipitate in the vacuum pump flow path where the exhaust gas flow stagnates. When by-products precipitate in the flow path, things that should not normally come into contact come into contact, which can damage the vacuum pump or cause variations in temperature distribution due to changes in the heat transfer performance of the internal structure, potentially compromising safety and productivity.

[0005] For this reason, vacuum pumps are sometimes provided with a heating means for heating components that form the gas flow path in order to prevent by-products from being deposited in the gas flow path. For example, Patent Document 1 discloses a structure in which a heating unit is provided that heats stator components on the fixed blade side by electromagnetic induction heating.

[0006] The heating unit includes a yoke fixed to the stator component, a coil placed 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. The heating plate and yoke have inherent electrical resistance, generating Joule heat. Iron loss heat is also generated in the heating plate and yoke, and copper loss heat is also generated in the coil, which also heats the stator component. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2014 / 119191 Summary of the Invention [Problem to be solved by the invention]

[0008] In the vacuum pump described in Patent Document 1, metal members are present around the coil, which means that areas other than the intended heating area are also heated at the same time, making it impossible to heat the heating plate efficiently, which may result in the deposition of by-products inside the pump.

[0009] The present invention has been made to solve the above-mentioned problems, and has an object to provide a vacuum pump that can suppress the deposition of by-products inside the pump. [Means for solving the problem]

[0010] The above object can be achieved by the invention described in (1) below.

[0011] (1) A vacuum pump according to the present invention comprises a casing, a rotor shaft arranged within the casing, and a rotor blade rotatable together with the rotor shaft, and exhausts gas by rotation of the rotor blade. The vacuum pump has a heating means for heating a gas flow path within the vacuum pump, and the heating means comprises a coil, a heated part which is a magnetic material heated by electromagnetic induction caused by passing an alternating current through the coil, and a high-permeability magnetic material covering the side of the coil opposite to the front side where the heated part is arranged. [Effects of the Invention]

[0012] The vacuum pump described in (1) above can form a magnetic path so that the magnetic flux passes through the high-permeability magnetic material on the opposite side of the front side of the coil where the heated part is located, and therefore can efficiently heat the heated part that is heated by electromagnetic induction.As a result, the vacuum pump can efficiently heat the gas flow path and suppress the deposition of by-products inside the pump.

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

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

[0015] (4) The vacuum pump according to any one of (1) to (3) above may have a magnetic bearing that magnetically levitates and supports the rotor shaft. This allows the gas flow path of the vacuum pump having the magnetic bearing to be heated efficiently. When the heated part is connected to the rotor blade, the rotor blade, which is difficult to energize, can be heated effectively.

[0016] (5) In the vacuum pump according to any one of (1) to (4) above, the frequency of the current applied to the coil may be equal to or a multiple of the control frequency of the magnetic bearing, thereby suppressing noise caused by the difference between the frequency of the current applied to the coil and the control frequency of the magnetic bearing.

[0017] (6) In the vacuum pump according to any one of (1) to (5), a part of the high-permeability magnetic body may be disposed on a lateral side perpendicular to a direction from the coil toward the heated part in a cross section perpendicular to the current-carrying direction of the coil. This allows the vacuum pump to form a magnetic path so that magnetic flux passes through the high-permeability magnetic body on the side and opposite to the front side of the coil where the heated part is disposed, thereby enabling efficient heating of the heated part.

[0018] (7) In the vacuum pump according to any one of (1) to (6) above, the coil may be disposed in the gas flow path, whereby the coil forms a magnetic path in the high-vacuum flow path, thereby enabling efficient heating of the heated part.

[0019] (8) In the vacuum pump according to any one of (1) to (7), the high-permeability magnetic material may be a soft magnetic ferrite containing manganese and zinc. This allows the high-permeability magnetic material to have high resistivity, making it less likely to generate eddy currents and resulting in low loss at high frequencies. This suppresses heat generation in the high-permeability magnetic material, enabling efficient heating of the heated portion. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 2 is a vertical cross-sectional view of a vacuum pump. [Figure 2] FIG. 2 is a circuit diagram of an amplifier circuit. [Figure 3] 10 is a time chart showing control when a current command value is larger than a detection value. [Figure 4] 10 is a time chart showing control when a current command value is smaller than a detection value. [Figure 5]1 is a vertical cross-sectional view of a vacuum pump according to a first embodiment. [Figure 6] FIG. [Figure 7] FIG. 2 is an enlarged cross-sectional view of the vicinity of a heating means of the vacuum pump according to the first embodiment. [Figure 8] FIG. 10 is a vertical cross-sectional view of a vacuum pump according to a second embodiment. [Figure 9] FIG. 10 is an enlarged cross-sectional view of the vicinity of a heating means of a vacuum pump according to a second embodiment. [Figure 10] FIG. 4 is a partially enlarged cross-sectional view showing a modified example of the vacuum pump according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that dimensions in the drawings may be exaggerated for convenience of explanation and may differ from actual dimensions. Furthermore, in this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant explanations will be omitted.

[0022] The vacuum pump 100 is a turbomolecular pump that exhausts gas by ejecting gas molecules with rotating blades of a rotor that rotates at high speed. The turbomolecular pump 100 is used to suck and exhaust gas from a chamber of, for example, a semiconductor manufacturing device. First, the basic configuration of the turbomolecular pump 100 will be described.

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

[0024] The upper radial electromagnets 104 are arranged in pairs on the X-axis and the Y-axis. Four upper radial sensors 107 are provided adjacent to the upper radial electromagnets 104 and corresponding to each upper radial electromagnet 104. The upper radial sensors 107 are, for example, inductance sensors or eddy current sensors having conductive windings, and detect the position of the rotor shaft 113 based on changes in the inductance of the conductive windings, which change according to the position of the rotor shaft 113. The upper radial sensors 107 are configured to detect the radial displacement of the rotor shaft 113, i.e., the rotor 103 fixed thereto, and send the detected radial displacement to the control device 200.

[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 a position signal detected by the upper radial sensor 107, and an amplifier circuit 150 (described later) shown in Figure 2 controls the excitation of the upper radial electromagnet 104 based on this excitation control command signal, thereby adjusting the upper radial position of the rotor shaft 113.

[0026] The rotor shaft 113 is made of a high magnetic permeability material (iron, stainless steel, etc.) and is attracted by the magnetic force of the upper radial electromagnets 104. Such adjustment is performed independently in the X-axis direction and the Y-axis direction. The lower radial electromagnets 105 and the lower radial sensors 108 are arranged in the same manner as the upper radial electromagnets 104 and the upper radial sensors 107, and adjust the radial position of the lower side of the rotor shaft 113 in the same manner as the radial position of the upper side.

[0027] Furthermore, axial electromagnets 106A and 106B are arranged above and below a circular metal disk 111 provided at the bottom of rotor shaft 113. Metal disk 111 is made of a highly magnetic permeable material such as iron. An axial sensor 109 is provided to detect the axial displacement of rotor shaft 113, and an axial position signal is sent to control device 200.

[0028] In the control device 200, a compensation circuit having, for example, a PID adjustment function generates excitation control command signals for the axial electromagnet 106A and the axial electromagnet 106B based on the axial position signal detected by the axial sensor 109, and the amplifier circuit 150 controls the excitation of the axial electromagnet 106A and the axial electromagnet 106B based on these excitation control command signals, so that the axial electromagnet 106A attracts the metal disc 111 upward by magnetic force, and the axial electromagnet 106B attracts the metal disc 111 downward, thereby adjusting the axial position of the rotor shaft 113.

[0029] In this way, the control device 200 appropriately adjusts the magnetic forces that the axial electromagnets 106A and 106B exert on the metal disk 111, magnetically levitating the rotor shaft 113 in the axial direction and holding it in space without contact. The amplifier circuit 150 that controls the excitation of the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B will be described later.

[0030] Meanwhile, motor 121 has a plurality of magnetic poles arranged circumferentially so as to surround rotor shaft 113. Each magnetic pole is controlled by control device 200 so as to rotate rotor shaft 113 via electromagnetic force acting between the magnetic pole and rotor shaft 113. Motor 121 also incorporates a rotational speed sensor (not shown), such as a Hall element, resolver, or encoder, and the rotational speed of rotor shaft 113 is detected by the detection signal of this rotational speed sensor.

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

[0032] A plurality of fixed blades 123 (123a, 123b, 123c...) are arranged at small gaps from the rotating blades 102 (102a, 102b, 102c...). Each of the rotating blades 102 (102a, 102b, 102c...) is formed at an angle of a predetermined degree from a plane perpendicular to the axis of the rotor shaft 113 in order to transport exhaust gas molecules downward through collision. The fixed blades 123 (123a, 123b, 123c...) are made of metal such as aluminum, iron, stainless steel, copper, or an alloy containing any of these metals as an ingredient.

[0033] Similarly, the fixed blades 123 are formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged in a staggered manner with the rows of rotor blades 102 toward the inside of the outer cylinder 127. The outer peripheral ends of the fixed blades 123 are supported by being inserted between a plurality of stacked rows of fixed blade spacers 125 (125a, 125b, 125c, etc.).

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

[0035] Furthermore, depending on the application of the turbomolecular pump 100, a threaded spacer 131 (fixed member) is disposed between the lower portion of the fixed vane spacer 125 and the base portion 129. The threaded spacer 131 is a cylindrical member made of a metal such as aluminum, copper, stainless steel, iron, or an alloy containing any of these metals, and has a plurality of spiral thread grooves 131a engraved on its inner circumferential surface. The spiral direction of the threaded grooves 131a corresponds to the direction in which exhaust gas molecules are transported toward the exhaust port 133 when they move in the rotational direction of the rotor 103. A cylindrical portion 102d hangs down from the lowest portion of the rotor 103, adjacent to the rotating vanes 102 (102a, 102b, 102c, etc.). The outer circumferential surface of this cylindrical portion 102d is cylindrical and protrudes toward the inner circumferential surface of the threaded spacer 131, and is adjacent to the inner circumferential surface of the threaded spacer 131 with a predetermined gap therebetween. The exhaust gas transferred to the thread groove 131a by the rotor 102 and the fixed blade 123 is sent to the base portion 129 while being guided by the thread groove 131a.

[0036] The base portion 129 is a disk-shaped member that forms the base of the turbomolecular pump 100, and is generally made of metal such as iron, aluminum, stainless steel, etc. The base portion 129 not only physically holds the turbomolecular pump 100, but also functions as a heat conduction path, so it is desirable to use a metal that is rigid and has high thermal conductivity, such as iron, aluminum, or copper.

[0037] In this configuration, when the rotor 102 is rotated together with the rotor shaft 113 by the motor 121, the action of the rotor 102 and the stator 123 draws exhaust gas from the chamber through the intake port 101. The rotational speed of the rotor 102 is typically 20,000 rpm to 90,000 rpm, and the peripheral speed at the tip of the rotor 102 reaches 200 m / s to 400 m / s. The exhaust gas drawn in through the intake port 101 passes between the rotor 102 and the stator 123 and is transported to the base 129. At this time, the temperature of the rotor 102 rises due to frictional heat generated when the exhaust gas comes into contact with the rotor 102 and conduction of heat generated by the motor 121, but this heat is transferred to the stator 123 side by radiation or conduction through gas molecules of the exhaust gas.

[0038] The stator spacers 125 are joined together at their outer peripheries and transmit to the outside heat received by the stator 123 from the rotor 102 and frictional heat generated when exhaust gas comes into contact with the stator 123.

[0039] 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 circumferential surface of the thread groove spacer 131. However, conversely, there are also cases where thread grooves are engraved on the outer circumferential surface of the cylindrical portion 102d, and a spacer having a cylindrical inner circumferential surface is disposed around it.

[0040] Depending on the application of the turbomolecular pump 100, the electrical equipment section may be surrounded by a stator column 122 to prevent the gas sucked in from the intake port 101 from entering the electrical equipment section, which is composed of the upper radial electromagnet 104, the upper radial sensor 107, the motor 121, the lower radial electromagnet 105, the lower radial sensor 108, the axial electromagnets 106A and 106B, the axial sensor 109, etc., and the interior of this stator column 122 may be kept at a predetermined pressure by purge gas.

[0041] In this case, piping (not shown) is provided in the base portion 129, and purge gas is introduced through this piping. The introduced purge gas is sent to the exhaust port 133 through gaps between the protective bearing 120 and the rotor shaft 113, between the rotor and stator of the motor 121, and between the stator column 122 and the inner cylindrical portion of the rotor blades 102.

[0042] Here, the turbomolecular pump 100 requires control based on specific parameters (e.g., various characteristics corresponding to the model) that have been individually adjusted and identified for the model. To store these control parameters, the turbomolecular pump 100 is provided with an electronic circuit section 141 within its body. The electronic circuit section 141 is composed of a semiconductor memory such as an EEPROM, electronic components such as semiconductor elements for accessing the memory, and a substrate 143 for mounting these components. The electronic circuit section 141 is housed below a rotational speed sensor (not shown) near the center of a base section 129 that constitutes the lower part of the turbomolecular pump 100, and is closed by an airtight bottom lid 145.

[0043] In the semiconductor manufacturing process, some process gases introduced into a chamber have the property of solidifying when their pressure exceeds a predetermined value or their temperature falls below a predetermined value. Inside the turbomolecular pump 100, the pressure of the exhaust gas is lowest at the inlet port 101 and highest at the outlet port 133. If the pressure of the process gas exceeds a predetermined value or the temperature falls below a predetermined value while the process gas is being transferred from the inlet port 101 to the outlet port 133, the process gas solidifies and adheres to and accumulates inside the turbomolecular pump 100.

[0044] For example, when SiCl4 is used as the process gas in an Al etching system, the low vacuum (760 [torr] to 10 -2The vapor pressure curve shows that at low pressures (approximately 20°C) and high pressures (approximately 20°C), solid products (e.g., AlCl3) precipitate and adhere to and accumulate inside the turbomolecular pump 100. When process gas deposits accumulate inside the turbomolecular pump 100, these deposits narrow the pump flow path, causing a decrease in the performance of the turbomolecular pump 100. The aforementioned products tend to solidify and adhere to high-pressure areas near the exhaust port 133 and the thread groove spacer 131.

[0045] Therefore, in order to solve this problem, conventionally, a heater (not shown) or a circular water-cooled pipe 149 is wrapped around the outer periphery of the base portion 129, etc., and a temperature sensor (e.g., a thermistor) (not shown) is embedded in the base portion 129, and the heating of the heater and the cooling by the water-cooled pipe 149 are controlled based on the signal from this temperature sensor to maintain the temperature of the base portion 129 at a constant high temperature (set temperature) (hereinafter referred to as TMS; Temperature Management System).

[0046] Next, a description will be given of the amplifier circuit 150 that controls excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B in the turbomolecular pump 100. A circuit diagram of this amplifier circuit 150 is shown in FIG.

[0047] 2, one end of the electromagnet winding 151 constituting the upper radial electromagnet 104 etc. is connected to a positive electrode 171a of a power supply 171 via a transistor 161, and the other end is connected to a negative electrode 171b of the power supply 171 via a current detection circuit 181 and a transistor 162. The transistors 161 and 162 are so-called power MOSFETs, and have a structure in which a diode is connected between the source and drain.

[0048] At this time, the transistor 161 has a diode cathode terminal 161a connected to the positive electrode 171a and an anode terminal 161b connected to one end of the electromagnet winding 151. The transistor 162 has a diode cathode terminal 162a connected to the current detection circuit 181 and an anode terminal 162b connected to the negative electrode 171b.

[0049] Meanwhile, current regeneration diode 165 has its cathode terminal 165a connected to one end of electromagnet winding 151 and its anode terminal 165b connected to negative electrode 171b. Similarly, current regeneration diode 166 has its cathode terminal 166a connected to positive electrode 171a and its anode terminal 166b connected to the other end of electromagnet winding 151 via current detection circuit 181. Current detection circuit 181 is configured, for example, with a Hall sensor type current sensor or an electrical resistance element.

[0050] The amplifier circuit 150 configured as above corresponds to one electromagnet. Therefore, if the magnetic bearing is controlled in five axes and there are a total of ten electromagnets 104, 105, 106A, and 106B, a similar amplifier circuit 150 is configured for each electromagnet, and the ten amplifier circuits 150 are connected in parallel to the power supply 171.

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

[0052] The amplifier control circuit 191 compares the current value detected by the current detection circuit 181 (a signal reflecting this current value is called a current detection signal 191c) with a predetermined current command value. Based on the comparison result, the amplifier control circuit 191 determines the size of the pulse width (pulse width times Tp1 and Tp2) to be generated within a control cycle Ts, which is one period under PWM control. As a result, gate drive signals 191a and 191b having these pulse widths are output from the amplifier control circuit 191 to the gate terminals of the transistors 161 and 162.

[0053] It is necessary to control the position of rotor 103 at high speed and with strong force when, for example, the rotor 103 passes through a resonance point during acceleration of its rotational speed or when a disturbance occurs during constant-speed operation. For this reason, a voltage of, for example, about 50 V is used as power supply 171 so that the current flowing through electromagnet winding 151 can be rapidly increased (or decreased). In addition, a capacitor (not shown) is usually connected between positive electrode 171a and negative electrode 171b of power supply 171 to stabilize power supply 171.

[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 electromagnet current iL) increases, and when both are turned off, the electromagnet current iL decreases.

[0055] Furthermore, when one of the transistors 161 and 162 is turned on and the other is turned off, a so-called flywheel current is maintained. By passing a flywheel current through the amplifier circuit 150 in this manner, hysteresis loss in the amplifier circuit 150 can be reduced, and the power consumption of the entire circuit can be kept low. Furthermore, by controlling the transistors 161 and 162 in this manner, high-frequency noise such as harmonics generated in the turbomolecular pump 100 can be reduced. Furthermore, by measuring this flywheel current with the current detection circuit 181, the electromagnet current iL flowing through the electromagnet winding 151 can be detected.

[0056] That is, when the detected current value is smaller than the current command value, both transistors 161 and 162 are turned on for a time period corresponding to pulse width time Tp1 only once in a control cycle Ts (for example, 100 μs), as shown in Fig. 3. Therefore, during this period, the electromagnet current iL increases toward a current value iLmax (not shown) that can flow from the positive electrode 171a to the negative electrode 171b via the transistors 161 and 162.

[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 for a time period corresponding to pulse width time Tp2 only once during the control cycle Ts, as shown in Fig. 4. Therefore, the electromagnet current iL during this period decreases toward a current value iLmin (not shown) that can be regenerated from the negative pole 171b to the positive pole 171a via diodes 165 and 166.

[0058] In either case, after the pulse width times Tp1 and Tp2 have elapsed, one of the transistors 161 and 162 is turned on. Therefore, a flywheel current is maintained in the amplifier circuit 150 during this period.

[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 includes a casing 310 that forms the outer shell of the vacuum pump 300, a rotor shaft 113 that is rotatably arranged inside the casing 310, a magnetic bearing 320 that supports the rotor shaft 113, a motor 121 that rotates the rotor shaft 113, multiple stages of rotor blades 102 that are fixed to the rotor shaft 113 and rotatable together with the rotor shaft 113, multiple stages of fixed blades 123 that are fixed to the casing 310 and arranged 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 by multiple stator components. Specifically, the casing 310 includes an upper case 311, a lower case 312, a stator spacer 125, and a base 129. Furthermore, the casing 310 includes a heater spacer 330 and a threaded spacer 131 inside the lower case 312. The casing 310 has a generally cylindrical shape with the base 129 at its bottom, and various interior components are installed in its internal space. These components are arranged coaxially and integrally connected by fastening members such as bolts. In this embodiment, the stator component heated by the heating means 340 is the threaded spacer 131, but this is not limited to the threaded spacer 131 and may be another stator component. The stator 123 may also be a stator component heated by the heating means 340.

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

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

[0064] The heater spacer 330 is disposed to heat the thread groove spacer 131. The heater spacer 330 is formed in a substantially cylindrical shape and is disposed inside the lower case 312. The heater spacer 330 is disposed between the fixed blade spacer 125 and the base portion 129 in the axial direction.

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

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

[0067] The high-permeability magnetic material 341 is a ring-shaped member placed in the first recess 331. It has a circumferentially extending recessed accommodation portion 345 on its front surface 344, which is the surface on which the heated portion 343 is placed. The accommodation portion 345 can accommodate the coil 342. The accommodation portion 345 has a first wall surface 346 located on the inner periphery of the coil 342, a second wall surface 347 located on the outer periphery of the coil 342, and an accommodation surface 348 facing the heated portion 343 between the first wall surface 346 and the second wall surface 347. The accommodation portion 345 has holes or grooves formed on its outer surface for introducing the metal wire of the coil 342 from the outside. The high-permeability magnetic material 341 covers the side of the coil 342 opposite the front surface 344 on which the heated portion 343 is placed. The thickness of high permeability magnetic body 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 magnetic 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 containing ferric oxide as the main component, and is preferably an Mn-Zn ferrite, which is a soft magnetic ferrite containing manganese and zinc, or an Ni-Zn ferrite, which is a soft magnetic ferrite containing nickel and zinc. The high-permeability magnetic material 341 is more preferably an Mn-Zn ferrite.

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

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

[0071] The heated portion 343 is formed of a ring-shaped flat plate having a substantially uniform thickness corresponding to the shape of the accommodation portion 345 of the high-permeability magnetic material 341. The heated portion 343 is spaced a small distance from the front surface 344 of the accommodation portion 345. The heated portion 343 is formed of 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 portion 343 are electromagnetically coupled, generating eddy currents inside the heated portion 343. The frequency of the applied alternating current is, for example, 20 kHz to 60 kHz, but may be a different frequency. The voltage is, for example, but not limited to, 100 V to 300 V. The heated portion 343 has an inherent electrical resistance, so eddy currents generate Joule heat. The heated portion 343 also generates iron loss heat. As a result, the heated portion 343 becomes hot, and can heat the thread groove spacer 131 in contact with it. Note that the high-permeability magnetic material 341 is a poor conductor of electricity, so Joule heat due to eddy currents is not generated. Furthermore, by arranging the coil 342 in the housing portion 345 of the high-permeability magnetic material 341, the coil 342 is covered by the high-permeability magnetic material 341 on the side opposite to the direction in which the front surface 344 faces (the downstream side in this embodiment) and on the lateral sides (the radially inner and outer sides in this embodiment). Therefore, as shown in FIG. 7, magnetic flux leakage from the coil 342 is suppressed. Therefore, it is possible to suppress the generation of heat due to Joule heat or loss in the metal material (heater spacer 330 in this embodiment) located outside the high-permeability magnetic material 341. Therefore, the heating means 340 can efficiently heat the heated portion 343.

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

[0075] Note that the high-permeability magnetic body 341 only needs to cover the side of the coil 342 opposite to the front surface 344 on which the heated portion 343 is disposed, and does not necessarily have to be disposed on the lateral side (the radially inner and outer sides in this embodiment) perpendicular to the direction from the coil 342 to the heated portion 343 in a cross section perpendicular to the current-carrying direction of the coil 342. That is, the high-permeability magnetic body 341 does not need to have the first wall surface 346 and / or the second wall surface 347 as long as it has the housing surface 348. However, in this case, the magnetic flux is more likely to be affected by surrounding metal components (e.g., the heater spacer 330). Therefore, it is preferable to ensure a sufficient distance between the coil 342 and the heater spacer 330 on the side on which the high-permeability magnetic body 341 is not disposed.

[0076] As described above, the vacuum pump 300 according to the first embodiment includes a casing 310, a rotor shaft 113 disposed within the casing 310, and a rotor 102 rotatable together with the rotor shaft 113. The vacuum pump 300 exhausts gas by rotation of the rotor 102. The vacuum pump 300 also includes a heating means 340 for heating a gas flow path within the vacuum pump 300. The heating means 340 includes a coil 342, a heated portion 343 that is a magnetic material heated by electromagnetic induction when an alternating current is passed through the coil 342, and a high-permeability magnetic material 341 that covers the side of the coil 342 opposite to the front surface 344 on which the heated portion 343 is disposed. This allows the vacuum pump 300 to form a magnetic path that allows magnetic flux to pass through the high-permeability magnetic material 341 that is disposed on the side of the coil 342 opposite to the front surface 344 on which the heated portion 343 is disposed, thereby efficiently heating the heated portion 343 that is heated by electromagnetic induction. Therefore, the vacuum pump 300 can efficiently heat the gas flow passage and suppress the deposition of by-products inside the pump.

[0077] Furthermore, the heated portion 343 is connected to a stator component (thread groove spacer 131) that forms a gas flow path, or is a part of the stator component, so that the vacuum pump 300 can heat the stator vanes 123 effectively.

[0078] The vacuum pump 300 also has a magnetic bearing 320 that magnetically levitates and supports the rotor shaft 113. This allows for efficient heating of the gas flow path of the vacuum pump 300 that has the magnetic bearing 320. When the heated portion 343 is connected to the rotor 102, the rotor 102, which is difficult to energize, can be effectively heated.

[0079] Furthermore, the frequency of the current applied to coil 342 is the same as or a multiple of the control frequency of magnetic bearing 320. This makes it possible to suppress the generation of noise caused by the difference between the frequency of the current applied to coil 342 and the control frequency of magnetic bearing 320.

[0080] Furthermore, a portion of the high-permeability magnetic material 341 is disposed on a lateral side perpendicular to the direction from the coil 342 toward the heated portion 343 in a cross section perpendicular to the current flow direction of the coil 342. This allows the vacuum pump 300 to form a magnetic path such that magnetic flux passes through the high-permeability magnetic material 341 on the side opposite to the front surface 344 of the coil 342 where the heated portion 343 is disposed, and on the lateral side, thereby enabling the heated portion 343 to be heated efficiently.

[0081] In the first embodiment, the coil 342 is installed on the vacuum side, but it may be installed on the atmosphere side. Considering that measures to prevent discharge of the coil 342 are required when the coil 342 is installed on the vacuum side, the atmosphere 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 loss at high frequencies. This suppresses heat generation in the high-permeability magnetic material 341, enabling the heated portion 343 to be heated efficiently.

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

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

[0085] The high-permeability magnetic body 441 is a cylindrical member, and the coil 442 is wound around the surface on which the heated portion 443 is disposed, i.e., the outer peripheral surface, the front surface 444. The upstream end of the high-permeability magnetic body 441 is preferably located upstream of the upstream end of the coil 442 in order to suppress magnetic flux leakage from the coil 442. The downstream end of the high-permeability magnetic body 441 is preferably located downstream of the downstream end of the coil 442. In the second embodiment, the high-permeability magnetic body 441 does not have a recessed housing portion, but may have a recessed housing portion 445 as in the first embodiment. That is, a portion of the high-permeability magnetic body 441 may be located on a lateral side (the upstream side and / or downstream side in the second embodiment) perpendicular to the direction from the coil 442 to the heated portion 443 in a cross section perpendicular to the current-carrying direction of the coil 442. The coil 442 is disposed in the gas flow path. That is, the 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 102. The heated portion 443 may be a member fixed to the inner circumferential surface of the rotor 102 by plating or the like. The heated portion 443 is made of a magnetic metal material such as stainless steel. Note that when the rotor 102 is made of a magnetic metal material such as stainless steel, the heated portion 443 may be a part of the rotor 102.

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

[0088] In the vacuum pump 400 according to the second embodiment, when the rotor 102 rotates, the heated portion 443 connected to the rotor 102 or the heated portion 443 that is a part of the rotor 102 rotates. When a high-frequency alternating current flows through the stationary coil 442 in this state, the coil 442, the high-permeability magnetic material 441, and the heated portion 443 are electromagnetically coupled, generating eddy currents inside the heated portion 443. The heated portion 443 generates Joule heat and iron loss heat due to the eddy currents. This heats the heated portion 443, heating the rotor 102 connected to the heated portion 443 or the rotor 102 that has the heated portion 443. Therefore, the heating unit 440 can efficiently heat the rotor 102 using the coil 442 located on the fixed side. The high-permeability magnetic material 441 is a poor conductor of electricity and therefore does not generate Joule heat due to eddy currents. Furthermore, since coil 442 is disposed on the outer peripheral surface of high-permeability magnetic body 441, magnetic flux leakage from coil 442 is suppressed, as shown in Fig. 9. This makes it possible to suppress the generation of heat due to Joule heat or loss in the metal material (stator column 122 in this embodiment) located radially inside high-permeability magnetic body 441. Therefore, heating means 440 can efficiently heat portion to be heated 443.

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

[0090] Furthermore, the coil 442 is disposed in a high-vacuum gas flow path, whereby the coil 442 forms a magnetic path near the heated portion 443, thereby enabling efficient heating.

[0091] In the second embodiment, the coil 442 is installed on the vacuum side, but may be installed on the atmosphere side. Considering the need for measures to prevent discharge of the coil 442 when it is installed on the vacuum side, the atmosphere side is preferable, but the present invention is not limited to this.

[0092] The present invention is not limited to the above-described embodiments, and various modifications and combinations may be made by those skilled in the art within the technical spirit of the present invention. For example, the first and second embodiments may be combined.

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

[0094] The vacuum pump 300 may also have a structure consisting of only a turbomolecular pump without a thread groove pump portion. The thread groove pumps in the above-described embodiments are Holweck-type thread groove pumps with axial spiral grooves, but they may also be Sigbahn-type thread groove pumps with radial spiral grooves, or may have a configuration having both. [Explanation of symbols]

[0095] 102 Rotor 113 Rotor shaft 123 Fixed wing 131 Thread groove spacer (stator part) 300, 400 vacuum pump 310 Casing 320 Magnetic Bearings 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. A casing; a rotor shaft disposed within the casing; a rotor blade rotatable together with the rotor shaft; a vacuum pump that exhausts gas by rotation of the rotor, a heating means for heating a gas flow path in the vacuum pump; The heating means is A coil and a heated portion that is a magnetic body that is heated by electromagnetic induction caused by passing an alternating current through the coil; a high-permeability magnetic body covering the coil opposite to the front side on which the heated portion is disposed.

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

3. 2. The vacuum pump according to claim 1, wherein the heated portion is connected to the rotor or is a part of the rotor.

4. 2. A vacuum pump according to claim 1, further comprising a magnetic bearing for supporting said rotor shaft in a magnetically levitated manner.

5. 5. The vacuum pump according to claim 4, wherein the frequency of the current applied to the coil is equal to or a multiple of the control frequency of the magnetic bearing.

6. 2. The vacuum pump according to claim 1, wherein a portion of the high-permeability magnetic material is arranged on a lateral side perpendicular to a direction from the coil toward the heated portion in a cross section perpendicular to a current flow direction of the coil.

7. 2. The vacuum pump according to claim 1, wherein the coil is disposed within the gas flow path.

8. 2. The vacuum pump according to claim 1, wherein the high-permeability magnetic material is a soft magnetic ferrite containing manganese and zinc.

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