Vacuum pump, vacuum pump parts and manufacturing method thereof

Abstract

A vacuum pump and vacuum pump component, and a method for manufacturing the same, are provided that are capable of effectively heating a portion formed from a material with low heating efficiency in electromagnetic induction heating by electromagnetic induction heating. [Solution] A vacuum pump (300) that exhausts gas by rotation of the rotor (102) and that includes a casing (310), a rotor shaft (113) arranged within the casing (310), a rotor (102) that can rotate together with the rotor shaft (113), and a heating means (340) that heats by electromagnetic induction by passing an alternating current through a coil (342), and the heated part (350) heated by the heating means (340) has a magnetic metal plating layer (351).

Description

[Technical Field]

[0001] The present invention relates to a vacuum pump, a vacuum pump component, and a method for manufacturing the same. [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, components are heated by electromagnetic induction heating, so if the components to be heated are made of a material with low magnetic properties, it is difficult to heat them.

[0009] The present invention has been made to solve the above-mentioned problems, and aims to provide a vacuum pump, vacuum pump components, and a manufacturing method thereof that can effectively heat parts formed from materials with low heating efficiency in electromagnetic induction heating by electromagnetic induction heating. [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, a rotor blade that can rotate together with the rotor shaft, and a heating means that heats by electromagnetic induction by passing an alternating current through a coil, and exhausts gas by the rotation of the rotor blade, characterized in that the heated portion heated by the heating means has a magnetic metal plating layer. [Effects of the Invention]

[0012] In the vacuum pump described in (1) above, the portions formed of a material with low heating efficiency in electromagnetic induction heating are covered with a magnetic metal plating layer, thereby increasing the heating efficiency in electromagnetic induction heating.

[0013] (2) In the vacuum pump described in (1) above, the metal plating layer may include a first metal plating layer having magnetic properties formed by electroless plating, and a second metal plating layer having magnetic properties formed on the first metal plating layer by electrolytic plating. The first metal plating layer formed by electroless plating can uniformly plate complex shapes regardless of whether the object to be plated is magnetic or conductive, thereby improving corrosion resistance and plating adhesion. Then, the second metal plating layer is appropriately formed on the first metal plating layer as a base by electrolytic plating, which has a high metal purity but is difficult to control the film thickness. Therefore, the metal plating layer can improve the heating efficiency of electromagnetic induction heating.

[0014] (3) In the vacuum pump described in (1) above, the metal plating layer may have a columnar crystal structure extending in a direction away from the surface of the plated part coated with the metal plating layer, thereby making it easier for eddy currents to flow along the direction of extension of the crystal structure due to electromagnetic induction from a heating means disposed in a direction away from the surface of the plated part, thereby improving the heating efficiency of the metal plating layer by electromagnetic induction heating.

[0015] (4) In the vacuum pump according to any one of (1) to (3), the metal plating layer may be a plating layer containing nickel as a main component, which allows the metal plating layer to have high heating efficiency in electromagnetic induction heating and high corrosion resistance.

[0016] (5) A vacuum pump component according to the present invention is a vacuum pump component constituting part of a gas flow path of a vacuum pump, and includes a magnetic metal plating layer heatable by electromagnetic induction. The metal plating layer includes a first magnetic metal plating layer formed by electroless plating and a second magnetic metal plating layer formed on the first metal plating layer by electrolytic plating. This allows the vacuum pump component to form the first metal plating layer by electroless plating, which can uniformly plate complex shapes regardless of whether the target is magnetic or conductive. Then, the second metal plating layer can be appropriately formed on the first metal plating layer by electrolytic plating, which has a high metal purity but is difficult to control the film thickness. Therefore, the method for manufacturing a vacuum pump component allows for effective heating by electromagnetic induction heating of a portion formed of a material with low heating efficiency in electromagnetic induction heating.

[0017] (6) A method for manufacturing a vacuum pump component according to the present invention is a method for manufacturing a vacuum pump component that constitutes a part of a gas flow path of a vacuum pump, and is characterized by the steps of forming a first metal plating layer on a surface of a portion to be plated of the vacuum pump component by electroless plating, and forming a second metal plating layer, which is magnetic and heatable by electromagnetic induction, on the surface of the first metal plating layer by electrolytic plating. This method for manufacturing a vacuum pump component allows the first metal plating layer to be formed by electroless plating, which can uniformly plate even complex shapes regardless of whether the object is magnetic or conductive, and then the second metal plating layer to be appropriately formed on the first metal plating layer by electrolytic plating, which uses a metal material with high purity but whose thickness is difficult to control. This method for manufacturing a vacuum pump component allows for effective heating by electromagnetic induction heating of a portion formed of a material with low heating efficiency in electromagnetic induction heating.

[0018] (7) In the method for manufacturing a vacuum pump component described in (6) above, the plating solution used for electrolytic plating of the second metal plating layer may not contain a brightener. This allows the second metal plating layer to have a columnar crystal structure extending away from the surface of the plated part, facilitating the flow of eddy currents and improving the heating efficiency of electromagnetic induction heating.

[0019] (8) In the method for manufacturing a vacuum pump component according to (6) or (7), at least the second metal plating layer may be subjected to a baking treatment, which eliminates layer boundaries that hinder current flow in the formed second metal plating layer, thereby improving the heating efficiency of electromagnetic induction heating. [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. 2 is an enlarged cross-sectional view of the vicinity of a heating means and a heated portion of the vacuum pump according to the first embodiment. [Figure 7] FIG. [Figure 8] 1 is a photograph showing a cross section of a metal plating layer containing a brightener and formed by electrolytic plating using nickel as a main component. [Figure 9] 1 is a photograph showing a cross section of a metal plating layer containing a brightener and formed by electroplating with nickel as the main component, after baking treatment. [Figure 10] FIG. 2 is a schematic cross-sectional view of a metal plating layer containing nickel as a main component and not containing a brightener, formed by electrolytic plating. [Figure 11] Fig. 10 is a vertical cross-sectional view of a vacuum pump according to a second embodiment.Fig. 11 is a perspective view showing a heating means. [Figure 12] FIG. 10 is a perspective view showing a heating means of a vacuum pump according to a second embodiment. [Figure 13] FIG. 1 is a schematic diagram showing a test apparatus. [Figure 14] 1 is a graph showing the temperature of a test piece versus heating time in a plating evaluation test. [Figure 15] 1 is a graph showing the temperature of the coil versus heating time in a plating evaluation test. [Figure 16] 1 is a graph showing the temperature of a test piece not containing a gloss agent versus heating time in a baking treatment temperature evaluation test. [Figure 17] 1 is a graph showing the temperature of a test piece containing a gloss agent versus heating time in a baking treatment temperature evaluation test. [Figure 18] 1 is a graph showing the temperature of a test piece containing a gloss agent versus heating time in a baking treatment time evaluation test. [Figure 19] 1 is a graph showing the temperature of a test piece not containing a brightener versus heating time in a baking treatment time evaluation test. 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 stator column 122 that surrounds the electrical equipment, 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, heating means 340 that heats the gas flow path inside the vacuum pump 300, and a heated portion 350 that is fixed to the rotor blades 102 by plating.

[0061] The heating means 340 heats the heated portion 350 in a non-contact manner by electromagnetic induction caused by passing an alternating current through a coil. As shown in Figures 5 and 6, the heating means 340 has a cylindrical high-permeability magnetic body 341 that covers the outer peripheral surface of the stator column 122 (stator component) that surrounds the electrical equipment section, and a coil 342 that is arranged to wind around the outer peripheral surface of the high-permeability magnetic body 341.

[0062] The high-permeability magnetic body 341 is a cylindrical member, and the coil 342 is wound around the surface on which the heated portion 350 is disposed, i.e., the outer peripheral surface, the front surface 344. From the viewpoint of suppressing magnetic flux leakage from the coil 342, the upstream end of the high-permeability magnetic body 341 is preferably located upstream of the upstream end of the coil 342. Furthermore, the downstream end of the high-permeability magnetic body 341 is preferably located downstream of the downstream end of the coil 342. The high-permeability magnetic body 341 may have a recess that accommodates the coil 342. The coil 342 is disposed in the gas flow path. That is, the coil 342 is disposed under high vacuum in the gas flow path.

[0063] High-permeability magnetic body 341 covers the side of coil 342 opposite to front surface 344 on which heated portion 350 is disposed. 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.

[0064] 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.

[0065] The 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). The coil 342 may be formed by arranging multiple coils in parallel.

[0066] The heated portion 350 is, for example, a portion that is coated by plating on the inner circumferential surface (plated portion) of a substantially cylindrical portion of the rotor 102. The heated portion 350 is heated by electromagnetic induction by the heating means 340.

[0067] The heated portion 350 has a magnetic metal plating layer 351 formed on the rotor blade 102 by plating. The metal forming the metal plating layer 351 is nickel, which is a magnetic conductor and can be plated, but is not particularly limited as long as it is magnetic, conductive, and can be plated. The metal plating layer 351 may be formed by electroless plating using a chemical reaction, or by electrolytic plating using electrolysis.

[0068] Furthermore, metal plating layer 351 may be formed as a single layer, or may have multiple layers with different properties. For example, as shown in Fig. 7, metal plating layer 351 may have a first metal plating layer 352 coated by plating on the surface of rotor 102, and a second metal plating layer 353 coated by plating on the surface of first metal plating layer 352 and having properties different from those of first metal plating layer 352. The thickness of metal plating layer 351 (particularly second metal plating layer 353) is preferably a certain thickness, for example, 30 µm to 200 µm, more preferably 50 µm to 150 µm, in order to improve the heating efficiency of electromagnetic induction heating.

[0069] The first metal plating layer 352 is formed by electroless plating. Electroless plating can uniformly plate metal even on complex shapes, regardless of the magnetic or conductive properties of the part to be plated. Therefore, even if the part to be plated, i.e., the rotor blade 102, is made of an aluminum alloy or other material with low magnetic and conductive properties, the first metal plating layer 352 can be uniformly coated on the surface of the rotor blade 102.

[0070] The second metal plating layer 353 is formed by electrolytic plating on the surface of the first metal plating layer 352 formed by electroless plating. Electrolytic plating produces high-purity metals, but film thickness control is difficult. Furthermore, electrolytic plating cannot be performed on materials with low magnetic or electrical conductivity. The second metal plating layer 353 formed by electrolytic plating in this embodiment can be formed on a plated portion with low electrical conductivity by using the first metal plating layer 352 formed by electroless plating as a base.

[0071] The metal plating layer 351 may or may not contain a brightening agent that imparts a gloss to the surface. Examples of brightening agents include butynediol-based and saccharin-based additives.

[0072] The metal plating layer 351 may or may not contain a pitting prevention agent that prevents the formation of pits. Examples of the pitting prevention agent include coumarin-based and butynediol-based additives.

[0073] When the plating solution used for electroplating does not contain a brightener, the metal of the formed metal plating layer 351 (particularly, the second metal plating layer 353) forms a columnar crystal structure perpendicular to the surface of the part to be plated (the rotor 102 in this embodiment), as shown in Figure 10. In contrast, when the plating solution used for electroplating contains a brightener, the metal of the metal plating layer 351 (particularly, the second metal plating layer 353) forms a layered crystal structure parallel to the surface of the part to be plated, as shown in the photograph in Figure 8.

[0074] Metal plating layer 351 containing a brightener is likely to be formed in multiple layers, which makes it difficult for current to flow in the direction in which the layers overlap, and this may reduce the heating efficiency of electromagnetic induction heating.

[0075] The metal plating layer 351 may be subjected to a baking treatment. The baking treatment of the metal plating layer 351 formed of nickel is performed, for example, by heating at 150°C to 300°C for 30 to 180 minutes. As described above, the metal plating layer 351 containing a brightener or pit prevention agent tends to form a layered crystalline structure parallel to the surface of the plated portion. However, by performing the baking treatment, it is thought that the separated layers tend to bond together, as shown in the photograph in FIG. 9. Therefore, it is thought that the baking treatment makes it easier for eddy currents to flow in the metal plating layer 351 containing the brightener, thereby improving the heating efficiency by electromagnetic induction heating.

[0076] Next, the operation of the vacuum pump 300 according to the first embodiment will be described.

[0077] In the vacuum pump 300 according to the first embodiment, when the rotor 102 rotates, the heated portion 350, which is coated on the rotor 102 by plating, rotates. When a high-frequency alternating current flows through the stationary coil 342 in this state, the coil 342, the high-permeability magnetic material 341, and the heated portion 350 are electromagnetically coupled, generating eddy currents inside the heated portion 350. The applied alternating current has a frequency of, for example, 20 kHz to 60 kHz, but may have a different frequency. The voltage is, for example, but not limited to, 100 V to 300 V. The heated portion 350 has a certain thickness (for example, about 100 μm), which generates Joule heat due to eddy currents and iron loss heat. Therefore, the heated portion 350 reaches a high temperature, which heats the rotor 102 having the heated portion 350. Therefore, the heating unit 340 can efficiently heat the rotor 102 using the coil 342 disposed on the fixed side. Note that the high-permeability magnetic body 341 does not easily conduct electricity, and therefore does not generate Joule heat due to eddy current. Furthermore, since the coil 342 is disposed on the outer peripheral surface of the high-permeability magnetic body 341, magnetic flux leakage from the coil 342 is suppressed, as shown in FIG. 6. This makes it possible to suppress the generation of heat due to Joule heat or loss in the metal material (the stator column 122 in this embodiment) located radially inside the high-permeability magnetic body 341. Therefore, the heating means 340 can efficiently heat the heated portion 350.

[0078] Furthermore, the heated portion 350 is coated by plating the rotor 102. This allows the vacuum pump 300 to effectively heat the rotor 102, which is difficult to heat from the outside.

[0079] 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, a rotor 102 rotatable together with the rotor shaft 113, and a heating means 340 that heats by electromagnetic induction by passing an alternating current through a coil 342, and exhausts gas by rotation of the rotor 102, and the heated portion 350 heated by the heating means 340 has a magnetic metal plating layer 351. As a result, the vacuum pump 300 can improve the heating efficiency in electromagnetic induction heating because portions formed of a material with low heating efficiency in electromagnetic induction heating are covered with the magnetic metal plating layer 351.

[0080] Alternatively, the metal plating layer 351 may include a first metal plating layer 352 having magnetic properties formed by electroless plating, and a second metal plating layer 353 having magnetic properties formed on the first metal plating layer 352 by electrolytic plating. The first metal plating layer 352 is formed by electroless plating, which can uniformly plate complex shapes regardless of whether the object to be plated is magnetic or conductive, thereby improving corrosion resistance and ease of plating adhesion. Then, the second metal plating layer 353 is appropriately formed using the first metal plating layer 352 as a base by electrolytic plating, which uses a highly pure metal material but is difficult to control the film thickness of. Therefore, the metal plating layer 351 can improve the heating efficiency of electromagnetic induction heating.

[0081] Furthermore, the metal plating layer 351 may have a columnar crystal structure extending in a direction away from the surface of the plated portion coated with the metal plating layer 351. This allows the vacuum pump 300 to easily generate eddy currents along the direction in which the crystal structure extends due to electromagnetic induction from the heating means 340 arranged in a direction away from the surface of the plated portion, thereby improving the heating efficiency of the metal plating layer 351 by electromagnetic induction heating.

[0082] Furthermore, the metal plating layer 351 may be a plating layer containing nickel as a main component, which allows the metal plating layer 351 to have high heating efficiency in electromagnetic induction heating and high corrosion resistance.

[0083] Furthermore, the vacuum pump component (e.g., impeller 102) in this embodiment is a vacuum pump component that constitutes part of the gas flow path of vacuum pump 300 and includes a magnetic metal plating layer 351 that can be heated by electromagnetic induction. Metal plating layer 351 includes a magnetic first metal plating layer 352 formed by electroless plating and a magnetic second metal plating layer 353 formed on first metal plating layer 352 by electrolytic plating. This allows the vacuum pump component to first form first metal plating layer 352 by electroless plating, which can uniformly plate complex shapes regardless of whether the target is magnetic or conductive. Then, using first metal plating layer 352 as a base, the second metal plating layer 353 can be appropriately formed by electrolytic plating, which uses a high-purity metal material but is difficult to control the film thickness. Therefore, the method for manufacturing a vacuum pump component allows for effective heating by electromagnetic induction heating of a portion formed of a material with low heating efficiency in electromagnetic induction heating.

[0084] Furthermore, the method for manufacturing a vacuum pump component according to this embodiment is a method for manufacturing a vacuum pump component that constitutes a part of the gas flow path of a vacuum pump 300, and includes the steps of forming a first metal plating layer 352 by electroless plating on the surface of a portion to be plated of the vacuum pump component, and forming a second metal plating layer 353, which is magnetic and heatable by electromagnetic induction, on the surface of the first metal plating layer 352 by electrolytic plating. This method for manufacturing a vacuum pump component forms the first metal plating layer 352 by electroless plating, which can uniformly plate even complex shapes regardless of whether the portion to be plated is magnetic or conductive. Then, using the first metal plating layer 352 as a base, the second metal plating layer 353 can be appropriately formed by electrolytic plating, which uses a metal material with high purity but whose thickness is difficult to control. This method for manufacturing a vacuum pump component therefore enables effective heating of a portion made of a material with low heating efficiency in electromagnetic induction heating by electromagnetic induction heating.

[0085] Furthermore, in the method for manufacturing a vacuum pump component, the plating solution used in the electrolytic plating of second metal plating layer 353 does not need to contain a brightener. This allows second metal plating layer 353 to have a columnar crystal structure extending away from the surface of the plated portion, which makes it easier for eddy currents to flow and improves the heating efficiency of electromagnetic induction heating.

[0086] Furthermore, in the method for manufacturing a vacuum pump component, a baking treatment may be performed on at least second metal plating layer 353. This allows second metal plating layer 353 to eliminate layer boundaries that hinder the flow of eddy currents, thereby improving the heating efficiency of electromagnetic induction heating.

[0087] Second Embodiment Next, a vacuum pump 400 according to a second embodiment will be described. As shown in Figures 11 and 12, the second embodiment differs from the first embodiment in that a heating means 440 for heating a gas flow path in the vacuum pump 400 and a heated portion 450 are arranged in a casing 410 that forms the outer shell of the vacuum pump 400.

[0088] The casing 410 is formed by multiple stator components. Specifically, the casing 410 includes an upper case 411, a lower case 412, and a base 129. Furthermore, the casing 410 includes a heater spacer 430 and a thread groove spacer 131 inside the lower case 412. The casing 410 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 440 is the thread groove spacer 131, but this is not limited to the thread groove spacer 131 and may be another stator component. Furthermore, the stator vanes 123 may also be a stator component heated by the heating means 440.

[0089] An intake port 101 is arranged on the upstream side (intake side) of the upper case 411, and an exhaust port 133 is arranged in a heater spacer 430 on the upstream side of the base part 129.

[0090] The lower case 412 is formed in a cylindrical shape and is provided at a distance from the heater spacer 430 so as to cover the outer peripheral surface of the heater spacer 430 .

[0091] The heater spacer 430 is disposed to heat the thread groove spacer 131. The heater spacer 430 is formed in a substantially cylindrical shape and is disposed inside the lower case 412. The heater spacer 430 is disposed between the fixed blade spacer 125 and the base portion 129 in the axial direction.

[0092] The heater spacer 430 is substantially cylindrical, and has a ring-shaped first recess 431 for arranging the heating means 440 on the surface facing the upstream side (intake side) that contacts the thread groove spacer 131.

[0093] Heating means 440 has high-permeability magnetic body 441 arranged in first recess 431 , and coil 442 arranged adjacent to high-permeability magnetic body 441 .

[0094] High-permeability magnetic material 441 is a ring-shaped member placed in first recess 431, and has a circumferentially extending recessed accommodation portion 445 on front surface 444, which is the surface on the side where heated portion 450 is placed. Accommodation portion 445 is capable of accommodating coil 442. Accommodation portion 445 includes a first wall surface 446 located on the inner circumferential side of coil 442 to be accommodated, a second wall surface 447 located on the outer circumferential side of coil 442, and an accommodation surface 448 facing heated portion 450 between first wall surface 446 and second wall surface 447. Accommodation portion 445 has holes or grooves formed on its outer surface for introducing the metal wire of coil 442 from the outside.

[0095] The heated portion 450 is formed by plating so as to cover a portion of the thread groove spacer 131 that forms the gas flow path. The heated portion 450 is arranged so as to cover the accommodation portion 445 of the high permeability magnetic material 441. The heated portion 450 is formed by plating on the downstream (intake side) surface of the thread groove spacer 131 that contacts the heater spacer 430. The heated portion 450 is formed to have a substantially constant thickness corresponding to the shape of the accommodation portion 445 of the high permeability magnetic material 441. The heated portion 450 is spaced a small distance from the front surface 444 of the accommodation portion 445. The heated portion 450 has a metal plating layer 351, similar to the first embodiment.

[0096] Next, the operation of the vacuum pump 400 according to the second embodiment will be described.

[0097] When a high-frequency alternating current flows through the coil 442, the coil 442, the high-permeability magnetic material 441, and the heated portion 450 are electromagnetically coupled, generating eddy currents inside the heated portion 450. 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. Since the heated portion 450 has an inherent electrical resistance, Joule heat is generated by the eddy current. The heated portion 450 also generates iron loss heat. As a result, the heated portion 450 becomes hot, and the thread groove spacer 131 can be heated.

[0098] In the second embodiment, the coil 342 is installed on the vacuum side, but it may also be installed on the atmosphere side. Considering the need for measures to prevent discharge of the coil 342 when it is installed on the vacuum side, the atmosphere side is preferable, but is not limited to this.

[0099] <Plating evaluation test> Several test specimens were prepared and tested to evaluate the heating efficiency of electromagnetic induction heating. Test specimen 1 was prepared by forming a first metal plating layer 352 of nickel with a thickness of approximately 8 μm as a base on one surface of an aluminum (A5083) plate with a side length of 200 mm and a thickness of 10 mm by electroless plating, and then forming a second metal plating layer 353 of nickel with a thickness of approximately 100 μm and containing a brightener on the surface of first metal plating layer 352 by electrolytic plating.

[0100] Test specimen 2 was prepared by subjecting a structure similar to that of test specimen 1 to a baking treatment at 300°C for 2 hours.

[0101] A first metal plating layer 352 of nickel having a thickness of approximately 8 μm was formed as a base on one surface of an aluminum alloy (A5083) plate material having a side length of 200 mm and a thickness of 10 mm by electroless plating, and a second metal plating layer 353 of nickel having a thickness of approximately 100 μm and not containing a brightener was formed on the surface of the first metal plating layer 352 by electrolytic plating to produce test piece 3.

[0102] A nickel metal plating layer 351 having a thickness of approximately 100 μm was formed by electroless plating on one surface of an aluminum alloy (A5083) plate material having a side length of 200 mm and a thickness of 10 mm, and the plate was then baked at 300°C for two hours to produce test piece 4.

[0103] A plate made of aluminum alloy (A5083) with a side length of 200 mm and a thickness of 10 mm was used as the reference specimen 5. The aluminum alloy (A5083) is an example of a metal material with low magnetic properties.

[0104] A plate made of stainless steel (SUS430) with a side length of 200 mm and a thickness of 10 mm was used as the reference specimen 6. Stainless steel (SUS430) is an example of a highly magnetic metal material.

[0105] The test was performed using a test device 500 shown in Fig. 13. The test device 500 had a 100V AC power supply 501, a first ammeter 502, a transformer 503, a second ammeter 504, an IH power supply 505, an oscilloscope 506, a heating means 507, a first thermometer 508, and a second thermometer 509.

[0106] The IH power supply 505 includes an output board 510 that outputs a high-frequency current for performing electromagnetic induction heating, and a control board 511 that controls the IH power supply 505 .

[0107] The heating means 507 was a part for heating the test specimen, and had a coil 513 connected to an output board 510 of the IH power supply 505, and a ring-shaped, high-permeability magnetic body 514 made of ferrite with a groove formed on the upper surface to accommodate the coil 513.

[0108] The transformer 503 was disposed between the AC power supply 501 and the output board 510. The first ammeter 502 was disposed between the AC power supply 501 and the transformer 503. The oscilloscope 506 detected the voltage and current of the high-frequency current output from the output board 510.

[0109] The first thermometer 508 detected the temperature of the test piece heated by the heating means 507. The second thermometer 509 detected the temperature of the coil.

[0110] The total input power A input to the evaluation device was calculated from the current value detected by the first ammeter 502 and the voltage value of the AC power supply 501. The output board input power B input to the output board 510 was calculated from the current value detected by the second ammeter 504 and the voltage value detectable from the transformer 503. The coil power E (active power C - coil power consumption D) was calculated by subtracting the coil power consumption D calculated from the resistance value of the coil 513 and the current value detected by the oscilloscope 506 from the active power C calculated from the current and voltage values ​​detected by the oscilloscope 506. A first efficiency F (E / A × 100 [%]) indicating the ratio of the coil power E to the total input power A and a second efficiency G (E / B × 100 [%]) indicating the ratio of the coil power E to the output board input power B were then calculated. The first efficiency F and second efficiency G calculated from the test results of each test specimen are shown in Table 1. In Table 1, the arrows in the columns for coil power E, first efficiency F, and second efficiency G indicate changes in values ​​during the test.

[0111] [Table 1]

[0112] FIG. 14 is a graph showing the temperature of the test piece versus the heating time in the plating evaluation test, and FIG. 15 is a graph showing the temperature of the coil versus the heating time in the plating evaluation test.

[0113] 14 and 15, it was confirmed that in specimens 1 to 4, the temperature of the plated portion could be raised to a higher temperature than in reference specimen 5, which was an aluminum alloy plate.

[0114] Furthermore, by comparing the results of specimen 1 and specimen 2, it was confirmed that the baking treatment allowed the temperature of the specimen to be raised to a high temperature in a short period of time. Furthermore, Table 1 shows that the first efficiency F and second efficiency G of specimen 1, which was not baked, decreased significantly over time, whereas the first efficiency F and second efficiency G of specimen 2, which was baked, did not change significantly over time. This confirms that the portion to be plated can be stably heated by baking the metal plating layer 351.

[0115] Furthermore, it was confirmed that specimen 2, which had undergone a baking treatment on the second metal plating layer 353 containing a brightener formed by electroplating, was able to heat the plated area to a higher temperature than reference specimen 6, which was a stainless steel plate.

[0116] Furthermore, it was confirmed that specimen 3, in which the second metal plating layer 353 formed by electroplating and not containing a brightener was not subjected to a baking treatment, was able to heat the plated portion to a high temperature, despite not being subjected to a baking treatment.

[0117] Furthermore, by comparing the results of test specimen 2 and test specimen 4, it was confirmed that test specimen 2, in which a baking treatment was performed on the second metal plating layer 353 formed by electrolytic plating, was able to heat the plated area to a higher temperature in a shorter time than test specimen 4, in which a baking treatment was performed on the metal plating layer 351 formed by electroless plating.

[0118] Furthermore, Table 1 confirms that specimen 3, in which the second metal plating layer 353 formed by electroplating and not containing a brightener was not subjected to a baking treatment, had a higher first efficiency F and second efficiency G than specimen 1, in which the second metal plating layer 353 formed by electroplating and containing a brightener was not subjected to a baking treatment, and specimen 4, in which the metal plating layer 351 formed by electroless plating was subjected to a baking treatment.

[0119] <Baking treatment temperature evaluation test> Test specimens 7 and 8, which will be described later, were prepared and tested by varying the baking temperature.

[0120] Test specimen 7 was prepared by forming a first metal plating layer 352 of nickel approximately 8 μm thick as a base on one surface of a rectangular aluminum (A5083) plate with sides 67 mm and 50 mm long and a thickness of 0.5 mm by electroless plating, and then forming a second metal plating layer 353 of nickel approximately 100 μm thick and containing no brightener on the surface of first metal plating layer 352 by electrolytic plating.

[0121] Specimen 8 was prepared by forming a first metal plating layer 352 of nickel approximately 8 μm thick as a base on one surface of a rectangular aluminum (A5083) plate with sides 67 mm and 50 mm long and a thickness of 0.5 mm by electroless plating, and then forming a second metal plating layer 353 of nickel approximately 100 μm thick containing a brightener on the surface of first metal plating layer 352 by electrolytic plating.

[0122] Specimen 7 was baked at 135°C for 2 hours, then at 150°C for 2 hours, then at 175°C for 2 hours, then at 200°C for 2 hours, then at 225°C for 2 hours, then at 250°C for 2 hours, and then at 300°C for 2 hours. After baking at each temperature condition, a test was performed using the above-mentioned test apparatus 500. The results are shown in FIG. 16.

[0123] Test specimen 8 was baked at 135°C for 2 hours, then at 150°C for 2 hours, then at 175°C for 2 hours, then at 200°C for 2 hours, then at 225°C for 2 hours, and then at 250°C for 2 hours. After baking at each temperature condition, a test was performed using the above-mentioned test apparatus 500. The results are shown in FIG.

[0124] As a result, it was confirmed that for both specimen 7 and specimen 8, the higher the baking temperature, the more quickly the temperature of the plated portion can be raised.

[0125] It was also confirmed that specimen 7, which does not contain a glossing agent, changed so that the temperature of the specimen could be raised in a shorter time at a lower baking temperature than specimen 8, which contains a glossing agent.

[0126] <Baking processing time evaluation test> The aforementioned specimen 8 (a specimen having a second metal plating layer 353 of nickel containing a brightener formed by electrolytic plating), specimen 9, which had a structure similar to specimen 8 but was baked for two hours at 135°C and two hours at 150°C for a total of four hours, and specimen 10, which had a structure similar to specimen 8 but was baked for 10 hours at 150°C, were fabricated and tested using the aforementioned testing apparatus 500. The results are shown in Fig. 18.

[0127] As a result, it was confirmed that the temperature of the plated area of ​​specimens 9 and 10 after baking could be raised in a shorter time than that of specimen 8, which had not been baked. However, no significant difference was confirmed between specimens 9 and 10, which had been baked for different times.

[0128] Next, the aforementioned specimen 7 (a specimen having a second metal plating layer 353 of nickel without a brightener formed by electrolytic plating) and specimen 11, which had the same structure as specimen 7 but was baked at 150°C for 10 hours, were prepared and tested using the aforementioned testing device 500. The results are shown in Fig. 19.

[0129] As a result, it was confirmed that the baking-treated specimen 11 was able to heat the plated portion to a higher temperature in a shorter time than the specimen 7 which had not been baked.

[0130] 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. [Explanation of symbols]

[0131] 102 Rotor 113 Rotor shaft 123 Fixed wing 131 Thread groove spacer 300, 400 vacuum pump 310 Casing 320 Magnetic Bearings 340, 440 Heating means 342, 442 coils 350, 450 Heated part 351 Metal plating layer 352 First metal plating layer 353 Second metal plating layer

Claims

1. A casing; a rotor shaft disposed within the casing; a rotor blade rotatable together with the rotor shaft; a heating means for heating by electromagnetic induction by passing an alternating current through a coil; a vacuum pump that exhausts gas by rotation of the rotor, A vacuum pump characterized in that the heated portion heated by the heating means has a magnetic metal plating layer.

2. 2. The vacuum pump according to claim 1, wherein the metal plating layer comprises a first metal plating layer having magnetic properties formed by electroless plating, and a second metal plating layer having magnetic properties formed on the first metal plating layer by electrolytic plating.

3. 3. The vacuum pump according to claim 1, wherein the metal plating layer has a columnar crystal structure extending in a direction away from the surface of the plated portion coated with the metal plating layer.

4. 4. The vacuum pump according to claim 3, wherein the metal plating layer is a plating layer containing nickel as a main component.

5. A vacuum pump component that constitutes a part of a gas flow path of a vacuum pump, a metal plating layer that is magnetic and can be heated by electromagnetic induction; The metal plating layer comprises a first metal plating layer having magnetic properties formed by electroless plating, and a second metal plating layer having magnetic properties formed on the first metal plating layer by electrolytic plating.

6. A method for manufacturing a vacuum pump component that constitutes a part of a gas flow path of the vacuum pump, comprising: forming a first metal plating layer on a surface of a portion to be plated of the vacuum pump component by electroless plating; and forming a second metal plating layer, which is magnetic and can be heated by electromagnetic induction, on the surface of the first metal plating layer by electrolytic plating.

7. 7. The method for manufacturing a vacuum pump part according to claim 6, wherein the plating solution used for electrolytic plating of the second metal plating layer does not contain a brightener.

8. 8. The method for manufacturing a vacuum pump part according to claim 6, further comprising the step of subjecting at least the second metal plating layer to a baking treatment.

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