Vacuum pump, rotor of vacuum pump, and upstream rotation vane of vacuum pump

Abstract

To suppress inflow of heat from a downstream rotation vane to an upstream rotation vane.SOLUTION: A vacuum pump 100A includes: a first rotation vane 20A; a second rotation vane 30A provided on a downstream side of the first rotation vane 20A; a rotation shaft 113 that transmits rotation to the first rotation vane 20A and the second rotation vane 30A; a drive mechanism 121 of the rotation shaft 113; and a casing 127 that includes the rotation shaft 113, the first rotation vane 20A, and the second rotation vane 30A therein. A gap n1 is provided between the facing surfaces of the first rotation vane 20A and the second rotation vane 30A. At least a part of the facing surface of the first rotation vane 20A is configured to have lower emissivity compared to the surface other than the above facing surface.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a vacuum pump, a rotor of the vacuum pump, and an upstream rotor of the vacuum pump. [Background technology]

[0002] To perform the vacuum evacuation, a vacuum pump that utilizes the high speed rotation of a rotor is used. In recent years, vacuum pumps have been constructed with rotors separated into upstream and downstream rotors, with each rotor being made of a different material. In a vacuum pump, the downstream rotor becomes hotter than the upstream rotor because the downstream side is under high pressure. In addition, the motor that drives the pump is generally placed downstream of the rotor, and in that case, the downstream rotor becomes even hotter due to heat dissipation from the motor. For this reason, a highly heat-resistant material that can withstand high temperatures is used for the downstream rotor, and a material with a lower heat resistance than the downstream rotor is used for the upstream rotor, thereby reducing material costs. In addition, the term "heat resistance" as used herein refers to the high-temperature strength of a material, and when "heat resistance" is high, it means that physical properties such as strength are less likely to deteriorate at higher temperatures. The same applies hereinafter throughout the entire description of this specification.

[0003] In addition, the gas exhausted during evacuation may contain solidified components depending on the object being evacuated. Since these solidified components sublimate and solidify under high pressure or low temperature, a high temperature state exceeding the sublimation temperature of the solidified components may be required in the area passing through the downstream rotor to prevent adhesion or deposition on the downstream rotor.

[0004] For this reason, a clear temperature difference was required, so that the upstream rotor was low temperature and the downstream rotor was high temperature. In order to meet such demands, conventional vacuum pumps have had a thermal insulating material inserted between the upstream and downstream rotors to suppress heat flow from the downstream rotor to the upstream rotor (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2022-31036 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the conventional vacuum pump described above was unable to suppress the effect of radiant heat from the downstream rotor to the upstream rotor, and there was room for improvement in maintaining the temperature difference between the upstream rotor and the downstream rotor.

[0007] An object of the present invention is to suppress the flow of heat from the downstream rotor to the upstream rotor. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides A first rotor; A second rotor disposed downstream of the first rotor; a rotating shaft that transmits rotation to the first rotor and the second rotor; A drive mechanism for the rotating shaft; a casing containing the rotating shaft, the first rotor, and the second rotor; A vacuum pump having The present invention is characterized in that a gap is provided between the opposing surface portions of the first rotor and the second rotor, and at least a portion of the opposing surface portion of the first rotor has a lower emissivity than the surface portions other than the opposing surface portion.

[0009] In order to solve the above problems, the present invention provides a method for producing a liquid crystal display comprising: A first rotor; A second rotor disposed downstream of the first rotor; a rotating shaft that transmits rotation to the first rotor and the second rotor; A rotating body of a vacuum pump having The present invention is characterized in that a gap is provided between the opposing surface portions of the first rotor and the second rotor, and at least a portion of the opposing surface portion of the first rotor has a lower emissivity than the surface portions other than the opposing surface portion.

[0010] In order to solve the above problems, the present invention provides a method for producing a liquid crystal display comprising: An upstream rotor of a vacuum pump in which rotors are provided on the upstream and downstream sides of a common rotor shaft, The present invention is characterized in that at least a portion of an inner circumferential surface of the upstream rotor, which is radially inward and spaced from the rotor shaft, has a lower emissivity than a surface portion other than the inner circumferential surface. Effect of the Invention

[0011] In the vacuum pump of the present invention, at least a part of the surface of the first rotor that faces the second rotor with a gap therebetween has a lower emissivity than the other surface parts. This makes it possible to suppress the incidence of radiant heat from the surface of the second rotor that is hotter than the first rotor, and to suppress the temperature rise of the first rotor due to the inflow of heat from the second rotor.

[0012] Furthermore, if the first rotor is configured to be at a lower temperature than the second rotor when the vacuum pump is operating, this, combined with the effect of suppressing heat penetration from the second rotor by lowering the emissivity of a portion of the surface of the second rotor, makes it possible to more effectively maintain the first rotor at a lower temperature than the second rotor.

[0013] Furthermore, if the vacuum pump is provided with a heating means for the second rotor, when the gas used for evacuation contains solidified components, it is possible to suppress sublimation of the solidified components and suppress adhesion to the rotor and deposition inside the pump. In particular, since the configuration is capable of suppressing heat penetration from the second rotor to the first rotor, it is possible to heat the second rotor to a temperature at which sublimation of the solidified components can be more effectively suppressed.

[0014] Furthermore, when the vacuum pump is equipped with a cooling means for the first rotor, in addition to the effect of suppressing heat intrusion from the second rotor by reducing the emissivity of a portion of the surface of the second rotor, it is possible to suppress the temperature rise of the first rotor even when rotating at higher speeds or when the second rotor is heated.

[0015] Furthermore, when the second material forming the second rotor of the vacuum pump is a material having higher heat resistance than the first material forming the first rotor, it is possible to reduce the amount of expensive, highly heat-resistant material used by concentrating its use on the second rotor, thereby reducing material costs.

[0016] Furthermore, when the vacuum pump is configured to form a turbomolecular pump mechanism using multiple stages of rotating blade cascades and stationary blade cascades, it is possible to perform continuous evacuation with little pulsation.

[0017] Furthermore, when the vacuum pump has a Holweck type drag pump mechanism formed by a rotating cylindrical portion and a stationary cylindrical portion, the gas can be compressed to a higher pressure downstream of the Holweck type drag pump mechanism, making it possible to achieve a higher degree of vacuum.

[0018] Furthermore, when the vacuum pump has a Sigburn drag pump mechanism formed of a rotating disk portion and a stationary disk portion, the gas can be compressed to a higher pressure downstream of the Sigburn drag pump mechanism, making it possible to achieve a higher degree of vacuum.

[0019] Furthermore, in the rotor of the vacuum pump of the present invention, a gap is provided between the mutually facing surface portions of the upstream first rotor and the downstream second rotor, and at least a part of the facing surface portion of the first rotor has a lower emissivity than the surface portion other than the facing surface portion. Therefore, when this rotor is applied to a vacuum pump, it is possible to suppress the incidence of radiant heat from the surface portion of the second rotor, which has a higher temperature than the first rotor, and to suppress the temperature rise of the first rotor due to the inflow of heat from the second rotor.

[0020] Furthermore, when the vacuum pump rotor of the present invention is applied to the upstream rotor in a vacuum pump in which rotors are arranged on the upstream and downstream sides of a common rotor shaft, the emissivity is reduced for at least a part of the inner circumferential surface that is radially inward and away from the rotor shaft, thereby making it possible to suppress the inflow of radiant heat from the downstream rotor and suppress the temperature rise of the upstream rotor. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a vertical cross-sectional view of a vacuum pump having a basic structure. [Diagram 2] FIG. 2 is a circuit diagram of an amplifier circuit. [Diagram 3] 6 is a time chart showing control when a current command value is larger than a detection value. [Figure 4] 6 is a time chart showing control when a current command value is smaller than a detection value. [Diagram 5] 1 is a vertical sectional view of a vacuum pump according to a first embodiment. FIG. [Figure 6] FIG. 6 is an enlarged partial cross-sectional view of a part of FIG. 5. [Figure 7] FIG. 11 is a vertical sectional view of a vacuum pump according to a second embodiment. [Figure 8] FIG. 8 is an enlarged partial cross-sectional view of a part of FIG. [Figure 9] FIG. 11 is a vertical sectional view of a vacuum pump according to a third embodiment. [Figure 10] FIG. 11 is a vertical sectional view of a vacuum pump according to a fourth embodiment. [Figure 11] FIG. 11 is a vertical sectional view of a vacuum pump according to a fifth embodiment. [Figure 12] FIG. 13 is a vertical sectional view of a vacuum pump according to a sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] [Basic structure of a vacuum pump] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the dimensions and ratios of each part in the drawings may be exaggerated for convenience of explanation and may differ from the actual dimensions or ratios. Furthermore, in this specification and the drawings, components having substantially the same functional configurations are given the same reference numerals to avoid duplicated explanations. Also, the same reference numerals may be used in common among multiple embodiments. A vacuum pump having a basic structure will be described. The example shown here is a turbomolecular pump 100 that exhausts gas by using rotor blades rotating at high speed to flick off gas molecules. There are no particular limitations on the object from which gas is exhausted, but the following description will be given assuming that the turbomolecular pump 100 is used to suck in and exhaust gas from a chamber of a semiconductor manufacturing device or the like, as an example.

[0023] 1 shows a vertical cross-sectional view of a turbomolecular pump 100. As shown in the figure, the turbomolecular pump 100 has an intake port 101 formed at the upper end of an outer cylinder 127 serving as a cylindrical casing. Then, provided inside outer cylinder 127 is rotor 103 having multiple rotating blade portions 102a, 102b, 102c..., which are turbine blades for sucking in and exhausting gas, formed radially and in multiple stages around its periphery. In the following description, when there is no need to particularly distinguish between multiple rotating blade portions 102a, 102b, 102c..., they may be referred to as "rotating blade portion 102." A rotor shaft 113 is attached to the center of the rotating body 103 as a rotating shaft, and this rotor shaft 113 is supported in the air and its position is controlled by, for example, a five-axis controlled magnetic bearing. The rotating body 103 is generally made of a 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, and four upper radial sensors 107 are provided adjacent to the upper radial electromagnets 104 and corresponding to each of the upper radial electromagnets 104. The upper radial sensor 107 is, for example, an inductance sensor or an eddy current sensor having a conductive winding, and detects the position of the rotor shaft 113 based on a change in inductance of the conductive winding that changes according to the position of the rotor shaft 113. The upper radial sensor 107 is configured to detect the radial displacement of the rotor shaft 113, i.e., the rotating body 103 fixed thereto, and send the detected 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] This 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 electromagnet 104. Such adjustment is performed independently in the X-axis direction and the Y-axis direction. In addition, a lower radial electromagnet 105 and a lower radial sensor 108 are arranged in the same manner as the upper radial electromagnet 104 and the upper radial sensor 107, and adjust the lower radial position of the rotor shaft 113 in the same manner as the upper radial position.

[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 high magnetic permeability 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, for example, a compensation circuit having a PID adjustment function generates an excitation control command signal for each of the axial electromagnets 106a and 106b based on an axial position signal detected by the axial sensor 109, and the amplifier circuit 150 controls the excitation of the axial electromagnets 106a and 106b based on these excitation control command signals, so that the axial electromagnet 106a attracts the metal disk 111 upward by magnetic force and the axial electromagnet 106b attracts the metal disk 111 downward, thereby adjusting the axial position of the rotor shaft 113.

[0029] In this way, the control device 200 appropriately adjusts the magnetic force that the axial electromagnets 106a, 106b exert on the metal disk 111, magnetically levitating the rotor shaft 113 in the axial direction and holding it in a non-contact manner in space. The amplifier circuit 150 that controls the excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106a, 106b will be described later.

[0030] On the other hand, motor 121 as a drive mechanism 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. Also, motor 121 incorporates a rotation speed sensor such as a Hall element, resolver, or encoder (not shown), and the rotation speed of rotor shaft 113 is detected by a detection signal from this rotation speed sensor.

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

[0032] A plurality of stationary blade portions 123a, 123b, 123c... are disposed with a small gap between each of the rotating blade portions 102a, 102b, 102c.... The rotating blade portions 102a, 102b, 102c... are formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transport exhaust gas molecules downward by collision. In the following description, when there is no need to particularly distinguish between the multiple stationary blade portions 123a, 123b, 123c, etc., they may be referred to as "stationary blade portion 123." Each stationary blade portion 123 is made of a metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components.

[0033] Similarly, the stationary blade portions 123 are formed at an inclination at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged alternately with the stages of the rotating blade portions 102 toward the inside of the outer cylinder 127. The outer peripheral end of the stationary blade portions 123 is supported in a state where it is inserted between a plurality of stacked spacers 125a, 125b, 125c, etc. In the following description, when there is no need to particularly distinguish between the multiple spacers 125a, 125b, 125c, etc., they may be referred to as "spacers 125."

[0034] The spacer 125 is a ring-shaped member and is made of metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components. An outer cylinder 127 is fixed to the outer periphery of the spacer 125 with a small gap therebetween. 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 serving as a stationary cylindrical portion is disposed between the lower portion of the spacer 125 and the base portion 129. The threaded spacer 131 is a cylindrical member made of metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals, and has a plurality of helical thread grooves 131a engraved on its inner peripheral surface. The helical direction of the thread groove 131a is the direction in which the molecules of the exhaust gas are transported toward the exhaust port 133 when the molecules move in the rotation direction of the rotor 103. A rotating cylinder portion 102d hangs down from the lowest portion of the rotor 103, following the multiple rotating blade portions 102. The outer peripheral surface of this rotating cylinder portion 102d is cylindrical and protrudes toward the inner peripheral surface of the threaded spacer 131, and is adjacent to the inner peripheral surface of the threaded spacer 131 with a specified gap between them. The exhaust gas transferred to the thread groove 131a by the rotating blade portion 102 and the stationary blade portion 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 constitutes the base of the turbomolecular pump 100, and is generally made of metal such as iron, aluminum, stainless steel, etc. The base portion 129 physically holds the turbomolecular pump 100 and also functions as a heat conduction path, so it is desirable to use a metal that has rigidity and high thermal conductivity, such as iron, aluminum, or copper.

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

[0038] The spacers 125 are joined to each other at their outer peripheries and transmit to the outside heat received by the stationary blade portion 123 from the rotating blade portion 102 and frictional heat generated when exhaust gas comes into contact with the stationary blade portion 123.

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

[0040] Depending on the application of the turbomolecular pump 100, in order 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., the electrical equipment section may be covered all around with a stator column 122, and the inside of this stator column 122 may be kept at a predetermined pressure by a purge gas.

[0041] In this case, a pipe 134 (see FIG. 5) is provided in the base portion 129, and a purge gas is introduced through this pipe 134. The introduced purge gas is sent to an 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 rotating blade portion 102.

[0042] Here, the turbomolecular pump 100 requires control based on specific parameters (e.g., various characteristics corresponding to the model) that are individually adjusted and identified as a model. In order to store these control parameters, the turbomolecular pump 100 has an electronic circuit section 141 in its main 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 cover 145.

[0043] Incidentally, when a pump is used to evacuate a chamber used in a semiconductor manufacturing process, some process gases introduced into the chamber have the property of becoming solid when their pressure exceeds a predetermined value or their temperature falls below a predetermined value. Inside the turbomolecular pump 100, the pressure of the exhaust gas is lowest at the intake port 101 and highest at the exhaust port 133. If the pressure of the process gas becomes higher than a predetermined value or the temperature falls below a predetermined value while the process gas is being transferred from the intake port 101 to the exhaust port 133, the process gas becomes solid and adheres to and accumulates inside the turbomolecular pump 100.

[0044] For example, when SiCl4 is used as the process gas in an Al etching device, low vacuum (760[torr]~10 -2It can be seen from the vapor pressure curve that at a vapor pressure of 100 MPa (100 [torr]) and low temperature (approximately 20 [°C]), solid products (e.g., AlCl3) precipitate and adhere to and accumulate inside the turbomolecular pump 100. As a result, when precipitates of the process gas accumulate inside the turbomolecular pump 100, the deposits narrow the pump flow path, causing a decrease in the performance of the turbomolecular pump 100. The above-mentioned products are prone to solidification and adhesion in high-pressure areas near the exhaust port 133 and near the threaded spacer 131.

[0045] Therefore, in order to solve this problem, in the past, a heater (not shown) or a circular water-cooled tube 149 was wrapped around the outer periphery of the base portion 129, etc., and, for example, a temperature sensor (not shown, for example a thermistor) was embedded in the base portion 129, and the heating of the heater and the cooling by the water-cooled tube 149 were controlled based on the signal from this temperature sensor to keep the temperature of the base portion 129 at a constant high temperature (set temperature) (hereinafter referred to as TMS: Temperature Management System).

[0046] Next, an amplifier circuit 150 that controls excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106a, 106b in the turbo molecular pump 100 configured as described above will be described. A circuit diagram of this amplifier circuit 150 is shown in FIG.

[0047] 2, one end of an electromagnet winding 151 constituting the upper radial electromagnet 104 etc. is connected to a positive electrode 171a of a power source 171 via a transistor 161, and the other end is connected to a negative electrode 171b of the power source 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 cathode terminal 161a of the diode 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 cathode terminal 162a of the diode connected to the current detection circuit 181, and an anode terminal 162b connected to the negative electrode 171b.

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

[0050] The amplifier circuit 150 configured as above corresponds to one electromagnet. Therefore, when the magnetic bearing is controlled by 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) of the control device 200, and this amplifier control circuit 191 switches the transistors 161 and 162 on / off.

[0052] The amplifier control circuit 191 is adapted to compare 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. Then, based on the result of this comparison, the magnitude of the pulse width (pulse width times Tp1, Tp2) to be generated within a control cycle Ts, which is one period of PWM control, is determined. As a result, gate drive signals 191a, 191b having this pulse width are output from the amplifier control circuit 191 to the gate terminals of the transistors 161, 162.

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

[0054] In this configuration, when both transistors 161, 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] Moreover, when one of the transistors 161, 162 is turned on and the other is turned off, a so-called flywheel current is maintained. Then, by passing a flywheel current through the amplifier circuit 150 in this manner, it is possible to reduce hysteresis loss in the amplifier circuit 150 and keep the power consumption of the entire circuit low. Also, by controlling the transistors 161, 162 in this manner, it is possible to reduce high-frequency noise such as harmonics generated in the turbo molecular pump 100. Furthermore, by measuring this flywheel current with the current detection circuit 181, it is possible to detect the electromagnet current iL flowing through the electromagnet winding 151.

[0056] That is, when the detected current value is smaller than the current command value, both of the transistors 161 and 162 are turned on for a time period corresponding to the pulse width time Tp1 only once in a control cycle Ts (for example, 100 [μs]) as shown in Fig. 3. Therefore, the electromagnet current iL during this period 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, when the detected current value is larger than the current command value, both of the transistors 161 and 162 are turned off for a time period corresponding to the 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 the 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] A turbomolecular pump 100A according to a first embodiment of the invention will be described below. Fig. 5 is a longitudinal sectional view of the turbomolecular pump 100A, and Fig. 6 is an enlarged partial sectional view of a portion of Fig. 5. This turbomolecular pump 100A is a partly modified version of the turbomolecular pump 100 having the basic structure shown in Fig. 1. The same components of the turbomolecular pump 100A as those of the turbomolecular pump 100 are designated by the same reference numerals, and duplicated explanations will be omitted. Although the control device 200 is not shown in Fig. 5, the turbomolecular pump 100A also includes the same control device 200. In this embodiment, the turbo molecular pump 100A will be described mainly with respect to differences from the turbo molecular pump 100.

[0060] In this specification, the terms "upstream" and "downstream" refer to "upstream" and "downstream" in the case where gas is transferred by driving a pump. In addition, in this specification, the terms "upper" and "lower" refer to the upper and lower sides when the pump is placed on a horizontal plane with the intake port 101 facing upward.

[0061] In the turbo molecular pump 100 described above, all of the rotating blade portions 102 and the rotating cylindrical portion 102d are integrally constructed. In contrast, the turbomolecular pump 100A is composed of two components: a first rotor 20A which integrally comprises all of the rotating blade portions 102, and a second rotor 30A which comprises the aforementioned rotating cylindrical portion 102d.

[0062] The first rotor 20A has a substantially cylindrical main body 21A, and all of the rotary blade portions 102 are integrally formed on the outer circumferential surface of the main body 21A. The lower part of the main body 21A is open, and the upper part is closed by a ceiling part 22A. A through hole is formed in the center of the ceiling part 22A of the main body 21A, and the upper end part of the rotor shaft 113 is inserted therethrough. In addition, the inside of the main body portion 21A is spaced radially outward from the rotor shaft 113 and has an inner circumferential surface 211A with an approximately constant inner diameter, and an inward tapered surface 221A inclined relative to the inner circumferential surface 211A is formed at the boundary between the lower surface of the ceiling portion 22A and the inner circumferential surface 211A.

[0063] The second rotor 30A is integrally formed with a substantially cylindrical main body 31A, a flange portion 33A extending radially outward from the lower end of the main body 31A, and a rotating cylindrical portion 102d hanging down from the outer periphery of the flange portion 33A.

[0064] A ceiling portion 32A that closes the upper portion is provided on the main body portion 31A of the second rotor 30A. The main body portion 31A is disposed inside the main body portion 21A of the first rotor 20A. The ceiling portion 32A of the second rotor 30A abuts against the ceiling portion 22A of the first rotor 20A from below, and the upper end portion of the rotor shaft 113 is inserted simultaneously through a through hole formed in the center of the ceiling portion 32A of the second rotor 30A and through a through hole in the ceiling portion 22A of the first rotor 20A. This allows centering to be performed so that the first rotor 20A and the second rotor 30A are concentric.

[0065] The outer diameter of the main body 31A of the second rotor 30A is slightly smaller than the inner diameter of the main body 21A of the first rotor 20A, and the outer peripheral surface 311A ​​of the main body 31A of the second rotor 30A and the inner peripheral surface 211A of the main body 21A of the first rotor 20A are closely opposed to each other with a gap n1 between them. In addition, an outward tapered surface 321A inclined relative to the outer circumferential surface 311A ​​is formed on the outer periphery of the upper surface of the ceiling portion 32A of the second rotor 30A, and this tapered surface 321A also faces closely to the inward tapered surface 221A of the first rotor 20A described above via a gap n1. The gap n1 between the inner circumferential surfaces 211A, 311A ​​and the gap n1 between the tapered surfaces 221A, 321A may have the same gap width or may have different gap widths. By providing the above-mentioned gap n1 between the first rotor 20A and the second rotor 30A, the contact area between the first rotor 20A and the second rotor 30A is reduced, making it possible to reduce heat transfer by thermal conduction.

[0066] The first rotor 20A and the second rotor 30A are integrally connected to the rotor shaft 113 by fastening with fastening members such as bolts. That is, the first rotor 20A, the second rotor 30A and the rotor shaft 113 constitute a rotor 103A that rotates integrally. In this specification, the direction along the center of rotation of the rotor 103A may be referred to as the axial direction. In the turbo molecular pump 100A, the axial direction is parallel to the up-down direction.

[0067] In the turbo molecular pump 100A, the first rotor 20A is disposed on the upstream side, and the second rotor 30A is disposed on the downstream side. Furthermore, the stator column 122 of the motor 121 is disposed close to the inside of the cylindrical main body 31A of the second rotor 30A, but not in contact with it. When the pump is driven, the temperatures of the first rotor 20A and the second rotor 30A rise due to frictional heat with the gas, heat generated by the motor 121, etc. In particular, the second rotor 30A on the downstream side is subjected to high pressure around it and is also close to the motor 121, so it becomes hotter than the first rotor 20A on the upstream side.

[0068] Therefore, the first material forming the first rotor 20A is made of a relatively lightweight material, such as an aluminum alloy, taking into consideration the rotation performance of the rotational force rather than heat resistance. Furthermore, the first rotor 20A is surface-treated over almost the entire surface thereof to further increase the emissivity, such as nickel oxide plating with high emissivity. The first rotor 20A suppresses the rise in temperature by radiating heat to the surroundings. The first material and the plating material for performing the surface treatment thereon are merely examples and are not limited to those mentioned above.

[0069] In contrast, the second material forming the second rotor 30A is made of a metal, such as stainless steel, that is more heat resistant than the first rotor 20A, in consideration of the high temperatures that will be encountered. In addition, the entire surface of the second rotor 30A is subjected to a surface treatment, such as electroless nickel plating, to enhance corrosion resistance. The second material and the plating material for which the surface treatment is performed are also merely examples and are not limited to those mentioned above.

[0070] As shown in FIG. 6, the inner surface 211A and the tapered surface 221A, which are the surface portions of the first rotor 20A that face the second rotor 30A across a gap n1, are easily affected by heat radiation from the second rotor 30A, which becomes hot. For this reason, the inner circumferential surface 211A and tapered surface 221A of the main body 21A of the first rotor 20A are subjected to removal of the surface treatment of the high emissivity nickel oxide plating. Therefore, the inner circumferential surface 211A and tapered surface 221A of the main body 21A of the first rotor 20A have the emissivity of the aluminum alloy as the base material, and have a lower emissivity than other surface parts (for example, the blade surfaces of each rotor blade part 102 on the outer periphery side). Hereinafter, the range consisting of the inner circumferential surface 211A and tapered surface 221A, which have a lower emissivity than other surface parts, will be referred to as the "low emissivity region." In FIG. 6, the low emissivity region S1 is shown by light-density dotted lines.

[0071] The method of making the emissivity of the low emissivity region S1 of the first rotor 20A lower than that of the other surface parts is not limited to removing the high emissivity surface treatment described above. For example, the low emissivity region S1 may be masked when high emissivity plating is applied to the entire surface of the first rotor 20A, or a low emissivity treatment such as forming a low emissivity coating on the low emissivity region S1 may be applied from above.

[0072] In addition to the low emissivity region S1 described above, there is a surface portion of the first rotor 20A that faces the second rotor 30A with a gap therebetween. Specifically, it is the lower end surface of the main body portion 21A of the first rotor 20A and a radially inner part of the lower surface of the blade of the most downstream rotating blade portion 102, which face the upper surface of the flange portion 33A of the second rotor 30A. These are referred to as the "opposing region." In Figure 6, the opposing region S2 is indicated by dark dots. The emissivity of the facing region S2 may also be lower than that of other surface portions other than the low emissivity region S1. However, the facing region S2 may radiate heat while maintaining the high emissivity, thereby suppressing the temperature rise of the first rotor 20A. Therefore, it is preferable to set the facing region S2 to a low emissivity when the effect of suppressing the temperature rise of the first rotor 20A by setting the facing region S2 to a low emissivity exceeds the effect of suppressing the temperature rise by setting the facing region S2 to a high emissivity.

[0073] The operation of the turbo molecular pump 100A will now be described. The entire rotor 103A is rotated by driving the motor 121. This causes gas to be sucked from the chamber through the intake port 101. The gas sucked through the intake port 101 is transported downstream by the action of a turbo molecular pump mechanism formed by the rotating blade portion 102 and the stationary blade portion 123 of the first rotor 20A. The gas transported downstream is guided further downstream by the action of a Holweck-type drag pump mechanism formed by the rotating cylindrical portion 102d of the second rotor 30A and the stationary cylindrical portion, that is, the threaded spacer 131, and is transported to the exhaust port 133.

[0074] [Technical effect of the first embodiment] In the turbo molecular pump 100A, at least the inner circumferential surface 211A and the tapered surface 221A of the surface portion of the first rotor 20A that faces the second rotor 30A with a gap n1 therebetween have a lower emissivity than the other surface portions. This makes it possible to suppress the incidence of radiant heat from the surface of the second rotor 30A, which has a higher temperature than the first rotor 20A, and to suppress a rise in temperature of the first rotor 20A. This allows for a wider range of material choices for the first material forming the first rotor 20A. For example, it is possible to select a material for the first rotor 20A with consideration given to rotation performance of the rotational force rather than heat resistance. In addition, the second rotor 30A is allowed to have a higher temperature than before, which can prevent solidified components contained in the gas from solidifying and accumulating inside the pump. This reduces the amount of cleaning work inside the pump, and can reduce the workload.

[0075] In addition, in the turbo molecular pump 100A, the second material forming the second rotor 30A is a material having higher heat resistance than the first material forming the first rotor 20A. Specifically, an aluminum alloy is exemplified as the second material, and stainless steel is exemplified as the first material. Therefore, while the second material ensures high-temperature strength against the high temperatures required for the second rotor 30A, the range of material choices for the first material is broadened, making it possible to select a material that satisfies other requirements, such as improving the rotational performance of the first rotor 20A or achieving cost reduction.

[0076] Moreover, the turbomolecular pump 100A is configured to realize the function of a turbomolecular pump mechanism with a cascade of multiple stages of the rotating blade section 102 and the cascade of the stationary blade section 123, so it is possible to perform continuous evacuation with little pulsation. Also, it is possible to meet a wide range of vacuum degree requirements for the object to be evacuated.

[0077] Furthermore, since the turbo molecular pump 100A has a Holweck type drag pump mechanism formed by the rotating cylindrical portion 102d and the threaded spacer 131, which is a stationary cylindrical portion, the gas can be compressed to a higher pressure downstream of the Holweck type drag pump mechanism, and the object to be evacuated, such as a chamber, can be evacuated to a higher degree of vacuum.

[0078] [Second embodiment] A turbomolecular pump 100B according to a second embodiment of the present invention will now be described. Fig. 7 is a vertical cross-sectional view of the turbomolecular pump 100B, and Fig. 8 is an enlarged partial cross-sectional view of a portion of Fig. 7. This turbomolecular pump 100B is a modification of the turbomolecular pump 100A described above. The same components of the turbomolecular pump 100B as those of the turbomolecular pump 100A are designated by the same reference numerals, and duplicated explanations will be omitted. Although the control device 200 is not shown in FIG. 7, the turbomolecular pump 100B also includes the same control device 200. In this embodiment, the turbo molecular pump 100B will be described mainly with respect to the differences from the turbo molecular pump 100A.

[0079] The turbomolecular pump 100B has a first rotor 20B and a second rotor 30B, and the first rotor 20B, the second rotor 30B, and the rotor shaft 113 are integrally connected to each other. That is, the first rotor 20B, the second rotor 30B, and the rotor shaft 113 configure a rotor 103B that rotates integrally.

[0080] In the turbomolecular pump 100A described above, the first rotor 20A has all of the rotating blade portions 102, but as in this turbomolecular pump 100B, a configuration in which a portion of the downstream rotating blade portions 102 are provided by the second rotor 30B may also be used.

[0081] That is, the vertical length of the substantially cylindrical main body 21B of the first rotor 20B is shortened, and a part of the upstream rotating blade portion 102 is integrally formed on the outer circumferential surface thereof. In contrast, the second rotor 30B has an upper portion of a substantially cylindrical main body 31B whose diameter is slightly smaller than the inner diameter of the main body 21B of the first rotor 20B, and a lower portion of the main body 31B whose diameter is equal to the outer diameter of the main body 21B. Furthermore, the remaining downstream rotary blade portion 102 is integrally formed on the outer periphery of the lower portion of the main body portion 31B of the second rotor 30B.

[0082] Moreover, the first rotor blade 20B is formed from the same material as the first rotor blade 20A described above, and is surface-treated with the same material. Further, the second rotor 30B is formed from the same material as the above-mentioned second rotor 30A, and is subjected to a surface treatment using the same material.

[0083] As shown in FIG. 8, in the turbo molecular pump 100B, an outer peripheral surface 311B of an upper part of a main body 31B of a second rotor 30B and an inner peripheral surface 211B of a main body 21B of a first rotor 20B closely face each other with a gap n2 therebetween. Further, tapered surface 321A of second rotor 30B and tapered surface 221A of first rotor 20A are closely opposed to each other via gap n2. Therefore, the inner circumferential surface 211B and the tapered surface 221A of the main body 21B of the first rotor 20B form the low emissivity region S3. The method for making the inner circumferential surface 211B and the tapered surface 221A lower in emissivity than the other surface portions is the same as in the turbo molecular pump 100A.

[0084] In the case of the turbomolecular pump 100B, in addition to the low emissivity region S3 described above, the lower end surface (referred to as the opposing region S4) of the main body 21B of the first rotor 20B and the upper end surface of the large-diameter lower portion of the main body 31B of the second rotor 30B are closely opposed to each other with a gap therebetween. This facing region S4 may also have a low emissivity. However, it is also possible for the opposing region S4 to radiate heat while maintaining the high emissivity, thereby suppressing the temperature rise of the first rotor 20 B. Therefore, in the case of the opposing region S4, it is preferable to set the opposing region S4 to a low emissivity when the effect of suppressing the temperature rise of the first rotor 20 B by making the opposing region S4 have a low emissivity exceeds the effect of suppressing the temperature rise by making the opposing region S4 have a high emissivity.

[0085] Furthermore, the lower surface of the most downstream rotating blade portion 102 held by the first rotor 20B and the upper surface of the most upstream rotating blade portion 102 held by the second rotor 30B face each other with a gap between them. However, since the stationary blade portion 123 is disposed between these rotating blade portions 102 and they do not face each other directly, it is preferable that the lower surface of the most downstream rotating blade portion 102 of the first rotor 20B remains high emissivity rather than being made low emissivity.

[0086] With the above-mentioned configuration, the turbomolecular pump 100B according to the second embodiment has the same technical effects as the turbomolecular pump 100A described above.

[0087] [Third embodiment] A turbomolecular pump 100C according to a third embodiment of the present invention will now be described with reference to Fig. 9, which is a vertical cross-sectional view of the turbomolecular pump 100C. This turbomolecular pump 100C is a modification of the turbomolecular pump 100B described above, and the same components of the turbomolecular pump 100C as those of the turbomolecular pump 100B are designated by the same reference numerals and will not be described again. Although the control device 200 is not shown in FIG. 9, the turbomolecular pump 100C also includes the same control device 200.

[0088] The turbomolecular pump 100C differs from the turbomolecular pump 100B in that a stationary blade portion 123 is not disposed between the most downstream rotating blade portion 102 held by the first rotor 20B and the most upstream rotating blade portion 102 held by the second rotor 30B. In this case, the lower surface of the most downstream rotating blade portion 102 of the first rotor 20B and the upper surface of the most upstream rotating blade portion 102 of the second rotor 30B directly face each other via a gap. Therefore, when the effect of suppressing a temperature rise of the first rotor 20B by making the lower surface of the most downstream rotating blade portion 102 of the first rotor 20B low emissivity exceeds the effect of suppressing a temperature rise by making the lower surface of the most downstream rotating blade portion 102 of the first rotor 20B high emissivity, it is preferable to make the lower surface of the most downstream rotating blade portion 102 of the first rotor 20B low emissivity. Other than this, the range in which the first rotor 20B should have a low emissivity is the same as that of the turbomolecular pump 100B.

[0089] With the above-mentioned configuration, the turbomolecular pump 100C according to the third embodiment has the same technical effects as the turbomolecular pump 100B described above.

[0090] [Fourth embodiment] A turbo molecular pump 100D according to a fourth embodiment of the present invention will now be described with reference to Fig. 10, which is a vertical cross-sectional view of the turbo molecular pump 100D. This turbomolecular pump 100D is a modification of the turbomolecular pump 100A described above. The same components of the turbomolecular pump 100D as those of the turbomolecular pump 100A are designated by the same reference numerals, and duplicated explanations will be omitted. Although the control device 200 is not shown in FIG. 10, the turbomolecular pump 100D also includes the same control device 200. In this embodiment, the turbo molecular pump 100D will be described mainly with respect to the differences from the turbo molecular pump 100A.

[0091] The turbomolecular pump 100D has a first rotor 20D and a second rotor 30D, and the first rotor 20D, the second rotor 30D, and the rotor shaft 113 are integrally connected to each other. That is, the first rotor 20D, the second rotor 30D, and the rotor shaft 113 configure a rotor 103D that rotates integrally.

[0092] The turbomolecular pump 100A described above has a configuration in which a Holweck type drag pump mechanism is provided downstream within the pump, but the turbomolecular pump 100D has a Sigburn type drag pump mechanism instead of the Holweck type drag pump mechanism.

[0093] Due to the above changes, the first rotor 20D has a substantially cylindrical main body 21D with a shorter vertical length, and the rotating blade section 102 is integrally formed on its outer circumferential surface with fewer stages in the axial direction than the turbomolecular pump 100A. Note that the number of stages of the rotating blade section 102 can be changed by adjusting the overall vertical length of the turbomolecular pump 100D, and it is not essential to reduce the number of stages of the rotating blade section 102.

[0094] The second rotor 30D has a substantially cylindrical main body 31D, which is disposed inside the main body 21D of the first rotor 20D. The outer diameter of the main body 31D of the second rotor 30D is slightly smaller than the inner diameter of the main body 21D of the first rotor 20D, and the outer peripheral surface 311D and tapered surface 321A of the main body 31D of the second rotor 30D face the inner peripheral surface 211D and tapered surface 221A of the main body 21D of the first rotor 20D with a gap therebetween.

[0095] Furthermore, three rotating disks 34D extending radially outward are provided on the outer circumferential surface of the lower part of the main body 31D of the second rotor 30D at equal intervals vertically. The upper and lower surfaces of each rotating disk 34D are both flat.

[0096] The turbomolecular pump 100D has two stationary disk portions 135 fixedly supported inside the outer cylinder 127. The two stationary disk portions 135 are individually inserted into two gaps formed by the three rotating disk portions 34D. The upper and lower surfaces of each stationary disk portion 135 are closely opposed to the lower surface of the upper rotating disk portion 34D and the upper surface of the lower rotating disk portion 34D, respectively. Furthermore, a plurality of spiral grooves 136 are formed radially from the center of rotation of the rotor 103D on the upper and lower surfaces of each stationary disk portion 135. Each groove 136 reaches from the inside to the outside of the stationary disk portion 135. Furthermore, the grooves 136 on the upper surface side are formed in a direction to guide gas traveling in the rotation direction of the second rotor 30D radially inward, and the grooves 136 on the lower surface side are formed in a direction to guide gas traveling in the rotation direction of the second rotor 30D radially outward. This allows the gas to be transported downstream by the rotation of the second rotor 30A.

[0097] The first rotor blade 20D is formed from the same material as the first rotor blade 20A described above, and is surface-treated with the same material. Further, the second rotor 30D is formed from the same material as the above-mentioned second rotor 30A, and is surface-treated with the same material.

[0098] As described above, the outer circumferential surface 311D and tapered surface 321A of the main body portion 31D of the second rotor 30D and the inner circumferential surface 211D and tapered surface 221A of the main body portion 21D of the first rotor 20D face each other via a gap. For this reason, in the turbo molecular pump 100D as well, the inner circumferential surface 211D and the tapered surface 221A of the main body 21D of the first rotor 20D have a lower emissivity than the other surface portions.

[0099] In the case of the turbomolecular pump 100D, in addition to the inner circumferential surface 211D and tapered surface 221A described above, the lower end surface of the main body portion 21D of the first rotor 20D and the lower surface of the rotating blade portion 102 located most downstream are closely opposed to the upper surface of the rotating disk portion 34D most upstream of the second rotor 30D via a gap. Therefore, the lower end surface of the main body portion 21D and the lower surface of the rotating blade portion 102 located at the most downstream side may also be made to have a low emissivity. However, it is also possible for the lower end surface of main body 21D and the lower surface of rotating blade section 102 located at the most downstream position to radiate heat while maintaining the high emissivity, thereby suppressing the temperature rise of first rotor 20D. Therefore, for the lower end surface of main body 21D and the lower surface of rotating blade section 102 located at the most downstream position, it is preferable to use low emissivity when the effect of suppressing the temperature rise of first rotor 20D by using low emissivity exceeds the effect of suppressing the temperature rise by using high emissivity.

[0100] With the above-mentioned configuration, the turbomolecular pump 100D according to the fourth embodiment has the same technical effects as the turbomolecular pump 100A described above. Furthermore, the turbomolecular pump 100D has a Sigburn type drag pump mechanism consisting of a rotating disk portion 34D disposed on the second rotor 30D and a stationary disk portion 135 disposed axially opposite to the rotating disk portion 34D. This makes it possible to compress gas to a higher pressure downstream of the Sigburn type drag pump mechanism, and to achieve a higher degree of vacuum in the object to be evacuated, such as a chamber.

[0101] [Fifth embodiment] A turbo molecular pump 100E according to a fifth embodiment of the present invention will now be described with reference to Fig. 11, which is a vertical cross-sectional view of the turbo molecular pump 100E. This turbomolecular pump 100E is a modification of the turbomolecular pumps 100A and 100D described above. The same components of the turbomolecular pump 100E as those of the turbomolecular pumps 100A and 100D are designated by the same reference numerals, and duplicated explanations will be omitted. Although the control device 200 is not shown in FIG. 11, the turbomolecular pump 100E also includes the same control device 200. In this embodiment, the turbo molecular pump 100E will be described mainly with respect to the differences from the turbo molecular pumps 100A and 100D.

[0102] The turbomolecular pump 100E has a first rotor 20E and a second rotor 30E, and the first rotor 20E, the second rotor 30E and the rotor shaft 113 are integrally connected to each other. That is, the first rotor 20E, the second rotor 30E and the rotor shaft 113 configure a rotor 103E that rotates integrally.

[0103] The turbomolecular pump 100A described above has a configuration in which a Holweck type drag pump mechanism is provided downstream in the pump, and the turbomolecular pump 100D has a configuration in which a Sigburn type drag pump mechanism is provided downstream in the pump. In contrast, the turbomolecular pump 100E has a Sigburn type drag pump mechanism provided downstream in the pump, and a Holweck type drag pump mechanism provided further downstream. The turbomolecular pump 100E also differs from the turbomolecular pump 100D in that a stationary blade portion 123 is disposed downstream of and opposed to the most downstream rotating blade portion 102 held by the first rotor 20E.

[0104] Due to the above changes, the first rotor 20E has a substantially cylindrical main body 21E with a shorter vertical length, and the rotating blade section 102 is integrally formed on its outer circumferential surface with fewer stages in the axial direction than the turbomolecular pump 100D. Note that the number of stages of the rotating blade section 102 can be changed by adjusting the overall vertical length of the turbomolecular pump 100E, and it is not essential to reduce the number of stages of the rotating blade section 102.

[0105] The second rotor 30E has a substantially cylindrical main body 31E, which is disposed inside the main body 21E of the first rotor 20E. The outer diameter of the main body 31E of the second rotor 30E is slightly smaller than the inner diameter of the main body 21E of the first rotor 20E, and the outer peripheral surface 311E and tapered surface 321A of the main body 31E of the second rotor 30E face the inner peripheral surface 211E and tapered surface 221A of the main body 21E of the first rotor 20E via a gap.

[0106] Furthermore, like the second rotor 30D, the second rotor 30E has three rotating disk portions 34D provided on the outer circumferential surface of the lower portion of the main body portion 31E. In addition, the second rotor 30E is the same as the second rotor 30A in that a flange portion 33A and a rotating cylindrical portion 102d suspended from the outer periphery of the flange portion 33A are integrally formed on the lower side of the three rotating disk portions 34D.

[0107] In the turbo molecular pump 100E, two stationary disk portions 135 are disposed inside the outer cylinder 127 and are individually inserted into two gaps formed by the three rotating disk portions 34D. Further, a threaded spacer 131 is disposed on the inner lower part of the outer cylinder 127 so as to face the outer circumferential surface of the rotating cylindrical portion 102d from the outside in the radial direction.

[0108] The first rotor 20E is formed from the same material as the first rotor 20A described above, and is surface-treated with the same material. Further, the second rotor 30E is formed from the same material as the above-mentioned second rotor 30A, and is surface-treated with the same material.

[0109] As described above, the outer circumferential surface 311E and tapered surface 321A of the main body portion 31E of the second rotor 30E and the inner circumferential surface 211E and tapered surface 221A of the main body portion 21E of the first rotor 20E face each other via a gap. For this reason, in the turbo molecular pump 100E as well, the inner circumferential surface 211E and the tapered surface 221A of the main body 21E of the first rotor 20E have a lower emissivity than the other surface portions.

[0110] In the case of the turbomolecular pump 100E, in addition to the inner circumferential surface 211E and the tapered surface 221A described above, the lower end surface of the main body portion 21E of the first rotor 20E and the upper surface of the most upstream rotating disk portion 34D of the second rotor 30E are closely opposed to each other with a gap therebetween. Therefore, the lower end surface of the main body 21E may also have low emissivity. However, it is also possible for the lower end surface of main body 21E to radiate heat while maintaining the high emissivity, thereby suppressing the temperature rise of first rotor 20E. Therefore, it is preferable to make the lower end surface of main body 21E have low emissivity when the effect of suppressing the temperature rise of first rotor 20E by making the lower end surface of main body 21E low emissivity exceeds the effect of suppressing the temperature rise by making the lower end surface of main body 21E high emissivity.

[0111] In addition, the lower surface of the most downstream rotating blade portion 102 held by the first rotor 20E and the upper surface of the most upstream rotating disk portion 34D held by the second rotor 30E face each other with a gap therebetween. However, the stationary blade portion 123 is disposed between the rotating blade portion 102 and the rotating disk portion 34D, and they do not face each other directly, so that it is possible to reduce the inflow of radiant heat from the first rotor 20E to the second rotor 30E. Furthermore, the lower surface of the most downstream rotating blade portion 102 of the first rotor 20D may be made high emissivity instead of low emissivity.

[0112] With the above-mentioned configuration, the turbo molecular pump 100E according to the fifth embodiment has the same technical effects as the turbo molecular pump 100A described above. Furthermore, since the turbomolecular pump 100E has a Sigburn type drag pump mechanism and a Holweck type drag pump mechanism on the downstream side of the pump, the gas can be compressed to a higher pressure on the downstream side of the pump, making it possible to achieve an even higher degree of vacuum in the object to be evacuated, such as a chamber.

[0113] [Sixth embodiment] A turbomolecular pump 100F according to a sixth embodiment of the present invention will now be described with reference to Fig. 12, which is a vertical cross-sectional view of the turbomolecular pump 100F. This turbomolecular pump 100F is a modification of the turbomolecular pump 100E described above, and the same components of the turbomolecular pump 100F as those of the turbomolecular pump 100E are designated by the same reference numerals and will not be described again. Although the control device 200 is not shown in FIG. 12, the turbomolecular pump 100F also includes the same control device 200.

[0114] The turbomolecular pump 100F differs from the turbomolecular pump 100E in that the stationary blade portion 123 is not disposed downstream of and opposed to the most downstream rotating blade portion 102 held by the first rotor 20E. In this case, the lower surface of the most downstream rotating blade portion 102 of the first rotor 20E and the upper surface of the most upstream rotating disk portion 34D of the second rotor 30E directly face each other via a gap. Therefore, when the effect of suppressing the temperature rise of the first rotor 20E by making the lower surface of the most downstream rotating blade portion 102 low emissivity exceeds the effect of suppressing the temperature rise by making it high emissivity, it is preferable to make the lower surface of the most downstream rotating blade portion 102 of the first rotor 20E low emissivity. Other than this, the range in which the first rotor 20E should have a low emissivity is the same as that of the turbomolecular pump 100E.

[0115] With the above-mentioned configuration, the turbomolecular pump 100F according to the sixth embodiment has the same technical effects as the turbomolecular pump 100E described above.

[0116] [others] Above, each embodiment of the present invention has been described. However, the present invention is not limited to the above-mentioned embodiments. For example, in the embodiments, a component integrally formed from a single member may be replaced with a component divided into a plurality of members and connected or fixed to each other. Also, a component formed by connecting a plurality of members may be replaced with a component integrally formed from a single member. In addition, the details shown in the embodiments can be appropriately changed without departing from the spirit of the invention.

[0117] Below, an example of the modification will be described using the turbo molecular pump 100A as an example, but similar modifications can also be made to the other turbo molecular pumps 100B to 100F.

[0118] In the turbomolecular pump 100A, the ceiling portion 22A of the first rotor 20A is fastened to the rotor shaft 113 together with the ceiling portion 32A of the second rotor 30A, so that the lower surface of the ceiling portion 22A of the first rotor 20A and the upper surface of the ceiling portion 32A of the second rotor 30A are pressed against each other, and heat conduction due to contact can occur from here. Therefore, a sheet or plate made of a low thermal conductivity material having a lower thermal conductivity than the material forming the first rotor 20A and the material forming the second rotor 30A may be inserted between the underside of the ceiling portion 22A of the first rotor 20A and the upper surface of the ceiling portion 32A of the second rotor 30A to avoid direct contact between them. In this case, the low thermal conductivity material is not particularly limited, but examples thereof include ceramics such as zirconium dioxide, resin materials such as polyamideimide, and porous materials with many fine holes. The porous material may be formed by machining a large number of holes in a metal material, ceramics, or resin material, or by sintering powder of the material.

[0119] In addition, the emissivity of the first rotor 20A does not have to be low for the entire surface that faces the second rotor 30A across a gap. As described above, the emissivity of the facing region S2 does not have to be low. Furthermore, the emissivity may be low only for a part of the inner circumferential surface 211A or the tapered surface 221A of the first rotor 20A.

[0120] Furthermore, the turbo molecular pump 100A may be configured to provide a temperature difference so that the first rotor 20A is at a lower temperature than the second rotor 30A during pump operation. For example, a heating means for the second rotor 30A may be provided as shown by reference numeral 110 in Fig. 5. The heating means 110 may be formed of a heater element disposed in the base portion 129 near the second rotor 30A, for example. In this case, the second rotor 30A can be maintained at a high temperature while suppressing the temperature rise of the first rotor 20A, and if the gas used for vacuum evacuation contains solidified components, sublimation of the solidified components can be suppressed, making it possible to more effectively suppress adhesion to the rotors and deposition inside the pump.

[0121] As a configuration for creating a temperature difference between the first rotor 20A and the second rotor 30A, a cooling means for the first rotor 20A may be provided as shown by reference numeral 112 in Fig. 5. The cooling means 112 may be formed, for example, from a low-temperature element such as a Peltier element disposed in the outer cylinder 127 near the first rotor 20A or a water jacket. In this case, even when the rotor 103A rotates at a higher speed or when the second rotor 30A is configured to be heated, it is possible to more effectively suppress the temperature rise of the first rotor 20A.

[0122] Also, examples of modifications of the turbo molecular pumps 100A, 100B, 100C, 100E, and 100F having a Holweck type drag pump mechanism will be described. The threaded spacer 131 of the Holweck-type drag pump mechanism has been illustrated as having a thread groove 131a formed on its inner circumferential surface. However, the threaded spacer 131 may have a smooth inner circumferential surface and the rotating cylindrical portion 102d may have a thread groove formed on its outer circumferential surface.

[0123] Also, instead of the threaded spacer 131, a stationary cylindrical portion may be provided facing the inner peripheral surface of the rotating cylindrical portion 102d. The stationary cylindrical portion is supported by the outer tube 127 or the base portion 129, is disposed inside the rotating cylindrical portion 102d, and has an outer peripheral surface closely facing the inner peripheral surface of the rotating cylindrical portion 102d. Furthermore, a configuration may be adopted in which a plurality of helical thread grooves are engraved on the outer peripheral surface of the stationary cylindrical portion or the inner peripheral surface of the rotating cylindrical portion 102d, the thread grooves being directed downstream in the rotation direction of the rotor 103.

[0124] Also, examples of modifications of the turbo molecular pumps 100D, 100E, and 100F having a Sigburn type drag pump mechanism will be described. Although the Sigburn type drag pump mechanism has been exemplified with the spiral groove 136 formed in the stationary disk portion 135, the spiral groove 136 may be formed in the rotating disk portion 34D. In that case, the spiral groove 136 may be formed on the surface of the rotating disk portion 34D facing the stationary disk portion 135. In addition, the number of the rotating disk parts 34D and the stationary disk parts 135 can be increased or decreased. The rotating disk parts 34D and the stationary disk parts 135 may be adjacent to each other and may be one or more of each, and the difference in the number of the rotating disk parts 34D or the stationary disk parts 135 may be one or less so that there are no surplus parts that are not opposed to either one.

[0125] The present invention is not limited to the above-described embodiments, and various modifications and combinations of the embodiments are possible without departing from the scope of the present invention. [Explanation of symbols]

[0126] 20A, 20B, 20D, 20E First rotor 21A, 21B, 21D, 21E Main body 22A Ceiling 30A, 30B, 30D, 30E Second rotor 31A, 31B, 31D, 31E Main body 32A Ceiling 33A Flange part 34D Rotating disc section 100,100A~100F Turbo molecular pump (vacuum pump) 102, 102a to 102c Rotating blade section (rotating blade) 102d Rotating cylinder 103, 103A, 103B, 103D, 103E Rotating body 110 Heating means 112 Cooling means 113 Rotor shaft (rotating shaft) 121 Motor (drive mechanism) 123, 123a, 123b Stationary blade section (stationary blade) 125, 125a, 125b spacer 127 Casing 129 Base 131 Threaded spacer (static cylindrical part) 131a Thread groove 133 Exhaust port 135 Stationary disk part 136 Groove 211A, 211B, 211D, 211E Inner surface 221A Tapered surface 311A, 311B, 311D, 311E outer surface 321A Tapered surface S1,S3 Low emissivity area S2,S4 Opposing area n1, n2 gap

Claims

1. A first rotor; a second rotor disposed downstream of the first rotor; a rotating shaft that transmits rotation to the first rotor and the second rotor; A drive mechanism for the rotating shaft; a casing containing the rotating shaft, the first rotor, and the second rotor; A vacuum pump having A vacuum pump characterized in that a gap is provided between opposing surface portions of the first rotor and the second rotor, and at least a portion of the opposing surface portion of the first rotor has a lower emissivity than a surface portion other than the opposing surface portion.

2. 2. The vacuum pump according to claim 1, wherein the first rotor is configured to have a lower temperature than the second rotor during operation of the vacuum pump.

3. 3. A vacuum pump according to claim 2, further comprising a heating means for said second rotor.

4. 3. A vacuum pump according to claim 2, further comprising a cooling means for cooling said first rotor blade.

5. 2. The vacuum pump according to claim 1, wherein the second material forming the second rotor blade is a material having a higher heat resistance than the first material forming the first rotor blade.

6. The first rotor has a cascade of multiple stages of rotor blades arranged on an outer periphery of the first rotor, The vacuum pump includes a cascade of stationary blades disposed between the cascades of the multiple stages of rotating blades, 2. The vacuum pump according to claim 1, wherein the plurality of stages of rotating blade cascades and the plurality of stages of stationary blade cascades form a turbomolecular pump mechanism.

7. the second rotor has at least one rotating cylindrical portion disposed thereon; The vacuum pump has at least one stationary cylindrical portion disposed opposite to an outer circumferential surface or an inner circumferential surface of the rotating cylindrical portion, 2. The vacuum pump according to claim 1, wherein said rotating cylindrical portion and said stationary cylindrical portion form a Holweck type drag pump mechanism.

8. the second rotor has at least one rotating disk portion disposed on the second rotor, The vacuum pump has at least one stationary disk portion disposed axially opposite to the rotating disk portion, 2. The vacuum pump according to claim 1, wherein said rotating disk portion and said stationary disk portion form a Sigburn type drag pump mechanism.

9. A first rotor; a second rotor disposed downstream of the first rotor; a rotating shaft that transmits rotation to the first rotor and the second rotor; A rotating body of a vacuum pump having A vacuum pump rotor, characterized in that a gap is provided between opposing surface portions of the first rotor and the second rotor, and at least a portion of the opposing surface portion of the first rotor has a lower emissivity than a surface portion other than the opposing surface portion.

10. An upstream rotor of a vacuum pump in which rotors are provided on the upstream and downstream sides of a common rotor shaft, 1. An upstream rotor of a vacuum pump, wherein at least a portion of an inner circumferential surface of the upstream rotor, which is radially inward of the upstream rotor and spaced from the rotor shaft, has a lower emissivity than a surface portion other than the inner circumferential surface.

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