vacuum pump

Abstract

To provide a vacuum pump capable of preventing the attachment of product materials during the stop of a rotary body or the like by heating the rotary body using an AC magnetic field, while actualizing more efficient power consumption necessary for the heating.SOLUTION: Between a protection bearing 1 and an upper side radial sensor 107, bipolar heating electromagnet 3A and heating electromagnet 3B are opposed to each other across a rotary body 103. The heating electromagnet 3A and the heating electromagnet 3B are each equivalent to a heating device 3, and an AC current is supplied to the heating device 3 by a heating power supply 21. The heating electromagnet 3A and the heating electromagnet 3B are excited by the AC current to generate an AC magnetic field. In this construction, the generated AC magnetic field intersects with the rotary body 103. Around the intersecting AC magnetic field, an eddy current is generated. The eddy current heats the rotary body 103. The heating can further prevent the accumulation of product materials, thus improving the operation efficiency of the pump.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vacuum pump, and more particularly to a vacuum pump that can prevent the adhesion of products to the rotor, even when the rotor is stopped, by heating the rotor using an AC magnetic field, and can heat the rotor with high efficiency. [Background technology]

[0002] With the recent development of electronics, the demand for semiconductors such as memory and integrated circuits has increased dramatically. These semiconductors are manufactured by doping extremely pure semiconductor substrates with impurities to give them electrical properties, and by etching the semiconductor substrates to form minute circuits.

[0003] These operations must be carried out in a chamber under high vacuum conditions to avoid the effects of dust in the air, etc. Vacuum pumps are generally used to evacuate the chamber, but turbomolecular pumps, a type of vacuum pump, are often used because they leave little residual gas and are easy to maintain.

[0004] Furthermore, semiconductor manufacturing processes involve many steps in which various process gases are applied to semiconductor substrates, and turbomolecular pumps are used not only to create a vacuum inside the chamber, but also to exhaust these process gases from the chamber.

[0005] In some cases, process gases are introduced into the chamber at high temperatures to enhance their reactivity. When these process gases are cooled and cooled to a certain temperature during exhaust, they may solidify and precipitate products in the exhaust system. When this type of process gas cools down inside the turbomolecular pump, it may solidify and adhere to and deposit inside the turbomolecular pump.

[0006] When deposits of the process gas accumulate inside the turbomolecular pump, the deposits narrow the pump flow passage, causing a decrease in the performance of the turbomolecular pump. To solve this problem, a heater is provided around the base of the turbomolecular pump, and the heating of this heater is controlled.

[0007] In order to more efficiently prevent the adhesion of the by-products, it is desirable to heat not only the periphery of the base portion and the stator but also the rotor side. As a method for heating a rotating body, for example, Patent Document 1 discloses a method in which a DC magnetic field generated by a permanent magnet or an electromagnet crosses the rotating body. Also, Patent Document 2 discloses a method in which the rotating body is heated by reducing the efficiency of the motor. Another possible method is to heat the stator side and then heat the rotating body side with the radiant heat. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 59-32697 [Patent Document 2] Japanese Patent Application Publication No. 2019-031969 Summary of the Invention [Problem to be solved by the invention]

[0009] Incidentally, it is desirable to prevent the adhesion of such products not only while the pump is operating but also continuously when the pump is stopped. In the configuration of Patent Document 1, the magnetic field that intersects with the rotor is direct current, so there is no need to provide a heating power source that can supply alternating current, but the rotor can only be heated when the rotor is rotating, and cannot be heated when the rotor is stopped. In addition, when controlling heating to prevent the adhesion of by-products, it is necessary to make efficient use of the power consumption required for heating.

[0010] The present invention has been made in consideration of these conventional problems, and aims to provide a vacuum pump that can prevent the adhesion of products, even when the rotor is stopped, by heating the rotor using an AC magnetic field, and that can heat the rotor with high efficiency. [Means for solving the problem]

[0011] Therefore, the present invention (claim 1) provides a method for producing a rotating body, a motor for rotating the rotating body, a motor power supply for supplying power for rotating the motor, a heating electromagnet for generating an AC magnetic field of a predetermined magnetic field frequency to heat the rotating body, and a heating power supply for supplying power to the heating electromagnet by AC current, wherein the AC magnetic field generated by the heating electromagnet is caused to cross the rotating body, thereby generating eddy currents around the crossed AC magnetic field in the rotating body. , the rigid body mode natural frequency of the rotor is ω res When the magnetic field frequency is defined as ω res greater than / √2 It is characterized by:

[0012] The heating electromagnet generates an AC magnetic field of a predetermined magnetic field frequency using an AC current supplied from a heating power supply. When the AC magnetic field crosses the rotor, eddy currents are generated around the crossed AC magnetic field in the rotor. These eddy currents generate eddy current loss, allowing the rotor to be heated. Because the magnetic field generated by the heating electromagnet is an AC magnetic field, eddy current loss can be generated even when the rotor is stopped, allowing the rotor to be heated. Since deposits are expected to form even when the rotor is stopped, the formation of deposits can be effectively prevented. Furthermore, since eddy current loss can be generated directly in the rotor, the present invention allows the rotor to be heated more efficiently than when the stator side is heated and the rotor side is heated by the resulting radiant heat. While the AC magnetic field heats the rotor, it also generates an attractive force on the rotor. This attractive force causes the rotor to vibrate. However, if the magnetic field frequency is ω res By making it larger than / √2, it is possible to reduce vibration of the rotor compared to when a DC magnetic field of the same magnitude of magnetic flux density is made to cross the rotor.

[0013] Furthermore, the present invention (claim 2) is characterized in that the rotating body is provided with an object to be heated that has a predetermined conductivity and is a target for crossing the AC magnetic field.

[0014] In this method, an object to be heated is provided on the rotor, so that eddy currents can be generated efficiently, and therefore the rotor can be heated with high efficiency.

[0017] Furthermore, the present invention (claims 3 )teeth, a rotating body, a motor for driving the rotating body to rotate, a motor power supply for supplying electric power for driving the motor to rotate, a heating electromagnet for generating an AC magnetic field of a predetermined magnetic field frequency to heat the rotating body, and a heating power supply for supplying electric power to the heating electromagnet by AC current, wherein the AC magnetic field generated by the heating electromagnet is caused to cross the rotating body, thereby generating an eddy current around the crossed AC magnetic field in the rotating body, The magnetic field frequency is higher than a rated rotation frequency defined based on the mechanical angle of the rotor.

[0018] Generally, the spectrum of pump vibrations generated by the rotation of the rotor shows a large peak of the rotor's rotational frequency component. This peak frequency varies depending on the operating state, and its maximum value is the rated rotational frequency defined based on the rotor's mechanical angle. Therefore, if the frequency of the AC magnetic field generated by the heating electromagnet is higher than the rated rotational frequency defined based on the rotor's mechanical angle, the peak of the pump vibration spectrum generated by the AC magnetic field will not coincide with the peak of the vibration spectrum generated by the rotor's rotation. This makes it possible to reduce pump vibrations.

[0019] Furthermore, the present invention (claims 4 )teeth, a rotating body, a motor for driving the rotating body to rotate, a motor power supply for supplying electric power for driving the motor to rotate, a heating electromagnet for generating an AC magnetic field of a predetermined magnetic field frequency to heat the rotating body, and a heating power supply for supplying electric power to the heating electromagnet by AC current, wherein the AC magnetic field generated by the heating electromagnet is caused to cross the rotating body, thereby generating an eddy current around the crossed AC magnetic field in the rotating body, The magnetic field frequency is higher than the frequency of the current flowing through the motor at rated rotation.

[0020] Generally, the spectrum of pump vibrations caused by the current flowing through the motor shows a large peak due to the frequency component of the current flowing through the motor. This peak frequency varies depending on the operating state, with the maximum value being the frequency of the current flowing through the motor at its rated speed. Therefore, if the frequency of the AC magnetic field generated by the heating electromagnet is higher than the frequency of the current flowing through the motor at its rated speed, the peak of the pump vibration spectrum caused by the AC magnetic field will not coincide with the peak of the vibration spectrum caused by the current flowing through the motor. This makes it possible to reduce pump vibrations.

[0021] Furthermore, the present invention (claims 5)teeth, a rotating body, a motor for driving the rotating body to rotate, a motor power supply for supplying electric power for driving the motor to rotate, a heating electromagnet for generating an AC magnetic field of a predetermined magnetic field frequency to heat the rotating body, and a heating power supply for supplying electric power to the heating electromagnet by AC current, wherein the AC magnetic field generated by the heating electromagnet is caused to cross the rotating body, thereby generating an eddy current around the crossed AC magnetic field in the rotating body, The motor inverter converts the output voltage of the motor power supply and applies a voltage to the motor, and the motor inverter controller controls the motor inverter, and the magnetic field frequency is greater than half the control frequency of the motor inverter controller.

[0022] If the magnetic field frequency is greater than half the control frequency of the motor inverter controller, heating can be achieved with an AC magnetic field of a higher frequency than when the motor inverter passes an AC current superimposed on the current flowing in the motor and generates an AC magnetic field for heating superimposed on the motor's magnetic field to heat the rotor. As a result, the magnetic flux density of the AC magnetic field required to obtain the same eddy current loss in the rotor can be reduced, the external force generated in the rotor by the AC magnetic field can be reduced, and vibration of the rotor can be reduced.

[0023] Furthermore, the present invention (claims 6 )teeth, a rotating body, a motor for driving the rotating body to rotate, a motor power supply for supplying electric power for driving the motor to rotate, a heating electromagnet for generating an AC magnetic field of a predetermined magnetic field frequency to heat the rotating body, and a heating power supply for supplying electric power to the heating electromagnet by AC current, wherein the AC magnetic field generated by the heating electromagnet is caused to cross the rotating body, thereby generating an eddy current around the crossed AC magnetic field in the rotating body, The magnetic bearing comprises a magnetic bearing that supports the rotating body in the air, a magnetic bearing power supply that supplies power to the magnetic bearing, a magnetic bearing inverter that converts the output voltage of the magnetic bearing power supply and applies voltage to the magnetic bearing, and a magnetic bearing inverter controller that controls the magnetic bearing inverter, wherein the magnetic field frequency is greater than half the control frequency of the magnetic bearing inverter controller.

[0024] If the magnetic field frequency is greater than half the control frequency of the magnetic bearing inverter controller, heating can be achieved with an AC magnetic field of a higher frequency than when the magnetic bearing inverter passes an AC current superimposed on the current flowing in the magnetic bearing and generates an AC magnetic field for heating superimposed on the magnetic field of the magnetic bearing to heat the rotor. As a result, the magnetic flux density of the AC magnetic field required to obtain the same eddy current loss in the rotor can be reduced, the external force generated in the rotor by the AC magnetic field can be reduced, and vibration of the rotor can be reduced.

[0025] Furthermore, the present invention (claims 7 )teeth, a rotating body, a motor for driving the rotating body to rotate, a motor power supply for supplying electric power for driving the motor to rotate, a heating electromagnet for generating an AC magnetic field of a predetermined magnetic field frequency to heat the rotating body, and a heating power supply for supplying electric power to the heating electromagnet by AC current, wherein the AC magnetic field generated by the heating electromagnet is caused to cross the rotating body, thereby generating an eddy current around the crossed AC magnetic field in the rotating body,The device comprises a magnetic bearing that supports the rotating body in a suspended state in the air, a magnetic bearing power supply that supplies power to the magnetic bearing, a displacement sensor that measures the position of the rotating body non-contactly based on a position signal modulated at a predetermined sensor frequency, and a demodulation circuit that includes a low-pass filter that demodulates the position signal, and is characterized in that the magnetic field frequency is higher than the cutoff frequency of the low-pass filter.

[0026] If the magnetic field frequency is higher than the cutoff frequency of the low-pass filter that demodulates the position signal of the displacement sensor, the pump vibration component generated by the AC magnetic field contained in the demodulated position signal of the displacement sensor will be small. As a result, the pump vibration generated by the AC magnetic field will not affect the position control of the rotor, allowing for more stable magnetic bearing control.

[0027] Furthermore, the present invention (claims 8 )teeth, a rotating body, a motor for driving the rotating body to rotate, a motor power supply for supplying electric power for driving the motor to rotate, a heating electromagnet for generating an AC magnetic field of a predetermined magnetic field frequency to heat the rotating body, and a heating power supply for supplying electric power to the heating electromagnet by AC current, wherein the AC magnetic field generated by the heating electromagnet is caused to cross the rotating body, thereby generating an eddy current around the crossed AC magnetic field in the rotating body, The magnetic bearing supports the rotating body in a suspended state in the air, a power supply for the magnetic bearing supplies power to the magnetic bearing, and a displacement sensor measures the position of the rotating body in a non-contact manner based on a position signal modulated at a predetermined sensor frequency, and the magnetic field frequency is greater than the sensor frequency.

[0028] If the magnetic field frequency is greater than the sensor frequency, the pump vibration component generated by the AC magnetic field and included in the displacement sensor position signal will be smaller, so the pump vibration generated by the AC magnetic field will not affect the position control of the rotor, enabling more stable magnetic bearing control.

[0029] Furthermore, the present invention (claims 9 ) is characterized in that the heating power source is also used as the motor power source.

[0030] The heating electromagnet is supplied with AC current from the motor power supply, which allows for a space-saving and inexpensive configuration.

[0031] Furthermore, the present invention (claims 10) is characterized in that it comprises a magnetic bearing that supports the rotating body in the air and a magnetic bearing power supply that supplies power to the magnetic bearing, and the heating power supply also serves as the magnetic bearing power supply.

[0032] The heating electromagnet is supplied with AC current from the magnetic bearing power supply, which allows for a space-saving and inexpensive configuration.

[0033] Furthermore, the present invention (claims 11 ) is characterized in that the heating power source is also used as the magnetic bearing power source.

[0034] The heating electromagnet is supplied with AC current from the magnetic bearing power supply, which allows for a space-saving and inexpensive configuration. [Effects of the Invention]

[0035] As described above, according to the present invention, a heating electromagnet that generates an AC magnetic field of a predetermined magnetic field frequency is provided to heat a rotating body, and the AC magnetic field generated by the heating electromagnet is configured to cross the rotating body. Therefore, the AC magnetic field generates eddy currents around the crossed AC magnetic field in the rotating body. These eddy currents generate eddy current loss, allowing the rotating body to be heated. Because the magnetic field generated by the heating electromagnet is an AC magnetic field, eddy current loss can be generated even when the rotating body is stopped. Since deposits are expected to form even when the pump is stopped, the formation of deposits can be effectively prevented. Furthermore, because eddy current loss can be generated directly in the rotating body, the rotating body can be heated with high efficiency. [Brief explanation of the drawings]

[0036] [Figure 1] FIG. 1 is a diagram illustrating the configuration of a turbomolecular pump used in an embodiment of the present invention. [Figure 2] Control device power supply configuration diagram [Figure 3] Diagram showing how an external force is generated by an AC magnetic field [Figure 4] Configuration diagram of forced vibration model [Figure 5] Diagram showing the relationship between amplitude and frequency [Figure 6] PWM control timing chart [Figure 7] A diagram explaining the cutoff frequency of the low-pass filter when extracting the position signal. [Figure 8] Example of a 4-pole heating device configuration [Figure 9] Another example of a 4-pole heating device configuration [Figure 10] Another example of a two-pole heating device configuration [Figure 11] A diagram explaining how to install a heating device on a turbomolecular pump. [Figure 12] Diagram of the heating device installed at the location indicated by arrow A [Figure 13] Diagram of the heating device installed at the location indicated by arrow B [Figure 14] Diagram of the heating device installed at the locations indicated by arrows C and D [Figure 15] Example of applying a heating device to a centrifugal pump [Figure 16] Example of heating devices installed at multiple locations on the pump [Figure 17] Example of supplying AC current by connecting heating devices in series [Figure 18] Example of supplying AC current by connecting heating devices in parallel [Figure 19] An example in which a heating power supply is installed independently for each heating device [Figure 20] An example where the motor power supply also serves as the heating power supply DETAILED DESCRIPTION OF THE INVENTION

[0037] An embodiment of the present invention will now be described. FIG. 1 shows a configuration diagram of a turbomolecular pump used in an embodiment of the present invention. In FIG. 1, a turbomolecular pump 100 has an intake port 101 formed at the upper end of a cylindrical outer tube 127. Inside the outer tube 127, a rotor 103 is provided, the rotor 103 having a plurality of rotors 102 (102a, 102b, 102c, etc.) which are turbine blades for sucking and exhausting gas and arranged radially and in multiple stages around its periphery. A rotor shaft 113 is attached to the center of the rotor 103, and the 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 a metal such as aluminum or an aluminum alloy.

[0038] 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 rotating body 103 fixed thereto, and send the detected displacement to a central processing unit (CPU) (not shown) inside the control device 200 shown in FIG. 2.

[0039] This central processing unit is equipped with the functions of a magnetic bearing controller, and for example, a compensation circuit having a PID adjustment function generates an excitation control command signal for the upper radial electromagnet 104 based on the position signal detected by the upper radial sensor 107, and the magnetic bearing inverter 16 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.

[0040] 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.

[0041] 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 the axial position signal is sent to a central processing unit (CPU) of control device 200.

[0042] In the magnetic bearing controller mounted on the central processing unit, a compensation circuit having, for example, a PID adjustment function generates excitation control command signals for each of the axial electromagnets 106A and 106B based on the axial position signal detected by the axial sensor 109, and the magnetic bearing inverter 16 controls the excitation of each 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.

[0043] In this way, the control device 200 appropriately adjusts the magnetic force exerted on the metal disk 111 by the axial electromagnets 106A and 106B, magnetically levitating the rotor shaft 113 in the axial direction and holding it in space without contact.

[0044] 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.

[0045] 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. 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.

[0046] 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.). 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.

[0047] Furthermore, depending on the application of the turbomolecular pump 100, a threaded spacer 131 is disposed between the lower portion of the stator 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 multiple 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 rotor blades 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.

[0048] 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.

[0049] 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 fixed blades 123 causes exhaust gas to be drawn in from a chamber (not shown) through the intake port 101. The rotation 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 fixed blades 123 and is transferred to the base part 129.

[0050] In the above description, the threaded spacer 131 is disposed on the outer periphery of the cylindrical portion 102d of the rotor 103, and the thread groove 131a is formed on the inner circumferential surface of the threaded spacer 131. However, there are also cases where the thread groove is formed on the outer circumferential surface of the cylindrical portion 102d, and a spacer having a cylindrical inner circumferential surface is disposed around the outer circumferential surface of the cylindrical portion 102d.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] For example, when SiCl4 is used as the process gas in an Al etching system, the low vacuum (760 [torr] to 10 -2 The vapor pressure curve shows that at low pressures (approximately 20°C) and pressures of 100[torr], 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 threaded spacer 131.

[0056] 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).

[0057] Next, the heating control of the rotor 103 will be described. As mentioned above, heating has traditionally been performed on the base portion 129 side, but in recent years, there has been a demand for further heating, including the rotor 103 side, in order to improve the operating efficiency of the pump by preventing the accumulation of products. A method for controlling the heating of the rotating body 103 in this manner will be described with reference to Figures 1 and 2. In Figure 1, two-pole heating electromagnets 3A and 3B are arranged opposite each other across the rotor shaft 113 between the protective bearing 1 and the upper radial sensor 107. These heating electromagnets 3A and 3B correspond to the heating device 3, and as shown in Figure 2, an AC current is supplied to this heating device 3 from a heating power source 21. This AC current excites the heating electromagnets 3A and 3B, generating an AC magnetic field.

[0058] In this configuration, the generated AC magnetic field intersects with the rotor shaft 113. Eddy currents are generated around the intersecting AC magnetic field. At this time, a conductive object to be heated (not shown) may be fixed to the rotor shaft 113, and the AC magnetic field may penetrate this object to generate eddy currents. Examples of materials for the object to be heated include conductive metals such as iron, stainless steel, and aluminum, but ferromagnetic materials such as iron and stainless steel are more preferable. The rotating body 103 is then heated by these eddy currents.

[0059] The AC magnetic field may be a sine wave, or other waveforms such as a square wave or a triangular wave, or a combination of these. A DC magnetic field may be offset from the AC magnetic field. In the case of other waveforms, the fundamental wave component of each waveform is considered to be the frequency of the magnetic field.

[0060] Regarding the eddy current loss that occurs at this time, according to page 59 ((2) Eddy current loss) of "Magnetic Bearing Guidebook for Rotating Machine Designers" published by Japan Industrial Publishing, the plate thickness t, the frequency f of the magnetic field fluctuation, the volume V of the magnetic material subjected to the magnetic field fluctuation, and the maximum magnetic flux density B m , and the specific resistance of the magnetic material is defined as ρ, and the eddy current loss P e can be expressed by the following equation. [Number 1] According to TIFF0007756504000001.tif13170 number 1, eddy current loss P e It can be seen that increases with the square of the frequency of the AC magnetic field. Therefore, by using an AC magnetic field, the eddy current loss P e The heat generated by the eddy current loss P e The magnetic flux density B required to obtain m It can be seen that decreases in inverse proportion to the fluctuating frequency f of the magnetic field.

[0061] In addition, when an AC magnetic field crosses the rotor 103, eddy current loss P e This can occur even when the rotation of the rotor shaft 113 is stopped. Since deposits are expected to occur even when the pump is stopped, the formation of deposits can be effectively prevented.

[0062] Next, we will consider vibrations of the rotor 103 and the pump. Vibrations of the rotor 103 can cause failure of the rotor 103. In particular, in a pump that uses a magnetic bearing to levitate the rotor 103, increased vibration of the rotor 103 can make it impossible to control the magnetic bearing, and touchdown, in which the rotor shaft 113 comes into contact with the protective bearings 1 and 120, may occur. Furthermore, vibrations of the rotor 103 are transmitted to the entire pump via the bearings, motor 121, etc.

[0063] Furthermore, the stator of the pump includes upper radial electromagnet 104, lower radial electromagnet 105, and axial electromagnets 106A and 106B that constitute the magnetic bearings, as well as electromagnets of motor 121 and heating electromagnets 3A and 3B of heating device 3. In these electromagnets, current flows through the coils to generate a magnetic field, which causes the core to deform due to interaction between the magnetic field and the core, resulting in vibration. This vibration is transmitted throughout the pump.

[0064] These vibrations may result in noise generation and adversely affect the semiconductor manufacturing process due to the vibrations being transmitted to the chamber (not shown) through the intake port 101. Therefore, it is desirable to suppress the vibrations of the rotating body and the pump as much as possible.

[0065] The vibration of the rotor 103 caused by the AC magnetic field crossing the rotor shaft 113 will be examined. Eddy current loss P e When an AC magnetic field is made to cross the rotor shaft 113 to generate an external force, this AC magnetic field generates an external force. The state in which this AC magnetic field generates an external force is shown in FIG. 3. FIG. 3 shows the state of the magnetic field and external force in the two-pole arrangement shown in FIG. 1 and FIG. 2. In the case of an isotropic pole arrangement, ideally, the left and right external forces F L and F R However, in reality, external forces are generated on the rotor shaft 113 due to factors such as variations in shape due to machining precision, eccentricity of the rotor shaft 113 due to imbalance, and variations in the magnetic properties of the material. Also, even in the case of an anisotropic pole arrangement, external forces may be generated on the rotor shaft 113. For this reason, in order to rotate the rotor 103 stably with low vibration, it is necessary to minimize the external force F on the rotor shaft 113. L、 F R It is desirable to reduce

[0066] External force F generated when the AC magnetic field crosses the rotor shaft 113 R is the magnetic flux density B in the gap between the heating electromagnet 3B and the rotor shaft 113 as shown in Equation 2. g is proportional to the square of [Number 2] TIFF0007756504000002.tif9170 Here is the external force F of number 2 R proportionality constant K g Using this, we define number 3. [Number 3] TIFF0007756504000003.tif9170

[0067] Magnetic flux density B in the gap at time t g The amplitude B of Equation 4 g1 , assuming a sine wave with angular frequency ω0, [Number 4] TIFF0007756504000004.tif7170External force F acting on rotor shaft 113 R becomes the number 5. [Number 5] TIFF0007756504000005.tif11170

[0068] Here, the number is 6, [Number 6] TIFF0007756504000006.tif7170B g1 If we can reduce it to 1 / n, the external force F R The maximum value of 2 It will double. This external force F R The influence of external force is examined using the forced vibration model in Figure 4. Here, we define k as the spring constant in the direction of the external force of the rotor and stator, γ as the damping coefficient in the direction of the external force of the rotor and stator, m as the mass of the rotor, and F as the external force applied by the magnetic field.

[0069] At this time, the natural angular frequency ω of the rigid body mode of the rotor in the direction in which the external force is applied is res teeth [Number 7] If we define TIFF0007756504000007.tif15170, then when the attenuation coefficient γ is Equation 8, we obtain Equation 9. [Number 8] TIFF0007756504000008.tif11170[number 9] TIFF0007756504000009.tif9170

[0070] On the other hand, when the attenuation coefficient γ is expressed by Equation 10, it is defined as Equation 11. [Number 10] TIFF0007756504000010.tif11170[number 11] TIFF0007756504000011.tif7170

[0071] In this case, if the AC current satisfies equation 12, the displacement of rotor shaft 113 (response to forced vibration) for the same magnetic flux density will be smaller than in the case of DC current as expressed in equation 13. The higher the frequency of the AC magnetic field, the smaller this displacement will be. Figure 5 shows what happens during this period. [Number 12] TIFF0007756504000012.tif12170[number 13] TIFF0007756504000013.tif7170

[0072] Next, we will prove this forced vibration model. The equation of motion for the forced vibration model is given by equation 14, and F / m is assumed to be a sine wave based on the forced vibration of equation 15. Here, x is the displacement of the rotor shaft, and ω1 is the angular frequency of the external force F. [Number 14] TIFF0007756504000014.tif12170[number 15] TIFF0007756504000015.tif11170

[0073] If the solution for x is number 16, then a becomes number 17. [Number 16] TIFF0007756504000016.tif7170[number 17] TIFF0007756504000017.tif13170When a DC magnetic field is made to cross the rotor axis, that is, when ω0 = 0, the external force F is given by equation 18, so ω1 = 0 and a is given by equation 19. [Number 18] TIFF0007756504000018.tif10170[number 19] TIFF0007756504000019.tif16170

[0074] On the other hand, when an AC magnetic field crosses the rotor shaft, the external force F is expressed as the sum of DC and AC components. [Number 20] TIFF0007756504000020.tif11170The amplitude a of the rotor shaft 113 for the DC component of the force is given by the equation 21. [Number 21] TIFF0007756504000021.tif12170

[0075] Therefore, if the amplitude of the AC component of the external force with angular frequency ω1 is less than 22, the amplitude of the displacement of the rotor shaft 113 due to the forced vibration caused by the AC magnetic field is smaller than when a DC magnetic field having the same maximum magnetic flux density as the AC magnetic field is applied. [Number 22] TIFF0007756504000022.tif12170ω1, which is the number 23, is the number 24. Also, ω0 and ω1 are related by the number 25. [Number 23] TIFF0007756504000023.tif13170[number 24] TIFF0007756504000024.tif8170[number 25] TIFF0007756504000025.tif7170

[0076] Therefore, at the frequency of the AC magnetic field that satisfies Equation 26, the amplitude of displacement of rotor shaft 113 due to forced vibration caused by the AC magnetic field is smaller than when a DC magnetic field having the same maximum magnetic flux density as the AC magnetic field is applied. [Number 26] TIFF0007756504000026.tif12170

[0077] Next, we will consider the vibrations that occur in the pump due to the AC magnetic field generated by heating electromagnets 3A and 3B of the heating device. In Figure 3, heating electromagnets 3A and 3B are composed of core 6, which is mainly made of laminated steel plate or ferrite, and coils 4a and 4b wound around salient poles 7a and 7b of core 6. When AC current supplied from the heating power supply flows through coils 4a and 4b, a magnetomotive force is generated, and an AC magnetic field of the same frequency as the AC current is generated in core 6. The generated AC magnetic field crosses rotor shaft 113 through a gap, forming closed loops 5a and 5b of magnetic field lines.

[0078] When an AC magnetic field is generated, the interaction between the AC magnetic field and core 6 causes deformation of core 6, and vibrations of the frequency components of the AC magnetic field are generated in heating electromagnets 3A and 3B. These vibrations of heating electromagnets 3A and 3B are transmitted to the entire pump via the joints between heating electromagnets 3A and 3B and the pump.

[0079] Next, we will consider the vibration of the rotor 103 that occurs due to its rotation. When the rotor 103 rotates, an external force is applied to the rotor 103 due to factors such as variations in shape due to machining accuracy, eccentricity of the rotor 103 due to imbalance, and variations in the magnetic properties of the material, causing vibration. The spectrum of this vibration shows a large peak in the rotational frequency component of the rotor 103. This peak frequency changes depending on the operating state, and the maximum value is the rated rotational frequency defined based on the mechanical angle of the rotor 103.

[0080] Therefore, when the frequency of the AC magnetic field generated by heating electromagnets 3A and 3B is higher than the rated rotational frequency defined based on the mechanical angle of rotor 103, the peak of the vibration spectrum of the pump generated by the AC magnetic field does not coincide with the peak of the vibration spectrum generated by the rotation of rotor 103. Therefore, the peak of the vibration spectrum of the pump can be reduced.

[0081] Next, we will consider the vibration of the pump caused by the current flowing through the motor 121. The motor 121 consists of a stator, which is an electromagnet with a coil wound around a core and is fixed to the pump, and a rotor, which transmits torque generated by interaction with the magnetic field generated by the stator to a rotor. If the motor 121 is, for example, a permanent magnet synchronous motor, the frequency of the current at rated rotation is equal to the electrical angular frequency, and this electrical angular frequency can be calculated by multiplying the mechanical angular frequency by the number of pole pairs.

[0082] In the stator of the motor 121, the interaction between the magnetic field and the core causes deformation of the core, generating vibrations of the frequency components of the current flowing through the motor. These vibrations are transmitted to the entire pump via the joint between the motor and the pump.

[0083] The motor 121 is driven by PWM (Pulse Width Modulation) control using the motor inverter 18. As shown in FIG. 6, this PWM control is performed at a period t0. The control frequency f0 = 1 / t0 corresponds to the control frequency of the motor inverter controller. The frequency f of the voltage that the motor inverter 18 can output is f = f0 / 2, which is half the control frequency f0. In other words, if the rotating body 103 is heated by an AC magnetic field at a frequency greater than twice the control frequency of the motor inverter controller, heating can be performed with an AC magnetic field of a higher frequency than when the motor inverter 18 heats the rotating body 103 by superimposing an AC current on the current flowing through the motor 121 and generating an AC magnetic field for heating by superimposing it on the magnetic field of the motor 121. Therefore, the magnetic flux density of the AC magnetic field required to obtain the same eddy current loss of the rotating body 103 can be reduced, the external force generated on the rotating body 103 by the AC magnetic field can be reduced, and the vibration of the rotating body 103 can be reduced.

[0084] Furthermore, this point also applies to PWM control using the magnetic bearing inverter 16 that controls the magnetic bearing. The timing chart is the same as in FIG. 6 and is therefore omitted. As in FIG. 6, the PWM control that controls the magnetic bearing is also controlled with a period t0. In other words, if the rotating body 103 is heated using an AC magnetic field with a frequency greater than twice the control frequency of the magnetic bearing inverter controller, heating can be performed with an AC magnetic field of a higher frequency than when the magnetic bearing inverter 16 heats the rotating body 103 by passing an AC current superimposed on the current flowing through the magnetic bearing and generating an AC magnetic field for heating superimposed on the magnetic field of the magnetic bearing. Therefore, the magnetic flux density of the AC magnetic field required to obtain the same eddy current loss of the rotating body 103 can be reduced, the external force generated on the rotating body 103 by the AC magnetic field can be reduced, and the vibration of the rotating body 103 can be reduced.

[0085] Furthermore, an inductance sensor or an eddy current sensor is used for the lower radial sensor 108 and the upper radial sensor 107. A modulated wave of a predetermined sensor frequency is superimposed on the displacement signals detected by the lower radial sensor 108 and the upper radial sensor 107, and based on this modulated wave, an optimum frequency for the AC magnetic field generated by the heating electromagnets 3A and 3B will be determined.

[0086] 7, the position signals output from the lower radial sensor 108 and the upper radial sensor 107 are demodulated by a demodulation circuit 11 including a low-pass filter (LPF), and then the signals are adjusted by a magnetic bearing controller 13, which then excites and drives the lower radial electromagnet 105 and the upper radial electromagnet 104. If the frequency of the AC magnetic field generated by the heating electromagnet 3A and the heating electromagnet 3B is higher than the cutoff frequency of the low-pass filter (the frequency that is 3 dB lower than the flat part of the passband), the pump vibration component generated by the AC magnetic field, which is included in the demodulated position signal of the displacement sensor, becomes smaller. Therefore, the pump vibration generated by the AC magnetic field does not affect the position control of the rotor 103, and more stable magnetic bearing control can be achieved.

[0087] Furthermore, if the frequency of the AC magnetic field generated by heating electromagnets 3A and 3B is greater than the sensor frequency, the pump vibration component generated by the AC magnetic field and included in the position signal of the displacement sensor will be smaller. As a result, the pump vibration generated by the AC magnetic field will not affect the position control of rotor 103, enabling more stable magnetic bearing control to be achieved.

[0088] 1 and 2 show an example of heating device 3 configured with two poles, heating electromagnet 3A and heating electromagnet 3B, while Fig. 8 shows an example of the configuration of a heating device with four poles. In this case, heating device 23 includes heating electromagnet 23A, heating electromagnet 23B, heating electromagnet 23C, and heating electromagnet 23D, which are spaced 90 degrees apart from one another around rotor shaft 113, and coils 24a, 24b, 24c, and 24d are evenly positioned relative to salient pole portions 27a, 27b, 27c, and 27d of core 26. A magnetic field passes through rotor shaft 113, and four closed magnetic field loops 25a, 25b, 25c, and 25d are formed around rotor shaft 113, passing through salient pole portions 27a, 27b, 27c, and 27d.

[0089] 9 shows another example of the configuration of a heating device with four poles. In this case, heating device 31 has heating electromagnets 33A and 33B each consisting of coils 34a and 34b disposed around two salient poles 37a and 37b of U-shaped core 36a, forming a closed loop 35a of a magnetic field in the positive direction of the x-axis, while heating electromagnets 33C and 33D each consisting of coils 34c and 34d disposed around two salient poles 37c and 37d of U-shaped core 36b, forming a closed loop 35b of a magnetic field in the negative direction of the x-axis.

[0090] 10 shows another example of the configuration of a heating device with two poles. In this case, heating device 41 is configured such that heating electromagnets 33A and 33B, each consisting of coils 34a and 34b respectively disposed on two salient poles 37a and 37b of U-shaped core 36a, form a closed loop 35a of magnetic field only in the positive direction of the x-axis. Even in this asymmetric configuration, eddy current loss P e can be generated.

[0091] The coils of the heating electromagnets are preferably connected in series to one heating power source, but the coils of the heating electromagnets may be connected in parallel, or a plurality of heating power sources may be provided for the coils.

[0092] Furthermore, the core material of each heating electromagnet is preferably one with low electrical conductivity and high magnetic permeability, such as laminated steel plate or ferrite. However, ordinary iron or stainless steel, for example, may also be used. This configuration is useful when heating the stator side simultaneously with the rotor. It is also possible to use a non-magnetic metal such as aluminum, an insulator such as plastic, or an air-core coil without a core material as the heating electromagnet.

[0093] Next, a method of installing a heating device in a turbo molecular pump 100 will be described with reference to Fig. 11. First, the heating device 41 installed at the location indicated by arrow A in Fig. 11 has a coil 43 wound in one direction around a rotor shaft 113 as shown in Fig. 12. Grooves are formed on the outer circumferential surface of the rotor shaft 113, and a conductive object to be heated 45 is embedded in the grooves. An AC current is passed through the coil 43, generating an AC magnetic field around it. This AC magnetic field crosses the object to be heated 45, generating an eddy current loss P e Therefore, the object to be heated 45 generates heat. Unlike conventional heating using radiant heat when heating the base part 129, the object to be heated 45 can be heated directly, and therefore the rotating body 103 can be heated efficiently.

[0094] 11 is configured by winding a coil 53 in one direction around a rotor shaft 113 as shown in FIG. An AC current is passed through the coil 53, generating an AC magnetic field around it. This AC magnetic field crosses the rotor 102, generating an eddy current in the rotor 102. This eddy current generates an eddy current loss P eTherefore, the rotor 102 generates heat. Since the rotor 102 can be heated directly, the rotor 103 can be heated efficiently.

[0095] Furthermore, the heating device 61 installed at the location indicated by arrow C in Figure 11 is configured by winding a coil 63 in one direction around the rotor shaft 113 inside the fixed blade spacer 125 or outer cylinder 127 as shown in Figure 14. An AC current is passed through the coil 63, generating an AC magnetic field around it. This AC magnetic field crosses the rotor 102, generating an eddy current in the rotor 102. This eddy current generates an eddy current loss P e Therefore, the rotor 102 generates heat. Since the rotor 102 can be heated directly, the rotor 103 can be heated efficiently.

[0096] Furthermore, the heating device 71 installed at the location indicated by arrow D in Figure 11 is configured by winding the coil 71 in one direction around the rotor shaft 113 inside a threaded spacer 131 as shown in Figure 14. An AC current is passed through the coil 71, generating an AC magnetic field around it. This AC magnetic field crosses the cylindrical portion 102d of the rotor 102, generating an eddy current in the rotor 102. This eddy current generates an eddy current loss P e Therefore, the rotor 102 generates heat. Since the rotor 102 can be heated directly, the rotor 103 can be heated efficiently. However, the coil 73 may be embedded on the stator column 122 side. Then, by causing the AC magnetic field generated by this coil 73 to cross the cylindrical portion 102d of the rotor 102, the eddy current loss P e may be generated.

[0097] Next, a case where the heating device of the present invention is applied to a centrifugal pump will be described. As shown in Fig. 15, a plurality of blades 81 are attached to the head of a rotor shaft 113. A coil 83 is disposed on the stator side so as to face the tip of the blade 81. An AC current is passed through this coil 83, generating an AC magnetic field around it. This AC magnetic field crosses the tip of the blade 81, generating an eddy current at the tip of the blade 81, and this eddy current causes eddy current loss P e This causes the blades 81 to generate heat. In order to heat the side of the blade 81, a coil 85 may be disposed facing the side of the blade 81. In this case, the AC magnetic field generated by the coil 85 crosses the side of the blade 81. Therefore, an eddy current is generated at the side of the blade 81, and this eddy current causes an eddy current loss P e can be generated.

[0098] Next, a method of connecting a heating power source when the heating device of the present invention is disposed at a plurality of locations on the pump will be described. Fig. 16 shows an example in which heating device 91 is provided for heating rotor shaft 113, while heating devices 93 and 95 are provided at two locations axially separated for heating blades 102. Heating power source 97 may supply AC current by connecting heating devices 91, 93, and 95 in series as shown in Fig. 17, or may supply AC current by connecting heating devices 91, 93, and 95 in parallel as shown in Fig. 18. Alternatively, as shown in Fig. 19, heating power sources 97A, 97B, and 97C may be provided independently for heating device 91, heating device 93, and heating device 95, respectively, to supply AC current.

[0099] 20, heating device 91 may be connected midway through the U-phase cable of motor 121, heating device 93 may be connected midway through the V-phase cable, and heating device 95 may be connected midway through the W-phase cable. In this case, motor power supply 19 and motor inverter 18 also serve as heating power supplies. Heating devices 91, 93, and 95 are supplied with AC current from motor power supply 19 and motor inverter 18. In this case, it is desirable to connect heating devices with the same resistance and inductance in series to each of the three phases of the motor. However, it is also possible to connect heating devices to only certain phases of the motor, to connect the motor and heating devices in parallel, or to have different resistances and inductances for each heating device.

[0100] Although not shown in the drawings, this also applies to the magnetic bearing power supply 17, and the magnetic bearing power supply 17 may be configured to also function as a heating power supply.

[0101] The heating power supply can be configured with an inverter, an LC resonant circuit, a linear amplifier, or the like. The heating power supply may also be configured, for example, by installing an inverter in parallel with the motor inverter and connecting its output to the heating device, so that the power of the motor power supply is supplied to the heating device. Furthermore, for example, if the motor power supply is an AC commercial power supply, the motor power supply may be connected directly to the heating device and used as the heating power supply. A similar configuration can be considered when using a power supply that also serves as a magnetic bearing power supply and a heating power supply.

[0102] It should be noted that the present invention can be modified in various ways without departing from the spirit of the present invention, and it goes without saying that the present invention also covers such modifications. Furthermore, the above-described embodiments may be combined in various ways. [Explanation of symbols]

[0103] 1 Protective Bearing 3, 23, 31, 41, 51, 61, 71, 91, 93, 95 Heating device 3A, 3B Heating electromagnet 4a, 4b, 24a, 24b, 24c, 24d, 34a, 34b, 34c, 34d coils 5a, 5b, 25a, 25b, 25c, 25d, 35a, 35b Closed loop magnetic field 6, 26, 36a, 36b Core 7a, 7b, 27a, 27b, 27c, 27d, 37a, 37b, 37c, 37d Salient pole part 11 Demodulation circuit 13 Magnetic bearing controller 16 Magnetic bearing inverter 17 Magnetic bearing power supply 18 Motor inverter 19 Motor power supply 21, 97, 97A, 97B, 97C Heating power supply 23A, 23B, 23C, 23D, 33A, 33B, 33C, 33D Heating electromagnet 43, 53, 63, 71, 73, 83, 85 coils 45 Heating object 81 Feather 100 Turbomolecular Pump 101 Air intake 102, 102a, 102b, 102c rotor blades 102d Cylindrical part 103 Rotating Body 104 Upper radial electromagnet 105 Lower radial electromagnet 106A, 106B Axial electromagnet 107 Upper radial sensor 108 Lower radial sensor 111 Metal Disc 113 Rotor shaft 120 Protective Bearing 121 Motor 122 Stator column 123, 123a, 123b, 123c fixed wing 125, 125a, 125b, 125c Fixed wing spacers 127 Outer cylinder 129 Base 131 Threaded spacer 131a screw groove 200 control device

Claims

1. A rotating body; a motor that rotates the rotor; a motor power supply that supplies power to the motor for rotational drive; a heating electromagnet that generates an AC magnetic field of a predetermined magnetic field frequency in order to heat the rotating body; a heating power supply that supplies power to the heating electromagnet by AC current; The AC magnetic field generated by the heating electromagnet is caused to cross the rotating body, thereby generating an eddy current around the crossed AC magnetic field in the rotating body; A vacuum pump characterized in that, when the rigid body mode natural frequency of the rotor is defined as ω res , the magnetic field frequency is greater than ω res / √2.

2. 2. A vacuum pump according to claim 1, wherein the rotor is provided with an object to be heated, which has a predetermined conductivity and is a target for crossing the AC magnetic field.

3. A rotating body, a motor that rotates the rotor; a motor power supply that supplies power to the motor for rotational drive; a heating electromagnet that generates an AC magnetic field of a predetermined magnetic field frequency in order to heat the rotating body; a heating power supply that supplies power to the heating electromagnet by AC current; The AC magnetic field generated by the heating electromagnet is caused to cross the rotating body, thereby generating an eddy current around the crossed AC magnetic field in the rotating body; A vacuum pump characterized in that the magnetic field frequency is greater than a rated rotational frequency defined based on the mechanical angle of the rotor.

4. A rotating body, a motor that rotates the rotor; a motor power supply that supplies power to the motor for rotational drive; a heating electromagnet that generates an AC magnetic field of a predetermined magnetic field frequency in order to heat the rotating body; a heating power supply that supplies power to the heating electromagnet by AC current; The AC magnetic field generated by the heating electromagnet is caused to cross the rotating body, thereby generating an eddy current around the crossed AC magnetic field in the rotating body; A vacuum pump characterized in that the magnetic field frequency is higher than the frequency of the current flowing through the motor at rated rotation.

5. A rotating body, a motor that rotates the rotor; a motor power supply that supplies power to the motor for rotational drive; a heating electromagnet that generates an AC magnetic field of a predetermined magnetic field frequency in order to heat the rotating body; a heating power supply that supplies power to the heating electromagnet by AC current; The AC magnetic field generated by the heating electromagnet is caused to cross the rotating body, thereby generating an eddy current around the crossed AC magnetic field in the rotating body; a motor inverter that converts the output voltage of the motor power supply and applies the voltage to the motor; a motor inverter controller for controlling the motor inverter; A vacuum pump characterized in that the magnetic field frequency is greater than half the control frequency of the inverter controller for the motor.

6. A rotating body, a motor that rotates the rotor; a motor power supply that supplies power to the motor for rotational drive; a heating electromagnet that generates an AC magnetic field of a predetermined magnetic field frequency in order to heat the rotating body; a heating power supply that supplies power to the heating electromagnet by AC current; The AC magnetic field generated by the heating electromagnet is caused to cross the rotating body, thereby generating an eddy current around the crossed AC magnetic field in the rotating body; a magnetic bearing that levitates and supports the rotating body in the air; a magnetic bearing power supply that supplies power to the magnetic bearing; a magnetic bearing inverter that converts the output voltage of the magnetic bearing power supply and applies the voltage to the magnetic bearing; a magnetic bearing inverter controller for controlling the magnetic bearing inverter, A vacuum pump characterized in that the magnetic field frequency is greater than half the control frequency of the magnetic bearing inverter controller.

7. A rotating body, a motor that rotates the rotor; a motor power supply that supplies power to the motor for rotational drive; a heating electromagnet that generates an AC magnetic field of a predetermined magnetic field frequency in order to heat the rotating body; a heating power supply that supplies power to the heating electromagnet by AC current; The AC magnetic field generated by the heating electromagnet is caused to cross the rotating body, thereby generating an eddy current around the crossed AC magnetic field in the rotating body; a magnetic bearing that levitates and supports the rotating body in the air; a magnetic bearing power supply that supplies power to the magnetic bearing; a displacement sensor that measures the position of the rotating body in a non-contact manner based on a position signal modulated at a predetermined sensor frequency; a demodulation circuit including a low-pass filter that demodulates the position signal; A vacuum pump characterized in that the magnetic field frequency is higher than the cutoff frequency of the low-pass filter.

8. A rotating body, a motor that rotates the rotor; a motor power supply that supplies power to the motor for rotational drive; a heating electromagnet that generates an AC magnetic field of a predetermined magnetic field frequency in order to heat the rotating body; a heating power supply that supplies power to the heating electromagnet by AC current; The AC magnetic field generated by the heating electromagnet is caused to cross the rotating body, thereby generating an eddy current around the crossed AC magnetic field in the rotating body; a magnetic bearing that levitates and supports the rotating body in the air; a magnetic bearing power supply that supplies power to the magnetic bearing; a displacement sensor that measures the position of the rotating body in a non-contact manner based on a position signal modulated at a predetermined sensor frequency, A vacuum pump characterized in that the magnetic field frequency is greater than the sensor frequency.

9. 9. The vacuum pump according to claim 1, wherein the heating power source also serves as the motor power source.

10. 6. The vacuum pump according to claim 1, further comprising: a magnetic bearing that supports the rotating body in a levitated state in the air; and a magnetic bearing power supply that supplies power to the magnetic bearing, wherein the heating power supply also serves as the magnetic bearing power supply.

11. 9. The vacuum pump according to claim 6, wherein the heating power source is also used as the magnetic bearing power source.

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