Vacuum pump, control device and control method

Abstract

To provide a vacuum pump, a control device, and a control method that can restrain the temperature of the control device from being excessively increased by stopping of cooling of the control device fixed to a vacuum pump body in a predetermined state of the vacuum pump body.SOLUTION: A vacuum pump 100 comprises a magnetic bearing type vacuum pump body 210, and a control device 200 fixed to the vacuum pump body 210. The control device 200 comprises a rotation control unit 226 for controlling the rotation of a rotor shaft 113, a temperature control unit 227 for controlling the temperature of the vacuum pump body 210, and a cooling unit 224 for cooling the control device 200. The temperature control unit 227 performs control so as to decrease the temperature of the control device 200 to a predetermined temperature or lower by decreasing a heating temperature caused by a heating unit 213 when detecting stopping of cooling in the cooling unit 224 in a predetermined state of the vacuum pump body 210.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a vacuum pump, a control device, and a control method.

Background Art

[0002] Semiconductor manufacturing equipment, liquid crystal manufacturing equipment, electron microscopes, surface analysis equipment, or microfabrication equipment, etc. need to make the environment inside the equipment in a high-vacuum state. A vacuum pump is used to make the inside of these devices in a high-vacuum state. As an example of the vacuum pump used, for example, a composite pump combining a turbo molecular pump and a screw groove pump can be mentioned.

[0003] A vacuum pump combining a turbo molecular pump and a screw groove pump has, for example, as disclosed in Patent Document 1, a screw groove pump disposed on the downstream side of a turbo pump having rotating blades and stationary blades arranged alternately in the axial direction. The exhaust gas taken in from the intake port is compressed by the turbo molecular pump and the screw groove pump and discharged to the outside of the vacuum pump from the exhaust port.

[0004] The screw groove pump is composed of a rotating rotor cylindrical portion and a screw groove spacer on the casing side that houses the rotor. Screw grooves are formed on the opposing surfaces of the rotor cylindrical portion or the screw groove spacer. Therefore, by rotating the rotor cylindrical portion inside the screw groove spacer, the gas can be transferred to the exhaust port side.

[0005] The exhaust gas shows the behavior of molecular flow in the turbo molecular pump, but in the screw groove pump and the flow path downstream thereof, due to the relatively high pressure, it shows a behavior like viscous flow. Therefore, by-products are likely to precipitate at locations where the flow of the exhaust gas stagnates in the screw groove pump and the flow path downstream thereof. When by-products precipitate in the flow path, an event occurs where locations that do not normally come into contact come into contact, which may cause damage to the vacuum pump and variations in the temperature distribution due to changes in the heat transfer performance of the internal structure, thereby impairing safety and productivity.

[0006] Therefore, the vacuum pump is equipped with a heater and cooling pipes, as well as a temperature sensor and control device. The temperature management system (TMS) of the control device controls heating by the heater and cooling by the cooling pipes based on the temperature sensor in order to maintain the vacuum pump temperature at a constant high temperature. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2010 / 060041 [Overview of the project] [Problems that the invention aims to solve]

[0008] Cooling of the control device is necessary due to the heat generated by the electronic components within the control device when power is supplied. In particular, in vacuum pumps where the control device is fixed to the vacuum pump body equipped with a turbomolecular pump and a screw groove pump, the temperature of the vacuum pump body is transferred to the control device, so the control device needs to be cooled at all times.

[0009] Incidentally, vacuum pumps sometimes stop the rotation of the rotor shaft in a standby state where the temperature is maintained at a predetermined high temperature in order to enable rapid start-up. In the standby state, heating by a heating unit and cooling by cooling pipes are performed to maintain the temperature of the vacuum pump body at the predetermined high temperature. If the cooling water is stopped in this standby state for maintenance or energy saving purposes, the control unit may overheat due to the rise in temperature of the entire vacuum pump by the heating unit and the heat generated by the electronic components of the control unit due to the power supply. When the vacuum pump detects an overheating abnormality in the control unit, a safety mechanism is activated and the power supply to the heating unit is cut off, causing the temperature of the entire vacuum pump to drop and making rapid start-up difficult.

[0010] The present invention has been made to solve the above-mentioned problems, and aims to provide a vacuum pump, a control device, and a control method that can suppress the temperature of a control device from rising too high by stopping the cooling of the control device fixed to the vacuum pump body in a predetermined state of the vacuum pump body. [Means for solving the problem]

[0011] The present invention, which achieves the above objective, is a vacuum pump having a magnetic bearing type vacuum pump body and a control device fixed to the vacuum pump body, wherein the vacuum pump body has a casing, a rotor shaft rotatably supported inside the casing, a magnetic bearing supporting the rotor shaft, a plurality of stages of rotor blades fixed to the rotor shaft and rotatable together with the rotor shaft, a plurality of stages of fixed blades fixed to the casing and arranged between the rotor blades, and a heating unit for heating the vacuum pump body, wherein the control device has a rotation control unit for controlling the rotation of the rotor shaft, a temperature control unit for controlling the temperature of the vacuum pump body, and a cooling unit for cooling the control device, wherein the temperature control unit, when it detects the cessation of cooling in the cooling unit in a predetermined state of the vacuum pump body, controls the temperature of the control device to be below a predetermined temperature by lowering the heating temperature of the heating unit.

[0012] The control device according to the present invention, which achieves the above objective, is a control device fixed to a magnetic bearing type vacuum pump body, and comprises a rotation control unit that controls the rotation of the rotor shaft of the vacuum pump body, a temperature control unit that controls the temperature of the vacuum pump body, and a cooling unit that cools the control device, wherein the temperature control unit, when it detects the cessation of cooling in the cooling unit in a predetermined state of the vacuum pump body, controls the temperature of the control device to be below a predetermined temperature by lowering the heating temperature of a heating unit arranged in the vacuum pump body.

[0013] A control method according to the present invention that achieves the above objective is a temperature control method performed by a control device fixed to a magnetic bearing type vacuum pump body, characterized by comprising: determining whether or not the cessation of cooling in a cooling unit that cools the control device has been detected in a predetermined state of the vacuum pump body; and, if the cessation of cooling in the cooling unit has been detected, controlling the temperature of the control device to be below a predetermined temperature by lowering the heating temperature of a heating unit arranged in the vacuum pump body. [Effects of the Invention]

[0014] The vacuum pump, control device, and control method configured as described above can prevent the temperature of the control device from rising too high because, when cooling in the cooling section of the control device stops in a predetermined state of the vacuum pump body, the heating temperature of the heating section that heats the vacuum pump body is reduced.

[0015] The predetermined state of the vacuum pump body may be an operating standby state in which the rotational speed of the rotor shaft is zero and acceleration is immediately possible. This allows the vacuum pump to suppress the temperature of the vacuum pump body from dropping too low due to heating by the heating unit while the operating standby state of the vacuum pump body is in place, and to suppress the temperature of the control device from rising too high when cooling in the cooling unit stops.

[0016] The control device may have a status transmitter that, when it detects that cooling in the cooling section has stopped in the predetermined state of the vacuum pump body, transmits information indicating a warning or information indicating that the heating temperature of the heating section of the vacuum pump body has been reduced to a low-temperature control state. This allows the vacuum pump to communicate to the outside that cooling in the cooling section has stopped, thereby improving safety.

[0017] The control device includes a first temperature sensor that measures the temperature of the control device. The vacuum pump body includes a second temperature sensor that measures the temperature of a portion heated by the heating unit. The temperature control unit receives temperature information detected by the first temperature sensor or the second temperature sensor, and when the temperature detected by the first temperature sensor or the second temperature sensor becomes equal to or higher than a predetermined threshold value, it may be determined that the cooling in the cooling unit has stopped. Thereby, the vacuum pump can effectively detect the stop of cooling in the cooling unit by using the temperature information detected by the temperature sensor.

[0018] The temperature control unit receives flow rate information detected by a flow rate sensor that detects the flow rate of the medium flowing through the cooling unit, and when the flow rate detected by the flow rate sensor is equal to or lower than a predetermined value, it may be determined that the cooling in the cooling unit has stopped. Thereby, the vacuum pump can effectively detect the stop of cooling in the cooling unit by using the flow rate information of the medium detected by the flow rate sensor.

Brief Description of the Drawings

[0019] [Figure 1] It is a longitudinal sectional view of a vacuum pump. [Figure 2] It is a circuit diagram of an amplifier circuit. [Figure 3] It is a time chart showing control when the current command value is larger than the detected value. [Figure 4] It is a time chart showing control when the current command value is smaller than the detected value. [Figure 5] It is a schematic configuration diagram of the vacuum pump according to the present embodiment. [Figure 6] It is a flowchart showing an example of the control flow in the temperature control unit of the control device. [Figure 7] It is a timing chart showing an example of temperature control by the control device. [Figure 8] It is a flowchart showing a modified example of the control flow in the temperature control unit of the control device.

Embodiments for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the dimensions in the drawings may be exaggerated for convenience of explanation and may differ from the actual dimensions. Also, in this specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

[0021] The vacuum pump 100 according to an embodiment of the present invention is a turbo molecular pump 100 that exhausts gas by the rotating blades of a rotating body rotating at high speed hitting and ejecting gas molecules. The turbo molecular pump 100 is used, for example, to suck and exhaust gas from a chamber such as a semiconductor manufacturing apparatus. First, the basic configuration of the turbo molecular pump 100 will be described.

[0022] A longitudinal sectional view of this turbo molecular pump 100 is shown in FIG. 1. In FIG. 1, an intake port 101 is formed at the upper end of a cylindrical outer cylinder 127 of the turbo molecular pump 100. And inside the outer cylinder 127, a rotor 103 is provided with a plurality of rotating blades 102 (102a, 102b, 102c ···) which are turbine blades for sucking and exhausting gas, formed radially and in multiple stages on the circumference. A rotor shaft 113 is attached to the center of this rotor 103, and this rotor shaft 113 is levitated and position-controlled in the air by, for example, a magnetic bearing with five-axis control. The rotor 103 is generally made of a metal such as aluminum or an aluminum alloy.

[0023] The upper radial electromagnet 104 consists of four electromagnets arranged in pairs along the X and Y axes. Four upper radial sensors 107 are provided in close proximity to the upper radial electromagnet 104, and each sensor corresponds to one of the upper radial electromagnets 104. The upper radial sensors 107 are, for example, inductance sensors or eddy current sensors with conduction windings, and detect the position of the rotor shaft 113 based on the change in the inductance of these conduction windings, which changes according to the position of the rotor shaft 113. These upper radial sensors 107 are configured to detect the radial displacement of the rotor shaft 113, i.e., the rotor 103 fixed to it, and send the data to the control device 200.

[0024] In this control device 200, for example, a compensation circuit having a PID adjustment function generates an excitation control command signal for the upper radial electromagnet 104 based on the position signal detected by the upper radial sensor 107, and the amplifier circuit 150 (described later) shown in Figure 2 controls the excitation of the upper radial electromagnet 104 based on this excitation control command signal, thereby adjusting the upper radial position of the rotor shaft 113.

[0025] The rotor shaft 113 is made of a high-permeability material (such as iron or stainless steel) and is attracted by the magnetic force of the upper radial electromagnet 104. This adjustment is performed independently in the X-axis and Y-axis directions. The lower radial electromagnet 105 and lower radial sensor 108 are arranged in the same way as the upper radial electromagnet 104 and upper radial sensor 107, and adjust the lower radial position of the rotor shaft 113 in the same way as the upper radial position.

[0026] Furthermore, axial electromagnets 106A and 106B are positioned above and below a disc-shaped metal disk 111 located at the bottom of the rotor shaft 113. The metal disk 111 is made of a high-permeability material such as iron. An axial sensor 109 is provided to detect the axial displacement of the rotor shaft 113, and its axial position signal is sent to the control device 200.

[0027] Then, in the control device 200, for example, a compensation circuit having a PID adjustment function generates excitation control command signals for the axial electromagnets 106A and 106B based on the axial position signal detected by the axial sensor 109, and the amplifier circuit 150 excites the axial electromagnets 106A and 106B based on these excitation control command signals, so that the axial electromagnet 106A attracts the metal disk 111 upward with magnetic force, and the axial electromagnet 106B attracts the metal disk 111 downward, thereby adjusting the axial position of the rotor shaft 113.

[0028] Thus, the control device 200 appropriately adjusts the magnetic force exerted by the axial electromagnets 106A and 106B on the metal disk 111, causing the rotor shaft 113 to levitate axially and be held in contact with space. The amplifier circuit 150 that excites and controls the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B will be described later.

[0029] On the other hand, the motor 121 is equipped with multiple magnetic poles arranged circumferentially around the rotor shaft 113. Each magnetic pole is controlled by the control device 200 to rotate the rotor shaft 113 via the electromagnetic force acting between it and the rotor shaft 113. The motor 121 also incorporates a rotational speed sensor, such as a Hall element, resolver, or encoder (not shown), and the rotational speed of the rotor shaft 113 is detected by the detection signal from this rotational speed sensor.

[0030] Furthermore, for example, a phase sensor (not shown) is attached near the lower radial sensor 108 to detect the phase of rotation of the rotor shaft 113. The control device 200 uses both the detection signals from this phase sensor and the rotational speed sensor to detect the position of the magnetic pole.

[0031] Multiple fixed blades 123 (123a, 123b, 123c...) are arranged with a small gap between them and the rotating blades 102 (102a, 102b, 102c...). Each of the rotating blades 102 (102a, 102b, 102c...) is formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transport exhaust gas molecules downward by collision. The fixed blades 123 (123a, 123b, 123c...) are made of metals such as aluminum, iron, stainless steel, copper, or alloys containing these metals as components.

[0032] Similarly, the fixed wing 123 is formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and is arranged alternately with the stages of the rotor blade 102 toward the inside of the outer cylinder 127. The outer edge of the fixed wing 123 is supported by being fitted between a plurality of stacked fixed wing spacers 125 (125a, 125b, 125c, etc.).

[0033] The fixed-wing spacer 125 is a ring-shaped member and is made of a metal such as aluminum, iron, stainless steel, or copper, or an alloy containing these metals as components. An outer cylinder 127 is fixed to the outer circumference of the fixed-wing spacer 125 with a small gap in between. A base portion 129 is provided at the bottom of the outer cylinder 127. An exhaust port 133 is formed in the base portion 129 and communicates with the outside. Exhaust gas that enters the intake port 101 from the chamber (vacuum chamber) side and is transferred to the base portion 129 is sent to the exhaust port 133.

[0034] Furthermore, depending on the application of the turbomolecular pump 100, a screw groove spacer 131 (fixing member) is provided between the lower part of the fixed-blade spacer 125 and the base part 129. The screw groove spacer 131 is a cylindrical member made of a metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals, and has multiple helical screw grooves 131a engraved on its inner circumferential surface. The direction of the helix of the screw grooves 131a is such that when exhaust gas molecules move in the direction of rotation of the rotor 103, these molecules are transported toward the exhaust port 133. A cylindrical part 102d hangs down from the lowest part following the rotor 103's rotating blades 102 (102a, 102b, 102c...). The outer surface of this cylindrical portion 102d is cylindrical and protrudes toward the inner surface of the screw groove spacer 131, and is in close proximity to the inner surface of the screw groove spacer 131 with a predetermined gap between them. The exhaust gas that has been transported to the screw groove 131a by the rotor blades 102 and the fixed blades 123 is guided by the screw groove 131a and sent to the base portion 129.

[0035] The base portion 129 is a disc-shaped component that forms the base of the turbomolecular pump 100, and is generally made of a metal such as iron, aluminum, or stainless steel. The base portion 129 not only physically holds the turbomolecular pump 100 but also functions as a heat conduction path, so it is desirable to use a metal that is rigid and has high thermal conductivity, such as iron, aluminum, or copper.

[0036] In this configuration, when the rotor blade 102 is rotated by the motor 121 together with the rotor shaft 113, exhaust gas is drawn in from the chamber through the intake port 101 due to the action of the rotor blade 102 and the fixed blade 123. The rotational speed of the rotor blade 102 is usually 20,000 rpm to 90,000 rpm, and the peripheral speed at the tip of the rotor blade 102 reaches 200 m / s to 400 m / s. The exhaust gas drawn in from the intake port 101 passes between the rotor blade 102 and the fixed blade 123 and is transferred to the base section 129. At this time, the temperature of the rotor blade 102 rises due to frictional heat generated when the exhaust gas comes into contact with the rotor blade 102 and heat conduction generated by the motor 121, but this heat is transferred to the fixed blade 123 side by radiation or conduction by gas molecules of the exhaust gas.

[0037] The fixed-wing spacers 125 are joined to each other at their outer circumference, and they transmit heat received by the fixed wing 123 from the rotor blade 102, as well as frictional heat generated when exhaust gases come into contact with the fixed wing 123, to the outside.

[0038] In the above description, the screw groove spacer 131 is positioned on the outer circumference of the cylindrical portion 102d of the rotor 103, and the screw groove 131a is engraved on the inner surface of the screw groove spacer 131. However, conversely, there are also cases where the screw groove is engraved on the outer circumference of the cylindrical portion 102d, and a spacer having a cylindrical inner surface is positioned around it.

[0039] Furthermore, depending on the application of the turbomolecular pump 100, the electrical components, which consist of an upper radial electromagnet 104, an upper radial sensor 107, a motor 121, a lower radial electromagnet 105, a lower radial sensor 108, axial electromagnets 106A, 106B, and an axial sensor 109, may be covered by a stator column 122 to prevent the gas drawn in from the intake port 101 from entering the electrical components, and the inside of this stator column 122 may be maintained at a predetermined pressure with purge gas.

[0040] In this case, piping (not shown) is provided in the base section 129, and purge gas is introduced through this piping. The introduced purge gas is sent to the exhaust port 133 through the gaps between the protective bearing 120 and the rotor shaft 113, between the rotor and stator of the motor 121, and between the stator column 122 and the inner cylindrical part of the rotor blade 102.

[0041] Here, the turbomolecular pump 100 requires model identification and control based on individually adjusted unique parameters (e.g., characteristics corresponding to the model). To store these control parameters, the turbomolecular pump 100 is equipped with an electronic circuit section 141 within its body. The electronic circuit section 141 consists of electronic components such as semiconductor memory such as EEP-ROM and semiconductor elements for accessing it, and a substrate 143 for mounting them. This electronic circuit section 141 is housed, for example, below a rotational speed sensor (not shown) near the center of the base section 129 that constitutes the lower part of the turbomolecular pump 100, and is closed by an airtight bottom cover 145.

[0042] Incidentally, in the semiconductor manufacturing process, some process gases introduced into the chamber have the property of becoming solid when their pressure exceeds a predetermined value or their temperature falls below a predetermined value. Inside the turbomolecular pump 100, the exhaust gas pressure is lowest at the intake port 101 and highest at the exhaust port 133. If the process gas pressure exceeds a predetermined value or its temperature falls below a predetermined value while it is being transferred from the intake port 101 to the exhaust port 133, the process gas becomes solid and adheres to and accumulates inside the turbomolecular pump 100.

[0043] For example, if SiCl4 is used as the process gas in an Al etching apparatus, the low vacuum (760 [torr] ~ 10 -2The vapor pressure curve shows that when the pressure is low (torr) and the temperature is low (approximately 20°C), solid products (e.g., AlCl3) precipitate and adhere to the inside of the turbomolecular pump 100. As a result, when process gas precipitates accumulate inside the turbomolecular pump 100, these deposits narrow the pump flow path, causing a decrease in the performance of the turbomolecular pump 100. Furthermore, the aforementioned products were prone to solidifying and adhering in areas with high pressure, such as near the exhaust port 133 and near the screw groove spacer 131.

[0044] Therefore, in order to solve this problem, conventional methods involve wrapping a heater (not shown) or an annular water-cooling pipe 149 around the outer circumference of the base portion 129, and embedding a temperature sensor (e.g., a thermistor) (not shown) in the base portion 129. Based on the signal from this temperature sensor, heating by the heater and cooling by the water-cooling pipe 149 are controlled (hereinafter referred to as TMS; Temperature Management System) to maintain the temperature of the base portion 129 at a constant high temperature (set temperature).

[0045] Next, we will describe an amplifier circuit 150 that energizes and controls the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B of the turbomolecular pump 100 configured in this way. The circuit diagram of this amplifier circuit 150 is shown in Figure 2.

[0046] In Figure 2, the electromagnet winding 151, which constitutes the upper radial electromagnet 104, has one end connected to the positive terminal 171a of the power supply 171 via transistor 161, and the other end connected to the negative terminal 171b of the power supply 171 via current detection circuit 181 and transistor 162. Transistors 161 and 162 are so-called power MOSFETs, and have a structure in which a diode is connected between their source and drain.

[0047] In this configuration, transistor 161 has its diode cathode terminal 161a connected to the positive terminal 171a, and its anode terminal 161b connected to one end of the electromagnet winding 151. Transistor 162 has its diode cathode terminal 162a connected to the current detection circuit 181, and its anode terminal 162b connected to the negative terminal 171b.

[0048] On the other hand, the diode 165 for current regeneration has its cathode terminal 165a connected to one end of the electromagnet winding 151, and its anode terminal 165b connected to the negative terminal 171b. Similarly, the diode 166 for current regeneration has its cathode terminal 166a connected to the positive terminal 171a, and its anode terminal 166b connected to the other end of the electromagnet winding 151 via the current detection circuit 181. The current detection circuit 181 is composed of, for example, a Hall sensor type current sensor or an electrical resistance element.

[0049] The amplifier circuit 150 configured as described above corresponds to one electromagnet. Therefore, if the magnetic bearing is 5-axis controlled and there are a total of 10 electromagnets 104, 105, 106A, and 106B, a similar amplifier circuit 150 is configured for each electromagnet, and the 10 amplifier circuits 150 are connected in parallel to the power supply 171.

[0050] Furthermore, the amplifier control circuit 191 is configured, for example, by a digital signal processor (hereinafter referred to as the DSP section) of the control device 200 (not shown), and this amplifier control circuit 191 is configured to switch transistors 161 and 162 on and off.

[0051] The amplifier control circuit 191 compares the current value detected by the current detection circuit 181 (the signal reflecting this current value is called the current detection signal 191c) with a predetermined current command value. Based on this comparison, it determines the magnitude of the pulse width (pulse width time Tp1, Tp2) to be generated within the control cycle Ts, which is one period of PWM control. As a result, gate drive signals 191a and 191b with this pulse width are output from the amplifier control circuit 191 to the gate terminals of transistors 161 and 162.

[0052] Furthermore, when the rotor 103 passes a resonance point during acceleration operation or when disturbances occur during constant-speed operation, it is necessary to control the position of the rotor 103 with high speed and strong force. For this reason, a high voltage of, for example, 50V 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 is usually connected between the positive electrode 171a and the negative electrode 171b of the power supply 171 to stabilize the power supply 171 (not shown).

[0053] In this configuration, when both transistors 161 and 162 are turned on, the current flowing through the electromagnet winding 151 (hereinafter referred to as the electromagnet current iL) increases, and when both are turned off, the electromagnet current iL decreases.

[0054] Furthermore, by turning one of transistors 161 and 162 on and the other off, a so-called flywheel current is maintained. By allowing this flywheel current to flow through the amplifier circuit 150, hysteresis loss in the amplifier circuit 150 can be reduced, and the overall power consumption of the circuit can be kept low. In addition, by controlling transistors 161 and 162 in this way, high-frequency noise such as harmonics generated in the turbomolecular pump 100 can be reduced. Moreover, by measuring this flywheel current with the current detection circuit 181, the electromagnet current iL flowing through the electromagnet winding 151 can be detected.

[0055] In other words, if the detected current value is smaller than the current command value, both transistors 161 and 162 are turned on only once during the control cycle Ts (e.g., 100 μs) for a duration corresponding to the pulse width time Tp1, as shown in Figure 3. Therefore, the electromagnet current iL during this period increases from the positive electrode 171a to the negative electrode 171b, towards the current value iLmax (not shown) that can flow through transistors 161 and 162.

[0056] On the other hand, if the detected current value is greater than the current command value, both transistors 161 and 162 are turned off only once during the control cycle Ts for a duration corresponding to the pulse width time Tp2, as shown in Figure 4. Therefore, during this period, the electromagnet current iL decreases from the negative electrode 171b towards the positive electrode 171a, towards a regenerative current value iLmin (not shown) via diodes 165 and 166.

[0057] In either case, after the pulse width time Tp1 and Tp2 have elapsed, one of transistors 161 or 162 is turned on. Therefore, during this period, the flywheel current is maintained in the amplifier circuit 150.

[0058] Next, the vacuum pump 100 according to this embodiment will be described. As shown in Figure 5, the vacuum pump 100 has a magnetic bearing type vacuum pump body 210 and a control device 200 fixed to the vacuum pump body 210. The method by which the control device 200 is fixed to the vacuum pump body 210 is not particularly limited and may be fixed directly or indirectly via other parts, for example, but the control device 200 is close enough to the vacuum pump body 210 that heat from the vacuum pump body 210 is transferred to the control device 200. The control device 200 is fixed, for example, to the base portion 129 in which the exhaust port 133 of the vacuum pump 100 is formed.

[0059] The vacuum pump body 210 includes a casing 211, a rotor shaft 113 rotatably supported inside the casing 211, a magnetic bearing 212 supporting the rotor shaft 113, multiple stages of rotor blades 102 fixed to the rotor shaft 113 and rotatable with the rotor shaft 113, multiple stages of fixed blades 123 fixed to the casing 211 and positioned between the rotor blades 102, and a heating section 213 for heating the vacuum pump body 210. The vacuum pump body 210 further includes a body temperature sensor 214 (second temperature sensor) for detecting the temperature of the vacuum pump body 210 and a motor temperature sensor 215 (second temperature sensor) for detecting the temperature of the motor 121. The heating section 213 is a heating means such as a heater that heats up when an electric current flows through it. The heating section 213 may also be a heater spacer, which is a component on which a heater is arranged. A heater spacer is a component that has a high temperature due to the attachment of a heating means such as a heater, and combines the function of heating other components with the function of a spacer. The position where the main body temperature sensor 214 is placed is not particularly limited as long as it can detect the temperature of the vacuum pump body 210, but for example it may be placed on the base portion 129.

[0060] The control device 200 includes a housing 221 fixed to the vacuum pump body 210, a control unit 222 composed of electronic circuits located within the housing 221, a first temperature sensor 223 for measuring the temperature of the control device 200, and a cooling unit 224 for cooling the control device 200. The cooling unit 224 is, for example, a water-cooled pipe through which cooling water flows as a medium. The cooling water is supplied from a cooling water source 232. The piping through which the cooling water from the cooling water source 232 flows passes through a valve 231 and a flow sensor 225 before branching. One of the branched pipes is connected to the water-cooled pipe 149 via a solenoid valve 230. The other branched pipe is connected to the cooling unit 224. The valve 231 is operated manually, but the operation of the solenoid valve 230 is controlled by the control unit 222. The flow sensor 225 detects the flow rate of cooling water supplied from the cooling water source 232 to the water cooling pipe 149 and the cooling unit 224, and transmits a signal indicating the detection result to the control unit 222.

[0061] The control unit 222 includes a rotation control unit 226 that controls the rotation of the rotor shaft 113 and a temperature control unit 227 that controls the temperature of the vacuum pump body 210. The rotation control unit 226 controls the magnetic bearing 212 and the motor 121.

[0062] The temperature control unit 227 receives detection signals from the main unit temperature sensor 214, the motor temperature sensor 215, and the first temperature sensor 223, and monitors the temperature of the vacuum pump body 210 and the control device 200. Furthermore, the temperature control unit 227 can transmit on / off control command signals to the heating unit 213, and can also transmit on / off control command signals to the solenoid valve 230 that controls the flow of cooling water to the water cooling pipe 149 located in the vacuum pump body 210. The temperature control unit 227 also has a status transmission unit 228 that transmits information to the outside.

[0063] When the temperature control unit 227 transmits an ON command signal to the heating unit 213, heating by the heating unit 213 begins, and when an OFF command signal is transmitted, heating by the heating unit 213 stops. When the temperature control unit 227 transmits an ON command signal to the solenoid valve 230, the valve opens and cooling water flows into the water cooling pipe 149, and when an OFF command signal is transmitted, the valve closes and the flow of cooling water to the water cooling pipe 149 stops. The valve 231 that supplies cooling water to the control device 200 is not an ON / OFF controlled solenoid valve, but is a structure that is opened and closed manually, and after being opened, it remains open until it is closed. Note that the valve 231 may be an ON / OFF controlled solenoid valve controlled by the temperature control unit 227. If the valve 231 is a solenoid valve, when the temperature control unit 227 transmits an ON command signal to the valve 231, the valve opens and cooling water flows into the cooling unit 224, and when an OFF command signal is transmitted, the valve closes and the flow of cooling water to the cooling unit 224 stops. The water cooling pipe 149 that cools the vacuum pump body 210 and the cooling unit 224 that cools the control device 200 may be supplied with cooling water separately by different valves, or they may be supplied with cooling water simultaneously by a common valve.

[0064] Next, the control flow in the temperature control unit 227 of the vacuum pump 100 according to this embodiment will be explained with reference to the flowchart shown in Figure 6 and the timing chart shown in Figure 7.

[0065] When the temperature control unit 227 starts control, it repeatedly controls the heating of the heating unit 213 and the cooling of the cooling unit 224 until it receives a control stop instruction signal from an input device such as one used by an operator. First, the temperature control unit 227 determines whether or not the vacuum pump 100 is operating (step S1). If the temperature control unit 227 determines that the vacuum pump 100 is operating, it sets the target temperature of the heating unit 213 to the normal target temperature T1 and sends an ON command signal to the solenoid valve 230 to supply cooling water to the water cooling pipe 149. The valve 231, which is a cooling water introduction control device that supplies cooling water to the solenoid valve 230 and the cooling unit 224, is always open and supplies cooling water to the solenoid valve 230 and the cooling unit 224.

[0066] If the temperature control unit 227 determines that the vacuum pump 100 is not operating at time t1 (step S1), it identifies that the vacuum pump 100 is in a standby state (step S2). The control device 200 can, for example, receive information on the rotational speed of the rotor shaft 113 of the vacuum pump 100 from the rotational control unit 226 and determine whether the vacuum pump 100 is operating based on whether the rotational speed is zero or not.

[0067] In the standby state, the temperature control unit 227 controls the heating unit 213 and the cooling unit 224 to maintain the temperature detected by the main unit temperature sensor 214 of the vacuum pump body 210 (the temperature of the heating unit 213, or the temperature of the part heated by the heating unit 213) at the normal target temperature T1. Then, in the standby state, the temperature control unit 227 determines whether or not cooling by the cooling unit 224 has stopped (step S3).

[0068] The temperature control unit 227 receives a signal from the first temperature sensor 223 located in the control device 200 to determine whether the cooling by the cooling unit 224 has stopped because the supply of cooling water by the valve 231, which is a cooling water introduction control device, has stopped. It can determine that cooling by the cooling unit 224 has stopped when the temperature of the control device 200 exceeds a predetermined temperature (cooling unit stop detection threshold A) for a period of time t3. Note that there is a time lag between the time t2 when cooling by the cooling unit 224 actually stops and the time t3 when cooling by the cooling unit 224 is detected, so time t3 will be later than time t2.

[0069] The temperature control unit 227 can also determine that cooling by the cooling unit 224 has stopped if the temperature of the vacuum pump body 210 detected by the main body temperature sensor 214 (for example, the temperature of the base part 129) or the temperature of the motor 121 detected by the motor temperature sensor 215 exceeds a predetermined temperature, rather than the temperature of the control device 200. Alternatively, the temperature control unit 227 may determine whether cooling by the cooling unit 224 has stopped based on the flow rate information detected by the flow rate sensor 225. If the flow rate detected by the flow rate sensor 225 is zero or less than a predetermined flow rate, the temperature control unit 227 can determine that cooling by the cooling unit 224 has stopped. Or, the temperature control unit 227 may determine whether the vacuum pump 100 is in operation (step S1), and if it determines that the vacuum pump 100 is not in operation at time t1, it may forcibly determine that cooling by the cooling unit 224 has stopped (step S3). In this case, even if cooling by the cooling unit 224 has not actually stopped, it is determined that cooling by the cooling unit 224 has stopped, and the target temperature of the vacuum pump body 210 is lowered in step S5, which will be described later.

[0070] When the temperature control unit 227 determines that cooling by the cooling unit 224 has stopped, it changes the target temperature of the vacuum pump body 210 in temperature control to a standby target temperature T2, which is lower than the normal target temperature T1 (step S4). As a result, the heating temperature of the vacuum pump body 210 by the heating unit 213 decreases, and the vacuum pump 100 enters a low-temperature control state. Therefore, the temperature rise of the control device 200 due to the cessation of cooling by the cooling unit 224 in the standby state is suppressed, and an overheating abnormality of the control device 200 can be avoided. The temperature control unit 227 may also temporarily stop heating in the heating unit 213 when it determines that cooling by the cooling unit 224 has stopped (time t3). Stopping heating in the heating unit 213 also corresponds to a decrease in the heating temperature of the heating unit 213. After temporarily stopping cooling by the cooling unit 224, the temperature control unit 227 restarts heating in the heating unit 213 after the temperature of the control device 200 detected by the main unit temperature sensor 214 has decreased to a predetermined temperature. This control mechanism causes the temperature of the heating unit 213 to drop below the optimal temperature for rapid operation, but it prevents the temperature of the control device 200 from exceeding a predetermined temperature (overheat detection threshold B) and triggering an abnormal detection. Therefore, it is possible to avoid cutting off the power supply to the heating unit 213, and thus maintain a minimum temperature for the vacuum pump 100.

[0071] When the vacuum pump 100 enters a low-temperature control state, the temperature control unit 227 transmits information indicating that the vacuum pump 100 is in a low-temperature control state, or warning information, from the status transmission unit 228 (step S5). The information transmitted from the status transmission unit 228 can be communicated to operators, etc., by monitors (image devices) or speakers (sound devices) located on or away from the vacuum pump 100.

[0072] The temperature control unit 227 monitors whether cooling by the cooling unit 224 has stopped (step S6) and controls the temperature of the vacuum pump 100. If the temperature control unit 227 determines that cooling by the cooling unit 224 is working normally, it changes the target temperature in the temperature control from the second target temperature T2 to the first target temperature T1 (step S9), returns to step S1 described above, and continues the temperature control repeatedly. The method for determining whether cooling by the cooling unit 224 has stopped is the same as in step S3 described above.

[0073] If the temperature control unit 227 determines in step S6 that cooling by the cooling unit 224 is not functioning properly, it performs temperature control in standby mode until it determines that the vacuum pump 100 is operating (step S8), and then returns to step S6 to repeatedly monitor whether cooling by the cooling unit 224 has stopped. If the temperature control unit 227 determines that the vacuum pump 100 is operating, it changes the target temperature in temperature control from the second target temperature T2 to the first target temperature T1 (step S9), and returns to step S1 described above to continue repeating temperature control.

[0074] Furthermore, as shown in the modified control flow in Figure 8, the control in the temperature control unit 227 does not necessarily need to include step S6, which monitors whether or not cooling by the cooling unit 224 has stopped. In this case, regardless of whether or not cooling by the cooling unit 224 has resumed, the target temperature of the temperature control unit 227 will be returned from the second target temperature T2 to the first target temperature T1 (step S9).

[0075] As described above, the vacuum pump 100 according to this embodiment is a vacuum pump 100 having a magnetic bearing type vacuum pump body 210 and a control device 200 fixed to the vacuum pump body 210, wherein the vacuum pump body 210 comprises a casing 211, a rotor shaft 113 rotatably supported inside the casing 211, a magnetic bearing 212 supporting the rotor shaft 113, a plurality of stages of rotor blades 102 fixed to the rotor shaft 113 and rotatable together with the rotor shaft 113, and a plurality of stages fixed to the casing 211 and arranged between the rotor blades 102 The control device 200 has a fixed blade 123 and a heating unit 213 that heats the vacuum pump body 210. The control device 200 has a rotation control unit 226 that controls the rotation of the rotor shaft 113, a temperature control unit 227 that controls the temperature of the vacuum pump body 210, and a cooling unit 224 that cools the control device 200. When the temperature control unit 227 detects that the cooling unit 224 has stopped working in a predetermined state of the vacuum pump body 210, it controls the temperature of the control device 200 to be below a predetermined temperature (overheat detection threshold B) by lowering the heating temperature of the heating unit 213.

[0076] As described above, the vacuum pump 100, when the vacuum pump body 210 is in a predetermined state, can suppress the temperature of the control device 200 from rising to an undesirable predetermined temperature (overheat detection threshold B) because it reduces the heating temperature of the heating unit 213 that heats the vacuum pump body 210, even if the cooling in the cooling unit 224 of the control device 200 is stopped for maintenance or energy saving purposes.

[0077] The predetermined state of the vacuum pump body 210 is an operating standby state in which the rotational speed of the rotor shaft 113 is zero and acceleration is immediately possible. As a result, the vacuum pump 100 can prevent the temperature of the vacuum pump body 210 from dropping too low due to heating by the heating unit 213 while the operating standby state of the vacuum pump body 210 is enabled, and also prevent the temperature of the control device 200 from rising to an undesirable predetermined temperature (overheat detection threshold B) when cooling in the cooling unit 224 stops.

[0078] The control device 200 has a status transmitting unit 228 that, when it detects that cooling in the cooling unit 224 has stopped in the predetermined state of the vacuum pump body 210, transmits information indicating a warning or information indicating that the heating temperature by the heating unit 213 of the vacuum pump body 210 has been reduced to a low-temperature control state. As a result, the vacuum pump 100 can communicate to the outside that cooling in the cooling unit 224 has stopped, thereby improving safety.

[0079] The control device 200 is equipped with a first temperature sensor 223 that measures the temperature of the control device 200, and the vacuum pump body 210 is equipped with a second temperature sensor (body temperature sensor 214 or motor temperature sensor 215) that measures the temperature of the part heated by the heating unit 213. The temperature control unit 227 receives temperature information detected by the first temperature sensor 223 or the second temperature sensor, and may determine that cooling in the cooling unit 224 has stopped when the temperature detected by the first temperature sensor 223 or the second temperature sensor exceeds a predetermined threshold. As a result, the vacuum pump 100 can effectively detect the cessation of cooling in the cooling unit 224 by utilizing the temperature information detected by the temperature sensors.

[0080] The temperature control unit 227 receives flow rate information detected by the flow sensor 225, which detects the flow rate of the medium flowing through the cooling unit 224. If the flow rate detected by the flow sensor 225 is below a predetermined value, the temperature control unit 227 may determine that cooling in the cooling unit 224 has stopped. This allows the vacuum pump 100 to effectively detect the cessation of cooling in the cooling unit 224 by utilizing the flow rate information of the medium detected by the flow sensor 225.

[0081] It should be noted that the present invention is not limited to the embodiments described above, and various modifications and combinations are possible by those skilled in the art within the technical concept of the present invention. For example, in another embodiment, when transitioning to a brake mode that reduces the rotational speed from the rated rotational speed, or when the rotational speed becomes zero, the heating temperature by the heating unit 213 may be lowered regardless of the detection of the cessation of cooling in the cooling unit 224, thereby changing the target temperature of the vacuum pump body 210 to a standby target temperature T2 that is lower than the normal target temperature T1. This makes it possible to suppress the temperature of the control device 200 from rising to an undesirable predetermined temperature (overheat detection threshold B) due to heat generation in the control device 200 in brake mode (heat generation from electronic components such as regenerative resistors that consume the electrical energy generated by regenerative power generation from the motor 121), as well as heat exchange with the vacuum pump body 210. [Explanation of symbols]

[0082] 100 Vacuum pump 102 Rotary blades 113 Rotor shaft 121 Motor 123 Fixed wing 129 Base section 133 Exhaust vent 210 Vacuum pump body 211 Casing 212 Magnetic bearing 213 Heating section 214 Main unit temperature sensor (second temperature sensor) 215 Motor temperature sensor (second temperature sensor) 200 Control device 221 cabinet 222 Control Unit 223 First temperature sensor 224 Cooling section 225 Flow Sensor 226 Rotation Control Unit 227 Temperature Control Unit 228 Status Transmitter 230 Solenoid valve 231 valve

Claims

1. A vacuum pump having a magnetic bearing type vacuum pump body and a control device fixed to the vacuum pump body, The vacuum pump body includes: A casing; a rotor shaft rotatably supported inside the casing; a magnetic bearing supporting the rotor shaft; a plurality of stages of rotor blades fixed to the rotor shaft and rotatable together with the rotor shaft; a plurality of stages of fixed blades fixed to the casing and disposed between the rotor blades; a heating unit that heats the vacuum pump body, The control device a rotation control unit that controls the rotation of the rotor shaft; a temperature control unit for controlling the temperature of the vacuum pump body; a cooling unit that cools the control device, a temperature control unit that controls the temperature of the control device to be below a predetermined temperature by reducing the heating temperature of the heating unit when it detects that cooling in the cooling unit has stopped while the vacuum pump main body is in a predetermined state.

2. 2. The vacuum pump according to claim 1, wherein the predetermined state of the vacuum pump body is a standby state in which the rotational speed of the rotor shaft is zero and acceleration is possible immediately.

3. 2. The vacuum pump according to claim 1, wherein the control device has a state transmitting unit that transmits information indicating a warning or information indicating that the vacuum pump body is in a low-temperature control state in which the heating temperature of the heating unit is lowered when the control device detects that cooling in the cooling unit has stopped while the vacuum pump body is in the predetermined state.

4. the control device includes a first temperature sensor that measures a temperature of the control device; the vacuum pump body includes a second temperature sensor that measures the temperature of a portion heated by the heating unit; 2. The vacuum pump according to claim 1, wherein the temperature control unit receives information on the temperature detected by the first temperature sensor or the second temperature sensor, and determines that cooling in the cooling unit has stopped when the temperature detected by the first temperature sensor or the second temperature sensor becomes equal to or higher than a predetermined threshold value.

5. 2. The vacuum pump according to claim 1, wherein the temperature control unit receives information on a flow rate detected by a flow rate sensor that detects a flow rate of the medium flowing through the cooling unit, and determines that cooling in the cooling unit has stopped when the flow rate detected by the flow rate sensor is equal to or less than a predetermined value.

6. A control device fixed to a magnetic bearing type vacuum pump body, a rotation control unit that controls the rotation of a rotor shaft of the vacuum pump body; a temperature control unit for controlling the temperature of the vacuum pump body; a cooling unit that cools the control device, The control device is characterized in that, when the temperature control unit detects that cooling in the cooling unit has stopped while the vacuum pump main body is in a predetermined state, the temperature control unit controls the temperature of the control device to be below a predetermined temperature by reducing the heating temperature of the heating unit arranged in the vacuum pump main body.

7. A temperature control method performed by a control device fixed to a magnetic bearing type vacuum pump body, comprising: a step of determining whether or not a stop of cooling in a cooling unit that cools the control device has been detected in a predetermined state of the vacuum pump main body; and when the stop of cooling in the cooling section is detected, controlling the temperature of the control device to be below a predetermined temperature by reducing the heating temperature of a heating section arranged in the vacuum pump main body.

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