Vacuum pump

Abstract

To obtain a vacuum pump with which temperature of a gas flow passage is appropriately managed to reduce restriction on a gas flow rate caused by the temperature control.SOLUTION: A cooling pipe 305 adjusts the temperature of a gas flow passage. A temperature sensor 401 is disposed in a position closer to the gas flow passage than the cooling pipe 305, and a temperature sensor 402 is disposed in a position closer to the cooling pipe 305 than the gas flow passage. A control device 200 controls (an open / closed valve of) the cooling pipe 305 on the basis of a sensor signal from the temperature sensor 401 and a sensor signal from the temperature sensor 402 such that the temperature of the gas flow passage approaches a prescribed gas flow passage target temperature.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vacuum pump. [Background technology]

[0002] Generally, a vacuum pump is provided with a cooling means and a heating means to suppress a temperature rise in the rotor section, adjust the temperature of the gas flow path, etc. One vacuum pump is provided with multiple temperature sensors, and controls at least one of the cooling means and the heating means based on sensor signals output from the multiple temperature sensors (see, for example, Patent Document 1). In this vacuum pump, temperature sensors are provided in the base section and the motor section, and the opening of the solenoid valve for cooling water and the turning on and off of the heater are performed based on the sensor signals. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2011 / 021428 Summary of the Invention [Problem to be solved by the invention]

[0004] In a vacuum pump, a temperature sensor is usually installed near a gas flow path to be temperature controlled or near a cooling means or heating means, and the cooling means or heating means is controlled in accordance with a sensor signal from the temperature sensor.

[0005] Generally, the gas flow rate in the gas flow passage of a vacuum pump varies depending on the process upstream of the vacuum pump, and when the gas flow rate exhausted by the vacuum pump increases, the gas flow passage temperature in the vacuum pump increases, and when the gas flow rate exhausted by the vacuum pump decreases, the gas flow passage temperature in the vacuum pump decreases. Therefore, even if the gas flow rate changes, it is necessary to adjust the gas flow passage temperature during operation of the vacuum pump so that it is within an allowable range from a lower limit at which gas deposits do not occur to an upper limit for thermal expansion of the rotor, etc.

[0006] When the above-mentioned temperature sensor is installed near the gas flow path to be temperature controlled, the distance (distance along the heat flow path) from the cooling means or heating means to the temperature sensor becomes long, and when the gas flow rate changes and the measured temperature of the temperature sensor changes, it takes time for the temperature change of the cooling means or heating means to be transmitted to the temperature sensor, which makes it easy for the temperature sensor to overshoot or undershoot in the temperature sensor installation location and, in turn, the temperature of the gas flow path. Therefore, in this case, since the gas flow path temperature is difficult to converge to the target temperature, the gas flow rate that can be stably exhausted by the vacuum pump is limited in order to keep the gas flow path temperature within the allowable range.

[0007] Furthermore, when the above-mentioned temperature sensor is installed near the cooling means or heating means, the distance from the gas flow path to the temperature sensor (the distance along the heat flow path) becomes long, and although overshoot or undershoot is unlikely to occur at the installation location of the temperature sensor, the temperature error due to temperature control (i.e., the difference between the actual gas flow path temperature and the temperature measured by the temperature sensor) becomes large, and this temperature error becomes larger as the gas flow rate increases. Therefore, in this case, since the measurement error of the gas flow path temperature relative to the target temperature changes depending on the gas flow rate, the gas flow rate that can be stably exhausted by the vacuum pump is also limited in order to keep the gas flow path temperature within the allowable range.

[0008] In this way, the gas flow rate that can be stably exhausted by the vacuum pump is limited by the characteristics of the temperature measurement system.

[0009] An object of the present invention is to provide a vacuum pump that appropriately controls the temperature of a gas flow passage and reduces restrictions on the gas flow rate caused by temperature control. [Means for solving the problem]

[0010] The vacuum pump of the present invention is a vacuum pump that discharges gas taken in by the rotation of a rotor, and is equipped with a temperature adjustment means for adjusting the temperature of a gas flow path, a first temperature sensor arranged at a position closer to the gas flow path than the temperature adjustment means, a second temperature sensor arranged at a position closer to the temperature adjustment means than the gas flow path, and a control device that controls the temperature adjustment means based on a sensor signal of the first temperature sensor and a sensor signal of the second temperature sensor so that the temperature of the gas flow path approaches a predetermined gas flow path target temperature. Then, based on a change in the measured temperature based on the sensor signal of the first temperature sensor, the control device changes the control temperature set value, which is the target temperature of the temperature adjustment means, in a direction opposite to the change in the measured temperature. Effect of the Invention

[0011] According to the present invention, a vacuum pump is obtained in which the temperature of a gas flow passage is appropriately controlled and restrictions on the gas flow rate caused by temperature control are reduced.

[0012] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a vertical sectional view showing a turbo-molecular pump as a vacuum pump according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a circuit diagram showing an amplifier circuit that controls excitation of the electromagnets of the turbo molecular pump shown in FIG. [Diagram 3] FIG. 3 is a time chart showing the control when the current command value is larger than the detection value. [Figure 4] FIG. 4 is a time chart showing the control when the current command value is smaller than the detection value. [Diagram 5] FIG. 5 is a diagram illustrating the temperature control of the vacuum pump shown in FIG. [Figure 6] FIG. 6 is a vertical sectional view showing a turbo molecular pump as a vacuum pump according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0015] Embodiment 1

[0016] A longitudinal cross-sectional view of this turbomolecular pump 100 is shown in Fig. 1. In Fig. 1, the turbomolecular pump 100 has an intake port 101 formed at the upper end of a cylindrical outer tube 127. Inside the outer tube 127, a rotor 103 is provided, the rotor 103 having a plurality of rotors 102 (102a, 102b, 102c, ...) which are turbine blades for sucking in and exhausting gas, formed radially on its periphery in multiple stages. A rotor shaft 113 is attached to the center of the rotor 103, and the rotor shaft 113 is supported in the air and position-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.

[0017] 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 of the upper radial electromagnets 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 the change in inductance of the conductive windings that changes 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 the control device 200.

[0018] In this control device 200, for example, a compensation circuit having a PID adjustment function generates an excitation control command signal for the upper radial electromagnet 104 based on a position signal detected by the upper radial sensor 107, and an amplifier circuit 150 (described later) shown in Figure 2 controls the excitation of the upper radial electromagnet 104 based on this excitation control command signal, thereby adjusting the upper radial position of the rotor shaft 113.

[0019] The rotor shaft 113 is made of a material with high magnetic permeability (iron, stainless steel, etc.) and is attracted by the magnetic force of the upper radial electromagnet 104. Such adjustment is performed independently in the X-axis direction and the Y-axis direction. The lower radial electromagnet 105 and the lower radial sensor 108 are arranged in the same manner as the upper radial electromagnet 104 and the upper radial sensor 107, and adjust the lower radial position of the rotor shaft 113 in the same manner as the upper radial position.

[0020] Furthermore, axial electromagnets 106A and 106B are arranged above and below a circular metal disk 111 provided at the bottom of rotor shaft 113. Metal disk 111 is made of a high magnetic permeability material such as iron. An axial sensor 109 is provided to detect the axial displacement of rotor shaft 113, and an axial position signal is sent to control device 200.

[0021] In the control device 200, a compensation circuit having, for example, a PID adjustment function generates an excitation control command signal for each of the axial electromagnets 106A and 106B based on the axial position signal detected by the axial sensor 109, and the amplifier circuit 150 controls the excitation of the axial electromagnets 106A and 106B based on these excitation control command signals, so that the axial electromagnet 106A attracts the metal disk 111 upward by magnetic force and the axial electromagnet 106B attracts the metal disk 111 downward, thereby adjusting the axial position of the rotor shaft 113.

[0022] In this way, the control device 200 appropriately adjusts the magnetic force that the axial electromagnets 106A, 106B exert on the metal disk 111, magnetically levitating the rotor shaft 113 in the axial direction and holding it in a non-contact manner in space. The amplifier circuit 150 that controls the excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A, 106B will be described later.

[0023] 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. Also, motor 121 incorporates a rotation speed sensor such as a Hall element, resolver, or encoder (not shown), and the rotation speed of rotor shaft 113 is detected by a detection signal from this rotation speed sensor.

[0024] Furthermore, for example, a phase sensor (not shown) is attached near the lower radial sensor 108 to detect the phase of rotation of the rotor shaft 113. The control device 200 detects the position of the magnetic poles using the detection signals of both this phase sensor and the rotation speed sensor.

[0025] A plurality of fixed blades 123 (123a, 123b, 123c...) are arranged with a small gap between the rotor blades 102 (102a, 102b, 102c...). The rotor blades 102 (102a, 102b, 102c...) are formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transport exhaust gas molecules downward through collision. The fixed blades 123 (123a, 123b, 123c...) are made of metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components.

[0026] Similarly, the fixed blades 123 are formed at an inclination at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged alternately with the stages of the rotor blades 102 toward the inside of the outer cylinder 127. The outer peripheral ends of the fixed blades 123 are supported in a state where they are inserted between a plurality of stacked stages of fixed blade spacers 125 (125a, 125b, 125c, etc.).

[0027] The fixed wing spacer 125 is a ring-shaped member, and is made of metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components. An outer cylinder 127, an annular member 301, and an outer cylinder member 302 are fixed to the outer periphery of the fixed wing spacer 125 with a gap therebetween. A base portion 129 is disposed at the bottom of the outer cylinder member 302. An exhaust port 133 is disposed above the base portion 129 and communicates with the outside. Exhaust gas transferred from the chamber (vacuum chamber) through the intake port 101 is sent to the exhaust port 133.

[0028] Furthermore, depending on the application of the turbo molecular pump 100, a threaded spacer 131 is disposed between the lower part of the fixed vane spacer 125 and the base part 129. The threaded 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 a plurality of helical thread grooves 131a engraved on its inner peripheral surface. The helical direction of the thread groove 131a is the direction in which, when the molecules of the exhaust gas move in the rotation direction of the rotor 103, the molecules are transferred toward the exhaust port 133. A cylindrical part 102d hangs down from the lowest part of the rotor 103, which is connected to the rotor vanes 102 (102a, 102b, 102c, etc.). The outer peripheral surface of this cylindrical part 102d is cylindrical and protrudes toward the inner peripheral surface of the threaded spacer 131, and is adjacent to the inner peripheral surface of the threaded spacer 131 with a 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.

[0029] The base portion 129 is a disk-shaped member that constitutes the base of the turbomolecular pump 100, and is generally made of metal such as iron, aluminum, stainless steel, etc. The base portion 129 physically holds the turbomolecular pump 100 and also functions as a heat conduction path, so it is desirable to use a metal that has rigidity and high thermal conductivity, such as iron, aluminum, or copper.

[0030] In this configuration, when the rotor 102 is rotated together with the rotor shaft 113 by the motor 121, the exhaust gas is sucked from the chamber through the intake port 101 by the action of the rotor 102 and the fixed blade 123. The rotation speed of the rotor 102 is usually 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 sucked through the intake port 101 passes between the rotor 102 and the fixed blade 123 and is transferred to the base part 129. At this time, the temperature of the rotor 102 rises due to frictional heat generated when the exhaust gas comes into contact with the rotor 102 and conduction of heat generated by the motor 121, and the like, but this heat is transferred to the fixed blade 123 side by radiation or conduction by gas molecules of the exhaust gas, and the like.

[0031] The fixed blade spacers 125 are joined to each other at their outer peripheries, and transmit heat received by the fixed blades 123 from the rotor blades 102, frictional heat generated when exhaust gas comes into contact with the fixed blades 123, and the like to the outside.

[0032] 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 periphery of the threaded spacer 131. However, there are also cases where the thread groove is formed on the outer periphery of the cylindrical portion 102d, and a spacer having a cylindrical inner periphery is disposed around the outer periphery of the cylindrical portion 102d.

[0033] Depending on the application of the turbomolecular pump 100, in order to prevent the gas sucked in from the intake port 101 from entering the electrical equipment section, which is composed of the upper radial electromagnet 104, the upper radial sensor 107, the motor 121, the lower radial electromagnet 105, the lower radial sensor 108, the axial electromagnets 106A and 106B, the axial sensor 109, etc., the electrical equipment section may be covered all around with a stator column 122, and the inside of this stator column 122 may be kept at a predetermined pressure by a purge gas.

[0034] 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.

[0035] Here, the turbomolecular pump 100 requires control based on specific parameters (e.g., various characteristics corresponding to the model) that are individually adjusted and identified as a model. In order to store these control parameters, the turbomolecular pump 100 has an electronic circuit section 141 in its main body. The electronic circuit section 141 is composed of a semiconductor memory such as an EEPROM, electronic components such as semiconductor elements for accessing the memory, and a substrate 143 for mounting these components. The electronic circuit section 141 is housed below a rotational speed sensor (not shown) near the center of a base section 129 that constitutes the lower part of the turbomolecular pump 100, and is closed by an airtight bottom cover 145.

[0036] 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 turbo molecular pump 100, the pressure of the exhaust gas is lowest at the intake port 101 and highest at the exhaust port 133. If the pressure of the process gas becomes higher than a predetermined value or the temperature falls below a predetermined value while the process gas is being transferred from the intake port 101 to the exhaust port 133, the process gas becomes solid and adheres to and accumulates inside the turbo molecular pump 100.

[0037] For example, SiCl is used as a process gas in an Al etching device. 4 When low vacuum (760[torr]~10 -2 At low temperatures (approximately 20°C) and at low temperatures (approximately 20°C), solid products (e.g., AlCl 3) precipitates and adheres to and accumulates inside the turbomolecular pump 100. As a result, when precipitates of the process gas accumulate inside the turbomolecular pump 100, the deposits narrow the pump flow path, causing a decrease in the performance of the turbomolecular pump 100. The above-mentioned products are prone to solidification and adhesion in high-pressure areas near the exhaust port 133 and near the threaded spacer 131.

[0038] Therefore, in order to solve this problem, in the past, a heater (not shown) or a circular water-cooled tube 149 was wrapped around the outer periphery of the base portion 129, and a temperature sensor (e.g., a thermistor) (not shown) was embedded in the base portion 129, and the heating of the heater and the cooling by the water-cooled tube 149 were controlled based on the signal from this temperature sensor to keep the temperature of the base portion 129 at a constant high temperature (set temperature) (hereinafter referred to as TMS; Temperature Management System).

[0039] Next, regarding the turbo molecular pump 100 configured as described above, an amplifier circuit 150 that controls excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B will be described. A circuit diagram of this amplifier circuit 150 is shown in FIG.

[0040] 2, one end of an electromagnet winding 151 constituting the upper radial electromagnet 104 etc. is connected to a positive electrode 171a of a power source 171 via a transistor 161, and the other end is connected to a negative electrode 171b of the power source 171 via a current detection circuit 181 and a transistor 162. The transistors 161 and 162 are so-called power MOSFETs, and have a structure in which a diode is connected between the source and drain.

[0041] At this time, the transistor 161 has a cathode terminal 161a of the diode connected to the positive electrode 171a, and an anode terminal 161b connected to one end of the electromagnet winding 151. The transistor 162 has a cathode terminal 162a of the diode connected to the current detection circuit 181, and an anode terminal 162b connected to the negative electrode 171b.

[0042] On the other hand, the current regeneration diode 165 has its cathode terminal 165a connected to one end of the electromagnet winding 151 and its anode terminal 165b connected to the negative electrode 171b. Similarly, the current regeneration diode 166 has its cathode terminal 166a connected to the positive electrode 171a and its anode terminal 166b connected to the other end of the electromagnet winding 151 via a current detection circuit 181. The current detection circuit 181 is composed of, for example, a Hall sensor type current sensor or an electric resistance element.

[0043] The amplifier circuit 150 configured as above corresponds to one electromagnet. Therefore, when the magnetic bearing is controlled by five axes and there are a total of ten electromagnets 104, 105, 106A, and 106B, a similar amplifier circuit 150 is configured for each electromagnet, and the ten amplifier circuits 150 are connected in parallel to the power supply 171.

[0044] Furthermore, the amplifier control circuit 191 is configured, for example, by a digital signal processor section (hereinafter referred to as a DSP section) (not shown) of the control device 200, and this amplifier control circuit 191 switches the transistors 161 and 162 on / off.

[0045] The amplifier control circuit 191 is adapted to compare the current value detected by the current detection circuit 181 (a signal reflecting this current value is called a current detection signal 191c) with a predetermined current command value. Then, based on the result of this comparison, the magnitude of the pulse width (pulse width times Tp1, Tp2) to be generated within a control cycle Ts, which is one period of PWM control, is determined. As a result, gate drive signals 191a, 191b having this pulse width are output from the amplifier control circuit 191 to the gate terminals of the transistors 161, 162.

[0046] In addition, when the rotor 103 passes through a resonance point during an accelerating operation of the rotation speed, or when a disturbance occurs during a constant speed operation, it is necessary to control the position of the rotor 103 at high speed and with a strong force. For this reason, a high voltage of, for example, about 50 V is used as the power supply 171 so that the current flowing through the electromagnet winding 151 can be rapidly increased (or decreased). In addition, a capacitor (not shown) is usually connected between the positive pole 171a and the negative pole 171b of the power supply 171 to stabilize the power supply 171.

[0047] In this configuration, when both transistors 161, 162 are turned on, the current flowing through the electromagnet winding 151 (hereinafter referred to as electromagnet current iL) increases, and when both are turned off, the electromagnet current iL decreases.

[0048] Moreover, when one of the transistors 161, 162 is turned on and the other is turned off, a so-called flywheel current is maintained. By passing a flywheel current through the amplifier circuit 150 in this manner, the hysteresis loss in the amplifier circuit 150 can be reduced, and the power consumption of the entire circuit can be kept low. Furthermore, by controlling the transistors 161, 162 in this manner, high-frequency noise such as harmonics generated in the turbo molecular pump 100 can be reduced. Furthermore, by measuring this flywheel current with the current detection circuit 181, the electromagnet current iL flowing through the electromagnet winding 151 can be detected.

[0049] That is, when the detected current value is smaller than the current command value, both of the transistors 161 and 162 are turned on for a time period corresponding to the pulse width time Tp1 only once in a control cycle Ts (e.g., 100 μs) as shown in Fig. 3. Therefore, the electromagnet current iL during this period increases toward a current value iLmax (not shown) that can flow from the positive electrode 171a to the negative electrode 171b via the transistors 161 and 162.

[0050] On the other hand, when the detected current value is larger than the current command value, both of the transistors 161 and 162 are turned off for a time period corresponding to the pulse width time Tp2 only once during the control cycle Ts, as shown in Fig. 4. Therefore, the electromagnet current iL during this period decreases toward a current value iLmin (not shown) that can be regenerated from the negative pole 171b to the positive pole 171a via the diodes 165 and 166.

[0051] In either case, after the pulse width times Tp1 and Tp2 have elapsed, one of the transistors 161 and 162 is turned on. Therefore, a flywheel current is maintained in the amplifier circuit 150 during this period.

[0052] The main parts of the turbomolecular pump 100 are configured as described above. The turbomolecular pump 100 is an example of a vacuum pump. In FIG. 1, the rotor 102 and rotor 103 are the rotor of the turbomolecular pump 100, the fixed blade 123 and fixed blade spacer 125 are the stator part of the turbomolecular pump part, and the threaded spacer 131 is the stator part of the thread groove pump part at the rear stage of the turbomolecular pump part. The intake port 101, exhaust port 133, outer cylinder 127, annular member 301, and outer cylinder member 302 are the casing of the turbomolecular pump 100, and house the rotor and the multiple stator parts. That is, the rotor is rotatably held in the casing, and the multiple stator parts are arranged opposite the rotor and have a gas compression function. The gas sucked in by the rotation of the rotor is transported along the gas flow path and discharged from the exhaust port 133.

[0053] Furthermore, the annular member 301 is an annular member that is one of the members stacked from the base portion 129 toward the intake port 101 side. A stator portion formed by the fixed blades 123 and the fixed blade spacer 125 contacts the annular member 301 along the axial direction. Also, one end of the annular member 303 contacts the annular member 301, and the other end of the annular member 303 contacts the threaded spacer 131. Furthermore, the other end of the threaded spacer 131 does not contact the base portion 129.

[0054] As a temperature adjustment means for adjusting the temperature of the gas flow path, a heater 304 is provided on the annular member 132 that is in contact with the threaded spacer 131 that constitutes the inner wall of the gas flow path, and a cooling pipe 305 is provided on the annular member 301 that constitutes the inner wall of the gas flow path.

[0055] Therefore, heat flows from the heater 304 through the annular member 132 to the threaded spacer 131, which changes the temperature of the threaded spacer 131, i.e., the temperature of the gas flow path. Heat also flows from the annular member 301 to the cooling pipe 305, which changes the temperature of the annular member 301, i.e., the temperature of the gas flow path.

[0056] Furthermore, in the first embodiment, two temperature sensors 401, 402 are provided in annular member 301 corresponding to cooling pipe 305, and one temperature sensor 501 is provided in threaded spacer 131 corresponding to heater 304. That is, a temperature sensor is provided for each of heater 304 and cooling pipe 305 as temperature adjustment means.

[0057] The temperature sensor 401 is disposed in the vicinity of the gas flow passage, at a position closer to the gas flow passage than the cooling pipe 305 serving as a temperature adjustment means.

[0058] The temperature sensor 402 is disposed near the cooling pipe 305 serving as a temperature adjusting means, at a position closer to the cooling pipe 305 than the gas flow path. Specifically, the temperature sensor 402 is disposed near the opening / closing valve (solenoid valve) of the cooling pipe 305.

[0059] Then, based on the sensor signal output from temperature sensor 401 and the sensor signal output from temperature sensor 402, control device 200 controls the on / off of an opening / closing valve (solenoid valve) of cooling pipe 305 so that the temperature of the gas flow path (specifically, the gas flow path of the turbo molecular pump portion) approaches a predetermined gas flow path target temperature.

[0060] In addition, based on a sensor signal output from a temperature sensor 501, the control device 200 controls the heater 304 to turn on and off so that the temperature of the gas flow path (specifically, the gas flow path of the thread groove pump portion) approaches a predetermined gas flow path target temperature.

[0061] Specifically, the control device 200 controls the opening and closing valve (solenoid valve) of the cooling pipe 305 so that the measured temperature based on the sensor signal of the temperature sensor 402 approaches the control temperature set value, thereby bringing the temperature of the gas flow path closer to a predetermined gas flow path target temperature. Then, the control device 200 changes the control method of the cooling pipe 305 based on the measured temperature at the installation position of the temperature sensor 401 based on the sensor signal of the temperature sensor 401.

[0062] For example, the control device 200 identifies the measured temperature at the installation position of the temperature sensor 401 based on the sensor signal of the temperature sensor 401, and adjusts the above-mentioned control temperature setting value based on the measured temperature, thereby changing the control method for the cooling pipe 305.

[0063] Specifically, when the measured temperature at the installation position of temperature sensor 401 based on the sensor signal of temperature sensor 401 rises, the above-mentioned control temperature set value is made smaller (from the current value), and when the measured temperature at the installation position of temperature sensor 401 based on the sensor signal of temperature sensor 401 falls, the above-mentioned control temperature set value is made larger (from the current value).

[0064] Alternatively, for example, the control device 200 may adjust the transfer function of the temperature control system of the cooling pipe 305 based on the measured temperature, along with the above-mentioned control temperature setpoint.

[0065] Next, the operation of the vacuum pump according to the first embodiment will be described.

[0066] When the vacuum pump is in operation, motor 121 operates and the rotor rotates under the control of control device 200. As a result, gas flowing in through intake port 101 is transported along the gas flow path between the rotor and the stator, and is discharged from exhaust port 133 to an external piping.

[0067] When the vacuum pump is in operation, the control device 200 does not directly monitor the gas flow rate, but acquires the sensor signals of the temperature sensors 401, 402, and 501 to monitor the measured temperatures at the installation positions of the temperature sensors 401, 402, and 501. Then, the control device 200 controls the opening and closing valves of the heater 304 and the cooling pipe 305 (i.e., the refrigerant flow rate) based on the measured temperatures, thereby controlling the temperature of the gas flow path.

[0068] Fig. 5 is a diagram for explaining the temperature control of the vacuum pump shown in Fig. 1. Specifically, for example, as shown in Fig. 5, when the gas load (gas flow rate) is small, the actual gas flow path temperature is relatively low, and the measured temperature of the temperature sensor 401 (gas flow path measured temperature) is also relatively low.

[0069] Here, when the gas load (gas flow rate) increases, the actual gas flow path temperature rises, and the temperature measured by the temperature sensor 401 (gas flow path measured temperature) also rises. Therefore, the control device 200 lowers the control temperature set value of the cooling pipe 305 (i.e., the cooling target temperature) by a decrease amount corresponding to the increase amount of the measured temperature.

[0070] As a result, the temperature drop in the vicinity of the cooling pipe 305 is transmitted to the gas flow path, and the gas flow path temperature approaches the gas flow path target temperature.

[0071] On the other hand, when the gas load (gas flow rate) decreases, the actual gas flow path temperature decreases, and the temperature measured by the temperature sensor 401 (gas flow path measured temperature) also decreases. Therefore, the control device 200 increases the control temperature set value of the cooling pipe 305 (i.e., the cooling target temperature) by an amount corresponding to the amount of increase corresponding to the decrease in the measured temperature.

[0072] As a result, the temperature rise in the vicinity of the cooling pipe 305 is transmitted to the gas flow path, and the gas flow path temperature approaches the gas flow path target temperature.

[0073] By using two temperature sensors 401, 402 in this manner, the gas flow path temperature is adjusted with a small temperature error in response to fluctuations in the gas load (gas flow rate).

[0074] As described above, according to the first embodiment, the cooling pipe 305 adjusts the temperature of the gas flow path. The temperature sensor 401 is disposed at a position closer to the gas flow path than the cooling pipe 305, and the temperature sensor 402 is disposed at a position closer to the cooling pipe 305 than the gas flow path. The control device 200 controls the cooling pipe 305 (the opening and closing valve) based on the sensor signal of the temperature sensor 401 and the sensor signal of the temperature sensor 402 so that the temperature of the gas flow path approaches a predetermined gas flow path target temperature.

[0075] As a result, even if the gas flow rate fluctuates, the gas flow path temperature is appropriately controlled while suppressing overshoot and undershoot, so that the gas flow path temperature is less likely to deviate from the above-mentioned allowable range, and restrictions on the gas flow rate due to temperature management are reduced.

[0076] Embodiment 2

[0077] FIG. 6 is a vertical sectional view showing a turbo molecular pump as a vacuum pump according to the second embodiment.

[0078] In the second embodiment, in the threaded spacer 131, the heater 304 is provided, and temperature sensors 501 and 502 are also provided.

[0079] Temperature sensor 501 is installed at a position closer to heater 304 than the position of the gas flow path whose temperature is to be adjusted, and temperature sensor 502 is installed at a position closer to the gas flow path than heater 304 .

[0080] When the gas load (gas flow rate) increases, the actual gas flow path temperature rises, and the temperature measured by the temperature sensor 401 (gas flow path measured temperature) also rises. Therefore, the control device 200 lowers the control temperature set value of the heater 304 (i.e., the heating target temperature) by an amount corresponding to the increase in the measured temperature.

[0081] On the other hand, when the gas load (gas flow rate) decreases, the actual gas flow path temperature decreases, and the temperature measured by the temperature sensor 401 (gas flow path measured temperature) also decreases. Therefore, the control device 200 increases the control temperature set value of the heater 304 (i.e., the heating target temperature) by an amount corresponding to the amount of increase corresponding to the decrease in the measured temperature.

[0082] By using two temperature sensors 501, 502 in this manner, the gas flow path temperature is adjusted with a small temperature error in response to fluctuations in the gas load (gas flow rate).

[0083] Other configurations and operations of the vacuum pump according to the second embodiment are similar to those of the first embodiment, so the description thereof will be omitted.

[0084] As described above, according to the second embodiment, by using two temperature sensors 501, 502 corresponding to the heater 304 as a temperature adjustment means, as in the first embodiment, even if the gas flow rate fluctuates, the gas flow path temperature is appropriately controlled while suppressing overshoot and undershoot, so that the gas flow path temperature is less likely to deviate from the above-mentioned allowable range, and the restriction of the gas flow rate due to temperature management is reduced.

[0085] It should be noted that various changes and modifications to the above-described embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing its intended advantages. In other words, such changes and modifications are intended to be included within the scope of the claims.

[0086] For example, in the first embodiment, two temperature sensors 501 and 502 may be provided for the heater 304 as in the second embodiment, and the heater 304 may be controlled based on the sensor signals of the temperature sensors 501 and 502. [Industrial Applicability]

[0087] The present invention is applicable to, for example, a vacuum pump. [Explanation of symbols]

[0088] 304 Heater (an example of a temperature control means) 305 Cooling pipe (an example of temperature control means) 401, 501 Temperature sensor (an example of a first temperature sensor) 402, 502 Temperature sensor (an example of a second temperature sensor)

Claims

1. In a vacuum pump that exhausts gas sucked in by the rotation of a rotor, A temperature adjusting means for adjusting the temperature of the gas flow path; a first temperature sensor disposed at a position closer to the gas flow path than the temperature adjusting means; a second temperature sensor disposed at a position closer to the temperature adjusting means than the gas flow path; a control device that controls the temperature adjusting means based on a sensor signal of the first temperature sensor and a sensor signal of the second temperature sensor so that the temperature of the gas flow path approaches a predetermined gas flow path target temperature; Equipped with the control device changes a control temperature set value, which is a target temperature of the temperature adjustment means, in a direction opposite to the change in the measured temperature based on a sensor signal of the first temperature sensor; A vacuum pump characterized by:

2. 2. The vacuum pump according to claim 1, wherein the control device controls the temperature adjustment means so that a measured temperature based on a sensor signal of the second temperature sensor approaches the control temperature set value, thereby bringing the temperature of the gas flow path closer to a predetermined gas flow path target temperature.

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