Vacuum pump and method for operating a vacuum pump

Abstract

To detect presence / absence of contact between a fixed blade and a rotary blade in a vacuum pump.SOLUTION: A control device 200 of a vacuum pump 100 determines an axial floating position of a rotor shaft 113 as a predetermined reference position, keeps the rotor shaft 113 in a predetermined prescribed operation state, and then offsets a position of the rotor shaft 113 by a predetermined amount continuously. The control device 200 detects presence / absence of contact of the rotary blade 102 and the fixed blade 123 by change of speed data of the rotor shaft 113.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a vacuum pump and a method for operating the vacuum pump.

Background Art

[0002] For example, a turbo molecular pump, which is a type of vacuum pump, includes rotating blades fixed to a rotor shaft and stationary blades fixed to a casing, and exhausts gas in the casing by rotating the rotating blades. The rotating blades and the stationary blades are arranged in a plurality of stages in the vertical direction with a minute gap therebetween. The rotating blades rotate in a magnetically levitated state between the stationary blades during driving (Patent Document 1). Therefore, in order to operate the vacuum pump appropriately, it is necessary to appropriately maintain the gap between the rotating blades and the stationary blades. However, for various reasons, such as poor assembly, component abnormalities, component deformation due to aging deterioration, deposition of products, etc., the gap between the rotating blades and the stationary blades may become smaller. In this case, if the rotating blades deviate from the reference of the floating position, there is a risk of contacting the stationary blades.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventionally, there has been no method for checking the gap between the rotating blades and the stationary blades after assembling the vacuum pump. A method for detecting excessive contact between the rotor shaft and the protective bearing from the deceleration of the rotational speed of the rotor shaft is disclosed in Patent Document 1. However, this method does not disclose a method for checking the interval between the stationary blades and the rotating blades and detecting the presence or absence of contact between the stationary blades and the rotating blades.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a vacuum pump and a method for operating a vacuum pump that can detect the presence or absence of contact between a fixed blade and a rotating blade of the vacuum pump.

Means for Solving the Problems

[0006] To achieve the above object, the vacuum pump of the present invention includes a casing, a rotor shaft disposed within the casing, a magnetic bearing device that supports the rotor shaft in a non-contact manner and rotatably by magnetically levitating the rotor shaft, a plurality of rotating blades rotatable together with the rotor shaft, a plurality of fixed blades facing the plurality of rotating blades, and is a vacuum pump provided with state data acquisition means for acquiring state data of the vacuum pump, control the magnetic bearing device to set the floating position of the rotor shaft in the axial direction to a preset reference position and set the rotor shaft to a preset predetermined operating state, and while the rotor shaft is in the predetermined operating state, control the magnetic bearing device to offset the position of the rotor shaft by a predetermined amount from the reference position, and detect contact of the plurality of rotating blades based on a change in the state data acquired by the state data acquisition means; and is characterized by comprising

[0007] In the above vacuum pump, the state data is speed-related data correlated with the rotational speeds of the rotor shaft and the plurality of rotating blades, and the detection means may detect the contact based on the value at the time of the offset of the approximate line of a plurality of rotational speed data as the speed-related data.

[0008] In the above vacuum pump, The predetermined amount may be determined by the following formula (1) from the allowable clearance amount between the plurality of rotating blades and the plurality of stationary blades allowed during normal operation of the vacuum pump within the movable range in the axial direction of the rotor shaft. Allowable clearance amount between the plurality of rotating blades and the plurality of stationary blades ≦ Predetermined amount ≦ Movable range in the axial direction of the rotor shaft ··· (1)

[0009] In the above vacuum pump, The predetermined operating state may be a deceleration state in a free-run mode without the addition of external torque for the rotor shaft and the rotating blades.

[0010] Also, the method for operating a vacuum pump of the present invention is A method for operating a vacuum pump including a rotor shaft, a plurality of rotating blades rotatable together with the rotor shaft, and a plurality of stationary blades facing the plurality of rotating blades, A step of rotating the rotor shaft and the plurality of rotating blades, and decelerating in a free-run mode without the addition of external torque after the rotational speed reaches a predetermined rotational speed set in advance; A step of setting the floating position in the axial direction of the rotor shaft to a position offset by a predetermined amount from a reference position during deceleration of the rotor shaft in the free-run mode; A step of comparing the difference in the value at the time of offset of an approximate line of a plurality of rotational speed data as speed-related data correlated with the rotational speeds of the plurality of rotating blades in the free-run mode before and after the offset with a reference value of the predetermined difference; A step of determining the presence or absence of contact of the plurality of rotating blades based on the comparison result; Characterized by comprising.

Advantages of the Invention

[0011] According to the present invention, it is possible to detect the presence or absence of contact between the stationary blades and the rotating blades of the vacuum pump.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0013] (Embodiment) The vacuum pump and its operation method according to an embodiment of the present invention will be described by taking a turbo molecular pump and its control method as an example. As shown in Fig. 1, the turbo molecular pump 100 according to this embodiment has an intake port 101 formed at the upper end of a cylindrical outer cylinder (casing) 127. 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, radially and multi-staged on the circumferential part. A rotor shaft 113 is attached to the center of this rotor 103. 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.

[0014] The upper radial electromagnet 104 has four electromagnets arranged in pairs with respect to the X-axis and the Y-axis. Four upper radial sensors 107 are provided in proximity to the upper radial electromagnet 104 and corresponding to each of the upper radial electromagnets 104. For the upper radial sensor 107, for example, an inductance sensor having a conductive winding or an eddy current sensor is used, and the position of the rotor shaft 113 is detected based on the change in the inductance of this conductive winding that changes according to the position of the rotor shaft 113. This upper radial sensor 107 detects the radial displacement of the rotor shaft 113, that is, the rotor 103 fixed thereto, and sends an upper radial position signal to the control device 200.

[0015] The rotor shaft 113 is formed of a high magnetic permeability material (such as iron or stainless steel) 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, respectively. Also, 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, detect the radial position below the rotor shaft 113 in the same manner as the upper radial position, and send a lower radial position signal to the control device 200.

[0016] In the control device 200, a radial control circuit 201, which will be described later with reference to FIG. 5, generates an upper radial excitation signal based on the upper radial position signal from the upper radial sensor 107 and supplies it to the upper radial electromagnet 104. Also, based on the lower radial position signal from the lower radial sensor 108, it generates a lower radial excitation signal and supplies it to the lower radial electromagnet 105, thereby performing excitation control of the upper radial electromagnet 104 and the lower radial electromagnet 105. As a result, the upper radial position and the lower radial position of the rotor shaft 113 are adjusted.

[0017] Furthermore, axial electromagnets 106A and 106B are arranged so as to sandwich a disk-shaped metal disk 111 provided at the lower part of the rotor shaft 113 from above and below. The 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 the rotor shaft 113, and its axial position signal is sent to the control device 200. The axial electromagnets 106A and 106B and the metal disk 111 function as a magnetic bearing device that magnetically levitates and holds the rotor shaft 113 in a non-contact manner.

[0018] In the control device 200, an axial control circuit 202, which will be described later with reference to FIG. 5, generates an upper axial excitation signal and a lower axial excitation signal based on the axial position signal detected by the axial sensor 109, and supplies them to the axial electromagnet 106A and the axial electromagnet 106B respectively, thereby performing excitation control of the axial electromagnet 106A and the axial electromagnet 106B respectively. As a result, the axial electromagnet 106A attracts the metal disk 111 upward by magnetic force, the axial electromagnet 106B attracts the metal disk 111 downward, and the axial position of the rotor shaft 113 is adjusted.

[0019] In this way, the control device 200 appropriately adjusts the magnetic force exerted by the axial electromagnets 106A and 106B on the metal disk 111, magnetically levitates the rotor shaft 113 in the axial direction, and holds it in a non-contact manner in space.

[0020] The motor 121 is composed of, for example, a pulse motor and includes a plurality of magnetic poles arranged circumferentially so as to surround the rotor shaft 113. Each magnetic pole is controlled by the control device 200 so as to rotationally drive the rotor shaft 113 via the electromagnetic force acting between the magnetic pole and the rotor shaft 113. Further, at a position facing the rotor shaft 113 of the motor 121, a rotational speed sensor 121a such as a hall element, a resolver, an encoder, etc. is arranged, and the rotational speed of the rotor shaft 113 is detected by this rotational speed sensor 121a. The rotational speed of the rotor shaft 113 is an example of state data indicating the operating state of the vacuum pump and rotational speed-related data directly or indirectly indicating the rotational speed of the rotor shaft 113. The rotational speed sensor 121a is an example of state data acquisition means.

[0021] Furthermore, for example, a phase sensor (not shown) is attached near the lower radial sensor 108, and the rotation phase of the rotor shaft 113 is detected. In the control device 200, the motor control circuit 203, which will be described later with reference to FIG. 5, outputs a drive signal to the motor 121 using this phase signal and the rotational speed signal from the rotational speed sensor 121a.

[0022] A plurality of fixed blades 123 (123a, 123b, 123c ···) are arranged with a slight gap from the rotating blades 102 (102a, 102b, 102c ···). The rotating blades 102 (102a, 102b, 102c ···) are each inclined by a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transfer the molecules of the exhaust gas downward by collision. The fixed blades 123 (123a, 123b, 123c ···) are made of, for example, metals such as aluminum, iron, stainless steel, copper, or alloys containing these metals as components.

[0023] Similarly, the fixed blades 123 are also formed to be inclined by a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged alternately with the stages of the rotating blades 102 toward the inside of the outer cylinder 127. And the outer peripheral ends of the fixed blades 123 are supported in a state of being inserted between a plurality of stacked fixed blade spacers 125 (125a, 125b, 125c ···).

[0024] The fixed-wing spacer 125 is a ring-shaped member, and is made of, for example, metals such as aluminum, iron, stainless steel, copper, or alloys containing these metals as components. An outer cylinder 127 is fixed to the outer periphery of the fixed-wing spacer 125 with a slight gap therebetween. A base portion 129 is disposed at the bottom of the outer cylinder 127. An exhaust port 133 is formed in the base portion 129 and communicates with the outside. The 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.

[0025] Furthermore, depending on the use of the turbo molecular pump 100, a threaded spacer 131 is disposed between the lower part of the fixed-wing spacer 125 and the base portion 129. The threaded spacer 131 is a cylindrical member made of a metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals as components, and a plurality of spiral thread grooves 131a are engraved on its inner peripheral surface. The direction of the spiral of the thread groove 131a is the direction in which the molecules of the exhaust gas are transferred toward the exhaust port 133 when the molecules move in the rotational direction of the rotating body 103. A cylindrical portion 102d hangs down at the lowermost part following the rotating blades 102 (102a, 102b, 102c ···) of the rotating body 103. The outer peripheral surface of this cylindrical portion 102d is cylindrical and protrudes toward the inner peripheral surface of the threaded spacer 131, and is close 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 rotating blades 102 and the fixed-wing 123 is sent to the base portion 129 while being guided by the thread groove 131a.

[0026] The base portion 129 is a disk-shaped member that constitutes the base of the turbo molecular pump 100, and is generally made of metals such as iron, aluminum, and stainless steel. Since the base portion 129 physically holds the turbo molecular pump 100 and also functions as a heat conduction path, it is desirable to use a metal with high rigidity and high thermal conductivity such as iron, aluminum, or copper.

[0027] In such a configuration, when the rotary blade 102 is rotationally driven by the motor 121 together with the rotor shaft 113, gas is sucked from the chamber through the intake port 101 due to the action of the rotary blade 102 and the fixed blade 123. The rotational speed of the rotary blade 102 is usually 20,000 rpm to 90,000 rpm, and the peripheral speed at the tip of the rotary blade 102 reaches 200 m / s to 400 m / s. The gas sucked from the intake port 101 passes between the rotary blade 102 and the fixed blade 123, is transferred to the base portion 129, and is exhausted from the exhaust port 133. At this time, when the exhaust gas contacts the rotary blade 102, the temperature of the rotary blade 102 rises due to the frictional heat generated and the conduction of the heat generated by the motor 121. This heat is transferred to the fixed blade 123 side by radiation or conduction by gas molecules of the exhaust gas.

[0028] The fixed blade spacer 125 is joined to each other at the outer peripheral portion, and transfers heat received by the fixed blade 123 from the rotary blade 102, frictional heat generated when the exhaust gas contacts the fixed blade 123, etc. to the outside.

[0029] In the above description, the threaded spacer 131 is disposed on the outer periphery of the cylindrical portion 102d of the rotating body 103, and the thread groove 131a is engraved on the inner peripheral surface of the threaded spacer 131. However, conversely, there may be a case where a thread groove is engraved on the outer peripheral surface of the cylindrical portion 102d, and a spacer having a cylindrical inner peripheral surface is disposed around it.

[0030] Also, depending on the application of the turbo molecular pump 100, in order to prevent the gas sucked from the intake port 101 from entering the electrical component portion 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 component portion is covered by the stator column 122 around it, and the inside of this stator column 122 may be maintained at a predetermined pressure with purge gas.

[0031] In this case, pipes (not shown) are disposed in the base portion 129, and purge gas is introduced through these pipes. 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 the stator of the motor 121, and between the stator column 122 and the inner peripheral cylindrical portion of the rotary blade 102.

[0032] Here, the turbo molecular pump 100 requires control based on the specification of the model and specific parameters adjusted individually (for example, various characteristics corresponding to the model). To store this control parameter, the turbo molecular pump 100 is provided with an electronic circuit section 141 inside its main body. The electronic circuit section 141 is composed of semiconductor memories such as EEP-ROM, electronic components such as semiconductor elements for accessing them, a substrate 143 for mounting them, etc. This electronic circuit section 141 is housed in the lower part of the base portion 129 that constitutes the lower part of the turbo molecular pump 100, and is closed by an airtight bottom cover 145.

[0033] By the way, in the semiconductor manufacturing process, among the process gases introduced into the chamber, there are some that become solid when their pressure becomes higher than a predetermined value or their temperature becomes lower than a predetermined value. Inside the turbo molecular pump 100, the pressure of the exhaust gas is the lowest at the intake port 101 and the highest at the exhaust port 133. If the pressure of the process gas becomes higher than a predetermined value or its temperature becomes lower than 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 and accumulates inside the turbo molecular pump 100.

[0034] For example, when SiCl4 is used as the process gas in an Al etching apparatus, in a low vacuum (760 [torr] to 10 -2When the pressure is low (e.g., [torr]) and the temperature is low (about 20 [°C]), it can be seen from the vapor pressure curve that solid products (e.g., AlCl₃) precipitate and adhere and deposit inside the turbo molecular pump 100. As a result, when deposits of process gas accumulate inside the turbo molecular pump 100, these deposits narrow the pump flow path, causing a decrease in the performance of the turbo molecular pump 100. And the above-mentioned products were in a situation where they were likely to solidify and adhere in parts with high pressure near the exhaust port 133 and near the threaded spacer 131.

[0035] Therefore, in order to solve this problem, conventionally, a heater (not shown) or an annular water cooling pipe 149 is wound around the outer periphery of the base portion 129, etc., and a temperature sensor (e.g., thermistor) not shown is embedded in the base portion 129, for example. Based on the signal of this temperature sensor, the temperature of the base portion 129 is controlled to be kept at a certain high temperature (set temperature) by heating the heater and cooling by the water cooling pipe 149 (hereinafter referred to as TMS. TMS; Temperature Management System).

[0036] Next, regarding the turbo molecular pump 100 configured as described above, an amplifier circuit 150 for exciting and controlling the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B will be described. The circuit diagram of this amplifier circuit 150 is shown in FIG. 2.

[0037] In FIG. 2, one end of the electromagnet winding 151 constituting the upper radial electromagnet 104 etc. is connected to the positive electrode 171a of the power supply 171 via the transistor 161, and the other end is connected to the negative electrode 171b of the power supply 171 via the current detection circuit 181 and the transistor 162. And the transistors 161 and 162 are so-called power MOSFETs and have a structure in which a diode is connected between their source and drain.

[0038] At this time, for transistor 161, the cathode terminal 161a of its diode is connected to the positive electrode 171a, and the anode terminal 161b is connected to one end of the electromagnet winding 151. Also, for transistor 162, the cathode terminal 162a of its diode is connected to the current detection circuit 181, and the anode terminal 162b is connected to the negative electrode 171b.

[0039] On the other hand, for the current regeneration diode 165, its cathode terminal 165a is connected to one end of the electromagnet winding 151, and its anode terminal 165b is connected to the negative electrode 171b. Similarly, for the current regeneration diode 166, its cathode terminal 166a is connected to the positive electrode 171a, and its anode terminal 166b is connected to the other end of the electromagnet winding 151 via the current detection circuit 181. And the current detection circuit 181 is composed of, for example, a Hall sensor type current sensor or an electric resistance element.

[0040] The amplifier circuit 150 configured as described above corresponds to one electromagnet. Therefore, when the magnetic bearing is under 5-axis control and there are a total of 10 electromagnets 104, 105, 106A, 106B, similar amplifier circuits 150 are configured for each of the electromagnets, and 10 amplifier circuits 150 are connected in parallel to the power supply 171.

[0041] Furthermore, the amplifier control circuit 191 is composed of, for example, a digital signal processor section (hereinafter referred to as the DSP section) not shown in the control device 200, and this amplifier control circuit 191 is configured to switch the on / off of transistors 161 and 162.

[0042] The amplifier control circuit 191 is configured to compare the current value detected by the current detection circuit 181 (a signal reflecting this current value is referred to as the current detection signal 191c) with a predetermined current command value. Then, based on this comparison result, the magnitudes of the pulse widths (pulse width times Tp1, Tp2) generated within the control cycle Ts, which is one cycle of PWM control, are determined. As a result, the gate drive signals 191a, 191b having these pulse widths are output from the amplifier control circuit 191 to the gate terminals of the transistors 161, 162.

[0043] Note that when passing through the resonance point during the acceleration operation of the rotational speed of the rotating body 103 or when a disturbance occurs during the constant speed operation, etc., it is necessary to control the position of the rotating body 103 with high speed and strong force. Therefore, as the power supply 171, a high voltage of about 50 V, for example, is used so that a rapid increase (or decrease) in the current flowing through the electromagnet winding 151 can occur. Also, a normal capacitor is connected between the positive electrode 171a and the negative electrode 171b of the power supply 171 for stabilizing the power supply 171 (not shown in the figure).

[0044] In such a configuration, when both of the transistors 161, 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.

[0045] Also, when one of the transistors 161, 162 is turned on and the other is turned off, a so-called flywheel current is maintained. And by flowing the flywheel current through the amplifier circuit 150 in this way, the hysteresis loss in the amplifier circuit 150 can be reduced, and the power consumption of the entire circuit can be kept low. Also, by controlling the transistors 161, 162 in this way, 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.

[0046] That is, when the detected current value is smaller than the current command value, as shown in FIG. 3, for only once during the control cycle Ts (for example, 100 μs), both transistors 161 and 162 are turned on for a time corresponding to the pulse width time Tp1. Therefore, during this period, the electromagnetic current iL increases toward the current value iLmax (not shown) that can flow from the positive electrode 171a to the negative electrode 171b via the transistors 161 and 162.

[0047] On the other hand, when the detected current value is larger than the current command value, as shown in FIG. 4, for only once during the control cycle Ts, both transistors 161 and 162 are turned off for a time corresponding to the pulse width time Tp2. Therefore, during this period, the electromagnetic current iL decreases toward the current value iLmin (not shown) that can be regenerated from the negative electrode 171b to the positive electrode 171a via the diodes 165 and 166.

[0048] And in any case, after the elapse of the pulse width times Tp1 and Tp2, one of the transistors 161 and 162 is turned on. Therefore, during this period, the flywheel current is held in the amplifier circuit 150.

[0049] Next, the configuration of the control device 200 will be described. As shown in FIG. 5, the control device 200 includes the aforementioned radial control circuit 201, axial control circuit 202, motor control circuit 203, and gap detection control circuit 204.

[0050] Based on the upper radial position signal supplied from the upper radial sensor 107 and the lower radial position signal supplied from the lower radial sensor 108, the radial control circuit 201 outputs an upper radial excitation signal and a lower radial excitation signal to the upper radial electromagnet 104 and the lower radial electromagnet 105, and controls the radial position of the rotating body 103.

[0051] Based on the axial position signal supplied from the axial sensor 109, the axial control circuit 202 outputs an excitation signal to the upper axial electromagnet 106A and the lower axial electromagnet 106B, and controls the axial position of the rotating body 103.

[0052] Based on the rotation speed signal from the rotation speed sensor 121a and the phase signal from the phase sensor, the motor control circuit 203 outputs a drive pulse signal to the motor 121 to control the rotation speed and phase of the rotor of the motor 121.

[0053] The gap detection control circuit 204 is composed of, for example, a microprocessor with a built-in processor and memory. In response to an external instruction signal, the gap detection control circuit 204 executes the gap detection process shown in FIGS. 6 and 7 to detect whether the fixed blade 123 and the rotating blade 102 are in contact and the axial position of the rotating body 103 when they are in contact. Thereby, the size of the gap between the fixed blade 123 and the rotating blade 102 is obtained. The gap detection control circuit 204 is an example of a detection means for detecting whether the fixed blade 123 and the rotating blade 102 are in contact and the axial position of the rotating body 103 when they are in contact. Note that the contact between the fixed blade 123 and the rotating blade 102 includes contact via deposits such as products.

[0054] Next, the operation of the turbo molecular pump 100 having the above configuration will be described. (Normal operation) During normal operation, the radial control circuit 201 controls the excitation signals supplied to the upper radial electromagnet 104 and the lower radial electromagnet 105 according to the upper radial position signal output from the upper radial sensor 107 and the lower radial position signal output from the lower radial sensor 108, and maintains the radial position of the rotating body 103 at an appropriate position.

[0055] Also, the axial control circuit 202 supplies an upper axial excitation signal and a lower axial excitation signal supplied to the axial electromagnets 106A and 106B according to the axial position signal output from the axial sensor 109, respectively, to maintain the axial position of the rotating body 103 at an appropriate position in a magnetically levitated state. Thereby, the axial position of the rotating blade 102 is controlled to maintain the gap between the fixed blade 123 and the rotating blade 102 at an appropriate value.

[0056] Further, the motor control circuit 203 gives a drive pulse signal in response to the speed signal output from the rotation speed sensor 121a and the phase signal output from the phase sensor, and rotates the motor 121 at the target rotation speed.

[0057] (Gap detection operation) Next, a gap detection process for detecting the gap between the fixed wing 123 and the rotary wing 102 will be described with reference to the flowcharts of FIGS. 6 and 7. Note that the following processes are executed by the gap detection control circuit 204 controlling the radial control circuit 201, the axial control circuit 202, and the motor control circuit 203. However, for the sake of easy understanding, references to the radial control circuit 201, the axial control circuit 202, and the motor control circuit 203 are omitted.

[0058] First, the gap detection control circuit 204 sets the offset amount Δoff for offsetting the axial direction of the rotating body 103 to a minute amount ΔP set in advance (corresponding to an example of the predetermined amount of offset in the claims) (step S1). The magnitude of the minute amount ΔP is arbitrary, but for example, it is set to about 0.005 to 0.2 mm. In the following example, ΔP = 0.01 mm. Note that in the present embodiment, ΔP is a positive value. In the present embodiment, the upward direction is defined as the positive direction.

[0059] Next, the gap detection control circuit 204 determines the presence or absence of contact between the rotary wing 102 and the fixed wing 123 when the rotating body 103 is offset (moved) upward by the offset amount Δoff (step S2). The process for determining the presence or absence of contact will be described later with reference to FIG. 8.

[0060] On the other hand, in step S3, when it is determined that "no contact" and it is determined that "the offset amount Δoff does not exceed the upper limit position" (step S3: No), Δoff = Δoff + ΔP, the offset amount Δoff is set to +ΔP, and the process returns to step S2 to repeat the same process.

[0061] On the one hand, in step S3, if it is determined that "contact exists" or it is determined that "the offset amount Δoff exceeds the upper limit position" (step S3: Yes), the process proceeds to step S5. Note that the upper limit position of the offset amount Δoff is, for example, 0.07 to 0.09 mm. Hereinafter, the upper limit position of the offset amount Δoff is set to 0.08 mm. The reason for setting the upper limit position is to enable measurement until the rotor shaft 113 contacts the protective bearing 120.

[0062] In step S5, the gap detection control circuit 204 sets the offset amount Δoff for offsetting the axial direction of the rotating body 103 to a negative value -ΔP of a preset minute amount ΔP (step S5).

[0063] Next, the gap detection control circuit 204 determines the presence or absence of contact between the rotating blade 102 and the fixed blade 123 when the rotating body 103 is offset (moved) downward by the offset amount Δoff (step S6). The process of determining the presence or absence of contact is the same as that in step S2 and will be described later with reference to FIG. 8.

[0064] In step S6, if it is determined that "no contact" and it is determined that "the offset amount Δoff does not exceed the lower limit position" (step S7: No), then Δoff = Δoff - ΔP, the offset amount Δoff is updated, and the process returns to step S6 to repeat the same process. Note that the reason for setting the lower limit position is the same as the reason for setting the upper limit position, which is to enable measurement until the rotor shaft 113 contacts the protective bearing 120.

[0065] On the other hand, in step S7, if it is determined that "contact exists" or it is determined that "the offset amount Δoff exceeds the lower limit position" (step S7: Yes), the process proceeds to step S8. Subsequently, the detection result, for example, the presence or absence of contact and the offset amount Δoff at the time of contact are output (step S8), and the process ends.

[0066] Next, the contact presence / absence determination process executed in steps S2 and S6 will be described in detail. When the contact presence / absence determination process (steps S2 and S6) starts, the gap detection control circuit 204 starts recording the rotation speed of the rotating body 103 (step S11). The recording is executed, for example, at a fixed sampling period, for example, about 1 ms.

[0067] Next, the gap detection control circuit 204 controls the axial control circuit 202 to control the axial floating amount of the rotating body 103 and position it at the reference position P0. Also, the gap detection control circuit 204 controls the motor control circuit 203 to increase the rotation speed of the rotating body 103 to the reference rotation speed S0 (step S12). The reference rotation speed S0 is arbitrary, but for example, it may be set from 2000 rpm (33.3 Hz) to 1500 rpm (25 Hz).

[0068] While maintaining the floating state, the gap detection control circuit 204 releases the brake of the rotating body 103 to make the rotating body 103 in a free-run state (step S13). In the free-run state, the rotation speed of the rotating body 103 gradually decreases.

[0069] Next, the gap detection control circuit 204 waits for a certain period of time. When the rotation speed reaches, for example, 1500 rpm, it controls the axial control circuit 202 to offset the axial position of the rotating body 103 by an offset amount +Δoff (step S14). That is, it moves by +Δoff. Here, the moving direction is upward in step S2 and downward in step S6.

[0070] If there is no contact between the fixed wing 123 and the rotating wing 102 even after the offset, the free-run state of the rotating body 103 is maintained and its speed is gradually decreased. The flow waits until a certain period of time elapses. On the other hand, if the rotating wing 102 of the rotating body 103 contacts the fixed wing 123 due to the offset, the rotating body 103 rapidly decreases its speed due to friction. All these speed changes are recorded.

[0071] When the gap detection control circuit 204 detects that a certain period of time has elapsed after the offset (step S15: Yes), it stops the rotation and magnetic levitation of the rotating body 103.

[0072] Subsequently, the gap detection control circuit 204 processes the recorded series of discrete rotational speed data. The content of the data processing will be described with reference to FIGS. 8 to 10.

[0073] First, in the internal memory of the gap detection control circuit 204, a series of speed data groups D1 and D2 of time versus speed illustrated in FIGS. 8(A) and (B) are recorded. Note that the speed data group D1 is the data before the offset timing (offset addition time) t0 of step S14, and the speed data group D2 is the data after the offset timing t0.

[0074] The speed data groups D1 and D2 shown in FIG. 8(A) are examples of data when there is no contact between the fixed wing 123 and the rotating wing 102. In this case, before and after the offset timing t0, the rotating body 103 maintains a free-running state. Therefore, the rotational speed of the rotating body 103 gradually changes with a substantially similar trend before and after the offset.

[0075] On the other hand, the speed data groups D1 and D2 shown in FIG. 8(B) are examples when the fixed wing 123 and the rotating wing 102 are in contact due to the offset. In this case, before and after the offset timing t0, the rotational state of the rotating body 103 changes significantly, and after the offset timing t0, the rotational speed rapidly decreases due to the contact between the fixed wing 123 and the rotating wing 102. However, visually, the difference is not clear. In particular, when the degree of contact is small, the difference in the degree of speed reduction is small.

[0076] Therefore, as shown in FIGS. 9(A) and (B), the gap detection control circuit 204 obtains approximation lines C1 and C2 for the speed data groups D1 and D2. The approximation lines C1 and C2 may be approximation straight lines or approximation curves. From the viewpoint of accuracy, an approximation curve is desirable. Specifically, approximation lines of the speed data are obtained before and after the offset timing t0 after free run (step S16). For the sake of distinction, the approximation line obtained from the speed data group D1 before the offset timing t0 is C1, and the approximation line obtained from the speed data group D2 after the offset timing t0 is C2. The method for obtaining the approximation line is arbitrary. For example, a regression line or a regression curve may be obtained by regression analysis. The same applies to the following approximation lines.

[0077] Next, as shown in FIGS. 10(A) and (B), the gap detection control circuit 204 analyzes the approximation lines C1 and C2 respectively, and obtains values Rate (sec / Hz) indicating the time required for the rotation speed (rotational speed) to change by a reference value Hr, for example, 1 Hz, before and after the offset timing t0. Rate (sec / Hz) means the reciprocal of the rotational acceleration (Hz). As a specific process, an approximation line E1 that approximates Rate by the approximation line C1 and an E2 that approximates Rate by the approximation line C2 are obtained (step S17).

[0078] The approximation lines E1 and E2 are as shown in FIGS. 10(A) and (B) depending on the presence or absence of contact. When there is no contact, the approximation lines E1 and E2 are curves showing a substantially continuous tendency. On the other hand, when there is contact, as shown in FIG. 10(B), the approximation lines E1 and E2 are discontinuous curves with the offset timing t0 as a boundary.

[0079] Next, the gap detection control circuit 204 obtains the respective intercepts V1 and V2 of the approximation lines E1 and E2 at the offset timing t0 (step S18). Here, for the sake of distinction, the value of the approximation line E1 at the offset timing t0 is the intercept V1, and the value of the approximation line E2 is the intercept V2. As shown in FIG. 10(A), the difference DA between the intercepts V1 and V2 in the case of no contact is small. On the other hand, as shown in FIG. 10(B), the difference DB between the intercepts V1 and V2 in the case of contact is large.

[0080] The gap detection control circuit 204 compares the difference (V1 - V2) between the intercepts V1 and V2 obtained in step S18 with a preset reference value. The reference value is a value obtained in advance through experiments or the like, and is, for example, 2.3.

[0081] When the difference between the two intercepts (V1 - V2) ≥ the reference value (step S19: Yes), a flag indicating "contact present" is set (step S20). When the difference between the two intercepts (V1 - V2) < the reference value (step S19: No), a flag indicating "no contact" is set (step S21).

[0082] Thus, in this embodiment, the gap between the fixed wing 123 and the rotary wing 102 can be measured as the offset amount Δoff when the two come into contact. Thereby, it is possible to grasp assembly defects, component abnormalities, the presence or absence of component deformation after a predetermined time has elapsed, changes in the gap due to deposits such as products, and the like.

[0083] Also, in this embodiment, by controlling the variable range of the offset amount Δoff, it is also possible to detect that contact does not occur within an appropriate range of the gap size.

[0084] Also, in this embodiment, an example of scanning the offset amount Δoff has been shown, The offset amount Δoff may be set as a single fixed value such as 0.08 mm, for example. In this case, it is possible to detect that the fixed wing 123 and the rotary wing 102 do not contact / are not in contact at a certain offset amount Δoff.

[0085] The present invention has been described above by way of embodiments. However, the present invention is not limited to the embodiments, and various modifications and combinations are possible. For example, in the above embodiment, an example has been described in which the rotating body 103 is axially offset with a period during which the rotating body 103 is decelerated in a free-running mode without the addition of external torque as a predetermined operating state. However, the predetermined operating state is not limited to the decelerated state in the free-running mode, and may be any constant speed state or the like. In addition, the predetermined operating state is arbitrary.

[0086] Further, as shown in Equation 2 (corresponding to Equation 1), the offset amount Δoff, which is a predetermined amount, may be set from a clearance (allowable clearance amount) that is predicted to cause problems in the safe operation and exhaust performance of the turbo molecular pump 100 when the clearance between the rotating blade 102 and the stationary blade 123 becomes smaller due to component deformation due to aging deterioration, deposition of products, etc.

[0087] Allowable clearance amount between the plurality of rotating blades 102 and the plurality of stationary blades 123 ≤ Predetermined amount of offset amount Δoff ≤ Axial movable range of the rotor shaft 113 ···(2)

[0088] Note that the axial movable range of the rotor shaft 113 means a movable range in design, such as the distance until it contacts the protective bearing 120.

[0089] Thereby, the present invention can be applied to preventive maintenance against troubles of the turbo molecular pump 100, determination of the necessity of overhaul, prediction of the timing to be carried out, and the like.

[0090] Further, in the above embodiment, an example has been described in which the method shown in FIGS. 8 to 10 is used as a method for determining whether or not there is contact. However, the present invention is not limited to this, and for example, it may be obtained from the approximate lines C1 of the speed data groups D1 and D2 and the slope of C1.

Explanation of reference numerals

[0091] 100 Turbo molecular pump 101 Intake port 102 (102a, 102b, 102c ···) Rotor blade 102d Cylindrical part 103 Rotating body 104 Upper radial electromagnet 105 Lower radial electromagnet 106A, 106B Axial electromagnets 107 Axial sensor 108 Lower radial sensor 109 Axial sensor 111 Metal disk 113 Rotor shaft 121 Motor 123 (123a, 123b, 123c ···) Fixed wing 125 Fixed wing spacer 127 Outer cylinder (casing) 129 Base part 131 Threaded spacer 131a Thread groove 133 Exhaust port 200 Control device 201 Radial control circuit 202 Axial control circuit 203 Motor control circuit 204 Gap detection control circuit

Claims

1. A casing, A rotor shaft disposed within the casing, A magnetic bearing device that supports the rotor shaft in a non - contact and rotatable manner by magnetically levitating the rotor shaft, A plurality of rotating blades rotatable together with the rotor shaft, A plurality of fixed blades facing the plurality of rotating blades, A vacuum pump comprising: State data acquisition means for acquiring state data of the vacuum pump; Control the magnetic bearing device to set the floating position of the rotor shaft in the axial direction to a preset reference position and set the rotor shaft to a preset predetermined operating state. While the rotor shaft is in the predetermined operating state, control the magnetic bearing device to offset the position of the rotor shaft by a predetermined amount from the reference position, and detect contact of the plurality of rotating blades based on a change in the state data acquired by the state data acquisition means; A vacuum pump, characterized by comprising the above.

2. The state data is speed - related data correlated with the rotational speeds of the rotor shaft and the plurality of rotating blades, The detection means detects the contact based on a value at the time of the offset of an approximate line of a plurality of rotational speed data as the speed - related data. The vacuum pump according to claim 1, characterized by the above.

3. The predetermined amount is determined by the following formula (1) from the allowable clearance amount between the plurality of rotating blades and the plurality of fixed blades allowed during normal operation of the vacuum pump within the movable range of the rotor shaft in the axial direction. The vacuum pump according to claim 1, characterized by the above. Allowable clearance amount between the plurality of rotating blades and the plurality of fixed blades ≤ the predetermined amount ≤ movable range of the rotor shaft in the axial direction... (1)

4. The predetermined operating state is a deceleration state in a free - run mode without the addition of external torque to the rotor shaft and the rotating blades. The vacuum pump according to any one of claims 1 to 3, characterized in that...

5. A method for operating a vacuum pump comprising a rotor shaft, a plurality of rotating blades rotatable together with the rotor shaft, and a plurality of stationary blades facing the plurality of rotating blades, rotating the rotor shaft and the plurality of rotating blades, and after reaching a predetermined rotational speed set in advance, decelerating in a free-run mode without addition of torque from the outside; during deceleration of the rotor shaft in the free-run mode, setting the floating position of the rotor shaft in the axial direction to a position offset by a predetermined amount from a reference position; comparing a difference in values at the time of the offset of an approximate line of a plurality of rotational speed data as speed-related data correlated with the rotational speeds of the plurality of rotating blades in the free-run mode before and after the offset with a reference value of the difference determined in advance; determining the presence or absence of contact of the plurality of rotating blades based on the comparison result; A method for operating a vacuum pump, characterized by comprising the above steps.

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