JP2020020272A - Deposition monitoring device and vacuum pump - Google Patents

Abstract

To provide a deposition monitoring device that can further accurately determine whether matters are excessively deposited inside a vacuum pump.SOLUTION: A control unit 44 that is a deposition monitoring device includes: an operation unit 410 for calculating a variation rate of the power consumed by a motor 10; and a determination unit 411 for determining whether matters are excessively deposited inside a pump body on the basis of the variation rate calculated by the operation unit 410.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a deposit monitoring device and a vacuum pump.

  When a turbo molecular pump is used in a semiconductor manufacturing apparatus typified by an etching apparatus or the like, a product resulting from a process gas is easily deposited inside the turbo molecular pump (for example, see Patent Document 1). When the exhaust efficiency of the turbo-molecular pump is reduced due to product accumulation, even when the same gas flow rate is exhausted, the energy required for exhaust (that is, motor power consumption) increases according to the amount of accumulated product. In the deposit detection device described in Patent Literature 1, the deposit in the pump is detected based on a change in the motor current value due to product deposition, and the notification is performed.

Japanese Patent No. 5767632

  However, in the invention of Patent Literature 1, since the deposit detection is performed only by the change in the motor current value, the accuracy of the deposit detection is insufficient.

A deposit monitoring device according to a preferred embodiment of the present invention is a deposit monitoring device of a vacuum pump that exhausts gas by rotating a rotor with a motor, and the variation in power consumption of the motor, the variation in inverter current, A calculation unit that calculates at least one of a change amount of an input current value or power consumption of a pump power supply device that drives and controls the vacuum pump, and a change amount of a rotation speed of the rotor with respect to a predetermined rotation speed; A determining unit that determines whether or not the deposit in the vacuum pump is excessive based on the calculated change amount.
In a further preferred aspect, a storage unit that stores a threshold value of the change amount is further provided, wherein the determination unit determines that the deposit in the vacuum pump is excessive when the change amount calculated by the calculation unit exceeds the threshold value. Is determined.
In a further preferred aspect, the apparatus further includes an inverter that drives the motor, and a PWM signal generation unit that generates a PWM control signal that controls on / off of a switching element of the inverter, wherein the calculation unit is generated by the PWM signal generation unit. An amount of change in power consumption of the motor is calculated based on the PWM control signal.
In a further preferred aspect, the calculation unit calculates at least one of the plurality of change amounts and a change amount of the motor current value, and the determination unit determines at least one of the plurality of change amounts calculated by the calculation unit. First, it is determined whether or not the deposit in the vacuum pump is excessive based on the amount of change in the motor current value calculated by the arithmetic unit.
In a further preferred aspect, the rotor is supported in a non-contact manner by a magnetic bearing, and the calculation unit includes a change amount of the power consumption of the motor, a change amount of the inverter current, and an input current of a pump power supply device that controls driving of the vacuum pump. At least one of a change amount of a value or power consumption, a change amount of a rotation speed of the rotor, and a change amount of an electromagnet current value of the magnetic bearing is calculated.
In a further preferred aspect, the magnetic bearing has a plurality of pairs of electromagnets opposed to each other with the rotor interposed therebetween, and based on respective electromagnet current values of the plurality of pairs of electromagnets, the plurality of pairs of electromagnets vertically upward from the plurality of pairs of electromagnets. And an estimating unit for estimating the electromagnet disposed in the estimating unit, and the calculation unit calculates a change amount of the electromagnet current value of the electromagnet estimated by the estimating unit.
A vacuum pump according to a preferred embodiment of the present invention includes a pump main body including a rotor and a motor that rotationally drives the rotor, a pump power supply device that drives and controls the pump main body, and the deposit monitoring device according to the above-described aspect.

  ADVANTAGE OF THE INVENTION According to this invention, the excess of the deposit in a vacuum pump can be determined more correctly.

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a turbo-molecular pump. FIG. 2 is a block diagram illustrating a schematic configuration of the pump power supply device. FIG. 3 is a block diagram showing details of the control unit. FIG. 4 is a diagram illustrating an example of a temporal change in motor power when a plurality of processes are performed. FIG. 5 is a diagram showing a distribution of the sampled motor power. FIG. 6 is a diagram illustrating a change in the motor power according to a change in the accumulation amount. FIG. 7 is a block diagram illustrating a schematic configuration of a pump power supply device according to the second embodiment. FIG. 8 is a diagram schematically showing the amount of reduction in the number of revolutions immediately after gas introduction when three processes are performed in order. FIG. 9 is a schematic diagram showing the arrangement of the magnetic bearing electromagnets. FIG. 10 is a diagram showing the arrangement of the bearing electromagnets in the case of the horizontal posture.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
-1st Embodiment-
FIG. 1 is a view showing one embodiment of the present invention, and is a cross-sectional view showing a schematic configuration of a turbo-molecular pump 1. The turbo-molecular pump 1 includes a pump main body 1a for evacuating and a pump power supply device 1b for driving and controlling the pump main body 1a.

  The pump body 1a has a turbo pump stage composed of the rotating blades 21 and the fixed blades 31, and a thread groove pump stage composed of the cylindrical portion 22 and the stator 32. In the screw groove pump stage, a screw groove is formed in the stator 32 or the cylindrical portion 22. The rotary wing 21 and the cylindrical portion 22 are formed on the pump rotor 2a. The pump rotor 2a is fastened to the shaft 2b. The rotator unit 2 is constituted by the pump rotor 2a and the shaft 2b.

  A plurality of stages of stationary blades 31 are alternately arranged with respect to a plurality of stages of rotating blades 21 arranged in the axial direction. Each fixed wing 31 is mounted on the base 3 via a spacer ring 33. When the pump casing 30 is bolted to the base 3, the laminated spacer ring 33 is sandwiched between the base 3 and the locking portion 30 a of the pump casing 30, and the fixed blade 31 is positioned.

  The shaft 2 b is supported in a non-contact manner by magnetic bearings 34, 35, 36 provided on the base 3. Although not shown in detail, each of the magnetic bearings 34 to 36 includes an electromagnet and a displacement sensor. The displacement of the floating position of the shaft 2b is detected by the displacement sensor. The shaft 2b is driven to rotate by the motor 10. The motor 10 includes a motor stator 10a provided on the base 3 and a motor rotor 10b provided on the shaft 2b.

  When the magnetic bearing is not operating, the shaft 2b is supported by emergency mechanical bearings 37a, 37b. When the rotating body unit 2 is rotated at a high speed by the motor 10, the gas on the pump inlet side is exhausted in order by the turbo pump stage (rotary blade 21, fixed blade 31) and the thread groove pump stage (cylindrical portion 22, stator 32). And is discharged from the exhaust port 38.

  FIG. 2 is a block diagram illustrating a schematic configuration of the pump power supply device 1b. An AC input from the outside is converted from AC to DC by a DC power supply 40 provided in the pump power supply device 1b. The DC power supply 40 generates a power supply for the inverter 41, a power supply for the excitation amplifier 45, and a power supply for the control unit 44, respectively. The inverter 41 that supplies current to the motor 10 includes a plurality of switching elements. The motor 10 is driven by controlling on / off of these switching elements by the control unit 44.

  The plurality of electromagnets 46 shown in FIG. 2 indicate electromagnets provided on the respective magnetic bearings 34, 35, 36. The magnetic bearing used in the turbo-molecular pump shown in FIG. 1 is a five-axis control type magnetic bearing, and the radial magnetic bearings 34 and 35 are two-axis magnetic bearings, each having two pairs (4 pairs). ) Electromagnets 46. The axial magnetic bearing 36 is a single-axis magnetic bearing and includes a pair (two) of electromagnets 46. A displacement sensor 43 is provided for each electromagnet 46. Each displacement sensor 43 is provided with a sensor circuit 42. An excitation amplifier 45 for supplying a current to the electromagnets 46 is provided for each of the ten electromagnets 46.

  The control unit 44 that controls the drive of the motor 10 and the drive of the magnetic bearings 34 to 36 includes, for example, a digital arithmetic unit such as an FPGA (Field Programmable Gate Array) and its peripheral circuits. The control unit 44 inputs a PWM (Pulse Width Modulation) control signal 301 for controlling on / off of a plurality of switching elements provided in the inverter 41 to the inverter 41. The current of the motor 10 is detected by the current detection unit 47, and the detected motor current information 307 is input to the control unit 44. The voltage of the motor 10 is detected by the voltage detection unit 48, and the detected motor voltage information 308 is input to the control unit 44.

  The control unit 44 inputs a PWM control signal 303 for turning on and off a switching element provided in the excitation amplifier 45 to each excitation amplifier 45. Each excitation amplifier 45 inputs an electromagnet current signal 304 of each electromagnet 46 to the control unit 44. Further, the control unit 44 inputs a sensor carrier signal (carrier signal) 305 to each sensor circuit 42. Each sensor circuit 42 inputs the sensor signal 306 modulated by the displacement of the shaft 2b to the control unit 44.

  FIG. 3 is a block diagram showing a motor control function and a motor power estimation function in the control unit 44. The deposit monitoring based on the power consumption of the motor 10 (hereinafter, referred to as motor power) will be described with reference to FIG. The control unit 44 includes a sine wave drive control unit 400 related to motor drive control, a calculation unit 410 related to deposit monitoring, a determination unit 411, a storage unit 412, and a notification unit 413. The sine wave drive control unit 400 includes a speed control unit 401, an Id / Iq setting unit 402, an equivalent circuit voltage conversion unit 403, a dq two-phase voltage conversion unit 404, a two-phase to three-phase voltage conversion unit 405, and a PWM signal generation unit. 406 and a rotational speed / magnetic pole position estimating unit 407. In the present embodiment, the motor 10 is a sensorless motor having no rotation sensor for detecting the rotation position of the motor rotor, and estimates the rotation speed and the magnetic pole position based on the motor current information 307 and the motor voltage information 308. .

  The three-phase current flowing through the motor 10 is detected by the current detection unit 47, and the detected current detection signal is input to the low-pass filter 427. On the other hand, the three-phase voltage of the motor 10 is detected by the voltage detector 48, and the detected voltage detection signal is input to the low-pass filter 428. The current detection signal (that is, motor current information 307) that has passed through the low-pass filter 427 and the voltage detection signal (that is, motor voltage information 308) that has passed through the low-pass filter 428 are respectively the rotational speed / magnetic pole position estimating unit of the sine wave drive control unit 400. 407 is input.

  The rotation speed / magnetic pole position estimating unit 407 estimates the rotation speed ω and the magnetic pole position (electric angle θ) of the motor 10 based on the current detection signal and the voltage detection signal. Although details of the calculation for estimating the rotational speed ω and the magnetic pole position (electrical angle θ) are omitted here, they are described in, for example, JP-A-2014-147170. Since the magnetic pole position is represented by the electric angle θ, the magnetic pole position is hereinafter referred to as the magnetic pole electric angle θ. The calculated rotation speed ω is input to the speed control unit 401, the Id / Iq setting unit 402, and the equivalent circuit voltage conversion unit 403. The calculated magnetic pole electrical angle θ is input to the dq-2 phase voltage converter 404.

  The speed control unit 401 performs PI control (proportional control and integral control) or P control (proportional control) based on the difference between the input target rotational speed ωi and the estimated current rotational speed ω, Outputs I. The Id / Iq setting unit 402 sets the current commands Id and Iq in the rotating coordinate dq system based on the current command I.

  The equivalent circuit voltage conversion unit 403 converts the current commands Id and Iq based on the rotation speed ω calculated by the rotation speed / magnetic pole position estimation unit 407 and the electric equivalent circuit constant of the motor 10 into voltage commands Vd, Convert to Vq. Note that the equivalent circuit is divided into a resistance component r and an inductance component L of the motor coil. The values of the electric equivalent circuit constants r and L are obtained from the motor specifications and the like, and are stored in the storage unit 412 in advance.

  The dq-two-phase voltage converter 404 converts the voltage commands Vd, Vq in the rotating coordinate dq system based on the converted voltage commands Vd, Vq and the magnetic pole electrical angle θ input from the rotation speed / magnetic pole position estimator 407. Are converted into voltage commands Vα and Vβ of the fixed coordinate αβ system. The two-phase to three-phase voltage converter 405 converts the two-phase voltage commands Vα, Vβ into three-phase voltage commands Vu, Vv, Vw. The PWM signal generation unit 406 generates and outputs a PWM control signal for turning on / off (conducting or cutting off) the switching element provided in the inverter 41 based on the three-phase voltage commands Vu, Vv, Vw. The inverter 41 turns on and off the switching element based on the PWM control signal output from the PWM signal generation unit 406, and applies a drive voltage to the motor 10.

  In the pump main body 1a, products resulting from the exhaust gas are likely to accumulate. In particular, when the product is deposited in the downstream region of the pump, the clearance between the cylindrical portion 22 of the thread groove pump stage and the stator 32 is small. 32 may come into contact with each other. On the other hand, when the product accumulates in the pump, the exhaust performance deteriorates. When the pump downstream pressure increases due to a decrease in exhaust performance, the motor power required to maintain the rotation of the rotor increases. Therefore, it is possible to estimate the state of product accumulation based on the change in motor power.

  Therefore, a threshold value of the motor power at which the accumulation amount is determined to be excessive (hereinafter, referred to as an excessive determination value) is stored in the storage unit 412 of the control unit 44 in advance. The calculation unit 410 provided in the control unit 44 calculates the motor power based on the motor current information 307 and the motor voltage information 308. The determination unit 411 determines whether or not the amount of change in the motor power calculated by the calculation unit 410 has exceeded the excess determination value, that is, whether or not the accumulation amount of the product has exceeded the allowable accumulation amount. When the amount of change in the motor power exceeds the excess determination value, the determination unit 411 causes the notification unit 413 to output a notification signal indicating that maintenance regarding product accumulation is necessary.

  By the way, when a plurality of processes are sequentially performed in one process chamber, the motor power also differs depending on the process because the exhaust conditions are different for each process. Therefore, when the motor power is used as an index of the deposition amount, it is necessary to extract the motor power under the same pump use conditions (the same process).

  FIG. 4 is a diagram illustrating an example of a temporal change in motor power when a plurality of processes are performed. Line L1 shows the motor power. Note that a plurality of black circles shown on the line L1 indicate sampling data. In the example shown in FIG. 4, three processes indicated by reference numerals A, B, and C are performed in one process, and these processes are repeatedly executed.

  The processes A, B, and C have different pump loads and different motor powers because the types of gas, gas inflow, processing pressure, and processing time are different. When the turbo molecular pump 1 is mounted in a process chamber, generally, a pressure adjusting valve capable of adjusting the opening is provided between the pump main body 1a and the process chamber. During each process, the gas inflow amount and the opening of the pressure regulating valve are adjusted so that the pressure in the process chamber becomes the respective processing pressure. In the example shown in FIG. 4, the motor power in the process A is Wa, the motor power in the process B is Wb, the motor power in the process C is Wc, and Wa> Wc> Wb.

  Before and after each process, the flow of the processing gas is stopped, and the opening of the pressure regulating valve is increased to temporarily reduce the pressure in the process chamber. In FIG. 4, the flow of the processing gas is stopped during the periods t2 to t3, t4 to t5, and t6 to t7, and the valve opening is increased. Therefore, during this period, the motor power is lower than Wa to Wc. Prolonged use of a vacuum pump in such a process increases the amount of product buildup in the pump, and thus the motor power. However, the change in the motor power in a short time as shown in FIG. 4 is very small, and particularly in a period in which the accumulation amount is not so long after the processing is started and the accumulation amount can be regarded as almost zero, the change in the motor power is small. It may be regarded as almost zero.

(How to determine pump operating conditions)
As shown in FIG. 4, the motor power differs depending on the process, and the motor power greatly differs during the process and during the non-process. For example, immediately after the start of the process after the pump maintenance, the motor powers Wa, Wb, and Wc that are not affected by the product accumulation are detected in the A process, the B process, and the C process. The time during which each of the motor powers Wa, Wb, and Wc is continuously detected substantially corresponds to the processing time of each process (that is, the period during which the processing gas flows). Further, between the A, B, and C processes, there is a period in which the motor power is significantly reduced (that is, a period in which the processing gas is not flowing).

  Looking at the distribution of a large number of motor powers sampled during an arbitrary fixed period (for example, a period longer than the period from time t1 to time t7 in FIG. 4), as shown in FIG. 5, the motor powers Wa, Wb, Wc , W0. It can be considered that the data group G1 having the largest power value is sampled during the process A, and the data group G2 having the smallest power value is sampled when there is no gas inflow. That is, when the average power value of the data group G1 is calculated, it is almost Wa, and when the average power value of the data group G2 is calculated, it is almost W0. Of course, the current value of any one data of the data group G1 may be set as the motor power Wa as the accumulation amount index, and the current value of any one data of the data group G2 may be set as the motor electric power W0 as the accumulation amount index.

  Hereinafter, the motor power Wa will be described both when using the average power value and when using individual motor power that varies.

  As described above, the motor power Wa as the deposition amount index increases as the pump operating time elapses, as indicated by Wa1 and Wa2 in FIG. 6, and changes as indicated by the curve L2. ΔWth is the above-mentioned excess determination value. The calculation unit 410 in FIG. 3 calculates the motor power based on the sampled current value and voltage value of the motor 10, and performs the processing shown in FIG. 5 to extract the motor power Wa1 and Wa2 in the A process. The extracted motor powers Wa1 and Wa2 are input to the determination unit 411, and the determination unit 411 determines whether the motor power change amounts (Wa1−Wa) and (Wa2−Wa) exceed the excess determination value ΔWth. judge. When the determination unit 411 determines that the change amount exceeds the excess determination value ΔWth, the determination unit 411 causes the notification unit 413 to output a notification signal as described above. This notification signal is a signal for notifying that it is the maintenance time for deposit cleaning.

  In the above description, the motor power Wa in the process A is used for the excess deposit determination, but the motor powers Wb and Wc in the B or C process may be used for the excess deposit determination. In this case, the excess determination value ΔWth relating to the motor powers Wb and Wc is stored in the storage unit 412 in advance and used for the determination. The process of extracting the B or C process by extracting the motor power Wb or Wc is performed in the same manner as the process A. However, the increase in the motor power with respect to the increase in the deposition amount becomes more remarkable when the gas flow rate is large. Therefore, it is preferable to determine the deposition amount of the product using the motor power in the A process having the largest gas flow rate.

  In the above-described embodiment, the motor 10 is a sensorless motor, and the deposition amount is determined using the motor power based on the motor current information 307 and the motor voltage information 308 used for estimating the rotational speed and the magnetic pole position. . However, the present invention can be similarly applied to a motor having a rotation sensor as long as the motor includes a detection unit that detects a motor current and a motor voltage.

  In the first embodiment described above, when the amount of change in the motor power exceeds the excess determination value ΔWth, it is determined that the amount of deposits in the pump is excessive. Therefore, by using the determination result, for example, by outputting a notification signal based on the determination result, it is possible to easily know that the maintenance time for the deposit has come. Furthermore, since the change in the motor power is used as an index of the excess amount of deposition, not only the change in the motor current but also the change in the motor voltage is reflected, which is more accurate than when only the change in the motor current is used. It can be determined that the amount of deposition is excessive.

  In the embodiment described above, the determination of excess deposit is made based on the amount of change in the motor power calculated from the motor current value and the motor voltage value. For example, the power consumption and the current value of the pump power supply device 1b are determined. , The change in the inverter current of the inverter 41 in FIG. 3, or the PWM control signal output from the PWM signal generation unit 406 in FIG. 3, the determination of the deposition amount may be performed. In the case of using the PWM control signal, the motor power is calculated from the duty ratio of the PWM control signal using a known calculation formula, and the determination of excess deposit is performed based on the calculated change amount of the motor power. As will be described later, when a product accumulates in the pump, the electromagnet current increases, and the power consumption of the magnetic bearing increases. Therefore, when the power consumption of the pump power supply device 1b is used, the change in the power consumption of the pump power supply device 1b includes an increase in the power consumption of the motor and an increase in the power consumption of the magnetic bearings. The change amount becomes larger. The same applies to the case where the change in the current value of the pump power supply device 1b is used. Therefore, the determination of the excess deposit can be performed more accurately.

-2nd Embodiment-
FIG. 7 is a diagram for explaining the second embodiment, and is a block diagram showing a schematic configuration of the pump power supply device 1b as in the case of FIG. 2 described above. In the block diagram shown in FIG. 7, instead of the current detection unit 47 and the voltage detection unit 48 provided in FIG. 2, a rotation speed sensor 23 for detecting the rotor rotation speed (that is, the rotation speed of the shaft 2b in FIG. 1). Was provided. The rotation speed information 302 detected by the rotation speed sensor 23 is input to the control unit 44. The control unit 44 includes a calculation unit 410, a determination unit 411, a storage unit 412, and a notification unit 413, as in the case of FIG.

  When performing process processing, generally, the process chamber is once evacuated to a high vacuum before introducing the process gas, and then, when the process gas is introduced and the pressure in the chamber reaches a predetermined process pressure, the process processing is performed. Be started. In the turbo molecular pump 1, when the rotor speed detected by the speed sensor 23 changes from a predetermined speed (generally, a rated speed), the motor current is controlled to return the changed rotor speed to the predetermined speed. Like that. Therefore, immediately after the introduction of the gas, the rotor rotation speed decreases from the predetermined rotation speed due to a sudden change in the gas load.

  The amount of decrease in the number of revolutions immediately after the introduction of the gas is greater as the gas load is larger, and is larger as the amount of deposited product is larger. FIG. 8 is a diagram schematically showing the amount of decrease in the number of rotations immediately after gas introduction when three processes are sequentially performed. In FIG. 8, A process, B process, and C process are performed in each of the processing sections A, B, and C indicated by arrows. In each of the processing sections A, B, and C, the processing proceeds in the order of gas introduction, process processing, and gas stop. Immediately after gas introduction, the rotor rotation speed decreases from the predetermined rotation speed N0 and returns to the predetermined rotation speed N0 again. After returning, the process is performed. After the processing section C, the wafer unloading / loading processing is performed in the wafer replacement section, and thereafter, the A process, the B process, and the C process are sequentially performed on the replaced wafer.

  In the example shown in FIG. 8, the gas introduction amount is the largest in the process A, and decreases in the order of the process C and the process B. Therefore, the magnitude relationship between the rotor rotation speed reduction amounts ΔNa, ΔNb, and ΔNc immediately after gas introduction in the processing sections A, B, and C is as follows: ΔNa> ΔNc> ΔNb. Although the amount of decrease in the rotor speed depends not only on the gas introduction amount but also on the gas molecular weight and the like, here, only the gas introduction amount will be considered for the sake of simplicity.

  The calculation unit 410 of the control unit 44 illustrated in FIG. 7 calculates the rotor rotation speed reduction amounts ΔNa, ΔNb, and ΔNc based on the rotation speed information 302 from the rotation speed sensor 23. For example, regarding the rotor speed data N (m) sampled in the section Δt of the process A, the difference = N (m) −N (m−1) becomes a negative value. Therefore, the absolute value of the sum of the differences in the section where the difference is a negative value is the rotor rotation speed reduction amount ΔNa. Alternatively, by using the rotor speed data N (m-1) at the timing when the sign of the difference = N (m) -N (m-1) changes from minus to plus, N0-N (m-1) is converted to the rotor. The rotation speed reduction amount ΔNa may be used.

  In addition, even when the rotation of the rotor is not immediately after the introduction of the gas, the rotation speed of the rotor may slightly deviate from the predetermined rotation speed N0. The calculation of ΔNa, ΔNb, and ΔNc may be performed.

  When the rotor rotation speed reduction amount ΔNa is used for the determination of excess deposits, the rotation speed reduction amount is calculated from a plurality of rotation speed reduction amounts sampled during a predetermined time (for example, a time longer than the sum of the processing sections A, B, and C). Data with a large decrease is referred to as a decrease in rotor speed ΔNa. The calculation of the rotor speed reduction amount ΔNa is performed by the calculation unit 410. The determination unit 411 compares the rotor rotation speed reduction amount ΔNa with the threshold value ΔNth stored in the storage unit 412, and determines whether ΔNa> ΔNth. When it is determined that ΔNa> ΔNth, the determination unit 411 causes the notification unit 413 to output a notification signal regarding deposit maintenance. Note that the determination of the accumulation amount may be performed using the rotor rotation speed decrease amount ΔNb or ΔNc. In that case, the threshold value Nth according to the rotor speed reduction amounts ΔNb and ΔNc to be used is stored in the storage unit 412.

  As described above, in the present embodiment, when the amount of decrease in the rotor speed exceeds the threshold, it is determined that the amount of accumulation is excessive, so that only the amount of change in the motor current value is considered without considering the change in motor voltage. It is possible to make a more accurate determination as compared with the case where it is determined that the deposition amount is excessive. Note that, as shown in FIGS. 2 and 3 of the first embodiment, a rotor speed is calculated from the rotation speed ω of the motor 10 estimated by the rotation speed / magnetic pole position estimating unit 407 without providing a rotation speed sensor. The present embodiment can be applied to such a configuration.

-Third embodiment-
In the above-described first embodiment, the excess deposit determination is performed based on the amount of change in the electric power value such as the motor power, and in the second embodiment, the excess deposit determination is performed based on the decrease in the rotor speed. However, in the third embodiment, the excess deposit determination is performed based on the amount of change in the electromagnet current value.

  FIG. 9 is a diagram schematically showing the arrangement of the magnetic bearings 34 to 36 with respect to the shaft 2b of the electromagnet. The axial direction of the shaft 2b is set to the z-axis direction of the magnetic bearings 34 to 36 constituting the five-axis control type magnetic bearing. The magnetic bearing 34 includes a pair of electromagnets 34x11 and 34x12 arranged along the x1 axis with the shaft 2b interposed therebetween, and a pair of electromagnets 34y11 and 34y12 arranged along the y1 axis with the shaft 2b interposed therebetween. ing. The magnetic bearing 35 includes a pair of electromagnets 35x21, 35x22 arranged along the x2 axis with the shaft 2b interposed therebetween, and a pair of electromagnets 35y21, 35y22 arranged along the y2 axis with the shaft 2b interposed therebetween. ing. The magnetic bearing 36 includes a pair of electromagnets 36z1 and 36z2 that are arranged to face each other across the thrust disk 200 of the shaft 2b. These ten electromagnets 34x11, 34x12, 34y11, 34y12, 35x21, 35x22, 35y21, 35y22, 36z1 and 36z2 correspond to the electromagnets 46 shown in FIG. 2 and FIG.

The electromagnet current flowing through each electromagnet is composed of a bias current ib and a levitation control current ic when divided into components by function. Here, the components of the electromagnet current flowing through the opposing electromagnets have the same sign for the bias current and the opposite sign for the levitation control current because of the necessity of magnetic levitation control and the need to detect the position signal (displacement signal) well. It is configured to be. For example, assuming that the electromagnet current of the electromagnet 34x11 arranged in the positive direction of the x1 axis of the magnetic bearing 34 is Ip and the electromagnet current of the electromagnet 34x12 arranged in the negative direction is Im, the electromagnet currents Ip and Im are represented by the following equations (1). , (2).
Ip = ib + ic (1)
Im = ib-ic (2)

  The bias current ib is a direct current or an extremely low frequency band, and is used as a bias for balancing force with gravity acting on the rotating body, improving linearity of levitation force, and sensing displacement. The levitation control current ic is a current used for controlling force for levitation of the shaft 2b to a predetermined position. Since the levitation control current ic changes according to the fluctuation of the levitation position, its frequency band is on the order of 1 kHz from DC.

  Normally, when the turbo molecular pump 1 is used in the upright posture, the z-axis positive direction in FIG. 9 coincides with the vertical upward direction. Generally, the shaft 2b is supported at the center position of the magnetic bearings 34 and 35, which are radial magnetic bearings, and the thrust disk 200 provided on the shaft 2b is supported at an intermediate position between the electromagnets 36z1 and 36z2. Thus, the electromagnet current of each electromagnet is controlled. In the case of the upright posture, the levitation control current ic is controlled so that the attraction force of the electromagnet 36z1 becomes larger so that the influence of gravity is canceled and the electromagnet 36z1 is supported at the intermediate position. If the electromagnet current of the electromagnet 36z1 is represented by Ip in equation (1) and the electromagnet current of the electromagnet 36z2 is represented by Im in equation (2), the control is performed as Ip> Im. On the other hand, when used in an inverted posture, control is performed as Im> Ip.

  When the turbo molecular pump 1 is used in a horizontal position, it is used in a pump position as shown in FIG. 10A or 10B. FIG. 10 shows the arrangement of the electromagnets 34x11, 34x12, 34y11, and 34y12 of the magnetic bearing 34 in the case of the horizontal orientation. In the pump posture shown in FIG. 10A, the electromagnets 34y11 and 34y12 are arranged along the vertical direction. In the pump posture shown in FIG. 10B, the axis x1 on which the electromagnets 34x11 and 34x12 are arranged and the axis y1 on which the electromagnets 34y11 and 34y12 are arranged form an angle of 45 degrees with respect to the vertical direction.

  In any case, the levitation control current ic is controlled so that the influence of gravity is canceled and the shaft 2b is magnetically levitated at the center of the magnetic bearing 34. In the case of FIG. 10A, the electromagnet current Ip of the electromagnet 34y11 is controlled so as to be larger than the electromagnet current Im of the electromagnet 34y12. In the case of FIG. 10B, the electromagnet current Ip of the electromagnets 34x11 and 34y11 is reduced to the electromagnets 34x12 and 34x12. The control is performed so as to be larger than the electromagnet current Im of 34y12.

  In any of the pump postures of the upright posture in FIG. 9, the horizontal posture and the inverted posture (not shown) in FIGS. 10A and 10B, the electromagnet disposed vertically above the pair of electromagnets The electromagnet current becomes larger than the electromagnet current of the other electromagnet. In the case of FIG. 9, among the five axes, the electromagnet currents Ip and Im on the z axis are controlled such that Ip> Im, and the electromagnet currents Ip and Im on the other x1, x2, y1 and y2 axes are It is controlled as Ip = Im. In the case of FIG. 10A, of the five axes, the electromagnet currents Ip and Im on the y1 axis and the y2 axis are controlled such that Ip> Im, and the electromagnet currents Ip on the other x1, ax2 and z axes are controlled. , Im are controlled such that Ip = Im. In the case of FIG. 10B, of the five axes, the electromagnet currents Ip and Im of the x1, x2, y1 and y2 axes are controlled such that Ip> Im, and the electromagnet currents Ip of the other z axes are controlled. , Im are controlled such that Ip = Im. Therefore, by comparing the respective electromagnet currents Ip and Im of the magnetic bearings 24, 25 and 26, it is possible to recognize what pump attitude the turbo molecular pump 1 is arranged in.

  By the way, when products accumulate on the pump rotor 2a, the weight of the pump rotor 2a increases. As a result, the current of the electromagnet arranged on the upper side in the vertical direction in FIGS. 9, 10A and 10B increases. As described above, the electromagnet arranged vertically above can be determined by comparing the respective electromagnet currents Ip and Im of the magnetic bearings 24, 25, and 26. Therefore, the change of the electromagnet current of the electromagnet recognized as the vertically upper side ( Increase) can be used to determine excess product sediment.

  The aforementioned changes in the motor power and the rotor speed are susceptible to the process because the gas flow rate and the gas molecular weight differ depending on the process. However, the amount of change in the electromagnet current depends on the weight of the product deposited on the pump rotor 2a and is not affected by the process. Therefore, the excess deposit can be determined without being affected by the process.

  The calculation unit 410 of the control unit 44 (see FIG. 7) estimates the electromagnet arranged vertically above based on the electromagnet current signal 304, calculates the estimated electromagnet current increase amount of the electromagnet, and sends it to the determination unit 411. input. For example, in the case of the pump posture (the upright posture) in FIG. 9, the electromagnet 36z1 is estimated to be the electromagnet arranged on the upper side in the vertical direction, and the increase amount of the electromagnet current of the electromagnet 36z1 is input to the determination unit 411. The determination unit 411 compares the input electromagnet current increase amount with the threshold value of the electromagnet current increase amount stored in the storage unit 412, and determines whether (electromagnet current increase amount)> (threshold). When it is determined that (electromagnet current increase)> (threshold), the determination unit 411 causes the notification unit 413 to output a notification signal regarding deposit maintenance.

(C1) As described above, the control unit 44, which is the deposit monitoring device, controls the amount of change in the power consumption of the motor 10, the input current value of the pump power supply device 1b that drives and controls the pump main body 1a of the turbo-molecular pump 1, or the consumption. A computing unit 410 for calculating at least one of the amount of change in the electric power and the amount of change in the rotation speed of the pump rotor 2a; a storage unit 412 in which a threshold value of the amount of change is stored; When the change amount exceeds the threshold value, a determination unit 411 that determines that the deposit in the pump main body 1a is excessive is provided.

  As described above, when the determination of excess deposit is performed using the amount of change in the power consumption of the motor 10 or the amount of change in the number of revolutions of the pump rotor 2a, only the amount of change in the motor current value is considered without considering the change in the motor voltage. The determination can be performed more accurately than when the determination is performed. In addition, when the determination of excess deposit is performed using the input current value or the amount of change in power consumption of the pump power supply device 1b that drives and controls the pump main body 1a, only the amount of change in the power consumption or the current value of the motor 10 is used. In addition, since the change in the power consumption of the magnetic bearing is also included, the amount of change is larger and the excess deposit can be more accurately determined. By providing a detection unit that detects the current value and the voltage value of the DC power supply 40, the power consumption and the input current value of the pump power supply device 1b can be obtained based on the detection result of the detection unit.

  Furthermore, the reliability of the determination can be improved by determining the excess of the deposit for a plurality of different amounts of change. In that case, a notification signal may be output when all of the plurality of changes exceed the respective thresholds, or a notification signal is output when any one of the plurality of changes exceeds the threshold. You may do it.

(C2) As shown in FIG. 3, an inverter 41 that drives the motor 10 and a PWM signal generation unit 406 that generates a PWM control signal that controls on / off of the switching element of the inverter 41 are provided. The variation of the power consumption of the motor 10 may be calculated based on the PWM control signal generated by the unit 406.

(C3) Further, the calculating unit 410 determines at least one of a change in the power consumption of the motor 10, a change in the input current value or the power consumption of the pump power supply device 1b, and a change in the rotor speed, and a change in the motor current value. The amount may be calculated, and when the amount of change calculated by the arithmetic unit 410 exceeds the threshold value of the amount of change, it may be determined that the amount of deposits in the pump body 1a is excessive. In addition to the change amount of the motor current value detected by the current detection unit 47 in FIG. 2, the change amount of the power consumption of the motor 10, the change amount of the input current value or the power consumption of the pump power supply device 1b, and the change of the rotor speed. By performing the determination of excess deposit using at least one of the amounts, the reliability of the determination can be improved.

(C4) In the case of a vacuum pump in which the rotor is supported in a non-contact manner by the magnetic bearing, the amount of change in the electromagnet current value of the magnetic bearing may be used as the amount of change in the determination of excess deposit. When the change amount of the electromagnet current value is used, it is possible to determine the excess deposit without being affected by the process. In addition, the change amount of the electromagnet current value and the other change amount (the change amount of the motor power consumption, the change amount of the power consumption and the input current value of the pump power supply device 1b, the change amount of the rotor rotation speed) are combined with each other, and the excess The determination may be made. Thereby, the reliability of the determination can be improved.

(C5) In the case where the determination of excess deposit is performed using the change amount of the electromagnet current value, the arithmetic unit 410 estimates the electromagnet arranged vertically above based on each electromagnet current value of a plurality of pairs of electromagnets. As a result, the electromagnet current value to be used for determining the excess of the deposit is automatically determined. Of course, the operator confirms the pump attitude at the time of installing the vacuum pump, and sends the electromagnet current to be used for the excess deposit determination in the pump attitude from the input unit (not shown) of the pump power supply device 1b to the control unit 44. It is good also as composition which inputs and sets.

  Although various embodiments and modified examples have been described above, the present invention is not limited to these contents. Other embodiments that can be considered within the scope of the technical concept of the present invention are also included in the scope of the present invention. For example, the first to third embodiments described above may be combined and applied. Further, in the above-described embodiment, a magnetic bearing type turbo-molecular pump has been described as an example, but the present invention can also be applied to a non-magnetic bearing type turbo-molecular pump, a screw groove pump, and the like.

  DESCRIPTION OF SYMBOLS 1 ... Turbo molecular pump, 1a ... Pump main body, 1b ... Pump power supply unit, 2 ... Rotating body unit, 2a ... Pump rotor, 2b ... Shaft, 10 ... Motor, 23 ... Rotation speed sensor, 34, 35, 36 ... Magnetic bearing , 40 DC power supply, 41 inverter, 44 control unit, 46 electromagnet, 47 current detection unit, 48 voltage detection unit, 406 PWM signal generation unit, 410 arithmetic unit, 411 determination unit, 412 Storage unit, 413: notification unit

Claims (7)

A deposit monitoring device for a vacuum pump that exhausts gas by rotating a rotor with a motor,
The amount of change in the power consumption of the motor, the amount of change in the inverter current, the amount of change in the input current value or the amount of power consumption of the pump power supply that drives and controls the vacuum pump, and the amount of change in the number of rotations of the rotor with respect to a predetermined number of rotations An arithmetic unit for calculating at least one of:
A determination unit configured to determine whether the amount of deposits in the vacuum pump is excessive based on the amount of change calculated by the calculation unit. The deposit monitoring device according to claim 1,
Further comprising a storage unit for storing a threshold value of the change amount,
The deposit monitoring device, wherein the determination unit determines that the deposit in the vacuum pump is excessive when the amount of change calculated by the calculation unit exceeds the threshold. The deposit monitoring device according to claim 1 or 2,
An inverter that drives the motor;
A PWM signal generation unit that generates a PWM control signal that controls on / off of a switching element of the inverter,
The deposit monitoring device, wherein the calculation unit calculates a change in power consumption of the motor based on the PWM control signal generated by the PWM signal generation unit. In the deposit monitoring device according to any one of claims 1 to 3,
The calculation unit calculates at least one of the plurality of change amounts and a change amount of the motor current value,
The determination unit is configured to determine that the amount of deposits in the vacuum pump is excessive based on at least one of the plurality of change amounts calculated by the calculation unit and the change amount of the motor current value calculated by the calculation unit. A sediment monitoring device that determines whether or not it is. In the deposit monitoring device according to any one of claims 1 to 3,
The rotor is non-contact supported by a magnetic bearing,
The calculation unit is configured to change the power consumption of the motor, the change amount of the inverter current, the input current value or the power consumption of the pump power supply that drives and controls the vacuum pump, the rotation speed change amount of the rotor, A deposit monitoring device for calculating at least one of the changes in the electromagnet current value of the magnetic bearing. The deposit monitoring device according to claim 5,
The magnetic bearing has a plurality of pairs of electromagnets opposed to each other across the rotor,
Based on each electromagnet current value of the plurality of pairs of electromagnets, an estimating unit that estimates an electromagnet arranged vertically above from the plurality of pairs of electromagnets,
The deposit monitoring device, wherein the calculation unit calculates a change amount of an electromagnet current value of the electromagnet estimated by the estimation unit. A pump body including a rotor and a motor that rotationally drives the rotor,
A pump power supply for driving and controlling the pump body;
A vacuum pump comprising: the deposit monitoring device according to any one of claims 1 to 6.

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