JP2012251486A - Magnetic levitation vacuum pump, whirling estimation method, rotor balance inspection method, and method for adjusting magnetic bearing control gain - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a whirling estimation method that can facilitate estimating whirling by using a waveform amplitude value, without measuring the whirling in a high-speed rotation state.SOLUTION: The whirling estimation method for a magnetic levitation vacuum pump includes: a magnetic levitation step of magnetically levitating a rotor 30 to a target levitation position; a current measuring step of making the rotor 30, which is magnetically levitated at the target levitation position, sequentially stop at a plurality of rotation positions, and subsequently measuring each current of two pairs of electromagnets in each stopped state; a difference calculation step of calculating differences in the current of the paired electromagnets about each of the plurality of rotation positions, regarding at least one of the two paired electromagnets; an amplitude value calculation step of calculating amplitude values in difference changes while the rotor 30 fully rotates; and an estimation step of estimating a whirling amount of the rotor 30, based on the relationship between a predetermined whirling amount and amplitude value, and the amplitude value calculated in the amplitude value calculation step.

Description

  The present invention relates to a magnetic levitation vacuum pump, a swing estimation method of a magnetic levitation vacuum pump, a rotor balance inspection method, and a magnetic bearing control gain adjustment method.

  In the case of a magnetic levitation turbomolecular pump, the rotor position is detected by a displacement sensor, the sensor signal is taken into a control circuit, and the electromagnet current is controlled based on the sensor signal. In a magnetic bearing device, PID control is generally used as a feedback control system to attenuate a steady deviation with respect to a steady disturbance (see Patent Document 1).

  A magnetic bearing device that supports such a rotor has two natural vibration modes. One is called a cylindrical mode, in which the rotor shaft draws a cylindrical trajectory around the bearing center axis. The second is called a conical mode, in which the rotor shaft draws a conical locus around the bearing center axis. Because of the existence of the natural vibration mode, when the rotational speed of the rotor is increased or decreased, resonance may occur when the rotational frequency matches the natural vibration frequency, which may cause an excessive amplitude of the rotor. .

JP 2004-270778 A

  Normally, the initial balance is corrected by a balancer, but since it differs from the actual rotational speed, the unbalance can be reduced only to a certain extent. Further, since the unbalanced state of each rotating body has a large variation and the finished state is unknown, the optimum gain and the control phase are not known when performing compensation for stabilization in the control of the magnetic bearing. Therefore, if the unbalance is not within the specified value after rotating at high speed, repeat the process of correcting the balance so that it is within the specified value, rotating it again and checking, and balance until stable control is possible. I was working on it.

  However, when the unbalance during high-speed rotation is larger than the specified value, the balance of the rotating body is corrected again by the balancer. To that end, it is necessary to disassemble the assembled pump. After correcting the balance, the pump must be assembled again to check for unbalance due to high-speed rotation. For this reason, the assembly / inspection work is time-consuming, which increases the cost.

The invention according to claim 1 is a method for estimating a whirling of a magnetic levitation vacuum pump including at least a biaxial radial magnetic bearing in which two pairs of electromagnets are arranged with a rotor interposed therebetween, wherein the rotor is magnetized at a target levitation position. A pair of a magnetic levitation step of levitation, a current measurement step of sequentially stopping the rotor magnetically levitated at a target levitation position at a predetermined plurality of rotation positions, and measuring the currents of two pairs of electromagnets at each stop, A difference calculation step of calculating a difference between currents of the electromagnets formed for at least one pair of two pairs of electromagnets, and an amplitude value calculation step of calculating an amplitude value of a difference during one rotation of the rotor. And an estimation step for estimating the amount of swing of the rotor based on the correlation between the amount of swing and the amplitude value and the amplitude value calculated in the amplitude value calculation step.
According to a second aspect of the present invention, in the swing estimation method according to the first aspect, with respect to a plurality of magnetic levitation vacuum pumps, the amplitude value calculated by the amplitude value calculation step and the swing amount measured at the time of high-speed rotation are calculated. Data (amplitude value, measured swing amount) are obtained, and the correlation is calculated based on a plurality of acquired data (amplitude value, measured swing amount).
The invention according to claim 3 is a rotor balance inspection method for a magnetically levitated vacuum pump including a biaxial radial magnetic bearing in which two pairs of electromagnets are arranged with a rotor interposed therebetween, and corrects the mechanical balance of the rotor. A correction step, a step of incorporating the rotor into a pump base provided with a radial magnetic bearing, and a runout estimation method of the rotor according to the runout estimation method according to claim 1, wherein the estimated runout amount is a predetermined reference. A determination step for determining whether or not the value exceeds the value, and the correction step is performed again when it is determined in the determination step that the run-out amount exceeds the predetermined reference value.
The invention according to claim 4 is a magnetic bearing control gain adjusting method for a magnetic levitation vacuum pump including a biaxial radial magnetic bearing in which two pairs of electromagnets are arranged with a rotor interposed therebetween, Based on the run-out amount estimated by the run-out estimation method, the control gain of the radial magnetic bearing is set in advance so that the run-out amount of the rotor during rotational drive is smaller than a predetermined reference value. The gain value is set to be larger than that.
The invention according to claim 5 is a magnetic levitation type vacuum pump including a biaxial radial magnetic bearing in which two pairs of electromagnets are arranged with a rotor interposed therebetween, and is estimated by the whirling estimation method according to claim 1. And a storage unit for storing the amount of run-out, and based on the run-out amount stored in the storage unit, the initial gain value stored in advance is corrected to a correction gain value, and the correction gain value is converted into a radial magnetic bearing. A control gain control unit for setting the control gain of the control unit, and a current control unit for controlling the electromagnet current of the radial magnetic bearing based on the control gain set by the control gain control unit.
A sixth aspect of the present invention is the magnetic levitation vacuum pump according to the fifth aspect, further comprising a rotation sensor for detecting the rotation speed of the rotor, and the control gain control unit is configured such that the rotor rotation speed detected by the rotation sensor is resonant If it is in the critical speed range, set the correction gain value to the control gain, and if the rotor rotational speed detected by the rotation sensor is not in the resonance critical speed range, set the initial gain value to the control gain. It is characterized by.
The invention according to claim 7 is the magnetic levitation vacuum pump according to claim 5 or 6, wherein the pump body provided with the rotor and the storage unit, the power supply device provided with the control gain control unit and the current control unit, The power supply apparatus reads the amount of run-out from the storage unit of the pump body, and sets the control gain by the control gain control unit based on the amount of run-out.

  According to the present invention, it is possible to easily estimate the run-out using the waveform amplitude value without performing the run-around measurement in the high-speed rotation state.

It is a figure which shows schematic structure of a magnetic levitation type vacuum pump. It is a figure explaining a 5-axis control type magnetic bearing. It is a figure which shows the relationship between the rotation position of the shaft 30a at the time of deviation | shift amount (DELTA) measurement, and an electromagnet. It is a figure which shows an example of the measurement result of deviation | shift amount (DELTA). It is a figure which shows the correlation with a waveform amplitude value and the amount of pump rotations actually measured. It is a flowchart for demonstrating the 1st application example of a whirling estimation method. It is a flowchart which shows an example of the conventional assembly process. It is a block diagram for demonstrating the 1st application example of a whirling estimation method. It is a block diagram which shows the structure at the time of using the switching part 90. FIG.

  Embodiments for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a magnetic levitation turbomolecular pump. The turbo molecular pump includes a pump body 1 and a power supply device 4, and the pump body 1 is connected to the power supply device 4 by a power cable (not shown). In the present embodiment, the pump main body 1 and the power supply device 4 are separated, but the present invention can also be applied to an integrated pump in which both are integrated.

  The rotor 30 is supported in a non-contact manner by radial magnetic bearings 37 and 38 and an axial magnetic bearing 39. The magnetic bearing 39 is disposed so as to sandwich the thrust disk 35 fixed to the lower part of the shaft 30 a that is the rotating shaft of the rotor 30 in the axial direction. The flying position of the rotor 30 is detected by radial displacement sensors 27 and 28 and an axial displacement sensor 29.

  The rotor 30 magnetically levitated by the magnetic bearings is driven to rotate at high speed by the motor 36. As the motor 36, a three-phase motor (for example, a brushless DC motor) is used. In FIG. 1, the motor 36 is schematically described, but more specifically, a portion indicated by reference numeral 36 constitutes a motor stator, and a motor rotor (permanent magnet) is provided on the shaft 30a side. .

  The rotation of the rotor 30 is detected by a rotation sensor 33 constituted by an inductance type gap sensor. A sensor target 34 is provided at the lower end of the shaft 30 a that is rotationally driven by the motor 36. The sensor target 34 rotates integrally with the shaft 30a. The axial displacement sensor 29 and the rotation sensor 33 described above are disposed at positions facing the lower surface of the sensor target 34. 26a and 26b are emergency mechanical bearings. When the magnetic bearing is not operating, the rotor 30 is supported by these mechanical bearings 26a and 26b.

  The rotor 30 is formed with a plurality of stages of rotating blades 32 and a cylindrical screw rotor 31 that constitute the rotation-side exhaust function unit. On the other hand, the fixed side is provided with a fixed blade 22 and a screw stator 24 which are fixed-side exhaust function units. The plurality of stages of fixed blades 22 are alternately arranged with the rotary blades 32 in the axial direction. The screw stator 24 is provided on the outer peripheral side of the screw rotor 31 with a predetermined gap.

  In addition, if it is a magnetic bearing type vacuum pump, this invention can be applied not only to a turbo-molecular pump. For example, the present invention can be applied to an all-blade type turbo molecular pump without the screw rotor 31 and the screw stator 24, a drag pump without a rotating blade, or the like.

  Each fixed wing 22 is placed on the base 20 via the spacer ring 23. When the fixing flange 21c of the pump casing 21 is fixed to the base 20 with a bolt, the stacked spacer ring 23 is sandwiched between the base 20 and the pump casing 21, and the fixed blade 22 is positioned. The base 20 is provided with an exhaust port 25, and a back pump is connected to the exhaust port 25. When the rotor 30 is magnetically levitated and driven at high speed by the motor 36, the gas molecules on the intake port 21a side are exhausted to the exhaust port 25 side.

  The power supply device 4 is a device that drives and controls the pump body 1 and includes a CPU, a ROM, a RAM, and other peripheral circuits. The power supply device 4 includes a main control unit 40, a motor control unit 41, and a magnetic bearing control unit 42. The motor control unit 41 drives and controls the motor 36 based on the output signal of the rotation sensor 33. The magnetic bearing control unit 42 controls the electromagnet currents of the magnetic bearings 37 to 39 based on the output signals of the radial displacement sensors 27 and 28 and the axial displacement sensor 29, and magnetically floats the rotor 30 to a predetermined position.

  FIG. 2 is a conceptual diagram showing the arrangement of the electromagnets of the magnetic bearings 37 to 39 constituting the 5-axis control type magnetic bearing, and the rotation axis of the rotor 30 is shown as the z-axis. The magnetic bearing 37 constituting the radial magnetic bearing has a pair of electromagnets 37x + and 37x− and a pair of electromagnets 37y + and 37y− which are arranged to face each other with the shaft 30a interposed therebetween. The arrangement direction of the electromagnets 37x + and 37x− is the x axis, and the arrangement direction of the electromagnets 37y + and 37y− is the y axis. Similarly, the magnetic bearing 38 constituting the radial magnetic bearing has a pair of electromagnets 38x + and 38x− and a pair of electromagnets 38y + and 38y− which are arranged to face each other with the shaft 30a interposed therebetween. The magnetic bearing 39 which is an axial magnetic bearing has a pair of electromagnets 39z + and 39z− disposed opposite to each other in the z-axis direction with the thrust disk 35 interposed therebetween.

  The magnetic bearing 37 adjusts the floating position in the x-axis direction of the shaft 30a by attracting the shaft 30a by the electromagnets 37x + and 37x−, and attracts the shaft 30a by the electromagnets 37y + and 37y−, respectively. The floating position in the y-axis direction is adjusted. The magnetic bearing 38 is the same as the magnetic bearing 37. The magnetic bearing 39 adjusts the floating position of the shaft 30a in the z-axis direction by attracting the thrust disk 35 with the electromagnets 39z + and 39z−. The radial displacement sensors 27 and 28 in FIG. 1 are composed of two sets of sensors corresponding to the electromagnets 37x +, 37x−, 37y +, 37y−, 38x +, 38x−, 38y +, and 38y−.

(Explanation of the whirling estimation method)
Next, with reference to FIGS. 3 to 5, “a method for estimating a whirling around resonance” in the present embodiment will be described. FIGS. 3A to 3D are views of the shaft 30a and the upper radial electromagnets 37x +, 37x−, 37y +, 37y− seen from the direction of the rotation axis. A black circle B shown on the shaft 30a is shown for easy understanding of the rotational position. In step S30, the rotor rotation angle positions are positioned at the four rotation angle positions shown in FIGS. 3A to 3D, the electromagnet currents at the respective rotation angle positions are measured, and the data about the swing of the rotor 30 ( (Waveform amplitude value described later) is acquired. In addition, as a method of positioning the rotor 30 at the respective rotation angle positions in FIGS. 3A to 3D, a method of positioning the rotor 30 by manually rotating the rotor 30 or a motor 36 provided in the pump is controlled. Then there are methods for positioning each.

  First, the shaft 30a is positioned at the 0 degree position shown in FIG. Then, the electromagnet currents of the electromagnets 37x +, 37x−, 37y +, and 37y− are measured. The electromagnet currents are Ix +, Ix−, Iy +, and Iy−, respectively. Next, the shaft 30a is rotated 90 degrees clockwise to position the shaft 30a at the 90-degree position as shown in FIG. Then, electromagnet currents Ix +, Ix−, Iy +, Iy− at the 90-degree position are measured.

  Next, the shaft 30a is further rotated 90 degrees clockwise, and the shaft 30a is positioned at a 180-degree position as shown in FIG. Then, the electromagnet currents Ix +, Ix−, Iy +, Iy− at the 180-degree position are measured. Next, the shaft 30a is further rotated 90 degrees clockwise, and the shaft 30a is positioned at a position of 270 degrees as shown in FIG. Then, electromagnet currents Ix +, Ix−, Iy +, and Iy− at a position of 270 degrees are measured.

  As described above, the shaft 30a is attracted in the x-axis plus direction by the electromagnet 37x + and the shaft 30a is attracted in the x-axis minus direction by the electromagnet 37x- to adjust the attraction force. Is magnetically levitated on the target levitation position, generally the z-axis of FIG. 2, which is an intermediate position (x = 0) between the electromagnets 37x + and 37x−. In the following description, it is assumed that the z-axis is the target flying position in the radial direction.

  If the rotor 30 is an ideal rotor with no mechanical and magnetic imbalance, the shaft 30a is supported at the target floating position when the attractive forces of the electromagnets 37x + and 37x− are equal. The magnetic imbalance is caused by, for example, the influence of the attraction of the motor 6 or the shaft 30a itself being magnetized. In addition, misalignment between the sensor and the electromagnet, and the roundness of the sensor and the electromagnet are affected.

  However, in reality, the occurrence of mechanical and magnetic imbalance in the rotor 30 is unavoidable. Therefore, the shaft 30a is brought to the target floating position by adjusting the attractive force (that is, the electromagnet current) of the electromagnets 37x + and 37x−. Magnetic levitation is attempted. Therefore, if there is an imbalance, the magnitudes of the electromagnet currents Ix + and Ix− when the magnetic levitation is performed at the target levitation position are different. The same applies to the electromagnets 37y + and 37y− in the y-axis direction.

  FIG. 4 shows the measurement results. In FIG. 4, the rotor phase on the horizontal axis represents the rotational angle position of the shaft 30a described above, the state of FIG. 3A represents the rotor phase = 0 degrees, and the state of FIG. It represents 90 degrees. On the other hand, ΔI on the vertical axis is obtained by standardizing the current difference value measured at each rotation angle position with a predetermined value, and represents a ratio (%) with respect to the predetermined value. Here, ΔI is referred to as a deviation amount. For example, the x-axis direction is obtained by {(Ix +) − (Ix −) / (Ix +) + (Ix −)} × 100. Therefore, when the current difference value regarding the electromagnets 37x + and 37x− in the x-axis direction is “(Ix +) − (Ix−)”, the deviation amount ΔI becomes a positive value if (Ix +)> (Ix−). If (Ix +) <(Ix−), the shift amount ΔI is a negative value.

  FIG. 4 shows the deviation amount ΔIx measured for the electromagnets 37x + and 37x− in the x-axis direction and the deviation amount ΔIy measured for the electromagnets 37y + and 37y− in the y-axis direction. The curves Lx and Ly are approximate curves for the actually measured deviation amounts ΔIx and ΔIy. Here, the deviation amounts ΔIx and ΔIy are approximated by a sine curve. If the trends of ΔIx and ΔIy are the same, it can be estimated that the generation of the deviation amount ΔI is an influence of the motor. On the other hand, if ΔIx and ΔIy show different tendencies, another factor can be considered. The example shown in FIG. 4 shows the case of a two-pole motor.

  The difference ΔIx between the current value Ix + of the electromagnet 37x + and the current value Ix− of the electromagnet 37x− is influenced by the imbalance of the rotor 30. In the example shown in FIG. 4, the waveform amplitude (half amplitude) of the approximate curve Lx is about 50, but it can be considered that the larger the waveform amplitude value, the larger the imbalance. Therefore, with respect to a plurality of pumps, the actual measured values ΔIx and ΔIy shown in FIG. 4 or the waveform amplitude values of the approximate curves Lx and Ly are compared with the actually measured pump swing amount (μm). saw. As a result, it has been found that there is a correlation as shown in FIG. 5 between the waveform amplitude value and the actually measured vibration amount (μm) at the time of resonance.

  In obtaining the correlation shown in FIG. 5, as the waveform amplitude, either the waveform amplitude related to ΔIx or ΔIy may be used, or the larger of the two waveform amplitudes may be used.

  Note that the value 50 of the waveform amplitude value of the approximate curve Lx shown in FIG. 4 depends on the size of the reference value (the above-mentioned predetermined value) at the time of normalization. Less than 50. Therefore, it is necessary to align reference values when obtaining the correlation of FIG.

  In FIG. 5, data (waveform amplitude, amount of swing) indicated by ▲ is data relating to one pump, and FIG. 5 is a plot of the data (waveform amplitude, amount of swing) described above for a number of pumps. As the waveform amplitude increases, the amount of swirling tends to increase, and most of the data falls between the lines L11 and L12. Therefore, the amount of run-out can be estimated from the magnitude of the waveform amplitude without actually measuring the amount of run-out.

  For example, when the waveform amplitude value is 40, it can be seen that the amount of swing is about 40 μm to 60 μm. Therefore, if the waveform amplitude value is managed so as to be 40 or less, the swing amount is managed to be 60 μm or less.

  As described above, by using the runout estimation method according to the present embodiment, it is possible to eliminate the need for dynamic runout measurement after the completion of the pump as in the prior art. Further, the measurement of the waveform amplitude value in the above-described whirling estimation method can be performed without setting the pump in a completed state. Therefore, by using this whirling estimation method, it is possible to reduce the assembly cost as shown below.

(Application 1)
FIG. 6 shows an application example of the run-out estimation method, and shows a procedure when the above run-out estimation method is used for the unbalance adjustment at the time of pump assembly. In step S10, balancing is performed with the rotor 30 alone. Specifically, first, the rotor 30 is mounted on the balancer, and the unbalance measurement of the rotor 30 is performed. Next, when the measured unbalance amount is equal to or less than the reference value, the balance of the rotor 30 is corrected by deleting a part of the rotor 30 or adding mass to the rotor 30.

  Next, in step S20, the rotor 30 is incorporated into the base 20 on which the motor 36 and the magnetic bearings 37, 38, 39 are mounted. And it progresses to step S30, an electromagnet current is measured in the procedure shown in FIG. 3, and the waveform amplitude value shown in FIG. 4 is acquired. In step S40, the amount of whirling is estimated based on the acquired waveform amplitude value and the correlation shown in FIG. For example, the amount of whirling is estimated using the line L12 in FIG. If the waveform amplitude value acquired in step S30 is 40, it is estimated that the amount of run-around is 60 μm. Here, the estimation is performed using the line L12. However, for example, a correlation represented by an intermediate line between the line L11 and the line L12 may be used.

  In step S50, it is determined whether or not the run-out amount estimated in step S40 is equal to or less than a predetermined reference value. The reference value here is an upper limit value of the amount of run-out for allowing the dangerous speed region where resonance occurs to pass stably. For example, if the determination reference line shown in FIG. 5 (runout amount = 60 μm) and the actually measured data is below the determination reference line, it is determined to be acceptable, and if the measured data is above, it is not acceptable. Judged as passing.

  If it is determined in step S50 that the test has failed (exceeds the reference value), the process proceeds to step S55 where the rotor 30 is removed from the base 20, and the process returns to step S10 to perform balancing again. On the other hand, if it is determined that the result is acceptable (below the reference value) in step S50, the process proceeds to step S60 where the fixed blades, casing, and the like are assembled to complete the pump body 1. In step S70, a leakage inspection of the pump body 1 is performed. Thereafter, in step S80, the power supply device 4 is connected to the pump body 1, and it is confirmed that the operation operation is normally performed, and the series of assembly steps is finished.

  FIG. 7 is a flowchart showing an example of a conventional pump assembly procedure. Steps for performing the same processing as the steps shown in FIG. 6 are denoted by the same reference numerals as in FIG. In the conventional case, if the process from step S30 to step S50 shown in FIG. 6 is not performed and the operation confirmation process in step S80 is completed, it is determined in next step S90 whether or not the unbalance is OK. In step S90, the swing around the resonance point is actually confirmed, and if the swing amount is equal to or less than the above-described determination reference value, it is determined to be acceptable and the series of assembly steps is completed.

  If it is determined as NO (NO) in step S90, the process proceeds to step S55 and the pump disassembly work is performed. And it progresses to step S10 and balances the rotor 30 again. In this case, since the disassembly is performed after the assembly of the pump body 1 is completed, the disassembling work is troublesome and the operations of Step S60, Step S70 and Step S80 are wasted.

  On the other hand, the measurement of the waveform amplitude in step S30 in FIG. 6 does not require dynamic measurement with the pump body 1 in a completed state unlike the conventional swing measurement, and the rotor 30 is incorporated into the base 20 and statically measured. Can be measured. Therefore, as shown in FIG. 6, it is possible to determine the amount of swing around before the steps S60, S70 and S80, and the disassembly work in step S55 does not take time and labor as in the prior art. Even when balancing is performed again, the operations in steps S60, S70, and S80 are not wasted. As a result, the assembly cost can be reduced.

(Application example 2)
In Application Example 1 described above, instead of actually measuring the amount of run-out at the final stage of the assembly process, run-out estimation is performed at the stage where the rotor 30 is incorporated into the base 20 to correct the unbalance. On the other hand, in application example 2 described below, the pump is stably operated by adjusting the control gain using the estimated amount of swing.

  For example, in the assembling process shown in FIG. 6, even if the balancing in step S10 is repeated and the mechanical unbalance is reduced, the run-out amount is the reference due to unbalance due to other factors such as magnetic unbalance. It may not be less than the value and may not pass in step S50. In such a case, by setting the control gain higher than the reference gain set in advance on the basis of the waveform amplitude value measured in step S30, it is possible to suppress the vibration around the resonance. Moreover, even if it is a case where it passes by step S50, you may make it automatically tune a control gain using a waveform amplitude value.

  FIG. 8 is a block diagram illustrating a configuration example in the case of adjusting the control gain using the waveform amplitude value. 8, the position sensor 80 corresponds to the radial displacement sensors 27 and 28 in FIG. 1, and the electromagnet 81 corresponds to the electromagnets 37x +, 37x−, 37y +, 37y−, 38x +, 38x−, 38y +, and 38y− in FIG. ing. The control gain control unit 82 provided in the magnetic bearing control unit 42 sets a control gain for controlling the electromagnet current based on the sensor signal from the position sensor 80. The PID controller 83 generates an electromagnet current based on the control gain set by the control gain control unit 82 and supplies it to the electromagnet 81. The main control unit 40 is provided with a storage unit 84 for storing the waveform amplitude values described above.

When the waveform amplitude value is measured in step S30 of the assembly process and the amount of swing is estimated in step S40, the amount of swing is stored in the storage unit 84 of the power supply device 4 to be connected to the pump body 1. The control gain control unit 82 sets the control gain according to the equation (1) based on the swing amount stored in the storage unit 84 and a preset reference gain. At this time, the control gain is set so that the swing amount of the rotor 30 during the rotational drive is smaller than a predetermined reference value (the above-described upper limit value of the swing amount). The PID controller 83 generates an electromagnet current based on the control gain set by Expression (1). The control gain control unit 82 sets a reference gain that is set in advance as a control gain when the swing amount is not stored in the storage unit 84.
(Control gain) = (reference gain) + (running amount) × (correction coefficient 1) (1)

Formula (1) for setting the control gain is an example, and there are various setting methods. For example, the waveform amplitude value measured in step S <b> 30 is stored in the storage unit 84 of the power supply device 4 instead of the estimated swing amount. Then, the control gain may be set by the equation (2) using the waveform amplitude value. In this case, the correction coefficient 2 is “(correction coefficient 2) = (correlation) between the correction coefficient 1 of the equation (1) using the correlation coefficient between the amount of swing and the waveform amplitude value. (Number) × (correction coefficient 1) ”.
(Control gain) = (reference gain) + (waveform amplitude value) × (correction coefficient 2) (2)

  Further, as shown in the block diagram of FIG. 9, the gain correction may be performed only in the dangerous speed region by switching the control gain by the switching unit 90. The switching unit 90 performs switching based on the rotation speed signal from the rotation sensor 33. The switching unit 90 switches to the reference gain when the rotational speed of the rotor 30 based on the rotational speed signal is in the dangerous speed region, and corrects the value set by Expression (1) when the rotational speed is not in the dangerous speed region. Switch to the later control gain. In other words, since the corrected control gain is used when passing through the dangerous speed region, the swing around can be suppressed and the dangerous speed region can be stably passed. If the dangerous speed region is passed, the switching unit 90 switches to the reference gain again.

  In the example shown in FIGS. 8 and 9, the swing amount or the waveform amplitude value is stored in the storage unit 84 in the power supply device 4. However, the storage unit 84 in which the swing amount or the waveform amplitude value is stored. May be provided on the pump body side. Normally, the pump body 1 is provided with a storage unit (for example, SRAM or the like is used) in which data necessary for pump operation such as magnetic bearing control parameters is stored. When the pump main body 1 and the power supply device 4 are configured separately, the correspondence between the pump main body 1 and the power supply device 4 is not necessarily one-to-one. Generally, the device 4 can be used. In some cases, the same power supply device 4 can be used for pump bodies 1 of different types.

  In the case of such a configuration, by providing the storage unit 84 on the pump body 1 side, the power supply device 4 can be easily replaced with respect to the pump body 1. The power supply device 4 connected to the pump body 1 reads the swing amount or waveform amplitude value from the storage unit 84 provided on the pump body 1 side into the control gain control unit 82, and converts the swing amount or waveform amplitude value to the read swing amount or waveform amplitude value. Based on this, the control gain is set. Further, in the case where the storage unit is not provided, a method of automatically executing steps S30 to S50 in FIG. 6 when the power is turned on, estimating the swing amount, and deriving the control gain is also conceivable.

  In the above-described embodiment, the magnetic levitation type turbo molecular pump has been described as an example. However, the present invention is not limited to the turbo molecular pump, but can be applied to a magnetic levitation type vacuum pump. Further, the present invention can be applied not only to a 5-axis control type magnetic bearing but also to a 3-axis control type magnetic bearing including a 2-axis radial magnetic bearing and an axial magnetic bearing. Further, the above-described estimation of the amount of whirling is not limited to the stage in which the rotor 30 is incorporated in the base 20 as shown in FIG. 6, but can be performed even after the pump body 1 is completed.

  Each of the embodiments described above may be used alone or in combination. This is because the effects of the respective embodiments can be achieved independently or synergistically. In addition, the present invention is not limited to the above embodiment as long as the characteristics of the present invention are not impaired.

  DESCRIPTION OF SYMBOLS 1: Pump main body, 4: Power supply device, 20: Base, 27-29: Displacement sensor, 30: Rotor, 30a: Shaft, 33: Rotation sensor, 35: Thrust disk, 36: Motor, 37, 38: Radial magnetic bearing 39: axial magnetic bearing, 40: main control unit, 41: motor control unit, 42: magnetic bearing control unit, 82: control gain control unit, 83: PID controller, 84: storage unit, 90: switching unit

Claims (7)

A method for estimating a whirling of a magnetic levitation vacuum pump including a biaxial radial magnetic bearing in which two pairs of electromagnets are arranged with a rotor interposed therebetween,
A magnetic levitation step for magnetically levitating the rotor to a target levitation position;
A current measuring step of sequentially stopping the rotor magnetically levitated at the target levitating position at a plurality of rotational positions and measuring currents of the two pairs of electromagnets at the time of each of the stops;
A difference calculating step of calculating a difference in current between the electromagnets forming a pair for each of a plurality of rotational positions with respect to at least one of the two pairs of electromagnets;
An amplitude value calculating step of calculating an amplitude value of a change in the difference during one rotation of the rotor;
An estimation step for estimating a swing amount of the rotor based on a correlation between a swing amount and an amplitude value obtained in advance and the amplitude value calculated in the amplitude value calculation step. Method. In the whirling estimation method according to claim 1,
With respect to a plurality of magnetically levitated vacuum pumps, data (amplitude value, measured swing amount) consisting of the amplitude value calculated in the amplitude value calculation step and a swing amount actually measured during high-speed rotation are obtained, A shake estimation method, wherein the correlation is calculated based on the plurality of data (amplitude values, measured shake amounts). A rotor balance inspection method for a magnetically levitated vacuum pump comprising a biaxial radial magnetic bearing in which two pairs of electromagnets are disposed across a rotor,
A correction step of correcting the mechanical balance of the rotor;
Incorporating the rotor into a pump base provided with the radial magnetic bearing;
A determination step of estimating a swing amount of the rotor by the swing estimate method according to claim 1 and determining whether or not the estimated swing amount exceeds a predetermined reference value,
The rotor balance inspection method according to claim 1, wherein the correction step is performed again when it is determined in the determination step that the amount of run-out exceeds the predetermined reference value. A magnetic bearing control gain adjustment method for a magnetic levitation vacuum pump comprising a biaxial radial magnetic bearing in which two pairs of electromagnets are arranged across a rotor,
The control gain of the radial magnetic bearing is set so that the amount of rotation of the rotor during rotation driving is smaller than a predetermined reference value based on the amount of rotation estimated by the method of estimating the amount of rotation according to claim 1. A magnetic bearing control gain adjustment method, wherein a gain value larger than a preset initial gain value is set. A magnetically levitated vacuum pump comprising a biaxial radial magnetic bearing in which two pairs of electromagnets are arranged across a rotor,
A storage unit for storing a swing amount estimated by the swing estimate method according to claim 1;
A control gain control unit that corrects an initial gain value stored in advance to a correction gain value based on the swing amount stored in the storage unit, and sets the correction gain value as a control gain of the radial magnetic bearing; ,
A magnetic levitation vacuum pump comprising: a current control unit that controls an electromagnet current of the radial magnetic bearing based on a control gain set by the control gain control unit. In the magnetic levitation vacuum pump according to claim 5,
A rotation sensor for detecting the rotation speed of the rotor;
The control gain control unit
When the rotor rotation speed detected by the rotation sensor is in a resonance occurrence dangerous speed region, the correction gain value is set to the control gain,
The magnetic levitation vacuum pump, wherein the initial gain value is set to the control gain when the rotor rotation speed detected by the rotation sensor is not in a resonance occurrence critical speed region. In the magnetic levitation vacuum pump according to claim 5 or 6,
A pump body provided with the rotor and the storage unit;
A power supply device provided with the control gain control unit and the current control unit,
The magnetic power levitation vacuum pump, wherein the power supply device reads the amount of swinging from the storage unit of the pump body, and sets a control gain by the control gain control unit based on the amount of swinging.

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