CN117795213A - Magnetic bearing device and vacuum pump - Google Patents

Abstract

Provided are a magnetic bearing device and a vacuum pump which are excellent in operation efficiency, capable of safely recovering from an abnormal state such as oscillation, and which have fewer false detection of abnormality and high reliability, in a levitation system using a magnetic bearing. The device is provided with: a magnetic bearing for magnetically suspending the rotor in the air; and a magnetic bearing controller controlling the magnetic bearing; the device is provided with: a 1 st abnormality detection means for detecting an abnormality of control by the magnetic bearing controller based on a predetermined 1 st abnormality condition; a control parameter correction means for correcting the control parameter of the magnetic bearing controller while continuing the operation of the magnetic bearing device when the abnormality of the control is detected by the 1 st abnormality detection means; a 2 nd abnormality detection means for detecting an abnormality of control by the magnetic bearing controller based on a predetermined 2 nd abnormality condition having a degree of abnormality greater than the 1 st abnormality condition; and a stopping mechanism for stopping the operation of the magnetic bearing device when the abnormality of the control is detected by the 2 nd abnormality detecting mechanism.

Description

Magnetic bearing device and vacuum pump

Technical Field

The present invention relates to a magnetic bearing device and a vacuum pump, and more particularly, to a magnetic bearing device and a vacuum pump which are excellent in operation efficiency, capable of safely recovering from an abnormal state such as oscillation, and which are less in erroneous detection of abnormality and have high reliability in a suspension system using a magnetic bearing.

Background

With recent development of electronics, the demand for semiconductors such as memories and integrated circuits has been rapidly increasing.

These semiconductors are manufactured by doping a semiconductor substrate having extremely high purity with impurities to impart electrical properties, or by forming a fine circuit on the semiconductor substrate by etching.

Further, these operations need to be performed in a high vacuum chamber in order to avoid the influence of dust in the air or the like. A vacuum pump is generally used for exhausting the chamber, but a turbo molecular pump, which is one of the vacuum pumps, is often used particularly because of the fact that the residual gas is small and maintenance is easy.

In addition, in the manufacturing process of semiconductors, there are a large number of processes for applying various process gases to a substrate of a semiconductor, and a turbo molecular pump is used not only for setting a vacuum in a chamber but also for exhausting these process gases from the chamber.

Further, in equipment such as an electron microscope, a turbo molecular pump is also used in a state in which the environment in a chamber of the electron microscope is highly evacuated in order to prevent refraction of an electron beam due to dust or the like.

The turbo molecular pump includes a magnetic bearing device for magnetically suspending a rotating body. In addition, in this magnetic bearing device, it is necessary to control the position of the rotating body at a high speed and with a strong force when the rotating body passes a resonance point during acceleration operation, when noise is generated during constant speed operation, or the like.

The position control of the rotating body is performed by feedback control. In the feedback control, if vibration occurs in the rotating body, the vibration is suppressed by means of a magnetic force synchronized with the vibration. Therefore, when the feedback control is not properly designed, an oscillation phenomenon may occur. In addition to this oscillation phenomenon, various abnormalities may occur in the turbomolecular pump depending on the environment such as noise, vibration, and power failure.

For the occurrence of such an abnormality, patent document 1 discloses the following example: when the reset is set, resetting the magnetic bearing device by restarting the magnetic bearing device and continuing the operation to restore the magnetic bearing device to normal; on the other hand, when the setting is made such that the automatic reset is not possible, the operation of the magnetic bearing device is stopped.

In addition, when the magnetic bearing device is applied to a machine tool that requires replacement of a tool, the natural frequency of the rotor changes according to the type of the tool and the presence or absence of the tool. Patent documents 2 and 3 disclose a method for setting a filter that can be controlled stably even when the change occurs.

Further, the flexural natural frequency of the rotor varies according to the rotational speed of the rotor. Patent document 4 discloses a method for setting a filter that can be controlled stably even when the change occurs.

However, as in patent document 1, there is a concern that the normal state cannot be recovered only by resetting, for example, when the state of the system changes such as the rotational speed, the temperature, the time, and the like. In order to recover from the anomalies caused by these, readjustment of the control parameters is required.

Further, in patent documents 2 and 3, since no change in natural vibration during the operation of the pump is assumed, the adjustment is performed immediately after the tool replacement, that is, during the stop of the operation of the pump.

Further, patent document 4 discloses a method for setting a filter in consideration of a change in natural vibration caused by a rotational speed, with respect to a natural vibration mode designated in advance.

However, when an abnormality such as an oscillation of an unexpected natural vibration mode occurs during the operation of the pump or when attenuation or line width of a notch filter set in advance is inappropriate, there is a concern that the change of the natural vibration frequency or the like due to a temperature change or a change with time may not be handled.

Further, there are cases where instantaneous noise unexpectedly occurs in the operation of the pump. In the case of such noise, an alarm or the like is not necessarily required, and there are many cases where there is no problem even if the operation is continued. Thus, the following example is disclosed (patent document 5): even if noise is detected, it is determined whether or not the abnormal signal has continued for about 2 seconds so that the malfunction is not caused, and if so, an alarm is sounded or displayed.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2006-145006

Patent document 2: japanese patent laid-open No. 2001-293637

Patent document 3: japanese patent laid-open No. 2002-188630

Patent document 4: japanese patent laid-open No. 9-236122

Patent document 5: japanese patent laid-open No. 2000-110777

Disclosure of Invention

Problems to be solved by the invention

However, in general, readjustment of the control parameter of the magnetic bearing device is performed after the operation of the pump is stopped due to abnormality detection. Therefore, in readjustment, time is required for stopping the operation of the pump and restarting the pump, and therefore the operation efficiency is deteriorated.

If the control parameter is readjusted during the operation of the pump, the control parameter may be abnormally deteriorated by erroneous readjustment or the like, and may land (touchdown), cause damage to equipment, or the like. Therefore, it is unsafe and requires time and cost for repair.

In addition, when the magnetic bearing device is operated in a state very close to the stability limit due to poor setting of control parameters or the like, an abnormality such as hunting is likely to occur with respect to a slight environmental change. In such a state, the influence of manufacturing dispersion and installation environment is easily received.

Further, when the control parameter of the magnetic bearing device is corrected, noise may be generated in association with the correction. Further, the noise may be judged as an abnormal state by the magnetic bearing device. However, this is temporary and does not need to be handled but is naturally eliminated. Therefore, abnormality should not be judged.

In the method described in patent document 5, it is possible to reduce erroneous detection of an abnormality due to noise associated with correction of a control parameter, and delay in detection of an abnormality occurs other than when the control parameter is corrected. In particular, if abnormality is not immediately detected and dealt with at the time of oscillation of the rotating body, there is a concern that the rotating body contacts the landing bearing to shorten the life of the landing bearing.

The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a magnetic bearing device and a vacuum pump which are excellent in operation efficiency, capable of safely recovering from an abnormal state such as oscillation, and having less false detection of abnormality and high reliability, in a suspension system using a magnetic bearing.

Means for solving the problems

Accordingly, the present invention (claim 1) is a magnetic bearing device comprising: a rotating body; a magnetic bearing for magnetically suspending the rotor in the air; and a magnetic bearing controller controlling the magnetic bearing; the device comprises the following parts: a 1 st abnormality detection means for detecting an abnormality in control by the magnetic bearing controller based on a predetermined 1 st abnormality condition; control parameter correction means for correcting a control parameter of the magnetic bearing controller while continuing the operation of the magnetic bearing device when the abnormality of the control is detected by the 1 st abnormality detection means; a 2 nd abnormality detection means for detecting an abnormality of the control by the magnetic bearing controller based on a predetermined 2 nd abnormality condition having a degree of abnormality greater than the 1 st abnormality condition; and a stopping means for stopping the operation of the magnetic bearing device when the abnormality of the control is detected by the 2 nd abnormality detecting means.

By readjusting the control parameter, it is possible to cope with an abnormality caused by a state change of the system. Thus, the robustness of the magnetic bearing control is enhanced, and the operation efficiency is improved. Further, the control parameter can be readjusted without stopping the operation. Therefore, the time until the recovery is shortened, and the operation efficiency is improved. Further, since a plurality of abnormality references are provided and the operation is stopped when necessary, safety can be ensured.

The present invention (claim 2) is an invention of a magnetic bearing device, wherein the control parameter correction means comprises: a changing step of changing the control parameter from the control parameter before 1 step; a control step of performing control by the magnetic bearing controller with the control parameter changed by the changing step; and a state improvement judging step of judging whether or not a result of the control performed by the control step is improved in the abnormal state of the control compared with a result of the control performed before the 1 step in the control step, and when it is judged that the control is improved in the abnormal state of the control, maintaining the changed value as the control parameter, and when it is judged that the control is not improved in the abnormal state of the control, returning the control parameter to the control parameter before the 1 step.

This can prevent deterioration when the state is instead deteriorated by readjustment of the control parameter. Since the recovery from erroneous readjustment is possible immediately, the safety can be improved, and the readjustment time can be shortened, thereby improving the operation efficiency.

Further, the present invention (claim 3) is an invention of a magnetic bearing device, wherein the control parameter correction means comprises: and a 1 st abnormality elimination determination step of determining whether or not the abnormal state of the control is eliminated based on the 1 st abnormality condition, returning to the changing step when it is determined that the abnormal state of the control determined by the 1 st abnormality condition is not eliminated, and holding the control parameter at that point when it is determined that the abnormal state of the control determined by the 1 st abnormality condition is eliminated, in a subsequent stage of the state improvement determination step when it is determined that the abnormal state of the control is improved.

This shortens the time until the 1 st abnormality is eliminated by readjustment of the control parameter, thereby improving the operation efficiency.

Further, the present invention (claim 4) is the magnetic bearing device, wherein the control parameter correction means further includes: a stability evaluation step of evaluating whether or not the operation of the magnetic bearing device to which the control parameter stored in the 1 st abnormality elimination determination step is applied has a predetermined stability at which abnormality of the control by the magnetic bearing controller does not occur, in a subsequent stage of the 1 st abnormality elimination determination step in which it is determined that the abnormal state of the control determined by the 1 st abnormality condition has been eliminated; when the stability evaluation step evaluates that the stability is insufficient, the correction of the control parameter of the magnetic bearing controller is performed again.

This allows readjustment in consideration of stability. The 1 st abnormality is eliminated but an abnormality is also prevented from occurring. Therefore, the operation efficiency is improved and the safety is improved.

Further, the present invention (claim 5) is the magnetic bearing device according to the present invention, wherein the stability evaluation step evaluates at least one of addition of an excitation signal, increase of a control gain of the magnetic bearing controller, and decrease of the control gain of the magnetic bearing controller.

This makes it possible to easily implement the stability evaluation step.

Further, the present invention (claim 6) is the magnetic bearing device according to the present invention, wherein the control parameter correction means is configured to stop the operation of the magnetic bearing device based on the control parameter set in the past when an abnormality of the control determined based on the 2 nd abnormality condition is detected during the correction of the control parameter by the control parameter correction means.

This makes it possible to shift to the operation stop state with the best control parameter at this point in time. In the process of correcting the control parameter, even when the state is deteriorated by readjustment and an immediate operation stop is required, the operation stop can be performed in a relatively safe state.

Further, the present invention (claim 7) is the magnetic bearing device according to the present invention, wherein the control parameter correction means corrects the control parameter of the magnetic bearing controller while performing the decelerating operation of the rotating body when the abnormality of the control is detected by the 1 st abnormality detection means.

Since readjustment of the control parameter of the magnetic bearing controller is performed during the decelerating operation of the rotating body, the rated rotation speed can be reached more quickly than in the case where readjustment is performed after stopping the operation as the rotation speed zero. Therefore, the operation efficiency improves.

Further, since readjustment is performed during the decelerating operation of the rotating body, the rotation speed at the time of readjustment is smaller than that at the time of abnormality detection. The damage at landing becomes smaller as the rotation speed becomes smaller, and particularly if the rotation speed is equal to or smaller than a predetermined rotation speed, the damage at landing can be ignored. Thus, damage in the case where landing occurs due to abnormal increase in readjustment can be reduced. Thus, the safety is improved.

Further, according to the present invention (claim 8), in the control parameter correction means, when the abnormality of the control is detected by the 1 st abnormality detection means, the rotation speed control of the rotating body is stopped, and the control parameter of the magnetic bearing controller is corrected in a state where the rotating body is free to run.

By stopping the rotation speed control and allowing the rotating body to freely rotate, the absolute value of the torque acting on the rotating body becomes small. Thereby, the vibration of the rotating body is reduced. Therefore, the signal-to-noise ratio of the input signal to the magnetic bearing controller becomes good, and the readjustment accuracy becomes good. Thus, readjustment can be performed at high speed.

Further, the rotational speed can be reached more quickly than in the case of readjusting after decelerating the rotational body or stopping the operation, so that the operation efficiency is improved.

Further, the present invention (claim 9) is the magnetic bearing device according to the present invention, wherein the control parameter correction means corrects the control parameter of the magnetic bearing controller while controlling the rotation speed of the rotating body to a constant speed at the rotation speed at which the abnormality is detected, when the abnormality of the control is detected by the 1 st abnormality detection means.

By setting the rotation body to the constant speed control, the state when an abnormality occurs can be maintained. Therefore, the cause thereof can be searched for efficiently.

The rotational speed can be reached more quickly than in the case of readjusting after decelerating or stopping the rotation of the rotating body, so that the operation efficiency is improved.

Further, according to the present invention (claim 10), in the control parameter correction means, when the abnormality of the control is detected by the 1 st abnormality detection means, the control parameter of the magnetic bearing controller is corrected while the acceleration operation of the rotating body is performed.

Since readjustment is performed during acceleration of the rotating body, acceleration is continued immediately after the 1 st abnormality is eliminated, so that the rated rotation speed can be reached at the fastest speed. Therefore, the operation efficiency improves.

Further, the present invention (claim 11) is the magnetic bearing device according to the present invention, wherein the acceleration of the rotating body is performed when the abnormal state under the 1 st abnormal condition is eliminated after the control parameter of the magnetic bearing controller is corrected.

Since acceleration is continued immediately after the 1 st abnormality is eliminated, the rated rotation speed can be reached faster. Therefore, the operation efficiency improves.

Further, the present invention (claim 12) is the vacuum pump according to the present invention, wherein the magnetic bearing device according to any one of claims 1 to 11 is mounted.

In a vacuum pump, there is a concern that the number of natural vibration modes such as a rotary body is large and oscillation due to the natural vibration occurs, but abnormality due to a change in the state of the system can be handled by readjusting the control parameter. By shortening the time until recovery, the operation efficiency of the vacuum pump is improved.

Further, the present invention (claim 13) is a magnetic bearing device comprising: a rotating body; a magnetic bearing for magnetically suspending the rotor in the air; and a magnetic bearing controller controlling the magnetic bearing; the device comprises the following parts: an abnormality detection means for detecting an abnormality in control by the magnetic bearing controller based on a predetermined abnormality condition; a control parameter correction means for correcting a control parameter of the magnetic bearing controller; a region of a predetermined range including a point on a time axis, a rotation axis, and a frequency axis, where the control parameter correction means corrects the control parameter; and a mitigating mechanism configured to mitigate the predetermined abnormal condition in the predetermined range.

An abnormality of control by the magnetic bearing controller is detected based on a prescribed abnormality condition. When correction of the control parameter is performed, noise is liable to be generated in the control system. However, since the noise is not caused by an abnormality, erroneous detection is not caused. Therefore, the predetermined abnormal condition is alleviated in the region of the predetermined range. On the other hand, when the correction of the control parameter is not performed, since the determination is made in the abnormal condition that is not alleviated, the abnormality can be detected promptly.

Further, the present invention (claim 14) is the magnetic bearing device, wherein the predetermined abnormal condition is constituted by a plurality of types; the abnormal conditions alleviated by the alleviating means include abnormal conditions based on the displacement signal.

The types of abnormal conditions include displacement, abnormal current, contact with the landing bearing, passage of time abnormality, abnormal change in dc link voltage, and the like. Here, as the abnormal condition that is alleviated in the correction of the control parameter, for example, only the displacement is set, and the other abnormal conditions are not alleviated.

In the correction of the control parameter, a large noise tends to occur in the displacement signal, while the noise of the other signals is small. Therefore, noise generated when the control parameter is corrected is not erroneously detected, and an abnormal state such as a power failure, which occurs occasionally with correction of the control parameter, can be detected at a high speed, thereby improving reliability.

Further, the present invention (claim 15) is the magnetic bearing device, wherein the predetermined range region is constituted by a front region forward of the point and a rear region rearward of the point, and the rear region is larger than the front region.

There is a concern that noise accompanying the correction of the control parameter is not generated before the correction of the control parameter, and noise is generated about 1 to 2 seconds immediately after the correction. Therefore, the region located at the rear of a certain point on the time axis, the rotation axis, and the frequency axis, on which the control parameter is corrected, is set to be larger in time, rotation speed, or frequency than the region located at the front.

Further, the present invention (claim 16) is the magnetic bearing device, wherein the region in the predetermined range is constituted only by a rear region rearward of the spot.

Since noise is not generated before the point where the control parameter is corrected, the structure may not include a relief area.

Further, the present invention (claim 17) is the vacuum pump according to the present invention, wherein the magnetic bearing device according to claim 13 or claim 14 is mounted.

Effects of the invention

As described above, according to the present invention, the magnetic bearing control is configured to include: a control parameter correction means for correcting the control parameter of the magnetic bearing controller while continuing the operation of the magnetic bearing device when the abnormality of the control is detected by the 1 st abnormality detection means; and a stopping mechanism for stopping the operation of the magnetic bearing device when the abnormality of the control is detected by the 2 nd abnormality detecting mechanism; therefore, abnormality caused by a change in the state of the system can be handled by readjustment of the control parameter. Thus, the robustness of the magnetic bearing control is enhanced, and the operation efficiency is improved. Further, the control parameter can be readjusted without stopping the operation. Therefore, the time until the recovery is shortened, and the operation efficiency is improved. Further, since a plurality of abnormality references are provided and the operation is stopped when necessary, safety can be ensured.

Drawings

Fig. 1 is a block diagram of a turbo molecular pump used in an embodiment of the present invention.

Fig. 2 is a conceptual flow diagram of a method of readjusting control parameters.

Fig. 3 is a flow chart specifically illustrating a method of readjusting control parameters.

Fig. 4 is a diagram illustrating the adjustment sequence of each adjustment step based on a hypothetical case.

Fig. 5 is a processing method when the 2 nd abnormality is detected.

Fig. 6 is another processing method when the 2 nd abnormality is detected.

Fig. 7 is an explanatory diagram of a readjustment processing method in consideration of stability.

Fig. 8 shows a specific operation example (1) of the relationship between readjustment and pump operation when the 1 st abnormality is detected.

Fig. 9 shows a specific working example (2).

Fig. 10 shows a specific working example (3).

Fig. 11 shows a specific working example (4).

Fig. 12 shows a specific working example (5).

Fig. 13 shows a specific working example (6).

Fig. 14 shows a specific working example (7).

Fig. 15 shows a specific working example (8).

Fig. 16 shows a specific working example (9).

Fig. 17 shows a specific working example (10).

Fig. 18 shows a specific example of the operation (11).

Fig. 19 is a control parameter correction flowchart.

Fig. 20 is a control parameter correction timing chart.

Fig. 21 is an operation example (1) of the case of correcting the control parameter.

Fig. 22 is an operation example (2) of the case of correcting the control parameter.

Fig. 23 is an operation example of the case of correcting the control parameter (3).

Detailed Description

Hereinafter, embodiments of the present invention will be described. Fig. 1 is a block diagram of a turbo molecular pump used in an embodiment of the present invention. In fig. 1, a turbo molecular pump 100 has an intake port 101 formed at the upper end of a cylindrical outer tube 127. Further, a rotor 103 is provided inside the outer tube 127, and a plurality of turbine blades 102 (102 a, 102b, 102c … …) for sucking and discharging gas are radially and multiply formed on the periphery of the rotor 103. A rotor shaft 113 is mounted in the center of the rotor 103, and the rotor shaft 113 is supported in the air by a 5-axis controlled magnetic bearing, for example, and is position-controlled. The rotating body 103 is generally made of a metal such as aluminum or an aluminum alloy.

The upper radial electromagnet 104 is provided with 4 electromagnets in pairs in the X-axis and the Y-axis. 4 upper radial sensors 107 are provided near the upper radial electromagnet 104 and corresponding to the upper radial electromagnet 104. The upper radial sensor 107 detects the position of the rotor shaft 113 based on a change in inductance of a conductive winding that changes according to the position of the rotor shaft 113, using, for example, an inductance sensor having the conductive winding, an eddy current sensor, or the like. The upper radial sensor 107 is configured to detect a radial displacement of the rotor shaft 113, i.e., the rotor 103 fixed thereto, and to transmit the radial displacement to a Central Processing Unit (CPU) of a control device, not shown.

In the central processing unit, a compensation circuit having a function of, for example, PID control is mounted on the magnetic bearing controller, and based on a position signal detected by the upper radial sensor 107, an excitation control command signal of the upper radial electromagnet 104 is generated, and based on the excitation control command signal, an unillustrated magnetic bearing inverter (inverter) performs excitation control of the upper radial electromagnet 104, whereby the upper radial position of the rotor shaft 113 is adjusted.

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

Further, the axial electromagnets 106A and 106B are disposed so as to sandwich a disk-shaped metal disk 111 provided at the lower portion of the rotor shaft 113. The metal plate 111 is made of a high magnetic permeability material such as iron. The axial sensor 109 is provided to detect axial displacement of the rotor shaft 113, and an axial position signal thereof is transmitted to a Central Processing Unit (CPU) of a control device, not shown.

In the magnetic bearing controller mounted on the central processing unit, for example, a compensation circuit having a PID adjustment function generates excitation control command signals for each of the axial electromagnet 106A and the axial electromagnet 106B based on the axial position signal detected by the axial sensor 109, and an unshown magnetic bearing inverter performs excitation control for each of the axial electromagnet 106A and the axial electromagnet 106B based on these excitation control command signals, whereby the axial electromagnet 106A attracts the metal disc 111 upward by magnetic force, the axial electromagnet 106B attracts the metal disc 111 downward, and the axial position of the rotor shaft 113 is adjusted.

In this way, the control device appropriately adjusts the magnetic force applied to the metal disk 111 by the axial electromagnets 106A, 106B to magnetically levitate the rotor shaft 113 in the axial direction and hold it in a non-contact manner in space.

On the other hand, the motor 121 includes a plurality of magnetic poles circumferentially arranged so as to surround the rotor shaft 113. Each magnetic pole is controlled by the control device to rotationally drive the rotor shaft 113 via electromagnetic force acting between the magnetic pole and the rotor shaft 113. A rotational speed sensor, not shown, such as a hall element, a resolver (resolver), or an encoder, is incorporated in the motor 121, and the rotational speed of the rotor shaft 113 is detected from a detection signal of the rotational speed sensor.

Further, for example, a phase sensor, not shown, is mounted near the lower radial sensor 108, and detects the phase of the rotation of the rotor shaft 113. In the control device, the detection signals of the phase sensor and the rotational speed sensor are used together to detect the position of the magnetic pole.

A plurality of stationary blades 123 (123 a, 123b, 123c … …) are arranged with a slight clearance from the rotary blades 102 (102 a, 102b, 102c … …). The rotary blades 102 (102 a, 102b, 102c … …) are formed to be inclined at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 so as to transfer the molecules of the exhaust gas downward by collision. The fixed blades 123 (123 a, 123b, 123c … …) are made of a metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components.

The fixed blades 123 are also formed to be inclined at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are disposed alternately with the layers of the rotating blades 102 toward the inside of the outer tube 127. The outer peripheral ends of the fixed blades 123 are supported in a state of being interposed between a plurality of laminated fixed blade spacers 125 (125 a, 125b, 125c … …).

The fixed blade spacer 125 is an annular member, and is made of a metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components. An outer tube 127 is fixed to the outer periphery of the fixed vane spacer 125 with a slight gap. A base portion 129 is disposed at the bottom of the outer tube 127. An exhaust port 133 is formed in the base portion 129 and communicates with the outside. The exhaust gas that has entered the inlet 101 from the chamber (vacuum chamber) side and has been transferred to the base portion 129 is sent to the exhaust port 133.

Further, according to the use of the turbomolecular pump 100, a threaded spacer 131 is disposed between the lower portion of the fixed vane 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, and a plurality of spiral thread grooves 131a are engraved in the inner peripheral surface thereof. The direction of the spiral of the screw groove 131a is a direction in which molecules of the exhaust gas are transferred to the exhaust port 133 side when the molecules move in the rotation direction of the rotating body 103. A cylindrical portion 102d is provided at the lowermost portion of the rotating body 103, which is continuous with the rotating blades 102 (102 a, 102b, 102c … …). The outer peripheral surface of the 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. The exhaust gas transferred to the screw groove 131a by the rotary vane 102 and the fixed vane 123 is guided by the screw groove 131a and is transferred to the base portion 129.

The base portion 129 is a disk-shaped member constituting the base portion of the turbomolecular pump 100, and is generally made of a metal such as iron, aluminum, or stainless steel. The base portion 129 physically holds the turbo molecular pump 100 and also has a function of a heat conduction path, and therefore, it is preferable to use a metal having rigidity such as iron, aluminum, or copper and having high heat conductivity.

Further, a landing bearing 141 is disposed at the upper end portion of the stator post 122 between the upper radial sensor 107 and the rotating body 103. On the other hand, a landing bearing 143 is disposed below the lower radial sensor 108.

The landing bearing 141 and the landing bearing 143 are each constituted by ball bearings. The landing bearing 141 and the landing bearing 143 are provided so that the rotating body 103 can be safely transferred to the non-levitation state when the rotating body 103 is no longer magnetically levitated for some main reason, such as when the rotation of the rotating body 103 is abnormal or when power is off.

In such a configuration, if the rotary vane 102 is driven to rotate together with the rotor shaft 113 by the motor 121, exhaust gas is sucked from a chamber, not shown, through the inlet 101 by the action of the rotary vane 102 and the fixed vane 123. The rotational speed of the rotary blade 102 is generally 20000rpm to 90000rpm, and the circumferential speed at the front end of the rotary blade 102 reaches 200m/s to 400m/s. The exhaust gas sucked through the inlet 101 passes between the rotary vane 102 and the fixed vane 123 and is transferred to the base portion 129.

Here, when unexpected abnormality such as hunting occurs in the rotating body 103, it is desirable to readjust the control parameters in the magnetic bearing controller and continue the operation. The readjustment method of the control parameter will be described below.

Fig. 2 is a conceptual flowchart of a method for readjusting a control parameter by correction by a control parameter correction means. In step 1 (abbreviated as s1 in the figure, the same applies hereinafter), a Central Processing Unit (CPU) of the control device detects the 1 st abnormality based on a predetermined judgment criterion.

The 1 st abnormality determination criterion is a case where it is desirable to continue the operation of the pump by readjusting the magnetic bearing control parameter even when an abnormality occurs. The predetermined criterion for the 1 st abnormality is, for example, when oscillation is assumed, when the amplitude of the displacement spectrum (spectrum) reaches 0.5 μm, or when the current spectrum amplitude reaches 0.2A, for example.

As a criterion for the 1 st abnormality, for example, when the peak-to-peak (peak to peak) value of the displacement time waveform reaches 20 μm may be set. Since this value is a time waveform, fourier transform is not required, and the amount of computation by a Central Processing Unit (CPU) can be reduced.

Further, as a criterion for determining the 1 st abnormality, for example, when the peak-to-peak value of the current time waveform reaches 1A, may be set.

The 1 st abnormality determination criterion may be set to different values for each frequency component of the spectrum. For example, since the amplitude of the frequency spectrum is large with respect to the rotation frequency component of the magnetic bearing and the harmonic component thereof, the reference is set to be large.

The criterion for the 1 st abnormality may be changed according to the operation state. For example, when the motor 121 is not energized, the displacement spectrum amplitude of 0.5 μm is set as the determination reference value as described above, but when the motor 121 is energized, the displacement spectrum amplitude of 1 μm is set as the determination reference value. This is because the signal-to-noise ratio (S/N ratio) of the non-energized time-varying bit signal is better.

In step 3, a Central Processing Unit (CPU) corrects the magnetic bearing control parameters. The correction at this time is performed by newly setting a filter such as a notch filter, a phase lead filter, a low-pass filter, or a band-pass filter, or by removing an existing filter. The correction may be performed by changing parameters such as the center frequency, line width, and size of the conventional filter. Further, in the case of gain scheduling or the like, the correction may be performed by taking a correlation with information such as the rotation speed and the temperature of the rotating body 103, and changing the control parameters of the filter in accordance with the correlation.

The correction may be performed by changing the proportional gain, the integral gain, and the differential gain of the control parameter by a Central Processing Unit (CPU).

The correction of this period may be performed during suspension of the rotor 103 and rotation of the rotor 103, or may be performed during suspension of the rotor 103 and stationary of the rotor 103.

In step 9, the Central Processing Unit (CPU) detects the 2 nd abnormality based on a predetermined judgment reference. The 2 nd abnormality is an abnormality which cannot be handled by readjustment of the magnetic bearing control parameter, or an abnormality in which the operation should be stopped immediately in a situation. That is, when the amplitude is larger than the 1 st abnormal oscillation, the rotor 103 is in contact with the land bearing 141 and the landing bearing 143, or the time set in the contact state is exceeded, or the dc link voltage is abnormally increased or decreased, or another abnormality occurs.

Specifically, the predetermined criterion for the 2 nd abnormality is a value larger than the predetermined criterion for the 1 st abnormality. For example, when the 1 st abnormality condition is set to the case where the amplitude of the displacement spectrum reaches 0.5 μm or the current spectrum amplitude reaches 0.2A, the 2 nd abnormality condition is set to the case where the amplitude of the displacement spectrum reaches 5 μm or the current spectrum amplitude reaches 0.5A.

For example, when the condition of the 1 st abnormality is set to 20 μm peak-to-peak of the displacement time waveform or 1A peak-to-peak of the current time waveform, the criterion of the 2 nd abnormality is set to 50 μm peak-to-peak of the displacement time waveform or 2A peak-to-peak of the current time waveform. Since this value is a time waveform, fourier transform is not required, and the amount of computation by a Central Processing Unit (CPU) can be reduced.

The determination criterion for the 2 nd abnormality may be set to different values for the frequency components of the spectrum. For example, the rotation frequency component of the magnetic bearing and its harmonic components are set to be large because the amplitude of the frequency spectrum is large.

The criterion for the 2 nd abnormality may be changed according to the operation state. For example, when the motor 121 is not energized, the displacement spectrum amplitude 5 μm is set as the determination reference value as described above, but when the motor 121 is energized, the displacement spectrum amplitude 10 μm is set as the determination reference value. This is because the signal-to-noise ratio of the non-power-on time-varying bit signal is better.

Further, as the criterion for the 2 nd abnormality, it may be set that the rotor 103 is estimated to be in contact with the landing bearing 141 and the landing bearing 143 when the displacement detected by the upper radial sensor 107, the lower radial sensor 108, and the axial sensor 109 exceeds a predetermined value, or that the rotor 103 is confirmed to be in contact with the landing bearing 141 and the landing bearing 143 by a contact detection sensor not shown. The contact may be set 1 time or a predetermined number of times.

The determination criterion for the 2 nd abnormality may be set to be set when the 1 st abnormality is not eliminated even if readjustment of the control parameter is performed a predetermined number of times. Alternatively, the 1 st abnormality may be set so that it is not eliminated even when a predetermined time has elapsed.

Further, as the criterion for the 2 nd abnormality, it may be set to a power failure, a disconnection, another fault detection side, or the like, and when an abnormality that cannot be handled by the control parameter is detected.

The criterion for the 2 nd abnormality may be changed according to the operation state. For example, when the rotational speed of the rotating body 103 is zero, the above-described contact with the land bearing 141 and the landing bearing 143 is excluded from the determination criteria of the 2 nd abnormality, and the operation of the pump is continued. This is because, when the rotational speed of the rotating body 103 is zero, even if the rotating body 103 contacts the landing bearing 141 and the landing bearing 143, it is safe. On the other hand, when the rotor 103 is rotating, the operation of the pump is stopped when contact with the land bearing 141 and the landing bearing 143 is determined.

In order to detect the natural frequency, when the Central Processing Unit (CPU) temporarily increases the gain, the determination criterion of the 2 nd abnormality may be changed. For example, the reference for the 2 nd abnormality is set to 30 μm in the displacement spectrum amplitude, and the reference for the normal operation is set to 15 μm in the displacement spectrum amplitude. This is because it is known in advance that the gain is temporarily increased, and the dangerous state is released immediately.

When the Central Processing Unit (CPU) detects the 2 nd abnormality in step 9, the Central Processing Unit (CPU) stops the operation of the pump in step 11. The method of stopping the operation at this time is performed by decelerating the vehicle by setting the rotation speed command value to zero. Further, at this time, the suspension of the rotating body 103 is continued.

Alternatively, the levitation of the rotating body 103 is stopped by stopping the energization of the magnetic bearing. However, the stoppage of the energization may be performed by stopping energization of any one of the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B.

The operation stop may be performed by a method of decelerating the rotation speed command value set to zero during the rotation of the rotating body 103 or a method of stopping the energization of the magnetic bearing. On the other hand, in the stationary levitation state, only a method of stopping the energization of the magnetic bearing can be performed.

As described above, the readjustment method of the control parameter shown in fig. 2 can be performed by an operation of a Central Processing Unit (CPU). However, the operation may be performed by an externally set device.

In addition, whether readjustment of the control parameter is possible may be set as permitted or not permitted. For example, the shift to permission may be performed at the time of initial setting immediately after shipment, immediately after the power supply is put into operation, when a certain time elapses, when the pump is attached/detached, when the cable is replaced, when there is a change in temperature, or when a state change is detected, or when a user designates. On the other hand, the shift to the unauthorized state may be performed when the rated rotation speed is reached in the authorized state, when the operation is stopped after the rated rotation speed is reached in the authorized state, or when the user designates the operation.

The rotation driving device of the rotor 103 is not limited to the motor 121, and may be applied to a generator, a gas turbine, a steam turbine, a turbine, and a turbine.

As described above, by readjusting the control parameter, it is possible to cope with an abnormality caused by a change in the state of the system. Thus, the robustness of the magnetic bearing control is enhanced, and the operation efficiency is improved. Further, the control parameter can be readjusted without stopping the operation. Therefore, the time until the recovery is shortened, and the operation efficiency is improved. Further, since a plurality of abnormality references are provided and the operation is stopped when necessary, safety can be ensured.

Next, a method of readjusting the control parameter by the correction by the control parameter correction means will be described more specifically with reference to fig. 3 and 4. Fig. 4 is a diagram illustrating the adjustment sequence of each adjustment step based on a hypothetical case. In fig. 3, in step 21, the Central Processing Unit (CPU) detects the 1 st abnormality based on the above-described predetermined judgment criterion. In step 41 of fig. 3, the Central Processing Unit (CPU) detects the 2 nd abnormality based on the predetermined judgment criterion.

At this time, a situation is assumed in which the 1 st abnormality is detected and the 2 nd abnormality is not detected by the Central Processing Unit (CPU). The time series number 0 in fig. 4 is an initial state, that is, a state immediately before the 1 st abnormality detection. The time series number 1 indicates an adjustment step immediately after the 1 st abnormality is detected. When the 1 st abnormality is detected, the routine proceeds to step 23, where the control parameter of the time series number 0 in the initial state is stored in a Central Processing Unit (CPU). Then, in step 25, the Central Processing Unit (CPU) changes the control parameter (changing step) and performs magnetic bearing control (controlling step) using the control parameter. That is, as shown in time series number 1 of fig. 4, at this time, the filter a is added to a Central Processing Unit (CPU) which performs magnetic bearing control. In the following, the control parameter correction is described as adding a filter for simplicity, but other methods are also possible.

As a result of this control, in step 27, the Central Processing Unit (CPU) determines whether or not the state of the 1 st abnormality is improved (state improvement determination step). Specifically, in time series number 1 of fig. 4, a Central Processing Unit (CPU) determines whether the 1 st abnormal state is improved over that before 1 step. The improvement here is a result of comparison with the state before 1 step, and does not necessarily mean that the 1 st abnormality is eliminated. If so, the control parameter at this point is held, and the process proceeds to step 29, where it is determined whether or not the 1 st abnormality is eliminated (1 st abnormality elimination determination step). In time series number 1 of fig. 4, although the 1 st abnormal state is improved, the 1 st abnormal state is not eliminated, so that the process returns to step 23. Thus, the filter set at the end of time sequence number 1 in fig. 4 is filter a.

Since the processing returned to step 23 is the processing of the 2 nd round, it is indicated by time series number 2 in fig. 4. First, in step 23, the filter a, which is a control parameter set in the time series number 1, is stored in a Central Processing Unit (CPU). In step 25, the Central Processing Unit (CPU) adds a filter b (changing step) in addition to the filter a, and performs magnetic bearing control (control step) using the control parameter. Then, in step 27, the Central Processing Unit (CPU) determines whether or not the state of the 1 st abnormality is improved (state improvement determination step). That is, in the time series number 2, it is judged whether the 1 st abnormal state is improved as compared with before the 1 st step. In time series number 2 of fig. 4, since the abnormal state is improved, the control parameter at this point is held, and the process proceeds to step 29, where it is determined whether the 1 st abnormality is eliminated (1 st abnormality elimination determination step). Since the 1 st abnormality is not eliminated, the process returns to step 23 again. Thus, the filters set at the end of time sequence number 2 in fig. 4 are filter a and filter b.

Since the processing in step 23 is the 3 rd round of processing, the processing is indicated by time sequence number 3 in fig. 4. First, in step 23, the filters a and b, which are control parameters set in the time series number 2, are stored in a Central Processing Unit (CPU). In step 25, the Central Processing Unit (CPU) adds a filter c (changing step) in addition to the filters a and b, and performs magnetic bearing control (control step) using the control parameters.

Then, in step 27, the Central Processing Unit (CPU) determines whether or not the state of the 1 st abnormality is improved (state improvement determination step). That is, in the time series number 3, it is judged whether or not the 1 st abnormal state is improved as compared with before the 1 st step. In time series number 3 of fig. 4, the Central Processing Unit (CPU) determines that the abnormal state is not improved. At this time, the process proceeds to step 31, and the Central Processing Unit (CPU) returns the filter setting to the values of the time series number 2 before 1 step, that is, the filter a and the filter b. Then, the process returns to step 23 again. Thus, the filters set at the time point when the time sequence number 3 of fig. 4 ends are the filter a and the filter b as they are.

Since the processing in step 23 is the 4 th round of processing, the processing is indicated by time series number 4 in fig. 4. First, in step 23, the filters a and b, which are control parameters set in the time series number 3, are stored in a Central Processing Unit (CPU). In step 25, the Central Processing Unit (CPU) adds a filter d (changing step) in addition to the filters a and b, and performs magnetic bearing control (control step) using the control parameters. Then, in step 27, the Central Processing Unit (CPU) determines whether or not the state of the 1 st abnormality is improved (state improvement determination step). That is, in the time series number 4, it is judged whether or not the 1 st abnormal state is improved as compared with before the 1 st step. In time series No. 4 of fig. 4, since the 1 st abnormality state is improved, the control parameter at this point is held, and the process proceeds to step 29, where it is determined whether or not the 1 st abnormality is eliminated (1 st abnormality elimination determination step). Since the 1 st abnormality is not eliminated, the process returns to step 23 again. Thus, the filters set at the time point when the time sequence number 4 of fig. 4 ends are the filter a, the filter b, and the filter d.

Since the processing in step 23 is the 5 th round of processing, the processing is indicated by a time sequence number 5 in fig. 4. First, in step 23, the filters a, b, and d, which are control parameters set in the time series number 4, are stored in a Central Processing Unit (CPU). In step 25, the Central Processing Unit (CPU) adds a filter e (changing step) in addition to the filters a, b, and d, and performs magnetic bearing control (control step) using the control parameters. Then, in step 27, the Central Processing Unit (CPU) determines whether or not the state of the 1 st abnormality is improved (state improvement determination step). That is, in the time series number 5, it is judged whether or not the 1 st abnormal state is improved as compared with before the 1 st step. In the time series number 5 of fig. 4, since it is determined in step 27 that the 1 st abnormality state is improved, the control parameter at this point is held, and the process proceeds to step 29, where it is determined whether or not the 1 st abnormality is eliminated (1 st abnormality elimination determination step). Since it is determined in step 29 that the 1 st abnormality is eliminated, the control parameter at that time is held, and the process proceeds to step 35. In step 35, the filters a, b, d, and e set at this point are stored, and readjustment is completed. Thus, the filters set at the end of time sequence number 5 in fig. 4 are filter a, filter b, filter d, and filter e. The subsequent operations are performed by the control parameters stored in step 35.

In addition, in time series numbers 0 to 5 in fig. 4, it is assumed for simplicity that no abnormality 2 is detected in step 41.

Next, a processing method when the 2 nd abnormality is detected will be described with reference to fig. 5.

In fig. 5, since the time sequence number 0 to the time sequence number 3 are the same as those in fig. 4, the description thereof is omitted. In time series No. 4 of fig. 5, first, in step 23, the filters a and b, which are control parameters set in time series No. 3, are stored in a Central Processing Unit (CPU). In step 25, the Central Processing Unit (CPU) adds a filter d (changing step) in addition to the filters a and b, and performs magnetic bearing control (control step) using the control parameters.

Then, in step 27, the Central Processing Unit (CPU) determines whether or not the state of the 1 st abnormality is improved (state improvement determination step). That is, in the time series number 4, it is judged whether or not the 1 st abnormal state is improved as compared with before the 1 st step. In time series No. 4 of fig. 5, the Central Processing Unit (CPU) determines that the 1 st abnormal state is not improved. At this time, the process proceeds to step 31, and the Central Processing Unit (CPU) returns the control parameters to the values before 1 step, that is, the filter a and the filter b. Then, the process returns to step 23 again. Thus, the filters set at the end of time sequence number 4 in fig. 5 are the original filters a and b.

Since the processing in step 23 is the 5 th round of processing, the processing is indicated by a time sequence number 5 in fig. 5. First, in step 23, the filters a and b, which are control parameters set in the time series number 4, are stored in a Central Processing Unit (CPU). In step 25, the Central Processing Unit (CPU) adds a filter e (changing step) in addition to the filters a and b, and performs magnetic bearing control (control step) using the control parameters.

Here, it is assumed that the filter e is not properly set, but rather the abnormality of the magnetic bearing control is deteriorated, and the 2 nd abnormality occurs.

In step 41 of simultaneously performing the processing in parallel at this time, the 2 nd abnormality is detected by the Central Processing Unit (CPU). Therefore, the flow forcedly proceeds to step 43, and the Central Processing Unit (CPU) returns the control parameter to the past value. That is, in the case of fig. 5, the filters a and b are set as the best parameters at this point, and the process proceeds to step 45, and the operation is stopped.

As described above, even when the readjustment deteriorates the state and the immediate operation stop is required, the control parameter is returned to the past value, so that the operation can be stopped in a relatively safe state.

In addition, in order to ensure safety, it is important that the 2 nd abnormality is immediately detected at the time of occurrence to stop the operation. Therefore, it is desirable to execute step 41 as frequently as possible independently of the step of readjustment after abnormality detection of 1 st.

Next, another processing method when the 2 nd abnormality is detected will be described with reference to fig. 6. In fig. 6, since the sequence numbers 0 to 4 are the same as those in fig. 5, the description thereof is omitted.

In the time series number 5 of fig. 6, similarly to fig. 5, in step 41, the Central Processing Unit (CPU) detects the 2 nd abnormality. Therefore, the process proceeds to step 43 forcibly, and the control parameter is returned to the past value. That is, in the case of fig. 6, the control parameter is returned to the initial value by the Central Processing Unit (CPU). If the filter is at the initial value, the routine proceeds to step 45, where the routine proceeds to a state where the operation of the pump is stopped.

Next, a readjustment processing method in consideration of stability will be described.

In fig. 7, in step 51, the Central Processing Unit (CPU) detects the 1 st abnormality based on the above-described predetermined judgment criterion. In step 71 of fig. 7, the Central Processing Unit (CPU) detects the 2 nd abnormality based on the predetermined judgment criterion.

When the Central Processing Unit (CPU) detects the 1 st abnormality in step 51 and the 2 nd abnormality is not detected in step 71, first, in step 52, the control parameter is stored in the Central Processing Unit (CPU). Then, in step 53, the Central Processing Unit (CPU) changes the control parameter (changing step) and performs magnetic bearing control (controlling step) using the control parameter.

Then, in step 54, the Central Processing Unit (CPU) determines whether or not the state of the 1 st abnormality is improved (state improvement determination step). If the control parameter has not been improved, the control parameter is returned to the original value in step 56, and the process returns to step 52. On the other hand, if the abnormality is to be resolved, the control parameter at that point is held, and the flow proceeds to step 55, where a Central Processing Unit (CPU) determines whether or not the 1 st abnormality is resolved (state improvement determination step). In the case where the 1 st abnormality is not eliminated, the process returns to step 52. On the other hand, when it is determined in step 55 that the 1 st abnormality is eliminated, the routine proceeds to step 57, where a Central Processing Unit (CPU) performs stability evaluation (stability evaluation step). This is not only confirmation that the 1 st abnormality is eliminated, but also whether the elimination is not temporary but stable. The stability evaluation is performed, for example, by a Central Processing Unit (CPU) generating an excitation signal and applying the excitation signal to the magnetic bearing device and measuring a transfer function thereof. Alternatively, a Central Processing Unit (CPU) generates an excitation signal and applies the excitation signal to the magnetic bearing device, and the Central Processing Unit (CPU) measures a step response or a measured impulse response.

Here, the excitation signal is, for example, a step signal, a pulse signal, white noise, a sine wave of a single frequency, a sine wave of a sweep frequency, a sweep sine (sine), or the like. Further, the Central Processing Unit (CPU) may determine the stability by increasing or decreasing the magnetic bearing control gain to determine whether the 1 st abnormality or the 2 nd abnormality has occurred. Further, the transfer function measurement, the step response measurement, and the impulse response measurement may be combined with the increase and decrease of the magnetic bearing control gain. The excitation signal may be generated by a Central Processing Unit (CPU), but may be input from an external device.

This allows readjustment in consideration of stability. It is possible to prevent a state in which abnormality 1 is eliminated but abnormality occurs. Therefore, the operation efficiency is improved and the safety is improved.

When the Central Processing Unit (CPU) detects the 2 nd abnormality in step 71, the operation of the pump is stopped in step 73.

Next, the relationship between readjustment and operation of the pump when the 1 st abnormality is detected will be described based on a specific operation example.

First, in the operation example of fig. 8, when the 1 st abnormality is detected by the Central Processing Unit (CPU) at the point indicated by "X1" in the figure at the time of starting the pump, the Central Processing Unit (CPU) readjusts while performing deceleration control of the rotating body 103. The deceleration control here refers to control for applying torque for reducing the rotational speed such as regenerating the motor and outputting the generator. Then, at the point indicated by "X2", the Central Processing Unit (CPU) confirms the elimination of the 1 st abnormality, and then the Central Processing Unit (CPU) accelerates the rotating body 103.

Thus, even when the 1 st abnormality occurs, the time until the rated rotation speed is reached at the point indicated by "X3" can be saved. That is, since readjustment is performed during the deceleration operation of the rotating body 103, the rated rotation speed can be reached more quickly than when readjustment is performed after the rotation speed is set to zero and the operation is stopped. Therefore, the operation efficiency improves.

Further, since the Central Processing Unit (CPU) performs readjustment during the deceleration operation of the rotating body 103, the rotation speed at the readjustment is smaller than that at the time of abnormality detection. The damage at landing becomes smaller as the rotation speed becomes smaller, and particularly if the rotation speed is equal to or lower than a predetermined rotation speed, the damage at landing can be ignored. Thus, damage in the case of landing due to abnormal increase during readjustment can be reduced. Thus, the safety is improved.

Next, in the operation example of fig. 9, when the Central Processing Unit (CPU) detects the 1 st abnormality at the point indicated by "X1" in the figure at the time of starting the pump, the Central Processing Unit (CPU) readjusts the rotation body 103 while decelerating the rotation body as in the operation example of fig. 8. Then, when the Central Processing Unit (CPU) detects the 2 nd abnormality at the point indicated by "X4", the Central Processing Unit (CPU) stops the rotating body 103. This ensures the safety of the pump.

Next, in the operation example of fig. 10, when the 1 st abnormality is detected by the Central Processing Unit (CPU) at the point indicated by "X1" in the figure at the time of starting the pump, the Central Processing Unit (CPU) decelerates or freely runs the rotating body 103. The term "free running" as used herein means that the motor or generator is stopped from being energized. In free running, the disturbance force acting on the rotating body by stopping the energization and the noise of the signal to the sensor are reduced, and the signal to noise ratio of the displacement signal of the rotating body and the current signal of the magnetic bearing, which are input signals to the magnetic bearing controller, is improved. Then, when the rotation speed drops to a point indicated by "X5" in the figure, a Central Processing Unit (CPU) performs constant speed control. Here, the point indicated by "X5" is a point where damage at landing is supposed to be less. In this case, the readjustment may be performed while the Central Processing Unit (CPU) is decelerating or while waiting for the speed to be constant.

Then, when the Central Processing Unit (CPU) confirms that the 1 st abnormality has been eliminated at the point indicated by "X6", the Central Processing Unit (CPU) accelerates the rotating body 103. Thus, even when the 1 st abnormality occurs, the time until the rated rotation speed is reached at the point indicated by "X7" can be saved. That is, since the Central Processing Unit (CPU) performs readjustment during the deceleration operation or the constant speed operation of the rotating body 103, the rated rotation speed can be reached more quickly than in the case of readjusting after the rotation speed is set to zero and the operation is stopped. Therefore, the operation efficiency improves.

Next, in the operation example of fig. 11, when the 1 st abnormality is detected by the Central Processing Unit (CPU) at the point indicated by "X8" in the figure during the operation at the rated rotation speed, the Central Processing Unit (CPU) starts readjustment before the rotation speed becomes zero even if the operation is assumed to be decelerated or free running.

At this time, when the Central Processing Unit (CPU) confirms that the 1 st abnormality has been eliminated at the point indicated by "X9", the Central Processing Unit (CPU) accelerates the rotating body 103. Thus, even when the 1 st abnormality occurs, the time until the rated rotation speed is reached at the point indicated by "X10" can be saved, and the recovery to the rated rotation speed can be made faster.

Next, the operation example of fig. 12 is substantially the same as the operation example of fig. 8, but differs in the following point: when the 1 st abnormality is detected by the Central Processing Unit (CPU) at the point indicated by "X1" in the figure, the Central Processing Unit (CPU) readjusts the rotating body 103 while allowing it to freely run. By stopping the energization of the motor 121 and setting it to free running, the current no longer flows. Thereby, the vibration of the motor 121 is reduced and the noise is reduced. Therefore, the signal to noise ratio of the displacement signal of the rotating body and the current signal of the magnetic bearing, which are input signals to the magnetic bearing controller, becomes good, and the readjustment accuracy becomes good. Thus, readjustment can be performed at high speed.

Next, the operation example of fig. 13 is substantially the same as the operation example of fig. 9, but differs in the following point: when the 1 st abnormality is detected by the Central Processing Unit (CPU) at the point indicated by "X1" in the figure, the Central Processing Unit (CPU) readjusts the rotation body 103 while allowing the rotation body to freely run as in fig. 12. Then, when the Central Processing Unit (CPU) detects the 2 nd abnormality at the point indicated by "X12", the Central Processing Unit (CPU) stops the rotating body 103. This ensures the safety of the pump.

Next, in the operation example of fig. 14, when the 1 st abnormality is detected by the Central Processing Unit (CPU) at the point indicated by "X1" in the figure, the Central Processing Unit (CPU) readjusts while performing constant speed control to the point indicated by "X13" in the figure. By setting the constant speed control, the abnormal state can be maintained. Therefore, the cause thereof can be searched for efficiently.

Then, when the Central Processing Unit (CPU) confirms that the 1 st abnormality has been eliminated at the point indicated by "X13", the Central Processing Unit (CPU) accelerates the rotating body 103.

This saves time until the rated rotation speed is reached at the point indicated by "X14", and thus the recovery to the rated rotation speed is faster.

Next, in the operation example of fig. 15, when the 1 st abnormality is detected by the Central Processing Unit (CPU) at the point indicated by "X1" in the figure, the Central Processing Unit (CPU) performs readjustment while performing constant speed control. However, when the Central Processing Unit (CPU) detects the 2 nd abnormality at the point indicated by "X15" in the figure, the Central Processing Unit (CPU) stops the rotating body 103. This ensures the safety of the pump.

Next, fig. 16 is a diagram showing characteristics of a change in natural frequency of the rotating body 103 due to the gyroscopic effect in the operation example of fig. 14. By the gyro effect, the natural frequency of the rotation body 103 changes according to the rotation speed. When the rotational speed is changed as in fig. 14, the natural frequency of the rotating body 103 is as a relationship between the time and the natural frequency in fig. 16. The turbomolecular pump 100 includes the rotary vane 102, and is prone to occurrence of an abnormality such as oscillation due to its natural vibration. In this case, the Central Processing Unit (CPU) readjusts the constant speed control from the point indicated by "X16" to the point indicated by "X17" in the figure. That is, since the natural frequency is constant during readjustment, the readjustment accuracy is improved. Therefore, the operation efficiency of the pump can be improved.

Next, in the operation example of fig. 17, when the 1 st abnormality is detected by the Central Processing Unit (CPU) at the point indicated by "X1" in the figure, the Central Processing Unit (CPU) performs readjustment while performing acceleration control. Then, when the Central Processing Unit (CPU) confirms that the 1 st abnormality has been eliminated at the point indicated by "X18", the Central Processing Unit (CPU) continues to accelerate the rotating body 103. The readjustment is performed during acceleration, and acceleration is continued immediately after abnormality elimination, so that the rated rotation speed can be reached at the fastest speed.

Next, in the operation example of fig. 18, when the 1 st abnormality is detected by the Central Processing Unit (CPU) at the point indicated by "X1" in the figure, the Central Processing Unit (CPU) performs readjustment while performing acceleration control. However, naturally, when the Central Processing Unit (CPU) detects the 2 nd abnormality at the point indicated by "X20" in the figure, the Central Processing Unit (CPU) stops the rotating body 103. This ensures the safety of the pump.

The processing methods described in the above-described respective working examples are preferably used separately from each other according to the operation state immediately before the detection of the 1 st abnormality. For example, when the immediately preceding operation state is acceleration, it is preferable to accelerate in order to quickly reach the rated value, so that the Central Processing Unit (CPU) selects readjustment during acceleration operation. Further, if the immediately preceding operation state is deceleration, there is no meaning even if acceleration is occurring, so the Central Processing Unit (CPU) selects to readjust it while decelerating it as it is. Further, if the immediately preceding operation state is such that the temperature changes and oscillates during the rated rotation, the Central Processing Unit (CPU) selects to stop the energization to the motor 121 and set it to free operation because of the desire to reduce noise.

Thus, even when an abnormality such as hunting occurs due to an improper control parameter, the operation of the pump can be recovered without stopping.

Next, a method will be described in which an abnormality of the pump can be detected promptly, and noise generated by correction of the control parameter is not erroneously detected as an abnormality.

For example, when the control parameters such as proportional gain, differential gain, phase lead filter, notch filter, ABS (Auto Balance System; automatic balance system) are corrected, the control parameters are changed. When the control parameter is changed, noise is likely to occur in the control system. However, since the noise is not caused by an abnormality, the Central Processing Unit (CPU) does not erroneously detect the noise. On the other hand, the Central Processing Unit (CPU) can quickly detect noise generated by a change other than the control parameter as an abnormality.

The operation will be described below based on the control parameter correction flowchart of fig. 19 and the parameter correction time chart of fig. 20.

In step 81 of fig. 19, the operation is performed under the abnormality detection condition in the normal state. In the time chart of fig. 20, the operation under the abnormality detection condition in the normal state is performed between time 0 and time t 1. The normal state abnormality detection condition is a condition that can be set to detect the 1 st abnormal state or the 2 nd abnormal state in the case of the above-described embodiment, for example. In step 83, the Central Processing Unit (CPU) determines whether or not a condition for changing a predetermined control parameter is satisfied. In this case, the determination is, for example, that the Central Processing Unit (CPU) has determined that preparation for changing the control parameter is made such that the filter a is added to the Central Processing Unit (CPU) as indicated by the time series number 1 in fig. 4. Then, in step 85, the abnormality detection condition is switched to the relaxed state at time t1 in fig. 20. The abnormality detection condition is switched to the relaxed state in such a manner that the abnormality detection condition is relaxed so that the abnormality is not detected by the Central Processing Unit (CPU) due to noise accompanying the processing of changing the control parameter.

As a moderating example, when the 1 st and 2 nd abnormal states are detected, for example, detection of an abnormality by an abnormality detection means of a Central Processing Unit (CPU) is stopped.

In addition, in the Central Processing Unit (CPU), the reference value of the abnormality detection condition may be increased. For example, the 1 st abnormality is set to 1 μm in displacement spectrum amplitude at the time of alleviation and 0.5 μm in displacement spectrum amplitude at the time of normal operation.

Furthermore, the specific frequency component may be ignored. For example, the vibration component of 100Hz or less is ignored during the relaxation, and the abnormality is detected at all the frequency components including 100Hz or less in the case of the normal operation. Since the response of the displacement signal due to the noise accompanying the change of the control parameter is slower than the natural vibration of the rotary blade, the influence of the noise accompanying the change of the control parameter can be reduced, and the abnormality due to the natural vibration of the rotary blade can be immediately detected.

Next, in step 87, the control parameter is changed at time t0 in fig. 20. At this time, in the example of fig. 4, the filter a is added to the Central Processing Unit (CPU) at the time series number 1. Then, in step 89, standby is performed for a predetermined time from time t0 to time t2 in fig. 20. Then, at a time t2 in fig. 20, the abnormality detection condition is switched to the normal state in step 91, and the operation is continued in step 93.

If the operation during this period is described in detail based on fig. 20, the timing of the control parameter change is set to t0, and at least one of the 1 st abnormality detection condition and the 2 nd abnormality detection condition is relaxed only for a time from the timing t1 before the change to the timing t2 after the change. That is, the abnormal detection condition is alleviated in the black part of fig. 20.

If Δt1=t0-t1, Δt2=t2-t0 is set, the relationship between Δt1 and Δt2 is preferably 0.ltoreq.Δt1< Δt2. This is because the displacement signal is not disturbed before the control parameter is changed, and the displacement signal is disturbed for about 1 to 2 seconds immediately after the control parameter is changed. Thus, for example, for a controller with a control period of 0.005 seconds, Δt1=0.005 seconds, Δt2=2 seconds is set. That is, the standby time equal to or longer than the minimum unit amount of the control cycle is set before the control parameter is changed. However, Δt1=0 seconds may be used. In this case, the abnormality detection means is stopped and the control parameter is changed at the same time.

In the case where the relationship between the time and the rotation speed is considered to be linearly variable during acceleration or deceleration of the pump as shown in fig. 20, the rotation speeds ω0, ω1, ω2 may be used instead of the times t0, t1, t2 to perform the same setting.

Examples of the case of correcting the control parameter include (1) a case of changing the filter according to a predetermined rotation speed, (2) a case of detecting the 1 st abnormality and correcting the control parameter by the control parameter correction means of the Central Processing Unit (CPU), and (3) a case of inputting a control parameter correction command by external communication to the magnetic bearing controller.

Thus, the Central Processing Unit (CPU) sets the relaxation time in a planned manner only at a limited time point when the control parameter is corrected.

Since noise accompanying correction is not erroneously detected as an abnormality at the time of correction of the control parameter and no relaxation time is set as in the past other than at the time of correction of the control parameter, the speed of abnormality detection can be increased and the reliability of the magnetic bearing device can be improved as compared with the case where a constant relaxation time after abnormality detection is always set.

That is, noise caused by correction of the control parameter is not erroneously detected in, for example, 2 seconds, in which the Central Processing Unit (CPU) sets the relaxation time, and occurrence of an abnormality can be instantaneously detected in a time zone other than the detection time.

Next, a specific operation example concerning the alleviation of the abnormality detection condition will be described.

First, an operation example of the case where the filter is changed according to the predetermined rotation speed in the above (1) will be described.

For a filter ABS (Auto Balance System; automatic balancing system) for removing rotational speed synchronizing components from a displacement signal at a predetermined rotational speed or higher, for example, in a vacuum pump rated at a rotational speed of 27000rpm, the ABS is turned ON (ON) when the rotational speed is 12000rpm or higher, and is turned OFF (OFF) when the rotational speed is less than 12000 rpm. In this case, during acceleration, the abnormality detection condition is alleviated when the rotational speed reaches 11940rpm, the ABS is switched from off to on when the rotational speed reaches 12000rpm, and the abnormality detection condition is returned to the normal state when the rotational speed reaches 12240 rpm.

In a filter for phase lead introduced to suppress the resonance mode of the rotating body in a certain rotation speed region, for example, in a vacuum pump rated at 27000rpm, the filter is turned on when the rotation speed is 18000rpm or more and less than 24000rpm, and is turned off when the rotation speed is other. In this case, during acceleration, the abnormality detection condition is alleviated when the rotational speed reaches 17940rpm, the filter is switched from off to on when the rotational speed reaches 18000rpm, and the abnormality detection condition is returned to the normal state when the rotational speed reaches 18240 rpm. Then, the abnormality detection condition is again alleviated when the rotational speed reaches 23940rpm, the filter is switched from on to off when the rotational speed reaches 24000rpm, and the abnormality detection condition is returned to the normal state when the rotational speed reaches 24240 rpm.

Next, an operation example will be described in which the control parameter correction means corrects the control parameter in the case where the 1 st abnormality is detected in (2) above.

In this case, for example, during rotation at a rated rotation speed of 27000rpm, the control parameter correction means of the Central Processing Unit (CPU) newly sets the notch filter having a center frequency of 800 Hz. As shown in fig. 21, at time t1, the abnormality detection condition is first relaxed, the control parameter is changed at time t0 after 0.005 seconds, and the abnormality detection condition is returned to the normal state at time t2 after 2 seconds. Alternatively, the abnormality detection condition may be first alleviated and the control parameter may be changed at the same time, and the abnormality detection condition may be returned to the normal state after 2 seconds have elapsed.

In addition, in the case where the filter c is added to the time series number 3 of fig. 4 or the value before returning to 1 step is changed, as shown in fig. 22, the abnormality detection condition is first relaxed at time t1, the filter c is added at time t0 after 0.005 seconds, and the abnormality detection condition is returned to the normal state at time t2 after 2 seconds. On the other hand, when the filter c is removed and returned to the value before 1 step, the abnormality detection condition is first relaxed at time t11, the filter c is removed at time t10 after 0.005 seconds, and the abnormality detection condition is returned to the normal state at time t12 after 2 seconds.

Next, an operation example of the case where the control parameter correction command by external communication in (3) is input to the magnetic bearing controller will be described.

In the operation of the pump, as shown in fig. 23, at time t3, a correction instruction of a control parameter by external communication is input to the magnetic bearing controller by a user operation. For example, when the notch filter is newly set to a center frequency of 800Hz during rotation at a rated rotation speed of 27000rpm, when the center frequency of the notch filter is changed from 800Hz to 900Hz, when the proportional gain is changed to 0.9 times as high as that immediately before, and the like. In this case, at time t1, the Central Processing Unit (CPU) of the control device transmits an instruction. The Central Processing Unit (CPU) first eases the abnormality detection condition and changes the control parameter at time t0 after 0.005 seconds. Then, the abnormality detection condition is returned to the normal state at time t2 after 2 seconds have elapsed.

However, it is also possible to first perform the alleviation of the abnormality detection condition and the modification of the control parameter at the time t0 and to return the abnormality detection condition to the normal state at the time t2 after 2 seconds have elapsed.

As described above, the abnormality detection conditions mounted on the Central Processing Unit (CPU) are excessive displacement or current due to oscillation, contact of the landing bearings 141 and 143, and dc link voltage, and the fluctuation of the displacement spectrum and the current spectrum, but the abnormality detection conditions that are temporarily alleviated may be some or all of the mounted abnormality detection conditions. Preferably, only the abnormality detection condition based on the displacement signal is relaxed, and the abnormality detection conditions other than the abnormality detection condition are not relaxed. In the correction of the control parameter, a large noise tends to occur in the displacement signal, while the noise of the other signals is small. This makes it possible to detect, at high speed, abnormal states other than noise such as power failure, which is caused by the noise caused by the control parameter correction, at the same time as the noise caused by the control parameter correction, without erroneously detecting the noise.

The time t0 and the time t10 and the rotation speed ω0 correspond to points on the time axis, the rotation speed axis, and the frequency axis, in which the control parameter is corrected, and the range from the time t1 to the time t2 and the range from the rotation speed ω1 to the rotation speed ω2 correspond to a predetermined range. The range from time t1 to t0 and the range from rotation speed ω1 to ω0 correspond to the front region, and the range from time t0 to t2 and the range from rotation speed ω0 to ω2 correspond to the rear region.

The present invention is not limited to the above-described embodiments, but may be modified in various ways without departing from the spirit of the invention. The above embodiments may be variously combined.

Description of the reference numerals

100 turbine molecular pump

102 rotating blade

103 rotating body

104 upper radial electromagnet

105 underside radial electromagnet

106A, 106B axial electromagnet

107 upper radial sensor

108 underside radial sensor

109 axial sensor

111 metal plate

113 rotor shaft

121 motor

141. 143 landing bearing

Claims (17)

1. A magnetic bearing device is provided with:

a rotating body;

a magnetic bearing for magnetically suspending the rotor in the air; and

a magnetic bearing controller that controls the magnetic bearing;

characterized by comprising:

a 1 st abnormality detection means for detecting an abnormality in control by the magnetic bearing controller based on a predetermined 1 st abnormality condition;

control parameter correction means for correcting a control parameter of the magnetic bearing controller while continuing the operation of the magnetic bearing device when the abnormality of the control is detected by the 1 st abnormality detection means;

a 2 nd abnormality detection means for detecting an abnormality of the control by the magnetic bearing controller based on a predetermined 2 nd abnormality condition having a degree of abnormality greater than the 1 st abnormality condition; and

And a stopping means for stopping the operation of the magnetic bearing device when the abnormality of the control is detected by the 2 nd abnormality detecting means.

2. The magnetic bearing device according to claim 1,

the control parameter correction means includes:

a changing step of changing the control parameter from the control parameter before 1 step;

a control step of performing control by the magnetic bearing controller with the control parameter changed by the changing step; and

a state improvement judging step of judging whether or not the result of the control performed by the control step is improved in the abnormal state of the control compared with the result of the control performed before the 1 step in the control step, and when it is judged that the result of the control performed by the control step is improved in the abnormal state of the control, the state improvement judging step holds the changed value as the control parameter, and when it is judged that the result of the control performed by the control step is not improved in the abnormal state of the control, the control parameter is returned to the control parameter before the 1 step.

3. The magnetic bearing device according to claim 2, wherein,

the control parameter correction means includes: and a 1 st abnormality elimination determination step of determining whether or not the abnormal state of the control is eliminated based on the 1 st abnormality condition, returning to the changing step when it is determined that the abnormal state of the control determined by the 1 st abnormality condition is not eliminated, and holding the control parameter at that point when it is determined that the abnormal state of the control determined by the 1 st abnormality condition is eliminated, in a subsequent stage of the state improvement determination step when it is determined that the abnormal state of the control is improved.

4. The magnetic bearing device according to claim 3,

the control parameter correction means further includes: a stability evaluation step of evaluating whether or not the operation of the magnetic bearing device to which the control parameter stored in the 1 st abnormality elimination determination step is applied has a predetermined stability at which abnormality of the control by the magnetic bearing controller does not occur, in a subsequent stage of the 1 st abnormality elimination determination step in which it is determined that the abnormal state of the control determined by the 1 st abnormality condition has been eliminated;

when the stability evaluation step evaluates that the stability is insufficient, the correction of the control parameter of the magnetic bearing controller is performed again.

5. The magnetic bearing device according to claim 4,

the stability evaluation step evaluates at least one of the addition of the excitation signal, the increase of the control gain of the magnetic bearing controller, and the decrease of the control gain of the magnetic bearing controller.

6. The magnetic bearing device according to claim 1 to 5,

when an abnormality of the control determined based on the 2 nd abnormality condition is detected during the correction of the control parameter by the control parameter correction means, the operation of the magnetic bearing device is stopped based on the control parameter set in the past applied by the control parameter correction means.

7. The magnetic bearing device according to claim 1 to 5,

in the control parameter correction means, when the abnormality of the control is detected by the 1 st abnormality detection means, the control parameter of the magnetic bearing controller is corrected while the decelerating operation of the rotating body is performed.

8. The magnetic bearing device according to claim 1 to 5,

in the control parameter correction means, when the abnormality of the control is detected by the 1 st abnormality detection means, the rotational speed control of the rotating body is stopped, and the control parameter of the magnetic bearing controller is corrected in a state where the rotating body is free to run.

9. The magnetic bearing device according to claim 1 to 5,

in the control parameter correction means, when the abnormality of the control is detected by the 1 st abnormality detection means, the control parameter of the magnetic bearing controller is corrected while the rotational speed of the rotating body is controlled to be constant at the rotational speed at which the abnormality is detected.

10. The magnetic bearing device according to claim 1 to 5,

In the control parameter correction means, when the abnormality of the control is detected by the 1 st abnormality detection means, the control parameter of the magnetic bearing controller is corrected while the rotating body is being accelerated.

11. The magnetic bearing device according to claim 7,

after correcting the control parameter of the magnetic bearing controller, the acceleration of the rotating body is performed when the abnormal state under the 1 st abnormal condition is eliminated.

12. A vacuum pump is characterized in that,

a magnetic bearing device according to any one of claims 1 to 5.

13. A magnetic bearing device is provided with:

a rotating body;

a magnetic bearing for magnetically suspending the rotor in the air; and

a magnetic bearing controller that controls the magnetic bearing;

characterized by comprising:

an abnormality detection means for detecting an abnormality in control by the magnetic bearing controller based on a predetermined abnormality condition;

a control parameter correction means for correcting a control parameter of the magnetic bearing controller;

a region of a predetermined range including a point on a time axis, a rotation axis, and a frequency axis, where the control parameter correction means corrects the control parameter; and

And a mitigating means for mitigating the predetermined abnormal condition in the region of the predetermined range.

14. The magnetic bearing device according to claim 13,

the predetermined abnormal condition is composed of a plurality of types;

the abnormal conditions alleviated by the alleviating means include abnormal conditions based on the displacement signal.

15. A magnetic bearing device according to claim 13 or 14,

the predetermined range includes a front region forward of the location and a rear region rearward of the location, and the rear region is larger than the front region.

16. A magnetic bearing device according to claim 13 or 14,

the region in the predetermined range is constituted only by a rear region rearward of the spot.

17. A vacuum pump is characterized in that,

a magnetic bearing device according to claim 13 or 14.