JPH0942290A - Magnetic bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform floating control responding to the arrangement direction of a device by providing a compensating circuit to control a magnetic bearing part so that a shaft is held in a given position based on a displacement fluctua tion amount of a rotary shaft and switching a control constant in the compensat ing circuit according to the arrangement direction of the rotary shaft. SOLUTION: In a control constant in a compensating circuit 3, a control constant A is selected and outputted by a change-over switch 31 when an angle θfrom an arrangement direction in which, for example, a magnetic bearing device is vertically arranged is 0 deg. <=θ(R)45 deg. and 135 deg.<=θ<=180 deg., and a control constant B is selected and outputted when the angle is 45 deg.<θ<135 deg.. In the control constant, an optimum floating control constant in an angle section is previously determined and set in the compensating circuit 3. The change-over switch 31 comprises, for example, a relay and is switched by means of a switch change-over signal from the outside. This constitution sets an optimum control constant according to the arrangement direction of the magnetic bearing device and performs floating control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bearing device, and more particularly to a magnetic bearing device used for high speed rotating equipment such as a vacuum pump.

[0002]

2. Description of the Related Art High-speed rotating equipment such as a vacuum pump such as a turbo molecular pump is required to be oil-free in order to obtain a good vacuum. Therefore, magnetic bearings have been developed in place of conventional bearings using oil lubrication. Since this magnetic bearing floats completely in the vacuum space without contact, and rotates, the generated vibration is very small. Therefore, it is suitable for an apparatus that is extremely reluctant to vibrate, such as an electron microscope or an X-ray drawing apparatus.

Conventionally, as this magnetic bearing, a five-degree-of-freedom motion (translational motion of the center of gravity of three degrees of freedom, rotational motion around the center of gravity of two degrees of freedom) except for the degree of freedom around the rotation axis is actively controlled. A shaft control type magnetic bearing is known. In this five-axis control type magnetic bearing, eight electromagnets are provided in the radial direction of the rotating body as radial magnetic bearings, and two electromagnets are provided in the axial direction as axial magnetic bearings. A displacement sensor that detects the state of the rotating body is installed at approximately the same position as this electromagnet to form a feedback control system, and the current flowing through each electromagnet is adjusted to adjust the attraction force of the electromagnet, and the rotating body is centered. Supporting the position.

As this feedback control system, for example, three control systems are known, which are a classic PID control system with one input and one output, an optimal regulator system with multiple inputs and multiple outputs, or an expanded optimal regulator system. By performing PID control by proportional, differential, and integral elements, the expanded optimum regulator system enables control of precession and damping of steady deviation with respect to steady disturbance.

FIG. 9 is a block diagram for explaining a control system of an expanded optimum regulator system in a conventional magnetic bearing.
The control system of FIG. 9 detects the radial displacement of the rotary shaft 4
The displacement variation amount detected by one displacement sensor Sxf, Sxr, Syf, Syr, and one displacement sensor Sz for detecting the axial displacement is PID-controlled and provided in the radial direction of the rotating body.
This is a control system that drives one electromagnet and two electromagnets provided in the axial direction. The part surrounded by the alternate long and short dash line in FIG. 9 is the PID.
The compensation circuit is based on control, and is controlled by a predetermined control constant (hereinafter referred to as control constant A).

The electromagnets are arranged so as to face each other with the rotating shaft interposed therebetween. By passing an exciting current determined by the PID control through each exciting magnet through the exciting amplifier, the opposing electromagnets attract the rotating shaft. , The rotation axis is controlled to an appropriate position.

[0007]

As an example of application of the magnetic bearing device, there is a bearing for a rotating shaft in a turbo molecular pump, for example. When such a turbo molecular pump is installed in a vacuum chamber, the mounting direction differs depending on the structure of the vacuum chamber, the installation position of an accessory device, and the like. Therefore, it is required that the turbo molecular pump can be attached to the vacuum chamber in any direction. FIG. 10 shows an example of the installation position where the magnetic bearing device is installed in the vacuum chamber of the turbo molecular pump. In the installation position example of FIG. 10, assuming that the direction of the arrow is the direction of gravity, the magnetic bearing device is, for example, in the vertical direction, the inverted direction 180 ° to the vertical direction, and the horizontal direction inclined 90 ° from the vertical direction. It shows the case of mounting in the diagonal direction.

Therefore, the installation direction of the magnetic bearing device is also
There may be various directions depending on the mounting direction of the turbo molecular pump. Depending on the installation direction of the magnetic bearing device, the direction component of the rotor rotation shaft with respect to the bearing differs. FIG.
FIG. 1 is a diagram illustrating force components received by a thrust bearing and a radial bearing depending on the installation direction of a magnetic bearing device. FIG.
(A) shows the case where the rotating shaft is in the vertical direction. In this case, the installation direction of the rotating shaft and the gravity direction are the same direction, and the gravity component is added to the thrust bearing portion. Further, FIG. 11C shows the case where the rotary shaft is horizontal, and in this case, the installation direction of the rotary shaft and the gravity direction are orthogonal to each other, and the gravity component is added to the radial bearing portion. Further, FIG. 11B shows a case where the rotating shaft is in an oblique direction. In this case, the gravity component is distributed to the thrust bearing portion and the radial bearing portion according to the inclination direction of the rotating shaft. In this way, the distribution of the gravity component to each bearing changes depending on the installation direction of the magnetic bearing device. The magnetic bearing device is required to always stably control the levitation of the rotor in such different installation directions.

In the conventional magnetic bearing device, the control constant of the feedback control circuit for controlling the levitation of the rotor is obtained with the case where the magnetic bearing device is installed in the vertical direction with respect to the direction of gravity as a reference position, and when the magnetic bearing device is installed in the vertical direction. The control constant is a representative control constant for all directions, and control is performed using the same control constant regardless of the installation direction of the magnetic bearing device. Therefore, depending on the installation direction of the magnetic bearing device, it is difficult to ensure the optimum levitation control, and there is a problem that the response is not optimal with respect to sudden external vibration.

Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional magnetic bearing device and to provide a magnetic bearing device capable of performing levitation control corresponding to the installation direction of the magnetic bearing device.

[0011]

SUMMARY OF THE INVENTION The present invention is a magnetic bearing device comprising a magnetic bearing portion for supporting a rotary shaft and a drive portion for rotationally accelerating and decelerating the rotary shaft. A compensation circuit is provided for controlling the magnetic bearing unit so as to hold the shaft at a predetermined position, and the compensation circuit achieves the above-mentioned object by switching the control constant in the compensation circuit according to the installation direction of the rotating shaft.

According to the embodiment of the present invention, the control constant of the compensating circuit is switched based on the amount of current applied to the electromagnet of the magnetic bearing portion, whereby the automatic constant is adjusted according to the installation direction of the magnetic bearing device. The control constant can be changed. According to another embodiment of the present invention, the exciting current to the electromagnet of the magnetic bearing portion, which serves as a basis for switching the control constant of the compensation circuit,
The exciting current is used for the electromagnet of the thrust magnetic bearing portion or the electromagnet of the radial magnetic bearing portion.

In the magnetic bearing device of the present invention, the control constant of the compensating circuit according to the installation direction is previously obtained by experiments, etc., and the control constant is set from among the plurality of control constants obtained when the magnetic bearing device is installed. A control constant according to the direction is selected, and the control constant of the compensation circuit is switched to this selected control constant. As a result, the control constant in the compensation circuit can be a control constant corresponding to the installation direction of the magnetic bearing device.

The switching of the control constant is performed by, for example, a switching signal input to the compensation circuit by an operator when installing the magnetic bearing device, or a switching signal input to the compensation circuit based on the amount of current applied to the electromagnet of the magnetic bearing portion. Can be used. When operated by an operator, a switching signal is input to the compensation circuit when the magnetic bearing device is installed to set the control constant of the compensation circuit corresponding to the installation direction of the magnetic bearing device.

The amount of current applied to the electromagnet of the magnetic bearing portion changes depending on the installation direction of the magnetic bearing device. Therefore, set the control constant according to this current amount in advance,
By switching according to the amount of electric current, the control constant corresponding to the installation direction can be automatically set.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a schematic structural diagram of a 5-DOF controlled magnetic bearing. The magnetic bearing shown is a five-axis control type magnetic bearing that actively controls movement in five degrees of freedom excluding the degree of freedom around the rotation axis, with the center of gravity G of the rotation axis R as the origin,
The X, Y, and Z coordinates with the Z axis on the rotation axis R are shown.
This 5-axis control type magnetic bearing has 3
It has five degrees of freedom, one degree of freedom and two degrees of freedom for the rotational movement around the center of gravity.

In this 5-axis control type magnetic bearing, eight electromagnets (Mxfp, Mxfn, Mxr) are arranged in the radial direction of the rotating shaft.
p, Mxrn, Myfp, Myfn, Myrp, Myrn), and a radial magnetic bearing is constituted by these electromagnets. Here, M represents an electromagnet, and the subscript x
Indicates the X coordinate axis direction, the subscript y indicates the Y coordinate axis direction, the subscript f indicates one side of the rotation axis R with respect to the center of gravity G, and the subscript r indicates the center of gravity G.
On the other side of the rotation axis R, the subscript p indicates the positive direction of the coordinate axis, and the subscript n indicates the negative direction of the coordinate axis. Therefore, on one side of the rotation axis R with respect to the center of gravity G, the electromagnet Mxfp and the electromagnet Mxfn are arranged so as to face each other in the X axis direction with the rotation axis R interposed therebetween, and the electromagnet Myfp and the electromagnet Myfn are arranged.
Are arranged to face each other in the Y-axis direction with the rotation axis R interposed therebetween. Further, the electromagnets Mxrp, Mxrn, Myrp, Myrn are similarly arranged on the other side of the rotation axis R with respect to the center of gravity G.

Further, this 5-axis control type magnetic bearing is provided with two electromagnets (Mzp, Mzn) in the axial direction of the rotary shaft R, and these electromagnets constitute a thrust magnetic bearing. The suffix z indicates the direction of the Z coordinate axis. Further, this 5-axis control type magnetic bearing has a displacement sensor (Sxf, Sx) that detects the state of the rotary shaft R at substantially the same position as these electromagnets.
yf, Sxr, Syr, Sz). In addition, the subscript of the displacement sensor S is the same as the subscript used for the electromagnet. For example, the displacement sensor Sxf is a sensor that detects a displacement of the rotation axis R in the X-axis direction on one side of the rotation axis R with respect to the center of gravity G.

Further, the electromagnet M and the displacement sensor S form a feedback control system, and the attraction force of the electromagnet is adjusted by adjusting the current flowing through each electromagnet using the displacement variation amount detected by the displacement sensor S. Then, the control is performed so that the rotation axis is located at the center position. The rotary shaft R is driven by a motor m attached to the rotary shaft.

In the figure, the electromagnet M and the rotary shaft R are
The displacement fluctuation amount d between and is the electromagnet M that is the target of displacement.
It is indicated by the subscript. For example, regarding the electromagnet Mxfp and the electromagnet Mxfn, the distance between the electromagnet Mxfp and the rotation axis R is indicated by dMxf. Further, the displacement variation amount d between the displacement sensor S and the rotation axis R is indicated by adding the subscript of the displacement sensor S that is performing the detection. For example, regarding the displacement sensor Sxf, the distance between the displacement sensor Sxf and the rotation axis R is indicated by dSxf. The axial distance l from the center of gravity G to the electromagnet M is indicated by lMf and lMr, and the axial distance l from the center of gravity G to the displacement sensor S is l.
This is indicated by Sf and lSr. Further, regarding the motor m, the displacement variation amount with respect to the rotation axis R is dmx, Y
It is indicated by dmy in the axial direction, and the axial distance from the center of gravity G is lm.
Indicated by The displacement variation amount and the center of gravity G have the equilibrium position as the origin.

In the magnetic bearing structure of FIG. 2, when the fluctuation amount from the floating equilibrium position between the rotary shaft and the sensor at the sensor position is ds and the PID feedback control system is constituted by the electromagnet M and the displacement sensor S, the equation of motion is For example, it is represented by the following formula. _{d s''' = T s} N -1 (G y T s -1 -TM t K Mi K D) d s''+ T s N -1 {T M t K Ms T M T s -1 -T M ^t K _Mi K _P } d _s '-T _s N ^-1 T _M ^t K _Mi K _I d _s (1) In addition, "'" represents a derivative and Ts is a matrix relating to the distance between the center of gravity and the sensor. Yes, N is a matrix relating to the mass of the rotating shaft and the moment of inertia in the radial direction, Gy is a matrix relating to the gyro effect of the rotor, TM is a matrix relating to the distance between the center of gravity and the electromagnet in the Z axis direction, and KMi Is an electromagnet coefficient relating to an exciting current, KMs is an electromagnet coefficient relating to gap variation, KP is a proportional gain (P gain), KD is a differential gain (D gain), and KI is an integral gain (I gain).

P of the magnetic bearing device represented by the above formula (1)
The ID feedback control system can be realized, for example, by a configuration including a compensation circuit shown in FIG. 9, and four displacement sensors Sxf, Sxr, for detecting the radial displacement of the rotating shaft,
SID, Syr, and the displacement variation detected by one displacement sensor Sz that detects displacement in the axial direction are PID-controlled,
The control system drives eight electromagnets provided in the radial direction of the rotating body and two electromagnets provided in the axial direction. A set of PID coefficients in this control system will be represented as a control constant A.

As shown in FIGS. 10 and 11, when the installation direction of the magnetic bearing device is different, the component of the rotor itself in the axial direction and the size of the radial line segment change. In the case of the same direction, gravity is supported by the thrust direction magnetic bearing, and when the rotor shaft is in the direction perpendicular to the gravity, gravity is supported by the radial direction magnetic bearing. When the gravity is supported by the thrust magnetic bearing, a large exciting current flows in the electromagnet installed in the thrust magnetic bearing in the opposite direction to the gravity, and when the gravity is supported by the radial magnetic bearing. In the radial magnetic bearing, a large exciting current flows in the electromagnet installed in the direction opposite to gravity.

Therefore, the exciting current flowing through each electromagnet in the levitation equilibrium state changes according to the installation direction of the magnetic bearing device (direction of the rotor magnetic bearing). Depending on the magnitude of the exciting current in the equilibrium state, the PI of the magnetic bearing device is
The gain of the D feedback control system changes. Therefore, in order to maintain a stable equilibrium state when the installation direction of the magnetic bearing device changes, it is necessary to change the control constant in the compensation circuit in the magnetic bearing device in accordance with the installation direction.

In the first embodiment of the present invention, as shown in the block diagram of FIG. 1, a control system including a displacement sensor 2, a compensation circuit 3, an inverter 4, an adder 5, an exciting amplifier 6 and an electromagnet 7. 1, a plurality of control constants (two control constants A, in FIG. 1) corresponding to the installation direction of the magnetic bearing device in the compensation circuit 3 are provided.
The case where the control constant B is provided is shown), and the control constants A and B are switched by the changeover switch 31 and output.
In the control system shown in the figure, a constant current of the same magnitude is preset as a bias component for the electromagnets of the respective axes arranged oppositely by the configuration of the inverter 4 and the adder 5, and this bias current is It is configured to increase or decrease by the control current of the same magnitude.

The control constant in the compensation circuit 1 is, for example, as shown in FIG.
As shown in 0, when the angle θ from the installation direction in which the magnetic bearing device is vertically installed is in the angle section A1 (0 ° ≦ θ ≦ 45 °) and the angle section A2 (135 ° ≦ θ ≦ 180 °). , The control constant A is selected and output by the changeover switch 31, and when the angle θ is in the angle section B (45 ° <θ <135 °), the control constant B is selected and output by the changeover switch 31. The control constant in each angle section can be set in the compensation circuit by previously obtaining the optimum flying control constant in the angle section. Further, the changeover switch 31 can be constituted by, for example, a relay or the like, and can perform a changeover operation by a switch changeover signal from the outside, and this switch changeover signal can be inputted by an operator. Thereby, the optimum control constant can be set according to the installation direction of the magnetic bearing device.

Next, a second embodiment of the present invention will be described. FIG. 3 is a block diagram for explaining the second embodiment of the present invention. Also in the block diagram of FIG. 3, similarly to FIG. 1, a control system 1 including a displacement sensor 2, a compensation circuit 3, an inverter 4, an adder 5, an excitation amplifier 6, and an electromagnet 7.
In the compensating circuit 3, a plurality of control constants A and B are provided corresponding to the installation direction of the magnetic bearing device (FIG. 3 shows the case of two control constants).
B is a changeover switch 31 and a window comparator 32
To switch and output. For example, there is a relationship between the installation direction of the magnetic bearing device and the exciting current of the electromagnet in the levitation equilibrium state as shown in FIGS. 7 and 8
Indicates the value corresponding to the exciting current.

Hereinafter, this relationship will be described using equations. FIG. 4 is a diagram schematically showing the relationship between the rotary shaft R and the electromagnets M that are installed to face each other with the rotary shaft R interposed therebetween.
When the exciting currents In and Ip flow in and the distances between the rotating shaft R and the electromagnet M are Dn and Dp, respectively,
The forces of fn and fp shown in the following equations respectively act.

Fn = k (In / Dn) ² (2) fp = k (Ip / Dp) ² (3) where k is a proportional constant.

Here, when the rotating shaft and the rotor are tilted by an angle θ as shown in FIG. 5, and the exciting current Ip flowing through the electromagnet in the thrust direction is given, the following equation is obtained. m · g · cos θ = fp−fn (4) I (constant) = Ip + In (5) D (constant) = Dp = Dn (6) From the formulas (1) to (5), the electromagnet in the thrust direction is obtained. The exciting current Ip flowing through is expressed by the following equation. Ip = (D ² · m · g · cos θ) / (2 · k · I) + I / 2 (7) FIG. 7 shows the first embodiment of the above-mentioned implementation using the relation expressed by the equation (7). In the same manner as in the above form, the angle section is changed to the angle section A1 (0
° ≦ θ ≦ 45 °, angle section A2 (135 ° ≦ θ ≦ 18
0 °) and the angle section B (45 ° <θ <135 °), and the control constant A and the control constant B are switched in each angle section. In the second embodiment, this switching is performed by changing the excitation current. It is done according to the size. The excitation current equivalent value in FIG. 7 can be an output signal from the excitation amplifier in FIG. 3, for example.

In FIG. 7, the angle section A1 (0 ° ≦ θ ≦
45 °) corresponds to the case where the excitation current equivalent value is I2 or more,
The angle section A2 (135 ° ≦ θ ≦ 180 °) corresponds to the case where the exciting current equivalent value is I1 or less, and the angle section B (4
5 ° <θ <135 °) corresponds to the case where the exciting current equivalent value is between I1 and I2. The angle section (-45
For angle ≤ θ ≤ 0 °, the angle section A1 and the angle section (-180
(° ≦ θ ≦ −135 °) corresponds to the angle section A2, and the angle section (−135 ° <θ <−45 °) corresponds to the angle section B.

Therefore, in the second embodiment shown in FIG. 3, the output signal from the exciting amplifier is used as the exciting current equivalent value and input to the window comparator 32 for thresholding the values corresponding to I1 and I2 in FIG. Then, the installation direction of the magnetic bearing device is determined by this, and a switch changeover signal is output to the changeover switch 31 in the compensation circuit 3. The changeover switch 31 determines the control constant A based on this switch changeover signal.
Alternatively, the control constant B is selected to switch the control constant.

The threshold value of the window comparator 32 is
It can be determined in advance when the rotor is floating and in a non-rotating state, and can be determined by the exciting current equivalent value.
The control constant in the compensation circuit 1 can be set similarly to the first embodiment. As a result, in the second embodiment, the excitation constant supplied to the electromagnet in the thrust bearing can be used to automatically set the control constant according to the installation direction of the magnetic bearing device.

The automatic setting of the control constant according to the second embodiment is usually performed every time the control power supply for the pump is started up, when the installation of the magnetic bearing device is changed, and the like. Does not. As a result, switching of the control constant due to disturbance such as vibration can be prevented.

Next, a third embodiment of the present invention will be described. In the second embodiment, the installation direction of the magnetic bearing device is determined by using the exciting current Ip flowing through the electromagnet in the thrust direction, and the control constant is switched accordingly, whereas the third embodiment is executed. In the above form, the installation direction of the magnetic bearing device is determined by using the exciting current Ip flowing through the electromagnet in the radial direction, and the control constant is switched accordingly.

FIG. 6 shows a case in which the rotary shafts are tilted in the direction of 45 ° with respect to the radial electromagnets arranged opposite to each other, and in this case, the same relations as in the equations (2) to (6) are given. When the equation is obtained and the exciting current Ip flowing through the electromagnet in the radial direction on the f side is obtained, it can be expressed by the following equation. Ip = (l _Mr · D ² · m · g · sin θ) / {2 · √2 · k · I · (l _Mf + l _Mr )} + I / 2 (8) Formula (8) is a radial on the f side. It is shown that the exciting current Ip flowing through the electromagnet in the direction changes depending on the installation direction θ of the magnetic bearing device, and the control constant is switched according to the magnitude of the exciting current, as in the above equation (7). Shows what can be done. Therefore, the third embodiment of the present invention
In the form of FIG.
As a signal to be input to the control unit, it is possible to use the f-side or r-side electromagnet Mx or the electromagnet My instead of the electromagnet M to switch the control constant in the same manner as in the second embodiment. When the tilt direction of the rotation axis is other than 45 °, the value of √2 in the equation (8) changes.

Next, a fourth embodiment of the present invention will be described. In the first to third embodiments, the number of control constants is two, but the number of control constants may be two or more. For example, as shown in FIG. It is possible to set three control constants of control constant A to control constant C by dividing every 36 °. Furthermore, it is also possible to divide the angle section into smaller pieces and set more control constants.

As a fifth embodiment of the present invention,
It is also possible to configure the control constants and changeover switches in the compensation circuit by software. For example, the control constants may be stored in a memory and the corresponding control constants may be read out and output based on the switch changeover signal. You can also

[0039]

As described above, according to the present invention,
It is possible to provide a magnetic bearing device capable of performing levitation control corresponding to the installation direction of the magnetic bearing device. Also,
By using this magnetic bearing device for a pump or the like, optimum levitation control can be ensured, stability can be improved even against sudden external vibration, and highly reliable operation becomes possible. In addition, the excitation compensation current in the levitation equilibrium state automatically determines the pump installation compensation circuit to perform the switching operation, reducing the hassle of changing control constants when the pump installation direction is changed frequently. Can be made.

[Brief description of drawings]

FIG. 1 is a block diagram of a control system for explaining a first embodiment of the present invention.

FIG. 2 is a schematic structural diagram of a 5-DOF control type magnetic bearing.

FIG. 3 is a block diagram of a control system for explaining a second embodiment of the present invention.

FIG. 4 is a schematic diagram for explaining a relationship between a rotating shaft and an electromagnet.

FIG. 5 is a diagram for explaining an exciting current flowing through an electromagnet in a thrust direction.

FIG. 6 is a diagram for explaining an exciting current flowing in a radial electromagnet.

FIG. 7 is a diagram illustrating a relationship between an installation direction of a magnetic bearing device and an exciting current equivalent value.

FIG. 8 is a diagram illustrating a relationship between an installation direction of a magnetic bearing device and an exciting current equivalent value.

FIG. 9 is a block diagram illustrating a control system of an enlarged optimum regulator system in a conventional magnetic bearing.

FIG. 10 is a diagram showing an example of installation positions where a magnetic bearing device is installed in a vacuum chamber of a turbo molecular pump.

FIG. 11 is a diagram illustrating force components received by the thrust bearing and the radial bearing depending on the installation direction of the magnetic bearing device.

[Explanation of symbols]

1 ... Control system, 2, S ... Displacement sensor, 3 ... Compensation circuit, 4 ...
Inverter, 5 ... Adder, 6 ... Excitation amplifier, 7 ... Electromagnet, 3
1 ... Changeover switch, 32 ... Window comparator, R ...
Rotating shaft, M ... Electromagnet, m ... Motor, PID ... PID control unit.

[Procedure amendment]

[Submission date] August 21, 1995

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction contents]

The automatic setting of the control constant according to the second embodiment is usually performed every time the control power supply for the pump is started up, or when the installation of the magnetic bearing device is changed, and the rotation of the rotor is performed. Do not do it while driving. As a result, switching of the control constant due to disturbance such as vibration can be prevented.

Claims (1)

[Claims] 1. A magnetic bearing device comprising a magnetic bearing portion for supporting a rotary shaft and a drive portion for rotationally accelerating and decelerating the rotary shaft, wherein the rotary shaft is held at a predetermined position based on a displacement variation amount of the rotary shaft. The magnetic bearing device is characterized in that the compensating circuit for controlling the magnetic bearing portion is provided, and the compensating circuit switches the control constant in the compensating circuit according to the installation direction of the rotating shaft.