JP2002349567A - Magnetic bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enlarge load capacity by an electro-magnet without enlarging an excitating current fed to the electro-magnet. SOLUTION: A rotating body 5 is non-contact supported in the axial control shaft direction and the radial control shaft direction by a plurality of pairs of electro-magnets 26a, 26b. The magnetic bearing device is provided with a pair of electro-magnets; position detection means 23, 13 for detecting a position of the rotating body and outputting a position detection signal Zs; a levitation referential position signal outputting means for outputting a levitation referential position signal; an electro-magnet control signal outputting means for outputting electro-magnet control signals (Io+Ic), (Io-Ic) including an integrated output based on the levitation referential position signal and the position detection signal; and an electro-magnet driving means 14 for driving the electro-magnets based on the electro-magnet control signal. The levitation referential position signal outputting means changes the levitation referential position signal such that the integrated output becomes in a range of control system integrated output previously set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a magnetic bearing device,
More specifically, the present invention relates to a magnetic bearing device in which a plurality of sets of magnetic bearings support a rotating body in a non-contact manner in an axial control axial direction and a radial control axial direction to magnetically levitate.

[0002]

2. Description of the Related Art As a magnetic bearing device of this type, a plurality of magnetic bearings having a plurality of electromagnets that support a rotating body in a non-contact manner in an axial control axial direction and a radial control axial direction, an axial control axial direction and a radial control of the rotating body are provided. A position detection device that detects a position in the axial direction and outputs a position detection signal;
An electromagnet control device that controls an electromagnet of a magnetic bearing based on a position detection signal, and a protective bearing (touch-down) as a mechanical regulation unit that mechanically regulates a movable range of a rotating body in an axial control axial direction and a radial control axial direction. Bearings) are known.

Each magnetic bearing includes one or two pairs of electromagnets facing each other with the rotating body sandwiched from both sides in the control axis direction. The position detection device includes a plurality of position sensors. Usually, the position sensor in the axial control axis direction includes one axial position sensor that faces the position detection end face of the rotating body from one side in the axial control axis direction. The position sensors in the radial control axis direction include a plurality of pairs of radial position sensors opposed to each other while sandwiching the rotating body from both sides in two control axis directions orthogonal to each other. An electromagnet control device includes: a levitation reference position signal output unit that outputs a levitation reference position signal for each control axis direction; an electromagnet control signal output unit that outputs an electromagnet control signal based on the levitation position reference signal and the position detection signal; An electromagnet driving means for driving the electromagnet based on the control signal is provided.

[0004] Electromagnet control signal output means of each control axis outputs an excitation current signal to a pair of electromagnets of the control axis,
The electromagnet driving means supplies an exciting current proportional to the exciting current signal to the pair of electromagnets. The exciting current signal for each electromagnet is a sum of the steady current signal and the control current signal, and the exciting current supplied to each electromagnet is the sum of the steady current and the control current. The steady current (and the steady current signal) is a constant value regardless of the position of the rotating body in the control axis direction. The control current (and the control current signal) changes depending on the position of the rotating body in the control axis direction. For a pair of electromagnets of each control axis, the absolute values of the control currents (and control current signals) are equal to each other, and the signs are opposite to each other.

The magnetic bearing device as described above includes a mechanical center position in an axial control axial direction and a radial control axial direction with respect to a movable range of a protective bearing, and an axial control axial direction and a radial control shaft with respect to a position of an electromagnet of the magnetic bearing. There is a magnetic center position in the direction and a sensor center position relative to the position of the position sensor. The mechanical center position is the center position of the movable range regulated by the protective bearing.
The magnetic center position in each control axis direction is the position of the center of two electromagnets forming a pair in the control axis direction. The center position of the sensor with respect to the axial control axis direction is a position at which the distance between the position detection end face of the rotating body and the axial position sensor becomes a predetermined value set in advance. The sensor center position in the radial control axis direction is the center position of the two radial position sensors forming a pair in the control axis direction. The magnetic bearing device is designed such that the mechanical center position, the magnetic center position, and the center position with respect to the sensor all coincide. Actually, an error may occur between the above three center positions due to a manufacturing error or an assembly error, but this error is generally small.

In an ordinary magnetic bearing device, the electromagnet of the magnetic bearing is controlled so that the rotating body is held at the center position of the sensor, that is, the center of the rotating body coincides with the center position of the sensor. For this reason, the rotating body is held at a substantially magnetic center position. Alternatively, the rotating body is held at the magnetic center position. As described above, when the rotating body is held at the magnetic center position or substantially the magnetic center position, the size of the gap between the pair of electromagnets and the rotating body is equal to or substantially equal to each other.

If the axial control axis is the Z axis and the two radial control axes are the X axis and the Y axis, respectively, in a vertical type magnetic bearing device, the Z axis is in the vertical direction and the horizontal type magnetic bearing is used. In the apparatus, usually, one of the X axis and the Y axis is in the vertical direction.

[0008]

In the magnetic bearing device, an external force other than the magnetic attraction of the electromagnet sometimes acts in a certain control axis direction. In such a case, in order to support the rotating body near the magnetic center position against external force, it is necessary to supply a large exciting current to one of the electromagnets, and in some cases, the load capacity is insufficient. In some cases, the rotating body cannot be supported near the magnetic center position. Next, the reason will be described.

The magnetic attraction by the electromagnet is inversely proportional to the square of the size of the gap with the rotating body, and proportional to the square of the exciting current value. Normally, since the same pair of electromagnets is used for each control axis, their proportionality constants are the same. Therefore, if the size of the gap with the rotating body and the exciting current are equal to each other, the magnetic attraction force of the pair of electromagnets is also equal to each other.

When no external force other than gravity acts on the rotating body, no external force acts on the control axis in the horizontal direction in the direction of the control axis. The body is supported in a fixed position. Therefore, when the rotating body is supported at the magnetic center position where the gap between the pair of electromagnets is equal to each other, the magnitude of the exciting current supplied to the pair of electromagnets is equal to each other.
That is, the control current for the pair of electromagnets becomes zero.

On the other hand, with respect to the vertical control axis, gravity acts in the control axis direction and the weight of the rotating body is supported by a pair of electromagnets. , The magnetic attraction of the lower electromagnet is greater by the weight of the rotating body. For this reason, the control current for the upper electromagnet has a positive value (the same sign as the steady current), and the control current for the lower electromagnet has a negative value (the opposite sign as the steady current).
The magnitude of the exciting current supplied to the upper electromagnet becomes larger than the magnitude of the exciting current supplied to the lower electromagnet. Therefore, in order to support a heavy rotating body, it is necessary to supply a large exciting current to the upper electromagnet. In particular, when a vertical-type magnetic bearing device is used for a turbo-molecular pump, when gas is introduced from above into the pump, the axial direction (Z
Axial direction) A large load acts downward, and it is necessary to support the weight of the rotating body and this load with a pair of electromagnets in the Z-axis direction. Therefore, it is necessary to supply a very large exciting current to the upper electromagnet. is there. In order to supply a large exciting current to the electromagnet, it is necessary to increase the size of the electromagnet and the amplifier of the electromagnet drive circuit, which leads to an increase in cost. When the external force acting on the rotating body increases, the absolute value of the control current increases in proportion to this, and the exciting current increases in the upper electromagnet, and the exciting current decreases in the lower electromagnet. Then, when the absolute value of the control current becomes equal to the steady-state current, the value of the exciting current supplied to the lower electromagnet becomes 0, and when the external force further increases, the rotating body cannot be supported.

[0012] The same problem occurs in the horizontal control axis when some external force acts in the control axis direction.

An object of the present invention is to solve the above problems,
An object of the present invention is to provide a magnetic bearing device capable of increasing a load capacity of an electromagnet without increasing an exciting current supplied to the electromagnet.

[0014]

In the magnetic bearing device according to the present invention, the rotating bodies are in non-contact with each other in the axial control axial direction and the two radial control axial directions orthogonal to each other by the magnetic attraction of a plurality of pairs of electromagnets. A magnetic bearing device supported and magnetically levitated, wherein a pair of electromagnets arranged so as to sandwich the rotating body from both sides in the control axis direction in each of the control axis directions, the control shaft of the rotating body Position detection means for detecting a position in the direction and outputting a position detection signal, levitation reference position signal output means for outputting a levitation reference position signal, electromagnet control including at least an integral output based on the levitation reference position signal and the position detection signal An electromagnet control signal output unit that outputs a signal, and an electromagnet drive unit that drives the electromagnet based on the electromagnet control signal. Upper reference position signal output means, said floating reference position signal, and wherein the integral output is one which changed to be preset control system integrator output range.

For each control axis, a pair of electromagnets usually have the same characteristics. For each electromagnet, a constant steady-state current signal is output from the electromagnet control signal output means to the control axis direction of the rotating body. An excitation current signal that combines a control current signal that changes according to the position of the motor is output, and an excitation current that combines a constant steady current that is proportional to the steady current signal and a control current that is proportional to the control current signal is supplied from the electromagnet driving unit. Is done.

According to the magnetic bearing device of the present invention, as described below, even when an external force acts in the control axis direction, the exciting current supplied to the electromagnet is not increased, and the load capacity of the electromagnet is reduced. Can be increased to support the rotating body.

In the pair of electromagnets of each control axis, the values of the steady currents are equal to each other, and the absolute values of the control currents are equal to each other and have opposite signs. The absolute value of the control current is proportional to the integral output of the electromagnet control signal output means.

In the case where the control shaft is vertical and gravity acts on the rotating body other than the magnetic attraction of the electromagnet, when the rotating body is supported in a non-contact position at a certain position in the direction of the control axis, the upper side (external force) The upward magnetic attraction force of the electromagnet on the side that generates the magnetic attraction force in the opposite direction matches the downward magnetic attraction force of the electromagnet on the lower side (the side that generates the magnetic attraction force in the same direction as the external force) and gravity. Is balanced with the power. Therefore, when the rotating body is supported at the magnetic center position, the control current of the upper electromagnet is a positive value, and the control current of the lower electromagnet is a negative value. Absent. When the gravity is small, the integrated output may be within the control system integrated output range even if the rotating body is supported at the magnetic center position. In such a case, the rotating body is supported at the magnetic center position, but since the integral output is within the control system integral output range, the absolute value of the control current is also within the predetermined range. It cannot be larger. If the gravity is large, trying to support the rotating body at the magnetic center position will cause the integral output to exceed the control system integral output range.In such a case, make sure that the integral output falls within the control system integral output range. , The floating reference position signal is changed to the upper electromagnet side. As a result, the floating reference position of the rotating body is changed to the upper electromagnet side, and the size of the gap between the rotating body and the upper electromagnet is reduced, so that even when the excitation current is reduced, the rotating body can be supported. The required magnetic attraction force can be obtained. Then, if the floating reference position of the rotating body is moved to the upper side of the electromagnet to some extent and the integrated output is within the control system integrated output range, the rotating body is supported at that position. As described above, by changing the levitation reference position signal of the rotating body so that the integrated output is within the control system integrated output range, the exciting current can be limited to a certain range and the rotating body can be supported. .

The same applies to the case where the control axis is oblique. The same applies when an external force other than gravity acts in the control axis direction even when the control axis is horizontal.

When no external force other than the magnetic attractive force of the electromagnet acts on the rotating body, such as when the control shaft is horizontal, when the rotating body is supported at a certain position in the direction of the control axis,
The magnetic attraction forces of the two electromagnets on the rotating body are equal to each other. For this reason, the value of the exciting current in each electromagnet is equal to each other. That is, the value of the control current in each electromagnet is 0. When the position of the rotating body deviates from the magnetic center position, the integrated output becomes a value other than 0, and an exciting current combining the steady current and the non-zero control current is supplied to each electromagnet. Since the integrated output at this time is small and within the control system integrated output range, the rotating body is supported at the magnetic center position.

In the magnetic levitation state, the rotating body is an electromagnet,
In order to prevent the position sensor or the protective bearing from approaching abnormally, it is preferable to limit the levitation reference position of the rotating body so that it is within a predetermined range including the magnetic center position.

For example, the levitation reference position signal output means fixes the levitation reference position signal when the integrated output falls within a preset control system integrated output range.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a five-axis control type magnetic bearing device will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing a main part of a mechanical part of a five-axis control type magnetic bearing device, FIG. 2 is a transverse sectional view of the same, and FIG. 3 is a block diagram showing an example of an electrical configuration thereof. .

The magnetic bearing device includes a machine body (1) and a controller (2) connected by a cable. This magnetic bearing device is of a vertical installation type in which a vertically rotating body (5) rotates inside a vertically cylindrical casing (4). As described above, the axis of the rotating body (5) in the axial direction (vertical direction) is the Z axis, and the axes in the two radial directions (horizontal directions) orthogonal to the Z axis and orthogonal to each other are the X axis and the Y axis. .

The machine body (1) includes a set of axial magnetic bearings (6) for supporting the rotating body (5) in a non-contact manner in the Z-axis direction, and a rotating body.
Two sets of upper and lower radial magnetic bearings (7) and (8) that support (5) non-contact in the X-axis direction and Y-axis direction at two locations in the axial direction, and the axial position of the rotating body (5) and the two A position detector (9) for detecting the position in the X-axis direction and the Y-axis direction at each location, a built-in electric motor (10) for rotating the rotating body (5) at high speed, and a rotating body (5). When the rotating body (5) cannot be supported by the magnetic bearings (6) (7) (8) by restricting the movable range in the axial and radial directions, the rotating body (5) is mechanically moved at the extreme position of the movable range. Two sets of upper and lower protective bearings (11) and (12) are provided as mechanically restricting means for mechanical support. Z
The axis is a control axis in the axial direction. In the upper magnetic bearing (7), the control axis in the X-axis direction is the upper X-axis, the control axis in the Y-axis direction is the upper Y-axis, and the lower magnetic bearing
In the portion (8), the control axis in the X-axis direction is the lower X-axis, and the control axis in the Y-axis direction is the lower Y-axis.

The controller (2) includes a sensor circuit (13),
An electromagnet drive circuit (14) as an electromagnet drive means, an inverter (15) and a DSP board (16) are provided, and the DSP board (16) has a DSP (18) as a digital processing means capable of software program, a ROM (31), a flash memory (19) as a storage means, an AD converter (20), and a DA converter (21) are provided. DSP is an abbreviation of digital signal processor, and digital signal processor refers to dedicated hardware that inputs a digital signal, outputs a digital signal, is software-programmable, and is capable of high-speed real-time processing.

The position detector (9) includes a single axial position sensor (2) for detecting the position of the rotating body (5) in the Z-axis direction.
3) and two sets of upper and lower radial position sensor units (24) and (25) for detecting the positions of the rotating body (5) in the X-axis direction and the Y-axis direction.

The axial magnetic bearing (6) is disposed so as to sandwich the flange (5a) integrally formed at the lower portion of the rotating body (5) from both sides in the Z-axis direction, and magnetically attracts the rotating body (5). 1 to do
A pair of axial electromagnets (26a) (26b) is provided. Axial electromagnets are collectively referred to by reference numeral (26). The pair of axial electromagnets 26 have the same characteristics.

The axial position sensor (23) includes a rotating body (5)
And outputs a distance signal proportional to the size of the gap with the lower end surface of the rotating body (5).

The two sets of radial magnetic bearings (7) and (8) are arranged at predetermined intervals in the vertical direction above the axial magnetic bearing (6), and the motor (10) is arranged between them. Have been. The upper radial magnetic bearing (7) is a rotating body (5)
Is disposed so as to sandwich it from both sides in the X-axis direction, and the rotating body (5)
A pair of upper radial electromagnets (27a) (27b) for magnetically attracting
And a pair of upper radial electromagnets (27c) and (27d) arranged to sandwich the rotating body (5) from both sides in the Y-axis direction and magnetically attract the rotating body (5). These radial electromagnets are collectively referred to by reference numeral (27). Similarly, the lower radial electromagnet
(8) also has two pairs of lower radial electromagnets (28a) (28b) (28c) (28
d). These radial electromagnets are also designated (28)
Collectively. As for the radial bearings (27) and (28), at least a pair of electromagnets having the same control shaft have the same characteristics. Preferably, all radial electromagnets (27) (2
8) The same characteristics are used.

The upper radial position sensor unit (24)
Located near the upper radial magnetic bearing (7), X
A pair of upper radial position sensors (29a) (29b) arranged so as to sandwich the rotating body (5) from both sides in the X-axis direction in the vicinity of the axial electromagnets (27a) (27b), and in the Y-axis direction electromagnet
(27c) Rotating body from both sides in the Y-axis direction near (27d)
It has a pair of upper radial position sensors (29c) (29d) arranged so as to sandwich (5). These radial position sensors are collectively referred to by reference numeral (29). Similarly, the lower radial position sensor unit (25) is disposed near the lower radial magnetic bearing (8) and has two pairs of lower radial position sensors.
(30a), (30b), (30c), and (30d). These radial position sensors are also collectively referred to by reference numeral (30). Each of the radial displacement sensors (29) and (30) outputs a distance signal proportional to the size of the gap between the radial displacement sensor and the outer peripheral surface of the rotating body (5).

Electromagnets (26) (27) (28) and position sensor (23)
(29) and (30) are fixed to the casing (4).

The upper protective bearing (11) is made of a rolling bearing such as a deep groove ball bearing, and is capable of receiving a radial load. The outer ring (11a) of the bearing (11) is fixed to the casing (4), and the inner ring (11b) is arranged so as to face the outer peripheral surface of the rotating body (5) with an appropriate gap. The lower protective bearing (12) is made of a rolling bearing such as a deep groove ball bearing, and is capable of receiving both an axial load and a radial load. Outer ring (12a) of this bearing (12)
Is fixed to the casing (4), and the inner ring (12b) is made to face the portion of the annular groove (17) formed on the outer peripheral surface of the rotating body (5) with an appropriate gap in the axial direction and the radial direction. I have. Then, the inner ring (12b) of the lower bearing (12) and the rotating body (4)
Due to the size of the axial gap between
The movable range in the axial direction of (5) is restricted, and each bearing (1
1) The radial movable range of the rotating body (5) is regulated by the size of the radial gap between the inner ring (11b) (12b) of the (12) and the rotating body (5). And, even in a state where the rotating body (2) is supported by the protective bearings (11) and (12) at the extreme position of the movable range, the rotating body (5) and the electromagnets (26) (27) (28) and the position sensor ( There is a gap between (23), (29) and (30), and the rotating body (5) is composed of electromagnets (26) (27) (28) and position sensors (23) (29)
Never touch (30).

The sensor circuit (13) of the controller (2) drives each of the position sensors (23), (29), and (30) of the position detecting section (9), and the position sensors (23), (29), and (30). Based on the distance signal which is the output of, the position of the rotating body (5) in the Z-axis direction and the positions of the upper and lower radial position sensor units (24) and (25) in the X-axis direction and the Y-axis direction are calculated. , And outputs the position signal, which is the operation result, to the DSP (18) via the AD converter (20). The position detecting device (9) and the sensor circuit (13) constitute a position detecting device as position detecting means for detecting a position of the rotating body (5) in each control axis direction and outputting a position detection signal.

The ROM (31) stores processing programs for the DSP (18). Flash memory (1
9) is provided with a control parameter table that stores control parameters of the magnetic bearing, a bias current value table that stores a bias current (steady current) value described later, and the like. The DSP (18) has an AD converter (20) for each control axis.
Each of the electromagnets (26) of each magnetic bearing (6) (7) (8) based on the digital position signal representing the position of the rotating body (5) input from
(27) The excitation current signal (electromagnet control signal) for (28) is
Output to the electromagnet drive circuit (14) via the A converter (21).
Then, the drive circuit (14) supplies the exciting current based on the exciting current signal from the DSP (18) to the corresponding electromagnets (26) (27) (28) of the magnetic bearings (6) (7) (8). Thereby, the rotating body (5) is supported in a non-contact manner at a later-described floating reference position. DSP (18)
This constitutes an electromagnet control signal output means for outputting an electromagnet control signal based on a levitation reference position signal and a position detection signal, which will be described later.

The DSP (18) also outputs a rotational speed command signal to the motor (10) to the inverter (15),
(15) controls the rotation speed of the motor (10) based on this signal. And, as a result, the rotating body (5) becomes a magnetic bearing (6).
(7) In the state of being supported in a non-contact manner at the target floating position by (8),
It is rotated at high speed by a motor (10).

FIG. 4 shows the configuration of the controller (2).
This shows only a part related to control of a pair of axial electromagnets (26a) (26b) in the axial magnetic bearing (6). Next, the control of the pair of axial electromagnets (26a) (26b) by the controller (2) will be described with reference to FIG.

First, the sensor circuit (13) determines the position of the rotating body (5) in the Z-axis direction from the output signal of the axial position sensor (23), and outputs a position signal Zs proportional to this position. The position signal Zs from the sensor circuit (13) is
It is converted into a digital value by (20) and input to the DSP (18). The DSP (18) calculates the displacement of the rotating body (5) with respect to the floating reference position from the digital position signal Zs as described later, and based on the displacement, the control signal corresponding to each of the pair of electromagnets (26). A pair of exciting current signals as D
Output to the A converter (21). The first excitation current signal (Io +
Ic) is converted into an analog signal by the DA converter (21) and supplied to the first power amplifier (35) of the electromagnet drive circuit (14) as a first excitation current signal (Io + Ic), and the first power The amplifier (35) amplifies the first exciting current signal (Io + Ic) and supplies an exciting current proportional to the signal to the first electromagnet (26a). The second exciting current value (Io-Ic) is determined by the DA converter (2
The signal is converted into an analog signal by 1) and supplied to the second power amplifier (36) of the electromagnet drive circuit (14) as a second excitation current signal (Io-Ic), and the second power amplifier (36) The second exciting current signal (Io-Ic) is amplified and an exciting current proportional thereto is supplied to the second electromagnet (26a). As a result, the rotating body (5) is supported at the floating reference position in the Z-axis direction.

FIG. 5 shows the controller shown in FIG.
In the part (2), the operation of the DSP (18) is represented by functional blocks. The DSP (18) functionally includes a subtraction means (22), a floating reference position signal output means (32), a control current calculation means (37), and an excitation current calculation means (38). The subtraction means (22) is a floating reference position signal output means as described later based on the position signal Zs input from the AD converter (20).
By subtracting the floating reference position signal Zo input from (32), a displacement value ΔZ of the rotating body (5) from the floating reference position is obtained, and this is output to the control current calculating means (37). The control current calculation means (37) performs electromagnets (26a) (26b) based on the displacement value ΔZ from the subtraction means (22) by, for example, PID calculation.
And calculates a control current value Ic with respect to, and is composed of an integral operation unit (integral operation unit) (40), a proportional / differential operation unit (proportional / differential operation unit) (41), and an addition unit (42). .
The integral operation unit (40) computes the integral component Ici of the control current value Ic based on the displacement value ΔZ using the integral operation control parameters stored in the table of the flash memory (19). The proportional / differential operation unit (41) uses the proportional operation control parameter and the differential operation control parameter stored in the table of the flash memory (19), and based on the displacement value ΔZ, the proportional / differential component Icpd of the control current value Ic. Is calculated. The adder (42) includes the integral component Ici and the proportional / differential component Icp.
The control current value Ic is obtained by adding d, and this is output to the excitation current calculation means (38). Note that the proportional / differential operation unit (41) is divided into a proportional operation unit and a differential operation unit, and a proportional component output from the proportional operation unit, a differential component output from the differential operation unit, and the above-described integral operation unit ( The control current value Ic may be obtained by adding the integral component Ici which is the output of 40). The exciting current calculating means (38) adds the control current value Ic from the control current calculating means (37) to the bias current value Io stored in the table of the flash memory (19), and obtains a value obtained as a result ( Io + Ic) as a first excitation current signal to the DA converter (21), subtracts the control current value Ic from the bias current value Io, and outputs the resulting value (Io−Ic) to the second Is output to the DA converter (21) as the exciting current signal. The floating reference position signal output means (32) outputs a floating reference position signal Zo described later.

Although illustration is omitted, the same applies to a portion related to control of the pair of axial electromagnets (26) and (27) in the upper and lower X-axis and Y-axis.

The above-described magnetic bearing device has a mechanical center position, a magnetic center position, and a sensor neutral position. The mechanical center position is the position of the center of the movable range regulated by the protective bearings (11) and (12) .In the axial direction, the inner ring (12b) of the lower protective bearing (12) is Groove (1
At the center in the axial direction of 7), the size of the gap in the axial direction between the end face of the inner ring (12b) and the side face of the groove (17) opposed thereto is equal to each other on both sides. The radial of the rotating body (5) and the inner ring (12b) of the rotating body (5) and the protective bearings (11) and (12) coincides with the center of the two sets of protective bearings (11) and (12). This is a position where the size of the gap in the direction becomes equal over the entire circumference. The magnetic center position is the position of the center of each pair of electromagnets (26) (27) (28) facing each other of the magnetic bearings (6) (7) (8). The neutral position with respect to the sensor is such a position that a gap in the axial direction between the lower end surface of the rotating body (5) and the axial position sensor (23) has a predetermined value in the axial direction, Regarding the radial direction, each pair of radial position sensors (2,
9) This is the center position of (30).

In the above magnetic bearing device, before starting operation for the first time, a magnetic center position is obtained for each control shaft by an appropriate means, and this is the first floating reference position. The coordinate value of the magnetic center position is set to 0 for each control axis. Thereafter, during the operation, the levitation reference position output means (for the respective control axes, so that the integral component Ici, which is the integral output from the integral operation unit (40), falls within the preset control system integral output range. At 32), the flying reference position signal is changed. Thereby, the rotating body (5) is supported at the changed floating reference position for each control axis.

FIG. 6 is a flowchart showing one example of the processing in the floating reference position output means (32) for the Z axis. FIG. 7 is a time chart showing the change in the exciting current value of the electromagnet (26) at that time. It is a chart. FIG. 8 is a drawing corresponding to FIG. 7 when the levitation reference position is fixed to the magnetic center position as in the conventional magnetic bearing device. 7 and 8, (a) is a load acting on the rotating body (5) in the Z-axis direction, (b) is an exciting current value of the upper electromagnet (26a), and (c) is a lower electromagnet (26b ) Indicates the exciting current value, (d) indicates the floating reference position, and (e) indicates the integrated output. As for the load of (a), the downward direction (Z-axis direction negative side direction) is defined as the positive direction. The upper side of the floating reference position is the positive side.

First, a conventional case in which the floating reference position is fixed to the magnetic center position will be described with reference to FIG.

In this case, as shown on the left side of FIG. 8 (a), while the load is 0, the integrated output is 0, the control current is 0, and the excitation current value of the upper and lower electromagnets (26a) (26b) Is equal to the steady-state current value Io. As shown on the right side of FIG. 8 (a), when the load gradually increases, the integral output also increases in proportion thereto, whereby
Since the control current value also increases in proportion, the upper electromagnet (26a)
In, the exciting current value increases linearly and the lower electromagnet (26b)
, The exciting current value decreases linearly. Then, when the load increases and the exciting current value of the lower electromagnet (26b) becomes 0, the rotating body (5) cannot be supported for a load larger than that.

Next, an example of the operation of the Z-axis floating reference position output means (32) in the above embodiment will be described with reference to FIGS.

In the flowchart of FIG. 6, when the control of the magnetic bearing is started, the levitation reference position signal Zo is set to 0 (= magnetic center position) (S1), and the magnetic levitation of the rotating body (5) starts ( S2). Thus, the rotating body (5) is first supported at the magnetic center position. Then, it is checked whether or not the integral output Ici is within the control system integral output range, that is, whether or not the integral output Ici is between -A and A (S3). The signal Zo is fixed to the value at that time, and the process returns to S3. Thereby, the rotating body (5) is supported at the fixed floating reference position. If the integral output Ici is not within the control system integral output range in S3, the process proceeds to S5 to change the floating reference position signal Zo, and it is checked whether or not the integral output Ici is smaller than -A. If the integral output Ici is smaller than -A in S5, the process proceeds to S6, where the flying reference position signal Zo is decreased by ΔZ. In S5, if the integral output Ici is not smaller than -A,
Proceeding to S7, the flying reference position signal Zo is raised by ΔZ. S
Upon completion of the process in S6 or S7, the process returns to S3. Thereby, the rotating body (5) is supported at the changed floating reference position.

In the time chart of FIG. 7, FIG.
As shown on the left side, while the load is 0, the integrated output is 0, the control current is 0, and the exciting current values of the upper and lower electromagnets (26a) (26b) are equal to the steady current value Io. Therefore, the floating reference position is fixed to the magnetic center position. As shown on the right side of FIG. 8, as the load gradually increases, the integral output also increases.
When the integrated output exceeds the range A, the floating reference position is shifted to the + side by Δ.
Since Z is changed, the integrated output does not exceed the range A. For this reason, the control current is also limited to a certain range, and as a result, the steady-state current does not exceed a certain value. When the load no longer increases, the floating reference position is fixed to the value at that time.

When the load increases in the negative direction,
The same is true.

When no external force acts on the X-axis or Y-axis, the load is 0, so the integrated output is also 0. Similarly to the case where the load is 0 on the Z-axis, the levitation reference position is the magnetic center position. Fixed to

In the above embodiment, the floating reference position signal output means (32) is constituted by the DSP (18). However, the floating reference position signal output means is other than the DSP, such as a personal computer or a microprocessor. It may be configured.

In the above embodiment, the inner rotor type magnetic bearing device in which the rotating body rotates inside the casing, which is the fixed portion, is shown. However, the present invention relates to the outer rotor type magnetic bearing device in which the rotating body rotates outside the fixed portion. It can also be applied to magnetic bearing devices.

In the above embodiment, the vertical magnetic bearing device in which the rotating body is arranged vertically is shown. However, the present invention is applied to a horizontal magnetic bearing device in which the rotating body is horizontally arranged. Can also be applied.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part of a mechanical part of a magnetic bearing device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the same.

FIG. 3 is a block diagram showing an example of an electrical configuration of the magnetic bearing device.

FIG. 4 is a block diagram showing a portion related to a pair of axial electromagnets of the controller shown in FIG. 3;

FIG. 5 is a block diagram showing functions of a DSP part of FIG. 4;

FIG. 6 is a flowchart illustrating an example of processing in a flying reference position output unit.

FIG. 7 is a time chart showing changes in signals and the like of each unit when processing according to the embodiment of the present invention is performed.

FIG. 8 is a time chart showing changes in signals and the like of respective parts when processing in a conventional magnetic bearing device is performed.

[Explanation of symbols]

(5) Rotating body (6) Axial magnetic bearing (13) Sensor circuit (18) Digital signal processor (DSP) (19) Flash memory (23) Axial position sensor (26a) (26b) Axial electromagnet (27a) (27b) ) (27c) (27d) Radial electromagnet (28a) (28b) (28c) (28d) Radial electromagnet (29a) (29b) (29c) (29d) Radial position sensor (30a) (30b) (30c) (30d) Radial position sensor (37) Control current calculation means (32) Levitation reference position signal output means (40) Integral calculation section

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Manabu Taniguchi 3-5-8 Minamisenba, Chuo-ku, Osaka Koyo Seiko Co., Ltd. F-term (reference) 3J102 AA01 BA03 BA17 BA18 CA23 DA02 DA03 DA08 DA09 DB05 DB10 DB11 DB22 DB31 5H607 DD03 GG21 HH01

Claims (2)

[Claims] 1. A magnetic bearing device in which a rotating body is supported in a non-contact manner in a direction of an axial control axis and a direction of two radial control axes orthogonal to each other by magnetic attraction of a plurality of pairs of electromagnets and magnetically levitated. A pair of electromagnets arranged so as to sandwich the rotating body from both sides in the control axis direction in the control axis direction, and position detecting means for detecting a position of the rotating body in the control axis direction and outputting a position detection signal Levitation reference position signal output means for outputting a levitation reference position signal, electromagnet control signal output means for outputting an electromagnet control signal including at least an integrated output based on the levitation reference position signal and the position detection signal, and the electromagnet control signal. An electromagnet driving means for driving the electromagnet based on the levitation reference position signal output means. A magnetic bearing device wherein the force is changed so as to fall within a preset control system integral output range. 2. The floating reference position signal output means for fixing the floating reference position signal when the integrated output is within the control system integrated output range. Magnetic bearing device.