JPH0968221A - Magnetic bearing device - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To eliminate the residual magnetic flux generated in the electromagnet when the operation of the magnetic bearing is stopped by the next startup so that the startup can be surely performed. SOLUTION: A thrust disk 13 made of a ferromagnetic material is fixed to a rotating shaft 12. The electromagnets 14a and 14b are arranged at positions facing each other with the thrust disk 13 interposed therebetween. The axial position of the rotary shaft 12 is detected by the displacement sensor 15,
A position detection signal is given to the control device 16. Control device 16
Are the electromagnets 14a, 1 depending on the displacement of the thrust disk 13.
The suction force of 4b is controlled to hold it in a predetermined position. The degaussing device 22 is connectable to the electromagnets 14a and 14b via the changeover switches 18a and 18b, supplies a degaussing current that decays and vibrates when the control of the magnetic bearing is stopped, performs a degaussing operation, and leaves the electromagnets 14a and 14b. Degauss magnetic flux.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a displacement of a rotary shaft from a predetermined position by a displacement sensor and gives a control signal to a control means in accordance with the amount of displacement so that the attraction force of the electromagnet with respect to the rotary shaft can be obtained. The present invention relates to a magnetic bearing device that is controlled to hold its rotating shaft in a predetermined position in a non-contact state.

[0002]

FIG. 4 shows a conventional magnetic bearing device. The figure shows a thrust magnetic bearing device. A thrust disk 2 made of a magnetic material is fixed to the rotating shaft 1. Electromagnets 3a and 3b are provided at positions facing each other across the thrust disk 2 with a predetermined interval. A displacement sensor 4 is arranged on one end side of the rotary shaft 1 so as to detect a displacement along the axial direction and give a position detection signal to the control circuit 5. In this case, the displacement sensor 4 increases as the distance from the rotation shaft 1 increases.
The value of the position detection signal is configured to be large.
The control circuit 5 sets an exciting current to be applied to the electromagnets 3a and 3b on the basis of a position detection signal from the displacement sensor 4, and is connected to the electromagnet 3a through a power amplifier 6a and to the electromagnet 3b for phase inversion. The circuit 7 and the power amplifier 6b are connected in series.

A bearing portion 1a having a small diameter is formed at both ends of the rotary shaft 1 (only one is shown).
a is held by the auxiliary bearing 8. In this case, the auxiliary bearing 8 is fixed to the electromagnet 3a side by the mounting bracket 9. The auxiliary bearing 8 is arranged so as not to come into contact with the rotary shaft 1 in a normal use state,
With respect to the thrust direction, the thrust disk 2 and the electromagnet 3a,
It is provided so that an air gap of about 1/2 of the air gap with 3b is set, and an air gap of about 1/2 of the air gap of a radial magnetic bearing (not shown) is set in the radial direction. Is provided.
Then, when the holding state by the radial or thrust magnetic bearing is stopped, the rotary shaft 1 uses the auxiliary bearing 8
Is supported by the rotary shaft 1 in the supported state.
Further, the thrust disk 2 does not come into contact with the electromagnets 3a and 3b or the radial magnetic bearing.

According to the above structure, the displacement of the rotary shaft 1 is detected by the displacement sensor 4. For example, when the axial position of the rotary shaft 1 moves away from a predetermined position, the displacement sensor 4 moves at a position corresponding to the distance. It comes to output the detection signal. When the position detection signal is input, the control circuit 6 generates and outputs a control signal based on this. In this case, when the thrust disk 2 of the rotary shaft 1 is away from the predetermined position, a control signal is output to increase the attraction force of the electromagnet 3a or 3b on the far side.

As a result, in the power amplifier 6a, an exciting current is supplied to the electromagnet 3a so as to attract and return the electromagnet 3a to a predetermined position, and in the power amplifier 6b, the phase of the electromagnet 3a is reversed. The signal is given through the phase inversion circuit 7, so that the electromagnet 3
An exciting current is applied to b so that the attractive force is reduced. Then, when the thrust disk 2 returns to the predetermined position, the exciting currents are applied from the electromagnets 3a and 3b so as to have the same attractive force.

In this case, the electromagnet 3 of the thrust magnetic bearing
It is generally known that the magnetic attraction force generated by a and 3b is proportional to the square of the magnetic flux density generated in the air gap between the thrust disk 2 and the thrust disk 2 facing each other.
However, the magnetic flux density that is actually generated depends on the electromagnets 3a, 3
b or the thrust disk 2 has hysteresis characteristics that differ depending on the magnetization characteristics of the material used, so that the following problems occur.

That is, normally, in the magnetic bearing device, the electromagnet is energized in one direction, and the magnetic attraction is controlled by controlling the magnitude of the energizing current. Therefore, when the control operation of the magnetic bearing is stopped, the electromagnets 3a and 3b and the thrust disk 2 are in a state where residual magnetic flux is generated and a magnetic attraction force remains. As a result, the rotating shaft 1 is stopped in the gap between the auxiliary bearings 8 due to the magnetic attraction force generated due to the residual magnetic flux, being biased to the side of the electromagnets 3a and 3b having the larger residual magnetic flux. .

Then, when the control operation is started next time, the electromagnets 3a, 3b on the side closer to the thrust disk 2 still have a magnetic attraction force due to the residual magnetic flux, so that the electromagnets 3a, 3b located far away are affected by the magnetic attraction force. It is necessary to generate enough magnetic attraction to overcome the magnetic attraction due to the residual magnetic flux. However, since the air gap provided in the auxiliary bearing is half the size of the air gap on the magnetic bearing side,
Thrust disk 2 when the deviation when stopping is the maximum
Is about 1/2 of the air gap for one of the electromagnets 3a, 3b and about 3/2 for the other. As a result,
There may be a case where the ratio of the two distances is three times different.

On the other hand, since the attractive force that can be generated by the electromagnet is inversely proportional to the square of the distance of the air gap from the thrust disk 2, in some cases, a magnetic attractive force that overcomes the magnetic attractive force due to the residual magnetic flux. It may not be able to be generated. Then, the thrust magnetic bearing cannot be activated, and there is a problem that the rotation of the rotary shaft 1 cannot be held in a non-contact state.

Further, when it is necessary to disassemble the magnetic bearing device for some reason, if there is a magnetic attraction force due to the residual magnetic flux as described above, the electromagnet 3a is generated at the time of disassembly.
Alternatively, the thrust disk 2 which is close to either one of 3b or 3b is further attracted to the close position by the magnetic attraction force, and the attraction force is further increased, which may make disassembly work impossible.

The present invention has been made in view of the above circumstances, and an object thereof is to eliminate the magnetic attraction force resulting from the residual magnetic flux of the electromagnet when the energization of the electromagnet is stopped and to perform the next operation. (EN) It is possible to provide a magnetic bearing device which prevents uncontrollability and prevents an electromagnet and a rotary shaft from being in an adsorbed state during disassembly work so as not to hinder disassembly work.

[0012]

According to the present invention, the displacement of a rotary shaft from a predetermined position is detected by a displacement sensor, and a control signal is given by the control means in accordance with the amount of displacement to attract the rotary shaft to the rotary shaft. The present invention is intended for a magnetic bearing device in which a force is controlled to hold a rotating shaft at a predetermined position in a non-contact state, and a degaussing current for degaussing a residual magnetic flux can be supplied to the electromagnet. It is characterized by being provided with a degaussing device.

According to the above construction, in the state where the control operation for supplying the electric current to the electromagnet and holding the rotary shaft in a non-contact state is stopped, an unnecessary magnetic attraction force is generated due to the residual magnetic flux generated in the electromagnet. Although remaining, by operating the degaussing device, it becomes possible to supply a degaussing current to the electromagnet for degaussing. This makes it possible to reduce the magnetic attraction force due to the residual magnetic flux to almost zero, prevent it from falling out of control the next time it is operated, and also during disassembly work, the electromagnet and rotating shaft. It is also possible to prevent the and from being in an adsorbed state, and the disassembling work can be efficiently performed.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a thrust magnetic bearing device 11 as a magnetic bearing device, in which a thrust disk 13 fixed to a rotary shaft 12 is held at a predetermined position in a non-contact state.
That is, the thrust disk 12 made of a magnetic material is firmly fixed to the rotating shaft 12. This thrust disk 1
3, electromagnets 14a and 14b are arranged at positions facing each other with a predetermined distance therebetween.

A displacement sensor 15 for detecting displacement in the axial direction is provided on the rotary shaft 12 at one end side at a predetermined interval. The displacement sensor 15 outputs a position detection signal having a magnitude proportional to the distance from the rotary shaft 12. The control circuit 16 uses the displacement sensor 15
A position detection signal is given from the above, and a control signal for the electromagnets 14a and 14b is output based on the signal.

A power amplifier 17a, which is a power amplifier circuit,
Reference numeral 17b gives an exciting current to the electromagnets 14a and 14b via the changeover switches 18a and 18b, respectively. The power amplifier 17a is adapted to receive a control signal from the control circuit 16, and the power amplifier 17b is provided with a phase inverting circuit. A control signal is supplied from the control circuit 16 via 19. In this case, the phase inversion circuit 1
For example, when the control circuit 16 outputs a control signal for increasing the magnetic attraction force to the electromagnet 14a, the reference numeral 9 inverts the phase so as to be a control signal for decreasing the magnetic attraction force of the electromagnet 14b accordingly. The power amplifier 17b is configured so as to be supplied to the power amplifier 17b.

A bearing portion 12a having a small diameter is formed at both ends of the rotary shaft 12 (only one is shown), and the bearing portion 12a is held by an auxiliary bearing 20. . This auxiliary bearing 20 has a mounting bracket 2
1 is fixed so as to be integrated with the electromagnets 14a and 14b, and when the magnetic bearing device 11 is in use, the rotating shaft 1
It is arranged so as not to come into contact with 2.

In this case, the air gap is set to about 1/2 of the air gap set between the thrust disk 13 and the electromagnets 14a and 14b in the thrust direction, and the air gap is set in the radial direction. Is provided so that an air gap of about 1/2 of the air gap of the radial magnetic bearing (not shown) is set. And
When the holding operation by the magnetic bearing device 11 is stopped, the rotating shaft 12 is supported by the auxiliary bearing 20, and the rotating shaft 12 is configured so as not to come into contact with the electromagnets 14a and 14b or the radial magnetic bearing device (not shown). Has been done.

The degaussing device 22 outputs the degaussing current of the electromagnets 14a and 14b, and the changeover switches 18a and 18b.
It is connected to the electromagnets 14a and 14b via b. Then, the degaussing device 22 is configured to generate and output a degaussing current having a waveform whose amplitude becomes smaller as time passes. In this case, the maximum amplitude of the damping current is set to be the magnitude of the currents Imax and -Imax that generate a magnetic flux density equal to or higher than the maximum magnetic flux density expected during the operation of the magnetic bearing.

The changeover switches 18a and 18b are set to be changed over by a control means (not shown), and are set on the side of the power amplifiers 17a and 17b when controlling the magnetic bearing. When the control operation is stopped, the degaussing device 22 is switched and set.

Next, the operation of this embodiment will be described with reference to FIG. In the operating state of the magnetic bearing that supports the rotating shaft 12 in a non-contact state, the changeover switches 18a and 18b are
The power amplifiers 17a and 17b are set on their respective sides. In the thrust magnetic bearing 11, the displacement of the rotary shaft 12 in the axial direction is detected by the displacement sensor 15 and is output as a position detection signal. For example, when the position of the rotating shaft 12 is displaced in a direction away from the displacement sensor 15, the control circuit 16 controls the position detection signal of the displacement sensor 15 so that the attraction force of the electromagnet 14a becomes large. Will be output.

As a result, the power amplifier 17a supplies an exciting current so that the magnetic attraction force of the electromagnet 14a becomes large, and the power amplifier 17b receives the magnetic attraction force of the electromagnet 14b by the signal given through the phase inversion circuit 19. An exciting current is supplied so that the force becomes small. Then, the thrust disk 13 of the rotary shaft 12 is connected to the electromagnets 14a,
It is controlled to return to the reference position by the magnetic attraction force of 14b. When the rotating shaft 12 is displaced in the direction in which it approaches the displacement sensor 15, the magnetic attraction force by the electromagnet 14b is controlled to be large and the magnetic attraction force by the electromagnet 14a is small, contrary to the above. Control to be.
As a result, the thrust attraction force of the electromagnets 14a and 14b is controlled so that the thrust disk 13 is always held at the reference position.

Also in the radial magnetic bearing device (not shown), the displacement of the rotary shaft 12 from the reference position in the radial direction is detected by a displacement sensor and the electromagnet is controlled by the magnetic attraction force. It is controlled to be held at the reference position.

Now, as described above, the electromagnets 14a, 1
The magnetic attraction force to the thrust disk 13 generated in 4b is
Although it is proportional to the square of the magnetic flux density in the air gap between the two, the generated magnetic flux density has a hysteresis characteristic that differs depending on the magnetization characteristic of the magnetic material used for the electromagnets 14a and 14b or the thrust disk 13. Because
In order to control this, the magnetic attraction force is usually controlled by controlling the exciting currents of the same polarity. Therefore, for the above-mentioned reason, when the control operation of the magnetic bearing is stopped, a residual magnetic flux is generated in the electromagnets 14a and 14b and the thrust disk 13, and the magnetic attraction force is stopped in this state.

Then, the control means (not shown) switches the changeover switches 18a and 18b at the time of the stop so that the electromagnets 14a and 14b are connected to the degaussing device 22 side. The degaussing device 22 comes to supply a degaussing current as shown in FIG. In this case, as described above, the degaussing current has an AC signal waveform of which the maximum current value is Imax and a current value capable of generating a magnetic flux density equal to or higher than the maximum magnetic flux density expected during the operation of the magnetic bearing device. Attenuating current whose amplitude is reduced with the passage of time is generated and output.

When such a degaussing current is supplied to the electromagnets 14a and 14b via the changeover switches 18a and 18b, the energizing directions to the electromagnets 14a and 14b are different from those in the control operation of the magnetic bearing device described above. In phase,
This causes the magnetic circuit formed by the electromagnets 14a and 14b to generate magnetic flux so as to form a closed circuit. That is, by forming the magnetic circuit in this way, the air gap length of the magnetic circuit is determined irrespective of the stop position of the thrust disk 13, and the demagnetizing operation can be performed with the magnetic resistance kept constant. It becomes.

When a demagnetizing current as shown in FIG. 2 is supplied to the electromagnets 14a and 14b, the electromagnets 14a and 14b are
The residual magnetic flux of the yoke b and the thrust disk 13 is gradually attenuated due to the relationship of the hysteresis characteristic, and the residual magnetic flux amount also becomes zero when the degaussing current finally becomes almost zero. As a result, when the magnetic bearing device 21 is stopped, the magnetic attraction force due to the residual magnetic flux is almost eliminated, and when the magnetic bearing device 21 is started next time, a large exciting current for overcoming the magnetic attraction force caused by the residual magnetic flux is overcome. It becomes unnecessary to supply, and it will be possible to activate it without difficulty.

Further, since the residual magnetic flux disappears in this way, for example, even when the magnetic bearing device is disassembled, the thrust disk 13 and the electromagnet are generated by the magnetic attraction generated due to the residual magnetic flux at the time of disassembly. The problem that the disassembling work is time-consuming due to the state in which 14a and 14b are more strongly suctioned is solved, and the work efficiency is improved.

According to the present embodiment as described above, when the control operation by the magnetic bearing device 21 is stopped, the degaussing device 22 can perform the degaussing operation to eliminate the residual magnetic flux of the electromagnets 14a and 14b and the thrust disk 13. The magnetic attraction force does not remain, and when the control operation is performed next time, the control is not lost, and a good control operation can always be performed. Further, for the same reason, the work efficiency is improved because the magnetic attraction force is not adversely affected during the disassembly work.

Further, according to this embodiment, during the degaussing operation by the degaussing device 22, the electromagnets 14a, 1 arranged opposite to each other.
Since the magnetic circuit of the magnetic flux generated by 4b is a closed circuit, each electromagnet 14 depending on the stop position of the thrust disk 13
Even if the air gap length between a and 14b changes,
The air gap length of the magnetic circuit formed can be made constant as a value including them, and the magnetic flux density generated thereby can be made constant irrespective of the position of the thrust disk 13 and is always constant. A certain degaussing effect can be obtained, and stable operation can be ensured.

FIG. 3 shows a second embodiment of the present invention. The difference from the first embodiment is that the power amplifier 17
a and 17b to the changeover switches 18a and 18b and the electromagnet 14
a power amplifier 17
The control signals from the control circuit 16 are power-amplified in a and 17b, and the degaussing signal from the degaussing device 23 provided in place of the degaussing device 22 is power-amplified.

Also, according to the second embodiment having such a configuration, it is possible to obtain substantially the same effect as that of the first embodiment, and it is not necessary to provide the degaussing device 23 with a power amplification function. By sharing the amplifiers 17a and 17b, the cost can be reduced.

In this embodiment, the degaussing device 2
3, the demagnetization operation is performed individually for each of the electromagnets 14a and 14b. Therefore, for example, when demagnetizing one electromagnet 14a, the thrust disk 13 is attracted to the electromagnet 14a side. As a result, the magnetic flux density increases, and the degaussing effect due to the degaussing current can be enhanced. Also, when demagnetizing the other electromagnet 14b, it can be performed with the thrust disk 13 attracted by the attraction force, so that it can be performed with a high magnetic flux density, and the efficiency of the degaussing operation as a whole can be improved. You will be able to raise it.

The present invention is not limited to the above embodiment, but can be modified or expanded as follows. It can be applied to the radial magnetic bearing device in exactly the same manner. The changeover switches 18a and 18b may be configured by relays or may be configured by using switching elements.

[0035]

As described above, according to the magnetic bearing device of the present invention, the following effects can be obtained. That is, in the magnetic bearing device according to claim 1, the demagnetizing device can demagnetize the residual magnetic flux of the electromagnet or the magnetic circuit while the magnetic bearing control operation is stopped. Therefore, a large magnetic attraction force is generated at the time of restart. Since it is not necessary to control it by means of it, and unnecessary suction operation is eliminated even during disassembly work, workability is improved.

In the magnetic bearing device according to claim 2,
When the control operation of the magnetic bearing is stopped, the changeover switch is switched to perform the degaussing operation by the degaussing device, so that the magnetic attraction force due to the residual magnetic flux is not adversely affected in the stopped state.

In the magnetic bearing device according to claim 3,
Since the demagnetizing current is supplied to the electromagnets arranged facing each other so that the magnetic circuit becomes a closed circuit, a constant air gap can always be maintained regardless of the position of the rotating shaft with respect to the electromagnet, which is proportional to the demagnetizing current. The magnetic flux density can also be stably generated, and a stable degaussing operation can always be performed.

In the magnetic bearing device according to claim 4,
The degaussing device demagnetizes each of the electromagnets that are arranged to face each other, so that the air gap between the electromagnet and the rotating shaft can be minimized when performing the degaussing operation. The degaussing magnetic flux can be generated, and the degaussing effect of the residual magnetic flux can be efficiently performed.

In the magnetic bearing device according to claim 5,
The power amplifier can be shared in both cases of the control operation of the magnetic bearing and the degaussing operation by the degaussing device, and the structure of the degaussing device can be simplified.

[Brief description of drawings]

FIG. 1 is a block diagram of the overall configuration showing a first embodiment of the present invention.

[Figure 2] Waveform diagram of degaussing current

FIG. 3 is a view corresponding to FIG. 1, showing a second embodiment of the present invention;

FIG. 4 is a view corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

11 is a thrust magnetic bearing device, 12 is a rotating shaft, 13 is a thrust disk, 14a and 14b are electromagnets, 15 is a displacement sensor, 16 is a control device, 17a and 17b are power amplifiers (power amplification circuits), and 18a and 18b are switching. Switch, 1
Reference numeral 9 is a phase inverting circuit, 20 is an auxiliary bearing, and 22 and 23 are degaussers.

Claims (5)

[Claims] 1. A displacement sensor detects a displacement of a rotating shaft from a predetermined position, and a control signal is given by a control means in accordance with the displacement amount to control an attraction force of the electromagnet to the rotating shaft to control the rotating shaft. In a magnetic bearing device, which holds the magnet in a non-contact state at a predetermined position, a degaussing device capable of supplying a degaussing current for degaussing the residual magnetic flux to the electromagnet is provided. 2. A switching means is provided which can switch between a control operation for holding the rotating shaft with respect to the electromagnet and a degaussing operation by the degaussing device, and the switching means stops the control operation of the rotating shaft by the electromagnet. 2. The degaussing operation is performed by switching to the degaussing device side at the point of time.
The magnetic bearing device according to claim 1. 3. A degaussing operation by the degaussing device is controlled so that a degaussing current is simultaneously supplied to the electromagnets arranged to face each other so that a magnetic path of a magnetic flux generated by the facing electromagnets forms a closed circuit. The magnetic bearing device according to claim 1 or 2, wherein the magnetic bearing device is configured as described above. 4. The magnetic bearing device according to claim 1, wherein the degaussing operation by the degaussing device is configured to be performed for each one of the electromagnets arranged to face each other. 5. A power amplifier circuit for supplying a current to the electromagnet according to a signal given from the degaussing device and the control means.
The magnetic bearing device according to any one of 1.