JPH10271747A - Magnetic bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic bearing in which touch-down can be prevented upon power interruption without using a large and high capacity battery. SOLUTION: Upon interruption of a power supply 21, a rotary shaft sustains inertial rotation to supply each part of a magnetic bearing 3 with a current i1 generated by electromotive force induced in a motor 2 thus sustaining magnetic levitation of the rotary shaft. Electromotive force being induced in the motor 2 decreases as them revolution decreases and when it reaches a limit level where electromagnets 6, 7 can not levitate a rotator 1, a battery 23 begins to power supply to each part of the magnetic bearing 3 through a diode 24. Consequently, the rotary shaft 1 can be stopped without causing touch-down. Since touch-down is prevented through combination of the electromotive force induced in the motor 2 and the battery 23 power in case of power interruption, battery capacity can be reduced.

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 used for a vacuum pump or a main shaft of a machine tool.

[0002]

2. Description of the Related Art Conventionally, as this type of magnetic bearing device,
For example, the one shown in FIG. 3 is known. As shown in FIG. 3, the magnetic bearing device includes a rotating shaft 1, a motor 2 provided around the center of the rotating shaft 1 for rotating the rotating shaft 1, and both ends of the rotating shaft 1 by magnetism. And a magnetic bearing 3 which is levitated and supported. Motor 2
Is configured to be able to rotate the rotating shaft 1 by driving a motor driving coil 5 fixed around the center of the rotating shaft 1 by a motor driving circuit 4. The magnetic bearing 3 is, as shown in FIG.
, And displacement sensors 8, 9 arranged near each of the electromagnets 6, 7 for detecting displacement of the rotating shaft 1 in the radial direction.

When the displacement detected by the displacement sensor 8 is supplied to the PID controller 10, the magnetic bearing 3
The controller 10 is configured to compare the detected displacement with a target value and supply a signal such that the two coincide with each other to the amplifier 11 (electromagnet drive circuit). Further, the magnetic bearing 3 is configured such that the displacement detected by the displacement sensor 9 is
2, the PID controller 12 compares the detected displacement with a target value, and supplies a signal that matches the two to an amplifier (electromagnet drive circuit) 13. For this reason, the amplifiers 11 and 13 drive the corresponding electromagnets 6 and 7 so that the rotating shaft 1 comes to the target position. On the other hand, although not shown, power for operating the motor drive circuit 4 is supplied to the motor drive circuit 4 constituting the motor 2. Further, DC power for operating the respective components of the magnetic bearing 3 is supplied to the respective components of the magnetic bearing 3 such as the PID controllers 10 and 12 and the amplifiers 11 and 13.

In such a conventional magnetic bearing device, when power supply to each part of the magnetic bearing 3 is stopped when a power failure occurs, the electromagnets 6 and 7 of the magnetic bearing 3 function to magnetically levitate the rotating shaft 1. On the other hand, since the rotating shaft 1 cannot immediately stop rotating due to inertia, the rotating shaft 1 may damage the electromagnets 6, 7 and the like of the magnetic bearing 3 (hereinafter, this phenomenon is referred to as touchdown). As a method of preventing the touch-down when such a power failure occurs, a battery use type using a battery for power failure prevention and a no-battery type using no battery are known. The battery use type is a method of simultaneously supplying power from a battery to each part of the magnetic bearing 3 when a power failure occurs, thereby protecting the magnetic bearing 3 from rotation due to inertia of the rotating shaft 1. On the other hand, the no-battery type is a method of protecting the magnetic bearing 3 by supplying an electromotive force generated in the motor 2 by inertia of the rotating shaft 1 to each part of the magnetic bearing 3 simultaneously with the start of the power failure when a power failure occurs. It is.

[0005]

However, in the case of the battery type, there are problems in that the battery is large in capacity and large, the whole device is large, and the life of the battery is short. On the other hand, in the no-battery type, the electromotive force generated in the motor 2 at the time of a power failure is used, so that the electromotive force decreases as the rotation speed of the motor 2 decreases, and the electromotive force of the motor 2 is When the electric power is equal to or less than the electric power, the magnetic bearing 3 cannot magnetically levitate the rotating shaft 1 with the electromotive force from the motor 2 and touches down to perform electromagnets 6 and 7.
May be damaged. Therefore, in a magnetic bearing device used for a vacuum pump or the like, a protective bearing is provided to protect the magnetic bearing 3 by touchdown. However, in consideration of the influence of the magnetic bearing device on peripheral devices and the life of the protective bearing, it is preferable that touchdown does not occur.

Accordingly, an object of the present invention is to provide a magnetic bearing device capable of preventing a touchdown at the time of a power failure without using a large-capacity, large-sized battery.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a rotating shaft and a magnetic shaft supporting the rotating shaft with an electromagnet so that the rotating shaft is at a target position. Bearing, a motor for rotating a rotating shaft, first power supply means for supplying power to the motor and the magnetic bearing, and second power supply means for supplying power generated by the motor to the magnetic bearing when a power failure occurs And third power supply means for supplying battery power to the magnetic bearing when the power generated by the motor drops to a predetermined value when a power failure occurs.

In the present invention having such a configuration, when a power failure occurs, immediately after the power failure, the second power supply means supplies the generated power of the motor 2 to the magnetic bearing 3. Thereafter, when the generated power of the motor 2 decreases to a predetermined value, the third power supply unit supplies the power of the battery 23 to the magnetic bearing 3.
As described above, in the present invention, when a power failure occurs, the power generated by the motor 2 and the power of the battery 23 are used in combination to prevent touchdown, so that a large-capacity, large-sized battery is not used. Touchdown at the time of power failure can be prevented. In the present invention, the predetermined value of the electric power generated by the motor 2 is desirably a limit value at which the magnetic bearing 3 cannot maintain the magnetic levitation of the rotating shaft 1. This way,
It is possible to further reduce the size and the life of the battery 23.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of the present invention will be described with reference to FIGS. FIG.
FIG. 1 is a block diagram showing an overall configuration of a magnetic bearing device according to an embodiment of the present invention. This magnetic bearing device is shown in FIG.
As shown in FIG. 2, a rectifier circuit (converter) 22 for converting AC power of an AC power supply 21 into DC power is provided, and the DC power converted by the rectifier circuit 22 is supplied to the motor drive circuit 4 of the motor 2. Is configured. The configuration of the motor 2 is the same as that of the motor 2 in FIG.
The description is omitted. The DC power converted by the rectifier circuit 22 is controlled to a constant voltage by the DC-DC converter 25, and then the PID controller 10, the amplifier 11, the PID controller 12, and the amplifier 13
And so on, to drive these components. The configuration of the magnetic bearing 3 is the same as that of the magnetic bearing 3 in FIG. Further, a part of the DC power converted by the rectifier circuit 22 is supplied to a charging circuit 26, which charges the battery 23 via a diode 27.

Further, in this magnetic bearing device, when a power failure occurs, the electromotive force generated in the motor 2 due to the rotation of the rotary shaft 1 due to inertia is supplied to each part of the magnetic bearing 3 via the DC-DC converter 25. At the beginning of the power failure, the electromagnets 6 and 7 maintain the magnetic levitation of the rotating shaft 1 so that touchdown can be prevented. When a power failure occurs, the DC power of the battery 23 is
It is configured to be supplied to each part of the magnetic bearing 3 via the C-DC converter 25. That is, when the electromotive force generated by the motor 2 decreases to a predetermined value at which the rotating body 1 cannot be magnetically levitated by the electromagnets 6 and 7 when a power failure occurs, the components of the magnetic bearing 3 Is used to stop the rotation of the rotating body 1 without starting the supply of electric power. As the battery 23, a lead storage battery, a lithium battery, or the like is used.

Next, the operation of the embodiment configured as described above will be described with reference to FIG. Usually,
The rectifier circuit 22 converts AC power into DC power, and the converted DC power is used as the motor drive circuit 4 and the DC-D
It is supplied to each part of the magnetic bearing 3 via the C converter 25. At this time, the output voltage V of the rectifier circuit 22 is, for example, about 60 to 120 (V) as shown in FIG. Therefore, at normal times, the motor drive circuit 4 and the magnetic bearing 3 are driven by the DC power supplied from the rectifier circuit 22, so that the motor 2 rotates the rotating shaft 1, and the electromagnet 6 and the electromagnet 7 1 is magnetically levitated to a target position.

On the other hand, as shown in FIG. 2, when a power failure occurs at time t1, the supply of power from the AC power supply 21 to the rectifier circuit 22 is stopped, so that the motor drive circuit 4 and the magnetic bearing 3 Also, the DC power supplied to each section is stopped. However, since the rotating shaft 1 continues to rotate due to inertia, the electromotive force generated in the motor 2 is DC-DC
The output current i1 of the DC-DC converter 25 is supplied to the converter 25 and flows to each part of the magnetic bearing 3, and the necessary power is supplied to each part, so that the rotating shaft 1 does not touch down. However, the generated electromotive force of the motor 2 gradually decreases as the rotation speed decreases, as shown in FIG. When the generated electromotive force is equal to or lower than Vt, the electromagnets 6 and 7 of the magnetic bearing 3 cannot magnetically levitate the rotating body 1 and the rotating shaft 1 touches down.

When the generated electromotive force of the motor 2 drops to a limit value (hereinafter referred to as a threshold value) Vt at which the rotating shaft 1 cannot be magnetically levitated as shown in FIG. At time t2 when the voltage has dropped to the value Vt, the battery 23 starts supplying power to each part of the magnetic bearing 3 via the diode 24 and the DC-DC converter 25. Therefore, the rotating shaft 1 can be stopped without touching down. Here, the threshold value Vt is, for example, 12 to 1
It is about 5 (V). Therefore, the output voltage (rated voltage) Vb of the battery 23 is Vb = (Vt + Vd), where Vd is the forward voltage drop of the diode 24, and the battery 23 only needs to satisfy this condition. In addition,
The threshold value Vt is preferably a limit value at which the rotation shaft 1 cannot be magnetically levitated, but may be a value exceeding the limit value.

As described above, in this embodiment, when a power failure occurs, power is supplied to each part of the magnetic bearing 3 using the induced electromotive force of the motor 2 at the initial stage.
As a result, the magnetic levitation of the rotating shaft 1 is maintained, and when the electromotive force from the motor 2 decreases to a value at which the magnetic levitation of the rotating shaft 1 cannot be maintained, power sufficient to maintain the magnetic levitation is supplied from the battery 23 to the magnetic bearing. 3 was supplied to each part. Therefore, according to this embodiment, when a power failure occurs,
The rotating shaft 1 can be stopped immediately without touching down. In addition, when a power failure occurs, the touchdown is prevented by using both the electromotive force of the motor 2 and the power from the battery 23, so that the capacity of the battery 23 can be reduced and its life can be extended. Furthermore, since the battery 23 is reduced in size, there is an advantage that the entire device can be reduced in size.

In the above-described embodiment, the battery 23 is integrally incorporated in the apparatus main body. But,
For example, in order to separate the battery 23 shown in FIG. 1 from the above-described circuit and install the battery 23 outside the apparatus main body, and to electrically connect to the anode side of the diode 24 and connect to the battery 23 installed outside. May be provided so that the user can make an electrical connection between the battery 23 and the external connection terminal by using a connector such as a connector as needed. With such a configuration, the user can select the use of the battery 23 as necessary, so that usability is improved. At that time, the charging circuit 26 may be provided outside similarly to the battery 23, and may be configured independently as a battery charger.

[0016]

As described above, according to the present invention, when a power failure occurs, the touchdown of the rotating shaft is prevented by using both the generated power of the motor and the power of the battery.
Touchdown at the time of power failure can be prevented without using a large capacity and large battery.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram illustrating an operation of the embodiment.

FIG. 3 is a block diagram of a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotation axis 2 Motor 3 Magnetic bearing 4 Motor drive circuit 6, 7 Electromagnet 8, 9 Displacement sensor 10, 12 PID controller 11, 13 Amplifier 21 AC power supply 22 Rectification circuit 23 Battery 24 Diode 25 DC-DC converter 26 Charging circuit

Claims (3)

[Claims] A rotating shaft, a magnetic bearing that magnetically supports the rotating shaft with an electromagnet, controls a magnetic force of the electromagnet so that the rotating shaft is at a target position, and a motor that rotates the rotating shaft. First power supply means for supplying power to the motor and the magnetic bearing; second power supply means for supplying the generated power of the motor to the magnetic bearing when a power failure occurs; A magnetic bearing device comprising: a third power supply unit that supplies battery power to the magnetic bearing when the generated power decreases to a predetermined value. 2. The magnetic bearing device according to claim 1, wherein the predetermined value is a limit value at which the magnetic bearing cannot maintain the magnetic levitation of the rotating shaft. 3. The apparatus according to claim 1, wherein the battery is freely installed outside the apparatus main body, and connection means for electrically connecting the battery to be installed outside and the third power supply means is provided. Or the magnetic bearing device according to claim 2.