JPS62155326A - Magnetic bearing device - Google Patents

Abstract

PURPOSE:To obtain a magnetic bearing having high bearing rigidity by providing a drive control system for driving electric magnets by detecting a rotor, a stator including electric magnets for supporting the rotor magnetically and an amount of displacement of the rotor. CONSTITUTION:Displacement of a rotor 2 is detected by displacement sensors 5 and 5' for outputting thereof as a position signal of a level d from a position signal generating circuit 6. Subsequently, after the signal is compared of its difference DELTAd from a reference signal with threshold voltage V0 by a displacement signal generating circuit 9, the signal is used to control electric magnets 4 and 4'. As the maximum allowable displacement of the rotor for machine tools and the like is 10mum, V0 is so established as to correspond to said value. When the displacement of the rotor 2 exceeds 10mum, as DELTAd becomes larger than V0, a resistor in a variable gain amplifier 11 is switched over for making DELTAd smaller than V0 so as to input thereof to subsequent circuits.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a magnetic bearing device, and more particularly to a magnetic bearing device that provides high bearing rigidity with a low output power amplifier.

(Prior Art) Conventionally, three types of magnetic bearing devices are known: a passive type that uses permanent magnets, a hybrid type that uses a combination of permanent magnets and electromagnets, and an active type that uses electromagnets. Among these, an active magnetic bearing device is required when it is necessary to overcome changes in external forces such as unbalance of a movable body or fluctuations in pressure. Generally, this active magnetic bearing device consists of a movable body (hereinafter referred to as the rotor), a bearing section (hereinafter referred to as the stator), an electromagnet and a displacement sensor provided on the stator, and a control section. By transmitting the result of detecting the displacement t of the spatial position relative to the stator by the displacement sensor to the electromagnet via the control section, the rotor is attracted and supported at a predetermined position by magnetic force from around the rotor. Regarding this n-type magnetic bearing, please refer to the magazine "Mechanical Design", Volume 29, No. 3 (1
The principle etc. are described in detail in the March 1985 issue).

When the rotor is at rest, the rotor is in contact with a portion of the stator due to gravity, and the amount of displacement of the rotor is maximum relative to the set reference position, which is the position at which the rotor should be held during bearing operation. At startup, this maximum displacement is detected by a displacement sensor such as a eddy-flow type non-contact displacement meter, and the sensor output corresponding to the displacement corresponds to the displacement when the rotor is at the set reference position. It is compared with the voltage command value. Therefore, the maximum rated output of the power amplifier when supplying gravity to an electromagnet such as a coil must be set to correspond to the comparison value (difference) when the displacement wave of the rotor is at its maximum. On the other hand, in order to prevent minute displacements of the rotor near the set reference position during bearing operation as much as possible, that is, to increase bearing rigidity, the output from the power amplifier should be made large enough to respond to minute displacements.
There must be. Therefore, there is a problem in that a considerably large amplifier must be used in order to achieve the full rated output for the maximum displacement.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems in the prior art, and it is possible to reduce the amount of mechanical damage near the set reference position of the rotor during normal bearing operation without using a power amplifier with a particularly large rated output. The present invention provides a magnetic bearing device that has high displacement prevention and recovery performance, that is, high bearing rigidity.

(Summary of the Invention) The above-mentioned problems are solved by: a rotor; a stator including an electromagnet that generates a magnetic field for magnetically supporting the rotor; This is achieved by a magnetic bearing device having a displacement sensor that detects the amount of displacement of the rotor, and a drive control system that drives an electromagnet according to the output of the displacement sensor.

(Embodiment) FIG. 1 is a block diagram showing a control system of a magnetic bearing device that is an embodiment of the present invention. Magnetic bearing device ff 1 includes a stator 3 that holds a rotor (movable body) 2 at its center, and a rotor 2
Electromagnets 4, 4' that generate magnetic attraction to float
and displacement sensors 5, 5' for detecting the gap t between the loader 2 and the stator 3. displacement sensor 5
, 5' may be of the conventionally known inductance type, and by utilizing the fact that the inductance of the sensor coil changes when the gap changes, f# can be determined over a wide range of, for example, 500 μm.
The displacement t can be detected with high accuracy. displacement sensor 5,
5' is output from the position signal generating circuit 6 at level d.
The signal is output as a position signal, and is input to a displacement signal generation circuit 9 via a low-pass filter γ for noise removal and the like and a phase compensation circuit 8. A difference Δd (=vs−d) between the sensor output level d and the reference level v8 corresponding to the set reference position is calculated in the displacement signal generation circuit 9. The predetermined reference position here refers to the spatial position, usually the central position, in which the rotor 2 must be held in the stator 3 during bearing movement.

Next, this level Δd is compared with the threshold voltage Vo in the comparator circuit 10. Here, the threshold value means the range of deviation from the reference position within which high bearing rigidity must be maintained. That is, within this range, high bearing rigidity is guaranteed, and in this example, it is at a level corresponding to 10 μm.

The output of the displacement signal generating circuit 9 is input to the variable gain amplifier a11, and the comparison result in the comparator circuit 10 is also input as a reference level to the amplifier 11, where the gain is controlled. Circuit 13, addition circuit 14, processing circuit 15, and power amplifier 16.16'f! I: Used to control the magnetic force of the electromagnets 4, 4'.

FIG. 42 is a detailed diagram of the variable gain amplifier 11 among the blocks in FIG.

The OTf gain amplifier 11 is composed of an analog switch 17 known as a CMOS switch, a switching resistor 18 made up of resistors kl and i2, and a differential amplifier 19 with a resistor RO.

In this embodiment, the analog switch 1T is, for example, AD7510DI, A manufactured by Analog Devices, Inc.
D7511DI or AD7512DI is used. Further, the relationship between the resistance and the island in the switching resistor 18 is 〉u2.

For magnetic bearings that are used in machine tools, etc., it is most important that the rotor 2 not vibrate at the set reference position, and the maximum allowable displacement is 10μ.
It is m.

Therefore, the threshold voltage Vo referenced by the comparison circuit 10
is this maximum displacement! It is set to correspond to 10 μm. Now, returning to the variable gain amplifier 11, its operation will be explained. If the displacement of rotor 2 exceeds 10 μm,
That is, when the comparison result that the output level Δd of the displacement signal generation circuit 9 is larger than the threshold voltage Vo is input from the comparison circuit 10 to the analog switch 17 of the variable gain amplifier 611, the analog switch 11 Change the resistor to one with a higher resistance value. On the other hand, when the amount of displacement of the rotor 2 is less than 10 .mu.m, .DELTA.d is lower than Vo, so the resistance value of the analog switch 17 is small and remains on the 2 side. Here, the differential amplifier 19
Since the resistance of is R, the gain G of the variable gain amplifier 11 is
can be expressed as G=Ro7vts (t is l or 2). Therefore, it is mutually equal to resistor R1! In relation to this, the gain G becomes higher when the roof tile 2 having a smaller resistance value is conductive. In other words, the gain G of the variable gain amplifier 11 is configured to be lower when the amount of displacement of the rotor 2 is 10 μm or more than when it is less than that.

Returning to FIG. 1 again, the output from the variable gain amplifier 11 is input to the PI control circuit 12 for proportional/integral control, and to the D control circuit for differential control. The signal from which the steady-state deviation has been eliminated by the PI control circuit 12 and the signal from which the deviation caused by disturbance or the like has been quickly recovered by the D control circuit 13 are input to the adder circuit 14, respectively. The level of the signal added by the adding circuit 14 is vi, and the signal is then input to the processing circuit 15. Incidentally, since the P control circuit 12, the D control circuit 13, and the addition circuit 14 are well known, a detailed explanation thereof will be omitted here. For example, such a circuit was published in the magazine "Electronic Science J19
March 1973 issue, No. 19-28, (Hiroshi Yanagisawa).

Attraction of the rotor 2 by magnetic force must be carried out taking into consideration the influence of gravity, external force, etc., and naturally the electric power supplied to the electromagnets 4, 4' will be different. Processing circuit 15Fi is a circuit 69 that performs processing for this purpose, the details of which are shown in FIG. In FIG. 3, the processing circuit 15 is an amplifier At
and A. Constant Voltage Source 20. and resistors Rs and RO arranged as shown. The output level vt signal from the adder circuit 14 is inputted to the positive input of amplifier A and the negative input of amplifier A2, respectively, while the output level v3 from the constant width pressure source 20 is inputted to the negative input of amplifier A1 and amplifier A2, respectively. input to the positive input of゛Here, the outputs v1 and v2 of the amplifiers A and A2 are respectively expressed by the following equations.

vl = −Ro (Vs +vi) /Rev
2 ==Ro (Vo -vl)/Rs In this way, a large voltage v'+ (and therefore a large current) will be supplied to the electromagnet with the larger displacement of the rotor 2. On the other hand, since a small voltage Vz (therefore, a small current) is supplied to the magnet with the smaller displacement, the electromagnets interact in the direction in which the displacement of the rotor 2 is eliminated.

In addition, the output levels v1 and V! of the processing circuit 15 which take into account the effects of gravity and external forces! Since the gain is controlled by the variable gain amplifier 11 according to the f position of the rotor 2, a large gain can be obtained for a small displacement. After the power is amplified by 16.16', it is supplied to the magnet 4.4' and can be used for magnetic attraction operation.

(Effects) As explained above, according to the present invention, when the displacement position of the rotor is larger than an arbitrarily set reference value, such as during startup, the gain in the control system is lowered, and the displacement is A magnetic bearing device is provided in which automatic cut-off control is set to OT so that the gain in the control system is high when the value is smaller than the above-mentioned reference value, for example, when there is minute vibration. Therefore, it is possible to realize a magnetic bearing device that does not require an excessively large power amplifier as in the prior art in order to obtain a high bearing rigidity t-.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the control system of the magnetic bearing device according to the invention, Figure 2 is a detailed diagram of the variable gain amplifier of the blocks in Figure 1, and Figure 3 is a block diagram of the processing circuit and the blocks of Figure 21. It is a detailed diagram of a power amplifier. [Explanation of symbols of main parts] Movable part...2 Bearing part...3 Detection means...5, 5' Drive means...・・7, 8.9, 10.11, 12゜13.14, 15.16.16' Otsu d

Claims (1)

[Claims] 1. A bearing section including a movable part and a means for generating a magnetic field to magnetically support the movable part, a detection means for detecting the amount of displacement of the movable part, and an output of the detection means. What is claimed is: 1. A magnetic bearing device comprising means for driving the magnetic field generating means in accordance with the output of the detecting means, wherein the driving means changes its gain in accordance with the output of the detecting means. 2. In the magnetic bearing device according to claim 1, the gain of the driving means is reduced when the output of the detection means is greater than or equal to a predetermined value, and the gain of the driving means is reduced when the output of the detection means is less than a predetermined value. A magnetic bearing device characterized in that it is made larger. 3. The magnetic bearing device according to claim 1, wherein the drive means includes means for switching the gain in response to a comparison result between the output of the detection means and the predetermined value. Bearing device.