JP2002161918A - Magnetic bearing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic bearing unit well controllable and suppressible of energy consumption as much as possible by utilizing a permanent magnet efficiently. SOLUTION: Under the condition of the bearing gaps S1 and S2 arranged between a rotator 1 and a bearing, the magnetic bearing unit is provided with magnetic cores 10 and 40 using plate- or ring-shape permanent magnets 20 and 50, a rotator 1 is lifted up by magnetic force, and the thicknesses t2 and t1 of the permanent magnets 20 and 50 are not less than the bearing gaps S2 and S1 but not greater than 4 times of them.

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 having good controllability in which a permanent magnet is interposed in a part of a magnetic circuit for generating and controlling a magnetic force.

[0002]

2. Description of the Related Art As a conventional magnetic bearing device, for example, there is one as shown in FIG. 6 (Japanese Utility Model Publication No. 3-43467). In the figure, reference numerals 7a and 7b denote excitation coils, and permanent magnets 5a and 5b, fixed body yokes 6a and 6b on the fixed body 3 side, and a rotating body yoke 4 connected to the rotating body 2, which are arranged vertically.
a, 4b form a magnetic circuit. Rotating body 2
Is attracted upward or downward in the figure due to the attraction generated by the permanent magnets 5a, 5b via the rotating yokes 4a, 4b. In order to eliminate this unbalanced force, the position of the rotating body 2 is known by the position detector 8, and a control current is applied to the exciting coils 7a and 7b according to the position, so that the rotating body 2 is kept at a fixed position in the thrust direction. Will be retained. In addition, by making the shapes of the rotating bodies yokes 4a and 4b concentric with each other in an annular shape, when the rotating body 2 moves in the radial direction, it is intended to return to the original position concentric with the fixed bodies yokes 6a and 6b. Magnetic restoring force works. In this way, the positioning operation of the rotating body 2 in the thrust direction and the radial direction occurs.

Further, as a prior art relating to a magnetic bearing device, there is a magnetic levitation type transfer device disclosed in Japanese Patent Application Laid-Open No. 63-2774309.

[0004]

However, in the above-mentioned conventional magnetic bearing device, the upper and lower permanent magnets 5a, 5b
The magnetomotive force forms a magnetic circuit and exerts a strong magnetic attraction force. The current flowing through the pair of excitation coils 7a and 7b of the magnetic circuit is adjusted so that the magnetic attraction force balances the own weight of the rotating body 2. Control to minimize as much as possible. However, the thickness t of the permanent magnets 5a, 5b in the thrust direction is
However, since the distance between the rotor yokes 4a and 4b and the fixed yokes 6a and 6b is considerably larger than the bearing gap s, the control current flowing when the position deviates from the balanced position becomes extremely large. This acts as a gap by the thickness of the permanent magnets 5a and 5b, so that the magnetic resistance increases and the exciting coil 7
This is because the control magnetic force generated by a and 7b decreases. Therefore, there is a problem that the controllability of the exciting coils 7a and 7b is deteriorated and it is difficult to perform good control.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic bearing device which can solve the disadvantages of the prior art, effectively use permanent magnets, suppress energy consumption as much as possible, and have good controllability. And

[0006]

In order to achieve the above object, according to the present invention, there is provided a rotating body, a bearing for supporting the rotating body, and a gap between the rotating body and the bearing. A magnetic circuit forming means for forming a magnetic circuit through the magnetic circuit, wherein the magnetic bearing device lifts the rotating body by a magnetic force formed by the magnetic circuit. Provided is a magnetic bearing device characterized in that the gap is equal to or more than four times as large as the gap.

[0007] With the above configuration, the permanent magnet has an appropriate size to supply a magnetic force required for floating the rotating body, and can supply a bias magnetic force required for control. In addition, since the thickness of the permanent magnet acts appropriately as a gap in the control, it is not necessary to supply an excessive current to supply a magnetic force required for the magnetic circuit.

[0008]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view taken along the axis of a magnetic bearing device having a thrust magnetic bearing and a homopole-type radial magnetic bearing according to an embodiment of the present invention, and FIG.
FIG. 3 is a layout view showing the relationship between the magnet thickness and the bearing gap of the thrust magnetic bearing, FIG. 4 is a characteristic diagram showing the relationship between the control current ratio and the magnet attraction ratio, and FIG.
FIG. 3 is a sectional view corresponding to FIG. 2 and showing a heteropole type radial magnetic bearing.

In FIG. 1 and FIG. 2, a shaft 1 which is a rotating body is shown.
The touch-down bearings 10 at both ends of the housing 100
0a, the two radial magnetic bearings 110, 110 and the thrust magnetic bearing 120 support the shaft in a non-contact state during rotation. The thrust magnetic bearing portion 120 is a disk-shaped thrust flange 80 fitted and fixed to the center of the shaft 1.
(A partial cross section is shown in FIG. 1) in such a manner as to closely surround both sides.

As shown in FIG. 3, the thrust magnetic bearing 120 includes a thrust flange 80 and a thrust flange 8.
A magnetic circuit is formed by the thrust coil 60 facing the zero and the thrust magnetic core 40. The thrust magnetic core 40 includes a ring-shaped permanent magnet 50 and yokes 40c and 40d that face the thrust flange 80 and hold the thrust coil 60 and the permanent magnet 50. The thrust magnetic bearing 120 attracts the thrust flange 80, and causes the thrust flange 80 to float with a thrust gap s1 between the thrust flange 80 and the thrust flange 80.

On the other hand, the radial magnetic bearing 110 includes the rotor 12, the radial coil 30, and the radial magnetic core 10
Constitutes a magnetic circuit. The radial magnetic core 10 is composed of yokes 10c and 10d to which a plate-shaped permanent magnet 20 and a radial coil 30 are attached. The radial magnetic bearing 110 attracts the circumferentially laminated cylindrical rotor 12 attached to the shaft 1, and causes the shaft 1 to radially float with a radial gap s2.

The thicknesses t1 and t2 of the permanent magnets 50 and 20 (hereinafter simply referred to as the magnets 50 and the like) are directly related to the magnetomotive force of the magnets and are sources of magnetic force necessary for floating the shaft 1. In addition, since it is a source of the bias magnetic force necessary for the control, there is an appropriate magnitude required. Thickness t of the surface on the axis 1 side of magnet 50 which is a part of thrust magnetic core 40
1, and a thickness t2 of a surface of the magnet 20 which is a part of the radial magnetic core 10 and is orthogonal to the axis 1, as shown in FIG.
Thrust flange 80 (or shaft 1) and thrust magnetic bearing 1
The gap (bearing gap) s1 (or s2) with the gap 20 (or the radial magnetic bearing 110) is set to be equal to or more than four times and equal to or less than four times.

In this configuration, the axial position signal of the shaft 1 is detected by the thrust sensor 70, and based on this signal, the floating of the thrust is controlled using a control device (not shown). In addition, a radial position signal of the shaft 1 is detected by the radial sensor 90, and based on the signal, a control device (not shown) controls radial levitation.

Further, as described above, the thickness t1 of the magnet 50,
And the thickness t2 of the magnet 20 are the bearing gaps s1 and s, respectively.
Since it is set to be equal to or larger than 2 and equal to or smaller than 4 times, magnet 5
0,20 is a size necessary for the thrust and radial floating of the shaft 1 and can supply a bias magnetic force required for control, and a magnet thickness t1, t for control.
2 acts as an air gap moderately, so that it is not necessary to supply an excessive current to the thrust coil 60 and the radial coil 30 to supply a necessary control magnetic force as in the related art.

This is represented by a characteristic line shown in FIG. The figure shows that, in the thrust magnetic bearing 120, when the control current of the thrust coil 60 and the magnetic attraction force are controlled so that the magnetic attraction force and the own weight of the shaft 1 are balanced, the ratio of the magnet thickness t1 to the bearing clearance s1 is obtained. It shows how it changes. However, the control current and the magnetic attraction force are:
When the bearing gap s1 and the magnet thickness t1 are (s1 = t1), each is set to 1, and the control current ratio C and the magnetic attraction force ratio F, which are represented by relative ratios, are plotted on the vertical axis.

The magnetic attraction force ratio F stabilizes to a predetermined value when (t1 / s1) on the abscissa exceeds 1, which is why the magnet thickness t1 is equal to or more than the same as the bearing gap s1. It is here. On the other hand, the control current ratio C is (t1 / s1) is 4
The reason is that the magnet thickness t1 is set to four times or less the bearing gap s1 in order to avoid this increase in current. Similar characteristics in the radial magnetic bearing can be obtained by setting the horizontal axis of FIG. 4 to (t2 / s2), and thus the description is omitted.

In the embodiment of the present invention, the radial magnetic core 110 of the separation type in the thrust direction is shown as the radial magnetic bearing 110. However, when the radial magnetic core 11 of the heteropole type is used as shown in FIG. The present invention can also be applied.

[0018]

As described above, since the thickness of the permanent magnet interposed in the magnetic circuit is made equal to or more than four times the bearing gap, the permanent magnet is large enough to supply the magnetic force required for floating the rotating body. In addition, a bias magnetic force required for control can be supplied. Since the reduction of the control magnetic force due to the bias current can be suppressed as much as possible by the action of the thickness of the permanent magnet, the floating of the rotating body can be controlled without flowing an excessive bias current to the magnetic coil. Therefore, a magnetic bearing device with good controllability can be realized with minimum energy loss.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view along an axis of a magnetic bearing device including a thrust magnetic bearing and a homopole-type radial magnetic bearing according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an AA section in FIG. 1;

FIG. 3 is a layout diagram showing a relationship between a magnet thickness and a bearing gap of a thrust magnetic bearing.

FIG. 4 is a characteristic diagram showing a relationship between a control current ratio and a magnetic attraction force ratio and a magnet thickness.

FIG. 5 is a sectional view corresponding to FIG. 2 and showing a radial bearing of a circumferentially disassembled type.

FIG. 6 is a longitudinal sectional view along the axis of a rotating body showing a conventional magnetic bearing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Shaft (rotating body) 10, 11 ... Radial magnetic core 10c, 10d, 11c, 11d ... Yoke of radial magnetic core 12 ... Rotor 20, 50 ... Permanent magnet 30 ... Radial coil 40 ... Thrust magnetic core 40c, 40d ... Thrust Magnetic core yoke 60 Thrust coil 70 Thrust sensor 80 Thrust flange 90 Radial sensor 100 Housing 100a Bearing part 110 Radial magnetic bearing 120 Thrust magnetic bearing s, s1, s2 Gap (bearing gap) t, t1, t2 ... magnet thickness

Claims (1)

[Claims] 1. A rotating body, a bearing for supporting the rotating body, and magnetic circuit forming means for forming the rotating body with a magnetic circuit via a gap between the rotating body and the bearing,
A magnetic bearing device for levitating the rotating body by a magnetic force formed by the magnetic circuit, wherein a thickness of a permanent magnet installed in the magnetic circuit is equal to or more than equal to and equal to or less than four times the gap. Magnetic bearing device.