JPS6256617A - Magnetic bearing device - Google Patents

Abstract

PURPOSE:To increase the speed of rotation of a rotor and to enhance durability by disposing electromagnets in such a manner that magnetic circuits connecting N-poles and S-poles are substantially parallel to the center line of a rotary shaft, and positioning magnetic poles of the same polarity on one circumference. CONSTITUTION:Electromagnets 60-63 are disposed in such a manner that magnetic circuits connecting N-poles and S-poles are substantially parallel to the center line of a rotary shaft 57, and the respective designated electric currents are applied to the respective sets of control coils L5, and L7, and L6 and L8 by the respective control systems. The respective electromagnets 60-63 are provided with proximity sensors, and the deviation of the rotary shaft 57 is detected. Necessary control electric currents are applied to the respectively control coils L5-L8 by a control circuit such as a signal comparator or the like to return the rotary shaft 57 to its initial position. Accordingly, the peak number of an eddy current generated on the surface of the rotary shaft 57 is dispersed, so that power loss can be reduced by half, loss of heat generation can be remarkably decreased, and the speed of rotation and durability can be remarkably increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic bearing device, and particularly to a magnetic bearing device suitable for use in high-speed cutting machines, spindles for vacuum equipment, and the like.

[Conventional technology]

A magnetic bearing is intended to magnetically levitate and support a rotating shaft, and is generally known as a bearing that does not have mechanical contact parts. This bearing is easy to rotate at high speeds.

These bearings have distinctive features that differ from conventional ordinary bearings, such as low vibration and no need for lubricating oil.

This will be explained in more detail using FIGS. 5 and 6. In FIGS. 5 and 6, the magnetic bearing device 10 is
A cylindrical support case 1, a drive motor section 2 for driving a shaft provided at the center of the support case 1, a thrust bearing section 4 disposed at the bottom of the drive motor section 2, and this thrust bearing. The radial bearings 5.6 are installed on the lower side of the section 4 in FIG. 5 and on the upper side of the drive motor section 2, respectively.
With this, the rotating shaft 7 disposed on the center line of the support case 1 is connected to the thrust I-magnetic bearing section 4.
It is magnetically attracted and floated by the action of
Rotation can be driven by the action of the drive motor section 2.

Further, 8 and 9 indicate auxiliary bearings fixed to the support case 1 side, and 7A indicates a collar portion supported by the thrust magnetic bearing section 4.

On the other hand, each of the radial magnetic bearings 5.6, specifically, as shown in FIG. 13
a power source 14 for exciting the electromagnets 10 to 13;
The control system 15 and the like control the suction force as necessary.

To explain this in more detail, each of the electromagnets 10 to 13 has one fixed bias coil LltLz, L3, L
4 and 1 control coil! ,,L,.

L7. Le, and the N-pole and S-pole attracting surfaces formed by each coil face the outer peripheral surface of the rotating shaft 7 on the same circumference as shown in the figure (with a structure in which they are arranged alternately). (See Figure 6).Then, each of the coils 1 to L,
Of these, the fixed bias coils L, ~L4 are connected in series with the DC power supply 14 and have a magnetic flux Fl in the same direction as shown in FIG.
, F2°F:I, F4, respectively.

In addition, in each of the other coils Ls, Ls, Lw are connected to the one control system 15, and L, , L are connected to the other control system (not shown), as described later. As a result, the control magnetic fluxes Fs+F7 and F6.
F and are formed as required, respectively, as shown in FIG.

Here, each of the above-mentioned coils and the electromagnet 1 wound with ~Lll
To explain in more detail the actions of 0 to 13, first, electromagnets 10.12 shown in FIG. 6 act as one set, and electromagnets 11.
13 each constitute the other set. And the rotating shaft 7
is at the predetermined reference position, Ix+=Ix□=
It is 0.

On the other hand, if the rotating shaft 7 is tilted toward the electromagnet 12, for example, a force acts to return it to the center. Specifically, the proximity sensor 15A first detects the deviation of the rotating shaft 7, and sends the signal to the signal comparator 20. On the one hand, this signal comparator 20 constantly inputs the reference signal from the reference signal generating means 21, compares the signal from the aforementioned proximity sensor 15A with this reference signal, and corrects the resulting level difference. Alternatively, it is output as a negative deviation signal. Then, the deviation signal is sent to the voltage amplifier 22.
The power is amplified to a predetermined level by the power amplification circuit 24 via the two-phase compensation circuit 23, and is electrically connected to the coils LS and L7 described above.

In this case, if the same direction as the magnetic flux F + "F a generated by the fixed bias current described above is positive and the opposite direction is negative, a positive magnetic flux F5 is generated in the control coil of the electromagnet 10 as shown in FIG. , and the control coil L of the electromagnet 12 generates magnetic flux F7 in the negative direction, which increases the attractive force of the electromagnet 10, while at the same time weakening the attractive force of the electromagnet 12 by that amount. , the rotary shaft 7 is attracted by the electromagnet 10 and immediately returns to the central position.When the rotary shaft 7 returns to its original position, the output from the comparator 20 becomes zero, and F'',
-F? "" O is in equilibrium.

The other set of electromagnets 11, 13 and their control system are also constructed in the same manner as the one set of electromagnets 10 and 12 described above, and the proximity of the rotating shaft 7 detected by the other proximity sensor 35A is Alternatively, a similar control operation is performed by the other control system (not shown) based on the separation information.

[Problem that the invention seeks to solve]

In the above conventional example, an electromotive force is generated in the direction indicated by ■■ in FIG. Eddy currents occur as shown in the figure. Since this eddy current is continuously generated along the entire circumference of the surface facing each magnetic pole as the rotating shaft 7 rotates, for example, at point P in FIG. 8, the eddy current shown in FIG. A current change like this occurs. For this reason, the rotating shaft 7 has a rotational speed of, for example, 10,000 (RPM).
120,000 (Hz) for a spindle of
A high frequency current flows to point P, and therefore, this phenomenon acts as an electromagnetic brake that brakes the rotation, and at the same time causes abnormal heat generation in the electromagnets 10 to 13 of the rotating shaft 7. When such a situation occurs, rotational power is lost, and at the same time, the rotating shaft 7 itself is deformed during high-speed rotation, or the electromagnets 10-
Inconveniences such as thermal destruction of the covering member on the 13 side occur, which is a significant obstacle in practical use.

For this reason, in recent years, a method has been adopted in which a laminated steel plate section made by laminating thin silicon steel plates in an annular shape is provided on the outer periphery of the rotating shaft 7 in order to reduce the generation of eddy currents as described above. has been done.

However, if other members are installed around the outer circumference of the rotating shaft that rotates at high speed, the attached members are likely to be damaged by the action of the centrifugal force, which puts a limit on high-speed rotation, and furthermore, the diameter of the rotating body 7 is This caused the inconvenience of having to be made smaller in order to reduce speed.

This has led to the inconvenience that, for example, various cutting machines that require high-speed cutting have their own limits on their cutting capabilities.

[Purpose of the invention]

The present invention aims to overcome the disadvantages of the conventional example and provide a magnetic bearing device that suppresses temperature rise due to heat generation in the radial bearing portion of the rotating shaft and increases the durability of the entire device. purpose.

[Means for solving problems]

Therefore, in the present invention, a radial magnetic bearing section is provided at an upper part and a lower part of a rotating shaft, and a thrust magnetic bearing section is provided at an intermediate part of the rotating shaft, and each of the radial magnetic bearings is connected to a fixed bias coil. In a magnetic bearing device comprising at least four electromagnets wound with variable force control coils, a magnetic circuit connecting north and south poles of each of the electromagnets is substantially parallel to the center line of the rotating shaft. The electromagnets are arranged so that the electromagnets are arranged so that the magnetic poles have the same polarity as one of the magnetic poles, and a magnetic pole with the same polarity is positioned on the same circumference as one of the magnetic poles. be.

[For production]

It is assumed that each of the one and the other radial magnetic bearing portions is composed of, for example, four electromagnets. In the present invention, since the N pole and S pole of each electromagnet are arranged parallel to the center line of the rotating shaft, the portion facing the N pole on the rotating shaft is always The portion facing only the north pole and the south pole always faces only the south pole during one rotation. For this reason, four peaks of eddy current occur in the same direction at different locations during one revolution of the rotating shaft, and the number of eddy currents generated is smaller than that of the conventional eight peak currents. The number is halved.

Therefore, the overall loss caused by eddy current is ``(current) 2 x resistance'' compared to the conventional example.

((1/2)"
The temperature rise at each point is suppressed to a significantly smaller level than in the conventional case.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

First, in FIG. 1, the magnetic bearing device 50 includes a cylindrical support case 51, a shaft drive means 52 provided in the center of the support case 51, and a shaft drive means 52, similar to the conventional example described above. Thrust bearing section 54 arranged at the bottom of
and radial magnetic bearing portions 55 and 56 provided on the lower side of the thrust bearing portion 54 in FIG. The rotating shaft 57 disposed on the center line is magnetically attracted and levitated by the action of the above-mentioned sluth EH air ring bearing section 54.

Rotation can be driven by the action of the shaft drive means 2.

Although a high-frequency motor is used as the shaft drive means 52 in this embodiment, other drive means such as an air turbine (in this case, installed at the upper end of the rotating shaft) may be used. .

The thrust bearing portion 54 includes donut-shaped coils 54A disposed on the upper surface side and the lower surface side of the rotating shaft 57, respectively, with a collar portion 57A formed approximately in the center of the rotation shaft 57 in FIG. , 54B, and one suction support member 54C that engages and supports the respective coils 54A, 54B and generates an attractive force to the outside by using the magnetic flux generated by the respective coils 54A, 54B as N and S poles. and a suction support member 54D.

Furthermore, the same radial magnetic bearings 55 and 56 are used in this embodiment.

Therefore, to explain the lower radial bearing section 55 in FIG. 1, the radial magnetic bearing section 55 in this embodiment consists of four attraction-type electromagnets 60, 61 arranged as shown in FIG. It consists of ゜62.63.

Each of the electromagnets 60 to 63 has fixed bias coils L+, LZ, L3 . L
4 and attraction force variable control coil I, S+ L6. L? ,
The magnetic poles Le are wound so that the magnetic pole located on the opposite side of FIG. 2 forms the north pole, and the magnetic pole located below forms the south pole. That is, in this embodiment, each electromagnet 60 to
63 are arranged, and the magnetic poles of each of these electromagnets 10 to 13 are arranged opposite to the outer peripheral surface of the rotating shaft 57 and spaced apart from each other by 90''.

Here, a constant current similar to that of the conventional example described above is applied to each of the fixed bias coils L and L6. 14 indicates a DC power supply for fixed bias.

Then, as in the case of the conventional example described above, one set of control coils LS, L? One control system (No. 6 No. 15)
Reference).

Also, the other control coil L6. L! A predetermined current is applied to each of the two control systems from the other control system as necessary. The directions and magnitudes of the magnetic fluxes F, .about.FIl generated in the control systems of the one and the other coils and the coils +"Le are exactly the same as in the conventional example described above.

Further, 69 indicates a position sensor for detecting vertical positional deviation of the rotating shaft 57. Then, a control system for the thrust magnetic bearing (not shown) operates based on the output signal from this position sensor, and the above-mentioned thrust bearing section 54
The strength of the current applied to each of the coils 54A, 54, and B is controlled.

15A, 15B, 35A, 35B (see Figure 1) are
Each of the figures shows a proximity sensor similar to that of the conventional example described above.

Further, 70 and 71 each indicate a cover, 8 and 9 each indicate an auxiliary bearing, and 40 indicates a removably attached cutting cutter. The other configurations are completely the same as the conventional example described above.

Next, the heat generating effect of the rotating shaft 57 that occurs in the above embodiment will be explained. First, as the rotating shaft 57 rotates, eddy currents as shown in FIG. 3 are generated on the surface of the rotating shaft 57. Since this eddy current is generated continuously around the entire circumference of the surface facing each magnetic pole as the rotating shaft 57 rotates, for example, at points p, Pz in FIG. A current change occurs as shown in the diagram. The number of peaks of this current change is dispersed as shown in (1) and (2) in FIG. 3 when compared to the conventional example described above, and is half of that in the conventional example at the same location. Therefore, the overall power loss is reduced by half to C(1/2)''X2=1/2, since the current is approximately 1/2 from ((current)2×resistance).

For this reason, heat loss on the surface of the rotating shaft 57 can be significantly reduced, which can prevent thermal damage to the covering member and greatly increase the rotational speed. In order to suppress the heat generation of the rotating shaft 57, this embodiment does not include the N steel plates that were arranged in the conventional example. It has the advantage that it can be forced.

In the above embodiment, each electromagnet 60 is arranged in the vertical direction.
~63 Although the description has been made on the assumption that the ON pole and the S pole are separated, the magnetic attraction may be increased (based on magnetoresistive force) by bringing the respective magnetic poles as close as possible to each other.

Further, the number of electromagnets in the radial magnetic bearing portions 55, 56 may be six or eight or more.

〔Effect of the invention〕

Since the present invention is configured and functions as described above, it is possible to significantly reduce the generation of eddy current on the surface of the rotating body facing each magnetic pole of the electromagnet, and thus further increase the rotational speed of the rotating body. It is possible to provide a magnetic bearing device equipped with an unprecedentedly excellent radial magnetic bearing portion that can be raised and has improved overall durability.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG.
A schematic perspective view showing the main parts of the radial magnetic bearing part in the figure, FIG. 3 is an explanatory diagram showing the eddy current generated on the rotating shaft,
Figures 4 (1) and (2) are diagrams showing the current changes at the point P+=Pz in Figure 3, Figure 5 is a sectional view of the conventional example, and Figure 6 is the radial magnetic bearing in Figure 5. Figures 7 to 8 are explanatory diagrams showing the direction of electromotive force and current flow generated on the rotating shaft in Figure 5, and Figure 9 is an explanatory diagram showing the current at point P in Figure 8. It is a line diagram showing a change. 54------Thrust magnetic bearing section, 55.56
-111-Radial magnetic bearing section, 60-63 -1111 Electromagnet, L, ~L4 - tp Constant bias coil, I-5-L8-- Attraction force variable control coil. Patent applicant Maruwa Electric Co., Ltd. (1 other person) Figure 1 Figure 2 Figure 3 Figure 4 (c) Figure 5

Claims (1)

[Claims] (1) It has radial magnetic bearings at the upper and lower parts of the rotating shaft, and a thrust magnetic bearing at the middle of the rotating shaft, and each of the radial magnetic bearings is connected to a fixed bias coil and an attractive force. In a magnetic bearing device constituted by at least four electromagnets wound with variable control coils, a magnetic circuit connecting the north and south poles of each electromagnet is substantially parallel to the center line of the rotating shaft. What is claimed is: 1. A magnetic bearing device characterized in that each of the electromagnets is arranged as shown in FIG.