JP2001146917A - Thrust magnetic bearing using both of electromagnet and permanent magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the required magnetomotive force in a thrust magnetic bearing using both of an electromagnet and a permanent magnet. SOLUTION: The permanent magnet 6 is not installed on a magnetic path 8 of the electromagnet, and a magnetic path 7 of the permanent magnet 6 and the magnetic path 8 of the electromagnet are separated from each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a thrust magnetic bearing using both an electromagnet and a permanent magnet.

[0002]

2. Description of the Related Art As shown in FIG. 7, there is conventionally known a technique for attracting an object 23 using an electromagnet including an iron core 21 and an electromagnet coil 22 wound therearound. FIG.
The magnetic path 24 is a magnetic circuit of the magnetic flux generated by the electromagnet. However, since the object 23 is attracted only by the electromagnet,
Requires a lot of power.

In order to reduce power consumption and reduce the size of the electromagnet, a technique using both an electromagnet and a permanent magnet is known from Japanese Patent Application Laid-Open Nos. Hei 6-26519 and Hei 2-102918. FIG. 8 shows an example in which a permanent magnet 25 constantly generates a required attractive force by using a composite magnet 26 in which a permanent magnet 25 is inserted into a magnetic path 24 of the electromagnet, and the attractive force is variably changed by the electromagnet. Control.

[0004] In particular, Japanese Patent Application Laid-Open No. 2-102918 discloses a thrust magnetic bearing using both an electromagnet and a permanent magnet. FIG. 9 shows an example thereof. The thrust magnetic bearing includes a thrust disk 2 attached to a shaft to be supported (not shown), and a pair of composite magnets 26A arranged so as to sandwich the thrust disk 2 at intervals.
26B. Each of the composite magnets 26A and 26B has a permanent magnet 25 inserted in the magnetic path 24 of the electromagnet. In such a thrust magnetic bearing, a gap sensor 27 is disposed at an interval facing substantially the center of the thrust disk 2, and a displacement (gap) 28 in the thrust direction is measured by the gap sensor 27. When the position of the shaft is corrected, the attraction force of one composite magnet 26A is increased, and when the position is corrected to the right in the drawing, the attraction force of the other composite magnet 26B is increased. Provide non-contact support.

[0005]

In the above-described conventional composite magnets 26, 26A and 26B, the magnetic path of the permanent magnet 25 is the same as the magnetic path 24 of the electromagnet. For this reason, when the permanent magnet 25 is used in combination, the magnetic resistance of the magnetic path 24 tends to be larger than when the electromagnet is designed alone. When the magnetic resistance increases, the magnetomotive force of the electromagnet required to change the magnetic flux density in the gap increases. Therefore, there is a problem that the electromagnet cannot be made smaller than expected.

[0006] An object of the present invention is to provide a thrust magnetic bearing capable of reducing the required magnetomotive force of an electromagnet.

[0007]

According to a first aspect of the present invention, there is provided a thrust magnetic bearing comprising a thrust disk mounted on a shaft, and a composite magnet combining an electromagnet and a permanent magnet, wherein the permanent magnet is an electromagnet. Characterized by being disposed separately from the magnetic path.

A thrust magnetic bearing according to a second aspect of the present invention is the thrust magnetic bearing according to the first aspect, wherein the height of the composite magnet decreases toward the outer periphery.

A thrust magnetic bearing according to a third aspect of the present invention is the thrust magnetic bearing according to the first aspect, wherein the distal end of the composite magnet is narrowed, and the diameter of the composite magnet opposed to the thrust disk is increased at the base end. Is smaller than the diameter of

A thrust magnetic bearing according to a fourth aspect of the present invention is the thrust magnetic bearing according to the first or second or third aspect, wherein at least three pairs of gap sensors and tilt-controlling electromagnets arranged opposite to the thrust disk are provided. And a control means for controlling a tilt of the thrust disc by flowing a current to the electromagnet for tilt control based on an output of the gap sensor.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

First Embodiment A thrust magnetic bearing shown in FIG. 1 will be described as a first embodiment of the present invention. The thrust magnetic bearing of this example has a thrust disk 2 attached to a shaft (rotating shaft) 1 to be supported, and two composite magnets 3A and 3B provided at an interval, and includes two composite magnets 3A and 3B. The thrust disk 2 is arranged between them.

Each of the composite magnets 3A and 3B includes an iron core 4, an electromagnet coil 5, a permanent magnet 6, and the like. A magnetic path 7 for the magnetic flux generated by the permanent magnet 6 and a magnetic path 8 for the magnetic flux generated by the electromagnet are I know.

More specifically, the iron core 4 includes a yoke 9 and a yoke 9.
And a ring-shaped inner magnetic pole 11 erected on a yoke 9 coaxially with the ring-shaped outer magnetic pole 10. The electromagnet coil 5 includes a ring-shaped outer magnetic pole 1.
The permanent magnet 6 is wound up around 0 and stands upright at the center of the yoke 9. That is, the permanent magnet 6 is a ring-shaped inner magnetic pole 11.
It is located more inside.

In this embodiment, the magnetic path 7 of the magnetic flux generated by the permanent magnet 6 is composed of the permanent magnet 6 itself, a part of the thrust disk 2, a ring-shaped inner magnetic pole 11 and a part of the yoke 9, and the magnetic flux generated by the electromagnet. The magnetic path 8 includes a ring-shaped outer magnetic pole 10, a part of the thrust disk 2, a ring-shaped inner magnetic pole 11, and a part of the yoke 9.

Accordingly, although the ring-shaped inner magnetic pole 11 is shared by the two magnetic paths 7 and 8, the permanent magnet 6 does not exist in the magnetic path 8 of the electromagnet, and the two magnetic paths 7 and 8 are substantially separated. It can be said that.

In the illustrated thrust magnetic bearing, the position of the thrust disk 2 is controlled by attracting the thrust disk 2 by the composite magnets 3A and 3B on both sides thereof, and the thrust direction of the shaft 1 connected to the thrust disk 2 is controlled. Is determined.

As described above, since there is no permanent magnet 6 in the magnetic path 8 of the electromagnet, the magnetomotive force of the electromagnet can be designed to be small. This makes it possible to reduce the capacity of a power supply for supplying a current to the electromagnet or to reduce the number of turns of the electromagnet coil 5, and the electromagnet is correspondingly reduced in size.

In FIG. 1, in the left composite magnet 3B,
The shape of the permanent magnet 6 is a ring shape, which is for passing the shaft 1. In the composite magnet 3A on the right side, the permanent magnet 6 may be formed in a ring shape.

Further, in each of the illustrated composite magnets 3A and 3B, the ring-shaped outer magnetic pole 10, the ring-shaped inner magnetic pole 11, and the permanent magnet 6 are arranged in order from the outside, but the order may be reversed. For example, a ring-shaped large-diameter permanent magnet on the outermost periphery, a ring-shaped magnetic pole on the inside thereof, a ring-shaped magnetic pole on the innermost periphery, and an electromagnet coil 5 wound around the innermost ring-shaped magnetic pole may be used. The magnetic path 7 of the permanent magnet 6 and the magnetic path 8 of the electromagnet can be separated.

By the way, as shown in FIG. 1, since two types of magnetic paths (the magnetic path 7 of the permanent magnet 6 and the magnetic path 8 of the electromagnet) are provided, the diameter of the iron core 4 is increased, and the diameter of the iron core 4 is correspondingly increased. The diameter increases. Then, depending on the method of measuring the position of the thrust magnetic bearing, a phenomenon in which the thrust disk 2 is obliquely attracted to the magnet as shown in FIG. 9 may be considered.

Here, the diameter of the thrust magnetic bearing is L_
Assuming that {thrust} and the inclination of the thrust disk 2 are θ, the displacement Δ in the gap direction at the end of the thrust disk 2
L is represented by the following equation (1). ΔL = L_ {thrust} / 2 × cos (π / 2−θ) Equation (1)

Therefore, assuming that the maximum value of the gap direction displacement ΔL is constant (this is determined by the gap of the thrust magnetic bearing), the thrust disk 2 is magnetized with a smaller inclination θ as the diameter L_ {thrust} increases. Comes into contact with

Further, as shown in FIG.
When the thrust disk 2 faces the center of the thrust disk 2, the output from the gap sensor 27 when the thrust disk 2 contacts the composite magnet has substantially the same value as when the thrust disk 2 is at the target position. Therefore, the state is regarded as a stable state, and it is impossible to return to the non-contact supporting state from the state where the thrust disk 2 is sucked obliquely.

To avoid such a phenomenon, the following (1)
The measure (2) can be considered. (1) The structure is such that the thrust disk is difficult to be absorbed at an angle. (2) Increasing the number of gap sensors and measuring the inclination of the thrust disk 2.

Second Embodiment FIG. 2 shows, as a second embodiment of the present invention, a thrust magnetic bearing having a structure in which the thrust disk 2 is hardly inclined. In the thrust magnetic bearing of this example, the height of the composite magnets 3A, 3B is made lower as going to the outer periphery as compared with that of FIG. Specifically, in each of the composite magnets 3A and 3B, the height of the portion of the iron core 4, that is, the height of the ring-shaped inner magnetic pole 11 and the ring-shaped outer magnetic pole 10 is gradually reduced in order.
Other configurations are the same as those shown in FIG.

As described above, the composite magnet 3 becomes closer to the outer periphery.
By reducing the height of A, 3B, the inclination θ_max at which the attraction to the composite magnets 3A, 3B occurs when the thrust disk 2 is inclined increases. Therefore, the maximum inclination θ_max
When the inclination θ is smaller, the effect that the suction does not occur and the suction is not performed, that is, the range where the contact is not performed is widened is obtained.

In the example shown in FIG. 2, the height of each of the composite magnets 3A and 3B decreases stepwise toward the outer periphery, but the tips of the permanent magnet 6, the ring-shaped inner magnetic pole 11, and the ring-shaped outer magnetic pole 10 are slanted. May be formed so as to be smoothly lowered.

[Third Embodiment] FIG. 3 shows another thrust magnetic bearing having a structure in which the thrust disk 2 is hardly inclined, as a third embodiment of the present invention. The thrust magnetic bearing of the present embodiment has composite magnets 3A, 3B
Of the thrust disk 2 is narrowed inward so that the diameter of the portion facing the thrust disk 2 does not increase. Specifically, the tip portion of the iron core 4, that is, the tip portion 10a of the ring-shaped outer magnetic pole 10 and the tip portion 11a of the ring-shaped inner magnetic pole 11 are respectively extended and squeezed into a tapered conical shape. The diameter of the opposing distal end portion is smaller than the diameter of its proximal end portion. Accordingly, the diameter of the thrust disk 2 is also reduced.
Other configurations are the same as those shown in FIG.

As described above, in each of the composite magnets 3A and 3B, the diameter L_ {thrust} of the thrust magnetic bearing is smaller than that in FIG. ), The displacement ΔL in the gap direction at the end of the thrust disk 2 can be reduced, and the resistance to the inclination θ of the thrust disk 2 can be increased.

In order to make the heights of the composite magnets 3A, 3B uniform as a whole, a magnetic body 6a is provided at the tip of the permanent magnet 6, and the height is adjusted. In the composite magnet 3B on the left, the magnetic body 6a has a ring shape. Instead of providing the magnetic body 6a extending, the length of the permanent magnet 6 itself may be adjusted.

A ring-shaped large-diameter permanent magnet is provided on the outermost periphery.
In the case of a configuration in which a ring-shaped outer magnetic pole is arranged inside and a ring-shaped inner magnetic pole is arranged at the innermost circumference, and an electromagnet coil is wound around the ring-shaped inner magnetic pole, a tapered conical magnetic body is formed at the tip of the ring-shaped permanent magnet. The object is achieved by extending the tip of the ring-shaped outer magnetic pole and squeezing it into a tapered conical shape.

As described above, in addition to reducing the diameter of the thrust magnetic bearing by narrowing the tip of each of the composite magnets 3A and 3B inward, the height of each of the composite magnets 3A and 3B shown in FIG. However, it may be set lower.

In the second embodiment and the third embodiment, the thrust disk 2 is hardly brought into the contact state shown in FIG. 9, but the contact state shown in FIG. If it falls into the state, it does not have the ability to return to the non-contact support state by itself. So, usually,
These thrust magnetic bearings are preferably used together with a mechanism for controlling the radial direction, such as a radial magnetic bearing, so as to return to a non-contact support state.

Fourth Embodiment FIGS. 4 and 5 show, as a fourth embodiment of the present invention, a thrust magnetic bearing which returns to a non-contact support state and stabilizes even when the thrust disk 2 is inclined. Show.

In the thrust magnetic bearing of this embodiment, a set of the gap sensor 12 and the electromagnet 13 is installed near the outer surface of the iron core 4 so as to face one surface near the outer periphery of the thrust disk 2 for tilt control. At least three sets of the gap sensor 12 and the electromagnet 13 are used to control the inclination of the plane. Other configurations are the same as those shown in FIG.

Each gap sensor 12 detects a gap with the thrust disk 2 in order to control the inclination of the thrust disk 2. By comparing each signal (gap signal) representing the displacement measured by each of the three gap sensors 12 with the reference signal (displacement reference signal), it can be determined to which direction the thrust disk 2 is displaced. Each electromagnet 13 attracts the thrust disk 2 according to the displacement in order to correct the inclination of the thrust disk 2.

FIG. 6 shows an example of a control device used for controlling the inclination of the thrust disk 2. The control device 14 shown in FIG. 6 includes a comparison unit 15, a controller unit 16, and a limiter unit 17.
And a current amplifier 18. In this example, such a control device 14 is provided for each set of the gap sensor 12 and the electromagnet 13.

In FIG. 6, the gap signal from the tilt control gap sensor 12 is compared with the displacement reference signal by the comparison means 15 to obtain the displacement of the thrust disk 2 with respect to the reference position. This displacement is input to the controller 16.

The controller 16 determines a command signal representing a current value required to return the thrust disk 2 to the reference position from the displacement input from the comparator 15. The controller means 16 uses something like a PID.

The command signal from the controller 16 is passed through a limiter 17 as necessary, and
8 is input. The limiter 17 limits an excessive signal to a specified value.

The current amplifier 18 outputs a current according to the command signal. This current flows through the electromagnet coil of the electromagnet 13 for tilt control, and the thrust disk 2 is sucked.

By the processing of each of the control devices 14 described above, control for making the inclination of the thrust disk 2 zero is performed.
That is, the inclination of the thrust disk 2 can be corrected, and the non-contact support can be stably performed. Normally, a larger current flows through the tilt control electromagnet 13 as the displacement is larger than the reference displacement. However, if the displacement is smaller than the reference displacement, the current need not be passed.

In this embodiment, as described above, the inclination control process is performed independently by each of the gap sensors 12 and the control electromagnets 13. However, the gap signals from all the gap sensors 12 are combined into one controller. Take in,
The inclination may be corrected and controlled by one control device.

4 and 5, the gap sensor 12 and the tilt controlling electromagnet 1 are provided only on one side of the thrust disk 2.
3, the gap sensor 12 and the control electromagnet 13 may be provided on both sides. Also, the inclination control can be performed by providing three or more sets of the gap sensor 12 and the inclination control electromagnet 13 irrespective of one side or both sides of the thrust disk 2.

[0046]

According to the first aspect of the present invention, in the thrust magnetic bearing using both the electromagnet and the permanent magnet, the magnetic path is separated so that the permanent magnet is not disposed in the magnetic path of the electromagnet. The required magnetomotive force of the electromagnet can be reduced.

According to the second aspect of the present invention, the thrust disk tilts with respect to the shaft and is attracted to the magnet portion. The inclination at which the occurrence occurs becomes large, and it is difficult to adsorb.

According to the third aspect of the invention, the core of the thrust magnetic bearing is narrowed and the diameter of the thrust magnetic bearing is reduced in response to the phenomenon that the thrust disk is inclined with respect to the shaft and is attracted to the magnet. By being small, the inclination at which the adsorption occurs becomes large, and the adsorption is difficult.

According to the fourth aspect of the present invention, since the electromagnet and the gap sensor for tilt control and the control means are provided, the thrust disk can be prevented from tilting and can be stably supported in a non-contact manner.

[Brief description of the drawings]

FIG. 1 is a sectional view of a thrust magnetic bearing according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a thrust magnetic bearing according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a thrust magnetic bearing according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a thrust magnetic bearing according to a fourth embodiment of the present invention.

FIG. 5 is a right side view of FIG. 4;

FIG. 6 is a block diagram showing an example of control means of a thrust magnetic bearing according to a fourth embodiment.

FIG. 7 is a diagram showing a conventional technique using only electromagnets.

FIG. 8 is a diagram showing a conventional technique using both an electromagnet and a permanent magnet.

FIG. 9 is a diagram showing a conventional technology of a thrust magnetic bearing using both an electromagnet and a permanent magnet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shaft 2 Thrust disk 3A, 3B Composite magnet 4 Iron core 5 Electromagnet coil 6 Permanent magnet 6a Magnetic body at the end of permanent magnet 7 Magnetic path of permanent magnet 8 Magnetic path of electromagnet 9 Yoke 10 Ring-shaped outer magnetic pole 10a Cone of ring-shaped outer magnetic pole Tip 11 Ring-shaped inner magnetic pole 11a Conical tip of ring-shaped inner magnetic pole 12 Gap sensor for tilt detection 13 Electromagnet for tilt control 14 Controller 15 Comparison means 16 Controller means 17 Limiter means 18 Current amplifier

Claims (4)

[Claims] 1. A thrust magnetic bearing including a thrust disk attached to a shaft and a composite magnet using both an electromagnet and a permanent magnet, wherein the permanent magnet is disposed separately from a magnetic path of the electromagnet. Thrust magnetic bearing. 2. The thrust magnetic bearing according to claim 1, wherein the height of the composite magnet decreases toward the outer periphery. 3. The thrust magnetic bearing according to claim 1, wherein a distal end of the composite magnet is narrowed, and a diameter of the composite magnet facing the thrust disk is smaller than a diameter of a base end thereof. 4. The tilt control electromagnet according to claim 1, 2 or 3, wherein at least three sets of gap sensors and tilt control electromagnets are disposed to face the thrust disk, and the tilt control is performed based on an output of the gap sensor. A thrust magnetic bearing having a control means for controlling the inclination of the thrust disk by passing a current through the electromagnet.