JPH07139545A - Magnetic bearing device - Google Patents

Abstract

PURPOSE:To stably support a rotary shaft without using non-magnetic material for a frame casing and the like by specifying the direction of polarity of the magnetic flux formed by coils on the outer diameter side and the inner diameter side opposed to each other putting a thrust disc between. CONSTITUTION:Displacement of a rotary shaft in the axial direction is with a thrust displacement sensor 27, displacement in the radial direction is with a radial displacement sensor 28 respectively detected, and sent to a control device. In coils 31a on the outer diameter side and coils 31b on the inner diameter side opposed to each other putting a thrust disc 22 between, polarities of the magnetic flux are set mutually in opposite directions, and set in the same direction on the same side. Hence, the magnetic flux formed in the coils 31a, 31b of a magnetic bearing 25 by current from the control device are mutually canceled in the rotary shaft 21, the electromagnet 32 of a radial magnetic bearing 26, a frame casing, and the like, do not flow except magnetic poles 30a, 30b, 30c, and hence even if external force is acted on the rotary shaft 21 to generate large displacement of the shaft, control of the thrust magnetic bearing 25 is not dissipated and the rotary shaft 21 can be stably supported.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active magnetic bearing device for supporting a rotary shaft in a non-contact manner by a thrust magnetic bearing and a radial magnetic bearing, and particularly, when an external force in the thrust direction acts on the rotary shaft. The present invention relates to a magnetic bearing device that stabilizes the support.

[0002]

2. Description of the Related Art An example of the construction of a conventional magnetic bearing device which is a combination of a thrust magnetic bearing and one radial magnetic bearing will be described with reference to FIGS. 5 is an axial sectional view of the magnetic bearing device, FIG. 6 is a sectional view taken along the line AA of FIG. 5, and FIGS. 7 and 8 are axial partial sectional views for explaining the flow of the magnetic flux of the thrust electromagnet in each state. is there.

As shown in FIGS. 5 to 8, a thrust disk 2 made of a magnetic material and a rotor core 3 of a radial magnetic bearing made of an electromagnetic steel plate are firmly fixed to a rotary shaft 1.
The rotating shaft is surrounded by a frame casing 4, and the frame casing 4 is provided with a thrust magnetic bearing 5, a radial magnetic bearing 6, displacement sensors 7, 8 and the like.

The thrust magnetic bearing 5 is composed of a pair of electromagnets 9 arranged on both axial sides of the thrust disk 2 with a thrust gap interposed therebetween, and these electromagnets 9 respectively have an outer diameter side magnetic pole 10a, an inner diameter side magnetic pole 10b and an inner diameter side magnetic pole 10b. Coil 1
It consists of 1. The thrust displacement sensor 7, which is one of the displacement sensors, is attached to the shaft end of the rotary shaft 1 and
Detects the axial displacement of.

The radial magnetic bearing 6 is composed of an electromagnet 12, and four electromagnets 12 are arranged vertically and horizontally around the rotor core 3 of the rotary shaft 1 with a radial gap therebetween. Radial displacement sensor 8 which is the other of the displacement sensors
Is for detecting the radial displacement of the rotary shaft 1, and at least one is arranged in each of the vertical and horizontal directions of the rotary shaft 1.

At the shaft end of the rotary shaft 1, a mechanical auxiliary bearing 13 that supports the rotary shaft 1 instead of the magnetic bearing when the magnetic bearing cannot be controlled is provided on the frame casing 4 with a bearing bracket 14. Is fixed through.

Next, the operation of the prior art will be described. The axial displacement of the rotary shaft 1 is detected by the thrust displacement sensor 7.
The radial displacement is detected by the radial displacement sensor 8 and converted into an electric signal. The converted electrical signal is
A control device (not shown) converts the signal into a signal that stably supports the rotary shaft 1, further amplifies the power, and supplies the current signal to the electromagnet 9 of the thrust magnetic bearing 5 and the electromagnet 12 of the radial magnetic bearing 6. The electromagnet 9 of the thrust magnetic bearing 5 and the electromagnet 12 of the radial magnetic bearing 6 attract the rotating shaft 1 by the magnetic attraction force corresponding to the current flowing in each coil, and stably support it without contact.

At this time, the magnetic flux generated by the electromagnet 9 of the thrust magnetic bearing 5 flows so as to surround each coil 11 as shown by a and b in FIG. Then, in addition to the path of the outer diameter side magnetic pole 10a, the thrust disk 2, and the inner diameter side magnetic pole 10b, which are supposed to flow the magnetic flux, the rotary shaft 1,
Magnetic flux also flows through the paths of the rotor core 3, the electromagnet 12, and the frame casing 4 of the radial magnetic bearing 6. In this case, when the external force in the axial direction is not applied to the rotating shaft 1 and the magnetic attraction forces of the electromagnets 9 of the thrust magnetic bearings 5 facing each other are equally balanced, the magnetic fluxes generated by the electromagnets 9 are also equal and the rotating shaft 1 , Rotor core of radial magnetic bearing 6,
The magnetic fluxes c and d in the paths of the electromagnet 12 and the frame casing 4 cancel each other out, and the magnetic fluxes generated by the electromagnets 9 of the thrust magnetic bearing 5 are generated in the outer diameter side magnetic pole 10a, the thrust disk 2, and the inner diameter side magnetic pole 10b. It flows only through the route and has no particular adverse effect on control.

However, when a large external force acts in the axial direction of the rotary shaft 1 and the magnetic attraction force of the electromagnets 9 of the thrust magnetic bearings 5 facing each other with the thrust disk 2 in between is unbalanced, the control system is adversely affected. It is possible to affect.

That is, in general, the axial gap between the auxiliary bearing 13 and the rotary shaft 1 is set to half the gap between the thrust magnetic bearing 5 and the thrust disk 2. Therefore, consider a case where an external force F in the axial direction indicated by an arrow in FIG. 5 acts on the rotating shaft 1 and the rotating shaft 1 is displaced until just before it comes into contact with the auxiliary bearing 13. In this case, when the gap between the thrust disk 2 and the electromagnet 9 of the thrust magnetic bearing 5 before the external force F is applied is G, when the external force F acts on the rotating shaft 1, the electromagnet 9 on the left side of FIG. The gap between (9a) and the thrust disk 2 changes to (1/2) G, for example, and the gap between the right electromagnet 9 (9b) and the thrust disk 2 changes to (2/3) G. In this case, if the magnetic resistance of the magnetic material portion in the path through which the magnetic flux flows is ignored, the magnetic flux that is inversely proportional to the length of the gap in the magnetic path will flow, so that the external force F applied to the rotating shaft 1 will be supported. Right side electromagnet 9 (9b)
Of the magnetic flux generated by the magnetic flux d in one path is twice that in the other path c, which increases the magnetic flux density in the gap of the left electromagnet 9 (9a), and the magnetic attraction force generated by the thrust magnetic bearing 5 is generated. f becomes in the same direction as the external force F applied to the rotary shaft 1, the control system diverges, and overcomes the external force F to make it impossible to stably support the rotary shaft 1 in the axial direction.

Therefore, in order to avoid this problem, it is conceivable that a part or all of the magnetic path having a bad influence is made of a non-magnetic material. For example, the frame casing 4 is made of SUS material, or a sleeve of SUS material is inserted between the rotary shaft 1 and the rotor core 3 of the radial magnetic bearing 6. However, in the former case, the SUS material is more expensive than the general steel material, and there are problems such as difficulty in processing.
Further, in the latter case, there is a problem that the shaft diameter becomes thin and the natural frequency of the shaft decreases. Further, since there are a plurality of magnetic paths that adversely affect control, not a single magnetic path, it is almost impossible to block all magnetism.

[0012]

As described above, in the conventional magnetic bearing device, the magnetic path passing through the rotary shaft, the radial magnetic bearing, and the frame casing is formed, and a large external force is applied in the axial direction of the rotary shaft. However, there is a problem that the control system diverges when it is largely displaced in the axial direction and stable support in the axial direction becomes impossible. In order to avoid this problem, there are problems such as an increase in the cost of the device, difficulty in processing, and a decrease in the natural frequency of the shaft, and it has not been possible to completely avoid it in the past.

The present invention has been made in view of such circumstances, and it is not necessary to form the rotating shaft and the frame casing with a non-magnetic material, and even if a large external force acts on the rotating shaft and a large axial displacement occurs, the rotating shaft does not rotate. An object of the present invention is to provide a magnetic bearing device that can stably support a shaft.

[0014]

In order to achieve the above object, the present invention supports a rotating shaft in a non-contact manner by a thrust magnetic bearing and a radial magnetic bearing provided in a frame casing, and each of the magnetic bearings is supported. In the magnetic bearing device in which the current flowing through the electromagnet is controlled by the output signal of the displacement sensor, the thrust magnetic bearing has a pair of electromagnets facing each other on both sides of the thrust disk protruding in the radial direction of the rotating shaft. However, each of the electromagnets includes an inner diameter side coil arranged on the inner diameter side of the outer diameter side coil arranged on the outer diameter side of the thrust disk and a magnetic pole surrounding these both coils, and an outer diameter side coil of each electromagnet. The polarities of the magnetic fluxes formed by the inner diameter side coil and the inner diameter side coil are set in the same direction, and the outer diameter side coils and the inner diameter side coil which are opposed to each other with the thrust disk sandwiched therebetween. Wherein the polarity of the magnetic flux formed by each other set in opposite directions.

[0015]

According to the above-described structure of the present invention, the magnetic flux produced by each coil of the electromagnet of each thrust magnetic bearing is
Since the electromagnets of the radial magnetic bearings, frame casings, etc. cancel each other out and flow only to the magnetic poles of the electromagnets of each thrust magnetic bearing, the thrust magnetic bearings can be controlled even if external force acts on the rotating shaft to cause large axial displacement. The rotating shaft can be stably supported without diverging.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an axial sectional view of a magnetic bearing device including a combination of a thrust magnetic bearing and one radial magnetic bearing, FIG. 2 is a sectional view taken along line BB of FIG. 1, and FIGS. 4 and 4 show thrust electromagnets in various states. It is an axial direction partial sectional view explaining the flow of a magnetic flux.

As shown in FIGS. 1 to 4, a thrust disk 22 made of a magnetic material and a rotor core 23 of a radial magnetic bearing made of an electromagnetic steel plate are firmly fixed to a rotary shaft 21. The rotating shaft 21 is surrounded by a frame casing 24,
This frame casing 24 has a thrust magnetic bearing 2
5, radial magnetic bearing 26 and displacement sensors 27, 28
Etc. are provided.

The thrust magnetic bearing 25 is the thrust disk 2
2 is formed by a pair of electromagnets 29 arranged on both sides in the axial direction with a thrust gap interposed therebetween.
Is composed of an outer diameter side magnetic pole 30a, an inner diameter side magnetic pole 30b, an intermediate magnetic pole 30c and coils 31a and 31b. The thrust displacement sensor 27, which is one of the displacement sensors, is attached to the shaft end of the rotary shaft 21 and detects the axial displacement of the rotary shaft 21.

The radial magnetic bearing 26 is composed of an electromagnet 32, which is the rotor core 2 of the rotary shaft 21.
Four of them are arranged on the upper, lower, left, and right sides of the circumference of 3 through the radial gap. The radial displacement sensor 28, which is the other of the displacement sensors, detects the radial displacement of the rotary shaft 21, and is arranged at least one in each of the vertical and horizontal directions of the rotary shaft 21.

At the shaft end of the rotary shaft 21, there is provided a mechanical auxiliary bearing 33 for supporting the rotary shaft 21 instead of the magnetic bearing when the magnetic bearing cannot be controlled.
It is being fixed to 4 through the bearing bracket 34.

More specifically, in the present embodiment, the thrust magnetic bearing 25 has a pair of electromagnets 29 opposed to both side surfaces of the thrust disk 22 protruding in the radial direction of the rotary shaft 21, and each electromagnet 29 is a thrust disk. An outer diameter side coil 31a arranged on the outer diameter side of 22, an inner diameter side coil 31b arranged on the inner diameter side, and three magnetic poles 30a, 30b on the outer diameter side, the inner diameter side, and the middle that surround these coils 31a, 31b,
It is equipped with 30c.

The outer diameter side coil 31 of each electromagnet 29
The polarities of the magnetic fluxes formed by a and the inner diameter side coil 31b are set in the same direction, and the polarities of the magnetic flux formed by the outer diameter side coils 31a and the inner diameter side coils 31b that face each other with the thrust disk 22 in between. Are set in opposite directions.

Next, the operation will be described. The axial displacement of the rotary shaft 21 is detected by the thrust displacement sensor 27, and the radial displacement is detected by the radial displacement sensor 28, and converted into an electric signal. The converted electric signal is converted into a signal that stably supports the rotating shaft 21 by a control device (not shown), further power-amplified, and supplied to the electromagnet 29 of the thrust magnetic bearing 25 and the electromagnet 32 of the radial magnetic bearing 26 as a current signal. Supplied. The electromagnet 29 of the thrust magnetic bearing 25 and the electromagnet 32 of the radial magnetic bearing 26 attract the rotating shaft 21 with a magnetic attraction force corresponding to the current flowing in each coil, and stably support it without contact.

At this time, when no external force acts on the rotary shaft 21, as shown in FIG. 3, the magnetic fluxes e, f, g formed by the coils 31a, 31b of the electromagnets 29a, 29b of the thrust bearing 5 respectively. , H are their electromagnets 29a, 2
9b, for example, the rotary shaft 21 and the radial bearing 26
The electromagnet 32, the frame casing 24, and the like cancel each other out and do not flow into them.

That is, the magnetic fluxes e and f formed by the currents flowing through the coils 31a and 31b of the electromagnet 29a on the left side in FIG. 3 are all thrust disks 22 and the electromagnet 29a on the left side.
Of the three magnetic poles 30a, 30b, 30c, and the magnetic fluxes g, h formed by the coils 31a, 31b of the right electromagnet 29b are the three magnetic poles 30a, 30b of the thrust disk 2 and the right electromagnet 29b. It flows only to 30c.

This is the same when a large axial force F acts on the rotary shaft 21 (FIG. 4), and there is no change. The magnetic flux flowing through the electromagnets 29a, 29b other than the magnetic poles 30a, 30b, 30c is the electromagnet 2 of each thrust magnetic bearing 25.
Two coils 31 having the same number of turns provided on 9a and 29b
Since it is canceled by applying the same current to a and 31b, it is not related to the magnitude of the external force in the axial direction or the displacement amount.

Therefore, according to the present embodiment, the coils 31 of the electromagnets 29a and 29b of the thrust magnetic bearings 25 are arranged.
The magnetic flux formed by a and 31b is the rotary shaft 21, the electromagnet 32 of the radial magnetic bearing 26, and the frame casing 2.
4 and the like cancel each other out and flow only to the magnetic poles 30a, 30b, 30c of the electromagnets 29a, 29b of the thrust magnetic bearings 25. Therefore, even if external force acts on the rotary shaft 21 to cause a large axial displacement, the thrust magnetic bearings The control of 25 does not diverge, and the rotating shaft 21 can be stably supported.

[0028]

As described above, according to the magnetic bearing of the present invention, since the magnetic flux flowing in the rotating shaft, the radial magnetic bearing, the frame casing, etc. can be made almost zero, the suction force of the intake air due to a large external force is reduced. Even if the balance and the large axial displacement occur, the thrust magnetic bearing system does not diverge, and it is possible to stably support the magnetic bearing system.

[Brief description of drawings]

FIG. 1 is an axial sectional view of a magnetic bearing device according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line BB of FIG.

FIG. 3 is a partial axial cross-sectional view illustrating the flow of magnetic flux of the thrust electromagnet in a stable state of the magnetic bearing device according to the embodiment.

FIG. 4 is a partial axial cross-sectional view illustrating the flow of magnetic flux of the thrust electromagnet when an external force is applied in the axial direction of the magnetic bearing device according to the embodiment.

FIG. 5 is an axial sectional view of a conventional magnetic bearing device.

6 is a cross-sectional view taken along the line AA of FIG.

FIG. 7 is a partial axial cross-sectional view illustrating the flow of magnetic flux of a thrust electromagnet in a stable state of a magnetic bearing device according to a conventional technique.

FIG. 8 is a partial axial cross-sectional view for explaining the flow of magnetic flux of the thrust electromagnet when an external force is applied in the axial direction of the magnetic bearing device according to the related art.

[Explanation of symbols]

 21 rotary shaft 22 thrust disk 24 frame casing 25 thrust magnetic bearing 26 radial magnetic bearing 27 thrust displacement sensor 28 radial displacement sensor 29 (29a, 29b) electromagnet 30a outer diameter side magnetic pole 30b inner diameter side magnetic pole 30c middle magnetic pole 31a outer diameter side coil 31b Inner diameter coil

Claims (1)

[Claims] 1. A rotary shaft is supported in a non-contact manner by a thrust magnetic bearing and a radial magnetic bearing provided in a frame casing, and a current flowing through an electromagnet of each magnetic bearing is controlled by an output signal of a displacement sensor. In the magnetic bearing device, the thrust magnetic bearing has a pair of electromagnets opposed to both side surfaces of a thrust disk projecting in the radial direction of the rotating shaft, and each electromagnet is disposed on the outer diameter side of the thrust disk. The inner diameter side coil disposed on the inner diameter side of the outer diameter side coil and the magnetic poles surrounding these coils are provided, and the polarities of the magnetic fluxes formed by the outer diameter side coil and the inner diameter side coil of each electromagnet are set in the same direction. At the same time, the polarities of the magnetic fluxes formed by the outer diameter side coils and the inner diameter side coils that face each other across the thrust disk are set in mutually opposite directions. A magnetic bearing device characterized in that