JPH04337110A - Magnetic bearing - Google Patents

Abstract

PURPOSE:To improve restoring force of a bearing and to improve rigidity thereof while usefully applying a feature of a contactless bearing, in the case of a magnetic bearing. CONSTITUTION:In the case of a structure for rotationally supporting a rotor 2 with a magnetic bearing, a gas bearing 12 is provided between thrust rotary surfaces where the rotor 2 is opposed to a stator 3, and the rotor 2 is levitation- supported from the stator 3 by overcoming rotor weight and attractive force acting among opposed magnetic poles 4 to 7 in a steady rotational condition so as to continue this condition maintained even in the case of a magnetic pole air gap E sufficiently small. Space holding protrusions 13a, 13b in the gas bearing 12 are constituted of non-magnetic ceramics to prevent the fellow opposite magnetic poles 4 to 7 from coming into contact with each other, before sufficient floating force is displayed by the gas bearing 12, and to prevent also seizure by friction of the fellow space holding protrusions 13a, 13b.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bearing, which is one type of non-contact type bearing.

0002

2. Description of the Related Art Conventional techniques for magnetic bearings include, for example, Japanese Patent Application Laid-Open Nos. 1-145420 and 2-85012. In the former example, a magnetic shield made of, for example, a superconducting material is buried between opposing magnetic poles with a comb-shaped cross section, and by concentrating the magnetic flux on the opposing magnetic poles, it is possible to improve the restoring force against external forces. are doing.

0003

[Problem to be Solved by the Invention] In order to improve the restoring force in a magnetic bearing, in addition to the above, it is necessary to increase the magnetizing force of the magnet and to reduce the opposing gap between opposing magnetic poles (hereinafter referred to as the magnetic pole gap). It is possible to think of this. Although it is not very difficult to increase the magnetic force of a magnet, it is inevitably disadvantageous in that either the space occupied by the magnet increases or the cost increases due to the use of a high-performance magnet. On the other hand, since the magnetic force changes in inverse proportion to the square of the distance, if the magnetic pole gap is set sufficiently small, the restoring force can be improved and the rigidity of the bearing can be increased. For example, by bringing the magnetic pole gap as close to zero as possible, a large restoring force can be exerted.

However, the smaller the magnetic pole gap becomes, the more difficult it becomes to maintain that state. When using a magnetic bearing as a radial bearing, a magnetic pole gap is secured in the thrust direction, but if there is even a slight play in the thrust direction in the rotating shaft, the opposing magnetic poles of the magnetic bearing will come into contact with each other and lose their function. . Additionally, it is possible to mechanically determine the positioning in the thrust direction by providing a step between the rotating shaft and the bearing that abuts each other, but in this case, friction and wear occur at the step, so non-contact bearings are used. benefits will be halved.

The present invention has been proposed in view of the above, and its purpose is to utilize the characteristics of a non-contact bearing while also reducing the restoring force of the magnetic bearing by using a gas bearing to maintain the magnetic pole gap during operation. The purpose is to realize improvement and improve its rigidity.

[0006]

[Means for Solving the Problem] In the invention of claim 1, as shown in FIG. A plurality of opposing magnetic poles (4) to (7) are arranged concentrically through a magnet (8) that generates a restoring magnetic force between both opposing magnetic poles (4) to (7) against external force.
is provided on at least one of the rotor (2) or the stator (3), and a non-magnetic material that maintains the minimum facing gap (e) between the opposing magnetic poles (4) to (7) between the thrust rotating surfaces. Gap retaining protrusion (13a) made of ceramic
, (13b), and holding protrusions (13a), (1
3b) Due to the airflow pressure flowing between the opposing magnetic poles (4) to
(7) A gas bearing (12) is required to float and support the rotor (2) from the stator (3) against the attractive magnetic force acting therebetween.

[0007]

[Operation] In the invention of claim 1, when the rotor rotation speed reaches a predetermined value, the gas bearing (12)
(13b) The airflow pressure flowing radially outward between the rotor (2) overcomes the attractive magnetic force and rotor weight acting between the opposing magnetic poles (4) to (7), and the stator (3)
) and maintain that state. At this time, the gap retaining protrusions (13a), (13) in the gas bearing (12)
b) prevents the opposing magnetic poles (4) to (7) from coming into contact with each other and maintains the function of the magnetic bearing until the rotor rotational speed reaches the above-mentioned predetermined value from the stopped state. There is. In order to prevent seizure during this startup rotation, the gap retaining protrusions (13a) and (13b) are made of non-magnetic ceramics.

As described above, when the thrust direction position of the rotor (2) is defined by the gas bearing (12) in the steady rotation state, the attractive magnetic force between the opposing magnetic poles (4) to (7) and the rotor (2) are For the external load in the thrust direction,
Since the gas bearing (12) exerts a sufficient counterforce, the magnetic pole gap (E) can be reduced in a completely non-contact state.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. 1 to 3 show a magnetic bearing according to an embodiment of the invention. In FIG. 1, the magnetic bearing consists of a rotor (2) attached to one end of a rotating shaft (1) and a stator (3) disposed below the rotor (2).
And inner and outer dual opposing magnetic poles (4) are placed on each of the opposing thrust rotating surfaces of the stator (3) via a magnetic pole gap (E).
- (7) are provided, and a ring-shaped permanent magnet (8) is embedded inside the wall of the stator (3).

The rotor (2) has a boss part (9) fitted onto the rotating shaft (1), and a disc-shaped flange part (10) continuous to the lower part of the boss part (9). A pair of opposing magnetic poles (4) and (5) is provided in a ring shape on the inner and outer peripheral edges of the lower surface of the portion (10), respectively. On the other hand, the stator (3
) is formed in the shape of a circular block, and ring-shaped opposing magnetic poles (6) and (7) are protruded from the inner and outer peripheries of the upper surface corresponding to the opposing magnetic poles (4) and (5) of the rotor (2). It will be done. The magnet (8) is arranged with the S pole located on the outside in the radial direction, and as shown by the broken line in FIG.
A symmetrical magnetic flux is formed with the central axis of the two sides in between.

Magnetic pole gap (E) of magnetic bearing during operation
A gas bearing (12) is provided between the thrust rotating surfaces to maintain the thrust rotating surfaces in a non-contact state. This gas bearing (12) has opposing magnetic poles (4) to
In order to maintain the minimum facing gap (e) of (7), a pair of upper and lower gap retaining protrusions (13a) and (13b) are provided.

[0012] The upper gap retaining protrusion (13a) is connected to the rotor (2).
), and the lower protrusion (13b) is attached to the side of the stator (3
), and both are made of non-magnetic ceramics. The lower protrusion (13b) is ring-shaped, and its upper end surface faces the opposing magnetic pole (6) with respect to the stator (3).
), (7) are fixed so as to protrude from the upper end surfaces by the dimension (a). Similarly, the upper projection (13a) is fixed such that its lower end surface protrudes by the dimension (a) from the lower end surfaces of the opposing magnetic poles (4) and (5) on the rotor (2) side. In this way, connect both protrusions (13a) and (13b) to the opposing magnetic poles (
When protruding in the opposite direction from 4) to (7), both protrusions (1
3a) and (13b) come into contact vertically before other parts, so as shown in Fig. 3, the minimum facing gap (e) between the facing magnetic poles (4) to (7) is can continue to be maintained. In addition, the above dimension (a) is 1 to several 10
It is preferable to set it in the range of μm.

As described above, the lower protrusion (13b) is formed in a ring shape, but the lower surface of the upper protrusion (13a) is
As shown in , a large number of radial spiral bodies (14), (14),
... are formed, and these are arranged at equal intervals in the circumferential direction on the flange portion (10). In other words, the upper protrusion (13a
) acts as a kind of fan blade, and when the rotor (2) rotates, the multiple radial spiral bodies (14), (14), ... in the upper protrusion (13a) create a connection with the lower protrusion (13b). In between, an airflow is generated radially outward, and this airflow pressure allows the rotor (2) to be floated and supported from the stator (3).
12) is constructed by using both upper and lower projections (13a) and (13b) as element members. In order to circulate air toward the thrust rotating surface, a ventilation passage (1) is provided in the center of the stator (3).
5) is provided in a vertically penetrating manner.

Next, the operation of the magnetic bearing will be explained. The magnetic bearing in the stopped state is a gas bearing (1) as shown in Figure 3.
The upper and lower projections (13a) and (13b) in 2) are in contact with each other. When the rotor (2) is rotationally driven from this state, the radial spiral bodies (14), (14) of the upper projection (13a)
,... creates a centrifugal airflow between the lower protrusion (13b), but since the rotor (2) is subjected to thrust loads such as the weight and the attractive magnetic force of the magnet (8), the airflow pressure The state shown in FIG. 3 is maintained until the load is overcome. During this rising rotation, the upper and lower protrusions (13a), (
13b) come into frictional contact, but since they are both made of ceramic, there will be no wear or seizure due to frictional heat.

As the rotational speed of the rotor (2) increases, the pressure of the airflow generated at the upper protrusion (13a) also increases, eventually overcoming the thrust load and causing the entire rotor (2) to move as shown in FIG. Float and support to maintain the magnetic pole gap (E). If a downward external force is applied to the rotor (2) in this state, the distance between the upper and lower protrusions (13a) and (13b) will tend to shrink, but the smaller the distance, the higher the airflow pressure will be, so the air gap will resist the external force. can continue to hold. Therefore, even if the magnetic pole gap (E) is set to be sufficiently small, that state can be reliably maintained without contact. This means that the opposing magnetic poles (4
) to (7) means that the restoring force can be improved by applying a large magnetic force, and the bearing rigidity can be improved compared to conventional magnetic bearings.

FIGS. 4 and 5 show an embodiment in which the above magnetic bearing is applied to a motor. In FIG. 4, the motor has a motor rotor (18), a rotor shaft (19) that supports this, and a stator coil (20) in a housing (17), and the upper and lower parts of the rotor shaft (19) are magnetically connected to each other. It is supported by bearings (21A) and (21B). The upper magnetic bearing (21A) is the same as a conventional magnetic bearing and is composed of a rotor (2a), a stator (3a), a magnet (8a), and the like. This bearing (21A) functions only as a radial bearing.

The lower magnetic bearing (21B) has basically the same structure as the magnetic bearing of the above embodiment, but as shown in FIG. Heavy opposing magnetic poles (22) to (29) are provided, and three gap maintaining protrusions (13) are provided between these magnetic poles (22) to (29).
A gas bearing (12) is constituted by the gap holding protrusion (13).

FIG. 6 shows an embodiment in which the form of the magnetic bearing is changed. In this embodiment, the rotor (
2) is extended into a disk shape, and opposing magnetic poles (30) to (33) are provided protruding from the inner and outer edges of the upper and lower surfaces, respectively. Further, a stator (3) is provided to sandwich the rotor (2) from above and below, and opposing magnetic poles (35) to (38) are provided protrudingly in correspondence with the opposing magnetic poles (30) to (33), and the rotor (2) is ) and the lower side wall of the stator (3), a gap retaining protrusion (13) constituting the gas bearing (12) is provided.

[0019] In addition to the above-mentioned embodiments, this invention includes the following:
For example, the following variant can be adopted. That is, the radial spiral body in the gas bearing (12) is provided on both the rotor side and the stator side of the thrust rotating surface. Furthermore, only one of the upper and lower protrusions can be made to protrude by the required amount, and the other can be made to be recessed to the same level as or more than the protruding end surface of the opposing magnetic pole.

[0020]

As explained above, in the invention of claim 1, when the rotor is rotationally supported by a magnetic bearing, a gas bearing is provided between the opposing thrust rotating surfaces of the rotor and the stator, and this gas bearing allows the steady state to be maintained. In a rotating state, an airflow is generated radially outward, and the airflow pressure overcomes the weight of the rotor and the attractive magnetic force acting between the opposing magnetic poles, allowing the rotor to float and be supported from the stator, even when the magnetic pole gap is sufficiently small. We made it possible to continue to maintain the . Therefore, according to the magnetic bearing of the present invention, the magnetic pole gap can be made sufficiently small to strengthen the attractive magnetic force that acts between the opposing magnetic poles without any problems, exert a large restoring force against rotor misalignment, and increase the rigidity of the bearing. can be improved. In addition, since spacing projections made of non-magnetic ceramics are provided on each of the thrust rotating surfaces as a component of the gas bearing, it is possible to prevent the opposing magnetic poles from coming into contact with each other before the gas bearing exerts sufficient levitation force. It is also possible to prevent seizure due to friction between the spacing projections. Moreover, since the rotor can be supported in a completely non-contact state during operation, there is no decrease in durability due to wear or fatigue, and it is advantageous in that it can be widely used in harsh environments or under adverse conditions. It is particularly suitable for rotating the rotor at high speeds of tens of thousands of revolutions per minute or more.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view of a magnetic bearing according to an embodiment of the invention.

FIG. 2 is a view taken along the line II-II in FIG. 1;

FIG. 3 is a longitudinal sectional front view of the magnetic bearing in a non-levitating state.

FIG. 4 is a schematic vertical cross-sectional view of a motor showing an example of application of a magnetic bearing.

5 is an enlarged view of the V section in FIG. 4. FIG.

FIG. 6 is a longitudinal sectional view showing another embodiment of this magnetic bearing.

[Explanation of symbols]

(2)... Rotor (3)... Stator (4)... Opposing magnetic pole (5)... Opposing magnetic pole (6)... Opposing magnetic pole (7)... Opposing magnetic pole (8)... Magnet (12)... Gas bearing (13a), ( 13b)...Gap holding protrusion (14)...Radiating spiral body (E)...Magnetic pole gap (e)...Minimum opposing gap

Claims (1)

[Claims] Claim 1: A plurality of opposing magnetic poles (4) to (7) are arranged concentrically on each of the opposing thrust rotating surfaces of the rotor (2) and the stator (3) with a magnetic pole gap (E) interposed therebetween. A magnet (8) that generates a restoring magnetic force between the opposing magnetic poles (4) to (7) against external force is provided on at least one of the rotor (2) and the stator (3), and the above-mentioned thrust Between the rotating surfaces, opposing magnetic poles (4) to (7)
It has gap holding protrusions (13a) and (13b) made of non-magnetic ceramic that maintain a minimum facing gap (e) of , and the air pressure flowing between the holding protrusions (13a) and (13b) causes A magnetic bearing characterized in that a gas bearing (12) is provided to float and support a rotor (2) from a stator (3) against an attractive magnetic force acting between (4) and (7).