JPH0366532B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a high-rigidity magnetic bearing that supports a rotor portion with respect to a stator portion without contacting the stator portion using attractive or repulsive force caused by magnetic force.

[Conventional technology]

A magnetic bearing is a bearing that uses magnetic force to support rotating objects, and its lifespan is not limited by wear or fatigue. In addition, since the frictional torque is extremely small, it has excellent compatibility with special environments such as vacuum, high temperature, and low temperature, so it has been actively researched in recent years. Examples of its uses include centrifugal separators, vacuum pumps,
It is seen as promising for use in gyroscopes, precision measuring instruments, etc.

An example of a conventional magnetic bearing will be explained with reference to the sectional view shown in FIG. This magnetic bearing has an axial center line C
A substantially cylindrical stator section 2 is arranged around a rotor section 1 that rotates around the rotor section 1 . In the stator section 2, two annular stator yokes 3, 3 made of a magnetic material such as soft iron are arranged on both sides in the axial direction along the center line C.
Two permanent magnets 4, 4 are sandwiched between the permanent magnets 3, and an annular stator yoke 5 made of a magnetic material such as soft iron is sandwiched between the permanent magnets 4, 4. Further, the rotor portion 1, which is made of a magnetic material such as soft iron, has a substantially “king”-shaped cross section, and faces the magnetic poles of the stator yokes 3, 3, and 5 via air magnetic paths 6, 6, and 7, respectively. It consists of a rotor yoke 8 having magnetic poles. The rotor yoke 8 of the rotor section 1 and the stator section 2 sandwich the empty magnetic path 7 therebetween.
The stator yoke 5 of 2 has a short axial length.
Two magnetic poles 9a, 9b and 10a, 10b are formed facing each other with an interval in the axial direction. In addition,
The permanent magnets 4, 4 have a north pole on the stator yoke 3 side and a south pole on the stator yoke 5 side, respectively.

In the magnetic bearing configured in this way, the steady magnetic flux φ emitted from the permanent magnets 4, 4 while the rotor portion 1 is rotating is vertically symmetrical to the stator yoke 3, the empty magnetic path 6, the rotor yoke 8, Magnetic poles 9a, 9b, empty magnetic path 7, magnetic poles 10a, 10
b. Since the flow sequentially passes through the stator yoke 5, an empty magnetic path 6,
When magnetic attraction forces act across 6 and 7 and these magnetic attraction forces are balanced in the horizontal direction, the rotor portion 1 is supported by the stator portion 2 without contact.
However, since the horizontal magnetic attraction force caused by the permanent magnet 4 is an unstable force, it is necessary to separately control the magnetic attraction force due to the magnetic flux of the electromagnet in order to achieve stable equilibrium, but this is a known fact. Therefore, the explanation is omitted here. Here, when the rotor section 1 and the stator section 2 are displaced relative to each other in the axial direction due to the action of an external force, the magnetic flux φ passing through the air magnetic paths 6, 6, and 7 flows between the rotor section 1 and the stator section 2. Since it has to pass diagonally, a restoring force is generated in the axial direction opposite to the displacement to correct this, and this is called the axial restoring force.

Here, since the two upper and lower empty magnetic paths 6, 6 have relatively large lengths in the axial direction of the magnetic poles on both sides, there is no large change in magnetic resistance even if there is a slight deviation from each other in the axial direction. , there is no significant change in the magnetic flux φ passing through the empty magnetic paths 6, 6, and it hardly contributes to the axial restoring force.

On the other hand, in the empty magnetic path 7, the magnetic poles 10a, 9
Since a, 10b, and 9b have short axial lengths, their magnetic flux density is higher than that of the empty magnetic path 6, and when mutual misalignment occurs in the axial direction, the axial restoring force that tries to restore it to its original state is generated. It will have a big effect. but,
Although there are concave portions between the magnetic poles 9a and 9b and between 10a and 10b, some magnetic flux φ' passes through these concave portions as well, causing deterioration of the axial restoring force, that is, the rigidity. That is, this axial restoring force depends on the axial component of the magnetic flux passing between the magnetic poles 10a, 9a and 10b, 9b, and the presence of the magnetic flux φ' causes the axial component to be reduced as a result. To become.

[Purpose of the invention]

An object of the present invention is to partially provide a magnetic shield with a very low relative magnetic permeability in the air magnetic path between the rotor and the stator, thereby allowing the magnetic flux to pass through the magnetic shield without passing through the magnetic shield. It is an object of the present invention to provide a high-rigidity magnetic bearing that allows only the magnetic pole portion without a shield to pass through and increases the axial restoring force.

[Summary of the invention]

The gist of the present invention to achieve the above objects is as follows:
It consists of a rotor part and a stator part, which rotate relative to each other without contacting each other. A magnetic circuit in which a permanent magnet is interposed between the yokes of at least one of the rotor section and the stator section, and the magnetic flux from the permanent magnet passes through the annular air magnetic path between the rotor section and the stator section and the yoke. a magnetic bearing configured to prevent relative movement of a rotor portion with respect to the stator portion in a direction perpendicular to the magnetic flux crossing the air magnetic path, the rotor portion and the stator portion facing the air magnetic path; This is a high-rigidity magnetic bearing characterized in that an annular magnetic shield having a small relative magnetic permeability is attached to at least one of the magnetic flux bearings, thereby concentrating magnetic flux in a magnetic flux passage portion having a small area.

[Embodiments of the invention]

The present invention will be explained in detail based on the embodiments shown in FIGS. 1 to 4.

FIG. 1 is a sectional view of the first embodiment of the present invention, and shows two parts of the stator yoke 5 of the conventional example shown in FIG.
An annular magnetic shield 11 is provided between the two magnetic poles 10a and 10b. This magnetic shield 11 is made of a material with extremely low relative magnetic permeability, and is said to have extremely high magnetic resistance.

In the high-rigidity magnetic bearing configured in this way, the steady magnetic flux φ emitted from the permanent magnets 4, 4 is distributed between the stator yoke 3, the air magnetic path 6, the rotor yoke 8, the magnetic poles 9a, 9b, and the air magnetic path, as shown by the solid line. The magnetic attraction force passes through the path 7, the magnetic poles 10a, 10b, and the stator yoke 5 in order, and the magnetic attraction force acts between the rotor section 1 and the stator section 2 with the air magnetic paths 6, 6, 7 in between, and the rotor section 1 Supported. Here, the magnetic flux φ passing between the rotor yoke 8 and the stator yoke 5 is caused by the magnetic shield 1 between the magnetic poles 10a and 10b of the stator yoke 5.
1, most of the magnetic flux φ passes through the magnetic poles 10a and 9a and 10b and 9b, which have low magnetic resistance, in a concentrated manner, and almost no magnetic flux φ passes through the magnetic shield 11.

Here, if the rotor part 1 and the stator part 2 are slightly misaligned in the axial direction, the magnetic flux φ emitted from the magnetic poles 9a and 9b cannot pass through the empty magnetic path 7 due to the magnetic shield 11, and is forced to The magnetic poles 10a, 1
Enter 0b. At this time, the axial component of the magnetic flux φ increases by the amount of forced bending compared to the case without the magnetic shield 11, and as a result, the axial direction that depends on the axial component of the magnetic flux φ increases. Resilience will increase.

FIG. 2 is a graph obtained by computer simulation of the relationship between axial displacement and axial restoring force of a conventional magnetic bearing and a high-rigidity magnetic bearing according to the present invention. This shows that the magnitude of the axial restoring force against displacement, that is, the rigidity, increases by about 50% compared to the conventional example shown.

In this first embodiment, the magnetic shield 11
Although there are two sets of magnetic poles facing the air magnetic path 7 provided with the above, there is no problem if there is only one set or three or more sets. In addition, actually the magnetic flux φ emitted from the permanent magnet 4
When the equilibrium of It is.

FIG. 3 shows a second embodiment, in which one stator yoke 3 and one permanent magnet 4 are provided.
The magnetic flux φ emitted from the stator yoke 3 returns to the permanent magnet 4 from the magnetic poles 10a, 10b of the stator yoke 5 via the rotor yoke 8, magnetic poles 9a, 9b. In this configuration as well, the rigidity in the axial direction is increased.

Further, FIG. 4 shows a third embodiment, in which the rotor 1
The rotor yoke 8 is approximately annular, and the center portions 12 and 13 of the rotor 1 and stator 2 are made of a non-magnetic material through which the magnetic flux φ is difficult to pass. There is. In this case, since the magnetic flux φ passes through the empty magnetic paths 6 and 7 in a direction parallel to the central axis C, the rigidity in the radial direction is strengthened.

In the first and second embodiments described above, a substantially cylindrical stator section 2 is provided around the rotor section 1.
However, it goes without saying that the same effect can be obtained even if the substantially cylindrical rotor part 1 is arranged around the stator part 2.

〔Effect of the invention〕

As explained above, the high-rigidity magnetic bearing according to the present invention concentrates the magnetic flux between the magnetic poles by attaching a magnetic shield having an extremely low relative magnetic permeability to a part of the air-magnetic path. It has the effect of increasing restoring force, or rigidity.

[Brief explanation of drawings]

Drawings 1 to 4 show an embodiment of a high-rigidity magnetic bearing according to the present invention, FIG. 1 is a sectional view of the first embodiment, and FIG. 2 is a cross-sectional view of the high-rigidity magnetic bearing of the present invention and a conventional A graph comparing the multiple forces of magnetic bearings, Figure 3.
FIG. 4 is a sectional view of the second and third embodiments, respectively, and FIG. 5 is a sectional view of a conventional magnetic bearing. 1 is a rotor part, 2 is a stator part, 3 and 5 are stator yokes, 4 is a permanent magnet, 6 and 7 are empty magnetic paths, 8 is a rotor yoke, 9a, 9b, 10a, 1
0b is a magnetic pole, and 11 is a magnetic shield.

Claims (1)

[Claims] 1 Consisting of a rotor part and a stator part, which rotate relative to each other without contacting each other, the rotor part and the stator part each have one or more annular or disc-shaped yokes made of a magnetic material, A permanent magnet is interposed between the yokes of at least one of the rotor section and the stator section, and magnetic flux from the permanent magnet passes through the annular air magnetic path between the rotor section and the stator section and the yoke. Configure the circuit and the sky
A magnetic bearing that prevents relative movement of a rotor section with respect to the stator section in a direction perpendicular to a magnetic flux crossing a magnetic path, the bearing having a relative permeability to at least one of the rotor section and the stator section facing the air magnetic path. A high-rigidity magnetic bearing characterized by attaching an annular magnetic shield with low magnetic flux to concentrate magnetic flux in a small-area magnetic flux passage section.