JPS5826265B2 - Magnetic bearing vibration damping device - Google Patents

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to a vibration damping device for a magnetic bearing.

[Prior art]

FIG. 1 shows a cross section of a conventional vibration damping device for a magnetic bearing.

A rotor yoke 2 made of a magnetic material is attached to a rotatable shaft 1, and rotor teeth 3 are integrally formed with the rotor yoke 2.

4a and 4b are permanent magnets.

These permanent magnets 4a, 4b are magnetically short-circuited by a stator yoke 5 made of a magnetic material.

A support plate 6 supports the permanent magnets 4a, 4b and the stator yoke 5.

Permanent magnets 4a and 4b are installed within the nonmagnetic conductor 7.

Nonmagnetic conductor 7 is attached to stator yoke 5.

A pair of grooves are provided on the opposite side of the stator yoke 5 of the nonmagnetic conductor 7.

These grooves are arranged on the extension line of the permanent magnets 4a, 4b in the axial direction of the shaft 1.

A pair of rotor teeth 3 provided on the rotor yoke 5 are inserted into each of the aforementioned grooves so as to form a gap with the nonmagnetic conductor 7.

A nonmagnetic conductor 7 is fixed to permanent magnets 4a and 4b.

The magnetic flux 8 generated by the permanent magnets 4a and 4b passes along the broken line in FIG.

If the shaft 1 vibrates in its radial direction, the rotor teeth 3 also vibrate in the radial direction of the shaft 1 (vibration direction 10).

Therefore, permanent magnets 4a, 4b, stator yoke 5.1
As the magnetic path consisting of the pair of rotor teeth 3 and the rotor yoke 2 vibrates in the radial direction of the shaft 1, the magnetic flux 8 also changes as will be described in detail later.

At this time, an eddy current is generated due to a change in the magnetic flux passing through the nonmagnetic conductor 7.

Since this eddy current flows so as to prevent changes in the magnetic flux 8, it acts as an allocation force and damps the vibration of the rotating body.

However, conventional vibration damping devices for magnetic bearings have not been able to achieve a large damping effect.

[Purpose of the invention]

An object of the present invention is to provide a magnetic bearing allocation device that can increase the generated eddy current and increase the vibration damping effect.

[Summary of the invention]

A feature of the present invention is that the width of some of the teeth of the rotating magnetic yoke is made thinner.

The present invention was made by studying in detail the functions of the conventional magnetic bearing vibration damping device shown in FIG.
The results of this study will be explained in detail below.

In FIG. 1, when the shaft 1 vibrates in its radial direction and swings around, the rotor teeth 3 attached to the shaft 1 also vibrate in the radial direction of the shaft 1.

Therefore, the positional relationship between the permanent magnets 4a, 4b and the rotor teeth facing them changes over time in the radial direction of the shaft 1.

At this time, since the gap length between the rotor teeth 3 and the magnets facing them also changes over time, the amount of magnetic flux passing through the gap also changes accordingly.

A change in the amount of magnetic flux means a change in the magnetic flux density in the gap.

When the above-mentioned amount of magnetic flux changes, eddy currents (9a, 9b) that try to prevent the change in magnetic flux flow in the non-magnetic conductor 7 so as to surround the magnetic flux as shown in FIG.

The polarity of the eddy currents 9a and 9b is reversed depending on when the magnetic flux is increasing or decreasing.

When the eddy current flows in the nonmagnetic conductor γ, an eddy current product is generated in the nonmagnetic conductor T.

Vibration energy of the rotating body is indirectly absorbed by this eddy current product, producing a vibration damping effect.

The larger the generated eddy current, the larger the eddy current product, and the greater the vibration damping effect.

FIG. 3 shows the vicinity of one rotor tooth 3 in FIG. 1 and the permanent magnet 4a facing it.

If the tooth width of the rotor teeth 3 is wide and equal to the width of the magnet 4a, a leakage magnetic flux 49 and 0 is generated that enters the root of the rotor teeth 3 as shown in FIG.

Therefore, the amount of magnetic flux passing through the gap between the rotor teeth 3 and the permanent magnets 4a decreases, and the magnetic flux density in the gap decreases.

The magnetic flux density is reduced, the generation of eddy currents is reduced, and the damping effect is reduced.

The magnitude of the eddy current to produce the allocation effect depends on the amount of magnetic flux passing through the air gap.

That is, even if the rotor teeth 3 vibrate in the radial direction of the shaft 1 and the gap length between the magnet 4a and the rotor tooth 3 facing it changes, the leakage magnetic flux shown in FIG. It is not affected by the magnetic resistance of the air gap.

The amount of leakage magnetic flux does not change, and no eddy current is generated based on it.

On the other hand, the rotor tooth 3 passes from the magnet 4a through the gap.
The amount of magnetic flux incident on the tip of the shaft changes due to changes in magnetic resistance in the gap caused by vibration of the rotor teeth 3 in the radial direction of the shaft 1.

Eddy currents are generated within the nonmagnetic conductor 7 due to this change in the amount of magnetic flux.

The induced voltage e for generating an eddy current in the nonmagnetic conductor T is determined by the following equation.

e=dΦ/dt (1) In other words, it can be said that the larger the magnetic flux amount Φ, the larger the induced voltage.

Moreover, the following relationship exists between the magnetic flux amount Φ and the magnetic flux density B.

Φ=B-8 (2) Therefore, if the magnetic flux passing area S is constant, the higher the magnetic flux density B is, the larger the magnetic flux amount Φ is, and therefore the induced voltage e is also larger.

That is, the higher the magnetic flux density B, the greater the generated eddy current.

From the above, in order to increase the vibration damping effect of the magnetic bearing, it is necessary to reduce the leakage magnetic flux that enters the root of the rotor tooth 3 from the magnet (the ear opening in Fig. 3), and The objective is to increase the magnetic flux incident on the tip of the hole 3 and increase the magnetic flux density B in the gap.

In the present invention, in order to increase the magnetic flux density B in the gap, the tooth width of a part of the rotor teeth is made thinner as described above.

[Embodiments of the invention]

A preferred embodiment of the present invention will be described based on FIG. 4.

FIG. 4 corresponds to the magnet 4a of FIG. 1 and the vicinity of the rotor tooth 3 facing it.

A pair of rotor teeth 11 are attached to the rotor yoke 2, extending in the axial direction of the shaft 1 and facing the magnets 4a and 4b (FIG. 1).

The rotor teeth 11 consist of a tip portion 12 with a thick tooth width and a root portion 13 with a thin tooth width.

The tooth width of the tip part 12 is equal to the width of the magnet, and the tooth width of the root part 13 is thinner than that of the magnet.

The length of the tip 12 facing the magnet in the axial direction is short.

In this embodiment having such a structure, the only magnet A leaks from the magnet 4a to the rotor yoke 2 side, as shown in FIG.

No leakage magnets such as those shown in Figure 3 and C are generated.
These magnetic fluxes are guided to the tip 12 in a concentrated manner.

That is, in this embodiment, the tips 12 of the rotor teeth 3 are separated from the magnets.
The magnetic flux incident on is increased compared to that in FIG.

This leads to an increase in the magnetic flux density in the gap portion.

When shaft 1 vibrates in its radial direction (vibration direction 10),
As described above, due to the change in the magnetic resistance of the gap, an eddy current 9a is generated in the nonmagnetic conductor 7 so as to surround the magnetic flux in the gap, as shown in FIGS. 4 and 5.

In this embodiment, since the leakage magnetic flux is small, the change in the amount of magnetic flux due to the change in magnetic resistance is also large, and as a result, the eddy current generated in the nonmagnetic conductor T becomes large.

Therefore, the eddy current product also increases, and the vibration damping effect of the rotating body increases.

Furthermore, since the spread of magnetic flux can be suppressed, it is also possible to reduce the thickness of the nonmagnetic conductor in the radial direction, resulting in the effect of weight reduction.

〔Effect of the invention〕

According to the present invention, by reducing the thickness of a portion of the rotor teeth, it is possible to prevent the spread of magnetic flux and to concentrate the magnetic flux at the tips of the rotor teeth.

This increases the magnetic flux density in the gap within the nonmagnetic conductor, generating a large eddy current and providing a magnetic bearing with a large distribution effect.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a conventional magnetic bearing vibration damping device, Fig. 2 is a sectional view taken along the line ■-■ in Fig. 1, Fig. 3 is a detailed view of the vicinity of the rotor teeth of the magnet 4a in Fig. 1, and The figure is a detailed view of the main parts of a vibration damping device for a magnetic bearing, which is an embodiment of the present invention, and FIG.
■It is a sectional view. 2...Rotor yoke, 4a, 4b...Permanent magnet, 5
... Stator yoke, 7... Nonmagnetic conductor, 11...
- Rotor teeth, 12...tip part, 13...root part.

Claims (1)

[Claims] 1. A rotating magnetic yoke having a plurality of teeth, a non-magnetic conductor for eddy current generation fixed with a plurality of annular grooves into which each of the teeth is inserted, and a non-magnetic conductor for generating an eddy current fixed to each of the teeth. In a vibration damping device for a magnetic bearing, which includes a plurality of magnets provided oppositely on the non-magnetic conductor and a stator yoke in contact with each of the magnets, the tooth width of the teeth of the magnetic yoke is A magnetic bearing allocation device characterized in that the width is equal to the width of the magnet facing the tip at the tip, and thinner than the width of the magnet at the base side of the tooth.