JPS62221855A - Dc brushless motor - Google Patents

Abstract

PURPOSE:To eliminate a leakage of magnetic flux ranging from a rotor magnet and a seal magnet to a magnetic disc supported by a rotor by providing the seal magnet magnetized in a prescribed state between a motor housing and the rotor. CONSTITUTION:A magnetic fluid seal 32 is provided between a motor housing 21 and a rotor 25 supported by this housing 21 through a bearing 24. Poles of a seal magnet 33 of this magnetic fluid seal 32 as many as poles of a rotor magnet 31 furnished at the rotor 25 are subjected to magnetization while this seal magnet 31 is fitted at the rotor 25 and the polarities of magnetically opposite poles of both magnets 31, 33 are made to differ from each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a DC brushless motor used to rotate a magnetic disk in a magnetic storage device.

[Conventional technology]

FIG. 5 shows a conventional DC brushless motor for driving a magnetic disk, in which 1 is a motor housing, 2 is a stator, 3 is a bearing, and 4 is a rotor. The rotor 4 has a hub 6 connected to one end of a rotating shaft 5 supported by a bearing 3, and a rotor yoke 8 connected to the other end via a connecting member 7.
It becomes by concatenating. A rotor magnet 9 is attached to the rotor yoke 8, which is magnetized into, for example, four poles, and whose inner circumferential surface faces the circumferential surface of the stator 3. A magnetic fluid seal 10 is provided between the motor housing 1 and the hub 6 of the rotor 4.
This prevents volatile components from the lubricating oil of the bearing 3 and fine particles from entering the rotor yoke 8 side to the magnetic disk side supported by the hub 6.

This magnetic fluid seal 10 has ring-shaped magnetic plates 12 adhered to both sides of a ring-shaped seal magnet 11, and a seal sleeve 13 on the outer surface of a rotating shaft fitting cylinder 6a provided on a hub 6. The magnetic fluid 14 is held between the outer circumferential surface of the sleeve 13 and the inner circumferential surface of the seal magnet 11. As illustrated in FIG. 6, the seal magnet 11 has only one pole (for example, S pole) on the outer circumference, and the other pole (for example, the S pole) on the inner circumference.
For example, those magnetized along the radial direction so that only the north pole is used are used. In addition, in FIG. 5, 15 is a sleeve inserted between the bearings 3, and 16 is a motor housing 1.
This is a magnetic shield plate attached to.

[Problem that the invention seeks to solve]

In this way, in the conventional DC brushless motor, the seal magnet 11 is attached to the fixed motor housing 1 with respect to the rotor magnet 9, so as the rotor 4 rotates, the magnetic poles of the rotor 4 and the magnetic poles of the seal magnet 11 change. The positional relationship changes.

For this reason, for example, as mentioned above, the rotor magnet 9 is
When the magnet 9 is polarized, the two magnetic poles of the magnet 9 always magnetically repel as the rotor 4 rotates due to the relationship with the polarity of the seal magnet 11. Separate magnetic fields are formed in the magnetized acid portions of each magnet 9 and 11 where magnetic repulsion has occurred, as indicated by arrows in FIG. 5.

However, since the above leakage magnetic flux from the rotor magnet 9 can be blocked by the magnetic shield plate 16, it will not have an adverse effect on the magnetic disk (not shown) supported by the hub 6. The problem was that it required . Along with this, the magnetic shield plate 16 has a seal magnet 11 disposed on the hub 6 side.
Since leakage magnetic flux from the hub 6 cannot be blocked, there is a problem in that this leakage magnetic flux has an adverse effect on the magnetic disk supported by the hub 6.

[Means for solving problems]

The present invention magnetizes a seal magnet of a magnetic fluid seal provided between a motor housing and a rotor supported by this housing via a bearing to have the same number of poles as the rotor magnet provided in the rotor. By attaching this seal magnet to the rotor and making the polarities of the magnetically opposing magnetic poles of these two magnets different from each other, the conventional problems described in - are solved.

[Effect]

In the direct current brushless motor equipped with the above solution, by attaching the seal magnet to the rotor provided with the rotor magnet, the magnetic opposing relationship between these two magnets can be kept constant. The above magnetic relationship, which is maintained constant in this way, is maintained by magnetizing the seal magnet to have the same number of poles as the rotor magnet, and
Since both of these magnets are arranged so that their different poles are magnetically opposed to each other, the magnetic path can always be closed and leakage magnetic flux can be eliminated.

〔Example〕

In FIGS. 1 to 4 showing one embodiment of the present invention, reference numeral 21 denotes a motor housing made of non-magnetic metal, and a through hole 22 is provided approximately in the center of the motor housing. A stator 23 is attached to the motor housing 21. The stator 23 is formed by winding a phase winding around each salient pole of a stator core formed by laminating a plurality of silicon steel plates.

A pair of bearings 24 are provided in the through hole 22 of the motor housing 21.
are installed internally, and a rotating shaft 26 made of a non-magnetic metal included in a rotor 25 is supported through these bearings 24 . In addition, 27 in FIG. 1 is a sleeve that fits into the middle portion of the rotating shaft 26 and is provided with both ends abutting the inner rings of the pair of bearings 24, and is made of magnetic metal.

The rotor 25 includes a rotating shaft 26, a non-magnetic metal hub 28 connected to one end of the rotating shaft 26, and a magnetic hub 28 connected to the other end of the rotating shaft 26 via a magnetic metal connecting member 29. It is formed from a metal rotor yoke 30 and a ring-shaped rotor magnet 31 attached to the inner peripheral surface of the yoke 30.

The hub 28 supports a magnetic disk (not shown). The inner circumferential surface of the rotor magnet 31 is opposed to the outer circumferential surface of the stator 23, and the magnet 31 is magnetized, for example, into four poles along the radial direction as shown in FIG.

A magnetic fluid seal 32 is provided between the motor housing 21 and the rotor 25.

The magnetic fluid seal 32 includes a ring-shaped seal magnet 33, a ring-shaped magnetic plate 34 attached to both sides of the magnet 33, a magnetic metal seal sleeve 35, and a magnetic fluid 3δ. It is formed from.

The seal magnet 33 used is one magnetized to have the same number of poles as the rotor magnet 31, as shown in FIG. Note that the arrows in FIG. 2 each indicate the direction of magnetization. And this seal magnet 33
and the magnetic plates 34 arranged on both sides of the rotor 25
is attached to the back surface of the hub 28 provided with the hub 28. Moreover,
The seal magnet 33 is attached to the rotor 25 in a magnetically opposing relationship between its magnetic pole and the magnetic pole of the rotor magnet 31, as shown in FIG. It is done with different considerations. Further, the seal sleeve 35 is attached to the hub-side end of the motor housing 21 with a gap provided therebetween. At the same time, the magnetic fluid 36 is held within a small gap between the outer peripheral surface of the seal magnet 33 and the inner peripheral surface of the seal sleeve 35 arranged as described above.

In the outer rotor type DC brushless motor having the following configuration, the magnetic fluid 36 is a seal magnet.
3 and a magnetic circuit formed across the magnetic plate 34 and the sealing sleeve 35, the sealing magnet 33 and the sealing sleeve 35 are held within a small gap.

As a result, the rotor 25 is allowed to rotate, and a seal is formed between the rotor 25 and the motor housing 21, so that volatile components from the π1 lubricant of the bearing 24 and fine particles from the rotor yoke 30 side are transferred to the magnetic disk side. can prevent intrusion.

In this DC brushless motor, by attaching the seal magnet 33 to the rotor 25 including the rotor magnet 31, the magnetic opposing relationship between the two magnets 31 and 33 can be kept constant regardless of the rotation of the rotor 25. Furthermore, the above magnetic relationship, which is maintained constant in this way, is maintained by magnetizing the seal magnet 33 to have the same number of poles as the rotor magnet 31, and by magnetizing both magnets 31 and 33 as shown in FIG. Since the arrangement is such that the different poles are magnetically opposed to each other, both magnets 31.
In order to prevent magnetic repulsion between the
The magnetic path between both magnets 31 and 33 can always be closed.

In other words, the inner circumferential extension 1 of the rotor magnet 31 is the north pole and the outer circumferential side is the south pole, and the seal magnet 33
As shown by the arrow in FIG. 2, the N pole of the rotor magnet 31 is A magnetic path is formed from the poles to the S pole of the seal magnet 33 through the stator 23, and the seal magnet 3
A magnetic path is formed from the N pole of No. 3 through the seal sleeve 35, upper bearing = 9-24, sleeve 27, lower bearing 24, connection member 29, and rotor yoke 30 in this order to the S pole of the rotor magnet 33. be done. In addition, in other magnetic pole areas adjacent to this magnetic pole area, the polarity of the magnetic poles is opposite to the magnetic pole area described above, so the magnetic path (left side in Figure 4) is opposite to the magnetic pole area described above. (shown in half arrow)
is formed.

In this way, the magnetic path can always be kept closed, so that leakage of magnetic flux toward the magnetic disk supported by the hub 28 can be eliminated regardless of the rotation of the rotor 25. Therefore, there is no need to attach a magnetic shield plate to the motor housing 21, and the number of parts and assembly steps can be reduced, and an adverse effect on the magnetic disk can be prevented.

Although the above-mentioned embodiment is constructed as described above, in carrying out the present invention, specific modifications such as the motor housing, bearing, rotor, rotor magnet, magnetic fluid seal, seal magnet, etc. It goes without saying that the structure, shape, position, number of poles of each magnet, etc. are not limited to the one embodiment described above, and can be configured and implemented in various ways.

〔Effect of the invention〕

According to the present invention, the gist of which is the structure described in the above claims, it is possible to eliminate leakage of magnetic flux from the rotor magnet and seal magnet to the magnetic disk supported by the rotor, thereby reducing leakage magnetic flux toward the magnetic disk side. This has the effect that a magnetic shield plate for blocking can be omitted and that an adverse effect on the magnetic disk can be prevented.

[Brief explanation of drawings]

Figures 1 to 4 show an embodiment of the present invention, with Figure 1 being a longitudinal sectional side view, Figure 2 being a plan view of the magnet showing the magnetization structure of the seal magnet, and Figure 3 being a rotor magnet. FIG. 4, which is a diagram showing the positional relationship of each magnetic pole of the seal magnet, is a diagram illustrating a magnetic path in a section corresponding to the section taken along line A--A in FIG. FIG. 5 is a longitudinal sectional view showing the conventional example, and FIG. 6 is a plan view of the seal magnet used in the conventional example shown in FIG. 5, showing the magnetization structure of the same. 21... Motor housing, 24... Bearing, 25...
...Rotor, 31...Rotor magnet, 32...
Magnetic fluid seal, 33... Seal magnet.

Claims (1)

[Claims] A DC brushless motor in which a magnetic fluid seal is provided between a motor housing and a rotor supported by the housing via a bearing, wherein the rotor includes a seal magnet of the magnetic fluid seal. A direct current brushless motor characterized in that the seal magnet is magnetized to have the same number of poles as the magnet, and the seal magnet is attached to the rotor, and the polarities of the magnetically opposing magnetic poles of both magnets are made different from each other. .