JP2583645Y2 - Brushless motor - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor having a seal structure using a magnetic fluid, and more particularly to an HDD.
The present invention relates to a brushless motor suitable for driving a disk in (Hard Disk Drive) or the like.

[0002]

2. Description of the Related Art A spindle motor having a seal structure using a magnetic fluid is disclosed in, for example, Japanese Utility Model Laid-Open No. 2-139474.
Is disclosed in Japanese Patent Application Laid-Open Publication No. HEI 9-203 (1995). FIG. 3 shows the right half of a cross section along the center of rotation of such a motor. FIG. 4 is an enlarged view of the upper part of FIG. In these figures, a cylindrical hub 16 is rotatably attached to a shaft 10 via bearings 12 and 14. The shaft 10 is formed integrally with a motor base 18 at a lower portion.
8 is fixed to a HDD chassis (not shown).
Inside the lower part of the hub 16, a coil 20 with a core is provided on the shaft 10, and a magnet 22 is attached to the inner peripheral surface of the hub 16 so as to face the coil 20.

[0003] A disk holder 2 is provided on the lower outer periphery of the hub 16.
4, a hard disk 28 is held between the disk holder 24 and the clamper 26.
The upper hard disk 28 is fixed by a clamper 30 screwed to the upper surface of the hub 16. Access to the hard disk 28 is performed by the head 3
2 is performed on both sides.

A sleeve 3 is provided above the shaft 10.
The magnetic fluid seal 36 is provided on the hub 16 side so as to face the sleeve 34. A magnetic fluid 38 is filled between the sleeve 34 and the magnetic fluid seal 36, thereby performing an oil seal on the bearings 12 and 14. A top cover 40 is provided above the clamper 30 and the magnetic fluid seal 36 (see FIG. 4).

Next, the procedure for assembling the magnetic fluid seal portion will be described with reference to FIG. 5. First, the magnetic fluid seal 36 is inserted into the hub 16 by light press-fitting (step SA in FIG. 5). Next, the hub 16 and the magnetic fluid seal 36
The adhesive 42 is applied to the joint portion with (Step S)
B). Then, this motor assembly is connected to UV (Ultra Vi
olet) Place in an oven to cure the adhesive 42 with ultraviolet light (step SC). Thus, the magnetic fluid seal 36
Is fixed to the hub 16, the magnetic fluid 38 is injected into the gap portion at the tip of the magnetic fluid seal 36 by a microdispenser (not shown) (step SD), and the assembly of the seal portion is completed.

When a current is applied to the coil 20 while controlling the direction of current flow, the magnetic field generated by the coil 20 and the magnetic field generated by the magnet 22 act to rotate the hub 16 in the direction of the arrow FA (or the opposite direction). . Thereby, the head 3
2, the hard disk 28 rotates.
The head 32 moves in the left-right direction in the figure to access a desired track.

[0007]

However, the above prior art has the following disadvantages. (1) Since the magnetic fluid 38 is injected using a microdispenser, an interval of about 0.8 to 1.2 mm is absolutely necessary. Therefore, when the adhesive is cured in the UV furnace, the magnetic fluid seal 36 and the magnetic fluid 38 are also irradiated with ultraviolet rays from the gap. Accordingly, the performance of the magnetic material constituting the magnetic fluid seal 36 is deteriorated, and particularly, the magnetic force is reduced by heating.

(2) As shown by arrow FB in FIG. 4, the magnetic fluid 38 may adhere to the top cover 40. Then, loss or destruction of the magnetic fluid 38 itself occurs.
Further, if the magnetic fluid 38 adheres to the disk 28 through the top cover 40, the contamination is affected and a head crash occurs. (3) As shown by the arrow FC in FIG.
When the magnetic fluid 38 adheres to the upper surface of 6 for some reason,
The magnetic fluid 38 may adhere to the disk 28 due to the reticulation phenomenon through the joint between the hub 16 and the disk holder 30, which may cause a head crash.

(4) As indicated by an arrow FD in FIG. 4, the magnetic fluid 38 may be scattered or broken by vacuum evacuation when performing a clean pack of the assembly. (5) Further, in order to prevent the above-mentioned inconveniences from occurring, considerable strictness is required for managing the height h and the injection amount of the magnetic fluid 38.

[0010] The present invention focuses on these points.
In addition to preventing a decrease in sealing performance, it also successfully reduces the adverse effects on the disk such as head crashes caused by scattering or destruction of the magnetic fluid, and simplifies the management of injection volume and height. It is an object of the present invention to provide a brushless motor capable of solving various problems described above.

[0011]

According to the present invention, there is provided a magnetic fluid seal provided outside a bearing for rotatably supporting a hub with respect to a shaft;
A sleeve by the magnetic material provided on the shaft outer circumference and the magnetic fluid seal facing said magnetic fluid seal and a magnetic fluid filled in the gap portion between the sleeve, the entire circumference with a constant gap G between the sleeve Over
Non-magnetic material magnetic fluid covering the upper side of the magnetic fluid seal
And a cover, and the outer peripheral portion of the magnetic fluid cover is irradiated with ultraviolet rays.
Brushless adhesively fixed to the hub with a hardening adhesive
A motor, provided on an outer peripheral portion of the magnetic fluid cover.
The bottom of the collar contacts the top of the magnetic fluid seal.
And the magnetic fluid seal and the Kariki magnetic fluid cover
A space having a height H is formed for
The relationship with the height H is set to satisfy G / H ≦ 0.4 .

[0012]

According to the present invention, the magnetic fluid cover is attached to the outside of the magnetic fluid seal. This cover is set so that the gap interval with respect to the sleeve is 40% or less of the height with respect to the magnetic fluid seal. For this reason, the performance deterioration of the magnetic member and the scattering of the magnetic fluid due to the ultraviolet rays at the time of curing the adhesive can be favorably prevented by the magnetic fluid cover.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a brushless motor according to the present invention will be described in detail with reference to the accompanying drawings. Note that the same reference numerals are used for the same components as those of the above-described related art or components corresponding to the related art.

FIG. 1 shows a cross section of a main part of this embodiment. Referring to FIG.
A sleeve 34 made of a magnetic material is provided on the shaft 10 side in a concave portion on one of the bearings 12 among the bearings rotatably supporting the bearing 6. A magnetic fluid seal 36 is provided on the hub 16 side. The magnetic fluid seal 36 has a configuration in which a magnet 36A is sandwiched between sealing materials 36B and 36C made of a magnetic material, and a gap between the sealing materials 36B and 36C and the sleeve 34 is filled with a magnetic fluid 38.

Further, in this embodiment, a magnetic fluid cover 50 is provided above the sealing material 36B. The magnetic fluid cover 50 is formed of a non-magnetic material,
It is bent in a crank shape on the 6 side and joined to the seal material 36B. The relationship between the height H of the magnetic fluid cover 50 with respect to the sealing material 36B and the gap G between the magnetic fluid cover 50 and the sleeve 34 is G / H ≦ 0.4, that is, when the gap G is 4
It is set to be 0% or less. The hub 16 side of the magnetic fluid cover 50 is adhered by an adhesive 42. As described later, since the magnetic fluid cover 50 is attached after the magnetic fluid 38 is filled,
There is no need to consider the space for inserting the microdispenser. Other components are the same as in the above-described conventional example.

Next, a procedure for assembling the motor of the embodiment having the above-described configuration will be described with reference to FIG. First, the magnetic fluid seal 36 is lightly pressed (or inserted).
(Step S1 in the figure). At this point, the microfluidic seal 36 is
Is filled with the magnetic fluid 38 (step S2), and then the magnetic fluid cover 50 is inserted by light press-fitting (or insertion) (step S3). An adhesive 52 is applied to the joint between the magnetic fluid cover 50 and the hub 16.
Is applied (step S4), and the motor assembly is placed in a UV furnace to cure the adhesive 52 (step S5).

Next, the operation of the embodiment constructed as described above will be described. (1) First, when the adhesive is cured in the UV furnace, the ultraviolet rays are blocked by the magnetic fluid cover 50, so that the performance deterioration of the magnetic fluid seal 36 and the magnetic fluid 38 is prevented well. Become like Especially,
It has been experimentally confirmed that when the gap interval G is set to 40 % or less of the height H, the magnetic fluid 38 is more effectively shielded from light by the diffraction phenomenon of ultraviolet rays. Is prevented.

(2) Next, the magnetic fluid 3 shown by arrows FB to FC in FIG.
Adhesion and scattering of 8 are both well prevented by the magnetic fluid cover 50. For this reason, the occurrence of a head crash due to the destruction of the magnetic fluid 38 or the deterioration of the contamination is successfully prevented. In particular, the magnetic fluid cover 50 is formed of a non-magnetic material as described above. Therefore, there is no inconvenience that a magnetic path is formed between the magnetic fluid cover 50 and the sleeve 34 or the sealing member 36B made of a magnetic material and the magnetic fluid 38 is scattered. (3) Further, since various inconveniences are prevented as described above, the strictness of the control of the height and the injection amount of the magnetic fluid 38 is greatly reduced.

<Other Embodiments> The present invention is not limited to the above-described embodiments, but includes, for example, the following. (1) Since the present invention is an improvement of a magnetic fluid sealing portion, other portions, for example, a portion of a magnetic circuit that generates torque, a portion of a disk, and the like may be appropriately configured as needed. (2) The present invention is suitable for a spindle motor of an HDD, but does not prevent application to other brushless motors.

[0020]

As described above, the brushless motor according to the present invention has the following effects. (1) Since the magnetic fluid seal and the magnetic fluid cover made of a non-magnetic material are provided outside the magnetic fluid, the ultraviolet rays are well blocked, and the performance deterioration of the magnetic part is reduced.
This has the effect of preventing the magnetic fluid from being scattered into each part and facilitating the management of the injection amount and height of the magnetic fluid. (2) The magnetic fluid cover has a gap interval of 40 in height.
% Or less, the ultraviolet rays are blocked well, the performance degradation of the magnetic part is reduced, the scattering of the magnetic fluid to each part is prevented, and the injection amount and height of the magnetic fluid can be easily controlled. Is more remarkable.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an embodiment of a brushless motor according to the present invention, taken along a rotation axis direction.

FIG. 2 is an explanatory diagram showing an assembling procedure of a main part in the embodiment.

FIG. 3 is a cross-sectional view of a conventional brushless motor provided with a general magnetic fluid seal in a rotation axis direction.

FIG. 4 is an enlarged sectional view showing a magnetic fluid seal portion of the conventional example.

FIG. 5 is an explanatory view showing an assembling procedure of a magnetic fluid seal portion of the conventional example.

[Explanation of symbols]

10 ... shaft, 12 ... bearing, 16 ... hub, 18
... Motor base, 20 ... Coil, 22 ... Magnet, 2
4: Disk holder, 26, 30 Clamper, 28: Disk, 32: Head, 34: Sleeve, 36: Magnetic fluid seal, 36A: Magnet, 36B, 36C: Seal material, 38: Magnetic fluid, 50: Magnetic fluid cover , 52 ...
Adhesive, G: gap, H: height.

Claims (1)

(57) [Scope of request for utility model registration] And 1. A magnetic fluid seal provided on the outside of the bearing that rotatably supports the hub relative to the shaft, and the sleeve by the magnetic material provided in the magnetic fluid seal and opposed to the shaft periphery, wherein and magnetic fluid filled in the gap portion between the sleeve and the magnetic fluid seal, with a constant gap G between the sleeve the all around
Non-magnetic material magnetic fluid cover over the top of magnetic fluid seal
And the outer peripheral portion of the magnetic fluid cover is cured by ultraviolet rays.
Brushless mode that is adhesively fixed to the hub with an adhesive
A data, the bottom surface of the flange portion provided on the outer periphery of the magnetic fluid cover before
By contacting the upper surface of the magnetic fluid seal,
A height H between the magnetic fluid seal and the magnetic fluid cover
A space is formed, and the relationship between the constant interval G and the height H is represented by G / H ≦
A brushless motor characterized by having a value of 0.4 .