JP3351174B2 - 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 structure of a brushless motor for driving a magnetic disk in which at least one magnetic disk of a magnetic disk drive is mounted and driven to rotate, and in particular, an inner diameter of a hub for mounting the magnetic disk. The present invention relates to a structure of an outer rotor type brushless motor (hereinafter referred to as a motor) in which a rotor magnet is fixed to a portion.

[0002]

2. Description of the Related Art Due to the technological trend of increasing the capacity and speed of computer systems, the rotational speed of a motor of a magnetic disk drive device is changed from 3600 rpm to 5400 rpm or 6300 rpm. In recent years, a demand of 7200 rpm is expected and it is expected that it will reach 10,000 rpm. Is done.
Also, 3.5 inch magnetic disk drives are about to replace 8 inch and 5 inch magnetic disk drives. Along with this, it is necessary to support disk arrays and MR heads in order to improve storage performance,
In particular, the MR head has a gap of 0.1 μm with the magnetic disk.
m or less, and has reached the limit in reliability. As a result, dust from the motor, grease scattering from the bearings,
In addition, outgassing requirements are only becoming very demanding.

[0003] A conventional motor will be described below. FIG. 7 is a sectional view of a conventional motor.

In FIG. 7, reference numeral 1 denotes a fixed shaft of a motor;
Is a spacer, which is located between the upper bearing 7 and the lower bearing 8 supported by the fixed shaft 1. Reference numeral 2 denotes a hub for mounting the magnetic disk 33, and a disk spacer 3 for keeping a space between the magnetic disks 33.
4 is fixed by the clamper 35 and the clamper screw 31. Heads (not shown) for writing and reading information to and from the magnetic disks 33 are in contact with both surfaces of each of the magnetic disks 33, and have a function of moving on the surfaces of the magnetic disks 33. Reference numeral 3 denotes a bracket to which the fixed shaft 1 is attached at the center and extends to the magnetic disk mounting side 29. The bracket 3 is fixed to a chassis 28 of the magnetic disk drive with mounting screws 30. Reference numeral 27 denotes a cover, and the fixed shaft 1 has mounting screws 3
Fixed at 2. Reference numeral 4 denotes a cylindrical rotor magnet fixed to the hub 2, and reference numeral 5 denotes a stator core provided at a position facing the rotor magnet 4, on which a winding 6 is wound. 13 is a lower holder. The stator core 5 is attached to the lower holder 13, and the lower holder 13 is attached to the center of the fixed shaft 1. By means of labyrinth sealing means, a fine gap A (41 in the figure) formed by the lower holder 13 and the hub 2 and a fine gap B (42 in the figure) formed by the lower holder 13 and the lower bearing 8 are used.
The grease is prevented from scattering from the lower bearing 8 and the cleanness of the clean room 36 is maintained. A preload spring 10 is located between the lower bearing 8 and the lower holder 13 and applies a preload to the upper bearing 7 and the lower bearing 8. Reference numeral 9 denotes a stator substrate, which is attached to the bracket 3. A position detecting element 15 for controlling the excitation of the winding 6 is arranged on the stator substrate 9. Reference numeral 11 denotes an upper magnetic fluid seal, which holds a magnetic fluid 16 between itself and the fixed shaft 1 to prevent grease from scattering from the upper bearing 7 and the lower bearing 8. Reference numeral 14 denotes a magnetic fluid seal holder that holds the upper magnetic fluid seal 11, and is fixed to the hub 2. Reference numeral 19 denotes an adhesive which hermetically secures the upper magnetic fluid seal 11 to the magnetic fluid seal holder 14. The adhesive is preferably a UV-curable or epoxy-based thermosetting adhesive. Reference numeral 17 denotes a magnetic fluid protection plate for preventing scattering of the magnetic fluid, which is hermetically fixed to the magnetic fluid seal holder 14 with an adhesive 18. The adhesive 18 uses the same kind of adhesive as the adhesive 19.

[0005] The cleanliness of the motor configured as described above will be described with reference to Figs.

FIG. 8 is a diagram showing a state of pressure distribution in the conventional motor shown in FIG. Here, A to E in FIG.
These correspond to the following sections A, B, C, D, and E. When the winding 6 is energized, an electromagnetic force is generated between the rotor magnet 4 and the rotor magnet 4, and the rotor magnet 4, the hub 2, and the magnetic disk 33 rotate integrally. At this time, the air flows from the portion E to the inside of the lower bearing 8, and a minute gap B (42 in the figure) formed by the lower holder 13 and the lower bearing 8 and a minute gap A between the hub 2 and the lower holder 13.
(In the figure, 41), it flows into the clean room 36 through C part.
This flow is shown by the air flow 40. The external space 39 indicated by A in the drawing has a pressure of 0 mmAq.
The portion E has a negative pressure due to the movement of air, and the portions B and C also have a negative pressure due to the pump action. Conversely, air accumulates in part D and the pressure increases.

[0007]

However, in the above-described conventional configuration, the rotation speed is low, for example, from 5400 rpm to 6300 rpm.
No problem up to rpm. However, as the rotation speed increases, the pressure difference between the motor and the magnetic disk increases,
The inside of the motor has a large negative pressure level. Thus, the air inside the motor is pulled, and the grease is scattered to the clean room 36 where the magnetic disk is located. Furthermore, the level of cleanliness becomes sharper than the reduction of the head gap, and there is a problem that a head crash or a malfunction of writing and reading of information occurs.

An object of the present invention is to solve the above-mentioned conventional problems, and a first object of the present invention is to provide a motor which keeps the cleanliness of a clean room high with respect to high revolutions. It is a second object of the present invention to provide a motor that eliminates the pressure difference between the external space and the clean room caused by the above. It is a third object of the present invention to eliminate a pressure difference between the external space and the clean room during rotation and stop.

[0009]

In order to achieve this object, a motor according to the present invention comprises a fixed shaft fixed to a bracket, a hub for rotating a magnetic disk, a hub for rotating and holding the hub and supported by the fixed shaft. A motor provided with a magnetic fluid seal and a labyrinth seal (both may be a labyrinth seal, a sealing plate and a labyrinth seal) at both ends of the bearing, and having a breathing hole in the fixed shaft. It is.

[0010]

According to this structure, the pressure difference between the motor and the magnetic disk can be reduced, so that even if the air inside the motor is pulled, external air is supplied through the breathing hole (external air with poor cleanliness). Use a filter to keep the cleanliness from entering the clean room as it is). Air in the space of the bearing portion is less likely to come out of the labyrinth seal. Therefore, it is possible to prevent the grease generated from the bearing from scattering at high rotation without complicating the labyrinth seal structure. In addition, due to heat generation inside the motor and changes in environmental temperature, an air flow is generated through the breathing hole, so that a pressure difference can be eliminated during both rotation and stop.

[0011]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

The same parts as those in the conventional configuration are denoted by the same reference numerals as in the conventional example, and the description thereof is omitted.

FIG. 1 is a sectional view of a motor according to a first embodiment of the present invention. In FIG. 1, reference numeral 101 denotes a fixed shaft of a motor, and a breathing hole 38 is provided.
Reference numeral 113 denotes a lower holder, which is attached to the center of the fixed shaft 101. Reference numeral 103 denotes a bracket on which the fixed shaft 101 is fixed at the center and the stator core 5 is attached. Reference numeral 37 denotes a filter, which is fixed with an adhesive tape or the like and collects dust so that the dirty air in the external space 39 does not enter the clean room 36.

The cleanness of the motor configured as described above will be described. FIG. 2 is a pressure distribution in the embodiment of the present invention. This will be described with reference to FIGS.

When the winding 6 is energized, an electromagnetic force is generated between the winding 6 and the rotor magnet 4.
The hub 2 and the magnetic disk 33 rotate integrally. At this time, air moves from the external space 39 through the filter 37 to the cleaning chamber 36 through the breathing hole 38 of the fixed shaft 101. That is, it corresponds to the flow 140 of the air. The pressure is the same in the portions a, b, and c and becomes 0 mmAq. The portion e is substantially equal to the portions a, b and c due to the channel resistance of the minute gap A41 formed by the hub 2 and the lower holder 113 and the minute gap B42 formed by the lower holder and the lower bearing 8. As the air gap between the minute gap A41 and the minute gap B42 becomes smaller, the pressure of the part e becomes a part, b part, and c.
Part and even more. Outer diameter part d of the magnetic disk 33
In the portion, the pressure increases due to the pumping action as the magnetic disk 33 rotates. The motor of the present invention has e
Air moving from the section can be minimized.

Although there is no pressure difference when the fixed shaft 101 is stopped, the external space 39 and the clean room 3
6, a flow of air is generated by the breathing hole 38 in the present invention.
6 can be eliminated. Further, even during rotation, the pressure in the clean room 36 increases due to heat generation inside the motor,
Also in this case, air flow is generated from the clean room 36 to the external space 39 by the breathing hole 38, and the pressure difference can be eliminated.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. The same parts as those in the configuration of the first embodiment of the present invention are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 3 is a sectional view of a motor according to a second embodiment of the present invention. In FIG. 3, reference numeral 201 denotes a fixed shaft, on which a breathing hole 138 is provided. In this case, the flow of air is the same as in the conventional example, but the pressure distribution is close to 0 mmAq and the pressure difference is smaller than in the conventional example. Further, similarly to the first embodiment, even when heat is generated inside the motor and the environmental temperature changes, an air flow is generated through the breathing hole 138, so that the pressure difference can be eliminated during both rotation and stop.

Embodiment 3 Hereinafter, a third embodiment of the present invention will be described with reference to the drawings. The first of the present invention
The same parts as those in the configuration of the second embodiment are denoted by the same reference numerals, and description thereof is omitted.

FIG. 4 is a sectional view of a motor according to a third embodiment of the present invention. In FIG. 4, reference numeral 301 denotes a fixed shaft, on which a breathing hole 238 is provided. Numeral 37 denotes a filter which collects dust so that the dirty air in the external space 39 does not enter the clean room 36.

The cleanness of the motor configured as described above will be described. FIG. 5 shows a pressure distribution in the third embodiment of the present invention. This will be described with reference to FIGS.

When the winding 6 is energized in the same manner as in the first embodiment, an electromagnetic force is generated between the winding 6 and the rotor magnet 4, and the rotor magnet 4, the hub 2, and the magnetic disk 3
3 rotates together. At this time, it passes through the filter 37 from the external space 39, passes through the breathing hole 238 of the fixed shaft 301, passes through the minute gap B42 formed by the lower holder 13 and the lower bearing 8, and the minute gap A41 formed by the hub 2 and the lower holder. The air moves to the clean room 36. That is,
It corresponds to the flow 240 of air. Further, the pressure becomes 0 mmAq in the f section, becomes slightly negative in the j section, and becomes slightly negative in the g section and the h section. The pressure of the portion i is increased by the pump action. In this structure, it is better to set the small gap A41 and the small gap B42 to be smaller, but it is larger than the gap of the shield plate of the bearing, and the pressure in the j, g, and h portions approaches 0 mmAq to prevent the grease from scattering. You can also. Further, similarly to the first and second embodiments, the flow of air is generated through the breathing hole 238 due to the heat generation inside the motor and the change in the environmental temperature, and the pressure difference can be eliminated during both rotation and stop.

(Embodiment 4) A fourth embodiment of the present invention will be described below with reference to the drawings. The same components have the same reference characters allotted, and description thereof will not be repeated.

FIG. 6 is a sectional view of a motor according to a fourth embodiment of the present invention. In FIG. 6, reference numeral 401 denotes a fixed shaft, on which a breathing hole 338 is provided. Numeral 37 denotes a filter which collects dust so that the dirty air in the external space 39 does not enter the clean room 36. Reference numeral 43 denotes a sealing plate, which is hermetically fixed by an adhesive 44. UV as adhesive
Curing type or thermosetting type (including epoxy type) is preferable. 127 is a cover, which is an external space 39 and a clean room 3
6 is attached to the chassis to separate it.

The cleanliness and pressure distribution of the motor constructed as described above are exactly the same as in the first embodiment.
Further, similarly to the first embodiment, a flow of air is generated through the breathing hole 238 due to heat generation inside the motor and a change in environmental temperature, so that a pressure difference can be eliminated during both rotation and stop.

[0026]

As described above, the present invention maintains the cleanliness of a clean room by having a structure in which a fixed shaft is provided with a breathing hole, and is particularly effective for a high-rotation type motor. Also, the particle size of 0.1 μm or more satisfies the class of 100 or less (1CF), and the grease scattered from the bearing adheres to the magnetic disk and the head crash can be reduced. Also, it is only necessary to machine the breathing hole on the shaft without the need for a complicated and expensive machining labyrinth structure for high rotation, and the dimensional tolerance of the breathing hole may be large, so it is excellent in cost. I have. In addition, when the temperature of the heat generating environment inside the motor changes, an air flow is generated through the breathing hole, so that the pressure difference can be eliminated during both rotation and stop.

[Brief description of the drawings]

FIG. 1 is a sectional view of a brushless motor according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a pressure distribution in the brushless motor shown in FIG.

FIG. 3 is a sectional view of a brushless motor according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a brushless motor according to a third embodiment of the present invention.

FIG. 5 is a diagram showing a pressure distribution in the brushless motor shown in FIG. 3;

FIG. 6 is a sectional view of a brushless motor according to a fourth embodiment of the present invention.

FIG. 7 is a sectional view of a conventional brushless motor.

FIG. 8 is a view showing a pressure distribution in the brushless motor shown in FIG. 7;

[Explanation of symbols]

 1, 101, 201, 301, 401 Fixed shaft 2 Hub 3, 103 Bracket 4 Rotor magnet 5 Stator core 6 Winding 7 Upper bearing 8 Lower bearing 9 Stator substrate 10 Preload spring 11 Upper magnetic fluid seal 12 Spacer 13, 113 Lower holder 14 Magnetic fluid seal holder 15 Position detecting element 16 Magnetic fluid 17 Magnetic fluid protection plate 18, 19, 44 Adhesive 27, 127 Cover 28 Chassis 29 Magnetic disk mounting side 30, 32 Mounting screw 31 Clamper screw 33 Magnetic disk 34 Disk spacer 35 Clamper 36 Clean room 37 Filter 38, 138, 238, 338 Breathing hole 39 External space 40, 140, 240 Air flow 41 Micro gap A 42 Micro gap B 43 Seal plate

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-61884 (JP, A) JP-A-7-107696 (JP, A) JP-A-5-336717 (JP, A) JP-A-3- 285548 (JP, A) JP-A-4-140040 (JP, A) JP-A-62-180563 (JP, A) JP-A-6-2980 (JP, U) JP-A-3-91067 (JP, U) (58) Field surveyed (Int.Cl. ⁷ , DB name) H02K 29/00 H02K 21/00 H02K 5/10 H02K 5/16 H02K 5/173

Claims (2)

(57) [Claims] 1. A bracket for mounting and fixing to a magnetic disk drive, a fixed shaft fixed toward the magnetic disk mounting side of the bracket, a hub for rotating a magnetic disk, a rotor magnet, and the rotor magnet A stator core provided with a winding provided opposite to the rotor, an upper bearing and a lower bearing which rotate and hold the hub and are disposed above the stator core, and a magnetic fluid seal is provided above the upper bearing. provided, comprising a labyrinth seal on the lower side of the lower bearing, a breathing hole for introducing outside air is provided on the fixed shaft, wherein the breathing hole, the Sutetako
And the space having the rotor magnet and the outside air
Binding to, a brushless motor having a filter on the breathing hole. 2. The brushless motor according to claim 1, wherein a sealing plate is provided above the upper bearing, and a labyrinth seal is provided below the lower bearing.