JP2000116050A - Spindle motor for driving recording disc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize labyrinth seal action surely and stably while preventing oil migration. SOLUTION: A microgap 17c is formed at a position facing the end face of the inner ring 7b or outer ring 7a of a ball bearing 7 closely thereto between an outer circumferential side labyrinth bush 17b and an inner circumferential side labyrinth bush 17a. Furthermore, a tapered face defining an annular recess 20 in conjunction with the outer circumferential of a shaft 2 is formed at least the ball bearing side end part of the inner circumferential surface of the inner circumferential side labyrinth bush 17a. According to the structure, oil oozing out from the ball bearing 2 can be prevented from flowing out to the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor incorporated in various OA equipment and used for a rotary drive of a recording disk such as a magnetic disk or a magneto-optical disk.

[0002]

2. Description of the Related Art In a disk drive device which rotates a recording disk such as a magnetic disk by a spindle motor, when fine particles such as dust adhere to the disk surface when the disk is driven, a head for reading and writing data to and from the disk is provided. Particles such as dust may enter between, causing data destruction or head crash, and when reading / writing data from / to the recording disk,
Inconvenience occurs.

[0003] For this reason, it is necessary to keep the disk accommodating chamber in the disk drive device clean, but at the same time, it is necessary to prevent dust from flowing out from inside the spindle motor that rotates the disk. In particular, a ball bearing is used inside the motor to rotatably support the rotor, but in order to prevent grease as a lubricant contained in the ball bearing from becoming fine particles at the time of rotation and diverging, various types of conventionally have been used. A seal structure is adopted.

FIG. 3 shows a conventional spindle motor having such a seal structure. A shaft 2 is integrally formed at a central portion of a bracket 1 as a stationary member, and a stator 3 is fixed on the bracket 1 concentrically with the shaft 2. A rotor hub 4 as a rotating member is connected to the shaft 2 via a pair of ball bearings 7 and 8.
Are rotatably supported. A rotor magnet 5 is supported on the rotor hub 4 via a yoke 11, and the rotor magnet 5 faces the stator 3 via a slight gap.

[0005] An annular labyrinth bush 6, which constitutes sealing means, is arranged outside the motor between the rotor hub 4 and the shaft 2. This labyrinth bush 6
Is located immediately above the ball bearing 7, the outer peripheral surface of the labyrinth bush 6 is on the inner peripheral surface of the rotor hub 4, and the bottom surface 6 a
Are fixed by using an adhesive in a state where they are in contact with the end surface of the outer ring of the ball bearing 7. Labyrinth bush 6
The inner peripheral surface of the small shaft 1 has a small gap 1 on the outer peripheral surface of the fixed shaft 2.
5a, the labyrinth seal is formed, and a small gap is also formed between the bottom surface 6a of the labyrinth bush 6 and the end surface of the inner ring of the ball bearing 7,
Enhances the sealing effect. In addition, a minute gap forming a labyrinth seal is also formed between the inner peripheral surface of the annular concave portion of the bracket 1 and the outer peripheral surface of the yoke 11.

[0006] In these labyrinth seal structures, when the air pressure inside and outside the motor is kept in an equilibrium state, an air layer is formed in a minute gap forming the air, and substantially no air flows between the inside and outside of the motor. The fine particles of
The air does not pass through the minute gap because of being blocked by the air layer, and leakage to the outside of the motor is suppressed. Even if there is a pressure difference between the inside and outside of the motor, the air layer acts as a resistance, so that leakage of fine particles such as grease is suppressed.

[0007]

However, in the spindle motor having the above-mentioned structure, a sealing effect is exerted on dust scattered from the ball bearings 7, 8, etc., but grease in the ball bearing is transmitted along the surface of the member. It has no deterrent effect on soaking, so-called oil migration. In particular, there is a problem that the seepage of oil along the peripheral surface of the shaft 2 via the end surface of the inner ring of the ball bearing cannot be substantially prevented.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and has as its object to prevent oil migration and at the same time achieve a stable and reliable labyrinth sealing effect. An object of the present invention is to provide a disk drive spindle motor.

[0009]

In order to achieve the above object, a spindle motor according to the present invention comprises a rotor hub on which a shaft and a recording disk are mounted, and a pair of rotor hubs interposed between the shaft and the rotor hub. A spindle motor having a labyrinth sealing means, which is located between the shaft and the rotor hub on the outside of the motor of the ball bearing, and substantially seals the inside and outside of the motor. A sealing means, an annular outer labyrinth bush fixed to the inner peripheral side of the rotor hub, an annular inner labyrinth bush fixed to the outer peripheral surface of the shaft,
It is characterized by comprising an annular minute gap formed between the inner peripheral surface of the outer labyrinth bush and the outer peripheral surface of the inner labyrinth bush.

On the outer side of the motor of the ball bearing, an annular minute gap is formed between the outer labyrinth bush fixed to the rotor hub and the inner labyrinth bush fixed to the shaft. By forming an air layer in the minute gap by the relative rotation, the leakage of fine particles such as scattered grease from the ball bearing to the outside of the motor is suppressed. The grease inside the ball bearing oozes along the surface of the member, but even if it oozes out from the inner ring of the ball bearing to the shaft surface, it further oozes due to the presence of the inner labyrinth bush fixed to the shaft surface. Delivery is suppressed.

In the above spindle motor, a tapered surface which forms an annular recess between the outer peripheral surface of the shaft and the outer peripheral surface of the shaft is formed at least on the inner peripheral end of the inner peripheral labyrinth bush on the ball bearing side. desirable.
When grease in the ball bearing tries to ooze along the inner ring surface and the shaft surface, the grease is stored and retained in the annular concave portion by the surface tension of the grease. Therefore, neither subsequent outflow nor scattering occurs.

In this case, it is preferable that an outer tapered surface having a taper angle substantially equal to the tapered surface on the ball bearing side is also formed on the inner peripheral side of the inner peripheral labyrinth bush on the inner peripheral side in the axial direction. By doing so, the inner peripheral labyrinth bush may be mounted either up or down when assembling the motor, and there is no directionality of the parts, so that the assembling work is remarkably improved.

In the spindle motor, it is preferable that the minute gap of the labyrinth sealing means is opposed to an end surface of an inner ring or an outer ring of the ball bearing. If a pressure difference occurs between the inside and outside of the motor, especially when the pressure inside the motor rises, the air inside the motor tries to flow out through the small gap, but the small gap faces the end face of the inner ring or outer ring of the bearing. Then, the gap between the labyrinth bush and the end face becomes the resistance of air from the inside of the motor to the minute gap, and the sealing effect is further enhanced.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described in detail with reference to FIGS. In the drawings, the same reference numerals as those described in the related art indicate the same or corresponding parts.

FIG. 1 is an overall sectional view showing a first embodiment of the spindle motor according to the present invention, and FIG. 2 is a partially enlarged view of the labyrinth sealing means of FIG. .

The spindle motor shown in FIG. 1 has a substantially dish-shaped bracket 1 having an annular groove as a stationary member. The bracket 1 includes an annular flange portion 1a provided at the outermost periphery and an outer peripheral wall portion 1b located inside the annular flange portion 1a.
And an annular bottom portion 1 formed at an inner lower portion of the outer peripheral wall portion 1b
c. A large-diameter inner peripheral wall 1 is provided inside the bottom 1c.
d and a small-diameter inner peripheral wall 1e are provided. Further, at the center of the small-diameter inner peripheral wall portion 1e, a columnar shaft 2 is provided integrally extending in the axial direction.

A stator 3 is fitted and fixed to the outer peripheral surface of the small-diameter inner peripheral wall 1e of the bracket 1, and is supported on the upper surface of the large-diameter inner peripheral wall 1d. The stator 3 includes a stator core 3a
And the stator coil 3b is wound. An annular insulating paper 9 is attached to the upper surface 1f of the bottom 1c of the bracket 1 in order to ensure insulation from the opposed stator coil 3b.

Reference numeral 4 denotes a rotor hub formed in a substantially annular bowl shape as a rotating member. The rotor hub 4 is made of, for example, an aluminum alloy or the like, and has a cylindrical base 4a fitted into a central hole of a recording disk (not shown), and a flange formed on the outer periphery of the lower end of the base 4a and on which the recording disk is mounted. 4b. A cylindrical yoke 11 is caulked and fixed below the flange portion 4b, and a cylindrical rotor magnet 5 is adhesively fixed to the inner periphery of the yoke 11.

In the inner peripheral portion of the rotor hub 4, bearing holding holes 10a and 10b are provided vertically, and the upper bearing holding hole 10a is provided.
Further, a large-diameter fitting hole 10c is formed on the upper side. The rotor hub 4 is rotatably supported on the shaft 2 of the bracket 1 with first and second ball bearings 7 and 8 interposed as a pair of bearing members. The first and second ball bearings 7 and 8 have respective outer rings 7a and 8a fitted and held in bearing holding holes 10a and 10b of the rotor hub 4, respectively.

Further above the first ball bearing 7 located above the pair of ball bearings 7 and 8,
An annular outer labyrinth bush 17b and an annular inner labyrinth bush 17a that constitute labyrinth sealing means are arranged. Outer labyrinth bush 1
Reference numeral 7b is fitted into the large-diameter fitting hole 10a of the rotor hub 4, and is fixed using an adhesive with its bottom surface in contact with the upper end surface of the outer ring 7a of the first ball bearing 7. The inner peripheral side labyrinth bush 17a is connected to the outer peripheral side 2a of the shaft 2.
It is fixed to. An annular micro gap 17c having a labyrinth sealing function is formed between the outer peripheral surface of the inner labyrinth bush 17a and the inner peripheral surface of the outer labyrinth bush 17b. The inner diameter of the outer labyrinth bush 17b and the outer diameter of the inner labyrinth bush 17a are formed smaller than the outer diameter of the inner ring 7b of the ball bearing 7. Therefore, the minute gap 17c faces the upper end surface of the inner ring 7b. I have. Here, the inner labyrinth bush 17a and the outer labyrinth bush 17b
Of the inner ring 7b with respect to the upper end surface of the inner ring 7b.
7d.

Here, the inner circumferential labyrinth bush 17a
In the inner peripheral portion, tapered surfaces 18a and 18b formed by chamfering or the like at the axial end portions, that is, upper and lower end portions, are formed at the same taper angle with respect to the axial center, and the inner peripheral labyrinth bush 17a is provided with respect to the shaft 2. After the fitting, an adhesive 19 is filled between the outer peripheral surface of the shaft 2 and the upper tapered surface 18a to fix the inner labyrinth bush 17a. The lower tapered surface 18b of the inner peripheral labyrinth bush 17a forms an annular recess 20 having a shape that expands downward with the outer peripheral surface of the shaft 2. Since both tapered surfaces 18a and 18b of the inner peripheral side labyrinth bush 17a are set to have substantially the same taper angle, there is no vertical direction, and the workability of component mounting at the time of assembly is enhanced.

In the spindle motor configured as described above, when the rotor hub 4 rotates with respect to the shaft 2,
Outer labyrinth bush 1 fixed to rotor hub 4
The relative rotation between the inner labyrinth bush 17a fixed to the shaft 2 and 7b exerts a labyrinth sealing effect in the minute gap 17c, thereby preventing grease from the first ball bearings 7 and the like from scattering outside the motor. In this case, the outer labyrinth bush 17b
The small gap 17c formed between the inner ring labyrinth bush 17a and the inner ring labyrinth bush 17a is provided at a position close to and opposed to the end face of the inner ring 7b of the first ball bearing 7, so that the gap between the inner and outer rings 7a, 7b is provided. Small gap 1 from the space
The air resistance of the path leading to 7c can be increased, and the above-mentioned labyrinth sealing effect can be further enhanced.

On the other hand, in the ball bearings 7 and 8, the grease filled therein may ooze along the surface of the member. However, in the above-described configuration, the grease oil, which tends to ooze above the motor along the surface of the shaft 2, is filled with the annular recess 2 formed by the shaft 2 and the inner labyrinth bush 17 a.
The oil is encouraged by the capillary action due to the tapered shape, so that the oil is prevented from flowing out. in this case,
Although it is conceivable that oil may seep into the joint surface (press-fit surface) between the shaft 2 and the inner labyrinth bush 17a, the oil is leaked to the outside of the motor because it is sealed by the adhesive 19 filled in the upper tapered surface 18a. Is reliably prevented.

The above-described seal structure is formed only by changing or adding members without making significant design changes of the conventional motor, so that the sealing performance can be improved at low cost.

Although the embodiment of the spindle motor according to the present invention has been described above, the present invention is not limited to this, and various changes and modifications can be made without departing from the gist of the present invention.
Modifications are possible. For example, the inner diameter of the outer labyrinth bush and the outer diameter of the inner labyrinth bush may be set to be equal to or less than the outer diameter of the outer ring of the ball bearing and equal to or greater than the inner diameter.

[0025]

According to the spindle motor for driving a recording disk of the present invention, the following effects can be obtained because of the above-mentioned configuration. That is, since the labyrinth sealing means is constituted by the outer labyrinth bush, the inner labyrinth bush and the minute gap formed between both labyrinth bushes, the same labyrinth sealing effect as before can be obtained by the minute gap, Since the inner peripheral labyrinth bush exists on the shaft surface axially outside the ball bearing, the oil that has oozed from the ball bearing does not flow any further outside due to the presence of the inner peripheral labyrinth bush. Can be prevented.

In the spindle motor, an annular concave portion is formed at least at an end of the inner peripheral surface of the inner peripheral labyrinth bush on the ball bearing side between the inner peripheral surface and the outer peripheral surface of the shaft, so that the inner peripheral labyrinth bush seeps from the ball bearing. The generated oil can be held in the annular concave portion between the tapered surface of the inner peripheral labyrinth bush and the shaft, and the oil can be prevented from flowing out of the motor.

Further, in the above spindle motor,
By providing a tapered surface whose taper angle is set to be almost the same as the tapered surface on the ball bearing side on the axially outer side of the inner peripheral surface of the inner labyrinth bush, the inner labyrinth bush can be used as a component alone in the vertical direction. Therefore, the workability of component mounting at the time of assembly can be improved.

Further, by setting the minute gap of the labyrinth seal means close to and facing the end surface of the inner ring or the outer ring of the ball bearing, the air resistance of the air passage (including the minute gap) from the inside to the outside of the motor is set to be larger. And the labyrinth sealing effect can be enhanced.

[Brief description of the drawings]

FIG. 1 is an overall sectional view showing an embodiment of a recording disk driving spindle motor according to the present invention.

FIG. 2 is an enlarged sectional view of a main part of FIG.

FIG. 3 is an overall sectional view of a conventional spindle motor.

[Brief description of reference numerals]

 2 shaft 4 rotor hub 7 first ball bearing 8 second ball bearing 17a inner labyrinth bush 17b outer labyrinth bush 17c minute gap 18a, 18b tapered surface 20 annular concave portion

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) H02K 7/08 H02K 7/08 B 7/14 7/14 CF term (Reference) 3J016 AA02 BB17 CA08 5D109 BA14 BA18 BA20 BA28 BB13 BB16 BB21 BC01 BC18 5H605 AA02 AA03 BB05 BB19 CC01 CC02 CC04 CC05 DD16 EB04 EB23 EB28 EB33 5H607 AA05 AA06 BB01 BB14 BB17 CC01 DD03 EE10 GG04 JJ10 5H621 JK07 JK10 JK19

Claims (4)

[Claims] 1. A shaft, a rotor hub on which a recording disk is mounted, and a pair of ball bearings interposed between the shaft and the rotor hub and rotatably supporting the rotor hub with respect to the shaft. A spindle motor comprising a labyrinth seal means, which is located between the shaft and the rotor hub on the motor outer side of the ball bearing and substantially seals the inside and the outside of the motor, wherein the labyrinth seal means comprises: An annular outer labyrinth bush fixed to the inner peripheral surface of the rotor hub; an annular inner labyrinth bush fixed to the outer peripheral surface of the shaft; an inner peripheral surface of the outer labyrinth bush and the inner periphery An annular minute gap formed between the surface side labyrinth bush and the outer peripheral side Storage disk drive spindle motor, wherein the door. 2. A tapered surface which forms an annular recess between the inner peripheral surface of the shaft and an outer peripheral surface of the shaft is formed at least at an end of the inner peripheral surface of the inner peripheral labyrinth bush on the ball bearing side. 2. A spindle motor for driving a recording disk according to claim 1. 3. An outer tapered surface having a taper angle substantially equal to a tapered surface on the ball bearing side is formed on an axially outer side of an inner peripheral surface of the inner peripheral labyrinth bush. The spindle motor for a recording disk according to the above. 4. The spindle motor for driving a recording disk according to claim 1, wherein the minute gap of the labyrinth seal means is opposed to an end surface of an inner ring or an outer ring of the ball bearing.