JPH06311696A - Spindle motor - Google Patents

Abstract

PURPOSE:To effectively prevent a lubricant from being leaked by a method wherein a herringbone groove is formed in a shaft body which had been fitted into, and fixed to, a through hole in a base board between the shaft body and a sleeve member which has been mounted externally so as to be freely rotatable and an expansion part whose length in the axial-line direction is short and which has a gap in the radial direction is formed in the shaft body at its lower part. CONSTITUTION:The lower end of a fixed-shaft body 12 is fitted into a through hole 10c formed of an upper protrusion part 10b which has been erected and installed in a recessed part 10a on a base board 10, and the inner circumference of a stator core 14 is fixed and bonded to its outer circumference. A thrust plate 18 which protrudes in the radial direction is formed integrally at the upper part of the fixed-shaft body 12, and a thrust pressure plate 22 catches a thrust by the sleeve member 20. The sleeve member 20 is supported so as to be freely rotatable via a herringbone groove 34 formed at the upper part of the fixed-shaft body 12. A radial receiver part 12a which is comparatively short in the axial-line direction and an expansion part 12b having a gap in the radial direction are formed at the fixed-shaft body 12 at the lower part of the herringbone groove 34. Thereby, a lubricant which is interposed by the rotation of the sleeve member 20 is supplied satisfactorily, and it is possible to effectively prevent it from being leaked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor in which a sleeve body is externally fitted to a shaft body so as to freely rotate relative to the shaft body through a lubricant.

[0002]

2. Description of the Related Art As devices such as personal computers become smaller and have higher capacities, spindle motors for driving recording media (for example, hard disks) incorporated therein are required to have further smaller sizes and higher capacities. ing. Along with this, the bearings of spindle motors are required to be further downsized and have higher capacities. Conventionally,
Ball bearings are often used as bearings for spindle motors. However, as the spindle motor becomes smaller, especially as the outer diameter decreases, if a ball bearing with a smaller outer diameter is used, the inner and outer rings are likely to be deformed during motor assembly. It tends to be practically difficult to achieve. Also, noise and vibration problems are likely to occur.

In the case of a spindle motor for driving a recording medium, high speed rotation is required as the outer diameter becomes smaller, and these problems are further aggravated. Furthermore, regardless of the size of the appearance, there is a limit to the accuracy of the ball bearing, and it may be considered that the required specifications are not satisfied. Therefore, mainly as a small-sized spindle motor, a rotary sleeve portion is provided on the inner peripheral side of the base portion of the rotor hub portion, and the rotary sleeve portion is externally fitted to the fixed shaft body and rotatably supported, whereby the dynamic pressure radial bearing is provided. A spindle motor in which the parts are constructed has been proposed.

[0004]

In this type of spindle motor, the dynamic pressure generated in the lubricant is increased by providing the dynamic pressure radial bearing portion with a herringbone groove or the like.
Improves rotation accuracy. However, while it is necessary to supply a sufficient amount of lubricant to the dynamic pressure radial bearing section, a magnetic head or the like is floated on the surface of a recording medium that is rotationally driven in the micron or submicron order for reading / writing. In the case of a spindle motor, etc., it is necessary to prevent the lubricant of the bearing from scattering and contaminating the surface of the recording medium.

The present invention has been made in view of the above-mentioned problems existing in the prior art. The problem is to use a dynamic pressure radial bearing which can effectively prevent leakage of a lubricant. To provide a spindle motor of.

[0006]

In order to achieve the above object, a spindle motor according to the present invention has a shaft body having a substantially cylindrical outer peripheral portion and an outer peripheral portion fitted to the substantially cylindrical outer peripheral portion. And a sleeve body having a substantially cylindrical surface-shaped inner peripheral portion, wherein the sleeve body can freely rotate relative to the shaft body via a lubricant. Radial motion provided with a groove portion for generating a load bearing pressure on the interposed lubricant by the relative rotation of the sleeve body with respect to the shaft body in the gap between the outer peripheral portion of the surface shape and the inner peripheral portion of the substantially cylindrical surface shape. A pressure bearing portion is provided, and an annular lubricant outflow prevention portion having a relatively short axial length is provided at one end side of the gap portion, and the lubricant outflow prevention portion is arranged in the radial direction more than the radial dynamic pressure bearing portion. The gap is enlarged and provided on the shaft body. That.

[0007]

When the motor rotates, the lubricant interposed in the clearance is drawn into the groove of the radial dynamic pressure bearing. When the rotation is stopped, the lubricant drawn into the groove portion of the radial dynamic pressure bearing portion during the rotation tends to flow out. Since the lubricant outflow prevention part is provided on the shaft body with a larger radial gap than the lubricant radial dynamic pressure bearing part, the lubricant outflow to the lubricant outflow prevention part depends on the surface tension. Is prevented by. Therefore, it is possible to prevent the lubricant from leaking from one end of the gap through the lubricant outflow prevention portion.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a spindle motor according to the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of a spindle motor for driving a recording medium of a fixed shaft type according to an embodiment of the present invention, and FIGS. 2 and 3 are enlarged views of essential parts thereof. The target recording medium may be the hard disk 60 or various other recording media.

The base 10 of the disk chamber has an upper protruding portion 10b on the inner peripheral portion of an annular recess 10a of the upper opening.
A vertical through hole 10 is provided at the center of the upper protruding portion 10b.
c is provided. The base 10 is attached to the frame 70. It is of course possible to use a bracket separate from the disc chamber instead of the base 10.

The lower end of a substantially cylindrical fixed shaft body 12 (shaft body) is fitted and fixed in the through hole 10c of the base board 10, and thus the fixed shaft body 12 is erected at the center of the base board 10. ing. The stator core 14 is provided on the outer peripheral portion of the upper protruding portion 10b.
The lower part of the inner circumference is fixed by external fitting. An annular spacer 15 for positioning the stator core 14 in the axial direction is provided between the lower end surface of the inner peripheral portion of the stator core 14 and the bottom surface of the annular recess 10a. A stator coil 16 is wound around the stator core 14. The lead-out portion 14a of the stator coil 14 is pulled out downward through a lead-out hole 10e that penetrates the bottom plate of the annular recess 10a of the base plate 10.

An annular thrust plate 18 is integrally formed on the upper portion of the fixed shaft body 12 so as to project radially outward. The upper and lower surfaces of the thrust plate 18 are perpendicular to the outer peripheral portion of the fixed shaft body 12 having a substantially cylindrical surface shape.

The sleeve member 20 (sleeve body) has a substantially cylindrical shape in which the outer diameter of the upper end portion is widened, and the inner peripheral portion has a radial sliding portion 20a having a generally small cylindrical surface shape.
It is composed of a (substantially cylindrical surface-shaped inner peripheral portion) and a large inner diameter portion 20c whose diameter is enlarged above the inner peripheral portion.

The sleeve member 20 is fitted onto the fixed shaft body 12 from below the fixed shaft body 12 before the fixed shaft body 12 is fitted and fixed in the through hole 10c.
An annular thrust presser plate 22 is fitted in the inner peripheral portion of the fixed shaft body 12 with a slight radial gap therebetween.
For example, the upper portion of the large inner diameter portion 20c is swaged inward at four places at 90-degree center angles, so that the thrust holding plate 2
2 is fixed.

A protrusion 22d is integrally formed on the lower portion of the outer periphery of the thrust pressing plate 22. Then, the thrust plate 18 and the sleeve member 20 fit the thrust plate 18 into the annular recess 24 formed on the inner side of the protrusion 22d and having the radially inner opening. Fixed shaft 1
The lower part of 2 projects below the sleeve member 20, and most of it is fitted in the through hole 10 c of the base 10. Less than,
A portion of the substantially cylindrical outer peripheral portion of the fixed shaft body 12 facing the radial sliding portion 20a is referred to as a radial receiving portion 12a.

The rotor hub 28 made of a ferromagnetic material has a substantially cylindrical shape. The rotor hub 28 is coaxial with the sleeve member 20 by being externally fitted and fixed to the outer peripheral portion of the upper portion of the sleeve member 20 at the upper portion thereof. The lower end portion of the rotor hub 28 is inserted into the annular recess 10a, and the outer peripheral portion of the rotor hub 28 has an annular protrusion for supporting the lower surface of the inner peripheral portion of the hard disk 60 fitted and fixed to the rotor hub 28. The portion 28a is provided. It should be noted that the rotor hub 28 and the sleeve member 20 may be integrally formed.

A cylindrical rotor magnet 32, which faces the stator core 14 with a radial gap, is fitted and fixed to the inner peripheral portion of the rotor hub 28. The rotor magnet 32 is positioned in the axial direction by contacting the upper end surface thereof with the lower end surface of the upper outer peripheral portion of the sleeve member 20.

A herringbone groove 34 is formed in the annular portion of the upper half portion of the radial sliding portion 20a of the sleeve member 20.
Is provided, and the herringbone groove 34 and the fixed shaft body 1 are provided.
The gap between the two radial receiving portions 12a, that is, the radial dynamic pressure bearing portion 36, causes the sleeve member 20 to rotate in the forward direction.
A radial load supporting pressure is generated in the liquid lubricant 39 interposed therein. In particular, due to the herringbone groove 34,
The load bearing pressure is increased. The herringbone groove 34 is formed in the radial receiving portion 12a of the fixed shaft body 12.
It may be provided at the same position, and its position can be variously set according to the design. Further, it is possible to adopt a groove other than the herringbone groove, for example, a spiral groove or the like. The radial dynamic pressure bearing portion 36 includes the radial receiving portion 12 a and the radial sliding portion 20.
Since it is provided at one place in the gap with a, the labor for forming the groove portion such as the herringbone groove 34 can be reduced and the manufacturing cost can be reduced.

As shown in FIG. 2, in the radial sliding portion 20a of the sleeve member 20, the lower portion of the herringbone groove 34 (on the side of the base plate 10) is slightly enlarged in diameter and extends downward in the drawing. The part 20f is formed. Also, this expanded part 2
A lubricant outflow prevention groove 12b is formed on the fixed shaft body 12 so as to face 0f over the entire circumference. The gap formed by the lubricant outflow prevention groove 12b and the enlarged diameter portion 20f of the sleeve member 20 is the lubricant outflow prevention portion 40.

The axial length of the lubricant outflow prevention portion 40 is relatively short, and in this embodiment, it is about one fifth of the axial length of the radial dynamic pressure bearing portion 36. Also, the lubricant outflow prevention groove 1
In the embodiment, the groove depth of 2b is about three times the size of the gap between the expanded diameter portion 20f of the sleeve member 20 and the fixed shaft body 12,
The gap as the lubricant outflow prevention portion 40, which is a combination of the gap with the expanded diameter portion 20f of the sleeve member 20, is the sleeve member 20.
It is set to be about four times or more the size of the gap between the expanded diameter portion 20f and the fixed shaft body 12.

Therefore, the relationship between the axial length and the clearance in the lubricant outflow prevention portion 40 depends on the viscosity of the lubricant, but it is desirable to make the axial length and the clearance dimension as equal as possible. In the lubricant outflow prevention portion 40, the enlarged diameter portion 20f of the stator member 20 and the lubricant outflow prevention groove 1 are provided.
An oil repellent treatment is applied to the inner surface of 2b. In addition, in the present embodiment, the fixed shaft body 1 is used as the lubricant outflow prevention portion 40.
Although the lubricant outflow prevention groove 12b is provided on the second side, the lubricant outflow prevention groove may be provided on both sides of the fixed shaft body 12 and the sleeve member 20 in addition to the lubricant outflow prevention groove on the sleeve member 20 side. . Even in that case, the relationship between the axial length and the gap in the lubricant outflow prevention portion 40 is relatively unchanged.

Of the enlarged diameter portion 20f formed in the radial sliding portion 20a of the sleeve member 20, the herringbone groove 34 is included.
An annular lubricant storage groove 20e is formed between the and the lubricant outflow prevention portion 40. The lubricant storage groove 20e and the fixed shaft body 12
The gap formed by the radial receiving portion 12a has a relatively long axial length (in the embodiment, the radial dynamic pressure bearing portion 3).
6 is about half the axial length. ) The lubricant reservoir 42 is configured.

In this way, the lubricant reservoir 42 has a larger radial gap than the radial dynamic pressure bearing 36, and the lubricant outflow prevention unit 40 has a radial gap several times that of the lubricant reservoir 42. Has been expanded.

The upper and lower annular surfaces of the thrust plate 18 (axial receiving portions) and the upper and lower annular surfaces of the annular recess 24 (axial sliding portions)
And constitute axial dynamic pressure bearing portions A1 and A2, respectively. The upper and lower annular surfaces of the thrust plate 18 and the upper and lower annular surfaces of the annular recess 24 face each other in parallel, and a liquid lubricant 39 is present between them to separate a slight axial gap. A herringbone-shaped groove (not shown) is provided over the entire circumference of the upper and lower annular surfaces of the thrust plate 18. The herringbone-shaped grooves generate a high pressure in the lubricant 39 interposed between the sleeve member 20 and the thrust pressing plate 22 in the forward direction and between the upper and lower annular surfaces of the annular recess 24. It should be noted that such a herringbone-shaped groove may be provided in the lower annular surface of the thrust pressing plate 22 and the upper annular surface of the sleeve member 20, which face the upper and lower annular surfaces of the thrust plate 18. It is also possible to adopt a groove other than the herringbone-shaped groove.

As shown in FIG. 3, the thrust pressing plate 22
Has a pressing plate side annular groove 22a whose inner surface has been subjected to oil repellent treatment at an axially intermediate position in the inner peripheral part of A shaft-side annular groove 12c having an oil repellent treatment on its inner surface is provided over the intermediate position of the annular groove 22a. Since the fixed shaft body 12 and the thrust plate 18 are integrally formed, the shaft-side annular groove 12c can be easily formed when the thrust plate 18 is processed.

On the inner peripheral portion of the lower end of the thrust pressing plate 22,
It has an annular notch 22b. In addition, an annular cross section L is formed at an inner peripheral corner portion of the lower end of the large inner diameter portion 20c of the sleeve member 20.
The thrust pressing plate 22 has a groove portion 20d, and a substantially L-shaped cut-out portion 22c having an annular cross-section facing the L-shaped groove portion 20d at the lower end outer peripheral corner portion. The oil repellent treatment is also applied to the inner surfaces of the groove portion 20d having the L-shaped cross section and the cutout portion 22c having the L-shaped cross section.

The oil repellent treatment is also applied to the inner surfaces of the groove portion 20d having the L-shaped cross section and the notch portion 22c having the L-shaped cross section. Further, in the large inner diameter portion 20c of the sleeve member 20,
On the upper part of the groove 20d having the L-shaped section, an oil-repellent groove 20g is formed over the entire circumference.

In this manner, the sleeve member 20, the rotor hub 28, etc. are configured to be freely rotatable with respect to the fixed shaft body 12, the stator core 14, etc. via the lubricant 39. Further, the radial dynamic pressure bearing portion 36 can sufficiently suppress the radial displacement with respect to the fixed shaft body 12 during the rotation of the sleeve member 20, and the axial dynamic pressure bearing portions A1 and A2 can prevent the sleeve member 20 from rotating. The axial displacement with respect to the fixed shaft body 12 can be sufficiently suppressed.

When the sleeve member 20 rotates with respect to the fixed shaft body 12, the sleeve member 20 and the thrust pressing plate 22.
The lubricant 39 interposed in the gap between the fixed shaft body 12 and
It is drawn into the herringbone groove 34 of the radial dynamic pressure bearing portion 36 and the herringbone groove portions of the axial dynamic pressure bearing portions A1 and A2. The radial dynamic pressure bearing portion 36 mainly generates a load bearing pressure in the radial direction on the lubricant 39 interposed therein, and the axial dynamic pressure bearing portions A1 and A2.
Generates a load bearing pressure mainly in the axial direction in the lubricant 39 interposed therein.

When the rotation is stopped, the lubricant 39 drawn into the herringbone groove 34 of the radial dynamic pressure bearing portion 36 and the herringbone groove of each of the axial dynamic pressure bearing portions A1 and A2 flows out during rotation, and the radial agent 39 flows out. Dynamic bearing 3
It is stored in the lubricant storage portion 42 having a larger radial gap than that of No. 6, and in the gap between the annular cutout portion 22b and the upper surface of the thrust plate 18.

The lubricant storage portion 42 has a larger radial gap than the radial dynamic pressure bearing portion 36, and has a single radial radial pressure bearing portion 36, so that the axial length thereof is relatively long. Therefore, the lubricant 39 can be stored in a relatively large amount. Therefore, it is possible to sufficiently supply the lubricant 39 to the radial dynamic pressure bearing portion 36 at the time of rotation of the motor to sufficiently lubricate the same and to prepare for the dissipation of the lubricant 39 due to evaporation or leakage. Therefore, in this respect, good reliability can be realized.

Further, even when a relatively large amount of the lubricant 39 flows into the lubricant storage portion 42 due to thermal expansion or the like, it is possible to retain the lubricant 39 in the lubricant storage portion 42, and moreover, the lubricant outflow prevention portion. The radial gap of 40 is larger than that of the lubricant storage portion 42, and the expanded diameter portion 20f of the sleeve member 20 and the shaft side lubricant outflow prevention groove 12 constituting the gap 40 are formed.
Since the oil repellent treatment is applied to the inner surface of b, the lubricant 39 in the lubricant storage portion 42 is sufficiently prevented from flowing out to the lubricant outflow prevention portion 40 by the surface tension. Therefore, it is possible to effectively prevent the lubricant from leaking from one end of the gap through the lubricant outflow prevention portion 40. The leakage preventing effect can be further enhanced by performing the oil-repelling treatment on the upper portion of the lubricant outflow prevention portion 40 in FIG. 2, that is, on a part of the lubricant storage groove 20e.

On the other hand, the annular notch 22b and the thrust plate 1
The lubricant 39 stored in the gap between the upper surface of the shaft 8 and the inner peripheral portion of the thrust holding plate 22 is
Also, due to the gap between the holding plate side annular groove 22a and the fixed shaft body 12, upward leakage is effectively prevented in two stages.

Further, the lubricant 39 present in the gap between the annular recess 24 and the thrust plate 18 passes between the thrust pressing plate 22 and the sleeve member 20, and the inside of the outer peripheral portion of the thrust pressing plate 22 and the large inner diameter portion 20c. Exudation from between the peripheries is effectively prevented. In the middle of the exudation path, lubricant 39
This is because it has a groove portion 20d having an L-shaped cross section and a notch portion 22c having an L-shaped cross section, which face each other, and can further store a groove portion 20g. Moreover, since the thrust pressing plate 22 is fixed by crimping the upper portion of the large inner diameter portion 20c inward, the lubricant 39 is effectively prevented from seeping out.

By the way, as shown in FIG. 3, the upper and lower annular surfaces (axial receiving portions) of the thrust plate 18 and the upper and lower annular surfaces (axial sliding portions) of the annular recess 24 form the axial dynamic pressure bearing portions A1 and A2. It is configured. The gap size defining each of the dynamic pressure bearings A1 and A2 is defined by the thickness size of the protruding portion 22d of the thrust pressing plate 22 and the thickness size of the thrust plate 18. Therefore, in comparison with the case where the sleeve member 20 is provided with, for example, a stepped shape so as to correspond to the thickness dimension of the thrust plate 18, the shape of the component itself (the thrust pressing plate 22) is larger in the above embodiment. Relatively simple and easy to process. Therefore, the dimensional accuracy can be improved.

FIG. 4 shows another embodiment of the portion where the thrust plate 18 of FIG. 3 is formed. In FIG. 4, a flat plate-shaped thrust pressing plate 50 is provided in place of the thrust pressing plate 22 of FIG. 3, and an annular spacer 51 is interposed in the annular recess 24 in accordance with the thickness dimension of the thrust plate 18. There is. In this case, assembling can be performed corresponding to the thickness dimension of the thrust plate 18 by dimensional control of only the thickness dimension of the annular spacer 51. Therefore, as compared with the case of FIG. 3, the machining and productivity can be further improved, the dimensional accuracy can be improved, and a more precise spindle motor can be obtained. It is needless to say that the prevention of the leaching of the lubricant 39 is the same as that shown in FIG. 3 and has a high prevention effect.

The vertical positional relationship in the above description of each embodiment is merely for the convenience of description based on the drawings, and does not limit the actual use state or the like.

[0037]

Since the spindle motor of the present invention has the above-mentioned structure, it has the following effects. Since the surface tension prevents the lubricant in the lubricant reservoir from flowing out to the lubricant outflow prevention part, it is effective that the lubricant leaks out from one end of the gap through the lubricant outflow prevention part. It can be prevented.

[Brief description of drawings]

FIG. 1 is a sectional view showing an entire spindle motor according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of an essential part showing an enlarged part of FIG.

FIG. 3 is an enlarged view of an essential part showing an enlarged part of FIG.

FIG. 4 is an enlarged sectional view of a main part of a spindle motor according to a second embodiment of the present invention.

[Explanation of symbols]

 12 Shaft 12a Radial receiving part 20 Sleeve member 36 Radial dynamic pressure bearing part

Claims (1)

[Claims] 1. A shaft body having a substantially cylindrical surface-shaped outer peripheral portion, and a sleeve body having a substantially cylindrical surface-shaped inner peripheral portion externally fitted to the substantially cylindrical surface-shaped outer peripheral portion. In the spindle motor, wherein the sleeve body can freely rotate relative to the shaft body via a lubricant, in a gap between the substantially cylindrical surface-shaped outer peripheral portion and the substantially cylindrical surface-shaped inner peripheral portion, A radial dynamic pressure bearing portion having a groove portion for generating a load supporting pressure is provided to the interposed lubricant by the relative rotation of the sleeve body with respect to the shaft body, and a relatively axial direction is provided at one end side of the gap portion. An annular lubricant outflow prevention part having a short length is provided, and the lubricant outflow prevention part is provided on the shaft body so that a radial gap is larger than that of a radial dynamic pressure bearing part. motor.