JPH06245427A - Spindle motor - Google Patents

Abstract

PURPOSE:To easily obtain sufficient spread of lubricant to a dynamic radial bearing between a sleeve and a shaft, and to effectively prevent the leakage of lubricant from between the sleeve and the shaft and adherence of lubricant to a part protruding from the sleeve of the shaft. CONSTITUTION:A sleeve member 20 is externally engaged with a stationary shaft 12. A lower part of the shaft 12 protruding downward of the member 20 is engaged with a through hole 10d. A sleeve side intermediate groove 20d and a shaft side intermediate groove 12c are opposed to a radial slide 20a and a radial receiver 12b between upper and lower radial dynamic shafts 36 and 38. An annular shaft side lubricant flow-out preventing groove 12d treated with oil repellency on an inner surface is provided under the shaft 38 of the receiver 12b.

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 Due to further miniaturization and higher capacity of devices such as personal computers,
Further miniaturization and higher precision are also required for spindle motors for driving recording media (for example, hard disks) incorporated therein. Along with this, further miniaturization and higher precision are required for the bearings of the spindle motor.

Conventionally, ball bearings have been widely used as bearings used in spindle motors. However, as miniaturization of spindle motors, especially smaller outer diameters progresses, ball bearings with smaller outer diameters that match the smaller spindle motors may be used, which may cause deformation of the inner and outer rings 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, so these problems are further aggravated. Furthermore, regardless of the size of the outer diameter, there is a limit to the accuracy of the ball bearing, and it may be possible that the required specifications are not satisfied.

Therefore, 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 to move. A spindle motor having a pressure radial bearing has been proposed.

However, in the case of a spindle motor for reading / writing by flying a magnetic head or the like on the surface of a recording medium that is rotationally driven in the order of microns or submicrons, the lubricant of the bearing is scattered. Therefore, it is necessary to prevent the recording medium surface and the like from being soiled, so that the dynamic pressure radial bearing portion between the rotating sleeve portion and the fixed shaft body can be sufficiently spread with the lubricant, and the rotating sleeve portion and the fixed shaft body can be covered. Leakage of lubricant from between and should be prevented. Further, when a portion of the fixed shaft protruding from the rotary sleeve is fixed to a bracket or the like by press fitting or adhesion, if lubricant adheres to the outer peripheral surface of such a protruding portion, it must be removed. It is desirable to prevent such lubricants from adhering, as they cannot be properly fixed.

The present invention has been made in view of the above problems existing in the prior art, and an object of the present invention is to provide a dynamic pressure radial bearing portion between a sleeve body and a shaft body. The lubricant can be easily spread sufficiently, and the leakage of the lubricant from between the sleeve body and the shaft body and the adhesion of the lubricant to the portion of the shaft body protruding from the sleeve body are effective. (EN) Provided is a spindle motor using a dynamic pressure radial bearing which can be prevented.

[0008]

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 outer peripheral portion of the substantially cylindrical outer surface. And a sleeve body having a substantially cylindrical inner surface, wherein the sleeve body can freely rotate relative to the shaft body through a lubricant, and one end of the shaft body is provided. On the side, there is a protruding portion that protrudes from the substantially cylindrical surface-shaped inner peripheral portion of the sleeve body. Has an annular lubricant outflow prevention groove with oil repellent treatment on the surface,
In the gap between the outer peripheral portion of the substantially cylindrical surface shape and the inner peripheral portion of the substantially cylindrical surface shape, at least two positions on the opposite side to the protruding portion when viewed from the lubricant outflow prevention groove are formed by relative rotation of the sleeve body with respect to the shaft body. , Having a radial dynamic pressure bearing portion for generating a load bearing pressure on the interposed lubricant, between the radial dynamic pressure bearing portions, the substantially cylindrical surface-shaped outer peripheral portion and the substantially cylindrical surface-shaped inner peripheral portion, respectively. The shaft-side intermediate groove portion and the sleeve-side intermediate groove portion are provided so as to face each other.

[0009]

When the shaft body is inserted into the inner peripheral portion of the substantially cylindrical surface of the sleeve body from the protruding portion of the shaft body and is inserted into the lubricant outflow prevention groove, the inner surface of the sleeve body is substantially cylindrical. When a lubricant is arranged at the inlet of the peripheral portion and the shaft body is further inserted, the lubricant is gradually drawn between the outer peripheral portion of the substantially cylindrical surface shape and the inner peripheral portion of the substantially cylindrical surface shape.

As the insertion of the shaft advances, the intermediate groove portion on the shaft side takes in a large amount of the lubricant disposed therein when passing through the entrance of the inner peripheral portion of the substantially cylindrical surface shape, and at the same time the substantially cylindrical shape of the sleeve body. It is inserted in the inner peripheral portion of the surface shape. Thereby,
In the gap between the outer peripheral portion of the substantially cylindrical surface shape and the inner peripheral portion of the substantially cylindrical surface shape, the lubricant is sufficiently distributed to the shaft-side intermediate groove portion, the sleeve-side intermediate groove portion, and the radial dynamic pressure bearing portion sandwiching them.

However, the lubricant outflow prevention groove is inserted in the substantially cylindrical inner peripheral portion before the lubricant is disposed at the inlet of the substantially cylindrical inner peripheral portion of the sleeve body. The radial gap is expanded in the lubricant outflow prevention groove and the oil repellent treatment is applied to the inner surface, so the surface tension prevents the lubricant from flowing into the lubricant outflow prevention groove when the shaft is inserted. To be done. Therefore, it is possible to prevent the lubricant from adhering to the outer peripheral surface of the shaft body further on the protrusion side than the lubricant outflow prevention groove.

Even after the shaft is completely inserted, when the lubricant intervening between the outer peripheral portion of the substantially cylindrical surface shape and the inner peripheral portion of the substantially cylindrical surface shape tries to move to the protruding portion side, similarly due to the surface tension, It is prevented from moving beyond the lubricant outflow prevention groove to the protruding portion side.

Since the radial gap is large at the portion where the sleeve-side intermediate groove portion and the shaft-side intermediate groove portion face each other,
The resistance of the lubricant when the motor rotates becomes lower than that of the radial dynamic pressure bearing portion.

[0014]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a 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.
Is an enlarged view of the relevant part. The target recording medium may be a hard disk or various other recording media.

The bracket 10 has an upper projecting portion 10b on the inner peripheral portion of an annular recess 10a of the upper opening, and a flange portion 10c on the outer peripheral side of the annular recess 10a. A vertical through hole 10d is provided in the central portion of the upper protruding portion 10b. The bracket 10 can of course be integrally formed in the base of the hard disk drive, for example.

A lower end portion of a cylindrical fixed shaft body 12 (shaft body) is fitted and fixed in the through hole 10d of the bracket 10, so that the fixed shaft body 12 is erected at the central portion of the bracket 10. There is. An upward annular protrusion 10b1 is provided on the outer peripheral portion of the upward protrusion 10b.
The lower inner peripheral portion of the stator core 14 is externally fitted and fixed to the outer peripheral portion of 1. In the stator core 14, the stator coil 1
6 is wound. Pull-out portion 1 of the stator coil 14
4a is pulled out downward through a pull-out hole 10e that penetrates the annular recess 10a of the bracket 10.

The annular thrust plate 18 is externally fitted and fixed to the upper portion of the fixed shaft body 12. 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 thrust plate may be formed integrally with the fixed shaft body.

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.
(Inner peripheral portion of substantially cylindrical surface), a medium inner diameter portion 20b having a diameter enlarged above it, and a large inner diameter portion 20c having a diameter further enlarged above the middle inner diameter portion 20b.

The sleeve member 20 is externally fitted to the fixed shaft body 12, and has an annular shape with a large inner diameter portion 20c of the sleeve member 20 such that the inner peripheral portion thereof forms a slight radial gap with the fixed shaft body 12. The thrust retainer plate 22 is fitted in the large inner diameter portion 20c.
The thrust pressing plate 22 is fixed by crimping the upper end of the thrust pressing plate 22 inward. Then, the thrust pressing plate 22
The thrust plate 18 is fitted in the annular recess 24 formed in the inner diameter portion 20b by the sleeve member 20 and having an opening in the radial direction. The lower part of the fixed shaft body 12 projects below the sleeve member 20, and most of it is in the bracket 1.
It is fitted in the 0 through hole 10d. Hereinafter, the fixed shaft body 12
Of these, the protruding portion is referred to as a protruding portion 12a. Also,
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 12b.

The rotor hub 28 has a substantially cup shape.
A base portion 28b having a circular opening in the center is located inside the upper end of the peripheral wall portion 28a of the rotor hub 28, and an outward projecting portion 28c is located outside the lower end of the peripheral wall portion 28a. The rotor hub 28 is coaxial with the sleeve member 20 by being externally fitted and fixed to the upper end portion of the sleeve member 20 at the base portion 28b. Then, with the adhesive 29, the base 2
The inner peripheral portion of the upper end of 8b, the upper end portion of the large inner diameter portion 20c, and the outer peripheral end portion of the thrust pressing plate 22 are fixed, and the space between them is sealed. The rotor hub 28 and the sleeve member 2
It does not matter even if 0 is integrally formed.

A cylindrical rotor yoke 30 is internally fitted and fixed to the inner peripheral portion of the peripheral wall portion 28a, and the rotor magnet 32 held on the inner peripheral side thereof faces the stator core 14 with a radial gap therebetween. There is. On the base portion 28b, a clamper (not shown) for holding a recording medium (not shown) such as a hard disk fitted on the peripheral wall portion 28a between the outer protrusion portion 28c and a recording medium is screwed. A screw hole 34 for stopping is formed.

The upper and lower annular portions of the radial sliding portion 20a of the sleeve member 20 are provided with upper and lower herringbone grooves (not shown), and the upper and lower herringbone grooves and the radial receiving portion 12b of the fixed shaft body 12. The gaps between the upper and lower radial dynamic pressure bearing portions 36, 38 generate a radial load supporting pressure in the liquid lubricant 39 interposed therein by the forward rotation of the sleeve member 20.
In particular, the upper and lower herringbone grooves increase the load bearing pressure. Note that such a herringbone groove may be provided in the radial receiving portion 12b of the fixed shaft body 12. It is also possible to adopt a groove other than the herringbone groove.

Between the upper and lower radial dynamic pressure bearing portions 36 and 38, the radial sliding portion 20a and the radial receiving portion 12 are provided.
b, the sleeve-side intermediate groove portion 20d and the shaft-body-side intermediate groove portion 12c are faced to each other. FIG. 2 is an enlarged view of this portion. In the present embodiment, the sleeve-side intermediate groove portion 20d and the shaft-body-side intermediate groove portion 12c have the same axial length and the same axial position, but these are not essential conditions.

Below the lower radial dynamic pressure bearing portion 38 of the radial receiving portion 12b of the fixed shaft body 12, there is provided an annular shaft side lubricant outflow prevention groove 12d having an oil repellent treatment on its inner surface. Further, in the radial sliding portion 20a of the sleeve member 20,
It has a sleeve side lubricant outflow prevention groove 20e facing the shaft side lubricant outflow prevention groove 12d. FIG. 3 is an enlarged view of this portion. The sleeve side lubricant outflow prevention groove 20e is
The central groove portion 20e1 and upper and lower side groove portions 20e2 and 20e3, which are located on both sides in the axial direction of the central groove portion 20e1 and are shallower than the central groove portion 20e1, have an oil repellent treatment on the inner surface. The central groove portion 20e1 has the same axial length as the axial body side lubricant outflow prevention groove 12d, and also coincides with the axial position.

Upper and lower annular surfaces of the thrust plate 18 (axial receiving portions) and 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 recessed portion 24 face each other in parallel, and a liquid lubricant 39 is interposed between them to separate a slight axial gap. Herringbone-shaped grooves (not shown) are provided over the entire circumference of the upper and lower annular surfaces of the thrust plate 18. This herringbone groove is
By the forward rotation of the sleeve member 20 and the thrust pressing plate 22, a high pressure is generated in the lubricant 39 interposed between the sleeve member 20 and the thrust pressing plate 22 and the upper and lower annular surfaces of the annular recess 24. It should be noted that such herringbone-shaped grooves may be provided on the upper and lower annular surfaces of the annular recess 24. It is also possible to adopt a groove other than the herringbone-shaped groove.

An inner peripheral surface of the thrust pressing plate 22 is provided with an annular groove 22a on the pressing plate side, the inner surface of which is oil-repellent treated, at an intermediate position in the axial direction. It has a shaft-side annular groove 12e facing the plate-side annular groove 22a. The inner surface of the shaft-side annular groove 12e is also oil-repellent treated. FIG. 4 is an enlarged view of this portion. The holding plate side annular groove 22a includes a central groove portion 22a1 and the central groove portion 22a.
It is located on both sides of a1 in the axial direction and is composed of upper and lower side groove portions 22a2 and 22a3 which are shallower than the central groove portion 22a1. I am doing it.

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. The upper and lower radial dynamic pressure bearing portions 36 and 38 allow the fixed shaft body 12 to rotate while the sleeve member 20 is rotating.
Radial displacement with respect to
By the axial dynamic pressure bearings A1 and A2, the axial displacement of the sleeve member 20 with respect to the fixed shaft body 12 during rotation can be sufficiently suppressed.

When the sleeve member 20 rotates relative to the fixed shaft body 12, the upper and lower radial dynamic pressure bearing portions 36, 38 are
The load bearing pressure mainly in the radial direction is generated in the lubricant 39 interposed therein, and the axial dynamic pressure bearing portions A1 and A
2 mainly generates a load bearing pressure in the axial direction on the lubricant 39 interposed therein. When the lubricant 39 leaks to the upper groove portion 20e2 of the sleeve side lubricant outflow prevention groove 20e adjacent to the lower radial dynamic pressure bearing portion 38 in the rotation stopped state, the lubricant 39 is leaked to the lower radial dynamic pressure bearing portion 38. Take in. Similarly, the holding plate side annular groove 2
When the lubricant 39 leaks to the lower groove portion 22a3 of the 2a, the lubricant 39 is taken into the axial dynamic pressure bearing portion A1.

Since the radial gap is large in the portion where the sleeve-side intermediate groove portion 20d and the shaft-side intermediate groove portion 12c face each other, the resistance of the interposed lubricant 39 at the time of motor rotation is lower than that of the radial dynamic pressure bearing portion. Therefore, the rotation resistance as a whole is reduced.

When the rotation is stopped and a relative inclination is generated between the fixed shaft body 12 and the sleeve member 20, the lubricant 39 which cannot be retained in the lower radial dynamic pressure bearing portion 38 is retained in the upper groove portion 20e2. The lubricant 39 that leaks and cannot be held in the axial dynamic pressure bearing portion A1 leaks to the lower groove portion 22a3.

However, the lubricant 39 is retained in the upper groove portion 20e2 and the lower groove portion 22a3 by capillarity. The lubricant 39 is further applied to the shaft side lubricant outflow prevention groove 12d, the central groove portion 20e1, and the shaft side annular groove 1.
Even if an attempt is made to flow out to 2e or the central groove portion 22a1, such outflow is prevented by the surface tension of the lubricant 39. Further, therefore, the lubricant 39 is effectively prevented from leaking and contaminating the space outside the motor. The action of preventing the lubricant 39 from flowing into the shaft-side lubricant outflow prevention groove 12d and the shaft-side annular groove 12e by the surface tension has the effect of preventing the sleeve-side lubricant outflow prevention groove 20e and the holding plate side annular groove 22a. Can be realized without.

When assembling the spindle motor described above, as shown in FIG. 5, the insertion of the fixed shaft body 12 into the radial sliding portion 20a of the sleeve member 20 is started from the projecting portion 12a thereof, and then, as shown in FIG. As shown in FIG. 4, when the lubricant is prevented from entering the shaft side lubricant outflow prevention groove 12d, the lubricant 39 is arranged around the fixed shaft body 12 at the upper entrance of the radial sliding portion 20a of the sleeve member 20, and the fixed shaft body is further fixed. When the insertion of 12 is advanced, the lubricant 39 is gradually drawn between the radial receiving portion 12b and the radial sliding portion 20a.

As the insertion of the fixed shaft body 12 progresses, as shown in FIG. 7, when the shaft body side intermediate groove portion 12c passes through the entrance of the radial sliding portion 20a, a large amount of the lubricant 39 disposed therein is introduced. It is inserted into the radial sliding portion 20a of the sleeve member 20 while being taken in. Thereby, as shown in FIG. 8, the radial receiving portion 12b and the radial sliding portion 20 are provided.
The lubricant 39 is sufficiently distributed in the shaft-side intermediate groove portion 12c, the sleeve-side intermediate groove portion 20d, and the upper and lower radial dynamic pressure bearing portions 36 and 38 that sandwich them in the gap a.

However, the shaft side lubricant outflow preventing groove 12d is
The lubricant 39 is inserted into the radial sliding portion 20a before being arranged at the entrance of the radial sliding portion 20a of the sleeve member 20, and the radial gap in the shaft side lubricant outflow prevention groove 12d is enlarged. Further, since the inner surface is subjected to the oil repellent treatment, the surface tension prevents the lubricant 39 from flowing into the shaft side lubricant outflow preventing groove 12d when the fixed shaft 12 is inserted. Therefore, the protrusion 12a is further than that.
It is also possible to prevent the lubricant 39 from adhering to the outer peripheral surface of the fixed shaft body 12 on the side.

The axial dimension of the shaft-side intermediate groove portion 12c is preferably set large within a range that does not affect the effective area of the upper and lower radial dynamic pressure bearing portions 36 and 38.
Thereby, when the fixed shaft body 12 is inserted, the radial receiving portion 1
This is because the speed at which the lubricant 39 is taken into the gap between the 2b and the radial sliding portion 20a is increased, and the productivity is improved. It is more preferable that the axial dimension of the shaft-side intermediate groove portion 12c is longer than that of the upper radial dynamic pressure bearing portion 36. When inserting the fixed shaft body 12, the upper end of the shaft body side intermediate groove portion 12c is located above the upper entrance of the radial sliding portion 20a, and the lower end of the shaft body side intermediate groove portion 12c is the sleeve side intermediate groove portion 20d.
This is because the state of being located below the upper end of is realized, and the speed at which the lubricant 39 is taken into the gap between the radial receiving portion 12b and the radial sliding portion 20a is further increased. The vertical positional relationship in the description of each of the above embodiments is merely for convenience of description based on the drawings, and does not limit the actual usage state or the like.

[0036]

According to the spindle motor of the present invention, when the shaft body is inserted into the inner peripheral portion of the sleeve body having the substantially cylindrical surface shape from its protruding portion and is inserted into the lubricant outflow preventing groove,
By disposing a lubricant at the entrance of the inner surface of the cylindrical body of the sleeve body and by further inserting the shaft body, the lubricant can be sufficiently spread over the dynamic pressure radial bearing section between the sleeve body and the shaft body. In addition, the outer peripheral surface of the shaft body on the projecting side of the lubricant outflow prevention groove is prevented from adhering the lubricant when the shaft body is inserted. Also, after the shaft is completely inserted, the lubricant existing between the outer peripheral portion of the substantially cylindrical surface shape and the inner peripheral portion of the substantially cylindrical surface shape moves over the lubricant outflow prevention groove to the protruding side and leaks to the outside. Is prevented.
Furthermore, since the resistance of the lubricant during motor rotation is low at the portion where the sleeve-side intermediate groove portion and the shaft-side intermediate groove portion face each other, the overall rotational resistance is reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a spindle motor.

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

FIG. 3 is an enlarged view of a main part of FIG.

FIG. 4 is an enlarged view of a main part of FIG.

FIG. 5 is an assembly process diagram of a spindle motor.

FIG. 6 is an assembly process diagram of a spindle motor.

FIG. 7 is an assembly process diagram of a spindle motor.

FIG. 8 is an assembly process diagram of a spindle motor.

[Explanation of sign]

 12 Fixed shaft body 12b Radial receiving part 12c Shaft side intermediate groove part 12d Shaft side lubricant outflow prevention groove 20 Sleeve member 20a Radial sliding part 20d Sleeve side intermediate groove part 36 Radial dynamic pressure bearing part 38 Radial dynamic pressure bearing part 39 Lubricant

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 in which the sleeve body can freely rotate relative to the shaft body via the lubricant, a protruding portion protruding from the substantially cylindrical inner surface of the sleeve body is provided on one end side of the shaft body. Having a portion of the outer peripheral portion of the substantially cylindrical surface of the shaft body facing the inner peripheral portion of the substantially cylindrical surface of the sleeve body,
It has an annular lubricant outflow prevention groove with oil repellent treatment on the inner surface, and protrudes from the lubricant outflow prevention groove in the gap between the outer peripheral part of the substantially cylindrical surface shape and the inner peripheral part of the substantially cylindrical surface shape. At least two locations on the side opposite to the section have radial dynamic pressure bearing portions for generating load supporting pressure on the interposed lubricant by relative rotation of the sleeve body with respect to the shaft body. A spindle motor characterized by having a shaft-side intermediate groove portion and a sleeve-side intermediate groove portion facing each other on a substantially cylindrical surface-shaped outer peripheral portion and a substantially cylindrical surface-shaped inner peripheral portion, respectively.