JP3234030B2 - Spindle 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 spindle motor in which a sleeve is externally fitted to a shaft so that the sleeve can freely rotate relative to the shaft via a lubricant.

[0002]

2. Description of the Related Art As devices such as personal computers have become smaller and have higher capacities,
There is also a demand for a spindle motor for driving a recording medium (for example, a hard disk) incorporated therein, which is further downsized and has higher accuracy. Accordingly, further miniaturization and higher accuracy of the spindle motor bearing are also required.

Conventionally, ball bearings are often used as bearings for spindle motors. However, as spindle motors have become smaller, especially smaller outer diameters, the use of ball bearings with smaller outer diameters has required sufficient rotational accuracy because the inner and outer rings are likely to deform during motor assembly. It tends to be difficult in practice. 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 is reduced, and these problems are further promoted. Further, regardless of the size of the outer diameter, the accuracy of the ball bearing is limited and may not satisfy the required specifications.

[0005] Therefore, as a small-sized spindle motor, a rotary sleeve portion is provided on the inner peripheral side of the base of the rotor hub portion, and the rotary sleeve portion is externally fitted to a fixed shaft body and rotatably supported by being rotatably supported. A spindle motor having a pressure radial bearing has been proposed.

However, in the case of a spindle motor for reading / writing by floating a magnetic head or the like on a rotating or driven recording medium surface on the order of microns or submicrons, lubricant of a bearing is scattered. Therefore, it is necessary to prevent the lubricant from spreading to the dynamic pressure radial bearing portion between the rotating sleeve portion and the fixed shaft body, and to prevent the rotating sleeve portion and the fixed shaft body from becoming dirty. It is necessary to prevent the leakage of the lubricant from the space between the two. Also, when a portion of the fixed shaft protruding from the rotating sleeve portion is fixed to a bracket or the like by press-fitting or bonding, if lubricant adheres to the outer peripheral surface of such a protruding portion, it must be removed. Since the fixing cannot be performed properly, it is desired that the adhesion of such a lubricant is prevented.

The present invention has been made in view of the above-mentioned problems in the prior art, and has as its object to provide a dynamic pressure radial bearing portion between a sleeve body and a shaft body. The lubricant can be sufficiently distributed easily, 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 can be effectively performed. An object of the present invention is to provide a spindle motor utilizing 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 is provided with a shaft having a substantially cylindrical outer peripheral portion, and a shaft body externally fitted to the substantially cylindrical outer peripheral portion. A sleeve body having a substantially cylindrical inner peripheral portion, the sleeve body being capable of freely rotating relative to the shaft body via a lubricant, one end of the shaft body. Side has a protruding portion protruding from the inner peripheral portion of the substantially cylindrical surface of the sleeve body, and has an annular thrust plate on the other end side of the shaft body. A portion of the body facing the substantially cylindrical inner peripheral portion has an annular lubricant outflow preventing groove having an inner surface subjected to oil repellent treatment, and a substantially cylindrical outer peripheral portion and a substantially cylindrical inner peripheral portion. And at least two locations on the opposite side of the protrusion from the lubricant outflow prevention groove, A radial dynamic pressure bearing portion that generates a load supporting pressure on the interposed lubricant by relative rotation of the sleeve body with respect to the outer peripheral portion and the substantially cylindrical surface between the radial dynamic pressure bearing portions. On the inner periphery of the shape,
Possess in each state of each other facing shaft side intermediate groove and the sleeve-side intermediate groove portion, the substantially cylindrical surface shape outer peripheral portion and a substantially cylindrical surface
Among the gaps in the inner peripheral part of the shape, the shaft-side intermediate groove and the sleeve
Side intermediate grooves and radial dynamic pressure bearings that sandwich them
It is assumed that the lubricant is sufficiently distributed .

[0009]

The shaft body is inserted into the substantially cylindrical inner peripheral portion of the sleeve body from the projecting portion of the shaft body, and when the shaft body is inserted into the lubricant outflow preventing groove, the sleeve body is inserted into the substantially cylindrical surface shape of the sleeve body. When the lubricant is provided at the entrance of the peripheral portion and the insertion of the shaft is further advanced, the lubricant is gradually drawn into between the substantially cylindrical outer peripheral portion and the substantially cylindrical inner peripheral portion.

As the insertion of the shaft is advanced, the shaft-side intermediate groove takes in a large amount of the lubricant disposed therethrough when passing through the entrance of the inner peripheral portion of the substantially cylindrical shape, and at the same time, the substantially cylindrical portion of the sleeve body. It is inserted into the inner peripheral part of the surface shape. Thereby,
In the gap between the outer peripheral portion of the substantially cylindrical surface and the inner peripheral portion of the substantially cylindrical surface, the lubricant sufficiently spreads 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 into the substantially cylindrical inner peripheral portion before the lubricant is disposed at the entrance of the substantially cylindrical inner peripheral portion of the sleeve body. The radial gap increases in the lubricant outflow prevention groove and the oil repellent treatment is applied to the inner surface, so that the lubricant flows out of the lubricant outflow prevention groove when the shaft is inserted is prevented by surface tension Is done. Therefore, it is possible to prevent the lubricant from adhering to the outer peripheral surface of the shaft body further protruding than the lubricant outflow prevention groove.

Also, even after the shaft body is completely inserted, if the lubricant interposed between the outer peripheral portion of the substantially cylindrical surface and the inner peripheral portion of the substantially cylindrical surface moves to the protruding portion side, the lubricant is similarly caused by surface tension. Movement to the protruding portion side beyond the lubricant outflow prevention groove is prevented.

In the portion where the sleeve side intermediate groove portion and the shaft body side intermediate groove portion face each other, the radial gap is large.
The resistance of the lubricant during rotation of the motor is lower than that of the radial dynamic pressure bearing.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 main part. Examples of the target recording medium include a hard disk and various other recording media.

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

The lower end of a cylindrical fixed shaft 12 (shaft) is fitted and fixed in the through hole 10d of the bracket 10, and the fixed shaft 12 is erected at the center of the bracket 10. I have. An upwardly extending annular projection 10b1 is provided on the outer periphery of the upper projection 10b.
The inner peripheral lower portion of the stator core 14 is externally fitted and fixed to the outer peripheral portion of the stator core 14. The stator core 1 includes a stator coil 1
6 is wound. Leader 1 of stator coil 14
4a is drawn out downward through a drawing hole 10e penetrating the annular concave portion 10a of the bracket 10.

An annular thrust plate 18 is externally fitted and fixed to an upper portion of the fixed shaft body 12. The upper and lower surfaces of the thrust plate 18 are perpendicular to the substantially cylindrical outer periphery of the fixed shaft body 12. The thrust plate may be formed integrally with the fixed shaft.

The sleeve member 20 (sleeve body) has a substantially cylindrical shape in which the outer diameter of the upper end portion is expanded, and the inner peripheral portion has a radially smooth portion 20a having a small diameter and substantially cylindrical surface shape as a whole.
(A substantially cylindrical inner peripheral portion), a middle inner diameter portion 20b whose diameter is expanded above, and a large inner diameter portion 20c whose diameter is further expanded above the middle inner diameter portion 20b.

The sleeve member 20 is externally fitted to the fixed shaft body 12 and is formed in an annular shape on the large inner diameter portion 20c of the sleeve member 20 with the inner peripheral portion thereof being slightly spaced from the fixed shaft body 12 in the radial direction. The thrust holding plate 22 is fitted inside the large-diameter portion 20c.
Is crimped inward to fix the thrust holding plate 22. And the thrust holding plate 22
The thrust plate 18 is fitted into an annular concave portion 24 having a radially inward opening formed inside the middle inner diameter portion 20b by the and the sleeve member 20. The lower portion of the fixed shaft body 12 projects below the sleeve member 20, and most of the
0 through hole 10d. Hereinafter, the fixed shaft 12
This protruding portion is referred to as a protruding portion 12a. Also,
The portion of the substantially cylindrical outer peripheral portion of the fixed shaft body 12 that faces 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 at the center is located inside the upper end portion 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 of the sleeve member 20 at the base 28b. Then, the base portion 2 is formed by the adhesive 29.
The upper end inner peripheral portion of 8b, the upper end portion of the large inner diameter portion 20c, and the outer peripheral end portion of the thrust holding plate 22 are fixed, and the space therebetween is sealed. The rotor hub 28 and the sleeve member 2
0 may be integrally formed.

A cylindrical rotor yoke 30 is internally fixed to the inner peripheral portion of the peripheral wall portion 28a, and a rotor magnet 32 held on the inner peripheral side faces the stator core 14 with a radial gap therebetween. I have. The base portion 28b is provided with a clamper (not shown) for holding a recording medium (not shown) such as a hard disk (not shown) externally fitted to the peripheral wall portion 28a with the outwardly projecting portion 28c. A screw hole 34 for stopping is formed.

Upper and lower herringbone grooves (not shown) are provided in upper and lower annular portions of the radial sliding portion 20a of the sleeve member 20, and the upper and lower herringbone grooves and the radial receiving portion 12b of the fixed shaft body 12 are provided. , That is, the upper and lower radial dynamic pressure bearing portions 36 and 38 generate a radial load supporting pressure on the liquid lubricant 39 interposed therein by the forward rotation of the sleeve member 20.
In particular, the load supporting pressure is increased by the upper and lower herringbone grooves. In addition, 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 20d and the shaft-body-side intermediate groove 12c face each other. FIG. 2 is an enlarged view of this part. In the present embodiment, the sleeve-side intermediate groove 20d and the shaft-body-side intermediate groove 12c have the same axial length and the same axial position, but these are not essential conditions.

An annular shaft-side lubricant outflow prevention groove 12d having an oil-repellent inner surface is provided below the lower radial dynamic pressure bearing portion 38 in the radial receiving portion 12b of the fixed shaft body 12. Also, on the radial sliding portion 20a of the sleeve member 20,
There is a sleeve-side lubricant outflow prevention groove 20e facing the shaft body-side lubricant outflow prevention groove 12d. FIG. 3 is an enlarged view of this part. The sleeve-side lubricant outflow prevention groove 20e is
A central groove 20e1 and upper and lower grooves 20e2 and 20e3, which are located on both axial sides of the central groove 20e1 and are shallower than the central groove 20e1, are subjected to an oil-repellent treatment on the inner surface. The center groove 20e1 has the same length in the axial direction as the shaft body-side lubricant outflow prevention groove 12d, and also has the same axial position.

The upper and lower annular surfaces of the thrust plate 18 (axial receiving portion) and the upper and lower annular surfaces of the annular concave portion 24 (axial smooth portion).
Axial dynamic pressure bearings A1 and A2 are respectively configured by these. The upper and lower annular surfaces of the thrust plate 18 and the upper and lower annular surfaces of the annular recess 24 are opposed to each other in parallel, and a slight gap in the axial direction is interposed between them by a liquid lubricant 39 interposed therebetween. A herringbone-shaped groove (not shown) is provided over the entire circumference of the upper and lower annular surfaces of the thrust plate 18. This herringbone groove is
The forward rotation of the sleeve member 20 and the thrust holding plate 22 generates a high pressure in the lubricant 39 interposed between the sleeve member 20 and the upper and lower annular surfaces of the annular concave portion 24. In addition, such a herringbone-shaped groove may be provided on the upper and lower annular surfaces of the annular concave portion 24. It is also possible to adopt a groove other than the herringbone-shaped groove.

At the axially intermediate position of the inner peripheral portion of the thrust retainer plate 22, there is a retainer plate-side annular groove 22a having an inner surface subjected to an oil-repellent treatment. 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 subjected to an oil-repellent treatment. FIG. 4 is an enlarged view of this part. The holding plate-side annular groove 22a has a central groove 22a1 and the central groove 22a.
a1 and upper and lower grooves 22a2 and 22a3 which are shallower than the central groove 22a1. The central groove 22a1 has the same axial length as the shaft-side annular groove 12e, and the axial position is also one. I do.

In this manner, the sleeve member 20, the rotor hub 28, and the like can be freely rotated via the lubricant 39 with respect to the fixed shaft body 12, the stator core 14, and the like. The fixed shaft 12 during rotation of the sleeve member 20 is formed by the upper and lower radial dynamic pressure bearing portions 36 and 38.
Radial displacement with respect to
By the axial dynamic pressure bearing portions A1 and A2, axial displacement with respect to the fixed shaft body 12 during rotation of the sleeve member 20 can be sufficiently suppressed.

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

Since the gap between the sleeve side intermediate groove portion 20d and the shaft body side intermediate groove portion 12c facing each other has a large radial gap, the resistance of the interposed lubricant 39 when the motor rotates is lower than that of the radial dynamic pressure bearing portion. Therefore, the rotation resistance as a whole is reduced.

When the rotation stops and the relative inclination between the fixed shaft body 12 and the sleeve member 20 occurs, the lubricant 39 that cannot be retained in the lower radial dynamic pressure bearing portion 38 is transferred to the upper groove portion 20e2. The lubricant 39 that cannot leak 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 20e2 and the lower groove 22a3 by capillary action, respectively. The lubricating agent 39 further reduces the shaft-side lubricant outflow preventing groove 12d, the central groove 20e1, and the shaft-side annular groove 1
Even if an attempt is made to flow out to 2e or the central groove 22a1, such outflow is prevented by the surface tension of the lubricant 39. Therefore, it is possible to effectively prevent the lubricant 39 from leaking and contaminating the space outside the motor. The effect of preventing the lubricant 39 from flowing out to the shaft-side lubricant outflow preventing groove 12d and the shaft-body-side annular groove 12e by the surface tension is caused by the sleeve-side lubricant outflow preventing groove 20e and the holding plate-side annular groove 22a. It can be realized even without.

When assembling the spindle motor described above, as shown in FIG. 5, the insertion of the fixed shaft 12 into the radial sliding portion 20a of the sleeve member 20 is started from its protruding portion 12a. As shown in the figure, when the shaft-side lubricant outflow preventing groove 12d is inserted, a lubricant 39 is disposed around the fixed shaft body 12 at the upper entrance of the radial sliding portion 20a of the sleeve member 20, and further, the fixed shaft body When the insertion of the lubricating member 12 is advanced, the lubricant 39 is gradually drawn in between the radial receiving portion 12b and the radial sliding portion 20a.

When the insertion of the fixed shaft 12 is advanced, as shown in FIG. 7, the shaft-side intermediate groove 12c makes a large amount of the lubricant 39 disposed therein when passing through the entrance of the radial sliding portion 20a. And inserted into the radial sliding portion 20a of the sleeve member 20. Thereby, as shown in FIG. 8, the radial receiving portion 12b and the radial sliding portion 20 are formed.
In the gap a, the lubricant 39 sufficiently spreads to 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 sandwiching them.

However, the shaft body side lubricant outflow prevention 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 increases in the shaft body side lubricant outflow preventing groove 12d, Further, since the inner surface is subjected to the oil-repellent treatment, the surface tension prevents the lubricant 39 from flowing out into the shaft body side lubricant outflow prevention groove 12d when the fixed shaft body 12 is inserted. Therefore, the protruding portion 12a
The adhesion of the lubricant 39 to the outer peripheral surface of the fixed shaft body 12 on the side is also prevented.

The axial dimension of the shaft-side intermediate groove 12c is desirably set to be large within a range that does not affect the effective area of the upper and lower radial dynamic pressure bearings 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 radial lubrication portion 20a and the radial lubrication portion 20b increases, thereby improving productivity. It is more preferable that the axial dimension of the shaft-side intermediate groove portion 12c be longer than that of the upper radial dynamic pressure bearing portion 36. When the fixed shaft 12 is inserted, the upper end of the shaft-side intermediate groove 12c is located above the upper entrance of the radial sliding portion 20a, and the lower end of the shaft-side intermediate groove 12c is positioned at the sleeve-side intermediate groove 20d.
This is because the state of being located below the upper end is realized, and the speed of taking in the lubricant 39 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 embodiment described above is merely for convenience of description based on the drawings, and does not limit the actual use state and the like.

[0036]

According to the spindle motor of the present invention, the insertion of the shaft into the inner peripheral portion of the substantially cylindrical surface of the sleeve starts from the projecting portion, and when the shaft is inserted to the lubricant outflow preventing groove,
Lubricant is placed at the entrance of the inner peripheral part of the substantially cylindrical surface of the sleeve body, and further insertion of the shaft body is performed, so that the lubricant is sufficiently distributed to the dynamic pressure radial bearing portion between the sleeve body and the shaft body. In addition, the outer peripheral surface of the shaft, which is closer to the protruding portion than the lubricant outflow preventing groove, is prevented from adhering the lubricant when the shaft is inserted. Also, after the shaft body is completely inserted, the lubricant interposed between the outer peripheral portion of the substantially cylindrical surface and the inner peripheral portion of the substantially cylindrical surface moves to the protruding portion side beyond the lubricant outflow prevention groove and leaks to the outside. Is prevented.
Further, in the portion where the sleeve side intermediate groove and the shaft body side intermediate groove face each other, the resistance of the lubricant during rotation of the motor is low, so that the rotational resistance as a whole is reduced.

[Brief description of the 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. 1;

FIG. 4 is an enlarged view of a main part of FIG. 1;

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

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

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

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

[Description of sign]

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

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-178492 (JP, A) JP-A-8-86311 (JP, A) JP-A-63-86422 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) H02K 5/10 H02K 5/16-5/167 H02K 7/08 F16C 17/02

Claims (1)

(57) [Claims] 1. A shaft body having a substantially cylindrical outer peripheral portion, and a sleeve body having a substantially cylindrical inner peripheral portion externally fitted to the substantially cylindrical outer peripheral portion. A spindle motor in which a sleeve body can freely rotate relative to a shaft body via a lubricant, and a protruding portion protruding from an inner peripheral portion of a substantially cylindrical surface of the sleeve body is provided at one end side of the shaft body. An annular thrust plate is provided on the other end side of the shaft body, and a portion of the substantially cylindrical outer peripheral portion of the shaft body opposite to the substantially cylindrical inner peripheral portion of the sleeve body is repelled to the inner surface. It has an oil-treated annular lubricant outflow prevention groove. Of the gap between the substantially cylindrical outer periphery and the substantially cylindrical inner periphery, the protrusion is opposite to the protrusion when viewed from the lubricant outflow prevention groove. In at least two places on the side of the side, the load bearing pressure is applied to the interposed lubricant by the relative rotation of the sleeve body with respect to the shaft body. A radial dynamic pressure bearing portion to be generated, and between the radial dynamic pressure bearing portions, the shaft-side intermediate groove portion and the sleeve-side intermediate groove portion face the substantially cylindrical outer peripheral portion and the substantially cylindrical inner peripheral portion, respectively. possess in the state, before
The gap between the outer periphery of the substantially cylindrical surface and the inner periphery of the substantially cylindrical surface
That is, the shaft-side intermediate groove portion, the sleeve-side intermediate groove portion, and the same.
Lubricating agent spreads sufficiently to the radial dynamic pressure bearing
Spindle motor, characterized in that there I.