JPH06319240A - Spindle motor - Google Patents

Abstract

PURPOSE:To prevent an outflow to the outside of a lubricant by forming a lubricant outflow preventive groove having a tapered section, in which a radial clearance with the inner circumferential surface of a sleeve body is expanded gradually. CONSTITUTION:Radial clearances with the inner circumferential surface of a sleeve body 20 are expanded gradually toward the outside in the axial direction as a whole in the tapered sections 12c1, 12c2, 12e1, 12e2 of lubricant outflow preventive grooves 12c, 12e, and angles to an axis are formed comparatively largely in outer circumferential surfaces on the insides in the axial direction and angles to the axis are formed comparatively small in outer circumferential surfaces on the outsides in the axial direction in the tapered sections 12c1, 12c2, 12e1, 12e2. Consequently, the capacitance of the lubricant outflow preventive grooves 12c, 12e is large. Since the angles to the axis of the outer circumferential surfaces on the insides in the axial direction are particularly large in the tapered sections 12c1, 12c2, the outflow preventive action of a lubricant 39 by surface tension strongly works, and the angles to the axis of the outer circumferential surfaces on the outsides of the axial direction are small, thus resulting in the high stability of the outflow preventive action of the lubricant 39 to the sudden change of the position of the surface of the lubricant 39.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As a spindle motor in which a sleeve body is externally fitted to a shaft body so as to freely rotate relative to a shaft body, there is a spindle motor as shown in FIG. Are known. In this spindle motor, the thrust plate a protruding above the fixed shaft body a
The upper and lower parts of the thrust plate a1
The outer peripheral portion of the fixed shaft body a below is configured as a radial bearing portion, and is provided on the inner peripheral portion of the bush b above the thrust plate a1 and the inner peripheral portion of the sleeve member c below the radial bearing portion, respectively. The sealing grooves d and e prevent the lubricant f from leaking.

A conventional sealing groove e as shown in FIG.
Then, the gap with the fixed shaft a is suddenly enlarged at the end of the sealing groove e. Therefore, as shown in FIG. 5, in the state where the lubricant f faces the end of the sealing groove e, the surface tension strongly hinders the lubricant f from entering the sealing groove e. Once the lubricant f intrudes into the sealing groove e as shown in FIG. 6 due to the expansion and impact force of the lubricant due to, the lubricant f flows into the sealing groove e relatively easily thereafter. However, the sealing effect is substantially lost. In particular, in a relatively large dynamic pressure bearing, the self-weight of the lubricant in the bearing may be larger than the surface tension of the sealing groove e, and the sealing effect may not be substantially obtained.

Further, when such a conventional sealing groove e is used, the relative amount of the lubricant is changed due to the increase / decrease of the lubricant due to the temperature change, the error of the lubricant injection amount, the design tolerance of each member and the like. A lubricant reservoir must be provided to absorb.
In the spindle motor of FIG. 4, the lubricant reservoir g is provided by chamfering the inner peripheral portion of the lower end of the bush.

The present invention has been made in view of the above problems existing in the prior art, and its purpose is to lose the sealing effect all at once due to a sudden temperature change or impact force. In this way, it is possible to absorb the relative increase or decrease of the lubricant due to temperature change, the error of the lubricant injection amount, the relative amount of the lubricant due to the design tolerance of each member, etc., and to prevent the lubricant from leaking to the outside. An object of the present invention is to provide an excellent spindle motor using a dynamic pressure bearing.

[0006]

In order to achieve the above object, a spindle motor according to the present invention comprises a shaft body and a sleeve body externally fitted to the shaft body. Is a spindle motor that can freely rotate relative to each other via a lubricant, has a dynamic pressure bearing portion in the gap between the shaft body and the sleeve body, and has a dynamic pressure bearing portion sandwiching the dynamic pressure bearing portion. A lubricant outflow prevention groove having a taper portion in which the outer diameter gradually decreases outward in the axial direction to gradually increase the radial gap with the inner peripheral surface of the sleeve body is provided. Among them, the outer peripheral surface inward in the axial direction makes a relatively large angle with respect to the axis, and the outer peripheral surface outward in the axial direction has a relatively small angle with respect to the axis. Lubricant was filled in the gap between the shaft and the sleeve. It is as.

The spindle motor of the present invention comprises a shaft body and a sleeve body externally fitted to the shaft body,
A spindle motor in which a sleeve body can freely rotate relative to a shaft body via a lubricant, and a dynamic pressure bearing portion is provided in a gap between the shaft body and the sleeve body, and an axial direction of the dynamic pressure bearing portion. A lubricant outflow prevention groove having a tapered portion on the outer peripheral portion of the shaft body on both outer sides, in which the outer diameter gradually decreases outward in the axial direction to gradually expand the radial gap with the inner peripheral surface of the sleeve body. Is provided, the gap between the shaft body and the sleeve body between the lubricant outflow prevention grooves is filled with the lubricant, and the radial gap is expanded to a position axially outward from the lubricant outflow prevention groove. Further, the air cushion portion is provided, and the gap reducing portion in which the radial gap is reduced to reduce the gas outflow velocity is provided outside the air cushion portion in the axial direction.

[0008]

According to the present invention, in the tapered portion of the lubricant outflow prevention groove, the radial gap with the inner peripheral surface of the sleeve body gradually expands outward in the axial direction as a whole, and , The outer peripheral surface inward in the axial direction is formed to have a relatively large angle with respect to the axis, and the outer peripheral surface outward in the axial direction is formed to have a relatively small angle with respect to the axis. The capacity is larger than when the axial length and the radial depth are the same and the angle of the taper portion is constant. In particular,
Since the outer peripheral surface of the tapered portion inward in the axial direction makes a relatively large angle with respect to the axial line, the lubricant outflow prevention function due to surface tension works strongly, and the axially outward portion in the tapered portion is Since the angle formed by the outer peripheral surface with respect to the axis is relatively small, the stability of the lubricant outflow prevention action against a sudden change in the surface position of the lubricant is high. Moreover, since the lubricant outflow prevention groove is provided in the shaft body located inside the sleeve body, centrifugal force does not act in a direction that reduces the lubricant outflow prevention action when the spindle motor rotates. therefore,
Even if the entire surface of the spindle motor or its bearing undergoes a sudden temperature change or shock, etc., causing a sudden change in the lubricant surface position, the lubricant outflow prevention function due to surface tension is highly stable and effective, and the temperature change It is possible to sufficiently absorb the relative amount of the lubricant due to the increase or decrease in the volume of the lubricant, the error of the lubricant injection amount, the design tolerance of each member of the spindle motor, and the like.

Further, since the lubricant is filled in the gap between the shaft body and the sleeve body between the lubricant outflow preventing grooves, both lubricant outflows irrespective of the posture of the spindle motor and the atmospheric pressure. According to the atmospheric pressure and surface tension acting on the lubricant surface in the prevention groove, the weight of the lubricant, and the like, the positions of both the lubricant surfaces are automatically located at the balanced position to prevent the lubricant from leaking.

According to the second aspect of the present invention, in the taper portion of the lubricant outflow prevention groove, the radial gap with the inner peripheral surface of the sleeve body gradually expands outward in the axial direction. Even if the bearing surface undergoes a sudden change in temperature or impact force, which causes a sudden change in the lubricant surface position, the lubricant outflow prevention function due to surface tension functions effectively, and the volume of the lubricant changes with temperature changes. It is possible to absorb the relative amount of the lubricant amount due to the error of the lubricant injection amount, the design tolerance of each member of the spindle motor, and the like. Moreover, since the lubricant outflow prevention groove is provided in the shaft body located inside the sleeve body,
Centrifugal force does not act in a direction that reduces the lubricant outflow prevention action when the spindle motor rotates.

Further, since the lubricant is filled in the gap between the shaft body and the sleeve body between the lubricant outflow prevention grooves, both lubricant outflows are performed regardless of the attitude of the spindle motor or the atmospheric pressure. According to the atmospheric pressure and surface tension acting on the lubricant surface in the prevention groove, the weight of the lubricant, and the like, the positions of both the lubricant surfaces are automatically located at the balanced position to prevent the lubricant from leaking.

Further, an air cushion portion having an enlarged radial gap is provided at a position axially outward of the lubricant outflow prevention groove to reduce the gas outflow velocity axially outward of the air cushion portion. Since there is a reduced-diameter portion in which the radial clearance is reduced, even if a sudden or large impact force is applied to the entire spindle motor or its bearing portion, outflow of gas in the air cushion portion is suppressed by the reduced-gap portion. It
Therefore, the lubricant is prevented from scattering to the outside through the gap reducing portion.

[0013]

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 as one embodiment of the present invention, and FIG.
FIG. 3 is a schematic explanatory view of the spindle motor of FIG. The target recording medium may be a hard disk or various other recording media. Further, it is not limited to the fixed shaft type, but may be a rotary type.

The bracket 10 has an upward projecting portion 10b on the inner peripheral portion of an annular recess 10a which is open upward. A vertical through hole 10c is provided in the center of the upper protruding portion 10b. Of course, the base of the hard disk drive, for example, can be used as the bracket 10 as it is.

By fitting and fixing the lower end portion of the substantially cylindrical fixed shaft body 12 (shaft body) into the through hole 10c of the bracket 10, the fixed shaft body 12 is located at the center of the annular recess 10a. It is erected. The lower inner peripheral portion of the stator core 14 is externally fitted and fixed to the upper portion of the upper protruding portion 10b. Inner peripheral lower end surface of stator core 14 and annular recess 10
An annular spacer 15 for positioning the stator core 14 in the axial direction is interposed between the bottom surface of a and a.

The stator core 14 has a stator coil 1
6 is wound. The lead-out portion of the stator coil 16 is pulled out downward through a lead-out hole 10e penetrating the bottom plate of the annular recess 10a of the bracket 10.

An annular thrust plate 12a is formed integrally 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 12a are perpendicular to the outer peripheral portion of the fixed shaft body 12 having a substantially cylindrical surface shape. It should be noted that the thrust plate may be separate from the fixed shaft body and may be fixed by press fitting or the like.

The sleeve member 20 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 (a substantially cylindrical surface-shaped inner peripheral surface) having a generally small diameter and substantially cylindrical surface shape. Portion) and the inner diameter portion 20 having an enlarged diameter above it.
b, and a large inner diameter portion 20c that is further expanded above the middle inner diameter portion 20b.

The sleeve member 20 is externally fitted to the fixed shaft body 12 from below before the fixed shaft body 12 is fitted and fixed in the through hole 10c, and the large inner diameter portion 20c of the sleeve member 20 is provided.
In addition, the annular thrust pressing plate 22 is internally fitted and fixed in a state where the inner peripheral portion is spaced from the fixed shaft body 12 by a slight radial gap. Then, the thrust pressing plate 22 and the sleeve member 2
The thrust plate 12a is fitted in the annular recess 24, which is formed inside the middle inner diameter portion 20b by 0 and has a radially inward opening. The sleeve body is composed of a thrust pressing plate 22 and a sleeve member 20. The upper end inner peripheral corner of the radial sliding portion 20a and the inner peripheral lower end corner of the thrust pressing plate 22 in the sleeve member 20 are chamfered.

The lower part of the fixed shaft body 12 is a sleeve member 20.
Of the bracket 10, most of which is fitted into the through hole 10c of the bracket 10. Hereinafter, a portion of the outer peripheral portion of the substantially cylindrical surface 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 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 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.

Upper and lower herringbone grooves 34 and 35 are provided in the upper and lower annular portions of the radial sliding portion 20a of the sleeve member 20, and the herringbone grooves 34.3 are provided.
5, and the gap between the radial receiving portion 12b of the fixed shaft body 12,
That is, the radial dynamic pressure bearing portions 36 and 37 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 herringbone grooves 34, 35 enhance their load bearing pressure. 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.

An annular lower lubricant outflow preventing groove 12c is provided below the lower herringbone groove 35 in the radial receiving portion 12b of the fixed shaft body 12. The lower lubricant outflow prevention groove 12c has a taper surface 12c1 in which an outer diameter gradually decreases outward in the axial direction (downward in this case) to gradually increase a radial gap between the sleeve member 20 and the radial sliding portion 20a. And 12c2 and the vertical plane 1 orthogonal to the axial direction
2c3. The taper surface 12c1 inward in the axial direction (upper in this case) is formed to have a relatively large angle with respect to the axis, and the taper surface 12c2 continuous to the lower side thereof in the axial direction with respect to the axis is compared. It is formed to be small. The lower end of the tapered surface 12c2 intersects with the inner circumference of the vertical surface 12c3. The angles of the tapered surfaces 12c1 and 12c2 are determined in consideration of the variation amount of the lubricant, etc.
Is preferably about 5 to 30 degrees, and the angle formed by the tapered surface 12c1 with respect to the axis is larger than the angle formed by the tapered surface 12c2, and is preferably about 10 to 45 degrees. The inner surface of the lower lubricant outflow prevention groove 12c is oil-repellent treated.

A radial gap is enlarged at a position axially outward from the lower lubricant outflow prevention groove 12c, that is, at a lower axial distance from the lower lubricant outflow prevention groove 12c. It has a lower air cushion portion 40. The lower air cushion portion 40 is the radial receiving portion 1 of the fixed shaft body 12.
2b and the radial sliding portion 20a of the sleeve member 20 are constituted by annular grooves 12d and 20d having a rectangular cross section, which are provided so as to face each other in the radial direction. In addition,
The lower air cushion portion 40 may be configured only by either the annular groove 12d or the annular groove 20d,
The sectional shape of the annular groove is not limited to the rectangular shape.

The radial gap between the fixed shaft body 12 and the sleeve member 20 below the lower air cushion portion 40 is between the lower air cushion portion 40 and the lower lubricant outflow prevention groove 12c in order to reduce the air outflow velocity. It is formed in the lower gap reducing portion 42 (the gap is, for example, about 20 μm or less) which is smaller than the radial gap.

By the upper and lower annular surfaces (axial receiving portions) of the thrust plate 12a and the upper and lower annular surfaces (axial sliding portions) of the annular recessed portion 24, the axial dynamic pressure bearing portions A1 and A, respectively.
2 are configured. The upper and lower annular surfaces of the thrust plate 12a and the upper and lower annular surfaces of the annular recess 24 face each other in parallel,
A liquid lubricant 39 is interposed between them to separate a slight axial gap. And thrust plate 12a
Herringbone-shaped grooves (not shown) are provided over the entire circumference of the upper and lower annular surfaces. The herringbone-shaped groove is provided in the sleeve member 20 and the thrust pressing plate 22.
The forward rotation causes the lubricant 39 existing between the upper and lower annular surfaces of the annular recess 24 to generate a high pressure. It should be noted that such a herringbone-shaped groove may be provided in the upper and lower annular surfaces of the annular recess 24 facing the upper and lower annular surfaces of the thrust plate 12a. It is also possible to adopt a groove other than the herringbone-shaped groove.

An annular upper lubricant outflow prevention groove 12e is provided in the lower portion of the outer peripheral portion of the fixed shaft body 12 above the thrust plate 12a facing the inner peripheral side of the thrust pressing plate 22. The upper lubricant outflow prevention groove 12e has a taper surface 12e1 in which an outer diameter gradually decreases outward in the axial direction (upward in this case), so that a radial gap with the inner peripheral surface of the thrust pressing plate 22 gradually increases. And 12e2 and a vertical surface 12e3 orthogonal to the axial direction. The taper surface 12e1 inward in the axial direction (lower side in this case) is formed to have a relatively large angle with respect to the axis, and the taper surface 12e2 continuous to the upper side in the axial direction and has a relatively large angle with respect to the axis. It is formed small. And taper surface 1
The upper end of 2e2 intersects with the inner circumference of the vertical surface 12e3. The angles of the tapered surfaces 12e1 and 12e2 are determined in the same manner as the angles of the tapered surfaces 12c1 and 12c2. The inner surface of the upper lubricant outflow prevention groove 12e is oil-repellent.

An upper air cushion portion 44 similar to the lower air cushion portion 40 is provided at a position axially outward of the upper lubricant outflow prevention groove 12e. Also, the upper air cushion portion 44
The radial gap between the fixed shaft body 12 and the thrust pressing plate 22 above the upper part of the upper part of the upper gap reducing part 4 is similar to the lower gap reducing part 42.
6 is formed.

In addition, an annular groove 20e is formed on the inner side of the lower end of the large inner diameter portion 20c of the sleeve member 20, and the inner surface of the annular groove 20e is also oil-repellent treated.

The fixed shaft body 12, the sleeve member 20, and the thrust pressing plate 2 between the upper and lower lubricant outflow preventing grooves 12c and 12e.
2 is filled with a lubricant 39, and the upper and lower surfaces of the lubricant 39 are attached to the upper and lower lubricant outflow prevention grooves 12c and 12 respectively.
It is located within e. In this way, the fixed shaft body 12
And the stator core 14, etc., the sleeve member 20, the thrust pressing plate 22, the rotor hub 28, etc.
It is configured so that it can freely rotate via the. The radial dynamic pressure bearing portions 36 and 37 can sufficiently reduce the radial displacement of the sleeve member 20 with respect to the fixed shaft body 12 during rotation, and the axial dynamic pressure bearing portions A1 and A2 cause the sleeve member 20 to move. The axial displacement with respect to the fixed shaft body 12 during rotation can be suppressed sufficiently small.

Tapered surface 12 of upper lubricant outflow prevention groove 12e
e1 and 12e2 are thrust pressing plates 22 as a whole.
The radial gap with the inner peripheral surface of the (sleeve body) gradually expands upward (outward in the axial direction), and the lower tapered surface 12e.
1 has a relatively large angle with respect to the axis, and the upper tapered surface 12e2 has a relatively small angle with respect to the axis. Therefore, the capacity of the upper lubricant outflow prevention groove 12e is equal to the axial length. And the depth in the radial direction is the same and the angle is larger than the case where the angle of the tapered surface is constant. In particular, since the lower taper surface 12e1 makes a relatively large angle with respect to the axis, the lubricant outflow prevention function due to surface tension works strongly at that portion, and the upper taper surface 12e2 makes a relatively small angle with the axis. The stability of the lubricant outflow prevention action against a sudden change in the surface position of the lubricant is high. Further, since the upper lubricant outflow prevention groove 12e is provided in the fixed shaft body 12 located inside the thrust pressing plate 22, centrifugal force acts in a direction to reduce the lubricant outflow prevention action when the spindle motor rotates. (When the shaft is used as a rotating shaft, it is more effective because the centrifugal force acts in a direction that prevents the lubricant from flowing out.) Therefore, even if the entire surface of the spindle motor or its bearing undergoes a sudden temperature change or impact force, which causes a sudden change in the lubricant surface position, the lubricant outflow prevention function due to the surface tension is highly stable and effective. It is possible to sufficiently absorb the relative amount of the lubricant due to the increase or decrease in the volume of the lubricant due to the temperature change, the error of the lubricant injection amount, the design tolerance of each member of the spindle motor, and the like. The same applies to the lower lubricant outflow prevention groove 12c.

The upper and lower lubricant outflow prevention grooves 12e and 12
Since the lubricant 39 is filled in the gap between the fixed shaft body 12 between the c and the sleeve member 20 and the thrust pressing plate 22, the vertical lubricant is prevented from flowing out regardless of the attitude of the spindle motor or the atmospheric pressure. Depending on the atmospheric pressure and surface tension acting on the surface of the lubricant 39 in the grooves 12e and 12c, the self-weight of the lubricant 39, and the like, the positions of both surfaces of the lubricant 39 are automatically located at the balanced position, and the lubricant 39 To prevent the leakage.

Further, since the upper air cushion portion 44 is provided at a position above the upper lubricant outflow prevention groove 12e and the upper gap reducing portion 46 is provided above the upper air cushion portion 44, the entire spindle motor or the bearing thereof is provided. Even if a sudden or large impact force is applied to the portion, the outflow of air in the upper air cushion portion 44 is suppressed by the upper gap reducing portion 46. Therefore, the lubricant 39 is prevented from scattering to the outside through the upper gap reducing portion 46.

Further, the lubricant 39 located in the gap between the annular recess 24 and the thrust plate 12a passes between the thrust pressing plate 22 and the sleeve member 20, and the outer peripheral portion of the thrust pressing plate 22 and the large inner diameter portion 20c. Exudation from between the inner peripheral portions means that the oil-repellent treated annular groove 20 is provided in the middle of the exudation path.
By providing e, it is effectively prevented.

FIG. 3 is an enlarged view of a main portion of a spindle motor for driving a recording medium, which is a fixed shaft type, as another embodiment of the present invention. The overall structure is the same as that of the above embodiment, but the shapes of the upper and lower lubricant outflow prevention grooves are different.

Fixed shaft body 5 facing the thrust pressing plate 50
An upper lubricant outflow prevention groove 54 is provided on the outer peripheral portion of 2, an upper air cushion portion 56 is provided above it, and an upper gap reduction portion 58 is provided above it.
This upper lubricant outflow prevention groove 54 has a tapered surface 54a.
Forms a constant angle with respect to the axis, and the outer diameter gradually decreases upward, whereby the radial gap with the inner peripheral surface of the thrust pressing plate 50 gradually increases. The angle of the tapered surface 54a with respect to the axis is determined in consideration of the amount of fluctuation of the lubricant and the like, but generally, it is desirable to be about 5 to 30 degrees. In addition,
Although not shown, the lower lubricant outflow preventing groove, the lower air cushion portion, and the lower gap reducing portion are also configured in the same manner.

In the case of this embodiment, the upper lubricant outflow prevention groove 5
Since the capacity of 4 (lower lubricant outflow prevention groove) is smaller than that in the above-described embodiment, the stability of the lubricant outflow prevention action by itself and the relative absorptivity of the lubricant amount are not as high as those in the above-mentioned embodiments. Although not provided, the upper air cushion portion 56 and the upper gap reducing portion 5
8 (lower air cushion portion and lower gap reduction portion), the leakage of the lubricant to the outside due to various factors such as sudden temperature change and impact force is effectively prevented.

Unless otherwise stated, the dimensions, the number, the material, the shape, and the relative arrangement of the constituent parts in the description of the above embodiments are not limited thereto.
The scope of the present invention is not intended to be limited to these, but is merely an example of explanation.

[0040]

According to the spindle motor of the first aspect, of the tapered portion of the lubricant outflow preventing groove provided on the shaft body, the outer peripheral surface inward in the axial direction is formed with a relatively large angle with respect to the axis line. The outer peripheral surface in the axial direction is formed with a relatively small angle with respect to the axis, and the capacity of the lubricant outflow prevention groove is large, so even if a sudden temperature change or impact is applied, the lubricant due to surface tension The outflow prevention function is highly stable and effective, and can absorb more or less the relative amount of the lubricant due to temperature changes, lubricant injection amount errors, design tolerances, and the like. Also, since the gap between the shaft body and the sleeve body between the lubricant outflow prevention grooves is filled with lubricant, the position of both lubricant surfaces is automatically adjusted regardless of the posture of the spindle motor or the atmospheric pressure. Located in a balanced position. Therefore, it is highly effective in preventing the lubricant from leaking to the outside due to various factors such as a sudden temperature change and impact force.

In the spindle motor of the second aspect, since the lubricant outflow prevention groove provided in the shaft body has the taper portion,
Even if a sudden temperature change or impact force is applied, the effect of preventing lubricant outflow due to surface tension will function effectively, and the relative amount of lubricant due to temperature change, lubricant injection amount error, design tolerance, etc. Can be absorbed. Also, since the gap between the shaft body and the sleeve body between the lubricant outflow prevention grooves is filled with lubricant, the position of both lubricant surfaces is automatically adjusted regardless of the posture of the spindle motor or the atmospheric pressure. Located in a balanced position. Further, even when a sudden or large impact force is applied, the outflow of gas in the air cushion portion is suppressed by the gap reducing portion, and the lubricant is prevented from scattering outside through the gap reducing portion. Therefore, it is highly effective in preventing the lubricant from leaking to the outside due to various factors such as a sudden temperature change and impact force.

[Brief description of drawings]

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

FIG. 2 is a schematic explanatory view of the spindle motor of FIG.

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

FIG. 4 is a schematic sectional view of a main part of a conventional spindle motor.

FIG. 5 is an enlarged explanatory view of a main part of FIG.

FIG. 6 is an enlarged explanatory view of a main part of FIG.

[Explanation of sign]

 12 Fixed shaft body 12c Lower lubricant outflow prevention groove 12c1 Tapered surface 12c2 Tapered surface 12e Upper lubricant outflow prevention groove 12e1 Tapered surface 12e2 Tapered surface 36 Radial dynamic pressure bearing portion 37 Radial dynamic pressure bearing portion 39 Lubricant 40 Lower air cushion portion 42 Lower clearance reduction section 44 Upper air cushion section 46 Upper clearance reduction section A1 Axial dynamic pressure bearing section A2 Axial dynamic pressure bearing section

Claims (2)

[Claims] 1. A spindle motor comprising a shaft body and a sleeve body fitted onto the shaft body, wherein the sleeve body is freely rotatable relative to the shaft body through a lubricant.
A dynamic pressure bearing portion is provided in the gap between the shaft body and the sleeve body, and the outer diameter is gradually reduced outward in the axial direction on the outer peripheral portions of the shaft body on both sides in the axial direction that sandwich the dynamic pressure bearing portion. A lubricant outflow prevention groove having a taper portion in which a radial gap with the inner peripheral surface of the sleeve body gradually expands is provided, and the outer peripheral surface of the taper portion inward in the axial direction has a relatively large angle with respect to the axis. The outer peripheral surface of the large outer side in the axial direction is formed with a relatively small angle with respect to the axis, and the gap between the shaft body and the sleeve body between the lubricant outflow prevention grooves is filled with the lubricant. Characteristic spindle motor. 2. A spindle motor comprising a shaft body and a sleeve body externally fitted to the shaft body, wherein the sleeve body is freely rotatable relative to the shaft body through a lubricant.
A dynamic pressure bearing portion is provided in the gap between the shaft body and the sleeve body, and the outer diameter is gradually reduced outward in the axial direction on the outer peripheral portion of the shaft body on both sides in the axial direction of the dynamic pressure bearing portion. Is provided with a lubricant outflow prevention groove having a taper portion in which a radial gap between the sleeve body and the inner peripheral surface is gradually expanded, and a lubricant is provided in a gap between the shaft body and the sleeve body between the lubricant outflow prevention grooves. In addition to being filled, it has an air cushion part with an enlarged radial gap at a position axially outward of the lubricant outflow prevention groove,
A spindle motor, characterized in that it has a gap reduction portion in which a radial gap is reduced outside the air cushion portion in the axial direction to reduce the gas outflow velocity.