JP3184787B2 - Air dynamic pressure bearing, spindle motor, and rotating device using the spindle motor as a driving source of the rotating body - 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 having an air dynamic pressure bearing having a radial dynamic pressure bearing portion and a thrust dynamic pressure bearing portion, and to rotating this spindle motor such as a magnetic disk, an optical disk or a polygon mirror. The present invention relates to a rotating body device serving as a body driving source, and more particularly to prevention of wear due to contact sliding of a thrust dynamic pressure bearing surface at the time of startup.

[0002]

2. Description of the Related Art In a rotating device such as a magnetic disk device, an optical disk device or a scanner including a polygon mirror, a driving source for driving a rotating member such as a magnetic disk, an optical disk or a polygon mirror is provided with an air dynamic pressure bearing. Spindle motors are widely used. This is because the air dynamic pressure bearing has a simple structure and can be miniaturized, and because it rotates in a non-contact manner during rated rotation, there is no vibration or uneven rotation caused by the bearing, and it has excellent high-speed durability In addition, since oil and grease are not used, there is a feature that there is no contamination due to scattering of a lubricant.

However, a spindle motor having an air dynamic pressure bearing has a problem in that the dynamic pressure generating surface of the thrust bearing comes into solid contact when the rotation stops, and therefore, when it starts up, it comes into contact with the surface and wear occurs. This will be described more specifically with reference to FIG. 5, which is a conventional spindle motor having an air dynamic bearing. In FIG. 5, the thrust dynamic pressure bearing is a donut disk-shaped thrust member 5 provided at the lower end of the hub 7 on the rotor side and a donut disk provided on the base plate 1 on the stator side so as to face the donut disk-shaped thrust member 5. And a thrust pressing member 6. The thrust dynamic pressure generating surface is the lower surface of the donut disk-shaped thrust member 5 provided with the thrust dynamic pressure generating groove as shown in FIG. 4 and the smooth upper surface of the donut disk-shaped thrust pressing member 6. It is a very narrow thing. At the time of rated rotation, the dynamic pressure air is pushed into the narrow gap by the pump action, so that the air comes out of contact. Is seated on the upper surface of the donut-shaped thrust holding member 6, and the dynamic pressure generating surface comes into solid contact. Then, at the time of startup, the lower surface of the donut disk-shaped thrust member 5 rotates while being in contact with the upper surface of the donut disk-shaped thrust pressing member 6, so that wear due to contact sliding occurs.

[0004] Wear due to contact sliding generated on the thrust dynamic pressure generating surface shortens the life of the air dynamic pressure bearing and therefore the life of the spindle motor. To cope with this problem, Japanese Patent Application Laid-Open No. Hei 7-259 discloses a method in which a material having high wear resistance such as ceramic is used for the components of the thrust dynamic pressure bearing.
There is a device devised in the structure disclosed in Japanese Patent No. 849. The latter will be described with reference to FIG. 5. The gap between the radial dynamic pressure bearing surfaces, that is, the cylindrical member which is a smooth surface and the outer peripheral surface of the cylindrical member 3 in which the radial dynamic pressure generating groove is formed as shown in FIG. 3. 4 is smaller than the gap between the lower surface of the donut-shaped thrust member 5 provided with the thrust dynamic pressure generating groove and the upper surface of the donut-shaped thrust pressing member 6 which is a smooth surface. On the other hand, contact sliding on the radial dynamic pressure bearing surface is unavoidable, and only contact sliding on the thrust dynamic pressure bearing surface is prevented. In this case, a material having high wear resistance, such as ceramic, is used as a component of the radial dynamic pressure bearing. However, all of them have a problem that processing and assembly are difficult.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thrust hydrodynamic bearing surface at the time of startup in a spindle motor having an air dynamic pressure bearing or a rotary device using the spindle motor as a driving source of a rotary body. Is to prevent contact sliding.

[0006]

A radial dynamic pressure bearing portion including a cylindrical member having a closed end, and a cylindrical member inserted with a bearing clearance in the cylindrical member, a donut-shaped thrust member and a donut. rotator apparatus an air dynamic pressure bearing comprising a thrust dynamic pressure bearing portion, and this <br/> drive source of the rotating body of the spindle motor or spindle motor for supporting the rotor to the stator by comprising a disk-shaped thrust pressing member In the radial dynamic pressure bearing portion, by forming a wind pressure generating groove for applying wind pressure to a closed end clearance between the bottom surface of the cylindrical member having the closed end and the insertion end surface of the cylindrical member, The rotor, which has been lowered to the first predetermined position, is raised to the second predetermined position at the time of rated rotation, and a donut disk-shaped thrust which is a constituent member of the thrust dynamic pressure bearing portion is provided. And so as to generate a thrust dynamic pressure in the gap between the wood and the donut-shaped thrust pressing member.

In other words, conventionally, the donut disk-shaped thrust member and the donut disk-shaped thrust holding member had to be in contact with each other at the time of stoppage. The bearing members are arranged so as to be sufficiently separated from each other, and at the time of rated rotation, these thrust dynamic pressure bearing members are brought close to an interval at which thrust dynamic pressure is generated. The thrust dynamic pressure bearing member, i.e., the donut disk-shaped thrust member and the donut disk-shaped thrust holding member are brought close to each other at the time of rated rotation by utilizing wind pressure generated by a wind pressure generating groove provided in the radial dynamic pressure bearing portion. And do it.

[0008]

FIG. 1 shows a fixed shaft type spindle motor in which a rotor is supported on a stator by an air dynamic pressure bearing having a radial dynamic pressure bearing portion and a thrust dynamic pressure bearing portion. In FIG. 1, reference numeral 1 denotes a base plate of a stator;
Is a columnar member that also serves as a shaft and stands upright on the base plate 1, and 4 is a cylindrical member having a closed end. The cylindrical member 4 having a closed end has its closed end facing upward,
It is rotatably fitted into the columnar member 3. In other words, the cylindrical member 3 is inserted from the open end of the cylindrical member 4 with a narrow clearance on the order of microns. 5 is a donut-shaped thrust member integrally formed on the outer peripheral surface of the cylindrical member 4, 6 is a donut-shaped thrust holding member provided to face the thrust member, and 7 is formed integrally with the cylindrical member 4. 9 is a rotor magnet arranged and mounted on the outer peripheral surface near the lower end of the cylindrical member 4, 8 is a stator coil arranged and mounted on the base plate 1 so as to face the rotor magnet 9, and 10 is a hub 7 A rotating body such as a polygon mirror supported by the base plate 11 is a substantially cylindrical cover member that forms a bearing cover together with the base plate 1, and a donut-shaped thrust holding member 6 is fixed to the upper end thereof.

In the radial dynamic pressure bearing portion composed of the cylindrical member 3 and the cylindrical member 4, a radial dynamic pressure generating groove G1 and a wind pressure generating groove G3 are formed on the outer peripheral surface of the cylindrical member 3, and The inner peripheral surface of the cylindrical member 4 is a smooth surface. In a thrust dynamic pressure bearing portion composed of a donut disk-shaped thrust member 5 and a donut disk-shaped thrust holding member 6, a thrust dynamic pressure generating groove G is formed on the upper surface of the thrust member 5.
2 are formed, and the lower surface of the thrust holding member is a smooth surface. The radial dynamic pressure generating groove G1 is a herringbone groove as shown in FIG. 3, and the thrust dynamic pressure generating groove G2 is a spiral groove as shown in FIG. The wind pressure generating groove G3 is a spiral groove or a plurality of oblique grooves having a constant angle.

In the fixed shaft type spindle motor shown in FIG. 1 constructed as described above, when stopped, the rotor is lowered by the load including the rotating body 10 supported, and the cylindrical member 4 is seated on the cylindrical member 3. ing. In the present invention,
The position of the rotor in this state is referred to as a first predetermined position. In this state, the closed end clearance S between the bottom surface of the cylindrical member 4 having the closed end and the insertion end surface of the cylindrical upper member 3 is minimum or almost zero, so that the upper surface of the donut-shaped thrust member 5 has a donut-shaped top. The distance between the lower surface of the thrust holding member 6 and the lower surface of the thrust holding member 6 is sufficiently large, and these two members never come into contact with each other.

When the motor start switch is turned on, a current flows through the stator coil 8, and the rotor rotates at a high speed in a fixed direction, clockwise in FIG. Then, the dynamic pressure air is pushed into the narrow gap on the order of microns between the outer peripheral surface of the columnar member 3 and the inner peripheral surface of the cylindrical member 4 by the pumping action of the radial dynamic pressure generating groove G1. The cylindrical member 4 functions as a radial dynamic pressure bearing.

A spiral groove G3 is formed on the outer peripheral surface of the cylindrical member 3 in addition to the radial dynamic pressure generating groove G1, but when the rotor rotates clockwise in FIG. Since the air in the gap between the outer peripheral surface of the member 3 and the inner peripheral surface of the cylindrical member 4 is forcibly pushed upward, the blockage between the bottom surface of the cylindrical member 4 having a closed end and the insertion end surface of the cylindrical member 3. Wind pressure is applied to the end clearance S. Then, the closed end gap S is expanded, and the cylindrical member 4 having the closed end, that is, the rotor rises while rotating at high speed. Then, the donut-shaped thrust member 5 also rises while rotating at a high speed, and approaches the donut-shaped thrust holding member 6. When the clearance between the upper surface of the donut disk-shaped thrust member 5 and the lower surface of the donut disk-shaped thrust pressing member 6 is on the order of microns by the rise of the rotor, a thrust dynamic pressure is generated in this clearance. The position of the rotor in this state is referred to as a second predetermined position in the present invention.

FIG. 2 shows a rotary shaft type spindle motor in which a rotor is supported on a stator by an air dynamic pressure bearing having a radial dynamic pressure bearing portion and a thrust dynamic pressure bearing portion. In FIG. 2, the cylindrical member 4 having a closed end is erected on the base plate 1 with the open end facing upward. A radial dynamic pressure generating groove G1 and a wind pressure generating groove G3 are formed on the outer peripheral surface of a cylindrical member 3 which also serves as a rotating shaft and is inserted with a narrow clearance of the order of microns in the cylindrical member 4. The donut disk-shaped thrust member 5 is fixed to the columnar member 3. The donut disk-shaped thrust holding member 6 is fixed to the upper end of the substantially cylindrical cover member 11. The rotor magnet 9 is disposed and mounted on the lower surface of the donut disk-shaped thrust member 5, and the stator coil 8 is disposed at a position facing the rotor magnet and mounted on the base plate 1.

In the shaft rotary type spindle motor shown in FIG. 2, the rotor is lowered by the load including the rotating body 10 supported at the time of stop, and the columnar member 3 is seated on the cylindrical member 3. ing. In this state, the closed end clearance S between the insertion end surface of the columnar member 3 and the bottom surface of the cylindrical member 4 is minimum or almost zero, so that the upper surface of the donut disk-shaped thrust member 5 has a donut disk-shaped thrust pressing member. The distance from the lower surface of 6 is sufficiently large that these two members never come into contact.

When the start switch of the motor is turned on, a current flows through the stator coil 8, and the rotor rotates at a high speed in the clockwise direction by the electromagnetic action of the current and the rotor magnet. Then, the dynamic pressure air is pushed into the narrow gap on the order of microns between the outer peripheral surface of the columnar member 3 and the inner peripheral surface of the cylindrical member 4 by the pumping action of the radial dynamic pressure generating groove G1. The cylindrical member 4 functions as a radial dynamic pressure bearing.

The outer peripheral surface of the cylindrical member 3 and the cylindrical member 4 are formed by a spiral groove G3 formed on the outer peripheral surface of the cylindrical member 3.
Since the air gap of the inner circumferential surface is pushed forcibly under side of the wind pressure is applied to the closed end gap S between the insertion end face of the bottom and the cylindrical member 3 of the cylindrical member 4. Then, the closed end clearance S is expanded, and the columnar member 3, that is, the rotor rises while rotating at high speed. Then, the donut-shaped thrust member 5 also rises while rotating at a high speed, and approaches the donut-shaped thrust holding member 6. When the clearance between the upper surface of the donut disk-shaped thrust member 5 and the lower surface of the donut disk-shaped thrust pressing member 6 is on the order of microns by the rise of the rotor, a thrust dynamic pressure is generated in this clearance.

The wind pressure generating groove G3 is provided between the upper surface of the donut disk-shaped thrust member 5 and the upper surface of the donut disk-shaped thrust pressing member 6 for stopping the rotor, which has been lowered to the first predetermined position due to the load of the rotor including the rotating body 10 when stopped. Designed to generate a wind pressure required to raise the clearance with the lower surface to a position on the order of microns, that is, a second predetermined position,
The outer peripheral surface of the columnar member 3 is formed. The design of the wind pressure generation groove G3 is performed by determining various conditions such as the weight of the rotor including the rotating body 10, the length and the outer diameter of the cylindrical member, the length and the inner diameter of the cylindrical member 4, the number of rotations of the rotor, and the like. .

Although the columnar member 3 is formed integrally with the shaft, the shaft may be press-fitted and fixed to a columnar member having a shaft hole. In addition, the cylindrical member 4 having the closed end has the cylindrical portion and the bottom portion formed integrally, but these may be manufactured separately and connected later. Furthermore, if the insertion end surface of the cylindrical member 3 having a smooth surface is spherical and the bottom surface of the cylindrical member 4 having a closed end is a smooth surface, the friction torque due to the contact at the time of startup between these members is reduced. Can be smaller.

FIG. 6 shows a sundle motor SM according to the present invention.
Shows a hard disk drive using the medium 12, which is a rotating body, as a drive source.

[0020]

The present invention is a spindle motor having a structure in which the donut disk-shaped thrust member 5 is disposed below the donut disk-shaped thrust holding member 6, so that when the motor is stopped, the load is applied to the rotor to reach the first predetermined position. Descend, and these two thrust dynamic pressure bearing components are sufficiently separated from each other.
These two members do not slide at all. In the present invention, the means for raising the rotor at the first predetermined position at the time of stop to the second predetermined position at the time of rated rotation is provided by the bottom surface of the cylindrical member 4 having the closed end and the insertion end surface of the cylindrical member 3. Is applied by applying a wind pressure generated by a wind pressure generating groove G3 on the outer peripheral surface of the columnar member 3 to the closed end gap S. Therefore, no special component is added as the rotor elevating means, so that the feature of the compact air dynamic pressure bearing is not impaired. The wind pressure generating means has a simple structure, and its design and manufacture are easy.

[Brief description of the drawings]

FIG. 1 is a sectional view of a fixed shaft type spindle motor provided with an air dynamic pressure bearing according to the present invention.

FIG. 2 is a sectional view of a rotary shaft type spindle motor provided with an air dynamic bearing according to the present invention.

FIG. 3 is a diagram illustrating an example of a radial dynamic pressure generation groove.

FIG. 4 is a diagram illustrating an example of a thrust dynamic pressure generation groove.

FIG. 5 is a cross-sectional view of an example of a fixed shaft type spindle motor provided with a conventional air dynamic pressure bearing.

FIG. 6 is a perspective view of a hard disk drive using a spindle motor as a drive source.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base plate 2 Shaft 3 Columnar member 4 Cylindrical member 5 Thrust member 6 Thrust holding member 7 Hub 8 Stator coil 9 Rotor magnet 10 Rotating body 11 Bearing cover member 12 Media G1 Radial dynamic pressure generating groove G2 Thrust dynamic pressure generating groove G3 Wind pressure Generation groove SM Spindle motor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI H02K 21/14 H02K 21/14 M

Claims (8)

(57) [Claims] 1. A radial dynamic pressure bearing portion including a cylindrical member having a closed end, and a cylindrical member inserted with a bearing clearance provided in the cylindrical member, a donut-shaped thrust member, and a donut-shaped thrust retainer. A blockage between a bottom surface of a cylindrical member having the closed end and an insertion end surface of the columnar member in a spindle motor in which a rotor is supported on a stator by an air dynamic pressure bearing including a thrust dynamic pressure bearing portion including a member. By forming a wind pressure generating groove for applying a wind pressure to the end clearance in the radial dynamic pressure bearing portion, the rotor which is lowered to the first predetermined position at the time of stop is raised to the second predetermined position at the time of rated rotation, and the thrust A thrust dynamic pressure is generated in a clearance between a donut-shaped thrust member and a donut-shaped thrust holding member, which are constituent members of the dynamic pressure bearing portion. A spindle motor. 2. A radial dynamic pressure bearing portion including a cylindrical member having a closed end, and a cylindrical member inserted with a bearing clearance provided in the cylindrical member, a donut-shaped thrust member, and a donut-shaped thrust retainer. In a spindle motor that supports a rotor to a stator by an air dynamic pressure bearing including a thrust dynamic pressure bearing portion including a member, the cylindrical member having the closed end and the donut-shaped thrust member are referred to as rotor-side dynamic pressure bearing members. The cylindrical member and the donut disk-shaped thrust holding member are used as a stator-side dynamic pressure bearing member, and further, in a closed end gap between the bottom surface of the cylindrical member having the closed end and the insertion end surface of the cylindrical member. By forming a wind pressure generating groove for applying a wind pressure in the radial dynamic pressure bearing portion, the rotor descending to the first predetermined position at the time of a stop can be rotated by a rated number of times. During rotation, the thrust dynamic pressure is raised to a second predetermined position, and a thrust dynamic pressure is generated in a clearance between a donut-shaped thrust member and a donut-shaped thrust pressing member, which are constituent members of the thrust dynamic pressure bearing portion. Shaft fixed type spindle motor. 3. A radial dynamic pressure bearing section including a cylindrical member having a closed end, and a cylindrical member inserted with a bearing clearance in the cylindrical member, a donut-shaped thrust member and a donut-shaped thrust retainer. And a thrust dynamic pressure bearing portion including a thrust dynamic pressure bearing portion, wherein the cylindrical member and the donut-shaped thrust member are rotor-side dynamic pressure bearing members, and A cylindrical member having an end and the donut disk-shaped thrust holding member are used as a stator-side dynamic pressure bearing member, and a closed end clearance between the bottom surface of the cylindrical member having the closed end and the insertion end surface of the cylindrical member. By forming a wind pressure generating groove for applying a wind pressure in the radial dynamic pressure bearing portion, the rotor descending to the first predetermined position at the time of a stop can be rotated by a rated number of times. During rotation, the thrust dynamic pressure is raised to a second predetermined position, and a thrust dynamic pressure is generated in a clearance between a donut-shaped thrust member and a donut-shaped thrust pressing member, which are constituent members of the thrust dynamic pressure bearing portion. And the spindle motor. 4. A cylindrical member having a radial dynamic pressure generating groove and a wind pressure generating groove formed therein.
Or 3 spindle motors. 5. A radial dynamic pressure bearing portion including a cylindrical member having a closed end and a cylindrical member inserted with a bearing clearance in the cylindrical member, a donut-shaped thrust member and a donut-shaped thrust press. A blockage between a bottom surface of a cylindrical member having the closed end and an insertion end surface of the columnar member in a spindle motor in which a rotor is supported on a stator by an air dynamic pressure bearing including a thrust dynamic pressure bearing portion including a member. By forming a wind pressure generating groove for applying a wind pressure to the end clearance in the radial dynamic pressure bearing portion, the rotor which is lowered to the first predetermined position at the time of stop is raised to the second predetermined position at the time of rated rotation, and the thrust A thrust dynamic pressure is generated in a clearance between a donut-shaped thrust member and a donut-shaped thrust holding member, which are constituent members of the dynamic pressure bearing portion. A rotating body device using a spindle motor as a drive source for the rotating body. 6. A cylindrical member having a closed end, and said cylindrical member
And a cylindrical member that is inserted with a bearing clearance
Including radial dynamic pressure bearings and donut-shaped thrust members
And a thrust including a donut-shaped thrust holding member
An air dynamic pressure bearing comprising a dynamic pressure bearing portion;
Cylindrical member having an end and the donut-shaped thrust member
Is a rotor side dynamic pressure bearing member, and the cylindrical member is
The donut-shaped thrust holding member is attached to the stator-side dynamic pressure shaft.
A bottom surface of a cylindrical member having a closed end as a receiving member;
Between the closed end of the cylindrical member and the insertion end of the cylindrical member.
Wind pressure generating groove for applying pressure is formed in the radial dynamic pressure bearing part
By stopping When stopped, descends to the first predetermined position
The rotor-side dynamic pressure bearing member is
The thrust dynamic pressure bearing is raised to a second predetermined position.
Donut-shaped thrust member and donut which are constituent members of
Thrust dynamic pressure is generated in the gap with the plate-shaped thrust holding member.
An air dynamic pressure bearing characterized by being produced. 7. A cylindrical member having a closed end, and said cylindrical member
And a cylindrical member that is inserted with a bearing clearance
Including radial dynamic pressure bearings and donut-shaped thrust members
And a thrust including a donut-shaped thrust holding member
An air dynamic pressure bearing comprising a dynamic pressure bearing portion;
-Shaped member and the donut-shaped thrust member are subjected to rotor-side dynamic pressure.
A cylindrical member having a closed end as a bearing member;
The donut-shaped thrust holding member is attached to the stator-side dynamic pressure shaft.
A bottom surface of a cylindrical member having a closed end as a receiving member;
Between the closed end of the cylindrical member and the insertion end of the cylindrical member.
Wind pressure generating groove for applying pressure is formed in the radial dynamic pressure bearing part
By doing so, when stopped, it descends to the first predetermined position
The rotor-side dynamic pressure bearing member is
The thrust dynamic pressure bearing is raised to a second predetermined position.
Donut-shaped thrust member and donut which are constituent members of
Thrust dynamic pressure is generated in the gap with the plate-shaped thrust holding member.
An air dynamic pressure bearing characterized by being produced. 8. A radial dynamic pressure generating groove formed in the columnar member.
7. A wind pressure generating groove is formed.
7 air dynamic pressure bearing.