JPH09191599A - Motor with dynamic pressure fluid bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the leakage of a lubricating fluid by making a bubble easy to release into the air, which is easy to be stored into the lubricating fluid in the vicinity of the upper part of the outer circumference of a thrust plate. SOLUTION: A rotary sleeve body 62 is rotatably and externally fitted to a fixed shaft body 52. A communicating hole 65 is provided which is headed inwardly in the radial direction from the outer circumferential surface, bent upward in the middle part in the radial direction and reaches the upper surface. A lubricating oil 70 is filled into a gap between the fixed shaft body 52 and the rotary sleeve body 62 and between the fixed shaft body 52 and a thrust cover 64 and the communicating hole 65. The inner circumferential end part of the lubricating oil 70 in the gap on the upper side of the thrust plate 52a is made to communicating with the air. The upper surface opening of the communicating hole 65 is located slightly nearer to the outer circumferential side than the inner circumferential end part of the lubricating oil 70 held on the upper side of the thrust plate 52a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor provided with thrust dynamic pressure fluid bearing means which utilizes dynamic pressure of a lubricating fluid.

[0002]

2. Description of the Related Art A shaft member such as a fixed shaft or a rotary shaft provided with a thrust plate and a rotating or fixed shaft member holding member having a thrust plate holding portion are held in a gap. In a spindle motor equipped with a hydrodynamic bearing means that utilizes the dynamic pressure generated in the lubricating fluid during relative rotation, the lubricating fluid is applied to the radial gap between the thrust plate and the thrust plate holding part and to the gaps on both sides in the axial direction. Can be continuously filled to form the thrust dynamic pressure fluid bearing means.

When the spindle motor rotates at high speed, the lubricating fluid flows radially outward due to the action of centrifugal force due to the rotation. Therefore, when the rotation axis is almost vertical and the lubricating fluid contains air bubbles, the air bubbles near the upper part of the outer periphery of the thrust plate out of the lubricating fluid that fills the gap between the thrust plate and the thrust plate holding part. Are likely to be retained, and it is often difficult for these bubbles to be released to the outside air.

When the air bubbles expand due to a rise in temperature accompanying the use of the motor, the lubricating fluid leaks from the end of the gap communicating with the outside, shortening the life of the bearing or polluting the outside with the leaked lubricating fluid. The fear increases.

The present invention has been made in view of the above problems existing in the prior art, and its object is to be retained in the lubricating fluid near the upper outer periphery of the thrust plate. Another object of the present invention is to provide a motor capable of easily releasing air bubbles formed into the outside air to prevent leakage of lubricating fluid.

[0006]

A motor according to the present invention achieves the above object, wherein a shaft body and a shaft body holding body having a shaft center line in a substantially vertical direction are the shaft center lines of the shaft body. Is a motor in which one of the shaft body and the shaft body holding body is integral with the rotor and the other is integral with the stator, the thrust plate being provided in the shaft body, and the shaft. Thrust plate holding portions in the body holding body, and a lubricating fluid that continuously fills the radial gaps and the gaps on both sides in the axial direction of the body form thrust dynamic fluid bearing means. In the gap, the inner peripheral end portion of the lubricating fluid in the gap on the upper side in the axial direction of the gap is held by the capillary phenomenon in a state of communicating with the outside air, and the thrust plate is lubricated on its outer peripheral surface and its upper surface. Slightly outside the inner peripheral edge of the fluid Has a communication hole connecting the side, the communication hole is to be satisfied with a lubricating fluid.

Here, the outside air means the atmosphere outside the gap between the shaft body and the shaft body holder, and it may be inside or outside the motor or inside or outside the device incorporating the motor. The pressure of the outside air may be atmospheric pressure or not.

Since the outer peripheral surface of the thrust plate and the upper surface of the upper surface of the upper surface of the thrust plate, which is slightly outer peripheral than the inner peripheral end portion of the lubricating fluid, are connected by a communication hole, the lubricating fluid is subjected to centrifugal force generated by rotation of the motor. By the action, it flows outward in the radial direction in the gap between the thrust plate and the thrust plate holding portion in the axially upper direction, and the lubricating fluid in the radial gap between the thrust plate and the thrust plate holding portion passes through the communication hole in the axial direction. The lubricating fluid in the upper gap flows slightly outward from the inner peripheral end.

As described above, the lubricating fluid passes from the gap between the thrust plate and the thrust plate holding portion on the axially upper side to the vicinity of the outer peripheral upper portion of the thrust plate and the radial gap between the thrust plate and the thrust plate holding portion. , Through the communication hole, the lubricating fluid circulates in the gap on the axially upper side to the outer peripheral side slightly from the inner peripheral end. Therefore, bubbles in the lubricating fluid that tend to collect near the upper outer periphery of the thrust plate move to the outer peripheral side of the inner peripheral end of the lubricating fluid in the axially upper gap through the communication hole as the lubricating fluid circulates. To do. Since the inner peripheral end of the lubricating fluid communicates with the outside air, bubbles in the lubricating fluid are likely to be released into the outside air here.

The number of the communication holes may be one or two or more. The cross-sectional shape of the communication hole can be circular or any other shape.

Further, the relative positions of both ends of each communication hole, that is, the relative positions of the opening on the outer peripheral surface of the thrust plate and the opening on the upper surface may or may not pass through a straight line connecting them. For example, the opening on the outer peripheral surface is in the direction of forward rotation more than the opening on the upper surface, for example, about 10 at the center angle.
The position can be shifted by about 30 degrees.

In each of the above-mentioned cases and the above-mentioned cases, the path of each communication hole from the outer peripheral surface of the thrust plate to the upper surface is, for example,
(a): Along the line of intersection of a plane that includes the straight line connecting the outer peripheral surface opening and the upper surface opening of the thrust plate and includes or is parallel to the axis of rotation, and the plane perpendicular to the axis of rotation. , Which goes inward from the opening on the outer peripheral surface of the thrust plate and then heads to the opening on the upper surface of the thrust plate parallel to the axis of rotation, (b): between the outer peripheral surface opening and the upper surface opening As in the case of (a), after going inward from the opening on the outer peripheral surface of the thrust plate, it inclines inward upward and reaches the opening on the upper surface of the thrust plate,
(c): It is possible to employ, for example, one in which the opening on the outer peripheral surface of the thrust plate and the opening on the upper surface are connected by an inclined straight line. In addition,
The path of each communication hole from the outer peripheral surface of the thrust plate to the upper surface may be curved.

The cross-sectional shape of the communication hole, the relative positions of both ends of each communication hole, the path of each communication hole from the outer peripheral surface of the thrust plate to the upper surface, and the like are such that the lubricating fluid flows from the opening of the outer peripheral surface of the thrust plate during motor rotation. Although it can be selected within a range that does not hinder the flow toward the opening on the upper surface, examples suitable for manufacturing include those having a circular cross section and corresponding to the above (a).

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a schematic sectional view of a spindle motor for driving a recording medium (for example, a hard disk) incorporated in a recording medium driving device as an example of an embodiment of the present invention.

In this example, the base 50 of the recording medium driving device is used.
The lower end portion of a fixed shaft body 52 having a vertical axis line is fitted and fixed in the circular fitting hole 50a. Fixed shaft 52
The thrust plate 52a is externally fitted and fixed on the upper part, and the cover plate 54 is externally fitted and fixed on the upper end. The fixed shaft body 52 has a cylindrical hole 5 extending from the lower end surface to the upper and lower intermediate portions.
6 is provided coaxially, and a communication hole 58 in the radial direction is provided between the upper end portion of the cylindrical hole 56 and the outer peripheral portion of the fixed shaft body 52.
(The number is two in this example, but is not limited to this.). Further, in the cylindrical hole 56, a rod-shaped member 60 having a tapered lower end is arranged coaxially with the upper end fixed to the upper surface of the cylindrical hole 56.

The fixed shaft body 52 has a rotating sleeve body 62.
Is rotatably fitted on the outside. A small-diameter sleeve portion 62a at the lower portion of the rotary sleeve body 62 is externally fitted to a portion of the fixed shaft body 52 below the thrust plate 52a. The enlarged diameter portion 62b of the upper portion of the rotary sleeve body 62 is provided with the thrust cover 64 fixedly fitted in the upper end portion thereof along with the thrust plate 52a.
It surrounds the top, bottom, and outer circumference.

FIG. 2 is a schematic plan view of a main part of the thrust plate 52a. The thrust plate 52a is provided with one or two or more communication holes 65 extending radially inward from the outer peripheral surface of the thrust plate 52a and bending upward in the radial middle portion to reach the upper surface. A straight line connecting the outer peripheral opening 65a at both ends of the communication hole 65 and the upper surface opening 65b passes through the rotation axis. The path through which the communication hole 65 extends from the outer peripheral opening 65a to the upper surface opening 65b includes a straight line connecting the outer peripheral opening 65a and the upper surface opening 65b, and a line of intersection between a plane including the rotation axis center line and a plane perpendicular to the rotation axis center line. After going inward from the outer peripheral opening 65a, it goes toward the upper surface opening 65b parallel to the axis of rotation.

A substantially cylindrical hub 66 is externally fitted and fixed to the outer peripheral portion of the rotary sleeve body 62, and a rotor magnet 67 is internally fitted and fixed to the lower inner peripheral side of the hub 66. A stator 68, which is formed by winding a stator coil around a stator core, is provided on the base 50, and constitutes a rotary drive unit in a radial direction facing the rotor magnet 67.

A lower inner peripheral portion of the thrust cover 64 is formed into a taper portion 64a inclined inward and upward, and a portion of the outer peripheral portion of the fixed shaft body 52 facing the lower end portion of the sleeve portion 62a is inclined inward and downward. It is formed on the tapered portion 52b.

A lubricating oil 70, which is an example of a lubricating fluid (liquid), is filled in the gap between the fixed shaft body 52, the rotating sleeve body 62, and the thrust cover 64. Lubricating oil 70 at one end thereof, that is, in the gap above the thrust plate 52a
The inner peripheral end portion of the above is exposed between the base of the taper portion 64a of the thrust cover 64 and the upper surface of the thrust plate 52a and communicates with the outside air, and the other end is inside the base portion of the taper portion 52b of the fixed shaft body 52 and the sleeve portion 62a. The lubricating oil 70 is retained by the capillary phenomenon in a state where it faces the outer surface and communicates with the outside air.
As a result, thrust dynamic pressure fluid bearing means is formed above and below the thrust plate 52a, and radial dynamic pressure fluid bearing means is formed on the outer peripheral portion of the sleeve portion 62a.

A space between the inner peripheral surface of the cylindrical hole 56 and the outer peripheral surface of the rod-shaped member 60 is larger than the lubricating oil holding gap of the radial and thrust hydrodynamic bearing means and is sufficient to hold the lubricating oil 70 by capillary action. A small gap is formed as the holding channel 69, in the communication hole 58 and in the holding channel 6.
Lubricating oil 70 is held upward from the upper and lower intermediate portions of 9. When the lubricating oil 70 in the gap between the radial and thrust hydrodynamic bearing means decreases, the lubricating oil 70 held in the holding channel 69 is sequentially replenished through the communication hole 58 to the gap.

The communication hole 65 of the thrust plate 52a is also filled with the lubricating oil 70, and the upper opening of the communication hole 65 is slightly outside the inner peripheral end of the lubricating oil 70 held above the thrust plate 52a. Located on the side.

Grooves 72 and 74, such as herringbone grooves, and 76 and 78 (shown by broken lines) are provided on the upper and lower surfaces of the thrust plate 52a and the inner peripheral surface of the sleeve portion 62a, respectively. Cover 64
By the forward rotation of the lubricating oil 70 at each position,
It generates thrust load bearing pressure and radial load bearing pressure, respectively. In particular, these grooves increase and stabilize their load bearing pressure. These grooves can also be provided on the sides of the members facing each other.

When the spindle motor rotates, if the upper and lower grooves 72 and 74 of the thrust plate 52a are herringbone grooves, the lubricating oil 7 near the central portion in the radial direction of each groove 7
The pressure of 0 becomes particularly high, and the bubbles contained in the lubricating oil 70 are likely to move to the inner peripheral side or the outer peripheral side of the thrust plate 52a. The bubbles that have moved to the inner peripheral side on the upper side of the thrust plate 52a are effectively released from the inner peripheral end portion of the lubricating oil 70 to the outside air. On the other hand, the bubbles that have moved to the outer peripheral side of the thrust plate 52a are likely to collect in the lubricating oil 70 in the radial gap between the outer peripheral surface of the thrust plate 52a and the rotary sleeve body 62. Further, when the bubbles in the lubricating oil 70 in the radial gap expand due to the temperature rise or the pressure reduction of the outside air, the lubricating oil 70 may be pushed out.

On the other hand, the lubricating oil 70 is supplied when the spindle motor rotates, that is, when the rotating sleeve body 62 and the thrust cover 64 forming the rotor rotate.
Due to the action of the centrifugal force, it flows radially outward in the gap between the upper surface of the thrust plate 52a and the thrust cover 64,
The lubricating oil 70 in the radial gap between the outer peripheral surface of the thrust plate 52a and the rotary sleeve body 62 flows through the communication hole 65 to the slightly outer peripheral side of the inner peripheral end portion of the lubricating oil 70 on the upper side of the thrust plate 52a.

As described above, the lubricating oil 70 is used for the thrust plate 5
2a, from the gap above the outer periphery of the thrust plate 52a and the outer peripheral surface of the thrust plate 52a to the rotary sleeve 62.
Through a communication hole 65, and the lubricating oil 70 circulates to a slightly outer peripheral side than an inner peripheral end of the lubricating oil 70 in an axially upper clearance. Therefore, air bubbles in the lubricating oil 70, which tend to collect near the upper outer periphery of the thrust plate 52 a, pass through the communication holes 65 as the lubricating oil 70 circulates.
The lubricating oil 70 in the gap on the upper side of “a” moves slightly to the outer peripheral side from the inner peripheral end. Since the inner peripheral end portion of the lubricating oil 70 communicates with the outside air, the bubbles in the lubricating oil 70 are effectively released here to the outside air.

An annular recess 80, which is provided in an upward opening and extends over the inner periphery of the circular fitting hole 50a of the base 50 and the taper portion 52b of the lower portion of the fixed shaft 52, holds fine particles of the lubricating oil 70 and the like. Then, it is to prevent scattering to the outside of the motor.

Further, the thrust cover 64 has an inner peripheral portion close to the outer peripheral surface of the fixed shaft body 52, and a thrust cover 64 on the lower surface and the outer peripheral surface of the cover plate 54, respectively.
Since they are close to each other, scattering of fine particles of the lubricating oil 70 to the outside can be prevented by a labyrinth seal-like effect. At the same time, the annular groove at the lower inner periphery of the cover plate 54 and the downward annular groove 82 and the radially inward annular groove 84 respectively provided in the portion of the thrust cover 64 facing the outer peripheral lower portion of the cover plate 54.
However, it prevents particles of the lubricating oil 70 and the like from being retained and scattered outside the motor.

In the description of the above embodiment, the number of components, the material, the shape, the relative arrangement, etc., of the components are within the scope of the invention unless otherwise specified. It is not intended to be limited to these, but merely an example of explanation.

[0031]

In the motor of the present invention, the lubricating fluid circulates through the communication holes, and the bubbles in the lubricating fluid that tend to collect near the upper outer periphery of the thrust plate form the axial center line between the thrust plate and the thrust plate holding portion. In the gap on the upper side in the direction, the lubricating fluid communicating with the outside air is easily released to the outside air in the vicinity of the inner peripheral end, so that the risk of leakage of the lubricating fluid due to thermal expansion of bubbles can be effectively prevented, and the bearing due to insufficient lubricating fluid can be prevented. It is possible to avoid shortening the service life and causing external pollution due to leakage of lubricating fluid.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a spindle motor for driving a recording medium.

FIG. 2 is a schematic plan view of a main part of a thrust plate.

[Description of sign]

 52 Fixed shaft body 52a Thrust plate 62 Rotating sleeve body 64 Thrust cover 65 Communication hole 70 Lubricating oil

Claims (1)

[Claims] 1. A shaft body having a substantially vertical axis and a shaft holder are configured to be rotatable relative to each other about the axis of the shaft, and among the shaft and the shaft holder. A motor, one of which is integral with a rotor and the other of which is integral with a stator, includes a thrust plate included in the shaft body, a thrust plate holding portion of the shaft body holding body, a radial gap between them, and a shaft center line. With the lubricating fluid that continuously fills the gap on both sides in the direction,
Thrust dynamic pressure fluid bearing means is configured, and the lubricating fluid is held in the gap by a capillary phenomenon in a state where an inner peripheral end portion of the lubricating fluid in a gap on an axially upper side of the gap communicates with the outside air, The thrust plate has a communication hole that connects the outer peripheral surface of the thrust plate and a part of the upper surface of the upper surface that is slightly outer peripheral than the inner peripheral end portion of the lubricating fluid, and the communication hole is filled with the lubricating fluid. And a motor.