JP3611387B2 - Motor with hydrodynamic bearing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor provided with thrust dynamic pressure fluid bearing means utilizing the dynamic pressure of a lubricating fluid.
[0002]
[Prior art and problems to be solved by the invention]
Utilizing the dynamic pressure at the time of relative rotation generated in the lubricating fluid held in the gap between the shaft body such as the fixed shaft or the rotating shaft provided with the thrust plate and the rotating or fixed shaft body holding body having the thrust plate holding portion. In a spindle motor having a hydrodynamic bearing means, a thrust hydrodynamic bearing means is provided by continuously filling a lubricating fluid in the radial gap between the thrust plate and the thrust plate holding portion and the gaps on both sides in the axial direction. Can be configured.
[0003]
When the spindle motor rotates at a high speed, the lubricating fluid flows outward in the radial direction by the action of centrifugal force due to the rotation. For this reason, when the rotational axis is substantially in the vertical direction and the lubricating fluid contains bubbles, bubbles are formed near the upper periphery of the thrust plate of the lubricating fluid filled in the gap between the thrust plate and the thrust plate holding portion. Are likely to be suspended, and it is often difficult to release these bubbles to the outside air.
[0004]
If the bubbles expand due to temperature rises associated with the use of the motor, etc., the lubricating fluid may leak out from the end of the gap that leads to the outside, reducing the life of the bearings or causing the outside to be contaminated by the leaked lubricating fluid. Become.
[0005]
The present invention has been made in view of the above-mentioned problems existing in the prior art, and its object is to eliminate bubbles that tend to be retained in the lubricating fluid near the upper periphery of the thrust plate. An object of the present invention is to provide a motor that can be easily released to the outside air and prevent leakage of a lubricating fluid.
[0006]
[Means for Solving the Problems]
The motor of the present invention achieves the above object,
A shaft body having a substantially axial center line and a shaft body holding body are configured to be relatively rotatable around the shaft center line of the shaft body, and one of the shaft body and the shaft body holding body is integrated with the rotor. And the other is a motor integrated with the stator,
A thrust dynamic pressure fluid is provided by a thrust plate provided in the shaft body, a thrust plate holding portion in the shaft body holding body, and a lubricating fluid continuously filled in a radial gap and gaps on both sides in the axial direction. Bearing means are configured,
The lubricating fluid is held in the gap by capillary action in a state where the inner peripheral end of the lubricating fluid in the gap on the axially upper side of the gap is in communication with the outside air,
The thrust plate has a communication hole that connects the outer peripheral surface thereof and the outer peripheral side of the upper surface, which is slightly outer than the inner peripheral end portion of the lubricating fluid,
The communication hole is filled with a lubricating fluid.
[0007]
Here, the outside air refers to an atmosphere outside the gap between the shaft body and the shaft body holding body, and may be inside or outside the motor or inside or outside the apparatus incorporating the motor. It does not matter whether the pressure of the outside air is atmospheric pressure or not.
[0008]
Since the outer peripheral surface of the thrust plate and the outer peripheral side of the upper surface of the thrust plate are slightly connected to the outer peripheral side of the inner peripheral end of the lubricating fluid, the lubricating fluid is caused by the centrifugal force due to the rotation of the motor. The lubricating fluid in the radial gap between the thrust plate and the thrust plate holding portion flows radially outward in the axially upper gap between the thrust plate and the thrust plate holding portion, and the lubricating fluid in the radial gap between the thrust plate and the thrust plate holding portion passes through the communication hole. Flows slightly to the outer peripheral side from the inner peripheral end of the lubricating fluid.
[0009]
In this way, the lubricating fluid passes through the axially upper gap between the thrust plate and the thrust plate holding portion, near the upper peripheral portion of the thrust plate, and through the radial gap between the thrust plate and the thrust plate holding portion. Circulates to the outer peripheral side slightly from the inner peripheral end of the lubricating fluid in the gap on the upper side in the axial direction. For this reason, bubbles in the lubricating fluid that tend to gather near the upper periphery of the thrust plate move slightly outside the inner peripheral edge 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 portion of the lubricating fluid is in communication with the outside air, the bubbles in the lubricating fluid are likely to be released to the outside air here.
[0010]
1 or 2 or more may be sufficient as the said communicating hole. The cross-sectional shape of the communication hole can be a circular shape or other shapes.
[0011]
The relative positions of both ends of each communication hole, that is, the relative positions of the outer peripheral surface opening and the upper surface opening of the thrust plate are as follows: (1) When the straight line connecting the two passes through the rotation axis and (2) When not passing With respect to (2), the opening on the outer peripheral surface can be set to a position shifted by, for example, about 10 to 30 degrees in the direction of the forward rotation from the opening on the upper surface.
[0012]
The path from the outer peripheral surface of the thrust plate to the upper surface of each communication hole is, for example, either (a): a straight line connecting the opening on the outer surface of the thrust plate and the upper surface. And along the intersection of a plane that includes or is parallel to the axis of rotation and a plane perpendicular to the axis of rotation, and is directed inward from the opening on the outer peripheral surface of the thrust plate, and then the axis of rotation Parallel to the line, toward the opening on the upper surface of the thrust plate, (b): Between the opening on the outer peripheral surface and the opening on the upper surface, inward from the opening on the outer peripheral surface of the thrust plate as in (a) It is possible to adopt the one that inclines inward and reaches the opening on the upper surface of the thrust plate, (c): the one that connects the opening on the outer peripheral surface of the thrust plate and the opening on the upper surface with an inclined straight line, etc. . In addition, the path | route which each communicating hole goes to the upper surface from the outer peripheral surface of a thrust board may be a curve.
[0013]
The cross-sectional shape of the communication holes, the relative positions of both ends of each communication hole, and the path of each communication hole from the outer peripheral surface of the thrust plate to the upper surface, etc., allow the lubricating fluid to open from the outer peripheral surface opening to the upper surface when the motor rotates. Although it can be selected within a range that does not hinder the flow toward the surface, examples suitable for production include those having a circular cross section and corresponding to the above (1) and (a).
[0014]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
[0015]
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 apparatus as an example of an embodiment of the present invention.
[0016]
In this example, a lower end portion of a fixed shaft body 52 having a vertical axis is fitted and fixed in a circular fitting hole 50a of the base 50 of the recording medium driving device. The fixed shaft body 52 is configured such that a thrust plate 52a is fitted and fixed to an upper portion, and a cover plate 54 is fitted and fixed to an upper end. The fixed shaft body 52 is provided with a cylindrical hole 56 coaxially from the lower end surface to the upper and lower intermediate portions, and the gap between the upper end portion of the cylindrical hole 56 and the outer peripheral portion of the fixed shaft body 52 is a diameter. The direction communication holes 58 (two in this example, but not limited thereto) communicate with each other. Further, in the cylindrical hole 56, a rod-like member 60 having a tapered lower end is disposed coaxially with the upper end fixed to the upper surface of the cylindrical hole 56.
[0017]
A rotating sleeve body 62 is rotatably fitted on the fixed shaft body 52. A small-diameter sleeve portion 62 a below the rotary sleeve body 62 is externally fitted to the lower portion of the thrust plate 52 a in the fixed shaft body 52. An enlarged diameter portion 62b on the upper portion of the rotating sleeve body 62 surrounds the upper and lower and outer peripheral portions of the thrust plate 52a together with a thrust cover 64 fitted and fixed to the upper end portion.
[0018]
FIG. 2 is a schematic plan view of the main part of the thrust plate 52a. The thrust plate 52a is provided with one or more communication holes 65 that are radially inward from the outer peripheral surface thereof and bent upward at the radial intermediate portion to reach the upper surface. A straight line connecting the outer peripheral opening 65a and the upper surface opening 65b which are both ends of the communication hole 65 passes through the rotation axis. The path of the communication hole 65 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 an intersection line between a surface including the rotation axis and a surface perpendicular to the rotation axis. Along the direction from the outer peripheral opening 65a to the inward direction, the direction toward the upper surface opening 65b is parallel to the rotation axis.
[0019]
A substantially cylindrical hub 66 is fitted and fixed to the outer peripheral portion of the rotating sleeve body 62, and a rotor magnet 67 is fixed and fitted to the lower inner peripheral side of the hub 66. A stator 68 in which a stator coil is wound around a stator core is provided on a base 50, and constitutes a rotational drive unit relative to the rotor magnet 67 in the radial direction.
[0020]
An inner peripheral lower portion of the thrust cover 64 is formed in a tapered portion 64a inclined inward and upward, and a portion of the outer peripheral portion of the fixed shaft body 52 that is opposed to the lower end portion of the sleeve portion 62a is a tapered portion 52b inclined inward and downward. Is formed.
[0021]
A gap between the fixed shaft body 52, the rotary sleeve body 62, and the thrust cover 64 is filled with lubricating oil 70 as an example of a lubricating fluid (liquid). One end thereof, that is, the inner peripheral end portion of the lubricating oil 70 in the upper gap of the thrust plate 52a faces between the base portion of the tapered 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 fixed. The lubricating oil 70 is held by capillary action in a state where it faces between the base portion of the tapered portion 52b of the shaft body 52 and the inner peripheral surface of the sleeve portion 62a and communicates with the outside air. As a result, thrust dynamic pressure fluid bearing means are configured above and below the thrust plate 52a, and radial dynamic pressure fluid bearing means are configured on the outer peripheral portion of the sleeve portion 62a.
[0022]
Between the inner peripheral surface of the cylindrical hole 56 and the outer peripheral surface of the rod-like member 60, there is a gap that is larger than the lubricant holding gap of the radial and thrust hydrodynamic bearing means and small enough to hold the lubricant 70 by capillary action. The lubricating oil 70 is formed as a holding channel 69, and the lubricating oil 70 is held in the communication hole 58 and the upper and lower intermediate portions of the holding channel 69. When the lubricating oil 70 in the gap between the radial and thrust hydrodynamic fluid bearing means decreases, the lubricating oil 70 held in the holding channel 69 is sequentially supplied to the gap through the communication hole 58.
[0023]
The communication hole 65 of the thrust plate 52a is also filled with the lubricating oil 70, and the upper surface opening of the communication hole 65 is located slightly outside the inner peripheral end of the lubricating oil 70 held on the upper side of the thrust plate 52a. To do.
[0024]
Grooves 72 and 74 and 76 and 78 (shown by broken lines) such as herringbone grooves are provided on the upper and lower surfaces of the thrust plate 52a and the inner peripheral surface of the sleeve portion 62a, respectively. Through forward rotation, a thrust load support pressure and a radial load support pressure are generated in the lubricating oil 70 at each position. In particular, these grooves increase and stabilize their load bearing pressure. These grooves can also be provided on the opposite member sides.
[0025]
When the spindle motor rotates, when the upper and lower grooves 72 and 74 of the thrust plate 52a are herringbone grooves, the pressure of the lubricating oil 70 near the center in the radial direction of each groove becomes particularly high and is included in the lubricating oil 70. The bubbles 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 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 gather in the lubricating oil 70 in the radial gap between the outer peripheral surface of the thrust plate 52a and the rotating sleeve body 62. Further, if bubbles in the lubricating oil 70 in the radial gap expand due to a rise in temperature or a decrease in the pressure of the outside air, the lubricating oil 70 may be pushed out.
[0026]
On the other hand, when the spindle motor rotates, that is, when the rotating sleeve body 62 and the thrust cover 64 constituting the rotor rotate, the lubricating oil 70 is caused by a centrifugal force to act between the upper surface of the thrust plate 52a and the thrust cover 64. In the radial direction between the outer peripheral surface of the thrust plate 52a and the rotating sleeve body 62, the lubricating oil 70 flows from the inner peripheral end of the lubricating oil 70 above the thrust plate 52a through the communication hole 65. Slightly flows to the outer periphery.
[0027]
As described above, the lubricating oil 70 passes through the gap on the upper side of the thrust plate 52 a, the vicinity of the upper peripheral portion of the thrust plate 52 a, the radial gap between the outer peripheral surface of the thrust plate 52 a and the rotary sleeve body 62, and the axial line through the communication hole 65. It circulates to the outer peripheral side slightly from the inner peripheral end portion of the lubricating oil 70 in the gap on the upper side in the direction. For this reason, bubbles in the lubricating oil 70 that tend to gather near the upper peripheral portion of the thrust plate 52a are connected to the inner peripheral end portion of the lubricating oil 70 in the gap above the thrust plate 52a through the communication hole 65 as the lubricating oil 70 circulates. Move slightly to the outer circumference. 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 to the outside air here.
[0028]
An annular recess 80 provided in an upward opening shape across the inner peripheral upper portion of the circular fitting hole 50a of the base 50 and the tapered portion 52b of the lower portion of the fixed shaft body 52 holds fine particles of the lubricating oil 70, etc. This prevents it from splashing outside.
[0029]
Further, since the inner peripheral portion of the thrust cover 64 is close to the outer peripheral surface of the fixed shaft body 52 and the lower surface and the outer peripheral surface of the cover plate 54 are also close to the thrust cover 64, fine particles of the lubricating oil 70, etc. Can be prevented by the labyrinth seal effect. At the same time, there are an annular groove on the inner peripheral lower portion of the cover plate 54, and a downward annular groove 82 and a radially inward annular groove 84 provided on the thrust cover 64 at portions corresponding to the outer peripheral lower portion of the cover plate 54, respectively. , The fine particles of the lubricating oil 70 are retained and prevented from scattering outside the motor.
[0030]
In the description of the above embodiment, the scope of the invention is limited only to the number of components, the material, the shape, the relative arrangement, etc. unless otherwise specified. It is not intended to be limiting, but merely an illustrative example.
[0031]
【The invention's effect】
In the motor of the present invention, the lubricating fluid circulates through the communication hole, and bubbles in the lubricating fluid that tend to collect in the vicinity of the upper peripheral portion of the thrust plate are formed in the gap between the thrust plate and the thrust plate holding portion in the axial center direction upper side. Since it is easy to be released to the outside air near the inner peripheral edge of the lubricating fluid that communicates with the outside air, it is possible to effectively prevent the leakage of the lubricating fluid due to the thermal expansion of the bubbles. Incurring external contamination due to fluid leakage is avoided.
[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.
[Explanation of sign]
52 Fixed shaft body 52a Thrust plate 62 Rotating sleeve body 64 Thrust cover 65 Communication hole 70 Lubricating oil

Claims (1)

A shaft body having a substantially axial center line and a shaft body holding body are configured to be relatively rotatable around the shaft center line of the shaft body, and one of the shaft body and the shaft body holding body is integrated with the rotor. And the other is a motor integrated with the stator,
A thrust dynamic pressure fluid is provided by a thrust plate provided in the shaft body, a thrust plate holding portion in the shaft body holding body, and a lubricating fluid continuously filled in a radial gap and gaps on both sides in the axial direction. Bearing means are configured,
The lubricating fluid is held in the gap by capillary action in a state where the inner peripheral end of the lubricating fluid in the gap on the axially upper side of the gap is in communication with the outside air,
The thrust plate has a communication hole that connects the outer peripheral surface thereof and the outer peripheral side of the upper surface of the thrust plate slightly from the inner peripheral end portion of the lubricating fluid,
A motor characterized in that the communication hole is filled with a lubricating fluid.

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