JP3572796B2 - Hydrodynamic bearing - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydrodynamic bearing used for a high-speed rotary polygon mirror driving device or a spindle motor having particularly high rotation unevenness accuracy.
[0002]
[Prior art]
A conventional hydrodynamic bearing will be described.
In FIGS. 3 and 4, the sleeve 1 is provided with two herringbone grooves 2 at two locations. The inner diameter of this portion is slightly reduced to form the bearing portions 6 and 7, and the inserted rotary shaft is formed. Lubricating oil 4 is injected as a fluid into a gap between the shaft 3 and the shaft 3 to form a radial hydrodynamic bearing. On the other hand, a thrust bearing 5 is provided at one end of the rotating shaft 3 and rotatably supports the thrust direction. On the thrust side, a ventilation hole 13 communicating with outside air is provided.
[0003]
In this configuration, when the rotating shaft 3 rotates, dynamic pressure is generated in the bearings 6 and 7, and the lubricating oil 4 is moved in the direction of the thrust bearing or the other end in accordance with the variation of the herringbone pattern. At this time, the air layer 9 remaining in the space 8 between the bearing portions 6 and 7 plays a role of an air pocket that prevents the movement, and the phenomenon that the movement of the lubricating oil is not performed smoothly is caused. appear. For example, when the lubricating oil 4 moves in a direction in which the air layer 9 is compressed, when a certain pressure is reached, a part of the air layer 9 is pushed out of the bearing at once, and the position of the oil surface is stabilized. Then, the length L of the lubricating oil 4 between the bearings 6 and 7 and the rotary shaft 3 in FIG. 3 changes to L ′, and the bearing loss decreases.
[0004]
When the loss fluctuates, the rotation unevenness of the rotating shaft 3 becomes worse. Moreover, this phenomenon is remarkable at high speed rotation, and does not occur in a conventional VTR cylinder or FDD. In these conventional applications, the lubricating oil moves slowly because of low-speed rotation.
In order to solve this problem, it is effective to provide a communication hole communicating with the outside of the sleeve 1 in the space 8 as shown in Japanese Patent Publication No. 56-148564.
[0005]
This figure is shown in FIG. By providing the communication hole 14 at the center between the bearings of the sleeve 1, the above-mentioned problem is solved because the air layer 9 between the bearings can freely enter and exit.
However, when the communication hole 14 is formed in the sleeve 1, it is difficult to perform machining when the lateral posture or the dimension between the bearings is small, and new problems such as generation of burrs inside the bearing occur. It is desired to solve the problem of occurrence of loss fluctuation due to expansion and contraction of the air layer 9 without providing the air layer 9.
[0006]
[Problems to be solved by the invention]
In this hydrodynamic bearing, it is possible to suppress loss fluctuation at the start of rotation and obtain excellent performance without rotation unevenness without a complicated structure such as a communication hole, and especially suitable for a drive device used at high speed rotation. It is intended to be.
[0007]
[Means for Solving the Problems]
In order to solve this problem, the present invention provides a rotating shaft, a sleeve surrounding the outer periphery of the rotating shaft, rotatably holding the rotating shaft and freeing one end, and supporting one end of the rotating shaft and supporting the other end of the sleeve. A thrust bearing fixed to the thrust bearing side, having a ventilation hole communicating with external air on the thrust bearing side, providing a herringbone pattern at either one of the rotating shaft or the sleeve, and providing the thrust bearing with When the pattern width on the thrust bearing side of the closer herringbone pattern is b and the pattern width on the other shaft end side is a, the difference d in the pattern width is
d = ba > 0
When the pattern width on the thrust bearing side of the other herringbone pattern is b ′ and the pattern width on the other shaft end side is a ′, the difference d ′ in the pattern width is also
d '= b'-a'> 0
It is what it was. As a result, the lubricating oil in the bearing portion of the sleeve provided with the two herringbone patterns moves in the same direction, and moves toward the open end opposite to the thrust bearing. The influence can be reduced, and the lubricating oil can move smoothly according to the herringbone pattern. In particular, when the width is set to d ′> d, an excellent performance with a small loss change can be obtained by an effect such that the influence of the air expansion between the bearings can be minimized.
[000 8 ]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention relates to a rotating shaft, a sleeve surrounding the outer periphery of the rotating shaft, rotatably holding the rotating shaft and freeing one end, and a thrust bearing fixed to the other end of the supporting sleeve supporting one end of the rotating shaft. The thrust bearing side has a ventilation hole communicating with external air , a herringbone pattern is provided at one of two positions of the rotating shaft or the sleeve, and a herringbone pattern closer to the thrust bearing is provided. When the pattern width on the thrust bearing side is b and the pattern width on the other shaft end side is a, the difference d in the pattern width is
d = ba > 0
When the pattern width on the thrust bearing side of the other herringbone pattern is b ′ and the pattern width on the other shaft end side is a ′, the difference d ′ in the pattern width is also
d '= b'-a'> 0
The lubricating oil in the bearing portion of the sleeve provided with the two herringbone patterns moves in the same direction, and moves toward the open end opposite to the thrust bearing, so that it exists in the space between the bearings. The effect of the air layer can be reduced, the lubricating oil can move smoothly in accordance with the herringbone pattern, and the effect of suppressing rapid loss fluctuation can be obtained.
[000 9 ]
Also, the pattern width difference d and d ′ is d ′ > d.
The lubricating oil can be moved smoothly even at the time of high-speed rotation such as several thousand to tens of thousands of rpm or rotation start at low temperature, and the rapid It has the effect that loss fluctuation can be suppressed.
[00 10 ]
When the larger of a + b or a ′ + b ′ of the pattern width is L,
L / 10 ≧ d, d ′ > 0
This limits the level at which the amount of transfer of the lubricating oil does not become excessive, and has the effect of preventing the effect of a short start-up time or the influence of the air layer in the thrust portion.
[001 1 ]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Example 1)
In FIG. 1, the sleeve 1 is provided with two herringbone grooves 10 and 11 at two locations, and these portions have slightly smaller inner diameters to form the bearing portions 6 and 7, and the rotating shaft inserted therein. A lubricating oil 4 is injected as a fluid into a gap between the bearing 3 and a fluid dynamic bearing. On the other hand, a thrust bearing 5 is provided at one end of the rotating shaft 3 and rotatably supports the thrust direction. On the thrust side, a ventilation hole 13 communicating with outside air is provided. The patterns of the herringbone grooves 10 and 11 each have a pattern width b and b ′ in a direction close to the thrust bearing 5 and have widths a and a ′ on the opposite side, and a difference d and d in the pattern width. Are d = ba and d '= b'-a, respectively.
d > 0 and d ′ > 0
, And d and d ′ are substantially equal.
[001 2 ]
In this configuration, when the rotating shaft 3 rotates, dynamic pressure is generated in the bearing portions 6 and 7, and the lubricating oil 4 is moved from the thrust bearing side toward the other end in accordance with the herringbone pattern. That is, a dynamic pressure is generated from the long side to the short side of the herringbone pattern. At this time, the change in the volume of the space 8 between the bearing portions 6 and 7 is minimized, and the remaining air layer 9 moves in the same manner as the movement of the lubricating oil 4 and does not hinder the movement of the lubricating oil 4. Therefore, a sudden loss fluctuation can be suppressed. When the air layer 9 is relatively large, if d ′> d, it is possible to absorb air expansion due to a rapid temperature rise at the time of starting the bearing portions 6 and 7. If the values of d ′ and d are too large, the movement of the lubricating oil 4 becomes abrupt and the air layer 12 at the thrust bearing 5 is affected. Is set to L, it is most effective to set d ′ and d between approximately 0 and L / 10.
[001 3 ]
【The invention's effect】
As described above, according to the present invention, there is obtained an advantageous effect that the fluctuation of the load loss of the bearing immediately after the start is suppressed, and good rotation unevenness can be obtained immediately after the start.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a hydrodynamic bearing according to a first embodiment of the present invention; FIG. 2 is a conceptual diagram for explaining the operation of the hydrodynamic bearing in the first embodiment; FIG. FIG. 4 is a conceptual view for explaining the operation of a conventional hydrodynamic bearing. FIG. 5 is a cross-sectional view for explaining countermeasures of the conventional hydrodynamic bearing.
DESCRIPTION OF SYMBOLS 1 Sleeve 2,10,11 Herringbone groove 3 Rotating shaft 4 Lubricating oil 5 Thrust bearing 6,7 Bearing part 8 Space 9,12 Air layer 13 Vent hole 14 Communication hole

Claims (3)

Consists of a rotary shaft, and the outer circumference of the rotary shaft surrounds the rotatably holds the rotating shaft, one end of which is release sleeve, which is fixed to the other end of the sleeve supporting the one end of the rotary shaft and the thrust bearing, this On the thrust bearing side, there is a ventilation hole that communicates with external air, and a herringbone pattern is provided at either one of the rotating shaft or the sleeve, and the herringbone pattern closer to the thrust bearing on the thrust bearing side. When the pattern width is b and the pattern width on the other shaft end side is a, the pattern width difference d is
d = ba > 0
When the pattern width on the thrust bearing side of the other herringbone pattern is b ′ and the pattern width on the other shaft end side is a ′, the difference d ′ in the pattern width is also
d '= b'-a'> 0
A hydrodynamic bearing comprising: The pattern width difference d and d 'is d'> d
The hydrodynamic bearing according to claim 1, wherein When the larger of a + b or a ′ + b ′ of the pattern width is L,
L / 10 ≧ d, d ′ > 0
The hydrodynamic bearing according to any one of claims 1 to 2, wherein

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