JP4290111B2 - Hydrodynamic bearing device - Google Patents

Description

  The present invention relates to a hydrodynamic bearing device used for OA equipment and AV equipment.

  The hydrodynamic bearing device is employed in a rotary head cylinder of a table type VTR or a camera-integrated type VTR, a polygon scanner motor of a laser copying machine, a rotational drive unit of a recording medium of a floppy (registered trademark) disk device or a hard disk device.

  Specifically, since the memory capacity of a hard disk device is increased and the data transfer speed is increased, the disk rotation device used in this type of recording device requires high speed and high precision rotation. .

A hydrodynamic bearing device as disclosed in Patent Document 1 is used for the rotating main shaft portion. This is configured as shown in FIGS.
A fixed shaft 1 and a rotating sleeve 2 pivotally supported by the fixed shaft 1 are provided. The base end of the fixed shaft 1 is fixed to the lower case 3. A hard disk 4 is attached to the outer periphery of the rotating sleeve 2.

  A radial-side dynamic pressure generating portion 5 formed between the fixed shaft 1 and the rotating sleeve 2 has a dynamic pressure generating groove 6 formed on the outer peripheral surface of the fixed shaft 1. A fixed thrust plate 9 is attached to the tip of the fixed shaft 1 by an extension shaft 8 formed with a male screw portion 7 that is screwed onto the fixed shaft 1.

  A concave portion 10 is formed on the rotating sleeve 2 side corresponding to the fixed thrust plate 9. The opening of the recess 10 is closed by a rotating thrust plate 12 having a center hole 11 having a diameter larger than the outer diameter of the extension shaft 8 at the center, and is locked to the rotating sleeve 2 by a screw 13.

  In this way, the thrust side dynamic pressure generating portion 14 formed between the concave portion 10 on the rotating sleeve 2 side, the fixed thrust plate 9 and the rotating thrust plate 12 moves on the upper and lower surfaces of the fixed thrust plate 9. Pressure generating grooves 15 and 16 are formed. The thrust side dynamic pressure generator 14 and the radial side dynamic pressure generator 5 are filled with a lubricating fluid.

  In the lower case 3, a stator winding 17 is disposed around the base end portion of the fixed shaft 1, and a magnet 18 is attached to the inner peripheral portion of the rotating sleeve 2 so as to face the stator winding 17. The extension shaft 8 is fixed to the upper case 19 with screws 20.

  In the hydrodynamic bearing device configured as described above, when the stator winding 17 is excited, the hard disk 4 rotates at high speed in a sealed space formed between the lower case 3 and the upper case 19 via the rotating sleeve 2.

By rotating the rotating sleeve 2 with respect to the fixed shaft 1, the rotating sleeve 2 rotates in a non-contact manner by pumping the lubricating fluid. The dynamic pressure generating grooves 15 and 16 of the thrust side dynamic pressure generating portion 14 are not specifically described in Patent Document 1, but are generally configured as seen in Patent Document 2 and the like. As shown in FIG. 8, the thrust dynamic pressure generating groove is formed by a circumferential herringbone groove 22, and a position 23 connecting the vertices of the herringbone is set to 1 in the radial direction of the thrust side dynamic pressure generating portion. The position is set to / 2.

  However, the above configuration has the following problems. This type rotates at a very high speed and the upper part of the thrust dynamic pressure part is open, so the temperature rises during use of the lubricating fluid, expansion of the lubricating fluid due to use in a high temperature environment, bubbles contained in the lubricating fluid ( The air tends to leak due to various factors, such as temperature expansion due to temperature rise or use in high temperature environments, and more due to variations in dispenser injection amount when lubricating fluid is injected. Has the disadvantages.

  An object of the present invention is to provide a hydrodynamic bearing device capable of preventing bearing locking and seizure due to lack of lubricating fluid generated in a high-speed rotation and high-temperature environment.

The hydrodynamic bearing device according to claim 1 of the present invention has a fixed shaft whose base end is attached to the casing, and is rotatably supported by the fixed shaft, and a recess having a larger diameter than the fixed shaft is formed at the end. A rotating sleeve having a load attached to the outer peripheral portion thereof, and being attached to the fixed shaft, one surface of which faces the bottom surface of the concave portion of the rotating sleeve , and the outer peripheral surface thereof opposes the inner peripheral surface of the concave portion. A fixed thrust plate and a disk-shaped rotary thrust plate disposed opposite to the surface opposite to the one surface of the fixed thrust plate and attached to the opening of the concave portion of the rotary sleeve ; A radial dynamic pressure generating groove is formed in a radial dynamic pressure generating portion formed by the outer peripheral surface of the fixed shaft and the inner peripheral surface of the central hole of the rotary sleeve, and the rotary thrust plate and the fixed thrust plate Opposite surface, A thrust dynamic pressure generating grooves formed in two thrust-side dynamic pressure generating portion is formed in the surface facing the bottom surface of the opening of the spare the recess of the rotary sleeve and the stationary thrust plate, the radial side dynamic pressure generating unit and the lubricant filled into the thrust side dynamic pressure generating portion, the position of the maximum pressure generating portion of the two said thrust dynamic pressure generation groove than half the radial direction of the thrust-side dynamic pressure generating portion also set to an outer diameter side of the stationary thrust plate, the effective inner diameter of the rotating thrust side in the thrust-side dynamic pressure generating portion d1, the outer diameter of the fixed thrust plate d2, and the rotating thrust plate and said fixed thrust plate the diameter of the maximum pressure generating portion of the thrust dynamic pressure generation grooves between the d3, the inner diameter of the opening of the rotary sleeve when the d4, d2 (d4-d2) > d1 ((d3 -D1)-(d2-d3)).

A hydrodynamic bearing device according to a second aspect of the present invention is the hydrodynamic bearing device according to the first aspect, wherein the thrust dynamic pressure generating groove is formed by a herringbone groove in the circumferential direction, and a position connecting the apexes of the herringbone is determined by the thrust side motion. It is characterized in that it is set on the outer diameter side of the fixed thrust plate from 1/2 in the radial direction of the pressure generating portion.
A hydrodynamic bearing device according to a third aspect of the present invention is the hydrodynamic bearing device according to the first or second aspect, wherein the effective inner diameter d1 on the rotary thrust side, the outer diameter d2 of the fixed thrust plate, and the thrust dynamic pressure generation The diameter d3 of the maximum pressure generating portion of the groove for use is d2 ² −d3 ² = d3 ² −d1 ²
It is characterized by satisfying the relationship .

  According to this configuration, there is no reduction in the flying height in the thrust direction, and it is possible to prevent locking and burning due to lack of lubricating fluid generated under high-speed rotation and high-temperature environments, and a highly reliable device that operates stably over a long period of time. It can be realized. Therefore, it is possible to realize a hydrodynamic bearing device particularly suitable for a hard disk device.

Embodiments of the present invention will be described with reference to FIGS. 1 to 5 and FIG. 9.
FIG. 1 shows a hydrodynamic bearing device used in a hard disk device. Although this hydrodynamic bearing device is illustrated with a fixed-shaft cantilever structure, it can also be used as a fixed-shaft cantilever structure.

The overall configuration shown in FIG. 1 is the same as the conventional configuration shown in FIGS. 6 and 7, but differs in detail. In addition, the same code | symbol is attached | subjected and demonstrated to what has the effect | action similar to a prior art example.
In FIG. 1, the base end of the fixed shaft 1 is fixed to the lower case 3 with a screw 24. On the rotating sleeve 2 side, a fixed thrust plate 9 is attached to the tip of the fixed shaft 1 with an extension shaft 8.

  On the rotating sleeve 2 side, there is provided a recess 10 composed of a lower surface and an upper surface of the fixed thrust plate 9 and an opposing surface along the outer peripheral surface connecting the lower surface and the upper surface, and between the fixed shaft 1 and the rotating sleeve 2. A thrust-side dynamic pressure generating portion 14 formed of a fixed thrust plate 9 and a recess 10 is formed at one end of the radial-side dynamic pressure generating portion 5 formed in the above. In the radial side dynamic pressure generating portion 5, a dynamic pressure generating groove 6 is formed on the outer peripheral surface of the fixed shaft 1. In the thrust side dynamic pressure generating portion 14, a dynamic pressure generating groove 15 is formed on the upper surface of the fixed thrust plate 9, and a dynamic pressure generating groove 16 is formed on the lower surface of the fixed thrust plate 9.

  As shown in FIG. 2, when the thickness of the fixed thrust plate 9 is t and the width of the opening of the recess 10 is ΔL, the radial gap Δd (see FIG. 3) was set to Δd> ΔL − t.

  The lubricating fluid 21 was filled from the radial side dynamic pressure generating part 5 to the thrust side dynamic pressure generating part 14. The lubricating fluid used is 95% or more of ester oil, and the remaining 5% or less is mineral oil, olefin, hydrocarbon or the like. The surface tension was adjusted to 25 dyn / cm (at 29 ° C.) or more.

  Further, in FIG. 1, the gap between the rotary sleeve 2 and the fixed shaft 1 located at the lower end of the radial dynamic pressure generating portion 5 has a taper portion 1a in which the diameter of the fixed shaft 1 gradually decreases toward the base end. The corresponding inner diameter of the rotary sleeve 2 is also made larger than that of the radial dynamic pressure generating portion 5, and a section in which the lubricating fluid does not enter due to surface tension is formed by both of them. .

  The rotating sleeve 2 is made of a copper alloy and an aluminum alloy, and a magnetic steel plate 25 is interposed between the rotating sleeve 2 and the magnet 18 in order to reduce magnetic leakage. With this configuration, when the stator winding 17 is energized, the hard disk 4 rotates at high speed in the sealed atmosphere S formed between the lower case 3 and the upper case 19 via the rotating sleeve 2, and is fixed to the fixed shaft 1. On the other hand, when the rotating sleeve 2 rotates, the lubricating fluid is pumped and the rotating sleeve 2 rotates in a non-contact manner.

The gap between the upper surface of the fixed thrust plate 9 and the lower surface of the rotating thrust plate 12 in the rotating thrust side dynamic pressure generating portion 14 is 5 μm, and the gap between the lower surface of the fixed thrust plate 9 and the lower surface of the rotating thrust plate 2 and the facing surface of the rotating sleeve 2. In the case of 10 μm, suitable performance was obtained. This is ΔL = t + 15 μm
Can be expressed as

From the viewpoint of improving the impact resistance performance in the thrust direction, it is preferable that this gap is small. However, from the viewpoint of reliability of realistic machining accuracy, the lower limit is ΔL = t + 10 μm.
Was the limit. In addition, the upper limit is ΔL = t + 30 μm from the allowable range of 500G impact resistance which is the target value.
Was the limit. Therefore, the tolerance is
ΔL = t + 10 μm to 30 μm
Can be expressed as FIG. 4 shows the measurement results of the gap and impact resistance.

If the impact resistance value, which is the target value within the practical range, is lowered without increasing the processing accuracy,
ΔL = t + 20 μm to 40 μm
Was acceptable.

Further, as shown in FIG. 3, when the gap between the upper surface of the fixed thrust plate 9 and the lower surface of the rotating thrust plate 12 is 5 μm and ΔL = t + 15 μm, the radial gap Δd at the open end is set as described above. When the clearance of the lubrication fluid used is set to 15 μm as a gap that does not allow the lubrication fluid to enter, and the splashing of the lubrication fluid from the open end of the thrust side dynamic pressure generating part during operation is verified. Fluid scattering was not confirmed. The allowable range of the radial gap Δd is Δd> ΔL−t
Met.

  The dynamic pressure generating groove 15 formed on the upper surface of the fixed thrust plate 9 in the thrust side dynamic pressure generating portion 14 is composed of a circumferential herringbone groove 22 as shown in FIG. Is set on the outer diameter side of the fixed thrust plate 9 with respect to 1/2 of the radial direction of the thrust side dynamic pressure generating portion in the radial direction.

  A position 23 connecting the vertices of the herringbone groove 22 is a maximum pressure generating portion formed in the thrust side dynamic pressure generating portion, and an inner peripheral side 26 divided at the position 23 in the thrust side dynamic pressure generating portion 14 during operation. And the outer peripheral side 27 have the same surface tension and the same amount of lubricating fluid on both sides thereof, eliminating the lubricating fluid flowing out from the inner peripheral side 26 to the outer peripheral side 27, and reducing the floating amount of the rotating sleeve 2 It can prevent the motor from being locked and burned due to lack of lubricating fluid generated under high-speed rotation and high-temperature environment.

This position 23 can be expressed as follows. As shown in FIGS. 2 and 3, the effective internal diameter d1 on the rotating thrust side in the thrust side dynamic pressure generating portion is the rotational thrust when considering the dynamic pressure generating groove 15 formed on the upper surface of the fixed thrust plate 9. The inner diameter of the plate 12. When the outer diameter of the fixed thrust plate 9 is d2, the diameter of the maximum pressure generating portion of the thrust dynamic pressure generating groove formed in the thrust side dynamic pressure generating portion is d3,
d2 ² -d3 ² = d3 ² -d1 ²
This can be realized by setting the areas of the inner peripheral side and the outer peripheral side substantially equal.

When the inner diameter of the opening of the recess 10 of the rotating sleeve 2 is d4,
d2 (d4-d2)> d1 ((d3-d1)-(d2-d3))
Set to . Here, even if the bubbles generated on the inner peripheral side of the thrust side dynamic pressure generating portion in the long-term operation move to the recess 10 between the fixed thrust plate 9 and the rotating sleeve 2, the maximum width of the bubbles in the outer peripheral portion is increased. the value,
(D1 / d2) * ((d3-d1)-(d2-d3))
Never exceed . At this time, by making the width of the opening inner diameter of the recess 10 between the fixed thrust plate 9 and the rotating sleeve 2 wider than the maximum width of the bubbles, the lubricating fluid in the recess 10 is caused by the bubbles located on the outer peripheral side. Since it is not divided , the lubricating fluid can be supplied from the outer periphery of the fixed thrust plate 9 to the herringbone groove, and a long-life hydrodynamic bearing device can be realized.

Specific numerical values of each part of the above embodiment are as follows:
d1 = 2.70 mm
d2 = 6.50 mm
d3 = 4.98 mm
d4 = 6.90 mm
Met.

  In each of the above embodiments, the dynamic pressure generating groove 15 on the upper surface of the fixed thrust plate 9 has been described. However, the same applies to the dynamic pressure generating groove 16 on the lower surface of the fixed thrust plate 9. When 16 is formed by pressing, the workability of the fixed thrust plate 9 is good by setting the positions of d3 of the dynamic pressure generating grooves 15 and 16 to be the same.

In the above embodiment, the dynamic pressure generating grooves 15 and 16 are formed by herringbone grooves, but the present invention is not limited to this, and may be formed by grooves having other shapes. Therefore, in the present invention, the technical range is limited based on the position of the maximum pressure generating portion of the thrust dynamic pressure generating groove formed in the thrust side dynamic pressure generating portion.

  INDUSTRIAL APPLICABILITY The present invention can stably operate a rotary drive unit used in various drive motors used for OA equipment and AV equipment for a long period of time, and can contribute to the realization of a highly reliable device.

Sectional drawing of embodiment of this invention Enlarged view of the main part of the same embodiment Enlarged view of the main part of the same embodiment Measurement diagram of thrust gap and impact resistance of the same embodiment A plan view and a sectional view showing a herringbone groove of the fixed thrust plate of the same embodiment Sectional view of a conventional hydrodynamic bearing device Enlarged view of the main part of FIG. Plan view showing the herringbone groove of a typical fixed thrust plate

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixed axis | shaft 2 Rotating sleeve 3 Lower case 4 Hard disk 5 Radial side dynamic pressure generating part 6 Dynamic pressure generating groove 7 Male thread part 8 Extension shaft 9 Fixed thrust plate 10 Recess 11 on the side of the rotating sleeve Central hole 12 of the rotating thrust plate Rotating thrust Plate 13 Screw 14 Thrust side dynamic pressure generating portion 15, 16 Dynamic pressure generating groove 17 of fixed thrust plate Stator winding 18 Magnet 19 Upper case 20 Screw 21 Lubricating fluid 24 Screw

Claims (4)

A fixed shaft whose base end is attached to the casing;
A rotating sleeve pivotally supported by the fixed shaft, a recess having a larger diameter than the fixed shaft is formed at an end, and a load is attached to an outer peripheral portion;
A fixed thrust plate attached to the fixed shaft, one surface of which faces the bottom surface of the concave portion of the rotating sleeve , and the outer peripheral surface of which faces the inner peripheral surface of the concave portion ;
A disk-shaped rotating thrust plate that is disposed opposite to the surface opposite to the one surface of the fixed thrust plate and is attached to the opening of the concave portion of the rotating sleeve ,
Forming a radial dynamic pressure generating groove in a radial dynamic pressure generating portion formed by the outer peripheral surface of the fixed shaft and the inner peripheral surface of the central hole of the rotary sleeve;
Thrust on the opposing surface, and the two thrust side dynamic pressure generating portion is formed in the surface facing the bottom of the opening and the fixed thrust plate of the recess of the rotary sleeve and the rotary thrust plate and the fixed thrust plate Forming a dynamic pressure generating groove,
Filling the radial side dynamic pressure generating portion and the thrust side dynamic pressure generating portion with a lubricating fluid,
Two positions of the maximum pressure producing site of the thrust dynamic pressure generation groove than half the radial direction of the thrust-side dynamic pressure generating portion is set on the outer diameter side of the stationary thrust plate,
The effective inner diameter of the rotating thrust side in the thrust-side dynamic pressure generating portion d1
The outer diameter of the fixed thrust plate d2
The diameter of the maximum pressure generating portion of the thrust dynamic pressure generation groove between the fixed thrust plate and the rotating thrust plate d3
When the inner diameter of the opening of the rotating sleeve is d4,
d2 (d4-d2)> d1 ((d3-d1)-(d2-d3))
Hydrodynamic bearing device set to The thrust dynamic pressure generating groove is constituted by a herringbone groove in the circumferential direction, and the fixed thrust plate is positioned at a position connecting the vertices of the herringbone more than ½ in the radial direction of the thrust side dynamic pressure generating portion. The hydrodynamic bearing device according to claim 1, wherein the hydrodynamic bearing device is set on the outer diameter side. The effective inner diameter d1 on the rotating thrust side, the outer diameter d2 of the fixed thrust plate, and the diameter d3 of the maximum pressure generating portion of the thrust dynamic pressure generating groove are:
d2 ² -d3 ² = d3 ² -d1 ²
The hydrodynamic bearing device according to claim 1, wherein the relationship is satisfied . A motor using the hydrodynamic bearing device according to any one of claims 1 to 3 .

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