JP3681018B2 - Hydrodynamic bearing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydrodynamic bearing having a structure for preventing leakage of a lubricant.
[0002]
[Prior art]
Conventionally, as a hydrodynamic bearing, as shown in FIG. 3, there is one that is incorporated in a spindle motor that rotationally drives a recording disk such as an optical / magnetic disk drive device. For example, a stainless steel shaft 101 and, for example, a copper-based alloy sleeve 102 constitute the dynamic pressure bearing. A magnet 103 is fixed to the sleeve 102, and a base portion 105 of the shaft 101 is fitted and fixed to, for example, an aluminum alloy disk member 106. A magnetic coil 107 is fixed to the disk member 106 so as to face the magnet 103.
[0003]
The shaft 101 has a small diameter portion 110 formed at one end in the axial direction, a flange portion 111 adjacent to the small diameter portion 110, and a large diameter portion 112 adjacent to the flange portion 111. On the outer peripheral surface of the large-diameter portion 112, a dynamic pressure groove 113 having a V shape, a herringbone shape or a double helical shape is formed so as to be arranged in the circumferential direction. A cover portion (thrust cover) 115 of the sleeve 102 is opposed to the small diameter portion 110 of the shaft 101, and an inner cylinder portion 116 of the sleeve 102 is opposed to the large diameter portion 112 of the shaft 101. The lid portion 115 and the inner cylinder portion 116 of the sleeve 102 are opposed to each other with the flange portion 111 of the shaft 101 interposed therebetween. Axial support dynamic pressure grooves 117 are formed on the axial surface 111 </ b> A of the flange portion 111.
[0004]
In the spindle motor, the magnet 103 and the sleeve 102 are integrally rotated by a rotating magnetic field generated by the magnetic coil 107. Then, the dynamic pressure groove 113 formed in the large diameter portion 112 of the shaft 101 generates a dynamic pressure in the radial direction in the oil as the lubricant, and supports the sleeve 102 in the radial direction with respect to the shaft 101. On the other hand, the dynamic pressure grooves 117 formed in the flange portion 111 of the shaft 101 generate axial dynamic pressure in the lubricant, and support the sleeve 102 in the axial direction with respect to the shaft 101.
[0005]
[Problems to be solved by the invention]
By the way, the hydrodynamic bearing has a structure in which the small-diameter portion 111 is inserted into the through hole 120 of the lid portion 115 and the lid is not provided on the upper portion.
[0006]
However, since the through hole 120 is open to the outside, oil as a lubricant may leak out from the through hole 120. For example, air may be mixed in the oil of the dynamic pressure bearing when the dynamic pressure bearing is assembled or when the motor rotates. In such a case, when the temperature of the dynamic pressure bearing part rises or the outside of the motor becomes low pressure with respect to the dynamic pressure bearing part, the air expands significantly and oil is pushed out of the dynamic pressure bearing to the outside. Will occur. On the other hand, for some reason, an impact load or centrifugal force may be applied to the motor from the outside of the motor. Also in this case, the oil that cannot be held by the hydrodynamic bearing is scattered and causes oil leakage.
[0007]
When oil leakage occurs, the amount of oil retained in the fluid dynamic pressure bearing decreases, making it difficult to support the bearing with high accuracy and stability, and significantly reducing the bearing life. In addition, the oil leaked to the outside of the motor contaminates the disk storage chamber and causes a disk read / write failure. The present invention has been made in view of the above-mentioned problems existing in the prior art, and the problem is that a lubricating fluid caused by a difference in atmospheric pressure inside or outside the motor, a load applied from the outside of the motor, or the like. It is an object of the present invention to provide a hydrodynamic bearing that can eliminate the leakage of the fluid with a simple configuration.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a hydrodynamic bearing according to the invention of claim 1 includes a small diameter portion formed at one end in the axial direction, a large diameter portion adjacent to the small diameter portion, and a flange portion adjacent to the large diameter portion. And a sleeve having a through-hole that encloses the shaft and into which the small-diameter portion of the shaft is fitted, and the dynamic pressure is applied to the axial surface of the flange portion or the bearing surface of the sleeve facing the axial surface. A hydrodynamic bearing in which a groove is formed,
A first annular path formed by a peripheral surface of the large-diameter portion of the shaft and a large-diameter inner peripheral surface of the sleeve facing the peripheral surface;
A second annular narrow passage formed by the peripheral surface of the small-diameter portion and the small-diameter inner peripheral surface of the through hole of the sleeve facing the peripheral surface;
An introduction passage that is continuous with the first annular passage and the second annular passage and extends radially outward between the first annular passage and the second annular passage;
And a lubricant reservoir communicating with the introduction path.
[0009]
According to the first aspect of the present invention, the lubricant traveling outward in the axial direction from between the flange portion of the shaft and the sleeve is first, by the first annular narrow passage between the large diameter portion of the shaft and the sleeve, Progress is hindered. In the unlikely event that the lubricant has passed through the first annular passage, it is stored in the lubricant reservoir through the introduction passage extending radially outward in accordance with the centrifugal force. Progress is suppressed. Furthermore, in the unlikely event that the lubricant advances from the lubricant reservoir or the introduction path to the small diameter portion of the shaft, it is prevented from advancing by the second annular narrow path between the small diameter portion and the sleeve. Therefore, according to the first aspect of the present invention, the leakage of the lubricant can be prevented almost completely.
[0010]
According to a second aspect of the present invention, in the hydrodynamic bearing according to the first aspect, the first annular narrow passage is tapered toward the flange portion.
[0011]
Therefore, according to the invention of claim 2, a so-called capillary seal effect that prevents leakage to the outside using the surface tension of the lubricant existing in the first annular passage can be exhibited, and the sealing performance can be further improved. Can do.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.
[0013]
[First Embodiment]
FIG. 1 shows the structure of the main part of the first embodiment of the hydrodynamic bearing of the present invention. In this embodiment, a shaft 1 and a sleeve 2 surrounding the shaft 1 are provided. The shaft 1 includes a small diameter portion 3 formed at one end in the axial direction, a large diameter portion 5 adjacent to the small diameter portion 3, and a flange portion 6 adjacent to the large diameter portion 5. Axial-supporting dynamic pressure grooves 7 are formed on the axial surface 6A of the flange portion 6.
[0014]
On the other hand, the sleeve 2 has a sleeve body 8 and a lid 10. The sleeve body 8 has a radial recess 14 that accommodates the flange portion 6, and the bearing surface 14 </ b> A of the recess 14 faces the axial surface 6 </ b> A of the flange portion 6. The opposing clearance on both sides is set to 5 to 20 μm.
[0015]
The lid 10 is fitted and fixed to an annular recess 11 formed at one end of the sleeve body 8 in the axial direction. And the small diameter part 3 of the axis | shaft 1 is inserted by the through-hole 12 formed in the center of this cover part 10. As shown in FIG. The peripheral surface 3A of the small diameter portion 3 and the small diameter inner peripheral surface 12A of the through hole 12 facing the peripheral surface 3A constitute a second annular narrow passage 16. The clearance dimension of the narrow path 16 is set to 30 to 70 μm.
[0016]
The annular recess 11 has a deep portion 11A on the outer peripheral side and a shallow portion 11B on the inner peripheral side. The deep portion 11 </ b> A and the inner surface 10 </ b> A of the lid portion 10 form a lubricant reservoir 17. The shallow portion 11 </ b> B and the inner surface 10 </ b> A of the lid portion 10 form an introduction path 18. The introduction path 18 communicates straight with the radial narrow path 20 formed by the inner surface 10A of the lid portion 10 and the step surface 5B of the large diameter portion 5. Therefore, the introduction path 18 communicates with the second annular path 16 via the path 20.
[0017]
The sleeve body 8 has a large-diameter inner peripheral surface 13 that faces the peripheral surface 5A of the large-diameter portion 5 of the shaft 1. The inner peripheral surface 13 and the peripheral surface 5A constitute a first annular narrow passage 15. The first annular channel 15 communicates with the introduction channel 18 and the channel 20. In FIG. 1, the portion below the surface 22 passing through the axial center of the flange portion 6 may be symmetrical to the portion shown in the drawing above the surface 22. Alternatively, it may have the same structure as the lower part of the flange shown in FIG.
[0018]
The hydrodynamic bearing is filled with the lubricant 23 up to the level of the bearing surface 14 </ b> A of the recess 14 that faces the flange portion 6 in the axial direction.
[0019]
When the sleeve 2 rotates around the central axis of the shaft 1, the dynamic pressure groove 7 formed in the flange portion 6 is formed in the lubricant 23 between the recess 14 and the bearing surface 14 </ b> A. The sleeve 2 is supported in the axial direction with respect to the shaft 1 by generating dynamic pressure in the direction. According to the first embodiment, the lubricant 23 traveling outward in the axial direction from between the flange portion 6 of the shaft 1 and the sleeve 2 is first between the large-diameter portion 5 of the shaft 1 and the sleeve 2. The first annular passage 15 prevents the progress. In the unlikely event that the lubricant 23 has passed through the first annular passage 15, the lubricant 23 is stored in the lubricant reservoir 17 through the introduction passage 18 extending radially outward in accordance with the centrifugal force. The outward progress of is suppressed. Furthermore, in the unlikely event, the lubricant 23 traveling from the lubricant reservoir 17 or the introduction path 18 to the small diameter portion 3 of the shaft 1 is prevented from traveling by the radial narrow path 20 and the second annular narrow path 16. Is done. Therefore, according to this embodiment, the leakage of the lubricant can be prevented almost completely. It is more desirable in terms of preventing oil leakage if an oil repellent is applied to either the small-diameter portion peripheral surface 3A of the shaft or the small-diameter inner peripheral surface 12A of the through-hole 12 opposed thereto.
[0020]
[Second Embodiment]
Next, FIG. 2 shows a second embodiment of the hydrodynamic bearing of the present invention. In the second embodiment, the large-diameter portion 35 of the shaft 1 has a truncated cone shape (the gradient with respect to the shaft center is set to 10 to 30 degrees) widening toward the flange portion 6. Only differs from the first embodiment. Therefore, the points different from the first embodiment will be mainly described.
[0021]
In the present embodiment, the first annular fine shape in which the peripheral surface 35A of the large-diameter portion 35 having a truncated cone shape and the large-diameter inner peripheral surface 13 of the sleeve body 8 facing the peripheral surface 35A are tapered toward the flange portion 6 is provided. A path 37 is formed. Therefore, according to this embodiment, the capillary seal effect can be exhibited using the surface tension of the lubricant 23 reaching the tapered annular narrow passage 37, and leakage to the outside can be prevented. Therefore, the sealing performance can be further improved.
[0022]
In the first and second embodiments, the dynamic pressure groove 7 is formed in the flange portion 6, but the dynamic pressure groove may be formed in the bearing surface 14A of the sleeve 2. In the first and second embodiments, the sleeve 2 may rotate with respect to the fixed shaft 1, or the sleeve 2 may be fixed and the shaft 1 may rotate. May be. Moreover, although the sleeve 2 was comprised with the sleeve main body 8 and the cover part 10, the sleeve 2 may be an integrally molded product.
[0023]
【The invention's effect】
As apparent from the above, the hydrodynamic bearing according to the first aspect of the present invention has a small diameter portion formed at one end in the axial direction, a large diameter portion adjacent to the small diameter portion, and a flange portion adjacent to the large diameter portion. And a sleeve having a through-hole that encloses the shaft and into which the small-diameter portion of the shaft is fitted, and the dynamic pressure is applied to the axial surface of the flange portion or the bearing surface of the sleeve facing the axial surface. A hydrodynamic bearing in which a groove is formed, a first annular narrow passage formed by a peripheral surface of a large-diameter portion of the shaft and a large-diameter inner peripheral surface of a sleeve facing the peripheral surface, and the small-diameter portion And a second annular narrow passage formed by a circumferential inner surface of the sleeve and a small-diameter inner circumferential surface of the through hole of the sleeve facing the circumferential surface, the first annular narrow passage, and the second annular narrow passage, An introduction path extending radially outward between the first annular path and the second annular path; And a lubricant reservoir that it is.
[0024]
According to the first aspect of the present invention, the lubricant traveling outward in the axial direction from between the flange portion of the shaft and the sleeve is first, by the first annular narrow passage between the large diameter portion of the shaft and the sleeve, Progress is hindered. In the unlikely event that the lubricant has passed through the first annular passage, it is stored in the lubricant reservoir through the introduction passage extending radially outward in accordance with the centrifugal force. Progress is suppressed. Furthermore, in the unlikely event, the lubricant that travels from the lubricant reservoir or the introduction path to the small diameter portion of the shaft is prevented from proceeding by the second annular narrow path between the small diameter portion and the sleeve. Therefore, according to the first aspect of the present invention, the leakage of the lubricant can be prevented almost completely.
[0025]
According to a second aspect of the present invention, in the hydrodynamic bearing according to the first aspect, the first annular narrow passage is tapered toward the flange portion.
[0026]
Therefore, according to the invention of claim 2, a so-called capillary seal effect that prevents leakage to the outside by utilizing the surface tension of the lubricant existing in the first annular narrow passage is exhibited, and the sealing performance is further improved. be able to.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an essential part of a first embodiment of a hydrodynamic bearing of the present invention.
FIG. 2 is a cross-sectional view of an essential part of a second embodiment of the hydrodynamic bearing of the present invention.
FIG. 3 is a sectional view of a spindle motor including a conventional hydrodynamic bearing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Shaft, 2 ... Sleeve, 3 ... Small diameter part, 3A ... Circumferential surface, 5 ... Large diameter part,
5A ... peripheral surface, 5B ... stepped surface, 6 ... flange, 6A ... axial surface, 7 ... dynamic pressure groove,
8 ... Sleeve body, 10 ... Lid, 10A ... Inner surface, 11 ... Annular recess,
11A ... deep part, 11B ... shallow part, 12 ... through-hole, 12A ... small diameter inner peripheral surface,
13 ... Large inner diameter surface, 14 ... Recess, 14A ... Bearing surface, 15 ... First annular narrow passage,
16 ... second annular passage, 17 ... lubricant reservoir, 18 ... introduction passage,
20 ... radial direction narrow path, 22 ... surface.

Claims (2)

A shaft having a small-diameter portion formed at one end in the axial direction, a large-diameter portion adjacent to the small-diameter portion, and a flange portion adjacent to the large-diameter portion, and surrounding the shaft, the small-diameter portion of the shaft is fitted A hydrodynamic bearing having a hydrodynamic groove formed on a bearing surface of the sleeve facing the axial direction surface of the flange portion or the axial direction surface.
A first annular path formed by a peripheral surface of the large-diameter portion of the shaft and a large-diameter inner peripheral surface of the sleeve facing the peripheral surface;
A second annular narrow passage formed by the peripheral surface of the small-diameter portion and the small-diameter inner peripheral surface of the through hole of the sleeve facing the peripheral surface;
An introduction passage that is continuous with the first annular passage and the second annular passage and extends radially outward between the first annular passage and the second annular passage;
A fluid dynamic bearing comprising a lubricant reservoir communicating with the introduction path. The hydrodynamic bearing according to claim 1,
The hydrodynamic bearing, wherein the first annular narrow passage is tapered toward the flange portion.

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