JP3410615B2 - Dynamic pressure bearing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing device configured to generate dynamic pressure in a lubricant and support the rotary member with respect to a fixed member by the dynamic pressure.

[0002]

2. Description of the Related Art In recent years, in various devices such as motors, various types of dynamic pressure bearing devices have been studied and proposed, which utilize dynamic pressure of a lubricant such as oil so as to cope with high speed rotation. This dynamic pressure bearing device has a dynamic pressure bearing portion in which the dynamic pressure surface on the fixed member side and the dynamic pressure surface on the rotary member side are arranged to face each other, and at least one of these opposing dynamic pressure surfaces is provided. A dynamic pressure generating groove is formed as a dynamic pressure generating means, and a predetermined lubricant such as oil interposed in the bearing space between the opposing surfaces of the rotating member and the fixed member is used when the rotating member rotates. The pressure is raised by the pumping action of the dynamic pressure generation groove, and the rotary member is rotatably supported by the dynamic pressure of the lubricant.

As described above, since the dynamic pressure bearing device has a lubricant (hereinafter simply referred to as a lubricant) such as oil or magnetic fluid in the bearing portion, the lubricant leaks to the dynamic pressure bearing device. A lubricant seal means for preventing the above is provided. As the lubricant sealing means, for example, Japanese Patent Application Laid-Open No. 58-58
The capillary seal portion described in Japanese Patent Publication No. -50321 is known.

The capillary seal portion is arranged outside the dynamic pressure bearing portion, and the gap between the fixed member and the rotary member, which is located outside the dynamic pressure bearing portion, faces the outside. The gas-liquid interface of the lubricant continuously filled up to this gap is held by a capillary force to prevent the lubricant from leaking to the outside.

In the dynamic pressure bearing device having the capillary seal portion, if air remains in the lubricant, the expansion of the air causes the lubricant to be pushed out to the outside and leak from the capillary seal portion. Because of fear, when filling the lubricant, a means such as vacuum injection is taken to eliminate air residue.

[0006]

By the way, the solubility of air in a lubricant is generally proportional to the pressure and gradually decreases as the temperature rises. Here, in the dynamic pressure bearing part,
During use (when the rotating member rotates), the pressure becomes extremely high (for example, 10 atmospheres or more in some cases), so when the rotating member continuously rotates, it eventually reaches saturation, and the solubility at that pressure is high. And the air melts. After that, when the rotation is stopped, the lubricant returns to the atmospheric pressure, so that the dissolved air becomes supersaturated. This supersaturation will be gradually eliminated at the gas-liquid interface at the capillary seal portion, but a dynamic pressure bearing device having the dynamic pressure bearing portion and a lubricant reservoir portion between the dynamic pressure bearing portions. Then, if there is a trigger such as the presence of foreign matter that can serve as nuclei of dust, abrasion powder, etc. in the lubricant reservoir, it will lead to the generation of bubbles. During this time, if there is a change in atmospheric pressure or environmental temperature, there is a fear that more bubbles will be generated.

As described above, when air bubbles are generated in the dynamic pressure bearing portion or the lubricant reservoir portion and the air bubbles stay, the lubricant is pushed out by the expansion of the air bubbles and leaks from the capillary seal portion. Defect occurs. In particular, in the dynamic pressure bearing device having the above-mentioned lubricant reservoir, bubbles are easily formed in the lubricant reservoir having a wide gap, and stable large bubbles are formed, and the air bubbles are generated in the lubricant reservoir. Since it will stay, the above-mentioned leakage tendency becomes more remarkable.

That is, as described above, even if a means such as vacuum injection is taken to eliminate residual air at the time of filling the lubricant, bubbles are generated and the lubricant leaks as described above. There was a problem.

Such a problem similarly occurs in a dynamic pressure bearing device having a so-called pole piece type magnetic fluid seal as a lubricant seal means other than the above-mentioned capillary tube seal portion. That is, this pole piece type magnetic fluid seal is arranged on the outer side of the above-mentioned dynamic pressure bearing portion, and the gap between the fixed member and the rotating member located on the outer side of the dynamic pressure bearing portion is the above. Unlike the capillary seal portion, it is constant, and has a magnet and a pair of pole pieces provided so as to sandwich the magnet in the axial direction, and faces the inner peripheral surface of the pole piece and the inner peripheral surface of the pole piece. The magnetic fluid is magnetically held between the inner and outer pole pieces and the dynamic pressure bearing, and the leakage of lubricant is located between the inner and outer parts of the dynamic pressure bearing. In the dynamic pressure bearing device including such a pole piece type magnetic fluid seal, when the above-mentioned bubbles are generated, the lubricant is moved to the outside of the gas-liquid interface. The above magnetic fluid Torn Lumpur, lubricant there is a problem that leakage.

Therefore, an object of the present invention is to provide a dynamic pressure bearing device capable of satisfactorily preventing lubricant leakage due to the generation of bubbles.

[0011]

In order to achieve the above object, a dynamic pressure bearing device according to a first aspect of the present invention includes a dynamic pressure bearing portion for rotatably supporting a rotating member with respect to a fixed member, and this dynamic pressure bearing. A lubricant having a gas-liquid interface located outside the dynamic pressure bearing part, the lubricant being filled in a bearing space defined by the part and continuously filled from the dynamic pressure bearing part. A dynamic pressure bearing device comprising: a dynamic pressure generating means for generating a pressure; and a lubricant sealing means arranged on the outer side of the dynamic pressure bearing portion for preventing the lubricant from leaking to the outside. At the inner side of the liquid interface and the outer side of the dynamic pressure bearing portion, a bubble generating means made of a material having a wettability with respect to the lubricant lower than that of the member immersed in the lubricant is provided to rotate the rotating member. exposed from the gas-liquid interface of the lubricant at the time of stopping Immersed in is characterized in that provided as free.

According to the dynamic pressure bearing device of the first aspect, the bubble generating means is provided so as to be immersed in the lubricant on the inner side of the gas-liquid interface of the lubricant and on the outer side of the dynamic pressure bearing portion. Therefore, this bubble generating means triggers the generation of bubbles, and the supersaturated air quickly becomes bubbles in the vicinity of the gas-liquid interface and is discharged to the outside. Bubble generation in the lubricant reservoir is eliminated. In particular, parts immersed in lubricant
Made of a material that is less wettable to the lubricant than
Therefore, air bubbles are generated by the material with poor wettability.
Being urged (triggered), a supersaturated sky near the gas-liquid interface
Qi quickly becomes bubbles.

At this time, various kinds of lubricant sealing means can be adopted. For example, as described in claim 2, the gap between the fixed member and the rotating member is gradually increased toward the outside. With the expanding capillary seal part, the generation of bubbles in the dynamic pressure bearing part and the lubricant reservoir part is eliminated as described above, so that the leakage of the lubricant retained by the capillary force in the capillary seal part is good. Will be prevented.

[0014]

[0015]

Further, the bubble generating means, for example as described in claim 3, is composed of resin, and the member that is immersed in the lubricant composed of metal, is the wettability toward the resin from the metal Since it is bad, bubble generation is promoted by the bubble generating means, and the supersaturated air is quickly made into bubbles near the gas-liquid interface.

Further, the bubble generating means, for example as described in claim 4, the wettability of a resin which is immersed in the lubricant is bad resin, air bubbles generated by the bubble generating means is promoted The supersaturated air is immediately made into bubbles near the gas-liquid interface.

[0018]

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is applied to a so-called fixed shaft type HDD spindle motor will be described in detail below with reference to the drawings. First, H shown in FIG.
Explaining the overall structure of the DD spindle motor, this H
The DD spindle motor is composed of a stator set 1 as a fixed member and a rotor set 2 as a rotating member assembled to the stator set 1 from the upper side in the drawing. Of these, the stator set 1 has a frame 11 screwed to a fixed base side (not shown), and a fixed shaft 12 erected at a substantially central portion of the frame 11.
, Extends upward in the drawing. This fixed shaft 12
Is made of SUS material, and its tip (upper end in the drawing) is screwed to a fixed base (not shown).

Further, the frame 11 has a hollow cylindrical support holder 13, and this support holder 13
The stator core 14 is fitted around the outer periphery of the stator core 14, and the winding 15 is wound around the salient pole portion of the stator core 14.

On the other hand, the rotor set 2 has a hub 21 (not shown) for supporting a predetermined recording medium, and the hub 21 has a pair of radials arranged at the center of the hub 21. It is rotatably supported on the outer peripheral side of the fixed shaft 12 via the dynamic pressure bearing portions 22a and 22b.
The hub 21 (including the radial dynamic pressure bearing portions 22a and 22b, of course) is made of phosphor bronze.

The hub 21 has a substantially cylindrical body portion 21a for mounting a magnetic recording medium such as a magnetic disk on the outer peripheral portion, and a back yoke 21b is provided on the inner peripheral side of the body portion 21a. The drive magnet 21c is annularly mounted. The drive magnet 21c is arranged close to the outer peripheral end surface of the stator core 14 so as to face it in an annular shape.

The pair of radial dynamic pressure bearing portions 22 are also provided.
The a and 22b are integrally formed with the hub 21 on the inner peripheral side of the hub 21, and are arranged so as to be separated in the axial direction by a predetermined distance and arranged in parallel. Each of these radial dynamic pressure bearing portions 2
The inner peripheral surfaces of 2a and 22b and the outer peripheral surface of the fixed shaft 12 are arranged to face each other with a gap of several μm (for example, 3 μm) therebetween.

Then, each of the above radial dynamic pressure bearing portions 22
At least one of the opposing surfaces of the a and 22b and the fixed shaft 12 has a herringbone-shaped radial dynamic pressure generating groove (dynamic pressure generating means) 23b and 23 as shown in FIG.
b is recessed so as to be aligned in a ring shape. Note that FIG.
In FIG. 1, only the radial dynamic pressure generating grooves 23b and 23b formed on at least one side of the opposing surfaces of the radial dynamic pressure bearing portion 22b and the fixed shaft 12 on the lower side in the drawing are drawn. The radial dynamic pressure generating groove having a different shape is provided on the upper side in the drawing with the radial dynamic pressure bearing portion 22 a and the fixed shaft 12.
It is similarly formed on at least one side of both facing surfaces.

A predetermined lubricant 24 made of oil, magnetic fluid, or the like is interposed between the opposed surfaces, and the lubricant is generated by the pumping action of the radial dynamic pressure generating groove when the hub 21 rotates. 24 is boosted and dynamic pressure is generated,
Due to the dynamic pressure generated in the lubricant 24, the hub 2
1 is configured to be axially supported in the radial direction.

As the lubricant 24 in the present embodiment, trimethylolpropane (TMP) or pentaerythritol (PE) and a carbon number of 5 are used so that the life of the lubricant 24 and good bearing characteristics can both be achieved. Oils having a structure in which straight chain or branched fatty acids of up to 18 are esterified are used. Among them, especially the evaporation rate is 10 ^-7 g / h
・ When the viscosity is below cm ² (at 40 ° C), the viscosity is 30 cP (at 4
Oil below 0 ° C) is used.

In order to inject the lubricant 24 into the bearing, the assembled motor is put in a vacuum chamber once, and the capillary force or the external atmospheric pressure is used in the vacuumed state. This makes it possible to fill the entire interior of the bearing with the lubricant 24 with a low air content rate.

Further, two thrust dynamic pressure bearing portions 16 are provided in the middle portion of the fixed shaft 12 on the tip end side (the upper end side in the drawing).
A ring-shaped thrust plate 16 forming a and 16b is fixed. The thrust plate 16 is made of phosphor bronze, and the two thrust dynamic pressure bearing portions 16a and 16b made of the thrust plate 16 are adjacent to the radial dynamic pressure bearing portion 22a arranged on the upper side in the figure. It is arranged to.

That is, the lower surface side of the thrust plate 16 shown in the drawing is the radial dynamic pressure bearing portion 2 arranged on the upper side of the drawing.
The thrust plate 16 is disposed so as to face the end face (upper end face in the figure) of 2a, and the upper end face in the figure of the thrust plate 16 is the end face (lower end face in the figure) of the thrust pressing plate 25 screwed to the central portion of the hub 21. It is arranged so as to face
Herringbone-shaped thrust dynamic pressure generating grooves (dynamic pressure generating means) are annularly formed on both axial end faces of the thrust plate 16 constituting the thrust dynamic pressure bearing portions 16a and 16b. The thrust pressing plate 25 is made of phosphor bronze.

Further, the thrust plate 16 and the radial dynamic pressure bearing portion 22a are opposed to each other between their facing surfaces, and the thrust plate 16 is also provided.
The lubricant 24 on the radial dynamic pressure bearing portions 22a and 22b side is continuously filled in the gaps between the thrust pressing plate 25 and the opposing surfaces, and when the hub 21 rotates, The pumping action of the thrust dynamic pressure generating groove pressurizes the lubricant 24 to generate dynamic pressure, and the dynamic pressure generated in the lubricant 24 axially supports the hub 21 in the thrust direction. There is.

At this time, the thrust pressing plate 25 is joined to the hub 21 after the above-mentioned dynamic pressure bearing portions are assembled, but the joining portion facing the filled portion of the lubricant 24 is the thrust pressing plate. Only the joint portion by the plate 25 and the other portions with respect to the portion filled with the lubricant 24 are integrally molded to ensure hermeticity.

The joint portion between the thrust pressing plate 25 and the hub 21 is joined by an adhesive so as to form a completely sealed structure before the lubricant 24 is injected, whereby the lubricant 24
Good sealing performance is secured. The adhesive to be filled in this joint portion is designed to be continuously filled without interruption in the entire circumference of the joint portion by a capillary force of an annular guide groove (not shown) formed in the joint portion.
This completes the closed structure.

Further, a thin plate-like stopper plate 27 is provided on the thrust pressing plate 25 from the outside (the upper side in the drawing) through an absorbent cloth 26. By the absorbent cloth 26 and the stopper plate 27, in the worst case. However, the lubricant 24 is prevented from scattering outside.

The above-mentioned two radial dynamic pressure bearing portions 22
a, 22b, and two thrust dynamic pressure bearing portions 16a, 1
6b are provided side by side so as to define a series of bearing spaces extending in the axial direction, and these four dynamic pressure bearing parts 16a, 1 are provided.
At both axial end portions of the bearing space including 6b, 22a and 22b, two capillary seal portions (lubricant seal means) 31a are formed by narrowing the gap between the fixed shaft 12 and the rotating side members 22b and 25. , 31b are provided so as to sandwich the four dynamic pressure bearing portions 16a, 16b, 22a, 22b from both sides in the axial direction.

Each of these capillary seal portions 31a, 31b
Of these, the capillary seal portion 31b on the lower side in the drawing is provided on a part of the radial dynamic pressure bearing portion 22b arranged on the lower side in the drawing as shown in FIG. 2, and more specifically, It is formed by narrowing the gap between the inner peripheral wall of the axially outer end portion (lower end portion in the figure) of the radial dynamic pressure bearing portion 22b and the outer peripheral surface of the fixed shaft 12. Therefore, the narrow gap that constitutes the lower capillary seal portion 31b in the figure is directly communicated with the gap that constitutes the bearing portion of the lower radial dynamic pressure bearing portion 22b in the figure, and the capillary seal portion No recess is formed in the communicating portion between the portion 31b and the radial dynamic pressure bearing portion 22b so as to enlarge the gap.

On the other hand, the capillary seal portion 31a on the upper side in the figure
Is the thrust dynamic pressure bearing portion 16a, as shown in FIG.
Is formed by the gap between the thrust pressing plate 25 and the fixed shaft 12 that constitute the
It is formed by narrowing the gap between the inner peripheral wall of and the outer peripheral surface of the fixed shaft 12.

Capillary sealing parts 3 on the upper and lower sides of these drawings
1a and 31b are provided along the axial direction so that the narrow gaps forming the capillary seal portions 31a and 31b open outward in the vertical direction in the drawing. The inner wall of the thrust pressing plate 25 facing the fixed shaft 12 so as to form a narrow gap between the capillary seal portions 31a and 31b, and the radial dynamic pressure bearing portion 22b on the lower side in the drawing. The peripheral wall is formed as an inclined wall so as to continuously expand the dimension of the gap outward in the axial direction, and the size of the continuously expanding narrow gap is 20 μm to 300 μm.
The portions with μm are the capillary seal portions 31a and 31b.
I am trying. In addition, each of these capillary seal portions 31a,
An outer portion of 31b is provided with a portion coated with an oil repellant for preventing leakage of the lubricant 24 due to external diffusion.

As described above, the four dynamic pressure bearing portions 16
In the bearing space portion between the above two capillary seal portions 31a, 31b including a, 16b, 22a, 22b,
The lubricant 24 is continuously filled, and the lubricant 24
The position of each liquid surface (gas-liquid interface) at the upper and lower ends of
And, as shown by solid lines B and A in FIG. 3, respectively, it is set so as to be a predetermined position inside each of the capillary seal portions 31a and 31b.

As shown in FIG. 3, a bubble generating means 50 for immersing in the lubricant 24 is arranged on the inner side (lower side in the drawing) of the gas-liquid interface A in the upper capillary sealing portion 31a in the drawing. There is. The bubble generating means 50 is a member immersed in the lubricant 24, that is, the fixed shaft 12 made of SUS material,
Hub 21 made of phosphor bronze (radial dynamic pressure bearing portion 22
a, 22b), the thrust plate 16, and the thrust pressing plate 25, which is a coating film made of, for example, a fluorine resin as a member having a poorer wettability to the lubricant 24 than the thrust pressing plate 25. The concave groove is coated so that its outer surface is exposed from the fixed shaft 12.

Returning to FIG. 1 again, on the axially outer side (upper side in the drawing) of the above-mentioned upper capillary sealing portion 31a in the drawing, a lubricant injecting portion is formed so as to be axially continuous with the capillary sealing portion 31a. 32 is provided. The lubricant injection portion 32 is composed of an enlarged gap continuous with the narrow gap forming the capillary seal portion 31a, and the inner peripheral wall of the thrust pressing plate 25 facing the fixed shaft 12 side is
It is formed by inclining at an opening angle larger than that of the inclined wall forming the capillary seal portion 31a.

The slanted wall forming the lubricant injecting portion 32 is formed with an opening angle of 70 degrees or less so that the lubricant 24 can satisfactorily enter in the axial direction. The gap at the outermost end of the injection portion 32 in the axial direction is 40
It is set to be 0 μm or more. Further, the internal volume of the gap of the lubricant injecting portion 32 is set to be larger than the internal volume of the bearing space connecting the two capillary seal portions 31a and 31b described above.
4 can be once injected into the lubricant injecting portion 32, and thereafter, it is guided to the inner side (lower side in the drawing) by the capillary force, and the lubricant is spread over the entire length of the bearing space by opening to the atmosphere. 24 are being filled.

The radial dynamic pressure bearing portion 22 described above is also used.
A lubricant accumulating portion 33, which is formed by denting the inner peripheral surface to enlarge the gap with the fixed shaft 12, is provided in a portion between a and 22b in the axial direction. The gap size of the lubricant reservoir 33 in the present embodiment is the same as the radial dynamic pressure bearing 22.
More than 3 times the bearing clearance in a, 22b or 40
It is set to μm or more. This is to secure a certain amount or more of the lubricant 24 in the lubricant reservoir 33 so as to allow the lubricant 24 to have a sufficient margin with respect to the bearing portion, thereby extending the service life.

A lubricant reservoir X1 (see FIG. 1) is also formed between the outer peripheral surface of the thrust plate 16 and the inner peripheral surface of the hub 21 which faces the outer peripheral surface, and is also shown in the lower part of the drawing. The lubricant reservoir portion X2 (see FIG. 3) is also present at the boundary between the side thrust bearing portion 16b and the upper radial bearing portion 22a in the figure.
Are formed. That is, the hydrodynamic bearing device of the present embodiment includes two thrust bearing portions 16a and 16b, two radial bearing portions 22a and 22b, and three lubricant reservoir portions 33, X1 and X2.

According to the apparatus of such an embodiment, first, the liquid surface position of the lubricant 24 is determined by the fixed shaft 12 and the rotating member 25,
22b, a capillary seal portion 31a consisting of a narrow gap,
Since it exists in 31b, the capillary sealing force is always in operation at the time of rotation as well as at the time of stop, and the lubricant 24 is held at a predetermined position on the inner side by the pulling back force based on this capillary sealing force. .

On the other hand, when a large inertial force is applied, a dynamic pressure due to the fluid viscosity resistance of the lubricant 24 is generated in the capillary seal portions 31a and 31b having a narrow gap, and the dynamic pressure due to the fluid viscosity resistance of the lubricant 24 is generated. The pressure is the main holding force, and the outward diffusion of the lubricant 24 is prevented.

When rotating, the dynamic pressure bearing portion 16
The dynamic pressure generated by a, 16b, 22a, 22b causes the lubricant 24 to have a high solubility and the air is melted, and at the time of stoppage, the lubricant 24 returns to the atmospheric pressure and the melted air becomes supersaturated. . At this time, as described above, the wettability of the fluorine-based resin forming the bubble generating means 50 to the lubricant 24 is the member immersed in the lubricant 24, that is, the fixed shaft 12, the hub 21 (radial dynamic pressure bearing). Parts 22a, 2
2b) and the thrust plate 16 and the thrust pressing plate 25 are worse than the wettability of the lubricant 24, the bubble generating means 50 triggers the generation of bubbles, and the supersaturated air rapidly generates bubbles near the gas-liquid interface A on the upper side in the drawing. Is discharged to the outside.

Further, since the supersaturated air is positively formed into bubbles in the vicinity of the gas-liquid interface A and is quickly discharged to the outside, the lubricant on the inside, that is, the dynamic pressure bearing portion 16a,
The degree of supersaturation of the lubricant present in 16b, 22a, 22b and the lubricant present in lubricant reservoirs 33, X1, X2 is reduced, and the dynamic pressure bearings 16a, 16b,
Air bubbles are eliminated in 22a, 22b and the lubricant reservoir 33, X1, X2.

Therefore, the leakage of the lubricant 24 from the capillary seal portion 31a caused by the generation and retention of air bubbles can be effectively prevented.

Further, the capillary seal portion 31 according to the present invention.
Since a and 31b have a simple structure with an inclined surface, the manufacture is facilitated and the productivity is improved.

Incidentally, if the above-mentioned bubble generating means 50 is provided on the inner side (upper side in the figure) of the gas-liquid interface B in the lower capillary seal portion 31b in the figure, it is oversaturated in the vicinity of the lower side in the figure. Since air becomes bubbles, and there is a fear that the bubbles pass through the radial dynamic pressure bearing portion 22b on the lower side in the drawing and stay in the lubricant reservoir 33, the bubble generating means 50 is attached to the capillary seal portion 31b on the lower side in the drawing. It is not preferable to provide it.

When the HDD spindle motor is installed horizontally (vertically installed in FIG. 1), the air bubble generating means 50 is located inside the gas-liquid interfaces A and B in the capillary seal portions 31a and 31b. It is better to provide each. According to this structure, the supersaturated air is quickly made into bubbles near the gas-liquid interfaces A and B and discharged to the outside.

FIG. 4 (a) is a partial enlarged transverse sectional view showing another embodiment of the bubble generating means shown in FIG. Figure 4
In the embodiment shown in (a), the bubble generating means 50 described above.
Is the other member that constitutes the capillary seal portion 31a (a member other than the fixed shaft 12 that constitutes the capillary seal portion 31a),
That is, it is provided on the thrust pressing plate 25 side. Specifically, it is applied in a recessed groove formed in an annular shape on the inner peripheral surface of the thrust pressing plate 25 so that its inner surface is exposed from the thrust pressing plate 25. This bubble generating means 5
Similarly to that shown in FIG. 3, 0 is arranged on the inner side of the gas-liquid interface A in the capillary seal portion 31a on the upper side in the drawing.

Therefore, it goes without saying that it is possible to obtain the same effect as that of the previous embodiment.

By the way, in each of the embodiments described with reference to FIGS. 3 and 4A, the bubble generating means 50 is arranged on the inner side of the gas-liquid interface A in the capillary seal portion 31a on the upper side of the drawing. As described above, the reason why the bubble generating means 50 is disposed on the inner side of the gas-liquid interface A in the capillary seal portion 31a on the upper side in the drawing is that the fluorine-based resin forming the bubble generating means 50 gets wet with the lubricant 24. When the outer end of the bubble generating means 50 is exposed from the gas-liquid interface A, the gas-liquid of the lubricant 24 retained by the capillary seal part 31a is changed due to the poor contact property and the high contact angle. The concave curvature of the interface is reduced, the capillary force (sealing force) is weakened, and the lubricant 2
This is because the fear of leakage of No. 4 increases.

[0055]

[0056]

[0057]

On the other hand, in the embodiment shown in FIG. 5, the two radial bearing portions 42a and 42b juxtaposed in the axial direction are provided.
The present invention is applied to a dynamic pressure bearing device having: a shaft member 40 made of, for example, SUS material and a cylindrical member 41 via two radial bearing portions 42a, 42b made of, for example, phosphor bronze. Are supported so that they can rotate relative to each other.

The above two radial bearing portions 42a, 42b
Is fixed to the cylindrical member 41 side, and at least one side of both opposing surfaces of the radial dynamic pressure bearing portions 42a and 42b and the shaft member 40 has, for example, a herringbone-shaped radial dynamic pressure generating groove. Are recessed so as to be arranged in parallel in an annular shape, and a predetermined lubricant 44 made of oil, magnetic fluid, or the like is interposed between the opposing surfaces.

That is, the two radial dynamic pressure bearing portions 42a, 42b are provided side by side so as to define a series of bearing spaces extending in the axial direction, and the two radial dynamic pressure bearing portions 42a, 42b are included. At both axial end portions of the bearing space, there are two capillary seal portions 45a and 45b formed by narrowing the gap between the radial dynamic pressure bearing portions 42a and 42b and the shaft member 40, and the two radial dynamic pressure bearing portions. Four
It is provided so as to sandwich 2a and 42b from both sides in the axial direction.

That is, each of the capillary seal portions 45a,
45b is provided in a part of each radial dynamic pressure bearing portion 42a, 42b which is respectively arranged at the upper and lower sides in the drawing, and therefore, the narrow gaps forming these respective capillary seal portions 45a, 45b are different from each other in each radial dynamic pressure bearing. The gaps are directly communicated with the gaps that form the bearing portions of the portions 42a and 42b, and the gaps are enlarged in the communication portions between the capillary seal portions 45a and 45b and the radial dynamic pressure bearing portions 42a and 42b. Such a recess is not provided.

Capillary seal parts 4 on the upper and lower sides of these figures
5a and 45b are provided along the axial direction so that the narrow gaps forming the capillary seal portions 45a and 45b open outward in the vertical direction in the drawing. The radial dynamic pressure bearing portion 4 facing the shaft member 40 side so as to form a narrow gap between the capillary seal portions 45a and 45b.
The inner peripheral wall of 2a, 42b is formed as an inclined wall whose gap size is continuously expanded outward in the axial direction.

As described above, the above-mentioned two capillary seal portions 4 including the two radial dynamic pressure bearing portions 42a and 42b.
In the bearing space between 5a and 45b, the lubricant 44
Are continuously filled, and the liquid level positions of the lubricant 44 at the upper and lower ends in the figure are as shown by solid lines A and B in the figure, respectively.
Is set to be a predetermined position inside.

As shown in FIG. 6, a bubble generating means 52 for immersing in the lubricant 44 is arranged on the inner side (lower side in the drawing) than the gas-liquid interface A in the upper capillary sealing portion 45a in the drawing. There is. The bubble generating means 52 is, for example, a fluorine-based member as a member which is dipped in the lubricant 44, that is, a member which is less wettable to the lubricant 44 than the shaft 40 made of SUS material and the radial dynamic pressure bearing portions 42a, 42b made of phosphor bronze. The coating film is made of resin, and is applied in a ring shape on the outer peripheral surface of the shaft 40.

Further, the radial dynamic pressure bearing portions 42a, 42b
A lubricant reservoir 46 similar to that of the previous embodiment is provided in the axially-interposed portion between them. The reference numeral 48 represents a radial dynamic pressure generating groove formed in the radial dynamic pressure bearing portion.

Therefore, the bubble generation means 52 made of the fluorine resin general-purpose resin having poor wettability promotes the bubble generation (trigger), and the supersaturated air rapidly becomes bubbles near the gas-liquid interface A on the upper side in the drawing. While being discharged to the outside, the supersaturation degree of the inside lubricant is alleviated, and the generation of bubbles in the dynamic pressure bearing portions 42a and 42b and the lubricant reservoir 46 is eliminated. It goes without saying that even with such a configuration, it is possible to obtain the same effect as that of the previous embodiment.

Incidentally, if the bubble generating means 52 is made of a general-purpose resin such as acrylic or epoxy which has a not so high contact angle, the outer end of the bubble generating means 52 is exposed from the gas-liquid interface A. However, since the concave curvature of the gas-liquid interface A does not decrease so much, there is no problem as described in the above embodiment.

Further, the bubble generating means 52 may be provided not on the shaft 40 but on the inner peripheral wall constituting the capillary seal portion 45a of the radial dynamic pressure bearing portion 42a, and in the same manner as described in the previous embodiment. Alternatively, the shaft 40 or the radial dynamic pressure bearing portion 42a may be embedded in the inner peripheral wall of the capillary seal portion 45a so as not to be convex.

FIG. 7 is a partially enlarged transverse sectional view showing an embodiment in which the arrangement structure of the bubble generating means shown in FIG. 6 is changed. In this embodiment, the upper radial dynamic pressure bearing portion 42
a and the upper side capillary seal portion 45a where the gas-liquid interface A is located
A space 53 is formed between the space and the space 53. The space 53 does not expand toward the outside and is constant and is larger than the bearing space (bearing space) of the radial dynamic pressure bearing portion 42a. The above-mentioned bubble generating means 52 on the fixed shaft 40 side of the
Are arranged.

Even with this structure, the bubble generating means 52 promotes the generation of bubbles (becomes a trigger).
In the space 53 near the bubble generating means 52 (a little lower than the vicinity of the gas-liquid interface A mentioned above in the figure), the supersaturated air is quickly made into bubbles and discharged to the outside, and the degree of supersaturation of the internal lubricant is relaxed. Thus, the generation of bubbles in the dynamic pressure bearing portions 42a and 42b and the lubricant reservoir portion 46 is eliminated. That is, even with such a configuration, it is possible to expect the same effect as that of the previous embodiment.

In this embodiment, of course, the bubble generating means 52 may be provided not on the shaft 40 but on the radial dynamic pressure bearing portion 42a side in the space 53, and in order not to have a convex shape. It may be configured to be embedded in the shaft 40 or the radial dynamic pressure bearing portion 42a in the space 53. Further, the bubble generating means 52, the outer side end yet good as extended upward in the drawing so as to be positioned in the upper capillary seal portion 45a.

Further, the embodiment shown in FIG. 8 has two thrust bearing parts 58a, 58b arranged side by side in the axial direction.
The present invention is applied to a dynamic pressure bearing device having a shaft member 59 and a cylindrical member 51 made of, for example, phosphor bronze, the two thrust bearing portions 58a and 58b.
Is rotatably supported via a thrust plate 58 made of, for example, phosphor bronze.

The above two thrust bearing portions 58a and 58b
The thrust plate 58, which constitutes the above, is integrally fixed to the shaft member 59 side.
8b and the cylindrical member 51 are opposed to each other, at least on one side thereof, for example, a herringbone-shaped thrust dynamic pressure generating groove is formed so as to be annularly juxtaposed, and between the opposed surfaces. A predetermined lubricant 54 made of oil, magnetic fluid, or the like is interposed in this.

The above two thrust dynamic pressure bearing portions 58a, 5a
8b is provided so as to be separated by a predetermined distance in the axial direction, but these two thrust dynamic pressure bearing portions 58a, 58b are
A series of bearing spaces are provided side by side so as to define a U-shaped cross section, and the cylindrical member 51 and the thrust plate 58 are provided at both end portions of the bearing space including the thrust dynamic pressure bearing portions 58a and 58b. Two capillary seal portions 55a and 55b are provided to narrow the gap between and.

Each of these capillary seal portions 55a, 55b
Are provided at the innermost peripheral portions of the thrust dynamic pressure bearing portions 58a and 58b, respectively, to reduce the axial gap between the inner peripheral portion of the thrust plate 58 and the inner peripheral portion of the cylindrical member 51. It is formed by doing. Therefore, the narrow gaps forming the respective capillary seal portions 55a and 55b are directly communicated with the gaps forming the bearing portions of the thrust dynamic pressure bearing portions 58a and 58b, and at the same time, the respective capillary seal portions are formed. 55a, 55b and thrust dynamic pressure bearing portion 5
No recesses are provided in the communicating portions with 8a and 58b to enlarge the gap.

The capillary seal portions 55a, 55b on the upper and lower sides in FIG.
The narrow gap forming 55b is provided so as to open to the inner peripheral side. Then, each of these capillary seal portions 55
thrust plate 58 so as to form a narrow gap between a and 55b.
The inner peripheral side wall of the cylindrical member 51 facing to is formed as an inclined wall whose gap size continuously increases toward the inner peripheral side.

As described above, the above-mentioned two capillary seal portions 5 including the two thrust dynamic pressure bearing portions 58a and 58b.
In the bearing space portion between the 5a and 55b, the lubricant 54
Are continuously filled, and the liquid level positions at both ends of the lubricant 54 are predetermined positions inside the capillary seal parts 55a and 55b, as shown by solid lines A and B in FIG. Is set to be

As shown in FIG. 8, a bubble generating means 50 for immersing in the lubricant 54 is disposed on the inner side of the gas-liquid interface A in the capillary seal portion 55a on the upper side of the drawing. The bubble generating means 50 is a member dipped in the lubricant 54, that is, a thrust plate 58 made of phosphor bronze, and a coating film made of, for example, a fluorine resin as a member having a wettability to the lubricant 54 lower than that of the cylindrical member 51. It is embedded in the cylindrical member 51 so that the surface thereof is exposed to the lubricant 54.

Even with this structure, the bubble generating means 50 promotes the generation of bubbles (becomes a trigger).
The supersaturated air is rapidly made into bubbles near the gas-liquid interface A and discharged to the outside, and the supersaturation degree of the lubricant on the inner side is relaxed, so that the dynamic pressure bearings 58a and 58b and the lubricant reservoir 5 are provided.
The bubble generation in 7 is eliminated. That is, even with such a configuration, it is possible to obtain the same effect as that of the previous embodiment.

In this embodiment, of course, the bubble generating means 50 may be provided not on the cylindrical member 51 but on the thrust plate 58 side forming the capillary seal portion 55a on the upper side in the figure, and on the upper side in the figure. yet good a structure provided so as to protrude into the cylindrical member 51 or the thrust plate 58 side constituting the capillary seal portion 55a.

FIG. 9 is a partially enlarged transverse sectional view showing still another reference example of the bubble generating means. In this reference example , the bubble generating means 60 located on the inner side of the gas-liquid interface A and on the outer side of the dynamic pressure bearing portion 42a has a saw-tooth shape, and the lubricant 44 is vaporized by the sawtooth-shaped bubble generating means 60. The liquid is agitated in the vicinity of the liquid interface A to promote the generation of bubbles. That is, the same effect as that of the above-described embodiment can be expected.

Such sawtooth-shaped bubble generating means 60
May be provided on either the rotary member side or the fixed member side, but if provided on the rotary member side, the stirring of the lubricant 44 near the gas-liquid interface A is further promoted.
More preferable.

Further, as the bubble generating means 60, one having a sharp edge like a sawtooth shape is better for the lubricant 4
It is more preferable because the stirring in the vicinity of the gas-liquid interface A of 4 is further promoted, but the bubble generating means 60 is not limited to such a sawtooth shape, and may be, for example, an uneven shape, or a spherical shape. , May be wavy. Further, the surface roughness may be roughened to serve as a bubble generating means.

FIG. 10 is a partially enlarged transverse sectional view showing still another reference example of the bubble generating means. In this reference example , the bubble generating means 70 located inside the gas-liquid interface A and outside the dynamic pressure bearing portion 42a is a small groove, and the small groove 70 is formed in the radial dynamic pressure bearing portion 42a. Groove-shaped (herringbone) dynamic pressure generating groove 4
8 is smaller than that of No. 8 and has a small groove shape (that is, ">" shape) that faces in the opposite direction to the "V" shape.

Accordingly, if the relative rotation is performed so that the dynamic pressure is generated by the dynamic pressure generating groove 48, depending on the small groove 70,
The lubricant 44 receives a force so that a negative pressure is generated in its central portion, and the lubricant 44 near the gas-liquid interface A becomes a negative pressure, and this negative pressure causes a strong supersaturated state near the gas-liquid interface A. The supersaturated air is quickly made into bubbles and discharged to the outside. That is, the same effect as that of the above-described embodiment can be expected.

Bubble generating means 70 comprising such a small groove.
May be provided on either the rotary member side or the fixed member side, but if provided on the rotary member side, the stirring of the lubricant 44 near the gas-liquid interface A is further promoted.
More preferable.

FIG. 11 is a partially enlarged transverse sectional view showing an embodiment in which the present invention is applied to a dynamic pressure bearing device in which the lubricant sealing means is a pole piece type magnetic fluid seal. In this embodiment, the pole piece type magnetic fluid seal 62 is used.
Is disposed on the outer side of the upper dynamic pressure bearing portion 67, and is a gap between the shaft 61 made of a magnetic material and located on the outer side of the dynamic pressure bearing portion 67, and the member 68 facing the shaft 61. Is constant unlike the capillary seal portion, and the magnet 69 is
And a pair of pole pieces 63, 63 made of a magnetic material, which are provided so as to sandwich the magnet 69 in the axial direction, and the inner peripheral surfaces of the pole pieces 63, 63 and the inner peripheral surfaces of the pole pieces 63, 63. The magnetic fluids 64, 64 are magnetically held between the magnetic fluid seals 6 and the shaft 61 facing each other.
4, 64 are configured to prevent the leakage of the lubricant 66 in which the gas-liquid interface A is located between the inner (lower side in the figure) pole piece and the outer side of the dynamic pressure bearing portion 67.

The bubble generating means 65 similar to that described in the above embodiment is immersed in the lubricant 66 inside the upper gas-liquid interface A and outside the upper dynamic pressure bearing 67.
Is provided.

Therefore, the bubble generation means 65 promotes the generation of bubbles (becomes a trigger), and the supersaturated air is promptly formed into bubbles in the vicinity of the gas-liquid interface A and discharged to the outside. The degree of supersaturation is relaxed, and the generation of bubbles in the dynamic pressure bearing portion and the lubricant reservoir portion is eliminated. That is, the magnetic fluid seals 64, 64 are not broken by the rise of the gas-liquid interface A due to the generation and retention of bubbles, and the leakage of the lubricant is prevented.

Although the embodiments of the invention made by the present inventor have been specifically described above, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the spirit of the invention. Needless to say.

For example, in the above embodiment, the bubble generating means is directly provided on the rotating member or the fixed member, but the bubble generating means may be suspended so as to be immersed in the gas-liquid interface A, or It may be floated on the gas-liquid interface A of the lubricant.

The dynamic pressure generating groove to which the present invention is applied is
The present invention is not limited to the herringbone shape as in the above-described embodiment, and the present invention can be similarly applied to any other dynamic pressure generating grooves.

In the above embodiment, the bubble generating means is made of resin, and the member immersed in the lubricant is made of metal.
By combining those having extremely different wettability, the bubble generating means side with poor wettability actively generates bubbles and discharges them to the outside. A member immersed in the lubricant. Even if the resin has better wettability to the lubricant than the resin forming the bubble generating means, the same action and effect as those of the above-described embodiment can be expected. That is, if the member forming the bubble generating means is a member having a wettability of the member immersed in the lubricant to the lubricant,
It is possible to expect the same actions and effects as those of the above embodiment.

In the above-described embodiment, the present invention has been described by taking a so-called fixed shaft type motor as an embodiment, but the present invention can be similarly applied to a shaft rotating type motor. .

The present invention is also described in, for example, US Pat.
5,275, a dynamic pressure bearing device having a so-called lubricant circulation structure, and a so-called single bag holding structure described in US Pat. No. 5,427,456,
In addition, in the dynamic pressure bearing device as shown in FIG. 5, the lubricant reservoir 46 between the radial dynamic bearings 42a and 42b is communicated with the atmosphere, and the lubricant reservoir 46 is filled with air to perform the radial motion. The same applies to a dynamic pressure bearing device or the like having a so-called lubricant separation structure in which the lubricant filling the pressure bearing portion 42a side and the lubricant filling the radial dynamic pressure bearing portion 42b side are separated. Can be applied to.

Furthermore, the present invention can be similarly applied to a dynamic pressure bearing device used in addition to the above-mentioned HDD motor.

[0097]

As described above, according to the present invention, the dynamic pressure bearing device according to claim 1, Oite the bubble generating means, the outer side than the inner side and the dynamic pressure bearing portion than the gas-liquid interface of the lubricant during rotation stop It is provided so as to be immersed in the lubricant, and this bubble generating means is used as a trigger for bubble generation to expel supersaturated air promptly as bubbles in the vicinity of the gas-liquid interface to the outside. Since it is configured so as to alleviate the occurrence of bubbles in the dynamic pressure bearing portion and the lubricant reservoir portion,
It is possible to favorably prevent the leakage of the lubricant due to the generation of bubbles in the dynamic pressure bearing portion and the lubricant reservoir portion.

At this time, various kinds of lubricant sealing means can be adopted. For example, as described in claim 2, the gap between the fixed member and the rotating member is gradually increased toward the outside. If the expanding capillary seal portion is used, the occurrence of bubbles in the dynamic pressure bearing portion and the lubricant reservoir portion is eliminated as described above, so that the leakage of the lubricant held by the capillary force in the capillary seal portion can be favorably performed. It becomes possible to prevent it.

[0099]

[0100]

[0102] Also, the air bubble generating means, as described for example in claim 3, configured from the resin, be constituted of a metal member which is immersed in the lubricant, is poor wettability toward the resin from the metal Since the bubble generation means promotes the generation of bubbles to rapidly turn the supersaturated air into bubbles in the vicinity of the gas-liquid interface, it is possible to obtain the above-described actions and effects.

If the bubble generating means is made of a resin having a wettability lower than that of the resin immersed in the lubricant as described in claim 4 , the bubble generating means promotes the generation of bubbles and the gas-liquid Since the supersaturated air is quickly made into bubbles near the interface, it is possible to obtain the above-described actions and effects.

[0103]

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an HDD spindle motor including a dynamic pressure bearing device according to an embodiment of the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing a lower capillary seal portion shown in FIG.

FIG. 3 is a partially enlarged cross-sectional view showing an upper capillary seal portion and a bubble generating means shown in FIG.

FIG. 4 is another embodiment of the bubble generating means shown in FIG.
It is each partial expanded transverse sectional view showing (a) and a reference example (b) .

FIG. 5 is a semi-transverse sectional view showing an embodiment in which the present invention is applied to a dynamic pressure bearing device having two radial dynamic pressure bearing portions.

FIG. 6 is a partially enlarged cross-sectional view showing the upper capillary seal portion and bubble generating means shown in FIG.

FIG. 7 is a partially enlarged cross-sectional view showing an embodiment in which the arrangement structure of the bubble generating means shown in FIG. 6 is changed.

FIG. 8 is a semi-transverse sectional view showing an embodiment in which the present invention is applied to a dynamic pressure bearing device having two thrust dynamic pressure bearing portions.

FIG. 9 is a partially enlarged transverse cross-sectional view showing still another reference example of the bubble generating means.

FIG. 10 is a partially enlarged transverse sectional view showing still another reference example of the bubble generating means.

FIG. 11 is a partially enlarged cross-sectional view showing an embodiment in which the present invention is applied to a dynamic pressure bearing device in which a lubricant sealing means is a pole piece type magnetic fluid seal.

[Explanation of symbols]

12 fixing members 16a, 16b, 22a, 22b, 42a, 42b, 5
8a, 58b, 67 Dynamic pressure bearing portion 21, 25 Rotating member 23b, 48 Dynamic pressure generating means 24, 44, 54, 66 Lubricants 31a, 45a, 55a Capillary seal portion (lubricant sealing means) 50, 52, 60, 65, 70, 80 Bubble generating means 62 Pole-piece type magnetic fluid seal (lubricant sealing means) A Gas-liquid interface

─────────────────────────────────────────────────── --- Continuation of front page (56) Reference JP-A-8-210364 (JP, A) JP-A-7-170740 (JP, A) JP-A-8-152024 (JP, A) JP-A-63- 167111 (JP, A) JP-A-1-135914 (JP, A) JP-A-9-191599 (JP, A) JP-A-10-184691 (JP, A) JP-A-10-339321 (JP, A) JP-A-6-319240 (JP, A) JP-A-6-178492 (JP, A) JP-A-58-50321 (JP, A) JP-A-6-307452 (JP, A) JP-A-9-133126 (JP, A) JP-A-9-79263 (JP, A) Actual development: 6-35660 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F16C 17 / 00-17 / 26 F16C 33/00-33/28

Claims (4)

(57) [Claims] 1. A dynamic pressure bearing portion that rotatably supports a rotary member with respect to a fixed member, and a bearing space defined by the dynamic pressure bearing portion is filled and continuously from the dynamic pressure bearing portion. A lubricant whose gas-liquid interface is located on the outer side of the dynamic pressure bearing portion, dynamic pressure generating means for generating a dynamic pressure in the lubricant, and the above-mentioned lubricant for preventing external leakage of the lubricant. In a dynamic pressure bearing device provided with a lubricant seal means arranged on the outer side of the dynamic pressure bearing portion, the lubricant is immersed in the lubricant on the inner side of the gas-liquid interface and on the outer side of the dynamic pressure bearing portion. The bubble generating means made of a material having a wettability to the lubricant lower than that of the member being immersed so as not to be exposed from the gas-liquid interface of the lubricant when the rotation of the rotating member is stopped. Characteristic hydrodynamic bearing device. 2. The lubricant seal means is a capillary seal portion in which the gap between the fixed member and the rotary member gradually widens toward the outside, and the gas-liquid interface of the lubricant held in the capillary seal portion. On the inner side and on the outer side of the dynamic pressure bearing portion, a bubble generating means composed of a material having a wettability to the lubricant lower than that of the member immersed in the lubricant is provided from the gas-liquid interface of the lubricant. The hydrodynamic bearing device according to claim 1, wherein the hydrodynamic bearing device is provided so as not to be exposed. 3. The hydrodynamic bearing device according to claim 1, wherein the material of the member immersed in the lubricant is metal, and the material forming the bubble generating means is resin. 4. The material of the member immersed in the lubricant is a resin, and the material forming the bubble generating means is a resin having a lower wettability than the resin immersed in the lubricant. Item 5. The dynamic pressure bearing device according to item 1 or 2.