JP3526703B2 - 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 a dynamic pressure in a lubricant and rotatably support a shaft and an outer cylinder 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. In this dynamic pressure bearing device, a dynamic pressure surface on the shaft side and a dynamic pressure surface on the outer cylinder side fitted on the outer peripheral side of the shaft with a predetermined gap are circumferentially opposed to each other, and both of them are arranged. A groove for dynamic pressure generation is formed on at least one side of the opposed dynamic pressure surface, and a predetermined lubricant such as oil interposed between the opposed surfaces of the shaft and the outer cylinder generates dynamic pressure during rotation. The pressure is raised by the pumping action of the working groove, and both members are rotatably supported by the dynamic pressure of the lubricant.

As described above, since the dynamic pressure bearing device has a lubricant such as oil (hereinafter, simply referred to as a lubricant) in the bearing portion, a seal structure for preventing external leakage of the lubricant is required. Becomes As a seal structure of the lubricant, one utilizing a capillary force is disclosed in, for example, Japanese Patent Laid-Open No. 58-5032.
No. 1, JP-A-63-167111, US Pat. No. 5,112,142, and the like. In the capillary force seal structures disclosed in these documents, a seal inclined wall surface is provided at the outer outlet portion of the bearing portion so as to continuously expand the gap between the shaft and the outer cylinder toward the outside.

[0004]

However, the above-mentioned conventional dynamic pressure bearing structures have the following problems.
First, JP-A-58-50321 and US Pat. No. 51.
In the device described in Japanese Patent No. 12142, since the inclined wall surface is provided on the outer cylinder side, especially when centrifugal force is exerted strongly such as during high speed rotation, the lubricant on the seal inclined wall surface is It may be blown off along the inclined wall surface of the seal, failing to fulfill the sealing function. JP-A-5
Japanese Patent Application Laid-Open No. 8-50321 discloses applying an oil repellent agent made of a fluorine-based resin or the like to the seal inclined surface, but it is difficult to apply the oil repellent agent to the inclined surface with high positional accuracy. Since the adhesion is weak, there is a problem in durability and it becomes more expensive.

On the other hand, JP-A-63-167111
If the seal inclined surface is provided on the shaft side as in the device described in the publication, the above-mentioned centrifugal force countermeasure can be taken, but since the shaft is generally formed from a hard material such as quenched SUS, etc. However, it is not easy to form the seal inclined surface on the shaft side, and when a shaft having a small diameter is used recently, the rigidity of the shaft becomes insufficient so that it cannot be adopted.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a dynamic pressure bearing device having a simple and low-cost structure and capable of excellently preventing lubricant leakage.

[0007]

In order to achieve such an object, in the invention described in claim 1, an outer cylinder is fitted on the outer peripheral side of the shaft with a predetermined gap, and the shaft and the outer cylinder are fitted. In the dynamic pressure bearing device, a lubricant is interposed in the gap between the shaft and the outer peripheral cylinder so that the shaft and the outer cylinder are relatively rotatably supported by the dynamic pressure bearing. At an axially outer side portion of the dynamic pressure bearing portion in the gap between the outer cylinder and
A capillary seal portion formed by continuously enlarging the gap in the axially outward direction is provided, and a lubricant is continuously filled from the dynamic pressure bearing portion to the capillary seal portion to form a gas of the lubricant. A first corner portion having an oil-repellent function is formed in the capillary seal portion at a liquid interface, and at an axially outer side of the gas-liquid interface on at least one side of the shaft and the outer cylinder defining the gap. Is provided on the entire circumference, and a second corner portion having an oil repellent function is provided on the entire circumference on the outer side in the axial direction of the first corner portion . The internal angle is θ (e), the radial distance between the outer peripheral surface of the shaft and the first corner portion is a, the radius of the shaft is r, and the relative rotational angular velocity between the shaft and the outer cylinder. Where ω is ω, the first corner is (50 / a ² ) · (1+ cos
It is formed so as to satisfy θ (e))> r · ω ² .

According to the above-mentioned means of claim 1,
By the surface tension action of the first and second corner portions provided in the capillary seal portion, the lubricant that is about to flow out along the inclined wall surface of the capillary seal portion is retained in the corner portion, and the sealing function of the capillary seal portion is improved. It is being maintained well. Also, in this way, the second corner is attached to the first corner.
By using the corners together, the lubricant is applied to the first corners.
Even if it passes, the lubricant leaks at the second corner.
Is being prevented.

That is, the apparent contact angle θ of the corners
Is expressed by the following equation. θ = θ (f) + (180 ° −θ (e)) where θ (f) is the contact angle between the lubricant on the plane and the member forming the corner, and θ (e) is It is the inner angle of the corner. θ
It is preferable that (f) is small in order to obtain a strong capillary force at the time of stop, and therefore it is preferable that the liquid surface has a concave shape with a large curvature. On the other hand, since generally used metal materials are well wetted by the lubricant, the first term θ in the above equation is used.
(f) becomes smaller than the second term (180 ° -θ (e)) and may be set to 0 in calculation. In addition, although θ (e) is different between the corner having an ideal edge and the corner actually obtained industrially, as a result of trying various processing conditions, a slight deburring process was performed. It was confirmed that even the rounded corners had no problem in practical use. Rather, when trying to obtain a sharp edge, there is a risk of chipping on a part of the circumference and causing oil leakage from there.

As described above, when the corners are provided on the metal material or the like, the apparent contact angle can be increased with a simple structure, the diffusion of the oil film due to the centrifugal force is prevented, and the oil repellent as described above is used. Problems such as cost, reliability, workability, etc. in the application means are all solved.

[0011]

[0012]

[0013]

[0014]

Furthermore, in the invention of claim 2 , the first and second corner portions of claim 1 are provided on both sides of the shaft and the outer cylinder, respectively, and both corner portions are opposed to each other in the radial direction. Is provided.

If the corners are provided so as to face each other on both sides of the shaft and the outer cylinder in this way, bleeding due to the diffusion of the lubricant, etc., especially at the time of stopping, can be prevented, and also a strong impact at the time of stopping. Even when the liquid surface moves to the outside due to the force or the expansion of the lubricant, it is possible to effectively prevent the leakage.

On the other hand, in the invention described in claim 3 , claim 1
An absorbent cloth for capturing the lubricant is arranged on the outer side in the axial direction of the first and second corners described.

In this way, if the absorbent cloth for capturing the lubricant is arranged in addition to the corner portions, the final capturing of the lubricant is performed by the absorbent cloth even in the unlikely case.
External scattering of lubricant is surely eliminated.

[0019]

Further, in the invention of claim 4 , the radial distance a between the first and second corners of claim 1 and the outer peripheral surface of the shaft is set to 0.5 mm or less. ing.

Furthermore, in the invention described in claim 5 , the first and second corners on the shaft side according to claim 2 are separated from the edge part of the opening of the annular groove recessed in the outer peripheral part of the shaft. Has been formed.

On the other hand, in the invention described in claim 6 , claim 5
The axis-side first corner portion described is formed from an edge portion on one side of the opening portion of the annular groove , and the second corner portion.
But Ru Tei is formed from the edge of the other side of the opening in the annular groove.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 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, the overall structure of the HDD spindle motor shown in FIG. 1 will be described.
The HDD 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 that is screwed to the fixed base side (not shown), and a fixed shaft 12 erected at a substantially central portion of the frame 11 is directed upward in the figure. It is extended. The tip portion (upper end portion in the drawing) of the fixed shaft 12 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 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.
a and 22b are formed in a gap between the inner peripheral surface of the bearing sleeve 22 serving as an outer cylinder fixed to the inner peripheral side of the hub 21 and the outer peripheral surface of the fixed shaft 12, and have a predetermined distance in the axial direction. It is arranged so as to be separated and in parallel. The inner peripheral surface of the bearing sleeve 22 and the outer peripheral surface of the fixed shaft 12 in the parts forming the radial dynamic pressure bearing portions 22a and 22b are several μ.
They are arranged to face each other with a gap of m.

Then, each of the above radial dynamic pressure bearing portions 22
A predetermined lubricant (not shown) made of oil, magnetic fluid, or the like is interposed in the gap between the bearing sleeve 22 and the fixed shaft 12, which form a and 22b, and the bearing sleeve 22 and the fixed shaft 12 are also provided. At least one side of both facing surfaces with respect to 12 is provided with herringbone-shaped radial dynamic pressure generating grooves 23a and 23b which are annularly arranged in parallel so as to be parallel to each other. At the time of rotation, the pumping action of the radial dynamic pressure generating grooves 23a and 23b raises the pressure of the lubricant to generate dynamic pressure, and the dynamic pressure generated in the lubricant causes the hub 21 to be axially supported in the radial direction. Is configured.

As the lubricant in the present embodiment,
In order to achieve both the life of the lubricant and good bearing properties, a structure of trimethylolpropane (TMP) or pentaerythritol (PE) and a linear or branched fatty acid having 5 to 18 carbon atoms is esterified. Oil is used. Among them, the evaporation rate is 10-7 g / h · cm2 (at
Oil whose viscosity is 30 cP (at 40 ° C.) or less at 40 ° C. or less is used.

In order to inject such a lubricant into the inside of 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. Thus, it is possible to meet the lubricant throughout the interior bearing in a low air containing ratio state.

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

That is, the lower surface side of the thrust plate 16 shown in the figure is arranged so as to face the upper end surface of the bearing sleeve 22 shown in the figure, and the upper end surface of the thrust plate 16 shown in the figure is screwed to the central portion of the hub 21. The thrust pressing plate 25 is arranged so as to face the lower end surface of the thrust pressing plate 25 that is stopped, and the axial end surfaces of the thrust plate 16 that form the thrust dynamic pressure bearing portions 16a and 16b have a herringbone shape (not shown). The thrust dynamic pressure generating grooves are formed in an annular shape.

The radial dynamic pressure bearing portion 22a described above is provided in the gaps between the facing surfaces of the thrust plate 16 and the bearing sleeve 22 and between the thrust plate 16 and the thrust pressing plate 25 and the facing surfaces. , 22b are continuously filled with the lubricant,
When the hub 21 rotates, the lubricant is pressurized by the pumping action of the thrust dynamic pressure generating groove to generate dynamic pressure, and the dynamic pressure generated in the lubricant axially supports the hub 21 in the thrust direction. Is configured.

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

The joint portion between the thrust pressing plate 25 and the hub 21 is joined by an adhesive before the injection of the lubricant so as to form a completely closed structure, whereby a good sealing property against the lubricant is secured. There is. The adhesive that fills the joint is designed so that the capillary force of an annular guide groove (not shown) formed in the joint fills the entire circumference of the joint continuously without interruption. This completes the sealed structure.

Further, the thrust pressing plate 25 and the bearing sleeve 22 are provided with a thin plate-like stopper plate 27 from the outside (the upper side and the lower side in the drawing) via an absorbent cloth 26. The absorbent cloth 26 and the stopper are provided. By the plate 27,
Even in the worst case, the lubricant 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 arranged 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
At both axial end portions of the bearing space including 6b, 22a, 22b, that is, the outermost end portions, two capillary seal portions 31a are formed by narrowing the gap between the fixed shaft 12 and the rotating side members 22b, 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
Among them, the capillary seal portion 31b on the lower side in the drawing is provided at the axially outer end portion (lower end portion in the drawing) of the bearing sleeve 22, and more specifically, the inner peripheral wall of the lower end portion in the drawing of the bearing sleeve 22. Is formed by narrowing the gap between the fixed shaft 12 and the outer peripheral surface. Therefore, the narrow gap that constitutes the lower capillary seal portion 31b in the figure is communicated with the gap that constitutes the lower radial dynamic pressure bearing portion 22b in the figure, and the capillary seal portion 31b.
No concave portion for expanding the gap is provided in the communicating portion between b and the radial dynamic pressure bearing portion 22b.

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

Capillary seal 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 peripheral wall of the thrust pressing plate 25 and the inner peripheral wall of the bearing sleeve 22 on the lower side in the drawing, which face the fixed shaft 12 so as to form the narrow gaps between the capillary seal portions 31a and 31b, respectively,
A portion formed on the inclined wall A so as to continuously increase the dimension of the above-mentioned gap outwardly in the axial direction, and the dimension of the continuously expanding narrow gap is 20 μm to 300 μm. Are the capillary seal portions 31a and 31b.

As described above, the four dynamic pressure bearing portions 16
A lubricant is continuously filled in the bearing space portion between the two capillary seal portions 31a, 31b, including a, 16b, 22a, 22b. The surface, that is, the position of the gas-liquid interface is set to be a predetermined position inside each of the capillary seal portions 31a and 31b.

For example, in the upper capillary seal portion 31a shown in FIG. 2, the lubricant 32 is continuously filled from the upper radial dynamic pressure bearing portion 22a to the capillary seal portion 31a. The gas-liquid interface 32a of the lubricant 32 is arranged at an intermediate position inside the capillary seal portion 31a.

A first corner portion 25a having an oil repellent function is provided on the entire circumference of the inclined wall A of the thrust pressing plate 25 which defines the capillary seal portion 31a on the upper side of the drawing. The first corner portion 25a is formed by the lubricant 3 described above.
The first corner portion 25a is provided on the outer side of the gas-liquid interface 32a, that is, on the upper side in the figure.
The internal angle θ (e) of is set in the range of 90 ° to 160 °.

At this time, the internal angle θ of the first corner portion 25a is
With respect to (e) (deg), the radial distance between the outer peripheral surface of the fixed shaft 12 and the first corner portion 25a is set to a (mm), and the radius of the fixed shaft 12 is set to r (mm). ) And fixed shaft 12
When the rotational angular velocity of the rotor set 2 with respect to is ω (rad / sec), the first corner portion 25a satisfies 50 / a ² · (1+ cos θ (e))> r · ω ² ... Is formed.

The above equation is derived by the calculation based on the experimental result shown in FIG. 3, and is the force for supporting the lubricant 32 by the surface tension of the first corner portion 25a and the lubricant. This is related to the centrifugal force applied to 32. That is, from the state where the lubricant 32 is supported by the surface tension on the first corner portion 25a, the capillary seal portion 31a
When centrifugal force due to rotation is applied to the lubricant 32 in the lubricant 32, the lubricant 32 is proportional to the magnitude of the centrifugal force ,
The shape is raised in a. Then, the limit state (maximum swelling state) is a state in which the swelling thickness at the first corner portion 25a matches the clearance dimension between the corner portion 25a and the fixed shaft 12. Therefore, in this limit state, if the lubricant 32 is set to be supported by the first corner portion 25a, external leakage of the lubricant 32 can be completely prevented.

The force supported by the oil film at the first corner portion 25a can be expressed by the product of the surface tension γ of the lubricant 32 and the contact angle θ, and the interior angle of the first corner portion 25a is θ (e). (≒ 1
80 ° -θ), (2γ / a) (cos θ + cos
θ (e)). Further, the lubricant 32 in the above-mentioned extreme state
The centrifugal force applied to can be expressed by a function of the rotational angular velocity ω, the shaft diameter r, the clearance dimension a, and the specific gravity ρ of the lubricant (ρ · a
・ R · ω ² ) . At this time, the surface tension γ of the general lubricant
Is in the range of about 25 mN to 30 mN / m, and if the lower value of 25 mN / m is considered as a representative value for safety, the obtained results can be applied to almost all lubricants. . The same applies to the specific gravity ρ, and since many lubricants have a value of 0.8 to 1.0, it can be represented by 1.0.

Based on such an idea, the first corner portion 25
The relationship between the internal angle θ (e) of (a) (≈180 ° −θ) and the clearance a and the bearing conditions r and ω2 was investigated, and a diagram as shown in FIG. 3 was obtained by experiments and calculations. The above formula was derived. That is, FIG. 3 shows the relationship between the rotational speed (horizontal axis: rpm) of the rotor and the internal angle θ (e) (vertical axis: deg) of the first corner portion 25a in the above-mentioned extreme state, with the shaft diameter r as a parameter. And the inner angle θ (e) of the first corner portion 25a is set to 0.1 mm, for example.
It is understood that no oil leakage occurs even if the shaft diameter r is 4 mm and the rotation speed ω is 15000 rpm when the bearing is set to about 90 °. In the present embodiment, the first
The distance a in the radial direction between the corner portion 25a and the outer peripheral surface of the fixed shaft 12 is set to 0.5 mm or less.

Further, the capillary seal portion 31b on the lower side in the figure
The first corner portion 25b having the same structure is also provided at the lower end portion of the bearing sleeve 22 defining the above, at a portion outside the gas-liquid interface of the lubricant, that is, a portion on the lower side in the drawing.

On the other hand, outside the corner portions 25a and 25b, another second corner portion 25 is provided via another inclined groove A '.
c and 25d are provided all around. This second corner 2
5c and 25d do not satisfy the above equation,
Should first corner 25a described above, even if the result has not been held up lubricant to 25b, lubricant came transmitted the inclined wall surface A ', the second corner 25c, the surface tension of 25d It is configured to prevent external leakage.

As is clear from the above equation, the internal angle θ (e) of the first corner portion 25a can be set to an obtuse angle of 90 ° or more in many cases by setting the gap a and the shaft diameter r, Thereby, the second corner portions 25c and 25d can be provided. If the internal angle θ (e) of the first corner portion 25a is correctly set, external leakage of the lubricant will not normally occur, but if the initial injection amount of the lubricant is not appropriate or the original specifications are not satisfied. If a large impact force exceeding the range is applied, external leakage may occur. In particular, when used for driving a hard disk, even if a small amount of lubricant leaks out of the motor, it may stain the disk and cause inoperability. Even in such a case, it is preferable that the second corner portions 25c and 25d are provided to prevent the lubricant from leaking to the outside.

From this point of view, the second corners 25c, 2
5d is provided, but this second corner portion 25c, 25
It is considered that a small amount of lubricant leaks to d.
It is not necessary to give a strong constraint condition to the corner portions 25c and 25d, so that the inner angle of the second corner portions 25c and 25d can be set to a relatively large angle.

Further, in the above-described embodiment, the first corner portions 25a and 25b and the second corner portion 25 provided on the outer cylinder side, that is, the thrust pressing plate 25 and the bearing sleeve 22 side.
In addition to c and 25d, the first corner 12 is also provided on the fixed shaft 12 side.
a, 12b and second corners 12c, 12d are provided. The first corners 12a and 12b on the fixed shaft 12 side
The second corners 12c and 12d are formed by the opening edges of the annular groove 12e that is recessed in the outer peripheral portion of the fixed shaft 12.

At this time, the first corners 12a, 12b and the second corners 12c, 12d on the fixed shaft 12 side are the first corners 25a provided on the thrust pressing plate 25 and the bearing sleeve 22 side. , 25b and second corners 25c, 25d
Are arranged at substantially the same height position as each of the above, so that they are provided so as to face each other in the radial direction.

As described above, according to the apparatus of this embodiment, the first corner portion 25 provided in each of the capillary seal portions 31a and 31b.
Due to the surface tension action of a and 25b, the capillary seal portion 3
The lubricant 32, which tends to flow out along the inclined wall surfaces of 1a and 31b, is retained at the first corner portions 25a and 25b, and the sealing function of the capillary seal portions 31a and 31b is maintained well. .

In some of the already known dynamic pressure bearing devices, the inclined surface constituting the seal portion is similar to the corner portion. For example, JP-A-58-50
In Japanese Patent No. 321, a small groove is formed adjacent to the inclined surface of the seal portion, and an edge portion of the small groove forms a corner portion at the end of the inclined surface. However, according to the description in the publication, the small groove constitutes a lubricant reservoir and has a lubricant supply function to the inclined surface. Therefore, the angular edge portion of the small groove does not prevent the lubricant flow unlike the corner portion of the present invention, and does not satisfy the internal angle θ (e) expressed by the equation.

Such capillary tube sealing portions 31a, 31b
The first corner portions 25a and 25b provided on the base plate are easily and properly formed by being set so as to satisfy the above-described formula.

Further, if the second corners 25c and 25d are arranged outside the first corners 25a and 25b as in the above-described embodiment, the first corners 25a and 25b are covered with the lubricant 32. The second corner 25c,
The leakage of the lubricant is reliably prevented at 25d.

Furthermore, in the present embodiment, the first corner portion 12 is also provided on the fixed shaft 12 side so as to face the first corner portions 25a and 25b and the second corner portions 25c and 25d.
Since the a and 12b and the second corners 12c and 12d are provided, leaching due to diffusion of the lubricant 32 at the time of stopping is prevented, and strong impact force and expansion of the lubricant at the time of stopping are also prevented. As a result, even if the liquid surface of the lubricant 32 moves to the outside, effective leakage prevention can be achieved. In this case, the second corners 12c and 12d
Are formed at the bottom of the annular groove 12e and at two points on the shaft surface, the corners of these two points prevent leakage of the lubricant that has passed through the first corner and the corners on the bottom first. After being prevented by the portions, the corners on the shaft surface side are further favorably prevented.

At this time, it is not easy to form each corner described above so as to have an ideal edge. In order to increase the contact angle of the lubricant, it is preferable to finish the corners sharply. However, as shown in FIG.
If there is 1 or a chip, a strong capillary force acts on that part, which is rather the opposite effect. The following may be considered as a processing example capable of stable mass production and obtaining an effective contact angle.

First, deburring is indispensable when using a cutting tool such as lace processing. Deburring means in this case include a barrel and a chamfer.
When chamfering 42 is performed as shown in (b), the effective angle θ2 becomes smaller than the apparent angle θ1. Further, when the barrel processing 43 is performed as shown in FIG. 4C, the corners are rounded, which makes it difficult to quantify the effective angle. In this case,
Although it is affected by the roughness of the surfaces forming the corners, it was confirmed that if the radius of curvature is about 0.1 mm, the difference from the apparent angle is small and there is no practical problem. Further, when molding is performed using a mold such as injection molding or forging, the radius of curvature on the mold side may be finished to 0.1 mm or less.

In addition to this, in the present embodiment, the corner portions 25a, 25b, 25c, 25d, 12a, 12b, 1 are formed.
In addition to 2c and 12d, since the absorbent cloth 26 for finally capturing the lubricant 32 is arranged, even in the unlikely event, the final capturing of the lubricant 32 is performed by the absorbent cloth 26. External scattering of the lubricant 32 is surely eliminated.

On the other hand, in the embodiment shown in FIG.
An annular groove 25e is formed on the outer cylinder side, that is, on the inclined wall B of the thrust pressing plate 25, and both opening edges of the annular groove 25e form a first corner portion 25f and a second corner portion 25g. . Further, similarly to the above-described embodiment, the annular groove 12e is also formed on the fixed shaft 12 side, and the first corner portion 12a and the second annular portion 12e are formed by the opening edges of the annular groove 12e.
Corner portions 12c are formed, and the first corner portions 25f, 12a and the second corner portions 25g, 12c are arranged so as to face each other in the radial direction at substantially the same height. Even in such an embodiment apparatus, the same operation and effect as those of the above-described embodiment can be obtained.
The corner portions 25g and 12c of the above have the operation already described in FIG.

In the embodiment shown in FIG. 6, the present invention is applied to a thrust bearing, in which the thrust plate 45 fixed to the shaft 42 is replaced by the thrust receiving plate 46.
Are arranged so as to face each other in the axial direction, and a thrust dynamic pressure bearing portion is formed in a gap between the two members 45 and 46. The thrust plate 45 and the thrust receiving plate 46 in the portion that constitutes the thrust dynamic pressure bearing portion are several μm.
Are arranged facing each other through the gap of, and in the gap,
A predetermined lubricant 52 such as oil or magnetic fluid is interposed, and the thrust plate 45 and the thrust receiving plate 46 are included.
A groove for thrust dynamic pressure generation having a predetermined shape is formed in a ring shape on at least one side of both facing surfaces. The lubricant 52 is pressurized by the pumping action of the thrust dynamic pressure generating groove at the time of rotation to generate dynamic pressure, and the dynamic pressure generated in the lubricant is configured to support the shaft in the thrust direction. There is.

At the outermost end of the bearing space including the thrust dynamic pressure bearing portion, the thrust plate 45 and the thrust receiving plate 4 are provided.
6 is provided with a capillary seal portion 41a having a narrow gap. The thrust plate 45 forming the capillary seal portion 41a has an inclined wall C, and the inclined wall C continuously enlarges the dimension of the gap outward in the radial direction. . The liquid level of the lubricant 52, that is, the gas-liquid interface 52a is set at a predetermined position inside the capillary seal portion 41a.

An annular groove 46a is formed in the wall surface of the thrust receiving plate 46 which defines the capillary seal portion 41a, and both opening edges of the annular groove 46a are
A first corner 46b and a second corner 46c are formed.

According to the apparatus of this embodiment, the first corner portion 46b and the second corner portion 46b provided in the capillary seal portion 41a are provided.
The lubricant 52 which tends to flow out along the inclined wall surface of the capillary seal portion 41a by the surface tension action of the corner portion 46c of the
Are held at the first corner portion 46a and the second corner portion 46c, so that the sealing function of the capillary seal portion 41a is maintained well.

Although the embodiments of the invention made by the present inventors 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-mentioned embodiment, the corners are provided on both sides of the shaft and the outer cylinder which define the gap of the dynamic pressure bearing portion, but it is also possible to provide the corners on only one side.

In the above-described embodiment, the present invention is applied to a so-called fixed shaft type motor,
The present invention can be similarly applied to a shaft rotation type motor.

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

[0071]

As described above, according to the present invention, the first and second corner portions having the oil-repellent function are provided as lubricants on at least one side of the shaft and the outer cylinder defining the gap of the dynamic pressure bearing portion. Is provided on the outer side of the gas-liquid interface, and the surface tension action of the first and second corner portions holds the lubricant that is about to flow out along the inclined wall surface of the capillary seal portion at the corner portion. Since it is configured to maintain a good sealing function, it has a simple and low-cost structure, and it is possible to prolong lubricant life while satisfactorily preventing lubricant leakage. Can be expanded, and the reliability of the dynamic pressure bearing device can be dramatically improved. Furthermore
And a second corner portion having an oil-repellent action on the outside of the first corner portion.
The lubricant passes through the first corner because
Even if it does, the leakage of the lubricant is sure at the second corner.
It is possible to further improve the above-mentioned effects.
Wear.

[0072]

[0073]

Furthermore, if the first and second corner portions are provided so as to face each other on both sides of the shaft and the outer cylinder as in the invention described in claim 2 , it is possible to prevent the lubricant from being diffused, especially when the engine is stopped. In addition to preventing bleeding, it is possible to effectively prevent leakage even when the liquid surface moves to the outside due to a strong impact force at the time of stop or expansion of the lubricant, etc. The effect of can be further improved.

On the other hand, if the absorbent cloth for capturing the lubricant is arranged in addition to the above-mentioned first and second corner portions as in the invention described in claim 3, it is possible in the case of emergency. Even if there is, the final capture of the lubricant is performed by the absorbent cloth, so that the lubricant is reliably prevented from being scattered outside.

[Brief description of drawings]

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

FIG. 2 is a lateral cross-sectional explanatory view showing an enlarged main part of the present invention.

FIG. 3 shows the internal angle θ (e) of the corner by correlating the force that supports the lubricant by the surface tension of the corner and the centrifugal force applied to the lubricant.
FIG. 6 is a diagram showing an experimental result of investigating the relationship between the bearing conditions and

FIG. 4 is a cross-sectional explanatory diagram illustrating a processed state of a corner portion.

FIG. 5 is an explanatory transverse cross-sectional view corresponding to FIG. 2 showing a main part of a hydrodynamic bearing device according to another embodiment of the present invention.

FIG. 6 is a transverse cross-sectional explanatory view corresponding to FIG. 2 showing a main part of a hydrodynamic bearing device according to still another embodiment of the present invention.

[Explanation of symbols]

12 fixed shaft 22 bearing sleeve (outer cylinder) 25 thrust pressing plate 12a, 12b, 25a, 25b, 25f, 46b first corner portion 12c, 12d, 25c, 25d, 25g, 46c second corner portion 26 absorbent cloth 31a , 31b, 41a Capillary seal parts 32, 52 Lubricants 32a, 52a Gas-liquid interface

Continuation of the front page (56) Reference JP-A-8-149748 (JP, A) JP-A-6-178492 (JP, A) JP-A-8-74864 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) F16C 17/00-17/26 F16C 33/00-33/28 F16C 33/72-33/82

Claims (6)

(57) [Claims] 1. An outer cylinder is fitted on the outer peripheral side of the shaft with a predetermined clearance, and a lubricant is interposed in the clearance between the shaft and the outer cylinder to form a dynamic pressure bearing portion. In a hydrodynamic bearing device in which the shaft and the outer cylinder are supported by a pressure bearing portion so as to be rotatable relative to each other, in the axially outer side portion of the dynamic pressure bearing portion in the gap between the shaft and the outer cylinder, A capillary seal portion formed by continuously expanding the gap outward in the axial direction is provided, and a lubricant is continuously filled from the dynamic pressure bearing portion to the capillary seal portion to form a gas-liquid lubricant. An interface is formed in the capillary seal portion, and a first corner portion having an oil-repellent function is provided on a portion axially outside the gas-liquid interface on at least one side of the shaft and the outer cylinder defining the gap. Along the entire circumference, the first corner is axially outside A second corner portion having an oil repellent function is provided on the entire circumference, and the inner angle of the first corner portion is θ (e), the outer peripheral surface of the shaft and the first corner portion are
When the radial distance between the first corner portion and the corner portion is a, the radius of the shaft is r, and the relative rotational angular velocity between the shaft and the outer cylinder is ω, the first corner portion is (50 / a ² ) · (1+ cos θ (e))> r · ω ² is formed. 2. The first and second corners according to claim 1 are respectively provided on both sides of the shaft and the outer cylinder, and the two corners are provided so as to face each other in the radial direction. Dynamic bearing device. 3. A hydrodynamic bearing device, wherein an absorbent cloth for capturing a lubricant is arranged axially outside of the first and second corners according to claim 1. 4. The radial distance a between the first and second corner portions of claim 1 and the outer peripheral surface of the shaft is 0.5 m.
A hydrodynamic bearing device characterized by being set to m or less. 5. The shaft-side first and second corner portions according to claim 2 are formed from an edge portion of an opening of an annular groove recessed in an outer peripheral portion of the shaft. Dynamic bearing device. 6. The shaft-side first corner portion according to claim 5 is formed from an edge portion on one side of the opening portion of the annular groove, and the second corner portion is opened in the annular groove. A hydrodynamic bearing device, characterized in that it is formed from an edge portion on the other side of the portion.