JPH10196646A - Dynamic pressure bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily keep quality of lubricating oil for a long time in both an oil containing bearing function and a dynamic pressure bearing function. SOLUTION: Capillary force of bearings 5, 6 is set larger than that of a sintered oil bearing 3. Lubricating oil of the bearings 5, 6 is not contained by the oil bearing 3, while being satisfactorily held. Even when the lubricating oil of the bearings 5, 6 is oozed to the outside of the bearings 5, 6 through sintering pores of a porous material, the oozed lubricating oil is returned to the bearings 5, 6 in accordance with the relation of the capillary forces between the bearings 5, 6 and oil introduction parts 10, 11 continued to the bearings 5, 6. The lubricating oil is thus always supplemented to the bearings 5, 6. Even when bubbles are generated and expanded in any portion of the bearing device, the bubbles are moved to the position where the capillary force is small, and held inside the oil introduction parts 10, 11 or an oil reservoir 13 outside the bearings 5, 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrodynamic bearing device configured to have both an oil-impregnated bearing function and a hydrodynamic bearing function.

[0002]

2. Description of the Related Art In recent years, dynamic pressure bearing devices utilizing the dynamic pressure of lubricating oil have been widely used especially in various rotating devices such as motors rotating at high speed. The so-called hybrid type bearing, which has the advantages of a dynamic pressure bearing and the advantages of an oil-impregnated bearing, is disclosed in Japanese Utility Model Laid-Open No. 59-164822.
Has been proposed.

[0003] In this hybrid type bearing, a groove for generating dynamic pressure is formed in a sintered porous material constituting the bearing.
In order to support the dynamic pressure, the bottom face and the side face of the groove for generating dynamic pressure are subjected to blind processing. On the other hand, since the slipperiness of the oil-impregnated bearing depends on the oozing action of oil from the surface pores of the sintered porous material, no portion other than the groove for generating dynamic pressure is subjected to blind processing.

[0004]

However, in the hybrid type bearing having such a configuration, since there is a portion which is not subjected to the blinding process as described above, several parts are required.
The lubricating oil in the bearing part escapes to the outside through the sintering hole due to the dynamic pressure of about 10 atm, and the dynamic pressure of the bearing part tends to gradually decrease. Part of the lubricating oil that escaped from the bearing part is returned to the bearing part but is not 100%. Therefore, the lubricating oil in the bearing part gradually decreases, and the pulsating pressure decreases accordingly. It may not function as a pressure bearing.

[0005] In addition, when air bubbles are generated or expanded in the bearing portion due to a rise in temperature or pressure reduction, etc.
Bubbles compressed by the dynamic pressure easily enter the sintering holes, thereby promoting the above-described leakage of the lubricating oil.

Accordingly, an object of the present invention is to provide a dynamic pressure bearing device capable of satisfactorily satisfying both functions of an oil-impregnated bearing function and a dynamic pressure bearing function for a long period of time.

[0007]

In order to achieve the above object, in a hydrodynamic bearing device according to the present invention, a bearing provided so as to rotate relative to a shaft is provided by an oil-impregnated bearing made of a sintered porous material. While being configured, lubricating oil is filled in a bearing portion in which the respective bearing surfaces of the sintered oil-impregnated bearing and the shaft face each other with a predetermined gap, and at least one of the bearing surfaces of the sintered oil-impregnated bearing and the shaft is filled with lubricating oil. The lubricating oil is pressurized by the formed hydrodynamic grooves, so that the hydrodynamic bearing device is configured to have both the oil-impregnated bearing function and the dynamic pressure bearing function. An inclined surface extending continuously from the bearing surface to the outside of the bearing;
An oil introduction portion including a narrow gap formed between the bearing surface and the shaft side is provided so as to guide lubricating oil outside the bearing portion into the bearing portion by capillary force of the narrow gap in the oil introduction portion. And the capillary force in the vicinity of the bearing portion in the oil introduction portion is set to be smaller than the capillary force in the bearing portion and larger than the average value of the capillary force in the sintered hole of the sintered oil-impregnated bearing. Characteristic hydrodynamic bearing device.

[0008] According to such a hydrodynamic bearing device according to the present invention, since the capillary force in the bearing portion is set to be larger than that of the sintered hole of the sintered oil-impregnated bearing, the lubricating oil in the bearing portion is sintered oil-impregnated. It is held well without getting inside the bearing. Further, even if the lubricating oil in the bearing part oozes out of the bearing part through the sintered hole of the sintered porous material, the oozing lubricating oil is transferred to the oil introduction part and the bearing arranged so as to be continuous with the bearing part. The lubricating oil is moved back to the bearing portion through the oil introduction portion and circulated, and the lubricating oil is constantly replenished to the bearing portion, since the lubricating oil moves to the bearing portion side according to the magnitude relationship of the capillary force with the portion. It has become.

Further, when air bubbles are generated or expanded in any part of the bearing due to temperature rise or pressure reduction, the lubricating oil leaks out by bubbling from the surface hole of the bearing end surface of the sintered oil-impregnated bearing. However, since the bubbles are crushed in the space of the oil holding portion and the lubricating oil is held in the oil holding portion, the bubbles are not introduced into the bearing portion and the oil is introduced into the oil outside the bearing portion. It is designed to be held inside the section and the oil sump section.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a dynamic bearing device according to the present invention is applied to an HDD spindle motor will be described below with reference to the drawings. First, in the embodiment of the shaft rotation type HDD spindle motor shown in FIG. 1, an inner peripheral portion of a substantially hollow cylindrical bearing holder 2 erected at a substantially central portion of a motor frame 1 as a fixing member. To
An oil-impregnated bearing 3 made of a sintered porous material is fixed. The sintered oil-impregnated bearing 3 constitutes a radial dynamic pressure bearing having both functions of an oil-impregnated bearing and a dynamic pressure bearing, and a rotating shaft 4 is shown on an inner peripheral portion of the sintered oil-impregnated bearing 3. It is rotatably mounted via lubricating oil which is omitted.

That is, between the inner peripheral surface of the sintered oil-impregnated bearing 3 and the outer peripheral surface of the rotary shaft 4, bearing portions 5, 6 each having a narrow gap are arranged at predetermined intervals in the axial direction. ,
On at least one of the bearing surface of the sintered oil-impregnated bearing 3 and the bearing surface of the rotating shaft 4, which constitute these bearing portions 5 and 6, for example, a number of herringbone-shaped dynamic pressure generating grooves (not shown). ) Are arranged in a ring. Then, the lubricating oil continuously filled in the bearings 5 and 6 is boosted by the pumping action of the dynamic pressure generating groove when the rotary shaft 4 rotates, and the rotating shaft is driven by the dynamic pressure of the lubricating oil. Four bearings are to be performed.

At this time, a thrust receiving plate 7 is fixed by screws 8 to the bottom opening on the lower side in the figure of the bearing holder 2, and the thrust receiving plate 7 closes and closes the thrust receiving plate 7.
Lubricating oil is filled in a bag-shaped cylindrical space including the bearing portions 5 and 6 on the inner side of the defined bearing holder 2.

The first bearing 5 is connected to the upper and lower sides of the bearing 5 in the drawing, so that the first
The oil introduction unit 10 and the second oil introduction unit 11 are provided. These oil introduction portions 10 and 11 are disposed at both axial end portions (upper and lower end portions in the drawing) of the sintered oil-impregnated bearing 3, and the bearings on the sintered oil-impregnated bearing 3 side constituting the bearing portion 5 are provided. Of an inclined surface formed so as to extend continuously from the surface to the outside of the bearing (vertical direction in the figure), and a bearing surface (outer peripheral surface) of the rotating shaft 4 facing the inclined surface in the radial direction. It is composed of narrow gaps formed between them.

The narrow gaps constituting each of the oil introduction portions 10 and 11 are defined so as to continuously expand toward the outside of the bearing (vertical direction in the drawing), and are formed by capillary action occurring in the narrow gaps. The lubricating oil on the outer side of the bearing 5 is guided into the bearing 5 based on the magnitude relationship between the obtained capillary force and the capillary force obtained by the capillary phenomenon generated in the bearing 5. That is, the gap size between these two oil introduction portions 10 and 11 is gradually formed to be larger than the bearing surface gap size of the bearing portion 5 by being formed of an inclined surface, whereby the oil introduction portions 10 and 11 are formed. Is set so that the capillary force of the bearing portion 5 gradually becomes smaller than the capillary force of the bearing portion 5.

Further, the capillary force in the vicinity of the bearing portion in the oil introduction portions 10 and 11 is set to be larger than the capillary force in the sintered hole of the sintered oil-impregnated bearing 3. That is,
The gap size in the vicinity of the bearing portion of the oil introduction portions 10 and 11 is formed smaller than the average gap size of the sintered holes of the sintered porous material constituting the sintered oil-impregnated bearing 3. At the time of rotation, the lubricating oil existing in the bearing portion 5 is retained in the bearing portion 5 without entering into the sintered hole of the sintered oil-impregnated bearing 3 by capillary action,
The lubricating oil existing in the vicinity of the oil introduction portions 10 and 11 is held so as to be continuous on the bearing portion 5 side.

Further, an oil holding portion 12 is provided at an axially outer portion (upper portion in the drawing) of the first oil introduction portion 10. The oil holding portion 12 has a shield plate 12 a disposed close to the upper end face of the sintered oil-impregnated bearing 3 in the figure, and is formed between the shield plate 12 a and the upper end face of the sintered oil-impregnated bearing 3 in the figure. The formed space constitutes a capillary seal portion utilizing a capillary phenomenon. That is, the configuration is such that the oil leaking to the upper surface side through the upper end surface in the figure of the sintered oil-impregnated bearing 3 is retained by the capillary force of the lubricating oil when the lubricating oil in the oil retaining portion 12 oozes out. The gap between the illustrated upper end surface of the oil-impregnated bearing 3 and the shielding plate 12a is set such that the lubricating oil does not leak even when the oil holding portion 12 faces downward. Further, the oil holding capacity of the capillary seal portion constituting the oil holding portion 12 is set to a capacity that allows oil leaking from the sintered oil-impregnated bearing 3.

Further, an oil sump portion is formed on the axially inward portion of the second oil introduction portion 11 (the center portion on the lower bearing side in the figure) so as to be continuous with the second oil introduction portion 11. 13
Is provided. The oil reservoir 13 is formed of a space having a gap dimension substantially the same as the maximum enlarged gap at the inner end (lower end in the figure) of the second oil introduction section 11, and the oil reservoir formed as the maximum enlarged gap The capillary force in the portion 13 is set to be smaller than the average value of the capillary force in the sintered hole of the sintered oil-impregnated bearing 3 and is set to be larger than the capillary force in the oil holding portion 12 described above. .

As described above, the magnitude of the capillary force with respect to the lubricating oil is made different at each part, and the
With respect to the order of the capillary force, the bearing portion 5, the vicinity of the bearing portion of the oil introduction portions 10 and 11, the sintered hole of the sintered oil-impregnated bearing 3,
The oil reservoir 13 and the oil holder 12 are arranged in this order. In addition, the capillary force in the oil holding unit 12 corresponds to the oil holding unit 1.
The lubricating oil is set to a size that can withstand the own weight of the lubricating oil stored in the lubrication oil 2, but normally no lubricating oil exists in the oil holding unit 12.

As for the lower bearing 6 shown in the figure, the above-mentioned upper bearing 5 shown in FIG.
The structure relating to the upper and lower parts in the figure is configured symmetrically, and the oil introduction part 14, the bearing part 6, and the oil introduction part 15 are continuously provided from the above-mentioned oil sump 13 toward the bottom side (the lower side in the figure). Have been. At this time, the magnitude of the capillary force at each of the above-described portions is determined by the bearing portion 6, the vicinity of the bearing portion of the oil introduction portions 14 and 15,
The average value of the sintered holes and the oil sump 13 are set in this order.

In order to obtain such a relationship of capillary force,
For example, when the gap size of the bearing portions 5 and 6 is several (3 to 5) μm, the gap size of the oil introduction portions 14 and 15 is 5 to 1
00 μm, the average gap size of the sintered hole of the sintered oil-impregnated bearing 3 is several tens μm, and the gap size of the oil reservoir 13 is 100 to 200 μm.
m, the gap size of the oil holding unit 12 is set to 200 to 500 μm.

The distal end (the lower part in the figure) of the rotary shaft 4 is slidably and slidably contacted with the thrust receiving plate 7. The surface forms a dynamic pressure sliding surface in the thrust direction. A flange-shaped retaining plate 16 is fixed to the tip of the rotating shaft 4, and the retaining plate 16 prevents the rotating shaft 4 from falling off. On the other hand, the stator core 21
Is fitted, and a winding 22 is wound around the salient pole portion of the stator core 21.

Further, a central portion of a hub 24 constituting a rotor set is fixed to an axially outer end (upper end in the drawing) of the rotating shaft 4 so as to rotate integrally. Hub 2
Reference numeral 4 denotes a substantially cylindrical body 24a formed of an aluminum material and having a plurality of magnetic disks mounted on an outer peripheral portion thereof.
The mounting portion 24b has a back yoke 25
The drive magnet 26 is annularly mounted so as to face the stator core 21 via the.

According to the hydrodynamic bearing device according to such an embodiment, the capillary force in the bearing portions 5 and 6 is larger than the capillary force in the sintered hole of the sintered sintered porous material of the sintered oil-impregnated bearing 3. Since it is set, the lubricating oil in the bearing portions 5 and 6 is favorably held without entering the sintered oil-impregnated bearing 3.

Further, even if the lubricating oil in the bearing portions 5 and 6 oozes out of the bearing portion through the sintered holes of the sintered oil-impregnated bearing 3, the oozing lubricating oil flows into the bearing portions 5 and 6. According to the magnitude relationship of the capillary forces between the oil introduction portions 10, 11 and the bearing portions 5, 6 arranged so as to be continuous, the oil moves from the oil introduction portions 10, 11 to the bearing portions 5, 6 side. Circulation is performed by returning to the bearing portions 5 and 6 again through the introduction portions 10 and 11, and as a result, lubricating oil is always supplied to the bearing portions 5 and 6.

Further, when air bubbles are generated or expanded at any part in the bearing due to temperature rise or pressure reduction, the lubricating oil leaks out by bubbling from the surface holes of the bearing end face (upper end face in the figure). However, the bubbles may be
Then, the lubricating oil is held in the oil holding unit 12. Therefore, the air bubbles are generated in the bearing portions 5 and 5.
The lubricating oil is retained inside the oil introduction portions 10 and 11 and the oil sump portion 13 outside the bearing portions 5 and 6 without entering the inside of the bearing portion 6. It is supplied to bearings and the like.

FIG. 2 shows an embodiment of a fixed shaft type HDD spindle motor. In this embodiment, a fixed shaft 32 is provided upright at a substantially central portion of a motor frame 31 as a fixed member, and a hub 33 as a rotating member is provided on the fixed shaft 32 with an oil-impregnated bearing function. It is rotatably supported via a radial sintered oil-impregnated bearing 34 having both pressure bearing functions. The radial sintered oil-impregnated bearing 34 is fixed to the inner peripheral portion of the hub 33, and the inner peripheral portion of the radial sintered oil-impregnated bearing 34 is rotatable with respect to the fixed shaft 31 via lubricating oil. It is installed.

That is, the radial sintered oil-impregnated bearing 34
Between the inner peripheral surface of the rotary shaft 32 and the outer peripheral surface of the rotating shaft 32, bearing portions 35, 36 each having a small gap are arranged at predetermined intervals in the axial direction, and constitute these bearing portions 35, 36. Bearing surface on the radial sintered oil-impregnated bearing 34 side and the fixed shaft 3
On at least one side of the two bearing surfaces, for example, a number of herringbone-shaped dynamic pressure generating grooves are annularly arranged.
Then, the lubricating oil continuously filled in these two bearing portions 35 and 36 is boosted by the pumping action of the dynamic pressure generating groove when the hub 33 rotates, and the dynamic pressure of the lubricating oil causes the hub 33 to rotate. Bearings are being performed.

Since the structure of the sintered oil-impregnated bearing 34 constituting such a radial dynamic pressure bearing is the same as that of the above-described embodiment, detailed description thereof will be omitted. , Bearing portions 35, 36, near the bearing portions of oil introduction portions 40, 41, 44, 45, sintered oil-impregnated bearing 3
No. 4, the sintering hole, the oil reservoir 43, and the oil holding part 42 are formed in this order. In addition, the oil holding part 42 in the present embodiment
Is disposed below the sintered oil-impregnated bearing 34 in the figure.

A thrust sintered oil-impregnated bearing 51 having both an oil-impregnated bearing function and a dynamic pressure bearing function is fixed to the upper portion of the fixed shaft 32 in the figure. The lower surface in the axial direction of the thrust sintered oil-impregnated bearing 51 is disposed so as to be opposed to the illustrated upper end face of the radial sintered oil-impregnated bearing 34 from above in the axial direction, and a bearing portion 52 is provided between these two members. Are defined so as to extend in the radial direction. The axially upper surface of the thrust sintered oil-impregnated bearing 51 is axially close to and opposed to the illustrated lower surface of a thrust holding plate 53 screwed to the upper surface of the hub 33. A narrow gap forming the bearing portion 54 is also defined between the and the thrust holding plate 53 so as to extend in the radial direction.

Bearing portions 52, which are defined by radial gaps respectively defined on the upper and lower surfaces of the thrust sintered oil-impregnated bearing 51 in the drawing,
The oil passage 54 communicates with the thrust sintered oil-impregnated bearing 51 through an axial gap 55 defined on the outer peripheral side thereof, and has a substantially U-shaped oil passage in the cross section of FIG. The oil passage is filled with lubricating oil so as to be continuous from the radial sintered oil-impregnated bearing 34 described above, and this lubricating oil is formed on the upper and lower surfaces of the thrust sintered oil-impregnated bearing 51 in the drawing. The pressure is increased by the action of the dynamic pressure generating groove (not shown) to form a thrust dynamic pressure bearing.

At this time, the lower and upper bearings 5
A first oil introduction portion 56 and a second oil introduction portion 57 are attached to the bearing portions 2 and 54 so as to be continuous with the inner peripheral ends of the bearing portions 52 and 54. Each of these oil introduction sections 56,
57 is disposed at the radially inner end portion of the thrust sintered oil-impregnated bearing 51 and is continuous from the bearing surface of the thrust sintered oil-impregnated bearing 51 constituting the bearing portions 52 and 54 to the outside of the bearing (toward the center). An inclined surface formed so as to extend
It is constituted by a narrow gap formed between each end face of the radial sintered oil-impregnated bearing 34 and the thrust holding plate 53 facing the respective inclined surfaces in the axial direction.

The narrow gaps constituting each of the oil introduction portions 56 and 57 are defined so as to continuously expand outward (inward in the radial direction) of the bearing.
And the bearing forces of the bearings 52 and 54
The lubricating oil on the outer side of the bearings 52 and 54 is configured to be guided into the bearings 52 and 54 according to the magnitude relationship with the capillary force. That is, these oil introduction sections 5
6, 57 is formed larger than the gap size of the bearing portions 52, 54, whereby the capillary force at the oil introduction portions 56, 57 is set smaller than the capillary force at the bearing portions 52, 54. Have been.

The capillary force in the vicinity of the bearing in the oil introduction portions 56 and 57 is set smaller than the capillary force in the sintered hole of the sintered oil-impregnated bearing 51. That is,
The clearance dimension near the bearing portion of the oil introduction portions 56 and 57 is as follows:
The sintered oil-impregnated bearing 51 is formed to have a size smaller than the average gap size of the sintered holes of the sintered porous material. The lubricating oil present near the bearings of the oil introduction portions 56 and 57 is held so as to be supplied to the bearings, while being held without entering the sintered holes of the sintered oil-impregnated bearing 51.

Further, an oil holding portion 58 comprising a gap between the thrust holding plate 53 and the fixed shaft 31 is provided at an axially outer portion (upper portion in the drawing) of the second oil introduction portion 57. I have. The oil holding portion 58 is configured as a capillary seal portion similarly to the above-described shield plate 12, and is formed by the capillary force of the oil holding portion 58 from the bearing portion 54 and the second oil introduction portion 57. It is configured to retain oil that has leaked out. This oil holding part 5
The oil holding capacity of the capillary seal portion that constitutes 8 is set to a capacity that allows leakage oil from the thrust sintered oil-impregnated bearing 51.

As described above, in this embodiment, the bearing portions 52, 5 are arranged in descending order of the magnitude of the capillary force against the lubricating oil.
4. The vicinity of the bearings of the oil introduction portions 56 and 67, the sintered holes of the thrust sintered oil-impregnated bearing 51, and the oil holding portion 58 are set.

According to the hydrodynamic bearing device according to the second embodiment, the same operation and effect as those of the first embodiment described above can be obtained not only in the radial sintered oil-impregnated bearing but also in the thrust sintered oil-impregnated bearing. Is similarly obtained.

Since the drive system of the motor according to the second embodiment is the same as that of the first embodiment, the description of the corresponding components will be omitted.

As described above, the invention made by the inventor has been specifically described based on each embodiment. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the invention. Needless to say, For example, the present invention relates to an HDD as in each of the above embodiments.
The present invention is not limited to the hydrodynamic bearing device in the spindle motor, and can be similarly applied to various kinds of hydrodynamic bearings.

[0039]

As described above, in the hydrodynamic bearing device according to the present invention, the lubricating oil in the bearing portion is sintered by setting the capillary force in the bearing portion larger than that of the sintered hole of the sintered oil-impregnated bearing. Even if the lubricating oil in the bearing part oozes out of the bearing part through the sintered holes of the sintered porous material, the oozed lubricating oil is retained in the bearing part. By moving the oil introduction section and the bearing section, which are arranged so as to be continuous with the section, toward the bearing section by the magnitude relationship of the capillary force, the oil is circulated back to the bearing section through the oil introduction section, and the lubricating oil for the bearing section is In addition to constantly replenishing, even if air bubbles are generated and expanded in any part of the bearing device, the air bubbles are moved to a part with a small capillary force, and the oil outside the bearing part without entering the bearing part. Introduction The lubricating oil can be stably held in the bearing part because it is configured to be held inside the oil reservoir, and both the oil-impregnated bearing function and the dynamic pressure bearing function can be well balanced for a long time. Thus, the reliability of the dynamic pressure bearing device can be greatly improved.

In particular, a rotation region that cannot be covered by a mere dynamic pressure, that is, a low rotation region in which the shaft and the bearing come into contact with each other only at the time of starting and stopping, and a bearing where only the dynamic pressure is applied due to high speed rotation. The hydrodynamic oil-impregnated bearing as in the present invention is effective in the rotating region where the loss is greatly increased. However, the hydrodynamic bearing device used in such a case has an extremely large effect. Having.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view showing an embodiment in which the present invention is applied to a shaft-rotating HDD spindle motor.

FIG. 2 is an explanatory cross-sectional view showing an embodiment in which the present invention is applied to a fixed-shaft HDD spindle motor.

[Explanation of symbols]

 3 Radial sintered oil-impregnated bearing 4 Rotating shaft 5, 6 Bearing section 10, 11, 14, 15 Oil introduction section 12 Oil holding section 13 Oil reservoir section 32 Fixed shaft 34 Radial sintered oil-impregnated bearing 35, 36 Bearing section 40, 41, 44, 45 Oil introduction part 42 Oil holding part 43 Oil reservoir part 51 Thrust bearing 52, 54 Bearing part 56, 57 Oil introduction part 58 Oil holding part

Claims (6)

[Claims] A bearing provided so as to rotate relative to a shaft is constituted by an oil-impregnated bearing made of a sintered porous material, and each bearing surface of the sintered oil-impregnated bearing and the shaft has a predetermined shape. Lubricating oil is filled in the bearing portion facing with a gap, and the lubricating oil is pressurized by the dynamic pressure generating grooves formed on at least one of the bearing surfaces of the sintered oil-impregnated bearing and the shaft, so that the oil-impregnated oil is impregnated. In a hydrodynamic bearing device configured to have both a bearing function and a hydrodynamic bearing function, an inclined surface extending continuously outward from the bearing surface on the sintered oil-impregnated bearing side, and a bearing on the shaft side An oil introduction portion formed of a small gap formed between the oil introduction portion and the oil introduction portion is provided so as to guide lubricating oil outside the bearing portion into the bearing portion by capillary force of the small gap in the oil introduction portion; In the introduction Wherein the capillary force in the vicinity of the bearing portion is set smaller than the capillary force in the bearing portion and larger than the average value of the capillary force in the sintered hole of the sintered oil-impregnated bearing. . 2. The dynamic pressure bearing device according to claim 1, wherein the bearing portion comprises a radial bearing portion or a thrust bearing portion. 3. The oil introduction part according to claim 1, comprising a first and a second oil introduction part disposed so as to be continuous with both ends in the axial direction of the radial bearing part. An oil holding portion for holding oil leaking from the sintered oil-impregnated bearing by capillary force is provided at an axially outer portion of the introduction portion, and is continuous with the second oil introduction portion,
An oil reservoir is provided in which the gap between the second oil introduction portions is continuously enlarged, and the capillary force of the enlarged gap in the oil reservoir is larger than the average value of the capillary force in the sintered hole of the sintered oil-impregnated bearing. small,
The dynamic pressure bearing device is set to be larger than the capillary force of the oil holding portion. 4. The oil retaining portion according to claim 3, wherein the oil retaining portion is formed from a gap between an axially outer end face of the sintered oil-impregnated bearing and a member disposed close to the outer end face of the sintered oil-impregnated bearing. A hydrodynamic bearing device comprising a capillary seal portion, wherein the oil holding capacity of the capillary seal portion is set to a capacity that allows oil leakage from the sintered oil-impregnated bearing. 5. The oil retaining portion according to claim 3, wherein the oil retaining portion is disposed axially outward of the sintered oil-impregnated bearing, and the oil reservoir is disposed axially centrally of the sintered oil-impregnated bearing shaft. A dynamic bearing device. 6. The oil introduction part according to claim 1 is arranged so as to be continuous with the thrust bearing part, and the oil leakage from the sintered oil-impregnated bearing is provided outside the oil introduction part by a capillary force. Wherein a capillary force of the oil holding portion is set to be smaller than an average value of a capillary force in a sintered hole of the sintered oil-impregnated bearing.