JP2004183766A - Dynamic pressure bearing, spindle motor with the dynamic pressure bearing, and disc driving device using the spindle motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent bubbles from being included in an oil by a dynamic pressure generating groove, to prevent the problems caused by the bubbles from arising. <P>SOLUTION: In this dynamic pressure bearing having a radial bearing part adjacent to a gas-liquid interface of the oil and the air at least at its one end part, the dynamic pressure generating groove row composed of herringbone grooves having the shape to induce the axial flow of the oil from the gas-liquid interface side toward the other end part side is formed on the radial bearing part, and the spiral groove part positioned at the gas-liquid interface side where the herringbone grooves are formed, has a bent part of which a groove angle is changed to be reduced in the rotating direction. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a dynamic pressure bearing that uses oil as a working fluid, a spindle motor provided with the dynamic pressure bearing, and a disk drive using the spindle motor.
[0002]
[Prior art]
Conventionally, as a bearing for a spindle motor used in a disk drive device for driving a recording disk such as a hard disk, a lubricating fluid such as oil interposed between the shaft and the sleeve to support the shaft and the sleeve so as to be relatively rotatable. Various dynamic pressure bearings utilizing the above fluid pressure have been proposed.
[0003]
The configuration of a spindle motor having such a conventional dynamic pressure bearing will be described. A shaft is rotatably supported at the center of a sleeve via a pair of upper and lower radial fluid bearings, and the sleeve is integrally fixed to the base. This constitutes a fixing member. A hub on which a magnetic disk is mounted is mounted on the upper end of a shaft that projects upward through the center of the sleeve. The outer diameter surface of the lower end of the shaft has a retaining function and a thrust fluid bearing. Are fixed rotatably. The thrust plate is housed in a stepped recess provided at the lower part of the sleeve.
[0004]
A radial bearing surface constituting the radial fluid bearing is formed on an outer peripheral surface of a shaft, and a radial bearing surface opposed thereto is formed on an inner diameter surface of a sleeve. At least one of the radial receiving surface of the shaft and the sleeve has a dynamic pressure generating surface. Grooves are formed.
[0005]
Further, a thrust receiving surface constituting the thrust fluid bearing is formed on both upper and lower planes of a thrust plate, and opposed thrust bearing surfaces are formed on an inner surface of a lower recess of the sleeve and an upper surface of the thrust cover, Grooves for generating dynamic pressure are formed on at least one of the thrust bearing surfaces of the thrust plate, sleeve and thrust cover. (For example, see Patent Document 1).
[0006]
However, in recent years, a disk drive device using such a spindle motor has been applied to a small device such as a portable information terminal, and a demand for further reduction in thickness has been increasing.
[0007]
For this reason, the applicant of the present application has made it possible to eliminate the need for a thrust plate for forming the thrust bearing portion, to reduce the size and thickness of the motor, and to increase the distance between the radial bearing portions as much as possible. A spindle motor for a disk drive device capable of obtaining rigidity has been proposed (see Patent Document 2).
[0008]
More specifically, a thrust bearing portion is formed between the upper end surface of the sleeve through which the shaft is inserted and the lower surface of the rotor hub, and a pair of radial bearing portions is formed by the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve. At the same time, oil is continuously held between the thrust bearing portion and the radial bearing portion on the side adjacent to the thrust bearing portion, and a desired levitation force is applied to the rotor by the cooperation of the two bearing portions. The magnetic attraction to the side balances the floating force of the rotor generated between the thrust bearing portion and one of the radial bearing portions.
[0009]
The oil held in the pair of radial bearings is separated in the axial direction by the air held in the air interposed part formed between the shaft and the sleeve, and forms a gas-liquid interface between the oil and the air. The oil held by the thrust bearing portion is held by forming a gas-liquid interface between oil and air in a taper seal portion formed on the radially outer side of the thrust bearing portion. . That is, the oil held in the dynamic pressure bearing is divided into oil held between the thrust bearing portion and the radial bearing portion adjacent to the thrust bearing portion, and oil held by the other radial bearing portion. Is divided and held.
[0010]
[Patent Document 1]
JP-A-2000-197306 (pages 2-4, FIG. 1-3)
[Patent Document 2]
Japanese Patent Application Laid-Open No. 2000-113582 (pages 5-6, FIG. 2)
[0011]
[Problems to be solved by the invention]
A bearing configuration that enables a thrust bearing and a radial bearing to cooperate to generate a floating force of a rotor, such as a dynamic pressure bearing in a spindle motor for a disk drive disclosed in Patent Document 2 described above. In this case, the end of the groove is exposed to the air held by the air interposed portion during rotation due to the effect of the pumping of the dynamic pressure generating groove provided on the radial bearing portion toward the thrust bearing portion.
[0012]
Naturally, the gap between the shaft and the sleeve is larger in the dynamic pressure generating groove than in the hill formed between the adjacent grooves, so that the groove end is exposed to air. In the hill portion, the oil interface is pulled up toward the center of the bearing, and in the groove portion, the oil interface is pulled down conversely. Then, as the motor rotates, the raising and lowering of the interface occurs intermittently in the circumferential direction, so that the oil interface undulates and shakes, and the air entrained in the oil along with this Appears as bubbles.
[0013]
The bubbles appearing in the oil try to enter the dynamic pressure generating groove together with the oil toward the center of the bearing due to the rotation of the motor, but the shaft and the sleeve forming the dynamic pressure generating groove and the bearing surface of the radial bearing portion. If the surface processing can maintain the specified accuracy, the air entrained in the oil cannot enter beyond the maximum dynamic pressure generation area of the radial bearing part, and from inside the groove to the hill. And is then recirculated to the interface side of the low-pressure oil and discharged into the air held by the air interposed part. However, when the radial bearing portion includes a processing error and a shape error of the dynamic pressure generating groove and the bearing surface, bubbles entrained in the oil due to pressure variation, etc. will cause the maximum dynamic pressure of the radial bearing portion to increase. It has been newly discovered that the fluid enters the thrust bearing portion side beyond the generation region and stays in oil held in a region between the thrust bearing portion and the radial bearing portion due to a pressure gradient.
[0014]
As is well known, if air bubbles stay in the oil held in the bearing portion, oil leakage due to changes in the external environment of the bearing such as temperature and pressure, and abnormal vibration due to the contact between the dynamic pressure generating groove and the air bubbles occur. . In addition, the aggregation of the bubbles causes the oil to be cut off, and the resulting metal contact causes various adverse effects such as seizure of the bearing portion. Therefore, a solution has been expected.
[0015]
An object of the present invention is to provide a dynamic pressure bearing capable of preventing air from being trapped in a bearing by a dynamic pressure generating groove.
[0016]
Another object of the present invention is to provide a highly reliable spindle motor and a disk drive device using the spindle motor by providing the above-described dynamic pressure bearing as a bearing means, thereby avoiding problems caused by bubbles. That is.
[0017]
[Means for Solving the Problems]
The invention according to claim 1 is a dynamic pressure bearing having at least one end portion having a radial bearing portion adjacent to a gas-liquid interface between oil and air, wherein the radial bearing portion has the air bearing against the oil. The spiral groove located on the gas-liquid interface side has a larger axial dimension than the spiral groove located on the other end side to induce an axial flow from the liquid interface side to the other end side. A dynamic pressure generating groove row composed of a plurality of herringbone grooves having a curved shape is provided, and the spiral groove located on the gas-liquid interface side forming the herringbone groove has a groove angle with respect to the rotation direction. A bent portion that changes to be smaller is provided.
[0018]
As described above, in the dynamic pressure bearing using oil as the working fluid, among the herringbone grooves provided as the dynamic pressure generation grooves in the radial bearing portion, the groove angle with respect to the rotation direction of the spiral groove portion located on the gas-liquid interface side is reduced. By providing the bent portion in the middle, the contact angle between the gas-liquid interface and the dynamic pressure generating groove is reduced even when the groove end is exposed to air during rotation. Therefore, the turbulence of the gas-liquid interface is suppressed, and the generation of bubbles due to the entrainment of air is prevented.
[0019]
That is, the present invention makes it possible to suppress the intrusion of air bubbles from the end of the radial bearing portion and the stagnation in the dynamic pressure bearing, thereby preventing the above-mentioned various problems related to air bubbles.
[0020]
According to a second aspect of the present invention, in the dynamic pressure bearing according to the first aspect, of the spiral groove located on the gas-liquid interface side, an axial dimension from a bearing center of the radial bearing to the bent portion is provided. Is set to be substantially equal to the spiral groove located on the other end side.
[0021]
According to a third aspect of the present invention, in the dynamic pressure bearing according to the first or second aspect, the other end of the radial bearing opposite to the end adjacent to the gas-liquid interface is a thrust bearing. And a thrust bearing portion is provided with a dynamic pressure generating groove row composed of a plurality of spiral grooves having a pump-in shape.
[0022]
According to a fourth aspect of the present invention, a shaft, a sleeve having a through hole through which the shaft is freely rotatably inserted, and an axially opposed upper end surface of the sleeve, wherein the shaft is provided at the rotation axis. A rotor having an integral circular top plate, wherein a minute gap for holding oil is formed between an upper end surface of the sleeve and a bottom surface of the top plate. In addition, a thrust bearing portion is formed by providing a dynamic pressure generating groove for inducing fluid dynamic pressure in oil held in the minute gap according to the rotation of the rotor, thereby forming a thrust bearing portion, and an inner peripheral surface of a through hole of the sleeve. A minute gap for holding oil is formed between the shaft and the outer peripheral surface of the shaft, and a dynamic pressure generation that induces fluid dynamic pressure in the oil held in the minute gap in accordance with the rotation of the rotor. Groove It is configured the radial bearing portion by being dynamic pressure bearing made of said thrust bearing portion and the radial bearing portion, characterized in that it is a dynamic pressure bearing according to claim 3.
[0023]
According to a fifth aspect of the present invention, there is provided a disk drive device in which a recording disk capable of recording information is rotatably driven, a housing, a spindle motor fixed inside the housing to rotate the recording disk, and A disk drive device having information access means for writing or reading information at a position, wherein the spindle motor is the pindle motor according to claim 4.
[0024]
By the way, the inventions described in the claims other than claim 1 relate to the configuration according to the embodiment of the present invention. The principle will be described in detail in the following embodiments of the invention and effects of the invention.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a dynamic pressure bearing according to the present invention will be described together with a spindle motor using the same, and each embodiment of a disk drive device using the spindle motor will be described with reference to the drawings. It is not limited to the embodiment shown.
[0026]
The spindle motor shown in FIG. 1A forms a thrust bearing S for generating a floating force of the rotor 2 between the bottom surface of the rotor 2 and the upper end surface of the sleeve 4, and is integrated with the rotor 2. An upper radial bearing portion for acting on the alignment of the rotor 2 and preventing the rotor 2 from falling down between the outer peripheral surface of the shaft 6 and the inner peripheral surface of the sleeve 4 provided through the air interposed portion 8 communicating with the outside air. R1 and a lower radial bearing portion R2. A stator 12 is mounted on the base member 10 to which the sleeve 4 is fixed, and a rotor magnet 14 is fixed to the rotor 2 so as to face the stator 12.
[0027]
The schematic configuration of the thrust bearing portion S and the upper radial bearing portion R1 in the spindle motor will be described with reference to FIGS. 1 (b) and 1 (c). FIG. 1B is a partially enlarged sectional view showing a schematic configuration in the vicinity of the thrust bearing portion S and the upper radial bearing portion R1, and FIG. 1C is a sectional view of a spiral groove SG provided in the thrust bearing portion S. It is a top view of the upper end surface of the sleeve 4 which shows a schematic shape. Further, as shown in an enlarged manner in FIG. 1B, between the thrust bearing portion S and the upper radial bearing portion R1, oil as a working fluid is continuously held without interruption.
[0028]
In this configuration, a pump-in type in which oil flows toward the radially inward direction indicated by an arrow A in FIG. A row of dynamic pressure generating grooves by the spiral groove SG is provided. The shape of the spiral groove SG is shown in FIG.
[0029]
Further, a herringbone groove HG1 is formed on the inner peripheral surface upper side of the sleeve 4 as a dynamic pressure generating groove row provided in the upper radial bearing portion R1 disposed radially inward of the thrust bearing portion S.
[0030]
As shown in FIG. 1B, the herringbone groove HG1 has a spiral groove RS1 located on the thrust bearing S side, a spiral groove RS2 connected to the spiral groove RS1, and a spiral continuous with the spiral groove RS2. The groove RS3 is formed. At this time, the spiral groove portions RS1 and RS2 are set so that the specifications such as the axial dimension, the groove angle, the groove width, and the groove depth are substantially the same, but the spiral groove portion RS3 is continuous with the spiral groove portion RS2. It is formed as a herringbone groove HG1 having an unbalanced shape in the direction of the divided axis. Thus, in the upper radial bearing portion R1, oil flow in the direction indicated by the arrow B in FIG. 1B is induced, and a radial supporting force on the upper end side of the shaft 6 is obtained.
[0031]
As described above, the thrust bearing portion S is provided with the pump-in type spiral groove SG as a dynamic pressure generating groove, and the upper radial bearing portion R1 extends from the radial outer end of the spiral groove SG of the thrust bearing portion S. The internal pressure of the oil held in the region up to the upper end (rotor 2 side) end of the spiral groove RS1 has a substantially uniform pressure distribution with no gradient when the motor rotates, and this pressure A predetermined levitation force is applied.
[0032]
Although the shape of the dynamic pressure generating groove is not particularly shown, the axial dimension of the pair of spiral grooves is substantially lower than the inner peripheral surface of the sleeve 4 as the dynamic pressure generating groove of the lower radial bearing portion R2. And a herringbone groove HG2 having an axially symmetrical shape set in the same manner as described above, whereby a radial supporting force on the lower end side of the shaft 6 is obtained. That is, the rotor 2 is supported at the upper and lower ends of the shaft 6 in the axial direction by the upper and lower radial bearings R1 and R2.
[0033]
Further, a ring-shaped member 16 made of a ferromagnetic material such as stainless steel is arranged at a position of the base member 10 facing the rotor magnet 14 in the axial direction, and between the rotor magnet 14 and the ring-shaped member 16. The supporting force in the direction of suppressing the floating of the rotor 2 is obtained by the acting magnetic attraction force. The levitation force on the rotor 2 due to the dynamic pressure generated in the thrust bearing portion S and the upper radial bearing portion R1 and the magnetic attraction force acting between the rotor magnet 14 and the ring-shaped member 16 are balanced and applied to the rotor 2. Supports axial loads.
[0034]
In the spindle motor having the above configuration, as shown in FIG. 1B, as means for preventing oil held in the thrust bearing portion S from leaking out of the bearing, the outer peripheral portion of the sleeve 4 and the bottom surface of the rotor 2 are provided. An axial taper seal portion TS1 is formed between the inner peripheral surface of the provided annular protrusion 2a and the meniscus gas-liquid interface is formed by balancing the internal pressure of oil and the atmospheric pressure with the taper seal portion TS1. Formed and retained.
[0035]
An annular recess is provided on the inner peripheral surface of the sleeve 4 corresponding to the opening of the communication hole 18 communicating with the outside of the bearing on the inner peripheral surface side of the sleeve 4. An annular recess is also provided on the outer peripheral surface of the shaft 6. The upper end side (the side adjacent to the upper radial bearing portion R1) in the axial direction of each annular concave portion provided on the sleeve 4 and the shaft 6 has a gap formed between the annular concave portions toward the upper radial bearing portion R1 side. Of the oil held by the upper radial bearing portion R1 is axially lower (opposite to the rotor 2). The gas comes into contact with the air taken into the intervening portion 8 to form a gas-liquid interface between the oil and the air. That is, the space formed on the upper end side in the axial direction of each annular concave portion provided on the sleeve 4 and the shaft 6 functions as the tapered seal portion TS2. Therefore, both ends of the oil continuously held between the thrust bearing portion S and the upper radial bearing portion R1 are located inside these taper seal portions TS1 and TS2.
[0036]
One end of the oil held by the lower radial bearing portion R2 is located on the lower end side in the axial direction of the annular concave portions provided on the sleeve 4 and the shaft 6 (on the side opposite to the upper radial bearing portion R1). It is located at a taper seal portion (specific configuration is not shown) having the same configuration as the provided taper seal portion TS2, and the other end is attached to the lower end of the outer peripheral surface of the shaft 6. A taper seal (see FIG. 1 (FIG. 1)) which is formed by an axial tapered gap formed between the outer peripheral surface of the retaining ring 22 and the inner peripheral surface of the step provided at the lower end of the inner peripheral surface of the sleeve 4. a)).
[0037]
When the spindle motor having the above configuration starts rotating, in the thrust bearing portion S, the flow of oil in the direction indicated by the arrow A in the drawing is induced by the pump-in spiral groove SG1. In the upper radial bearing portion R1, oil flow in the direction indicated by the arrow B in the drawing is induced by the herringbone groove HG1 having an unbalanced shape in the direction of the axis in which the spiral groove portion RS3 is provided. By pumping the spiral groove SG1 and the herringbone groove HG1, the gas-liquid interface located in the tapered seal portions TS1 and TS2 is pulled up to the thrust bearing portion S and the upper radial bearing portion R1, respectively.
[0038]
Thereafter, as the rotation speed of the spindle motor increases, the lifting of the gas-liquid interface toward the bearing portion is continued. When the end of the herringbone groove HG1 on the taper seal portion TS2 side, that is, the spiral groove portion RS3 of the herringbone groove HG1, which is disposed adjacent to the upper side in the axial direction of the taper seal portion TS2, is exposed in the air as the gas-liquid interface rises, the herringbone groove is formed. Unbalanced pumping in the direction of arrow B by HG1 is eliminated, and the lifting of the gas-liquid interface on the taper seal portion TS2 side is stopped. Further, the lifting of the gas-liquid interface on the taper seal portion TS1 side, which balances with the gas-liquid interface on the taper seal portion TS2 side, is also stopped.
[0039]
A herringbone groove provided on the radial bearing portion is for obtaining a necessary load supporting pressure by stimulating the flow of a fluid such as oil from the upper and lower ends of the axial direction toward a connecting portion of a pair of spiral grooves forming the herringbone groove. Therefore, each spiral groove is inclined at a predetermined groove angle with respect to the rotation direction. The groove angle is usually set to about 25 degrees in consideration of a necessary load supporting pressure and a loss caused by resistance.
[0040]
In the present embodiment, the end of the spiral groove RS3 on the side of the taper seal portion TS2 on the side of the spiral groove RS1 is a thrust bearing so that the unbalanced spiral groove RS3 has a different groove angle from the other spiral grooves RS1 and / or RS2. The connecting portion between the spiral grooves RS2 and RS3 is bent so as to be located on the rotation direction front side of the S-side end. That is, in the herringbone groove HG1, the spiral groove portions RS2 and RS3 that perform pumping from the taper seal portion TS2 side change to different groove angles at the bent portion. In this case, the groove angle of the spiral groove RS3 with respect to the rotation direction is set to about 20 degrees.
[0041]
When the gas-liquid interface on the side of the tapered seal portion TS2 is raised so that the spiral groove portion RS3 is exposed to the air, a herringbone groove HG1 on the surface of the sleeve 4 where the gap dimension between the shaft 6 and the shaft 6 is reduced is provided. In the non-hill portion, the gas-liquid interface between oil and air is further pulled up to the connection portion between the spiral grooves RS1 and RS2, and in the spiral groove RS3 where the gap dimension between the shaft and the shaft is relatively large, The gas-liquid interface is located at a portion closer to the tapered seal portion TS2 than the hill portion. This is considered to be due to a change in the capillary force due to a change in the size of the gap formed by the hill and the groove.
[0042]
In any case, in the hydrodynamic bearing, since the hills and the grooves appear intermittently in the circumferential direction, the gas-liquid interface between oil and air also becomes wavy in the circumferential direction. Since the spiral groove RS3 of the herringbone groove HG1 is set to have a smaller groove angle with respect to the rotation direction than the spiral groove RS2, the amplitude in the axial direction of the waving of the gas-liquid interface becomes smaller and the spiral groove RS3 enters the oil. Of air bubbles is suppressed.
[0043]
In this way, the entrapment of air into the oil by the spiral groove portion RS3 is suppressed, so that oil leaks and abnormal vibrations due to bubbles remaining in the oil held in the bearing portion, and occurrence of seizure of the bearing portion are caused. Various adverse effects such as the above can be eliminated.
[0044]
Next, a disk drive device using a spindle motor according to the embodiment of the present invention will be described with reference to FIG.
[0045]
FIG. 2 is a schematic diagram showing the internal configuration of a general disk drive device 50. The inside of the housing 51 forms a clean space with extremely small amount of dust and the like, and a spindle motor 52 having a disk-shaped disk plate 53 for storing information installed therein is installed therein. In addition, inside the housing 51, a head moving mechanism 57 for reading and writing information from and to the disk plate 53 is arranged. The head moving mechanism 57 supports a head 56 for reading and writing information on the disk plate 53, and supports the head. The actuator 55 is configured to move the arm 55, the head 56, and the arm 55 to a required position on the disk plate 53.
[0046]
By using the spindle motor of each of the above embodiments as the spindle motor 52 of such a disk drive device 50, a highly reliable disk drive device can be obtained.
[0047]
As described above, the dynamic pressure bearing according to the present invention, the spindle motor including the dynamic pressure bearing, and the disk drive device according to one embodiment have been described. However, the present invention is not limited to the embodiment, and the scope of the present invention is not limited to the embodiment. Various changes and modifications are possible without departing from the scope of the invention.
[0048]
For example, the upper radial bearing R1 in each of the above-described embodiments has a configuration in which one end of the bearing is adjacent to the gas-liquid interface between oil and air, and the other end is adjacent to another bearing. In the radial bearing portion, it is possible to use any structure of the dynamic pressure bearing and the spindle motor.
[0049]
That is, a radial bearing portion adjacent to a thrust bearing portion constituted by a thrust plate provided at one end of a shaft like the dynamic pressure bearing disclosed in Patent Document 1 described above, or a gap formed in the bearing portion The present invention is also applicable to a bearing portion disposed adjacent to a gas-liquid interface in a so-called full-fill dynamic pressure bearing in which oil is entirely filled.
[0050]
Further, the groove angle of the spiral groove portion RS3, which is the unbalanced portion of the herringbone groove HG1 in the upper radial bearing portion R1, differs from the groove angle of the spiral groove portion RS2 only in a part of the herringbone groove HG1 forming the dynamic pressure generating groove row. It is also possible to set as follows.
[0051]
【The invention's effect】
ADVANTAGE OF THE INVENTION The dynamic pressure bearing of this invention can suppress the entrapment of air in oil, can eliminate the bad influence by the retention of air bubbles, and can maintain stable performance.
[0052]
Further, in the spindle motor according to the present invention, it is possible to suppress the vibration during the operation of the rotor and at the same time to avoid the occurrence of the problem due to the stagnation of air bubbles, so that a highly reliable spindle motor can be obtained. .
[0053]
Further, in the disk drive device of the present invention, since problems caused by air bubbles staying in the bearing portion of the spindle motor are also avoided, a very stable and highly reliable disk drive device can be provided.
[Brief description of the drawings]
FIG. 1A is a cross-sectional view showing an application example of a dynamic pressure bearing of the present invention to a spindle motor, and FIG. 1B is a partially enlarged cross-sectional view showing a part of the bearing portion. FIG. 1C is a plan view showing a shape of a spiral groove provided in the thrust bearing portion.
FIG. 2 is a cross-sectional view schematically showing an internal configuration of the disk drive device.
[Explanation of symbols]
R1 Radial bearing HG1 Herringbone groove RS1, RS2, RS3 Spiral groove

Claims (5)

In a dynamic pressure bearing having at least one end portion having a radial bearing portion adjacent to a gas-liquid interface between oil and air, the radial bearing portion includes, from the gas-liquid interface side with respect to the oil, the other end side. A spiral groove located on the gas-liquid interface side so as to induce an axial flow toward the head is formed from a plurality of herringbone grooves having a shape in which the axial dimension is set larger than the spiral groove located on the other end side. And a spiral groove which is formed on the gas-liquid interface side forming the herringbone groove is provided with a bent portion which changes so that the groove angle becomes smaller with respect to the rotation direction. A dynamic pressure bearing. Among the spiral groove portions located on the gas-liquid interface side, the axial dimension from the bearing center of the radial bearing portion to the bent portion is set to be substantially equal to the spiral groove portion located on the other end side. The dynamic pressure bearing according to claim 1, wherein: The other end of the radial bearing opposite to the end adjacent to the gas-liquid interface is adjacent to a thrust bearing, and the thrust bearing includes a pump-in-shaped spiral groove. The dynamic pressure bearing according to claim 1 or 2, wherein a pressure generating groove row is provided. A shaft, a sleeve having a through-hole through which the shaft is freely rotatably inserted, and a circular ceiling in which the shaft is opposed to the upper end surface of the sleeve in the axial direction and the shaft is integrally formed with the rotation axis. A spindle motor comprising a rotor having a plate,
A minute gap for holding the oil is formed between the upper end surface of the sleeve and the bottom surface of the top plate, and a fluid dynamic pressure is induced in the oil held in the minute gap according to the rotation of the rotor. The thrust bearing portion is constituted by providing the dynamic pressure generating groove
A minute gap for holding oil is formed between the inner peripheral surface of the through hole of the sleeve and the outer peripheral surface of the shaft, and the oil retained in the minute gap in response to the rotation of the rotor. A radial bearing portion is formed by providing a dynamic pressure generating groove for inducing a fluid dynamic pressure,
4. A spindle motor according to claim 3, wherein a dynamic pressure bearing comprising said thrust bearing portion and said radial bearing portion is the dynamic pressure bearing according to claim 3. In a disk drive device in which a recording disk capable of recording information is driven to rotate, a housing, a spindle motor fixed inside the housing and rotating the recording disk, and a device for writing or reading information at a required position on the recording disk 5. A disk drive device comprising the information access means of claim 4, wherein the spindle motor is the spindle motor according to claim 4.

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