JP2005299862A - Fluid dynamic bearing device and spindle motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid dynamic bearing device and a spindle motor capable of reducing the number of components, the manufacturing assembling man-hour and the manufacturing cost while preventing the leakage of working fluid such as lubricant to the external, further coping with the miniaturization of a hard disc device, and keeping high bearing rigidity. <P>SOLUTION: A shaft 1 is formed of a sintered body, a radial dynamic pressure generating groove 7 is formed on an outer peripheral face of the shaft 1, and a sleeve 3 is made out of a material impervious to working fluid 6. By applying this constitution, the leakage of working fluid to the external can not be found even when the shaft 1 is made out of a porous member composed of the sintered body. Further a bracket mounted at an outer side of the sleeve 3 is unnecessary, and a function of the sleeve can be achieved by one member. The shaft 1 and the radial dynamic pressure generating groove 7 can be formed with high accuracy by press molding and the like while saving labor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydrodynamic bearing device using a hydrodynamic bearing and a spindle motor including the hydrodynamic bearing device.

  As a bearing device used in a spindle motor of a hard disk device, a hydrodynamic bearing device that is superior in rotation accuracy and quietness more than a ball bearing device is used in place of a conventionally used ball bearing device. is there.

  In Patent Document 1 and Patent Document 2, as shown in FIG. 7, a sleeve 52 made of a sintered body having a radial dynamic pressure generating groove 51 formed on the inner peripheral surface thereof is passed through a lubricating oil as a working fluid. A structure in which a radial fluid bearing is formed between the sleeve 52 and the shaft 54 by wrapping with a bracket 53 formed of a non-material is disclosed. In addition, a thrust fluid bearing is configured between the thrust plate 56 and a thrust flange 57 fixed to one end of the shaft 54 by fixing a thrust plate 56 in which a thrust dynamic pressure generating groove 55 is formed to the bottom of the bracket 53. doing. Lubricating oil as a working fluid is filled between the sleeve 52 and the shaft 54 and between the thrust flange 57 and the thrust plate 56 including at least a portion constituting the radial fluid bearing and the thrust fluid bearing.

  According to this configuration, the sleeve 52 is formed of a sintered body made of a sintered metal or the like, so that the sintered product is placed in a mold and press-molded to form the radial dynamic pressure generating groove 51. Since this can be formed, the radial dynamic pressure generating groove 51 can be manufactured by press molding with high accuracy and without labor, and the sleeve 52 can be manufactured when a general metal material is used. It is not necessary to perform the grooving by such a precision cutting process in a subsequent process, and the manufacturing cost can be reduced.

  In addition, since the sintered body has a large number of small holes in the inside thereof, when the sleeve 52 is formed of a sintered body, if the sleeve 52 is used alone, lubricating oil as a working fluid is discharged from the sleeve 52 to the outside. Leaking, causing a decrease in lubricating oil and hindering the fluid bearing, or when the motor is driven to rotate, the lubricating oil leaks from the radial dynamic pressure generating groove 51 into the sleeve 52 and the pressure generated by the dynamic pressure generating groove is increased. As a result, there arises a problem that the bearing rigidity as a radial bearing is lowered.

  In order to cope with these problems, in the hydrodynamic bearing device disclosed in Patent Document 1 or Patent Document 2, a sleeve 52 formed of a sintered body is wrapped with a bracket 53 formed of a material that does not allow lubricating oil to pass through. The lubricating oil is prevented from leaking outside from the sleeve 52. Further, in the hydrodynamic bearing device disclosed in Patent Document 2, the inner peripheral surface of the sleeve is crushed to close the air holes, and the lubricating oil leaks into the sleeve from the radial dynamic pressure generating groove when the motor is driven to rotate. This is intended to prevent the bearing rigidity from decreasing as a radial bearing.

  In Patent Document 3, the shaft is formed of a sintered body made of a sintered metal or the like, and the lubricating oil is included in the shaft of the sintered body, and the sleeve into which the shaft is inserted penetrates the lubricating oil. There is disclosed a so-called round plain bearing configuration in which the shaft is made of a solid metal that is slidable and is slidably supported on the sleeve by the contained lubricating oil.

According to this configuration, since the shaft is formed of a sintered body instead of the sleeve, and the sleeve is made of a material that does not penetrate the lubricating oil, the lubricating oil remains on the sleeve side even when the shaft itself is impregnated with the lubricating oil. There is no leakage.
JP 2003-65323 A JP-A-7-63220 JP 2003-333792 A

  However, in the conventional hydrodynamic bearing devices disclosed in Patent Document 1 and Patent Document 2, a bracket formed of a material that does not allow the lubricating oil to pass outside the sleeve formed of a sintered body is required. Therefore, there is a problem in that the number of parts increases, resulting in an increase in manufacturing assembly man-hours and an increase in manufacturing costs. In recent years, there is a high demand for miniaturization of hard disk devices, but it is difficult to miniaturize because two articles, a sleeve and a bracket, are required.

  In addition, since the hydrodynamic bearing device having the conventional configuration disclosed in Patent Document 3 simply constitutes a perfect plain bearing, the bearing rigidity decreases as the porosity increases, and the bearing rigidity is reduced. Can't cope with decline.

  The present invention solves the above-mentioned problems and problems, can prevent working fluid such as lubricating oil from leaking to the outside, can reduce the number of parts, can reduce the manufacturing assembly man-hours and manufacturing cost, and moreover is a hard disk device It is an object of the present invention to provide a hydrodynamic bearing device and a spindle motor that can cope with downsizing of the motor and can maintain good bearing rigidity.

  In order to solve the above-mentioned problems and problems, the present invention comprises a shaft and a sleeve arranged on the outer periphery with a minute gap with respect to the shaft, and a fluid filled with a working fluid between the shaft and the sleeve The bearing device is characterized in that the shaft is formed of a sintered body, a radial dynamic pressure generating groove is formed on the outer peripheral surface of the shaft, and the sleeve is formed of a material that does not allow the working fluid to pass therethrough.

  With this configuration, the shaft is wrapped from the outer peripheral side by a sleeve formed of a material that does not penetrate the working fluid such as lubricating oil, so that the working fluid is external even if the shaft is a porous body made of a sintered body. There is no worry of leaking. Further, it is not necessary to provide a bracket or the like outside the sleeve, and the function of the sleeve can be formed by a single member. Further, at the time of manufacturing, the shaft and its radial dynamic pressure generating groove can be manufactured by press molding or the like with high accuracy and without labor. In addition, since the shaft is wrapped with working fluid and a radial dynamic pressure generating groove is formed on the outer peripheral surface, an even generated pressure is applied to the inside of the shaft from the outer periphery by the radial dynamic pressure generating groove. In addition, it is possible to prevent the working fluid from flowing from the porous portion to reduce the generated pressure.

  Further, in addition to the above-described configuration, a thrust flange that protrudes radially outward from the shaft, and a thrust plate that is disposed at a position facing the thrust flange via a minute gap, the shaft and the sleeve Or a thrust flange and a sleeve and a thrust plate are filled with a working fluid, and the sleeve and the thrust plate are formed of a material that does not allow the working fluid to pass through, so that a thrust bearing is configured and positioned in the thrust direction. Can be regulated.

  Further, the thrust flange may be formed of a sintered body and a thrust dynamic pressure generating groove may be formed on the surface of the thrust flange, and the sleeve and the thrust plate may be formed of a material that does not allow the working fluid to pass therethrough.

  Further, the sleeve may be formed of a sintered body and the inner peripheral surface of the sleeve may be subjected to crushing treatment, coating treatment, or plating treatment, and the thrust plate may be formed of a material that does not allow the working fluid to pass through.

  Further, a thrust bearing or a pivot bearing may be formed on the end face of the shaft without providing a thrust flange.

  According to the present invention, the shaft is formed of a sintered body, the radial dynamic pressure generating groove is formed on the outer peripheral surface of the shaft, and the sleeve is formed of a material that does not pass a working fluid such as lubricating oil. Even if it is a porous body made of a sintered body, it is possible to prevent the working fluid from leaking to the outside and cause troubles, and it is possible to reduce the number of parts compared to the conventional configuration that requires a bracket, and to manufacture and assemble The number of man-hours and manufacturing costs can be reduced, and the shaft and its radial dynamic pressure generating groove can be manufactured with high accuracy and reduced labor by press molding at the time of manufacturing. Therefore, it is possible to obtain a small spindle motor that can meet the demand for miniaturization of the hard disk device. In addition, since the shaft is wrapped with working fluid and the radial dynamic pressure generating groove is formed on the outer periphery, evenly generated pressure is applied to the inside of the shaft from the outer periphery by the radial dynamic pressure generating groove. It can be prevented that the working fluid flows from the porous portion and the generated pressure is lowered.

  Further, the thrust flange may be formed of a sintered body and a thrust dynamic pressure generating groove may be formed on the surface of the thrust flange, and the sleeve and the thrust plate may be formed of a material that does not allow the working fluid to pass therethrough.

  As a result, the shaft and the thrust flange can be integrally formed, and the accuracy can be further improved by reducing the number of components, and the radial dynamic pressure generating groove and the thrust dynamic pressure generating groove can be improved by pressing and sintering processes. Can be saved at the same time, and cost can be reduced. Even when the shaft and the thrust flange are manufactured separately, there is an advantage that the thrust flange having the thrust dynamic pressure generating groove can be manufactured relatively inexpensively and with high accuracy.

  Further, the sleeve may be formed of a sintered body, and the inner peripheral surface of the sleeve may be subjected to crushing treatment, coating treatment, or plating treatment, and the thrust plate may be formed of a material that does not pass the working fluid. Furthermore, since the sleeve can be formed of a sintered body, the cost can be further reduced.

  Furthermore, without providing a thrust flange, a thrust dynamic pressure generating groove or a pivot bearing may be formed on the end surface of the shaft, which further simplifies the structure and reduces the manufacturing cost.

Hereinafter, a hydrodynamic bearing device according to an embodiment of the present invention and a spindle motor including the hydrodynamic bearing device will be described with reference to the drawings.
(Embodiment 1)
As shown in FIG. 1, the hydrodynamic bearing device of the spindle motor is disposed on the outer periphery of the shaft 1, the thrust flange 2 projecting radially outward from the shaft 1, and a small gap with respect to the shaft 1. And a thrust plate 4 disposed at a position facing the thrust flange 2 via a minute gap.

  The sleeve 3 is fixed to the base 5 of the spindle motor, and an insertion hole 3a is formed at the center. The shaft 1 is inserted into the insertion hole 3a with a minute gap, and the minute gap between the shaft 1 and the sleeve 3 is filled with lubricating oil 6 as a working fluid. Further, the thrust flange 2 is attached to the inner end of the shaft 1 so as to be integrally fixed by a screw or an external fitting, and the thrust plate 4 is disposed so as to face the circular flat portion of the thrust flange 2. The lubricating oil 6 is filled even in the gap between the thrust flange 2 and the thrust plate 4.

  In this hydrodynamic bearing device, in particular, the shaft 1 is formed of a sintered body made of a metal sintered material. In addition, a radial dynamic pressure generating groove 7 such as a spiral or fishbone pattern is formed on the outer peripheral surface of the shaft 1 by pressing to constitute a radial bearing. Here, the metal sintered material may be composed of a sintered metal made of metal particles containing iron or copper, but is not limited thereto. Moreover, you may use the sintered metal which consists of iron-type particle | grains which have a stainless steel-type particle | grain. The sintered body is a porous body having a large number of pores inside, and as a manufacturing method thereof, metal powder and a lubricant are blended in a predetermined ratio, mixed, filled into a mold, and pressed. After the compression molding, the compressed powder compact is manufactured by heating and sintering at a high temperature below the melting point for a predetermined time. In this production process, the radial dynamic pressure generating groove 7 may be formed by, for example, further putting a sintered body into a mold and recompressing it, but is not limited to this, and the first step before sintering is performed. You may form by the compression molding process by a press.

  In this embodiment, while the shaft 1 is formed of a sintered body, the sleeve 3, the thrust flange 2, and the thrust plate 4 are made of a material that does not allow the lubricating oil 6 to pass through, that is, a metal solid that is not a porous body. It is made of a material such as synthetic resin. As shown in FIG. 1, in this embodiment, radial bearings each including a radial dynamic pressure generating groove 7 are provided at two locations on the outer peripheral surface of the shaft 1, that is, a region closer to the back side and a region closer to the opening. .

  Further, a thrust dynamic pressure generating groove 8 such as a spiral or fishbone pattern is formed on at least one surface of the opposing surfaces of the thrust flange 2 and the thrust plate 4 to constitute a thrust bearing. Further, a thrust dynamic pressure generating groove 8 is formed in at least one of the surface of the thrust flange 2 adjacent to the back end portion of the shaft 1 and the surface of the sleeve 3 facing this surface to constitute a thrust bearing. FIG. 1 shows a case where the thrust dynamic pressure generating grooves 8 are formed on the surface of the sleeve 3 and the surface of the thrust plate 4 facing the thrust flange 2, respectively.

  A hub 9 as a rotating member to which, for example, a magnetic recording disk is fixed is fitted on the outer periphery of the protruding side end portion 1a protruding from the opening portion of the sleeve 3 in the shaft 1 in a press-fit state. In this embodiment, the rotor magnet 10 is attached to the outer periphery of the hub 9 near the base. A stator core 12 around which a stator coil 11 is wound is attached to the base 5 so as to face the rotor magnet 10. The rotor magnet 10 and the stator core 12 constitute a spindle motor drive unit that applies a rotational drive force between the shaft 1 and the sleeve 3.

  When the hub 9, the shaft 1, and the thrust flange 2 are rotationally driven by the spindle motor drive unit, the radial direction is lubricated by the radial dynamic pressure generating groove 7, and the thrust direction is lubricated by the thrust dynamic pressure generating groove 8. Hydrodynamic pressure is generated in the oil 6, and the shaft 1 and the thrust flange 2 are rotatably supported by these fluid bearings (radial bearing and thrust bearing) in a non-contact state with respect to the sleeve 3 and the thrust plate 4 with a minute gap maintained. The

  According to this configuration, since the shaft 1 is wrapped from the outer peripheral side by the sleeve 3 formed of a material that does not penetrate the lubricating oil 6, the shaft 1 is a porous body made of a sintered body. There is no worry that the lubricating oil 6 leaks to the outside. Accordingly, there is no reduction due to leakage of the lubricating oil 6 to the outside, and no trouble is caused as a fluid bearing due to such a problem, and good reliability can be maintained. Further, it is not necessary to provide a bracket or the like outside the sleeve 3, and the function of the sleeve 3 can be formed by a single member. Thereby, compared with the conventional structure which requires a bracket, a number of parts can be reduced and the reduction of a manufacturing assembly man-hour and the reduction of manufacturing cost can be aimed at. In addition, the shaft 1 and its radial dynamic pressure generating groove 7 can be manufactured with high precision and with less labor by press molding at the time of manufacturing, and by precision cutting as in the case of using a general metal material. It is not necessary to perform grooving in a subsequent process, and the manufacturing cost can be further reduced. In addition, since the number of parts can be reduced, it is possible to obtain a small spindle motor that can meet the demand for miniaturization of the hard disk device.

  Further, since the shaft 1 is wrapped with the lubricating oil 6 and the radial dynamic pressure generating groove 7 is formed on the outer periphery, the uniform generated pressure by the radial dynamic pressure generating groove 7 is applied to the inside of the shaft 1 from the outer periphery. Therefore, it is possible to prevent the lubricating oil 6 from flowing from the porous portion and reducing the generated pressure even when the dynamic pressure is generated. Further, since the radial dynamic pressure generating groove 7 is formed on the shaft 1 formed of a sintered body, the area of the radial dynamic pressure generating groove 7 is increased, or the shape of the radial dynamic pressure generating groove 7 is devised. You can do it freely. By these, bearing rigidity can be kept favorable and high reliability can be maintained.

(Embodiment 2)
As shown in FIG. 2, in this spindle motor hydrodynamic bearing device, the shaft 1 and the thrust flange 2 are also formed of a sintered body, and the shaft 1 and the thrust flange 2 are integrally formed at the time of the manufacturing process. Yes.

  Further, not only the radial dynamic pressure generating groove 7 is formed on the outer peripheral surface of the shaft 1 to constitute a radial bearing, but also the thrust dynamic pressure generating groove 8 is formed on the upper and lower circular plane portions of the thrust flange 2 to provide a thrust. It constitutes a bearing.

On the other hand, the sleeve 3 and the thrust plate 4 are formed of a material that does not allow the lubricating oil 6 to pass therethrough, that is, a material such as a metal solid or a synthetic resin that is not a porous body.
According to the above configuration, since the shaft 1 and the thrust flange 2 are integrally formed, the accuracy can be further improved by reducing the number of parts. Further, since the radial dynamic pressure generating groove 7 and the thrust dynamic pressure generating groove 8 are formed at the same time by the pressing and sintering process, further labor can be saved and the cost can be reduced.

  Further, since the shaft 1 and the thrust flange 2 are wrapped from the outside by the sleeve 3 and the thrust plate 4, there is no fear that the lubricating oil 6 leaks to the outside even if the shaft 1 or the thrust flange 2 is a porous body. . Further, the shaft 1 and the thrust flange 2 are wrapped with the lubricating oil 6, and the dynamic pressure generating grooves 7 and 8 are formed on the outer periphery of the shaft 1 and the upper and lower surfaces of the thrust flange 2. A uniform generated pressure by the dynamic pressure generating grooves 7 and 8 is applied to the inside of the flange 2. Therefore, even when dynamic pressure is generated, the lubricating oil 6 does not flow from the porous portion and the generated pressure does not decrease, and reliability does not decrease due to a decrease in rigidity.

  The shaft 1 and the thrust flange 2 may be manufactured separately. Even in this case, there is an advantage that the thrust flange 2 having the thrust dynamic pressure generating groove 8 can be manufactured relatively inexpensively and with high accuracy.

(Embodiment 3)
As shown in FIG. 3, in this hydrodynamic bearing device for a spindle motor, the shaft 1 is formed of a sintered body, the radial dynamic pressure generating groove 7 is formed on the outer peripheral surface of the shaft 1, and the sleeve 3 is also formed of a sintered body. Forming. Here, the inner peripheral surface (insertion hole 3a) of the sleeve 3 is subjected to a crushing process, a coating process, or a plating process so that the lubricating oil 6 does not pass from the inner peripheral surface of the sleeve 3 to the inside. It has become.

  According to the above configuration, at least the sleeve 3 can also be formed of a sintered body, so that the cost can be further reduced. Further, since the inner peripheral surface (insertion hole 3a) of the sleeve 3 is subjected to a crushing process, a coating process, or a plating process, there is no fear that the lubricating oil 6 leaks even if the sleeve 3 is a porous body.

(Embodiment 4)
As shown in FIG. 4, in the hydrodynamic bearing device for the spindle motor, the thrust flange 2 is eliminated and the inner diameter of the sleeve 3 is constant. A thrust dynamic pressure generating groove 8 is formed on the bottom surface of the shaft 1. A stepped portion is formed at the protruding side end 1a of the shaft 1, and a retaining member 13 for the shaft 1 is attached to the sleeve 3 so as to cover the stepped portion from above, so that the shaft 1 comes off from the sleeve 3. Is preventing.

According to this configuration, since the inner diameter of the sleeve 3 is constant, there is an advantage that the crushing process can be easily performed.
In addition, without providing the retaining member 13, the cover 14 that covers the motor driving unit may also be used as the retaining function of the shaft 1. Further, the present invention is not limited by the presence or absence of the stopper and its location.

(Embodiment 5)
As shown in FIG. 5, in this spindle motor hydrodynamic bearing device, the shaft 1 is formed of a sintered body, a radial dynamic pressure generating groove 7 is formed on the outer peripheral surface of the shaft 1, and a pivot bearing is formed at the lower end of the shaft 1. 15 is formed.

According to this configuration, since the thrust bearing portion is changed to the pivot bearing 15, the structure becomes simple and the manufacturing cost can be reduced.
(Embodiment 6)
As shown in FIG. 6, in the hydrodynamic bearing device of this spindle motor, the shaft 1 is formed of a sintered body, the radial dynamic pressure generating groove 7 is formed on the outer peripheral surface of the shaft 1, and the pivot bearing is formed at the lower end of the shaft 1. 15 is formed, and the sleeve 3 is formed of a sintered body, and the inner peripheral surface of the sleeve 3 is subjected to crushing treatment, coating treatment, or plating treatment.

  With the above configuration, the thrust bearing portion can be changed to the pivot bearing 15, and at least the sleeve 3 can be formed of a sintered body, so that the manufacturing cost can be further reduced.

  The present invention can be applied to a hydrodynamic bearing device particularly suitable for a spindle motor of a hard disk device or other devices, but can also be applied to other devices. Although it is particularly suitable when lubricating oil is used as the working fluid, it can be applied to a hydrodynamic bearing device that uses air or other gas as the working fluid.

Sectional drawing of the spindle motor provided with the hydrodynamic bearing apparatus which concerns on the 1st Embodiment of this invention Sectional drawing of the spindle motor provided with the hydrodynamic bearing apparatus which concerns on the 2nd Embodiment of this invention Sectional drawing of the spindle motor provided with the hydrodynamic bearing apparatus which concerns on the 3rd Embodiment of this invention Sectional drawing of the spindle motor provided with the hydrodynamic bearing apparatus which concerns on the 4th Embodiment of this invention Sectional drawing of the spindle motor provided with the hydrodynamic bearing apparatus which concerns on the 5th Embodiment of this invention Sectional drawing of the spindle motor provided with the hydrodynamic bearing apparatus which concerns on the 6th Embodiment of this invention Sectional view of a spindle motor equipped with a conventional hydrodynamic bearing device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shaft 2 Thrust flange 3 Sleeve 4 Thrust plate 5 Base 6 Lubricating oil 7 Radial dynamic pressure generating groove 8 Thrust dynamic pressure generating groove 9 Hub 10 Rotor magnet 11 Stator coil 12 Stator core 15 Pivot bearing

Claims (9)

A hydrodynamic bearing device comprising a shaft and a sleeve arranged on the outer circumference with a minute gap with respect to the shaft, wherein a working fluid is filled between the shaft and the sleeve,
A hydrodynamic bearing device in which a shaft is formed of a sintered body, a radial dynamic pressure generating groove is formed on an outer peripheral surface of the shaft, and a sleeve is formed of a material that does not allow a working fluid to pass therethrough. A thrust flange projecting radially outward from the shaft, and a thrust plate disposed at a position facing the thrust flange via a minute gap,
Fill the working fluid between the shaft and the sleeve or between the thrust flange and the sleeve and the thrust plate,
2. The hydrodynamic bearing device according to claim 1, wherein the sleeve, the thrust flange, and the thrust plate are formed of a material that does not allow the working fluid to pass therethrough. A thrust flange projecting radially outward from the shaft, and a thrust plate disposed at a position facing the thrust flange via a minute gap,
Fill the working fluid between the shaft and the sleeve or between the thrust flange and the sleeve and the thrust plate,
A thrust flange is formed of a sintered body and a thrust dynamic pressure generating groove is formed on the surface of the thrust flange.
The hydrodynamic bearing device according to claim 1, wherein the sleeve and the thrust plate are made of a material that does not allow the working fluid to pass therethrough. A thrust flange projecting radially outward from the shaft, and a thrust plate disposed at a position facing the thrust flange via a minute gap,
Fill the working fluid between the shaft and the sleeve or between the thrust flange and the sleeve and the thrust plate,
A thrust dynamic pressure generating groove is formed on at least one of the surface of the thrust flange, the surface of the sleeve facing the surface of the thrust flange, or the surface of the thrust plate facing the surface of the thrust flange,
The sleeve is formed of a sintered body, and at least the inner peripheral surface of the sleeve is subjected to crushing treatment, coating treatment, or plating treatment,
The hydrodynamic bearing device according to claim 1, wherein the thrust plate is formed of a material that is impermeable to working fluid. A thrust plate disposed at a position facing the end face of the shaft through a minute gap,
Fill the working fluid between the shaft and the sleeve, or between the shaft end face and the thrust plate,
A thrust dynamic pressure generating groove is formed on the end face of the shaft or the thrust plate,
The hydrodynamic bearing device according to claim 1, wherein the sleeve and the thrust plate are made of a material that does not allow the working fluid to pass therethrough. A thrust plate disposed at a position facing the end face of the shaft through a minute gap,
Fill the working fluid between the shaft and the sleeve, or between the shaft end face and the thrust plate,
A thrust dynamic pressure generating groove is formed on the end face of the shaft or the thrust plate,
The sleeve is formed of a sintered body, and at least the inner peripheral surface of the sleeve is subjected to crushing treatment, coating treatment, or plating treatment,
The hydrodynamic bearing device according to claim 1, wherein the thrust plate is formed of a material that is impermeable to working fluid. Comprising a thrust plate disposed opposite the end face of the shaft;
Fill the working fluid between the shaft and the sleeve, or between the shaft end face and the thrust plate,
A pivot bearing is formed on the end face of the shaft,
The hydrodynamic bearing device according to claim 1, wherein the sleeve and the thrust plate are made of a material that does not allow the working fluid to pass therethrough. Comprising a thrust plate disposed opposite the end face of the shaft;
Fill the working fluid between the shaft and the sleeve, or between the shaft end face and the thrust plate,
A pivot bearing is formed on the end face of the shaft,
The sleeve is formed of a sintered body, and at least the inner peripheral surface of the sleeve is subjected to crushing treatment, coating treatment, or plating treatment,
The hydrodynamic bearing device according to claim 1, wherein the thrust plate is formed of a material that is impermeable to working fluid. A spindle motor comprising: the hydrodynamic bearing device according to claim 1; and a driving unit that applies a rotational driving force between the shaft and the sleeve.

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