JP2006266367A - Fluid dynamic bearing, motor, and recording medium driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid dynamic bearing capable of preventing working liquid in a dynamic bearing part from scattering even when shock being expected to be applied by a portable terminal unit device is applied and to provide a motor and a recording medium driving device using the fluid dynamic bearing. <P>SOLUTION: This fluid dynamic bearing is provided with a shaft body having a column-like part formed into a substantially circular cylindrical shape, a supporting body 22 having a blocking end and a cylindrical part 38 for storing the column-like part rotatably, and working liquid F filled into at least a clearance between the column-like part and the cylindrical part 38. Contact angle control processing for forming a contact angle with the working liquid F of 15° or less is applied on contact faces 43, 53 arranged in the vicinity of liquid level of the working liquid F in the shaft body and the supporting body. Leakage prevention means 61, 63 for preventing the working liquid F from leaking and spreading to the outside through a clearance between the shaft body and the supporting body are provided on the contact faces 43, 53 or faces adjacent to the contact faces 43, 53. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fluid dynamic pressure bearing, a motor, and a recording medium driving device.

  Generally, as a bearing of a hard disk device (hereinafter referred to as HDD) mounted on a stationary personal computer, a sliding bearing or a dynamic pressure bearing using oil as a lubricant is used. In particular, when a hydrodynamic bearing is used as the bearing, if the amount of oil is insufficient, sufficient dynamic pressure cannot be generated, and the HDD rotation shaft cannot be rotatably supported. Had to hold on.

However, since the HDD described above requires a clean environment due to its nature, a means for preventing oil used in the bearing from entering the HDD is provided. In particular, in the case of a dynamic pressure bearing that holds a relatively large amount of oil in the bearing portion, oil leakage from the bearing portion is prevented from the viewpoint of protecting the function of the HDD and maintaining the function of the dynamic pressure bearing. Techniques have been proposed (see, for example, Patent Documents 1 to 3).
JP-A-8-232966 Japanese Patent No. 2937833 US Pat. No. 5,667,309

  In the above-mentioned Patent Documents 1 to 3, a technical idea of providing a gap changing portion on the outer side in the axial direction of the radial bearing portion and setting an inclination angle in the gap changing portion to 45 degrees or less, and a rotating member in the gap changing portion Alternatively, a technical idea that the contact angle between the fixing member and the oil is 15 degrees or more, and a technical idea that uses a material that reduces the surface tension in the region that comes into contact with the oil, such as plastic, in order to increase the contact angle. And are disclosed.

According to the technical ideas disclosed in Patent Documents 1 to 3 described above, oil can be prevented from leaking from the bearing portion to the outside due to wet expansion (rising phenomenon).
Further, even when an impact assumed when the HDD is used in a stationary personal computer is applied to the HDD, external oil can be prevented from scattering from the bearing portion.

However, the impact (about 10000 m / s ² to about 15000 m / s ² (about 1000 G−) is about 5 to 7.5 times higher than the impact (about 2000 m / s ² (about 200 G)) assumed for a stationary personal computer. When the HDD is mounted on a portable information appliance such as a portable notebook computer, a portable telephone, or a digital camera that is assumed to be about 1500G)), the above-mentioned Patent Documents 1 to 3 In the disclosed technology, there is a problem that oil is scattered from the bearing portion to the outside.

  The present invention has been made to solve the above-described problem, and is a fluid dynamic pressure capable of preventing the scattering of the working liquid in the dynamic pressure bearing portion even when an impact assumed to be applied by a portable terminal device or the like is applied. It is an object to provide a bearing, a motor using the bearing, and a recording medium driving device.

In order to achieve the above object, the present invention provides the following means.
The present invention includes a shaft body having a columnar portion formed in a substantially columnar shape, a support body having a closed end and a cylindrical portion that rotatably accommodates the columnar portion, and at least the columnar portion and the cylindrical portion. And a contact surface disposed in the vicinity of the surface of the working liquid of the shaft body and the support has a contact angle with the working liquid of 15 ° or less. The contact angle control process is performed, and leakage preventing means for preventing the working liquid from spreading wet from the gap between the shaft body and the support body to the contact surface or a surface adjacent to the contact surface is provided. A fluid dynamic pressure bearing is provided.

  According to the present invention, the contact angle with the working liquid on the contact surface is set to 15 ° or less by performing the contact angle control process on the contact surface disposed near the liquid surface of the working liquid on the shaft body and the support. can do. By setting the contact angle to 15 ° or less, it is possible to prevent the working liquid from jumping out of the fluid dynamic pressure bearing even when an impact is applied to the fluid dynamic pressure bearing from the outside.

  Further, since the leakage preventing means is provided on the contact surface or the surface adjacent to the contact surface, it is possible to prevent the working liquid from spreading to the outside more than the leakage preventing means. Further, the area subjected to the contact control process is likely to wet and spread the working liquid, but by providing the leakage preventing means, it is possible to prevent the working liquid from leaking outside from the fluid dynamic pressure bearing.

Moreover, in the said invention, it is desirable that the said contact angle control process is a surface treatment which makes the surface roughness of the said contact surface larger than predetermined value.
According to the present invention, the contact angle with the working liquid on the contact surface can be reduced to 15 ° or less by performing a surface treatment that makes the surface roughness of the contact surface larger than a predetermined value.
Examples of the surface treatment include cutting of the contact surface. Specifically, a method of forming the contact surface by a lathe process or the like and leaving the processed pattern as it is can be exemplified. According to this method, even a material that is difficult to be mirror-finished (for example, stainless steel) can be easily used as a material for a shaft body and a support body.

Furthermore, in the above invention, it is desirable that the leakage preventing means is a liquid repellent layer made of a material that repels the working liquid and is provided on the surfaces of the shaft body and the support body.
According to the present invention, in the liquid repellent layer, the working fluid spreading wet on the surfaces of the shaft body and the support can be blocked, so that the working liquid can be prevented from spreading wet from the region where the liquid repellent layer is formed. .

In the above invention, it is desirable that the leakage preventing means is a ridge line portion protruding in a convex shape from the surfaces of the shaft body and the support body.
According to the present invention, since the working fluid that spreads wet on the surfaces of the shaft body and the support body can be blocked in the ridge line portion protruding convexly, the working liquid can be prevented from spreading over the ridge line portion to the outside. .

  In the above invention, the shaft body is provided with a shaft body disk portion that is supported by the columnar portion and extends in the radial direction, and the support body is supported by the cylindrical portion and extends in the radial direction. A support disc portion is provided, and the shaft disc portion and the support disc portion are disposed so as to face each other, and the shaft disc portion or the opposed surface of the support disc portion At least one of the shaft body disk portion and the support body disk portion is formed with a dynamic pressure generating groove that draws the working liquid in a radial direction when the shaft body and the support body are relatively rotated. Are preferably arranged adjacent to the contact surface.

  According to the present invention, when the shaft body and the support body are relatively rotated, the working liquid is drawn in the radial direction by the dynamic pressure generating groove. Furthermore, since the shaft disk part and the support disk part are disposed adjacent to the contact surface, the working fluid existing between the contact surface, the shaft disk part, and the support disk part. Is drawn between the shaft disk part and the support disk part. As a result, when the shaft body and the support body are relatively rotated, even if an impact is applied to the fluid dynamic pressure bearing from the outside, the working liquid can be prevented from jumping out of the fluid dynamic pressure bearing.

In the above invention, the dynamic pressure generating groove draws the working liquid radially outward when the shaft body and the support body are relatively rotated, so that the shaft body disk portion and the support body circle are drawn. It is desirable that the plate portion is disposed adjacent to the outer side in the radial direction of the contact surface.
According to the present invention, when the shaft body and the support body are relatively rotated, the working liquid is drawn radially outward by the dynamic pressure generating groove.
Further, since the shaft disc portion and the support disc portion are arranged adjacent to the outer side in the radial direction of the contact surface, the dynamic pressure generating groove can be formed in the outer side in the radial direction with a high peripheral speed. It is possible to increase the pulling force of the working liquid.

In the above invention, the dynamic pressure generating groove draws the working liquid inward in the radial direction when the shaft body and the support body are relatively rotated, and the shaft disk portion and the support body circle It is desirable that the plate portion is disposed adjacent to the inside in the radial direction of the contact surface.
According to the present invention, when the shaft body and the support body are relatively rotated, the working liquid is drawn inward in the radial direction by the dynamic pressure generating groove.

In the said invention, it is desirable that the said shaft body and the said support body are formed from stainless steel.
According to the present invention, by forming the shaft body and the support body from stainless steel, corrosion of the shaft body and the support body and generation of rust can be prevented.

The present invention provides a motor comprising the fluid dynamic pressure bearing of the present invention and drive means for relatively rotating the shaft body and the support body of the fluid dynamic pressure bearing.
According to the present invention, by using the fluid dynamic pressure bearing of the present invention, the working fluid used in the fluid dynamic pressure bearing does not leak to the outside even when an impact is applied from the outside, and cleanliness is required. The motor can also be used in a certain environment.

The present invention provides a recording medium driving apparatus comprising the motor according to the present invention and provided with a fixing portion for fixing the recording medium to the shaft body or the support.
According to the present invention, by using the motor using the fluid dynamic pressure bearing of the above invention, the working liquid used in the fluid dynamic pressure bearing does not leak to the outside even when an impact is applied from the outside. Therefore, the inside of the recording medium driving device can be prevented from being contaminated by the working liquid.

According to the fluid dynamic pressure bearing of the present invention, the motor using the fluid dynamic bearing, and the recording medium driving device, contact angle control processing is performed on the contact surfaces of the shaft body and the support that are in contact with the liquid surface of the working liquid, By setting the contact angle with the liquid to 15 ° or less, even if an impact assumed to be applied by a portable terminal device or the like is applied, it is possible to prevent scattering of the working liquid in the hydrodynamic bearing portion.
In addition, since the leakage prevention means is provided in a region outside the region in contact with the working liquid of the shaft body and the support, it is possible to prevent the working liquid from spreading wet outside the leakage prevention means. There is an effect that the working liquid of the part can be prevented from leaking to the outside.

[First Embodiment]
Hereinafter, a fluid dynamic pressure bearing, a motor, and a recording medium driving device according to a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional view showing the overall configuration of the recording medium driving apparatus according to the present embodiment.
A fluid dynamic pressure bearing 10 according to this embodiment is applied to a recording medium driving apparatus 1 as shown in FIG. The recording medium driving apparatus 1 includes a stator 11 including electromagnets 13 arranged in an annular shape, and a rotor (shaft body) 16 including a permanent magnet 14 disposed opposite to the electromagnets 13 disposed inside the stator 11. The motor 17 includes a fluid dynamic pressure bearing 10 that rotatably supports the rotor 16 with respect to the stator 11. The electromagnet 13 provided in the stator 11 and the permanent magnet 14 provided in the rotor 16 constitute drive means 15 that rotationally drives the rotor 16 relative to the stator 11.

  The rotor 16 is provided with a fitting portion (fixing portion) 18 for fitting a ring plate-like recording medium HD, and a screw hole 21 for a screw 20 for attaching a pressing member 19 for fixing the recording medium HD is formed. Has been. The pressing member 19 is made of an annular plate member having a convex cross-sectional shape, and is attached to the rotor 16 with screws 20. The recording medium HD is fitted into the fitting portion 18 of the rotor 16 and is pressed against the fitting portion 18 by the pressing member 19 so that the rotor 16 and the recording medium HD are configured integrally. Yes.

The stator 11 includes a boss portion 12 disposed in the center of the electromagnet 13. By fitting a sleeve (support) 22 of the fluid dynamic pressure bearing 10 to be described later to the boss portion 12, the permanent magnet 14 provided in the rotor 16 is disposed to face the electromagnet 13. A shield plate 23 is disposed between the electromagnet 13 and the recording medium HD to block the magnetic field formed by the electromagnet 13 and the permanent magnet 14.
Further, the stator 11 is formed with a stator opening 24 for accommodating a coil 25 of an electromagnet 13 described later.

  As shown in FIG. 1, the electromagnet 13 includes a coil 25 that generates an alternating magnetic field when supplied with a three-phase alternating current, and a core plate 26 that includes a plurality of metal plates around which the coil 25 is wound. .

FIG. 2 is a cross-sectional view showing a configuration of a fluid dynamic pressure bearing in the recording medium driving apparatus of FIG.
As shown in FIG. 2, the fluid dynamic pressure bearing 10 according to the present embodiment includes the above-described rotor 16, a sleeve 22 that rotatably supports the rotor 16, and a retainer that prevents the rotor 16 from coming out of the sleeve 22. Part (shaft body) 33.
At least the rotor 16, the sleeve 22, and the retaining portion 33 constituting the fluid dynamic pressure bearing 10 are formed of stainless steel. By forming the rotor 16, the sleeve 22, the retaining portion 33, etc. from stainless steel, the fluid dynamic pressure bearing 10 can be prevented from being corroded or rusted.

  The rotor 16 includes a substantially cylindrical shaft (columnar portion) 34, and a bowl-shaped disc portion (shaft disc portion) 35 that extends radially outward on the outer peripheral surface of the shaft 34 at one end of the shaft 34. Are integrally formed. On the surface of the disk portion 35 that faces the sleeve 22, a recess 36 that houses a thrust bearing portion described later, and a yoke 52 that holds the retaining portion 33 and the permanent magnet 14 are formed. Further, on the upper surface (the upward surface in FIG. 2) of the disc portion 35, a fitting portion 18 that fits the recording medium HD is formed.

On the outer peripheral surface of the shaft 34, radial dynamic pressure generating grooves 37 called herringbone grooves are formed in two rows in the axial direction of the shaft 34. These radial dynamic pressure generating grooves 37 are inclined in one direction from one end of the shaft 34 with respect to the generatrix of the cylindrical surface forming the outer peripheral surface of the shaft 34, and are inclined in the opposite direction from the disk portion 35 side. And a groove extending in the direction. That is, the pair of grooves is configured to expand toward the rotation direction of the shaft 34.
As shown in FIG. 1, the radial dynamic pressure generating groove 37 is formed so that the pair of grooves intersect with each other as a single bent groove. It may be formed.

The sleeve 22 includes a cylindrical portion 38 that rotatably supports the shaft 34, and a flange-shaped thrust bearing portion (supporting disc portion) 39 that extends radially outward from the entire outer peripheral surface of one end of the cylindrical portion 38. And is composed of.
A bottom plate 40 that forms the bottom surface of the cylindrical portion 38 is disposed at an end portion below the cylindrical portion 38 (downward in FIG. 2).

FIG. 3 is an enlarged cross-sectional view illustrating the configuration of the fluid dynamic pressure bearing 10 of FIG.
As shown in FIGS. 2 and 3, a sleeve fitting portion 41 that is fitted to the boss portion 12 of the stator 11 is formed below the cylindrical portion 38, and the thrust bearing portion 39 and the sleeve fitting portion 41 are connected to each other. A sleeve seal surface (contact surface) 43 that forms a ring-shaped open end portion 42 is formed between the seal portion 53 and a retaining portion seal surface 53 described later. The sleeve seal surface 43 is formed as an inclined surface inclined inward in the radial direction toward the sleeve fitting portion 41.

  An annular sleeve groove 44 is formed at the boundary between the sleeve seal surface 43 and the sleeve fitting portion 41, and a ridge line portion (leakage prevention means) 61 is formed at the boundary between the sleeve seal surface 43 and the sleeve groove 44. Is formed. Further, an oil repellent layer (leakage prevention means, liquid repellent layer) 63 coated with an oil repellent material exhibiting oil repellency with respect to oil described later is formed in the sleeve groove portion 44.

  In addition, it is preferable that the inclination angle of the sleeve seal surface 43 is an inclination angle at which the angle formed with the retaining portion seal surface 53 is 30 ° or less. Furthermore, the surface roughness of the sleeve seal surface 43 is preferably processed to a surface roughness that makes the contact angle with oil, which will be described later, 15 ° or less.

FIG. 4A is a plan view for explaining a thrust dynamic pressure generating groove formed on the upper end surface of the thrust bearing portion of the fluid dynamic pressure bearing in the present embodiment, and FIG. It is a top view explaining the thrust dynamic-pressure generation groove formed in the lower end surface of the thrust bearing part in.
As shown in FIGS. 4A and 4B, the thrust bearing 39 has an upper end surface 39a and a lower end surface 39b formed over the entire circumference in the radial direction. And an annular thrust surface 46 disposed adjacent to the radially outer side of the protrusion 45. A large number of thrust dynamic pressure generating grooves (dynamic pressure generating grooves) 47 called herringbone grooves are formed on the thrust surface 46. Each of these thrust dynamic pressure generating grooves 47 is inclined in one direction with respect to the radial direction and extends in an arc shape from the side of the convex portion 45 toward the outer side in the radial direction, and then bent at an intermediate position (midway portion). It inclines in the opposite direction and extends to the outer periphery.

FIG. 5 is a plan view for explaining another form of the thrust dynamic pressure generating groove in the present embodiment. FIG. 5A is a view for explaining a thrust dynamic pressure generating groove formed on the upper end face of the thrust bearing portion, and FIG. 5B is a thrust motion formed on the lower end face of the thrust bearing portion. It is a figure explaining a pressure generating groove.
The thrust dynamic pressure generating groove 47 may be formed as a herringbone groove as described above, or as shown in FIGS. 5A and 5B, the oil F is pumped out radially outward. It may be formed as a spiral groove. A thrust dynamic pressure generating groove (dynamic pressure generating groove) 47 ′ formed as a spiral groove for pumping out is formed to be inclined outward in the radial direction and rearward in the rotational direction. Further, the thrust dynamic pressure generating groove 47 ′ is formed so as to extend to the front of the outer peripheral edge, and is not communicated with the outer peripheral edge. Therefore, the oil F pumped out radially outward generates pressure by being dammed at the outer end of the thrust dynamic pressure generating groove 47 ′.
The above-mentioned rotation direction is a relative rotation direction between the thrust bearing portion 39 and the disc portion 35 or a relative rotation direction between the thrust bearing portion 39 and the retaining disc 50.

  Further, as shown in FIGS. 2 and 4, the thrust bearing portion 39 is provided with two through holes 48 that penetrate the thrust bearing portion 39 in the thickness direction. These through holes 48 are formed at the same radial position with an angular interval of 180 ° around the central axis of the shaft 34. Each through-hole 48 is formed in the thrust surface 46 at a position adjacent to the dented portion 45, and has a tapered chamfered portion 49 that gradually widens in the opening direction at the opening that opens in the thrust surface. . The chamfered portion 49 is formed at a position overlapping the relief portion 45 on the opening end side. As a result, the groove wall of the relief portion 45 is partially cut away to form a communication recess that connects the through hole 48 and the relief portion 45.

As shown in FIGS. 2 and 3, the retaining portion 33 forms a ring-shaped open end portion 42 between the sleeve 22 and the retaining disc 50 that prevents the rotor 16 from coming off the sleeve 22. The seal cylinder 51 is schematically configured.
The retaining disk 50 is formed so as to hold the thrust bearing 39 between the recess 36 by being fixed to the yoke 52 of the rotor 16. The retaining disk 50 and the yoke 52 may be fixed by an adhesive G or may be fixed by welding, and it is preferable that the retaining disk 50 and the yoke 52 are fixed without a gap. By fixing without any gaps as described above, oil described later does not leak from the gap between the retaining disk 50 and the yoke 52.

The seal cylinder 51 is disposed on the inner peripheral surface of the retaining disc 50 so as to extend substantially vertically downward toward the stator 11 side. On the inner periphery of the seal cylinder 51, there is a retaining portion seal surface (contact surface) 53 that forms a ring-shaped open end portion 42 with the sleeve seal surface 43 in a region facing the sleeve seal surface 43 described above. Is formed.
The retaining portion seal surface 53 is formed as a surface extending substantially vertically downward toward the stator 11 side. An end region on the stator 11 side of the retaining portion seal surface 53 is formed with a retaining portion groove 55 having a V-shaped cross section, and the retaining portion groove 55 and the retaining portion seal surface 53. A ridge line portion 61 is formed at the boundary.
Further, the retaining portion seal surface 53 on the side of the stator 11 with respect to the retaining portion groove 55 is disposed away from the outside in the radial direction.

An oil repellent layer 63 coated with an oil repellent material exhibiting oil repellency with respect to oil described later is formed in the retaining portion groove 55.
In addition, it is desirable that the surface roughness of the retaining portion seal surface 53 is processed to a surface roughness such that a contact angle with oil, which will be described later, is 15 ° or less.

  As shown in FIG. 2, clearances C1 and C4 are provided between the shaft 34 and the sleeve 22 and between the sleeve 22 and the retaining portion 33, respectively. That is, between the thrust surface 46 of one end surface 45 of the thrust bearing portion 39 in which the thrust dynamic pressure generating groove 47 is formed and the inner surface of the concave portion 36 of the rotor 16 facing this, and the thrust surface of the other end surface 45. Clearances C <b> 1 and C <b> 2 are formed between 46 and the surface of the retaining portion facing this, respectively. Further, a uniform gap C3 is provided between the outer peripheral surface of the shaft 34 in which the radial dynamic pressure generating groove 37 is formed and the inner peripheral surface of the cylindrical portion 38 with the shaft 34 being disposed at the center of the cylindrical portion 38. Is to be formed. Further, a gap C4 is formed between the end face of the shaft 34 and the bottom plate 40 of the sleeve 22.

  The gaps C1, C2, and C3 are filled with oil (working fluid) F so that the liquid level of the oil F is positioned at the open end 42. Therefore, the open end 42 is formed with a capillary seal that holds the oil F so as not to leak to the outside due to its surface tension.

  Thus, when the rotor 16 is rotated in one direction around the central axis with respect to the sleeve 22, the sleeve 22 extends along the radial dynamic pressure generation groove 37 in the radial dynamic pressure generation groove 37 formation region of the gap C <b> 3. Oil F is drawn from the bottom plate 40 side and the disc portion 35 side. As a result, a region where the dynamic pressure reaches a peak is formed over the entire circumference at a position where the drawn oil F gathers. Due to this dynamic pressure, the shaft 34 is held substantially in the center of the sleeve 22 in the radial direction.

  Further, the oil F is drawn into the gap C <b> 1 and the gap C <b> 2 from the outer peripheral side of the thrust surface 46 and the side of the relief portion 45 along the thrust dynamic pressure generating groove 47. As a result, an annular dynamic pressure generation region A in which dynamic pressure is generated is formed over the entire circumference. Due to this dynamic pressure, the thrust bearing portion 39 can be rotated while being held at a substantially central position in the axial direction between the inner surface of the recess 36 and the surface of the retaining portion 33.

  Further, since the thrust bearing portion 39 is disposed at a position adjacent to the open end portion 42 in the radially outward direction, the oil F is drawn from the outer peripheral edge side of the thrust surface 46, thereby existing in the open end portion 42. Oil F to be drawn is drawn into the gap C2. Therefore, it is possible to make it difficult for the oil F to jump out from the open end 42. In particular, since the thrust bearing portion 39 is disposed adjacent to the radially outer side of the open end portion 42, the thrust dynamic pressure generating groove 47 can be disposed radially outward with a high peripheral speed. Therefore, the pulling force of the oil F can be increased, and the oil F can be made difficult to jump out from the open end portion 42.

The operation of the fluid dynamic pressure bearing 10 according to this embodiment configured as described above, the motor 17 including the fluid dynamic bearing 10 and the recording medium driving apparatus 1 will be described below.
In order to start the recording medium driving device 1 and rotate the recording medium HD, first, an alternating magnetic field is generated in the coil 25 by supplying a three-phase alternating current to the coil 25 of the stator 11 constituting the motor 17. . When this alternating magnetic field acts on the permanent magnet 14, the rotor 16 is rotated. Since the recording medium HD is fixed to the rotor 16, when the rotor 16 is rotated, the recording medium HD is rotated together with the rotor 16.

  When the rotor 16 is rotated in one direction, the shaft 34 integrated with the rotor 16 is also rotated in one direction. At this time, dynamic pressure is generated in the gaps C1, C2, and C3 by the radial dynamic pressure generating groove 37 provided in the shaft 34 and the thrust dynamic pressure generating groove 47 provided in the sleeve 22. Since the dynamic pressure generated on the outer circumferential surface of the shaft 34 is uniformly generated over the entire circumference, the shaft 34 is held in a balanced manner at the central axis position of the sleeve 22. Further, since the dynamic pressure generated on the thrust surface 46 of the thrust bearing portion 39 presses the thrust bearing portion 39 in the thickness direction with the same dynamic pressure, the thrust bearing portion 39 is in contact with the inner surface of the recess 36 of the rotor 16. And a space between the surface of the retaining portion 33 and the axially central position of the space in a balanced manner.

  In this case, since the dynamic pressure is not generated when the motor 17 is stopped, the rotor 16 is lowered in the direction of gravity in the sleeve 22. Therefore, for example, when the recording medium driving device 1 is installed in a vertical relationship as shown in FIG. 1, the rotor 16 is lowered in the axial direction with respect to the sleeve 22, and the upper gap C1 is on the lower side. It becomes smaller than the gap C2. When the motor 17 is started in this state, in each of the gaps C1 and C2, the oil F is drawn outward in the radial direction by the thrust dynamic pressure generation groove 47 from the side of the relief portion 45. At this time, according to the fluid dynamic pressure bearing 10 according to the present embodiment, since the through hole 48 opened in the thrust surface 46 is provided, the through hole 48 is formed in the upper narrow gap C1 from the lower wide gap C2. Oil F is supplied through this.

As a result, the occurrence of an excessive negative pressure state due to the oil F being drawn in the narrow gap C1 is prevented, and the generation of bubbles in the oil F is prevented in advance. In particular, the oil F can be directly supplied to the thrust surface 46 by opening the through hole 48 at a position on the thrust surface 46 adjacent to the open end 42 in the radial direction. The generation of bubbles can also be prevented by drawing in the oil F.
Further, according to the present embodiment, the chamfered portion 49 is provided at the opening of the through hole 48, so that the oil supplied from the through hole 48 to the dynamic pressure generating region A is smoothly spread to the dynamic pressure generating portion A. This is more effective.

By preventing the generation of bubbles in the oil F, fluctuations in the dynamic pressure generated in the dynamic pressure generation region A can be prevented, and the rotor 16 can be stably rotated without vibrating. Further, by preventing the generation of bubbles, the oil F can always be interposed between the rotor 16 and the sleeve 22 and between the sleeve 22 and the retaining portion 33. As a result, damage due to contact between the rotor 16 and the sleeve 22 or contact between the sleeve 22 and the retaining portion 33 can be prevented.
Furthermore, it is possible to prevent the oil F from being expelled from the gaps C1 to C4 due to the generation of bubbles, thereby preventing the occurrence of problems such as oil leakage. Further, since the occurrence of oil leakage can be prevented, it is not necessary to provide an absorbing member that absorbs the leaked oil, and the recording medium driving device 1 can be easily thinned.

If bubbles are generated or if bubbles are mixed, the rotor 16 rotates to draw the bubbles into the through hole 48. Since the drawn air bubbles stay in the through hole 48, the air bubbles stay in the dynamic pressure generation region A, and the above-described various problems can be prevented.
Further, in the fluid dynamic pressure bearing 10 according to the present embodiment, since the through holes 48 are provided at two axial positions with respect to the central axis, the oil F can be distributed and supplied to the dynamic pressure generation region A. . Further, the weight balance and rotation balance of the rotor 16 can be achieved.
Then, according to the recording medium driving apparatus 1 including the fluid dynamic pressure bearing 10 and the motor 17 according to the present embodiment configured as described above, the recording medium HD can be stably rotated without vibrating. . Therefore, it is possible to accurately write information to the recording medium HD and read information from the recording medium HD.

  For example, the thrust dynamic pressure generating groove 47 may be configured such that the bending point of the thrust dynamic pressure generating groove 47 is positioned outward in the radial direction, or the height of the thrust dynamic pressure generating groove 47 is changed between inward and outward in the radial direction. Thus, the generated dynamic pressure is higher in the periphery of the outer peripheral edge than in the periphery of the inner peripheral edge of the dynamic pressure generating region A. Therefore, the force for supporting the rotor 16 and the sleeve 22 at the outer peripheral edge of the dynamic pressure generation region A is increased. As a result, the rotor 16 can be stably supported when the rotor 16 is rotating, and NRRO (Non-Repeatable Runout) is also improved.

  Further, the oil F in the open end portion 42 is pushed in such a direction that its liquid surface area is reduced by surface tension, that is, in a direction in which the interval between the sleeve seal surface 43 and the retaining portion seal surface 53 is narrowed. Work. Therefore, the open end 42 can be held so that the oil F does not leak to the outside.

  According to the above configuration, since the surface roughness of the sleeve seal surface 43 and the retaining portion seal surface 53 is formed to be rougher than the predetermined roughness, the contact angle with the oil F can be made 15 ° or less. By setting the contact angle F with the oil F to 15 ° or less, it is possible to prevent the working liquid from jumping out of the fluid dynamic bearing 10 even when an impact that is assumed to be applied from the outside by a portable terminal device or the like is applied.

  Since the ridge line portion 61 is formed on the sleeve seal surface 43 and the retaining portion seal surface 53, it is possible to prevent the oil F from spreading outside the ridge line portion 61. In addition, since the oil repellent layer 63 is formed in the sleeve groove portion 44 of the sleeve seal surface 43 and in the retaining portion groove 55 of the retaining portion seal surface 53, the oil F spreads outside the oil repellent layer 63. Can be prevented.

  As described above, the ridgeline portion 61 and the oil repellent layer 63 may be formed on the sleeve seal surface 43 and the retaining portion seal surface 53 to prevent wetting and spreading of the oil F to the outside. A spiral groove that works in the direction of pushing the oil F inward by relative rotation with the oil F 22 may be formed to prevent the oil F from spreading to the outside.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS.
FIG. 6 is a cross-sectional view showing the overall configuration of the recording medium driving apparatus according to the present embodiment.
In addition, about the component same as 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

The motor 110 including the fluid dynamic pressure bearing 113 according to the present embodiment is applied to the recording medium driving device 101 shown in FIG. The recording medium driving device 101 includes a motor 110 that rotationally drives the recording medium HD.
The motor 110 includes a stator 111 including an electromagnet 120 arranged in an annular shape, a rotor (shaft body) 112 including a permanent magnet 114 disposed inside the stator 111 and opposed to the electromagnet 120, and the stator 111. And a fluid dynamic bearing 113 that rotatably supports the rotor 112. The rotor 112 is rotationally driven with respect to the stator 111 by the magnetic force acting between the electromagnet 120 provided in the stator 111 and the permanent magnet 114 provided in the rotor 112.

The permanent magnet 114 is formed in an annular shape and has a rectangular cross section.
The rotor 112 formed in a cup shape is formed on a flange 115 formed in a bowl shape from the outer periphery of the side wall of the rotor 112, a yoke 116 that holds the permanent magnet 114 together with the flange 115, and a central axis of the rotor 112, A fitting hole 117 for fitting with a shaft 131 described later and a fitting portion (fixing portion) 118 for fitting a ring plate-shaped recording medium HD are formed.

  By fitting the recording medium HD into the fitting portion 118 of the rotor 112, the rotor 112 and the recording medium HD are integrally configured. Further, the rotor 112 and the shaft 131 are integrally configured by fitting one end of the shaft 131 into the fitting hole 117 of the rotor 112. Therefore, the shaft 131, the rotor 112, and the recording medium HD are configured to rotate together.

A boss portion 119 is formed on the stator 111 substantially on the central axis of the electromagnet 120. By fitting a housing 132 of a fluid dynamic pressure bearing 113, which will be described later, into the boss portion 119, the permanent magnet 114 provided in the rotor 112 is disposed opposite to the electromagnet 120.
A shield plate 121 that blocks a magnetic field formed by the electromagnet 120 and the permanent magnet 114 is disposed between the electromagnet 120 and the recording medium HD.

  In addition, the stator 111 is formed with a stator opening 122 that houses a stator coil 123 of an electromagnet 120 described later. By housing the stator coil 123 in the stator opening 122 in this way, the arrangement position of the electromagnet 120 can be made closer to the stator 111 side (lower side in the figure), and the recording medium driving device 101 can be made thinner. Can do.

As shown in FIG. 6, the fluid dynamic pressure bearing 113 includes a shaft 131 and a housing (support) 132 that houses the shaft 131.
At least the shaft 131, the housing 132, and the upper plate described later that form the fluid dynamic pressure bearing 113 are made of stainless steel. By forming the shaft 131, the housing 132, the upper plate, etc. from stainless steel, it is possible to prevent the fluid dynamic pressure bearing 113 from being corroded or rusted.

  The shaft 131 includes a substantially cylindrical shaft body (columnar portion) 133 and a saddle-shaped thrust bearing plate (shaft disk) that extends radially on the outer peripheral surface of the shaft body 133 at an intermediate position in the axial direction. Part) 134. The housing 132 has an inner surface that is arranged with a small gap with respect to each outer surface of the shaft 131. A gap between the inner surface of the housing 132 and the outer surface of the shaft 131 is filled with oil F.

FIG. 7 is an enlarged cross-sectional view illustrating the configuration of the fluid dynamic bearing 113 in FIG.
A shaft body outer peripheral surface (contact surface) 165 that forms a capillary seal is formed on the side surface of the shaft body 133 above the thrust bearing plate 134 (upper side in FIG. 7) together with an inner peripheral surface of a through-hole described later. A shaft body groove portion 166 formed in an annular shape is formed on the shaft body outer circumferential surface 165, and a ridge line portion 61 is formed at the boundary between the shaft body groove portion 166 and the shaft body outer circumferential surface 165. An oil repellent layer 63 coated with an oil repellent material that exhibits oil repellency to the oil F is formed on the inner surface of the rotor 12 (the lower surface in FIG. 7) from the side surface above the shaft body groove 166 of the shaft body 133. Is formed.
The surface roughness of the outer peripheral surface 165 of the shaft body is preferably processed to have a surface roughness such that a contact angle with oil, which will be described later, is 15 ° or less.

The shaft body 133 and the thrust bearing plate 134 are integrally formed to form a shaft 131. A plurality of radial dynamic pressure grooves called herringbone grooves are formed on the outer peripheral surface on the lower end (lower end in FIG. 7) side of the shaft body 133 as in the first embodiment. Similarly to the first embodiment, a plurality of thrust dynamic pressure generating grooves (dynamic pressure generating grooves) called herringbone grooves are formed on both end faces in the thickness direction of the thrust bearing plate 134 (see FIG. 4).
The thrust dynamic pressure generating groove may be formed as a herringbone groove as described above, or may be formed as a spiral groove that pumps out the oil F radially outward (see FIG. 5).

  As shown in FIGS. 6 and 7, the housing 132 has a substantially cylindrical housing body (cylindrical portion) 135 whose one end is closed and the other end is opened, and one end of the shaft body 133 is protruded. And an upper plate (supporting disc portion) 136 that closes the open end of the housing 132. The housing main body 135 is formed with a radial portion receiving hole 137 for receiving the lower end side of the shaft body 133 in which a radial dynamic pressure generating groove is formed, and a thrust portion receiving hole 138 for receiving the thrust bearing plate 134. .

  The upper plate 136 is formed in a ring plate shape, and a through hole through which the shaft body 133 is passed is formed in the approximate center of the ring plate. The through hole is formed such that the inner peripheral surface (contact surface) 139 of the through hole becomes a tapered surface whose diameter gradually increases from the thrust portion accommodation hole 138 toward the outside. As a result, an annular capillary seal is formed between the shaft body outer peripheral surface 165 of the shaft body 133 passed through the through hole and the through hole inner peripheral surface 139 of the through hole. The capillary seal can hold the oil F filled between the housing 132 and the shaft 131 so as not to leak to the outside due to its shape and the surface tension of the oil.

In addition, it is preferable that the inclination | tilt angle of the through-hole inner peripheral surface 139 is an inclination angle used as the angle formed with the shaft outer peripheral surface 165 at 30 degrees or less. Further, the surface roughness of the through-hole inner peripheral surface 139 is preferably processed to a surface roughness such that a contact angle with oil described later is 15 ° or less.
A ridge line portion 61 is formed at the boundary between the upper surface 167 of the upper plate 136 and the inner peripheral surface 139 of the through hole. An oil repellent layer 63 coated with an oil repellent material that exhibits oil repellency to the oil F is formed on the upper surface 167.

The operation of the motor 110 configured as described above and the recording medium driving apparatus 101 including the motor 110 will be described below.
In order to start the recording medium driving device 101 and rotate the recording medium HD, first, an alternating magnetic field is applied to the stator coil 123 by supplying a three-phase alternating current to the stator coil 123 of the stator 111 constituting the motor 110. generate. The rotor 112 is rotated by the alternating magnetic field acting on the permanent magnet 114. Since the recording medium HD is fixed to the rotor 112, when the rotor 112 is rotated, the recording medium HD is rotated together with the rotor 112.

  As described above, when the rotor 112 is rotated in one direction, the shaft 131 integrated with the rotor 112 is also rotated in one direction. At this time, dynamic pressure is generated in the gap with the housing 132 by the radial dynamic pressure generating groove provided on the shaft 131 and the thrust dynamic pressure generating groove provided on the thrust bearing plate 134. Since the dynamic pressure generated on the outer circumferential surface of the shaft 131 is uniformly generated over the entire circumference, the shaft 131 is held in a balanced manner at the central axis position of the housing 132. Further, since the dynamic pressure generated at both end faces of the thrust bearing plate 134 presses the thrust bearing plate 134 in the thickness direction with the same dynamic pressure, the thrust bearing plate 134 is connected to the housing 132 and the upper plate 136. It is kept balanced at a substantially central position in the axial direction.

  According to said structure, since the surface roughness of through-hole inner peripheral surface 139 and shaft body outer peripheral surface 165 is formed more coarsely than predetermined roughness, a contact angle with the oil F can be 15 degrees or less. By setting the contact angle F with the oil F to 15 ° or less, it is possible to prevent the working liquid from jumping out of the fluid dynamic bearing 113 even when an impact that is assumed to be applied from the outside by a portable terminal device or the like is applied.

  Since the ridge line portion 61 is formed on the inner peripheral surface 139 of the through hole and the outer peripheral surface 165 of the shaft body, it is possible to prevent the oil F from spreading out from the ridge line portion 61 to the outside. Further, since the oil repellent layer 63 is formed on the inner surface of the rotor 12 and the upper surface 167 of the upper plate 136 from the side surface above the shaft body groove portion 166 of the shaft body 133, the oil F moves outward from the oil repellent layer 63. We can prevent wetting and spreading.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS.
FIG. 8 is a cross-sectional view showing the overall configuration of the recording medium driving apparatus according to the present embodiment.
In addition, about the component same as 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  A fluid dynamic pressure bearing 210 according to this embodiment is applied to a recording medium driving device 201 as shown in FIG. This recording medium driving device 201 includes a stator 211 having electromagnets 213 arranged in an annular shape, and a rotor (shaft body) 216 having permanent magnets 214 disposed opposite to the electromagnets 213 arranged inside the stator 211. The motor 217 includes a fluid dynamic pressure bearing 210 that rotatably supports the rotor 216 with respect to the stator 211. The electromagnet 213 provided in the stator 211 and the permanent magnet 214 provided in the rotor 216 constitute driving means 15 that rotationally drives the rotor 216 with respect to the stator 211.

  The rotor 216 is provided with a fitting portion 18 for fitting a ring plate-shaped recording medium (not shown), and a screw hole 21 for a screw for attaching a pressing member (not shown) for fixing the recording medium. Is formed.

The stator 211 includes a boss portion 12 disposed at the center of the electromagnet 213. By fitting a sleeve (support) 222 of a fluid dynamic pressure bearing 210, which will be described later, into the boss portion 12, the permanent magnet 214 provided in the rotor 216 is disposed to face the electromagnet 213. A shield plate 223 that blocks a magnetic field formed by the electromagnet 213 and the permanent magnet 214 is disposed between the electromagnet 213 and the recording medium.
As shown in FIG. 8, the electromagnet 213 includes a coil 25 that generates an alternating magnetic field when supplied with a three-phase alternating current, and a core plate 226 that includes a plurality of metal plates around which the coil 25 is wound. .

FIG. 9 is a cross-sectional view showing a configuration of a fluid dynamic pressure bearing in the recording medium driving apparatus of FIG.
As shown in FIG. 9, the fluid dynamic bearing 210 according to the present embodiment is roughly configured by the rotor 216 described above and a sleeve 222 that rotatably supports the rotor 216.
At least, the rotor 216, the sleeve 222, and the stainless steel constituting the fluid dynamic pressure bearing 210 are formed. By forming the rotor 216, the sleeve 222, etc. from stainless steel, the fluid dynamic pressure bearing 210 can be prevented from corroding and generating rust.

The rotor 216 includes a substantially cylindrical shaft (columnar portion) 234, and a flange-shaped disc portion (shaft disc portion) 235 extending radially outwardly on the outer peripheral surface of the shaft 234 at one end thereof. A yoke 252 extending downward from the outer peripheral portion of the disc portion 235 is integrally formed.
A rotor facing surface 236 is formed on a surface of the disc portion 235 facing the sleeve 222 so as to face a thrust bearing portion described later. A rotor seal surface (contact surface) 237 facing a sleeve seal surface, which will be described later, is formed on the surface of the yoke 252 facing the sleeve 222, and the permanent magnet 214 is held on the yoke 252. The rotor seal surface 237 is formed as a surface substantially parallel to the central axis of the shaft 234.

Below the rotor seal surface 237, an oil repellent layer 63 coated with an oil repellent material exhibiting oil repellency with respect to oil described later is formed.
Note that the surface roughness of the rotor seal surface 237 is preferably processed to a surface roughness such that a contact angle with oil, which will be described later, is 15 ° or less.
Similar to the first embodiment, radial dynamic pressure generating grooves (not shown) called herringbone grooves are formed in two rows in the axial direction of the shaft 234 on the outer peripheral surface of the shaft 234. Since these radial dynamic pressure generating grooves are formed in the same manner as in the first embodiment, detailed description thereof is omitted.

The sleeve 222 includes a cylindrical portion 238 that rotatably supports the shaft 234, and a flange-shaped thrust bearing portion (supporting disc portion) 239 that extends radially outward over the entire outer peripheral surface at one end of the cylindrical portion 238. And is composed of.
A bottom surface is formed at the lower end of the cylindrical portion 238 (downward in FIG. 9) so as to form a bag portion inside the cylindrical portion 238.

FIG. 10 is a plan view for explaining a thrust dynamic pressure generating groove formed on the end face of the thrust bearing portion of the fluid dynamic pressure bearing in the present embodiment.
As shown in FIG. 10, a number of thrust dynamic pressure generating grooves (dynamic pressure generating grooves) 247 called herringbone grooves are formed on the upper end surface of the thrust bearing portion 239. These thrust dynamic pressure generating grooves 247 are inclined in one direction with respect to the radial direction from the radially inner side to the radially outer side and extend in an arc shape, and then bent at a midway position (midway portion). It inclines in the opposite direction and extends to the outer periphery. The bending of the thrust dynamic pressure generating groove 247 is formed at a position closer to the inner side in the radial direction on the upper end surface of the thrust bearing portion 239.

FIG. 11 is a view for explaining another embodiment of the thrust dynamic pressure generating groove shown in FIG.
The thrust dynamic pressure generating groove 247 may be formed as a herringbone groove as described above, or as a spiral groove for pumping in the oil F radially inward as shown in FIG. Also good. A thrust dynamic pressure generating groove (dynamic pressure generating groove) 247 ′ formed as a spiral groove for pumping in is formed to be inclined inward in the radial direction and forward in the rotational direction. The thrust dynamic pressure generating groove 247 ′ is formed so as to extend to the front of the inner peripheral edge and is not communicated with the inner peripheral edge. Therefore, the oil F pumped in radially inward generates pressure by being dammed at the inner end of the thrust dynamic pressure generating groove 247 ′.
In addition, the above-mentioned rotation direction is a relative rotation direction between the thrust bearing portion 239 and the disc portion 235.

  As shown in FIG. 9, a sleeve fitting portion 241 fitted to the boss portion 12 of the stator 211 is formed below the cylindrical portion 238, and the rotor seal surface described above is formed on the outer peripheral surface of the thrust bearing portion 239. A sleeve seal surface (contact surface) 243 that forms a ring-shaped open end portion 42 is formed between the sleeve 237 and the 237. The sleeve seal surface 243 is formed as an inclined surface inclined inward in the radial direction toward the sleeve fitting portion 241. A ring-shaped open end portion 42 is formed between the sleeve seal surface 243 and the rotor seal surface 237, and the open end portion 42 is disposed at a position adjacent to the thrust bearing portion 239 radially outward. ing.

An annular sleeve groove 44 is formed at the boundary between the sleeve seal surface 243 and the sleeve fitting portion 241, and a ridge line portion 61 is formed at the boundary between the sleeve seal surface 243 and the sleeve groove 44. . Further, an oil repellent layer 63 coated with an oil repellent material exhibiting oil repellency with respect to oil described later is formed in the sleeve groove portion 44.
The inclination angle of the sleeve seal surface 243 is preferably an inclination angle at which the angle formed with the rotor seal surface 237 is 30 ° or less. Further, the surface roughness of the sleeve seal surface 243 is preferably processed to a surface roughness such that a contact angle with oil, which will be described later, is 15 ° or less.

The operation of the fluid dynamic pressure bearing 210 according to the present embodiment configured as described above, the motor 217 including the fluid dynamic bearing 210, and the recording medium driving device 201 will be described below.
First, when a three-phase alternating current is supplied to the coil 25 constituting the motor 217, an alternating magnetic field is generated in the coil 25. When this alternating magnetic field acts on the permanent magnet 214, the rotor 216 is rotated in one direction, and the shaft 234 and the disc portion 235 formed integrally with the rotor 216 are also rotated in one direction.

At this time, similarly to the first embodiment, dynamic pressure is generated around the shaft 234 by the radial dynamic pressure generating groove, and the shaft 234 is held in a balanced manner at the central axis position of the sleeve 222.
In addition, the oil F is drawn inward in the radial direction by the thrust dynamic pressure generating groove 247 on the upper end surface of the thrust bearing portion 239 to generate dynamic pressure. The rotor facing surface 236 of the disc portion 235 is supported by the generated dynamic pressure, and the rotor 216 is rotatably supported. In this way, when the oil F is drawn inward in the radial direction, the oil F present at the open end 42 is drawn inward in the radial direction. Therefore, it is possible to make it difficult for the oil F to jump out from the open end 42.

  According to the above configuration, since the surface roughness of the sleeve seal surface 243 and the rotor seal surface 237 is formed to be rougher than the predetermined roughness, the contact angle with the oil F can be made 15 ° or less. By setting the contact angle F with the oil F to 15 ° or less, it is possible to prevent the working liquid from jumping out of the fluid dynamic pressure bearing 210 even when an impact assumed to be applied from the outside by a portable terminal device or the like is applied.

  Since the ridge line portion 61 is formed on the sleeve seal surface 243, it is possible to prevent the oil F from spreading outward from the ridge line portion 61. In addition, since the oil repellent layer 63 is formed in the sleeve groove portion 44 of the sleeve seal surface 243 and in the rotor seal surface 237, the oil F can be prevented from spreading outward from the oil repellent layer 63.

  As described above, the ridgeline portion 61 and the oil repellent layer 63 may be formed on the sleeve seal surface 243 and the rotor seal surface 237 to prevent the oil F from spreading out to the outside, or the rotor 216 and the sleeve 222 A spiral groove that works in the direction of pushing the oil F inward by the relative rotation of the oil F may be formed to prevent the oil F from spreading out to the outside.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above embodiment, the fluid dynamic pressure bearing has been described as applied to an inner rotor type motor. However, the present invention is not limited to this inner rotor type motor, and other various types such as an outer rotor type motor. It can be applied to a motor.

1 is a cross-sectional view illustrating an overall configuration of a recording medium driving device according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a configuration of a fluid dynamic pressure bearing in the recording medium driving device of FIG. 1. It is an expanded sectional view explaining the structure of the fluid dynamic pressure bearing of FIG. It is a top view explaining the thrust dynamic pressure generation groove formed in the thrust bearing part of the fluid dynamic pressure bearing of FIG. It is a top view explaining another form of the thrust dynamic pressure generating groove of FIG. It is sectional drawing which shows the whole structure of the recording-medium drive device which concerns on the 2nd Embodiment of this invention. It is an expanded sectional view explaining the structure of the fluid dynamic pressure bearing of FIG. It is sectional drawing which shows the whole structure of the recording-medium drive device which concerns on the 3rd Embodiment of this invention. It is sectional drawing which shows the structure of the fluid dynamic pressure bearing in the recording-medium drive device of FIG. It is a top view explaining the thrust dynamic pressure generation groove formed in the end surface of the thrust bearing part of the fluid dynamic pressure bearing of FIG. It is a figure explaining another embodiment of the thrust dynamic pressure generating groove shown in FIG.

Explanation of symbols

1, 101, 201 Recording medium driving device 10, 113, 210 Fluid dynamic pressure bearing 15 Driving means 16, 112, 216 Rotor (shaft body)
17, 110 Motor 18, 118 Fitting part (fixed part)
22, 222 Sleeve (support)
33 Retaining part (shaft)
34,234 Shaft (columnar part)
35,235 disc part (shaft disc part)
38 Cylindrical part 39,239 Thrust bearing part (support disk part)
43,243 Sleeve seal surface (contact surface)
47, 47 ', 247, 247' Thrust dynamic pressure generating groove (dynamic pressure generating groove)
53 Sealing surface of retaining part (contact surface)
61 Ridge part (leakage prevention means)
63 Oil repellent layer (leakage prevention means, liquid repellent layer)
132 Housing (support)
133 Shaft (columnar part)
134 Thrust bearing plate (shaft disc)
135 Housing body (cylindrical part)
136 Upper plate (support disk part)
139 Through hole inner peripheral surface (contact surface)
165 Shaft body outer peripheral surface (contact surface)
237 Rotor seal surface (contact surface)
F oil (working fluid)
HD recording media

Claims (10)

A shaft body having a columnar portion formed in a substantially cylindrical shape;
A support body having a closed end and having a cylindrical portion that rotatably accommodates the columnar portion;
A working liquid filled in a gap between at least the columnar part and the cylindrical part,
The contact surface disposed near the liquid surface of the working liquid of the shaft body and the support is subjected to a contact angle control process in which a contact angle with the working liquid is 15 ° or less,
A fluid dynamic pressure bearing provided with leakage preventing means for preventing the working liquid from spreading out to the outside from a gap between the shaft body and the support body on the contact surface or a surface adjacent to the contact surface.   The fluid dynamic pressure bearing according to claim 1, wherein the contact angle control process is a surface process that makes a surface roughness of the contact surface larger than a predetermined value.   The fluid dynamic pressure bearing according to claim 1, wherein the leakage preventing means is a liquid repellent layer made of a material that repels the working liquid and is provided on the surfaces of the shaft body and the support body.   3. The fluid dynamic bearing according to claim 1, wherein the leakage prevention means is a ridge portion protruding in a convex shape from the surfaces of the shaft body and the support body. The shaft body is provided with a shaft body disk portion that is supported by the columnar portion and extends in the radial direction,
The support body is provided with a support disk portion that is supported by the cylindrical portion and extends in the radial direction,
The shaft body disk portion and the support body disk portion are disposed so as to face each other, and the shaft body is disposed on at least one of the shaft body disk portion and the opposing surface of the support body disk portion. A dynamic pressure generating groove is formed to draw the working liquid in a radial direction when the support is rotated relative to the support;
The fluid dynamic pressure bearing according to any one of claims 1 to 4, wherein the shaft disk portion and the support disk portion are disposed adjacent to the contact surface. The dynamic pressure generating groove draws the working liquid radially outward when the shaft body and the support body are relatively rotated,
The fluid dynamic bearing according to claim 5, wherein the shaft disc portion and the support disc portion are disposed adjacent to the outer side in the radial direction of the contact surface. The dynamic pressure generating groove draws the working liquid radially inward when the shaft body and the support are relatively rotated,
The fluid dynamic bearing according to claim 5, wherein the shaft disc portion and the support disc portion are disposed adjacent to each other inward in the radial direction of the contact surface.   The fluid dynamic pressure bearing according to any one of claims 1 to 7, wherein the shaft body and the support body are made of stainless steel. A fluid dynamic pressure bearing according to any one of claims 1 to 8,
A motor comprising drive means for relatively rotating the shaft body and the support body of the fluid dynamic pressure bearing. A motor according to claim 9,
A recording medium driving device provided with a fixing portion for fixing a recording medium to the shaft body or the support.

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