JP4800047B2 - Hydrodynamic bearing device and manufacturing method thereof, spindle motor and recording / reproducing device - Google Patents

Description

  The present invention relates to a hydrodynamic bearing device used in a magnetic disk drive device and the like, and more particularly, to a hydrodynamic bearing device that requires high precision mounting accuracy, a manufacturing method thereof, a spindle motor, and a recording / reproducing apparatus.

In recent years, a hydrodynamic bearing device has been used for a motor for rotating a recording medium such as a hard disk in consideration of performance aspects such as quietness and impact resistance. As a basic configuration of this hydrodynamic bearing device, for example, a motor bearing configuration described in Japanese Patent Application Laid-Open No. 2000-324753 is known.
Specifically, as shown in FIG. 4 of JP 2000-324753 A, a thrust plate 26 is fixed to a shaft 21 serving as a rotation center axis, and a sleeve end surface facing both axial surfaces of the thrust plate 26. A thrust bearing portion is formed between the counter plate surface, and a radial bearing portion is formed between the outer diameter of the shaft and the inner cylindrical surface of the sleeve.

  The radial bearing portion is formed between the shaft 21 and the sleeve 11, whereas the thrust bearing portion is formed between the thrust plate 26 fixed to the shaft 21, the end surface of the sleeve 11, and the counter plate 14. In particular, the shaft 26 and the thrust plate 26 are fixed as well as being a part that serves as a retainer, and the fixing strength that can withstand the desired impact resistance and external force during assembly is required. It becomes.

As a method for fixing the shaft and the thrust plate, various methods such as a screwing method, a press-fit adhesion method, a shrink fitting method, a welding method and the like are employed.
Among these, from the viewpoint of thinning and miniaturization of the motor, reliability of the bearing, the amount of warpage of the surface forming the thrust bearing portion, and the like, a fixing method between the shaft and the thrust flange adopting the welding method is frequently used ( For example, refer to JP 2000-324753 A).

  In this publication, after the rotary shaft 21 and the thrust plate 26 are press-fitted or inserted to such an extent that the perpendicularity does not deteriorate, the content of welding the joint boundary portion between the two from the surface portion is disclosed. At this time, a relief portion 30 that is recessed in the axial direction is formed in a ring shape on the surface portion of the welding boundary portion, and the rotary shaft 21 and the thrust plate 26 are welded to the relief portion.

However, if the rotary shaft and the thrust plate are press-fitted to such an extent that the squareness does not deteriorate, press-fitting powder is generated by the press-fitting, and the press-fitting powder is mixed into the bearing gap where a minute gap is formed. There is a risk of significantly reducing the bearing performance.
In addition, although the perpendicularity does not deteriorate, when a thrust flange is inserted into the shaft, a gap is formed between the outer peripheral portion of the rotating shaft and the inner peripheral portion of the thrust plate. Accurate positioning in the axial direction is required, making it difficult to obtain desired touch accuracy.

On the other hand, as a method of welding by inserting a thrust plate into the shaft, there is a method disclosed in Japanese Patent Application Laid-Open No. 2004-183809.
Here, in the shaft 1 provided with the stepped portion 1a at the outer peripheral edge of the end surface forming the rotation axis and the disc-shaped thrust bearing 2 in which the stepped portion 2b is formed around the central through hole 2a, the shaft 1 The height of the convex portion 1b formed by providing the step portion 1a is adjusted to the height of the bottom portion of the step portion 2b of the thrust bearing 2. A gap of about 0.02 to 0.04 mm is formed in the joint portion 16 where the through hole 2a and the convex portion 1b are in contact. In this state, the joint portion 16 where the through-hole 2a and the convex portion 1b are in contact with each other is continuously laser-irradiated at three locations of the irradiation point 6 from the surface side, and 120 degrees to the final irradiation point 7 along the circumferential direction It is rotated as described above and is continuously welded and fixed by a laser.

In the welding method disclosed in the above publication, the air regulator 12 presses the stepped portion 1a of the shaft against the thrust bearing 2, and the push pin 10 is pushed up by the air cylinder 11 by about 0.1 mm and fixed. Thereby, it is possible to weld the thrust bearing 2 in close contact without being inclined at the contact surface of the shaft step portion 1a.
JP 2000-324753 A (published on November 24, 2000) Japanese Patent Application Laid-Open No. 2004-183809 (released on July 2, 2004)

However, the conventional hydrodynamic bearing device has the following problems.
That is, in the method for manufacturing a hydrodynamic bearing device disclosed in the above publication, when the shaft and the thrust flange are welded, when the welded portion is melted and solidified, the surface is welded to the thrust flange. The pulling force works, and the result is the same as when the thrust flange is plastically deformed. For this reason, if the jig | tool used at the time of welding is removed, a thrust flange will warp to the surface side to be welded. Due to the occurrence of such warpage, the stepped portion of the shaft that defines the perpendicularity is separated from the surface opposite to the weld surface of the thrust flange, and the thrust against the rotating shaft when the hydrodynamic bearing device is rotated. The occurrence of planar vibration of the flange cannot be effectively suppressed. As a result, there is a variation in the size of the gap forming the thrust bearing, and the magnitude of the dynamic pressure generated in the thrust bearing portion becomes unstable, which may lead to a problem that the reliability of the hydrodynamic bearing device is lowered. There is.

  An object of the present invention is to provide a highly reliable hydrodynamic bearing device and a method for manufacturing the same, for example, even when the shaft and the thrust flange are fixed by welding, suppressing the occurrence of runout in a plane substantially perpendicular to the rotation axis A spindle motor and a recording / reproducing apparatus are provided.

The hydrodynamic bearing device according to the first aspect of the present invention generates dynamic pressure on at least one of the fixed and rotating surfaces by rotating the rotation side relative to the fixed side about the rotation axis. A hydrodynamic bearing device that generates dynamic pressure in a dynamic pressure generating portion including a groove, and includes a first member and a second member. The first member has a step portion formed on a plane intersecting the rotation axis at one end. The second member is attached to a surface along the rotation axis of the first member by welding in a state where the second member is engaged with the step portion along a plane intersecting the rotation axis. It is a disk-shaped member which forms a thrust dynamic pressure generating part in between. The first member and the second member are inclined in a direction in which the surface intersecting the rotation axis constituting the stepped portion is away from the surface of the second member as the distance from the surface along the rotation axis increases. In the direction intersecting with the surface at a position close to the surface along the rotation axis constituting the stepped portion.

  Here, in a hydrodynamic bearing device that rotates a rotation side about a rotation axis with respect to a fixed side and generates dynamic pressure at a portion where the rotation side and the fixed side face each other, a disk-shaped second member (for example, , A thrust flange) and a first member (for example, a shaft) formed with a stepped portion into which the second member is fitted are joined by welding. The first member has a first surface at a position closer to the surface along the rotation axis constituting the step portion on the intersecting surface of the surfaces along the rotation axis constituting the step portion. It abuts against the two members. In other words, on the surface intersecting the rotation axis in the stepped portion into which the disc-shaped second member is fitted, the first member and the second member abut at a position as close as possible to the surface along the rotation axis. It is configured as follows.

  Here, the rotating shaft includes those that rotate while the rotating shaft itself is included in the rotating side, and those that rotate only on the rotating side and do not rotate. The first member includes members such as a shaft and a sleeve. On the other hand, the second member includes a thrust flange attached to the shaft (first member), a rotor, a thrust plate attached to the sleeve (first member), and the like.

  Normally, when the disk-shaped second member is joined to the first member by welding in this way, welding is performed at the end of the stepped portion of the first member at the fitting position with the second member. For this reason, the second member warps in a direction away from the plane intersecting the rotation axis constituting the stepped portion due to thermal contraction. In this case, as a result of the surface of the disk-shaped second member undulating, the gap between the surface that is a part of the rotation side and the surface of the second member that faces the surface varies. The generated dynamic pressure cannot be generated, and the reliability as the hydrodynamic bearing device may be reduced.

Therefore, in the hydrodynamic bearing device of the present invention, the rotation that forms the step portion as much as possible on the surface intersecting the rotation axis of the step portion formed on the first member side at the joint portion of the first member and the second member. The two members are brought into contact with each other so as to support the second member at a position close to the surface along the axis.
As a result, when the disk-shaped second member is joined to the surface along the rotation axis of the first member by welding, warpage occurs in the plane where the disk-shaped second member intersects the rotation axis. Even in this case, in the stepped portion of the first member in which the second member is fitted, there is no gap at the portion where the first member and the second member are in contact. As a result, even when warpage occurs after welding in the disk-shaped second member, the back surface side of the second member can be firmly supported by the first member, so that the disk-shaped second member with respect to the rotating shaft Therefore, it is possible to obtain a fluid bearing device with high reliability.

The hydrodynamic bearing device is the hydrodynamic bearing device according to the first aspect of the invention, and the surface intersecting the rotating shaft constituting the stepped portion is separated from the surface of the second member as the surface is separated from the surface along the rotating shaft. Inclined in the direction.
Here, the surface intersecting the rotation axis forming the step portion formed at the end portion of the first member is inclined so as to move away from the second member as the distance from the surface along the rotation axis increases.

  Thereby, in the surface which cross | intersects the rotating shaft in a level | step-difference part, the closest position to the 2nd member will be a position near the surface along a rotating shaft. That is, when the rotation axis is arranged along the vertical direction and the second member is joined to the stepped portion of the first member from above, the highest position in the stepped portion constitutes the stepped portion. It is the side close to the surface along the substantially vertical direction. As a result, the position where the first member and the second member abut on the stepped portion formed at one end of the first member can be the closest position to the surface along the substantially vertical direction of the stepped portion.

A hydrodynamic bearing device according to a second invention is the hydrodynamic bearing device according to the first invention, wherein the first member is a shaft and the second member is a thrust flange.
Here, as a combination of the first member and the second member, the present invention is applied to a portion where the shaft and the thrust flange are welded using the shaft and the thrust flange.
Thus, when the thrust flange is attached to the step formed on one end of the shaft, even if the thrust flange is warped to the welding side, There is no gap between the surface opposite to the welding side and the stepped portion of the shaft. As a result, it is possible to obtain a highly reliable hydrodynamic bearing device by suppressing the occurrence of vibration on the surface of the thrust flange with respect to the rotating shaft of the shaft.

A hydrodynamic bearing device according to a third invention is the hydrodynamic bearing device according to the first invention, wherein the first member is a shaft and the second member is a rotor.
Here, as a combination of the first member and the second member, the present invention is applied to a portion where the shaft and the rotor are welded using the shaft and the rotor.
Thereby, when the rotor is attached to the stepped portion formed at one end of the shaft, even when the rotor is warped to the welding side, the welding side of the rotor that is in contact with the stepped portion of the shaft There is no gap between the opposite surface and the stepped portion of the shaft. As a result, it is possible to obtain a highly reliable hydrodynamic bearing device by suppressing the occurrence of vibration on the rotor surface with respect to the rotating shaft of the shaft.

A hydrodynamic bearing device according to a fourth invention is the hydrodynamic bearing device according to the first invention, wherein the first member is a sleeve and the second member is a thrust plate.
Here, as a combination of the first member and the second member, the present invention is applied to a portion where a sleeve and a thrust plate are welded using a sleeve and a thrust plate.
Thus, when the thrust plate is attached to the step portion formed at one end of the sleeve, even if the thrust plate warps toward the welding side, There is no gap between the surface opposite to the welding side and the stepped portion of the sleeve. As a result, it is possible to obtain a highly reliable hydrodynamic bearing device by suppressing the occurrence of vibration on the surface of the thrust plate with respect to the rotating shaft of the shaft.

A spindle motor according to a fifth aspect of the present invention includes any one of the first to fourth aspects of the hydrodynamic bearing device.
As a result, since the thrust accuracy in the thrust direction is stabilized, it is possible to reduce and stabilize the axial RRO variation required for the spindle motor.

Sixth recording reproducing apparatus according to the present invention includes a spindle motor according to a fifth aspect of the present invention.
Thus, by using the spindle motor for the recording / reproducing apparatus, it becomes possible to read / write data on the disk mounted on the motor hub via the head without causing any trouble.

  According to the hydrodynamic bearing device according to the first aspect of the present invention, it is possible to prevent the deflection accuracy of the disc-shaped second member with respect to the rotating shaft from being lowered, and to obtain a highly reliable hydrodynamic bearing device.

  According to the hydrodynamic bearing device according to the second aspect of the present invention, the position where the first member and the second member abut on the step portion formed at one end of the first member is positioned on the surface along the substantially vertical direction of the step portion. It can be the closest position.

  According to the hydrodynamic bearing device according to the third aspect of the present invention, it is possible to obtain a highly reliable hydrodynamic bearing device by suppressing the occurrence of vibration on the surface of the thrust flange with respect to the rotating shaft of the shaft.

  With the hydrodynamic bearing device according to the fourth aspect of the present invention, it is possible to obtain a highly reliable hydrodynamic bearing device by suppressing the occurrence of runout on the rotor surface with respect to the rotating shaft of the shaft.

  With the hydrodynamic bearing device according to the fifth aspect of the invention, it is possible to obtain a highly reliable hydrodynamic bearing device by suppressing the occurrence of vibration on the surface of the thrust plate with respect to the rotating shaft.

  According to the method for manufacturing a hydrodynamic bearing device according to the sixth aspect of the invention, the welding operation can be performed accurately by performing welding while the first member and the second member are firmly fixed, and the second member. The degree of warping can be suppressed.

  According to the method for manufacturing a hydrodynamic bearing device according to the seventh aspect of the present invention, a highly reliable hydrodynamic bearing device can be obtained by reducing the degree of occurrence of vibration on the surface of the second member relative to the rotating shaft.

  According to the spindle motor of the eighth aspect of the invention, since the thrust accuracy in the thrust direction is stabilized, it is possible to reduce and stabilize the axial RRO variation required for the spindle motor.

  According to the spindle motor of the ninth aspect of the invention, since the shake accuracy in the thrust direction is stabilized, it is possible to reduce and stabilize the axial RRO variation required for the spindle motor.

  According to the recording / reproducing apparatus of the tenth aspect, by using the spindle motor for the recording / reproducing apparatus, data on the disk mounted on the motor hub is read / written without causing any trouble via the head. It becomes possible.

A spindle motor equipped with a hydrodynamic bearing device according to an embodiment of the present invention will be described below with reference to FIGS.
[Configuration of the entire spindle motor 10]
As shown in FIG. 1, the spindle motor 10 according to the present embodiment includes a rotor hub (rotation side) 15, a rotor magnet (rotation side) 16, a stator (fixed side) 17, a base (fixed side) 18, and a hydrodynamic bearing device 20. Etc.

The hydrodynamic bearing device 20 includes a sleeve (fixed side) 11, a shaft (rotation side, first member) 12, a thrust flange (rotation side, second member) 13, and a thrust plate (fixed side) 14. .
The sleeve 11 has a bearing hole 11 a and is formed of a metal material such as iron, iron alloy, copper, or copper alloy, and is fixed to the base 18. In addition, the sleeve 11 is provided with a first step portion 11b facing the outer diameter portion of the thrust flange 13, and the outer diameter portion of the thrust flange 13 is located with a gap from the first step portion 11b. ing. Further, the sleeve 11 is provided with a second step portion 11c having a diameter larger than that of the first step portion 11b, and the disc-shaped thrust plate 14 is bonded, caulked, press-fitted to the second step portion 11c, It is fixed by a method such as welding.

Furthermore, on the inner peripheral surface side of the bearing hole 11a of the sleeve 11, a herringbone-shaped radial dynamic pressure generating groove is formed side by side in the axial direction. The radial dynamic pressure generating groove may have a spiral shape. The sleeve 11 may be nickel-plated on the surface.
The shaft 12 is a member (for example, a columnar member or a cylindrical member) having a cylindrical outer peripheral surface having a diameter of about 3.0 mm, which is made of a metal material that is not a sintered body, and is formed in the bearing hole 11a. Inserted in a rotatable state. Further, a stepped portion 12a (see FIGS. 2 and 3) is formed at the lower end portion of the shaft 12, and a disc-shaped thrust flange 13 having a circular opening at the center portion at the stepped portion 12a. Are joined by a welding method along the welding position X (see FIG. 3). In addition, since the shaft 12 is used as an axis of rotation center, for example, a hard material such as SUS is used and processed by a molding tool or the like.

  The step portion 12a formed at the lower end portion of the shaft 12 is formed on the outer side in the radial direction than the cylindrical portion having a diameter of about 1.9 mm at the lower end portion of the shaft 12, and the depth in the axial direction is about 0.3 mm. It is a step. And this level | step-difference part 12a is comprised by 1st surface 12aa formed along an axial direction (substantially vertical direction), and 2nd surface 12ab formed along the direction substantially perpendicular | vertical to an axial direction. The Among these, as shown in FIG. 3, the second surface 12ab is formed so as to incline downward toward the radially outer side of a circle centered on the rotation axis of the shaft 12. For this reason, in the 2nd surface 12ab, the side close | similar to 1st surface 12aa is the highest in the axial direction. As a result, a back surface 13b of a thrust flange 13 and a second surface of the stepped portion 12a of the shaft 12, which will be described later, are shafts on the radially outer side of a circle centering on the rotational axis of the shaft 12 with the machining relief portion 12b interposed therebetween. The contact is made at the contact position P closest to the first surface 12aa on the 12 side.

3 is a groove-like portion formed when machining the stepped portion 12a at one end of the shaft 12, and has a width of about 230 μm and a depth of about 50 μm. Yes.
As shown in FIG. 2 and the like, the thrust flange 13 has a circular opening having a diameter of about 1.9 mm at the center portion, a thick portion is 0.5 mm, and a thin portion from the stepped portion 12a of the shaft 12 is formed. A disk-shaped member having a thickness of 0.33 mm and a diameter of about 5.6 mm, which is attached to the stepped portion 12a formed at the lower end portion of the shaft 12 by a welding method as described above. Yes. The thrust flange 13 is accommodated in a space surrounded by the step portion 11b of the sleeve 11 and the thrust plate 14 which is a thrust bearing member. The lower surface of the thrust flange 13 faces the thrust plate 14, and the peripheral portion of the upper surface faces the step portion 11 b of the sleeve 11. A thrust dynamic pressure generating groove is formed on the surface of the step portion 11 b of the sleeve 11 facing the upper surface of the thrust flange 13.

In addition, the joining method by welding of the thrust flange 13 with respect to the level | step-difference part 12a of the shaft 12 is explained in full detail in a back | latter stage.
The thrust plate 14 is a substantially disk-like member attached so as to cover the lower portion of the hydrodynamic bearing device 20, and a thrust dynamic pressure generating groove is formed on the upper surface thereof. The surface on which the thrust dynamic pressure generating groove is formed is not limited to the configuration of the present embodiment, and may be formed on any one of the opposing members while forming a gap in the axial direction. That is, a thrust dynamic pressure generating groove may be formed on the lower surface of the thrust flange 13 or the upper surface of the thrust flange 13.

  The rotor hub 15 has a substantially bowl-like shape, a through hole is formed in a substantially central portion, and the upper end portion of the shaft 12 is fixed by a press-fit adhesive method or the like. A rotor magnet 16 of a spindle motor is attached to the rotor hub 15 and faces the stator 17 in the radial direction. A magnetic recording disk or the like (not shown) is fixed to the rotor hub 15 and constitutes a magnetic recording / reproducing device such as a hard disk device as a whole together with other components.

Further, between the shaft 12 including the radial dynamic pressure generating groove and the thrust dynamic pressure generating groove and the bearing hole 11 a of the sleeve 11, between the thrust flange 13 and the sleeve 11, and between the thrust flange 13 and the thrust plate 14. Is filled with a lubricating oil 26.
The rotor magnet 16 is attached at equal intervals in the circumferential direction on the inner peripheral surface side of the rotor hub 15, and is attracted and repelled with the opposing stator 17, so that the rotor hub 15 is centered on the shaft 12. Rotate.

  The base 18 is formed with a recess 18a for accommodating a motor unit including the stator 17, the rotor magnet 16, and the like. And the hole 18b for adhering the sleeve 11 is provided in the approximate center part of the recessed part 18a. A stator 17 formed of a core around which a coil is wound is fixed to a portion of the base 18 where the hole 18b is formed by a method such as adhesion.

[Bonding of shaft 12 and thrust flange 13]
Here, as a manufacturing method of the above-described hydrodynamic bearing device 20, steps in joining the shaft 12 and the thrust flange 13 included in the hydrodynamic bearing device 20 by welding will be described with reference to FIGS. 4 to 7. It is as follows.
That is, as shown in the flowchart of FIG. 4, in the method for manufacturing the hydrodynamic bearing device 20 according to the present embodiment, in step S1, the stepped portion 12a is formed by machining at one end of the shaft 12 shown in FIG.

Next, in step S <b> 2, the portion of the opening 13 a formed in the central portion of the thrust flange 13 is fitted into the stepped portion 12 a formed at one end of the shaft 12.
Next, in step S3, the shaft 12 and the thrust flange 13 are set in the joining jigs 31 and 32 shown in FIG. 5 with the thrust flange 13 fitted into the stepped portion 12a of the shaft 12. Note that the joining jigs 31 and 32 shown in FIG. 5 are divided into a first joining jig 31 and a second joining jig 32, and the outer periphery of the shaft 12 is fixed by the first joining jig 31. The upper and lower planes of the thrust flange 13 are fixed by the first joining jig 31 and the second joining jig 32.

  Next, in step S4, with the shaft 12 and the thrust flange 13 fixed by the joining jigs 31 and 32, as shown in FIG. Laser irradiation is performed. More specifically, laser irradiation is performed on three irradiation positions X1 to X3 arranged at equal angular intervals (120 degrees) in the circumferential direction around the rotation center at the end of the shaft 12.

  Next, in step S5, the laser irradiation position is rotated clockwise by 120 degrees or more from the laser irradiation state shown in FIG. That is, the laser irradiation position is rotated such that the irradiation positions adjacent to the irradiation positions X1a, X1b,. The same applies to the irradiation position X2 and the irradiation position X3. Here, the entire circumference of the joint portion between the shaft 12 and the thrust flange 13 can be welded by rotating the laser irradiation position by 120 degrees or more.

  Next, in step S6, the welded portion between the shaft 12 and the thrust flange 13 is cooled. At this time, the gap portion between the first surface 12aa forming the stepped portion 12a of the shaft 12 and the inner peripheral surface of the opening 13a of the thrust flange 13 is heated by the above-described laser irradiation welding. Therefore, when this is cooled, the thrust flange 13 may be warped in a direction away from the second surface 12ab forming the stepped portion 12a of the shaft 12, as shown in FIG.

  However, in the hydrodynamic bearing device 20 of the present embodiment, as shown in FIG. 3, the second surface 12ab forming the stepped portion 12a of the shaft 12 and the back surface 13b of the thrust flange 13 form the stepped portion 12a. Since the contact is made at the position on the innermost side closest to the first surface 12aa, there is no gap between them. For this reason, the surface of the thrust flange 13 is firmly supported by the second surface 12ab forming the stepped portion 12a of the shaft 12 by firmly supporting the back surface 13b of the thrust flange 13 even after welding in which the thrust flange 13 is warped. Occurrence of fluctuations in can be reduced.

Next, in step S <b> 7, the shaft 12 and the thrust flange 13 are removed from the joining jigs 31 and 32.
In the method for manufacturing the hydrodynamic bearing device 20 of the present embodiment, the shaft 12 and the thrust flange 13 are joined using the joining jigs 31 and 32 as described above.
Thereby, since welding can be performed in a state where the thrust flange 13 is firmly fixed to the shaft 12, the assembly accuracy can be improved. Furthermore, the occurrence of warpage of the thrust flange 13 can be reduced by welding and cooling the thrust flange 13 that warps after welding from above and below.

And at the time of welding, it welds by rotating the laser beam irradiated to three points at equal intervals in the circumferential direction by 120 degrees or more.
Thereby, the joint part of the shaft 12 and the thrust flange 13 can be welded all around in a uniform state.
For example, as shown in FIG. 8, the vibration of the surface of the thrust flange 13 described above is caused by rotating the thrust flange 13 together with the shaft 12 around the rotation axis of the shaft 12, and measuring points on the surface of the thrust flange 13. It is detected by measuring the amount of movement of the contact terminal in contact.

[Features of hydrodynamic bearing device 20]
(1)
In the hydrodynamic bearing device 20 of the present embodiment, as shown in FIG. 3, when joining the shaft 12 and the thrust flange 13, the step portion 12 a formed on the back surface 13 b side of the thrust flange 13 and one end of the shaft 12. The innermost peripheral side of a circle centering on the rotation axis of the shaft 12 so that the second surface 12ab forming the step is close to the first surface 12aa along the substantially vertical direction forming the stepped portion 12a. The abutting position P is configured to abut.

  As a result, after the shaft 12 and the thrust flange 13 are joined by welding, even if the thrust flange 13 warps as shown in FIG. 7, the thrust flange 13 remains on the innermost circumferential side in the stepped portion 12 a of the shaft 12. Therefore, the occurrence of vibration on the surface of the thrust flange 13 can be reduced. As a result, the hydrodynamic bearing device 20 having high reliability can be provided by stabilizing the magnitude of the dynamic pressure generated in the thrust dynamic pressure generating portion formed between the thrust flange 13 and the opposing surface.

(2)
In the hydrodynamic bearing device 20 of the present embodiment, as shown in FIG. 3, in the step portion 12 a formed at one end of the shaft 12, the second surface 12 ab substantially perpendicular to the vertical direction forming the step portion 12 a has a diameter. It is formed so as to incline downward toward the outside in the direction.
Thus, the second surface 12ab necessarily has the highest position on the innermost peripheral side, and therefore, the back surface 13b of the thrust flange 13 can be supported on the innermost peripheral side of the second surface 12ab. As a result, as described above, a highly reliable hydrodynamic bearing device 20 is provided by stabilizing the magnitude of the dynamic pressure generated in the thrust dynamic pressure generating portion formed between the thrust flange 13 and the opposing surface. can do.

(3)
In the hydrodynamic bearing device 20 of the present embodiment, the present invention is applied to the joint portion between the shaft 12 and the thrust flange 13.
Thereby, generation | occurrence | production of the shake | fluctuation of the surface of the thrust flange 13 at the time of rotating it centering on the rotating shaft of the shaft 12 can be suppressed, and the fluid bearing apparatus 20 with high reliability can be provided.

(4)
In the method of manufacturing the hydrodynamic bearing device 20 of the present embodiment, as shown in FIG. 4, when the shaft 12 and the thrust flange 13 are joined, the shaft is used by using joining jigs 31 and 32 as shown in FIG. 12 and the thrust flange 13 are fixed and processes such as welding are performed.
Thereby, since it can weld in the state which fixed the shaft 12 and the thrust flange 13 firmly, the hydrodynamic bearing apparatus 20 excellent in the assembly precision can be manufactured. Further, even when the thrust flange 13 is along the direction shown in FIG. 7 along with the cooling of the welded portion after welding, the upper and lower surfaces of the thrust flange 13 are fixed by the joining jig 32 shown in FIG. The occurrence of warpage can be reduced.

(5)
In the manufacturing method of the hydrodynamic bearing device 20 of the present embodiment, as shown in FIG. 4, when the shaft 12 and the thrust flange 13 are joined by welding, as shown in FIG. Laser is irradiated to the three irradiation positions X1 to X3 that are arranged, and this is rotated 120 degrees or more to perform all-around welding.

  Thereby, since heat is transmitted from the welded portion to the thrust flange 13 almost evenly, occurrence of vibration on the surface of the thrust flange 13 can be reduced. As a result, it is possible to provide a highly reliable hydrodynamic bearing device 20 by substantially equalizing the magnitude of the dynamic pressure generated in the thrust dynamic pressure generating portion formed between the surface of the thrust flange 13 and the opposing surface. Can do.

[Other Embodiments]
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of invention.
(A)
In the above embodiment, the shaft 12 and the thrust flange 13 are used as the first member and the second member, and the present invention is applied to the joint portion of the step portion 12a formed at one end of the shaft 12 with the thrust flange 13. Explained with examples. However, the present invention is not limited to this.

  For example, as shown in FIG. 9, a shaft 12 and a rotor hub 15 may be used as the first member and the second member. That is, the present invention can also be applied to the joint between the stepped portion formed on the upper end side of the shaft 12 and the rotor hub 15 (see the portion B in the figure). Even in this case, the occurrence of planar vibration of the rotor hub 15 when the shaft 12 is rotated can be reduced, and a highly accurate hydrodynamic bearing device and a spindle motor including the same can be provided.

(B)
In the above embodiment, the shaft 12 and the thrust flange 13 are used as the first member and the second member, and the present invention is applied to the joint portion of the step portion 12a formed at one end of the shaft 12 with the thrust flange 13. Explained with examples. However, the present invention is not limited to this.

For example, as shown in FIG. 10, a hydrodynamic bearing device 50 using a sleeve 51 and a thrust plate 61 as the first member and the second member may be used. That is, the present invention can also be applied to the joint portion C between the step portion formed on the upper end side of the sleeve 51 and the thrust plate 61.
Even in this case, when the sleeve 51, the thrust plate 61, the rotor hub 55, and the like are rotated around the shaft 52, the occurrence of planar vibration of the thrust plate 61 with respect to the rotation axis is reduced. It is possible to provide a highly accurate hydrodynamic bearing device and a spindle motor including the same by equalizing the magnitude of the dynamic pressure generated in the thrust dynamic pressure generating portion formed between the flange 53 and the opposing flange 53. .

(C)
In the above embodiment, the contact position P between the stepped portion 12a formed at one end of the shaft 12 and the back surface 13b of the thrust flange 13 is disposed on the innermost circumferential side with the machining relief portion 12b on the shaft 12 side interposed therebetween. Explained with an example. However, the present invention is not limited to this.
For example, when a thrust flange is joined to a stepped portion of a shaft formed so as not to have a machining relief portion, the portion where the first surface and the second surface of the stepped portion intersect, that is, the stepped portion On the innermost peripheral side, the back surface of the thrust flange and the surface of the step portion of the shaft may be in contact.
Even in this case, even when the thrust flange is warped in the axial direction during welding of the thrust flange, the contact portion between the back surface of the thrust flange and the substantially horizontal surface of the stepped portion of the shaft is not separated. As a result, as in the above embodiment, it is possible to provide a highly accurate hydrodynamic bearing device by reducing runout on the surface of the thrust flange.

(D)
In the above embodiment, as shown in FIG. 3, in the stepped portion 12 a formed at one end of the shaft 12, the second surface 12 ab substantially perpendicular to the vertical direction forming the stepped portion 12 a is directed radially outward. An example in which it is formed to be inclined downward has been described. However, the present invention is not limited to this.

For example, the second surface may be formed such that the outermost portion in the radial direction is the next highest after the innermost portion, instead of the second surface being smoothly inclined downward toward the radially outer side. .
Even in this case, since the abutting against the back surface 13b of the thrust flange 13 is the innermost peripheral portion in the radial direction, the same effect as described above can be obtained.
In particular, when the step portion is formed, since the unevenness is formed on the second surface during processing, the second surface does not need to be smoothly inclined downward in the radial direction, and has an unevenness. However, what is necessary is just to be comprised so that the thrust flange 13 may be supported in the innermost circumference side.

(E)
In the above embodiment, the example in which the hydrodynamic bearing device 20 and the rotor hub 15 are separately provided in the spindle motor 10 has been described. However, the present invention is not limited to this.
For example, it may be a hydrodynamic bearing device configured to include a rotor hub.

(F)
In the above-described embodiment, an example in which the present invention is applied to the hydrodynamic bearing device 20 of the shaft rotation one side open type has been described. However, the present invention is not limited to this.
For example, as shown in FIG. 10, the present invention can also be applied to a hydrodynamic bearing device 50 that is open at both ends of a fixed shaft.
Furthermore, the present invention can also be applied to a hydrodynamic bearing device of a shaft rotation both ends open type and a shaft fixed one side open type.

(G)
In the above embodiment, the example in which the present invention is applied to the hydrodynamic bearing device 20 has been described. However, the present invention is not limited to this.
For example, the present invention can also be applied to the spindle motor 10 on which the hydrodynamic bearing device 20 described in the above embodiment is mounted, or the recording / reproducing apparatus including the spindle motor 10.

  The hydrodynamic bearing device of the present invention has an effect of providing a highly reliable hydrodynamic bearing device by suppressing the occurrence of vibration on the surface of the thrust flange even when, for example, the shaft and the thrust flange are fixed by welding. Therefore, the present invention can be widely applied to various motors and the like that require high-quality hydrodynamic bearing devices.

A sectional view showing composition of a spindle motor carrying a fluid dynamic bearing device concerning one embodiment of the present invention. Sectional drawing which shows the shaft and thrust flange which comprise the hydrodynamic bearing apparatus contained in the spindle motor of FIG. The enlarged view of A part in FIG. The flowchart which shows the flow of the process of joining the shaft and thrust flange which are contained in the hydrodynamic bearing apparatus of FIG. Sectional drawing which shows a part of joining process using the joining jig | tool used in the joining process of FIG. (A), (b) is a top view which shows the joining method by the welding method included in the joining process of FIG. Sectional drawing which shows the state of the curvature of the thrust flange which generate | occur | produces after the welding process shown to Fig.6 (a). The perspective view which shows the measuring method of the deflection | deviation of the surface of the thrust flange contained in the hydrodynamic bearing apparatus of FIG. Sectional drawing which shows the hydrodynamic bearing apparatus which concerns on other embodiment of this invention. Sectional drawing which shows the hydrodynamic bearing apparatus which concerns on further another embodiment of this invention.

10 Spindle motor 11 Sleeve (fixed side)
12 Shaft (Rotating side, 1st member)
12a Stepped portion 12b Processing relief portion 12aa First surface (surface along the rotation axis)
12ab 2nd surface (surface intersecting the rotation axis)
13 Thrust flange (rotating side, second member)
13a Opening 13b Back surface 14 Thrust plate (fixed side)
15 Rotor hub (rotating side, second member)
16 Rotor magnet (rotating side)
17 Stator (fixed side)
18 Base (fixed side)
20 Fluid Bearing Device 26 Lubricating Oil 31 First Joining Jig (Jig)
32 Second joining jig (jig)
50 Hydrodynamic bearing device 51 Sleeve (first member)
52 Shaft (Rotating shaft)
53 Flange 55 Rotor hub 61 Thrust plate (second member)
S Step P Contact position X Welding position X1 to X3 Irradiation position

Claims (6)

By rotating the rotation side with respect to the fixed side around the rotation axis, the dynamic pressure generating unit includes a dynamic pressure generating groove formed on at least one of the fixed side and the opposing surface of the rotation side. A hydrodynamic bearing device for generating pressure,
A first member having a step formed on a plane intersecting the rotation axis at one end;
The first member is attached to a surface along the rotation axis by welding in a state of being engaged with the step portion along a plane intersecting the rotation axis, and between the opposed planes A disc-shaped second member that forms a thrust dynamic pressure generating portion in FIG.
With
The first member and the second member are inclined in a direction away from the surface of the second member as a surface intersecting the rotation axis constituting the stepped portion is separated from the surface along the rotation axis. And abuts at a position close to a surface along the rotation axis constituting the stepped portion in a direction intersecting the rotation axis.
Fluid bearing device. The first member is a shaft, and the second member is a thrust flange;
The hydrodynamic bearing device according to claim 1 . The first member is a shaft and the second member is a rotor;
The hydrodynamic bearing device according to claim 1 . The first member is a sleeve and the second member is a thrust plate;
The hydrodynamic bearing device according to claim 1 . The hydrodynamic bearing device according to any one of claims 1 to 4 , comprising:
Spindle motor. The spindle motor according to claim 5 is provided.
Recording / playback device.

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