JP4265207B2 - Dynamic pressure bearing device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dynamic pressure bearing device used for a magnetic disk recording device or the like, and more particularly to a fixing method between members requiring high mounting accuracy.
[0002]
[Prior art]
In the conventional dynamic pressure bearing device, the shaft and the thrust bearing are press-fitted or inserted to such an extent that the squareness is not deteriorated, and then the joint boundary between the two is welded from the surface side. In this case, a relief portion that is recessed in the axial direction is formed in a ring shape on the surface portion of the joint boundary portion, and the shaft and the thrust bearing are welded in the relief portion. (For example, see Patent Document 1)
Hereinafter, a conventional dynamic pressure bearing device will be described with reference to FIG. FIG. 7 is a plan view and a sectional view of a conventional hydrodynamic bearing device after welding. As shown in FIG. 7, a recess 17 is formed between the shaft 1 and the thrust bearing 2, and a metal melted by melting energy such as a laser is poured into the recess 17, and the shaft 1 and The thrust bearing 2 is firmly tightened.
[0003]
[Patent Document 1]
JP 2000-324753 A (pages 5 to 6, FIG. 1)
[0004]
[Problems to be solved by the invention]
In the conventional welding technique described above, there is a method in which a metal is melted by a melting energy such as a laser in a recess between members to be welded to a shaft and a thrust bearing, and a plurality of spots are welded all around or on a concentric circle. However, when a laser is irradiated, a high-temperature spot is generated at one point. Therefore, thermal expansion and contraction stress during cooling occur, and the shaft is necessary for the hydrodynamic bearing motor. There was a problem that accuracy such as flatness and perpendicularity with the thrust bearing could not be secured.
[0005]
The present invention solves the above problems and can provide a dynamic pressure bearing device in which the members are firmly fastened while ensuring the flatness, squareness, etc. between the shaft and the thrust bearing.
[0006]
[Means for Solving the Problems]
In order to solve the above-described conventional problems, the dynamic pressure bearing device and the manufacturing method thereof according to the present invention use a jig for bringing the contact surface of the shaft and the thrust bearing into close contact with each other without inclining them. The shaft and the thrust bearing are fixed by means of irradiating and welding all around.
[0007]
As a result, the influence of the thermal contraction of the entire thrust bearing is reduced, so that deformation is reduced and the accuracy of the thrust bearing after welding is ensured.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Dynamic pressure 受装 location according to claim 1 of the present invention includes a shaft having a step portion on the end face outer peripheral portion forming a rotational shaft, the dynamic pressure in at least one end face in order to generate a dynamic pressure in the axial direction A disc-shaped thrust bearing formed with a through hole for engaging with the stepped portion of the shaft at the center of the stepped portion formed with a groove and recessed from an end surface with the dynamic pressure groove. a dynamic pressure 受装 location fixed by laser welding the joint between the bearing and the shaft, the engagement between the said thrust bearing shaft as well as the clearance fit, the circumference equal division of the joint (the N 2 or more integer) multiple points N Le in - shines the irradiation, is characterized in that it has fixed by circumferential welding.
In the hydrodynamic bearing device according to claim 2 of the present invention, the thrust bearing and the shaft are engaged with a clearance fit, and the height of the convex portion of the shaft and the height of the bottom portion of the step portion of the thrust bearing. It is characterized by combining the same .
[0009]
Next, a manufacturing method of dynamic pressure 受装 location according to claim 3 of the present invention includes a shaft having a step portion on the end face outer peripheral edge portion forming an axis of rotation in order to generate a dynamic pressure in the axial direction A disk-shaped thrust bearing having a dynamic pressure groove formed at least on one end surface, and a through-hole for engaging with the stepped portion of the shaft at the center of the stepped portion recessed from the end surface having the dynamic pressure groove; has, the thrust bearing method of manufacturing a dynamic pressure 受装 location joined fixed to the shaft, fixedly joined between the thrust bearing and the shaft, the engagement between the shaft and the thrust bearing A laser welding laser is applied to a plurality of circumferentially equally divided points N (N is an integer of 2 or more) at the same time in a state where the clearance is pressed and pressed at a predetermined pressure. Weld all around by rotating the joint more than 360 / N degrees It is characterized in.
[0010]
According to the first and second aspects of the present invention, when multiple points are irradiated at an equal angle with respect to the entire circumference at the same time as compared with irradiation at one place, the tension, compression, torsion and the like associated with thermal expansion and contraction are reduced. It is easy to balance the stress, can reduce the influence of thermal expansion such as warping, tilting, eccentricity, movement, deformation, etc., and can obtain the advantages that the welding time is shortened and the productivity is improved.
[0011]
Next, a manufacturing method of dynamic pressure 受装 location according to claim 4 of the present invention, using the method of claim 3, while for angular rotation of the joint 360 / N degree constant laser output in welding, in the subsequent rotation, gradually - and it is characterized in that to complete the output by reducing welding tHE. When the jig is rotated to start welding and the welded parts start to overlap, the heat input becomes excessively large and the metal penetration varies. For this reason, the finished surface of the overlapping portion becomes rough and the strength also decreases. By reducing the welding trace from the overlapped portion of the welded portion which is the method of the present invention, the overlapped portion can be finished cleanly, and the weld strength of the shaft and the thrust bearing can be increased by suppressing the heat input of the overlapped portion. is there.
[0012]
Next, a manufacturing method and dynamic pressure 受装 location according to claim 5 of the present invention, using the method according to claim 3 or 4, the guide holes for guiding and holding the shaft in the axial direction A holder having a holding surface for holding the thrust bearing, a pressing plate for sandwiching and fixing the thrust bearing between the holding surface of the holder, and pressing and fixing the step portion of the shaft against the thrust bearing A thrust pin inserted into a guide hole of the holder, a moving means for moving the push pin up and down, and a jig having pressure means for pressing the push pin against the shaft with a predetermined pressure, After being fixed to the holding surface of the holder by the pressing plate, the push pin is moved by the moving means to engage the stepped portion of the shaft with the through hole of the thrust bearing. While, pressed at a predetermined pressure by the pressure means, and characterized in that it has welded Thereafter, when manufacturing the hydrodynamic 受装 location using the jig, the shaft and the thrust bearing Fix the flatness, squareness, etc. of the bearing in place and prevent the thrust bearing from lifting from the shaft receiving surface, and also prevent welding from entering, and hold down until the weld has cooled after welding. Therefore, those capable of producing a highly accurate dynamic pressure 受装 location by the effects of thermal deformation by reducing firmly fixed in place.
[0013]
Next, a manufacturing method and dynamic pressure 受装 location according to claim 6 of the present invention, using the method of claim 5, in the press pin, a shape to press the central shaft hemispherical The pressing pin is used to press against the shaft, and then fixed by welding.
[0014]
Next, a manufacturing method and dynamic pressure 受装 location according to claim 7 of the present invention, using the method according to claim 5, means for pressing the center of the shaft, ball ahead of the push pins And the ball is pressed against the shaft and then fixed by welding.
[0015]
According to the inventions of claims 6 and 7 , by using a hemispherical push pin or a sphere, the shaft can be pushed at one central point instead of being pushed by the surface, and the shaft is not inclined. A pressing force can be applied in the axial direction of the shaft, and the flatness and perpendicularity between the shaft and the thrust bearing can be fixed with higher accuracy.
[0016]
(Embodiment 1)
Hereinafter, Embodiment 1 according to claims 1 to 3 of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of a magnetic disk recording device used in an embodiment of the present invention, and FIG. 2 is a plan view and a cross-sectional view of a dynamic pressure bearing device in an embodiment of the present invention. FIG. 2A shows before welding, and FIG. 2B shows after welding.
As shown in FIG. 1, a thrust bearing 2 having a dynamic pressure groove formed at the end of the shaft 1 is inserted, and the shaft 1 is inserted into a sleeve 3 having a dynamic pressure groove formed on the inner peripheral surface. The plate 4 is press-fitted and fixed to the sleeve 3 side. Thereafter, lubricating oil is injected from the gap between the shaft 1 and the sleeve 3 to complete the bearing unit A. Thereafter, the end of the shaft 1 protruding from the bearing unit A is pressed into the motor hub 5 while being pressed from the opposite side.
[0017]
Further, as shown in FIG. 2, 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 height of the convex portion 1 b formed by providing the step portion 1 a of the shaft 1 is matched with the height of the bottom portion of the step portion 2 b of the thrust bearing 2. The joint portion 16, which is a portion where the through hole 2 a contacts the convex portion 1 b, has a clearance of about 0.02 to 0.04. Although it is possible to temporarily fix by press fitting, caulking, etc. before welding, in the embodiment of the present invention, a clearance is provided in order not to give internal stress at the time of press fitting and to eliminate the press fitting process. Yes.
[0018]
In this state, the joint 16 where the through-hole 2a and the projection 1b are in contact with each other is continuously laser-irradiated at the three locations of the irradiation point 6 from the surface side, and the final irradiation rotated 120 degrees or more on the circumference. Rotate to point 7 and fix continuously by laser welding all around.
[0019]
In order to increase the strength, welding was continuously performed this time. However, a plurality of points or a plurality of points may be welded at the same time, and then the jig may be rotated to further weld a plurality of points.
In the present embodiment, a laser welding method is used in which the materials to be joined together are melted and joined together. Although the diameter of the welded portion is as small as φ2, the laser irradiation diameter can be set to about 0.2, and the entire circumference can be welded by irradiating three places in a small place while maintaining the strength.
Note that, in laser irradiation at a plurality of points, variation in the output of the branched lasers is suppressed to within 10%.
[0020]
Next, the relationship between the laser irradiation output and the work rotation will be described.
FIG. 3 is a graph showing the relationship between the laser output and the rotation of the jig fixing the shaft and the sleeve bearing in the first embodiment of the present invention, from the start of laser irradiation. 2 shows the progress of the laser output when the motor is rotated. FIG. 4 is a plan view showing a state of laser welding in the first embodiment of the present invention. Symbols a, b, and c in FIG. 4 correspond to symbols a, b, and c in FIG. .
From the laser irradiation start a, the jig on which the shaft and the thrust bearing are fixed is welded at a constant output until it rotates 120 degrees b. After exceeding 120 degrees b, the output is gradually reduced to around 130 degrees c where welding is finished.
[0021]
(Embodiment 2)
Hereinafter, a second embodiment according to claims 4 to 6 of the present invention will be described with reference to FIGS. FIG. 5 is a cross-sectional view of a jig according to Embodiment 2 of the present invention. FIG. 6 is a cross-sectional view of a jig according to another embodiment 2 of the present invention showing another example of FIG. In FIG. 6, the same components as those in FIG. 5 are denoted by the same reference numerals, description thereof is omitted, and differences from FIG. 5 will be described.
[0022]
In FIG. 5, the structure of the jig used for manufacturing the hydrodynamic bearing device includes a guide hole 14 for guiding and holding the shaft 1 in the axial direction, a holder 9 having a holding surface 9a for holding the thrust bearing 2, and a thrust. A pressing plate 8 for sandwiching and fixing the bearing 2 between the holding surface 9a of the holder 9 and a press inserted into the guide hole 13 of the holder 9 for pressing and fixing the step portion 1b of the shaft 1 to the thrust bearing 2 It has a pin 10, an air cylinder 11 as a moving means for moving the push pin 10 up and down, and an air regulator 12 as a pressure means for pressing the push pin 10 against the shaft 1 with a predetermined pressure. The tip shape of the push pin 10 that presses the shaft 1 is hemispherical, and pushes one point at the center of the shaft 1.
[0023]
About the jig | tool comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.
[0024]
The shaft 1 is inserted into the guide hole 13 of the holder 9 that holds the shaft 1 and placed on the tip of the hemispherical pin of the push pin 10. Next, the thrust bearing 2 is placed on the contact surface of the shaft step portion 1a so that the convex portion 1b provided on the outer peripheral edge portion of the shaft end surface engages with the penetrating portion 2a of the thrust bearing 2, and the thrust bearing 2 is held by the holder 8 by the presser 8. 9 is fixed to the holding surface 9a, and 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 and fixed by the air cylinder 11 by about 0.1 mm. Thereby, the thrust bearing 2 is brought into close contact with the contact surface of the shaft step portion 1a without being inclined. After fixing the shaft 1 and the thrust bearing 2 to the jig, the jig is rotated, and at the same time, laser irradiation is performed at three points, and the entire circumference is welded by rotating it 120 degrees or more on a concentric circle.
If the force that presses the shaft 1 against the thrust bearing 2 is too large, the thrust bearing 2 is deformed. Therefore, a force of about 300 g that does not deform the thrust bearing 2 is applied. The force with which the push pin 10 presses the shaft 1 and the shaft 1 presses the thrust bearing 2 is adjusted using an air regulator 12.
[0025]
FIG. 6 shows another embodiment in which the hemispherical push pin 10 of FIG. 5 is replaced with a flat push pin 14 and a ball 15 is placed on the tip of the push pin. The same function and effect as the pin 10 can be obtained.
[0026]
【The invention's effect】
As described above, according to the hydrodynamic bearing device and the manufacturing method thereof of the present invention, the laser irradiation is continuously performed at three points simultaneously using the jig for bringing the thrust bearing and the contact surface of the shaft into close contact with each other without inclining. Thus, the entire circumference is welded, and the accuracy such as the flatness and perpendicularity between the rotating shaft and the thrust bearing necessary for the fluid bearing motor can be fixed with high accuracy.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a magnetic disk recording device used in Embodiment 1 of the present invention. FIG. 2 is a plan view and a cross-sectional view of a dynamic pressure bearing device in Embodiment 1 of the present invention. Fig. 4 is a graph showing the relationship between laser output and jig rotation in Embodiment 1 of the present invention. Fig. 4 is a plan view showing a state of laser welding in Embodiment 1 of the present invention. Sectional view of jig in embodiment 2 FIG. 6 is a sectional view of jig in another embodiment 2 of the present invention. FIG. 7 is a plan view and a sectional view of a conventional hydrodynamic bearing device after welding. ]
DESCRIPTION OF SYMBOLS 1 Shaft 1a Step part 1b Convex part 2 Thrust bearing 2a Through hole 2b Step part 3 Sleeve 4 Thrust plate 5 Motor hub 6 Irradiation point 7 Final irradiation point 8 Presser 9 Holder 9a Holding surface 10 Push pin 11 Air cylinder 12 Air regulator 13 Guide hole 14 Push pin 15 Ball 16 Joint 17 Recess

Claims (7)

A shaft provided with a step on the outer peripheral edge of the end surface forming the rotation axis, and a step formed with a dynamic pressure groove on at least one end surface for generating dynamic pressure in the axial direction and recessed from the end surface with the dynamic pressure groove A disc-shaped thrust bearing in which a through-hole for engaging with the stepped portion of the shaft is formed at the center of the shaft, and a hydrodynamic shaft in which a joint portion between the thrust bearing and the shaft is fixed by laser welding a 受装 location, the engagement between the thrust bearing and the shaft while the clearance fit, a plurality of points N of circumferentially equal division of the joint (N is an integer of 2 or more) les to - and the irradiation A hydrodynamic bearing device characterized by being welded and fixed all around. 2. The motion according to claim 1, wherein the engagement between the thrust bearing and the shaft is a clearance fit, and the height of the convex portion of the shaft is matched with the height of the bottom portion of the step portion of the thrust bearing. Pressure bearing device. A shaft provided with a step on the outer peripheral edge of the end surface forming the rotation axis, and a step formed with a dynamic pressure groove on at least one end surface for generating dynamic pressure in the axial direction and recessed from the end surface with the dynamic pressure groove in the has a disk-shaped thrust bearing through hole for engagement with the stepped portion of the shaft is formed in the center, a manufacturing method of the dynamic pressure 受装 location joined secure the thrust bearing in the shaft The thrust bearing and the shaft are joined and fixed with a clearance fit between the thrust bearing and the shaft, and the circumference of the joint is equally divided while being pressed with a predetermined pressure. plurality of points N (N is an integer of 2 or more) at the same time record for laser welding - by irradiating tHE, characterized by circumferential welding by rotating the joint 360 / N degrees of angle or more dynamic method of manufacturing the pressure bearing 受装 location. The welding is completed at a constant laser output while the joint is rotated at an angle of 360 / N degrees, and the laser output is gradually reduced to complete the welding after that rotation. dynamic pressure 受装 location method according to 3. A guide hole for guiding and holding the shaft in the axial direction; a holder having a holding surface for holding the thrust bearing; and a pressing plate for sandwiching and fixing the thrust bearing between the holding surface of the holder; A push pin inserted into a guide hole of the holder for pressing and fixing the step portion of the shaft against the thrust bearing, a moving means for moving the push pin up and down, and a force for pressing the push pin against the shaft with a predetermined pressure Using a jig having pressure means, the thrust bearing is fixed to the holding surface of the holder by the pressing plate, and then the push pin is moved by the moving means so that the stepped portion of the shaft is moved to the thrust bearing. together to engage the through holes, pressed at a predetermined pressure by the pressure means, according to claim 3 also characterized by being welded thereafter Dynamic pressure 受装 location method according to any one of 4. In the press pin, a shape to press the center of the shaft and hemispherically, pressed against the shaft with the push pin, dynamic pressure 受装 of claim 5, characterized in that the welded thereafter Manufacturing method. Means for pressing the center of the shaft, placing the ball ahead of the push pin, pressing the ball to the shaft, the dynamic pressure 受装 location according to claim 5, characterized in that the welded thereafter Production method.

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