JP2004183809A - Dynamic pressure bearing device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dynamic pressure bearing device and its manufacturing method capable of keeping high accuracy in flatness and perpendicularity of a rotating shaft and a thrust bearing necessary for a dynamic pressure bearing motor, and obtaining the firm joining strength. <P>SOLUTION: The accuracy in flatness and perpendicularity of the shaft 1 and the thrust bearing 2 necessary for the fluid bearing motor A is secured by welding the whole circumference by using a jig for bringing the thrust bearing 2 and the shaft 1 into closely contact with each other without inclining a contact face, by simultaneously applying the laser to a plurality of points while rotating the jig, simultaneously applying the laser to a plurality of points N (N is integer of 2 or more) obtained by dividing the circumference of a joint part, and rotating the joint part 16 by an angle of more than 360/N degrees. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD 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 method for fixing members that require high mounting accuracy.
[0002]
[Prior art]
In the conventional dynamic pressure bearing device, after the shaft and the thrust bearing are press-fitted or inserted to such an extent that the right angle does not deteriorate, the joint boundary between them is welded from the surface side. At this time, a relief portion which is previously depressed in the axial direction is formed in an annular shape on the surface portion of the joining 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 dynamic pressure bearing device after welding. As shown in FIG. 7, a concave portion 17 is formed between the shaft 1 and the thrust bearing 2, and a material obtained by melting a metal by melting energy of a laser or the like is poured into the concave portion 17, and the shaft 1 is The structure is such that the thrust bearing 2 is firmly fastened.
[0003]
[Patent Document 1]
JP-A-2000-324753 (pages 5 to 6, FIG. 1)
[0004]
[Problems to be solved by the invention]
In the conventional welding technique described above, a method is used in which a metal is melted by a dissolving energy of a laser or the like in a recess between members to which a shaft and a thrust bearing are welded, and the entire circumference or a part of the metal is welded concentrically. However, at the time of laser irradiation, a high-temperature spot is generated at one point, so that stress of thermal expansion and contraction at the time of cooling occurs, causing deformation and causing a problem with the shaft necessary for the fluid bearing motor. There was a problem that the accuracy such as flatness and squareness with the thrust bearing could not be ensured.
[0005]
The present invention can solve the above-mentioned problems, and can provide a dynamic pressure bearing device in which members are firmly fastened while ensuring accuracy such as flatness and perpendicularity between a shaft and a thrust bearing.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned conventional problems, a dynamic pressure bearing device and a method of manufacturing the same according to the present invention use a jig for tightly contacting a shaft and a contact surface of a thrust bearing without tilting, and simultaneously lay out a plurality of points. The shaft and the thrust bearing are fixed by means of laser irradiation and full-circle welding.
[0007]
Thus, the effect of thermal shrinkage of the entire thrust bearing is reduced, so that the deformation is reduced, which has an effect of ensuring the accuracy of the thrust bearing after welding.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The dynamic pressure bearing device according to claim 1 of the present invention has a shaft provided with a stepped portion on an outer peripheral edge of an end surface forming a rotating shaft, and a dynamic pressure groove formed on at least one end surface for generating dynamic pressure in the axial direction. A disk-shaped thrust bearing formed with a through-hole for engaging the step portion of the shaft at the center of the step portion recessed from the end face having the dynamic pressure groove, wherein the thrust bearing and A dynamic pressure bearing device in which a joint with the shaft is fixed by laser welding, wherein, during welding, the engagement between the thrust bearing and the shaft is a clearance fit and is pressed at a predetermined pressure. Laser irradiation is simultaneously applied to a plurality of points N (N is an integer of 2 or more) at equal divisions of the circumference of the joint to rotate the joint at an angle of 360 / N degrees or more, thereby welding the entire circumference. And is fixed.
[0009]
Next, a method of manufacturing a dynamic pressure bearing device according to a second aspect of the present invention includes: a shaft provided with a stepped portion at an outer peripheral edge of an end surface forming a rotary shaft; A disk-shaped thrust bearing in which a dynamic pressure groove is formed on an end surface, and a through hole for engaging with the step portion of the shaft is formed at the center of the step portion recessed from the end surface having the dynamic pressure groove; The thrust bearing is joined and fixed to the shaft, and the thrust bearing and the shaft are joined and fixed in such a manner that the engagement between the thrust bearing and the shaft is a clearance fit and a predetermined pressure. In the pressed state, a laser for laser welding is simultaneously applied to a plurality of points N (N is an integer of 2 or more) at equal divisions of the circumference of the joint to thereby irradiate the joint at 360 / N degrees. Rotating more than an angle to weld all around It is an butterfly.
[0010]
According to the invention of claims 1 and 2 of the present invention, it is preferable to irradiate a plurality of points at an equal angle with respect to the entire circumference at the same time as compared with irradiation of one place, and it is possible to reduce tension, compression, torsion and the like accompanying thermal expansion and contraction. The advantage is that stress can be easily balanced, the influence of thermal expansion such as warpage, inclination, eccentricity, movement, deformation, etc. can be reduced, and the welding time can be shortened to improve productivity.
[0011]
Next, a method of manufacturing a dynamic pressure bearing device according to a third aspect of the present invention uses the method of the second aspect to weld with a constant laser output while rotating the joint at an angle of 360 / N degrees. In the subsequent rotation, the output of the laser is gradually reduced to complete the welding.
When the jig is rotated and welding is started, and the welding spots start to overlap, the heat input becomes excessively large, and the penetration of the metal varies. For this reason, the finished surface of the overlapping portion becomes rough and the strength is reduced. In the method of the present invention, by reducing welding marks from the overlapping portion of the welding portion, the overlapping portion can be finished finely, and the welding strength of the shaft and the thrust bearing can be increased by suppressing the heat input of the overlapping portion. is there.
[0012]
Next, a dynamic pressure bearing device according to a fourth aspect of the present invention and a method for manufacturing the same, using the method according to the second or third aspect, a guide hole 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 a pressing plate for pressing and fixing a step portion of the shaft to the thrust bearing. Using a jig having a push pin inserted into the guide hole of the holder, moving means for moving the push pin up and down, and pressure means for pressing the push pin against the shaft with a predetermined pressure, the thrust bearing is fixed to the holder. After being fixed to the holding surface by the pressing plate, the push pin is moved by the moving means so that the step portion of the shaft is inserted into the through hole of the thrust bearing. Together with a predetermined pressure by the pressure means, and then fixed by welding, when manufacturing a dynamic pressure bearing device using this jig, the shaft and the thrust bearing Welding is performed with the flatness, squareness, etc. positioned and fixed to prevent the thrust bearing from floating from the shaft receiving surface, while preventing the ingress of dust, and after welding, press down until the weld cools down. In addition, a highly accurate dynamic pressure bearing device can be manufactured by firmly fixing the bearing at a predetermined position while reducing the influence of thermal deformation.
[0013]
Next, the dynamic pressure bearing device and the manufacturing method thereof according to claim 5 of the present invention use the method according to claim 4 to make the push pin press the center of the shaft in a hemispherical shape. The shaft is pressed against the shaft using the push pin, and then fixed by welding.
[0014]
Next, in the dynamic pressure bearing device according to claim 6 of the present invention and the method for manufacturing the same, the means for pressing the center of the shaft uses the method described in claim 4 to place a ball on the tip of the push pin. The sphere is pressed against the shaft and then fixed by welding.
[0015]
According to the invention of claims 5 and 6 of the present invention, by using a hemispherical push pin or a sphere, the shaft can be pushed at a central point instead of being pushed with a surface, and the shaft is not tilted. A pressing force can be applied in the axial direction of the shaft, and the flatness and the perpendicularity between the shaft and the thrust bearing can be fixed with higher accuracy.
[0016]
(Embodiment 1)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a 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 sectional view of a dynamic pressure bearing device in the embodiment of the present invention. FIG. 2A shows the state before welding, and FIG. 2B shows the state after welding.
As shown in FIG. 1, a thrust bearing 2 having a dynamic pressure groove formed at an end of the shaft 1 is inserted, and the shaft 1 is inserted into a sleeve 3 having a dynamic pressure groove formed at an inner peripheral surface thereof. 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, and the bearing unit A is completed. Thereafter, the end of the shaft 1 protruding from the bearing unit A is pressed and fixed to the motor hub 5 while being pressed from the opposite side.
[0017]
In addition, as shown in FIG. 2, a shaft 1 having a stepped portion 1a at an outer peripheral edge of an end surface forming a rotation axis and a disk-shaped thrust bearing 2 having a stepped portion 2b formed around a central through hole 2a. The height of the projection 1b formed by providing the step 1a of the shaft 1 is adjusted to the height of the bottom of the step 2b of the thrust bearing 2. The joint portion 16 where the through hole 2a and the convex portion 1b are in contact has a clearance of about 0.02 to 0.04. It is also possible to temporarily fix by press-fitting, caulking, etc. before welding, but in the embodiment of the present invention, not to have internal stress at the time of press-fitting, and to provide a gap to eliminate the press-fitting step. I have.
[0018]
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 and continuously laser-irradiated from the surface side to three irradiation points 6, and the final irradiation is rotated by 120 degrees or more on the circumference. Rotate to point 7 and continuously weld and fix the entire circumference with a laser.
[0019]
This time, in order to increase the strength, welding was performed continuously, but it is also possible to weld a plurality of points or a plurality of points at the same time, then rotate the jig, and further weld a plurality of points.
In this embodiment, a laser welding method is used in which materials to be joined to each other are melted to join them. Although the diameter of the welded portion is as small as φ2, the laser irradiation diameter is set to about φ0.2, so that it is possible to irradiate three places in a small place and weld the entire circumference while maintaining strength.
In laser irradiation at a plurality of points, variations in the outputs of the branched lasers are suppressed to within 10%.
[0020]
Next, the relationship between the output of laser irradiation and the rotation of the work 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. Shows the progress of the laser output when is rotated. FIG. 4 is a plan view showing a state of laser welding according to 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 start of laser irradiation a, the jig to which the shaft and the thrust bearing are fixed is welded at a constant output until the jig rotates 120 degrees b. After exceeding 120 degrees b, the output is gradually reduced to around 130 degrees c at which welding is completed.
[0021]
(Embodiment 2)
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a sectional view of a jig according to Embodiment 2 of the present invention. FIG. 6 is a sectional view of a jig according to another embodiment 2 of the present invention, which shows another example of FIG. In FIG. 6, the same components as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted, and points different from FIG. 5 will be described.
[0022]
In FIG. 5, a jig used for manufacturing the dynamic pressure 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 bearing. A pressing plate 8 for sandwiching and fixing the bearing 2 between the holding surface 9a of the holder 9 and a pressing plate 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 at a predetermined pressure. The tip of the push pin 10 for pressing the shaft 1 is hemispherical, and pushes a central point of the shaft 1.
[0023]
The operation and operation of the jig configured as described above will be described below.
[0024]
The shaft 1 is inserted into the guide hole 13 of the holder 9 that holds the shaft 1, and is placed at the tip of a 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 projection 1b provided on the outer peripheral edge of the shaft end face engages with the through portion 2a of the thrust bearing 2, and the thrust bearing 2 is held by the holder 8 by the holding member 8. After fixing between the shaft 9 and the holding surface 9a, the step portion 1a of the shaft is pressed against the thrust bearing 2 by the air regulator 12, and the push pin 10 is pushed up by about 0.1 mm by the air cylinder 11 and fixed. Thus, the thrust bearing 2 is brought into close contact with the contact surface of the shaft step portion 1a without tilting. After fixing the shaft 1 and the thrust bearing 2 to the jig, the jig is rotated, and at the same time, three points are irradiated with a laser, and the concentric circle is rotated by 120 degrees or more to continuously weld the entire circumference.
If the force for pressing the shaft 1 against the thrust bearing 2 is too large, the thrust bearing 2 will be 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 push pin 14 having a flat tip, and a ball 15 is placed on the tip of the push pin. Functions and effects similar to those of the pin 10 can be obtained.
[0026]
【The invention's effect】
As described above, according to the dynamic pressure bearing device and the method of manufacturing the same of the present invention, laser irradiation is continuously performed at three points simultaneously by using a jig for bringing the thrust bearing and the shaft contact surface into close contact without tilting. By doing so, the entire circumference can be welded, and the accuracy of the flatness and the perpendicularity between the rotating shaft and the thrust bearing required 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 a first embodiment of the present invention. FIG. 2 is a plan view and a cross-sectional view of a dynamic pressure bearing device in a first embodiment of the present invention. FIG. 4 is a graph showing the relationship between laser output and jig rotation in Embodiment 1. FIG. 4 is a plan view showing the state of laser welding in Embodiment 1 of the present invention. FIG. FIG. 6 is a sectional view of a jig in another embodiment 2 of the present invention. FIG. 7 is a plan view and a sectional view of a conventional dynamic pressure bearing device after welding. ]
Reference Signs List 1 shaft 1a stepped portion 1b convex portion 2 thrust bearing 2a through hole 2b stepped portion 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 (6)

A shaft provided with a step on the outer peripheral edge of an end face forming a rotation axis, and a step formed with a dynamic pressure groove formed on at least one end face for generating a dynamic pressure in the axial direction, the step being recessed from an end face having the dynamic pressure groove And a disk-shaped thrust bearing having a through hole formed in the center of the shaft for engaging with a stepped portion of the shaft, and a dynamic pressure bearing in which a joint between the thrust bearing and the shaft is fixed by laser welding. A thrust bearing and the shaft are engaged with each other at a plurality of points N (N (2 is an integer of 2 or more) at the same time, and the joint is rotated by an angle of 360 / N degrees or more and welded all around to be fixed. A shaft provided with a step on the outer peripheral edge of an end face forming a rotation axis, and a step formed with a dynamic pressure groove formed on at least one end face for generating a dynamic pressure in the axial direction, the step being recessed from an end face having the dynamic pressure groove A thrust bearing having a disc-shaped thrust bearing formed with a through hole for engaging with a stepped portion of the shaft at a center of the thrust bearing, wherein the thrust bearing is fixedly joined to the shaft. The joint between the bearing and the shaft is fixed by a plurality of points N (where N is 2) at which the engagement between the thrust bearing and the shaft is a clearance fit and is pressed at a predetermined pressure. A laser welding laser at the same time as the above integer, and rotating the joint at an angle of 360 / N degrees or more to perform full-circle welding. . The welding is performed at a constant laser output while the joint is rotated at an angle of 360 / N degrees, and in subsequent rotations, the output of the laser is gradually reduced to complete the welding. Item 6. A method for manufacturing a dynamic pressure bearing device according to item 2. A guide hole for guiding and holding the shaft in the axial direction, a holder having a holding surface for holding the thrust bearing, a holding 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 a step portion of the shaft to the thrust bearing, a moving means for moving the push pin up and down, and a device for pushing the push pin against the shaft with a predetermined pressure. After fixing the thrust bearing to the holding surface of the holder with the holding plate by using a jig having a pressure means, the push pin is moved by the moving means to move the step portion of the shaft to the thrust bearing. 3. The method as claimed in claim 2, wherein said second pressure unit is engaged with said through hole and pressed by said pressure means at a predetermined pressure, and then fixed by welding. Method for producing the dynamic pressure bearing device according to 3. 5. The dynamic pressure bearing device according to claim 4, wherein the push pin has a hemispherical shape in which the center of the shaft is pushed, and is pressed against the shaft using the push pin, and then fixed by welding. 6. Production method. 5. The method for manufacturing a dynamic pressure bearing device according to claim 4, wherein the means for pressing the center of the shaft places a ball on the tip of the push pin, presses the ball against the shaft, and then fixes the ball by welding. .

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