JP4688347B2 - Inside diameter finishing tool for hydrodynamic bearing sleeve and machining apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inner diameter finishing tool for a fluid bearing sleeve applied to a hard disk device or the like, and a processing apparatus using the same.
[0002]
[Prior art]
A rotating body such as a hard disk device is provided integrally with a fluid bearing sleeve that is rotatably supported by a fixed shaft. This hydrodynamic bearing sleeve has a fishbone-shaped dynamic pressure groove formed on the inner surface of a shaft hole into which a fixed shaft is fitted, and lubricating oil is injected into the dynamic pressure groove. When the hydrodynamic bearing sleeve rotates around the fixed shaft, the lubricating oil in the dynamic pressure groove is pressurized and the sleeve is brought into a non-contact state with respect to the fixed shaft, thereby enabling high-speed rotation.
[0003]
In recent years, with the increase in capacity and speed of hard disk drives, high precision and low cost are required for processing of the sleeve of the fluid bearing. The conventional hydrodynamic bearing sleeve is processed by first machining a shaft hole 26 in the hydrodynamic bearing sleeve 25 as shown in FIG. 5A, and then forming a groove machining tool shown in FIG. 5B on the inner surface of the shaft hole 26. 27, two sets of dynamic pressure grooves 28 as shown in FIG. This grooving tool 27 is a tool in which a holder 30 holding a plurality of rolling balls 29 on its outer peripheral surface is attached to the tip of a shaft. The circumscribed diameter D of the rolling ball 29 is set to be approximately 10 microns larger than the inner diameter of the shaft hole 26 of the fluid bearing sleeve 25. This grooving tool 27 is inserted into the inner surface of the hydrodynamic bearing sleeve 25 and rotated while being pushed in, and is rotated in the opposite direction in the middle to form half of the first dynamic pressure grooves 28, and then in the same manner. Half of the second dynamic pressure grooves 28 are formed. Then, when the same operation is performed while the grooving tool 27 is pulled out to form the other half of the second and first dynamic pressure grooves 28, the number of the dynamic pressure grooves is twice the number of the rolling balls 29. 28 is formed.
[0004]
Since the inner surface of the hydrodynamic bearing sleeve 25 is pressed by the rolling ball 29 and plastically deformed in the dynamic pressure groove 28 formed in this way, a rolling burr is generated in the vicinity of the dynamic pressure groove 28. For this reason, it is necessary to finish the inner diameter to remove the rolling burrs. In the conventional inner diameter finishing process, a rolling burr is formed by pushing a steel ball 31 larger by about 10 microns than the inner diameter of the fluid bearing sleeve 25 through the shaft hole 26 of the fluid bearing sleeve 25 as shown in FIG. A crushing method was used.
[0005]
[Problems to be solved by the invention]
However, in such a conventional method for finishing the inner diameter of the fluid bearing sleeve 25, when the steel ball 31 is pushed into the shaft hole 26 of the fluid bearing sleeve 25, the opening edge A of the shaft hole 26 is larger than the central portion of the steel ball 31. Therefore, the opening edge A is finished to have a diameter of about 4 microns larger than the inner diameter of the central portion. This level of accuracy degradation is not a problem with fluid bearings used in general equipment, but long-term reliability and high rotational accuracy cannot be maintained with hard disk drives that require higher capacity and higher speed as in recent years. There was a problem.
[0006]
The present invention has been made in view of such conventional problems, and is particularly suitable for a hydrodynamic bearing sleeve of a hard disk drive that requires high capacity and high speed. It is an object to provide a processing tool and a processing apparatus using the processing tool.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a hydrodynamic bearing sleeve inner diameter finishing tool according to the present invention comprises a hydrodynamic groove formed on the inner surface of a hydrodynamic bearing sleeve and then inserted into the hydrodynamic bearing sleeve to finish the inner diameter. In the inner diameter finishing tool, a taper portion serving as a guide when inserted into the fluid bearing sleeve, a centering portion having a circular cross-section for centering the fluid bearing sleeve, a plurality of partial cylindrical surfaces and a plurality of outer peripheral surfaces A non-circular cross-section processed portion having a processing edge for finishing the inner diameter of the fluid bearing sleeve extending in the axial direction at the boundary between the partial cylindrical surface and the non-cylindrical surface.
A groove extending in the axial direction is formed on at least one partial cylindrical surface of the machining portion, and a cutting edge is formed at the boundary between the inclined surface of the groove located on the upstream side in the rotation direction of the machining tool and the partial cylindrical surface. .
[0008]
The machining tool of the present invention is inserted into the fluid bearing sleeve by the guide of the tapered portion at the tip, aligned with the fluid bearing sleeve by the centering portion having a circular cross section, and the burr of the dynamic pressure groove is formed by the machining edge of the processing portion. It is removed and finished with high accuracy and low cost.
[0009]
In addition, the burrs in the hydrodynamic groove of the fluid bearing sleeve are more reliably removed by the cutting blade at the boundary between the inclined surface of the groove and the partial cylindrical surface, and the fluid bearing sleeve is finished with higher accuracy and lower cost. .
[0010]
It is preferred to coat the outer surface with an abrasion resistant material. This wear-resistant material prevents the fluid bearing sleeve material from coming into direct contact with the processing tool during processing, stabilizes the processing accuracy and improves the life of the processing tool.
[0011]
In order to solve the above-mentioned problems, an internal diameter finishing apparatus for a fluid bearing sleeve according to the present invention includes a machining head having a chuck that holds one end of the machining tool, and a machining tool that holds the machining head on the chuck. Lifting unit for lifting and lowering in the axial direction, a work holder for holding the fluid bearing sleeve in the coaxial direction with the processing tool, and a moving unit for moving the work holder in two directions orthogonal to the axial direction of the processing tool held by the chuck And a stopper for restricting the movement of the work holder within a range that allows the machining tool to be inserted into the fluid bearing sleeve held by the work holder.
[0012]
In the machining apparatus of the present invention, even if the fluid bearing sleeve is misaligned or the machining tool is eccentric, the machining tool reliably enters the fluid bearing sleeve with the tapered portion at the tip as a guide. Is prevented from being damaged or deformed. In addition, the fluid bearing sleeve is aligned by a processing tool and is supported movably by a moving unit consisting of a slide bearing at that time. A low cost hydrodynamic bearing sleeve can be obtained stably.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0014]
FIG. 1 (A) shows a first embodiment of an inner diameter finishing tool 1 for a hydrodynamic bearing sleeve of the present invention. The machining tool 1 includes a tapered portion 2, an alignment portion 3, a machining portion 4, and a holding portion 5 from the tip. The taper portion 2 is a portion that serves as a guide when inserted into the hydrodynamic bearing sleeve (see FIG. 6A), and is tapered toward the tip. The aligning portion 3 is a portion that performs centering with respect to the hydrodynamic bearing sleeve, and has a circular cross section that is continuous with the rear end of the tapered portion 2. The processing portion 4 is a portion that finishes the inner diameter of the fluid bearing sleeve, and a plurality of (four in the same embodiment) partial cylindrical surfaces 6 having the same diameter as the alignment portion 3 on the outer peripheral surface, and adjacent partial cylindrical surfaces 6. There are a plurality (four in the same embodiment) of non-cylindrical surfaces 7. When the total length in the circumferential direction of the partial cylindrical surface 6 is 50% or less of the circumscribed circle shown by the two-dot chain line in FIG. 1 (B), good finishing accuracy can be obtained. As shown in FIG. 1B, the non-cylindrical surface 7 is a flat surface, and is formed by cutting a crescent-shaped portion from a circular cross-sectional portion indicated by a one-dot chain line by grinding. A boundary between the partial cylindrical surface 6 and the non-cylindrical surface 7 adjacent to the partial cylindrical surface 7 is a machining edge 8 extending in the axial direction. The diameter of the partial cylindrical surface 6 of the aligning portion 3 and the processed portion 4 is about 2 microns larger than the diameter of the shaft hole of the fluid bearing sleeve. The holding part 5 is a part that is held by a chuck of a processing apparatus to be described later.
[0015]
In order to perform inner diameter finishing for removing the burrs of the dynamic pressure grooves 28 formed on the inner peripheral surface of the shaft hole 26 of the fluid bearing sleeve 25 using this processing tool 1, the processing tool 1 is moved in the direction of the arrow. While being rotated, the taper portion 2 is inserted into the shaft hole 26 of the fluid bearing sleeve 25. Even when there is a misalignment between the machining tool 1 and the shaft hole 26 of the fluid dynamic bearing sleeve 25 during insertion, the edge of the shaft hole 26 is prevented from being damaged by the presence of the tapered portion 2. When the alignment section 3 having a circular cross section enters the shaft hole 26 of the fluid bearing sleeve 25 following the taper section 2, the machining tool 1 is aligned with the shaft hole 26 of the fluid bearing sleeve 25. Next, when the processing portion 4 enters the shaft hole 26 of the fluid bearing sleeve 25, the burrs of the dynamic pressure groove 28 are removed by the processing edge 8 at the boundary between the partial cylindrical surface 6 and the non-cylindrical surface 7 of the processing portion 4. The shaft hole 26 is finished. At this time, since the alignment of the machining tool 1 has already been completed by the alignment section 3, even if the machining tool 1 rotates with some eccentricity, the influence on the machining accuracy of the shaft hole 26 of the fluid bearing sleeve 25 is not affected. Get smaller.
[0016]
FIG. 2A shows an inner diameter finishing tool 9 according to a modification of the first embodiment. In this machining tool 9, as shown in FIG. 2 (B), the non-cylindrical surface 10 of the machining portion 4 is not a flat surface but is formed by a groove having a V-shaped cross section with an opening angle of approximately 90 °, and is formed by electric discharge machining. ing. The diameters of the alignment portion 3 of the machining tool 9 and the partial cylindrical surface 6 of the machining portion 4 are equal to or larger than the diameter of the shaft hole 26 of the fluid bearing sleeve 25 by about 1 micron. Since the machining by the machining tool 9 of this modification is the same as that of the machining tool 1 of the first embodiment described above, description thereof is omitted.
[0017]
FIG. 3A shows a second embodiment of the inner diameter finishing tool 11 of the hydrodynamic bearing sleeve of the present invention. Like the first embodiment, the processing tool 11 includes a tapered portion 2, an alignment portion 3, a processing portion 4, and a holding portion 5 from the tip, and a cutting edge 12 is provided on a partial cylindrical surface 6 of the processing portion 4. Since it is substantially the same as the first embodiment except that it is provided, the corresponding parts are denoted by the same reference numerals and description thereof is omitted. The cutting edge 12 of the partial cylindrical surface 6 forms a groove 13 having a V-shaped cross section in the longitudinal direction of at least one partial cylindrical surface 6 of the four partial cylindrical surfaces 6, so that the machining tool 11 rotates upstream. It is formed at the boundary between the slope of the groove 13 located on the side and the partial cylindrical surface 6. Here, the angle a of the cutting edge 12 is formed larger than the angle b of the machining edge 8 at the boundary surface between the partial cylindrical surface 6 and the non-cylindrical surface 7. The diameters of the aligning portion 3 of the machining tool 11 and the partial cylindrical surface 6 of the machining portion 4 are equal to or larger than the diameter of the shaft hole 26 of the fluid bearing sleeve 25 by about 1 micron.
[0018]
The machining by the machining tool 11 of the second embodiment is the same as that of the inner diameter finishing machining tool 1 of the first embodiment described above, but only the action of the machining part 4 having the cutting blade 12 is different. Explain and omit others. That is, when the processing portion 4 enters the shaft hole 26 of the fluid bearing sleeve 25, the processing edge 8 at the boundary between the partial cylindrical surface 6 and the non-cylindrical surface 7 of the processing portion 4, and the inclined surface of the partial cylindrical surface 6 and the groove 13. The burrs of the dynamic pressure groove 28 are removed by the cutting blade 12 between them. Since the processing edge 8 has a small angle, the processing edge 8 is processed so as to crush the burr. However, since the cutting edge 12 has a large angle, the burr is cut off. As a result, the shaft hole 26 is finished with higher accuracy than in the first embodiment described above.
[0019]
The third embodiment of the inner diameter finishing tool for the hydrodynamic bearing sleeve of the present invention is not shown, but is outside the processing tools 1, 9, and 11 of the first and second embodiments shown in FIGS. The surface is provided with an abrasion resistant coating. The wear-resistant coating can be selected from those generally recommended for cutting and drilling. Specifically, when the material of the processing tool is brass, diamond-like carbon (DLC) is used. In the case of stainless steel, titanium nitride (TiN) is preferred.
[0020]
The machining with the machining tool of the third embodiment is the same as the inner diameter finishing machining tools 1, 9, and 11 of the first embodiment described above, but only the action of the wear-resistant coating is different, so only the action will be described. Others are omitted. In general, the alignment portion 3 and the processing portion 4 that are in contact with the shaft hole 26 of the fluid bearing sleeve 25 at the time of processing are microscopically viewed from the material near the dynamic pressure groove 28 of the fluid bearing sleeve 25 by the processing tool 1.9. .11 is repeatedly adhered and detached, which causes unstable machining accuracy and shortens the life of the machining tools 1, 9 and 11. Therefore, in the machining tool of the third embodiment, the outer surface of the machining tools 1, 9, 11 is coated with an abrasion resistant coating so that the material in the vicinity of the dynamic pressure groove 28 of the fluid bearing sleeve 25 is changed to the machining tools 1, 9. , 11 is prevented from coming into direct contact with adhesion or separation. For this reason, in this 3rd Embodiment, processing accuracy is stabilized and the life of processing tools 1, 9, and 11 improves.
[0021]
FIG. 4 shows an inner diameter finishing apparatus for the shaft hole 26 of the fluid bearing sleeve 25 of the present invention that uses the processing tools 1, 9, and 11 of the above-described embodiments. In a column 15 erected on the base 14, a machining head 17 having a chuck 16 that holds one end of the machining tools 1, 9, 11 can be moved up and down by a lifting unit 20 including a motor 18 and a ball screw 19. Is provided. The base 14 has a moving unit 22 composed of a slide bearing for moving the work holder 21 holding the fluid bearing sleeve 25 in two directions orthogonal to the axial direction of the processing tools 1, 9 and 11 held by the chuck 16. Is provided. Around the moving unit 22 is an annular shape that restricts the movement of the work holder 21 within a range that allows the machining tools 1, 9, 11 to be inserted into the fluid bearing sleeve 25 held by the work holder 21. A stopper 23 is arranged. That is, the alignment amount B of the stopper 23 is set smaller than the taper amount C of the taper portion 2 of the machining tools 1, 9, 11. Further, the machining tools 1, 9, 11 are adjusted and fixed to the chuck 16 so that the deflection amount during rotation of the machining tools 1, 9, 11 is less than the alignment amount B of the stopper 24. Reference numeral 24 denotes a control device that controls the machining head 17 and the elevating unit 20, and rotates and stops the machining tool, raises and lowers the machining head 17, and further adjusts its speed.
[0022]
Next, the operation of the processing apparatus having the above-described configuration will be described. The fluid bearing sleeve 25 in which the shaft hole 26 and the dynamic pressure groove 28 are already processed in a separate process is attached to the work holder 21, and the chuck 16 of the processing head 17. The processing tools 1, 9, 11 are held. The machining head 17 is lowered while the machining tools 1.9 and 11 are rotated, and is inserted into the fluid bearing sleeve 25. At this time, even if the fluid bearing sleeve 25 is misaligned or the machining tools 1, 9, 11 are eccentric, the machining tools 1, 9, 11 are surely guided by the tapered portion 2 at the tip to ensure fluid bearing sleeves. Thus, the fluid bearing sleeve 25 is prevented from being damaged or deformed. Next, by lowering the machining head 17 by a predetermined amount, the rolling burrs of the fluid bearing sleeve 25 are removed and finished as described above. Even when the machining tools 1, 9, and 11 are shaken during the machining, the runout amount is smaller than the alignment amount B of the stopper 23, so that the fluid bearing sleeve 25 can freely move within the range of the alignment amount B. Can move. Since the fluid bearing sleeve 25 is aligned by the processing tools 1, 9, and 11 and is supported by the moving unit 20 comprising a slide bearing at that time, the inner diameter finishing accuracy is reduced due to factors of the processing apparatus. Therefore, the fluid bearing sleeve 25 with high accuracy and low cost can be stably obtained.
[0023]
【The invention's effect】
As is apparent from the above description, according to the inner diameter finishing tool for a hydrodynamic bearing sleeve of the present invention, a tapered section that serves as a guide when inserted into the hydrodynamic bearing sleeve and a circular cross-section that performs centering with respect to the hydrodynamic bearing sleeve. The alignment portion has a plurality of partial cylindrical surfaces and a plurality of non-cylindrical surfaces on the outer peripheral surface, and has a machining edge for finishing the inner diameter of the hydrodynamic bearing sleeve extending in the axial direction at the boundary between the partial cylindrical surface and the non-cylindrical surface. A groove having a non-circular cross section, wherein a groove extending in the axial direction is formed on at least one partial cylindrical surface of the processed portion, and the boundary between the inclined surface of the groove located on the upstream side in the rotation direction of the processing tool and the partial cylindrical surface cut since the formation of the blade is inserted into the fluid bearing sleeve guide of the tapered portion of the tip, the core adjusted to the fluid bearing sleeve by alignment of the circular cross-section, the working edge of the working portion Bali grooves is removed, with high accuracy, and is finished at a low cost.
[0024]
In addition , the burrs in the hydrodynamic groove of the fluid bearing sleeve are more reliably removed by the cutting blade at the boundary between the inclined surface of the groove and the partial cylindrical surface, and the fluid bearing sleeve is finished with higher accuracy and lower cost. .
[0025]
Further, since the outer surface is coated with the wear-resistant material, the material of the fluid bearing sleeve is prevented from coming into direct contact with the processing tool during processing, the processing accuracy is stabilized, and the life of the processing tool is improved.
[0026]
According to the fluid bearing sleeve inner diameter finishing apparatus according to the present invention, the machining head provided with the chuck for holding one end of the machining tool, and the movement for moving the machining head in the axial direction of the machining tool held by the chuck. A unit, a work holder that holds the fluid bearing sleeve in the same direction as the machining tool, a moving unit that moves the work holder in two directions perpendicular to the axial direction of the machining tool held by the chuck, and the work holder. Since it includes a stopper that restricts the movement of the work holder within a range that allows the machining tool to be inserted into the fluid bearing sleeve, the machining tool can be used even if the fluid bearing sleeve is misaligned or the machining tool is eccentric. Is surely entered into the hydrodynamic bearing sleeve with the tapered portion at the tip as a guide, and damage and deformation of the hydrodynamic bearing sleeve are prevented. In addition, the fluid bearing sleeve is aligned by a processing tool and is supported movably by a moving unit consisting of a slide bearing at that time. A low cost hydrodynamic bearing sleeve can be obtained stably.
[Brief description of the drawings]
FIG. 1A is a front view of a first embodiment of an inner diameter finishing tool for a hydrodynamic bearing sleeve of the present invention, and FIG. 1B is a cross-sectional view taken along line II of FIG.
FIG. 2A is a front view of a modified example of the first embodiment of the inner diameter finishing tool for a hydrodynamic bearing sleeve of the present invention, and FIG. 2B is a sectional view taken along line II-II in FIG.
3A is a front view of a second embodiment of an inner diameter finishing tool for a hydrodynamic bearing sleeve of the present invention, and FIG. 3B is a sectional view taken along line III-III in FIG.
FIG. 4 is a side view of the hydrodynamic bearing sleeve inner diameter finishing apparatus of the present invention.
5A is a cross-sectional view of a fluid processing bearing before dynamic pressure groove machining, and FIG. 5B is a partial cross-sectional side view of the dynamic pressure groove machining tool.
6A is a cross-sectional view after hydrodynamic groove machining of a fluid machining bearing, and FIG. 6B is a side view of a conventional inner diameter finishing tool.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Processing tool 2 Tapered part 3 Alignment part 4 Processing part 6 Partial cylinder 7 Non-cylindrical surface 8 Processing edge 9 Processing tool 10 Non-cylindrical surface 12 Cutting blade 13 Groove 16 Chuck 17 Processing head 20 Lifting unit 21 Work holder 22 Moving unit 23 Stopper 25 Fluid bearing sleeve 28 Dynamic pressure groove

Claims (4)

A hydrodynamic bearing sleeve inner diameter finishing tool for forming a hydrodynamic groove on the inner surface of the fluid bearing sleeve and then inserting the fluid bearing sleeve to finish the inner diameter, and a taper portion serving as a guide for insertion into the fluid bearing sleeve; A center section having a circular cross-section for centering the fluid bearing sleeve, a plurality of partial cylindrical surfaces and a plurality of non-cylindrical surfaces on the outer peripheral surface, and extending in the axial direction at the boundary between the partial cylindrical surface and the non-cylindrical surface A non-circular cross-section processed portion having a processing edge for finishing the inner diameter of the fluid bearing sleeve,
A groove extending in the axial direction is formed on at least one partial cylindrical surface of the machining portion, and a cutting edge is formed at the boundary between the inclined surface of the groove located on the upstream side in the rotation direction of the machining tool and the partial cylindrical surface. An inner diameter finishing tool for a hydrodynamic bearing sleeve. 2. The hydrodynamic bearing sleeve inner diameter finishing tool according to claim 1, wherein an angle of the cutting edge is formed larger than an angle of the machining edge .   3. The inner diameter finishing tool for a hydrodynamic bearing sleeve according to claim 1, wherein an outer surface is coated with a wear-resistant material.   A machining head comprising a chuck for holding one end of the machining tool according to any one of claims 1 to 3, a lifting unit for raising and lowering the machining head in the axial direction of the machining tool held by the chuck, and a fluid bearing A work holder for holding a sleeve in the same direction as the machining tool, a moving unit for moving the work holder in two directions orthogonal to the axial direction of the machining tool held by the chuck, and a fluid bearing held by the work holder An apparatus for finishing an inner diameter of a hydrodynamic bearing sleeve, comprising: a stopper for restricting movement of the work holder within a range allowing insertion of the processing tool into the sleeve.

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