JP4355192B2 - Method for manufacturing hydrodynamic bearing device - Google Patents

Description

  The present invention relates to a hydrodynamic bearing device in which a shaft member of a hydrodynamic bearing device or a material of the bearing member is used as a workpiece, and deburring processing is performed to remove burrs generated on a workpiece surface of the workpiece. It relates to a manufacturing method.

  In recent years, development of a hydrodynamic bearing device has been advanced so that various rotating bodies can be stably supported even under high-speed rotation. In the hydrodynamic bearing device, a hydrodynamic surface provided on the bearing sleeve (bearing member) side, and a hydrodynamic surface provided on the shaft bush (shaft member) side inserted so as to be relatively rotatable with respect to the bearing sleeve portion, However, a radial or thrust dynamic pressure bearing portion is configured by being opposed to each other in the radial direction or the thrust direction, and a hydrodynamic fluid such as lubricating oil is formed in the bearing space including the dynamic pressure bearing portion. Is filled. When the rotation-side member is driven to rotate, dynamic pressure is generated in the dynamic pressure fluid by a pumping force of an appropriate dynamic pressure generating means, and the bearing sleeve described above is based on the dynamic pressure of the dynamic pressure fluid. And the shaft bush are supported smoothly without contact.

  On the other hand, in such a dynamic pressure bearing device, in order to stably generate dynamic pressure in the dynamic fluid, it is necessary to finish each surface such as the dynamic pressure surface of the shaft member or the bearing member as smooth as possible. There is. Therefore, a deburring process for removing burrs generated on each surface of the shaft member or the bearing member has been conventionally performed.

And as a conventional deburring process,
(1) A needle-shaped electrolysis method in which an electrode for electrolysis is arranged in the vicinity of the surface to be processed so that the metal surface is dissolved electrochemically,
(2) a chemical polishing method in which a metal surface is dissolved by chemical polishing using chemicals;
(3) A machining method for removing metal burrs by mechanical machining means using a brush or a file,
Etc. are adopted.

  However, in any of the conventional methods using the deburring means, in the hydrodynamic bearing device, fine machining powder is generated at the time of processing, and contamination due to micron-order particles and contaminants is a problem. May cause problems such as a locked state due to seizure due to the fine processing powder generated during the deburring process.

  Furthermore, since the hydrodynamic surface of the hydrodynamic bearing device is required to have a high-precision smooth surface, if the deburring process is performed so that the accuracy conforms to it, the processing equipment becomes expensive. In addition, there is a possibility that the dynamic pressure characteristics of the hydrodynamic bearing device may be deteriorated by giving a dimensional effect to a region around the part where the deburring process is performed.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a hydrodynamic bearing device that can perform deburring processing on a material of a shaft member or a bearing member with low cost and high accuracy.

In order to achieve the above object, in the method for manufacturing a hydrodynamic bearing device according to claim 1 of the present invention, a radial hydrodynamic bearing portion and a thrust hydrodynamic bearing portion used in the hydrodynamic bearing device using the dynamic pressure of the lubricating fluid. The material of the bearing member having a workpiece is used as a workpiece, and deburring is performed to remove burrs generated on the workpiece surface of the workpiece, and an annular thrust motion is applied to the workpiece surface of the workpiece. In the method of manufacturing a hydrodynamic bearing device in which the groove for forming the pressure generating groove is formed, the surface to be processed penetrates around the opening of the hole in which the rotation shaft of the motor of the workpiece is disposed. One of the openings of the formed at least one circulation hole is provided, and the electrode tool has an electrode surface disposed facing the processing surface, and the electrode surface of the electrode tool is used as the circulation hole of the processing surface. The burr generated at the opening of Previously formed in an annular shape including, the said annular electrode surface shape, and arranged substantially concentrically with respect to the center of the thrust dynamic pressure generating grooves of the annular said workpiece By placing the electrode tool so as to oppose the processing surface with an appropriate gap, and passing the electrolyte while flowing the electrolyte in the gap between the workpiece and the electrode tool, the workpiece The burr generated on the surface to be processed is removed by electrolytic processing.
According to the method of manufacturing a hydrodynamic bearing device according to claim 1 having such a configuration, the surface to be processed of the workpiece is formed into a highly accurate surface in a short time by simple electrolytic processing, and deburring processing is performed. Is performed well and efficiently, and at the time of processing, the processing powder as in the prior art is not generated, so that the cleanliness is well maintained.
In addition, since the work surface of the work piece is electrolytically processed so as to form an annular shape substantially concentric with the rotation center of the hydrodynamic bearing device, the lubricating fluid flows along the annular work surface. The fluid flows substantially uniformly in the circumferential direction, and the dynamic pressure generated in the lubricating fluid is maintained in a substantially uniform state along the circumferential direction.

Further, in the method for manufacturing a hydrodynamic bearing device according to claim 2 of the present invention, a masking member having a through hole pattern formed so as to include a burr generated on the surface to be processed according to claim 1 is prepared. The masking member having the communication hole pattern is brought into close contact with the surface to be processed of the workpiece, and then the electrolyte is supplied to the gap between the masking member and the electrode tool. The electrolyte solution enters the inside of the communication hole pattern to flow.
According to the manufacturing method of the hydrodynamic bearing device according to claim 2 having such a configuration, the communication hole pattern of the masking member in which the electrolyte supplied to the workpiece is brought into close contact with the workpiece. It is allowed to flow only into the inside, and the electrolytic processing to the non-working surface is surely prevented by the masking action on the non-working surface around the site to be deburred. In addition, it is possible to improve the fluidity of the electrolyte by widening the gap between the workpiece and the electrode tool, and the shape corresponding to the communication hole pattern of the masking member is highly accurate for the workpiece. Thus, the deburring process is favorably performed.

Furthermore, in the electrolytic processing method according to claim 3 of the present invention, the material of the bearing member having the radial dynamic pressure bearing portion and the thrust dynamic pressure bearing portion used in the dynamic pressure bearing device using the dynamic pressure of the lubricating fluid is processed. As a product, a deburring process for removing burrs generated on the work surface of the work piece is performed, and a groove process for forming a thrust dynamic pressure generating groove on the work surface of the work piece is performed. In the method for manufacturing a hydrodynamic bearing device, the surface to be processed includes one of openings of a circulation hole formed through the workpiece, and a communication hole pattern corresponding to an opening shape of the thrust dynamic pressure generating groove And a through hole pattern having a shape including a burr generated on the surface to be processed is formed through the same masking member, and the masking member having the through hole pattern is formed in the front. After close contact with the workpiece surface of the workpiece, the relative workpiece surface of a workpiece, and arranged to face the electrode tool at an appropriate gap between these workpiece and electrode tool By energizing while flowing the electrolyte solution in the gap, the electrolyte solution enters the communication hole pattern of the masking member, and at the same time performing the groove processing of the thrust dynamic pressure generating groove by electrolytic processing, The burrs generated on the surface of the workpiece are removed by electrolytic processing.
According to the method for manufacturing a hydrodynamic bearing device according to claim 3 having such a configuration, the surface to be processed of the workpiece is formed into a highly accurate surface in a short time by simple electrolytic processing, and dynamic pressure is generated. Both grooving and deburring of the grooving grooves are performed simultaneously and efficiently, and the processing powder is not generated at the time of processing so that the cleanliness is maintained well. It has become.

In addition, the electrolytic solution supplied to the workpiece is allowed to flow only in the communication hole pattern of the masking member in close contact with the workpiece, so that a dynamic pressure generating groove should be formed. The masking action on the non-machined surface around the site and the site to be deburred ensures that the electrochemical machining on the non-machined surface is prevented. In addition, it is possible to improve the fluidity of the electrolyte by widening the gap between the workpiece and the electrode tool, and the shape corresponding to the communication hole pattern of the masking member is highly accurate for the workpiece. Therefore, both the groove processing and the deburring processing of the dynamic pressure generating groove are performed satisfactorily.

In the method for manufacturing a hydrodynamic bearing device according to claim 4 of the present invention, the masking member according to claim 2 or 3 is a fluorine-modified insulating member having flexibility and at least a surface of a metal member. made from those provided in a portion, in the method of manufacturing a dynamic pressure bearing device according to claim 5 of the present invention, the masking member in the claim 2 or claim 3, insulating plastic material having flexibility Formed from.
According to the method of manufacturing a hydrodynamic bearing device according to claim 4 or 5 having such a configuration, the flexible masking member is a portion or burr that forms a dynamic pressure generating groove on the surface to be processed. The non-machined surface of the non-machined surface is surely prevented from being bent along the non-machined surface around the part to be machined. Is ensured, and the electrolytic processing of the portion to be processed is performed well.

Furthermore, in the method for manufacturing a hydrodynamic bearing device according to claim 6 of the present invention, the electrode surface provided on the electrode tool according to claim 3 has an annular shape including burrs generated on the surface to be processed. The annular electrode surface is arranged so as to be substantially concentric with the rotation center of the hydrodynamic bearing device, and electrolytic processing is performed.
According to the method of manufacturing a fluid dynamic bearing device according to claim 6 having such a configuration, the surface to be processed of the workpiece has an annular shape substantially concentric with the rotation center of the fluid dynamic bearing device. Since the electrolytic processing is performed, the lubricating fluid flows substantially uniformly in the circumferential direction along the annular processing surface, and the dynamic pressure generated in the lubricating fluid is also substantially uniform along the circumferential direction. To be maintained.

On the other hand, in the method for manufacturing a hydrodynamic bearing device according to claim 7 of the present invention, since a liquid mixture with a surfactant is used as the electrolytic solution in claim 1 or claim 3, Various particles such as the eluted electrolytic product are easily separated by the surfactant in the electrolytic solution, and a smooth flow of the electrolytic solution is ensured.

Further, in the method for manufacturing a hydrodynamic bearing device according to claim 8 of the present invention, ultrasonic vibration generating means for applying ultrasonic vibration to the electrolytic solution according to claim 1 or 3 is provided. Various particles such as electrolytic products eluted from the workpiece are smoothly flowed by ultrasonic vibration applied to the electrolytic solution.

Furthermore, in the manufacturing method of the hydrodynamic bearing device according to claim 9 , the energization for ultrasonic vibration in claim 8 is performed independently from the energization for electrolytic processing, and in the electrolytic processing method according to claim 10 , The energization for ultrasonic vibration and the energization for electrolytic processing in claim 9 are performed alternately or at least a part of each energization is overlapped. The best machining state is always obtained by appropriately switching between the energization for electrolytic processing and the energization for ultrasonic vibration.

Furthermore, in the method for manufacturing a hydrodynamic bearing device according to an eleventh aspect of the present invention, the both side walls of the concave portion forming the dynamic pressure generating groove in the third aspect are continuous from the bottom wall surface toward the opening. In other words, it is formed on a tapered surface inclined in the direction of enlargement.
According to the method for manufacturing a hydrodynamic bearing device according to claim 11 having such a configuration, the corners of the opening edge of the hydrodynamic pressure generating groove are formed in a chamfered state, and when starting and stopping the rotation For example, even when the counterpart member contacts the corner portion, contact wear at the chamfered corner portion is reduced, and shortening of the life of the hydrodynamic bearing device is prevented.

  As described above, the manufacturing method of the hydrodynamic bearing device according to the present invention uses the shaft member or the material of the bearing member used in the hydrodynamic bearing device using the dynamic pressure of the lubricating fluid as a workpiece, and the workpiece is processed. By placing the electrode tool so as to oppose the workpiece surface with an appropriate gap, and applying current while flowing the electrolyte in the gap between the workpiece and the electrode tool, Since it is configured to perform the groove processing or deburring processing of the generating groove with good and efficient electrolytic processing and maintain good cleanliness, the deburring processing on the material of the shaft member or the bearing member or The groove processing of the dynamic pressure generating groove can be performed at low cost and with high accuracy, and a low-cost and highly reliable dynamic pressure bearing device can be easily obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Prior to that, an outline of a spindle motor for a hard disk drive (HDD) as an example in which a hydrodynamic bearing device according to the present invention is employed will be described. Let me explain.

  The entire shaft rotation type HDD spindle motor shown in FIG. 8 includes a stator set 20 as a fixed member and a rotor set 30 as a rotary member assembled to the stator set 20 from the upper side in the drawing. It is configured. Among them, the stator set 20 has a fixed frame 21 that is screwed to the fixed base side (not shown). The fixed frame 21 is made of an aluminum-based metal material in order to reduce the weight, but the inner peripheral surface of the annular bearing holder 22 formed so as to be erected at the substantially central portion of the fixed frame 21. On the side, a bearing sleeve 23 as a dynamic pressure bearing member formed in a hollow cylindrical shape is joined to the bearing holder 22 by press fitting or shrink fitting. The bearing sleeve 23 is made of a copper-based material, particularly phosphor bronze in the present embodiment, in order to facilitate processing of a small-diameter hole.

  A stator core 24 made of a laminated body of electromagnetic steel sheets is fitted on the outer peripheral side mounting surface of the bearing holder 22, and a drive coil 25 is mounted on each salient pole portion provided on the stator core 24. It is wound.

  Further, a rotary shaft 31 constituting the rotor set 30 is rotatably inserted into a center hole provided in a bearing sleeve 23 as the dynamic pressure bearing member. That is, the dynamic pressure surface formed on the inner peripheral wall portion of the bearing sleeve 23 described above is disposed so as to face the dynamic pressure surface formed on the outer peripheral surface of the rotating shaft 31 close to the radial direction, Two radial dynamic pressure bearing portions RB and RB are formed in a bearing space including a small facing gap between the two dynamic pressure surfaces with an appropriate interval in the axial direction. More specifically, the dynamic pressure surface on the bearing sleeve 23 side and the dynamic pressure surface on the rotating shaft 31 side in the radial dynamic pressure bearing portion RB are arranged to oppose each other in a circumferential manner with a slight facing gap of several μm, Lubricating fluid such as lubricating oil or magnetic fluid is injected into the bearing space including the minute facing gap so as to continue in the axial direction.

  Furthermore, on at least one side of both the dynamic pressure surfaces of the bearing sleeve 23 and the rotating shaft 31, a radial dynamic pressure generating groove having a herringbone shape, for example, is divided into two blocks in the axial direction and is annularly recessed. During rotation, the lubricating fluid (not shown) is pressurized by the pumping action of the radial dynamic pressure generating groove to generate dynamic pressure, and the rotational pressure described later together with the rotary shaft 31 is generated by the dynamic pressure of the lubricating fluid. The hub 22 is configured to be axially supported in a non-contact state in the radial direction with respect to the bearing sleeve 23.

  On the other hand, the rotating hub 32 that constitutes the rotor set 30 together with the rotating shaft 31 is formed of a substantially cup-shaped member made of aluminum, stainless steel, or the like, and is formed through the central portion of the rotating hub 32. The joint hole 32a is integrally joined to the illustrated upper end portion of the rotary shaft 31 by press fitting or shrink fitting. The rotating hub 32 has a substantially cylindrical barrel portion 32b on which a recording medium disk such as a magnetic disk (not shown) is mounted on the outer peripheral portion, and projects by projecting radially outward from the barrel portion 32b. The recording medium disk is provided with a disk mounting portion 32c for supporting the medium disk in the axial direction, and is fixed to the recording medium disk by a pressing force from the upper side of the figure by a clamper (not shown) screwed so as to be covered from the upper side of the figure. Is to be done.

  An annular drive magnet 32e is attached to the inner peripheral wall surface side of the body portion 32b of the rotary hub 32 via a yoke 32d made of an annular magnetic member. The inner peripheral surface of the annular drive magnet 32e is arranged so as to be close to and opposed to the end surface on the outer peripheral side of each salient pole portion of the stator core 24 described above, and the axially lower side of the annular drive magnet 32e. The end face is in a positional relationship facing the magnetic attraction plate 26 attached to the above-described fixed frame 21 side in the axial direction, and the above-described rotating hub is caused by the magnetic attraction force between these members 32e and 26. The whole 32 is magnetically attracted in the axial direction so that a stable rotational state can be obtained.

  Further, an opening provided on the lower end side of the bearing sleeve 23 is closed by a cover 23a so that the lubricating fluid in each of the radial dynamic pressure bearing portions RB described above does not leak to the outside. .

  Furthermore, the illustrated upper end surface of the bearing sleeve 23 and the illustrated lower end surface of the center side portion of the rotating hub 32 are disposed so as to face each other in a state of being close to each other in the axial direction. A thrust dynamic pressure bearing portion SB continuous from the above-described radial bearing portion RB is provided in a bearing space including a facing gap between the illustrated upper end surface and the illustrated lower end surface of the rotating hub 32. That is, on at least one side of the opposed dynamic pressure surfaces 23 and 32 constituting the opposed region, for example, a thrust having a herringbone shape as shown in FIG. 9 or a spiral shape not shown. A dynamic pressure generating groove SG is formed, and the axially opposed portion including the thrust dynamic pressure generating groove SG is formed in the thrust dynamic pressure bearing portion SB.

  A small clearance of several μm is present between the dynamic pressure surface on the upper end surface side of the bearing sleeve 23 constituting the thrust dynamic pressure bearing portion SB and the dynamic pressure surface on the lower end surface side of the rotating hub 32 adjacent to the bearing sleeve 23. And a lubricating fluid such as oil or magnetic fluid is continuously filled from the above-described radial dynamic pressure bearing portion RB in the bearing space formed by the minute gap. During rotation, the lubricating fluid is pressurized by the pumping action of the thrust dynamic pressure generating groove described above to generate dynamic pressure, and the rotating shaft 31 and the rotating hub 32 float in the thrust direction by the dynamic pressure of the lubricating fluid. The shaft is supported in a non-contact state.

  Further, a fluid seal portion including a capillary seal portion SS is defined by the outer peripheral wall surface of the bearing sleeve 23 as the dynamic pressure bearing member. That is, the capillary seal portion SS as the fluid seal portion is provided so as to be continuously provided from the radially outer side with respect to the bearing space including the thrust dynamic pressure bearing portion SB described above. The capillary seal portion SS is defined by an outer peripheral wall surface of the counter plate 34 and an inner peripheral wall surface of the counter plate 34 as a retaining member formed so as to face the outer peripheral wall surface of the bearing sleeve 23 in the radial direction. The counter plate 34 is composed of a ring-shaped member fixed to a flange portion 32f provided so as to protrude in the axial direction from the rotary hub 32 described above. A taper-shaped seal space is defined by continuously expanding a gap between the outer peripheral wall surface and the opening on the lower side in the figure. The lubricating fluid in the thrust dynamic pressure bearing portion SB described above is continuously filled up to the capillary seal portion SS.

  At this time, the upper end portion of the bearing sleeve 23 shown in the drawing is provided with a retaining collar 23b so as to project outward in the radial direction, and a part of the retaining collar 23b is described above. It arrange | positions so that a part of counterplate 34 may be opposed to an axial direction. These two members 23b and 34 are configured to prevent the rotating hub 32 from coming off in the axial direction.

  On the other hand, the bearing sleeve 23 described above may be formed with a bypass passage (circulation hole) BP for adjusting the pressure of the lubricating fluid as shown in FIG. 10, for example. The reason why the pressure adjusting bypass passage (circulation hole) BP is provided will be described together with the structure. First, in each of the two radial dynamic pressure bearing portions RB arranged in the minute gap between the bearing sleeve 23 and the rotary shaft 31, The radial dynamic pressure generating grooves as described above are formed. The radial dynamic pressure generating groove is formed, for example, from an annular assembly of herringbone-shaped bent grooves formed so as to form a substantially "<" shape. It is basically configured to form a groove shape that is symmetrical in the axial direction, with the position corresponding to the apex portion of the shaft as the center, and the pumping action by the radial dynamic pressure generating groove having the symmetrical groove shape is as follows. , A balanced state in the axial direction.

  Therefore, in terms of design, the lubricating fluid is not pushed to one side in the axial direction by the balanced pumping force by each of the radial dynamic pressure bearing portions RB described above. The gap size in each radial dynamic pressure bearing portion RB, the groove shape (groove length) of the dynamic pressure generating groove, etc. may be formed into an unbalanced shape in the axial direction due to manufacturing errors, etc. The pumping force in the radial dynamic pressure bearing portion RB may be in an unbalanced state.

  For this reason, in the embodiment shown in FIG. 10, a plurality of pressure adjusting bypass passages (circulation holes) BP are formed through the bearing sleeve 23 in the axial direction. Yes. A plurality of pressure adjusting bypass passages BP provided in the bearing sleeve 23 are formed so as to penetrate the bearing sleeve 23 in the axial direction separately from the bearing space including the radial dynamic pressure bearing portions RB described above. The bearing sleeve 23 is formed so as to have openings BP1 and BP2 on both end surfaces in the axial direction. Of these openings BP1 and BP2, the opening BP2 arranged on the upper end surface of the bearing sleeve 23 is a gap between the lower surface of the rotating hub 62 and the upper end surface of the bearing sleeve 23. The thrust dynamic pressure bearing portion SB formed on the upper surface and the radial dynamic pressure bearing portion RB on the upper side of the drawing arranged so as to be continuous with the thrust dynamic pressure bearing portion SB are disposed so as to open in the bearing space. ing.

  That is, the opening BP2 on the upper side of the pressure adjusting bypass passage BP is formed to have a larger axial interval than the thrust dynamic pressure bearing portion SB at a portion radially inward of the thrust dynamic pressure bearing portion SB. The enlarged gap portion LS is opened, and by providing such an enlarged gap portion LS, a good communication state is formed between the pressure adjusting bypass passage BP and the bearing space. The flow of this is done well. Of the openings BP1 and BP2 of the pressure adjusting bypass passage BP, the opening BP1 disposed on the lower end surface of the bearing sleeve 23 is formed by the lower end surface of the bearing sleeve 23 and the cover 53a. It arrange | positions so that it may open toward the space of the axial direction outer side defined.

  On the other hand, such a pressure adjusting bypass passage BP is cut by using a long tool such as a drill. At that time, the pressure adjusting bypass passage BP is formed at the peripheral edge portions of both end openings BP1 and BP2 of the pressure adjusting bypass passage BP. Will occur so that the burr | flash by processing protrudes from an end surface. In the present invention, such a processing burr is quickly and satisfactorily removed by an electrolytic processing method using an electrolytic processing apparatus as shown in FIG. 1, FIG. 2, FIG. 3, and FIG. .

  That is, the deburring process in the present embodiment is performed by electrolytic machining simultaneously with the groove machining of the thrust dynamic pressure generating groove SG as shown in FIG. 9 described above. For example, as shown in FIG. 11, the workpiece W composed of the bearing sleeve 23 (or the rotating hub 32) is first subjected to a rolling process to roughen the thrust dynamic pressure generating groove SG. Then, degreasing is performed thereafter, and then an electrolytic machining process as described below is performed to perform deburring, and at the same time, a thrust dynamic pressure generating groove having a groove depth of, for example, 14 μm to 20 μm. SG is formed. Hereinafter, an embodiment of the electrolytic processing step at this time will be described together with the structure of the electrolytic processing apparatus.

  That is, first, as shown in FIGS. 1, 2, 3, and 4, a work mounting recess is provided in the substantially central portion of the work support jig 42 mounted on the main body base 41. In the workpiece mounting recess, the material W (hereinafter simply referred to as the workpiece) W of the bearing sleeve 23 or the rotary hub 32 as the workpiece is placed in the horizontal direction. Held in a state. As the workpiece W in the present embodiment, a material made of, for example, a phosphor bronze material is employed.

  A masking member 43 made of a thin disc-shaped insulating member as shown in FIG. 3 is mounted on the surface of the workpiece W on the upper side in the drawing so as to be in close contact therewith. The masking member 43 is formed of a disk-shaped member having a diameter slightly larger than the outer diameter of the workpiece W, and the outer peripheral edge portion of the masking member 43 is formed by the cap-shaped member 44 with the work support jig. It is fixed so as to be pressed downward in the figure with respect to the 42 side.

  The masking member 43 is formed of an insulating member having flexibility, but it is sufficient that an insulating material is formed at least on the surface portion. For example, a metal metal member made of stainless steel (SUS) or the like is used. At least the surface portion is provided with a fluorine-modified flexible insulating member coated from 10 μm to 30 μm or a flexible insulating plastic material. Moreover, what electroplated with respect to the stainless steel plate (SUS) etc. is employable. The plate thickness of such a masking member 43 is set to a thin thickness of about 0.05 mm to 0.1 mm, for example.

  In the masking member 43 in this embodiment, two types of communication hole patterns 43a and 43b are formed so as to penetrate in the plate thickness direction. That is, in the present embodiment, a configuration in which a masking member used for electrolytic processing for deburring and a masking member used for electrolytic processing of the dynamic pressure generating groove SG is used in common, and deburring and dynamics are adopted. The groove processing of the pressure generating groove SG is simultaneously performed by electrolytic processing.

  More specifically, of the communication hole patterns 43a and 43b, the communication hole pattern 43a has a substantially arc shape so as to include the circular shapes of the both end openings BP1 and BP2 of the pressure adjusting bypass passage BP. The non-processed surface corresponding to the periphery of the openings BP1 and BP2 of the pressure adjusting bypass passage BP is covered with the main body of the masking member 43 described above. It has been masked. On the non-processed surface around the openings BP1 and BP2 of the pressure adjusting bypass passage BP that has been masked in this way, the electrolytic processing is prevented, while the pressure positioned in the inner region of the communication hole pattern 43a. Deburring processing by electrolytic processing is performed on the openings BP1 and BP2 of the adjustment bypass passage BP.

  On the other hand, the other communication hole pattern 43b provided in the masking member 43 has a shape corresponding to the thrust dynamic pressure generating groove SG and is formed so as to penetrate in the plate thickness direction. Further, the portion other than the communication hole pattern 43b, that is, as shown in FIG. 5, the outer surface of the convex portion extending in the horizontal direction in the drawing from both opening edge portions SGa and SGa of the dynamic pressure generating groove SG The portions corresponding to SGb and SGb are covered and masked by the masking member 43 described above. Electrolytic machining is prevented on the outer surfaces SGb and SGb of the convex portions subjected to this masking.

  As described above, in the present embodiment, in addition to the substantially arc-shaped communication hole pattern 43a including the circular shape of the both end openings BP1 and BP2 of the pressure adjusting bypass passage BP, the shape corresponding to the dynamic pressure generating groove SG. The communication hole pattern 43b is formed so as to penetrate the same common masking member.

  Returning to FIG. 1 again, an electrode tool 45 made of a hollow bar-like member is arranged so as to stand in a substantially vertical direction at a position immediately above the workpiece W and the masking member 43 described above. The electrode tool 45 is fixed or held to the main body arm portion 46 extending above the main body base portion 41 described above. In particular, as shown in FIG. The lower end portion is arranged so as to form a gap δ of, for example, about 1 mm during the electrolytic processing with the masking member 43. In addition, a negative electrode (−) of a DC power source having an output voltage of, for example, about 5 V to 45 V is connected to the electrode tool 45, and a positive electrode (+ electrode) of the DC power source is connected to the workpiece W. Connected to the side.

  Furthermore, a liquid passage 45a is formed through the central portion of the electrode tool 45 along the axial direction, and electrolysis is performed from the upper end side of the liquid passage 45a by an electrolyte supply means (pump) (not shown). The liquid is supplied. As the electrolytic solution at this time, for example, a 10-30 wt% solution of NaNo3 is used, and the electrolytic solution fed from the upper side of the electrode tool 45 in the drawing passes through the liquid passage 45a and is shown on the lower end side in the drawing. Is supplied so as to fall on the above-described masking member 43 and the workpiece W through the outlet portion provided in the workpiece. The electrolyte supplied to the central portion flows radially outward in the radial direction and is stored in a tray (not shown). In addition, as the above-described electrolytic solution, 3 to 10% by weight of KOH, 3 to 10% by weight of NaOH, 5 to 15% by weight of Na2Co3, or the like may be used.

  In this way, energization is performed between the electrode tool 45 and the workpiece W while flowing the electrolyte in the gap δ between the electrode tool 45 and the masking member 43 and the workpiece W. In this case, the electrolytic solution flows into the inside of the communication hole pattern 43 a provided in the masking member 43, and the electrolytic solution flows while contacting the exposed surface of the workpiece W from the masking member 43. To do. And the part which the electrolyte solution of the to-be-processed object W contacted is eluted electrochemically, and the to-be-processed object W is electrolytically processed.

  Furthermore, a vibration exciter 47 constituting ultrasonic vibration generating means is attached to the uppermost end portion of the electrode tool 45 shown in the figure. As the vibrator 47 in the present embodiment, a horn type that amplifies the amplitude to 20 to 22 μm is used, and by vibrating the electrode tool 45, the above-described electrolyte solution is used. It is comprised so that an ultrasonic vibration may be given.

  At this time, in the present embodiment, the energization for electrolytic processing and the energization for ultrasonic vibration are performed independently, and the actual energization mode is as shown in FIG. Using rectangular pulsed current, energization Pa for electrolytic machining and energization Pb for ultrasonic vibration are alternately performed, or as shown in FIG. The energization Ca and the energization Cb for ultrasonic vibration can be performed so as to partially overlap each other. In both methods, particles such as electrolytic products can be removed by ultrasonic vibration while performing electrolytic processing.

  Furthermore, as the above-described electrolytic solution, a mixed solution of a surfactant is used. The surfactant used in the present embodiment is a nonionic surfactant alkyl ether, which is added in an amount of 0.03% or more by volume.

  As described above, in this embodiment, the surface to be processed of the material of the bearing sleeve 23 as the workpiece W is formed into a highly accurate surface in a short time by simple electrolytic processing. Both the groove processing of the pressure generating groove SG and the deburring processing of the inside of the pressure adjusting bypass passage BP and the peripheral portions of the openings BP1 and BP2 are simultaneously and efficiently performed. And at the time of the electrolytic processing, the conventional processing powder does not generate | occur | produce and the clean environment is favorably maintained. It should be noted that such deburring by electrolytic processing can be performed separately and independently from the groove processing of the thrust dynamic pressure generating groove SG.

  Actually, when the deburring process was performed on the peripheral portions of the openings BP1 and BP2 of the pressure adjusting bypass passage BP using the above-described electrolytic processing apparatus, for example, as shown in FIG. It was measured that the machining burr A previously formed into a protrusion shape was removed so as to form an almost perfect smooth surface as shown in FIG. 13 after electrolytic machining. And it was confirmed that the electrolytic processing at that time is performed extremely well and quickly.

  Further, in the present embodiment, the electrolytic solution supplied to the workpiece W is caused to flow only inside the communication hole patterns 43a and 43b of the masking member in close contact with the workpiece W. Even if the gap between the masking member 43 and the workpiece W and the electrode tool 45 is widened to improve the fluidity of the electrolytic solution, the formation site of the thrust dynamic pressure generating groove SG and the deburring site The masking action on the non-processed surface in the peripheral region of the substrate reliably prevents electrolytic processing on the non-processed surface. Further, by widening the gap between the workpiece W and the electrode tool, it is possible to improve the fluidity of the electrolyte, and the shape corresponding to the communication hole patterns 43a and 43b in the masking member 43 has a shape corresponding to the workpiece. By being formed with high accuracy with respect to W, both the formation of the thrust dynamic pressure generating groove SG and the deburring process are favorably performed.

  In particular, in the above-described embodiment, since the masking member 43 is formed of an insulating member, energization to the portions other than the communication hole patterns 43a and 43b in the masking member 43 is almost completely cut off. The deburring process and the groove processing of the thrust dynamic pressure generating groove SG are formed with higher accuracy.

  Furthermore, in the above-described embodiment, the outer surfaces SGb, SGb of the convex portions extending in the horizontal direction in the drawing from the both opening edge portions SGa, SGa of the thrust dynamic pressure generating groove SG are covered with the masking member 43 for masking. Therefore, even when phosphor bronze having high ionization property is used as the workpiece W as in the present embodiment, the electrolytic machining is surely prevented, and the outer surface SGb of the convex portion, The shape of SGb is satisfactorily formed.

  In the present embodiment, since the above-described masking member 43 is formed of a flexible insulating fluorine-modified material or plastic material, the non-processed surface around the portion to be deburred, and the above-mentioned The flexible masking member 43 is in close contact with the outer surface SGb of the convex portion continuous with the opening edge portions SGa and SGa of the thrust dynamic pressure generating groove SG. Due to the good adhesion of the masking member 43 to the opening edges SGa, SGa of the generating groove SG, electrolytic processing to the outer surface SGb of the convex part is reliably prevented, and the opening edge SGa of the thrust dynamic pressure generating groove SG. Electrolytic processing for both side wall surfaces SGd and SGd extending from the SGa toward the bottom wall surface side SGc is reliably performed.

  This point will be described in more detail. Both side wall surfaces SGd and SGd of the concave portion forming the thrust dynamic pressure generating groove SG described above are opened edge portions from the bottom wall surface SGc side of the thrust dynamic pressure generating groove SG. The taper surface which inclines in the direction which expands an opening part toward SGa and SGa side is formed favorably, and the outside of the convex part by which electrolytic processing is prevented reliably by the masking member 43 as mentioned above Both side wall surfaces SGd, SGd of the thrust dynamic pressure generating groove SG continuous from the surface SGb are formed to have a tapered surface shape by electrolytic processing, so that the opening edges SGa, SGa of the thrust dynamic pressure generating groove SG are formed. Will be formed in an R-shaped or C-shaped chamfered state. Even when the rotation of the motor after assembling is started or stopped, even when the counterpart member contacts the opening edge SGa, SGa of the thrust dynamic pressure generating groove SG described above, the portion is chamfered. Therefore, the contact wear is reduced, and accordingly, the shortening of the life of the hydrodynamic bearing device is prevented.

  Furthermore, in this embodiment, since a mixed solution with a surfactant is used as the electrolytic solution, various particles such as electrolytic products from the workpiece W are absorbed by the surfactant in the electrolytic solution. As a result, smooth flow is ensured.

  Furthermore, in this embodiment, since the ultrasonic vibration generating means 47 for applying ultrasonic vibration to the electrolytic solution is provided, various particles such as electrolytic products eluted from the workpiece W are applied to the electrolytic solution. It is made to flow smoothly by ultrasonic vibration.

  In addition, in the manufacturing method of the hydrodynamic bearing device in the present embodiment, the energization for electrolytic processing and the energization for ultrasonic vibration are performed independently, and the energization Pa and Ca for electrolytic processing and ultrasonic vibration are performed. Current energization Pb and Cb are alternately performed or at least a part of each of the current energies is overlapped. Therefore, depending on the situation of electrolytic machining, the current for electrolytic machining and ultrasonic vibration are used. The best machining state is always obtained by appropriately switching between energization.

  On the other hand, in the embodiment shown in FIG. 14, the masking member as in the above-described embodiment is not used, and the electrode surface 55b provided on the electrode tool 55 serves as the workpiece W described above. With respect to the material of the bearing sleeve 23, the arrangement relationship is directly opposed in the axial direction without interposing a masking member.

  That is, the electrode tool 55 used in this embodiment is formed so as to have a hollow cylindrical shape, and is formed so that a liquid passage 55a for feeding the electrolyte into the hollow penetrates in the axial direction. In addition, the electrode surface 55b formed on the lower end surface in the figure is formed in an annular shape. The annular electrode surface 55a is formed so as to include a processing burr generated on the surface to be processed, and the annular electrode surface 55a is formed on the above-described hydrodynamic bearing device. Electrolytic processing is performed while feeding the electrolytic solution through the liquid passage 55a in a state of being arranged so as to be substantially concentric with the center of rotation.

  According to the present embodiment having such a configuration, when the work W is deburred, the work surface of the work W (the material of the bearing sleeve 23) is a hatched region in FIG. As indicated by W1, it is electrolytically processed so as to form an annular shape substantially concentric with the rotation center of the hydrodynamic bearing device. As a result, the lubricating fluid flows substantially uniformly in the circumferential direction along the processing surface W1 having the annular shape, and the dynamic pressure generated in the lubricating fluid is maintained in a substantially uniform state along the circumferential direction. As a result, good dynamic pressure characteristics are maintained.

  As mentioned above, although the embodiment of the invention made by the present inventor has been specifically described, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. Not too long.

  For example, in the above-described embodiment, the present invention is applied to a hydrodynamic bearing device of a hard disk drive motor (HDD). However, other hydrodynamic bearing devices and various workpieces W are used. The same can be applied to the electrolytic processing method.

  In the above-described embodiment, the deburring process is performed simultaneously with the groove processing of the thrust dynamic pressure generating groove SG using the masking member 43. However, only the deburring process is performed using the masking member. Also good.

  Furthermore, in the above-described embodiment, the masking member 43 is formed of an insulating member having flexibility. However, the masking member 43 does not necessarily have flexibility. In particular, the masking member 43 does not have to be flexible when the processing accuracy of the workpiece is not required as in the deburring process. Therefore, the masking member 43 includes polyetheretherketone (PEEK), polyimide (PI), polyamideimide (PAI), duracon, urethane, fluorine-modified urethane, fluororubber, polytetrafluoroethylene, fluorine-modified electrodeposition paint, PI An insulating member such as an electrodeposition coating can be used without considering the flexibility.

  The present invention described above can be widely applied to a hydrodynamic bearing device used in various types of rotary drive devices including various motors.

It is front sectional explanatory drawing showing the schematic structure of an example of the electrolytic processing apparatus for implementing this invention. It is side surface explanatory drawing showing the schematic structure of the electrolytic processing apparatus for implementing this invention shown in FIG. FIG. 3 is an explanatory plan view showing the structure of a masking member used in the electrolytic processing apparatus shown in FIGS. 1 and 2. FIG. 4 is an external explanatory view of a main part of the apparatus showing a use state of the electrolytic processing apparatus shown in FIGS. 1 to 3. FIG. 5 is a diagram illustrating an example of an energized state in the electrolytic processing apparatus illustrated in FIGS. 1 to 4. FIG. 5 is a diagram showing another example of the energized state in the electrolytic processing apparatus shown in FIGS. 1 to 4. FIG. 3 is a partially enlarged longitudinal sectional view showing a state in which a masking member is mounted on a work surface of a bearing sleeve as a work W. It is longitudinal cross-sectional explanatory drawing showing the structural example of the hard disk drive motor (HDD) as an example of an apparatus which has a hydrodynamic bearing apparatus manufactured by the electrolytic processing of this invention. It is plane explanatory drawing showing an example of the shape of groove | channel SG for thrust dynamic pressure generation manufactured by the electrolytic processing of this invention. It is process explanatory drawing showing an example of all the processes which manufacture the groove | channel SG for thrust dynamic pressure generation by the electrolytic processing of this invention. It is longitudinal cross-sectional explanatory drawing which expanded and represented the principal part of the dynamic pressure bearing apparatus. FIG. 12 is an enlarged diagram of a result of measuring a shape of a processing burr generated on an end surface of a bearing sleeve of the fluid dynamic bearing device illustrated in FIG. 11. FIG. 12 is an enlarged diagram of a result of measuring a shape after removing a processing burr generated on an end surface of a bearing sleeve of the fluid dynamic bearing device illustrated in FIG. 11 by electrolytic processing. It is an external appearance perspective explanatory drawing which expanded and represented the site | part of the electrode surface of the electrode tool in embodiment made to perform an electrolytic process without using a masking member. FIG. 15 is an explanatory plan view illustrating an end surface portion of a bearing sleeve that has been subjected to electrolytic processing using the electrode tool according to the embodiment illustrated in FIG. 14.

20 Stator assembly 23 Bearing sleeve 30 Rotor assembly 31 Rotating shaft 32 Rotating hub 34 Counter plate SG Thrust thrust dynamic pressure generating groove SG
SB Thrust dynamic pressure bearing BP Pressure adjustment bypass passage (circulation hole for lubricating fluid)
BP1, BP2 Opening part 41 Main body base part 42 Work support jig 43 Masking member 43a, 43b Communication hole pattern 44 Cap-like member 45 Electrode tool 45a Liquid passage 47 Exciter W Workpiece

Claims (11)

A bearing member material having a radial dynamic pressure bearing portion and a thrust dynamic pressure bearing portion used in a hydrodynamic bearing device using the dynamic pressure of a lubricating fluid is used as a workpiece, and is generated on the workpiece surface of the workpiece. In the method of manufacturing a hydrodynamic bearing device, in which a deburring process for removing burrs is performed , and a groove for forming a thrust dynamic pressure generating groove in an annular shape is formed on a processing surface of the workpiece ,
The surface to be processed includes one of openings of at least one circulation hole formed through the periphery of the opening of the hole in which the rotation shaft of the motor of the workpiece is disposed,
The electrode tool has an electrode surface disposed facing the surface to be processed,
The electrode surface of the electrode tool is formed in an annular shape including burrs generated at the opening of the circulation hole on the surface to be processed,
The annular electrode surface is arranged so as to be substantially concentric with the center of the annular dynamic groove for generating thrust dynamic pressure , and an appropriate gap is provided with respect to the workpiece surface of the workpiece. And place the electrode tools facing each other,
The burrs generated on the workpiece surface of the workpiece are removed by electrolytic machining by energizing the electrolyte while flowing the gap between the workpiece and the electrode tool. Method for manufacturing a hydrodynamic bearing device. Preparing a masking member having a through hole pattern formed in a shape including burrs generated on the surface to be processed;
After adhering the masking member having the communication hole pattern to the workpiece surface of the workpiece,
2. The electrolyte solution is supplied into a gap between the masking member and the electrode tool so that the electrolyte solution enters and flows into the communication hole pattern of the masking member. The manufacturing method of the hydrodynamic bearing apparatus of description. A bearing member material having a radial dynamic pressure bearing portion and a thrust dynamic pressure bearing portion used in a hydrodynamic bearing device using the dynamic pressure of a lubricating fluid is used as a workpiece, and is generated on the workpiece surface of the workpiece. In the method of manufacturing a hydrodynamic bearing device, in which a deburring process for removing burrs is performed and a groove process for forming a thrust dynamic pressure generating groove is formed on a processing surface of the workpiece,
The surface to be processed includes one of openings of circulation holes formed through the workpiece.
A communication hole pattern corresponding to the opening shape of the thrust dynamic pressure generating groove and a communication hole pattern having a shape including a burr generated on the surface to be processed are formed through the same masking member.
After adhering the masking member having the communication hole pattern to the workpiece surface of the workpiece,
Arrange the electrode tool to face the workpiece surface of the workpiece with an appropriate gap,
By energizing the electrolyte while flowing the electrolyte in the gap between the workpiece and the electrode tool, the electrolyte enters the communication hole pattern of the masking member, and the groove of the thrust dynamic pressure generating groove A method of manufacturing a hydrodynamic bearing device, wherein burrs generated on a surface to be processed of the workpiece are removed by electrolytic processing simultaneously with processing by electrolytic processing.   4. The motion according to claim 2, wherein the masking member has a configuration in which a fluorine-modified insulating member having flexibility is provided on at least a surface portion of the metal member. A manufacturing method of a pressure bearing device.   4. The method of manufacturing a hydrodynamic bearing device according to claim 2, wherein the masking member is made of an insulating plastic material having flexibility.   The electrode tool has an electrode surface that is disposed facing the workpiece surface of the workpiece,
  The electrode surface of the electrode tool is formed in an annular shape including burrs generated on the surface to be processed,
  4. The hydrodynamic bearing device according to claim 3, wherein the annular electrode surface is electrolytically processed while being arranged so as to be substantially concentric with the rotation center of the hydrodynamic bearing device. Manufacturing method.   The method for manufacturing a hydrodynamic bearing device according to claim 1, wherein a liquid mixture with a surfactant is used as the electrolytic solution.   4. The method for manufacturing a hydrodynamic bearing device according to claim 1, further comprising ultrasonic vibration generating means for applying ultrasonic vibration to the electrolytic solution.   9. The method for manufacturing a hydrodynamic bearing device according to claim 8, wherein the energization for electrolytic processing and the energization for ultrasonic vibration are performed independently.   The hydrodynamic bearing according to claim 9, wherein the energization for electrolytic processing and the energization for ultrasonic vibration are alternately performed or at least a part of both energizations are overlapped. Device manufacturing method.   4. The both side wall surfaces of the concave portion forming the dynamic pressure generating groove are formed as tapered surfaces inclined in a direction of continuously expanding from the bottom wall surface toward the opening. The manufacturing method of the hydrodynamic bearing apparatus of description.

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