JP2007113722A - Fluid dynamic bearing device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high-performance and a long life fluid dynamic bearing which has a dynamic pressure generating groove with a sufficient depth and a high precision and besides raises no pressure leakage by sealing residual air holes on a bearing surface, and also to provide its manufacturing method. <P>SOLUTION: The dynamic pressure generating groove is manufactured with a high precision by processes comprising steps of: inserting a shaft into a bearing hole of a sleeve in relatively and freely rotatable manners; providing a bearing surface with the dynamic pressure generating groove in the bearing hole of the sleeve; forming the sleeve by molding metallic powders into a hallow cylinder, next sintering the sleeve thus formed into a sintered metallic raw material; then forming the dynamic pressure generating groove by press-fitting a rolling tool into an internal circle of the sintered metallic raw material; molding, in a small-diameter portion of a core rod, a bearing inner surface with the dynamic pressure generating groove by inserting the core rod with a large-diameter portion and the small-diameter portion in the cylinder surface into the internal circle of the sintered metallic raw material; at the same time shaping a large-diameter portion on an inner-circumference surface of the sleeve using the large-diameter portion of the core rod; and shaping an internal circle by taking the core rod out of the sintered metallic raw material; thus making, as the bearing surface, the internal circle with the dynamic pressure generating groove in the sleeve thus shaped; and making the large-diameter portion of the sleeve as lubricating fluid reservoir. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device using a hydrodynamic bearing.

  In recent years, recording devices using rotating disks have increased their information storage capacity and the data transfer speed has been increased, so the bearings of the recording devices used for these devices always maintain the disk load with high accuracy. High performance and reliability are required so that it can be rotated. Therefore, a hydrodynamic bearing device suitable for high-speed rotation is used for these recording devices.

  In a hydrodynamic bearing device, a lubricating fluid (generally oil, which has the same effect as an ionic liquid) is interposed between a shaft and a sleeve, and a pumping pressure is generated during rotation by a dynamic pressure generating groove. As a result, the shaft rotates without contact with the sleeve. The hydrodynamic bearing device is suitable for high-speed rotation because it is non-contact and has no mechanical friction.

  Hereinafter, an example of a conventional hydrodynamic bearing device will be described with reference to FIGS. FIG. 15 is a cross-sectional view schematically showing the configuration of a conventional hydrodynamic bearing device. In FIG. 15, the hydrodynamic bearing device includes a shaft 31, a flange 32, a sleeve 33, a thrust plate 34, a sleeve cover 35, an oil 36, a rotor 37, a disk 38, a rotor magnet 39, a stator 40, and a base 41. The shaft 31 integrally has a flange 32, and the shaft 31 is rotatably inserted into the bearing hole 33 </ b> A of the sleeve 33, and the flange 32 is accommodated in the sleeve cover 35 on the lower surface portion of the sleeve 33. Dynamic pressure generating grooves 33B and 33C are provided on at least one of the outer peripheral surface of the shaft 31 and the inner peripheral surface of the sleeve 33, the surface of the flange 32 facing the sleeve 33, the flange 32, the thrust plate 34, and the like. Are provided with dynamic pressure generating grooves 32A and 32B, and the thrust plate 34 is fixed to the sleeve cover 35. The bearing gaps near the respective dynamic pressure generating grooves 33B, 33C, 32A, 32B are filled with at least the lubricating fluid 36. The rotor 37 is fixed to the shaft 31, and a disk 38 is fixed to the rotor 37 by a clamper (not shown).

  On the other hand, since the sleeve 33 is made of a sintered metal body and voids remain inside the sintered metal body, the lubricating fluid 36 is previously injected into these holes and then lightly press-fitted into the sleeve cover 35. By covering the entire sleeve 33 that is porous, the lubricating fluid 36 barely flows out of the surface holes of the sleeve 33 to the outside, causing insufficient lubrication inside the sleeve 33, and the lubricated fluid that has flowed out. The fluid 36 is configured not to gasify and contaminate the surroundings of the hydrodynamic bearing device. Cover 35 is fixed to base 41, rotor magnet 39 is attached to rotor 37, and motor stator 40 is fixed to base 41 at a position facing rotor magnet 37.

  The operation of the conventional hydrodynamic bearing device configured as described above will be described. In FIG. 15, when a rotating magnetic field is generated in the stator 40 by an electronic circuit (not shown), a rotational force is applied to the rotor magnet 39, and the rotor 37, the shaft 31, the flange 32, and the disk 38 start to rotate. Due to the rotation, the dynamic pressure generating grooves 33B, 33C, 32A and 32B collect the lubricating fluid 36 and generate a pumping pressure between the shaft 31 and the sleeve 33 and between the flange 32 and the sleeve 33 and the thrust plate 34. As a result, the shaft 31 rotates in a non-contact manner with respect to the sleeve 33 and the thrust plate 34, and data is recorded on and reproduced from the disk 38 by a magnetic head or an optical head (not shown). In the conventional hydrodynamic bearing device of FIG. 15, the sleeve 33 is made of a copper alloy metal sintered body that is inexpensive and has a rust prevention effect.

  A conventional method for manufacturing the sleeve 33 will be described below with reference to FIGS. FIG. 16 shows a schematic structural example of a molding apparatus for manufacturing the sleeve 33 shown in FIG. 15 by processing the bearing hole 33 and the dynamic pressure generating grooves 33B and 33C using a sintered metal material 46 prepared in advance. . In FIG. 16, this molding apparatus has a lower mold 42, an upper mold 43, a core rod 44, and an outer mold 45. The outer die 45 is slidably provided on the coaxial outer peripheral surface of the upper die 43, and the core rod 44 is slidably provided on the coaxial inner peripheral surface of the outer die 45. The bone-shaped concave portions 44B and 44C are separately processed using an etching method, a shot peening method, or the like so that the depths of the concave portions are uniform.

  In FIG. 16, first, the sintered metal material 46 is set on the lower die 42, and then, as shown in FIG. 17, the upper die 43 is lowered as shown by the arrow in the drawing and brought into contact with the sintered metal material 46, Next, the core rod 44 is inserted into the inner diameter of the sintered metal material 46. Next, as shown in FIG. 18, the outer mold 45 is lowered. At this time, the inner peripheral surface of the outer mold applies pressure to the outer peripheral surface of the sintered metal material 46 and descends while squeezing. In this way, as shown in FIG. 19, the sintered metal material 46 plastically flows and flows into the recesses 44 </ b> B and 44 </ b> C of the core rod 44 and bites.

Next, as shown in FIG. 20, when the outer mold 45 is raised, the inner and outer diameters of the sintered metal material 46 are enlarged by about 2 micrometers due to the springback characteristics. Next, as shown in FIG. 21, when the upper mold 43 is raised, the sintered metal material 46 can be taken out from this molding apparatus. The sintered metal material 46 has its shape and inner diameter 33A and dynamic pressure generating grooves 33B and 33C. The processing is completed and the sleeve 33 shown in FIG. 21 is molded.
JP 11-294458 A

  However, in the above-described conventional hydrodynamic bearing device, as shown in FIGS. 20 to 21, the sleeve 33 that bites into the core rod 44 is pulled out due to insufficient spring back characteristics such that the inner diameter of the sleeve 33 extends only 2 micrometers. As shown in FIG. 22, the dynamic pressure generating grooves 33B and 33C could only be processed by shallow grooves of about 1 micrometer. In the case of such a shallow groove, as shown in FIG. 25, the generated pressure of the hydrodynamic bearing device shown in FIG. 15 was only about 30% of the required pressure, and the performance and reliability of the rotating device were poor.

  Further, when it is desired to increase the depth of the dynamic pressure generating grooves 33B and 33C to, for example, about 5 micrometers, the fish bone-shaped concave portions 44B and 44C of the core rod 44 shown in FIGS. 20 to 21 are processed deeply. However, in this case, as shown in FIG. 23, the sintered metal material 46 has a springback amount that is insufficient, so that the core rod 44 must be forcibly removed, and the dynamic pressure generating grooves 33B and 33C and the fish bones of the core rod 44 The concave portions 44B and 44C are interfered. Therefore, as shown in FIG. 24, the dynamic pressure generating grooves 33B and 33C have broken shapes. Accordingly, since the conventional hydrodynamic bearing device does not generate sufficient dynamic pressure, if the rotating device continuously rotates at a high speed for a long time under high temperature conditions, the rotating device will cause a short time to generate heat and generate heat and the lubricating fluid 36 is gas. The bearings sometimes rubbed.

  In addition, since the sleeve made of a sintered metal is porous and the surface has pores of 2% or more in the case of general manufacturing conditions, dynamic pressure is generated by rotation in FIG. Grooves 33B, 33C, 32A, 32B collect lubricating fluid 36 and generate pumping pressure between shaft 31 and sleeve 33 and between flange 32 and sleeve 33 and thrust plate 34, but about 30 percent of the generated pressure. Leaks from the surface holes and the required pressure on the inner peripheral surface of the bearing cannot be obtained, and the hydrodynamic bearing device is used at a high temperature and the viscosity of the oil 36 is lowered. In such a case, the shaft 31 may not float with respect to the sleeve 33 and the thrust plate 34, and may generate heat or be rubbed.

  Therefore, the present invention ensures the depth of the dynamic pressure generating groove and the fineness of the surface shape (shape accuracy) of the sleeve made of a metal sintered body, which is insufficient with the above-described conventional technology, and also from the bearing surface of the sleeve. This solves the problem of performance deterioration due to the pressure leakage, and improves the durability and rotational accuracy of the hydrodynamic bearing device and reduces the cost.

  In order to solve the conventional problem, a hydrodynamic bearing device of the present invention has a shaft and a bearing hole, and the shaft is inserted in a relatively rotatable state. A first groove (small diameter portion) having a dynamic pressure surface on the peripheral surface, and a dynamic pressure generating groove formed on the inner peripheral surface, and a second groove (diameter) for forming a lubricating fluid pool portion The dynamic pressure generating groove formed in the small diameter portion has a substantially arc shape in cross section, and the depth of the dynamic pressure generating groove is larger than the depth of the large diameter portion. A hydrodynamic bearing comprising at least a formed sleeve made of sintered metal and a lubricating fluid held between the shaft and the sleeve.

In the present invention, the surface of the sleeve is impregnated with at least one of the following methods: impregnating the surface of the sleeve with resin or water glass, impregnating with a heat-dissolved metal, or forming an oxide film. In addition to sealing, a thin film is formed by metal plating containing nickel to improve the surface hardness of the sleeve more than the inside.

  The sintered sleeve of the present invention has a bearing hole, a dynamic pressure generating groove on the inner peripheral surface of the bearing hole, and is inserted into the bearing hole in a state where the shaft is relatively rotatable. A method of manufacturing a hydrodynamic bearing having a sleeve, wherein the sleeve is formed by molding a metal powder into a hollow cylindrical shape to form a first molded body (metal material), and the metal material A third step of forming a dynamic pressure generating groove by rolling on the inner peripheral surface of the sintered second molded body (sintered metal material), and the sintering A core rod having a large diameter portion and a small diameter portion is inserted into the formed second molded body (sintered metal material) and then pressurized from above and below and from the side, and a bearing having a dynamic pressure groove at the small diameter portion of the core rod An inner diameter surface is formed and a second groove is formed on the inner peripheral surface of the sleeve at the large diameter portion of the core rod at the large diameter portion. A fourth step and method for producing a hydrodynamic bearing, characterized by consisting of molding the sleeve by pulled out the rod.

In order to further improve the processing accuracy, the sleeve surface is sealed by impregnating the surface of the sleeve with resin or water glass, impregnating with a metal melted by heating, or forming an oxide film on the surface of the sleeve. That is. Further, if a thin film is formed on the sleeve surface by metal plating containing nickel or DLC coating, the surface hardness of the sleeve is improved more than the inside, and the sleeve becomes optimum.

  As described above, according to the present invention, the sleeve is formed by molding a metal powder into a hollow cylindrical shape, and then sintering this to obtain a sintered metal material. Next, the inner diameter of the sintered metal material is adjusted to the outer diameter of the shank. A rolling tool having a plurality of balls is press-fitted to form a dynamic pressure generating groove, and then the sintered metal material is pressed from above and below and from the outer diameter direction, and the inner diameter of the sintered metal material is Inserting a core rod having a small diameter part in part, forming a bearing inner surface having a dynamic pressure groove at the small diameter part of the core rod, and simultaneously molding the large diameter part on the sleeve inner peripheral surface at the large diameter part of the core rod, Next, the connecting rod is manufactured by removing the connecting rod from the sintered metal material, and the inner diameter of the sleeve manufactured in this way having the dynamic pressure generating groove is the bearing surface, and the large diameter portion is the lubricating fluid reservoir. The pressure generating grooves 33B and 33C are deep and beautifully formed, Since the surface is dense with no residual voids on the surface, the pressure generated in the dynamic pressure generating groove does not leak and high pressure can be generated on the fluid bearing surface, so that the shaft 31 is stable against the sleeve 33 and the thrust plate 34. It can float and the performance and reliability of the hydrodynamic bearing are good.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIGS. 1-14 is a figure which shows the structure and manufacturing method of the hydrodynamic bearing apparatus of this invention. In FIG. 1, the hydrodynamic bearing device includes a shaft 1, a flange 2, a sleeve 3, a thrust plate 4, an oil 6, a rotor 7, a disk 8, a rotor magnet 9, a stator 10, and a base 5. The shaft 1 integrally has a flange 2, and the shaft 1 is rotatably inserted into a bearing hole 3 </ b> A of the sleeve 3, and the flange 2 is accommodated in a concave portion of the sleeve at the lower surface portion of the sleeve 3. At least one of the outer peripheral surface of the shaft 1 and the inner peripheral surface of the sleeve 3 is provided with dynamic pressure generating grooves 3B and 3C, the surface of the flange 2 facing the sleeve 3, and the flange 2 and the thrust plate 4 Are provided with dynamic pressure generating grooves 2 </ b> A and 2 </ b> B, and the thrust plate 4 is fixed to the sleeve 3. The bearing gaps near the respective dynamic pressure generating grooves 3B, 3C, 2A, 2B are filled with at least oil 6. The rotor 7 is fixed to the shaft 1, and a disk 8 is fixed to the rotor 7 by a clamper (not shown) or the like. 3D is a large diameter portion, which is a lubricating fluid reservoir.

  On the other hand, the material of the sleeve 3 is composed of a sintered metal body 3E as shown in a partial cross-sectional view in FIG. 2, and the holes 3F remaining inside the sintered metal body 3E are preliminarily filled with resin, water glass as necessary. Or the like, or a low melting point metal such as tin or zinc is injected at a high temperature and then solidified at a normal temperature, or high temperature steam at 400 to 700 ° C. as necessary on the surface of the sleeve 3 The surface of the sleeve 3 is sealed by at least one method of providing the layer 3G of triiron tetroxide to a thickness of about 1 to 10 micrometers by treatment.

  Furthermore, the surface of the sleeve 3 is formed with a nickel-containing component plating or a DLC hard coating 3H to a thickness of 1 to 10 micrometers as required. Thus, since the surface of the sleeve 3 is completely sealed, a sleeve cover is unnecessary as in the case of the conventional hydrodynamic bearing device, and the lubricating fluid flows out from the surface holes, resulting in insufficient lubricating fluid inside. The lubricating fluid 6 that flows out does not gasify and contaminate the surroundings of the hydrodynamic bearing device. The sleeve 3 is directly fixed to the base 5 with an adhesive or the like without using a sleeve cover. A rotor magnet 9 (not shown) is attached to the rotor 7, and a motor stator 10 is attached to the base 5 at a position facing the rotor magnet 9. Fixed. Since the sleeve 3 can be directly fixed to the base 5 without using a sleeve cover, the perpendicularity and coaxiality at the time of attachment can be easily obtained and can be assembled with high accuracy.

  The operation of the hydrodynamic bearing device of the present invention configured as described above will be described. In FIG. 1, when a rotating magnetic field is generated in the stator 10 by an electronic circuit (not shown), a rotational force is applied to the rotor magnet 9, and the rotor 7, the shaft 1, the flange 2, and the disk 8 start to rotate. Due to the rotation, the dynamic pressure generating grooves 3B, 3C, 2A and 2B collect the lubricating fluid 6 and generate a pumping pressure between the shaft 1 and the sleeve 3 and between the flange 2 and the sleeve 3 and the thrust plate 4. As a result, the shaft 1 rotates in a non-contact manner with respect to the sleeve 3 and the thrust plate 4, and data is recorded on and reproduced from the disk 8 by a magnetic head or an optical head (not shown). In the present invention, the sleeve cover is not required, and the lubricating fluid flows out from the surface holes and causes a shortage of the lubricating fluid. The outflowing lubricating fluid 6 is gasified and contaminates the surroundings of the hydrodynamic bearing device. There is no.

  Below, the manufacturing method of the sleeve 3 is demonstrated using FIGS. FIG. 3 shows a first sizing mold for molding the shape of the sintered metal material 11. 12 is a lower mold, 13 is an upper mold, 14 is a pin, and 15 is an outer mold. The sintered metal body 11 is a semi-finished product in which iron powder or copper powder is pre-compressed with a mold (not shown), and then the compressed metal powder is pre-sintered using a firing furnace (not shown). 3, the sintered metal material 11 is set on the lower mold 12, and the upper mold 13 and the outer mold 15 are lowered as indicated by the arrows in the drawing to compress the sintered metal material 11.

  The sintered metal material 11A after compression molding is set on the mounting base 16 of the groove rolling apparatus shown in FIG. 4, and the clamp 17 is lowered in the direction of the arrow in the figure so that the sintered metal body does not shift during processing. The rolling tool in which a plurality of balls 18B are integrally arranged on the outer peripheral surface of the shank 18A is press-fitted into the inner diameter of the sintered metal material 11A and fed in the vertical direction while feeding the shank up and down. Rotation and reverse rotation are applied, and the dynamic pressure generating groove 11E is processed in the sintered metal material 11 by the balls 18B. At this time, the dynamic pressure generating groove 11E processed into the sintered metal body 11A has a groove depth (hg) of about 10 micrometers as shown in FIG. A lot of 11F remains. Since the dynamic pressure generating groove is formed by ball rolling as described above, the cross-sectional shape thereof is a substantially arc shape. Furthermore, the surface roughness of the groove bottom surface and the groove side surface is smooth due to the surface ironing effect that the rolled ball gives to the groove.

  In addition, the semi-finished product of the sintered metal body 11 that has been compression-molded and fired with a mold (not shown) is subjected to the groove rolling process of FIG. 4 while omitting the process using the first sizing mold shown in FIG. Also good. However, when the first sizing mold shown in FIG. 3 is used, the dimensional variation in the inner diameter of the sintered metal material 11 is reduced during the groove rolling shown in FIG. 4, and the depth of the dynamic pressure generating groove 11E is reduced. Is stable.

  Next, using the second sizing mold shown in FIGS. 7 to 12, finishing the inner surface of the sintered metal material 11 </ b> A after grooving and a large diameter portion for obtaining the function of the oil reservoir shown in FIG. 11. 3D processing is performed. In FIG. 7, the second sizing mold has a lower mold 19, an upper mold 20, a core rod 21, and an outer mold 22. The outer die 22 is slidably provided on the coaxial outer peripheral surface of the upper die 20, and the core rod 21 is slidably provided on the inner peripheral surface coaxial with the upper die 20. The outer peripheral surface has a small diameter portion 21B coaxially and a large diameter portion 21C having the same diameter as that of the outer peripheral surface 21A. The small diameter portion 21B is processed to have a thin diameter of about 2 micrometers by polishing or the like. The cylindrical surface of the diameter portion is processed into a highly accurate and smooth cylindrical surface necessary as a mold.

  In FIG. 7, first, the sintered metal material 11A in which the dynamic pressure groove 11E has been processed is set on the lower mold 19, the upper mold 20 is lowered in the direction of the arrow in the drawing to contact the sintered metal material 11A, and the core rod 21 is moved. Insert into the inner diameter of the sintered metal material 11A. Next, as shown in FIG. 8, the outer die 22 is lowered. At this time, the inner peripheral surface of the outer die 22 applies pressure to the outer peripheral surface of the sintered metal material 11A and descends while squeezing. Thus, as shown in FIG. 8, the sintered metal material 11 </ b> A plastically flows into the small diameter portion 21 </ b> A of the core rod 21 to form the bearing inner diameter surface, and the large diameter portion having substantially the same diameter as the outer peripheral surface 21 </ b> A of the core rod 21. 21C molds the thick portion 3D to the inner diameter of the sintered metal material 11A. The depth and shape of the dynamic pressure generating groove at this point are molded to a depth of about 5 micrometers as shown by symbol hg in FIG.

  A symbol dR shown in FIG. 12 indicates a step formed by the large-diameter portion 21C of the core rod 21, and this step is about 1 micrometer. Next, when the upper die 20 and the outer die 22 are raised as shown in FIG. 9, the inner and outer diameters of the metal sintered material 11A are enlarged by about 2 micrometers due to the springback characteristics, and the core rod 21 and the metal sintered body 11A are expanded. There is a minute gap between the two. Next, as shown in FIG. 10, when the core rod 21 is raised, the sintered metal material 11A can be taken out from the second sizing mold, and the sintered metal material 11A has its shape, inner diameter, and dynamic pressure generating groove processed. The sleeve 3 is completed as shown in FIGS. 1 and 11.

  FIG. 13 is data showing the relationship between various shapes of the dynamic pressure generating grooves 3B and 3C of the sleeve 3 and the bearing life of the hydrodynamic bearing device shown in FIG. According to our experiment, the groove depth (hg) indicated by symbol (A) in the figure is insufficient, the bearing life under the condition of 1 micrometer (in the case of the groove shape similar to FIG. 22), and symbol (B The groove depth (hg) shown in FIG. 5 is sufficient to be 5 micrometers, but the shape of the dynamic pressure generating groove 33B is broken and a smooth cylindrical surface is not formed on the bearing surface (similar to FIG. 24). In the case of the groove shape, the bearing life of all of them could only satisfy about half of the required life. If the dynamic pressure generating groove is too shallow (A), the pumping force is insufficient and performance and reliability cannot be obtained. On the other hand, if the dynamic pressure generating groove is broken (B) Since the cylindrical surface cannot be formed in the sleeve bearing hole that must face the surface of the shaft, it is considered that the pumping pressure is hardly generated due to this. On the other hand, as shown in FIG. 1C, the groove depth (hg) is 5 micrometers, as shown in FIG. 1, and there is a sufficient depth as shown in FIG. The hydrodynamic bearing device has a necessary and sufficient life. Further, as described above, since the dynamic pressure generating groove is formed by ball rolling, the cross-sectional shape of the groove is a substantially arc shape, and the fluid flow is smoother than in other shapes (for example, a rectangular shape). It was found that the rotation performance was excellent. Furthermore, the surface roughness of the groove bottom surface and side surface of the dynamic pressure generating groove formed by ball rolling is smooth due to the surface squeezing effect that the rolling ball gives to the groove surface, and the fluid flow becomes smooth. It was also found that it contributed to the improvement of rotational performance.

  In this example, the material of the shaft 1 was stainless steel, high manganese chrome steel, or carbon steel. The surface roughness of the radial bearing surface of the shaft 1 is a material finished by machining in the range of 0.01 to 0.8 micrometers.

  In the sleeve 3 of FIG. 2 of the present embodiment, the surface hardened layer 3H employs electroless plating mainly composed of nickel and phosphorus, and the surface thereof has a Vickers hardness of 600 or more. Alternatively, coating by three-dimensional DLC processing (Kurita Seisakusho) is performed, and the surface has a Vickers hardness of 800 or more. By providing any one of these hardened layers 3H, the wear resistance and reliability of the hydrodynamic bearing device are improved.

  In the sleeve of FIG. 2, the holes 3F were impregnated with a thermosetting or anaerobic curable acrylic resin in a low pressure tank. Since these resins are thoroughly washed before being cured, all the resin adhering to the vicinity of the surface is removed, and only the resin impregnated inside remains and is cured. That is, the inside of the sleeve is sealed with the resin 3F, and the surface is sealed with the iron oxide film 3G or the plating layer 3H.

In addition, regarding the components of the sleeve 3 in FIG. 1, the metal powder used for compacting may be copper-based, such as brass, but in order to reduce the difference in the coefficient of thermal expansion from the rotating shaft of the motor, an iron component is used. Preference is given to iron-based powders or pure iron comprising components accounting for 80% by weight or more of the total. After iron powder is compacted, it is sintered to form a sintered body material for bearings. In general, the clearance between the sleeve 3 and the shaft 1 in the hydrodynamic bearing device is set to about 2 to 5 micrometers, and there is a problem of temperature difference in use environment due to surface treatment accuracy after sealing treatment and difference in coefficient of thermal expansion during use. Is important for hydrodynamic bearing devices. Further, by employing an iron-based material as the component of the sleeve 3, it is possible to easily form a triiron tetroxide (Fe ₃ O ₄ ) film on the porous surface of the compacted metal sintered body material 11A.

  The hydrodynamic bearing device of this embodiment is, for example, disclosed in Japanese Patent Application Laid-Open No. 2000-197309 (a motor equipped with a fluid dynamic pressure bearing and a recording disk drive device equipped with this motor) as shown in FIG. The rotor is fixed and a ring-shaped member is attached to the lower side of the shaft. The periphery of the ring-shaped member has a lubricating fluid reservoir adjacent to the radial bearing surface, and the thrust lower surface is opposed to the upper surface of the sleeve. The present invention can also be applied to a hydrodynamic bearing device having a bearing surface.

  The hydrodynamic bearing device of the present embodiment can also be applied to a hydrodynamic bearing having a fixed shaft bearing structure (not shown) in which both ends of the shaft are fixed and a sleeve rotates around the shaft.

(Embodiment 2)
FIG. 14 is a block diagram showing the bearing portion of the hydrodynamic bearing device of the second embodiment. 1 is a shaft, 2 is a flange, 23 is a sleeve, 23A is a bearing hole, 23B and 23C are dynamic pressure generation grooves, 2A and 2B are dynamic pressure generation grooves provided in the flange 2, 23D is a large diameter portion, and 23J is a communication The hole 24 is a cap.

  The operation of the hydrodynamic bearing device of the second embodiment is the same as that of the first embodiment shown in FIG. However, when the air 25 contained in the lubricating fluid 6 in the bearing expands from the communication hole 23J provided in at least one place in the sleeve 23, the dynamic pressure generating grooves 23B, 23C, 2A are discharged to the outside of the bearing. In 2B, it is possible to prevent the presence of bubbles and to reliably form an oil film of the lubricating fluid 6 and improve the reliability of the hydrodynamic bearing device.

  The communication hole 23J may be formed by drilling a sleeve 23 made of a sintered metal body with a drill (not shown), or a sleeve 23 having a straight groove-shaped communication hole 23J on the outer peripheral surface as shown in FIG. The pipes 23K are both molded from a sintered metal body and sintered at a high temperature, and then the sleeve 23 is press-fitted into the pipe 23K to be integrated, and at the same time, a communication hole 23J is formed. Thereafter, as in the first embodiment, FIG. You may process by the method of shape | molding using the groove rolling apparatus shown and the 2nd sizing metal mold | die shown in FIGS. If the sleeve 23 and the pipe 23K are combined in this way, the communication hole 23J can be configured at the lowest cost. The presence of the communication hole 23J is very effective for ensuring the performance and reliability of the hydrodynamic bearing device at high speed rotation. Thus, the communication hole 23J is configured by combining two sintered metal bodies. Economic effect is great.

  Also with this hydrodynamic bearing device, the same effect as the hydrodynamic bearing device of the first embodiment can be obtained.

  The present invention relates to a hydrodynamic bearing device used in a hard disk device and other devices, and has a bearing surface in which a shaft is relatively rotatably inserted into a bearing hole of a sleeve and has a dynamic pressure generating groove in the bearing hole of the sleeve. The sleeve is formed by forming a metal powder into a hollow cylindrical shape to form a metal material, a second step of sintering the metal material, and an inner peripheral surface of the sintered metal material. A third step of forming a dynamic pressure generating groove by manufacturing; inserting a core rod having a large diameter portion and a small diameter portion into the sintered metal material; And forming the inner diameter surface of the bearing having a dynamic pressure groove at the same time, forming the larger diameter portion on the inner peripheral surface of the sleeve at the larger diameter portion of the core rod, and then molding the sleeve by removing the core rod. And formed in this way The sleeve's inner diameter with the dynamic pressure generating groove is used as the bearing surface, and the large diameter portion of the sleeve is used as the lubricating fluid reservoir, so that the dynamic pressure generating groove is processed with high accuracy, and there is no pressure leakage and high performance and long service life. A fluid bearing and a manufacturing method thereof are obtained.

Sectional drawing of the hydrodynamic bearing apparatus which concerns on the 1st Embodiment of this invention Detailed partial sectional view of sleeve in the fluid dynamic bearing device Sectional view of first sizing die in the fluid bearing device Cross section of dynamic pressure generating groove rolling device in the same hydrodynamic bearing device Sectional view of the sintered metal body of the hydrodynamic bearing device Partial sectional view of sintered metal body of the hydrodynamic bearing device Second sizing mold cross-sectional view of the fluid bearing device Second sizing mold cross-sectional view of the fluid bearing device Second sizing mold cross-sectional view of the fluid bearing device Second sizing mold cross-sectional view of the fluid bearing device Cross-sectional view of sleeve in the hydrodynamic bearing device Partial sectional view of the sleeve of the hydrodynamic bearing device Illustration of bearing life of the hydrodynamic bearing device Sectional drawing of the hydrodynamic bearing apparatus which concerns on the 2nd Embodiment of this invention. Sectional view of a conventional hydrodynamic bearing device Cross-sectional view of a sleeve molding device in a conventional hydrodynamic bearing device Cross-sectional view of a sleeve molding device in a conventional hydrodynamic bearing device Cross-sectional view of a sleeve molding device in a conventional hydrodynamic bearing device Cross-sectional view of a sleeve molding device in a conventional hydrodynamic bearing device Cross-sectional view of a sleeve molding device in a conventional hydrodynamic bearing device Cross-sectional view of a sleeve molding device in a conventional hydrodynamic bearing device Cross-sectional view of a sleeve portion of a conventional hydrodynamic bearing device Explanatory drawing of core rod of conventional hydrodynamic bearing device Cross-sectional view of a sleeve portion of a conventional hydrodynamic bearing device Explanatory diagram of pump pressure of conventional hydrodynamic bearing device

Explanation of symbols

1, 31 Shaft 2, 32 Flange 3, 23, 33 Sleeve 3A, 33A Bearing hole 3B, 3C, 2A, 2B, 33A, 33B, 33C Dynamic pressure generating groove 3D Large diameter portion 4, 34 Thrust plate 5, 41 Base 6 , 36 Lubricating fluid 7, 37 Rotor 8, 38 Disc 9, 39 Rotor magnet 10, 40 Stator 11, 46 Sintered metal material 12, 19, 43 Lower mold 13, 20, 42 Upper mold 14 Pin 15, 22, 45 Outside Type 18A Shank 18B Ball 21, 44 Core rod 23K Pipe 24 Cap

Claims (10)

The axis,
Having a bearing hole, the shaft is inserted in a relatively rotatable state,
A dynamic pressure surface on the inner peripheral surface of the bearing hole;
The inner peripheral surface has a first groove in which a dynamic pressure generating groove is formed, and a second groove for forming a lubricating fluid reservoir,
The cross-sectional shape of the first groove in which the dynamic pressure generating groove is formed on the inner peripheral surface is a substantially arc shape, and the depth of the dynamic pressure generating groove is larger than the depth of the second groove. A sleeve made of formed sintered metal,
And at least a lubricating fluid held between the shaft and the sleeve. The hydrodynamic bearing according to claim 1, wherein the surface of the sleeve is impregnated with resin or water glass to seal the surface.   The hydrodynamic bearing according to claim 1, wherein the surface of the sleeve is impregnated with heat-dissolved metal to seal the surface.   The hydrodynamic bearing according to claim 1, wherein an oxide film is formed on the surface of the sleeve to seal the surface. 5. A hydrodynamic bearing, wherein a thin film is formed on the surface of the sleeve according to claim 1 by metal plating containing nickel to improve the surface hardness of the sleeve from the inside. 5. A hydrodynamic bearing, wherein a thin film is formed by DLC coating on the surface of the sleeve according to claim 1 to improve the surface hardness of the sleeve from the inside. The hydrodynamic bearing according to any one of claims 1 to 6,
A hub fixed to the hydrodynamic bearing and enabling the hydrodynamic bearing to rotate;
A magnet fixed to the hub;
A base plate for fixing the hydrodynamic bearing;
A stator fixed to the base plate so as to face the magnet;
A spindle motor equipped with. A sleeve having a bearing hole, a dynamic pressure generating groove on an inner peripheral surface of the bearing hole, and a shaft inserted into the bearing hole in a relatively rotatable state;
A method of manufacturing a hydrodynamic bearing comprising:
The sleeve is formed by molding a metal powder into a hollow cylindrical shape to form a first molded body;
A second step of sintering the first molded body;
A third step of forming the first groove of the dynamic pressure generating groove by rolling on the inner peripheral surface of the sintered second molded body;
A core rod having a large-diameter portion and a small-diameter portion is inserted into the sintered second molded body, and then pressurized from above and below and from the side, and a first groove having a dynamic pressure groove at the small-diameter portion of the core rod. A second inner groove is formed on the inner peripheral surface of the sleeve at the larger diameter portion of the core rod, and then the sleeve is formed by removing the core rod. Process,
A method of manufacturing a hydrodynamic bearing characterized by comprising:   9. The hydrodynamic bearing according to claim 8, further comprising impregnating a surface of the sleeve with a resin or water glass, impregnating a metal melted by heating, or forming an oxide film on the surface of the sleeve. Manufacturing method.   10. A method of manufacturing a hydrodynamic bearing, wherein a thin film is formed on the sleeve surface by metal plating containing nickel or DLC coating after the step according to claim 8 or 9.

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