JP2007263224A - Dynamic pressure bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain cost reduction and high rotational accuracy of a dynamic pressure bearing device. <P>SOLUTION: A bearing member 7 is an injection-molded article whose outer peripheral surface has a mounting face for a base member as a constructional element of a motor. In the bearing member, at least an area of an inner peripheral surface facing a radial bearing clearance is formed of an electro-cast part 8. The electro-cast part 8 is a metallic layer precipitated and formed on a master surface by electrocasting. Because of the characteristics of the electrocasting, high inner peripheral surface accuracy can be secured at low cost. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device.

  The hydrodynamic bearing device is configured so that the shaft member is not rotatable by the dynamic pressure action of the lubricating fluid (for example, lubricating oil) generated in the bearing gap due to the relative rotation between the bearing member and the shaft member inserted in the inner periphery of the bearing member. This is a bearing device that supports contact. This hydrodynamic bearing device has features such as high-speed rotation, high rotation accuracy, and low noise. Information equipment, for example, magnetic disk devices such as HDD and FDD, CD-ROM, CD-R / RW, DVD- Optical disk devices such as ROM / RAM, spindle motors for disk drives in magneto-optical disk devices such as MD and MO, polygon scanner motors for laser beam printers (LBP), color wheels for projectors, fan motors for personal computers (PCs), Or the use is expanding in recent years as a bearing apparatus mounted in small motors, such as an axial fan.

For example, in a hydrodynamic bearing device mounted on a spindle motor for a disk device such as an HDD, a radial bearing that supports a shaft member in a non-contact manner in a radial direction and a shaft member in a non-contact manner in a thrust direction. And a supporting thrust bearing. In the radial bearing portion, a dynamic pressure generating portion (radial dynamic pressure generating portion) such as a dynamic pressure groove provided on the inner peripheral surface of the bearing member or the outer peripheral surface of the shaft member opposed via the radial bearing gap is a radial bearing. It is formed by generating pressure in the gap by the dynamic pressure action of the lubricating fluid. In addition, the thrust bearing portion includes dynamic pressure grooves or the like provided on both end surfaces of the flange portion of the shaft member or member end surfaces (for example, the end surface of the bearing member, the inner bottom surface of the housing, etc.) facing each other through the thrust bearing gap. The pressure generating portion (thrust dynamic pressure generating portion) is formed by generating pressure in the thrust bearing gap by the dynamic pressure action of the lubricating fluid (see, for example, Patent Document 1).
JP 2002-61641 A

  Along with the price reduction of information equipment, the demand for cost reduction of the hydrodynamic bearing device is becoming stricter. In order to meet this demand, the use of resin for the bearing member that constitutes the hydrodynamic bearing device has been studied. On the other hand, with the improvement in performance of information equipment, the demand for high rotational accuracy for hydrodynamic bearing devices has become increasingly severe. To meet this type of request, the bearing clearance must be set to the expected value. It is important to manage. However, molding of the resin is unavoidable, and in order to obtain the desired bearing gap width, a precise finishing process is required particularly in the region that becomes the bearing surface, and thus the cost merit by resinization cannot be fully enjoyed. In general, resin has a large coefficient of linear expansion, and is easily affected by temperature changes during bearing operation. Furthermore, it is inferior in wear resistance as compared with metal, and the wear of the bearing surface is likely to proceed due to sliding contact with the shaft member particularly at the time of starting and stopping.

  An object of the present invention is to make it possible to simultaneously achieve cost reduction and high rotational accuracy of a hydrodynamic bearing device.

  In order to achieve the above object, a hydrodynamic bearing device according to the present invention includes a bearing member having a mounting surface for mounting to a base member, and a shaft member that is inserted into the inner periphery of the bearing member and includes a shaft portion and a flange portion. A radial dynamic pressure generating portion that generates pressure by the dynamic pressure action of the lubricating fluid in a radial bearing gap between the inner peripheral surface of the bearing member and the outer peripheral surface of the shaft member, and the bearing member has at least an inner peripheral surface It is an injection molded product in which an electroformed part is arranged in a portion facing a radial bearing gap.

  As described above, in the present invention, the bearing member has an electroformed portion in at least a portion (radial bearing surface) facing the radial bearing gap on the inner peripheral surface. The electroformed part is a metal layer formed by depositing metal on the master surface, and can be formed by a technique according to electrolytic plating or electroless plating. Due to the characteristics of the electroforming process, the surface shape of the master is transferred to the inner surface of the electroformed part with a very fine level to a very fine level. Therefore, if the surface accuracy of the master is increased, a highly accurate radial bearing surface can be obtained at low cost without any special finishing process. In addition, since the radial bearing surface is a metal surface, the temperature dependency can be reduced and the wear resistance can be increased to suppress fluctuations in the radial bearing gap width compared to the case where the radial bearing surface is made of resin. . Since the bearing member is injection-molded by inserting the electroformed part having the above characteristics, the assembly work between the members becomes unnecessary, and a highly accurate bearing member can be obtained at low cost.

  The bearing member is provided between the small-diameter inner peripheral surface provided with the electroformed portion, the large-diameter inner peripheral surface located on the outer-diameter side of the flange portion, and the small-diameter inner peripheral surface and the large-diameter inner peripheral surface. It can be set as the structure which has an end surface. During the operation of the hydrodynamic bearing device, the lubricating fluid that fills the internal space may become negative pressure in some areas, and the generation of such negative pressure leads to the generation of bubbles and the leakage of lubricating oil, and the bearing performance is reduced. There is a risk of lowering. Such a problem can be solved by providing the bearing member with an axial through-hole that opens in the first end surface and securing a path for the lubricating fluid to flow in the internal space of the bearing device.

  In the configuration in which the first end surface is provided on the bearing member, a thrust dynamic pressure generating portion that generates pressure by the dynamic pressure action of the lubricating fluid in the thrust bearing gap between the first end surface of the bearing member and one end surface of the flange portion. Thus, the shaft member can be supported in a non-contact manner in the thrust direction. In this case, if an electroformed part is arranged on the first end surface of the bearing member, the portion facing the thrust bearing gap (thrust bearing surface) can be formed at low cost and with high accuracy in the same manner as described above. The fluctuation amount of the bearing gap width can also be suppressed.

  The hydrodynamic bearing device having the above configuration can be preferably used for a motor having a rotor magnet and a stator coil, for example, a spindle motor for a disk drive device such as an HDD.

  As described above, according to the present invention, it is possible to simultaneously achieve cost reduction and high rotation accuracy of the hydrodynamic bearing device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 conceptually shows a configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device 1 according to an embodiment of the present invention. This spindle motor for information equipment is used for a disk drive device such as an HDD, and includes a dynamic pressure bearing device 1, a disk hub 3 attached to a shaft member 2 of the dynamic pressure bearing device 1, and a radial gap, for example. The stator coil 4 and the rotor magnet 5 and the base member 6 that are opposed to each other are provided. The stator coil 4 is attached to the outer periphery of the base member 6, and the rotor magnet 5 is attached to the inner periphery of the disk hub 3. The disk hub 3 holds one or more disks D such as magnetic disks on the outer periphery thereof. A bearing member 7 of the hydrodynamic bearing device 1 is mounted on the inner periphery of the base member 6. When the stator coil 4 is energized, the rotor magnet 5 is rotated by electromagnetic force generated between the stator coil 4 and the rotor magnet 5, and accordingly, the disk hub 3 and the shaft member 2 are rotated together.

  FIG. 2 shows an example of the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 has a shaft member 2 having a shaft portion 2a at the center of rotation, a mounting surface for mounting on the base member 6, and a bearing member capable of inserting the shaft portion 2a into the inner periphery thereof. 7, a lid member 10 that seals the opening at one end of the bearing member 7, and a seal member 11 that is positioned at the other end of the bearing member 7. For convenience of explanation, the lid member 10 side will be described below, and the seal member 11 side will be described as an upper side.

  The shaft member 2 is made of, for example, a metal material such as stainless steel, and includes a shaft portion 2a and a flange portion 2b provided at one end of the shaft portion 2a. Or it can also be set as the hybrid structure which comprised the shaft part 2a with the metal and the flange part 2b with resin. In the present embodiment, the outer peripheral surface 2a1 of the shaft portion 2a is formed in a perfect circle shape with no irregularities. Moreover, both end surfaces 2b1 and 2b2 of the flange portion 2b are formed in a flat surface shape without irregularities.

  The bearing member 7 is composed of an electroformed portion 8 formed by electroforming, which will be described in detail later, and a holding portion 9 that is injection-molded by inserting the electroformed portion 8. It is formed with a resin composition. The base resin constituting the resin composition is not particularly limited as long as it can be injected. For example, polysulfone (PSU), polyethersulfone (PES), polyphenylsulfone (PPSU), polyetherimide (PEI), etc. In addition to amorphous resins, crystalline resins such as liquid crystal polymer (LCP), polyetheretherketone (PEEK), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS) can be used. These base resins are mixed with one or two or more kinds of fillers such as reinforcing materials (regardless of fiber, powder, etc.), lubricants, conductive materials and the like.

  In addition to the resin material, a metal material can be used as the injection material. As the metal material, for example, a low melting point metal material such as a magnesium alloy or an aluminum alloy can be used. In addition, the holding part 9 can also be formed by so-called MIM molding in which after the injection molding with a mixture of metal powder and binder, degreasing and sintering. In addition, ceramic can also be used as an injection material.

  The holding portion 9 has a cylindrical sleeve portion 9a having an electroformed portion 8 disposed on the inner periphery, and extends downward from the outer diameter side of the sleeve portion 9a, and is positioned on the outer diameter side of the flange portion 2b of the shaft member 2. The first large-diameter portion 9b and a second large-diameter portion 9c extending upward from the outer diameter side of the sleeve portion 9a are formed, and the respective portions 9a to 9c are formed as an integrated product having no interface. In addition, in the example of illustration, although the inner periphery of the 1st large diameter part 9b and the 2nd large diameter part 9c is formed in the same diameter, it is good also as a different diameter.

  On the inner peripheral surface (small-diameter inner peripheral surface) 7a of the bearing member 7 (electroformed portion 8), two upper and lower regions serving as the radial bearing surface A of the radial bearing portions R1 and R2 are provided separately in the axial direction. As shown in FIG. 3, a plurality of dynamic pressure grooves 7a1 and 7a2 arranged in a herringbone shape, for example, are formed in these two regions as radial dynamic pressure generating portions. The upper dynamic pressure groove 7a1 is formed axially asymmetric with respect to the axial center (the axial center of the upper and lower inclined groove regions) m, and the axial dimension X1 of the upper region from the axial center m is the lower region. It is larger than the axial dimension X2. On the other hand, the lower dynamic pressure grooves 7a2 are formed symmetrically in the axial direction, and the axial dimensions of the upper and lower regions thereof are respectively equal to the axial dimension X2. In this case, when the shaft member 2 rotates, the pulling force (pumping force) of the lubricating oil by the dynamic pressure groove is relatively larger in the upper dynamic pressure groove 7a1 than in the lower symmetrical dynamic pressure groove 7a2. When such a pumping force is not required, the upper dynamic pressure groove 7a1 can be symmetrical in the axial direction, like the lower dynamic pressure groove 7a2. In addition to providing the electroformed portion 8 over the entire surface of the small-diameter inner peripheral surface 7a of the bearing member 7 as shown in the illustrated example, it can also be provided only in the region that becomes the radial bearing surface A. In this case, the electroformed portion 8 is Discontinuous in the axial direction.

  Further, a first thrust bearing portion is provided in the whole or part of the annular region of the lower end surface 7b of the bearing member 7 (the first end surface provided between the small-diameter inner peripheral surface 7a and the first large-diameter inner peripheral surface 7c). A thrust bearing surface B of T1 is formed, and a plurality of dynamic pressure grooves 7b1 arranged in a spiral shape as shown in FIG. 3B are formed on the thrust bearing surface B as thrust dynamic pressure generating portions.

  On the inner peripheral surface (first large-diameter inner peripheral surface) 7c of the first large-diameter portion 9b of the bearing member 7 (holding portion 9), a bottomed substantially cylindrical lid member 10 made of resin or metal material is provided. Fixed. The lid member 10 includes a cylindrical side portion 10a and a bottom portion 10b that seals a lower end opening of the side portion 10a, and these are integrally formed. A thrust bearing surface C of the second thrust bearing portion T2 is formed in the whole or a part of the annular region of the upper end surface 10b1 of the bottom portion 10b, and the thrust bearing surface C is arranged in a spiral shape, for example, as a thrust dynamic pressure generating portion. A plurality of dynamic pressure grooves are formed (not shown).

  The outer peripheral surface 10a1 of the lid member 10 is fixed to the inner peripheral surface 7c of the first large-diameter portion 9b of the bearing member 7 (holding portion 9) by an appropriate means such as press fitting or adhesion. At this time, the flange portion 2 b of the shaft member 2 is accommodated in a space formed between the lower end surface 7 b of the bearing member 7 and the upper end surface 10 b 1 of the bottom portion 10 b of the lid member 10. The upper end surface 10a2 of the side portion 10a of the lid member 10 is in contact with the lower end surface 7b of the bearing member 7, whereby a later-described thrust bearing gap is managed to a specified width.

  On the inner peripheral surface 7e of the second large diameter portion 9c of the bearing member 7 (holding portion 9), an annular seal member 11 formed of a metal material or a resin material is press-fitted, bonded, or an appropriate means using this in combination. It is fixed with. The inner peripheral surface 11a of the seal member 11 increases in diameter in a tapered shape as it goes upward. Between the inner peripheral surface 11a and the outer peripheral surface 2a1 of the shaft portion 2a facing the inner peripheral surface 11a, An annular seal space S in which the radial dimension gradually increases as it goes to is formed. Lubricating oil, for example, is injected as a lubricating fluid into the internal space of the dynamic pressure bearing device 1 sealed with the seal member 11, and the inside of the dynamic pressure bearing device 1 is filled with the lubricating oil. In this state, the oil level of the lubricating oil is always maintained within the range of the seal space S. The seal member 11 can be formed integrally with the bearing member 7 in order to reduce the number of parts and the number of assembly steps.

  In the hydrodynamic bearing device 1 having the above-described configuration, when the shaft member 2 rotates, the region that forms the radial bearing surface A that is spaced apart at two upper and lower portions of the electroformed portion 8 that constitutes the bearing member 7 is the outer periphery of the shaft member 2. It faces the surface 2a1 through a radial bearing gap. As the shaft member 2 rotates, a dynamic pressure of lubricating oil is generated in each radial bearing gap, and the shaft member 2 is supported in a non-contact manner in the radial direction by the pressure. As a result, the first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 2 in a non-contact manner so as to be rotatable in the radial direction are formed.

  Further, when the shaft member 2 rotates, the region that becomes the thrust bearing surface B formed on the lower end surface 7b of the bearing member 7 faces the upper end surface 2b1 of the flange portion 2b of the shaft member 2 through the thrust bearing gap. . At the same time, when the shaft member 2 rotates, the region that becomes the thrust bearing surface C formed on the upper end surface 10b1 of the lid member 10 faces the lower end surface 2b2 of the flange portion 2b of the shaft member 2 through the thrust bearing gap. . As the shaft member 2 rotates, dynamic pressure of lubricating oil is generated in both thrust bearing gaps, and the shaft member 2 is supported in a non-contact manner so as to be rotatable in both thrust directions. Thereby, the 1st thrust bearing part T1 and the 2nd thrust bearing part T2 which support the shaft member 2 in a non-contact manner so as to be rotatable in the thrust direction are formed.

  During operation of the hydrodynamic bearing device 1, the lubricating oil filled in the internal space may become a negative pressure in a part of the region. The generation of such negative pressure causes the generation of bubbles, the leakage of lubricating oil, the generation of vibrations, etc., and causes a decrease in rotational performance. Therefore, in this embodiment, in order to prevent the generation of local negative pressure, the dynamic pressure groove shape on the inner periphery upper side of the bearing member 7 is made asymmetric in the axial direction as described above, and the lubricating oil satisfying the radial bearing clearance is And a circulation path 12 for returning the lubricating oil pushed downward to the upper end of the radial bearing gap to forcibly circulate the lubricating oil inside the hydrodynamic bearing device 1. Adopted.

  The circulation path 12 illustrated in FIG. 2 is formed in the axial through hole 12a opened from the seal space S opened to the atmosphere to the first end surface 7b of the bearing member 7 and the lower end surface 11b of the seal member 11. The first radial flow path 12b, an annular flow path 12c formed on the upper end surface 7d of the bearing member 7, and a second radial flow path 12d connected from the annular flow path 12c to the upper end of the radial bearing gap. Yes. In the illustrated example, the case where the first radial flow path 12b is formed on the lower end face 11b of the seal member 11 and the second radial flow path 12d is formed on the upper end face 7d of the bearing member 7 is illustrated. The radial flow paths 12b and 12d may be formed on the opposing surfaces.

  Thus, by providing the circulation path 12, during the operation of the hydrodynamic bearing device 1, the thrust bearing gap → the axial through hole 12a → the first radial flow path 12b → the annular flow path 12c → the second radius. Lubricating oil circulates in the bearing device through the path of the directional flow path 12d → the upper end of the radial bearing gap. As a result, local negative pressure generation of the lubricating oil in the internal space of the hydrodynamic bearing device 1 can be prevented, and high bearing performance can be maintained. In the illustrated example, the through holes 12a are formed to have the same diameter in the axial direction. However, the through holes 12a may have different diameters at respective portions in the axial direction (for example, the diameter may be gradually reduced upward in the axial direction).

  Next, the manufacturing process of the hydrodynamic bearing device 1 will be described based on the drawings with a focus on the manufacturing process of the bearing member 7.

  4A to 4C show a part of the manufacturing process of the bearing member 7 in the fluid dynamic bearing device 1. More specifically, FIG. 4 (a) is a process of manufacturing the master member 13, FIG. 4 (b) is a process of masking a required portion of the master member 13, and FIG. 4 (c) is a process of forming the electroformed member 15 by electroforming. The process to form is shown. After these steps, the bearing member 7 is manufactured through a step of molding the electroformed portion 8 of the electroformed member 15 with a resin material and a step of separating the electroformed portion 8 and the master member 13.

  In the process shown in FIG. 4A, a solid shaft-shaped master member 13 formed of a conductive material, for example, stainless steel, nickel chrome steel, other nickel alloy, chromium alloy, or the like that has been subjected to a quenching process is formed. It is formed. In addition to these metal materials, the master member 13 can also be formed of a non-ferrous metal material such as ceramic subjected to a conductive treatment (for example, forming a conductive film on the surface).

  Formed in a partial region of the outer peripheral surface 13 a of the master member 13 is a forming portion N for forming the electroformed portion 8 of the bearing member 7. The forming part N has a shape in which the concavo-convex pattern of the inner peripheral surface of the electroformed part is reversed, and in two axial directions, there are circumferential rows of recesses 13a1 and 13a2 forming the hills between the dynamic pressure grooves 7a1 and 7a2. Is formed in the direction. Of course, the shape of the recesses 13a1 and 13a2 may correspond to the shape of the dynamic pressure generating portion and may be formed in a spiral shape or the like.

  In the step shown in FIG. 4B, masking 14 (indicated by a dotted pattern in the figure) is applied to the outer surface of the master member 13 except for the molding portion N (masking step). As the covering material for the masking 14, an existing product having non-conductivity and corrosion resistance against the electrolyte solution is appropriately selected and used.

  In electroforming, after the master member 13 is immersed in an electrolyte solution containing metal ions such as Ni and Cu, the master member 13 is energized, and the masking 14 is applied to the outer surface of the master member 13. It is carried out by depositing the target metal (electrolytic deposition) in a non-existing region (molded part N). The electrolyte solution may contain a sliding material such as carbon or PTFE (polytetrafluoroethylene) or a stress relaxation material such as saccharin as necessary. The type of electrodeposited metal is appropriately selected according to physical properties such as hardness and fatigue strength required for the bearing surface of the hydrodynamic bearing, and chemical properties.

  The electroformed part 8 can also be formed by a method according to electroless plating in addition to the method according to the electrolytic plating described above. In that case, the conductivity of the master member 13 and the insulation of the masking 14 are not required.

  By passing through the above process, as shown in FIG.4 (c), the electroformed member 15 which adhered the electroformed part 8 to the shaping | molding part N of the master member 13 is formed. At this time, the shape of the concave portions 13a1 and 13a2 formed in the molding portion N is transferred to the inner peripheral surface of the electroformed portion 8, and the plurality of dynamic pressure grooves 7a1 and 7a2 shown in FIG. Formed apart. In addition, if the thickness of the electroformed part 8 is too thick, the peelability from the master member 13 is lowered. Conversely, if the thickness is too thin, the durability of the electroformed part 8 is reduced. Furthermore, it is set to an optimum thickness (for example, about 5 μm to 200 μm) according to the application.

  Next, the electroformed member 15 formed through the above steps is transferred to a molding step. Although illustration is omitted, in the molding process, the electroformed member 15 is set as an insert part in a predetermined mold, and then injection molding (insert molding) is performed using the resin material. After injection of the resin material, when the mold was opened by solidifying the resin material, the electroformed member 15 including the master member 13 and the electroformed portion 8 and the holding portion 9 were integrated as shown in FIG. A molded product is obtained. At this time, on the lower end surface 7b of the bearing member 7, a plurality of dynamic pressure grooves 7b1 arranged in a spiral shape shown in FIG. Note that the axial through hole 12a, the annular flow path 12c, and the second radial flow path 12d can also be formed simultaneously with the injection molding.

  This molded product is then transferred to the separation step, where the electroformed part 8 is peeled off from the outer periphery of the master member 13, and the electroformed part 8 and the holding part 9 are integrated (bearing member 7), the master member 13, Separated. In this separation step, for example, an impact is applied to the electroformed member 15 or the bearing member 7, and the inner peripheral surface of the electroformed portion 8 is radially expanded to have a minute gap (radial dimension) between the outer peripheral surface of the master member 13. Then, the master member 13 is pulled out from the inner periphery of the electroformed part 8. In addition, the master member 13 can also be separated using the difference in thermal expansion between the electroformed part 8 and the master member 13.

  The shaft member 2 manufactured separately from the master member 13 is inserted into the bearing member 7 separated from the master member 13 as described above, and other components are assembled, and then the internal space of the bearing member 7 is lubricated. The fluid dynamic bearing device 1 shown in FIG. 2 is completed by filling the oil. On the other hand, since the separated master member 13 can be repeatedly used for electroforming, the highly accurate bearing member 7 can be mass-produced stably and at low cost.

  As described above, in the present invention, the bearing member 7 has the electroformed portion 8 in at least a portion (radial bearing surface A) facing the radial bearing gap on the inner peripheral surface. The electroformed part 8 is a metal layer formed by electroforming. Due to the characteristics of electroforming, the inner peripheral surface of the electroformed part 8 has high accuracy up to a very fine surface shape of the master member 13. Therefore, if the molding part N of the master member 13 is formed with high precision, the radial bearing surface A of the electroformed part 8 can be formed with high precision and low cost without any special post-processing. can do.

  Further, since the linear expansion coefficient of the radial bearing surface A is lower than in the conventional configuration in which the radial bearing surface A is provided in the resin portion, the amount of variation in the radial bearing gap width due to temperature change can be suppressed. Further, since the wear resistance of the radial bearing surface A is increased, the amount of wear of the radial bearing surface A can be reduced even if sliding contact with the shaft member 2 is repeated during starting and stopping. From the above, according to the present invention, it is possible to simultaneously achieve cost reduction and high rotation accuracy of the hydrodynamic bearing device 1.

  In the above description, the hydrodynamic bearing device 1 having a configuration in which the radial bearing surface A is provided in the electroformed portion 8 has been described. However, in addition to the radial bearing surface A, a thrust bearing surface (in this embodiment, a thrust bearing surface). B) can also be provided in the electroformed part 8. FIG. 6 shows an example thereof, in which the electroformed part 8 has a radial electroformed part 81 having a radial bearing surface A, and a thrust electroformed part having a thrust bearing surface B formed integrally with the radial electroformed part 81. 82. By providing the thrust bearing surface B in the electroformed part 8 in this way, high rotational accuracy can be obtained even in the first thrust bearing part T1 due to the above-described characteristics of electroforming. The other constituent members and functions are the same as those of the hydrodynamic bearing device 1 shown in FIG.

  The bearing member 7 shown in FIG. 6 can be formed using, for example, a master member 23 as shown in FIG. The master member 23 includes a first cylindrical portion 23a having a small diameter and a second cylindrical portion 23b having a large diameter continuous with the first cylindrical portion 23a in the axial direction. Masking 14 is applied to the outer peripheral surface of the first cylindrical portion 23a except for a partial axial direction region continuous with the upper end surface of the second cylindrical portion 23b and the upper end surface of the second cylindrical portion 23b. When electroforming is performed using the master member 23, the electroformed member 25 in which the radial electroformed portion 81 and the thrust electroformed portion 82 are integrally formed is obtained. Then, by performing insert molding using the electroformed member 25, the bearing member 7 shown in FIG. 6 is formed.

  In the embodiment shown in FIG. 6, the radial electroformed part 81 and the thrust electroformed part 82 are illustrated as an integral structure, but both may be separated. When both are made into separate structures, the formation area of the masking 14 may be changed, for example.

  Although the embodiments of the present invention have been exemplified above, the present invention is not limited to these embodiments, and can be suitably used in the configuration examples of the hydrodynamic bearing device as shown below. In the following description, members and elements having the same functions as those in the embodiment shown in FIG.

  FIG. 8 shows another embodiment of the hydrodynamic bearing device 1. In the hydrodynamic bearing device 1 shown in FIG. 1, the second thrust bearing portion T2 mainly includes an upper end surface 7d on the outer diameter side of the bearing member 7, and a lower end surface 3a1 of the plate portion 3a in the disk hub 3 facing the upper end surface 7d. 2 in that the seal space S is formed between the tapered outer peripheral surface 7f of the bearing member 7 and the inner peripheral surface 3b1 of the cylindrical portion 3b of the disk hub 3. Different form and configuration. In addition, in the figure, although the structure which provided only the radial bearing surface A in the electroformed part 8 is illustrated, the thrust bearing surface B which forms 1st thrust bearing part T1 similarly to embodiment shown in FIG. Alternatively, any one of the thrust bearing surfaces C forming the second thrust bearing portion T2 may be provided in the electroformed portion 8 that is integral with or separate from the radial bearing surface A.

  FIG. 9 shows another embodiment of the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 in the figure is mainly provided with flange portions 21 and 22 spaced apart at two axial positions of the shaft member 2, one end surface of both flange portions and both end surfaces 9 a 2 of the bearing member 7, The thrust bearing portions T1 and T2 are provided between 9a3 and the seal space is provided at both end openings of the bearing member 7. The seal spaces S1 and S2 are the outer peripheral surfaces 21a of the flange portions 21 and 22, respectively. 2 is different from the embodiment shown in FIG. 2 in that it is provided between 22a and the large-diameter inner peripheral surface of the bearing member 7. In this embodiment as well, as in the embodiment shown in FIG. 6, either one of the thrust bearing surface B forming the first thrust bearing portion T1 or the thrust bearing surface C forming the second thrust bearing portion T2 is used. Also, it can be configured to be provided in the electroformed portion 8 that is integral with or separate from the radial bearing surface A.

  In the embodiment described above, the herringbone shape or spiral shape dynamic pressure groove is illustrated as the radial dynamic pressure generating portion, but the present invention is not limited to this, for example, the radial dynamic pressure generation As a portion, a plurality of arc surfaces, axial grooves, or harmonic wave surfaces are provided, and either or both of the radial bearing portions R1, R2 are so-called multi-arc bearings, step bearings, or non-circular bearings. (Not shown). These dynamic pressure generating portions can be formed in the electroformed portion 8 of the bearing member 7 in the same manner as in the above-described embodiment. However, the forming method conforms to each step in forming the dynamic pressure grooves, and thus the details are provided. The detailed explanation is omitted.

  In the above description, the radial bearing portions are separated from each other in the axial direction by two locations like the radial bearing portions R1 and R2, but one location is provided over the upper and lower regions of the inner peripheral surface of the bearing member 7. Or it is good also as a structure which provided the radial bearing part of three or more places.

  Further, in the embodiment described above, the case where a radial dynamic pressure generating portion such as a dynamic pressure groove is formed in the electroformed portion 8 constituting the bearing member 7 is illustrated, but the radial dynamic pressure generating portion is the electroformed portion 8. Can be formed on the outer peripheral surface 2a1 of the shaft portion 2a facing each other via a radial bearing gap using an appropriate means such as machining or etching such as rolling or cutting, or ink jet printing. In this case, the electroformed part 8 is formed in a cylindrical surface shape without irregularities.

  Further, in the above description, the dynamic pressure grooves arranged in a spiral shape or a herringbone shape are illustrated as the thrust dynamic pressure generating portion. However, the thrust dynamic pressure generating portion includes a plurality of other radial groove shapes. Are provided at predetermined intervals in the circumferential direction, and one or both of the thrust bearing portions T1 and T2 may be constituted by so-called step bearings, so-called wave-type bearings (step-type wave type). Yes (not shown). Moreover, you may form a thrust dynamic pressure generation | occurrence | production part in the both end surfaces of the flange part 2b etc. which oppose the bearing member 7 and the cover member 10 through a thrust bearing clearance gap.

  Further, in the above embodiment, the lubricating oil is exemplified as the lubricating fluid that fills the inside of the hydrodynamic bearing device 1, but other fluids that can generate a dynamic pressure in each bearing gap, such as a magnetic fluid, for example. In addition, a gas such as air can be used.

It is sectional drawing which shows an example of the spindle motor for information devices incorporating the hydrodynamic bearing apparatus which has a structure of this invention. It is sectional drawing of the dynamic pressure bearing apparatus which concerns on this invention. (A) A figure is a longitudinal cross-sectional view of a bearing member, (b) A figure is a figure which shows the 1st end surface of a bearing member. (A) is a perspective view of a master member, (b) is a perspective view showing a state where masking is applied to the master member, and (c) is a perspective view of an electroformed member. It is sectional drawing of the bearing member immediately after insert molding. It is sectional drawing which shows the other form of a hydrodynamic bearing apparatus. It is a perspective view which shows the other form of an electroformed member. It is sectional drawing which shows the other form of a hydrodynamic bearing apparatus. It is sectional drawing which shows the other form of a hydrodynamic bearing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 2 Shaft member 7 Bearing member 8 Electroformed part 9 Holding part 13, 23 Master member 14 Masking 15, 25 Electroformed member A Radial bearing surface B, C Thrust bearing surface 7a1, 7a2 Dynamic pressure grooves R1, R2 Radial bearing part T1, T2 Thrust bearing part S, S1, S2 Seal space

Claims (5)

A bearing member having a mounting surface for mounting to the base member, a shaft member inserted on the inner periphery of the bearing member and including a shaft portion and a flange portion, and between the inner peripheral surface of the bearing member and the outer peripheral surface of the shaft member In a dynamic pressure bearing device comprising a radial dynamic pressure generating section that generates pressure by a dynamic pressure action of a lubricating fluid in a radial bearing gap,
The hydrodynamic bearing device, wherein the bearing member is an injection-molded product in which an electroformed part is arranged at least on a portion of the inner peripheral surface facing the radial bearing gap.   The bearing member is provided between the small-diameter inner peripheral surface provided with the electroformed portion, the large-diameter inner peripheral surface located on the outer-diameter side of the flange portion, and the small-diameter inner peripheral surface and the large-diameter inner peripheral surface. The hydrodynamic bearing device according to claim 1, further comprising an end surface.   The hydrodynamic bearing device according to claim 2, wherein the bearing member is provided with an axial through hole that opens in the first end surface.   3. The hydrodynamic bearing device according to claim 2, further comprising a thrust dynamic pressure generating portion that generates pressure by a dynamic pressure action of a lubricating fluid in a thrust bearing gap between the first end surface of the bearing member and one end surface of the flange portion.   The hydrodynamic bearing device according to claim 4, wherein an electroformed part is disposed on the first end surface of the bearing member.

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