JP4937675B2 - Hydrodynamic bearing device - Google Patents

Description

  The present invention relates to a hydrodynamic bearing device.

  The hydrodynamic bearing device supports a rotating member of a pair of relatively rotating members with a film of fluid generated in a bearing gap. This type of bearing device has features such as high-speed rotation, high rotation accuracy, and low noise, and more specifically as a bearing device for motors installed in various electrical equipment including information equipment. As a bearing device for a spindle motor of a disk drive in an optical disk device such as a magnetic disk device such as CD-ROM, CD-R / RW, DVD-ROM / RAM, or a magneto-optical disk device such as MD or MO, or a laser It is preferably used as a bearing device for a motor such as a polygon scanner motor of a beam printer (LBP), a color wheel motor of a projector, or a fan motor.

  For example, in a hydrodynamic bearing device incorporated in a spindle motor for HDD, one or both of a radial bearing portion that supports a shaft member in the radial direction and a thrust bearing portion that supports the shaft member in a thrust direction are configured by a dynamic pressure bearing. There is a case. In this case, a dynamic pressure groove that forms a dynamic pressure generating portion is formed on either the inner peripheral surface of the bearing sleeve or the outer peripheral surface of the shaft member facing the bearing sleeve, and the radial bearing gap between the two surfaces is radial. A bearing part is often formed (see, for example, Patent Document 1).

  Each component part of the hydrodynamic bearing device including these shaft members is required to have high processing accuracy and assembly accuracy in order to ensure the high rotational performance required as the performance of information equipment increases. On the other hand, the cost reduction requirements for hydrodynamic bearing devices are becoming more and more severe.

  As a measure for reducing the cost of the hydrodynamic bearing device, it has been proposed to form the shaft member with a resin (see, for example, Patent Document 2).

However, when the shaft member is made of resin, the shaft member expands to the outer diameter side as the temperature rises, and as a result, the radial bearing gap may be reduced. A means to maintain the bearing gap by forming the bearing sleeve with the same kind of resin is also conceivable, but resin parts need to be set with molding dimensions (mold dimensions) taking into account shrinkage during molding. It is difficult to mold the part with high accuracy. In addition, when the members that form the bearing gap are both formed of resin, it is difficult to obtain a highly accurate bearing gap because of variations in the molding dimensions of both.
JP 2003-239951 A JP 2000-330066 A

  In view of the above circumstances, an object of the present invention is to provide a hydrodynamic bearing device that can exhibit high bearing performance by forming a highly accurate bearing gap at low cost.

In order to solve the above-mentioned problems, the present invention comprises a bearing gap, a fixed member that forms the bearing gap, and a rotating member, and an outer peripheral surface that faces the bearing gap. In the structure in which the rotating member is supported by the formed fluid film, the region facing the bearing gap on the outer peripheral surface of the shaft is constituted by a metal plating portion made of metal deposited on the inner periphery of the master, and the metal plating portion of the shaft The resin area is made of resin, and the resin part is an injection molded part with the metal plating part as the insert part. The outer peripheral surface of the metal plating part separates the metal plating part from the master inner periphery after injection molding of the resin part. Provided is a hydrodynamic bearing device characterized in that it is a surface on the deposition start side obtained by making it possible .

  As described above, the present invention is characterized in that the region facing the bearing gap on the outer peripheral surface of the shaft constituting one of the fixed member and the rotating member is formed by the metal plating portion. According to this configuration, since the region facing the bearing gap in the outer peripheral surface of the shaft is covered with the metal plating portion, for example, even when the resin forming region of the shaft expands at high temperatures, the metal plating that covers this By suppressing the expansion of the resin part to the outer diameter side at the part, it is possible to minimize the fluctuation of the bearing gap. Therefore, with the shaft having the above-described configuration, it is possible to ensure a highly accurate bearing gap while reducing the size. Moreover, since it can form very thinly if it is a metal plating part, the ratio of the resin part can be increased as much as possible, and the merit of cost reduction by resinization can be enjoyed.

  In addition, the metal plating part in this invention contains what was formed by the method according to the electroless-plating process other than what was formed by the method according to electroplating process. The electroless plating mentioned here means a method in which metal is deposited by the action of a reducing agent added to an aqueous solution of a metal salt without using electricity. Of course, the electroformed part described later includes those formed by the same method.

  A region facing the bearing gap in the outer peripheral surface of the shaft can be formed, for example, on the surface on the deposition start side of the metal plating portion. What has such a configuration is called an electroformed part, and is obtained by electrolytically depositing a metal on the surface of a master (master) and then peeling it off from the master. In the case of the electroformed part formed in this way, the surface shape of the master is high to a very fine level on the master side surface (deposition start side surface) of the electroformed part due to the characteristics of the above various plating processes. Transferred with accuracy. Therefore, if the surface accuracy of the master is increased and the surface on the deposition start side of the electroformed part is used as a surface for forming the bearing gap, a bearing surface with high surface accuracy can be produced at low cost without any special post-processing. Can get to. Further, the processing accuracy (surface accuracy) depends only on the surface accuracy of the corresponding master, and does not depend on the size. Therefore, a shaft provided with an electroformed part can ensure high processing accuracy (surface accuracy) while achieving downsizing.

  Further, as described above, when the metal plating part is formed on the outer periphery of the shaft, it is preferable to provide the resin part with an engaging part that engages with the metal plating part in the axial direction. At the time of molding the resin part, shrinkage occurs toward the axis center side, so the adhesion with the metal plating part formed on the outer periphery of the resin part is lowered, and in some cases, there is a risk of falling off, but the above-mentioned As described above, by providing the engagement portion, it is possible to prevent the metal plating portion from being removed. Such an engaging portion is formed by forming a resin portion using a molding die provided with a portion corresponding to the engaging portion (for example, provided with an annular step portion) before forming the metal plating portion. Can do. Alternatively, if the resin part is injection-molded using the electroformed part (and master) as an insert part, the resin part is formed by molding the resin part so that the resin wraps around both ends of the electroformed part in the axial direction. A part can also be formed.

  The shaft configured as described above may constitute either a rotating member or a fixed member. In this case, it is also possible to form at least a part of the shaft-side member (rotating member or fixed member) integrally with the resin portion of the shaft.

  Moreover, it is the master used for forming a metal plating part (electroformed part), and a bearing clearance can also be formed between the outer peripheral surfaces of the electroformed part. Alternatively, the fixing member can be formed integrally with the housing by resin injection molding using the master as an insert part. Since both of these use the master as a bearing sleeve as it is, the outer peripheral surface of the electroformed part and the inner peripheral surface of the master that form a bearing gap with each other are in the relationship between the transfer source surface and the transfer destination surface. is there. Therefore, if the bearing gap is configured with the electroformed part and the master, a highly accurate bearing gap with very little variation can be obtained, and a matching process between the shaft and the bearing sleeve that may be normally performed is performed. Can be omitted.

  The hydrodynamic bearing device having the above-described configuration can be used as, for example, a motor including the bearing device, and can be suitably used for a small motor such as an axial fan.

  As described above, according to the present invention, it is possible to provide a hydrodynamic bearing device that can exhibit high bearing performance by forming a highly accurate bearing gap at low cost.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. The “up and down” direction in the following description merely indicates the up and down direction in each drawing for the sake of convenience, and does not specify the installation direction, usage mode, or the like of the hydrodynamic bearing device. The same applies to the description of other embodiments shown in FIG.

  FIG. 1 shows a cross-sectional view of a motor provided with a hydrodynamic bearing device 1 according to an embodiment of the present invention. This motor is used as a cooling motor provided with a fan, for example, as shown in the figure. A hydrodynamic bearing device 1 that rotatably supports a shaft 2 and a rotor plate provided at one end of the shaft 2 are used. For example, a drive unit 4 including a stator coil 4a and a rotor magnet 4b opposed to each other via a radial gap, and a base 5 that fixes a housing 8 of the hydrodynamic bearing device 1 to the inner periphery. A rotor magnet 4b is fixed to the inner diameter side of the rotor plate portion 3 via a yoke 7, and one or more fans (blades) 6 are disposed on the outer diameter side thereof. The fan 6 can be formed integrally with the rotor plate portion 3 or can be fixed to the rotor plate portion 3 by retrofitting it.

  In the motor having the above configuration, when the stator coil 4a is energized, the rotor magnet 4b is rotated by the exciting force between the stator coil 4a and the rotor magnet 4b, and is thereby fixed to the rotor plate portion 3 and the rotor plate portion 3. The fan 6 rotates integrally with the shaft 2. By this rotation, the fan 6 generates an air flow in the direction of the rotation axis of the motor, and the air flow is sent toward a component to be cooled (not shown) to cool the component. .

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a housing 8 fixed to a base 5, a bearing member 9 disposed on an inner periphery of the housing 8, a shaft 2 that rotates relative to the housing 8 and the bearing member 9, and a housing 8. And a seal portion 10 that seals fluid between the shaft 2 and the housing 8. In this embodiment, the rotating member is constituted by the shaft 2 integrally having the rotor plate portion 3. The housing 8, the bearing member 9, and the seal portion 10 constitute a fixing member.

  The housing 8 has a bottomed cylindrical shape, and is formed of, for example, a resin material. In this embodiment, the housing 8 is formed by resin injection molding integrally with the seal portion 10 using the bearing member 9 disposed on the inner peripheral side as an insert part. The upper end surface 8a at the bottom of the housing 8 is in contact with one end surface 12a of the shaft 2 when the shaft 2 is inserted into the inner periphery of the bearing member 9, and between the shaft 2 when the shaft 2 is rotated. A pivot bearing described later is configured.

  The bearing member 9 has a sleeve shape, and is formed of, for example, a sintered metal whose main component is one or both of Cu and Fe. A radial bearing gap is formed between the inner peripheral surface 9a of the bearing member 9 and the outer peripheral surface 11a of the electroformed portion 11 as a metal plating portion to be described later. In this embodiment, although not shown, a region in which a plurality of dynamic pressure grooves are arranged in a predetermined shape (for example, a herringbone shape) is provided as a dynamic pressure generating portion on the entire surface or a partial region of the inner peripheral surface 9a. It is done. The bearing member 9 may be formed of a metal other than sintered metal (such as cast iron or foam metal), or a material other than metal such as resin or ceramic. Moreover, when it has a void | hole inside, the quantity and size of the said void | hole are not ask | required.

  The seal portion 10 is disposed on one end open side of a radial bearing gap formed between the bearing member 9 and the shaft 2. The inner peripheral surface 10a of the seal portion 10 has a shape that gradually increases in diameter toward the open side to the atmosphere, and between the outer peripheral surface of the shaft 2 (here, the large diameter surface 12c of the resin portion 12) facing this surface. A tapered seal space S is formed.

  The axis | shaft 2 consists of the electroformed part 11 and the resin part 12 as a metal plating part. Specifically, at least a region facing the radial bearing gap in the outer peripheral surface of the shaft 2 is configured by the electroformed portion 11, and a region excluding the electroformed portion 11 of the shaft 2 is configured by the resin portion 12. In this embodiment, the shaft 2 having the resin portion 12 and the rotor plate portion 3 integrally is formed by resin injection molding using the cylindrical electroformed portion 11 as an insert part. The radial width dimension of the radial bearing gap is slightly smaller than the radial width dimension of the shaft 2 and the bearing member 9, but in FIG. 2, it is drawn larger than the actual dimension for ease of understanding. Yes. The same applies to the radial bearing gaps of FIGS. 6 and 9 described later.

  The shaft 2 having the above configuration is manufactured through the following steps, for example.

  The shaft 2 includes a step of masking the surface of the master 21 used in electrolytic plating with an insulating material, a step of forming an electroformed portion 11 by performing electrolytic plating on the masked master 21, and the electroformed portion 11 and It is manufactured through a process of performing mold forming (insert molding) of the shaft 2 using the master 21 as an insert part and a process of separating the electroformed part 11 from the master 21.

  The master 21 serving as a mother mold of the electroformed part 11 is formed in a sleeve shape from, for example, stainless steel. Of the surface of the master 21, a region where the electroformed part 11 is to be formed on the inner peripheral surface 21 a has a shape that follows the outer peripheral surface 11 a of the electroformed part 11 to be deposited. In this embodiment, as shown in FIG. 3, an inner peripheral surface 21a having a shape corresponding to the outer peripheral surface 11a of the electroformed part 11 is formed so as to have a perfect circular cross section. In this case, since the surface accuracy of the inner peripheral surface 21a directly affects the surface accuracy of the outer peripheral surface 11a of the electroformed part 11 serving as a radial bearing surface, it is desirable that the surface accuracy be finished as high as possible.

  As a material of the master 21, in addition to stainless steel, for example, a chromium-based alloy or a nickel-based alloy can be arbitrarily selected regardless of a metal or a non-metal as long as it has masking property, conductivity, and chemical resistance. is there.

  As shown in FIG. 3, the surface of the master 21 is masked except for the area where the electroformed part 11 is to be formed. In this embodiment, the masking part 22 is formed in the area | region except the outer peripheral surface of a master 21 which makes | forms a sleeve shape, both end surfaces, and the formation area of the electroformed part 11 of the internal peripheral surface 21a (a dotted point in FIG. 3). Area shown by pattern). As the covering material for forming the masking portion 22, a material having insulating properties and corrosion resistance against the electrolyte solution is selectively used.

  In the electroplating process, the master 21 is immersed in an electrolyte solution containing metal ions such as Ni and Cu, and the target metal is energized in the electrolyte solution to remove the target metal from the inner peripheral surface 21a of the master 21. It is carried out by electrolytic deposition. The electrolyte solution can contain a sliding material such as PTFE or carbon, or a stress relaxation material such as saccharin, if necessary. In this embodiment, PTFE particles are used as a sliding material in an electrolyte solution. The kind of the deposited metal is appropriately selected according to required properties such as hardness required for the bearing surface of the bearing or resistance to lubricating oil (oil resistance).

  By passing through the above process, as shown in FIG. 4, the thin cylindrical electroformed part 11 is formed in the area | region which is not coat | covered with the masking part 22 of the master internal peripheral surface 21a. If the thickness of the electroformed part 11 is too thin, the durability of the bearing surface (outer peripheral surface 11a) will be reduced, and if it is too thick, the peelability from the master 21 may be lowered. The optimum thickness is set in accordance with performance, bearing size, application, etc., for example, in the range of 5 μm to 200 μm. In addition to the method according to the above-described electrolytic plating, it is possible to adopt a method according to so-called electroless plating in which a target metal is deposited on the master surface by the action of a reducing agent, as a method for forming the electroformed part 11. It is.

  The electroformed part 11 formed through the above steps is supplied and arranged as an insert part integrally with, for example, the master 21 in a mold for insert molding the resin part 12. In this case, the molding dies 23 and 24 to be used have a cavity 25 that follows the shaft 2 (and the rotor plate portion 3) as shown in FIG. By using the molding dies 23, 24, for example, the molten resin is filled into the cavity 25 from the gate 26 and solidified, whereby the resin portion 12 and the electroformed portion 11 having the shapes shown in FIG. Then, the shaft 2 integrally having the rotor plate portion 3 is formed.

  The material of the resin part 12, that is, the material filled in the cavity 25 of the molding dies 23, 24 may be a material having a lower freezing point than the material of the electroformed part 11, and for example, resin or metal can be used. It is. Among these, examples of the resin material include crystalline resins such as liquid crystal polymer (LCP), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyacetal (POM), polyamide (PA), or polyphenylsulfone. Amorphous resins such as (PPSU), polyethersulfone (PES), polyetherimide (PEI), and polyamideimide (PAI) can be used as the base resin. Moreover, you may add various fillers, such as a reinforcement (regardless of forms, such as a fiber form and a powder form), a lubrication agent, and a electrically conductive agent as needed.

  After the molding, the molded product in which the master 21, the electroformed part 11, and the resin part 12 (in this embodiment, the resin part 12 and the rotor plate part 3) are integrated is removed from the molds 23 and 24. This molded product is separated into the shaft 2 and the master 21 in a subsequent separation step.

  In the separation step, for example, the outer peripheral surface 11 a of the electroformed part 11 is peeled off from the inner peripheral surface 21 a of the master 21 by applying an impact to the master 21 or the electroformed part 11. Thereby, the master 21 is pulled out from the electroformed part 11 and the resin part 12, and the axis | shaft 2 as a finished product is obtained.

  As the separating means for the electroformed part 11, in addition to the above means, for example, the electroformed part 11 and the master 21 are heated (or cooled), and a difference in thermal expansion amount is produced between them, or both. Means using both means (impact and heating) can be used.

  The shaft 2 formed as described above is inserted into the inner periphery of the bearing member 9 fixed to the housing 8, and lubricating oil is injected from the air release side (the seal portion 10 side) of the radial bearing gap. Thereby, the hydrodynamic bearing device 1 in which the bearing internal space including the radial bearing gap is filled with the lubricating oil is completed. Further, a seal space S is formed between the inner peripheral surface 10a of the seal portion 10 and the outer peripheral surface of the shaft 2 (here, the large-diameter surface 12c of the resin portion 12), but as described above. In a state where the bearing internal space is filled with the lubricating oil, the oil level of the lubricating oil is always maintained in the seal space S.

  In the hydrodynamic bearing device 1 configured as described above, when the shaft 2 rotates, the outer peripheral surface 11a of the electroformed part 11 faces the inner peripheral surface 9a of the bearing member 9 as a radial bearing surface. A radial bearing gap is formed between the dynamic pressure groove array region (not shown) formed on the inner peripheral surface 9 a and the outer peripheral surface 11 a of the electroformed part 11. As the shaft 2 rotates, the lubricating oil in the bearing inner space is drawn into the radial bearing gap by the dynamic pressure groove formed in the inner peripheral surface 9a, and the pressure in the gap increases. By such a dynamic pressure action of the dynamic pressure generating portion (dynamic pressure groove), a radial bearing portion R for supporting the shaft 2 in the radial direction in a non-contact manner is formed in the radial bearing gap. At the same time, the one end surface 12a of the shaft 2 is contact-supported (pivot supported) by the upper end surface 8a of the bottom portion of the housing 8 facing this, thereby supporting the shaft 2 rotatably between the both surfaces 12a and 8a in the thrust direction. A thrust bearing portion T is formed.

  As described above, the outer peripheral portion of the shaft 2 including the radial bearing surface is formed by the metal plating portion (here, the electroformed portion 11), and the remaining portion excluding the electroformed portion 11 of the shaft 2 is configured by the resin portion 12. Thus, expansion of the resin portion 12 to the outer diameter side can be suppressed by the electroformed portion 11 provided on the outer diameter side. Therefore, the shaft 2 expands to the outer diameter side as the temperature rises, and a situation in which the radial bearing gap formed between the inner peripheral surface 9a of the bearing member 9 fluctuates greatly is avoided, and the bearing gap is kept at an appropriate interval. Can be maintained.

  Moreover, since the electroformed part 11 is formed by the method according to the electrolytic plating process or the electroless plating process as described above, the surface (outer periphery) of the electroformed part 11 on the deposition start side due to the characteristics of the process. The surface shape of the master 21 (here, the surface shape of the inner peripheral surface 21a) is transferred to the surface 11a) with high accuracy to a very fine level. Therefore, if the surface accuracy of the inner peripheral surface 21a of the master 21 is increased and the surface on the deposition start side of the electroformed part 11 is used as a radial bearing surface, it is highly accurate without performing post-processing such as surface finishing. The outer peripheral surface 11a can be obtained at low cost. Further, since the processing accuracy (surface accuracy) depends only on the surface accuracy of the corresponding master 21 and does not depend on the size, the electroformed part having high surface accuracy even when the shaft 2 is downsized. 11 outer peripheral surfaces 11a can be obtained. Therefore, it is possible to form the hydrodynamic bearing device 1 having a high surface accuracy and thus a high-accuracy bearing gap at a low cost while reducing the size.

  Further, when electrolytic plating is performed on the master 21 having this type of shape, the tendency is that the outermost surface (in this case, the inner peripheral surface 11b) of the electroformed part 11 formed on the inner periphery of the master 21 becomes rough. Thus, the retaining action of the electroformed part 11 can be imparted to the shaft 2. That is, by forming the resin portion 12 in a state where the inner peripheral surface 11b of the electroformed portion 11 is appropriately roughened, the adhesion force with the small diameter surface 12b of the resin portion 12 that becomes the close contact surface with the electroformed portion 11 is increased. Thus, it is possible to prevent the electroformed part 11 from being removed.

  In this embodiment, the shaft 2 is die-molded using the electroformed part 11 as an insert part, so that the part (resin part 12) other than the electroformed part 11 of the shaft 2 is molded and assembled. It can be performed simultaneously in the process, leading to cost reduction. In addition, by inserting the electroformed part 11 integrally with the master 21, even when the electroformed part 11 is thin, it can be easily formed integrally with the resin part 12, and the electroformed part 11 alone It is not necessary to consider the handling characteristics.

  Further, by forming the shaft 2 by resin injection molding using the electroformed part 11 as an insert part, a member to be attached to one end of the shaft 2 such as the rotor plate part 3 is formed integrally with the shaft 2. Can do. Therefore, when the hydrodynamic bearing device 1 is used, it is possible to prevent the lubricating oil from leaking from between the shaft 2 and a member attached to one end of the shaft 2 (between the fixed surfaces).

  As mentioned above, although one Embodiment of this invention was described, this invention is not restricted to the said embodiment, The axis | shaft 2 is comprised with the metal plating part and resin part 12 which face a radial bearing clearance gap. As long as other forms are possible.

  Although the said embodiment demonstrated the case where the resin part 12 which comprises the axis | shaft 2 was made into different diameter shape and integrated by fixing the electroformed part 11 to the outer periphery of a small diameter part, the retaining force of the electroformed part 11 was demonstrated. It is possible to adopt other configurations for improvement. For example, by forming one end of the resin portion 12 of the cavity 25 in a large diameter in advance, the resin portion 12 can be formed so that the resin wraps around the upper and lower ends of the electroformed portion 11. Thus, for example, as shown in FIG. 6, a large diameter portion 12d having a larger diameter than the small diameter portion having the electroformed portion 11 provided on the outer periphery is provided on one end side of the resin portion 12 (the tip end side of the shaft 2). The diameter part 12d can be engaged with the electroformed part 11 in the axial direction using the engaging part. Therefore, it becomes possible to improve the retaining force of the electroformed part 11. Moreover, as shown in the figure, by further clamping the electroformed part 11 from both sides in the axial direction, it is possible to further improve the retaining force.

  Alternatively, as shown in FIG. 7, a masking portion 27 (two locations in the figure) is provided in a part of the area planned to form the electroformed portion 11 of the master inner peripheral surface 21 a, and the regions 22 subjected to these masking, The electroformed part 11 is formed in a region other than 27. In this way, by leaving the electroformed part 11 on the masking part 27 without forming it, a recess (here, a hole) 28 is formed at a location corresponding to the masking part 27 of the cylindrical electroformed part 11. be able to. Therefore, by inserting the electroformed part 11 having the recess 28 and molding the shaft 2 (resin part 12), the molten resin flows into the space (recess 28) formed by the masking part 27 and solidifies. Since the portion that has flowed into the recess 28 and solidified acts as an engaging portion that engages with the electroformed portion 11 in the axial direction, this can be used to prevent the electroformed portion 11 from being removed. In addition, as long as it acts as a retaining for the electroformed part 11, the shape of the recess 28 is arbitrary. In addition to the hole shape shown in FIG. 8, various shapes such as a belt shape extending in the circumferential direction can be adopted. Needless to say, not only the electroformed part 11 but also a metal plating part can be formed, for example, by devising the mold shape of the resin part 11 to form the engaging part.

  Moreover, in the said embodiment, after insert-molding of the axis | shaft 2, what separated and extracted the electroformed part 11 from the master 21 is inserted in the inner periphery of the bearing member 9 fixed to the housing 8 integrally. Although the case where the fluid dynamic bearing device 1 is configured is illustrated, the master 21 can be used as the bearing member 9 as it is. For example, although illustration is omitted, after the electroformed part 11 is separated from the master 21 and pulled out, the housing 8 shown in FIG. 2 is integrally molded with resin in a state where the master 21 is inserted into a molding die. Thus, the master 21 can be used as a bearing member by inserting the shaft 2 into the inner periphery of the master 21 disposed on the inner periphery side of the housing 8. Of course, after separating the electroformed part 11 from the master 21, the master 21 can be used as the bearing member 9 as it is without pulling out the electroformed part 11 (the shaft 2 having the electroformed part 11). In this case, the outer peripheral surface 11a of the electroformed part 11 and the inner peripheral surface 21a of the master 21 that form a radial bearing gap are in a relationship between the transfer source surface and the transfer destination surface. Therefore, if a bearing gap is formed by the electroformed part and the master, a highly accurate bearing gap with very little variation can be obtained. Moreover, in practice, since dimensional variations occur for each product, for example, it is normal to perform matching between the plurality of shafts 2 and the bearing member 9 so that the radial bearing gap is within a predetermined range. However, if the bearing gap is formed by this kind of method, the above-described matching process can be omitted, which is efficient.

  Moreover, although the said embodiment demonstrated the case where the rotating member of the hydrodynamic bearing device 1 was comprised with the axis | shaft 2 which consists of the electroformed part 11 and the resin part 12, on the contrary, the fixing member of the hydrodynamic bearing device 1 was used. It is also possible to configure with the shaft 2. FIG. 9 shows an example thereof. In the hydrodynamic bearing device 1 shown in FIG. 9, the shaft 2 composed of the electroformed portion 11 and the resin portion 12 is formed integrally with the housing 8. Further, a cylindrical portion 13 having the bearing member 9 as an insert part is formed, and this cylindrical portion 13 is provided integrally with the rotor plate portion 3. The seal portion 10 is formed integrally with the tube portion 13. Accordingly, in this embodiment, the shaft 2 and the housing 8 constitute a fixing member, and the bearing member 9, the seal portion 10, and the cylindrical portion 13 constitute a rotating member. In this case, the lower end surface 13b of the lid portion 13a covering the upper end side of the cylindrical portion 13 is contact-supported (pivot supported) by the one end surface 12a of the shaft 2 facing this, thereby having the bearing member 9 and the cylindrical portion 13. The rotating member is supported so as to be rotatable in the thrust direction. The above-described configuration is not limited to the electroformed part 11 but can be applied as long as a metal plating part is provided on the shaft 2.

  As described above, the application example of the present invention to the hydrodynamic bearing device 1 has been described. The hydrodynamic bearing device 1 having the above-described configuration is not limited to the illustrated fan motor, but includes a spindle motor for a disk drive including an HDD spindle motor. The present invention can be suitably applied as a bearing device for various electric motors such as a bearing device. For example, when the hydrodynamic bearing device 1 according to the present invention is applied to an HDD motor, a hub for mounting a disk is used. When the hydrodynamic bearing device 1 is used for a polygon scanner motor, a turntable that holds a polygon mirror, etc. Are attached to the shaft 2 or formed integrally with the shaft 2 as shown. At this time, parts other than the electroformed part 11 and the master 21, for example, the yoke 7 and the rotor magnet 4b including the yoke 7 can be integrally formed.

  Moreover, in the above description, as the dynamic pressure generating portion constituting the radial bearing portion R, an example in which a plurality of dynamic pressure grooves are arranged in a predetermined shape (such as a herringbone shape) is illustrated. It is not limited to this. That is, the hydrodynamic bearing device 1 according to the present invention only needs to include the shaft 2 including the electroformed portion 11 having the radial bearing surface and the resin portion 12, and the presence or absence of the dynamic pressure generating portion does not matter. Therefore, the hydrodynamic bearing device 1 according to the present invention may have a dynamic pressure generating portion provided on either side of the bearing member 9 and the shaft 2, or constitute a so-called fluid perfect bearing having no dynamic pressure generating portion. You may do. Further, the dynamic pressure generating portion is not limited to the above-described arrangement shape, and a dynamic pressure generating portion having an arbitrary form (for example, a spiral-shaped dynamic pressure groove region, a step bearing, a multi-arc bearing, or the like) can be configured.

  Further, in the above description, the case where the thrust bearing portion T is constituted by a pivot bearing has been exemplified. However, like the radial bearing portion R, a thrust bearing gap is interposed between both axially opposed surfaces 12a and 8a. The thrust bearing portion T can also be configured by providing a dynamic pressure generating portion that generates a dynamic pressure action in the gap on any one surface. Of course, in this case, various dynamic pressure generating portions such as a herringbone shape and a spiral dynamic pressure groove arrangement region can be employed as in the case of the radial bearing portion.

  In the above description, the lubricating oil is exemplified as the fluid that fills the inside of the hydrodynamic bearing device 1 and can form a fluid film of the fluid in the radial bearing gap. It is also possible to use a fluid capable of generating water, for example, a gas such as air, a fluid lubricant such as a magnetic fluid, or lubricating grease.

It is sectional drawing of the motor which comprised the hydrodynamic bearing apparatus which concerns on one Embodiment of this invention. It is sectional drawing of a hydrodynamic bearing apparatus. It is a longitudinal cross-sectional view of the master of the state which provided the masking part. It is a longitudinal cross-sectional view of the master in which the electroformed part was formed. It is sectional drawing of the shaping | molding die of the axis | shaft of the state which inserted the electroformed part. It is sectional drawing of the hydrodynamic bearing apparatus provided with the axis | shaft of another structure. It is a longitudinal cross-sectional view of the master of the state which provided the masking part of another structure. It is a longitudinal cross-sectional view of the master in which the electroformed part of another structure was formed. It is sectional drawing of the hydrodynamic bearing apparatus which concerns on other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid dynamic bearing apparatus 2 Shaft 8 Housing 9 Bearing member 9a Inner peripheral surface 11 Electroformed part (metal plating part)
11a Outer peripheral surface 12 Resin portion 21 Master 21a Inner peripheral surface 22 Masking portion R Radial bearing portion T Thrust bearing portion

Claims (4)

A bearing gap, a fixed member that forms the bearing gap, and a rotating member are configured, and an outer peripheral surface is provided with a shaft that faces the bearing gap, and the rotating member is supported by a fluid film formed in the bearing gap. In the hydrodynamic bearing device
The region facing the bearing gap on the outer peripheral surface of the shaft is composed of a metal plating portion made of metal deposited on the inner periphery of the master, and the region excluding the metal plating portion of the shaft is composed of a resin portion ,
Precipitation obtained when the resin part is an injection-molded product with a metal-plated part as an insert part, and the outer peripheral surface of the metal-plated part is separable from the inner circumference of the master after the injection molding of the resin part A hydrodynamic bearing device which is a start side surface . In some of the resin portion to form an engaging portion which engages with a metal plating section in the axial direction, according to claim 1 which constitutes a peripheral surface of the shaft with the outer peripheral surface of the metal plating section in the outer peripheral surface of the engagement portion Fluid bearing device. The hydrodynamic bearing device according to claim 1, wherein a bearing gap is formed between the inner peripheral surface of the master and the outer peripheral surface of the metal plating portion. The motor provided with the hydrodynamic bearing apparatus in any one of Claims 1-3 .

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