JP2008281068A - Fluid bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid bearing device at a low cost which can stably keep a required bearing performance. <P>SOLUTION: The fluid bearing device 1 comprises a bearing member 6 having a sleeve portion 8 forming a radial bearing clearance between the sleeve portion 8 and a shaft member 2 retained in the inner circumference of the sleeve portion 8 and having a housing portion 7 retaining the sleeve portion 8 in the inner circumference of the housing portion 7, and lubricating oil for filling the radial bearing clearance. The lubricating oil can circularly flow through an axial circulation passage 11 formed in the bearing member 6. The circulation passage 11 is formed by being irradiated with a laser beam after the sleeve portion 8 has been inserted and the housing portion 7 has been formed by the injection molding. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device.

  The hydrodynamic bearing device is a bearing device that rotatably supports a shaft member with an oil film formed in a bearing gap by relative rotation between the shaft member and the bearing member. This hydrodynamic bearing device has characteristics such as high-speed rotation, high rotation accuracy, and low noise. In recent years, the hydrodynamic bearing device has been utilized as a motor bearing device for motors mounted on various electrical devices including information devices. More specifically, magnetic disk devices such as HDDs, optical disk devices such as CD-ROM, CD-R / RW, DVD-ROM / RAM, spindle motors such as magneto-optical disk devices such as MD and MO, laser beams, etc. It is suitably used as a bearing device for a motor such as a polygon scanner motor or a fan motor of a printer (LBP).

  This type of hydrodynamic bearing device includes a hydrodynamic bearing having a dynamic pressure generating portion for generating dynamic pressure in lubricating oil that fills the bearing gap, and a true circular bearing having no dynamic pressure generating portion (the bearing cross section is true). It is roughly divided into a circular bearing.

  By the way, during the operation of the hydrodynamic bearing device, the lubricating oil that fills the internal space may become negative pressure in some areas due to various factors. The generation of such a negative pressure causes the generation of bubbles, the leakage of lubricating oil, the generation of vibrations, etc., and causes a decrease in bearing performance. In order to avoid this type of trouble, it is effective to flow and circulate the lubricating oil inside the hydrodynamic bearing device. For the purpose of realizing the flow circulation of the lubricating oil, an axial groove is provided on the outer peripheral surface of the sleeve portion, and the lubricating oil can be flow-circulated between the groove and the inner peripheral surface of the housing portion. The structure which formed this is well-known (for example, refer patent document 1).

On the other hand, the demand for cost reduction of the hydrodynamic bearing device has become increasingly severe in recent years, and in order to meet this demand, there is a case where the sleeve portion is inserted and the housing portion is injection molded. However, in this case, even if the housing part is injection-molded in a state where the groove constituting the circulation path is provided in advance on the surface of the sleeve part, the groove is filled with a molten material such as resin supplied at the time of injection molding. A circuit cannot be formed. Then, what formed the circulation path by inject-molding the housing part in the state which supplied the circulation path formation material to the groove | channel provided in the surface of the sleeve part, and melt | dissolving the circulation path formation material after that is proposed ( For example, see Patent Document 2).
JP 2003-232353 A JP 2006-300188 A

  However, since the circulation path generally has a minute hole diameter of about several tens of μm to several hundreds of μm, it is not easy to supply the circulation path forming material with an accuracy corresponding to the hole diameter. In addition, if the circulation path forming material cannot be completely removed, the lubricating oil may not flow smoothly, and the remaining circulation path forming material may become contaminated and adversely affect the bearing performance. The circuit forming material must be carefully removed. As described above, the conventional configuration requires special consideration for both supply and removal of the circulation path forming material. Therefore, there are cases where the cost merit of inserting the sleeve portion and injection molding the housing portion cannot be fully enjoyed. It was.

  An object of the present invention is to provide a hydrodynamic bearing device capable of stably maintaining desired bearing performance at low cost.

  In order to solve the above-described problems, in the present invention, a bearing member having a sleeve portion that forms a radial bearing gap between the shaft member housed in the inner periphery and a housing portion in which the sleeve portion is arranged on the inner periphery, and the radial bearing gap In the hydrodynamic bearing device that allows the lubricating oil to flow and circulate in the circulation path formed in the bearing member, the circulation path inserts the sleeve portion and injection-molds the housing portion, A hydrodynamic bearing device characterized by being formed by irradiation is provided.

  As described above, the present invention is characterized in that the circulation path is formed by irradiating a laser after inserting the sleeve portion and injection molding the housing portion. With such a configuration, the sleeve portion is inserted and the housing portion is injection-molded, so that a highly accurate bearing member can be obtained at a low cost. On the other hand, a small-diameter circulation path can be formed by only one step of laser irradiation. It can be formed with high accuracy. For this reason, the formation of the circulation path requires at least two steps except for the injection molding step of the housing portion, and the manufacturing cost can be reduced as compared with the conventional configuration that requires special consideration for the two steps. .

  Moreover, if it is the said structure, a circulation path can be formed in the arbitrary site | parts of a bearing member. That is, the circulation path can be provided in the sleeve portion, in the housing portion, or in the sleeve portion and the housing portion. These can be appropriately changed according to the structure (use) of the hydrodynamic bearing device. Note that “providing the circulation path in the sleeve part and the housing part” is a concept including a case where the circulation path is formed on the boundary surface between the sleeve part and the housing part and a case where the circulation path is formed in both parts. .

  In the above configuration, the circulation path can be formed by using various known lasers such as a carbon dioxide laser, YAG laser, fiber laser, etc., but the quality of the laser beam (laser beam) is high and necessary for the formation of the circulation path. A carbon dioxide laser is particularly suitable because it is possible to obtain a stable output easily and stably.

  As described above, if the configuration of the present invention is adopted, the circulation path can be formed at an arbitrary portion of the bearing member, so that there is no particular restriction on the shape of the housing part to be injection-molded. That is, for example, the housing portion can be injection molded so that the sleeve portion and the housing portion are engaged with each other in the axial direction. With such a configuration, since the coupling strength between the sleeve portion and the housing portion can be increased, the impact resistance of the hydrodynamic bearing device can be increased.

  As described above, according to the present invention, the circulation path indispensable for maintaining stable bearing performance can be formed with high accuracy and at low cost. Therefore, a fluid bearing device capable of stably maintaining desired bearing performance can be manufactured at low cost. Can be provided.

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

  FIG. 1 conceptually shows one configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device. This spindle motor is used for a disk drive device such as an HDD, and has a hydrodynamic bearing device 1 that rotatably supports a shaft member 2, a disk hub 3 mounted on the shaft member 2, and a radial gap, for example. And a stator coil 4a and a rotor magnet 4b that are opposed to each other. The stator coil 4 a is attached to the outer periphery of the bracket 5, and the rotor magnet 4 b is attached to the inner periphery of the disk hub 3. The bearing member 6 of the hydrodynamic bearing device 1 is mounted on the inner periphery of the bracket 5. The disk hub 3 holds one or more disks D such as magnetic disks. When the stator coil 4a is energized, the rotor magnet 4b is rotated by the electromagnetic force between the stator coil 4a and the rotor magnet 4b, whereby the disk hub 3 and the shaft member 2 are rotated together.

  FIG. 2 shows a first embodiment of a hydrodynamic bearing device according to the present invention. The hydrodynamic bearing device 1 shown in FIG. 1 includes a bearing member 6, a shaft member 2 inserted into the inner periphery of the bearing member 6, a seal member 9 that seals one end opening of the bearing member 6, and the other end of the bearing member 6. A lid member 10 that seals the opening is provided as a main component. The bearing member 6 includes a sleeve portion 8 that houses the shaft member 2 on the inner periphery, and a housing portion 7 that arranges the sleeve portion 8 on the inner periphery. In the following description, for convenience of explanation, the description will be made with the seal member 9 side as the upper side and the axially opposite side (the lid member 10 side) as the lower side.

  The shaft member 2 is formed of, for example, a metal material such as stainless steel, and includes a shaft portion 2a and a flange portion 2b provided integrally or separately at the lower end of the shaft portion 2a. The shaft member 2 may be entirely formed of a metal material, or may be a hybrid structure of metal and resin, for example, the entire flange portion 2b or a part thereof (for example, both end surfaces) made of resin.

  The sleeve portion 8 constituting the bearing member 6 is formed in a cylindrical shape with a porous body made of sintered metal, in particular, a sintered metal porous body mainly containing copper. Note that the sleeve portion 8 can be formed of not only a sintered metal but also a metal material other than a porous body, for example, a soft metal such as brass. Moreover, it is also possible to form with porous bodies other than a sintered metal.

  The inner peripheral surface 8a of the sleeve portion 8 is provided with two upper and lower regions that are radial bearing surfaces of the first radial bearing portion R1 and the second radial bearing portion R2, and are separated in the axial direction. For example, a plurality of dynamic pressure grooves 8a1 and 8a2 arranged in a herringbone shape as shown in FIG. 3A are formed. The upper dynamic pressure groove 8a1 is formed axially asymmetric with respect to the axial center m (the axial center of the upper and lower inclined groove regions), and the axial dimension X1 of the upper region is lower than the axial center m. It is larger than the axial dimension X2 of the side region. The dynamic pressure groove may be formed on the outer peripheral surface 2a1 of the shaft portion 2a, and the shape thereof may be other known shapes such as a spiral shape.

  The lower end surface 8b of the sleeve portion 8 is provided with a region to be a thrust bearing surface of the first thrust bearing portion T1, and, as shown in FIG. The dynamic pressure groove 8b1 is formed. The dynamic pressure groove 8b1 may be formed on the upper end surface 2b1 of the flange portion 2b, and the shape thereof may be other known shapes such as a herringbone shape.

  A circumferential groove 8c1 is formed in a substantially central portion in the radial direction of the upper end surface 8c of the sleeve portion 8, and one or a plurality of radial grooves 8c2 are formed in a region on the inner diameter side of the circumferential groove 8c1. In the present embodiment, the radial grooves 8c2 are equally arranged at three locations in the circumferential direction.

  The sleeve portion 8 is provided with one or a plurality of circulation paths 11 for communicating the both end faces 8b and 8c. In the present embodiment, the sleeve portion 8 is equally distributed at three places in the circumferential direction as shown in FIG. ing.

  The housing part 7 has a substantially cylindrical shape, and the sleeve part 8 is inserted to be injection-molded with resin. In addition to the resin, the housing part 7 can be injection-molded with a low melting point metal such as an aluminum alloy.

  The lower end opening of the housing part 7 is sealed with a bottomed cylindrical lid member 10 integrally having a disk part 10a and a cylindrical part 10b. The inner bottom surface 10a1 of the disk portion 10a is provided with a region to be a thrust bearing surface of the second thrust bearing portion T2, and although not shown in the drawing, for example, a plurality of dynamic pressure grooves arranged in a spiral shape Is formed. The dynamic pressure groove may be formed on the lower end surface 2b2 of the flange portion 2b, and the shape thereof may be other known shapes such as a herringbone shape. One or more radial grooves 10b11 are formed on the upper end face 10b1 of the cylindrical portion 10b.

  The seal member 9 is formed in a ring shape from a soft metal material such as brass, other metal materials, or a resin material, for example. The inner peripheral surface 9a of the seal member 9 faces the outer peripheral surface 2a1 of the shaft portion 2a via a predetermined seal space S1. The outer diameter side region 9b1 of the lower end surface 9b of the seal member 9 is formed in a state of being slightly retreated upward in the axial direction from the inner diameter side region.

  The manufacturing process of the hydrodynamic bearing device 1 composed of the above constituent members will be described below with a focus on the manufacturing process of the bearing member 6. The bearing member 6 is manufactured through an injection molding step (A) in which the sleeve portion 8 is inserted and the housing portion 7 is injection molded, and a circulation path 11 is formed in the sleeve portion 8 (B). Is done.

(A) Injection molding step In this step, the housing portion 7 is injection molded by inserting the sleeve portion 8 using the mold shown in FIG. At this stage, the circulation path 11 is not formed in the sleeve portion 8. The mold shown in the figure is mainly composed of an upper mold 12 on the movable side and a lower mold 13 on the fixed side, and a cavity 15 corresponding to the shape of the housing part 7 is constituted by both molds 12 and 13. The upper mold 12 is provided with a gate 16 for injecting the molten resin P into the cavity 15. As the shape of the gate 16, an arbitrary shape corresponding to the shape of the housing part 7 to be molded can be selected. A fixing pin 14 is provided on the axis of the lower mold 13, and the sleeve portion 8 is positioned on the outer periphery of the fixing pin 14. The outer peripheral surface 14a of the fixing pin 14 is set to an outer diameter that can elastically hold the sleeve portion 8, for example.

  In the mold having the above-described configuration, after the sleeve portion 8 is positioned and disposed so that the lower end surface 8b is in contact with the inner bottom surface 13a of the lower mold 13, the upper mold 12 is brought close to the lower mold 13 and clamped. After completion of the mold clamping, the molten resin P is injected and filled into the cavity 15 through the gate 16, and the housing part 7 is molded integrally with the sleeve part 8. When the mold opening is performed after the solidification of the molten resin P is completed, the bearing member 6 in which the housing portion 7 and the sleeve portion 8 are integrated is obtained.

  As the base resin constituting the molten resin P, either an amorphous resin or a crystalline resin can be used. Examples of the amorphous resin that can be used include polysulfone (PSU), polyethersulfone (PES), polyphenylsulfone (PPSU), and polyetherimide (PEI). Examples of the crystalline resin that can be used include liquid crystal polymer (LCP), polyether ether ketone (PEEK), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), and the like. The above base resin can be added with a filler that imparts various properties thereto. The type of filler that can be used is not particularly limited. For example, fibrous fillers such as glass fibers, whisker-like fillers such as potassium titanate, scaly fillers such as mica, carbon fibers, and carbon black Fibrous or powdery conductive fillers such as graphite, carbon nanomaterial, and metal powder can be used. These fillers may be used alone or in combination of two or more.

(B) Circulation path formation process The bearing member 6 formed as described above is transferred to the formation process of the circulation path 11 shown in FIG. 4B. In this process, the sleeve portion 8 is irradiated by irradiating a laser. A circulation path 11 is formed. The apparatus for forming the circulation path 11 shown in FIG. 1 mainly includes a fixing pin 17 that supports the bearing member 6 and a laser irradiation device 18 that is disposed on one end side (the upper end side in the illustrated example) of the bearing member 6. Prepare as.

  The laser irradiation device 18 includes an excitation source such as a discharge lamp or a semiconductor laser, and irradiates a laser beam 19 having a predetermined power from the tip portion thereof toward the bearing member 6 (sleeve portion 8 in the present embodiment). It arrange | positions so that the laser beam 19 of a direction parallel to an axis line may be irradiated. As the laser, various known lasers such as a carbon dioxide laser, a YAG laser, and a fiber laser can be used. However, the quality of the laser beam 19 is high, and an output necessary for forming the circulation path 11 can be obtained easily and stably. For this reason, a carbon dioxide laser is used. The irradiation method of the laser beam 19 in the laser irradiation device 18 may be either a continuous type or a pulse type, but a continuous type is particularly preferable. The power of the laser beam 19 to be irradiated can be arbitrarily adjusted.

  Although not shown, a beam diameter adjusting means having a convex lens or a concave lens can be disposed between the laser irradiation device 18 and the bearing member 6. By providing such a beam diameter adjusting means, it becomes possible to easily adjust the beam diameter according to the hole diameter of the circulation path 11 to be formed.

  In the apparatus for forming the circulation path 11 having the above configuration, the laser beam 19 is irradiated from the laser irradiation device 18 in a state where the bearing member 6 is held by the fixing pin 17, and the both end surfaces 8b and 8c of the sleeve portion 8 are communicated. A book circulation path 11 is formed. After forming one circulation path 11, the bearing member 6 and the laser irradiation device 18 are rotated relative to each other to form the second circulation path 11 in the sleeve portion 8. Further, a third circulation path 11 is formed in the same manner. After the circulation path 11 is formed in three places in the circumferential direction of the sleeve portion 8 in this way, when the bearing member 6 is removed from the fixing pin 17, the finished bearing member 6 shown in FIGS. 2 and 3 is obtained. .

  In the above, the laser irradiation device 18 is disposed at one place in the circumferential direction, and the three irradiation paths 11 are formed in the sleeve portion 8 by rotating the laser irradiation device 18 and the bearing member 6 relative to each other. Although the configuration is adopted, it is also possible to arrange the laser irradiation devices 18 at three locations in the circumferential direction and simultaneously form the three circulation paths 11.

  The shaft member 2 is inserted into the inner periphery of the bearing member 6 (sleeve portion 8) manufactured as described above, and the seal member 9 and the lid member 10 are bonded and press-fitted into the upper end opening and the lower end opening of the housing portion 7, respectively. Etc. are fixed by appropriate means. Then, the hydrodynamic bearing device 1 shown in FIG. 2 is completed by filling the internal space of the bearing member 6 sealed with the seal member 9 with lubricating oil including the internal holes of the sleeve portion 8. In the present embodiment, the axial distance between the upper end surface 10b1 of the cylindrical portion 10b constituting the lid member 10 and the inner bottom surface 10a1 of the disc portion 10a is the width of the flange portion 2b and the axial dimension of both thrust bearing gaps. It is set to the sum of and. Therefore, the thrust members of both thrust bearing portions T1 and T2 are fixed by simply fixing the lid member 10 to the inner periphery of the housing portion 7 so that the upper end surface 10b1 of the cylindrical portion 10b is brought into contact with the lower end surface 8b of the sleeve portion 8. The bearing gap width is set with high accuracy.

  In the hydrodynamic bearing device 1 having the above-described configuration, when the shaft member 2 rotates, the upper and lower two regions serving as the radial bearing surface of the inner peripheral surface 8a of the sleeve portion 8 are different from the outer peripheral surface 2a1 of the shaft portion 2a. Opposing through the bearing gap. As the shaft member 2 rotates, the oil film formed in each radial bearing gap has its oil film rigidity increased by the dynamic pressure action of the dynamic pressure grooves 8a1 and 8a2 respectively formed on the radial bearing surfaces. Thus, the shaft member 2 is supported in a non-contact manner so as to be rotatable in the radial direction. 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 of the lower end surface 8b of the sleeve portion 8 faces the upper end surface 2b1 of the flange portion 2b via the thrust bearing gap, and the inner bottom surface 10a1 of the lid member 10 is formed. The region serving as the thrust bearing surface is opposed to the lower end surface 2b2 of the flange portion 2b via the thrust bearing gap. As the shaft member 2 rotates, the oil film formed in the thrust bearing gaps has its oil film rigidity increased by the dynamic pressure action of the dynamic pressure grooves formed on the thrust bearing surfaces. 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 non-contact-support the shaft member 2 rotatably in both thrust directions are formed.

  Further, when the shaft member 2 rotates, as described above, the seal space S1 has a tapered shape that gradually decreases toward the inner side of the bearing member 6, so that the lubricating oil in the seal space S1 is caused by capillary force. By the pulling-in action, the seal space is pulled in the direction of narrowing, that is, toward the inside of the bearing member 6. Thereby, the leakage of the lubricating oil from the inside of the bearing member 6 is effectively prevented. Further, the seal space S1 has a buffer function of absorbing a volume change amount accompanying a temperature change of the lubricating oil filled in the internal space of the bearing member 6, and within the range of the assumed temperature change, the oil of the lubricating oil The face is always in the seal space S1.

  The upper dynamic pressure groove 8a1 is formed axially asymmetric with respect to the axial center m, and the axial dimension X1 in the upper region from the axial center m is larger than the axial dimension X2 in the lower region. It has become. Therefore, when the shaft member 2 rotates, the lubricating oil pulling force (pumping force) by the dynamic pressure groove 8a1 is relatively larger in the upper region than in the lower region. The lubricating oil filled in the gap between the inner peripheral surface 8a of the sleeve portion 8 and the outer peripheral surface 2a1 of the shaft portion 2a due to the differential pressure of the pulling force becomes the thrust bearing gap of the first thrust bearing portion T1. The radial groove 10b11 of the upper end surface 10b1 of the lid member 10 → the circulation path 11 → the annular gap between the outer diameter side region 9b1 of the lower end surface 9b of the seal member 9 and the upper end surface 8c of the sleeve portion 8 → the sleeve portion 8 It circulates along the path of the circumferential groove 8c1 on the upper end face 8c and the radial groove 8c2 on the upper end face 8c of the sleeve portion 8, and is drawn again into the radial bearing gap of the first radial bearing portion R1.

  In this way, by configuring the lubricating oil to flow and circulate in the internal space of the bearing member 6, the phenomenon that the pressure of the lubricating oil in the internal space becomes a negative pressure locally is prevented, and negative pressure is generated. It is possible to solve problems such as generation of bubbles, leakage of lubricating oil, deterioration of bearing performance, generation of vibrations, and the like due to generation of bubbles. Further, even if bubbles are mixed in the lubricating oil for some reason, when the bubbles circulate with the lubricating oil, it is discharged from the oil surface (gas-liquid interface) of the lubricating oil in the seal space S1 to the outside air. The adverse effects due to the bubbles are more effectively prevented.

  As described above, in the present invention, the circulation path 11 is formed by laser processing after the sleeve portion 8 is inserted and the housing portion 7 is injection-molded. With this configuration, since the housing portion 7 is injection-molded by inserting the sleeve portion 6, a highly accurate bearing member 6 can be obtained at a low cost, but only through a step of irradiating a laser (laser beam 19). Thus, the highly accurate circulation path 11 can be formed. As a result, the formation of the circulation path 11 requires at least two steps, excluding the step of injection molding the housing portion 7, and the manufacturing cost is reduced compared to the conventional configuration that requires special consideration for the two steps. Can be planned. Therefore, the hydrodynamic bearing device 1 capable of stably maintaining the bearing performance can be provided at a low cost.

  Although one embodiment of the hydrodynamic bearing device according to the present invention has been described above, the present invention is not limited to the hydrodynamic bearing device configured as described above. Hereinafter, other embodiments of the hydrodynamic bearing device to which the present invention is applied will be described. However, the configuration according to the hydrodynamic bearing device 1 shown in FIG.

  FIG. 5 shows a second embodiment of a hydrodynamic bearing device according to the present invention. The main difference between the hydrodynamic bearing device 1 shown in FIG. 2 and the hydrodynamic bearing device shown in FIG. 2 is that the second thrust bearing portion T2 has a lower end surface 3a of the disk hub 3 fixed to the shaft member 2 and a housing portion 7. And the seal space S1 is formed between the upper outer peripheral surface 7c of the housing portion 7 and the inner peripheral surface 3b of the disk hub 3.

  FIG. 6 shows a third embodiment of the hydrodynamic bearing device according to the present invention. The hydrodynamic bearing device 1 shown in FIG. 5 is a modification of the hydrodynamic bearing device 1 shown in FIG. 5 and is different from the hydrodynamic bearing device shown in FIG. 5 in that the circulation path 11 is provided on the inner diameter side. Make the configuration different.

  FIG. 7 shows a fourth embodiment of the hydrodynamic bearing device according to the present invention. The main difference between the hydrodynamic bearing device 1 shown in FIG. 2 and the hydrodynamic bearing device 1 shown in FIG. 2 is that the upper end surface 8 c of the sleeve portion 8 and the lower end surface 29 b of the first seal member 29 fixed to the shaft member 2. A first thrust bearing portion T1 and a second thrust bearing portion T2 are provided between the lower end surface 8b of the sleeve portion 8 and the upper end surface 30b of the second seal member 30 fixed to the shaft member 2, respectively. The inner peripheral small diameter portion 71 and the inner peripheral large diameter portion 72 are provided in the portion 7, and between the first inner peripheral surface 72 a of the inner peripheral large diameter portion 72 and the outer peripheral surface 29 a of the first seal member 29, and the large inner periphery. The seal space S1, S2 is provided between the second inner peripheral surface 72b of the diameter portion 72 and the outer peripheral surface 30a of the second seal member 30. In the present embodiment, the axial separation distance between the thrust bearing portions T1 and T2 is longer than that of the hydrodynamic bearing device 1 shown in FIG. 2, so that the load capacity (moment rigidity) against the moment load can be increased. In the present embodiment, the circulation path 11 is provided so as to communicate with the upper and lower end surfaces 71 b and 71 c of the inner peripheral small diameter portion 71 of the housing portion 7 in the bearing member 6.

  FIG. 8 shows a fifth embodiment of a hydrodynamic bearing device according to the present invention. The hydrodynamic bearing device 1 shown in the figure is a modification of the hydrodynamic bearing device shown in FIG. 7, and the upper and lower end surfaces 71 b and 71 c of the inner peripheral small-diameter portion 71 constituting the housing portion 7 are formed at the formation site of the circulation path 11. Recessed relief portions 71d and 71e are provided, respectively. Such a configuration is effective when a bulge (burr) of meat is formed in the vicinity of the upper end surface 71b and the lower end surface 71c as the laser beam 19 is irradiated. That is, for example, if the burr is formed beyond the upper and lower end surfaces 71b and 71c, the width accuracy of the thrust bearing gap may be adversely affected. Therefore, it is necessary to remove this, but the above-described escape portions 71d and 71e are required. Is formed at the same time as the injection molding of the housing portion 7, so that the burrs can be absorbed by the relief portions 71d and 71e. As a result, it is not necessary to remove the burrs. In the illustrated example, the relief portions 71d and 71e are provided intermittently in the circumferential direction, but it is also possible to provide them over the entire circumference, that is, in an annular shape. In the illustrated example, the escape portion has a rectangular cross section, but it may be formed by so-called chamfering. The escape portion can be provided in the sleeve portion 8.

  FIG. 9 shows a sixth embodiment of the hydrodynamic bearing device according to the present invention. The main difference between the hydrodynamic bearing device 1 shown in the figure and the hydrodynamic bearing device shown above is that the inner peripheral surface of the housing portion 7 is divided into a large-diameter inner peripheral surface 7a1 and a small-diameter inner peripheral surface 7a2, The sleeve portion 8 is disposed on the inner periphery of the peripheral surface 7a1, in other words, the sleeve portion 8 and the housing portion 7 are engaged with each other in the axial direction. With this configuration, since the coupling strength between the sleeve portion 8 and the housing portion 7 can be increased, the impact resistance of the hydrodynamic bearing device 1 can be increased.

  In the above, the hydrodynamic bearing device in which the circulation path 11 is provided in the sleeve portion 8 or the housing portion 7 has been described. However, the formation site of the circulation path 11 can be arbitrarily selected. For example, although not shown, the circulation path 11 can be provided on both the sleeve part 8 and the housing part 7 in addition to the circulation path 11 provided on the fixed interface between the sleeve part 8 and the housing part 7.

  In the above description, the radial bearing portions R1 and R2 and the thrust bearing portions T1 and T2 are exemplified by the configuration in which the dynamic pressure action of the lubricating oil is generated by the dynamic pressure grooves having a herringbone shape or a spiral shape. So-called step bearings, multi-arc bearings, or non-circular bearings may be used as the portions R1 and R2, and so-called step bearings and wave bearings may be employed as the thrust bearing portions T1 and T2. Moreover, although the structure which provided the radial bearing part in the axial direction two places was illustrated above, a radial bearing part can also be provided in the axial direction one place or three places or more.

  Moreover, although the case where both radial bearing part R1, R2 was comprised with the dynamic pressure bearing was demonstrated above, one or both of radial bearing part R1, R2 can also be comprised with a bearing other than this. For example, although illustration is omitted, the outer peripheral surface 2a1 of the shaft member 2 is formed in a perfect circular outer peripheral surface, and the inner peripheral surface 8a of the bearing sleeve 8 facing the outer peripheral surface is made a perfect circular inner peripheral surface. A so-called perfect circle bearing can also be configured.

  In the above description, both the thrust bearing portions T1 and T2 are configured by dynamic pressure bearings. However, in the hydrodynamic bearing device 1 having the configuration shown in FIGS. 2 and 5, for example, the lower end of the shaft member 2 is formed in a convex spherical shape. By forming, the thrust bearing portion can be constituted by a pivot bearing.

It is sectional drawing which shows notionally an example of the spindle motor for information devices incorporating the hydrodynamic bearing apparatus. It is sectional drawing which shows 1st Embodiment of the hydrodynamic bearing apparatus which concerns on this invention. (A) A figure is sectional drawing of a bearing member, (b) figure is the figure which looked at the bearing member from the downward direction. FIG. 4A is a sectional view conceptually showing a process of injection molding a housing portion, and FIG. 4B is a sectional view conceptually showing a process of forming a circulation path in a bearing member. It is sectional drawing which shows 2nd Embodiment of the hydrodynamic bearing apparatus which concerns on this invention. It is sectional drawing which shows 3rd Embodiment of the hydrodynamic bearing apparatus which concerns on this invention. It is sectional drawing which shows 4th Embodiment of the hydrodynamic bearing apparatus which concerns on this invention. It is sectional drawing which shows 5th Embodiment of the hydrodynamic bearing apparatus which concerns on this invention. It is sectional drawing which shows 6th Embodiment of the hydrodynamic bearing apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid dynamic bearing apparatus 2 Shaft member 6 Bearing member 7 Housing part 8 Sleeve part 11 Circulation path 12 Upper mold | type 13 Lower mold | type 15 Cavity 18 Laser irradiation apparatus 19 Laser beam R1, R2 Radial bearing part T1, T2 Thrust bearing part S1, S2 Seal space

Claims (6)

A bearing member having a sleeve portion that forms a radial bearing gap between the shaft member housed in the inner circumference and a housing portion in which the sleeve portion is arranged on the inner circumference, and lubricating oil that fills the radial bearing gap is provided. In the hydrodynamic bearing device that enables the flow circulation of the lubricating oil in the formed axial circulation path,
A hydrodynamic bearing device, wherein the circulation path is formed by irradiating a laser after inserting a sleeve portion and injection molding a housing portion.   The hydrodynamic bearing device according to claim 1, wherein a circulation path is provided in the sleeve portion.   The hydrodynamic bearing device according to claim 1, wherein a circulation path is provided in the housing portion.   The hydrodynamic bearing device according to claim 1, wherein a circulation path is provided in the sleeve portion and the housing portion.   2. The hydrodynamic bearing device according to claim 1, wherein a carbon dioxide laser is used as the laser.   The hydrodynamic bearing device according to claim 1, wherein the sleeve portion and the housing portion are engaged with each other in the axial direction.

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