JP2007247675A - Fluid bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compact the axial direction of a fluid bearing device. <P>SOLUTION: Sealing members 9, 10 are arranged at the inner periphery of an opening part of a housing 7. A first tapered face 11 whose diameter is gradually contracted toward the direction of the outside of the bearing device is formed on outer peripheral faces 9a, 10a of the sealing members 9, 10, and a second tapered face 12 whose diameter is gradually extended toward the direction of the outside is formed on second and third inner peripheral faces 7b, 7c of the housing 7. Sealing spaces S1, S2 are formed between the first tapered face 11 and the second tapered face 12. <P>COPYRIGHT: (C)2007,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 to be supported by a fluid lubricating film generated in a bearing gap. This hydrodynamic bearing device has characteristics such as high-speed rotation, high rotation accuracy, and low noise. In recent years, by utilizing the characteristics, information devices such as magnetic disk devices such as HDD and FDD, CD-ROM, CD -For spindle motors mounted on optical disk devices such as R / RW and DVD-ROM / RAM, magneto-optical disk devices such as MD and MO, etc., and mounted on personal computers (PCs), etc., to cool the heat source. Widely used as a bearing for a fan motor, a polygon scanner motor of a laser beam printer (LBP), or the like.

  For example, in a hydrodynamic bearing device incorporated in a spindle motor of a disk device such as an HDD, as shown in FIG. 8, a radial bearing portion R that rotatably supports the shaft member 20 in the radial direction, and the shaft member 20 in the thrust direction. A thrust bearing portion T that is rotatably supported is provided. As the bearing of the radial bearing portion R, a dynamic pressure bearing in which a dynamic pressure generating portion such as a dynamic pressure groove is provided on the outer peripheral surface of the shaft portion 21 constituting the shaft member 20 or the inner peripheral surface of the bearing sleeve 80 may be used. Many. As the thrust bearing portion T, for example, both end surfaces of the flange portion 22 of the shaft member 20, or surfaces facing the flange portion 22 (for example, the end surface 81 of the bearing sleeve, the end surface 71a of the thrust member 71 fixed to the housing 70, etc.) ) And a case where a so-called pivot bearing that supports and supports one end of the shaft member is used (not shown).

Usually, the bearing sleeve 80 is fixed at a predetermined position of the housing 70, and the lubricating fluid (for example, lubricating oil) that fills the inside of the bearing device leaks to the outside at the opening side of the housing 70 from the bearing sleeve 80. A seal space S is provided to prevent this. The seal space S is provided, for example, between the inner peripheral surface of the seal member 100 fixed to the opening of the housing 70 and the outer peripheral surface of the shaft portion 21, and the seal space S is one of two opposing surfaces. In general, one side is inclined. For example, the outer peripheral surface of the shaft portion 21 on the rotation side is formed into a tapered surface that is gradually reduced in diameter toward the shaft end. The volume of the seal space S is set so that the lubricating oil filled in the internal space of the bearing becomes larger than the amount of change in volume due to thermal expansion / contraction within the operating temperature range. Therefore, even when there is a change in the volume of the lubricating oil accompanying a change in temperature, the oil level of the lubricating oil is always maintained in the seal space S (see, for example, Patent Document 1).
JP 2003-336636 A

  As described above, in the conventional hydrodynamic bearing device, the seal space is formed between the inner peripheral surface of the seal member fixed to the opening of the housing and the outer peripheral surface of the shaft member. In order to provide a function (buffer function) for absorbing the volume change amount of the lubricating oil accompanying a temperature change, it is necessary to ensure a relatively large axial dimension of the seal space. Therefore, it is necessary to lower the axial center position of the bearing sleeve relative to the bottom side of the housing in the interior of the housing by design, so that the separation distance between the bearing center of the radial bearing portion and the center of gravity of the rotating body is reduced. Depending on the use conditions, etc., the moment stiffness may be insufficient.

  An object of the present invention is to make it possible to further reduce the axial dimension of the seal space in this type of hydrodynamic bearing device, thereby reducing the size of the hydrodynamic bearing device or increasing the moment rigidity.

  In order to solve the above problems, a hydrodynamic bearing device according to the present invention includes a housing, a bearing sleeve disposed on an inner periphery of the housing, a shaft member that rotates relative to the housing and the bearing sleeve, and an atmosphere. An open seal space, and a radial bearing portion that supports the shaft member in a radial direction with a fluid lubricating film that fills a radial bearing gap between the bearing sleeve and the shaft member, and the seal space has an opening portion Toward the first taper surface, the first taper surface gradually decreases in diameter and the second taper surface gradually increases in diameter.

  As described above, in the present invention, the seal space is formed between the first tapered surface that gradually decreases in diameter and the second tapered surface that gradually increases in diameter toward the opening. As a result, the volume of the seal space can be increased without increasing the axial dimension of the seal space as compared with the conventional configuration in which one of the two surfaces forming the seal space is a tapered surface. Therefore, the axial dimension of the seal space can be reduced, and the hydrodynamic bearing device can be made compact in the axial direction. Alternatively, the axial dimension of the bearing sleeve can be increased, and the separation distance between the radial bearing portions can be increased. Stiffness can be increased.

  Specific examples of the configuration include a configuration in which a shaft member is provided with a seal member that protrudes to the outer diameter side, the first taper surface is provided on the seal member, and a second taper surface is provided on the housing. Can do. With this configuration, the seal space is placed on the outer diameter side as compared with the configuration in which the seal space is provided between the outer peripheral surface of the shaft member and the inner peripheral surface of the seal member fixed to the housing (see, for example, FIG. 8). The required volume of the seal space can be secured even if the axial dimension of the seal space is further reduced by the amount that can be provided. Thereby, the hydrodynamic bearing device can be made more compact, or the moment rigidity can be further increased.

  By the way, in the case of the seal space shape as described above, there is a possibility that the lubricating fluid is likely to leak from the seal space when an impact load is applied. Therefore, in the present invention, a thrust bearing gap connected to the seal space on the outer diameter side is provided between the end face of the housing and the end face of the seal member facing the housing, and the two faces facing each other through the thrust bearing gap. One of these was provided with a dynamic pressure generating portion for drawing the lubricating fluid toward the inner diameter side. With this configuration, in addition to the pulling force due to the capillary force, the pulling force due to the dynamic pressure generating portion (thrust dynamic pressure generating portion) acts on the lubricating oil that fills the sealing space. Leakage can be effectively prevented.

  The shape of the thrust dynamic pressure generating portion is not particularly limited as long as it has a function (pump-in function) for flowing lubricating oil from the outer diameter side to the inner diameter side, and a representative example is a dynamic pressure groove arranged in a spiral shape. be able to. In addition to this, even if the pump-in function and the pump-out function are combined, such as a herringbone-shaped dynamic pressure groove, the inner diameter side by the pump-in function is more than the flow to the outer diameter side by the pump-out function. If the flow to the flow is dominant, since the lubricating oil flows from the outer diameter side to the inner diameter side in the entire thrust bearing gap, it is possible to employ this type of dynamic pressure generating portion.

  The seal space can be provided at both end openings by opening both ends of the housing. If the seal spaces are provided at both ends in the axial direction in this way, the buffer function of the entire bearing device can be enhanced as compared with the configuration in which the seal space is provided only at the opening on the one end side of the housing. The axial dimension can be reduced, and the hydrodynamic bearing device can be made more compact, or the bearing sleeve can be lengthened to increase the moment rigidity.

  The hydrodynamic bearing device having the above configuration can be preferably used for a motor having the hydrodynamic bearing device, a stator coil, and a rotor magnet.

  As described above, according to the present invention, it is possible to further reduce the axial dimension of the seal space, thereby further reducing the size of the hydrodynamic bearing device or increasing the moment rigidity.

  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 hydrodynamic bearing device 1 according to the present invention. This spindle motor is used in a disk drive device such as an HDD, and includes a hydrodynamic bearing device 1 that rotatably supports a shaft member 2, a rotor (disk hub) 3 mounted on the shaft member 2, and a radial direction, for example. The stator coil 4 and the rotor magnet 5 are provided to face each other through the gap. The stator coil 4 is attached to the outer periphery of the bracket 6, and the rotor magnet 5 is attached to the inner periphery of the disk hub 3. The housing 7 of the hydrodynamic bearing device 1 is attached to the inner periphery of the bracket 6. The disk hub 3 holds one or more disks D such as magnetic disks. When the stator coil 4 is energized, the rotor magnet 5 is rotated by the electromagnetic force between the stator coil 4 and the rotor magnet 5, whereby the disk hub 3 and the shaft member 2 are rotated together.

  FIG. 2 shows an example of the hydrodynamic bearing device 1 used in the spindle motor. The hydrodynamic bearing device 1 includes a rotation-side shaft member 2, seal members 9 and 10 fixed to the shaft member 2, a fixed-side housing 7, and a bearing sleeve 8 fixed to the inner periphery of the housing 7. It is provided as a main component. For convenience of explanation, the description will be given with the side from which the shaft member 2 protrudes from the opening of the housing 7 as the upper side and the opposite side in the axial direction as the lower side.

  The shaft member 2 is formed of a metal material such as stainless steel. The shaft member 2 as a whole has a shaft shape with substantially the same diameter, and an intermediate portion is formed with a relief portion 2b formed to have a slightly smaller diameter than other portions. In the outer peripheral surface 2a of the shaft member 2, a recessed portion, for example, a circumferential groove 2c is formed at a fixing position of the first and second seal members 9, 10.

  The bearing sleeve 8 is formed in a cylindrical shape, for example, a porous body made of sintered metal, particularly a sintered metal porous body mainly composed of copper, and is bonded, press-fitted, or press-fitted to a predetermined position of the housing 7. It is fixed by such means. The bearing sleeve 8 can be formed of a soft metal material such as brass in addition to the sintered metal.

  The inner peripheral surface 8a of the bearing sleeve 8 is provided with two upper and lower regions which are the radial bearing surfaces A of the first radial bearing portion R1 and the second radial bearing portion R2 and are separated from each other in the axial direction. For example, herringbone-shaped dynamic pressure grooves 8a1 and 8a2 as shown in FIG. 3 are formed as dynamic pressure generating portions (radial dynamic pressure generating portions). For example, by making the axial width of the upper region groove of the upper dynamic pressure groove 8a1 longer than that of the lower region groove, the lubricating fluid is moved downward in the axial direction when the shaft member 2 rotates. The pushing force (pumping force) can be applied. The dynamic pressure grooves 8a1 and 8a2 can be formed in other known shapes such as a spiral shape.

  The first seal member 9 and the second seal member 10 are each formed in a ring shape from a soft metal material such as brass, other metal materials, or a resin material, and the outer peripheral surface of the shaft member 2 at both ends of the bearing sleeve 8. For example, it is bonded and fixed to 2a. At the time of bonding and fixing, the adhesive applied to the shaft member 2 is filled in the circumferential groove 2c as an adhesive reservoir and solidified, whereby the adhesive strength of the seal members 9 and 10 to the shaft member 2 is improved.

  The housing 7 is made of a soft metal such as an aluminum alloy or brass, and is formed in a substantially cylindrical shape with both ends opened. The inner peripheral surface of the housing 7 is a first inner peripheral surface 7 a having a fixed surface with the bearing sleeve 8. Provided on the upper side in the axial direction of the first inner peripheral surface 7a, provided on the second inner peripheral surface 7b having a larger diameter than the first inner peripheral surface 7a, and on the lower side in the axial direction of the first inner peripheral surface 7a, 1 is divided into a third inner peripheral surface 7c having a larger diameter than the inner peripheral surface 7a. The housing 7 is fixed to the inner peripheral surface of the bracket 6 shown in FIG.

  The housing 7 can be formed of a resin other than a metal material. In this case, for example, a crystalline resin such as a liquid crystal polymer (LCP), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), or polysulfone ( PSU), polyethersulfone (PES), polyphenylsulfone (PPSU) and the like can be injection-molded using a resin composition containing an amorphous resin as a base resin. One or more kinds of various fillers such as a reinforcing material, a conductive material, and a lubricant are blended in the base resin according to required characteristics.

  A thrust bearing surface of the first thrust bearing portion T1 is formed in a part or all of the annular region of the upper end surface 7d connecting the first inner peripheral surface 7a and the second inner peripheral surface 7b of the housing 7, and the thrust bearing surface is formed on the thrust bearing surface. As a dynamic pressure generating portion (thrust dynamic pressure generating portion), a plurality of dynamic pressure grooves arranged in a spiral shape are formed so as to perform a pump-in function. A thrust bearing surface of the second thrust bearing portion T2 is formed in a part or all of the annular region of the lower end surface 7e that connects the first inner peripheral surface 7a and the third inner peripheral surface 7c of the housing 7, and the thrust A plurality of dynamic pressure grooves arranged in a spiral shape are formed on the bearing surface as a thrust dynamic pressure generating portion so as to perform a pump-in function. The thrust dynamic pressure generating portion can also be formed on the lower end surface 9 b of the first seal member 9 and the upper end surface 10 b of the second seal member 10 that face each other in the axial direction.

  As the thrust dynamic pressure generating portion, other shapes having a pump-in function such as the above-described spiral-shaped dynamic pressure grooves can be adopted, and examples of this type of shape include a herringbone shape. The herringbone-shaped dynamic pressure groove has both a pump-in function and a pump-out function, but the flow of lubricant to the inner diameter side by the pump-in function is the flow of lubricant to the outer diameter side by the pump-out function. If it becomes more dominant, since the lubricating oil flows from the outer diameter side to the inner diameter side in the entire thrust bearing gap, this type of thrust dynamic pressure generating portion can also be adopted.

  The second inner peripheral surface 7 b of the housing 7 forms a first seal space S 1 having a predetermined volume with the outer peripheral surface 9 a of the first seal member 9 fixed to the shaft member 2. The surface 7c forms a second seal space S2 having a predetermined volume with the outer peripheral surface 10a of the second seal member 10. In the present embodiment, the outer peripheral surface 9a of the first seal member 9 and the outer peripheral surface 10a of the second seal member 10 constitute a first tapered surface 11 that is gradually reduced in diameter toward the outside (opening) of the bearing device. The second inner peripheral surface 7b and the third inner peripheral surface 7c of the housing 7 constitute a second tapered surface 12 that gradually increases in diameter toward the outer side (opening) of the bearing device. Therefore, both the seal spaces S1 and S2 have a tapered shape that is gradually reduced in the direction of approaching each other. When the shaft member 2 rotates, the lubricating oil in both the seal spaces S1 and S2 is pulled by the capillary force so that the seal space is reduced. It is drawn in the direction of narrowing (inner direction of the housing 7). In order to prevent leakage of the lubricating oil, a film made of an oil repellent agent is formed on the upper and lower end surfaces of the housing 7, the upper end surface 9c of the first seal member 9, and the lower end surface 10c of the second seal member 10, respectively. (Not shown).

  The first and second seal spaces S <b> 1 and S <b> 2 have a buffer function that absorbs a volume change amount associated with a temperature change of the lubricating oil filled in the internal space of the housing 7. The oil level is always in both the seal spaces S1 and S2 within the assumed temperature change range. In order to realize this, the sum of the volumes of the seal spaces S1, S2 is set to be larger than at least the volume change amount associated with the temperature change of the lubricating oil filled in the internal space.

  In the above configuration, the first seal member 9 and the second seal member 10 are disposed at both ends of the bearing sleeve 8 so that a thrust bearing gap having a predetermined width can be formed between both end surfaces of the bearing sleeve 8. The second seal members 9 and 10 are bonded and fixed to predetermined portions of the shaft member 2. When the assembly of the hydrodynamic bearing device 1 is completed in this way, the internal space of the housing 7 sealed with the seal members 9 and 10 is filled with, for example, lubricating oil as a lubricating fluid including the internal pores of the bearing sleeve 8.

  Lubricating oil is injected, for example, by immersing an unlubricated hydrodynamic bearing device in lubricating oil and then releasing it to atmospheric pressure. At this time, since both ends of the housing 7 are open in the hydrodynamic bearing device 1 of the present embodiment, the air in the internal space can be reliably lubricated as compared with a configuration in which one end of the housing 7 is closed (see, for example, FIG. 8). Thus, adverse effects caused by residual air, for example, oil leakage at high temperatures can be reliably avoided. In addition to such an oil supply method using reduced pressure, oil supply (for example, pressurized oil supply of lubricating oil) can be performed under normal pressure, and the manufacturing cost can be reduced through simplification of the oil supply device and process. .

  In the hydrodynamic bearing device 1 having the above-described configuration, when the shaft member 2 rotates, the regions that become the radial bearing surfaces A that are spaced apart at the upper and lower portions of the bearing sleeve 8 respectively serve as the outer peripheral surface 2a of the shaft member 2 and the radial bearing gap. Opposite through. As the shaft member 2 rotates, the oil film generated in the radial bearing gap is enhanced in its oil film rigidity by the dynamic pressure action of the dynamic pressure grooves 8a1 and 8a2 formed on both radial bearing surfaces. Non-contact supported 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 spaced apart in the axial direction.

  Further, when the shaft member 2 rotates, a region serving as a thrust bearing surface of the upper end surface 7d of the housing 7 faces the lower end surface 9b of the first flange portion 9 via a predetermined thrust bearing gap. A region serving as a thrust bearing surface of the lower end surface 7e faces the upper end surface 10b of the second flange portion 10 via a predetermined thrust bearing gap. As the shaft member 2 rotates, the oil film generated 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, and the shaft member 2 rotates in both thrust directions. It is supported non-contact freely. 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. Both thrust bearing gaps communicate with the first seal space S1 and the second seal space, respectively, on the outer diameter side.

  As described above, in the present invention, the seal spaces S <b> 1 and S <b> 2 are formed between the first tapered surface 11 that gradually decreases in diameter toward the opening of the housing 7 and the second tapered surface 12 that gradually increases in diameter. . As described above, in the present invention, the seal space is formed between the first and second tapered surfaces 11 and 12 inclined in the direction of gradually expanding the radial dimension toward the opening, so that the seal space is formed. Compared to the conventional configuration in which one of the surfaces is a tapered surface, the required volume of the seal space can be secured while reducing the axial dimension of the seal space. In particular, in the present embodiment, the second taper surface 12 is housed on the outer peripheral surface 9a of the first seal member 9 and the outer peripheral surface 10a of the second seal member 10 in which the first taper surface 11 projects from the shaft member 2 to the outer diameter side. 7 is formed on the second and third inner peripheral surfaces 7b and 7c, so that a seal space is formed between the outer peripheral surface of the shaft member and the seal member fixed to the housing (see FIG. 8). The required volume of the seal space can be ensured while the axial dimensions of the members 9 and 10 are further reduced.

  Further, in the present embodiment, both ends of the housing 7 are opened, and the seal spaces S1 and S2 are provided at the opening portions at both ends, so that the entire bearing device is compared with the configuration in which the seal space is formed only at one end opening of the housing. The buffer function of the lubricating oil by the seal space can be enhanced, and thereby the volume of the seal spaces S1 and S2 can be reduced from the volume of the seal space S. From the above, according to the present invention, the axial dimensions of the seal spaces S1, S2 (seal members 9, 10) can be reduced, and the hydrodynamic bearing device 1 can be made compact in the axial direction, or the bearing sleeve 8 can be made compact. It is possible to increase the moment rigidity of the hydrodynamic bearing device 1 by increasing the axial direction to increase the axial separation distance between the first radial bearing portion R1 and the second radial bearing portion R2.

  In addition, when the seal space is formed by the two tapered surfaces 11 and 12 inclined in the direction in which the radial dimensions of the seal spaces S1 and S2 are gradually enlarged toward the housing opening as described above, an impact load is applied. In some cases, the lubricating oil may easily leak. On the other hand, in the present invention, since the outer diameter side of the thrust bearing gap in which the fluid force of the lubricating oil is generated on the inner diameter side is connected to the seal spaces S1 and S2, the lubricating oil in the seal spaces S1 and S2 is used as a capillary tube. In addition to the pull-in force due to the force, the pull-in force due to the thrust dynamic pressure generator acts, so that leakage of the lubricating oil from the seal spaces S1, S2 can be effectively prevented.

  By the way, the thrust bearing gap may be formed between the end surface of the bearing sleeve and the end surface of the member facing the bearing sleeve. However, like the hydrodynamic bearing device 1 of the present embodiment, the outer peripheral surface of the seal member and the inner peripheral surface of the housing. If a seal space is provided between the seal member 9 and the housing 7, both the seal members 9 and 10 can be positioned on both the housing 7 and the bearing sleeve 8 while positioning the bearing sleeve 8 in the axial direction with respect to the housing 7 with high accuracy. Therefore, the assembly process becomes complicated and the manufacturing cost increases. On the other hand, if the thrust bearing gap is formed between the seal members 9, 10 and the housing 7 as described above, the bearing sleeve 8 can be roughly positioned with respect to the housing 7, and the seal member 9, Since it is sufficient to perform the positioning of 10 only in consideration of the positional relationship with the housing 7, the complexity of the assembly process can be avoided and the manufacturing cost can be reduced.

  In order to avoid complication of the assembly process, the housing 7 and the bearing sleeve 8 can be integrally formed although illustration is omitted. In this case, if this integral product is injection-molded with resin or the like, the radial bearing surface A and the dynamic pressure generating portions of both thrust bearing surfaces can be formed simultaneously with the molding, and the cost can be reduced.

  As mentioned above, although one Embodiment of this invention was described, this invention can be preferably applied not only to the fluid bearing apparatus 1 of the said form but to the fluid bearing apparatus of another structure. Hereinafter, other configuration examples of the hydrodynamic bearing device will be described with reference to the drawings, but the same reference numerals are assigned to the components and elements having the same functions and operations as those shown in FIG. To do.

  FIG. 4 shows a second embodiment of the hydrodynamic bearing device 1 according to the present invention. This configuration is used when it is difficult to obtain an axial dimension capable of securing the required moment rigidity with only one bearing sleeve due to molding problems and the like. The configuration differs from that of the hydrodynamic bearing device 1 shown in FIG. 2 in that two bearing sleeves 81 and 82 are arranged side by side in the axial direction. In the hydrodynamic bearing device 1 shown in the figure, the first radial bearing portion R1 is formed between the inner peripheral surface 81a of the upper bearing sleeve 81 and the outer peripheral surface 2a of the shaft member 2, and the second radial bearing portion R2 is the lower portion. It is formed between the inner peripheral surface 82 a of the side bearing sleeve 82 and the outer peripheral surface 2 a of the shaft member 2.

  In the hydrodynamic bearing device 1 having this configuration, since the amount of oil increases as the internal space increases, the axial dimension of the seal space tends to increase. However, by applying the configuration of the present invention described above, the seal By reducing the axial dimension of the space to obtain a relatively compact hydrodynamic bearing device 1 having high moment rigidity, or by increasing the axial dimension of the bearing sleeves 81 and 82, higher moment rigidity can be obtained. The hydrodynamic bearing device 1 can be obtained.

  In the hydrodynamic bearing device 1 of this embodiment, from the viewpoint of securing moment rigidity, the radial bearing surface of the first bearing sleeve 81 is located at the end (upper side) away from the second bearing sleeve 82 and the second bearing. In general, the radial bearing surface of the sleeve 82 is formed at an end portion (lower side) away from the first bearing sleeve 81. However, in this case, since the inner diameter dimension of the bearing sleeve is different between the upper region and the lower region, it may be difficult to ensure the coaxiality between the upper and lower end surfaces of the individual bearing sleeves and between the bearing sleeves. In this case, although not shown in the figure, the above-mentioned problem can be solved by providing convex portions having substantially the same diameter as the hills that define the dynamic pressure grooves on the radial bearing surface in regions separated from the radial bearing surface in the axial direction. Can be resolved. In this case, it is desirable to form the convex portion in a belt shape or the like that does not have a dynamic pressure generating function from the viewpoint of avoiding torque increase.

  Further, in the configuration in which a plurality of bearing sleeves are arranged in the axial direction as in the hydrodynamic bearing device 1 of this embodiment, the number of members increases when a thrust bearing gap is provided between the end surface of the bearing sleeve and the end surface of the member facing it. However, as the number of parts requiring management of assembly accuracy increases, the assembly of each member becomes more complicated as compared with the hydrodynamic bearing device 1 having the configuration shown in FIG. On the other hand, if the thrust bearing gap is provided between the housing 7 and the seal members 9, 10, the cost merit due to the simplification of the assembly process can be obtained more remarkably.

  When the axial lengths of the first and second bearing sleeves 81 and 82 are the same as in the illustrated example, there is little difference in the appearance of the two, so there is a possibility that the upper and lower positions of both sleeves are mistaken and assembled during assembly. . Therefore, although not shown, the axial lengths of the first bearing sleeve 81 and the second bearing sleeve 82 may be different in order to prevent this kind of human error.

  FIG. 5 shows a third embodiment of the hydrodynamic bearing device 1 according to the present invention. In the hydrodynamic bearing device 1 of this embodiment, a ring-shaped spacer member 83 is interposed between the first and second bearing sleeves 81 and 82 fixed to the inner periphery of the housing 7. In this case, if the spacer member 83 is formed of a non-porous material different from a sintered metal (porous material) such as a soft metal material such as brass, other metal materials, or a resin material, the spacer member 83 is lubricated. Since the amount of oil can be reduced by an amount that does not require impregnation, the hydrodynamic bearing device 1 can be made compact in the axial direction by reducing the axial width of the seal spaces S1, S2.

  In addition, although illustration is abbreviate | omitted, in embodiment described above, either the 1st seal member 9 or the 2nd seal member 10 can also be integrally formed with the shaft member 2, Thereby, The number of members and assembly man-hours can be reduced, and the cost of the hydrodynamic bearing device 1 can be further reduced.

  In the above description, the configuration in which the seal space is provided in the opening at both ends of the housing 7 is shown. However, the configuration of the present invention has a configuration in which the seal space is provided in the one end opening of the housing 7 as shown in FIG. The present invention can also be preferably applied to the hydrodynamic bearing device 1. In the hydrodynamic bearing device 1 shown in the figure, the shaft member 2 is composed of a shaft portion 21 and a flange portion 22 that is integral with or separate from the shaft portion 21, and the upper end surface 22 a of the flange portion 22 and the lower end surface of the housing 7. A second thrust bearing portion T2 is provided between 7e. Even in this configuration, the axial dimension of the seal space S can be reduced and the hydrodynamic bearing device 1 can be made compact in the axial direction as compared with the conventional configuration shown in FIG. The moment rigidity can be increased by increasing the size and increasing the separation distance between the radial bearing portions. In the case of this embodiment, the housing 7 and the bearing sleeve 8 can be integrally formed as in the fluid bearing device 1 in FIG.

  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. The invention is not limited to this.

  For example, although illustration is omitted, one or both of the radial bearing portions R1 and R2 are, for example, so-called step bearings in which a plurality of axial grooves are provided at equal intervals in the circumferential direction in the region to be the radial bearing surface A, You may employ | adopt what is called a multi-arc bearing which provided the some circular arc surface in the area | region used as the radial bearing surface A. FIG. In addition, one or both of the thrust bearing portions T1 and T2 are, for example, so-called step bearings, so-called wave bearings (step-type bearings) in which a plurality of radial grooves are provided at predetermined intervals in the circumferential direction in a region serving as a thrust bearing surface. May also be used.

  Moreover, although the form which comprises both the 1st radial bearing part R1 and the 2nd radial bearing part R2 by the dynamic pressure bearing was illustrated in the above description, the 1st radial bearing part R1 and the 2nd radial bearing part R2 were illustrated. One or both of them can be constituted by a perfect circle bearing.

  In the above description, the bearing sleeve has been described with respect to one or two axial positions. However, the bearing sleeve may be disposed at three or more axial positions.

  In the above description, the lubricating oil is exemplified as the fluid that fills the inside of the hydrodynamic bearing device 1. However, other fluids that can generate dynamic pressure in the bearing gaps, such as a gas such as air, A magnetic fluid or the like can also be used.

  In the above, the form in which the hydrodynamic bearing device is used by being incorporated in the spindle motor for the disk device has been exemplified. However, the hydrodynamic bearing device having the configuration of the present invention rotates at a high speed and is high in addition to the spindle motor for information equipment. It can also be preferably used for a motor that requires moment rigidity, for example, a fan motor.

  FIG. 7 shows a fan motor incorporating the hydrodynamic bearing device 1 according to the present invention, and in particular, a so-called radial gap type fan motor in which the stator coil 4 and the rotor magnet 5 are opposed to each other through a gap in the radial direction (radial direction). An example is shown conceptually. In the illustrated motor, the rotor 33 fixed to the outer periphery of the upper end of the shaft member 2 has blades on the outer peripheral surface, and the bracket 36 serves as a casing for housing each component of the motor. The configuration is different from that of the spindle motor shown in FIG. The other constituent members have the same functions and functions as the constituent members of the motor shown in FIG.

It is sectional drawing of the spindle motor for information devices incorporating the hydrodynamic bearing apparatus. It is sectional drawing of the hydrodynamic bearing apparatus which has a structure of this invention. It is a longitudinal cross-sectional view of a bearing sleeve. 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. It is sectional drawing which shows the other form of a hydrodynamic bearing apparatus. It is sectional drawing of the fan motor incorporating the hydrodynamic bearing apparatus. It is sectional drawing which shows the conventional hydrodynamic bearing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid dynamic bearing apparatus 2 Shaft member 3 Disc hub 4 Stator coil 5 Rotor magnet 6 Bracket 7 Housing 8 Bearing sleeve 9 1st seal member 10 2nd seal member 11 1st taper surface 12 2nd taper surface 8a1, 8a2 Dynamic pressure groove R1 , R2 Radial bearing part T1, T2 Thrust bearing part S1, S2 Seal space

Claims (5)

A housing, a bearing sleeve disposed on the inner periphery of the housing, a shaft member that rotates relative to the housing and the bearing sleeve, a seal space that is open to the atmosphere, and a space between the bearing sleeve and the shaft member; In a hydrodynamic bearing device comprising a radial bearing portion for supporting the shaft member in a radial direction with a fluid lubricating film formed in a radial bearing gap of
The hydrodynamic bearing device, wherein the seal space is formed between a first tapered surface that gradually decreases in diameter and a second tapered surface that gradually increases in diameter toward the opening. Furthermore, a seal member provided to protrude to the outer diameter side of the shaft member is provided,
The hydrodynamic bearing device according to claim 1, wherein the first tapered surface is provided on the seal member, and the second tapered surface is provided on the housing.   A thrust bearing gap connected to the seal space on the outer diameter side is provided between the end face of the housing and the end face of the seal member, and lubricating fluid is applied to either one of the two faces facing through the thrust bearing gap. The hydrodynamic bearing device according to claim 2, further comprising a dynamic pressure generating portion that is drawn to the inner diameter side.   The hydrodynamic bearing device according to claim 1, wherein the seal spaces are provided at both ends in the axial direction.   A motor comprising the hydrodynamic bearing device according to claim 1, a stator coil, and a rotor magnet.

Images