JP4874004B2 - Hydrodynamic bearing device - Google Patents

Description

  The present invention relates to a hydrodynamic bearing device.

  The dynamic pressure bearing device is a bearing device that supports a shaft member in a non-contact manner by a dynamic pressure action of a lubricating fluid generated in a bearing gap. This hydrodynamic bearing device has characteristics such as high-speed rotation, high rotation accuracy, and low noise, and in recent years, taking advantage of the characteristics, the bearing device for motors mounted on various electric devices including information equipment. More specifically, magnetic disk devices such as HDD, 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, lasers, etc. 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, a structure having a structure shown in FIG. 9 is known as a dynamic pressure bearing device incorporated in a spindle motor for a disk device. In the dynamic pressure bearing device shown in the figure, a dynamic pressure generating portion such as a dynamic pressure groove is provided on the inner peripheral surface 80a of a single bearing sleeve 80 fixed to the housing 70 so as to be spaced apart at two upper and lower positions. Radial bearing portions R and R are formed between the outer peripheral surface 61a of the shaft portion 61 constituting the shaft portion 61. Further, a dynamic pressure generating portion such as a dynamic pressure groove is provided on both end faces 80 b and 80 c of the bearing sleeve 80, and the end face 62 a of the flange portion 62 provided so as to protrude toward the outer diameter side of the shaft portion 61 and the seal member 90. Thrust bearing portions T and T are formed between the end surface 90b (see, for example, Patent Document 1).
JP 2005-321089 A

  By the way, the rotational accuracy of the hydrodynamic bearing device greatly depends on the width accuracy of the radial bearing gap of the radial bearing portion and the thrust bearing gap of the thrust bearing portion. Therefore, the assembly of the bearing sleeve to the housing needs to be performed with high accuracy. However, as described above, when the bearing gap is formed on the inner peripheral side and both end sides of the bearing sleeve, it is necessary to fix the bearing sleeve to the housing while considering both the radial direction and the axial direction. In some cases, the cost may increase.

  In addition, in information equipment motors such as the above-described spindle motor, recording media are being stacked and high-speed rotation is progressing as the amount of information processing increases. Accordingly, the hydrodynamic bearing device is required to improve the bearing rigidity, particularly the load capacity (moment rigidity) with respect to the moment load.

  An object of the present invention is to provide a hydrodynamic bearing device that facilitates assembly of a bearing sleeve and is excellent in rotational accuracy, particularly load capacity against moment load.

  In order to solve the above-mentioned problems, in the present invention, a housing, a bearing sleeve fixed to the housing, a shaft member inserted into the inner periphery of the bearing sleeve, and a protruding outer shaft of the shaft member are provided. A protrusion disposed at both ends of the sleeve, a radial bearing gap formed between the inner circumferential surface of the bearing sleeve and the outer circumferential surface of the shaft member, and a thrust bearing gap. In a hydrodynamic bearing device that supports a shaft member in a non-contact manner by pressure action, the housing has a small-diameter inner peripheral surface that serves as a fixed portion of the bearing sleeve, a large-diameter inner peripheral surface that is located on the outer-diameter side of the protruding portion, and a small-diameter inner There is provided a hydrodynamic bearing device characterized in that a step surface connecting a peripheral surface and a large-diameter inner peripheral surface is provided, and the step surface faces a thrust bearing gap.

  In the above configuration, the thrust bearing gap is provided on the end surface side of the housing, and the bearing sleeve does not participate in the formation of the thrust bearing gap. Just go. Therefore, the assembly of the bearing sleeve is facilitated, and the cost of the hydrodynamic bearing device can be reduced. Further, since the thrust bearing gap can be provided on the outer diameter side as compared with the conventional configuration, the rotation accuracy can be increased through an increase in the bearing area.

  By the way, means for expanding the bearing span of the radial bearing portion is effective in increasing rotational accuracy, particularly moment rigidity. In order to expand the bearing span, it is necessary to lengthen the bearing sleeve, but as the length increases, it may be difficult to ensure the accuracy of the bearing sleeve. In particular, when the bearing sleeve is made of a sintered metal, it is difficult to obtain a uniform density at the time of compacting, and there is a possibility that desired bearing performance cannot be exhibited. Therefore, there is a limit to further expanding the bearing span of the radial bearing portion using a single bearing sleeve.

  Therefore, the present invention provides a configuration in which a plurality of bearing sleeves are arranged in the axial direction in addition to the above configuration. By adopting such a configuration, it is possible to increase the span between the radial bearing portions, increase the load capacity against moment load, and facilitate the manufacture of the bearing sleeve. As described above, when a plurality of bearing sleeves are provided in the axial direction, the coaxiality between the inner peripheral surfaces of the bearing sleeves and the perpendicularity between the inner peripheral surface of each bearing sleeve and the housing step surface are problems. By setting the concentricity between the inner peripheral surfaces of the sleeves to 3 μm or less and the perpendicularity between the inner peripheral surface of each bearing sleeve and the stepped surface of the housing to 5 μm or less, the rotational accuracy is deteriorated. Problems such as wear of members can be avoided.

  As a means for fixing the bearing sleeve to the housing, gap adhesion is desirable. Gap adhesion is a method of adhering and fixing in a state where the fit between the outer peripheral surface of the bearing sleeve and the inner peripheral surface of the housing is a gap fit, even when there is variation in the shape of the bearing sleeve, particularly in the radial direction, The variation can be absorbed by the bonding gap. For example, in fixing methods that involve press-fitting (press-fitting, press-fitting adhesion, etc.), the inner peripheral surface of the bearing sleeve follows the shape of the outer peripheral surface, which may make it difficult to secure the coaxial between the radial bearings. This kind of problem will not occur. This configuration is particularly effective when a plurality of bearing sleeves are used.

  If the housing is a molded product, mass production of the housing can be facilitated, and the cost of the hydrodynamic bearing device can be reduced. Also, when forming a dynamic pressure generating part such as a dynamic pressure groove that generates fluid dynamic pressure in the thrust bearing gap on the stepped surface of the housing, when forming the housing, the dynamic pressure generating part shape is formed on the molded part of the housing stepped surface. The dynamic pressure generating portion can be formed simultaneously with the molding of the housing simply by forming a corresponding molding die. When this kind of dynamic pressure groove is formed on the end face of a bearing sleeve made of sintered metal as in the past, there are concerns about an increase in processing steps and an increase in processing cost. Therefore, such an increase in cost can be avoided.

  When the bearing sleeves are arranged at a plurality of positions in the axial direction, a non-porous spacer can be provided between two adjacent bearing sleeves. By adopting such a configuration, it is possible to secure the bearing span of the radial bearing portion while reducing the amount of lubricating fluid filling the bearing. In this case, the volume (axial dimension) of the seal space provided in the opening of the housing can be reduced by the reduction in the amount of lubricating fluid, thereby further increasing the bearing span of the radial bearing, in other words, the moment rigidity. be able to.

  As described above, according to the present invention, it is possible to reduce the cost of the hydrodynamic bearing device by facilitating the assembly of the bearing sleeve, improve the load capacity against moment load, and have excellent rotational accuracy. An apparatus can be provided.

  Embodiments of a hydrodynamic bearing device having the configuration of the present invention will be described below with reference to the drawings. 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 limit the installation direction or usage mode of the hydrodynamic bearing device.

  FIG. 1 shows a hydrodynamic bearing device 1 according to the first embodiment. The hydrodynamic bearing device 1 is used by being incorporated in a spindle motor for HDD, for example. The hydrodynamic bearing device 1 includes a housing 2, a plurality of (herein, two) bearing sleeves (first bearing sleeve 3 and second bearing sleeve 4) fixed to the housing 2, and inner circumferences of both bearing sleeves 3 and 4. A shaft member 5 inserted into the shaft member 5 and seal members 6 and 7 as projecting portions provided to project to the outer diameter side of the shaft member 5 are provided as constituent members.

  Although details will be described later, in the illustrated hydrodynamic bearing device 1, a first radial bearing portion R1 is provided between the inner peripheral surface 3a of the first bearing sleeve 3 and the outer peripheral surface 5a of the shaft member 5, and the second A second radial bearing portion R <b> 2 is provided between the inner peripheral surface 4 a of the bearing sleeve 4 and the outer peripheral surface 5 a of the shaft member 5. In this embodiment, the first thrust bearing portion T1 is provided between the first step surface 2d of the housing 2 and the lower end surface 6b of the seal member 6, and the second step surface 2e of the housing 2 and the seal member 7 are provided. The second thrust bearing portion T2 is provided between the upper end surface 7b of the first thrust bearing portion 7b and the second thrust bearing portion T2.

  The housing 2 is formed in a substantially cylindrical shape by injection molding of a molten material, for example, a molten resin, and the inner peripheral surface thereof includes a small-diameter inner peripheral surface 7a serving as a fixing portion of the bearing sleeves 3 and 4 and a small-diameter inner peripheral surface 7a. Are divided into first and second large-diameter inner peripheral surfaces 2b and 2c having a larger diameter than the small-diameter inner peripheral surface 7a. The first and second large-diameter inner peripheral surfaces 2b and 2c are connected to the small-diameter inner peripheral surface 2a via first and second step surfaces 2d and 2e, respectively. The small-diameter inner peripheral surface 2 a of the housing 2 is formed to have a slightly larger diameter than the outer diameter of the first and second bearing sleeves 3 and 4.

  As shown in FIG. 2 (a), a region that becomes the thrust bearing surface of the first thrust bearing portion T1 is formed in a part or all of the annular region of the first step surface 2d of the housing 2, and the thrust bearing surface is provided with the thrust bearing surface. Is formed with a plurality of dynamic pressure grooves 2d1 arranged in a herringbone shape. In addition, as shown in FIG. 2 (c), a part or the whole annular region of the second step surface 2e of the housing 2 is formed with a region to be a thrust bearing surface of the second thrust bearing portion T2, and the thrust bearing A plurality of dynamic pressure grooves 2e1 arranged in a herringbone shape are formed on the surface. One or both of the dynamic pressure grooves 2d1 and 2e1 may be arranged in other known shapes such as a spiral shape. The dynamic pressure grooves 2d1 and 2e1 are formed in the housing 2 by providing a mold portion corresponding to the shape of the dynamic pressure groove in the formation region of the first step surface 2d and the second step surface 2e in the mold of the housing 2. It is formed at the same time as molding.

  The base resin used for molding the housing 2 can be any amorphous resin or crystalline resin as long as it can be injection-molded. For example, as the amorphous resin, polysulfone (PSU), polyethersulfur can be used. Liquid crystalline polymers (LCP), polyetheretherketone (PEEK), polybutylene terephthalate (PBT), polyphenylenesulfide (PET), polyphenylsulfone (PPSU), polyetherimide (PEI), etc. PPS) or the like can be used. Of course, these are only examples, and other base resins can be used in consideration of the use environment and applications. In addition, one or more known various fillers can be blended into the above base resin for the purpose of increasing strength and imparting electrical conductivity.

  The housing 2 can also be a molten metal injection molded product. As the metal material, for example, a low-melting-point metal material such as a magnesium alloy or an aluminum alloy can be used, and in this case, strength and conductivity can be improved as compared with the case of using a resin material. In addition, so-called MIM molding may be employed in which after the injection molding with a mixture of metal powder and binder, degreasing and sintering. In addition, injection molding (so-called CIM molding) can also be performed with ceramic.

  The shaft member 5 is formed of a metal material such as stainless steel, and has a shaft shape with substantially the same diameter as a whole. Furthermore, in this embodiment, the annular seal members 6 and 7 are fixed to the shaft member 5 by an appropriate fixing means, for example, adhesion or press-fit adhesion (combination of press-fit and adhesion). The seal members 6 and 7 protrude from the outer peripheral surface 5a of the shaft member 5 to the outer diameter side. The inner peripheral side of the first large diameter inner peripheral surface 2b and the second large diameter inner peripheral surface 2c of the housing 2, respectively. Is housed. Further, in order to increase the fixing strength by the adhesive, circumferential grooves 5a1 and 5a2 serving as adhesive reservoirs are provided on the outer peripheral surface 5a of the shaft member 5 serving as a fixing position of the seal members 6 and 7. The seal members 6 and 7 may be formed of a soft metal material such as brass (brass), other metal materials, or a resin material. Further, either one of the seal members 6 and 7 may be integrally formed with the shaft member 5 in order to reduce the number of parts and the number of assembly steps.

  The outer peripheral surface 6a of the seal member 6 forms a seal space S1 having a predetermined volume with the first large-diameter inner peripheral surface 2b of the housing 2, and the outer peripheral surface 7a of the seal member 7 is the second large-diameter inner peripheral surface of the housing 2. A predetermined volume of the seal space S2 is formed between the surface 2c. In this embodiment, the outer peripheral surface 6 a of the seal member 6 and the outer peripheral surface 7 a of the seal member 7 are each formed in a tapered surface shape that is gradually reduced in diameter toward the outside of the housing 2. Therefore, the seal spaces S <b> 1 and S <b> 2 have a tapered shape that gradually decreases toward the inner side of the housing 2.

  The first and second bearing sleeves 3 and 4 are both formed into a cylindrical shape, for example, a porous body made of sintered metal, particularly a sintered metal porous body mainly composed of copper. In the present embodiment, the first bearing sleeve 3 is fixed to the small-diameter inner peripheral surface 2a of the housing 2 so that the upper end surface 3b thereof is positioned below the first step surface 2d of the housing 2 by δ1 in the axial direction. (See FIG. 3). Although not shown, the lower end surface 4b of the second bearing sleeve 4 is positioned above the second step surface 2e of the housing 2 by a predetermined dimension (δ1) in the axial direction, like the first bearing sleeve 3. Thus, it is fixed to the small-diameter inner peripheral surface 2 a of the housing 2. The bearing sleeves 3 and 4 can be made of a solid soft metal material such as a copper alloy in addition to the sintered metal.

  In this embodiment, the bearing sleeves 3 and 4 are fixed to the small-diameter inner peripheral surface 2a of the housing 2 so that the coaxiality between the inner peripheral surfaces 3a and 4a is 3 μm or less. Further, the two bearing sleeves 3 and 4 have a small diameter of the housing 2 such that the inner peripheral surfaces 3a and 4a have a squareness of 5 μm or less with respect to the first and second step surfaces 2d and 2e of the housing 2, respectively. It is fixed to the inner peripheral surface 2a.

  As shown in FIG. 2 (b), an area that becomes the radial bearing surface A of the first radial bearing portion R1 is formed on the inner peripheral surface 3a of the first bearing sleeve 3, and the herringbone is formed on the radial bearing surface A. A plurality of dynamic pressure grooves 3a1 arranged in a shape are formed. The radial bearing surface A is formed at an end portion on the side (upper side) away from the second bearing sleeve 4. Further, a belt-like convex portion B is formed at an end portion on the opposite side (lower side) of the inner peripheral surface 3a that is separated from the radial bearing surface A in the axial direction. The convex portion B is formed to have substantially the same diameter (including the case of the same diameter) as the hill portion defining the dynamic pressure groove 3a1. A plurality of (three in the illustrated example) axial grooves 3d1 are formed on the outer peripheral surface 3d at regular intervals in the circumferential direction.

  In addition, a region to be a radial bearing surface A ′ of the second radial bearing portion R2 is formed on the inner peripheral surface 4a of the second bearing sleeve 4, and a plurality of dynamic pressure grooves 4a1 are herringed on the radial bearing surface A ′. It is arranged in a bone shape. The radial bearing surface A ′ is formed at an end portion on the side (lower side) away from the first bearing sleeve 3. In addition, a belt-like convex portion B ′ is formed at an end portion on the opposite side (upper side) spaced apart from the radial bearing surface A ′ in the axial direction in the inner peripheral surface 4 a. The convex portion B 'is formed to have substantially the same diameter (including the case of the same diameter) as the hill portion that defines the dynamic pressure groove 4a1. A plurality of (three in the illustrated example) axial grooves 4d1 are formed on the outer peripheral surface 4d at regular intervals in the circumferential direction.

  Next, an assembling method of the hydrodynamic bearing device 1 composed of the above-described components will be described based on the drawings with a focus on the process of assembling both bearing sleeves 3 and 4 to the housing 2.

  4A and 4B conceptually show a process of positioning and fixing the first and second bearing sleeves 3 and 4 to the small-diameter inner peripheral surface 2a of the housing 2. FIG. The assembling apparatus 10 used in this process includes a base portion 12, a positioning portion 13 protruding from the upper end surface 12b of the base portion 12 by δ1 in the axial direction, and a pin extending upward in the axial direction from the upper end surface 13a of the positioning portion 13. Part 11 and a disk part 14 fitted on the outer periphery of the upper end of pin part 11. The outer peripheral surface 11a of the pin portion 11 is formed to have a larger diameter than the inner peripheral surfaces 3a and 4a of the bearing sleeves 3 and 4 so that both can slide relative to each other with the bearing sleeves 3 and 4 inserted. .

  In the assembling apparatus 10 described above, the accuracy of the outer peripheral surface 11a of the pin portion 11 directly affects the coaxiality between the inner peripheral surfaces 3a and 4a of the both bearing sleeves. (3 μm or less) is satisfied. In addition, the perpendicularity between the upper end surface 12b of the base portion 12 and the outer peripheral surface 11a of the pin portion 11, the molding accuracy of the disc portion 14 and the assembly accuracy of the disc portion 14a in the state of being externally fitted to the pin portion 11, Since the perpendicularity of the bearing sleeve inner peripheral surfaces 3a and 4a with respect to the step surfaces 2d and 2e of the housing 2 directly influences, these are finished so as to satisfy the required perpendicularity (5 μm or less). Further, the outer peripheral surface 12a of the base portion 12 and the outer peripheral surface 14a of the disc portion 14 are finished so as not to rattle between the large-diameter inner peripheral surfaces 2b and 2c of the housing 2 and to deteriorate the accuracy. .

  In the above configuration, first, as shown in FIG. 4A, the second bearing sleeve 4 is press-fitted into the pin portion 11 (including light press-fitting), and its lower end surface 4b is brought into contact with the upper end surface 13a of the positioning portion 13. Make contact. Next, in a state where an adhesive is applied to a predetermined region of the small-diameter inner peripheral surface 2a of the housing 2, the second bearing sleeve 4 is configured such that the second step surface 2e of the housing 2 is brought into contact with the upper end surface 12b of the base portion 12. The disk portion 14 is fitted on the pin portion 11 so that the lower end surface 14b is in contact with the first step surface 2d of the housing 2.

  As the adhesive, a thermosetting adhesive, a photocurable adhesive, a room temperature curable adhesive, or the like can be used. However, in this embodiment, a special curing apparatus is not required and the curing is performed in a short time. Possible room-temperature curable adhesives, in particular, anaerobic adhesives that can be reliably bonded and fixed by blocking air and can eliminate special confirmation work.

  As described above, in the inner circumferential surface 4 a of the second bearing sleeve 4, the convex portion B ′ having the same diameter as that of the radial bearing surface A ′ is provided in a region separated in the axial direction from the radial bearing surface A ′. Yes. Therefore, by assembling in the above-described manner, it is possible to ensure the coaxiality of the inner peripheral surface 4a of the second bearing sleeve 4 with respect to the small-diameter inner peripheral surface 2a of the housing 2, and to the second step surface 2e of the housing 2 The perpendicularity of the inner peripheral surface 4a of the second bearing sleeve 4 is ensured. Then, by holding this state for a while and solidifying the adhesive, the lower end surface 4b of the housing 2 is positioned at a position separated by δ1 in the axial direction from the second step surface 2e. The second bearing sleeve 4 is bonded and fixed to the small-diameter inner peripheral surface 2a.

  The above assembly is once removed from the assembly apparatus 10. Next, as shown in FIG. 4B, the first bearing sleeve 3 is press-fitted into the pin portion 11, and the upper end surface 3 b is brought into contact with the upper end surface 13 a of the positioning portion 13. Then, the first step surface 2d of the housing 2 is applied to the upper end surface 12b of the base portion 12 in a state where the top and bottom of the assembly product is reversed and an adhesive is applied to a predetermined region of the small-diameter inner peripheral surface 2a of the housing 2. The above assembly is arranged on the outer diameter side of the first bearing sleeve 3 so as to abut. When this state is maintained for a while and the adhesive is solidified, the small-diameter inner periphery of the housing 2 is positioned such that the upper end surface 3b is spaced from the first step surface 2d of the housing 2 by δ1 in the axial direction. The first bearing sleeve 3 is bonded and fixed to the surface 2a.

  At this time, similarly to the above, the inner peripheral surface 3a of the first bearing sleeve 3 is also provided with the convex portion B having the same diameter as the radial bearing surface A. The coaxiality of the inner peripheral surface 3a of the first bearing sleeve 3 with respect to the small-diameter inner peripheral surface 2a is ensured, and the perpendicularity of the inner peripheral surface 3a of the first bearing sleeve 3 with respect to the first step surface 2d of the housing 2 is ensured. The Furthermore, since both the first bearing sleeve 3 and the second bearing sleeve 4 are press-fitted into the pin portion 11, between the inner peripheral surface 3 a of the first bearing sleeve 3 and the inner peripheral surface 4 a of the second bearing sleeve 4. A predetermined coaxiality (within 3 μm) is ensured. In the state shown in FIG. 4B, the disk portion 14 is formed on the upper end portion of the pin portion 11 as shown in FIG. 4A because the second bearing sleeve 4 is positioned on the upper outer diameter side of the pin portion 11. Even if it is not externally fitted, the posture of the housing 2 does not deteriorate and the required accuracy is ensured. Needless to say, the second bearing sleeve 4 may be positioned using the disk portion 14 as in the case of fixing the second bearing sleeve 4 to the housing 2.

  By the way, as described above, the small-diameter inner peripheral surface 2a of the housing 2 is formed to have a larger diameter than the outer peripheral surfaces 3d and 4d of the both bearing sleeves 3 and 4, so that the both bearing sleeves 3 and 4 are bonded to the housing 2. Fixing is so-called gap adhesion. By adhering the gap, even if there is a variation in the radial shape between the bearing sleeves 3 and 4, the variation can be absorbed by the adhesion gap, and coaxiality is ensured between the inner peripheral surfaces 3 a and 4 a. Can be done reliably. Note that if the width of the adhesive gap is too large, the adhesive strength is lowered. On the other hand, if the width is too small, the adjustment allowance in the radial direction is reduced. Therefore, the width of the adhesive gap is set to about 10 μm to 50 μm, more preferably about 15 μm to 20 μm.

  In the above description, the second bearing sleeve 4 is fixed first, but of course, the second bearing sleeve 4 may be fixed to the housing 2 after the first bearing sleeve 3 is fixed to the housing 2. Further, the above assembling process may be performed after applying an adhesive to the outer peripheral surfaces of the bearing sleeves 3 and 4 instead of the small-diameter inner peripheral surface 2a of the housing 2.

  By fixing the bearing sleeves 3 and 4 to the housing 2 as described above, the upper end surface 3b of the first bearing sleeve 3 is fixed by being spaced apart from the first step surface 2d of the housing 2 by δ1 in the axial direction. The lower end surface 4b of the second bearing sleeve 4 is also fixed at a distance of δ1 from the second step surface 2e of the housing 2 in the axial direction. At the same time, a predetermined coaxiality (3 μm or less) is ensured between the inner peripheral surfaces 3a and 4a of the bearing sleeves 3 and 4, and the inner peripheral surfaces of the bearing sleeve with respect to the first and second step surfaces 2d and 2e of the housing 2 A predetermined squareness (5 μm or less) of 3a and 4a is secured. Then, the shaft member 5 is inserted into the inner circumferences of the bearing sleeves 3 and 4, and the seal members 6 and 7 are placed at predetermined locations (circumferential) of the shaft member 5 while maintaining a predetermined axial gap (axial gap) width. The outer periphery of the grooves 5a1 and 5a2 is fixed. At this time, in order to simplify the assembly of the seal member, either one of the seal members 6 and 7 is fixed to the shaft member 5 in advance before insertion or formed integrally with the shaft member 5. You can also.

  In addition, as a result of fixing both the bearing sleeves 3 and 4 to the small diameter inner peripheral surface 2a of the housing 2 in the above-described manner, as shown in FIGS. 1 and 2, the lower end surface 3c of the first bearing sleeve 3 and the second bearing There may be a slight gap between the upper end surface 4 c of the sleeve 4. Of course, depending on the axial dimensions of the first and second bearing sleeves 3 and 4 and the housing 2, the bearing sleeves 3 and 4 may contact each other.

  After the assembly is completed through the above steps, the internal space of the housing 2 sealed with the seal members 6 and 7 is filled with, for example, lubricating oil as a lubricating fluid including the internal pores of the bearing sleeves 3 and 4. Filling the lubricating oil can be performed, for example, by immersing the hydrodynamic bearing device 1 that has been assembled in the lubricating oil in a vacuum chamber and then releasing it to atmospheric pressure.

  In the hydrodynamic bearing device 1 having the above configuration, when the shaft member 5 rotates, the radial bearing surface A of the inner peripheral surface 3a of the first bearing sleeve 3 faces the outer peripheral surface 5a of the shaft member 5 with a radial bearing gap interposed therebetween. . On the radial bearing surface A, the pressure of the lubricating oil filled in the radial bearing gap is increased by the dynamic pressure action of the dynamic pressure groove 3a1, thereby supporting the shaft member 2 in a non-contact manner so as to be rotatable in the radial direction. In the present embodiment, a radial bearing gap is formed between the convex portion B and the outer peripheral surface 5 a of the shaft member 5, and an oil film is formed in the radial bearing gap by the oil that has oozed from the first bearing sleeve 3. The shaft member 5 is supported by the oil film so as to be rotatable in the radial direction. As a result, the first radial bearing portion R1 that supports the shaft member 5 rotatably in the radial direction is formed by the dynamic pressure bearing and the perfect circle bearing. Similarly, in the second bearing sleeve 4 as well, a dynamic pressure bearing is formed by the radial bearing surface A ′, and a perfect circle bearing is formed by the convex portion B ′, and the second radial which supports the shaft member 5 in a non-contact manner so as to be rotatable in the radial direction. A bearing portion R2 is formed.

  Further, when the shaft member 5 rotates, the thrust bearing surface formed on the first step surface 2d of the housing 2 faces the lower end surface 6b of the seal member 6 with a predetermined thrust bearing gap therebetween, so that the second The thrust bearing surface formed on the step surface 2e faces the upper end surface 7b of the seal member 7 via a predetermined thrust bearing gap. As the shaft member 2 rotates, the lubricating oil filled in the thrust bearing gaps is increased by the dynamic pressure action of the dynamic pressure grooves 2d1 and 2e1, and the shaft member 5 is non-rotatable in both thrust directions. Touch supported. Thereby, the 1st thrust bearing part T1 and the 2nd thrust bearing part T2 which support the shaft member 5 in a non-contact manner so as to be rotatable in both thrust directions are formed.

  Further, when the shaft member 5 is rotated, the seal spaces S1 and S2 formed on the outer peripheral surface 6a side of the seal member 6 and the outer peripheral surface 7a side of the seal member 7 are formed on the inner side of the housing 2 as described above. Since the taper shape gradually decreases toward the bottom, the lubricating oil in both the seal spaces S1 and S2 is narrowed by the pulling action by the capillary force and the pulling action by the centrifugal force at the time of rotation, that is, It is pulled toward the inside of the housing 2. Thereby, the leakage of the lubricating oil from the inside of the housing 2 is effectively prevented. Further, the seal spaces S1 and S2 have a buffer function of absorbing a volume change amount accompanying a temperature change of the lubricating oil filled in the internal space of the housing 2, and within the range of the assumed temperature change, The oil level is always in the seal space S1, S2.

  Further, the fluid passage formed by the axial groove 3d1 of the first bearing sleeve 3, the fluid passage formed by the axial groove 4d1 of the second bearing sleeve 4, and each bearing gap (the first radial bearing portion R1 and the second radial bearing portion R1). A series of circulation passages are formed inside the housing 2 by the radial bearing gap of the radial bearing portion R2 and the thrust bearing gap of the first thrust bearing portion T1 and the second thrust bearing portion T2. Then, the lubricating oil filled in the internal space of the housing 2 flows and circulates through the circulation passage, so that the pressure balance of the lubricating oil is maintained, and at the same time, bubbles are generated due to the generation of local negative pressure. In addition, leakage of lubricating oil and generation of vibration due to the generation of bubbles are prevented.

  Although not shown, the axial fluid passage formed between the bearing sleeves 3, 4 and the housing 2 is formed by providing an axial groove on the small-diameter inner peripheral surface 2 a of the housing 2. You can also.

  As described above, in the present invention, the thrust bearing portions T1, T2 are provided between the first and second step surfaces 2d, 2e of the housing 2 and the lower end surfaces 6b, 7b of the seal members 6, 7. It is done. Therefore, since it is sufficient to assemble the bearing sleeves 3 and 4 with respect to the housing 2 only in consideration of the radial position, the assembly of the bearing sleeves 3 and 4 can be facilitated and the cost of the hydrodynamic bearing device 1 can be reduced. It becomes possible to plan. Further, since the thrust bearing portions T1 and T2 are provided on the outer diameter side as compared with the conventional configuration, the rotation accuracy can be increased through the expansion of the bearing area.

  Further, since the bearing sleeves are arranged side by side at two locations in the axial direction, it is possible to increase the load capacity against the moment load through expansion of the bearing span of the radial bearing portion, and it is possible to facilitate the manufacture of the bearing sleeve. Further, the coaxiality between the inner peripheral surfaces of the bearing sleeves 3 and 4 is set to 3 μm or less, and the inner peripheral surfaces 3a and 4a of the bearing sleeves 3 and 4 and the first and second step surfaces 2d and 2e of the housing 2 are set. Since the perpendicularity between them is set to 5 μm or less, it is possible to provide the hydrodynamic bearing device 1 that avoids wear associated with sliding contact of each member and is excellent in rotational accuracy.

  FIG. 5 shows a fluid dynamic bearing device according to a second embodiment of the present invention. The main difference of the hydrodynamic bearing device 1 shown in FIG. 1 from the embodiment shown in FIG. 1 is that the axial dimensions of the first and second bearing sleeves 23, 24 are reduced and the bearing sleeves 23, 24 are spaced apart from each other. The ring spacer 8 is interposed. Although illustration is omitted, since the axial dimensions of the bearing sleeves 23 and 24 are reduced, the posture deterioration of the bearing sleeves 23 and 24 during assembly can be eliminated as much as possible. For this reason, in the present embodiment, the inner peripheral surface of each bearing sleeve 23, 24 is not provided with a convex portion having the same diameter as that of the radial bearing surface. Of course, if there is a concern about posture deterioration at the time of assembly, a convex portion having the same diameter as the radial bearing surface may be provided on the inner peripheral surface of each bearing sleeve 23, 24.

  The spacer 8 is fixed to a substantially central portion of the small-diameter inner peripheral surface 2a of the housing 2 so that the lower end surface 8c thereof is located at a position that is separated from the second step surface 2e of the housing 2 by a predetermined dimension in the axial direction. Yes. The spacer 8 is made of a non-porous material such as a soft metal material such as brass, other metal materials, or a resin material, and has an inner diameter larger than that of the both bearing sleeves 23 and 24. Accordingly, no radial bearing gap is formed between the inner peripheral surface 8 a of the spacer 8 and the outer peripheral surface 5 a of the shaft member 5. Since other items are the same as those in the first embodiment, a common reference number is assigned and a duplicate description is omitted.

  Hereinafter, the assembly process of the hydrodynamic bearing device 1 having the above configuration will be described focusing on the process of positioning and fixing the bearing sleeves 3 and 4 and the spacer 8 on the inner periphery of the housing 2 (FIGS. 6A to 6C). To do. Also in the description of the process, the same reference numerals are assigned to the substantially same configurations as those in FIGS. 4A and 4B, and the duplicate description is omitted.

  First, as shown in FIG. 6A, the spacer 8 is formed on the inner peripheral surface 2a of the housing 2 so that the lower end surface 8c thereof is separated from the second step surface 2e of the housing 2 by a predetermined dimension in the axial direction. Glue the gap. In this case, unlike the configuration shown in FIG. 4, the spacer 8 in the above manner is used by using the positioning portion 18 in which the axial separation distance between the upper end surface 18 b and the upper end surface 17 b of the base portion 17 is equal to the predetermined dimension. Is fixed. By the way, since the inner peripheral surface 8a of the spacer 8 is formed to have a larger diameter than the bearing sleeves 3 and 4 and the radial bearing gap is not formed on the inner peripheral side, the fixing accuracy in the radial direction does not matter so much. For this reason, the spacer 8 can be fixed to the small-diameter inner peripheral surface 2a of the housing 2 by, for example, press-fitting, in addition to the gap bonding similarly to the bearing sleeves 3 and 4.

  After the spacer 8 is fixed, the above assembly is temporarily removed, and the second bearing sleeve 4 is attached to one end side of the spacer 8 (the lower side in FIG. 5) of the housing 2 as shown in FIG. A gap is bonded to the small-diameter inner peripheral surface 2a. After the bonding and fixing, the assembly to which the second bearing sleeve 4 is assembled is removed, and the first inner surface 2a on the other end side (the upper side in FIG. 5) is removed as shown in FIG. 6 (c). The bearing sleeve 3 is bonded to the gap. The shaft member 5 is inserted into the inner periphery of the bearing sleeves 3 and 4 and the spacer 8 assembled to the small-diameter inner peripheral surface 2a of the housing 2 in this way, and the seal member 6 is maintained in a state where a predetermined axial gap width is maintained. 7 is fixed to a predetermined location of the shaft member 5, and the interior space of the housing 2 is then filled with lubricating oil, thereby completing the fluid dynamic bearing device 21 having the configuration shown in FIG.

  In the hydrodynamic bearing device 1 of this embodiment, a part of the sintered metal bearing sleeve is replaced with the non-porous spacer 8, so that the amount of lubricating oil filled in the bearing is reduced accordingly. Can do. Therefore, the axial span (volume) of the seal spaces S1 and S2 can be reduced, so that the bearing span of the radial bearing portions R1 and R2 can be increased, and the load capacity (moment rigidity) against moment load is further increased. be able to.

  In the above description, the configuration in which the bearing sleeves are arranged at a plurality of locations (two locations) in the axial direction has been described. However, even in the configuration using a single bearing sleeve as shown in FIG. The thrust bearing portions T1 and T2 can be formed on the end side. By adopting such a configuration, the assembly of the bearing sleeve can be facilitated and the cost can be reduced compared to the conventional configuration, and the moment rigidity can be increased (not shown).

  Further, the bearing sleeves may be arranged not only at one or two locations in the axial direction but also at three or more locations.

  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 or radial bearings in which a plurality of axial grooves are provided at equal intervals in the circumferential direction in a region serving as a radial bearing surface. You may employ | adopt what is called a multi-arc bearing which provided the some circular arc surface in the area | region used as a bearing surface. 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.

  In the above description, the lubricating oil is exemplified as the lubricating 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 air, are also used. Gas, magnetic fluid, etc. can also be used.

  FIG. 7 conceptually shows a configuration example of a spindle motor for HDD incorporating the hydrodynamic bearing device 1 according to an embodiment of the present invention, in particular, the embodiment shown in FIG. The spindle motor includes a stator coil opposed to the dynamic pressure bearing device 1 and a rotor (disk hub) 32 mounted on the shaft member 5 of the dynamic pressure bearing device 1 via, for example, a radial (radial direction) gap. 30 and a rotor magnet 31. The stator coil 30 is attached to the outer periphery of the bracket 9, and the rotor magnet 31 is attached to the inner periphery of the disk hub 32. The housing 2 of the hydrodynamic bearing device 1 is mounted on the inner periphery of the bracket 9. The disk hub 32 holds one or more disks D such as magnetic disks. When the stator coil 30 is energized, the rotor magnet 31 is rotated by electromagnetic force between the stator coil 30 and the rotor magnet 31, whereby the disk hub 32 and the disk D held by the disk hub 32 are integrated with the shaft member 5. Rotate to.

  The hydrodynamic bearing device 1 having the above-described configuration is not limited to the above-described spindle motor for HDD, but also includes optical disk devices such as CD-ROM, CD-R / RW, DVD-ROM / RAM, and magneto-optical disks such as MD and MO. The present invention can be suitably applied as a bearing device for electrical equipment including information equipment such as a spindle motor mounted on information equipment such as equipment. In addition, it is suitably used for a disk drive device equipped with a plurality of disks D corresponding to an increase in capacity of information equipment or a motor that requires high rotational performance under high-speed rotation. be able to.

  For the above reasons, the hydrodynamic bearing device according to the present invention is not limited to the spindle motor, and can be preferably used for other motors that require high rotational accuracy, such as a fan motor.

  FIG. 8 shows a so-called fan motor incorporating the hydrodynamic bearing device 1 according to the first embodiment of the present invention, in which the stator coil 30 and the rotor magnet 31 are opposed to each other via a radial (radial) gap. An example of a radial gap type fan motor is shown notionally. In the illustrated motor, the rotor 33 fixed to the outer periphery of the upper end of the shaft member 5 has blades on the outer peripheral surface, and the bracket 9 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 respective constituent members of the spindle motor shown in FIG.

It is sectional drawing which shows 1st Embodiment of a hydrodynamic bearing apparatus. (A) is a top view showing a state where a bearing sleeve is assembled to a housing, (b) is a sectional view thereof, and (c) is a bottom view thereof. It is an enlarged step view which shows the upper part of a housing. (A) and (b) are schematic views showing the manufacturing process of the fluid dynamic bearing device according to the first embodiment. It is sectional drawing which shows 2nd Embodiment of a hydrodynamic bearing apparatus. (A)-(c) figure is schematic which shows the manufacturing process of the hydrodynamic bearing apparatus concerning 2nd Embodiment. It is the schematic which shows an example of the spindle motor incorporating the dynamic pressure bearing apparatus. It is the schematic which shows an example of the fan motor incorporating the dynamic pressure bearing apparatus. It is sectional drawing which shows the hydrodynamic bearing apparatus of a conventional structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 2 Housing 3 1st bearing sleeve 4 2nd bearing sleeve 5 Shaft member 6, 7 Seal member 8 Spacer 11 Pin part 12 Base part 13 Positioning part A, A 'Radial bearing surface R1, R2 Radial bearing part T1 , T2 Thrust bearing part S1, S2 Seal space

Claims (5)

A housing, a bearing sleeve fixed to the housing, a shaft member inserted on the inner periphery of the bearing sleeve, and provided to project to the outer diameter side of the shaft member, and disposed at both ends of the bearing sleeve A projecting portion; a radial bearing gap formed between an inner circumferential surface of the bearing sleeve and an outer circumferential surface of the shaft member; and a thrust bearing gap. In a hydrodynamic bearing device that supports a member in a non-contact manner,
A stage connecting the housing with a small-diameter inner peripheral surface serving as a fixed portion of the bearing sleeve, a large-diameter inner peripheral surface located on the outer-diameter side of the protrusion, and the small-diameter inner peripheral surface and the large-diameter inner peripheral surface. A hydrodynamic bearing device characterized in that a step surface is provided so as to face the thrust bearing gap. A plurality of the bearing sleeves are arranged in the axial direction,
The coaxiality between the inner peripheral surfaces of each bearing sleeve is set to 3 µm or less, and the perpendicularity between the inner peripheral surface of each bearing sleeve and the step surface of the housing is set to 5 µm or less. Hydrodynamic bearing device.   The hydrodynamic bearing device according to claim 1, wherein the bearing sleeve is fixed by gap adhesion.   The hydrodynamic bearing device according to claim 1, wherein the housing is a molded product.   The hydrodynamic bearing device according to claim 2, wherein a non-porous spacer is disposed between two adjacent bearing sleeves.

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