JP2010019289A - Fluid dynamic pressure bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance fixing strength of a cover member, without enlarging a fluid dynamic pressure bearing device and reducing bearing performance. <P>SOLUTION: The cover member 10 for blocking up one opening part in the axial direction of a bearing sleeve 8, is fixed to an outer peripheral surface 8d of the bearing sleeve 8. Thus, the fixing strength of the cover member 10 can be enhanced without expanding a dimension in the axial direction of the bearing device and reducing a bearing span in a radial bearing part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fluid dynamic bearing device that rotatably supports a shaft member by a dynamic pressure action of a fluid film generated in a radial bearing gap between an outer peripheral surface of the shaft member and an inner peripheral surface of a bearing sleeve.

  Due to its high rotational accuracy and quietness, the fluid dynamic pressure bearing device is driven by a magnetic disk drive for information equipment (for example, HDD), an optical disk drive such as CD / DVD / Blu-ray disc, or a magneto-optical disk drive such as MD / MO It is used for spindle motors of devices, for polygon scanner motors of laser beam printers (LBP), for color wheel motors of projectors, or for small motors such as fan motors used for cooling electrical equipment.

  For example, Patent Document 1 discloses a shaft member, a bearing sleeve in which a shaft member is inserted on the inner periphery, a cylindrical housing that holds the bearing sleeve on the inner periphery, and a lid member that closes one opening of the housing. A fluid dynamic bearing device is shown. The lid member is fixed to the inner peripheral surface of the housing by an appropriate means such as adhesion, press-fitting, or caulking.

JP 2003-336636 A

  When an impact load is applied to the fluid dynamic bearing device, the end of the shaft member may abut against the lid member. In particular, in a fluid dynamic pressure bearing device incorporated in a disk drive device of an HDD, when a plurality of disks are mounted to increase the capacity of the HDD, the weight on the shaft member side increases and the impact applied to the lid member is large. Become. In such a case, the fixing strength of the lid member is important. When the lid member is fixed to the inner peripheral surface of the housing as in the fluid dynamic pressure bearing device of Patent Document 1, if the thickness of the lid member is increased, the fixing area between the housing and the lid member is increased, and the lid member is fixed. Strength can be increased. However, if the thickness of the lid member is increased, the axial dimension of the bearing device is increased and the bearing span of the radial bearing portion is reduced. Therefore, the lid member cannot be increased in thickness.

  An object of the present invention is to increase the fixing strength of a lid member of a fluid dynamic pressure bearing device without causing an increase in size or a decrease in bearing performance.

  In order to solve the above-described problems, the present invention provides a shaft member, a bearing sleeve in which the shaft member is inserted on the inner periphery, a holding member that holds the bearing sleeve from the outer periphery and that is open at both ends in the axial direction, and an outer periphery of the bearing sleeve. The cover member that is fixed to the surface and closes one opening of the bearing sleeve in the axial direction and the fluid film generated in the radial bearing gap between the outer peripheral surface of the shaft member and the inner peripheral surface of the bearing sleeve in the radial direction A fluid dynamic pressure bearing device having a radial bearing portion supported on the surface is provided.

  As described above, in the fluid dynamic pressure bearing device of the present invention, the lid member is fixed to the outer peripheral surface of the bearing sleeve. Therefore, even if the fixing area of the lid member is expanded to improve the fixing strength of the lid member, the bearing There is no increase in the axial dimension of the device or reduction in the bearing span of the radial bearing portion. That is, when the lid member is closed to the outer peripheral surface of the bearing sleeve while closing the one end opening of the bearing sleeve with the lid member, the portion that closes the opening (see, for example, the plate portion 10a in FIG. 2), and the outer peripheral surface And a portion (for example, refer to the cylindrical portion 10b in FIG. 2). In order to enlarge the fixed area of both, the contact area between the lid member and the outer peripheral surface of the bearing sleeve may be enlarged by extending the fixed portion in the axial direction. Therefore, the fixing strength between the lid member and the bearing sleeve can be increased without changing the thickness of the plate portion that affects the axial dimension of the bearing device and the bearing span of the radial bearing portion.

  When the shaft member is provided with a flange, and a thrust bearing that supports the shaft member in the thrust direction with a fluid film of the thrust bearing gap facing both end faces of the flange, the clearance width of the thrust bearing gap is set with high accuracy. There is a need to. At this time, if each member is processed with high accuracy, the width accuracy of the thrust bearing gap can be increased, but such high-precision processing leads to high costs. In view of this point, if an axial gap is provided between the holding member and the lid member, relative approach movement of the two in the axial direction is allowed. Therefore, the width of the thrust bearing gap is set by the following method. It can be performed. First, the bearing sleeve and the lid member are brought into contact with both end faces of the flange portion so that the gap width of the thrust bearing gap is zero, and the lid member is moved by a predetermined amount in a direction away from the bearing sleeve from this state. According to this method, since the width of the thrust bearing gap can be set by the amount of movement of the lid member without depending on the accuracy of each member, the processing accuracy of each part is relaxed and the processing cost is reduced. Can do.

  For example, if the bearing sleeve is formed of a porous body (for example, sintered metal), the lubricating fluid impregnated in the internal holes of the bearing sleeve can be sequentially supplied to the bearing gap, so that the lubricity can be improved. At this time, if the outer peripheral surface of the bearing sleeve exposed from the axial gap between the holding member and the lid member is sealed, it is possible to prevent the lubricating fluid that has oozed out from the surface opening of the bearing sleeve from leaking to the outside. .

  In general, the adhesive strength between metal materials is higher than the adhesive strength between metal materials and resin materials, for example, so if both the bearing sleeve and lid member are made of metal materials and bonded together, they are firmly fixed. can do.

  When the lid member is fixed to the outer peripheral surface of the bearing sleeve, the influence of the fixing (for example, shrinkage due to solidification of the adhesive or pressing force due to press-fitting) may reach the inner peripheral surface of the bearing sleeve and the inner peripheral surface may be reduced in diameter. is there. At this time, if the amount of diameter reduction of the inner peripheral surface of the bearing sleeve is different in the axial region of the radial bearing portion, the gap width of the radial bearing gap becomes non-uniform in the axial direction, which may deteriorate the bearing performance. Therefore, if the end of the lid member is extended to a position beyond the axial region of the radial bearing portion, the outer diameter side of the radial bearing portion is entirely covered with the lid member, so the inner peripheral surface of the bearing sleeve is the shaft of the radial bearing portion. The diameter can be uniformly reduced over the entire direction. Thereby, the gap width of the radial bearing gap is constant in the axial direction, and excellent bearing performance can be obtained. Further, the same effect as described above can be obtained by extending the end of the holding member to a position beyond the axial region of the radial bearing.

  When a bracket for attaching the stator coil is provided, the fixing strength of the lid member can be further increased by fixing the outer peripheral surface of the lid member to the bracket.

  As described above, according to the present invention, it is possible to increase the fixing strength of the lid member of the fluid dynamic pressure bearing device without causing an increase in the size of the bearing device or a decrease in bearing performance.

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

  FIG. 1 conceptually shows a configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device 1 according to an embodiment of the present invention. The spindle motor is used in a disk drive device such as an HDD, and includes a fluid dynamic bearing device 1 that rotatably supports a shaft member 2, a disk hub 3 fixed to the upper end of the shaft member 2, and a radius. A stator coil 4 and a rotor magnet 5 which are opposed to each other with a gap in a direction, and a motor bracket 6 are provided. The stator coil 4 is attached to the outer periphery of the motor bracket 6, and the rotor magnet 5 is attached to the inner periphery of the disk hub 3. The fluid dynamic bearing device 1 is fixed to the inner periphery of the motor bracket 6. The disc hub 3 holds one or a plurality of discs D (two in this embodiment) as information recording media, and is fixed by a clamping device (not shown). When the stator coil 4 is energized, the rotor magnet 5 rotates, and accordingly, the disk hub 3 and the disk D held by the disk hub 3 rotate integrally with the shaft member 2.

  A fluid dynamic bearing device 1 shown in FIG. 2 includes a shaft member 2, a bearing sleeve 8 in which the shaft member 2 is inserted on the inner periphery, a holding member 9 that holds the bearing sleeve 8 from the outer periphery, and opens both axial ends. And a cover member 10 that closes one opening of the bearing sleeve 8 in the axial direction. For convenience of explanation, the opening side of the bearing sleeve 8 in the axial direction is referred to as the upper side, and the closing side is referred to as the lower side.

  The shaft member 2 has a substantially cylindrical shaft portion 2a and a flange portion 2b provided at the lower end of the shaft portion 2a. The shaft portion 2a and the flange portion 2b are formed separately from each other with a metal material (for example, SUS steel) having high wear resistance, and then joined by, for example, welding.

  The flange portion 2b is formed with a communication hole 11 that opens to the upper end surface 2b1 and the lower end surface 2b2. Specifically, the communication hole 11 has a radial portion 11a and an axial portion 11b, and opens at different radial positions on the upper end surface 2b1 and the lower end surface 2b2 of the flange portion 2b. More specifically, as shown in FIG. 5, one end of the communication hole 11 is provided at the upper end surface 2b1 of the flange portion 2b, the inner peripheral chamfer 8c2 of the lower end surface 8c of the bearing sleeve 8, and the lower end portion of the shaft portion 2a. The other end of the communication hole is formed in the space P formed between the lower end surface 2b2 of the flange portion 2b and the upper end surface 10a1 of the plate portion 10a of the lid member 10. An opening is formed in the inner diameter side region of the two thrust bearing portion T2. In the illustrated example, the other end of the communication hole 11 opens at a position adjacent to the inner diameter side of the second thrust bearing portion T2. The communication hole 11 is formed by previously forming a radial groove serving as the radial portion 11a and an axial hole serving as the axial portion 11b in the flange portion 2b, and then joining the flange portion 2b and the shaft portion 2a. The

  As shown in FIG. 3, the bearing sleeve 8 is formed in a cylindrical shape with a porous body, for example, a sintered metal mainly composed of copper. In addition, the bearing sleeve 8 can be formed of other metals, resins, ceramics, or the like. Both the inner peripheral surface 8a and the outer peripheral surface 8d of the bearing sleeve 8 are formed in a cylindrical surface shape having a constant radial dimension in the axial direction. Further, an inner peripheral chamfer and an outer peripheral chamfer are formed on the upper end surfaces 8b and 8c of the bearing sleeve 8, respectively.

  On the inner peripheral surface 8a of the bearing sleeve 8, a radial dynamic pressure generating portion for generating a dynamic pressure action on the fluid film (oil film) in the radial bearing gap is formed. In this embodiment, as shown in FIG. In addition, herringbone-shaped dynamic pressure grooves 8a1 and 8a2 are formed in two regions separated in the axial direction. Of the two dynamic pressure groove regions, the portions with cross hatching excluding the dynamic pressure grooves 8a1 and 8a2 are hills. The upper dynamic pressure groove 8a1 is formed in an axially asymmetric shape. Specifically, the axial dimension X1 of the upper groove is lower than the band-shaped portion formed in the substantially central part in the axial direction of the hill. It is larger than the axial dimension X2 of the groove (X1> X2). The lower dynamic pressure groove 8a2 is formed in an axially symmetrical shape.

  The lower end face 8c of the bearing sleeve 8 is formed with a thrust dynamic pressure generating portion for generating a dynamic pressure action on the oil film in the thrust bearing gap. In this embodiment, as shown in FIG. It has a configuration in which dynamic pressure grooves 8c1 and hill portions 8c2 bent in a V shape are alternately arranged in the circumferential direction in a bone shape.

  The holding member 9 has a cylindrical shape that is open at both ends in the axial direction. In the illustrated example, the cylindrical portion 9a has a constant thickness, and a seal portion that extends from the upper end of the cylindrical portion 9a toward the inner diameter side. 9b. The cylindrical portion 9a holds the bearing sleeve 8 from the outer periphery, and its lower end portion 9a1 extends to the lower side beyond the first radial bearing portion R1. The inner peripheral surface 9a2 and the outer peripheral surface 9a3 of the cylindrical portion 9a each have a cylindrical surface shape with a constant diameter in the axial direction. The inner peripheral surface 9b1 of the seal portion 9b is formed in a tapered surface shape that is gradually reduced in diameter downward, and a radial direction is formed downward between the tapered inner peripheral surface 9b1 and the outer peripheral surface 2a1 of the shaft portion 2a. A wedge-shaped seal space S whose size is gradually reduced is formed. The internal space of the bearing sealed with the seal portion 9b is filled with lubricating oil. In the seal space S, an oil surface (gas-liquid interface) of the lubricating oil filled in the bearing is formed, and the oil surface is always held in the seal space S by the pulling action of the capillary force of the wedge-shaped seal space S. . The volume of the seal space S is set so that the oil level of the lubricant can always be kept within the range of the seal space S even when the lubricant filled in the bearing expands and contracts with a change in temperature.

  On the outer diameter side of the upper end of the holding member 9 that becomes the boundary between the cylindrical portion 9a and the seal portion 9b, the corner portion is thinned. Since the thickness of the holding member 9 is substantially uniform in the region from the cylindrical portion 9a to the seal portion 9b, the wall removal portion 9c suppresses deformation of the inner peripheral surface 9b1 of the seal portion 9b due to resin molding shrinkage. The shape accuracy of the seal space S can be ensured.

  The holding member 9 is formed integrally with the cylindrical portion 9a and the seal portion 9b by resin injection molding using the bearing sleeve 8 as an insert part. The resin material of the holding member 9 is not particularly limited. For example, a crystalline resin such as liquid crystal polymer (LCP), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyphenylsulfone (PPSU), polyethersulfide, or the like. A resin composition based on an amorphous resin such as phon (PES) or polyetherimide (PEI) can be used. In this resin material, various kinds of fillers can be blended in appropriate amounts according to the purpose, for example, fibrous fillers such as glass fibers, whisker-like fillers such as potassium titanate, scaly fillers such as mica, Fibrous or powdery conductive fillers such as carbon fiber, carbon black, graphite, carbon nanomaterial, and various metal powders can be blended.

  The lid member 10 is fitted and fixed to the outer peripheral surface 8 d of the bearing sleeve 8 and closes the lower opening of the bearing sleeve 8. In the illustrated example, the lid member 10 includes a substantially disk-shaped plate portion 10a and a cylindrical portion 10b extending upward from the outer diameter end of the plate portion 10a. The lid member 10 is integrally formed with a plate portion 10a and a cylindrical portion 10b, for example, by pressing a metal material.

  The upper end face 10a1 of the plate portion 10a is formed with a thrust dynamic pressure generating portion for generating a dynamic pressure action on the oil film in the thrust bearing gap. In this embodiment, as shown in FIG. In this configuration, the dynamic pressure grooves 10a11 and the hill portions 10a12 bent in a shape are alternately arranged in the circumferential direction.

  The inner peripheral surface 10b1 of the cylindrical portion 10b is fixed to the outer peripheral surface 8d of the bearing sleeve 8 by, for example, adhesion. The upper end portion 10b2 of the cylindrical portion 10b extends upward beyond the second radial bearing portion R2, and opposes the lower end portion 9a1 of the holding member 9 via the axial gap δ (see an enlarged view of FIG. 2). The axial gap δ is sealed around the entire periphery with, for example, an adhesive G.

  Since the axial gap δ is provided between the lid member 10 and the holding member 9, both can be relatively approached in the axial direction. Therefore, the lid member 10 is attached to the bearing sleeve 8 by the following method. Can be fixed. First, the inner peripheral surface 10b1 of the cylindrical portion 10b of the lid member 10 is fitted to the outer peripheral surface 8d of the bearing sleeve 8 to which an adhesive is applied in advance, and the bearing sleeve 8 and the lid member are fitted to both end surfaces 2b1 and 2b2 of the flange portion 2b. 10 plate portions 10a are brought into contact with each other (that is, the gap width of the thrust bearing gap is set to 0). At this time, the dimension of each component is set so that the upper end portion 10b2 of the lid member 10 and the lower end portion 9a1 of the holding member 9 do not contact each other. Thereafter, the lid member 10 is pulled back with respect to the holding member 9 by the amount corresponding to the total gap width of each thrust bearing gap (in a direction away from the holding member 9), and the adhesive is solidified in this state. In this way, by setting the width of the thrust bearing gap by the amount of movement of the lid member 10, the machining accuracy of each component is relaxed, and the machining cost can be reduced.

  When the lid member 10 is fixed to the outer periphery of the bearing sleeve 8 in this way, an adhesive is applied to the outer peripheral surface 8d of the bearing sleeve 8, so that the surface opening of the outer peripheral surface 8d is sealed. Further, by fitting the cylindrical portion 10b of the lid member 10 from below, a part of the adhesive on the outer peripheral surface 8d of the bearing sleeve 8 is captured by the upper end portion 10b2 of the cylindrical portion 10b, and this captured adhesion The agent is disposed in the axial gap δ between the lower end portion 9 a 1 of the holding member 9. As a result, the axial gap δ is sealed with an adhesive, and it is possible to avoid the risk that the lubricating oil that has exuded from the surface opening of the outer peripheral surface of the bearing sleeve 8 exposed from the axial gap δ leaks to the outside. Note that after the lid member 10 is fixed to the bearing sleeve 8, the axial gap δ may be further filled with an adhesive so as to be surely sealed. Moreover, you may seal not only with the sealing by an adhesive agent but with a resin material, for example.

  The outer peripheral surface 10b3 of the cylindrical portion 10b is fixed to the inner peripheral surface 6a of the motor bracket 6 by adhesion, for example. In this way, not only the lid member 10 is fixed to the bearing sleeve 8 but also the motor bracket 6 is adhesively fixed, whereby the fixing strength of the lid member 10 can be increased and the pull-out resistance can be improved. At this time, if the outer peripheral surface 10b3 of the lid member 10 and the outer peripheral surface 9a3 of the holding member 9 are set to have the same diameter, both can be easily fixed to the inner peripheral surface of the bracket 6. Therefore, the fluid dynamic pressure bearing device 1 and the motor The fixing strength with the bracket 6 can be increased. Further, by forming the lid member 10 from a metal material as described above, static electricity charged by the rotation of the disk D is discharged to the outside via the path of the shaft member 2 → the lid member 10 → the motor bracket 6. be able to. As a result, the material forming the holding member 9 is not required to be conductive, and the range of material selection is widened. For example, the carbon fiber added as a filler to the resin material of the holding member 9 is reduced or omitted. You can do it. In this way, the material cost can be suppressed by reducing the amount of carbon fiber or the like that is a relatively expensive material.

  The internal space of the fluid dynamic bearing device 1 having the above configuration, that is, the space sealed by the holding member 9 and the lid member 10 is filled with, for example, lubricating oil as a lubricating fluid including the internal holes of the bearing sleeve 8. At this time, if a lubricating fluid having conductivity is used, it is possible to energize between the rotation-side shaft member 2 that is in a non-contact state when the shaft member 2 rotates, and the fixed-side bearing sleeve 8 and the lid member 10. Thus, static electricity generated on the shaft member 2 side can be discharged through the lid member 10.

  In the fluid dynamic bearing device 1 configured as described above, when the shaft member 2 rotates, a radial bearing gap is formed between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a. The pressure of the oil film in the radial bearing gap is increased by the dynamic pressure grooves 8a1 and 8a2, thereby forming the first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 2 in a non-contact manner in the radial direction. At the same time, between the upper end surface 2b1 of the flange portion 2b of the shaft member 2 and the lower end surface 8c of the bearing sleeve 8, and the lower end surface 2b2 of the flange portion 2b of the shaft member 2 and the plate portion 10a of the lid member 10. Thrust bearing gaps are respectively formed between the upper end surface 10a1 of the first and second end surfaces 10a1. The pressure of the oil film in each thrust bearing gap is increased by the dynamic pressure grooves 8c1 and 10a11, thereby forming the first thrust bearing portion T1 and the second thrust bearing portion T2 that support the shaft member 2 in a non-contact manner in the thrust direction.

  By the way, when the cylindrical portion 10b of the lid member 10 is fixed to the outer peripheral surface 8d of the bearing sleeve 8, the bearing sleeve 8 is compressed from the outer diameter side by the shrinkage at the time of solidification of the adhesive and the pressing force at the time of press-fitting. 8a may be reduced in diameter. At this time, as described above, the upper end portion 10b2 of the lid member 10 reaches the upper side beyond the second radial bearing portion R2, and the outer diameter side of the second radial bearing portion R2 is entirely covered with the cylindrical portion 10b of the lid member 10. Therefore, the radial bearing surface (dynamic pressure groove 8a2 formation region) of the bearing sleeve 8 constituting the second radial bearing portion R2 is uniformly pressed in the axial direction. For this reason, the gap width of the radial bearing gap does not differ in the axial direction, and a reduction in the width accuracy of the radial bearing gap due to the fixing of the lid member 10 can be suppressed.

  Further, the bearing sleeve 8 may be pressed from the outer diameter side due to the molding shrinkage of the holding member 9, and the inner peripheral surface 8a may be reduced in diameter. At this time, as described above, the lower end portion 9a1 of the holding member 9 reaches the lower side beyond the first radial bearing portion R1, and the outer diameter side of the first radial bearing portion R1 is entirely covered with the cylindrical portion 9a of the holding member 9. Therefore, the radial bearing surface (dynamic pressure groove 8a1 formation region) of the bearing sleeve 8 constituting the first radial bearing portion R1 is uniformly compressed in the axial direction. For this reason, it is possible to suppress a decrease in the width accuracy of the radial bearing gap due to the injection molding of the holding member 9 using the bearing sleeve 8 as an insert part. In particular, as shown in FIG. 2, since the thickness of the cylindrical portion 9a is constant in the axial direction on the outer diameter side of the bearing sleeve 8, the molding shrinkage of the cylindrical portion 9a is constant in the axial direction. The sleeve 8 is compressed uniformly in the axial direction.

  In this embodiment, since the dynamic pressure groove 8a1 of the first radial bearing portion R1 is formed to be axially asymmetric (X1> X2) (see FIG. 3), the dynamic pressure groove 8a1 is rotated when the shaft member 2 is rotated. The pulling force (pumping force) of the lubricating oil by the upper groove is relatively larger than the pulling force of the lower groove. Due to the differential pressure of the pulling force, the lubricating oil in the radial bearing gap of the first radial bearing portion R1 is pushed downward, and the closed side space inside the bearing, in particular, the lower end surface 2b2 of the flange portion 2b and the lid member 10 The pressure in the space (bottom space P, see FIG. 3) between the upper end surface 10a1 of the plate portion 10a is increased, and the generation of bubbles due to negative pressure in the closed space P can be prevented.

  However, if the pressure in the bottom space P is excessively increased, the floating force of the shaft member 2 becomes too large, and the contact between the upper end surface 2b1 of the flange portion 2b and the lower end surface 8c of the bearing sleeve 8 increases, and these surfaces are increased. Will lead to early wear. In the present embodiment, as shown in FIG. 5, by providing a communication hole 11 opened in the upper end surface 2b1 and the lower end surface 2b2 of the flange portion 2b, the bottom space P is formed with the upper end surface 2b1 of the flange portion 2b and the bearing sleeve. 8 can communicate with the space between the lower end surface 8c and the pressure in the bottom surface space P can be released to the space on the upper end surface 2b1 side of the flange portion 2b, and the pressure in the bottom surface space P is within an appropriate range. Can be maintained.

  As described above, in the present invention, the pressure in the bottom space P tends to increase. Therefore, when the dynamic pressure groove 10a11 of the second thrust bearing portion T2 is formed into a pump-in type spiral shape often used in conventional products, a thrust bearing is provided. Since the oil in the gap is pushed into the inner diameter side, the pressure increase in the bottom space P is promoted. In order to avoid this, it is desirable that the dynamic pressure groove 10a11 of the second thrust bearing portion has a herringbone shape (see FIG. 4) as described above. Since the upper first thrust bearing portion T1 does not cause this kind of problem, a pump-in type spiral-shaped dynamic pressure groove is used instead of the herringbone-shaped dynamic pressure groove 8c1 shown in FIG. It can also be adopted.

  The present invention is not limited to the above embodiment. Hereinafter, other embodiments of the present invention will be described. In the following description, parts having the same configuration and function as those of the above embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the above embodiment, the resin is used as the injection material of the holding member 9, but the present invention is not limited to this, and a low melting point metal material such as a magnesium alloy or an aluminum alloy can be used. In the above embodiment, the holding member 9 is injection-molded using the bearing sleeve 8 as an insert part, but these may be formed separately. In this case, the holding member 9 can also be formed by so-called MIM molding in which degreasing and sintering are performed after injection molding with a mixture of metal powder and binder, or press molding of a soft metal such as a metal material such as brass. Further, the cylindrical portion 9a and the seal portion 9b of the holding member 9 are not necessarily formed integrally, and can be formed separately.

  Moreover, in said embodiment, when fixing the cover member 10 to the bearing sleeve 8, the case where the cylindrical part 10b of the cover member 10 was fitted to the outer peripheral surface 8d of the bearing sleeve 8 which apply | coated the adhesive previously is shown. However, it is not limited to this. For example, after the lid member 10 and the bearing sleeve 8 are first fitted and the width of the thrust bearing gap is set, an adhesive is supplied from the axial gap δ, and the outer peripheral surface 8d of the bearing sleeve 8 and the tubular portion You may fix both by drawing in an adhesive agent with the capillary force of the micro clearance gap between 10b1 inner peripheral surfaces 10b1. In this case, the adhesive may be supplied until the outer peripheral surface 8d of the bearing sleeve 8 exposed from the axial gap δ is sealed. Moreover, although the case where the cover member 10 and the bearing sleeve 8 were fixed by adhesion was shown in the above embodiment, the present invention is not limited to this, and may be fixed by means such as press-fitting, press-fitting adhesion, or welding. In the case of fixing without using an adhesive, the outer peripheral surface 8d of the bearing sleeve 8 may be sealed by supplying an adhesive or a resin from the axial gap δ after the both are fixed.

  Further, in the above embodiment, the shaft portion 2a and the flange portion 2b are formed separately in order to provide the communication hole 11 in the flange portion 2b of the shaft member 2, but it is not necessary to form the communication hole 11. In this case, for example, the shaft portion 2a and the flange portion 2b may be integrally formed by forging a metal material.

  In the above embodiment, the dynamic pressure generating portions of the radial bearing portions R1 and R2 and the thrust bearing portions T1 and T2 are the inner peripheral surface 8a, the lower end surface 8c of the bearing sleeve 8, and the plate portion 10a of the lid member 10, respectively. The upper end surface 10a1 of the shaft portion 2a is opposed to each other through a bearing gap, that is, the outer peripheral surface 2a1 of the shaft portion 2a, the upper end surface 2b1 of the flange portion 2b, and the lower end surface 2b2. Good.

  Further, in the above embodiment, the herringbone-shaped dynamic pressure grooves are exemplified as the radial dynamic pressure generating portions of the radial bearing portions R1 and R2. However, the present invention is not limited to this, for example, so-called step bearings and wave-shaped bearings. Alternatively, a multi-arc bearing can be employed. Also, so-called perfect circular bearings in which both the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft member 2 are cylindrical surfaces can be adopted as the radial bearing portions R1 and R2. In this case, there is no dynamic pressure generating part that positively generates a dynamic pressure action on the fluid film in the radial bearing gap, but when the shaft member rotates, a dynamic pressure action occurs on the fluid film due to the viscosity of the lubricating fluid, Radial bearing portions R1 and R2 are formed.

  In the above embodiment, the spiral dynamic pressure grooves are exemplified as the thrust dynamic pressure generating portions of the thrust bearing portions T1 and T2. However, the present invention is not limited thereto, and for example, a step bearing or a wave bearing is adopted. You can also. Alternatively, a pivot bearing that contacts and supports the end portion of the shaft member may be employed as the thrust bearing portions T1 and T2.

  Further, in the above embodiment, the radial bearing portions R1 and R2 are provided separately in the axial direction, but these may be provided continuously in the axial direction. Alternatively, only one of these may be provided.

  In the above embodiment, the lubricating oil is used as the lubricant filled in the internal space of the hydrodynamic bearing device. However, the present invention is not limited thereto, and for example, lubricating grease, magnetic fluid, or the like can be used. In addition, since it is preferable that the lubricating fluid has electrical conductivity, a gas such as air is difficult to use. However, when the thrust direction is supported by contact support such as a pivot bearing, a gas such as air can be used.

  The fluid dynamic pressure bearing device of the present invention is not limited to the spindle motor used in the disk drive device such as the HDD as described above, but is used under high-speed rotation, such as a spindle motor for driving a magneto-optical disk of an optical disk. It can also be suitably used as a fan motor for supporting a rotating shaft in a small motor for information equipment, a polygon scanner motor of a laser beam printer, or for cooling electric equipment.

It is sectional drawing of a spindle motor. It is sectional drawing of a fluid dynamic pressure bearing apparatus. (A) is sectional drawing of a bearing sleeve, (b) is the bottom view. It is a top view of a lid member. It is sectional drawing which shows the communicating hole vicinity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid dynamic pressure bearing apparatus 2 Shaft member 2a Shaft part 2b Flange part 3 Disk hub 4 Stator coil 5 Rotor magnet 6 Motor bracket 8 Bearing sleeve 9 Holding member 9a Cylindrical part 9b Seal part 10 Lid member 10a Plate part 10b Cylindrical part 11 Communication hole R1 / R2 Radial bearing part T1 / T2 Thrust bearing part S Seal space δ Axial clearance

Claims (7)

  A shaft member, a bearing sleeve with the shaft member inserted into the inner periphery, a holding member that holds the bearing sleeve from the outer periphery and that is open at both ends in the axial direction, and is fixed to the outer peripheral surface of the bearing sleeve. Fluid dynamic pressure having a lid member that closes the opening, and a radial bearing portion that supports the shaft member in the radial direction with a fluid film generated in a radial bearing gap between the outer peripheral surface of the shaft member and the inner peripheral surface of the bearing sleeve Bearing device.   The shaft member is provided with a flange portion, and a thrust bearing portion for supporting the shaft member in the thrust direction with a fluid film of a thrust bearing gap facing both end surfaces of the flange portion is provided, and both shafts are disposed between the holding member and the lid member. The fluid dynamic bearing device according to claim 1, wherein an axial gap is provided to allow relative movement in the direction.   The fluid dynamic pressure bearing device according to claim 2, wherein the bearing sleeve is formed of a porous body, and an outer peripheral surface of the bearing sleeve exposed from the axial gap between the holding member and the lid member is sealed.   The fluid dynamic pressure bearing device according to claim 1, wherein both the bearing sleeve and the lid member are made of a metal material, and both are bonded and fixed.   The fluid dynamic bearing device according to claim 1, wherein an end portion of the lid member is extended to a position beyond an axial region of the radial bearing portion.   The fluid dynamic bearing device according to claim 1, wherein an end portion of the holding member is extended to a position beyond an axial region of the radial bearing portion.   The fluid dynamic pressure bearing device according to any one of claims 1 to 6, further comprising a bracket for attaching the stator coil, and an outer peripheral surface of the lid member fixed to the bracket.

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