JP2012247052A - Fluid dynamic pressure bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluid dynamic pressure bearing device including an annular projected part roughly in the diametrical-direction center of the disk part of a hub, in which fastening strength and assembling accuracy of the hub and a shaft part are secured, and which is easily manufactured thereby having increased productivity.SOLUTION: In the disk part 3a of a hub 3, a first region 3a nearer to the inner diameter side than at least an annular projected part 3d is integrally formed with a shaft part 2 to configure a flange integral shaft A, and the annular projected part 3d formed separately from the flange integral shaft A is fixed thereto.

Description

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

  Since the fluid dynamic bearing device has excellent rotational accuracy and quietness, for example, for spindle motors of various disk drive devices (such as HDD magnetic disk drive devices and CD-ROM optical disk drive devices), laser beams, etc. It is suitably used for a polygon scanner motor of a printer (LBP) or a color wheel motor of a projector.

  For example, a fluid dynamic bearing device disclosed in Patent Document 1 includes a shaft portion, a hub provided at the upper end of the shaft portion, and a bearing member (sleeve) having a shaft portion inserted into the inner periphery. The hub includes a disc portion fixed to the upper end of the outer peripheral surface of the shaft portion, a cylindrical portion extending downward from the outer peripheral portion of the disc portion, a flange portion protruding from the lower end of the cylindrical portion to the outer diameter, and a diameter of the disc portion. And an annular projecting portion projecting downward from a substantially central portion in the direction. When the shaft portion rotates, a radial bearing gap is formed between the outer peripheral surface of the shaft portion and the inner peripheral surface of the bearing member, and a thrust is formed between the upper end surface of the bearing member and the lower end surface of the hub disk portion. Bearing gaps are formed, and the shaft portion and the hub are rotatably supported by the dynamic pressure action generated in the oil films of these radial bearing gaps and thrust bearing gaps. In addition, a wedge-shaped seal space is formed between the inner peripheral surface of the annular projecting portion of the hub and the outer peripheral surface of the bearing member. By holding the oil level inside the seal space, the bearing member has an inner surface. Prevents the leakage of filled oil to the outside.

  In recent years, HDDs and the like have become smaller, thinner, and lighter, and the above characteristics are strongly demanded for fluid dynamic bearing devices incorporated in HDDs and the like. For example, if the hub is made thinner, the weight can be reduced by reducing the material, and the fluid dynamic bearing device can be made smaller and thinner by the reduced thickness. However, in the above fluid dynamic bearing device, the shaft portion and the hub are formed separately, and the inner peripheral surface of the disc portion of the hub is fitted and fixed to the outer peripheral surface of the shaft portion. Then, the fitting area between the shaft portion and the hub decreases, and the fastening strength and assembly accuracy (perpendicularity, etc.) of both may decrease.

  For example, as in the fluid dynamic pressure bearing device disclosed in Patent Document 2, if the shaft portion and the hub are integrally formed by forging, the fastening strength (boundary portion) between the two is greater than when they are formed separately. Strength), squareness, etc. can be increased. As a result, the hub can be thinned, and the fluid dynamic bearing device can be reduced in size, thickness, and weight.

JP 2005-45876 A JP-A-2005-45924

  However, since the hub of the fluid dynamic pressure bearing device described above is provided with an annular projecting portion projecting downward at a substantially central portion in the radial direction of the disc portion, it is extremely difficult to integrally form the disc portion and the annular projecting portion by forging. It is.

  Further, in the above fluid dynamic pressure bearing device, the shaft portion and the annular projecting portion surrounding the outer periphery thereof are integrally formed, and thus various problems occur when grinding the outer peripheral surface of the shaft portion. Specifically, since a part of the outer peripheral surface of the shaft portion is surrounded by the annular projecting portion, it becomes difficult to access the grindstone to the outer peripheral surface of the shaft portion, and productivity is reduced. In addition, since the size of the grindstone is limited to a size that can be inserted into the gap between the shaft portion and the annular protrusion, only a very small grindstone can be used, and it is necessary to replace it frequently due to wear. This will further reduce productivity.

  The present invention has been made in view of the above circumstances, and in a fluid dynamic bearing device having an annular projecting portion at a substantially central portion in the radial direction of the disk portion of the hub, the fastening strength and assembly between the hub and the shaft portion are provided. Ensuring accuracy and facilitating manufacturing to increase productivity are technical issues to be solved.

  The present invention made in order to solve the above problems includes a shaft portion having a bearing surface subjected to grinding on the outer periphery, a disk portion extending from one end of the shaft portion to the outer diameter side, and a radius of the disk portion. A hub having an annular projecting portion projecting from the intermediate portion in the axial direction to the other end side in the axial direction, a bearing member in which the shaft portion is inserted into an inner periphery, a bearing surface of the shaft portion, and an inner peripheral surface of the bearing member Formed between a radial bearing portion that rotatably supports the shaft portion by a dynamic pressure action of a fluid generated in a radial bearing gap between the inner peripheral surface of the annular projecting portion and an outer peripheral surface of the bearing member, In the fluid dynamic pressure bearing device including a seal space that holds an interface between the fluid filled in the bearing member and the outside air, at least the first region on the inner diameter side of the annular projecting portion of the disk portion. A flange integrated shaft is formed integrally with the shaft portion, and the flange is formed. It is characterized in that it has fixed the annular protruding portion formed separately from the this-di integral shaft.

  As described above, in the fluid dynamic pressure bearing device according to the present invention, at least the first region on the inner diameter side of the annular projecting portion of the disc portion of the hub is integrally formed with the shaft portion to constitute the flange integrated shaft, An annular protrusion formed separately from the flange integrated shaft was fixed. Specifically, for example, in the disk portion, a second region on the outer diameter side of the annular projecting portion is integrally formed with the annular projecting portion to constitute the annular member, and the flange portion of the flange integrated shaft (the first portion of the disc portion). It is possible to adopt a configuration in which an annular member is fitted and fixed to the outer peripheral surface of one region. In this way, by dividing the disk portion with the annular protrusion as a boundary and providing the annular protrusion at the inner diameter end of the second region, compared to the case where the hub portion is integrally protruded from the radial intermediate portion of the disk portion, Formation can be facilitated. Accordingly, for example, the flange-integrated shaft and the annular member can be manufactured by grinding each of the shaped members formed by plastic working.

  In addition, since the flange-integrated shaft and the annular protrusion are formed separately as described above, the outer peripheral bearing surface of the shaft portion can be ground before the annular protrusion is assembled to the flange-integrated shaft. The grinding of the bearing surface is not hindered by the annular protrusion, and the productivity is improved.

  Also, by fitting and fixing the outer peripheral surface of the flange portion of the flange-integrated shaft and the inner peripheral surface of the annular member, for example, the diameter of the fitting portion is larger than when the hub is fitted and fixed to the outer periphery of the shaft portion. Thus, since the fitting area between the two increases, both the fastening strength and the assembling accuracy can be increased.

  In consideration of the assembly accuracy between the annular member and the flange-integrated shaft, it is preferable to press-fit the inner peripheral surface of the annular member and the outer peripheral surface of the flange portion of the flange-integrated shaft.

  If the fitting portion between the inner peripheral surface of the annular member and the outer peripheral surface of the flange portion of the flange-integrated shaft is sealed with laser welding or an adhesive, the fastening strength between the two can be further increased, and the lubricating fluid from the fitting portion Can be reliably prevented.

  If stepped portions are provided on both the inner peripheral surface of the annular member and the outer peripheral surface of the flange portion of the flange-integrated shaft, and the both are fitted with a spigot, the fitting area is increased compared to the case where the cylindrical surfaces are fitted with each other. The fastening strength can be further increased. Further, the annular member and the first region of the disk portion are pivoted by bringing the stepped portions (flat surfaces) provided on the inner peripheral surface of the annular member and the outer peripheral surface of the flange portion of the flange-integrated shaft into axial contact with each other. Since positioning can be performed in the direction, the assembling accuracy can be further increased.

  The configuration of the hub is not limited to the above. For example, a flange-integrated shaft is formed by integrally forming the entire disk portion and the shaft portion, and an annular protruding portion is formed on the end surface of the disk portion constituting the flange portion of the flange-integrated shaft. A fixed configuration may also be used. In this way, by forming the disc portion and the annular protrusion separately, the shape of the hub can be simplified and the formation can be facilitated. This makes it possible to produce a hub integrated shaft. Further, by integrally forming the shaft portion and the disk portion of the hub in this way, the fastening strength (strength at the boundary portion) and the squareness of the shaft portion and the disk portion are compared with the case where they are formed separately. Can be increased.

  In the above case, the fixing strength and fixing accuracy of the annular protrusion with respect to the flange-integrated shaft become a problem. For example, if a seal member having an annular protruding portion and an extending portion extending from one end of the annular protruding portion to the inner diameter is provided and the inner peripheral surface of the extending portion is fitted to the outer peripheral surface of the shaft portion, the outer periphery of the shaft portion The positional accuracy (coaxiality etc.) of the annular protrusion with respect to the surface can be increased. Further, if the end surface of the extending portion of the seal member is fixed to the end surface of the flange portion of the flange-integrated shaft, a sufficient fixing area can be secured and the fixing strength can be increased.

  If an annular adhesive reservoir filled with an adhesive is formed between the end surface of the extending portion of the seal member and the end surface of the flange portion of the flange integral shaft, the fixing strength between the seal member and the flange portion is further increased. In addition, the gap between the extending portion of the seal member and the flange portion of the flange-integrated shaft can be sealed with an adhesive, so that it is ensured that the lubricating fluid leaks outside through this gap. Can be prevented.

  In order to increase the fixing accuracy between the seal member and the shaft portion, it is desirable to press-fit (light press-fit) the inner peripheral surface of the extending portion of the seal member to the outer peripheral surface of the shaft portion. However, since the flange portion (the disk portion of the hub) is integrally formed at one end of the shaft portion, the seal member has to be press-fitted while sliding with the bearing surface from the other end side of the shaft portion. There is a risk of hurting. Therefore, if a guide portion having a larger diameter than the bearing surface is provided at one end of the outer peripheral surface of the shaft portion, and the inner peripheral surface of the extending portion of the seal member is press-fitted into this guide portion, the inner portion of the extending portion of the seal member is Since a gap can be provided between the peripheral surface and the bearing surface of the shaft portion, damage to the bearing surface can be prevented. If this guide portion is ground, the accuracy of fixing the seal member to the shaft portion can be further increased.

  Of the end faces of the flange portion of the flange-integrated shaft, if at least the region facing the end surface of the extending portion of the seal member is ground, the adhesion between the two can be improved. The accuracy of fixing is improved.

  As described above, according to the fluid dynamic pressure bearing device of the present invention, the flange integrated shaft is configured by integrally forming at least the first region on the inner diameter side of the annular projecting portion of the disc portion of the hub with the shaft portion. By fixing an annular protrusion formed separately from the flange-integrated shaft, the hub and the shaft are compared with a case where a hub having an annular protrusion is formed integrally at a substantially central portion in the radial direction of the disk portion. The fastening strength and the assembling accuracy can be ensured, and the manufacturing can be facilitated to increase the productivity.

It is sectional drawing of the spindle motor for HDD provided with the fluid dynamic pressure bearing apparatus which concerns on embodiment of this invention. It is sectional drawing of the said fluid dynamic pressure bearing apparatus. It is an expanded sectional view of the fitting part of the flange integrated shaft and annular member of the fluid dynamic pressure bearing device. It is sectional drawing of the bearing sleeve of the said fluid dynamic pressure bearing apparatus. It is a top view of the said bearing sleeve. It is a bottom view of the said bearing sleeve. It is an expanded sectional view of the fitting part of the flange integrated shaft and annular member of the fluid dynamic bearing device according to another embodiment. It is an expanded sectional view of the fitting part of the flange integrated shaft and annular member of the fluid dynamic bearing device according to another embodiment. It is sectional drawing of the fluid dynamic pressure bearing apparatus which concerns on other embodiment. FIG. 10 is an enlarged cross-sectional view of the vicinity of a seal member of the fluid dynamic bearing device of FIG. 9. It is sectional drawing of the fluid dynamic pressure bearing apparatus which concerns on other embodiment.

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

  FIG. 1 shows a spindle motor used in, for example, a 2.5-inch HDD disk drive device. The spindle motor includes a fluid dynamic pressure bearing device 1 according to an embodiment of the present invention, a bracket 6 to which the fluid dynamic pressure bearing device 1 is attached, a stator coil 4 and a rotor that are opposed to each other via a radial gap. A magnet 5 is provided. The stator coil 4 is attached to the bracket 6, and the rotor magnet 5 is attached to the hub 3 of the fluid dynamic bearing device 1. A predetermined number of disks (not shown) as rotating bodies are mounted on the hub 3. 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 hub 3, the shaft portion 2, and the disk rotate together.

  As shown in FIG. 2, the fluid dynamic pressure bearing device 1 includes a shaft portion 2, a hub 3 provided at one end of the shaft portion 2, and a bearing member that rotatably supports the shaft portion 2. In this embodiment, the bearing member includes a bearing sleeve 8 in which the shaft portion 2 is inserted on the inner periphery, and a bottomed cylindrical housing 7 that holds the bearing sleeve 8 on the inner periphery. A retaining member 9 is provided at the lower end of the shaft portion 2. In the following, for convenience of explanation, the opening side of the housing 7 in the axial direction is the upper side and the closing side is the lower side.

  The shaft portion 2 is set to have an outer diameter of about 2 to 4 mm. The shaft portion 2 has a straight cylindrical outer peripheral surface 2a having no irregularities and an axial hole 2b provided in the shaft center. The axial hole 2b is provided so as to penetrate the shaft portion 2 in the axial direction, and a screw groove is formed on the inner peripheral surface thereof. The outer peripheral surface 2a of the shaft portion 2 functions as a radial bearing surface.

  The hub 3 has a disk part 3a extending from the upper end of the shaft part 2 to the outer diameter, a cylindrical part 3b extending downward in the axial direction from the outer peripheral part of the disk part 3a, and further extending from the lower end part of the cylindrical part 3b to the outer diameter. The flange portion 3c and a cylindrical annular projecting portion 3d extending downward from a radial intermediate portion (in the illustrated example, a substantially central portion in the radial direction) of the disc portion 3a. A disc mounting surface 3e is formed on the upper end surface of the flange portion 3c, and a disc fitting surface 3f is formed on the outer peripheral surface of the cylindrical portion 3b. The disc inner hole is fitted to the disc fitting surface 3f, and the disc is placed on the disc mounting surface 3e. In this state, the upper surface of the disc is pressed by the clamper (not shown) and pressed onto the disc mounting surface 3e. Thus, the disk is held by the hub 3. In addition, the upper part of the axial direction hole 2b of the axial part 2 functions as a screw hole for fixing a clamper.

  In the present embodiment, the disk portion 3a of the hub 3 is formed by being divided into a first region 3a1 on the inner diameter side of the annular projecting portion 3d and a second region 3a2 on the outer diameter side of the annular projecting portion 3d. . The first region 3a1 and the shaft portion 2 of the disk portion 3a are integrally formed to constitute the flange integrated shaft A, and the second region 3a2, the cylindrical portion 3b, the flange portion 3c, and the annular projecting portion of the disk portion 3a. 3d is integrally formed to constitute the annular member B.

  In this manner, the hub 3 in which the annular protrusion 3d protrudes from the radial intermediate portion of the disk portion 3a is divided and formed with the annular protrusion 3d as a boundary, thereby annularly protruding from the radial intermediate portion of the disk portion 3a. Compared with the case where the portion 3d is protruded integrally, the shape of each member (the flange integrated shaft A and the annular member B) can be simplified to facilitate the formation. As a result, the flange integrated shaft A and the annular member B can be manufactured by grinding a base material formed by metal plastic processing (for example, press processing of a metal plate). In addition, the raw material of the flange integrated shaft A and the annular member B is not limited to plastic working, and can be formed by machining such as turning.

  As the metal material of the flange integral shaft A and the annular member B, for example, steel (stainless steel, general structural steel, etc.), aluminum alloy, titanium alloy, or the like can be used. Further, the flange-integrated shaft A and the annular member B can be formed of different materials. For example, the flange-integrated shaft A is formed of a metal having excellent wear resistance (for example, martensitic stainless steel), and the annular member B is formed of a magnetic metal (for example, ferritic stainless steel) for mounting the rotor magnet 5. can do. In order to reduce the rotational torque, the annular member B may be formed of a material that is lighter (low density) than the flange-integrated shaft A.

  Out of the flange-integrated shaft A, the outer peripheral surface 2a of the shaft portion 2 that functions as a radial bearing surface, the lower end surface 3a10 of the flange portion A1 (first region 3a1 of the disk portion 3a) that functions as a thrust bearing surface, and a thrust bearing Grinding (preferably simultaneous grinding with one grindstone) is performed on the lower end surface 2c of the shaft portion 2 that comes into contact with the flange portion 9a of the retaining member 9 having a surface. In addition to this, the disc mounting surface 3e and the disc fitting surface 3f of the annular member B may be ground.

  The outer peripheral surface 2a of the shaft portion 2 may be subjected to surface hardening treatment or coating treatment, or both of them. Examples of the surface hardening treatment include surface hardening treatment such as vacuum quenching, vacuum carburizing treatment, vacuum nitriding treatment, gas soft nitriding treatment, or ion nitriding treatment. Examples of the coating process include a coating process using electroless Ni plating, DLC, TiN, TiAlN, or TiC. The surface treatment and the coating treatment may be performed not only on the outer peripheral surface 2a of the shaft portion 2, but also on other regions, for example, the lower end surface 3a10 of the disk portion 3a of the hub 3 facing the thrust bearing gap. Alternatively, if the wear resistance of the outer peripheral surface 2a of the shaft portion 2 is sufficient, the surface effect treatment or the coating treatment may be omitted.

  The annular member B is fitted and fixed (for example, press-fitted and fixed) to the outer peripheral surface of the flange portion A1 (the first region 3a1 of the disk portion 3a) of the flange integrated shaft A. In the present embodiment, as shown in FIG. 3, step portions are provided on the inner peripheral surface of the annular member B and the outer peripheral surface of the flange portion of the flange-integrated shaft A, and the both are fitted with a spigot. Specifically, on the outer peripheral surface of the flange portion of the flange-integrated shaft A, a large-diameter outer peripheral surface 3a11, a small-diameter outer peripheral surface 3a12, and a flat surface 3a13 that is provided between them and orthogonal to the axial direction are formed. A large-diameter inner peripheral surface 3a21, a small-diameter inner peripheral surface 3a22, and a flat surface 3a23 perpendicular to the axial direction, which are provided between them, are formed at the upper end of the inner peripheral surface. The large-diameter outer peripheral surface 3a11 and the small-diameter outer peripheral surface 3a12 of the flange-integrated shaft A are press-fitted into the large-diameter inner peripheral surface 3a21 and the small-diameter inner peripheral surface 3a22 of the annular member B, respectively. The coaxiality, in particular, the coaxiality between the outer peripheral surface 2a (bearing surface) of the shaft portion 2 and the inner peripheral surface 3d1 (seal surface) of the annular protrusion 3d is set with high accuracy. Further, the flat surface 3a13 of the flange-integrated shaft A and the flat surface 3a23 of the annular member B come into contact with each other, whereby the positional accuracy in the axial direction of the annular member B with respect to the flange-integrated shaft A, particularly the first region 3a1 of the disk portion 3a. The position accuracy in the axial direction of the disk mounting surface 3e with respect to the lower end surface 3a10 (thrust bearing surface) is set with high accuracy.

  The fitting portion between the flange integrated shaft A and the annular member B is sealed by laser welding or an adhesive. In the example of illustration, the cyclic | annular sealing part G which seals the upper end of a fitting part over a perimeter is provided. Thereby, while fixing strength of a fitting part is raised, the oil leak from a fitting part can be prevented reliably.

  The retaining member 9 is made of metal or resin, and has a disk-shaped flange portion 9a and a fixing portion 9b extending upward from the axis of the flange portion 9a. A screw groove is formed on the outer periphery of the fixing portion 9b, and is fixed to the lower end of the screw hole formed on the inner peripheral surface of the axial hole 2b of the shaft portion 2. The flange portion 9 a protrudes to an outer diameter from the outer peripheral surface 2 a of the shaft portion 2, and its upper end surface 9 a 1 is in contact with the lower end surface 2 c of the shaft portion 2. The flange portion 9 a is disposed between the lower end surface 8 c of the bearing sleeve 8 and the upper end surface 7 b 1 of the bottom portion 7 b of the housing 7, and engages with the bearing sleeve 8 in the axial direction, whereby the bearing of the shaft portion 2. Prevents the sleeve 8 from coming off.

  The upper end surface 9a1 of the flange portion 9a functions as a thrust bearing surface. Since the lower end surface 2c of the shaft portion 2 is finished to be a high-precision flat surface by grinding, the upper end surface 9a1 of the flange portion 9a is in good contact with the entire lower end surface 2c of the shaft portion 2, so that the shaft portion 2, the flange portion 9a can be positioned with high accuracy. Further, since the upper end surface 9a1 of the flange portion 9a and the lower end surface 2c of the shaft portion 2 are brought into close contact with each other around the circumference, the intrusion of the lubricating oil into the axial hole 2b of the shaft portion 2 can be suppressed. The risk of the lubricating oil filling the inside leaking out through the axial hole 2b can be reduced.

  The bearing sleeve 8 is formed of a metal or a resin in a cylindrical shape, and in this embodiment, is formed of, for example, copper or a sintered metal mainly composed of copper and iron. As shown in FIG. 4, herringbone-shaped dynamic pressure grooves 8a1 and 8a2 are formed on the inner peripheral surface 8a of the bearing sleeve 8 as radial dynamic pressure generating portions, for example, in two regions separated in the axial direction. (Cross hatching is hill). In the illustrated example, the upper dynamic pressure groove 8a1 is formed asymmetrically in the axial direction. Specifically, the axial dimension X1 of the region above the axial center part m is the axial dimension X2 of the lower region. (X1> X2). The lower dynamic pressure groove 8a2 is formed symmetrically in the axial direction. An axial groove 8d1 is formed over the entire length in the axial direction on the outer peripheral surface 8d of the bearing sleeve 8. For example, three axial grooves 8d1 are equally arranged in the circumferential direction.

  As shown in FIGS. 5 and 6, for example, pump-in type spiral-shaped dynamic pressure grooves 8b1 and 8c1 are formed on the upper end surface 8b and the lower end surface 8c of the bearing sleeve 8 as thrust dynamic pressure generating portions, respectively. (Cross hatching is a hill). An axial groove 8 d 1 is formed on the outer peripheral surface 8 d of the bearing sleeve 8. The number of the axial grooves 8d1 is arbitrary. For example, three axial grooves 8d1 are arranged at equal intervals in the circumferential direction.

  The housing 7 is formed of metal or resin, and in this embodiment, is formed by, for example, resin injection molding. As shown in FIG. 2, the housing 7 is formed in a bottomed cylindrical shape integrally having a side portion 7a and a bottom portion 7b. The inner peripheral surface 7a1 of the side portion 7a is formed in a straight cylindrical surface shape, and the outer peripheral surface 8d of the bearing sleeve 8 is fixed by gap bonding, press-fitting, press-fitting with an adhesive interposed therebetween, or the like. At the upper end of the outer peripheral surface of the side portion 7a, as shown in FIG. 2, a tapered seal surface 7a3 that gradually increases in diameter upward is formed. The seal surface 7a3 forms an annular seal space S whose radial dimension is gradually reduced upward, between the seal surface 7a3 and the cylindrical inner peripheral surface 3d1 of the annular protrusion 3d of the hub 3. The seal space S is a thrust bearing gap of the first thrust bearing portion T1 through a gap between the lower end surface 3a10 of the disk portion 3a of the hub 3 and the upper end surface 7a2 of the housing 7 when the shaft portion 2 rotates. And the upper end of the axial groove 8d1. The capillary force of the seal space S prevents the lubricating oil filled in the housing 7 from leaking out.

  After assembling the above-described configuration, the fluid dynamic bearing device 1 shown in FIG. 2 is completed by filling the space inside the housing 7 including the internal pores of the bearing sleeve 8 with lubricating oil. At this time, the oil level is held inside the seal space S.

  When the shaft portion 2 rotates, a radial bearing gap is formed between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a of the shaft portion 2, and by the radial dynamic pressure generating portions (dynamic pressure grooves 8a1, 8a2). The pressure of the lubricating oil filled in the radial bearing gap is increased, and by this pressure (dynamic pressure action), radial bearing portions R1 and R2 are configured to support the shaft portion 2 and the hub 3 in a non-contact manner so as to be rotatable in the radial direction. The

  At the same time, between the lower end surface 3a10 of the first region 3a1 of the disk portion 3a of the hub 3 and the upper end surface 8b of the bearing sleeve 8, and the upper end surface 9a1 of the flange portion 9a of the retaining member 9 and the bearing sleeve 8 Thrust bearing gaps are formed between the lower end face 8c and the thrust dynamic pressure generating portions (dynamic pressure grooves 8b1, 8c1) to increase the pressure of the lubricating oil filled in the thrust bearing gaps. The first thrust bearing portion T1 that supports the shaft portion 2 and the hub 3 in a non-contact manner so as to be rotatable in one thrust direction (lifting direction) by pressure (dynamic pressure action), and the other in the thrust direction (push down the shaft portion 2 and the hub 3). And a second thrust bearing portion T2 that is supported in a non-contact manner so as to be freely rotatable in the direction).

  At this time, the axial groove 8d1 formed in the outer peripheral surface 8d of the bearing sleeve 8 forms a communication path through which lubricating oil can flow. This communication path can prevent a local negative pressure from being generated in the lubricating oil filled in the housing 7. In particular, in this embodiment, as shown in FIG. 4, the upper dynamic pressure groove 8 a 1 formed on the inner peripheral surface 8 a of the bearing sleeve 8 is formed in an axially asymmetric shape. Along with this, the lubricating oil in the radial bearing gap is pushed downward, and the lubricating oil circulates through the communication passage, thereby reliably preventing the occurrence of local negative pressure.

  The present invention is not limited to the above embodiment. Hereinafter, although other embodiment of this invention is described, the same code | symbol is attached | subjected to the location which has the same function as said embodiment, and duplication description is abbreviate | omitted.

  For example, the fitting state between the flange integrated shaft A and the annular member B is not limited to the above embodiment. In the embodiment shown in FIG. 7, the fitting portion between the large-diameter outer peripheral surface 3a11 and the large-diameter inner peripheral surface 3a21 is located below the fitting portion between the small-diameter outer peripheral surface 3a12 and the small-diameter inner peripheral surface 3a22, The flat surface 3a23 of the member B is supported from below by the flat surface 3a13 of the flange integrated shaft A. Thereby, the weight of the disk mounted on the disk mounting surface 3e of the annular member B can be supported by the flat surface 3a13 of the flange integrated shaft A.

  In the embodiment shown in FIG. 8, the outer peripheral surface 3a14 of the flange portion of the flange-integrated shaft A and the inner peripheral surface 3a24 of the annular member B facing this are both cylindrical surfaces, which are fitted and fixed (for example, press-fit fixed). )is doing.

  The sealing part G for sealing the fitting part between the flange integrated shaft A and the annular member B is not limited to the case where it is provided at the upper end of the fitting part as shown in FIG. 3, but as shown in FIG. It can also be provided at the lower end of the fitting portion between the A flange portion A1 and the annular member B, or at the upper and lower ends of the fitting portion as shown in FIG.

  Moreover, in said embodiment, although the case where the disc part 3a of the hub 3 was divided | segmented into 1st area | region 3a1 and 2nd area | region 3a2 was shown, it is not restricted to this. For example, in the embodiment shown in FIG. 9, the entire disk portion 3 a and the shaft portion 2 are integrally formed to constitute the flange integrated shaft A. Specifically, the shaft portion 2, the disc portion 3a, the cylindrical portion 3b, and the flange portion 3c are integrally formed, and the annular projecting portion 3d is fixed to the lower end surface 3a10 of the disc portion 3a. From the upper end of the annular projecting portion 3d, a substantially disc-shaped extending portion 3g extends toward the inner diameter, and the annular projecting portion 3d and the extending portion 3g constitute the seal member 10.

  The seal member 10 is integrally formed by, for example, metal machining (such as turning) or plastic processing (such as press molding or forging). As shown in FIG. 10, the seal member 10 is configured to fit the inner peripheral surface 3g1 of the extending portion 3g to the outer peripheral surface 2a of the shaft portion 2, and to connect the upper end surface 3g2 of the extending portion 3g to the lower side of the disk portion 3a. It is fixed to the end face 3a10. In the illustrated example, a small-diameter outer peripheral surface 2a1 and a large-diameter outer peripheral surface 2a2 are provided on the outer peripheral surface 2a of the shaft portion 2 and an upper side thereof, and the small-diameter outer peripheral surface 2a1 functions as a radial bearing surface facing the radial gap. The large-diameter outer peripheral surface 2a2 functions as a guide portion into which the inner peripheral surface 3g1 of the extending portion 3g of the seal member 10 is press-fitted, whereby the positional accuracy of the seal member 10 with respect to the shaft portion 2 is increased. Since the coaxiality of the inner peripheral surface 3d1 (seal surface) of the annular projecting portion 3d of the seal member 10 with respect to the bearing surface of the outer peripheral surface 2a of the shaft portion 2 is set with high accuracy, the volume of the seal space S is highly accurate. Is set. Further, the seal member 10 is extrapolated from below the shaft portion 2, but the inner peripheral surface 3 g 1 of the extending portion 3 g of the seal member 10 has a larger diameter than the small-diameter outer peripheral surface 2 a 1 of the shaft portion 2. 10 can avoid the situation where the small-diameter outer peripheral surface 2a1 (radial bearing surface) of the shaft portion 2 is damaged.

  Between the upper end surface 3g2 of the extending portion 3g of the seal member 10 and the lower end surface 3a10 of the disk portion 3a, an annular adhesive reservoir 11 filled with an adhesive is provided. In the example of illustration, the adhesive reservoir 11 is comprised by the recessed part 3g20 provided in the upper end surface 3g2 of the extension part 3g, and the flat lower end surface 3a10 of the disk part 3a. By providing the annular adhesive reservoir 11 in this way, the fixing strength between the sealing member 10 and the disk portion 3a is increased, and the gap between the extending portion 3g of the sealing member 10 and the disk portion 3a is sealed all around. Therefore, oil leakage through this gap can be reliably prevented. The recess for forming the adhesive reservoir 11 is not limited to being provided in the extending portion 3g of the seal member 10, but can also be formed in the lower end surface 3a10 of the disk portion 3a or both of them.

  It is preferable to grind the large-diameter outer peripheral surface 2a2 of the shaft portion 2, so that the positional accuracy between the shaft portion 2 and the seal member 10 is further enhanced. Moreover, it is preferable to grind at least a region facing the upper end surface 3g2 of the extending portion 3g of the seal member 10 in the lower end surface 3a10 of the disc portion 3a, whereby the seal against the disc portion 3a is provided. The positional accuracy of the member 10 is increased. In particular, in the illustrated example, since the lower end surface 3g3 of the extending portion 3g of the seal member 10 functions as a thrust bearing surface facing the thrust bearing gap, the perpendicularity to the outer peripheral surface 2a (bearing surface) of the shaft portion 2 and the like Position accuracy is important. Accordingly, the outer peripheral surface 2a (small diameter outer peripheral surface 2a1 and large diameter outer peripheral surface 2a2) of the shaft portion 2 and the inner peripheral portion of the lower end surface 3a10 of the disk portion 3a are subjected to grinding (preferably simultaneous grinding with one grindstone). By finishing these surfaces with high accuracy, the positional accuracy of the seal member 10 with respect to the shaft portion 2, particularly the positional accuracy of the thrust bearing surface and the seal surface with respect to the radial bearing surface, can be increased. Is improved.

  Further, in order to increase the rotation accuracy of the disk mounted on the disk mounting surface 3e, a radial bearing surface (small-diameter outer peripheral surface 2a1 of the shaft portion 2) and a thrust bearing surface (extension portion of the seal member 10) with respect to the disk mounting surface 3e. The accuracy of the lower end surface 3g3 of 3g and the upper end surface 9a1) of the flange portion 9a of the retaining member 9 is important. Therefore, while supporting the disk mounting surface 3e (or a surface ground simultaneously with this surface) as a reference, the outer peripheral surface 2a of the shaft portion 2 serving as a radial bearing surface, the lower side of the disk portion 3a with which the seal member 10 abuts. It is preferable to simultaneously grind the end surface 3a10 and the lower end surface 2c of the shaft portion 2 with which the flange portion 9a of the retaining member 9 abuts with one grindstone.

  In the above embodiment, the flange portion 9a is fixed to the lower end surface 2c of the shaft portion 2 by screws. However, the present invention is not limited to this, and for example, it can be fixed by welding, adhesion, or welding. In this case, if the gap between the lower end surface 2c of the shaft portion 2 and the upper end surface 9a1 of the flange portion 9a is completely sealed with an adhesive or the like, oil leakage through the axial hole 2b of the shaft portion 2 is ensured. Can be prevented.

  Further, in the above-described embodiment, the case where the retaining member 9 is fixed to the lower end of the shaft portion 2 has been described. However, the present invention is not limited to this, and for example, as illustrated in FIG. Can be omitted, and the retaining member 12 can be provided on the inner periphery of the annular projecting portion 3d of the hub 3. The retaining member 12 can be provided in a plurality of locations that are annular or spaced apart in the circumferential direction. The shaft portion 2 is formed in a cup shape by closing the lower end of the axial hole 2b. When the retaining member 12 and the outer periphery of the housing 7 are engaged in the axial direction, the shaft portion 2 and the hub 3 are prevented from being detached from the bearing member. In this embodiment, the second thrust bearing portion T2 is not provided.

  In the above embodiment, the thrust bearing gap of the first thrust bearing portion T1 is formed between the upper end surface 8b of the bearing sleeve 8 and the lower end surface 3a10 of the disk portion 3a of the hub 3. Not limited. For example, a thrust bearing gap of the first thrust bearing portion T1 may be formed between the upper end surface 7a2 of the housing 7 and the lower end surface 3a10 of the disk portion 3a of the hub 3.

  In the above embodiment, the radial dynamic pressure generating portions (dynamic pressure grooves 8a1 and 8a2) and the thrust dynamic pressure generating portions (dynamic pressure grooves 8b1 and 8c1) are respectively provided on the inner peripheral surface 8a and the upper and lower end surfaces 8b of the bearing sleeve 8. Although the case where it forms in 8c was shown, it is not restricted to this, The surface which opposes these surfaces, ie, the outer peripheral surface 2a of the axial part 2, the lower end surface 3a10 of the disk part 3a of the hub 3, and a retaining member A dynamic pressure generating portion may be formed on the upper end surface 9a1 of the nine flange portions 9a.

  In the above embodiment, the lubricating fluid is a lubricating oil. However, the present invention is not limited to this, and for example, a magnetic fluid can be used.

  In the above embodiment, an example in which the fluid dynamic bearing device 1 according to the present invention is incorporated in a spindle motor of an HDD is shown, but the present invention is not limited to this. For example, the fluid dynamic pressure bearing device 1 of the present invention can be applied to a polygon scanner motor or a color wheel motor.

DESCRIPTION OF SYMBOLS 1 Fluid dynamic pressure bearing apparatus 2 Shaft part 3 Hub 3a Disk part 3a1 1st area | region 3a2 2nd area | region 3b Cylindrical part 3c Eaves part 3d Annular protrusion part 3e Disc mounting surface 3f Disc fitting surface 3g Extension part 4 Stator coil 5 Rotor Magnet 6 Bracket 7 Housing 8 Bearing sleeve 10 Seal member 11 Retaining member A Flange integrated shaft A1 Flange part B Annular member G Sealing part R1, R2 Radial bearing part T1, T2 Thrust bearing part S Seal space

Claims (14)

A shaft portion having a bearing surface subjected to grinding on the outer periphery, a disk portion extending from one end of the shaft portion to the outer diameter side, and an annular shape protruding from the radial intermediate portion of the disk portion to the other end side in the axial direction And a hydrodynamic pressure action of fluid generated in a radial bearing gap between a hub having a protruding portion, a bearing member in which the shaft portion is inserted on the inner periphery, and a bearing surface of the shaft portion and an inner peripheral surface of the bearing member. A radial bearing part that rotatably supports the shaft part, a fluid formed between the inner peripheral surface of the annular projecting part and the outer peripheral surface of the bearing member and filled with the fluid and the outside air. In a fluid dynamic pressure bearing device having a seal space for holding an interface,
Of the disk part, at least a first region on the inner diameter side of the annular projecting part is integrally formed with the shaft part to constitute a flange integral shaft, and the annular projecting part formed separately from the flange integral shaft. A fluid dynamic pressure bearing device characterized by fixing a part.   Of the disk part, a second region on the outer diameter side of the annular projecting part is integrally formed with the annular projecting part to constitute an annular member, and the second part of the disk part constituting the flange part of the flange integral shaft. The fluid dynamic bearing device according to claim 1, wherein an inner peripheral surface of the annular member is fitted and fixed to an outer peripheral surface of one region.   3. The fluid dynamic bearing device according to claim 2, wherein the flange integrated shaft and the annular member are each formed by grinding a material formed by plastic working.   The fluid dynamic bearing device according to claim 2 or 3, wherein the inner peripheral surface of the annular member and the outer peripheral surface of the flange portion of the flange integral shaft are press-fitted.   The fluid dynamic bearing device according to any one of claims 2 to 4, wherein a fitting portion between an inner peripheral surface of the annular member and an outer peripheral surface of a flange portion of the flange integral shaft is sealed by laser welding.   The fluid dynamic pressure bearing device according to any one of claims 2 to 4, wherein a fitting portion between an inner peripheral surface of the annular member and an outer peripheral surface of a flange portion of the flange integral shaft is sealed with an adhesive.   The fluid dynamic pressure bearing device according to any one of claims 2 to 6, wherein stepped portions are provided on both of the inner peripheral surface of the annular member and the outer peripheral surface of the flange portion of the flange-integrated shaft, and both of them are fitted together.   The said disk part and the said shaft part are integrally formed, the said flange integral axis | shaft is comprised, The said cyclic | annular protrusion part is fixed to the end surface of the said disk part which comprises the flange part of the said flange integral axis | shaft. Fluid dynamic bearing device.   9. The fluid dynamic bearing device according to claim 8, wherein the flange-integrated shaft is formed by grinding a shaped material formed by plastic working.   A seal member having an annular protrusion and an extending part extending from the one end of the annular protrusion to an inner diameter is provided, and an inner peripheral surface of the extending part is fitted to an outer peripheral surface of the shaft part, and the extension The fluid dynamic pressure bearing device according to claim 8 or 9, wherein an end surface of the existing portion is fixed to an end surface of the flange portion of the flange integral shaft.   The fluid dynamic bearing device according to claim 10, wherein an annular adhesive reservoir filled with an adhesive is formed between an end surface of the extending portion of the seal member and an end surface of the flange portion of the flange integral shaft.   The fluid motion according to claim 10 or 11, wherein a guide portion having a diameter larger than that of the bearing surface is provided at one end of the outer peripheral surface of the shaft portion, and the inner peripheral surface of the extending portion of the seal member is press-fitted into the guide portion. Pressure bearing device.   The fluid dynamic bearing device according to claim 12, wherein the guide portion is ground.   The fluid dynamic bearing device according to any one of claims 10 to 13, wherein at least a region facing an end surface of the extending portion of the seal member is ground among end surfaces of the flange portion of the flange integral shaft.

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