JP2009058006A - Shaft member for fluid bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable easy manufacture of a shaft member for a fluid bearing device with high degree of accuracy and strength. <P>SOLUTION: This shaft member 2 is provided with a shaft section 21 with a radial bearing surface A, and a flange section 22 with thrust bearing surfaces B, C, which is arranged in one end of the shaft section 21. The shaft section 21 and the flange section 22 are fixedly welded together in a line-contact with an aligning mechanism 11 interposed therebetween. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a shaft member for a hydrodynamic bearing device.

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

  For example, a hydrodynamic bearing device for a spindle motor includes a bearing sleeve and a shaft member that is inserted into the inner periphery of the bearing sleeve and rotates relative to the bearing sleeve. As the shaft member, a member having a shaft portion having a radial bearing surface and a flange portion having a thrust bearing surface and provided at one end of the shaft portion is often used. As the shaft member with flange, there are an integrated type in which the shaft portion and the flange portion are integrally formed by machining such as cutting, and a separate type in which the shaft portion and the flange portion manufactured individually are integrated by appropriate means. is there.

  The integral-type flanged shaft member can secure a high fastening strength between the shaft portion and the flange portion, but on the other hand, a dedicated processing facility is required for the production thereof, so that high cost becomes a problem. Therefore, recently, the flanged shaft member may be a separate type.

Various types of shaft members with flanges have been proposed as separate types, but, for example, those in which both are resistance-welded are known as securing a high fastening strength between the shaft portion and the flange portion ( For example, see Patent Document 1). Specifically, a minute annular protrusion and a recess are provided adjacent to one of the shaft part and the end face of the flange part opposite to each other, and the voltage is applied with the tip of the protrusion being in contact with the other. It is a shaft member in which the shaft portion and the flange portion are welded and fixed by applying and melting the protrusions. With such a shaft member, the melt of the protrusion is accommodated in the recess, and the melt can be prevented from entering between the contact surfaces of the shaft portion and the flange portion outside the welded portion. Accuracy is increased.
JP 2004-340368 A

  By the way, in this type of flanged shaft member, it is important to ensure a predetermined degree of coaxiality between the shaft portion and the flange portion from the viewpoint of preventing swinging during rotation. Further, since the flange portion functions as a retaining member that engages with the bearing sleeve in the axial direction, it is also important to ensure a high fastening strength between the shaft portion and the flange portion. In Patent Document 1, the coaxiality is secured by constraining the outer peripheral surfaces of the shaft portion and the flange portion with an assembly jig, but even if the posture of the shaft portion and the flange portion is restricted with a jig. For example, when the perpendicularity between the end surface of the shaft portion and the outer peripheral surface is insufficient, the shaft portion and the flange portion are spotted, and it is difficult to ensure uniform welding strength over the entire circumference.

  An object of the present invention is to provide a highly accurate and high-strength shaft member for a hydrodynamic bearing device.

  In order to solve the above problems, in the present invention, in a shaft member for a hydrodynamic bearing device including a shaft portion having a radial bearing surface and a flange portion having a thrust bearing surface and provided at one end of the shaft portion, the shaft portion A shaft member for a hydrodynamic bearing device is provided in which the flange portion and the flange portion are welded and fixed with a centering mechanism interposed therebetween and in a state where they are in line contact with each other. The radial bearing surface and the thrust bearing surface here are intended to form a radial bearing clearance and a thrust bearing clearance, respectively, between the opposing surfaces when the shaft member is incorporated in the fluid dynamic bearing device. It does not matter whether dynamic pressure generating portions such as dynamic pressure grooves are formed on these surfaces. In addition, the alignment mechanism here refers to a mechanism that realizes a relationship in which either one of the shaft portion and the flange portion can swing with respect to the other.

  As described above, according to the present invention, the shaft portion and the flange portion are welded and fixed in such a state that an alignment mechanism is interposed therebetween and both are in line contact, preferably in a ring shape. It is a feature. With such a configuration, as described above, since either the shaft portion or the flange portion can swing with respect to the other, the relative posture between the shaft portion and the flange portion is only regulated by the assembly jig. Thus, the shaft portion and the flange portion can be aligned, and the centering between them can be accurately performed. At this time, since the two are welded in a line contact, preferably in a ring shape, the welding strength can be increased. Therefore, a highly accurate and high strength shaft member can be easily obtained.

  In addition, as a welding method, although resistance welding can also be used like patent document 1, laser welding is more desirable. Resistance welding tends to increase the welding strength as the contact area between the members to be welded is smaller. Therefore, in the configuration of the present invention in which the shaft portion and the flange portion are welded and fixed in a line contact state, the welding strength This is because an advantage can be given in this respect. In resistance welding, the material for forming the shaft portion and the flange portion is limited to conductive metal. However, in laser welding, it is not necessary to consider the strength or absence of conductivity, and even different metals are high. Welding strength can be ensured. Therefore, the shaft portion and the flange portion can be formed of an optimum material that can satisfy the quality required for the shaft member without considering the weldability.

  As a specific configuration of the above alignment mechanism, an alignment surface formed on one of the shaft portion and the flange portion and reduced in diameter toward the member on the other side, and provided on the other member is aligned. What has a recessed part which accommodates the front-end | tip of a surface is mentioned. The aligning mechanism can be configured by providing a separate member different from the shaft portion and the flange portion, but it is not desirable because the cost increases due to the provision of the separate member. In this regard, as described above, if the alignment mechanism is formed by the alignment surface formed on one of the shaft portion and the flange portion and the concave portion provided on the other side, the above-described increase in cost can be prevented. ,desirable.

  The alignment surface can be formed by a tapered surface or a convex curved surface. In consideration of the ease of processing (processing cost) of the aligning surface, it is advantageous that the aligning surface is a tapered surface. On the other hand, as described above, the alignment mechanism referred to in the present invention is a mechanism that realizes a relationship in which either one of the shaft portion and the flange portion can swing with respect to the other, that is, centering of the shaft portion and the flange portion. It is a mechanism that can correct not only the perpendicularity between the two. Therefore, in consideration of such matters, it may be advantageous that the alignment surface is a convex curved surface. Specifically, when the alignment surface is a convex curved surface, the inner peripheral edge of the concave portion can have any shape, and while the line contact state between the shaft portion and the flange portion is ensured, centering and perpendicularity correction between the two can be performed simultaneously. Can be done. On the other hand, when the alignment surface is a tapered surface, while securing the line contact state between the shaft portion and the flange portion, and trying to achieve centering and perpendicularity correction at the same time, the inner peripheral edge of the recess is It needs to be a convex curved surface (R surface). From the above, whether the alignment surface is a tapered surface or a convex curved surface is not uniquely determined considering only the ease of processing of the alignment surface, but the forming material of the shaft portion and the flange portion, etc. That is, it can be arbitrarily selected in consideration of the processing cost of the entire shaft member.

  In the above configuration, the shaft portion and the flange portion can be fixed by welding inside the recess. If both of them are welded and fixed inside the recesses in this way, the heat effect during welding becomes difficult to reach the radial bearing surface of the shaft portion and the thrust bearing surface of the flange portion, and the surface accuracy of both bearing surfaces deteriorates. It can be avoided as much as possible. Further, it is possible to effectively avoid that the welding mark protrudes to the outer periphery of the shaft portion or one end of the flange portion and adversely affects the bearing performance. Furthermore, when both are laser-welded, the melted material scatters along with the laser irradiation, and this may adhere to the end face of the flange portion. Therefore, the possibility that the melted material adheres to the end surface (thrust bearing surface) of the flange portion can be reduced.

  Since the shaft member has a shaft portion and a flange portion assembled with high accuracy and high strength, a hydrodynamic bearing device including the shaft member and a bearing sleeve that accommodates the shaft member in an inner periphery is a bearing. The gap can be managed with high accuracy, and high rotation performance is stably maintained.

  As described above, according to the present invention, a highly accurate and high-strength shaft member for a hydrodynamic bearing device can be provided.

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

  FIG. 1 conceptually shows one configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device. This spindle motor is used for a disk drive device such as an HDD, and has a hydrodynamic bearing device 1 that rotatably supports a shaft member 2, a disk hub 3 mounted on the shaft member 2, and a radial gap, for example. And a stator magnet 4a and a rotor magnet 4b that are opposed to each other. The stator coil 4 a is attached to the outer periphery of the bracket 5, and the rotor magnet 4 b is attached to the inner periphery of the disk hub 3. The housing 7 of the hydrodynamic bearing device 1 is attached to the inner periphery of the bracket 5. The disk hub 3 holds one or a plurality of disks 6 such as magnetic disks. When the stator coil 4a is energized, the rotor magnet 4b is rotated by the electromagnetic force between the stator coil 4a and the rotor magnet 4b, whereby the disk hub 3 and the disk 6 held thereby rotate together with the shaft member 2. To do.

  FIG. 2 shows the hydrodynamic bearing device 1 according to the first embodiment of the present invention. The hydrodynamic bearing device 1 shown in FIG. 1 includes a bearing sleeve 8, a shaft member 2 inserted in the inner periphery of the bearing sleeve 8, a housing 7 that houses the bearing sleeve 8 and the shaft member 2 in the inner periphery, A lid member 9 for sealing one end opening and a seal member 10 for sealing the other end opening of the housing 7 are provided. For convenience of explanation, the following explanation will be given with the side of the seal member 10 as the upper side and the opposite side to the axial direction as the lower side.

  The housing 7 is formed in a cylindrical shape with a metal material such as brass or a resin material. The inner peripheral surface of the housing 7 is divided into a large-diameter inner peripheral surface 7a having a relatively large diameter in the axial direction and a relatively small-diameter inner peripheral surface 7b. A bearing sleeve 8 is provided on the large-diameter inner peripheral surface 7a. The lid member 9 is fixed to the small-diameter inner peripheral surface 7b by appropriate means such as adhesion, press-fitting, and welding.

  The bearing sleeve 8 is formed in a cylindrical shape with a porous body of sintered metal whose main component is copper, for example. Besides the sintered metal, the bearing sleeve 8 can be formed of a soft metal material such as brass or another porous body (for example, a porous resin) that is not a sintered metal.

  On the inner peripheral surface 8a of the bearing sleeve 8, as shown in FIG. 3 (A), a region in which a plurality of dynamic pressure grooves 8a1 and 8a2 are arranged in a herringbone shape as a radial dynamic pressure generating portion is separated at two upper and lower positions. Formed. In the present embodiment, the upper dynamic pressure groove 8a1 is formed axially asymmetric with respect to the axial center m (the axial center of the upper and lower inclined groove regions), and the axis in the upper region from the axial center m. The direction dimension X1 is larger than the axial direction dimension X2 of the lower region. On the other hand, the lower dynamic pressure groove 8a2 is formed symmetrically in the axial direction, and the axial dimensions of the upper and lower regions thereof are respectively equal to the axial dimension X2. The dynamic pressure groove may be formed on a radial bearing surface A of the shaft portion 21 described later, and the shape thereof may be other known shapes such as a spiral shape.

  As shown in FIG. 3B, an annular region in which a plurality of dynamic pressure grooves 8b1 are arranged in a spiral shape is formed on the lower end surface 8b of the bearing sleeve 8 as a thrust dynamic pressure generating portion. The dynamic pressure groove (thrust dynamic pressure generating portion) can be formed on a thrust bearing surface B of the flange portion 22 to be described later, and the shape thereof can be other known shapes such as a herringbone shape. .

  On the outer peripheral surface 8c of the bearing sleeve 8, one or a plurality of axial grooves 8c1 opened at both end surfaces are formed. The upper end surface 8d of the bearing sleeve 8 is formed with one or more annular grooves 8d1 and one or more radial grooves 8d2 connected to the inner diameter side of the annular groove 8d1.

  The lid member 9 is formed in a disk shape from, for example, a metal material or a resin material. Although not shown in the drawings, the upper end surface 9a of the lid member 9 is formed with an annular region in which a plurality of dynamic pressure grooves are arranged in a spiral shape or a herringbone shape as a thrust dynamic pressure generating portion. The dynamic pressure groove may be formed on a thrust bearing surface C of the flange portion 22 described later.

  The seal member 10 is formed in a ring shape from, for example, a soft metal material such as brass, another metal material, or a resin material, and is fixed to the upper end portion of the inner peripheral surface 7a of the housing 7 by an appropriate means such as adhesion or press fitting. Is done. A predetermined seal space S is formed between the inner peripheral surface 10 a of the seal member 10 and the outer peripheral surface 21 a of the shaft portion 21. The seal space S has a buffer function that absorbs the volume change accompanying the temperature change of the lubricating oil filled in the hydrodynamic bearing device 1, and the oil level of the lubricating oil is always sealed within the assumed temperature change range. It is within the space S.

  The shaft member 2 includes a shaft portion 21 and a flange portion 22 protruding to the outer diameter side of the shaft portion 21. Both the shaft portion 21 and the flange portion 22 are formed of a metal material, here both are made of stainless steel. . The outer peripheral surface 21a of the shaft portion 21 has a smooth cylindrical surface shape, and radial bearing surfaces A and A that are opposed to the formation regions of the dynamic pressure grooves 8a1 and 8a2 provided on the inner peripheral surface 8a of the bearing sleeve 8 in the radial direction. Two locations are formed apart in the axial direction. Between both the radial bearing surfaces A and A, a sumi portion 21b having a smaller diameter than the radial bearing surface A is formed.

  The upper end surface 22a of the flange portion 22 is provided with a thrust bearing surface B opposed to the dynamic pressure groove 8b1 formation region provided in the lower end surface 8b of the bearing sleeve 8 in the thrust direction, and the lower end surface 22b includes A thrust bearing surface C facing the dynamic pressure groove forming region provided in the upper end surface 9a of the lid member 9 in the thrust direction is provided. Both thrust bearing surfaces B and C are smooth flat surfaces having no dynamic pressure grooves or the like.

  The shaft portion 21 and the flange portion 22 are welded and fixed with the alignment mechanism 11 interposed therebetween and in a state where they are in line contact with each other. In the present embodiment, the aligning mechanism 11 includes a convex curved surface (spherical) aligning surface 12 that gradually decreases in diameter toward the flange portion 22 side (lower side) formed at the lower end of the shaft portion 21, and a flange. The recess 22 is formed in the portion 22 and accommodates the tip of the alignment surface 12 of the shaft portion 21. In the present embodiment, the recess 13 is a through hole opened in both end faces 22 a and 22 b of the flange portion 22, and the shaft portion 21 and the flange portion 22 are welded portions formed inside the recess 13 of the flange portion 22. 14 is fixed by welding. The method for manufacturing the shaft member 2 will be described in detail later.

  The hydrodynamic bearing device 1 includes the above-described components, and the internal space of the housing 7 sealed with the seal member 10 is filled with lubricating oil including the internal pores of the bearing sleeve 8.

  In the hydrodynamic bearing device 1 having the above configuration, when the shaft member 2 rotates, a radial bearing gap is formed between the dynamic pressure groove 8a1 and 8a2 formation region of the bearing sleeve 8 and the radial bearing surfaces A and A of the shaft portion 21. Is formed. As the shaft member 2 rotates, the oil film formed in the radial bearing gap is enhanced in its rigidity by the dynamic pressure action of the dynamic pressure grooves 8a1 and 8a2, and the shaft member 2 rotates in the radial direction by this pressure. It is supported non-contact freely. As a result, radial bearing portions R1 and R2 that support the shaft member 2 in a non-contact manner so as to be rotatable in the radial direction are spaced apart at two locations in the axial direction.

  At the same time, a thrust bearing gap is formed between the thrust bearing surfaces B and C of the flange portion 22 and the lower end surface 8 b of the bearing sleeve 8 and the upper end surface 9 a of the lid member 9. As the shaft member 2 rotates, the oil film formed in the thrust bearing gaps has its oil film rigidity increased by the dynamic pressure action of the dynamic pressure grooves, and the shaft member 2 can rotate in both thrust directions by this pressure. Is supported in a non-contact manner. Thereby, the 1st thrust bearing part T1 and the 2nd thrust bearing part T2 which support the shaft member 2 in a non-contact manner so as to be rotatable in both thrust directions are formed.

  In addition, when the shaft member 2 rotates, as described above, the seal space S has a tapered shape that gradually decreases toward the inside of the housing 7, so that the lubricating oil in the seal space S is drawn by capillary force. By the action, the seal space is drawn in the direction of narrowing, that is, toward the inside of the housing 7. Thereby, the leakage of the lubricating oil from the inside of the housing 7 is effectively prevented.

  Further, as described above, the upper dynamic pressure groove 8a1 is formed axially asymmetric with respect to the axial center m, and the axial dimension X1 of the upper region from the axial center m is the axial direction of the lower region. It is larger than the dimension X2. Therefore, when the shaft member 2 rotates, the lubricating oil pulling force (pumping force) by the dynamic pressure groove 8a1 is relatively larger in the upper region than in the lower region. Then, due to the differential pressure of the pulling force, the lubricating oil filled in the gap between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 21a of the shaft portion 21 flows downward, and the lower end surface of the bearing sleeve 8 8b and the gap between the upper end surface 22a of the flange portion 22 → the fluid passage formed by the axial groove 8c1 of the bearing sleeve 8 → the fluid passage formed by the radial groove 10b1 of the seal member 10 → the circle of the bearing sleeve 8 It circulates through a path called a fluid passage formed by the annular groove 8d1 and the radial groove 8d2, and is drawn into the radial bearing gap of the first radial bearing portion R1 again.

  In this way, by configuring the lubricating oil to flow and circulate in the internal space of the housing 7, the pressure balance of the lubricating oil is maintained, and at the same time, the generation of bubbles accompanying the generation of local negative pressure, Problems such as leakage of lubricating oil and generation of vibration due to generation can be solved. Since the sealing space S communicates with the above circulation path, even if bubbles are mixed in the lubricating oil for some reason, when the bubbles circulate with the lubricating oil, the lubricating oil in the sealing space S It is discharged from the oil surface (gas-liquid interface) to the outside air. Therefore, adverse effects due to air bubbles can be more effectively prevented.

  Next, the manufacturing method of the said shaft member 2 is explained in full detail based on FIG.

  4A and 4B conceptually show the manufacturing process of the shaft member 2. The assembly apparatus shown in FIG. 1 includes a first jig 31, a second jig 32 arranged coaxially with the first jig 31, and a laser irradiation apparatus (not shown) that irradiates a laser 33 from above the second jig 32. And as a main component. The first jig 31 and the second jig 32 can be moved relative to each other in the axial direction by a drive mechanism (not shown). In this embodiment, the first jig 31 is on the fixed side and the second jig 32 is on the movable side. is there.

  The 1st jig | tool 31 has the holding hole 31a which can insert the axial part 21, and hold | maintains the inserted axial part 21. FIG. The second jig 32 has a small-diameter portion 32a in which the lower end surface 32a2 contacts the lower end surface 22b (thrust bearing surface C) of the flange portion 22, and a large-diameter portion 32b that accommodates the flange portion 22 on the inner periphery. As the laser irradiation apparatus, a known laser such as a YAG laser, a carbon dioxide gas laser, a semiconductor laser, or a fiber laser can be used. However, the beam quality and economical efficiency of the irradiated laser 33, and further, the welding strength, ease of welding, etc. In view of the above, a YAG laser or a carbon dioxide laser is preferable. The irradiation method of the laser 33 may be either a continuous type or a pulse type.

  Although not shown, a beam diameter adjusting means for adjusting the beam diameter of the laser 33 can be disposed between the laser irradiation device and the second jig 32. By providing such a beam diameter adjusting means, it is possible to easily adjust the formation range of the welded portion 14 to be formed. Similarly, although not shown, in order to prevent the vicinity of the formation part of the welded part 14 from being oxidized during the welding operation, an inert gas such as argon gas or nitrogen gas is used to block the surrounding air. It is also possible to arrange a shield gas injection device for spraying.

  By the way, in this type of shaft member with flange, the perpendicularity of the thrust bearing surfaces B and C of the flange portion 22 with respect to the radial bearing surface A of the shaft portion 21 affects the bearing performance. Therefore, in order to ensure a predetermined squareness between these bearing surfaces, the perpendicularity of the lower end surface 32a2 of the small diameter portion of the second jig 32 with respect to the inner peripheral surface of the holding hole 31a of the first jig 31, It is desirable that the degree of parallelism or the like of the small-diameter lower end surface 32a2 of the second jig 32 with respect to the upper end surface 31b is sufficiently increased in advance.

  In the above configuration, first, as shown in FIG. 4A, after inserting the shaft portion 21 into the holding hole 31a of the first jig 31, the tip portion of the alignment surface 12 provided on the shaft portion 21 is recessed with the concave portion 13. The flange portion 22 is placed on the shaft portion 21 (on the alignment surface 12) so as to be accommodated in the inner portion. Since the alignment surface 12 provided on the shaft portion 21 is formed in a convex curved surface, when the flange portion 22 is placed on the shaft portion 21, both of them maintain a line contact state in a ring shape over the entire circumference. Meanwhile, the flange portion 22 can swing and swing with respect to the shaft portion 21.

  Next, as shown in FIG. 4B, the second jig 32 is brought close to the first jig 31, and the lower end surface 32 b 1 of the large diameter portion 32 b of the second jig 32 is set to the upper end surface of the first jig 31. It is made to contact 31b. When the second jig 32 is brought closer to the first jig 31, if the lower end surface 32 a 2 of the small diameter portion of the second jig 32 comes into contact with the lower end surface 22 b of the flange portion 22, the flange is formed on the alignment surface 12 of the shaft portion 21. The portion 22 swings, and the posture of the flange portion 22 with respect to the shaft portion 21 is corrected to a specified one. As described above, since a predetermined squareness or the like is secured between the surfaces of the first and second jigs 31 and 32, the first jig 31 and the second jig 32 are in contact with each other. At the same time as the centering between the shaft portion 21 and the flange portion 22 is performed, a predetermined squareness is ensured between the radial bearing surface A of the shaft portion 21 and the thrust bearing surfaces B and C of the flange portion 22. The

  Next, an annular contact portion between the shaft portion 21 and the flange portion 22 is irradiated with a laser 33 so as to pass through the inner circumference of the small diameter portion 32a of the second jig 32 from a laser irradiation device (not shown) to form the annular welded portion 14. To do. Then, after the irradiation of the laser 33 is stopped and the second jig 32 is returned to the origin, when the shaft portion 21 is taken out from the first jig 31, the shaft member 2 as a finished product shown in FIG. 2 is obtained.

  As described above, in the present invention, the alignment mechanism 11 is interposed between the shaft portion 21 and the flange portion 22, and the flange portion 22 can swing and swing relative to the shaft portion 21. By just restricting the relative posture of the shaft portion 21 and the flange portion 22 with the shafts 31 and 32, the shaft portion 21 and the flange portion 22 can be aligned and the centering between them can be accurately performed. In addition, since the relative postures of the jigs 31 and 32 can be regulated in this way, they can be welded and fixed in a state where they are in line contact with each other (the welded portion 14 can be formed in a ring shape). ), Welding strength can be increased. Therefore, the highly accurate and high-strength shaft member 2 can be easily manufactured. In particular, in the present embodiment, since both are welded and fixed by laser welding rather than resistance welding in which a difference (variation) occurs in the bonding strength depending on the contact area, a stable welding strength can be obtained.

  Further, since the aligning mechanism 11 is composed of the aligning surface 12 provided in the shaft portion 21 and the recess 13 provided in the flange portion 22, the cost increase which is a concern when aligning both with separate members. This problem can be effectively prevented.

  In the present embodiment, since the alignment surface 12 is formed in a convex curved surface (spherical surface), the shaft portion 21 and the flange portion 22 can swing freely in a line contact state regardless of the shape of the concave portion 13. It becomes. Therefore, when the jigs 31 and 32 are brought into contact with each other, not only the coaxiality between the shaft portion 21 and the flange portion 22 but also the thrust bearing surfaces B and C of the flange portion 22 with respect to the radial bearing surface A of the shaft portion 21. The perpendicularity can be easily secured.

  Further, since the shaft portion 21 and the flange portion 22 are welded and fixed inside the concave portion 13, the surfaces of the radial bearing surface A of the shaft portion 21 and the thrust bearing surfaces B and C of the flange portion 22 due to the heat effect during welding. It is possible to avoid the deterioration of accuracy as much as possible. Further, it is possible to effectively avoid the adverse effect on the bearing performance due to the welding mark projecting to the outer periphery of the shaft portion 21 or the end portion side of the flange portion 22, that is, the radial bearing gap or the thrust bearing gap. Furthermore, in the configuration of the present embodiment in which the welded portion 14 is formed by the irradiation of the laser 33, there is a concern about the scattering of the melt accompanying the irradiation of the laser 33, but the shaft portion 21 and the flange portion 22 are welded inside the recess 13. Then, the welded portion can be covered with the inner wall surface of the recess 13 (the inner peripheral surface of the flange portion 22), so that it is effective that the melted material scatters and adheres to the end surfaces 22a, 22b, etc. of the flange portion 22. Can be prevented.

  In the present embodiment, the shaft portion 21 and the flange portion 22 are formed of the same kind of stainless steel. However, if laser welding is used, high welding strength can be obtained even between dissimilar metals where it is difficult to ensure high welding strength by resistance welding. Can be secured. Therefore, as long as the strength required for the shaft member 2 can be ensured, the choice of the material for forming the shaft portion 21 and the flange portion 22 can be expanded, that is, the optimum material corresponding to the required quality can be selected and used. From this point, the cost of the shaft member 2 can be reduced. For example, the shaft portion 21 can be formed of stainless steel, while the flange portion 23 can be formed of brass or the like.

  As long as the centering between the shaft portion 21 and the flange portion 22 and the perpendicularity between the bearing surfaces can be secured, the shapes of the shaft portion 21 and the flange portion 22 can be arbitrarily changed.

  For example, as shown in FIG. 5A, the shaft portion 21 may further be provided with a small-diameter portion 21c that extends downward from the alignment surface 12 and is accommodated in the inner periphery of the concave portion 13 (through hole) of the flange portion 22. Is possible. With this configuration, the space formed in the inner periphery of the flange portion 22 can be filled with the small diameter portion 21c, and therefore the amount of lubricating oil to be filled in the bearing is reduced compared to the configuration shown in FIG. be able to. Therefore, it is possible to reduce the size of the seal space S in the axial direction and reduce the size of the hydrodynamic bearing device.

  Further, for example, as shown in FIG. 5B, the recess 13 provided in the flange portion 22 can be formed in a hollow shape instead of a through hole. In this case, the shaft portion 21 and the flange portion 22 are welded and fixed by forming the welded portion 13 in an annular gap formed between the alignment surface 12 of the shaft portion 21 and the upper end surface 22a of the flange portion 22. be able to.

  The case where the alignment mechanism 11 is configured by the alignment surface 12 provided on the shaft portion 21 and the concave portion 13 provided on the flange portion 22 has been described above, but the alignment surface 12 provided on the flange portion 22 has been described. It is also possible to configure the alignment mechanism 11 with the recess 13 provided in the shaft portion 21. Specifically, as shown in FIGS. 5C and 5D, for example, the flange portion 22 is provided with an alignment surface 12 formed in a convex spherical shape whose diameter is reduced toward the shaft portion 21 side, and the shaft By providing the through hole or the recessed recess 13 in the portion 21, the shaft portion 21 and the flange portion 22 can be welded and fixed in a ring shape.

  2 and 5 (A) and 5 (C), the shaft portion 21 and the flange portion 22 are welded and fixed by forming the welded portion 14 inside the concave portion 13, but FIG. Similarly to (D), the welded portion 14 may be formed in an annular gap between the lower end surface of the shaft portion 21 and the upper end surface 22a of the flange portion 22. Alternatively, for the purpose of further increasing the strength of the shaft member 2, the shaft portion 21 and the flange portion 22 may be welded and fixed by forming the welded portion 14 both inside the recess 13 and in the annular gap. it can.

  Although one embodiment of the present invention has been described above, the shaft member 2 according to the present invention is not limited to the hydrodynamic bearing device having the above-described configuration. Hereinafter, other embodiments of the hydrodynamic bearing device to which the shaft member 2 according to the present invention can be applied will be described with reference to the drawings. In the following description, components similar to those described above are denoted by common reference numerals, and redundant description is omitted.

  FIG. 6 shows a second embodiment of a hydrodynamic bearing device incorporating the shaft member 2 according to the present invention. The main difference of the hydrodynamic bearing device shown in FIG. 2 from that shown in FIG. 2 is that the thrust bearing surface C is not formed on the lower end surface 22b of the thrust member 22 of the shaft member 2, and the second thrust bearing portion T2 is The point provided between the lower end surface 3 a 1 of the disk portion 3 a of the disk hub 3 fixed to the upper end of the shaft portion 21 and the upper end surface 7 c of the housing 7, and the seal space S are the tapered outer peripheral surface of the housing 7. 7d and the inner peripheral surface 3b1 of the cylindrical portion 3b of the disc hub 3. In the illustrated example, the same shaft member 2 as that shown in FIG. 2 is used. Of course, the shaft member 2 having the configuration shown in FIGS. 5A to 5D can also be used.

  FIG. 7 shows a third embodiment of a hydrodynamic bearing device incorporating the shaft member 2 according to the present invention. In the hydrodynamic bearing device shown in the figure, the shaft member 2 further includes a second flange portion 42 fixed to a substantially central portion of the shaft portion 21 in the axial direction, and the second thrust bearing portion T2 is a second flange portion. 42 and the upper end surface 8 d of the bearing sleeve 8, and the outer peripheral surfaces 22 c and 42 c of both flange portions 22 and 42 form a seal space S between the inner peripheral surface 7 a of the housing 7. Thus, the configuration is different from that of the embodiment shown in FIGS. As described above, even when the shaft member 2 having the two flange portions 22 and 42 provided on the shaft portion 21 is used, an integrated product of the shaft portion 21 and the flange portion 22 provided on the lower end of the shaft portion 21 is used. The above-described configuration of the present invention can be applied. Of course, also in this embodiment, it is possible to use the shaft member 2 having the configuration shown in FIGS.

  The shaft member 2 having the aligning surface 12 formed in a convex curved surface (spherical shape) and the hydrodynamic bearing device 1 incorporating the same have been described above. The aligning surface 12 is shown in FIG. It is also possible to form such a tapered surface. In this case, the inner peripheral edge of the recess 13, strictly speaking, at least the inner peripheral edge on the side on which the alignment surface 12 is introduced (in the illustrated example, the upper inner peripheral edge of the flange portion 22) 13 a is formed on a convex curved surface (R surface). It is desirable to do. By adopting such a configuration, the shaft portion 21 and the flange portion 22 are in a swingable relationship as in the embodiment described above, and when the shaft portion 21 and the flange portion 22 are welded, It is possible to ensure not only the coaxiality between them but also a perpendicularity at the same time. Such a configuration can be suitably employed in any of the embodiments described above.

  In consideration of ease of processing (processing cost) of the aligning surface 12, it is more advantageous to form the aligning surface 12 into a tapered surface than to form it into a convex curved surface. If it is attempted to secure both the coaxiality and perpendicularity at the same time during welding and fixing, it is necessary to process the inner peripheral edge 13a of the recess 13 into an R surface as described above. The processing cost depends on the forming material of the shaft portion 21 and the flange portion 22, the processing method, and the like. Therefore, which configuration is to be adopted may be appropriately selected depending on the material used.

  In addition, in any of the fluid dynamic bearing devices described above, the housing 7 and the bearing sleeve 8 are separate components. However, the shaft member according to the present invention is also applied to the fluid dynamic bearing device in which both are integrated. 2 can be preferably employed. In particular, in the hydrodynamic bearing device shown in FIG. 2, the lid member 9 or the seal member 10 can be further integrated with the housing 7.

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

  Moreover, although the case where both radial bearing part R1, R2 was comprised with the dynamic pressure bearing was demonstrated above, one or both of radial bearing part R1, R2 can also be comprised with a bearing other than this. For example, although not shown in the drawings, the radial bearing surface A of the shaft member 2 is formed in a perfect circle shape, and the inner peripheral surface 8a of the bearing sleeve 8 that is opposed is a perfect circular inner peripheral surface. Can also be configured.

It is sectional drawing which shows notionally an example of the spindle motor for information devices incorporating the hydrodynamic bearing apparatus. It is sectional drawing which shows 1st Embodiment of a hydrodynamic bearing apparatus. (A) is a sectional view of the bearing sleeve, and (B) is a diagram showing a lower end surface of the bearing sleeve. It is sectional drawing which shows notionally the manufacturing process of a shaft member. (A)-(D) figure is a principal part expanded sectional view which shows the modification of a shaft member. It is sectional drawing which shows 2nd Embodiment of a hydrodynamic bearing apparatus. It is sectional drawing which shows 3rd Embodiment of a hydrodynamic bearing apparatus. It is a principal part expanded sectional view which shows the other example of a shaft member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid dynamic bearing apparatus 2 Shaft member 11 Alignment mechanism 12 Alignment surface 13 Recess 14 Welded portion 21 Shaft portion 22 Flange portion 31 First jig 32 Second jig 33 Laser A Radial bearing surface B, C Thrust bearing surface R1, R2 Radial bearing part T1, T2 Thrust bearing part

Claims (6)

In a fluid dynamic bearing device shaft member comprising a shaft portion having a radial bearing surface, and a flange portion having a thrust bearing surface and provided at one end of the shaft portion,
A shaft member for a hydrodynamic bearing device, wherein the shaft portion and the flange portion are welded and fixed with a centering mechanism interposed between the shaft portion and the flange portion and in a state in which both are in line contact.   An alignment mechanism is formed on one of the shaft portion and the flange portion and has a diameter reduced toward the other member, and a recess provided on the other member that accommodates the tip of the alignment surface. The shaft member for a hydrodynamic bearing device according to claim 1.   The shaft member for a hydrodynamic bearing device according to claim 2, wherein the alignment surface is a tapered surface.   The shaft member for a hydrodynamic bearing device according to claim 2, wherein the alignment surface is a convex curved surface.   The shaft member for a hydrodynamic bearing device according to any one of claims 2 to 4, wherein the shaft portion and the flange portion are fixed by welding inside the recess.   A hydrodynamic bearing device comprising: the shaft member according to any one of claims 1 to 5; and a bearing sleeve that houses the shaft member on an inner periphery thereof.

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