JP5122205B2 - Method for assembling hydrodynamic bearing device - Google Patents

Description

  The present invention relates to a method for assembling a hydrodynamic bearing device that rotatably supports a shaft member with a fluid film generated in a bearing gap.

  Due to its high rotational accuracy and quietness, the hydrodynamic bearing device is an information device, for example, a magnetic disk drive device such as HDD, an optical disk drive device such as CD-ROM, CD-R / RW, DVD-ROM / RAM, MD, MO, etc. For spindle motors such as magneto-optical disk drive devices, etc., for polygon scanner motors of laser beam printers (LBP), for motors for color wheels of projectors, or for small motors such as fan motors used for cooling electrical equipment, etc. Can be preferably used.

  For example, in the hydrodynamic bearing device disclosed in Patent Document 1, the shaft member has a stepped shape, and an annular seal portion is provided on the inner periphery of the housing opening, and this seal portion is formed on the step portion (shoulder surface) of the shaft member. The shaft member is prevented from coming off by being engaged with each other in the axial direction.

JP-A-2005-113987

  In this hydrodynamic bearing device, the shaft member is allowed to move in the axial direction by the amount of the axial clearance formed between the seal portion and the shoulder surface of the shaft member. If this axial clearance is too large, the axial movement (stroke amount) of the shaft member will be excessive, causing an axial backlash in the HDD disk or the like attached to the shaft member, which will deteriorate the disk reading accuracy. There is a risk of interference between the disk and the head. Therefore, the axial gap formed between the seal portion and the shoulder surface of the shaft member needs to be set with high accuracy.

  However, in the above hydrodynamic bearing device, since the seal portion is positioned by being brought into contact with the sleeve portion fixed to the inner periphery of the housing, the accuracy of fixing the seal portion to the housing is the axial dimension of the sleeve portion. Depends on the machining accuracy. Therefore, in order to manage the stroke amount of the shaft member with high accuracy, it is necessary to process the sleeve portion with high accuracy, resulting in an increase in processing cost.

  The subject of this invention is providing the assembly method of the hydrodynamic bearing apparatus which can manage the stroke amount of a shaft member with high precision and low cost.

In order to solve the above problems, the present invention has a small-diameter outer peripheral surface, a large-diameter outer peripheral surface, a shoulder surface formed therebetween , and a spherical convex portion formed at one end in the axial direction. A shaft member, a cylindrical side portion, and a housing having a bottom portion that closes one end in the axial direction of the side portion and contacts and supports the spherical convex portion of the shaft member, and an inner periphery of the side portion of the housing A seal space provided between the sleeve portion with the shaft member inserted in the inner periphery and the inner periphery of the housing, and preventing leakage of the lubricating fluid inside the bearing to the outside between the small-diameter outer surface of the shaft member And a seal portion that engages with the shoulder surface of the shaft member in the axial direction to prevent the shaft member from coming off, and is formed between the large-diameter outer peripheral surface of the shaft member and the inner peripheral surface of the sleeve portion. and a radial bearing gap, the sealing portion and the sleeve portion is moved away in the axial direction, the seal portion and the sleeve Axial clearance is a method of assembling a large fluid bearing device than the axial clearance between the shoulder surface of the sealing portion and the shaft member, the sleeve portion on the inner periphery of the housing, the shaft member, and the seal portion between the A step of bringing the spherical convex portion of the shaft member into contact with the bottom portion of the housing and bringing the seal portion into contact with the shoulder surface of the shaft member; and the seal portion on the shoulder surface of the shaft member toward the housing opening side And a step of setting an axial clearance between the seal portion and the shoulder surface of the shaft member by moving the seal member.

  Thus, in the method of assembling the hydrodynamic bearing device of the present invention, the axial gap between the seal portion and the shoulder surface of the shaft member, which is the stroke amount of the shaft member, is not set on the basis of the sleeve portion, It is set by moving the seal part in the axial direction relative to the housing. Thereby, since the stroke amount of the shaft member can be managed regardless of the shape accuracy of the sleeve portion, the processing accuracy of the sleeve portion is relaxed, and the processing cost can be reduced.

As described above, in the present invention, the setting of the axial clearance due to movement of the sealing portion, it houses the shaft member and the seal portion inner periphery of the housing, after the seal portion is in contact with the shoulder surface of the shaft member Then, the seal member is moved by a predetermined amount toward the opening side of the housing by the shaft member.

  In this hydrodynamic bearing device, when the small-diameter outer peripheral surface, the large-diameter outer peripheral surface, and the shoulder surface of the shaft member are integrally processed, the perpendicularity and coaxiality of these surfaces can be processed with high accuracy. Therefore, the radial bearing gap facing the large-diameter outer peripheral surface and the seal space facing the small-diameter outer peripheral surface can be set with high accuracy, and excellent bearing performance and sealing function can be obtained.

  The shaft member can be formed of a shaft portion and a sleeve portion fixed to the outer peripheral surface of the shaft portion. At this time, the shoulder surface of the shaft member is formed by the end surface of the sleeve portion. Thereby, it becomes possible to simplify the shape of the shaft part and sleeve part which comprise a shaft member, and the reduction of the processing cost of each member is achieved. In addition, when the shaft member is composed of the shaft portion and the sleeve portion in this way, if the shaft portion is used as an insert part and the sleeve portion is molded, the assembly process of the shaft portion and the sleeve portion becomes unnecessary. Cost can be further reduced.

  When the seal part is moved relative to the housing, if the lubricant is interposed on the mating surface between the seal part and the housing, the seal part can be moved smoothly and a more accurate clearance can be set. Become. At this time, when an adhesive is used as the lubricant, in addition to the above effects, the fixing strength between the seal portion and the housing can be improved.

  In addition, after positioning the seal portion, the atmosphere opening side of the fitting surface between the seal portion and the housing is adhesively sealed, so that the lubricating fluid inside the bearing leaks out from the fitting surface between the seal portion and the housing. Can be surely prevented.

  As described above, according to the assembling method of the present invention, the stroke amount of the shaft member can be managed with high accuracy and at low cost.

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

  FIG. 1 conceptually shows a configuration example of a spindle motor for information equipment incorporating a hydrodynamic bearing device 1 according to an embodiment of the present invention. This spindle motor is used in a disk drive device such as an HDD, and is a stator that is opposed to a hydrodynamic bearing device 1 that rotatably supports a shaft member 2 to which a disk hub 3 is attached, for example, via a radial gap. A coil 4 and a rotor magnet 5 and a motor bracket 6 are provided. The stator coil 4 is attached to the outer periphery of the motor bracket 6, and the rotor magnet 5 is attached to the inner periphery of the disk hub 3. The housing 7 of the hydrodynamic bearing device 1 is fixed to the inner periphery of the motor bracket 6. The disk hub 3 holds one or more (two in FIG. 1) disk-shaped information recording media (hereinafter simply referred to as disks) D such as magnetic disks. In the spindle motor configured as described above, when the stator coil 4 is energized, the rotor magnet 5 is rotated by the electromagnetic force generated between the stator coil 4 and the rotor magnet 5. The disk D held by the hub 3 rotates integrally with the shaft member 2.

  As shown in FIG. 2, the hydrodynamic bearing device 1 includes a shaft member 2, a sleeve portion 8 in which the shaft member 2 is inserted on the inner periphery, a bottomed cylindrical housing 7 that holds the sleeve portion 8 from the outer periphery, 7 is mainly provided with a seal portion 9 provided in the opening portion. In the following description, the opening side of the housing 7 is the upper side and the closing side is the lower side in the axial direction.

  The shaft member 2 has a large-diameter outer peripheral surface 2a, a small-diameter outer peripheral surface 2b, a shoulder surface 2c formed therebetween, and a spherical convex portion 2d formed at the lower end portion, such as SUS steel. It is integrally processed by turning the metal material. The large-diameter outer peripheral surface 2 a forms a radial bearing gap with the inner peripheral surface 8 a of the sleeve portion 8, and the small-diameter outer peripheral surface 2 b forms a seal space S with the inner peripheral surface 9 a of the seal portion 9.

  The sleeve portion 8 is formed in a cylindrical shape, for example, from a sintered metal porous body mainly composed of copper. In addition, the sleeve portion 8 can be formed of another metal, resin, ceramic, or the like.

  On the entire surface of the inner peripheral surface 8a of the sleeve portion 8 or a partial cylindrical region, as a radial dynamic pressure generating portion, for example, as shown in FIG. Two places are formed apart in the axial direction. The formation regions (shown by dotted lines in FIG. 2) of the dynamic pressure grooves G1 and G2 are opposed to the large-diameter outer peripheral surface 2a of the shaft member 2 as radial bearing surfaces, and when the shaft member 2 rotates, the large-diameter outer peripheral surface 2a A radial bearing gap is formed between the radial bearing portions R1 and R2 described later. The upper dynamic pressure groove G1 is formed axially asymmetric with respect to the annular smooth portion formed between the upper and lower inclined grooves, and the axial dimension X1 of the upper region from the annular smooth portion is the lower region. Is larger than the axial dimension X2 (X1> X2).

  On the outer peripheral surface 8d of the sleeve portion 8, one or a plurality of grooves 8d1 extending in the axial direction are formed over the entire length in the axial direction. One or more grooves 8c1 extending in the radial direction are formed on the lower end surface 8c of the sleeve portion 8. The axial groove 8d1 and the radial groove 8c1 provide a communication path for the lubricating oil between the inner peripheral surface 7a1 and the inner bottom surface 7b1 of the opposing housing 7 in a state where the sleeve portion 8 is fixed to the inner periphery of the housing 7. Configure (see FIG. 2). The axial groove 8d1 and the radial groove 8c1 are formed by providing portions corresponding to the axial groove 8d1 and the radial groove 8c1 in advance in a green compact forming die that forms the body of the sleeve portion 8, for example. It can be molded simultaneously with the green compact molding of the main body.

  The housing 7 is made of a crystalline resin such as liquid crystal polymer (LCP), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), or polyphenylsulfone (PPSU), polyethersulfone (PES), polyetherimide ( It is injection molded with a resin composition having an amorphous resin such as PEI) as a base resin, and is formed into a bottomed cylindrical shape. In this embodiment, as shown in FIG. 2, the side part 7a and the bottom part 7b which obstruct | occludes the lower end part of the side part 7a are shape | molded integrally. Examples of the resin composition forming the housing 7 include fibrous fillers such as glass fibers, whisker-like fillers such as potassium titanate, scaly fillers such as mica, carbon fibers, carbon black, graphite, carbon A material in which an appropriate amount of a fibrous or powdery conductive filler such as nanomaterials or various metal powders is blended with the base resin according to the purpose can be used.

  The injection material of the housing 7 is not limited to the above, and for example, a low melting point metal material such as a magnesium alloy or an aluminum alloy can be used. Alternatively, the housing 7 can be formed by so-called MIM molding in which degreasing and sintering are performed after injection molding with a mixture of a metal powder and a binder, or press molding of a soft metal such as a metal material such as brass. The housing bottom 7b is not necessarily integrated with the side 7a, and can be formed separately from the side 7a.

  The outer peripheral surface 8d of the sleeve portion 8 is fixed to the inner peripheral surface 7a1 of the housing 7 by an appropriate means such as bonding (including loose bonding or press-fitting bonding), press-fitting, or welding.

  The inner bottom surface 7 b 1 of the housing 7 functions as a thrust receiver T that contacts and supports the spherical convex portion 2 d at the lower end portion of the shaft member 2. In the present embodiment, the thrust receiver T is formed directly on the housing 7 as described above. However, the present invention is not limited to this. For example, a thrust washer separately formed of a metal material or the like is disposed on the inner bottom surface 7b1 of the housing 7, The thrust receiver T may be configured with a washer. In this case, since the housing 7 does not slide in contact with the shaft member 2, the housing 7 does not need wear resistance, and the range of material selection for the housing 7 is widened.

  The seal portion 9 is formed in a ring shape from a metal material or a resin material, and is fixed to the inner periphery of the upper end portion of the side portion 7a of the housing 7 by, for example, press fitting. The inner peripheral surface 9a of the seal portion 9 is formed in a tapered surface shape whose diameter is gradually increased upward. In a state where the seal portion 9 is fixed to the inner periphery of the housing 7, the inner peripheral surface 9a of the seal portion 9 faces the small-diameter outer peripheral surface 2b of the shaft member 2, and the radial dimension gradually decreases downward therebetween. An annular seal space S is formed. Lubricating oil, for example, is injected into the internal space of the housing 7 sealed by the seal portion 9 as a lubricating fluid, and the inside of the housing 7 is filled with the lubricating oil (a dotted area in FIG. 2). In this state, the oil level of the lubricating oil is maintained within the range of the seal space S. At this time, as shown in the enlarged view of FIG. 2, the space between the inner peripheral chamfer 9 b 1 of the lower end surface 9 b of the seal portion 9 and the small-diameter outer peripheral surface 2 b of the shaft member 2 or the upper end surface 8 b of the sleeve portion 8. The space between the inner peripheral chamfer 8b1 and the large-diameter outer peripheral surface 2a of the shaft member 2 is also filled with lubricating oil.

  An axial gap L is formed between the lower end surface 9 b of the seal portion 9 and the shoulder surface 2 c of the shaft member 2, and this axial gap L becomes the stroke amount of the shaft member 2. When the hydrodynamic bearing device 1 is used for an HDD spindle motor as in this embodiment, the axial gap L is set to 30 μm or less, preferably 20 μm or less, in order to prevent interference between the disk and the head. It is desirable. Furthermore, it is desirable that the axial clearance L is set to be equal to or smaller than the smallest radial dimension L ′ in the seal space S (L ≦ L ′). As a result, a capillary force equal to or greater than that of the seal space S can be obtained in the axial gap L, so that leakage of the lubricating oil to the outside can be prevented more reliably. As shown in FIG. 2, the shoulder surface 2 c of the shaft member 2 is positioned axially above the upper end surface 8 b of the sleeve portion 8, so that the lower end surface 9 b of the seal portion 9 and the upper side of the sleeve portion 8 are An axial gap L ″ larger than the axial gap L is formed between the end face 8b.

  In the hydrodynamic bearing device 1 configured as described above, when the shaft member 2 rotates, the radial bearing surface of the sleeve portion 8 (the dynamic pressure grooves G1 and G2 formation region of the inner peripheral surface 8a) is the same as the large-diameter outer peripheral surface 2a of the shaft member 2. Opposes through radial bearing gap. As the shaft member 2 rotates, the lubricating oil in the radial bearing gap is pushed toward the annular smooth portion at the axial center of the dynamic pressure grooves G1, G2, and the pressure rises. Due to the dynamic pressure action of the dynamic pressure grooves G1 and G2, the first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 2 in a non-contact manner in the radial direction are configured.

  At the same time, the spherical convex portion 2d provided at the lower end of the shaft member 2 and the inner bottom surface 7b1 of the housing 7 as the thrust receiver T slide in contact with each other, so that the shaft member 2 is contacted and supported in the thrust direction.

  A communication path is formed between the sleeve portion 8 and the housing 7 by the axial groove 8d1 formed on the outer peripheral surface 8d of the sleeve portion 8 and the radial groove 8c1 formed on the lower end surface 8c. One end of this communication path opens into an axial gap L ″ between the seal portion 9 and the sleeve portion 8, and the other end is a spherical projection of the thrust receiver T (inner bottom surface 7 b 1 of the housing 7) and the shaft member 2. It opens to the space P between the parts 2d. As a result, the space P formed on the housing closing side communicates with the seal space S via the communication path, the axial gaps L ″ and L, so that the lubricating oil filled in the space P is locally localized. A situation in which a negative pressure is generated can be avoided, and a decrease in bearing performance due to the generation of bubbles can be prevented.

  Further, in this embodiment, the dynamic pressure groove G1 of the first radial bearing portion R1 is formed axially asymmetric (X1> X2) with respect to the annular smooth portion at the axially intermediate portion (see FIG. 3). When the shaft member 2 rotates, the pulling force (pumping force) of the lubricating oil by the dynamic pressure groove G1 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 sleeve portion 8 and the large-diameter outer peripheral surface 2a of the shaft member 2 flows downward, and the closed side of the housing 7 The space P → the radial groove 8c1 → the axial groove 8d1 → the axial gap L ″ is circulated and drawn into the radial bearing gap of the first radial bearing portion R1 again. In this way, by forcibly flowing and circulating the lubricating oil inside the bearing, a situation in which a local negative pressure is generated in the lubricating oil can be more effectively prevented. In order to circulate the lubricating oil in the direction opposite to the above path, for example, the imbalance of the dynamic pressure groove G1 may be formed in the direction opposite to the example shown in FIG. 3, that is, X1 <X2. Further, when it is not necessary to forcibly circulate the lubricating oil inside the bearing as described above, both the dynamic pressure grooves G1 and G2 may be formed symmetrically in the axial direction.

  Hereinafter, an embodiment of a method for assembling a hydrodynamic bearing device according to the present invention will be described with reference to FIG.

  First, as shown in FIG. 4A, the sleeve portion 8 and the shaft member 2 are accommodated on the inner periphery of the housing 7, and the lower end surface 8 c of the sleeve portion 8 and the lower end of the shaft member 2 are placed on the inner bottom surface 7 b 1 of the housing 7. The spherical convex portion 2d is brought into contact. In this state, the axial dimension of the large-diameter outer peripheral surface 2a of the shaft member 2 and the sleeve portion 8 is such that the shoulder surface 2c of the shaft member 2 is positioned above the upper end surface 8b of the sleeve portion 8 (housing opening side). Is designed in advance.

  Next, as shown in FIG. 4B, the seal portion 9 is inserted into the inner peripheral surface 7 a 1 of the housing 7 from above, and the lower end surface 9 b is brought into contact with the shoulder surface 2 c of the shaft member 2. Thereafter, as shown by an arrow in FIG. 4B, the shaft member 2 is pulled up with respect to the housing 7 so that the seal portion 9 engaged with the shoulder surface 2c of the shaft member 2 is removed from the axial gap L shown in FIG. Is moved upward with respect to the housing 7. In this state, the axial clearance L is set by fixing the seal portion 9 to the inner peripheral surface 7a1 of the housing 7. The seal portion 9 and the housing 7 are fixed by, for example, press-fitting. In this case, the positioning and fixing of the seal portion 9 are completed when the shaft member 2 is pulled up by a predetermined amount. At this time, if a lubricant is interposed between both the fitting surfaces, the seal portion 9 can be smoothly moved with respect to the housing 7, and the axial gap L can be set with higher accuracy. If an adhesive is used as the lubricant, in addition to the above effects, both fixing strengths can be increased. Further, after positioning the seal portion 9, it is formed by the air release side of the fitting surface between the seal portion 9 and the housing 7, that is, the outer peripheral chamfer on the upper end surface of the seal portion 9 and the inner peripheral surface 7a1 of the housing 7 in FIG. By adhering and sealing the annular space to be formed, it is possible to reliably prevent the lubricating fluid inside the bearing from leaking out from the fitting surface between the seal portion 9 and the housing 7.

  According to this method, the axial gap L, which is the allowable stroke amount of the shaft member 2, can be set with high accuracy by the lifting amount of the shaft member 2. That is, the stroke amount of the shaft member 2 can be directly managed not by the processing accuracy of the sleeve portion 8 but by the lift amount of the shaft member 2. Therefore, the stroke amount of the shaft member 2 can be managed with high accuracy, the processing accuracy of the sleeve portion 8 can be relaxed, and the manufacturing cost can be reduced.

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

FIG. 5 shows a method for positioning the seal portion 9 according to the reference example . First, as shown in FIG. 5A, the sleeve portion 8 and the shaft member 2 are accommodated in the inner periphery of the housing 7, and the seal portion 9 is moved to the reference position of the inner periphery of the housing 7 (for example, the upper end surface of the seal portion 9). 9c is arranged at a position that is flush with the upper end surface 7c of the housing 7. At this time, a gap larger than the axial gap L ″ shown in FIG. 2 is provided between the seal portion 9 and the sleeve portion 8.

  Next, the seal portion 9 is pushed downward by a predetermined amount. For example, as shown in FIG. 5B, the seal portion 9 is pushed downward (in the direction of the arrow) by the pushing member 10 having the base portion 10a and the cylindrical portion 10b. The base portion 10a is provided with a reference surface 10a1 that defines the amount of pushing, and the cylindrical portion 10b has an inner periphery fitted to the small-diameter outer peripheral surface 2b of the shaft member 2 and a lower end surface 10b1 that is an upper side of the seal portion 9. It becomes a pushing surface which pushes in the end surface 9c. Then, as shown in FIG. 5C, the pushing operation is completed when the reference surface 10 a 1 of the pushing member 10 comes into contact with the upper end portion 2 b 2 of the shaft member 2. In this case, when the axial dimension of the small-diameter outer peripheral surface 2b of the shaft member 2 is Y1, the axial distance between the reference surface 10a1 of the pushing member 10 and the pushing surface 10b1 is Y2, and the axial dimension of the seal portion 9 is Y3, The difference between Y1 and Y2 + Y3 is the axial gap L (L = Y1- (Y2 + Y3)). Therefore, the stroke amount of the shaft member 2 can be managed with high accuracy by setting Y1, Y2, and Y3 with high accuracy.

The configuration of the hydrodynamic bearing device to which the assembling method of the present invention is applied is not limited to the above . FIG. 6 shows a hydrodynamic bearing device 21 according to a reference example . In the above embodiment, the shaft member 2 is an integral product. However, in the hydrodynamic bearing device 21, the shaft member 2 is composed of a cylindrical shaft portion 20 and a sleeve portion 8. The shaft member 2 is formed by fixing the outer peripheral surface 20a of the shaft portion 20 and the inner peripheral surface 8a of the sleeve portion 8 by appropriate means such as press-fitting, bonding, and press-fitting adhesion. In this shaft member 2, the upper end surface 8 b of the sleeve portion 8 is the shoulder surface 2 c of the shaft member 2, the outer peripheral surface 8 d of the sleeve portion 8 is the large-diameter outer peripheral surface 2 a of the shaft member 2, and the outer peripheral surface 20 a of the shaft portion 20 is. The small-diameter outer peripheral surface 2 b of the shaft member 2 is configured, and the spherical convex portion 2 d is formed at the lower end portion of the shaft portion 20.

  On the large-diameter outer peripheral surface 2a of the shaft member 2 (the outer peripheral surface 8d of the sleeve portion 8), dynamic pressure grooves G1 and G2 serving as radial dynamic pressure generating portions are formed at two locations separated vertically (dotted line in FIG. 6). And a radial bearing gap is formed between the housing 7 and the inner peripheral surface 7a1. Further, an axial gap L serving as a stroke amount of the shaft member 2 is formed between the shoulder surface 2c of the shaft member 2 (the upper end surface 8b of the sleeve portion 8) and the lower end surface 9b of the seal portion 9 ( (See enlarged view of FIG. 6). An axial groove 8 a 1 is formed on the inner peripheral surface 8 a of the sleeve portion 8, and a communication path is formed with the outer peripheral surface 20 a of the shaft portion 20. This communication path is a space P formed on the closed side of the housing 7, more specifically, the spherical convex portion 2 d and the lower end surface 8 c of the sleeve portion 8 formed on the lower end portion of the shaft portion 20, and the inside of the housing 7. A space P formed between the bottom surface 7b1 and the seal space S is communicated.

  In this way, by configuring the shaft member 2 with the shaft portion 20 and the sleeve portion 8, the stepped processing as in the shaft member 2 shown in FIG. 2 is not required, so the processing cost of each member is reduced. can do. Further, by forming the large-diameter outer peripheral surface 2a of the shaft member 2 with the outer peripheral surface 8d of the sleeve portion 8, the radial bearing gap facing the large-diameter outer peripheral surface 2a is larger in diameter than the hydrodynamic bearing device 1 shown in FIG. Since the radial bearing portions R1 and R2 can be enlarged, the bearing performance in the radial direction can be improved.

FIG. 7 shows a hydrodynamic bearing device 31 according to a reference example . This hydrodynamic bearing device 1 differs from the embodiment shown in FIG. 7 in that the support in the thrust direction of the shaft member 2 is non-contact support. Specifically, a thrust bearing gap is formed between the lower end surface 8c of the sleeve portion 8 and the inner bottom surface 7b1 of the housing 7, and when the shaft member 2 rotates, the spiral shape formed on the lower end surface 8c of the sleeve portion 8 is formed. A dynamic pressure groove G3 having a step shape or the like generates a dynamic pressure action on the lubricating oil in the thrust bearing gap, thereby forming a thrust bearing portion T that directs the shaft member 2 in the thrust direction. In this case, the axial clearance L between the lower end surface 9b of the seal portion 9 and the shoulder surface 2c of the shaft member 2 (the upper end surface 8b of the sleeve portion 8) is larger than the thrust bearing clearance of the thrust bearing portion T. Is set as follows.

  As shown in FIGS. 6 and 7, when the shaft member 2 is composed of the shaft portion 20 and the sleeve portion 8, they are separately formed and fixed as described above, and the shaft portion 20 is used as an insert part. The part 8 may be molded. Thereby, the assembly process of the axial part 20 and the sleeve part 8 becomes unnecessary, and the manufacturing process of the axial member 2 can be simplified.

  In the embodiment shown in FIG. 2, the housing 7 and the sleeve portion 8 are formed separately, but they may be formed integrally. For example, if the housing 7 and the sleeve portion 8 are integrally formed by injection molding, the manufacturing process can be omitted, so that the cost can be reduced.

  Further, in the above embodiment, herringbone-shaped dynamic pressure grooves G1 and G2 are formed on the inner peripheral surface 8a of the sleeve portion 8 as a dynamic pressure generating portion for generating a dynamic pressure action on the lubricating fluid in the radial bearing gap. However, the present invention is not limited to this, and for example, a spiral dynamic pressure groove, a step bearing, or a multi-arc bearing may be employed. Alternatively, both the inner peripheral surface 8a of the sleeve portion 8 and the large-diameter outer peripheral surface 2a of the shaft member 2 may be formed into a cylindrical surface shape to constitute a so-called circular bearing.

  Further, in the above embodiment, the dynamic pressure grooves G1 and G2 are formed on the inner peripheral surface 8a of the sleeve portion 8, but the large-diameter outer peripheral surface 2a of the shaft member 2 facing this surface through a bearing gap is formed. A dynamic pressure groove may be formed.

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

  Further, in the above embodiment, the lubricating oil is exemplified as the fluid that fills the inside of the hydrodynamic bearing device 1 and generates the dynamic pressure action in the radial bearing gap. However, other than that, the dynamic pressure action can be generated in each bearing gap. A simple fluid such as a gas such as air, a magnetic fluid, or lubricating grease can also be used.

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

It is sectional drawing which shows the spindle motor for HDD incorporating the hydrodynamic bearing apparatus. It is sectional drawing of a hydrodynamic bearing apparatus. It is sectional drawing of a sleeve part. (A), (b) is sectional drawing which shows the assembly method concerning this invention. (A)-(c) is sectional drawing which shows the assembly method concerning a reference example . It is sectional drawing of the hydrodynamic bearing apparatus concerning a reference example . It is sectional drawing of the hydrodynamic bearing apparatus concerning a reference example .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid dynamic bearing apparatus 2 Shaft member 2a Large diameter outer peripheral surface 2b Small diameter outer peripheral surface 2c Shoulder surface 2d Spherical convex part 7 Housing 8 Sleeve part 9 Seal part L Axial direction gap G1, G2 Dynamic pressure groove R1, R2 Radial bearing part T Thrust Receiver (thrust bearing)
S Seal space

Claims (5)

A small diameter outer peripheral surface, a large diameter outer peripheral surface, a shoulder surface formed between them, a shaft member having a spherical convex portion formed at one end in the axial direction , a cylindrical side portion, and a side A housing having a bottom portion that closes one end of the shaft in the axial direction and that contacts and supports the spherical convex portion of the shaft member, and a sleeve that is provided on the inner periphery of the side portion of the housing and into which the shaft member is inserted A seal space that is fixed to the inner periphery of the housing and the small-diameter outer peripheral surface of the shaft member and prevents leakage of the lubricating fluid inside the bearing to the outside, and the shoulder surface of the shaft member and the axial direction A seal portion that engages with the shaft member to prevent the shaft member from coming off, and a radial bearing gap formed between the large-diameter outer peripheral surface of the shaft member and the inner peripheral surface of the sleeve portion. The axial gap between the seal part and the sleeve part is separated from the seal part and the shaft part. A method of assembling a large fluid bearing device than the axial clearance between the shoulder surface,
Housing a sleeve portion, a shaft member, and a seal portion on the inner periphery of the housing, bringing the spherical convex portion of the shaft member into contact with the bottom portion of the housing, and bringing the seal portion into contact with the shoulder surface of the shaft member; And a step of setting an axial clearance between the seal portion and the shoulder surface of the shaft member by moving the seal portion to the housing opening side on the shoulder surface of the shaft member. Assembly method.   The method of assembling a hydrodynamic bearing device according to claim 1, wherein a shaft member in which a small-diameter outer peripheral surface, a large-diameter outer peripheral surface, and a shoulder surface are integrally processed is used.   2. The method of assembling a hydrodynamic bearing device according to claim 1, wherein the seal portion is moved in a state in which a lubricant is interposed on a fitting surface between the seal portion and the housing. 4. The method for assembling a hydrodynamic bearing device according to claim 3 , wherein the lubricant is an adhesive.   2. The method of assembling a hydrodynamic bearing device according to claim 1, wherein after the seal portion is positioned, the atmosphere opening side of the fitting surface between the seal portion and the housing is bonded and sealed.

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