JP4738964B2 - Hydrodynamic bearing device and motor having the same - Google Patents

Description

  The present invention relates to a hydrodynamic bearing device.

  The hydrodynamic bearing device is a bearing device that supports a shaft member in a non-contact manner by a dynamic pressure action of a lubricating fluid generated in a bearing gap. This hydrodynamic bearing device has features such as high-speed rotation, high rotation accuracy, and low noise. Information equipment such as magnetic disk devices such as HDD and FDD, CD-ROM, CD-R / RW, DVD-ROM / Spindle motor for disk drive in optical disk device such as RAM, magneto-optical disk device such as MD, MO, etc., for small motor such as polygon scanner motor of laser beam printer (LBP), color wheel of projector, or axial fan It is suitable as.

  This type of fluid dynamic bearing includes a dynamic pressure bearing having a dynamic pressure generating means for generating a dynamic pressure in the lubricating oil in the bearing gap, and a so-called perfect bearing having no dynamic pressure generating means (the bearing surface is a perfect circle). The bearings are roughly classified into shapes.

For example, in a hydrodynamic bearing device incorporated in a spindle motor of a disk drive device such as an HDD, a radial bearing portion that rotatably supports a shaft member in a radial direction and a thrust bearing portion that supports the shaft member in a thrust direction are provided. As the radial bearing portion, a dynamic pressure bearing in which a dynamic pressure generating portion such as a dynamic pressure groove is provided on any one of two surfaces opposed via a radial bearing gap is used. As the thrust bearing portion, for example, a case where a dynamic pressure bearing in which a dynamic pressure generating portion is provided on both end surfaces of the flange portion of the shaft member or a surface facing the flange portion is used (for example, see Patent Document 1), a shaft A bearing (so-called pivot bearing) having a structure in which one end surface of the member is in contact with and supported may be used (see, for example, Patent Document 2).
JP 2002-61641 A Japanese Patent Laid-Open No. 11-191943

  In the above-described hydrodynamic bearing device, the demand for cost reduction has become more severe with the recent price reduction of information equipment. Therefore, as an example of means for reducing the cost of the hydrodynamic bearing device, an attempt has been made to replace a component of the hydrodynamic bearing device, such as a housing, from a metal machined product to a resin injection molded product. For example, the fluid bearing device is incorporated into the motor by inserting the outer periphery of the resin housing into the inner periphery of the bracket (holding member).

  By the way, when the housing is injection-molded with resin, no matter how accurately the mold operation is managed, the outer peripheral surface area of the housing corresponding to the mold mating surface is used as a trace of the mold mating surface. A parting line is formed. The parting line has a protruding shape formed in an annular shape on the outer peripheral surface of the housing, and many of them appear as burrs. If this parting line is present on the fixed surface with the holding member, when inserted into the holding member (when incorporated in the motor), it interferes with the inner peripheral surface of the holding member, causing contamination. A spindle motor for a disk device may cause a head crash. Moreover, there is a possibility that the fixing strength with the holding member is lowered. In this case, finishing may be performed after injection molding to remove the parting line, but complete removal is difficult, and if complete removal is desired, the processing cost increases as the number of processes increases. To do.

  An object of the present invention is to provide a hydrodynamic bearing device capable of avoiding contamination that adversely affects motor performance.

In order to achieve the above object, a hydrodynamic bearing device of the present invention holds a shaft member, a molded outer cylinder, and a partial area in the axial direction of the outer peripheral surface of the outer cylindrical body by a cylindrical inner peripheral surface. A holding member and a radial bearing portion that is disposed inside the outer cylindrical body and supports the shaft member in a radial direction in a radial direction with a fluid lubricating film formed in the radial bearing gap . the outer peripheral surface, a region which is fixed to the holding member, is characterized in that it has an axial spaced apart is formed by an annular parting line from this region. The “outer cylinder” referred to in the present invention is, for example, formed separately from a bearing sleeve into which a shaft member can be inserted on the inner periphery, and in addition to a housing that covers the outer periphery of the bearing sleeve, Examples thereof include a member (bearing member) integrally formed with the housing.

  According to the configuration of the present invention, since the fixing region with the holding member on the outer peripheral surface of the outer cylindrical body is a mold forming surface, if the mold is finished with high accuracy, of the outer peripheral surface of the outer cylindrical body, The fixed region with the holding member can be a smooth smooth surface. For this reason, it is possible to prevent the occurrence of contamination that becomes a problem during insertion into the holding member without performing removal processing of the parting line. Further, in this case, the fixing accuracy and fixing strength of the outer cylindrical body with respect to the holding member can be improved.

  In addition to the above-described configuration, in the hydrodynamic bearing device having a configuration in which a hub portion projecting from one end of the shaft member to the outer diameter side is provided, the hub portion is opposed to the outer cylinder body through a minute gap of about several tens to several hundreds of μm. For example, a labyrinth seal may be formed between the hub portion and the outer cylinder. At this time, if the parting line of the outer cylinder exists in a region facing the hub part, the parting line may interfere with the hub part when the shaft member is rotated, which may cause contamination. For this reason, it is desirable that the parting line of the outer cylindrical body is provided in a region excluding the surface facing the hub portion.

  The outer peripheral surface of the outer cylindrical body may form a seal space filled with a lubricating fluid (for example, lubricating oil) between the outer peripheral surface and the inner peripheral surface of a member facing the outer cylindrical surface. At this time, if the parting line of the outer cylindrical body is present in the region serving as the seal space, foreign matter (contamination) may be directly mixed into the lubricating oil filled in the seal space, leading to a decrease in bearing performance. Therefore, it is desirable that the parting line of the outer cylinder is provided in a region other than the seal space filled with the lubricating fluid.

  The parting line described above can be removed by performing removal processing such as cutting and polishing after the outer cylindrical body is formed unless there is a particular problem in cost. If the parting line is in the fixed area with the holding member, the internal structure with the filler will appear on the surface even if removal processing is performed, so the filler will fall off due to sliding contact during insertion into the holding member. However, this may cause contamination, but if the parting line removal processing surface exists on a surface other than the fixing surface with the holding member, the region facing the hub, or the formation surface of the seal space, The problem can be avoided.

  The hydrodynamic bearing device having the above configuration can be preferably used for a motor having a rotor magnet and a stator coil, for example, a spindle motor for a disk device such as an HDD.

  From the above, according to the present invention, it is possible to provide a hydrodynamic bearing device capable of preventing the occurrence of contamination that adversely affects motor performance.

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

  FIG. 1 shows a configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device 1 according to the present invention. This spindle motor is used for a disk drive device such as an HDD, and has a hydrodynamic bearing device 1 and a disk hub 3 as a hub portion attached to a shaft member 2 of the hydrodynamic bearing device 1, for example, a gap in the radial direction. And a holding member 6 as a member for holding the housing 7 of the hydrodynamic bearing device 1. The stator coil 4 is attached to the outer periphery of the holding member 6, and the rotor magnet 5 is attached to the inner periphery of the disk hub 3. The disk hub 3 holds one or more disks D such as magnetic disks on the outer periphery thereof. Further, a housing 7 is attached to the inner periphery of the holding member 6, whereby the hydrodynamic bearing device 1 is fixed to the holding member 6. When the stator coil 4 is energized, the rotor magnet 5 is rotated by electromagnetic force generated between the stator coil 4 and the rotor magnet 5, and accordingly, the disk hub 3 and the shaft member 2 are rotated together.

  FIG. 2 is an enlarged cross-sectional view showing an example of the hydrodynamic bearing device 1 used in the spindle motor. The hydrodynamic bearing device 1 includes a shaft member 2 having a shaft portion 2a at the center of rotation, a bearing sleeve 8 into which the shaft portion 2a can be inserted into the inner periphery, and an outer cylinder that fixes the bearing sleeve 8 to the inner periphery. A housing 7 and a seal member 9 that seals one end opening of the housing 7 are provided as main components. In the following description, for convenience of explanation, the description will be made with the side sealed by the seal member 9 as the upper side and the opposite side in the axial direction as the lower side.

  In the hydrodynamic bearing device 1 shown in the figure, a first radial bearing portion R1 and a second radial bearing portion R2 are connected between an inner peripheral surface 8a of the bearing sleeve 8 and an outer peripheral surface 2a1 of the shaft portion 2a of the shaft member 2. They are spaced apart in the direction. A first thrust bearing portion T1 is provided between the lower end surface 8b of the bearing sleeve 8 and the upper end surface 2b1 of the flange portion 2b of the shaft member 2, and the inner bottom surface 7b1 of the bottom portion 7b of the housing 7 and the flange portion 2b A second thrust bearing portion T2 is provided between the lower end surface 2b2.

  The shaft member 2 is made of, for example, a metal material such as stainless steel, and includes a shaft portion 2a and a flange portion 2b provided at one end of the shaft portion 2a. Or it can also be set as the hybrid structure (For example, the shaft part 2a is formed with a metal material, and the flange part 2b is formed with a resin material) which consists of a metal part and a resin part.

  The bearing sleeve 8 is formed in a cylindrical shape and is fixed to the inner peripheral surface of the housing 7. The bearing sleeve 8 in this embodiment is formed of a porous body made of sintered metal, particularly a sintered metal porous body mainly composed of copper. Note that the bearing sleeve 8 can be formed not only of sintered metal but also of soft metal such as brass.

  On the inner peripheral surface 8a of the bearing sleeve 8, as shown in FIG. 3A, two upper and lower regions serving as the radial bearing surfaces A of the first radial bearing portion R1 and the second radial bearing portion R2 are separated in the axial direction. Is provided. On each radial bearing surface A, for example, herringbone-shaped dynamic pressure grooves 8a1 and 8a2 are formed as dynamic pressure generating portions. 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 axial dimension X1 of the upper region is lower than the axial center m. It is larger than the axial dimension X2 of the side region. Therefore, when the shaft member 2 rotates, the drawing force (pumping force) of the fluid (for example, lubricating oil) by the upper dynamic pressure groove 8a1 is relatively larger than that of the lower symmetrical dynamic pressure groove 8a2.

  Further, a thrust bearing surface B of the first thrust bearing portion T1 is formed in a partial annular region of the lower end surface 8b of the bearing sleeve 8, and the thrust bearing surface B is formed as shown in FIG. 3 (b). As the dynamic pressure generating portion, for example, a plurality of dynamic pressure grooves 8b1 arranged in a spiral shape are formed.

  The housing 7 is formed in a bottomed cylindrical shape, and includes a cylindrical side portion 7a and a bottom portion 7b provided integrally or separately at the lower end of the side portion 7a (in this embodiment, an integral structure). Further, a stepped portion 7c is integrally formed at a position away from the inner bottom surface 7b1 in the axial direction by a predetermined dimension. When the hydrodynamic bearing device 1 is assembled, the bearing sleeve 8 is positioned relative to the housing 7 by bringing the lower end face 8b of the bearing sleeve 8 into contact with the stepped portion 7c. A flange portion 2b of the shaft member 2 is accommodated in a space formed between the lower end surface 8b of the bearing sleeve 8 and the inner bottom surface 7b1 of the housing 7.

  A thrust bearing surface C of the second thrust bearing portion T2 is formed in a partial annular region of the inner bottom surface 7b1 of the bottom portion 7b, and the thrust bearing surface C is arranged in a spiral shape, for example, as a dynamic pressure generating portion. A plurality of dynamic pressure grooves are formed (not shown).

  The housing 7 in the present embodiment is, for example, a molded product that is injection-molded with resin using a mold that can be divided in the axial direction. As shown in the enlarged sectional view of FIG. 2, a parting line 11 is formed on the outer peripheral surface 7 a 1 of the housing 7 as a trace of the mating surface of the mold. The parting line 11 excludes a region facing the inner peripheral surface 6a of the holding member 6 that holds the outer peripheral surface 7a1 of the housing 7 and the inner peripheral surface 3b1 of the cylindrical portion 3b of the disc hub 3 when assembled into the motor. In the axial direction α, the entire circumference is projected. The parting line 11 in the illustrated example shows a state as it is after molding, that is, a state where burrs formed on the mating surfaces of the molds remain as they are.

  The resin material forming the housing 7 can be used regardless of amorphous resin or crystalline resin as long as it is a resin material that can be injection-molded. For example, as the amorphous resin, polysulfone (PSU), polyethersulfone ( Liquid crystalline polymer (LCP), polyetheretherketone (PEEK), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS) as crystalline resins such as PES), polyphenylsulfone (PPSU), polyetherimide (PEI) Etc. can be used. Of course, these are only examples, and other resin materials suitable for the application and use environment of the bearing can also be used. One or more kinds of various fillers such as a reinforcing material (fibrous, powdery form, etc.), a lubricant, and a conductive material are blended in the resin material as necessary.

  In addition, as a material to be injected, a metal material can be used in addition to a resin material. As the metal material, for example, a low melting point metal material such as a magnesium alloy or an aluminum alloy can be used. In addition, so-called MIM molding may be employed in which after the injection molding with a mixture of metal powder and binder, degreasing and sintering. In addition, ceramic can also be used as the material to be injected.

  An annular seal member 9 formed of a metal material or a resin material is fixed to the inner periphery of the upper end opening of the housing 7 by, for example, press fitting, bonding, or a combination thereof. The inner peripheral surface 9a of the seal member 9 is opposed to the tapered surface 2a2 provided on the outer peripheral surface 2a1 of the shaft portion 2a via the seal space S. The tapered surface 2a2 of the shaft portion 2a is gradually reduced in diameter toward the upper side, and functions as a centrifugal force seal by the rotation of the shaft member 2. After assembly of the hydrodynamic bearing device, the internal space of the hydrodynamic bearing device 1 sealed with the seal member 9 is filled with, for example, lubricating oil as a lubricating fluid. In this state, the oil level of the lubricating oil is within the range of the sealing space S. Maintained.

  In the hydrodynamic bearing device 1 having the above-described configuration, when the shaft member 2 rotates, the upper and lower two regions serving as the radial bearing surface A of the inner peripheral surface 8a of the bearing sleeve 8 each have a radial bearing gap between the outer peripheral surface 2a1 of the shaft portion 2a. Opposite through. As the shaft member 2 rotates, the oil film rigidity of the lubricating film formed in the radial bearing gap is increased by the dynamic pressure action of the dynamic pressure groove formed in the radial bearing surface A, thereby causing the shaft member 2 to move in the radial direction. A first radial bearing portion R1 and a second radial bearing portion R2 that are rotatably supported in a non-contact manner are formed.

  When the shaft member 2 rotates, the upper end surface 2b1 of the flange portion 2b of the shaft member 2 faces the thrust bearing surface B formed on the lower end surface 8b of the bearing sleeve 8 via the thrust bearing gap. As the shaft member 2 rotates, the oil film rigidity of the lubricating film formed in the thrust bearing gap is increased by the dynamic pressure action of the dynamic pressure groove formed in the thrust bearing surface B, thereby moving the shaft member 2 in the thrust direction. A first thrust bearing portion T1 that is rotatably supported in a non-contact manner is formed. Similarly, the lower end surface 2b2 of the flange portion 2b faces the thrust bearing surface C formed on the inner bottom surface 7b1 of the bottom portion 7b of the housing 7 via a thrust bearing gap. As the shaft member 2 rotates, the oil film rigidity of the lubricating film formed in the thrust bearing gap is increased by the dynamic pressure action of the dynamic pressure groove formed on the thrust bearing surface C, thereby rotating the shaft member 2 in the thrust direction. A second thrust bearing portion T2 that is freely contactlessly supported is formed.

  During the rotation of the shaft member 2, since the lubricating oil is pushed into the bottom 7b of the housing 7, the pressure in the thrust bearing gap between the thrust bearing portions T1 and T2 increases extremely, and the lubrication occurs due to this. There is concern about the generation of bubbles in oil, leakage of lubricating oil, or generation of vibration. Even in this case, for example, as shown in the figure, if a flow path 10 that communicates the thrust bearing gap (particularly the thrust bearing gap of the first thrust bearing portion T1) and the seal space S is provided, the flow path 10 passes through. Since the lubricating oil flows between the thrust bearing gap and the seal space S, the pressure difference is eliminated at an early stage, and the above-described adverse effects can be prevented. In FIG. 2, as an example, the axial groove 10a on the outer peripheral surface 8d of the bearing sleeve 8, the first radial groove 10b on the lower end surface 9b of the seal member 9, the annular groove 10c on the upper end surface 8c of the bearing sleeve 8, and the bearing sleeve. The flow path 10 was constituted by the second radial groove 10d of the upper end surface 8c of the eighth. In this case, the path of the thrust bearing gap of the first thrust bearing portion T1 → the axial groove 10a → the first radial groove 10b → the annular groove 10c → the second radial groove 10d → the radial bearing gap of the first radial bearing portion R1. The lubricating oil circulates inside the bearing.

  The hydrodynamic bearing device 1 composed of the above components and elements is incorporated in a motor (see FIG. 1). For example, the hydrodynamic bearing device 1 is incorporated into the motor by inserting or press-fitting the hydrodynamic bearing device 1 from above the holding member 6 in a state where the holding member 6 is set in a metal mold. This is performed by adhering the direction area to the inner peripheral surface 6 a of the holding member 6.

Further, when the motor is assembled, the disk hub 3 for mounting the disk D (see FIG. 1) is fixed to the upper end of the shaft member 2 by means such as press-fitting, bonding, or press-fitting adhesion. The disk hub 3 in the present embodiment includes a substantially disc-shaped plate portion 3a covering the upper side of the housing 7, a cylindrical cylindrical portion 3b extending axially downward from the outer periphery of the plate portion 3a, and an outer periphery at the lower end of the cylindrical portion 3b. And a disk mounting portion 3c provided so as to protrude from the outer diameter side. The disc D is fitted on the outer periphery of the cylindrical portion 3b and placed on the upper end surface of the disc mounting portion 3c.
In a state of being fixed to the shaft member 2, the lower end surface 3 a 1 of the plate portion 3 a of the disk hub 3 faces the upper end surface of the housing 7 through a minute axial gap (about several tens to several hundreds of μm), Further, the inner peripheral surface 3b1 of the cylindrical portion 3b is opposed to a partial axial direction region of the outer peripheral surface 7a1 of the housing 7 through a minute radial gap (about several tens to several hundreds μm). A labyrinth seal is formed by the radial and axial gaps having a very small width formed between the disk hub 3 and the housing 7, and the sealing function of the hydrodynamic bearing device 1 is further enhanced.

  As described above, in the present invention, the parting line 11 as the trace of the mating surface of the mold for molding the housing 7 is used as the inner peripheral surface 6 a of the holding member 6 and the inner peripheral surface of the disk hub 3. It provided in the axial direction area | region (alpha) except the area | region facing the surface 3b1. Therefore, in the outer peripheral surface of the housing 7, the fixing region with the motor (holding member 6) and the region facing the disk hub 3 can be a mold forming surface, that is, a smooth smooth surface. For this reason, it is possible to prevent the parting line 11 from interfering with other members during assembly into the motor and during operation without preventing the parting line 11 from being removed. Can do. Further, the accuracy and strength of fixing the housing 7 to the holding member 6 can be improved.

  In the above description, the configuration in which the parting line 11 is left as it is after molding the housing 7 has been described. However, the parting line 11 is removed by performing removal processing such as cutting and polishing after the housing 7 is molded. May be. When the removal process is performed, the internal structure of the housing 7 having the filler appears on the surface, which may cause contamination, but in the present invention, the parting line 11 is connected to the holding member 6 on the outer peripheral surface of the housing. This kind of problem can be avoided because it is provided in the axial region α excluding the region facing the inner peripheral surface 6a and the inner peripheral surface 3b1 of the disk hub 3.

  As mentioned above, although one Embodiment of the hydrodynamic bearing apparatus 1 which has a structure of this invention was described, this invention is not limited to the hydrodynamic bearing apparatus of this embodiment, For example, as shown in FIGS. It can be preferably used also in a hydrodynamic bearing device. In the following description, members and elements having the same functions as those in the embodiment shown in FIG.

FIG. 4 shows another embodiment of the hydrodynamic bearing device 1 according to the present invention. The hydrodynamic bearing device 1 shown in FIG. 1 mainly includes a bearing sleeve 8 and a housing 7 which are separate from each other in FIG. 2, and a lower end opening of the integrally formed member (bearing member 17). 2 is different from the hydrodynamic bearing device 1 shown in FIG. 2 in that it is sealed with a bearing member 17 and a separate lid member 18. The radial bearing portions R1 and R2 are formed between the inner peripheral surface 17a of the bearing member 17 and the outer peripheral surface 2a1 of the shaft member 2, and the first thrust bearing portion T1 includes a lower end surface 17b and an upper end surface 2b1 of the flange portion 2b. The second thrust bearing portion T2 is formed between the upper end surface 18a of the lid member 18 and the lower end surface 2b2 of the flange portion 2b.
The bearing member 17 in the present embodiment is a molded product like the housing 7 of FIG. 2, and the parting line 11 as a trace of the mating surface of the mold for molding the bearing member 17 is the outer periphery of the bearing member 17. Of the surface 17 d, the surface 17 d is provided in an axial region α excluding a region facing the inner peripheral surface 6 a of the holding member 6 and the inner peripheral surface 3 b 1 of the disc hub 3. Therefore, the same operation and effect as described above can be obtained.

  FIG. 5 shows another embodiment of the hydrodynamic bearing device 1 according to the present invention. The hydrodynamic bearing device 1 shown in the figure differs from the hydrodynamic bearing device 1 shown in FIG. 2 in that the step 7c of the housing 7 is deleted. In this case, as compared with the hydrodynamic bearing device 1 having the configuration shown in FIG. 2, the support area in the thrust bearing portions T <b> 1 and T <b> 2 can be expanded, and the load capacity for the moment load in the thrust bearing portion can be improved. Although not shown in the figure, in this embodiment as well, as in the embodiment shown in FIG. 4, the housing 7 and the bearing sleeve 8 are constituted by an integral bearing member 17 except for the bottom portion 7 c, and the lower end opening of the bearing member 17 is formed. It can also be set as the structure which seals a part with the cover member 18 of another body.

FIG. 6 shows another embodiment of the hydrodynamic bearing device according to the present invention. In the hydrodynamic bearing device 21 shown in the figure, unlike the hydrodynamic bearing device 1 shown in FIGS. 2, 4, and 5, the inner peripheral surface 33 b 1 of the disk hub 33 in which the seal space S is formed integrally with the shaft member 2 and the housing. 7 and the second thrust bearing portion T2 are formed between the lower end surface 33a1 of the disk hub 33 and the upper end surface 7a2 of the housing 7.
In the present embodiment, the parting line 11 of the housing 7 is a fixed surface to the holding member 6 and the tapered surface 7a11 that forms the seal space S between the outer peripheral surface 7a1 and the inner peripheral surface 33b1 of the disk hub 33. 7a12 is provided within the range of the axial region α. Therefore, in addition to preventing the occurrence of contamination, which is a problem when the hydrodynamic bearing device 21 (housing 7) is inserted into the holding member 6, and ensuring the fixing accuracy and fixing strength, the seal space filled with lubricating oil. It is possible to prevent foreign matters from entering S. Although illustration is omitted, also in the present embodiment, the housing 7 and the bearing sleeve 8 can be constituted by an integral bearing member 17 as in the embodiment shown in FIG.

  In the above description, the radial bearing portions R1 and R2 and the thrust bearing portions T1 and T2 have exemplified the configuration in which the fluid dynamic pressure action is generated by the herringbone shape or spiral shape dynamic pressure grooves. However, the present invention is not limited to this. For example, so-called multi-arc bearings or step bearings may be adopted as the radial bearing portions R1 and R2.

  FIG. 7 shows an example of a case where one or both of the radial bearing portions R1 and R2 are constituted by multi-arc bearings. In this example, the region that becomes the radial bearing surface of the inner peripheral surface 8a of the bearing sleeve 8 is configured by three arc surfaces 8a3, 8a4, and 8a5 (so-called three arc bearings). The centers of curvature of the three arcuate surfaces 8a3, 8a4, 8a5 are offset from the axial center O of the bearing sleeve 8 by an equal distance. In each region defined by the three arcuate surfaces 8a3, 8a4, and 8a5, the radial bearing gap has a shape that is gradually reduced in a wedge shape in both circumferential directions. For this reason, when the bearing sleeve 8 and the shaft portion 2a rotate relative to each other, the lubricating fluid in the radial bearing gap is pushed into the minimum gap side reduced in a wedge shape in accordance with the direction of the relative rotation, and the pressure rises. The bearing sleeve 8 and the shaft portion 2a are supported in a non-contact manner by the dynamic pressure action of the lubricating fluid. A deeper axial groove called a separation groove may be formed at the boundary between the three arcuate surfaces 8a3, 8a4, 8a5.

  FIG. 8 shows another example in the case where one or both of the radial bearing portions R1 and R2 are constituted by multi-arc bearings. In this example as well, the region that becomes the radial bearing surface of the inner peripheral surface 8a of the bearing sleeve 8 is configured by three arc surfaces 8a6, 8a7, and 8a8 (so-called three arc bearings), but the three arc surfaces 8a6, In each region divided by 8a7 and 8a8, the radial bearing gap has a shape gradually reduced in a wedge shape with respect to one direction in the circumferential direction. The multi-arc bearing having such a configuration may be referred to as a taper bearing. Further, deeper axial grooves 8a9, 8a10, 8a11 called separation grooves are formed at boundaries between the three arcuate surfaces 8a6, 8a7, 8a8. Therefore, when the bearing sleeve 8 and the shaft portion 2a are relatively rotated in a predetermined direction, the lubricating fluid in the radial bearing gap is pushed into the minimum gap side reduced in a wedge shape, and the pressure rises. The bearing sleeve 8 and the shaft portion 2a are supported in a non-contact manner by the dynamic pressure action of the lubricating fluid.

  FIG. 9 shows another example in the case where one or both of the radial bearing portions R1 and R2 are configured by multi-arc bearings. In this example, in the configuration shown in FIG. 8, the predetermined regions θ on the minimum gap side of the three circular arc surfaces 8 a 6, 8 a 7, 8 a 8 are each configured by concentric arcs with the axis O of the bearing sleeve 8 as the center of curvature. ing. Therefore, in each predetermined area θ, the radial bearing gap (minimum gap) is constant. The multi-arc bearing having such a configuration may be referred to as a tapered flat bearing.

  The multi-arc bearings in the above examples are so-called three-arc bearings, but are not limited to this, and so-called four-arc bearings, five-arc bearings, and multi-arc bearings composed of more than six arc surfaces are adopted. You may do it. Further, when the radial bearing portion is constituted by a multi-arc bearing, in addition to the configuration in which two radial bearing portions are provided apart from each other in the axial direction as in the radial bearing portions R1 and R2, the inner peripheral surface of the bearing sleeve 8 is provided. It is good also as a structure which provided the one radial bearing part over the up-and-down area | region of 8a.

  Note that one or both of the radial bearing portions R1 and R2 may be configured by step bearings (not shown). In the step bearing, for example, a plurality of axial groove-shaped dynamic pressure grooves are provided at predetermined intervals in the circumferential direction in a region serving as a radial bearing surface of the inner peripheral surface 8 a of the bearing sleeve 8.

  Although the case where both the radial bearing portions R1 and R2 are configured by dynamic pressure bearings has been described above, one or both of the radial bearing portions R1 and R2 can also be configured by other bearings. For example, although not shown, the outer peripheral surface 2a1 of the shaft member 2 is formed into a perfect circular outer peripheral surface, and the inner peripheral surface 8a of the bearing sleeve 8 facing the outer peripheral surface 2a1 of the shaft member 2 is formed into a perfect circular inner periphery. By using the surface, a so-called perfect circle bearing can be configured.

  Although illustration is omitted, one or both of the thrust bearing portions T1 and T2 is provided with a plurality of radial groove-shaped dynamic pressure grooves at predetermined intervals in the circumferential direction, for example, in a region serving as a thrust bearing surface. Further, it can be constituted by a so-called step bearing, a so-called wave bearing (the step mold is a wave form), or the like.

  Further, the thrust bearing portion may be a pivot bearing in which, for example, one end of the shaft portion 2a is formed in a convex spherical shape and is in contact with and supported by the inner bottom surface of the housing, in addition to the dynamic bearing.

  In the above description, the lubricating oil is exemplified as the lubricating fluid that fills the inside of the hydrodynamic bearing device 1, but other fluids that can generate dynamic pressure in each bearing gap, such as magnetic fluid and air, are also exemplified. A gas such as can also be used.

It is sectional drawing which shows an example of the spindle motor incorporating the hydrodynamic bearing apparatus. It is sectional drawing of the hydrodynamic bearing apparatus which has a structure of this invention. (A) is a sectional view of the bearing sleeve, and (b) is a plan view showing a lower end surface of the bearing sleeve. It is sectional drawing which shows the other structural example of a hydrodynamic bearing apparatus. It is sectional drawing which shows the other structural example of a hydrodynamic bearing apparatus. It is sectional drawing which shows the other structural example of a hydrodynamic bearing apparatus. It is sectional drawing which shows the other form of a radial bearing part. It is sectional drawing which shows the other form of a radial bearing part. It is sectional drawing which shows the other form of a radial bearing part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid dynamic bearing apparatus 2 Shaft member 2a Shaft part 3 Disc hub 6 Holding member 7 Housing 7a Side part 7b Bottom part 8 Bearing sleeve 9 Seal member 11 Parting line 17 Bearing member alpha axial direction area | region R1 1st radial bearing part R2 2nd radial Bearing portion S Seal space T1 First thrust bearing portion T2 Second thrust bearing portion

Claims (5)

A shaft member, a molded outer cylinder, a holding member that holds a partial area in the axial direction of the outer peripheral surface of the outer cylinder with a cylindrical inner peripheral surface, and a radial bearing disposed inside the outer cylinder In a hydrodynamic bearing device including a radial bearing portion that non-contact supports a shaft member in a radial direction with a lubricating film of a lubricating fluid formed in a gap,
The outer peripheral surface of the outer cylinder body, and a region which is fixed to the holding member, the fluid bearing apparatus characterized by having a parting line of the annular formed spaced apart from the region in the axial direction.   The shaft member further includes a hub portion projecting from one end of the shaft member to the outer diameter side and having a surface facing the outer cylindrical body, and the parting line is provided except for a region facing the surface facing. The hydrodynamic bearing device according to claim 1.   2. The hydrodynamic bearing device according to claim 1, wherein the parting line is provided in a region other than the seal space filled with the lubricating fluid.   The hydrodynamic bearing device according to claim 1, wherein a parting line removal process is performed on the outer cylindrical body.   A motor comprising the hydrodynamic bearing device according to claim 1, a rotor magnet, and a stator coil.

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