JP4808457B2 - Hydrodynamic bearing device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a hydrodynamic bearing device that supports a shaft member with a lubricating film of fluid generated in a radial bearing gap, and a manufacturing method thereof. This bearing device is a spindle motor such as an information device, for example, a magnetic disk device such as an HDD, an optical disk device such as a CD-ROM, CD-R / RW, DVD-ROM / RAM, or a magneto-optical disk device such as MD or MO, It is suitable for polygon scanner motors of laser beam printers (LBP) and other small motors.

  In addition to high rotational accuracy, the various motors are required to have high speed, low cost, low noise, and the like. One of the components that determine the required performance is a bearing that supports the spindle of the motor. In recent years, the use of a fluid bearing having characteristics excellent in the required performance has been studied or actually used. .

  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 supports a shaft member in a non-contact manner in a radial direction and a shaft member is supported in a non-contact manner in a thrust direction. A thrust bearing portion is provided, and a bearing (dynamic pressure bearing) in which a groove (dynamic pressure groove) for generating dynamic pressure is provided on the inner peripheral surface of the bearing sleeve or the outer peripheral surface of the shaft member is used as the radial bearing portion. As the thrust bearing portion, for example, a dynamic pressure bearing in which dynamic pressure grooves are 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). Alternatively, a bearing having a structure in which one end surface of the shaft member is in contact with and supported by the thrust member (so-called pivot bearing) may be used as the thrust bearing portion (see, for example, Patent Document 2).

This type of hydrodynamic bearing device is composed of parts such as a housing, a bearing sleeve, and a shaft member. In order to ensure the high bearing performance required as the performance of information equipment increases, the processing accuracy of each part and Efforts are being made to increase assembly accuracy. On the other hand, along with the trend of lowering the price of information equipment, the demand for cost reduction for this type of hydrodynamic bearing device has become increasingly severe.
JP 2002-61641 A Japanese Patent Laid-Open No. 11-191943

  As a means for reducing the cost of this type of hydrodynamic bearing device, it is conceivable to mold the housing with a resin material (injection molding). In the resin injection molding, a gate for filling a molten resin in a cavity of a molding die is provided, and the molten resin is injected into the cavity from this gate. Then, after the molten resin in the cavity is cooled and solidified, the molded product (housing) is taken out by opening the mold. In the state before the mold opening, the molded product is connected to the gate resin part formed in the gate. However, when the mold is opened, the gate resin part is divided and a part of the gate resin part is gated. It remains on the molded product side as a mark.

  However, when the mold is opened, the gate resin part is divided as if it were torn off, so that the part of the gate trace remaining on the molded product side as a part of the gate resin part is a rough divided section having sharp irregularities. For example, when the resin material contains a filler such as a fiber, the filler is partially exposed. In this case, the filler and other foreign matters are easily removed from the gate trace of the housing. The dropped filler or the like adheres to the surface of the housing or the like, and may be mixed as contamination in the lubricating oil filled in the bearing device when the bearing device is assembled.

  An object of the present invention is to suppress the occurrence of contamination from the housing in this type of hydrodynamic bearing device and maintain the cleanliness inside or around the bearing device at a high level.

In order to solve the above problems, a hydrodynamic bearing device according to the present invention includes a housing, a bearing sleeve disposed inside the housing, a shaft member inserted into the inner circumferential surface of the bearing sleeve, and an inner circumferential surface of the bearing sleeve. And a radial bearing portion for supporting the shaft member in a non-contact manner in the radial direction with a lubricating film of a fluid generated in a radial bearing gap between the shaft member and the outer peripheral surface of the shaft member, wherein the housing is an injection molding of a resin containing a filler The protrusion of the divided part formed at the tip of the gate mark of the housing is pushed down, and the divided section is covered with the pushed-down protrusion .

  In this way, if the gate trace remaining in the housing after injection molding is molded, the sharp surface irregularities of the gate trace dividing portion are smoothed. That is, of the surface unevenness of the divided portion, the convex portion is plastically pushed down by the pressure at the time of molding, so that the surface unevenness of the gate trace is leveled. In addition, the divided section is covered by the pushed-down convex portion, and the divided section itself is prevented from being exposed. Accordingly, it is possible to prevent the filler and other foreign matters (hereinafter referred to as “filler etc.”) from dropping from the gate mark. The gate trace can be formed, for example, by pressing a jig against the gate trace.

  As the surface shape of the gate mark after molding, a convex curved surface, for example, a partially convex spherical surface is conceivable. This shape is obtained, for example, by using a molding jig formed in a partially concave spherical shape. If this jig is pressed against the gate trace, the convex part of the gate trace splitting part is guided by the concave molding surface of the jig and pushed down along the inclination direction of the molding surface. Can be given. Therefore, the smoothness of the gate trace surface is increased.

In order to solve the above problems, a method for manufacturing a hydrodynamic bearing device according to the present invention includes a housing, a bearing sleeve disposed inside the housing, a shaft member inserted into the inner peripheral surface of the bearing sleeve, and a bearing. Provided is a method of manufacturing 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 fluid generated in a radial bearing gap between an inner peripheral surface of the sleeve and an outer peripheral surface of the shaft member After the housing is injection-molded with a resin material containing a filler and released from the mold , the protruding portion of the divided portion formed at the tip of the gate mark is pushed down with a jig to cover the divided section. It is characterized by.

  If the jig is rotated when forming the gate trace with the jig, the convex part of the cross section of the gate trace is pushed and bent while receiving the force in the rotating direction with the frictional force between the molding surface of the jig, More regularity can be provided depending on the direction in which the protrusions fall. Further, since the resin component is softened by the frictional heat at that time, it is easier to push and bend the convex portion.

  For the reasons described above, the gate trace of the housing is preferably molded, but it is further preferable that the periphery of the gate trace is molded. According to such a configuration, for example, when forming the gate trace, even if the meat of the gate trace (particularly the meat of the divided section) is pushed out by the molding pressure, the divided section cannot be completely formed. By molding the periphery of the gate mark, it is possible to more reliably prevent the filler from falling off.

  The housing having the above-described configuration can be obtained, for example, by molding with a jig provided with a first molding surface for molding the gate trace and a second molding surface for molding the periphery of the gate trace.

In order to solve the above problems, a hydrodynamic bearing device according to the present invention includes a housing integrally having a bottom portion, a bearing sleeve disposed inside the housing, and a shaft member inserted into an inner peripheral surface of the bearing sleeve. A hydrodynamic bearing device including a radial bearing portion that non-contact-supports the shaft member in a radial direction by a fluid pressure generated in a radial bearing gap between the inner circumferential surface of the bearing sleeve and the outer circumferential surface of the shaft member. A resin injection-molded product with a hollow at the bottom of the housing, a gate mark is formed on the bottom of the hollow, and a split portion is formed at the tip of the gate mark. By filling, the entire gate trace including the divided portion is covered with a covering material.

  In such a configuration, since the gate trace is sealed to the outside, it is possible to prevent the filler contained in the resin from falling off the gate trace. Filler that has already fallen off the gate trace before the coating material is supplied is captured by the coating material by the subsequent supply of the coating material, so that dissipation can be prevented. Even when the gate mark is not completely covered and a part of the filler protrudes from the surface of the covering material, the base of the protruding portion is constrained by the covering material, so that it can be prevented from falling off.

  When the housing has a bottomed cylindrical shape, it is preferable to have a gate mark on the axis of the bottom. When the gate mark is formed in this way, the gate for injection into the cavity is located at a position corresponding to the axial center (center) of the end surface of the housing bottom of the molding die (dot gate), The number of gates is one. Therefore, if the gate is provided as described above, the molten resin fed into the cavity through the gate spreads uniformly in the radial direction from the center of the bottom, and the inside of the cavity is uniformly made of molten resin. Filled. Therefore, it is possible to stably obtain a molded product with improved dimensional accuracy by avoiding the occurrence of welds.

  The hydrodynamic bearing device can also be provided as a motor including a hydrodynamic bearing device, a rotor magnet, and a stator coil.

  According to the present invention, it is possible to suppress the occurrence of contamination from the housing in this type of hydrodynamic bearing device and maintain the cleanliness inside or around the bearing device at a high level.

  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 (dynamic pressure bearing device) 1 according to an embodiment of the present invention. This spindle motor for information equipment is used in a disk drive device such as an HDD, and includes a hydrodynamic bearing device 1 that rotatably supports the shaft member 2 in a non-contact manner, a disk hub 3 attached to the shaft member 2, and, for example, A stator coil 4 and a rotor magnet 5 which are opposed to each other through a gap in the radial direction, and a bracket 6 are provided. The stator coil 4 is attached to the outer periphery of the bracket 6, and the rotor magnet 5 is attached to the inner periphery of the disk hub 3. The bracket 6 has the hydrodynamic bearing device 1 mounted on the inner periphery thereof. The disk hub 3 holds one or more disk-shaped information recording media (hereinafter simply referred to as disks) D such as magnetic disks on the outer periphery thereof. In the spindle motor for information equipment configured as described above, when the stator coil 4 is energized, the rotor magnet 5 is rotated by the exciting force between the stator coil 4 and the rotor magnet 5, and accordingly, the disk hub 3 and The disk D held by the disk hub 3 rotates integrally with the shaft member 2.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a housing 7 having a bottom 7b at one end, a bearing sleeve 8 fixed to the housing 7, a shaft member 2 inserted into the inner periphery of the bearing sleeve 8, and a seal member 9. Configured as For convenience of explanation, the following description will be made with the bottom 7b side of the housing 7 as the lower side and the side opposite the bottom 7b as the upper side.

  The shaft member 2 is formed of, for example, a metal material such as stainless steel, and includes a shaft portion 2a and a flange portion 2b provided integrally or separately at the lower end of the shaft portion 2a.

  The bearing sleeve 8 is formed in a cylindrical shape with a porous body made of sintered metal, for example, a sintered metal porous body mainly composed of copper, and is fixed to a predetermined position on the inner periphery of the housing 7 described later. .

  On the inner peripheral surface 8a of the bearing sleeve 8, two upper and lower regions facing the radial bearing gap between the first radial bearing portion R1 and the second radial bearing portion R2 are provided apart in the axial direction. For example, although not shown in the drawing, a dynamic pressure groove having a herringbone shape or the like is formed as a dynamic pressure generating portion.

  Although not shown in the figure, the entire surface of the lower end surface 8b of the bearing sleeve 8 or a part of the annular region is provided with, for example, a spiral-shaped dynamic pressure groove as a dynamic pressure generating portion.

  The housing 7 is made of, for example, a crystalline resin such as liquid crystal polymer (LCP), polyphenylene sulfide (PPS), or polyetheretherketone (PEEK), or polyphenylsulfone (PPSU), polyethersulfone (PES), or polyetherimide. It is injection-molded with a resin composition based on an amorphous resin such as (PEI). As shown in FIG. 2, the housing 7 includes a cylindrical side portion 7a and a bottom portion 7b provided integrally with the lower end of the side portion 7a. Of the upper end surface 7c of the bottom portion 7b, in a partially annular region facing the flange portion 2b of the shaft member 2, for example, a spiral-shaped dynamic pressure groove is formed. A recess 7e is formed at the center of the lower end surface 7d of the bottom 7b, and a gate mark 12 having a convex surface 12d is formed at the center thereof. A step portion 7f that engages with the lower end surface 8b of the bearing sleeve 8 to perform axial positioning is formed integrally with the side portion 7a above the upper end surface 7c.

  Examples of the resin composition constituting 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 An appropriate amount of a fibrous or powdery conductive filler such as a nanomaterial or various metal powders can be blended depending on the purpose.

  The housing 7 is manufactured through the following steps, for example.

  FIG. 3 conceptually shows the molding process of the housing 7. The molding die used in this step is composed of a fixed mold and a movable mold, and includes a runner 10a, a dotted gate 10b, and a cavity 10c. In this embodiment, the dotted gate 10b is formed at one position corresponding to the center of the lower end surface 7d (upper surface in FIG. 3) of the housing bottom 7b of the cavity 10c. The gate area is set to an appropriate size in consideration of the viscosity and injection speed when the molten resin is melted.

  The molten resin P injected from a nozzle of an injection molding machine (not shown) is filled into the cavity 10c through the runner 10a and the dotted gate 10b of the molding die. In this way, by filling the cavity 10c with the molten resin P from the dotted gate 10b, the molten resin P is in the radial direction (mainly corresponding to the bottom 7b) and the axial direction (mainly the side 7a) of the cavity 10c. The corresponding area) is uniformly filled. Thereby, generation | occurrence | production of a weld can be avoided and the housing 7 which has high dimensional accuracy is obtained.

  After the molten resin P filled in the cavity 10c is solidified, the molding die 7 is opened and the molded housing 7 is taken out. As the mold is opened, the gate resin portion 11 formed in the dotted gate 10 b is divided, and the gate trace 12 remains in the housing 7. A divided section 12b formed at the tip of the divided portion 12a of the gate mark 12 has a sharp concavo-convex shape. The gate mark 12 is formed at a position corresponding to the dotted gate 10b, in this embodiment, on the axis of the recess 7e formed in the housing bottom 7b as shown in FIG. Further, a part of the tip protrudes from the lower end surface 7d of the housing bottom 7b.

  Next, as shown in FIG. 4, the forming jig 13 is pressed against the divided portion 12 a of the gate mark 12 and pressed in the axial direction. The jig 13 includes a molding surface 13a having a concave curved surface, for example, a partially concave spherical surface (including a shape similar to this). By pressing the jig 13 against the gate mark 12 in this way, the needle-like convex portion 12c is guided by the molding surface 13a among the surface irregularities of the divided portion 12a by the applied pressure at that time, and along the inclined direction thereof. It is pushed and bent plastically and falls. Each projecting part 12c that has fallen covers the dividing surface 12b by, for example, being entangled with another projecting part 12c or fitting into a recessed part. Accordingly, the unevenness of the divided portion 12a is leveled, and as shown in FIG. 5, the surface 12d of the gate mark 12 is formed into a partially convex spherical shape corresponding to the shape of the forming surface 13a. As a result, falling off of the filler from the gate mark is suppressed. Further, by pressing the dividing portion 12a toward the inner peripheral side (opening side) of the housing 7, as shown in FIG. 5, for example, the protrusion from the lower end surface 7d of the dividing portion 12a can be suppressed.

  If the jig 13 is rotated while being pressed in the axial direction during the molding, not only the axial force but also the force that pushes and bends in the rotational direction is applied to the convex portion 12c of the gate mark 12. Thereby, it is possible to provide more regularity in the lying direction of the convex portion 12c, and to further smooth the surface irregularities of the divided portion 12a. When frictional heat is generated by the rotation of the jig 13, the resin component in the surface irregularities of the gate trace 12 is softened, so that the convex portions 12 c can be easily bent or the binding force between the convex portions 12 c is increased. . Accordingly, the smoothness of the gate trace surface 12d after molding can be improved, and the shape of the surface 12d of the gate trace 12 after molding can be stably maintained. The gate trace 12 can be heated using frictional heat or a heating device provided separately.

  The shaft member 2 and the bearing sleeve 8 are inserted into the inner circumference of the housing 7 manufactured as described above, and the bearing sleeve 8 is positioned in the axial direction of the bearing sleeve 8 by the stepped portion 7f, and then the inner circumference of the housing 7 is obtained. Secure to. Then, the seal member 9 is fixed to the inner periphery of the upper end of the side portion 7 a of the housing 7. Then, the assembly of the hydrodynamic bearing device 1 is completed by filling the internal space of the housing 7 with lubricating oil. At this time, the oil surface of the lubricating oil filled in the internal space of the housing 7 sealed by the seal member 9 is a tapered surface 9 a provided on the inner periphery of the seal member 9 and the outer peripheral surface of the shaft portion 2 a of the shaft member 2. It is maintained within the range of the seal space S formed between 2a1.

  In the hydrodynamic bearing device 1 configured as described above, when the shaft member 2 is rotated, dynamic pressure groove formation regions (upper and lower two places) on the inner peripheral surface 8a of the bearing sleeve 8 and formation regions of these dynamic pressure grooves are formed. In the radial bearing gap between the shaft portion 2a and the outer peripheral surface 2a1 facing each other, pressure is generated by the dynamic pressure action of the lubricating oil, and the shaft portion 2a of the shaft member 2 is supported in a non-contact manner so as to be rotatable in the radial direction. The As a result, the first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 2 in a non-contact manner so as to be rotatable in the radial direction are formed. Further, a thrust bearing gap between the dynamic pressure groove region formed on the lower end surface 8b of the bearing sleeve 8 and the upper end surface 2b1 of the flange portion 2b facing the dynamic pressure groove region, and the upper end surface 7c of the bottom portion 7b. In the thrust bearing gap between the dynamic pressure groove region formed in the shaft and the lower end surface 2b2 of the flange portion 2b opposed to the dynamic pressure groove region, pressure due to the dynamic pressure action of the lubricating oil is generated respectively. The two flange portions 2b are supported in a non-contact manner so as to be rotatable in both thrust directions. 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 the thrust direction are formed.

  Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment.

  In the above-described embodiment, the case where the gate mark 12 is formed by the jig 13 having the molding surface 13a having the concave spherical shape has been described. However, it is also possible to mold using the jig 13 other than this. For example, FIG. 6 conceptually shows another form of the step of forming the gate mark 12, and the jig 13 used in FIG. 6 includes a concave spherical surface 13a (first molding surface) and a molding surface. A tapered molding surface 13b (second molding surface) provided on the outer diameter side of 13a.

  As shown in FIG. 6, for example, when the gate trace 12 has a concave shape, the jig 13 needs to be pushed deeply into the bottom 7b in order to form the dividing surface 12b over the entire surface. If the jig 13 is simply pushed, the part 12b of meat is pushed out around the gate mark 12, and the part 12b may not be completely formed. Here, if molding is performed using the jig 13 shown in FIG. 6, the meat of the section 12b extruded to the periphery is also molded by the second molding surface 13b provided on the outer diameter side of the first molding surface 13a. be able to. Thereby, the gate mark 12 and its periphery can be shape | molded, and dropping-out of a filler etc. can be prevented more reliably.

  Further, in this embodiment, the first molding surface 13a and an annular lower end surface 13c continuous on the outer diameter side thereof, and a cylindrical surface 13d connecting the lower end surface 13c and the second molding surface 13b are formed on the jig 13. Is provided. Among these, the 2nd shaping | molding surface 13b and the cylindrical surface 13d are provided in the state inclined with respect to the pressing direction of the jig | tool 13. As shown in FIG. Therefore, when the jig 13 is pushed in, these surfaces 13b and 13d come into contact with the gate mark 12 and the surrounding surface at a relatively gentle angle, so that molding can be performed without causing corners or burrs. it can.

  In the housing 7 molded as described above, as shown in FIG. 7, the hemispherical surface 12d by the first molding surface 13a, the tapered surface 12e by the second molding surface 13b, and the hemispherical surface 12d and the tapered surface 12e are formed. In the meantime, the surfaces 12f and 12g by the lower end surface 13c and the cylindrical surface 13d of the jig 13 are respectively formed. Further, the flat surface 7e1 and the tapered surface 12e in the recess 7e are smoothly connected, and the tapered surface 12e and the cylindrical molding surface 12g are smoothly connected.

  Alternatively, the dividing section 12b can be molded without omission by pressing the jig 13 having the first and second molding surfaces 13a and 13b deep into the bottom 7b of the convex gate trace 12 shown in FIG. This makes it possible to more reliably suppress the falling off of the filler from the dividing surface 12b. In this case, as shown in FIG. 8, the surface (convex surface) 12d of the gate mark 12 by the first molding surface 13a is molded on the lower side in the axial direction (housing opening side) than the flat surface 7e1 of the recess 7e. The A tapered surface 12e smoothly connected to the flat surface 7e1 is formed around the gate mark 12 by the second forming surface 13b.

  In addition, as shown in FIG. 6, by using a jig 13 in which a first molding surface 13a for directly molding the gate trace 12 is protruded downward (housing 7 side) from the second molding surface 13b, the gate trace 12 is used. It is possible to perform molding without imposing an excessive load on the housing 7 by minimizing the area into which the housing 7 is directly pushed. Thereby, for example, it is possible to perform molding while avoiding deformation of the dynamic pressure groove forming region formed on the upper end surface 7c of the bottom 7b as much as possible. In addition, by using the above-described shape, the gate mark 12 can be used (also used) when it is convex or concave, and is economical.

  In any case, the taper angle (inclination angle) δ of the second molding surface 13b that molds the taper surface 12e is, for example, from the viewpoint of smoothly connecting the flat surface 7e1 and the taper surface 12e of the jig 13 shown in FIG. It is desirable to incline by 10 ° to 20 ° from a plane perpendicular to the indentation direction line (dashed line).

  Moreover, in the above embodiment, the case where the gate at the time of injection is provided at one position corresponding to the axis of the bottom 7b of the molding die (in the illustrated example, the center of the recess 7e of the lower end surface 7d) is provided. Although described, it is not limited to this form. For example, the present invention can be applied to the case where the gate is provided at a location other than the axis of the bottom portion 7b or at a plurality of locations. Further, the present invention is not limited to the above-described gate shape (dot-shaped gate) but can be applied to a case where a film-like (annular) gate is provided.

  Moreover, although the above embodiment demonstrated the case where the part 12a of the gate trace 12 was shape | molded with the jig | tool 13 after the injection molding of the housing 7, another method can also be taken. For example, as shown in FIG. 6, the covering material 14 is supplied to the surface of the gate trace 12 and the surface of the gate trace 12 is covered with the coating material 14. Can be prevented. As the covering material 14, for example, a photocurable resin can be used, and it is particularly preferable to use an ultraviolet curable resin having a short curing time.

  In the above embodiment, the radial bearing portions R1 and R2 and the thrust bearing portions T1 and T2 are configured to generate the dynamic pressure action of the lubricating fluid by the herringbone shape or spiral shape dynamic pressure grooves. However, the present invention is not limited to this.

  For example, so-called step bearings or multi-arc bearings may be employed as the radial bearing portions R1 and R2.

  As the step bearing, although not shown, for example, a plurality of axial groove-shaped dynamic pressure grooves are circularly formed in a region facing the radial bearing gap on the inner peripheral surface 8a of the bearing sleeve 8 (region serving as the radial bearing surface). The thing provided in the circumferential direction predetermined interval is mentioned. One or both of the radial bearing portions R1 and R2 are configured by the step bearing.

  As the multi-arc bearing, for example, although not shown in the figure, there is an example in which a region that becomes a radial bearing surface of the inner peripheral surface 8a of the bearing sleeve 8 is configured by three arc surfaces (so-called three-arc bearing). The centers of curvature of the three arc surfaces are offset from each other by an equal distance from the shaft center of the bearing sleeve 8 (shaft portion 2a). In each region defined by three arcuate surfaces, the radial bearing gap has a shape 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 in the multi-arc bearing having such a configuration, and one or both of the radial bearing portions R1 and R2 are configured. Note that a deeper axial groove called a separation groove may be formed at the boundary between the three arc surfaces.

  The multi-arc bearing can take other configurations. For example, although illustration is omitted, a region that becomes a radial bearing surface of the inner peripheral surface 8a of the bearing sleeve 8 is configured by three arc surfaces (so-called three arc bearings), and in each region partitioned by the three arc surfaces, The radial bearing gap may be formed in 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. A deeper axial groove called a separation groove can also be formed at the boundary between the three arc surfaces. In this case, when the bearing sleeve 8 and the shaft portion 2a rotate relative to each other 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 in the multi-arc bearing having such a configuration, and one or both of the radial bearing portions R1 and R2 are configured.

  The multi-arc bearing can also take another configuration. For example, although not shown in the figure, in the above-mentioned three arc bearings, the circumferential predetermined regions on the minimum gap side of the three arc surfaces are concentric and concentric with the axis center of the bearing sleeve 8 (shaft portion 2a) as the center of curvature. It can also be constituted by a circular arc of a diameter. Accordingly, the radial bearing gap (minimum gap) is constant in each predetermined region. The multi-arc bearing having such a configuration is called a taper / flat bearing, and constitutes one or both of the radial bearing portions R1 and R2.

  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. May be. Further, when the radial bearing portion is constituted by a step bearing or a multi-arc bearing, in addition to the configuration in which the two radial bearing portions are separated from each other in the axial direction as in the radial bearing portions R1 and R2, the bearing sleeve 8 It is good also as a structure which provided the one radial bearing part over the up-and-down area | region of the internal peripheral surface 8a.

  Further, one or both of the thrust bearing portions T1 and T2 are, for example, so-called step bearings, so-called wave bearings, in which a plurality of radial groove-shaped dynamic pressure grooves are provided at predetermined intervals in the circumferential direction in a region serving as a thrust bearing surface. It can also be constituted by a mold bearing (a step type having a wave shape) or the like.

  Further, the radial bearing portions R1 and R2 and the thrust bearing portions T1 and T2 can be configured by bearings other than the dynamic pressure bearing. For example, a pivot bearing can be used as the thrust bearing portion, and a round bearing can be used as the radial bearing portion. .

  In the above embodiment, the hydrodynamic bearing device 1 is filled and the radial bearing gap between the bearing sleeve 8 and the shaft member 2 or the thrust bearing between the bearing sleeve 8 and the housing 7 and the shaft member 2 is filled. Lubricating oil is exemplified as the fluid that forms the lubricating film in the gap, but other fluids that can form the lubricating film in the bearing gaps, for example, a gas such as air, or a lubricant having fluidity such as magnetic fluid Can also be used.

1 is a cross-sectional view of a spindle motor for information equipment incorporating a hydrodynamic bearing device according to an embodiment of the present invention. It is sectional drawing of a hydrodynamic bearing apparatus. It is sectional drawing which shows the formation process of a housing notionally. It is sectional drawing which shows notionally an example of gate mark shaping | molding of a housing. It is an expanded sectional view showing an example around a gate mark. It is sectional drawing which shows notionally the other example of gate mark shaping | molding of a housing. It is an expanded sectional view showing other examples around a gate mark. It is an expanded sectional view showing other examples around a gate mark. It is sectional drawing which shows notionally an example of the covering process of the gate trace of a housing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid dynamic bearing apparatus 2 Shaft member 3 Disc hub 4 Stator coil 5 Rotor magnet 7 Housing 7a Side part 7b Bottom part 7c Upper side end face 7d Lower side end face 7e Recessed part 8 Bearing sleeve 9 Seal member 10a Runner 10b Point gate 10c Cavity 11 Gate Resin portion 12 Gate mark 12a Divided portion 12b Divided section 12c Protruding portion 12d Surface 12e Tapered surface 13 Jig 13a First molding surface 13b Second molding surface R1, R2 Radial bearing portion T1, T2 Thrust bearing portion

Claims (10)

Fluid generated in a housing, a bearing sleeve disposed inside the housing, a shaft member inserted into the inner peripheral surface of the bearing sleeve, and a radial bearing gap between the inner peripheral surface of the bearing sleeve and the outer peripheral surface of the shaft member A hydrodynamic bearing device including a radial bearing portion that non-contact supports the shaft member in the radial direction with the lubricating film of
The housing is a resin injection molded product containing a filler .
A hydrodynamic bearing device, characterized in that a projecting portion of a divided portion formed at a tip of a gate mark of a housing is pushed down, and a divided section is covered with the pushed-down convex portion . A housing integrally having a bottom, a bearing sleeve disposed inside the housing, a shaft member inserted into the inner peripheral surface of the bearing sleeve, and a radial between the inner peripheral surface of the bearing sleeve and the outer peripheral surface of the shaft member In a hydrodynamic bearing device including a radial bearing portion that non-contact-supports a shaft member in a radial direction by a fluid pressure generated in a bearing gap,
The housing is a resin injection-molded product, a recess is provided at the bottom of the housing, a gate mark is formed on the bottom surface of the recess, and a split part is formed at the tip of the gate mark,
A hydrodynamic bearing device, wherein the entire gate mark including the divided portion is covered with a covering material by filling the indentation with a covering material .   The hydrodynamic bearing device according to claim 1, wherein the surface of the gate mark is a smooth convex curved surface.   2. The hydrodynamic bearing device according to claim 1, wherein the periphery of the gate mark is formed. The hydrodynamic bearing device according to claim 1, wherein the housing has a bottomed cylindrical shape and has a gate mark at an axis center of the bottom portion. A motor comprising the hydrodynamic bearing device according to claim 1, a rotor magnet, and a stator coil. Fluid generated in a housing, a bearing sleeve disposed inside the housing, a shaft member inserted into the inner peripheral surface of the bearing sleeve, and a radial bearing gap between the inner peripheral surface of the bearing sleeve and the outer peripheral surface of the shaft member In the method of manufacturing a hydrodynamic bearing device comprising a radial bearing portion that non-contact supports the shaft member in the radial direction with the lubricating film of
A hydrodynamic bearing characterized in that a housing is injection-molded with a resin material containing a filler and released from the mold, and then a convex portion of a divided portion formed at the tip of a gate mark is pushed down with a jig to cover a divided section. Device manufacturing method.   8. The method of manufacturing a hydrodynamic bearing device according to claim 7, wherein the gate mark is formed while rotating the jig.   The method of manufacturing a hydrodynamic bearing device according to claim 7, wherein the gate mark is formed while being heated. 8. The method of manufacturing a hydrodynamic bearing device according to claim 7, wherein the forming is performed by a jig having a first forming surface for forming a gate mark and a second forming surface for forming the periphery of the gate mark.

Images