JP2010065843A - Dynamic pressure bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dynamic pressure bearing device that is more inexpensive owing to reduced manufacturing costs of a bearing sleeve having dynamic pressure grooves. <P>SOLUTION: The bearing sleeve 8 includes a body 81 cylindrically formed of a porous body of sintered metal, and a resin layer 82 formed from an inner periphery to a lower end face of the body 81. The dynamic pressure grooves 8a1, 8a2 and 8c1 are formed in bearing surfaces of the bearing sleeve 8 defined by the resin layer 82. The dynamic pressure grooves 8a1, 8a2 and 8c1 are molded as the resin layer 82 is molded. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device (fluid hydrodynamic bearing device) that supports a rotating member in a non-contact manner by a hydrodynamic action of a lubricating fluid generated in a bearing gap. This bearing device is a spindle of information equipment such as magnetic disk devices such as HDD and FDD, optical disk devices such as CD-ROM, CD-R / RW and DVD-ROM / RAM, and magneto-optical disk devices such as MD and MO. It is suitable for a motor, a polygon scanner motor of a laser beam printer (LBP), or an electric device such as a small motor such as an axial fan.

  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, and in recent years, as this type of bearing, the use of a hydrodynamic bearing having characteristics excellent in the required performance has been studied. Or it is actually used.

  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 the radial direction, and a thrust bearing portion that supports the shaft member in a non-contact manner in a thrust direction. As the radial bearing portion, a dynamic pressure bearing in which a groove for generating dynamic pressure (dynamic pressure groove) is provided on the inner peripheral surface of the bearing sleeve or the outer peripheral surface of the shaft member is used. As the thrust bearing portion, for example, a motion in which dynamic pressure grooves are provided on both end surfaces of the flange portion of the shaft member, or on the surfaces facing this (the end surface of the bearing sleeve, the end surface of the thrust member fixed to the housing, etc.). A pressure bearing is used (for example, refer to Patent Document 1).

  Usually, the bearing sleeve is formed of a metal material such as sintered metal or soft metal. However, when a dynamic pressure groove is provided in the bearing sleeve, rolling, etching, pressing, or the like is adopted as a method of forming the dynamic pressure groove. (For example, Patent Documents 2 and 3).

JP 2000-291648 A Japanese Patent No. 2541208 Japanese Patent Laid-Open No. 10-306827

  The method of forming a dynamic pressure groove on the inner peripheral surface of a metal bearing sleeve by rolling (PTL 2) requires not only complicated equipment but also post-processing after forming the dynamic pressure groove. There is a problem in terms of manufacturing cost. In addition, the method of forming the dynamic pressure groove by etching has a large number of processing steps and has a problem in terms of manufacturing cost, and at the same time, it is difficult to finish the shape and dimensions of the dynamic pressure groove with high accuracy.

  On the other hand, the method of forming the dynamic pressure groove by press working (Patent Document 3) does not have the disadvantages described above, and the dynamic pressure groove can be formed with a simple facility, with a small number of steps, and with high accuracy. it can. However, in this forming method, after forming the dynamic pressure groove, the dynamic pressure groove forming mold is released from the inner peripheral surface of the bearing sleeve by using the spring back of the sintered sleeve bearing sleeve. When applying the method, the inner diameter, thickness, and axial length of the bearing sleeve may be limited.

  An object of the present invention is to reduce the manufacturing cost of a bearing sleeve having a dynamic pressure groove, and to provide a dynamic pressure bearing device that is much lower in cost.

  Another object of the present invention is to provide a hydrodynamic bearing device in which the hydrodynamic groove of the bearing sleeve can be formed with relatively few man-hours with relatively high accuracy, and the inner diameter, thickness, and axial length of the bearing sleeve are limited. Is to provide.

In order to solve the above problems, the present invention provides a housing, a bearing sleeve provided in the housing, a rotating member that rotates relative to the bearing sleeve, a radial bearing gap between the bearing sleeve and the rotating member, and In a hydrodynamic bearing device comprising a radial hydrodynamic bearing portion and a thrust hydrodynamic bearing portion that support a rotating member in a non-contact manner by the hydrodynamic action of a lubricating fluid generated in a thrust bearing gap , and the interior space of the housing is filled with the lubricating fluid The bearing sleeve has a base made of sintered metal, and has a resin layer that prevents the lubricating fluid from passing through the inner peripheral surface and end face of the base. The resin layer formed on the inner peripheral surface of the base The resin layer formed on the end face of the base body has a radial bearing surface that faces the bearing gap, and has a thrust bearing surface that faces the thrust bearing gap. With each dynamic pressure grooves on the bearing surface is formed, the dynamic pressure grooves of the radial bearing surface provides a structure that is formed asymmetrically in the axial direction so as to flow the lubricating fluid to the side of the thrust bearing portion.

  Here, the lubricating fluid includes gases such as air in addition to lubricating oil and lubricating grease. That is, the dynamic pressure bearing of the present invention includes a so-called gas bearing.

  Since the base of the bearing sleeve is formed of sintered metal, the dimensional change due to water absorption and temperature change is small and superior in dimensional stability compared to a so-called resin bearing formed entirely of a resin material. Therefore, there is little variation in the bearing gap between the bearing sleeve and the rotating member, and a stable dynamic pressure action can be obtained. Further, since the bearing surface of the bearing sleeve that faces the bearing gap is formed of a resin layer, the dynamic pressure action of the lubricating fluid in the bearing gap is not sufficiently exhibited, for example, when the dynamic pressure bearing device is started or stopped. Even if direct contact between the bearing surface and the rotating member occurs in the state, the bearing surface and the surface of the rotating member facing the bearing surface are hardly damaged, and a stable bearing function can be obtained over a long period of time. The bearing sleeve may have at least a radial bearing surface that supports the rotating member in a non-contact manner in the radial direction, and may further include a thrust bearing surface that supports the rotating member in a non-contact manner in the thrust direction.

  Further, in the configuration in which the bearing surface (resin layer) is provided on the inner peripheral surface of the bearing sleeve, the dynamic pressure groove forming die is used by utilizing the elasticity of the resin layer itself after forming the dynamic pressure groove. It becomes possible to release from the surface. Therefore, restrictions on the inner diameter, thickness, and axial length of the bearing sleeve are relaxed, and the degree of freedom in design and manufacturing is improved.

  The base of the bearing sleeve is made of, for example, one or more metal powders selected from copper, iron, and aluminum as the main raw material, and, if necessary, powders of tin, zinc, lead, graphite, molybdenum disulfide, etc. Alternatively, these alloy powders are mixed (a small amount of a binder may be added as necessary in order to improve moldability and releasability), formed into a predetermined shape, and sintered by firing. It can be formed by subjecting the body (sintered metal) to post-treatment such as sizing as necessary. In such a matrix, there are a large number of internal pores due to the porous structure of the sintered metal, and the surface of the matrix has a large number of surface openings formed by opening the internal pores to the outside. . The internal pores of the matrix may be impregnated with lubricating oil or lubricating grease, for example, by vacuum impregnation.

  The structure of the resin layer constituting the bearing surface may be one that allows the lubricating fluid to pass therethrough or may not allow the lubricating fluid to pass. In the former case, the lubricating fluid can be configured to circulate between the inside of the matrix and the bearing gap via the resin layer. In the latter case, since the lubricating fluid in the bearing gap does not escape to the inside of the base via the resin layer, there is no pressure loss of the lubricating fluid in the bearing gap, and high bearing rigidity is obtained. Normally, when using a bearing sleeve made of sintered metal, the bearing surface is often sealed before forming the dynamic pressure groove, but the bearing surface is not completely sealed, and a predetermined ratio (several % To more than 10%) of surface openings are left. For this reason, some pressure loss tends to occur in the bearing gap. In the latter case, since the sealing treatment of the bearing surface is completely performed by the formation of the resin layer, the problem of pressure loss as described above is solved, and at the same time, the conventional sealing treatment process is eliminated, The process can be simplified (the cleaning process after the sealing process can also be reduced). The configuration in which the bearing surface is completely sealed is particularly advantageous in a gas bearing.

  The resin layer of the bearing sleeve is formed on a predetermined surface of the base body by, for example, insert molding, and has a bearing surface facing a bearing gap between the rotating member. When the resin layer is molded, the molten resin that forms the resin layer enters the internal pores of the surface layer portion from the surface openings on the surface of the base material and solidifies, so the resin layer adheres firmly to the surface of the base material by a kind of anchor solidification To do. For this reason, the resin layer is hardly peeled off or detached from the surface of the base material, and high durability is obtained.

  The dynamic pressure groove of the resin layer is obtained by, for example, processing a groove mold for forming the dynamic pressure groove in a required portion of the mold for molding the resin layer (portion for forming the bearing surface). It can be formed by transferring the groove shape onto the bearing surface of the resin layer. In this way, by forming the dynamic pressure groove of the resin layer simultaneously with the molding of the resin layer, the dynamic pressure groove of the bearing sleeve can be formed with a relatively high accuracy with a small number of man-hours.

  The resin layer is preferably formed of a resin material having excellent sliding characteristics, and oil or a solid lubricant may be blended as necessary. The resin material that forms the resin layer includes polyethylene, polyamide, polyacetal, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyphenylene sulfide, polyethersulfone, polyetherimide, polyamideimide, polyetheretherketone, thermoplastic polyimide, heat Examples thereof include curable polyimide, epoxy resin, and phenol resin.

  Examples of the solid lubricant include polytetrafluoroethylene, graphite, molybdenum disulfide, boron nitride, tungsten disulfide and the like, and examples of the oil include spindle oil, refrigerator oil, turbine oil, machine oil, Commonly used lubricating oils such as mineral oils such as dynamo oil, synthetic oils such as hydrocarbons, esters, polyglycols, silicone oils, fluorine oils and the like can be mentioned.

  An appropriate filler can be added to the resin material forming the resin layer in order to improve the friction / wear characteristics and to reduce the linear expansion coefficient. For example, glass fiber, carbon fiber, pitch carbon fiber, PAN carbon fiber, aramid fiber, alumina fiber, polyester fiber, boron fiber, silicon carbide fiber, boron nitride fiber, silicon nitride fiber, metal fiber, asbestos, coal wool, etc. Fibers, knitted fabrics, minerals such as calcium carbonate, talc, silica, clay, mica, inorganic whiskers such as aluminum borate, whiskers, potassium titanate whiskers, carbon black, graphite, polyimide Various heat resistant resins such as resin and polybenzimidazole can be used. Furthermore, carbon fiber, metal fiber, graphite powder, zinc oxide, or the like may be added for the purpose of improving the thermal conductivity of the resin layer. Further, carbonates such as lithium carbonate and calcium carbonate, phosphates such as lithium phosphate and calcium phosphate, and the like may be blended.

  In addition, an additive that can be widely applied to general synthetic resins may be used in combination as long as the effects of the present invention are not impaired. For example, industrial additives such as mold release agents, flame retardants, antistatic agents, weather resistance improvers, antioxidants, and colorants may be added as appropriate. Further, within the range that does not impair the lubricity of the resin layer, in the form of the intermediate product or the final product, modification for improving properties can be performed separately by chemical or physical treatment such as annealing treatment.

{Linear expansion coefficient of resin material (° C ⁻¹ )} × {Resin layer thickness (μm)} in the resin layer is preferably 0.15 or less, more preferably 0.13 or less, and still more preferably. Is preferably 0.10 or less. If the above value is greater than 0.15, the bearing gap will fluctuate relatively greatly due to the dimensional change of the resin layer due to water absorption or temperature change, which tends to lead to torque fluctuation or reduction in rotational accuracy. On the other hand, the moldable resin layer has a thickness of about 50 μm, and if it is thinner than this, molding becomes difficult. Therefore, the above value is preferably 0.003 or more, more preferably 0.01 or more, and still more preferably 0.015 or more.

  As described above, according to the present invention, it is possible to reduce the manufacturing cost of the bearing sleeve having the dynamic pressure grooves, and to provide a further low cost dynamic pressure bearing device.

  Further, according to the present invention, the dynamic pressure groove of the bearing sleeve can be formed with relatively little man-hours with relatively high accuracy, and there are few restrictions on the inner diameter, thickness, and axial length of the bearing sleeve. A hydrodynamic bearing device with a high degree of freedom can be provided.

1 is a cross-sectional view of a spindle motor for information equipment incorporating a fluid dynamic bearing device according to an embodiment of the present invention. It is sectional drawing which shows the dynamic pressure bearing apparatus which concerns on embodiment of this invention. It is the figure which looked at the housing from the A direction of FIG. FIG. 5 is a cross-sectional view of a bearing sleeve {FIG. 4 (a)}, a lower end surface {FIG. 4 (b)}, and an upper end surface {FIG. 4 (c)}. It is sectional drawing of the bearing sleeve which concerns on other embodiment type | system | group.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 conceptually shows one configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device (fluid fluid dynamic bearing device) 1 according to this embodiment. This spindle motor is used in a disk drive device such as an HDD, and includes a dynamic pressure bearing device 1 that rotatably supports a shaft member 2 as a rotating member in a non-contact manner, and a rotor (disc hub) mounted on the shaft member 2. ) 3 and, for example, a stator 4 and a rotor magnet 5 which are opposed to each other through a gap in the radial direction. The stator 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 housing 7 of the hydrodynamic bearing device 1 is attached to the inner periphery of the bracket 6. The disk hub 3 holds one or more disks D such as magnetic disks. When the stator 4 is energized, the rotor magnet 5 is rotated by the electromagnetic force between the stator 4 and the rotor magnet 5, whereby the disk hub 3 and the shaft member 2 are rotated together.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a housing 7, a bearing sleeve 8 and a seal member 9 fixed to the housing 7, and a shaft member 2.

  Between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a of the shaft member 2, the first radial bearing portion R1 and the second radial bearing portion R2 are provided apart from each other in the axial direction. A first thrust bearing portion T1 is provided between the lower end surface 8c 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. For convenience of explanation, the description will proceed with the bottom 7b side of the housing 7 as the lower side and the side opposite to the bottom 7b as the upper side.

  For example, the housing 7 is formed into a bottomed cylindrical shape by injection molding a resin material in which 3 to 8 wt% of carbon nanotubes as a conductive filler are blended in a liquid crystal polymer (LCP) as a crystalline resin. Side portion 7a and a bottom portion 7b provided integrally with the lower end of the side portion 7a. As shown in FIG. 3, a spiral dynamic pressure groove 7b2 is formed on the inner bottom surface 7b1 of the bottom portion 7b, which is the thrust bearing surface of the second thrust bearing portion T2. The dynamic pressure groove 7b2 is formed when the housing 7 is injection molded. That is, a groove mold for forming the dynamic pressure groove 7b2 is processed in a required portion of the mold for forming the housing 7 (a portion for forming the inner bottom surface 7b1), and the shape of the groove mold is changed during the injection molding of the housing 7. By transferring to the inner bottom surface 7 b 1 of the housing 7, the dynamic pressure groove 7 b 2 can be molded simultaneously with the molding of the housing 7. Further, a step portion 7d is formed at a position separated from the inner bottom surface 7b1 in the axial direction by a predetermined dimension x.

  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 includes a porous body made of sintered metal, in particular, a base body 81 formed into a cylindrical shape with a porous body of sintered metal mainly composed of copper, and a resin layer 82 formed on a predetermined surface of the base body 81. It consists of. In this embodiment, the resin layer 82 is formed from the inner peripheral surface to the lower end surface of the base body 81, and the inner peripheral surface 8 a and the lower end surface 8 c of the bearing sleeve 8 are constituted by the resin layer 82.

The resin layer 82 of the bearing sleeve 8 is formed from the inner peripheral surface of the base body 81 to the lower end surface by, for example, insert molding (injection molding). When the resin layer 82 is molded, the molten resin forming the resin layer 82 enters the internal pores of the surface layer portion from the surface opening of the surface of the base 81 and is solidified. Therefore, the resin layer 82 is solidified by a kind of anchor solidification. Firmly adheres to the surface. In the resin layer 82, {the linear expansion coefficient of the resin material (° C ⁻¹ )} × {the thickness of the resin layer (μm)} is 0.15 or less.

  On the inner peripheral surface 8a of the bearing sleeve 8 constituted by the resin layer 82, two upper and lower regions serving as radial bearing surfaces of the first radial bearing portion R1 and the second radial bearing portion R2 are provided apart in the axial direction. In these two regions, for example, herringbone-shaped dynamic pressure grooves 8a1 and 8a2 as shown in FIG. 4A are formed. 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. In addition, a region serving as a thrust bearing surface of the first thrust bearing portion T1 is provided on the lower end surface 8c of the bearing sleeve 8 formed of the resin layer 82, and, for example, as illustrated in FIG. Such a spiral-shaped dynamic pressure groove 8c1 is formed. The dynamic pressure grooves 8a1, 8a2, and 8c1 on the bearing surface constituted by the resin layer 82 are formed on the required portion of the mold for molding the resin layer 82 (the portion on which the bearing surface is molded). It is possible to form the groove mold by processing the groove mold and transferring the shape of the groove mold onto the bearing surface of the resin layer 82 when the resin layer 82 is formed. Thus, by forming the dynamic pressure grooves 8 a 1, 8 a 2, 8 c 1 on the bearing surface of the resin layer 82 simultaneously with the molding of the resin layer 82, the bearing sleeve 8 can be formed with relatively little man-hour and relatively high accuracy. Further, after the resin layer 82 is molded, the mold can be released from the inner peripheral surface 8a of the bearing sleeve 8 without breaking the dynamic pressure grooves 8a1 and 8a2 by utilizing the elastic deformation of the resin layer 82 itself. .

  In addition, one or a plurality of axial grooves 8d1 are formed over the entire length in the axial direction on the outer peripheral surface 8d of the bearing sleeve 8 formed of the base body 81. In this example, three axial grooves 8d1 are formed at equal intervals in the circumferential direction.

  As shown in FIG. 4 (c), the upper end surface 8b of the bearing sleeve 8 formed of the base body 81 has an inner diameter side region 8b2 and an outer diameter side region by a circumferential groove 8b1 provided in a substantially central portion in the radial direction. One or a plurality of radial grooves 8b21 are formed in the inner diameter side region 8b2. In this example, three radial grooves 8b21 are formed at equal intervals around the circumference.

  The bearing sleeve 8 as described above is fixed at a predetermined position on the inner peripheral surface 7 c of the housing 7.

  For example, the seal member 9 is fixed to the inner periphery of the upper end portion of the side portion 7a of the housing 7, and the inner peripheral surface 9a faces the taper surface 2a2 provided on the outer periphery of the shaft portion 2a via a predetermined seal space S. To do. The tapered surface 2a2 of the shaft portion 2a is gradually reduced in diameter toward the upper side (outside of the housing 7), and functions as a centrifugal force seal by the rotation of the shaft member 2. Further, the outer diameter side region 9b1 of the lower end surface 9b of the seal member 9 is formed to have a slightly larger diameter than the inner diameter side region.

  The hydrodynamic bearing device 1 of this embodiment is assembled by the following process, for example.

  First, the shaft member 2 is mounted on the bearing sleeve 8. Then, the bearing sleeve 8 is inserted into the inner peripheral surface 7 c of the side portion 7 a of the housing 7 together with the shaft member 2, and the lower end surface 8 c is brought into contact with the step portion 7 d of the housing 7. Thereby, the axial position of the bearing sleeve 8 with respect to the housing 7 is determined. In this state, the bearing sleeve 8 is fixed to the housing 7 by appropriate means, for example, ultrasonic welding.

  Next, the seal member 9 is inserted into the inner periphery of the upper end portion of the side portion 7 a of the housing 7, and the inner diameter side region of the lower end surface 9 b is brought into contact with the inner diameter side region 8 b 2 of the upper end surface 8 b of the bearing sleeve 8. In this state, the seal member 9 is fixed to the housing 7 by an appropriate means such as ultrasonic welding. In addition, if the convex rib 9c is provided in the outer peripheral surface of the sealing member 9, it is effective in improving the fixing force by welding.

  When the assembly is completed as described above, the shaft portion 2a of the shaft member 2 is inserted into the inner peripheral surface 8a of the bearing sleeve 8, and the flange portion 2b is connected to the lower end surface 8c of the bearing sleeve 8 and the inner bottom surface 7b1 of the housing 7. It will be in the state accommodated in the space part between. Thereafter, the internal space of the housing 7 sealed with the seal member 9 is filled with a lubricating fluid, for example, lubricating oil, including the internal pores of the bearing sleeve 8. The oil level of the lubricating oil is maintained within the range of the seal space S.

  When the shaft member 2 rotates, the regions (two upper and lower regions) of the inner peripheral surface 8a of the bearing sleeve 8 are opposed to the outer peripheral surface 2a1 of the shaft portion 2a via the radial bearing gap. Further, the region serving as the thrust bearing surface of the lower end surface 8c of the bearing sleeve 8 faces the upper end surface 2b1 of the flange portion 2b via the thrust bearing gap, and the region serving as the thrust bearing surface of the inner bottom surface 7b1 of the housing 7 is the flange. It faces the lower end surface 2b2 of the portion 2b via a thrust bearing gap. As the shaft member 2 rotates, a dynamic pressure of the lubricating oil is generated in the radial bearing gap, and the shaft portion 2a of the shaft member 2 is rotated in the radial direction by the oil film of the lubricating oil formed in the radial bearing gap. It is supported non-contact freely. Thus, 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 configured. At the same time, the dynamic pressure of the lubricating oil is generated in the thrust bearing gap, and the flange portion 2b of the shaft member 2 is rotatably supported in both thrust directions by the oil film of the lubricating oil formed in the thrust bearing gap. . Thereby, the 1st thrust bearing part T2 and the 2nd thrust bearing part T2 which non-contact-support the shaft member 2 rotatably in a thrust direction are comprised. The thrust bearing clearance (δ1) of the first thrust bearing portion T1 and the thrust bearing clearance (δ2) of the second thrust bearing portion T2 are the shafts from the inner bottom surface 7b1 to the step portion 7d of the housing 7. X−w = δ1 + δ2 can be accurately managed by the direction dimension x and the axial direction dimension (referred to as w) of the flange portion 2b of the shaft member 2.

  As described above, the dynamic pressure groove 8a1 of the first radial bearing portion R1 is formed to be axially asymmetric with respect to the axial center m, and the axial dimension X1 of the upper region from the axial center m is the lower region. It is larger than the axial dimension X2 of {Fig. 4 (a)}. Therefore, when the shaft member 2 rotates, the lubricating oil pulling force (pumping force) by the dynamic pressure groove 8a1 is relatively larger in the upper region than in the lower region. Then, due to the differential pressure of the pulling force, the lubricating oil filled in the gap between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a flows downward, and the first thrust bearing portion T1 Thrust bearing gap → axial groove 8d1 → annular gap between outer diameter side area 9b1 of lower end face 9b of seal member 9 and outer diameter side area 8b3 of upper end face 8b of bearing sleeve 8 → upper end face of bearing sleeve 8 It circulates through the path of the circumferential groove 8b1 of 8b → the radial groove 8b21 of the upper end surface 8b of the bearing sleeve 8, and is drawn again into the radial bearing gap of the first radial bearing portion R1. In this way, the structure in which the lubricating oil flows and circulates in the internal space of the housing 7 prevents a phenomenon in which the pressure of the lubricating oil in the internal space becomes a negative pressure locally, resulting in the generation of negative pressure. Problems such as generation of bubbles, leakage of lubricating oil and generation of vibration due to generation of bubbles can be solved. In addition, even if bubbles are mixed in the lubricating oil for some reason, when the bubbles circulate along with the lubricating oil, it is discharged from the oil surface (gas-liquid interface) of the lubricating oil in the seal space S to the outside air. The adverse effects due to the bubbles are more effectively prevented.

  FIG. 5 shows a bearing sleeve 8 according to another embodiment. In this embodiment, only two upper and lower regions of the inner peripheral surface 8a of the bearing sleeve 8 that are the radial bearing surfaces of the first radial bearing portion R1 and the second radial bearing portion R2 are configured by the resin layers 82, and the upper and lower A space between the resin layers 82 is formed on the surface of the base 81. When the shaft member 2 rotates, the lubricating oil filled (impregnated) in the internal pores of the base body 81 passes through the surface openings on the surface of the base body 81 located between the upper and lower resin layers 82, and the bearing sleeve 8. The phenomenon that the lubricating oil pressure in the inner space of the housing 7 becomes a negative pressure locally is more effectively prevented by oozing into the gap between the inner peripheral surface 8a of the shaft and the outer peripheral surface 2a1 of the shaft portion 2a. Is done.

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 2 Shaft member 7 Housing 8 Bearing sleeve 81 Base body 82 Resin layer 8a1, 8a2, 8c1 Dynamic pressure groove R1, R2 Radial bearing part T1, T2 Thrust bearing part

Claims (3)

Lubricating fluid generated in a housing, a bearing sleeve provided in the housing, a rotating member that rotates relative to the bearing sleeve, and a radial bearing gap and a thrust bearing gap between the bearing sleeve and the rotating member In the hydrodynamic bearing device comprising a radial hydrodynamic bearing portion and a thrust hydrodynamic bearing portion that support the rotating member in a non-contact manner by the hydrodynamic action, and the interior space of the housing is filled with a lubricating fluid ,
The bearing sleeve has a resin layer that prevents the lubricating fluid from passing through the inner peripheral surface and the end surface of the mother body, and the mother body is formed of a sintered metal .
The resin layer formed on the inner peripheral surface of the base body has a radial bearing surface facing the radial bearing gap, and the resin layer formed on the end face of the base body has a thrust bearing surface facing the thrust bearing gap. And
A dynamic pressure groove is formed on each of the radial bearing surface and the thrust bearing surface of the resin layer, and the dynamic pressure groove on the radial bearing surface is asymmetric in the axial direction so that lubricating fluid flows to the thrust bearing portion side. A hydrodynamic bearing device characterized by being formed. The hydrodynamic bearing device according to claim 1, wherein the dynamic pressure groove of the resin layer is formed simultaneously with the molding of the resin layer. 3. The hydrodynamic bearing according to claim 1, wherein { the linear expansion coefficient of the resin material (° C ⁻¹ ) × the thickness of the resin layer (μm)} in the resin layer is 0.15 or less. apparatus.

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