JP2007327545A - Dynamic-pressure bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dynamic-pressure bearing device that boasts high reliability while suppressing deterioration in bearing performance due to the occurrence of contaminants as much as possible. <P>SOLUTION: The dynamic-pressure bearing device 1 is provided with: a shaft member 5; bearing sleeves 3, 4 that are arranged on the outer-diameter side of the shaft member 5; radial bearing clearances between the outer peripheral face 5a of the shaft member 5 and the respective inner peripheral faces 3a, 4a of both bearing sleeves 3, 4; and a radial dynamic-pressure generation part that generates a fluid dynamic-pressure in each radial bearing clearance. A spacer member 8 made of a porous body is arranged between the bearing sleeves 3, 4. The radial dynamic-pressure generation part is formed into a shape that allows lubricating oil to flow toward the spacer member 8. A circulation path for the lubricating oil that passes through the spacer member 8 composed of a porous body is thereby formed so as to capture the contaminants mixed into the lubricating oil in internal cavities of the spacer member 8 along with the lubricating-oil flow. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device.

  The dynamic pressure 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 characteristics such as high-speed rotation, high rotation accuracy, and low noise, and in recent years, taking advantage of the characteristics, the bearing device for motors mounted on various electric devices including information equipment. More specifically, magnetic disk devices such as HDD, optical disk devices such as CD-ROM, CD-R / RW, DVD-ROM / RAM, spindle motors such as magneto-optical disk devices such as MD and MO, lasers, etc. It is preferably used as a bearing device for a motor such as a polygon scanner motor of a beam printer (LBP), a color wheel motor of a projector, or a fan motor.

  For example, a configuration shown in FIG. 8 is known as a hydrodynamic bearing device incorporated in a spindle motor of a disk device such as an HDD. In the hydrodynamic bearing device shown in the figure, a radial bearing portion R for supporting the shaft member 20 in a non-contact manner in a radial direction and a thrust bearing portion T, T for supporting the shaft member 20 in a non-contact manner in a thrust direction. And are provided. The radial bearing portion R is formed by providing a dynamic pressure generating portion such as a dynamic pressure groove on the outer peripheral surface of the shaft portion 21 or the inner peripheral surface of the bearing sleeve 24 opposed via the radial bearing gap. Further, the thrust bearing portions T and T are, for example, both end surfaces of the flange portion 22 of the shaft member 20, or surfaces (for example, the end surface 24 b of the bearing sleeve 24, It is formed by providing a dynamic pressure generating part such as a dynamic pressure groove on the inner bottom surface 23a or the like.

Further, in the above-described dynamic pressure bearing device, the bearing sleeve 24 has a communication groove 25 that communicates with the outer peripheral surface 24a at both ends, and a communication that communicates the outer peripheral surface 24a and the inner peripheral surface of the bearing sleeve 24 with the opposite end surface of the thrust bearing. A groove 26 is provided. By providing the communication grooves 25 and 26, a series of circulation passages of radial bearing gap → thrust bearing gap → communication groove 25 → communication groove 26 → each bearing gap is constructed. The inside of the bearing flows along the passage (see, for example, Patent Document 1).
JP 2003-232353 A

  By the way, when the above-described hydrodynamic bearing device is operated, particularly when starting and stopping, the contact region may be worn due to sliding contact between the shaft member and the bearing sleeve and the shaft member and the housing. Particularly in recent disk apparatuses, the number of disks mounted on a shaft member (strictly speaking, a disk hub provided on the shaft member), that is, the weight of the rotating body increases, and the amount of wear increases for the purpose of increasing the capacity. There is a tendency. For this reason, the generated wear powder is mixed into the lubricating oil as contamination and distributed to various locations inside the bearing through the circulation passage. As a result, there is an increased risk of lowering the lubrication performance, and consequently lowering the bearing performance. Further, when contamination such as wear powder accumulates in the bearing gap, there is a possibility that rotation may be stopped, and there is a concern that reliability may be lowered.

  An object of the present invention is to provide a hydrodynamic bearing device that suppresses a decrease in bearing performance due to the occurrence of contamination as much as possible and boasts high reliability.

  In order to solve the above problems, the present invention provides a shaft member, a bearing sleeve disposed on the outer diameter side of the shaft member, and a radial bearing formed between the outer peripheral surface of the shaft member and the inner peripheral surface of the bearing sleeve. In a hydrodynamic bearing device including a clearance and a radial dynamic pressure generating portion that generates a dynamic pressure action on a lubricating fluid that satisfies the radial bearing clearance, a porous member that is separate from the bearing sleeve is provided, and the radial dynamic pressure generating portion is Provided is a fluid dynamic bearing device characterized in that a lubricating fluid flows toward a porous member and a circulation passage for the lubricating fluid passing through the porous member is formed.

  As described above, according to the present invention, a lubricating fluid circulation passage is formed that is provided separately from the bearing sleeve and passes through a porous member made of sintered metal, porous resin, or the like. According to this configuration, when the bearing is operated, the lubricating fluid flows through the porous member through the porous member. Therefore, even when contamination such as wear powder is mixed in the lubricating fluid, the contaminant is mixed with the lubricating fluid. The lubricating fluid can be trapped by the internal holes and kept in a clean state. Therefore, it is possible to avoid the above-described problems caused by contamination.

  The dynamic pressure bearing device having the above-described configuration may further include a thrust bearing gap and a thrust dynamic pressure generating section that generates a dynamic pressure action on the lubricating fluid that fills the thrust bearing gap. Thereby, it becomes possible to comprise a thrust bearing part with a hydrodynamic bearing which is excellent in rotation accuracy, for example, compared with the case where a thrust bearing part is constituted with a pivot bearing, generation of wear powder can be controlled. At this time, if the thrust dynamic pressure generating portion is formed in a shape in which the lubricating fluid flows toward the porous member, even if contamination such as wear powder is mixed in the lubricating fluid satisfying the thrust bearing gap, As the bearing is operated, the contamination can flow into the porous member together with the lubricating fluid, and the contamination can be captured by the internal holes of the porous member.

  The surface opening diameter of the porous member is desirably maximized in a region serving as a lubricating fluid inflow portion. By adopting such a configuration, it is possible to reduce the possibility that the contamination once flowing into the porous member flows out to the outside, and the above-described problems are further less likely to occur. In addition, the surface opening diameter said here says what averaged the sum total of the area of each opening which exists per unit area.

  The bearing sleeve is preferably formed of a porous body such as sintered metal in consideration of lubricity and formability. In this way, when the bearing sleeve is formed of a porous body, at least the surface opening diameter of the inner peripheral surface facing the radial bearing gap is smaller than the surface opening diameter of the region serving as the lubricating fluid inflow portion in the porous member. It is desirable to set it. By adopting such a configuration, for example, it is possible to avoid as much as possible a situation in which contamination such as wear powder enters the surface opening of the inner peripheral surface and reduces the amount of lubricating fluid that seeps into the bearing gap (lubrication failure). When the thrust bearing gap is provided on the end side of the bearing sleeve, the surface opening diameter of the end surface is set to be larger than the surface opening diameter of the region serving as the inflow portion of the lubricating fluid in the porous member, similarly to the inner peripheral surface. It is desirable to set it small. Such a configuration can be obtained relatively easily by making the particle diameters of the metal powders forming the bearing sleeve and the porous member different from each other, for example.

  The porous member can be provided separately from the bearing sleeve, but this makes it difficult for the lubricating fluid to flow toward the porous member, and the risk of contamination spreading inside the bearing increases. Therefore, it is desirable that the porous member is provided in contact with the bearing sleeve, whereby contamination can be captured at a location relatively close to each bearing gap that is a main source of contamination such as wear powder. It is possible to suppress the contamination from diffusing to various places inside the bearing. On the other hand, particularly when the bearing sleeve is formed of a porous body, a clean lubricating fluid from which contamination has been eliminated can be smoothly supplied to the bearing sleeve through the internal holes of both, which is favorable. Lubricity can be maintained.

  As described above, according to the present invention, it is possible to provide a dynamic pressure generating device that can suppress a decrease in bearing performance due to the occurrence of contamination as much as possible and boasts high reliability.

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

  FIG. 1 shows a hydrodynamic bearing device 1 according to the first embodiment. The hydrodynamic bearing device 1 is used by being incorporated in a spindle motor, for example, a spindle motor for HDD. The hydrodynamic bearing device 1 includes a shaft member 5 and a plurality of, for example, two bearing sleeves (a first bearing sleeve 3 and a second bearing sleeve 4) disposed on the outer diameter side of the shaft member 5 so as to be separated from each other in the axial direction. A spacer member 8 disposed between the first and second bearing sleeves 3 and 4 and a housing 2 capable of fixing the first and second bearing sleeves 3 and 4 and the spacer member 8 to the inner periphery. It is provided as a major component. For convenience of explanation, the description will be made with the side from which the end of the shaft member 5 protrudes from the housing 2 as the upper side and the opposite side in the axial direction as the lower side.

  For example, the housing 2 is formed in a substantially cylindrical shape by injection molding a resin material, and the first inner peripheral surface 2a to which the bearing sleeves 3 and 4 and the spacer member 8 are fixed is formed in a straight cylindrical surface. Further, second and third inner peripheral surfaces 2b and 2c having a diameter larger than that of the first inner peripheral surface 2a are provided on both end sides of the first inner peripheral surface 2a, and the second and third inner peripheral surfaces are provided. 2b and 2c are connected to the 1st inner peripheral surface 2a through the step surfaces 2d and 2e, respectively.

  The base resin used for the resin material forming the housing 2 can be any amorphous resin or crystalline resin as long as it can be injection-molded. For example, as the amorphous resin, polysulfone (PSU), Polyethersulfone (PES), polyphenylsulfone (PPSU), polyetherimide (PEI), etc. As crystalline resins, liquid crystal polymer (LCP), polyetheretherketone (PEEK), polybutylene terephthalate (PBT), Polyphenylene sulfide (PPS) or the like can be used. Of course, these are only examples, and other base resins can be used in consideration of the use environment and the like. Also, the type of filler to be filled in the base resin is not particularly limited. For example, as the filler, a fibrous filler such as glass fiber, a whisker-like filler such as potassium titanate, and a scaly filler such as mica Fibrous or powdery conductive fillers such as materials, carbon fibers, carbon black, graphite, carbon nanomaterials, and metal powders can be used. These fillers may be used alone or in combination of two or more.

  In addition, the housing 2 can be formed of a soft metal material such as brass or an aluminum alloy, or other metal materials.

  The shaft member 5 is formed of a metal material such as stainless steel, and has a shaft shape with substantially the same diameter as a whole. Furthermore, in this embodiment, the annular seal members 6 and 7 are fixed to the shaft member 5 by an appropriate fixing means, for example, adhesion or press-fit adhesion (combination of press-fit and adhesion). The seal members 6 and 7 protrude from the outer peripheral surface 5a of the shaft member 5 to the outer diameter side, and are accommodated on the inner peripheral sides of the second and third inner peripheral surfaces 2b and 2c of the housing 2, respectively. Further, in order to increase the fixing strength by the adhesive, circumferential grooves 5a1 and 5a2 serving as adhesive reservoirs are provided on the outer peripheral surface 5a of the shaft member 5 serving as a fixing position of the seal members 6 and 7. The seal members 6 and 7 may be formed of a soft metal material such as brass (brass), other metal materials, or a resin material. One of the seal members 6 and 7 may be integrally formed with the shaft member 5.

  A predetermined volume of seal space S1 is formed between the outer peripheral surface 6a of the seal member 6 and the second inner peripheral surface 2b of the housing 2, and the outer peripheral surface 7a of the seal member 7 is in contact with the third inner peripheral surface 2c of the housing 2. A seal space S2 having a predetermined volume is formed therebetween. In this embodiment, the outer peripheral surface 6 a of the seal member 6 and the outer peripheral surface 7 a of the seal member 7 are each formed in a tapered surface shape that is gradually reduced in diameter toward the outside of the housing 2. Therefore, the seal spaces S <b> 1 and S <b> 2 have a tapered shape that gradually decreases toward the inner side of the housing 2.

  The first and second bearing sleeves 3 and 4 are both cylindrical, for example, a porous body made of sintered metal, particularly a sintered metal porous body mainly composed of copper, or a metal material such as a copper alloy. In this embodiment, both are formed of sintered metal. Both bearing sleeves 3 and 4 are fixed to the first inner peripheral surface 2a of the housing 2 by means such as press-fitting, bonding, or press-fitting adhesion.

  As shown in FIG. 2 (b), the inner peripheral surface 3a of the first bearing sleeve 3 is formed with a region to be a radial bearing surface A1 of the first radial bearing portion R1, and the radial bearing surface A1 has a radial motion. A herringbone-shaped dynamic pressure groove 3a1 is formed as a pressure generating portion. In addition, a region that becomes the radial bearing surface A2 of the second radial bearing portion R2 is formed on the inner peripheral surface 4a of the second bearing sleeve 4, and the radial bearing surface A2 has a herringbone shape as a radial dynamic pressure generating portion. A dynamic pressure groove 4a1 is formed. In addition, you may provide the dynamic pressure grooves 3a1 and 4a1 in the outer peripheral surface 5a of the shaft member 5 which opposes via a radial bearing clearance.

  In this embodiment, each of the dynamic pressure grooves 3a1 and 4a1 is formed to be axially asymmetric with respect to the axial center m (the axial center of the region between the upper and lower inclined grooves), and the dynamic pressure groove 3a1 is the axial center m. The axial dimension X1 of the upper area is larger than the axial dimension X2 of the lower area, while the dynamic pressure groove 4a1 has an axial dimension X2 of the lower area from the axial center m greater than the axial dimension X1 of the upper area. Is also formed large. Therefore, when the shaft member 5 is rotated, the pulling force (pumping force) of the lubricating fluid by the dynamic pressure groove 3a1 is larger in the downward direction than the upward direction, and the pumping force of the lubricating fluid by the dynamic pressure groove 4a1 is larger than that in the downward direction. growing. Accordingly, in the radial bearing gap formed between the inner peripheral surface 3a of the first bearing sleeve 3 and the outer peripheral surface 5a of the shaft member 5, the lubricating fluid flows downward, and the inner peripheral surface 4a of the second bearing sleeve 4 and the shaft In the radial bearing gap formed between the outer peripheral surface 5a of the member 5, the lubricating fluid flows upward.

  Further, as shown in FIG. 2 (a), a region that becomes the thrust bearing surface of the first thrust bearing portion T1 is formed in a part or all of the annular region of the upper end surface 3b of the first bearing sleeve 3, and the thrust A herringbone-shaped dynamic pressure groove 3b1 is formed as a thrust dynamic pressure generating portion on the bearing surface so as to exert a pumping force toward the inner diameter side. Furthermore, a plurality of (three in the illustrated example) axial grooves 3d1 are formed on the outer peripheral surface 3d at regular intervals in the circumferential direction.

  Further, as shown in FIG. 2 (c), a part or the whole annular region of the lower end surface 4b of the second bearing sleeve 4 is formed with a region to be a thrust bearing surface of the second thrust bearing portion T2. A herringbone-shaped dynamic pressure groove 4b1 is formed on the thrust bearing surface as a thrust dynamic pressure generating portion so as to exert a pumping force toward the inner diameter side. Further, a plurality of (three in the illustrated example) axial grooves 4d1 are formed on the outer peripheral surface 4d at regular intervals in the circumferential direction. Either one or both of the dynamic pressure grooves 3b1 and 4b1 may be provided on the end surfaces 6b and 7b of the seal members 6 and 7 facing each other through the thrust bearing gap.

  Between the first and second bearing sleeves 3 and 4, a cylindrical spacer member 8 as a porous member referred to in the present application is arranged such that the upper end face 8 b is connected to the lower end face 3 c of the first bearing sleeve 3 and the lower end face 3 c. In a state where the side end face 8 c is in contact with the upper end face 4 c of the second bearing sleeve 4, the side end face 8 c is fixed to the first inner peripheral face 2 a of the housing 2 by means such as press fitting, bonding, or press fitting. The inner peripheral surface 8 a of the spacer member 8 is formed to have a larger diameter than the inner peripheral surfaces 3 a and 4 a of the both bearing sleeves 3 and 4, and a radial bearing gap is not between the shaft member 5 and the shaft member 5 during rotation. Not formed. As a material for forming the spacer member 8, a material having a known porous structure such as a sintered metal, a porous resin, or a ceramic can be selected. In this embodiment, the spacer member 8 is formed of a sintered metal. A plurality of (for example, three) axial grooves 8d1 are formed on the outer peripheral surface 8d at regular intervals in the circumferential direction. The axial grooves 3d1, 4d1, and 8d1 of the both bearing sleeves 3 and 4 and the spacer member 8 can be communicated by chamfers provided at the outer peripheral edges of both ends of the both bearing sleeves 3 and 4. There is no need for circumferential positioning.

  The surface opening diameter of the inner peripheral surface 8 a of the spacer member 8 is formed to be the largest among the surface opening diameters of the spacer member 8. Further, in this embodiment, the surface opening diameter of the inner peripheral surface 8a is the surface opening diameter of the inner peripheral surface 3a and the upper end surface 3b of the first bearing sleeve 3, and the inner peripheral surface 4a and the lower end surface 4b of the second bearing sleeve 4. It is formed larger than. The spacer member 8 having the above-described configuration is compression-molded using, for example, a metal powder having a particle diameter larger than that of the both bearing sleeves 3 and 4 and thereafter sizing (for example, rotational sizing) other than the inner peripheral surface 8a. Can be formed. In addition, even when a metal powder having the same particle diameter as that of the bearing sleeves 3 and 4 is used, the same configuration as described above can be obtained by reducing the compression rate and then sizing the metal powder.

  The hydrodynamic bearing device 1 composed of the above-described components is assembled, for example, by the following process.

  First, in a state where the lower end surface 3c of the first bearing sleeve 3 and the upper end surface 8b of the spacer member 8, and the upper end surface 4c of the second bearing sleeve 4 and the lower end surface 8c of the spacer member 8 are in contact with each other, the housing 2 is fixed to the first inner peripheral surface 2a. With these fixed, the upper end surface 3b of the first bearing sleeve 3 is flush with the upper step surface 2d of the housing 2 or protrudes from the step surface 2d by a slight dimension. Further, each member is predetermined so that the lower end surface 4b of the second bearing sleeve 4 is flush with the lower step surface 2e of the housing 2 or protrudes by a slight dimension from the step surface 2e. Are formed in the axial dimension. The two bearing sleeves 3 and 4 are centered so as to have a predetermined coaxiality (for example, 3 μm or less) because the coaxiality between the inner peripheral surfaces 3a and 4a greatly affects the rotational performance. Fixed in state.

  Next, the shaft member 5 is inserted into the inner circumferences of the first and second bearing sleeves 3 and 4 and the spacer member 8, and the seal members 6 and 7 are placed between the first and second bearing sleeves 3 and 4 in a predetermined manner. The shaft member 5 is fixed to a predetermined position (the outer diameter side of the circumferential grooves 5a1 and 5a2) with the axial gap secured. In order to simplify the assembly, either one of the seal members 6 and 7 can be fixed to the shaft member 5 in advance before insertion, or can be formed integrally with the shaft member 5.

  After the assembly is completed through the above-described steps, the inner space of the housing 2 sealed by the seal members 6 and 7 includes the inner holes of both the bearing sleeves 3 and 4 and the spacer member 8 as a lubricating fluid, for example, lubricating oil. Fill. Filling the lubricating oil can be performed, for example, by immersing the hydrodynamic bearing device 1 that has been assembled in the lubricating oil in a vacuum chamber and then releasing it to atmospheric pressure.

  In the hydrodynamic bearing device 1 having the above configuration, when the shaft member 5 rotates, the radial bearing surface A1 of the first bearing sleeve 3 and the radial bearing surface A2 of the second bearing sleeve 4 are respectively in radial relation with the outer peripheral surface 5a of the shaft member 5. Opposing through the bearing gap. As the shaft member 5 rotates, the lubricating oil filled in each radial bearing gap is increased in pressure by the dynamic pressure action of the dynamic pressure grooves 3a1 and 4a1 formed on the radial bearing surfaces A1 and A2, respectively. The shaft member 5 is supported in a non-contact manner so as to be rotatable in the radial direction by the pressure. Thus, the first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 5 in a non-contact manner so as to be rotatable in the radial direction are formed.

  Further, when the shaft member 5 rotates, the thrust bearing surface of the upper end surface 3b of the first bearing sleeve 3 faces the lower end surface 6b of the seal member 6 via a predetermined thrust bearing gap, and the bottom of the second bearing sleeve 4 The thrust bearing surface of the side end surface 4b faces the upper end surface 7b of the seal member 7 via a predetermined thrust bearing gap. As the shaft member 5 rotates, the lubricating oil filled in the thrust bearing gaps is increased in pressure by the dynamic pressure action of the dynamic pressure grooves 3b1, 4b1, and the shaft member 5 is non-rotatable in both thrust directions. Contact supported. Thereby, the 1st thrust bearing part T1 and the 2nd thrust bearing part T2 which support the shaft member 5 in a non-contact manner so as to be rotatable in both thrust directions are formed.

  The hydrodynamic bearing device 1 of the present embodiment has a relatively large axial separation distance between the radial bearing portions R1 and R2 and the thrust bearing portions T1 and T2 as compared with the hydrodynamic bearing device having the configuration shown in FIG. It can be taken big. Therefore, the structure is superior in load capacity (moment rigidity) with respect to moment load as compared with the hydrodynamic bearing device having the configuration shown in FIG.

  In the hydrodynamic bearing device 1 having the above-described configuration, as a result of the pumping force in the bearing internal direction being applied to the lubricating oil by the radial bearing portions R1 and R2 and the thrust bearing portions T1 and T2, the thrust bearing of the first thrust bearing portion T1. Clearance, radial bearing clearance of the first radial bearing portion R1, clearance between the inner peripheral surface 8a of the spacer member 8 and the outer peripheral surface 5a of the shaft member 5, spacer member 8 (internal void), shaft of the spacer member 8 A first circulation passage is constructed by the directional groove 8 d 1 and the axial groove 3 d 1 of the first bearing sleeve 3. Further, the thrust bearing gap of the second thrust bearing portion T2, the radial bearing gap of the second radial bearing portion R2, the gap between the inner peripheral surface 8a of the spacer member 8 and the outer peripheral surface 5a of the shaft member 5, the spacer member 8 ( ), The axial groove 8d1 of the spacer member 8 and the axial groove 4d1 of the second bearing sleeve 4 constitute a second circulation passage.

  As the shaft member 5 rotates, the lubricating oil circulates inside the bearing along the circulation path, and even if contamination such as wear powder is mixed in the lubricating oil, the contamination is an internal hole in the spacer member 8. The lubricating oil that has been trapped and passed through the spacer member 8 becomes clean. At this time, since the surface opening diameter of the spacer member 8 is formed so as to be maximized on the inner peripheral surface 8a serving as the lubricating oil inflow portion, the contamination once flowing into the spacer member 8 together with the lubricating oil is The air is reliably captured by the internal holes of the spacer member 8 without flowing out of the spacer member 8. Therefore, during operation of the hydrodynamic bearing device 1, for example, when wear powder generated in the bearing gap due to repeated sliding contact such as starting and stopping is mixed as contamination in the lubricating oil, the contamination may be excluded from the lubricating oil. Thus, it is possible to suppress a decrease in bearing performance due to a decrease in lubrication performance due to contamination.

  As described above, the surface opening diameters of the inner peripheral surface 3a and the upper end surface 3b of the first bearing sleeve 3 facing the bearing gap and the inner peripheral surface 4a and the lower end surface 4b of the second bearing sleeve 4 are spacer members. 8 is formed to be smaller than the surface opening diameter of the inner peripheral surface 8a of the spacer 8, the lubricating oil of the spacer member 8 (porous member) is larger than the radial bearing surfaces A1 and A2 of the bearing sleeves 3 and 4 and the thrust bearing surface. It is easy to flow inside. For this reason, it is possible to avoid a situation in which contamination such as wear powder enters the surface opening of the radial bearing surfaces A1 and A2 and the thrust bearing surface as the lubricating oil flows and reduces the amount of lubricating oil that oozes into the bearing gap. it can.

  Further, the lubricating oil filled in the internal space of the housing 2 flows and circulates through the circulation passage, so that the pressure balance of the lubricating oil is maintained, and at the same time, air bubbles generated due to the generation of local negative pressure are reduced. Occurrence of leakage of lubricating oil or vibration due to generation and generation of bubbles is prevented. In particular, in the present embodiment, the spacer member 8 and the two bearing sleeves 3 and 4 are fixed in a state in which the end surfaces are in contact with each other. 4 can be supplied directly with clean lubricating oil, and such a problem can be prevented more effectively. In addition, one end of the axial groove 3d1 of the first bearing sleeve 3 and one end of the axial groove 4d1 of the second bearing sleeve 4 communicate with the seal spaces S1 and S2 on the atmosphere release side, respectively. For this reason, even if bubbles are mixed in the lubricating oil for some reason, the bubbles are discharged to the open side when circulating with the lubricating oil, so that the adverse effects of the bubbles can be more effectively prevented.

  Further, when the shaft member 5 is rotated, the seal spaces S1 and S2 formed on the outer peripheral surface 6a side of the seal member 6 and the outer peripheral surface 7a side of the seal member 7 are formed on the inner side of the housing 2 as described above. Since the taper shape gradually decreases toward the bottom, the lubricating oil in both the seal spaces S1 and S2 is narrowed by the pulling action by the capillary force and the pulling action by the centrifugal force at the time of rotation, that is, It is pulled toward the inside of the housing 2. Thereby, the leakage of the lubricating oil from the inside of the housing 2 is effectively prevented. Further, the seal spaces S1 and S2 have a buffer function of absorbing a volume change amount accompanying a temperature change of the lubricating oil filled in the internal space of the housing 2, and within the range of the assumed temperature change, The oil level is always in the seal space S1, S2.

  Further, since the bearing sleeves 3 and 4 and the spacer member 8 are separate structures, the porosity of the bearing sleeves 3 and 4 and the spacer member 8 can be made different from each other, thereby filling the internal space of the housing 2. It is also possible to reduce the amount of lubricating oil. In this case, it is possible to reduce the volume of the seal spaces S1 and S2, in other words, to reduce the axial dimension of the hydrodynamic bearing device 1 by reducing the axial dimension of the seal spaces S1 and S2, or a double bearing sleeve. It is also possible to increase the moment rigidity of the hydrodynamic bearing device 1 by lengthening the axial dimensions of 3 and 4.

  Although the case where the spacer member 8 as the porous member is formed of a sintered metal has been described in the above embodiment, the spacer member 8 can be formed of, for example, a porous resin. In this case, for example, the spacer member 8 as a porous member is constituted by two porous resin portions having different opening diameters (hole diameters), and the one having a relatively large surface opening diameter is provided on the inner diameter side. By doing so, the same configuration as above can be obtained.

  In this case, each porous resin portion is formed by, for example, forming a resin composition containing a pore-forming material into a predetermined shape by injection molding or the like and then removing the pore-forming material with a solvent such as water or alcohol. Is done. Speaking of the porous member (spacer member 8) having the above-described configuration, for example, one of the members formed in a ring shape in advance can be used as an insert part, and the other can be formed by injection molding (insert molding). . With such a configuration, it is possible to adjust the area of the lubricating oil inflow portion (inner peripheral surface 8a) and the hole diameter in other areas relatively easily.

  When the spacer member 8 is formed of a porous resin, the base resin may be a thermoplastic resin or a thermosetting resin that can be injection-molded and satisfies the required heat resistance, oil resistance, mechanical strength, and the like. Any resin can be used, and for example, one or a plurality of materials selected from the material group exemplified below can be used. One or more kinds of various fillers such as a reinforcing material, a lubricant, and a conductive material can be blended with the base resin. When the spacer member 8 made of a porous resin is formed as described above, a base resin having a melting point higher than that of the base resin used for insert molding is used as the base resin to be inserted.

  Here, as resin materials that can be used as the base resin, for example, polyphenylene sulfide (PPS), polyether ketone (PEK), polyether ether ketone (PEEK), polyether imide (PEI), polyether sulfone (PES) , Polyamideimide (PAI), thermoplastic polyimide (TPI), thermosetting polyimide, polyamide (PA), polyamide 6T, polyamide 9T, and other aromatic polyamides, tetrafluoroethylene / hexafluoropropylene copolymer (PFA), ethylene -Fluorine-based copolymer resins such as tetrafluoroethylene copolymer (ETFE).

  A resin composition used for molding each part of the spacer member 8 is obtained by mixing the pore forming material and the filler with the above base resin by a kneading method generally used for resin mixing such as dry blending or melt kneading. can get. As a pore forming material, in order to prevent melting at the time of molding, it has a melting point higher than the melting temperature of the selected base resin, and after blending with the base resin to mold the spacer member 8, the base resin is dissolved. Those which can be removed using a non-solvent are used. Among these, in particular, weak alkaline substances that can be easily removed after molding (for example, water-soluble) and can be used as a rust preventive agent can be suitably used.

  As the pore-forming material, organic alkali metal salts represented by sodium benzoate, sodium acetate, sodium sebacate, sodium succinate, or sodium stearate, potassium carbonate, sodium molybdate, potassium molybdate, sodium tungstate, Inorganic alkali metal salts such as sodium triphosphate and sodium pyrophosphate can be used. Among these, sodium benzoate, sodium acetate, and sodium sebacate are particularly preferable because they have a high melting point, increase the degree of freedom in selecting a base resin, and exhibit excellent water solubility. These metal salts may be used alone or in combination of two or more. In this way, when the spacer member 8 is formed of a porous resin, since the function of capturing contamination such as wear powder is determined by the particle size of the pore forming material to be used, the particle size of the pore forming material is An appropriate one considering the size is selected and used.

  In addition, the spacer member 8 as a porous member can also be formed using a ceramic other than said sintered metal and porous resin.

  In the above description, the bearing sleeves 3 and 4 are formed of sintered metal. However, when the bearing sleeves 3 and 4 are made of a porous body, the porous member is formed in the same manner as the spacer member 8. It can also be formed of resin or ceramic. The bearing sleeves 3 and 4 may be formed of a non-porous body (non-porous body) of metal or resin in addition to the porous body.

  Although one embodiment of the hydrodynamic bearing device according to the present invention has been described above, the present invention can be applied not only to the above hydrodynamic bearing device 1 but also to other hydrodynamic bearing devices. Is possible. Hereinafter, the hydrodynamic bearing device will be described with reference to FIGS. 3 to 5, but members / elements having the same functions / actions are given common reference numerals, and redundant description is omitted.

  FIG. 3 shows a hydrodynamic bearing device 11 according to the second embodiment. In the dynamic pressure bearing device 11, the first and second radial bearing portions R 1 and R 2 are provided on the inner peripheral surface 13 a of the bearing sleeve 13 made of sintered metal provided at the substantially central portion in the axial direction of the housing 2 and the shaft member 5. Between the outer peripheral surface 5a and the outer peripheral surface 5a. Cylindrical first sleeve member 12 and second sleeve member 14 formed of a porous body such as sintered metal, porous resin, or ceramic are provided on both axial sides of bearing sleeve 13. The upper end surface 13 b of the bearing sleeve 13 and the lower end surface 12 c of the first sleeve member 12, and the lower end surface 13 c of the bearing sleeve 13 and the upper end surface 14 c of the second sleeve member 14 are in contact with each other. The first thrust bearing portion T1 is formed between the lower end surface 14b of the second sleeve member 14 and the upper end surface 7b of the seal member 7 between the upper end surface 12b of the first sleeve member 12 and the lower end surface 6b of the seal member 6. A second thrust bearing portion T2 is formed therebetween. The inner peripheral surfaces 12 a and 14 a of the first and second sleeve members 12 and 14 are formed with a larger diameter than the inner peripheral surface 13 a of the bearing sleeve 13, and accordingly, the inner peripheral surfaces of the first and second sleeve members 12 and 14. A radial bearing gap is not formed between the surfaces 12 a and 14 a and the outer peripheral surface 5 a of the shaft member 5. In this embodiment, the 1st, 2nd sleeve members 12 and 14 comprise the porous member said by this application.

  As shown in FIG.4 (b), the area | region used as radial bearing surface A1, A2 of radial bearing part R1, R2 is provided in the inner peripheral surface 13a of the bearing sleeve 13, and it is provided in two axial directions apart, On the radial bearing surfaces A1 and A2, a plurality of dynamic pressure grooves 13a1 and 13a2 arranged in a herringbone shape are formed as radial dynamic pressure generating portions. The dynamic pressure grooves 13a1 and 13a2 are formed to be axially asymmetric with respect to the axial center m, and the upper dynamic pressure groove 13a1 has an axial dimension X2 in a region below the axial center m in the axial direction of the upper region. On the other hand, the lower dynamic pressure groove 13a2 is formed so that the axial dimension X1 in the upper region from the axial center m is larger than the axial dimension X2 in the lower region. Therefore, when the shaft member 5 rotates, the lubricating oil flows upward in the radial bearing gap formed between the radial bearing surface A1 and the outer peripheral surface 5a of the shaft member 5, and the radial bearing surface A2 and the outer peripheral surface 5a of the shaft member 5 The lubricating oil flows upward in the radial bearing gap formed between the two.

  Further, as shown in FIG. 4A, a region that becomes the thrust bearing surface of the first thrust bearing portion T1 is formed in a part or all of the annular region of the upper end surface 12b of the first sleeve member 12, and the thrust A herringbone-shaped dynamic pressure groove 12b1 is formed on the bearing surface as a thrust dynamic pressure generating portion so as to exert a pumping force toward the inner diameter side. Furthermore, a plurality of (three in the illustrated example) axial grooves 12d1 are formed on the outer peripheral surface 12d at regular intervals in the circumferential direction.

  Further, as shown in FIG. 4C, a region that becomes the thrust bearing surface of the second thrust bearing portion T2 is formed in a part or all of the annular region of the lower end surface 14b of the second sleeve member 14, and the thrust A herringbone-shaped dynamic pressure groove 14b1 is formed on the bearing surface as a thrust dynamic pressure generating portion so as to exert a pumping force toward the inner diameter side. Furthermore, a plurality of (three in the illustrated example) axial grooves 14d1 are formed on the outer peripheral surface 14d at equal intervals in the circumferential direction. The dynamic pressure grooves 12b1 and 14b1 may be formed on the end surfaces 6b and 7b of the seal members 6 and 7 that face each other through the thrust bearing gap.

  In the present embodiment, for example, the thrust bearing gap of the first thrust bearing portion T1 and the first radial bearing are generated by the pumping force generated in the first thrust bearing portion T1 and the first radial bearing portion R1 as the shaft member 5 rotates. The radial bearing gap of the portion R1, the gap between the inner peripheral surface 12a of the first sleeve member 12 and the outer peripheral surface 5a of the shaft member 5, the first sleeve member 12 (internal void thereof), the shaft of the first sleeve member 12 Lubricating oil circulates along a circulation path composed of the directional groove 12d1 and the axial groove 13d1 of the bearing sleeve 13. At this time, the surface opening diameter of the inner peripheral surface 12a of the first sleeve member 12 is maximized among the surface hole diameters of the first sleeve member 12, and the surface opening diameter of the inner peripheral surface 13a of the bearing sleeve 13 is set. If it is formed so as to be larger than that, as in the fluid dynamic bearing device 1 of the first embodiment, contamination such as abrasion powder mixed in the lubricating oil is caused by the flow circulation of the lubricating oil in the first sleeve member. 12 can be captured inside.

  In addition, a series of circulation passages through which the lubricating oil flows are constructed between the bearing sleeve 13 and the second sleeve member 14 as well, such as wear powder mixed in the lubricating oil as the lubricating oil flows and circulates. Contamination is captured inside the second sleeve member 14.

  FIG. 5 shows a hydrodynamic bearing device 31 according to the third embodiment. The hydrodynamic bearing device 31 is the same as the hydrodynamic bearing device 1 according to the first embodiment described above, in that the inner peripheral surface 2a of the housing 2 has a uniform diameter and extends to the end surface of the housing 2, and accordingly, a seal member. 6 and 7 have a relatively small diameter. Compared to the hydrodynamic bearing device 1 of the first embodiment, there is an advantage that the shape of the housing 2 can be simplified and the diameter can be reduced. Of course, this configuration can also be applied to the hydrodynamic bearing device 11 according to the second embodiment shown in FIGS.

  In the above description, the herringbone-shaped dynamic pressure groove is exemplified as the radial dynamic pressure generating portion that generates fluid dynamic pressure in the radial bearing gaps of the radial bearing portions R1 and R2, but the dynamic pressure of spiral shape or other shapes is exemplified. A groove may be used. Similarly, a herringbone-shaped dynamic pressure groove has been exemplified as a thrust dynamic pressure generating portion for generating fluid dynamic pressure in the thrust bearing gaps of the thrust bearing portions T1, T2, but a spiral-shaped or other shape dynamic pressure groove is also exemplified. Good.

  In the above description, the lubricating oil has been exemplified as a fluid that fills the inside of the hydrodynamic bearing device and generates a hydrodynamic action in the radial bearing gap and the thrust bearing gap. A fluid capable of generating a pressure action, for example, a gas such as air, a fluid lubricant such as a magnetic fluid, or lubricating grease may be used.

  FIG. 6 conceptually shows a structural example of a spindle motor for HDD incorporating the hydrodynamic bearing device 1 according to an embodiment of the present invention, particularly the embodiment shown in FIG. The spindle motor includes a stator coil that is opposed to the dynamic pressure bearing device 1 and a rotor (disk hub) 17 mounted on the shaft member 5 of the dynamic pressure bearing device 1 via, for example, a radial (radial direction) gap. 15 and the rotor magnet 16. The stator coil 15 is attached to the outer periphery of the bracket 9, and the rotor magnet 16 is attached to the inner periphery of the disk hub 17. The housing 2 of the hydrodynamic bearing device 1 is mounted on the inner periphery of the bracket 9. The disk hub 17 holds one or more disks D such as magnetic disks. When the stator coil 15 is energized, the rotor magnet 16 is rotated by the electromagnetic force between the stator coil 15 and the rotor magnet 16, whereby the disk hub 17 and the disk D held by the disk hub 17 are integrated with the shaft member 5. Rotate to.

  The hydrodynamic bearing device 1 having the above-described configuration is not limited to the above-described spindle motor for HDD, but also includes optical disk devices such as CD-ROM, CD-R / RW, DVD-ROM / RAM, and magneto-optical disks such as MD and MO. The present invention can be suitably applied as a bearing device for electrical equipment including information equipment such as a spindle motor mounted on information equipment such as equipment. In addition, as in the present invention, if the hydrodynamic bearing device is capable of removing contamination such as wear powder from the lubricating oil, the lock is generated due to accumulation of wear powder during continuous operation. It can certainly be avoided. For this reason, it can be suitably used as a highly reliable bearing device even for devices that require stable rotation performance over a long period of time, such as a server HDD. In addition, it is suitably used for a disk drive device equipped with a plurality of disks D corresponding to an increase in capacity of information equipment or a motor that requires high rotational performance under high-speed rotation. be able to.

  For the above reasons, the hydrodynamic bearing device according to the present invention is not limited to the spindle motor, but can be preferably used for other motors that require stable rotation performance over a long period of time, such as a fan motor.

  FIG. 7 shows a so-called fan motor incorporating the hydrodynamic bearing device 1 according to the first embodiment of the present invention, in which the stator coil 15 and the rotor magnet 16 are opposed to each other through a gap in the radial direction (radial direction). An example of a radial gap type fan motor is shown notionally. In the illustrated motor, the rotor 18 fixed to the outer periphery of the upper end of the shaft member 5 has blades on the outer peripheral surface, and the bracket 9 serves as a casing for housing each component of the motor. The configuration is different from that of the spindle motor shown in FIG. The other constituent members have the same functions and functions as the respective constituent members of the spindle motor shown in FIG.

It is sectional drawing of the dynamic pressure bearing apparatus which concerns on 1st Embodiment. (A) is a top view showing a state in which the bearing sleeve is fixed to the housing, (b) is a sectional view thereof, and (c) is a bottom view thereof. It is sectional drawing of the hydrodynamic bearing apparatus which concerns on 2nd Embodiment. (A) The figure is a top view which shows the state which fixed the bearing sleeve to the housing in 2nd Embodiment, (b) A figure is the sectional drawing, (c) A figure is the bottom view. It is sectional drawing of the hydrodynamic bearing apparatus which concerns on 3rd Embodiment. It is sectional drawing which shows notionally the spindle motor incorporating the dynamic pressure bearing apparatus. It is sectional drawing which shows notionally the fan motor incorporating the dynamic pressure bearing apparatus. It is sectional drawing of the hydrodynamic bearing apparatus of a conventional structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11, 21 Dynamic pressure bearing apparatus 2 Housing 3 1st bearing sleeve 4 2nd bearing sleeve 5 Shaft member 6 Seal member 7 Seal member 8 Spacer member (porous member)
13 Bearing sleeve 12, 14 Sleeve member (porous member)
R1 1st radial bearing part R2 2nd radial bearing part T1 1st thrust bearing part T2 2nd thrust bearing part S1, S2 Seal space

Claims (5)

A shaft member, a bearing sleeve disposed on the outer diameter side of the shaft member, a radial bearing gap formed between an outer peripheral surface of the shaft member and an inner peripheral surface of the bearing sleeve, and the radial bearing gap In a hydrodynamic bearing device comprising a radial dynamic pressure generating section that generates a dynamic pressure action on a lubricating fluid to be filled,
A porous member that is separate from the bearing sleeve is provided, the radial dynamic pressure generating portion is formed in a shape in which the lubricating fluid flows toward the porous member, and a circulation passage for the lubricating fluid passing through the porous member is formed. A hydrodynamic bearing device characterized by being formed.   Furthermore, a thrust bearing gap and a thrust dynamic pressure generating section that generates a dynamic pressure action on the lubricating fluid that fills the thrust bearing gap are provided, and the lubricating fluid flows toward the porous member through the thrust dynamic pressure generating section. The hydrodynamic bearing device according to claim 1, wherein the hydrodynamic bearing device is formed into a shape to be formed.   The hydrodynamic bearing device according to claim 1, wherein the surface opening diameter of the porous member is maximized in a region serving as a lubricating fluid inflow portion.   4. The hydrodynamic bearing device according to claim 3, wherein the bearing sleeve is made of a porous body, and at least a surface opening diameter of an inner peripheral surface is set smaller than a surface opening diameter of an inflow portion of the lubricating fluid in the porous member.   The hydrodynamic bearing device according to claim 1, wherein the porous member is in contact with the bearing sleeve.

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