JP2007321965A - Fluid bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a fluid bearing device from being contaminated with oil when oiling. <P>SOLUTION: The fluid bearing device is provided with an oil repellent part P1 by applying an oil repellent agent to an upper end face 7a3 of a holding member 7. Consequently, even if oil overflows until flowing over the outer diameter end of a sealing member 9 from a seal space S when oiling from the seal space S formed at the inner periphery of the sealing member 9, oil can be prevented from further spreading to the outer diameter side by the oil repellent action of the oil repellent part P1. Further, the outer peripheral surface 7a2 of the bearing device can be prevented from being contaminated with oil. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device that rotatably supports a shaft portion with an oil film formed in a bearing gap.

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

  For example, in the hydrodynamic bearing device shown in Patent Document 1, a seal member is arranged on the open end side to the outside of the radial bearing gap, and the shaft is inserted into the inner peripheral surface of the seal member and the inner periphery of the seal member. A seal space is formed between the outer peripheral surface of the member. The oil level of the lubricating oil filled in the internal space of the bearing device including the radial bearing gap is always held in this seal space. In this bearing device, an oil repellent agent is applied to the end surface and inner peripheral surface of the seal member in order to more reliably prevent oil leakage from the seal space when the bearing device is used (whether the motor is started or stopped). Alternatively, the seal member itself is formed of a resin material having oil repellency.

  On the other hand, as a method of injecting lubricating oil at the time of assembling the bearing device, for example, Patent Document 2 discloses that after the lubricating oil is dropped on the open end of the bearing gap of the bearing device exposed to a reduced pressure atmosphere, the bearing device is opened to the atmosphere. By doing so, a so-called dripping oil impregnation method in which lubricating oil is filled in the bearing gap is shown. According to this method, it is possible to lubricate without contaminating the outer peripheral surface of the bearing device.

JP 2004-176815 A JP 2002-174243 A

  In the method of Patent Document 2, it is necessary to appropriately control the amount of oil dripped onto the end face of the bearing device. However, in the case of a small bearing device, the amount of oil filled in the bearing is extremely small, so dripping It becomes difficult to adjust the amount of oil to be used. In such a case, in order to avoid oil shortage, more oil than the appropriate amount may be dripped. For example, when lubricating the bearing device of Patent Document 1, the dropped oil may reach the outer diameter end of the bearing device beyond the end surface of the oil-repellent seal member and contaminate the outer peripheral surface. When the outer peripheral surface of the bearing device is contaminated with oil in this way, the adhesive strength is reduced, or a process for removing the oil on the outer peripheral surface is required to prevent this, resulting in an increase in cost.

  An object of the present invention is to prevent the outer peripheral portion of a hydrodynamic bearing device from being contaminated with oil during lubrication.

  In order to solve the above problems, the present invention is arranged on the outer diameter side of the seal member, a radial bearing gap filled with lubricating oil, a seal member forming a seal space connected to the radial bearing gap on the inner periphery, In a hydrodynamic bearing device including a holding member that holds a seal member, an oil repellent portion is provided on an end surface of the holding member.

  Thus, in the present invention, the oil repellent portion is provided on the end face of the holding member disposed on the outer diameter side of the seal member. As a result, when oil is poured from the seal space formed on the inner periphery of the seal member, even when oil overflows from the seal space to beyond the outer diameter end of the seal member, The spread of oil to the outer diameter side can be prevented. Therefore, contamination of the outer peripheral portion of the bearing device with oil can be prevented.

  Further, in this bearing device, if the recess is formed between the end surface of the holding member and the end surface of the seal member, the oil returned to the inner diameter side by the oil repellent action of the oil repellent portion can be captured. It is possible to more reliably prevent contamination of the outer periphery of the oil by oil.

  Further, when the oil repellent portion is provided on the end face of the seal member, oil leakage from the seal space during use of the bearing device can be prevented. As described above, when the oil repellent part is provided on the end face of the holding member and the end face of the seal member, the oil overflowing from the seal space at the time of lubricating oil reaches the outer diameter end of the holding member at a stretch so as to slide on the oil repellent part. There is a risk of contaminating the outer periphery of the bearing device. In view of this point, when a non-oil repellent region is provided between the oil repellent portion on the end surface of the seal member and the oil repellent portion on the end surface of the holding member, the oil repelled by the oil repellent portion of the holding member is removed. Therefore, it is possible to more reliably prevent the oil from spreading to the outer diameter side. The term “non-oil repellency” as used herein means that the treatment for positively imparting oil repellency such as application of an oil repellant is not performed (the same applies in the following description).

  As described above, according to the present invention, it is possible to prevent the hydrodynamic bearing device from being contaminated with oil during lubrication.

  Hereinafter, an embodiment 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. The spindle motor is used in a disk drive device such as an HDD, and is opposed to a dynamic pressure bearing device 1 having a shaft member 2 and a disk hub 3 attached to the shaft member 2 through, for example, a radial gap. The stator coil 4, the rotor magnet 5, and the bracket 6 are provided. The stator coil 4 is attached to the bracket 6, and the rotor magnet 5 is fixed to the disk hub 3. The hydrodynamic bearing device 1 is fixed to the inner periphery of the bracket 6. The disk hub 3 holds one or a plurality of disks D (two sheets in FIG. 1) as information recording media. In the spindle motor configured as described above, when the stator coil 4 is energized, the rotor magnet 5 is rotated by an exciting force generated between the stator coil 4 and the rotor magnet 5, and accordingly, the disk hub 3 and the disk are rotated. The disk held by the hub 3 rotates integrally with the shaft member 2.

  FIG. 2A shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a shaft member 2, a bearing sleeve 8 having the shaft member 2 inserted on the inner periphery, a seal member 9 disposed at one end opening of the bearing sleeve 8, a bearing sleeve 8 and a seal member 9. And a cup-shaped holding member 7 that holds the bearing sleeve 8 and the seal member 9. For convenience of explanation, the side where the holding member 7 is open will be described as the upper side, and the side where the holding member 7 is closed will be described as the lower side.

  The shaft member 2 includes a shaft portion 2a and a flange portion 2b provided at the lower end of the shaft portion 2a, and is formed integrally or separately from a metal material such as SUS steel. An annular groove 2a2 for preventing oil leakage is formed in the upper part of the outer peripheral surface 2a1 of the shaft part 2a. Each part of the shaft member 2 can be made of the same kind of material or a different material. For example, the shaft portion 2a can be formed of a metal material, and a part or all of the flange portion 2b can be formed of a resin material. In this case, the shaft member 2 is a resin injection molding using the shaft portion 2a as an insert part. It is possible to make with.

  The bearing sleeve 8 is formed, for example, in a cylindrical shape with a sintered metal containing copper as a main component, and is bonded, press-fitted, and press-fitted under the presence of adhesive (hereinafter referred to as press-fitting adhesion) to the inner peripheral surface 7 a 1 of the holding member 7. Or by welding or other suitable means. The bearing sleeve 8 can be formed of other metal materials, resin materials, ceramics, or the like.

  A region where a plurality of dynamic pressure grooves are arranged as a radial dynamic pressure generating portion is formed on the entire inner surface or a part of the cylindrical region of the inner peripheral surface 8 a of the bearing sleeve 8. In this embodiment, for example, as shown in FIG. 3A, two regions having a plurality of dynamic pressure grooves 8a1 and 8a2 arranged in a herringbone shape are formed apart from each other in the axial direction. When the shaft portion 2a rotates, the dynamic pressure grooves 8a1 and 8a2 formation regions face the outer peripheral surface 2a1 of the shaft portion 2a via the radial bearing gaps of the radial bearing portions R1 and R2.

  On the entire or part of the annular region of the lower end surface 8b of the bearing sleeve 8, there is a region in which a plurality of dynamic pressure grooves 8b1 are arranged in a spiral shape as a thrust dynamic pressure generating portion, for example, as shown in FIG. It is formed. When the shaft portion 2a rotates, the dynamic pressure groove 8b1 formation region faces the upper end surface 2b1 of the flange portion 2b of the shaft portion 2a via the thrust bearing gap of the first thrust bearing portion T1.

  The holding member 7 is integrally formed in a cup shape having a side portion 7a and a bottom portion 7b. A step portion 7c is formed at the lower end portion of the inner peripheral surface 7a1 of the side portion 7a and abuts on the lower end surface 8b of the bearing sleeve 8. As shown in FIG. 2B, an oil repellent portion P1 made of an oil repellent is provided on the upper end surface 7a3 of the side portion 7a.

  Although not shown in the drawings, a region where a plurality of dynamic pressure grooves are arranged in a spiral shape is formed on the entire upper surface 7b1 of the bottom 7b of the holding member 7 or a partial annular region. When the shaft portion 2a rotates, the dynamic pressure groove forming region faces the lower end surface 2b2 of the flange portion 2b of the shaft portion 2a via the thrust bearing gap of the second thrust bearing portion T2.

  The holding member 7 is formed of, for example, a resin material. Examples of the resin material include crystalline resins such as liquid crystal polymer (LCP), polyphenylene sulfide (PPS), and polyether ether ketone (PEEK), and polyphenylsulfone (PPSU). ), Polyethersulfone (PES), polyetherimide (PEI) and other resin compositions based on an amorphous resin can be used. Examples of fillers that can be added to the resin include fibrous fillers such as carbon fibers and glass fibers, whisker-like fillers such as potassium titanate, scaly fillers such as mica, carbon black, graphite, and carbon nano Examples thereof include conductive fillers such as materials and various metal powders. These fillers are blended in an appropriate amount in the base resin depending on the purpose, such as reinforcement of the holding member 7 or imparting conductivity. Further, the material forming the holding member 7 is not limited to resin, and a metal material such as brass can also be used.

  The seal member 9 is formed in a ring shape with a metal material or a resin material, and the lower end surface 9b is in contact with the upper end surface 8c of the bearing sleeve 8 at the upper end portion of the inner peripheral surface 7a1 of the holding member 7, For example, it is fixed by bonding or press-fitting (press-fitting with an adhesive interposed). The inner peripheral surface 9a of the seal member 9 has a tapered surface that gradually increases in diameter upward, and the cross-sectional area gradually increases upward from the outer peripheral surface 2a1 of the shaft portion 2a. A seal space S connected to the gap is formed. The capillary oil in the seal space S pulls the lubricating oil into the bearing device, and the seal space S absorbs the increase in volume due to the thermal expansion of the lubricating oil in the bearing, thereby leaking the oil in the bearing to the outside. Can be prevented.

  The upper end face 9c of the seal member 9 and the annular groove 2a2 of the shaft portion 2a are provided with oil repellent portions P2 and P3 made of an oil repellent as shown in FIG. Thereby, it is possible to more effectively prevent the lubricating oil in the seal space S from leaking to the outside. Further, between the upper end surface 9c of the seal member 9 and the upper end surface 7a3 of the holding member 7, as shown in FIG. 4, the outer peripheral chamfer portion 9d of the upper end surface 9c of the seal member 9 and the upper end surface 7a3 of the holding member 7 are provided. An annular space is formed by the inner chamfer portion 7a4. The inner part of the annular space can be used as an adhesive reservoir G when the sealing member 9 and the holding member 7 are bonded and fixed. As will be described later, the opening side of the annular space serves as a recess F that captures oil that has overflowed during oiling.

  After assembling the hydrodynamic bearing device 1 having the above-described configuration, lubricating oil is injected therein, and the internal space of the hydrodynamic bearing device 1 including the radial bearing gap and the thrust bearing gap is filled with the lubricating oil. Various types of lubricating oil can be used, but the lubricating oil provided to the hydrodynamic bearing device for a disk drive device such as an HDD is low in consideration of temperature changes during use or transportation. Ester lubricants excellent in evaporation rate and low viscosity, such as dioctyl sebacate (DOS), dioctyl azelate (DOZ) and the like can be suitably used.

  The lubricating oil is injected into the bearing by so-called dripping oil impregnation. Specifically, the lubricating oil is dropped into the seal space S of the fluid dynamic bearing device 1 in a state where the pressure in the chamber in which the fluid dynamic bearing device 1 before lubrication is disposed is reduced. At this time, when a relatively large amount of lubricating oil is dropped in order to supply sufficient oil to the inside of the bearing, when the dropped oil reaches the outer diameter end of the upper end surface 7a3 of the holding member 7, the outer periphery of the holding member 7 It flows down to the surface 7a2, and the outer peripheral surface 7a2 is contaminated with oil. In the present invention, as shown in FIG. 4, the lubricating oil is repelled by the oil repellent part P1 of the upper end surface 7a3 of the holding member 7 and stays on the inner diameter side from the oil repellent part P1 in a state of rising due to surface tension. 7a2 can be prevented from being contaminated with oil.

  Further, in the present embodiment, as shown in FIG. 4, a recess G is formed by the chamfer portion 7 a 4 of the holding member 7 and the chamfer portion 9 d of the seal member 9. The recess G provides an effect of capturing the lubricating oil repelled by the oil repellent part P1.

  By the way, when the oil repellent portion is provided on the entire upper end surface 7a3 of the holding member 7 and the upper end surface 9c of the seal member 9 including the concave portion G, the oil overflowing from the seal space S during oil injection As a result, the outer diameter end of the holding member 7 may be reached at once, and the outer peripheral surface 7a2 may be contaminated. In the present embodiment, as shown in FIG. 4, the oil repelled in the oil repellent part P1 is retained in the recess F by forming a non-oil repellent region (recessed part F) on the inner diameter side of the oil repellent part P1. Therefore, the oil can be kept on the inner diameter side of the oil repellent portion P1.

  In the hydrodynamic bearing device 1 filled with lubricating oil as described above, it is formed between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a when the shaft portion 2a rotates. Lubricating oil in the radial bearing gap is pushed toward the axial center of the dynamic pressure grooves 8a1 and 8a2, and the pressure rises. As described above, the first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 2 in a non-contact manner in the radial direction are configured by the dynamic pressure action of the lubricating oil generated by the dynamic pressure grooves 8a1 and 8a2. .

  At the same time, the thrust bearing gap between the lower end surface 8b of the bearing sleeve 8 and the upper end surface 2b1 of the flange portion 2b, and the lower end surface 2b2 of the flange portion 2b and the upper end surface 7b1 of the bottom portion 7b of the holding member 7 The pressure of the oil film formed in the thrust bearing gap is increased by the dynamic pressure action of the dynamic pressure groove 8b1 and the like. The first thrust bearing portion T1 and the second thrust bearing portion T2 that support the shaft member 2 in the thrust direction in a non-contact manner are constituted by the pressure of these oil films.

  In the present embodiment, one or a plurality of, for example, three axial grooves 8 d arranged at equal intervals in the circumferential direction are formed on the outer peripheral surface of the bearing sleeve 8. The axial groove 8d, the radial groove 7c1 formed in the step 7c provided on the inner periphery of the holding member 7, the outer diameter portion of the lower end surface 9b of the seal member 9, and the upper end surface 8c of the bearing sleeve 8 Between the outer diameter end of the thrust bearing gap and the circumferential groove 8c2 formed on the upper end surface 8c of the bearing sleeve 8 and the radial groove 8c1 formed on the inner diameter side of the circumferential groove 8c2. The upper end of the radial bearing gap can be communicated. This makes it possible to circulate the lubricating oil inside the bearing and prevent local negative pressure from being generated in the lubricating oil inside the bearing or preventing local deterioration of the lubricating oil. It is possible to prevent the bearing performance from deteriorating due to these. Moreover, in this embodiment, as shown in FIG. 3, the dynamic pressure groove 8a1 has an asymmetric shape in the axial direction with respect to the axial center. As a result, when the shaft portion 2a rotates, the lubricating oil in the radial bearing gap is pushed downward, and forced circulation occurs in the lubricating oil inside the bearing, causing problems such as local negative pressure generation and deterioration of the lubricating oil. Can be more effectively prevented.

  The embodiment of the present invention is not limited to the above. In the above embodiment, the oil repellent portion P1 is formed by applying an oil repellent to the upper end surface 7a3 of the holding member 7. However, the present invention is not limited to this. For example, the holding member 7 includes at least the upper end surface 7a3. The oil repellent part P1 can also be formed by forming the region or the whole with a material having oil repellency, for example, a resin material blended with PTFE.

  Moreover, in said embodiment, although the side part 7a and the bottom part 7b of the holding member 7 are integrally formed, you may form these separately. In the above description, the bearing sleeve 8 and the holding member 7 are formed separately. However, the bearing sleeve 8 and the side portion 7a of the holding member 7 are integrally formed of resin or the like, and one end opening is separated. You may block | close with the bottom part 7b formed in the body.

  In the above, the radial dynamic pressure generating portion is formed on the inner peripheral surface 8a of the bearing sleeve 8, and the thrust dynamic pressure generating portion is formed on the lower end surface 8b of the bearing sleeve 8 and the upper end surface 7b1 of the bottom portion 7b. However, the present invention is not limited to this, and the dynamic pressure generating portion can be formed on the surface facing the bearing gap, that is, the outer peripheral surface 2a1 of the shaft portion 2a, the upper end surface 2b1 and the lower end surface 2b2 of the flange portion 2b. .

  In addition, the shape of the dynamic pressure generating portion is not limited to the above, and for example, as a dynamic pressure generating portion of the radial bearing portion, a spiral dynamic pressure groove, a step bearing, a multi-arc bearing, or the like can be formed. Further, a herringbone-shaped dynamic pressure groove, a step bearing, a wave bearing, or the like can be formed as the dynamic pressure generating portion of the thrust bearing portion.

  Alternatively, the outer peripheral surface 2a1 of the shaft member 2 and the inner peripheral surface 8a of the bearing sleeve 8 can be formed into a perfect circle shape, and the radial bearing portion R can be configured by a so-called perfect circular bearing. In addition, a thrust bearing portion is formed of a so-called pivot bearing by using a shaft member having a spherical convex portion at the lower end and sliding the tip of the spherical convex portion and the inner bottom surface 7b1 of the holding member 7 in contact with each other. You can also.

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

It is sectional drawing of the spindle motor incorporating the dynamic pressure bearing apparatus. 2A is a cross-sectional view of the hydrodynamic bearing device 1 and FIG. It is (a) sectional drawing of the bearing sleeve 8, and (b) bottom view. It is sectional drawing which shows the state which lubricates the hydrodynamic bearing apparatus 1 by dripping oil impregnation.

Explanation of symbols

1 Fluid bearing device (dynamic pressure bearing device)
2 Shaft member 7 Holding member 7a Side portion 7b Bottom portion 8 Bearing sleeve 9 Seal members P1, P2, P3 Oil repellent portion R1, R2 Radial bearing portion T1, T2 Thrust bearing portion S Seal space F Recessed portion (non-oil repellent region)
G Adhesive reservoir

Claims (4)

A fluid comprising a radial bearing gap filled with lubricating oil, a seal member that forms a seal space connected to the radial bearing gap on the inner periphery, and a holding member that is disposed on the outer diameter side of the seal member and holds the seal member In the bearing device,
A hydrodynamic bearing device, wherein an oil repellent portion is provided on an end surface of a holding member.   The hydrodynamic bearing device according to claim 1, wherein a recess is formed between an end surface of the holding member and an end surface of the seal member.   The hydrodynamic bearing device according to claim 1, wherein an oil repellent portion is provided on an end surface of the seal member.   4. The hydrodynamic bearing device according to claim 3, wherein a non-oil repellent region is provided between the oil repellent portion on the end face of the seal member and the oil repellent portion on the end face of the holding member.

Images