JP2005337490A - Dynamic pressure bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent abrasion dust from entering the inside of a housing caused by fixing work for the housing and a bottom member, and to perform sealing of a fixed part of the bottom member in a small number of steps. <P>SOLUTION: The press-in surface 10c1 of the outer periphery 10c of the bottom member 10 is pressed in to the inner periphery 7c1 of the press-in part of the housing 7 with a predetermined press-in margin, and an outer tapered space Q2 is adjacent to the press-in part on the outside of the housing 7. An adhesive M is held by a capillary tube force of the outer tapered space Q2, and the press-in part of the bottom member 10 is sealed with the adhesive M. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydrodynamic bearing device in which a shaft member is rotatably supported in a non-contact manner by a hydrodynamic action of lubricating oil generated in a bearing gap, and a manufacturing method thereof. 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 rotatably supports a shaft member in a radial direction and a non-contact support that rotates a shaft member in a thrust direction. A dynamic bearing having a dynamic pressure generating groove (dynamic pressure groove) on the inner peripheral surface of the bearing sleeve or the outer peripheral surface of the shaft member is used as the radial bearing portion. As the thrust bearing portion, for example, a dynamic pressure bearing in which dynamic pressure grooves are provided on both end surfaces of the flange portion of the shaft member or on the surfaces (the end surface of the bearing sleeve, the end surface of the housing bottom portion, etc.) facing this is used. For example, see Patent Document 1).

A housing used in this type of hydrodynamic bearing device is usually provided with a cylindrical side portion and a bottom portion provided on one end side of the side portion. In addition to being formed integrally with the side part, the bottom part may be fixed to the inner periphery on one end side of the side part as a separate bottom member.
JP 2002-061641 A

  In the fluid dynamic bearing device as described above, for example, press fitting is conceivable as means for fixing the bottom member to the inner periphery of one end of the housing. However, when press-fitting is employed as the means for fixing the bottom member, the following problems may occur.

  That is, each component of the hydrodynamic bearing device is cleaned after manufacture to remove fine metal powder such as cutting powder generated during processing, but when press-fitting the bottom member, the outer periphery of the bottom member and the housing There is a possibility that fine metal powder and resin powder (hereinafter referred to as “wear powder”), including wear powder, are generated by sliding friction with the inner periphery and enter the housing. Wear powder that has entered the housing is mixed with the lubricating fluid and enters the bearing portion, which adversely affects the performance and life of the bearing. Further, in the structure in which the bottom member is press-fitted, sealing of the press-fitted portion may be insufficient. On the other hand, after press-fitting the bottom member, a method of filling the press-fitted part with an adhesive from the outside of the housing and sealing the press-fitted part with the adhesive is also conceivable. A filling process is required and the assembly process is complicated.

  SUMMARY OF THE INVENTION An object of the present invention is to prevent wear powder from entering the housing accompanying the fixing operation of the housing and the bottom member, and to seal the fixing portion of the bottom member with a small number of steps. .

  In order to solve the above problems, the present invention provides a housing, a bearing sleeve fixed to the inner periphery of the housing, a rotating member having a shaft portion inserted into the bearing sleeve, and a bottom member that seals the opening of the housing. , A radial bearing portion that generates radial pressure by the dynamic pressure action of the lubricating fluid in the radial bearing gap, and a thrust bearing portion that generates pressure in the thrust direction by the dynamic pressure action of the lubricating fluid in the thrust bearing gap In the pressure bearing device, the bottom member is press-fitted and fixed to the opening of the housing under the presence of an adhesive, and the press-fitted portion of the bottom member is bonded to the press-fitted portion and the space adjacent to the outside of the housing. A configuration sealed with an agent is provided. In this configuration, the bottom member is a member separate from the housing and does not face the thrust bearing gap.

  According to the above configuration, even if wear powder is generated when the bottom member is press-fitted into the inner periphery of the housing, the wear powder is captured by the adhesive and is contained in the adhesive by solidifying the adhesive. For this reason, intrusion of wear powder accompanying press-fitting of the bottom member is prevented. In addition, since the adhesive acts as a lubricant when the bottom member is press-fitted, generation of wear powder during press-fitting is reduced, and the press-fitting operation is facilitated. Furthermore, since the press-fitted portion of the bottom member is sealed by the adhesive held in the space portion adjacent to the press-fitted portion and the outside of the housing, the press-fitted portion is reliably sealed, and after press-fitting There is no need to separately fill the adhesive.

The present invention has the following effects.
(1) Even if the wear powder is generated when the bottom member is press-fitted, the wear powder is captured by the adhesive and is contained in the adhesive by solidifying the adhesive. For this reason, intrusion of wear powder accompanying the press-fitting of the bottom member is prevented. In addition, since the adhesive acts as a lubricant when the bottom member is press-fitted, generation of wear powder during press-fitting is reduced, and the press-fitting operation is facilitated.

  (2) Since the press-fitted portion of the bottom member is sealed by the adhesive held in the space adjacent to the press-fitted portion and the outside of the housing, the press-fitted portion is securely sealed, and the press-fitted portion There is no need to separately fill the adhesive later.

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

  FIG. 1 conceptually shows a configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device 1 according to an embodiment of the present invention. This spindle motor for information equipment is used in a disk drive device such as an HDD, and is provided with a dynamic pressure bearing device 1 that rotatably supports a rotating member 3, for example, a stator 4 that is opposed via a radial gap, and A rotor magnet 5 and a motor bracket 6 are provided. The stator coil 4 is attached to the outer periphery of the motor bracket 6, and the rotor magnet 5 is attached to the outer periphery of the rotating member 3. The housing 7 of the hydrodynamic bearing device 1 is mounted on the inner periphery of the motor bracket 6. When the stator 4 is energized, the rotor magnet 5 is rotated by the magnetic force generated between the stator 4 and the rotor magnet 5, thereby rotating the rotating member 3 integrally.

  For example, as shown in FIG. 2, the hydrodynamic bearing device 1 includes a housing 7, a bottom member 10 that seals an opening on one end side of the housing 7, a bearing sleeve 8 that is fixed to the inner periphery of the housing 7, and a housing 7 and a rotating member 3 that rotates relative to the bearing sleeve 8. For convenience of explanation, the description will be made with the side covered by the bottom member 10 of the housing 7 as the downward direction and the side opposite to the axial direction as the upward direction.

  In the hydrodynamic bearing device 1, the first radial bearing portion R1 and the second radial bearing portion R2 are axially disposed between the inner peripheral surface 8a of the bearing sleeve 8 and the rotating member 3 (the outer peripheral surface of the shaft portion 2). Are provided apart from each other. A first thrust bearing portion T1 is provided between the rotating member 3 (the lower end surface 9a1 of the hub portion 9) and the housing 7 (the upper end surface 7a1 of the side portion 7a), and the rotating member 3 (the upper side of the flange portion 11). A second thrust bearing portion T2 is provided between the end face 11a) and the lower end face 8c of the bearing sleeve 8.

  The rotating member 3 includes a cylindrical shaft portion 2 that is inserted into the inner periphery of the bearing sleeve 8, a hub portion 9 that extends from the upper end of the shaft portion 2 to the outer diameter side, and covers the upper and outer peripheral upper ends of the housing 7. 2 and a disk-shaped flange portion 11 fixed to the lower end of 2. In the illustrated example, the case where the shaft portion 2 and the hub portion 9 are integrally formed is illustrated, but this may be a separate member. Although the fixing method of the shaft part 2 and the flange part 11 is arbitrary, FIG. 2 shows a case where screw connection is adopted as an example.

  The hub portion 9 functions as a disc hub, and includes a disc-like plate-like portion 9a extending from the upper end of the shaft portion 2 to the outer diameter side, a cylindrical portion 9b extending downward in the axial direction from the outer periphery of the plate-like portion 9a, A disk mounting surface 9c and a flange 9d are formed so as to protrude from the outer diameter side of the cylindrical portion 9b. One or more magnetic disks (not shown) are fitted on the outer periphery of the plate-like portion 9a. These disks are supported from below by the disk mounting surface 9c and are positioned and held by appropriate holding means (not shown).

  The bearing sleeve 8 is formed in a cylindrical shape, for example, with a porous body made of sintered metal, in particular, a sintered metal porous body mainly composed of copper.

  On the inner peripheral surface 8a of the bearing sleeve 8, as shown in FIG. 2, 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. ing. For example, herringbone-shaped dynamic pressure grooves 8a1 and 8a2 as shown in FIG. 3A are formed in the two regions. 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. Further, one or a plurality of axial grooves 8b1 are formed on the outer peripheral surface 8b of the bearing sleeve 8 over the entire axial length. In this embodiment, three axial grooves 8b1 are formed at equal intervals in the circumferential direction.

  For example, a spiral dynamic pressure groove 8c1 as shown in FIG. 3B is formed in a region of the lower end surface 8c of the bearing sleeve 8 which becomes the thrust bearing surface of the thrust bearing portion T2.

  The housing 7 is constituted by a cylindrical side portion 7a, and is formed of a resin material in this embodiment. For example, a spiral-shaped dynamic pressure groove 7a11 as shown in FIG. 4 is formed in the region of the upper end surface 7a1 of the side portion 7a that becomes the thrust bearing surface of the thrust bearing portion T1. The dynamic pressure groove 7a11 can be molded simultaneously with the injection molding of the side portion 7a by forming a molding die for the dynamic pressure groove 7a11 on the surface of the mold for molding the side portion 7a of the housing 7.

  Further, as shown in FIG. 2, a tapered outer wall 7b that gradually increases in diameter upward is formed on the outer periphery of the side portion 7a. The tapered outer wall 7b forms an annular seal space S with a gap width reduced upwardly between the inner peripheral surface 9b1 of the cylindrical portion 9b. The seal space S communicates with the outer diameter side of the thrust bearing gap of the thrust bearing portion T1 when the shaft portion 2 and the hub portion 9 are rotated.

  A press-fit portion 7c into which the bottom member 10 is press-fitted is formed at the lower end portion of the side portion 7a. The inner peripheral surface 7c1 of the press-fit portion 7c has a larger diameter than the inner peripheral surface 7d to which the bearing sleeve 8 is fixed, and the thickness of the press-fit portion 7c is thinner than the side portion 7a. A step portion 7c11 (see FIG. 7) facing the outside of the housing 7 is formed on the inner periphery 7c1 of the press-fit portion. In this embodiment, the step portion 7c11 has a tapered surface in a direction in which the diameter gradually increases downward. ing. A fixed surface 7e fixed to the inner periphery of the motor bracket 6 shown in FIG. 1 is formed on the outer periphery of the housing 7 (the outer periphery of the side portion 7a).

  The bottom member 10 is formed of, for example, a metal material such as stainless steel or brass, and is fixed by press-fitting / adhering to the inner periphery of the press-fitting portion 7c of the housing 7 according to a procedure described later. As shown in FIG. 5, the outer periphery 10c of the bottom member 10 has a press-fitting surface 10c1 that is press-fitted into the inner periphery 7c1 of the press-fitting portion of the housing 7, and a taper that extends from the upper end of the press-fitting surface 10c1 in the inner diameter side inclination direction and reaches the upper end surface 10a. The surface 10c2 and a tapered surface 10c3 extending from the lower end of the press-fitting surface 10c1 in the inner diameter side inclination direction and reaching the lower end surface 10b. The press-fit surface 10c1 is parallel to the axis.

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

  First, the bearing sleeve 8 is fixed to the inner peripheral surface 7d of the housing 7 by an appropriate means such as press-fitting or adhesion, combined use of press-fitting and adhesion, or welding. Next, the shaft portion 2, which is an integrally molded product composed of the hub portion 9 and the shaft portion 2, is inserted into the inner periphery of the bearing sleeve 8. The bearing sleeve 8 is fixed to the housing 7 and the inner diameter thereof is measured. By matching the outer diameter of the shaft portion 2 (measured in advance), the radial bearing gap is accurately measured. It can be set well.

  Next, after attaching the flange portion 11 as a retaining member to the shaft portion 2, the bottom member 10 is press-fitted and fixed to the inner periphery 7 c 1 of the press-fit portion 7 c of the housing 7 to a predetermined position under the presence of an adhesive. Specifically, as shown in an enlarged view in FIG. 6, the adhesive M is applied to the lower end portion of the press-fit portion inner periphery 7c1 of the housing 7, and then the bottom member 10 is press-fitted into the press-fit portion inner periphery 7c1. Since the adhesive M serves as a lubricant when the bottom member 10 is press-fitted, the generation of wear powder during press-fitting is reduced, and the press-fitting operation is facilitated.

  FIG. 7 shows a state where the press-fitting of the bottom member 10 is completed. The press-fitting surface 10c1 of the outer periphery 10c of the bottom member 10 is press-fitted into the press-fitting portion inner periphery 7c1 of the housing 7 with a predetermined press-fitting allowance. An external tapered space Q2 is adjacent to the outside. The internal tapered space Q1 is formed between the upper tapered surface 10c2 of the outer periphery 10c and the press-fitting portion inner periphery 7c1, and has a shape that gradually decreases toward the press-fitted portion. The outer tapered space Q2 is formed between the lower tapered surface 10c3 of the outer periphery 10c and the press-fitting portion inner periphery 7c1, and has a shape gradually reduced toward the press-fitted portion. Both the inner tapered space Q1 and the outer tapered space Q2 open to the upper end surface 10a and the lower end surface 10b of the bottom member 10.

  At the time of press-fitting the bottom member 10, the adhesive M that has turned around to the front side in the press-fitting direction of the bottom member 10 is held by the capillary force of the internal tapered space Q1. The wear powder P generated when the bottom member 10 is press-fitted is captured by the adhesive M in the internal tapered space Q1 and is contained in the adhesive M by the solidification of the adhesive M. Due to the holding effect of the adhesive M by the internal tapered space Q1, the flow of the adhesive M toward the shaft portion 2 is prevented, and the effect of capturing and containing the abrasion powder P by the adhesive M is also enhanced.

  Further, the adhesive M is held by the capillary force of the external tapered space Q2, and the press-fitted portion of the bottom member 10 is sealed by the adhesive M. In particular, as in this embodiment, if the step 7c11 is provided on the inner periphery 7c1 of the press-fitting portion of the housing 7, the amount of the adhesive M remaining in the external tapered space Q2 after the press-fitting of the bottom member 10 increases. The sealing effect of the press-fitted portion is further enhanced.

  When the assembly is completed as described above, the shaft portion 2 of the rotating member 3 is inserted into the inner peripheral surface 8a of the bearing sleeve 8, and the flange portion 11 is connected to the lower end surface 8c of the bearing sleeve 8 and the upper end surface 10a of the bottom member 10. It will be in the state accommodated in the space between. Thereafter, the internal space surrounded by the housing 7, the hub portion 9, and the bottom member 10 is filled with a lubricating fluid, for example, lubricating oil, including the internal pores of the bearing sleeve 8. At this time, the oil level of the lubricating oil is maintained within the range of the seal space S.

  When the rotating member 3 rotates, the upper and lower two regions that become the radial bearing surface of the inner peripheral surface 8a of the bearing sleeve 8 are opposed to the outer peripheral surface 2a of the shaft portion 2 via the radial bearing gap. As the shaft portion 2 rotates, the lubricating oil filled in the radial bearing gap generates a dynamic pressure action, and the shaft portion 2 is supported in a non-contact manner in the radial direction by the pressure. Thereby, the first radial bearing portion R1 and the second radial bearing portion R2 that support the rotating member 3 in a non-contact manner so as to be rotatable in the radial direction are configured.

  Further, a thrust bearing gap is formed between the upper end surface 7a1 of the side portion 7a of the housing 7 and the lower end surface 9a1 of the hub portion 9, and the thrust bearing gap is filled as the rotating member 3 rotates. The applied lubricating oil generates a dynamic pressure action, and the rotary member 3 is supported in a non-contact manner so as to be rotatable in the thrust direction by the pressure. As a result, a thrust bearing portion T1 that supports the rotating member 3 in a non-contact manner so as to be rotatable in the thrust direction is configured. Similarly, a thrust bearing gap is formed between the lower end face 8c of the bearing sleeve 8 and the upper end face 11a of the flange portion 11, and the dynamic pressure action of the lubricating oil is generated in the thrust bearing gap to cause the rotating member 3 to move in the thrust direction. A second thrust bearing portion T2 that is supported in a non-contact manner is configured.

  According to this hydrodynamic bearing device, the thrust bearing portion T1 is formed between the upper end surface 7a1 of the housing 7 and the lower end surface 9a1 of the hub portion 9, thereby sealing the upper end opening of the housing 7. Is disposed on the outer peripheral side of the housing 7. Therefore, the axial dimension of the hydrodynamic bearing device 1 can be reduced as compared with the case where the seal space S is provided above the housing 7.

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

  For example, in the present embodiment, the first and second thrust bearing portions T1 and T2 are provided to support the thrust load in both directions. However, if there is no particular problem, the second thrust bearing portion T2 may be omitted. it can. In this case, the dynamic pressure groove 8c1 formed in the flange portion 11 of the rotating member 3 and the lower end surface 8c of the bearing sleeve 8 is not necessary.

  In the present embodiment, a configuration in which the first thrust bearing portion T1 between the housing 7 and the rotating member 3 is formed between the upper end surface 7a1 of the housing 7 and the lower end surface 9a1 of the hub portion 9 is exemplified. In addition to this, although not shown, for example, a thrust plate different from the bottom member 10 is provided on the housing opening side with respect to the bottom member 10, and a thrust bearing portion T1 is provided between the thrust plate and the flange portion 11. The present invention can be similarly applied to the case of configuring the above.

  Moreover, the bearing structure of radial bearing part R1 * R2 is not limited to the above illustration, It can change into various bearing structures. For example, an arc bearing or a step bearing can be used.

1 is a cross-sectional view of a spindle motor for information equipment using a fluid dynamic bearing device according to the present invention. It is sectional drawing which shows one Embodiment of the hydrodynamic bearing apparatus which concerns on this invention. (A) is sectional drawing of a bearing sleeve, (b) is the top view which looked at the bearing sleeve from the A direction of Fig.3 (a). It is the top view which looked at the housing from the B direction of FIG. It is sectional drawing of a bottom member. It is a partial expanded sectional view which shows the periphery of the lower end opening part of a housing. It is a partial expanded sectional view which shows the state which press-fit the bottom member to the lower end inner periphery of a housing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 2 Shaft part 3 Rotating member 4 Stator 5 Rotor magnet 6 Motor bracket 7 Housing 7c Press-fit part 7c1 Inner peripheral surface 7c11 Step part 8 Bearing sleeve 8a1, 8a2 Dynamic pressure groove 9 Hub part (thrust member)
DESCRIPTION OF SYMBOLS 10 Bottom member 10c Outer periphery 10c1 Press-fit surface 10c2 Tapered surface 10c3 Tapered surface 11 Flange part R1, R2 Radial bearing part T1, T2 Thrust bearing part M Adhesive S Seal space

Claims (1)

A housing, a bearing sleeve fixed to the inner periphery of the housing, a rotating member having a shaft portion inserted into the bearing sleeve, a bottom member for sealing the opening of the housing, and a lubricating fluid in a radial bearing gap. In a hydrodynamic bearing device comprising a radial bearing portion that generates a radial direction pressure by a dynamic pressure action, and a thrust bearing portion that generates a thrust direction pressure by a dynamic pressure action of a lubricating fluid in a thrust bearing gap,
The bottom member is press-fitted and fixed to the opening of the housing under the presence of an adhesive,
The hydrodynamic bearing device, wherein the press-fitted portion of the bottom member is sealed with the adhesive held in a space portion adjacent to the press-fitted portion on the outside of the housing.

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