JP4633388B2 - Hydrodynamic bearing device - Google Patents

Description

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

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

  For example, in a hydrodynamic bearing device incorporated in a spindle motor of a disk drive device such as an HDD, a radial bearing portion that 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 motion in which dynamic pressure grooves are provided on both end surfaces of the flange portion of the shaft member, or surfaces facing the flange portion (the end surface of the bearing sleeve, the end surface of the thrust member fixed to the housing, etc.). A pressure bearing is used (for example, refer to Patent Document 1).

Usually, the bearing sleeve is fixed at a predetermined position on the inner periphery of the housing. Further, in order to prevent the lubricating oil injected into the internal space of the housing from leaking to the outside, a seal member may be attached to the inner periphery of the opening on one end side of the housing.
Japanese Patent Laid-Open No. 2002-061641

  In such a hydrodynamic bearing device, press fitting is considered as a general means for fixing the seal member to the inner periphery of the housing. However, in the press-fitting, wear powder, fine metal powder, resin powder and the like (hereinafter referred to as “wear powder”) are generated by sliding friction between the outer periphery of the seal member and the inner periphery of the housing, and the housing. There is a possibility of entering inside. 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.

  Even when the seal member is fixed by a method other than press fitting, when the seal member is pushed into the inner periphery of the housing, there is a risk of galling between the outer periphery of the seal member and the inner periphery of the housing, and similarly generating abrasion powder. There is.

  It is an object of the present invention to reliably capture the wear powder and prevent entry into the housing.

The present invention provides a housing in which one end is opened and the other end is closed, a bearing sleeve disposed inside the housing, a shaft member inserted into the bearing sleeve, and an opening of the housing is sealed. A hydrodynamic bearing device that includes a seal member that abuts against the end face of the shaft and holds the shaft member and the bearing sleeve in a non-contact manner by a hydrodynamic action of a lubricating fluid generated in a radial bearing gap between the shaft member and the bearing sleeve The outer periphery of the seal member is adhesively fixed to the inner periphery of the housing, and is opened between the outer periphery of the seal member and the inner periphery of the housing at the end surface of the seal member facing the bearing sleeve, and gradually on the closed side of the housing enlarged, a first tapered space for holding the adhesive is interposed, the end face and the end abutting the bearing sleeve of the adhesive held in the first tapered space seal member Not in contact with, outside diameter side than the contact portion between the bearing sleeve and the seal member, and the inner diameter side than the first tapered space, and the end face of the sealing member is spaced from the end face of the bearing sleeve In addition, a slimming portion that communicates with the first tapered space is provided, and the lubricating fluid circulates and flows in the internal space of the housing including the slackness portion and the radial bearing gap . The part that closes the other end of the housing may be formed integrally with the housing or may be formed as a separate part. The tapered space can be opened on at least one of both end faces of the seal member.

  According to the above configuration, even if wear powder is generated when the seal member is pushed into the inner periphery of the opening of the housing, the wear powder is captured by the adhesive and is contained in the adhesive by solidifying the adhesive. Therefore, invasion of wear powder into the housing due to sliding between the seal member and the housing is prevented. Further, since the adhesive acts as a lubricant when the seal member is pushed into the inner periphery of the housing, the generation of wear powder is reduced and the push-in operation is facilitated.

In addition, since the adhesive is held on the reduced side of the first tapered space by the capillary force of the first tapered space, the adhesive can be reliably interposed between the inner periphery of the housing and the outer periphery of the seal member. And high adhesive strength can be obtained.

In particular, when the seal member is pushed into the inner periphery of the housing, the adhesive wraps around the front side in the push direction of the seal member. When the wraparound is remarkable, the end face of the seal member and the bearing where the adhesive contacts each other It is also expected that it will enter the end face of the sleeve and adversely affect the bearing performance. In this case, as in the present invention, the first tapered space, if a shape gradually to expand the occlusion side of the housing, the adhesive wrapping around the forward side pushing of the seal member, a first tapered Since the taper portion is held on the reduced side of the tapered portion by the capillary force of the cylindrical space, the adhesive is prevented from entering the front side in the pressing direction. In addition, as a result of increasing the adhesive holding effect, the effect of capturing and containing the abrasion powder by the adhesive is also increased.

In the above invention, the second tapered space holding the adhesive, which is open at the end surface on the housing opening side of the sealing member and gradually enlarged on the opening side of the housing, between the outer periphery of the sealing member and the inner periphery of the housing. as long as it is interposed, after shoved sealing member circumferentially within the housing, seals the closed side of the housing than the tapered space by the adhesive held in the capillary force of the second tapered space This is preferable . In this case, in particular, if a step portion located in the second tapered space and facing the outside of the housing is provided on the inner periphery of the housing, it remains in the second tapered space after the seal member is pushed in . Since the amount of the adhesive increases, the sealing effect is further enhanced.

  Each tapered space described above can be formed by providing a tapered surface on at least one of the outer periphery of the seal member and the inner periphery of the housing. Preferably, a tapered surface is provided on the outer periphery of the seal member.

According to the present invention, even if wear powder is generated when the seal member is pushed into the inner periphery of the housing, the wear powder is captured by the adhesive and is contained in the adhesive by the solidification of the adhesive. Therefore, the wear powder can be reliably captured, and the wear powder can be prevented from entering the housing. Further, since the adhesive is reliably held on the reduced side by the capillary force of the first tapered space, a high fixing force can be obtained.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 shows a configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device 1 according to this embodiment. This spindle motor is used in a disk drive device such as an HDD, and includes a hydrodynamic bearing device 1 that rotatably supports the shaft member 2 in a non-contact manner, a rotor (disk hub) 3 mounted on the shaft member 2, For example, a stator 4 and a rotor magnet 5 are provided to face each other with a gap in the radial direction. The disk hub 3 includes a small-diameter cylindrical portion 3a and a large-diameter cylindrical portion 3b, and one or more disks such as a magnetic disk (not shown) are held on the outer periphery of the small-diameter cylindrical portion. The stator 4 is attached to the outer periphery of the bracket 6, and the rotor magnet 5 is attached to the inner periphery of the large-diameter cylindrical portion 3 b of the disk hub 3. The housing 7 of the hydrodynamic bearing device 1 is attached to the inner periphery of the bracket 6. When the stator 4 is energized, the rotor magnet 5 is rotated by the electromagnetic force between the stator 4 and the rotor magnet 5, whereby the disk hub 3 and the shaft member 2 are rotated together.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a bottomed cylindrical housing 7 that is open at one end and closed at the other end, a bearing sleeve 8 and a seal member 10 that are fixed to the inner periphery of the housing 7, and a shaft member 2. Consists of main components.

  Between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a of the shaft member 2, the first radial bearing portion R1 and the second radial bearing portion R2 are provided apart from each other in the axial direction. A first thrust bearing portion S1 is provided between the lower end surface 8c of the bearing sleeve 8 and the upper end surface 2b1 of the flange portion 2b of the shaft member 2, and the inner bottom surface 7c1 and the flange portion 2b of the bottom portion 7c of the housing 7 are provided. A second thrust bearing portion S2 is provided between the lower end surface 2b2. For convenience of explanation, the description will proceed with the bottom 7c side of the housing 7 as the lower side and the side opposite to the axial direction as the upper side.

  The housing 7 is formed of, for example, a soft metal material such as brass or a resin material such as a thermoplastic resin, and includes a cylindrical side portion 7b and a bottom portion 7c formed integrally with a lower end of the side portion 7b. Of the outer peripheral surface of the side portion 7b, the upper portion 7b1 is formed with a smaller diameter than the other portion. As shown in FIG. 1, the small-diameter outer peripheral surface 7b1 and the inner peripheral surface 3a1 of the small-diameter cylindrical portion 3a of the disc hub 3 are formed. A labyrinth seal L is formed between them. The bottom 7c can also be formed as a separate member from the side 7b.

  The shaft member 2 includes, for example, a shaft portion 2a formed of a metal material such as stainless steel and having an outer peripheral surface 2a1 in a cylindrical shape, and a flange portion 2b provided integrally or separately at the lower end of the shaft portion 2a. ing.

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

  On the inner peripheral surface 8a of the bearing sleeve 8 formed of this sintered metal, two upper and lower regions serving as radial bearing surfaces of the first radial bearing portion R1 and the second radial bearing portion R2 are provided apart in the axial direction. In these two regions, for example, herringbone-shaped dynamic pressure grooves 8a1 and 8a2 as shown in FIG. 3A are formed. The upper dynamic pressure groove 8a1 is formed axially asymmetric with respect to the axial center m (the axial center of the upper and lower inclined groove regions), and the axial dimension X1 of the upper region is lower than the axial center m. It is larger than the axial dimension X2 of the side region. Further, one or a plurality of axial grooves 8d1 are formed on the outer peripheral surface 8d of the bearing sleeve 8 over the entire axial length. In this example, three axial grooves 8d1 are formed at equal intervals around the circumference. Further, chamfers 8e and 8f are formed at the outer peripheral corners of the upper end surface 8b and the lower end surface 8c of the bearing sleeve 8, respectively.

  A spiral dynamic pressure groove 8c1 as shown in FIG. 3B, for example, is formed on the lower end surface 8c of the bearing sleeve 8 serving as a thrust bearing surface of the first thrust bearing portion S1. Spiral dynamic pressure grooves (not shown) are also formed on the inner bottom surface 7c1 of the housing bottom 7c, which is the thrust bearing surface of the second thrust bearing S2. In any thrust bearing surface, a herringbone shape, a radial groove shape, or the like may be employed as the shape of the dynamic pressure groove. Thrust bearing surfaces having dynamic pressure grooves can also be formed on both end surfaces 2 b 1 and 2 b 2 of the flange portion 2 b of the shaft member 2.

  As shown in FIG. 3C, the upper end surface 8b of the bearing sleeve 8 is formed into an inner diameter side region 8b2 and an outer diameter side region 8b3 by a circumferential groove 8b1 having a V-shaped cross section provided at a substantially central portion in the radial direction. One or a plurality of radial grooves 8b21 are formed in the inner diameter side region 8b2. In this example, three radial grooves 8b21 are formed at equal intervals in the circumferential direction.

  The seal member 10 is formed in a ring shape from a metal material such as brass or a resin material, and is fixed to the inner periphery of the upper end portion of the side portion 7 b that is the opening side of the housing 7. The inner peripheral surface 10a of the seal member 10 has a tapered surface shape in which the diameter is gradually expanded upward, and a tapered shape is formed between the inner peripheral surface 10a and the cylindrical outer peripheral surface 2a1 of the shaft portion 2a facing the inner peripheral surface 10a. The sealing space A is formed. The seal space A retains the lubricating oil inside the housing 7 by capillary force, and restricts leakage to the outside of the housing 7. Contrary to the illustrated example, the seal space 10 can also be formed by making the inner peripheral surface of the seal member 10 into a cylindrical surface and forming the outer peripheral surface 2a1 of the shaft portion 2a facing this into a tapered surface.

  4, the lower end surface 10b of the seal member 10 has a step, the inner diameter side region 10b1 of the step contacts the upper end surface 8b of the bearing sleeve 8, and the outer diameter side region 10b2 is a bearing. A Nusumi portion P is formed between the sleeve 8 and the upper end surface 8b apart from the upper end surface 8b.

  An outer periphery 10c of the seal member 10 extends in a cylindrical surface 10c1, a tapered surface 10c2 extending from the lower end of the cylindrical surface 10c1 in the inner diameter side inclination direction to the lower end surface 10b, and extending from the upper end of the cylindrical surface 10c1 in the inner diameter side inclination direction. And a tapered surface 10c3 reaching the upper end surface 10d. The cylindrical surface 10c1 is parallel to the axis, and is fitted to the inner periphery 7d of the housing opening by a clearance fit with an adhesive interposed.

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

  First, the shaft member 2 is arranged in the housing 7, and then the bearing sleeve 8 is pushed into the inner periphery 7 d of the housing 7 while the shaft portion 2 a is inserted into the inner peripheral hole thereof, and the lower end face 8 c is set to the bottom side of the housing 7. It is made to contact | abut to the step part 7e formed. As a result, the bearing sleeve 8 is positioned in the axial direction with respect to the housing 7. The bearing sleeve 8 can be fixed to the inner circumference 7d of the housing 7 by press-fitting, adhesion, combined use of press-fitting and adhesion, or other appropriate fixing means.

Thereafter, the seal member 10 is pushed into the opening on one end side of the housing 7, pushed forward to a predetermined position under the presence of an adhesive, and fixed to the housing 7 by solidification of the adhesive. Specifically, an adhesive is applied to the upper end portion (fixed region of the seal member 10) of the inner periphery 7d of the housing 7, and then the seal member 10 is pushed into the inner periphery 7d from the upper end opening of the housing 7 to seal the seal. The lower end surface 10 b (inner diameter side region 10 b 1) of the member 10 is brought into contact with the upper end surface 8 b of the bearing sleeve 8. When the seal member 10 is pushed in, the adhesive interposed between the cylindrical surface 10c1 and the inner periphery 7d serves as a lubricant, so that the generation of wear powder is reduced and the push-in operation is facilitated.

  FIG. 4 shows a state where the pushing of the seal member 10 is completed. In this state, the cylindrical surface 10c1 of the outer periphery 10c of the seal member 10 faces the inner periphery 7d of the housing 7 via an adhesive (not shown). The first tapered space T1 is adjacent to the closed side of the housing 7 from this portion, and the second tapered space T2 is adjacent to the opening side of the housing 7. The first tapered space T1 is formed between the lower tapered surface 10c2 of the outer periphery 10c of the seal member 10 and the inner periphery 7d of the housing 7, and is a lower side (housing closed side) in which the seal member 10 is pushed in. It has a shape that gradually expands toward). The second tapered space T2 is formed between the upper tapered surface 10c3 of the outer periphery 10c of the seal member 10 and the inner periphery 7d of the housing 7, and gradually expands upward toward the opening side of the housing 7. Has the shape. Both of the tapered spaces T1 and T2 open to the lower end surface 10b and the upper end surface 10d of the seal member 10, and the first tapered space T1 is in particular in communication with the pusmy part P and the circumferential groove 8b1.

  As the seal member 10 is pushed in, the adhesive M that wraps around the front side in the press-fitting direction of the seal member 10 is held by the capillary force of the first tapered space T1. At the time of pushing in, wear powder generated by galling between the seal member 10 and the housing inner periphery 7d is captured by the adhesive M in the first tapered space T1, and the adhesive M solidifies into the adhesive M. Contained. Due to the holding effect of the adhesive M by the first tapered space T1, the flow of the adhesive M toward the end face 8b of the bearing sleeve 8 is prevented, and the effect of capturing and containing the abrasion powder by the adhesive M is also enhanced. .

  In addition, the adhesive M is held by the capillary force of the second tapered space T2, and the adhesive M ensures a gap between the seal member outer periphery 10c and the housing inner periphery 7d on the inner side of the housing. Sealed. Particularly in this case, as shown by a broken line in FIG. 4, if the step portion 12 is provided on the inner periphery 7 d of the housing 7 facing the second tapered space T <b> 2, the second tapered shape after the seal member 10 is mounted. Since the amount of the adhesive M remaining in the space T2 increases, the sealing effect is further enhanced.

  In the above embodiment, the case where the seal member 10 is pushed into the inner periphery 7d of the housing 7 with a clearance fit is illustrated. However, the seal member 10 is press-fitted and fixed to the inner periphery of the housing 7 under the presence of an adhesive. You can also. In the case of press-fitting, the amount of generated abrasion powder increases due to sliding with the housing inner periphery 7d, but even in that case, the entry of abrasion powder into the housing 7 can be reliably prevented.

  Moreover, although the above embodiment illustrates the case where both the first tapered space T1 and the second tapered space T2 are provided, only one of the tapered spaces is provided as necessary. You can also.

When the assembly is completed as described above, the shaft portion 2a of the shaft member 2 is inserted into the inner peripheral surface 8a of the bearing sleeve 8, and the flange portion 2b is connected to the lower end surface 8c of the bearing sleeve 8 and the inner bottom surface 7c1 of the housing 7. It will be in the state accommodated in the space part between. Thereafter, the internal space of the housing 7 sealed with the seal member 10 is filled with a lubricating fluid, for example, lubricating oil, including the internal pores of the bearing sleeve 8. The oil level of the lubricating oil is maintained within the range of the seal space A.

When the shaft member 2 rotates, the regions (two upper and lower regions) of the inner peripheral surface 8a of the bearing sleeve 8 are opposed to the outer peripheral surface 2a1 of the shaft portion 2a via the radial bearing gap. Further, the region serving as the thrust bearing surface of the lower end surface 8c of the bearing sleeve 8 faces the upper end surface 2b1 of the flange portion 2b via the thrust bearing gap, and the region serving as the thrust bearing surface of the inner bottom surface 7c1 of the housing 7 is the flange. It faces the lower end surface 2b2 of the portion 2b via a thrust bearing gap. As the shaft member 2 rotates, the dynamic pressure of the lubricating oil is generated in the radial bearing gap, and the shaft portion 2a of the shaft member 2 is rotated in the radial direction by the lubricating oil film formed in the radial bearing gap. It is supported non-contact freely. Thus, the first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 2 in a non-contact manner so as to be rotatable in the radial direction are configured. At the same time, the dynamic pressure of the lubricating oil is generated in the thrust bearing gap, and the flange portion 2b of the shaft member 2 is rotatably supported in both thrust directions by the oil film of the lubricating oil formed in the thrust bearing gap. . Thereby, the first thrust bearing portion S1 and the second thrust bearing portion S2 that support the shaft member 2 in a non-contact manner so as to be rotatable in the thrust direction are configured.

As described above, the dynamic pressure groove 8a1 of the first radial bearing portion R1 is formed to be axially asymmetric with respect to the axial center m, and the axial dimension X1 of the upper region from the axial center m is the lower region. It is larger than the axial dimension X2 of {Fig. 3 (a)}. Therefore, when the shaft member 2 rotates, the lubricating oil pulling force (pumping force) by the dynamic pressure groove 8a1 is relatively larger in the upper region than in the lower region. Then, due to the differential pressure of the pulling force, the lubricating oil filled in the gap between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a flows downward, and the first thrust bearing portion S1 Thrust bearing gap → axial groove 8d1 → Nusumi part P → circumferential groove 8b1 → radial groove 8b21
The inner circumferential surface 8a of the bearing sleeve 8 and the outer circumferential surface 2a1 of the shaft portion 2a are circulated through the path.
Is returned to the radial bearing gap of the first radial bearing portion R1. In this way, the structure in which the lubricating oil flows and circulates in the internal space of the housing 7 prevents a phenomenon in which the pressure of the lubricating oil in the internal space becomes a negative pressure locally, resulting in the generation of negative pressure. Problems such as generation of bubbles, leakage of lubricating oil and generation of vibration due to generation of bubbles can be solved. Even if bubbles are mixed in the lubricating oil for some reason, when the bubbles circulate along with the lubricating oil, it is discharged from the oil surface (gas-liquid interface) of the lubricating oil in the seal space A to the outside air. The adverse effects due to the bubbles are more effectively prevented.

  In addition, the bearing structure of each bearing part R1 * R2 and T1 * T2 is not limited to the above illustration, It can change into various bearing structures. For example, the radial bearing portions R1 and R2 can be constituted by arc bearings or step bearings, and the thrust bearing portions T1 and T2 can also be constituted by pivot bearings that contact and support the shaft end of the shaft member 2 at the housing bottom portion 7c. .

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. It is a figure which shows sectional drawing {FIG. 3 (a)}, a lower end surface {FIG. 3 (b)}, and an upper end surface {FIG. 3 (c)} of a bearing sleeve. It is a partial expanded sectional view which shows the periphery of the upper end side inner periphery of a housing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 2 Shaft member 2a Shaft part 2b Flange part 7 Housing 7c Bottom part 7c1 Inner bottom surface 8 Bearing sleeve 8a Inner peripheral surface 10 Seal member 10c Outer periphery 10c1 Cylindrical surface 10c2 Tapered surface 10c3 Taper surface R1 Radial bearing part R2 Radial bearing part S1 Thrust bearing portion S2 Thrust bearing portion M Adhesive T1 Tapered space (first tapered space)
T2 Tapered space (second tapered space)

Claims (4)

A housing having one end opened and the other end closed, a bearing sleeve disposed inside the housing, a shaft member inserted into the bearing sleeve, and an opening of the housing are sealed to contact the end surface of the bearing sleeve. A hydrodynamic bearing device comprising a sealing member in contact with the shaft member and the bearing sleeve in a non-contact manner by a hydrodynamic action of a lubricating fluid generated in a radial bearing gap between the shaft member and the bearing sleeve;
The outer periphery of the seal member is bonded and fixed to the inner periphery of the housing. The seal member opens between the outer periphery of the seal member and the inner periphery of the housing at the end face of the seal member facing the bearing sleeve, and gradually expands on the closed side of the housing. The first tapered space holding the adhesive is interposed,
The adhesive held in the first tapered space is not in contact with the end surface of the bearing sleeve that contacts the end surface of the seal member,
The end face of the seal member is separated from the end face of the bearing sleeve on the outer diameter side of the contact portion between the bearing sleeve and the seal member and on the inner diameter side of the first taper space. There is a thin section that communicates with the
A hydrodynamic bearing device, characterized in that a lubricating fluid circulates and flows in an internal space of a housing including a relief portion and a radial bearing gap .   Between the outer periphery of the seal member and the inner periphery of the housing, a second tapered space that holds the adhesive and that opens at the housing opening side end surface of the seal member and gradually expands at the opening side of the housing is interposed. The hydrodynamic bearing device according to claim 1.   A hydrodynamic bearing device in which a tapered surface forming a tapered space according to claim 1 or 2 is provided on an outer periphery of a seal member.   A motor provided with the hydrodynamic bearing apparatus as described in any one of Claims 1-3.