JP4360482B2 - Hydrodynamic bearing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
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.
[0002]
[Prior art]
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.
[0003]
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).
[0004]
Normally, the bearing sleeve is fixed at a predetermined position on the inner periphery of the housing, and a seal portion is often provided at the opening of the housing in order to prevent the lubricating oil injected into the inner space of the housing from leaking to the outside. .
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-061641
[Problems to be solved by the invention]
In such a dynamic pressure bearing device, an adhesive may be used as means for fixing the bearing sleeve to the housing. In this case, for example, an adhesive is applied in advance to the inner peripheral surface of the housing, and after the bearing sleeve is inserted into the inner peripheral surface of the housing and positioned at a predetermined position, the adhesive is solidified. However, depending on the amount of adhesive applied, when the bearing sleeve is inserted into the inner peripheral surface of the housing and moved to a predetermined position, the excess amount of adhesive wraps around the front of the bearing sleeve in the moving direction, and positioning of the bearing sleeve May adversely affect bearing performance.
[0007]
For example, in the hydrodynamic bearing device described in Patent Document 1, the bearing sleeve housing is brought into contact with an inner surface of a seal portion (a collar portion) provided at one end portion of the housing by contacting one end surface of the bearing sleeve. However, if there is excess adhesive wrap around, the adhesive will enter between the end surface of one end of the bearing sleeve and the inner surface of the seal when the bearing sleeve is moved to the final position. The position of the sleeve relative to the housing may not be determined accurately.
[0008]
Further, the applicant forms a longitudinal groove on the outer peripheral surface of the bearing sleeve, and forms a lateral groove on the end surface on one end side of the bearing sleeve so that the longitudinal groove communicates with the inner peripheral surface of the bearing sleeve. An application has already been filed for a hydrodynamic bearing device in which a circulation path of a lubricating fluid filled in a space is formed (Japanese Patent Application No. 2002-117297). In this hydrodynamic bearing device, the lateral groove may be blocked by the adhesive due to the wraparound of the excess adhesive.
[0009]
An object of the present invention is to prevent the surplus adhesive from wrapping around and to avoid the influence of the surplus adhesive wraparound.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a housing, a bearing sleeve fixed to the inner peripheral surface of the housing, a shaft member having a shaft portion and a flange portion, a seal portion provided at one end portion of the housing, A radial bearing part that is provided between the thrust part provided at the other end of the housing and between the bearing sleeve and the shaft part, and that supports the shaft part in a radial direction by the dynamic pressure action of lubricating oil generated in the radial bearing gap. And a thrust bearing portion provided between the bearing sleeve and the thrust portion and the flange portion and supporting the flange portion in the thrust direction by the dynamic pressure action of lubricating oil generated in the thrust bearing gap, and an internal space of the housing in the dynamic pressure bearing device lubricating fluid is filled, the bearing sleeve is adhesively secured to the inner peripheral surface of the housing, the inner surface of the seal portion, bearing at its inner diameter side region Partially contact the inner diameter side region of the end surface on the one end side of the rib, and the outer diameter side region forms a nose portion away from the one end side end surface of the bearing sleeve, and the bearing sleeve is located on the inner diameter side region of the one end side end surface. Provided is a configuration having a radial groove, an axial groove on the outer peripheral surface, and a concave adhesive reservoir provided between the inner peripheral surface of the housing and the outer peripheral surface of the bearing sleeve.
[0011]
According to the above configuration, the lubricating fluid filled in the internal space of the housing can be circulated and circulated in the internal space, whereby the pressure of the lubricating oil in the internal space becomes a negative pressure locally. Can be eliminated, and problems such as generation of bubbles accompanying the generation of negative pressure, leakage of lubricating oil and generation of vibration due to the generation of bubbles can be solved. In addition, when the bearing sleeve is fixed to the inner peripheral surface of the housing with the adhesive, even if the adhesive wraps around, the gap between the outer diameter side region on the inner side surface of the seal portion and the end surface on the one end side of the bearing sleeve. Since there is a blank portion having a required space volume, it is difficult for the adhesive to flow in the direction of the radial groove, and thus it is possible to avoid a situation where the radial groove is blocked by the adhesive. Further, even when an excess amount of the adhesive is generated depending on the amount of application, the excess adhesive is captured by the concave adhesive reservoir, and the wraparound of the adhesive that adversely affects the positioning of the bearing sleeve and the bearing performance is prevented. .
[0012]
The adhesive reservoir can be formed on the inner peripheral surface of the housing or the outer peripheral surface of the bearing sleeve. Alternatively, the concave portions formed on both the inner peripheral surface of the housing and the outer peripheral surface of the bearing sleeve face each other, and the concave space formed by both can be used as the adhesive reservoir. Preferably, the adhesive reservoir is formed on the inner peripheral surface of the housing. Moreover, you may provide an adhesive agent in multiple places.
[0013]
The shape of the adhesive reservoir is not particularly limited, but is preferably a shape that gradually decreases toward both sides in the axial direction. When the bearing sleeve is inserted into the inner peripheral surface of the housing, an excessive amount of adhesive may be trapped in the adhesive reservoir. Even in such a case, the adhesive is positioned after the bearing sleeve is positioned. The adhesive trapped excessively in the adhesive reservoir flows to both sides in the axial direction narrowed by the capillary phenomenon until it solidifies, and the original fixing part (the outer peripheral surface of the bearing sleeve and the inner peripheral surface of the housing) In the filling gap). Therefore, there is no excess or deficiency in the amount of adhesive at the fixing site, and a stable fixing state can be obtained.
[0017]
In the above configuration, the bearing sleeve can be formed of sintered metal.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0019]
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 stator 4 is attached to the outer periphery of the bracket 6, and the rotor magnet 5 is attached to the inner periphery of the disk hub 3. The housing 7 of the hydrodynamic bearing device 1 is attached to the inner periphery of the bracket 6. The disk hub 3 holds one or more disks D such as magnetic disks. When the stator 4 is energized, the rotor magnet 5 is rotated by the electromagnetic force between the stator 4 and the rotor magnet 5, whereby the disk hub 3 and the shaft member 2 are rotated together.
[0020]
FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a housing 7, a bearing sleeve 8 and a thrust member 10 fixed to the housing 7, and a shaft member 2.
[0021]
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 lower end surface of the end surface 10a of the thrust member 10 and the flange portion 2b. 2nd thrust bearing part S2 is provided between 2b2. For convenience of explanation, the description will be given with the side of the thrust member 10 as the lower side and the side opposite to the thrust member 10 as the upper side.
[0022]
The housing 7 is made of, for example, a soft metal material such as brass or a resin material such as a thermoplastic resin, and has a cylindrical side portion 7b and an annular seal portion 7a integrally extending from the upper end of the side portion 7b to the inner diameter side. And. The inner peripheral surface 7a1 of the seal portion 7a is opposed to the tapered surface 2a2 provided on the outer periphery of the shaft portion 2a via a predetermined seal space S. The tapered surface 2a2 of the shaft portion 2a is gradually reduced in diameter toward the upper side (outside of the housing 7), and functions as a centrifugal force seal by the rotation of the shaft member 2.
[0023]
The shaft member 2 is formed of, for example, a metal material such as stainless steel, and includes a shaft portion 2a and a flange portion 2b provided integrally or separately at the lower end of the shaft portion 2a.
[0024]
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 at a predetermined position on the inner peripheral surface 7 c of the housing 7. .
[0025]
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 face 8b and the lower end face 8c, respectively.
[0026]
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. In addition, as a shape of the dynamic pressure groove, a herringbone shape, a radiation groove shape, or the like may be adopted.
[0027]
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 around the circumference.
[0028]
As shown in FIG. 2, in this embodiment, a concave adhesive reservoir U is formed on the inner peripheral surface 7 c of the housing 7. For example, the adhesive reservoir U is formed in a circumferential groove shape on the inner peripheral surface 7 c of the housing 7, and both axial side regions thereof are formed by tapered surfaces U <b> 1. Therefore, the adhesive reservoir U has a shape that gradually decreases toward both axial sides.
[0029]
Further, the inner side surface 7a2 of the seal portion 7a partially contacts the inner diameter side region 8b2 of the upper end surface 8b of the bearing sleeve 8 in the inner diameter side region 7a21, and the outer diameter side region 7a22 thereof is the upper end surface of the bearing sleeve 8. It is formed in an inclined shape or a curved shape so as to be separated from 8b. Therefore, a waste portion P having a required space volume is formed between the outer diameter side region 7a22 of the inner side surface 7a2 and the upper end surface 8b (including the chamfer 8e). An inner diameter side of the Nusumi part P communicates with the circumferential groove 8b1, and an outer diameter side has a tapered space formed between the chamfer 8e.
[0030]
The thrust member 10 is formed of a metal material such as brass, for example, and is fixed to the lower end portion of the inner peripheral surface 7 c of the housing 7. As shown in FIG. 4, for example, a herringbone-shaped dynamic pressure groove 10 a 1 is formed on the end surface 10 a of the thrust member 10 that becomes the thrust bearing surface of the second thrust bearing portion S <b> 2. In addition, you may employ | adopt spiral shape, a radiation groove shape, etc. as a shape of a dynamic pressure groove.
[0031]
The hydrodynamic bearing device 1 of this embodiment is assembled by the following process, for example.
[0032]
First, a predetermined amount of adhesive is applied to the inner peripheral surface 7 c of the housing 7. Then, the bearing sleeve 8 is inserted into the inner peripheral surface 7c of the housing 7, and the upper end surface 8b is brought into contact with the inner side surface 7a2 of the seal portion 7a. Thereby, the bearing sleeve 8 is positioned with respect to the housing 7. When this state is maintained and the adhesive is solidified, the bearing sleeve 8 is fixed while being positioned with respect to the housing 7.
[0033]
In this embodiment, since the adhesive reservoir U is provided on the inner peripheral surface 7c of the housing 7, even when an excess amount of the adhesive T (see the enlarged view in the circle in FIG. 2) is generated depending on the application amount, The surplus adhesive is captured by the concave adhesive reservoir U, and the wraparound of the adhesive T that adversely affects the positioning of the bearing sleeve 8 and the bearing performance is prevented. Further, since the adhesive reservoir U has a shape gradually reduced toward both sides in the axial direction due to the tapered surface U1, the adhesive reservoir U remains in the adhesive reservoir U after the positioning of the bearing sleeve 8 until the adhesive T is solidified. The excessively trapped adhesive T flows to both sides in the axial direction narrowed by capillary action, and is originally fixed (filling gap between the outer peripheral surface 8d of the bearing sleeve 8 and the inner peripheral surface 7c of the housing 7). Filled. Therefore, there is no excess or deficiency in the amount of adhesive at the fixing portion of the bearing sleeve 8, and a stable fixing state can be obtained.
[0034]
In addition, since the Nusumi portion P having a required space volume is formed between the outer diameter side region 7a22 of the inner side surface 7a2 of the seal portion 7a and the upper end surface 8b (including the chamfer 8e) of the bearing sleeve 8, Even if the adhesive wraps around, the adhesive T hardly flows in the direction of the radial groove 8b21. In particular, in this embodiment, there is a tapered space (formed between the chamfer 8e) on the outer diameter side of the Nusumi portion P, and the adhesive T in the Nusumi portion P is fixed by the capillary phenomenon of the tapered space. Since it is attracted in the direction of the portion (the filling gap between the outer peripheral surface 8d of the bearing sleeve 8 and the inner peripheral surface 7c of the housing 7), the flow in the radial groove 8b21 direction is more effectively prevented. Thereby, the situation where the radial direction groove | channel 8b21 is obstruct | occluded with the adhesive agent T is avoided.
[0035]
Next, the shaft member 2 is mounted on the bearing sleeve 8. The inner diameter of the bearing sleeve 8 is measured in a state where the bearing sleeve 8 is fixed to the housing 7, and the radial bearing clearance is reduced by matching the outer diameter of the shaft portion 2a (measured in advance). It can be set with high accuracy.
[0036]
Thereafter, the thrust member 10 is mounted on the lower end portion of the inner peripheral surface 7c of the housing 7, positioned at a predetermined position, and then fixed by an appropriate means such as an adhesive.
[0037]
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 end surface 10a of the thrust member 10. It will be in the state accommodated in the space part between. Thereafter, the internal space of the housing 7 sealed by the seal portion 7 a is filled with a lubricating fluid, for example, lubricating oil, including the internal pores of the bearing sleeve 8. The oil level of the lubricating oil is maintained within the range of the seal space S.
[0038]
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 that becomes 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 that becomes the thrust bearing surface of the end surface 10a of the thrust member 10 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.
[0039]
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 The clearance between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a is circulated through the path of the thrust bearing clearance → the axial groove 8d1 → the Nusumi portion P → the circumferential groove 8b1 → the radial groove 8b21. Returning 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. In addition, even if bubbles are mixed in the lubricating oil for some reason, when the bubbles circulate with the lubricating oil, it is discharged from the oil surface (gas-liquid interface) of the lubricating oil in the seal space S to the outside air. The adverse effects due to the bubbles are more effectively prevented.
[0040]
【The invention's effect】
The present invention has the following effects.
( 1 ) The lubricating fluid filled in the internal space of the housing is made to flow and circulate in the internal space by the Nusumi portion, the radial groove, and the axial groove, so that the pressure of the lubricating oil in the internal space is locally The phenomenon of negative pressure can be prevented, and problems such as the generation of bubbles due to the generation of negative pressure, the leakage of lubricating oil and the occurrence of vibration due to the generation of bubbles can be solved. In addition, when the bearing sleeve is fixed to the inner peripheral surface of the housing with an adhesive, even if the adhesive wraps around, the adhesive does not easily flow in the radial groove direction due to the nuisance part. A situation in which the groove is blocked by the adhesive can be avoided.
( 2 ) Since there is a concave adhesive reservoir between the inner peripheral surface of the housing and the outer peripheral surface of the bearing sleeve, even if an excess amount of adhesive is generated depending on the amount of application, the excessive adhesive is a concave adhesive reservoir. This prevents trapping of the adhesive, which adversely affects the positioning of the bearing sleeve and the bearing performance.
( 3 ) By forming the adhesive reservoir into a shape that gradually decreases toward both sides in the axial direction, the adhesive trapped excessively in the adhesive reservoir flows to both sides in the axial direction narrowed by capillary action, Since the fixing portion (filling gap between the outer peripheral surface of the bearing sleeve and the inner peripheral surface of the housing) is filled, there is no excess or deficiency in the amount of adhesive at the fixing portion of the bearing sleeve, and a stable fixing state can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a spindle motor for information equipment using a hydrodynamic bearing device according to the present invention.
FIG. 2 is a cross-sectional view showing an embodiment of a hydrodynamic bearing device according to the present invention.
3 is a cross-sectional view of a bearing sleeve {FIG. 3 (a)}, a lower end face {FIG. 3 (b)}, and an upper end face {FIG. 3 (c)}.
FIG. 4 is a view showing an end face of a thrust member.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 2 Shaft member 2a Shaft part 2b Flange part 7 Housing 7a Seal part 7a2 Inner side surface 7a21 Inner diameter side area | region 7a22 Outer diameter side area | region 7c Inner peripheral surface 8 Bearing sleeve 8a Inner peripheral surface 8b Upper end surface 8b1 Circumferential groove 8b2 Inner diameter region 8b21 Radial groove 8c Lower end surface 8d Outer peripheral surface 8d1 Axial groove R1 Radial bearing portion R2 Radial bearing portion S1 Thrust bearing portion S2 Thrust bearing portion U Adhesive reservoir P Nusumi portion 10 Thrust member

Claims (5)

A housing, a bearing sleeve fixed to the inner peripheral surface of the housing, a shaft member having a shaft portion and a flange portion, a seal portion provided at one end portion of the housing, and a second end portion of the housing; A radial bearing portion that is provided between the thrust portion, the bearing sleeve and the shaft portion, and supports the shaft portion in a radial direction by a dynamic pressure action of lubricating oil generated in a radial bearing gap, and the bearing sleeve and A thrust bearing portion provided between the thrust portion and the flange portion and configured to support the flange portion in a non-contact manner in a thrust direction by a dynamic pressure action of lubricating oil generated in a thrust bearing gap, and a lubricating fluid is provided in an internal space of the housing In the hydrodynamic bearing device filled with
The bearing sleeve is fixed to the inner peripheral surface of the housing with an adhesive,
The inner surface of the seal portion partially contacts the inner diameter side region of the one end surface of the bearing sleeve in the inner diameter side region, and the outer diameter side region is separated from the one end side end surface of the bearing sleeve. Form the
The bearing sleeve has a radial groove in the inner diameter side region of the end surface on the one end side and an axial groove on the outer peripheral surface;
A hydrodynamic bearing device , wherein a concave adhesive reservoir is provided between an inner peripheral surface of the housing and an outer peripheral surface of the bearing sleeve .   The hydrodynamic bearing device according to claim 1, wherein the adhesive reservoir is provided on an inner peripheral surface of the housing.   The hydrodynamic bearing device according to claim 1, wherein the adhesive reservoir has a shape that gradually decreases toward both axial sides. The bearing sleeve dynamic pressure bearing device according to any one of claims 1 to 3, characterized in that it is formed of a sintered metal. Motor comprising the fluid dynamic bearing device according to any one of claims 1-4.

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