JP4177975B2 - Hydrodynamic bearing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fluid dynamic bearing device configured by press-fitting a thrust plate into a shaft, and a method for fixing the thrust plate to a shaft.
[0002]
[Prior art]
A motor for rotationally driving a recording disk such as a hard disk is mainly composed of a fixed shaft and stator and a rotor to which a rotor magnet facing the stator is fixed. For example, a plurality of recording disks are fixed to the outer peripheral surface of the rotor, and the inner peripheral surface is rotatably supported on the outer peripheral surface of the shaft.
[0003]
As a bearing means for rotatably supporting the rotor shaft, there is a hydrodynamic bearing device in which a large number of grooves are provided on the shaft or the surface of the bearing and the rotor is supported by fluid pressure generated by the rotation of the rotor. A thrust dynamic pressure bearing portion of a dynamic pressure bearing device disclosed in Japanese Patent Application Laid-Open No. 8-105445 includes a pair of thrust plates disposed on the upper and lower portions in the axial direction of the shaft and facing each other, and the thrust of each thrust plate The rotor is composed of a thrust surface facing the surface in the axial direction and a lubricating fluid (oil) held between the thrust surfaces. On the thrust surface of the thrust plate, a dynamic pressure generating groove for generating a dynamic pressure in the lubricating fluid by the rotation of the rotor is formed.
[0004]
In such a configuration, the structure of the bearing portion is symmetrical and gives the same characteristics to any posture, so that it is easy to obtain stable rotation of the motor. In addition, since the dynamic pressure generating groove only needs to be formed on one side of the thrust plate, the yield of member processing is improved.
[0005]
[Problems to be solved by the invention]
A pair of thrust plates constituting such a thrust dynamic pressure bearing portion is generally fixed to the outer peripheral surface of the shaft by press fitting.
[0006]
When the thrust plate is press-fitted into the shaft, metal powder may be generated at the contact surface between the two and pushed out to the thrust surface side of the thrust plate. This metal powder is collected in the bearing portion together with oil by pumping the dynamic pressure generating groove during the operation of the motor, and may be caught and damaged in the bearing portion. Further, when the metal powder collects and adheres, it grows to a larger mass than the bearing gap, and the bearing portion may be seized. As described above, the durability of the bearing is lowered by the metal powder generated during press-fitting, and the reliability may be impaired.
[0007]
The subject of this invention is suppressing the malfunction by the metal powder which generate | occur | produces when the thrust plate which press-fits a thrust plate in a shaft in the hydrodynamic bearing apparatus by which the thrust plate which forms a thrust surface was press-fit in the shaft.
[0008]
[Means for Solving the Problems]
  The hydrodynamic bearing device according to a first aspect includes a shaft, a thrust plate, a cylindrical sleeve, and an adhesive. The thrust plate is press-fitted into the shaft and has a thrust surface inward in the axial direction. The cylindrical sleeve is formed between a radial inner peripheral surface facing a radial minute gap where a lubricating fluid is held between the thrust plate and the outer peripheral surface of the shaft on the thrust surface side of the thrust plate, and the thrust surface of the thrust plate. And a thrust surface facing each other through a thrust minute gap in which the lubricating fluid is held. The lubricating fluid is continuously filled from the radial minute gap to the thrust minute gap without interruption.
  The adhesive is cured in a state where metal powder generated by press-fitting is captured between the inner peripheral edge of the thrust plate on the thrust surface side and the outer peripheral surface of the shaft. Further, the axially inner side portion of the adhesive is positioned on the axially outer side from the thrust surface and is in contact with the lubricating fluid.
[0009]
In this hydrodynamic bearing device, the thrust plate is fixed to the shaft by press-fitting and bonding, and the adhesive is cured in a state where the metal powder generated at the press-fitting is captured. Therefore, the metal powder does not give a problem to the bearing portion made of the thrust surface of the thrust plate. As a result, desired durability can be obtained, and reliability as a bearing is maintained.
[0010]
The adhesive referred to here is a fluid that has a relatively high viscosity in the initial state, but is hardened under a predetermined condition and solidifies. When the metal powder adheres in the fluid state, the metal powder cannot be detached. It has the following properties.
[0012]
In this dynamic pressure bearing device, since the adhesive is held in a groove formed on the thrust surface side of the inner peripheral surface of the thrust plate, the adhesive reliably captures the metal powder generated during press-fitting.
[0013]
  A groove part here means the part whose diameter is larger than the press-fit surface closely_contact | adhered to a shaft in the internal peripheral surface of a thrust plate.The present inventionIn the hydrodynamic bearing deviceThe grooveThe portion is formed so that the radial dimension increases inward in the axial direction, and includes an adhesive reservoir where the surface of the adhesive is located.
[0014]
When uncured adhesive flows out of the groove and protrudes toward the bearing and hardens, it comes into contact with the sleeve during rotation and the fine adhesive is contained in the lubricating fluid held in the radial and / or thrust minute gaps. There is a concern that the metal powder captured in the powder or the adhesive diffuses, and the occurrence of damage, abnormal wear, seizure, or the like of the above-described bearing portion is increased. However, in this hydrodynamic bearing device, since the interface of the adhesive is located in the taper-shaped adhesive reservoir portion of the groove, the adhesive is kept until the adhesive is cured after the thrust plate and the shaft are fastened. The interface is pressed by atmospheric pressure, and a meniscus is formed at a position where the pressing force due to atmospheric pressure in the adhesive reservoir portion and the internal pressure of the adhesive balance. Therefore, the pressing force due to the atmospheric pressure becomes resistance, and the movement of the uncured adhesive from the groove side to the bearing portion side is suppressed. That is, it is possible to prevent problems caused by the outflow of the adhesive. The adhesive is cured while maintaining the meniscus.
[0015]
  Further, in claim 2In the hydrodynamic bearing device, it continues to the adhesive reservoir,A concave shape formed on the inner peripheral surface of the thrust plateIt further includes an adhesive groove.
[0016]
In this hydrodynamic bearing device, since the gap between the adhesive groove of the thrust plate and the shaft is very small, the adhesive is surely filled in the gap. As described above, since the cavity due to the insufficient adhesive is less likely to be generated, the adhesive can more reliably capture the metal powder generated during the press-fitting.
[0017]
In the hydrodynamic bearing device according to claim 3, the outer peripheral surface of the shaft is formed such that the outer diameter of the shaft gradually changes inward in the axial direction in the adhesive reservoir.
A portion on the inner side in the axial direction of the adhesive forms a meniscus in the adhesive reservoir.
[0018]
When uncured adhesive flows out of the groove and protrudes toward the bearing and hardens, it comes into contact with the sleeve during rotation and the fine adhesive is contained in the lubricating fluid held in the radial and / or thrust minute gaps. There is a concern that the metal powder captured in the powder or the adhesive diffuses, and the occurrence of damage, abnormal wear, seizure, or the like of the above-described bearing portion is increased. However, in this hydrodynamic bearing device, the radial dimension formed between the adhesive reservoir portion of the groove having the taper-shaped groove and the shaft-side adhesive reservoir portion gradually changes inward in the axial direction. Because it is located in the annular gap, the interface of the adhesive is pressed by the atmospheric pressure until the adhesive is cured after the thrust plate and the shaft are fastened, and the pressing force by the atmospheric pressure in the adhesive reservoir A meniscus is formed at a position where the internal pressure of the adhesive and the like balance. Therefore, the pressing force due to the atmospheric pressure becomes resistance, and the movement of the uncured adhesive from the groove side to the bearing portion side is suppressed. That is, it is possible to prevent problems caused by the outflow of the adhesive. The adhesive is cured while maintaining the meniscus.
[0019]
    Of the present inventionThe hydrodynamic bearing device includes a shaft, a thrust plate having a thrust surface on the inner side in the axial direction and fixed to the shaft, and a sleeve opposed to the shaft via a radial minute gap and opposed to the thrust surface via a thrust minute gap. And a lubricating fluid filled continuously from the radial minute gap to the thrust minute gap without interruption. Of this hydrodynamic bearing devicepreferableThe manufacturing method includes the following steps.
[0020]
  ◎ Adhesive supply process to supply adhesive to the inner peripheral edge of the thrust surface of the thrust plate,
  ◎ Press-in process in which a thrust plate supplied with adhesive is pressed into the shaft from the thrust surface side, and the metal powder generated during press-fitting is captured by the adhesive,
  ◎ Adhesive curing process to cure the adhesive that captured the metal powder,
◎ The process of inserting the sleeve into the shaft,
◎ When lubricating fluid is supplied from the radial minute gap to the thrust minute gap, the axially inward portion of the cured adhesive is located axially outward from the thrust surface and is in contact with the lubricating fluid Process.
thisManufacturingIn the method, the thrust plate is fixed to the shaft by press-fitting and bonding, and the adhesive captures the metal powder generated during the press-fitting and then hardens in that state. Therefore, the metal powder does not give a problem to the bearing portion made of the thrust surface of the thrust plate. As a result, desired durability can be obtained, and reliability as a bearing is maintained.
[0021]
  Of the present inventionOf hydrodynamic bearing deviceThe preferred manufacturing method isA groove portion forming step of forming an annular groove portion on the thrust surface side of the inner peripheral surface of the last plate is further provided. In the adhesive supply step, the adhesive is supplied to the groove portion of the thrust plate.
[0022]
  thisProduction methodThen, since the adhesive is held in a groove formed on the thrust surface side of the inner peripheral surface of the thrust plate, the adhesive can reliably capture the metal powder generated during press-fitting.
[0023]
  In a preferable manufacturing method of the hydrodynamic bearing device of the present invention, the grooveThe portion includes an adhesive reservoir portion formed so that the radial dimension increases toward the thrust surface side.
  In this fixing method in which the adhesive forms a meniscus in the adhesive reservoir after the press-fitting process, the adhesive meniscus is located in the tapered adhesive reservoir in the groove, so that the thrust plate is fastened to the shaft. When the adhesive in the fluid state tries to move to the thrust surface side, the curvature of the liquid surface tends to gradually decrease, which becomes a resistance and the movement is suppressed. Due to this sealing effect, the adhesive does not easily flow out from the groove portion to the bearing portion side at the time of press-fitting and until the adhesive is cured after the press-fitting.
[0024]
  In a preferable manufacturing method of the hydrodynamic bearing device of the present invention, the grooveThe portion further includes an adhesive groove that is continuous with the adhesive reservoir and forms a minute gap filled with the adhesive between the outer peripheral surface of the shaft.
[0025]
  thisManufacturingIn the method, since the gap between the adhesion groove of the thrust plate and the outer peripheral surface of the shaft is very small, the adhesive is reliably filled in the gap. As described above, since the cavity due to the insufficient adhesive is less likely to be generated, the adhesive can more reliably capture the metal powder generated during the press-fitting.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
(1) Overall motor structure
FIG. 1 is a longitudinal sectional view schematically showing a schematic configuration of a motor 1 in which a fluid dynamic bearing device 5 as an embodiment of the present invention is employed. The motor 1 is a recording disk drive motor, but the present invention is not limited to this embodiment.
[0027]
In FIG. 1, the recording disk drive motor 1 includes a bracket 2, a shaft 3 whose lower end is fitted and fixed in a central opening 2 a of the bracket 2, and a rotor 4 that is rotatable with respect to the shaft 3. Prepare. The rotor 4 includes a rotor hub 4a on which a recording disk (not shown) is placed on the outer peripheral portion, and a sleeve portion that is positioned on the inner peripheral side of the rotor hub 4a and is axially supported by the shaft 3 via the hydrodynamic bearing device 5. 4b. A rotor magnet 6 is fixed to the inner peripheral portion of the rotor hub 4a by means such as adhesion, and the stator 7 is mounted on the bracket 2 so as to face the rotor magnet 6 in the radial direction.
[0028]
Note that OO shown in FIG. 1 is the center line of the motor 1, that is, the rotation axis of the rotor 4. In the present embodiment, the vertical direction in FIG. 1 is referred to as the “axis vertical direction” for convenience, but the direction in the actual mounting state of the motor 1 is not limited.
[0029]
(2) Structure of hydrodynamic bearing device
The hydrodynamic bearing device 5 has a structure for rotatably supporting the rotor 4 with respect to the shaft 3 via the lubricating fluid 8. The upper bearing portion 11 and the lower bearing provided in the shaft 3 so as to be separated from each other in the axial direction. Part 12. Further, each bearing portion 11, 12 is composed of a thrust bearing portion 13 and a radial bearing portion 14.
[0030]
(1) Position of the hydrodynamic bearing device
A through hole 4c that penetrates the sleeve portion 4b in the axial direction so as to form a minute gap in which the lubricating fluid 8 is held between the inner peripheral surface and the outer peripheral surface 3a of the shaft 3 at the substantially central portion of the sleeve portion 4b. Is formed.
[0031]
An annular recess 3b is formed at a substantially central portion of the outer peripheral surface 3a of the shaft 3 so that a gap with the inner peripheral surface of the through hole 4c is enlarged. A communication hole 27 communicating with the outside air formed in the shaft 3 is opened in the recess 3b, and the outside air taken into the minute gap from the opening is substantially at the center of the inner peripheral surface of the recess 3b and the through hole 4c. An annular gas interposition part 15 is formed between the two. The lubricating fluid 8 held in the minute gap between the outer peripheral surface 3a of the shaft 3 and the inner peripheral surface of the through hole 4c by the gas intervening portion 15 is divided vertically in the axial direction, and the upper bearing portion 11 described later and Located in the lower bearing portion 12.
[0032]
The communication hole 27 is connected to the lower counter plate that is continuous with the vertical hole 27a that passes through the shaft 3 in the axial direction, the first opening 27b that opens from the vertical hole 27a to the concave portion 3b that extends in the radial direction, and the lower bearing portion 12. 19 and a second opening 27 c that opens to a space communicating with the outside air through a minute gap defined between the outer peripheral surface of the shaft 3. In addition, the vertical hole 27a is sealed with sealing members 28 and 29 made of an elastic member such as rubber, for example, at both ends of the shaft 3 after the shaft 3 is processed and cleaned. That is, the communication hole 27 communicates with the outside air only through a minute gap defined between the second opening 27 c and the inner peripheral surface of the lower counter plate 19 and the outer peripheral surface of the shaft 3.
[0033]
At both ends of the through hole 4c, openings 4d are formed in which thrust plates 16 described later are respectively disposed. As shown in FIG. 2, each opening 4d has an inner peripheral surface 4e that is radially separated from the outer peripheral surface 3a of the shaft 3, and a thrust surface 4f that faces outward in the axial direction. The thrust surface 4f extends from the radial inner peripheral surface 4g (described later) of the through hole 4c to the inner peripheral surface 4e of the opening 4d. Each opening 4d is closed by a ring-shaped counter plate 19 having an opening 19a through which the shaft 3 is inserted at the center.
[0034]
Hereinafter, the structure of the upper bearing portion 11 will be described, and the lower bearing portion 12 is the same as the upper bearing portion 11 and will not be described.
(2) Radial bearing structure
FIG. 2 is a partially enlarged view of FIG. 1 and is a longitudinal sectional view schematically showing a schematic configuration of the upper bearing portion 11. The radial bearing portion 14 is formed between the radial inner peripheral surface 4 g formed on the upper portion of the inner peripheral surface of the through hole 4 c of the rotor 4 and the outer peripheral surface 3 a of the shaft 3. The radial inner peripheral surface 4g faces the outer peripheral surface 3a of the corresponding shaft 3 so as to secure a radial minute gap in which the lubricating fluid 8 is held. A herringbone groove 24 for generating dynamic pressure in the lubricating fluid 8 is formed on the radial inner peripheral surface 4g. The herringbone groove 24 is formed by connecting spiral grooves in opposite directions to each other, and the generated dynamic pressure pumps the lubricating fluid 8 outward in the axial direction as indicated by an arrow B in FIG. Thus, the spiral groove located outward in the axial direction is shorter than the spiral groove located inward in the axial direction.
[0035]
Thus, the radial bearing part 14 is comprised by the radial inner peripheral surface 4g of the rotor 4, the outer peripheral surface 3a of the shaft 3, and the lubricating fluid 8 between them.
The herringbone groove 24 of the radial bearing portion 14 is shaped so that the generated dynamic pressure pumps the lubricating fluid 8 outward in the axial direction, so that the radial bearing portion 14 is filled with the lubricating fluid 8 or the like. Bubbles generated in the retained lubricating fluid 8 move from the high pressure bearing portion to the boundary surface side with the low pressure gas interposition portion 15 and are released from the gas interposition portion 15 to the atmosphere through the communication hole 27. .
[0036]
(3) Thrust bearing structure
The thrust plate 16 is an annular or disk-shaped member having a central hole formed therein, and is fixed to the outer peripheral surface 3a of the shaft 3 by press-fitting and bonding within the opening 4d.
[0037]
More specifically, the thrust plate 16 includes a cylindrical portion 16a having a hole to which the outer peripheral surface 3a of the shaft 3 is fixed on the inner peripheral surface, and a radially outer side from the lower end portion (the inner end portion in the axial direction). It consists of the disk-shaped part 16b extended in this. The disk-like portion 16b can reduce the thickness of the outer peripheral side portion of the thrust plate 16, and can reduce the amount of the lubricating fluid 8 held around. On the other hand, by making the fastening portion of the thrust plate 16 to the shaft 3 cylindrical, the contact area between the shaft 3 and the thrust plate 16 can be increased, the fastening strength can be maintained, and the assembly can be easily and accurately performed. be able to.
[0038]
The disc-like portion 16b of the thrust plate 16 has a thrust surface 16c facing inward in the axial direction, and the thrust surface 16c secures a thrust minute gap in which the lubricating fluid 8 is interposed with respect to the thrust surface 4f of the sleeve portion 4b. So as to face each other. A spiral groove 22 for generating dynamic pressure in the lubricating fluid 8 as the rotor 4 rotates is formed in the thrust surface 16 c of the thrust plate 16. The spiral groove 22 has a shape in which the generated dynamic pressure faces inward in the radial direction so that the lubricating fluid 8 is pumped inward in the radial direction, for example, as indicated by an arrow A in FIG. Yes.
[0039]
Thus, the thrust bearing portion 13 is constituted by the thrust surface 16c of the thrust plate 16, the thrust surface 4f of the sleeve portion 4b, and the lubricating fluid 8 therebetween.
[0040]
Further, the outer peripheral surface 16 d of the thrust plate 16 secures a predetermined gap between the inner peripheral surface 4 e of the opening 4 d and the inner peripheral surface of the counter plate 19.
Since the dynamic pressure generating means of the thrust bearing portion 13 is the spiral groove 22 as described above, the outer diameter of the thrust plate can be reduced compared with the case where the herringbone groove is used. The influence of the thrust bearing portion 13 on the magnetic circuit portion composed of the rotor magnet 6 and the stator 7 can be reduced, and a sufficient driving torque can be obtained. Further, the bearing loss of the thrust bearing portion 13 can be reduced, the electric efficiency of the motor 1 can be increased, and the power consumption can be suppressed.
[0041]
In this configuration, the dynamic pressure generating means formed in the thrust bearing portion 13 is a spiral groove, so that it cannot generate the necessary load supporting pressure by itself, but the adjacent radial bearing portion 14 is unbalanced in the axial direction. As shown by the arrow B, the lubricating fluid 8 is pumped outward in the axial direction (in the direction of the thrust bearing portion 13) and has a dynamic pressure required for the thrust portion by the cooperation of both bearing portions. Is generated to support the load.
[0042]
(4) Fixing structure of thrust plate to shaft
FIG. 3 is a partially enlarged view of FIG. 2, and is a longitudinal sectional view schematically showing a schematic configuration of the inner peripheral edge portion of the thrust plate 16 on the thrust surface 16 c side. A press-fit surface 16e is formed on the inner peripheral surface of the through hole of the thrust plate 16, and a groove portion 17 is formed on the inner periphery in the axial direction, that is, on the thrust surface 16c side. The groove portion 17 is annular, and is an annular recess having a diameter larger than that of the press-fit surface 16 e on the inner peripheral surface of the thrust plate 16, and holds the adhesive 18. The groove portion 17 is composed of an adhesive groove 17a extending with a small gap on the outer peripheral surface 3a of the shaft 3, and a taper-shaped adhesive reservoir portion 17b having a radial dimension increasing from the adhesive groove 17a toward the thrust surface 16c. Has been.
[0043]
The adhesive 18 is disposed in the groove portion 17, more specifically, is filled in a minute gap between the adhesive groove 17 a and the outer peripheral surface 3 a, and the surface is positioned near the middle of the adhesive reservoir portion 17 b. As the adhesive 18, an acrylic anaerobic adhesive or an epoxy adhesive can be used. However, since the lubricating fluid 8 comes into contact, the adhesive 18 is preferably an adhesive having a strong sealing property against oil.
[0044]
In the state of FIG. 3, the adhesive 18 is in a cured state, and minute metal powder generated when the thrust plate 16 is press-fitted is captured therein. That is, the fine metal powder generated during press-fitting is sealed with the adhesive 18. In particular, since the groove portion 17 has an adhesive groove 17a that secures a minute gap between the groove 3 and the shaft 3, the adhesive 18 is surely filled in a small amount, and a cavity or the like is hardly generated. ing. Therefore, the adhesive 18 can reliably capture the metal powder during press-fitting, and does not adversely affect the dynamic pressure generated on the bearing surface.
[0045]
An annular shaft side adhesive reservoir 26 is formed at a position corresponding to the adhesive reservoir 17b on the outer peripheral surface 3a. The shaft-side adhesive reservoir portion 26 is smoothly curved from the axially inner edge to the outer peripheral surface 3a, and a tapered surface 26a on which the surface of the adhesive 18 is positioned with the radial dimension decreasing inward in the axial direction. And a concave surface 26b. That is, an annular gap in which the outer diameter increases toward the inside in the axial direction and the inner diameter decreases is formed by the adhesive reservoir portion 17b and the shaft-side adhesive reservoir portion 26 of the groove portion 17. become.
[0046]
By the way, when the uncured adhesive flows out from the inside of the groove portion and protrudes and hardens to the bearing portion side, the adhesive comes into contact with the sleeve during rotation and is retained in the lubricating fluid held in the radial minute gap and / or the thrust minute gap. There is a concern that the fine powder or the metal powder trapped in the adhesive may diffuse and increase the occurrence of damage, abnormal wear, or seizure of the bearing portion. However, the interface of the adhesive 18 is in an annular gap where the radial dimension formed between the adhesive reservoir 17b of the groove and the shaft side adhesive reservoir 26 gradually changes inward in the axial direction. Therefore, until the adhesive 18 is cured after the thrust plate 16 and the shaft 3 are fastened, the interface of the adhesive 18 is pressed outward in the axial direction by the atmospheric pressure, and the adhesive reservoir portion A meniscus is formed at a position where the pressing force by the atmospheric pressure and the internal pressure of the adhesive balance in an annular gap formed between 17b and the shaft-side adhesive reservoir 26. Therefore, the pressing force by the atmospheric pressure becomes resistance, and the movement of the uncured adhesive 18 from the groove portion 17 side to the bearing portion side is suppressed. That is, it is possible to prevent a problem caused by the outflow of the uncured adhesive 18.
[0047]
Since the thrust plate 16 is press-fitted into the shaft 3 by press-fitting and adhesion, the fixing strength of both is improved compared to the case of only press-fitting. Also, the amount of adhesive used is significantly less than the amount of fixing using only the adhesive.
[0048]
Next, each dimension in the thrust plate 16 and its relationship will be described. However, the specific numerical values of this embodiment listed here are used for illustration of one embodiment using the present invention, and are not intended to limit the present invention itself.
[0049]
The thickness dimension a (axial dimension) of the thrust plate 16 is 2.2 mm in the present embodiment, and is preferably in the range of 2.0 to 2.5 mm. The axial dimension b of the groove portion 17 is 0.57 mm in the present embodiment, and is preferably in the range of 0.5 mm to 0.6 mm. The axial dimension c of the adhesive groove 17a is 0.40 mm in this embodiment, and is preferably in the range of 0.35 mm to 0.45 mm. The dimension d in the axial direction of the adhesive reservoir 17b is 0.17 mm in this embodiment, and is preferably in the range of 0.15 mm to 0.20 mm. The width dimension e (radial dimension) of the adhesive groove 17a is 0.03 mm in this embodiment, and is preferably 0.01 to 0.05 mm. The interference f between the thrust plate 16 and the shaft 3 is 0.00475 mm in the present embodiment, and is preferably 0.004 to 0.005 mm. The diameter of the shaft 3 is 4 mm.
[0050]
With the above numerical relationship, the object of capturing the metal powder at the time of press-fitting can be reliably achieved, and the amount of adhesive applied can be set appropriately. In particular, when the axial dimension d of the adhesive groove 17a, the ratio of the axial dimension d of the adhesive groove 17a to the thickness dimension a of the thrust plate 16, the width dimension e of the adhesive groove 17a, etc. are within the above ranges, The object of the present invention of capturing the metal powder can be achieved by the amount of the adhesive, and the thrust plate 16 can be fixed to the shaft 3 accurately and reliably in cooperation with the press-fitting.
(3) Assembly operation of the hydrodynamic bearing device
(1) Overall
Next, an assembly procedure of the hydrodynamic bearing device 5 of the recording disk drive motor 1 having the above-described configuration will be described.
[0051]
First, the lower thrust plate 16 is press-fitted into the shaft 3 while maintaining the accuracy of the perpendicularity to the shaft 3, and the shaft 3 is inserted into the through hole 4c of the sleeve portion 4b. Thereafter, the sleeve portion 4b is positioned at a predetermined position using a jig or the like, the gap between the sleeve portion 4b and the upper thrust surface 4f is measured, and the upper thrust plate 16 is press-fitted into the predetermined position. Next, after a predetermined amount of lubricating fluid 8 is injected from the upper and lower openings 4d of the through holes 4c, each counter plate 19 is attached.
[0052]
(2) Thrust plate fixation
The operation of fixing the thrust plate 16 to the shaft 3 will be described in detail. First, a predetermined adhesive 18 is applied to the groove portion 17 of the thrust plate 16. In this adhesive application step, the adhesive 18 is mainly filled in the adhesive groove 17a of the groove portion 17.
[0053]
Next, the thrust plate 16 is pressed into the shaft 3 before the adhesive is cured. In this press-fitting process, metal powder is generated by friction between the press-fitting surface 16e of the thrust plate 16 and the outer peripheral surface 3a of the shaft 3, and this metal powder is pushed out inward in the axial direction of the thrust plate 16, and the groove portion 17 is trapped in the adhesive within. Therefore, the metal powder generated by the press-fitting does not enter the thrust surface 16c side. For this reason, durability of the thrust bearing part 13 and the radial bearing part 14 improves, and reliability is maintained.
[0054]
When the press-fitting is completed and the thrust plate 16 is disposed at the fastening position on the shaft 3, the adhesive 18 is formed in an annular shape formed between the adhesive reservoir 17b of the groove 17 and the shaft-side adhesive reservoir 26. A meniscus is formed and held in the gap. Therefore, as described above, adverse effects on the thrust bearing portion 13 and the radial bearing portion 14 due to the outflow of the uncured adhesive 18 are unlikely to occur.
[0055]
Finally, the adhesive 18 is cured. This adhesive curing step may be a predetermined time or a special curing process depending on the type of adhesive. The adhesive is cured while maintaining the meniscus.
(4) Other embodiments
Although one embodiment of the recording disk driving motor according to the present invention has been described above, the present invention is not limited to this embodiment, and various modifications and corrections can be made without departing from the scope of the present invention. is there.
[0056]
The shape of the adhesive retaining groove provided on the thrust plate and the shaft is not limited to the above embodiment. For example, the length of each surface of the groove, the radial width, and the ratio thereof can be changed as appropriate.
[0057]
【The invention's effect】
In the hydrodynamic bearing device according to the first aspect, the thrust plate is fixed to the shaft by press-fitting and bonding, and the adhesive is cured in a state where the metal powder generated at the press-fitting is captured. Therefore, the metal powder does not give a problem to the bearing portion made of the thrust surface of the thrust plate. As a result, the durability of the bearing is improved and the reliability is maintained.
[0058]
In the hydrodynamic bearing device according to claim 2, since the adhesive is held in a groove formed on the thrust surface side of the inner peripheral surface of the thrust plate, the adhesive reliably captures the metal powder generated during press-fitting. is doing.
[0059]
In the hydrodynamic bearing device according to claim 3, since the meniscus of the adhesive is located in the taper-shaped adhesive reservoir portion of the groove, the adhesive in the fluid state with the thrust plate fastened to the shaft is Even if it tries to move to the surface side, the pressing force by the atmospheric pressure acting on the adhesive acts as a resistance and the movement is suppressed. Due to this sealing effect, the adhesive is unlikely to flow out from the groove portion to the bearing portion side at the time of press-fitting and until it hardens after press-fitting.
[0060]
In the hydrodynamic bearing device according to the fourth aspect, since the gap between the adhesion groove of the thrust plate and the shaft is very small, the adhesive is surely filled in the gap. As described above, since the cavity due to the insufficient adhesive is less likely to be generated, the adhesive can more reliably capture the metal powder generated during and after the press-fitting.
[0061]
In the hydrodynamic bearing device according to claim 5, the radial dimension in which the meniscus of the adhesive is formed between the adhesive reservoir portion of the groove and the shaft-side adhesive reservoir portion gradually increases inward in the axial direction. Because it is located in the changing annular gap, the interface of the adhesive is pressed outward in the axial direction by the atmospheric pressure until the adhesive is cured after the thrust plate and the shaft are fastened. A meniscus is formed at a position where the pressing force due to atmospheric pressure and the internal pressure of the adhesive balance in the gap. Therefore, the pressing force due to the atmospheric pressure becomes resistance, and the movement of the uncured adhesive from the groove portion side to the bearing portion side is suppressed. That is, it is difficult for the adhesive to flow out from the groove portion to the bearing portion side until the adhesive is cured after press-fitting.
[0062]
  Preferred manufacturing method of the hydrodynamic bearing device of the present inventionThen, the thrust plate is fixed to the shaft by press-fitting and bonding, and the adhesive captures the metal powder generated during the press-fitting and then hardens in that state. Therefore, the metal powder does not give any trouble to the bearing portion formed of the thrust surface of the thrust plate, and the durability of the hydrodynamic bearing is improved and the reliability is maintained.
[0063]
  Preferred manufacturing method of the hydrodynamic bearing device of the present inventionThen, since the adhesive is held in a groove formed on the thrust surface side of the inner peripheral surface of the thrust plate, the adhesive can reliably capture the metal powder generated during press-fitting.
[0064]
  Preferred manufacturing method of the hydrodynamic bearing device of the present inventionSince the adhesive interface is located in the taper-shaped adhesive reservoir in the groove, the adhesive interface is pressed by atmospheric pressure until the adhesive cures after the thrust plate and shaft are fastened. Then, a meniscus is formed at a position where the pressing force due to the atmospheric pressure in the adhesive reservoir portion and the internal pressure of the adhesive balance. Therefore, the pressing force due to the atmospheric pressure becomes resistance, and the movement of the uncured adhesive from the groove side to the bearing portion side is suppressed. That is, it is difficult for the adhesive to flow out from the groove portion to the bearing portion side until the adhesive is cured after press-fitting.
[0065]
  Preferred manufacturing method of the hydrodynamic bearing device of the present inventionThen, since the gap between the adhesive groove of the thrust plate and the outer peripheral surface of the shaft is very small, the adhesive is surely filled in the gap. As described above, since the cavity due to the insufficient adhesive is less likely to be generated, the adhesive can more reliably capture the metal powder generated during the press-fitting.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view schematically showing a schematic configuration of a motor according to an embodiment of the present invention.
FIG. 2 is a partial cross-sectional view schematically showing a schematic configuration of an upper thrust bearing portion and an upper radial bearing portion of the motor shown in FIG.
FIG. 3 is a longitudinal sectional view schematically showing an adhesion portion of a thrust plate.
[Explanation of symbols]
1 Motor
3 Shaft
4 Rotor
5 Hydrodynamic bearing device
16 Thrust plate
17 Groove
18 Adhesive

Claims (3)

A shaft extending in the axial direction ;
A thrust plate press-fitted into the shaft and having a thrust surface inward in the axial direction;
Lubricating between a radial inner peripheral surface facing a radial minute gap in which a lubricating fluid is held between the thrust plate and the outer peripheral surface of the shaft on the thrust surface side of the thrust plate, and the thrust surface of the thrust plate A cylindrical sleeve having a thrust surface opposed through a thrust micro-gap in which fluid is retained;
The lubricating fluid continuously filled without interruption from the radial minute gap to the thrust minute gap,
Between the thrust surface side inner peripheral edge of the thrust plate and the outer peripheral surface of the shaft, the adhesive is cured in a state where the metal powder generated by press-fitting is captured, and the inner side in the axial direction of the adhesive A portion is located axially outward from the thrust surface and contacts the lubricating fluid ;
A groove is formed in the axial direction inward from the press-fitting site between the thrust plate and the outer peripheral surface of the shaft,
The groove is
Adjacent to the press-fitting site, a minute gap configured between the outer peripheral surface of the shaft and the inner peripheral surface of the thrust plate and filled with the adhesive,
An adhesive reservoir portion that is adjacent to the minute gap and has a radial dimension larger than the minute gap and in which a portion on the inner side in the axial direction of the adhesive is located;
The hydrodynamic bearing device , wherein the press-fitting site, the minute gap, and the adhesive reservoir are arranged in this order from the outside in the axial direction toward the inside .   2. The hydrodynamic bearing device according to claim 1, wherein the minute gap further includes a concave adhesive groove formed on an inner peripheral surface of the thrust plate, which is continuous with the adhesive reservoir portion. The outer peripheral surface of the shaft is formed such that the outer diameter of the shaft gradually changes inward in the axial direction in the adhesive reservoir.
The hydrodynamic bearing device according to claim 1 or 2, wherein a portion on the inner side in the axial direction of the adhesive forms a meniscus in the adhesive reservoir.

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