JP5389209B2 - Fluid dynamic pressure bearing manufacturing method, fluid dynamic pressure bearing, motor, and disk drive device - Google Patents

Description

  The present invention relates to a manufacturing method of a fluid dynamic pressure bearing, a fluid dynamic pressure bearing manufactured by the manufacturing method, a motor including the fluid dynamic pressure bearing, and a disk drive device including the motor, and more particularly to a lubricant in the fluid dynamic pressure bearing. It relates to the technology of filling.

  As devices for recording and reproducing digital data, magnetic disk drive devices such as hard disk drives, and optical disk drive devices such as CD (Compact Disc) devices and DVD (Digital Versatile Disc) devices are known. These devices include a motor for rotating the disk. In recent years, fluid dynamic pressure bearings are often used in this motor.

  Various methods represented by the following Patent Document 1, Patent Document 2, and Patent Document 3 have been proposed as manufacturing methods for fluid dynamic bearings.

JP 2002-5170 A JP 2005-98393 A JP-A-2005-273908

About the manufacturing method of a fluid dynamic pressure bearing, this inventor recognized the following subjects.
The fluid dynamic pressure bearing has a storage region for storing a lubricant. An oil repellent area for repelling the lubricant is provided in the vicinity of the entrance of the storage area to prevent the lubricant from leaking out. In the conventional method of manufacturing a fluid dynamic pressure bearing, the lubricant adheres to the oil-repellent region when the lubricant is injected into the storage region. This adhered lubricant may impair the function of the oil repellent region.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method of manufacturing a fluid dynamic bearing that reduces contamination by a lubricant.

One embodiment of the present invention relates to a method of manufacturing a fluid dynamic bearing. This manufacturing method prepares a fluid dynamic pressure bearing in which no lubricant is injected in a predetermined working space, and prevents leakage of the lubricant in the vicinity of an inlet of a storage region for storing the lubricant of the fluid dynamic pressure bearing. The step of covering the oil repellent area provided for the purpose with a mask jig, the step of reducing the working space, and the lubricant to be poured enter the entrance of the storage area with the oil repellent area covered with the mask jig. A step of pouring the lubricant into the storage region, a step of restoring the working space, and a step of removing the mask jig after pouring the lubricant into the storage region .

  According to this aspect, since the lubricant is discharged after the nozzle that discharges the lubricant is inserted into the storage region in which the lubricant is stored, adhesion of the lubricant to other than the storage region can be reduced.

  Another aspect of the present invention is also a method for manufacturing a fluid dynamic pressure bearing. This manufacturing method prepares a fluid dynamic pressure bearing in which no lubricant is injected in a predetermined working space, and prevents leakage of the lubricant in the vicinity of an inlet of a storage region for storing the lubricant of the fluid dynamic pressure bearing. A step of covering the oil-repellent region provided for the purpose, a step of depressurizing the working space, and at least two positions at a distance from the storage region so that the injected lubricant droplets enter the storage region. A step of determining the aim of the nozzle, a step of ejecting an amount of lubricant droplets from at least two nozzles so as not to overflow the storage region, and a step of restoring the working space.

  According to this aspect, since the lubricant is injected after covering the oil-repellent region, adhesion of the lubricant to the oil-repellent region can be reduced.

  Note that any combination of the above-described constituent elements, and those obtained by replacing the constituent elements and expressions of the present invention with each other among methods, apparatuses, systems, etc. are also effective as an aspect of the present invention.

  According to the present invention, contamination by a lubricant can be reduced.

It is a longitudinal cross-sectional view of the brushless motor manufactured by the manufacturing method of the fluid dynamic pressure bearing which concerns on 1st and 2nd embodiment. 2A to 2C are process diagrams showing a method for manufacturing a fluid dynamic pressure bearing according to a comparative technique. FIGS. 3A to 3D are process diagrams showing a method of manufacturing a fluid dynamic pressure bearing according to the first embodiment. FIG. 4 is an enlarged view in which a tip portion on the discharge side of the discharge nozzle of FIG. 3 is enlarged. FIGS. 5A to 5D are process diagrams showing a method of manufacturing a fluid dynamic bearing according to the second embodiment.

  Hereinafter, the present invention will be described based on preferred embodiments and comparative techniques with reference to the drawings. The same or equivalent components and members shown in the drawings are denoted by the same reference numerals, and repeated descriptions are appropriately omitted. In addition, the dimensions of the members in each drawing are appropriately enlarged or reduced for easy understanding. In addition, in the drawings, some of the members that are not important for explaining the comparative technique and the embodiment are omitted.

The first and second embodiments of the present invention relate to a method of manufacturing a fluid dynamic pressure bearing, and more particularly to a method of injecting a lubricant such as oil into a predetermined storage region of the fluid dynamic pressure bearing. In the manufacturing method according to the first embodiment, when the lubricant is injected, the lubricant is injected after a nozzle having a flat tip is inserted into the storage region. Thereby, it can prevent that a lubricant adheres to the entrance vicinity of a storage area. In particular, it is possible to prevent the lubricant from adhering to the oil-repellent region provided near the entrance of the storage region and prevent the lubricant from leaking out, and to prevent the lubricant from leaking out more reliably.
In the manufacturing method according to the second embodiment, the lubricant is first injected after covering the oil-repellent region.

  The fluid dynamic pressure bearing manufactured using the manufacturing method according to the first or second embodiment is mounted on a brushless motor. Such a brushless motor is suitably used as a brushless motor that is mounted on a hard disk drive and drives a magnetic recording disk, and a disk drive motor that is mounted on an optical disk drive device such as a CD device or a DVD device.

  FIG. 1 is a vertical cross-sectional view of a brushless motor 100 manufactured by a method of manufacturing fluid dynamic bearings according to first and second embodiments. The brushless motor 100 includes a hub 2, a shaft 13, an annular magnet 8, a base plate 5, a laminated core 6, a coil 7, a sleeve 11, a plate 14, a lubricant 20, a thrust ring 12, Is provided. Hereinafter, the side on which the hub 2 is provided with respect to the base plate 5 will be described as the upper side.

  The hub 2, the shaft 13, the thrust ring 12, and the annular magnet 8 constitute a rotor, and these rotate together around the motor rotation axis R when the brushless motor 100 rotates. One end of the shaft 13 is fixed to an opening provided in the center of the hub 2 in a press-fitted state. The hub 2 has a cylindrical hanging part 2b having a shape hanging from the lower surface thereof. The thrust ring 12 is fixed to the inner peripheral surface of the hanging part 2b.

  An annular magnet 8 is bonded and fixed to the inner peripheral surface 2 a of the substantially cup-shaped hub 2. The annular magnet 8 is made of a rare earth material such as neodymium, iron, or boron, and faces 12 salient poles of a laminated core 6 described later in the radial direction. The annular magnet 8 is magnetized for driving with 8 poles in the circumferential direction.

The base plate 5, the laminated core 6, the coil 7, the sleeve 11, and the plate 14 constitute a stator, and rotatably support the rotor when the brushless motor 100 rotates. The base plate 5 is integral with the base of the hard disk drive. The base plate 5 is provided with an opening around the motor rotation axis R, and a sleeve 11 is bonded and fixed to the inner peripheral surface of the opening. A shaft 13 is accommodated in the sleeve 11. A plate 14 is bonded and fixed to the lower surface of the sleeve 11 and sealed.
The base plate 5 may be separate from the base of the hard disk drive.

  The laminated core 6 has an annular portion and 12 salient poles extending outward in the radial direction therefrom. The laminated core 6 is formed by laminating nine thin electromagnetic steel plates and integrating them by laser welding. A coil 7 is wound around each salient pole. When a three-phase substantially sinusoidal drive current flows through the coil 7, a drive magnetic flux is generated along the salient pole. The laminated core 6 is bonded and fixed to the base plate 5.

  Lubricant 20 is injected into a storage region 16 between the shaft 13, thrust ring 12 and hub 2 which are part of the rotor, and the sleeve 11 and plate 14 which are part of the stator. The shaft 13, the thrust ring 12, the hub 2, the sleeve 11, the plate 14, and the lubricant 20 constitute a fluid dynamic pressure bearing 18 that is a bearing that uses the dynamic pressure generated in the lubricant 20.

  A set of herringbone-shaped radial dynamic pressure grooves spaced apart from each other are formed on the inner peripheral surface of the sleeve 11. A herringbone-shaped thrust dynamic pressure groove is formed on the upper end surface of the sleeve 11. When the brushless motor 100 rotates, the rotor is supported in the thrust direction and the radial direction by the dynamic pressure generated in the lubricant 20 by these dynamic pressure grooves. When the lubricant 20 is supplied to the storage region 16, the lubricant 20 is also supplied to the radial dynamic pressure groove and the thrust dynamic pressure groove.

The outer peripheral surface 11a close to the upper end side of the sleeve 11 is an inclined surface having a larger diameter as it approaches the upper end surface. An inclination angle of the inclined surface with respect to the motor rotation axis R is defined as an inclination angle θis. The inner peripheral surface 12a of the thrust ring 12 that faces the outer peripheral surface 11a of the sleeve 11 is an inclined surface that increases in diameter toward the upper side. An inclination angle of the inclined surface with respect to the motor rotation axis R is defined as an inclination angle θth. The brushless motor 100 is designed so that 0 <θth <θis.
Therefore, the inlet space 22 sandwiched between the outer peripheral surface 11a of the sleeve 11 and the inner peripheral surface 12a of the thrust ring 12 has a shape that expands downward. As a result, a capillary phenomenon in which the lubricant 20 is drawn upward of the inlet space 22 occurs, so that the lubricant 20 once filled is difficult to leak out.
The vicinity of the lower end where the inclination of the inner peripheral surface 12 a of the thrust ring 12 ends is defined as the inlet 16 a of the inlet space 22. This is also the inlet 16 a of the storage area 16 including the inlet space 22.

  In order to prepare for the lubricant 20 to decrease due to evaporation or the like, the filling amount of the lubricant 20 is set to such an extent that the liquid level is located in the middle of the inlet space 22.

A so-called oil migration phenomenon in which a lubricant 20 such as oil diffuses along the surface of a member is known. In order to prevent the lubricant 20 from leaking to the outside due to this oil migration phenomenon, a first oil repellent region 30 a and a second oil repellent region 30 b are formed in the vicinity of the inlet 16 a of the storage region 16. The first oil-repellent region 30a is formed by applying an oil-repellent material such as a fluororesin to the surface near the lower end where the inclination of the outer peripheral surface 11a of the sleeve 11 ends. The second oil repellent region 30 b is formed by applying an oil repellent material such as a fluororesin to the lower surface of the thrust ring 12.
The first oil repellent region 30a and the second oil repellent region 30b repels the lubricant 20 even if it diffuses from the storage region 16 due to the oil migration phenomenon, so that leakage of the lubricant to the outside can be reduced.

  A manufacturing method according to the comparative technique for manufacturing the fluid dynamic bearing 18 included in the brushless motor 100 described above will be described. 2A to 2C are process diagrams showing a method for manufacturing the fluid dynamic bearing 18 according to the comparative technique.

FIG. 2A shows a preparation process for preparing to inject the lubricant 20. In this preparation process, the fluid dynamic pressure bearing before injecting the lubricant 20 is placed in the work space with the lower surface facing up. Then, the storage area 16 is depressurized by depressurizing the work space.
FIG. 2B shows an infusion process for instilling the lubricant 20. In this drip process, the nozzle 24 is brought close to the outside of the inlet 16a of the storage region 16, and a desired amount of the lubricant 20 is dipped there, and adhered to the vicinity of the inlet 16a by its surface tension. This desired amount is an amount sufficient to fill the storage region 16.
FIG. 2 (c) shows a drawing process for drawing the lubricant 20 into the storage region 16. In this drawing step, the working space is restored to atmospheric pressure, and the lubricant 20 is drawn into the storage region 16 due to a pressure difference between the inside and the outside of the storage region 16. Thereby, the storage region 16 is filled with the lubricant 20.

  In the manufacturing method according to the comparative technique, as shown in FIG. 2B, the lubricant 20 inevitably adheres to the first oil repellent region 30a and the second oil repellent region 30b. Therefore, after manufacturing the fluid dynamic pressure bearing 18, the lubricant 20 is removed from the first oil repellent region 30a and the second oil repellent region 30b by wiping or the like.

Here, the present inventor has found the following problems with the comparative technique.
The lubricant 20 adhering to the first oil repellent region 30a and the second oil repellent region 30b cannot be completely removed even by a method such as wiping. In the oil-repellent region, the portion where the lubricant 20 remains (hereinafter referred to as an oil passage) reduces the effect of preventing the oil migration phenomenon.

  Considering the oil path, it is understood that it is created by the residual lubricant 20 “adjusting” to the surface of the oil repellent area. That is, when an oil droplet hits a surface with increased surface tension such as an oil repellent region, the oil droplet is repelled to maintain its particle shape unless the amount of the oil droplet is large. However, if a large amount of oil droplets are hit and as a result, even if a single line of oil is dripped, an oil thin film is formed there, the surface tension is lowered, and the dripping is maintained. Then, oil gathers further in the oil dripping due to the difference in surface tension with the surroundings, and the oil dripping increases. It can be understood that the above-described oil passage is formed by this phenomenon.

  Once the oil passage is formed in the first oil repellent region 30a and the second oil repellent region 30b, the lubricant 20 diffuses outside through the passage. In addition, the oil passage is accelerated to the periphery as the lubricant 20 collects. If the lubricant 20 diffuses to the outside in this way, the surface of the recording disk may be contaminated and cause a problem. Further, if the leakage of the lubricant 20 continues, the lubricant 20 in the storage region 16 will eventually run out, and the fluid dynamic pressure bearing 18 may be burned out or the electric power for driving the brushless motor 100 may increase. There is.

  In view of such a problem of the comparative technique, the present inventor has created a method for manufacturing a fluid dynamic pressure bearing according to the first and second embodiments. FIGS. 3A to 3D are process diagrams showing a method of manufacturing a fluid dynamic pressure bearing according to the first embodiment.

  FIG. 3A shows a preparation process for preparing to inject the lubricant 20. In this preparation process, the fluid dynamic pressure bearing before injecting the lubricant 20 is placed in a work space where pressure can be reduced with the inlet 16a of the storage region 16 facing upward. And the storage area | region 16 is pressure-reduced by reducing the working pressure which is the atmospheric pressure of a working space to 100 (Pa) or less, for example.

FIG. 3B shows an injection process for injecting the lubricant 20. In this injection step, first, a discharge nozzle 26 for discharging the lubricant 20 is inserted into the inlet space 22. At this time, the discharge nozzle 26 moves to a horizontal position corresponding to the inlet 16 a of the storage region 16, and then moves vertically to the inside of the inlet space 22. Thereby, when setting the fluid dynamic pressure bearing before inject | pouring the lubricant 20 in a working space, the discharge nozzle 26 does not get in the way, and the fluid dynamic pressure bearing can be set easily in a short time.
After the discharge nozzle 26 is inserted into the inlet space 22, the lubricant 20 is discharged from the discharge nozzle 26. The amount of the lubricant 20 to be discharged is an amount that does not overflow from the storage region 16, for example, an amount that fills the inlet space 22.

  FIG. 3C shows a drawing process for drawing the lubricant 20 into the storage area 16. In this drawing step, the working space is restored to a pressure higher than the pressure inside the storage area 16 such as atmospheric pressure, and the lubricant 20 is drawn into the storage area 16 due to the pressure difference between the inside and the outside of the storage area 16. Thereby, the storage region 16 is filled with the lubricant 20.

  Note that the lubricant temperature, which is the temperature of the lubricant 20 to be discharged and filled, is preferably 40 ° C. or higher and 120 ° C. or lower. When the lubricant temperature is 40 ° C. or higher, the viscosity is sufficiently lowered, so that the above discharge and filling can be performed smoothly in a short period of time. Further, keeping the lubricant temperature at 120 ° C. or lower is advantageous in terms of evaporation.

  If the ratio of the capacity of the inlet space 22 to the capacity of the storage area 16 is larger than 50%, the liquid level of the lubricant 20 is located in the middle of the inlet space 22 after the drawing step of FIG. Therefore, even if the manufacturing variation of the fluid dynamic pressure bearing 18 and an appropriate margin are taken into consideration, if the ratio of the capacity of the inlet space 22 to the capacity of the storage region 16 is 60% or more, the fluid dynamic pressure obtained after the drawing-in process is obtained. It can be said that the bearing 18 has an appropriate amount of the lubricant 20. However, when the ratio is smaller than 50% or when it is intended to obtain a larger margin, a step of adding the lubricant 20 is further required.

  FIG. 3D shows an addition process for adding the lubricant 20 to a desired amount. In this additional step, at the atmospheric pressure, the tip of the discharge nozzle 26 is again inserted into the storage region 16, particularly below the liquid level of the lubricant 20 already filled. Then, the lubricant 20 is additionally discharged from the discharge nozzle 26 until a desired amount is obtained.

  Here, the discharge nozzle 26 will be described. FIG. 4 is an enlarged view in which the tip portion on the discharge side of the discharge nozzle 26 is enlarged. As the discharge nozzle 26, for example, a stainless pipe material such as SUS316 having an outer diameter φ of 0.35 (mm) and a wall thickness t of 0.05 (mm) is used. When inserted into the inlet space 22 in the injection step of FIG. 3B, a predetermined insertion angle with respect to the vertical direction, for example from 0 degrees, is set so that no part of the discharge nozzle 26 touches the sleeve 11. It is inserted from an angular direction of 45 degrees. In this case, since the amount of insertion into the inlet space 22 can be increased, the possibility of the lubricant 20 leaking outside when the lubricant 20 is injected can be reduced.

The shape of the tip portion on the discharge side of the discharge nozzle 26 will be described. In order for the discharge nozzle 26 to be inserted into the inlet 16a of the storage region 16, the outer dimension of one end (hereinafter referred to as the discharge end 26a) of the discharge nozzle 26 that discharges the lubricant 20 is 90% or less of the interval between the inlets 16a. Is necessary. However, if the outer dimension of the discharge end 26a is reduced, the discharge hole opened there also becomes smaller, so the time required to discharge the desired amount of the lubricant 20 increases, and the productivity may decrease.
Therefore, in the discharge nozzle 26 according to the first embodiment, the cross section 32 of the discharge end 26a has a flat shape such as an elliptical shape. This is realized by crushing the discharge end 26a with an appropriate force. In this case, the cross-sectional area can be increased even when the interval between the inlets 16a is narrow due to the flat shape. Therefore, the discharge of the desired amount of the lubricant 20 can be achieved in a short time, which contributes to the improvement of productivity.

When the discharge nozzle 26 is inserted into the inlet 16a, the direction in which the width of the flat shape is longer is aligned with the tangential direction of the ring-shaped inlet 16a. Further, if the inlet 16a of the storage region 16 is too wide, the diffusion amount of the lubricant 20 increases, so that the inlet 16a should be, for example, about 0.4 to 0.1 (mm). It is found from experience. Accordingly, the shorter width A of the flat shape of the discharge nozzle 26 is 90% of the interval between the inlets 16a, that is, 0.36 to 0.09 (mm).
In addition, it is preferable in terms of durability of the discharge nozzle 26 to make the longer width B of the flat shape 1.5 to 5 times the shorter width A.

  The flat discharge hole 34 opened at the discharge end 26a preferably has a shorter width C of 1/3 to 2/3 of the shorter width A of the discharge end 26a. In terms of the relationship with the interval between the inlets 16a of the storage region 16, the shorter width C of the discharge holes 34 is preferably 60% or less of the interval between the inlets 16a. If the shorter width C of the discharge hole 34 is not less than 1/3 of the shorter width A of the discharge end 26a, it does not take much time to discharge the lubricant 20. If the shorter width C of the discharge hole 34 is 2/3 or less of the shorter width A of the discharge end 26a, the thickness t (tube thickness) of the portion around the discharge hole 34 is sufficient. Therefore, a desired strength can be obtained and deformation is difficult.

  In the first embodiment, the interval between the inlets 16a of the storage region 16 is 0.25 (mm), the shorter width A of the flat discharge end 26a is 0.2 (mm), and the longer width B is 0. .4 (mm), the shorter width C of the discharge hole 34 is 0.1 (mm), and the longer width D is 0.3 (mm). Further, the discharge nozzle 26 is inserted into the inlet space 22 from an angle direction of 20 degrees with respect to the vertical direction.

  According to the method of manufacturing a fluid dynamic bearing according to the first embodiment, the lubricant 20 is discharged after the discharge nozzle 26 is inserted into the storage region 16, so that the lubricant 20 is discharged outside the storage region 16. Lubricant 20 becomes difficult to adhere. Therefore, the lubricant 20 is less likely to adhere to the first oil repellent region 30a and the second oil repellent region 30b, and diffusion of the lubricant 20 through the oil passage can be reduced.

  Further, according to the method of manufacturing the fluid dynamic pressure bearing according to the first embodiment, the lubricant 20 is low even when the ratio of the capacity of the inlet space 22 to the capacity of the storage region 16 is low, that is, even when the inlet space 22 is small. The desired amount of lubricant 20 can be filled. Therefore, this manufacturing method is suitably used for more types of fluid dynamic pressure bearings.

  Moreover, the addition process of the lubricant 20 is performed under atmospheric pressure. Therefore, work becomes easier. Furthermore, since the tip of the discharge nozzle 26 is inserted below the liquid level of the lubricant 20 that has already been filled, it becomes difficult to entrain air when the lubricant 20 is added.

  In the first embodiment, the case where the working pressure is reduced to 100 (Pa) or less in the preparation process has been described, but the present invention is not limited to this. For example, if the working pressure is reduced to 10 (Pa) or less, it is preferable in that air is less likely to be entrained in the lubricant, and if the working pressure is 5 (Pa) or less, it is preferable in that air is difficult to dissolve in the lubricant. .

  Although 1st Embodiment demonstrated the case where the lubricant 20 was added under atmospheric pressure in an addition process, it is not restricted to this. For example, re-discharge may be performed under a reduced pressure environment. In this case, it is preferable because air entrainment in the lubricant can be reduced.

  In the first embodiment, the case where the same discharge nozzle 26 as the discharge nozzle 26 used in the injection step is used when the lubricant 20 is added in the addition step is described, but the present invention is not limited to this. Since a reduced pressure environment is not required to add the lubricant 20, for example, after the fluid dynamic pressure bearing 18 is moved to a place different from the work space where pressure reduction is possible, lubrication is performed using a nozzle different from the discharge nozzle 26. An agent may be added. In this case, since it is not necessary to use a decompression device that can be a large scale in the additional step, the utilization efficiency of the decompression device can be improved. In addition, a lubricant discharge device more suitable for each of the injection process and the additional process can be used. For example, a discharge device having a large flow rate of lubricant per unit time can be used in the injection step, and a device capable of accurately controlling the discharge amount can be used in the additional step. This makes it possible to further improve productivity and quality.

  In the first embodiment, the discharge end 26 a of the discharge nozzle 26 may be formed of a material softer than the material constituting the fluid dynamic pressure bearing 18, for example, a fluororesin. In this case, even if the discharge end 26a hits the member of the fluid dynamic pressure bearing 18, the wall surface is hardly damaged. Further, since the contact between the discharge end 26a and the fluid dynamic pressure bearing 18 does not have to be so much concerned, the size of the discharge end 26a can be increased to supply more lubricant in a short time. The same effect can be obtained by coating the outer periphery of the discharge end 26a with resin or the like.

  A manufacturing method according to the second embodiment will be described. FIGS. 5A to 5D are process diagrams showing a method of manufacturing a fluid dynamic bearing according to the second embodiment.

  FIG. 5A shows a preparation process for preparing to inject the lubricant 20. In this preparation process, the fluid dynamic pressure bearing before injecting the lubricant 20 is placed in a work space where pressure can be reduced with the inlet 16a of the storage region 16 facing upward. Next, a cup-shaped first mask jig 44 is fitted from the plate 14 side of the sleeve 11 to cover the first oil-repellent region 30a. The ring-shaped second mask jig 43 is set on the lower surface of the thrust ring 12 so as to cover the second oil repellent region 30b. After the first mask jig 44 and the second mask jig 43 are set, the storage area 16 is depressurized by reducing the working pressure of the working space to, for example, 100 (Pa) or less.

  FIG. 5B shows an injection introduction process for injecting and introducing the lubricant 20. In this injection introducing step, two lubricant tanks 40a and 40b that hold the lubricant 20 therein, and two injection nozzles 41a and 41b that inject the lubricant 20 held in the lubricant tanks 40a and 40b, A temperature control device (not shown) for controlling the working space inside the manufacturing apparatus and the injected lubricant 20 within ± 10 ° C. with respect to a desired temperature is prepared.

  The two injection nozzles 41 a and 41 b face each other and are arranged so as to surround the inlet 16 a of the storage region 16. Further, the two injection nozzles 41 a and 41 b are arranged at positions away from the storage area 16. The aim of each of the injection nozzles 41a, 41b is determined so that the droplets 42 of the lubricant 20 injected from the two injection nozzles 41a, 41b enter the inlet 16a of the storage region 16.

  Each of the two lubricant tanks 40a and 40b includes pressure control means such as a piezoelectric element for controlling the pressure of the lubricant 20 inside. By applying a voltage pulse to the pressure control means, the hydraulic pressure of the lubricant 20 in the lubricant tank can be instantaneously increased. In this way, the hydraulic pressure is increased instantaneously, and the lubricant 20 is pushed out from the injection nozzle 41. The extruded lubricant 20 flies into the inlet space 22 as fine droplets 42. The amount of the lubricant 20 injected from the two injection nozzles 41 a and 41 b is set to an amount that does not overflow from the inlet space 22.

  FIG. 5C shows a drawing process for drawing the lubricant 20 into the storage region 16. In this drawing step, the working space is restored to a pressure higher than the pressure inside the storage area 16 such as atmospheric pressure, and the lubricant 20 is drawn into the storage area 16 due to the pressure difference between the inside and the outside of the storage area 16. Thereby, the storage region 16 is filled with the lubricant 20. Thereafter, the first mask jig 44 and the second mask jig 43 are removed.

As described in the first embodiment, in some cases, it is necessary to add the lubricant 20 after the pulling-in process.
FIG. 5 (d) shows an additional step of adding the lubricant 20 to a desired amount. In this additional step, the same steps as the above-described preparation step and injection introduction step are repeated, and thus description thereof is omitted. The storage area 16 is filled with the lubricant 20 until a desired amount is reached by the additional process. As described in the first embodiment, the additional step may be performed under a reduced pressure environment or an atmospheric pressure environment.

  According to the method of manufacturing a fluid dynamic bearing according to the second embodiment, the first oil repellent region 30a and the second oil repellent region 30b are covered with a mask jig when the lubricant 20 is injected. Therefore, adhesion of the lubricant 20 to the first oil repellent region 30a and the second oil repellent region 30b can be prevented.

  Further, in the fluid dynamic pressure bearing manufacturing method according to the second embodiment, it is not necessary to insert the two injection nozzles 41 a and 41 b into the inlet space 22, so that it is difficult to damage the wall surface of the fluid dynamic pressure bearing. . In addition, since the lubricant 20 is injected as fine droplets 42, the lubricant 20 can be preferably injected even when the inlet 16a of the storage region 16 is narrow. When the injection time and the number of voltage pulses are considered to be proportional to the injection amount, the injection amount of the lubricant 20 can be adjusted more accurately by controlling them.

  Further, in the method of manufacturing the fluid dynamic pressure bearing according to the second embodiment, the lubricant 20 can be injected using the two injection nozzles 41a and 41b simultaneously. Therefore, the work time can be shortened accordingly.

  Further, the temperature of the injected lubricant 20 is controlled within ± 10 ° C. with respect to a desired temperature by the temperature control device. Accordingly, the flight trajectory of the droplets 42 that vary depending on the temperature can be stabilized, and the lubricant 20 can be injected more efficiently. Note that a temperature control device that controls the temperature of the lubricant 20 within ± 5 ° C. with respect to a desired temperature is more preferable from the viewpoint of stabilizing the trajectory of the droplets 42.

  In the second embodiment, the case where the two injection nozzles 41a and 41b are used has been described. However, the present invention is not limited to this, and any number of injection nozzles may be used as long as space allows.

  In the second embodiment, the case where the lubricant 20 is injected by applying a voltage pulse to pressure control means such as a piezoelectric element has been described, but the present invention is not limited to this. For example, a heater may be provided inside the lubricant tank and the heater may be heated. Bubbles are generated in the lubricant by heating with the heater, and the lubricant is injected by the pressure of the bubbles. In this case, a heater for controlling the temperature of the lubricant and a heater for injecting the lubricant can be used together, which is convenient.

  If the lubricant 20 is present in the inlet space 22 of the fluid dynamic pressure bearing 18 more than necessary, the possibility that the lubricant 20 leaks due to unintended vibration or the like increases. For this reason, in the manufacturing methods according to the first and second embodiments, after the lubricant 20 is filled, a nozzle for sucking out the lubricant 20 is inserted into the lubricant 20, and the amount of the lubricant 20 is increased. A sucking step of sucking out until a desired amount is obtained may be further included. In this sucking process, the lubricant 20 is sucked out while measuring the amount of the lubricant 20 by a measuring means such as a laser sensor under atmospheric pressure. In this case, excess lubricant 20 can be sucked out, and the possibility that the lubricant 20 leaks can be reduced. Further, the cost can be reduced by reusing the sucked lubricant 20.

In the first embodiment and the second embodiment described above, the fluid dynamic pressure bearing 18 may be heated to work. When the fluid dynamic pressure bearing 18 is heated, the sleeve 11 and the thrust ring 12 are thermally expanded, and the capacity of the storage region 16 and the inlet space 22 is temporarily expanded. As a result, the lubricant 20 is filled more smoothly into the storage region 16 and the working efficiency is improved.
The temperature at which the fluid dynamic pressure bearing 18 is heated is desirably 40 ° C. or higher and 120 ° C. or lower. If it becomes 40 degreeC or more, since the capacity | capacitance of the storage area | region 16 and the entrance space 22 is fully expanded, the above-mentioned filling can be performed smoothly in a short period of time. Further, keeping the temperature of the lubricant 20 at 120 ° C. or less is advantageous in terms of evaporation.

  Although the present invention has been described based on the embodiments, the embodiments merely show the principle and application of the present invention, and the embodiments are defined in the claims. Needless to say, many modifications and arrangements can be made without departing from the spirit of the present invention.

The technical idea according to the embodiment may be defined by the following items.
(Item 1)
Preparing a fluid dynamic bearing 18 into which a lubricant 20 is not injected in a predetermined working space;
Depressurizing the working space;
Inserting a nozzle 26 for discharging a lubricant into the storage region 16 for storing the lubricant 20 of the fluid dynamic bearing 18;
Discharging a quantity of lubricant 20 that does not overflow from the storage area 16 to the storage area 16;
And a step of restoring pressure in the working space.
(Item 2)
The method for manufacturing a fluid dynamic pressure bearing according to item 1, wherein the fluid dynamic pressure bearing is heated in the discharging step.
(Item 3)
3. The method according to item 1 or 2, further comprising a step of inserting a nozzle 24 for discharging the lubricant 20 into the storage region 16 and additionally discharging the lubricant 20 after the step of returning the pressure. Manufacturing method of the fluid dynamic pressure bearing 18.
(Item 4)
The width of the inlet of the storage region 16 is not less than 0.1 millimeters and not more than 0.4 millimeters,
4. The fluid motion according to any one of items 1 to 3, wherein a tip of the nozzle 26 has a flat shape, and a width in a minor axis direction thereof is 90% or less of a width of an inlet of the storage region 16. A manufacturing method of the pressure bearing 18.

  2 hub, 5 base plate, 6 laminated core, 7 coil, 8 annular magnet, 11 sleeve, 12 thrust ring, 13 shaft, 14 plate, 16 storage area, 18 fluid dynamic pressure bearing, 20 lubricant, 22 inlet space, 24 Nozzle, 26 discharge nozzle, 30a first oil repellent area, 30b second oil repellent area, 40 lubricant tank, 41 injection nozzle, 42 droplets, 43 second mask jig, 44 first mask jig, 100 brushless motor .

Claims (7)

Preparing a fluid dynamic pressure bearing in which no lubricant is injected in a predetermined working space;
A step of covering an oil-repellent region provided in the vicinity of an inlet of a storage region for storing the lubricant of the fluid dynamic pressure bearing with a mask jig provided to prevent leakage of the lubricant;
Depressurizing the working space;
In a state where the oil repellent region is covered with the mask jig, the step of pouring the lubricant into the storage region so that the lubricant to be poured enters the entrance of the storage region;
Restoring the working space;
Removing the mask jig after pouring the lubricant into the storage area ;
A method for manufacturing a fluid dynamic pressure bearing, comprising:   The pouring step includes preparing at least two lubricant injection ports at positions away from the storage region, and injecting the lubricant from the at least two injection ports. A method for manufacturing a fluid dynamic pressure bearing according to claim 1.   The method of manufacturing a fluid dynamic bearing according to claim 2, wherein the pouring step is performed such that the at least two injection ports are arranged so as to surround an inlet of the storage region.   2. The mask jig includes a ring-shaped first portion and a second portion covering an oil-repellent region different from the oil-repellent region covered by the first portion. 4. A method for producing a fluid dynamic pressure bearing according to any one of 3 above.   5. The method for manufacturing a fluid dynamic bearing according to claim 1, wherein in the pouring step, an amount of lubricant that does not overflow from the storage region is poured.   6. The fluid dynamic bearing manufacturing method according to claim 1, further comprising a step of additionally pouring a lubricant so as to enter an inlet of the storage area after the step of returning to pressure. Method.   The fluid according to any one of claims 1 to 6, further comprising a step of inserting a suction port for sucking out the lubricant into the lubricant, and sucking out until the amount of the lubricant reaches a predetermined amount. A manufacturing method of a hydrodynamic bearing.

Images