JP4478297B2 - Viscous fluid filling method of fluid bearing, motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a viscous fluid charging method of a fluid bearing generating no irregulality in generating of dynamic pressure, by certainly removing bubble in lubricating oil 25, viscous fluid generating the dynamic pressure, and certainly charging the lubricating oil in a predetermined space. SOLUTION: In this charging method, pressure of environment around an assembly body into which the lubricating oil 25 has been injected is reduced to previously exhaust air inside the bearing (process shown in Fig. 1 (B)), and then the pressure of the environment around the assembly body is returned to a normal value to press and charge the viscous fluid into the predetermined space (process shown in Fig. 1 (C)).

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor for a hard disk drive (HDD) or a CD-ROM drive, for example, and a viscous fluid filling method of a fluid bearing when manufacturing the motor.
[0002]
[Prior art]
Conventionally, a shaft body (shaft, shaft), a bearing body (bearing, sleeve, fluid bearing portion) having a hole (insertion hole) into which the shaft body is inserted, and a predetermined space where the shaft body and the bearing body face each other. A motor having a fluid bearing having a viscous fluid (lubricating oil, air, etc.) to be held, and the bearing body rotatably supporting the shaft body by dynamic pressure generated in the viscous fluid when the shaft body and the bearing body rotate relative to each other Is well known.
[0003]
Conventionally, the following methods have been known as a method of injecting a liquid viscous fluid such as lubricating oil into a fluid bearing as a viscous fluid that generates dynamic pressure. That is, (1) a method of immersing the entire bearing device in lubricating oil and then depressurizing the entire device and injecting lubricating oil (described in US Pat. No. 5,112,142, hereinafter referred to as “first prior art”),
(2) A method in which lubricating oil is applied to the outer peripheral surface of the bearing assembly and injected by capillary action (hereinafter referred to as “second prior art”),
(3) A method in which lubricating oil is applied in advance to components constituting the fluid bearing before the bearing device is assembled (hereinafter referred to as “third prior art”),
(4) A method of injecting and infiltrating lubricating oil from the bearing opening under the normal pressure environment after the assembly of the bearing device (hereinafter referred to as “fourth prior art”),
(5) A method of applying lubricating oil, which is a viscous fluid, several times while assembling parts constituting the bearing (hereinafter referred to as “fifth prior art”).
[0004]
[Problems to be solved by the invention]
When fluid bearings are used for HDD motors and CD-ROM drive motors, the important points in motor assembly are that there are no bubbles in the lubricating oil of the dynamic pressure generating part, which is unnecessary and harmful to the outer periphery of the motor. It is to prevent the lubricant from remaining.
The reason for this is that if air bubbles remain in the lubricating oil, the generation of dynamic pressure may become uneven and the fluid bearing may not function properly.If unnecessary lubricating oil remains on the outer periphery of the motor, it will become an unclean substance. This is because it may adhere to the disk recording medium or the like and hinder the function and performance of the disk medium drive device.
[0005]
However, the first prior art described above has a problem that it is necessary to remove the lubricating oil adhering to the unnecessary portion other than the entire surface of the bearing device, and it is impossible to completely remove the unnecessary lubricating oil other than the bearing gap portion. It was not easy.
For this reason, although the technique of Claim 3 of Unexamined-Japanese-Patent No. 8-270653 is devised, the new problem that the number of processes increased and efficiency deteriorated was caused.
[0006]
In addition, the second prior art has a problem that it is difficult to fill the entire portion of the gap with the lubricating oil, and bubbles remain in the portion where the lubricating oil is not filled, so that the bubbles cannot be removed.
Further, the third conventional technique may cause uneven coating or uneven application, and requires skill in the work. The fourth conventional technique requires extra assembly time, and the fifth conventional technique. Had their own problems of requiring extra man-hours.
[0007]
Therefore, the present invention has been made in view of the above-described problems, and in particular, a dropping step for dropping a predetermined amount of viscous fluid onto the periphery of the hole portion while being in contact with the outer peripheral surface of the shaft body inserted into the hole portion. Next, the outside of the assembly into which the viscous fluid is dropped is decompressed, and the exhaust step of exhausting the air in the insertion hole from the opening portion side, and then when the decompressed state returns to the normal pressure state The filling step fills the insertion hole with the viscous fluid at the periphery of the hole at atmospheric pressure, so that unnecessary and harmful bubbles in the viscous fluid held by the fluid bearing are reliably removed and the viscous fluid is filled. The space to be filled is surely filled with viscous fluid, and excess viscous fluid can be easily removed, there is no risk of uneven dynamic pressure, and viscous fluid such as lubricating oil becomes an unclean substance. Fluid shaft that does not contaminate disc recording media And to provide a method for the viscous fluid-filled.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a viscous fluid filling method for a fluid bearing and a motor according to the following (1) and (2).
(1) A shaft body (shaft, shaft) 2;
An inner peripheral surface portion (hole portion 1a) close to the outer peripheral surface of the shaft body 2 inserted so as to be rotatable from the opening portion (opening portion above the hole portion 1a) toward the bottom side (motor base side in FIG. 6). An insertion hole (inner peripheral surface) and a reservoir (a space below the hole 1a inside the bearing 1) that is continuous with the inner peripheral surface and faces the outer peripheral surface of the shaft body 2 with a predetermined gap. Viscous fluid filling method for a fluid bearing in which the inside of the insertion hole is filled with a viscous fluid (lubricating oil) 25 dropped on the periphery of the opening portion in an assembly including a fluid bearing portion (bearing) 1 having a hole portion 1a. Because
A dropping step (step shown in FIG. 1A) in which a predetermined amount of the viscous fluid 25 is dropped on the periphery of the opening portion while being in contact with the outer peripheral surface of the shaft body 2 inserted into the opening portion;
Next, an evacuation step (step shown in FIG. 1 (B)) in which the outside of the assembly into which the viscous fluid 25 is dropped is decompressed and the air in the insertion hole 1a is exhausted from the opening portion side;
Next, there is a filling step (step shown in FIG. 1C) that fills the insertion hole 1a with the viscous fluid 25 at the periphery of the opening at atmospheric pressure when the reduced pressure state returns to the normal pressure state. A viscous fluid filling method for a fluid dynamic bearing.
(2) A motor configured using the assembly filled with a viscous fluid (lubricating oil) 25 by the viscous fluid filling method for a hydrodynamic bearing according to claim 1,
A motor (FIG. 6 spindle motor for CD-ROM drive) 100, comprising a stator (FIG. 6 motor base) 9 to which the bottom of the assembly (FIG. 6 bottom of the bearing 1) is fixed.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred example according to the embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is an explanatory view of each step of filling a viscous fluid in a fluid bearing method and motor according to an embodiment of the present invention, and FIG. 2 is provided with a recess for supplying lubricating oil in the motor of FIG. FIG. 3 is a sectional view of a fluid bearing having an oil repellent application region in one embodiment of the motor of the present invention, FIG. 4 is an assembly view of the fluid bearing of the motor of FIG. 1, and FIG. FIG. 6 is a cross-sectional view of the motor of FIG. 1, and FIG. 6 is an explanatory view of a process for removing excess lubricating oil by centrifugal force in the motor of 1. The same parts as those described above are denoted by the same reference numerals, and the description thereof is omitted.
[0010]
First, the structure of a spindle motor 100 for a CD-ROM drive which is a motor of this embodiment will be described with reference to a cross-sectional view of FIG.
[0011]
In FIG. 6, the lower end (bottom) of the bearing 1 of the spindle motor 100 is fixed to a motor base 9 formed of an iron base printed board.
Further, the bearing 1 and the shaft 2 inserted into the hole 1a formed in the bearing 1 constitute a fluid bearing.
[0012]
In a radial bearing that is a fluid bearing that supports the shaft 2 in the radial direction, a dynamic pressure groove portion 8 that generates dynamic pressure during rotation is formed in the inner periphery of the bearing 1 and / or the outer periphery of the shaft 2. The bearing 1 is configured to rotatably support the shaft 2 by the dynamic pressure generated in the shaft.
The dynamic pressure groove 8 shown in FIG. 6 is schematically drawn in a plan view.
[0013]
A thrust bearing 5, which is a fluid bearing that supports the shaft 2 in the thrust direction, is formed by processing spiral dynamic pressure grooves (not shown) on the upper and lower corresponding surfaces of the thrust portion formed at the lower end of the shaft 2, respectively. It is composed. (Up and down directions are based on the posture shown in FIG. 6. The same applies hereinafter)
[0014]
The same effect can be obtained regardless of which surface the dynamic pressure groove is processed.
Lubricating oil is filled in a predetermined space between the shaft 2 and the bearing 1, and dynamic pressure is generated inside the lubricating oil by the rotation of the shaft 2, and functions as a bearing device.
[0015]
Since the lubricating oil of the fluid bearing is not able to rotate when the shaft 2 or the bearing 1 flows out of the bearing due to the rotation of the shaft 2 or the bearing 1, seal portions are formed on the upper and lower sides of the fluid bearing to prevent the fluid from flowing out.
[0016]
A core 12 around which a coil 13 is wound concentrically with the bearing 1 is fixed to the motor base 9, and a rotor 22 rotatably held by a fluid bearing has a rotor yoke 17 and a ring shape on the lower inner peripheral side. A magnet 16 is fixed.
[0017]
Next, a method of filling the predetermined space to be filled with the lubricating oil in the fluid dynamic bearing of the spindle motor 100 will be described.
[0018]
First, the structure of the fluid bearing will be described with reference to the assembly diagram of FIG. 4. In the bearing 1, two dynamic pressure grooves 8 are formed in the inner peripheral portion of the hole 1a, and a thrust portion 23 having upper and lower surfaces is formed at the lower end of the shaft 2. The plate 3 has a dynamic pressure groove formed on a surface thereof facing the lower surface of the thrust portion 23 of the shaft 2.
The hole 1 a inside the bearing 1 that houses the thrust portion 23 forms a space having a larger diameter than other portions, and serves as a reservoir portion filled with the lubricating oil 25.
[0019]
When the fluid bearing shown in FIG. 4 is assembled, the shaft 2 is inserted into the hole 1a of the bearing 1 and the plate 3 is fitted from below, and the outer periphery of the plate 3 is fixed to the lower portion of the bearing 1 by bonding or caulking.
[0020]
Next, a method for injecting and filling lubricating oil into the fluid bearing after assembly will be described in order with reference to FIG.
[0021]
FIG. 1A is an explanatory diagram for supplying the lubricating oil 25 to the gap portion (predetermined space in which the lubricating oil should be retained) between the bearing 1 and the shaft 2 and the plate 3. Lubricating oil 25 is gently dripped and supplied to the periphery of the opening above the hole 1a while the dispenser 4 is in contact with the shaft 2 while rotating the bearing 1 at a low speed as shown in the figure.
At this time, there is air in the bearing gap, and the lubricating oil 25 stays in the vicinity of the entrance of the gap portion of the bearing and does not sufficiently reach the entire predetermined space.
[0022]
Next, as shown in FIG. 1B, the assembly into which the lubricating oil has been injected is stored in a sealed vacuum chamber 7, and the internal air is reduced to 0.01 to 0.001 Pa by the vacuum pump 6. Thereby, the air remaining in the bearing gap is removed (exhausted) as bubbles.
[0023]
Subsequently, as shown in FIG. 1C, the throttle valve 24 is opened, air is introduced into the vacuum chamber 7, and the internal pressure is gradually returned to normal pressure.
The air returning into the chamber 7 applies pressure from the outside so as to push the lubricating oil further into the interior, so that every corner of the predetermined space (gap, hole 1a) where the lubricating oil should hold the lubricating oil as a fluid bearing. Until it is pressed and filled.
Bubbles remaining inside the lubricating oil after filling are 1% or less. At this time, if the temperature is maintained at 60 ° C. to 100 ° C., the amount of bubbles is further reduced.
[0024]
Next, as shown in FIG. 1 (D), a surplus amount of lubricating oil that overflows and fills the gap portion, which is a predetermined space, is vacuumed and sucked 10 by a metal or plastic resin tube 14 such as brass or copper. The excess lubricating oil sucked up is stored in the lubricating oil reservoir 18.
By the above method, the amount of air bubbles remaining in the lubricating oil is limited, the lubricating oil is completely filled in the predetermined space required as a fluid bearing, and a fluid bearing assembly in which excess lubricating oil is removed is completed. .
[0025]
FIG. 2 shows another preferred configuration of the present embodiment, in which a recess 11 is provided around the opening of the hole 1a, which is a portion for supplying lubricating oil, so that more lubricating oil can be injected efficiently without flowing out, and surplus 2 is a cross-sectional view of a fluid bearing assembly configured to facilitate removal of a quantity of lubricating oil. FIG.
[0026]
FIG. 3 shows another embodiment of the present invention, which is configured as a fluid bearing 60 provided with an oil repellent application region in which the oil repellent 20 is applied around the opening of the hole 1a, and more than the actual rotational speed of the spindle motor. It is explanatory drawing of the state which has inject | poured lubricating oil to the gap | interval part, rotating at low speed.
The spindle motor equipped with the hydrodynamic bearing 60 shown in FIG. 3 has the oil repellent 20 applied to the opening end (around the hole 1a) of the bearing 1, so that the remaining lubricating oil at the end is already in the predetermined space. Demonstrates the effect of being easily separated and separated from the required amount.
[0027]
FIG. 5 is a view for explaining another method of this embodiment for removing the excess amount of the lubricating oil that overflows and fills the gap that is the predetermined space to be filled with the lubricating oil 25. As shown in FIG. FIG. 6 is an explanatory diagram of a process of rotating the bearing more quickly than the actual use rotation speed of the bearing and removing the lubricant oil by a rotational centrifugal force in the lubricant scattering prevention cover 50 covering the bearing.
According to the method shown in FIG. 5, the lubricating oil can be removed more strongly and reliably by the centrifugal force, and the operation is simplified compared to the method of sucking with the nozzle described above, and automation is easier. There is an effect.
[0028]
According to the embodiment of the present invention described above, bubbles in the lubricating oil can be reduced, and there is an effect that the lubricating oil can be filled regardless of the variation in the volume of the bearing gap portion. Further, unlike the method of immersing in the lubricating oil, only the lubricating oil supply section needs to remove the lubricating oil, so the operation is simple. By applying an oil repellent to the lubricating oil supply section, it is possible to remove the lubricating oil easily and reliably.
[0029]
【The invention's effect】
As described above in detail, the present invention particularly includes a dropping step for dropping a predetermined amount of viscous fluid to the periphery of the aperture while contacting the outer peripheral surface of the shaft inserted in the aperture, and then dropping the viscous fluid. Exhaust step of exhausting the air in the insertion hole from the opening side, and then the viscosity of the periphery of the opening at atmospheric pressure when the reduced pressure state returns to normal pressure. And a filling step for filling the fluid into the insertion hole, so that unnecessary and harmful bubbles in the viscous fluid held by the fluid bearing are surely removed, and the space to be filled with the viscous fluid is surely viscous without any gap. Fills the fluid and easily removes excess amount of viscous fluid, there is no risk of uneven dynamic pressure, and there is no risk of viscous fluid such as lubricating oil becoming an unclean substance and contaminating disc recording media. To provide a viscous fluid filling method for a fluid bearing Can.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory diagram of each step of performing viscous fluid filling in an embodiment of a viscous bearing filling method and motor of the present invention.
2 is a cross-sectional view of a fluid bearing having a configuration in which a recess for supplying lubricating oil is provided in the motor of FIG.
FIG. 3 is a cross-sectional view of a fluid bearing having an oil repellent application region in an embodiment of the motor of the present invention.
4 is an assembly diagram of a fluid bearing of the motor of FIG. 1. FIG.
5 is an explanatory diagram of a process of removing excess lubricating oil by centrifugal force in the motor of FIG.
6 is a cross-sectional view of the motor of FIG.
[Explanation of symbols]
1 Bearing (fluid bearing)
1a Hole (insertion hole)
2 shaft (shaft body)
9 Motor base (stator)
25 Lubricating oil (viscous fluid)
100 Spindle motor (motor) for CD-ROM drive

Claims (2)

A shaft,
An inner peripheral surface portion that is close to the outer peripheral surface of the shaft body that is inserted so as to be rotatable toward the bottom side from an aperture portion that is coated with an oil repellent agent, and is connected to the inner peripheral surface portion and is connected to the shaft. Viscosity dropped in a recessed portion in which an upper portion provided at the periphery of the opening portion is opened in an assembly including a fluid bearing portion having an insertion hole provided with a reservoir portion facing the outer peripheral surface of the body with a predetermined gap. A viscous fluid filling method of a fluid bearing for filling the inside of the insertion hole with a fluid,
A dropping step of dropping a predetermined amount of viscous fluid onto the periphery of the aperture while rotating the fluid bearing at a speed lower than the actual rotation speed and contacting the outer peripheral surface of the shaft inserted into the aperture When,
Next, an exhausting step of exhausting the air in the insertion hole from the opening portion side by setting the outside of the assembly to which the viscous fluid is dropped to a reduced pressure state,
And a filling step of filling the viscous fluid at the periphery of the opening portion so as to reach every corner of the predetermined space in the insertion hole at atmospheric pressure when the reduced pressure state returns to the normal pressure state. A viscous fluid filling method for a fluid bearing. A motor configured using the assembly filled with a viscous fluid by the viscous fluid filling method for a fluid bearing according to claim 1,
A motor comprising a stator to which a bottom portion of the assembly is fixed.

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