JP2002034203A - Fluid dynamic-pressure bearing motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the driving characteristics and vibrating characteristics of a motor by keeping oil pressure, between a fluid dynamic pressure bearing and a shaft uniform wholly, thereby improving lubrication performance. SOLUTION: This bearing motor includes a housing, a sleeve which is connected to the housing and has a shaft hole permitting a shaft to be inserted into its central portion which is tubular and protrudes upward, a core connected to the outer periphery of the sleeve, a shaft which is inserted vertically and rotatably into the shaft hole in the sleeve and with which a plate-type thrust is integrally formed on its lower stage, a hub which is integrally connected to the upper end of the shaft and has a magnet of generating electromagnetic force by interaction with the core on the inner periphery of the dead end of extension extending downward, a cover plate sealing the lower-stage portion of the shaft hole of the sleeve in which the shaft is inserted, and a plurality of through-holes, through which the thrust is inserted vertically for guiding the flow of oil at upper and lower portions of the thrust.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor mounted on a small precision instrument, and more particularly, to generating a stable dynamic pressure on a sleeve by maintaining the same pressure balance in the axial direction, thereby improving vibration characteristics. The present invention relates to an improved fluid dynamic bearing motor.

[0002]

2. Description of the Related Art In general, a motor used in a precision device such as a hard disk driver is required not only to have a high driving force but also to be capable of precise control.

[0003] In a motor requiring such characteristics,
Inevitably there is a rotational load and shaft support force, and recently to solve this, as a means to support the shaft,
There is a trend to adopt a fluid dynamic pressure bearing with a small driving load in place of a conventional metal bearing or ball bearing.

[0004] Such a fluid dynamic bearing motor is
Usually, oil is used as a means for supporting the rotating body so that it can rotate smoothly at high speed.

[0005] Such oil is filled between the shaft and the sleeve that covers the outer peripheral edge of the shaft, so that the frictional force due to direct contact between the shaft and the sleeve is minimized, and the shaft is always kept in contact. It is located at the center of the sleeve.

FIGS. 1 and 2 show a conventional fluid dynamic bearing motor. As shown in FIG. 1, the motor comprises a housing 100, a sleeve 110, and a core 120. Member and shaft 1
30 and a rotating member including the hub 140 and the magnet 150.

The sleeve 110 has a central portion penetrated in the vertical direction, a shaft 130 is rotatably inserted, and a groove 111 for generating dynamic pressure is formed on an inner diameter surface. Fluid dynamic pressure is generated in the direction.

In particular, the inner diameter of the sleeve 110 has a disk-shaped thrust 160 formed integrally with the lower end of the shaft 130 so as to be rotatable together with the shaft 130, and the outer diameter has a coil wound around the outer peripheral edge. The core 120 is fixedly mounted.

Here, the thrust 160 has a groove 161 for generating a dynamic pressure on an upper surface and a lower surface, so that a fluid dynamic pressure is generated in an axial direction.

On the other hand, the lower portion of the sleeve 110 is shielded from the outside by the inner diameter portion being shielded by a cover plate 170. A thrust 160 is rotatably contacted on the upper side of the cover plate 170.

A hub 14 is rotatably inserted into the inner diameter of the sleeve 110 and has a hub 14 at its upper end.
The hub 140 has a cap shape that is open downward, and a magnet 150 is magnetized on the inner diameter surface of the extension end so as to face the outer diameter surface of the core 120. .

With such a structure, an oil gap G is minutely formed between the inner diameter surface of the sleeve 110 and the shaft 130 and the thrust 160. The oil gap G is filled with oil having a predetermined viscosity.

The oil in the oil gap G is
While the shaft 130 rotates, the oil gap G is constantly maintained while being concentrated on the dynamic pressure generating groove 111 of the sleeve 110 and the dynamic pressure generating groove 161 of the thrust 160, so that the shaft 130 is stably formed. It is to be driven.

In the conventional fluid dynamic bearing motor having the above-described structure, when an external power is transmitted to the core 120, the magnet 150 is driven by the mutual electromagnetic force between the core 120 and the magnet 150. The attached hub 140 is rotated, so that the shaft 130 connected to the hub 140 is simultaneously rotated.

When such a motor is driven, the sleeve 11
The shaft 130 inserted into the inner diameter of the sleeve 1
The fluid dynamic pressure generated between the dynamic pressure generating grooves 111 formed on the inner diameter surface of the shaft 10 and the outer diameter surface of the shaft 130 enables the sleeve 110 to rotate smoothly without contact with the inner diameter surface of the sleeve 110. become.

That is, between the outer diameter surface of the shaft 130 and the inner diameter surface of the sleeve 110, an appropriate amount of oil has already been supplied.
The dynamic pressure is generated while the oil flows in accordance with the dynamic pressure generating groove 111 formed on the inner diameter surface of the oil. Thus, high-speed rotation is smoothly performed while the rotation load is minimized.

[0017]

However, such a conventional fluid dynamic bearing motor as described above has a shaft 1
When lubrication is performed by driving the motor with oil filled between the sleeve 30 and the sleeve 110, the flow of oil may not be smooth due to the thrust 160 formed on the shaft 130.

Therefore, in the prior art, the shaft 130
Therefore, there is a problem that the fluid pressure in each part of the sleeve 110 and the sleeve 110 is different, so that the overall lubricating action is reduced.

In addition, since the lubrication characteristics are unstable, the coaxiality of the shaft is deviated, and NRRO (Non-Repeatable Run Out), which is the vibration characteristics of the motor, and RRO
Of course, (Repeatable Run Out) becomes large, and there is a problem that the drive characteristics of the motor become unstable.

The present invention has been made to solve such various problems of the prior art.
It is an object of the present invention to provide a fluid dynamic bearing motor in which a lubricating pressure acting between a sleeve and a shaft in a fluid dynamic bearing motor is uniformly maintained as a whole and stable driving characteristics are ensured.

[0021]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention has a housing, and a shaft hole which is connected to the housing and which is formed in a tube-shaped upwardly projecting central portion to allow insertion of a shaft. A sleeve, a core coupled to an outer peripheral surface of the sleeve, a shaft vertically rotatably inserted into a shaft hole of the sleeve, and a plate-shaped thrust integrally formed in a lower portion; and an upper end portion of the shaft A hub having a magnet that generates an electromagnetic force due to interaction with the core attached to the inner peripheral surface of the terminal end of the extended end extending downward, and a lower step portion of the shaft hole of the sleeve into which the shaft is inserted. The gist of the invention is to include a cover plate that seals the thrust and a plurality of through holes that penetrate the thrust vertically and guide oil flow above and below the thrust.

[0022]

3 and 4 show a first embodiment of a fluid dynamic bearing motor according to the present invention. As shown, the fluid dynamic bearing motor is in a fixed state. And a rotating member that is rotated by the interaction of the fixed member with power supply.

As described above, the fixing member in the fluid dynamic bearing motor is largely composed of the sleeve 20 and the housing 1.
0, and the core 40, and the rotating member includes the shaft 50, the hub 30, and the magnet 15.

On the other hand, a shaft 50 as a rotating member is rotatably inserted into a shaft hole 21 formed through the center of the sleeve 20.

Such a sleeve 20 is usually provided in the shaft hole 2.
By forming the groove 22 for generating a dynamic pressure on the inner diameter surface of the shaft 1, fluid dynamic pressure in the radial direction of the shaft 50 is formed.

On the other hand, the sleeve 20 and the shaft 50 are separated from each other at a predetermined interval to form an oil gap G. The oil gap G is filled with oil for suppressing mutual friction between the sleeve 20 and the shaft 50.

When the shaft 50 rotates, such oil flows in the rotational direction of the shaft 50 and forms a constant fluid pressure. The shaft 50 tends to move in the direction perpendicular to the axis and in the axial direction due to the influence of the fluid pressure.

Therefore, conventionally, grooves 51 and 22 for generating dynamic pressure are formed on at least one side surface of the outer diameter surface of the shaft 50 or the inner diameter surface of the sleeve 20 facing the shaft 50 so that the oil gap G extends in a direction perpendicular to the axis. A strong fluid dynamic pressure is generated, and the fluid dynamic pressure at this time maintains the oil gap G between the sleeve 20 and the shaft 50 uniformly.

The dynamic pressure generating groove 22 formed as a means for generating the fluid dynamic pressure in the direction orthogonal to the axis is usually formed on the outer peripheral surface of the shaft 50.
When a groove for generating dynamic pressure is formed on the shaft 50 which is a rotating member, the friction between the shaft 50 and the oil increases, and the shaft 50 acts on a rotational load. Dynamic pressure generating groove 2 for generating a fluid dynamic pressure in a direction perpendicular to the axis on the inner diameter surface of sleeve 20
Generally, 2 is formed.

On the other hand, a core 40 on which a coil to which power is applied is wound and fixed to the outer peripheral edge of the outer diameter portion of the sleeve 20. The core 40 is attached to the inner peripheral surface of the hub 30 described later. By being arranged to face the attached magnet 15, a predetermined electromagnetic force is generated by the interaction.

A plate-like cover plate 16 is attached to the lower portion of the sleeve 20 with an adhesive or the like.
The lower part of the shaft hole 21 penetrating vertically is shielded from the outside. A shaft 50 having a thrust 55 is rotatably contacted on the upper side of the cover plate 16.

Here, the thrust 55 is
The shaft 50 is provided at a lower portion of the shaft 50 as a means for generating the fluid dynamic pressure in the direction perpendicular to the axis line and the fluid dynamic pressure in the direction perpendicular to the axis generated by the dynamic pressure generation groove 21 formed in the shaft 50. .

At the upper end of the shaft 50,
A cap-shaped hub 30 having an open bottom and attached with a magnet 15 is connected to the inner peripheral surface of an extended end portion extending downward from the outer end. The magnet 15 attached to the hub 30 is arranged so as to face the outer diameter surface of the core 40.

In the fluid dynamic bearing motor having such a structure, when power is applied from the outside, the hub 30 and the shaft 50 are driven to rotate by the electromagnetic force generated by the interaction between the core 40 and the magnet 15. .

The structure as described above is almost the same as the structure of the conventional fluid dynamic bearing motor. However, according to the present invention, the shaft 50 is provided with a plurality of oils so that the oil filled in the oil gap G formed between the sleeve 20 and the shaft 50 maintains a uniform pressure even when the motor is driven. The most remarkable feature is that the through holes 56 are formed to smoothly circulate the oil.

That is, as shown in FIG. 4, a large number of through holes 56 having a predetermined diameter and penetrating vertically through a thrust 55 integrally formed in a lower portion of the shaft 50 are formed at regular intervals. .

The through-hole 56 is formed by penetrating at least one or more portions of the upper and lower portions of the thrust 55 so that oil is circulated through the through-hole 56 and the oil gap G is filled. The oil will maintain a uniform pressure throughout.

In the fluid dynamic bearing motor having such a configuration, when power is externally transmitted to the core 40,
The mutual electromagnetic force between the core 40 and the magnet 15 rotates the hub 30 to which the magnet 15 is attached, so that the shaft 50 connected to the hub 30 is simultaneously rotated.

When the motor is driven, the shaft 50 inserted into the inner diameter of the sleeve 20 is
The rotation is accomplished in a state where the oil filled in the sleeve 20 is not in contact with the inner diameter surface of the sleeve 20.

At this time, the driving of the motor usually causes
An axial pressure difference is generated between the sleeve 20 and the thrust 55. When the pressure difference in the axial direction is generated as described above, the oil circulates through the through hole 56, so that the pressure can be maintained uniform.

That is, when the oil rotates,
Since the fluid flows along the through holes 56 formed in the thrust 55, a uniform dynamic pressure is generated as a whole, and thus the rotation load of the shaft 50 is minimized, and the high-speed rotation is smoothly performed. Can be done.

FIGS. 5 and 6 show a second embodiment of the fluid dynamic bearing motor according to the present invention. As shown, a first portion extending upward from a bottom surface at a central portion of a shaft 50 is shown. A through hole 57 and a second through hole 58 extending in the horizontal direction at an upper end portion of the first through hole 57 are formed.

Here, the first through-hole 57 is formed in the center of the shaft 50, has an entrance formed in the bottom surface, and extends vertically upward by a predetermined height.

On the other hand, the second through-hole 58 is an intermediate portion of the shaft 50 that receives the most pressure, and is connected to the first through-hole 57 and is extended in the horizontal direction so that the upper end portion of the shaft 50 with a small load. By making the oil circulate through the oil, uniformity of the oil pressure is improved.

In the fluid dynamic bearing motor having such a configuration, when power is transmitted from the outside to the core 40,
The mutual electromagnetic force between the core 40 and the magnet 15 rotates the hub 30 to which the magnet 15 is attached, so that the shaft 50 connected to the hub 30 is simultaneously rotated.

When such a motor is driven, the shaft 50 inserted into the inner diameter of the sleeve 20 is
The rotation is achieved in a state where the oil filled in the sleeve 20 is not in contact with the inner diameter surface of the sleeve 20.

At this time, the driving of the motor usually causes
An axial pressure difference is generated between the sleeve 20 and the thrust 55. However, when a pressure difference occurs in the axial direction, the oil circulates through the first through hole 57 and the second through hole 58, so that the pressure can be maintained uniformly.

Therefore, when the motor is driven, oil is circulated along the first through hole 57 and the second through hole 58,
The overall pressure of the oil can be kept uniform.

[0049]

As described above, the fluid dynamic bearing motor according to the present invention can correct the pressure difference generated between the sleeve and the thrust through the through-hole, thereby reducing the NRRO and RRO characteristics of the motor. In addition to this, there is an advantage that noise due to uneven oil pressure can be reduced.

Further, the present invention can maintain a uniform dynamic pressure balance in the axial direction in the sleeve, so that a stable dynamic pressure can be generated in the sleeve.

Accordingly, the present invention has a very useful advantage that not only can the service life of a product be extended, but also the reliability of performance can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a fluid dynamic bearing motor according to the related art.

FIG. 2 is an exploded perspective view of a main part of FIG.

FIG. 3 is a sectional view showing a first embodiment of a fluid dynamic pressure bearing according to the present invention.

FIG. 4 is a longitudinal sectional view of the shaft of FIG. 3;

FIG. 5 is a sectional view showing a second embodiment of the fluid dynamic pressure bearing according to the present invention.

FIG. 6 is a longitudinal sectional view of the shaft of FIG. 5;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Housing, 15 ... Magnet, 16 ... Cover plate, 20 ... Sleeve, 21 ... Shaft hole, 22 ... Dynamic pressure generation groove, 30 ... Hub, 40 ... Core, 50 ... Shaft, 51
... Groove for generating dynamic pressure, 55 ... Thrust, G ... Oil gap.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3J011 AA04 BA05 BA08 CA01 CA02 JA02 KA02 KA03 MA05 MA08 MA27 5H605 AA00 AA04 BB10 BB19 CC02 CC04 EB03 EB06 EB21 5H607 AA00 AA04 BB07 BB09 BB14 BB17

Claims (2)

[Claims] 1. A housing, a sleeve coupled to the housing and having a tube-shaped upwardly projecting central portion through which a shaft hole allowing insertion of a shaft is formed, and a core coupled to an outer peripheral surface of the sleeve. A shaft, which is vertically rotatably inserted into the shaft hole of the sleeve, and has a plate-shaped thrust integrally formed in a lower portion, and an extended end portion integrally connected to an upper end portion of the shaft and extending downward. A hub having a magnet that generates an electromagnetic force by interaction with a core attached to the inner peripheral surface of the terminal end of the hub, a cover plate that seals a lower portion of a shaft hole of the sleeve into which the shaft is inserted, and a vertically penetrating thrust. And a plurality of through-holes for guiding oil flow above and below the thrust. 2. A housing connected to the housing, a sleeve having a tube-shaped upwardly protruding central portion formed with a shaft hole for allowing insertion of a shaft, and a core connected to an outer peripheral surface of the sleeve. A shaft, which is vertically rotatably inserted into the shaft hole of the sleeve and has a plate-shaped thrust integrally formed at a lower portion thereof; and an extended end portion integrally coupled to an upper end portion of the shaft and extending downward. A hub having a magnet that generates an electromagnetic force by interaction with a core attached to an inner peripheral surface of a terminal end of the hub, a cover plate that seals a lower portion of a shaft hole of the sleeve into which the shaft is inserted, and a bottom portion inside the shaft. A first through-hole penetrating from a surface to a certain height, and a second through-hole extending in a horizontal direction at an intermediate portion of a shaft having the highest pressure according to the extension of the first through-hole. Hydrodynamic bearing motor, characterized in that it is configured to include a hole.