JP2000354349A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent fluid from leaking out to the outside during high speed rotation, in a motor having a thrust bearing formed out of a pair of thrust plates. SOLUTION: A ring-shaped gas-filled part is formed around a part, where a communicating hole is open in a shaft 4. With a fluid retained at the axially- upper and lower parts of an air-interposed part of a minute gap which is formed by the shaft 4 and a rotor 6 facing in the radial direction, a herringbone-shaped groove 24 having an axially unbalanced shape is formed on at least one of the shaft or the rotor, so that the fluid can be press-fed in the direction counterpoising the gas-filled part, thereby forming a pair of radial bearing parts 26, 28. With the fluid retained continuously from the fluid held in the radial bearing parts in a minute gap formed by a pair of thrust plates 4a, 4b and the rotor 6 facing in an axial direction, a spiral-shaped groove 14 having a shape with the fluid capable of being press-fed in the radially inward direction is formed on at least one of a pair of thrust plates and the rotor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a motor for rotating a recording disk, for example, and more particularly to a motor provided with a fluid dynamic bearing having a pair of thrust plates.

[0002]

2. Description of the Related Art As bearing means for rotatably supporting a rotor, for example, a pair of thrust plates are arranged at upper and lower portions in the axial direction of a shaft, and axially inner surfaces of respective opposed thrust plates are arranged. A pair of thrust bearing portions is formed by holding a lubricating fluid (oil) between surfaces facing in the axial direction and forming a dynamic pressure generating groove for generating dynamic pressure in the lubricating fluid by rotation of the rotor. There is one configured to support the load in the thrust direction of the motor.

In such a configuration, the structure is symmetrical and gives the same characteristics to any posture, or a dynamic pressure generating groove may be formed only on one surface of the thrust plate. There is an advantage that the yield is improved.

[0004]

In a hydrodynamic bearing having a pair of thrust plates disclosed in JP-A-9-217735 as an example of such a structure, the dynamic pressure of the thrust bearing during rotation is increased. A tapered seal portion in which the groove is configured to be exposed in the outer circumferential direction of the lubricating fluid, or in which the distance gradually increases radially outward between one surface of the thrust plate and the rotor axially opposed thereto A thrust bearing portion is formed by forming a minute gap with a groove, holding the lubricating fluid interface in this tapered seal portion, and forming a spiral groove in the thrust plate as a dynamic pressure generating groove. are doing.

[0005] In the above-mentioned hydrodynamic fluid bearing, the lubricating fluid held in the thrust bearing portion is pressure-fed radially inward of the thrust bearing portion by using a spiral groove as the dynamic pressure generating groove, and the thrust bearing portion is formed. It is configured for the purpose of preventing leakage of lubricating fluid to the outside of the bearing by disposing a tapered seal portion at the radially outer end of
In such a configuration, the tapered seal portion acts to retain the lubricating fluid in the thrust bearing portion. However, at the molecular level of the lubricating fluid, the thrust plate and the rotor that constitute the thrust bearing portion due to the characteristics of the lubricating fluid. A migration phenomenon tends to diffuse along the surface from the bearing portion to a portion where no lubricating fluid exists (exists). When the motor rotates, the lubricating fluid is also forced to rotate with the rotation of the rotor.As a result, a centrifugal force acts on the molecules constituting the lubricating fluid in the outer peripheral direction, and this migration phenomenon is promoted. The Rukoto.

[0006] During the rotation of the rotor, the action of the spiral groove formed in the thrust plate causes the lubricating fluid (molecules) diffused outward in the bearing due to the migration phenomenon to the bearing portion direction (in this case, radially inward). However, it is difficult to completely prevent the migration phenomenon and the migration phenomenon promoted by centrifugal force.

Further, when the dynamic pressure generating groove is not formed on the rotor side which is the rotating member as in the above configuration,
There is no means for preventing the migration phenomenon on the rotor surface, and the diffusion of the lubricating fluid toward the outer peripheral portion of the thrust plate is continued. As a result, the lubricating fluid to be held in the bearing portion is depleted, and the function as the bearing is lost. Will be

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a pair of disk-shaped thrust plates fixed to two fixed axially separated positions of a fixed shaft, and the two thrust plates of the shaft. A radial inner peripheral surface facing the outer peripheral surface between the plates via the radial minute gap, a radially inner peripheral surface facing the opposing surfaces of the thrust plate and the outer peripheral surfaces of the two thrust plates facing each other via the thrust minute gap, respectively. A motor having a rotor having a surrounding inner peripheral surface surrounding the rotor, a rotor magnet mounted on the rotor, and a fixed stator disposed so as to face the rotor magnet, An annular gas intervening portion is provided at the center of the radial minute gap between the rotor and the rotor. Fluid is held at both ends in the axial direction of the gas intervening portion of the minute gap, and the shaft is formed with a communication hole that opens to the gas intervening portion and communicates the gas intervening portion to the outside air. At both ends in the axial direction of the gas interposition part, the fluid is pumped to at least one of the outer peripheral surface of the shaft and the radial inner peripheral surface of the rotor in a direction opposite to the gas interposition part. A pair of radial bearing portions are formed by forming a herringbone-shaped groove having a balanced shape, and the radial bearing portions are respectively provided in the thrust minute gaps between the thrust plates and the thrust inner surface of the rotor. The fluid is held continuously to the fluid of at least one of the opposing surface of the thrust plate and the thrust inner peripheral surface of the rotor. A pair of thrust bearings is formed by forming a spiral groove for pumping the body inward in the radial direction, and the fluid of the thrust bearings is at least the outer peripheral surface of the thrust plate and the rotor. It is characterized by being continuous with the gap between the surrounding inner peripheral surface.

In this configuration, a spiral groove is formed in the thrust bearing portion, and a necessary dynamic pressure cannot be generated by itself, but the adjacent radial bearing portion has an unbalanced (asymmetric) herringbone in the axial direction. Since the fluid is pressure-fed with the groove, the required dynamic pressure is generated in the thrust portion by the cooperation of the two bearing portions to support the load. In this case, when the motor rotates, the end boundary of the fluid near the radial bearing moves into the radial bearing, exposing a part of the unbalanced herringbone-shaped groove to the atmosphere, and balancing with the dynamic pressure of the thrust bearing. Set the groove specifications to perform.

[0010] Further, a communication hole is provided in the shaft, which is open to a minute gap formed between the outer peripheral surface of the shaft and the inner peripheral surface of the rotor, and this gap is communicated with the atmosphere. An annular gas intervening portion is formed by the surface tension of the fluid intervening portion, and the fluid retained in the gap is divided into upper and lower portions in the axial direction by the gas intervening portion. A radial bearing is formed.

Further, in each radial bearing portion, fluid is continuous with the adjacent thrust bearing portion, and the dynamic pressure is maximized at only one point from the boundary surface of one fluid to the boundary surface of the other fluid. There is no minimum point, so that even if bubbles are contained in the fluid, the fluid can be automatically excluded from the atmosphere where the pressure is minimized.

In addition, in this configuration, when the rotor is stopped, the fluid that is continuous with the fluid in the thrust bearing portion is supplied between at least the outer peripheral surfaces of the pair of thrust plates and the inner peripheral surface of the rotor radially opposed thereto. If the fluid is kept to have an interface with the outside air in the formed gap, even if the fluid moves radially outward due to centrifugal force during rotation of the motor, further movement is prevented by the inner circumferential surface of the rotor. Further, the fluid diffused to the thrust plate and the rotor surface by the migration phenomenon moves radially outward due to the action of the centrifugal force, is returned to the fluid held in the thrust bearing portion, and is prevented from leaking out of the motor. You.

In this case, when the gap between the outer peripheral surface of the thrust plate and the inner peripheral surface of the rotor radially opposed to the thrust plate is configured to expand outward in the axial direction, the holding force due to the surface tension of the fluid is obtained. This improves the sealing effect.

Further, the axial gap formed between the axially outer surface of the thrust plate and the counter plate axially opposed to the thrust plate is configured to expand radially inward, thereby forming a tapered shape. A seal is formed.

In this case, a centrifugal force acts on the fluid during rotation of the rotor, and the fluid is pumped radially outward, so that the interface between the fluid and the outside air moves from the outer peripheral portion of the thrust plate to the axially outer surface of the thrust plate. And a counter plate that is opposed to the counter plate in the axial direction, and the boundary surface between the fluid and the outside air is balanced and held at the seal portion by the surface tension of the outside air. It is carbonized by the fluid held in the seal portion, and leakage to the outside of the motor is prevented.

Further, a circular opening through which a shaft is inserted is formed in the center of the pair of counter plates, and a radial dimension of a gap between an outer peripheral surface of the shaft and an inner peripheral surface of the circular opening is defined as: By setting it as small as possible,
Creates a labyrinth seal effect. Accordingly, the resistance of the vapor generated by the vaporization of the fluid to the outside can be increased, and the vapor pressure in the vicinity of the boundary surface of the fluid can be kept high, so that further vaporization of the fluid can be effectively prevented.

Furthermore, the rotor is magnetically urged in the axial direction to increase the load on the thrust plate side with high assembly accuracy and the load on the thrust plate side with low assembly accuracy to prevent occurrence of abnormal wear and the like. In addition, this magnetic biasing force is provided by disposing a magnetic material or a permanent magnet that magnetically attracts or repels the rotor magnet at a position facing the rotor magnet in the axial direction, or by moving the magnetic center of the rotor magnet and the stator to each other in the axial direction. It can be provided by offset arrangement.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a motor according to the present invention will be described with reference to FIGS. 1 to 3 by taking a case where the motor is used as a recording disk drive motor as an example. The present invention is not limited to the illustrated embodiments.

FIG. 1 is a longitudinal sectional view schematically showing a schematic configuration of a motor according to an embodiment of the present invention. Also, FIG.
FIG. 2 is a partial cross-sectional view schematically illustrating a schematic configuration of an upper thrust bearing and an upper radial bearing of the motor illustrated in FIG. 1.

In FIG. 1, the recording disk drive motor 1 comprises a bracket 2, a shaft 4 having one end externally fixed in a central opening 2 a of the bracket 2,
A rotor 6 rotatable relative to the shaft 4; The rotor 6 includes a rotor hub 6a on which a recording disk D is mounted on an outer peripheral portion, and a sleeve portion which is located on the inner peripheral side of the rotor hub 6a and is axially supported by the shaft 4 via a minute gap in which a lubricating fluid 8 is held. 6b. A rotor magnet 10 is fixed to the inner peripheral portion of the rotor hub 6a by bonding or the like.
2 is installed.

At a substantially central portion of the sleeve portion 6b, a through hole 6c passing through the sleeve portion 6b in the axial direction so as to form a minute gap between the inner peripheral surface and the outer peripheral surface of the shaft 4 for holding the lubricating fluid 8 therebetween. Are formed. A disk-shaped upper thrust plate 4a and a lower thrust plate 4b projecting radially outward are attached to the upper and lower portions of the shaft 4, respectively, and correspond to the upper thrust plate 4a and the lower thrust plate 4b of the through hole 6c. An upper opening 6d and a lower opening 6e having a diameter larger than the outer diameter of each of the thrust plates 4a and 4b are formed in the portion. The upper opening 6d and the lower opening 6e are ring-shaped upper and lower counter plates 7a and 7b having openings 7a2 and 7b2 through which the shaft 4 is inserted at the center.
b.

The lubricating fluid 8 is provided between the upper thrust surface 6f extending from the inner peripheral portion of the through hole 6c to the outer peripheral portion of the upper opening 6d and the lower surface (axially inner surface) of the upper thrust plate 4a.
Is formed on the lower surface of the upper thrust plate 4a, and a spiral groove 14 for generating a dynamic pressure in the lubricating fluid 8 with the rotation of the rotor 6 is formed.
Are formed to form the upper thrust bearing portion 16.
Further, a small gap for holding the lubricating fluid 8 is provided between the lower thrust surface 6g extending from the inner peripheral portion of the through hole 6c to the outer peripheral portion of the lower opening 6e and the upper surface (axially inner surface) of the lower thrust plate 4b. Is formed on the upper surface of the lower thrust plate 4b, and a spiral groove 14 for generating a dynamic pressure in the lubricating fluid 8 with the rotation of the rotor 6 is formed to form a lower thrust bearing portion 18. Spiral grooves 14 formed in the upper and lower thrust bearing portions 16 and 18 cause the generated dynamic pressure to pump the lubricating fluid 8 radially inward, for example, as indicated by an arrow A in FIG. So as to face inward in the radial direction.

As described above, by using the spiral groove 14 as the dynamic pressure generating means of each of the thrust bearing portions 16 and 18, the outer diameter of the thrust plate can be reduced as compared with the case where the herringbone groove is used. Therefore, the influence of the lower thrust bearing portion 18 on the magnetic circuit portion including the rotor magnet 10 and the stator 12 can be reduced, and a sufficient driving torque can be obtained. Further, the bearing loss of the thrust bearing portions 16 and 18 can be reduced, the electric efficiency of the motor 1 can be increased, and power consumption can be suppressed.

Outer peripheral surface 4a1 of upper thrust plate 4a
Is formed in a tapered shape so that the gap between the inner peripheral surface of the upper opening 6d of the rotor 6 and the radially opposed upper surface of the upper opening 6d is increased toward the outside in the axial direction. When the motor 1 is stationary, the lubricating fluid 8 forms a boundary surface 8a with the atmosphere in a gap between the outer peripheral surface 4a1 of the upper thrust plate 4a and the inner peripheral surface of the upper opening 6d of the rotor 6. ing. Similarly, the outer peripheral surface 4b1 of the lower thrust plate 4b is formed in a tapered shape so that the gap between the outer peripheral surface 4b1 and the inner peripheral surface of the lower opening 6e of the rotor 6 which faces in the radial direction increases in the axial direction. The lubricating fluid 8 held in the lower thrust bearing 18 is supplied to the outer peripheral surface 4b1 of the lower thrust plate 4b and the lower opening 6e of the rotor 6 when the motor 1 is stationary.
A boundary surface with the atmosphere is formed in the gap between the inner peripheral surface and the inner surface.

The lubricating fluid 8 held by the upper and lower thrust bearing portions 16 and 18 is supplied to the outer peripheral surfaces 4a1 and 4b1 of the upper and lower thrust plates 4a and 4b and the upper opening 6d and the lower portion of the rotor 6 radially opposed thereto. By holding the boundary between the opening 6e and the inner peripheral surface so as to form a boundary surface with the atmosphere, even when the fluid moves radially outward due to centrifugal force during rotation of the motor 1, the upper opening 6d and Further movement is prevented by the inner peripheral surface of the lower opening 6e. Further, the lubricating fluid 8 diffused to the surfaces of the upper and lower thrust plates 4a, 4b and the rotor 6 due to the migration phenomenon moves radially outward by the action of centrifugal force, and returns to the lubricating fluid 8 from the interface with the atmosphere. Thus, leakage to the outside of the motor 1 is prevented.

In this case, the gap between the outer peripheral surfaces of the upper and lower thrust plates 4a and 4b and the inner peripheral surfaces of the upper openings 6d and 6e of the rotor 6 radially opposed to each other is increased outward in the axial direction. By configuring so as to expand, the upper first tapered seal portion 17a and the lower first tapered seal portion 19b are formed, the surface tension of the lubricating fluid 8 and the atmospheric pressure are balanced, and the sealing effect is exerted by the holding force. improves.

Lower surface 7a1 of upper counter plate 7a
Is formed in a tapered shape in which the gap in the axial direction between the upper surface (axially outer surface) of the upper thrust plate 4a is increased toward the inside in the radial direction, and the upper second tapered seal portion 17b is formed. . The upper tapered seal portion 17b communicates with and opens to the outside air through a gap between the opening 7a2 and the outer peripheral surface of the shaft 4, and when the motor 1 rotates, the lubricating fluid 8 flows as shown by the broken line in FIG. A boundary surface 8b with the outside air is formed and held in the upper second tapered seal portion 17b. The upper surface 7b1 of the lower counter plate 7b is formed in a tapered shape in which the axial gap between the lower counter plate 7b and the lower surface (axial outer surface) of the lower thrust plate 4b increases inward in the radial direction. A tapered seal portion 19b is formed. Similarly, the lower second tapered seal portion 19b is opened to communicate with the outside air through a gap between the opening 7b2 and the outer peripheral surface of the shaft 4, so that when the motor 1 rotates, the lubricating fluid 8 Tapered seal portion 19b
At a boundary surface with the outside air.

Thus, when the motor 1 is rotating,
Since the boundary surface of the lubricating fluid 8 is in each of the second tapered seal portions 17b and 19b facing inward in the radial direction, the motor 1
Due to the centrifugal force acting on the lubricating fluid 8 during rotation of the lubricating fluid, the lubricating fluid 8 diffused by the migration phenomenon is pressed outward in the radial direction, and each second tapered seal portion 1
The fluid is returned to the lubricating fluid 8 held by the lubrication fluids 7b and 19b, and leakage to the outside of the motor 1 is prevented.

The spiral grooves 14 of the upper and lower thrust bearing portions 16 and 18 are formed so that the dynamic pressure generated respectively pushes the lubricating fluid 8 radially inward, so that the lubricating fluid 8 can be filled. Each thrust bearing part 16, 1
Bubbles generated in the lubricating fluid 8 held in 8 move from the high-pressure bearing portion to the boundary surface side of the low-pressure lubricating fluid 8 and are released to the atmosphere.

An annular recess 4c is formed substantially at the center of the outer peripheral surface of the shaft 4 so as to increase the gap between the shaft 4 and the inner peripheral surface of the through hole 6c.
A communication hole 20 communicating with the outside air formed therein is opened, and the outside air taken into the minute gap from this opening is formed in the concave portion 4c.
An annular gas intervening portion 22 is formed between the gas passage and the inner peripheral surface of the through hole 6c. The lubricating fluid 8 held in the minute gap between the outer peripheral surface of the shaft 4 and the inner peripheral surface of the through hole 6c by the gas intervening portion 22 is divided vertically in the axial direction. Through hole 2
A herringbone-shaped groove 24 for generating a dynamic pressure in the lubricating fluid 8 with the rotation of the rotor 6 is formed at a portion corresponding to the lubricating fluid 8 which is divided and held above and below on the inner peripheral surface of c. Thus, an upper radial bearing portion 26 and a lower radial bearing portion 28 are configured. The herringbone-shaped grooves 24 formed in the upper and lower radial bearing portions 26 and 28 are formed by connecting spiral grooves in opposite directions to each other, and the generated dynamic pressure is indicated by, for example, an arrow B in FIG. As described above, the spiral groove located outside in the axial direction is shorter than the spiral groove located inside in the axial direction so as to pump the lubricating fluid 8 outward in the axial direction.

The herringbone-shaped grooves 24 of the upper and lower radial bearing portions 26 and 28 are shaped so that the generated dynamic pressure pumps the lubricating fluid 8 outward in the axial direction. Each radial bearing 2
Bubbles generated in the lubricating fluid 8 held in 6, 6 move from the high pressure bearing portion to the interface with the low pressure gas interposition portion 22, and from the gas interposition portion 22 to the atmosphere through the communication hole 20. Be released.

In this configuration, the thrust bearing portion 16,
Since the dynamic pressure generating means formed in the groove 18 is a spiral groove, the required load supporting pressure cannot be generated by itself, but the adjacent radial bearings 26 and 28 have an unbalanced herringbone groove in the axial direction. 24, the lubricating fluid 8 is pressure-fed outwardly in the axial direction (in the direction of the thrust bearings 16 and 18) as shown by the arrow B, so that the required dynamic pressure is generated in the thrust portion by the cooperation of both bearing portions. Support the load. In this case, when the motor 1 rotates, the end boundary of the lubricating fluid 8 near the gas bearing portion 22 near the radial bearing portions 26, 28 moves into the radial bearing portions 26, 28, and one of the unbalanced herringbone-shaped grooves 24. The parts are exposed to the atmosphere, and the groove specifications are set so as to be balanced with the dynamic pressure of the thrust bearings 16 and 18.

In each of the radial bearing portions 26 and 28, the lubricating fluid 8 is continuous with the adjacent thrust bearing portions 16 and 18, from the boundary surface of one lubricating fluid 8 to the boundary surface of the other lubricating fluid 8. There is only one point where the dynamic pressure is maximum and there is no point where the dynamic pressure is minimum. Therefore, even if bubbles are contained in the lubricating fluid 8, the lubricating fluid 8 is automatically excluded from the atmosphere where the pressure is minimized. You can do it.

As described above, the bubbles generated in the lubricating fluid 8 held in each bearing part move sequentially to the low pressure side and are released to the atmosphere from the boundary of each lubricating fluid 8, so that the bubbles are lubricated. The lubricating fluid does not stay in the fluid 8 and the lubricating fluid is prevented from leaking out of the bearing due to the thermal expansion of the bubbles when the temperature of the motor 1 rises.

Upper and lower counter plates 7a, 7b
By setting the radial gap between the inner peripheral surfaces 7a2 and 7b2 of the shaft 4 and the outer peripheral surface of the shaft 4 as small as possible, a labyrinth sealing effect is generated, and the steam generated by the vaporization of the lubricating fluid 8 Therefore, the vapor pressure in the vicinity of the boundary surface of the lubricating fluid 8 can be kept high, so that further evaporation of the lubricating fluid 8 can be prevented. The above effect can be further enhanced by applying an oil repellent made of, for example, a fluorine-based material to each of these surfaces.

A thrust yoke 30 made of a magnetic material is disposed at a portion of the bracket 2 facing the rotor magnet 10 in the axial direction, and a magnetic attraction force generated between the rotor magnet 10 and the thrust yoke 30 causes the magnet to thrust. The magnetic biasing force acting on the bracket 6 side acts on the rotor 6. The magnetic biasing force can also be applied by disposing the magnetic center of the rotor magnet 10 above the magnetic center of the stator 12 in the axial direction (opposite to the bracket 2 direction).

Next, the procedure for assembling the bearing portion of the recording disk drive motor 1 having the above configuration will be described.

First, the lower thrust plate 4b is press-fitted into the shaft 4 while maintaining the accuracy of the perpendicularity to the shaft 4, and the shaft 4 is inserted into the through hole 6c of the sleeve portion 6b. Thereafter, the sleeve portion 6b is positioned at a predetermined position using a jig or the like, a gap between the sleeve portion 6b and the upper thrust surface 6f is measured, and the upper thrust plate 4a is pressed into the predetermined position. Next, upper and lower openings 6d, 6e of the through hole 6c.
After injecting a predetermined amount of the lubricating fluid 6, the respective counter plates 7a and 7b are mounted.

As described above, in the assembly procedure of the bearing portion,
Since the upper thrust plate 4a is attached in a semi-assembled state, there is a concern that the accuracy of the perpendicularity to the shaft 4 and the gap size between the upper thrust surface 6f and the lower thrust bearing portion 18 are inferior to those of the lower thrust bearing portion 18. However, since the upper and lower thrust bearings 16 and 18 use the spiral grooves 14 as the dynamic pressure generating means, each thrust plate 4
a and 4b can be reduced in diameter, and can be assembled relatively accurately as compared with the case of using a herringbone-shaped groove. Even when an error occurs in the assembly accuracy, the rotor magnet 10 and the thrust yoke 30 By supplementing the thrust load to be supported by the upper thrust bearing portion 16 at the time of starting and stopping by the action of the magnetic urging force on the rotor 6 by
When the motor 1 is started and stopped, sliding and galling between the upper thrust plate 4a and the upper thrust surface 6f are prevented, and the influence of the assembly accuracy of the upper thrust bearing 16 on the shaft support can be minimized.

When the upper thrust plate 4a is press-fitted into the shaft 4 first and then the lower thrust plate 4b is mounted, the above-mentioned effect can be obtained by setting the magnetic biasing force on the rotor 6 in the direction opposite to the bracket 2. The same effect as described above can be obtained. In this case, instead of the thrust yoke 30, a permanent magnet magnetized so as to repel the rotor magnet 10 mutually is disposed at a portion of the bracket 2 that faces the rotor magnet 10 in the axial direction, or the magnetic force of the rotor magnet 10 is reduced. It can be provided by disposing the center so as to be located axially below the magnetic center of the stator 12 (on the side of the bracket 2).

Although the embodiment of the recording disk driving motor according to the present invention has been described above, the present invention is not limited to such an embodiment, and various modifications and corrections can be made without departing from the scope of the present invention. Is possible.

For example, like a motor 50 shown in FIG.
Instead of using the through hole 6c of the sleeve portion 6b as a component surface of each bearing portion, upper and lower thrust surfaces 6f1, 6g1
Each of the bearings can also be configured by fitting the cylindrical member 32 constituting the radial bearing surface into the through hole 6c1 of the sleeve 6b1.

[0043]

According to the motor of the present invention, in each radial bearing portion, the fluid is continuous in the adjacent thrust bearing portion, and the dynamic pressure is maximized from the boundary surface of one fluid to the boundary surface of the other fluid. There is only one point and there is no minimum point. Therefore, even if bubbles are contained in the fluid, the fluid can be automatically excluded from the atmosphere where the pressure is minimized.

The fluid of the thrust bearing portion is formed so that an interface with the outside air is formed in a gap formed between the outer peripheral surfaces of the pair of thrust plates and the inner peripheral surface of the rotor radially opposed to the pair of thrust plates. When the fluid is continuously held, even if the fluid moves radially outward due to centrifugal force during rotation of the motor, further movement is prevented by the inner circumferential surface of the rotor. Further, the fluid diffused to the thrust plate and the rotor surface by the migration phenomenon moves radially outward due to the action of the centrifugal force, is returned to the fluid held in the thrust bearing portion, and is prevented from leaking out of the motor. You.

In this case, if the gap between the outer peripheral surface of the thrust plate and the inner peripheral surface of the rotor radially opposed to the thrust plate is enlarged outward in the axial direction, the holding force due to the surface tension of the fluid is obtained. This improves the sealing effect.

Further, the axial gap formed between the axially outer surface of the thrust plate and the counter plate axially opposed thereto is enlarged radially inward, so that the tapered shape is obtained. A seal is formed.

In this case, a centrifugal force acts on the fluid when the rotor rotates, and the fluid is pumped radially outward, so that the interface between the fluid and the outside air moves from the outer peripheral portion of the thrust plate to the axially outer surface of the thrust plate. And a counter plate that is opposed to the counter plate in the axial direction, but the boundary surface between the fluid and the outside air is balanced and held by the surface tension of the outside air in the seal portion. Is returned to the fluid held in the seal portion, and leakage to the outside of the motor is prevented.

Further, a circular opening through which the shaft is inserted is formed in the center of the pair of counter plates, and the radial dimension of the gap between the outer peripheral surface of the shaft and the inner peripheral surface of the circular opening is defined as: By setting it as small as possible,
Creates a labyrinth seal effect. This increases the outflow resistance of the vapor generated by the vaporization of the fluid to the outside and keeps the vapor pressure near the boundary surface of the fluid high, so that further vaporization of the fluid can be effectively prevented.

In addition, the rotor is magnetically urged in the axial direction to greatly increase the load on the thrust plate side with high assembling accuracy.
The load on the thrust plate side with a low assembling accuracy can be reduced to prevent abnormal wear and the like.

[0050]

[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 sectional view schematically showing a schematic configuration of an upper thrust bearing and an upper radial bearing of the motor shown in FIG.

FIG. 3 is a longitudinal sectional view schematically showing a schematic configuration of a motor according to another embodiment of the present invention.

[Explanation of symbols]

 2 Bracket 4 Shaft 4a, 4b Thrust Plate 6 Rotor 10 Rotor Magnet 12 Stator 14 Spiral Groove 16, 18 Thrust Bearing 24 Herringbone Groove 26, 28 Radial Bearing

Claims (5)

[Claims] 1. A pair of disk-shaped thrust plates fixed at two places separated in a direction of an axis of a fixed shaft, and a radially opposed inner peripheral surface between the two thrust plates of the shaft via a minute radial gap. A rotor having a peripheral surface, a thrust inner surface opposed to the opposing surfaces of the thrust plate facing each other via a small thrust gap, and a surrounding inner peripheral surface surrounding the outer peripheral surfaces of both thrust plates via the gap; and A motor comprising: a mounted rotor magnet; and a fixed stator disposed to face the rotor magnet, wherein a center portion of the radial minute gap between the shaft and the rotor has an annular shape. Gas intervening portions are provided, and each of the radial minute gaps is provided at both axial ends of the gas intervening portions. Fluid is retained in the shaft,
A communication hole that opens to the gas interposition portion and communicates the gas interposition portion to the outside air is formed, and at both ends in the axial direction of the gas interposition portion in the radial minute gap, the outer peripheral surface of the shaft and the radial inside of the rotor. A pair of radial bearings is formed by forming a herringbone-shaped groove having an unbalanced shape in the axial direction so as to pressure-feed the fluid in a direction opposite to the gas interposition part on at least one of the peripheral surfaces, In the thrust minute gaps between the thrust plates and the thrust inner surface of the rotor, fluids are respectively held continuously from the fluid of the radial bearing portion, and the opposing surfaces of the thrust plate and the thrust inner periphery of the rotor are respectively held. A pair of thrusts is formed on at least one of the surfaces by forming a spiral groove for pumping the fluid radially inward. Motor receiving portion is formed, and the fluid in the thrust bearing portion, characterized in that continuously until the gap between the outer peripheral surface and surrounding the peripheral surface of the rotor of at least the thrust plate. 2. A gap between an outer peripheral surface of each of the thrust plates and a surrounding inner peripheral surface of the rotor is formed so that a radial dimension increases outward in an axial direction. The motor according to claim 1. 3. A circular opening through which the shaft is inserted is formed at the center of the both thrust plates in the axial direction outside thereof, and a gap is formed between the thrust plate and the thrust plate so that the axial dimension increases radially inward. A pair of counter plates having thrust outer surfaces opposed to each other with a thrust plate interposed therebetween, wherein a boundary of the fluid end of the thrust bearing portion exists between the thrust plate and the counter plate. A motor according to claim 1. 4. A labyrinth seal is formed between an outer peripheral surface of the shaft and an inner peripheral surface of a circular opening of the pair of counter plates, and the pair of thrust bearings are opened to the outside air through the labyrinth seal. The motor according to claim 3, wherein: 5. The motor according to claim 1, wherein the rotor is urged in the axial direction by a magnetic force.