JP2002054636A - Bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing device capable of securing a life longer than a regular life even if using lower viscosity lubricating oil and applying low electric current by securing dimensions in an axial direction necessary to obtain a required dynamic pressure and enlarging a capacity of a lubricating oil reservoir while securing sufficient dimensions of a surface tension seal part. SOLUTION: This bearing device includes a bearing 18 relatively rotatably supporting a shaft 20 and lubricating oil lying between the shaft 20 and the bearing 18. A taper seal part 30, 32 with a clearance gradually spreading to prevent the lubrication oil from leaking to outside is formed, and the taper seal part includes a turn-up taper seal part 32 formed on a turn-up part turning from a radius direction to an axial direction, and a gas liquid interface of the lubricating oil is positioned.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing device in which lubricating oil is interposed between a shaft and a bearing, such as a radial dynamic pressure bearing, a thrust dynamic pressure bearing, and a sintered oil-impregnated bearing.

[0002]

2. Description of the Related Art For example, a motor using a dynamic pressure bearing is being put to practical use as a motor for a hard disk drive. In this type of dynamic pressure bearing, a plurality of dynamic pressure bearings, for example, two radial dynamic pressure bearings and two thrust dynamic pressure bearings are connected through a lubricating oil reservoir. One end of the dynamic pressure bearing (usually the side with the thrust bearing) is closed in a bag shape, and the other end of the dynamic pressure bearing is tapered in order to prevent the leakage of lubricating oil to the outside. A surface tension seal is provided. The surface tension seal is configured such that the distance between a shaft and a bearing that supports the shaft so as to be relatively rotatable gradually increases outward in the axial direction.

[0003] The surface tension seal is filled with lubricating oil so that the boundary between the lubricating oil and air is located in the seal portion, and the outflow of lubricating oil is prevented by the surface tension acting on the boundary. Things.

[0004]

However, a bearing device using a conventional hydrodynamic bearing cannot sufficiently respond to a constant current, thinner, and higher speed motor. The reason is as follows. When the motor is made thinner, the ratio of the height dimension of the surface tension seal to the overall height of the motor increases, and it is necessary to obtain the optimal allocation of dynamic pressure bearings, that is, to obtain the dynamic pressure required for dynamic pressure bearings. It is impossible to secure a proper axial dimension. To reduce the current of a motor using a hydrodynamic bearing, it is necessary to reduce the loss of the hydrodynamic bearing,
For that purpose, it is effective to lower the viscosity of the lubricating oil.
However, low-viscosity lubricating oils evaporate more than high-viscosity lubricating oils, and it is necessary to increase the volume of the lubricating oil reservoir in order to maintain a specified or longer life, and the dynamic pressure bearing occupies that much. Space is increased. When the motor speed is increased, a large centrifugal force is generated, and in the surface tension seal configured so that the distance between the shaft and the bearing gradually increases outward in the axial direction, the lubricating oil may be scattered by the large centrifugal force. was there.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and it has been necessary to secure a sufficient size of a surface tension seal portion and to obtain an axial dimension required for obtaining a required dynamic pressure. It is an object of the present invention to provide a bearing device capable of ensuring the above. The present invention also provides a bearing device capable of maintaining a specified or longer service life even when the current is reduced by using a low-clay lubricating oil by enabling the volume of the lubricating oil reservoir to be increased. The purpose is to provide. Another object of the present invention is to provide a bearing device that can prevent lubricating oil from scattering due to centrifugal force even when the bearing device is rotated at high speed.

[0006]

According to the first aspect of the present invention,
In a bearing device having a bearing that supports a shaft so as to be relatively rotatable, and a lubricating oil interposed between the shaft and the bearing, a taper seal in which a gap gradually increases to prevent the lubricating oil from leaking outside. Portion is formed, the tapered seal portion has a folded tapered seal portion formed at a folded portion directed from the radial direction to the axial direction, and the gas-liquid interface of the lubricating oil is located at the tapered seal portion. I do.

According to a second aspect of the present invention, in the first aspect of the present invention, a dynamic pressure bearing portion is formed between the shaft and the bearing, and the bearing device operates the shaft by dynamic pressure generated in the dynamic pressure bearing portion. A hydrodynamic bearing device for supporting relative rotation, wherein the bearing has a one-bag structure in which one side in the axial direction is sealed and the other side is opened, and a surface tension seal comprising a tapered seal portion on the other side of the bearing. A portion is formed, and the lubricating oil is filled from one side of the bearing to a surface tension portion provided on the other side.

According to a third aspect of the present invention, in the second aspect of the present invention, a radial dynamic pressure bearing portion is formed between the shaft and the bearing, and the tapered seal portion includes the radial dynamic pressure bearing portion and the folded taper seal. A radial taper seal formed by being bent in the radial direction between the tapered seal portion and the folded taper seal portion, and a gas-liquid interface of the lubricating oil is located in the folded taper seal portion.

According to a fourth aspect of the present invention, in the second aspect of the present invention, two radial dynamic pressure bearing portions are formed between the shaft and the bearing, and a thrust plate is fixed to the shaft. A thrust dynamic pressure bearing is formed between the thrust plate and the bearing, a radial taper seal portion is formed between the folded taper seal portion and the radial dynamic pressure bearing portion, and a gas-liquid interface of the lubricating oil is formed in the folded taper seal portion. Is located.

According to a fifth aspect of the present invention, in the third or fourth aspect, the gap interval between the folded taper seal portions is larger than the gap interval between the radial taper seal portions.

According to a sixth aspect of the present invention, in the first aspect of the invention, a radial bearing portion is formed between the shaft and the bearing, and the tapered seal portion is provided between the radial bearing portion and the folded taper seal portion. And a radial taper seal formed by being bent in the radial direction, wherein a gap interval between the folded taper seal portions is larger than a gap interval between the radial taper seal portions.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a bearing device according to an embodiment of the present invention. Figure 1
In the above, the frame 10 of the motor has a cylindrical holder part 12 integrally formed at the center part, and the inner periphery of the stator core 14 is fitted and fixed to the outer periphery side of the holder part 12. The stator core 14 is a laminated core having a plurality of salient poles in a radial pattern, and a driving coil 16 is wound around each salient pole.

A cylindrical bearing 18 is fitted and fixed to the inner peripheral side of the holder portion 12. A shaft 20 is inserted into a center hole of the bearing 18, and the shaft 20 is supported by the bearing 18 so as to be relatively rotatable. A thrust plate 22 is fitted and fixed to the outer periphery of the lower end of the shaft 20. The lower end surface of the shaft 20 and the lower surface of the thrust plate 22 are on the same plane. A thrust receiver 25 is embedded in a lower end of the bearing 18, and a joint surface between the bearing 18 and the thrust receiver 25 is sealed. In this manner, the bearing 18 has a single-bag structure in which one side in the axial direction, that is, the lower part is sealed, and the other side, that is, the upper part is opened.

There are minute gaps between the upper surface of the thrust plate 22 and the opposing surface of the bearing 18 and between the lower surface of the thrust plate 22 and the upper surface of the thrust receiver 25 corresponding thereto. Lubricating oil is interposed in this gap. And
A dynamic pressure groove is formed on at least one of the upper surface of the thrust plate 22 and the opposing surface of the bearing 18 with respect to the thrust plate 22, and at least one of the lower surface of the thrust plate 22 and the upper surface of the thrust receiver 25 therewith. A pressure bearing 25 is formed. When the thrust plate 22 rotates together with the shaft 20, the pressure of the lubricating oil is increased by the dynamic pressure groove,
Dynamic pressure is generated. This dynamic pressure is a dynamic pressure in the thrust direction, and the shaft 20 is supported in the thrust direction without contact.

There is also a minute gap between the outer peripheral surface of the shaft 20 and the inner peripheral surface of the bearing 18, and lubricating oil is also interposed in this gap. A region near the lower end on the inner peripheral side of the bearing 18, at least one of the outer peripheral surfaces of the shaft 20 opposed thereto, and the bearing 1
A dynamic pressure groove is formed in a region near the upper end on the inner peripheral side of the shaft 8 and at least one surface of the outer peripheral surface of the shaft 20 opposed thereto, and a radial dynamic pressure bearing portion 26 and a radial dynamic pressure bearing portion 28 are formed. It is formed up and down. When the shaft 20 rotates, dynamic pressure is generated in the radial dynamic pressure bearing portion 26 and the radial dynamic pressure bearing portion 28, and the shaft 20 is supported in the circumferential direction without contact.

A flat cup-shaped rotor housing 36 is provided on the outer periphery of the upper end of the shaft 20 projecting upward from the upper end of the bearing 18.
And the rotor housing 36 is held so as to be rotatable integrally with the shaft 18. Rotor housing 3
6, a cylindrical rotor magnet 38 is fixed to the inner surface of the outer peripheral wall. The inner peripheral surface of the rotor magnet 38 and the outer peripheral surface of the stator core 14 face each other at a predetermined interval. By controlling the energization of each drive coil 16 according to the rotational position of the rotor magnet, the rotor can be rotationally driven. Although the illustrated motor has the shape of a motor for a hard disk drive, the use of the bearing device according to the present invention is arbitrary.

The minute gaps formed in the thrust bearing section 25, the radial dynamic pressure bearing section 26, and the radial dynamic pressure bearing section 28 are connected to each other, and lubricating oil is interposed in the connected minute gaps. I have.

As shown in detail in FIG. 2, between the upper end surface 21 of the bearing 18 and the ceiling surface of the rotor housing 36 opposed thereto, a minute gap communicating with the minute gap of the radial dynamic pressure bearing portion 26 is provided. There is a gap. Lubricating oil is also interposed in this gap. The upper end surface 21 of the bearing 18 is a gently tapered surface that gradually decreases toward the outer periphery. On the other hand, the rotor housing 3 facing the tapered surface
The ceiling surface of No. 6 is a flat horizontal surface. Therefore, a radial taper seal portion 30 is formed between the tapered surface 21 and the ceiling surface of the rotor housing 36 facing the tapered surface 21 so that the gap gradually increases toward the outer periphery.

The outer periphery of the upper end of the bearing 18 is cut off to form a step 19. The portion of the rotor housing 36 facing the step 19 is a protrusion 37 toward the step 19.
The bearing 18 is located on the inner peripheral side of the protrusion 37.
The upper end of has entered. Outer peripheral surface 2 of upper end of bearing 18
There is also a gap communicating with the radial taper seal portion 30 between 3 and the inner peripheral surface of the projecting portion 37. Lubricating oil is also interposed in this gap. Outer peripheral surface 2 of upper end of bearing 18
Reference numeral 3 denotes a gently tapered surface whose diameter gradually decreases downward. On the other hand, the inner peripheral surface of the protruding portion 37 facing the tapered surface is a vertical surface having the same diameter. Therefore, between the tapered surface 23 and the inner peripheral surface of the protruding portion 37 facing the tapered surface 23, a folded tapered seal portion 32 is formed, the gap of which gradually increases downward.

The radial taper seal portion 30 and the folded taper seal portion 3 in the embodiment described above.
The two taper seal portions 2 are seal portions for preventing the lubricating oil interposed in the dynamic pressure bearing portion from leaking to the outside, and extend from the radial taper seal portion 30 to the folded taper seal portion 32. The spacing is gradually expanding. That is, the radial taper seal portion 30 and the folded taper seal portion 32 can be regarded as a continuous taper seal portion. Also,
These taper seal portions are bent in the radial direction from the axial direction of the shaft 20, and are further bent in the axial direction. Further, the gas-liquid interface 34 of the lubricating oil is located in the folded taper seal portion 32.

Incidentally, an example of the main specifications of the above embodiment will be given. Motor height: 8 mm Bearing height: 6.5 mm (including surface tension seal) Single-bag structure with shaft rotation type, two radial dynamic pressure bearings, and two thrust dynamic pressure bearings Rotational speed: 4200 rpm

In the above specification, the surface tension seal for preventing leakage of the lubricating oil is composed of the radial taper seal portion 30 and the folded taper seal portion 32. With a diameter of 5 mm, all of them can be used for bearing applications, and a dynamic pressure bearing with excellent performance can be obtained. On the other hand, according to the structure of the conventional bearing device, the surface tension seal portion is arranged along the axis,
Since it is necessary to secure about 1 mm to face the shaft, the remaining bearing height is reduced to 5.5 mm, and the performance of the dynamic pressure bearing is sacrificed accordingly.

According to the above embodiment of the present invention, since the surface tension seal is constituted by the radial taper seal portion 30 and the folded taper seal portion 32, the volume of the lubricating oil reservoir can be increased. Even if the current is reduced by using a low-clay lubricating oil that easily evaporates, by retaining a sufficient amount of the lubricating oil, it is possible to maintain a specified or longer life.

Further, by forming the surface tension seal with the radial taper seal portion 30 and the folded taper seal portion 32, the surface tension seal portion can be lengthened, and the effect of preventing leakage of lubricating oil can be improved. Can be enhanced. Therefore, even if the centrifugal force is increased by increasing the rotation speed, leakage of the lubricating oil can be prevented.

The longer the radial tapered seal portion 30, the greater the centrifugal force applied to the lubricating oil. Therefore, it is desirable to reduce the length of the radial taper seal portion 30 and make the folded taper seal portion 32 as long as possible, as far as the conditions allow in relation to other structures. When the length of the radially tapered seal portion 30 is reduced, if the length of the folded tapered seal portion 32 is sufficiently long, the portion corresponding to the radially tapered seal portion 30 is formed into a parallel gap without tapering, and the folded tapered seal portion is formed. The tapered seal portion may be formed only by the portion 32.

The present invention is not limited to the dynamic pressure bearing, but can be applied to any type of bearing device using lubricating oil for the bearing portion. For example, the present invention is also applicable to a bearing device using a sintered oil-impregnated bearing impregnated with lubricating oil as a radial bearing or a thrust bearing. The present invention is also applicable not only to the shaft rotation type but also to a shaft fixed type. A type in which a sleeve corresponding to a bearing rotates on the outer peripheral side with respect to a fixed shaft, wherein a surface tension seal portion is formed between an end surface of the rotating sleeve and a surface of a stator opposed thereto. Is also applicable.

[0027]

According to the present invention, the tapered seal portion for preventing the lubricating oil from leaking to the outside is formed by a folded tapered seal portion formed at a folded portion extending from the radial direction to the axial direction. Since the gas-liquid interface of the lubricating oil is located in the tapered seal portion, the length of the tapered seal portion can be increased while meeting the demand for thinning. Therefore, by retaining more surplus lubricating oil, it is possible to have a buffer function against the reduction of lubricating oil due to evaporation, even if using a low-viscosity lubricating oil that easily evaporates,
The predetermined life can be maintained, and the current can be reduced.

Further, since the seal portion is constituted by the radial taper seal portion and the folded taper seal portion outside the range of the radial bearing, the seal portion and the radial bearing can be designed without being influenced by each other, and the design can be improved. The degree of freedom can be increased. Therefore, the bearing can be optimized in a limited space, and when applied to a motor, the thickness of the motor can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a motor having a bearing device according to the present invention.

FIG. 2 is an enlarged sectional view showing a tapered seal portion of the bearing device.

[Explanation of symbols]

 Reference Signs List 18 bearing 20 shaft 22 thrust plate 24 thrust receiver 25 thrust dynamic pressure bearing 26 radial dynamic pressure bearing 28 radial dynamic pressure bearing 30 radial taper seal part 32 folded taper seal part 34 gas-liquid interface

Claims (6)

[Claims] 1. A bearing device having a shaft, a bearing for supporting the shaft so as to be relatively rotatable, and a lubricating oil interposed between the shaft and the bearing, wherein the lubricating oil is prevented from leaking to the outside. For this reason, a tapered seal portion whose interval gradually increases is formed, and the tapered seal portion has a folded tapered seal portion formed at a folded portion directed from the radial direction to the axial direction, and the lubrication is provided at the tapered seal portion. A bearing device, wherein a gas-liquid interface of oil is located. 2. A dynamic pressure bearing unit is formed between a shaft and a bearing, and the bearing device is a dynamic pressure bearing device that supports the shaft so as to be relatively rotatable by dynamic pressure generated in the dynamic pressure bearing unit. The bearing has a single-bag structure in which one side in the axial direction is sealed and the other side is opened, and a surface tension seal portion including a taper seal portion is formed on the other side of the bearing,
The bearing device according to claim 1, wherein the lubricating oil is filled from one side of the bearing to a surface tension portion provided on the other side. 3. A radial dynamic pressure bearing portion is formed between the shaft and the bearing, and the tapered seal portion is formed by bending in a radial direction between the radial dynamic pressure bearing portion and the return taper seal portion. 3. The bearing device according to claim 2, further comprising a radial tapered seal portion, wherein a gas-liquid interface of the lubricating oil is located in the folded taper seal portion. 4. A radial dynamic pressure bearing portion is formed between a shaft and a bearing, and a thrust plate is fixed to the shaft, and a thrust dynamic pressure bearing is provided between the thrust plate and the bearing. The bearing according to claim 2, wherein a radial taper seal portion is formed between the folded taper seal portion and the radial dynamic pressure bearing portion, and a gas-liquid interface of lubricating oil is located in the folded taper seal portion. apparatus. 5. The bearing device according to claim 3, wherein a gap interval between the folded taper seal portions is larger than a gap interval between the radial taper seal portions. 6. A radial bearing portion is formed between the shaft and the bearing, and the tapered seal portion is formed between the radial bearing portion and the return tapered seal portion by being bent in a radial direction. It has a taper seal portion, the gap interval of the folded taper seal portion is better,
The bearing device according to claim 1, wherein the clearance is larger than a gap interval of the radial taper seal portion.