JP2000213532A - Air dynamic pressure bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve productivity for an air dynamic pressure bearing device. SOLUTION: Inexpensive and proper moldability can be obtained, and also a dynamic pressure bearing function in use can be properly maintained, by forming at least one side of a shaft member 3 and a bearing member 12 by an oil-impregnation sintered material, and providing oil discharge grooves 7 for discharging lubricating oil, infiltrating into a dynamic pressure bearing part from the oil-impregnation material, to the outside of a dynamic pressure contact part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air dynamic pressure bearing in which a dynamic pressure is generated in air as a bearing fluid, and a shaft member and a bearing member are rotatably supported by the dynamic pressure. Related to the device.

[0002]

2. Description of the Related Art In recent years, polygon mirrors, magnetic disks,
Various proposals have been made regarding hydrodynamic bearing devices for rotationally driving various types of rotating plates such as optical disks. In this dynamic pressure bearing device, the dynamic pressure surface of the shaft member and the dynamic pressure surface of the bearing member are provided so as to oppose each other in the radial direction via a predetermined gap, and a dynamic bearing portion is formed in the opposing gap. Have been. Further, a dynamic pressure generating means is formed on one of the two dynamic pressure surfaces, and a bearing fluid such as air or oil injected into the dynamic bearing portion is provided between the shaft member and the bearing member. Pressure is applied by the pumping action during relative rotation, and both the shaft member and the bearing member are rotatably supported by the dynamic pressure of the bearing fluid.

[0003] In general, such a dynamic pressure bearing device is intended to prevent damage or seizure when the shaft member and the bearing member come into contact with each other when the dynamic pressure bearing device is started or stopped, or when an external force such as vibration contacts the shaft member. For this purpose, for example, molding using a ceramic material or forming a resin coating film containing a solid lubricant represented by PTFE (polytetrafluoroethylene) on a dynamic pressure surface has been performed. Among them, in a bearing device in which a resin coating film containing a solid lubricant is formed, a lubricating paint is applied to one surface of both dynamic pressure surfaces of the shaft member or the bearing member, and a surface of the other dynamic pressure surface is applied to the surface of the other dynamic pressure surface. They are plated and used in combination.

For example, when applying a lubricating paint to a bearing member, first, a blank of the bearing member is formed by casting or die casting using an aluminum or aluminum alloy material, and the corrosion resistance and coating adhesion are improved. After performing a base treatment such as chromate treatment or anodic oxidation treatment, and masking a part of the outer surface, the inner peripheral surface of the blank is subjected to, for example, PTFE.
A (polytetrafluoroethylene) -containing lubricating paint is applied by spraying or the like. Next, after drying, the same spray coating is repeated three to five times again to perform thick coating. The reason why such thick coating is performed is that unevenness due to foaming or dripping of the coating is likely to occur in the coating layer.

On the other hand, when plating the dynamic pressure surface of the shaft member, if a dynamic pressure generating groove is required, the dynamic pressure generating groove is formed before plating. More specifically, the blank is subjected to masking printing on a portion other than the portion where the dynamic pressure generating groove is formed, capping the end face, and performing etching or the like, thereby processing the dynamic pressure generating groove. Next, the plating process is started, and after performing pretreatments such as degreasing and activation, the end face is again capped and replaced with zinc, and a plating process such as electroless nickel plating is performed.

[0006]

However, when a lubricating paint is formed as a film as described above, it is difficult to control the paint to disperse the fixed lubricant moderately, and it is also necessary to carry out the process from base processing to painting and finishing. A complicated process is required. Further, when a ceramic material is used, a great deal of labor is required to obtain a precise bearing surface because the material itself is hard and difficult to machine. As described above, in manufacturing the conventional hydrodynamic bearing device, it is necessary to perform troublesome processing,
There is a problem that the product must be expensive.

Accordingly, an object of the present invention is to provide an air dynamic pressure bearing device capable of maintaining good bearing characteristics at low cost.

[0008]

According to the first aspect of the present invention, a dynamic pressure surface formed on a shaft member and a dynamic pressure surface formed on a bearing member are circumferentially opposed to each other. Air as a bearing fluid is interposed between the two dynamic pressure surfaces, and the shaft member and the bearing member are separated by a dynamic pressure obtained by pressurizing the air by dynamic pressure generating means provided on at least one of the two dynamic pressure surfaces. In the air dynamic pressure bearing device which is relatively rotatably supported, at least one of the shaft member and the bearing member is formed of a sintered oil-impregnated material in which porous pores are impregnated with lubricating oil. An oil discharge groove for discharging the lubricating oil leached from the sintered oil-impregnated material to the outside of the bearing is provided on at least one of the shaft member and the bearing member.

According to the second aspect of the present invention, a dynamic pressure generating groove is formed as the dynamic pressure generating means according to the first aspect,
The dynamic pressure generating groove is provided so as to double as the oil discharge groove.

Further, in the invention according to claim 3, the lubricating oil according to claim 1 or 2 contains a solid lubricant.

Further, in the invention according to claim 4, the lubricating oil according to claim 1 or 2 or 3 is
It is a semi-solid lubricant.

[0012] According to the first aspect of the present invention having such a structure, the shaft member or the bearing member is formed of a sintered oil-impregnated material. The lubricant that sometimes oozes out of the sintered oil-impregnated material into the bearing portion is discharged from the bearing portion to the outside of the bearing through the oil discharge groove, so that the dynamic pressure bearing function is favorably maintained. .

At this time, if the dynamic pressure generating groove also serves as the oil discharge groove, it is possible to simultaneously process both of these grooves, Due to the pumping action of the pressure generating groove, the external discharge function of the oil discharge groove can be obtained extremely well.

According to the third aspect of the present invention, the lubricating oil impregnated in the sintered oil-impregnated material contains a solid lubricant to reduce the damage to the dynamic pressure surface. Realized reliably.

Further, when a semi-solid lubricant is used for the lubricating oil impregnated in the sintered oil-impregnated material, the amount of oozing of the lubricating oil is reduced. , And the dynamic pressure characteristics are maintained better,
In particular, instability such as load fluctuation due to external discharge of lubricating oil is eliminated.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which an air dynamic bearing device according to the present invention is applied to a fixed-shaft type polygon mirror driving motor will be described below in detail with reference to the drawings.

FIG. 1 is a cross-sectional view showing an embodiment of an air dynamic pressure bearing device according to the present invention, and is an outer rotor type having a fixed shaft type air dynamic pressure bearing device for rotating a polygon mirror. It is a figure showing an example of a motor. The motor provided with the air dynamic pressure bearing device includes a stator set 2 as a fixed member mounted on the frame 1 side, and a rotating member mounted on the stator set 2 so as to be fitted from above in the figure. And a rotor set 11 of FIG.

The stator set 2 cylindrically surrounds the fixed shaft 3 erected substantially at the center of the frame 1 and at a fixed radial distance from the outer peripheral surface of the fixed shaft 3. It includes a bearing holder 4, a stator core 5 mounted on a cylindrical outer peripheral surface of the bearing holder 4, and a drive coil 6 wound around salient pole portions of the stator core 5.

A disk-shaped flange portion 3a extending outward in the radial direction is integrally provided at a base end portion (lower end portion in the figure) of the fixed shaft 3, and is provided on an outer peripheral portion of the flange portion 3a. A hollow cylindrical bearing holder 4 is attached to the formed annular attachment portion 3b. The bearing holder 4 includes a bearing sleeve 12 as a bearing member of a rotor set 11 rotatably mounted on the outer peripheral cylindrical surface of the fixed shaft 3.
Are arranged concentrically with a constant radial gap from the outer peripheral surface of the.

The outer peripheral cylindrical surface of the fixed shaft 3 in the stator set 2 is provided with the bearing sleeve 1 in the rotor set 11.
A dynamic pressure surface is formed together with the inner peripheral cylindrical surface of No. 2 and these two dynamic pressure surfaces are annularly opposed to each other via a narrow gap in the radial direction to form a radial dynamic pressure bearing portion.

At a substantially central portion of the outer peripheral cylindrical surface of the fixed shaft 3 in the axial direction, an air reservoir 7a formed of an annular concave groove surrounding the outer peripheral surface is formed. Both shaft end directions of fixed shaft 3 (vertical direction in the figure)
A slant type dynamic pressure generating groove 7 extending toward the upper surface is concavely provided in two upper and lower blocks.

Each of the dynamic pressure generating grooves 7, 7 is formed by annularly arranging a large number of single grooves extending obliquely at a predetermined angle with respect to the axial direction. Both end portions are closed, and the closed end portion is set at a maximum pressure point corresponding to the most downstream position by the pumping action. The front end portion of the lower dynamic pressure generating groove 7 in the figure is
The outer peripheral surface of the bearing sleeve 12 described above and the bearing holder 4
The fluid pressure bearing portion communicates with the space on the outside of the dynamic pressure bearing portion via a radial gap between the inner peripheral surface and the inner peripheral surface.

The fixed shaft 3 is formed by subjecting an aluminum blank to the dynamic pressure generating grooves 7, 7 having the above-described shape, and then performing a hard anodizing process. As the fixed shaft 3 in the embodiment, φ12 mm
The outer diameter is adopted.

An air supply hole 8 extends axially downward from the shaft end on the upper side in the figure on the inner side of the fixed shaft 3. It opens toward the reservoir 7a. Further, an annular portion 3 protruding in the axial direction is provided on the outer peripheral portion of the upper shaft end of the fixed shaft 3.
The fixed side magnet 9 for thrust floating of the rotor set 11 is provided on the inner peripheral wall of the annular portion 3c.
Are mounted in an annular shape.

On the other hand, the rotor set 11 has a substantially hollow cylindrical bearing sleeve 12 as a bearing member fitted so as to cover the fixed shaft 3 from above the fixed shaft 3. A hexagonal flat-plate-shaped polygon mirror 15 is mounted on the outer peripheral cylindrical portion of the sleeve 12 so as to be in contact with a holding portion 16 provided so as to protrude in the radial direction. 20 fixed.

Bearing sleeve 12 as bearing member
Constitutes a dynamic pressure bearing portion by being rotatably mounted on the fixed shaft 3 of the stator set 11 as described above, and the closing surface portion 12a on the upper side in the drawing is
Are arranged so as to face the upper end face in the drawing.

The bearing sleeve 12 in this embodiment is
It is formed from a sintered oil-impregnated material in which a predetermined lubricating oil is impregnated by molding a metal powder of iron-copper based metal, and the crushing level of the porous pores of the sintered oil-impregnated material is determined by an open ratio. Less than 10%. Further, as the impregnated lubricating oil,
A liquid greased semi-solid lubricant based on VG20 class ester oil is used. When a solid lubricant is mixed in the semi-solid lubricant, PT
When the decomposition temperature is lower than the sintering temperature of the bearing sleeve, such as FE (polytetrafluoroethylene), the case where the decomposition temperature is directly mixed with the semi-solid lubricant, and the case where the sintering temperature of the bearing sleeve, such as graphite, is lower. If it can withstand, it may be indirectly mixed in the semi-solid lubricant by mixing it in advance with the metal powder as the sintering material.

At this time, the above-mentioned dynamic pressure generating grooves 7, 7
The bearing sleeve 12 is also provided so as to serve also as an oil discharge groove for discharging lubricating oil that oozes out of the sintered oil-impregnated material constituting the bearing sleeve 12 and leaches into the dynamic pressure bearing portion toward the outside of the bearing portion. That is, the lubricating oil oozing into the dynamic pressure bearing portion from the sintered oil-impregnated material of the bearing sleeve 12 is guided to the shaft end side along the flow of air in the dynamic pressure generating grooves 7, 7. On the other hand, the front end portion of the dynamic pressure generating groove 7 on the lower side in the figure is connected to the bearing sleeve 12 as described above.
Is connected to the external space of the dynamic pressure bearing through a gap between the outer peripheral surface of the bearing and the inner peripheral surface of the bearing holder 4.
The lubricating oil guided to the lower shaft end portion by the pumping action of the dynamic pressure generating grooves 7, 7 is discharged to the outside of the bearing together with the air.

The disk-shaped holding portion 16 provided on the outer circumferential surface of the bearing sleeve 12 has the holding portion 16.
A substantially cup-shaped rotor flange 17 extending radially outward from the rotor core 17 is provided so as to cover the stator core 5 described above, and projects downward from the outer peripheral portion of the rotor flange 17 in the figure. A drive magnet 19 is annularly mounted on the inner peripheral wall surface of the mounting plate 18 via a back yoke made of a magnetic material, and the annular magnet 19 faces the outer peripheral surface of the stator core 5 in the radial direction. It is arranged to be.

A fine air orifice 13 having a predetermined airflow resistance is formed in the upper portion of the bearing sleeve 12 in the figure at the center thereof in the axial direction. On the lower outer peripheral surface of the air orifice 13, a rotating magnet 14 for thrust floating is annularly mounted, and is provided so as to face the fixed magnet 9 on the fixed shaft 3 described above. The rotating side magnet 14 and the fixed side magnet 9 are magnetized to have opposite polarities in the axial direction (vertical direction in the drawing), so that magnetic attraction is generated vertically in the axial direction. It is configured. Then, by the suction action, the rotor set 11 is held in a state of floating by a predetermined amount in the thrust direction.

When a predetermined drive voltage is applied to the drive coil 6 of the motor having the air dynamic pressure bearing device thus configured, the polygon mirror 1 and the bearing sleeve 12 are applied.
5 rotates, and the laser light converged on the polygon mirror 15 by the rotation of the polygon mirror 15 scans an image recording medium (not shown).

At this time, the air inside the rotor set 11 (between the bearing sleeve 12 and the fixed shaft 3) is supplied to the air reservoir 7a in the dynamic pressure bearing through the air supply hole 8,
Pressurization is performed by the pumping action of the dynamic pressure generating grooves 7, 7 to obtain a predetermined radial dynamic pressure bearing action. At this time, the stator set 2 and the rotor set 11 are supported in the thrust direction by the damper effect due to the ventilation resistance of the air orifice 13.

On the other hand, the lubricating oil that oozes out of the sintered oil-containing material constituting the bearing sleeve 12 into the dynamic pressure bearing portion also
The lubricating oil guided to the shaft end side along the flow of the air in the dynamic pressure generating grooves 7, 7 and guided to the lower shaft end portion by the pumping action of the dynamic pressure generating grooves 7, 7 together with the air. The gas is discharged to the outside of the bearing through a gap between the outer peripheral surface of the bearing sleeve 12 and the inner peripheral surface of the bearing holder 4.

As described above, in the air dynamic pressure bearing device according to the present embodiment, the bearing sleeve 1 as a bearing member is used.
Since No. 2 is formed of a sintered oil-impregnated material, good moldability at low cost is obtained, and productivity is improved. When the dynamic pressure bearing device is used, the bearing sleeve 1
The lubricant oozing out of the sintered oil-impregnated material 2 and leaching into the bearing portion is discharged to the outside of the bearing through the dynamic pressure generating groove 7 which also serves as an oil discharge groove, and the dynamic pressure bearing function is favorably maintained. It has become.

Actually, an air motor for LBP using the hydrodynamic bearing device having the above-described configuration is rotated at 25 rpm.
When it was rotated at 000 rpm, it was found that the bearing loss and the jitter characteristics were maintained at the same level as the conventional product, even though the structure was inexpensive, and the bearing had excellent performance in seizure resistance when an impact force was applied.

Further, in this embodiment, since the dynamic pressure generating groove 7 is provided so as to also serve as the oil discharge groove, it is possible to simultaneously process both of these grooves, and a more inexpensive structure can be obtained. In addition, the function of discharging the oil discharge groove to the outside can be obtained very well by the pumping action of the dynamic pressure generation groove.

Further, in this embodiment, the bearing sleeve 1
Since the solid lubricant is contained in the lubricating oil impregnated in the sintered oil-impregnated material of No. 2, the damage to the dynamic pressure surface is reduced, and the seizure resistance is further improved.

Furthermore, in this embodiment, since the semi-solid lubricant is used for the lubricating oil impregnated in the sintered oil-impregnated material of the bearing sleeve 12, the amount of the seeping out of the lubricating oil is reduced, and While the pressure characteristics are maintained better,
In particular, concerns about instability such as load fluctuation when the lubricating oil is discharged outside are eliminated.

Although the embodiments of the present invention made by the inventor have been specifically described above, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the gist thereof. Needless to say.

For example, in the above-described embodiment, the bearing sleeve 12 side as the bearing member is formed of a sintered oil-impregnated material, but the shaft member side may be formed of a sintered oil-impregnated material.

The oil discharge groove may be formed separately from the dynamic pressure generating groove, and may be provided not on the shaft member but on the bearing member side or on both of them as in the above embodiment. Is also possible.

Further, in the above embodiment, the lubricating oil impregnated in the sintered oil-impregnated material is semi-solidified in a grease state and contains a solid lubricant. However, only a liquid lubricant is employed. It is possible.

Furthermore, not only when the bearing member side is provided as a rotating member as in the above-described embodiment,
The present invention can be similarly applied even when the shaft member side is provided as a rotor.

The present invention can be applied to the case where the dynamic pressure generating grooves are formed on the bearing member side or both of them, only when the dynamic pressure generating grooves are provided on the shaft member side. can do.

On the other hand, the present invention can be similarly applied to a motor other than the polygon mirror driving motor as in the above-described embodiment, or to various other various rotary driving devices. For example, the present invention can be similarly applied to a dynamic pressure bearing device provided in a hard disk drive (HDD) motor shown in FIG.

In the embodiment shown in FIG. 2, members corresponding to those in the embodiment shown in FIG. 1 are denoted by the same reference numerals, but the feature of the embodiment shown in FIG. The center cylindrical portion of the hub 21 that constitutes the rotor is rotatably supported via an air dynamic bearing device. A recording medium such as a disk is held substantially horizontally.

[0047]

As described above, according to the first aspect of the present invention, at least one of the shaft member and the bearing member is formed of a sintered oil-impregnated material, and the sintered oil-impregnated material is inserted into the hydrodynamic bearing portion. By providing an oil discharge groove for discharging the leaching lubricating oil to the outside of the dynamic pressure bearing part, it was configured to obtain good moldability at low cost and to maintain good dynamic pressure bearing function during use. Therefore, the productivity can be improved while maintaining the reliability of the air dynamic pressure bearing device.

According to the second aspect of the present invention, the dynamic pressure generating groove is provided so as to also serve as the oil discharge groove, so that both grooves can be processed at the same time, and the dynamic pressure generating groove has a pumping action. Since the external discharge function of the oil discharge groove can be obtained extremely well, the above-described effects can be further improved.

The third aspect of the present invention is configured such that a solid lubricant is contained in the lubricating oil impregnated in the sintered oil-impregnated material so as to reduce the damage to the dynamic pressure surface. The effect can be further improved.

Further, according to the present invention, a semi-solid lubricant is used for the lubricating oil impregnated in the sintered oil-impregnated material, thereby reducing the amount of the lubricating oil seeping out and further improving the dynamic pressure characteristics. In addition to the above, the above-described effect can be further improved because the configuration is made to improve the responsiveness to instability such as load fluctuation due to the external discharge of the lubricating oil.

[Brief description of the drawings]

FIG. 1 is a cross-sectional explanatory view showing an example of a fixed-shaft type polygon mirror driving motor provided with a dynamic pressure bearing to which the present invention is applied.

FIG. 2 is an explanatory cross-sectional view showing an example of a fixed shaft type hard disk drive motor provided with a dynamic pressure bearing to which the present invention is applied.

[Explanation of symbols]

 2 Stator set 3 Fixed shaft (shaft member) 4 Bearing holder 7 Dynamic pressure generating groove (oil discharge groove) 11 Rotor set 12 Bearing sleeve (bearing member)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Michiaki Takizawa 5329 Shimosuwa-cho, Suwa-gun, Nagano F-term in Sankyo Seiki Seisakusho Co., Ltd. (reference) 3J011 AA04 BA02 CA01 CA02 JA02 LA01 MA04 MA23 SE04

Claims (4)

[Claims] A dynamic pressure surface formed on a shaft member and a dynamic pressure surface formed on a bearing member are circumferentially opposed to each other, and air as a bearing fluid is interposed between the two dynamic pressure surfaces. An air dynamic pressure bearing device configured to support the shaft member and the bearing member in a relatively rotatable manner by a dynamic pressure obtained by pressurizing the air by a dynamic pressure generating means provided on at least one side, At least one of the shaft member and the bearing member is formed of a sintered oil-impregnated material in which porous pores are impregnated with a lubricating oil, and an oil discharge for discharging the lubricating oil leached from the sintered oil-impregnated material to outside the bearing. An air dynamic pressure bearing device, wherein a groove is provided on at least one of the shaft member and the bearing member. 2. A dynamic pressure generating means according to claim 1, wherein a dynamic pressure generating groove is formed, and said dynamic pressure generating groove is provided so as to also serve as an oil discharge groove. Air dynamic pressure bearing device. 3. The air dynamic bearing device according to claim 1, wherein the lubricating oil according to claim 1 contains a solid lubricant. 4. The air dynamic pressure bearing device according to claim 1, wherein the lubricating oil is a semi-solid lubricant.