JPH07109215B2 - Fluid bearing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrodynamic bearing device used in a disk drive device or the like.

2. Description of the Related Art In recent years, disk devices and the like have been made higher in density and thinner, and the main shaft portion for rotational drive thereof has a thin radial bearing span and is thin, and the shaft runout is 1 micrometer or less. Such a highly accurate drive device is required.

An example of the above-described conventional fluid bearing device will be described below with reference to the drawings. 2 to 3 are sectional views of a conventional fluid bearing device. In FIG. 2, reference numeral 11 is a chassis, and a sleeve 12 is fixed by screws or the like. A shaft 13 is rotatably inserted in the center of the sleeve 12. The bottom portion 13B of the shaft 13 is in contact with the thrust bearing 14 and receives a thrust load to form a pivot bearing. The thrust bearing 14 is supported by a thrust receiving plate 15 fixed to the sleeve 12 with screws or the like.
A hub 16 and a rotor 17 are fixed near the top 13A of the shaft 13 and rotate together with the shaft 13. A ventilation hole 12B is provided in the sleeve 12, and a dynamic pressure generating groove 12A such as a herringbone is provided on the inner surface of the bearing hole. The dynamic pressure generating groove 12A generally has a groove angle B of about 30 degrees and a groove depth of 2 to 3 μm, which is almost the same as the radial bearing radial clearance. Lubricants 18A and 18B mainly made of mineral oil or the like are lubricated between the sleeve 12, the shaft 13, and the thrust bearing 14, and the rotating disk 19 is attached to the hub 16.

The operation of the fluid dynamic bearing device configured as described above will be described below. First, when a motor (not shown) is energized and the rotor 17, the hub 16, and the shaft 13 start to rotate, the lubricant 18A generates pressure by the pumping action of the dynamic pressure generating groove 12A, and the shaft 13 rotates without contact.

SUMMARY OF THE INVENTION However, the above-mentioned configuration has the following problems.

First, the sleeve 12 required vent holes 12B.
Without this vent hole 12B, as shown in FIG. 3, the ambient temperature rises and the air 20 mixed in the bearing portion expands thermally, and the lubricant 18A adhering to the shaft 13 is shown in 18C in the figure. Thus, there was a problem that the amount of the lubricant 18A became insufficient after the repetition of this, because the lubricant was pushed out of the bearing portion. Further, this ventilation hole 12B has a problem that the diameter is small, the processing speed due to drilling cannot be increased, and the productivity is poor.

Secondly, regarding the shape of parts of the shaft 13, in order to prevent wear of the bottom 13B of the shaft 13 and the thrust bearing 14 in FIG. Larger (for example, 5
6 millimeters) must be configured. The thrust bearing 14 is made of silicon carbide or silicon nitride, and is made of a lubricant.
18A, 18B must use mineral oil of high viscosity, for example, about 100 centistokes at 20 ° C, and the friction tricks of radial bearings and thrust bearings become very large at a temperature of 0 ° C. Also, the top 13 of the shaft 13
In A, since the radius of the spherical surface is made small (about 3 millimeters) in order to secure the insertability of the rotary disc 19, the radii are different at both ends of the shaft 13, and it is difficult to determine the direction of the parts.
There has been a problem that the line operation rate is lowered due to a discrimination error in the mass production process.

Therefore, the present invention provides a fluid dynamic bearing device that does not need a vent hole, has a symmetrical shaft shape, has good productivity, and is excellent in wear resistance.

Means for Solving the Problems In order to solve the above-mentioned problems, a fluid dynamic bearing device of the present invention has a sleeve and a shaft at its center, and one end of the shaft abuts a thrust receiver attached to the sleeve. A dynamic pressure generating group is provided on the inner circumference of the sleeve or the outer circumference of the shaft, and a bearing gap composed of the sleeve, the thrust receiver and the shaft is filled with a lubricant composed of perfluoropolyether, and the thrust receiver is made of titanium carbide. And the top and bottom of the shaft have spherical surfaces of the same radius.

Effect of the Invention With the above-described configuration, the present invention makes it possible to reliably discharge the mixed air even if the ventilation hole is eliminated by making the groove angle sufficiently small and making the groove depth sufficiently deep.

Also, by using titanium carbide for the thrust bearing and using a combination of perfluoropolyether for the lubricant, even if the sphere radius of the top and bottom of the shaft is the same, sufficient wear resistance of the thrust pivot bearing is obtained. It is possible to obtain a fluid bearing device having the same.

As a result, since the shaft has the same shape in the axial direction and loses its directivity, it is not necessary to determine the direction when manufacturing the shaft, and it is possible to prevent the operating rate of the manufacturing line from decreasing. .

Example A fluid bearing device according to an example of the present invention will be described below with reference to FIG. FIG. 1 is a sectional view of the fluid bearing of this embodiment. In FIG. 1, 1 is a chassis, and a sleeve 2 is caulked and fixed by a caulking portion 2D. A shaft 3 is rotatably inserted in the center of the sleeve 2. The bottom portion 3B of the shaft 3 comes into contact with the thrust bearing 4 and receives a thrust load to form a pivot bearing. The thrust bearing 4 is caulked and fixed to the sleeve 2 by the caulking portion 2c, and the bearing portion is sealed. A rotor hub 5 is fixed near the top 3A of the shaft 3 and rotates together with the shaft 3.

The sleeve 2 is provided with a dynamic pressure generating groove 2A for generating dynamic pressure and an oil sump 2B having a large gap. Dynamic pressure generation groove 2A
The groove angle B is 17 degrees or less, and the groove depth is set to about 4 to 9 microns, which is deeper than the radial gap of 2 to 3 microns. The bottom of the shaft 3 that constitutes the pivot bearing
3B has the same spherical radius as the top 3A. 6A and 6B are fluorine-based lubricants (for example, perfluoropolyether having a low viscosity of about 30 centistokes at 20 ° C, such as Z-03 of Montefreos Co. and SJ-30 of NOK Co.). , 8 are air mixed in the bearing portion. A rotating disk 7 is inserted into the top portion 3A of the shaft 3 and rotates together with the shaft 3.

The first aspect of the fluid dynamic bearing device configured as described above
The operation will be described with reference to the drawings.

First, when a motor (not shown) is energized, the rotor hub 5, the shaft 3, and the rotary disk 7 start to rotate. This rotation causes the lubricant 6A to generate a pressure due to the pumping action of the dynamic pressure generation groove 2A, and the shaft 3 rotates without contact. At this time, the air 8 mixed in the bearing gap thermally expands due to an increase in ambient temperature, but the dynamic pressure generating groove 2A provided in the sleeve 2 has a sufficient depth of 4 microns or more.
During the stop, the air 8 can be discharged through the groove. Further, since the groove angle B is an acute angle of 17 degrees or less with respect to the direction of rotation or the direction of flow velocity, the air 8 can be smoothly transmitted through the groove and discharged to the outside of the bearing even while the shaft 3 is rotating. The oil sump 2B is for holding a lubricant 6A for refilling the groove after the air 8 is discharged. In this way, it is possible to obtain stable rotation without the vent hole unlike the conventional example.

Further, in this embodiment, the shaft 3 is a hard martensite-hardened stainless steel, the thrust bearing 4 is titanium carbide or partially stabilized zirconia (PSZ), and its surface roughness is 0.3. Precisely finished to a micron or less. A fluorine-based lubricant is used as the lubricant 6B, and wear is extremely small. Due to these combinations, when the diameter of the shaft 3 is about 4 millimeters, the bottom portion 3B of the shaft 3 has sufficient wear resistance even with the same spherical radius (about 3 millimeters) as the top portion 3A.
As for the wear resistance of the thrust bearing, the order is alumina <silicon carbide = silicon nitride <PSZ = titanium carbide, and it is possible to guarantee the required life by using PSZ or titanium carbide. .

As described above, according to the present embodiment, by using the fluorine-based lubricant and the titanium carbide, sufficient wear resistance can be obtained even if the radii of the top portion and the lower portion of the shaft are the same.

As a result, since the shaft has the same shape in the axial direction and loses its directivity, it is not necessary to determine the direction when manufacturing the shaft, and it is possible to prevent the operating rate of the manufacturing line from decreasing. .

In the above embodiment, the dynamic pressure generating groove is the same not only on the inner circumference of the sleeve but on the outer circumference of the shaft. The same applies when the shaft does not rotate and the sleeve and thrust receiver rotate.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to enhance the wear resistance as a bearing by using titanium carbide in the thrust receiver and using perfluoropolyether in the lubricant, and as a result, the thrust bearing is improved. Abrasion will occur even if the shape of the shaft bottom that makes contact with the receiver and rotates relative to it is spherical, and if the spherical shape of this shaft bottom has the same radius as the spherical shape of the shaft top, the shaft will move in the axial direction. Since the shape is the same and there is no directionality, it is not necessary to determine the direction when manufacturing the shaft, and it is possible to prevent a decrease in the operating rate of the manufacturing line.

[Brief description of drawings]

FIG. 1 is a sectional view of a fluid bearing device according to an embodiment of the present invention, FIG. 2 is a sectional view of a conventional fluid bearing device, and FIG. 3 is a sectional view showing problems of the device. 2 ... Sleeve, 2A ... Dynamic pressure generating groove, 3 ... Shaft,
3A ... Top, 3B ... Bottom, 4 ... Thrust bearing, 6A, 6
B ... Lubricant.

Claims (1)

[Claims] 1. A sleeve and a shaft in its center, one end of the shaft abuts a thrust receiver attached to the sleeve, and a dynamic pressure generating group is provided on an inner circumference of the sleeve or an outer circumference of the shaft. , The sleeve,
A fluid bearing device in which a bearing gap formed of a thrust receiver and a shaft is filled with a lubricant made of perfluoropolyether, the thrust receiver is made of titanium carbide, and a top portion and a bottom portion of the shaft have spherical surfaces with the same radius.