JPS6388313A - Dynamic pressure bearing - Google Patents

Abstract

PURPOSE:To improve the abrasion resistance of the bearing in the caption by forming a rugged pattern made of a hard film, for generating lifting force, on at least any one of surfaces of a rotary shaft or the bearing. CONSTITUTION:Grooves 3 are formed after stretching the coating of a hard film 2 on the surface of a disc-type base 1 so as to obtain a spiral rugged pattern. The surface 1a of the base 1 is pre-finished to be flat and smooth so as to make the surface 2a of the hard film 2 smooth as well. Accordingly, it is possible to make the sliding resistance small at the time of starting and stopping of the rotation of a shaft. In addition, the rugged pattern forming surface is made of the hard material 2, so as to make the abrasion resistance high and restrict the depth change of the grooves 3 to the slight extent despite a long-term service. Therefore, it is possible to improve the service life of a dynamic pressure bearing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a hydrodynamic bearing used in bearings for precision instruments and the like.

[Conventional technology]

In precision equipment such as video tape recorders and floppy disk drives, hydrodynamic bearings with high rotational accuracy and low noise and vibration have been used for the bearings of rotating shafts. As shown in Fig. 3, there are two types of hydrodynamic bearings: a radial bearing R formed around the shaft and a thrust bearing S formed on the end face of the shaft. The bearing has a diameter of several μm in depth by etching, etc.
- Grooves of approximately several tens of micrometers are drilled to form a predetermined uneven pattern. When the shaft rotates, the uneven backing generates lift, allowing the shaft and bearing to rotate without contact. It was something.

[Problems with conventional technology]

However, in such conventional hydrodynamic bearings, both the shaft and the bearing were made of stainless steel, which caused severe wear. While the shaft is rotating, there is no contact, so there is no wear, but since the shaft and bearings slide directly at the start and stop of rotation, they wear out over repeated use, forming especially uneven backbones. When this surface wears out, the grooves become shallower, resulting in the inconvenience that the bearing no longer functions as a hydrodynamic bearing.

[Failure to solve the problem]

In view of the above, the present invention provides a hydrodynamic bearing by depositing a hard film on the surface of at least one of the rotating shaft or the bearing to form an uneven pattern for generating lift.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1(a) and 1(b) show a thrust bearing S, in which a hard film 2 is adhered to the surface of a disc-shaped base 1 to form grooves 3 to form a spiral pattern of protrusions and recesses. Surface 1a of base 1
Since the hard film 2 has a flat and smooth surface in advance, the surface 2a of the hard film 2 also becomes a smooth surface, and the sliding resistance at the time of starting and stopping rotation of the shaft can be reduced. Furthermore, since the surface on which the uneven pattern is formed is made of a hard material, it has high wear resistance, and the change in the depth of the grooves 3 is small even after long-term use.

Next, as another example, the radial bearing R shown in FIG. This radial bearing R can achieve the same effect as the thrust bearing S shown in FIGS.
In this case, the radius of the rotation axis increases by the thickness t of the hard film 2, so as shown in Fig. 2(c), a recess 1θb with the same depth as the film thickness is formed in advance on the substrate lO. Ok,
A hard film 20 may be deposited in the recess lOb.

The manufacturing method of the hydrodynamic bearing according to the present invention is shown in Fig. 1 (aJ(b)) below.
This will be explained using the thrust bearing S shown in FIG.

First, prepare a base l made of stainless steel, ceramic, etc., and select the surface! Let a be a flat, smooth surface. Next, a mask is attached using resin, photoresist, etc. to the portions of this surface la that will become the grooves 8, and the entire surface is coated with SiC%
S i3. N4, Al2O3, diamond, TiC,
A hard film 2 is formed by depositing a hard material such as TiN by sputtering or the like. After deposition, if the mask is removed, the hard film 2 is not deposited on the masked portion, so the groove 3 is removed.
As a result, a concavo-convex pattern is formed. At this time, the depth of the groove 3 can be adjusted relatively easily by changing the sputtering time depending on the thickness t of the hard film 2, and the shape of the groove 3 can be adjusted relatively easily by changing the shape of the mask. It is possible to form a concavo-convex bag having an optimal depth and shape depending on the size of the rotating shaft, the number of rotations, the magnitude of the load, etc.

In addition, the surface 2a of the hard film 2 is a smooth surface with a surface roughness of 0.8s or less in order to reduce friction when starting and stopping rotation. After forming the hard film 2 as necessary, the surface 2af: @ is polished.

Next, the thrust bearing S shown in FIG.
.

Prototypes were made with A I 2.03, and a conventional one made of stainless steel without the hard film 2 was used as a comparative example, and a wear resistance test was conducted. The depth of groove 3 is 3 μm,
Using grease as a lubricant, we rotated at 2000 rpm and applied a load of 500g, which is heavier than normal, to forcibly cause wear.The results of investigating the relationship between rotation time and depth of groove 3 are as follows. It was as shown in Figure 4.

From FIG. 4, it can be seen that in the conventional thrust bearing not coated with hard film 2, the groove 8 was worn to a depth of 18 m or less in about 600 hours, and the groove 3 disappeared after 800 hours. In contrast, all of the thrust bearings according to the examples of the present invention have little wear, and in particular, the one using SiC as the hard film 2 shows wear of only about 1.5 μm even after 1000 hours, making it fully usable. It was a state. Note that this experiment was a time compression test in which wear was forcibly caused by increasing the load, so it goes without saying that the product can be used for a longer period of time under normal use.

The above experiment was shown only for thrust bearing S, but
The results were exactly the same in the case of the radial bearing R, and even when TiC, diamond, or the like was used as the material for the hard film 2, almost the same tendency was exhibited, and the results were excellent. Further, although only stainless steel is shown as the material of the base 1, other materials such as ceramic may also be used.

In addition, in the above embodiment, an example was given in which the hard X film was coated on only one of the rotating shaft or the bearing to form a groove, but the invention is not limited to this. By forming the shape, it is possible to generate a predetermined lift force even on a rotating shaft that rotates at a relatively low speed.

〔Effect of the invention〕

As described above, according to the present invention, the whole structure of the hydrodynamic bearing is formed by forming a concavo-convex pattern made of a hard X film on at least one surface of the rotating shaft or the blade bearing to generate lift. The surface with the uneven pattern is highly abrasive, so even after long-term use, there is little change in the depth of the groove, resulting in a longer service life.The surface with the uneven pattern is smooth, which reduces sliding resistance at the start of rotation. It has good reaction characteristics because of its small value.

In addition, by changing the thickness of the hard film and the shape of the mask, the depth and shape of the groove can be easily adjusted and a predetermined uneven pattern can be formed. can be provided.

[Brief explanation of the drawing]

FIG. 1(a) is a perspective view showing a hydrodynamic bearing according to an embodiment of the present invention, and FIG. 1(b) is a sectional view taken along the line x-X in the same figure (ai. A perspective view showing another embodiment of the present invention,
Figure 2 (bl is a cross-sectional view taken along the line Y-Y in the figure (al), and Figure 2 (c) is a cross-sectional view showing another embodiment of the present invention. Figure 3 shows a conventional hydrodynamic bearing. Figure 4 is a clear diagram showing the relationship between the opening during rotation and the depth of the groove. 1.10...Base, 2,2o...Hard film , 8゜30...groove.

Claims (1)

[Claims] 1. A hydrodynamic bearing characterized in that a pattern of protrusions and recesses made of a hard film is formed on at least one surface of the rotating shaft or the bearing for generating lift.