JPH03277808A - Dynamic pressure bearing device - Google Patents

Abstract

PURPOSE:To enhance abrasion resistance so as to improve durability by applying a salt bath nitriding treatment to thrust bearing surfaces of a rotor body and bearing member. CONSTITUTION:A shaft 3 is supported by a thrust bearing surface 9 at an upper face of a ball body 2 fitted under pressure into a lower end portion inside of a cylinder body 1 serving as a bearing member and a thrust bearing surface 10 at the underside of the shaft 3. The shaft 3 is made of stainless steel, and the ball body 2 is formed of bearing steel of the secondary group. A salt bath nitriding treatment is applied to the shaft 3 and the ball body 2. Therefore, abrasion resistance and durability of the bearing surfaces 9, 10 can be enhanced, and high accuracy can be maintained for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a hydrodynamic bearing device used to support high-precision rotating parts such as video recorders, video disks, magnetic disks, and the like.

[Conventional technology]

Conventionally, in supporting parts of rotating parts of audio equipment and information processing equipment, dynamic pressure generating grooves such as herringbone grooves or spiral grooves have been installed on one side of the opposing surface of the rotating body that rotates at high speed and the bearing member that supports it. The developed hydrodynamic bearing device is used.

In such hydrodynamic bearing devices, when the rotating body rotates at high speed, fluid is sent into the bearing gap between the rotating body and the bearing member by the pumping action of the dynamic pressure generation groove, and the rotating body is supported by the fluid. The rotational accuracy of the rotating body is high, and the generation of noise and vibration is extremely low.

[Problems to be Solved by the Invention] In the above hydrodynamic bearing device, when the rotating body is stopped, the rotating body is in contact with the bearing surface of the bearing member. Secondly, the rotating body rotates in contact with the bearing member, causing wear on the contact portion.

In particular, in hydrodynamic bearing devices in which dynamic pressure generating grooves are formed on the radial bearing surface and the thrust bearing surface is in contact, the thrust bearing is constantly in contact, so the thrust bearing surface is subject to large wear. This causes a problem in that the rotating body is displaced in the axial direction, resulting in reduced durability.

The present invention solves the above problems and provides a hydrodynamic bearing device with significantly improved durability by improving the wear resistance of the thrust bearing surface.

[Means to solve the problem]

In order to solve the above problems, the present invention employs a configuration in which the thrust bearing surfaces of the rotating body and the bearing member are subjected to salt bath nitriding treatment.

Further, in the above configuration, the thrust bearing surface of the rotating body can be contacted and supported by the thrust bearing surface of the bearing member, and at least one of the thrust bearing surfaces can be formed of stainless steel.

In addition, the salt bath nitriding treatment here refers to a temperature of 520°C to 58°C.
Cyan oxide (KCNOlNaC)
This is a treatment in which active nitrogen (N) generated from oxides of nitrogen (NO, etc.) is introduced into the surface of the steel.

[Function] As described above, when a nitride compound is formed on the surface of the thrust bearing surface by performing salt bath nitriding treatment, the wear resistance of the thrust bearing surface is significantly improved, and wear due to contact can be suppressed.

Further, when the thrust bearing surface is formed of stainless steel, a high hardness surface with a surface hardness of Hv1000 or more can be obtained by salt bath nitriding treatment, and wear resistance can be greatly improved.

〔Example〕

Hereinafter, the present invention will be described in detail based on the accompanying drawings.

In the hydrodynamic bearing device of the embodiment shown in FIG. 1, a sphere 2 is press-fitted into the inner lower end of a cylindrical body 1 as a bearing member, and a shaft 3 as a rotating body is inserted into the inside of the cylindrical body 1 by means of the sphere 2. The lower end surface of is supported in contact with it. In this case, shaft 3
The lower end surface of the sphere 2 and the upper surface of the sphere 2 become the thrust bearing surface 9.10.

Further, radial bearing surfaces 4 are formed in two stages, upper and lower, on the inner diameter surface of the cylinder 1, while dynamic pressure generating grooves 5 are formed on the outer diameter surface of the shaft 3 at positions facing the radial bearing surfaces 4. It is formed.

FIG. 2 shows another example of a hydrodynamic bearing device, in which a thrust plate 6 is fixed to the inner lower end of the cylindrical body 1 instead of the sphere 2 in FIG. It contacts and supports a spherical portion 7 formed at the lower end.

In the device shown in FIGS. 1 and 2, when the shaft 3 is rotated at high speed, a radial bearing clearance 8 is formed between the radial bearing surface 4 and the outer diameter surface of the shaft 3 due to the pumping action of the dynamic pressure generating groove 5. Pressure fluid is pumped into. Therefore, the shaft 3 is supported by the pressure fluid and rotates without contacting the radial bearing surface 4, and the shaft 3 and the thrust bearing surface 9.10 formed on the sphere 2 or the thrust plate 6 are in contact with each other. Rotate in the state.

In the above hydrodynamic bearing device, the shaft 3 is made of stainless steel, and the sphere 2 or thrust plate 6 is made of two types of bearing steel (
SUJ2) and both of them are subjected to salt bath nitriding treatment.

In this salt bath nitriding process, for example, a carbonate such as NazCO2 is added to a mixture of KCNO and KCN in a ratio of approximately 60:40, and the mixture is heated to around 550°C and melted. This is done by nitriding the shaft 3 and sphere 2 or thrust plate 6 to be treated in a salt bath using cyanide oxide (KNCO). In this salt bath, active nitrogen N generated by the decomposition of cyanide oxide penetrates the surface of the steel and forms nitride compounds on the surface.

By this salt bath nitriding treatment, the surface hardness of the shaft 3 made of stainless steel becomes Hv 1 (100 or more), and extremely high wear resistance is obtained.

On the other hand, the surface hardness of the sphere 2 and thrust plate 6 made of low carbon bearing steel is in the range of Hv 500 to 600, but the presence of the nitride compound significantly improves the wear resistance of the surface. The above surface hardness is relatively low compared to the conventional gas nitriding method, but conversely, this low hardness eliminates the brittleness of the material surface and prevents micro-chips in the surface layer of the thrust bearing surface that comes into contact with it. It has the effect of suppressing stiffness.

By performing the salt bath nitriding treatment in this way, the wear resistance of the thrust bearing surfaces 9.10 is greatly improved, so that the wear caused by mutual contact can be reduced. Therefore, axial displacement between the shaft 3 and the bearing member is reduced, and high support accuracy can be maintained over a long period of time.

By the way, in addition to the salt bath nitriding treatment described above, nitriding treatment is known as a method of increasing the hardness of a steel surface by introducing nitrogen into the steel.

This nitriding treatment involves adding NH and gas to an endothermic atmospheric gas during quenching heating above the A1 transformation point (720°C) to infiltrate the steel surface with nitrogen. It has the effect of improving wear resistance.

Here, in order to see the difference in the effects of salt bath nitriding treatment and nitriding treatment, in this example (salt bath nitriding treated product), shaft 3 and sphere 2 were subjected to salt bath nitriding treatment in the structure shown in Fig. 1. 83, a nitrided product in which a shaft and sphere made of similar materials were subjected to nitriding treatment, and a shaft and sphere made of bearing steel.
180” after quenching at a temperature of around 0°C to 840°C
A standard heat-treated product tempered with C was prepared, and part 3
A continuous rotation test was carried out on two types of bearings, and the amount of wear on the thrust bearing surface was compared. Figure 3 shows the results.

In the above comparative test, there was no difference between the shaft 3 and the sphere 2.
．． Add a thrust force of 1 kgf and reduce the sliding speed to 0.1
m/sin, and the nitriding roughness of the thrust bearing surface was 0.33.

Moreover, each bar graph in FIG. 3 shows the amount of wear obtained by a plurality of test pieces, and the shaded part in each bar graph shows the amount of wear of the sphere. moreover,
The report also includes a line a connecting each average value of the amount of wear on the thrust bearing surface and a line connecting each average value of the amount of wear on the sphere.

From the results shown in Figure 3, the wear amount of the nitrided product is greatly reduced compared to the standard heat treated product, but the wear of the salt bath nitrided product is even smaller than that of the nitrided product. It is clear that salt bath nitriding treatment is extremely effective in suppressing wear on the thrust bearing surface.

In addition, salt bath nitriding treatment has the effect of suppressing wear when used in combination with other treatment methods, such as nitriding treatment, but salt bath nitriding treatment is more effective in suppressing wear when used in combination with other treatment methods. A greater suppressive effect can be achieved by performing bath nitriding treatment.

For example, in the structure shown in Fig. 1, when the shaft 3 is subjected to salt bath nitriding treatment, the sphere 2 is subjected to nitriding treatment, and the shaft 3 is subjected to salt bath nitriding treatment, and both are rotated continuously, the former In the combination type, approximately 6n of wear occurred on the thrust bearing surface after 2,000 hours of operation, whereas in the latter, the amount of wear was less than 3-n even after 4,000 hours. This shows the difference in wear resistance obtained between salt bath nitriding treatment and nitriding treatment, and salt bath nitriding treatment has a greater effect on improving wear resistance than low carbon steel such as bearing steel. This is considered to indicate that.

In addition, in the hydrodynamic bearing device shown in FIGS. 1 and 2,
Although the cylinder 1 was used as a bearing member and the shaft 3 was used as a rotating body,
Contrary to the above, the cylinder 1 may be a rotating body and the shaft 3 may be a bearing member.

〔Effect of the invention〕

As described above, according to the present invention, the abrasion resistance of the bearing surfaces is improved by subjecting the thrust bearing surfaces of the rotating body and the bearing member to salt bath nitriding treatment, which greatly improves durability and improves long-term durability. This has the effect of realizing a bearing with high precision over time.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view showing an embodiment of a hydrodynamic bearing device according to the present invention, FIG. 2 is a longitudinal sectional front view showing another embodiment, and FIG. 3 is a graph showing the results of a wear test. 1... cylinder, 2... sphere,
3...Shaft, 4...Radial bearing surface, 5...Dynamic pressure generation groove, 6...
... Thrust plate, 7... Spherical part, Fig. 1 Fig. 2 Fig. 3 Standard heat treated product f2 Nitrogen treated product Salt bath nitrided product

Claims (2)

[Claims] (1) In a hydrodynamic bearing device in which a dynamic pressure generating groove is formed on one side of the opposing surfaces of a rotating body that rotates at high speed and a bearing member that rotatably supports the rotating body, the thrust bearing surface of the rotating body and the bearing member is provided with a hydrodynamic groove. A dynamic pressure bearing device characterized by being subjected to salt bath nitriding treatment. (2) The dynamic pressure according to claim (1), characterized in that the thrust bearing surface of the rotating body is contacted and supported by the thrust bearing surface of the bearing member, and at least one of the thrust bearing surfaces is formed of stainless steel. Bearing device.