JPH0127833B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a rotating shaft having a highly accurate spherical surface at the shaft end.

As shown in Fig. 1, it consists of a rotating shaft 1 having a convex spherical receiving surface at the shaft end and a catch 2 having a concave spherical receiving surface. In the case shown, a shallow spiral groove 3 is carved on the convex ball receiving surface side), and during operation, high pressure is generated between the convex ball receiving surface and the concave ball receiving surface due to the presence of the spiral groove 3.
In the case of a hydrodynamic bearing with a spherical spiral groove in which the rotating shaft 1 is supported while floating above the receiving surface of the seat 2, the convex spherical surface of the rotating shaft 1 requires high precision.

Conventionally, when manufacturing such a rotating shaft 1, it has been difficult to directly machine a spherical surface on the tip of the shaft due to accuracy and machining problems. Therefore, a manufacturing method is adopted in which high-precision steel balls with good roundness, which are normally used as the rolling elements of ball bearings, are used and the ball 4 made of the steel balls is welded to the tip of the shaft 5 made of a round bar. It has been. In addition, the welding method in this case is the second welding method.
The electric resistance method involves welding by applying mechanical pressure to a sphere 4 and a shaft 5 as shown in the figure and utilizing the heat generated through an electric current. There is an electron beam method in which welding is performed by applying an electron beam to the part to generate heat.

By the way, the steel balls used as the rolling elements of ball bearings are high carbon chromium bearing steel subjected to general heat treatment, and when the ball 4 made of these steel balls and the shaft 5 are welded by the above welding method, It was unavoidable that the thermal effect of the heat generated in the welded portion would affect the spherical bearing surface of the sphere 4. This thermal effect deformed the bearing spherical surface, resulting in a decrease in spherical accuracy. Further, in electric resistance welding, electrolytic corrosion and local thermal deformation often occur on the contact surface of the sphere 4 with the electrode.

In this way, the high precision originally possessed by the sphere could not be maintained even after welding, and due to deformation and electrolytic corrosion of the bearing sphere,
Bearing performance was significantly reduced. Note that in order to correct the spherical surface so as to eliminate these deformations and electrolytic corrosion, the spherical surface must be rewrapped, which significantly impairs workability.

The present invention has been made to improve and eliminate the above-mentioned conventional drawbacks, and the configuration of the present invention will be described below with reference to embodiments.

This invention uses heat-resistant steel balls that have undergone special heat treatment instead of conventional high-carbon chromium bearing steel balls that have been subjected to general heat treatment as the steel balls used for the sphere. This greatly reduces the decrease in accuracy.

General heat treatment for high carbon chromium bearing steel involves uniformly heating to a predetermined quenching temperature, that is, a quenching temperature in the austenite range above the _A1 transformation point, quenching in a refrigerant, and then tempering at a temperature of 100 to 180℃. It is.

On the other hand, in special heat treatment, after the quenching in the general heat treatment step, tempering is performed at a temperature of 250 to 450°C, which is higher than that in the general heat treatment.
This specially heat-treated steel ball releases residual stress generated during quenching, and its structure is stable and does not easily deform even if left alone. In other words, by increasing the tempering temperature, the amount of retained austenite decreases,
Dimensional stability at high temperatures during welding is improved.
It should be noted that the same heat-resistant effect can be achieved with a carburized and quenched steel ball made of carburized steel, if the same method as the above-mentioned special heat treatment is used during tempering. In addition, as in the case of using steel balls for ball bearings, it is possible to perform general heat treatment by quenching, followed by tempering at 100 to 180°C, and then repeating tempering at 250 to 450°C. good.

Next, we used a laser interference device (GH manufactured by ZYGC, USA).
We will explain the results of observing the state of deformation of a sphere due to welding using interference fringes. The welding conditions at this time were as follows.

Steel ball 1/4” Pressure force 80Kg Current application time 3 cycles Current 35KA First, to briefly explain the measurement principle with reference to Figure 9A, the laser beam emitted from the laser oscillator 11 passes through the condensing lens 12 and is condensed. The focus of the optical lens and the center of the spherical surface coincide with the reference spherical surface 13. A part of the laser beam is reflected by this reference spherical surface and returns along the same optical path as the incident light. On the other hand, the laser beam that passes through the reference spherical surface 13 is It is reflected by the surface of the measurement object 14 and returns along the same optical path.These two reflected lights are reflected on the screen 16 by the roof mirror 15, but if the phases are the same, they will be intensified and become brighter, and if the phases are opposite, they will become darker and cause interference. This phenomenon occurs in each part of the measurement surface, so if the object to be measured is not a true sphere, interference fringes of dark and bright parts will occur.Therefore, by observing these interference fringes, the spherical shape can be measured. The interference fringes of the sphere before welding with high precision sphericity are
On the other hand, the interference fringes of a sphere with a deformed spherical surface are curved as shown in FIG. 5. By setting the interval between the interference fringes in advance, it is possible to measure the deviation from a true sphere, that is, the sphericity, from the degree of curvature of the interference fringes (FIG. 9B). For example, when the interval between interference fringes is set to 0.3μ, the deviation from a true sphere per intersection of interference fringes is 0.3μ.

When welding steel balls that have undergone general heat treatment, the fifth
As shown in Figure a, the interference fringes are largely curved, and it can be seen that the closer they get to the weld, the more thermal deformation occurs. In addition, in the electric resistance welding method, Fig. 5b
As shown in Figure 2, it can be seen that galvanic corrosion and local thermal deformation occur on the contact surface of the sphere with the electrode.

On the other hand, when welding is performed using the specially heat-treated steel balls of this invention, the curvature of the interference fringes, that is, thermal deformation, is considerably reduced, and the deformation area is also limited to the very vicinity of the welded part, as shown in Figure 6. It will be done. Therefore,
In fact, the hemispherical surface on the anti-weld side, which becomes the bearing surface, is hardly deformed and can maintain the highly accurate sphericity before welding.

It should be noted that welding deformation, electrolytic corrosion, local deformation, etc. discussed here were previously very difficult to measure and observe, but now they can be easily inspected, especially with the use of laser interference equipment, and this invention This laser interference posed a problem, and it became possible to take countermeasures and evaluate the results, which led to the present invention.

In addition, we measured the roundness of the sphere on its equator using a Talyrond (10,000x magnification) to determine the state of deformation of the sphere due to welding, and found that when using a steel ball that has been subjected to general heat treatment, as shown in Figure 7. It can be seen that the deformation is large (roundness 0.9μ), and when the special heat-treated steel ball of the present invention is used, the deformation is considerably small (roundness 0.3μ) as shown in FIG.

As explained above, this invention greatly reduces thermal deformation due to welding by using specially heat-treated steel balls, and prevents electrolytic corrosion and local thermal deformation from occurring even during electric resistance welding. was completed. This made it possible to easily form a high-precision spherical surface on the shaft end by welding high-precision steel balls, which was the original goal, and to significantly improve performance such as dynamic pressure and axial pressure.

Note that when a steel ball is subjected to the special heat treatment of this invention, its hardness is somewhat lower than that of a steel ball subjected to general heat treatment. This decrease in hardness causes problems such as a decrease in capacity in ball bearings that make rolling contact, but does not cause any problems in non-contact hydrodynamic bearings.

[Brief explanation of drawings]

Fig. 1 is a drawing showing a spiral groove hydrodynamic bearing as an example of applying the method of the present invention, Figs. 2 and 3 are drawings showing a welding method, Fig. 2 is an electric resistance welding method, and Fig. 3 is a drawing showing a welding method. Electron beam welding is shown respectively. Figures 4 to 6 are drawings showing the results of observing the spherical surface of a sphere using a laser interference device using interference fringes. Figure 4 shows a steel ball with high precision sphericity before welding, and Figure 5 Figure 5a shows the steel ball after welding that has undergone general heat treatment, Figure 5b shows the steel ball that has undergone the general heat treatment after welding using the electrical resistance method, and Figure 6 shows the steel ball that has undergone the special heat treatment of this invention after welding. are shown respectively. Figures 7 and 8 are graphs showing the roundness measurement results after welding measured by Talyrond. The cases in which steel balls treated with this method are used are shown in each case. 9A and 9B are principle diagrams of the laser interference device.

Claims (1)

[Claims] 1. When manufacturing a shaft with a high-precision spherical surface at the shaft end by welding a sphere to the shaft, A ₁ uniform heating to the austenitic region above the transformation point is performed, followed by rapid cooling.
A method for manufacturing a rotating shaft having a highly accurate spherical surface at the shaft end, characterized in that heat-resistant steel balls tempered at 250 to 450°C are welded to the shaft end.