JPH1162988A - Rolling bearing and machinery using rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dissolve a crack of an inner ring and a creep phenomenon caused by thermal expansion at a high temperature without increasing the number of part items by heat treating the inner ring of a rolling bearing press-fitted to an aluminium alloy shaft for generating compressive residual stress. SOLUTION: In a rolling bearing, heat treatment such as malstressing for generating compressive residual stress is applied to an inner ring formed of high-carbon chrome bearing steel or the like. An inner ring crack generation test is executed, and the relation between the circumferential stress of the inner ring at the time of press-fitting and working temperature is illustrated. In the illustration, marks ▵ and ▵(black) are in the case of applying malstressing to high-carbon chromium bearing steel, and the residual stress of the inner ring raceway surface is -10--15 kgf/mm<2> (-40 deg.C), and marks ○and ○(black) are in the case of applying normal heat treatment to the same bearing steel, and the residual stress of the raceway surface is -3-+3 kgf/mm<2> (-40 deg.C). Residual stress generating the fatigue crack of the inner ring is 17 kgf/mm<2> or more, and a working limit temperature range not generating a crack can be made high as illustrated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a low-temperature (-40 ° C.)
The present invention relates to a mechanical device having an aluminum alloy shaft widely used from high to high temperatures (180 ° C.), and a rolling bearing used by press-fitting the aluminum alloy shaft.

[0002]

2. Description of the Related Art In recent years, there has been a tendency to reduce the weight of the entire apparatus by changing from a material such as iron to an aluminum alloy. Conventionally, for example, from low temperature (−40 ° C.) to high temperature (180 ° C.).
For machine tools and industrial machines widely used up to ℃), this type of machinery with aluminum alloy shafts uses rolling bearings made of high carbon chrome bearing steel bearing rings and rolling elements made of aluminum alloy. It is generally used by being pressed into a shaft. However, in this type of equipment that is widely used from low to high temperatures, bearings are press-fitted with fittings set so that there is interference at low temperatures.However, the thermal expansion coefficient of aluminum alloy shafts is lower than that of bearing steel. Therefore, interference is increased due to thermal expansion at a high temperature, the circumferential stress of the inner ring is increased, and fatigue cracks in the inner ring may occur. In order to avoid the inner ring crack, a method of eliminating interference is conceivable. However, at a certain temperature or lower, a gap may be generated, which may cause a creep phenomenon.

Further, as a means for solving the problem caused by the thermal expansion, it is conceivable to fix a resin ring on the outer periphery of the aluminum alloy shaft and press-fit the inner ring of the rolling bearing with a margin. However, in the above technique, the number of components is increased, and a means for preventing sliding of the resin ring must be separately provided, which may lead to an increase in cost.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and has as its object to increase the number of parts in a machine having an aluminum alloy shaft. An object of the present invention is to provide a rolling bearing that can sufficiently solve the conventional problems caused by thermal expansion at high temperatures without causing any problem, and to provide a mechanical device configured by using the bearing.

[0005]

The technical solution of the present invention to achieve the above object is a bearing press-fitted into an aluminum alloy shaft, which has been subjected to a heat treatment for generating a compressive residual stress in the inner ring. That is.

A mechanical device is formed by press-fitting a rolling bearing into an aluminum alloy shaft, and performs a heat treatment for generating a compressive residual stress on an inner race of the rolling bearing.

[0007]

Embodiments of the present invention will be described below.

The rolling bearing of the present invention is a bearing having a general shape composed of a bearing ring, a rolling element, and the like. An inner ring made of high carbon chromium bearing steel or carburized steel has a compressive residual stress. The resulting heat treatment, for example marstressing, carburizing, carbonitriding, is applied.

The above-mentioned rolling bearing may be any one of a ball bearing and a roller bearing as long as it is formed by being press-fitted into an aluminum alloy shaft of various mechanical devices, and may be arbitrarily selected and used within the scope of the present invention. You.

Examples of the mechanical device of the present invention that uses the above-mentioned rolling bearing include a light motor used for a machine tool, an industrial machine and the like. The above specific example is merely an embodiment of the mechanical device of the present invention, and is not limited to this embodiment at all, and is arbitrarily selected within the scope of the present invention.

[0011]

[Embodiments] Here, embodiments of the present invention will be described. A test for generating an inner ring crack or a crack was performed by the tester shown in FIG. 2 under the following conditions. FIG. 1 shows the test results. [Condition] Test Bearing: 6819 radial load: 800 kgf rotational speed: 2000 rpm Test Time: 216 (Hr) (3 times the calculated life L ₁₀₎ test temperature: Each temperature of the graphs

In FIG. 1, the symbols indicated by symbols △ and ▲ indicate the case where an inner ring obtained by applying a marstressing treatment to high carbon chromium bearing steel (SUJ2) is used (Example 1). In the case where the inner ring obtained by performing carburizing treatment on the carburized steel is used (Example 2), those indicated by symbols ◇ and 場合 are the case where the inner ring obtained by performing carbonitriding treatment on the carburized steel is used (Example 3). Symbols marked with ○ and ● are high carbon chromium bearing steel (S
This is a case in which an inner ring subjected to ordinary heat treatment is used for UJ2) (comparative example).

In the first embodiment, the carbon content of the core portion of the inner raceway surface is 1.02%, the carbon content of the surface layer portion is 1.2 to 1.5%, and the residual stress of the raceway surface is-. 10
−15 kgf / mm ² , and in Examples 2 and 3, the carbon content of the core of the inner raceway surface was 0.21.
~ 0.41%, carbon content of surface layer is 0.82-1.1
%, And the residual stress on the raceway surface is -18 to -28 kgf /
mm ² , and in the comparative example, the residual stress on the raceway surface was −
3 to +3 kgf / mm ² . The test temperature was 12
When the temperature is 0 ° C. or less, a normal tempering temperature (180 ° C.) is performed because the dimensional expansion with time is small. Or sub-zero processing (-
(100 ° C. or less), a bearing having dimensional stability was used.

○ △ □ ◇ is 216Hr without any abnormality, ● ▲ ●
The symbol “未 満” indicates that an inner ring crack or a crack occurred at less than 216 hours. As shown in FIG. 1, the inner ring circumferential stress is 17 k.
When it exceeds gf / mm ² , it can be seen that an inner ring crack or a crack occurs.

[0015] High carbon chromium bearing steel (SUJ2) subjected to ordinary heat treatment (comparative example) could be used only up to about 60 ° C, whereas high carbon chromium bearing steel (SUJ2) had a It can be used in a wide range of temperatures up to about 130 ° C. in the case of lessing treatment (Example 1), and about 180 ° C. in the case of carburizing steel (Example 2) and carbonitriding (Example 3). You can see that there is.

FIG. 3 shows the relationship between the circumferential stress of the inner ring at the time of press-fitting the shaft and the operating temperature in the comparative example. As shown in FIG. 7, when the circumferential stress of the inner ring exceeds 17 kgf / mm ² , inner ring fatigue cracking occurs. As shown in FIG. FIG. 4 shows this relationship in terms of the relationship between the interference between the shaft and the inner ring and the operating temperature. In the case of, creep occurs at 60 ° C. or less. FIG. 5 shows the relationship between the circumferential stress of the inner ring and the working temperature during the shaft press-fitting in Example 1, and FIG. 6 shows the relationship between the interference between the shaft and the inner ring and the working temperature. FIG. 7 shows the relationship between the circumferential stress of the inner race and the working temperature at the time of press-fitting the shaft in the second and third embodiments, and FIG. 8 shows the relationship between the interference between the shaft and the inner race and the working temperature. As described above, the inner ring can be used at a high temperature within a range in which the circumferential stress does not exceed 17 kgf / mm ^2, and the interference can be set as the interference that does not cause the inner ring to creep.

[0017]

According to the present invention, the inner ring of a rolling bearing press-fitted into an aluminum alloy shaft is subjected to a heat treatment that generates compressive residual stress, so that the inner ring circumferential stress at high temperatures is alleviated and the number of parts is increased. The present invention provides a rolling bearing that can sufficiently solve the disadvantages of the prior art, in which interference is increased due to thermal expansion at high temperatures and inner ring fatigue cracks occur without causing a problem, and a mechanical device using the bearing is provided. Could also be achieved. Therefore, even if the fit is set so that there is an interference at a low temperature as before, the problem that the conventional technology has that the interference increases due to thermal expansion at a high temperature and inner ring fatigue cracking does not occur, In addition, there is no possibility that the cost will rise.

[Brief description of the drawings]

FIG. 1 is a graph showing a test result of an inner ring crack.

FIG. 2 is a view showing a confirmation test of an inner ring crack.

FIG. 3 is a graph showing a relationship between a circumferential stress of an inner ring at the time of axial press fitting and a use temperature in a comparative example.

FIG. 4 is a graph showing the relationship between interference between shafts and inner rings and operating temperatures in a comparative example.

FIG. 5 is a graph showing the relationship between the circumferential stress of the inner ring and the operating temperature at the time of axial press-fitting in the first embodiment.

FIG. 6 is a graph showing the relationship between the interference between the shaft and the inner ring and the operating temperature in the first embodiment.

FIG. 7 is a graph showing the relationship between the circumferential stress of the inner ring and the operating temperature during axial press fitting in Examples 2 and 3.

FIG. 8 is a graph showing the relationship between the interference between the shaft and the inner ring and the operating temperature in the second and third embodiments.

Claims (2)

[Claims] 1. A rolling bearing which is press-fitted into an aluminum alloy shaft, wherein a heat treatment for generating a compressive residual stress in an inner race is performed. 2. A mechanical device configured by press-fitting a rolling bearing into an aluminum alloy shaft, wherein the rolling bearing has been subjected to a heat treatment for generating a compressive residual stress in an inner ring. apparatus.