JP2769206B2 - Roller bearing - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller bearing, and more particularly, to a roller bearing that has a long life even when a mating surface is rough or has a good finish.

[Conventional technology and problems to be solved]

It is well known that the surface roughness of the raceway surface or rolling surface is an important factor in the life of the bearing ring and rolling elements in a roller bearing, and the rolling fatigue life is generally determined by the hardness and residual stress of the surface layer. Affected by

Regarding the former surface roughness, it was conventionally thought that it was better to finish the raceway surface and rolling surface as smooth as possible, but repeated trial and error to improve the rolling contact fatigue life of the bearing Among them, it has been found that even if the finish of the raceway surface or the rolling surface is not improved, it is effective for a long life.

The bearing ring or rolling element as described above has a structure in which the raceway surface or the rolling surface is formed on a rough surface of a random scratch of R _max 0.3 to 0.8 μm, and can exhibit a long life effect. However, the oil film formation is insufficient for a partner with a good finished surface, which may lead to abrasion of the partner surface or peeling damage of the partner surface. Found the need for improvement.

As for the rolling fatigue life of the latter, it is known that high hardness has a long life in terms of hardness, and that the state of large compressive stress has a long life with respect to residual stress in the surface layer.

[Object of the invention]

Therefore, the present invention focuses on the evaluation of the surface roughness of the raceway surface or the rolling surface of the bearing ring and the rolling element not only in the axial direction but also in the rolling direction, and suppresses the surface roughness in the axial direction and the circumference to a certain range. The object of the present invention is to provide a long-life roller bearing that can favorably form a hot-melt film, furthermore, shows a situation where the surface hardness and the residual reaction of the surface layer are favorable, and can cope with any of the surface roughness of the mating surface. is there.

[Means for achieving the purpose]

In order to achieve the above object, the present invention provides a roller bearing in which independent minute concave recesses are formed at random on at least one of a raceway surface and a rolling element surface in a roller bearing. In, the hardness of the surface layer provided with the micro-dents is 30 to 60 in Hv with respect to the internal hardness.
The hardness is high, and the compressive residual stress of the surface layer is set to 600 MPa or more.

[Action]

One or both of the raceway and the surface of the rolling element are formed on a random micro-rough surface, and for example, a finished surface roughness parameter RMS of the micro-rough surface is obtained in the axial direction (L) and the circumferential direction (C). If the ratio RMS (L) / RMS (C) is 1.0 or less and the parameter SK value is -1.6 or less in both the axial and circumferential directions, the oil film formation rate on the raceway surface or the rolling surface is improved, Regardless of the surface roughness, no peeling damage or wear occurs on the mating surface, and a long life can be obtained.

Further, by providing the above minute depressions, the surfaces of the bearing ring and the rolling element have high hardness, and the residual stress of the surface layer has a large compressive stress, and the rolling fatigue life is improved.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 illustrates a roller bearing 4 in which a large number of cylindrical roller rolling elements 3 are arranged in an inner ring 1 and an outer ring 2.

At least one of the surfaces of the inner ring 1 and the outer ring 2 or the surface of the rolling element 3 in the roller bearing 4 is formed as a micro-rough surface 5 in a random direction. When each of the directions is obtained and displayed as a parameter RMS, the ratio RMS (L) / RMS (C) of the axial surface roughness RMS (L) to the circumferential surface roughness RMS (C) is 1.0 or less, for example. , 0.7 to 1.0, and the parameter SK value of the surface roughness is -1.6 or less in both the axial direction and the circumferential direction.

In the surface processing for obtaining the rough surface conditions as described above, a desired finished surface can be obtained by special barrel polishing.

The parameter SK value refers to the degree of distortion (SKEWNESS) of the distribution curve of the surface roughness, and the SK value of a target shape distribution such as a Gaussian distribution is 0. The set value of -1.6 or less is a range in which the shape and distribution of the surface concave portions are advantageous for forming an oil film.

Fig. 2 shows the finished surface condition of the standard roller rolling element, and Fig. 3
The figure compares the condition of the finished surface in which the surface of the inner ring or the rolling element is subjected to micro-roughening.

When the surface of the inner and outer rings 1 and 2 or the rolling elements 3 which are the components of the roller bearing is subjected to special barrel polishing in order to obtain the micro-rough surface 5, the hardness of the surface layer of the member having the micro-rough surface 5 is increased. Can have a higher hardness than the inside, and at the same time, a compressive residual stress in the surface layer can be positively generated.

FIG. 4 shows a roller rolling body having a micro-rough surface 5 machined on its surface,
4 shows the measurement results of the cross-sectional hardness distribution of a standard roller rolling body having a surface tumbled.

As is clear from FIG. 4, there is no significant difference between the hardness of the surface layer and the internal hardness of the standard roller rolling element.

On the other hand, in the roller in which the micro-rough surface 5 is machined, the hardness of the surface layer is 30 to 60 points higher in hardness Hv than the internal hardness.

Next, the measurement results of the compressive residual stress of each surface layer of the roller rolling element whose surface was polished, the roller rolling element whose surface was polished by a migaki tumbler, and the roller rolling element whose micro-roughened surface was processed were measured.
Shown in the figure.

As shown in the figure, the compressive residual stress was 250 MPa
Migaki tumbler finish is 450-500MPa, whereas micro-rough surface is 600MPa or more, specifically 850-900
MPa.

In this way, the rolling element having the finely roughened surface has a high hardness in the surface layer, a large compressive stress in the residual stress in the surface layer, and can improve the rolling fatigue life.

Next, a description was given of the results of a life test in which a plurality of types of needle bearings were manufactured by applying different surface treatments to the raceway surface of the inner ring and the rolling surface of the rolling element with different finishing surfaces, and the effect of the micro-rough surface was confirmed. I do.

The roller bearings used in the life test were, as shown in FIG.
Outer diameter Dt = 38mm, inner diameter dr = 28mm, diameter D of rolling element 3 = 5m
This is a needle bearing with a retainer 6 using m and length L = 13 mm and using 14 rolling elements.

The test bearing is a conventional bearing A in which the inner race is ground and the rolling elements are also standard finished, and a first bearing B of the present invention in which a fine rough surface is processed on the raceway surface of the inner race and a standard finished product is used for the rolling elements. ,
Three types of the second bearing C of the present invention, in which both the raceway surface of the inner race and the rolling surface of the rolling element were machined into minute rough surfaces, were manufactured.

In each test bearing, the condition of the standard finished surface and the finished surface subjected to the micro-rough surface processing is as shown in FIGS. 2 and 3.

The test apparatus used was a radial load tester 11 as schematically shown in FIG. 7, and test bearings A to C were mounted on both sides of a rotating shaft 12, and the test was performed by applying rotation and load. Is what you do.

In addition, the inner ring grinding finished surface has a Rmax of 0.4 to 4 μm.
The fine rough surfaces of the bearings B and C are Rmax 2.5 μm and 4 μm. Outer race (outer ring) is ground finish Rmax1.6μm
Is common to both cases.

 The test conditions are as follows.

Bearing radial load 1465kgf Number of revolutions 3050rpm Lubricant Turbine oil The test results for each of the test bearings A, B and C under the above conditions are shown in FIGS. 8 and 9.

FIG. 8 shows the life data of the rolling elements in the test bearings A, B, and C, and FIG. 9 shows the results of the inner ring ground surface finish and the durability life in each test bearing. As is clear from the test results as described above, the test bearings B and C of the present invention all exhibited a longer life than the conventional test bearing A.

That is, as compared with the conventional test bearing A, the test bearing B of the present invention has a third life and the test bearing C has a life about seven times as long.

In addition, peeling damage was often found on the finished upper surface side when rolling the finished upper surface and the rough surface, but was not observed in the test bearings B and C of the present invention.

Fig. 10 and Fig. 11 show the SK values, RM of each test bearing A, B, C.
The results of the L / C and life (L ₁₀ ) of S are shown.

As shown in FIG. 10, the test bearings B and C having the SK value of -1.6 or less have a long life.

It was also found that the axial roughness RMS (L / C) was long even with a special barrel polishing of 1.0 as shown in FIG.

It was also found that the RMS (L / C) value alone was not sufficient to evaluate the rolling elements of a long-life bearing.

Next, Table 1 shows the calculated values of the oil film parameter Λ based on Grubin's equation based on the combination of the test bearings A and B with the standard rollers under the test conditions.

As a result of the calculation, the oil film parameter Λ is greatly affected by the roughness of the mating surface.
Becomes 0.78.

Generally, there is a relationship between the oil film parameter and the oil film formation rate as shown in FIG. 12, and it is said that the oil film parameter should be large from the viewpoint of life, but as is clear from the life test results, it is generally only Λ Can not explain.

Regarding the confirmation of the oil film formation state on the inner ring finishing surface and the peeling resistance, using a two-cylinder testing machine, under free rolling conditions, a test piece having the same surface condition as the test bearing B of the present invention and the conventional test bearing A was used. Was used to perform an accelerated peeling test. The state of formation of the oil film was confirmed by a direct current method.

Test conditions Maximum contact surface pressure 227 kgf / mm ² peripheral speed 4.2 m / sec (2000 rpm) Lubricant Turbine oil Repeated load frequency 4.8 × 10 ⁵ (4 hr) The oil film formation rate in this test is shown in Figs. 13 and 14. As shown, the formation rate of the oil film on the finished surface of the test bearing B of the present invention was improved by about 20% at the start of operation as compared with the conventional test bearing A.

In addition, it was confirmed that an oil film was formed almost completely when the number of repetitive loads was 1.2 × 10 ⁵ .

Further, on the finished surface of the conventional test bearing A, many occurrences and developments of peeling having a length of about 0.1 mm were observed, whereas no damage was found on the finished surface of the test bearing B of the present invention.

〔effect〕

As described above, according to the present invention, in the roller bearing in which independent minute concave dents are formed at random on at least one of the surface of the bearing ring and the surface of the rolling element, the minute dents are formed. The hardness of the provided surface layer was set to 30 to 60 hardness higher in Hv with respect to the internal hardness, and the combined compressive residual stress of the surface layer was set to 600 MPa or more, so the surface layer became harder and the compressive stress increased, thereby The rolling fatigue life can be improved.

[Brief description of the drawings]

1 is a cross-sectional view of a roller bearing, FIGS. 2 and 3 are schematic diagrams showing a finished surface condition of a rolling element, FIG. 4 is a graph showing a measurement result of a cross-sectional hardness distribution of the rolling element, and FIG. FIG. 6 is a graph showing the results of measuring the compressive residual stress of the rolling element surface layer, FIG. 6 is a cross-sectional view of the needle bearing used for the life test, FIG. 7 is a schematic diagram of the test apparatus, and FIGS. A graph showing the results of the rolling fatigue life test, FIG. 10 is a graph showing the relationship between SK value and life, FIG. 11 is a graph showing a relationship between RMS (L / C) value and life, and FIG. 12 is an oil film parameter FIG. 13 and FIG. 14 are graphs showing the oil film formation rate. 1 ... inner ring, 2 ... outer ring, 3 ... rolling element, 4 ... roller bearing, 5 ... fine rough surface.

Claims (1)

(57) [Claims] 1. A roller bearing in which independent minute concave recesses are formed at random on at least one of a raceway surface and a rolling element surface in a roller bearing. A roller bearing characterized in that the hardness of the surface layer is 30-60 higher in Hv than the internal hardness, and the compressive residual stress of the surface layer is 600 MPa or more.