JP2002213461A - Roller bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of cracks with an impression as a starting point, even when an axial dislocation quantity is large, and contact bearing pressure of a rolling surface of a roller and raceway surfaces of inner and outer races is high in a roller bearing. SOLUTION: A bus bar 31, forming the rolling surface of the roller 3, is formed of a single circular arc (a projection surface). A bus bar, forming the raceway surfaces 10 and 20 of the inner and outer races 1 and 2, is formed of first bus bars 11 and 21 of a shaft directional central part, and second bus bars 12 and 22 of shaft directional both end parts. The second bus bars 12 and 22 have a radius of curvature, such as separating from the bus bar 31 forming the rolling surface of the roller 3. After forming the inner race 1, the outer race 2, and the roller 3 of an iron and steel material having the prescribed composition, carburization or carbonitriding processing and quenching-tempering are carried out, so that the remaining austenite quantity of the surface layer part of the raceway surfaces and the rolling surface is set to 20.0 to 40.0 volume %.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a roller bearing.

[0002]

2. Description of the Related Art Conventionally, in a roller bearing, in order to prevent a large end load from being generated at an axial end portion of the roller and causing the bearing to be damaged at an early stage, the bearing surface is provided on the raceway surface of the inner and outer rings or the rolling surface of the roller. A crowning process (a process in which a bus bar forming a raceway surface or a rolling surface has a very slight taper or curvature) is performed.

For example, when a tapered roller bearing is displaced in the axial direction between the inner and outer rings (the state in which the axis of the outer ring and the axis of the inner ring cross each other)
When used in a position where the occurrence of pitting may occur, the following differences occur depending on the degree of the crowning processing. If the degree of crowning is relatively large (the radius of curvature is small), the amount of axial deviation (relative inclination angle of the axis of the inner and outer rings) is a certain amount (for example, 0.0
Until the size exceeds 02 rad), the generation of the end load is prevented, and the bearing can operate normally. On the other hand,
When the amount of axial deviation is extremely small (for example, 0.002 rad or less), the axis between the rolling surface of the rollers and the raceway surface of the inner and outer races is compared with the case where the degree of crowning is relatively small (the radius of curvature is large). Since the contact dimension in the direction becomes smaller and the effective track width for supporting the load becomes narrower, the bearing life may be shortened.

[0004] When the degree of crowning is relatively small, the bearing life when the amount of axial deviation is very small is relatively long. On the other hand, when the amount of axial deviation is relatively large, the end load cannot be prevented, so that abrasion is likely to occur between the end of the roller and the raceway surface of the inner and outer rings. As a roller bearing capable of solving such problems, Japanese Patent Application Laid-Open No. 12-74075 discloses that one of a rolling surface at a raceway surface of an inner ring and an outer ring is formed by a concave bus, and the other is a convex bus. The central part in the axial direction of one of the concave buses and the convex buses is formed of a first bus having a constant curvature, and both ends in the axial direction adjacent to the central part in the axial direction of the one bus. Describes a roller bearing consisting of a second bus bar having a radius of curvature away from the other bus bar.

In this roller bearing, for example, as shown in FIG. 1, a bus bar 31 forming the rolling surface of the roller 3 is formed by a single arc (convex surface), and the raceways 10, 10 of the inner and outer rings 1, 2 are formed. 20
Are the first buses 11 and 21 and the second buses 12 and 22
And a tapered roller bearing whose central portion (first bus) in the axial direction is concave, and whose end (second bus) is convex on the outer ring and concave on the inner ring.

According to this tapered roller bearing, the bearing life is relatively long when the amount of axial deviation is extremely small, and when the amount of axial deviation is large (depending on the load, for example, 0.005 r.
ad)), the bearing can operate normally without wear between the end of the roller and the raceway surface of the inner and outer rings. That is, according to the roller bearing described in this publication, it is expected that the service life can be made longer than that of the conventional roller bearing regardless of the magnitude of the axial deviation amount.

[0007]

However, in the roller bearing described in the above-mentioned publication, the self-aligning property such as the self-aligning roller bearing (even if the axis is shifted, the entire rolling surface of the spherical roller has the raceway surface of the outer ring. The contact area between the rolling surface of the roller and the raceway surface of the inner and outer rings becomes smaller when the amount of axial deviation is large, and the surface pressure at this contact surface is reduced. Is larger than when there is no or small axis deviation.

[0008] In such a state of high surface pressure, if dents due to foreign matter or the like are generated on the raceway surfaces of the inner and outer races and the rolling surfaces of the rollers,
When high carbon chromium bearing steel such as SUJ2 or SUJ3 is used as the material of the inner and outer rings and rollers as in the past,
Cracks originating from these indentations may occur, leading to early peeling and shortening the service life. In the roller bearing described in the above publication, the present invention can prevent the generation of cracks starting from indentations even when the amount of axial deviation is large and the contact surface pressure between the rolling surface of the rollers and the raceway surfaces of the inner and outer rings is high. The task is to do so.

[0009]

In order to solve the above-mentioned problems, the present invention provides a method in which one of a raceway surface and a raceway surface of an inner ring and an outer ring is formed by a concave bus bar, and the other is a convex bus bar. The central portion in the axial direction of any one of the concave busbar and the convex busbar is formed of a first busbar having a constant curvature, and both end portions in the axial direction adjacent to the axial center portion of the one busbar are formed. A roller bearing comprising a second bus bar having a radius of curvature away from the other bus bar;
At least one of the outer ring and the rollers contains 0.2% or more and 0.5% or less of carbon (C) and 0.5% or more and 0.5% or less of manganese (Mn) as alloy components. 2
% Or less, and chromium (Cr) in a range of 0.5% or more and 2.0% or less (more preferably, molybdenum (Mo) in a range of 0.5% or more and 1.5% or less) After being formed by, carburizing or carbonitriding treatment and quenching and tempering are performed, and the carbon concentration of the surface layer of the raceway surface and / or the rolling surface is reduced to 0.7% by weight or more and 1.2% by weight or less,
When the amount of retained austenite in the surface layer portion is 20.0% by volume or more and 40.0% by volume or less, the hardness of the surface layer portion is Hv70.
The present invention provides a roller bearing characterized by being equal to or greater than 0 (preferably Hv750 or greater).

The critical significance of each numerical limitation in the present invention will be described below. [C content in the steel material used: 0.2% or more and 0.5
% Or less] In order to obtain the surface hardness (HRC 60 or more) required for the bearing components (the inner and outer rings and the rollers), the carbon content of the surface layer of the bearing components needs to be 0.2% or more. In the case of performing surface hardening by carburizing or carbonitriding, if the carbon content before the treatment is less than 0.2%, the treatment time becomes longer, the cost increases, and the productivity decreases. In addition, the core has insufficient hardness, so that the core tends to be plastically deformed, and the life of the bearing is reduced.

On the other hand, if the carbon content exceeds 0.5%, the toughness is greatly reduced. [Mn content in steel material used: 0.5% or more
Manganese is an element that forms retained austenite, which is effective for improving the hardenability of steel and for improving the rolling life under the inclusion of foreign matter. Manganese content is 0.5
%, These effects cannot be sufficiently obtained.

On the other hand, since manganese is also an element for strengthening the ferrite structure, if it is added in an amount of more than 1.2%, the cold workability is significantly reduced. [Cr content in steel material used: 0.5% or more.2.
0% or less] Chromium improves the hardenability of the steel, strengthens the solid solution of the steel, combines with carbon during carburizing or carbonitriding, and forms hard and fine carbides, nitrides and carbonitrides on the surface layer. It is an element to be deposited. That is, chromium has the effect of improving the hardness of the core portion and the surface layer portion and extending the rolling fatigue life of the bearing. If the chromium content is less than 0.5%, this effect cannot be sufficiently obtained.

On the other hand, if a large amount of chromium is added, chromium oxide is likely to be formed on the surface, and this chromium oxide hinders the entry of carbon and nitrogen from the surface during the carburizing or carbonitriding treatment. Productivity decreases. To avoid this, the chromium content is set to 2.0% or less. [Mo content in steel material used: 0.5% or more.
Molybdenum improves the hardenability and temper softening resistance of steel. Further, it is a very strong carbide-forming element and an element that produces various fine carbides (double carbides) after quenching and tempering. The hardness of this double carbide is Hv 1400 to 1800 and the hardness of cementite Hv 1200, as described in “The Lecture on Modern Metallurgy Materials, 4 Steel Materials, June 1985, p. 137” edited by The Institute of Metals, Japan. It is larger than 1600.

Since the formation and growth of this double carbide requires the concentration of molybdenum atoms, coarsening is delayed when maintained at a predetermined temperature during carburization and quenching, and a finely dispersed state is maintained. Molybdenum has the effect of extending the life of the bearing. This double carbide is remarkably formed when the molybdenum content is 0.5% or more. If the molybdenum content exceeds 1.5%, the double carbides become coarse, and the effect of extending the bearing life cannot be obtained. [Amount of retained austenite in surface layer portion (of raceway surface and / or rolling surface): 20.0 vol% or more and 40.0 vol% or less] Suitable amount (20.0 vol% or more 40.0 vol%)
Below) by the presence of retained austenite
When an indent is formed, the concentration of stress on the edge of the indent can be reduced, and the occurrence of cracks can be suppressed. In addition, for example, if there are indentations on the surface layer of the rolling surface of the roller, when the raceway surface of the bearing ring passes through the indentation relatively more than a predetermined number of times during bearing rotation, deformation applied to the rolling surface Due to the energy, a phenomenon occurs in which the retained austenite existing in the surface layer of the rolling surface is transformed into martensite and hardened. As a result, the life of the bearing under lubrication mixed with foreign matter can be extended. [Hardness of surface portion: Hv700 or more, carbon concentration of surface portion:
0.7% by weight or more and 1.2% by weight or less] When the carbon concentration of the surface layer is less than 0.7% by weight, the required hardness Hv7 is obtained.
00 or more cannot be obtained. If the content exceeds 1.2% by weight, cementite is formed in a network at the prior austenite grain boundaries, so that the toughness is reduced and cracks and chips are likely to occur.

When the carbonitriding treatment is performed, it is preferable that the nitrogen content in the surface layer of the raceway surface and / or the rolling surface is 0.03% by weight or more. Carbonitride is formed on the surface layer by carbonitriding in addition to carbide. Since the carbonitride is harder than the carbide, the wear resistance is further improved as compared with the case of carburizing. Therefore, it is preferable to perform carbonitriding. In addition, since nitrogen that forms a solid solution by carbonitriding is an austenite stabilizing element, the amount of retained austenite can be increased by performing carbonitriding while maintaining hardness of Hv 700 or more.

[0016]

Embodiments of the present invention will be described below. The inner ring 1, the outer ring 2, and the roller 3 of the roller bearing having the structure shown in FIG. 1 were manufactured by using a material made of each steel material shown in Table 1 below and performing heat treatment under each condition shown in this table.

By using the obtained inner ring 1, outer ring 2 and rollers 3 and combining the same materials obtained under the same conditions to assemble the roller bearings, Example No.
Samples Nos. 1 to 13 and Comparative Examples Nos. 1 to 3 were obtained. The basic structure of the manufactured roller bearing is the reference number HR32217.
It is the same as the tapered roller bearing of J, except that the shapes of the raceway surfaces and the rolling surfaces of the inner and outer rings 1 and 2 are changed as follows.
In Comparative Examples Nos. 4 and 5, tapered roller bearings having the same structure as the reference number HR32217J were manufactured instead of the structure of FIG.

In the roller bearing of FIG. 1, the rolling surface of the roller 3 is formed by a convex bus bar 31 composed of a single arc. A central portion in the axial direction of the raceway surface 10 of the inner race 1 is formed by a concave first bus bar 11, and both axial end portions are formed by a concave second bus bar 12. That is, in this embodiment, the buses 11, 12, 21, 22 forming the raceways of the inner ring and the outer ring correspond to one bus, and the bus 31 forming the rolling surface of the rollers corresponds to the other bus.

The radius of curvature of the first bus bar 11 of the inner ring 1 is very slightly larger than the radius of curvature of the convex bus bar 31 of the roller 3. The radius of curvature of the second bus 12 is slightly larger than the radius of curvature of the first bus 11. As a result, the second bus bar 12 has a radius of curvature that is away from the convex bus bar (the other bus bar) 31 of the roller 3. A line A in FIG. 1 shows a boundary position between these buses 11, 12, and both buses 11, 1
2 is formed so as to share a tangent line at the boundary position.
At both ends in the axial direction of the raceway surface 10 of the inner ring 1, flanges 14 and 15 are provided.
Are formed.

An axial center portion 21 of the raceway surface 20 of the outer race 2 is formed by a concave first bus bar 21, and both axial end portions are formed by a convex second bus bar 22. The radius of curvature of the first bus bar 21 is slightly larger than the radius of curvature of the convex bus bar 31 of the roller 3. The radius of curvature of the second bus bar 22 is slightly larger than the radius of curvature of the first bus bar 21. Thereby, the second bus bar 22 has a radius of curvature that is away from the bus bar of the roller 3 (the other bus bar). The line B in FIG. 1 shows the boundary position between these buses 21 and 22,
Reference numerals 1 and 22 are formed so as to share a tangent line at the boundary position.

The heat treatment conditions are as follows. When performing carbonitriding, first, a temperature of 870 to 950 ° C. and a holding time of 8
Time, Rx gas + enriched gas + ammonia gas 7%
Carbonitriding was performed under atmospheric conditions. Next, oil temperature of 60 ° C
Oil cooling. Next, quenching was performed by holding at 820 to 860 ° C. for 40 minutes and then oil cooling. Next, 160 ~
Tempering at 200 ° C. for 2 hours was performed. Note that the tempering temperature of Comparative Example 2 was 240 ° C. For Comparative Example 3, the quenching temperature after carbonitriding was 900 ° C.
And

When carburizing is carried out, first, the temperature is 870-9.
Carburizing was performed under the conditions of 50 ° C., a holding time of 8 hours, and an atmosphere of Rx gas + enriched gas. Next, oil cooling was performed at an oil temperature of 60 ° C. Next, quenching was performed by holding at 820 to 860 ° C. for 40 minutes and then oil cooling. Next, 160-200
Tempering at 2 ° C. for 2 hours was performed. When performing sobuyaki, first heat at 840 ° C. for 40 minutes, then heat at 60 ° C.
Quenching by oil cooling was performed. Next, 160-20
Tempering at 0 ° C. for 2 hours was performed.

For each of the obtained sample roller bearings,
A rotation test was performed under the following conditions, and the rolling life under lubrication mixed with foreign matter was examined. The time until the surface origin peeled off was defined as the life, and the relative value was calculated with the life of Comparative Example No. 1 being "1". <Rotation test conditions> Load (P / Cr) = 0.14 Rotation speed: 2000 rpm Inner and outer ring axis deviation angle: 0.005 rad Lubrication method: Foreign matter (F) in oil bath containing lubricant "VG32"
e ₃ C-based powder) at a concentration of 300 ppm and supplied into the bearing from this oil bath.

Test pieces corresponding to each sample were prepared, and the carbon concentration of the surface layer, the amount of retained austenite, and the Vickers hardness (Hv) were measured. The results are shown in Table 1 below. In Table 1, data outside the scope of the present invention is underlined. Also, the embodiment
FIG. 2 is a graph showing the relationship between the amount of retained austenite (γ _R ) and the bearing life ratio based on the obtained data for Nos. 1 to 13 and Comparative Examples 1 to 3.

[0025]

[Table 1]

As can be seen from Table 1, Examples Nos. 1 to 13 satisfying all of the limiting conditions of the present invention are Comparative Examples No. 1 to No. 1 satisfying at least one of the limiting conditions of the present invention.
5, the axial deviation angle of the inner and outer rings is 0.005 ra.
When d is large, the bearing life under lubrication mixed with foreign matter is prolonged. Examples Nos. 11 to 13 are examples in which the content of molybdenum is less than 0.50% by weight, and have shorter lives than Examples Nos. 1 to 10 in which the content of molybdenum is 0.50% by weight or more. However, the life was at least twice as long as that of Comparative Example No. 1 using conventional SUJ2. This is because the amount of retained austenite in the surface layer was 8.0% by volume in No. 1, whereas 20.0% by volume or more in Examples Nos. 11 to 13.
This is because it was not more than 0.0% by volume.

From the graph of FIG. 2, it is found that the amount of retained austenite in the surface layer of the raceway surface and the rolling surface is 20.0% by volume.
By setting the content to 40.0% by volume or less, the service life of the roller bearing having the special structure shown in FIG. 1 can be remarkably prolonged under lubrication with contaminants when the axial deviation angle of the inner and outer rings is as large as 0.005 rad. I understand. Comparative Example No. 4 is an example in which only the structure of the bearing is different from Example 1, and Comparative Example 5 is an example in which only the structure of the bearing is different from Comparative Example 1.

In the structure of the roller bearing of the present invention, in addition to the structure shown in FIG. 1, for example, as shown in FIGS. 3 and 4, a bus forming a rolling surface of the roller corresponds to one bus, and A structure in which the bus forming the raceway surface of the outer ring corresponds to the other bus. In FIG. 3, the raceway surface of the inner ring 1 is formed by a concave bus bar 10a formed of a single arc. The raceway surface of the outer ring 2 is formed by a concave bus bar 20a composed of a single arc. The axial center part of the rolling surface of the roller 3 is formed by a convex first bus bar 32, and both axial end portions are formed by a convex second bus bar 33. The line C in FIG.
33 shows a boundary position, and both buses 32 and 33 are formed so as to share a tangent at the boundary position.

The radius of curvature of the first bus bar 32 of the roller 3 is very slightly larger than the radius of curvature of the concave bus bars 10a and 20a on the raceway surfaces of the inner and outer races. The radius of curvature of the second bus 33 is
It is slightly larger than the radius of curvature of the bus bar 32. Thus, the second bus 33 has a radius of curvature that is away from the bus of the inner and outer rings (the other bus). In FIG. 4, the raceway surface of the inner ring 1 is formed by a convex bus bar 10b formed of a single arc. The raceway surface of the outer ring 2 is formed by a convex bus bar 20b composed of a single arc. An axial center portion of the rolling surface of the roller 3 is formed by a concave first bus bar 34, and both axial end portions are formed by a concave second bus bar 35. A line D in FIG. 4 shows a boundary position between these buses 34 and 35, and both buses 34 and 35 are formed so as to share a tangent at the boundary position.

The radius of curvature of the first bus bar 34 of the roller 3 is very slightly larger than the radius of curvature of the convex bus bars 10b and 20b on the raceway surfaces of the inner and outer rings. The radius of curvature of the second bus 35 is
The radius of curvature of the bus 34 is slightly larger. Thus, the second bus 35 has a radius of curvature that is away from the bus of the inner and outer rings (the other bus).

[0031]

As described above, according to the roller bearing of the present invention, even when the axial deviation of the inner and outer rings is large and the contact surface pressure between the rolling surface of the rollers and the raceway surface of the inner and outer rings is high, Since the occurrence of cracks originating from the indentation can be prevented, the bearing life can be prolonged under conditions in which indentation is likely to occur, such as under contaminated lubrication.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of the structure of a roller bearing according to the present invention.

FIG. 2 shows Example Nos. 1 to 13 and Comparative Examples 1 to 3.
4 is a graph showing the relationship between the retained austenite amount (γ _R ) and the bearing life ratio from the obtained data.

FIG. 3 is a sectional view showing an example of the structure of the roller bearing of the present invention.

FIG. 4 is a sectional view showing an example of the structure of the roller bearing of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inner ring 2 Outer ring 3 Roller 10 Inner raceway surface 10a Concave bus (other bus) forming inner raceway surface 10b Convex bus (other bus) forming inner raceway surface 11 First bus (one bus) 12 2nd bus (one bus) 14 brim 15 brim 20 Track surface of outer ring 20a Concave bus (other bus) forming track surface of outer ring 20b Convex bus (other bus) forming track surface of outer ring 21 1st bus (One bus) 22 second bus (one bus) 31 convex busbar (the other bus) forming the rolling surface of the roller 32 first bus (one bus) 33 second bus (one bus) 34 1 bus (one bus) 35 second bus (one bus) A Line indicating the boundary position between the first bus and the second bus of the inner ring B Line indicating the boundary position between the first bus and the second bus of the outer ring Indicating the boundary position between the first bus and the second bus D Line indicating the boundary position between the first bus and the second bus

Claims (1)

[Claims] 1. One of a rolling surface at a raceway surface of an inner ring and an outer ring is formed by a concave bus bar, and the other is formed by a convex bus bar, and any one of the concave bus bar and the convex bus bar is formed. The axial center portion is formed of a first generatrix having a constant curvature, and both ends in the axial direction adjacent to the axial center portion of the one generatrix have a radius of curvature such that they are separated from the other generatrix. In a roller bearing composed of a bus bar, at least one of the inner ring, the outer ring, and the roller contains, as an alloy component, carbon (C) in an amount of 0.2% to 0.5% by weight (mass%), and manganese (Mn). ) To 0.5
% Or more and 1.2% or less, and after being formed of a steel material containing chromium (Cr) in a range of 0.5% or more and 2.0% or less, carburizing or carbonitriding and quenching and tempering are performed. The carbon concentration in the surface layer portion of the raceway surface and / or the rolling surface is 0.7% by weight or more and 1.2% by weight or less, and the amount of retained austenite in the surface layer portion is 20.0% by volume or more and 40.0% by volume or less. A roller bearing, wherein the hardness of the surface layer is Hv700 or more.