JP2010196754A - Rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low cost rolling bearing which suppress life deterioration caused by surface damage even under a high speed, high load and high temperature environment, or when a foreign matter is mixed into grease or lubricating oil. <P>SOLUTION: The rolling bearing is characterized in that: a plurality of rolling element is retained rollably between races by a retainer; and the nitrogen concentration of the rolling element is higher by 0.1-1.0% than that of the race. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rolling bearing formed by nitriding or carbonitriding a bearing ring and rolling elements.

  Since a rolling bearing is used under repeated shear stress under high surface pressure, it is necessary to withstand this shear stress and ensure a rolling fatigue life. Therefore, as the races and rolling elements, two types of high-carbon chromium bearing steel (SUJ2) are quenched and tempered, or case-hardened steel (SCR420, SCN420, etc.) is carburized or carbonitrided, quenched and tempered. The thing which surface hardness was raised to Hv650-800 by giving a process is used.

  Furthermore, in recent years, rolling bearings used in these mechanisms have also been increased in speed and load in order to achieve higher efficiency and downsizing of power transmission mechanisms and support mechanisms for automobiles, machine tools, general industrial machines, steel equipment, etc. It is increasingly used in harsh environments such as high temperatures. In particular, in rolling bearings used under high loads, an oil film is difficult to form on the raceway surface, and metal contact occurs between the raceway surface and the rolling element surface, resulting in a large tangential force on the rolling surface. Is likely to occur. Also, in rolling bearings used at high temperatures, slippage due to skew is likely to occur between the raceway surface and the rolling element surface, and repeated shear stress and large tangential force are generated between the raceway surface and the rolling element surface. Surface damage is likely to occur.

  Surface damage also occurs when foreign materials such as metal chips, shavings, burrs, and wear powder are mixed with grease or lubricating oil, causing indentations on the rolling surface due to the inclusion of foreign materials, and stress on the edges of the indentations. The cause is concentration.

  Since surface damage leads to a reduction in life, improvements have been made to the constituent materials of bearings. For example, in Patent Document 1, at least the bearing ring is in a weight ratio, the C content is 0.8 to 1.2%, the Si content is 0.4 to 1.0%, and the Cr content is 0.2. After processing the raw material which consists of steel which is -1.2% and Mn content rate is 0.8-1.5% into a predetermined shape, carbonitriding is performed, quenching at 830-870 ° C., and 160-190 It is produced by performing a tempering treatment at 0 ° C., and it is proposed that the retained austenite of the surface layer portion is 25 to 50% by volume. In Patent Document 2, at least the rollers are in a weight ratio, the C content is 0.8 to 1.5%, the Si content is 0.4 to 1.2%, and the Mn content is 0.8 to After the material made of steel with 1.5% and Cr content of 0.8-1.8% is processed into a predetermined shape, it is carbonitrided, and it is made by quenching and tempering, and its surface layer It is proposed that the retained austenite of the part is 20 to 40% by volume and the surface hardness is Hv750 or more.

Japanese Patent Laid-Open No. 7-190072 JP 2000-234147 A

  However, in the technologies described in Patent Document 1 and Patent Document 2, since the life is improved by increasing both the amount of retained austenite and hardness of the surface layer to a specific value, there is a limit to the reduction in manufacturing cost. There is. Further, only the life of the raceway member in which the life reduction due to surface damage is a problem is considered, and the life of other rolling members is not considered. For this reason, even if only the life of the race member is increased, the life of the rolling member may be insufficient and the life of the entire bearing cannot be increased.

  Accordingly, an object of the present invention is to provide an inexpensive rolling bearing in which a decrease in life due to surface damage is suppressed even under a high speed, high load, high temperature environment, or when foreign matter is mixed in grease or lubricating oil. .

  In order to achieve the above-mentioned object, the present invention comprises a cage in which a plurality of rolling elements are rotatably held by a cage, and the nitrogen concentration of the rolling elements is higher than the nitrogen concentration of the bearing rings. Provided is a rolling bearing characterized by being 0.1 to 1.0% higher. The raceway is preferably nitriding or carbonitriding.

  In the rolling bearing according to the present invention, the nitrogen concentration of the rolling element is increased by a specified amount relative to the raceway and is strengthened, so that it can be used in high-speed, high-load, high-temperature environments, or when foreign matter enters grease or lubricating oil. Even if the indentation is formed on the raceway surface, the generation and propagation of cracks starting from the indentation edge can be delayed, and the entire bearing has a long life. Further, only the rolling elements may be subjected to nitriding treatment or carbonitriding treatment, and the cost can be reduced.

It is sectional drawing which shows an example of a tapered roller bearing. It is sectional drawing which shows an example of a ball bearing. It is a graph which shows the relationship between the nitrogen concentration difference of a rolling-element surface and a raceway surface, and a lifetime ratio in the case of not performing a nitriding process to a starting surface. It is a graph which shows the relationship between the nitrogen concentration difference of a rolling-element surface and a raceway surface, and a lifetime ratio when the nitriding process is performed to the starting surface.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  In the present invention, the type of rolling bearing is not limited, and examples include a conical bearing shown in FIG. 1 and a ball bearing shown in FIG. The tapered roller bearing shown in FIG. 1 is configured by holding a tapered roller as a plurality of rolling elements 1 between a outer ring 2 and an inner ring 3 with a cage 4, and grease or lubricating oil (not shown). It is lubricated by. Reference numeral 2a denotes an outer ring raceway surface, and 3a denotes an inner ring raceway surface. Further, the ball bearing shown in FIG. 2 is configured by holding balls, which are a plurality of rolling elements 1, between the outer ring 2 and the inner ring 3 with a cage 4, and is lubricated with grease or lubricating oil (not shown). Is done. Reference numeral 2a denotes an outer ring raceway surface, and 3a denotes an inner ring raceway surface.

  In the present invention, the rolling element 1 (tapered roller or ball) is subjected to nitriding treatment or carbonitriding treatment so that the nitrogen concentration is 0.1 to 1.0%, preferably 0.8%, than the nitrogen concentration of the outer ring 2 and the inner ring 3. 4 to 0.8% higher to strengthen the surface. If such a nitrogen concentration difference is less than 0.1%, the lifespan becomes insufficient, and if it exceeds 1.0%, the effect is not only saturated, but the treatment time is not increased and the cost is increased. Nitrogen treatment and carbonitriding can be performed by ordinary methods, and the gas composition, treatment temperature, and treatment time are appropriately set so that the above nitrogen content is obtained.

  Further, it is preferable that the outer ring 2 and the inner ring 3 are also subjected to nitriding treatment or carbonitriding treatment to strengthen the outer ring raceway surface 2a and the inner ring raceway surface 3a so that indentation is less likely to occur. Also in this case, the nitrogen concentration of the rolling element 1 is made to be 0.1 to 1.0%, preferably 0.4 to 0.8% higher than the nitrogen concentration of the outer ring 2 and the inner ring 3.

  Note that the rolling element 1, the outer ring 2 and the inner ring 3 before nitriding or carbonitriding may all be made of ordinary bearing materials.

  Moreover, the rolling element 1, the outer ring 2 and the inner ring 3 may be subjected to quenching and tempering. Processing conditions are not limited and may be as usual.

  For the rolling bearing, grease or lubricating oil is used for lubrication, but any known bearing may be used.

  The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

Example 1
It was processed into balls, outer rings, and inner rings using SUJ2 steel. And only the balls were subjected to carbonitriding to produce balls having different nitrogen concentrations. The nitrogen concentration was adjusted by the heating time in the carbonitriding process. As the processing gas, a mixed gas obtained by adding 10% by volume of ammonia gas to NX gas was used. The heating temperature was set to 850 ° C., and immediately after heating, the mixture was immediately cooled in oil having an oil temperature of 100 ° C. Tempering was performed at 180 ° C. for 2 hours.

And the bearing was assembled and the rolling fatigue life was performed. The test conditions are as follows. The results are shown in FIG. 3, and are shown as relative values (life ratios) where the rolling fatigue life of a bearing using balls having a nitrogen concentration of 0% is 1.
・ Load Fr; 17.64kN
・ Contact surface pressure Pmax: 2.6 GPa
・ Rotation speed: 2000rpm
・ Lubrication; Turbine 56 oil bath lubrication

  As shown in the figure, the life ratio is high when the difference between the nitrogen concentration of the ball and the nitrogen concentration of the outer ring and the inner ring (ΔN%) is 0.1 to 1.0%, particularly 0.4 to 0.8%. I understand that

(Example 2)
The inner ring and the outer ring were subjected to carbonitriding, and the life ratio was determined in the same manner as in Example 1. The results are shown in FIG.

  As shown in the figure, the inner ring and the outer ring are carbonitrided and strengthened to enhance the life as compared with FIG. 3, but similarly, the nitrogen concentration of the ball and the nitrogen of the outer ring and the inner ring are increased. It can be seen that the life ratio becomes higher when the concentration difference (ΔN%) is in the range of 0.1 to 1.0%, particularly 0.4 to 0.8%.

1 Rolling elements (cone rollers or balls)
2 Outer ring 2a Outer ring raceway surface 3 Inner ring 3a Inner ring raceway surface 4 Cage

Claims (2)

  A plurality of rolling elements are rotatably held by a cage between the bearing rings, and the nitrogen concentration of the rolling elements is 0.1 to 1.0% higher than the nitrogen concentration of the bearing rings. Characteristic rolling bearing.   The rolling bearing according to claim 1, wherein the bearing ring is nitrided or carbonitrided.

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