Sealed rolling bearing

Abstract

A sealed rolling bearing is proposed which makes it possible to reduce the torque loss while ensuring high sealing performance. Seal lips of seal members secured to the outer ring of the bearing at both ends thereof are in sliding contact with both ends of the outer periphery of the inner ring of the bearing. These portions of the inner ring that are in sliding contact with the seal lips are subjected to minute shot peening in which minute shots of molybdenum disulfide having a particle diameter of 20 to 200 micrometers are struck against these portions at a high speed of 50 meters per second. This decreases the friction torque attendant to sliding contact of the seal lips and makes it possible to decrease the torque loss of the bearing even if the contact pressure of the seal lips is increased sufficiently to ensure high sealing performance.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to a sealed rolling bearing which has its bearing space sealed by seals. [0002] Among sealed rolling bearings which have their bearing space sealed by seals to avoid leakage of a lubricating agent such as grease filled therein, there is a type which has an outer ring, an inner ring, rolling elements disposed between the inner and outer rings, and seal members secured to one of the inner and outer rings, the seal members each having seal lips kept in sliding contact with the opposing metal face of the other of the inner and outer rings or the surface of a metallic member mounted to the other of the inner and outer rings, such as a slinger. [0003] In order to ensure good sealing performance with this type of sealed rolling bearings, it is required that the seal lips, which are made of rubber or the like, be brought into sliding contact with the metal surface with a sufficiently high contact pressure. In order to ensure h...

AI Technical Summary

Benefits of technology

[0010] The minute shot peening treatment is attracting attention as a means for improving the surface quality of metal products. In the minute shot peening, minute shots having a hardness equal to or over the hardness of the metal product to be treated and having a particle size of 20 to 200 micrometers are struck against the metal surface at a speed of 50 meters per second or over. By doing so, the surface of the metal product, which has a low specific heat, is heated instantly to the A3 transformation point or over if the metal product is an iron metal or to the recrystallization point or over if the metal product is a non-iron metal, and instantly cooled. This cycle repeats itself. It is known that the peening causes work hardening as well as solution, recrystallization, refining of crystallized particles, etc. Also, by striking minute shots having a hardness equal to or over the hardness of the metal against the metal surface at high speed, minute ruggedness is formed on the metal surface.

[0011] In view of such characteristics of minute shot peening, the inventor of the present invention inferred that by subjecting the metal surface on which seal lips of a sealed rolling bearing slidably contact to minute shot peening, minute ruggedness will be retained by the abovementioned surface improving effect without being abraded, and that owing to the lubricating agent retaining effect by the minute ruggedness, it is possible to reduce the friction torque attendant to sliding contact even if the seal lips are brought into sliding contact with the metal surface with a sufficient contact pressure to ensure high sealing performance. Based on this inference, the inventor measured changes in the friction torque when rubber lips were brought into sliding contact with the outer periphery of tubular test specimens that have been subjected to minute shot peening and mounted on a rotary shaft. The results of measurement confirmed that the inference is correct. Thus, the inventor adopted the above arrangement as a means for decreasing the torque loss while ensuring the sealing performance of a sealed type rolling bearing.

[0012] By using molybdenum disulfide as the material of minute shots, it is possible to cause molybdenum disulfide having solid lubricating function to attach to the metal surface, thereby reducing the friction torque attendant to sliding contact of seal lips.

[0015] By the arrangement according to the present invention, combined effects of ensuring high sealing performance and reducing the torque loss are achievable.

Problems solved by technology

However, increasing the contact pressure of each seal lip or increasing the number of seal lips to insure the sealing performance will result in increased friction torque of the seal lips attendant to sliding contact with the metal surface, which will in turn increase the torque loss of the bearing.

Therefore, the method of the publication 2003-262231 does not effectively decrease the friction torque attendant to sliding contact of the seal lips on the metal surface.

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