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Bearings used for fan motors and pump motors are subject to restrictions during assembly of the motor. In many cases, it is necessary to install (gap fit) in a state where there is a gap between the outer ring and the casing. In this state, if an eccentric load is applied to the bearing, the outer ring will have a phenomenon of "creep" moving in the opposite direction to the rotation direction depending on the condition, and the life of the bearing will be shortened due to wear.
In particular, in recent years, as motors have become increasingly lightweight, an example of using an aluminum alloy casing is increasing. In this case, due to the difference in the amount of thermal expansion, the gap between the bearing and the casing is increased as compared with the conventional cast iron casing, and creep is likely to occur. As a result, deterioration and leakage of the grease occur due to heat generation and wear of the mating surface, and noise is increased or sintering or peeling occurs. In addition, the motor also suffers from increased casing wear, vibration and noise, and shortened life.
The creep-free bearing has two O-rings in the outer ring. With the elastic force and repulsive force of the O-ring, it has twice the creep resistance compared with the bearing without the O-ring. In addition, by optimizing the size, spring force, repulsive force of the O-ring and the outer ring outer groove size of the O-ring, the creep resistance is increased by more than 20%.
In addition, the material composition of the O-ring is improved to reduce the permanent deformation of the O-ring in the high temperature environment to 1/5 of the previous one. Since the stable creep resistance can be achieved at a high temperature of 120 ° C, the maintenance period of the bearing can be extended.
Through the improvement of the O-ring, the oil resistance of the ester grease will also be increased by 7 times. When the motor is assembled, the grease applied to the outer diameter of the bearing and the inner diameter of the casing can be used not only with mineral oil but also with ester grease, thereby improving the operability during assembly.
Seiko has developed a "no creep bearing" bearing with a creep resistance greater than 20% higher than that of a fan motor and a pump motor for clean rooms, and has begun sampling.