Abstract: The oil-free chain is obtained by connecting a pair of inner link plates which are connected by oil-impregnated bushings and a pair of outer link plates, which are connected by pins inserted into adjacent oil-impregnated bushings of adjacent inner link plates alternately. The oil-impregnated bushing is obtained by impregnating a bushing made of a metal sintered body with perfluoropolyether having a kinematic viscosity at 40° C. equal to or higher than 350 mm2/s. The bushing is impregnated with perfluoropolyether having a kinematic viscosity corresponding to the operating temperature of the oil-free chain.

Abstract: The oil-free chain is obtained by connecting a pair of inner link plates which are connected by oil-impregnated bushings and a pair of outer link plates, which are connected by pins inserted into adjacent oil-impregnated bushings of adjacent inner link plates alternately. The oil-impregnated bushing is obtained by impregnating a bushing made of a metal sintered body with perfluoropolyether having a kinematic viscosity at 40° C. equal to or higher than 350 mm2/s. The bushing is impregnated with perfluoropolyether having a kinematic viscosity corresponding to the operating temperature of the oil-free chain.

Abstract: An oilless chain is configured to connect alternately a pair of outer plates having two pins for coupling each other and a pair of inner plates, disposed adjacent to the pair of outer plates, having two bushings for coupling each other, by incorporating one of the pins into one of the bushings. After perfluoropolyether is impregnated into the bushings, the bushings are immersed in a lubricating oil composition prepared by blending perfluoropolyether with polytetrafluoroethylene. The polytetrafluoroethylene has a primary particle diameter adapted to the diameter of the pores of the bushings through which the lubricating oil composition flows.

Abstract: A barrel-shaped coil spring roller is formed by closely winding spring wire rods having fine crepe-like concave-convex surfaces on the surface of the barrel-shaped coil spring roller. The fine crepe-like concave-convex surfaces serve as a lubricating oil reservoir and are formed by a shotpeening process. Lubricating oil is retained on the fine crepe-like concave-convex surfaces formed by the shot-peening process. Sliding noises between the spring wire rods adjacent to each other, which noises are generated by elastic deformation of the barrel-like coil spring roller when in engagement with the toothed surface of the sprocket, are reduced by the lubricating oil. The wear on both of the barrel-shaped coil spring roller and the sprocket is lessened and the power loss is reduced. The low noise chain is capable of retaining a lubricating oil on the surface of spring wire rods of a barrel-shaped coil spring roller for long periods of time, while still maintaining a noise reduction effect.