In this study, in order to solve the quality problem (Safety accident) that the chain breaks out of the wheel gear due to the problem of the spare tire carrier device, the wheel gear is rotated in such a way that the upper part of the chain is caught on one side of the triangular wheel gear. When falling, the tire falls due to the chain falling off and the chain is caught by the wheel gear so that it cannot bear the tire load and slip occurs. Also, in order to solve the quality problem that the chain is caught (Due to malfunction), the “ㄷ” shaped chain the guide should play the role of guiding the movement of the chain by holding the chain in the direction. The technical development goal is to solve the problem of the chain dropping and the chain hanging from the wheel gear of this product.

Recently, automotive engines have changed to the silent chain system in order to reduce noise and to improve reliability. High contact fatigue strength is needed for the sprockets of silent chain system. As a result, a high-contact-fatigue-strength P/M material was developed using the technology of surface rolling, which densifies the surface layer of sintered parts. It was established that the contact fatigue strength of the developed material was a great improvement over that of the conventionally used sintered material.