Abstract
Geared transmissions are used in various machines such as automobile transmissions but these mechanisms lose driving force during shifting. A novel ratio variation system was proposed to solve this problem. This transmission mechanism uses noncircular gears which can realize the reduction ratios of two gears. In order to transmit rotation constantly, this noncircular gear pair must always be in mesh. Therefore, this report discusses the contact ratio of noncircular gears and shows a calculation result regarding the contact ratio.