Air flow visualization at mesh end region have been performed by using a high speed camera and smoke wire method. Among two major roll of lubrication, reducing friction and cooling, cooling is quite important for maintaining gear durability because high temperature have metallurgical effect. Lubrication also makes excess power loss by squeezing effect at mesh area as well as by various losses existing in feeding system such as pump loss. Therefore, for the efficient contribution of lubricant, it is necessary to find an optimum arrangement of oil feeding especially for the purpose of cooling. The present paper is a trial to find such paths to feed lubricant to the tooth surfaces just after finishing engagement with as less power and as less amount of lubricant as possible. The visualization indicated there are flows going into tooth spaces that are just opposing to tangential movement of gear teeth even though the pitching line velocity is of about 10m/s.
