The Lubricant Churning Loss in Spur Gear Systems

Due to the greater power loss caused by higher operating powers and speeds the-operating temperatures of gear systems in use nowadays are higher causing the strength of tooth surfaces to decrease. Usually, the power loss consists of (1) the tooth friction, (2) the lubricant churning loss and (3) the bearing loss. In this paper, the churning loss is discussed. Essentially, lubricants are used for decreasing tooth friction and for dissipating the heat generated, and in order to know the best method of lubrication the amount of churning loss and its cause should be determined. In the present experiment, the churning loss of a spur gear system with jet lubrication is measured, and several analyses are proposed. From the results thereof, it becomes clear that the churning loss consists of the power required to trap the oil between the mating gears and to accelerate the oil in the tooth space. And it is considered that at high speeds the churning loss does not become so large regardless of the viscosity of the lubricating oil.