Review of Gear Efficiency Equation and Force Treatment

With the present interest in energy saving, the improvement of gear efficiency is being looked at again. In this paper, differences between Buckingham's and Merritt's gear efficiency equations are described. These equations are of the same calculation form, but the manner in which they are used differs. The equations are valid under the assumption that input energy is calculated as the product of the normal force and displacement along the line of action. The author clarifies that an incorrect manner of calculating input power in the meshing gear may lead to trouble, and that Buckingham's and Merritt's equations are approximations. Moreover, in this paper a problem derived from the treatment of pitch point force is described. From the results of this study, it is concluded that the use of a tangential force of the pitch circle leads to an incorrect theory. The author deals with the locking phenomenon of the planetary gear mechanism as an example.