Abstract
This paper presents the procedure to simulate the transmission error of a pair of an internal gear and an external gear. The procedure is based on the existing method for a pair of external helical gears. However, the proposed method incorporates tooth surface errors of all teeth and pitch errors. As the analytical result shows good correlation with the experimental result, the proposed method is accurate enough for the practical use. Finally the developed method is applied for improving gear noise of rotary engine. The prototype gear shows some improvements in gear noise. Therefore, the proposed method is useful for the development of internal gears.