Abstract: The calculation method of positive and negative transmission mechanical efficiency of one tooth difference 2K-H cycloid-needle planet transmission with backlash is studied for the solution to the problem of self-locking performance instability of adjustable-angle mechanism of seat on automobile. A perfect mathematical model of instantaneous and average efficiency of the converted mechanism of the original epicyclic gear train is proposed based on mechanics analysis of the gear pair actual meshing transmission process. The mechanical effi-ciency of 2K-H epicyclic gear train is obtained through the efficiency of the converted mechanism calculated by mathe-matical model presented. Computerized program of the effi-ciency calculation is developed. The formula is available with both theoretic calculation and test result of adjustable-angle product. The relationship between mechanical efficiency and kinematics parameter are studied by using the program calcula-tion. The research conclusion is drawn that increasing friction coefficient, decreasing the offset and the difference between tooth numbers of two needle gears, increasing the number of pairs of teeth in contact at same time, changing the distribution of acting force and the initial relative angle of the centers of two pieces of cycloid gear can improve the self-locking performance, which is used to guide the improvement of self-locking performance of adjustable-angle mechanism of seat on automobile. The presented mathematical model pro-vides a basis for further researches such as the efficiency with machining tolerance, optimum design of the mechanism and transmission performance of tooth profile modified.

Key words: Angle adustment, Backlash, Mathematical modeling, Mechanical efficiency, Needle cycloid planetary transmission, Self locking performance