TY - JOUR TI - Mathematical model of energy efficiency in internal spur gears AU - Dobratić Predrag S AU - Ristivojević Mileta R AU - Rosić Božidar B AU - Mitrović Radivoje M AU - Trifković Dragan R JN - Thermal Science PY - 2019 VL - 23 IS - 15 SP - 1801 EP - 1813 PT - Article AB - The impact of geometric parameters of teeth and lubricating oils to the efficiency of involute internal spur gears, when the transverse contact ratio is 2 < εα ≤ 3, has been analyzed in this paper. The mathematical model and computer program for determining the current and the effective value of the efficiency have been developed. The influence of the character of load distribution and energy losses due to heating effects during the meshing period is included in the factor of load distribution. The results of computer simulation are given in the form of a diagram of the current values of the efficiency during the meshing period. Also, the values of effective efficiency for the considered cylindrical gear pairs have been calculated.