Classification and analysis of electric-powered lateral torque-vectoring differentials

An electric-powered lateral torque-vectoring differential utilizes the output torque of an electric motor for generating the torque difference between the right and the left wheels. Compared with conventional torque-vectoring differentials which utilize the slipping clutch or brake for torque vectoring, electric-powered lateral torque-vectoring differentials have advantages, namely the response and the control accuracy of the torque difference. However, an electric-powered lateral torque-vectoring differential is complex as it is composed of a single electric motor and some planetary gear units; therefore it is difficult to understand its mechanism and characteristics. This paper describes the classification and analysis of electric-powered lateral torque-vectoring differentials. Electric-powered lateral torque-vectoring differentials are studied using the velocity diagram which is utilized for analysis of the conventional torque-vectoring differentials. The analysis shows that the simplest electric-powered lateral torque-vectoring differential is a mechanism of five elements with two degrees of freedom; the mechanism is composed of a single electric motor, one differential gear unit and two planetary gear units; the gear ratios of the planetary gear units are equal to each other. The simplest mechanisms are classified into nine kinds and these have two differences in their characteristics, namely the torque amplification factor between the electric motor and the vectoring torque, and the revolution speeds of one rotational element. Finally, the best mechanism is evaluated from the differences of the characteristics.