Drive force control system for electric vehicle

A drive force control system for an electric vehicle, comprising:

• a first motor that drives a first wheel as one of a front wheel and a rear wheel;
• and
• another prime mover that drives a second wheel as the other one of the front wheel and the rear wheel;
• wherein a four-wheel drive mode in which the electric vehicle is propelled by the first motor and the another prime mover is available,
• the drive force control system comprises a controller that controls the first motor, and
• the controller comprises:
• an upper limit torque determiner configured to employ a torque of the first motor at a point when a temperature of the first motor reaches a first predetermined temperature as an upper limit torque of the first motor, in a case that the temperature of the first motor is equal to or higher than a first predetermined temperature but lower than a first restrictive temperature set to a level possible to protect the first motor;
• a restrictive torque determiner configured to employ a first limit torque that is smaller than the torque employed by the upper limit torque determiner and that is set in accordance with the temperature of the first motor, as the upper limit torque of the first motor, in a case that the temperature of the first motor is equal to or higher than the first restrictive temperature;
• and
• a target torque determiner configured to determine a torque of the another prime mover based on the upper limit torque of the first motor, a target torque ratio between a torque driving the front wheel and a torque driving the rear wheel to achieve a required driving torque to propel the electric vehicle, or the required driving torque.