A torque sharing function (TSF) method is one of the torque control methods that drives each phase of a switched reluctance motor so that the overall torque becomes a constant torque. The conventional TSF method defined the TSF only at a positive torque production region, which causes a poor torque-speed performance as the speed increases due to the delay of the current rising and falling time. This paper extends the definition region of the TSF to the negative torque region to have enough time to raise or decrease the current at the positive torque region. This extended TSF enables to increase the positive torque even in relatively high speed operation. Optimal determination of the TSF is investigated for various control objectives in mathematical and experimental ways.