POWER EFFICIENCY CHARACTERISTICS OF A TRACTOR DRIVE TRAIN

摘要

According to a field test, power transmission efficiency of a tractor drive train varied from 56% to 86% with a mean value of 72.5%. This indicates that a constant-power transmission efficiency model used commonly for the simulation of a power drive train performance may not properly represent the variability that exists. To simulate the actual power transmission efficiency, a drag torque was introduced, and a new model based on the transmission input torque was proposed. The model involves two components, one of which is associated with torque load acting on the wheel axle and the other with the drag torque regardless of the torque load. The power loss by the drag torque, about 61% of the entire power loss occurring during the transporting operation, must be considered in the evaluation of power transmission efficiency of tractor drive trains. The power transmission efficiency predicted by the model agreed well with the experimentally determined power transmission efficiency within a 1.5% difference on average. Although more experimental data may be required before the model can be used practically, a drag torque must be taken into consideration for a better understanding of the power train performance of tractors