拖拉机当作固定动力使用时,发动机的功率经传动系传到动力输出轴,向外输出(手扶拖拉机是由三角皮带轮输出),称为输出轴功率。当拖拉机作为移动动力使用时,发动机的功率经传动系传到驱动轮,再通过驱动轮与地面作用,推动拖拉机行进,动力由牵引挂钩向外输出,称为牵引功率。动力在传动过程中有损失,因此,牵引功率和输出轴功率都小于发动机有效功率。 When the tractor is used as a fixed power, the power of the engine is transmitted to the power output shaft via the transmission line and output to the outside (the manual tractor is output by a V-belt pulley) and is called output shaft power. When the tractor is used as mobile power, the power of the engine is transmitted to the driving wheel through the transmission train, and then the driving wheel and the ground act to push the tractor to travel. The power is output by the pulling hook and is called traction power. Power loss in the transmission process, therefore, the traction power and output shaft power are less than the effective power of the engine.