Tractors are powered by diesel engines, but diesel engines should not be operated at low speeds for long periods of time. The reason is as follows: The atomization quality of the injector is mainly related to the injection pressure, the diameter of the injector and the rotation speed of the camshaft. Since the injection hole diameter is fixed, the quality of the atomization of the diesel engine depends on the pressure of the injection nozzle and the cam rotation speed. The greater the pressure of the injection nozzle, the faster the camshaft rotation speed, the better the atomization of the fuel injection, and the camshaft. The rotation speed varies with the crankshaft rotation speed. When the diesel engine speed is lower than the rated rotation speed, the atomizing quality of the injector exhibits a supersaturation state. Once the time passes, the diesel engine will not operate normally. When the diesel engine is overloaded, the temperature of the engine increases and the temperature of the oil rises. As a result, the oil pump is insufficiently supplied at a low speed, resulting in poor lubrication of the associated parts. When the speed is low and the work is not stable, the connecting rod and the bearing bush are used. The parts will also work under abnormal loads, resulting in accidents such as dropping of the bearing alloy.