Rotary tillage operation is a typical field operation condition of tractors. During operation, 50% – 75% of the engine power is transmitted to the rotary tillage machine through the PTO shaft. The power output transmission system is the core component system for power transmission. In the face of complex field working environment and heavy work tasks, tractor transmission system will produce various parts failure problems. The dynamic characteristics of the tractor power output transmission system are directly affected by the field load excitation, and are closely related to the change of the working load. Therefore, it is of great significance to study the influence of rotary tillage operation load change on tractor power output transmission system.
The tractor gear train is the key component of the power output transmission system. For the dynamic modeling of tractor gear train, the classical 8-DOF model was originally proposed by BARTELMUS. Then, considering the meshing friction of tractor gears, the model was improved and applied to the dynamic analysis of tractor gear failures. LUNDVALL et al. and CHEN et al. studied the dynamic performance of tractor gear transmission system in detail considering transmission error, tooth surface friction, time-varying meshing stiffness and tooth side clearance. Other scholars also discussed different modeling methods for tractor planetary gear sets. upper
For the load of tractor transmission system, domestic and foreign scholars have mainly carried out relevant research on test data collection, damage assessment, etc. KIM et al. tested the load of the input shaft of the tractor gearbox under ploughing, rotary tillage and transportation conditions, and discussed the severity of the load on the transmission system. LEE et al. obtained the PTO torque under rotary tillage and packaging operations through tests, and obtained the load spectrum by rain flow counting, and compared and analyzed the fatigue damage degree of PTO under different working conditions. KIM and others have also carried out similar research. Fang Zaihua et al. studied the statistical characteristics such as fluctuation, normality and randomness of tractor engine load for plowing and rotary tillage operations.
(1) The torsional vibration coupling spatial dynamics model of the power output transmission system is constructed. This model describes the load transfer relationship and mechanism inside the transmission system, and considers the transverse and vertical tractor gear transfer effects in detail.
(2) The simulation results of the model are verified by the tractor PTO loading test bench. The comparison results in time domain and frequency domain show that the amplitude of transverse vibration is obviously greater than that of vertical vibration due to the action of the meshing force of the tractor gear, and the time domain data is basically consistent with the simulation results; The maximum meshing frequency errors of transverse and vertical directions are 4.24% and 5.12% respectively, which meet the modeling requirements.
(3) The operation data acquisition system was set up to collect the field rotary tillage operation data of the tractor in L1 (2.07km/h), L2 (3.10km/h) and L3 (5.29km/h) common gears. The model was used to simulate and analyze the influence of PTO load in different operation gears on the transmission characteristics of the tractor gears. The results showed that the higher the rotary tillage operation gear of the tractor, the greater the vibration displacement of the transmission system caused by PTO load fluctuation, And it is mainly reflected in the lateral vibration.
However, the above research is limited by experimental means and methods, and there is no in-depth study on the load transfer process and its impact of field work load in the tractor power take-off transmission system. In the field of road transport and rail transport (such as automobile, high-speed railway, etc.), scholars at home and abroad have also carried out relevant research in power transmission system modeling, operation/operation load dynamic characteristics analysis, vehicle environment interaction, etc.
Based on the above discussion, the method of system dynamics modeling, bench test verification, field test and simulation analysis is proposed to study the impact of tractor rotary tillage operation load on the power output transmission system. The specific technical route is: to build a theoretical model describing the load transmission of tractor power output transmission system; The time domain and frequency domain data of the model are verified by bench loading test; Set up a field test system and collect the PTO load of rotary tillage operation under different working gears, and use the above model to carry out simulation analysis on the transmission characteristics of tractor gears.