Design and Application of Front Drive Axle for Heavy Tractors

The front drive axle is one of the key components of a heavy-duty tractor. Its function is to connect the tractor body and the front wheels. It bears the weight of the front of the tractor and allows the front wheels to deflect relative to the body, enabling the tractor to steer and travel. The performance of the front axle significantly impacts the tractor's traction characteristics, reliability, and ride comfort. Most high-end heavy-duty tractors in China rely on imported front drive axles, making it one of the current technological bottlenecks in China's heavy-duty tractor industry.
(1) This study analyzes the technological development and the current research status at home and abroad of front drive axles for heavy-duty tractors. Based on the design requirements of the L-series heavy-duty wheeled tractors, this research investigates the determination methods of design parameters such as transmission ratio, load capacity, and turning radius from the perspective of load-bearing under actual operating conditions. Through calculation and analysis of the tractor's front drive axle parameters, the design process and methods of the tractor's front drive axle are improved; the main design parameters of the front drive axle are determined.
(2) According to the overall load-bearing requirements and the configuration of the front drive axle system, a transmission structure of the front drive axle is designed, consisting of a central main reduction gear, a differential gear, and a final planetary gear reducer. The transmission ratio is determined through calculation to meet the overall operational needs. To improve reliability, bearing life calculation and selection were completed under extreme operating conditions (maximum load and maximum operating speed). The calculations show that the selected bearings can meet the 8000h service life requirement. The gear transmission system was designed, parameters were determined, and strength was verified. ANSYS software was used for stress calculation and gear modification of the sun gear system, significantly improving gear strength, reducing meshing heat, and ensuring the reliability of the front drive axle.
(3) Through the matching design of the front drive axle system and shell optimization, the design strength of the drive axle meets the actual load-bearing requirements. ANSYS software was used to build and simulate various modules of the front drive axle and conduct stress characteristic analysis. Based on this, a simulation model of the entire system was established to calculate and analyze the life and strength coefficient of the bearings, shafts, and gears. The results show that all core components of the front drive axle meet the load-bearing requirements.
(4) Using finite element theory and methods, a multi-rigid body model of the front drive axle housing was established. The stress and deformation of each part of the housing were calculated, and the structural parameters of the housing were optimized. The safety factor of the two high-stress areas of the housing was increased by 23.7% and 26.9%, respectively, meeting the design requirements. To prevent resonance during tractor operation, modal calculation and analysis were performed on the front drive axle housing. The results show that the engine resonance band is 88-132 Hz, the road excitation resonance band is 1-21 Hz, and the minimum natural frequency of the front axle housing is 194.09 Hz. Therefore, the front axle housing structure will not resonate.
(5) The designed front drive axle components underwent bench testing and whole-machine application. The bench test results show that the front drive axle prototype meets the requirements of loading tests, whole-machine rotating drum tests, and reliability tests. The L-series heavy-duty tractor underwent 2000 hours of reliability verification under typical operating conditions such as plowing, shoveling, and land preparation. The overall performance was reliable and trouble-free, and the wear of the gears and bearings on the front drive axle was normal, with no signs of pitting or burns. The complete machine product passed the appraisal and has been put into application.