Front axle suspension parameters match and its impact on vibration characteristics of tractor

Compared with cars, buses and trucks, tractor often drives on the dirt road in the field of rural areas, together with the simple vibration damping device, so the vibration of tractor is particularly intense. Severe vibration of tractor would cause serious harm to driver's health, and cause fatigue and failure of tractor parts and hence seriously affect the life of the tractor. In addition, excessive vibration of the tractor will exacerbate farmland soil compaction and reduce crop yields. How to effectively reduce the vibration of tractors to improve ride comfort and driving safety and reduce farmland damage is an important research topic for researchers and tractor manufacturing enterprises. The study of foreign scholars have found when the tractor is installed with front axle suspension, the ride comfort and driving safety is improved. When farm tools hangs on the front of tractor, tractor damping effect depends on the matching between front axle suspension stiffness and damping coefficient. Installing the front axle suspension of tractor can significantly reduce tractor's pitching vibration. By the method of theoretical analysis, the theoretical system of front axle suspension of tractor was established, the vibration was analyzed and the theoretical formula was deduced, aiming to provide a theoretical basis for parameter matching of tractor front axle suspension. In this paper, CF700 tractor from Jiang Su Chang-Fa group was taken as the research object, and the theoretical model of front axle suspension tractor was established, including plane vibration model of front axle suspension tractor with 3 degrees of freedom, vibration differential equation and tractor vibration characteristics evaluation. Taking body vertical vibration acceleration, body pitching vibration angular acceleration, seat-mounted vertical vibration acceleration, front and rear wheels' dynamic load and front axle suspension dynamic deflection as the evaluation means, theoretical calculation method was adopted to optimize the matching of front axle suspension stiffness and damping coefficient, getting the best matching value between front axle suspension stiffness and damping coefficient (120 000 N/m, 8 000 N·s/m). Calculate and compare the vibration characteristics of the tractors installed with and without front axle suspension. When the tractor traveled on the roads of Grade D in international standard with the speed of 3-18 km/h, the root mean square values of body vertical vibration acceleration and pitching vibration angular acceleration of the tractor installed with front axle suspension averagely decreased by 24.03% and 42.46%, respectively, and those of seat-mounted vertical vibration acceleration and front wheel's dynamic load averagely decreased by 29.77% and 21.72%, respectively. The results show that the tractor installed with front axle suspension plays significant role to improve ride comfort and driving safety. The findings provide a theoretical basis and a certain reference value for the design and optimization of tractor front axle suspension.