Assessment Study of the Design and Characteristic of Front-axle Hydro-pneumatic Spring of the Tractor
The paper discussed the improvement of design and characteristics of front-axle hydro-pneumatic spring of the tractor. For the experimental purposes, tractor with the model number of CF700 and the vibrational differential equation was established and also the three degrees of freedom vibration model of the front-axle suspension tractor was built up. According to the requirements of the tractor model number CF700 for front-axle suspension parameters, hydro-pneumatic spring with the controllable stiffness and damping was designed. The stiffness and damping non-linear mathematical model of hydro-pneumatic spring was established and the structural parameters of hydro-pneumatic spring were calculated. The performance of hydro-pneumatic springs was studied by simulation and the static and dynamic characteristics of the hydro-pneumatic spring were studied in the experiment. From the investigated results shows that the stiffness characteristics of hydro-pneumatic spring were studied and the static stiffness of hydro-pneumatic spring in equilibrium position was 72.6 kN.m-1. The influence of proportional valve current size, the opening of the throttle valve size and excitation frequency to the output force of hydro-pneumatic spring was studied by dynamic experiment. Further, from the results, it was showed that the designed hydro-pneumatic spring can adjust output force on a wide range of sizes. However, from the investigated results, it was concluded that the study provides an important basis for the later development of the semi-active hydro-pneumatic suspension of tractor front axle suspension.