MODEL OF HYDROPNEUMATIC THREE POINT HITCH

This paper presents a model of a hydropneumatic three point hitch system for farm tractors. A model of hydropneumatic three point hitch is derived to suit the control task of oscillations damping of the tractor aggregate. The reaction forces of the tractor hitch system hydraulic cylinder were determined, corresponding to different weight positions of the implement. The hitch mechanism is divided in three kinematic groups (unit of upper link and implement, unit of lift arm and unit of lower link) for calculations. From the simulation with the program Working Model it was established that the tractor hitch system lower link and mounted soil cultivation tool at low amplitude oscillations during transport can be simplified as a single beam. The necessary stiffness characteristics for beam suspension, depending on the implement weight and its position, were determined. Uses of hydraulic accumulators were provided for obtaining different stiffness characteristics of suspension. The volume and necessary charge pressure were determined for hydraulic accumulators.