Hydro-pneumatic driven axle suspension

A hydro-pneumatic suspension system for a front axle of a vehicle, having a pair of hydraulic cylinders, coupled between a chassis of the vehicle and an axle body, each cylinder having a rod end chamber and a piston end chamber, each rod end chamber being connected to a rod end accumulator and to a valve circuit fed by a hydraulic pump, the valve circuit controlling a position of the chassis relative to the axle body, and controlling fluid pressure in the accumulator as a function of load on the axle body, the improvement wherein:

• the suspension system include components which are designed to resiliently suspend the chassis under all loads expected to be applied to the axle body;
• a position sensor senses a position of the chassis relative to the axle and generates a position signal representative thereof;
• the valve circuit maintains a pressure in the accumulator sufficient to resiliently suspend the axle body under all load and operating conditions, the valve circuit comprising a pair of electromagnetically controlled level control valves, each level control valve having a first port communicated with the hydraulic pump and a second port communicated with a reservoir, one of the level control valves having a third port communicated with the rod end chamber via a first pilot controlled check valve, the other level control valve having a third port communicated with the piston end chamber via a second pilot controlled check valve, each check valve preventing fluid backflow out of the corresponding rod end chamber and piston end chamber;
• and
• a control unit controls the valve circuit as a function of the position signal.