A study of a shock-absorber for a front-end loader modified for agricultural purposes with an electrohydraulic directional valve

Abstract

A front-end loader for agricultural purposes is the most commonly used implement for agri-tractors in Korea. As it is operated to raise, lower and carry various objects in a farming field, it introduces a large amount of stress to a tractor, causing vibrations and often lead to a mechanical breakdown. These high stresses are observed at the starting and ending points of operation, that is, the points at which the highest acceleration and deceleration occur. To reduce the sudden change of the speed, soft-start & end operation were tested with an electrohydraulic directional valve, which has a built-in ramp time spool control function. This valve was controlled by SAE-J1939 associated messages via CANBUS. This shock-absorbing system contains three ECUs (Electronic Control Unit): (a) a loader ECU for receiving and transmitting loader position data, (b) a Joystick ECU to convert a lever position that is constantly being changed by an operator into CAN messages, and (c) a valve ECU to regenerate all messages into the J1939 standard to be understood by the electrohydraulic directional valve. By sensing the loader position and speed, the ramp activation point is determined. As expected, applying ramp time control to the front-end loader control system proved to be effective for reducing the shock level, in contrast to that of the conventional control using a hydraulic manual valve.