Hydraulic control circuit for a hydraulic motor

A hydraulic control circuit for hydraulic fluid for a hydraulic motor operable at least at two displacements, comprising a proportional speed control valve with a control valve spool continuously moveable by means of a force generated by a pilot pressure being controlled by a continuously, electrically adjustable pilot valve having an electrical actuator, wherein the control valve spool is moveable between:

• a full-torque end position,
• a reduced-torque end position, and
• at least one intermediate position,
• wherein a time related control current function is provided for controlling the current applied to the electrical actuator for controlling the pilot pressure, wherein the control current function comprises:
• a pre-current portion along a normal operation time span prior to a displacement switching command at a command time during which pre-current portion a pre-current level does not generate a pilot pressure level allowing the speed control valve spool to move out of one of its two end positions,
• a current ramp portion during a ramp time span ending at a pre-set switching time after the command time, wherein the current is raised or lowered continuously in that current ramp portion from a ramp starting current level to an intermediate current level and is changed abruptly to a switching current level at the end of the current ramp portion for allowing by means of the pilot pressure the movement of the speed control valve spool from one of the two end positions via the at least one intermediate switching position into the other end position.