Importance

Loading Importance Indicators...

Abstract

A hydraulic control circuit for a hydraulic motor operable at least at two displacements, having 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. A time related control current function is provided for controlling the current applied to the electrical actuator for controlling the pilot pressure including a pre-current portion with a constant non-zero current and a current ramp portion during which the current is raised or lowered continuously from a ramp starting current level to an intermediate current level. The current is changed abruptly to a switching current level at the end of the current ramp portion for allowing 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.

Loading the Abstract Image...

First Claim