Patent ID: 6401856
Filing Date: 2002-06-11
Classification: E02F,F16H

Abstract:
A method for a power shiftable change-over of a hydrostatic vehicle drive of a mobile construction machine with at least one axle, said vehicle drive having at least one controlled hydrostatic variable displacement pump, a hydrostatic drive motor, a hydraulic circuit, and a powershift transmission with at least two stages to propel the at least one axle of the construction machine, said hydrostatic drive motor comprising at least one of a fixed displacement hydrostatic drive motor and a variable displacement hydrostatic drive motor, wherein the transmission is shifted with at least one of pneumatic pressure, hydraulic pressure, and electric voltage and via at least one change-over valve, the method comprising:activating a switch by the operator; actuating a switching element with at least two pressure switches with differing contact pressures dependent on preset load conditions in the hydraulic circuit; electrically actuating the change-over valve with the switching element; activating a relay with an output of a vehicle speed monitoring frequency dependent switch, wherein the relay is closed by the frequency dependent switch at frequencies higher than zero to allow a shifting into second gear; creating a voltage signal in a predetermined frequency window by another output of the frequency dependent switch and feeding the voltage signal via another relay in an operative connection of the switch and the relay to the change-over valve to actuate a shifting of the transmission.