STEUERUNGSSYSTEM FÜR HYDRAULISCHE ERDBAUMASCHINE

摘要

Whether the running condition or the working condition is discriminated, when the running condition is discriminated, the highest RPM of a prime mover is limited by a 1st RPM, and the maximum displacement value by a 1st volume value, and, when the working condition is discriminated, the highest RPM is limited by a 2nd RPM equal to or lower than the 1st RPM and the maximum displacement volume is limited by the 2nd volume value larger than the 1st volume value. The 1st and 2nd RPM's and the 1st and 2nd volume values are determined to satisfy the relation, (1st RPM x 1st volume value at least at the flat land running pressure) < (2nd RPM x 2nd volume value at the pressure lower than the torque limit control range). With this arrangement, the pump discharge flowrate at least during the flat land running is lowered than that during the working, the pressure loss during the running can be decreased, the motor effective pressure is increased at one and the same pump pressure, the output torque can be increased, and the maximum displacement volume of the motor can be decreased in proportion to the decreased amount of the maximum discharge flowrate of the pump, thus making the circuit arrangement compact in size.