Abstract: A large hydraulic excavator permits an easy change from a machine mode corresponding to a backhoe excavator to a machine mode corresponding to a loader excavator, and vice versa. A hydraulic circuit is provided with hydraulic pumps and directional control valves, solenoid valves for controlling the hydraulic pumps and the directional control valves, and a controller for controlling the solenoid valves in accordance with operation of control lever devices and control pedal devices. The controller performs its control in a backhoe mode or loader mode selectively instructed by a mode instruction unit. Control of the solenoid valves in the backhoe mode makes the hydraulic circuit function as a backhoe hydraulic drive circuit, while control in the loader mode makes the hydraulic circuit function as a loader hydraulic drive circuit.

Abstract: To permit a precise and easy adjustment of a pump absorption torque of a main pump in accordance with environmental conditions when a sub-pump different in characteristics from the main pump is connected to a prime mover. A main controller 12 includes a processor means for setting the level of an absorption torque of a cooling fan pump 20 at a maximum absorption torque in use, a processor means for incrementing an adjustment target absorption torque for a main pump 13 at a slow rate from a sufficiently small pump absorption torque, and a processor means for repeating loading of a load factor signal and the increment of the adjustment target absorption torque as long as “NO” is determined by a fourth determination means, and a processor means for storing the adjustment target absorption torque as an adjustment value when “YES” has been determined by the fourth determination means.

Abstract: The present invention includes: a displacement altering unit for generating a displacement control pressure corresponding to a displacement control signal; an input unit for inputting a target displacement; a pressure calculating unit for calculating a displacement control pressure corresponding to the target displacement based upon predetermined reference characteristics of the displacement altering unit; a pressure detecting unit for detecting a pressure corresponding to the displacement control pressure; a signal calculating unit for calculating a displacement control signal corresponding to the input target displacement; and a correcting unit for correcting the displacement control signal calculated by the signal calculating unit based upon the displacement control pressure having been calculated by the pressure calculating unit and the measured pressure detected by the pressure detecting unit.

Abstract: [Problem] To provide a large hydraulic excavator permitting an easy change from a machine mode corresponding to a backhoe excavator to a machine mode corresponding to a loader excavator, and vice versa. [MEANS for Solving the Problem] Arranged are a hydraulic circuit 1 provided with hydraulic pumps 11-18 and directional control valves 21-35, solenoid valves 41-43, 51-66 for controlling hydraulic pumps 11-18 and the directional control valves 21-35, and a controller 70 for controlling the solenoid valves 41-43, 51-66 in accordance with operation of control lever devices 80-83 and control pedal devices 84-87. The controller 70 performs control of the solenoid valves 41-43, 51-66 in a backhoe mode or loader mode selectively instructed by a mode instruction means 71.

Abstract: [Object] To permit an precise and easy adjustment of a pump absorption torque of a main pump in accordance with environmental conditions or the like when a sub-pump different in characteristics from the main pump is connected to a prime mover. [MEANS FOR ACHIEVING THE OBJECT] An adjustment switch 25 is arranged.

Abstract: The present invention includes: a displacement altering means 4 for generating a displacement control pressure P corresponding to a displacement control signal i; an input means 12 for inputting a target displacement ?; a pressure calculating means 10 for calculating a displacement control pressure P corresponding to the target displacement ? based upon predetermined reference characteristics of the displacement altering means 4; a pressure detecting means 5 for detecting a pressure Pa corresponding to the displacement control pressure P; a signal calculating means 10 for calculating a displacement control signal i corresponding to the input target displacement ?; and a correcting means 10 for correcting the displacement control signal calculated by the signal calculating means 10 based upon the displacement control pressure P having been calculated by the pressure calculating means 10 and the measured pressure Pa detected by the pressure detecting means 5.