Abstract: To provide an engine control system for a construction machine, which can decrease a consumption of energy to be required for the reduction of an engine lag-down that occurs upon a sudden increase in load, such as upon quick manipulation of a control device, is provided with a load condition detecting unit, a charge amount detecting unit, a boost pressure sensor, and a determination processing unit. The load condition detecting unit includes a manipulation stroke detector for detecting that a control device has been fully manipulated, and also, a first computation unit of a controller. The charge amount detecting unit can detect an amount of charge in a capacitor. The determination processing unit includes a determination processing unit of the controller.

Abstract: On the basis of reference torque and torque correction amount output units (T1 and T2), a torque control command pressure is calculated so that the input torques of first and second pumps are increased. The calculated torque command instruction pressure is then supplied as external command pressure to the varying mechanism of a regulator used for the first and second pumps so as to prevent the input torques of the first and second pumps from being decreased more than necessary. As a result, even when three variable displacement hydraulic pumps are used with the discharge pressure of one of the hydraulic pumps reduced by a pressure reducing valve and further the input torques of the other two hydraulic pumps are decreased by that pressure, the engine output can be efficiently utilized, and the work rate does not decrease.

Abstract: To provide an engine lug-down suppressing device for hydraulic work machinery, capable of suppressing deterioration in operability of a hydraulic actuator when the hydraulic actuator is caused to operate quickly from a stopped state. Pilot pressure to a tilting control unit of a variable displacement hydraulic pump is controlled by a solenoid valve. A controller controls the solenoid valve in accordance with a target rotational speed signal from an input unit. This control differs according to whether or not a detector detects the pilot pressure created by an operating lever device. In an entire range of the target engine rotational speed, pump absorption torque at the time when the pilot pressure is not detected, falls within a range equal to or smaller than pump absorption torque at the time when the pilot pressure is detected, and is set to approach the pump absorption torque at the time when the pilot pressure is detected with an increase in the target engine rotational speed.

Abstract: To provide an engine control system for a construction machine, which can decrease a consumption of energy to be required for the reduction of an engine lag-down that occurs upon a sudden increase in load, such as upon quick manipulation of a control device, is provided with a load condition detecting unit, a charge amount detecting unit, a boost pressure sensor, and a determination processing unit. The load condition detecting unit includes a manipulation stroke detector for detecting that a control device has been fully manipulated, and also, a first computation unit of a controller. The charge amount detecting unit can detect an amount of charge in a capacitor. The determination processing unit includes a determination processing unit of the controller.

Abstract: Torque control for a construction machine three-pump system that can accurately control the total absorption torque of first, second, and third hydraulic pumps and effectively use the output torque of an engine. A pump base torque computation section 42 calculates a pump base torque Tr from a target rotation speed. A subtraction section 44 calculates a reference value Tf for the maximum absorption torque available to the first and second hydraulic pumps 2, 3 by subtracting a third pump reference absorption torque T3r from the pump base torque Tr. A correction torque computation section 45 calculates a correction torque value from the delivery pressure of the third hydraulic pump 4. An addition section 46 calculates a target absorption torque Tn by adding the correction torque value Tm to the reference value Tf. A first regulator 31 is controlled so as to obtain the target absorption torque Tn.

Abstract: On the basis of reference torque and torque correction amount output units (T1 and T2), a torque control command pressure is calculated so that the input torques of first and second pumps are increased. The calculated torque command instruction pressure is then supplied as external command pressure to the varying mechanism of a regulator used for the first and second pumps so as to prevent the input torques of the first and second pumps from being decreased more than necessary. As a result, even when three variable displacement hydraulic pumps are used with the discharge pressure of one of the hydraulic pumps reduced by a pressure reducing valve and further the input torques of the other two hydraulic pumps are decreased by that pressure, the engine output can be efficiently utilized, and the work rate does not decrease.