Construction machine

Abstract

An object of the present invention is to provide a construction machine that is capable of effectively charging electrical power into the capacitor in consideration of the drive of a swing section and hydraulic work device. To achieve the object, the present invention grasps the status of the construction machine ( 2 ) in advance to calculate energy, predicts the next operation, determines the amount of energy to be charged into a capacitor ( 13 ), and controls a DC-DC converter ( 15 ) accordingly. Consequently, the loss in a conventional battery (lead storage battery) during regeneration can be reduced to provide increased efficiency.

1 . A construction machine comprising:
 an engine;   a hydraulic pump that is driven by the engine;   a motor-generator that is coupled to the engine and to the hydraulic pump and capable of generating electrical power;   a hydraulic work device that is driven by a hydraulic fluid discharged from the hydraulic pump;   a swing structure on which the hydraulic work device is mounted;   an AC motor that drives the swing structure;   a power supply system having a capacitor that supplies electrical power to the motor-generator and/or to the AC motor and that becomes charged with electrical power regenerated by the motor-generator and/or by the AC motor; and   a controller that controls the power supply system;   wherein the controller includes
 an motion estimation section that estimates the next motion of the hydraulic work device and/or the swing structure in accordance with the current operation performed by an operator, 
 an energy calculation section that calculates the amount of electrical power to be regenerated by the motor-generator and/or by the AC motor, in accordance with the estimated next operation, and 
 a capacitor control section that sets a target voltage for the capacitor in accordance with the calculated amount of electrical power. 
   
     
     
         2 . The construction machine according to  claim 1 ,
 wherein the capacitor control section includes a capacitor status detection section that detects the current voltage of the capacitor, a capacitor charge/discharge command calculation section that calculates a charge/discharge command for the capacitor in accordance with the calculated amount of electrical power and with the detected current voltage, and a capacitor target voltage setup section that sets a target voltage for the capacitor in accordance with the calculated charge/discharge command.   
     
     
         3 . The construction machine according to  claim 1 ,
 wherein the capacitor control section corrects the target voltage for the capacitor in accordance with the rotation speed of the engine, a torque command for the AC motor, and/or a torque command for the motor-generator.   
     
     
         4 . The construction machine according to  claim 1 ,
 wherein the controller includes a body control section that calculates the amount of electrical power to be requested from the swing structure in accordance with the current operation performed by the operator.   
     
     
         5 . A construction machine comprising:
 a power supply system having a capacitor that supplies electrical power to an AC motor for driving a swing structure and that becomes charged with electrical power regenerated by a motor-generator and/or by the AC motor, the swing structure being a structure on which the motor-generator and/or a hydraulic work device are mounted, the motor-generator being coupled to an engine and to a hydraulic pump and capable of generating electrical power, the hydraulic work device being driven by a hydraulic fluid discharged from the hydraulic pump; and   a controller that controls the power supply system;   wherein the controller estimates the next operation of the hydraulic work device and/or the swing structure in accordance with the current operation performed by an operator, calculates the amount of electrical power to be regenerated by the motor-generator and/or by the AC motor in accordance with the estimated next operation, and sets a target voltage for the capacitor in accordance with the calculated amount of electrical power.   
     
     
         6 . The construction machine according to  claim 5 ,
 wherein the controller calculates a charge/discharge command for the capacitor in accordance with the calculated amount of electrical power and sets the target voltage for the capacitor in accordance with the calculated charge/discharge command.   
     
     
         7 . The construction machine according to  claim 5 ,
 wherein the controller calculates the amount of electrical power in accordance with the rotation speed of the AC motor.   
     
     
         8 . The construction machine according to  claim 5 ,
 wherein the controller compares the current voltage of a capacitor to the target voltage for the capacitor, and if the current voltage of the capacitor is higher than the target voltage for the capacitor, supplies electrical power stored in the capacitor to the AC motor that drives the swing structure.