Patent ID: 9598842
Date: 2017-03-21
CPC Classifications: E02F,F15B

Claim:
1. A construction machinery comprising: an actuator; a first hydraulic pump for discharging hydraulic oil for driving the actuator; a first prime mover for driving the first hydraulic pump; a second hydraulic pump for discharging hydraulic oil for driving the actuator; a second prime mover for driving the second hydraulic pump; an energy storage device for storing energy for driving the second prime mover; and a hydraulic oil supply circuit including a hydraulic oil switching section that accepts hydraulic oil discharged from the first hydraulic pump and hydraulic oil discharged from the second hydraulic pump and supplies either a mixture of the accepted hydraulic oils or a selected one of the accepted hydraulic oils to the actuator; wherein the construction machinery comprises a control device that, when drive efficiency of the second hydraulic pump is higher than a preselected setting value, outputs a switch command to the hydraulic oil switching section and a drive command to the second prime mover; wherein the control device that, when the drive efficiency of the second hydraulic pump is lower than the preselected setting value, outputs the switch command to the hydraulic oil switching section and a rotation speed reduction command or a stop command to the second prime mover; wherein the construction machinery comprises a discharge pressure sensor for detecting a discharge pressure of the first hydraulic pump, wherein the control device acquires the discharge pressure of the first hydraulic pump, which is detected by the discharge pressure sensor, outputs the drive command to the second prime mover when the discharge pressure of the first hydraulic pump is higher than a predetermined reference pressure, and outputs the rotation speed reduction command or the stop command to the second prime mover when the discharge pressure of the first hydraulic pump is lower than the predetermined reference pressure, and wherein the control device outputs the switch command to the hydraulic oil switching section so as to accept the hydraulic oil discharged from the first hydraulic pump and the hydraulic oil discharged from the second hydraulic pump and supply either the mixture of these two hydraulic oils or the hydraulic oil discharged from the second hydraulic pump to the actuator when the discharge pressure of the first hydraulic pump is higher than the predetermined reference pressure, and supply the hydraulic oil discharged from the first hydraulic pump to the actuator when the discharge pressure of the first hydraulic pump is lower than the predetermined reference pressure.