Construction machine

摘要

Construction machine capable of incorporating an engine and using an external power source. The construction machine includes an electrical storage device performing a charge with the external power source, uses the electrical storage device to provide assist when the power of the engine is insufficient, uses an electrical charge in the electrical storage device systematically in accordance with work time, and efficiently uses the electrical storage device by controlling its discharge amount in accordance with load status. The construction machine includes the engine, accessory loads connected to the engine, an assist electric motor driven by the engine, electrical power converters for converting an AC current, which is the output current of the assist electric motor, to a DC current, and the electrical storage device connected to the DC side of each electrical power converter. The electrical storage device becomes charged through a charging device from the external power source.

主权项

1. A construction machine having an engine, an assist electric motor that is coaxially and mechanically connected to the engine, and an electrical power converter that is connected to the assist electric motor and to an electrical storage device in order to control the voltage of the assist electric motor and the voltage of the electrical storage device, the construction machine comprising:
a charging device connected to the electrical storage device, the electrical storage device being capable of becoming charged through the charging device from an external power source (EPS); and charge-discharge control means for:
determining a charge amount target value (Q*) for the electrical storage device in accordance with estimated work time (Ts) of the construction machine; andcontrolling a charge/discharge amount by charging the electrical storage device when a charge amount (Q) of the electrical storage device is lower than a first threshold value determined using the charge amount target value (Q*) and discharging the electrical storage device when the charge amount (Q) of the electrical storage device exceeds a second threshold value determined using the charge amount target value (Q*), wherein the charge amount target value (Q*) is set to be equal to a minimum charge amount (Qmin) of the electrical storage device at the end of work time period,wherein the charge/discharge control means includes a charge amount target value computation section that computes the charge amount target value (Q*) for the electrical storage device in accordance with work time (T) of the construction machine and with the predefined estimated work time (Ts), and a charge/discharge target value computation section that discharges the electrical storage device when the charge amount (Q) of the electrical storage device is larger than the second threshold value that is a charge amount (Q*+Qa) determined in accordance with the charge amount target value (Q*) and with a predetermined value (Qa), and charges the electrical storage device when the charge amount (Q) of the electrical storage device is smaller than the first threshold value that is a charge amount (Q*−Qc) determined in accordance with the charge amount target value (Q*) and with a predetermined value (Qc).