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Hybrid construction machine

  • US 8,924,100 B2
  • Filed: 08/18/2011
  • Issued: 12/30/2014
  • Est. Priority Date: 09/08/2010
  • Status: Active Grant
First Claim
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1. A hybrid construction machine comprising:

  • a variable displacement hydraulic pump which discharges hydraulic oil for a hydraulic actuator;

    an engine which drives the hydraulic pump;

    an electric motor which is driven by the engine to charge generated electric power into an electric storage device and which is driven by the electric power charged in the electric storage device so as to assist the engine to drive the hydraulic pump; and

    a controller which controls driving of the hydraulic pump, the engine and the electric motor;

    characterized in that;

    the controller includes an engine power calculating unit which calculates power generated by the engine, a first rotation speed calculating unit which calculates a rotation speed of the engine to minimize fuel required for generating the engine power, a second rotation speed calculating unit which determines a lower limit of a target rotation speed of the engine, a target rotation speed calculating unit which selects a larger one of a first rotation speed outputted from the first rotation speed calculating unit and a second rotation speed outputted from the second rotation speed calculating unit, an engine control unit which controls the engine so as to make a real rotation speed of the engine approach the target rotation speed, a target flow rate calculating unit which calculates a target flow rate of the hydraulic oil discharged from the hydraulic pump, and a hydraulic pump control unit which controls displacement of the hydraulic pump based on the real rotation speed or the target rotation speed of the engine so that a flow rate of the hydraulic oil discharged from the hydraulic pump approaches the target flow rate;

    a target maximum total power calculating unit which calculates a target maximum value of total power of the engine and the electric motor is provided;

    the second rotation speed calculating unit calculates a minimum rotation speed of the engine required for generating the target maximum total power in the engine and the electric motor; and

    the target maximum total power calculating unit calculates the target maximum total power based on a dial position of an engine control dial.

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