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Charge depleting energy management strategy for plug-in hybrid electric vehicles

  • US 8,140,204 B2
  • Filed: 12/10/2007
  • Issued: 03/20/2012
  • Est. Priority Date: 12/10/2007
  • Status: Active Grant
First Claim
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1. An energy management method for a plug-in hybrid electric vehicle powertrain having an engine, at least one electric machine, a battery, and a power transmission mechanism for delivering engine power and battery power to vehicle traction wheels, the method comprising:

  • monitoring battery state-of-charge;

    controlling the battery state-of-charge whereby battery power discharge is below a power discharge limit;

    monitoring driver demand for power at the vehicle traction wheels;

    maintaining the engine in an engine-off state to achieve an all-electric drive when battery state-of-charge is greater than a predetermined battery charge threshold and driver demand for power is less than a minimum calibrated engine power threshold level for an engine start below which engine thermal efficiency becomes low;

    controlling the engine to turn the engine on when the driver demand for power is equal to or greater than the minimum calibrated engine power threshold level; and

    increasing engine power when a driver demand for power is greater than a sum of minimum engine power and the power discharge limit whereby the engine operates at an engine power level greater than the minimum engine power.

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