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Hybrid work vehicle with load dependent target state of charge

  • US 9,598,838 B2
  • Filed: 11/06/2013
  • Issued: 03/21/2017
  • Est. Priority Date: 11/07/2012
  • Status: Active Grant
First Claim
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1. A work vehicle comprising:

  • an engine;

    an accelerator pedal for controlling a speed of the engine;

    a motor generator driven by the engine;

    a hydraulic pump driven by at least either of the motor generator and the engine;

    a work device driven by hydraulic fluid from the hydraulic pump;

    an operating device for outputting operation signals for driving the work device in accordance with an operation amount;

    an electric traction motor for driving a plurality of wheels;

    a brake pedal for controlling a braking force for the wheels;

    an electrical storage device connected to the motor generator and to the electric traction motor and charged electrically on a basis of a target value of a state of charge (SOC) of the electrical storage device as a target SOC; and

    a control device configured to vary the target SOC for the electrical storage device on a basis of a total demanded power value that totals a first power value demanded by the hydraulic pump and a second power value demanded by the electric traction motor, and to control a current SOC of the electrical storage device to approach the target SOC,wherein the control device is further configured to;

    calculate the first power value from input values including the operation amount of the operating device, and calculate the second power value from input values including a speed of the work vehicle and a stepping amount of the accelerator or brake pedal, thereby calculating the total demanded power value,determine a load condition of the work vehicle to be a light load when the total demanded power value is lower than a first setting value P1, determine the load condition of the work vehicle to be an intermediate load when the total demanded power value is lower than a second setting value P2 and higher than the first setting value P1, and determine the load condition of the work vehicle to be a heavy load when the total demanded power value is higher than or equal to the second setting value P2,set the target SOC to be higher when the load condition of the work vehicle is determined to be the light load than when the load condition of the work vehicle is determined to be the intermediate load,calculate a power generation command for the motor generator for use in charging the electrical storage device on the basis of a deviation between the current SOC of the electrical storage device and the target SOC, andcontrol the motor generator based on the power generation command, thereby controlling the current SOC of the electrical storage device to approach the target SOC.

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