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Load control structure for work vehicle

  • US 7,469,534 B2
  • Filed: 09/13/2006
  • Issued: 12/30/2008
  • Est. Priority Date: 09/26/2005
  • Status: Active Grant
First Claim
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1. A load control structure for a work vehicle comprising:

  • means for detecting operating position of a manually operated speed change operating element;

    engine load detection means for detecting load on an engine of the work vehicle;

    swash plate position detecting means for detecting an operating position of a swash plate of a variable displacement pump of a hydrostatic continuously variable speed change device;

    pump operating means for steplessly operating the swash plate of the variable displacement pump;

    motor operating means for operating a swash plate of a variable displacement motor of the hydrostatic continuously variable speed change device between at least two speed change positions including a higher speed position and a lower speed position; and

    control means for controlling the operations of the pump operating means and the motor operating means;

    wherein the control means has;

    automatic pump swash plate control means for controlling the operation of the pump operating means, based on detected information from the load detection means and detected information from the swash plate position detecting means, such that the greater an engine load is, greater is the extent to which the swash plate of the variable displacement pump is operated to a low speed side; and

    motor swash plate control means for controlling the motor operating means so as to change the position of the swash plate of the variable displacement motor between the at least two speed change positions, andwherein the control means further has automatic motor swash plate control means for controlling the motor operating means such that the swash plate of the variable displacement motor is moved from the higher speed position to the lower speed position when the engine load rises beyond a first predetermined value and such that the swash plate of the variable displacement motor is moved from the lower speed position to the higher speed position when the engine load decreases below a second predetermined value.

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