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System and method for controlling an automatic four-wheel drive transfer case which prevents excessive slippage

  • US 6,568,256 B1
  • Filed: 08/10/2000
  • Issued: 05/27/2003
  • Est. Priority Date: 08/10/2000
  • Status: Active Grant
First Claim
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1. A system for controlling a transfer case which is operatively disposed within a four-wheel drive vehicle of the type having a selectively positionable throttle, a front driveshaft which rotates at a first speed, and a rear driveshaft which rotates at a second speed, said transfer case being adapted to selectively provide torque to said front and said rear driveshaft and to selectively operate in an automatic four-wheel drive mode and in a locked four-wheel drive mode, said system comprising:

  • a first sensor which measures said first speed and which generates a first signal representing said first speed;

    a second sensor which measures said second speed and which generates a second signal representing said second speed;

    a third sensor which measures a position of said throttle and which generates a third signal representing said position; and

    a controller which is communicatively coupled to said transfer case and to said first sensor and to said second sensor, which receives said first, second, and third speeds, which utilizes said first signal and said second signal to calculate a delta shaft speed and which utilizes said delta shaft speed and said third signal to estimate an amount of heat generated by said transfer case, said controller being further effective, when operating in said automatic four-wheel drive mode, to automatically switch from said automatic four-wheel drive mode to said locked four-wheel drive mode when said estimated amount of heat exceeds a predetermined threshold value.

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