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Speed change control method and apparatus for an automatic transmission for vehicles traveling under various road conditions

  • US 5,390,116 A
  • Filed: 03/13/1992
  • Issued: 02/14/1995
  • Est. Priority Date: 03/13/1991
  • Status: Expired due to Fees
First Claim
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1. A speed change control method for an automatic transmission which is provided on a vehicle and which has a plurality of gear positions including a lowest-speed gearshift position, comprising the steps of:

  • (a) detecting a value of a parameter related to frictional resistance of a road surface on which the vehicle is traveling;

    (b) detecting a start of the vehicle from a stop position; and

    (c) prohibiting gearshift to said lowest-speed gearshift position if the frictional resistance of the road surface is judged to be low based on the value of the detected said related parameter at the time of detecting a start.

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