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Electronic shift controller for a multiple ratio automotive transmission

  • US 5,383,825 A
  • Filed: 05/25/1993
  • Issued: 01/24/1995
  • Est. Priority Date: 05/25/1993
  • Status: Expired due to Term
First Claim
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1. An electronic control system for a multiple ratio automatic transmission for use in an automotive vehicle driveline having a throttle controlled internal combustion engine, said transmission having gearing elements defining a first speed ratio and a second speed ratio;

  • fluid pressure actuated clutch and brake means for controlling the relative speeds of said gearing elements to effect speed ratio changes between said first and second speed ratios;

    said clutch and brake means including a friction brake adapted to anchor a reaction element of said gearing that is common to both of said speed ratios and a friction clutch adapted to connect two of said gearing elements together to effect said second speed ratio, said friction clutch being released and said friction brake being applied to effect a speed ratio downshift;

    a fluid pressure operated brake servo means for applying and releasing said brake and a fluid pressure operated actuator for applying and releasing said clutch, said brake servo having a pressure actuated piston defining in part a brake apply pressure chamber and a brake release pressure chamber; and

    means for regulating the rate of exhaust of pressure from said clutch actuator and from said brake release pressure chamber in response to changes in vehicle driveline operating variables thereby achieving smooth speed ratio changes.

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