Sequenced control of double transition powered downshifting in a

Details Sequenced control of double transition powered downshifting in a Sequenced control of double transition powered downshifting in a

1990-08-02

1992-05-12

Lall, Parshotam S.

Boots, shoes, and leggings

74866, 747321, B60K 4122, F16H 5946

Patent

active

051133431

ABSTRACT:
In an automatic transmission having an electronic control, a double transition powered downshift to a target range requires the release of two off-going clutches and the engagement of two on-coming clutches. The shift begins by releasing one clutch and applying another to begin (but not complete) an upshift to a third range having a speed ratio lower than both the initial range and the target range so that first an input speed increase occurs followed by an input speed decrease (pull-down). The speed decrease triggers respective application and release of the other clutches to arrest the upshift and complete the downshift. Each clutch application and release occurs gradually under an open loop control. Slip of the first off-going clutch, pull-down, speed sync at the low gear ratio and a near sync condition are determined from turbine speed and output speed and are used to time pressure command changes to smoothly coordinate clutch releases and applications.

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