Off-going clutch control for upshifting of an automatic transmission
 An improved transmission upshift control in which the off-going clutch is controlled to emulate the behavior of an ideal free-wheel device to thereby achieve nearly ideal timing of the off-going clutch disengagement relative to the on-coming clutch engagement. During the preparation phase of the shift, the off-going pressure is reduced in proportion to the estimated volume of fluid supplied to the on-coming clutch such that the off-going pressure is at a calibrated value when the on-coming clutch is filled. However, the calibrated value is adjusted upward in direct relation to the transmission input torque above a given level so as to emulate the reaction torque that would be exerted by an ideal free-wheel device for maintaining the current speed ratio. The torque phase of the control commences when the estimated volume indicates that the on-coming clutch is completely filled. At such point, the off-going clutch pressure decreases from the calibrated value at a rate determined as a function of the scheduled on-coming clutch torque to emulate the rate of decay that would occur with an ideal free-wheel device as the on-coming clutch engages. If the confidence level is low, the off-going clutch control parameters are biased to extend the engagement of the off-going clutch. If the extended engagement of the off-going clutch results in a tie-up condition due to engagement of the on-coming clutch, the off-going pressure is quickly released. 
General Motors Corporation
F F F
F16H F16H F16H
inventional additional additional
Gregory A Todd M
Hubbard Steinmetz