Shift control apparatus of automatic transmissions

Abstract

As the disengage pressure command value PO lowers and as the engagement pressure command value PC rises, a changeover shift is effected by bringing a disengagement side friction element into disengagement and a disengagement side friction element into engagement. The rising gradient of the engagement pressure command value PC at and after the ON instant t2 of the oil pressure switch, when the engagement side friction element takes the engaging capacity, is made as low as γ1 for a low throttle opening degree but as high as γ2 for a high throttle opening degree, and the lowering gradient of the disengagement side pressure command value PO is also made as small as β1 at the low throttle opening degree and as large as β2 at the high throttle opening degree. As apparent from the comparison (θ1<θ2) between (B) illustrating the time-series changes of the turbine speed Nt at the high throttle opening degree and (C) illustrating the time-series changes of the turbine speed Nt at the low throttle opening degree, therefore, the shift advances slowly at the low throttle opening degree, and the change in the transmission output torque TO in a zero cross TOT can be made gentle to cause neither any backlash noise, as apparent from the sound pressure level change, nor any tossing shock just after the end of the torque phase.

Dependencies are inferred from the claim text.