| 摘要 |
PURPOSE: A downshift control method of an automatic transmission is provided to reduce down shift shock by preventing non-matching time from lengthening excessively with varying the down shift line according to output of an engine. CONSTITUTION: The downshift is detected(100), and vehicle speed, throttle opening degree and atmospheric pressure are detected in shifting down(101). The detected atmospheric pressure is decided to be less than the reference value(102), and time is counted in case of the detected atmospheric pressure to be less than the reference value(103). Decision time for changing the downshift line is detected to be over the reference time, and pressure of surroundings is detected to be less than the atmospheric pressure(104). Variation of the shift line is calculated in case of the decision time changing the downshift line to be over the reference time(105). The shift line is changed in calculating the variation of the shift line(106), and downshifting is performed in changing the shift line(107). The downshift line is changed according to changes of engine output, and excessive extension of non-matching time is prevented.
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