| 摘要 |
A method is provided for controlling overspeed conditions of an electronically controlled transmission and engine wherein the transmission has an output shaft and is electronically shiftable by an electronic shift control module between forward and reverse gears to rotate the output shaft in forward and reverse directions and a neutral gear without shaft rotation. The transmission has an operator controlled shift lever for requesting a gear from the forward, neutral and reverse gears and operates in a present gear from among the forward, reverse and neutral gears. The method includes determining forced downshift shift points, overspeed downshift shift points, overspeed upshift shift points, a directional shift inhibit speed, and overspeed values for each gear based on transmission speed; determining output shaft speed; and operating the shift lever to request a gear. The method also includes downshifting the transmission to lowest possible gear, using the forced downshift shift points, without overspeeding for more than 2.2 seconds and sequentially changing gears until the requested gear is reached when the requested gear is a lower gear than the present gear and the requested gear has just been requested; temporarily upshifting the transmission, using the overspeed upshift shift points, when the transmission shaft output speed exceeds speed for present gear for more than 2.5 seconds, then downshifting to the requested gear using the overspeed downshift shift points; downshifting the transmission to lowest possible gear in requested direction of travel, using the forced downshift shift points, in response to a change of direction request when the transmission shaft output speed is overspeed for the requested gear but not above directional shift inhibit speed; and downshifting transmission to lowest possible gear in direction of travel, using the forced downshift shift points, in response to a change of direction request when the transmission shaft output speed exceeds direction shift inhibit speed.
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