Patent ID: 6520040
Filing Date: 2003-02-18
Classification: F16H,Y10T

Abstract:
A method for controlling range section shifting in a manually shifted, vehicular compound transmission having a manually shifted main section connected in series with a range section having a high range ratio and a low range ratio, said main transmission section having a plurality of ratio positions (1/5, 2/6, 3/7, 4/8) available in both high and low range, including a highest ratio position (4/8) and a lowest ratio position (1/5), a sensor for sensing a current position of a shift selector manually movable in a shift pattern to selectively engage and disengage main section ratios, a range section actuator for shifting the range section in response to command signals, a manually operated range switch for selecting engagement of one of the high or low range ratios, a speed sensor for sensing vehicle speed and providing a signal indicative thereof, and a controller for receiving input signals, including said signals indicative of the current position of the shift selector and of vehicle speed, and processing same according to predetermined logic rules to issue command output signals to system actuators, including said range section actuator, said method including the steps of:(i) determining vehicle speed, position of the range selector switch, previously engaged ratio and target ratio; (ii) if (a) vehicle speed exceeds a reference (OS>REF), (b) the range selector switch is in the low range ratio position, (c) the previously engaged ratio position is the highest ratio position (4/8), and (d) the target ratio position is the lowest ratio position (1/5), then commanding the range actuator to shift to the high range ratio; and (iii) if any one of (ii)(a), (ii)(b), (ii)(c) or (ii)(d) is not true, allowing the range actuator to shift the range section to the range ratio indicated by the range selector switch.