Patent ID: 6327529
Filing Date: 2001-12-04
Classification: F16H,Y10T

Abstract:
A method for controlling range shifting in a controller-assisted, manually shifted vehicular transmission system (10) comprising an internal combustion engine (12) driving an input shaft (24) of a compound transmission (16) having a multiple-ratio main section (16A) shifted by a shift lever (26) manually movable in a shift pattern and a range auxiliary section (16B) connected in series with said main section, a range shift mechanism (28) for automatically implementing manually initiated range shifts and a controller (54) for receiving input signals (52) indicative of system operating conditions and for processing same according to predetermined logic rules to issue command output signals (56) to system actuators, including said range shift mechanism, said method comprising the steps:(a) determining a corresponding low range ratio (GR.sub.CLR) for at least one high range ratio of said transmission; and(b) if (i) said transmission is engaged in one of said at least one high range ratio, (ii) calculated engine speed in said high range ratio is less than a predetermined minimum engine speed value (OS*GR<ES.sub.MIN), and (iii) calculated engine speed in said corresponding low range ratio of said high range ratio is less than a predetermined maximum engine speed value (OS*GR.sub.CLR <ES.sub.MAX), then commanding said range shift mechanism to downshift into said corresponding low range ratio without driver initiation of a range shift.