Range shift control

A control system which controls range shifting in a vehicular transmission system comprising a fuel-controlled engine, a compound transmission driven by said engine and having a main transmission section connected in series with a range section, said range section defining a high-range ratio and a low-range ratio, a range section shift actuator for shifting said range section, a manually operated shift selector for shifting said main transmission section, a range shift selector for selecting a shift in said range section, a fuel controller for controlling fueling of said engine, and a system controller for receiving input signals, including signals indicative of one or more of (i) vehicle speed, (ii) engine rotational speed, (iii) engaged condition of said main transmission section, (iv) engaged condition of said range section, and (v) operation of said range shift selector, and for processing said input signals in accordance with predetermined logic rules to determine vehicle operating conditions and to issue command output signals to system actuators including one or more of (i) said range shift actuator and (ii) said fuel controller, said system comprising:

• means for determining (i) a range shift has been initiated and (ii) the engaged conditions of said main transmission section and said range section;
• and
• means effective, if said main section is engaged while said range section is not engaged, for (i) determining a target gear ratio corresponding to the engaged main section gear ratio and for (ii) causing said fuel controller to fuel said engine to cause engine rotational speed to be substantially equal to engine synchronous speed for engaging said target ratio (ES=(OS*GR.sub.T).+-.Y) while continuing to complete shifting of said range section.

A computer program product which controls range shifting in a vehicular transmission system comprising a fuel-controlled engine, a compound transmission driven by said engine and having a main transmission section connected in series with a range section, said range section defining a high-range ratio and a low-range ratio, a range section shift actuator for shifting said range section, a manually operated shift selector for shifting said main transmission section, a range shift selector for selecting a shift in said range section, a fuel controller for controlling fueling of said engine, and a computer-based system controller for receiving input signals, including signals indicative of one or more of (i) vehicle speed, (ii) engine rotational speed, (iii) engaged condition of said main transmission section, (iv) engaged condition of said range section, and (v) operation of said range shift selector, and for processing said input signals in accordance with predetermined logic rules to determine vehicle operating conditions and to issue command output signals to system actuators including one or more of (i) said range shift actuator and (ii) said fuel controller, said program having codes for:

• determining a range shift has been initiated and the engaged conditions of said main transmission section and said range section;
• and if said main section is engaged while said range section is not engaged, determining a target gear ratio corresponding to the engaged main section gear ratio and causing said fuel controller to fuel said engine to cause engine rotational speed to be substantially equal to engine synchronous speed for engaging said target ratio (ES=(OS*GR.sub.T).+-.Y) while continuing to complete shifting of said range section.