Semi-automatic mechanical transmission control and control method

A method of controlling a semi-automatic mechanical change gear transmission system (10) comprising a manual fuel throttle control (24), a fuel throttle controlled engine (14), a multi-speed change gear mechanical transmission (12), a friction master clutch (16) interposed the engine and transmission, a manually operated master clutch control (3), a manually operated shift selection lever (1) moveable in a first direction from a centered position to select upshifts and in a second direction from said centered position to select downshifts from the currently engaged gear ratio, a central processing unit (38) for receiving inputs indicative of transmission input shaft and output shaft rotational speeds, of vehicle speed, of engine speed and of operation of said shift selection lever and for processing same according to predetermined logic rules to issue command output signals to non-manually controlled operators including a clutch operator (30), a fuel throttle control operator (26), and a transmission operator (34), said processing unit sensing operation of said manual shift selection lever including the direction of movement thereof and the number of displacements of said lever within a predetermined period of time from said centered position, and, in a first mode of operation, determining the transmission gear ratio selected by the operator to be shifted directly into from the currently engaged ratio by assuming each repetition of displacement from the centered position of said shift selection lever in a given direction indicates operator selection of a change of one additional consecutive ratio in said direction;

• said method comprising:
• providing said central processing unit with a signal (THPS) indicative of the operators manual engagement of the throttle control;
• providing said central processing unit with a signal indicative of manual disengagement of the friction master clutch;
• and,
• automatically selecting operation in a second mode of operation wherein a single displacement of said shift selection lever from the centered position in the second direction is interpreted as an operator selection of a downshift directly into transmission neutral if vehicle ground speed is less than a predetermined minimum vehicle ground speed reference value, the master clutch is manually disengaged and the operators manual engagement of the throttle control is not sensed.