| 摘要 |
<p>In a manual mode of a switch (40) engine speed control is determined by signal (SLP) from a speed lever (52), acting on the engine (10) by way of a governor (32) responsive also to an engine speed feedback signal from a sensor (48). The ratio of a multi-speed transmission is determined manually by means of a gear-shift lever (16). In an automatic mode a selector switch (42) determined whether the speed lever (52) commands engine speed or ground speed. In the former case the governor (32) acts as in the manual mode and an electronic control unit (30) takes over the transmission ratio selection via a stepping motor (24) and shifts down or up as may be needed to prevent the engine speed drooping or rising outside a permissible band centred on the commanded engine speed. In the automatic, ground speed mode, the speed lever signal (SLP) is treated as a commanded ground speed signal which the control unit (30) compares with actual ground speed, computed from the actual engine speed signal and the current transmission ratio or gear number signalled by an encoder (26). The control unit (30) now determines the signal (ESC) which command engine speed (instead of SLP) and also selects the appropriate transmission ratio via the stepping motor (24), seeking always to minimise fuel comsumption, which is signalled by a mass fuel flow signal (MFF).</p> |
