| 摘要 |
<p>A control system for controlling change speed gearing (A) of a vehicle for transmitting output of an engine (1) in varied speeds to wheels. This system has a first clutch mechanism mounted in a drive transmitting line between the engine and the change speed gearing, the first clutch mechanism including two hydraulically operable clutches (5, 6) for forward drive and backward drive, and a backward-forward changeover valve (32) for selectively operating the two clutches; a second clutch mechanism mounted in a drive transmitting line between the change speed gearing and the wheels, the second clutch mechanism including a quick operating clutch (19) for quickly making and breaking drive transmission, and a clutch control valve (26) for controlling the quick operating clutch; actuators (T1, T2) for shifting the change speed gearing; and a control unit (30) operatively connected to the backward-forward changeover valve, clutch control valve and actuators. In response to start of a shifting operation of the actuators, the quick operating clutch is disengaged and an engaged one of the hydraulically operable clutches of the first clutch mechanism is reduced to a predetermined low pressure. In response to completion of the shifting operation of the actuators, the quick operating clutch is engaged and the clutch of the first clutch mechanism is gradually raised from the predetermined low pressure.</p> |
