| 摘要 |
1. A pressure fluid, inter alia a hydraulic fluid, device for controlling ratio changes of a stepped-ratio gearbox by means of hydraulic rams (2, 3) each adapted to move a slider (4) actuating a ratio-changing fork (5), the rams being supplied with fluid seriatim by distribution means (D) controlled by an operator, inter alia the driver of a motor vehicle, a clutch system (E) being disposed between the gearbox input and a driving engine, the distribution means (D) comprising a rotary distributor (17) comprising an inlet port (18), exhausting means and connecting ports (20-23) connected to each ram, the distributor being adapted to connect in its consecutive angular positions a single connecting port and, therefore, a single ram to the inlet port (18), all the other connecting and ram ports being connected to the exhaust, the control device comprising a rotary selector (28) corotating with the distributor, characterised in that the rotary distributor (17) has at least one outlet port (19) and is adapted to connect thereto every ram except the ram connected to the inlet port (18) ; the distribution means (D) comprise an electrically controlled valve (24) disposed in a line (25) connected to the distributor inlet port (18), the electrically controlled valve being adapted to connect the inlet port (18), according to the state of the electrically controlled valve, either to a hydraulic inlet (26) or to an exhaust (27) ; and the rotary selector (28) is combined with electrical contacts to so control the electrically controlled valve (24) as to supply the inlet port with hydraulic fluid at least when the ratio is engaged, whereas the inlet port (18) is connected to the exhaust as long as the declutching and/or the disengagement of all the ratios is/are not operative. |
