| 摘要 |
A hydraulic operating circuit for friction power-shift clutches (1a-2b) for tractor gearboxes, in which the hydraulic actuators (2) of the clutches are operatively associated with respective valve units (13, 18) which are connected in series and are operated by electronically-controlled piloting means adapted to achieve the combined engagement and disengagement of the clutches for effecting changes of speed ratio without interrupting the transmission of torque. The circuit enables the simultaneous modulation of several clutches by a single electronically-controlled, proportional pressure reducing valve (20), the pressure of the remaining clutches being kept unchanged. The proportional valve (20) enables the piloting of the bringing together of the friction discs of the clutches, the modulation and the maintenance of the pressure. |
