| 摘要 |
A hydraulic actuation system, eg for an automatic transmission, comprises a clutch actuator 22, a clutch control valve 120, gear engagement actuators 114,115, a master control valve 150 and gear engagement control valves 152, 154. Upon initiation of a gear change, clutch control valve 120 is energized to move it from its first position (Fig 3) to a third position (Fig 5) which connects the clutch actuator 22 to the hydraulic accumulator 275 via the master control valve 150. At the same time, a current pulse moves gear engagement control valves 152, 154 from their first position (Fig 3) to their third (Fig 5) which connects the head ends of actuators 114, 115 to the main control valve 150. At the end of the pulse, a current is applied to the solenoids of gear engagement control valves 152, 154 to hold them in their second, null, position (Fig 4). At the same time a current pulse is applied to the solenoid of master control valve 150 until pressure in the rod ends of actuators 114, 115 and inlets of the gear engagement control valves 152, 154 begins to rise. The master control valve 150 is then energized to give a predetermined pressure to the rod ends, by switching itself between its first, second and third positions (Figs 3,4 and 5 respectively). The gear engagement control valves 152,154 are then moved to their first (Fig 3) or third (Fig 5) position to achieve movement of the actuators 114, 115 to select the required gear. The gear engagement control valves 152, 154 are then moved to their second, null, position (Fig 4) to lock the actuators 114, 115 in the selected gear. Clutch control valve 120 then connects actuator 22 to the reservoir, so that the clutch can re-engage. All the solenoids are then de-energized. |
