| 摘要 |
A powershift transmission includes a plurality of hydraulically operated clu tch packs which are selectively engaged and disengaged to enable various gear ratios. A control circuit for such a transmission includes a system pressure source, a fluid r eservoir, a control gallery, a plurality of control valves and a plurality of latching valves. E ach control valve and each latching valve is connected with a corresponding one of the clutch pack s, and is communicated with each other, with the system pressure source, with the rese rvoir and with the control gallery. The control valves, latching valves and the control gal lery cooperate to prevent pressurization of any one of the clutch packs before all the clutch packs are filled with hydraulic fluid. The control valves and the latching valves also cooper ate to maintain disengaged clutch packs at reservoir pressure, and to maintain engaged clutc h packs at system pressure. |
