| 摘要 |
A pressurized fluid-operated, three-position shift actuator piston assembly (12) and associated control system (10) are provided. The system requires only a single controlled source of pressurized fluid (A) to provide movement to and retention in a selected one of three axially displaced positions (D, N, OD). A differential area piston fixed for axial movement of a shift actuator, said (180A), said differential area piston having a larger face (20A) exposed to pressurized fluid in a selectably, variably pressurized first chamber (26) and an opposed smaller face (20B) exposed to pressurized fluid in a constantly pressurized second chamber (30), pressurized fluid on said larger face causing a force urging said shaft in said first axial direction and pressurized fluid on said smaller face causing a force urging said shaft in said second axial direction; and a secondary piston (22) having a face (22C) opposed to said smaller face of said differential area piston and exposed to pressurized fluid in said second chamber, said secondary piston effective to apply a force in said first axial direction to said shaft only if said controlled device is displaced in said second axial direction from said neutral position. |
