| 摘要 |
PROBLEM TO BE SOLVED: To provide a 3 position shift actuator for a transmission which is controllable via single variable pressure air source only. SOLUTION: A differential-area piston 20 and piston shaft 18 are slidably fitted in enlarged bore portion 16A of bore 16 and in reduced bore portion 16B of bore 16, respectively. A hollow piston 22 is fitted between a intermediate bore portions 16C of bore 16 and the piston shaft 18, with its movement being restricted by a stopper member 24. An on-board pressurized air source 44 is directly connected to the second chamber 30 facing to the small pressure surface 20B and is connected to the first chamber 26 facing to the large pressure surface 20A via a solenoid control valve 42. The force which acts on the piston shaft 18 and a differential-area piston 20 are changes stepwise by the movement of the hollow piston 22. Therefore, by changing the air pressure within the first chamber 26 via the solenoid control valve 42 with the air pressure within the second chamber 30 kept at a constant level, the piston shaft 18 can selectively be positioned among the neutral position N, the direct-drive position D or the over-drive position OD. |
