| 摘要 |
A rotary switch, used to select the operating range of an automatic transmission, controls solenoid-operated valves corresponding to the selected range to open and close a connection between a range valve and a control pressure source. The valve has three positions and is centered by one compression spring. One position opens the fluid pressure source to a line that is pressurized to produce forward drive, a second position opens a connection between the fluid pressure source and a line that is pressurized to produce reverse drive, and a third position vents those lines to sump. The spring locates the valve at the center position and makes the valve insensitive to tolerances and spring variations. For example, the range valve will not move until a predetermined control force is applied at either end of the valve spool.
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