| 摘要 |
Anti-gear hopping device for a power transmission mechanism for an automotive vehicle. The power transmission mechanism may be a torque transfer case of a four wheel drive system. The anti-gear hopping device prevents undesired shifting between high range speed and low range speed modes of operation. The anti-gear hopping device comprises: (A) a fluid pressure mechanism for controlling the movements of a shift member; (B) a valve mechanism for actuating the fluid pressure mechanism; and (C) a valve actuator. The fluid pressure mechanism may include either a diaphragm or a piston which divides a chamber into two cavities which may be at different pressures. An output member linked to the diaphragm or piston controls shifting. The valve means is preferably a four way valve which includes first and second inlet ports in respective communication with the cavities of the fluid pressure actuator, and first and second outlet ports which are in respective communication with a source of fluid under higher pressure, say the atmosphere, and a source of fluid under lower pressure, said a vacuum source. The valve mechanism in a first state places a first outlet port and first cavity in communication therewith in communication with one of said fluid pressure sources, and simultaneously places the second inlet port and cavity in communication therewith in communication with the other source of fluid. In the second state, the respective communications are reversed so that the first inlet port is in communication with the second outlet port, and the second inlet port is in communication with the first inlet port. The valve mechanism further has a third state in which the first and second inlet ports are both closed, so that pressures previously established in the cavities are maintained. This prevents undesired shifting. Finally, the valve actuator means may comprise a three position switch which makes it possible to selectively place the valve mechanism in a desired one of the three states.
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