| 摘要 |
An improved four wheel drive system for a vehicle is disclosed. The system includes a first carrier assembly connected to a power generation system of the vehicle and adapted to transmit power to a first pair of drive wheels. A second carrier assembly having an input member and an output member connected to a second pair of drive wheels is also provided. The second carrier assembly is adapted to transmit power from the input member to the output member. A mechanism is provided for selectively connecting the first carrier assembly to the input member of the second carrier assembly for transmitting power thereto. A biasing structure is further provided for moving one of the input and output members relative to the other of the input and output members prior to connecting the first carrier assembly to the input member of the second carrier assembly. In a first embodiment, a rack and pinion arrangement is provided to rotate the input member relative to the output member, while a clutch is connected between the first carrier assembly and the input member. A vacuum control circuit and an electrical control circuit sense the movement of the input member and prevent the clutch from connecting the first carrier assembly to the input member until the input member has moved a predetermined amount. In a second embodiment, drive gears and biasing gears are selectively connected to the input member by first and second clutches, respectively. A hydraulic control circuit and an electrical control circuit are provided to prevent the first clutch from connecting the drive gear to the input member prior to the second clutch connecting the biasing gear to the input member. |
