| 摘要 |
PURPOSE:To improve the durability of an overdriving planetary gear, by checking the gear shifting of a main transmission to its high speed step in the case where a sub-transmission is in a low speed step. CONSTITUTION:A transfer hydraulic control unit 200 is constituted of first and second solenoid valves 210 and 220, a selector valve 230, an inhibitor valve 240, a down-shift timing valve 260, a direct-connected oil passage 201 to be connected to a hydraulic servo C-3 of a multiple-disc clutch C3, a decelerating oil passage 202 to be connected to a hydraulic servo B-4 of a multiple-disc clutch B4, a four-wheel driving oil passage 203, and check valves 310, 320 and 330. When a shift step of a sub-transmission comes to a low-speed step, these first and second solenoid valves 210 and 220 are controlled, feeding the hydraulic servo B-4 with hydraulic pressure, whereby gear shifting of a main transmission to its high speed step is checked. With this constitution, an overdriving planetary gear will in no case come to rotation at high speed so that durability in the gear is well improved. |
