| 摘要 |
PURPOSE:To guarantee the effect of an engine brake in case of any emergency in an electronic control system, by setting a low-speed state holding circuit for leading low-speed stage engine brake range pressure, from a manual valve to a certain shift valve, and holding this shift valve in a specific condition. CONSTITUTION:I-Range pressure output from a low-speed stage holding circuit 131, holds the spool 40b of the second sift valve 40 in the right half part condition. Accordingly, as this shift valve condition can be held certainly by the I-range pressure, even if an electronic control system of the second shift solenoid 44 goes wrong, engine brake at the corresponding speed change stage can be got certainly. In addition, I-range pressure output from a low-speed stage holding circuit 131, holds an over-run clutch control valve 58 in the left half part condition. Accordingly, as this condition can be held certainly by the I-range pressure, for making the over-run clutch OR/C to be operatable, even if the electronic control system of the third shift solenoid 60 goes wrong, engine brake can be secured certainly.
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