| 摘要 |
PURPOSE: A hydraulic control device of an automatic transmission is provided to set at least two shift stages for avoiding a feeling of down-shift during a running failure and for maintaining sufficient driving force at restating after the failure. CONSTITUTION: A hydraulic control device for an automatic transmission comprises an oil pressure source(51), oil paths(L32,L31) connected thereto, hydraulic servos(82,81) connected thereto for operating friction members(C-2,C-1), control means(72,71) arranged on the oil paths to operate engagement/disengagement with supply/discharge of oil pressure to/from the hydraulic servos, and valves(55) arranged on the oil path(L31) to shut off the oil pressure from the oil pressure source to the hydraulic servo(81) using the oil pressure on the downstream side of the control means(72) as signal pressure. Second valves(60) are arranged on the oil path(L32) to shut off the oil pressure and the signal pressure to the hydraulic servo(82). The hydraulic control device prevents the shift to another shift stage due to engagement of the friction element(C-1) during a failure in a shift stage due to engagement of the other friction element and achieves two shift stages for engagement of one of the friction elements during the failure.
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