| 摘要 |
PROBLEM TO BE SOLVED: To provide a hydraulic control device of an automatic transmission considering the downsizing of the device and the fail-safe for achieving safety. SOLUTION: A fail-safe hydraulic circuit 15 has a first open/close valve 17 for feeding/cutting a C1 feed pressure from a hydraulic control unit 9 to a C1 clutch 7a, a first check valve 19 connected in parallel to the first open/ close valve 17 for feeding the C1 feed pressure to the C1 clutch 7a, bypassing the first open/close valve 17, when the first open/close valve 17 is fastened in a closed state, and a fine orifice 21 for dropping the oil pressure inside the C1 clutch 7a down to a drain. In the fail-safe oil pressure circuit 15, a hydraulic passage for feeding the oil pressure from the hydraulic control unit 9 to the C1 clutch 7a is communicated at ordinary time. When the engine is stopped, the hydraulic control unit 9 and the C1 clutch 7a are separated and the oil pressure from a motor-driven hydraulic pump 11 is fed to the C1 clutch 7a.
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