HYDRAULIC CONTROL DEVICE OF AUTOMATIC TRANSMISSION

摘要

PROBLEM TO BE SOLVED: To provide a hydraulic control device of an automatic transmission in which a reverse shift stage can be formed even when a solenoid valve which is normally energized during backward traveling is not energized.

SOLUTION: A C-4 relay valve 45 interposed between a linear solenoid valve SL4 and a hydraulic servo 54 is installed in the hydraulic control device 20 having: a manual shift valve 23 outputting a forward traveling range pressure PDor a backward traveling range pressure PR; and the linear solenoid valve SL4 outputting, when energized, an engagement pressure to the hydraulic servo 54 of a fourth clutch C-4 engaged during the backward traveling. The C-4 relay valve 45 is locked to the normal position when receiving the signal pressure from the solenoid valve SL, and supplies the engagement pressure from the linear solenoid valve SL4 to the hydraulic servo 54. When the relay valve is defective due to non-energization, it is changed over to the failure position by the reverse traveling range pressure PRto introduce the backward traveling range pressure PRto the hydraulic servo 54.

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