| 摘要 |
PROBLEM TO BE SOLVED: To certainly retain reverse travel inhibiting function in an automatic transmission without complicated process by a simple structure when a speed sensor is abnormal. SOLUTION: After abnormal state of an output shaft rotational speed sensor (speed sensor) 21 is detected, a B/U(back-up) vehicle speed using turbine rotational speed Nt from a turbine rotational speed sensor 19 and a gear ratio at this time is employed by converting into output shaft rotational speed (vehicle speed) from the output shaft rotational speed sensor 21, and the B/U vehicle speed and a predetermined reverse travel exhibiting speed are comparatively determined. Based on the comparatively determined result, oil supply of a frictional engaging element required at the time of reverse travel in an automatic transmission 1 is prohibited. Therefore, even though the output shaft rotational speed sensor 21 becomes abnormal, normal shift control in the automatic transmission 1 can be continued without changing a structure and without performing complicated process, and also reverse travel inhibiting (reverse inhibit) function can be certainly retained.
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