Oil pressure control device for automatic transmission, has fail safe valve that drains out oil of one brake with oil pressure of other brake at speed change and governs speed change with oil pressure of other brake

摘要

At the time of speed change of an automatic transmission, a spool of a fail safe valve forcefully drains out brake oil of a brake (2), using oil pressure of other brake (4). During speed change, oil pressure is controlled using oil pressure of brake (4). After completion of speed change, the brake (4) is switched to draining condition.