| 摘要 |
In a hydraulic control system for automatic transmissions of motor vehicles, a lock-up control circuit for controlling a direct-coupling clutch of a torque converter, the lock-up control circuit comprising: a lock-up control valve having a spring-biased valve spool and operated by solenoid pressure applied to a spring-loaded end of the valve spool and oil pressure applied to the other end of the spool upon shift to a predetermined gear position and in higher gear positions, connecting an oil pressure source with either a clutch engaging conduit or a clutch releasing conduit of the direct-coupling clutch of the torque converter; with ON-OFF operation of solenoid valve; and a solenoid valve provided in an oil conduit communicating with the spring-loaded end of the spool and adapted to produce the solenoid pressure in a gear position lower than said predetermined lock-up gear position.
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