HYDRAULIC CONTROLLER FOR LOCK-UP CLUTCH

PURPOSE:To obtain a sure fastening action by forming a throttle in an oil passage for discharging the oil pressure in a release chamber only the time when a lock-up control valve is switched from a release side position to a fastening side position and discharging the oil pressure in the release chamber free from the throttle effect after the fastening of a lock-up piston. CONSTITUTION:In the state where a lock-up clutch is in released state, if a hydraulic pressure acts into a lock-up instruction pressure oil passage 54, the spool 44 of a lock-up control valve 40 starts shift from a releases side position to a fastening side position. during the shift of the spool 44, the oil pressure in a release chamber 24 is gradually discharged through a narrow passage formed between the land 44c of the spool 44 of a lock-up control valve 40 and a valve opening 42. Therefore, the fastening of the clutch is carried out gently. When the spool 44 perfectly shifts to the fastening side position, the throttle action due to the spool 44 is eliminated, and the release chamber 24 is drained without using the communication through the narrow passage, and the generation of residual pressure in the release chamber 24 is prevented.