Lockup control system for automatic transmission

A lockup control system for an automatic transmission, comprising:

• a fluid joint for transmitting a rotary motive power from an input shaft to an output shaft through a fluid;
• a lockup clutch mechanism for linking said input and output shafts by bypassing said fluid joint;
• a switching valve for switching supply and discharge of pressurized fluid to said fluid joint and said lockup clutch mechanism;
• and
• a control valve for controlling a closed state of said lockup clutch mechanism by controlling a hydraulic pressure supplied to said lockup clutch mechanism, said hydraulic pressure being controlled by said control valve, and being supplied to said switching valve to switch said switching valve into a supply state, and also being supplied to said lockup control mechanism through said switching valve.

A lockup control system for an automatic transmission, comprising:

• a fluid joint for transmitting a rotary motive power from an input shaft to an output shaft through a fluid;
• a lockup clutch mechanism for linking said input and output shafts by bypassing said fluid joint;
• a first directional control valve for supplying/discharging pressure oil for switching closed state and released state of said lockup clutch mechanism;
• a first control valve for supplying/discharging pressure oil for operating said first directional control valve and for supplying a controlled hydraulic pressure to said lockup clutch mechanism via said first switching valve;
• a second directional control valve for switching a communication state in which an oil path which connects said first directional control valve and said first control valve is caused to communicate and a shut-off state in which said oil path is shut off and pressure oil is supplied to the oil path on the side of said first directional control valve to release said lockup clutch mechanism;
• and
• a second control valve for supplying/discharging pressure oil for causing said second directional control valve to put into the shut-off state.

A lockup control system for an automatic transmission, comprising:

• a hydraulic pressure source for generating a predetermined hydraulic pressure;
• a fluid joint for transmitting a rotary motive power from an input shaft to an output shaft through a fluid;
• a lockup clutch mechanism for linking said input and output shafts by bypassing said fluid joint;
• a control valve for generating a constant hydraulic pressure when deactivated and for generating a control hydraulic pressure which is lower than said constant hydraulic pressure when activated;
• and
• a directional control valve switched to a first state in response to said constant hydraulic pressure generated by said control valve, for releasing a linkage of said lockup clutch mechanism by supplying a predetermined hydraulic pressure to said lockup clutch mechanism therethrough, and switched to a second state in response to said control hydraulic pressure, for forming said linkage of said lockup clutch mechanism by supplying said control hydraulic pressure to said lockup clutch mechanism therethrough.