CONTROL MECHANISM OF LOCKUP CLUTCH FOR FLUID COUPLING IN AUTOMATIC STEPLESS SPEED CHANGER FOR VEHICLE

PURPOSE:To improve the durability of a directly coupled clutch, by enabling the spool of a lockup control valve to be displaced to a position in the engagement side of the directly coupled clutch only when a difference between pressing forces of an opposite oil pressure and an input signal oil pressure is below the preset value. CONSTITUTION:A lockup clutch control mechanism 80, which controls a directly coupled clutch 108 of a fluid coupling 100, inputs the output pressure of a secondary regulator valve 35, regulated in accordance with a vehicle running condition, as an input signal oil pressure while the working pressure of an output pulley in a V-belt type stepless speed changer as an opposite oil pressure to one end of a spool 82 of a lockup control valve 81, and enables the spool 82 to be displaced to the side engaging the directly coupled clutch 108 only when a difference between pressing forces by the both pressures of oil is below a prescribed level. In such way, reducing a frequency of engagement and disengagement of the directly coupled clutch, its durability is improved, further driving feeling can be improved.