CONTROL VALVE FOR HYDRAULIC SPEED CHANGE GEAR

PURPOSE:To permit clutch engagement operation in the state where generation of vibration is little, by forming the width in the direction of transfer of the spool of the partitioning wall between the opening of a pump-side oil passage and the opening of a drain-side oil passage smaller than the width in the direction of transfer of the spool of an inlet and allowing the pressurized the course of oil in a pressure chamber to be discharged in operation, in a control valve for operating a frictional clutch for speed change. CONSTITUTION:The width (l) along the direction of transfer of the spool 3A of the wall 16 for partitioning the opening 4 on a pump side and a pair of openings 5 and 5 on drain side is formed smaller than the width (L) along the direction of transfer of the spool of the inlets L1... in oil passages R1... for speed change operation. Therefore, in speed the course of change operation, the opening 4 on pump side can be connected to the opening 5 on drain side through the inlets L... of the oil passages for speed change operation. Therefore, a portion of the pressurized oil supplied into cylinder is accumulated in an accumulator pressure chamber and the clutch engagement operation can be carried-out in the state where generation of vibration is little, even if operation from a speed change state to another speed change state is carried-out.