Patent ID: 7854250

Claim:
A method for manufacturing a control valve body of an automatic transmission for use in a speed change operation of the automatic transmission, comprising: providing a mold having a fixed side die and a moving side die, the moving side die having at least one projecting portion; bringing the moving side die in contact with the fixed side die, and forming a casting mold having a hollow portion between the moving side die and the fixed side die, the at least one projecting portion protruding into the hollow portion; pressure injecting melted liquid magnesium or magnesium alloy into the hollow portion using a plunger; cooling the liquid magnesium or magnesium alloy in the casting mold to thereby mold a valve body having partitions with a draft angle less than two degrees a valve hole through which a valve passes being formed on the partitions, and a channel groove for hydraulic oil between the partitions, the channel groove being formed by the at least one projecting portion and the channel groove having a width of less than 3 mm; and moving the moving side die away from the fixed side die to release the valve body.