| 摘要 |
PURPOSE:To manufacture a valve lifter with a reduced weight and a low cost, by integrally forming a cam sliding portion of the valve lifter with a barrel portion thereof by back extrusion cold plastic working of an alloy tool steel, pressing a central portion of a head of the valve lifter into the barrel portion to plastically deform the head, and cutting the upper surface of the head. CONSTITUTION:A cam sliding portion 16D is integrally formed with a lifter barrel portion 16E by back extrusion cold plastic working of an alloy tool steel material of SKD 61 to obtain a cup-shaped cylindrical valve lifter 16. The upper surface of a head portion of the valve lifter 16 is pressed at its central portion into the barrel portion to plastically deform the head portion and thereby form a projection serving as a valve pushing portion at the inner surface of the head portion. Then, the upper surface of the head portion is cut to at least a recessed surface formed by the pressing plastic deformation at the central portion, so as to form a flat surface, thus obtaining a final product of the valve lifter. |
