| 摘要 |
A piston is provided with: a disk-shaped piston body (12); an annular valve seat (14) protruding axially from one end of the piston body; and one or more ports leading axially from the one end of the piston body from positions on the inner peripheral side of the annular valve seat to the other end of the piston body. The cross-sectional shape of the ports is a rounded rectangle and does not change along the length of the shape. Both ends of the cross-sectional shape are arcs located on the same circle (C). |
