To improve abrasion resistance, and eliminate generation of abnormal negative pressure and noise while maintaining a moderate contact condition on a contact surface by embedding hard particle on a surface of a valve element of a check valve with a constant area ratio.
In a check valve CH1, a valve element 13a is separated from a sheet part 7b of a piston 7 against a spring 14a in association with movement toward a pressure side of a piston rod 6, and it is allowed that oil flows only in one direction through a passage 7a. In a check valve CH2, a valve element 13b is separated from a sheet part 12c of a bottom plate 12 against a spring 14b in association with movement toward an expanding side of the piston rod 6, and it is allowed that oil in a reservoir chamber flows only in one direction toward an oil chamber through a passage 12a. Hard particle 15 is embedded on a valve element surface f of check valves CH1, CH2 with a constant area ratio. Even if collision of the valve elements 13, 13b with the sheet parts 7b, 12c of the piston 7 and the bottom plate 12 is repeated, abrasion of the valve elements 13a, 13b is suppressed and prescribed damping force is obtained.
TANAKA YUJI
MIZUNO KEIZO
