Damping force control type hydraulic shock absorber

摘要

A damping force control type hydraulic shock absorber is provided having a broad damping force control range and is capable of obtaining appropriate damping force over the entire piston speed range from a low speed region to a high speed region. A piston is fitted in a cylinder, and a reservoir is connected to the cylinder. A cylinder upper chamber and the reservoir are communicated through a main passage in which a main damping valve is provided. The cylinder upper and lower chambers are communicated through an extension sub-passage in which an extension sub-damping valve and an extension variable orifice are provided. The cylinder lower chamber and the reservoir are communicated through a compression sub-passage in which a compression sub-damping valve and a compression variable orifice are provided. By changing the flow path areas of the variable orifices, orifice characteristics for the extension and compression strokes are controlled, and the pilot pressure is also changed to control the valve opening pressure of the main damping valve.