Damping force control type hydraulic shock absorber

Abstract

In a damping force control type hydraulic shock absorber according to the invention, an extension-side bypass passage extends through an extension-side chamber (17b) in a shutter (17). A check valve (28) allows the flow of hydraulic fluid only during the extension stroke. A contraction-side bypass passage extends through a contraction-side chamber (17a) in the same shutter (17). Disk valves (30) allow the flow of hydraulic fluid only during the contraction stroke. By rotating the shutter (17), alignment between an extension-side inlet port (31) and an extension-side inlet opening (34) changes and alignment between a contraction-side inlet port (32) and a contraction-side inlet opening (33) also changes, thereby controlling the passage area of each of the extension- and contraction-side bypass passages, and thus enabling different damping force characteristics to be simultaneously selected for the extension and contraction sides. Since the extension- and contraction-side chambers (17a, 17b) are independent of each other, no turbulent flow will occur in the shutter (17) when the direction of stroke of a piston rod (8) changes, and hence no noise will be generated.