Hydraulic damper of adjustable damping force type

Abstract

A hydraulic damper of the adjustable damping force type includes a cylinder containing hydraulic liquid therein, a piston working in the cylinder and partitioning the interior thereof into two liquid chambers and having a damping force generating mechanism, a piston rod connected to the piston and extending through one of the liquid chambers to the outside of the cylinder, a coaxial bore formed in the piston rod, a liquid passage communicating the liquid chambers independently from the damping force generating mechanism and including at least a portion of the bore in the piston rod, an adjusting rod inserted into the coaxial bore and operated rotatably from the outside of the damper, and a rotary valve secured to the adjusting rod for selectively changing the effective passage area of the liquid passage. A generally cylindrical orifice tube having a plurality of circumferentially spaced first orifices is provided in a midportion of the liquid passage, the rotary valve slidingly engaging with the inner circumference of the orifice tube. A check valve having a plurality of second orifices normally resiliently engages with the outer circumference of the orifice tube. The second orifices in the check valve are aligned with the first orifices in the orifice tube, with the diameter of each second orifice being smaller than that of a corresponding first orifice.