Hydraulic damper of adjustable damping force type

Claim 1

A hydraulic damper of the adjustable damping force type, comprising: a cylinder; a piston-piston rod assembly disposed in said cylinder including a piston and a piston rod connected to said piston at its one end, said piston being slidably disposed in said cylinder and dividing the interior of said cylinder into two cylinder chambers; a first passage formed through said piston for providing communication between said two cylinder chambers; a first damping force generation valve provided on said piston for generating a damping force in extension and contraction strokes of said damper; a bypass passage in said piston-piston rod assembly communicating said two cylinder chambers; an annular member having opposite sides fitted into said bypass passage, said annular member having a second passage communicating said opposite sides thereof; a second damping force generation valve secured to said opposite sides of said annular member by means of a stud inserted through said annular member and a tightening member mounted on said stud, said second damping force generation valve being adapted to generate a damping force in the extension and contraction stroke of said damper; a through-hole extending axially through said stud; a third damping force generation valve on said stud for controlling flow of the hydraulic fluid through said through-hole; a shutter means in said bypass passage for controlling the flow passage area of said bypass passage, wherein said shutter means is so constructed that a passage route including said second damping force generation valve and a passage route including said third damping force generation valve in said bypass passage are selectively switched by said shutter means to control the flow passage area in said bypass passage; and wherein said third damping force generation valve is adapted to generate damping force in the extension and contraction strokes of said damper.