The utility model provides a variable damping force
viscous damper which comprises a cylinder
barrel, bushings connected to the two ends of the cylinder
barrel, a
piston movably arranged in the cylinder
barrel, a
piston rod penetrating through the center of the
piston, with the two ends penetrating through center holes of the bushings and extending outwards, and damping fluid filled in a
closed cavity defined by the cylinder barrel, the bushings, the piston and the
piston rod. An annular outer gap is formed between the outer wall of the piston and the inner wall of the cylinder barrel, the variable-
diameter guide rod is arranged in an
open hole of the piston in a penetrating mode, and the two ends of the variable-
diameter guide rod are fixedly arranged on the lining in an inserted mode. The inner
diameter of the
open hole is larger than the outer diameter of the first rod body and the outer diameter of the second rod body, and when the piston moves to the first rod body and the second rod body, a first annular inner gap and a second annular inner gap which are different in width can be formed between the inner wall of the
open hole and the outer wall of the variable-diameter guide rod, so that the overflowing area of a damping liquid flowing channel is changed, and the variable damping force effect is achieved.