Frequency sensitive shock absorber

A frequency sensitive shock absorber comprising:

• a piston rod coupled so that one side is located inside a cylinder and the other side is located outside the cylinder;
• a main valve coupled to the piston rod and partitioning an inner space of the cylinder into a compression chamber and a tension chamber;
• a sub-piston rod coupled to one side of the piston rod and interlocked with the piston rod to reciprocate along a longitudinal direction of the cylinder;
• and
• a sub-valve module coupled to the sub-piston rod and generating a damping force according to a frequency during a tension stroke,
• wherein the sub piston rod includes a working fluid discharge path formed to communicate with an inside of the sub-valve module to discharge a working fluid to adjust a pressure inside the sub-valve module when the pressure inside the sub-valve module increases due to the working fluid flowing into the sub-valve module during the tension stroke at low frequency,
• wherein the sub piston rod includes
• a head portion coupled to one side of the piston rod and
• a rod body portion extending along a longitudinal direction of the rod body portion from a lower surface of the head portion and having a size of a cross section crossing the longitudinal direction of the rod body portion formed smaller than a size of a cross section of the head portion crossing the longitudinal direction of the head portion, and
• wherein the working fluid discharge path includes
• a first discharge path formed on the lower surface of the head portion and concavely formed from an external profile of the head portion to an outer circumferential surface of the rod body portion in a radial direction toward the rod body portion, and
• a second discharge path formed on the outer circumferential surface of the rod body portion and formed by a set length along the longitudinal direction of the rod body portion.