Vibration control device and frequency-sensitive shock absorber having the same

A frequency-sensitive shock absorber comprising:

• a cylinder having a fluid stored in its inner space;
• a piston rod having a part coupled to be located inside the cylinder and reciprocating along a longitudinal direction of the cylinder;
• a main valve unit coupled to the piston rod and partitioning the inner space of the cylinder into a compression chamber and a tension chamber;
• a sub-piston rod coupled to a lower end of the piston rod and into which a fluid is introduced from the piston rod;
• a pilot valve unit penetrated by and coupled to the sub-piston rod, in which pressure is formed by the fluid introduced through the sub-piston rod;
• and
• a fixing member located below the pilot valve unit and fastened to the sub-piston rod to fix the pilot valve unit,
• wherein the pilot valve unit comprises a free piston configured to reciprocate in a vertical direction according to a pressure change formed by the fluid,
• wherein the pilot valve unit further comprises:
• a first pilot valve body penetrated by and coupled to the sub-piston rod and having
• pilot chambers formed at upper and lower sides to be filled with the fluid flowing through the sub-piston rod;
• a second pilot valve body located below the first pilot valve body and penetrated by and coupled to the sub-piston rod, and having a main chamber to be filled with the fluid flowing through the sub-piston rod;
• and
• a pilot valve located between the first pilot valve body and the second pilot valve body and elastically deformed according to a pressure change formed by the fluid in the first pilot valve body and the second pilot valve body,
• wherein the first pilot valve body comprises a first lower surface, a first upper surface spaced apart from the first lower surface by a predetermined distance, and a first side surface connecting the first lower surface and the first upper surface, and
• the pilot chamber comprises:
• a first pilot chamber concaved by a predetermined depth in a direction from the first lower surface toward the first upper surface;
• and
• a second pilot chamber concaved by a predetermined depth in a direction from the first upper surface toward the first lower surface,
• wherein an entirety of the free piston is provided in the second pilot chamber,
• wherein the first pilot valve body comprises a partition surface formed by a predetermined thickness by the first pilot chamber and the second pilot chamber, and
• a fluid flow path is formed in the partition surface to pass through along a vertical direction so that the fluid introduced into the first pilot chamber flows into the second pilot chamber,
• wherein the pilot valve unit further comprises an outlet disk provided on an upper side of the free piston, and the outlet disk is configured to contact the first upper surface of the first pilot valve body and a support protrusion of the piston body to shield the piston chamber,
• wherein a discharge slit is formed in the outlet disk to discharge the fluid of the piston chamber when pressure of the first pilot chamber and pressure of the second pilot chamber are unbalanced, and
• wherein the support protrusion extends into the discharge slit.