Shock absorber

A shock absorber comprising:

• a first piston including a first compression chamber that is connected to an end of the piston rod reciprocating within a cylinder and is formed by a plurality of rebound passages penetrating in a vertical direction, the first piston having an opened lower portion to form an inner space recessed upward;
• a pilot valve connected to the piston rod and disposed in the inner space to selectively open a lower end of the rebound passage;
• a second piston forming a second compression chamber that is connected to the piston rod, has an upper portion accommodated in the inner space, and is disposed under the first piston, wherein connection rebound passages respectively connected to the rebound passages penetrate the second compression chamber in a vertical direction, and the second compression chamber has an opened upper portion to communicate with the inner space;
• a rebound retainer including a fourth compression chamber that is connected to the piston rod, is disposed under the second piston, and is formed by extension rebound passages respectively connected to the connection rebound passages;
• a disk valve assembly connected to the piston rod, disposed under the rebound retainer, and opening and closing a passage while allowing a deformation through communication with the extension rebound passages;
• and
• a third compression chamber formed by a space between an inner peripheral surface of the first piston forming the inner space and an outer peripheral surface of the second piston, together with a plurality of compression passages penetrating in a vertical direction of the first piston.