Frequency-sensitive shock absorber

1. A frequency-sensitive shock absorber, which includes a cylinder filled with a working fluid and a piston rod having one end disposed inside the cylinder and the other end extending to the outside of the cylinder, the frequency-sensitive shock absorber comprising:

a main piston valve assembly installed at one end of the piston rod, and configured to

operate in a state in which the inside of the cylinder is divided into a rebound chamber and a compression chamber, and

generate a damping force varying according to a moving speed; and

an auxiliary piston valve assembly configured to

move together with the main piston valve assembly, and

generate a damping force varying according to a frequency, wherein the auxiliary piston valve assembly includes:

a housing;

a spool unit configured to open or close a communication passage for communicating the rebound chamber with the compression chamber while moving within the housing; and

upper and lower support members positioned inside the housing, the upper and lower support members being configured to support the spool unit,

wherein the upper and lower support members have protrusions protruding toward the spool unit, respectively, and as the spool unit moves, the communication passage is closed when the protrusions of the upper and lower support members contact the spool unit,

wherein the spool unit includes a spool configured to move upward and downward within the housing and upper and lower disks configured to support the spool disposed therebetween,

wherein the upper and lower disks have through-holes, and

wherein the through-holes are positioned outward of a position where the protrusions are contacted by the upper or lower disks, so as to block the communication passage when the upper and lower disks contact the protrusions.

2. The frequency-sensitive shock absorber according to claim 1 , wherein the communication passage includes

a connection passage inside the piston rod,

an upper space inside the housing,

through-holes formed in the upper and lower disks,

a lower space inside the housing, and

a hole formed in a lower washer mounted on a lower opening of the housing.

3. The frequency-sensitive shock absorber according to claim 1 , wherein the upper and lower support members are made of an elastic member.

4. The frequency-sensitive shock absorber according to claim 1 , wherein a distance in a direction that extends parallel to a movement of the piston rod, between the protrusion of the lower support member and the lower disk, is smaller than a distance in the direction that extends parallel to the movement of the piston rod, between the spool and a lower washer mounted on a lower opening of the housing.

5. The frequency-sensitive shock absorber according to claim 1 , wherein a distance in a direction that extends parallel to a movement of the piston rod, between the protrusion of the upper support member and the upper disk, is smaller than a distance in the direction that extends parallel to the movement of the piston rod, between the spool and the piston rod.