Shock absorber

1. A shock absorber comprising:

a cylinder which has an outer tube and an inner tube provided on an inner side of the outer tube in a radial direction at an interval from the outer tube, and in which oil is sealed;

a piston rod of which one end is inserted into the cylinder and the other end is extended outside the cylinder;

a piston which is connected to the one end of the piston rod and is provided in the inner tube so as to be slidable along a central axis direction of the inner tube, and which partitions an inner space of the inner tube into a rod-side oil chamber closer to the piston rod and a piston-side oil chamber on an opposite side to the piston rod;

a damping force generating unit which controls flow of the oil occurring when the piston slides in the inner tube according to a displacement of the piston rod, to generate damping force;

a reservoir that compensates the oil according to a change in advancement volume of the piston rod into the cylinder;

a reservoir communication path through which the damping force generating unit and the reservoir communicate with each other;

a compression-side communication path through which the piston-side oil chamber and the damping force generating unit communicate with each other;

an extension-side communication path through which the damping force generating unit and an annular passage formed between the outer tube and the inner tube communicate with each other; and

a compression-side port which is provided in the damping force generating unit, into which the oil flows from the compression-side communication path, and which has a compression-side valve that generates the damping force,

wherein a smallest cross-sectional area of the reservoir communication path is smaller than a smallest cross-sectional area of the compression-side port, and

a smallest cross-sectional area of the extension-side communication path is larger than the smallest cross-sectional area of the reservoir communication path.

2. The shock absorber according to claim 1 ,

wherein a smallest cross-sectional area of the compression-side communication path is equal to or larger than the smallest cross-sectional area of the compression-side port.

3. The shock absorber according to claim 1

wherein the damping force generating unit includes:

a compression-side piston having the compression-side port; and

a damper cylinder that accommodates the compression-side piston, and

wherein a smallest cross-sectional area between the compression-side piston and the damper cylinder into which the oil flows from the compression-side communication path is equal to or larger than the smallest cross-sectional area of the compression-side port and is equal to or smaller than the smallest cross-sectional area of the compression-side communication path.

4. The shock absorber according to claim 3 ,

wherein a compression-side port inlet portion is formed in the compression-side piston on an inlet side of the compression-side port so as to be open to an outer circumferential surface of the compression-side side piston, and

wherein an opening area of the compression-side port inlet portion is larger than the smallest cross-sectional area of the compression-side port.

5. The shock absorber according to claim 1 ,

wherein a smallest cross-sectional area of the annular passage is equal to or larger than the smallest cross-sectional area of the extension-side communication path.

6. The shock absorber according to claim 1 , further comprising:

an oil hole which is formed in the inner tube so as to allow communication between the annular passage and the rod-side oil chamber,

wherein a smallest cross-sectional area of the oil hole is equal to or larger than the smallest cross-sectional area of the annular passage.

7. The shock absorber according to claim 1 ,

wherein the damping force generating unit further includes:

an extension-side piston having an extension-side port into which the oil having flowed from the extension-side communication path into the damping force generating unit flows; and

a compression-side outlet port into which the oil having passed through the compression-side port of the compression-side piston flows,

wherein a smallest cross-sectional area between the damper cylinder and the extension-side piston is larger than the smallest cross-sectional area of the reservoir communication path.

8. The shock absorber according to claim 7 ,

wherein a smallest cross-sectional area of the compression-side outlet port is equal to or larger than the smallest cross-sectional area between the damper cylinder and the extension-side piston.

9. The shock absorber according to claim 7 ,

wherein a compression-side outlet port inlet portion is formed in the extension-side piston on an inlet side of the compression-side outlet port so as to be open to an outer circumferential surface of the extension-side piston, and

wherein an opening area of the compression-side outlet port inlet portion is larger than a smallest cross-sectional area of the compression-side outlet port.