Shock absorber

1. A shock absorber comprising:

a cylinder sealingly enclosing working fluid;

a piston slidably fitted in the cylinder and partitioning an inside of the cylinder into two chambers;

a piston rod including one end side coupled to the piston and an opposite end side extending to an outside of the cylinder;

a first passage allowing the working fluid to flow out from one of the chambers in the cylinder as a result of movement of the piston;

a second passage provided in parallel with the first passage;

a damping force generating mechanism provided in the first passage, and configured to generate a damping force;

a tubular case member including at least a part of the second passage formed therein;

a shaft part disposed in the case member;

a flexible annular disc disposed in the case member while being passed through by the shaft part, and supported on an inner peripheral side or an outer peripheral side, an annular elastic seal member configured to seal a gap between the flexible annular disc and the case member or a gap between the flexible annular disc and the shaft part on a non-supported side being provided; and

two chambers in the case member which are defined and provided by the disc,

wherein the disc is configured to block flow to at least one side of the second passage,

wherein an annular gap is provided between the disc and the case member or the shaft part, and

wherein the elastic seal member is provided by being fixed to both surfaces of the disc via the gap.

2. The shock absorber according to claim 1 , wherein the shaft part is the one end side of the piston rod.

3. The shock absorber according to claim 1 ,

wherein the cylinder includes a reservoir chamber configured to compensate entry and exit of the piston rod, and

wherein the first passage and the second passage are provided between one of the chambers in the cylinder and the reservoir chamber.

4. The shock absorber according to claim 3 , wherein a seal position of the seal member is provided on an upstream side of the disc during the flow to the one side.

5. The shock absorber according to claim 1 , wherein the inner peripheral side of the disc is not clamped from both surface sides, and is supported only on one surface side.

6. The shock absorber according to claim 1 ,

wherein the damping force generating mechanism includes:

a main valve configured to suppress flow of the working fluid generated by a slide of the piston to generate the damping force; and

a pilot chamber configured to apply a pressure in a closing direction to the main valve, and

wherein the damping force generating mechanism is configured to introduce part of the flow of the working fluid into the pilot chamber to control opening of the main valve through the pressure in the pilot chamber.

7. A shock absorber comprising:

a cylinder sealingly enclosing working fluid;

a piston slidably fitted in the cylinder and partitioning an inside of the cylinder into two chambers;

a piston rod including one end side coupled to the piston and an opposite end side extending to an outside of the cylinder;

a first passage allowing the working fluid to flow out from one of the chambers in the cylinder as a result of movement of the piston;

a second passage provided in parallel with the first passage;

a damping force generating mechanism provided in the first passage, and configured to generate a damping force;

a tubular case member including at least a part of the second passage formed therein;

a shaft part disposed in the case member;

a flexible annular disc disposed in the case member while being passed through by the shaft part, and supported on an inner peripheral side or an outer peripheral side;

an annular elastic seal member configured to seal a gap between the flexible annular disc and the case member or a gap between the flexible annular disc and the shaft part on a non-supported side, wherein at least part of the elastic seal member is located on an opposite side to a surface on which the disc is supported; and

two chambers in the case member which are defined and provided by the disc,

wherein the disc is configured to block flow to at least one side of the second passage, and

wherein the disc is configured to close the second passage throughout an extension stroke, and open the second passage in a compression stroke.

8. The shock absorber according to claim 7 , wherein the flow to the opposite side is permitted via a supported side of the disc.

9. A shock absorber comprising:

a cylinder sealingly enclosing working fluid;

an outer tube provided around the cylinder;

a piston slidably fitted in the cylinder;

a piston rod coupled to the piston, and extending to an outside of the cylinder; and

a damping force generating mechanism configured to control flow of working fluid generated by a slide of the piston in the cylinder to generate a damping force,

wherein a tubular case for containing the damping force generating mechanism is provided in the outer tube;

wherein the shock absorber includes in the case:

a housing having a bottomed tubular shape;

a main valve provided so as to close an opening of the housing, and configured to control the flow of the fluid generated by the slide of the piston in the cylinder to generate the damping force;

a pilot chamber formed by the housing and the main valve, and configured to apply an inner pressure in a closing direction to the main valve;

an introduction passage configured to introduce the fluid into the pilot chamber;

a pilot passage configured to cause the pilot chamber and a downstream side of the main valve to communicate with each other; and

a control valve provided in the pilot passage;

wherein a disc is provided in the pilot chamber so as to be movable relative to the housing, the disc forming a housing inner chamber between the disc and a bottom portion of the housing, and

wherein a seal member, configured to seal a gap between an outer peripheral edge portion of the disc and an inner periphery of the housing is integrally provided on one surface of the outer peripheral edge portion of the disc, the one surface facing the pilot chamber, and

wherein one surface of an inner peripheral edge portion of the disc is abutted on the housing, the one surface of the inner peripheral portion of the disc being opposite to the one surface of the outer peripheral portion of the disc.