Shock absorber

1. A shock absorber, comprising:

a cylinder sealingly containing hydraulic fluid;

a piston slidably fitted to the cylinder;

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

a damping force generating mechanism configured to generate a damping force through control of a flow of the hydraulic fluid that is caused by sliding of the piston in the cylinder, the damping force generating mechanism including:

a valve body, which has a communication passage formed therein, and includes an inner seat portion and an outer seat portion that are respectively formed on a center side and an outer peripheral side of the valve body across the communication passage;

a main valve, which is provided to be capable of being separated from and seated on the outer seat portion, and is opened by receiving a pressure of the hydraulic fluid, to thereby generate a damping force, a pressure of opening the main valve being adjusted by an internal pressure in a pilot chamber formed on a side opposite to the outer seat portion;

a control valve, which is a pressure control valve configured to control the internal pressure in the pilot chamber into which the hydraulic fluid is led; and

an auxiliary valve provided on an upstream side of the main valve in series with the main valve,

wherein the main valve is an annular disc valve that is opened and closed in such a manner that an outer peripheral side thereof is separated from and seated on a valve seat, and

wherein an inner peripheral side of the main valve is prevented from being clamped from both surface sides thereof, and the main valve is supported only from one surface side on the inner peripheral side by a first retainer,

the shock absorber further comprising a cutout valve, which is provided between the main valve and the seat portions of the valve body, and is formed of an annular disc valve having a cutout on an outer peripheral side thereof,

wherein an inner peripheral side of the cutout valve is clamped from both surface sides thereof, and

wherein the cutout valve includes a coupling portion that has low rigidity and is formed between the outer peripheral side and the inner peripheral side by cutting out a part of the cutout valve between the outer peripheral side and the inner peripheral side.

2. The shock absorber according to claim 1 , further comprising an annular sealing member, wherein the annular sealing member is provided on a side of the main valve facing the pilot chamber, and the annular sealing member is slidably and liquid-tightly fitted to an inner tube portion partly defining the pilot chamber.

3. The shock absorber according to claim 1 , wherein the coupling portion is formed so as to be symmetrical with respect to a center of the cutout valve.

4. The shock absorber according to claim 1 , further comprising a second retainer, which is provided on a side of the main valve opposite to the outer seat portion, and has a diameter larger than a diameter of the first retainer,

wherein the second retainer, which has the larger diameter, regulates a valve opening amount of the main valve.

5. A shock absorber, comprising:

a cylinder sealingly containing hydraulic fluid;

a piston slidably fitted to the cylinder;

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

a damping force generating mechanism configured to generate a damping force through control of a flow of the hydraulic fluid that is caused by sliding of the piston in the cylinder, the damping force generating mechanism including:

a valve body, which has a communication passage formed therein, and includes an inner seat portion and an outer seat portion that are respectively formed on a center side and an outer peripheral side of the valve body across the communication passage;

a main valve, which is provided to be capable of being separated from and seated on the outer seat portion, and is opened by receiving a pressure of the hydraulic fluid to thereby generate a damping force, a pressure of opening the main valve being adjusted by an internal pressure in a pilot chamber formed on a side opposite to the outer seat portion;

a control valve, which is a pressure control valve configured to control the internal pressure in the pilot chamber into which the hydraulic fluid is led; and

an auxiliary valve provided on an upstream side of the main valve in series with the main valve,

wherein the main valve is an annular disc valve that is opened and closed in such a manner that an outer peripheral side thereof is separated from and seated on a valve seat, and

wherein an inner peripheral side of the main valve is prevented from being clamped from both surface sides thereof, and the main valve is supported only from one surface side on the inner peripheral side by a first retainer,

the shock absorber further comprising a leakage prevention valve, which is configured to prevent the hydraulic fluid from leaking to the pilot chamber side through between the inner peripheral side of the main valve and the first retainer, the leakage prevention valve having an outer peripheral side that is to be brought into abutment on the outer seat portion side of the main valve, and having an inner peripheral side clamped from both surface sides of the leakage prevention valve.

6. The shock absorber according to claim 5 , further comprising an annular sealing member, wherein the annular sealing member is provided on a side of the main valve facing the pilot chamber, and the annular sealing member is slidably and liquid-tightly fitted to an inner tube portion partly defining the pilot chamber.

7. The shock absorber according to claim 5 , further comprising a second retainer, which is provided on a side of the main valve opposite to the outer seat portion, and has a diameter larger than a diameter of the first retainer,

wherein the second retainer, which has the larger diameter, regulates a valve opening amount of the main valve.