Shock absorber

1. A shock absorber comprising:

a cylinder in which fluid is sealed;

a piston that is slidably fitted into the cylinder;

a piston rod that is coupled to the piston and extends to an outside of the cylinder; and

a valve mechanism that controls a flow of the fluid caused by sliding of the piston in the cylinder,

wherein the valve mechanism includes:

a valve body that is urged by urging means in a valve opening direction of a channel in which the fluid flows;

a valve seat on which the valve body is seated to close the channel;

an actuator that moves the valve body in a valve closing direction with thrust of a solenoid; and

a fail-safe valve that is urged by a first elastic body in the valve closing direction of the valve body, at least a part of the fail-safe valve being seated on the valve body to close the channel and being spaced from the valve body to open the channel,

when the fluid does not flow in the valve opening direction of the valve body, the fail-safe valve is urged by the first elastic body to thereby come into contact with the valve body and close the channel,

when the fluid flows in the valve opening direction of the valve body, the fail-safe valve is spaced from the valve body by a fluid pressure to open the channel, and

when the valve body moves most in the valve opening direction from the valve seat, the fail-safe valve is brought into contact with the valve body, the channel is closed, and a supporting portion of the valve body supports a part of the fail-safe valve, and, when the fluid flows in the valve opening direction of the valve body, at least a part of the fail-safe valve, which is in contact with a non-supporting portion other than the supporting portion of the valve body, is spaced from the valve body by the fluid pressure to open the channel.

2. The shock absorber according to claim 1 , wherein the first elastic body is a combined elastic body, a modulus of elasticity of which changes in two or more stages.

3. The shock absorber according to claim 1 , wherein the fail-safe valve is a second elastic body, and

the fail-safe valve and the first elastic body forms a combined elastic body, a modulus of elasticity of which changes in two or more stages.

4. The shock absorber according to claim 1 , wherein the fail-safe valve is formed by at least one disk valve.

5. The shock absorber according to claim 4 , wherein the at least one disk valve includes a plurality of disk valves being stacked, and

a combined modulus of elasticity of the fail-safe valve is adjusted according to at least one of the number of stacks and thickness of the disk valves.

6. The shock absorber according to claim 5 , wherein the plurality of disk valves have at least different shapes or different sizes from one another.

7. The shock absorber according to claim 1 , wherein an orifice is formed in at least one of the fail-safe valve, the valve body, a place between the fail-safe valve and the valve body, and the valve seat.

8. The shock absorber according to claim 1 , wherein the urging means is a third elastic body and a fluid pressure.

9. The shock absorber according to claim 1 , wherein the supporting portion and the non-supporting portion are integrally formed by a same component.

10. The shock absorber according to claim 1 , wherein the supporting portion and the non-supporting portion are formed on a same plane.

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

a main valve that opens and closes for controlling a flow of the fluid caused by the sliding of the piston in the cylinder to generate a damping force;

a pilot chamber an internal pressure of which acts on the main valve in the valve closing direction;

a lead-in passage for leading the fluid into the pilot chamber; and

a pilot channel that connects the pilot chamber and a downstream side of the main valve,

wherein the valve mechanism is provided on the pilot channel and controls the internal pressure of the pilot chamber and the pilot channel.