Shock absorber

1. A shock absorber comprising:

a cylinder in which a working fluid is sealed;

a piston provided to be slidable in the cylinder and partitioning the inside of the cylinder into two chambers;

a piston rod connected to the piston and extending to the outside of the cylinder;

a first passage and a second passage through which the working fluid flows out from the chamber on an upstream side to the chamber on a downstream side in the cylinder due to movement of the piston;

a first damping force generation mechanism provided in the first passage formed in the piston to generate a damping force; and

a second damping force generation mechanism provided in an annular valve seat member disposed in one of the chambers and provided in the second passage in parallel with the first passage to generate a damping force, wherein

the second damping force generation mechanism includes:

a first sub-valve provided on one side of the second passage formed in the valve seat member and a second sub-valve provided on the other side thereof; and

a bottomed cylindrical cap member having an outer cylindrical part, a bottom part, and an inner cylindrical part which is provided on an inner circumferential side of the bottom part and through which the piston rod is able to be inserted, and

at least a part of the valve seat member is housed between the outer cylindrical part and the inner cylindrical part of the cap member.

2. The shock absorber according to claim 1 , wherein

the second sub-valve is housed between the outer cylindrical part and the inner cylindrical part of the cap member, and

the valve seat member is able to be sub-assembled to the cap member by a seal member provided on an outer circumference.

3. The shock absorber according to claim 1 , wherein

the second sub-valve is housed between the outer cylindrical part and the inner cylindrical part of the cap member, and

an outer circumference of the valve seat member is press-fitted into the cap member.

4. The shock absorber according to claim 1 , wherein a washer is provided between the bottom part and the second sub-valve in the cap member.

5. The shock absorber according to claim 1 , wherein the cap member includes:

a first cap member having the outer cylindrical part and the bottom part; and

a second cap member forming the inner cylindrical part.

6. The shock absorber according to claim 1 , wherein the cap member is formed by press forming.

7. The shock absorber according to claim 1 , wherein

the second damping force generation mechanism opens the valve while the first damping force generation mechanism is in a valve closed state in a region in which a piston speed is low, and

both the first damping force generation mechanism and the second damping force generation mechanism open the valves in a speed region in which the piston speed is higher than the low speed.

8. The shock absorber according to claim 1 , wherein, in the second damping force generation mechanism,

the valve seat member is provided in the cap member, the first sub-valve is provided in one of the chambers, and the second sub-valve is provided in a cap chamber between the bottom part of the cap member and the valve seat member, and

an orifice is provided in the second passage on an upstream side or a downstream side of a flow when the first sub-valve opens.

9. The shock absorber according to claim 1 , wherein the second damping force generation mechanism includes:

a cylindrical guide member provided in the piston rod and having a guide port on a side wall;

a shutter member fitted to be rotatable in the guide member and having a shutter port facing the guide port on the side wall; and

a driving means configured to drive the shutter member.