Shock absorber

A shock absorber comprising:

• a cylinder in which a working fluid is sealed;
• a piston provided in the cylinder to be movable and partitioning an inside of the cylinder into a first chamber and a second chamber;
• a piston rod connected to the piston and extending to an outside of the cylinder;
• a first passage provided in the piston and through which the working fluid moves from a chamber on an upstream side to a 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 to generate a damping force;
• a second passage provided in the piston rod;
• a fixing member fixed to the piston rod to form the second passage;
• and
• a second damping force generation mechanism provided in the second passage to generate a damping force, wherein
• the second damping force generation mechanism includes a throttle valve provided on one side of the second passage and having a plurality of notch parts at regular intervals in a circumferential direction to form a throttle flow path in the second passage due to the notch parts,
• a number of the notch parts of the throttle valve is expressed as n=px provided that n is the number of the notch parts formed in the throttle valve,
• p is a natural number larger than 1, and
• x is a natural number larger than 0,
• the second passage provided in the piston rod has one or more first openings formed on a first side and opening to an outer diameter surface on the piston side, and a second opening formed on a second side, penetrating the inside of the piston rod, and opening to the fixing member side,
• D=2r·sin (360/2p) is satisfied
• provided that D is a diameter of the first opening, and
• r is a radius of the piston rod at a position at which the throttle valve is disposed, and
• a minimum effective flow path area of a flow path formed of the throttle valve and the first openings is expressed as ae=a1·B(n/p)
• provided that ae is a minimum cross-sectional area of the flow path due to all the notch parts of the throttle valve,
• a1 is a minimum cross-sectional area of the flow path due to one notch part of the throttle valve, and
• B is the number of the first openings.