Shock absorber and damping force generation mechanism

A shock absorber comprising:

• a cylinder in which a working fluid is sealed;
• a piston fitted into the cylinder to be slidable and partitioning an inside of the cylinder into a first cylinder chamber and a second cylinder chamber;
• a first passage through which the working fluid flows from one chamber in the cylinder due to movement of the piston;
• a second passage provided parallel to the first passage;
• a valve mechanism provided in the first passage and operating when the first cylinder chamber is at an upstream pressure to allow a damping force to be adjusted by a pressure in a main-back pressure chamber;
• a frequency sensitive mechanism provided in the second passage and operating when the first cylinder chamber is at an upstream pressure to vary a volume according to movement of a movable member;
• a check valve provided in the second passage and operating when the second cylinder chamber is at an upstream pressure;
• and
• a first throttle mechanism provided downstream or upstream of the check valve and operating when the second cylinder chamber is at an upstream pressure to control a flow of the working fluid to the main-back pressure chamber-,
• wherein a sub-back pressure chamber is provided between the first throttle mechanism and the main-back pressure chamber.