Shock absorber

A shock absorber comprising:

• a cylinder in which hydraulic fluid is sealingly contained;
• a reservoir in which hydraulic fluid and gas are sealingly contained;
• a piston inserted in the cylinder in a slidable manner and configured to separate an interior portion of the cylinder into a first chamber and a second chamber;
• a base valve configured to separate the second chamber and the reservoir from each other;
• a first check valve provided in the piston and configured to allow a hydraulic fluid flow from the second chamber to the first chamber;
• a second check valve provided in the base valve and configured to allow a hydraulic fluid flow from the reservoir to the second chamber;
• a passage connecting the first chamber and the reservoir;
• and
• a damping force adjustment mechanism configured to be capable of adjusting a damping force from outside between soft characteristics of a low damping force and hard characteristics of a high damping force by controlling a hydraulic fluid flow in the passage,
• the first check valve being provided with orifice passages in parallel, the orifice passages being provided with a sub-check valve at passage openings of the orifice passages,
• the sub-check valve being configured to open at a lower pressure than the first check valve and allow hydraulic fluid to flow in a same direction,
• the first check valve being disposed in the first chamber, the sub-check valve being disposed in the second chamber,
• the sub-check valve being provided with a biasing member configured to bias the sub-check valve toward the passage openings,
• wherein the biasing member includes a protrusion formed on an outer peripheral side of the biasing member and a hole formed on a radially inner side with respect to the protrusion, the protrusion being configured to generate a biasing force toward the sub-check valve,
• wherein the sub-check valve is configured as a disc,
• wherein a disc valve is provided, the disc valve comprising a plurality of discs including the sub-check valve,
• wherein each orifice passage is partially configured by a respective notch extending radially inward from an outer peripheral edge of a first disc of the plurality of discs,
• wherein each passage opening is provided on a second disc of the plurality of discs, the first and second discs being in abutment with each other,
• wherein the hole is arranged such that a radially inner end of the hole is located radially inward of radially inner ends of the passage openings,
• wherein the hole is arranged such that a radially outer end of the hole is located radially outward of the radially inner ends of the passage openings, and
• wherein the protrusion is disposed so as to face the passage openings.