Check valve structure

A check valve structure comprising:

• an inflow path and an outflow path for a fluid;
• a valve casing communicating the inflow path with the outflow path;
• and
• a valve element disposed in the valve casing and composed of an elastic material, the valve element including (i) a thin portion having a substantially circular shape in a plan view, the thin portion having a first surface positioned at an outflow path side and a second surface positioned at an inflow path side, and (ii) a thick portion protruding from a center of the first surface of the thin portion, wherein:
• the valve casing includes:
• a valve element support portion shaving an annular bottom portion configured to support an outer edge of a bottom surface of the thick portion without obstructing a fluid flow at a radial center of the annular bottom portion, and a peripheral wall portion extending from an outer peripheral edge of the annular bottom portion;
• and
• a valve seat portion having a valve element contact portion configured to contact with a contact region of an outer peripheral edge portion on the second surface of the thin portion, and a valve seat surface disposed between the valve element contact portion and an outlet end of the inflow path, the valve seat surface being configured to contact the second surface of the thin portion inside of the contact region of the outer peripheral edge portion,
• a hole portion extends from the radial center of the annular bottom portion to the outflow path, and
• under a pressure of the fluid flowing from the inflow path to the outflow path, the contact region of the outer peripheral edge portion deforms elastically so as to separate from the check valve structure element contact portion and open the valve.