Relief valve

A relief valve comprising:

• a valve casing formed into a cylindrical shape and having
• a suction port opening on one end side in a cylinder axial direction,
• a valve hole communicating with the suction port,
• a valve chamber communicating with the valve hole, and
• a valve seat protruding cylindrically from a bottom surface of the valve chamber;
• a valve body that closes the valve hole in a valve-closed state, and is raised in the cylinder axial direction by pressure of gas flowing from the suction port to open the valve hole;
• and
• a biasing member that biases the valve body toward the valve hole,
• wherein the valve body includes:
• a seating portion where the valve seat is in contact with, and located on a back surface of the valve body;
• a first pressure receiving surface portion that closes the valve hole in the valve-closed state and receives the pressure of the gas flowing from the valve hole;
• a second pressure receiving surface portion that receives the pressure of the gas flowing from the valve hole into the valve chamber in a valve-opened state in which the valve body opens the valve hole;
• and
• a peripheral wall portion that surrounds the second pressure receiving surface portion and cylindrically and downward from an outer edge of the valve body extends along an inner peripheral surface of the valve casing,
• wherein the second pressure receiving surface portion is formed by at least a back surface of a flange portion extending laterally and outwardly from the seating portion in an annular shape, and an inner peripheral surface of the peripheral wall portion so as to form a large pressure receiving surface to receive the pressure of the gas in the valve-opened state.