Electronic Expansion Valve

An electronic expansion valve, comprising:

• a valve seat portion, the valve seat portion being provided with a valve cavity and a first flow passage;
• a sealing gasket located inside the valve seat portion and fitting with the valve seat portion, the sealing gasket being disposed around the first flow passage, the sealing gasket being provided with a second flow passage, and the first flow passage being in communication with the second flow passage;
• and
• a valve head movably arranged inside the valve cavity to open and close the second flow passage, the second flow passage, when open, being in communication with the valve cavity, and a hardness of the valve head and the valve seat portion being greater than a hardness of the sealing gasket;
• wherein the first flow passage and the second flow passage form a variable-diameter flow passage, flow areas at both ends of the variable-diameter flow passage being denoted as S1 and S2, respectively, and a minimum flow area in a middle of the variable-diameter flow passage being denoted as S3, wherein S3<S1 and S3<S2.