Impeller type flowmeter

The invention relates to the technical field of flow meters, and discloses an impeller type flow meter which comprises a body and a cover body which are connected in a sealed mode, a fluid containing cavity is formed in the body, an impeller is arranged in the fluid containing cavity, a rotating shaft of the impeller is rotationally arranged in the fluid containing cavity, and a plurality of blades are arranged on the outer side of the rotating shaft. The axial extension width of the blades in the rotating shaft is smaller than the length of the rotating shaft; magnets are arranged in the blades, and detection parts used for sensing the magnets are arranged on the body; a movable cavity is formed in the end, close to the fluid containing cavity, of the detection part, an elastic piece attracted to the magnet is arranged in the movable cavity, a plurality of piezoelectrics are arranged on one side of the elastic piece in the circumferential direction, and the piezoelectrics can generate electric energy through