Piezoelectric harvester with a second resonant mode cantilever piezoelement

Abstract

The invention is a piezoelectric energy harvester operating in the second mode of resonant frequencies. The piezoelectric harvester is of cantilever-type, comprising a mounting base (1), a cantilever (2), and a piezo element connected to the cantilever (3, 4), where the cantilever is an elongated (e.g. rectangular) oscillating plate tuned to the resonant frequency of the second mode, the thickness of which has a thinning from 1 / 3 to 1 of cantilever length in relation to anchoring in the length segment. In the preferred embodiment, the thinning is characterized: in the first segment (5) from anchoring to 0.376 of the total length, the maximum and constant, in the second segment (6) in length interval from 0.376 to 0.526 – the thickness decreases from 100 % to 33 % of the maximum thickness, in the third segment (7) from 0.526 to 0.857 the thickness does not change and is 33 % of the maximum thickness, and in length fourth segment (8) from 0.857 to 1, the thickness of the cantilever increases to 78 % of the max. thickness. Due to this special shape, up to 70 % higher stresses and at thereby the output of the electric potential value are obtained, rather than using the same cantilever with the same thickness along 5 the entire length.