Abstract
This paper deals with theoretical and experimental considerations of the changes in resonant frequency f, and quality factor Q of a vibrator with input energy level in low frequencies, for the purpose finding the limit of its miniaturization and stability. Firstly, flexural bars of uniform and stepped shape made of elinver alloy are considered. It is revealed that the step-formed bars are not suitable for vibrators of small size and high stability. The flexural uniform bar designed under consideration of f_r and Q in low input energy level and its changes in high level are also described. Furthermore, the flexural composite type bars on which a piezo-ceramic element is bonded are considered. The influences of the adhesive layer on changes in f_r, and Q are found experimentally to be marked for Q, but insignificant for f_r. Secondly, similar considerations are applied to longitudinal vibrators. Finally, it is proposed that a new figure of merit should be adopted for overall evaluation of low frequency vibrators. This is because, although many vibrators are developed so far no reasonable method is known that can be applied to the evaluation of vibrators with respect to dimensional smallness and high stability. By utilising the new figure of merit mentioned in this paper, low frequency vibrators can be ranked with respect to its stability and smallness in size.
