| 摘要 |
PURPOSE:To improve conversion efficiency by removing influence of electrostatic capacity by connecting the piezoelectric element side of a coil spring to the cable conductor of an MI cable electrically and by adequately selecting the inductance of the coil spring. CONSTITUTION:The lower end of the conductor of MI cable 6 is electrically connected to the lower end of coil spring 5 and electrode plate 3 and spring 5 is connected in parallel to piezoelectric element 2. Then, inductance Ls of spring 5 is so selected that satisfies Ls=1/(omega<2>Cd). In the expression, Cd is the sum of electrostatic capacity between the conductor of cable 6 and the sheath and that of element 2, and omega is an in-use angular frequency. Thus, electrostatic capacity Cd is canceled by inductance Ls to reduce extremely a reactive current flowing through the electrostatic capacity part between the MI cable and piezoelectric element and electric energy can be supplied to acoustic load (ra) effectively, so that the conversion efficiency can greatly be improved. |
