| 摘要 |
<p>PURPOSE:To enable other layered piezoelectric elements to continue their operation normally even if a certain element is short circuited, by connecting a circuit for applying a voltage between electrodes of the piezoelectric elements in series to a power circuit, and adding a circuit for shutting off excessively large current. CONSTITUTION:Each piezoelectric element 7 is interposed between electrodes 8 to provide a layered structure and terminals 10 are provided at both ends of the structure. Printed circuit boards 12 and 13 are coupled to lugs 11 of the electrodes 8. An insulation plate 16 is inserted between the rear face 6 of the terminal 10 and the electrode 81. The printed circuit board 12 has a conductive portion 172, polysilicon films 181-184 and conductive portions 191-194 which are patterned on a glass 21 provided with notches 201-204, and the lugs of the electrodes 81, 83, 85 and 87 are brazed respectively to these notches. The electrodes 8 are arranged alternately such that the lugs are not overlapped. In this arrangement, even if the element 71 for example is broken and abnormal current 24 flows in the polysilicon films 191 and 195 to fuse off these polysilicon films 191 and 195, the other elements continue their normal operation. Thus, the function of the unit as a whole will not be stopped.</p> |
