| 摘要 |
PURPOSE:To prevent a fissure and a crack in the dummy plates and the laminated ceramic piezo-electric single unit by a method wherein the dummy plate is provided on both end surfaces of the laminated ceramic piezoe-electric single unit and the specific inductive capacity of the dummy plate is chosen less than 1,200. CONSTITUTION:When a dummy plate 7 is arranged on both end surface of a laminated ceramic piezo-electric single unit A, the lifetime of the laminated ceramic piezo-electric material is significantly prolonged. However, when the material of the plate 7 is resin, the plate is easy to crack as the resin is large in expansion and contraction and when the material of the plate is Al2O3, the plate is easy to crack as well as the Al2O3 has a high Young's modulus. Furthermore, when the material of the plate is the same material as that of the ceramic single unit,the plate has a weakness of being eroded by discharge. In contrast thereto, when a material having a specific inductivity of less than 1,200 is chosen for the material, erosion of the dummy plate according to discharge is dwindled down to zero. Or, the dummy plate 7 having the specific inductivity of more than 1,200 can be coated with a resin materal 8 having a small specific inductivity. Moreover, when the Young's modulus of the dummy plate is chosen less than 7.0X10<10>N/cm<2>, the durability of the dummy plate is improved. By this constitution, a fissure and a crack in the dummy plats and the ceramic piezo-electric single unit are prevented at the time of use and the piezo-electric material havng an excellent durability can be obtained. |
