| 摘要 |
PURPOSE:To accurately know the generation of knocking by forming a nonpolarization part at a part which faces the connector part of an annular piezoelectric element. CONSTITUTION:A cylindrical connector part 17 is formed on a case 1 made of synthetic resin from the peripheral surface of its main body part 2 and two connection terminal levers 14 and 14 which project internally are surrounded with its cylindrical wall 16. The terminal levers 14 and 14 are connected to upper and lower electrode plates 9a and 9b of the piezoelectric element 8 through an internal resistance 15 in the case 1 and a potential difference corresponding to the thickness-directional strain of the element 8 due to the knocking is generated and fetched as a signal voltage. Then when the nonpolarization part alpha of the element 8 is arranged opposite a connector part 17, vibration from the connector part 17 is propagated to the element 8 while having directivity and the part of the element 8 facing the connector part 17 vibrates, but the nonpolarization part alpha generates no signal output. Therefore, the generation of a noise signal due to the vibration can be inhibited and the accurate knocking detection is enabled. |
