Patent ID: 7178383
Filing Date: 2007-02-20
Classification: G01L

Abstract:
1. A knock sensor comprising: a base having: an annular piezoelectric element having electrode portions formed on front and rear surfaces thereof so as to face each other, said piezoelectric element being fitted over said cylindrical portion; first and second terminal plates fitted over said cylindrical portion so as to hold said piezoelectric element from opposite sides, said first and second terminal plates closely contacting said electrode portions to extract an output signal from said piezoelectric element; an annular weight fitted over said cylindrical portion to impart a vibrational force to said piezoelectric element; a first insulating sheet interposed between said first terminal plate and said flange portion to insulate said first terminal plate and said flange portion from each other electrically; a second insulating sheet interposed between said second terminal plate and said weight to insulate said second terminal plate and said weight from each other electrically; and a holding means for clamping and holding a stacked body against said flange portion, said stacked body being constituted by said first insulating sheet, said first terminal plate, said piezoelectric element, said second terminal plate, said second insulating sheet, and said weight, wherein: said electrode portions are constituted by annular partial electrodes having a width narrower than a radial width of said piezoelectric element and formed on said front and rear surfaces of said piezoelectric element, and said first and second terminal plates have annular portions formed so as to have annular shapes having an outside diameter and an inside diameter substantially equal to those of said partial electrodes, and are stacked such that said annular portions are placed in close contact with entire surfaces of said partial electrodes.