Patent ID: 6756722
Filing Date: 2004-06-29
Classification: G01L,H01T

Abstract:
A spark plug comprising:a center electrode; a porcelain insulator having a first and a second length, the first length having said center electrode retained therein; a hollow cylindrical housing in which said center electrode is retained through said porcelain insulator and which has a ground electrode installed thereon; a piezoelectric sensor disposed on an outer periphery of the second length of said porcelain insulator, said piezoelectric sensor being responsive to pressure of combustion of fuel within an engine transmitted through said porcelain insulator to provide a signal indicative thereof; a holder welded to said housing so as to apply a given preload to the piezoelectric sensor at all times; and a shoulder formed on an outer periphery of said porcelain insulator and a seat member disposed between said shoulder and said piezoelectric sensor in direct contact with said shoulder for transmission of the pressure of combustion of fuel to said piezoelectric sensor through said seat member.