Patent ID: 6925878

Claim:
An acceleration sensor for detecting an acceleration caused by an object oscillated in an oscillation direction, comprising: a sensor casing having a center axis and to be positioned in coaxial alignment with said oscillation direction to receive said acceleration, said sensor casing including a cylindrical fixed case member having a supporting portion axially extending, and a cover assembly provided on said fixed case member to cover said fixed case member to define a closed space, an oscillation plate accommodated in said closed space of said sensor casing and having a central portion supported by said supporting portion of said fixed case member, and a peripheral portion integrally formed with said central portion and extending radially outwardly of said central portion to be freely movable with respect to said supporting portion of said fixed case member, and said oscillation plate being partly oscillatable along said center axis with respect to said fixed case member; a piezoelectric element held in contact with said oscillation plate to generate a voltage indicative of said acceleration when said acceleration is exerted on said sensor casing to have said oscillation plate partly oscillated along said center axis with respect to said sensor casing with said peripheral portion of said oscillation plate being deformed, and said piezoelectric element having first and second surfaces respectively having first and second electrodes mounted thereon to have said voltage indicative of said acceleration to output therethrough; a terminal pin extending through said cover assembly and terminating at the a printed board retained by said cover assembly to have said second electrode of said piezoelectric element and said terminal pin connected with each other, and in which said oscillation plate has a thickness t 1 and an radius R 1 , said piezoelectric element has a thickness t 2 , and a radius R 2 , said radius R 1 of said oscillation plate divided by said thickness t 1 of said oscillation plate is approximately equal to 3.3, said radius R 2 of said piezoelectric element divided by said radius R 1 of said oscillation plate is approximately equal to 0.5, and thickness t 1 of said oscillation plate divided by said thickness t 2 , of said piezoelectric element is approximately equal to 1.