Piezoelectric actuator and method of manufacturing the same

Claim 1

A piezoelectric actuator which comprises an electrostrictive effect element which is formed by stacking a plurality of electrostrictive materials and internal electrodes by turns, a metal case having a flanged mounting portion with a flat surface on a periphery thereof, a metal member having a flanged mounting portion with a flat surface on the periphery thereof and having an annular portion which rises from said flat surface of the flanged mounting portion by a certain amount, another metal member and hermetically sealed terminals; said electrostrictive effect element being hermetically sealed within the metal case, the metal members and the hermetic terminals; one of said metal case or said another metal member having an expansion and contraction portion, and said flat surface of the flanged mounting portion of said metal case being butted and joined hermetically to said raised portion of the flat surface of the flanged mounting portion of the metal member to crush said raised annular portion of the metal member by a certain amount to cause a gap between said flat surface of the flanged mounting portion of the metal case and said flat surface of the flanged mounting portion of the metal member and to apply a compression stress commensurate with the height of the crushed raised portion to said electrostriction effect element in the stacking direction thereof.