Patent ID: 7358643

Claim:
A piezoelectric actuator comprising: a vibration plate; a supporting member which includes a relieving section which relieves a deformation of the vibration plate, and a joining section which is joined to the vibration plate; a first electrode which is arranged on a surface of the vibration plate on a side opposite to the supporting member; a piezoelectric layer which is arranged on a surface of the first electrode on a side opposite to the vibration plate; a second electrode which is arranged on a surface of the piezoelectric layer on a side opposite to the vibration plate, in an area facing the relieving section; a contact section which is formed on the surface of the piezoelectric layer on the side opposite to the vibration plate, in an area facing the joining section, the contact section being connected to the second electrode; and a wire member which supplies a drive voltage to the contact section, wherein: an electroconductive bump is formed on one of a terminal section of the wire member and the contact section, the bump being projected toward the other of the terminal section and the contact section to electrically connect the contact section and the terminal section; and a reduced-stiffness section is provided between the vibration plate and the supporting member or between the vibration plate and the piezoelectric layer, at a portion facing the bump, the reduced-stiffness section having a stiffness reduced than a stiffness of a portion other than the portion facing the bump.