Nec Corporation

Tetsuo Shirasu

Eiji Takahashi

Osamu Yamashita

Takeshi Nishizawa

Hidekazu Takada

An internal electrode is printed on one surface of each electrostrictive ceramic green sheet by the screen printing. Two such electrostrictive ceramic green sheets each with an internal electrode layer are laid the electrostrictive ceramic layer of one on the internal electrode layer of the other and rolled together, and then sintered. Subsequently lead wires are soldered to the exposed portions of the corresponding internal electrodes. In virtue of this, small-size, low-voltage driven, highly reliable electrostrictive effect elements can be obtained, and the manufacture of them is very facilitated with the effect of remarkably reducing manufacture cost. In addition the electrostrictive effect element according to the present invention has the capability of radial expansion and contraction about the central axis of the rolled structure and thereby can be applied to new use out of the scope of the prior art.

Electrostrictive effect element and the process of manufacturing the same

A piezoelectric effect device has a piezoelectric body comprised of a sintered multilayer pillar composed of alternately laminated piezoelectric ceramic sheets and internal electrodes such that edges of the internal electrodes are alternately insulated every one another layers along opposite side faces of the sintered multilayer pillar, and a pair of external electrodes provided on the opposite side faces to electrically connect to noninsulated edges of the internal electrodes. There is provided a metal stem having a pair of hermetically sealed external terminals electrically coupled to the pair of external electrodes. A metal case having flexibility in a displacement direction of the piezoelectric body is seal-welded to the metal stem at their contacts to hermetically enclose the piezoelectric body. A pair of metal pads having a linear thermal expansion coefficient less than ten times as that of the piezoelectric body are provided to substantially cover opposite end faces of the piezoelectric body. One metal pad is centrally spot-welded to an inner face of the metal stem in opposed relation to one end face of the piezoelectric body and is secured thereto by an adhesive, and the other metal pad is centrally spot-welded to an inner face of the metal case in opposed relation to the other end face of the piezoelectric body and is secured thereto by an adhesive.

Piezoelectric effect device

A hermetically sealed electrostrictive actuator comprises a metal case and a metal cap for housing an electrostrictive element therein. The metal cap is provided with a pair of glass sealing terminals to be connected to a pair of lead wires of the electrostrictive element. The metal case is provided a flexible region so as to follow the expansion and constraction of the electrostrictive element without breaking the hermetic envelope of the metal case and the metal cap.

Hermetically sealed electrostrictive actuator

An electrostriction effect element having a simplified construction through the provision of a relatively thick connection portion disposed between two actuator portions. The connection portion preferably has a thickness greater than that of the solder or lead wires which are provided to connect the overall element. As a result, soldering is considerably simplified. Additionally, protection portions may be added at opposite ends of the pillar of electrostrictive material, sandwiching the actuator portions and the connection portion. The protection portions also preferably have a thickness greater than that of any of the electrostrictive layers in the pillar. Still further, buffer layers may be provided between the connection portion and each of the actuator portions, and also between the actuator portions and the protection portions. These buffer layers also preferably have a thickness greater than that of any of the electrostrictive layers in the pillar material. The overall element may be rectangular or cylindrical in cross-section.

Growing community of inventors

Tokyo, Japan

Tetsuo Shirasu