Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Utility Patent
1998-10-21
2001-01-02
Mayes, Curtis (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S089120, C310S324000
Utility Patent
active
06168680
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a zirconia diaphragm structure, a method of producing the same, and a piezoelectric/electrostrictive element including the zirconia diaphragm structure. In particular, the invention is concerned with such a diaphragm structure having a thin zirconia diaphragm that is free of buckling, cracks and other defects, and a method of producing the diaphragm structure, and is also concerned with a high-quality piezoelectric/electrostrictive film element including such a zirconia diaphragm structure.
2. Discussion of Related Art
A diaphragm structure having a substrate or base with at least one window or opening formed therethrough, and a thin diaphragm plate formed of a flexible material so as to close the window or windows, has been widely used for various kinds of sensors. In recent years, this diaphragm structure has been increasingly used for piezoelectric/electrostrictive actuators. When the diaphragm structure is used as a component of a sensor, the sensor has appropriate means for detecting the amount of bending or flexural displacement of a diaphragm of the diaphragm structure, which displacement is caused by an object (e.g., voltage) to be measured by the sensor. When the diaphragm structure is used as a component of a piezoelectric/electrostrictive actuator, the diaphragm of the diaphragm structure is deformed or deflected by a piezoelectric/electrostrictive element formed on the diaphragm. For example, the actuator utilizes a change in the pressure in a pressure chamber formed within the diaphragm structure.
The diaphragm structure as described above may be produced by forming an integral body consisting of the substrate serving as a base or support, and a film member which is supported by the substrate and which provides the diaphragm. For improved operating reliability, and increased heat resistance and corrosion resistance, the diaphragm structure is desirably formed as a fired integral ceramic body, as proposed in U.S. Pat. No. 4,894,635 (corresponding to JP-A-63-292032) owned by the assignee of the present application, and co-pending U.S. patent application Ser. No. 08/239,856 (corresponding to JP-A-5-29675) assigned to the present assignee. These publications disclose a piezoelectric/electrostrictive film element in the form of a fired integral body of a ceramic material, which is used for a pressure sensor and a piezoelectric/electrostrictive actuator.
The integral ceramic diaphragm structure as described above is generally formed by laminating a ceramic green substrate having a window with a thin ceramic green sheet for closing the window, to thus form an integral green laminar ceramic body having a diaphragm portion which closes the window at one of the opposite open ends of the window. The green laminar ceramic body is then fired into the integral diaphragm structure. The inventors of the present invention found that the thus prepared diaphragm structure tends to suffer from buckling or cracking at the diaphragm portion. The buckling and cracking at the diaphragm portion are detrimental to the intended function or operation of the diaphragm, resulting in reduced operating reliability.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide a zirconia diaphragm structure which is free from buckling, cracking and other physical defects at its diaphragm portion and which assures improved operating reliability.
It is a second object of the present invention to provide a method suitable for producing such a diaphragm structure.
It is a third object of the invention to provide a piezoelectric/electrostrictive film element using the diaphragm structure as described above, in particular, a piezoelectric/electrostrictive film element having an excellent quality.
The first object of the invention may be attained according to one aspect of the present invention, which provides a zirconia diaphragm structure comprising: a zirconia substrate having at least one window and containing 0.1-3.0% by weight of alumina, 0.1-3.0% by weight of silica, 0.1-5.0% by weight of alumina and silica, 0.1-5.0% by weight of alumina and magnesia, or 0.1-5.0% by weight of alumina, silica and magnesia; and a zirconia diaphragm plate formed integrally with the zirconia substrate so as to close each window of the zirconia substrate, at an open end of each window. The diaphragm plate includes at least one diaphragm portion which corresponds to the at least one window of the zirconia substrate.
The first object may also be attained according to another aspect of the present invention, which provides a zirconia diaphragm structure comprising a zirconia substrate having at least one window, and a zirconia diaphragm plate formed integrally with the zirconia substrate so as to close each of the at least one window at an open end of the each window, the zirconia diaphragm structure being produced by a method comprising the steps of: preparing a zirconia green substrate having at least one window and containing a source material which gives, after firing of the zirconia green substrate, 0.1-3.0% by weight of alumina, 0.1-3.0% by weight of silica, 0.1-5.0% by weight of alumina and silica, 0.1-5.0% by weight of alumina and magnesia, or 0.1-5.0% by weight of alumina, silica and magnesia; forming a zirconia green sheet on the zirconia green substrate, to provide an integral green laminar structure in which the at least one window of the zirconia green substrate is closed by the zirconia green sheet; and firing the integral green laminar structure into an integral sintered body in the form of the zirconia diaphragm structure wherein the zirconia diaphragm plate formed by firing of the zirconia green sheet provides at least one diaphragm portion which closes the at least one window of the zirconia substrate formed by firing of the zirconia green substrate.
In the zirconia diaphragm structure constructed or produced as described above according to the present invention, the diaphragm portion or portions closing the window or windows of the substrate is/are free from buckling, cracking and other defects. Thus, the present diaphragm structure has improved quality and enhanced operating reliability.
In one preferred form of the invention, the zirconia substrate and zirconia diaphragm plate are principally formed of partially stabilized zirconia or a material which is fired into partially stabilized zirconia. In this instance, the fired zirconia substrate and the thin diaphragm plate exhibit high physical or mechanical strength, and high degrees of heat resistance and corrosion resistance, and the diaphragm plate can be made sufficiently thin, exhibiting high flexibility. Thus, the present diaphragm structure has a wide range of applications.
The above-described second object may be attained according to a further aspect of the present invention, which provides a method of producing a zirconia diaphragm structure comprising a zirconia substrate having at least one window, and a zirconia diaphragm plate closing each of the at least one window at an open end of the each window, the method comprising the steps of: (a) preparing a zirconia green substrate having at least one window and containing a source material which gives, after firing of the green substrate, 0.1-3.0% by weight of alumina, 0.1-3.0% by weight of silica, 0.1-5.0% by weight of alumina and silica, 0.1-5.0% by weight of alumina and magnesia, or 0.1-5.0% by weight of alumina, silica and magnesia; (b) preparing a zirconia green sheet; (c) laminating the zirconia green sheet on the zirconia green substrate, to provide an integral green laminar structure in which the at least one window of the zirconia green substrate is closed by the zirconia green sheet; and (d) firing the integral green laminar structure into an integral sintered body in the form of the zirconia diaphragm structure wherein the zirconia diaphragm plate formed by firing the zirconia green sheet provides at least one diaphragm portion which closes the at least one window of
Masumori Hideo
Nanataki Tsutomu
Takeuchi Katsuyuki
Takeuchi Yukihisa
Burr & Brown
Mayes Curtis
NGK Insulators Ltd.
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