Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-01-31
2004-04-13
Nguyen, Judy (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06719409
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet printer head and a piezoelectric actuator for the head, in particular, in which ink filled in a pressure chamber is jetted by converting an electric energy into a mechanical vibration energy in high efficiency.
DESCRIPTION OF THE RELATED ART
Conventionally, a piezoelectric actuator, in which a vibration transferring plate and a piezoelectric plate having a characteristic, which is expanded and contracted by applying a voltage, are unified, has been developed and used for an ink jet printer head and a pressure pump. The piezoelectric actuator for the ink jet printer head is classified into two types. In one type, a vertical vibration of the piezoelectric plate is used, and in the other type, bending, which is generated by the vibration of the piezoelectric plate unified the vibration transferring plate, is used.
For example, a technical report, written by T. Katakura, “Technology to Make Ink Jet Printer Head High Performance ” Ultrasonic Wave TECHNO, 1998, pp. 33-36, describes a structure of an ink jet printer head used a piezoelectric actuator and its ink jet theory in detail.
FIG. 1
is a perspective view showing a structure of this conventional ink jet printer head and its piezoelectric actuator for this head. As shown in
FIG. 1
, this conventional ink jet printer head used the piezoelectric actuator consists of an upper electrode
91
, a piezoelectric plate
92
, a lower electrode
93
, a vibration transferring plate
94
, and a pressure chamber
95
.
An electric energy applied to the piezoelectric actuator is converted into a mechanical vibration energy by the upper electrode
91
, the piezoelectric plate
92
, and the lower electrode
93
. This mechanical vibration energy is transferred to liquid ink filled in the pressure chamber
95
via the vibration transferring plate
94
, and is converted into an acoustic energy. This acoustic energy is converted into a kinetic energy, which is required to make ink drops hit paper, at a small hole provided on the surface of a printer head. The kinetic energy makes the ink drops jet the paper. The amount of this kinetic energy depends on the size of the mechanical displacement, generated by the mechanical vibration energy by the piezoelectric actuator, of the vibration transferring plate
94
.
At the piezoelectric actuator, it is required that the energy conversion efficiency from the electric energy to the mechanical vibration energy is high, that is, it is required that the mechanical displacement of the vibration transferring plate
94
is large. This energy conversion efficiency is shown as follows: the energy conversion efficiency=the mechanical vibration energy/the applied electric energy. The larger the energy conversion efficiency is, the bigger the mechanical displacement becomes. Therefore, as shown in
FIG. 1
, the piezoelectric actuator, which consists of the vibration transferring plate
94
, the lower electrode
93
formed on the vibration transferring plate
94
, and the piezoelectric plate
92
having a long rectangle shape, disposed on the lower electrode
93
, and the upper electrode
91
formed on the piezoelectric plate
92
, is generally used.
However, at the conventional piezoelectric actuator mentioned above, the expanding and contracting movement in the width direction of the piezoelectric plate
92
is mainly used, and the expansion and contraction in the length direction does not contribute to the vibration. Consequently, the energy conversion efficiency from the applied electric energy to the mechanical vibration energy is very low. That is, there is a problem that the kinetic energy being sufficient to jet liquid ink cannot be obtained, because the mechanical displacement of the vibration transferring plate
94
is small.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an ink jet printer head and a piezoelectric actuator for the head, in which energy conversion efficiency from an electric energy to a mechanical vibration energy is high, and its mechanical displacement of a vibration transferring plate is large. Further, by using the piezoelectric actuator of the present invention, it is easily possible to realize a thin-sized and efficient pressure pump for the ink jet printer head.
According to a first aspect of the present invention for achieving the object mentioned above, there is provided an ink jet printer head. The ink jet printer head provides a pressure chamber, which is formed in a substrate as a cavity and provides an opening part having a designated contour shape on the upper surface side of the substrate, a vibration transferring plate, which is bonded to the pressure chamber in a state that the vibration transferring plate covers the opening part, and a piezoelectric actuator, which is formed by layering a lower electrode, a piezoelectric plate, and an upper electrode on the vibration transferring plate, and includes the vibration transferring plate and a pressure chamber side wall, bonded to the vibration transferring plate, of the pressure chamber. And the designated contour shape of the opening part of the pressure chamber is a rectangle, and the length ratio of the short side to the long side of the rectangle is 0.8 or more and 1.0 or less, and the contour of the piezoelectric plate of the piezoelectric actuator is positioned within the contour shape of the opening part of the pressure chamber above the opening part.
According to a second aspect of the present invention, in the first aspect, the area of the piezoelectric plate is 0.5 or more and 1.0 or less of the area of the opening part of the pressure chamber.
According to a third aspect of the present invention, in the second aspect, the piezoelectric plate having the lower electrode is formed on the vibration transferring plate at the position where the center position of the piezoelectric plate is made to be almost equal to the center position of the opening part of the pressure chamber.
According to a fourth aspect of the present invention, in the third aspect, the contour of the piezoelectric plate is a rectangle.
According to a fifth aspect of the present invention, in the fourth aspect, the contour of the piezoelectric plate is a similarity rectangle to the contour shape of the opening part of the pressure chamber.
According to a sixth aspect of the present invention, in the fifth aspect, the contour of the piezoelectric plate is an almost equal shape to the contour shape of the opening part of the pressure chamber.
According to a seventh aspect of the present invention, in the third aspect, the contour of the piezoelectric plate is a circle.
According to an eighth aspect of the present invention, in the seventh aspect, at least a part of the circumference of the circular contour of the piezoelectric plate having the lower electrode is positioned within the contour shape of the opening part of the pressure chamber, by disposing the vibration transferring plate between the piezoelectric plate having the lower electrode and the pressure chamber.
According to a ninth aspect of the present invention, in the seventh aspect, the circular contour of the piezoelectric plate having the lower electrode is positioned within the contour shape of the opening part of the pressure chamber, by disposing the vibration transferring plate between the piezoelectric plate having the lower electrode and the pressure chamber.
According to a tenth aspect of the present invention, in the third aspect, the contour of the piezoelectric plate is an ellipse.
According to an eleventh aspect of the present invention, in the tenth aspect, at least a part of the ellipse contour of the piezoelectric plate having the lower electrode is positioned within the contour shape of the opening part of the pressure chamber, by disposing the vibration transferring plate between the piezoelectric plate having the lower electrode and the pressure chamber.
According to a twelfth aspect of the present invention, in the tenth aspect, the ellipse contour of the
Nakamura Hirofumi
Ochi Atsushi
Sasaki Yasuhiro
Nguyen Judy
Young & Thompson
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