Ink jet print head and method of production thereof

Details Ink jet print head and method of production thereof Ink jet print head and method of production thereof

2002-03-08

2004-01-27

Meier, Stephen D. (Department: 2861)

Incremental printing of symbolic information

Ink jet

Ejector mechanism

C347S068000

Reexamination Certificate

active

06682179

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet print head for use in an office or industrial environment, and also to a method of producing the ink jet print head.
2. Description of the Related Art
FIG. 1
is a cross-sectional view showing an example of a conventional ink jet print head. The ink jet print head includes an orifice plate
102
formed with a nozzle
101
, a chamber plate
104
formed with a pressure chamber
103
, a restrictor plate
106
formed with a restrictor
105
, a diaphragm/filter plate
109
formed with a diaphragm
107
and a filter
108
, a housing
111
formed with a common ink channel
110
, a piezoelectric element
112
, and a piezoelectric element fixing plate
113
for fixing the piezoelectric element
112
in place. The piezoelectric element
112
is made up of a number of plate-shaped piezoelectric material pieces and a number or electrodes alternately stacked one on the other. For the sake of brevity, the piezoelectric element will be hereinafter referred to simply as “piezoelectric element”.
The housing
111
includes edges X
1
and Y
1
for setting the position of the piezoelectric element fixing plate
113
in the X and Y directions, respectively. The piezoelectric element fixing plate
113
is abutted against and fixed to the edges X
1
and Y
1
by adhesive (not shown). The adhesive must be applied according to the machining precision or the positioning edges X
1
, Y
1
and must be applied thinly.
However, in order to reduce variation in ink ejection, the diaphragm
107
and the piezoelectric element
112
need to be attached to each other with great positional accuracy. This requires that the housing
111
and the piezoelectric element fixing plate
112
be machined with extreme precision. For example, the distance from the positioning edge Y
2
of the piezoelectric element fixing plate
113
to where the piezoelectric element
112
is adhered to the diaphragm
107
must be extremely precise so the positioning edges X
1
, Y
1
must be machined in the housing
111
with extremely high precision. Also, the corners between various surfaces must be extremely close to perfect right angles. If not, the surface X
1
adhered to the piezoelectric element fixing plate
113
will lean toward or away from the diaphragm
107
, so that the surface of the piezoelectric element
112
that is adhered to the diaphragm
107
will also slant with regard to the diaphragm
107
. Full and uniform contact between the adhered surfaces of the piezoelectric element
112
and the diaphragm
107
cannot be achieved.
If the adhesive layer is too thin or non-uniform, then the piezoelectric element fixing plate
113
cannot be adhered in accordance with the reference edges X
1
, Y
1
. As a result, the adhering surfaces of the diaphragm
107
and the piezoelectric element
112
will not contact each other uniformly, resulting in the diaphragm
107
and the piezoelectric element
112
being adhered to each other at a slant.
When the housing ill and the piezoelectric element fixing plate
113
are made from different materials having different thermal expansion coefficients, then the ink jet head can suffer from warping if the piezoelectric element fixing plate
113
is fixed to the housing
111
by adhesive, for example. The warping can result in variations in ink ejection properties, especially at the end nozzles.
For these reasons, in order to reduce variation in ink ejection, the precision of all components and the thickness of the adhesive must be managed carefully. Components such as the housing
111
and the piezoelectric element fixing plate
113
must be made with high machining precision and so are expensive. As a result, the ink jet head is expensive to make.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to overcome the above-described problems and to provide an inexpensive ink jet print head with reduced variation in ink ejection properties and a method of manufacturing the ink jet print head.
In order to achieve the above and other objects, an ink jet print head according to the present invention includes a pressure chamber portion, an orifice plate, a restrictor plate, a diaphragm, piezoelectric elements, a piezoelectric element fixing plate, a housing, and a cover.
The pressure chamber portion has pressure chambers. The orifice plate is formed with nozzles in a one-to-one correspondence with the pressure chambers. Each nozzle brings a corresponding pressure chamber into fluid communication with atmosphere. The restrictor plate is formed with ink channels in fluid communication with the pressure chambers. The diaphragm forms a side of the pressure chambers. The piezoelectric elements are attached to the diaphragm in a one-to-one correspondence with the pressure chambers. Each piezoelectric element generates, through the diaphragm, a pressure fluctuation in a corresponding pressure chamber when applied with an electric signal. The piezoelectric element fixing plate is fixedly attached to and supports the piezoelectric elements.
The housing includes a common ink channel portion and internal side walls. The common ink channel portion is formed with a common ink channel in fluid communication with the channels in the restrictor plate. The internal side walls adjoin the diaphragm at one side to define a space that opens at an end opposite from the diaphragm. The piezoelectric element fixing plate and the piezoelectric elements are disposed at least partially in the space with a gap existing between the piezoelectric element fixing plate and the internal side walls that define the space.
The cover covers the piezoelectric element fixing plate. The cover is connected to the housing and is provided with an internal space large enough to maintain a gap between the cover and the piezoelectric element fixing plate.
With this configuration, the cover covers the piezoelectric element fining plate and moreover has an internal space large enough so that the piezoelectric element fixing plate can be inserted into while the gap is maintained between the housing and the piezoelectric element fixing plate. Because the internal space in the cover is, in the same manner as the opening in the housing, larger than the both piezoelectric element and the piezoelectric element fixing plate to which the piezoelectric element is fixed, the ink seal and the cover can be fixed on the housing without any external pressure being applied to the piezoelectric element fixing plate. As a result, the ink jet print head is less expensive and has fewer variations in ink ejection properties.
According to a method of the present invention, a piezoelectric element set, a front end set, and a positioning plate are prepared, but not necessarily in this order.
The piezoelectric element set includes a piezoelectric element fixing plate and piezoelectric elements. The piezoelectric elements are attached to the piezoelectric element fixing plate with a predetermined positioning.
The front end set includes a pressure chamber portion, an orifice plate, a restrictor plate, a diaphragm, and a housing. The pressure chamber portion has pressure chambers with positioning that corresponds to positioning of the piezoelectric elements on the piezoelectric element fixing plate. The orifice plate is formed with nozzles in a one-to-one correspondence with the pressure chambers. Each nozzle brings a corresponding pressure chamber into fluid communication with atmosphere. The restrictor plate is formed with ink channels in fluid communication with the pressure chambers. The diaphragm forms a side of the pressure chambers.
The housing of the front end set includes a common ink channel, a space, and positioning holes. The common ink channel is in fluid communication with the channels in the restrictor plate. The space is defined by internal side walls that adjoin the diaphragm at one side. The space is open at an open end thereof opposite from the diaphragm. The space is large enough to insert through the open end the piezoelec

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