JP2000272120A - Ink jet head and line ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ease an effect of an atmospheric pressure change, prevent liquid discharge failures and obtain a liquid-discharging apparatus appropriate to environmental atmospheric pressures of a wider range by setting a second air chamber communicating with an air chamber, and forming one or more steps to a face opposite to a displacement plate set to the second air chamber and, one electrode. SOLUTION: A second air chamber 25 is formed on a wiring board 13 to communicate with an air chamber 22. A displacement plate 26 is formed similarly to a diaphragm 18 to a part of a cavity plate 12 which is in touch with the air chamber 25. An electrode 27 is set opposite to the displacement plate 26 in the air chamber 25. Stair-like steps are formed to a face where the electrode 27 is set so as to change a distance to the displacement plate 26. A plurality of air chambers 22 and electrodes 19 are connected to the air chamber 25. The electrode 27 in the air chamber 25 is formed as an integrated body over the steps. When a voltage is impressed between the displacement plate 26 and the electrode 27, an electrostatic attraction force is generated, thereby attracting and deflecting the displacement plate 26 towards the electrode 27. When the voltage impression is stopped, the deflection is restored. Ink drops 20 are discharged from nozzles 10 by the oscillation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ink jet head in an ink jet printer.

[0002]

2. Description of the Related Art A bubble jet head is known as an ink jet head of an ink jet printer.
-284255 discloses a liquid ejecting apparatus that detects an ambient air pressure and changes a voltage waveform applied to the electrothermal transducer according to the air pressure.

[0003]

However, the above-mentioned prior art is effective for an ink jet head that heats and foams a liquid. However, the conventional example is applicable to an ink jet head that uses pressure vibration of a liquid generated by displacement of a diaphragm according to the present invention. Is less effective.

In an ink jet head that uses pressure vibration of a liquid generated by displacement of a vibration plate, the surrounding air pressure affects the driving of the vibration plate. There is a problem that the ejection failure cannot be suppressed by adjusting the driving voltage waveform.

An object of the present invention is to provide a liquid discharge apparatus suitable for a wider range of environmental pressures by mitigating the above-mentioned change in atmospheric pressure and preventing defective liquid discharge.

[0006]

A first feature of the present invention to solve the above-mentioned problem is that a displacement plate provided in the second air chamber has a second air chamber communicating with the air chamber. And one or more steps on a surface of the second air chamber facing the displacement plate, and one electrode provided on the surface.

A second feature of the present invention for solving the above-mentioned problems is that a displacement plate provided in a second air chamber and one displacement plate provided on a surface of the second air chamber facing the displacement plate are provided. The present invention has the above-mentioned steps and electrodes provided independently for each of the steps.

A third feature of the present invention for solving the above problems is that a displacement plate formed in a second air chamber and a surface of the second air chamber opposed to the displacement plate are connected to the displacement plate. The non-parallel surface is provided with an electrode.

A fourth feature of the present invention for solving the above problem is that an ink jet head having one or more of the first to third features has a plurality of nozzle rows of approximately one row. It is arranged as follows.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the embodiments of the present invention, an example of the structure and operation principle of an ink jet head according to the present invention will be described with reference to the drawings.

FIG. 1 is an external view of an ink jet head. This ink jet head has the nozzle 1
It is composed of a nozzle plate 11 in which 0 is formed, a cavity plate 12, and a wiring board 13.

FIG. 2 is a sectional view as seen from the direction of arrow 15 in FIG. One of the nozzles 10 is provided on the cavity plate 12.
A pressure chamber 16 is formed which communicates with the supply port 17 and the other communicates with the supply port 17, and a vibrating plate 18 is formed integrally with another one of the pressure chambers. The cavity plate 12 and the vibration plate 18 are conductors whose surfaces are covered with an insulator.

An air chamber 22 is provided on the wiring board 13 side of the diaphragm 18.
Is formed, and an electrode 19 is provided at a position facing the vibration plate 18 in the air chamber 22.

When a voltage is applied to the electrode 19 and the diaphragm 18, the diaphragm 18 bends due to the electrostatic attraction generated, and when the application of the voltage is stopped, the deflection is restored. Pressure oscillation is generated in the liquid ink (hereinafter abbreviated as ink) in the inside. The ink is pushed out from the nozzle 10 by the pressure vibration to eject the ink droplet 20.

For example, as shown in FIG. 3, focusing on the cavity plate 12 and the wiring board 13, when the air chamber 22 is not in communication with the surrounding air or is in communication with the surrounding air, the air chamber 22 has a large resistance to the flow of air. If the ambient pressure changes, the diaphragm 18 bends due to the pressure difference between the air pressure in the air chamber and the ambient pressure.

When the ambient pressure is lower than the air pressure in the air chamber 22, the diaphragm 18 bends upward in the figure. When the ambient pressure is higher than the air pressure in the air chamber 22, the diaphragm 18 moves downward in the figure. Deflection is well known.

The bending means that the distance between the diaphragm 18 and the electrode 19 changes, and is closely related to the electrostatic attraction force for driving the diaphragm 18. It is well known that the electrostatic attraction force is inversely proportional to the square of the distance between the electrodes. Therefore, it is obvious that the electrostatic attraction force generated between the vibration plate 18 and the electrode 19 due to the bending changes greatly. .

As described above, in the ink jet head using the pressure vibration of the liquid generated by the displacement of the vibration plate, when the surrounding air pressure changes, the electrostatic attraction force of the vibration plate 18 which generates the pressure vibration for discharging the ink is increased. If it changes and exceeds the allowable range, the ink ejection performance deteriorates.
The present invention solves the above problems.

<Example 1> Next, a first embodiment of the present invention will be described.

FIG. 5A illustrates a cross section.

A second air chamber 25 is formed on the wiring board 13 in communication with the air chamber 22, and a displacement plate 26 is formed at a portion of the cavity plate 12 in contact with the second air chamber 25, similarly to the vibration plate 18. In addition, an electrode 27 is provided in the second air chamber 25 so as to face the displacement plate 26.

A step is formed on the surface on which the electrode 27 is provided so that the distance from the displacement plate 26 is different.

FIG. 5B shows a plane arrangement of the air chamber and the electrodes. The plurality of air chambers 22 and the electrodes 19 communicate with the second air chamber 25. Electrode 2 in second air chamber 25
7 is integrated over the step shown by the broken line.

Next, the operation will be described. As shown in FIG. 6, when a voltage is applied between the displacement plate 26 and the electrode 27, an electrostatic attraction force is generated, and the displacement plate 26 is attracted to the electrode 27 side.
As a result of the bending, the portion where the displacement plate 26 and the electrode 27 are closest to each other comes into contact as shown by the broken line in the state, and the state is brought about. Next, when the applied voltage is increased, the next closest part is brought into contact, and a state is brought about. When the applied voltage is further increased, a state is established.

As shown in FIG. 7, as the state changes from the state before the application of the voltage to the state, the state, and the state, the volume in the air chamber 25 decreases, and the air pressure in the closed air chamber 25 increases.

When the applied voltage is lowered from the state, the displacement plate 26 is separated from the place where the deflection of the displacement plate 26 is the largest, and the state becomes the state. Next, when the applied voltage is reduced, the state changes, and when the applied voltage is further reduced, the state changes to a state before the voltage is applied.

Thus, from state to state, state,
The pressure in the air chamber 25 decreases as the state changes before the voltage application. As described above, the pressure in the air chamber 25 can be changed by the applied voltage.

As shown by the arrow in FIG. 6, when the pressure of the outside air increases, the pressure in the air chamber 22 becomes relatively lower than that of the outside air, and the vibrating plate 18 bends as indicated by a broken line. At this time, the displacement plate 2
If a voltage is applied to the electrode 6 and the electrode 27 and a voltage that minimizes the flexure of the diaphragm 18 is selected from the state or the state or the state, the flexure of the diaphragm 18 due to the external pressure is minimized, and the ink discharge performance can be maintained.

<Embodiment 2> Next, a second embodiment of the present invention will be described. In the present embodiment, the accuracy of the second air chamber corresponding to the atmospheric pressure is improved with respect to the first embodiment.

As shown in FIG. 8, a surface of the second air chamber 25a opposed to the displacement plate 26 is formed non-parallel to the displacement plate 26, and an electrode 27a is provided on the surface.

With this configuration, as shown in FIGS. 8 and 9, when the voltage applied between the displacement plate 26 and the electrode 27a exceeds a predetermined value, a portion of the displacement plate 26 and the electrode 27a Starts contact. Next, when the voltage is gradually increased, the contact portion is widened as the voltage increases, and the state changes continuously from state to state.

When the state changes continuously from state to state, the volume in the air chamber 25a also changes continuously.

As described above, according to the present embodiment, since the air pressure in the air chamber 25a can be changed in accordance with the change in the external air pressure, the deflection of the diaphragm 18 can be controlled more accurately, and The stability of the discharge performance is improved.

<Embodiment 3> Next, a third embodiment will be described.

In the present embodiment, as shown in FIG. 4A, a second air chamber 25b is formed on the wiring board 13 in communication with the air chamber 22, and the second air chamber 25 of the cavity plate 12 is formed.
The displacement plates 26b and 2
6c, an electrode 27b is provided facing the displacement plate 26b in the second air chamber 25b, and an electrode 27c is provided opposite the displacement plate 26c.

The surface on which the electrodes 27b and 27c are provided has a step-like step so that the distance between the electrode 27b and the displacement plate 26b is different from the distance between the electrode 27c and the displacement plate 26c.

FIG. 4B shows a plane arrangement of the air chamber and the electrodes. The plurality of air chambers 22 and the electrodes 19 communicate with the second air chamber 25b, and the electrodes 27 in the second air chamber 25b are connected.
Reference numerals b and 27c denote steps where the steps shown by broken lines are separate electrodes for Sakai.

This embodiment is different from the first embodiment in that the electrodes 2
It is characterized in that a voltage can be individually applied to 7b and 27c.

As the voltage applied between the displacement plate and the electrode, a constant voltage at which the displacement plate and the electrode abut is applied, and the pressure in the air chamber 25b can be changed by switching the electrode to be applied according to the change in the outside air pressure. .

According to this embodiment, there is no need to change the applied voltage, so that the ink ejection can be stabilized while reducing the circuit cost.

<Embodiment 4> Next, a fourth embodiment will be described. Although the operation principle described in FIGS. 1 and 2 is the same, this embodiment has a different structure, so the structure will be described with reference to FIG.

FIG. 10A is a plan view of the ink jet head. This ink jet head has an internal pressure chamber 16d shown by a broken line and a nozzle 10d opened on the side face.
Are arranged in columns. Hereinafter, the inkjet head is abbreviated as the head 30.

FIG. 10B is a cross-sectional view as seen from the direction of the arrow in FIG. A pressure chamber 16 is formed in the cavity plate 12d, and one of the pressure chambers 16 is
d communicates with the nozzle 10d formed at the point d.

The vibration plate 1 is provided on the side of the wiring board 13d of the pressure chamber 16d.
8d is formed, and an electrode 19d is provided on a surface of the air chamber 22d facing the diaphragm 18d.

When a voltage is applied to the electrode 19d and the vibrating plate 18d, pressure vibration is generated in the ink in the pressure chamber 16 as described above, and the ink is pushed out from the nozzle 10d to eject the ink droplet 20d.

The second air chamber 25 communicates with the air chamber 22d.
d, the electrode 27d is formed in a stepped step shape, and the displacement plate 2 is formed on the surface of the cavity plate 12d facing the electrode 27d.
6d is formed. The displacement plate 26 shown in FIG.
d, the second air chamber 25d, and the electrode 27d have substantially the same plane shape, and a plurality of air chambers 22d corresponding to the plurality of pressure chambers 16d communicate with one second air chamber 25d.

The structure of the second air chamber of the head 30 is shown in FIG.
In addition to the structure similar to the first embodiment shown in (b), a structure similar to the second or third embodiment may be employed.

FIG. 11 is an outline drawing of the line head. A plurality of heads 30 are arranged with the nozzles 10d aligned in one row. By arranging the heads 30 in this manner, the print width printable by the head can be widened, and a print width equal to or greater than the paper width to be used can be obtained, so that a line inkjet head with a high print speed can be realized. .

In such a line ink jet head, the number of nozzles is very large and a large number of air chambers 2 are provided.
The second air chamber requires more volume change to mitigate the 2d change in the outside air pressure. In this embodiment,
This problem has been solved by using the structure of the second air chamber shown in the first embodiment.

[0050]

The effects obtained by the present invention are listed.

(1) By providing a step between the electrodes in the second air chamber, it is possible to realize an ink jet head in which ejection failure does not occur in a wider pressure range.

(2) By forming the electrodes in the second air chamber as individual electrodes for each step, it is possible to realize an ink jet head which does not cause ejection failure in a wide pressure range without increasing the circuit cost. it can.

(3) By providing the electrodes in the second air chamber non-parallel to the displacement plate, it is possible to more accurately cope with external pressure and to realize an ink jet head stably free from ejection failure. it can.

As described above, according to the present invention, it is possible to provide an ink jet printer capable of performing stable printing from a low altitude of 0 meters or less above sea level to a high altitude or several thousand meters above sea level.

Further, it is possible to provide an ink jet head capable of printing stably with respect to an external pressure even in a line ink jet head having a very large number of nozzles.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an outline of an ink jet head of the present invention.

FIG. 2 is an explanatory sectional view of an inkjet head according to the present invention.

FIG. 3 is an explanatory sectional view of an air chamber of the ink jet head of the present invention.

FIG. 4 is a layout explanatory view of a third embodiment of the present invention.

FIG. 5 is an explanatory view of the arrangement according to the first embodiment of the present invention.

FIG. 6 is an operation explanatory diagram of the first embodiment of the present invention.

FIG. 7 is an explanatory diagram of voltage application according to the first embodiment of the present invention.

FIG. 8 is an operation explanatory diagram of the second embodiment of the present invention.

FIG. 9 is an explanatory diagram of voltage application according to the second embodiment of the present invention.

FIG. 10 is a structural explanatory view of a fourth embodiment of the present invention.

FIG. 11 is an external view illustrating a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Nozzle 11 Nozzle plate 12 Cavity plate 13 Wiring board 15 Arrow 16 Pressure chamber 17 Supply port 18 Vibration plate 19 Electrode 20 Ink droplet 22 Air chamber 25 Second air chamber 26 Displacement plate 27 Electrode

Claims (4)

[Claims] 1. A nozzle for discharging a liquid, a pressure chamber communicating with the nozzle and holding the liquid, a vibrating plate for applying pressure to the liquid in the pressure chamber, and a vibrating plate provided on a surface of the vibrating plate which is not in contact with the liquid. An ink jet head having a closed air chamber, a second air chamber communicating with the air chamber, wherein a displacement plate provided in the second air chamber is opposed to the displacement plate of the second air chamber. An ink jet head comprising one or more steps on a surface and one electrode provided on the surface. 2. A nozzle for discharging a liquid, a pressure chamber communicating with the nozzle and holding the liquid, a vibration plate for applying pressure to the liquid in the pressure chamber, and a vibration plate provided on a surface of the vibration plate which is not in contact with the liquid. An ink jet head having a closed air chamber, a second air chamber communicating with the air chamber, wherein a displacement plate provided in the second air chamber is opposed to the displacement plate of the second air chamber. An inkjet head comprising: one or more steps provided on a surface; and electrodes provided independently for each step. 3. A nozzle for discharging a liquid, a pressure chamber communicating with the nozzle and holding the liquid, a vibration plate for applying pressure to the liquid in the pressure chamber, and a vibration plate provided on a surface of the vibration plate that is not in contact with the liquid. An ink jet head having a second air chamber communicating with the air chamber, wherein a displacement plate formed in the second air chamber faces the displacement plate of the second air chamber. An ink jet head having a surface formed non-parallel to the mutating plate and electrodes provided on the non-parallel surface. 4. The ink-jet head according to claim 1, wherein said plurality of ink-jet heads have a nozzle of approximately one.
A line inkjet head characterized by being arranged in rows.