JP4269607B2 - Ink jet head and ink jet recording apparatus having the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inkjet head and an inkjet recording apparatus including the inkjet head.
[0002]
[Prior art]
As shown in FIG. 1 of Japanese Patent Laid-Open No. 9-1796, an ink jet recording apparatus, the volume of a pressure chamber containing ink liquid is changed by the displacement of an actuator to eject ink droplets from nozzle holes. Is printed by landing on the recording medium.
[0003]
Hereinafter, this point will be described in more detail. As shown in FIG. 15A, the ink jet head includes a plurality of pressure chambers 11 partitioned by a partition wall 10 and filled with ink liquid. An actuator 12 is provided corresponding to the chamber 11. A nozzle hole 15 through which ink droplets are ejected and a common liquid chamber 13 for supplying ink liquid into the pressure chamber 11 are formed in communication with the pressure chamber 11 via the ink supply path 22.
[0004]
The actuator 12 includes a piezoelectric film 16, an upper individual electrode 17 that applies a voltage to the piezoelectric film 16 and contracts and expands, and a lower diaphragm / common electrode 18. An ink droplet is ejected from the nozzle hole 15 by changing the volume of the pressure chamber 11 by the piezoelectric effect.
[0005]
When a voltage is applied to the electrodes 17 and 18 of the ink jet head having such a configuration to displace the actuator 12 (FIG. 15B), the pressure in the pressure chamber 11 rises and droplets are discharged from the nozzle holes 15. Discharged. At the same time, an increase in the pressure in the pressure chamber 11 causes an ink flow from the pressure chamber 11 to the common liquid chamber 13 through the ink supply path 22. Therefore, the amount of pressure fluctuation in the pressure chamber 11 due to the displacement of the actuator 12 is dispersed in the ink droplet ejection from the nozzle hole 15 and the ink flow to the common liquid chamber 13.
[0006]
Next, as shown in FIG. 15C, when the actuator 12 is displaced in the opposite direction and the pressure in the pressure chamber 11 decreases, the ink passes through the ink supply path 22 from the common liquid chamber 13 and the pressure is increased. It is introduced into the chamber 11.
[0007]
For this reason, the ink supply path 22 that connects the pressure chamber 11 and the common liquid chamber 13 causes the actuator 12 to deform the diaphragm / common electrode 18 and discharge the ink in the pressure chamber 11 from the nozzle hole 15. In this case, since it is better that the ink flows more in the direction of the nozzle holes 15, it is desirable that the cross-sectional area of the ink supply path 22 is small and the ink does not flow easily.
[0008]
On the other hand, in order to smoothly supply ink from the common liquid chamber 13 to the pressure chamber 11 after the ink discharge is finished, it is desirable that the ink supply path 22 has a large cross-sectional area so that the ink can easily flow.
[0009]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-1796 (FIG. 1)
[0010]
[Problems to be solved by the invention]
However, as described above, in the conventional technology, no consideration is given to the flow control in the ink supply path 22.
[0011]
Further, when the environmental temperature changes, the viscosity of the ink changes (low viscosity at high temperature and high viscosity at low temperature), and the ink supply path 22 having a small cross-sectional area is very susceptible to changes in viscosity. In order to obtain a constant discharge performance regardless of environmental changes, the ink supply path 22 preferably has a smaller cross-sectional area at high temperatures, and conversely a larger cross-sectional area at low temperatures.
[0012]
Accordingly, an object of the present invention is to provide a technique capable of obtaining an ink jet head having stable ink ejection characteristics and an ink jet recording apparatus including the ink jet head.
[0013]
[Means for Solving the Problems]
In order to solve this problem, an inkjet head according to the present invention communicates a plurality of pressure chambers filled with ink liquid, a common liquid chamber that supplies ink liquid into the pressure chamber, and the pressure chamber and the common liquid chamber. A plurality of first actuators formed on the ink supply path and the pressure chamber, respectively, and formed on the ink supply path, and a plurality of first actuators for changing the respective volumes of the pressure chamber to discharge the ink liquid in the pressure chamber from the nozzle holes. in the ink jet head is displaced to increase the pressure of the ink supply path, after ejecting the ink to have a second actuator for displacing so as to lower the pressure in the ink supply path when ejecting the ink liquid there, the second actuator are each opposed to the main portion respectively extending on clear distinction along the direction of the first actuator is provided, the double Between the main portion cross those composed of a connecting portion for connecting the.
[0014]
In this manner, the second actuator is formed on the ink supply path, and the main portions that face each of the first actuators and extend in one line along this direction are provided . Increase the pressure so that more ink flows in the direction of the nozzle holes, and after ink ejection, the pressure in the ink supply path is lowered so that the ink is smoothly introduced into the pressure chamber from the common liquid chamber through the ink supply path. can turn, it makes it possible to obtain a stable ink ejection characteristics.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
According to a first aspect of the present invention, there are provided a plurality of pressure chambers filled with ink liquid, a common liquid chamber for supplying ink liquid into the pressure chamber, and an ink supply path for communicating the pressure chamber and the common liquid chamber. If each is formed on the pressure chamber, a plurality of first actuators for ejecting ink of the pressure chamber from the nozzle hole by changing the respective volumes of the pressure chambers, are formed in the ink supply path, the ink liquid when discharge is displaced to increase the pressure of the ink supply path, after ejecting the ink liquid is a second inkjet head which have the actuator for displacement to reduce the pressure of the ink supply path, the Each of the two actuators is provided with a main portion facing each of the first actuators and extending in a line along this direction, and a connecting portion for connecting the plurality of main portions to each other. An ink jet head composed of, since provided respectively opposed to the main portion respectively extending on clear distinction along the direction of the first actuator, at the time of ink ejection by increasing the pressure of the ink supply path nozzle holes More ink flows in the direction of the ink, and after ink discharge, the pressure of the ink supply path is lowered so that the ink can be smoothly introduced from the common liquid chamber through the ink supply path to the pressure chamber. It has the effect that it becomes possible to obtain characteristics.
[0017]
According to a second aspect of the present invention, there are provided a plurality of pressure chambers filled with ink liquid, a common liquid chamber for supplying ink liquid into the pressure chamber, and an ink supply path for communicating the pressure chamber and the common liquid chamber. A plurality of first actuators formed on the pressure chambers, each of the pressure chambers changing the volume of each of the pressure chambers to eject ink liquid from the nozzle holes, and the ink supply path. An ink-jet head having a second actuator that is displaced so as to increase the pressure of the ink supply path when ejecting, and that is displaced so as to decrease the pressure of the ink supply path after ejecting the ink liquid . the actuators, ink jet, which are formed respectively extending on opposite clear distinction along this direction in each of the first actuator, mutually independent voltage is applied A head opposed to the respective first actuator since providing the second actuator respectively extending on clear distinction along this direction, at the time of ink ejection by increasing the pressure of the ink supply path in the direction of the nozzle hole More ink is flowed, and after ink discharge, the pressure of the ink supply path is lowered so that ink can be smoothly introduced from the common liquid chamber through the ink supply path to the pressure chamber, thereby obtaining stable ink discharge characteristics. It has the effect that it becomes possible.
[0018]
The invention according to claim 3 of the present invention is the invention according to claim 1 or 2 , wherein a temperature sensor for measuring the environmental temperature is provided, and the second actuator is higher than the case where the temperature measured by the temperature sensor is high. In the case of the lower limit, the ink jet head has a larger amount of displacement, and has an effect of obtaining stable ink ejection characteristics.
[0019]
Invention of Claim 4 of this invention is an ink jet type recording apparatus provided with the ink jet head as described in any one of Claims 1-3 , Since a stable ink discharge characteristic is obtained, it is a printed image. It has the effect that it becomes possible to achieve high quality.
[0020]
Hereinafter, embodiments of the present invention will be described with reference to FIGS. In these drawings, the same members are denoted by the same reference numerals, and redundant description is omitted.
[0021]
1 is a perspective view showing an overall schematic configuration of an ink jet recording apparatus using an ink jet head according to an embodiment of the present invention, FIG. 2 is a plan view showing the ink jet head according to an embodiment of the present invention, 3 is a cross-sectional view taken along line AA in FIG. 2, FIG. 4 is a block diagram showing a drive mechanism of an ink jet head according to an embodiment of the present invention, and FIG. 5 is an embodiment of the present invention. FIG. 6 is a graph showing the state of pressure fluctuation between the pressure chamber and the ink supply path in the ink jet head, FIG. 6 is a graph showing the voltage applied to the first actuator in the ink jet head according to one embodiment of the present invention, and FIG. FIG. 8 is a graph showing the displacement amount of the first actuator in the ink jet head according to one embodiment of the present invention, and FIG. 8 shows the ink jet head according to one embodiment of the present invention. FIG. 9 is a graph showing the voltage applied to the second actuator in the ink jet head according to the embodiment of the present invention. FIG. 9 is a graph showing the pressure fluctuation in the ink supply path when a voltage is applied only to the first actuator. FIG. 10 is a graph showing pressure fluctuations in the ink supply path when a voltage is applied to the first actuator and the second actuator in the inkjet head according to the embodiment of the present invention, and FIG. 11 is an embodiment of the present invention. FIG. 12 is a graph showing the displacement amount of the first actuator when voltage is applied to the first actuator and the second actuator in the inkjet head according to the embodiment. FIG. 12 shows an inkjet head according to another embodiment of the present invention. FIG. 13 is a plan view showing still another embodiment of the present invention. Plan view of an ink jet head, FIG. 14 is a block diagram showing a driving mechanism of further ink-jet head in the form of another embodiment of the present invention.
[0022]
An ink jet recording apparatus 40 shown in FIG. 1 includes an ink jet head 41 of the present invention that performs recording using the piezoelectric effect of a ferroelectric element that is an actuator. The ink droplets ejected from the ink jet head 41 are made of paper or the like. Recording on the recording medium 42 is performed by landing on the recording medium 42. The inkjet head 41 is mounted on a carriage 44 provided on a carriage shaft 43 arranged in the main scanning direction X, and reciprocates in the main scanning direction X as the carriage 44 reciprocates along the carriage shaft 43. Move. Further, the ink jet recording apparatus 40 includes a plurality of rollers (moving means) 45 for moving the recording medium 42 in the sub scanning direction Y substantially perpendicular to the width direction of the ink jet head 41 (that is, the main scanning direction X). .
[0023]
Next, an embodiment of the structure of the inkjet head 41 will be described with reference to FIGS.
[0024]
As shown in these drawings, the ink jet head includes a plurality of pressure chambers 11 that are partitioned by a partition wall 10 and filled with ink liquid, and a first actuator (actuator) is associated with each pressure chamber 11. ) 12 is provided. A nozzle hole 15 through which ink droplets are ejected is formed in communication with the pressure chamber 11.
[0025]
A common liquid chamber 13 for supplying ink liquid into the pressure chambers 11 arranged in the ink liquid supply direction is formed at a position adjacent to the pressure chamber 11 so as to communicate with the pressure chamber 11 via the ink supply path 22. ing. A second actuator 14 is formed in the ink supply path 22.
[0026]
Here, the first actuator 12 and the second actuator 14 include a piezoelectric film 16, an upper individual electrode 17 that applies a voltage to the piezoelectric film 16 to displace (shrink / extend), and a lower diaphragm. And a common electrode 18.
[0027]
The first actuator 12 is displaced by the piezoelectric effect of the piezoelectric film 16 due to voltage application to the electrodes 17 and 18, and the volume of the pressure chamber 11 is changed to cause the ink liquid in the pressure chamber 11 to pass through the nozzle holes 15. Discharge.
[0028]
In addition, the second actuator 14 causes the ink supply path 22 when the pressure in the pressure chamber 11 rises due to displacement of the first actuator 12 in order to eject ink liquid by applying voltage to the electrodes 17 and 18. When the first actuator 12 is displaced in the opposite direction and the pressure in the pressure chamber 11 is reduced, the pressure in the ink supply path 22 is reduced. Displacement to lower
[0029]
In the present embodiment, the common electrode and the diaphragm are integrated (the diaphragm also serves as the common electrode), but both may be formed separately. In that case, a diaphragm is formed on the partition wall 10 and a common electrode is formed thereon.
[0030]
In the present embodiment, the individual electrode 17 is formed of, for example, Pt (platinum), the piezoelectric film 16 is formed of, for example, lead zirconate titanate (PZT), and the diaphragm / common electrode 18 is formed of, for example, Cu (copper). ing. The individual electrode 17 is formed to a thickness of 0.2 μm, the piezoelectric film 16 is formed to a thickness of 3 μm, for example, and the diaphragm / common electrode 18 is formed to a thickness of 5.5 μm, for example. That is, the film structure of the first actuator 12 and the film structure of the second actuator 14 are the same. With such a configuration, the characteristics of both actuators can be made similar, and control of both actuators can be performed easily.
[0031]
The individual electrodes 17, the piezoelectric film 16, the diaphragm / common electrode 18 and the like can be formed by various known film forming methods, for example, a thick film method such as screen printing, a coating method such as dipping, a sputtering method, and a CVD method. Methods, vacuum vapor deposition methods, sol-gel methods, thin film formation methods such as plating, etc. are appropriately employed, and shapes can also be produced by die cutting by etching, but are not limited thereto.
[0032]
And it is preferable that the first actuator 12 and the second actuator 14 are produced by the same construction method, because it becomes easy to control both actuators. Furthermore, since the characteristics of the two actuators are almost the same because they are manufactured in the same process, the secular change, the temperature change and the like become almost the same, and the control and the like can be performed more easily.
[0033]
Note that layers other than these are provided between the diaphragm / common electrode 18, the piezoelectric film 16, and the individual electrode 17 shown in the present embodiment for the purpose of, for example, improving the bonding of the films. It may be interposed.
[0034]
Next, the drive mechanism of the ink jet head according to the present embodiment will be described with reference to FIG.
[0035]
As shown in the figure, a first drive waveform generation circuit 19 and a second drive waveform generation circuit 20 are provided.
[0036]
The first drive waveform generated by the first drive waveform generation circuit 19 is input to the selection circuit 21, and the selection circuit 21 selects the first actuator 12 to which the first drive waveform is applied by the control signal. . Then, the first drive waveform is applied from the selection circuit 21 to the selected first actuator 12.
[0037]
Further, the second drive waveform generated by the second drive waveform generation circuit 20 is applied to the second actuator 14. The second drive waveform is linked to the pressure fluctuation in the pressure chamber 11 due to the displacement of the first actuator 12 to which the first drive waveform is applied, so that the ink supply path 22 fluctuates. The waveform is such that the actuator 14 is displaced.
[0038]
That is, when a voltage is applied to the first actuator 12 in the ink jet head shown in FIG. 5A, the piezoelectric film 16 is deformed and the diaphragm / common electrode 18 is bent as shown in FIG. The pressure in the chamber 11 rises and ink droplets are ejected from the nozzle holes 15. At the same time, the second actuator 14 is displaced so as to increase the pressure of the ink supply path 22. Thereby, although the displacement of the diaphragm / common electrode 18 is about several tens of nanometers and the cross-sectional area of the ink supply path 22 is hardly changed, the ink flowing from the pressure chamber 11 to the common liquid chamber 13 due to the pressure increase in the ink supply path 22 is obtained. The flow is blocked and more flows in the direction of the nozzle hole 15.
[0039]
Next, as shown in FIG. 5C, when the first actuator 12 is displaced in the direction opposite to that shown in FIG. 5B and the pressure in the pressure chamber 11 decreases, the second actuator 14 also becomes ink. The supply passage 22 is displaced so as to reduce the pressure. Accordingly, the ink easily flows through the ink supply path 22, and the ink is smoothly introduced from the common liquid chamber 13 to the pressure chamber 11.
[0040]
Here, if the voltage of the waveform shown in FIG. 6 is applied to the first actuator 12, for example, the diaphragm of the first actuator 12 is displaced as shown in FIG. Then, as shown in FIG. 8, the pressure in the ink supply path 22 varies due to the pressure variation in the pressure chamber 11 due to the vibration of the first actuator 12. At this time, for example, a voltage having a waveform shown in FIG. 9 is applied to the second actuator 14 to control the pressure in the ink supply path 22 as shown in FIG. 10, thereby linking to the pressure fluctuation in the pressure chamber 11. The pressure of the ink supply path 22 fluctuates, and the ink discharge from the nozzle hole 15 and the ink introduction from the common liquid chamber 13 to the pressure chamber 11 after the ink discharge are performed smoothly. Note that the amount of displacement of the first actuator 12 in this case is as shown in FIG. 11, and it can be seen that the displacement of the first actuator 12 is increased by increasing the efficiency of ink flow.
[0041]
Thus, according to the present embodiment, the second actuator 14 is formed on the ink supply path 22, and when ink is ejected, the pressure of the ink supply path 22 is increased to increase the amount of ink in the direction of the nozzle holes 15. After the ink is discharged, the pressure of the ink supply path 22 is reduced so that the ink can be smoothly introduced from the common liquid chamber 13 through the ink supply path 22 into the pressure chamber 11. Can be obtained.
[0042]
Further, since the second actuator 14 can be formed by the same process and the same member as the first actuator 12, the cost does not increase.
[0043]
Furthermore, since the second actuator 14 does not need to be individually controlled and can be controlled with the same waveform by the integrated electrode, an increase in cost is suppressed.
[0044]
In addition, according to the ink jet recording apparatus provided with such an ink jet head 41, stable ink ejection characteristics can be obtained, so that it is possible to improve the quality of a printed image.
[0046]
In the above description, the second actuator 14 is described as being formed on the entire surface of the ink supply path 22 (see FIG. 2). However , as shown in FIG. 12, the second actuator 14 is opposed to each first actuator 12. It is preferable to form a plurality of main portions 14a extending in the shape of a plurality of main portions 14a and connecting portions 14b that connect the main portions 14a.
[0047]
Further, as shown in FIG. 13, the second actuators 14 may be divided and formed so as to face the respective first actuators 12, and mutually independent voltages may be applied. In this way, only the second actuator 14 corresponding to the displaced first actuator 12 can be driven.
[0048]
Note that a temperature sensor 23 for measuring the environmental temperature may be provided, and the displacement amounts of the first actuator 12 and the second actuator 14 may be controlled by the viscosity of ink that fluctuates due to temperature changes (FIGS. 9 and 14). reference).
[0049]
That is, since the ink has a low viscosity at a high temperature and a high viscosity at a low temperature, the displacement of the second actuator 14 is larger when the temperature measured by the temperature sensor 23 is lower than when the temperature is high. By applying such a voltage, the influence of environmental changes can be minimized. Similarly, the first actuator 12 applies a voltage with a larger displacement when the temperature measured by the temperature sensor 23 is lower than when the temperature is high.
[0050]
When the second actuator 14 is controlled according to the environmental temperature by the temperature sensor 23, the second actuator 14 is formed by a main portion 14a and a connecting portion 14b as shown in FIG. Alternatively, as shown in FIG. 13, the first actuator 12 may be divided to be formed.
[0051]
【The invention's effect】
As described above, according to the present invention, the second actuator is formed on the ink supply path, and when ink is ejected, the pressure in the ink supply path is increased to flow more ink in the direction of the nozzle holes. Is effective in reducing the pressure of the ink supply path so that ink can be smoothly introduced into the pressure chamber from the common liquid chamber through the ink supply path, so that stable ink ejection characteristics can be obtained. An effect is obtained.
[0052]
According to the ink jet recording apparatus provided with such an ink jet head, stable ink ejection characteristics can be obtained, so that an effective effect that it is possible to improve the quality of a printed image is obtained.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an overall schematic configuration of an ink jet recording apparatus using an ink jet head according to an embodiment of the present invention. FIG. 2 is a plan view showing the ink jet head according to an embodiment of the present invention. 3 is a cross-sectional view taken along the line AA in FIG. 2. FIG. 4 is a block diagram showing a drive mechanism of an ink jet head according to an embodiment of the present invention. FIG. 6 is a graph showing the state of pressure fluctuation between a pressure chamber and an ink supply path in an ink jet head. FIG. 6 is a graph showing a voltage applied to a first actuator in an ink jet head according to an embodiment of the invention. FIG. 8 is a graph showing the displacement amount of the first actuator in the ink jet head according to an embodiment of the present invention. FIG. 8 is an ink jet according to an embodiment of the present invention. FIG. 9 is a graph showing pressure fluctuations in the ink supply path when a voltage is applied only to the first actuator in the web. FIG. 9 shows an applied voltage to the second actuator in the ink jet head according to the embodiment of the invention. FIG. 10 is a graph showing pressure fluctuations in the ink supply path when a voltage is applied to the first actuator and the second actuator in the ink jet head according to the embodiment of the present invention. FIG. 12 is a graph showing the displacement amount of the first actuator when voltage is applied to the first actuator and the second actuator in the inkjet head according to the embodiment. FIG. 12 is an inkjet head according to another embodiment of the present invention. FIG. 13 is still another embodiment of the present invention. FIG. 14 is a block diagram showing a driving mechanism of an ink jet head according to still another embodiment of the present invention. FIG. 15 shows the vibration state of the head accompanying the displacement of the actuator in the conventional ink jet head. Illustration to show
10 partition wall 11 pressure chamber 12 first actuator (actuator)
13 Common liquid chamber 14 Second actuator 14a Main portion 14b Connecting portion 15 Nozzle hole 16 Piezoelectric film 17 Individual electrode 18 Diaphragm / common electrode 19 First drive waveform generation circuit 20 Second drive waveform generation circuit 21 Selection circuit 22 Ink supply path 23 Temperature sensor 40 Inkjet recording device 41 Inkjet head 42 Recording medium 43 Carriage shaft 44 Carriage 45 Roller (moving means)

Claims (4)

A plurality of pressure chambers filled with ink liquid;
A common liquid chamber for supplying the ink liquid into the pressure chamber;
An ink supply path communicating the pressure chamber and the common liquid chamber;
A plurality of first actuators that are respectively formed on the pressure chambers and change the respective volumes of the pressure chambers to discharge the ink liquid in the pressure chambers from the nozzle holes;
A second displacement is formed on the ink supply path and is displaced so as to increase the pressure of the ink supply path when ejecting the ink liquid, and is displaced so as to decrease the pressure of the ink supply path after the ink liquid is ejected. a inkjet head to have a an actuator,
The second actuator is provided with a main portion that faces each of the first actuators and extends in a line along the direction, and includes a connecting portion that connects the plurality of main portions to each other. An inkjet head characterized by that. A plurality of pressure chambers filled with ink liquid;
A common liquid chamber for supplying the ink liquid into the pressure chamber;
An ink supply path communicating the pressure chamber and the common liquid chamber;
A plurality of first actuators that are respectively formed on the pressure chambers and change the respective volumes of the pressure chambers to discharge the ink liquid in the pressure chambers from the nozzle holes;
A second displacement is formed on the ink supply path and is displaced so as to increase the pressure of the ink supply path when ejecting the ink liquid, and is displaced so as to decrease the pressure of the ink supply path after the ink liquid is ejected. An inkjet head comprising:
2. The ink jet head according to claim 1 , wherein each of the second actuators is formed so as to face each of the first actuators and extend in one line along the direction of the first actuator, and voltages independent from each other are applied. A temperature sensor that measures the environmental temperature is provided,
3. The ink jet head according to claim 1, wherein the second actuator has a larger displacement amount when the temperature measured by the temperature sensor is lower than when the temperature is high. 4. An ink jet recording apparatus comprising the ink jet head according to any one of claims 1 to 3 .

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