JP2004106217A - Ink jet head and ink jet recorder equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an ink jet head in which pressure variation in a common liquid chamber incident to pressure variation in a pressure chamber is reduced. <P>SOLUTION: The ink jet head comprises a plurality of pressure chambers 11 being filled with ink liquid, a common liquid chamber 13 communicating with the pressure chambers 11 and supplying ink thereto, a plurality of first actuators 12 formed on the pressure chambers 11 in order to eject ink liquid in the pressure chambers 11 from nozzle holes 15 by varying the volume of the pressure chambers 11, and second actuators 14 formed on the common liquid chamber 13 and displacing to cancel a pressure variation in the common liquid chamber 13 caused by displacement of the first actuators 12. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink jet head and an ink jet recording apparatus including the same.
[0002]
[Prior art]
The ink jet head of the ink jet type recording apparatus performs printing by changing the volume of a pressure chamber for accommodating an ink liquid by displacement of an actuator to eject ink droplets from nozzle holes and landing them on a recording medium.
[0003]
As shown in FIG. 16A, the inkjet head includes a plurality of pressure chambers 11 partitioned by partition walls 10 and filled with an ink liquid, and actuators 12 are provided corresponding to the respective pressure chambers 11. Have been. Further, a nozzle hole 15 from which ink droplets are ejected and a common liquid chamber 13 for supplying an ink liquid into the pressure chamber 11 are formed so as to communicate with the pressure chamber 11.
[0004]
The actuator 12 includes a piezoelectric film 16, an upper individual electrode 17 for applying a voltage to the piezoelectric film 16 to contract and expand, and a lower diaphragm / common electrode 18. The 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. 16B), the pressure wave generated in the pressure chamber 11 propagates into the common liquid chamber 13. As a result, the pressure in the common liquid chamber 13 fluctuates. Then, as shown in FIG. 16C, pressure fluctuation in the common liquid chamber 13 adversely affects the inside of the pressure chamber 11, so that the ejection cannot be stabilized.
[0006]
Thus, as a technique for alleviating such pressure fluctuation in the common liquid chamber 13, there is an ink jet head disclosed in, for example, JP-A-2001-6304. In other words, the technology described in this publication operates the wall surface of the common liquid chamber as a diaphragm, whereby the pressure wave generated in the pressure chamber is absorbed by the deflection of the diaphragm, and the pressure fluctuation occurs in the common liquid chamber. Is relaxing.
[0007]
Here, as the density of the ink jet head is increased, the pitch between the pressure chambers is reduced, so that the propagation of pressure waves from the pressure chambers to the common liquid chamber is also increased.
[0008]
In order to obtain a sufficient effect by applying the above-described conventional technology to a high-density inkjet head, it is necessary to reduce the thickness of the diaphragm or increase the area of the diaphragm.
[0009]
[Patent Document 1]
JP 2001-6304 A
[Problems to be solved by the invention]
However, when the diaphragm is made thin, the strength as a member is reduced, making it difficult to assemble, or the rigidity of the head is reduced. In addition, if the area of the diaphragm is increased, the size of the head is increased, which is against the demand for miniaturization.
[0011]
Therefore, an object of the present invention is to provide a technique capable of reducing the pressure fluctuation of the common liquid chamber accompanying the pressure fluctuation of the pressure chamber.
[0012]
[Means for Solving the Problems]
In order to solve this problem, an inkjet head according to the present invention includes a plurality of pressure chambers filled with an ink liquid, a common liquid chamber formed in communication with the pressure chamber, and supplying the ink liquid to the pressure chamber, A plurality of first actuators formed on a common chamber for changing the volume of the pressure chamber to discharge ink liquid in the pressure chamber from the nozzle holes; And a second actuator that is displaced so as to cancel the pressure fluctuation in the liquid chamber.
[0013]
As described above, the second actuator is formed on the common liquid chamber, and the pressure fluctuation on the common liquid chamber due to the displacement of the first actuator formed on the pressure chamber is actively canceled by the displacement of the second actuator. Therefore, it is possible to reduce the pressure fluctuation of the common liquid chamber due to the pressure fluctuation of the pressure chamber.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
According to the first aspect of the present invention, a plurality of pressure chambers filled with an ink liquid, a common liquid chamber formed in communication with the pressure chamber and supplying the ink liquid to the pressure chamber, A plurality of first actuators formed on the common liquid chamber for changing the volume of the pressure chamber to discharge the ink liquid in the pressure chamber from the nozzle holes; and a plurality of first actuators formed on the common liquid chamber and displaced by the first actuator. An ink jet head having a second actuator that is displaced so as to cancel the pressure fluctuation, and has an effect that the pressure fluctuation in the common liquid chamber due to the pressure fluctuation in the pressure chamber can be reduced.
[0015]
According to a second aspect of the present invention, in the first aspect, the second actuator includes a plurality of main portions extending to face the respective first actuators, and connects the main portions to each other. And an ink jet head comprising a connecting portion that has a function of reducing pressure fluctuations of the common liquid chamber due to pressure fluctuations of the pressure chambers.
[0016]
According to a third aspect of the present invention, in the first aspect of the invention, the second actuator is divided and formed so as to face each of the first actuators, and mutually independent voltages are applied to the second actuator. It is a head and has an effect that it is possible to reduce the pressure fluctuation of the common liquid chamber due to the pressure fluctuation of the pressure chamber.
[0017]
According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the second actuator has a first actuator side end on the common liquid chamber and an opposite side end. An ink jet head formed between the first actuator and a position closer to the first actuator by a predetermined length, and the pressure fluctuation of the common liquid chamber accompanying the pressure fluctuation of the pressure chamber can be reduced. Having.
[0018]
According to a fifth aspect of the present invention, there is provided an inkjet recording apparatus including the inkjet head according to any one of the first to fourth aspects, wherein pressure fluctuation of the common liquid chamber is reduced. This has the effect that the quality of the printed image can be improved.
[0019]
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 15. In these drawings, the same members are denoted by the same reference numerals, and redundant description is omitted.
[0020]
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 an ink jet head according to an embodiment of the present invention, FIG. 3 is a cross-sectional view taken along line AA of FIG. 2, FIG. 4 is a block diagram showing a driving mechanism of an inkjet head according to an embodiment of the present invention, and FIG. 5 is an embodiment of the present invention. FIG. 6 is an explanatory diagram showing a state of pressure fluctuation between the pressure chamber and the common liquid chamber in the ink jet head, FIG. 6 is a graph showing a voltage applied to a first actuator in the ink jet head according to an embodiment of the present invention, and FIG. FIG. 8 is a graph showing a displacement amount of a first actuator in an ink jet head according to an embodiment of the present invention. FIG. 8 is an ink jet head according to an embodiment of the present invention. And FIG. 9 is a graph showing a voltage applied to a second actuator in an inkjet head according to an embodiment of the present invention when a voltage is applied only to the first actuator. FIG. 10 is a graph showing the pressure fluctuation of the common liquid chamber when voltage is applied to the first actuator and the second actuator in the ink jet head according to one embodiment of the present invention, and FIG. 11 is one embodiment of the present invention. FIG. 12 is a graph showing the amount of displacement of the first actuator when a 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 an ink jet printer according to still another embodiment of the present invention. Plan view illustrating the Toheddo, FIG. 14 is a cross-sectional view showing an ink jet head which is another embodiment, FIG. 15 is an explanatory view showing the displacement of the second actuator in the inkjet head of FIG. 14 of the present invention.
[0021]
An ink jet recording apparatus 40 shown in FIG. 1 includes an ink jet head 41 of the present invention which performs recording by utilizing a piezoelectric effect of a ferroelectric element which is an actuator. The recording is performed on the recording medium 42 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). .
[0022]
Next, an embodiment of the structure of the inkjet head 41 will be described with reference to FIGS.
[0023]
As shown in these drawings, the ink jet head includes a plurality of pressure chambers 11 which are partitioned by partition walls 10 and are filled with an ink liquid, and a first actuator (actuator) corresponding to each pressure chamber 11. ) 12 are provided. In addition, a nozzle hole 15 for discharging ink droplets is formed in communication with the pressure chamber 11.
[0024]
At a position adjacent to the pressure chamber 11, a common liquid chamber 13 for supplying the ink liquid into the pressure chamber 11 arranged in the ink liquid supply direction is formed so as to communicate with the pressure chamber 11. Further, a second actuator 14 is formed in the common liquid chamber 13.
[0025]
Here, the first actuator 12 and the second actuator 14 are composed of a piezoelectric film 16, an upper individual electrode 17 for applying a voltage to the piezoelectric film 16 and displacing (contracting / extending) and a lower diaphragm. And a common electrode 18.
[0026]
Then, the first actuator 12 is displaced by the piezoelectric effect of the piezoelectric film 16 by applying a voltage to the electrodes 17 and 18, changes the volume of the pressure chamber 11, and moves the ink liquid in the pressure chamber 11 from the nozzle hole 15. Discharge.
[0027]
Further, the second actuator 14 applies a voltage to the electrodes 17 and 18 so that the pressure wave generated in the pressure chamber 11 due to the displacement of the first actuator 12 propagates into the common liquid chamber 13. The displacement is performed so as to cancel the pressure fluctuation in the common liquid chamber 13 that occurs.
[0028]
In this embodiment, the common electrode and the diaphragm are integrated (the diaphragm also serves as the common electrode), but they may be formed separately. In that case, a diaphragm is formed on the partition wall 10, and a common electrode is formed thereon.
[0029]
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 with a thickness of, for example, 0.2 μm, the piezoelectric film 16 is formed with a thickness of, for example, 3 μm, and the diaphragm / common electrode 18 is formed with a thickness of, for example, 5.5 μm. That is, since the film structure of the first actuator and the film structure of the second actuator are the same, the characteristics of both actuators 12 and 14 can be made similar, and control of both actuators can be easily performed. be able to.
[0030]
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. Method, a vacuum deposition method, a sol-gel method, a thin film forming method such as plating and the like are appropriately adopted, and in order to further form the shape, die cutting by etching or the like may be possible, but it is not limited to them at all. Absent.
[0031]
It is preferable that the first actuator 12 and the second actuator 14 are manufactured by the same method. Further, since the first actuator 12 and the second actuator 14 are manufactured by the same process, the film configurations and characteristics of both actuators are reduced. Since they are almost the same, changes over time and changes in temperature are almost the same.
[0032]
In addition, between the respective films of the diaphragm / common electrode 18, the piezoelectric film 16, and the individual electrode 17 shown in the present embodiment, other layers are provided for the purpose of, for example, improving the bonding of the respective films. It may be interposed.
[0033]
Next, a driving mechanism of the inkjet head according to the present embodiment will be described with reference to FIG.
[0034]
As shown, a first drive waveform generation circuit 19 and a second drive waveform generation circuit 20 are provided.
[0035]
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 a control signal. . Then, the first drive waveform is applied from the selection circuit 21 to the selected first actuator 12.
[0036]
The second drive waveform generated by the second drive waveform generation circuit 20 is applied to the second actuator 14. The second drive waveform applied to the second actuator 14 has a waveform that cancels the pressure fluctuation in the common liquid chamber 13 due to the displacement of the first actuator 12 to which the first drive waveform is applied. ing.
[0037]
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 as shown in FIG. The pressure in the chamber 11 increases, and ink droplets are ejected from the nozzle holes 15. Then, the pressure fluctuation of the pressure chamber 11 at this time is propagated to the common liquid chamber 13 communicating with the pressure chamber 11. If this state is maintained, the pressure of the common liquid chamber 13 increases due to the operation of the first actuator 12, but as described above, in the present application, the second actuator 14 is displaced so as to cancel the pressure fluctuation in the common liquid chamber 13. Therefore, as shown in FIG. 5C, the pressure fluctuation in the common liquid chamber 13 is reduced.
[0038]
Here, assuming that a voltage having, for example, a waveform shown in FIG. 6 is applied to the first actuator 12, the diaphragm of the first actuator 12 is displaced as shown in FIG. Then, as shown in FIG. 8, the pressure in the pressure chamber 11 accompanying the vibration of the first actuator 12 is transmitted to the common liquid chamber 13, and the pressure rises and gradually decreases. At this time, when a voltage having, for example, the waveform shown in FIG. 9 is applied to the second actuator 14, the pressure fluctuation in the common liquid chamber 13 can be canceled as shown in FIG. The displacement of the first actuator 12 in this case is as shown in FIG.
[0039]
As described above, according to the present embodiment, the second actuator 14 is formed on the common liquid chamber 13, and the pressure fluctuation on the common liquid chamber 13 due to the displacement of the first actuator 12 formed on the pressure chamber 11. Is actively canceled by the displacement of the second actuator 14, so that the pressure fluctuation of the common liquid chamber 13 due to the pressure fluctuation of the pressure chamber 11 can be reduced.
[0040]
Since the pressure fluctuation of the common liquid chamber 13 is actively absorbed by the second actuator 14 in this manner, the efficiency of absorbing the pressure fluctuation is good, and the common liquid chamber 13 does not become large.
[0041]
Further, since the second actuator 14 can be formed in the same process and with the same member as the first actuator, the cost does not increase.
[0042]
Further, since the second actuator 14 does not need to be individually controlled and can be controlled with the same waveform using the integrated electrode, an increase in cost is suppressed.
[0043]
According to the ink jet type recording apparatus having such an ink jet head 41, since the pressure fluctuation of the common liquid chamber 13 is reduced, the expected ejection performance is secured even if the ink jet head 41 is increased in density. In addition, it is possible to improve the quality of a printed image.
[0044]
Next, another embodiment of the structure of the inkjet head 41 will be described.
[0045]
In the above description, the second actuators 14 are formed on the entire surface of the common liquid chamber 13 (see FIG. 2), but as shown in FIG. And a connecting portion 14b for connecting the main portions 14a to each other. In this way, the displacement force of the second actuator 14 can be efficiently applied to a portion of the common liquid chamber 13 that communicates with the pressure chamber 11 where the pressure fluctuation is large.
[0046]
Further, as shown in FIG. 13, the second actuators 14 may be divided and formed so as to face the respective first actuators 12 so as to apply mutually independent voltages. In this way, only the second actuator 14 corresponding to the displaced first actuator 12 can be driven.
[0047]
In the case where the second actuator 14 is divided and applied with mutually independent voltages, a selection circuit similar to the selection circuit 21 shown in FIG. 4 is replaced with the second drive waveform generation circuit 20 and the second actuator 14. The second drive waveform is applied to any one of the second actuators 14 selected by the selection circuit. Alternatively, the second drive waveform generating circuit itself is provided corresponding to each of the second actuators 14 to apply the second drive waveform.
[0048]
Further, as shown in FIG. 14, the formation region of the second actuator 14 is shifted from the end on the first actuator 12 side on the common liquid chamber 13 by a predetermined length from the end on the opposite side to the first actuator 12 side. May be between the positions. In this way, as shown in FIG. 15, a large displacement can be obtained at the communication portion with the pressure chamber 11 where the pressure fluctuation is large, which is the communication portion with the pressure chamber 11.
[0049]
When the formation area of the second actuator 14 is set as described above, the upper surface of the second actuator 14 may have a rectangular shape as shown in FIG. 2, and the main portion 14a and the connecting portion 14b as shown in FIG. And may be divided and formed so as to face the first actuator 12.
[0050]
【The invention's effect】
As described above, according to the present invention, the second actuator is formed on the common liquid chamber, and the pressure fluctuation in the common liquid chamber due to the displacement of the first actuator formed on the pressure chamber is controlled by the second actuator. Since the displacement is actively canceled, an effective effect of reducing the pressure fluctuation of the common liquid chamber accompanying the pressure fluctuation of the pressure chamber can be obtained.
[0051]
According to the ink jet recording apparatus equipped with such an ink jet head, since the pressure fluctuation of the common liquid chamber is reduced, the expected ejection performance is ensured even if the density of the ink jet head is increased, and the printed image can be printed. This has an effective effect that it is possible to improve the quality of the device.
[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 an ink jet head according to an embodiment of the present invention. 3 is a cross-sectional view taken along the line AA of FIG. 2; FIG. 4 is a block diagram showing a driving mechanism of an inkjet head according to an embodiment of the present invention; FIG. 6 is an explanatory diagram showing a state of pressure fluctuation between a pressure chamber and a common liquid chamber in a certain inkjet head. FIG. 6 is a graph showing a voltage applied to a first actuator in an inkjet head according to an embodiment of the present invention. FIG. 8 is a graph showing the amount of displacement of a first actuator in an ink jet head according to an embodiment of the present invention. FIG. 8 is an ink jet head according to an embodiment of the present invention. FIG. 9 is a graph showing pressure fluctuation of the common liquid chamber when a voltage is applied only to the first actuator in FIG. 9; FIG. 10 is a graph showing a pressure fluctuation of a common liquid chamber when a voltage is applied to the first actuator and the second actuator in the ink jet head according to one embodiment of the present invention. FIG. 12 is a graph showing the amount of displacement of the first actuator when a 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. FIG. 13 is an ink jet printer according to still another embodiment of the present invention. FIG. 14 is a cross-sectional view showing an inkjet head according to still another embodiment of the present invention. FIG. 15 is an explanatory view showing displacement of a second actuator in the inkjet head of FIG. Explanatory diagram showing a vibration state of a head of an inkjet head according to a displacement of an actuator.
10 partition wall 11 pressure chamber 12 first actuator (actuator)
13 Common liquid chamber 14 Second actuator 14a Main part 14b Connecting part 15 Nozzle hole 16 Piezoelectric film 17 Individual electrode 18 Vibrating plate / common electrode 19 First drive waveform generation circuit 20 Second drive waveform generation circuit 21 Selection circuit 40 inkjet recording device 41 inkjet head 42 recording medium 43 carriage shaft 44 carriage 45 roller (moving means)

Claims (5)

A plurality of pressure chambers filled with ink;
A common liquid chamber formed in communication with the pressure chamber and supplying the ink liquid to the pressure chamber;
A plurality of first actuators formed on the pressure chamber and configured to change a volume of the pressure chamber and discharge the ink liquid in the pressure chamber from a nozzle hole;
An ink jet head comprising: a second actuator formed on the common liquid chamber and displaced so as to cancel a pressure change in the common liquid chamber due to a displacement of the first actuator. 2. The second actuator according to claim 1, wherein the second actuator includes a plurality of main portions extending to face the respective first actuators, and a connecting portion connecting the main portions to each other. 3. Ink jet head. 2. The ink-jet head according to claim 1, wherein the second actuators are separately formed so as to face the respective first actuators, and mutually independent voltages are applied. The second actuator is formed between the first actuator side end on the common liquid chamber and a position closer to the first actuator side by a predetermined length from the opposite end. The inkjet head according to any one of claims 1 to 3, wherein An ink jet recording apparatus comprising the ink jet head according to claim 1.

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