Patent Grant
8132897
This application claims priority from Japanese Patent Applications No. 2007-256922, filed on Sep. 29, 2007 and No. 2008-094150 filed on Mar. 31, 2008, the disclosures of which are incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a liquid-droplet jetting apparatus such as an ink-jet printer and a liquid-droplet jetting head such as an ink-jet head.
2. Description of the Related Art
Conventionally, as one of liquid-droplet jetting apparatuses, there is known an ink-jet printer provided with an ink-jet head having a cavity unit in which a plurality of pressure chambers are formed regularly and a piezoelectric actuator joined to the cavity unit for selectively jetting ink in the pressure chambers, and a voltage application mechanism for applying a voltage to the piezoelectric actuator. Then, as the piezoelectric actuator described above, there are known one using a vertical effect actuator of stacked type (see, for example, Japanese Patent Application Laid-open No. 2005-59551), and one using a unimorph actuator (see, for example, Japanese Patent Application Laid-open No. 2005-317952.
There are demands for increasing the density of the pressure chambers to secure high image quality or high quality of recording by increasing the number of nozzles in the ink-jet head of such an ink-jet printer. When the pressure chambers are arranged with high density, the distance between adjacent pressure chambers becomes short, and thus the influence to adjacent pressure chambers, a problem of so-called crosstalk occurs while driving.
Specifically, as shown in
Accordingly, there has been occurring a problem of fluctuation of jetting characteristics for the adjacent pressure chambers 940 (for example, a problem that unintended jetting of ink occurs from the nozzle holes 914b), namely, a problem of crosstalk.
To solve such a problem of crosstalk, various measures have been proposed. For example, in Japanese Patent Application Laid-open No. 2002-254640 (FIG. 2), there is described a structure in which a beam portion 100 is provided across partition walls 11 on both sides in a width direction of each pressure generating chamber 12 so as to improve the rigidity of the partition walls 11, and thereby occurrence of crosstalk is prevented between adjacent pressure generating chambers.
Further, in Japanese Patent Application Laid-open No. 2002-19113 (FIG. 1), there is described a structure in which an elastic body 7 having a predetermined depth from a nozzle plate 3 and a predetermined width is disposed on a side wall 5 that separates each pressurizing liquid chamber 4, thereby decreasing mechanical crosstalk.
However, these measures are becoming no longer perfect as the increase in density of the pressure chambers (ink jetting ch) proceeds.
An object of the present invention is to provide a liquid-droplet jetting apparatus and a liquid-droplet jetting head capable of suppressing crosstalk without increasing the number of individual electrodes, namely, the number of signal lines when structured with high density.
According to a first aspect of the present invention, there is provided a liquid-droplet jetting apparatus which jets droplets of a liquid, including:
a liquid-droplet jetting head including a cavity unit in which a plurality of pressure chambers arranged regularly are formed and a piezoelectric actuator which is joined to the cavity unit to cover the pressure chambers and which jets the liquid in the pressure chambers selectively, the piezoelectric actuator having first active portions each corresponding to a center portion of one of the pressure chambers and second active portions each corresponding to an outer peripheral portion, of one of the pressure chambers, which covers a portion located outside of the center portion of one of the pressure chambers; and
a voltage application mechanism which applies a voltage to the piezoelectric actuator;
wherein the first active portions and the second active portions expand in a first direction toward the pressure chambers and contract in a second direction orthogonal to the first direction when the voltage is applied to the first and second active portions by the voltage application mechanism; and
when a first voltage is applied to the first active portions the voltage application mechanism does not apply a second voltage to the second active portions, and when the first voltage is not applied to the first active portions the voltage application mechanism applies the second voltage to the second active portions.
Here, the “active portions” means portions which turn to a deformation state or a non-deformation state by application/non-application of voltage. Further, the “second active portions” include, besides the case of existing across portions corresponding to pressure chambers and portions corresponding to beam portions between the pressure chambers, the case of existing only in the portions corresponding to beam portions out of the portions corresponding to the pressure chambers and the case of existing only in the portions corresponding to the pressure chambers. The “first direction” means a direction in which the pressure chambers and the active portions are aligned, that is, a stacking direction of the piezoelectric actuator and the cavity unit.
In this manner, according to application/non-application of voltage, deformation occurs in reverse directions in the first active portions corresponding to the center portions of the pressure chambers and the second active portions corresponding to the portions on the outer peripheral sides which are more outside than the center portions of the pressure chambers. When the pressure chambers are arranged with high density and hence adjacent pressure chambers are close to each other, deformation of the first active portions is cancelled, when being transmitted to adjacent pressure chambers, by deformation of the second active portions, thereby suppressing so-called crosstalk which is propagation of deformation of the first active portions to adjacent pressure chambers. The first voltage applied to the first active portions may be same as the second voltage applied to the second active portions.
In the liquid-droplet jetting apparatus of the present invention, each of the second active portions may cover an inside portion located inside an outer peripheral edge of one of the pressure chambers.
In this case, not only the first active portions but the second active portions contribute to volumetric changes of the pressure chambers, and thus volumes of the pressure chambers can be changed larger than in the case only by the first active portions. Therefore, it is possible to improve jetting efficiency (jetting amount when voltage is applied) for jetting liquids in the pressure chambers selectively by applying the voltage to the piezoelectric actuator.
In the liquid-droplet jetting apparatus of the present invention, the piezoelectric actuator may include individual electrodes to which first potential and second potential different from the first potential are applied selectively, first constant potential electrodes to which the first potential is applied, and second constant potential electrodes to which the second potential is applied; each of the first active portions may include a piezoelectric material sandwiched between one of the individual electrodes and one of the first constant potential electrodes; and each of the second active portions may include a piezoelectric material sandwiched between one of the individual electrodes and one of the second constant potential electrodes.
In this case, just by applying the first potential and the second potential selectively to the individual electrodes, deformation of the first active portions and deformation of the second active portions (returning to an original state) can be made to occur at the same time completely. Thus, an attempt of the deformation of the first active portions to propagate to adjacent pressure chambers is cancelled by the deformation of the second active portions, thereby suppressing crosstalk without requiring highly precise timing control.
In the liquid-droplet jetting apparatus of the present invention, the individual electrodes may be formed across a first region corresponding to the first active portions and a second region corresponding to the second active portions of the piezoelectric actuator so as to cover the first and second regions; the first constant potential electrodes may be formed to cover the first region of the piezoelectric actuator; and the second constant potential electrodes may be formed to cover the second region of the piezoelectric actuator.
In this case, the electrodes can be arranged efficiently, and thereby arrangement without a waste becomes possible.
In the liquid-droplet jetting apparatus of the present invention, the first active portions may be polarized in a direction same as a direction of an electric field generated the applied voltage when the second potential is applied to the individual electrodes and the first potential is applied to the first constant potential electrodes; and the second active portions may be polarized in a direction same as a direction of an electric field generated by the applied voltage when the first potential is applied to the individual electrodes and the second potential is applied to the second constant potential electrodes.
In this case, in the first and second active portions, an application direction of voltage during driving and an application direction of voltage during polarization can all be aligned, and the electrodes can be used not only during driving (during deformation of active portions) but for polarization during manufacturing. Further, since the application direction of voltage during driving and the application direction of voltage during polarization (polarization direction) are the same, and a reverse electric field is not applied to a piezoelectric material layer during driving, occurrence of deterioration in deformation of the active portions can be suppressed. Note that, in this description the words “an application direction of voltage” is defined as a direction of an electric field generated by the applied voltage.
In the liquid-droplet jetting apparatus of the present invention, the first potential may be positive potential and the second potential may be ground potential. Further, the first potential may be ground potential and the second potential may be positive potential.
In these cases, by applying two kinds of potential, the positive potential and the ground potential selectively to the individual electrodes, driving can be controlled easily.
In the liquid-droplet jetting apparatus of the present invention, the second constant potential electrodes may be common in two adjacent pressure chambers among the pressure chambers.
In this case, since the second constant potential electrodes are shared by the adjacent two of the pressure chambers, the number of second constant potential electrodes can be reduced, and thus the electrodes as a whole can be simplified.
In the liquid-droplet jetting apparatus of the present invention, the piezoelectric actuator may have a piezoelectric material layer; and the individual electrodes may be formed on a side of one surface of the piezoelectric material layer and the first constant potential electrodes and the second constant potential electrodes may be formed on a side of the other surface of the piezoelectric material layer, and the first active portions and the second active portions may be formed on the same piezoelectric material layer. Here, “the piezoelectric material layer” includes, other than a piezoelectric sheet produced by burning a so-called green sheet, one produced by a method such as so-called AD method (aerosol deposition method).
In this case, an arrangement of required electrodes can be realized by having at least one piezoelectric material layer, and thus it is advantageous in the aspect of material cost.
In the liquid-droplet jetting apparatus of the present invention, an insulating layer thinner than the piezoelectric material layer may be provided to be sandwiched by the first constant potential electrodes and the second constant potential electrodes formed on the side of the other surface; and the first constant potential electrodes and the second constant potential electrodes may be isolated by the insulating layer.
In this case, since the first constant potential electrodes and the second constant potential electrodes are isolated sandwiching the insulating layer, the first constant potential electrodes and the second constant potential electrodes do not short circuit even when they are arranged close to each other. Thus, it becomes possible to arrange the first active portions and the second active portions close to each other, which is advantageous for downsizing.
In the liquid-droplet jetting apparatus of the present invention, the insulating layer may be formed of a material same as the piezoelectric material layer.
In this case, since the same material as the piezoelectric material layer is used for the insulating layer, manufacturing thereof is easy, which is also advantageous in the aspect of cost.
In the liquid-droplet jetting apparatus of the present invention, the first constant potential electrodes may be formed to be sandwiched between adjacent two pressure chambers among the pressure chambers to form rows with the two adjacent pressure chambers; and the second constant potential electrodes may be formed only on one side of the two pressure chambers.
In this case, the second active portions are arranged on one side of the pressure chambers, and crosstalk is suppressed only for the one side.
In the liquid-droplet jetting apparatus of the present invention, the piezoelectric actuator may have a plurality of piezoelectric material layers; the first constant potential electrodes or the second constant potential electrodes may be formed on a farthest surface not facing the pressure chambers, of a farthest layer, among the plurality of piezoelectric material layers, the farthest layer being located farthest from the pressure chambers; the individual electrodes may be formed on a surface of one of the piezoelectric material layers, the surface being different from the farthest layer; surface electrodes which are to be input terminals to the individual electrodes, respectively, may be formed in areas, of the farthest surface, overlapping with the outer peripheral portions; and the individual electrodes may be conducted to the surface electrodes via a conductive material filled in through holes penetrating the piezoelectric material layers.
In this case, when having a plurality of piezoelectric material layers, a reasonable arrangement of individual electrodes can be realized using surface electrodes and through holes.
In the liquid-droplet jetting apparatus of the present invention, the second active portions may be formed on a layer other than the farthest layer among the plurality of piezoelectric material layers; and each of the surface electrodes may be formed in an area, on the farthest surface, overlapping with a portion between the adjacent pressure chambers.
In this case, the surface electrodes are formed in regions between adjacent pressure chambers without interfering with the second active portions. Thus, freedom of positions to form the surface electrodes improves.
According to a second aspect of the invention, there is provided a liquid-droplet jetting apparatus which jets droplets of a liquid, including:
a liquid-droplet jetting head including a cavity unit in which a plurality of pressure chambers arranged regularly are formed and a piezoelectric actuator which is joined to the cavity unit to cover the pressure chambers and jets the liquid in the pressure chambers selectively, the piezoelectric actuator having first portions each located to correspond to a center portion of one of the pressure chambers and second portions each located to correspond to an outer peripheral portion which covers a portion located outside of the center portion of one of the pressure chambers; and
a voltage application mechanism which applies a voltage to the piezoelectric actuator;
wherein the voltage application mechanism switches application and non-application of a first voltage to the first portions so as to change a volume of each of the pressure chambers, and switches application and non-application of a second voltage to the second portions so as to suppress that deformation of the first portions generated in a pressure chamber among the pressure chambers due to switching to the application of voltage to the first portions, propagates to another pressure chamber adjacent to the pressure chamber.
According to the second aspect of the present invention, application and non-application of voltage to the first portions are switched so as to change the volumes of the pressure chambers, and application and non-application of voltage to the second portions are switched so as to suppress that deformation of the first active portions due to this switching propagates to the adjacent pressure chambers, thereby suppressing crosstalk.
According to the third aspect of the present invention, there is provided a liquid-droplet jetting head which jets droplets of a liquid, including:
a cavity unit in which a plurality of pressure chambers arranged regularly are formed; and
a piezoelectric actuator which is joined to the cavity unit to cover the pressure chambers and jets the liquid in the pressure chambers selectively, the piezoelectric actuator having first active portions each corresponding to a center portion of one of the pressure chambers, second active portions each corresponding to an outer peripheral portion, of one of the pressure chambers, which covers a portion located outside of the center portion of one of the pressure chambers, individual electrodes formed to across a first region corresponding to the first active portions and a second region corresponding to the second active portions so as to cover the first and second regions, first constant potential electrodes formed to cover the first region, and second constant potential electrodes formed to cover the second region.
In this case, deformation in reverse direction occurs according to application/non-application of voltage in the first active portions corresponding to the center portions of the pressure chambers and the second active portions corresponding to the portions on the outer peripheral sides which are more outside than the center portions of the pressure chambers, and hence crosstalk which is propagation of deformation of the first active portions to adjacent pressure chambers is suppressed.
As described above, the liquid-droplet jetting apparatus and the liquid-droplet jetting head of the present invention, deformation in reverse direction occurs according to application/non-application of voltage in the first active portions corresponding to the center portions of the pressure chambers and the second active portions corresponding to the portions on the outer peripheral sides which are more outside than the center portions of the pressure chambers. Accordingly, even when the pressure chambers are arranged with high density, crosstalk which is propagation of deformation of the active portions to adjacent pressure chambers can be suppressed.
Hereinafter, embodiments of the present invention will be explained according to the drawings.
In the ink-jet printer 1 according to the present invention, as shown in
Further, as shown in
As shown in
As shown in
The cavity unit 11 includes the plurality of nozzle holes 16a, the plurality of pressure chambers 40 communicating with the nozzle holes 16a respectively and manifolds 50 temporarily storing ink supplied to the pressure chambers 40. Further, the communication holes 51a, 51b communicate with each other and form the communication holes 51 allowing communication between the pressure chambers 40 and the manifolds 50. Furthermore, the communication holes 52a to 52e communicate with each other and form the communication holes 52 allowing communication between the pressure chambers 40 and the nozzle holes 16a.
The piezoelectric actuator 12 is formed by stacking a plurality of piezoelectric material layers 12a, 12b, 12c as shown in
Then, the piezoelectric actuator 12 includes, as viewed in a plan view (as viewed from a stacking direction of the cavity unit 11 and the piezoelectric actuator 12), first active portions 71, 72, 73 (first portions) corresponding to center portions of the pressure chambers 40 and second active portions 81, 82 (second portions) corresponding to left and right portions on outer peripheral sides which are more outside than the center portions of the pressure chambers 40. Here, as shown in
The second active portions 81, 82 include not only regions corresponding to beam portions (girder portions, column portions) 41 which are walls partitioning adjacent pressure chambers 40 but regions corresponding to portions more inside (center portion side) than outer peripheral edges 40a of the pressure chambers 40.
The first active portions 71 to 73 are, respectively, regions of the piezoelectric sheet 12a between individual electrodes 21A and first constant potential electrodes 22A, regions of the piezoelectric sheet 12b between the first constant potential electrodes 22A and individual electrodes 21B, and regions of the piezoelectric sheet 12c between the individual electrodes 21B and first constant potential electrodes 22B. On the other hand, both of the second active portions 81, 82 are regions of the piezoelectric sheets 12a to 12c between the individual electrodes 21A and the second constant potential electrodes 23. Note that the electrodes 21A, 21B, 22A, 22B are formed of Ag—Pd based metal materials or the like.
A driver IC 90 (see
A first potential (ground potential) and a second potential different therefrom (20 V for example) are applied selectively to the individual electrodes 21 via the flexible wiring board 13 to change volumes of the pressure chambers 40. Further, the first potential (ground potential) is applied constantly to the first constant potential electrodes 22A, 22B, and the second potential (20 V for example) is applied constantly to the second constant potential electrodes 23.
Thus, the piezoelectric actuator 12 has the individual electrodes 21 corresponding to the pressure chambers 40. The piezoelectric actuator 12 changes the volumes of the pressure chambers 40 to jet ink from the nozzle holes 16a, when the first potential (ground potential) and the second potential (positive potential) are applied selectively to the individual electrodes 21 as drive signals.
A length of the individual electrodes 21 is shorter than a length of the pressure chambers 40 in a direction Y orthogonal to the nozzle row direction X (see
The second constant potential electrodes 23 are formed to cover regions corresponding to the second active portions 81, 82 and regions corresponding to the beam potions 41 between the pressure chambers 40 which are adjacent to each other in a direction orthogonal to the nozzle row direction. That is, the second constant potential electrodes 23 extend to regions corresponding to side portions, of the pressure chambers 40, in the nozzle row direction, the side portions including the beam portions 41. Each of the second constant potential electrodes is shared for two pressure chambers 40 which are adjacent to each other in the nozzle row direction.
Specifically, the individual electrodes 21 are formed on a side of one surface (upper face in
Further, the electrodes 21, 22A, 22B, 23 of the respective piezoelectric sheets 12a to 12c are arranged in a plan view as shown in
On a lower side (second layer) of the piezoelectric material layer 12a, the first constant potential electrodes 22A are formed at a constant pitch in the nozzle row direction corresponding respectively to the pressure chambers 40. One ends of the first constant potential electrodes 22A are connected to one of first common electrodes 27A which is kept at the ground potential and extends in the nozzle row direction. Further, between the first constant potential electrodes 22A, the second constant potential electrodes 23 are formed respectively, and one ends thereof are also at positive potential (for example 20 V: constant) and connected to one of second common electrodes 28 extending in the nozzle row direction X. Then between the adjacent pressure chambers 40, middle electrodes 25 are formed in a zigzag form (see
In a lower face side of the piezoelectric material layer 12c, the first constant potential electrodes 22B are formed at a constant pitch in the nozzle row direction corresponding respectively to the pressure chambers 40, and one ends thereof are connected to one of first common electrodes 27B at the ground potential extending in the nozzle row direction X. Note that the first constant potential electrodes 22B located on the side of the pressure chambers 40 are formed longer in length in the nozzle row direction X than the first constant potential electrodes 22A located away from the pressure chambers 40.
Note that as shown in
The first constant potential electrodes 22A, 22B are always at the first potential (ground potential), and the second constant potential electrodes 23 are always at the second potential (positive potential). Then, the first potential (ground potential) and the second potential (positive potential) are applied to the individual electrodes 21 selectively for changing the volumes of the pressure chambers 40. That is, as shown in Table 1 below, the direction of the electric field generated by the applied voltage is the same during polarization and during driving. However, the first constant potential electrodes 22A, 22B are always at the ground potential (0 V), the second constant potential electrodes 23 are always at the positive potential (20 V: constant), and to the individual electrodes 21, the positive potential (20 V: constant) is applied or this application is released (see FIG. 27A). Therefore, when the positive potential is applied to the individual electrodes 21, the voltage is applied to the first active portions 71 to 73 but the voltage is not applied to the second active portions 81, 82. On the other hand, when the positive potential is not applied to the individual electrodes 21 and the individual electrodes 21 are at the ground potential, the voltage is not applied to the first active portions 71 to 73, and the voltage is applied to the second active portions 81, 82. Here, the voltage applied between electrodes during driving is, as shown in Table 1, smaller than the voltage applied during polarization, thereby suppressing deterioration due to repeated application of voltage between electrodes.
Since the electrodes 21, 22A, 22B, 23 are arranged as described above, during non-application of voltage to the first active portions 71 to 73 (during standby) in which the second potential (ground potential) is applied to the individual electrodes 21 by the voltage application mechanism, the first active portions 71 to 73 are in a state of non-expand/non-contract (non-deform) in the first and second directions Z, X. At this time, the second active portions 81, 82 are in a voltage applied state, and attempt to expand in a stacking direction Z (first direction) toward the pressure chambers 40 and contract in the nozzle row direction X (second direction) orthogonal to the stacking direction Z. Thus, by the operation of the top plate 15 as a binding plate (a restraint plate), the second active portions 81, 82 located at the side portions in the nozzle row directions deform to bend in a direction to depart from the pressure chambers 40. As shown in
On the other hand, during application of voltage (during driving) to the first active portions 71 to 73 in which the first potential (positive potential: 20 V) is applied to the individual electrodes 21, the first active portions 71 to 73, being applied with voltage in the same direction as the polarization direction, expand in the stacking direction Z toward the pressure chambers 40 and contract in the nozzle row direction X orthogonal to the stacking direction Z thereof by piezoelectric lateral effect. Accordingly, the first active portions 71 to 73 turn to a state of projecting and deforming in a direction toward insides of the pressure chambers 40. On the other hand, as the top plate 15 does not contract spontaneously because it is not influenced by electric field, a difference is made in distortion in the polarization direction and in the vertical direction between the piezoelectric material layer 12c located on the upper side and the top plate 15 located on the lower side. This and the top plate 15 being fixed to the cavity plate 14A together cause the piezoelectric material layer 12c and the top plate 15 to attempt to deform so as to project toward the side of the pressure chambers 40 (unimorph deformation). Accordingly, the volumes of the pressure chambers 40 decrease, the pressure of ink increases, and the ink is jetted from the nozzle holes 16a.
In this application period of voltage to the first active portions 71 to 73, the second active portions 81, 82 turn to a non application state of voltage, and hence return to a state of non-expand/non-contract (non-deform) in the first and second directions Z, X. Thus, when the first active portions 71 to 73 project and deform in the direction toward the pressure chambers 40, the second active portions 81, 82 return to a state of not deforming. Therefore, as shown in
Thereafter, when the individual electrodes 21 are returned to the same potential (ground potential) as the first constant potential electrodes 22A, 22B, the first active portions 71 to 73 turn to a state of not deforming as described above. Then, the second active portions 81, 82 deform to bend in a direction to depart from the pressure chambers 40, and the volumes of the pressure chambers 40 return to the original volumes. Thus, the ink is sucked into the pressure chambers from the manifolds 50.
The jetting operation of ink is repeated by such deformation of the first active portions 71 to 73 and the second active portions 81, 82, and volumetric changes of the pressure chambers 40 are made to be large in each jetting operation, thereby increasing jetting efficiency and suppressing crosstalk in the three directions.
Incidentally, the ratio of changes of cross-sectional areas of adjacent pressure chambers were obtained in the first embodiment and the conventional example (see
In the first embodiment, the second active portions 81, 82 are arranged across the first regions and the second regions, the first regions corresponding to the portions on the outer peripheral sides which are more outside than the center portions of the pressure chambers 40 in the nozzle row direction X, and the second regions corresponding to the beam portions 41. However, it is also possible to structure as shown in
Conversely, as shown in
Furthermore, as shown in
Incidentally, a relationship among the polarization direction, portions (first active portions) which are effective while being turned ON and effective during application of voltage and portions (second active portions) which are effective while being turned OFF and effective during non-application of voltage is shown in
In this manner, the first active portions 71, 72, 73a, 74 and the second active portions 81, 82, 83, 84 both perform deformation of vertical effect, not the uniform deformation, and hence the second active portions 81 to 84 cannot deform to bend away from the pressure chambers 40 like the uniform deformation (that is, deformation in a direction to enlarge the pressure chambers 40). Therefore, the effect of suppressing crosstalk can be obtained, but the effect of increasing volumetric changes of the pressure chambers 40 cannot be obtained.
Further, also regarding the structure in which the second constant potential electrodes 23A are provided only in the regions corresponding to the beam portions 41 (see
Incidentally, a relationship among the polarization direction, portions (first active portions) which are effective while being turned ON and effective during application of voltage and other portions (second active portions) which are effective while being turned OFF and effective during non-application of voltage is shown in FIGS. 13A, 13B.
As in the first embodiment, when forming the first and second constant potential electrodes 22A, 23 on the same surface alternately in the nozzle row direction X, it is not possible to take large intervals between these electrodes, and hence the lengths of these electrodes in the nozzle row direction cannot be taken long. However, as shown in the next second embodiment, an insulating layer with a small layer thickness can be used to increase the lengths of them.
In this embodiment, as shown in
Only first constant potential electrodes 22B are formed on one surface (upper surface) side of this insulating layer 12f at a constant pitch, and only second constant potential electrodes 23 are formed on the other surface (lower surface) side thereof at a constant pitch. Accordingly, the first constant potential electrodes 22B and the second constant potential electrodes 23 are electrically isolated with the insulating layer 12f, but similarly to the case of the first embodiment, they are formed between the piezoelectric material layer 12a and the piezoelectric material layer 12b. Thus, there are formed first active portions 71a, 72a, 73 corresponding respectively to the center portions of the pressure chambers 40, and second active portions 81c, 82 corresponding respectively to portions on outer peripheral sides thereof.
In this manner, since the first constant potential electrodes 22B and the second constant potential electrodes 23 are isolated by being sandwiching the insulating layer 12f therebetween, the lengths in the nozzle row direction of the first constant potential electrodes 22B formed between the piezoelectric material layer 12a and the piezoelectric material layer 12b can be made long, thereby realizing an electrode arrangement which is advantageous for increasing volumetric changes of the pressure chambers 40. Also in the case of the second embodiment, as shown in Table 2, the ratio of changes of cross-sectional areas of adjacent pressure chambers is 11%. Similarly to the case of the first embodiment, the change ratio decreases to almost half as compared to the case of the conventional example, and it can be seen that the effect of suppressing crosstalk is exhibited.
Using such an insulating layer with a small layer thickness, it can also be a structure as described in the next third embodiment.
In this embodiment, as shown in
Further, only one layer may exist as the piezoelectric material layers described above, and it can also be a structure as described in the next fourth embodiment.
In this example, as shown in
With this structure, the top plate 15 functions as a binding plate. Although the number of piezoelectric material layers is smaller than in the first to third embodiments and the amount of deformation becomes smaller, excellent jetting efficiency can be realized by unimorph deformation even with one piezoelectric material layer 12a.
Also in such a case of having one piezoelectric material layer, as described in the next fifth embodiment, it is also possible to have a structure using an insulating layer with a small layer thickness.
In this embodiment, as shown in
Also in this case, it can be seen that the effect of suppressing crosstalk is exhibited by application/non-application of voltage as shown in
When it is not necessary to provide, as in the above-described embodiments, the second active portions on both sides of the first active portions, and it is just needed to exhibit the effect of suppressing crosstalk only on one sides of the first active portions, the second active portions can be provided only on one sides of the first active portions, as described in sixth embodiment.
In this embodiment, as shown in
Then the individual electrodes 21A are formed on one surface (upper surface) side of the piezoelectric material layer 12a, and first and second constant potential electrodes 22A, 23A are formed corresponding respectively to side portions of the individual electrodes 21A on the other surface (lower surface) side thereof. Further, individual electrodes 21A are formed on an upper surface side of the piezoelectric material layer 12c, and first constant potential electrodes 22A are formed on a lower surface side thereof. Accordingly, there are formed first active portions 71, 72, 73a corresponding respectively to the center portions of the pressure chambers 40, and second active portions 81c, 82c corresponding respectively to portions of outer peripheral sides thereof.
With such a structure, the effect of suppressing crosstalk can be exhibited only on the side where the second active portions 81c, 82c are arranged.
Further, as in the next seventh embodiment, it is also possible to form first constant potential electrodes extending along the nozzle row direction, and to have them in common for the pressure chambers formed in rows in the nozzle row direction.
In this example, as shown in
Then the electrodes 21, 22B, 22C, 23 of the respective piezoelectric material layers 12a to 12d are arranged as shown in
Further, on the lower surface side of the piezoelectric material layer 12a, second constant potential electrodes 23 are formed at a constant pitch in the nozzle row direction corresponding to the pressure chambers 40, and one ends thereof are connected to one of common electrodes 28 extending in the nozzle row direction. Further, on the upper surface side of the piezoelectric material layer 12c and on a lower surface side of the piezoelectric material layer 12d, first constant potential electrodes 22C are formed to extend in the nozzle row direction corresponding respectively to the pressure chambers 40.
Thus, since the first constant potential electrodes 22C are formed in the nozzle row direction X and are shared by the pressure chambers 40 in the nozzle row direction, the arrangement of the electrodes 21, 21B, 22C, 23 becomes simple, which is advantageous for making the apparatus compact. Incidentally, a relationship among the polarization direction, portions (first active portions) which are effective while being turned ON and effective during application of voltage and portions (second active portions) which are effective while being turned OFF and effective during non-application of voltage is shown in
In the above-described first, second, fourth to seventh embodiments, since the connection portions to the flexible wiring board 13 are arranged on the piezoelectric material layer 12a which is farthest from the pressure chambers, there is a fear that during connection with solder, dispersion of deformation characteristics due to flowing in of the solder occurs. Accordingly, as in the next eighth embodiment, such a problem can be avoided by arranging the individual electrodes between the piezoelectric material layer 12a and the piezoelectric material layer 12b located more inside, similarly to the case of the third embodiment.
In this embodiment, among the plurality of piezoelectric material layers forming the piezoelectric actuator, surface individual electrodes for connection are formed on one surface (farthest surface) side of the piezoelectric material layer (farthest layer) which is farthest from the pressure chambers, and individual electrodes are formed on the other surface side thereof.
As shown in
The individual electrodes 21 are formed on a surface on the side of the pressure chambers 40 of the piezoelectric material layer 12a. That is, they are formed on a surface, which is a surface different from the farthest surface 31, of one of the piezoelectric material layers 12a to 12c and is a surface on the side of the pressure chambers 40 of the piezoelectric material layer 12a (farthest layer). Then the surface individual electrodes 29 to be input terminals to the individual electrodes 21 are formed in regions (regions corresponding to the beam portions 41) more outside than outer peripheral edges of the pressure chambers 40 of the farthest surface 31. These surface individual electrodes 29 and the individual electrodes 21 conduct to each other via the conductive materials 24 filled in the through holes penetrating the piezoelectric material layer 12a. The surface individual electrodes 29 are formed in regions of the farthest surface 31 between the adjacent pressure chambers 40 (regions corresponding to the so-called beam portions 41).
Accordingly, there are formed first active portions 71, 72 corresponding respectively to the center portions of the pressure chambers 40, and second active portions 182 corresponding respectively to portions on outer peripheral sides thereof. Therefore, the second active portions 182 are formed in the piezoelectric material layers 12b, 12c on the side of the pressure chambers 40, which are layers other than the farthest layer (piezoelectric material layer 12a) of the plurality of piezoelectric material layers 12a to 12c.
Further, the electrodes 21, 22D, 23A formed on the surfaces of the piezoelectric material layers 12a to 12c are arranged as shown in
On the lower surface side of the piezoelectric material layer 12a, the individual electrodes 21 are formed at a constant pitch in the nozzle row direction corresponding respectively to the pressure chambers 40, and connection terminal portions 26 thereof are connected respectively to the connection terminals 26B of the surface individual electrodes 29 using the conductive materials filled in the through holes 24 penetrating the piezoelectric material layer 12a (see
On the lower surface side of the piezoelectric material layer 12c, the first constant potential electrodes 22D which are in common to two adjacent rows of pressure chambers 40 are formed so as to extend in the nozzle row direction.
Thus, since the connection terminal portions 26B to which the connection terminals of the flexible wiring board 13 are connected are formed in the regions corresponding to the beam portions 41 which do not deform while driving, dispersion of deformation characteristics for the respective first active portions does not easily occur if solder flows in during connection with the connection terminals of the flexible wiring board 13.
Incidentally, a relationship among the polarization direction, portions (first active portions) which are effective while being turned ON and effective during application of voltage and portions (second active portions) which are effective while being turned OFF and effective during non-application of voltage is shown in
Then, in the above-described first to seventh embodiments, jetting occurs when voltage is applied to the first active portions (that is, when the second potential is applied to the individual electrodes) as shown in
Further, when using the surface individual electrodes similarly to the eighth embodiment, it is also possible to make jetting occur when voltage is applied to the first active portions similarly to the first to seventh embodiments by having a structure in the following ninth embodiment (see
In this embodiment, as shown in
In this manner, individual surface electrodes 21c to be connection portions with the flexible wiring board 13 (COP) are formed in regions corresponding to the beam portions 41 between the pressure chambers 40 as shown in
Further, the electrodes on upper and lower surfaces of the piezoelectric material layers 12a, 12b are arranged as shown in
On a lower surface side of the piezoelectric material layer 12a, individual electrodes 21 are formed at a constant pitch in the nozzle row direction corresponding respectively to the pressure chambers 40. Parts of the individual electrodes 21 are formed to project to be connection terminal portions 26, and are connected electrically to the surface individual electrodes 29A on the upper surface of the piezoelectric material layer 12a via through holes 24 filled with conductive materials inside.
On a lower surface side of the piezoelectric material layer 12b, first constant potential electrodes 22C are formed at a constant pitch in the nozzle row direction corresponding respectively to the pressure chambers 40, and end portions thereof are connected to the adjacent first constant potential electrodes 22C mutually via connection portions 27C.
Incidentally, a relationship among the polarization direction, portions (first active portions) which are effective while being turned ON and effective during application of voltage and portions (second active portions) which are effective while being turned OFF and effective during non-application of voltage is shown in
Further, with a structure as in the next tenth embodiment, short-circuit due to migration can be prevented similarly to the ninth embodiment, and the surface individual electrodes can be used to make jetting occur when application of voltage to the first active portions is released, similarly to the eighth embodiment (see
In this example, as shown in
In this case, a relationship among the polarization direction, portions (first active portions) which are effective while being turned ON and effective during application of voltage and portions (second active portions) which are effective while being turned OFF and effective during non-application of voltage is as shown in
In this case also, similarly to the ninth embodiment, dispersion of deformation characteristics during the connection due to flowing in of solder can be avoided. Further, a time in which a potential difference is generated between the first constant potential electrodes 22D, 22E and the individual electrodes 21 is short, and hence short-circuit by migration is avoided.
Furthermore, with a structure as in the next example 11, it is possible to have a less number of stacks without using surface individual electrodes or through holes, and to make jetting occur when application of voltage to the first active portions is released, similarly to the eighth and tenth embodiments (see
In this embodiment, as shown in
Further, the electrodes on the upper and lower surfaces of the piezoelectric material layers 12a, 12b are arranged as shown in
On the lower surface side of the piezoelectric material layer 12a, the second constant potential electrodes 23E are formed at a constant pitch in the nozzle row direction corresponding respectively to the pressure chambers 40, and one ends thereof are connected electrically to one of common electrodes 23Ea located therebetween. Further, on the lower surface side of the piezoelectric material layer 12b, there are formed first constant potential electrodes 22E extending in the nozzle row direction to be electrodes common to the pressure chambers 40 in the nozzle row direction.
Incidentally, a relationship among the polarization direction, portions (first active portions) which are effective while being turned ON and effective during application of voltage and portions (second active portions) which are effective while being turned OFF and effective during non-application of voltage is as shown in
In such a structure, since there is no junctions via through holes and the number of stacks is small, production at low cost is possible. Also, changes of cross-sectional areas become large, but there is excellent effect of suppressing crosstalk.
Further, with structures as in the next twelfth and thirteenth embodiments, not only intra-row crosstalk between pressure chambers adjacent in a pressure chamber row direction can be prevented, but also inter-row crosstalk between pressure chambers which belong to an adjacent pressure chamber row and adjacent in a direction orthogonal to the pressure chamber row direction can be suppressed.
In this example, as shown in
The second active portions 92 include not only regions corresponding to beam portions 41 which are walls partitioning adjacent pressure chambers 40 but also regions corresponding to portions more inside (center portion side) than outer peripheral edges 40a of the pressure chambers 40. Further, the third active portions 93 include regions more outside than the outer peripheral edges of the pressure chambers 40, that is, regions corresponding to beam portions 41A which are walls belonging to an adjacent pressure chamber row and partitioning adjacent pressure chambers 40.
The first active portions 91 are structured including a piezoelectric material (piezoelectric material layer 12a) sandwiched between individual electrodes 21 provided respectively for the pressure chambers 40 and second constant potential electrodes 23F. The second active portions 92 and the third active portions 93 are structured including piezoelectric materials (piezoelectric material layers 12a, 12b) sandwiched between the individual electrodes 21 and first constant potential electrodes 23G.
Then in the piezoelectric actuator 12, a positive potential (first potential) and the ground potential (second potential) are applied selectively as drive signals to the individual electrodes 21 to change volumes of the pressure chambers 40, so as to jet ink from the nozzle holes 16a.
To describe in more detail, the individual electrodes 21 are formed, as shown in
The individual electrodes 21 have, on one side in the orthogonal direction Y, portions formed longer than the second constant potential electrodes 23F, and the first constant potential electrodes 22G have portions formed with lengths equal to or longer than the individual electrodes 21 in the orthogonal direction Y in portions where the individual electrodes 21 are formed longer than the second constant potential electrodes 23F.
The first constant potential electrodes 22G are formed to extend to the regions corresponding to the second active portions 92 and cover regions corresponding to the beam portions 41 between the pressure chambers 40 adjacent in the pressure chamber row direction X. That is, the first constant potential electrodes 22G extend to regions corresponding to side portions in the pressure chamber row direction X including the regions corresponding to the beam portions 41, and are shared for two pressure chambers 40 adjacent to each other in the pressure chamber row direction X. Further, the first constant potential electrodes 22G are formed to extend to the regions corresponding to the third active portions 93 and to cover regions corresponding to the beam portions 41A between the pressure chambers 40 adjacent to each other in the direction Y orthogonal to the pressure chamber row direction X. That is, the first constant potential electrodes 22G extend to regions corresponding to side portions in the orthogonal direction Y including the regions corresponding to the beam portions 41A, and are common in two pressure chambers 40 adjacent to each other in the orthogonal direction Y.
Specifically, the first active portions 91 are formed by forming the individual electrodes 21 on an upper surface side of the piezoelectric material layer 12a on an upper side located away from the pressure chambers 40, and forming the second constant potential electrodes 23F on a lower surface side thereof. Further, the second and third active portions 92, 93 are formed by forming the first constant potential electrodes 22G on a lower surface side of the piezoelectric material layer 12b on the side of the pressure chambers 40.
Further, in a plan view, the electrodes 21, 23F, 22G of the piezoelectric material layers 12a, 12b are arranged as shown in
On the lower surface side (second layer) of the piezoelectric material layer 12a, the second constant potential electrodes 23F are formed at a constant pitch in the pressure chamber row direction X corresponding respectively to the pressure chambers 40, the adjacent second constant potential electrodes 23F are formed to be shifted by a half pitch in the pressure chamber row direction X, and one ends thereof are connected to one of connection electrodes 35 extending in the pressure chamber row direction X. Further, the first constant potential electrodes 22G are formed to be shared by the connection terminal portions 26 for two rows of individual electrodes 21 located opposing each other.
Note that as shown in
The second constant potential electrodes 23F are always at positive potential, and the first constant potential electrodes 22G are always at the ground potential. Then the individual electrodes 21 are applied selectively with the positive potential and the ground potential for changing the volumes of the pressure chambers 40. That is, although the direction of the electric field generated by the applied voltage is the same during polarization and during driving, the second constant potential electrodes 23F are always at the constant positive potential, the first constant potential electrodes 22G are always at the ground potential, and the individual electrodes 21 are applied with the positive potential or the application is released to turn them to the ground potential. Therefore, when the individual electrodes 21 are at the ground potential, voltage is applied to the first active portions 91, but the voltage is not applied to the second and third active portions 92, 93. On the other hand, when the positive potential is applied to the individual electrodes 21, voltage is not applied to the first active portions 91 but the voltage is applied to the second and third active portions 92, 93. Here, the voltage applied between electrodes during driving is smaller than the voltage which is applied during polarization, thereby suppressing deterioration due to repeated application of voltage between electrodes.
Thus, since the electrodes 21, 23F, 22G are arranged as described above, when jetting ink, the ground potential is applied first to the individual electrodes 21 by the above-described voltage application mechanism. Accordingly, the first active portions 91 are in a standby state. That is, the first active portions 91 are applied with voltage such that the direction of the electric field is the same as the direction as the polarization direction. Therefore the first active portions 91 expand in the stacking direction Z (first direction) toward the pressure chambers 40 and contracts in the directions X, Y (second directions) orthogonal to the stacking direction Z by piezoelectric lateral effect, and thereby project and deform in a direction toward insides of the pressure chambers 40.
Subsequently, when positive potential (for example 20 V) is applied to the individual electrodes 21, the first active portions 91 turn to a non-deformation state of not expanding/contracting in the stacking direction Z and the direction X orthogonal thereto. At this time, the second and third active portions 92, 93 turn to a voltage application state, and attempt to expand in the stacking direction Z (first direction) toward the pressure chambers 40 and attempt to contract in the two directions X, Y (second directions) orthogonal to the stacking direction Z. Thus, with the operation of the top plate 15 as a binding plate, the second active portions 92 located at both side portions of the pressure chamber row direction X as well as the third active portions 93 located at one side portions in the direction Y orthogonal to the pressure chamber row direction X deform to bend in a direction to depart from the pressure chambers 40. This deformation of the second and third active portions 92, 93 contributes to increasing of volumetric changes of the pressure chambers 40, and contributes to sucking of a large amount of ink from the manifolds 50 to the pressure chambers 40.
Then, when the ground potential is applied again to the individual electrodes 21, the first active portions 91 expand in the stacking direction Z toward the pressure chambers 40, contract in the directions X, Y orthogonal to the stacking direction Z, and thereby project and deform in the direction toward the insides of the pressure chambers 40. Accordingly, the volumes of the pressure chambers 40 decrease, the pressure of ink increases, and the ink is jetted from the nozzle holes 16a.
When the ground potential is applied to the individual electrodes 21 and the first active portions 91 are driven to jet the ink, the individual electrodes 21 and the first constant potential electrodes 22G are both at the ground potential, and the second and third active portions 92, 93 turn to a non-application state of voltage. Thus, the second and third active portions 92, 93 return to a state of not expanding/contracting (non-deform) in anyone of the directions Z, X, Y. Therefore, when the first active portions 91 project and deform in the direction toward the pressure chambers 40 (stacking direction Z), the second and third active portions 92, 93 return to a state of not deforming (this is equivalent to contracting in the stacking direction Z and expanding in the two directions X, Y orthogonal to the stacking direction Z). Thus, the influence of deformation of the first active portions 91 is suppressed in a manner of being cancelled by deformation of the second and third active portions 92 (see the parts P1, P2 in
Thereafter, when the individual electrodes 21 are returned to the same potential (positive potential) as the second constant potential electrodes 23F, as explained above, the first active portions 91 turn to a state of not deforming, and the second and third active portions 92, 93 deform to bend in a direction to depart from the pressure chambers 40, resulting in sucking of ink from manifolds 50 to the pressure chambers 40.
By such deformation of the first to third active portions 91 to 93, the jetting operation of ink is repeated, and volumetric changes of the pressure chambers 40 are made to be large in each jetting operation, thereby increasing jetting efficiency and suppressing crosstalk in the three directions.
In the above-described embodiment, it is not possible to suppress propagation to the adjacent pressure chambers 40 on the other side of the direction Y orthogonal to the pressure chamber row direction X (see the part P3 in
In this case, for example as shown in
When voltage is applied to the first active portions 91, the voltage is not applied to the fourth active portions 94. When voltage is not applied to the first active portions 91, the voltage is applied to the fourth active portions 94, in which when voltage is applied by the voltage application mechanism, they turn to a deformation state of expanding in the stacking direction Z and contracting in the directions X, Y orthogonal thereto, similarly to the second and third active portions 92, 93.
Accordingly, it is possible to suppress inter-row crosstalk that is propagation of the influence of deformation of the first active portions 91 to the adjacent pressure chambers 40 by the fourth active portions 94, similarly to the second and third active portions 92, 93. Note that as regions occupied by the fourth active portions 94 are, in a plan view, smaller on average than regions occupied by the third active portions 93, the effect of suppressing inter-row crosstalk is exhibited also by the fourth active portions 94, although it is slightly poorer than by the third active portions 93.
Further, in this case, in the pressure chamber row direction X, two of the connection electrodes for connecting the second constant potential electrodes 23F to the adjacent second constant potential electrodes 23F in the pressure chamber row direction X are arranged on the same side. However, as shown in
In this example 12, the third active portions are provided corresponding to the one side in a direction orthogonal to the predetermined direction with respect to the center portions of the pressure chambers. However, as shown in
In this example, as shown in
Further, a plurality of first active portions 101 are formed by portions corresponding respectively to center portions of the individual electrodes 21 in the piezoelectric materials (piezoelectric material layers 12a, 12B) sandwiched between the individual electrodes 21 and the first common constant potential electrode 22H. Further, second active portions 102 are formed by the piezoelectric material (piezoelectric material layer 12a) sandwiched between the individual electrodes 21 and the second common constant potential electrode 23G.
Then as shown in
Further, the individual electrodes 21 have, in a plan view, connection terminal portions 26 for applying voltage by the voltage application mechanism arranged outside the regions corresponding to the pressure chambers 40. The second common constant potential electrode 23G also have, in a plan view, portions overlapping with the connection terminal portions 26 of the individual electrodes 21, and hence parts of the second active portions 102 are formed also by the piezoelectric material layer 12a sandwiched between the overlapping portions and the connection terminal portions 26. Note that in adjacent pressure chamber rows, the individual electrodes 21 are formed to be shifted by a half pitch in the pressure chamber row direction X, and between rows thereof, connection terminal portions 26 of the individual electrodes 21 to be connected to the connection terminals (not shown) of the flexible wiring board 13 are formed in a zigzag pattern.
The openings 37 of the second common constant potential electrode 23G each have, in a plan view, a shape duplicating the shape of the pressure chambers 40 but smaller than the pressure chambers 40, and these openings 37 are also formed to be shifted by a half pitch in the pressure chamber row direction X in adjacent pressure chamber rows.
Further, to the individual electrodes 21, the driver IC 90 supplying driving signals is connected electrically via the flexible wiring board 13 (signal lines). The driver IC 90 and the flexible wiring board 13 form a voltage application mechanism for applying driving voltage to the first and second active portions 101, 102 of the piezoelectric actuator 12.
Specifically, to change volumes of the pressure chambers 40, the ground potential (first potential) and positive potential (second potential: 20 V for example) different therefrom are applied selectively to the individual electrodes 21 via the flexible wiring board 13. Further, the ground potential is applied constantly to the first common constant potential electrode 22H, and the positive potential is applied constantly to the second common constant potential electrode 23G.
Thus, the piezoelectric actuator 12 has the individual electrodes 21 corresponding respectively to the pressure chambers 40, and is structured to change the volumes of the pressure chambers 40 by applying the ground potential and the positive potential selectively to the individual electrodes 21 as a drive signal, so as to jet ink from the nozzle holes 16a.
To describe in more detail, in a plan view, the individual electrodes 21 are formed longer than the pressure chambers 40 both in the pressure chamber row direction X and in the direction Y orthogonal thereto and across regions corresponding to the first active portions 101 and regions corresponding to the second active portions 102 so as to cover both of these regions. Then the first common constant potential electrode 22H is formed to cover regions corresponding to the first active portions 101. The second common constant potential electrode 23G is then formed to cover, in a plan view, regions corresponding to the second active portions 102 and regions corresponding to the beam portions 41, 41A between the pressure chambers 40 adjacent to each other in the pressure chamber row direction X and the direction Y orthogonal thereto. That is, the second common constant potential electrode 23G extends to regions corresponding to side portions in the pressure chamber row direction of the pressure chambers 40 including the regions corresponding to the beam portions 41, and are shared for two pressure chambers 40 adjacent to each other in the pressure chamber row direction X of the pressure chambers 40.
Note that as shown in
The first common constant potential electrode 22H is always at the ground potential, and the second common constant potential electrode 23G is always at the positive potential. Then, to the individual electrodes 21, the ground potential and the positive potential are applied selectively for changing the volumes of the pressure chambers 40. The direction of the electric field generated by the applied voltage is the same during polarization and during driving. However, the first common constant potential electrode 22H is always at the ground potential (0 V), the second common constant potential electrode 23G is always at the positive potential (20 V: constant), and to the individual electrodes 21, the positive potential (20 V: constant) is applied or this application is released (see
Since the electrodes 21, 22H, 23G are arranged as described above, in a standby state, when the voltage application mechanism makes the individual electrodes 21 be at the ground potential, the electric field in the first active portions 101 is generated in the same direction as the polarization direction. Then, by piezoelectric lateral effect, the first active portions 101 expand in the stacking direction Z toward the pressure chambers 40 and contract in the directions X, Y orthogonal to the stacking direction Z, thereby attempting to project and deform in a direction toward insides of the pressure chambers 40. On the other hand, as the top plate 15 does not contract spontaneously because it is not influenced by electric field, a differences is made in distortion in the polarization direction and in the vertical direction between the piezoelectric material layer 12b located on the upper side and the top plate 15 located on the lower side. This and the top plate 15 being fixed to the cavity plate 14A together cause the piezoelectric material layer 12b and the top plate 15 to turn to a deformed state so as to project toward the side of the pressure chambers 40 (unimorph deformation), as shown in
When jetting ink, first the positive potential is applied by the individual electrodes 21 by the voltage application mechanism, and the first active portions 101 are in a state of not expanding/contracting (non-deform) in the pressure chamber row direction and the directions X, Y orthogonal thereto. At this time, the second active portions 102 are in a voltage applied state, and attempt to expand in the stacking direction Z (first direction) toward the pressure chambers 40 and contract in the directions X, Y (second directions) orthogonal to the stacking direction Z. Thus, by the operation of the top plate 15 as a binding plate, the second active portions 102 located at the side portions in the pressure chamber row direction deform to bend in a direction to depart from the pressure chambers 40. This deformation of the second active portions 102 contributes to increasing of volumetric changes of the pressure chambers 40 as shown in
Then, by turning the individual electrodes 21 again to the ground potential, and by applying the voltage to the first active portions 101 in the same direction as the polarization direction, there is created a state of projecting and deforming toward the insides of the pressure chambers 40, similarly to the above-described case. Accordingly, the volumes of the pressure chambers 40 decrease, the pressure of ink increases, and the ink is jetted from the nozzle holes 16a.
In this application period of voltage to the first active portions 101, the second active portions 102 turn to a non-application state of voltage, and hence return to a state of not expanding/contracting (non-deform) in the stacking direction Z and the directions X, Y orthogonal thereto. Thus, when the first active portions 101 project and deform in the direction (stacking direction Z) toward the pressure chambers 40, the second active portions 102 return to a state of not deforming (this is equivalent to contracting in the stacking direction Z and expanding in the two directions X, Y orthogonal to the stacking direction Z). Thus, as shown in
Thereafter, when jetting the ink again, the individual electrodes 21 are returned to the same potential (ground potential) as the first common constant potential electrode 22H, the first active portions 101 turn to a state of not deforming as described above, the second active portions 102 deform to bend in a direction to depart from the pressure chambers 40, and the volumes of the pressure chambers 40 return to the original volumes. Thus, the ink is sucked into the pressure chambers 40 from the manifolds 14Da, 14Ea.
Thus, deformation of the first active portions 101 and the second active portions 102 is repeated, and volumetric changes of the pressure chambers 40 are made to be large in each jetting operation. Thus, jetting efficiency is increased, and crosstalk is suppressed.
In the examples, the thicknesses of the piezoelectric material layers 12a, 12b and the top plate 15 (binding plate) are the same. Thus, when the piezoelectric actuator 12 including the top plate 15 deforms, a neutral plane in which deformation does not occur is located in a center portion in the thickness direction of the piezoelectric material layer 12b on a lower side. Therefore, deformation of the piezoelectric actuator 12 cannot be used effectively for deforming the pressure chambers 40 to allow jetting of the ink.
Accordingly, since the piezoelectric actuator 12 is stacked on the upper side of the cavity unit 11 via the top plate 15, when the thickness of the top plate (binding plate) and the thickness of a piezoelectric actuator 112 (piezoelectric material layers 112a, 112b) are made to be the same as shown in
Further, it is not necessary that the individual electrodes are provided on the upper surface side of the piezoelectric material layer on the upper side and the second common constant potential electrode is provided on the lower surface side as in the above-described embodiment. As shown in
In this example, in a plan view, the pressure chambers 40 each have an elliptic shape and the individual electrodes 21 each have a rectangular shape, but in the present invention, shapes of the pressure chambers as well as the individual electrodes having shapes corresponding thereto are not limited to these shapes, and can also be formed as shown in
In the above-described example, since the second constant potential electrodes are applied with positive potential, impedance thereof can be reduced to suppress voltage drop by forming the second constant potential electrodes as described in the next fourteenth embodiment, so that equal jetting performance can be obtained for any nozzle communicating with any one of the pressure chambers 40.
In the case of this example, as shown in
The individual electrodes 21 have connection terminal portions 26 arranged outside the pressure chambers 40, and it is arranged that voltage is applied to these connection terminal portions 26 by the voltage application mechanism.
The second common constant potential electrode 23K has a plurality of first portions 36A extending in the pressure chamber row direction between adjacent pressure chamber rows, and has a plurality of second portions 36B provided corresponding respectively to the pressure chambers 40 between adjacent two of the first portions 36A to couple them, and these second portions 36B extend in a direction orthogonal to (crossing) the pressure chamber row direction. Thus, the second common constant potential electrode 23K is formed in a mesh pattern. It is attempted to reduce impedance. Thus by reducing the impedance, voltage drop is suppressed, and equal jetting performance can be obtained for any nozzle communicating with any one of the pressure chambers 40.
Further, the first common constant potential electrode 22K has a plurality of third portions 36C extending in the pressure chamber row direction so as to overlap with a plurality of pressure chambers 40 forming a pressure chamber row, and has fourth portions 36D coupling end portions of the plurality of third portions 36C. Note that the third portions 36C are provided so as not to overlap with the first portions 36A of the second common constant potential electrode 23K.
Then there are provided a plurality of first active portions 103 formed by the piezoelectric material layer sandwiched between the individual electrodes 21 and the second common constant potential electrode 23K (second portions 36B), and second active portions 104 formed by the piezoelectric material layer sandwiched between the individual electrodes 21 and the first common constant potential electrode 22K (third portions 36C). Here, the second common constant potential electrode 23K taking part in forming of the first active portions 103 is formed in a mesh pattern for reducing impedance. Thus, voltage drop is suppressed in the second common constant potential electrode 23K, and equal jetting performance can be obtained for nozzles communication with any one of the pressure chambers 40.
To the individual electrodes 21, a driver IC 90 supplying driving signals is connected electrically via the flexible wiring board 13 (signal lines). The driver IC 90 and the flexible wiring board 13 form a voltage application mechanism for applying driving voltage to the first and second active portions 103, 104 of the piezoelectric actuator 12.
Then, by applying the positive potential (first potential) and the ground potential (second potential) as a drive signal selectively to the individual electrodes 21, the piezoelectric actuator 12 changes volumes of the pressure chambers 40 to jet ink from the nozzle holes 16a.
To describe in more detail, as shown in
The first common constant potential electrode 22K is formed to cover the regions corresponding to the second active portions 104 and regions corresponding to the beam portions 41 between the pressure chambers 40 adjacent to each other in the pressure chamber row direction X. That is, the first common constant potential electrode 22K extends to regions corresponding to side portions of the pressure chamber row direction X including the regions corresponding to the beam portions 41 and is shared for the pressure chambers 40 adjacent to each other in the pressure chamber row direction X.
Specifically, the first active portions 103 are formed by forming the individual electrodes 21 on the upper surface side of the piezoelectric material layer 12a on the upper side, and forming the second common constant potential electrode 23K on the lower surface side thereof. Further, the second active portions 104 are formed by forming the first common constant potential electrode 22K on the lower surface side of the piezoelectric material layer 12b on the lower side.
Further, the electrodes 21, 22K, 23K of the piezoelectric material layers 12a, 12b are, in a plan view, arranged as shown in
On the lower surface side (second layer) of the piezoelectric material layer 12a, the second portions 36B of the second common constant potential electrode 23K are formed to be arranged corresponding respectively to the pressure chambers 40, and both end portions of the second portions 36B are coupled respectively to the first portions 36A extending in the pressure chamber row direction between adjacent pressure chamber rows. Further, the third portions 36C of the first common constant potential electrode 22K extend in the pressure chamber row direction between adjacent two of the first portions 36A, and hence do not overlap with the first portions 36A of the second common constant potential electrode 23K.
Further, as shown in
Note that as shown in
The second common constant potential electrode 23K is always at the positive potential, and the first common constant potential electrode 22K is always at the ground potential. Then, to the individual electrodes 21, the positive potential and the ground potential are applied selectively for changing the volumes of the pressure chambers 40. That is, the direction of the electric field caused by the applied voltage is the same during polarization and during driving. The second common constant potential electrode 23K is always at the positive potential, the first common constant potential electrode 22K is always at the ground potential, and to the individual electrodes 21, the positive potential is applied or this application is released to change to the ground potential. Therefore, when the individual electrodes 21 are at the ground potential, the voltage is applied to the first active portions 103 but the voltage is not applied to the second active portions 104. On the other hand, when the positive potential is applied to the individual electrodes 21, the voltage is not applied to the first active portions 103, and the voltage is applied to the second active portions 104. Here, the voltage applied between electrodes during driving is smaller than the voltage applied during polarization, thereby suppressing deterioration due to repeated application of voltage between electrodes.
Since the electrodes 21, 22K, 23K are arranged as described above, when first the ground potential is applied by the voltage application mechanism to the individual electrodes 21 when jetting ink, the electric field in the first active portions 103 directs in the same direction as the polarization direction. Then, by piezoelectric lateral effect, first active portions 103 expand in the stacking direction Z (first direction) toward the pressure chambers 40 and contract in the directions X, Y (second directions) orthogonal to the stacking direction Z thereof, thereby turning to a standby state to project and deform in a direction (stacking direction Z) toward insides of the pressure chambers 40.
Subsequently, when the first potential (positive potential: 20 V) is applied to the individual electrodes 21, the first active portions 103 are in a state of not expanding/contracting, deforming in the stacking direction Z and the directions X, Y orthogonal thereto. At this time, the second active portions 104 are in a voltage applied state, and attempt to expand in the stacking direction Z (first direction) toward the pressure chambers 40 and contract in the two directions X, Y (second directions) orthogonal to the stacking direction Z. Thus, by the operation of the top plate 15 as a binding plate, the second active portions 104, 104 located at both side portions in the pressure chamber row direction X deform to bend in a direction to depart from the pressure chambers 40. This deformation of the second active portions 102 contributes to increasing of volumetric changes of the pressure chambers 40, and contributes to sucking of a large amount of ink from the manifolds 50 to the pressure chambers 40.
Then, when the ground potential is applied again to the individual electrodes 21, the first active portions 103 expand in the stacking direction Z toward the pressure chambers 40, contract in the directions X, Y orthogonal to the stacking direction Z, and thereby project and deform in the direction (stacking direction Z) toward the insides of the pressure chambers 40. Accordingly, the volumes of the pressure chambers 40 decrease, the pressure of ink increases, and the ink is jetted from the nozzle holes 16a.
When the ground potential is applied to the individual electrodes 21 and the first active portions 103 are driven to jet the ink, the individual electrodes 21 and the first common constant potential electrode 22K are both at the second potential, and the second active portions 104 turn to a non-application state of voltage. Thus, the second active portions 104 return to a state of not expanding/contracting (non-deform) in any one of the directions Z, X, Y. Therefore, when the first active portions 103 project and deform in the direction toward the pressure chambers 40, the second active portions 104 return to a state of not deforming (this is equivalent to contracting in the stacking direction Z and expanding in the two directions X, Y orthogonal to the stacking direction Z). Thus, the influence of deformation of the first active portions 103 is suppressed in a manner of being cancelled by deformation of the second active portions 104 and hardly reaches the pressure chambers 40 adjacent thereto in the pressure chamber row direction X and the direction Y orthogonal thereto, thereby suppressing crosstalk. That is, application and non-application of voltage to the second active portions 104 (second portions) are switched so as to suppress that deformation of the first active portions 103 (first portions) due to switching of application/non-application of voltage to the first active portions 103 propagates to the pressure chambers 40 adjacent to each other in both sides in the pressure chamber row direction X of the pressure chambers 40.
Thereafter, when the individual electrodes 21 are returned to the same potential (positive potential) as the second common constant potential electrode 23K, the first active portions 103 turn to a state of not deforming as described above, and the second active portions 104 deform to bend in a direction to depart from the pressure chambers 40. Thus, the ink is sucked into the pressure chambers 40 from the manifolds 50.
By such deformation of the first and second active portions 103, 104, jetting operation of ink is repeated, and volumetric changes of the pressure chambers 40 are made to be large in each jetting operation. Thus, jetting efficiency is increased, and crosstalk in the three directions is suppressed.
In the case of this embodiment, portions (piezoelectric material layer 12a) sandwiched, when seen in plan view, between the connection terminal portions 26 of the individual electrodes 21 which are arranged outside (beam portions 41) of the pressure chambers 40 and the second common constant potential electrode 23K also function as first active portions, and hence there is a fear that these portions operate in a direction of suppressing deformation of all the first active portions when jetting ink. Accordingly, as shown in
Further, the second portions 36B of the second common constant potential electrode 23K are provided in the direction Y orthogonal to the pressure chamber row direction X, but having portions overlapping with the pressure chambers 40 will suffice. For example, the second portions may be provided along a direction V inclining with respect to the pressure chamber row direction X. When they are provided to incline in a direction orthogonal to a predetermined direction, third active portions can be provided on one side in the crossing direction V corresponding to the inclining direction, or the third and fourth active portions can be provided on both sides thereof.
It should be noted that, although a predetermined electric potential is always applied to the constant potential electrodes in the above-described embodiments, it is not necessary to always apply the electric potential. For example, a predetermined constant electric potential may be applied when the recording apparatus is performing printing operation, and it may be kept at the ground potential in other time. In this case, since the predetermined constant electric potential is not always applied, the power consumption of the liquid-droplet jetting apparatus can be reduced.
The above embodiments are explained for the case where the liquid-droplet jetting apparatus is an ink-jet type recording apparatus, but the present invention is not limited to this. It may also be applied to another liquid-droplet jetting apparatus for applying a colored liquid with micro liquid-droplets, for forming a wiring pattern by jetting electrically conductive liquid, or the like.
Further, as the recording medium, not only the recording paper but various kinds of materials such as resin, cloth, and the like can be applied, and as the liquid to be jetted, not only the ink but various kinds of liquids such as colored liquid, functional liquid, and the like can be applied.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-256922 | Sep 2007 | JP | national |
| 2008-094150 | Mar 2008 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6450626 | Ikeda et al. | Sep 2002 | B2 |
| 6863383 | Takahashi | Mar 2005 | B2 |
| 6993812 | Takahashi | Feb 2006 | B2 |
| 7073894 | Isono et al. | Jul 2006 | B2 |
| 20030107622 | Sugahara | Jun 2003 | A1 |
| 20030142173 | Takahashi | Jul 2003 | A1 |
| 20050068380 | Ito | Mar 2005 | A1 |
| 20050231073 | Sugahara et al. | Oct 2005 | A1 |
| 20060038859 | Sugahara | Feb 2006 | A1 |
| 20060152556 | Sugahara | Jul 2006 | A1 |
| 20070109363 | Ito | May 2007 | A1 |
| 20070222825 | Takahashi | Sep 2007 | A1 |
| 20090085984 | Kojima | Apr 2009 | A1 |
| Number | Date | Country |
|---|---|---|
| 08017146.5 | Feb 2009 | EP |
| 2001179969 | Jul 2001 | JP |
| 2002019113 | Jan 2002 | JP |
| 2002-240273 | Aug 2002 | JP |
| 2002254640 | Sep 2002 | JP |
| 2003-224312 | Aug 2003 | JP |
| 2003-224312 | Jun 2004 | JP |
| 2005-59551 | Mar 2005 | JP |
| 2005-096350 | Apr 2005 | JP |
| 2005-317952 | Nov 2005 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20090096844 A1 | Apr 2009 | US |
