INK-JET HEAD AND INK-JET PRINTER

An ink-jet head includes a flow passage member formed with: a first common flow passage; a first ink supply port; first individual flow passages; a second common flow passage; a second ink supply port; and second individual flow passages, first pressure generators, second pressure generators, a first conductive part, and a second conductive part. The first ink supply port is positioned on one side in the first direction, the second ink supply port is positioned on the other side in the first direction, an end portion of the first conductive part positioned nearer to a control circuit is positioned on the other side in the first direction, and an end portion of the second conductive part positioned nearer to the control circuit is positioned on the one side in the first direction.

REFERENCE TO RELATED APPLICATIONS

This application claims priority from Japanese Patent Application No. 2023-046866 filed on Mar. 23, 2023. The entire content of the priority application is incorporated herein by reference.

BACKGROUND ART

Conventionally, an ink-jet head is known, which is provided with a flow passage unit and a piezoelectric actuator.

The flow passage unit is formed with a first nozzle row, a first manifold, a first ink supply port, a second nozzle row, a second manifold, and a second ink supply port. Each of the first nozzle row and the second nozzle row is formed by a plurality of nozzles which are aligned in a predetermined direction. The first manifold extends in the predetermined direction, and the first manifold is communicated with the plurality of nozzles which form the first nozzle row. The second manifold extends in the predetermined direction, and the second manifold is communicated with the plurality of nozzles which form the second nozzle row. The first ink supply port is communicated with the first manifold on one side in the predetermined direction with respect to the first nozzle row. The second ink supply port is communicated with the second manifold on one side in the predetermined direction with respect to the second nozzle row.

The piezoelectric actuator is provided with a plurality of first piezoelectric elements which correspond to the plurality of nozzles for forming the first nozzle row respectively, and a plurality of second piezoelectric elements which correspond to the plurality of nozzles for forming the second nozzle row respectively. The plurality of first piezoelectric elements are provided with a plurality of first common electrodes which are aligned in the predetermined direction. The plurality of first common electrodes are connected to a control substrate via a first connecting portion which extends in the predetermined direction. The plurality of second piezoelectric elements are provided with a plurality of second common electrodes which are aligned in the predetermined direction. The plurality of second common electrodes are connected to the control substrate via a second connecting portion which extends in the predetermined direction. Then, an end portion of the first connecting portion positioned on the side of the control substrate is positioned on one side in the predetermined direction with respect to the plurality of first piezoelectric elements, and an end portion of the second connecting portion positioned on the side of the control substrate is positioned on the other side in the predetermined direction with respect to the plurality of second piezoelectric elements.

SUMMARY

In the ink-jet head constructed as described above, the ink, which flows into the first manifold from the first ink supply port, flows from one side to the other side in the predetermined direction through the first manifold. Further, the ink, which flows into the second manifold from the second ink supply port, also flows from one side to the other side in the predetermined direction through the second manifold. On this account, the heat, which is generated in the plurality of first piezoelectric elements, has the influence on the ink contained in the first manifold, the influence being increased in the direction directed to the other side in the predetermined direction. In other words, when attention is focused on the influence of the heat generated in the plurality of first piezoelectric elements, the temperature of the ink contained in the first manifold is raised in the direction directed to the other side in the predetermined direction. Similarly, the heat, which is generated in the plurality of second piezoelectric elements, has the influence on the ink contained in the second manifold, the influence being increased in the direction directed to the other side in the predetermined direction as well. In other words, when attention is focused on the influence of the heat generated in the plurality of second piezoelectric elements, the temperature of the ink contained in the second manifold is raised in the direction directed to the other side in the predetermined direction.

On the other hand, in relation to the first connecting portion provided to connect the plurality of first common electrodes to the control substrate, the amount of movement of the electric charge is more increased at positions nearer to the end portion arranged on the side of the control substrate. On this account, in the case of the first connecting portion, the amount of heat generation is more increased at positions nearer to the end portion arranged on the side of the control substrate. In relation thereto, the end portion of the first connecting portion positioned on the side of the control substrate is positioned on one side in the predetermined direction. On this account, when attention is focused on the influence of the heat generation at the first connecting portion, the temperature of the ink contained in the first manifold is raised in the direction directed to one side in the predetermined direction. Similarly, also in relation to the second connecting portion provided to connect the plurality of second common electrodes to the control substrate, the amount of movement of the electric charge is more increased at positions nearer to the end portion arranged on the side of the control substrate. On this account, in the case of the second connecting portion, the amount of heat generation is more increased at positions nearer to the end portion arranged on the side of the control substrate. In relation thereto, the end portion of the second connecting portion positioned on the side of the control substrate is positioned on the other side in the predetermined direction. On this account, when attention is focused on the influence of the heat generation at the second connecting portion, the temperature of the ink contained in the second manifold is raised in the direction directed to the other side in the predetermined direction.

According to the above, the temperature of the ink contained in the first manifold tends to be constant in the predetermined direction on account of the influence of the heat generated in the plurality of first piezoelectric elements and the influence of the heat generation brought about in the first connecting portion. On this account, the viscosity of the ink contained in the first manifold tends to be constant in the predetermined direction, and the volume of the ink droplet ejected from the plurality of nozzles for forming the first nozzle row tends to be constant. On the contrary, the temperature of the ink contained in the second manifold is raised in the direction directed to the other side in the predetermined direction on account of the influence of the heat generated in the plurality of second piezoelectric elements and the influence of the heat generation brought about in the second connecting portion. On this account, the viscosity of the ink contained in the second manifold is consequently lowered in the direction directed to the other side in the predetermined direction, and thus the volume of the ink droplet ejected from the plurality of nozzles for forming the second nozzle row is increased in the direction directed to the other side in the predetermined direction. As a result, an image, which is printed by the ink-jet head constructed as described above, involves such a problem that any uneven density arises thereon.

The present teaching has been made in order to solve the problem as described above, an object of which is to provide an ink-jet head which can suppress the uneven density by mitigating the influence of heat generation caused by a pressure generator such as a piezoelectric element or the like and the influence of heat generation caused by a conductive part connected to the pressure generator, and an ink-jet printer which is provided with the ink-jet head.

According to a first aspect of the present teaching, there is provided an ink-jet head including: a flow passage member including: a first common flow passage extending in a first direction; a first ink supply port communicated with the first common flow passage; a plurality of first individual flow passages each connected to the first common flow passage and aligned in the first direction; a second common flow passage extending in the first direction and positioned to be deviated from the first common flow passage in a second direction orthogonal to the first direction; a second ink supply port communicated with the second common flow passage; and a plurality of second individual flow passages each connected to the second common flow passage and aligned in the first direction; a plurality of first pressure generators aligned in the first direction and configured to generate pressure to ink contained in the first individual flow passages; a plurality of second pressure generators aligned in the first direction and configured to generate pressure to the ink contained in the second individual flow passages; a first conductive part configured to electrically connect the first pressure generators to a control circuit; and a second conductive part configured to electrically connect the second pressure generators to the control circuit. The first ink supply port is positioned on one side in the first direction with respect to the first individual flow passages, and the second ink supply port is positioned on the other side in the first direction with respect to the second individual flow passages, and an end portion of the first conductive part positioned nearer to the control circuit is positioned on the one side in the first direction with respect to the first pressure generators and an end portion of the second conductive part positioned nearer to the control circuit is positioned on the other side in the first direction with respect to the second pressure generators, or the end portion of the first conductive part positioned nearer to the control circuit is positioned on the other side in the first direction with respect to the first pressure generators and the end portion of the second conductive part positioned nearer to the control circuit is positioned on the one side in the first direction with respect to the second pressure generators.

In the ink-jet head according to the first aspect of the present teaching, the first ink supply port is positioned on the one side in the first direction with respect to the plurality of first individual flow passages, and the second ink supply port is positioned on the other side in the first direction with respect to the plurality of second individual flow passages. On this account, when attention is focused on the influence of the heat generation brought about by the plurality of first pressure generators, the temperature of the ink contained in the first common flow passage is raised in the direction directed to the other side in the first direction. On the other hand, when attention is focused on the influence of the heat generation brought about by the plurality of second pressure generators, the temperature of the ink contained in the second common flow passage is raised in the direction directed to the one side in the first direction.

In relation thereto, when the end portion of the first conductive part positioned nearer to the control circuit is positioned on the one side in the first direction, and the end portion of the second conductive part positioned nearer to the control circuit is positioned on the other side in the first direction, then the temperature of the ink contained in the first common flow passage is raised in the direction directed to the one side in the first direction on account of the influence of the heat generation brought about by the first conductive part. On the other hand, the temperature of the ink contained in the second common flow passage is raised in the direction directed to the other side in the first direction on account of the influence of the heat generation brought about by the second conductive part. In other words, on account of the influences of the heat generation brought about by the plurality of first pressure generators and the heat generation brought about by the first conductive part, the temperature of the ink contained in the first common flow passage tends to be constant in the first direction. Similarly, on account of the influences of the heat generation brought about by the plurality of second pressure generators and the heat generation brought about by the second conductive part, the temperature of the ink contained in the second common flow passage also tends to be constant in the first direction. As a result, it is possible to suppress the uneven density on the image printed by the ink-jet head according to the first aspect.

Further, when the end portion of the first conductive part positioned nearer to the control circuit is positioned on the other side in the first direction, and the end portion of the second conductive part positioned nearer to the control circuit is positioned on the one side in the first direction, then the temperature of the ink contained in the first common flow passage is raised in the direction directed to the other side in the first direction on account of the influence of the heat generation brought about by the first conductive part. On the other hand, the temperature of the ink contained in the second common flow passage is raised in the direction directed to the one side in the first direction on account of the influence of the heat generation brought about by the second conductive part. In other words, on account of the influences of the heat generation brought about by the plurality of first pressure generators and the heat generation brought about by the first conductive part, the temperature of the ink contained in the first common flow passage is raised in the direction directed to the other side in the first direction. On the contrary, on account of the influences of the heat generation brought about by the plurality of second pressure generators and the heat generation brought about by the second conductive part, the temperature of the ink contained in the second common flow passage is raised in the direction directed to the one side in the first direction. In other words, the temperature gradient in the first direction of the ink contained in the first common flow passage is reverse to or opposite to the temperature gradient in the first direction of the ink contained in the second common flow passage. On this account, the volume of the ink droplet ejected from the plurality of first individual flow passages is increased in the direction directed to the other side in the first direction, while the volume of the ink droplet ejected from the plurality of second individual flow passages is increased in the direction directed to the one side in the first direction. Then, the plurality of first individual flow passages and the plurality of second individual flow passages are aligned in the second direction. As a result, it is possible to suppress the uneven density on the image printed by the ink-jet head according to the first aspect.

According to a second aspect of the present teaching, there is provided an ink-jet printer including: the ink-jet head according to the first aspect; and an ink supply unit which is constructed to supply the ink to the ink-jet head. The first ink supply port and the second ink supply port are communicated with the ink supply unit.

According to the ink-jet printer according to the second aspect of the present teaching, it is possible to obtain the effect which is the same as or equivalent to that of the ink-jet head according to the first aspect.

According to the present teaching, it is possible to provide the ink-jet head which can suppress the uneven density by mitigating the influence of heat generation caused by the pressure generator and the influence of heat generation caused by the conductive part connected to the pressure generator, and the ink-jet printer which is provided with the ink-jet head.

DESCRIPTION

First Embodiment

An explanation will be made below about a printer1provided with an ink-jet head11according to a first embodiment of the present teaching. With reference toFIG.1, the conveying direction of a medium M (recording medium) corresponds to the front-rear direction of the printer1. Further, the widthwise direction of the medium M corresponds to the left-right direction of the printer1. Further, the direction orthogonal to the front-rear direction and the left-right direction, i.e., the direction perpendicular to the paper surface ofFIG.1corresponds to the up-down direction of the printer1. Note that the widthwise direction and the left-right direction exemplify the first direction of the present teaching, the conveying direction and the front-rear direction exemplify the second direction of the present teaching, and the up-down direction exemplifies the third direction.

As depicted inFIG.1, the printer1is provided with, for example, a platen3which is accommodated in a casing2, four line heads10, two conveying rollers5A,5B, and a controller7. The medium M is placed on the upper surface of the platen3. The four line heads10are positioned to oppose to the platen3at positions over or above the platen3. The four line heads10are aligned in the front-rear direction. Each of the line heads10is provided with a plurality of ink-jet heads11(ten ink-jet heads11in this embodiment), and a holder12which holds the plurality of ink-jet heads11. The holder12is a rectangular plate-shaped member which is long in the left-right direction. The plurality of ink-jet heads11constitute two head rows which are aligned in the front-rear direction. Each of the head rows includes the five ink-jet heads11which are aligned in the left-right direction respectively. Note that the positions of the ink-jet heads11included in the two head rows are deviated from each other in the left-right direction. In other words, the ten ink-jet heads11are positioned in a zigzag form. Then, inks are supplied from ink tanks13(seeFIG.2) to the respective line heads10.

The two conveying rollers5A,5B are positioned at the front and the rear of the platen3respectively. The two conveying rollers5A,5B are driven by an unillustrated motor respectively to convey the medium M on the platen3to the downstream (rear) in the conveying direction. In this embodiment, the medium M is a lengthy medium which is wound in a roll form. The medium M, which is wound in the roll form, is installed to the conveying roller5A positioned upstream in the conveying direction. Note that the medium M is not limited thereto, which may be a lengthy medium constructed by mutually connecting end portions of a plurality of sheets of the medium, for example, with tape.

The controller7is connected to an external apparatus9such as a personal computer or the like so that the controller7can make mutual data communication therewith. The controller7controls the actions of respective parts of the printer1based on the instruction supplied from the external apparatus9or an unillustrated operation unit. For example, when the controller7receives a printing instruction from the external apparatus9, the controller7controls the conveying rollers5A,5B to convey the medium M in the conveying direction. Further, concurrently therewith, the controller7controls the four line heads10to eject the ink droplets from the ink-jet heads11toward the medium M. Accordingly, an image is printed on the medium M. Note that the operation unit is an interface for the user to input the instruction with respect to the printer1. The operation unit includes, for example, buttons and touch panels.

As depicted inFIG.2, a reservoir14is positioned over or above the plurality of ink-jet heads11in relation to each of the line heads10. The reservoir14is connected to the ink tank13via a tube16. A pressurizing pump15is positioned at the tube16. The ink, which is supplied from the ink tank13, is temporarily stored in the reservoir14. The lower portion of the reservoir14is connected to the plurality of ink-jet heads11. The ink is supplied from the reservoir14to the plurality of ink-jet heads11. The ink tank13, the reservoir14, the pressurizing pump15, and the tube16exemplify the ink supply unit of the present teaching.

Next, the structure of the ink-jet head11will be explained with reference toFIGS.3to5.

As depicted inFIG.3, a plurality of nozzles27(twelve in this embodiment) are open on the lower surface11aof the ink-jet head11. The twelve nozzles27form two nozzle rows27A,27B which are aligned in the front-rear direction. Each of the two nozzle rows27A,27B is formed by the six nozzles27which are aligned at equal intervals in the left-right direction. Note that the positions of the nozzles27included in the two nozzle rows27A,27B are deviated from each other in the left-right direction. In other words, the twelve nozzles27are formed in a zigzag form.

As depicted inFIGS.4and5, the ink-jet head11is provided with a flow passage member20and an actuator member30. As depicted inFIG.4, each of the flow passage member20and the actuator member30has a rectangular shape in which the length in the left-right direction is longer than the length in the front-rear direction. The sizes in the left-right direction and the front-rear direction of the flow passage member20are larger than those of the actuator member30.

As depicted inFIG.4, two ink supply ports41A,41B are formed on the upper surface of the flow passage member20. The two ink supply ports41A,41B are communicated with the reservoir14respectively. Further, the flow passage member20is formed with two manifolds42A,42B and a plurality of individual flow passages43. Note that the flow passage member20of this embodiment is formed with the twelve individual flow passages43corresponding to the twelve nozzles27respectively.

The two manifolds42A,42B are aligned in the front-rear direction, and the two manifolds42A,42B extend in the left-right direction respectively. The manifold42A is communicated with the ink supply port41A, and the manifold42B is communicated with the ink supply port41B. The twelve individual flow passages43include the six individual flow passages43A which are aligned in the left-right direction and the six individual flow passages43B which are aligned in the left-right direction. The six individual flow passages43A are connected to the manifold42A respectively, and the six individual flow passages43B are connected to the manifold42B respectively. The six individual flow passages43A and the six individual flow passages43B are deviated from each other in the left-right direction. The ink supply port41A is positioned on the right side with respect to the six individual flow passages43A. On the contrary, the ink supply port41B is positioned on the left side with respect to the six individual flow passages43B.

As depicted inFIG.5, the flow passage member20is composed of an ink sealing film21which is stacked in the up-down direction, and plates22to26each of which is made of metal.

The plate22is formed with through-holes which define a plurality of pressure chambers45. The plate23is formed with through-holes which define communication passages44,46that are provided for each of the pressure chambers45. Each of the communication passages44,46is overlapped in the up-down direction with one end or the other end in the front-rear direction of the corresponding pressure chamber45. The plate24is formed with through-holes which define communication passages47each of which is provided for each of the communication passages46. The plate25is formed with through-holes which define communication passages48each of which is provided for each of the communication passages47. The communication passages47,48are overlapped in the up-down direction with the corresponding communication passage46. The nozzle plate26is formed with through-holes which define the plurality of nozzles27. Each of the nozzles27is overlapped in the up-down direction with the communication passage48. Then, each of the individual flow passages43is constructed by the communication passage44, the pressure chamber45, the communication passages46to48, and the nozzle27.

Further, the plate24is formed with through-holes which define the manifolds42A,42B. The respective communication passages44of the six individual flow passages43A are overlapped in the up-down direction with the manifold42A, and the respective communication passages44of the six individual flow passages43B are overlapped in the up-down direction with the manifold42B. Accordingly, the six individual flow passages43A are communicated with the manifold42A, and the six individual flow passages43B are communicated with the manifold42B.

Note that the two ink supply ports41A,41B are formed respectively in areas of the upper surface of the plate22in which the ink sealing film21and the actuator member30are not formed. The ink supply port41A is communicated with the manifold42A via a through-hole which penetrates through the plates22,23. The ink supply port41B is communicated with the manifold42B via a through-hole which penetrates through the plates22,23.

The ink sealing film21is composed of, for example, a material such as stainless steel or the like having low ink permeability. The sizes of the ink sealing film21in the left-right direction and the front-rear direction are substantially the same as those of the actuator member30. The ink sealing film21is adhered to the upper surface of the plate22to seal all of the pressure chambers45formed in the plate22.

In the flow passage member20constructed as described above, the ink, which is contained in the reservoir14, is supplied to the manifolds42A,42B via the ink supply ports41A,41B. The ink, which is supplied to the manifold42A, is supplied to the six individual flow passages43A, and the ink, which is supplied to the manifold42B, is supplied to the six individual flow passages43B. Then, the actuator member30is driven as described later on. Accordingly, the pressure is generated and applied to the ink contained in the six individual flow passages43A and the ink contained in the six individual flow passages43B, and the ink droplets are ejected from the twelve nozzles27.

As depicted inFIGS.4and5, the actuator member30has two piezoelectric layers31,32, a plurality of individual electrodes34, and two common electrodes33A,33B.

Each of the two piezoelectric layers31,32is composed of a piezoelectric material having a main component of lead zirconate titanate or the like.

The piezoelectric layer31is formed on the upper surface of the ink sealing film21so that all of the individual flow passages43formed for the flow passage member20are covered therewith. The two common electrodes33A,33B, which are aligned in the front-rear direction, are formed on the upper surface of the piezoelectric layer31. Each of the two common electrodes33A,33B has a rectangular shape which is long in the left-right direction. The common electrode33A is positioned so that the common electrode33A is overlapped in the up-down direction with the six pressure chambers45communicated with the manifold42A. The common electrode33B is positioned so that the common electrode33B is overlapped in the up-down direction with the six pressure chambers45communicated with the manifold42B. The piezoelectric layer32is formed on the upper surfaces of the two common electrodes33A,33B and on an area of the upper surface of the piezoelectric layer31in which the two common electrodes33A,33B are not formed. Then, the plurality of individual electrodes34are formed on the upper surface of the piezoelectric layer32.

As depicted inFIG.4, the plurality of individual electrodes34are positioned so that the plurality of individual electrodes34are overlapped in the up-down direction with the plurality of pressure chambers45respectively. In other words, in this embodiment, the actuator member30has the twelve individual electrodes34which correspond to the twelve pressure chambers45respectively. The twelve individual electrodes34form two rows of individual electrode rows which are aligned in the front-rear direction. The individual electrode row positioned on the front side is formed by the six individual electrodes34which are aligned in the left-right direction, and the individual electrode row positioned on the rear side is also formed by the six individual electrodes34which are aligned in the left-right direction. The six individual electrodes34positioned on the front side and the six individual electrodes34positioned on the rear side are deviated from each other in the left-right direction.

As depicted inFIG.4, each of the individual electrodes34has a main portion34aand a protruding portion34b. The main portion34ais overlapped in the up-down direction with a central portion in the left-right direction of the corresponding pressure chamber45. As for each of the individual electrodes34positioned on the front side, the protruding portion34bprotrudes frontwardly from the front end of the main portion34a. On the other hand, as for each of the individual electrodes34positioned on the rear side, the protruding portion34bprotrudes rearwardly from the rear end of the main portion34a. Each of the protruding portions34bis not overlapped in the up-down direction with the corresponding pressure chamber45. A contact, which is to be electrically connected to an FPC (Flexible Printed Circuit) (not depicted), is positioned at the protruding portion34b. A driver IC50, which is mounted on the FPC, selectively applies any one of the driving electric potential and the ground electric potential to each of the individual electrodes34by the aid of the wiring of the FPC based on the control performed by the controller7.

As depicted inFIG.4, the left end portion of the common electrode33A is electrically connected to the FPC via a through-electrode36A which penetrates in the up-down direction through the piezoelectric layer32. The driver IC50, which is mounted on the FPC, maintains the common electrode33A at the ground electric potential by the aid of the wiring of the FPC and the through-electrode36A. On the other hand, the right end portion of the common electrode33B is electrically connected to the FPC via a through-electrode36B which penetrates in the up-down direction through the piezoelectric layer32. The driver IC50, which is mounted on the FPC, maintains the common electrode33B at the ground electric potential by the aid of the wiring of the FPC and the through-electrode36B.

The common electrode33A, the six individual electrodes34positioned on the front side, and six active portions32ainterposed by the common electrode33A and the six individual electrodes34positioned on the front side form six piezoelectric elements37A which are aligned in the left-right direction. Similarly, the common electrode33B, the six individual electrodes34positioned on the rear side, and six active portions32ainterposed by the common electrode33B and the six individual electrodes34positioned on the rear side form six piezoelectric elements37B which are aligned in the left-right direction. Then, the left end portion of the common electrode33A is positioned on the left side with respect to the six piezoelectric elements37A, and the right end portion of the common electrode33B is positioned on the right side with respect to the six piezoelectric elements37B.

An explanation will now be made about the action of the piezoelectric element37A corresponding to the nozzle27as exemplified by a case in which the ink droplets are ejected from one nozzle27positioned on the front side.

The driving electric potential is applied to the individual electrode34before the printer1starts the recording action. In this situation, the electric field, which is directed downwardly in the up-down direction, acts on the active portion32ainterposed by the common electrode33A and the individual electrode34of the piezoelectric layer32by means of the electric potential difference between the individual electrode34and the common electrode33A. In this situation, the polarization direction (downwardly in the up-down direction) of the active portion32ais coincident with the direction of the electric field. The active portion32alengthens in the thickness direction (up-down direction) of the piezoelectric layer32, and the active portion32ashrinks in the in-plane direction of the piezoelectric layer32. In accordance with the shrinkage deformation of the active portion32a, the portions of the piezoelectric layer31and the ink sealing film21, which are overlapped in the up-down direction with the pressure chamber45, are deformed to protrude (downwardly) toward the pressure chamber45. In this situation, the pressure chamber45has the small volume as compared with a case in which the piezoelectric layer31and the ink sealing film21are flat.

When the printer1starts the recording action, and the ink is ejected from the nozzle27, then the electric potential of the individual electrode34corresponding to the nozzle27is firstly switched from the driving electric potential to the ground electric potential. In this situation, the electric potential difference between the individual electrode34and the common electrode33A is decreased, and thus the shrinkage of the active portion32adisappears. Accordingly, the portions of the piezoelectric layer31and the ink sealing film21, which are overlapped in the up-down direction with the pressure chamber45, are in the flat state. Accordingly, the volume of the pressure chamber45is increased. The ink is drawn from the manifold42A into the pressure chamber45.

After that, the electric potential of the individual electrode34corresponding to the nozzle27is switched from the ground electric potential to the driving electric potential. In this situation, the electric field, which is directed in the downward direction that is equal to the polarization direction, is generated in the active portion32aby the electric potential difference between the individual electrode34and the common electrode33A. The active portion32ashrinks in the in-plane direction of the piezoelectric layer32. Accordingly, the portions of the piezoelectric layer31and the ink sealing film21, which are overlapped in the up-down direction with the pressure chamber45, are deformed to protrude (downwardly) toward the pressure chamber45. In this situation, the volume of the pressure chamber45is greatly decreased, and thus a large pressure is generated and applied to the ink contained in the pressure chamber45. The ink, which is drawn into the pressure chamber45, is ejected as the ink droplets from the nozzle27.

In this embodiment, the driver IC50exemplifies the control circuit, the common electrode33A exemplifies the first conductive part, and the common electrode33B exemplifies the second conductive part. Further, the left end portion of the common electrode33A exemplifies the end portion of the first conductive part positioned nearer to the control circuit, and the right end portion of the common electrode33B exemplifies the end portion of the second conductive part positioned nearer to the control circuit. The piezoelectric element37A exemplifies the first pressure generator, and the piezoelectric element37B exemplifies the second pressure generator.

Note that in this embodiment, the ink-jet head11has the twelve individual flow passages43and the twelve piezoelectric elements. However, the numbers of the individual flow passages43and the piezoelectric elements may be smaller than twelve or larger than twelve. Further, for example, when the ink-jet head11has a dummy flow passage which does not contribute to the ejection of the ink, and a piezoelectric element which corresponds to the dummy flow passage, it is not necessarily indispensable that the number of the individual flow passages43is the same as the number of the piezoelectric elements.

In the ink-jet head11of this embodiment, the ink supply port41A is positioned on the right side with respect to the six individual flow passages43A. The ink, which flows into the manifold42A from the ink supply port41A, flows through the manifold42A in the direction directed from the right to the left. In this case, when the electric power is applied to each of the piezoelectric elements, all of the electric energy applied to the piezoelectric element is not necessarily used for the physical deformation. In other words, any energy loss arises. The amount of the energy loss corresponds to the heat generation from the piezoelectric element. Then, the six piezoelectric elements are aligned in the direction in which the ink contained in the manifold42A advances. On this account, as for the ink contained in the manifold42A, the heat, which is accepted from the piezoelectric element, is increased as the ink advances leftwardly, and the temperature is raised. Further, the common electrode33A is connected to the driver IC50at the left end portion. In this case, as for the common electrode33A, the number of the individual electrodes34opposed to the common electrode33A is increased as the position advances leftwardly. On this account, as for the common electrode33A, the amount of movement of the electric charge is increased by an amount corresponding to the increase in the number of the individual electrodes34at positions nearer to the left end portion, and the amount of heat generation is increased. As a result, as for the ink contained in the manifold42A, the temperature is more raised as the ink advances leftwardly on account of the influence of the heat generation brought about by the common electrode33A.

On the other hand, the ink supply port41B is positioned on the left side with respect to the six individual flow passages43B. The ink, which flows into the manifold42B from the ink supply port41B, flows through the manifold42B in the direction directed from the left to the right. In this case, when the electric power is applied to each of the piezoelectric elements, all of the electric energy applied to the piezoelectric element is not necessarily used for the physical deformation. In other words, any energy loss arises. The amount of the energy loss corresponds to the heat generation from the piezoelectric element. Then, the six piezoelectric elements are aligned in the direction in which the ink contained in the manifold42B advances. On this account, as for the ink contained in the manifold42B, the heat, which is accepted from the piezoelectric element, is increased as the ink advances rightwardly, and the temperature is raised. Further, the common electrode33B is connected to the driver IC50at the right end portion. In this case, as for the common electrode33B, the number of the individual electrodes34opposed to the common electrode33B is increased as the position advances rightwardly. On this account, as for the common electrode33B, the amount of movement of the electric charge is increased by an amount corresponding to the increase in the number of the individual electrodes34at positions nearer to the right end portion, and the amount of heat generation is increased. As a result, as for the ink contained in the manifold42B, the temperature is more raised as the ink advances rightwardly on account of the influence of the heat generation brought about by the common electrode33B.

In other words, the temperature gradient of the ink contained in the manifold42A is raised in the direction directed from the right to the left, while the temperature gradient of the ink contained in the manifold42B is raised in the direction directed from the left to the right, wherein the temperature gradients are opposite to one another. On this account, if the entire ink-jet head11is taken into consideration, the temperature gradients are offset. In other words, the temperature gradient is hardly generated in relation to the entire ink-jet head11. The difference decreases in relation to the size of the ink droplet ejected from the nozzle27of the ink-jet head11. As a result, it is possible to suppress the uneven density on the image printed by the ink-jet head11of this embodiment.

In the case of the ink-jet head11of the first embodiment, the left end portion of the common electrode33A is connected to the driver IC50via the through-electrode36A, and the right end portion of the common electrode33B is connected to the driver IC50via the through-electrode36B. However, there is no limitation thereto. For example, as depicted inFIG.6, the right end portion of the common electrode33A may be connected to the driver IC50via the through-electrode36A, and the left end portion of the common electrode33B may be connected to the driver IC50via the through-electrode36B.

In this case, as for the common electrode33A, as having been already explained in the first embodiment, the amount of movement of the electric charge is more increased at positions nearer to the right end portion, and the amount of heat generation is more increased. On this account, when attention is focused on the influence of the heat generation brought about by the common electrode33A, the temperature of the ink contained in the manifold42A is raised in the direction directed to the right. On the contrary, when attention is focused on the influence of the heat generation brought about by the piezoelectric element, as having been already explained in the first embodiment, the temperature of the ink contained in the manifold42A is raised in the direction directed to the left. In other words, the temperature gradient, which is caused by the heat generation of the common electrode33A, is raised in the direction directed from the left to the right, while the temperature gradient, which is caused by the heat generation of the piezoelectric element, is raised in the direction directed from the right to the left. The temperature gradients are opposite to one another. As a result, the temperature gradients are offset. The temperature of the ink contained in the manifold42A tends to be constant in the left-right direction.

On the other hand, as for the common electrode33B, as having been already explained in the first embodiment, the amount of movement of the electric charge is more increased at positions nearer to the left end portion, and the amount of heat generation is more increased. On this account, when attention is focused on the influence of the heat generation brought about by the common electrode33B, the temperature of the ink contained in the manifold42B is raised in the direction directed to the left. On the contrary, when attention is focused on the influence of the heat generation brought about by the piezoelectric element, as having been already explained in the first embodiment, the temperature of the ink contained in the manifold42B is raised in the direction directed to the right. In other words, the temperature gradient, which is caused by the heat generation of the common electrode33B, is raised in the direction directed from the right to the left, while the temperature gradient, which is caused by the heat generation of the piezoelectric element, is raised in the direction directed from the left to the right. The temperature gradients are opposite to one another. As a result, the temperature gradients are offset. The temperature of the ink contained in the manifold42B tends to be constant in the left-right direction.

In other words, according to the construction of the first modification, the ink contained in the manifold42A and the ink contained in the manifold42B have the temperatures which tend to be constant in the left-right direction. On this account, the temperature gradient is hardly generated in relation to the entire ink-jet head11as well. The difference decreases in relation to the size of the ink droplet ejected from the nozzle27of the ink-jet head11. As a result, it is possible to suppress the uneven density on a printed image.

Further, as depicted inFIG.7, in the construction of the first modification, two ink discharge ports41C,41D may be formed on the upper surface of the flow passage member20. The ink discharge port41C may be formed at a position overlapped in the up-down direction with the left end portion of the manifold42A, and the ink discharge port41D may be formed at a position overlapped in the up-down direction with the right end portion of the manifold42B. Then, the ink, which is discharged from the ink discharge ports41C,41D, may be recovered to a recovery tank (not depicted), and then the ink may be recovered to the ink tank13by means of a pump (not depicted).

According to the construction of the second modification, the ink contained in the manifolds42A,42B is recovered from the ink discharge ports41C,41D. Accordingly, it is possible to raise the flow rate of the ink in the manifolds42A,42B. On this account, the ink contained in the manifolds42A,42B is hardly affected by the heat generation caused by the piezoelectric element. The temperature tends to be constant more easily in the left-right direction. Further, even if the ejection amount per unit time from the nozzle27is increased, and the flow rate of the ink is lowered in the manifolds42A,42B, then it is possible to suppress the uneven density on a printed image in accordance with the mechanism which is the same as or equivalent to that of the first modification.

Second Embodiment

Next, a second embodiment of the present teaching will be explained with reference toFIGS.8to11. An ink-jet head111according to the second embodiment has a different structure in relation to the actuator member30of the ink-jet head11according to the second modification described above. On this account, the structure, which is different from that of the second modification, will be explained below. Any explanation about the common structure will be omitted.

As depicted inFIGS.8and9, an actuator member130has three piezoelectric layers131to133, a plurality of (twelve in this embodiment) individual electrodes134, high electric potential electrode portions135A,135B, and a low electric potential electrode portion136.

Each of the three piezoelectric layers131to133is composed of a piezoelectric material having a main component of lead zirconate titanate or the like. The three piezoelectric layers131to133are stacked in the up-down direction. The piezoelectric layer131is adhered to the upper surface of the ink sealing film21with an adhesive.

The plurality of individual electrodes134, the high electric potential electrode portions135A,135B, and the low electric potential electrode portion136are positioned on the side opposite to the ink sealing film21in relation to the piezoelectric layer131.

As depicted inFIG.9, each of the individual electrodes134is formed on the upper surface of the piezoelectric layer133while corresponding to the pressure chamber45. The individual electrode134has a main portion134aand a protruding portion134b. The main portion134ais overlapped in the up-down direction with a substantially entire area of the corresponding pressure chamber45. The protruding portion134bprotrudes frontwardly or rearwardly from the main portion134a. The protruding portion134bis not overlapped in the up-down direction with the corresponding pressure chamber45. A contact, which is to be electrically connected to the FPC, is positioned at the protruding portion134b. The driver IC50, which is mounted on the FPC, selectively applies any one of the high electric potential (VDD electric potential) and the low electric potential (GND electric potential) to each of the individual electrodes134by the aid of the wiring of the FPC in accordance with the control performed by the controller7.

The high electric potential electrode portions135A,135B are formed on the upper surface of the piezoelectric layer132, and the high electric potential electrode portions135A,135B are aligned in the front-rear direction. As depicted inFIG.8, the high electric potential electrode portion135A is composed of a high electric potential wiring135A1and six high electric potential electrodes135A2. The high electric potential wiring135A1extends in the left-right direction at the front end portion of the actuator member130. The six high electric potential electrodes135A2extend rearwardly from the high electric potential wiring135A1respectively. The six high electric potential electrodes135A2correspond to the six pressure chambers45positioned on the front side and the six individual electrodes134positioned on the front side respectively. Each of the high electric potential electrodes135A2is overlapped in the up-down direction with the corresponding individual electrode134and the central portion in the left-right direction of the corresponding pressure chamber45. The high electric potential electrode portion135B is composed of a high electric potential wiring135B1and six high electric potential electrodes135B2. The high electric potential wiring135B1extends in the left-right direction at the rear end portion of the actuator member130. The six high electric potential electrodes135B2extend frontwardly from the high electric potential wiring135B1respectively. The six high electric potential electrodes135B2correspond to the six pressure chambers45positioned on the rear side and the six individual electrodes134positioned on the rear side respectively. Each of the high electric potential electrodes135B2is overlapped in the up-down direction with the corresponding individual electrode134and the central portion in the left-right direction of the corresponding pressure chamber45.

Then, the right end portion of the high electric potential wiring135A1is electrically connected to the FPC via a through-electrode137A which penetrates in the up-down direction through the piezoelectric layer133. A constant electric potential (VCOM electric potential), which is slightly higher than the VDD electric potential, is applied to the high electric potential electrode135A2by the driver IC50mounted on the FPC, by the aid of the wiring of the FPC, the through-electrode137A, and the high electric potential wiring135A1. On the other hand, the left end portion of the high electric potential wiring135B1is electrically connected to the FPC via a through-electrode137B which penetrates in the up-down direction through the piezoelectric layer133. The constant electric potential (VCOM electric potential), which is slightly higher than the VDD electric potential, is applied to the high electric potential electrode135B2by the driver IC50mounted on the FPC, by the aid of the wiring of the FPC, the through-electrode137B, and the high electric potential wiring135B1.

The low electric potential electrode portion136is formed on the upper surface of the piezoelectric layer131. The low electric potential electrode portion136is composed of a low electric potential wiring136A and fourteen low electric potential electrodes136B. The low electric potential wiring136A extends in the front-rear direction at a central portion in the front-rear direction of the actuator member130. Seven low electric potential electrodes136B of the fourteen low electric potential electrodes136B extend frontwardly from the low electric potential wiring136A, and another seven low electric potential electrodes136B extend rearwardly from the low electric potential wiring136A. Except for the low electric potential electrodes136B positioned at the both left and right ends, each of the low electric potential electrodes136B positioned frontwardly has a portion which ranges over the two pressure chambers45that are adjacent to one another on the left and the right and which is overlapped in the up-down direction with the two pressure chambers45. Then, the low electric potential electrode136B positioned at the left end has a portion which is overlapped in the up-down direction with the left end portion of the pressure chamber45positioned at the left end. The low electric potential electrode136B positioned at the right end has a portion which is overlapped in the up-down direction with the right end portion of the pressure chamber45positioned at the right end. Similarly, except for the low electric potential electrodes136B positioned at the both left and right ends, each of the low electric potential electrodes136B positioned rearwardly also has a portion which ranges over the two pressure chambers45that are adjacent to one another on the left and the right and which is overlapped in the up-down direction with the two pressure chambers45. Then, the low electric potential electrode136B positioned at the left end has a portion which is overlapped in the up-down direction with the left end portion of the pressure chamber45positioned at the left end. The low electric potential electrode136B positioned at the right end has a portion which is overlapped in the up-down direction with the right end portion of the pressure chamber45positioned at the right end.

Then, the left end portion of the low electric potential wiring136A is electrically connected to the FPC by the aid of a through-electrode137C which penetrates in the up-down direction through the piezoelectric layers132,133. The driver IC50, which is mounted on the FPC, applies the low electric potential (GND electric potential) to the low electric potential electrode136B by the aid of the wiring of the FPC, the through-electrode137C, and the low electric potential wiring136A.

As depicted inFIG.9, the portion of the piezoelectric layer133, which is interposed in the up-down direction between the individual electrode134and the high electric potential electrode135A2, is referred to as “first active portion138”. Similarly, the portion of the piezoelectric layer133, which is interposed in the up-down direction between the individual electrode134and the high electric potential electrode135B2, is also referred to as “first active portion138”. The portions of the piezoelectric layers132,133, which are interposed in the up-down direction between the individual electrode134and the low electric potential electrode136B, are referred to as “second active portions139”. The first active portion138is principally polarized in the upward direction, and the second active portion139is principally polarized in the downward direction. The actuator member130has pressure generators140for the respective pressure chambers45. Each of the pressure generators140includes one first active portion138and two second active portions139which interpose the first active portion138in the left-right direction.

With reference toFIGS.10and11, an explanation will now be made about the action of the pressure generator140corresponding to the nozzle27, as exemplified by a case in which the ink droplets are ejected from one nozzle27positioned on the front side.

As depicted inFIG.10, the low electric potential (GND electric potential) is applied to the respective individual electrodes134before the printer1starts the recording action. In this situation, the electric field, which is directed in the upward direction that is equal to the polarization direction, is generated in the first active portion138by the electric potential difference between the individual electrode134and the high electric potential electrode135A2. The first active portion138shrinks in the in-plane direction (direction along the left-right direction and the front-rear direction). Accordingly, the portion of the stack composed of the piezoelectric layers131to133, which is overlapped in the up-down direction with the pressure chamber45, warps so that the portion protrudes (downwardly) toward the pressure chamber45. In this situation, the volume of the pressure chamber45is decreased as compared with a case in which the stack is flat.

When the printer1starts the recording action to eject the ink from the nozzle27, as depicted inFIG.11, the electric potential of the individual electrode134corresponding to the nozzle27is firstly switched from the low electric potential (GND electric potential) to the high electric potential (VDD electric potential). In this situation, the electric potential difference between the individual electrode134and the high electric potential electrode135A2is decreased, and thus the shrinkage of the first active portion138is decreased. On the other hand, the electric field, which is directed in the downward direction that is equal to the polarization direction, is generated in the two second active portions139by the electric potential difference between the individual electrode134and the low electric potential electrode136B. The two second active portions139shrink in the in-plane direction. Accordingly, the portion of the stack composed of the piezoelectric layers131to133, which is overlapped in the up-down direction with the pressure chamber45, warps so that the portion protrudes (upwardly) in the direction to make separation from the pressure chamber45. Accordingly, the volume of the pressure chamber45is increased as compared withFIG.10, and the ink is drawn into the pressure chamber45from the manifold42A.

After that, as depicted inFIG.10, the electric potential of the individual electrode134corresponding to the nozzle27is switched from the high electric potential (VDD electric potential) to the low electric potential (GND electric potential). In this situation, the electric potential difference between the individual electrode134and the low electric potential electrode136B disappears, and thus the shrinkage of the second active portion139is eliminated. On the other hand, the electric field, which is directed in the upward direction that is equal to the polarization direction, is generated in the first active portion138by the electric potential difference between the individual electrode134and the high electric potential electrode135A2. The first active portion138shrinks in the in-plane direction. Accordingly, the portion of the stack composed of the piezoelectric layers131to133, which is overlapped in the up-down direction with the pressure chamber45, warps (downwardly) so that the portion protrudes toward the pressure chamber45. In this situation, the volume of the pressure chamber45is greatly decreased, and thus the large pressure is generated and applied to the ink contained in the pressure chamber45. The ink, which is drawn into the pressure chamber45, is ejected as the ink droplets from the nozzle27.

In this embodiment, the driver IC50exemplifies the control circuit, the high electric potential wiring135A1exemplifies the first conductive part, and the high electric potential wiring135B1exemplifies the second conductive part. Further, the right end portion of the high electric potential wiring135A1exemplifies the end portion of the first conductive part positioned nearer to the control circuit, and the left end portion of the high electric potential wiring135B1exemplifies the end portion of the second conductive part positioned nearer to the control circuit. The six pressure generators140positioned on the front side exemplify the first pressure generator, and the six pressure generators140positioned on the rear side exemplify the second pressure generator.

In this embodiment, the ink-jet head111has the twelve individual flow passages43and the twelve piezoelectric elements. However, the numbers of the individual flow passages43and the piezoelectric elements may be smaller than twelve or larger than twelve. Further, for example, when the ink-jet head111has a dummy flow passage which does not contribute to the ejection of the ink, and a piezoelectric element which corresponds to the dummy flow passage, it is not necessarily indispensable that the number of the individual flow passages43is the same as the number of the piezoelectric elements.

According to the construction of this embodiment, as for the high electric potential wiring135A1, the number of the connected first active portions138is increased as the position advances rightwardly. On this account, as for the high electric potential wiring135A1, the amount of movement of the electric charge is increased by the amount of increase in the number of the first active portions138as the position approaches the right end portion, and the amount of heat generation is increased. On this account, when attention is focused on the influence of the heat generation brought about by the high electric potential wiring135A1, the temperature of the ink contained in the manifold42A is raised in the direction directed to the right. On the other hand, as having been already explained in the first embodiment, when attention is focused on the influence of the heat generation brought about by the pressure generator140, the temperature of the ink contained in the manifold42A is raised in the direction directed to the left. In other words, the temperature gradient, which is caused by the heat generation brought about by the high electric potential wiring135A1, is raised in the direction directed from the left to the right, while the temperature gradient, which is caused by the heat generation brought about by the pressure generator140, is raised in the direction directed from the right to the left. The temperature gradients are opposite to one another. As a result, the temperature gradients are offset. The temperature of the ink contained in the manifold42A tends to be constant in the left-right direction.

On the other hand, as for the high electric potential wiring135B1, the number of the connected first active portions138is increased as the position advances leftwardly. On this account, as for the high electric potential wiring135B1, the amount of movement of the electric charge is increased by the amount of increase in the number of the first active portions138as the position approaches the left end portion, and the amount of heat generation is increased. On this account, when attention is focused on the influence of the heat generation brought about by the high electric potential wiring135B1, the temperature of the ink contained in the manifold42B is raised in the direction directed to the left. On the other hand, as having been already explained in the first embodiment, when attention is focused on the influence of the heat generation brought about by the pressure generator140, the temperature of the ink contained in the manifold42B is raised in the direction directed to the right. In other words, the temperature gradient, which is caused by the heat generation brought about by the high electric potential wiring135B1, is raised in the direction directed from the right to the left, while the temperature gradient, which is caused by the heat generation brought about by the pressure generator140, is raised in the direction directed from the left to the right. The temperature gradients are opposite to one another. As a result, the temperature gradients are offset. The temperature of the ink contained in the manifold42B tends to be constant in the left-right direction.

In other words, according to the construction of this embodiment, the temperatures of the ink contained in the manifold42A and the ink contained in the manifold42B tend to be constant in the left-right direction. Therefore, it is possible to suppress the uneven density on a printed image. Further, the ink contained in the manifolds42A,42B is recovered from the ink discharge ports41C,41D, and thus it is possible to raise the flow rate of the ink contained in the manifolds42A,42B. On this account, the ink contained in the manifolds42A,42B is hardly affected by the heat generation brought about by the pressure generator. The temperature tends to be constant more easily in the left-right direction. Further, even if the ejection amount per unit time from the nozzle27is increased, and the flow rate of the ink is lowered in the manifolds42A,42B, then the temperature gradient is hardly caused in the entire ink-jet head111, and hence the difference is decreased in relation to the size of the ink droplet ejected from the nozzle27in the ink-jet head111. As a result, it is possible to further suppress the uneven density on the printed image.

Next, an explanation will be made with reference toFIG.12about a modification (third modification) of the second embodiment. The structures of the flow passage member and the actuator member differ between an ink-jet head211of the third modification and the ink-jet head111of the second embodiment described above. Specifically, the structure of the manifold of the flow passage member differs, and the structures of the high electric potential electrode portion and the low electric potential electrode portion of the actuator member differ. On the other hand, the structures of the respective individual flow passages and the structures of the respective pressure generators of the ink-jet head211of the third modification are common to those of the second embodiment. On this account, in the following description, the structures, which are different from those of the second embodiment, will be explained below, and any explanation about the common structures will be omitted.

As depicted inFIG.12, a flow passage member220of the ink-jet head211of the third modification has four manifolds242A1,242A2,242B1,242B2which extend in the left-right direction respectively, and four connecting flow passages242A3,242A4,242B3,242B4which extend in the front-rear direction respectively. The right end of the manifold242A1and the right end of the manifold242A2are connected to the front end and the rear end of the connecting flow passage242A3respectively. The left end of the manifold242A1and the left end of the manifold242A2are connected to the front end and the rear end of the connecting flow passage242A4respectively. The right end of the manifold242B1and the right end of the manifold242B2are connected to the front end and the rear end of the connecting flow passage242B4respectively. The left end of the manifold242B1and the left end of the manifold242B2are connected to the front end and the rear end of the connecting flow passage242B3respectively. Then, the ink supply port241A is communicated with the connecting flow passage242A3, and the ink discharge port241C is communicated with the connecting flow passage242A4. Further, the ink supply port241B is communicated with the connecting flow passage242B3, and the ink discharge port241D is communicated with the connecting flow passage242B4.

The ink, which flows from the ink tank13via the ink supply port241A into the connecting flow passage242A3, advances in the front-rear direction. The ink flows in the leftward direction through the manifold242A1and the manifold242A2. Then, the ink, which flows through the manifold242A1and the manifold242A2, flows into the plurality of individual flow passages43which are communicated with the manifold242A1and the manifold242A2respectively. The ink, which does not flow into the plurality of individual flow passages43, flows into the connecting flow passage242A4at the left ends of the manifold242A1and the manifold242A2. The ink is recovered to the ink tank13via the ink discharge port241C.

On the other hand, the ink, which flows from the ink tank13via the ink supply port241B into the connecting flow passage242B3, advances in the front-rear direction. The ink flows in the rightward direction through the manifold242B1and the manifold242B2. Then, the ink, which flows through the manifold242B1and the manifold242B2, flows into the plurality of individual flow passages43which are communicated with the manifold242B1and the manifold242B2respectively. The ink, which does not flow into the plurality of individual flow passages43, flows into the connecting flow passage242B4at the right ends of the manifold242B1and the manifold242B2. The ink is recovered to the ink tank13via the ink discharge port241D.

Further, the actuator member230has two high electric potential electrode portions235A,235B. The two high electric potential electrode portions235A,235B are aligned in the front-rear direction.

The high electric potential electrode portion235A is composed of two high electric potential wirings235A1, a plurality of high electric potential electrodes235A2, and a connecting portion235A3. The two high electric potential wirings235A1are aligned in the front-rear direction, and the two high electric potential wirings235A1extend in the left-right direction respectively. The plurality of high electric potential electrodes235A2extend frontwardly or rearwardly from each of the high electric potential wirings235A1. The connecting portion235A3is connected to the right end portions of the respective high electric potential wirings235A1. The connecting portion235A3extends in the front-rear direction. The front end of the connecting portion235A3protrudes leftwardly. Then, the forward end portion of the connecting portion235A3, which protrudes leftwardly, is electrically connected to the FPC by the aid of a through-electrode237A which penetrates through the piezoelectric layer133.

The high electric potential electrode portion235B is composed of two high electric potential wirings235B1, a plurality of high electric potential electrodes235B2, and a connecting portion235B3. The two high electric potential wirings235B1are aligned in the front-rear direction, and the two high electric potential wirings235B1extend in the left-right direction respectively. The plurality of high electric potential electrodes235B2extend frontwardly or rearwardly from each of the high electric potential wirings235B1. The connecting portion235B3is connected to the left end portions of the respective high electric potential wirings235B1. The connecting portion235B3extends in the front-rear direction. The rear end of the connecting portion235B3protrudes rightwardly. Then, the forward end portion of the connecting portion235B3, which protrudes rightwardly, is electrically connected to the FPC by the aid of a through-electrode237B which penetrates through the piezoelectric layer133.

Further, the actuator member230has two low electric potential electrode portions236A,236B. The two low electric potential electrode portions236A,236B are aligned in the front-rear direction.

The low electric potential electrode portion236A is composed of two low electric potential wirings236A1, a plurality of low electric potential electrodes236A2, and a connecting portion236A3. The two low electric potential wirings236A1are aligned in the front-rear direction, and the two low electric potential wirings236A1extend in the left-right direction respectively. The plurality of low electric potential electrodes236A2extend frontwardly or rearwardly from each of the low electric potential wirings236A1. The connecting portion236A3is connected to the left end portions of the respective low electric potential wirings236A1. The front end portion of the low electric potential wiring236A1positioned frontwardly is electrically connected to the FPC by the aid of a through-electrode237C which penetrates through the piezoelectric layers132,133.

The low electric potential electrode portion236B is composed of three low electric potential wirings236B1, a plurality of low electric potential electrodes236B2, and a connecting portion236B3. The three low electric potential wirings236B1are aligned in the front-rear direction, and the three low electric potential wirings236B1extend in the left-right direction respectively. The plurality of low electric potential electrodes236B2extend frontwardly or rearwardly from each of the low electric potential wirings236B1. The connecting portion236B3is connected to the right end portions of the respective low electric potential wirings236B1. The rear end portion of the low electric potential wiring236B1positioned most rearwardly is electrically connected to the FPC by the aid of a through-electrode237D which penetrates through the piezoelectric layers132,133.

In the third modification, the high electric potential wiring235A1positioned frontwardly exemplifies the first control unit, the high electric potential wiring235A1positioned rearwardly exemplifies the third conductive part, the high electric potential wiring235B1positioned frontwardly exemplifies the fourth conductive part, and the high electric potential wiring235B1positioned rearwardly exemplifies the second conductive part. The right end portion of the high electric potential wiring235A1positioned frontwardly exemplifies the end portion of the first conductive part positioned nearer to the control circuit, and the right end portion of the high electric potential wiring235A1positioned rearwardly exemplifies the end portion of the third conductive part positioned nearer to the control circuit. The left end portion of the high electric potential wiring235B1positioned frontwardly exemplifies the end portion of the fourth conductive part positioned nearer to the control circuit, and the left end portion of the high electric potential wiring235B1positioned rearwardly exemplifies the end portion of the second conductive part positioned nearer to the control circuit. Further, the manifold242A1exemplifies the first common flow passage, the manifold242A2exemplifies the third common flow passage, the manifold242B1exemplifies the fourth common flow passage, and the manifold242B2exemplifies the second common flow passage. The ink supply port241A exemplifies the first ink supply port, the ink supply port241B exemplifies the second ink supply port, the ink discharge port241C exemplifies the first ink discharge port, and the ink discharge port241D exemplifies the second ink discharge port.

In the third modification, as for each of the high electric potential wirings235A1, as having been already explained in the second embodiment, the amount of movement of the electric charge is increased at positions nearer to the right end portion, and the amount of heat generation is increased. On this account, when attention is focused on the influence of the heat generation brought about by the respective high electric potential wirings235A1, the temperatures of the ink contained in the manifolds242A1,242A2are raised in the direction directed to the right. On the contrary, when attention is focused on the influence of the heat generation brought about by the pressure generator140, as having been already explained in the second embodiment, the temperatures of the ink contained in the manifolds242A1,242A2are raised in the direction directed to the left. In other words, the temperature gradient, which is caused by the heat generation of the respective high electric potential wirings235A1, is raised in the direction directed from the left to the right, while the temperature gradient, which is caused by the heat generation of the pressure generator140, is raised in the direction directed from the right to the left. The temperature gradients are opposite to one another. As a result, the temperature gradients are offset. The temperatures of the ink contained in the manifolds242A1,242A2tend to be constant in the left-right direction.

On the other hand, as for each of the high electric potential wirings235B1, as having been already explained in the second embodiment, the amount of movement of the electric charge is increased at positions nearer to the left end portion, and the amount of heat generation is increased. On this account, when attention is focused on the influence of the heat generation brought about by the respective high electric potential wirings235B1, the temperatures of the ink contained in the manifolds242B1,242B2are raised in the direction directed to the left. On the contrary, when attention is focused on the influence of the heat generation brought about by the pressure generator140, as having been already explained in the second embodiment, the temperatures of the ink contained in the manifolds242B1,242B2are raised in the direction directed to the right. In other words, the temperature gradient, which is caused by the heat generation of the respective high electric potential wirings235B1, is raised in the direction directed from the right to the left, while the temperature gradient, which is caused by the heat generation of the pressure generator140, is raised in the direction directed from the left to the right. The temperature gradients are opposite to one another. As a result, the temperature gradients are offset. The temperatures of the ink contained in the manifolds242B1,242B2tend to be constant in the left-right direction.

Further, also in the third modification, the ink discharge ports241C,241D are provided in the same manner as the second embodiment. Therefore, it is possible to raise the flow rate of the ink in the manifolds242A1,242A2,242B1,242B2. Further, even if the ejection amount per unit time from the nozzle27is increased, and the flow rate of the ink is lowered in the manifolds242A1,242A2,242B1,242B2, then the temperature gradient is hardly generated in the entire ink-jet head211. On this account, the difference is decreased in relation to the size of the ink droplet ejected from the nozzle27in the ink-jet head211.

According to the fact as described above, even in the case of the construction of the third modification, it is possible to obtain the effect which is the same as or equivalent to that of the second embodiment.

Next, an explanation will be made with reference toFIG.13about still another modification (fourth modification) of the second embodiment. The structure of the manifold differs between an ink-jet head311of the fourth embodiment and the ink-jet head211of the third modification described above. However, the structures of the other components are common to one another. On this account, the structure, which is different from that of the third modification, will be explained below. Any explanation will be omitted about the common structures.

As depicted inFIG.13, a flow passage member320of the ink-jet head311of the fourth modification has four manifolds342A1,342A2,342B1,342B2which extend in the left-right direction respectively, four ink supply ports341A,341B,341E,341F, and four ink discharge ports341C,341D,341G,341H. The right end and the left end of the manifold342A1are communicated with the ink supply port341A and the ink discharge port341C respectively. The left end and the right end of the manifold342A2are communicated with the ink supply port341E and the ink discharge port341G respectively. The right end and the left end of the manifold342B1are communicated with the ink supply port341F and the ink discharge port341H respectively. The left end and the right end of the manifold342B2are communicated with the ink supply port341B and the ink discharge port341D respectively.

The ink, which flows from the ink tank13via the ink supply port341A into the manifold342A1, flows in the leftward direction through the manifold342A1. Then, the ink, which flows through the manifold342A1, flows into a plurality of individual flow passages43which are communicated with the manifold342A1. The ink, which does not flow into the plurality of individual flow passages43, is recovered to the ink tank13via the ink discharge port341C at the left end of the manifold342A1.

The ink, which flows from the ink tank13via the ink supply port341E into the manifold342A2, flows in the rightward direction through the manifold342A2. Then, the ink, which flows through the manifold342A2, flows into a plurality of individual flow passages43which are communicated with the manifold342A2. The ink, which does not flow into the plurality of individual flow passages43, is recovered to the ink tank13via the ink discharge port341G at the right end of the manifold342A2.

The ink, which flows from the ink tank13via the ink supply port341F into the manifold342B1, flows in the leftward direction through the manifold342B1. Then, the ink, which flows through the manifold342B1, flows into a plurality of individual flow passages43which are communicated with the manifold342B1. The ink, which does not flow into the plurality of individual flow passages43, is recovered to the ink tank13via the ink discharge port341H at the left end of the manifold342B1.

The ink, which flows from the ink tank13via the ink supply port341B into the manifold342B2, flows in the rightward direction through the manifold342B2. Then, the ink, which flows through the manifold342B2, flows into a plurality of individual flow passages43which are communicated with the manifold342B2. The ink, which does not flow into the plurality of individual flow passages43, is recovered to the ink tank13via the ink discharge port341D at the right end of the manifold342B2.

In the fourth modification, the manifold342A1exemplifies the first common flow passage, the manifold342A2exemplifies the third common flow passage, the manifold342B1exemplifies the fourth common flow passage, and the manifold342B2exemplifies the second common flow passage.

In the fourth modification, as for each of the high electric potential wirings235A1, as having been already explained in the second embodiment, the amount of movement of the electric charge is increased at positions nearer to the right end portion, and the amount of heat generation is increased. On this account, when attention is focused on the influence of the heat generation brought about by the respective high electric potential wirings235A1, the temperatures of the ink contained in the manifolds342A1,342A2are raised in the direction directed to the right. On the other hand, when attention is focused on the influence of the heat generation brought about by the pressure generator140, as having been already explained in the second embodiment, the temperature of the ink contained in the manifold342A1is raised in the direction directed to the left, while the temperature of the ink contained in the manifold342A2is raised in the direction directed to the right. In other words, the temperature gradient, which is caused by the heat generation of the respective high electric potential wirings235A1, is raised in the direction directed from the left to the right. On the contrary, the temperature gradient, which is caused by the heat generation of the pressure generator140, is raised in the direction directed from the right to the left in relation to the manifold342A1, and the temperature gradient is raised in the direction directed from the left to the right in relation to the manifold342A2. As a result, the temperature gradients are offset in the manifold342A1, and the temperature of the ink contained in the manifold342A1tends to be constant in the left-right direction. On the other hand, the temperature gradients are superimposed in the manifold342A2, and the temperature of the ink contained in the manifold342A2is raised in the direction directed to the right.

On the other hand, as for each of the high electric potential wirings235B1, as having been already explained in the second embodiment, the amount of movement of the electric charge is increased at positions nearer to the left end portion, and the amount of heat generation is increased. On this account, when attention is focused on the influence of the heat generation brought about by the respective high electric potential wirings235B1, the temperatures of the ink contained in the manifolds342B1,342B2are raised in the direction directed to the left. On the other hand, when attention is focused on the influence of the heat generation brought about by the pressure generator140, as having been already explained in the second embodiment, the temperature of the ink contained in the manifold342B1is raised in the direction directed to the left, while the temperature of the ink contained in the manifold342B2is raised in the direction directed to the right. In other words, the temperature gradient, which is caused by the heat generation of the respective high electric potential wirings235B1, is raised in the direction directed from the right to the left. On the contrary, the temperature gradient, which is caused by the heat generation of the pressure generator140, is raised in the direction directed from the right to the left in relation to the manifold342B1, and the temperature gradient is raised in the direction directed from the left to the right in relation to the manifold342B2. As a result, the temperature gradients are offset in the manifold342B2, and the temperature of the ink contained in the manifold342B2tends to be constant in the left-right direction. On the other hand, the temperature gradients are superimposed in the manifold342B1, and the temperature of the ink contained in the manifold342B1is raised in the direction directed to the left.

In other words, the temperature gradient of the ink contained in the manifold342A2is opposite to the temperature gradient of the ink contained in the manifold342B1. The manifold342A2and the manifold342B1are adjacent to one another in the front-rear direction. Further, the temperature tends to be constant in the left-right direction in relation to the ink contained in the manifold342A1and the ink contained in the manifold342B2. On this account, it is possible to suppress the uneven density on an image printed by the ink-jet head311of the fourth modification.

Further, also in the fourth modification, the ink discharge ports341C,341G,341H,341D are provided. Therefore, it is possible to raise the flow rate of the ink in the manifolds342A1,342A2,342B1,342B2. Further, even if the ejection amount per unit time from the nozzle27is increased, and the flow rate of the ink is lowered in the manifold342A1,342A2,342B1,342B2, then the temperature gradient is hardly generated in the entire ink-jet head311. On this account, the difference is decreased in relation to the size of the ink droplet ejected from the nozzle27in the ink-jet head311.

According to the fact as described above, even in the case of the construction of the fourth modification, it is possible to obtain the effect which is the same as or equivalent to that of the second embodiment.

In the case of the actuator member30of the first embodiment, the respective individual electrodes34are positioned on the upper surface of the piezoelectric layer32. In addition, each of the individual electrodes34is composed of the main portion34aand the protruding portion34b, and the contact with the FPC is positioned at the protruding portion34b. However, there is no limitation thereto. For example, as depicted inFIG.14, individual wirings34b′ may extend from front ends or rear ends of respective individual electrodes34a′, and contacts34c′ with the FPC may be positioned at end portions of the individual wirings34b′ positioned on the side opposite to the individual electrodes34a′. Specifically, the respective individual electrodes34a′ and the respective individual wirings34b′ are positioned on the upper surface of the piezoelectric layer32. The individual wiring34b′, which extends from each of the individual electrodes34a′ positioned on the front side, is composed of a lead portion34b1which is drawn frontwardly from the front end of the individual electrode34a′, and an extending portion34b2which extends leftwardly from the front end of the lead portion34b1. Then, the contact34c′ with the FPC is positioned at the left end portion of the extending portion34b2. On the other hand, the individual wiring34b′, which extends from each of the individual electrodes34a′ positioned on the rear side, is composed of a lead portion34b1which is drawn rearwardly from the rear end of the individual electrode34a′, and an extending portion34b2which extends rightwardly from the rear end of the lead portion34b1. Then, the contact34c′ with the FPC is positioned at the right end portion of the extending portion34b2.

In this modification, the six individual wirings34b′, which extend from the six individual electrodes34a′ positioned on the front side respectively, exemplify the first conductive part. The six individual wirings34b′, which extend from the six individual electrodes34a′ positioned on the rear side respectively, exemplify the second conductive part.

According to the construction of this modification, the ink supply port41A is positioned on the right side with respect to the six individual flow passages43A. The ink, which flows into the manifold42A from the ink supply port41A, flows through the manifold42A in the direction directed from the right to the left. On this account, the ink contained in the manifold42A is affected by the heat generation caused by the piezoelectric element as the ink advances leftwardly, and the temperature is raised. Further, the six individual wirings34b′ are concentrated in the area positioned leftwardly from the six individual electrodes34a′ positioned on the front side on the piezoelectric layer32. On this account, the amount of heat generation is increased in the area. As a result, the temperature of the ink contained in the manifold42A positioned on the front side is more raised as the ink advances leftwardly on account of the influence of the heat generation caused by the six individual wirings34b′.

On the other hand, the ink supply port41B is positioned on the left side with respect to the six individual flow passages43B. The ink, which flows into the manifold42B from the ink supply port41B, flows through the manifold42B in the direction directed from the left to the right. On this account, the ink contained in the manifold42B is affected by the heat generation caused by the piezoelectric element as the ink advances rightwardly, and the temperature is raised. Further, the six individual wirings34b′ are concentrated in the area positioned rightwardly from the six individual electrodes34a′ positioned on the rear side on the piezoelectric layer32. On this account, the amount of heat generation is increased in the area. As a result, the temperature of the ink contained in the manifold42B positioned on the rear side is more raised as the ink advances rightwardly on account of the influence of the heat generation caused by the six individual wirings34b′.

In other words, the temperature gradient in the left-right direction of the ink contained in the manifold42A is opposite to the temperature gradient in the left-right direction of the ink contained in the manifold42B. As a result, it is possible to obtain the effect which is the same as or equivalent to that obtained in the first embodiment.

Further, in the first embodiment and the second embodiment as well as in the modifications thereof, the actuator member30has the plurality of piezoelectric elements. However, there is no limitation thereto. For example, as depicted inFIG.15, twelve heaters Ht may be positioned on the upper surface of the ink sealing film21. The twelve heaters Ht are positioned in a zigzag form in the left-right direction so that the twelve heaters Ht are opposed to the twelve pressure chambers45in the up-down direction respectively. Further, twelve individual wirings It and two common wirings Ct are positioned on the upper surface of the ink sealing film21. The twelve individual wirings It are connected to the twelve heaters Ht respectively. On the other hand, one common wiring Ct is commonly connected to the six heaters Ht positioned on the front side, and the other common wiring Ct is commonly connected to the six heaters Ht positioned on the rear side.

The individual wiring It, which is connected to each of the heaters Ht positioned on the front side, is composed of a lead portion It1which is drawn frontwardly from the front end of the heater Ht, and an extending portion It2which extends leftwardly from the front end of the lead portion It1. Then, the left end of the extending portion It2is electrically connected to the FPC. In relation thereto, the common wiring Ct, which extends in the left-right direction, is connected to the rear ends of all of the heaters Ht positioned on the front side via lead portions extending rearwardly. The left end of the common wiring Ct is electrically connected to the FPC. On the other hand, the individual wiring It, which is connected to each of the heaters Ht positioned on the rear side, is composed of a lead portion It1which is drawn rearwardly from the rear end of the heater Ht, and an extending portion It2which extends rightwardly from the rear end of the lead portion It1. Then, the right end of the extending portion It2is electrically connected to the FPC. In relation thereto, the common wiring Ct, which extends in the left-right direction, is connected to the front ends of all of the heaters Ht positioned on the rear side via lead portions extending frontwardly. The right end of the common wiring Ct is electrically connected to the FPC.

Then, the respective heaters Ht are connected to a heater power source via the common wiring Ct, and the respective heaters Ht are connected to a driving circuit of the FPC via the individual wirings It. The driving signal is applied from the driving circuit via the individual wiring It, and thus the heater Ht, which is connected to the individual wiring It, generates the heat. Accordingly, the ink, which is contained in the pressure chamber45opposed to the heater Ht subjected to the heat generation, is heated, and bubbles are formed. Then, in accordance with the pressure thereof, the ink droplets are ejected from the nozzle27communicated with the pressure chamber45.

According to the construction of this modification, the ink supply port41A is positioned on the right side with respect to the six heaters Ht positioned on the front side. The ink, which flows into the manifold42A from the ink supply port41A, flows in the direction directed from the right to the left through the manifold42A. On this account, the ink contained in the manifold42A is affected by the heat generation caused by the heater Ht as the ink advances to the left, and the temperature is raised. Further, the six individual wirings It, which are connected to the six heaters Ht positioned on the front side, are concentrated in the area positioned leftwardly with respect to the six heaters Ht positioned on the front side on the upper surface of the ink sealing film21. Further, the left end portion of the common wiring Ct commonly connected to the six heaters Ht positioned on the front side are also positioned in the area positioned leftwardly from the six heaters Ht positioned on the front side. On this account, the amount of heat generation is increased in the area. As a result, as for the ink contained in the manifold42A positioned on the front side, the temperature is more raised as the ink advances leftwardly on account of the influence of the heat generation caused by the common wiring Ct and the six individual wirings It.

On the other hand, the ink supply port41B is positioned on the left side with respect to the six heaters Ht. The ink, which flows into the manifold42B from the ink supply port41B, flows in the direction directed from the left to the right through the manifold42B. On this account, the ink contained in the manifold42B is affected by the heat generation caused by the heater Ht as the ink advances to the right, and the temperature is raised. Further, the six individual wirings It, which are connected to the six heaters Ht positioned on the rear side, are concentrated in the area positioned rightwardly with respect to the six heaters Ht positioned on the rear side on the upper surface of the ink sealing film21. Further, the right end portion of the common wiring Ct commonly connected to the six heaters Ht positioned on the rear side are also positioned in the area positioned rightwardly from the six heaters Ht positioned on the rear side. On this account, the amount of heat generation is increased in the area. As a result, as for the ink contained in the manifold42B positioned on the rear side, the temperature is more raised as the ink advances rightwardly on account of the influence of the heat generation caused by the common wiring Ct and the plurality of individual wirings It.

In other words, the temperature gradient in the left-right direction of the ink contained in the manifold42A is opposite to the temperature gradient in the left-right direction of the ink contained in the manifold42B. As a result, it is possible to obtain the effect which is the same as or equivalent to that of the first embodiment.

The embodiments and the modifications of the present teaching have been explained above. However, the present teaching is not limited thereto, for which it is possible to variously change the design within a scope defined in claims.

In the embodiments and the modifications described above, the printer1performs the printing on the medium M in accordance with the so-called line head system in which the ink is ejected from the line head10which is long in the widthwise direction and which is fixed with respect to the printer1. However, the printer1may perform the printing on the medium M in accordance with the so-called the serial head system in which the ink-jet head11is moved in the sheet widthwise direction by means of a carriage.

In the embodiments and the modifications described above, the exemplary cases have been explained, in which the present teaching is applied to the ink-jet head for ejecting the ink from the nozzle. However, there is no limitation thereto. The present teaching can be also applied to any liquid ejecting apparatus other than the ink-jet head for ejecting any liquid other than the ink from the nozzle.