Patent Publication Number: US-7712885-B2

Title: Liquid-droplet jetting apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application No. 2005-316895 filed on Oct. 31, 2005, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid-droplet jetting apparatus which jets a liquid droplet from a jetting port. 
     2. Description of the Related Art 
     In an ink-jet head (liquid-droplet jetting apparatus) which jets an ink from jetting ports of nozzles by applying pressure to the ink in pressure chambers, when pressure is applied to the ink in a certain pressure chamber among the pressure chambers, pressure wave is generated in the pressure chamber, and the generated pressure wave is propagated to a common liquid chamber communicating with the pressure chambers. This pressure wave is attenuated in the common liquid chamber to prevent the pressure wave from propagating further to another pressure chamber, thereby suppressing the variation in ink-jetting characteristics such as change in droplet speed. For example, an ink-jet type recording head (ink-jet head) described in Japanese Patent Application Laid-open No. 2003-127354, a plurality of pressure generating chambers (pressure chambers) communicating with nozzles respectively are communicated with an ink storage chamber (common liquid chamber) via ink supply channels, respectively; and a recess is formed in a head case at an area corresponding to the ink storage chamber. Further, a metallic vibration plate has an area overlapping with the area of the head case at which the recess is formed, and this area of the vibration plate functions as a damper which releases the pressure variation (damps or attenuates the pressure wave) in the ink storage chamber. 
     However, with respect to the ink-jet head described in Japanese Patent Application Laid-open No. 2003-127354, when an attempt is made to realize the high densification and miniaturization of the ink-jet head, it is necessary to decrease the size of the common liquid chamber, and if the common liquid chamber is decreased in size, there is a fear that the pressure wave is not sufficiently attenuated in the common liquid chamber. In such a case, it is conceivable to form a member, such as the vibration plate which functions as the damper, of a material with a low elasticity such as polyimide. This, however, in turn causes a problem such that, when this member is heated together with another member made of metal and joined to the another member, warpage deformation occurs due to the difference in linear expansion coefficient between the members. 
     An ink-jet head described in Japanese Patent Application Laid-open No. 11-309877 is provided with two reservoirs which supply an ink to pressure generating chambers communicating with nozzles, respectively, such that the reservoirs are overlapped in an up and down direction. The two reservoirs are partitioned by a partition plate which is provided with a pressure-absorbing section for absorbing a pressure wave generated when the ink droplets are discharged and directed in a direction opposite to openings of the nozzles. The partition wall is formed by joining a thin plate and a sealing plate which has a recess formed therein, and the pressure wave is absorbed by the thin plate and a thin wall defining the recess. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a liquid-droplet jetting apparatus which is capable of effectively attenuating the pressure wave in the common liquid chamber. 
     According to a first aspect of the present invention, there is provided a liquid-droplet jetting apparatus which has a body and which jets liquid droplets of a liquid, including: a plurality of first pressure chambers; a first pressure-chamber row in which the first pressure chambers are arranged in a first direction; a plurality of second pressure chambers; a second pressure-chamber row in which the second pressure chambers are arranged in the first direction; a first common liquid chamber which extends in the first direction and which communicates with each of the first pressure chambers; a second common liquid chambers which extends in the first direction and which communicates with each of the second pressure chambers; and a damper which extends in the first direction and which is located between the first and second common liquid chambers in a thickness direction of the body; wherein the first common liquid chamber has a width in a second direction, which is orthogonal to the first direction, so as to overlap with the second common liquid chamber in the thickness direction; the damper has a width in the second direction so as to overlap with each of the first and second common liquid chambers in the thickness direction; and each of the first common liquid chamber, the second common liquid chamber and the damper has the width in the second direction so as to overlap in the thickness direction with the first pressure-chamber row and the second pressure-chamber row. 
     The capacity of the damper to attenuate or damp the pressure wave greatly depends on a planar area of the damper. When a damper extends in a certain direction, as a width thereof in a short direction (length in the second direction) of the damper is greater, the attenuating capacity becomes greater than in a case in which the area is same but the width in the short direction is smaller. According to the liquid-droplet jetting apparatus of the present invention, the second common liquid chamber is formed such that the second common liquid chamber overlaps at least partially with the first common liquid chamber in the thickness direction of the body, it is possible to increase a length, of each of the first and second common liquid chambers, in the second direction. Therefore, it is possible to increase also the length, in the second direction, of the damper formed in the portion at which the first and second common liquid chambers are overlapped. Further, each of the first and second common liquid chambers and the damper is formed so as to partially overlap with the first and second pressure chambers. Accordingly, it is possible to secure a sufficiently great width for the first and second common liquid chamber and the damper, and to substantially increase acoustic capacitance in the first and second common liquid chambers, thereby making it possible to efficiently attenuate the pressure wave in the first and second common liquid chambers. 
     In the liquid-droplet jetting apparatus of the present invention, the damper may include: a first thin-walled portion which forms a wall surface of the first common liquid chamber; a first damper chamber in which a part of a wall surface thereof is defined by the first thin-walled portion and which has rigidity lower than that of the first thin-walled portion; a second thin-walled portion which forms a wall surface of the second common liquid chamber; and a second damper chamber in which a part of a wall surface thereof is defined by the second thin-walled portion and which has rigidity lower than that of the second thin-walled portion. According to this construction, it is possible to increase the length, of each of the first and second thin-walled portions and the first and second damper chambers, in the second direction. Accordingly, it is possible to substantially increase acoustic capacitance in the first and second common liquid chambers, thereby making it possible to efficiently attenuate the pressure wave in the first and second common liquid chambers. 
     In the liquid-droplet jetting apparatus of the present invention, the first thin-wall portion may define the wall surface, of the first common chamber, which faces the second common liquid chamber; the second thin-wall portion may define the wall surface, of the second common chamber, which faces the first common liquid chamber; and the first damper chamber and the second damper chamber may be integrated to form an integrated damper chamber. In this case, by forming the first thin-walled portion and the second thin-walled portion between the first common liquid chamber and the second common liquid chamber, it is possible to form an integrated chamber in which the first and second damper chambers are integrated. Therefore, it is possible to decrease the number of parts than in a case where the first and second damper chambers are formed separately. 
     In the liquid-droplet jetting apparatus of the present invention, the first thin-walled portion may be a thinned portion, in a first flat plate, defined by a first recess which is formed on a surface, of the first flat plate, opposite to the first common liquid chamber; and the second thin-walled portion may be a thinned portion, in a second flat plate, defined by a second recess which is formed on a surface, of the second flat plate, opposite to the second common liquid chamber. In this case, by forming the first recess in the first flat plate, the first thin walled portion is formed and the first recess becomes the first damper chamber. Therefore, it is possible to form the first thin-walled portion and the first damper chamber with one member. Further, by forming the second recess in the second flat plate, the second thin-walled portion is formed and the second recess becomes the second damper chamber. Therefore, it is possible to form the second thin-walled portion and the second damper chamber with one member. This makes it possible to decrease the number of parts. 
     In the liquid-droplet jetting apparatus of the present invention, a spacer may be intervened between the first thin-walled portion and the second thin-walled portion; and a thickness of the spacer may be same as a thickness of the integrated damper chamber. In this case, it is possible to easily form the integrated damper chamber by providing a spacer between the first and second thin-walled portions. 
     In the liquid-droplet jetting apparatus of the present invention, the first and second damper chambers may communicate with outside air. In this case, it is possible to prevent the damage of the liquid-droplet jetting apparatus which would be otherwise caused by the thermal expansion of air in the first and second damper chambers due to heating during the production process. 
     In the liquid-droplet jetting apparatus of the present invention, a plurality of first jetting ports communicating with the first pressure chambers respectively and a plurality of second jetting ports communicating with the second pressure chambers respectively may be formed in a side surface of the body. According to this construction, since the jetting ports are formed in a same plane, the liquid-droplet jetting characteristics hardly vary among the plurality of jetting ports. 
     In the liquid-droplet jetting apparatus of the present invention, each of the first pressure chambers and each of the second pressure chambers may be formed along a side surface of the body. According to this construction, the plurality of the pressure chambers is formed along a same plane. Therefore, it is possible to arrange an energy applying mechanism, which forms a wall of each of the pressure chambers, on a same plane, thereby making it possible to reduce the number of parts. 
     The liquid-droplet jetting apparatus of the present invention may further include an energy applying mechanism which applies jetting energy to each of the first pressure chambers and to each of the second pressure chambers; wherein the energy applying mechanism may include a piezoelectric layer which faces each of the first pressure chambers and each of the second pressure chambers, and a pair of electrodes which applies electric field to the piezoelectric layer. In this case, it is possible to apply the jetting energy to the liquid in the pressure chambers with a simple construction including the piezoelectric layer and the pair of electrodes. 
     In the liquid-droplet jetting apparatus of the present invention, the first common liquid chamber may be formed as a plurality of first common liquid chambers arranged in the second direction; the first thin-walled portion may be formed as a plurality of first thin-walled portions each of which forms a wall surface of one of the first common liquid chambers, and the first damper chamber may be formed as a plurality of first damper chambers in each of which a portion of a wall surface thereof is defined by one of the first thin-walled portions; the second common liquid chamber may be formed as a plurality of second common liquid chambers arranged in the second direction; and the second thin-walled portion may be formed as a plurality of second thin-walled portions each of which forms a wall surface of one of the second common liquid chambers, and the second damper chamber may be formed as a plurality of second damper chambers in each of which a portion of a wall surface thereof is defined by one of the second thin-walled portions. According to this construction, since the first common liquid chambers are formed at positions which are same in the thickness direction of the body, the rigidity is made to be uniform (uniformized) at portions around the first common liquid chambers, respectively. Therefore, the liquid-droplet jetting characteristics are made to be uniform among the jetting ports communicating with the first common liquid chambers, respectively. In a similar manner, since the second common liquid chambers are formed at positions which are same in the thickness direction of the body, the rigidity is made to be uniform at portions around the second common liquid chambers, respectively. Therefore, the liquid-droplet jetting characteristics are made to be uniform among the jetting ports communicating with the second common liquid chambers, respectively. 
     In the liquid-droplet jetting apparatus of the present invention, the liquid may include liquids of different kinds, and the liquids of different kinds may be supplied to the first common liquid chambers and the second common liquid chambers, respectively. In this case also, since the liquid-droplet jetting characteristics are made to be uniform among the jetting ports, respectively, which are communicated with each of the common liquid chambers, it is possible to uniformize the jetting characteristics of the jetting ports for the same liquid. 
     The liquid-droplet jetting apparatus of the present invention may further include: a first dummy common liquid chamber which is adjacent to the first common liquid chambers in the second direction and which extends in the first direction; a second dummy common liquid chamber which is adjacent to the second common liquid chambers in the second direction and which extends in the first direction; a first dummy thin-walled portion which defines a wall surface of the first dummy common liquid chamber; a first dummy damper chamber in which a part of a wall surface thereof is defined by the first dummy thin-walled portion and which has rigidity lower than that of the first dummy thin-walled portion; a second dummy thin-walled portion which defines a wall surface of the second dummy common liquid chamber; and a second dummy damper chamber in which a part of a wall surface thereof is defined by the second dummy thin-walled portion and which has rigidity lower than that of the second dummy thin-walled portion; wherein: one of the second common liquid chambers may have a width in the second direction so as to overlap at least partially with the first dummy common liquid chamber in the thickness direction; and one of the first common liquid chambers may have a width in the second direction so as to overlap at least partially with the second dummy common liquid chamber in the thickness direction. According to this construction, the first dummy common liquid chamber, the first dummy thin-walled portion, and the first dummy damper chamber are formed so as to overlap with one second liquid common chamber, which is among the second common liquid chambers and which overlaps, in the thickness direction, with none of the first common liquid chambers, thereby making it possible to make rigidity at a portion around this second common liquid chamber to be close to the rigidity at a portion around each of the remaining second common liquid chambers overlapping with the first common liquid chambers, respectively. Therefore, the rigidity is made to be uniform at portions around the second common liquid chambers, and thus the jetting characteristics are made uniform among the jetting ports communicating with the second common liquid chambers, respectively. Similarly, the second dummy common liquid chamber, the second dummy thin-walled portion, and the second dummy damper chamber are formed so as to overlap with one first liquid common chamber, which is among the first common liquid chambers and which overlaps in the thickness direction with none of the second common liquid chambers, thereby making it possible to make rigidity at a portion around this first common liquid chamber to be close to the rigidity at a portion around each of the remaining first common liquid chambers overlapping with the second common liquid chambers, respectively. Therefore, the rigidity is made to be uniform at portions around the first common liquid chambers, respectively, and thus the jetting characteristics are made uniform among the jetting ports communicating with the first common liquid chambers, respectively. 
     In the liquid-droplet jetting apparatus of the present invention, each of the first and second common liquid chambers and each of the first and second dummy common liquid chambers may have a constant-width area in which a length in the second direction is constant, and a narrowing area which is continued to the constant-width area and in which a length in the second direction is reduced toward an end in the first direction thereof. In this case, the length, of each of the first and second common liquid chambers, in the second direction is shortened (narrowed) toward an end portion in the first direction of the narrowing area. Therefore, the flow of the liquid easily occurs in this end portion, thereby making it possible to supply the liquid assuredly also to jetting ports, among the jetting ports, communicating with one of the first and second common liquid chambers at the end portion in the first direction thereof. 
     The liquid-droplet jetting apparatus may further include: a plurality of third dummy common liquid chambers each of which is adjacent, in the first direction, to the narrowing area of one of the first common liquid chambers; a plurality of fourth dummy common liquid chambers each of which is adjacent, in the first direction, to the narrowing area of one of the second common liquid chambers; wherein: a sum of a length, of each of the third dummy common liquid chambers, in the second direction and a length, of the narrowing area of each of the first common liquid chambers, in the second direction, may be substantially same as the length in the second direction of the constant-width area of each of the first common liquid chambers; and a sum of a length, of each of the fourth dummy common liquid chambers, in the second direction and a length, of the narrowing area of each of the second common liquid chambers, in the second direction, may be substantially same as the length in the second direction of the constant-width area of each of the second common liquid chambers. In this case, since the third dummy common liquid chamber is formed, it is possible to make a pressure chamber, which is included in the pressure chambers communicating with the first common liquid chambers respectively and which is located in the vicinity of the narrowing area, to have a rigidity close to that of another pressure chamber located in the vicinity of the constant-width area, thereby making the liquid-droplet jetting characteristics to be uniform among the jetting ports communicating with the first liquid common chambers, respectively. In addition, since the fourth dummy common liquid chamber is formed, it is possible to make a pressure chamber, which is included in the pressure chambers communicating with the second common liquid chambers respectively and which is located in the vicinity of the narrowing area, to have a rigidity close to that of another pressure chamber located in the vicinity of the constant-width area, thereby making the liquid-droplet jetting characteristics to be uniform among the jetting ports communicating with the second liquid common chambers, respectively. 
     According to a second aspect of the present invention, there is provided a liquid-droplet jetting apparatus which has a body and which jets liquid droplets of a liquid, the apparatus including: a plurality of first pressure chambers; a first pressure-chamber row in which the first pressure chambers are arranged in a first direction; a plurality of second pressure chambers; a second pressure-chamber row in which the second pressure chambers are arranged in the first direction; a first common liquid chamber which extends in the first direction and which communicates with each of the first pressure chambers; a second common liquid chambers which extends in the first direction and which communicates with each of the second pressure chambers; and a damper which extends in the first direction and which is located between the first and second common liquid chambers in a thickness direction of the body; wherein each of the first pressure chambers and each of the second pressure chambers extends in a second direction orthogonal to the first direction; the first common liquid chamber has a width in the second direction so as to overlap with the second common liquid chamber in the thickness direction; the damper has a width in the second direction so as to overlap with each of the first and second common liquid chambers in the thickness direction; and each of the first common liquid chamber, the second common liquid chamber and the damper has the width in the second direction which is greater than a length, of one of the first pressure chambers, in the second direction and which is greater than a length, of one of the second pressure chambers, in the second direction. 
     According to the liquid-droplet jetting apparatus of the present invention, the second common liquid chamber is formed such that the second common liquid chamber overlaps at least partially with the first common liquid chamber in the thickness direction of the body, it is possible to increase a length, of each of the first and second common liquid chambers, in the second direction. Accordingly, it is also possible to increase the length, in the second direction, of the damper formed in a portion at which the first and second common liquid chambers are overlapped. Further, each of the first common liquid chamber, the second common liquid chamber and the damper has the width which is greater than a length of one of the first pressure chambers and is greater than a length of one of the second pressure chambers. Accordingly, it is possible to secure a sufficiently great width for the first and second common liquid chamber and the damper, and to substantially increase acoustic capacitance in the first and second common liquid chambers, thereby making it possible to efficiently attenuate the pressure wave in the first and second common liquid chambers. 
     In the liquid-droplet jetting apparatus of the present invention, the width in the second direction of each of the first common liquid chamber, the second common liquid chamber and the damper may be substantially same as a sum of the length in the second direction of one of the first pressure chambers and the length in the second direction of one of the second pressure chambers; and the damper may have the width in the second direction so that the damper overlaps in the thickness direction substantially entirely with a portion in which the first and second common liquid chambers are overlapped in the thickness direction. In this case, it is possible to secure a sufficiently great width for each of the first and second common liquid chambers and the damper, and to substantially increase acoustic capacitance in the first and second common liquid chambers, thereby making it possible to efficiently attenuate the pressure wave in the first and second common liquid chambers. 
     In the liquid-droplet jetting apparatus of the present invention, the damper may communicate with outside air via an air hole. In this case, it is possible to prevent the damage of the liquid-droplet jetting apparatus which would be otherwise caused by the thermal expansion of air in the damper due to heating during the production process. 
     In the liquid-droplet jetting apparatus of the present invention, the first common liquid chamber may be formed as a plurality of first common liquid chambers arranged in the second direction; the second common liquid chamber may be formed as a plurality of second common liquid chambers arranged in the second direction; the damper may be formed as a plurality of dampers which extend in the first direction and each of which is located, in the thickness direction of the body, between one of the first common liquid chambers and one of the second common liquid chambers. According to this construction, since the first common liquid chambers are formed at a same position in the thickness direction of the body, the rigidity is made to be uniform at portions around the first common liquid chambers, respectively. Therefore, the liquid-droplet jetting characteristics are made to be uniform among the jetting ports communicating with the first common liquid chambers, respectively. In a same manner, since the second common liquid chambers are formed at a same position in the thickness direction of the body, the rigidity is made to be uniform at portions around the second common liquid chambers, respectively. Therefore, the liquid-droplet jetting characteristics are made to be uniform among the jetting ports communicating with the second common liquid chambers, respectively. 
     In the liquid-droplet jetting apparatus of the present invention, the dampers may communicate with outside air via an air hole. In this case, it is possible to prevent the damage of the liquid-droplet jetting apparatus which would be otherwise caused by the thermal expansion of air in the dampers due to heating during the production process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view showing an ink-jet printer according to an embodiment of the present invention; 
         FIG. 2  is a plan view of the ink-jet head in  FIG. 1 ; 
         FIG. 3  is a sectional view taken along a line III-III in  FIG. 2 ; 
         FIGS. 4A to 4C  are each a partially enlarged view of the ink-jet head in  FIG. 3 , wherein  FIG. 4A  is an enlarged view of the central portion of the ink-jet head,  FIG. 4B  is an enlarged view of the left end portion of the ink-jet head, and  FIG. 4C  is an enlarged view of the right end portion of the ink-jet head; 
         FIGS. 5A and 5D  are plan views showing two manifold plates in  FIG. 3 , respectively, and  FIGS. 5B and 5C  are plan views showing two damper plates in  FIG. 3 , respectively; 
         FIG. 6  is a sectional view of a first modification, corresponding to  FIG. 4A ; 
         FIGS. 7A to 7D  are sectional views of a second modification, corresponding to  FIGS. 5A to 5D ; and 
         FIGS. 8A to 8C  are plan views in which  FIG. 8A  shows a state in which the first common liquid chambers are projected in the thickness directions of the body,  FIG. 8B  shows a state in which the second common liquid chambers are projected in the thickness directions of the body, and  FIG. 8C  shows a state in which the integrated damper chambers are projected in the thickness directions of the body. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be explained as follows with respect to a preferred embodiment thereof, with reference to the drawings. This embodiment is an example in which the present invention is applied to an ink-jet head which jets an ink from nozzles. 
       FIG. 1  is a schematic perspective view of an ink-jet printer  1  according to the embodiment of the present invention. As shown in  FIG. 1 , the ink-jet printer  1  includes a carriage  2  which is movable in a scanning direction (left and right direction in  FIG. 1 : second direction); the ink-jet head (liquid-droplet jetting apparatus)  3  of serial type which is constructed to be movable together with the carriage  2  and which jets ink onto a recording paper P; transporting rollers  4  which feed or transport the recording paper P in a paper feeding direction (forward direction in  FIG. 1 : first direction); and the like. The ink-jet head  3  is constructed to move integrally with the carriage  2  in the scanning direction and to perform printing by jetting ink, onto the recording paper P, from jetting ports of nozzles  16  (see  FIG. 3 ) formed on the lower surface of the ink-jet head  3 . The recording paper P, for which printing has been performed thereon by the ink-jet head  3 , is discharged in the paper feeding direction by the transporting rollers  4 . 
     Next, the ink-jet head  3  will be explained with reference to  FIGS. 2 to 5 .  FIG. 2  is a plan view of the ink-jet head  3  in  FIG. 1 ;  FIG. 3  is a sectional view taken along line III-III in  FIG. 2 ;  FIGS. 4A to 4C  are each a partially enlarged view of the ink-jet head in  FIG. 3 , wherein  FIG. 4A  is an enlarged view of the central portion of the ink-jet head in  FIG. 3 ,  FIG. 4B  is an enlarged view of the left end portion of the ink-jet head in  FIG. 3 , and  FIG. 4C  is an enlarged view of the right end portion of the ink-jet head in  FIG. 3 ; and  FIGS. 5A to 5D  are plan views showing a manifold plate  25 , a damper plate  26 , a damper plate  27  and a manifold plate  28 , which construct the ink-jet head  3 , respectively. 
     As shown in  FIGS. 2 to 4C , the ink-jet head  3  includes a channel unit  5  in which a plurality of individual ink channels are formed, the individual ink channels being from manifold channels  11  or  12  and reaching to nozzles  16  via pressure chambers  10 , respectively; and a piezoelectric actuator (energy applying mechanism)  6  which is arranged on the upper surface of the channel unit  5  to apply pressure to the ink in the pressure chambers  10 . 
     The channel unit  5  includes a cavity plate  21 , a base plate  22 , an aperture plate  23 , a supply plate  24 , a manifold plate  25 , a manifold plate  28 , a damper plate (first flat plate)  26 , a damper plate (second flat plate)  27 , a cover plate  29  and a nozzle plate  30 ; and these ten plates  21  to  30  are joined and stacked as laminated layers. Among these ten plates, the nine plates  21  to  29 , except for the nozzle plate  30 , are formed of a metallic material such as stainless steel. In the plates  21  to  29 , the ink channels such as pressure chambers  10 , manifold channels  11  and  12 , and the like are formed by a method like etching. The nozzle plate  30  is formed of a synthetic resin material such as polyimide, and is bonded to the lower surface of the cover plate  29 . As shown in  FIG. 2 , in the nozzle plate  30 , a plurality of nozzles  16  which correspond to the pressure chambers  10  one by one, are formed in eight rows in a paper feeding direction (up and down direction in  FIG. 2 ), by a laser processing (to be described later on). Alternatively, this nozzle plate  30  may be formed also of a metallic material similar to the nine plates  21  to  29 . In this case, it is thus possible to prevent any warpage of the channel unit  5  which would be otherwise caused due to difference in linear expansion coefficient among the plates, and to prevent any deviation in positioning between the channels formed in the plates  21  to  29  and the nozzles  16 . 
     As shown in  FIGS. 2 to 4C , in the cavity plate  21 , a plurality of pressure chambers  10  are formed and aligned in eight rows in the paper feeding direction (up and down direction in  FIG. 2 : first direction). Each of the pressure chambers  10  is formed to have a substantially rectangular shape which is long in the scanning direction (left and right direction in  FIG. 2 : second direction). More specifically, the pressure chambers (first pressure chambers)  10  communicating with a manifold channel  11  (first common liquid chamber, to be explained later) and extending in the second direction form a plurality of first pressure-chamber rows aligned in the first direction; and the pressure chambers (second pressure chambers)  10 , communicating with a manifold channel (second common liquid chamber, to be explained later)  12  and extending in the second direction adjacently to the longitudinal direction of the pressure chambers (first pressure chambers)  10 , form a plurality of second pressure-chamber rows aligned in the first direction. The first and second pressure-chamber rows are arranged in the second direction. In the embodiment, eight pressure-chamber rows are formed. 
     A plurality of communication holes  14  are formed in the base plate  22  at positions each overlapping in a plane view with a portion in the vicinity of one end portion in the longitudinal direction of one of the pressure chambers  10 . The communication holes  14  communicate the pressure chambers  10  and apertures  13  (to be described later), respectively. In addition, a plurality of communication holes are formed in the base plate  22  at positions each overlapping in a plane view with a portion in the vicinity of the other end portion in the longitudinal direction of one of the pressure chambers  10 . Each of the communication holes constructs a part of one of the channels  15  communicating the pressure chambers  10  and the nozzles  16 , respectively. 
     A plurality of apertures  13  each of which extends in the longitudinal direction of one of the pressure chambers  10  and which communicate the pressure chambers  10  with the manifold channels  11  or  12 , respectively, are formed in the aperture plate  23 . In addition, a plurality of communication holes each of which constructs a part of one of the channels  15  are formed in the aperture plate  23 . Each of the apertures  13  has a portion in which a sectional channel area thereof is decreased or small between one of the pressure chambers  10  and the manifold channel  11  or  12 , so as to adjust an amount of the ink flowing into the pressure chamber  10  from the manifold  11  or  12 . Each of the apertures  13  prevents the ink from flowing back from one of the pressure chambers  10  to the manifold channel  11  or  12 , thereby suppressing the pressure wave generated in the pressure chamber  10  from propagating to the manifold channel  11  or  12 . 
     A plurality of communication holes each of which constructs a part of the channels  15 , a plurality of communication holes which construct a part of channels  17  communicating the apertures  13  and the manifold channels  12 , respectively, and a plurality of communication hole  18  which communicate the apertures  13  and the manifold channels  11 , respectively, are formed in the supply plate  24 . 
     In the manifold plate  25 , four manifold channels (first common liquid chambers)  11  extending in the paper feeding direction (first direction) and communicating with the pressure chambers (first pressure chambers)  10  are formed to align in the scanning direction (second direction). The ink is supplied from an ink inlet port  9   b  to two manifold channels  11 , among the four manifold channels  11  and disposed on the left side in  FIG. 2 ; and ink is supplied from an ink inlet port  9   d  to two manifold channels  11  disposed on the right side in  FIG. 2 . As shown in  FIG. 5A , each of the manifold channels  11  has a constant-width area  11   a  which extends in an up and down direction in  FIG. 5A  and with a substantially constant width (length in left and right direction in  FIG. 5A ); and a narrowing area  11   b  which continued to the constant-width area  11   a  at an end, of the narrowing area  11   b , opposite to the ink inlet port  9   b  or  9   d  and in which a width thereof is narrowed in a direction away from the ink inlet port  9   b  or  9   d  (toward upper portion in  FIG. 5A ). Namely, when a virtual plane is considered which is parallel to the cavity plate  21  and which includes the manifold plate  25  (manifold channels  11 ), then in this virtual plane, each of the manifold channels  11  is constructed of a constant-width area  11   a  in which a length in a direction orthogonal to the paper feeding direction is substantially constant, and a narrowing area  11   b  which is formed in the manifold channel  11  at an end portion in the downstream in the paper feeding direction to have a shape being narrowed toward the downstream end portion thereof. The constant-width area  11   a  and the narrowing area  11   b  are smoothly connected. Accordingly, the ink flowed from the ink inlet port  9   b  and  9   d  flows assuredly and entirely in the manifold channels  11  respectively. Note that the manifold channels  11  supply the ink to the pressure chambers  10  belonging to the third, fourth, seventh and eighth rows from the left in  FIG. 2 . 
     Further, a dummy manifold channel (first dummy common liquid chamber)  51  is formed in the manifold plate  25  at an area overlapping with a manifold channel (second common liquid chamber)  12  which is included in four manifold channels (second common liquid chambers, to be explained later)  12 , and which is disposed at the leftmost position shown in  FIG. 2 . The dummy manifold channel  51  extends in the up and down direction in  FIG. 5A , has a width same as that of the constant-width area  11   a  in one of the manifold channels  11 , and has an end portion at the upper side in  FIG. 5A  of which shape is substantially same as that of the narrowing area  11   b . Namely, as shown in  FIGS. 8A and 8B , among four areas (second areas)  112  formed by projecting the four manifold channels (the second common liquid chambers)  12  onto a virtual first plane  100  which is parallel to the cavity plate  21 , the leftmost area partially overlaps only with an area  151  formed by projecting the dummy manifold channel  51  to the first plane. In such a manner, in the manifold plate  25 , one dummy manifold channel  51  through which no ink flows, and four manifold channels  11  through which the ink flows are formed as through holes in this order from the left to right in  FIG. 2 . Each of the through holes has an overlapping portion which overlaps, in a direction in which the plates constructing the channel unit  5  are stacked (thickness direction of the body), with a damper portion (damper chamber and thin-walled portion) of the damper plate  26  (which will be described later on). Furthermore, a plurality of communication holes, each of which constructs a part of the channels  15 , and a plurality of communication holes, each of which constructs a part of the channels  17 , are formed in the manifold plate  25 . 
     In the damper plate (first plate)  26 , a plurality of recesses (first damper chambers, first recessed portions)  19  are formed on the lower surface thereof at portions overlapping in a plan view with the manifold channels  11 , respectively; and a recess (first dummy damper chamber, first dummy recessed portion)  49  is formed on the lower surface of the damper plate  26  at a portion overlapping in a plan view with the dummy manifold channel  51 . As shown in  FIGS. 4A and 4C , the portions in the damper plate  26  at which the recesses  19  are formed and consequently with decreased thickness are thin-walled portions (first thin-walled portions)  26   a . Further, as shown in  FIG. 4B , the portion in the damper plate  26  at which the recess  49  is formed and consequently with decreased thickness is a thin-walled portion (first dummy thin-walled portion)  26   b . As shown in  FIG. 5B , the recesses  19  have a substantially same shape and size as those of the manifold channels  11 , respectively, which are located above the recesses  19 ; and the recess  49  has a substantially same shape and size as those of the dummy manifold channel  51  located above the recess  49 . Each of the thin-walled portions  26   a  defines a lower wall surface of one of the manifold channels  11 , and is deformed to thereby attenuate pressure wave in the manifold channel  11 . Further, as shown in  FIG. 5B , an air hole  8  is formed in the damper plate  26 . The air hole  8  communicates the recesses  19  and the recess  49  with one another and is communicated to the outside air at side surfaces of the damper plate  26 . Furthermore, a plurality of communication holes forming a part of the channels  15  and  17 , respectively, are also formed in the damper plate  26 . 
     In the damper plate (second plate)  27 , recesses (second damper chambers, second recessed portions)  20  are formed on the upper surface thereof at portions overlapping in a plan view with the manifold channels  12 , respectively; and a recess (second dummy damper chamber, second dummy recessed portion)  48  is formed on the upper surface of the damper plate  27  at a portion overlapping in a plan view with a dummy manifold channel  52  (to be described later on). As shown in  FIGS. 4A and 4B , the portions in the damper plate  27  at which the recesses  20  are formed and consequently with decreased thickness are thin-walled portions (second thin-walled portions)  27   a . Further, as shown in  FIG. 4C , the portion in the damper plate  27  at which the recess  48  is formed and consequently with decreased thickness is a thin-walled portion (second dummy thin-walled portion)  27   b . As shown in  FIG. 5C , the recesses  20  have a substantially same shape and size as those of the manifold channels  12 , respectively, which are located below the recesses  20 ; and the recess  48  has a substantially same shape and size as those of the dummy manifold channel  52  located below the recess  48 . Each of the thin-walled portions  27   a  defines an upper wall surface of one of the manifold channels  12 , and is deformed to thereby attenuate pressure wave in the manifold channel  12 . Further, a plurality of communication holes forming a part of the channels  15  and  17 , respectively, are also formed in the damper plate  27 . 
     By staking the damper plates  26  and  27  in a laminated form, openings of the recesses formed in each of the damper plates  26  and  27  are closed by one another, thereby integrating the damper portions (damper chambers and the thin-walled portions) formed in the plates, respectively. Spaces are formed between the recesses  19  and  20 , between the recesses  20  and  49 , and between the recesses  19  and  48 ; and these spaces are communicated with one another and with the outside air via the air hole  8 . Here, a plurality of spaces  31  defined by the recesses  19  and  20 , respectively, are a plurality of integrated damper chambers integrating the first and second damper chambers according to the present invention; a space  32  defined by the recesses  49  and  20  is an integrated damper chamber integrating the first dummy damper chamber and the second damper chamber according to the present invention; and a space  33  defined by the recesses  48  and  19  is an integrated damper chamber integrating the second dummy damper chamber and the first damper chamber according to the present invention. Namely, the integrated damper chambers (dampers) extend in the first direction, and are located, in the thickness direction of the body, between the plurality of manifold channels  11  and a plurality of manifold channels  12 , respectively. The manifold channels  12  will be described later on. 
     Four manifold channels (second common liquid chambers)  12  extending in the paper feeding direction (first direction) and communicating with the pressure chambers (second pressure chambers)  10  respectively are formed to be aligned in the scanning direction (second direction) in the manifold plate  28 . Here, three manifold channels  12  from the right, among the four manifold channels  12  in  FIG. 2 , are formed at positions each overlapping with one of three manifolds  11  from the left, among the four manifold channels  11  in  FIG. 2 . Among the four manifold channels  12 , regarding two manifold channels  12  located at the left portion in  FIG. 5D , the ink is supplied thereto from an ink inlet port  9   a ; and regarding two manifold channels  12  located at the right portion in  FIG. 5D , the ink is supplied thereto from an ink inlet port  9   c . Each of the manifold channels  12  has a constant-width area  12   a  which extends in an up and down direction in  FIG. 5D  and with a substantially constant width; and a narrowing area  12   b  which continues to the constant-width area  12   a  formed at an upper end of the narrowing area  12   b  in FIG.  5 D, and in which a width is narrowed in a direction away from the ink inlet port  9   a  or  9   c  (toward upper portion in  FIG. 5D ). Namely, when a virtual plane is considered which is parallel to the cavity plate  21  and which includes the manifold plate  28  (manifold channels  12 ), then in this virtual plane, each of the manifold channels  12  is constructed of a constant-width area  12   a  in which a length in the direction orthogonal to the paper feeding direction is substantially constant, and a narrowing area  12   b  which is formed in the manifold channel  12  at an end portion in the downstream in the paper feeding direction to have a shape being narrowed toward the downstream end portion thereof. The constant-width area  12   a  and the narrowing area  12   b  are smoothly connected. Accordingly, the inks flowed from the ink inlet port  9   a  and  9   c  flows assuredly and entirely in the manifold channels  12 , respectively. Note that the manifold channels  12  supply the ink to the pressure chambers  10  belonging to the first, second, fifth and sixth rows from the left in  FIG. 2 . 
     Further, a dummy manifold channel (second dummy common liquid chamber)  52  is formed in the manifold plate  28  at an area overlapping with a manifold channel (first common liquid chamber)  11  which is included in four manifold channel (first common liquid chambers)  11  and is disposed at the rightmost position in  FIG. 2 . The dummy manifold channel  52  extends in the up and down direction in  FIG. 5D , has a width same as that of the constant-width area  12   a  in one of the manifold channels  12 , and has an end portion at the upper side in  FIG. 5D  of which shape is substantially same as that of the narrowing area  12   b . Namely, as shown in  FIGS. 8A and 8B , among four areas (first areas)  111  formed by projecting the four manifold channels (the first common liquid chambers)  11  onto the first plane  100 , the rightmost area partially overlaps only with an area  152  formed by projecting the dummy manifold channel  52  to the first plane  100 . In such a manner, in the manifold plate  28 , one dummy manifold channel  52  through which no ink flows, and four manifold channels  12  through which the ink flows are formed as through holes in this order from the right to left in  FIG. 2 . Each of the through holes has an overlapping portion which overlaps, in the stacking direction of the plates constructing the channel unit  5 , with a damper portion (damper chamber and thin-walled portion) of the damper plate  26  (described as above). Namely, as shown in  FIGS. 8A to 8C , a plurality of third areas  113  formed by projecting the integrated damper chambers in the stacking direction onto the first plane  100 , respectively, each overlaps at least partially with an area in which one of the first areas  111  formed by projecting the manifold channels (first common liquid chambers)  11  in the stacking direction onto the first plane  100  and one of the second areas  112  formed by projecting the manifold channels (second common liquid chambers)  12  in the stacking direction onto the first plane  100  are overlapped. Furthermore, a plurality of communication holes, each of which constructs a part of the channels  15 , are formed in the manifold plate  28 . 
     Here, since the dummy manifolds  51 ,  52  and the recesses  48 ,  49  are formed, the rigidity of the channel unit  5  in portions at the both left and right ends thereof is made to be similar to that at an inner portion thereof, thereby uniforminizing the jetting characteristics among a plurality of nozzles  16  (to be described later). Namely, as shown in  FIG. 5A , the dummy manifold  51  is located at the leftmost position in a manifold-channel row constructed of the manifold channels  11  and the dummy manifold  51 . Further, as shown in  FIG. 5D , the dummy manifold  52  is located at the rightmost position in a manifold-channel row constructed of the manifold channels  12  and the dummy manifold  52 . As shown in  FIGS. 2 and 4B , the manifold channel  12  which overlaps with the dummy manifold  51  is communicated with pressure chambers  10  belonging to a pressure-chamber row and extending in the cavity plate  21  toward pressure-chambers  10  belonging to another pressure-chamber row adjacent to the pressure-chamber row (extending in the rightward direction in  FIG. 2 ). Further, as shown in  FIGS. 2 and 4C , the manifold channel  11  which overlaps with the dummy manifold  52  is communicated with pressure chambers  10  belonging to a pressure-chamber row and extending in the cavity plate  21  toward pressure-chambers  10  belonging to another pressure-chamber row adjacent to the pressure-chamber row (extending in the leftward direction in  FIG. 2 ). As viewed from a direction in which the plates  21  to  30  are stacked, each of the pressure chambers  10  has an end to which the ink is supplied and which overlaps with the two manifold channels and two damper portions, regardless of the location at which the pressure chamber is arranged. On the other hand, each of the pressure chambers  10  communicates with one of the nozzles  16  at the other end thereof; and the other end of a certain pressure  10  belonging to one of the pressure chamber rows faces the other end of another pressure chamber  10  belonging to another pressure chamber row adjacent to the pressure chamber row to which the certain pressure chamber  10  belongs. In this embodiment, the nozzles  16 , which belong to adjacent nozzle rows respectively, form a staggered or zigzag arrangement as shown in  FIG. 2 . Corresponding to this, in each of the individual ink channels each from one of the two manifold channels commonly having one ink inlet port and reaching to one of the nozzles  16  via one of the pressure chambers  10 , the communication holes each from one of the pressure chambers  10  and reaching to one of the nozzles  16  also form a zigzag arrangement. As described above, the pressure chambers  10  have a similar three-dimensional structure in the channel unit  5 , and thus the portions, in the channel unit  5 , surrounding the pressure chambers  10  respectively are constructed to have a rigidity substantially same among themselves. Here, the term “jetting characteristic of the ink” means the droplet speed of the ink droplet jetted from the nozzles  16 , the volume of the ink droplet jetted from the nozzles  16 , and/or the like. 
     A plurality of communication holes each constructing a part of one of the channels  15  are formed in the cover plate  29 . The plurality of nozzles  16  are formed in the nozzle plate  30  at positions each overlapping in a plan view with one of the channels  15 . In other words, the nozzles  16  are arranged in eight rows in the up and down direction in  FIG. 2 , and the jetting ports of the nozzles  16  are formed in the lower surface of the nozzle plate  30 . When the nozzle plate  30  is formed of a synthetic resin material, the nozzles  16  can be formed by eximer-laser processing or the like. Alternatively, when the nozzle plate  30  is formed of a metallic material, the nozzles  16  can be formed by press processing or the like. In this embodiment, the above-described ink inlet ports  9   a  to  9   d  supply black (K), yellow (Y), cyan (c) and magenta (M) inks, respectively. The black ink is jetted from the nozzles  16  formed in the first and second nozzle rows from the left in  FIG. 2 ; the yellow ink is jetted from the nozzles  16  formed in the third and fourth nozzle rows from the left in  FIG. 2 ; the cyan ink is jetted from the nozzles  16  formed in the fifth and sixth nozzle rows from the left in  FIG. 2 ; and the magenta ink is jetted from the nozzles  16  formed in the seventh and eighth nozzle rows from the left in  FIG. 2 . 
     As described above, each of the manifold channels (second common liquid channels)  12  communicates with the pressure chambers (second pressure chambers)  10  via the channels  17 , the apertures  13  and the communication holes  14 , respectively; and each of the pressure chambers  10  in the manifold channel  12  communicates, via one of the channels  15 , with a jetting port (second jetting port) of one of the nozzles  16  formed in one of the first, second, fifth and sixth nozzle rows from the left in  FIG. 2 . On the other hand, each of the manifold channels (first common liquid chambers)  11  communicates with the pressure chambers (first pressure chambers)  10  via the communication holes  18 , the apertures  13  and the communication holes  14 , respectively; and each of the pressure chambers  10  in the manifold channel  11  communicates via one of the channels  15  with a jetting port (first jetting port) of one of the nozzles  16  formed in one of the third, fourth, seventh and eighth nozzle rows from the left in  FIG. 2 . In such a manner, the channel unit  5  is provided with a plurality of first individual ink channels (first individual liquid channels) which is formed in the channel unit  5  and each of which is from an outlet port (connection port) of one of the manifold channels  11  and arriving at one of the nozzles  16  via one of the pressure chambers  10 ; and a plurality of second individual ink channels (second individual liquid channels) which is formed in the channel unit  5  and each of which is from an outlet port (connection port) of one of the manifold channels  12  and arriving at one of the nozzles  16  via one of the pressure chambers  10 . 
     Here, an explanation will be given about the size in the second direction of and the relative positions in the second direction among the manifold channels (first common liquid chambers)  11 , the manifold channels (second common liquid chambers)  12 , the integrated damper chambers (dampers), two pressure chambers (first and second pressure chambers) mutually adjacent in the second direction, as viewed in the stacking direction. First, the manifold channels  11  and the manifold channels  12  have a positional relationship in the second direction in which each of the first areas  111 , formed by projecting the manifold channels  11  in the stacking direction onto the first plane  100 , partially overlaps with one of the second areas  112  formed by projecting the manifold channels  12  in the stacking direction onto the first plane  100 . In other words, the manifold channels  11  have a width in the second direction so that the manifold channels  11  overlap with the manifold channels  12  in the stacking direction. Further, as shown in  FIGS. 8A to 8C , the manifold channels  11 , the manifold channels  12 , and the integrated damper chambers have a positional relationship in the second direction such that overlapping areas, at which the first areas  111  and the second areas  112  overlap respectively, partially overlap with the third areas  113  formed by projecting the integrated damper chambers in the stacking direction onto the first plane  100 . In other words, the integrated damper chambers have a width in the second direction so that the integrated damper chambers overlap, in the stacking direction, with the manifolds  11  and the manifolds  12 , respectively. More specifically, the third areas  113  have a positional relationship in which the third areas  113  overlap substantially entirely with the overlapping areas in each of which one of the first areas  111  and one of the second areas  112  are overlapped. Furthermore, the first areas  111 , the second areas  112 , the third areas  113  have a positional relationship in which the first areas  111 , the second areas  112 , the third areas  113  overlap with both of areas  114  each formed by projecting one of the first pressure chambers in the stacking direction onto the first plane  100  and areas  115  each formed by projecting one of the second pressure chambers in the stacking direction onto the first plane  100 . Namely, each of the manifold channels  11 , the manifold channels  12  and the integrated damper chambers has a width in the second direction so that each of the manifold channels  11 , the manifold channels  12  and the integrated damper chambers overlaps, in the stacking direction, with the one of the first pressure chamber rows and one of the second pressure chamber rows. Further, each of the manifold channels  11 , manifold channels  12  and dampers has a width greater than the length of the first pressure chamber  10  and greater than the length of the second pressure chamber  11 . Furthermore, each of the manifold channels  11 , the manifold channels  12  and the dampers has the width substantially same as a sum of the length of one of the first pressure chambers and the length of one of the second pressure chambers. 
     A piezoelectric actuator  6  is formed on the upper surface of the channel unit  5 . The piezoelectric actuator  6  has five piezoelectric layers  43  stacked on the upper surface of the channel unit  5 ; and individual electrodes  41  and common electrodes  42  formed alternately between the piezoelectric layers  43 . 
     Among the piezoelectric layers  43 , a piezoelectric layer  43  disposed at the lowermost position is arranged on the upper surface of the cavity plate  21  and is jointed to the upper surface so that the lowermost piezoelectric layer  43  covers the pressure chambers  10 . As shown in  FIG. 2 , in the cavity plate  21 , the four ink inlet ports  9   a  to  9   d  are formed as a row at the lower end of the cavity plate  21 , and the piezoelectric layers  43  are arranged to avoid (not to overlap or interfere with) these ink inlet ports  9   a  to  9   d . The remaining four piezoelectric layers  43  are staked on the lowermost piezoelectric layer  43 . The piezoelectric layers  43  are formed by cutting a piezoelectric sheet (to be described below) into a predetermined size and by arranging the cut piezoelectric sheets on the channel unit  5 . The piezoelectric sheet is obtained by calcinating a green sheet of a piezoelectric material mainly composed of a lead zirconate titanate (PZT) that is a solid solution of lead titanate and lead zirconate and is a ferroelectric substance. The individual electrodes  41  and the common electrodes  42  are formed such that the electrodes  41  and  42  are alternately disposed between the stacked piezoelectric layers  43 , and that the electrodes  41  and  42  are mutually shifted in a plan view in the left and right direction in  FIG. 3  so as not to completely overlap with one another. Further, as shown in  FIGS. 4A to 4C , in each of the four piezoelectric layers  43 , excluding the lowermost piezoelectric layer  43 , a through hole  43   a  is formed at an area which overlaps in a plan view with the individual electrodes  41  and which does not overlap in a plan view with the common electrodes  42 ; and a through hole  43   b  is formed at an area which overlaps in a plan view with the common electrodes  42  and which does not overlap in a plan view with the individual electrodes  41 . Conductive materials  44  and  45  are filled in the through holes  43   a  and  43   b , respectively. 
     A Flexible Printed Circuit (FPC, not shown in the drawings) is arranged on the upper surface of the piezoelectric actuator  6 . The individual electrodes  41  are connected to a driver IC (not shown in the drawings) via the conductive material  44  and the FPC, and the drive IC controls electric potential of the individual electrodes  41 . The common electrodes  42  are connected to the driver IC via the conductive material  45  and the FPC, and are always kept at ground potential by the driver IC. 
     Next, an explanation will be given about a method for driving the piezoelectric actuator  6 . When predetermined voltage is selectively applied from the driver IC to the individual electrodes  41  via the FPC and the conductive material  44 , electric potential of the individual electrodes  41 , to which the voltage is applied is different from that of the common electrodes  42  kept at the ground potential. At this time, since an electric field is generated in a portion of the piezoelectric layer  43  sandwiched between one of the individual electrodes  41  and one of the common electrodes  42 , the piezoelectric layer  43  expands by the vertical piezoelectric effect in a thickness direction thereof in which the piezoelectric layer  43  is polarized. This consequently decreases the volume in pressure chambers  10  corresponding to the individual electrodes  41  applied with the voltage, thereby increasing the pressure of the ink in the pressure chambers  10  so as to jet the ink from nozzles  16  communicating with the pressure chambers  10 . The piezoelectric actuator  6  has the five piezoelectric layers  41 , and when the actuator  6  is driven, the four piezoelectric layers, excluding the lowermost piezoelectric layer, expand respectively in the thickness direction. Therefore, the deformation amount of the piezoelectric actuator  6  as a whole is great, thereby making it possible to apply a substantial pressure to the ink in the pressure chambers  10  by one drive. 
     At this time, a pressure wave is generated in the pressure chamber  10  by the increase in pressure in the pressure chamber  10 . A part of the pressure wave is propagated from the pressure chamber  10  to the manifold channel  11  or  12 . When the pressure wave is propagated to the manifold channel  11 , the thin-walled portion  26   a  of the damper plate  26  is deformed to attenuate the pressure wave. On the other hand, when the pressure wave is propagated to the manifold channel  12 , the thin-walled portion  27   a  of the damper plate  27  is deformed to attenuate the pressure wave. 
     Here, the attenuating effect of pressure wave in the manifold channels  11 ,  12  becomes greater as acoustic capacitance in the manifold channels  11 ,  12  are greater. The acoustic capacitance of the manifold channel  11 ,  12  is a sum of Cv and Cd, wherein Cv is an acoustic capacitance determined by the volume of the manifold channel  11 ,  12  and the elasticity of the ink, and Cd is an acoustic capacitance determined by the elastic deformation of damper. However, since the value of Cv is very smaller than the value of Cd, only the acoustic capacitance Cd is considered here. The acoustic capacitance Cd is represented by an expression [I d ·W d   5 (1−v d )]/[6OE d ·t d   3 ]. In the expression, I d  is a length of the thin-walled portion  26   a ,  27   a  in the up and down direction in  FIG. 2 ; W d  is a width (length in the left and right direction in  FIG. 2 ) of the thin-walled portion  26   a ,  27   a ; t d  is a thickness of the thin-walled portion  26   a ,  27   a ; Ed is an elasticity of the thin-walled portion  26   a ,  27   a ; and v d  is a Poisson&#39;s ratio of the thin-walled portion  26   a ,  27   a.    
     As described above, the acoustic capacitance of the manifold channel  11 ,  12  is proportional to the fifth power of W d , and is inversely proportional to the third power of t d . In other words, it is possible to effectively increase the acoustic capacitance of the manifold channel  11 ,  12  by increasing W d  or decreasing t d . In the embodiment of the present invention, since the manifolds  11  and  12  are arranged to overlap in a plan view, the width W d  of each of the thin-walled portions  26   a  and  27   a  can be great by an amount of an area in which the manifold channels  11  and  12  are overlapped. Accordingly, it is possible to make the acoustic capacitance of the manifold channels  11 ,  12  to be great, thereby effectively attenuating the pressure wave in the manifold channels  11 ,  12 . 
     According to the embodiment as explained above, since the manifold channels  12  are formed to overlap with the manifold channels  11  in a plan view, the width of the thin-walled portions  26   a ,  27   a  can be greater than a case in which the manifold channels  11 ,  12  are arranged side by side in a same plane. This in turn makes is possible to increase the acoustic capacitance of the manifold channels  11 ,  12 , thereby effectively attenuating the pressure wave in the manifold channels  11 ,  12 . Accordingly, the pressure wave generated in a certain pressure chamber  10  and propagated to the manifolds  11  and  12  is hardly propagated further to another pressure chamber  10 , thereby suppressing the crosstalk. 
     Further, by forming the recesses  19  and  20  in the damper plates  26  and  27  respectively, the thin-walled portions  26   a  and  27   a  are formed and a space between one of the recesses  19  and one of the recesses  20  forms a damper chamber in which the thin-walled portions  26   a  and  27   a  are deformed. Accordingly, there is no need to form spaces to be the damper chamber and the thin-walled portions  26   a ,  27   a  separately, thereby making it possible to reduce the number of parts. 
     Furthermore, the jetting ports (first jetting ports, second jetting ports) of the nozzles  16  are all formed in the lower surface of the nozzle plate  30  having a flat shape. In other words, the number of part for forming the jetting ports of the nozzles  16  is only one, and thus the nozzles  16  formed in a same member are processed highly accurately, thereby maintaining the mutual positional relationship highly precisely. This in turn contributes to decreasing the cost for the ink-jet head  3  and uniformizing the ink-jetting characteristics among the nozzles  16 . 
     Moreover, since the pressure chambers  10  communicating with the manifold channels  11  and the pressure chambers  10  communicating with the manifold channels  12  are all formed at same height, with respect to the up and down direction in  FIG. 3 , it is possible to make the rigidity to be uniform around all the pressure chambers  10 , and to arrange the energy applying mechanism on a same plane. Accordingly, it is possible to decrease the number of parts, and to increase the positioning accuracy between the individual electrodes  41  and the pressure chambers  10 . This further makes the ink-jetting characteristics to be uniform among the nozzles  16  communicating with the pressure chambers  10 . 
     Further, as shown in  FIG. 2 , since pressure chambers  10  communicating with nozzles  16  which jet an ink of a same color are communicated only with one of the manifold channels  11  or one of the manifold channels  12 . Accordingly, the ink of same color is supplied to the nozzles  16  via the ink channel of a same structure. This makes the ink-jetting characteristic to be uniform among the nozzles  16  which jet the ink of same color. 
     Note that the manifold channels  11  and  12  are located at positions which are mutually different in the stacking direction of the plates since the manifold channels  11  and  12  are formed to be in an overlapping relationship. Accordingly, there is a difference in a channel length between a channel route from the manifold channel  11  to the pressure chamber  10  and a channel route from the manifold channel  12  to the pressure chamber  10 , which causes in some cases a difference in the ink-jetting characteristics between the pressure chambers  10  communicating with the manifold channels  11  and  12 , respectively. In this case, it is allowable to consider the pressure chambers  10  communicating with the manifold channel  11  as one group and the pressure chambers  10  communicating with the manifold channel  12  as another group, and to drive these groups as appropriate. Further, in view of realizing high resolution, it is effective to allocate or assign an ink of one color to each of the manifold channels  11  and  12 . 
     Further, sine the dummy manifold channels  51  and  52 , and the recesses  49  and  48  are formed, the attenuating characteristics are substantially same in the channel unit  5  at the both left and right end portion and at the central portion in  FIG. 2 , thereby uniformizing the jetting characteristics of the ink jetted form the nozzles  16 . 
     Furthermore, as shown in  FIG. 5B , the spaces defined by the recesses  19  and  20 , by the recesses  19  and  48 , and by the recesses  20  and  49 , respectively, are communicated with the outside air via the air hole  8 . Accordingly, it is possible to prevent any unsatisfactory bonding between the damper plates  26  and  27  which would be otherwise caused by the air expansion in these spaces due to the heating in the production process of the channel unit  5 , and to further prevent the channel unit  5  from being broken. 
     Next, modified embodiments in which various changes are made to the embodiment will be explained. Same reference numerals will be given to parts or components having similar construction as those in the embodiment, and explanation therefor will be omitted as appropriate. 
     In a first modification, as shown in  FIG. 6 , two synthetic resin plates  71  and  73  each formed of a synthetic resin material are arranged between the manifold plates  25  and  28 . Further, a spacer plate  72 , which is arranged between the plates  71  and  73 , is provided with through holes  74  formed therein at areas each overlapping in a plan view with the manifold channels  11 ,  12 . In this case also, a portion (first thin-walled portion), of the synthetic resin plate  71 , which faces in a plan view with one of the through holes  74  can be deformed to attenuate the pressure wave in the manifold channel  11 ; and a portion (second thin-walled portion), of the synthetic resin plate  73 , which faces in a plan view with one of the through holes  74  can be deformed to attenuate the pressure wave in the manifold channel  12 . Further, in this case, the spacer plate  72  is arranged between the synthetic resin plates  71  and  73 , thereby making it possible to easily form a space (integrated damper chamber) in which the portions of the synthetic resin plates  71  and  73  are deformable, while precisely securing a gap for the deformation. Furthermore, the capacity to attenuate the pressure wave is uniform in the damper portion. It is preferable to use, as the synthetic resin used for the synthetic resin plates  71  and  73 , a resin having a gas permeability resistance, or to perform a treatment for gas permeability resistance for the synthetic resin plates  71  and  73  at least for the areas facing the manifold channels  11  and  12 . 
     In a second modification, as shown in  FIG. 7A , dummy manifold channels (third dummy common liquid chambers)  91  are formed in a manifold plate  85  at positions each of which is adjacent to the narrowing area  11   b , of one of the manifold channels  11 , in the extending direction of thereof. Further, as shown in  FIG. 7D , dummy manifold channels (fourth dummy common liquid chambers)  96  are formed in a manifold plate  88  at positions each of which is adjacent to the narrowing area  12   b , of one of the manifold channels  12 , in the extending direction thereof. In this case, a sum of the width of the narrowing area  11   a  of each of the manifold channels  11  and the width of each of the dummy manifold channels  91  has a length which is same as the width of the constant-width area  11   a  of each of the manifold channel  11 ; and a sum of the width of the narrowing area  12   a  of each of the manifold channels  12  and the width of each of the dummy manifold channels  96  has a length which is same as the width of the constant-width area  12   a  of each of the manifold channel  12 . 
     Further, as shown in  FIG. 7A , a dummy manifold channel (first dummy common liquid chamber)  92  is formed in the manifold plate  85 . The dummy manifold channel  92  has a rectangular planar shape which is substantially same as the shape formed by one of the manifold channels  11  and one of the dummy manifold channels  91 . Furthermore, as shown in  FIG. 7B , a recess  93  is formed in the damper plate  86  at a position overlapping in a plan view with the dummy manifold channel  92 . The recess  93  has a rectangular planar shape which is substantially same as that of the dummy manifold channel  92 . On the other hand, as shown in  FIG. 7D , a dummy manifold channel (second dummy common liquid chamber)  97  is formed in the manifold plate  88 . The dummy manifold channel  97  has a rectangular planar shape which is substantially same as the shape formed by one of the manifold channels  12  and one of the dummy manifold channels  96 . Further, as shown in  FIG. 7C , a recess  94  having a substantially rectangular planar shape similar to that of the dummy manifold channel  97  is formed in the damper plate  87  at a position overlapping in a plan view with the dummy manifold channel  97 . 
     In this case, since the dummy manifold channels  91 ,  96  are formed, the rigidity around pressure chambers  10 , which are included in the pressure chambers  10  (see  FIG. 2 ) and which are located at positions on a side of the narrowing areas  11   b ,  12   b , respectively, and disposed away (farther) from the ink inlet port  9   a  to  9   d , is substantially same as the rigidity around other pressure chambers  10 . Accordingly, the ink-jetting characteristics are made to be uniform among the nozzles  16  (see  FIG. 2 ) communicating with the pressure chambers  10 , respectively. In this case also, the spaces defined by the recesses  19  and  20 , by the recesses  19  and  94 , and by the recesses  20  and  93 , respectively when the damper plates  86  and  87  are stacked, are communicated with the outside air via the air hole  8  formed in the damper plate  86 . Accordingly, it is possible to prevent any unsatisfactory bonding between the damper plates  86  and  87  which would be otherwise caused by the air expansion in these spaces due to the heating in the production process, and to further prevent the channel unit from being broken. 
     In the embodiment and the modifications thereof as explained above, although the piezoelectric actuator  6  is an actuator utilizing the vertical piezoelectric effect, the actuator is not limited thereto. The actuator may be, for example, an unimorph-type actuator which utilizes the horizontal piezoelectric effect in combination with a vibration plate. In this case, when the vibration plate is an electrically conductive body, the vibration plate constructs a pair of electrodes together with one of individual electrodes arranged to face the vibration plate, sandwiching the piezoelectric layer therebetween. Alternatively, when the vibration plate is an insulative body, a common electrode may be arranged on the vibration plate. Still alternatively, it is allowable to adopt an actuator constructed by forming a pair of electrodes on a surface of the piezoelectric layer for each of the pressure chambers, and by alternately stacking a plurality of the piezoelectric layers sandwiched by the electrode pairs respectively. In this case, the slip displacement is caused by a structure in which a direction of the electric field and a direction in which the piezoelectric layer is polarized cross with each other. 
     In the embodiment and the modifications thereof as explained above, the piezoelectric actuator is employed as the energy applying mechanism. The energy applying mechanism, however, is not limited to the piezoelectric actuator. For example, it is allowable to provide, as the energy applying mechanism, a resistance wire which generates Joule heat in the pressure chambers by a drive signal. In this case, air bubbles are generated by heating and vaporizing the ink in the pressure chambers, and the ink can be jetted by the pressure exerted by the air bubbles. 
     Alternatively, in the damper chamber, a liquid may be filled therein instead of the air, provided that the liquid does not erode or alternate the thin-walled portion. Still alternatively, a porous resin having inner holes such as a sponge member or the like, may be filled in the damper chamber depending on a desired damper performance or property. 
     In the embodiment and the modifications thereof, the present invention is explained by an example in which the present invention is applied to an ink-jet head. The present invention, however, is also applicable to a liquid-droplet jetting apparatus which jets a liquid other than ink, such as reagent, biomedical solution, solution for wiring material, solution for electronic material, cooling medium, fuel, and the like.