Patent Publication Number: US-11020972-B2

Title: Liquid discharge head

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application No. 2018-183370 filed on Sep. 28, 2018, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     Field of the Invention 
     The present disclosure relates to a liquid discharge head configured to discharge liquid from nozzles. 
     Description of the Related Art 
     As an exemplary liquid discharge head discharging liquid from nozzles, there is known an ink-jet head discharging ink from nozzles. The publicly known ink-jet head has the following features. Multiple pressure chambers communicating individually with the nozzles communicate with one manifold. Such a group of the pressure chambers and one manifold is provided in the ink-jet head, and multiple groups are typically provided in the ink-jet head. Ink channels are formed by stacking plates on top of each other. Recesses are formed at a lower portion of the plate joined to a lower surface of the plate provided with the manifold. The portion interposed between each recess and the manifold of the plate is elastically deformed, forming a damper inhibiting ink pressure fluctuation in manifolds. The plate provided with the nozzles is joined to the lower surface of the plate provided with the recesses to cover the recesses. 
     SUMMARY 
     In the liquid discharge head such as the above ink-jet head, some plates may be joined to each other with adhesive. In the case of joining the plates with adhesive, the adhesive may protrude from a joined surface where the plate having the recesses is joined to the plate having the nozzles and may invade the recesses. The adhesive invading the recesses may adhere to the dampers. If the adhesive adheres to only some of the dampers corresponding to manifold channels and/or if the amount of adhesive used for joining the plates varies, the dampers would have mutually different deformation amounts. In other words, the effect for inhibiting the pressure fluctuation in the manifolds varies. 
     An object of the present disclosure is to provide a liquid discharge head including plates joined to each other with adhesive and allowing multiple channels provided with a damper to have the uniformity of effect for inhibiting the pressure fluctuation brought about by the damper. 
     According to an aspect of the present disclosure, there is provided a liquid discharge head, including:
         an individual channel member including a plurality of individual channel rows, each of the individual channel rows including a plurality of individual channels arranged in a first direction, the individual channels including a plurality of nozzles respectively, the individual channel rows being arranged in a second direction intersecting with the first direction,   a first common channel member stacked on the individual channel member in a third direction intersecting with the first direction and the second direction, the first common channel member including:
           a plurality of first common channels provided for each of the individual channel rows, connected to the individual channels forming one of the individual channel rows corresponding thereto, and arranged in the second direction, and   a first partitioning wall partitioning the first common channels adjacent to each other in the second direction, and   
           a damper joined to the first common channel member with adhesive so that the first common channel member is disposed between the individual channel member and the damper in the third direction,   wherein the damper has a plurality of first portions that are elastically deformable and overlap in the third direction with the first common channels and a second portion that is joined to the first partitioning wall, extends in the second direction to positions overlapping in the third direction with the first common channels, and is connected to the first portions, and   the second portion is longer in the third direction than the first portions.       

     In the liquid discharge head of the present disclosure, the first portions of the damper having a small thickness (the length in the third direction is short) are elastically deformable, which inhibits liquid pressure fluctuation in the first common channels. Further, in the liquid discharge head of the present disclosure, the second portion having a large thickness (the length in the third direction is long) is joined to the first partitioning wall, extends to positions overlapping with the pressure chambers, and is connected to the first portions. In that configuration, when the first common channel member is joined to the damper with adhesive, if the adhesive protrudes from the joining surface, the adhesive would adhere to the second portion and would not adhere to the first portions. The deformation of the first portions are thus not affected by the adhesive protruding from the joining surface, resulting in the uniformity of effect for inhibiting the pressure fluctuation in the first common channels. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically depicts a configuration of a printer. 
         FIG. 2  is an enlarged view of parts of head units depicted in  FIG. 1 . 
         FIG. 3  depicts the head unit when seen from a downstream side in a conveyance direction. 
         FIG. 4  is a plan view depicting parts of an individual unit and a lower-side manifold plate. 
         FIG. 5  is a cross-sectional view taken along a line V-V in  FIG. 4 . 
         FIG. 6A  is a plan view of the lower-side manifold plate, and  FIG. 6B  is a plan view of a damper. 
         FIG. 7A  is a plan view of the lowermost channel plate of a connection channel unit,  FIG. 7B  is a plan view of the second lowermost channel plate of the connection channel unit,  FIG. 7C  is a plan view of the second uppermost channel plate of the connection channel unit, and  FIG. 7D  is a plan view of the uppermost channel plate of the connection channel unit. 
         FIG. 8  is an enlarged view of part of  FIG. 7A . 
         FIG. 9A  is a plan view of the lowermost channel plate of an upper-side manifold unit,  FIG. 9B  is a plan view of a filter plate,  FIG. 9C  is a plan view of the second uppermost channel plate of the upper-side manifold unit, and  FIG. 9D  is a plan view of the uppermost channel plate of the upper-side manifold unit. 
         FIG. 10  is a plan view of a tube connection member. 
         FIG. 11A  illustrates a step of forming a first damper member on a second damper member,  FIG. 11B  illustrates a step of forming through holes in the second damper member, and  FIG. 11C  illustrates a step of joining the damper to the lower-side manifold plate and the connection channel unit. 
         FIG. 12  depicts a first modified embodiment and corresponds to  FIG. 8 . 
         FIG. 13  depicts a second modified embodiment and corresponds to  FIG. 6B . 
         FIG. 14  depicts a third modified embodiment and corresponds to  FIG. 5 . 
         FIG. 15  depicts a fourth modified embodiment and corresponds to  FIG. 5 . 
         FIG. 16  depicts a fifth modified embodiment and corresponds to  FIG. 5 . 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     An embodiment of the present disclosure is explained below. 
     &lt;Configuration of Printer&gt; 
     As depicted in  FIG. 1 , a printer  1  according to this embodiment includes an ink-jet head  2 , a platen  3 , and conveyance rollers  4  and  5 . 
     As depicted in  FIGS. 1 and 2 , the ink-jet head  2  includes four head units  11   a  to  11   d  and a holding member  12 . When the four head units  11   a  to  11   d  are not distinguished from each other, those head units are collectively referred to as head units  11 . The head unit  11  corresponds to a liquid discharge head of the present disclosure. The head unit  11  discharges ink from nozzles  10 , which are formed in a lower surface of the head unit  11 . More specifically, the nozzles  10  are aligned in a sheet width direction (hereinafter simply referred to as a width direction, a first direction of the present disclosure) to form each nozzle row  9 . The head unit  11  includes eight nozzle rows  9  arranged in a conveyance direction (a second direction of the present disclosure) orthogonal to the width direction. The width direction and the conveyance direction in this embodiment are defined as indicated in  FIG. 1 . Further, an up-down direction in this embodiment (a third direction of the present disclosure) is defined as indicated in  FIG. 3 . 
     Of the eight nozzle rows  9 , nozzles  10  forming odd-numbered nozzle rows  9  from an upstream side in the conveyance direction are shifted in the width direction from nozzles  10  forming even-numbered nozzle rows  9  by a length that is half of pitches between nozzles  10 . A black ink is discharged from nozzles  10  forming the first and second nozzle rows  9  from the upstream side in the conveyance direction. Similarly, a yellow ink is discharged from nozzles  10  forming the third and fourth nozzle rows  9  from the upstream side in the conveyance direction, a cyan ink is discharged from nozzles  10  forming the fifth and sixth nozzle rows  9  from the upstream side in the conveyance direction, and a magenta ink is discharged from nozzles  10  forming the seventh and eighth nozzle rows  9  from the upstream side in the conveyance direction. The following explanation is made by defining right and left sides in the width direction as indicated in  FIG. 1 . Further, in the following explanation, the n-th element from the upstream side in the conveyance direction is simply referred to as the n-th element. 
     The head unit  11   a  and the head unit  11   c  are arranged side by side in the width direction, and the head unit  11   b  and the head unit  11   d  are arranged side by side in the width direction. The head units  11   b  and  11   d  are positioned downstream of the head units  11   a  and  11   c  in the conveyance direction orthogonal to the width direction. The head units  11   b  and  11   d  are shifted right in the width direction from the head units  11   a  and  11   c.  Thus, in the ink-jet head  2 , the nozzles  10  of the four head units  11  are aligned to extend over an entire length in the width direction of a recording sheet P. Namely, the ink-jet head  2  is a line head. Detailed configurations of the head unit  11  are described below. 
     The holding member  12  is a plate-like rectangular member that is long in the width direction. The four head units  11  are secured to the holding member  12 . The holding member  12  has four rectangular through holes  12   a  that respectively correspond to the four head units  11 . The nozzles  10  of the head units  11  are exposed to a lower side (recording sheet P side) through the respective through holes  12   a.    
     The platen  3 , which is disposed below the ink-jet head  2 , faces the nozzles  10  of the four head units  11 . The platen  3  supports the recording sheet P from below. The conveyance roller  4  is disposed upstream of the ink-jet head  2  and the platen  3  in the conveyance direction. The conveyance roller  5  is disposed downstream of the ink-jet head  2  and the platen  3  in the conveyance direction. The conveyance rollers  4  and  5  convey the recording sheet P in the conveyance direction. 
     The printer  1  performs recording on the recording sheet P by conveying the recording sheet P in the conveyance direction by use of the conveyance rollers  4  and  5  and discharging ink(s) from the nozzles  10  of the four head units  11 . 
     &lt;Head Unit&gt; 
     Subsequently, the head units  11  are explained. As depicted in  FIGS. 2 to 9 , each head unit  11  includes an individual unit  21 , a lower-side manifold plate  22  (a common channel member, a first common channel member of the present disclosure), a damper  23 , a connection channel unit  24  (a damper chamber member of the present disclosure), an upper-side manifold unit  25  (a second supply channel member of the present disclosure), and a tube connection member  26 . 
     As depicted in  FIGS. 3 to 5 , the individual unit  21  includes a nozzle plate  31 , a channel substrate  32 , a vibration film  33 , driving elements  34 , and a protection substrate  35 . The nozzle plate  31  is made using, for example, a synthetic resin material. The nozzle plate  31  includes nozzles  10  forming the eight nozzle rows  9 . 
     The channel substrate  32 , which is made of silicon (Si), is disposed on an upper surface of the nozzle plate  31 . The channel substrate  32  includes pressure chambers  40  corresponding to the nozzles  10 , respectively. A center portion in the conveyance direction of each of the pressure chambers  40  overlaps in the up-down direction with the corresponding one of nozzles  10 . The channel substrate  32  includes eight pressure chamber rows  8  formed by aligning pressure chambers  40  in the width direction. The eight pressure chamber rows  8  are arranged in the conveyance direction. 
     The vibration film  33 , which is provided at an upper end of the channel substrate  32 , covers the pressure chambers  40 . The vibration film  33  is made using silicon dioxide (SiO2) or silicon nitride (SiN). The vibration film  33  is formed by oxidizing or nitriding the upper end of the channel substrate  32 . 
     The vibration film  33  has inflow holes  33   a  at portions that overlap in the up-down direction with downstream ends in the conveyance direction of the pressure chambers  40  forming the odd-numbered pressure chamber rows  8 . Similarly, the vibration film  33  has inflow holes  33   a  at portions that overlap in the up-down direction with upstream ends in the conveyance direction of the pressure chambers  40  forming the even-numbered pressure chamber rows  8 . Further, the vibration film  33  has outflow holes  33   b  at portions that overlap in the up-down direction with upstream ends in the conveyance direction of the pressure chambers  40  forming the odd-numbered pressure chamber rows  8 . Similarly, the vibration film  33  has outflow holes  33   b  at portions that overlap in the up-down direction with downstream ends in the conveyance direction of the pressure chambers  40  forming the even-numbered pressure chamber rows  8 . 
     The driving elements  34  are provided corresponding to the pressure chambers  40 , respectively. The driving elements  34  are arranged on an upper surface of the vibration film  33  at portions that overlap in the up-down direction with the pressure chambers  40 . The driving elements  34  are, for example, piezoelectric elements including piezoelectric bodies, electrodes, and the like. The configuration of the driving elements  34  is similar to that of conventional driving elements, and thus detailed explanation thereof is omitted here. 
     The protection substrate  35 , which is made using silicon (Si), is disposed on an upper surface of the channel substrate  32  provided with the vibration film  33  and the driving elements  34 . The protection substrate  35  includes, at portions that overlap in the up-down direction with the inflow holes  33   a,  supply throttle channels  35   a  that pass through the protection substrate  35  in the up-down direction. Further, the protection substrate  35  includes, at portions that overlap in the up-down direction with the outflow holes  33   b,  return throttle channels  35   b  that pass through the protection substrate  35  in the up-down direction. Further, recesses  35   c  are formed at portions of a lower portion of the protection substrate  35  that overlap in the up-down direction with the pressure chambers  40  forming each pressure chamber row  8 . The driving elements  34  corresponding to each pressure chamber row  8  are accommodated in the recesses  35   c.    
     In this embodiment, a channel formed by the nozzle  10 , the pressure chamber  40 , the supply throttle channel  35   a,  and the return throttle channel  35   b  corresponds to an individual channel of the present disclosure. A row (a row corresponding to each of the nozzle row  9  and the pressure chamber row  8 ) formed by arranging the individual channels in the width direction corresponds to an individual channel row of the present disclosure. A set or group of the nozzle plate  31 , the channel substrate  32 , and the protection substrate  35  including the individual channels corresponds to an individual channel member of the present disclosure. 
     As depicted in  FIGS. 3 to 6A , the lower-side manifold plate  22  is disposed on an upper surface of the protection substrate  35 . The lower-side manifold plate  22  includes four lower-side supply manifolds  41  and eight lower-side return manifolds  42 . 
     Each lower-side supply manifold  41  extends in the width direction along the supply throttle channels  35   a  that correspond to two pressure chamber rows  8  through which an ink in the same color flows. Each lower-side return manifold  42  extends in the width direction along the return throttle channels  35   b  that correspond to each pressure chamber row  8 . The lower-side return manifolds  42  are connected to the return throttle channels  35   b.  The lower-side return manifolds  42  extend beyond the lower-side supply manifolds  41  in the width direction. 
     Part of the lower-side manifold plate  22  between the lower-side supply manifold  41  and the lower-side return manifold  42  adjacent to each other in the conveyance direction and part of the lower-side manifold plate  22  between two lower-side return manifolds  42  adjacent to each other in the conveyance direction are partitioning walls  22   a  (a first partitioning wall of the present disclosure) that partition the manifolds  41  and  42 . The partitioning wall  22   a  between the lower-side return manifold  42  positioned at the downstream side that is included in two lower-side return manifolds  42  that correspond to the second pressure chamber row  8  and the lower-side return manifold  42  positioned at the upstream side that is included in two lower-side return manifolds  42  that correspond to the third pressure chamber row  8  is referred to as a partitioning wall  22   a   2  (a fourth partitioning wall of the present disclosure). Any other partitioning wall  22   a  than the partitioning wall  22   a   2  is referred to as a partitioning wall  22   a   1  (a third partitioning wall of the present disclosure). A length L 2  of the partitioning wall  22   a   2  is longer than a length L 1  of the partitioning wall  22   a   1 . 
     As depicted in  FIGS. 3, 5, and 6B , the damper  23  is disposed on an upper surface of the lower-side manifold plate  22  to cover the four lower-side supply manifolds  41  and the eight lower-side return manifolds  42 . The damper  23  includes a first damper member  46  and a second damper member  47 . 
     The first damper member  46  is made using, for example, a synthetic resin material such as polyamide imide, polyimide (PI), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), and polyethylene naphthalate (PEN). The first damper member  46  is a thin-film member of which length in the up-down direction is not more than 10 μm. The second damper member  47  is made using, for example, a metal material, such as stainless steel. The second damper member  47  is a member of which length in the up-down direction is approximately 150 μm. The second damper member  47  is disposed on the lower side of the first damper member  46 . The second damper member  47  is joined to the upper surface of the lower-side manifold plate  22  with adhesive. 
     The second damper member  47  has through holes  47   a  at portions overlapping in the up-down direction with portions of the manifolds  41  and  42  not including both ends thereof in the conveyance direction. The length in the conveyance direction of the through hole  47   a  is shorter toward the upper side (toward the first damper member  46 ). In that case, each inner wall surface of the through hole  47   a  is an inclined surface  47   b  that is inclined to the up-down direction so that the upper side of the inclined surface  47   b  is closer to a center portion in the conveyance direction of the through hole  47   a  than the lower side. In other words, a diameter of the through hole  47   a  at the upper side of the inclined surface  47   b  is smaller than a diameter of the through hole  47   a  at the lower side of the inclined surface  47   b.    
     In the damper  23  having the above configuration, portions of the first damper member  46  exposed from the through holes  47   a  are elastically-deformable first portions  23   a.  When the first portions  23   a  are elastically deformed, ink pressure fluctuation in the manifolds  41  and  42  can be reduced. For example, the first portions  23   a  are elastically deformed to an extent of approximately 60 μm at the maximum. In order to make the first portions  23   a  elastically deformable through the ink pressure fluctuation, the first damper member  46  can be made using a material of which Young&#39;s modulus is in a range of 5.5 to 6.5 GPa, preferably approximately 6 GPa. 
     In any other potions than the first portions  23   a  of the damper  23 , the first damper member  46  overlaps in the up-down direction with the second damper member  47  and the thickness of the portions other than the first portions  23   a  is larger than that of the first portions  23   a.  Portions of the damper  23 , in which the first damper member  46  overlaps with the second damper member  47 , positioned at both sides in the conveyance direction of the first portion  23   a  are second portions  23   b.  Each second portion  23   b  is joined to the partitioning wall  22   a  with adhesive, extends in the conveyance direction to positions overlapping in the up-down direction with the manifolds  41  and  42 , and connected to the first portions  23   a.    
     A portion of the second portion  23   b  joined to the partitioning wall  22   a   1  is referred to as a second portion  23   b   1  (a fourth portion of the present disclosure), and a portion of the second portion  23   b  joined to the partitioning wall  22   a   2  is referred to as a second portion  23   b   2  (a fifth portion of the present disclosure). Since the length L 2  of the partitioning wall  22   a   2  is longer than the length L 1  of the partitioning wall  22   a   1  in the conveyance direction, a length L 4  (&gt;L 2 ) of the second portion  23   b   2  is longer than a length L 3  (&gt;L 1 ) of the second portion  23   b   1 . Further, since the second portion  23   b  is longer than the first portion  23   a  in the up-down direction, portions included in the second portion  23   b  and overlapping in the up-down direction with the manifolds  41  and  42  are hardly deformed by ink pressure fluctuation in the manifolds  41  and  42 . 
     Each portion where the first damper member  46  and the second damper member  47  of the damper  23  overlap with each other have two portions that overlap in the up-down direction with both ends in the width direction of the manifolds  41  and  42 . The two portions are third portions  23   c.  Supply connection holes  23   d  and  23   e  are formed at portions included in the third portions  23   c  and overlapping in the up-down direction with the left and right ends in the width direction of the lower-side supply manifold  41 . Return connection holes  23   f  and  23   g  are formed at portions included in the third portions  23   c  and overlapping in the up-down direction with the right end and left ends in the width direction of the lower-side return manifold  42 . In this embodiment, the supply connection holes  23   d,    23   e  and the return connection holes  23   f,    23   g  correspond to first connection channels of the present disclosure. 
     &lt;Connection Channel Unit&gt; 
     As depicted in  FIGS. 3, 5, and 7 , the connection channel unit  24  is configured by four rectangular channel plates  51  to  54  that are stacked on top of each other in the up-down direction. The four channel plates  51  to  54  are long in the width direction. The channel plates  51  to  54  are made, for example, using  42  alloy or stainless steel. 
     The channel plate  51  is disposed on an upper surface of the damper  23 . As depicted in  FIG. 7A , the channel plate  51  has four supply channel holes  61   a,  four supply channel holes  62   a,  four return channel holes  63   a,  and four return channel holes  64   a.  The supply channel holes  61   a,    62   a  and the return channel holes  63   a,    64   a  are through holes that pass through the channel plate  51  in the up-down direction. 
     The four supply channel holes  61   a  correspond to the four supply channel holes  23   d.  Each supply channel hole  61   a  overlaps in the up-down direction with the corresponding supply channel hole  23   d.  The four supply channel holes  62   a  correspond to the four supply channel holes  23   e.  Each supply channel hole  62   a  overlaps in the up-down direction with the corresponding supply channel hole  23   e.    
     Each of the four return channel holes  63   a  corresponds to two return connection holes  23   f  through which an ink in the same color flows. Each return channel hole  63   a  extends across the corresponding two return connection holes  23   f  and is connected to the two return connection holes  23   f.  Each of the four return channel holes  64   a  corresponds to two return channel holes  23   g  through which an ink in the same color flows. Each return channel hole  64   a  extends across the corresponding two return channel holes  23   g  and is connected to the two return channel holes  23   g.    
     As depicted in  FIGS. 5, 7A, and 8 , the channel plate  51  includes, at portions overlapping in the up-down direction with the manifolds  41  and  42 , first damper chambers  65  extending in the width direction. Each first damper chamber  65  is a space for receiving an upward deformation of the damper  23 . In  FIG. 8 , potions not including the first damper chambers  65  are hatched to make  FIG. 8  easily viewable. 
     The first damper chambers  65  are formed by through holes passing through the channel plate  51 . A portion of the channel plate  51  between adjacent first damper chambers  65  is a partitioning wall  51   a  (a second partitioning wall of the present disclosure) that partitions the adjacent first damper chambers  65 . In this embodiment, a length L 5  in the conveyance direction of a partitioning wall  51   a   1  included in the partitioning wall  51   a  and overlapping in the up-down direction with the partitioning wall  22   a   1  is shorter than the length L 1  of the partitioning wall  22   a   1 . Further, a length L 6  in the conveyance direction of a partitioning wall  51   a   2  included in the partitioning wall  51   a  and overlapping in the up-down direction with the partitioning wall  22   a   2  is shorter than the length L 2  of the partitioning wall  22   a   2 . The partitioning wall  51   a   1  is positioned between both ends in the conveyance direction of the partitioning wall  22   a   1 , and the partitioning wall  51   a   2  is positioned between both ends in the conveyance direction of the partitioning wall  22   a   2 . 
     The channel plate  51  includes two first communication channels  51   b  and six second communication channels  51   c.  Each first communication channel  51   b  extends over all the first damper chambers  65  in the conveyance direction to allow the first damper chambers  65  to communicate with each other. The two first communication channels  51   b  are arranged in the width direction at an interval. 
     Of the six second communication channels  51   c,  three second communication channels  51   c  are arranged at the upstream side in the conveyance direction to extend in the conveyance direction, and remaining three second communication channels  51   c  are arranged at the downstream side in the conveyance direction to extend in the conveyance direction. The first damper chamber  65  disposed at the most upstream side in the conveyance direction, the first damper chamber  65  disposed at the most downstream side in the conveyance direction, and end surfaces in the conveyance direction of the channel plate  51  are connected to each other through the upstream-side second communication channels  51   c  and the downstream-side second communication channels  51   c.  This allows the first damper chambers  65  disposed at the most upstream and most downstream sides in the conveyance direction to communicate with the atmosphere. As described above, the first damper chambers  65  communicate with each other through the first communication channels  51   b.  All the first damper chambers  65  thus communicate with the atmosphere by causing the first damper chambers  65  disposed at the most upstream and most downstream sides in the conveyance direction to communicate with the atmosphere through the second communication channels  51   c.    
     The three second communication channels  51   c  disposed at the upstream side in the conveyance direction are arranged in the width direction at intervals, and the three second communication channels  51   c  disposed at the downstream side in the conveyance direction are arranged in the width direction at intervals. The positions in the width direction of the first communication channels  51   b  are different from those of the second communication channels  51   c.  The first communication channels  51   b  and the second communication channels  51   c  are formed by recesses in a lower surface of the channel plate  51 . 
     The channel plate  52  is disposed on an upper surface of the channel plate  51 . As depicted in  FIG. 7B , the channel plate  52  has four supply channel holes  61   b,  four supply channel holes  62   b,  four return channel holes  63   b,  and four return channel holes  64   b.  The supply channel holes  61   b,    62   b  and the return channel holes  63   b,    64   b  are through holes that pass through the channel plate  52  in the up-down direction. 
     The four supply channel holes  61   b  correspond to the four supply channel holes  61   a.  Each of the supply channel holes  61   b  overlaps in the up-down direction with the corresponding one of the supply channel holes  61   a.  The four supply channel holes  62   b  correspond to the four supply channel holes  62   a.  Each of the supply channel holes  61   b  overlaps in the up-down direction with the corresponding one of the supply channel holes  61   a.  The four return channel holes  63   b  correspond to the four return channel holes  63   a.  Each of the return channel holes  63   b  overlaps in the up-down direction with a center portion of the corresponding one of the return channel holes  63   a.  The four return channel holes  64   b  correspond to the four return channel holes  64   a.  Each of the return channel holes  64   b  overlaps in the up-down direction with a center portion of the corresponding one of the return channel holes  64   a.    
     The channel plate  53  is disposed on an upper surface of the channel plate  52 . As depicted in  FIG. 7C , the channel plate  53  has four supply channel holes  61   c,  four supply channel holes  62   c,  four return channel holes  63   c,  and four return channel holes  64   c.  The supply channel holes  61   c,    62   c  and the return channel holes  63   c,    64   c  are through holes that pass through the channel plate  53  in the up-down direction. 
     The four supply channel holes  61   c  correspond to the four supply channel holes  61   b.  Each of the supply channel holes  61   c  overlaps in the up-down direction with the corresponding one of the supply channel holes  61   b.  The first and second supply channel holes  61   c  extend from portions overlapping in the up-down direction with the supply channel holes  61   b  toward the upstream side in the conveyance direction. The third and fourth supply channel holes  61   c  extend from portions overlapping in the up-down direction with the supply channel holes  61   b  toward the downstream side in the conveyance direction. 
     The four supply channel holes  62   c  correspond to the four supply channel holes  62   b.  Each of the supply channel holes  62   c  overlaps in the up-down direction with the corresponding one of the supply channel holes  62   b.  The first and second supply channel holes  62   c  extend from portions overlapping in the up-down direction with the supply channel holes  62   b  toward the upstream side in the conveyance direction. The third and fourth supply channel holes  62   c  extend from portions overlapping in the up-down direction with the supply channel holes  62   b  toward the downstream side in the conveyance direction. 
     The four return channel holes  63   c  correspond to the four return channel holes  63   b.  Each of the return channel holes  63   c  overlaps in the up-down direction with the corresponding one of the return channel holes  63   b.  The first and second return channel holes  63   c  extend rightward from portions overlapping in the up-down direction with the return channel holes  63   b  such that inclination of the first and second return channel holes  63   c  to the width direction is greater toward the upstream side in the conveyance direction. The third and fourth return channel holes  63   c  extend rightward from portions overlapping in the up-down direction with the return channel holes  63   b  such that inclination of the third and fourth return channel holes  63   c  to the width direction is greater toward the downstream side in the conveyance direction. 
     The four return channel holes  64   c  correspond to the four return channel holes  64   b.  Each of the return channel holes  64   c  overlaps in the up-down direction with the corresponding one of the return channel holes  64   b.  The first and second return channel holes  64   c  extend leftward from portions overlapping in the up-down direction with the return channel holes  64   b  such that inclination of the first and second return channel holes  64   c  to the width direction is greater toward the upstream side in the conveyance direction. The third and fourth return channel holes  64   c  extend leftward from portions overlapping in the up-down direction with the return channel holes  64   b  such that inclination of the third and fourth return channel holes  64   c  to the width direction is greater toward the downstream side in the conveyance direction. 
     The channel plate  54  is disposed on an upper surface of the channel plate  53 . As depicted in  FIG. 7D , the channel plate  54  has four supply channel holes  61   d,  four supply channel holes  62   d,  four return channel holes  63   d,  and four return channel holes  64   d.  The supply channel holes  61   d  and  62   d  and the return channel holes  63   d  and  64   d  are through holes that pass through the channel plate  54  in the up-down direction. 
     The four supply channel holes  61   d  correspond to the four supply channel holes  61   c.  Each of the supply channel holes  61   d  overlaps in the up-down direction with an end of the corresponding one of the supply channel holes  61   c  that is opposite to the portion overlapping in the up-down direction with the supply channel hole  61   b.  The four supply channel holes  62   d  correspond to the four supply channel holes  62   c.  Each of the supply channel holes  62   d  overlaps in the up-down direction with an end of the corresponding one of the supply channel holes  62   c  that is opposite to the portion overlapping in the up-down direction with the supply channel hole  62   b.    
     The four return channel holes  63   d  correspond to the four return channel holes  63   c.  Each of the return channel holes  63   d  overlaps in the up-down direction with an end of the corresponding one of the return channel holes  63   c  that is opposite to the portion overlapping in the up-down direction with the return channel hole  63   b.  The four return channel holes  64   d  correspond to the four return channel holes  64   c.  Each of the return channel holes  64   d  overlaps in the up-down direction with an end of the corresponding one of the return channel holes  64   c  that is opposite to the portion overlapping in the up-down direction with the return channel hole  64   b.    
     &lt;Upper-Side Manifold Unit  25 &gt; 
     The upper-side manifold unit  25  is disposed on an upper surface of the connection channel unit  24 . As depicted in  FIGS. 3 and 9 , the upper-side manifold unit  25  includes a filter plate  82  and three channel plates  81 ,  83 , and  84 . The filter plate  82  and the channel plates  81 ,  83 , and  84  are rectangular plates that are long in the width direction. 
     As depicted in  FIG. 9A , the channel plate  81  includes four supply manifold portions  91   a  and four return manifold portions  92   a.  The four supply manifold portions  91   a,  which extend in the width direction, are arranged in the conveyance direction at intervals. The four return manifold portions  92   a,  which extend in the width direction, are arranged in the conveyance direction at intervals. Each of the supply manifold portions  91   a  is arranged adjacently to the corresponding one of the return manifold portions  92   a  in the conveyance direction. More specifically, the first and second return manifold portions  92   a  are adjacent respectively to upstream portions in the conveyance direction of the first and second supply manifold portions  91   a.  The third and fourth return manifold portions  92   a  are adjacent respectively to downstream portions in the conveyance direction of the third and fourth supply manifold portions  91   a.    
     Ends in the width direction of each supply manifold portion  91   a  overlap respectively with the supply channel holes  61   d  and  62   d  in the channel plate  54  of the connection channel unit  24 . Ends in the width direction of each return manifold portion  92   a  overlap respectively with the return channel holes  63   d  and  64   d  in the channel plate  54  of the connection channel unit  24 . 
     The filter plate  82  is disposed on an upper surface of the channel plate  81 . As depicted in  FIG. 9B , filters  82   a  are formed in the filter plate  82  at portions overlapping in the up-down direction with the supply manifolds  91   a  and at portions overlapping in the up-down direction with the return manifold portions  92   a.    
     The channel plate  83  is disposed on an upper surface of the filter plate  82 . As depicted in  FIG. 9C , the channel plate  83  includes four supply manifold portions  91   b  and four return manifold portions  92   b.  The four supply manifold portions  91   b,  which extend in the width direction, overlap in the up-down direction with the four supply manifold portions  91   a.  The four return manifold portions  92   b,  which extend in the width direction, overlap in the up-down direction with the four return manifold portions  92   a.    
     The first and third return manifold portions  92   b  extend leftward in the width direction beyond the first and third return manifold portions  92   a.  The second and fourth return manifold portions  92   b  extend rightward in the width direction beyond the second and fourth return manifold portions  92   a.  In that configuration, the positions of the ends in the width direction of the supply manifold portions  91   b  are different from the positions of the ends in the width direction of the return manifold portions  92   b.    
     The channel plate  84  is disposed on an upper surface of the channel plate  83 . As depicted in  FIG. 9D , the channel plate  84  has four supply holes  94  and four return holes  95 . The four supply holes  94  correspond to the four supply manifold portions  91   b.  The supply holes  94  overlap in the up-down direction with left ends in the width direction of the first and third supply manifold portions  91   b  and right ends in the width direction of the second and fourth supply manifold portions  91   b.    
     The four return holes  95  correspond to the four return manifold portions  92   b.  The return holes  95  overlap in the up-down direction with left ends in the width direction of the first and third return manifold portions  92   b  and right ends in the width direction of the second and fourth return manifold portions  92   b.    
     In the upper-side manifold unit  25 , the supply manifold portions  91   a  overlap in the up-down direction with the supply manifold portions  91   b  to form a manifold (hereinafter, referred to as an upper-side supply manifold  91 ). Further, the return manifold portions  92   a  overlap in the up-down direction with the return manifold portions  92   b  to form a manifold (hereinafter, referred to as an upper-side supply manifold  92 ). The filters  82   a  divide the upper-side supply manifold  91  into upper and lower portions. The filters  82   a  divide the upper-side return manifold  92  into upper and lower portions. 
     A channel formed by connecting the supply channel holes  61   a  to  61   d  is referred to as a supply connection channel  61 . The supply channel hole  23   d  and the supply connection channel  61  connect a right end in the width direction of one lower-side supply manifold  41  and a right end in the width direction of one upper-side supply manifold  91 . Further, a channel formed by connecting the supply channel holes  62   a  to  62   d  is referred to as a supply connection channel  62 . The supply channel hole  23   e  and the supply connection channel  62  connect a left end in the width direction of one lower-side supply manifold  41  and a left end in the width direction of one upper-side supply manifold  91 . 
     A channel formed by connecting the return channel holes  63   a  to  63   d  is referred to as a return connection channel  63 . The return connection hole  23   f  and the return connection channel  63  connect right ends in the width direction of two lower-side return manifolds  42  and a right end in the width direction of one upper-side return manifold  92 . Further, a channel formed by connecting the return channel holes  64   a  to  64   d  is referred to as a return connection channel  64 . The return connection hole  23   g  and the return connection channel  64  connect left ends in the width direction of two lower-side return manifolds  42  and a left end in the width direction of one upper-side return manifold  92 . 
     In this embodiment, the supply connection channel  63  and the return connection channel  64  correspond to second connection channels of the present disclosure. 
     &lt;Tube Connection Member&gt; 
     As depicted in  FIG. 3 , the tube connection member  26 , which is a block-like member having a rectangular parallelepiped shape, is made using a synthetic resin material and the like. The tube connection member  26  is disposed on an upper surface of the upper-side manifold unit  25 . As depicted in  FIG. 10 , the tube connection member  26  includes four supply channels  101  and four return channels  102 . 
     The four supply channels  101  correspond to the four supply holes  94  in the channel plate  84  of the upper-side manifold unit  25 . Each of the supply channels  101  extends in the up-down direction and is connected to the corresponding one of the supply holes  94 . The four return channels  102  correspond to the four return holes  95  in the channel plate  84 . Each of the return channels  102  extends in the up-down direction and is connected to the corresponding one of the return holes  95 . 
     The tube connection member  26  includes four supply tube connection portions  103  and four return tube connection portions  104 . The four supply tube connection portions  103  protrude upward from an upper surface of the tube connection member  26 . The four supply tube connection portions  103  correspond to the four supply channels  101 . Each of the supply tube connection portions  103  is connected to the corresponding one of the supply channels  101 . 
     Supply tubes  105  are connected to the respective supply tube connection portions  103 . Each of the supply tube connection portions  103  is connected to an ink tank  110  storing the corresponding color of ink via the corresponding one of the supply tubes  105 . A supply pump  111  is connected to part of the supply tube  105  between the supply tube connection portion  103  and the ink tank  110 . The supply pump  111  pumps ink from the ink tank  110  to the supply tube connection portion  103 . 
     The four return tube connection portions  104  protrude upward from the upper surface of the tube connection member  26 . The four return tube connection portions  104  correspond to the four return channels  102 . Each of the return tube connection portions  104  is connected to the corresponding one of the return channels  102 . 
     The respective return tube connection portions  104  are connected to return tubes  106 . Each of the return tube connection portions  104  is connected to an ink tank  110  storing the corresponding color of ink via the corresponding one of the return tubes  106 . A return pump  112  is connected to part of the return tube  106  between the return tube connection portion  104  and the ink tank  110 . The return pump  112  pumps ink from the return tube connection portion  104  to the ink tank  110 . 
     When the supply pump  111  and the return pump  112  are driven, the ink in the ink tank  110  flows through the supply tube  105 , the supply tube connection portion  103 , the supply channel  101 , the upper-side supply manifold  91 , the supply connection channels  61  and  62 , the lower-side supply manifold  41 , and the supply throttle channel  35   a  in that order, and then flows into the pressure chamber  40  through the inflow hole  33   a.  The ink in the pressure chamber  40  outflows through the outflow hole  33   b,  flows through the return throttle channel  35   b,  the lower-side return manifold  42 , the return connection channels  63  and  64 , the upper-side return manifold  92 , the return channel  102 , the return tube connection portion  104 , and the return tube  106  in that order, and returns to the ink tank  110 . Namely, the ink circulates between the ink tank  110  and each head unit  11 . 
     &lt;Method for Manufacturing Head Unit&gt; 
     Subsequently, a method for manufacturing the head unit  11  is explained. When the head unit  11  is manufactured, as depicted in  FIG. 11A , the first damper member  46  is formed on a surface of a metal member  147  by a known film forming method. Then, as depicted in  FIG. 11B , the metal member  147  is subjected to etching from a side opposite to the first damper member  46  to have through holes  47   a,  thus forming the metal member  147  as the second damper member  47 . The inner wall surfaces of the through holes  47   a  are the inclined surfaces  47   b  described above. Here, the damper  23  is completed. Next, the damper  23  is joined to members that form the heat unit  11  and are prepared separately. The damper  23  is joined to the lower-side manifold plate  22  and the connection channel unit  24  (the channel plate  51 ) with adhesive. The synthetic resin material used for the first damper member  46  typically has no polarity. An upper surface of the first damper member  46  is thus made to have polarity through plasma processing, and the first damper member  46  is joined to the channel plate  51  with adhesive. 
     &lt;Effects&gt; 
     In this embodiment, the first portions  23   a  of the damper  23  having a small thickness (a short length in the up-down direction) are elastically deformed, thus inhibiting the ink pressure fluctuation in the manifolds  41  and  42 . Portions included in the second portions  23   b,  which have a large thickness, and overlapping in the up-down direction with the manifolds  41  and  42  are hardly deformed owing to the pressure fluctuation in the manifolds  41  and  42 . 
     When the damper  23  is joined to the lower-side manifold plate  22  with adhesive, the adhesive may protrude from the joined surface. In this embodiment, however, the second portions  23   b  of the damper  23  are joined to the partitioning walls  22   a  so that they extend to the positions overlapping in the up-down direction with the manifolds  41  and  42 . Thus, as depicted in  FIG. 11C , although the adhesive S protruding from the joined surface adhere to the second portions  23   b,  it is not likely to reach the first portions  23   a.  The deformation of the first portions  23   a  is thus not likely to be affected by the adhesive, allowing the lower-side supply manifolds  41  and the lower-side return manifolds  42  to obtain the uniformity of effect for inhibiting the pressure fluctuation brought about by the damper  23 . 
     In this embodiment, the inner wall surfaces of the through holes  47   a  of the second damper member  47  are the inclined surfaces  47   b.  Thus, even when the adhesive protruding from a portion between the damper  23  and the lower-side manifold plate  22  reaches an edge of the through hole  47   a,  the adhesive adheres to the inclined surface  47   b  of the through hole  47   a  and hardly reaches the first portion  23   a.    
     When the damper  23  is joined to the connection channel unit  24  (the channel plate  51 ) with adhesive, the adhesive may protrude from the joined surface. Even in that case, although the adhesive adheres to the second portion  23   b,  it is not likely to reach the first portion  23   a.  This allows the lower-side supply manifolds  41  and the lower-side return manifolds  42  to obtain the uniformity of effect for inhibiting the pressure fluctuation brought about by the damper  23 , similarly to the above. 
     In this embodiment, since the partitioning wall  51   a  is positioned between both ends in the conveyance direction of the partitioning wall  22   a,  a length of the second portion  23   b  ranging from an edge of an adhesion surface between the second portion  23   b  of the damper  23  and the channel plate  51  to a boundary between the first portion  23   a  and the second portion  23   b  is long. Thus, when the adhesive protrudes from the adhesion surface between the damper  23  and the channel plate  51 , the adhesive protruding therefrom reliably fails to reach the first portion  23   a.    
     In this embodiment, the damper  23  is formed by stacking the film-like first damper member  46  on the second damper member  47 . Thus, for example, the damper  23  having the first portions  23   a  of which thickness is small is easily manufactured by forming the first damper member  46  having a small thickness on the second damper member  47  having a large thickness and then forming the through holes  47   a  in the second damper member  47  through etching. In this embodiment, the thickness (the length in the up-down direction) of the first damper member  46  is not more than 10 μm, which is very thin. It is thus difficult to manufacture the first damper member  46  independently. This embodiment, however, easily produces the damper  23  having the first damper member  46  and the second damper member  47 , as described above. 
     In this embodiment, the supply channel holes  23   d  and  23   e  and the return connection holes  23   f  and  23   g  are formed in the third portions  23   c  of the damper  23 . This makes it possible to form channels communicating with first common channels that are common to the manifolds  41  and  42  without making the head unit large. 
     In this embodiment, each first portion  23   a  is disposed between two third portions  23   c  arranged separately from each other in the width direction. This makes it possible to form the first portions for inhibiting the ink pressure fluctuation in the manifolds  41  and  42  and the channels communicating with the first common channels without making the head unit large. 
     In this embodiment, the number of the upper-side return manifolds  92  is smaller than the number of the lower-side return manifolds  42 , making the structure of channels of the upper-side manifold unit  25  simple. 
     In this embodiment, the length L 2  of the partitioning wall  22   a   2  is longer than the length L 1  of the partitioning wall  22   a   1 . Corresponding to this, the length L 4  of the second portion  23   b   2  joined to the partitioning wall  22   a   2  is longer than the length L 3  of the second portion  23   b   1  joined to the partitioning wall  22   a   1 . This enhances the strength of the head unit  11 . 
     In this embodiment, the first damper chambers  65  are arranged in the conveyance direction, the first communication channels  51   b  extending in the conveyance direction allow the first damper chambers  65  to communicate with each other, and the second communication channels  51   c  allow the first damper chambers  65  disposed at the most upstream side and the most downstream side in the conveyance direction to communicate with the atmosphere, thus allowing the first damper chambers  65  to communicate with the atmosphere. 
     In this embodiment, of the channel plates  51  to  54  forming the connection channel unit  24 , the channel plate  51  has the through holes corresponding to the first communication channels  51   b  and the second communication channels  51   c,  and the channel plates  52  to  54  have no through holes and no recesses corresponding to the first communication channels  51   b  and the second communication channels  51   c.  In that configuration, when the channel plates  51  to  54  are joined to each other with adhesive, the adhesive protruding from the joined surface between the channel plate  51  and the channel plate  52  is likely to flow into the first communication channel(s)  51   b  and the second communication channel(s)  51   c.  On the other hand, the adhesive protruding from the adhesive surfaces between the channel plates  52  to  54  is not likely to flow into the first communication channel(s)  51   b  and the second communication channel(s)  51   c.  The amount of the adhesive flowing into the first communication channel(s)  51   b  and the second communication channel(s)  51   c  is thus reduced. 
     Unlike this embodiment, the first communication channels  51   b  and the second communication channels  51   c  may be arranged at the same position in the width direction. In that case, the strength of portions of the channel plate  51  where the first communication channels  51   b  and the second communication channels  51   c  are formed in the width direction is extremely small, thus damaging the channel plate  51  easily. In order to solve that problem, the first communication channels  51   b  and the second communication channels  51   c  have mutually different positions in the width direction. This hardly damages the channel plate  51 . 
     &lt;Modified Embodiments&gt; 
     Although the embodiment of the present disclosure is explained above, the present disclosure is not limited to the above embodiment, and a variety of modifications are possible without departing from the claims. 
     In the above embodiment, the first communication channels  51   b  and the second communication channels  51   c  have mutually different positions in the width direction. The present disclosure, however, is not limited thereto. The first communication channels  51   b  and the second communication channels  51   c  may have the same position in the width direction. 
     In the above embodiment, the first communication channels  51   b  and the second communication channels  51   c  are formed by the recesses in the channel plate  51 . The present disclosure, however, is not limited thereto. For example, the first communication channels  51   b  and the second communication channels  51   c  may be formed by through holes in the channel plate  51 . In that configuration, the adhesive protruding from every joined surface between the channel plates  51  to  54  is not likely to flow into the first communication channel(s)  51   b  and the second communication channel(s)  51   c.  The amount of the adhesive flowing into the first communication channel(s)  51   b  and the second communication channel(s)  51   c  is thus reduced. 
     In the above embodiment and the first modified embodiment, only the channel plate  51  of the channel plates  51  to  54  has the through holes and recesses corresponding to the first communication channels  51   b  and the second communication channels  51   c.  The present disclosure, however, is not limited thereto. For example, two or more lower-side channel plates of the channel plates  51  to  54  may have the through holes and recesses corresponding to the first communication channels and the second communication channels. 
     In the above embodiment, the first communication channels  51   b  allow the first damper chambers  65  to communicate with each other, and the second communication channels  51   c  allow the first damper chambers  65  disposed at the most upstream side and the most downstream side in the conveyance direction to communicate with the atmosphere. The present disclosure, however, is not limited thereto. For example, no first damper chambers  65  may communicate with each other, and each first damper chamber  65  may communicate with the atmosphere individually. 
     In the above embodiment, second damper chambers may be provided separately from the first damper chambers  65  to hold the adhesive protruding from the joined surface between the damper  23  and the channel plate  51 . 
     For example, in the first modified embodiment depicted in  FIG. 12 , second damper chambers  151  extending in the width direction are arranged in the channel plate  51  at a position upstream of the first damper chamber  65  that is disposed at the most upstream side in the conveyance direction and at a position downstream of the first damper chamber  65  that is disposed at the most downstream side in the conveyance direction. The second damper chambers  151  do not overlap with the manifolds  41  and  42  in the up-down direction. Further, a length L 8  in the conveyance direction of the second damper chambers  151  is shorter than a length L 7  in the conveyance direction of the first damper chambers  65 . The length L 7  is approximately the same as the length in the conveyance direction of the lower-side manifolds  41  and  42 . 
     In the first modified embodiment, two first communication channels  152  extending in the conveyance direction allow the first damper chambers  65  and the two second damper chambers  151  to communicate with each other. Second communication channels  153  extending in the conveyance direction allow the second damper chambers  151  to communicate with the atmosphere. 
     In the configuration according to the first modified embodiment, the adhesive protruding from the joined surface between the damper  23  and the channel plate  51  is held by the second damper chamber(s)  151 . The adhesive is thus not likely to flow into the first damper chamber(s)  65 . 
     The volume of the second damper chambers  151  is not required to be so large provided that the second damper chambers  151  can hold the adhesive protruding from the joined surface. Thus, the channel plate  51  (connection channel unit  24 ) is prevented from having a large size in the conveyance direction by making the length L 8  in the conveyance direction of the second damper chambers  151  shorter than the length L 7  in the conveyance direction of the first damper chambers  65 . 
     In the first modified embodiment, the length L 8  in the conveyance direction of the second damper chambers  151  is shorter than the length L 7  in the conveyance direction of the first damper chambers  65 . The present disclosure, however, is not limited thereto. The length L 8  may be not less than the length L 7 . 
     In the lower-side manifold plate  22  of the above embodiment, the length L 2  of the partitioning wall  22   a   2  is longer than the length L 1  of the partitioning wall  22   a   1 . Corresponding to this, the length L 4  of the second portion  23   b   2  of the damper  23  is longer than the length L 3  of the second portion  23   b   1  of the damper  23 . The present disclosure, however, is not limited thereto. For example, all the partitioning walls  22   a  of the lower-side manifold plate  22  may have the same length in the conveyance direction. Corresponding to this, all the second portions  23   b  of the damper  23  may have the same length in the conveyance direction. 
     In the above embodiment, the number of the upper-side return manifolds  92  is smaller than the number of the lower-side return manifolds  42 , and the return connection channels  63  and  64  connect two lower-side return manifolds  42  and one upper-side return manifold  92 . The present disclosure, however, is not limited thereto. The number of the upper-side return manifolds  92  may be the same as the number of the lower-side return manifolds  42 , and the return connection channels may connect one lower-side return manifold  42  and one upper-side return manifold  92 . 
     In the above embodiment, only the ends in the width direction of the lower-side supply manifolds  41  and the upper-side supply manifolds  91  are connected with each other, and only the ends in the width direction of the lower-side return manifolds  42  and the upper-side return manifolds  92  are connected with each other. The present disclosure, however, is not limited thereto. 
     In a second modified embodiment, as depicted in  FIG. 13 , through holes  162   a  are formed at portions included in a damper  161  (second damper member  47 ) and overlapping in the up-down direction with right portions in the width direction of the manifolds  41  and  42 . Further, through holes  162   b  are formed at portions included in the damper  161  (second damper member  47 ) and overlapping in the up-down direction with left portions in the width direction of the manifolds  41  and  42 . In that configuration, portions of the damper  161  having the through holes  162   a  and  162   b  correspond to first portions  161   a  that are formed by the second damper member  47 . 
     An area of the damper  161  between the through holes  162   a  and  162   b  in the width direction is a third portion  161   b  (in which the first damper member  46  overlaps in the up-down direction with the second damper member  47 ) having no through holes. The damper  161  also has third portions  23   c  similar to those of the damper  23 . 
     In the configuration of the second modified embodiment, two first portions  161   a  are arranged separated from each other in the width direction, and the third portion  161   b  is disposed between the two first portions  161   a  in the width direction. 
     The third portion  161   b  has four supply connection holes  163   a  and eight return connection holes  163   b.  The four supply connection holes  163   a  correspond to the four lower-side supply manifolds  41  (see  FIG. 6A ). Each supply connection hole  163   a  overlaps in the up-down direction with a center portion in the width direction of the corresponding lower-side supply manifold  41 . The eight return connection holes  163   b  correspond to the eight lower-side return manifolds  42  (see  FIG. 6A ). Each return connection hole  163   b  overlaps in the up-down direction with a center portion in the width direction of the corresponding lower-side return manifold  42 . 
     Although the detailed explanation is omitted, the connection channel unit  24  of the second modified embodiment includes, in addition to the configurations similar to the above embodiment, a channel connecting one supply connection hole  163   a  and a center portion in the width direction of one upper-side supply manifold  91  and a channel connecting the two supply connection holes  163   a  and a center portion in the width direction of the upper-side return manifold  92 . Thus, in the second modified embodiment, the lower-side supply manifold  41  and the upper-side supply manifold  91  are connected to each other at three portions in the width direction (the left end, right end, and center portion in the width direction), and the lower-side return manifold  42  and the upper-side return manifold  92  are connected to each other at three portions in the width direction (the left end, right end, and center portion in the width direction). Further, in the connection channel unit  24 , two first damper chambers are provided for each of the manifolds  41  and  42  such that they are arranged in the width direction at an interval. 
     In the second modified embodiment, the first portions  161   a  are arranged separately from each other in the width direction, the third portion  161   b  is provided between the first portions  161   a  in the width direction, and the third portion  161   b  has the supply connection holes  161   a  and the return connection holes  163   b.  This makes it possible to form the first portions for inhibiting the ink pressure fluctuation in the manifolds  41  and  42  and the channels communicating with the manifolds  41  and  42  without making the head unit large. 
     Further, the positional relationship in the damper between the first portions and the third portions having the supply connection holes and the return connection holes is not limited to those described in the above embodiment and the second modified embodiment. For example, the third portion having the supply connection holes and the return connection holes may be disposed only at a portion overlapping in the up-down direction with one end in the width direction of the manifolds  41  and  42 . Or, the third portion having the supply connection holes and the return connection holes may be disposed only at a portion overlapping in the up-down direction with a center portion in the width direction of the manifolds  41  and  42 . 
     In the above embodiment, the connection channels  61  and  62  connecting the lower-side supply manifolds  41  and the upper-side supply manifolds  91  and the connection channels  63  and  64  connecting the lower-side return manifolds  42  and the upper-side return manifolds  92  are formed in the connection channel unit  24  including the first damper chambers  65 . The present disclosure, however, is not limited thereto. For example, a damper member, in which the first damper chambers  65  are formed and the connection channels  61  to  64  are not formed, may be provided instead of the connection channel unit  24 , and the connection channels connecting the lower-side supply manifolds  41  and the upper-side supply manifolds  91  and the connection channels connecting the lower-side return manifolds  42  and the upper-side return manifolds  92  may be formed in another member. 
     In the above embodiment, the length in the up-down direction of the first damper member  46  is not more than 10 μm. The present disclosure, however, is not limited thereto. The length in the up-down direction of the first damper member  46  may exceed 10 μm. In that case, the first damper member  46  may be manufactured independently, and the damper  23  may be manufactured by joining the first damper member  46  to the second damper member  47  having the through holes  47   a.    
     In the above embodiment, the inner wall surface of each through hole  47   a  in the second damper member  47  is the inclined surface  47   b  inclined to the up-down direction. The present disclosure, however, is not limited thereto. For example, the inner wall surfaces of each through hole  47   a  may be surfaces parallel to the up-down direction. For example, when the damper  23  is manufactured by joining the first damper member  46  to the second damper member  47 , the through holes  47   a  having the inner wall surfaces parallel to the up-down direction may be formed in the second damper member  47  through any other method than etching, such as laser processing. 
     In the above embodiment, parts of lower surfaces of the second portions  23   b  overlapping in the up-down direction with the manifolds  41  and  42  may have grooves. In that case, the adhesive protruding from surfaces between the second portions  23   b  and the lower-side manifold plate  22  is held in the grooves, and thus the adhesive is less likely to reach the first portions  23   a.    
     Here, the grooves in the second portions  23   b  are, for example, through holes passing through parts of the second damper member  47  corresponding to the second portions  23   b,  and upper surfaces of the grooves are formed by the first damper member  46 . Or, the grooves in the second portions  23   b  are, for example, recesses formed in lower surfaces of the second damper member  47  corresponding to the second portions  23   b.  In order to allow the grooves to hold a large amount of adhesive to inhibit the adhesive from reaching the first portions  23   a,  the grooves are preferably the through holes. 
     In the above embodiment, parts of the lower surfaces of the second portions  23   b  overlapping in the up-down direction with the manifolds  41  and  42  may have walls extending downward. In that case, the walls block the flow of adhesive protruding from the surfaces between the second portions  23   b  and the lower-side manifold plate  22 , and thus the adhesive is less likely to reach the first portions  23   a.    
     In this example, for example, portions that are included in portions of the second damper member  47  corresponding to the second portions  23   b  and overlap in the up-down direction with the respective partitioning walls  22   a  have recesses of which length in the conveyance direction is longer than the length in the conveyance direction of the partitioning walls  22   a.  In that case, portions that are included in the portions of the second damper member  47  corresponding to the second portions  23   b  and are different from said portions are the walls extending downward. Or, another member corresponding to the walls may be joined to the lower surface of the second damper member  47 . 
     In the above embodiment, the damper  23  is formed by disposing the film-like first damper member  46  on the upper surface of the second damper member  47  having the through holes  47   a.  The present disclosure, however, is not limited thereto. 
     In a third modified embodiment depicted in  FIG. 14 , a damper  171  is formed by disposing the first damper member  46  similar to that of the above embodiment on a lower surface of a second damper member  172 . The second damper member  172  has through holes  172   a  at portions that overlap in the up-down direction with portions of the manifolds  41  and  42  not including both ends in the conveyance direction. The length in the conveyance direction of the through hole  172   a  is shorter toward the lower side (toward the first damper member  46 ). In that case, each inner wall surface of the through hole  172   a  is an inclined surface  172   b  that is inclined to the up-down direction so that the lower side of the inclined surface  172   b  is closer to a center portion in the conveyance direction of the through hole  172   a  than the upper side. The positions of each through hole  172   a  in the width direction and the conveyance direction are similar to the positions of each through hole  47   a  in the above embodiment. 
     In the third modified embodiment, first portions  171   a  of the damper  171  where the first damper member  46  is exposed from the through holes  172   a  are elastically deformed to inhibit the pressure fluctuation in the manifolds  41  and  42 . Second portions  171   b  that are included in portions of the damper  171  where the first damper member  46  overlaps in the up-down direction with the second damper member  172  and are joined to the partitioning walls  22   a  extend in the conveyance direction to positions overlapping in the up-down direction with the manifolds  41  and  42  and are connected to the first portions  171   a.    
     In a fourth modified embodiment depicted in  FIG. 15 , a damper  181  includes the first damper member  46  and the second damper member  47  similar to those of the damper  23  of the above embodiment as well as the second damper member  172  that is similar to that of the third modified embodiment and is disposed on the upper surface of the first damper member  46 . 
     In the fourth modified embodiment, first portions  181   a  of the damper  181  where the first damper member  46  is exposed from the through holes  47   a  and  172   a  are elastically deformed to inhibit the pressure fluctuation in the manifolds  41  and  42 . Second portions  181   b  that are included in portions of the damper  181  where the first damper member  46  overlaps in the up-down direction with the second damper member  47 ,  172  and that are joined to the partitioning walls  22   a  extend in the conveyance direction to positions overlapping in the up-down direction with the manifolds  41  and  42  and are connected to the first portions  181   a.    
     The damper may not be formed by stacking multiple members on top of each other. In a fifth modified embodiment depicted in  FIG. 16 , a damper  191  is formed by one member made by using, for example, a metal material. A lower surface of the damper  191  has recesses  192  at portions that overlap in the up-down direction with portions of the manifolds  41  and  42  not including both ends in the conveyance direction. In that case, each inner wall surface of the recess  192  is an inclined surface  192   a  that is inclined to the up-down direction so that the upper side of the inclined surface  192   a  is closer to a center portion in the conveyance direction of the recess  192  than the lower side. The recesses  192  can be formed, for example, by half etching. The positions of each recess  192  in the width direction and the conveyance direction are similar to those of the through hole  47   a  in the above embodiment. 
     In the fifth modified embodiment, first portions  191   a  of the damper  191  where the length in the up-down direction is shortened by forming the recesses  192  are elastically deformed to inhibit the pressure fluctuation in the manifolds  41  and  42 . Second portions  191   b  that are included in portions of the damper  191  where no recesses  192  are not formed and that are joined to the partitioning walls  22   a  extend in the conveyance direction to positions overlapping in the up-down direction with the manifolds  41  and  42  and are connected to the first portions  191   a.    
     In the fifth modified embodiment, the recesses  192  are formed in the lower surface of the damper  191 . The present disclosure, however, is not limited thereto. Recesses may be formed in an upper surface of the damper  191  instead of the recesses  192 . Alternatively, recesses may be formed in the upper surface of the damper  191  in addition to the recesses  192 . 
     Also in the third to fifth modified embodiments, the adhesive protruding from the joined surface between the damper  191  and the lower-side manifold plate  22  and the adhesive protruding from the joined surface between the damper  191  and the connection channel unit  24  are not likely to reach the first portions. This allows the lower-side supply manifolds  41  and the lower-side return manifolds  42  to obtain the uniformity of effect for inhibiting the pressure fluctuation brought about by the damper. 
     In the above embodiment, the length L 5  of the partitioning wall  51   a   1  and the length L 6  of the partitioning wall  51   a   2  are shorter than the length L 1  of the partitioning wall  22   a   1  and the length L 2  of the partitioning wall  22   a   2 , the partitioning wall  51   a   1  is positioned between the both ends in the conveyance direction of the partitioning wall  22   a   1 , and the partitioning wall  51   a   2  is positioned between the both ends in the conveyance direction of the partitioning wall  22   a   2 . The present disclosure, however, is not limited thereto. For example, the position of at least one end in the conveyance direction of the partitioning wall  22   a   1  may be the same as that of the partitioning wall  51   a   1 , and the position of at least one end in the conveyance direction of the partitioning wall  22   a   2  may be the same as that of the partitioning wall  51   a   2 . Or, the partitioning wall  22   a   1  may be positioned between both ends in the conveyance direction of the partitioning wall  51   a   1 , and the partitioning wall  22   a   2  may be positioned between both ends in the conveyance direction of the partitioning wall  51   a   2 . 
     The first damper chambers and the partitioning walls partitioning the first damper chambers may not be provided. For example, no member may be disposed on the upper surface of the damper and the damper may be exposed to the outside. 
     The ink flowing direction in the above embodiment and modified embodiments may be reversed. Namely, the channel used for returning ink from the pressure chamber  40  to the ink tank  110  in the above embodiment and modified embodiments may be used as the channel for supplying ink from the ink tank  110  to the pressure chamber  40 . The channel used for supplying ink from the ink tank  110  to the pressure chamber  40  in the above embodiment and modified embodiments may be used as the channel for returning ink from the pressure chamber  40  to the ink tank  110 . 
     In the above embodiment and modified embodiments, the present disclosure is applied to the ink-jet head configured to discharge ink from nozzles and the printer including the ink-jet head. The present disclosure, however, is not limited thereto. The present disclosure is applicable to a liquid discharge head configured to discharge any other liquid than ink from nozzles and a liquid discharge apparatus including the liquid discharge head.