Patent Publication Number: US-11390077-B2

Title: Fluid discharge head and recording device

Description:
TECHNICAL FIELD 
     The present disclosure relates to a fluid discharge head and a recording device. 
     BACKGROUND ART 
     As a printing head, for example, there is a fluid discharge head that performs various types of printing by discharging a fluid onto a recording medium. In the fluid discharge head, for example, a large number of discharge holes through which a fluid is discharged are disposed to spread two-dimensionally. Droplets of a fluid discharged through the discharge holes land side by side on a recording medium, and printing is thereby performed (refer to, for example, PTL 1). 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Unexamined Patent Application Publication No. 2009-143168 
     SUMMARY OF INVENTION 
     A fluid discharge head according to one aspect of the present disclosure includes a channel member and a plurality of pressurization portions. The channel member includes a plurality of discharge holes, a plurality of pressurization chambers individually linked to the plurality of discharge holes, a first shared channel linked to the plurality of pressurization chambers, and a second shared channel linked to the plurality of pressurizing chambers. The plurality of pressurization portions individually pressurizes the plurality of pressurization chambers. The first shared channel opens at a plurality of first openings linked to the plurality of pressurization chambers. The first shared channel includes a first connection region that is a range of distribution of the plurality of first openings in a channel direction of the first shared channel. The second shared channel opens at a plurality of second openings linked to the plurality of pressurization chambers. The second shared channel includes a second connection region that is a range of distribution of the plurality of second openings in a channel direction of the second shared channel. The channel member further includes a bypass channel linked to the first connection region and the second connection region to be in parallel with the plurality of pressurization chambers. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1A  is a side view of a recording device including a fluid discharge head according to one embodiment of the present disclosure, and  FIG. 1B  is a plan view thereof. 
         FIG. 2A  is a plan view of a head body, which is a main portion of the fluid discharge head in  FIG. 1 , and  FIG. 2B  is a plan view in which a second channel member is removed from  FIG. 2A . 
         FIG. 3  is an enlarged plan view of a portion of  FIG. 2B . 
         FIG. 4  is an enlarged plan view of a portion of  FIG. 3 . 
         FIG. 5A  is a schematic partial longitudinal sectional view of the head body, and  FIG. 5B  is a longitudinal sectional view of another portion of the head body. 
         FIG. 6  is a schematic perspective view of a portion of a channel of the head body. 
         FIG. 7  is a partially enlarged plan view of a first shared channel and bypass channels. 
         FIG. 8  is a partially enlarged plan view of a second shared channel and bypass channels. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. The drawings used for the following description are schematically drawn, and dimensional ratios and the like in the drawings are not necessarily in coincidence with actual dimensional ratios and the like. To exaggerate shapes and the like, the dimensional ratios and the like are also sometimes not in coincidence with each other between the drawings in which identical members are illustrated. 
     [Overall Configuration of Printer] 
       FIG. 1A  is a schematic side view of a color inkjet printer  1  (hereinafter sometimes simply referred to as the printer), which is a recording device including a fluid discharge head  2  (hereinafter sometimes simply referred to as the head) according to one embodiment of the present disclosure.  FIG. 1B  is a schematic plan view thereof. The printer  1  transports a print sheet P, which is a recording medium, from a feed roller  80 A to a collection roller  80 B, thereby relatively moving the print sheet P with respect to the head  2 . The feed roller  80 A, the collection roller  80 B, and later-described various types of rollers constitute a moving portion  85  that relatively moves the print sheet P and the heads  2 . A control portion  88  controls the head  2  on the basis of print data or the like, which is data of images, characters, and the like to cause a fluid to be discharged toward the print sheet P and droplets to land on the print sheet P, thereby performing recording, such as printing, with respect to the print sheet P. 
     In the present embodiment, the head  2  is fixed to the printer  1 , and the printer  1  is a so-called line printer. An example of another embodiment of the recording device is a so-called serial printer that moves the head  2  by, for example, reciprocating the head  2  in an intersecting direction with respect to a transport direction of the print sheet P, for example, in a substantially orthogonal direction and alternately performs an operation of discharging droplets at an intermediate point of the movement and transportation of the print sheet P. 
     Four head mounting frames  70  (hereinafter sometimes simply referred to as the frames) each having a flat plate shape are fixed to the printer  1  to be substantially parallel to the print sheet P. Each of the frames  70  has five holes (not illustrated), and five heads  2  are mounted at the parts of respective holes. The five heads  2  mounted on one frame  70  constitute one head group  72 . The printer  1  includes four head groups  72 , and twenty heads  2  in total are mounted. 
     The heads  2  mounted on the frames  70  are each configured such that a part that discharges a fluid faces the print sheet P. A distance between the heads  2  and the print sheet P is, for example, about 0.5 to 20 mm. 
     The twenty heads  2  may be directly linked to the control portion  88  or may be connected thereto via a distribution portion that distributes print data. For example, the control portion  88  may send print data to one distribution portion, and the one distribution portion may distribute the print data to the twenty heads  2 . Alternatively, for example, the control portion  88  may distribute print data to four distribution portions corresponding to four head groups  72 , and each distribution portion may distribute the print data to the five heads  2  in a corresponding one of head groups  72 . 
     The head  2  has a long shape elongated in a direction from the near side toward the far side in  FIG. 1A , that is, in the up-down direction in  FIG. 1B . In one head group  72 , three heads are disposed side by side in an intersecting direction with respect to the transport direction of the print sheet P, for example, in a substantially orthogonal direction, and the other two heads  2  are disposed side by side in locations shifted from each other in the transport direction and one each between the three heads  2 . In other expressions, the heads  2  are disposed in zigzag in one head group  72 . The heads  2  are disposed such that ranges that are printable by respective heads  2  are linked to each other in the width direction of the print sheet P, that is, in an intersecting direction with respect to the transport direction of the print sheet P or such that ends of the printable ranges overlap each other. Thus, printing without gaps in the width direction of the print sheet P is enabled. 
     Four head groups  72  are disposed in the transport direction of the print sheet P. A fluid, for example, an ink is supplied from a fluid supply tank (not illustrated) to each of the heads  2 . The heads  2  belonging to one head group  72  is configured to be supplied with an ink of the same color. Thus, printing with inks of four colors can be performed with the four head groups  72 . The colors of the inks to be discharged from respective head groups  72  are, for example, magenta (M), yellow (Y), cyan (C), and black (K). A color image can be printed through printing with such inks controlled by the control portion  88 . 
     The number of the heads  2  mounted on the printer  1  may be one when printing with a single color is to be performed with respect to a range that is printable by one head  2 . The number of the heads  2  included in the head group  72  and the number of the head groups  72  are changeable, as appropriate, depending on a print object and printing conditions. For example, the number of the head groups  72  may be increased to further perform printing with multiple colors. When a plurality of the head groups  72  that perform printing with the same color is disposed and alternately performs printing in the transport direction, the transport speed can be increased even when the heads  2  having the same performance are used. Consequently, a print area per hour can be increased. A plurality of the head groups  72  that performs printing with the same color may be prepared and disposed to be shifted from each other in an intersecting direction with respect to the transport direction, and resolution in the width direction of the print sheet P may be increased. 
     In addition to printing with color inks, printing with a fluid, such as a coating agent, may be performed by the heads  2  uniformly or through patterning to perform surface treatment of the print sheet P. When a recording medium into which a fluid does not easily permeate is used, for example, a coating agent that forms a fluid receptor layer is usable to ease fixing of a fluid. When a recording medium into which a fluid easily permeates is used, another coating agent that forms a fluid permeation suppressing layer is usable to suppress a smear of a fluid from becoming excessively large and to suppress the fluid from mixing with another fluid that has landed next to the fluid. In addition to printing with the heads  2 , the coating agent may be uniformly applied by an applicator  76  controlled by the control portion  88 . 
     The printer  1  performs printing with respect to the print sheet P, which is a recording medium. The print paper P is in a state of being wound by a feed roller  80 A. The print sheet P that is fed out from the feed roller  80 A passes under the heads  2  mounted on the frames  70 , then passes between two transport rollers  82 C, and is eventually collected by the collection roller  80 B. For printing, the transport rollers  82 C are rotated, and the print sheet P is thereby transported at a constant speed and subjected to printing with the heads  2 . 
     Next, details of the printer  1  will be described in an order in which the print sheet P is transported. The print sheet P that has been fed out from the feed roller  80 A passes under the applicator  76  after passing between two guide rollers  82 A. The applicator  76  applies the aforementioned coating agent onto the print sheet P. 
     The print sheet P next enters a head chamber  74  that houses the frames  70  on which the heads  2  are mounted. The head chamber  74  is linked to the outside at a portion, such as a part through which the print sheet P enters and exits. However, the head chamber  74  is generally a space isolated from the outside. In the head chamber  74 , control factors, such as temperature, humidity, atmospheric pressure, and the like are controlled, as necessary, by the control portion  88  and the like. In the head chamber  74 , an influence of disturbance can be reduced compared with the outside where the printer  1  is installed. It is thus possible to reduce the ranges of variations of the above-described control factors compared with the outside. 
     Five guide rollers  82 B are disposed in the head chamber  74 . The print sheet P is transported above the guide rollers  82 B. As viewed from a side, the five guide rollers  82 B are disposed in a shape protruding at a center portion toward a direction where the frames  70  are disposed. Consequently, the print sheet P that is transported above the five guide rollers  82 B has an arc shape as viewed from a side. The print sheet P between the guide rollers  82 B is stretched to be planar in response to application of tension to the print sheet P. One frame  70  is disposed between two guide rollers  82 B. The frames  70  are installed at slightly different angles to be parallel to the print sheet P that is transported under the frames  70 . 
     The print sheet P that has exited to the outside from the head chamber  74  passes between the two transport rollers  82 C, passes inside a dryer  78 , passes between two guide rollers  82 D, and is collected by the collection roller  80 B. The transport speed of the print sheet P is, for example, 100 m/min. Each of the rollers may be controlled by the control portion  88  or may be manually operated by a person. 
     Due to drying by the dryer  78 , it is possible to suppress, at the collection roller  80 B, layers of the print sheet P wound to be superposed on each other from easily adhering to each other and an undried fluid from being rubbed. To perform printing at a high speed, drying is also to be performed quickly. To perform drying quickly, the dryer  78  may perform drying sequentially by multiple drying methods or may perform drying by multiple drying methods in combination. Drying methods to be used in such a situation are, for example, blowing of warm air, irradiation of an infrared ray, and contact with a heated roller. When irradiation of an infrared ray is performed, an infrared ray in a specific frequency range may be applied to perform drying quickly while reducing damage to the print sheet P. When the print sheet P is made to be in contact with a heated roller, the print sheet P may be transported along the cylindrical surface of the roller to thereby increase a period of time during which heat is transmitted. A range in which the print sheet P is transported along the cylindrical surface of the roller is preferably ¼ or more the circumference of the cylindrical surface of the roller and more preferably ½ or more the circumference of the cylindrical surface of the roller. When printing with a UV curable ink or the like is performed, a UV irradiation light source may be disposed as an alternative to the dryer  78  or in addition to the dryer  78 . The UV irradiation light source may be disposed between the frames  70 . 
     The printer  1  may include a cleaning portion that cleanses the heads  2 . The cleaning portion performs cleansing by, for example, wiping and capping. In wiping, for example, a surface of a part through which a fluid is to be discharged, for example, a discharge hole surface  4 - 2  (described later) is rubbed with a flexible wiper to thereby remove a fluid adhering to the surface. Cleansing by capping is performed, for example, as follows. First, a cap is placed (this is called capping) so as to cover a part through which a fluid is to be discharged, for example, the discharge hole surface  4 - 2 , thereby forming a space substantially sealed by the discharge hole surface  4 - 2  and the cap. In such a state, discharging of a fluid is repeated, thereby removing a fluid having higher viscosity than in a normal state, foreign matters, and the like that have been stuffed in a discharge hole  8  (described later). As a result of capping being performed, it is possible to suppress the fluid during cleansing from easily dispersing in the printer  1  and the fluid from easily adhering to the print sheet P and a transport mechanism, such as the rollers. The cleansed discharge hole surface  4 - 2  may be further subjected to wiping. Cleansing by wiping and capping may be performed by a person through manual operation of a wiper and a cap mounted on the printer  1  or may be performed automatically by the control portion  88 . 
     In addition to the print sheet P, a rolled fabric or the like may be employed as a recording medium. As an alternative to transporting the print sheet P directly, the printer  1  may transport a transport belt directly and transport a recording medium placed on the transport belt. As a result, a piece of paper, a cut fabric, a wood material, a tile, and the like can be recording media. The heads  2  may discharge a fluid containing conductive particles, thereby printing a wiring pattern and the like of an electronic device. The heads  2  also may discharge a predetermined amount of a fluid chemical agent or a fluid containing a chemical agent toward a reaction container and the like to cause a reaction, thereby producing a chemical product. 
     A position sensor, a speed sensor, a temperature sensor, and the like may be mounted on the printer  1 , and the control portion  88  may control each portion of the printer  1  in accordance with a state of each portion of the printer  1  known from information from each sensor. For example, when the temperature of the heads  2 , the temperature of the fluid in the fluid supply tank that supplies the fluid to the heads  2 , a pressure applied by the fluid in the fluid supply tank to the heads  2 , and the like influence the discharging characteristics, that is, the discharge amount, the discharge speed, and the like of the fluid to be discharged, a drive signal for discharging the fluid may be changed in accordance with information thereof. 
     [Fluid Discharge Head] 
     Next, the fluid discharge head  2  according to one embodiment of the present disclosure will be described.  FIG. 2A  is a plan view of a head body  2   a , which is a main portion of the head  2  illustrated in  FIG. 1 .  FIG. 2B  is a plan view of a state in which a second channel member  6  is removed from the head body  2   a .  FIG. 3  is an enlarged plan view of the head body  2   a  in a range indicated by the one-dot chain line in  FIG. 2B .  FIG. 4  is an enlarged plan view of the head body  2   a  in a range indicated by the one-dot chain line in  FIG. 3 .  FIG. 5A  is a schematic partial longitudinal sectional view of the head body  2   a . In  FIG. 5A , to illustrate a linked state of channels, the channels that are not actually present on the same longitudinal section are drawn as if present on the same longitudinal section. In  FIG. 5B , a signal transmission portion  60 , which is not drawn in  FIG. 2A , is drawn.  FIG. 6  is a schematic perspective view of a portion of a channel in the head body  2   a.    
     Each figure is drawn as follows for easy understanding of the drawings. In  FIGS. 2 to 4 , channels and the like that are present below other components and that should be drawn with broken lines are drawn with solid lines.  FIG. 4  is divided by a two-dot chain line to left and right. On the left side of the two-dot chain line, a channel from a first shared channel  20  to the discharge hole  8  is drawn. On the right side of the two-dot chain line, a channel from the discharge hole  8  to a second shared channel  22  is drawn. Regarding each of four pressurization chambers  10  in an upper left part of  FIG. 4 , an individual electrode  44  and a connection electrode  46  are also drawn. 
     The head  2  may include, in addition to the head body  2   a , a housing, a driver IC, a wiring substrate, and the like. The head body  2   a  includes a first channel member  4 , a second channel member  6  that supplies a fluid to the first channel member  4 , and a piezoelectric actuator substrate  40  in which a displacement element  50 , which is a pressurization portion, is incorporated. The head body  2   a  has a flat plate shape elongated in one direction. The direction is sometimes referred to as the longitudinal direction. The second channel member  6  functions as a support member that supports the structure of the head body  2   a . The head body  2   a  is fixed at each of both ends in the longitudinal direction of the second channel member  6  to the frame  70 . 
     [First Channel Member] 
     The first channel member  4  that constitutes the head body  2   a  has a flat plate shape and has a thickness of about 0.5 to 2 mm. A large number of the pressurization chambers  10  are disposed side by side in a planar direction at a pressurization chamber surface  4 - 1 , which is one surface of the first channel member  4 . At the discharge hole surface  4 - 2  of the first channel member  4  opposite to the pressurization chamber surface  4 - 1 , a large number of the discharge holes  8  through which a fluid is to be discharged are disposed side by side in a planar direction. The discharge holes  8  are respectively linked to the pressurization chambers  10 . Hereinafter, description will be provided on the basis that the pressurization chamber surface  4 - 1  is located above the discharge hole surface  4 - 2 . 
     At the first channel member  4 , a plurality of the first shared channels  20  and a plurality of the second shared channels  22  are disposed to extend in a first direction. Hereinafter, the first shared channel  20  and the second shared channel  22  are sometimes collectively referred to as the shared channels. Each first shared channel  20  and each second shared channel  22  are disposed to be superposed on each other at at least portions thereof. The first shared channel  20  and the second shared channel  22  are superposed on each other, for example, at 80% or more of the widths thereof or superposed at all of the widths. An intersecting direction with respect to the first direction is denoted by a second direction. Eight first shared channels  20  and eight second shared channels  22  are disposed side by side in the second direction. The first direction is identical to the longitudinal direction of the head body  2   a . A direction opposite to the first direction is denoted by a third direction, and a direction opposite to the second direction is denoted by a fourth direction. In some of the figures, the first to fourth directions are indicated by D 1  to  4 . 
     The pressurization chambers  10  linked to the first shared channels  20  and the second shared channels  22 , and the discharge holes  8  linked to the pressurization chambers  10  are disposed side by side along both sides of the first shared channels  20  and the second shared channels  22 . The pressurization chambers  10  linked to the first shared channels  20  and the second shared channels  22  constitute two lines of pressurization chamber lines  11 A on one side of the shared channels, that is, four lines in total on both sides thereof. The discharge holes  8  linked to the first shared channels  20  and the second shared channels  22  constitute two lines of discharge hole lines  9 A on one side of the shared channels, that is, four lines in total on both sides thereof. There are eight first shared channels  20  and eight second shared channels  22 . Thus, there are 32 lines of the pressurization chamber lines  11 A as a whole, and there are also 32 lines of the discharge hole lines  9 A as a whole. 
     Each first shared channel  20  and the four lines of the pressurization chambers  10  disposed side by side on both sides thereof are linked to each other via a first relay channel  12 . Each second shared channel  22  and the four lines of the pressurization chambers  10  disposed side by side on both sides thereof are linked to each other via a second relay channel  14 . 
     Due to such a configuration, at the first channel member  4 , a fluid that is supplied to the first shared channels  20  flows into the pressurization chambers  10  disposed side by side along the first shared channels  20 . A portion of the fluid that has flowed into the pressurization chambers  10  is discharged through the discharge holes  8 . The other portion of the fluid flows into the second shared channels  22  that are disposed to be superposed on the first shared channels  20  and is drained to the outside from the first channel member  4 . That is, the first shared channels  20  are channels in which a fluid to be supplied to the pressurization chambers  10  flows. The first shared channels  20  can be called supply channels. The second shared channels  22  are channels in which the fluid collected from the pressurization chambers  10  flows. The second shared channels  22  can be called collection channels. The flow of supplying and collecting the fluid, including the flows described below, may be reversed. 
     The first shared channels  20  are disposed to be superposed on the second shared channels  22 . Outside a range to which the first relay channel  12  is linked, each first shared channel  20  opens at openings  20   b  in both ends in the first direction and the third direction to the outside of the first channel member  4 . Outside a range to which the second relay channel  14  is linked and on the outer side of the openings  20   b  of the first shared channel  20 , each second shared channel  22  opens at openings  22   b  in both ends in the first direction and the third direction to the outside of the first channel member  4 . Due to the openings  22   b  of the second shared channel  22  on the lower side being on the outer side of the openings  20   b  of the first shared channel  20  on the upper side, the space efficiency is improved. The entirety, excluding both ends, of a second shared channel body  22   a  is on the lower side of the entirety, excluding both ends, of a first shared channel body  20   a.    
     Substantially identical amounts of a fluid is supplied through the openings  20   b  at the first direction end and the openings  20   b  at the third direction end of each first shared channel  20  and flows toward the center of the first shared channel  20 . When the amount of the fluid discharged through the discharge hole  8  linked to one first shared channel  20  and one second shared channel  22  is substantially constant regardless of the location, the flow in the first shared channel  20  becomes slower toward the center and becomes 0 (zero) near the center. Conversely, the flow in the second shared channel  22  is 0 (zero) near the center and becomes faster toward the outer side. 
     The head  2  is used to record various objects. Thus, distribution of the amount of a fluid discharged through the discharge holes  8  linked to one first shared channel  20  and one second shared channel  22  is various. When the discharge amount through the discharge holes  8  at the first direction end is large, a location where the flow becomes 0 (zero) is nearer to the first direction end than the center. Conversely, when the discharge amount through the discharge holes  8  at the third direction end is large, the location where the flow becomes 0 (zero) is nearer to the third direction end than the center. Thus, the distribution of discharging changes depending on an object to be recorded, and the location where the flow becomes 0 (zero) is thereby moved. Consequently, even when the flow becomes 0 (zero) and the fluid remains at a certain moment, remaining of the fluid in the location is eliminated by the change of the distribution of discharging. It is thus possible to suppress sedimentation of pigments, adhesion of a fluid, and the like from easily occurring as a result of the fluid continuing to remain in the same location. 
     Due to an influence of a pressure loss, a pressure to be applied to, of the first relay channel  12  linked to the first shared channel  20 , a part near the first shared channel  20  changes depending on a location (mainly, a location in the first direction) where the first relay channel  12  is linked to the first shared channel  20 . Due to an influence of a pressure loss, a pressure to be applied to a part near the second relay channel  14  linked to the second shared channel  22  changes depending on a location (mainly, a location in the first direction) where the second relay channel  14  is linked to the second shared channel  22 . When the pressure of the fluid in one discharge hole  8  is caused to be substantially 0 (zero), the above-described pressure change changes symmetrically. It is thus possible to cause the pressure of the fluid to be substantially 0 (zero) in all of the discharge holes  8 . 
     A lower surface of each first shared channel  20  is a damper  28 A. A surface of the damper  28 A opposite to a surface thereof facing the first shared channel  20  faces a damper chamber  29 A. The damper chamber  29 A contains a gas, such as air, and has a volume that changes in response to a pressure applied from the first shared channel  20 . The damper  28 A can vibrate in response to a change in the volume of the damper chamber  29 A. As a result of the vibration attenuating, a pressure variation generated in the first shared channel  20  can be attenuated. The provision of the damper  28 A can reduce the pressure variation of the resonance and the like of the fluid in the first shared channel  20 . 
     A lower surface of each second shared channel  22  is a damper  28 B. A surface of the damper  28 B opposite to a surface thereof facing the second shared channel  22  faces a damper chamber  29 B. As with the first shared channel, the provision of the damper  28 B can reduce the pressure variation of the resonance and the like of the fluid in the second shared channel  22 . 
     At one discharge hole line  9 A, the discharge holes  8  are disposed at intervals of 50 dpi (about 25.4 mm/50). There are 32 lines of the discharge hole lines  9 A. The discharge holes  8  included in the discharge hole lines  9 A are disposed to be shifted from each other in the first direction. Consequently, the discharge holes  8  are disposed at intervals of 1600 dpi as a whole. 
     Specifically, in  FIG. 3 , when the discharge holes  8  are projected in a direction orthogonal to the first direction, a total of 32 of the discharge holes  8  are projected in a range of a virtual straight line R. The discharge holes  8  are disposed side by side at intervals of 1200 dpi within the virtual straight line R. Consequently, when the print sheet P is transported in a direction orthogonal to the virtual straight line R and printed, printing with a resolution of 1200 dpi can be performed. 
     [Second Channel Member] 
     The second channel member  6  is joined to the pressurization chamber surface  4 - 1  of the first channel member  4 . The second channel member  6  includes a first integrated channel  24  that supplies a fluid to the first shared channel  20 , and a second integrated channel  26  that collects the fluid in the second shared channel  22 . The thickness of the second channel member  6  is thicker than the thickness of the first channel member  4  and is about 5 to 30 mm. 
     The second channel member  6  is joined in a region where the piezoelectric actuator substrate  40  is not connected, in the pressurization chamber surface  4 - 1  of the first channel member  4 . Specifically, the second channel member  6  is joined to surround the piezoelectric actuator substrate  40 . Consequently, it is possible to suppress a portion of the discharged fluid from becoming mist and adhering to the piezoelectric actuator substrate  40 . The first channel member  4  is fixed at the periphery such that the piezoelectric actuator substrate  40  is surrounded. Thus, the first channel member  4  vibrates with the drive of the displacement elements  50  and can reduce occurrence of resonance. 
     An opening  24   b  that opens in the upper surface of the second channel member  6  is disposed at an end of the first integrated channel  24  in the third direction. The first integrated channel  24  branches in an intermediate location into two channels. One of the channels is linked to the openings  20   b  of the first shared channels  20  at the third direction end. The other one is linked to the openings  20   b  of the first shared channels  20  at the first direction end. An opening  26   b  that opens in the upper surface of the second channel member  6  is disposed at an end of the second integrated channel  26  in the first direction. The second integrated channel  26  branches in an intermediate location into two channels. One of the channels is linked to the openings  22   b  of the second shared channels  22  at the first direction end. The other one is linked to the openings  22   b  of the second shared channels  22  at the third direction end. To perform printing, a fluid is supplied from the outside into the opening  24   b  of the first integrated channel  24 . The fluid that is not discharged is collected through the opening  26   b  of the second integrated channel  26 . 
     In the second channel member  6 , a through hole  6   a  vertically passing through the second channel member  6  is disposed. The signal transmission portion  60 , such as a FPC (flexible printed circuit), that transmits a drive signal for driving the piezoelectric actuator substrate  40  passes through the through hole  6   a.    
     By disposing the first integrated channel  24  at the second channel member  6 , which differs from the first channel member  4  and which is thicker than the first channel member  4 , it is possible to increase the sectional area of the first integrated channel  24 . Consequently, it is possible to reduce a difference in pressure loss due to a difference in the location where the first integrated channel  24  and the first shared channels  20  are linked to each other. The channel resistance of the first integrated channel  24  is preferably less than or equal to 1/100 the channel resistance of the first shared channels  20 . The channel resistance of the first integrated channel  24  is more exactly channel resistance in a region in the first integrated channel  24  where the first integrated channel  24  is linked to the first shared channels  20 . 
     By disposing the second integrated channel  26  at the second channel member  6 , which differs from the first channel member  4  and which is thicker than the first channel member  4 , it is possible to increase the sectional area of the second integrated channel  26 . Consequently, it is possible to reduce a difference in pressure loss due to a difference in the location where the second integrated channel  26  and the second shared channels  22  are linked to each other. The channel resistance of the second integrated channel  26  is preferably less than or equal to 1/100 the channel resistance of the second shared channels  22 . The channel resistance of the second integrated channel  26  is more exactly channel resistance in a range in the second integrated channel  26  where the second integrated channel  26  is linked to the first integrated channel  24 . 
     The first integrated channel  24  is disposed at one end of the second channel member  6  in the short direction. The second integrated channel  26  is disposed at the other end of the second channel member  6  in the short direction. The channels are structured to each extend toward the first channel member  4  and to be linked to the first shared channels  20  and the second shared channels  22 , respectively. Such a structure can increase the sectional areas of the first integrated channel  24  and the second integrated channel  26  and reduce the channel resistance. In such a structure, the first channel member  4  is fixed at the periphery thereof by the second channel member  6  and can increase rigidity. Moreover, with such a structure, the through hole  6   a  through which the signal transmission portion  60  passes can be disposed. 
     A groove that functions as the first integrated channel (first integrated channel body  24   a ) and a groove that functions as the second integrated channel  26  (second integrated channel body  26   a ) are disposed on the lower surface of the second channel member  6 . A portion of the lower surface of the groove that functions as the first integrated channel body  24   a  is covered by the upper surface of the first channel member  4 . The other portion of the lower surface is linked to the openings  20   b  of the first shared channels  20 . A portion of the lower surface of the groove that functions as the second integrated channel body  26   a  is covered by the upper surface of the first channel member  4 . The other portion of the lower surface is linked to the openings  22   b  of the second shared channels  22 . 
     The first integrated channel  24  and the second integrated channel  26  may be each disposed with a damper so that supplying or draining of a fluid is stable with respect to the variation of the discharge amount of the fluid. Filters may be disposed in inner portions of the first integrated channel  24  and the second integrated channel  26  or between the first channel member  4  and the first shared channels  20  or the second shared channels  22  to suppress foreign matter and air bubbles from easily entering the first channel member  4 . 
     [Arrangement of Drive System] 
     The upper surface of the second channel member  6  is covered by a metallic housing or the like. The signal transmission portion  60  is electrically connected to, for example, a wiring substrate in a housing. The wiring substrate and the control portion  88  are electrically connected to each other by a cable or the like. A driver IC that drives the displacement elements  50  may be mounted on the signal transmission portion  60 . It is possible to dissipate heat generated in the driver IC to the outside by making the driver IC be in contact with a metallic housing or with a member that causes heat to be easily transmitted to the housing. 
     The piezoelectric actuator substrate  40  including the displacement elements  50  is joined to the pressurization chamber surface  4 - 1 , which is the upper surface of the first channel member  4 . Each displacement element  50  is disposed to be located above the pressurization chambers  10 . The piezoelectric actuator substrate  40  occupies a region of a shape substantially identical to the shape of a pressurization chamber group constituted by the pressurization chambers  10 . An opening of each pressurization chamber  10  is closed by the piezoelectric actuator substrate  40  being joined to the pressurization chamber surface  4 - 1  of the first channel member  4 . The piezoelectric actuator substrate  40  has a rectangular shape elongated in the same direction as the head body  2   a.    
     The signal transmission portion  60  that supplies a signal to each displacement element  50  is connected to the piezoelectric actuator substrate  40 . The second channel member  6  has the through hole  6   a  at the center thereof. The through hole  6   a  passes through the second channel member  6  vertically. The signal transmission portion  60  is electrically linked to the control portion  88  through the signal transmission portion  60 . When the signal transmission portion  60  has a shape that extends in the short direction from an end of one long side of the piezoelectric actuator substrate  40  toward an end of the other long side thereof such that wires disposed at the signal transmission portion  60  extend in the short direction and are arranged side by side in the longitudinal direction, a distance between the wires can be increased. 
     [Layered Structure of First Channel Member] 
     The first channel member  4  has a layered structure in which a plurality of plates is layered. In the first channel member  4 , a plate  4   a  is disposed near the pressurization chamber surface  4 - 1 , and plates  4   b  to  4   o  are sequentially layered under the plate  4   a . The plate  4   a  that has a hole serving as a side wall of the pressurization chambers  10  is sometimes called the cavity plate  4   a . The plates  4   f ,  4   g ,  4   h ,  4   i ,  4   l , and  4   m  that have holes serving as side walls of the shared channels are sometimes called the manifold plates  4   f ,  4   g ,  4   h ,  4   i ,  4   l , and  4   m . The plate  4   o  in which the discharge holes  8  open is sometimes called the nozzle plate  4   o . Each plate has a large number of holes and grooves. The holes and the grooves are formed by, for example, preparing each of the plates with metal and etching the plate. The thickness of each of the plates is about 10 to 300 μm, which increases accuracy in forming holes to be formed. The plates are aligned and layered such that these holes are in communication with each other and constitute the first shared channels  20  and the like. 
     In the pressurization chamber surface  4 - 1  of the flat plate-shaped first channel member  4 , a pressurization chamber body  10   a  opens and the piezoelectric actuator substrate  40  is joined. In addition, the openings  20   b  through which a fluid is to be supplied to the first shared channels  20  and the openings  22   b  through which the fluid is to be collected from the second shared channels  22  open in the pressurization chamber surface  4 - 1 . In the discharge hole surface  4 - 2 , which is a surface opposite to the pressurization chamber surface  4 - 1 , of the first channel member  4 , the discharge holes  8  open. 
     [Channels Relating to Discharging] 
     As structures for discharging a fluid, the pressurization chambers  10  and the discharge holes  8  are present. Each pressurization chamber  10  is defined by the pressurization chamber body  10   a  that faces the displacement elements  50 , and a partial channel  10   b  that links the pressurization chamber body  10   a  to the discharge holes. The pressurization chamber body  10   a  is in the cavity plate  4   a . The partial channel  10   b  is defined as a result of the holes in the plates  4   b  to  4   n  overlapping each other and being closed (at a part other than the discharge holes  8 ) by the nozzle plate  4   o.    
     The first relay channel  12  is linked to the pressurization chamber body  10   a . The first relay channel  12  is linked to the first shared channels  20 . The first relay channel has a circular hole passing through the plate  4   b , an elongated through groove extending through the plate  4   c  in the planar direction, and a circular hole passing through the plates  4   d  and  4   e.    
     The second relay channel  14  is linked to the partial channel  10   b . The second relay channel  14  is linked to the second shared channels  22 . The second relay channel  14  includes an individual channel  14   a  linked to one pressurization chamber  10 , and a connection channel  14   b  linked also to the other pressurization chambers  10 . In the present embodiment, two individual channels  14   a  respectively linked to two pressurization chambers  10  are combined with each other, become one connection channel  14   b , and are then linked to the second shared channels  22 . The number of the connection channels  14   b  linked to one second shared channel  22  is plural. The number of the connection channels  14   b  linked to one second shared channel  22  is half the number of the pressurization chambers  10  linked to one second shared channel  22 . After being bound into the connection channel  14   b , a plurality of individual channels  14   a  is linked to the second shared channels  22 , and the space efficiency is thereby improved. The number of the individual channels  14   a  linked to the connection channel  14   b  may be three or more. 
     It may be regarded that two second relay channels  14  are disposed for two pressurization chambers  10  and share one connection channel  14   b  or regarded that one second relay channel  14  is disposed for two pressurization chambers  10  and one second relay channel  14  includes two individual channels  14   a . The present embodiment will be described by using mainly expressions based on the former. 
     The first shared channels  20  are each defined as a result of the holes in the plates  4   f  to  4   i  overlapping each other with the upper end thereof being closed by the plate  4   e  and the lower end thereof being closed by the plate  4   j . The second shared channels  22  are each defined as a result of the holes in the plates  4   l  and  4   m  overlapping each other with the upper end thereof being closed by the plate  4   k  and the lower end thereof being closed by the plate  4   n.    
     The flow of a fluid will be described in short as follows. A fluid supplied to the first integrated channel  24  enters the pressurization chambers  10  by sequentially passing through the first shared channel  20  and the first relay channel  12 , and a portion of the fluid is discharged through the discharge hole  8 . The fluid that is not discharged enters the second shared channel  22  through the second relay channel  14 , then enters the second integrated channel  26 , and is drained to the outside of the head body  2   a.    
     [Structure of Piezoelectric Actuator Substrate] 
     The piezoelectric actuator substrate  40  has a layered structure constituted by two piezoelectric ceramic layers  40   a  and  40   b , which are piezoelectric bodies. These piezoelectric ceramic layers  40   a  and  40   b  each have a thickness of about 20 In other words, the thickness of the piezoelectric actuator substrate  40  between the upper surface of the piezoelectric ceramic layer  40   a  and the lower surface of the piezoelectric ceramic layer  40   b  is about 40 The ratio between the thicknesses of the piezoelectric ceramic layer  40   a  and the piezoelectric ceramic layer  40   b  is 3:7 to 7:3 and, preferably, 4:6 to 6:4. The piezoelectric ceramic layers  40   a  and  40   b  each extend across a plurality of the pressurization chambers  10 . The piezoelectric ceramic layers  40   a  and  40   b  are constituted by, for example, a ferroelectric ceramic material of lead zirconate titanate (PZT), NaNbO 3 , BaTiO 3 , (BiNa)NbO 3 , BiNaNb 5 O 15 , or the like. In the present embodiment, the piezoelectric ceramic layer  40   b  acts as a vibration plate and does not directly piezoelectrically deforms. As a vibration plate, non-piezoelectric ceramics, metal plates, or the like may be used instead of the piezoelectric ceramic layer  40   b.    
     The piezoelectric actuator substrate  40  includes a shared electrode  42  constituted by a metal material of Ag—Pd or the like and the individual electrode  44  constituted by a metal material of Au or the like. The thickness of the shared electrode  42  is about 2 μm. The thickness of the individual electrode  44  is about 1 μm. 
     The individual electrode  44  is disposed in each of locations facing the pressurization chambers  10  in the upper surface of the piezoelectric actuator substrate  40 . The individual electrode  44  includes an individual electrode body  44   a  having a planar shape slightly smaller than that of the pressurization chamber body  10   a  and has a shape substantially similar to that of the pressurization chamber body  10   a , and an extraction electrode  44   b  extracted from the individual electrode body  44   a . The extraction electrode  44   b  includes a part extracted at one end to the outside of a region facing the pressurization chamber  10 . The connection electrode  46  is disposed at the extracted part. The connection electrode  46  is, for example, a conductive resin containing conductive particles, such as silver particles and has a thickness of about 5 to 200 μm. The connection electrode  46  is electrically joined to an electrode disposed at the signal transmission portion  60 . 
     A drive signal is to be supplied to the individual electrode  44  from the control portion  88  through the signal transmission portion  60 , which will be described later in detail. The drive signal is supplied periodically in synchronization with the transport speed of the print sheet P. 
     The shared electrode  42  is in a region between the piezoelectric ceramic layer  40   a  and the piezoelectric ceramic layer  40   b  substantially throughout the entire surface in the surface direction. That is, the shared electrode  42  extends to cover all of the pressurization chambers  10  in the region facing the piezoelectric actuator substrate  40 . The shared electrode  42  is linked via a through conductor passing through the piezoelectric ceramic layer  40   a  to a shared-electrode-use surface electrode (not illustrated) on the piezoelectric ceramic layer  40   a  in a location avoiding an electrode group constituted by the individual electrodes  44 . The shared electrode  42  is grounded via the shared-electrode-use surface electrode and retained at a ground potential. As with the individual electrode  44 , the shared-electrode-use surface electrode is connected to the control portion  88  directly or indirectly. 
     The piezoelectric ceramic layer  40   a  includes a part between the individual electrode  44  and the shared electrode  42 . The part is polarized in the thickness direction and serves as the displacement element  50  that has a unimorph structure and that is displaced when a voltage is applied to the individual electrode  44 . Specifically, with the individual electrode  44  caused to have a potential that differs from the potential of the shared electrode  42 , when an electric field is applied to the piezoelectric ceramic layer  40   a  in the polarized direction, a part to which the electric field is applied acts as an active part that is to be distorted by a piezoelectric effect. In this configuration, when the individual electrode  44  is caused to have a predetermined positive or negative potential with respect to the shared electrode  42  by the control portion  88  so that the electric field and the polarization are in the same direction, a part (active part) of the piezoelectric ceramic layer  40   a  between the electrodes contracts in the surface direction. As the piezoelectric ceramic layer  40   b , which is an inactive layer, does not receive the influence of the electric field, the piezoelectric ceramic layer does not contract spontaneously and attempts to restrict the deformation of the active part. As a result, a difference in distortion in the polarized direction is generated between the piezoelectric ceramic layer  40   a  and the piezoelectric ceramic layer  40   b , which causes the piezoelectric ceramic layer  40   b  to deform (unimorph deformation) to protrude toward the pressurization chamber  10 . 
     [Discharging Operation] 
     Next, an operation of discharging a fluid will be described. The displacement elements  50  are driven (displaced) by the drive signal supplied to the individual electrode  44  via the driver IC and the like in response to the control by the control portion  88 . In the present embodiment, various drive signals are usable to discharge a fluid. Here, a so-called pulling driving method will be described. 
     The individual electrode  44  is previously caused to have a higher potential (hereinafter referred to as the high potential) than the shared electrode  42 . The individual electrode  44  is caused to have the same potential (hereinafter referred to as the low potential) as the shared electrode  42  every time when discharging is requested and is then caused to have the high potential again at a predetermined time. Consequently, at the time when the individual electrode  44  is caused to have the low potential, the piezoelectric ceramic layers  40   a  and  40   b  (start to) return to the original (flat) shapes, and the volume of each pressurization chamber  10  increases compared with that in an initial state (a state in which the potentials of the two electrodes differ from each other). Consequently, a negative pressure is applied to the fluid in each pressurization chamber  10 . Then, the fluid in each pressurization chamber  10  starts to vibrate at a specific period of vibration. Specifically, first, the volume of each pressurization chamber  10  starts to increase, and the negative pressure gradually decreases. Next, the volume of each pressurization chamber  10  becomes maximum, and the pressure becomes substantially zero. Next, the volume of each pressurization chamber  10  starts to decrease, and the pressure increases. Then, at a time when the pressure becomes substantially maximum, the individual electrode  44  is caused to have the high potential. Thus, a vibration applied first and a vibration applied subsequently overlap, and a larger pressure is applied to the fluid. The pressure is propagated in the partial channel  10   b  and causes the fluid to be discharged through the discharge holes  8 . 
     In other words, it is possible to discharge droplets by supplying a drive signal of a pulse that causes the individual electrode  44  to have the low potential, based on the high potential, for a certain period to the individual electrode  44 . When the width of the pulse is set to an AL (acoustic length), which is a period of time half the specific period of vibration of the fluid in each pressurization chamber  10 , it is possible in principle to maximize the discharge speed and the discharge amount of the fluid. The specific period of vibration of the fluid in each pressurization chamber  10  is greatly influenced by the physical properties of the fluid and the shape of each pressurization chamber  10 . In addition to those, the physical properties of the piezoelectric actuator substrate  40  and the characteristics of the channels linked to the pressurization chambers  10  also influence the specific period of vibration. 
     [Details of Relay Channel] 
     To supply a fluid to be discharged, each first shared channel  20  preferably has a large sectional area. To cause a circulating fluid to flow, each second shared channel  22  also preferably has a sectional area that is large to a certain extent. Meanwhile, when the sectional areas of the shared channels are increased, the width of the head body  2   a  in the short direction increases, which increases a range in which the discharge holes  8  are distributed in the short direction. When the distributed range of the discharge holes  8  in the short direction increases, printing accuracy when the installation angle of the head  2  is shifted so as to rotate in the planar direction is greatly degraded, which is not desirable. 
     The arrangement interval of the shared channels is reduced to increase the sectional areas of the shared channels without greatly increasing the width of the head body  2   a  in the short direction. When the space efficiency of the arrangement of the channels between the shared channels is improved, the arrangement interval of the shared channels can be reduced. The second relay channels  14  are channels connected near the discharge holes  8  of the pressurization chambers  10 . Thus, when the space efficiency of the arrangement of the second relay channels  14  is improved, the arrangement interval of the shared channels can be reduced. 
     To reduce differences in discharging characteristics among droplets discharged through the discharge holes  8 , it is preferable that differences in channel characteristics among the second relay channels  14  be small. Therefore, it is preferable that the second relay channels  14  be designed to have substantially identical sectional areas and substantially identical lengths. In addition, the second relay channels  14  preferably have channel characteristics suitable for discharging. There are a specific sectional area and a specific length that are suitable to have the channel characteristics. If the purpose is only simply improve the space efficiency, for example, a channel that linearly links with the shortest distance may be disposed. It is however difficult with such a channel to obtain the channel characteristics described above. 
     Thus, the pressurization chambers  10  and the second shared channels  22  are not linked to each other by a completely individual channel, and a plurality of channels linked to the pressurization chambers  10  is bound together and then linked to the second shared channels  22 . Specifically, the individual channels  14   a  to each of which only one pressurization chamber  10  is linked are bound into the connection channels  14   b  and then linked to the second shared channels  22 . In other expressions, a plurality of individual channels  14   a  is linked to one connection channel  14   b . That is, a plurality of individual channels  14   a  is connected to an end at the upstream of each connection channel  14   b  constituting the second relay channel  14 , and the second shared channel  22  is connected to an end at the downstream of the connection channel  14   b . Consequently, it is possible to reduce a space required for arranging the channels more than when disposing completely individual channels. 
     A form is assumed such that, when two or more lines of the discharge hole lines  9 A (in another point of view, the pressurization chambers  10 ) are disposed at one side of one second shared channel  22 , as with the present embodiment, the pressurization chambers  10  and the second shared channels  22  are linked to each other by completely individual second relay channels with the second relay channels extending by the shortest distance. In this form, the second relay channels linked to the pressurization chambers  10  farther from the second shared channels  22  are longer than the second relay channels linked to the pressurization chambers  10  nearer to the second shared channels  22 . As a result, the channel characteristics thereof differ from each other. When, as with the present embodiment, portions of the second relay channels  14  connected to two pressurization chambers  10  that differ from each other in terms of distance from the second shared channels  22  are bound together, it is possible to lengthen the second relay channels linked to the pressurization chambers  10  near the second shared channels  22  and to efficiently dispose the long channels. 
     The longer the connection channels  14   b  than the individual channels  14   a , that is, the higher the ratio of the connection channels  14   b  occupying the second relay channels  14 , the more the space efficiency can be improved. 
     A portion of a pressure with which discharging has been performed is transmitted from a plurality of the pressurization chambers  10  to the fluid in the second shared channels  22 , and complex pressure vibrations are generated. A portion of the pressure vibrations is transmitted to the pressurization chambers  10  and may influence subsequent discharging. When the pressures from two pressurization chambers  10  are combined in the connection channels  14   b  before being transmitted to the second shared channels  22  and then are caused to be transmitted thereto, it is possible to reduce the complexity of the pressure vibrations in the second shared channels  22  and to reduce the influence on subsequent discharging. If a completely circular columnar channel is filled with a Newtonian fluid, pressure waves are transmitted independently from each other. However, with an actual channel shape and a real fluid, pressures influence each other. The connection channel  14   b  is preferably longer than the individual channel  14   a  so that combining of pressures is accelerated. 
     The discharging pressure generated in one pressurization chamber  10  passes through the individual channel  14   a  linked to the pressurization chamber  10  and then is transmitted to another pressurization chamber  10  through the individual channel  14   a  linked to the other pressurization chamber  10 . To reduce a change in discharging characteristics caused by such pressure propagation, it is preferable that the channel resistance of the individual channels  14   a  be larger than the channel resistance of the connection channels  14   b . As a result, pressure propagation such as that described above can be suppressed from easily occurring. 
     The space efficiency can be improved by binding a plurality of the individual channels  14   a  into the connection channels  14   b  and then linking the connection channels  14   b  to the second shared channels  22 . Consequently, the second relay channels  14  linked to the discharge holes  8  disposed in a first gap region between two second shared channels  22  can be disposed within the first gap region in plan view. 
     The space efficiency can be improved by binding a plurality of the individual channels  14   a  into the connection channels  14   b  and then linking the connection channels  14   b  to the second shared channels  22 . Consequently, the second relay channels  14  linked to the discharge holes  8  disposed in a second gap region between two first shared channels  20  can be disposed within the second gap region in plan view. 
     The second relay channels  14  are preferably linked near the discharge holes  8  of the partial channels  10   b  to suppress the fluid near the discharge holes  8  from remaining. Thus, the second relay channels  14  are preferably disposed nearer than the first shared channels  20  to the discharge hole surface  4 - 2 . Consequently, it becomes difficult for the second relay channels  14  to use a space more than the same plane as the first shared channels  20 . Even in such a state, the space efficiency can be improved by binding a plurality of individual channels  14   a  into the connection channels  14   b  and then linking the connection channels  14   b  to the second shared channels  22 , which enables the second shared channels  22  and the second relay channels  14  to be disposed nearer than the first shared channels  20  to the discharge hole surface  4 - 2 . In addition, the entirety, excluding both end, of the second shared channels  22  and the entirety of the second relay channels  14  can be disposed nearer than the first shared channels  20  to the discharge hole surface  4 - 2 . 
     Each individual channel  14   a  includes a first part  14   aa  directly linked to the pressurization chamber  10 , and a second part  14   ab  linking the first part  14   aa  and the connection channel  14   b  to each other. The first part  14   aa  is constituted as a result of a hole or a groove in one plate  4   n  being closed by the flat surface parts of the other plates  4   m  and  4   o . The second part  14   ab  is constituted as a result of a hole or a groove in the plate  4   m , which is different from the plate  4   n  that has the hole or the groove constituting the first part  14   aa , being closed by the flat surface parts of the other plates  4   l  and  4   n.    
     The channel resistance per unit length of the first part  14   aa  is larger than the channel resistance per unit length of the second part  14   ab . Consequently, the pressure from the pressurization chambers  10  is suppressed from being easily transmitted to the second relay channels  14 , and the pressure vibrations in the pressurization chambers  10  are suppressed from becoming complex. In the present embodiment, due to the first parts  14   aa  being directly connected to the pressurization chambers  10 , reflection of pressure waves occurs at mainly the connection parts. As a result, the pressure vibrations in the pressurization chambers  10  become relatively simple, and subsequent discharging can be relatively easily performed in accordance with the pressure vibrations. If a part in which channel resistance is high is present in an intermediate portion of the individual channel  14   a , refection of large pressure waves occurs in two locations of the connection part between the pressurization chamber  10  and the individual channel  14   a  and the part in which channel resistance is high. Thus, the pressure vibrations in the pressurization chamber  10  easily become complex and make it difficult to perform subsequent discharging in consideration of the pressure vibrations. Consequently, discharging characteristics are caused to easily change due to pressure vibrations. 
     The plate  4   m  is thicker than the plate  4   n . With such a configuration, required channel characteristics (channel resistance and the like) can be satisfied by the first part  14   aa . Meanwhile, the individual channels  14   a  can be linked to each other by the second part  14   ab  whose sectional area is larger than the sectional area of the first part  14   aa  and whose influence of the channel characteristics occupying the individual channel  14   a  is small. 
     When a plate having a hole or a groove that serves as the second shared channel  22  is employed as the plate  4   m , the number of required plates can be reduced. The AL of each pressurization chamber  10  can be shortened by making the plate  4   n  be thinner than the plate  4   m , which makes it possible to drive the head  2  in a short period. 
     At a connection location where two individual channels  14   a  and the connection channel  14   b  are connected to each other, an angle formed by the individual channels  14   a  is smaller than an angle formed by the individual channel  14   a  and the connection channel  14   b . The angle formed by the individual channels  14   a  is about 80 degrees. The angle formed by the individual channel  14   a  and the connection channel  14   b  is substantially 90 degrees due to the connection channel  14   b  being linked so as to extend upward with respect to the individual channel  14   a . Therefore, the magnitude relationship between these angles is as described above. 
     By establishing such a magnitude relationship of the angles, the pressure transmitted from one individual channel  14   a  is more easily transmitted to the connection channel  14   b  than the other individual channels  14   a . It is thus possible to reduce pressure propagation generated between the pressurization chambers  10  linked via the second relay channel  14 . 
     In the present embodiment, the two individual channels  14   a  both satisfy the conditions described above. However, even when only one individual channel  14   a  satisfies the conditions, the effects described above are provided regarding the one individual channel  14   a . When all of the individual channels  14   a  satisfy the conditions, the effects described above are provided regarding all of the individual channels  14   a.    
     [Bypass Channel] 
     As illustrated in  FIG. 6 , the first channel member  4  includes a bypass channel  16  that links the first shared channel  20  and the second shared channel  22  to each other. As already described, the pressurization chambers  10  also link the first shared channel  20  and the second shared channel  22  to each other. The bypass channel  16  is linked to the first shared channel  20  and the second shared channel  22  to be in parallel with the pressurization chambers  10 . As understood also from the figure, parallel here is parallel relating to connection (parallel relating to serial connection/parallel connection) and is not parallel in a spatial positional relationship (a state of extending parallel in the same direction). The bypass mentioned here does not necessarily mean circumvention (detour) and includes short-cut. That is, a path from the first shared channel  20  via the bypass channel  16  to the second shared channel  22  may be shorter than a path from the first shared channel  20  via the pressurization chambers  10  to the second shared channel  22 . 
     In more detail, the bypass channel  16  has one end connected to the first shared channel  20  and the other end connected to the second relay channel  14 . That is, the other end of the bypass channel  16  is linked to the second shared channel  22  via the connection channel  14   b . The bypass channel  16  can be regarded to share (the bypass channel  16  includes the connection channel  14   b ) the connection channel  14   b  with the second relay channel  14 . In the description of the present embodiment, however, the bypass channel  16  is expressed based on that the bypass channel  16  does not include the connection channel  14   b.    
     Hereinafter, a combination of various channels relating to, of a plurality of the first shared channels  20 , one first shared channel  20  is sometimes referred to as a unit channel  18 . The unit channel  18  includes one first shared channel  20  and one second shared channel  22  and includes a plurality of the first relay channels  12 , a plurality of the pressurization chambers  10 , a plurality of the second relay channels  14 , and a plurality of the bypass channels  16  that link the two shared channels to each other. The unit channel  18  further includes a plurality of the discharge holes  8  linked to the plurality of pressurization chambers  10  included in the unit channel  18 . 
     (Connection Location of Bypass Channel in Channel Direction of Shared Channels) 
       FIG. 7  and  FIG. 8  are plan views for describing the connection location of the bypass channels  16  in the channel direction of the shared channels. Specifically, regarding one unit channel  18 ,  FIG. 7  illustrates the first shared channel  20 , a plurality of the first relay channels  12 , and a plurality of the bypass channels  16 . Regarding one unit channel  18 ,  FIG. 8  illustrates the second shared channel  22 , a plurality of the second relay channels  14  (in more detail, the connection channels  14   b ), and a plurality of the bypass channels  16 . Here, one unit channel  18  will be described. The other unit channels  18  may be considered the same. 
     As described with reference to  FIG. 3  and other figures and as illustrated in  FIG. 7 , the first shared channel  20  includes a first connection region  20   e  (directly) connected to a plurality of the first relay channels  12  and a first non-connection region  20   f  not (directly) connected to the plurality of first relay channels  12 . Similarly, as described with reference to  FIG. 3  and other figures and as illustrated in  FIG. 8 , the second shared channel  22  includes a second connection region  22   e  (directly) connected to a plurality of the second relay channels  14  and a second non-connection region  22   f  not (directly) connected to the plurality of second relay channels  14 . At least some (all in the illustrated example) of the bypass channels  16  connect the first connection region  20   e  and the second connection region  22   e  (exactly, the connection channel  14   b  connected to the second connection region  22   e ; the same applies to the followings.) to each other. The plurality of bypass channels  16  may include the bypass channels  16  connected to the first non-connection region  20   f  and/or the second non-connection region  22   f.    
     The ranges of the first connection region  20   e  and the second connection region  22   e  may be defined, as appropriate. For example, specifically, it is defined as follows. 
     First, confirmatively describing, the first connection region  20   e  and the first non-connection region  20   f  are regions demarcated in the first shared channel  20  in the channel direction thereof (in other words, in the longitudinal direction or a direction in which an ink flows; the same applies to the second shared channel  22  and the like). The second connection region  22   e  and the second non-connection region  22   f  are regions demarcated in the second shared channel  22  in the channel direction thereof. 
     The first shared channel  20  has a plurality of first openings  20   h  individually linked to the plurality of first relay channels  12 . The plurality of first openings  20   h  are distributed in the channel direction of the first shared channel  20 . In more detail, the plurality of first openings  20   h  is disposed side by side in one or more rows (four rows in the illustrated example) in the channel direction. In such a configuration, the first opening  20   h  located nearest to one side (left side in the figure) in the channel direction is referred to as a first opening  20   h -A. The first opening  20   h  located nearest to the other side (right side in the figure) in the channel direction is referred to as a first opening  20   h -B. A region from the position of the first opening  20   h -A to the position of the first opening  20   h -B may be regarded as the first connection region  20   e . The position of the first opening  20   h -A may be based on, for example, of the first opening  20   h -A, an edge portion nearest to the one side (left side in the figure). Similarly, the position of the first opening  20   h -B may be based on, for example, of the first opening  20   h -B, an edge portion nearest to the other side (right side in the figure). 
     The same applies to the second connection region  22   e . Specifically, the second shared channel  22  has a plurality of second openings  22   h  individually linked to the plurality of the second relay channels  14 . The plurality of second openings  22   h  is distributed in the channel direction of the second shared channel  22 . In more detail, the plurality of second openings  22   h  is disposed side by side in one or more rows (two rows in the illustrated example) in the channel direction. In such a configuration, the second opening  22   h  located nearest to one side (left side in the figure) in the channel direction is referred to as a second opening  22   h -A. The second opening  22   h  located nearest to the other side (right side in the figure) in the channel direction is referred to as a second opening  22   h -B. A region from the position of the second opening  22   h -A to the position of the second opening  22   h -B may be regarded as the second connection region  22   e . For example, the position of the second opening  22   h -A may be based on, of the second opening  22   h -A, an edge portion nearest to the one side (left side in the figure). Similarly, for example, the position of the second opening  22   h -B may be based on, of the second opening  22   h -B, an edge portion nearest to the other side (right side in the figure). 
     Conversely, both outer sides from the first openings  20   h -A and  20   h -B may be regarded as the first non-connection region  20   f . Similarly, both outer sides from the second openings  22   h -A and  22   h -B may be regarded as the second non-connection region  22   f.    
     Differently from the present embodiment, it is possible to dispose the first opening  20   h -A and/or the first opening  20   h -B at an end of the first shared channel  20  and eventually not to dispose the first non-connection region  20   f  at both sides and/or one side of the first connection region  20   e . From another point of view, the first connection region  20   e  may be a portion of the first shared channel  20 , as with the embodiment, or may be the entirety of the first shared channel, differently from the embodiment. When the first non-connection region  20   f  is disposed, the length (in the channel direction) of the first non-connection region  20   f  may be longer, as with the embodiment, than a distance (or a pitch Pt) between the first openings  20   h  adjacent to each other in each row or may be shorter, differently from the embodiment, than a distance between the first openings  20   h  adjacent to each other in each row. The first non-connection region  20   f  has been described, and the same applies to the second non-connection region  22   f.    
     In the present embodiment, the first shared channel  20  has both ends. Accordingly, the first openings  20   h -A and  20   h -B may be regarded to be located nearest, among the plurality of first openings  20   h , to both ends in the channel direction of the first shared channel  20 , as described above. Although not particularly illustrated, the first shared channel may have an annular shape. Even in such a situation, a first opening nearest to an end may be specified by regarding, as an end of the first shared channel, the position of openings corresponding to the openings  20   b  that supply an ink to the first shared channel  20 . Regarding the second shared channel  22 , similarly, a second opening nearest to an end may be specified by regarding, as an end of the second shared channel, the position of openings corresponding to the openings  22   b.    
     In an annular first shared channel and the like, the first non-connection region may be disposed in a location away from the openings corresponding to the openings  20   b . For example, when the first shared channel extends in a U-shape, the first non-connection region may be disposed at the returning part and the periphery thereof. In such a situation, for example, specifying the first openings ( 20   h -A/ 20   h -B) defining the ends of the first connection region and determining presence/absence of the first non-connection region may be performed reasonably. 
     For example, the first connection region normally has a linear shape parallel to the pressurization chamber lines (discharge hole lines). Accordingly, a first opening nearest to the returning part may be regarded as a first opening located at an end of the first connection region. That is, even if there is a conventional art in which a bypass channel that connects a first shared channel and a second shared channel to each other is disposed at a returning part, the bypass channel does not correspond to the bypass channel  16  in the present embodiment. 
     In addition, for example, the plurality of first openings is basically arranged with a constant pitch (in another point of view, with a constant gap). For example, focusing on the first openings  20   h  in one row in the embodiment, the pitch in the channel direction is constant. In such a situation, a region from an end to an end of a plurality of the first openings relating to the constant pitch may be regarded as the first connection region. In other words, when a pitch larger than the constant pitch is present, a region that constitutes the relatively large pitch and that is between two first openings adjacent to each other in the channel direction may be determined as the first non-connection region. At a part where the first shared channel (in the channel direction) is not liner, the pitch may be measured, for example, with the length along the first shared channel (the same applies to the pitch of the second openings, the pitch of the bypass channels  16 , and the like). 
     In addition, for example, when the pitch of the plurality of first openings is not constant, the change thereof has a periodic characteristic. For example, when the first openings  20   h  in four rows in the embodiment are collectively considered, the pitch in the channel direction of the first shared channel may have a periodic characteristic, or the change of the pitch of the first openings  20   h  in one row may have a periodic characteristic. In such a situation, when a pitch is larger than the other pitches in a very small number of portions (for example, one to four locations in the channel direction) and the periodic characteristic is thereby disturbed, a region that constitutes the relatively large pitch and that is between two first openings adjacent to each other in the channel direction may be determined as the first non-connection region. 
     In addition, for example, even if no periodic characteristic is found in the change of the pitch, when a pitch is extremely larger (for example, five times or more) than the other pitches in a very small number of portions (for example, one to four locations in the channel direction), a region that constitutes the extremely large pitch and that is between two first openings adjacent to each other in the channel direction may be determined as the non-connection region. 
     It has been described that specifying the ends of the first connection region and determining presence/absence of the first non-connection region may be performed reasonably. Specifying ends of the second connection region and determining presence/absence of the second non-connection region may be also performed similarly. 
     (Relationship Among a Plurality of Bypass Channels) 
     A plurality of the bypass channels  16  is generally arranged, for example, at both sides of the first shared channel  20  and the second shared channel  22  to extend in the channel direction of these shared channels and constitutes a total of two lines of channel lines  17 A. In each channel line  17 A, the shapes of the plurality of bypass channels  16  are identical to each other. Among the channel lines  17 A connected to the same shared channel, the shapes of the bypass channels  16  are, for example, shapes (the illustrated example) that are line symmetrical with the center line of the shared channel being the axis of symmetry in plan view or shapes that are 180° rotation symmetrical in plan view. 
     In each channel line  17 A, the bypass channels  16  are, for example, disposed side by side with a constant pitch. In addition, for example, the size of the pitch of the bypass channels  16  is the same between two channel lines  17 A at both sides of the shared channel. Between two channel lines  17 A, the positions of the bypass channels  16  may be shifted from each other by an appropriate distance (a substantially half pitch in the illustrated example) or may be in coincident with each other. The size of the pitch of the plurality of bypass channels  16  in one channel line  17 A is, for example, equal to the size of the pitch of the pressurization chambers  10  in one pressurization chamber line  11 A. In the present embodiment, two lines of the pressurization chamber lines  11 A and one line of the channel line  17 A are disposed at one side of the shared channel. The bypass channels  16  are thus disposed one each per two pressurization chambers  10 . 
     When a feature in which a plurality of the bypass channels  16  is disposed side by side with a constant pitch is described in a superordinate concept, the plurality of bypass channels  16  is disposed side by side (disposed side by side in accordance with a constant rule) in each channel line  17 A regularly along the shared channels. Regularity in the arrangement of the plurality of bypass channels  16  is the same among a plurality of channel lines  17 A connected to the same shared channels. Even when regularity is the same among the plurality of channel lines  17 A, the positions (phase of the period) of the bypass channels  16  may be shifted from each other (shifted by a half pitch in the illustrated example) among the plurality of channel lines  17 A. The channel lines  17 A have been focused to describe that a plurality of the bypass channels  16  is regularly disposed side by side. In the illustrated example, the plurality of bypass channels  16  can be also regarded to be disposed side by side regularly in the channel direction of the shared channels even when the plurality (two here) of channel lines  17 A connected to the same shared channels is collectively considered. 
     When disposed side by side regularly, although not particularly illustrated, the plurality of bypass channels  16  may be disposed side by side, for example, in the following form in addition to a form of being disposed side by side with a constant pitch as described above. 
     The plurality of bypass channels  16  may be disposed side by side in a form in which the pitch changes periodically. Specifically, for example, bypass channels of two types whose shapes differ from each other may be arranged at one side of the shared channels alternately in one row generally, and two types of pitches may be present alternately. In such a situation, it may be regarded that two types of channel lines are disposed and the pitch is constant in one type of the channel line. Regarding the bypass channels of the two types whose shapes differ from each other, in addition to shapes that are line symmetrical to each other with respect to the axis of symmetry orthogonal to the shared channels in plan view, shapes that are not even symmetrical to each other are presented as examples. 
     In addition, for example, two lines of pressurization chamber lines may be present at one side of the shared channels, consequently, two types of relay channels may be arranged with two types of pitches at one side of the shared channels, and bypass channels having the same shape may be disposed in a location in accordance with the two types of the pitches. Even in such a situation, it is also possible to regard that two types of channel lines are disposed and the pitch is constant in one type of the channel line. 
     The pitch may be regarded, for example, based on the geometrical centers of gravity of the bypass channels  16 , as a distance between the centers of gravity. When the shapes of the plurality of bypass channels  16  are identical to each other, the pitch may be measured based on specific parts (for example, the first openings  20   h  or the second openings  22   h ) of the bypass channels  16 . 
     (Specific Connection Location of Each Bypass Channel) 
     Ends of the bypass channels  16  near the first shared channels  20  may be connected to any locations nearer to the first shared channels  20  than the pressurization chambers  10  and, for example, may be connected to locations nearer to the first shared channels  20  than, of the first relay channels  12 , parts (contracted parts) the sectional area of each of which is narrowest. In the illustrated example, the bypass channel  16  is directly connected to the first shared channel  20 . 
     When the bypass channels  16  are connected to the first shared channels  20 , each bypass channel  16  may be connected to any of the upper surface, the side surface, and the lower surface of the first shared channels  20 , may be connected to a combination of two or more of these surfaces, and may be connected to any locations in each surface. In the illustrated example, the bypass channel  16  is connected to the side surface of the first shared channel  20  and, specifically, opens at an upper portion of the side surface. 
     In the channel direction of the first shared channels  20 , the connection location of the bypass channels  16  with respect to the first shared channels  20  and the relative position thereof with respect to the pressurization chambers  10  and the like may be also set, as appropriate. For example, at one side of the sides of the first shared channels  20 , the connection location of each bypass channel  16  may overlap the positions of the first openings  20   h  relating to any of the pressurization chamber lines  11 A in the channel direction of the first shared channels  20  (illustrated example) or may not overlap the positions of the first openings  20   h  in any of the pressurization chamber lines  11 A. 
     Ends of the bypass channels  16  near the second shared channels  22  may be connected to any locations (including the second shared channels  22 ) nearer to the second shared channels than the pressurization chambers  10 . In the illustrated example, the bypass channel  16  is connected to the second relay channel  14  and, specifically, is connected to the connection channel  14   b  of the second relay channel  14 . More specifically, the bypass channel  16  is connected to, of the connection channel  14   b , a portion nearer to the individual channel  14   a  (at the upstream of the connection channel  14   b ) than the center thereof. Further specifically, the bypass channel  16  is connected to, of the connection channel  14   b , a connection location with respect to the individual channel  14   a . The connection location of the connection channel  14   b  with respect to the individual channel  14   a  is located at an end at the upstream of the connection channel  14   b . Consequently, it is possible to ensure the length of an intermediate part  16   b  (described later) of the bypass channel  16  and ensure a desired channel resistance in the intermediate part  16   b . From another point of view, the bypass channel  16  is connected to, of the second relay channel  14 , a portion nearer to the second shared channel  22  than the first part  14   aa  (a part whose sectional area is narrowest). Thus, the lengths of the individual channels  14   a  connected to respective discharge holes  8  are preferably identical to each other. The connection location of each connection channel  14   b  with respect to the individual channels  14   a  is a location where a plurality of the individual channels  14   a  (two individual channels  14   a  in the figure) merge together. Distances from the connection location to the discharge holes  8  each connected to a respective one of the plurality of individual channels  14   a  are preferably equal to each other. Each bypass channel  16  is preferably connected to the connection location whose distances from the discharge holes  8  are the same. Consequently, while suppressing differences in the discharging characteristics (variations in the discharging characteristics) among the plurality of discharge holes  8 , it is possible to replenish an ink to the second shared channels  22  through the bypass channels  16 . 
     When each bypass channel  16  is connected to, of the connection channel  14   b , the connection location with respect to the individual channel  14   a , for example, it is sufficient that at least a portion of an opening between the connection channel  14   b  and the individual channel  14   a  and at least a portion of an opening connecting the connection channel  14   b  and the bypass channel  16  to each other overlap each other in the channel direction of the connection channel  14   b . In the illustrated example, in the connection location (the end at the upstream of the connection channel  14   b ) between the connection channel  14   b  and the individual channel  14   a , these two channels are superposed on each other vertically, and the bypass channel  16  is further superposed thereon. In plan view, one of the opening connecting the connection channel  14   b  and the individual channel  14   a  to each other and the opening connecting the connection channel  14   b  and the bypass channel  16  to each other is present within the other or these openings are in coincident with each other. Accordingly, in the channel direction of the connection channel  14   b , the entirety of one of the two openings overlaps a portion of the other, or the entirety thereof overlap each other. 
     (Shape of Bypass Channel) 
     The shape of each bypass channel  16  may be set, as appropriate. For example, the entirety of each bypass channel  16  may be linear, or a portion or the entirety thereof includes a bent or curved part. The sectional area of each bypass channel  16  may be constant, or the sectional area may change. 
     In the illustrated example, the bypass channel  16  includes a first shared side part  16   a  that includes an end near the first shared channel  20 , a second shared side part  16   c  that includes an end near the second shared channel  22 , and the intermediate part  16   b  that connects the two shared side parts to each other. The intermediate part  16   b  is a part (a part whose sectional area is smallest in the bypass channel  16 ) whose sectional area is smaller than those of the first shared side part  16   a  and the second shared side part  16   c  and, from another point of view, a part whose channel resistance per unit length is larger than those of the first shared side part  16   a  and the second shared side part  16   c.    
     The first shared side part  16   a  is constituted by, for example, holes or grooves in all (in the illustrated example) or some of the plates  4   f  to  4   i  having holes or grooves that serve as the first shared channel  20 . The first shared side part  16   a  includes, for example, a part extending from the first shared channel  20  toward the side thereof and a part extending downward from the tip thereof. For example, in plan view, at least a portion of the first shared side part  16   a  is superposed on at least a portion of the connection channel  14   b . The sectional area of the first shared side part  16   a  may be set, as appropriate. For example, the sectional area of the narrowest part of the first shared side part  16   a  is ¼ times or more and four times or less the sectional area of the narrowest part of the partial channel  10   b  or the connection channel  14   b.    
     The intermediate part  16   b  is constituted by, for example, a hole or a groove in either ( 4   j  in the illustrated example) of the plates between the plates  4   f  to  4   i  having holes or grooves that serve as the first shared channel  20  and plates  4   l  to  4   m  having holes or grooves that serve as the second shared channel  22 . From another point of view, the intermediate part  16   b  is constituted by a hole or a groove in one plate. The intermediate part  16   b , for example, extends parallel to the discharge hole surface  4 - 2  from the first shared side part  16   a  and curves in plan view. For example, in plan view, at least a portion of the first shared side part  16   a  is superposed on at least a portion of the connection channel  14   b . The sectional area of the intermediate part  16   b  may be set, as appropriate, and is, for example, ¼ times or more and four times or less the sectional area of the narrowest part of the first relay channel  12  or the sectional area of the narrowest part (first part  14   aa ) of the second relay channel  14 . The intermediate part  16   b  is preferably disposed in the layer between the first shared channel  20  and the second shared channel  22 . Specifically, the intermediate part  16   b  is preferably disposed in the plate  4   j . The plate  4   j  is located on the lower surface of the first shared channel  20  and forms the damper  28 A while forming the damper chamber  29 A at a side of the damper  28 A opposite to the side thereof facing the first shared channel  20 . The plate  4   j  is a relatively thin plate. Thus, it is possible by disposing the intermediate part  16   b  in the thin plate to easily form a part (a part whose sectional area is smallest in the bypass channel  16 ) whose sectional area is smaller than those of the first shared side part  16   a  and the second shared side part  16   c  in the bypass channel  16 . 
     The second shared side part  16   c  is constituted by, for example, a hole or a groove in a plate ( 4   k  in the illustrated figure) between the plate  4   j  having a hole or a groove that serves as the intermediate part  16   b  and the plate  4   l  having a hole or a groove that serves as the connection channel  14   b . The second shared side part  16   c , for example, extends downward from the intermediate part  16   b  and is connected to the connection channel  14   b . The sectional area of the second shared side part  16   c  may be set, as appropriate. For example, the sectional area of the narrowest part of the second shared side part  16   c  is ¼ times or more and four times or less the sectional area of the narrowest part of the partial channel  10   b  or the connection channel  14   b.    
     (Channel Resistance of Bypass Channel) 
     The channel resistance of the bypass channels  16  may be set, as appropriate. For example, the channel resistance of the bypass channels  16  may be set such that the channel resistance from the first shared channel  20  to the second shared channel  22  via one bypass channel  16  is ¼ times or more and four times or less or ½ times or more and two times or less the channel resistance from the first shared channel  20  to the second shared channel  22  via two pressurization chambers  10 . Confirmatively describing, the former channel resistance includes the channel resistance of one connection channel  14   b . The latter channel resistance includes the channel resistance of two first relay channels  12  and the channel resistance of two relay channels  14  (two individual channels  14   a  and one connection channel  14   b ). 
     As described above, in the present embodiment, each fluid discharge head  2  includes the first channel member  4  and the plurality of pressurization portions (displacement elements  50 ). The first channel member  4  includes a plurality of the discharge holes  8 , a plurality of the pressurization chambers  10  individually linked to the plurality of discharge holes  8 , the first shared channel  20  linked to the plurality of pressurization chambers  10 , and the second shared channel  22  linked to the plurality of pressurization chambers  10 . The plurality of displacement elements  50  individually pressurizes the plurality of pressurization chambers  10 . The first shared channel  20  opens at a plurality of the first openings  20   h  linked to the plurality of pressurization chambers  10 . The first shared channel  20  includes the first connection region  20   e , which is a range of distribution of the plurality of first openings  20   h  in the channel direction of the first shared channel  20 . The second shared channel  22  opens at a plurality of second openings  22   h  linked to the plurality of pressurization chambers  10 . The second shared channel  22  includes the second connection region  22   e , which is a range of distribution of the plurality of second openings  22   h  in the channel direction of the second shared channel  22 . The first channel member  4  further includes the bypass channel  16  linked to the first connection region  20   e  and the second connection region  22   e  to be in parallel with the plurality of pressurization chambers  10 . 
     Accordingly, for example, it is possible to suppress a change (decrease) in the discharging characteristics. Specifically, for example, there is a possibility of a large amount of an ink being discharged through the discharge holes  8  depending on the content of an image. In such a situation, the ink that is collected from the pressurization chambers  10  into the second shared channel  22  via the second relay channel  14  decreases compared with when only a small amount an ink is discharged. There is also a possibility of occurrence of a backflow from the second relay channel  14  toward the pressurization chambers  10 . As a result, the pressure applied to the ink in the discharge holes  8  decreases, and eventually, the discharge amount of the ink decreases compared with an estimated discharge amount. That is, the discharging characteristics change. However, due to the bypass channel  16  connecting the first shared channel  20  and the second shared channel  22  to each other by a path that differs from the pressurization chambers  10 , it is possible to compensate a shortage amount of the ink in the second shared channel  22 . The connection location of the bypass channel  16  with respect to the first shared channel  20  and the second shared channel  22  is within the first connection region  20   e  and the second connection region  22   e  in which the pressurization chambers  10  are connected to the first shared channel  20  and the second shared channel  22 . Thus, the connection location is near the discharge holes  8 , compared with when the bypass channel is disposed outside thereof. It is thus possible in an early state to compensate ink shortage that influences the pressure applied to the discharge holes  8 . As a result, the change in the discharging characteristics is suppressed. Eventually, image quality is improved. 
     In the present embodiment, the first channel member  4  includes a plurality of bypass channels  16  arranged side by side regularly in the channel direction of the first shared channel  20 . 
     In such a situation, for example, the plurality of bypass channels  16  is disposed in accordance with a plurality of the first openings  20   h  and a plurality of the second openings  22   h  (in another point of view, a plurality of the pressurization chambers  10  and a plurality of the discharge holes  8 ) distributed in the channel direction of the first shared channel  20  and the second shared channel  22 . Accordingly, regarding the plurality of discharge holes  8 , it is possible to more uniformly replenish an ink to the second shared channel  22 . As a result, for example, a difference in the discharging characteristics (a variation in the discharging characteristics) among the plurality of discharge holes  8  is reduced. Eventually, image quality is improved. 
     In the present embodiment, the first channel member  4  includes a plurality of the second relay channels  14  linking the plurality of pressurization chambers  10  and the plurality of second openings  22   h  to each other. The bypass channel  16  is connected to at least one second relay channel  14  of the plurality of second relay channels  14  and linked to the second connection region  22   e  via the at least one second relay channel  14 . 
     In such a situation, for example, it is possible to replenish an ink to a location near the discharge holes  8 , compared with when the bypass channel  16  is directly connected to the second connection region  22   e . As a result, for example, it is possible to restore the discharging characteristics in an early stage. From another point of view, a portion (a portion of the second relay channel  14 ) of a path from the first shared channel  20  to the second shared channel  22  via the pressurization chambers  10  is commonly used as a path from the first shared channel  20  to the second shared channel  22  via the bypass channel  16 . As a result, for example, the space efficiency is improved. 
     In the present embodiment, the second relay channel  14  includes a plurality of the individual channels  14   a  and a plurality of the connection channels  14   b . The plurality of individual channels  14   a  is linked to a plurality of the pressurization chambers  10 . The plurality of connection channels  14   b  links two or more of the plurality of individual channels  14   a  and the second connection region  22   e  to each other. The number of the connection channels  14   b  is less than the number of the plurality of individual channels  14   a . The bypass channel  16  is connected to at least one connection channel  14   b  of the plurality of connection channels  14   b  and linked to the second connection region  22   e  via the at least one connection channel  14   b.    
     In such a situation, for example, it is possible to replenish an ink to two or more individual channels  14   a  without branching one bypass channel  16 . As a result, the space efficiency is improved. For example, it is possible to restore the discharging characteristics in an early stage. From another point of view, for example, it is possible to replenish an ink to a location near the discharge holes  8 , compared with when the bypass channel  16  is directly connected to the second connection region  22   e . It is thus possible to restore the discharging characteristics in an early stage. 
     In the present embodiment, the first shared channel  20  (at least a portion thereof) is superposed with respect to the second shared channel  22  (at least a portion thereof) at one side (upper) in the opening direction of the discharge holes  8 . The bypass channel  16  (at least a portion thereof) is superposed with respect to the second relay channel  14  (at least a portion thereof) linked to the bypass channel  16  at the one side (upper) in the opening direction. In such a situation, for example, the space efficiency is improved. 
     In the present embodiment, the first channel member  4  includes a plurality of pressurization chambers  10  and a plurality of the bypass channels  16  with a pitch in which the bypass channels  16  are disposed one each per a predetermined number (two in the illustrated example) of the pressurization chambers  10  in the channel direction of the first shared channel  20 . The channel resistance of a path from the first shared channel  20  to the second shared channel  22  via one bypass channel  16  is ½ times or more and two times or less the channel resistance of a path from the first shared channel  20  to the second shared channel  22  via the predetermined number of the pressurization chambers  10 . 
     In such a situation, for example, it is possible to compensate ink shortage in the second shared channel  22  in just proportion. As a result, while reducing the change in the discharging characteristics, it is possible to reduce circulation of an excess ink in the light of a purpose of circulating an ink (for example, in the light of sedimentation of pigments and adhesion of an ink). 
     In the present embodiment, each bypass channel  16  includes a first constituent part (first shared side part  16   a ) connected to the first shared channel  20 , and a second constituent part (intermediate part  16   b ) connected to the first shared side part  16   a  and linked to the first shared channel  20  via the first shared side part  16   a . Channel resistance per unit length of the intermediate part  16   b  is larger than channel resistance per unit length of the first shared side part  16   a.    
     Accordingly, for example, it is possible to reduce a possibility of pressure waves being propagated between the first shared channel  20  and the second shared channel  22  via the bypass channels  16 , compared with bypass channels (such a bypass channel may be included in the bypass channels according to the present disclosure) that have channel resistance identical as a whole to that of the bypass channels  16  having such a configuration and that are constant throughout the entire length thereof in terms of channel resistance per unit length. Meanwhile, it is possible to reduce a possibility that the pressure waves in the first shared channel  20  are absorbed at the first shared side part  16   a  due to the first shared side part  16   a  whose sectional area is relatively wide being connected to the first shared channel  20  and the pressure waves are propagated among the pressurization chambers  10 . As a result, it is possible to make the discharging characteristics stable. 
     In the present embodiment, the first channel member  4  includes a plurality of the unit channels  18 . Each unit channel  18  includes a combination of a plurality of the discharge holes  8 , a plurality of the pressurization chambers  10 , the first shared channel  20 , the second shared channel  22 , and the bypass channel  16 . 
     In such a situation, for example, the bypass channel  16  contributes reducing a difference in the discharging characteristics (a variation in the discharging characteristics) among the plurality of unit channels  18 . Specifically, when the discharge amount of an ink is increased only in a specific unit channel  18  in accordance with the content of an image, the unit channel  18  becomes short of the ink in the second shared channel  22 , and the discharging characteristics are changed (degraded), compared with the other unit channels  18 . The change in the discharge characteristics is, however, suppressed as a result of an ink being replenished to the second shared channel  22  through the bypass channel  16 . The variation in the discharge characteristics of the plurality of unit channels  18  are then reduced. 
     In the present embodiment, each of the plurality of unit channels  18  includes the discharge hole line  9 A in which a plurality of the discharge holes  8  are arranged. A plurality of the discharge hole lines  9 A is in parallel with each other. Each discharge hole line  9 A has a plurality of the discharge holes  8  in locations between a plurality of the discharge holes  8  of the other discharge hole lines  9 A as viewed in an intersecting direction (second direction D 2 ) with respect to the plurality of discharge hole lines  9 A. 
     In such a configuration, the above-described variation in the discharging characteristics among the plurality of unit channels  18  becomes a factor of generating periodical light and shade (periodical striped pattern, a plurality of lines extending in the second direction D 2 ) in a first direction D 1  orthogonal to the second direction D 2  in the print sheet P. As a result, image quality is degraded. It is however possible to reduce the periodical light and shade by disposing the bypass channel  16 . 
     It is new knowledge obtained as a result of earnest examination by the inventor of the present application that a variation in the discharging characteristics among the unit channels  18  due to ink shortage in the second shared channel  22  (collection end) influences the periodical light and shade. The inventor of the present application has performed an experiment in which a line having a width of 25 μm is drawn with each of a head according to a comparative example not including the bypass channel  16  and a head according to an example including the bypass channel  16 . As a result, as for the comparative example, a variation (a difference between the maximum width and the minimum width) of 3.5 μm to 4.0 μm is generated in the width of the line. As for the example, the variation in the width of the line is suppressed to about 2.0 μm. 
     The technology according to the present disclosure is not limited to the above-described embodiment and may be embodied in various forms. 
     The head may have only one unit channel. The shapes and the relative positions of the various types of channels in the unit channels are not limited to those in the illustrated shapes. The channels may have various shapes. For example, the first shared channel and the second shared channel may be disposed in parallel (for example parallel to each other) in an intersecting direction (planar direction) with respect to the opening direction of the discharge holes, instead of being disposed in a layered manner in the opening direction of the discharge holes. 
     In the present embodiment, the plurality of unit channels are arranged in the direction of the relative movement of the head and a recording medium. Each unit channel has a plurality of the discharge holes between a plurality of the discharge holes of the other unit channels as viewed in the direction of the relative movement of the head and a recording medium. However, for example, the plurality of unit channels may be arranged in an intersecting direction with respect to the relative movement of the head and a recording medium. The plurality of discharge holes may be arranged not to overlap each other in about one, two, or three unit channels as viewed in the direction of the relative movement of the head and a recording medium. From another point of view, unit channels (discharge hole lines) whose ranges do not overlap each other as viewed in the direction of the relative movement of the head and a recording medium may be present. 
     The discharge hole lines are not necessarily orthogonal to the direction of the relative movement of a recording medium and the head and may be inclined in the orthogonal direction. In each discharge hole line, the plurality of discharge holes may be arranged in a form in which a minute variation in a pitch and/or a minute displacement from a straight line are generated, instead of being arranged linearly with a constant pitch. 
     It is sufficient that at least one bypass channel is disposed. The number of the bypass channels may be smaller than the number of the pressurization chambers (the embodiment), or may be identical to or greater than the number of the pressurization chambers. From another point of view, the plurality of bypass channels may be disposed at a ratio of one each per a predetermined number of the pressurization chambers (the embodiment), may be disposed one each per one pressurization chamber, or may be disposed at a ratio of a predetermined number thereof per one pressurization chamber. 
     The second relay channel does not necessary share a portion (the connection channel  14   b ) with the other second relay channels. That is, the second relay channel may be completely independent for each pressurization chamber. The bypass channel may be connected to such a second relay channel that is completely independent for each pressurization chamber. Even in such a situation, a part (the second constituent part, the intermediate part  16   b ) whose channel resistance is suitably large and a part (the first constituent part, the first shared side part  16   a ) whose channel resistance is small may be included. 
     In the second relay channels that share a portion (the connection channel  14   b ) with each other, the shapes thereof are not limited to that presented as an example in the present embodiment. For example, in the present embodiment, in two second relay channels  14  that share the connection channel  14   b  with each other, the first parts  14   aa  extend in directions opposite to each other in a direction orthogonal to the shared channels, and the second parts  14   ab  have line symmetrical shapes and arrangements with respect to the axis of symmetry orthogonal to the shared channels. However, for example, the first parts may extend in directions opposite to each other in a direction along the shared channels, and the second parts may extend in directions opposite to each other in an intersecting direction with respect to the shared channels and merge together. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  color inkjet printer 
               2  fluid discharge head 
               2   a  head body 
               4  (first) channel member 
               4   a  to  o  plate 
               4 - 1  pressurization chamber surface 
               4 - 2  discharge hole surface 
               6  second channel member 
               6   a  through hole (of second channel member) 
               8  discharge hole 
               9 A discharge hole line 
               10  pressurization chamber 
               10   a  pressurization chamber body 
               10   b  partial channel 
               11 A pressurization chamber line 
               12  first relay channel 
               14  second relay channel 
               14   a  individual channel 
               14   aa  first part (of individual channel) 
               14   ab  second part (of individual channel) 
               14   b  connection channel 
               16  bypass channel 
               16   a  first shared side part 
               16   b  intermediate part 
               16   c  second shared side part 
               17 A channel line 
               18  unit channel 
               20  first shared channel 
               20   a  first shared channel body 
               20   b  opening (of first shared channel) 
               20   e  first connection region 
               20   f  first non-connection region 
               20   h ,  20   h -A,  20   h -B first opening 
               22  second shared channel 
               22   a  second shared channel body 
               22   b  opening (of second shared channel) 
               22   e  second connection region 
               22   f  second non-connection region 
               22   h ,  22   h -A,  22   h -B second opening 
               24  first integrated channel 
               24   a  first integrated channel body 
               24   b  opening (of first integrated channel) 
               26  second integrated channel 
               26   a  second integrated channel body 
               26   b  opening (of second integrated channel) 
               28 A, B damper 
               29 A, B damper chamber 
               40  piezoelectric actuator substrate 
               40   a  piezoelectric ceramic layer 
               40   b  piezoelectric ceramic layer (vibration plate) 
               42  shared electrode 
               44  individual electrode 
               44   a  individual electrode body 
               44   b  extraction electrode 
               46  connection electrode 
               50  displacement element (pressurization portion) 
               70  head mounting frame 
               72  head group 
               80 A feed roller 
               80 B collection roller 
               82 A guide roller 
               82 B transport roller 
               88  control portion 
             D 1  first direction 
             D 2  second direction 
             D 3  third direction 
             D 4  fourth direction 
             P print sheet