Patent Publication Number: US-11046076-B2

Title: Liquid discharge head and liquid discharge apparatus

Description:
The present application is based on, and claims priority from JP Application Serial Number 2019-030020, filed Feb. 22, 2019, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a liquid discharge head and a liquid discharge apparatus. 
     2. Related Art 
     A liquid discharge head having a liquid flow path and a liquid storing space has been proposed. JP-A-2015-147365 discloses a liquid ejecting apparatus having a liquid chamber communicating with nozzles, a common liquid chamber that stores liquid to be supplied to the liquid chamber, a supply flow path through which the liquid is supplied to the common liquid chamber, and a discharging flow path through which the liquid is discharged from the common liquid chamber. The liquid discharged from the common liquid chamber to the discharging flow path is circulated to the common liquid chamber through the supply flow path by a circulation pump. 
     In the configuration in which the liquid is circulated as in JP-A-2015-147365, depending on the shape of the common liquid chamber, a liquid flow directed from the common liquid chamber to the liquid chamber may be blocked, or bubbles in the liquid may flow in the liquid chamber along with the liquid flow. 
     SUMMARY 
     According to an aspect of the present disclosure, there is provided a liquid discharge head including: a liquid chamber that stores liquid; a supply flow path through which the liquid is supplied to the liquid chamber; a discharging flow path that is provided at a position away from the supply flow path in a horizontal direction and through which the liquid in the liquid chamber is discharged; a first connecting flow path that communicates between the liquid chamber and the supply flow path; and an energy generating chamber to which the liquid is supplied from the liquid chamber and that generates energy for discharging the liquid. The first connecting flow path has a bottom surface including a first supply bottom surface inclined downward with respect to a horizontal plane at a first angle from the supply flow path toward the liquid chamber, and a second supply bottom surface located between the first supply bottom surface and the liquid chamber and inclined downward with respect to the horizontal plane at a second angle from the first supply bottom surface toward the liquid chamber. The first angle is greater than or equal to 0 degrees and is less than 90 degrees, and the second angle is an angle greater than the first angle and is less than 90 degrees. 
     According to another aspect of the present disclosure, there is provided a liquid discharge apparatus including a liquid discharge head that discharges liquid, and a controller that controls the liquid discharge head. The liquid discharge head includes: a liquid chamber that stores liquid; a supply flow path through which the liquid is supplied to the liquid chamber; a discharging flow path that is provided at a position away from the supply flow path in a horizontal direction and through which the liquid in the liquid chamber is discharged; a first connecting flow path that communicates between the liquid chamber and the supply flow path; and an energy generating chamber to which the liquid is supplied from the liquid chamber and that generates energy for discharging the liquid. The first connecting flow path has a bottom surface including a first supply bottom surface inclined downward with respect to a horizontal plane at a first angle from the supply flow path toward the liquid chamber, and a second supply bottom surface located between the first supply bottom surface and the liquid chamber and inclined downward with respect to the horizontal plane at a second angle from the first supply bottom surface toward the liquid chamber. The first angle is greater than or equal to 0 degrees and is less than 90 degrees, and the second angle is an angle greater than the first angle and is less than 90 degrees. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a configuration of a liquid discharge apparatus according to a first embodiment. 
         FIG. 2  is an exploded perspective view of a liquid discharge head. 
         FIG. 3  is a sectional view of the liquid discharge head, taken along line III-III in  FIG. 2 . 
         FIG. 4  is a sectional view taken along line IV-IV in  FIG. 2 . 
         FIG. 5  is a sectional view of a first connecting flow path. 
         FIG. 6  is a sectional view of a second connecting flow path. 
         FIG. 7  is a sectional view of a first connecting flow path according to Comparative Example 1. 
         FIG. 8  is a sectional view of a first connecting flow path according to Comparative Example 2. 
         FIG. 9  is a sectional view of a first connecting flow path according to a second embodiment. 
         FIG. 10  is a sectional view of a first connecting flow path according to a modification. 
         FIG. 11  is a sectional view of a first connecting flow path according to a modification. 
         FIG. 12  is a sectional view of a first connecting flow path according to a modification. 
         FIG. 13  is a sectional view of a first connecting flow path according to a modification. 
         FIG. 14  is a sectional view of a first connecting flow path according to a modification. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     A. First Embodiment 
       FIG. 1  shows an example configuration of a liquid discharge apparatus  100  according to a first embodiment. The liquid discharge apparatus  100  according to the first embodiment is an ink jet printing apparatus that ejects ink, serving as an example liquid, onto a medium  12 . Typically, the medium  12  is printing paper. However, the medium  12  may be other printing objects that are made of desired materials, such as resin film, cloth, etc. As shown in  FIG. 1 , a liquid container  14  that stores ink is disposed in the liquid discharge apparatus  100 . For example, a cartridge that is removably attached to the liquid discharge apparatus  100 , a bag-like ink pack made of a flexible film, or a refillable ink tank is used as the liquid container  14 . 
     As shown in  FIG. 1 , the liquid discharge apparatus  100  includes a control unit  20 , a transport mechanism  22 , a moving mechanism  24 , and a liquid discharge head  26 . The control unit  20  includes a processing circuit, such as a central processing unit (CPU) or a field programmable gate array (FPGA), and a memory circuit, such as a semiconductor memory, and performs centralized control of the components of the liquid discharge apparatus  100 . The control unit  20  is an example controller. The transport mechanism  22  transports the medium  12  in the Y-axis direction under the control of the control unit  20 . 
     The moving mechanism  24  reciprocates the liquid discharge head  26  in the X-axis direction under the control of the control unit  20 . The X axis intersects the Y axis, along which the medium  12  is transported. Typically, the X axis and the Y axis are perpendicular to each other. The moving mechanism  24  according to the first embodiment includes a substantially box-shaped transport body  242  that accommodates a liquid discharge head  26 , and a transport belt  244  to which the transport body  242  is fixed. The transport body  242  is, for example, a carriage. It is also possible to employ a configuration in which a plurality of liquid discharge heads  26  are loaded on the transport body  242 , or a configuration in which the liquid container  14  is loaded on the transport body  242 , together with the liquid discharge head  26 . 
     The liquid discharge head  26  ejects ink, supplied from the liquid container  14 , onto the medium  12  through a plurality of nozzles under the control of the control unit  20 . As a result of the liquid discharge head  26  ejecting ink onto the medium  12  while the transport mechanism  22  transports the medium  12  and while the transport body  242  reciprocates, a desired image is formed on the surface of the medium  12 . 
       FIG. 2  is an exploded perspective view of the liquid discharge head  26 , and  FIG. 3  is a sectional view taken along line III-III in  FIG. 2 . As shown in  FIG. 2 , an axis perpendicular to an X-Y plane will be referred to as a Z axis. Typically, the Z axis is parallel to the vertical direction. 
     As shown in  FIGS. 2 and 3 , the liquid discharge head  26  includes a substantially rectangular flow-path substrate  32  elongated in the Y-axis direction. A pressure-chamber substrate  34 , a vibration plate  36 , a plurality of piezoelectric elements  38 , a housing portion  42 , and a sealing member  44  are provided on the −Z-side surface of the flow-path substrate  32 . A nozzle plate  46  and a damper  48  are provided on the +Z-side surface of the flow-path substrate  32 . These components of the liquid discharge head  26  are generally plate-like members elongated in the Y-axis direction, similarly to the flow-path substrate  32 , and are bonded together by using, for example, an adhesive. 
     As shown in  FIG. 2 , the nozzle plate  46  is a plate-like member having a plurality of nozzles N arrayed along the Y axis. The nozzles N are through-holes through which the ink passes. The flow-path substrate  32 , the pressure-chamber substrate  34 , and the nozzle plate  46  are formed by processing, for example, silicon (Si) single-crystal substrates by using a semiconductor manufacturing technique, such as etching. However, the respective components of the liquid discharge head  26  may be made of any desired material by using any desired manufacturing method. The Y axis can also be said as an axis along which the plurality of nozzles N are arrayed. 
     The flow-path substrate  32  is a plate-like member that forms ink flow paths. As shown in  FIGS. 2 and 3 , the flow-path substrate  32  has a first liquid chamber  322 , first communicating flow paths  324 , and second communicating flow paths  326 . The first liquid chamber  322  is an elongated through-hole provided so as to correspond to the plurality of nozzles N and so as to extend along the Y axis in plan view as viewed in the Z-axis direction. The first communicating flow paths  324  and the second communicating flow paths  326  are through-holes provided so as to correspond to the respective nozzles N. As shown in  FIG. 3 , a relay flow path  328  extending so as to correspond to the plurality of first communicating flow paths  324  is formed on the +Z-side surface of the flow-path substrate  32 . The relay flow path  328  communicates between the first liquid chamber  322  and the plurality of first communicating flow paths  324 . 
       FIG. 4  is a sectional view of the housing portion  42 , taken along line IV-IV in  FIG. 2 . The housing portion  42  is a structure produced by, for example, injection-molding a resin material and is fixed to a −Z-side surface of the flow-path substrate  32 . As shown in  FIG. 4 , the housing portion  42  includes a second liquid chamber  422 , a supply flow path  424 , a discharging flow path  426 , a first connecting flow path  425 , and a second connecting flow path  427 . As shown in  FIGS. 3 and 4 , the second liquid chamber  422  is a recess extending along the Y axis and having an external shape corresponding to the first liquid chamber  322  in the flow-path substrate  32 . As can be seen from  FIG. 3 , a space communicating between the first liquid chamber  322  in the flow-path substrate  32  and the second liquid chamber  422  in the housing portion  42  serves as a liquid reservoir R. 
     In  FIG. 4 , a plurality of beam members B are formed in the second liquid chamber  422  so as to be spaced apart in the Y-axis direction. The beam members B are formed as integral parts of the housing portion  42 . The beam members B extend between portions of an inner circumferential surface  221  of the second liquid chamber  422  facing each other in the X-axis direction, so as to be parallel to the X axis. By forming the plurality of beam members B, the mechanical strength of the housing portion  42  is improved. 
     The supply flow path  424  is a flow path through which the ink is supplied to the second liquid chamber  422 , and the discharging flow path  426  is a flow path through which the ink is discharged from the second liquid chamber  422 . The supply flow path  424  and the discharging flow path  426  are formed in a linear shape so as to extend in the +Z-axis direction from the surface of the housing portion  42  farther from the flow-path substrate  32 . As shown in  FIG. 2 , the supply flow path  424  and the discharging flow path  426  are provided at positions away from each other in the horizontal direction. For example, the supply flow path  424  is formed near the −Y-side end of the housing portion  42 , and the discharging flow path  426  is formed near the +Y-side end of the housing portion  42 . In plan view as viewed in the Z-axis direction, the second liquid chamber  422  is located between the supply flow path  424  and the discharging flow path  426 . 
     The first connecting flow path  425  communicates between the second liquid chamber  422  and the supply flow path  424 . In other words, the first connecting flow path  425  is formed so as to extend from the supply flow path  424  to the second liquid chamber  422 . The +Z-side end of the supply flow path  424  and the −Y-side end of the second liquid chamber  422  are joined to each other by the first connecting flow path  425 . The ink supplied from the liquid container  14  and passing through the supply flow path  424  and the first connecting flow path  425  is stored in the liquid reservoir R. 
     The second connecting flow path  427  communicates between the second liquid chamber  422  and the discharging flow path  426 . In other words, the second connecting flow path  427  is formed so as to extend from the second liquid chamber  422  to the discharging flow path  426 . The +Z-side end of the discharging flow path  426  and the +Y-side end of the second liquid chamber  422  are joined to each other by the second connecting flow path  427 . 
     As shown in  FIG. 4 , the liquid discharge apparatus  100  includes a circulation mechanism  92  for circulating the ink in the liquid reservoir R. The circulation mechanism  92  circulates the ink discharged from the liquid reservoir R to the liquid reservoir R. The circulation mechanism  92  includes, for example, a first flow path  921 , a second flow path  922 , and a circulation pump  923 . 
     The first flow path  921  is a flow path through which the ink is supplied to the supply flow path  424  and joins the supply flow path  424 . The ink supplied from the first flow path  921  to the supply flow path  424  passes through the first connecting flow path  425  and is stored in the second liquid chamber  422 . The second flow path  922  is a flow path through which the ink is discharged from the discharging flow path  426  and joins the discharging flow path  426 . The ink flowing from the second liquid chamber  422  to the second connecting flow path  427  is discharged from the discharging flow path  426  to the second flow path  922 . The circulation pump  923  is a pressure-feed mechanism that feeds the ink supplied from the second flow path  922  to the first flow path  921 . In other words, the ink discharged from the liquid reservoir R is circulated to the supply flow path  424  through the second flow path  922 , the circulation pump  923 , and the first flow path  921 . 
     As is understood from the description above, in the ink supplied from the first flow path  921  to the liquid reservoir R, the ink that is not ejected from the nozzles N is discharged into the second flow path  922  and is circulated to the first flow path  921  by the circulation pump  923 . In other words, the ink inside the liquid discharge head  26  circulates. 
     The damper  48  in  FIGS. 2 and 3  absorbs pressure fluctuations in the liquid reservoir R and includes, for example, an elastically deformable flexible sheet member. More specifically, the damper  48  is disposed on the +Z-side surface of the flow-path substrate  32  so as to close the first liquid chamber  322 , the relay flow path  328 , and the plurality of first communicating flow paths  324  in the flow-path substrate  32  and constitute the bottom surface of the liquid reservoir R. 
     As shown in  FIGS. 2 and 3 , the pressure-chamber substrate  34  is a plate-like member having a plurality of pressure chambers C corresponding to different nozzles N. The plurality of pressure chambers C are arrayed along the Y axis. Each pressure chamber C is an elongated opening extending along the X axis in plan view. The end of the pressure chamber C in the +X-axis direction overlaps one first communicating flow path  324  in the flow-path substrate  32  in plan view, and the end of the pressure chamber C in the −X-axis direction overlaps one second communicating flow path  326  in the flow-path substrate  32  in plan view. 
     The vibration plate  36  is provided on the surface of the pressure-chamber substrate  34  farther from the flow-path substrate  32 . The vibration plate  36  is an elastically deformable plate-like member. As shown in  FIG. 3 , the vibration plate  36  according to the first embodiment includes a first layer  361  and a second layer  362 . The second layer  362  is located on the opposite side of the first layer  361  from the pressure-chamber substrate  34 . The first layer  361  is an elastic film made of an elastic material, such as silicon oxide (SiO 2 ), and the second layer  362  is an insulating film made of an insulating material, such as zirconium oxide (ZrO 2 ). It is possible to form a portion or the entirety of the pressure-chamber substrate  34  and the vibration plate  36  as a single component by selectively removing, in the thickness direction, a portion of the plate-like member having a certain thickness, the portion corresponding to the pressure chambers C. 
     As is understood from  FIG. 3 , the flow-path substrate  32  and the vibration plate  36  face each other inside each pressure chamber C with a space therebetween. The pressure chamber C is located between the flow-path substrate  32  and the vibration plate  36  and applies pressure to the ink in the pressure chamber C. The ink stored in the liquid reservoir R flows from the relay flow path  328  into the respective first communicating flow paths  324  and is supplied and poured into the plurality of pressure chambers C in parallel. 
     As shown in  FIGS. 2 and 3 , the plurality of piezoelectric elements  38  corresponding to the different nozzles N are disposed on the surface of the vibration plate  36  farther from the pressure chambers C. The piezoelectric elements  38  are actuators that are deformed by receiving the supply of driving signals and have an elongated shape extending along the X axis in plan view. The plurality of piezoelectric elements  38  are arrayed along the Y axis so as to correspond to the plurality of pressure chambers C. When the vibration plate  36  vibrates in response to the deformation of the piezoelectric elements  38 , the pressures in the pressure chambers C fluctuate, ejecting the ink in the pressure chambers C through the second communicating flow paths  326  and the nozzles N. In other words, the pressure chambers C generate pressure for discharging ink. The pressure chambers C are an example of energy generating chambers. 
     The sealing member  44  shown in  FIGS. 2 and 3  is a structure for protecting the plurality of piezoelectric elements  38  and for increasing the mechanical strength of the pressure-chamber substrate  34  and the vibration plate  36 . The sealing member  44  is fixed to the surface of the vibration plate  36  with, for example, an adhesive. The plurality of piezoelectric elements  38  are accommodated in a recess formed in the surface of the sealing member  44  facing the vibration plate  36 . 
     As shown in  FIG. 3 , for example, a wiring substrate  50  is joined to the surface of the vibration plate  36 . The wiring substrate  50  is a surface-mounted component on which a plurality of wires (not shown) for electrically connecting the control unit  20  and the liquid discharge head  26  are formed. For example, a flexible wiring substrate  50 , such as a flexible printed circuit (FPC), a flexible flat cable (FFC), or the like, is suitably employed. Driving signals for driving the piezoelectric elements  38  are supplied from the wiring substrate  50  to the piezoelectric elements  38 . 
     Hereinbelow, the shape of the first connecting flow path  425  will be described.  FIG. 5  is an enlarged sectional view of the first connecting flow path  425  in  FIG. 4 . As shown in  FIGS. 4 and 5 , the first connecting flow path  425  includes a side wall surface  251 , a bottom surface  253 , and a top surface  255 . In the first connecting flow path  425 , the bottom surface  253  is located on the lower side in the vertical direction, and the top surface  255  is located on the upper side in the vertical direction. In other words, in the first connecting flow path  425 , the surface located on the +Z-side is the bottom surface  253 , and the surface located on the −Z-axis side is the top surface  255 . 
     The side wall surface  251  of the first connecting flow path  425  is a surface continuous with the inner circumferential surface  241  of the supply flow path  424 . The side wall surface  251  according to the first embodiment is formed along the Z axis. In the side wall surface  251 , the −Z-side edge joins the lower edge of the inner circumferential surface  241  of the supply flow path  424  in the vertical direction, and the +Z-side edge joins the bottom surface  253 . 
     More specifically, the top surface  255  of the first connecting flow path  425  is formed so as to extend from the inner circumferential surface  241  of the supply flow path  424  to a top surface  223  of the second liquid chamber  422 . The −Y-side edge of the top surface  255  of the first connecting flow path  425  joins the lower edge, in the vertical direction, of the inner circumferential surface  241  of the supply flow path  424 . The +Y-side edge of the top surface  255  joins the −Y-side edge of the top surface  223  of the second liquid chamber  422 . The top surface  255  according to the first embodiment is inclined downward with respect to the horizontal plane. More specifically, the top surface  255  is an inclined surface whose +Y-side edge is located below the −Y-side edge. The horizontal plane is a plane perpendicular to the vertical direction, that is, a plane parallel to the X-Y plane. 
     The bottom surface  253  of the first connecting flow path  425  is formed so as to extend from the side wall surface  251  to the inner circumferential surface  221  of the second liquid chamber  422 . The −Y-side edge of the bottom surface  253  joins the +Z-side edge of the side wall surface  251 . The +Y-side edge of the bottom surface  253  joins the −Y-side edge of the inner circumferential surface  221  of the second liquid chamber  422 . The bottom surface  253  according to the first embodiment includes a first supply bottom surface  531 , a second supply bottom surface  532 , and a third supply bottom surface  533 . The first supply bottom surface  531 , the second supply bottom surface  532 , and the third supply bottom surface  533  are positioned in this order from the −Y-axis side to the +Y-axis side. In other words, the first supply bottom surface  531 , the second supply bottom surface  532 , and the third supply bottom surface  533  are positioned in this order from the upstream side to the downstream side of the ink flow. In still other words, the first supply bottom surface  531  is closest to the supply flow path  424 , the third supply bottom surface  533  is closest to the second liquid chamber  422 , and the second supply bottom surface  532  is located between the first supply bottom surface  531  and the third supply bottom surface  533 . The second supply bottom surface  532  is located closer to the second liquid chamber  422  than the first supply bottom surface  531  is, and the third supply bottom surface  533  is located closer to the second liquid chamber  422  than the second supply bottom surface  532  is. 
     In the first embodiment, the first supply bottom surface  531  and the second supply bottom surface  532  are continuous, and the second supply bottom surface  532  and the third supply bottom surface  533  are continuous. More specifically, the +Y-side edge of the first supply bottom surface  531  joins the −Y-side edge of the second supply bottom surface  532 , and the +Y-side edge of the second supply bottom surface  532  joins the −Y-side edge of the third supply bottom surface  533 . The +Y-side edge of the third supply bottom surface  533  joins the −Y-side inner circumferential surface  221  of the second liquid chamber  422 . 
     As shown in  FIG. 5 , the first supply bottom surface  531  is located below the supply flow path  424  in the vertical direction. Specifically, the first supply bottom surface  531  is located on the extension of the central axis of the supply flow path  424 . In other words, the first supply bottom surface  531  faces an opening O, which is located at the end of the supply flow path  424  adjacent to the first connecting flow path  425 . In sectional view as viewed in the X-axis direction, the width of the first supply bottom surface  531  is larger than the width of the opening O. For example, the width of the first supply bottom surface  531  in the Y-axis direction is about twice the width of the opening O. 
     In the description below, the angle formed between the first supply bottom surface  531  and the horizontal plane will be referred to as a “first angle θ 1 ”, and the angle formed between the second supply bottom surface  532  and the horizontal plane will be referred to as a “second angle θ 2 ”. More specifically, the first angle θ 1  is an angle formed between the first supply bottom surface  531  and the horizontal plane passing through the edge of the first supply bottom surface  531  adjacent to the side wall surface  251 . The first angle θ 1  according to the first embodiment is greater than or equal to 0 degrees and less than 20 degrees. In the first embodiment, the first angle θ 1  is 0 degrees. The angle formed between the third supply bottom surface  533  and the horizontal plane is also 0 degrees. More specifically, the angle formed between the third supply bottom surface  533  and the horizontal plane passing through the edge of the third supply bottom surface  533  adjacent to the second supply bottom surface  532  is 0 degrees. As is understood from above, the first supply bottom surface  531  and the third supply bottom surface  533  are surfaces parallel to the horizontal plane. In other words, the first supply bottom surface  531  and the third supply bottom surface  533  are surfaces inclined downward by 0 degrees with respect to the horizontal plane, from the supply flow path  424  toward the second liquid chamber  422 . In still other words, the first supply bottom surface  531  and the third supply bottom surface  533  are inclined by 0 degrees from the upstream side to the downstream side of the ink flow; that is, the surfaces that are inclined downward by 0 degrees toward the +Y side are the first supply bottom surface  531  and the third supply bottom surface  533 . 
     The second angle θ 2  is an angle formed between the horizontal plane and a surface inclined downward from the supply flow path  424  toward the second liquid chamber  422  and is greater than the first angle θ 1 . More specifically, the second angle θ 2  is an angle formed between the horizontal plane passing through the edge of the second supply bottom surface  532  adjacent to the first supply bottom surface  531  and an inclined surface inclined downward with respect to the horizontal plane passing through the edge of the second supply bottom surface  532  adjacent to the first supply bottom surface  531 . In other words, the second supply bottom surface  532  is an inclined surface that is inclined downward with respect to the first supply bottom surface  531  or an inclined surface that is inclined upward with respect to the third supply bottom surface  533 . That is, the second supply bottom surface  532  is an inclined surface whose +Y-side edge is located below the −Y-side edge. In other words, a surface inclined downward toward the +Y side is the second supply bottom surface  532 . The second angle θ 2  in the first embodiment is less than 90 degrees.  FIG. 5  shows a case where the second angle θ 2  is about 45 degrees. When viewed in the Y-axis direction, the first supply bottom surface  531 , the second supply bottom surface  532 , and the third supply bottom surface  533  are positioned in this order from top to bottom in the vertical direction. The height of the bottom surface  253  in the vertical direction decreases from the −Y-side edge toward the +Y-side edge. 
     As shown in  FIG. 5 , the edge of the second supply bottom surface  532  adjacent to the second liquid chamber  422  is located below the edge of the first supply bottom surface  531  adjacent to the second liquid chamber  422  by the distance D in the vertical direction. If the distance D is too short, the ink is difficult to flow into the liquid reservoir R. If the distance D is too long, an excessive amount of ink flows into the liquid reservoir R, allowing the bubbles in the ink to more easily flow into the liquid reservoir R. Hence, it is desirable that the distance D be from 0.6 mm to 1.2 mm. More preferably, the distance D is from 0.8 mm to 1.0 mm. However, the distance D is not limited to these examples. 
       FIG. 6  is an enlarged sectional view of the second connecting flow path  427  in  FIG. 4 . As shown in  FIG. 6 , the second connecting flow path  427  has a different shape from the first connecting flow path  425 . More specifically, the second connecting flow path  427  includes a side wall surface  271 , a bottom surface  273 , and a top surface  275 . 
     The side wall surface  271  of the second connecting flow path  427  is formed so as to be continuous with an inner circumferential surface  261  of the discharging flow path  426 . The side wall surface  271  in the first embodiment is formed parallel to the vertical direction. The −Z-side edge of the side wall surface  271  joins the lower edge, in the vertical direction, of the inner circumferential surface  261  of the discharging flow path  426 , and the +Z-side edge of the side wall surface  271  joins the bottom surface  273 . 
     The top surface  275  of the second connecting flow path  427  is formed so as to extend from the top surface  223  of the second liquid chamber  422  to the inner circumferential surface  261  of the discharging flow path  426 . The edge of the top surface  275  adjacent to the second liquid chamber  422  joins the +Y-side edge of the top surface  223  of the second liquid chamber  422 , and the edge of the top surface  275  adjacent to the discharging flow path  426  joins the +Z-side edge of the inner circumferential surface  261  of the discharging flow path  426 . More specifically, the top surface  275  of the second connecting flow path  427  includes a first discharging top surface  751  and a second discharging top surface  752 . The first discharging top surface  751  and the second discharging top surface  752  are formed so as to be continuous. The first discharging top surface  751  is located on the upstream side, and the second discharging top surface  752  is located on the downstream side in the ink flow direction. 
     The first discharging top surface  751  is an inclined surface whose edge adjacent to the discharging flow path  426  is located above the edge adjacent to the second liquid chamber  422 . That is, the first discharging top surface  751  is inclined upward with respect to the horizontal plane passing through the edge of the first discharging top surface  751  adjacent to the second liquid chamber  422 . The second discharging top surface  752  is an inclined surface whose edge adjacent to the discharging flow path  426  is located above the edge adjacent to the second liquid chamber  422 . That is, the second discharging top surface  752  is inclined upward with respect to the horizontal plane passing through the edge of the second discharging top surface  752  adjacent to the second liquid chamber  422 . In the first embodiment, the inclination angle of the second discharging top surface  752  with respect to the horizontal plane is greater than the inclination angle of the first discharging top surface  751  with respect to the horizontal plane. 
     The bottom surface  273  of the second connecting flow path  427  is formed so as to extend from the inner circumferential surface  221  of the second liquid chamber  422  to the side wall surface  271 . The edge of the bottom surface  273  adjacent to the second liquid chamber  422  joins the +Y-side portion of the inner circumferential surface  221  of the second liquid chamber  422 . The edge of the bottom surface  273  adjacent to the discharging flow path  426  joins the +Z-side edge of the side wall surface  271 . The bottom surface  273  in the first embodiment includes a first discharging bottom surface  731  and a second discharging bottom surface  732 . The first discharging bottom surface  731  and the second discharging bottom surface  732  are positioned in this order from the upstream side to the downstream side in the ink flow direction. In other words, the first discharging bottom surface  731  is located closer to the second liquid chamber  422  than the second discharging bottom surface  732  is. 
     The first discharging bottom surface  731  joins the inner circumferential surface  221  of the second liquid chamber  422  and the second discharging bottom surface  732 . The second discharging bottom surface  732  joins the first discharging bottom surface  731  and the side wall surface  271 . That is, in the first embodiment, the first discharging bottom surface  731  and the second discharging bottom surface  732  are continuous. More specifically, the edge of the first discharging bottom surface  731  farther from the second liquid chamber  422  joins the edge of the second discharging bottom surface  732  adjacent to the second liquid chamber  422 . The side wall surface  271  joins the second discharging bottom surface  732  and the inner circumferential surface  261  of the discharging flow path  426 . 
     As shown in  FIG. 6 , the first discharging bottom surface  731  is inclined upward with respect to the horizontal plane by a third angle θ 3  from the second liquid chamber  422  toward the discharging flow path  426 . The third angle θ 3  is an angle formed between an inclined surface inclined upward and the horizontal plane passing through the edge of the first discharging bottom surface  731  adjacent to the second liquid chamber  422 . More specifically, the third angle θ 3  is 0 degrees. In other words, the first discharging bottom surface  731  is a surface parallel to the horizontal plane. The third angle θ 3  is not limited to 0 degrees. The third angle θ 3  may be any desired angle that is greater than or equal to 0 degrees. 
     The second discharging bottom surface  732  is inclined upward with respect to the horizontal plane by a fourth angle θ 4  from the first discharging bottom surface  731  toward the discharging flow path  426 . The fourth angle θ 4  is an angle formed between an inclined surface inclined upward and the horizontal plane passing through the edge of the second discharging bottom surface  732  adjacent to the first discharging bottom surface  731 . More specifically, the fourth angle θ 4  is greater than or equal to the third angle θ 3  and is less than 90 degrees. For example, the fourth angle θ 4  is equal to the inclination angle of the first discharging top surface  751 . In other words, the second discharging bottom surface  732  is an inclined surface that is inclined upward with respect to the first discharging bottom surface  731 . When the third angle θ 3  and the fourth angle θ 4  are equal, the second discharging bottom surface  732  and the side wall surface  271  form a single continuous plane. 
     The side wall surface  271  is inclined upward with respect to the horizontal plane by a fifth angle θ 5 . The fifth angle θ 5  is an angle formed between the side wall surface  271  and the horizontal plane passing through the edge of the side wall surface  271  adjacent to the second discharging bottom surface  732 . More specifically, the fifth angle θ 5  is greater than or equal to the fourth angle θ 4 . The fifth angle θ 5  in the first embodiment is 90 degrees; that is, the side wall surface  271  is a plane perpendicular to the horizontal plane. When the fourth angle θ 4  and the fifth angle θ 5  are equal, the second discharging bottom surface  732  and the side wall surface  271  form a single continuous plane. 
     As shown in  FIG. 4 , the top surface  223  of the second liquid chamber  422  joins the first connecting flow path  425  at the −Y-axis side edge and joins the second connecting flow path  427  at the +Y-axis side edge. The top surface  223  of the second liquid chamber  422  in the first embodiment includes a first surface  231 , a second surface  232 , and a third surface  233 . The first surface  231 , the second surface  232 , and the third surface  233  are positioned in this order from the −Y side to the +Y side. In other words, the first surface  231  is closest to the first connecting flow path  425 , the third surface  233  is closest to the second connecting flow path  427 , and the second surface  232  is located between the first surface  231  and the third surface  233 . 
     The first surface  231  is continuous with the second surface  232 , and the second surface  232  is continuous with the third surface  233 . More specifically, the −Y-side edge of the first surface  231  joins the top surface  255  of the first connecting flow path  425 , and the +Y-side edge of the first surface  231  joins the −Y-side edge of the second surface  232 . The −Y-side edge of the third surface  233  joins the +Y-side edge of the second surface  232 , and the +Y-side edge of the third surface  233  joins the top surface  275  of the second connecting flow path  427 . 
     The first surface  231  is an inclined surface whose +Y-side edge is located above the −Y-side edge. In other words, the first surface  231  is inclined upward with respect to the horizontal plane passing through the −Y-side edge of the first surface  231 . Because of the inclination of the first surface  231 , the bubbles in the ink that have passed through the supply flow path  424  move along the first surface  231  to the vicinity of the discharging flow path  426 . The second surface  232  is an inclined surface whose +Y-side edge is located below the −Y-side edge. In other words, the second surface  232  is inclined downward with respect to the horizontal plane passing through the −Y-side edge of the second surface  232 . The third surface  233  is a horizontal plane. The shape of the top surface  223  in the second liquid chamber  422  is not limited to the example above. For example, the top surface  223  may be formed solely of an inclined surface whose +Y-side edge is located above the −Y-side edge, or the top surface  223  may be formed solely of a surface parallel to the horizontal plane. 
       FIG. 7  is a sectional view of the first connecting flow path  425  in Comparative Example 1. In Comparative Example 1, the bottom surface  253  of the first connecting flow path  425  is inclined from the side wall surface  251  toward the second liquid chamber  422 . That is, in Comparative Example 1, the bottom surface  253  of the first connecting flow path  425  is formed solely of the second supply bottom surface  532  in the first embodiment. As indicated by solid-line arrows, in the configuration of Comparative Example 1, although the ink that has passed through the first connecting flow path  425  smoothly flows into the liquid reservoir R along the bottom surface  253 , the bubbles carried by the ink flow also easily flow into the pressure chambers C via the liquid reservoir R, as shown by dashed-line arrows. 
       FIG. 8  is a sectional view of the first connecting flow path  425  in Comparative Example 2. In Comparative Example 2, the bottom surface  253  of the first connecting flow path  425  is formed of a horizontal surface extending from the side wall surface  251  to the second liquid chamber  422 . That is, in Comparative Example 2, the bottom surface  253  of the first connecting flow path  425  is formed solely of the first supply bottom surface  531  in the first embodiment. As indicated by dashed-line arrows, in the configuration of Comparative Example 2, the bubbles that have passed through the supply flow path  424  collide with the bottom surface  253  of the first connecting flow path  425  and, as a result, float up toward the top surface  223  of the second liquid chamber  422 . Hence, the bubbles are less likely to flow into the pressure chambers C. However, as shown by solid-line arrows, the ink that has passed through the supply flow path  424  collides with the bottom surface  253  of the first connecting flow path  425 , which decreases the speed of ink flow and makes it difficult for the ink to flow into the liquid reservoir R. This leads to a problem in that the ink is not smoothly supplied to the pressure chambers C. 
     In contrast, in the first embodiment, the bottom surface  253  of the first connecting flow path  425  has the first supply bottom surface  531  that is parallel to the horizontal plane, and the second supply bottom surface  532  that is inclined downward by the second angle θ 2 , which is greater than the first angle θ 1  and less than the 90 degrees, with respect to the horizontal plane. Accordingly, as shown by dashed-line arrows in  FIG. 5 , the bubbles that have passed through the supply flow path  424  and collided with the first supply bottom surface  531  float up toward the top surface  255  of the first connecting flow path  425 . The floated bubbles move along the top surface  223  of the second liquid chamber  422  and are eventually discharged outside from the discharging flow path  426 . That is, the bubbles are less likely to flow into the pressure chambers C. As shown by solid-line arrows in  FIG. 5 , the ink that has passed through the supply flow path  424  and collided with the first supply bottom surface  531  smoothly flow into the pressure chambers C along the second supply bottom surface  532  located below the first supply bottom surface  531 . As is understood from the description above, the configuration of the first embodiment can inhibit the bubbles in the ink from flowing into the pressure chambers C without blocking the ink flow directed from the supply flow path  424  to the pressure chambers C. 
     In particular, in the first embodiment, because the first supply bottom surface  531  is located below the supply flow path  424  in the vertical direction, it is possible to effectively suppress the entrance of the bubbles into the pressure chambers C. Furthermore, the configuration of the first embodiment, in which the first supply bottom surface  531  is continuous the second supply bottom surface  532 , has an advantage in that the ink that has passed through the supply flow path  424  smoothly flows into the pressure chambers C along the first supply bottom surface  531  and the second supply bottom surface  532 . 
     B. Second Embodiment 
     A second embodiment will be described. In the examples below, components having the same functions as those in the first embodiment will be denoted by the same reference signs as used in the description of the first embodiment, and detailed descriptions thereof will be omitted where appropriate. 
       FIG. 9  is a sectional view of the first connecting flow path  425  according to the second embodiment. In the second embodiment, the shape of the bottom surface  253  of the first connecting flow path  425  is different from that in the first embodiment. More specifically, whereas the first supply bottom surface  531  in the first embodiment is parallel to the horizontal plane, the first supply bottom surface  531  in the second embodiment is inclined downward with respect to the horizontal plane from the supply flow path  424  toward the second liquid chamber  422 . More specifically, the first supply bottom surface  531  is inclined downward with respect to the horizontal plane passing through the +Z-side edge of the side wall surface  251 . The first angle θ 1  in the second embodiment is greater than 0 degrees and less than 90 degrees. More specifically, the first angle θ 1  is greater than 0 degrees and less than 20 degrees. Preferably, the first angle θ 1  is less than 12 degrees.  FIG. 9  shows an example case in which the first angle θ 1  is about 10 degrees. The second angle θ 2  at the second supply bottom surface  532  in the second embodiment is greater than twice the first angle θ 1 . The second angle θ 2  is, for example, about 45 degrees, as in the first embodiment. 
     Also in the second embodiment, the same advantages as those in the first embodiment are achieved. In the configuration of the second embodiment, in which the first supply bottom surface  531  is an inclined surface that is inclined downward with respect to the horizontal plane by an angle greater than 0 degrees and less than 90 degrees, compared with a configuration in which, for example, the first supply bottom surface  531  is a surface parallel to the horizontal plane, it is possible to inhibit the ink that has passed through the supply flow path  424  and collided with the first supply bottom surface  531  from stagnating at the connection between the first supply bottom surface  531  and the side wall surface  251 . 
     C. Modification 
     The above-described embodiments can be variously modified. Modifications applicable to the above-described embodiments will be described as examples below. Two or more aspects selected from the following examples may be combined as appropriate where they are consistent. 
     1. The first angle θ 1  at the first supply bottom surface  531  and the second angle θ 2  at the second supply bottom surface  532  are not limited to the examples described in the embodiments above. The first angle θ 1  may be any angle that is greater than or equal to 0 degrees and less than 90 degrees. The second angle θ 2  may also be any angle that is greater than the first angle θ 1  and less than 90 degrees. 
     2. In the above-described embodiments, an example configuration in which the bottom surface  253  of the first connecting flow path  425  includes the first supply bottom surface  531 , the second supply bottom surface  532 , and the third supply bottom surface  533  has been described. However, the shape of the bottom surface  253  of the first connecting flow path  425  is not limited thereto. For example, as shown in  FIG. 10 , it is possible that the bottom surface  253  of the first connecting flow path  425  do not have the third supply bottom surface  533 . It is also possible that the bottom surface  253  include a surface that does not block the ink flow, in addition to the first supply bottom surface  531 , the second supply bottom surface  532 , and the third supply bottom surface  533 . Examples of the surface that does not block the ink flow include a surface parallel to the horizontal plane, a surface inclined downward with respect to the horizontal plane from the supply flow path  424  toward the second liquid chamber  422 , a curved surface, or the like. As is understood from the description above, another surface may be disposed between the first supply bottom surface  531  and the second supply bottom surface  532 ; that is, the first supply bottom surface  531  and the second supply bottom surface  532  do not need to be continuous. 
     3. In the above-described embodiments, a flat surface parallel to the vertical direction has been described as the side wall surface  251  of the first connecting flow path  425 . However, for example, as shown in  FIG. 11 , the side wall surface  251  may be an inclined surface. For example, an inclined surface that is inclined such that the +Z-side edge is away from the second liquid chamber  422  may be used as the side wall surface  251 . 
     4. In the above-described embodiments, the side wall surface  251  of the first connecting flow path  425  is formed so as to be continuous with the inner circumferential surface  241  of the supply flow path  424 . However, the side wall surface  251  does not need to be continuous with the inner circumferential surface  241  of the supply flow path  424 . For example, as shown in  FIG. 12 , the position of the side wall surface  251  of the first connecting flow path  425  and the position of the inner circumferential surface  241  of the supply flow path  424  in the Y-axis direction may be differentiated. 
     5. As shown in  FIGS. 11 and 12 , the first connecting flow path  425  may include a portion that is located further on the −Y-axis side than the opening O of the supply flow path  424  is. In other words, the −Y-side edge of the first supply bottom surface  531  may be located at a position further away from the central axis P of the supply flow path  424  than the periphery of the opening O is. The −X-side and +X-side edges of the first supply bottom surface  531  may be located at positions further away from the central axis P of the supply flow path  424  than the periphery of the opening O is. As is understood from the description above, the first supply bottom surface  531  may be formed over a larger area than the opening O, as viewed in the Z-axis direction. 
     6. In the above-described embodiments, although the width of the first supply bottom surface  531  in the Y-axis direction is about twice the width of the opening O, the width of the first supply bottom surface  531  in the Y-axis direction is not limited thereto. For example, the width of the first supply bottom surface  531  in the Y-axis direction may be equal to the width of the opening O, as shown in  FIG. 13 , or may be smaller than the width of the opening O, as shown in  FIG. 14 . However, from the standpoint of suppressing the entrance of bubbles in the ink into the pressure chambers C, a configuration in which the first supply bottom surface  531  is formed at at least a portion facing the opening O in the X-Y plane is preferred. 
     7. In the above-described embodiments, although the top surface  255  of the first connecting flow path  425  is an inclined surface, the first connecting flow path  425  may have any shape. For example, the top surface  255  may be a surface parallel to the horizontal plane, or the top surface  255  may include a plurality of surfaces having different inclinations. 
     8. The shape of the second connecting flow path  427  is not limited to one described in the above-described embodiments. For example, the bottom surface  273  of the second connecting flow path  427  may include a plurality of surfaces having different inclinations. Alternatively, an inclined surface may be used as the side wall surface  271  of the second connecting flow path  427 . 
     9. In the above-described embodiments, although the supply flow path  424  is formed linearly so as to extend in the vertical direction, the supply flow path  424  may have any shape. For example, it is possible to employ a configuration in which the supply flow path  424  includes a portion inclined with respect to the vertical direction or a configuration in which the supply flow path  424  includes a portion extending linearly in the horizontal direction. The discharging flow path  426  may also have any shape. A member for preventing the bubbles that have flowed into the first connecting flow path  425  through the supply flow path  424  from returning to the supply flow path  424  may be provided near the opening O of the supply flow path  424 . 
     10. In the above-described embodiments, the supply flow path  424  and the discharging flow path  426  may be formed in a member different from the housing portion  42 . For example, a member having the supply flow path  424  and the discharging flow path  426  is coupled to the housing portion  42  having the second liquid chamber  422 , the first connecting flow path  425 , and the second connecting flow path  427 . 
     11. The driving elements that eject the liquid in the pressure chambers C from the nozzles N are not limited to the piezoelectric elements  38 , as described in the above-described embodiments. For example, it is possible to use, as the driving elements, heater elements that cause film boiling by means of heating, thus generating bubbles in the pressure chambers C and fluctuating the pressure. As is understood from this example, the driving elements are comprehensively expressed as elements that eject the liquid in the pressure chambers C from the nozzles N, and the operation method thereof (e.g., a piezoelectric method, a thermal method, or the like) and the detailed configuration thereof are not specifically limited. As is understood from the description above, the pressure chambers C are an example of energy generating chambers in which energy for discharging ink supplied from the liquid reservoir R is generated. 
     12. In the above-described embodiments, although the liquid discharge apparatus  100  of a serial type, in which the transport body  242  having the liquid discharge head  26  is reciprocated, has been described, the present disclosure may also be applied to a line-type liquid discharge apparatus, in which a plurality of nozzles N are distributed over the overall width of the medium  12 . 
     13. The liquid discharge apparatus  100  described in the above-described embodiments can be applied to various apparatuses, such as a facsimile machine, a copier, and the like, besides apparatuses used solely for printing. The use of the liquid discharge apparatus of the present disclosure is not limited to printing. For example, a liquid discharge apparatus that ejects a colorant solution is used as an apparatus for producing color filters of liquid-crystal display devices. A liquid discharge apparatus that ejects a conducting-material solution is used as an apparatus for producing wires and electrodes of wiring boards.