Liquid injection head and liquid injection system

Abstract

To provide a liquid jet head and a liquid jet system, which can more efficiently replace liquid in the vicinity of a nozzle.SOLUTION: A liquid jet had includes: a first flow passage 201 which extends in a first axial direction Y between a supply port and a discharge port; and a nozzle 21 which is provided to be branched from the first flow passage 201 and the nozzle 21 which discharges liquid along a second axial direction Z orthogonal to the first axial direction Y. The nozzle 21 has a first nozzle section 21a in which a first opening 211 for discharging liquid is formed and a second nozzle section 21b in which a second opening 212 to be a connection port with the first flow passage 201 is formed. A diameter r2 in the first axial direction Y in the second opening 212 is larger than a diameter r1 in the first axial direction Y in the first opening 211.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a liquid injection head for injecting a liquid from a nozzle and a liquid injection system, and particularly to an inkjet recording head for injecting ink as the liquid and an inkjet recording system.

Background Art

[0002] In a liquid injection head for injecting a liquid, for example, in order to discharge bubbles contained in the liquid, suppress thickening of the liquid, and suppress sedimentation of components contained in the liquid, a liquid injection system has been proposed in which the liquid in the liquid injection head is circulated (see, for example, Patent Document 1).

[0003] In the liquid injection head of Patent Document 1, by circulating the liquid in the liquid injection head through a branch flow path provided near the nozzle, thickening due to drying of the liquid not injected from the nozzle is suppressed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, there is a need for a liquid injection head that can more efficiently replace the liquid near the nozzle.

[0006] Note that such a problem exists not only in an inkjet recording head but also in a liquid injection head that injects a liquid other than ink.

[0007] In view of such circumstances, an object of the present invention is to provide a liquid injection head and a liquid injection system that can more efficiently replace the liquid near the nozzle. [Means for solving the problem]

[0008] An aspect of the present invention that solves the above problems is a liquid injection head comprising: a first flow path extending in a first axial direction between a supply port and a discharge port; and a nozzle branching off from the first flow path, which discharges liquid along a second axial direction perpendicular to the first axial direction, wherein the nozzle comprises a first nozzle portion having a first opening for discharging liquid, and a second nozzle portion having a second opening which is a connection port to the first flow path, and the diameter r2 in the first axial direction of the second opening is larger than the diameter r1 in the first axial direction of the first opening.

[0009] Another embodiment is a liquid injection system characterized by comprising the above-described liquid injection head and a mechanism that supplies liquid to the supply port and recovers the liquid from the discharge port to circulate the liquid. [Brief explanation of the drawing]

[0010] [Figure 1] This is a plan view of the recording head according to Embodiment 1. [Figure 2] This is a cross-sectional view of the recording head according to Embodiment 1. [Figure 3] This is a cross-sectional view of the recording head according to Embodiment 1. [Figure 4] This is a cross-sectional view of the recording head according to Embodiment 1. [Figure 5] This is a cross-sectional view illustrating the streamlines of the recording head according to Embodiment 1. [Figure 6] This is a cross-sectional view of a recording head according to another embodiment. [Figure 7] This is a cross-sectional view of a recording head according to another embodiment. [Figure 8] This figure shows a schematic configuration of a recording device according to one embodiment. [Figure 9] This is a block diagram illustrating a liquid injection system according to one embodiment. [Modes for carrying out the invention]

[0011] The present invention will be described in detail below based on embodiments. However, the following description represents one aspect of the present invention and can be arbitrarily modified within the scope of the invention. In each figure, the same reference numerals indicate the same components, and their descriptions are omitted as appropriate. In each figure, X, Y, and Z represent three mutually orthogonal spatial axes. In this specification, the directions along these axes are referred to as the X direction, Y direction, and Z direction. In each figure, the direction in which the arrow points is described as the positive (+) direction, and the opposite direction of the arrow is described as the negative (-) direction. Furthermore, the Z direction indicates the vertical direction, with the +Z direction indicating vertically downward and the -Z direction indicating vertically upward.

[0012] (Embodiment 1) An inkjet recording head, which is an example of a liquid jet head according to this embodiment, will be described with reference to Figures 1 to 6. Figure 1 is a plan view of an inkjet recording head, which is an example of a liquid jet head according to Embodiment 1 of the present invention, as seen from the nozzle side. Figure 2 is a cross-sectional view taken along line AA' of Figure 1. Figure 3 is an enlarged view of the main part of Figure 2. Figure 4 is a cross-sectional view taken along line BB' of Figure 3. Figure 5 is a diagram illustrating the streamlines in the flow path of Figure 3. Figure 6 is a diagram illustrating the streamlines in the flow path of a comparative example.

[0013] As shown in the figure, an inkjet type recording head 1 (hereinafter also simply referred to as recording head 1), which is an example of a liquid jet head of this embodiment, comprises a flow channel substrate including a flow channel forming substrate 10, a communication plate 15, a nozzle plate 20, a protective substrate 30, a case member 40, and a compliance substrate 49.

[0014] The channel-forming substrate 10 is made of a silicon single crystal substrate, and a diaphragm 50 is formed on one of its surfaces. The diaphragm 50 may be a single layer or a laminate selected from a silicon dioxide layer or a zirconium oxide layer.

[0015] The flow channel forming substrate 10 has multiple pressure chambers 12 that constitute individual flow channels 200, each partitioned by multiple partition walls. The multiple pressure chambers 12 are arranged at a predetermined pitch along the X direction, where multiple nozzles 21 for ejecting ink are arranged side by side. In this embodiment, there is one row of pressure chambers 12 arranged side by side in the X direction. The flow channel forming substrate 10 is arranged such that its in-plane direction includes the X and Y directions. In this embodiment, the portion of the flow channel forming substrate 10 between the pressure chambers 12 arranged side by side in the X direction is referred to as a partition wall. This partition wall is formed along the Y direction. That is, the partition wall refers to the portion of the flow channel forming substrate 10 that overlaps with the pressure chambers 12 in the Y direction.

[0016] In this embodiment, only a pressure chamber 12 is provided on the flow path forming substrate 10. However, a flow path resistance-imparting section may be provided, which has a narrower cross-sectional area that crosses the flow path than the pressure chamber 12, in order to impart flow path resistance to the ink supplied to the pressure chamber 12.

[0017] On one side in the -Z direction of such a flow channel forming substrate 10, a diaphragm 50 is formed. On this diaphragm 50, a first electrode 60, a piezoelectric layer 70, and a second electrode 80 are laminated by film formation and lithography methods to constitute a piezoelectric actuator 300. In this embodiment, the piezoelectric actuator 300 serves as an energy generating element that causes a pressure change in the ink within the pressure chamber 12. Here, the piezoelectric actuator 300 is also referred to as a piezoelectric element, referring to the portion including the first electrode 60, the piezoelectric layer 70, and the second electrode 80. Generally, either one of the electrodes of the piezoelectric actuator 300 is used as a common electrode, and the other electrode and the piezoelectric layer 70 are patterned for each pressure chamber 12 for configuration. In this embodiment, the first electrode 60 is used as the common electrode of the piezoelectric actuator 300, and the second electrode 80 is used as the individual electrode of the piezoelectric actuator 300. However, there is no problem even if this is reversed due to the convenience of the drive circuit and wiring. In the example described above, the diaphragm 50 and the first electrode 60 act as a diaphragm. Of course, it is not limited to this. For example, the diaphragm 50 may not be provided, and only the first electrode 60 may act as a diaphragm. Also, the piezoelectric actuator 300 itself may substantially serve as a diaphragm.

[0018] Also, a lead electrode 90 is connected to the second electrode 80 of each such piezoelectric actuator 300, and a voltage is selectively applied to each piezoelectric actuator 300 via this lead electrode 90. Also, a protective substrate 30 is joined to the surface of the flow channel forming substrate 10 in the -Z direction.

[0019] In the region facing the piezoelectric actuator 300 of the protection substrate 30, a piezoelectric actuator holding portion 31 having a space that does not inhibit the movement of the piezoelectric actuator 300 is provided. The piezoelectric actuator holding portion 31 only needs to have a space that does not inhibit the movement of the piezoelectric actuator 300, and this space may or may not be sealed. Further, the piezoelectric actuator holding portion 31 is formed in a size that integrally covers a plurality of columns of piezoelectric actuators 300 arranged in parallel in the X direction. Of course, the piezoelectric actuator holding portion 31 is not particularly limited thereto, and may individually cover the piezoelectric actuator 300, or may cover each group composed of two or more piezoelectric actuators 300 arranged in parallel in the X direction.

[0020] As such a protection substrate 30, it is preferable to use a material having substantially the same coefficient of thermal expansion as that of the flow path forming substrate 10, for example, glass, ceramic material, etc. In this embodiment, it is formed using a single crystal silicon substrate made of the same material as the flow path forming substrate 10.

[0021] Further, the protection substrate 30 is provided with through holes 32 penetrating the protection substrate 30 in the Z direction. And the vicinity of the end of the lead electrode 90 drawn from each piezoelectric actuator 300 is extended to be exposed within the through hole 32, and is electrically connected to the flexible cable 120 within the through hole 32. The flexible cable 120 is a wiring substrate having flexibility, and in this embodiment, a drive circuit 121 which is a semiconductor element is mounted thereon. Note that the lead electrode 90 and the drive circuit 121 may be electrically connected without passing through the flexible cable 120. Also, a flow path may be provided in the protection substrate 30.

[0022] Further, on the protection substrate 30, a case member 40 that defines a supply flow path communicating with the plurality of pressure chambers 12 together with the protection substrate 30 is fixed. The case member 40 is joined to the side of the protection substrate 30 opposite to the flow path forming substrate 10, and is also joined to a communication plate 15 described later.

[0023] Such a case member 40 is provided with a first liquid chamber section 41 that constitutes part of the first common liquid chamber 101 and a second liquid chamber section 42 that constitutes part of the second common liquid chamber 102. The first liquid chamber section 41 and the second liquid chamber section 42 are provided on both sides of a row of pressure chambers 12 in the Y direction.

[0024] Each of the first liquid chamber 41 and the second liquid chamber 42 has a concave shape that opens to the -Z side surface of the case member 40 and is continuously provided across a plurality of pressure chambers 12 arranged in parallel in the X direction.

[0025] Furthermore, the case member 40 is provided with a supply port 43 that communicates with the first liquid chamber 41 and supplies ink to the first liquid chamber 41, and a discharge port 44 that communicates with the second liquid chamber 42 and discharges ink from the second liquid chamber 42.

[0026] Furthermore, the case member 40 is provided with a connection port 45 through which a flexible cable 120 is inserted, communicating with the through-hole 32 of the protective substrate 30.

[0027] On the other hand, on the +Z side of the flow path forming substrate 10, which is the side opposite to the protective substrate 30, a communication plate 15, a nozzle plate 20, and a compliance substrate 49 are provided.

[0028] The nozzle plate 20 has multiple nozzles 21 formed therein that spray ink in the +Z direction, which is part of the second axial direction (Z direction). In this embodiment, as shown in Figure 1, the multiple nozzles 21 are arranged in a straight line along the X direction, forming a single row of nozzles 22. The surface of the nozzle plate 20 on the +Z side where the nozzles 21 open is referred to as the nozzle surface 20a. The nozzles 21 will be described in more detail later.

[0029] In this embodiment, the connecting plate 15 includes a first connecting plate 151 and a second connecting plate 152. The first connecting plate 151 and the second connecting plate 152 are stacked in the Z direction such that the -Z side is the first connecting plate 151 and the +Z side is the second connecting plate 152.

[0030] The first connecting plate 151 and the second connecting plate 152 that constitute such a connecting plate 15 can be manufactured from metals such as stainless steel, glass, ceramic materials, etc. It is preferable that the connecting plate 15 be made of a material with approximately the same coefficient of thermal expansion as the channel forming substrate 10, and in this embodiment, it was formed using a silicon single crystal substrate made of the same material as the channel forming substrate 10.

[0031] The communication plate 15 is provided with a first communication section 16 that communicates with the first liquid chamber section 41 of the case member 40 and forms part of the first common liquid chamber 101, and a second communication section 17 and a third communication section 18 that communicate with the second liquid chamber section 42 of the case member 40 and form part of the second common liquid chamber 102. Furthermore, the communication plate 15 is provided with a flow path that connects the first common liquid chamber 101 and the pressure chamber 12, a flow path that connects the pressure chamber 12 and the nozzle 21, and a flow path that connects the nozzle 21 and the second common liquid chamber 102, as will be described in more detail later. These flow paths provided on the communication plate 15 constitute part of the individual flow paths 200.

[0032] The first communication portion 16 is provided in the Z direction at a position overlapping the first liquid chamber portion 41 of the case member 40, and is provided penetrating the communication plate 15 in the Z direction so as to open on both the +Z side and the -Z side of the communication plate 15. The first communication portion 16 communicates with the first liquid chamber portion 41 on the -Z side to constitute the first common liquid chamber 101. That is, the first common liquid chamber 101 is composed of the first liquid chamber portion 41 of the case member 40 and the first communication portion 16 of the communication plate 15. Furthermore, the first communication portion 16 extends in the -Y direction to a position overlapping the pressure chamber 12 in the Z direction on the +Z side. Note that the first common liquid chamber 101 may be composed of the first liquid chamber portion 41 of the case member 40 without providing the first communication portion 16 on the communication plate 15.

[0033] The second communication section 17 is provided in the Z direction at a position overlapping the second liquid chamber section 42 of the case member 40, and is provided opening on the -Z side surface of the first communication plate 151. Furthermore, the second communication section 17 is provided widened on the +Z side toward the nozzle 21 in the +Y direction.

[0034] The third communication section 18 is provided by penetrating the second communication plate 152 in the Z direction, such that one end communicates with the portion of the second communication section 17 that is widened in the +Y direction. The opening of the third communication section 18 on the +Z side is covered by the nozzle plate 20. In other words, by providing the second communication section 17 on the first communication plate 151, only the opening of the third communication section 18 on the +Z side can be covered by the nozzle plate 20, so the nozzle plate 20 can be provided in a relatively small area, and costs can be reduced.

[0035] The second common liquid chamber 102 is formed by the second and third connecting portions 17 and 18 provided on the connecting plate 15 and the second liquid chamber portion 42 provided on the case member 40. Alternatively, the second common liquid chamber 102 may be formed by the second liquid chamber portion 42 of the case member 40 without providing the second and third connecting portions 17 and 18 on the connecting plate 15.

[0036] A compliance substrate 49 having a compliance portion 494 is provided on the +Z side surface of the communication plate 15 where the first communication portion 16 opens. This compliance substrate 49 seals the opening on the nozzle surface 20a side of the first common liquid chamber 101.

[0037] In this embodiment, such a compliance substrate 49 comprises a sealing film 491 made of a flexible thin film and a fixed substrate 492 made of a hard material such as metal. The region of the fixed substrate 492 facing the first common liquid chamber 101 is an opening 493 that is completely removed in the thickness direction, so that a part of the wall surface of the first common liquid chamber 101 becomes a compliance portion 494 which is a flexible portion sealed only by the flexible sealing film 491. By providing a compliance portion 494 on a part of the wall surface of the first common liquid chamber 101 in this way, pressure fluctuations of the ink in the first common liquid chamber 101 can be absorbed by the deformation of the compliance portion 494.

[0038] Furthermore, the flow path substrate, including the flow path forming substrate 10, the communication plate 15, the nozzle plate 20, and the compliance substrate 49, is provided with a plurality of individual flow paths 200 that communicate with the first common liquid chamber 101 and the second common liquid chamber 102, and send the ink from the first common liquid chamber 101 to the second common liquid chamber 102. Here, each individual flow path 200 in this embodiment is provided for each nozzle 21 and communicates with the first common liquid chamber 101 and the second common liquid chamber 102, and includes the nozzle 21. A plurality of such individual flow paths 200 are arranged in parallel along the X direction, which is the direction in which the nozzles 21 are arranged side by side. Two adjacent individual flow paths 200 in the X direction, which is the direction in which the nozzles 21 are arranged side by side, are provided to communicate with the first common liquid chamber 101 and the second common liquid chamber 102, respectively. In other words, each of the multiple individual flow paths 200 provided for each nozzle 21 is connected only through the first common liquid chamber 101 and the second common liquid chamber 102, and the multiple individual flow paths 200 do not communicate with each other anywhere other than the first common liquid chamber 101 and the second common liquid chamber 102. That is, in this embodiment, a flow path provided with one nozzle 21 and one pressure chamber 12 is referred to as an individual flow path 200, and each individual flow path 200 is connected to each other only through the first common liquid chamber 101 and the second common liquid chamber 102.

[0039] As shown in Figures 2 and 3, the individual flow path 200 comprises a nozzle 21, a pressure chamber 12, a first flow path 201, a second flow path 202, and a supply path 203.

[0040] As described above, the pressure chamber 12 is provided between the recess in the flow path forming substrate 10 and the communication plate 15, and extends in the Y direction. That is, the supply passage 203 is connected to one end of the pressure chamber 12 in the Y direction, and the second flow path 202 is connected to the other end in the Y direction, and the pressure chamber 12 is configured so that ink flows in the Y direction. In other words, the direction in which the pressure chamber 12 extends is the direction in which the ink flows within the pressure chamber 12.

[0041] In this embodiment, only a pressure chamber 12 is formed on the flow path forming substrate 10, but the embodiment is not limited to this, and a flow path resistance applying section with a narrower cross-sectional area than the pressure chamber 12 may be provided at the upstream end of the pressure chamber 12, i.e., the end in the +Y direction, to apply flow path resistance.

[0042] The supply passage 203 connects the pressure chamber 12 and the first common liquid chamber 101, and is provided penetrating the first communication plate 151 in the Z direction. The supply passage 203 communicates with the first common liquid chamber 101 at its +Z end and with the pressure chamber 12 at its -Z end. In other words, the supply passage 203 extends in the Z direction. Here, the direction in which the supply passage 203 extends is the direction in which the ink flows through the supply passage 203.

[0043] The first flow path 201 is provided extending in the Y direction between the supply port 43 and the discharge port 44. The direction in which the first flow path 201 extends is the direction in which the ink flows through the first flow path 201. In this embodiment, the first axial direction in which the first flow path 201 extends is the Y direction. This first flow path 201 communicates with the second flow path 202 at its +Y direction end and with the third communication section 18 of the second common liquid chamber 102 at its -Y direction end.

[0044] In this embodiment, the first flow path 201 is provided between the second communication plate 152 and the nozzle plate 20. Specifically, the first flow path 201 is formed by providing a recess in the second communication plate 152 and covering the opening of this recess with the nozzle plate 20. However, the first flow path 201 is not limited to this, and may also be formed by providing a recess in the nozzle plate 20 and covering the recess of the nozzle plate 20 with the second communication plate 152, or by providing recesses in both the second communication plate 152 and the nozzle plate 20.

[0045] In this embodiment, the first channel 201 is provided such that the cross-sectional area that crosses the ink flowing through the channel, that is, the cross-sectional area in the planar direction including the X and Z directions, is the same area over the Y direction. Note that the cross-sectional area of ​​the first channel 201 that crosses the channel is the same area over the Y direction refers to the portion excluding the protrusion 153, which will be described in more detail later. Alternatively, the first channel 201 may be provided such that the cross-sectional area that crosses it differs in the Y direction. Incidentally, different cross-sectional areas of the first channel 201 include cases where the height in the Z direction is different, the width in the X direction is different, or both are different.

[0046] Furthermore, the cross-sectional shape of the first channel 201 that crosses the channel, that is, the cross-sectional shape in the planar direction including the X and Z directions, is rectangular. However, the cross-sectional shape of the first channel 201 that crosses the channel is not particularly limited and may be trapezoidal, semicircular, semielliptical, etc.

[0047] The second flow path 202 is provided extending in the Z direction between the pressure chamber 12 and the first flow path 201. The direction in which the second flow path 202 extends is the direction in which the ink flows through the second flow path 202. In this embodiment, the direction in which the second flow path 202 extends is the Z direction, which is the same as the second axis direction. In this embodiment, such a second flow path 202 is provided penetrating the communication plate 15 in the Z direction, communicating with the pressure chamber 12 at its -Z end and with the first flow path 201 at its +Z end.

[0048] Furthermore, the second flow path 202 refers to the portion formed in the communication plate 15. That is, the second flow path 202 extends from the bottom surface in the +Z direction of the pressure chamber 12 to the portion covered by the nozzle plate 20.

[0049] Multiple nozzles 21 are provided on the nozzle plate 20. Each nozzle 21 is positioned to communicate with the middle of each first flow path 201. That is, the nozzles 21 are provided branching off from the first flow path 201, which extends in the Y direction, in the +Z direction. As a result, ink droplets are ejected from the nozzles 21 in the +Z direction, which is the second axial direction of the Z direction. In other words, the nozzles 21 are provided penetrating the nozzle plate 20 in the Z direction such that the end in the -Z direction communicates with the middle of the first flow path 201, and the end in the +Z direction opens onto the nozzle surface 20a, which is the +Z side surface of the nozzle plate 20. Therefore, the second axial direction in which the nozzles 21 eject ink droplets is the +Z direction.

[0050] Here, when we say that the nozzle 21 is provided branching off from the first flow path 201, we mean that the nozzle 21 is in communication with the middle of the first flow path 201. Furthermore, when we say that the nozzle 21 is in communication with the middle of the first flow path 201, we mean that when viewed from a plane in the Z direction, the nozzle 21 is positioned to overlap with the first flow path 201. Incidentally, when viewed from a plane in the Z direction, the nozzle 21 is positioned to overlap with the second flow path 202, and is not said to be provided to communicate with the middle of the first flow path 201. In other words, the first flow path 201 in this embodiment is the part that does not overlap with the second flow path 202 when viewed from a plane in the Z direction.

[0051] Furthermore, it is preferable that the cross-sectional area of ​​the ink flowing through the first channel 201, through which the nozzle 21 communicates, is smaller than the cross-sectional area of ​​the ink flowing through the second channel 202. Here, the cross-sectional area of ​​the first channel 201 refers to the area of ​​the cross-section in the planar direction including the X and Z directions. The cross-sectional area of ​​the second channel 202 refers to the area of ​​the cross-section in the planar direction including the Y and Z directions. By making the cross-sectional area of ​​the first channel 201 relatively small, the individual channels 200 can be arranged at high density in the X direction, and the nozzles 21 can be arranged at high density in the X direction, while suppressing the increase in size of the recording head 1 in the Z direction. In addition, by making the cross-sectional area of ​​the second channel 202 relatively large, it is possible to suppress the decrease in flow resistance from the pressure chamber 12 to the nozzle 21, thereby suppressing a decrease in the liquid discharge characteristics, particularly the weight of the discharged droplets. In particular, by widening the second channel 202 in the Y direction and increasing its cross-sectional area, the flow resistance of the second channel 202 can be reduced, and the low density arrangement of the individual channels 200 can be suppressed, allowing for a high-density arrangement of the individual channels 200. In this embodiment, the first channel 201 and the second channel 202 are provided with the same width in the X direction, and the width of the second channel 202 in the Y direction is made wider than the height of the first channel 201 in the Z direction, thereby making the cross-sectional area of ​​the first channel 201 smaller than the cross-sectional area of ​​the second channel 202. This increases the cross-sectional area of ​​the second channel 202 and allows for a high-density arrangement of the first channel 201 and the second channel 202 in the X direction.

[0052] Furthermore, the nozzle 21 refers to a member provided with the first flow path 201, which in this embodiment is a member different from the communication plate 15, and in this embodiment is formed on the nozzle plate 20.

[0053] Here, the nozzle 21 has a first nozzle portion 21a and a second nozzle portion 21b that are arranged side by side in the Z direction, which is the thickness direction of the nozzle plate 20.

[0054] The first nozzle portion 21a is located on the outside side of the nozzle plate 20, i.e., on the +Z side, and is provided with a first opening 211 from which ink droplets are ejected. In other words, ink droplets are ejected to the outside in the +Z direction from the first opening 211 on the +Z side of the first nozzle portion 21a of the nozzle plate 20.

[0055] Furthermore, in this embodiment, the first nozzle portion 21a is provided with the same shape as the first opening 211 over the Z direction. Here, the statement that the first nozzle portion 21a is provided with the same shape as the first opening 211 over the Z direction means that the cross-sectional shape and cross-sectional area of ​​the first nozzle portion 21a, including the X and Y directions, are the same over the Z direction. In this embodiment, the shape of the first opening 211 when viewed from the Z direction in plan is circular. Of course, the shape of the first opening 211 is not particularly limited to this, and may be elliptical, rectangular, polygonal, daruma-shaped, etc.

[0056] The second nozzle section 21b is located on the -Z side of the nozzle plate 20 and is provided with a second opening 212, which is a connection port to the first flow path 201 extending in the Y direction, as will be described in more detail later. In other words, the first axial direction, which is the direction in which the first flow path 201 extends, is the Y direction in this embodiment. These first axial direction (Y direction) and the second axial direction (Z direction) are orthogonal to each other.

[0057] Furthermore, the second nozzle portion 21b is provided with the same shape as the second opening 212 over the Z direction. Here, it is said that the second nozzle portion 21b is provided with the same shape as the second opening 212 over the Z direction, which means that the cross-sectional shape and cross-sectional area of ​​the second nozzle portion 21b, including the X and Y directions, are the same over the Z direction. Of course, the second nozzle portion 21b is not limited to being formed with the same opening shape over the Z direction, and may be provided so that the opening area gradually decreases toward the first nozzle portion 21a. In this embodiment, the shape of the second opening 212 when viewed from the Z direction is circular. Of course, the shape of the second opening 212 is not particularly limited to this, and may be elliptical, rectangular, polygonal, daruma-shaped, etc.

[0058] Furthermore, the diameter r2 in the Y direction of the second opening 212 of the second nozzle portion 21b constituting the nozzle 21 is larger than the diameter r1 in the Y direction of the first opening 211 of the first nozzle portion 21a. That is, r2 > r1. Here, the diameter r1 in the Y direction of the first opening 211 is the width dimension of the widest part of the first opening 211 in the Y direction. Similarly, the diameter r2 in the Y direction of the second opening 212 is the width dimension of the widest part of the second opening 212 in the Y direction. In addition, in this embodiment, the diameter in the X direction of the second opening 212 of the second nozzle portion 21b is larger than the diameter in the X direction of the first opening 211 of the first nozzle portion 21a. In other words, as shown in Figure 4, the first nozzle portion 21a and the second nozzle portion 21b of this embodiment have a circular shape when viewed from the Z direction. Therefore, the diameter r1 in the Y direction of the first nozzle portion 21a is the diameter of the first nozzle portion 21a, and the diameter r2 in the Y direction of the second nozzle portion 21b is the diameter of the second nozzle portion 21b. Furthermore, the first nozzle portion 21a and the second nozzle portion 21b are positioned such that their centers are at the same location when viewed from the Z direction; that is, the first opening 211 and the second opening 212 are concentric circles.

[0059] By providing the nozzle 21 with a first nozzle section 21a having a diameter r1 smaller than the diameter r2 of the second nozzle section 21b, the flow velocity of the ink passing through the first nozzle section 21a can be improved, thereby increasing the flight speed of the ink droplets ejected from the nozzle 21. Furthermore, by providing the nozzle 21 with a second nozzle section 21b having a diameter r2 larger than the diameter r1 of the first nozzle section 21a, when the ink in the individual flow path 200 flows from the first common liquid chamber 101 to the second common liquid chamber 102, as described in more detail later, in a so-called circulation process, the portion of the nozzle 21 that is not affected by the circulation flow can be reduced. That is, as shown in Figure 5, during circulation, the ink flowing through the first flow path 201 can enter the second nozzle section 21b, creating an ink flow within the second nozzle section 21b. This increases the velocity gradient within the nozzle 21, allowing the ink that has thickened due to drying within the nozzle 21 to be replaced with new ink supplied from upstream. Therefore, by increasing the viscosity of the ink inside the nozzle 21, it is possible to suppress misalignment of the landing position on the spray medium due to deviations in the flight direction of the ink droplets ejected from the nozzle 21, and to prevent ejection failures where ink droplets are not ejected from the nozzle 21.

[0060] However, if the diameter r2 of the second nozzle section 21b is made too large compared to the diameter r1 of the first nozzle section 21a, the inertance ratio (M2 / M1) between the second nozzle section 21b and the first nozzle section 21a becomes small, and the position of the ink meniscus within the nozzle 21 becomes unstable when ink droplets are continuously ejected. In other words, if the inertance ratio between the second nozzle section 21b and the first nozzle section 21a becomes small, the ink meniscus will not remain in the first nozzle section 21a but will move to the second nozzle section 21b, making it impossible to continuously eject stable ink droplets.

[0061] Furthermore, if the diameter r2 of the second nozzle section 21b is made too small, it becomes difficult for ink to flow within the second nozzle section 21b during circulation. Also, if the diameter r2 of the second nozzle section 21b is made too small, the flow resistance from the pressure chamber 12 to the nozzle 21 increases, and the pressure loss increases, resulting in a decrease in the weight of the ink droplets ejected from the nozzle 21. As a result, the piezoelectric actuator 300 must be driven with a higher drive voltage, which reduces the ejection efficiency.

[0062] Therefore, the ratio r2 / r1, which is the ratio of the diameter r2 of the second opening 212 to the diameter r1 of the first opening 211, is preferably 2 or more, and more preferably 2.5 or more. That is, r2 / r1≧2 is preferred, and r2 / r1≧2.5 is preferred.

[0063] Furthermore, the ratio r2 / r1, which is the ratio of the diameter r2 of the second opening 212 to the diameter r1 of the first opening 211, is preferably 5 or less, and more preferably 3.5 or less. That is, r2 / r1 ≤ 5 is preferred, and r2 / r1 ≤ 3.5 is preferred.

[0064] Furthermore, the ratio M2 / M1, which is the ratio of the inertance M1 of the first nozzle portion 21a to the inertance M2 of the second nozzle portion 21b, is preferably 0.28 or more and 0.9 or less. That is, 0.28 ≤ M2 / M1 ≤ 0.9 is preferred.

[0065] Here, the inertance M of a flow channel can generally be calculated using the following formula (1), where S is the cross-sectional area, l is the length, and ρ is the density of the ink. TIFF0007878363000001.tif10164

[0066] In other words, if the cross-sectional area S1 is the in-plane area including the X and Y directions of the first nozzle portion 21a, the length (depth) d1 is the length in the Z direction, and the ink density ρ is the density of the ink, then the inertance M1 of the first nozzle portion 21a is ρd1 / S1.

[0067] Furthermore, if the cross-sectional area S2 is the in-plane area including the X and Y directions of the second nozzle portion 21b, the length (depth) d2 is the length in the Z direction, and the ink density ρ is the density of the ink, then the inertance M2 of the second nozzle portion 21b is ρd2 / S2.

[0068] In this way, by setting the ratio M2 / M1, which is the ratio of the inertance M1 of the first nozzle section 21a to the inertance M2 of the second nozzle section 21b, to 0.9 or less, ink flow is generated within the second nozzle section 21b, thereby suppressing misalignment of the landing position on the spray medium and ejection failures caused by the thickened ink in the nozzle 21. Furthermore, by setting the ratio M2 / M1, which is the ratio of the inertance M1 of the first nozzle section 21a to the inertance M2 of the second nozzle section 21b, to 0.9 or less, the reduction in the weight of the ink droplet ejected from the nozzle 21 is suppressed, allowing the piezoelectric actuator 300 to be driven with a relatively low drive voltage, thereby improving ejection efficiency.

[0069] Furthermore, by setting the ratio M2 / M1, which is the ratio of the inertance M1 of the first nozzle section 21a to the inertance M2 of the second nozzle section 21b, to 0.28 or higher, the stability of the meniscus can be improved, and the decrease in ink droplet ejection stability when ink droplets are ejected continuously can be suppressed.

[0070] Furthermore, when the depth in the Z direction, which is the second axial direction, of the second nozzle portion 21b is denoted as d2, the ratio r2 / d2, which is the ratio of the diameter r2 of the second opening 212 to the depth d2 of the second nozzle portion 21b, is preferably 1.5 or more, and more preferably 3 or more. That is, r2 / d2≧1.5 is preferred, and r2 / d2≧3 is preferred.

[0071] In other words, the second nozzle portion 21b is shaped to be longer in the Y direction and shorter in the Z direction in a cross-section including the Z and Y directions as shown in Figure 3. This makes it easier for the ink flowing in the Y direction through the first flow path 201 to enter the +Z side end of the second nozzle portion 21b that reaches the first nozzle portion 21a, thereby creating an ink flow within the second nozzle portion 21b.

[0072] The nozzle plate 20 can be made of, for example, a metal such as stainless steel (SUS), an organic material such as polyimide resin, or a flat plate material such as silicon. The thickness of the nozzle plate 20 is preferably 60 μm or more and 100 μm or less. Using a nozzle plate 20 with such a thickness improves the handling of the nozzle plate 20 and thus improves the assembly of the recording head 1. Incidentally, shortening the length of the nozzle 21 in the Z direction reduces the portion within the nozzle 21 that is not affected by the circulation flow when the ink is circulated. However, shortening the length of the nozzle 21 in the Z direction requires reducing the thickness of the nozzle plate 20 in the Z direction. Reducing the thickness of the nozzle plate 20 in this way lowers its rigidity, which can lead to variations in the direction of ink droplet ejection due to deformation of the nozzle plate 20, and can also reduce assembly efficiency due to decreased handling of the nozzle plate 20. In other words, by using a nozzle plate 20 with a certain thickness as described above, it is possible to suppress a decrease in the rigidity of the nozzle plate 20, thereby suppressing variations in the discharge direction due to deformation of the nozzle plate 20 and a decrease in assembly ease due to reduced handling.

[0073] As described above, the inkjet recording head 1, which is an example of a liquid ejection head of this embodiment, includes a first flow path 201 extending in the Y direction, which is the first axial direction, between a supply port 43 and an outlet port 44, and a nozzle 21 branched from the first flow path 201, which ejects ink along the Z direction, which is the second axial direction perpendicular to the Y direction. The nozzle 21 comprises a first nozzle portion 21a having a first opening 211 for ejecting ink, and a second nozzle portion 21b having a second opening 212 which is a connection port to the first flow path 201, and the diameter r2 in the Y direction of the second opening 212 is larger than the diameter r1 in the Y direction of the first opening 211.

[0074] By connecting the nozzle 21 to the middle of the first flow path 201 which extends in the Y direction, the nozzle 21 can be positioned away from areas where ink tends to accumulate, such as the corners between the second flow path 202 and the nozzle plate 20. This makes it difficult for stagnant ink and air bubbles, whose components have settled, to move towards the nozzle 21. Therefore, clogging of the nozzle 21 due to stagnant ink and air bubbles, as well as variations in the composition of ink droplets ejected from the nozzle 21, can be suppressed.

[0075] Furthermore, by connecting the nozzle 21 to the middle of the first flow path 201 extending in the Y direction, air bubbles entering from the nozzle 21 can be carried downstream toward the second common liquid chamber 102 by the ink flowing through the first flow path 201. Therefore, it is possible to suppress air bubbles entering from the nozzle 21 from entering the pressure chamber 12 or the first common liquid chamber 101, thereby suppressing ink droplet ejection failure caused by the absorption of ink pressure fluctuations in the pressure chamber 12 by air bubbles that have entered the pressure chamber 12. Incidentally, if the nozzle 21 is positioned to communicate with the second flow path 202, air bubbles entering from the nozzle 21 are more likely to move toward the pressure chamber 12 due to buoyancy, against the flow of ink. When air bubbles enter the pressure chamber 12 from the nozzle 21, the air bubbles that have entered the pressure chamber 12 may absorb the ink pressure fluctuations in the pressure chamber 12, potentially causing ink droplet ejection failure.

[0076] Furthermore, by providing the nozzle 21 with a second nozzle section 21b having a diameter r2 larger than the diameter r1 of the first nozzle section 21a, the ink flowing in the Y direction within the first flow path 201 can be allowed to enter the second nozzle section 21b, thereby creating an ink flow within the nozzle 21. By creating an ink flow within the nozzle 21 in this way, the ink that has thickened due to drying within the nozzle 21 can be replaced with new ink supplied from upstream. This suppresses misalignment of the landing position on the spray medium due to deviations in the flight direction of ink droplets ejected from the nozzle 21 caused by the thickened ink, and also suppresses clogging of the nozzle 21.

[0077] Furthermore, by providing a first nozzle section 21a having a diameter r1 smaller than the diameter r2 of the second nozzle section 21b, the flow velocity of the ink passing through the first nozzle section 21a can be improved, thereby increasing the flight speed of the ink droplets ejected from the nozzle 21.

[0078] Furthermore, by positioning the nozzle 21 in a location that communicates with the first flow path 201, the degree of freedom in arranging the nozzle 21 in the Y direction can be increased.

[0079] Furthermore, in the recording head 1 of this embodiment, the ratio r2 / r1, which is the ratio of the diameter r2 of the second opening 212 to the diameter r1 of the first opening 211, is preferably 2 or more, and more preferably 2.5 or more. By setting the ratio r2 / r1, which is the ratio of the diameter r2 of the second opening 212 to the diameter r1 of the first opening 211, to 2 or more, and more preferably 2.5 or more, an ink flow is generated within the second nozzle section 21b, and the ink flow velocity is improved by the first nozzle section 21a, thereby improving the flight speed of the ink droplets.

[0080] Furthermore, in the recording head 1 of this embodiment, the ratio r2 / r1, which is the ratio of the diameter r2 of the second opening 212 to the diameter r1 of the first opening 211, is preferably 5 or less, and more preferably 3.5 or less. By setting the ratio r2 / r1, which is the ratio of the diameter r2 of the second opening 212 to the diameter r1 of the first opening 211, to 5 or less, and more preferably 3.5 or less, it is possible to suppress the inertance ratio (M2 / M1) between the first nozzle portion 21a and the second nozzle portion 21b from becoming too small, thereby stabilizing the position of the ink meniscus in the nozzle 21 when ink droplets are continuously ejected. Therefore, it is possible to suppress variations in the ejection characteristics of ink droplets when ink droplets are continuously ejected.

[0081] Furthermore, in the recording head 1 of this embodiment, the ratio r2 / d2, which is the ratio of the diameter r2 of the second opening 212 to the depth d2 of the second nozzle portion 21b in the Z direction, which is the second axial direction, is preferably 1.5 or more, and preferably 3 or more. In this way, by making the second nozzle portion 21b longer in the Y direction, which is the first axial direction, and shorter in the Z direction, which is the second axial direction, it is possible to easily allow the ink flowing in the Y direction through the first flow path 201 to enter the second nozzle portion 21b, thereby creating an ink flow within the second nozzle portion 21b.

[0082] Furthermore, in the recording head 1 of this embodiment, the ratio M2 / M1, which is the ratio of the inertance M1 of the first nozzle section 21a to the inertance M2 of the second nozzle section 21b, is preferably 0.28 or more and 0.9 or less. By defining the ratio of the inertances of the first nozzle section 21a and the second nozzle section 21b in this way, it is possible to create an ink flow within the nozzle 21 and stabilize the position of the ink meniscus within the nozzle 21, thereby enabling stable continuous ejection of ink droplets.

[0083] (Other embodiments) Although various embodiments of the present invention have been described above, the basic configuration of the present invention is not limited to those described above.

[0084] For example, in the embodiment 1 described above, the shape of the second opening 212 of the second nozzle portion 21b when viewed from the Z direction is circular, but it is not limited to this, and for example, as shown in Figure 6, the second opening 212 may be elliptical with its major axis in the Y direction. Here, when the second opening 212 is viewed from the Z direction, it includes elliptical, rectangular, and so-called rounded rectangle, egg shape, etc., which are based on an ellipse or rectangle with semicircular shapes at both ends in the longitudinal direction.

[0085] Thus, by making the second opening 212 an ellipse with its major axis in the Y direction, it is possible to easily allow the ink flowing in the Y direction through the first flow path 201 to enter the second nozzle section 21b, thereby creating an ink flow within the second nozzle section 21b. Furthermore, by making the second opening 212 an ellipse with its minor axis in the X direction, it is not necessary to widen the width of the first flow path 201 in the X direction, and the first flow path 201 can be arranged at a high density in the X direction. Moreover, by making the second opening 212 elliptical, it is possible to suppress a significant decrease in the flow resistance and inertance of the second nozzle section 21b. In other words, if the second opening 212 of the second nozzle section 21b were a circle with the same inner diameter as the major axis of the ellipse, the flow resistance and inertance of the second nozzle section 21b would decrease significantly. By making the second opening 212 elliptical with the Y direction as its major axis, a significant decrease in the flow resistance and inertance of the second nozzle section 21b is suppressed, making it easier for ink to enter the second nozzle section 21b and generating ink flow within the second nozzle section 21b.

[0086] Furthermore, in the above-described embodiment 1, the first nozzle portion 21a and the second nozzle portion 21b are provided to have the same opening shape over the Z direction, thereby creating a step between the first nozzle portion 21a and the second nozzle portion 21b. However, the invention is not limited to this, and for example, as shown in Figure 7, the inner surface of the second nozzle portion 21b may be an inclined surface that is inclined with respect to the Z direction. In other words, the opening area of ​​the second nozzle portion 21b in the planar direction, including the X and Y directions, may be provided to gradually decrease toward the first nozzle portion 21a. As a result, no step is formed between the first nozzle portion 21a and the second nozzle portion 21b, and the inner surfaces may be continuous. When the inner surfaces of the first nozzle portion 21a and the second nozzle portion 21b are continuous in this way, the first nozzle portion 21a refers to the portion in which the opening shape is substantially the same over the Z direction.

[0087] Furthermore, in the embodiment described above, for example, a configuration was illustrated in which the first axial direction is the Y direction and the second axial direction is the Z direction, and the nozzles 21 are arranged in parallel in the X direction which is perpendicular to both the Y and Z directions. However, the invention is not limited to this configuration, and for example, the nozzles 21 and pressure chambers 12 may be arranged in parallel in a direction inclined with respect to the X direction in the in-plane direction of the nozzle surface 20a.

[0088] Furthermore, in this embodiment, the first channel 201 of the individual channel 200 and the second common liquid chamber 102 are directly connected, but the invention is not limited to this, and other channels extending in the Z direction, which is the second axial direction, may be provided between the first channel 201 and the second common liquid chamber 102.

[0089] Here, an example of an inkjet recording device, which is an example of the liquid injection device of this embodiment, will be described with reference to Figure 8. Figure 8 is a diagram showing the schematic configuration of the inkjet recording device of the present invention.

[0090] As shown in Figure 8, in an inkjet recording device I, which is an example of a liquid ejection device, multiple recording heads 1 are mounted on a carriage 3. The carriage 3, on which the recording heads 1 are mounted, is provided to be axially movable on a carriage shaft 5 attached to the device body 4. In this embodiment, the direction of movement of the carriage 3 is the Y direction, which is the first axial direction.

[0091] Furthermore, the main body of the device 4 is provided with a tank 2, which is a storage means for storing ink as a liquid. The tank 2 is connected to the recording head 1 via a supply pipe 2a such as a tube, and ink from the tank 2 is supplied to the recording head 1 via the supply pipe 2a. The recording head 1 and the tank 2 are also connected via a discharge pipe 2b such as a tube, and ink discharged from the recording head 1 is returned to the tank 2 via the discharge pipe 2b, so-called circulation takes place. Note that the tank 2 may consist of multiple tanks.

[0092] The driving force of the drive motor 7 is transmitted to the carriage 3 via a plurality of gears and a timing belt 7a (not shown), causing the carriage 3, on which the recording head 1 is mounted, to move along the carriage axis 5. Meanwhile, the main body of the device 4 is provided with transport rollers 8 as a transport means, and the recording sheet S, which is the medium to be sprayed, such as paper, is transported by the transport rollers 8. Note that the transport means for transporting the recording sheet S is not limited to transport rollers 8, but may also be a belt or a drum. In this embodiment, the transport direction of the recording sheet S is the X direction.

[0093] In the inkjet recording device I described above, the example shown is one in which the recording head 1 is mounted on a carriage 3 and moves in the main scanning direction. However, the present invention is not limited to this, and can also be applied to so-called line-type recording devices in which, for example, the recording head 1 is fixed and printing is performed simply by moving a recording sheet S such as paper in the sub-scanning direction.

[0094] Furthermore, while each embodiment described an inkjet recording head as an example of a liquid ejection head and an inkjet recording device as an example of a liquid ejection device, the present invention broadly applies to liquid ejection heads and liquid ejection devices in general, and can of course be applied to liquid ejection heads and liquid ejection devices that eject liquids other than ink. Other examples of liquid ejection heads include various recording heads used in image recording devices such as printers, colorant ejection heads used in the manufacture of color filters for liquid crystal displays, electrode material ejection heads used in electrode formation for organic EL displays and FEDs (field emission displays), and bio-organic material ejection heads used in biochip manufacturing, and the present invention can also be applied to liquid ejection devices equipped with such liquid ejection heads.

[0095] Here, an example of the liquid ejection system of this embodiment will be described with reference to Figure 9. Figure 9 is a block diagram illustrating the liquid ejection system of an inkjet recording device, which is the liquid ejection device of the present invention.

[0096] As shown in Figure 9, the liquid injection system comprises the recording head 1 described above, and a main tank 500, a first tank 501, a second tank 502, a compressor 503, a vacuum pump 504, a first liquid transfer pump 505, and a second liquid transfer pump 506, which serve as a mechanism for supplying ink as liquid to the supply port 43 and recovering the ink from the discharge port 44 to circulate the ink.

[0097] The first tank 501 is connected to the recording head 1 and the compressor 503, and the compressor 503 supplies ink from the first tank 501 to the recording head 1 at a predetermined pressure.

[0098] The second tank 502 is connected to the first tank 501 via the first liquid transfer pump 505, and the ink from the second tank 502 is transferred to the first tank 501 by the first liquid transfer pump 505.

[0099] Furthermore, the second tank 502 is connected to the recording head 1 and the vacuum pump 504, and the ink from the recording head 1 is discharged into the second tank 502 under a predetermined negative pressure by the vacuum pump 504.

[0100] In other words, ink is supplied from the first tank 501 to the recording head 1, and the ink is discharged from the recording head 1 to the second tank 502. Then, the first liquid transfer pump 505 transfers ink from the second tank 502 to the first tank 501, thus circulating the ink.

[0101] Furthermore, the main tank 500 is connected to the second tank 502 via a second liquid transfer pump 506, and the ink consumed by the recording head 1 is replenished from the main tank 500 to the second tank 502. The replenishment of ink from the main tank 500 to the second tank 502 can be performed, for example, when the ink level in the second tank 502 falls below a predetermined height. [Explanation of Symbols]

[0102] I... Inkjet recording device (liquid ejection device), 1... Inkjet recording head (liquid ejection head), 2... Tank, 2a... Supply pipe, 2b... Discharge pipe, 3... Carriage, 4... Device body, 5... Carriage shaft, 7... Drive motor, 7a... Timing belt, 8... Conveyor roller, 10... Flow path forming substrate, 12... Pressure chamber, 15... Communication plate, 16... First communication section, 17... Second communication section, 18... Third communication section, 20... Nozzle plate, 20a... Nozzle surface, 21... Nozzle, 21a... First nozzle section, 21b... Second nozzle section, 211... First opening, 212... Second opening, 22... Nozzle row, 30... Protective substrate, 31... Piezoelectric actuator holder, 32... Through hole, 40... Case member, 41... First liquid chamber section, 42... Second liquid chamber section, 43... Supply port, 44... Discharge port 45...Connection port, 49...Compliance substrate, 50...Diaphragm, 60...First electrode, 70...Piezoelectric layer, 80...Second electrode, 90...Lead electrode, 101...First common liquid chamber, 102...Second common liquid chamber, 120...Flexible cable, 121...Drive circuit, 151...First communication plate, 152...Second communication plate, 200...Individual channel, 201...First channel, 202...Second channel, 203...Supply Feeding channel, 300... Piezoelectric actuator, 491... Sealing film, 492... Fixed substrate, 493... Opening, 494... Compliance section, 500... Main tank, 501... First tank, 502... Second tank, 503... Compressor, 504... Vacuum pump, 505... First liquid transfer pump, 506... Second liquid transfer pump, S... Recording sheet, r1... Diameter of the first opening, r2... Diameter of the second opening

Claims

1. A first flow path extending in the first axial direction between the supply port and the discharge port, A nozzle branched from the first flow path, which discharges liquid along a second axis perpendicular to the first axis, A second flow channel is provided between the supply port and the first flow channel, and extends in the second axial direction, A pressure chamber provided between the supply port and the second flow path is provided, The aforementioned nozzle is A first nozzle section having a first opening for discharging liquid, A second opening, which is a connection port to the first flow path, is formed in the second nozzle portion, which is arranged in the second axial direction alongside the first nozzle portion. It is equipped with, A step is provided between the first nozzle portion and the second nozzle portion. A liquid injection head characterized in that the diameter r2 in the first axial direction of the second opening is larger than the diameter r1 in the first axial direction of the first opening.

2. The liquid spray head according to claim 1, characterized in that the ratio r2 / r1, which is the ratio of the diameter r2 of the second opening to the diameter r1 of the first opening, is 2 or more.

3. The liquid spray head according to claim 2, characterized in that the ratio r2 / r1, which is the ratio of the diameter r2 of the second opening to the diameter r1 of the first opening, is 2.5 or more.

4. The liquid spray head according to any one of claims 1 to 3, characterized in that the ratio r2 / r1, which is the ratio of the diameter r2 of the second opening to the diameter r1 of the first opening, is 5 or less.

5. The liquid spray head according to claim 4, characterized in that the ratio r2 / r1, which is the ratio of the diameter r2 of the second opening to the diameter r1 of the first opening, is 3.5 or less.

6. The liquid spray head according to any one of claims 1 to 5, characterized in that the ratio r2 / d2, which is the ratio of the diameter r2 of the second opening to the depth d2 in the second axial direction of the second nozzle portion, is 1.5 or more.

7. The liquid spray head according to claim 6, characterized in that the ratio r2 / d2, which is the ratio of the diameter r2 of the second opening to the depth d2 in the second axial direction of the second nozzle portion, is 3 or more.

8. A first flow path extending in the first axial direction between the supply port and the discharge port, A nozzle branched from the first flow path, which discharges liquid along a second axis perpendicular to the first axis, A second flow channel is provided between the supply port and the first flow channel, and extends in the second axial direction, A pressure chamber provided between the supply port and the second flow path is provided, The aforementioned nozzle is A first nozzle section having a first opening for discharging liquid, A second opening, which is a connection port to the first flow path, is formed in the second nozzle portion, which is arranged in the second axial direction alongside the first nozzle portion. It is equipped with, A step is provided between the first nozzle portion and the second nozzle portion. The diameter r2 in the first axial direction of the second opening is greater than the diameter r1 in the first axial direction of the first opening. The ratio r2 / r1, which is the ratio of the diameter r2 of the second opening to the diameter r1 of the first opening, is between 2 and 5. The ratio r2 / d2, which is the ratio of the diameter r2 of the second opening to the depth d2 in the second axial direction of the second nozzle portion, is 1.5 or greater. A liquid spray head characterized in that the ratio M2 / M1, which is the ratio of the inertance M1 of the first nozzle portion to the inertance M2 of the second nozzle portion, is 0.28 or more and 0.9 or less.

9. A first flow path extending in the first axial direction between the supply port and the discharge port, A nozzle branched from the first flow path, which discharges liquid along a second axis perpendicular to the first axis, A second flow channel is provided between the supply port and the first flow channel, and extends in the second axial direction, A pressure chamber provided between the supply port and the second flow path is provided, The aforementioned nozzle is A first nozzle section having a first opening for discharging liquid, A second opening, which is a connection port to the first flow path, is formed in the second nozzle portion, which is arranged alongside the first nozzle portion. It is equipped with, The diameter r2 in the first axial direction of the second opening is greater than the diameter r1 in the first axial direction of the first opening. A liquid spray head characterized in that the second opening is an ellipse with its major axis in the direction of the first axial direction.

10. A liquid injection system characterized by comprising a liquid injection head according to any one of claims 1 to 9, and a mechanism for supplying liquid to the supply port and recovering the liquid from the discharge port to circulate the liquid.

11. The liquid spray head according to any one of claims 1 to 7, characterized in that the ratio M2 / M1, which is the ratio of the inertance M1 of the first nozzle portion to the inertance M2 of the second nozzle portion, is 0.28 or more and 0.9 or less.

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