Inkjet head

Abstract

The inkjet head includes: a plurality of pressure chambers that communicate with nozzles that eject ink; a first common flow path communicating with the plurality of pressure chambers; and a connection flow path connected to the first common flow path, the connection flow path having a bubble reservoir for storing bubbles.

Description

Technical Field

[0001] The present invention relates to an ink jet head. Background Art

[0002] In recent years, a method of manufacturing a device using an inkjet printing device has attracted attention. The inkjet printing device ejects droplets from the nozzles while controlling the positional relationship between the multiple nozzles included in the inkjet and the printing object, thereby applying the droplets to the printing object. In such an inkjet printing device, a drop-on-demand type inkjet head is sought that ejects a required amount of droplets to the printing object at a required time with high precision.

[0003] In a drop-on-demand inkjet head, a phenomenon known as fluid crosstalk is prone to occur. Fluid crosstalk refers to the phenomenon that changes in pressure affect adjacent nozzles via a flow path. As a countermeasure for fluid crosstalk, a structure in which damping is provided in the flow path to make it difficult for pressure to be transmitted to adjacent nozzles is widely used. However, due to the influence of the high density of nozzles in the inkjet head, it is difficult to fully ensure the surface area of ​​the damping. In addition, since the desired printing accuracy is also increasing, it becomes difficult to suppress the influence of fluid crosstalk to a level that can be ignored. In response to such a problem, a method of suppressing fluid crosstalk using bubbles is disclosed in Patent Document 1. Specifically, Patent Document 1 discloses a method of having a storage portion for accumulating bubbles at the end (stagnant water area) of a common flow path on the discharge side and using the storage portion as a damper.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 5475389 Summary of the invention

[0007] An inkjet head according to one embodiment of the present invention comprises: a plurality of pressure chambers connected to nozzles for ejecting ink; a first common flow path connected to the plurality of pressure chambers; and a connecting flow path connected to the first common flow path, wherein the connecting flow path has a bubble storage portion for storing bubbles. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is an exploded perspective view showing the basic structure of the inkjet head according to each embodiment.

[0009] Figure 2 It is a cross-sectional view in the XZ plane of the vicinity of the nozzle of the inkjet head according to each embodiment.

[0010] Figure 3A It is a plan view schematically showing the upstream common flow path and the connecting flow path according to the first embodiment.

[0011] Figure 3B It is along Figure 3A It is a longitudinal cross-sectional view along line III-III and shows an outline of the connecting flow path.

[0012] Figure 3C It is along Figure 3A It is a longitudinal sectional view along line III-III and is an explanatory diagram of the function of the connecting flow path.

[0013] Figure 4A This is a longitudinal sectional view schematically showing a portion including an upper descending step of the connecting flow path according to the first embodiment.

[0014] Figure 4B This is a longitudinal sectional view showing an example of a plate-like member used for forming the upper step-down step in the first embodiment.

[0015] Figure 4C This is a longitudinal sectional view showing another example of the plate-like member used for forming the upper step-down step in the first embodiment.

[0016] Figure 5A It is a longitudinal sectional view showing a modification of the first embodiment.

[0017] Figure 5B It is a longitudinal sectional view showing another modified example of the first embodiment.

[0018] Figure 5C This is a longitudinal sectional view showing still another modified example of the first embodiment.

[0019] Fig. 6A It is a plan view schematically showing the upstream common flow path and the connecting flow path according to the second embodiment.

[0020] Figure 6B It is along Fig. 6A It is a longitudinal cross-sectional view along the line VI-VI and shows an outline of the connecting flow path.

[0021] Fig. 7A It is a plan view schematically showing an upstream common flow path, a downstream common flow path, and a connecting flow path according to the third embodiment.

[0022] Figure 7B It is along Fig. 7A It is a longitudinal sectional view along line VII-VII of FIG. 1 and shows an outline of the connecting flow path.

[0023] Fig. 8A It is a plan view schematically showing an upstream common flow path, a downstream common flow path, and a connecting flow path according to a fourth embodiment.

[0024] Figure 8B It is along Fig. 8A It is a longitudinal cross-sectional view along the line VIII-VIII of FIG. 1 and shows an outline of the connecting flow path.

[0025] Fig.9A It is a plan view schematically showing an inkjet head according to a modified example of the fourth embodiment.

[0026] Fig. 9B This is a plan view schematically showing an inkjet head according to another modified example of the fourth embodiment.

[0027] Fig.10 It is an explanatory diagram of a method for forming a connecting flow channel according to the fifth embodiment.

[0028] Fig.11A It is a cross-sectional view in the YZ plane of the vicinity of the upstream common flow channel according to the seventh embodiment.

[0029] Fig. 11B It is a cross-sectional view in the YZ plane of the vicinity of the downstream common flow channel according to the seventh embodiment.

[0030] Fig. 12A It is a plan view schematically showing a connecting flow path according to a modified example.

[0031] Fig. 12B It is a longitudinal sectional view schematically showing a connecting flow path according to another modified example. DETAILED DESCRIPTION

[0032] In the method of storing bubbles in the stagnant water area as described in Patent Document 1, there is no force to discharge bubbles exceeding a constant amount under the action of the ink flow, so it becomes difficult to keep the amount of stored bubbles constant. If the amount of stored bubbles is not kept constant but fluctuates over time, the damping effect fluctuates, so the ejection speed and ejection volume fluctuate, and the ejection accuracy deteriorates.

[0033] Patent Document 1 describes a method of providing a bubble generating mechanism for generating bubbles and a bubble detecting mechanism for detecting bubbles in a flow path to generate bubbles according to the amount of bubbles detected. However, in the structure described in Patent Document 1, there is a trade-off between generation and miniaturization and manufacturing cost, so the obstacles to installing the bubble generating mechanism and the bubble detecting mechanism are high. In addition, with the detection accuracy of the commonly used bubble detecting mechanism or the accuracy of bubble generation control in the bubble generating mechanism, it is difficult to suppress the fluctuation of the bubbles over time and suppress the fluctuation of the ejection speed and ejection volume.

[0034] An object of the present invention is to provide an inkjet head capable of suppressing fluctuations in the ejection state of ink.

[0035] Hereinafter, an inkjet head according to an embodiment of the present invention will be described with reference to the accompanying drawings. It should be noted that in the following description and each figure, the direction parallel to the ink ejection direction from the inkjet head is defined as the Z-axis direction, the direction in which the nozzles in the inkjet head are arranged is defined as the Y-axis direction, and the direction orthogonal to the Z-axis direction and the Y-axis direction is defined as the X-axis direction. In addition, the ink ejection direction is defined as the -Z direction.

[0036] [Basic structure of inkjet head]

[0037] First, the basic structure of the inkjet head according to the embodiment will be described. Figure 1 It is an exploded perspective view showing the basic structure of an inkjet head.

[0038] like Figure 1 As shown, the inkjet head 1 includes a housing 10, a vibration plate 20, a flow path plate 30, a nozzle plate 40, and a pressure change portion 50. The nozzle plate 40 and the flow path plate 30, the flow path plate 30 and the vibration plate 20, the vibration plate 20 and the housing 10, and the vibration plate 20 and the pressure change portion 50 are fixed via adhesives, respectively. As the adhesive, for example, an epoxy adhesive having a thermosetting property can be used. It should be noted that the adhesive for joining the various components can use the same adhesive, or different adhesives can be used respectively. For example, a rubber adhesive can be used in the joining of specified components, and an epoxy adhesive can be used in the joining of other components.

[0039] The inkjet head 1 forms ink droplets and ejects the ink from nozzles 41 that penetrate through the nozzle plate 40. The nozzles 41 may be arranged in a row along the Y-axis direction, or may be arranged as shown in FIG. Figure 1 As shown, they are arranged in multiple rows along the Y-axis direction.

[0040] Next, the internal structure of the inkjet head will be described. Figure 2 It is a cross-sectional view in the XZ plane near the nozzle of the inkjet head.

[0041] The nozzle plate 40 is arranged on the bottom surface of the flow path plate 30 in such a manner that one surface in the thickness direction is orthogonal to the Z axis. The nozzle plate 40 is formed, for example, by molding a stainless steel plate member having a thickness of 100 μm by etching or stamping. A plurality of nozzles 41 arranged in the Y-axis direction are provided through the nozzle plate 40. The nozzle 41 ejects ink to the outside. The nozzle 41 is formed in such a manner that it penetrates the nozzle plate 40. The diameter of the nozzle 41 is, for example, not less than 3 μm and not more than 100 μm.

[0042] The flow path plate 30 is formed in a rectangular parallelepiped shape and is arranged between the vibration plate 20 and the nozzle plate 40 so that one surface in the thickness direction is orthogonal to the Z axis. The flow path plate 30 is formed by, for example, stacking plate-like members of stainless steel having a thickness of 10 μm or more and 100 μm or less formed by etching or stamping. The number of stacked layers of the stainless steel plate-like members is, for example, 3 or more and 10 or less.

[0043] The flow path plate 30 is provided with a plurality of pressure chambers 33 connected one-to-one with the plurality of nozzles 41, and a silo portion 36 connecting the pressure chambers 33 with the nozzles 41. The pressure chamber 33 is formed in a rectangular parallelepiped shape, and the upper wall forming the upper surface (the surface on the +Z direction side) is formed by the vibration plate 20. It should be noted that the pressure chamber 33 may not be a rectangular parallelepiped, but may be provided with a plurality of steps on at least one surface dividing the pressure chamber 33. The silo portion 36 connects the pressure chamber 33 with the nozzles 41 and stores ink. It should be noted that the silo portion 36 may be cylindrical or quadrangular.

[0044] In addition, the flow path plate 30 is formed with a plurality of upstream side individual flow paths 31, a first upstream side common flow path portion 32, a plurality of downstream side individual flow paths 34, and a first downstream side common flow path portion 35. The plurality of upstream side individual flow paths 31 are connected one-to-one with the pressure chamber 33 on the upstream side (+X direction side) of the ink flow direction relative to each pressure chamber 33 (hereinafter, sometimes referred to as "ink flow direction"). The first upstream side common flow path portion 32 is connected to the upstream side end portions of the plurality of upstream side individual flow paths 31. The plurality of downstream side individual flow paths 34 are connected one-to-one with the pressure chamber 33 on the downstream side (-X direction side) of the ink flow direction relative to each pressure chamber 33. The first downstream side common flow path portion 35 is connected to the downstream side end portions of the plurality of downstream side individual flow paths 34.

[0045] The vibration plate 20 is disposed between the housing 10 and the flow path plate 30 such that one surface in the thickness direction is perpendicular to the Z axis. The vibration plate 20 is a thin film having a thickness of 5 μm to 50 μm, for example, and is formed of polyimide, for example.

[0046] The vibration plate 20 is provided with an upstream opening 21 disposed just above the first upstream common flow path portion 32 (on the +Z direction side). In addition, the vibration plate 20 is provided with a downstream opening 22 disposed just above the first downstream common flow path portion 35. Instead of opening the entire surface of the upstream opening 21 and the downstream opening 22, the upstream opening 21 and the downstream opening 22 may be formed with a plurality of through holes having a diameter of 10 μm, for example, and have a filtering function.

[0047] The housing portion 10 is formed into a rectangular parallelepiped shape with a thickness of 1 cm in the Z-axis direction by cutting alloy steel such as stainless steel. The housing portion 10 is provided with a second upstream common flow path portion 12 disposed just above the upstream opening portion 21 and a second downstream common flow path portion 14 disposed just above the downstream opening portion 22. The second upstream common flow path portion 12, the first upstream common flow path portion 32, and the upstream opening portion 21 together constitute an upstream common flow path 61. In addition, the second downstream common flow path portion 14, the first downstream common flow path portion 35, and the downstream opening portion 22 together constitute a downstream common flow path 62.

[0048] In addition, the housing portion 10 is provided with an ink supply path (not shown) for supplying ink from the outside and an ink discharge path (not shown) for discharging the ink to the outside. The ink supply path is a path for supplying ink stored in a first ink tank (not shown) to the upstream common flow path 61. The ink supply path is formed in the housing portion 10, for example, along the Z-axis direction. The ink discharge path is a path for discharging ink in the downstream common flow path 62 to a second ink tank (not shown). The ink discharge path is formed in the housing portion 10, for example, along the Z-axis direction. The ink supplied from the ink supply path is discharged from the ink discharge path via the upstream common flow path 61, the upstream separate flow path 31, the pressure chamber 33, the downstream separate flow path 34, and the downstream common flow path 62. That is, the ink flow direction in each separate flow path 31, 34 (the upstream separate flow path 31 and the downstream separate flow path 34) is set to the -X direction. It should be noted that the ink flow direction in a predetermined individual flow passage 31 or 34 may be set to the +X direction, while the ink flow direction in the remaining individual flow passages 31 or 34 may be set to the −X direction.

[0049] It should be noted that, in order to circulate the ink, the following structure can be used: the pressure of the first and second ink tanks is set so that the pressure of the first ink tank connected to the ink supply path is higher than the pressure of the second ink tank connected to the ink discharge path, and the ink is caused to flow from the second ink tank to the first ink tank by using a pump not shown. In order to make the pressure of the first ink tank higher than the pressure of the second ink tank, each ink tank can be arranged in a manner such that the height in the Z-axis direction relative to the pressure chamber 33 is different, or the internal pressure of each ink tank can be individually controlled by a regulator. In addition, in order to circulate the ink, the thrust of the pump can also be used to circulate the ink. In this way, the ink is not retained in the pressure chamber 33 but circulated, so that the drying prevention function of the nozzle 41 can be exerted. Therefore, it is possible to prevent the ink from being retained in the pressure chamber 33 or the nozzle 41 and causing nozzle clogging.

[0050] The pressure changing unit 50 is arranged inside the housing 10 and generates pressure changes in the ink in the pressure chamber 33. The pressure changes propagate toward the nozzle 41, and the ink is ejected from the nozzle 41. It should be noted that, in order to receive the changes of the pressure changing unit 50, a plurality of convex portions 24 are formed on the vibration plate 20 in a manner arranged in the Y-axis direction, protruding in the +Z direction and extending along the X-axis direction. The pressure changing unit 50 includes a base 51, a piezoelectric element 52, a substrate 53, and a control unit (not shown).

[0051] The base portion 51 is formed into a rectangular parallelepiped extending in the Y-axis direction, and holds a piezoelectric element 52 and a substrate 53. A plurality of piezoelectric elements 52 are arranged on the bottom surface side of the base portion 51. The plurality of piezoelectric elements 52 are arranged in a manner of respectively contacting the protrusions 24 of the vibration plate 20 constituting the upper wall (the wall on the +Z direction side) of the pressure chamber 33. The piezoelectric element 52 is deformed in a manner of expanding and contracting along the Z-axis direction by applying a voltage. Specifically, the piezoelectric element 52 is a stacked piezoelectric actuator of the D33 mode. The substrate 53 applies a voltage to the piezoelectric element 52. The substrate 53 is, for example, a flexible printed substrate. The control unit controls the application of the voltage to the piezoelectric element 52.

[0052] The piezoelectric element 52 to which the voltage is applied by the substrate 53 is deformed so as to stretch in the Z-axis direction, and the convex portion 24 is pressed downward (in the −Z direction). As a result, the upper wall (the wall on the +Z direction side) of the pressure chamber 33 is deformed, and the pressure fluctuation of the ink in the pressure chamber 33 is generated. The pressure fluctuation is transmitted toward the nozzle 41 through the silo portion 36, so that the ink is ejected to the outside from the nozzle 41. In this way, the control unit controls the ejection of the ink by controlling the application of the piezoelectric element 52.

[0053] [First embodiment]

[0054] The first embodiment of the present invention is described. In the first embodiment, in an inkjet head 1 of a type that does not circulate ink, a structure is described in which bubbles are stored at a position upstream of the upstream common flow path 61 in the ink flow direction D (hereinafter, there is a case where the "upstream side of the ink flow direction D" is referred to as the "upstream side") to suppress fluid crosstalk. The upstream common flow path 61 of the first embodiment is equivalent to the first common flow path of the present invention. It should be noted that in the following embodiments, the +Z direction side is defined as the upper side of the inkjet head 1. Figure 3A It is a plan view schematically showing the upstream common flow path and the connecting flow path. Figure 3B It is along Figure 3A It is a longitudinal cross-sectional view along line III-III and shows an outline of the connecting flow path. Figure 3C It is along Figure 3A It is a longitudinal sectional view along line III-III and is an explanatory diagram of the function of the connecting flow path.

[0055] like Figure 3A As shown in FIG. 1 , one end of the connecting flow path 7 is connected to the upstream end of the upstream common flow path 61. The connecting flow path 7 is formed in a shape with a smaller cross-sectional area than the upstream common flow path 61. The other end of the connecting flow path 7 is connected to, for example, the ink supply path 11. It should be noted that when the connecting flow path 7 is formed inside the flow path plate 30, it is not indicated by a solid line in the top view, but is indicated by a solid line for the purpose of expressing the concept. Figure 3A The hatching pattern shown in the figure indicates that when connecting flow paths are shown in subsequent figures, the same hatching pattern may be used to indicate them.

[0056] like Figure 3B As shown in the figure, the connecting flow path 7 is constructed to include at least one step. That is, the upper wall surface 71 constituting the upper side of the connecting flow path 7 is constructed to include two upper side descending steps 72 formed in a manner that the height gradually decreases as it goes downstream, and two upper side ascending steps 73 formed in a manner that the height gradually increases as it goes downstream. In addition, the lower wall surface 74 constituting the lower side of the connecting flow path 7 is constructed to include two lower side descending steps 75 formed in a manner that the height gradually decreases as it goes downstream, and two lower side ascending steps 76 formed in a manner that the height gradually increases as it goes downstream. It should be noted that at least one of the upper side descending step 72, the upper side ascending step 73, the lower side descending step 75, and the lower side ascending step 76 is provided.

[0057] The upper descending step 72 is composed of a pair of first upper wall face portions 721 that guide ink in the -Y direction (first direction) and a second upper wall face portion 722 that connects the pair of first upper wall face portions 721 to each other and guides ink in the -Z direction (second direction). The upper ascending step 73 is composed of a pair of first upper wall face portions 731 and a second upper wall face portion 732 that connects the pair of first upper wall face portions 731 to each other and guides ink in the +Z direction (second direction). The lower descending step 75 is composed of a pair of first lower wall face portions 751 that guide ink in the -Y direction and a second lower wall face portion 752 that connects the pair of first lower wall face portions 751 to each other and guides ink in the -Z direction. The lower ascending step 76 is composed of a pair of first lower wall face portions 761 and a second lower wall face portion 762 that connects the pair of first lower wall face portions 761 to each other and guides ink in the +Z direction. The first upper wall surface portions 721 , 731 and the first lower wall surface portions 751 , 761 correspond to the first portion of the present invention, and the second upper wall surface portions 722 , 732 and the second lower wall surface portions 752 , 762 correspond to the second portion of the present invention.

[0058] The first upper wall surface 721 and the second upper wall surface 722 on the upstream side of the upper descending step 72 are connected to form a recessed corner 723. The second upper wall surface 732 and the first upper wall surface 731 on the downstream side of the upper ascending step 73 are connected to form a recessed corner 733. The second lower wall surface 752 and the first lower wall surface 751 on the downstream side of the lower descending step 75 are connected to form a recessed corner 753. The first lower wall surface 761 and the second lower wall surface 762 on the upstream side of the lower ascending step 76 are connected to form a recessed corner 763. The angle formed by each wall surface 721, 731, 751, 761 constituting each corner 723, 733, 753, 763 and each wall surface 722, 732, 752, 762 is preferably 90 degrees or less.

[0059] It should be noted that it is preferable to set the maximum width of the upstream common flow path 61 ( Figure 3A The length of the X-axis direction in the inkjet head 1 is set to 1 mm or more and 10 mm or less, the height of the upstream common flow path 61 is set to 0.3 mm or more and 3.0 mm or less, the width of the connecting flow path 7 is set to about 50 μm or more and 500 μm or less, the length of the connecting flow path 7 in the ink flow direction D is set to 1 mm or more and 10 mm or less, and the height of each step 72, 73, 75, 76 is set to about 10 μm or more and 200 μm or less. In addition, the length of the upstream common flow path 61 and the connecting flow path 7 in the ink flow direction D can be determined according to the flow path structure of the inkjet head 1.

[0060] Next, use Figure 3C The function and effect of forming the steps 72 , 73 , 75 , and 76 in the connecting flow path 7 will be described.

[0061] First, the flow rate of the ink flowing in the connecting flow path 7, the ink supply path 11, and the upstream common flow path 61 is greatly reduced due to the flow resistance of the connecting flow path 7 compared to the case where the connecting flow path 7 is not provided. In addition, the flow of the ink is partially weakened at the corners 723, 733, 753, and 763 of each step 72, 73, 75, and 76. Therefore, the main streamlines of the ink in the connecting flow path 7 are as follows: Figure 3C As indicated by the middle arrow D1 , the flow avoids the corners 723 , 733 , 753 , and 763 .

[0062] At each corner 723, 733, the buoyancy acting on the bubble B introduced into the connecting flow path 7 is limited by the upper wall surface 71, and the force of squeezing the bubble B due to the flow of ink is weak, so that a constant amount of bubble B is accumulated in each corner 723, 733. In addition, at each corner 753, 763, the buoyancy acting on the bubble B is limited by the flow of ink, so that a constant amount of bubble B is accumulated in each corner 753, 763. Therefore, the bubble B is accumulated in a predetermined range near each corner 723, 733, 753, 763 of the connecting flow path 7. Each step 72, 73, 75, 76 corresponds to the bubble reservoir of the present invention.

[0063] It should be noted that the air bubbles B may be introduced into the connecting flow path 7 by introducing ink containing the air bubbles B from the ink supply path 11 or by sucking the air bubbles B from the nozzle 41 and introducing them into the connecting flow path 7 .

[0064] In addition, the size of the bubble B introduced into the connecting flow path 7 may be the size that can be stored in each corner 723, 733, 753, 763, or may be larger than the size stored. This is because, even if the bubble B larger than the size stored in each corner 723, 733, 753, 763 is introduced, the bubble B is divided into smaller pieces while passing through the connecting flow path 7 having a smaller cross-sectional area, and is stored in a size that can be stored in each corner 723, 733, 753, 763.

[0065] In addition, the amount of the bubbles B introduced can be greater than the amount of the bubbles B stored in each corner 723, 733, 753, 763, and does not need to be strictly controlled. This is because the bubbles B that are not stored in each corner 723, 733, 753, 763 flow under the action of the flow of ink and are recovered by the first ink tank connected to the ink supply path or the second ink tank connected to the ink discharge path. Therefore, it is possible to store bubbles B of a size below the height of each step 72, 73, 75, 76 in the connecting flow path 7 without using precise bubble detection.

[0066] According to the first embodiment, the amount of the bubbles B stored in each corner 723, 733, 753, 763 varies depending on the processing fluctuation of each corner 723, 733, 753, 763 or the viscosity of the ink, but unlike the case where the bubbles are stored in the stagnant water area, it is difficult to change with time. The reason why the amount of bubbles B stored is difficult to change with time is that the bubbles B exceeding the amount that can be stored in each corner 723, 733, 753, 763 flow due to the flow of the ink, so that the amount of bubbles B stored in each corner 723, 733, 753, 763 is kept constant. Although the volume of the bubbles B stored in the corners 723, 733, 753, and 763 is smaller than the volume of the upstream common flow path 61, the elasticity of air is greater than that of ink, so even if the bubbles B stored in the corners 723, 733, 753, and 763 are minute in amount, the effect of suppressing fluid crosstalk is large. Therefore, the bubbles B can be stored in the connecting flow path 7 to suppress the influence of fluid crosstalk, and the temporal fluctuation of the amount of the stored bubbles B can be reduced, so the fluctuation of the ink ejection state (at least one of the ejection speed and the ejection amount) can be suppressed.

[0067] In addition, when there is no connection flow path 7 and the upstream common flow path 61 is directly connected to the ink supply path 11, there is no part that can accumulate bubbles on the upstream side (ink supply path 11 side) of the upstream common flow path 61. Therefore, it is impossible to suppress fluid crosstalk by utilizing the damping effect brought by bubbles. In addition, the downstream side (opposite side of the ink supply path 11) of the upstream common flow path 61 becomes a stagnant water area, so bubbles are easily accumulated, and the fluid crosstalk suppression effect by utilizing the damping effect brought by bubbles can be expected, but the fluid crosstalk suppression effect for the nozzle 41 arranged on the upstream side and the nozzle 41 arranged on the downstream side fluctuates. In contrast, in the first embodiment, there is also a connection flow path 7 that can accumulate bubbles B on the upstream side of the upstream common flow path 61, so that bubbles B can exist on the upstream side and the downstream side of the upstream common flow path 61. Therefore, the fluctuation of the ejection state of ink between the nozzles 41 can be suppressed by the fluid crosstalk suppression effect by utilizing the damping effect brought by the bubbles B.

[0068] Next, an example of a method for forming the connecting flow path 7 will be described. Figure 4A It is a longitudinal sectional view schematically showing a portion of the connecting flow path including an upper descending step. Figure 4B This is a longitudinal sectional view showing an example of a plate-like member used for forming the upper step-down step. Figure 4C It is a longitudinal sectional view showing another example of a plate-like member used in forming the upper descending step. It should be noted that, below, the method for forming the portion of the connecting flow path including the upper descending step 72 is exemplified, but the upper ascending step 73, the lower descending step 75 and the lower ascending step 76 can also be formed in the same manner.

[0069] like Figure 4A As shown in the figure, the upper descending step 72 is composed of a pair of first upper wall surface parts 721 and a second upper wall surface part 722 connecting the pair of first upper wall surface parts 721. The angle of the corner part 723 formed by the first upper wall surface part 721 and the second upper wall surface part 722 on the upstream side is set to be less than 90 degrees. In order to improve the effect of storing the bubbles B, the angle of the corner part 723 is more preferably less than 90 degrees.

[0070] In order to form the connecting flow path 7 including the upper descending step 72 of such a shape, it is desirable to use Figure 4B The method shown is a method of overlapping the thin film member (plate-shaped member) 70 having the through hole 701 for the flow path. This is because in the method of forming the upper step-down step 72 by machining one member, the machining accuracy tends to fluctuate, and the machining cost also increases.

[0071] When the thin film members 70 are overlapped to form the connecting flow path 7, an upper descending step 72 having an angle 723 less than 90° can be formed by paying attention to the method of forming the through hole 701 for the flow path. For example, when the through hole 701 for the flow path is formed using photolithography (single-sided etching method), as shown by arrow E1, an etching liquid is sprayed from the upper surface 702 side of the thin film member 70, so that the through hole 701 for the flow path that becomes thinner as it moves from the upper surface 702 to the lower surface 703 can be formed. That is, a through hole 701 for the flow path can be formed in which the angle between the upper surface and the inner peripheral surface of the through hole 701 for the flow path in a longitudinal section is less than 90°. By overlapping such thin film members 70 in a manner that the through hole 701 for the flow path is offset in the width direction, an upper descending step 72 having an angle 723 less than 90° can be formed. It should be noted that, as Figure 4C As shown in FIG. 1 , if a two-side etching method is used to etch from both sides of the thin film member 70 as shown by arrows E1 and E2, the angle between the upper surface of the through hole 701 for the flow path and the inner peripheral surface and the angle between the lower surface of the through hole 701 for the flow path and the inner peripheral surface are respectively less than 90°. By overlapping such thin film members 70 in a manner that the through hole 701 for the flow path is offset in the width direction, the upper side descending step 72 having a corner 723 less than 90° can be formed.

[0072] It should be noted that the height of the second upper wall surface 722 is preferably not less than 10 μm and not more than 200 μm. If the height of the second upper wall surface 722 exceeds 200 μm, the flow of ink increases, so that the bubbles B are not stored in the corner 723. On the other hand, if the height of the second upper wall surface 722 is less than 10 μm, it becomes difficult to ensure a space for storing the bubbles B.

[0073] In addition, the height of the second upper wall surface 722 is preferably the same height as the height of each individual flow path 31, 34. When the height of each individual flow path 31, 34 is not constant, the height of the second upper wall surface 722 is preferably the same height as the lowest part of each individual flow path 31, 34. This is because in order to make the flow path resistance of the connecting flow path 7 equal to the flow path resistance of each individual flow path 31, 34 of each nozzle 41, it is preferable to make use of the thin film member 70 constituting the flow path plate 30 to constitute the connecting flow path 7.

[0074] In addition, it is preferable that a plurality of steps 72, 73, 75, and 76 exist in the connecting flow path 7. This is because the amount of bubbles B stored in the corners 723, 733, 753, and 763 increases, thereby obtaining a higher damping effect. Figure 5A As shown in FIG. 1 , each step 72, 73, 75, 76 is formed in a manner that increases the number of steps that continuously descend or ascend. Alternatively, as shown in FIG. 1 , another modification of the connecting flow path 7 is shown. Figure 5B As shown in FIG. 1 , each step 72, 73, 75, 76 is formed in a manner that descends and ascends repeatedly. Figure 5C As shown, the steps 72, 73, 75, and 76 are formed so that the lengths of all the parts of the connecting flow path 7 that allow the ink to flow in the horizontal direction (XY plane direction) are not the same. The shapes of other parts of the connecting flow path 7 can be freely determined according to size constraints and the like.

[0075] The connecting flow path 7 may be formed to extend straight in the Y-axis direction, or may be formed to include both a portion extending straight in the Y-axis direction and a portion extending straight in the X-axis direction.

[0076] [Second embodiment]

[0077] Next, a second embodiment of the present invention will be described. In the second embodiment, in an inkjet head of a type that circulates ink flowing in the upstream common flow path 61 and does not circulate ink flowing in each individual flow path 31, 34, a structure is described in which bubbles are stored upstream and downstream of the upstream common flow path 61 to suppress fluid crosstalk. The upstream common flow path 61 of the second embodiment corresponds to the first common flow path of the present invention. Fig. 6A It is a plan view schematically showing the upstream common flow path and the connecting flow path. Figure 6B It is along Fig. 6AIt is a longitudinal cross-sectional view taken along the line VI-VI of the embodiment and shows an outline of the connecting flow path. It should be noted that the same names and the same reference numerals are sometimes used to designate the same structures as those in the first embodiment, and the description thereof may be simplified or omitted.

[0078] like Fig. 6A As shown in the figure, the upstream end of the upstream common flow path 61 is connected to one end of the connection flow path 7A having a smaller cross-sectional area than the upstream common flow path 61. The other end of the connection flow path 7A is connected to the ink supply path 11. The downstream end of the upstream common flow path 61 is connected to one end of the connection flow path 7B having a smaller cross-sectional area than the upstream common flow path 61. The other end of the connection flow path 7B is connected to the ink discharge path 13. With such a structure, the ink flowing through the upstream common flow path 61 returns to the upstream common flow path 61 via the ink discharge path 13, the second ink tank not shown, the pump, the first ink tank, and the ink supply path 11.

[0079] like Figure 6B As shown in the figure, each connecting flow path 7A, 7B is configured to include at least one step. That is, the upper wall surface 71A, 71B constituting the upper side of each connecting flow path 7A, 7B is configured to include two upper side descending steps 72 and two upper side ascending steps 73. In addition, the lower wall surface 74A, 74B constituting the lower side of the connecting flow path 7A is configured to include two lower side descending steps 75 and two lower side ascending steps 76.

[0080] With the above structure, when ink flows in the connecting flow path 7A, the upstream common flow path 61 and the connecting flow path 7B, bubbles are accumulated in a predetermined area near the corners 723 , 733 , 753 , 763 of the steps 72 , 73 , 75 , 76 .

[0081] In the case where the connecting flow path 7A and the connecting flow path 7B are not connected to the two ends of the upstream common flow path 61 and the upstream common flow path 61 is directly connected to the ink supply path 11 and the ink discharge path 13, there is no part in the upstream common flow path 61 where bubbles can be accumulated. Therefore, it is impossible to suppress fluid crosstalk by utilizing the damping effect brought about by the bubbles. In contrast, in the second embodiment, bubbles that suppress fluid crosstalk can be arranged near the two ends of the upstream common flow path 61 by connecting the connecting flow path 7A and the connecting flow path 7B to the two ends of the upstream common flow path 61. Therefore, the influence of fluid crosstalk can be made uniform among the multiple nozzles 41 arranged along the Y-axis direction.

[0082] In addition, by connecting the connection flow path 7A and the connection flow path 7B to both ends of the upstream common flow path 61, it is possible to prevent bubbles from being stored in the upstream common flow path 61. Therefore, by storing bubbles at a position upstream of the upstream common flow path 61, it is possible to suppress the occurrence of fluctuations in the ejection state of ink that are caused by the temporal variation in the amount of stored bubbles.

[0083] [Third embodiment]

[0084] Next, a third embodiment of the present invention will be described. In the third embodiment, in an inkjet head of a type that circulates ink flowing in each common flow path 61, 62 and each individual flow path 31, 34, a structure is described in which bubbles are stored at a position upstream of each common flow path 61, 62 to suppress fluid crosstalk. The upstream common flow path 61 of the third embodiment corresponds to the first common flow path of the present invention, and the downstream common flow path 62 corresponds to the second common flow path of the present invention. Fig. 7A It is a plan view schematically showing the upstream common flow path, the downstream common flow path, and the connecting flow path. Figure 7B It is along Fig. 7A It is a longitudinal cross-sectional view taken along line VII-VII of the embodiment and shows an outline of the connecting flow path. It should be noted that the same names and the same reference numerals may be used to designate the same structures as those in the first embodiment, and the description thereof may be simplified or omitted.

[0085] like Fig. 7A As shown, the upstream end of the upstream common flow path 61 is connected to one end of the connection flow path 7C having a smaller cross-sectional area than the upstream common flow path 61. The upstream end of the downstream common flow path 62 is connected to the other end of the connection flow path 7C. The ink supply path 11 is connected to the upstream side of the upstream common flow path 61. The ink discharge path 13 is connected to the downstream side of the downstream common flow path 62. With such a structure, a part of the ink flowing through the upstream common flow path 61 flows to the ink discharge path 13 via each individual flow path 31, 34 and the downstream common flow path 62. In addition, the remaining part of the ink supplied from the ink supply path 11 flows to the ink discharge path 13 via the connection flow path 7C and the downstream common flow path 62. The ink flowing to the ink discharge path 13 returns to the upstream common flow path 61 via the second ink tank, the pump, the first ink tank and the ink supply path 11, which are not shown.

[0086] like Figure 7B As shown in FIG. 1 , the connecting flow path 7C is configured to include at least one step. That is, the upper wall surface 71C constituting the upper side of the connecting flow path 7C is configured to include three upper side descending steps 72 and three upper side ascending steps 73. In addition, the lower wall surface 74C constituting the lower side of the connecting flow path 7C is configured to include three lower side descending steps 75 and three lower side ascending steps 76.

[0087] With the above-described structure, when ink flows in the connecting flow path 7C, bubbles are accumulated in a predetermined range of regions near the corners 723 , 733 , 753 , and 763 of the steps 72 , 73 , 75 , and 76 .

[0088] When the upstream end of the common flow path 62 on the downstream side is not connected to the connecting flow path 7C, the upstream side of the common flow path 62 on the downstream side becomes a stagnant water area, and the amount of bubbles accumulated therein cannot be controlled. Therefore, the fluid crosstalk suppression effect using the damping effect brought about by the bubbles changes over time, and although the fluid crosstalk suppression effect is obtained, the reproducibility of the ink landing cannot be improved. In contrast, in the third embodiment, by connecting the connecting flow path 7C to the upstream end of the common flow path 62 on the downstream side, the stagnant water area can be eliminated from the upstream end of the common flow path 62 on the downstream side, and on the other hand, a constant amount of bubbles can be accumulated in the connecting flow path 7C. Therefore, the fluid crosstalk suppression effect using the damping effect brought about by the bubbles can be obtained. In addition, the temporal change of the fluid crosstalk suppression effect can be suppressed, and the reproducibility of the ink landing can be improved.

[0089] In addition, by connecting the upstream ends of the upstream common flow path 61 and the downstream common flow path 62 via a connecting flow path 7C, bubbles that suppress fluid crosstalk can be arranged near the upstream ends of the upstream common flow path 61 and the downstream common flow path 62. Therefore, it is not necessary to connect different connecting flow paths to the upstream sides of the upstream common flow path 61 and the downstream common flow path 62, respectively, and it is possible to reduce processing costs or flow path formation space. That is, even in the case of constraints such as miniaturization and cost reduction, fluid crosstalk can be suppressed by storing bubbles near the ends of each common flow path 61, 62.

[0090] In addition, by connecting the upstream common flow path 61 and the downstream common flow path 62 via one connecting flow path 7C, the influence of the damping component caused by the bubbles in each of the upstream common flow path 61 and the downstream common flow path 62 can be made equal. Therefore, when the ink is ejected, the characteristics such as the flow path resistance on the upstream side and the downstream side can be made constant, and the ink ejection performance can be improved.

[0091] [Fourth embodiment]

[0092] Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, in an inkjet head of a type that circulates ink flowing in each common flow path 61, 62 and each individual flow path 31, 34, a structure is described in which bubbles are stored at positions upstream and downstream of each common flow path 61, 62 to suppress fluid crosstalk. The upstream common flow path 61 of the fourth embodiment corresponds to the first common flow path of the present invention, and the downstream common flow path 62 corresponds to the second common flow path of the present invention. Fig. 8AIt is a plan view schematically showing the upstream common flow path, the downstream common flow path, and the connecting flow path. Figure 8B It is along Fig. 8A The fourth embodiment is a longitudinal sectional view of the line VIII-VIII of the embodiment and shows an overview of the connecting flow path. It should be noted that the fourth embodiment differs from the third embodiment in that a connecting flow path 7D is provided, so the description will be centered on this difference. In addition, regarding the same structure as the first embodiment, the same name and the same figure mark are sometimes marked, and the description is simplified or omitted.

[0093] like Fig. 8A As shown in the figure, the downstream end of the upstream common flow path 61 is connected to one end of the connection flow path 7D having a smaller cross-sectional area than the upstream common flow path 61. The downstream end of the downstream common flow path 62 is connected to the other end of the connection flow path 7D. With such a structure, a part of the ink flowing through the upstream common flow path 61 flows to the ink discharge path 13 via each individual flow path 31, 34 and the downstream common flow path 62, or via the connection flow path 7D. In addition, the remaining part of the ink supplied from the ink supply path 11 flows to the ink discharge path 13 via the connection flow path 7C and the downstream common flow path 62. The ink flowing through the ink discharge path 13 returns to the upstream common flow path 61 via the second ink tank, the pump, the first ink tank, and the ink supply path 11, which are not shown.

[0094] like Figure 8B As shown in FIG. 1 , the connecting flow path 7D is configured to include at least one step. That is, the upper wall surface 71D of the connecting flow path 7D is configured to include three upper side descending steps 72 and three upper side ascending steps 73. In addition, the lower wall surface 74D constituting the lower side of the connecting flow path 7D is configured to include three lower side descending steps 75 and three lower side ascending steps 76.

[0095] With the above-described structure, when ink flows in the connecting flow paths 7C and 7D, bubbles are accumulated in a predetermined range of regions near the corners 723 , 733 , 753 , and 763 of the steps 72 , 73 , 75 , and 76 .

[0096] In the case where the upstream end of the downstream common flow path 62 is not connected to the connection flow path 7C, as described in the third embodiment, the fluid crosstalk suppression effect using the damping effect of the bubbles changes over time, and although the fluid crosstalk suppression effect is obtained, the reproducibility of the ink landing accuracy cannot be obtained. In addition, in the case where the downstream end of the upstream common flow path 61 is not connected to the connection flow path 7D, the downstream side of the upstream common flow path 61 becomes a stagnant water area, and the amount of bubbles accumulated therein cannot be controlled. Therefore, the fluid crosstalk suppression effect using the damping effect of the bubbles changes over time, and although the fluid crosstalk suppression effect is obtained, the reproducibility of the ink landing cannot be improved. In contrast, in the fourth embodiment, by connecting the connecting flow path 7C to the upstream end of the downstream common flow path 62 and connecting the connecting flow path 7D to the downstream end of the upstream common flow path 61, it is possible to eliminate the stagnant water area from the upstream end of the downstream common flow path 62 and the downstream end of the upstream common flow path 61, and on the other hand, a constant amount of bubbles can be accumulated in each connecting flow path 7C, 7D. Therefore, it is possible to obtain the fluid crosstalk suppression effect using the damping effect brought about by the bubbles. In addition, it is possible to suppress the temporal change of the fluid crosstalk suppression effect, and it is possible to improve the reproducibility of ink landing.

[0097] In addition, the number of steps 72, 73, 75, 76 of the connecting flow path 7D is made the same as the number of steps 72, 73, 75, 76 of the connecting flow path 7C, and the same amount of bubbles are present on the upstream side and the downstream side of each of the upstream common flow path 61 and the downstream common flow path 62, thereby being able to suppress the fluctuation of the ejection state of the ink between the nozzles 41 by utilizing the fluid crosstalk suppression effect brought by the damping effect of the bubbles.

[0098] In addition, by connecting the upstream ends of the upstream common flow path 61 and the downstream common flow path 62 to each other by the connecting flow path 7C, and connecting the downstream ends to each other by the connecting flow path 7D, bubbles that suppress fluid crosstalk can be arranged near both ends of the upstream common flow path 61 and the downstream common flow path 62. Therefore, it is not necessary to connect different connecting flow paths to the upstream end and the downstream end of each of the upstream common flow path 61 and the downstream common flow path 62, and it is possible to reduce processing costs or flow path formation space. That is, even in the case of constraints such as miniaturization and cost reduction, fluid crosstalk can be suppressed by storing bubbles near the ends of each common flow path 61, 62.

[0099] In addition, by connecting the upstream common flow path 61 and the downstream common flow path 62 via the connecting flow paths 7C and 7D, the influence of the damping component caused by the bubbles in each of the upstream common flow path 61 and the downstream common flow path 62 can be made equal. Therefore, when the ink is ejected, the characteristics such as the flow path resistance on the upstream side and the downstream side can be made constant, and the ink ejection performance can be improved.

[0100] In addition, bubbles that suppress fluid crosstalk can be arranged near both ends of the upstream common flow path 61 and the downstream common flow path 62. Therefore, the influence of fluid crosstalk can be made uniform among the plurality of nozzles 41 arranged along the Y-axis direction.

[0101] In addition, by connecting the connecting flow path 7C and the connecting flow path 7D to both ends of the upstream common flow path 61 and the downstream common flow path 62, respectively, it is possible to prevent bubbles from being stored in the upstream common flow path 61 and the downstream common flow path 62. Therefore, bubbles are stored in the ends of the upstream common flow path 61 and the downstream common flow path 62, and the occurrence of fluctuations in the ejection state of the ink caused by the temporal variation in the amount of the stored bubbles can be suppressed.

[0102] In order to achieve miniaturization of the inkjet head, the upstream common flow path 61 or the downstream common flow path 62 may be used in common for a plurality of nozzle rows. Fig.9A It is a plan view schematically showing an inkjet head according to a modified example of the fourth embodiment. Fig. 9B This is a plan view schematically showing an inkjet head according to another modified example of the fourth embodiment.

[0103] like Fig.9A As shown in FIG. 1 , the upstream common flow path 61 is formed to extend in the Y-axis direction in a plan view. The downstream common flow path 62 is composed of a first portion 62A formed to extend in the Y-axis direction on the +X direction side of the upstream common flow path 61 in a plan view, a second portion 62B formed to extend in the Y-axis direction on the -X direction side of the upstream common flow path 61 in a plan view, and a third portion 62C that connects the ends of the first portion 62A and the second portion 62B on the -Y direction side to each other. The ink supply path 11 is connected to the end on the +Y direction side of the upstream common flow path 61. The ink discharge path 13 is connected to the center of the length direction of the third portion 62C of the downstream common flow path 62. The upstream common flow path 61 and the first portion 62A of the downstream common flow path 62 are connected via a plurality of upstream separate flow paths 31, pressure chambers 33, and downstream separate flow paths 34, respectively. The upstream common flow passage 61 and the second portion 62B of the downstream common flow passage 62 are connected via a plurality of upstream individual flow passages 31 , pressure chambers 33 , and downstream individual flow passages 34 .

[0104] In addition, one end of the connection flow path 7E and one end of the connection flow path 7F are connected to the +Y direction side end of the upstream common flow path 61. The other end of the connection flow path 7E is connected to the +Y direction side end of the first portion 62A of the downstream common flow path 62. The other end of the connection flow path 7F is connected to the +Y direction side end of the second portion 62B of the downstream common flow path 62. One end of the connection flow path 7G is connected to the -Y direction side end of the upstream common flow path 61. The other end of the connection flow path 7G is connected to the vicinity of the connection portion connected to the ink discharge path 13 in the third portion 62C of the downstream common flow path 62. Each of the connection flow paths 7E, 7F, and 7G is formed so that their cross-sectional area is smaller than the cross-sectional area of ​​the upstream common flow path 61.

[0105] With the above-described structure, a portion of the ink supplied from the ink supply path 11 flows in the upstream common flow path 61 in the -Y direction, and flows to the first portion 62A or the second portion 62B of the downstream common flow path 62 via the upstream individual flow path 31, the pressure chamber 33, and the downstream individual flow path 34, or flows to the ink discharge path 13 via the connecting flow path 7G and the third portion 62C. In addition, the remaining portion of the ink supplied from the ink supply path 11 flows to the ink discharge path 13 via the connecting flow path 7E, the first portion 62A, and the third portion 62C, or via the connecting flow path 7F, the second portion 62B, and the third portion 62C. The ink that has flowed to the ink discharge path 13 returns to the upstream common flow path 61 via the second ink tank, the pump, the first ink tank, and the ink supply path 11, which are not shown.

[0106] Each of the connecting flow paths 7E, 7F, and 7G is configured to include at least one step. Fig.9A Although not shown in the figure, the structure includes an upper descending step 72, an upper ascending step 73, a lower descending step 75 and a lower ascending step 76.

[0107] With the above-described structure, when ink flows in the connecting flow paths 7E, 7F, and 7G, bubbles are stored in a predetermined range of regions near the corners 723, 733, 753, and 763 of the steps 72, 73, 75, and 76. That is, the steps of the connecting flow paths 7E, 7F, and 7G correspond to the bubble storage portions of the present invention.

[0108] In order to extend the connection flow path, more steps can be configured, or Fig. 9BThe inkjet head is constructed as shown. The inkjet head includes an upstream common flow path 61, a first downstream common flow path 62D, and a second downstream common flow path 62E. The upstream common flow path 61, the first downstream common flow path 62D, and the second downstream common flow path 62E are formed to extend along the Y-axis direction in a top view. The upstream common flow path 61 and the first downstream common flow path 62D are connected via multiple upstream separate flow paths 31, pressure chambers 33, and downstream separate flow paths 34, respectively. The upstream common flow path 61 and the second downstream common flow path 62E are connected via multiple upstream separate flow paths 31, pressure chambers 33, and downstream separate flow paths 34, respectively.

[0109] In addition, one end of the connection flow path 7H is connected to the +Y direction side end of the upstream common flow path 61. The ink supply path 11 is connected to the other end of the connection flow path 7H. One end of the connection flow path 7I and one end of the connection flow path 7J are connected to the ink supply path 11. The other end of the connection flow path 7I is connected to the +Y direction side end of the first downstream common flow path 62D. The other end of the connection flow path 7J is connected to the +Y direction side end of the second downstream common flow path 62E. One end of the connection flow path 7K is connected to the -Y direction side end of the upstream common flow path 61. The ink discharge path 13 is connected to the other end of the connection flow path 7K. One end of the connection flow path 7L and one end of the connection flow path 7M are connected to the ink discharge path 13. The other end of the connection flow path 7L is connected to the -Y direction side end of the first downstream common flow path 62D. The other end of the connection flow path 7M is connected to the -Y direction side end of the second downstream common flow path 62E. The connecting flow paths 7H, 7I, 7J, 7K, 7L, and 7M are formed so that their cross-sectional areas are smaller than the cross-sectional area of ​​the upstream common flow path 61 .

[0110] With the above-described structure, a portion of the ink supplied from the ink supply path 11 flows to the upstream common flow path 61 via the connecting flow path 7H. The ink flowing to the upstream common flow path 61 flows to the first downstream common flow path 62D or the second downstream common flow path 62E via the upstream individual flow path 31, the pressure chamber 33, and the downstream individual flow path 34, or flows to the ink discharge path 13 via the connecting flow path 7K. The remaining portion of the ink supplied from the ink supply path 11 flows to the first downstream common flow path 62D via the connecting flow path 7I, or flows to the second downstream common flow path 62E via the connecting flow path 7J. The ink flowing to the first downstream common flow path 62D flows to the ink discharge path 13 via the connecting flow path 7L. The ink flowing to the second downstream common flow path 62E flows to the ink discharge path 13 via the connecting flow path 7M. The ink that has flowed into the ink discharge path 13 is returned to the upstream common flow path 61 via the second ink tank, the pump, the first ink tank, and the ink supply path 11 (not shown).

[0111] Each of the connecting flow paths 7H, 7I, 7J, 7K, 7L, and 7M is configured to include at least one step. Fig. 9B Although not shown in the figure, the structure includes an upper descending step 72, an upper ascending step 73, a lower descending step 75 and a lower ascending step 76.

[0112] With the above structure, when ink flows in the connecting channels 7H, 7I, 7J, 7K, 7L, and 7M, bubbles are stored in a predetermined area near the corners 723 , 733 , 753 , and 763 of the steps 72 , 73 , 75 , and 76 .

[0113] like Fig.9A or Fig. 9B As shown, regardless of the configuration of the nozzle array or the structure of the upstream common flow path 61, the downstream common flow path 62, the first downstream common flow path 62D and the second downstream common flow path 62E, by connecting the two ends of the upstream common flow path 61, the downstream common flow path 62, the first downstream common flow path 62D and the second downstream common flow path 62E respectively using a connecting flow path with a step, the inkjet head can be miniaturized and the production cost and fluid crosstalk can be suppressed.

[0114] [Fifth Embodiment]

[0115] Next, a fifth embodiment of the present invention will be described. In the fifth embodiment, a method of forming a connecting flow path will be described. Fig.10 This is a diagram for explaining a method of forming a connecting flow path.

[0116] The connecting flow paths with steps shown in the first to fourth embodiments can also be formed by machining, but it is difficult to easily form steps by machining, and the machining cost becomes high. Therefore, it is preferable to effectively utilize the flow path plate 30 formed by the stacked structure (see Figure 2 ) is characterized in that a connecting flow path having a step is formed in the flow path plate 30. By forming through holes in each layer constituting the flow path plate 30 and stacking the layers with a portion of the through holes overlapping each other, a connecting flow path having a step can be formed.

[0117] For example, in order to form Fig. 8A The connecting flow paths 7C and 7D of the fourth embodiment shown in FIG. Fig.10 The first layer 81 to the fifth layer 85 shown constitute the flow path plate 30. When forming the flow path plate 30, the first layer 81, the second layer 82, the third layer 83, the fourth layer 84, and the fifth layer 85 are stacked in order from the bottom.

[0118] The fifth layer 85 is formed with a first connecting channel through hole 851 constituting the connecting channel 7C and a second connecting channel through hole 852 constituting the connecting channel 7D. The first connecting channel through hole 851 is formed so that at least a portion of the through hole 851 is aligned with the casing 10 (see FIG. 1 ). Figure 2 ) overlaps with the second upstream common flow path portion 12 of the shell portion 10. The second connecting flow path through hole 852 is formed so as to overlap with the second downstream common flow path portion 14 of the shell portion 10 at least in part.

[0119] In addition, the fifth layer 85 is provided with a pressure chamber through hole 853 constituting the pressure chamber 33 and a first upstream common flow path portion 32 (see Figure 2 ) and the first common flow path through hole 854 constituting the first downstream common flow path portion 35 (see Figure 2 ). The second upstream common flow path portion 12 is formed such that its length in the X-axis direction and the Y-axis direction is longer than the length in the X-axis direction and the Y-axis direction of the first common flow path through hole 854. The second downstream common flow path portion 14 is formed such that its length in the X-axis direction and the Y-axis direction is longer than the length in the X-axis direction and the Y-axis direction of the second common flow path through hole 855. Therefore, the first and second connecting flow path through holes 851, 852 are not connected to the first and second common flow path through holes 854, 855, but are connected to the first and second common flow path through holes 854, 855 via the second upstream common flow path portion 12 or the second downstream common flow path portion 14.

[0120] The fourth layer 84 is formed with a through hole 841 for the first connecting flow path constituting the connecting flow path 7C and a through hole 842 for the second connecting flow path constituting the connecting flow path 7D. The first connecting flow path through hole 841 is formed so as to partially overlap with the first connecting flow path through hole 851 of the fifth layer. The second connecting flow path through hole 842 is formed so as to partially overlap with the second connecting flow path through hole 852 of the fifth layer. In addition, the fourth layer 84 is formed with a through hole 841 for constituting the pressure chamber 33 and each of the individual flow paths 31 and 34 (see Figure 2 The pressure chamber through hole 843 is formed so that a part of it overlaps with the pressure chamber through hole 853 of the fifth layer 85 and the first and second common flow path through holes 854 and 855.

[0121] The third layer 83 is formed with a through hole 831 for the first connecting flow path constituting the connecting flow path 7C and a through hole 832 for the second connecting flow path constituting the connecting flow path 7D. The through hole 831 for the first connecting flow path is formed so that a portion thereof overlaps with the through hole 841 for the first connecting flow path of the fourth layer. The through hole 832 for the second connecting flow path is formed so that a portion thereof overlaps with the through hole 842 for the second connecting flow path of the fourth layer. In addition, the through hole 833 for the pressure chamber constituting the pressure chamber 33, the through hole 834 for the first common flow path constituting the first upstream common flow path portion 32, and the through hole 835 for the second common flow path constituting the first downstream common flow path portion 35 are formed in the third layer 83. Each through hole 833, 834, 835 is configured so that a portion thereof overlaps with the through hole 843 for the pressure chamber of the fourth layer 84.

[0122] The second layer 82 is formed with a through hole 821 for the first connecting flow path constituting the connecting flow path 7C. The first connecting flow path through hole 821 is formed so as to partially overlap with the first connecting flow path through hole 831 of the third layer. Figure 2 ), the first common flow path through hole 824 constituting the first upstream common flow path section 32, and the second common flow path through hole 825 constituting the first downstream common flow path section 35. The silo portion through hole 823 is formed to overlap with the pressure chamber through hole 833 of the third layer 83. The first and second common flow path through holes 824 and 825 are formed to overlap with the first and second common flow path through holes 834 and 835 of the third layer 83, respectively.

[0123] The first layer 81 is provided with a silo section through-hole 813 constituting the silo section 36. The silo section through-hole 813 is formed so as to overlap with the silo section through-hole 823 of the second layer 82.

[0124] Each through hole 821, 831, 832, 841, 842, 851, 852 for connecting flow paths is equivalent to the first through hole of the present invention, and each through hole 833, 843, 853 for pressure chambers is equivalent to the second through hole of the present invention. Fig.10In the embodiment, the first and second through holes for connecting flow paths constituting the connecting flow paths 7C and 7D are not formed in the first layer 81, but the first and second through holes for connecting flow paths may be formed in the first layer 81, so that the steps of the connecting flow paths 7C and 7D are deeper. In this case, a groove with a bottom may be formed instead of a through hole so that the ink does not leak from the first layer 81. In addition, it is not limited to the first layer 81, and a groove with a bottom may be formed, for example, instead of the first through hole 821 for connecting flow path of the second layer 82, in order to increase the flow resistance of the connecting flow path 7C. In addition, in order to make the angle of the corner of the depression of each step less than 90°, it is preferred to form each through hole 851, 852, 841, 842, 831, 832, 821 for connecting flow paths by etching. In addition, the size, shape, or number of the through holes 851, 852, 841, 842, 831, 832, 821 for each connecting flow path of the first layer 81 to the fifth layer 85 is an example and can be determined according to the length of the connecting flow paths 7C, 7D or the flow path resistance of the connecting flow paths 7C, 7D.

[0125] [Sixth embodiment]

[0126] Next, a sixth embodiment of the present invention will be described. In the sixth embodiment, preferred aspects of the connecting flow path and the individual flow paths will be described.

[0127] like Fig. 7A , Fig. 8A , Fig.9A , Fig. 9B As shown in FIG. 1 , in a structure in which the upstream common flow path 61 and the downstream common flow path 62 are connected via the connecting flow paths 7C, 7E, 7F, 7I, 7J, the ratio of the amount of ink flowing in the connecting flow paths 7C, 7E, 7F, 7I, 7J is determined by the ratio of the flow path resistance of the connecting flow paths 7C, 7E, 7F, 7I, 7J to the flow path resistance of the individual flow paths 31, 34 of each nozzle 41 (for example, the total value of the flow path resistance of the upstream individual flow path 31 and the flow path resistance of the downstream individual flow path 34). This is because at least a portion of the connecting flow paths 7C, 7E, 7F, 7I, 7J is arranged in parallel with the upstream individual flow path 31 and the downstream individual flow path 34.

[0128] For example, if the ink flow rate of a connecting flow path 7C is greater than the ink flow rate of each individual flow path 31, 34 (one individual flow path 31 or one individual flow path 34), the ink flow rate of the individual flow paths 31, 34 is reduced, and thus the drying prevention function of the nozzle 41 is reduced. On the other hand, if the ink flow rate of a connecting flow path 7C is less than the ink flow rate of each individual flow path 31, 34, the force for discharging the bubbles stored outside the corners 723, 733, 753, 763 is weakened, and thus there is a situation where bubbles cannot be stored. That is, the force for discharging the bubbles from the connecting flow path 7C is weakened, and there is a problem that the fluctuation of the amount of bubbles over time increases. Therefore, the ink flow rate of a connecting flow path 7C is preferably set to the same level as the ink flow rate of each individual flow path 31, 34 connected to each nozzle 41.

[0129] In order to make the ink flow rate of one connecting flow path 7C and the ink flow rate of each individual flow path 31, 34 equal to each other, it is preferable to form the connecting flow path 7C and each individual flow path 31, 34 in a manner satisfying the following formula (1) when the flow path resistance of each individual flow path 31, 34 of each nozzle 41 is set to R1 and the flow path resistance of one connecting flow path 7C is set to R2. This is because if the following formula (1) is not satisfied, the above-mentioned problem becomes apparent at a level that cannot be ignored.

[0130] (R2 / 5)<R1<(R2×5)…(1)

[0131] In order to satisfy the above formula (1), it is preferred that Fig.10 As shown, the connecting flow path 7C is formed using the layer for forming the upstream side individual flow path 31 and the downstream side individual flow path 34. The reason for this will be described below.

[0132] In order to increase the flow resistance of the individual flow paths 31 and 34, it is preferable to form the layers of the individual flow paths 31 and 34 (in Fig.10 In the example shown, the thickness of the fourth layer 84 is thinner than the other layers. In this case, in order to make the flow resistance of the connecting flow path 7C equal to that of the individual flow paths 31 and 34 by using a layer thicker than the fourth layer 84, the length of the connecting flow path 7C in the ink flow direction needs to be set to a corresponding length, so that it becomes difficult to miniaturize the inkjet head. In order to increase the flow resistance of the individual flow paths 31 and 34, the layer (in Fig.10 In the example shown, when the thickness of the fourth layer 84 is thinner than the other layers, the length of the fourth layer 84 in the X-axis direction is made equal to the individual flow paths 31, 34, thereby making it easy to make the flow resistance of the connecting flow path 7C equal to the flow resistance of the individual flow paths 31, 34, and to satisfy the above formula (1) while meeting the requirements of miniaturization.

[0133] For the above reasons, it is preferable that the connecting flow paths 7C, 7E, 7F, 7I, and 7J are formed using the layers forming the individual flow paths 31 and 34. It should be noted that, when the connecting flow paths 7C, 7E, 7F, 7I, and 7J are formed without using the layers forming the individual flow paths 31 and 34 for some design reasons, it is preferable to set the structure to satisfy the above formula (1).

[0134] [Seventh embodiment]

[0135] Next, a seventh embodiment of the present invention will be described. In the seventh embodiment, a preferred embodiment of the upstream common flow path 61 and the downstream common flow path 62 will be described. Fig.11A It is a cross-sectional view in the YZ plane near the upstream common flow channel. Fig. 11B It is a cross-sectional view in the YZ plane of the downstream common flow path and its vicinity. It should be noted that the same names and the same reference numerals may be used to designate the same structures as those in the first embodiment, and the description thereof may be simplified or omitted.

[0136] The bubbles introduced from the ink supply path 11 or the nozzle 41 are stored in the corner of the step connecting the flow path as described above, but the bubbles exceeding the allowable storage amount of the corner are preferably quickly discharged to the outside of the inkjet head via the ink supply path 11 or the ink discharge path 13. At this time, if the bubbles are stored in the upstream common flow path 61 or the downstream common flow path 62, it will cause the ink ejection state to fluctuate. In addition, if the bubbles invade the interior of the upstream common flow path 61 or the downstream common flow path 62, it will also cause the fluctuation of the ink ejection state to deteriorate. Therefore, it is necessary to quickly discharge the bubbles to the outside without storing the bubbles in the upstream common flow path 61 or the downstream common flow path 62.

[0137] So, if Fig.11A As shown in FIG. 1 , the upper surface 611 of the upstream common flow path 61 is preferably composed of an inclined surface that continuously descends as it moves away from the connection portion connected to the ink supply path 11. The connection flow path 7N is connected to the upstream end of the upstream common flow path 61. The connection flow path 7P is connected to the downstream end of the upstream common flow path 61. With such a structure, for example, when bubbles injected from the ink supply path 11 are not discharged from the connection flow path 7P or the connection flow path 7N and remain in the upstream common flow path 61, the bubbles located near the upper surface 611 can be discharged through the ink supply path 11 by buoyancy.

[0138] In addition, if Fig. 11BAs shown in FIG. 1 , the upper surface 621 of the downstream common flow path 62 is preferably formed of an inclined surface that rises continuously as it approaches the connection portion connected to the ink discharge path 13. The connection flow path 7Q is connected to the upstream end of the downstream common flow path 62. The connection flow path 7R is connected to the downstream end of the downstream common flow path 62. With such a structure, for example, when bubbles injected from the ink supply path 11 are not discharged from the connection flow path 7Q or the connection flow path 7R and remain in the downstream common flow path 62, the bubbles located near the upper surface 621 can be discharged through the ink discharge path 13 by utilizing buoyancy.

[0139] It should be noted that if the inclination angle of the upper surface 611 of the upstream common flow path 61 and the upper surface 621 of the downstream common flow path 62 is too small, the force of discharging bubbles by buoyancy is weakened, and if it is too large, the size of the inkjet head becomes large, so it is preferably formed to be greater than 1 degree and less than 5 degrees. The processing method of applying inclination to the upper surface 611 of the upstream common flow path 61 and the upper surface 621 of the downstream common flow path 62 is not particularly limited, but for example, a method of performing mechanical processing using a ball end mill while continuously changing the cutting depth can be exemplified.

[0140] [Variation example]

[0141] It should be noted that the present invention is not limited to the above-described embodiments, and can be appropriately modified within a scope not departing from the gist of the invention.

[0142] For example, the connection flow path includes the upper descending step 72, the upper ascending step 73, the lower descending step 75, and the lower ascending step 76, but may include only one, two, or three of these steps.

[0143] For example, as Figure 3A In the modified example of the structure shown in FIG. 1 , the connecting flow path 7 can also be replaced by Fig. 12A The connecting flow path 7S is configured as shown. The side wall surface constituting the side surface on the +X direction side of the connecting flow path 7S is configured to include two steps 77. The side wall surface constituting the side surface on the -X direction side of the connecting flow path 7S is configured to include two steps 78. With such a structure, the main flow line of the ink in the connecting flow path 7S can also be made to flow in a manner that avoids the corners 773 and 783 of the steps 77 and 78 as shown by the arrow D1, and the bubbles can be stored in the area of ​​a predetermined range near the corners 773 and 783 of the steps 77 and 78.

[0144] For example, you can also Fig. 12BAs shown in the figure, a protrusion 79 is formed in the connecting flow path 7T. In this case, the connecting flow path 7T includes a first wall portion 71T that guides ink in the -Y direction (first direction) and a second wall portion 791 that is connected to the downstream end of the first wall portion 71T in a manner that forms a recessed corner portion 793 and guides the ink in the -Z direction (second direction). The corner portion 793 is equivalent to the bubble storage portion of the present invention. The first wall portion 71T is equivalent to the first part of the present invention, and the second wall portion 791 is equivalent to the second part of the present invention. In such a structure, the main streamline of the ink in the connecting flow path 7T can also be made to flow in a manner that avoids the corner portion 793 as shown by the arrow D1, and the bubbles can be stored in an area of ​​a predetermined range near the corner portion 793.

[0145] According to the inkjet head of the present invention, it is possible to suppress fluctuations in the ejection state of ink.

[0146] Industrial Applicability

[0147] The present invention can be widely used in an inkjet head and a printing device equipped with the inkjet head.

[0148] Description of Reference Numerals

[0149] 1 Inkjet head

[0150] 7, 7A, 7B, 7C, 7D, 7E, 7F, 7G, 7H, 7I, 7J, 7K, 7L, 7M, 7N, 7P, 7Q, 7R, 7S, 7T Connection flow path

[0151] 10 Housing

[0152] 11 Ink supply path

[0153] 12 Second upstream common flow path portion

[0154] 13 Ink discharge path

[0155] 14 Second downstream common flow path portion

[0156] 20 Vibration Plate

[0157] 21 Upstream opening

[0158] 22 Downstream opening

[0159] 24 convex part

[0160] 30 Manifold board

[0161] 31 Upstream separate flow path

[0162] 32 First upstream common flow path portion

[0163] 33 Pressure Chamber

[0164] 34 Downstream separate flow path

[0165] 35 First downstream common flow path portion

[0166] 36 Silo Department

[0167] 40 Nozzle Plate

[0168] 41 Nozzle

[0169] 50 Pressure fluctuation part

[0170] 51 Base

[0171] 52 Piezoelectric element

[0172] 53 substrate

[0173] 61 Upstream common flow path

[0174] 62 Downstream common flow path

[0175] 62A First Part

[0176] 62B Second part

[0177] 62C Third Part

[0178] 62D First downstream common flow path

[0179] 62E Second downstream common flow path

[0180] 70 Thin film components

[0181] 71, 71A, 71B, 71C, 71D Upper wall

[0182] 71T First wall surface

[0183] 72, 73, 75, 76, 77, 78 stairs

[0184] 74, 74A, 74B, 74C, 74D Lower wall

[0185] 79 protuberance

[0186] 81 First floor

[0187] 82 Second Floor

[0188] 83 Third Floor

[0189] 84 Fourth Floor

[0190] 85 Fifth Floor

[0191] 611, 621 upper surface

[0192] 701 Through hole for flow path

[0193] 702 Upper surface

[0194] 703 Lower surface

[0195] 721, 731 First upper wall surface

[0196] 722, 732 Second upper wall surface

[0197] 723, 733, 753, 763, 773, 783 corner

[0198] 751, 761 First lower wall surface

[0199] 752, 762 Second lower wall surface

[0200] 791 Second Wall Face

[0201] 793 corner

[0202] 813 Silo through hole

[0203] 823 Silo through hole

[0204] 821, 831, 841, 851 First connecting flow path through hole

[0205] 824, 834, 854 First common flow path through hole

[0206] 825, 835, 855 Second common flow path through hole

[0207] 832, 842, 852 Second connecting flow path through hole

[0208] 833, 843, 853 Through hole for pressure chamber

[0209] B Bubbles.

Claims

1. An inkjet head, wherein: The inkjet head comprises: a plurality of pressure chambers connected to nozzles for ejecting ink; a first common flow path communicating with the plurality of pressure chambers; and a connecting flow path connected to the first common flow path, The connecting flow path includes a bubble storage portion for storing bubbles.

2. The inkjet head according to claim 1, wherein: The connecting flow path comprises: a first portion that guides the ink in a first direction; and a second part connected to the first part and guiding the ink in a second direction intersecting with the first direction; The bubble reservoir is a corner portion where the first portion and the second portion are connected.

3. The inkjet head according to claim 1, wherein: The bubble reservoir is a step formed in the connecting flow path.

4. The inkjet head according to claim 2, wherein: The connecting flow path is formed by stacking a plurality of plate-like members having first through holes.

5. The inkjet head according to claim 4, wherein: At least any one of the plurality of plate-shaped members has a second through hole that forms the plurality of pressure chambers.

6. The inkjet head according to any one of claims 1 to 5, wherein: The connecting flow path is located between an ink supply path that supplies the ink to the first common flow path and the first common flow path.

7. The inkjet head according to any one of claims 1 to 5, wherein: The connecting flow path is located between an ink discharge path that discharges the ink and the first common flow path.

8. The inkjet head according to any one of claims 1 to 5, wherein: The inkjet head further includes a second common flow path communicating with the plurality of pressure chambers. One end of the connecting flow path is connected to the first common flow path, and the other end of the connecting flow path is connected to the second common flow path.

9. The inkjet head according to claim 8, wherein: The connecting flow path is a flow path different from a flow path of the ink that flows from the first common flow path to the second common flow path via the plurality of pressure chambers.

10. The inkjet head according to any one of claims 1 to 5, wherein The inkjet head further includes a plurality of individual flow paths that individually connect the plurality of pressure chambers to the first common flow path. Each individual flow path and the connecting flow path are formed so as to satisfy the following formula (1): (R2 / 5)<R1<(R2×5)…(1) R1: flow resistance in the single flow path, R2: flow path resistance in the connecting flow path.

11. The inkjet head according to any one of claims 1 to 5, wherein: The inkjet head further includes a second common flow path communicating with the plurality of pressure chambers. The connecting flow path is located between an ink supply path that supplies the ink to the first common flow path and the second common flow path, and is connected to the second common flow path.

12. The inkjet head according to any one of claims 1 to 5, wherein: The inkjet head further includes a second common flow path communicating with the plurality of pressure chambers. The connecting flow path is located between an ink discharge path that discharges the ink and the second common flow path, and is connected to the second common flow path.

13. The inkjet head according to claim 1, wherein The upper surface of the first common flow path is higher upstream in the ink flow direction than downstream in the ink flow direction.

14. The inkjet head according to claim 1, wherein The inkjet head further includes a second common flow path communicating with the plurality of pressure chambers. The upper surface of the second common flow path is higher downstream in the ink flow direction than upstream in the ink flow direction.

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