Liquid ejection head

Abstract

To provide a liquid ejection head that is able to prevent back flow of liquid from a return manifold.SOLUTION: A liquid ejection head 10 includes: a first pressure chamber 32a in which an ejection pressure is applied to liquid; a first descender 33a extending in an extending direction from the first pressure chamber; a first return diaphragm 34a extending in a direction crossing the extending direction from the first descender; a first nozzle 21a connected to the first descender; a second pressure chamber 32b in which ejection pressure is applied to liquid; a second descender 33b extending in an extending direction from the second pressure chamber; a second return diaphragm 34b extending in a direction crossing the extending direction from the second descender; a second nozzle connected to the second descender; a connection passage 35 connected to the first return diaphragm and the second return diaphragm; and a coupling passage 36 connected to the connection passage between the first return diaphragm and the second return diaphragm and to a return manifold. Passage resistance when liquid flows in the coupling passage is larger than passage resistance when the liquid flows in the connection passage.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection head. [Background technology]

[0002] A conventional liquid ejection head is disclosed in Patent Document 1. This liquid ejection head has ejection holes, pressure chambers connected to the ejection holes by descenders, a first common flow path connected to the pressure chambers by first individual flow paths, and a second common flow path connected to the descenders by second individual flow paths. The second individual flow paths have a first section connected to the descenders and a second section connected to the first section and the second common flow path. The first section has individual parts connected to the descenders and an integrated section connected to the individual parts and the second section. A plurality of individual parts are connected to this integrated section. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 010880 Summary of the Invention [Problem to be solved by the invention]

[0004] In the liquid ejection head of Patent Document 1, liquid flows from the first common flow path through the first individual flow path into the pressure chamber, then flows through the descender, and a portion of the liquid is ejected from the ejection hole. The liquid that is not ejected passes through the individual portion, integrated portion, and second portion of the second individual flow path, then flows into the second common flow path, and is discharged to the outside of the head.

[0005] Here, when liquid is ejected from the ejection holes at a high ejection rate, the distance between the ejection holes and the first common flow path is long, so the amount of liquid supplied from the first common flow path to the ejection holes is insufficient to eject the liquid from the ejection holes, and there is a risk that the liquid will flow back from the second common flow path to the ejection holes. In this case, if the backflowing liquid contains impurities, the impurities may clog the ejection holes, resulting in ejection defects.

[0006] The present invention has been made to solve such problems, and has as its object to provide a liquid ejection head that can suppress backflow of liquid from the return manifold. [Means for solving the problem]

[0007] A liquid ejection head according to one aspect of the present invention comprises a first pressure chamber to which ejection pressure is applied to liquid, a first descender extending from the first pressure chamber in an extension direction, a first feedback orifice extending from the first descender in a direction intersecting the extension direction, a first nozzle connected to the first descender, a second pressure chamber to which ejection pressure is applied to the liquid, a second descender extending from the second pressure chamber in the extension direction, a second feedback orifice extending from the second descender in a direction intersecting the extension direction, a second nozzle connected to the second descender, a coupling path connected to the first feedback orifice and the second feedback orifice, the coupling path between the first feedback orifice and the second feedback orifice, and a connecting path connected to a return manifold, wherein the flow path resistance when the liquid flows through the connecting path is greater than the flow path resistance when the liquid flows through the connecting path. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram schematically illustrating a liquid ejection apparatus including a liquid ejection head according to an embodiment of the present invention. [Figure 2] FIG. 1 is a cross-sectional view schematically illustrating a liquid ejection head. [Figure 3] FIG. 3 is a view of the liquid ejection head of FIG. 2 as seen from above. [Figure 4]FIG. 3 is a cross-sectional view schematically showing the liquid ejection head of FIG. 2. [Figure 5] FIG. 10 is a cross-sectional view schematically showing a liquid ejection head according to a modified example. [Figure 6] FIG. 6 is a view of the liquid ejection head of FIG. 5 as seen from above. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, the same or corresponding elements will be designated by the same reference numerals throughout the drawings, and redundant description thereof will be omitted.

[0010] (Embodiment) <Liquid discharge device> A liquid ejection device 11 equipped with a liquid ejection head (hereinafter referred to as "head 10") according to an embodiment of the present invention is a device that ejects liquid such as ink, as shown in Fig. 1. Below, an example will be described in which the liquid ejection device 11 is applied to an inkjet printer that ejects liquid from the head 10 onto a recording medium A to form an image, but the liquid ejection device 11 is not limited to this. Furthermore, the recording medium A can be a sheet material such as paper or cloth.

[0011] The liquid ejection device 11 employs a line head system and includes a platen 12, a conveying unit 13, a head unit 14, a storage tank 15, and a control unit 16. The side of the head unit 14 that faces the platen relative to the head 10 is referred to as the lower side, and the opposite side is referred to as the upper side. Directions that intersect (for example, perpendicular to) this up-down direction and intersect (for example, perpendicular to) each other are referred to as the left-right direction and the front-rear direction. However, the arrangement of the liquid ejection device 11 is not limited to this.

[0012] The platen 12 is, for example, a rectangular flat plate, and has a flat upper surface on which the recording medium A is placed, and determines the distance between the recording medium A and the head unit 14.

[0013] The transport unit 13 has, for example, a pair of transport rollers 13a and a transport motor. The pair of transport rollers 13a are arranged parallel to each other with the platen 12 sandwiched between them in the front-to-rear direction. The central axis of the transport roller 13a extends in the left-to-right direction. One of the pair of transport rollers 13a is connected to a transport motor. When the transport motor is driven, the transport roller 13a rotates, and the recording medium A on the platen 12 is transported in the front-to-rear direction.

[0014] The head unit 14 extends elongatedly in the left-right direction, and its length in the left-right direction is equal to or greater than the length of the recording medium A. The head unit 14 is provided with a plurality of heads 10. The head 10 is provided with a discharge surface 40a (FIG. 2) that faces the upper surface of the platen 12, and a plurality of nozzles 21 that open to the discharge surface 40a. Details of the head 10 will be described later.

[0015] A storage tank 15 is provided for each type of liquid. For example, four storage tanks 15 store black, yellow, cyan, and magenta liquids, respectively. The storage tanks 15 supply the liquid to the nozzles 21 of the corresponding heads 10. When pressure is applied to the liquid by a drive element 60 (described later), the liquid is ejected from the nozzles 21.

[0016] The control unit 16 includes a calculation unit such as a CPU, a storage unit such as RAM and ROM, and a driver IC such as an ASIC. In the control unit 16, the calculation unit outputs various execution commands to the driver ICs of each unit based on the programs stored in the storage unit. This causes the control unit 16 to control the operation of the transport motor of the transport unit 13 and the drive element 60 of the head 10. For example, the control unit 16 executes a discharge operation to cause the head 10 to discharge liquid, as well as a transport operation to cause the transport unit 13 to transport the recording medium A. This causes the printing process to proceed, forming an image on the recording medium A using liquid.

[0017] <head> 2 to 4, the head 10 is provided with a flow path forming body 40 formed by a stack of multiple plates and having liquid flow paths 20, and a driving element 60 that applies pressure to the liquid in the liquid flow path 20. Note that Fig. 2 illustrates the connection relationship between each part of the liquid flow path 20 and the positional relationship between each part of the liquid flow path 20 and the plates of the flow path forming body 40 in an easy-to-understand manner. For this reason, the left-right direction of the paper surface of Fig. 2 may not correspond to the position of each part of the liquid flow path 20.

[0018] The flow path forming body 40 has, for example, a nozzle plate 41, a plurality of (e.g., 10) flow path plates, and a vibration plate 52. These plates have a rectangular flat plate shape, are stacked in this order, and are bonded to each other with an adhesive or the like. The stacking direction in which the plates are stacked in the flow path forming body 40 is referred to as the up-down direction. Also, directions that intersect (e.g., perpendicular to) this up-down direction and intersect (e.g., perpendicular to) each other are referred to as the left-right direction and the front-rear direction. However, the arrangement of the head 10 is not limited to these directions.

[0019] The plurality of flow path plates include a first flow path plate 42 to a tenth flow path plate 51, with the lower surface of the first flow path plate 42 bonded to the upper surface of the nozzle plate 41 and the upper surface of the tenth flow path plate 51 bonded to the lower surface of the diaphragm 52. The diaphragm 52 may be formed integrally with the tenth flow path plate 51. In this case, a pressure chamber 32, which will be described later, is formed by a recess recessed upward from the lower surface of the tenth flow path plate 51. The portion of the tenth flow path plate 51 above the pressure chamber 32 functions as the diaphragm 52.

[0020] Each plate is formed with through-holes that penetrate the plate and recesses that are recessed from the bottom or top surface of the plate. Inside the flow path forming body 40 where the plates are stacked, the through-holes and recesses are combined to form, for example, a plurality of nozzles 21, a plurality of individual flow paths 30, a supply manifold 22, and a return manifold 23 as liquid flow paths 20. For example, the plates are made of resin or metal, and the through-holes and recesses are formed by etching.

[0021] The supply manifold 22 and the return manifold 23 each extend long in the left-right direction and are connected to a plurality of individual flow paths 30. The upstream end of the supply manifold 22 and the downstream end of the return manifold 23 are connected to sub-tanks 17 provided in the head 10. These sub-tanks 17 are connected to corresponding storage tanks 15 (FIG. 1), and liquid is supplied from the storage tanks 15 to the sub-tanks 17.

[0022] Therefore, the sub-tank 17, supply manifold 22, individual flow paths 30, return manifold 23, and sub-tank 17 are connected in this order to form a first circulation path through which the liquid circulates in this order. A filter may be provided at the upstream end of the sub-tank 17 or the supply manifold 22. This may remove impurities contained in the liquid flowing into the supply manifold 22.

[0023] The downstream end of the supply manifold 22 and the upstream end of the return manifold 23 are connected to each other by a bypass 24. The bypass 24 is located outside the driving range in which the driving elements 60 are located in the head 10. As a result, the sub-tank 17, supply manifold 22, bypass 24, return manifold 23, and sub-tank 17 are connected in this order, forming a second circulation path in which the liquid circulates in this order.

[0024] The supply manifold 22 is formed by through holes that penetrate the sixth flow path plate 47 and the seventh flow path plate 48 in the vertical direction, and its upper end opening is covered by the eighth flow path plate 49, and its lower opening is covered by the fifth flow path plate 46.

[0025] The return manifold 23 is formed by a through hole that penetrates the second flow path plate 43 and the third flow path plate 44 in the vertical direction, and its upper end opening is covered by the fourth flow path plate 45 and its lower opening is covered by the first flow path plate 42.

[0026] The supply manifold 22 is disposed above the return manifold 23 so as to overlap the return manifold 23 when viewed from above. The cross-sectional area of the supply manifold 22 perpendicular to the left-right direction and the cross-sectional area of the return manifold 23 perpendicular to the left-right direction are equal to each other. The supply manifold 22 and the return manifold 23 may have the same shape and size.

[0027] A first damper 18 is provided below the supply manifold 22 in the up-down direction, and a second damper 19 is provided below the return manifold 23. In the front-rear direction, the rear end of the first damper 18 is disposed at the same position as or rearward of the rear end of the supply manifold 22, and the front end is disposed at the same position as or forward of the front end of the supply manifold 22. In the front-rear direction, the rear end of the second damper 19 is disposed at the same position as or rearward of the rear end of the return manifold 23, and the front end is disposed at the same position as or forward of the front end of the return manifold 23. Furthermore, in the left-right direction, the left ends of the first damper 18 and the second damper 19 are disposed at the same position as the left end of the driving range or to the left of it, and the right ends are disposed at the same position as the right end of the driving range or to the right of it.

[0028] The first damper 18 is formed by a recess recessed upward from the lower surface of the fifth flow path plate 46, and the lower end opening of the recess is a space covered by the fourth flow path plate 45. The upper part of the fifth flow path plate 46 between the supply manifold 22 and the first damper 18 is deformed by the pressure applied from the supply manifold 22. This changes the volume of the first damper 18, and damps the pressure fluctuations of the liquid in the supply manifold 22.

[0029] The second damper 19 is formed by a recess recessed upward from the lower surface of the first flow path plate 42, and the lower end opening of the recess is a space covered by the nozzle plate 41. The pressure applied from the return manifold 23 causes the upper part of the first flow path plate 42 between the return manifold 23 and the second damper 19 to deform. This changes the volume of the second damper 19, and damps the pressure fluctuation of the liquid in the return manifold 23. Second damper 19 may be disposed above the return manifold 23 rather than below it.

[0030] The plurality of nozzles 21 are formed to penetrate the nozzle plate 41 in the vertical direction. The nozzles 21 have a tapered shape in which the cross-sectional area perpendicular to the central axis thereof continuously decreases downward, and have a conical shape such as a truncated cone. However, the nozzles 21 may also have a columnar shape such as a cylindrical shape. On the ejection surface 40a, which is the lower surface of the nozzle plate 41, the plurality of nozzles 21 are arranged in the left-right direction to form nozzle rows, and the plurality of nozzle rows are aligned in the front-rear direction.

[0031] 3, the nozzles 21 include first nozzles 21a and second nozzles 21b. The first nozzles 21a form a first nozzle row, and the second nozzles 21b form a second nozzle row. The first nozzle row is located behind the second nozzle row in the front-rear direction and between the second nozzle row and the return manifold 23.

[0032] The upstream end of each individual flow path 30 is connected to the supply manifold 22, and the downstream end is connected to the return manifold 23, with the nozzle 21 connected between them. Each individual flow path 30 has a supply restrictor 31, a pressure chamber 32, a descender 33, a return restrictor 34, a coupling path 35, and a connecting path 36, which are connected in this order. Details of the return restrictor 34, the coupling path 35, and the connecting path 36 will be described later.

[0033] The individual flow paths 30 include a first individual flow path 30a connected to the first nozzle 21a and a second individual flow path 30b connected to the second nozzle 21b. The first individual flow path 30a and the second individual flow path 30b are connected to the same supply manifold 22 and the same return manifold 23. Therefore, the first nozzle 21a and the second nozzle 21b can eject liquid supplied from the same supply manifold 22.

[0034] The first individual flow path 30a has a first supply restrictor 31a which is a supply restrictor 31, a first pressure chamber 32a which is a pressure chamber 32 connected to the first supply restrictor 31a, a first descender 33a which is a descender 33 connected to the first pressure chamber 32a, a first feedback restrictor 34a which is a return restrictor 34 connected to the first descender 33a, a connecting path 35 connected to the first feedback restrictor 34a, and a connecting path 36 connected to the connecting path 35.

[0035] The second individual flow path 30b has a second supply restrictor 31b which is a supply restrictor 31, a second pressure chamber 32b which is a pressure chamber 32 connected to the second supply restrictor 31b, a second descender 33b which is a descender 33 connected to the second pressure chamber 32b, a second feedback restrictor 34b which is a return restrictor 34 connected to the second descender 33b, a coupling path 35 connected to the second feedback restrictor 34b, and a connecting path 36 connected to the coupling path 35.

[0036] The supply restrictor 31 is formed by a recess recessed upward from the lower surface of the ninth flow path plate 50, and its lower end opening is covered by the eighth flow path plate 49. The upstream end of the supply restrictor 31 passes through the eighth flow path plate 49 in the vertical direction and is connected to the upper end of the supply manifold 22. The downstream end of the supply restrictor 31 passes through the upper part of the ninth flow path plate 50 in the vertical direction and is connected to the lower end of the pressure chamber 32. The supply restrictor 31 extends forward and to the right from the supply manifold 22, and its cross-sectional area perpendicular to the extension direction is smaller than the cross-sectional area of the supply manifold 22.

[0037] The pressure chambers 32 are formed by through holes that pass through the tenth flow path plate 51 in the vertical direction, with their upper openings covered by the vibration plate 52 and their lower openings covered by the ninth flow path plate 50. The pressure chambers 32 extend forward from the supply restrictors 31 so as to be perpendicular to the nozzle row. The cross-sectional area of the pressure chambers 32 perpendicular to the extension direction is larger than the cross-sectional area of the supply restrictors 31.

[0038] The descender 33 is formed by a through-hole that penetrates the first flow path plate 42 to the ninth flow path plate 50 in the vertical direction, and its upper end is connected to the downstream end of the pressure chamber 32, extends downward from the pressure chamber 32, and its lower end opening is covered by the nozzle plate 41. The descender 33 has a central axis that passes through the center of its upper end and the center of its lower end and extends in the vertical direction, and has a columnar shape such as a cylindrical shape. The nozzle 21 is connected to the center of the lower end of the descender 33 and extends downward from the descender 33. The first descender 33a is located to the right of the second descender 33b in the left-right direction and is located behind the second descender 33b in the front-rear direction.

[0039] The driving element 60 is an element that applies ejection pressure to the liquid in the pressure chamber 32, and is, for example, a piezoelectric element. The driving element 60 includes a common electrode 61, a piezoelectric layer 62, and an individual electrode 63, which are arranged in this order. The common electrode 61 covers the entire surface of the vibration plate 52 via an insulating film 64, and the piezoelectric layer 62 covers the entire surface of the common electrode 61. The individual electrode 63 is provided for each pressure chamber 32, and is arranged on the piezoelectric layer 62 so as to overlap the pressure chamber 32 when viewed from above.

[0040] The individual electrodes 63 are electrically connected to a driver IC. This driver IC receives a control signal from the control unit 16 (FIG. 1), generates a drive signal (voltage signal), and applies it to the individual electrodes 63. In contrast, the common electrode 61 is always maintained at ground potential. Therefore, the piezoelectric layer 62 expands and contracts between the common electrode 61 and the individual electrodes 63 in response to the drive signal. This causes the vibration plate 52 to deform in cooperation with the individual electrodes 63, and the volume of the pressure chambers 32 to change in a direction that increases or decreases. Therefore, an ejection pressure is applied to the pressure chambers 32, causing the liquid to be ejected from the nozzles 21.

[0041] <Feedback iris, coupling path and connecting path> The feedback orifice 34 is formed by a recess recessed from the lower surface of the first flow path plate 42, and its lower opening is covered by the nozzle plate 41. The feedback orifice 34 has its upstream end connected to the front end of the lower part of the descender 33 so that its lower end is connected to the lower end of the descender 33, and extends while curving toward the front right or left from the descender 33. The cross-sectional area of the feedback orifice 34 perpendicular to its extension direction is smaller than the cross-sectional area of the descender 33 perpendicular to the up-and-down direction.

[0042] The first feedback orifice 34a extends from the first descender 33a toward the front, opposite the first pressure chamber 32a, then extends to the left, and then curves rearward and to the left. The second feedback orifice 34b extends from the second descender 33b toward the front, opposite the second pressure chamber 32b, then extends to the right, and then curves rearward and to the right. The first feedback orifice 34a and the second feedback orifice 34b have the same shape and size and are arranged symmetrically to each other in the left-right direction.

[0043] The coupling path 35 is formed by a through-hole that passes through the second flow path plate 43 in the vertical direction, with its upper end opening covered by the third flow path plate 44 and its lower end opening covered by the first flow path plate 42. The rear end of the coupling path 35 is connected to the downstream end of the first feedback throttle 34a, and its front end is connected to the downstream end of the second feedback throttle 34b.

[0044] The coupling path 35 extends linearly in the front-rear direction so that its rear end overlaps the first descender 33a and its front end overlaps the second descender 33b when viewed from the left. The coupling path 35 is disposed between the first descender 33a and the second descender 33b in the left-right direction and is inclined relative to the front-rear and left-right directions so that its front end is to the right of its rear end. The cross-sectional area of the coupling path 35 perpendicular to its extension direction is larger than the cross-sectional areas of the first feedback throttle 34a and the second feedback throttle 34b.

[0045] The connecting path 36 is formed by a through-hole that penetrates the third flow path plate 44 in the vertical direction, and its upper end opening is covered by the fourth flow path plate 45, and its lower end opening is covered by the second flow path plate 43. The third flow path plate 44 and the second flow path plate 43 in which the connecting path 35 is provided have the same thickness in the vertical direction, and therefore the connecting path 35 and the connecting path 36 have the same height in the vertical direction. Note that the return throttle 34, the connecting path 35, and the connecting path 36 may be formed by a through-hole that penetrates one or more plates, or a recess that is recessed from the upper or lower surface of a plate, or a combination of a through-hole and a recess.

[0046] The connecting passage 36 is disposed to the right of the combining passage 35, with its upstream end connected to the center of the combining passage 35 in the extension direction and its downstream end connected to the return manifold 23. The connecting passage 36 has an upstream portion extending linearly rearward and rightward from the combining passage 35, a curved portion curving rearward from the upstream portion, and a downstream portion extending linearly rearward from the curved portion. The upstream portion extends perpendicular to the combining passage 35, and the downstream portion extends perpendicular to the return manifold 23.

[0047] The cross-sectional areas perpendicular to the extension direction of the upstream portion, the curved portion, and the downstream portion are all the same. Therefore, the cross-sectional area perpendicular to the extension direction of the connecting path 36 is constant between the upstream end and the downstream end of the connecting path 36 and is smaller than the cross-sectional area perpendicular to the extension direction of the joining path 35. For example, the width W2 perpendicular to the up-down direction in the cross section perpendicular to the extension direction of the connecting path 36 is smaller than the width W1 perpendicular to the up-down direction in the cross section perpendicular to the extension direction of the joining path 35, and is preferably equal to or smaller than half the width W1 of the joining path 35.

[0048] <Liquid flow> Liquid is supplied from the storage tank 15 via the sub-tank 17 to the supply manifold 22, and flows to the left through the supply manifold 22, before flowing into each individual flow path 30 connected to the supply manifold 22. Liquid that does not flow from the supply manifold 22 into the individual flow paths 30 flows into the return manifold 23 via the bypass 24, and returns to the sub-tank 17, circulating through the second circulation path.

[0049] The liquid that has flowed into the individual flow path 30 flows through the supply restrictor 31, pressure chamber 32, and descender 33 in this order, and a portion of the liquid is supplied to the nozzle 21. When an ejection pressure is applied to the pressure chamber 32 by the drive element 60, the pressure is transmitted from the pressure chamber 32 to the nozzle 21 via the descender 33, and the liquid is ejected from the nozzle 21.

[0050] The liquid that is not ejected from the nozzle 21 flows through the return throttle 34, the coupling path 35, and the connecting path 36 in this order, and then flows into the return manifold 23. Since the liquid that flows into the return manifold 23 returns to the subtank 17, the liquid that is not ejected from the nozzle 21 circulates through the first circulation path.

[0051] Here, the liquid from the first feedback throttle 34a flows into the rear end of the combining passage 35 and flows forward, and the liquid from the second feedback throttle 34b flows into the front end of the combining passage 35 and flows rearward. These liquids then join together in the combining passage 35 and flow into the same connecting passage 36 to flow to the return manifold 23. Because the cross-sectional area of this connecting passage 36 is smaller than the cross-sectional area of the combining passage 35, the flow path resistance of the connecting passage 36 when the liquid flows through it is greater than the flow path resistance when the liquid flows through the combining passage 35.

[0052] <Actions and Effects> The liquid ejection head 10 includes a first pressure chamber 32a to which ejection pressure is applied to the liquid, a first descender 33a extending from the first pressure chamber 32a in the extension direction, a first feedback throttle 34a extending from the first descender 33a in a direction intersecting the extension direction, a first nozzle 21a connected to the first descender 33a, a second pressure chamber 32b to which ejection pressure is applied to the liquid, a second descender 33b extending from the second pressure chamber 32b in the extension direction, and a second return throttle 34a extending from the second descender 33b in the extension direction. The flow path 36 has a second feedback restrictor 34b extending in a direction intersecting the extension direction, a second nozzle 21b connected to the second descender 33b, a connecting path 35 connected to the first feedback restrictor 34a and the second feedback restrictor 34b, and a connecting path 36 connected to the connecting path 35 between the first feedback restrictor 34a and the second feedback restrictor 34b and the return manifold 23, and the flow path resistance when the liquid flows through the connecting path 36 is greater than the flow path resistance when the liquid flows through the connecting path 35.

[0053] This increases the flow path resistance of the connecting path 36. Therefore, even if liquid is discharged from the first nozzle 21a at a high discharge rate, backflow of liquid from the return manifold 23 to the first descender 33a via the connecting path 36, the joint path 35, and the first feedback orifice 34a is reduced. This reduces clogging of the first nozzle 21a connected to the first descender 33a by impurities contained in the backflow liquid, and suppresses poor discharge of liquid from the first nozzle 21a caused by impurities.

[0054] In addition, the flow path resistance of the connecting path 35 is small. Therefore, even if liquid is discharged from the first nozzle 21a at a high discharge rate, the liquid is supplied from the second descender 33b to the first nozzle 21a of the first descender 33a via the second return throttle 34b, the connecting path 35, and the first return throttle 34a. This reduces backflow from the return manifold 23 to the first descender 33a, and suppresses poor discharge of the liquid from the first nozzle 21a.

[0055] In the liquid ejection head 10, the cross-sectional area perpendicular to the direction in which the connecting path 36 extends is smaller than the cross-sectional area perpendicular to the direction in which the joining path 35 extends. This makes the flow path resistance of the connecting path 36 greater than the flow path resistance of the joining path 35. This reduces backflow from the return manifold 23 to the first descender 33a, and suppresses poor ejection of liquid from the nozzles 21.

[0056] The liquid ejection head 10 is provided with a stack of plates stacked in a stacking direction, and is provided with a coupling path 35 and a connecting path 36. The width W2 of the coupling path 36 in a direction perpendicular to the stacking direction in a plane perpendicular to the direction in which the coupling path 36 extends is smaller than the width W1 of the coupling path 35 in a direction perpendicular to the stacking direction in a plane perpendicular to the direction in which the coupling path 35 extends.

[0057] For example, if the connecting paths 36 and the connecting paths 35 are formed by through-holes that penetrate the plates in the stacking direction, the heights of the connecting paths 36 and the connecting paths 35 in the stacking direction are determined by the thicknesses of the plates in the stacking direction. In this case, if the heights of the connecting paths 36 and the connecting paths 35 are changed depending on the flow path resistance, the thicknesses of the plates must be changed, which increases costs. Even in such a case, by adjusting the width W2 of the connecting paths 36 and the width W1 of the connecting paths 35, it is possible to make the flow path resistance of the connecting paths 36 greater than the flow path resistance of the connecting paths 35 while reducing costs, thereby preventing poor ejection of liquid from the nozzles 21.

[0058] Furthermore, if the flow path resistance is reduced by shortening the length of the connecting path 35, for example, the adhesive area between the second flow path plate 43 in which the connecting path 35 is formed and the first flow path plate 42 and the third flow path plate 44 that are adhered to the second flow path plate 43 will increase. This will increase the amount of adhesive, which will increase costs and make it easier for excess adhesive to clog the liquid flow path 20. In response to this, by adjusting the width W2 of the connecting path 36 and the width W1 of the connecting path 35, it is possible to reduce cost increases and prevent clogging of the liquid flow path 20, while making the flow path resistance of the connecting path 36 greater than the flow path resistance of the connecting path 35, thereby preventing poor ejection of liquid from the nozzle 21.

[0059] In the liquid ejection head 10, the width W2 of the connecting passage 36 is equal to or less than half the width W1 of the joining passage 35. This more reliably reduces backflow from the return manifold 23 to the first descender 33a, thereby suppressing poor ejection of liquid from the nozzles 21.

[0060] <Modification> A liquid ejection head 10 according to a modified example is provided with a first descender 133a and a return manifold 23 in the above embodiment, and includes a stack of multiple plates stacked in the stacking direction, a first supply restrictor 31a connected to a first pressure chamber 32a, a second supply restrictor 31b connected to a second pressure chamber 32b, a supply manifold 22 connected to the first supply restrictor 31a and the second supply restrictor 31b and disposed above the return manifold 23 in the stacking direction, and a bypass 24 connected to the supply manifold 22 and the return manifold 23. The first descender 133a is inclined so that the further it is from the first pressure chamber 32a in the stacking direction, the further it is from the return manifold 23 in a direction perpendicular to the direction in which the return manifold 23 extends.

[0061] Specifically, in the example of FIGS. 5 and 6, the descender 133 includes a first descender 133a for the first individual flow path 30a and a second descender 133b for the second individual flow path 30b. The first descender 133a has an upper end connected to the first pressure chamber 32a and a lower end connected to the first nozzle 21a. The first descender 133a is inclined in the vertical direction so that it is more forward as it extends downward. Therefore, the first descender 133a is inclined in the vertical direction so that the further it is from the first pressure chamber 32a in the vertical direction, the further it is from the return manifold 23 in the front-to-rear direction. Note that the second descender 133b may also be inclined in the same manner as the first descender 133a. Alternatively, the second descender 133b may not be inclined, and the first descender 133a, which is closer to the return manifold 23 than the second descender 133b, may be inclined.

[0062] In the front-to-rear direction, the width of the return manifold 23 is wider than the width of the supply manifold 22. When viewed from above, the rear end of the return manifold 23 overlaps the rear end of the supply manifold 22, and the front end of the return manifold 23 is located forward of the front end of the supply manifold 22. For example, in the up-down direction, the height of the return manifold 23 and the height of the supply manifold 22 are equal to each other.

[0063] In this way, in the supply manifold 22 and return manifold 23 that extend in the left-right direction, the cross-sectional area of the return manifold 23 perpendicular to the left-right direction is larger than the cross-sectional area of the supply manifold 22 perpendicular to the left-right direction. As a result, the flow path resistance when liquid flows through the return manifold 23 is smaller than the flow path resistance when liquid flows through the supply manifold 22. As a result, a large flow rate of liquid flows through the first circulation path and the second circulation path even with a small pressure. Therefore, backflow from the return manifold 23 to the first feedback orifice 34a is reduced, and poor discharge of liquid from the nozzles 21 can be suppressed.

[0064] In addition, the cross-sectional area of the return manifold 23 is large, which reduces the adhesive area of the plates surrounding the return manifold 23 that are bonded to each other, thereby reducing the amount of adhesive.

[0065] Furthermore, as the width of the return manifold 23 increases in the front-rear direction, the width of the second damper 19, which is disposed so as to overlap the return manifold 23, also increases in the front-rear direction. This reduces the bonding area between the fifth flow path plate 46, on which the second damper 19 is formed, and the fourth flow path plate 45, which is bonded to the fifth flow path plate 46. This reduces the amount of adhesive used, making it possible to suppress increases in costs.

[0066] <Other variations> In the above embodiment and modified examples, the liquid ejection device 11 employs a line head system, but is not limited to this system and other systems, such as a serial head system, may also be employed. In this serial head system, the liquid ejection device 11 is provided with a carriage that mounts the head 10 and moves the head 10 in the left-right direction. The liquid ejection device 11 alternately performs a recording operation in which liquid is ejected from the head 10 while moving the carriage, and a transport operation in which the transport unit 13 transports the recording medium A, thereby performing a printing process in which an image is printed on the recording medium A.

[0067] In the above embodiment and modified examples, the liquid flow paths 20, such as the supply manifold 22 and the return manifold 23, are formed by through-holes that penetrate the plates. However, the liquid flow paths 20 are not limited to this. The liquid flow paths 20 may be formed by at least one of through-holes that penetrate one or more plates and recesses that are recessed from the bottom surface or top surface of the plate.

[0068] In the above embodiment and modified examples, the head 10 employs a system using a piezoelectric element (piezo system), but is not limited to this system. For example, the head 10 may employ a thermal system using a heating element, or an electrostatic system using a conductive diaphragm and electrodes.

[0069] The above-described embodiments and modifications may be combined with each other as long as they do not exclude each other. Furthermore, many improvements and other embodiments of the present invention will be apparent to those skilled in the art from the above description. Therefore, the above description should be construed as merely illustrative and is provided for the purpose of teaching those skilled in the art the best mode for carrying out the present invention. Details of the structure and / or function of the present invention may be substantially changed without departing from the spirit of the present invention. [Industrial Applicability]

[0070] The liquid ejection head of the present invention is useful as a liquid ejection head that can suppress backflow of liquid from the return manifold. [Explanation of symbols]

[0071] 10: Head 10: Liquid ejection head 19: Second damper 21: Nozzle 21a: First nozzle 21b: Second nozzle 22: Supply manifold 23: Feedback manifold 24: Bypass 31: Supply restriction 31a: First supply throttle 31b: Second supply throttle 32: Pressure chamber 32a: First pressure chamber 32b: Second pressure chamber 33: Descendant 33a: First descender 33b: 2nd descender 34: Feedback aperture 34a: First feedback aperture 34b: Second feedback aperture 35 :Connection path 36: Connecting road 133: Descendant 133a: First descender 133b: 2nd descender

Claims

1. a first pressure chamber to which a discharge pressure is applied to the liquid; a first descender extending from the first pressure chamber in an extension direction; a first feedback throttle extending from the first descender in a direction intersecting the extension direction; a first nozzle connected to the first descender; a second pressure chamber to which a discharge pressure is applied to the liquid; a second descender extending from the second pressure chamber in the extension direction; a second feedback diaphragm extending from the second descender in a direction intersecting the extension direction; a second nozzle connected to the second descender; a coupling path connected to the first feedback aperture and the second feedback aperture; the coupling path between the first feedback throttle and the second feedback throttle, and a connecting path connected to a feedback manifold; A liquid ejection head, wherein a flow path resistance when the liquid flows through the connecting path is greater than a flow path resistance when the liquid flows through the combining path.

2. 2. The liquid ejection head according to claim 1, wherein a cross-sectional area of the connecting path perpendicular to the direction in which the connecting path extends is smaller than a cross-sectional area of the connecting path perpendicular to the direction in which the connecting path extends.

3. a stacked body in which the coupling path and the connecting path are provided and a plurality of plates are stacked in a stacking direction; A liquid ejection head as described in claim 2, wherein the width of the connecting path in a direction perpendicular to the stacking direction in a plane perpendicular to the direction in which the connecting path extends is smaller than the width of the connecting path in a direction perpendicular to the stacking direction in a plane perpendicular to the direction in which the connecting path extends.

4. 4. The liquid ejection head according to claim 3, wherein the width of the connecting path is equal to or less than half the width of the joining path.

5. a stacked body including the first descender and the return manifold, and including a plurality of plates stacked in a stacking direction; a first supply throttle connected to the first pressure chamber; a second supply throttle connected to the second pressure chamber; a supply manifold connected to the first supply restrictor and the second supply restrictor and disposed above the return manifold in the stacking direction; a bypass connected to the supply manifold and the return manifold; A liquid ejection head described in any one of claims 1 to 3, wherein the first descender is inclined so that the further it is from the first pressure chamber side in the stacking direction, the further it is from the return manifold side in a direction perpendicular to the direction in which the return manifold extends.

6. 6. The liquid ejection head according to claim 5, wherein a cross-sectional area of the return manifold perpendicular to the direction in which the return manifold extends is larger than a cross-sectional area of the supply manifold perpendicular to the direction in which the return manifold extends.

7. 7. The liquid ejection head according to claim 5, further comprising a damper arranged closer to the supply manifold than the return manifold in the stacking direction or on the opposite side of the supply manifold, for damping pressure fluctuations of the liquid in the return manifold.

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