Liquid ejection head

Abstract

To provide a liquid ejection head that is able to suppress liquid ejection failure.SOLUTION: A liquid ejection head includes: a first descender that has a first extension portion extending in an extending direction from a first pressure chamber and a first projection portion extending in a first direction crossing the extending direction from the first extension portion; a first return diaphragm connected to the first descender; a second descender that has a second extension portion extending in the extending direction from a second pressure chamber and a second projecting portion extending in a second direction crossing the extending direction from the second extension portion; a second return diaphragm connected to the second descender; a connection passage connected to the first return diaphragm and the second return diaphragm; and a coupling passage that couples between the connection passage and a return manifold. The first projecting portion is connected to a first nozzle, and an opposite surface that is opposite to the first nozzle in the extending direction is positioned farther from the first nozzle than the first return diaphragm. The second projecting portion is connected to a second nozzle, and an opposite surface that is opposite to the second nozzle in the extending direction is positioned farther from the second nozzle than the second return diaphragm.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] As a conventional liquid ejection head, the liquid ejection head of Patent Document 1 has a discharge hole, a pressure chamber connected to the discharge hole via a partial flow path, a first common flow path connected to the pressure chamber via the partial flow path by a first flow path, and a second common flow path connected to the pressure chamber by a second flow path. Further, two first flow paths corresponding to two discharge holes located in the vicinity are connected to the first common flow path in a state where they merge after extending from the partial flow path and become one. Therefore, this first flow path communicates with a plurality of partial flow paths.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

[0005] Here, as described above, a plurality of partial flow paths (for example, a first partial flow path and a second partial flow path) are connected to the first flow path. For this reason, for example, when the discharge hole corresponding to the second partial flow path is clogged, or when the discharge rate from the discharge hole corresponding to the second partial flow path is less than the discharge rate from the discharge hole corresponding to the first partial flow path, the liquid in the second partial flow path may flow backward through the first flow path to the first partial flow path. In this case, if bubbles are mixed in the backward-flowing liquid, the bubbles may flow into the first partial flow path and block the discharge hole corresponding to the first partial flow path.

[0006] The present invention has been made to solve such problems, and an object thereof is to provide a liquid discharge head capable of suppressing poor discharge of liquid due to bubbles.

Means for Solving the Problems

[0007] A liquid discharge head according to an aspect of the present invention includes a first pressure chamber to which a discharge pressure is applied to a liquid, a first extending portion extending in an extending direction from the first pressure chamber, and a first projecting portion extending in a first direction intersecting the extending direction from the first extending portion, a first descender having the first projecting portion, a first feedback throttle connected to the first projecting portion, a first nozzle connected to the first projecting portion between the first extending portion and the first feedback throttle in the first direction, a second pressure chamber to which a discharge pressure is applied to a liquid, a second extending portion extending in the extending direction from the second pressure chamber, and a second projecting portion extending in a second direction intersecting the extending direction from the second extending portion, a second descender having the second projecting portion, a second feedback throttle connected to the second projecting portion, a second nozzle connected to the second projecting portion between the second extending portion and the second feedback throttle in the second direction, a connecting path connecting the first feedback throttle and the second feedback throttle, and a connecting path connecting between the connecting path and a feedback manifold, wherein a facing surface of the first projecting portion facing the first nozzle in the extending direction is located farther from the first nozzle than the first feedback throttle, and a facing surface of the second projecting portion facing the second nozzle in the extending direction is located farther from the second nozzle than the second feedback throttle.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. In the following, the same or corresponding elements are denoted by the same reference numerals throughout all the drawings, and the overlapping descriptions thereof are omitted.

[0010] (Embodiment) <Liquid Discharge Apparatus> A liquid discharge apparatus 11 including a liquid discharge head (hereinafter referred to as "head 10") according to an embodiment of the present invention is an apparatus that discharges a liquid such as ink, as shown in FIG. 1. Hereinafter, an example in which the liquid discharge apparatus 11 is applied to an inkjet printer that discharges a liquid from the head 10 onto a recording medium A to form an image will be described, but the liquid discharge apparatus 11 is not limited thereto. Further, as the recording medium A, a sheet material such as paper and cloth can be used.

[0011] The liquid ejection device 11 employs a line head system and includes a platen 12, a conveyance unit 13, a head unit 14, a storage tank 15, and a control unit 16. Here, the side of the platen is referred to as the bottom side with respect to the head 10 side of the head unit 14, and the opposite side is referred to as the top side. The directions that intersect (e.g., are orthogonal) in the vertical direction and intersect (e.g., are orthogonal) with each other are referred to as the left - right direction and the front - back direction. However, the arrangement of the liquid ejection device 11 is not limited to this.

[0012] The platen 12 has, for example, a rectangular flat plate shape 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 conveyance unit 13 has, for example, a pair of conveyance rollers 13a and a conveyance motor. The pair of conveyance rollers 13a sandwich the platen 12 between them in the front - back direction and are arranged parallel to each other. The central axis of the conveyance roller 13a extends in the left - right direction. One of the pair of conveyance rollers 13a is connected to the conveyance motor. When this conveyance motor is driven, the conveyance roller 13a rotates, and the recording medium A on the platen 12 is conveyed in the front - back direction.

[0014] The head unit 14 extends long 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. A plurality of heads 10 are provided in the head unit 14. The head 10 is provided with a discharge surface 40a (FIG. 2) facing the upper surface of the platen 12 and a plurality of nozzles 21 opening to the discharge surface 40a. Details of the head 10 will be described later.

[0015] The storage tank 15 is provided for each type of liquid. For example, the four storage tanks 15 store black, yellow, cyan, and magenta liquids respectively. The storage tank 15 supplies liquid to the nozzles 21 of the corresponding head 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 an arithmetic unit such as a CPU, a storage unit such as a RAM and a ROM, and a driver IC such as an ASIC. In the control unit 16, the arithmetic unit outputs various execution commands to the driver ICs of each unit based on the programs stored in the storage unit. Thereby, the control unit 16 controls the operation of the conveyance motor of the conveyance unit 13 and the drive element 60 of the head 10. For example, the control unit 16 executes a conveyance operation of conveying the recording medium A by the conveyance unit 13 together with a discharge operation of discharging liquid from the head 10. Thereby, the printing process of forming an image on the recording medium A with the liquid proceeds.

[0017] <Head> As shown in FIGS. 2 to 4, the head 10 includes a flow path forming body 40 in which a liquid flow path 20 is provided and which is formed by a laminate of a plurality of plates, and a drive element 60 that applies pressure to the liquid in the liquid flow path 20. In FIG. 2, the connection relationship between the respective parts of the liquid flow path 20 and the positional relationship between the respective parts of the liquid flow path 20 and the plates of the flow path forming body 40 are shown so as to be easily understandable. For this reason, the left - right direction of the paper surface of FIG. 2 may not correspond to the positions of the respective parts of the liquid flow path 20.

[0018] The flow path forming body 40 has, for example, a nozzle plate 41, a plurality (for example, 10) of flow path plates, and a diaphragm 52. These plates have a rectangular flat plate shape, are laminated in this order, and are adhered to each other with an adhesive or the like. In the flow path forming body 40, the lamination direction in which the plates are laminated is referred to as the vertical direction. Also, the directions that intersect (for example, are orthogonal) to this vertical direction and intersect (for example, are orthogonal) with 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 this direction.

[0019] In the flow path forming body 40, the lower surface of the first flow path plate 42 is adhered to the upper surface of the nozzle plate 41, and the upper surface of the tenth flow path plate 51 is adhered to the lower surface of the diaphragm 52. Note that the diaphragm 52 may be integrally formed with the tenth flow path plate 51. In this case, the pressure chamber 32 described later is formed by a recess that is recessed upward from the lower surface of the tenth flow path plate 51. In the tenth flow path plate 51, the portion above the pressure chamber 32 functions as the diaphragm 52.

[0020] Each plate is formed with a through hole that penetrates the plate and a recess that is recessed from the lower surface or the upper surface of the plate. Inside the flow path forming body 40 in which the plates are stacked, the through holes and the 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 the liquid flow path 20. For example, the plate is made of resin or metal, and the through holes and the recesses are formed by etching.

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

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

[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 arranged outside the driving range where the driving element 60 is arranged in the head 10. Thereby, the sub-tank 17, the supply manifold 22, the bypass 24, the return manifold 23, and the sub-tank 17 are connected in this order, constituting a second circulation path through which the liquid circulates in this order.

[0024] The supply manifold 22 is formed by through holes that vertically penetrate the sixth flow path plate 47 and the seventh flow path plate 48. 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 through holes that vertically penetrate the second flow path plate 43 and the third flow path plate 44. 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 arranged 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 orthogonal to the left-right direction and the cross-sectional area of the return manifold 23 orthogonal 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 damper 18 is provided between the supply manifold 22 and the return manifold 23 in the vertical direction. The damper 18 is formed by a recess that depresses upward from the lower surface of the fifth flow path plate 46, and is a space whose lower end opening of the recess is covered by the fourth flow path plate 45. The damper 18 attenuates the pressure fluctuation of the liquid in the supply manifold 22 by deforming the upper part of the fifth flow path plate 46 by the pressure applied from the supply manifold 22 and changing its volume. Note that the damper may be arranged below the return manifold 23. In this case, the damper attenuates the pressure fluctuation of the liquid in the return manifold 23.

[0028] The plurality of nozzles 21 are formed to penetrate the nozzle plate 41 in the vertical direction. The nozzle 21 has a tapered shape in which the cross-sectional area orthogonal to its central axis continuously decreases downward, and has a conical shape such as a truncated conical shape, for example. However, the nozzle 21 may have a columnar shape such as a cylindrical shape. On the discharge surface 40a which is the lower surface of the nozzle plate 41, a plurality of nozzles 21 are arranged in the left-right direction to form a nozzle row, and a plurality of nozzle rows are arranged in the front-rear direction.

[0029] In the example of FIG. 3, the nozzle 21 has a first nozzle 21f and a second nozzle 21s. The plurality of first nozzles 21f constitute a first nozzle row, and the plurality of second nozzles 21s constitute a second nozzle row. The first nozzle row is located rearward of the second nozzle row in the front-rear direction and is disposed between the second nozzle row and the return manifold 23.

[0030] The individual flow path 30 has its upstream end connected to the supply manifold 22 and its downstream end connected to the return manifold 23, and the nozzle 21 is connected therebetween. The individual flow path 30 has a supply throttle 31, a pressure chamber 32, a descender 33, a return throttle 34, a coupling path 35, and a connecting path 36, which are connected in this order. Details of the descender 33, the return throttle 34, the coupling path 35, and the connecting path 36 will be described later.

[0031] The individual flow path 30 has a first individual flow path 30f connected to the first nozzle 21f and a second individual flow path 30s connected to the second nozzle 21s. The first individual flow path 30f and the second individual flow path 30s are connected to the same supply manifold 22 and are connected to the same return manifold 23. Therefore, the first nozzle 21f and the second nozzle 21s can discharge the liquid supplied from the same supply manifold 22.

[0032] The first individual flow path 30f has a first supply throttle 31f which is the supply throttle 31, a first pressure chamber 32f which is the pressure chamber 32 connected to the first supply throttle 31f, a first descender 33f which is the descender 33 connected to the first pressure chamber 32f, a first feedback throttle 34f which is the feedback throttle 34 connected to the first descender 33f, a joining path 35 connected to the first feedback throttle 34f, and a connecting path 36 connected to the joining path 35.

[0033] The second individual flow path 30s has a second supply throttle 31s which is the supply throttle 31, a second pressure chamber 32s which is the pressure chamber 32 connected to the second supply throttle 31s, a second descender 33s which is the descender 33 connected to the second pressure chamber 32s, a second feedback throttle 34s which is the feedback throttle 34 connected to the second descender 33s, a joining path 35 connected to the second feedback throttle 34s, and a connecting path 36 connected to the joining path 35.

[0034] The supply throttle 31 is formed by a recess that depresses 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 throttle 31 penetrates 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 throttle 31 penetrates 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 throttle 31 extends forward and to the right from the supply manifold 22, and the cross-sectional area orthogonal to its extending direction is smaller than the cross-sectional area of the supply manifold 22.

[0035] The pressure chamber 32 is formed by a through hole that penetrates the tenth flow path plate 51 in the vertical direction, its upper opening is covered by the diaphragm 52, and its lower opening is covered by the ninth flow path plate 50. The pressure chamber 32 extends forward from the supply throttle 31 so as to be orthogonal to the nozzle row. The cross-sectional area of the pressure chamber 32 orthogonal to its extending direction is larger than the cross-sectional area of the supply throttle 31.

[0036] The drive element 60 is an element that applies a discharge pressure to the liquid in the pressure chamber 32, and is, for example, a piezoelectric element. The drive element 60 includes a common electrode 61, a piezoelectric layer 62, and individual electrodes 63, which are arranged in this order. The common electrode 61 covers the entire surface of the diaphragm 52 via an insulating film 64, and the piezoelectric layer 62 covers the entire surface of the common electrode 61. The individual electrodes 63 are provided for each pressure chamber 32 and are arranged on the piezoelectric layer 62 so as to overlap the pressure chamber 32 when viewed from above.

[0037] The individual electrodes 63 are electrically connected to the 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. On the other hand, the common electrode 61 is always held at the ground potential. For this reason, the piezoelectric layer 62 expands and contracts in response to the drive signal between the common electrode 61 and the individual electrodes 63. As a result, the diaphragm 52 deforms in cooperation, and the volume of the pressure chamber 32 changes in a direction of increasing or decreasing. Therefore, a discharge pressure for discharging the liquid from the nozzle 21 is applied to the pressure chamber 32.

[0038] <Descender, feedback throttle, coupling path, and connection path> The descender 33 has a first descender 33f and a second descender 33s. The first descender 33f has a first extending portion 33af extending in the extending direction from the first pressure chamber 32f, and a first protruding portion 33bf extending in a first direction intersecting the extending direction from the first extending portion 33af. The second descender 33s has a second extending portion 33as extending in the vertical direction from the second pressure chamber 32s, and a second protruding portion 33bs extending in a second direction intersecting the vertical direction from the second extending portion 33as.

[0039] In the following description, the extending direction is the vertical direction, the first direction is the front in the front-rear direction, and the second direction is the front in the front-rear direction. However, the arrangements of the first descender 33f and the second descender 33s are not limited to this. Also, in the following description, the first extending portion 33af and the second extending portion 33as may be referred to as the extending portion 33a, and the first protruding portion 33bf and the second protruding portion 33bs may be referred to as the protruding portion 33b.

[0040] The descender 33 has an L shape in that its protruding portion 33b extends forward from the lower part of the extending portion 33a. Therefore, in the descender 33, above the protruding portion 33b, the extending portion 33a has a columnar shape such as a cylindrical shape whose central axis extends in the vertical direction. On the other hand, in the portion where the protruding portion 33b is provided in the vertical direction, the extending portion 33a and the protruding portion 33b are integrated and have an oval shape or a rectangular shape with rounded corners whose length in the front-rear direction is longer than the width in the left-right direction when viewed from above. The length of the extending portion 33a in the left-right direction is equal to the length of the protruding portion 33b.

[0041] The extending portion 33a is formed by a through-hole that vertically penetrates the first flow path plate 42 to the ninth flow path plate 50. 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 protruding portion 33b is formed by a through-hole that vertically penetrates the first flow path plate 42. Its upper end is covered by the second flow path plate 43, and its lower end is covered by the nozzle plate 41.

[0042] The protruding portion 33b extends forward from the extending portion 33a such that its rear end is connected to the front end of the lower part of the extending portion 33a so that its lower end is connected to the lower end of the extending portion 33a. The cross-sectional area of the protruding portion 33b orthogonal to the front-rear direction is equal to or less than the cross-sectional area of the extending portion 33a orthogonal to the vertical direction.

[0043] The nozzle 21 is connected to the lower end of the protruding portion 33b, and the nozzle 21 extends downward from the protruding portion 33b. The nozzle 21 is connected to the protruding portion 33b between the extending portion 33a and the feedback throttle 34 in the front-rear direction. For example, the nozzle 21 is disposed at the center of the protruding portion 33b in the left-right direction and the front-rear direction.

[0044] The protruding portion 33b has its rear end connected to the extending portion 33a and its front end connected to the feedback throttle 34. In the protruding portion 33b, the connection port with the extending portion 33a and the connection port with the feedback throttle 34 face each other in the front-rear direction. The connection port of the protruding portion 33b with the extending portion 33a is larger than the connection port of the protruding portion 33b with the feedback throttle 34.

[0045] In the vertical direction, the upper surface of the protruding portion 33b, which is the opposing surface 33c facing the nozzle 21 connected to its lower end, is arranged above the upper surface 34c of the feedback throttle 34 facing the nozzle 21. The upper surface of this protruding portion 33b is formed by the lower surface of the second flow path plate 43, and the upper surface 34c of the feedback throttle 34 is formed by the lower surface of the upper part of the first flow path plate 42. The lower end of the protruding portion 33b is connected to the lower end of the feedback throttle 34, and in the vertical direction, the height H1 of the protruding portion 33b is higher than the height H2 of the feedback throttle 34.

[0046] The first descender 33f is arranged on the right side of the second descender 33s in the left-right direction, and is arranged behind the second descender 33s and near the feedback manifold 23 in the front-rear direction. The first direction in which the first protruding portion 33bf extends from the first extending portion 33af in the first descender 33f, and the second direction in which the second protruding portion 33bs extends from the second extending portion 33as in the second descender 33s are the same direction as each other. In the example of FIG. 3, it is the front in the front-rear direction. The first direction and the second direction are parallel to each other and orthogonal to the first nozzle row and the second nozzle row.

[0047] The return throttle 34 is formed by a recess that depresses upward from the lower surface of the first flow path plate 42, and its lower opening is covered by the nozzle plate 41. The upstream end of the return throttle 34 is connected to the front end of the center of the protruding portion 33b in the left - right direction, and extends while curving from the protruding portion 33b toward the front right side or the front left side. The cross - sectional area of the return throttle 34 orthogonal to its extending direction is smaller than the cross - sectional area orthogonal to the front - rear direction of the protruding portion 33b. Also, the downstream end of the return throttle 34 penetrates the first flow path plate 42 in the vertical direction and is connected to the lower end of the connection path 35.

[0048] The first return throttle 34f extends forward from the first protruding portion 33bf on the side opposite to the first extending portion 33af side, then extends to the left, and further curves so as to extend to the rear left side. Also, the second return throttle 34s extends forward from the second protruding portion 33bs on the side opposite to the second extending portion 33as side, then extends to the right, and further curves so as to extend to the rear right side. The first return throttle 34f and the second return throttle 34s have the same shape and size as each other, and are arranged symmetrically with respect to each other in the left - right direction.

[0049] The connection path 35 is formed by a through - hole that penetrates the second flow path plate 43 in the vertical direction, its upper opening is covered by the third flow path plate 44, and its lower opening is covered by the first flow path plate 42. The rear end of the connection path 35 is connected to the downstream end of the first return throttle 34f, and its front end is connected to the downstream end of the second return throttle 34s.

[0050] The coupling path 35 extends linearly in the front-rear direction such that, when viewed from the left side, its rear end overlaps with the first descender 33f and its front end overlaps with the second descender 33s. Further, the coupling path 35 is disposed between the first descender 33f and the second descender 33s in the left-right direction, and is inclined with respect to the front-rear direction and the left-right direction such that its front end is on the right side of its rear end. Of the angles formed between the direction in which the coupling path 35 extends and the first direction in which the first protruding portion 33bf extends, the smaller angle θ1 is 45° or less. Also, of the angles formed between the direction in which the coupling path 35 extends and the second direction in which the second protruding portion 33bs extends, the smaller angle θ2 is 45° or less.

[0051] The cross-sectional area orthogonal to the extending direction of the coupling path 35 is larger than the cross-sectional area orthogonal to the extending direction of the first feedback throttle 34f and the cross-sectional area orthogonal to the extending direction of the second feedback throttle 34s. Also, the cross-sectional area orthogonal to the extending direction of the coupling path 35 is larger than the cross-sectional area orthogonal to the first direction of the first protruding portion 33bf and the cross-sectional area orthogonal to the second direction of the second protruding portion 33bs. Preferably, the cross-sectional area orthogonal to the extending direction of the coupling path 35 is larger than twice the cross-sectional area orthogonal to the first direction of the first protruding portion 33bf and twice the cross-sectional area orthogonal to the second direction of the second protruding portion 33bs.

[0052] The connecting path 36 is formed by a through-hole that vertically penetrates the third flow path plate 44, the upper end opening of which is covered by the fourth flow path plate 45, and the lower end opening of which is covered by the second flow path plate 43. The connecting path 36 is disposed on the right side of the coupling path 35, its upstream end is connected to the center in the extending direction of the coupling path 35, and its downstream end is connected to the feedback manifold 23.

[0053] The connecting path 36 has an upstream portion that extends linearly from the coupling path 35 to the rear right side, a curved portion that curves rearward from the upstream portion, and a downstream portion that extends linearly rearward from the curved portion. This upstream portion extends perpendicular to the coupling path 35, and the downstream portion extends perpendicular to the feedback manifold 23.

[0054] The cross-sectional areas orthogonal to the stretching direction in each of the upstream portion, the curved portion, and the downstream portion are the same as each other. Therefore, the cross-sectional area orthogonal to the stretching direction of the connecting path 36 may be constant between the upstream end and the downstream end of the connecting path 36 and may be the same as the cross-sectional area orthogonal to the stretching direction of the connecting path 35, or may be larger than the cross-sectional area of the connecting path 35.

[0055] <Flow of liquid> Liquid is supplied from the storage tank 15 to the supply manifold 22 via the sub-tank 17, and while flowing to the left side of the supply manifold 22, it flows into each individual flow path 30 connected to the supply manifold 22. The liquid that did not flow into the individual flow path 30 from the supply manifold 22 flows into the return manifold 23 via the bypass 24 and returns to the sub-tank 17, thus circulating through the second circulation path.

[0056] The liquid that has flowed into the individual flow path 30 flows through the supply throttle 31, the pressure chamber 32, and the descender 33 in this order, and a part of the liquid is supplied to the nozzle 21. Here, when the discharge pressure is applied to the pressure chamber 32 by the drive element 60, the pressure is propagated from the pressure chamber 32 to the nozzle 21 via the descender 33, and the liquid is discharged from the nozzle 21.

[0057] The liquid that has not been discharged from the nozzle 21 flows through the return throttle 34, the connecting path 35, and the connection path 36 in this order and flows into the return manifold 23. Since the liquid that has flowed into the return manifold 23 returns to the sub-tank 17, the liquid that has not been discharged from the nozzle 21 circulates through the first circulation path.

[0058] Here, the liquid from the first return throttle 34f flows into the rear end of the connecting path 35 and flows forward, and the liquid from the second return throttle 34s flows into the front end of the connecting path 35 and flows backward. Then, these liquids merge in the connecting path 35, flow into the same connection path 36, and flow to the return manifold 23.

[0059] <Function, effect> The liquid ejection head 10 includes a first pressure chamber 32f to which ejection pressure is applied to the liquid, a first extension portion 33af extending in the extending direction from the first pressure chamber 32f, and a first descender 33f having a first protruding portion 33bf extending in a first direction intersecting the extending direction from the first extension portion 33af, a first feedback throttle 34f connected to the first protruding portion 33bf, a first nozzle 21f connected to the first protruding portion 33bf between the first extension portion 33af and the first feedback throttle 34f in the first direction, a second pressure chamber 32s to which ejection pressure is applied to the liquid, a second extension portion 33as extending in the extending direction from the second pressure chamber 32s, and a second descender 33s having a second protruding portion 33bs extending in a second direction intersecting the extending direction from the second extension portion 33as, a second feedback throttle 34s connected to the second protruding portion 33bs, a second nozzle 21s connected to the second protruding portion 33bs between the second extension portion 33as and the second feedback throttle 34s in the second direction, a coupling path 35 connected to the first feedback throttle 34f and the second feedback throttle 34s, and a connecting path 36 connecting between the coupling path 35 and the feedback manifold 23. The opposing surface 33c of the first protruding portion 33bf facing the first nozzle 21f in the extending direction is located farther from the first nozzle 21f than the first feedback throttle 34f. The opposing surface 33c of the second protruding portion 33bs facing the second nozzle 21s in the extending direction is located farther from the second nozzle 21s than the second feedback throttle 34s.

[0060] For example, liquid may be discharged from the first nozzle 21f at a discharge rate higher than the discharge rate of the second nozzle 21s. In this case, as shown in FIG. 5, the supply of liquid from the supply manifold 22 to the first nozzle 21f cannot keep up with the discharge of liquid from the first nozzle 21f, and liquid may flow backward into the first protruding portion 33bf to which the first nozzle 21f is connected via the second descender 33s, the second feedback throttle 34s, the connecting path 35, and the first feedback throttle 34f. In this case, as shown in FIG. 6, even if air bubbles B are mixed in the backward-flowing liquid, since the opposing surface 33c of the first protruding portion 33bf is farther from the first nozzle 21f than the upper surface of the first feedback throttle 34f in the stretching direction (for example, the vertical direction), the air bubbles B flow toward the opposing surface 33c side. Therefore, the clogging of the first nozzle 21f by air bubbles is reduced, and the discharge failure of liquid from the holes of the first nozzle 21f due to air bubbles can be suppressed.

[0061] Also, as shown in FIG. 5, in addition to the liquid flowing from the first extending portion 33af in the first direction (for example, forward) to the first protruding portion 33bf, liquid flowing from the first feedback throttle 34f in the direction opposite to the first direction (for example, backward) flows into the first protruding portion 33bf. As a result, in the first protruding portion 33bf, a flow of liquid in the left-right direction orthogonal to the front-back direction occurs between the connection port with the first extending portion 33af and the connection port with the first feedback throttle 34f. For this reason, even if air bubbles are mixed in the backward-flowing liquid, since the air bubbles are flowed in the left-right direction, it is difficult for them to flow into the first nozzle 21f connected to the lower end of the first protruding portion 33bf, and the discharge failure of liquid from the holes of the first nozzle 21f due to air bubbles can be suppressed.

[0062] In the liquid discharge head 10, in the first descender 33f, the portion having the first extending portion 33af and the first protruding portion 33bf has a width W1 in the first direction that is longer than a length L1 in the stretching direction and the direction orthogonal to the first direction. In the second descender 33s, the second extending portion 33as and the second protruding portion 33bs have a width W2 in the second direction that is longer than a length L2 in the stretching direction and the direction orthogonal to the second direction.

[0063] If the length L1 of the first protruding portion 33bf is longer than the width W1, the first protruding portion 33bf protrudes longer than the first feedback throttle 34f in the extending direction and the direction orthogonal to the first direction (for example, the left - right direction). Therefore, when the bubbles that have entered the first protruding portion 33bf from the first feedback throttle 34f flow in the left - right direction, they are likely to stay in the portion protruding beyond the first feedback throttle 34f. In this case, bubbles are likely to enter from the first protruding portion 33bf into the first nozzle 21f, and poor liquid discharge in the first nozzle 21f due to bubbles is likely to occur. On the other hand, by making the length L1 of the first protruding portion 33bf shorter than the width W1, it is possible to reduce such poor liquid discharge caused by bubbles.

[0064] In the liquid discharge head 10, the connecting path 35 extends in a direction intersecting the extending direction between the first feedback throttle 34f and the second feedback throttle 34s. The smaller of the angles θ1 formed by the direction in which the connecting path 35 extends and the first direction is 45 degrees or less, and the smaller of the angles θ2 formed by the direction in which the connecting path 35 extends and the second direction is 45 degrees or less.

[0065] According to this, the direction in which the liquid is discharged from the nozzle 21 depends on the flow direction of the liquid flowing through the descender 33 etc. connected to the nozzle 21. Therefore, by making the angles θ1 formed by the first direction and the direction in which the connecting path 35 extends and θ2 formed by the second direction and the direction in which the connecting path 35 extends 45 degrees or less, the direction in which the liquid is discharged from the first nozzle 21f and the direction in which the liquid is discharged from the second nozzle 21s can be aligned. For this reason, it is possible to reduce the expansion or contraction of the interval between the landing positions (dot positions) of the liquid from the first nozzle 21f and the landing positions (dot positions) of the liquid from the second nozzle 21s compared to the interval between the first nozzle 21f and the second nozzle 21s, and suppress the deterioration of the image quality due to non - uniform dot intervals.

[0066] In the liquid discharge head 10, the first direction in which the first protruding portion 33bf extends from the first extending portion 33af and the second direction in which the second protruding portion 33bs extends from the second extending portion 33as are the same direction as each other.

[0067] According to this, in the example of FIG. 3, the first protruding portion 33bf extends forward from the first extending portion 33af, and the second protruding portion 33bs extends forward from the second extending portion 33as. In this way, the first direction in which the first protruding portion 33bf extends and the second direction in which the second protruding portion 33bs extends can be aligned with each other. Thereby, the direction in which the liquid is discharged from the first nozzle 21f connected to the first protruding portion 33bf and the direction in which the liquid is discharged from the second nozzle 21s connected to the second protruding portion 33bs can be aligned with each other. Therefore, the landing position of the discharged liquid can be made uniform, and the deterioration of the image quality due to non-uniform intervals can be suppressed.

[0068] In the liquid ejection head 10, the first protruding portion 33bf extends from the first extending portion 33af to the side opposite to the return manifold 23, and the second protruding portion 33bs extends from the second extending portion 33as to the side opposite to the return manifold 23.

[0069] According to this, the connecting paths 35 connected to the first protruding portion 33bf and the second protruding portion 33bs are arranged away from the return manifold 23 side. For this reason, the connecting path 36 connecting the connecting path 35 and the return manifold 23 becomes long, and it becomes difficult for the liquid to flow back from the return manifold 23 to the first protruding portion 33bf and the second protruding portion 33bs through the connecting path 35. Therefore, even if bubbles are mixed in the backflow liquid from the return manifold 23, it is possible to reduce the ejection failure of the liquid caused by these bubbles.

[0070] In the liquid ejection head 10, the smaller of the angles formed by the direction orthogonal to the direction in which the return manifold 23 extends and the first direction is 45 degrees or less, and the smaller of the angles formed by the direction orthogonal to the direction in which the return manifold 23 extends and the second direction is 45 degrees or less. According to this, the ejection direction of the liquid from the nozzles 21 can be aligned with respect to the nozzle row extending along the return manifold 23, and the deterioration of the image quality due to non-uniform intervals of the landing positions of the liquid can be suppressed.

[0071] In the liquid ejection head 10, the connection path 35 extends in a direction intersecting the extending direction between the first feedback throttle 34f and the second feedback throttle 34s. The cross-sectional area orthogonal to the direction in which the connection path 35 extends is larger than either the cross-sectional area of the first protruding portion 33bf orthogonal to the first direction or the cross-sectional area of the second protruding portion 33bs orthogonal to the first direction.

[0072] According to this, since the cross-sectional areas of the first protruding portion 33bf and the second protruding portion 33bs are small, the flow velocity of the liquid flowing through the first protruding portion 33bf and the second protruding portion 33bs increases, and bubbles are easily discharged from the first protruding portion 33bf and the second protruding portion 33bs. Thereby, ejection failure caused by bubbles can be reduced in the first nozzle 21f connected to the first protruding portion 33bf and the second nozzle 21s connected to the second protruding portion 33bs.

[0073] Also, since the cross-sectional area of the connection path 35 is large, the flow velocity of the liquid flowing through the connection path 35 decreases, and it is reduced that bubbles flow backward from the connection path 35 to the first protruding portion 33bf through the first feedback throttle 34f or bubbles flow backward from the connection path 35 to the second protruding portion 33bs through the second feedback throttle 34s. Thereby, ejection failure caused by bubbles can be reduced in the first nozzle 21f connected to the first protruding portion 33bf and the second nozzle 21s connected to the second protruding portion 33bs.

[0074] In the liquid ejection head 10, the cross-sectional area orthogonal to the direction in which the connection path 35 extends is larger than either twice the cross-sectional area of the first protruding portion 33bf orthogonal to the first direction or twice the cross-sectional area of the second protruding portion 33bs orthogonal to the second direction. According to this, ejection failure caused by bubbles can be further reduced in the first nozzle 21f connected to the first protruding portion 33bf and the second nozzle 21s connected to the second protruding portion 33bs.

[0075] <Modification Example> In the liquid ejection head 10 according to the modified example, as shown in FIG. 7 in the above embodiment, the first direction in which the first protruding portion 133bf extends from the first extending portion 133af and the second direction in which the second protruding portion 133bs extends from the second extending portion 133as are opposite to each other.

[0076] In the example of FIG. 7, the front end of the first protruding portion 133bf of the first descender 133f is connected to the first extending portion 133af, and the rear end thereof is connected to the first feedback throttle 134f. In the first protruding portion 133bf, in the front-rear direction, the connection port with the first extending portion 133af and the connection port with the first feedback throttle 134f face each other.

[0077] The rear end of the second protruding portion 133bs of the second descender 133s is connected to the second extending portion 133as, and the front end thereof is connected to the second feedback throttle 134s. In the second protruding portion 133bs, in the front-rear direction, the connection port with the second extending portion 133as and the connection port with the second feedback throttle 134s face each other.

[0078] The first feedback throttle 134f is at the rear on the side opposite to the first extending portion 133af side from the first protruding portion 133bf, and extends toward the feedback manifold 23 side in the front-rear direction. The first feedback throttle 134f extends to the left therefrom, and is curved so as to further extend to the front left. Also, the second feedback throttle 134s is at the front on the side opposite to the second extending portion 133as side from the second protruding portion 133bs, and extends to the side opposite to the feedback manifold 23 side in the front-rear direction. The second feedback throttle 134s extends to the right therefrom, and is curved so as to further extend to the rear right. The first feedback throttle 134f and the second feedback throttle 134s have the same shape and size as each other, and are arranged symmetrically with respect to each other in the front-rear direction and the left-right direction.

[0079] According to this, the first feedback throttle 134f connected to the first protruding portion 133bf and the second feedback throttle 134bs connected to the second protruding portion 133bs can be formed symmetrically with respect to each other with respect to the coupling path 35. Thereby, the flow of the liquid in the first feedback throttle 134f and the second feedback throttle 134s can be made equal to each other, and the discharge performance of the first nozzle 21f and the second nozzle 21s can be made uniform.

[0080] <Other Modification Examples> In the above-described embodiment and modification examples, the liquid discharge device 11 employs the line head method, but is not limited to this method. For example, other methods such as the serial head method can also be employed. In this serial head method, the liquid discharge device 11 includes a carriage that mounts the head 10 and moves the head 10 in the left-right direction. The liquid discharge device 11 alternately executes a recording operation of discharging liquid from the head 10 while moving the carriage in the left-right direction and a conveyance operation of conveying the recording medium A in the front-rear direction by the conveyance unit 13, and executes a printing process of printing an image on the recording medium A.

[0081] In the above-described embodiment and modification examples, the head 10 employs a method using a piezoelectric element (piezo method), but is not limited to this method. For example, the head 10 can employ a thermal method using a heating element or an electrostatic method using an electroconductive diaphragm and electrodes.

[0082] In the above-described embodiment and modification examples, the liquid flow paths 20 such as the individual flow paths 30, the supply manifold 22, and the feedback manifold 23 are formed by through holes penetrating the plate. However, the liquid flow path 20 is not limited to this. The liquid flow path 20 may be formed by at least one of through holes penetrating one or a plurality of plates and recesses recessed from the lower surface or the upper surface of the plate.

[0083] The above embodiments and each modification example may be combined with each other as long as they do not exclude each other. Also, from the above description, many improvements and other embodiments of the present invention will be apparent to those skilled in the art. Therefore, the above description should be construed only as an example and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the present invention. Without departing from the spirit of the present invention, the details of its structure and / or function can be substantially changed.

Industrial Applicability

[0084] The liquid ejection head of the present invention is useful as a liquid ejection head or the like that can suppress poor liquid ejection due to bubbles.

Explanation of Signs

[0085] 10: Liquid ejection head (head) 21: Nozzle 21f: First nozzle 21s: Second nozzle 23: Return manifold 32: Pressure chamber 32f: First pressure chamber 32s: Second pressure chamber 33: Desender 33a: Extension part 33af: First extension part 33as: Second extension part 33bf: First protruding part 33bs: Second protruding part 33f: First desender 33s: Second desender 34: Return throttle 34f: First return throttle 34s: Second return throttle 35: Connection path 36: Linking path 133af: First extension part 133as: Second extension part 133bf: First protruding part 133bs: Second protruding part 133f: First desender 133s: Second descender 134f: First feedback throttle 134s: Second feedback throttle

Claims

1. A first pressure chamber to which a discharge pressure is applied to a liquid; A first descender having a first extending portion extending in an extending direction from the first pressure chamber, and a first protruding portion extending in a first direction intersecting the extending direction from the first extending portion; A first feedback throttle connected to the first protruding portion; A first nozzle connected to the first protruding portion between the first extending portion and the first feedback throttle in the first direction; A second pressure chamber to which a discharge pressure is applied to a liquid; A second descender having a second extending portion extending in the extending direction from the second pressure chamber, and a second protruding portion extending in a second direction intersecting the extending direction from the second extending portion; A second feedback throttle connected to the second protruding portion; A second nozzle connected to the second protruding portion between the second extending portion and the second feedback throttle in the second direction; A connecting path connected to the first feedback throttle and the second feedback throttle; A connecting path connecting between the connecting path and a feedback manifold, and comprising: In the first protruding portion, a facing surface facing the first nozzle in the extending direction is located farther from the first nozzle than the first feedback throttle; In the second protruding portion, a facing surface facing the second nozzle in the extending direction is located farther from the second nozzle than the second feedback throttle; The connecting path extends in a direction intersecting the extending direction between the first feedback throttle and the second feedback throttle; A liquid discharge head, wherein a cross-sectional area orthogonal to the direction in which the connecting path extends is larger than either a cross-sectional area of the first protruding portion orthogonal to the first direction or a cross-sectional area of the second protruding portion orthogonal to the first direction.

2. In the first descender, a portion having the first extending portion and the first protruding portion has a width in the first direction longer than lengths in the extending direction and a direction orthogonal to the first direction; The liquid discharge head according to claim 1, wherein, in the second descender, the second extending portion and the second protruding portion have a width in the second direction longer than lengths in the extending direction and a direction orthogonal to the second direction.

3. The connecting path extends in a direction intersecting the extending direction between the first feedback throttle and the second feedback throttle; Of angles formed by the direction in which the connecting path extends and the first direction, the smaller angle is 45 degrees or less. Of the angles formed by the direction in which the connection path extends and the second direction, the smaller angle is 45 degrees or less. The liquid ejection head according to claim 1 or 2.

4. The first direction in which the first protruding portion extends from the first extending portion and the second direction in which the second protruding portion extends from the second extending portion are the same direction as each other. The liquid ejection head according to any one of claims 1 to 3.

5. The first protruding portion extends from the first extending portion to the side opposite to the return manifold side. The second protruding portion extends from the second extending portion to the side opposite to the return manifold side. The liquid ejection head according to claim 4.

6. The first direction in which the first protruding portion extends from the first extending portion and the second direction in which the second protruding portion extends from the second extending portion are opposite directions to each other. The liquid ejection head according to any one of claims 1 to 3.

7. Of the angles formed by the direction orthogonal to the direction in which the return manifold extends and the first direction, the smaller angle is 45 degrees or less. Of the angles formed by the direction orthogonal to the direction in which the return manifold extends and the second direction, the smaller angle is 45 degrees or less. The liquid ejection head according to any one of claims 1 to 6.

8. The cross-sectional area orthogonal to the direction in which the connection path extends is larger than either twice the cross-sectional area of the first protruding portion orthogonal to the first direction and twice the cross-sectional area of the second protruding portion orthogonal to the second direction. The liquid ejection head according to claim 1.

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