Liquid dispensing device

Abstract

To provide a liquid ejection device that is able to uniformize a flow rate of liquid in a manifold while reducing crosstalk.SOLUTION: A liquid ejection device includes: a plurality of liquid passages each of which having: an individual channel including a nozzle; a supply manifold connected to the individual channel to supply liquid to the individual channel; and a return manifold connected to the individual channel to allow circulation of liquid not ejected from the nozzle; and a bypass connecting the supply manifold and the return manifold to allow circulation of liquid. The plurality of liquid passages include a first liquid passage, a second liquid passage, and a third liquid passage arranged in a predetermined first direction. The supply manifold of the first liquid passage is connected, via a first bypass of the bypass, only to the return manifold of the second liquid passage, and the return manifold of the first liquid passage is connected, via a second bypass of the bypass, only to the supply manifold of the third liquid passage.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] A known example of a conventional liquid ejection device is the liquid ejection device disclosed in Patent Document 1. This liquid ejection device includes a first supply manifold and a first return manifold connected to a first individual channel, and a second supply manifold and a second return manifold connected to a second individual channel. The first supply manifold and the second return manifold are connected by a first bypass path. The first individual channel has a first nozzle outlet, and ejects liquid from the first nozzle outlet by pressure applied to the liquid in the first individual channel by a piezoelectric element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-168853 Summary of the Invention [Problem to be solved by the invention]

[0004] In such a liquid ejection device, the first supply manifold is connected to the first return manifold by a first individual channel. Pressure waves imparted to the liquid in the first individual channel from the piezoelectric element propagate to the first supply manifold and also to the first return manifold. If the first supply manifold and the first return manifold were connected by a bypass path, a pressure wave propagating to the first supply manifold and a pressure wave propagating to the first return manifold would be superimposed in phase via the bypass path, generating a large-amplitude wave. This would cause crosstalk, which would destabilize the ejection of fluid from the nozzle outlets of the surrounding individual channels. In contrast, in the above-mentioned liquid ejection device, the first supply manifold is connected to the second return manifold by a first bypass path. This prevents the pressure wave propagating through the first supply manifold from merging with the pressure wave propagating through the first return manifold, which is in phase with the pressure wave. This reduces crosstalk.

[0005] However, when the liquid ejection device further includes a third supply manifold and a third return manifold connected by a third individual channel, the first supply manifold is connected to the second return manifold and the third return manifold by bypass paths. In contrast, the second supply manifold and the third supply manifold are connected to the first return manifold by bypass paths. Thus, the number of bypass paths of the manifold connected to the first supply manifold differs from that of the other manifolds, and the liquid flow rate in the first supply manifold differs from that of the other manifolds. Differences in flow rate between manifolds may result in uneven heat dissipation performance and bubble discharge performance of the head.

[0006] In view of the above, an object of the present invention is to provide a liquid ejection device that can reduce crosstalk and make the flow rate of liquid in a manifold uniform. [Means for solving the problem]

[0007] A liquid ejection device according to one aspect of the present invention comprises a plurality of liquid flow paths each having individual channels including a nozzle, a supply manifold connected to the individual channels to supply liquid to the individual channels, and a return manifold connected to the individual channels through which liquid not ejected from the nozzle flows, and a bypass connecting the supply manifold and the return manifold and through which liquid flows, wherein the plurality of liquid flow paths include a first liquid flow path, a second liquid flow path, and a third liquid flow path aligned in a predetermined first direction, and the supply manifold of the first liquid flow path is connected only to the return manifold of the second liquid flow path via a first bypass of the bypass, and the return manifold of the first liquid flow path is connected only to the supply manifold of the third liquid flow path via a second bypass of the bypass. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a top view of a liquid ejection device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a cross-sectional view showing a part of the head. [Figure 3] 3 is a diagram showing a flow path unit in the head of FIG. 2 as viewed from above. FIG. [Figure 4] FIG. 3 is an exploded view of the flow path unit of FIG. 2. [Figure 5] FIG. 3 is a perspective view of the flow path unit of FIG. 2. [Figure 6] FIG. 10 is a diagram showing a liquid ejection device according to a second modified example of the present invention, as viewed from the left. [Figure 7] FIG. 10 is a diagram showing a flow path unit of a liquid ejection device according to a fourth modified example of the present invention, as viewed from above. [Figure 8] FIG. 8 is a perspective view of the flow path unit of FIG. 7. [Figure 9] FIG. 11 is a perspective view of a flow path unit of a liquid ejection device according to a fifth modified example of the present invention. [Figure 10] FIG. 10 is a view of the flow path unit of FIG. 9 as seen from the left. [Figure 11] FIG. 13 is a perspective view of a flow path unit of a liquid ejection device according to a sixth modified example of the present invention. [Figure 12] FIG. 10 is a left view of a flow path unit of a liquid ejection device according to another modified example of the present invention. [Figure 13] FIG. 10 is a left view of a flow path unit of a liquid ejection device according to another modified example of the present invention. 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] <Liquid discharge device> As shown in Fig. 1, a liquid ejection device 10 according to an embodiment of the present invention is a device that ejects liquid such as ink. In the following, an example will be described in which the liquid ejection device 10 is applied to an inkjet printer that ejects liquid from a head 20 onto a recording medium A to form an image, but the liquid ejection device 10 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 10 employs a line head system and includes a platen 11, a head unit 12, a storage tank 13, a conveying device 17, and a control unit 14. Note that a predetermined first direction is referred to as the front-rear direction, a second direction intersecting (for example, perpendicular to) the first direction is referred to as the left-right direction, and a third direction intersecting (for example, perpendicular to) the first and second directions is referred to as the up-down direction. However, the arrangement of the liquid ejection device 10 is not limited to this.

[0012] The platen 11 is, for example, a rectangular flat plate, 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 20 in the vertical direction. The head 20 extends long in the left-right direction, and its length in the left-right direction is equal to or longer than the length of the recording medium A. The head unit 12 is provided with one or more heads 20. The head 20 is provided with a discharge surface 21 (FIG. 2) facing the upper surface of the platen 11, and a plurality of nozzles 31 opening into the discharge surface 21. Details of the head 20 will be described later.

[0013] A storage tank 13 is provided for each type of liquid. For example, four storage tanks 13 store black, yellow, cyan, and magenta liquids, respectively. The storage tanks 13 correspond to the nozzles 31 of the multiple heads 20, and supply liquid to the corresponding nozzles 31.

[0014] The transport device 17 has, for example, a pair of transport rollers 18 and a transport motor 19. The pair of transport rollers 18 are arranged to sandwich the platen 11 between them in the front-to-rear direction, with their axes extending in the left-to-right direction. The transport rollers 18 are connected to the transport motor 19, and are rotated around their axes by the transport motor 19. As a result, the recording medium A is transported in the front-to-rear direction on the platen 11.

[0015] The control unit 14 is a computer that includes an arithmetic circuit such as a CPU, and memories such as RAM and ROM. In the control unit 14, the arithmetic unit controls the operation of the transport motor 19 of the transport device 17 and the drive element 23 of the head 20 based on a program stored in the storage unit. For example, the control unit 14 executes a discharge operation that causes the drive element 23 to discharge liquid from the head 20 onto the recording medium A, and a transport operation that causes the transport device 17 to transport the recording medium A. As a result, the head 20 does not move, and the printing process of forming an image on the recording medium A using liquid proceeds.

[0016] <head> 2 and 3, the head 20 includes a flow path forming body 22 and a driving element 23, and is equipped with a sub-tank 15. The flow path forming body 22 is, for example, a laminated body in which a plurality of plates are stacked, and includes a nozzle plate 24, a plurality (e.g., eight) of flow path plates 25, and a vibration plate 26. These plates have a rectangular flat plate shape, are stacked in the vertical direction in this order, and are bonded to each other with an adhesive or the like.

[0017] Each plate is formed with through-holes that penetrate the plate and recesses that are recessed from the top or bottom surface of the plate. For example, the plates are made of resin or metal, and the through-holes and recesses are formed by etching. Inside the channel former 22, where the plates are stacked, the through-holes and recesses are combined to form, for example, a channel unit 27. The channel unit 27 includes a plurality of liquid channels 28 and a plurality of bypasses 60. The liquid channel 28 has a plurality of individual channels 30, a supply manifold 40, and a return manifold 50. The bypass 60 connects the supply manifold 40 and the return manifold 50, allowing the liquid to flow through. Details of the manifold and bypass 60 will be described later.

[0018] As shown in FIG. 2 , the individual channel 30 has a nozzle 31, a supply orifice 32, a pressure chamber 33, a descender 34, and a return orifice 35. The nozzle 31 penetrates the nozzle plate 24 in the vertical direction and opens to the ejection surface 21, which is the lower surface of the nozzle plate 24. The supply orifice 32 is connected to a supply manifold 40 and a pressure chamber 33. The cross-sectional area of ​​the supply orifice 32 perpendicular to the flow direction of the liquid therethrough is smaller than those of the supply manifold 40 and the pressure chamber 33. The upper end opening of the pressure chamber 33 is covered by a vibration plate 26. The descender 34 is connected to the pressure chamber 33 and the nozzle 31. The return orifice 35 is connected to the descender 34 and a return manifold 50, and the cross-sectional area of ​​the return orifice 35 perpendicular to the flow direction of the liquid therethrough is smaller than those of the descender 34 and the return manifold 50.

[0019] The driving element 23 is an element, such as a piezoelectric element, that applies an ejection pressure to the liquid in the pressure chamber 33. The driving element 23 expands and contracts upon receiving a control signal from the control unit 14 (FIG. 1). The diaphragm 26 between the driving element 23 and the pressure chamber 33 deforms in cooperation with the driving element 23, and changes in the direction of increasing or decreasing the volume of the pressure chamber 33. Therefore, an ejection pressure for ejecting from the nozzle 31 is applied to the liquid in the pressure chamber 33, and the liquid is ejected from the nozzle 31 that communicates with the pressure chamber 33.

[0020] <Manifold and bypass> As shown in Fig. 3, the supply manifold 40 and the return manifold 50 extend elongatedly in the left-right direction and are connected to a plurality of individual channels 30. For example, the supply manifold 40 has a supply port 41 at its right end and an outlet 42 at its left end. The return manifold 50 has a return port 51 at its right end and an inlet 52 at its left end. The supply port 41 is connected to the sub-tank 15 by a supply pipe 43, and the return port 51 is connected to the sub-tank 15 by a return pipe 44. The outlet 42 and the inlet 52 are connected by a bypass 60. The sub-tank 15 is connected to the storage tank 13 (Fig. 1) by a tube 13a.

[0021] The multiple liquid flow paths 28 include a first liquid flow path 28a, a second liquid flow path 28b, and a third liquid flow path 28c aligned in the front-to-rear direction. The first liquid flow path 28a includes a first supply manifold 40a that is the supply manifold 40, a first return manifold 50a that is the return manifold 50, and a first individual channel 30a that is the multiple individual channels 30 connected thereto. The second liquid flow path 28b includes a second supply manifold 40b that is the supply manifold 40, a second return manifold 50b that is the return manifold 50, and a second individual channel 30b that is the multiple individual channels 30 connected thereto. The third liquid flow path 28c includes a third supply manifold 40c that is the supply manifold 40, a third return manifold 50c that is the return manifold 50, and a third individual channel 30c that is the multiple individual channels 30 connected thereto.

[0022] The first supply manifold 40a, the second supply manifold 40b, and the third supply manifold 40c are arranged in this order from rear to rear. The first return manifold 50a, the second return manifold 50b, and the third return manifold 50c are arranged in this order from rear to rear. The first supply manifold 40a is arranged above the first return manifold 50a so as to overlap with the first return manifold 50a when viewed in the vertical direction. The second supply manifold 40b is arranged above the second return manifold 50b so as to overlap with the second return manifold 50b when viewed in the vertical direction. The third supply manifold 40c is arranged above the third return manifold 50c so as to overlap with the third return manifold 50c when viewed in the vertical direction.

[0023] The bypass 60 has a first bypass 61, a second bypass 62, and a third bypass 63. The first bypass 61 is connected to the outlet 42 of the first supply manifold 40a and the inlet 52 of the second return manifold 50b. The second bypass 62 is connected to the outlet 42 of the third supply manifold 40c and the inlet 52 of the first return manifold 50a. The third bypass 63 is connected to the outlet 42 of the second supply manifold 40b and the inlet 52 of the third return manifold 50c.

[0024] As shown in Fig. 4, the plurality of flow path plates 25 in the flow path formation body 22 include a first flow path plate 25a, a second flow path plate 25b, a third flow path plate 25c, and a fourth flow path plate 25d. The first flow path plate 25a, the second flow path plate 25b, the third flow path plate 25c, and the fourth flow path plate 25d are stacked in this order from top to bottom. For example, the dimensions of the first flow path plate 25a and the fourth flow path plate 25d are larger than the dimensions of the second flow path plate 25b and the third flow path plate 25c in the vertical direction. Note that Fig. 4 does not show the individual channels 30.

[0025] The first supply manifold 40a, the second supply manifold 40b, and the third supply manifold 40c are formed as through-holes that penetrate the first flow path plate 25a in the vertical direction and extend in the left-right direction. The first return manifold 50a, the second return manifold 50b, and the third return manifold 50c are formed as through-holes that penetrate the fourth flow path plate 25d in the vertical direction and extend in the left-right direction.

[0026] The first bypass 61 has a first upper portion 61a, a first middle portion 61b, and a first lower portion 61c, which are connected in this order. The first upper portion 61a penetrates the second flow path plate 25b in the vertical direction. In the front-rear direction, the dimension of the first upper portion 61a is larger than the dimension of the first supply manifold 40a, and the first upper portion 61a extends forward of the first supply manifold 40a. The first upper portion 61a overlaps with the first supply manifold 40a when viewed in the vertical direction, and the upper end of the first upper portion 61a is connected to the outlet 42 at the lower end of the first supply manifold 40a. The first middle portion 61b penetrates the third flow path plate 25c in the vertical direction. The first lower portion 61c penetrates the fourth flow path plate 25d in the vertical direction. In the front-to-rear direction, the dimensions of the first lower portion 61c are larger than the dimensions of the second return manifold 50b, and the first lower portion 61c extends further rearward than the second return manifold 50b. When viewed in the up-down direction, at the overlapping portion of the first upper portion 61a and the first lower portion 61c, the upper end of the first middle portion 61b is connected to the lower end of the first upper portion 61a, and the lower end of the first middle portion 61b is connected to the upper end of the first lower portion 61c. The front end of the first lower portion 61c is connected to the inlet 52, which is the rear end of the second return manifold 50b.

[0027] The second bypass 62 has a second upper portion 62a, a second middle portion 62b, and a second lower portion 62c, which are connected in this order. The second upper portion 62a penetrates the second flow path plate 25b in the vertical direction. In the front-rear direction, the dimension of the second upper portion 62a is larger than the dimension of the third supply manifold 40c, and the second upper portion 62a extends rearward beyond the third supply manifold 40c. The second upper portion 62a overlaps with the third supply manifold 40c when viewed in the vertical direction, and the upper end of the second upper portion 62a is connected to the outlet 42 at the lower end of the third supply manifold 40c. The second middle portion 62b penetrates the third flow path plate 25c in the vertical direction. The second lower portion 62c penetrates the fourth flow path plate 25d in the vertical direction. In the front-to-rear direction, the dimensions of the second lower portion 62c are larger than the dimensions of the first return manifold 50a, and the second lower portion 62c extends forward of the first return manifold 50a. When viewed in the up-down direction, at the overlapping portion of the second upper portion 62a and the second lower portion 62c, the upper end of the second middle portion 62b is connected to the lower end of the second upper portion 62a, and the lower end of the second middle portion 62b is connected to the upper end of the second lower portion 62c. The rear end of the second lower portion 62c is connected to the inlet 52, which is the front end of the first return manifold 50a.

[0028] The third bypass 63 has a third upper portion 63a, a third middle portion 63b, and a third lower portion 63c, which are connected in this order. The third upper portion 63a penetrates the second flow path plate 25b in the vertical direction. In the front-rear direction, the dimension of the third upper portion 63a is larger than the dimension of the second supply manifold 40b, and the third upper portion 63a extends forward of the second supply manifold 40b. The third upper portion 63a overlaps the second supply manifold 40b when viewed in the vertical direction, and the upper end of the third upper portion 63a is connected to the outlet 42 at the lower end of the second supply manifold 40b. The third middle portion 63b penetrates the third flow path plate 25c in the vertical direction. The third lower portion 63c penetrates the fourth flow path plate 25d in the vertical direction. In the front-to-rear direction, the dimensions of the third lower portion 63c are larger than the dimensions of the third return manifold 50c, and the third lower portion 63c extends further rearward than the third return manifold 50c. When viewed in the up-down direction, at the overlapping portion of the third upper portion 63a and the third lower portion 63c, the upper end of the third middle portion 63b is connected to the lower end of the third upper portion 63a, and the lower end of the third middle portion 63b is connected to the upper end of the third lower portion 63c. The front end of the third lower portion 63c is connected to the inlet 52, which is the rear end of the second return manifold 50b.

[0029] 5, the first supply manifold 40a of the first liquid flow path 28a is connected only to the second return manifold 50b of the second liquid flow path 28b via a first bypass 61 of the bypass 60. The first return manifold 50a of the first liquid flow path 28a is connected only to the third supply manifold 40c of the third liquid flow path 28c via a second bypass 62 of the bypass 60. The second supply manifold 40b of the second liquid flow path 28b is connected only to the third return manifold 50c of the third liquid flow path 28c via a third bypass 63 of the bypass 60. Note that the individual channels 30 are not shown in FIG. 5.

[0030] <Liquid flow> Liquid is supplied from the storage tank 13 to the subtank 15, passes from the subtank 15 through the supply pipe 43, and flows into the first supply manifold 40a via the supply port 41. The liquid then flows leftward through the first supply manifold 40a, and is supplied to each of the multiple first individual channels 30a connected to the first supply manifold 40a. In the first individual channel 30a, the liquid flows through the supply orifice 32, the pressure chamber 33, and the descender 34, and is supplied to the nozzle 31. Here, when pressure is applied to the liquid by the drive element 23, the liquid is ejected from the nozzle 31. Meanwhile, liquid that is not ejected from the nozzle 31 passes through the return orifice 35 and flows into the first return manifold 50a. The liquid flows rightward through the first return manifold 50a, passes through the return port 51 of the first return manifold 50a, and returns to the subtank 15 via the return pipe 44. In this way, the liquid circulates through the sub-tank 15, the first supply manifold 40a, the first individual channel 30a, the first return manifold 50a, and the sub-tank 15 as nozzle circulation.

[0031] Furthermore, the liquid that does not flow from the first supply manifold 40a into the first individual channel 30a while flowing leftward through the first supply manifold 40a passes from the outlet 42 of the first supply manifold 40a through the first bypass 61 and flows into the second return manifold 50b via the inlet 52. The liquid flows rightward through the second return manifold 50b, passes from the return port 51 of the second return manifold 50b through the return pipe 44, and is returned to the sub-tank 15. In this way, the liquid circulates through the sub-tank 15, the first supply manifold 40a, the first bypass 61, the second return manifold 50b, and the sub-tank 15, as a manifold circulation.

[0032] Similar to the first supply manifold 40a, the liquid flows from the sub-tank 15 into the second supply manifold 40b and is supplied to each of the plurality of second individual channels 30b while flowing through the second supply manifold 40b. When pressure is applied to the liquid in the second individual channel 30b by the drive element 23, the liquid is ejected from the nozzle 31. Meanwhile, the liquid that is not ejected from the nozzle 31 passes from the second individual channel 30b through the second return manifold 50b and returns to the sub-tank 15. In this way, the liquid circulates through the sub-tank 15, the second supply manifold 40b, the second individual channel 30b, the second return manifold 50b, and the sub-tank 15, as nozzle circulation.

[0033] Furthermore, the liquid that does not flow from the second supply manifold 40b into the second individual channel 30b flows from the second supply manifold 40b through the third bypass 63 into the third return manifold 50c, and is returned from the third return manifold 50c to the sub-tank 15. In this manner, the liquid circulates through the sub-tank 15, the second supply manifold 40b, the third bypass 63, the third return manifold 50c, and the sub-tank 15, as a manifold circulation.

[0034] Similar to the first supply manifold 40a, the liquid flows from the sub-tank 15 into the third supply manifold 40c and is supplied to each of the plurality of third individual channels 30c while flowing through the third supply manifold 40c. In the third individual channel 30c, the liquid is ejected from the nozzle 31 when pressure is applied by the drive element 23. Meanwhile, the liquid that is not ejected from the nozzle 31 passes from the third individual channel 30c through the third return manifold 50c and returns to the sub-tank 15. In this way, the liquid circulates through the sub-tank 15, the third supply manifold 40c, the third individual channel 30c, the third return manifold 50c, and the sub-tank 15 as nozzle circulation.

[0035] Furthermore, the liquid that does not flow from the third supply manifold 40c into the third individual channel 30c flows from the third supply manifold 40c through the second bypass 62 into the first return manifold 50a, and is returned from the first return manifold 50a to the sub-tank 15. In this manner, the liquid circulates through the sub-tank 15, the third supply manifold 40c, the second bypass 62, the first return manifold 50a, and the sub-tank 15, as a manifold circulation.

[0036] In this way, the first supply manifold 40a and the first return manifold 50a of the first liquid flow path 28a are connected to different liquid flow paths 28 by the bypass 60. The second supply manifold 40b and the second return manifold 50b of the second liquid flow path 28b are connected to different liquid flow paths 28 by the bypass 60. The third supply manifold 40c and the third return manifold 50c of the third liquid flow path 28c are connected to different liquid flow paths 28 by the bypass 60. Furthermore, the first supply manifold 40a is connected to the second return manifold 50b in a one-to-one relationship by the first bypass 61, the second supply manifold 40b is connected to the third return manifold 50c in a one-to-one relationship by the third bypass 63, and the third supply manifold 40c is connected to the first return manifold 50a in a one-to-one relationship by the second bypass 62. This makes it possible to reduce crosstalk and to equalize the flow rates of liquid in the manifolds 40, 50.

[0037] <Variation 1> In the liquid ejection device 10 according to the first modification, the second bypass 62 has a larger cross-sectional area through which the liquid flows than the first bypass 61 and the third bypass 63 in the above embodiment. For example, the cross-sectional area of ​​the second bypass 62 is an area perpendicular to the flow direction of the liquid from the third supply manifold 40c to the first return manifold 50a. The cross-sectional area of ​​the first bypass 61 is an area perpendicular to the flow direction of the liquid from the first supply manifold 40a to the second return manifold 50b. The cross-sectional area of ​​the third bypass 63 is an area perpendicular to the flow direction of the liquid from the second supply manifold 40b to the third return manifold 50c.

[0038] In the examples of FIGS. 4 and 5, the cross-sectional areas of the bypass 60 are different in its upper, middle, and lower portions. In such cases, corresponding portions of the first bypass 61, the second bypass 62, and the third bypass 63 may be compared. In this case, the cross-sectional area of ​​the second upper portion 62a is larger than the cross-sectional areas of the first upper portion 61a and the third upper portion 63a. The cross-sectional area of ​​the second middle portion 62b is larger than the cross-sectional areas of the first middle portion 61b and the third middle portion 63b. The cross-sectional area of ​​the second lower portion 62c is larger than the cross-sectional areas of the first lower portion 61c and the third lower portion 63c. Here, for example, the cross-sectional areas of the upper portions 61a, 62a, and 63a are cross-sectional areas perpendicular to the front-to-rear direction, the cross-sectional areas of the middle portions 61b, 62b, and 63b are cross-sectional areas perpendicular to the up-down direction, and the cross-sectional areas of the lower portions 61c, 62c, and 63c are cross-sectional areas perpendicular to the front-to-rear direction.

[0039] When the length of the second bypass 62 in the flow direction is longer than that of the first bypass 61 and the third bypass 63, the flow path resistance of the second bypass 62 is greater than that of the first bypass 61 and the third bypass 63. In contrast, the cross-sectional area of ​​the second bypass 62 in the direction of liquid flow is greater than that of the first bypass 61 and the third bypass 63. This results in a smaller flow path resistance of the second bypass 62 than that of the first bypass 61 and the third bypass 63. Therefore, the flow path resistances of the first bypass 61, the second bypass 62, and the third bypass 63 can be made equal to each other or reduced to a predetermined value or less, thereby making the flow rates uniform. For example, the flow path resistance of the bypass 60 is approximately 200 to 2000 (kPa / (cc / s)) when the viscosity range of the liquid, such as ink, is 2 to 10 (mPa·s).

[0040] The cross-sectional areas of the upper, middle, and lower portions of the bypass 60 may be equal to each other and constant. Alternatively, the second bypass 62 may be larger than the first bypass 61 and the third bypass 63 in at least one of the upper, middle, and lower portions, and the second bypass 62 may be the same as the first bypass 61 and the third bypass 63 in the other portions.

[0041] <Variation 2> In the liquid ejection device 10 according to the second modification, the supply manifold 40 and the return manifold 50 extend in the left-right direction in the above-described embodiment and the first modification. The second bypass 62 has a larger vertical dimension than the first bypass 61 and the third bypass 63.

[0042] For example, as shown in Fig. 6(a), the first upper portion 61a of the first bypass 61 and the third upper portion 63a of the third bypass 63 are formed on the second flow path plate 25b. In contrast, as shown in Fig. 6(b), the second upper portion 62a of the second bypass 62 is formed on the first flow path plate 25a and the second flow path plate 25b. Therefore, in the vertical direction, the dimensions of the first upper portion 61a and the third upper portion 63a are equal to the dimension hb of the second flow path plate 25b, and the dimension of the second upper portion 62a is equal to the sum of the dimension ha of the first flow path plate 25a and the dimension hb of the second flow path plate 25b. Therefore, the dimension of the second upper portion 62a is larger than the dimensions of the first upper portion 61a and the third upper portion 63a.

[0043] 6(c), the second upper portion 62a of the second bypass 62 is formed in the first flow path plate 25a, and the second middle portion 62b is formed in the second flow path plate 25b and the third flow path plate 25c. In this case, in the vertical direction, the dimensions of the first upper portion 61a and the third upper portion 63a are equal to the dimension hb of the second flow path plate 25b, and the dimension of the second upper portion 62a is equal to the dimension ha of the first flow path plate 25a. Here, the dimension ha of the first flow path plate 25a is larger than the dimension hb of the second flow path plate 25b. Therefore, in the vertical direction, the dimension of the second upper portion 62a is larger than the dimensions of the first upper portion 61a and the third upper portion 63a.

[0044] For example, in a cross section of the upper portion perpendicular to the front-rear direction, the vertical dimension is smaller than the horizontal dimension. In this case, increasing the vertical dimension rather than the horizontal dimension can reduce the flow resistance of the liquid along the front-rear direction. Therefore, the vertical dimension of the second upper portion 62a is made larger than the dimensions of the first upper portion 61a and the third upper portion 63a. This reduces the flow resistance of the second bypass 62 and allows for uniform flow rates in the first bypass 61, the second bypass 62, and the third bypass 63, even if the length of the second bypass 62 along the liquid flow direction is longer than the first bypass 61 and the third bypass 63.

[0045] 6(b) and 6(c), the vertical dimension of the second bypass 62 is larger than that of the first bypass 61 and the third bypass 63 for a part of the upper, middle, and lower portions. However, the overall dimension of the second bypass 62 may be larger than that of the first bypass 61 and the third bypass 63.

[0046] <Variation 3> In the liquid ejection device 10 according to Modification 3, in the above-described embodiment and Modification 1-2, the supply manifold 40 and the return manifold 50 extend in the left-right direction. The first individual channel 30a of the first liquid flow path 28a is located on one side of the left-right direction relative to the first bypass 61. The second individual channel 30b of the second liquid flow path 28b is located on one side of the left-right direction relative to the third bypass 63. The second bypass 62 is located on the other side of the left-right direction relative to both the first bypass 61 and the third bypass 63.

[0047] In the example of Fig. 3, the first individual channel 30a, the second individual channel 30b, and the third individual channel 30c are arranged to the right of the first bypass 61 and the third bypass 63 in the left-right direction. The second bypass 62 is arranged to the left of the first bypass 61 and the third bypass 63 in the left-right direction. As a result, as shown in Fig. 4, the first upper portion 61a, the second upper portion 62a, and the third upper portion 63a are formed on the same second flow path plate 25b. This makes it possible to prevent the head 20 from becoming larger in the up-down direction and the number of parts from increasing.

[0048] <Variation 4> In the liquid ejection device 10 according to Modification 4, in the above-described embodiment and Modification 1-2, the supply manifold 40 and the return manifold 50 extend in the left-right direction. The first individual channel 30a of the first liquid flow path 28a is located to one side of the left-right direction relative to the first bypass 61. The second individual channel 30b of the second liquid flow path 28b is located to one side of the left-right direction relative to the third bypass 63. The second bypass 62 is located between the first individual channel 30a of the first liquid flow path 28a and the first bypass 61, and between the second individual channel 30b of the second liquid flow path 28b and the third bypass 63, in the left-right direction.

[0049] In the example of FIGS. 7 and 8 , the first individual channel 30a, the second individual channel 30b, and the third individual channel 30c are arranged to the right of the second bypass 62 in the left-right direction. The first bypass 61 and the third bypass 63 are arranged to the left of the second bypass 62 in the left-right direction. As a result, the dimensions in the left-right direction of the third supply manifold 40c and the first return manifold 50a connected to the second bypass 62 are shorter than the first supply manifold 40a and the second return manifold 50b connected to the first bypass 61 and the second supply manifold 40b and the third return manifold 50c connected to the third bypass 63. As a result, even if the second bypass 62 is longer than the first bypass 61 and the third bypass 63, the third supply manifold 40c and the first return manifold 50a are shorter than the other manifolds. This allows for uniform flow rates in the supply manifold 40 and the return manifold 50.

[0050] <Variation 5> The liquid ejection device 10 according to Modification 5 includes, in the above-described embodiment and Modifications 1-4, a drive element 23 that applies an ejection pressure to the liquid in the individual channels 30 to eject the liquid from the nozzles 31. The supply manifold 40 and the return manifold 50 extend in the left-right direction. In the up-down direction, the drive element 23, the supply manifold 40, and the return manifold 50 are arranged in this order. The bypass 60 is arranged at the same position as the supply manifold 40 in the up-down direction, or at a position closer to the supply manifold 40 than the return manifold 50 in the up-down direction.

[0051] Specifically, in the example of FIGS. 4 and 5, the upper portions 61a, 62a, and 63a are formed on the second flow path plate 25b. In contrast, in the example of FIGS. 9 and 10, the upper portions 61a, 62a, and 63a are formed on the first flow path plate 25a. In this case, the flow path forming body 22 does not have the second flow path plate 25b. However, the upper portions 61a, 62a, and 63a may be formed on the first flow path plate 25a and the second flow path plate 25b. Alternatively, the middle portions 61b, 62b, and 63b may be formed on the second flow path plate 25b and the third flow path plate 25c. In this case, the flow path forming body 22 has the second flow path plate 25b.

[0052] The first upper portion 61a of the first bypass 61 penetrates the first flow path plate 25a in the vertical direction and extends forward from the first supply manifold 40a. The rear end of the first upper portion 61a is connected to the outlet 42 at the front end of the first supply manifold 40a. The second upper portion 62a of the second bypass 62 penetrates the first flow path plate 25a in the vertical direction and extends forward from the second supply manifold 40b. The rear end of the second upper portion 62a is connected to the outlet 42 at the front end of the second supply manifold 40b. The third upper portion 63a of the third bypass 63 penetrates the first flow path plate 25a in the vertical direction and extends rearward from the third supply manifold 40c. The front end of the third upper portion 63a is connected to the outlet 42 at the rear end of the third supply manifold 40c.

[0053] In this way, the bypass 60 is disposed at the same position as the supply manifold 40 in the vertical direction, or at a position closer to the supply manifold 40 in the vertical direction than the return manifold 50. In the vertical direction, the drive element 23 is closer to the supply manifold 40 than the return manifold 50. Therefore, the bypass 60 is closer to the drive element 23, and the drive element 23 can be cooled by the liquid flowing through the bypass 60, thereby reducing thermal deterioration of the drive element 23.

[0054] In the above case, all of the first bypass 61, the second bypass 62, and the third bypass 63 are formed in the first flow path plate 25a. However, at least one of the first bypass 61, the second bypass 62, and the third bypass 63 may be formed in the first flow path plate 25a, and the other bypasses 60 may be formed in the second flow path plate 25b. In the above case, the bypass 60 is disposed at the same position as the supply manifold 40 in the vertical direction. However, the bypass 60 may be disposed at a position closer to the supply manifold 40 than the midpoint between the supply manifold 40 and the return manifold 50 in the vertical direction.

[0055] <Variation 6> 11, the liquid ejection device 10 according to Modification 6 includes a plurality of flow path units 27, each including a plurality of liquid flow paths 28 and a bypass 60, in the above-described embodiment and Modifications 1-5. The supply manifold 40 included in one of the flow path units 27 is provided with a first supply port 41a through which liquid is supplied from the first tank 15a, and the supply manifold 40 included in the other of the flow path units 27 is provided with a second supply port 41b through which liquid is supplied from the second tank 15b. The bypasses 60 included in each of the plurality of flow path units 27 may have the same layout. Note that individual channels 30 are not shown in FIG. 11.

[0056] 11, the flow path unit 27 includes a first flow path unit 27a and a second flow path unit 27b that is different from the first flow path unit 27a. Each of the first and second flow path units 27a and 27b includes a plurality of liquid flow paths 28 and a plurality of bypasses 60. The plurality of liquid flow paths 28 include a first liquid flow path 28a, a second liquid flow path 28b, and a third liquid flow path 28c. The first liquid flow path 28a includes a first supply manifold 40a and a first return manifold 50a. The second liquid flow path 28b includes a second supply manifold 40b and a second return manifold 50b. The third liquid flow path 28c includes a third supply manifold 40c and a third return manifold 50c.

[0057] The first supply port 41a of the first flow path unit 27a includes the supply port 41 of the first supply manifold 40a, the supply port 41 of the second supply manifold 40b, and the supply port 41 of the third supply manifold 40c in the first flow path unit 27a. The second supply port 41b of the second flow path unit 27b includes the supply port 41 of the first supply manifold 40a, the supply port 41 of the second supply manifold 40b, and the supply port 41 of the third supply manifold 40c in the second flow path unit 27b. The first return port 51a of the first flow path unit 27a includes the return port 51 of the first return manifold 50a, the return port 51 of the second return manifold 50b, and the return port 51 of the third return manifold 50c in the first flow path unit 27a. The second return port 51b of the second flow path unit 27b has the return port 51 of the first return manifold 50a, the return port 51 of the second return manifold 50b, and the return port 51 of the third return manifold 50c in the second flow path unit 27b.

[0058] The sub-tank 15 includes a first tank 15a and a second tank 15b different from the first tank 15a. The first tank 15a and the second tank 15b are connected to different storage tanks 13 (FIG. 1). The first tank 15a is connected to a first supply port 41a of the first flow path unit 27a by a supply pipe 43, and is connected to a first return port 51a of the first flow path unit 27a by a return pipe 44. The second tank 15b is connected to a second supply port 41b of the second flow path unit 27b by a supply pipe 43, and is connected to a second return port 51b of the second flow path unit 27b by the return pipe 44. This allows the first flow path unit 27a and the second flow path unit 27b, through which liquids from different storage tanks 13 flow, to be arranged in the same head 20. In this case, the distance between the nozzles 31 of the first flow path unit 27a and the nozzles 31 of the second flow path unit 27b can be made smaller than when the first flow path unit 27a and the second flow path unit 27b are arranged in different heads 20. Therefore, the landing positions of the liquid ejected by the nozzles 31 of the first flow path unit 27a and the liquid ejected by the nozzles 31 of the second flow path unit 27b can be adjusted with high precision.

[0059] The multiple bypasses 60 include a first bypass 61, a second bypass 62, and a third bypass 63. The layout of the first bypass 61, the second bypass 62, and the third bypass 63 of the first flow path unit 27a is the same as the layout of the first bypass 61, the second bypass 62, and the third bypass 63 of the second flow path unit 27b. For example, in the examples of FIGS. 3 and 11, the first liquid flow path 28a, the second liquid flow path 28b, and the third liquid flow path 28c are arranged in this order in the first flow path unit 27a and the second flow path unit 27b. In the first flow path unit 27a and the second flow path unit 27b, the first bypass 61 is connected to the first supply manifold 40a and the second return manifold 50b, the second bypass 62 is connected to the second supply manifold 40b and the third return manifold 50c, and the third bypass 63 is connected to the third supply manifold 40c and the first return manifold 50a. Furthermore, in the first flow path unit 27a and the second flow path unit 27b, the individual channels 30 are arranged to the right of the first bypass 61 and the third bypass 63, and the second bypass 62 is arranged to the left of the first bypass 61 and the third bypass 63. This allows the same parts to be used to manufacture the first flow path unit 27a and the second flow path unit 27b, thereby improving manufacturing efficiency and reducing costs.

[0060] <Other variations> In the above-described embodiment and all of the modified examples, the flow path unit 27 has three liquid flow paths 28. However, the number of liquid flow paths 28 in the flow path unit 27 is not limited to this, and the flow path unit 27 may have more than three liquid flow paths 28. For example, as shown in FIG. 12 , the flow path unit 27 has n liquid flow paths 28. In this case, the flow path unit 27 has n bypasses 60. Of the n bypasses 60, (n−1) bypasses 60 are connected to, for example, the rear supply manifold 40 and the front return manifold 50 of adjacent liquid flow paths 28.

[0061] Of the n bypasses 60, the remaining bypass 60, the second bypass 62, is connected to the first return manifold 50a of the rear first liquid flow path 28a and the nth supply manifold 40n of the front nth liquid flow path 28n among the n liquid flow paths 28 aligned in the front-to-rear direction. In this way, the supply manifold 40 and the return manifold 50 of a certain liquid flow path 28 are connected to different liquid flow paths 28 in a one-to-one relationship by the bypass 60. This makes it possible to reduce crosstalk and make the flow rates of liquid in the manifolds 40, 50 uniform.

[0062] In the above-described embodiment and all of the modified examples, the first liquid flow path 28a, the second liquid flow path 28b, and the third liquid flow path 28c are arranged in a back-to-front arrangement in the flow path unit 27. However, the arrangement direction of the liquid flow paths 28 is not limited to this. For example, as shown in FIG. 13 , the first liquid flow path 28a, the second liquid flow path 28b, and the third liquid flow path 28c may be arranged in a front-to-back arrangement in the flow path unit 27. In this case, too, the first supply manifold 40a is connected only to the second return manifold 50b via the first bypass 61. The first return manifold 50a is connected only to the third supply manifold 40c via the second bypass 62. As a result, the supply manifold 40 and the return manifold 50 of a certain liquid flow path 28 are connected to different liquid flow paths 28 in a one-to-one relationship via the bypass 60. This reduces crosstalk and makes it possible to equalize the flow rates of liquid in the manifolds 40 and 50.

[0063] In the above embodiment and all of the modified examples, the liquid ejection device 10 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 10 is provided with a carriage that mounts the head 20 and moves the head 20 in the left-right direction. The liquid ejection device 10 alternately performs a recording operation in which liquid is ejected from the head 20 while moving the carriage, and a transport operation in which the transport device 17 transports the recording medium A, thereby performing a printing process in which an image is printed on the recording medium A.

[0064] In the above embodiment and modified examples, the head 20 employs a system using a piezoelectric element (piezo system), but is not limited to this system. For example, the head 20 may employ a thermal system using a heating element, or an electrostatic system using a conductive diaphragm and electrodes.

[0065] 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]

[0066] INDUSTRIAL APPLICABILITY The liquid ejection device of the present invention is useful as a liquid ejection device that can reduce crosstalk and achieve uniformity in the flow rate of liquid in the manifold. [Explanation of symbols]

[0067] 10:Liquid discharge device 15a: First tank 15b: Second tank 27: Flow path unit 28: Liquid flow path 28a: First liquid flow path 28b: Second liquid flow path 28c: Third liquid flow path 30: Individual channel 31: Nozzle 40: Supply manifold 41: Supply port 41a: 1st supply port 41b: 2nd supply port 50: Feedback manifold 60: Bypass 61: First Bypass 62: Second Bypass 63: Third Bypass

Claims

1. a plurality of liquid flow paths each including an individual channel including a nozzle, a supply manifold connected to the individual channel to supply liquid to the individual channel, and a return manifold connected to the individual channel through which liquid not ejected from the nozzle flows; a bypass connecting the supply manifold and the return manifold through which liquid flows; the plurality of liquid flow paths include a first liquid flow path, a second liquid flow path, and a third liquid flow path aligned in a predetermined first direction; the supply manifold of the first liquid flow path is connected only to the return manifold of the second liquid flow path via a first bypass of the bypass; the return manifold of the first liquid flow path is connected only to the supply manifold of the third liquid flow path via a second bypass of the bypass; A liquid ejection device, wherein the supply manifold of the second liquid flow path is connected only to the return manifold of the third liquid flow path via a third bypass of the bypass.

2. The liquid ejection device according to claim 1 , wherein the second bypass has a larger cross-sectional area through which the liquid flows than the first bypass and the third bypass.

3. the supply manifold and the return manifold extend in a second direction intersecting the first direction; 3. The liquid ejection device according to claim 1, wherein the second bypass has a larger dimension in a third direction intersecting the first direction and the second direction than the first bypass and the third bypass.

4. the supply manifold and the return manifold extend in a second direction intersecting the first direction; the individual channel of the first liquid flow path is located on one side of the second direction relative to the first bypass, and the individual channel of the second liquid flow path is located on one side of the second direction relative to the third bypass; 4. A liquid ejection device according to claim 1, wherein the second bypass is located in the second direction between the individual channel of the first liquid flow path and the first bypass, and between the individual channel of the second liquid flow path and the third bypass.

5. the supply manifold and the return manifold extend in a second direction intersecting the first direction; the individual channel of the first liquid flow path is located on one side of the second direction relative to the first bypass, and the individual channel of the second liquid flow path is located on one side of the second direction relative to the third bypass; The liquid ejection device according to claim 1 , wherein the second bypass is located on the other side of the second direction than both the first bypass and the third bypass.

6. a piezoelectric element that applies a discharge pressure to the liquid in the individual channel to discharge the liquid from the nozzle; the supply manifold and the return manifold extend in a second direction intersecting the first direction; the piezoelectric element, the supply manifold, and the return manifold are arranged in this order in a third direction intersecting the first direction and the second direction; The liquid ejection device according to claim 1 , wherein the bypass is disposed at the same position as the supply manifold in the third direction, or at a position closer to the supply manifold than the return manifold in the third direction.

7. a plurality of flow path units each including a plurality of the liquid flow paths and the bypass; 7. The liquid ejection device according to claim 1, wherein the supply manifold included in one set of the flow path units is provided with a first supply port through which liquid is supplied from a first tank, and the supply manifold included in the other set of the flow path units is provided with a second supply port through which liquid is supplied from a second tank.

8. The liquid ejection device according to claim 7 , wherein the bypasses of the plurality of flow path units have the same layout.

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