JP7552251B2 - Liquid ejection head - Google Patents

Description

The present invention relates to a liquid ejection head that ejects liquid such as ink.

Conventionally, a known configuration has been to include a supply manifold and a return manifold, and circulates ink between an ink tank and a liquid ejection head, with the aim of preventing the ink inside the nozzles from becoming too viscous.

For example, Patent Document 1 discloses a liquid ejection head with a two-story supply manifold and return manifold. Each manifold is provided with a damper section, so that even if the ink circulation and continuous ink ejection are suddenly stopped due to a power outage for some reason, water hammer is unlikely to occur due to inertial flow. In addition, the flow path length from the supply manifold to the nozzle is longer than the flow path length from the nozzle to the return manifold, so the inertial flow from the supply manifold is absorbed by the flow path between the supply manifold and the nozzle.

JP 2020-104294 A

However, because the supply manifold has a greater liquid flow rate than the return manifold, simply providing a damper as described above is not enough to prevent water hammer. This poses the risk of meniscus break. A meniscus break occurs when the force acting on the ink being ejected from the nozzle becomes greater than the surface tension of the ink, causing the ink to leak out of the nozzle. When such a meniscus break occurs, ink may adhere unnecessarily to the paper, or maintenance may be required to form a new meniscus.

The present invention aims to provide a liquid ejection head that can prevent meniscus breaks from occurring.

The liquid ejection head of the present invention includes a supply manifold to which liquid is supplied from the outside, a return manifold arranged below the supply manifold and through which the liquid is discharged to the outside, a return damper section provided in the return manifold, a plurality of individual flow paths each having an upstream end connected to the supply manifold and a downstream end connected to the return manifold and each individually communicating with a plurality of nozzles arranged in a row on the nozzle surface, a supply damper section provided in the supply manifold, and a return damper section provided in the return manifold, and the flow path length from the supply manifold to the nozzle is greater than the flow path length from the nozzle to the return manifold, and the compliance of the supply manifold is greater than the compliance of the return manifold.

According to the present invention, damper sections are provided in both the supply manifold and the return manifold, the flow path length from the supply manifold to the nozzle is greater than the flow path length from the nozzle to the return manifold, and the compliance of the supply manifold is greater than the compliance of the return manifold, so that sudden fluctuations in pressure in the flow path from the supply manifold to the nozzle are suppressed more than in the past. As a result, the occurrence of meniscus break can be suppressed.

The present invention provides a liquid ejection head that can prevent meniscus breaks from occurring.

1 is a plan view showing a schematic configuration of a liquid ejection device including a liquid ejection head according to a first embodiment. 2 is a cross-sectional view of the liquid ejection head of FIG. 1 taken along a line perpendicular to the extending direction. FIG. 2 is a side view showing the general shape of a supply manifold and a return manifold. FIG. 2 is a plan view showing a supply manifold, a return manifold, and individual flow paths. FIG. 2 is a plan view of a frame on which a plurality of liquid ejection heads are mounted. FIG. 11 is a cross-sectional view showing a modified example of the supply manifold. FIG. 11 is a cross-sectional view showing a further modified example of the supply manifold.

A liquid ejection head according to an embodiment of the present invention will be described below with reference to the drawings. The liquid ejection head described below is merely one embodiment of the present invention. Therefore, the present invention is not limited to the following embodiment, and additions, deletions, and modifications are possible without departing from the spirit of the present invention.

<Configuration of Liquid Ejection Apparatus>
A liquid ejection device 10 including a liquid ejection head 20 according to this embodiment ejects liquid such as ink. In the following, an example in which the liquid ejection device 10 is applied to an inkjet printer will be described, but the application of the liquid ejection device 10 is not limited to this.

As shown in FIG. 1, the liquid ejection device 10 employs, for example, a line head system and includes a platen 11, a conveying unit, a head unit 16, and a tank 12. However, the liquid ejection device 10 is not limited to the line head system, and may employ other systems, such as a serial head system.

The platen 11 is a flat member on whose upper surface the paper 14 is placed, and which plays a role in determining the distance between the paper 14 and the head unit 16. Note that the side of the platen 11 facing the head unit 16 is referred to as the upper side, and the opposite side is referred to as the lower side, but the arrangement of the liquid ejection device 10 is not limited to this.

The transport section has, for example, two transport rollers 15 and a transport motor (not shown). The two transport rollers 15 are connected to the transport motor and are arranged parallel to each other along a direction perpendicular to the transport direction of the paper 14 (orthogonal direction) with the platen 11 sandwiched between them. When the transport motor is driven, the transport rollers 15 rotate and the paper 14 on the platen 11 is transported in the transport direction.

The head unit 16 has a length equal to or greater than the length of the paper 14 in the orthogonal direction. The head unit 16 is provided with a plurality of liquid ejection heads 20.

The liquid ejection head 20 has a laminate of a flow path forming body and a volume changing section. The flow path forming body has a liquid flow path formed therein, and a plurality of nozzle holes 21a are opened in the ejection surface (nozzle surface) 40a. The volume changing section is driven to change the volume of the liquid flow path. In this case, the meniscus vibrates in the nozzle holes 21a, and liquid is ejected. Details of the liquid ejection head 20 will be described later.

When the liquid is, for example, ink, a tank 12 is provided for each type of ink. For example, four tanks 12 are provided, and black, yellow, cyan, and magenta ink are stored in each of the four tanks 12. The ink in the tanks 12 is supplied to the corresponding nozzle holes 21a.

<Configuration of Liquid Ejection Head>
As described above, the liquid ejection head 20 includes a flow path forming body and a volume changing portion. As shown in Fig. 2, the flow path forming body is a laminate of a plurality of plates (e.g., metal plates), and the volume changing portion includes a vibration plate 55 and a piezoelectric element 60.

The multiple plates include a nozzle plate 40, a first flow path plate 41, a second flow path plate 42, a third flow path plate 43, a fourth flow path plate 44, a fifth flow path plate 45, a sixth flow path plate 46, a seventh flow path plate 47, an eighth flow path plate 48, a ninth flow path plate 49, a tenth flow path plate 50, an eleventh flow path plate 51, a twelfth flow path plate 52, a thirteenth flow path plate 53, and a fourteenth flow path plate 54. These plates are stacked in this order.

Each plate has holes and grooves of various sizes. Inside the flow path forming body where the plates are stacked, the holes and grooves combine to form a number of nozzles 21, a number of individual flow paths 64, a supply manifold 22, and a return manifold 23 as liquid flow paths.

The nozzles 21 are formed penetrating the nozzle plate 40 in the stacking direction (vertical direction). In the ejection surface 40a of the nozzle plate 40, a plurality of nozzle holes 21a, which are the tips of the nozzles 21, are arranged in a direction (hereinafter referred to as the extension direction) along a predetermined row (nozzle row). The extension direction is perpendicular to the stacking direction and the width direction described below.

The supply manifold 22 extends in the extension direction and is connected to a plurality of individual flow paths 64. The return manifold 23 extends in the extension direction and is connected to a plurality of individual flow paths 64. The supply manifold 22 is disposed above the return manifold 23.

Here, the general shapes of the supply manifold 22 and the return manifold 23 will be described. Figure 3 is a perspective view showing the general shapes of the supply manifold 22 and the return manifold 23 in this embodiment. Note that the supply manifold 22 and the return manifold 23 are liquid flow paths and are hollow, and Figure 3 shows the hollows with external lines.

As shown in FIG. 3, in this embodiment, the supply manifold 22 and the return manifold 23 are both formed in an L-shape. The supply manifold 22 includes a main portion 122a extending along the extension direction and a standing portion 122b erected in the stacking direction at one end of the main portion 122a. The return manifold 23 includes a main portion 123a extending along the extension direction and a standing portion 123b erected in the stacking direction at one end of the main portion 123a. Furthermore, the supply manifold 22 and the return manifold 23 are connected by a bypass flow path 75. In detail, one end of the main portion 122a of the supply manifold 22 (the end opposite the standing portion 122b) and one end of the main portion 123a of the return manifold 23 (the end opposite the standing portion 123b) are connected by the bypass flow path 75.

The main part 122a of the supply manifold 22 is disposed above the main part 123a of the return manifold 23. More specifically, the main part 123a of the return manifold 23 is disposed below the main part 122a of the supply manifold 22 and is disposed so as to overlap the main part 122a of the supply manifold 22 in a plan view. The upright part 123b of the return manifold 23 is disposed outside the upright part 122b of the supply manifold 22 in a plan view at one end of the main part 123a in the extension direction. Also, the upright part 122b of the supply manifold 22 is disposed inside the upright part 123b of the return manifold 23 when viewed from the other side in the extension direction. In this configuration, one end of the supply manifold 22 (upright part 122b) is located inside the one end of the return manifold 23 (upright part 123b) in the extension direction of the supply manifold 22.

In this embodiment, the width (length in the width direction) of the main portion 122a of the supply manifold 22 is the same as the width (length in the width direction) of the erected portion 122b, and is, for example, 1 to 2 mm. The thickness H1 of the main portion 122a of the supply manifold 22 is, for example, 0.35 to 0.45 mm. The height H3 of the erected portion 122b of the supply manifold 22 is, for example, 0.1 to 0.2 mm. The length (length in the extension direction) L11 of the main portion 122a of the supply manifold 22 is, for example, 42 to 43 mm. Here, the liquid ejection head 20 of this embodiment is provided with, for example, 70 channels (ch), that is, 70 nozzles. The distance between the nozzles is, for example, 0.5 mm to 0.6 mm. And the channel portion length L1, which is the length from 1ch to 70ch, is, for example, 30 mm to 40 mm. In addition, the distance L2 from the outer surface of the erected portion 122b of the supply manifold 22 to 1ch is, for example, 6 to 8 mm. In addition, the maximum diameter (or aperture) of the erected portion 122b is, for example, 1 to 2 mm.

On the other hand, the width of the main portion 123a of the feedback manifold 23 is the same as the width of the standing portion 123b, and is, for example, 1 to 2 mm. The thickness H2 of the main portion 123a of the feedback manifold 23 is, for example, 0.25 to 0.34 mm. Thus, the thickness H1 of the main portion 122a of the supply manifold 22 is greater than the thickness H2 of the main portion 123a of the feedback manifold 23. Also, the height H4 of the standing portion 123b of the feedback manifold 23 is, for example, 0.5 to 0.6 mm. Also, the length (length in the extension direction) L21 of the main portion 123a of the feedback manifold 23 is, for example, 45 to 46 mm. Thus, the longitudinal length of the feedback manifold 23, i.e., the length L21 of the main portion 123a, is longer than the longitudinal length of the supply manifold 22, i.e., the length L11 of the main portion 122a. In addition, the distance L3 from the outer surface of the erected portion 123b of the return manifold 23 to 1ch is, for example, 9 to 11 mm. In addition, the maximum diameter (or aperture) of the erected portion 123b is, for example, 1 to 2 mm.

In this embodiment, the compliance of the supply manifold 22 is greater than the compliance of the return manifold 23. Hereinafter, the compliance of the return manifold 23 means the compliance of the main portion 123a of the return manifold 23, and the compliance of the supply manifold 22 means the compliance of the main portion 122a of the supply manifold 22. The compliance of each manifold can be calculated by the following formula. In the following calculation formula, V is the volume of each manifold, c is the ink sound speed in the manifold, and ρ is the ink density.

Compliance Cp = V/c ² × ρ

In this embodiment, the flow path length from the supply manifold 22 to the nozzle 21 is greater than the flow path length from the nozzle 21 to the return manifold 23. Specifically, the flow path length from the downstream end of the supply manifold 22 to the upstream end of the nozzle 21 is greater than the flow path length from the upstream end of the nozzle 21 to the upstream end of the return manifold 23. The volume of the main portion 122a of the supply manifold 22 is greater than the volume of the main portion 123a of the return manifold 23. The volume of the main portion 122a of the supply manifold 22 is, for example, 24 to 27 mm ³ , and the volume of the main portion 123a of the return manifold 23 is, for example, 20 to 23 mm ^3. The ratio of the volume of the main portion 122a of the supply manifold 22 to the volume of the main portion 123a of the return manifold 23 is, for example, 1.1. The ink density is, for example, 1054 kg/m ^3. The ink sonic speed in each manifold is, for example, 91 m/s. Note that this ink sonic speed takes into consideration the function of each damper section. In other words, the ink sonic speed is the speed used when calculating the compliance of each manifold including the effect of each damper section on the manifold. In this embodiment, the compliance of the supply manifold 22 is, for example, 2.4 to 2.8×10 ⁻¹⁵ m ³ /Pa, and the compliance of the return manifold 23 is, for example, 1.9 to 2.3×10 ⁻¹⁵ m ³ /Pa. Furthermore, the ratio of the compliance of the supply manifold 22 to the compliance of the return manifold 23 is less than 2.0. Specifically, the ratio of the compliance of the supply manifold 22 to the compliance of the return manifold 23 is, for example, 1.1 to 1.5.

The main portion 122a of the supply manifold 22 is formed by through holes penetrating the seventh flow path plate 47 to the eleventh flow path plate 51 in the stacking direction, and by recesses recessed from the lower surface of the twelfth flow path plate 52, which are overlapped in the stacking direction. Therefore, the lower end of the main portion 122a of the supply manifold 22 is covered by the sixth flow path plate 46, and its upper end is covered by the upper portion of the twelfth flow path plate 52. In addition, the erected portion 122b of the supply manifold 22 is formed by through holes penetrating the seventh flow path plate 47 to the fourteenth flow path plate 54 in the stacking direction.

The main portion 123a of the return manifold 23 is formed by through holes penetrating the second flow path plate 42 to the fourth flow path plate 44 in the stacking direction, and a recess recessed from the lower surface of the fifth flow path plate 45, which are overlapped in the stacking direction. Therefore, the lower end of the main portion 123a of the return manifold 23 is covered by the first flow path plate 41, and its upper end is covered by the upper part of the fifth flow path plate 45. In addition, the erected portion 123b of the return manifold 23 is formed by through holes penetrating the second flow path plate 42 to the fourteenth flow path plate 54 in the stacking direction.

An air layer 24, which is a buffer space, is disposed between the main portion 122a of the supply manifold 22 and the main portion 123a of the return manifold 23. The air layer 24 is formed by a recess recessed from the lower surface of the sixth flow path plate 46. By sandwiching the air layer 24 between the main portion 122a of the supply manifold 22 and the main portion 123a of the return manifold 23 in this manner, it is possible to reduce the mutual action of the liquid pressure in the main portion 122a of the supply manifold 22 and the liquid pressure in the main portion 123a of the return manifold 23. In addition, by forming the air layer 24, the upper portion of the sixth flow path plate 46 functions as a supply damper portion 70, and the upper portion of the fifth flow path plate 45 functions as a return damper portion 71.

The compliance of the supply damper section 70 is the same as the compliance of the return damper section 71. This means that the degree to which the provision of the supply damper section 70 affects the compliance of the supply manifold 22 (degree of pressure fluctuation damping function) is equal to the degree to which the provision of the return damper section 71 affects the compliance of the return manifold 23.

As shown in FIG. 4, a cylindrical supply port 22a is provided on the upper part of the upright portion 122b of the supply manifold 22. The upper end of the upright portion 122b, which is a supply path, is connected to the internal space of this supply port 22a. The upright portion 122b extends downward from the supply port 22a. For example, the upright portion 122b is formed by penetrating the upper part of the 12th flow path plate 52, the 13th flow path plate 53, the 14th flow path plate 54, the vibration plate 55, and the insulating film 56. The lower end of the upright portion 122b is connected to the supply port 22c provided in the main portion 122a of the supply manifold 22.

Also, as shown in FIG. 4, a cylindrical return port 23a is provided on the upper part of the standing portion 123b of the return manifold 23. The upper end of the standing portion 123b, which is a return path, is connected to this return port 23a. The standing portion 123b extends downward from the return port 23a. For example, the standing portion 123b is formed by penetrating the upper part of the fifth flow path plate 45, the upper part of the sixth flow path plate 46, the upper part of the seventh flow path plate 47, the eighth flow path plate 48, the ninth flow path plate 49, the tenth flow path plate 50, the eleventh flow path plate 51, the upper part of the twelfth flow path plate 52, the thirteenth flow path plate 53, the fourteenth flow path plate 54, the vibration plate 55, and the insulating film 56. The lower end of the standing portion 123b is connected to the return port 23c provided in the main portion 123a of the return manifold 23. The return port 23a is arranged outside the supply port 22a in the extension direction.

Returning to FIG. 2, the multiple individual flow paths 64 are connected to the supply manifold 22 and the return manifold 23. The upstream end of each individual flow path 64 is connected to the supply manifold 22, and the downstream end is connected to the return manifold 23, with the individual flow paths 64 connected to the base end of the nozzle 21 between them. Each individual flow path 64 has a first communication hole 25, a supply throttle path 26, a second communication hole 27, a pressure chamber 28, a descender 29, a return throttle path 31, and a third communication hole 32, which are arranged in this order.

The first communication hole 25 has a lower end connected to the upper end of the supply manifold 22, extends upward from the supply manifold 22 in the stacking direction, and penetrates the upper portion of the 12th flow path plate 52 in the stacking direction. The first communication hole 25 is located to one side (the right side in FIG. 2) of the center in the width direction of the supply manifold 22.

One end 26b (FIG. 4) of the supply throttle passage 26 is connected to the upper end of the first communication hole 25. The supply throttle passage 26 is formed, for example, by half etching, and is configured as a groove recessed from the lower surface of the thirteenth flow path plate 53. The second communication hole 27 has its lower end connected to the other end 26a (FIG. 4) of the supply throttle passage 26, extends upward in the stacking direction from the supply throttle passage 26, and penetrates the upper portion of the thirteenth flow path plate 53 in the stacking direction. The second communication hole 27 is located on the other side (left side in FIG. 2) of the center of the supply manifold 22 in the width direction.

One end 28b (FIG. 4) of the pressure chamber 28 is connected to the upper end of the second communication hole 27. The pressure chamber 28 is formed penetrating the 14th flow path plate 54 in the stacking direction.

The descender 29 penetrates the first flow path plate 41 to the thirteenth flow path plate 53 in the stacking direction, and is disposed on the other side (left side in FIG. 2) of the supply manifold 22 and the return manifold 23 in the width direction. The descender 29 has an upper end connected to the other end 28a (FIG. 4) of the pressure chamber 28, and a lower end connected to the nozzle 21. For example, the nozzle 21 overlaps the descender 29 in the stacking direction, and is disposed in the center of the descender 29 in the direction perpendicular to the stacking direction. The cross-sectional area of the descender 29 may be constant or may vary in the stacking direction.

The return throttle passage 31 has one end 31b (FIG. 4) connected to the lower end of the descender 29. The return throttle passage 31 is formed, for example, by half-etching, and is configured as a groove recessed from the lower surface of the first flow path plate 41.

The third communication hole 32 has its lower end connected to the other end 31a (FIG. 4) of the return throttle passage 31, extends upward in the stacking direction from the return throttle passage 31, and penetrates the upper portion of the first flow path plate 41 in the stacking direction. The third communication hole 32 has its upper end connected to the lower end of the return manifold 23. The third communication hole 32 is located on the other side (left side in FIG. 2) of the center of the return manifold 23 in the width direction.

The vibration plate 55 is laminated on the 14th flow path plate 54 and covers the upper end opening of the pressure chamber 28. The vibration plate 55 may be formed integrally with the 14th flow path plate 54. In this case, the pressure chamber 28 is formed recessed from the lower surface of the 14th flow path plate 54 in the lamination direction. The portion of the 14th flow path plate 54 above the pressure chamber 28 functions as the vibration plate 55.

The piezoelectric element 60 includes a common electrode 61, a piezoelectric layer 62, and an individual electrode 63, which are arranged in this order. The common electrode 61 covers the entire surface of the vibration plate 55 via an insulating film 56. The piezoelectric layer 62 is provided for each pressure chamber 28, and is arranged on the common electrode 61 so as to overlap the pressure chamber 28. The individual electrode 63 is provided for each pressure chamber 28, and is arranged on the piezoelectric layer 62. In this case, one piezoelectric element 60 is composed of one individual electrode 63, the common electrode 61, and the portion of the piezoelectric layer 62 (active portion) sandwiched between the two electrodes.

The individual electrodes 63 are electrically connected to a driver IC. This driver IC receives a control signal from a control unit (not shown), generates a drive signal (voltage signal), and applies it to the individual electrodes 63. In contrast, the common electrode 61 is always held at ground potential.

In response to the drive signal, the active portion of the piezoelectric layer 62 expands and contracts in the planar direction together with the two electrodes 61, 63. In response to this, the vibration plate 55 deforms in cooperation with the electrodes, changing the direction to increase or decrease the volume of the pressure chamber 28. As a result, an ejection pressure that ejects liquid from the nozzle 21 is applied to the pressure chamber 28 in accordance with the volume of the pressure chamber 28.

Next, FIG. 5 shows a plan view of a frame 65 on which multiple liquid ejection heads 20 of this embodiment are mounted.

As shown in FIG. 5, multiple liquid ejection heads 20 are arranged along the extension direction. As explained in FIG. 4, a supply port 22a and a return port 23a are provided on one side in the extension direction (the left side in FIG. 5). The supply port 22a and the return port 23a are provided for each supply manifold 22 and return manifold 23. Each supply port 22a and each return port 23a is arranged closer to the center in the width direction than the supply manifold 22 and the return manifold 23 located at one and the other ends in the width direction.

<Liquid flow>
The flow of liquid such as ink in the liquid ejection head 20 of this embodiment will be described. The supply port 22a is connected to the tank 12 via a supply pipe, and the return port 23a is connected to the tank 12 via a return pipe. In this configuration, when the pump of the supply pipe and the negative pressure pump (not shown) of the return pipe are driven, the liquid flows from the tank 12 through the supply pipe and into the supply manifold 22 via the supply port 22a.

During this time, a portion of the liquid flows into the individual flow paths 64. The liquid flows from the supply manifold 22 through the first communication hole 25 into the supply throttle path 26, and from the supply throttle path 26 through the second communication hole 27 into the pressure chamber 28. The liquid then flows in the stacking direction from the top end to the bottom end through the descender 29, and flows into the nozzle 21. When an ejection pressure is applied to the pressure chamber 28 by the piezoelectric element 60, the liquid is ejected from the nozzle hole 21a.

A portion of the liquid that is not ejected from the nozzle hole 21a flows through the return throttle passage 31 and enters the return manifold 23 via the third communication hole 32. The liquid that flows into the return manifold 23 via the third communication hole 32 flows through the return manifold 23, is discharged to the outside from the return port 23a, and returns to the tank 12 through the return piping. As a result, the liquid that is not ejected from the nozzle hole 21a circulates between the tank 12 and the individual flow paths 64.

As described above, according to the liquid ejection head 20 of this embodiment, damper sections are provided in both the supply manifold 22 and the return manifold 23, the flow path length from the supply manifold 22 to the nozzle 21 is greater than the flow path length from the nozzle 21 to the return manifold 23, and the compliance of the supply manifold 22 is greater than the compliance of the return manifold 23. This makes it possible to prevent the pressure in the flow path from the supply manifold 22 to the nozzle 21 from fluctuating suddenly more than in the past. This makes it possible to suppress the occurrence of meniscus breaks.

In addition, in this embodiment, the volume of the main portion 122a of the supply manifold 22 is larger than the volume of the main portion 123a of the return manifold 23. In this case, it is easier to increase the compliance by increasing the compliance of the main portion 122a of the supply manifold 22 rather than increasing the damping performance of the supply manifold 22. This is because the damper portion is formed by half etching, and it is difficult to control the depth of the half etching, whereas the supply manifold 22 is formed by full etching, and therefore it is easier to change the design than the half etching.

In addition, in this embodiment, the thickness H1 of the main portion 122a of the supply manifold 22 is greater than the thickness H2 of the main portion 123a of the return manifold 23. In this case, the thickness H1 of the supply manifold 22 can be easily increased by simply increasing the number of plates that constitute the supply manifold 22, and therefore the volume of the supply manifold 22 can be increased.

In addition, in this embodiment, the ratio of the compliance of the supply manifold 22 to the compliance of the return manifold 23 is less than 2.0 (e.g., 1.1). In this case, by making the compliance of the supply manifold 22 greater than the compliance of the return manifold 23 while avoiding an increase in the head size, it is possible to reduce the pressure fluctuation of the ejection.

In addition, in this embodiment, the compliance of the supply damper section 70 and the compliance of the return damper section 71 are the same. In other words, the degree to which the provision of the supply damper section 70 affects the compliance of the supply manifold 22 (degree of pressure fluctuation damping function) can be made equal to the degree to which the provision of the return damper section 71 affects the compliance of the return manifold 23. Also, by making the design of each damper section the same, each damper section can be manufactured using the same process.

In addition, in this embodiment, the main part 122a of the supply manifold 22 is disposed above the main part 123a of the return manifold 23. In this case, by forming a two-story structure of the main part 122a of the supply manifold 22 and the main part 123a of the return manifold 23, the head can be made smaller in the planar direction.

In addition, in this embodiment, the main portion 122a of the supply manifold 22 and the main portion 123a of the return manifold 23 are connected by a bypass flow path 75. In this case, by providing the bypass flow path 75, the flow rate of the liquid flowing through the supply manifold 22 and the return manifold 23 can be increased, and therefore the air discharge performance can be improved.

Furthermore, in this embodiment, one end (standing portion 122b) of the supply manifold 22 is located inside one end (standing portion 123b) of the return manifold 23 in the extension direction of the supply manifold 22. In this case, when realizing a two-story structure in which the main portion 122a of the supply manifold 22 is arranged above the main portion 123a of the return manifold 23, the supply port 22a and the return port 23a can be arranged without interfering with each other in the longitudinal direction of each manifold.

<Modification>
The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present invention. For example, the following modifications are possible.

The shape of the supply manifold may be modified as follows. As shown in FIG. 6, the supply manifold 222 has a lower portion 222b located on the return manifold 223 side, and an upper portion 222a located above the lower portion 222b and having a larger area in a plan view than the lower portion 222b. By configuring it in this way, the volume of the supply manifold 222 can be increased without changing the area of the supply damper section 70.

The shape of the supply manifold may be further modified as follows. The supply manifold 322 is formed of two or more plates. As shown in FIG. 7, the supply manifold 322 is formed of, for example, five plates 147-151. The through holes 322a of the upper plates 149-151 have a larger area in a plan view than the through holes 322b of the plates 147, 148 located below them. By configuring it in this way, the volume of the supply manifold 322 can be increased simply by changing the through hole area (i.e., the etched area) of the plates.

In addition, in the above embodiment, the main portion 122a of the supply manifold 22 and the main portion 123a of the return manifold 23 each extend in the extension direction, but this is not limited to this. The main portion 122a of the supply manifold 22 and the main portion 123a of the return manifold 23 may each extend in the width direction.

In addition, in the above embodiment, the supply damper section 70 is disposed below the main section 122a of the supply manifold 22, and the return damper section 71 is disposed above the main section 123a of the return manifold 23, but this is not limited to the above. Each damper section may be disposed to the side in the extension direction of each manifold.

In addition, in the above embodiment, the shape of the supply manifold 22 is L-shaped, but this is not limited to this, and the supply manifold 22 may be formed of only the main portion 122a. Also, the shape of the return manifold 23 is L-shaped, but this is not limited to this, and the return manifold 23 may be formed of only the main portion 123a.

REFERENCE SIGNS LIST 10 Liquid ejection device 20 Liquid ejection head 21 Nozzle 22, 222, 322 Supply manifold 22a Supply port 23, 223 Return manifold 23a Return port 31 Return throttle passage 40a Nozzle surface 64 Individual flow path 70 Supply damper section 71 Return damper section 75 Bypass flow path 122a Main portion of supply manifold 122b Standing portion of supply manifold 123a Main portion of return manifold 123b Standing portion of return manifold

Claims (9)

a supply manifold to which liquid is supplied from an external source;
a return manifold through which the liquid is discharged to the outside;
a plurality of individual flow paths each having an upstream end connected to the supply manifold and a downstream end connected to the return manifold, the individual flow paths being individually connected to a plurality of nozzles arranged in a row on the nozzle face;
A supply damper portion provided in the supply manifold;
A return damper portion provided in the return manifold,
a flow path length from the supply manifold to the nozzle is greater than a flow path length from the nozzle to the return manifold;
the compliance of the supply manifold is greater than the compliance of the return manifold;
The liquid ejection head, wherein the supply manifold is disposed above the return manifold . The liquid ejection head of claim 1, wherein the volume of the supply manifold is greater than the volume of the return manifold. The liquid ejection head according to claim 1 or 2, wherein the thickness of the supply manifold is greater than the thickness of the return manifold. The liquid ejection head according to any one of claims 1 to 3, wherein the ratio of the compliance of the supply manifold to the compliance of the return manifold is less than 2.0. The liquid ejection head according to any one of claims 1 to 4, wherein the compliance of the supply damper section and the compliance of the return damper section are the same. a supply manifold to which liquid is supplied from an external source;
a return manifold through which the liquid is discharged to the outside;
a plurality of individual flow paths each having an upstream end connected to the supply manifold and a downstream end connected to the return manifold, the individual flow paths being individually connected to a plurality of nozzles arranged in a row on the nozzle face;
A supply damper portion provided in the supply manifold;
A return damper portion provided in the return manifold,
a flow path length from the supply manifold to the nozzle is greater than a flow path length from the nozzle to the return manifold;
the compliance of the supply manifold is greater than the compliance of the return manifold;
The liquid ejection head further comprises a bypass flow path connecting the supply manifold and the return manifold. a supply manifold to which liquid is supplied from an external source;
a return manifold through which the liquid is discharged to the outside;
a plurality of individual flow paths each having an upstream end connected to the supply manifold and a downstream end connected to the return manifold, the individual flow paths being individually connected to a plurality of nozzles arranged in a row on the nozzle face;
A supply damper portion provided in the supply manifold;
A return damper portion provided in the return manifold,
a flow path length from the supply manifold to the nozzle is greater than a flow path length from the nozzle to the return manifold;
the compliance of the supply manifold is greater than the compliance of the return manifold;
The liquid ejection head, wherein the supply manifold has a lower portion located on the return manifold side, and an upper portion located above the lower portion and having a larger area in a plan view than the lower portion. a supply manifold to which liquid is supplied from an external source;
a return manifold through which the liquid is discharged to the outside;
a plurality of individual flow paths each having an upstream end connected to the supply manifold and a downstream end connected to the return manifold, the individual flow paths being individually connected to a plurality of nozzles arranged in a row on the nozzle face;
A supply damper portion provided in the supply manifold;
A return damper portion provided in the return manifold,
a flow path length from the supply manifold to the nozzle is greater than a flow path length from the nozzle to the return manifold;
the compliance of the supply manifold is greater than the compliance of the return manifold;
The liquid ejection head, wherein the supply manifold is formed of two or more plates, and a through hole of an upper one of the two or more plates has a larger area in a plan view than a through hole of a lower one of the upper one. a supply manifold to which liquid is supplied from an external source;
a return manifold through which the liquid is discharged to the outside;
a plurality of individual flow paths each having an upstream end connected to the supply manifold and a downstream end connected to the return manifold, the individual flow paths being individually connected to a plurality of nozzles arranged in a row on the nozzle face;
A supply damper portion provided in the supply manifold;
A return damper portion provided in the return manifold,
a flow path length from the supply manifold to the nozzle is greater than a flow path length from the nozzle to the return manifold;
the compliance of the supply manifold is greater than the compliance of the return manifold;
A liquid ejection head, wherein one end of the supply manifold in a longitudinal direction is located more inward in the longitudinal direction of the supply manifold than one end of the return manifold in the longitudinal direction.

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