Patent Grant
11285726
This application claims priority from Japanese Patent Application No. 2019-103638 filed on Jun. 3, 2019, the content of which is incorporated herein by reference in its entirety.
Aspects of the disclosure relate to a liquid ejection head and a liquid ejection apparatus including the liquid ejection head.
In order to reduce the difference in ejection characteristic caused by the ink temperature, a known liquid ejection head includes a thermistor disposed at or near a channel, and an actuator configured to, upon receipt of a drive voltage changed based on the ink temperature detected by the thermistor, apply ejection energy to ink in a pressure chamber. In this case, it is preferable to position the thermistor immediately upstream of the pressure chamber to reduce the difference between the ink temperature detected by the thermistor and the actual temperature of ink flowing into the pressure chamber. However, the thermistor is not be allowed to be positioned in the liquid ejection head filled with densely arranged components and is forcibly positioned spaced apart from the pressure chamber. This structure may cause a considerable difference between the ink temperature detected by the thermistor and the actual temperature of ink which reaches the pressure chamber after cooling off in the channel.
Aiming at reducing temperature changes of ink in a channel, another known liquid ejection head includes a supply manifold and a return manifold through which ink is circulated between an ink tank and the liquid ejection head. The supply manifold is disposed above the return manifold. A lower portion of the supply manifold is covered by the return manifold so as to be protected from an external space.
However, in the known liquid ejection head of the circulation type, it is desired to further reduce the difference between the ink temperature detected by a thermistor and the temperature of ink flowing into a pressure chamber because the ink is likely to cool off in a supply channel leading to the pressure chamber.
Aspects of the disclosure provide a liquid ejection head and a liquid ejection apparatus including the liquid ejection head, the liquid ejection head being configured to prevent or reduce, more than before, cooling of liquid before it reaches a pressure chamber.
According to one or more aspects of the disclosure, a liquid ejection head includes a supply manifold including a supply port through which liquid is supplied from an exterior, a return manifold including a return port through which liquid is discharged to the exterior, and a plurality of individual channels each connected, at an upstream end thereof, to the supply manifold and, at a downstream end thereof, to the return manifold. Each of the individual channels communicates with a corresponding one of nozzles arranged in an array on a nozzle surface. The supply manifold and the return manifold extend in an extending direction along the array of the nozzles. The return manifold includes a lower portion located below the supply manifold to overlap the supply manifold in plan view orthogonal to the nozzle surface, and a standing portion located at at least one of opposite ends of the lower portion in the extending direction to be outside the supply manifold in plan view. The standing portion has a height to cover at least a portion of an end of the supply manifold when viewed in the extending direction.
Aspects of the disclosure are illustrated by way of example and not by limitation in the accompanying figures in which like reference characters indicate similar elements.
Illustrative embodiments of the disclosure will be described with reference to the drawings. Liquid ejection heads to be described according to illustrative embodiments are merely examples and not limited thereto. Various changes, additions, and deletions may be applied in the illustrative embodiments without departing from the spirit and scope of the disclosure.
<Structure of Liquid Ejection Apparatus>
A liquid ejection apparatus 10 including a liquid ejection head 20 according to a first illustrative embodiment is configured to eject liquid, such as ink. Hereinafter, the liquid ejection apparatus 10 will be described by way of example as applied to, but not limited to, an inkjet printer.
As shown in
The platen 11 is a flat plate member to receive thereon a sheet 14 and adjust a distance between the sheet 14 and the head unit 16. Herein, one side of the platen 11 toward the head unit 16 is referred to as an upper side, and the other side of the platen 11 away from the head unit 16 is referred to as a lower side. However, the liquid ejection apparatus 10 may be positioned in other orientations.
The transport unit may include two transport rollers 15 and a transport motor (not shown). The two transport rollers 15 are connected to the transport motor and disposed parallel to each other in a direction (an orthogonal direction) orthogonal to a transport direction of the sheet 14 while interposing the platen 11 therebetween. When the transport motor is driven, the transport rollers 15 rotate to transport the sheet 14 on the platen 11 in the transport direction.
The head unit 16 has a length greater than or equal to the length of the sheet 14 in the orthogonal direction. The head unit 16 includes a plurality of liquid ejection heads 20.
Each liquid ejection head 20 includes a stack structure including a channel unit and a volume changer. The channel unit includes liquid channels formed therein and a plurality of nozzle holes 21a open on an ejection surface (a nozzle surface) 40a. The volume changer is driven to change the volume of a liquid channel. In this case, a meniscus in a nozzle hole 21a vibrates and liquid is ejected from the nozzle hole 21a. The ink ejection head 20 will be described in detail later.
Separate tanks 12 are provided for different kinds of inks which are examples of liquids. For example, each of four tanks 12 stores therein a corresponding one of black, yellow, cyan, and magenta inks. Inks of the tanks 12 are supplied to corresponding nozzle holes 21a.
<Structure of Liquid Ejection Head>
As described above, each liquid ejection head 20 includes the channel unit and the volume changer. As shown in
The plurality of plates include a nozzle plate 40, a first channel plate 41, a second channel plate 42, a third channel plate 43, a fourth channel plate 44, a fifth channel plate 45, a sixth channel plate 46, a seventh channel plate 47, an eighth channel plate 48, a ninth channel plate 49, a 10th channel plate 50, an 11th channel plate 51, a 12th channel plate 52, a 13th channel plate 53, and a 14th channel plate 54. These plates are stacked in this order.
Each plate has holes and grooves of various sizes. A combination of holes and grooves in the stacked plates of the channel unit defines liquid channels such as a plurality of nozzles 21, a plurality of individual channels, a supply manifold 22, and a return manifold 23.
The nozzles 21 are formed to penetrate the nozzle plate 40 in a stacking direction (an up-down direction). Nozzle holes 21a, which are ends of the nozzles 21, are arranged as a nozzle array in a predetermined direction (hereinafter referred to as an extending direction) on the ejection surface 40a of the nozzle plate 40. The extending direction is orthogonal to the stacking direction and a width direction to be described later.
The supply manifold 22 extends in the extending direction and is connected to each individual channel 64. The return manifold 23 extends in the extending direction and is connected to each individual channel 64. The supply manifold 22 is at least partially stacked on the return manifold 23. Thus, the supply manifold 22 and the return manifold 23 at least partially overlap each other in plan view.
The overall shapes of the supply manifold 22 and the return manifold 23 will now be described.
As shown in
The return manifold 23 includes a lower portion 123a and a standing portion 123b. In this embodiment, the lower portion 123a and the standing portion 123b have the same width.
The lower portion 123a of the return manifold 23 is located below the extending portion 122a of the supply manifold 22 so as to overlap the extending portion 122a of the supply manifold 22 in plan view. In other words, the extending portion 122a of the supply manifold 22 is located inside the lower portion 123a of the return manifold 23 in plan view. The lower portion 123a is slightly longer in the extending direction than the extending portion 122a so as to extend beyond one side (a side facing out of the page of
The standing portion 123b of the return manifold 23 is located, at one of opposite ends of the lower portion 123a in the extending direction, outside the standing portion 122b of the supply manifold 22 in plan view. The standing portion 122b of the supply manifold 22 is located inside the standing portion 123b of the return manifold 23 when viewed from the other side (a side facing into the page of
The extending portion 122a of the supply manifold 22 is formed by through-holes penetrating in the stacking direction the eighth channel plate 48 through the 11th channel plate 51, and a recess recessed from a lower surface of the 12th channel plate 52. The recess overlaps the through-holes in the stacking direction. A lower end of the supply manifold 22 is covered by the seventh channel plate 47, and an upper end of the supply manifold 22 is covered by an upper portion of the 12th channel plate 52. As shown in
The lower portion 123a of the return manifold 23 is formed by through-holes penetrating in the stacking direction the second channel plate 42 through the fifth channel plate 45, and a recess recessed from a lower surface of the sixth channel plate 46. The recess overlaps the through-holes in the stacking direction. A lower end of the lower portion 123a of the return manifold 23 is covered by the first channel plate 41, and an upper end of lower portion 123a of the return manifold 23 is covered by an upper portion of the sixth channel plate 46. As shown in
The extending portion 122a of the supply manifold 22 and the lower portion 123a of the return manifold 23 define therebetween an air layer 24 as a buffer space. The air layer 24 is formed by a recess recessed from a lower surface of the seventh channel plate 47. In the stacking direction, the extending portion 122a of the supply manifold 22 and the air layer 24 are adjacent to each other via an upper portion of the seventh channel plate 47, and the lower portion 123a of the return manifold 23 and the air layer 24 are adjacent to each other via the upper portion of the sixth channel plate 46. The air layer 24 sandwiched between the extending portion 122a of the supply manifold 22 and the lower portion 123a of the return manifold 23 may reduce interaction between the liquid pressure in the extending portion 122a of the supply manifold 22 and the liquid pressure in the lower portion 123a of the return manifold 23.
An upper portion of the standing portion 122b of the supply manifold 22 includes a supply port 22a which may be tubular. An upper end of a supply passage 22b is connected to an inner space of the supply port 22b. The supply passage 22b extends downward from the supply port 22a. For example, the supply passage 22b penetrates an upper portion of the 12th channel plate 52, the 13th channel plate 53, the 14th channel plate 54, the vibration plate 55, and an insulating film 56. A lower end of the supply passage 22b is connected to the supply port 22c for the supply manifold 22.
An upper portion of the standing portion 123b of the return manifold 23 includes a return port 23a which may be tubular. A lower end of a return passage (not shown) is connected to the return port 23a. The return passage extends upward from the return port 23a. For example, the return passage penetrates an upper portion of the 12th channel plate 52, the 13th channel plate 53, the 14th channel plate 54, the vibration plate 55, and the insulating film 56. The return port 23a is located further to one side (an upper side of the page of
As shown in
In addition to the above-described tank 12, the liquid ejection apparatus 10 further includes a thermistor 70, a heater 71, and a pump 72. The thermistor 70, the heater 71, the pump 72, and the tank 12 are disposed upstream of the liquid ejection head 20. The tank 12 is disposed upstream of the pump 72 which is disposed upstream of the heater 71 which is disposed upstream of the thermistor 70. After the pump 72 draws liquid stored in the tank 12, the liquid is heated by the heater 71 to a predetermined temperature and is supplied to the supply port 22a. Before the liquid is supplied to the supply port 22a, the thermistor 70 detects the temperature of the liquid. Based on the liquid temperature detected by the thermistor 70, a drive voltage for a piezoelectric element 60, which applies ejection energy to liquid in a corresponding pressure chamber 28, is controlled.
In
Referring back to
The first communication hole 25 is connected, at its lower end, to an upper end of the supply manifold 22, and extends upward from the supply manifold 22 in the stacking direction to penetrate an upper portion of the 12th channel plate 52 in the stacking direction. The first communication hole 25 is offset to one side (a right side in
One end 26b (refer to
The pressure chamber 28 is connected, at its one end 28b (refer to
The descender 29 penetrates the first channel plate 41 through the 13th channel plate 53 in the stacking direction and is located further to the other side (the left side in
The return throttle channel 31 is connected, at its one end 31b (refer to
The third communication hole 32 is connected, at its lower end, to the other end 31a (refer to
The vibration plate 55 is stacked on the 14th channel plate 54 to cover upper openings of the pressure chambers 28. The vibration plate 55 may be integral with the 14th channel plate 54. In this case, each pressure chamber 28 is recessed from a lower surface of the 14th channel plate 54 in the stacking direction. An upper portion of the 14th channel plate 54, which is above each pressure chamber 28, functions as the vibration plate 55.
Each 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 entirely covers the vibration plate 55 via the insulating film 56. Each piezoelectric layer 62 is located on the common electrode 61 to overlap a corresponding pressure chamber 28. Each individual electrode 63 is provided for a corresponding pressure chamber 28 and is located on a corresponding piezoelectric layer 62. In this case, a piezoelectric element 60 is formed by an active portion of a piezoelectric layer 62, which is sandwiched by an individual electrode 63 and the common electrode 61.
Each individual electrode 63 is electrically connected to a driver IC. The driver IC receives control signals from a controller (not shown) and generates drive signals (voltage signals) selectively to the individual electrodes 63. In contrast, the common electrode 61 is constantly maintained at a ground potential.
In response to a drive signal, an active portion of each selected piezoelectric layer 62 expands and contracts in a surface direction, together with the two electrodes 61 and 63. Accordingly, the vibration plate 55 corporates to deform to increase and decrease the volume of a corresponding pressure chamber 28. A pressure for liquid ejection from a nozzle 21 is applied to the corresponding pressure chamber 28 depending on its volume.
Next,
As shown in
Each supply port 22a and each return port 23a are located closer to a center of the liquid ejection heads 20 in the width direction than the supply and return manifolds 22 and 23 positioned at one end and the supply and return manifolds 22 and 23 positioned at the other end of the liquid ejection heads 20 in the width direction. Specifically, at least a portion of each supply port 22a and at least a portion of each return port 23a are located, in the width direction, between a nozzle 21 positioned at one end (an upper end in
<Liquid Flow>
Flow of liquid, such as ink, in the ink ejection head 20 in this embodiment will be described. The supply port 22a is connected to the tank 12 via a supply conduit (not shown), and the return port 23a is connected to the tank 12 via a return conduit (not shown). In this structure, when the pump 72 in the supply conduit and a negative-pressure pump (not shown) in the return conduit are driven, liquid from the tank 12 passes through the supply conduit into the supply manifold 22, via the supply port 22a.
Meanwhile, liquid partially flows into the individual channels 64. In each individual channel 64, liquid flows from the supply manifold 22, via the first communication hole 25, into the supply throttle channel 26 and further flows from the supply throttle channel 26, via the second communication hole 27, into the pressure chamber 28. Then, liquid flows from an upper end to a lower end of the descender 29 in the stacking direction to enter the nozzle 21. When the piezoelectric element 60 applies an ejection pressure to the pressure chamber 28, liquid is ejected from the nozzle hole 21a.
A part of liquid having not been ejected from the nozzle hole 21a flows through the return throttle channels 31 and enter the return manifold 23 via the third communication holes 32. Liquid entering the return manifold 23 via the third communication hole 32 flows through the return manifold 23, exits from the return port 23a to an exterior, and returns, via the return conduit, to the tank 12. Thus, liquid having not been ejected from the nozzle holes 21a circulates between the tank 12 and the individual channels 64.
In the liquid ejection head 20 according to the above-described embodiment, the lower portion 123a and the standing portion 123b of the return manifold 23, which are L-shaped, covers the supply manifold 22, thereby reducing, more than before, an area of the supply manifold 22 exposed to open air. This may prevent, more than before, cooling of liquid when it flows through the supply manifold 22 and reaches the pressure chambers 28. There is less of a difference between the temperature detected by the thermistor 70 and the temperature of liquid flowing into the pressure chambers 28. This allows control of a drive voltage for the piezoelectric elements 60 based on the temperature detected by the thermistor 70 which is close to the actual temperature of liquid. Thus, liquid ejection failures may be reduced.
In this embodiment, the standing portion 123b of the return manifold 23 has a width greater than the width in the width direction of the standing portion 122b of the supply manifold 22. Thus, the standing portion 123b of the return manifold 23 largely covers the standing portion 122b of the supply manifold 22. In other words, the standing portion 123b largely guards the standing portion 122b from an external space, thereby preventing cooling of liquid in the supply manifold 22.
In this embodiment, the supply manifold 22 and the return manifold 23 define the air layer 24 therebetween. The provision of the air layer 24, which has a lower thermal conductivity than metal, may further prevent cooling of liquid in the supply manifold 22.
In this embodiment, the individual channels 64 are formed in the metal plates in which channels are readily formed but which tend to cool off because of its high thermal conductivity. However, the lower portion 123a and the standing portion 123b of the return manifold 23, which are L-shaped, cover the supply manifold 22, thereby reducing the tendency of liquid to cool off.
In this embodiment, the distance L1 between the supply port 22a and the return port 23a in the extending direction is set to be greater than the distance L2 between the extending portion 122a of the supply manifold 22 and the lower portion 123a of the return manifold 23 in the stacking direction. This increases the thickness (in the extending direction) of a partition wall between the supply port 22a and the return port 23a. Thus, the supply port 22a and the return port 23a are readily formed and the anti-cooling space 66 is increased in volume.
In this embodiment, the supply port 22a and the return port 23a define therebetween the anti-cooling space 66 into which air flows. The provision of the anti-cooling space 66, which is filled with air having a low thermal conductivity, may further prevent cooling of liquid in the supply manifold 22.
At least a portion of each supply port 22a and at least a portion of each return port 23a are located, in the width direction, between the nozzle 21 positioned at one end (the upper end in
Furthermore, in this embodiment, at least a portion of each supply port 22a and at least a portion of a corresponding return port 23a are located to overlap each other when viewed in the extending direction. This allows each supply manifold 22 to be covered by a corresponding return manifold 23 reduced in size.
In the above-described first illustrative embodiment, the supply manifold 22 include the supply port 22a on its one side in the extending direction, and the return manifold 23 includes the return port 23a on its one side in the extending direction. However, as shown in
In the first illustrative embodiment, the lower portion 123a and the standing portion 123b of the return manifold 23, which are L-shaped, cover the supply manifold 22. However, in the second illustrative embodiment, the supply manifold 222 and the return manifold 223 may be shaped as described below.
In the second embodiment, as shown in
The return manifold 223 includes a lower portion 223a located below the extending portion 222a of the supply manifold 222 to extend in the extending direction, and standing portions 223b standing at opposite ends of the extending portion 223a in the extending direction.
In the liquid ejection head 20 according to this embodiment, the return manifold 223, including the lower portion 223a and the standing portions 223b opposite to each other in the extending direction, is U-shaped and covers the supply manifold 222, thereby reducing, more than before, an area of the supply manifold 222 exposed to open air. This may prevent, more than before, cooling of liquid when it flows through the supply manifold 222 and reaches pressure chambers 28. There is less of a difference between the temperature detected by a thermistor 70 and the temperature of liquid flowing into the pressure chambers 28. This allows control of a drive voltage for piezoelectric elements 60 based on the temperature detected by the thermistor 70 which is close to the actual temperature of liquid. Thus, liquid ejection failures may be reduced.
Modifications
The disclosure may not be limited to the above-described embodiments, and various changes may be applied therein without departing from the spirit and scope of the disclosure.
For example, as shown in
As shown in
In the above-described first illustrative embodiment, the supply manifold 22 is L-shaped but not so limited. The supply manifold 22 may only consist of the extending portion 122a.
In the above-described first illustrative embodiment, in plan view, the extending portion 122a of the supply manifold 22 is positioned within the lower portion 123a of the return manifold 23, and the one side (the side facing out of the page of
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2019-103638 | Jun 2019 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5574486 | Whitlow | Nov 1996 | A |
| 20090213163 | Bansyo | Aug 2009 | A1 |
| 20170151792 | Kobayashi et al. | Jun 2017 | A1 |
| 20190084303 | Sugiura | Mar 2019 | A1 |
| Number | Date | Country |
|---|---|---|
| 2008-290292 | Dec 2008 | JP |
| 2015-199181 | Nov 2015 | JP |
| 2019181707 | Oct 2019 | JP |
| Entry |
|---|
| Machine generated English translation of JP2019181707 to Machida, “Liquid Discharge Head and Liquid Discharge Device”; translation generated via FIT database on Oct. 23, 2021; 32pp. |
| Number | Date | Country | |
|---|---|---|---|
| 20200376846 A1 | Dec 2020 | US |
