Liquid discharge head and liquid discharge device

Abstract

To provide a technique that can suppress influence caused by bubbles, more surely.SOLUTION: A liquid discharge head is provided with: a discharge port for discharging liquid; a pressure chamber provided with an energy generating element that generates energy for making the discharge port discharge liquid; a first liquid storage part, communicated with one end of the pressure chamber, which can store liquid that is supplied to the pressure chamber; a first decompression chamber, arranged adjacent to the first liquid storage part through a first gas permeation film, whose inside can be decompressed; a second liquid storage part, communicated with the other end of the pressure chamber, which can store liquid collected from the pressure chamber; and a second decompression chamber, arranged adjacent to the second liquid storage part through a second gas permeation film, whose inside can be decompressed.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejection head and a liquid ejection apparatus. [Background technology]

[0002] When replacing an ink tank or liquid ejection head in a liquid ejection device, bubbles may be mixed in. If the mixed bubbles enter the pressure chamber of the liquid ejection head, the pressure required to eject the liquid is insufficient, resulting in a decrease in liquid ejection performance. Furthermore, if the mixed bubbles remain in the flow path of the liquid ejection head, they may expand depending on changes in the external environment of the liquid ejection device, potentially exposing the liquid. To mitigate the effects of such bubbles and ensure stable use of the liquid ejection device and liquid ejection head, a configuration is required that allows bubbles that have entered the liquid ejection head to be expelled to the outside.

[0003] Patent Document 1 discloses a liquid ejection head having an ink flow path provided with a filter chamber capable of collecting gas (bubbles) mixed in the liquid and an adjacent gas recovery space separated by a permeable partition wall. In this liquid ejection head, the pressure in the gas recovery space is set lower than the pressure in the filter chamber, so that the pressure difference causes the air in the filter chamber to pass through the permeable partition wall and be recovered in the gas recovery space. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-173961 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the liquid ejection head disclosed in Patent Document 1, the filter chamber is located vertically above the pressure chamber and is provided in a flow path that supplies introduced liquid to the pressure chamber. Furthermore, the filter provided in the filter chamber is configured to be difficult for gas to pass through. Therefore, in this liquid ejection head, bubbles generated in the pressure chamber or between the filter chamber and the pressure chamber cannot be collected from the gas recovery space, and the effects of bubbles cannot be sufficiently suppressed.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a technique that can more reliably suppress the effects of bubbles. [Means for solving the problem]

[0007] In order to achieve the above object, one embodiment of a liquid ejection head according to the present disclosure is characterized by having an ejection port for ejecting liquid, a pressure chamber provided with an energy generating element that generates energy for ejecting liquid from the ejection port, a first liquid storage section that communicates with one end of the pressure chamber and is capable of storing liquid to be supplied to the pressure chamber, a first decompression chamber that is adjacent to the first liquid storage section via a first gas-permeable membrane and is configured so that the interior can be decompressed, a second liquid storage section that communicates with the other end of the pressure chamber and is capable of storing liquid recovered from the pressure chamber, and a second decompression chamber that is adjacent to the second liquid storage section via a second gas-permeable membrane and is configured so that the interior can be decompressed. [Effects of the Invention]

[0008] According to the present disclosure, the effects of bubbles can be more reliably suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a liquid ejection device. [Figure 2] FIG. 3 is a schematic diagram showing a flow path of an ink supply unit. [Figure 3] 10A and 10B are schematic diagrams illustrating a pressurizing operation of a pressure chamber. [Figure 4]10A and 10B are schematic diagrams illustrating a pressurization maintaining operation. [Figure 5] FIG. 10 is a schematic diagram illustrating an ink supply operation. [Figure 6] FIG. 10 is a schematic diagram illustrating a bubble removal and decompression operation. [Figure 7] FIG. 2 is an exploded perspective view of the liquid ejection head. [Figure 8] FIG. 2 is a cross-sectional view of the liquid ejection head and the ejection module. [Figure 9] FIG. 2 is a schematic view showing the appearance of a circulation unit. [Figure 10] FIG. [Figure 11] FIG. 2 is a block diagram showing a schematic diagram of a circulation path. [Figure 12] FIG. 4 is a cross-sectional view showing an example of a pressure adjusting means. [Figure 13] FIG. 2 is an external perspective view of a circulation pump. [Figure 14] 14(a) is a cross-sectional view of the circulation pump taken along line XIV-XIV in FIG. 13(a). [Figure 15] 3A and 3B are diagrams illustrating the flow of ink inside a liquid ejection head. [Figure 16] FIG. 4 is a schematic diagram showing a circulation path in the discharge unit. [Figure 17] FIG. 10 is a diagram showing an aperture plate. [Figure 18] FIG. 2 is a diagram showing a discharge element substrate. [Figure 19] FIG. 4 is a cross-sectional view showing the flow of ink in the ejection unit. [Figure 20] FIG. 3 is a cross-sectional view showing the vicinity of a discharge port. [Figure 21] FIG. 10 is a cross-sectional view showing a comparative example near the ejection port. [Figure 22] FIG. 10 is a diagram showing a comparative example of a discharge element substrate. [Figure 23] FIG. 2 is a diagram showing a flow path configuration of a liquid ejection head. [Figure 24] FIG. 10 is a diagram schematically illustrating a backflow of ink near an ejection port. [Figure 25] FIG. 4 is a diagram illustrating ink supply within the ejection module. [Figure 26] 3 is a schematic diagram showing a connection state between a main body of the liquid ejection device and a liquid ejection head. FIG. [Figure 27] FIG. 2 is a schematic diagram of a bubble removal unit. [Figure 28] FIG. 10 is a cross-sectional view showing a modified example of the bubble removal unit. [Figure 29] FIG. 10 is a cross-sectional view showing a modified example of the deformation suppressing member. [Figure 30] 10A and 10B are schematic diagrams showing modified examples of the deformation suppressing member. [Figure 31] 5A and 5B are schematic diagrams showing the operation of the initial filling and bubble removal unit. [Figure 32] FIG. 2 is a diagram schematically illustrating a first configuration example of an ink path. [Figure 33] FIG. 10 is a diagram schematically illustrating a first modified example of a circulation path. [Figure 34] FIG. 2 is a diagram schematically illustrating the vicinity of a heated circulation pump. [Figure 35] FIG. 10 is a diagram schematically illustrating a first modified example of a circulation path. [Figure 36] FIG. 10 is a diagram schematically illustrating a second modified example of the circulation path. [Figure 37] FIG. 10 is a diagram schematically illustrating a second modified example of the circulation path. [Figure 38] FIG. 10 is a diagram schematically illustrating a third modified example of the circulation path. [Figure 39] FIG. 10 is a diagram schematically illustrating a third modified example of the circulation path. [Figure 40] FIG. 10 is a diagram schematically illustrating a second configuration example of an ink path. [Figure 41] FIG. 10 is a diagram schematically illustrating a fourth modified example of the circulation path. [Figure 42] FIG. 10 is a diagram schematically illustrating a fourth modified example of the circulation path. [Figure 43] FIG. 10 is a diagram schematically illustrating a fifth modified example of the circulation path. [Figure 44] FIG. 10 is a diagram schematically illustrating a fifth modified example of the circulation path. [Figure 45] FIG. 10 is a diagram schematically illustrating a sixth modified example of the circulation path. [Figure 46]FIG. 10 is a diagram schematically illustrating a sixth modified example of the circulation path. [Figure 47] FIG. 10 is a block diagram schematically showing another modified example of the circulation path. [Figure 48] FIG. 10 is a block diagram schematically showing another modified example of the circulation path. [Figure 49] FIG. 10 is a block diagram schematically showing another modified example of the circulation path. [Figure 50] 10 is a diagram illustrating the position of an opening connected to a flow path in a second pressure control chamber. FIG. [Figure 51] FIG. 10 is a diagram showing a modified example of the bubble removal unit. [Figure 52] 10A and 10B are diagrams showing a modified example of the connection of the bubble removal unit to the third air flow path. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. The following embodiments do not limit the scope of the present disclosure, and not all combinations of features described in the present embodiments are necessarily essential to the solutions of the present disclosure. The same reference numerals are used to designate the same components. In the present embodiments, an example is described in which a thermal method is used as an ejection element for ejecting liquid, in which an electrothermal conversion element generates bubbles to eject the liquid. However, this is not limited to this. The present invention can also be applied to liquid ejection heads that use an ejection method that ejects liquid using a piezoelectric element (piezo) or other ejection methods. Furthermore, the pump and pressure adjustment means described below are not limited to the configurations shown in the embodiments and drawings. In the following description, the basic configuration of the present disclosure will be described first, followed by a description of the characteristic features of the present disclosure.

[0011] <Liquid discharge device> Fig. 1 is a diagram for explaining a liquid ejection device, and is an enlarged view of a liquid ejection head of the liquid ejection device and its surroundings. First, the general configuration of a liquid ejection device 50 in this embodiment will be described with reference to Fig. 1. Fig. 1(a) is a perspective view that schematically shows a liquid ejection device that can be equipped with a liquid ejection head 1. The liquid ejection device 50 of this embodiment constitutes a serial type inkjet recording device that performs recording on a recording medium P by ejecting ink as a liquid while scanning the liquid ejection head 1.

[0012] The liquid ejection head 1 is mounted on a carriage 60. The carriage 60 moves back and forth along a guide shaft 51 in the main scanning direction (X direction). The recording medium P is transported in a sub-scanning direction (Y direction) that intersects (in this example, orthogonal to) the main scanning direction by upstream transport rollers 55 and 56 and downstream transport rollers 57 and 58. In each of the figures referred to below, the Z direction indicates the vertical direction, and intersects (in this example, orthogonal to) the XY plane defined by the X and Y directions. The liquid ejection head 1 is configured so that it can be removed from and attached to the carriage 60 by the user.

[0013] The liquid ejection head 1 is configured to include a circulation unit 54 (see FIG. 7) described below, and an ejection unit 3 (see FIG. 7). The specific configuration will be described later, but the ejection unit 3 is provided with a plurality of ejection ports and energy generating elements (hereinafter referred to as ejection elements) that generate ejection energy for ejecting liquid from each of the ejection ports.

[0014] The liquid ejection device 50 is also provided with an ink tank 2, which is an ink supply source, and an ink supply unit 400. The ink stored in the ink tank 2 is supplied to the liquid ejection head 1 by the ink supply unit 400 via a first supply path 111 and a second supply path 112. Gas such as bubbles generated in the liquid ejection head 1 is discharged to the outside of the liquid ejection head 1 by the ink supply unit 400 via a third air flow path 113.

[0015] The liquid ejection device 50 forms a predetermined image on the recording medium P by repeating a printing scan in which the liquid ejection head 1 mounted on the carriage 60 moves in the main scanning direction while ejecting ink to perform printing, and a transport operation in which the recording medium P is transported in the sub-scanning direction. The liquid ejection head 1 in this embodiment is capable of ejecting four types of ink: black (K), cyan (C), magenta (M), and yellow (Y), and is capable of recording a full-color image using these inks. However, the inks that can be ejected from the liquid ejection head 1 are not limited to the above four types of ink. The present disclosure is also applicable to liquid ejection heads for ejecting other types of ink. In other words, the types and number of inks ejected from the liquid ejection head are not limited. For example, the number of types of ink ejected from the liquid ejection head may be one, two, three, or five or more.

[0016] The liquid ejection device 50 is also provided with a control unit 100 and a cap member (not shown) capable of covering the ejection port surface on which the ejection ports of the liquid ejection head 1 are formed. The cap member is provided at a position in the liquid ejection device 50 that is offset in the X direction from the conveyance path of the recording medium P. The cap member covers the ejection port surface of the liquid ejection head 1 when not performing printing, and is used to prevent and protect the ejection ports from drying, to suck ink from the ejection ports, and so on. Signals output from the control unit 100 are transmitted to the liquid ejection head 1 and so on via signal lines 109.

[0017] FIG. 1B is a block diagram showing a control system of the liquid ejection device 50. The control unit 100 of the liquid ejection device 50 includes a CPU 103, a RAM 102, a ROM 101, a head driver 1A, motor drivers 104A and 105A, and pump drivers 404A and 500A. The CPU 103 functions as a control unit that controls the operation of each component of the liquid ejection device 50 based on programs, such as processing procedures, stored in the ROM 101. The RAM 102 is used as a work area when the CPU 103 executes processing. The CPU 103 receives image data from a host device 900 external to the liquid ejection device 50, controls the head driver 1A, and controls the driving of the ejection elements provided in the ejection unit 3. The CPU 103 also controls the drivers of various actuators provided in the liquid ejection device. For example, the CPU 103 controls a motor driver 104A that drives a conveyance motor 104 for conveying a recording medium P. The CPU 103 controls a motor driver 105A that drives a carriage motor 105 to move the carriage 60. The CPU 103 controls a pump driver 500A that drives a circulation pump 500 (described later). The CPU 103 controls a pump driver 404A that drives a one-way pump 404 (described later). Signals output from various sensors, such as a volume sensor, a pressure sensor 409, and a liquid sensor 416 (described later), are also input to the control unit 100. Note that while FIG. 1(b) shows a form in which processing is performed upon receiving image data from the host device 900, processing may also be performed by the liquid ejection device 50 without relying on data from the host device 900.

[0018] <Ink supply unit> Next, the configuration of the ink supply unit 400 will be described with reference to Fig. 2. Fig. 2 is a schematic diagram showing the flow paths of the ink supply unit 400.

[0019] The ink supply unit 400 has an intermediate tank 401 that temporarily stores ink supplied through a first supply path 111 from an ink tank 2 that is configured to be detachable from the liquid ejection device 50. A first check valve 222 is provided in the first supply path 111, and the first check valve 222 prevents ink from flowing back from the intermediate tank 401 to the ink tank 2. At least one surface of the intermediate tank 401 is formed by a flexible film 402, which makes it possible to change the volume of the intermediate tank 401. A volume sensor (not shown) is provided in the intermediate tank 401. The volume sensor can detect the volume of the intermediate tank 401 by measuring the displacement of the flexible film 402. The amount of ink in the intermediate tank 401 can be estimated from the volume of the intermediate tank 401 detected by the volume sensor. The amount of ink in the intermediate tank 401 may be estimated from the volume of the intermediate tank 401 detected by the volume sensor and the amount of ink consumed by forming an image on a recording medium, suctioning ink from the cap member, and the like.

[0020] The intermediate tank 401 is connected to a pressure chamber filled with air via a flexible membrane 402. Hereinafter, the pressure chamber of the intermediate tank 401 will be referred to as an intermediate pressure chamber 403. The pressure of the ink stored in the intermediate tank 401 can be changed by changing the pressure of the gas (air) in the intermediate pressure chamber 403. The ink stored in the intermediate tank 401 is supplied to the liquid ejection head 1 through a second supply path 112 connected to the intermediate tank 401 and the filter 110 of the liquid ejection head 1. A second check valve 223 is provided in the second supply path 112, and the second check valve 223 prevents the ink from flowing back from the liquid ejection head 1 to the intermediate tank 401. The ink supply unit 400 has a one-way pump 404 driven by a pump driver 404A. The one-way pump 404 is configured using, for example, a diaphragm pump, and is capable of sucking and ejecting air in one direction when driven by the pump driver 404A.

[0021] The intermediate pressure chamber 403 and the suction side of the one-way pump 404 are connected via a first air flow path 414. A first on-off valve 408 is provided in the first air flow path 414, and opening and closing the first on-off valve 408 makes it possible to switch between open and closed states of the first air flow path 414. A first branch air flow path 418 is provided in the first air flow path 414, branching between the first on-off valve 408 and the one-way pump 404 and having one end connected to the atmosphere. A third on-off valve 407 is provided in the first branch air flow path 418, and opening and closing the third on-off valve 407 makes it possible to switch between sealing the suction side of the one-way pump 404 and opening it to the atmosphere.

[0022] The intermediate pressure chamber 403 and the ejection side of the one-way pump 404 are connected via a second air flow path 415. A second on-off valve 405 is provided in the second air flow path 415, and opening and closing the second air flow path 415 allows the second air flow path 415 to be switched between open and closed. A second branch air flow path 419 is provided in the second air flow path 415, branching between the second on-off valve 405 and the one-way pump 404 and having one end connected to the atmosphere. A fourth on-off valve 406 is provided in the second branch air flow path 419, and opening and closing the fourth on-off valve 406 allows the ejection side of the one-way pump 404 to be switched between closed and open to the atmosphere. A liquid sensor 416 is provided at the end of the second branch air flow path 419 that is open to the atmosphere. The liquid sensor 416 is capable of detecting ink that has entered the air flow path. A pressure sensor 409 is provided at a position communicating with the intermediate pressure chamber 403. The pressure sensor 409 is capable of detecting the pressure of the gas (air) in the intermediate pressure chamber 403. The one-way pump 404 and a decompression chamber 760 of a bubble removal unit 770 in the liquid ejection head 1, which will be described later, are connected via a third air flow path 113. A third check valve 213 is provided in the third air flow path 113, and the third check valve 213 regulates the backflow of the gas (air) from the ink supply unit 400 to the decompression chamber 760.

[0023] Next, the operation of the ink supply unit 400 will be described with reference to Figures 3 to 6. In this embodiment, in order to perform recording on the recording medium P, the ink supply unit 400 mainly performs four operations (pressurizing the pressure chamber, maintaining the pressure, replenishing the ink, and depressurizing the bubble removal). Based on the detection results of a volume sensor (not shown), a pressure sensor 409, etc., the CPU 103 controls the one-way pump 404 and the first to fourth opening / closing valves to perform the pressurizing the pressure chamber, maintaining the pressure, replenishing the ink, and depressurizing the bubble removal, which will be described later.

[0024] <Pressure chamber pressurization> First, the pressure chamber pressurization operation will be described using FIG. 3. FIG. 3 is a schematic diagram illustrating the pressure chamber pressurization operation. The liquid ejection head 1 according to this embodiment is capable of stably ejecting ink by pressurizing and supplying ink, regardless of variations in the ink flow rate due to differences in the ejection amount from the liquid ejection head 1 and variations in ink pressure loss due to the viscosity of the ink, etc. The pressure chamber pressurization operation is an operation for pressurizing the intermediate pressure chamber 403 to pressurize the ink in the intermediate tank 401 via the flexible membrane 402, and supplying pressurized ink to the liquid ejection head 1 through the second supply path 112. When the ink in the intermediate tank 401 is consumed and the volume of the intermediate pressure chamber 403, which is in contact with the intermediate tank 401 via the flexible membrane 402, expands, the pressure of the gas in the intermediate pressure chamber 403 decreases. Furthermore, when the pressure of the gas in the intermediate pressure chamber 403 is reduced during an ink refill operation (described later) and then the first on-off valve 408 and the third on-off valve 407 are opened to expose the intermediate pressure chamber 403 to the atmosphere, the pressure of the gas in the intermediate pressure chamber 403 becomes atmospheric pressure. When the pressure of the gas in the intermediate pressure chamber 403 decreases or becomes atmospheric pressure, a pressure chamber pressurization operation is required. The pressure of the gas in the intermediate pressure chamber 403 is monitored by a pressure sensor 409, and when the pressure of the gas in the intermediate pressure chamber 403 is lower than a predetermined pressure required for stable ejection by the liquid ejection head 1, the ink supply unit 400 performs a pressure chamber pressurization operation. During pressure chamber pressurization, the ink supply unit 400 drives the one-way pump 404 to increase the pressure of the gas in the intermediate pressure chamber 403, with the first on-off valve 408 in a closed state, the second on-off valve 405 in an open state, the third on-off valve 407 in an open state, and the fourth on-off valve 406 in a closed state. When the pressure of the gas in the intermediate pressure chamber 403 increases, the ink in the intermediate tank 401 is pressurized via the flexible membrane 402, and the ink in the second supply path 112 is pressurized via the second check valve 223, making it possible to supply pressurized ink to the liquid ejection head 1. The pressure of the gas in the intermediate pressure chamber 403 is monitored by a pressure sensor 409, and when the pressure of the gas in the intermediate pressure chamber 403 is equal to or higher than a predetermined pressure, the ink supply unit 400 stops driving the one-way pump 404. During this time, the decompression chamber 760 is closed by the third check valve 213, and therefore the pressure inside the decompression chamber 760 is maintained at a low pressure (negative pressure).

[0025] <Pressure maintenance operation> Next, the pressurization maintenance operation will be described with reference to FIG. 4. FIG. 4 is a schematic diagram illustrating the pressurization maintenance operation. The pressurization maintenance operation is an operation for maintaining the gas pressure in the intermediate pressure chamber 403, which has been increased by the pressure chamber pressurization operation, at a high level. When recording on a recording medium, if the gas pressure in the intermediate pressure chamber 403 is equal to or higher than a predetermined pressure, the ink supply unit 400 performs the pressurization maintenance operation. Furthermore, if the gas pressure in the intermediate pressure chamber 403 remains high when the next recording is started, it is possible to start the next recording earlier without performing the pressure chamber pressurization operation. Therefore, it is preferable to maintain the gas pressure in the intermediate pressure chamber 403 at a high level. For this reason, even during standby time when recording on a recording medium is not being performed, if the gas pressure in the intermediate pressure chamber 403 is equal to or higher than a predetermined pressure, the ink supply unit 400 performs the pressurization maintenance operation. If the gas pressure in the intermediate pressure chamber 403 is equal to or higher than a predetermined pressure after the pressure chamber pressurization operation is performed, the ink supply unit 400 switches the first opening / closing valve 408 and the second opening / closing valve 405 to a closed state as the pressurization maintenance operation. At this time, the third on-off valve 407 and the fourth on-off valve 406 may be in a closed state or in an open state. This makes it possible to maintain the gas pressure in the intermediate pressure chamber 403, which has increased due to the pressure chamber pressurization operation, at a high pressure. Thereafter, the pressure sensor 409 monitors pressure fluctuations due to volume changes in the intermediate pressure chamber 403, and if the gas pressure in the intermediate pressure chamber 403 is lower than a predetermined pressure, the ink supply unit 400 performs the pressure chamber pressurization operation again. During this time, the decompression chamber 760 is closed by the third check valve 213, so the pressure in the decompression chamber 760 is maintained at a low pressure (negative pressure).

[0026] <Ink refill operation> Next, the ink supply operation will be described with reference to FIG. 5. FIG. 5 is a schematic diagram illustrating the ink supply operation. The ink supply operation is an operation in which ink stored in the ink tank 2 is drawn into the intermediate tank 401 via the first supply path 111 when the amount of ink in the intermediate tank 401 decreases below a predetermined amount sufficient for recording. When the volume of the intermediate tank 401 detected by a volume sensor (not shown) indicates that the amount of ink in the intermediate tank 401 is less than a predetermined amount sufficient for recording, the ink supply unit 400 performs the ink supply operation. During the ink supply operation, the ink supply unit 400 drives the one-way pump 404 to reduce the pressure of the gas in the intermediate pressure chamber 403 while keeping the first on-off valve 408 open, the second on-off valve 405 closed, the third on-off valve 407 closed, and the fourth on-off valve 406 open. When the pressure of the gas in the intermediate pressure chamber 403 decreases, the pressure of the ink in the intermediate tank 401 decreases via the flexible membrane 402. By lowering the ink pressure in the intermediate tank 401 (negative pressure), ink stored in the ink tank 2 can be drawn into the intermediate tank 401 via the first supply path 111. If the volume sensor detects that the amount of ink in the intermediate tank 401 is equal to or greater than a predetermined amount, the ink supply unit 400 stops driving the one-way pump 404. Furthermore, the ink supply unit 400 opens the first on-off valve 408 and the third on-off valve 407 to open the intermediate pressure chamber 403 to the atmosphere, thereby stopping the drawing of ink into the intermediate tank 401. After opening the intermediate pressure chamber 403 to the atmosphere, the ink supply unit 400 performs the pressure chamber pressurization operation described above to increase the pressure of the gas in the intermediate pressure chamber 403 from atmospheric pressure. During this time, the decompression chamber 760 is closed by the third check valve 213, so the pressure in the decompression chamber 760 is maintained at a low pressure (negative pressure).

[0027] <Debubble removal and pressure reduction operation> Next, the bubble removal decompression operation will be described with reference to FIG. 6. FIG. 6 is a schematic diagram illustrating the bubble removal decompression operation. The bubble removal decompression operation is an operation for reducing the pressure in the decompression chamber 760. The speed at which gas moves from the bubble reservoir chamber 520 of the bubble removal unit 770 in the liquid ejection head 1 to the decompression chamber 760 through the gas-permeable membrane 710 is proportional to the difference between the pressure in the bubble reservoir chamber 520 and the pressure in the decompression chamber 760. For this reason, it is desirable to maintain the pressure in the decompression chamber 760 at a low pressure. The third check valve 213 provided midway through the third air flow path 113 restricts the inflow of gas from the third air flow path 113 to the decompression chamber 760. However, the pressure in the decompression chamber 760 gradually increases over time due to the inflow of gas from the bubble reservoir chamber 520 through the gas-permeable membrane 710 and the inflow of gas that slightly permeates the components that make up the decompression chamber 760. When the pressure in the decompression chamber 760 gradually increases over time, a bubble removal decompression operation is required to reduce the pressure in the decompression chamber 760. If it is estimated that the pressure in the decompression chamber 760 exceeds a predetermined pressure based on the time elapsed since the previous bubble removal decompression operation, the ink supply unit 400 performs the bubble removal decompression operation. During the bubble removal decompression operation, the ink supply unit 400 drives the one-way pump 404 to reduce the pressure in the decompression chamber 760 while keeping the first on-off valve 408 in a closed state, the second on-off valve 405 in a closed state, the third on-off valve 407 in a closed state, and the fourth on-off valve 406 in an open state. If a predetermined time has elapsed since the one-way pump 404 was driven and it is estimated that the pressure in the decompression chamber 760 has dropped below the predetermined pressure, the ink supply unit 400 stops driving the one-way pump 404. During this time, the first on-off valve 408 and the second on-off valve 405 are closed, so the gas pressure in the intermediate pressure chamber 403 is maintained at a positive pressure. After the bubble removal and decompression operation, even if the pressure in the intermediate pressure chamber 403 and the first to third airflow paths fluctuates due to the aforementioned pressure chamber pressurization operation, pressure maintenance operation, ink replenishing operation, etc., the pressure in the decompression chamber 760 is maintained at a low pressure (negative pressure) because the third check valve 213 is closed. The bubble removal and decompression operation in this embodiment is performed once a day. However, this is not limited to this, and the frequency of the bubble removal and decompression operation may be increased, for example, after delivery or cleaning, when bubbles are likely to be generated.The frequency of the defoaming and depressurizing operation may be reduced as time passes after delivery or cleaning. The frequency of the defoaming and depressurizing operation may also be changed depending on the temperature, the state of use, etc.

[0028] <Liquid ejection head> Fig. 7 is an exploded perspective view of the liquid ejection head 1 of this embodiment. Fig. 8 is a cross-sectional view of the liquid ejection head 1 and the ejection module 300. Fig. 8(a) is a cross-sectional view of the liquid ejection head 1 shown in Fig. 7, taken along line VIIIa-VIIIa. Fig. 8(b) is an enlarged cross-sectional view of the ejection module 300 shown in Fig. 8(a). The basic configuration of the liquid ejection head 1 of this embodiment will be described below, mainly with reference to Fig. 7 and Fig. 8, and also with reference to Fig. 1 as appropriate.

[0029] 7, the liquid ejection head 1 is configured to include a circulation unit 54 and an ejection unit 3 for ejecting ink supplied from the circulation unit 54 onto a recording medium P. The liquid ejection head 1 in this embodiment is fixedly supported on a carriage 60 of the liquid ejection device 50 by positioning means and electrical contacts (not shown) provided on the carriage 60. The liquid ejection head 1 ejects ink while moving together with the carriage 60 in the main scanning direction (X direction) shown in FIG. 1, and performs recording on the recording medium P.

[0030] An ink supply unit 400 connected to an ink tank 2, which serves as an ink supply source, is provided with a first supply path 111 and a second supply path 112. A main body-side connecting member 470 (see FIG. 26) is provided at the end of the second supply path 112. When the liquid ejection head 1 is mounted on the liquid ejection device 50, the main body-side connecting member 470 provided at the end of the second supply path 112 is detachably connected to a head-side connecting member 800 provided on a head housing 53 of the liquid ejection head 1. This forms ink supply paths (first supply path 111 and second supply path 112) that run from the ink tank 2 through the ink supply unit 400 to the liquid ejection head 1. In this embodiment, four types of ink are used, so four sets of ink tanks 2, first supply paths 111, second supply paths 112, and circulation units 54 are provided, one for each ink, and four independent ink supply paths are formed corresponding to each ink. As described above, the liquid ejection device 50 of this embodiment is provided with an ink supply system to which ink is supplied from the ink tank 2 provided outside the liquid ejection head 1.

[0031] As shown in FIG. 8, the circulation units 54 include a circulation unit 54B for black ink, a circulation unit 54C for cyan ink, a circulation unit 54M for magenta ink, and a circulation unit 54Y for yellow ink. Each circulation unit has a substantially similar configuration, and in this embodiment, unless otherwise specified, they will all be referred to as a circulation unit 54. While the liquid ejection head 1 shown in FIG. 8 is provided with four circulation units 54 corresponding to four types of ink, it is sufficient that the liquid ejection head 1 includes a circulation unit 54 corresponding to the type of liquid to be ejected. Furthermore, multiple circulation units 54 may be provided for the same type of liquid. In other words, the liquid ejection head 1 may be configured to include one or more circulation units. It is also possible to circulate only one ink rather than all four types of ink.

[0032] 7 and 8(a), the discharge unit 3 includes two discharge modules 300, a first support member 4, a second support member 7, an electric wiring member (electric wiring tape) 5, and an electric contact substrate 6. As shown in FIG. 8(b), the discharge module 300 includes a silicon substrate 310 having a thickness of 0.5 mm to 1 mm, and a plurality of discharge elements 15 provided on one side of the silicon substrate 310. In this embodiment, the discharge elements 15 are configured by electrothermal conversion elements (heaters) that generate thermal energy as discharge energy for discharging liquid. Power is supplied to each discharge element 15 via electric wiring formed on the silicon substrate 310 by film formation technology.

[0033] Furthermore, an ejection port forming member 320 is formed on the surface (the lower surface in FIG. 8(b)) of the silicon substrate 310. In the ejection port forming member 320, a plurality of pressure chambers 12 corresponding to the plurality of ejection elements 15 and a plurality of ejection ports 13 for ejecting ink are respectively formed by photolithography. Furthermore, a common supply flow path 18 and a common recovery flow path 19 are formed in the silicon substrate 310. In addition, in the silicon substrate 310, a supply connection flow path 323 that connects the common supply flow path 18 with each pressure chamber 12, and a recovery connection flow path 324 that connects the common recovery flow path 19 with each pressure chamber 12 are formed. In this embodiment, one ejection module 300 is configured to eject two types of ink. That is, of the two ejection modules shown in FIG. 8(a), the ejection module 300 located on the left side in the figure ejects black ink and cyan ink, and the ejection module 300 located on the right side in the figure ejects magenta ink and yellow ink. Note that this combination is an example, and any combination of inks is acceptable. One ejection module may be configured to eject one type of ink, or may be configured to eject three or more types of ink. Two ejection modules 300 do not have to eject the same number of types of ink. One ejection module 300 may be provided, or three or more ejection modules 300 may be provided. Furthermore, in the example shown in FIG. 8, two ejection port arrays extending in the Y direction are formed for one color of ink. A pressure chamber 12, a common supply flow path 18, and a common recovery flow path 19 are formed for each of the multiple ejection ports 13 that make up each ejection port array.

[0034] An ink supply port and an ink recovery port, which will be described later, are formed on the back surface (top surface in FIG. 8(b)) of the silicon substrate 310. The ink supply port supplies ink from an ink supply flow path 48 to the multiple common supply flow paths 18, and the ink recovery port recovers ink from the multiple common recovery flow paths 19 to an ink recovery flow path 49.

[0035] The ink supply port and ink recovery port referred to here refer to openings that supply and recover ink during forward ink circulation, which will be described later. That is, during forward ink circulation, ink is supplied from the ink supply port to each common supply flow path 18, and ink is recovered from each common recovery flow path 19 to the ink recovery port. However, ink may also be circulated in the reverse direction. In this case, ink is supplied from the ink recovery port described above to the common recovery flow path 19, and ink is recovered from the common supply flow path 18 to the ink supply port.

[0036] As shown in FIG. 8(a), the back surface (upper surface in FIG. 8(a)) of the ejection module 300 is adhesively fixed to one surface (lower surface in FIG. 8(a)) of the first support member 4. An ink supply flow path 48 and an ink recovery flow path 49 are formed in the first support member 4, penetrating from one surface to the other. One opening of the ink supply flow path 48 is connected to the ink supply port in the silicon substrate 310, and one opening of the ink recovery flow path 49 is connected to the ink recovery port in the silicon substrate 310. The ink supply flow path 48 and the ink recovery flow path 49 are provided independently for each type of ink.

[0037] Furthermore, a second support member 7 having an opening 7a (see FIG. 7) through which the ejection module 300 is inserted is adhesively fixed to one surface (the lower surface in FIG. 8(a)) of the first support member 4. The second support member 7 holds an electrical wiring member 5 that is electrically connected to the ejection module 300. The electrical wiring member 5 is a member for applying an electrical signal to the ejection module 300 to eject ink. The electrical connection portion between the ejection module 300 and the electrical wiring member 5 is sealed with a sealant (not shown) to protect it from corrosion by ink and external impacts.

[0038] Furthermore, an electrical contact substrate 6 is thermocompression bonded to an end portion 5a (see FIG. 7) of the electrical wiring member 5 using an anisotropic conductive film (not shown), and the electrical wiring member 5 and the electrical contact substrate 6 are electrically connected. The electrical contact substrate 6 has an external signal input terminal (not shown) for receiving an electrical signal from the liquid ejection device 50.

[0039] Furthermore, a joint member 8 (FIG. 8(a)) is provided between the first support member 4 and the circulation unit 54. A supply port 88 and a recovery port 89 are formed in the joint member 8 for each type of ink. The supply port 88 and the recovery port 89 connect the ink supply flow path 48 and the ink recovery flow path 49 of the first support member 4 to the flow paths formed in the circulation unit 54. In FIG. 8(a), the supply port 88B and the recovery port 89B correspond to black ink, and the supply port 88C and the recovery port 89C correspond to cyan ink. Furthermore, the supply port 88M and the recovery port 89M correspond to magenta ink, and the supply port 88Y and the recovery port 89Y correspond to yellow ink.

[0040] The openings at one end of each of the ink supply channel 48 and the ink recovery channel 49 of the first support member 4 have a small opening area that matches the ink supply port and ink recovery port in the silicon substrate 310. In contrast, the openings at the other end of each of the ink supply channel 48 and the ink recovery channel 49 of the first support member 4 have a shape that is enlarged to the same opening area as the large opening area of ​​the joint member 8 that is formed to match the flow channels of the circulation unit 54. By adopting this configuration, it is possible to suppress an increase in flow channel resistance for ink collected from each recovery channel. However, the shapes of the openings at one end and the other end of each of the ink supply channel 48 and the ink recovery channel 49 are not limited to the above example.

[0041] In the liquid ejection head 1 having the above configuration, ink supplied to the circulation unit 54 passes through the supply port 88 of the joint member 8 and the ink supply channel 48 of the first support member 4, and then flows into the common supply channel 18 from the ink supply port of the ejection module 300. The ink then flows from the common supply channel 18 through the supply connection channel 323 into the pressure chamber 12, and some of the ink that has flowed into the pressure chamber is ejected from the ejection port 13 by driving the ejection element 15. The remaining ink that has not been ejected passes from the pressure chamber 12 through the recovery connection channel 324 and the common recovery channel 19, and flows into the ink recovery channel 49 of the first support member 4 from the ink recovery port. The ink that has flowed into the ink recovery channel 49 then flows into the circulation unit 54 through the recovery port 89 of the joint member 8, and is recovered.

[0042] <Components of the circulation unit> 9 is a schematic external view of one circulation unit 54 corresponding to one type of ink that is applied to the liquid ejection device 50 of this embodiment. The circulation unit 54 is provided with a filter 110, a first pressure adjustment means 120, a second pressure adjustment means 150, and a circulation pump 500. These components are connected by respective flow paths as shown in FIGS. 10 and 11, and form a circulation path within the liquid ejection head 1 that supplies and recovers ink to and from the ejection module 300.

[0043] <Circulation path inside the liquid ejection head> FIG. 10 is a vertical cross-sectional view schematically illustrating a circulation path for one type of ink (one color of ink) configured within the liquid ejection head 1. To more clearly explain the circulation path, the relative positions of each component (first pressure adjustment unit 120, second pressure adjustment unit 150, circulation pump 500, etc.) in FIG. 10 are simplified. Therefore, the relative positions of each component differ from those in FIG. 9. FIG. 11 is a block diagram schematically illustrating the circulation path shown in FIG. 10. As shown in FIGS. 10 and 11, the first pressure adjustment unit 120 includes a first valve chamber 121 and a first pressure control chamber 122. The second pressure adjustment unit 150 includes a second valve chamber 151 and a second pressure control chamber 152. The first pressure adjustment unit 120 is configured to have a relatively higher control pressure than the second pressure adjustment unit 150. In this embodiment, by using these two pressure adjustment units 120 and 150, circulation within a constant pressure range is achieved within the circulation path. Furthermore, the ink is configured to flow through the pressure chamber 12 (ejection element 15) at a flow rate that corresponds to the pressure difference between the first pressure adjustment means 120 and the second pressure adjustment means 150. Below, the circulation path in the liquid ejection head 1 and the flow of ink within the circulation path will be explained with reference to Figures 10 and 11. Note that the arrows in each figure indicate the direction of ink flow.

[0044] Furthermore, in this embodiment, a bubble removal unit 770 is provided inside the liquid ejection head 1, and is configured to discharge bubbles generated in the liquid ejection head 1 to the outside of the liquid ejection head 1. Although Figures 10(a) and 10(b) show a configuration in which two bubble removal units 770 are provided at different positions, a single bubble removal unit may be provided, and its location is not limited to this configuration as long as it is possible to discharge bubbles to the outside of the liquid ejection head 1. A specific configuration of the bubble removal unit 770 will be described later.

[0045] 10(a) and 10(b), one of the two bubble removal units 770 is referred to as the first bubble removal unit 770A, and the other of the two bubble removal units 770 is referred to as the second bubble removal unit 770B. As described above, the number of bubble removal units 770 is not limited to two, and the liquid ejection head 1 may be provided with only one, or three or more. Each of the first bubble removal unit 770A and the second bubble removal unit 770B is provided with one bubble reservoir chamber 520, which will be described later. The bubble reservoir chamber 520 provided in the first bubble removal unit 770A is referred to as the first bubble reservoir chamber 520A, and the bubble reservoir chamber 520 provided in the second bubble removal unit 770B is referred to as the second bubble reservoir chamber 520B. In FIG. 11, the bubble removal unit 770 and the gas flow path connected to the bubble removal unit 770 (for example, the third air flow path 113, etc.) are not shown.

[0046] First, the connection state of each component in the liquid ejection head 1 will be described.

[0047] An ink supply section 400, which supplies ink stored in an ink tank 2 outside the liquid ejection head 1 to the liquid ejection head 1, is connected to the circulation unit 54 via a second supply path 112 (see FIG. 26). A filter 110 is provided in the ink flow path located upstream of the circulation unit 54. An ink supply path (third supply path 910) located downstream of the filter 110 is connected to a first valve chamber 121 of a first pressure adjustment means 120. The first valve chamber 121 is connected to a first pressure control chamber 122 via a communication port 191A that can be opened and closed by a valve 190A shown in FIG.

[0048] The first pressure control chamber 122 is connected to the supply flow path 130, the bypass flow path 160, and the pump outlet flow path 180 of the circulation pump 500. The supply flow path 130 is connected to the common supply flow path 18 via the ink supply port provided in the ejection module 300. The bypass flow path 160 is connected to a second valve chamber 151 provided in the second pressure adjustment means 150. The second valve chamber 151 is connected to the second pressure control chamber 152 via a communication port 191B that is opened and closed by a valve 190B shown in FIG. 10. Note that FIGS. 10 and 11 show an example in which one end of the bypass flow path 160 is connected to the first pressure control chamber 122 of the first pressure adjustment means 120, and the other end of the bypass flow path 160 is connected to the second valve chamber 151 of the second pressure adjustment means 150. However, one end of the bypass flow path 160 may be connected to the supply flow path 130, and the other end of the bypass flow path may be connected to the second valve chamber 151.

[0049] The second pressure control chamber 152 is connected to the first recovery channel 140. The first recovery channel 140 is connected to the common recovery channel 19 via the ink recovery port provided in the ejection module 300. Furthermore, the second pressure control chamber 152 is connected to the circulation pump 500 via the pump inlet channel 170.

[0050] Next, we will explain the flow of ink in the liquid ejection head 1 having the above configuration. As shown in Figure 11, the ink stored in the ink tank 2 is pressurized by the one-way pump 404 (see Figure 2) of the ink supply unit 400 provided in the liquid ejection device 50, and is supplied to the circulation unit 54 of the liquid ejection head 1 as a positive pressure ink flow.

[0051] The ink supplied to the circulation unit 54 passes through the filter 110 to remove foreign matter such as dust and air bubbles, and then flows into the first valve chamber 121 provided in the first pressure adjustment means 120. The ink pressure decreases due to pressure loss when passing through the filter 110, but the ink pressure at this stage is in a positive pressure state. After that, the ink that has flowed into the first valve chamber 121 passes through the communication port 191A and flows into the first pressure control chamber 122 when the valve 190A is in the open state. Due to the pressure loss when passing through the communication port 191A, the ink that has flowed into the first pressure control chamber 122 switches from positive pressure to negative pressure.

[0052] Next, the flow of ink within the circulation path will be described. The circulation pump 500 operates to suck ink from the pump inlet flow path 170, which is located upstream, and deliver it to the pump outlet flow path 180, which is located downstream. This pump inlet flow path 170 is located vertically below the second pressure adjustment means 150, so that bubbles flowing into the second pressure adjustment means 150 from the bypass flow path 160 rise to the surface without being carried by the ink flow and remain vertically above the second pressure adjustment means 150. Note that the pump inlet flow path 170 does not necessarily have to be located vertically below the second pressure adjustment means 150, as long as bubbles flowing into the second pressure adjustment means 150 rise to the surface and are collected in the second bubble reservoir chamber 520B. When the pump is driven, ink supplied to the first pressure control chamber 122 flows into the supply flow path 130 and the bypass flow path 160 together with ink delivered from the pump outlet flow path 180. Although details will be described later, in this embodiment, a piezoelectric diaphragm pump, driven by a piezoelectric element attached to a diaphragm, is used as a circulation pump capable of pumping liquid. A piezoelectric diaphragm pump is a pump that changes the volume of the pump chamber by inputting a drive voltage to the piezoelectric element, and pumps liquid by alternately moving two check valves due to pressure fluctuations.

[0053] The ink that has flowed into the supply flow path 130 flows from the ink supply port of the ejection module 300 through the common supply flow path 18 into the pressure chamber 12, and some of the ink is ejected from the ejection port 13 by driving (heat generation) the ejection element 15. The remaining ink that has not been used for ejection flows through the pressure chamber 12, passes through the common recovery flow path 19, and then flows into the first recovery flow path 140 connected to the ejection module 300. The ink that has flowed into the first recovery flow path 140 flows into the second pressure control chamber 152 of the second pressure adjustment means 150.

[0054] Meanwhile, ink that flows from the first pressure control chamber 122 into the bypass flow path 160 flows into the second valve chamber 151, then passes through the communication port 191B and flows into the second pressure control chamber 152. The ink that flows into the second pressure control chamber 152 via the bypass flow path 160 and the ink recovered from the first recovery flow path 140 are sucked into the circulation pump 500 via the pump inlet flow path 170 by driving the circulation pump 500. The ink sucked into the circulation pump 500 is then sent to the pump outlet flow path 180 and flows back into the first pressure control chamber 122. Subsequently, the ink that flows from the first pressure control chamber 122 into the second pressure control chamber 152 via the supply flow path 130 and the ejection module 300, and the ink that flows into the second pressure control chamber 152 via the bypass flow path 160, both flow into the circulation pump 500. The ink is then sent from the circulation pump 500 to the first pressure control chamber 122. In this manner, ink circulates within the circulation path.

[0055] Here, the flow path connecting the first pressure adjustment means 120 and the pressure chamber 12 is referred to as the first flow path, and the flow path connecting the pressure chamber 12 and the circulation pump 500 is referred to as the second flow path. That is, the supply flow path 130 is referred to as the first flow path, and the first recovery flow path 140, the second pressure adjustment means 150, and the pump inlet flow path 170 are collectively referred to as the second flow path. Note that the second flow path does not necessarily have to include the second pressure adjustment means 150 and the pump inlet flow path 170. The pump outlet flow path 180 is also referred to as the third flow path. Therefore, in this embodiment, ink flows through the circulation path of the circulation pump 500, the third flow path, the first pressure adjustment means 120, the first flow path, the pressure chamber 12, the second flow path, and the circulation pump 500 in this order.

[0056] As described above, in this embodiment, the circulation pump 500 can circulate the liquid (ink) along the circulation path formed inside the liquid ejection head 1. This makes it possible to suppress thickening of the ink inside the ejection module 300 and accumulation of sedimentary components of the ink colorant, thereby maintaining good ink fluidity in the ejection module 300 and ejection characteristics at the ejection ports.

[0057] Furthermore, since the circulation path in this embodiment is configured to be completed within the liquid ejection head 1, the length of the circulation path can be significantly reduced compared to when ink is circulated between the ink tank 2 provided outside the liquid ejection head and the liquid ejection head 1. This makes it possible to circulate the ink using a small circulation pump.

[0058] Furthermore, the connection flow path between the liquid ejection head 1 and the ink tank 2 is configured to include only a flow path for supplying ink. In other words, this configuration eliminates the need for a flow path for recovering ink from the liquid ejection head 1 to the ink tank 2. Therefore, only an ink supply tube is required to connect the ink tank 2 to the liquid ejection head 1, and no ink recovery tube is required. This allows the liquid ejection device 50 to have a simpler configuration with fewer tubes, thereby achieving a more compact overall device. Furthermore, reducing the number of tubes reduces ink pressure fluctuations caused by tube oscillations associated with the main scanning of the liquid ejection head 1. Furthermore, the oscillations of the tubes during the main scanning of the liquid ejection head 1 impose a driving load on the carriage motor that drives the carriage 60. Therefore, reducing the number of tubes reduces the driving load on the carriage motor, enabling the simplification of the main scanning mechanism, including the carriage motor. Furthermore, since it is no longer necessary to recover ink from the liquid ejection head to the ink tank, the one-way pump 404 (see FIG. 2) of the ink supply unit 400 can also be made more compact. As described above, according to this embodiment, the liquid ejection device 50 can be made smaller and less expensive.

[0059] <Pressure adjustment means> FIG. 12 is a cross-sectional view showing an example of a pressure adjustment means. Referring to FIG. 12, the configuration and operation of the pressure adjustment means (first pressure adjustment means 120, second pressure adjustment means 150) built into the liquid ejection head 1 described above will be described in more detail. The first pressure adjustment means 120 and the second pressure adjustment means 150 have substantially the same configuration. Therefore, the following description will be given taking the first pressure adjustment means 120 as an example, and the second pressure adjustment means 150 will simply be described with the reference numerals of the parts corresponding to those of the first pressure adjustment means in FIG. 12. In the case of the second pressure adjustment means 150, the first valve chamber 121 described below will be read as the second valve chamber 151, and the first pressure control chamber 122 will be read as the second pressure control chamber 152.

[0060] The first pressure adjustment means 120 has a first valve chamber 121 and a first pressure control chamber 122 formed in a cylindrical housing 125. The first valve chamber 121 and the first pressure control chamber 122 are separated by a partition wall 123 provided in the cylindrical housing 125. However, the first valve chamber 121 communicates with the first pressure control chamber 122 via a communication port 191 formed in the partition wall 123. The first valve chamber 121 is provided with a valve 190 that switches between communication and blocking between the first valve chamber 121 and the first pressure control chamber 122 at the communication port 191. The valve 190 is held in a position facing the communication port 191 by a valve spring 200, and is configured to be able to come into close contact with the partition wall 123 by the biasing force of the valve spring 200. When the valve 190 comes into close contact with the partition wall 123, the flow of ink through the communication port 191 is blocked. In order to increase the close contact with the partition wall 123, it is preferable that the portion of the valve 190 that comes into contact with the partition wall 123 be made of an elastic material. Furthermore, a valve shaft 190s that is inserted into the communication port 191 protrudes from the center of the valve 190. By pressing this valve shaft 190s against the biasing force of a valve spring 200, the valve 190 moves away from the partition wall 123, allowing ink to flow through the communication port 191. Hereinafter, the state in which the valve 190 blocks the flow of ink through the communication port 191 will be referred to as the "closed state," and the state in which ink can flow through the communication port 191 will be referred to as the "open state."

[0061] The opening of the cylindrical housing 125 is closed by a flexible member 230 and a pressure plate 210. A first pressure control chamber 122 is formed by this flexible member 230, the pressure plate 210, the peripheral wall of the housing 125, and the partition wall 123. The volume of the first pressure control chamber 122 is variable, and the pressure plate 210 is configured to be displaceable in accordance with the displacement of the flexible member 230. The materials of the pressure plate 210 and the flexible member 230 are not particularly limited, but for example, the pressure plate 210 can be configured as a molded resin part, and the flexible member 230 can be configured as a resin film. In this case, the pressure plate 210 can be fixed to the flexible member 230 by thermal welding.

[0062] A pressure adjustment spring 220 (biasing member) is provided between the pressure plate 210 and the partition wall 123. The biasing force of the pressure adjustment spring 220 biases the pressure plate 210 and the flexible member 230 in a direction in which the internal volume of the first pressure control chamber 122 increases, as shown in FIG. 12( a). Furthermore, when the pressure in the first pressure control chamber 122 decreases, the pressure plate 210 and the flexible member 230 displace in a direction in which the internal volume of the first pressure control chamber 122 decreases, against the pressure of the pressure adjustment spring 220. When the internal volume of the first pressure control chamber 122 decreases to a certain amount, the pressure plate 210 abuts against the valve shaft 190s of the valve 190. Thereafter, when the internal volume of the first pressure control chamber 122 further decreases, the valve 190 moves together with the valve shaft 190s against the biasing force of the valve spring 220 and moves away from the partition wall 123. As a result, the communication port 191 is in an open state (the state shown in FIG. 12(b)).

[0063] In this embodiment, the connections within the circulation path are set so that the pressure in the first valve chamber 121 when the communication port 191 is in the open state is higher than the pressure in the first pressure control chamber 122. As a result, when the communication port 191 is in the open state, ink flows from the first valve chamber 121 into the first pressure control chamber 122. This ink inflow displaces the flexible member 230 and the pressure plate 210 in a direction that increases the internal volume of the first pressure control chamber 122. As a result, the pressure plate 210 moves away from the valve shaft 190s of the valve 190, and the valve 190 is brought into close contact with the partition wall 123 by the biasing force of the valve spring 200, and the communication port 191 enters the closed state (the state shown in FIG. 12(c)).

[0064] In this way, in the first pressure adjustment means 120 of this embodiment, when the pressure inside the first pressure control chamber 122 decreases below a certain pressure (for example, when the negative pressure becomes strong), ink flows in from the first valve chamber 121 via the communication port 191. This prevents the pressure in the first pressure control chamber 122 from decreasing any further. Therefore, the pressure in the first pressure control chamber 122 is controlled to be kept within a certain range.

[0065] Next, the pressure in the first pressure control chamber 122 will be described in more detail.

[0066] As described above, consider a state in which the flexible member 230 and the pressure plate 210 are displaced in response to the pressure in the first pressure control chamber 122, causing the pressure plate 210 to come into contact with the valve shaft 190s and open the communication port 191 (the state shown in FIG. 12(b)). At this time, the relationship between the forces acting on the pressure plate 210 is expressed by the following equation (1).

[0067] P2×S2+F2+(P1-P2)×S1+F1=0 (1) P1: Pressure (gauge pressure) of the first valve chamber 121 P2: Pressure (gauge pressure) of the first pressure control chamber 122 F1: Valve spring force 200 F2: Spring force of pressure adjusting spring 220 S1: Pressure-receiving area of ​​valve 190 S2: Pressure receiving area of ​​pressure plate 210

[0068] Furthermore, rearranging equation (1) for P2 gives the following equation (2). P2=-(F1+F2+P1×S1) / (S2-S1) ···(2)

[0069] Here, the spring force F1 of the valve spring 200 and the spring force F2 of the pressure adjustment spring 220 are positive (leftward in FIG. 12) in the direction in which they press the valve 190 and the pressure plate 210. Furthermore, the pressure P1 in the first valve chamber 121 and the pressure P2 in the first pressure control chamber 122 are configured to satisfy the relationship P1 ≧ P2.

[0070] The pressure P2 in the first pressure control chamber 122 when the communication port 191 is in the open state is determined by equation (2). When the communication port 191 is in the open state, the relationship P1≧P2 is satisfied, and ink flows from the first valve chamber 121 into the first pressure control chamber 122. As a result, the pressure P2 in the first pressure control chamber 122 does not decrease any further and is maintained within a certain pressure range.

[0071] As shown in FIG. 12(c), when the pressure plate 210 is not in contact with the valve shaft 190s and the communication port 191 is closed, the relationship of the forces acting on the pressure plate 210 is expressed by the following equation (3).

[0072] P3×S3+F3=0 (3) F3: The spring force of the pressure adjusting spring 220 when the pressure plate 210 and the valve shaft 190s are not in contact with each other P3: Pressure (gauge pressure) in the first pressure control chamber 122 when the pressure plate 210 and the valve shaft 190s are not in contact with each other S3: Pressure-receiving area of ​​the pressure plate 210 when the pressure plate 210 and the valve 190 are not in contact with each other

[0073] Here, by rearranging equation (3) for P3, the following equation (4) is obtained. P3=-F3 / S3 (4)

[0074] Note that Figure 12(c) shows a state in which the pressure plate 210 and flexible member 230 have been displaced to the left in the figure to their limit of displacement. The pressure P3 in the first pressure control chamber 122, the spring force F3 of the pressure adjustment spring 220, and the pressure-receiving area S3 of the pressure plate 210 change depending on the amount of displacement of the pressure plate 210 and flexible member 230 while they are displaced to the state shown in Figure 12(c). Specifically, when the pressure plate 210 and flexible member 230 are positioned more to the right in Figure 12(c), the pressure-receiving area S3 of the pressure plate 210 becomes smaller and the spring force F3 of the pressure adjustment spring 220 becomes larger. As a result, the pressure P3 in the first pressure control chamber 122 decreases according to the relationship in equation (4). Therefore, according to equations (2) and (4), the pressure in the first pressure control chamber 122 gradually increases (i.e., the negative pressure weakens and approaches a value closer to the positive pressure side) from the state shown in FIG. 12(b) to the state shown in FIG. 12(c). That is, the pressure plate 210 and the flexible member 230 gradually displace leftward from the state in which the communication port 191 is open, and the pressure in the first pressure control chamber gradually increases until the internal volume of the first pressure control chamber 122 finally reaches its limit of displacement. In other words, the negative pressure weakens. In this embodiment, the first pressure adjustment means 120 adjusts the pressure of the liquid in the first flow path, and the second pressure adjustment means 150 adjusts the pressure of the liquid in the pump inlet flow path 170 (in the inlet flow path).

[0075] <Circulation pump> Next, the configuration and operation of the circulation pump 500 built into the liquid ejection head 1 will be described in detail with reference to FIGS.

[0076] FIG. 13 is an external perspective view of the circulation pump 500. FIG. 13(a) is an external perspective view showing the front side of the circulation pump 500, and FIG. 13(b) is an external perspective view showing the rear side of the circulation pump 500. The outer shell of the circulation pump 500 is composed of a pump housing 505 and a cover 507 fixed to the pump housing 505. The pump housing 505 is composed of a housing main body 505a and a flow path connecting member 505b adhesively fixed to the outer surface of the housing main body 505a. The housing main body 505a and the flow path connecting member 505b each have a pair of through holes that communicate with each other and are provided at two different positions. The pair of through holes provided at one position form pump supply holes 501, and the pair of through holes provided at the other position form pump discharge holes 502. The pump supply hole 501 is connected to the pump inlet flow path 170 which is connected to the second pressure control chamber 152, and the pump discharge hole 502 is connected to the pump outlet flow path 180 which is connected to the first pressure control chamber 122. Ink supplied from the pump supply hole 501 passes through a pump chamber 503 (see FIG. 14) which will be described later, and is discharged from the pump discharge hole 502.

[0077] FIG. 14 is a cross-sectional view of the circulation pump 500 shown in FIG. 13(a) taken along line XIV-XIV. A diaphragm 506 is bonded to the inner surface of a pump housing 505, and a pump chamber 503 is formed between the diaphragm 506 and a recess formed in the inner surface of the pump housing 505. The pump chamber 503 is connected to a pump supply hole 501 and a pump discharge hole 502 formed in the pump housing 505. A check valve 504a is provided in the middle of the pump supply hole 501, and a check valve 504b is provided in the middle of the pump discharge hole 502. That is, the circulation pump 500 is provided with a check valve in a flow path connecting the second flow path and the third flow path. Specifically, the check valve 504a is arranged so that a portion of the check valve 504a can move leftward in the figure in a space 512a formed in the middle of the pump supply hole 501. Also, the check valve 504b is arranged so that a part of it can move to the right in the figure in a space 512b formed in the middle part of the pump discharge hole 502.

[0078] When diaphragm 506 is displaced and the volume of pump chamber 503 increases, reducing the pressure in pump chamber 503, check valve 504a moves away from the opening of pump supply hole 501 in space 512a (i.e., moves to the left in the figure). When check valve 504a moves away from the opening of pump supply hole 501 in space 512a, it enters an open state that allows ink to flow through pump supply hole 501. When diaphragm 506 is displaced and the volume of pump chamber 503 decreases, pressurizing pump chamber 503, check valve 504a comes into close contact with the wall surface surrounding the opening of pump supply hole 501. As a result, it enters a closed state that blocks the flow of ink through pump supply hole 501.

[0079] On the other hand, when the pump chamber 503 is depressurized, the check valve 504b comes into close contact with the wall surface surrounding the opening of the pump housing 505 and enters a closed state in which it blocks the flow of ink through the pump discharge hole 502. When the pump chamber 503 is pressurized, the check valve 504b moves away from the opening of the pump housing 505 and toward the space 512b (that is, moves to the right in the figure), thereby allowing the flow of ink through the pump discharge hole 502.

[0080] The material of each check valve 504a, 504b may be any material that can deform in response to the pressure in the pump chamber 503, and may be made of, for example, an elastic material such as EPDM or elastomer, or a film or thin plate such as polypropylene, but is not limited to these.

[0081] As described above, pump chamber 503 is formed by the joining of pump housing 505 and diaphragm 506. Therefore, the pressure in pump chamber 503 changes as diaphragm 506 deforms. For example, when diaphragm 506 is displaced toward pump housing 505 (displaced to the right in the figure) and the volume of pump chamber 503 decreases, the pressure in pump chamber 503 increases. This causes check valve 504b, which is disposed opposite pump discharge hole 502, to open, and ink is discharged from pump chamber 503. At this time, check valve 504a, which is disposed opposite pump supply hole 501, is in close contact with the wall surface surrounding pump supply hole 501, and therefore backflow of ink from pump chamber 503 to pump supply hole 501 is suppressed.

[0082] Conversely, when diaphragm 506 is displaced in the direction in which pump chamber 503 expands, the pressure in pump chamber 503 decreases. As a result, check valve 504a arranged opposite pump supply hole 501 opens, and ink is supplied to pump chamber 503. At this time, check valve 504b arranged at pump discharge hole 502 comes into close contact with the wall surface surrounding an opening formed in pump casing 505, closing the opening. As a result, backflow of ink from pump discharge hole 502 to pump chamber 503 is suppressed.

[0083] In this way, in the circulation pump 500, the diaphragm 506 deforms, changing the pressure inside the pump chamber 503, thereby suctioning and discharging ink. At this time, if bubbles get into the pump chamber 503, even if the diaphragm 506 is displaced, the expansion and contraction of the bubbles will reduce the change in pressure inside the pump chamber 503, and the amount of liquid delivered will decrease. Therefore, the pump chamber 503 is arranged parallel to gravity to make it easier for bubbles that get into the pump chamber 503 to collect above the pump chamber 503, and the pump discharge hole 502 is arranged above the center of the pump chamber 503. This makes it possible to improve the ability to discharge bubbles inside the pump, and stabilize the flow rate.

[0084] <Ink flow inside the liquid ejection head> FIG. 15 is a diagram illustrating the flow of ink within a liquid ejection head. The circulation of ink within the liquid ejection head 1 will be described with reference to FIG. 15. To more clearly illustrate the ink circulation path, the relative positions of the components (first pressure adjustment unit 120, second pressure adjustment unit 150, circulation pump 500, etc.) in FIG. 15 have been simplified. Therefore, the relative positions of the components differ from those in FIG. 9. FIG. 15(a) is a schematic diagram illustrating the flow of ink during a recording operation in which ink is ejected from the ejection ports 13 to perform recording. The arrows in the figure indicate the flow of ink. In this embodiment, both the ink supply unit 400 and the circulation pump 500 start operating during a recording operation. The ink supply unit 400 and the circulation pump 500 may be operating regardless of the recording operation. The ink supply unit 400 and the circulation pump 500 do not need to be driven in conjunction with each other, and may be driven independently.

[0085] During the recording operation, the circulation pump 500 is in an ON state (driving state), and the ink flowing out from the first pressure control chamber 122 flows into the supply flow path 130 and the bypass flow path 160. The ink that flows into the supply flow path 130 passes through the ejection module 300, then flows into the first recovery flow path 140, and is then supplied to the second pressure control chamber 152.

[0086] Meanwhile, ink that has flowed from the first pressure control chamber 122 into the bypass flow path 160 passes through the second valve chamber 151 and then flows into the second pressure control chamber 152. The ink that has flowed into the second pressure control chamber 152 passes through the pump inlet flow path 170, the circulation pump 500, and the pump outlet flow path 180, and then flows back into the first pressure control chamber 122. At this time, the control pressure of the first valve chamber 121 is set higher than the control pressure of the first pressure control chamber 122 based on the relationship of the above-mentioned equation (2). Therefore, the ink in the first pressure control chamber 122 is supplied again to the ejection module 300 via the supply flow path 130 without flowing into the first valve chamber 121. The ink that has flowed into the ejection module 300 passes through the first recovery flow path 140, the second pressure control chamber 152, the pump inlet flow path 170, the circulation pump 500, and the pump outlet flow path 180, and then flows back into the first pressure control chamber 122. In this manner, ink circulation is completed within the liquid ejection head 1.

[0087] In the ink circulation described above, the amount of ink circulating (flow rate) within the ejection module 300 is determined by the difference in control pressure between the first pressure control chamber 122 and the second pressure control chamber 152. This difference in pressure is set to a circulation amount that can suppress thickening of ink near the ejection ports within the ejection module 300. In addition, ink consumed during printing is supplied from the ink tank 2 to the first pressure control chamber 122 via the filter 110 and the first valve chamber 121. The mechanism by which the consumed ink is supplied will be described in detail below. As the amount of ink consumed during printing is reduced from the circulation path by the amount of ink consumed, the pressure within the first pressure control chamber decreases, and as a result, the amount of ink within the first pressure control chamber 122 also decreases. As the amount of ink within the first pressure control chamber 122 decreases, the internal volume of the first pressure control chamber 122 decreases. This decrease in the internal volume of the first pressure control chamber 122 opens the communication port 191A, and ink is supplied from the first valve chamber 121 to the first pressure control chamber 122. This supplied ink experiences a pressure loss as it passes from first valve chamber 121 through communication port 191A, and as it flows into first pressure control chamber 122, the ink changes from a positive pressure state to a negative pressure state. As ink flows from first valve chamber 121 into first pressure control chamber 122, the pressure inside the first pressure control chamber increases, increasing the internal volume of the first pressure control chamber and closing communication port 191A. In this way, communication port 191A alternates between an open state and a closed state depending on the consumption of ink. Furthermore, when ink is not consumed, communication port 191A remains closed.

[0088] FIG. 15B is a schematic diagram showing the flow of ink immediately after the recording operation is completed and the circulation pump 500 is turned off (stopped). When the recording operation is completed and the circulation pump 500 is turned off, the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152 are both at the control pressures during the recording operation. Therefore, ink movement occurs as shown in FIG. 15B depending on the pressure difference between the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152. Specifically, ink continues to flow from the first pressure control chamber 122 to the ejection module 300 via the supply flow path 130, and then through the first recovery flow path 140 to the second pressure control chamber 152. Furthermore, ink also continues to flow from the first pressure control chamber 122 to the second pressure control chamber 152 via the bypass flow path 160 and the second valve chamber 151.

[0089] The amount of ink that moves from the first pressure control chamber 122 to the second pressure control chamber 152 due to these ink flows is supplied to the first pressure control chamber 122 from the ink tank 2 via the filter 110 and the first valve chamber 121. Therefore, the internal volume of the first pressure control chamber 122 is maintained constant. From the relationship in equation (2) above, when the internal volume of the first pressure control chamber 122 is constant, the spring force F1 of the valve spring 200, the spring force F2 of the pressure adjustment spring 220, the pressure-receiving area S1 of the valve 190, and the pressure-receiving area S2 of the pressure plate 210 are maintained constant. Therefore, the pressure in the first pressure control chamber 122 is determined according to changes in the pressure (gauge pressure) P1 in the first valve chamber 121. Therefore, when there is no change in the pressure P1 in the first valve chamber 121, the pressure P2 in the first pressure control chamber 122 is maintained at the same pressure as the control pressure during the recording operation.

[0090] Meanwhile, the pressure in the second pressure control chamber 152 changes over time in response to changes in the volume of ink due to the inflow of ink from the first pressure control chamber 122. Specifically, from the state shown in FIG. 15(b) until the communication port 191 closes and the second valve chamber 151 and the second pressure control chamber 152 are not in communication, as shown in FIG. 15(c), the pressure in the second pressure control chamber 152 changes according to equation (2). Thereafter, the pressure plate 210 and the valve shaft 190s are not in contact with each other, and the communication port 191 is closed. Then, as shown in FIG. 15(d), ink flows from the first recovery channel 140 into the second pressure control chamber 152. This ink inflow displaces the pressure plate 210 and the flexible member 230, and the pressure in the second pressure control chamber 152 changes according to equation (4) until the volume of the second pressure control chamber 152 reaches its maximum. That is, the pressure increases.

[0091] 15(c), no ink flows from the first pressure control chamber 122 to the second pressure control chamber 152 via the bypass flow path 160 and the second valve chamber 151. Therefore, after the ink in the first pressure control chamber 122 is supplied to the ejection module 300 via the supply flow path 130, only a flow occurs that reaches the second pressure control chamber 152 via the first recovery flow path 140. As described above, the movement of ink from the first pressure control chamber 122 to the second pressure control chamber 152 occurs according to the pressure difference between the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152. Therefore, when the pressure in the second pressure control chamber 152 becomes equal to the pressure in the first pressure control chamber 122, the movement of ink stops.

[0092] Furthermore, when the pressure in the second pressure control chamber 152 becomes equal to the pressure in the first pressure control chamber 122, the second pressure control chamber 152 expands to the state shown in FIG. 15(d). When the second pressure control chamber 152 expands as shown in FIG. 15(d), a storage section capable of storing ink is formed in the second pressure control chamber 152. Note that the time required from stopping the circulation pump 500 to transition to the state shown in FIG. 15(d) generally takes about one to two minutes, although this time may vary depending on the shape and size of the flow path and the properties of the ink. When the circulation pump 500 is driven from the state shown in FIG. 15(d) in which ink is stored in the storage section, the ink in the storage section is supplied to the first pressure control chamber 122 by the circulation pump 500. As a result, the amount of ink in the first pressure control chamber 122 increases, as shown in FIG. 15(e), and the flexible member 230 and the pressure plate 210 are displaced in the expansion direction. Then, when the circulation pump 500 continues to be driven, the state inside the circulation path changes as shown in FIG. 15(a).

[0093] 15(a) has been described above as an example during a printing operation, but as mentioned above, ink may be circulated without a printing operation. Even in this case, ink flows as shown in FIGS. 15(a) to 15(e) occur depending on whether the circulation pump 500 is driven or stopped.

[0094] As described above, in this embodiment, the communication port 191B in the second pressure adjustment means 150 is in an open state when the circulation pump 500 is driven to circulate ink, and is in a closed state when the circulation of ink stops, but this is not limiting. The control pressure may be set so that the communication port 191B in the second pressure adjustment means 150 is in a closed state even when the circulation pump 500 is driven to circulate ink. Below, this will be described in detail together with the role of the bypass flow path 160.

[0095] The bypass flow path 160 connecting the first pressure adjustment means 120 and the second pressure adjustment means 150 is provided to prevent the negative pressure generated in the circulation path from being stronger than a predetermined value, for example, from affecting the ejection module 300. The bypass flow path 160 is also provided to supply ink to the pressure chamber 12 from both the supply flow path 130 and the first recovery flow path 140.

[0096] First, an example will be described in which the bypass flow path 160 prevents the negative pressure from being stronger than a predetermined value and thus affects the ejection module 300. For example, changes in the ambient temperature can change the ink characteristics (e.g., viscosity). When the ink viscosity changes, the pressure loss in the circulation path also changes. For example, when the ink viscosity decreases, the pressure loss in the circulation path decreases. As a result, the flow rate of the circulation pump 500, which is driven at a constant drive rate, increases, and the flow rate through the ejection module 300 also increases. Meanwhile, because the ejection module 300 is maintained at a constant temperature by a temperature adjustment mechanism (not shown), the viscosity of the ink in the ejection module 300 remains constant even when the ambient temperature changes. While the viscosity of the ink in the ejection module 300 remains unchanged, the flow rate of the ink flowing through the ejection module 300 increases, and the negative pressure in the ejection module 300 increases accordingly due to flow path resistance. In this way, if the negative pressure in the discharge module 300 becomes stronger than the predetermined value, the meniscus of the discharge port 13 may be destroyed, and external air may be drawn into the circulation path, preventing normal discharge. Even if the meniscus is not destroyed, the negative pressure in the pressure chamber 12 may become stronger than predetermined, which may affect discharge.

[0097] For this reason, in this embodiment, a bypass flow path 160 is formed in the circulation path. By providing the bypass flow path 160, when the negative pressure becomes stronger than a predetermined value, ink also flows through the bypass flow path 160, making it possible to maintain a constant pressure in the ejection module 300. Therefore, for example, the communication port 191B in the second pressure adjustment unit 150 may be configured with a control pressure that maintains the closed state even when the circulation pump 500 is being driven. The control pressure in the second pressure adjustment unit may be set so that the communication port 191 in the second pressure adjustment unit 150 is opened when the negative pressure becomes stronger than a predetermined value. In other words, as long as the meniscus does not collapse even when the pump flow rate changes due to viscosity changes such as environmental changes, or as long as a predetermined negative pressure is maintained, the communication port 191B may be closed when the circulation pump 500 is being driven.

[0098] Next, an example will be described in which the bypass flow path 160 is provided to supply ink to the pressure chamber 12 from both the supply flow path 130 and the first recovery flow path 140. Pressure fluctuations within the circulation path can also occur due to the ejection operation of the ejection element 15. This is because the ejection operation generates a force that draws ink into the pressure chamber.

[0099] Below, we will explain that when high-duty recording continues, ink is supplied to the pressure chamber 12 from both the supply flow path 130 side and the first recovery flow path 140 side. Note that the definition of duty can change depending on various conditions, but here, the state in which recording is performed by ejecting one 4 pL ink droplet onto a 1200 dpi grid will be considered to be 100%. High-duty recording means, for example, recording at a duty of 100%.

[0100] As recording at a high duty continues, the amount of ink flowing from the pressure chamber 12 into the second pressure control chamber 152 through the first recovery channel 140 decreases. Meanwhile, because the circulation pump 500 discharges ink at a constant rate, the balance between inflow and outflow in the second pressure control chamber 152 is disrupted, the ink in the second pressure control chamber 152 decreases, the negative pressure in the second pressure control chamber 152 increases, and the second pressure control chamber 152 shrinks. As the negative pressure in the second pressure control chamber 152 increases, the amount of ink flowing into the second pressure control chamber 152 through the bypass channel 160 increases, and the second pressure control chamber 152 stabilizes with the inflow and outflow balanced. As a result, the negative pressure in the second pressure control chamber 152 increases in accordance with the duty. Furthermore, as described above, when the circulation pump 500 is driven, in a configuration in which the communication port 191B is in a closed state, the communication port 191B opens depending on the duty, and ink flows from the bypass flow path 160 into the second pressure control chamber 152.

[0101] Then, as recording at an even higher duty continues, the amount of ink flowing from the pressure chamber 12 into the second pressure control chamber 152 through the first recovery channel 140 decreases, and instead the amount flowing into the second pressure control chamber 152 from the communication port 191B via the bypass channel 160 increases. As this state progresses further, the amount of ink flowing from the pressure chamber 12 into the second pressure control chamber 152 through the first recovery channel 140 becomes zero, and all of the ink flowing out to the circulation pump 500 becomes ink flowing in from the communication port 191B. As this state progresses further, ink now flows back from the second pressure control chamber 152 into the pressure chamber 12 through the first recovery channel 140. In this state, the ink flowing out from the second pressure control chamber 152 to the circulation pump 500 and the ink flowing out to the pressure chamber 12 flow into the second pressure control chamber 152 from the communication port 191B via the bypass channel 160. In this case, the pressure chamber 12 is filled with ink from the supply flow path 130 and ink from the first recovery flow path 140, and is ejected.

[0102] Incidentally, this backflow of ink that occurs when the printing duty is high is a phenomenon that occurs due to the provision of the bypass flow path 160. Also, in the above, an example has been described in which the communication port 191B in the second pressure adjustment means is opened in response to the backflow of ink, but backflow of ink can also occur when the communication port 191B in the second pressure adjustment means is opened. Also, even in a configuration that does not include a second pressure adjustment means, the provision of the bypass flow path 160 can cause the above-mentioned backflow of ink. Incidentally, the bypass flow path 160 may simply connect at least one of the first flow path and the first pressure adjustment means 120 to the second flow path without passing through the pressure chamber 12.

[0103] <Configuration of the discharge unit> FIG. 16 is a schematic diagram showing the circulation path for one color of ink in the ejection unit 3 of this embodiment. FIG. 16(a) is an exploded perspective view of the ejection unit 3 as seen from the first support member 4 side, and FIG. 16(b) is an exploded perspective view of the ejection unit 3 as seen from the ejection module 300 side. The arrows marked IN and OUT in the figure indicate the flow of ink. While only one color of ink is described, the other colors have similar flows. The second support member 7 and the electrical wiring member 5 are omitted from FIG. 16 and will also be omitted in the following description of the ejection unit configuration. The first support member 4 in FIG. 16(a) shows a cross section taken along line XVI-XVI in FIG. 8. As described above, the ejection module 300 includes a silicon substrate 310 and multiple ejection elements 15. The silicon substrate 310 includes an ejection element substrate 340 and an aperture plate 330. FIG. 17 illustrates the aperture plate 330, and FIG. 18 illustrates the ejection element substrate 340.

[0104] Ink is supplied to the discharge unit 3 from the circulation unit 54 via a joint member 8 (see FIG. 8(a)). The path of the ink from when the ink passes through the joint member 8 until it returns to the joint member 8 will be described. Note that the joint member 8 will not be shown in the following drawings.

[0105] The ejection module 300 includes an ejection element substrate 340 and an aperture plate 330 that constitute a silicon substrate 310, and further includes an ejection port forming member 320. The ejection element substrate 340, the aperture plate 330, and the ejection port forming member 320 are overlapped and joined together so that the ink flow paths communicate with each other to form the ejection module 300, which is supported by a first support member 4. The ejection module 300 is supported by the first support member 4 to form an ejection unit 3. The ejection port forming member 320 is provided on the surface (the lower surface in FIG. 16(b)) of the ejection element substrate 340. The ejection port forming member 320 includes multiple ejection port arrays, each of which has a plurality of ejection ports 13 arranged in rows. A portion of the ink supplied via the ink flow path in the ejection module 300 is ejected from the ejection ports 13. Unejected ink is collected via the ink flow path in the ejection module 300.

[0106] As shown in FIGS. 16 and 17, the aperture plate 330 has a plurality of arranged ink supply ports 311 and a plurality of arranged ink recovery ports 312. As shown in FIGS. 18 and 19, the ejection element substrate 340 has a plurality of arranged supply connection channels 323 and a plurality of arranged recovery connection channels 324. The ejection element substrate 340 further has a common supply channel 18 that communicates with the plurality of supply connection channels 323, and a common recovery channel 19 that communicates with the plurality of recovery connection channels 324. The ink flow channels in the ejection unit 3 are formed by connecting an ink supply channel 48 and an ink recovery channel 49 (see FIG. 8(a)) provided in the first support member 4 to channels provided in the ejection module 300. The support member supply port 211 is a cross-sectional opening that forms the ink supply channel 48, and the support member recovery port 212 is a cross-sectional opening that forms the ink recovery channel 49.

[0107] Ink supplied to the ejection unit 3 is supplied from the circulation unit 54 (see FIG. 8(a)) side to the ink supply flow path 48 (see FIG. 8(a)) of the first support member 4. The ink flows through the support member supply port 211 in the ink supply flow path 48, and is supplied to the common supply flow path 18 of the ejection element substrate 340 via the ink supply flow path 48 (see FIG. 8(a)) and the ink supply port 311 of the opening plate 330, and enters the supply connection flow path 323. This forms the supply side flow path. The ink then flows through the pressure chamber 12 (see FIG. 8(b)) of the ejection port forming member 320 to the recovery connection flow path 324, which is a recovery side flow path. The flow of ink in the pressure chamber 12 will be described in detail later.

[0108] In the recovery flow path, ink that has entered the recovery connection flow path 324 of the ejection element substrate 340 flows into the common recovery flow path 19. The ink then flows from the common recovery flow path 19 through the ink recovery port 312 of the opening plate 330 to the ink recovery flow path 49 of the first support member 4, and passes through the support member recovery port 212 to be recovered into the circulation unit 54.

[0109] The area of ​​the opening plate 330 that does not have the ink supply port 311 or the ink recovery port 312 corresponds to the area that separates the support member supply port 211 and the support member recovery port 212 in the first support member 4. The first support member 4 also does not have any openings in this area. Such an area is used as an adhesion area when the ejection module 300 and the first support member 4 are adhered to each other.

[0110] As shown in FIG. 17 , the aperture plate 330 is provided with a plurality of rows of apertures arranged in the X direction and a plurality of rows in the Y direction, where the supply (IN) apertures and the recovery (OUT) apertures are alternately arranged in the Y direction with a half-pitch offset in the X direction. The supply (IN) apertures are formed by ink supply ports 311, and the recovery (OUT) apertures are formed by ink recovery ports 312. As shown in FIG. 18 , the ejection element substrate 340 is alternately arranged in the X direction with common supply channels 18 communicating with a plurality of supply connection channels 323 arranged in the Y direction and common recovery channels 19 communicating with a plurality of recovery connection channels 324 arranged in the Y direction. The common supply channels 18 and the common recovery channels 19 are separated by ink type, and the number of common supply channels 18 and common recovery channels 19 is determined according to the number of ejection port rows for each color. The number of supply connection channels 323 and recovery connection channels 324 also corresponds to the number of ejection ports 13. It is not necessary to have a one-to-one correspondence, and one supply connection flow path 323 and one recovery connection flow path 324 may correspond to a plurality of discharge ports 13 .

[0111] Such an opening plate 330 and an ejection element substrate 340 are overlapped and joined together so that the flow paths of each ink are connected to form an ejection module 300, and by being supported by the first support member 4, an ink flow path is formed that includes the supply flow path and recovery flow path as described above.

[0112] Figure 19 is a cross-sectional view showing ink flow in different parts of the discharge unit 3. Figure 19(a) is a cross-section shown by XIXa-XIXa in Figure 16(a) and shows a cross-section of a part in the discharge unit 3 where the ink supply channel 48 and the ink supply port 311 communicate with each other. Figure 19(b) is a cross-section shown by XIXb-XIXb in Figure 16(a) and shows a cross-section of a part in the discharge unit 3 where the ink recovery channel 49 and the ink recovery port 312 communicate with each other. Figure 19(c) is a cross-section shown by XIXc-XIXc in Figure 16(a) and shows a cross-section of a part where the ink supply port 311 and the ink recovery port 312 do not communicate with the channels in the first support member 4.

[0113] In the supply flow path that supplies ink, ink is supplied from a portion where the ink supply flow path 48 of the first support member 4 and the ink supply port 311 of the aperture plate 330 overlap and communicate, as shown in FIG. 19(a). In the recovery flow path that recovers ink, ink is recovered from a portion where the ink recovery flow path 49 of the first support member 4 and the ink recovery port 312 of the aperture plate 330 overlap and communicate, as shown in FIG. 19(b). In the ejection unit 3, there are also regions where no openings are provided in the aperture plate 330, as shown in FIG. 19(c). In such regions, ink is not supplied or recovered between the ejection element substrate 340 and the first support member 4. Ink is supplied in a region where the ink supply port 311 is provided, as shown in FIG. 19(a), and ink is recovered in a region where the ink recovery port 312 is provided, as shown in FIG. 19(b). While the present embodiment has been described with reference to a configuration that uses the aperture plate 330, a configuration that does not use the aperture plate 330 may also be used. For example, a configuration may be adopted in which flow paths corresponding to the ink supply flow path 48 and the ink recovery flow path 49 are formed in the first support member 4, and the ejection element substrate 340 is joined to the first support member 4.

[0114] 20(a) and 20(b) are cross-sectional views showing the vicinity of the ejection ports 13 in the ejection module 300. FIGS. 21(a) and 21(b) are cross-sectional views showing, as a comparative example, an ejection module configured such that the common supply channel 18 and the common recovery channel 19 are widened in the X direction. The thick arrows shown in the common supply channel 18 and the common recovery channel 19 in FIGS. 20(a) and 20(b) and 21(a) and 21(b) indicate the ink oscillation in a configuration using a serial liquid ejection device 50. Ink supplied to the pressure chambers 12 via the common supply channel 18 and the supply connection channel 323 is ejected from the ejection ports 13 when the ejection elements 15 are driven. When the ejection elements 15 are not driven, ink is recovered from the pressure chambers 12 to the common recovery channel 19 via the recovery connection channel 324, which is a recovery channel.

[0115] In a configuration using a serial liquid ejection device 50, when ejecting ink from circulating ink in this manner, the ejection of ink is affected to a certain extent by the fluctuation of ink in the ink flow paths due to the main scanning of the liquid ejection head 1. Specifically, the influence of the fluctuation of ink in the ink flow paths can manifest as differences in the amount of ink ejected or deviations in the ejection direction. As shown in Figures 21(a) and 21(b), if the common supply flow path 18 and the common recovery flow path 19 have a cross-sectional shape that is wide in the X direction, which is the main scanning direction, the ink in the common supply flow path 18 and the common recovery flow path 19 is more susceptible to inertial forces in the main scanning direction, causing the ink to fluctuate significantly. As a result, the fluctuation of ink may affect the ejection of ink from the ejection ports 13. Furthermore, widening the common supply flow path 18 and the common recovery flow path 19 in the X direction increases the distance between colors, which may reduce printing efficiency.

[0116] Therefore, in the cross sections shown in FIGS. 20(a) and 20(b), the common supply flow path 18 and the common recovery flow path 19 of this embodiment extend in the Y direction, but are also configured to extend in the Z direction, which is perpendicular to the X direction, the main scanning direction. This configuration allows the width of each of the common supply flow path 18 and the common recovery flow path 19 in the main scanning direction to be reduced. Reducing the width of each of the common supply flow path 18 and the common recovery flow path 19 in the main scanning direction reduces ink oscillation (see the bold black arrows in the figure) due to inertial forces acting on the ink in the common supply flow path 18 and the common recovery flow path 19 in the direction opposite to the main scanning direction during main scanning. This reduces the impact of ink oscillation on ink ejection. Furthermore, extending the common supply flow path 18 and the common recovery flow path 19 in the Z direction increases the cross-sectional area of ​​the common supply flow path 18 and the common recovery flow path 19, thereby reducing flow path pressure loss.

[0117] As described above, by reducing the width of each of the common supply flow path 18 and the common recovery flow path 19 in the main scanning direction, the ink fluctuation in the common supply flow path 18 and the common recovery flow path 19 during main scanning is reduced, but this does not mean that the ink fluctuation is eliminated. In this embodiment, in order to suppress differences in the ejection of each type of ink that may still occur due to reduced ink fluctuation, the common supply flow path 18 and the common recovery flow path 19 are configured to be positioned so as to overlap in the X direction.

[0118] As described above, in this embodiment, the supply connection flow path 323 and the recovery connection flow path 324 are provided corresponding to the ejection port 13, and the supply connection flow path 323 and the recovery connection flow path 324 are arranged side by side in the X direction with the ejection port 13 sandwiched between them. Therefore, there are portions where the common supply flow path 18 and the common recovery flow path 19 do not overlap in the X direction, and if the corresponding relationship in the X direction between the supply connection flow path 323 and the recovery connection flow path 324 is disrupted, this will affect the flow and ejection of ink in the X direction in the pressure chamber 12. When the influence of ink fluctuation is added to this, there is a risk that this will further affect the ejection of ink from each ejection port.

[0119] Therefore, by arranging the common supply flow path 18 and the common recovery flow path 19 at positions where they overlap in the X direction, ink fluctuation during main scanning in the common supply flow path 18 and the common recovery flow path 19 becomes approximately the same at any position in the Y direction where the ejection ports 13 are arranged. As a result, the pressure difference between the common supply flow path 18 side and the common recovery flow path 19 side that occurs inside the pressure chamber 12 does not vary greatly, allowing for stable ejection.

[0120] Furthermore, in some liquid ejection heads that circulate ink, the flow path that supplies ink to the liquid ejection head and the flow path that recovers ink are configured as the same flow path, but in this embodiment, the common supply flow path 18 and the common recovery flow path 19 are separate flow paths. The supply connection flow path 323 and the pressure chamber 12 are connected to each other, and the pressure chamber 12 is connected to the recovery connection flow path 324, and ink is ejected from the ejection port 13 of the pressure chamber 12. In other words, the pressure chamber 12, which is a path connecting the supply connection flow path 323 and the recovery connection flow path 324, is configured to have the ejection port 13. Therefore, an ink flow from the supply connection flow path 323 side to the recovery connection flow path 324 side is generated in the pressure chamber 12, and the ink in the pressure chamber 12 is efficiently circulated. By efficiently circulating the ink in the pressure chamber 12, the ink in the pressure chamber 12, which is easily affected by evaporation of ink from the ejection port 13, can be kept fresh.

[0121] Furthermore, since the two flow paths, the common supply flow path 18 and the common recovery flow path 19, are connected to the pressure chamber 12, if it becomes necessary to eject ink at a high flow rate, it is possible to supply ink from both flow paths. In other words, compared to a configuration in which ink supply and recovery are configured using only one flow path, the configuration of this embodiment has the advantage of not only being able to circulate ink efficiently, but also being able to accommodate ejection at a high flow rate.

[0122] Furthermore, the common supply flow path 18 and the common recovery flow path 19 are less susceptible to the influence of ink fluctuations when they are positioned closer to each other in the X direction. Preferably, the distance between the flow paths is 75 μm to 100 μm.

[0123] FIG. 22 is a diagram showing an ejection element substrate 340 as a comparative example. Note that in FIG. 22, the supply connection channel 323 and the recovery connection channel 324 are not shown. Since ink that has received thermal energy from the ejection elements 15 in the pressure chambers 12 flows into the common recovery channel 19, ink with a relatively high temperature flows therethrough compared to the temperature of the ink in the common supply channel 18. At this time, in the comparative example, there is a portion in the X direction of the ejection element substrate 340 where only the common recovery channel 19 exists, such as the portion α surrounded by the dashed dotted line in FIG. 22. In this case, the temperature rises locally in that portion, causing temperature unevenness in the ejection module 300 and possibly affecting ejection.

[0124] In the common supply flow path 18, ink flows that is at a relatively low temperature relative to the common recovery flow path 19. Therefore, when the common supply flow path 18 and the common recovery flow path 19 are adjacent to each other, the temperatures in the common supply flow path 18 and the common recovery flow path 19 are partially offset, suppressing temperature increases in the vicinity thereof. Therefore, it is preferable that the common supply flow path 18 and the common recovery flow path 19 are adjacent to each other and have approximately the same length, and are positioned so as to overlap each other in the X direction.

[0125] 23(a) and 23(b) are diagrams showing the flow path configuration of a liquid ejection head compatible with three types of ink: cyan (C), magenta (M), and yellow (Y). In a liquid ejection head compatible with three types of ink, a circulation flow path is provided for each type of ink, as shown in FIG. 23(a). The pressure chambers 12 are provided along the X direction, which is the main scanning direction of the liquid ejection head. Also, as shown in FIG. 23(b), the common supply flow path 18 and the common recovery flow path 19 are provided along the ejection port array in which the ejection ports 13 are arranged, and extend in the Y direction so that the ejection port array is sandwiched between the common supply flow path 18 and the common recovery flow path 19.

[0126] <Ink backflow near the ejection port> FIG. 24 is a diagram schematically illustrating the backflow of ink near the ejection port. FIG. 24(a) is a longitudinal cross-sectional view schematically illustrating the backflow of ink occurring in the circulation path shown in FIG. 10(a), and FIG. 24(b) is an enlarged view schematically illustrating the backflow of ink occurring in the ejection module 300 shown in FIG. 8(b). FIGS. 24(a) and 24(b) show the flow of ink in the pressure chamber 12, flowing in from the common supply channel 18 or the common recovery channel 19, passing through the pressure chamber 12, and flowing out from the ejection port 13. As described above, when high-duty recording is continued, ink also flows back into the pressure chamber 12 from the first recovery channel 140 side. In other words, as shown in FIGS. 24(a) and 24(b), ink is refilled into the pressure chamber 12 from both the supply channel 130 (common supply channel 18) and the first recovery channel 140 (common recovery channel 19). That is, the ink supplied from the first pressure control chamber 122 to the bypass flow path 160 is supplied to the second pressure control chamber 152 via the second valve chamber 151 of the second pressure adjustment means 150. Then, a portion of the ink supplied to the second pressure control chamber 152 is supplied to the first recovery flow path 140 and then to the ejection port 13 via the common recovery flow path 19.

[0127] FIG. 25 is a diagram illustrating ink supply within the ejection module 300. FIG. 25(a) is a diagram illustrating a flow path configuration near the pressure chamber 12, illustrating a comparative example different from this embodiment. In FIG. 25(a), only one side of the pressure chamber 12 is connected to the flow path 2010. In this configuration, ink is supplied to the pressure chamber 12 from only the flow path 2010, resulting in a one-sided supply. In the configuration of FIG. 25(a), the independent supply port 2020 connected to the pressure chamber 12 is connected to the common supply flow path 18 or the common recovery flow path 19, or both. When a thermal-type ejection element is used as the ejection element 15, ink is ejected from the ejection port 13 due to bubble formation within the pressure chamber 12. Furthermore, the pressure chamber 12 is refilled with ink due to the defoaming associated with the bubble formation. In this flow path configuration, the width of the flow path 2010 connected to the pressure chamber 12 is narrowed or the length is increased to increase the rearward resistance during bubble formation. This makes the bubbles more symmetrical, improving droplet formation. On the other hand, with a configuration like that shown in FIG. 25(a), when ink is refilled into the pressure chamber 12 after the bubbles have disappeared after ejection, the increased rear resistance reduces the supply efficiency. Therefore, with the flow path configuration shown in FIG. 25(a), it is generally difficult to improve the refill frequency. In particular, when performing printing operations at a high duty, the amount of ink supplied to the ejection port 13 may decrease, which may result in a decrease in ejection stability.

[0128] On the other hand, FIG. 25(b) is a diagram showing the flow path configuration near the pressure chamber 12 in this embodiment. A supply connection flow path 323, which is a first independent supply port, connects the first liquid flow path 2030 leading to the pressure chamber 12 with the common supply flow path 18. A recovery connection flow path 324, which is a second independent supply port, connects the second liquid flow path 2040 leading to the pressure chamber 12 with the common recovery flow path 19. As described above, in this embodiment, ink ejected from the ejection port 13 is refilled from the first liquid flow path 2030 and the second liquid flow path 2040. As shown in FIG. 25(b), this is a double-sided supply configuration in which both sides of the pressure chamber 12 are connected to the first liquid flow path 2030 and the second liquid flow path 2040. In this configuration, as shown in FIG. 25(b), even if the width or length of the flow path leading to the pressure chamber 12 is increased or decreased, bubbling tends to become more symmetrical due to the symmetry of the rear resistance during bubbling. This facilitates improved ink droplet formation. Furthermore, since there is no need to increase the rear resistance when ink is refilled into the pressure chamber 12 when bubbles disappear after ejection, ink supply performance can be improved. Thus, according to this embodiment, ejection stability can be improved even when recording is performed at a high duty. In other words, it is possible to achieve both improved droplet formation and an increased refill frequency.

[0129] Although the above embodiment mainly describes the use of thermal ejection elements, piezo ejection elements may also be used. However, since the thermal method is more difficult to achieve both improved droplet formation and an increased refill frequency, this embodiment is more suitable for the thermal method.

[0130] <Connection between the main body and the liquid ejection head> 26 is a schematic diagram showing the connection state between the ink tank 2 and ink supply unit 400 provided in the main body of the liquid ejection device 50 of this embodiment and the liquid ejection head 1. The liquid ejection device 50 of this embodiment is configured to allow for easy replacement of the liquid ejection head 1 alone when a malfunction occurs in the liquid ejection head 1. Specifically, a main body side connecting member 470 and a head side connecting member 800 are provided, which allow for easy connection and disconnection of the second supply path 112 and third air flow path 113 connected to the ink supply unit 400 from the liquid ejection head 1. This makes it possible to easily attach and detach just the liquid ejection head 1 to and from the liquid ejection device 50.

[0131] 26, the head-side connecting member 800 is detachably attached to the head housing 53 of the liquid ejection head 1. The head-side connecting member 800 is connected to the ink supply path (third supply path 910) in the circulation unit 54 via a filter 110. The head-side connecting member 800 is also connected to the first bubble removal unit 770A and the second bubble removal unit 770B via a degassing flow path 541 in the circulation unit 54.

[0132] The main body side connecting member 470 is provided at the tip of the second supply path 112 and the third air flow path 113. The second supply path 112 is also referred to as an ink supply tube 450. The third air flow path 113 is also referred to as a degassing tube 460. The main body side connecting member 470 is connected to the second supply path 112 (ink supply tube 450) and also to the third air flow path 113 (degassing tube 460).

[0133] The body-side connecting member 470 is detachably connected to a head-side connecting member 800 attached to the head housing 53. When the body-side connecting member 470 is connected to the head-side connecting member 800, the second supply path 112 communicates with the ink supply path (third supply path 910) in the circulation unit 54 via the filter 110. Furthermore, when the body-side connecting member 470 is connected to the head-side connecting member 800, the third air flow path 113 communicates with the degassing path 541 in the circulation unit 54. This allows the second supply path 112 (ink supply tube 450) and the third air flow path 113 (degassing tube 460), which are connected to the ink supply unit 400, to be easily connected to and disconnected from the liquid ejection head 1. This makes it possible to easily attach, detach, and replace the liquid ejection head 1.

[0134] <Configuration of the defoaming unit> FIG. 27 is a schematic diagram of the bubble removal unit 770. FIG. 27(a) is a cross-sectional view of the bubble removal unit 770. FIG. 27(b) is a schematic diagram of the deformation suppression member 720 in the bubble removal unit 770. The second bubble removal unit 770B has the same configuration as the first bubble removal unit 770A. The second foam reservoir chamber 520B has the same configuration as the first foam reservoir chamber 520A. Therefore, the first bubble removal unit 770A and the second bubble removal unit 770B may be collectively described as the bubble removal unit 770. The first foam reservoir chamber 520A and the second foam reservoir chamber 520B may be collectively described as the foam reservoir chamber 520. 27(a), the bubble removal unit 770 (first bubble removal unit 770A and second bubble removal unit 770B) has a foam reservoir chamber 520 (first foam reservoir chamber 520A and second foam reservoir chamber 520B) and a decompression chamber 760. The bubble removal unit 770 also has a gas-permeable membrane 710, a deformation suppression member 720, a first communication port 751 for communicating the foam reservoir chamber 520 with the liquid flow path or the liquid chamber, and a second communication port 761 for communicating the decompression chamber 760 with the ink supply unit 400.

[0135] The bubble removal units 770 (first bubble removal unit 770A and second bubble removal unit 770B) are connected to an ink supply unit 400 provided in the main body of the liquid ejection device 50, and are depressurized by the operation of the ink supply unit 400. Furthermore, a third check valve 213 is provided between the bubble removal unit 770 and the ink supply unit 400, so that the depressurized state is maintained even when the liquid ejection device 50 is not constantly operating, thereby enabling the bubble removal operation. The third check valves 213 may be provided at branched portions of the third air flow path 113 between the ink supply unit 400 and the first bubble removal unit 770A and the second bubble removal unit 770B. The third check valves 213 may also be provided at concentrated portions of the third air flow path 113 between the ink supply unit 400 and the first bubble removal unit 770A and the second bubble removal unit 770B.

[0136] As shown in FIG. 10(a), the first bubble removal unit 770A is provided vertically above the supply flow path 130, and the second bubble removal unit 770B is provided vertically above the first recovery flow path 140, but this is not limiting. For example, one bubble removal unit 770 (first bubble removal unit 770A) may be provided only for the supply flow path 130. The bubble removal unit 770 may be provided vertically above the ink tank 2, first supply path 111, second supply path 112, third supply path 910, filter 110, pump inlet flow path 170, pump outlet flow path 180, bypass flow path 160, pressure chamber 12, etc. Also, as shown in FIG. 10(b), the first bubble storage chamber 520A may be connected to a side surface of the supply flow path 130, and the first bubble removal unit 770A may be formed to extend laterally from the first bubble storage chamber 520A. The second foam reservoir chamber 520B may be connected to a side surface of the first recovery channel 140, and the second foam removal unit 770B may be formed to extend laterally from the second foam reservoir chamber 520B. As long as the configuration is such that bubbles can be collected and brought into contact with the gas-permeable membrane 710, the foam reservoir chamber 520 may be connected to a side surface of a fluid communication part other than the supply channel 130 and the first recovery channel 140, and the foam removal unit 770 may be formed to extend laterally from the foam reservoir chamber 520. In other words, the foam removal unit 770 may be formed to extend horizontally from the foam reservoir chamber 520, rather than vertically above the foam reservoir chamber 520.

[0137] <Gas permeable membrane> As shown in FIG. 27( a), the gas-permeable membrane 710 is provided in the housing of the circulation unit 54 that forms the foam reservoir chamber 520 so as to separate the foam reservoir chamber 520 from the decompression chamber 760. Hereinafter, the housing of the circulation unit 54 that forms the foam reservoir chamber 520 will be referred to as the unit housing 540. The gas-permeable membrane 710 is bonded to the unit housing 540 by a bonding method such as heat welding, ultrasonic welding, or laser welding. Any bonding method such as heat welding, ultrasonic welding, or laser welding can be used as long as the liquid (ink) in the foam reservoir chamber 520 is sealed so as not to leak into the decompression chamber 760. The material of the gas-permeable membrane 710 is preferably a resin. Specific examples of the material of the gas-permeable membrane 710 include polypropylene (PP), polymethylpentene (TPX), and polytetrafluoroethylene (PTFE). To improve the bubble removal efficiency, it is desirable that the material of gas-permeable membrane 710 has high gas permeability. To obtain the bubble removal efficiency required for the product, the material of gas-permeable membrane 710 is required to have a certain level of gas permeability. Furthermore, the material of gas-permeable membrane 710 is required to have productivity, such as ease of bonding to unit housing 540 by heat welding. The material of gas-permeable membrane 710 is required to have reliability against tearing, peeling, etc. of gas-permeable membrane 710. The material of gas-permeable membrane 710 is required to have reliability as a liquid-contacting material. As such, it is desirable to select the material of gas-permeable membrane 710 from the perspectives of gas permeability, manufacturing method (productivity), and reliability.

[0138] The foam that flows into the foam reservoir 520 includes initial foam remaining after initial filling (approximately 0.2 cc), tank replacement foam that flows in during normal use (approximately 0.015 cc per month), and permeated foam that permeates from the outside (approximately 0.001 cc / day). To deal with these foams, the defoaming operation must be performed at a permeation rate of 0.01 cc / day or more. As specified in JIS K7126-1, the gas permeation rate through the gas-permeable membrane 710 can be verified using a pressure sensor method. The pressure sensor method measures gas permeability by maintaining a vacuum on one side (the low-pressure side) separated by a test piece, introducing a test gas into the other side (the high-pressure side), and measuring the increase in pressure on the low-pressure side. The pressure sensor method allows the gas permeability coefficient to be calculated from the gas permeability and the thickness of the test piece. The pressure sensor method allows the gas permeation rate through the gas-permeable membrane to be verified by measuring the gas permeability of the test piece using the test piece as the gas-permeable membrane. During the initial filling of the normal suction process (described later), ink is filled into the liquid ejection head 1, and the bubbles in the bubble reservoir chamber 520 are brought into contact with the entire gas-permeable membrane 710. The ink supply unit 400 maintains the gas pressure in the decompression chamber 760 at a negative pressure of approximately 50 kPa, and the head is left at room temperature and pressure. During this series of operations, the amount of bubbles in the bubble reservoir chamber 520 can be measured over time using computed tomography (CT) or other methods to verify the amount of bubbles (gas) passing through the gas-permeable membrane 710. Because the gas-permeable membrane 710 is welded to the unit housing 540 to seal the bubble reservoir chamber 520, it is desirable that the material of the gas-permeable membrane 710 be highly reliable in terms of both welding reliability and reliability as a liquid-contacting material. To achieve a bubble permeation rate of 0.01 cc / day or more, the thickness of the gas-permeable membrane 710 is desirably 0.1 mm or less.

[0139] <Bubble Chamber> As shown in FIG. 10( a), the first bubble reservoir chamber 520A is provided vertically above the supply flow path 130 so as to be fluidly connected to the supply flow path 130 via the first communication port 751. The second bubble reservoir chamber 520B is provided vertically above the first recovery flow path 140 so as to be fluidly connected to the first recovery flow path 140 via the first communication port 751. This allows bubbles that have become mixed into the ink in the first pressure adjustment means 120, the second pressure adjustment means 150, the supply flow path 130, the first recovery flow path 140, etc. due to circulation and ejection operations to be collected in the bubble reservoir chamber 520 and then removed from the ink by a bubble removal operation. Examples of bubbles that may become mixed into the ink include upstream bubbles that have entered the flow path due to replacement of the ink tank 2, elution bubbles that occur in the flow path due to environmental changes, and unexpected bubbles that have unexpectedly occurred in the flow path. However, the types of bubbles that may be removed by the bubble removal operation are not limited to these. If the amount of bubbles is large enough to be collected in the bubble reservoir 520 and large enough to ensure a sufficient bubble removal speed, the bubbles mixed in the ink can be discharged to the outside of the liquid ejection head 1.

[0140] Examples of materials for unit housing 540 that forms foam reservoir chamber 520 include polypropylene (PP), polyethylene (PE), etc. From the standpoints of reliability in welding gas-permeable membrane 710 and ease of handling, it is desirable that the material for unit housing 540 be polypropylene.

[0141] <Decompression chamber> As shown in FIG. 27(a), the decompression chamber 760 has an opening in which the gas-permeable membrane 710 is disposed, an opening facing the opening for welding the gas-permeable membrane 710, and a second communication port 761. The decompression chamber 760 is surrounded by the unit housing 540, the gas-permeable membrane 710, and the cover member 730. The second communication port 761 penetrates the side of the unit housing 540 and connects the decompression chamber 760 to the degassing channel 541 (see FIG. 26). The opening for welding the gas-permeable membrane 710 is sealed by bonding a separate cover member 730 to the unit housing 540. Examples of methods for bonding the cover member 730 include heat welding, ultrasonic welding, and laser welding. Examples of materials for the cover member 730 include polypropylene (PP) and polyethylene (PE). From the viewpoint of reliability of welding of cover member 730 and ease of handling, it is desirable that the material of cover member 730 be the same as the material of unit housing 540 that forms foam reservoir chamber 520 .

[0142] <Deformation suppression member> As shown in FIG. 27(b), the deformation suppression member 720 is formed using a stainless steel (SUS) mesh filter with a mesh pattern. In FIG. 27(b), a dot pattern is applied to the gas-permeable membrane 710 to make the deformation suppression member 720 easier to understand. The dot pattern applied to the gas-permeable membrane 710 in FIG. 27(b) does not represent a cross section of the gas-permeable membrane 710. When the ink supply unit 400 decompresses the decompression chamber 760, the gas-permeable membrane 710 tends to deform toward the decompression chamber 760. The deformation suppression member 720 contacts the gas-permeable membrane 710, which tends to deform toward the decompression chamber 760, thereby suppressing deformation of the gas-permeable membrane 710 and preventing tearing or peeling of the gas-permeable membrane 710. The deformation suppression member 720 is provided at the tip of the cover member 730. For example, deformation suppressing member 720 is adhered to the tip of cover member 730 by an adhesion method such as heat welding, ultrasonic welding, or laser welding. With cover member 730 adhered to unit housing 540, deformation suppressing member 720 is disposed so as to cover gas-permeable membrane 710 at a position in contact with gas-permeable membrane 710 or at a position spaced a certain distance from gas-permeable membrane 710. Examples of materials for deformation suppressing member 720 include stainless steel (SUS) and nickel (Ni). It is desirable that the material for deformation suppressing member 720 be one that allows for reliable welding of deformation suppressing member 720 and is easy to handle.

[0143] The foam reservoir 520 is formed by the unit housing 540, but is not limited to this. FIG. 28 shows a modified example of the foam removal unit 770. FIG. 28(a) shows an example in which a side film 780 is used in part of the foam reservoir 520. FIG. 28(b) shows an example in which a side film 780 is used in part of the decompression chamber 760. As shown in FIG. 28(a), part of the foam reservoir 520 may be formed by the side film 780 welded to the unit housing 540. To suppress the increase of bubbles in the foam reservoir 520, liquid flow path, liquid chamber, etc., it is desirable that the material of the side film 780 be a resin with high gas barrier properties, such as polyethylene terephthalate (PET) or nylon (Ny). The volume of the foam reservoir 520 need only be large enough to collect the amount of bubbles determined by the product's foam design.

[0144] As shown in FIG. 28( b), a portion of the decompression chamber 760 may be formed by a side film 780 welded to the unit housing 540. To reduce the amount of reduction in the degree of decompression in the decompression chamber 760, the material of the side film 780 is preferably a resin with high gas barrier properties, such as polyethylene terephthalate (PET) or nylon (Ny). The gas-permeable membrane 710 may be disposed between the foam reservoir chamber 520 and the unit housing 540, or between the decompression chamber 760 and the unit housing 540, with an elastic member sandwiched therebetween. In this case, the gas-permeable membrane 710 does not need to be welded to the foam reservoir chamber 520. Therefore, an opening of the decompression chamber 760 and a cover member 730 sealing the opening are not required, and the decompression chamber 760 may be formed by the unit housing 540 or the side film 780. The volume of the decompression chamber 760 needs to be large enough to capture the amount of foam determined by the foam design of the product.

[0145] FIG. 29 is a cross-sectional view showing a first modified example of the deformation suppression member 720. The deformation suppression member 720 is not limited to a mesh filter, and may be formed using, for example, a nonwoven fabric member with dense fibers as shown in FIG. 29. In this case, to prevent the nonwoven fabric member from being sucked into the ink supply unit 400 when the decompression chamber 760 is decompressed, it is necessary to use a nonwoven fabric member with a hardness equal to or greater than a certain value, or to keep the degree of decompression for the decompression chamber 760 below a certain value. In addition, the nonwoven fabric member has a certain degree of elasticity. Therefore, by designing the size of the deformation suppression member 720 to be approximately the same as the volume of the decompression chamber 760, it is possible to place the deformation suppression member 720 within the decompression chamber 760 without the cover member 730 extending into the decompression chamber 760.

[0146] FIG. 30 is a schematic diagram showing another modified example of the deformation suppressing member 720. FIG. 30(a) is a cross-sectional view showing a second modified example of the deformation suppressing member 720. FIG. 30(b) is a schematic diagram showing the second modified example of the deformation suppressing member 720. FIG. 30(c) is a schematic diagram showing a third modified example of the deformation suppressing member 720. As shown in FIG. 30(a), the deformation suppressing member 720 may be a ribbed member formed integrally with the cover member 730. The ribs of the deformation suppressing member 720 may be linear as shown in FIG. 30(b). The ribs of the deformation suppressing member 720 are not limited to linear ribs, and may also be lattice-like as shown in FIG. 30(c). In this case, in order to suppress the maximum deformation of the gas-permeable membrane 710, it is desirable that the ribs of the deformation suppressing member 720 be in contact with the vicinity of the center of the gas-permeable membrane 710. In order to suppress the maximum deformation of the gas-permeable membrane 710, it is desirable to increase the number of ribs constituting the deformation suppressing member 720. If deformation suppression member 720 is provided at the tip of cover member 730, and deformation suppression member 720 comes into contact with part of gas-permeable membrane 710, the effective area for passing bubbles through gas-permeable membrane 710 will be reduced, making it necessary to adjust the configuration of other members and the bubble design of the product. Also, if decompression chamber 760 is configured not to require cover member 730, deformation suppression member 720 may be installed in unit housing 540 that forms foam reservoir chamber 520, or in unit housing 540 that forms decompression chamber 760.

[0147] <Principle of defoaming> During the bubble removal operation, the pressure in the decompression chamber 760 is reduced, and the difference in pressure between the bubbles in the bubble reservoir chamber 520 and the gas pressure in the decompression chamber 760 causes the bubbles to permeate the gas-permeable membrane 710. The amount of permeation during the bubble removal operation is expressed by the following equation (5):

[0148] Q = P × p × S × t / L (5) Q: Gas permeability P: Permeability coefficient p: Degree of pressure reduction (gauge pressure) S: Foam contact area t: time L: Thickness of the gas-permeable membrane 710

[0149] The gas permeation rate represented by Q is the amount of gas contained in bubbles that permeates during the bubble removal operation. The permeability coefficient represented by P is a value determined by the material properties of the gas-permeable membrane 710, and represents the basic speed of the bubble removal operation. The pressure reduction level represented by p is the pressure reduction level (gauge pressure) of the pressure reduction chamber 760. The bubble contact area represented by S is the area of ​​contact between the bubbles and the gas-permeable membrane 710. The value represented by L is the thickness of the gas-permeable membrane 710.

[0150] <Initial filling> Figure 31 is a schematic diagram showing the operation of the initial filling and bubble removal unit. Figure 31(a) is a schematic diagram showing the ink flow and remaining bubbles during the initial filling of the liquid ejection head 1 with ink. Initial filling is performed by tightly attaching a cap member to the ejection port surface of the liquid ejection head 1, where the ejection ports are formed, and forcibly suctioning ink through the ejection ports. At this time, negative pressure from a negative pressure source connected to the cap member is applied to the ejection ports to forcibly suction ink through the ejection ports. During initial filling, if stagnation of the ink flow occurs due to variations in component molding or assembly, small amounts of bubbles may remain on the wall surface. Suction operations include normal suction and choke suction, and the filling state of the bubble removal unit changes depending on the suction method. During normal suction, suction is performed without any special operation. In the ink flow path shown in Figure 31(a), ink is supplied from the upstream side of the ink flow path, causing gas-liquid exchange and filling most of the ink flow path with ink. However, because the foam reservoir chamber 520 (first foam reservoir chamber 520A and second foam reservoir chamber 520B) does not function as an ink flow path, gas-liquid exchange does not occur, and bubbles remain in most of the foam reservoir chamber 520. In choke suction, the flow path upstream of the ink flow path is closed using a valve or the like, and the entire liquid ejection head 1 is sufficiently depressurized by suction. Then, the upstream valve is opened, allowing ink to flow into the liquid ejection head 1 from the upstream side of the ink flow path. Therefore, in the ink flow path shown in FIG. 31(a), ink fills most of the ink flow path, similar to normal suction. In the foam reservoir chamber 520, the amount of ink filled increases as the degree of depressurization due to suction increases. For example, when choke suction is performed at -50 kPa (gauge pressure), approximately half of the foam reservoir chamber 520 is filled with ink.

[0151] <Operation of the defoaming unit> FIG. 31(b) is a schematic diagram showing the state inside the circulation unit after initial filling. FIG. 31(c) is a schematic diagram showing the state of remaining bubbles after initial filling. After initial filling, bubbles remain in the foam reservoir chamber 520 (first foam reservoir chamber 520A and second foam reservoir chamber 520B). Therefore, the decompression chamber 760 is decompressed to remove the bubbles. Because gas constantly penetrates the foam reservoir chamber 520 from the outside through the unit housing or side film, decompression operations must be performed according to the product's bubble design. The decompression chamber 760 is decompressed by the ink supply unit 400 of the main body of the liquid ejection device 50 through the second communication port 761. The higher the degree of decompression, the greater the amount of bubble penetration. Therefore, to obtain a sufficient amount of bubble penetration to process bubbles generated during normal use, it is desirable to decompress the pressure to at least 10 kPa. Furthermore, if the degree of decompression is excessively high, the gas-permeable membrane 710 may deform significantly toward the decompression chamber 760, potentially causing peeling at the welded portion of the gas-permeable membrane 710. Therefore, the degree of decompression is preferably set to approximately 70 kPa or less. Furthermore, the ink supply unit 400 for decompressing the decompression chamber 760 utilizes a pressurizing means (e.g., the one-way pump 404) in the upstream flow path. Therefore, the degree of decompression of the decompression chamber 760 is affected by the operation or output of the pressurizing means. As can be seen from the above explanation, a decompression degree of approximately 50 kPa is desirable for achieving a sufficient amount of bubble permeation, ensuring high reliability of the gas-permeable membrane 710, and operating the ink supply unit 400. The decompression state of the decompression chamber 760 can be maintained by constantly operating the liquid ejection device 50. When the main body of the liquid ejection device 50 is not in operation, the third check valve 213 provided between the second communication port 761 (see FIG. 27(a)) and the ink supply unit 400 is used. The third check valve 213 seals the decompression chamber 760 when the decompression chamber 760 reaches a certain degree of decompression. As a result, even when the main body of the liquid ejection device 50 is not in operation, the decompression chamber 760 is maintained in a decompressed state, so that the bubble removal operation can continue, and it becomes possible to deal with bubbles that increase when the liquid ejection device 50 is left unused for a long period of time, for example. As shown in FIG. 31(a), after the initial filling, the ink supply unit 400 places the decompression chamber 760 in a decompressed state, and then the decompressed state is maintained by the third check valve 213, so that bubbles in the bubble reservoir chamber 520 are allowed to pass through and are discharged from the ink.When the ejection operation is performed, ink flows in from upstream, and bubbles present upstream also flow in at the same time. Furthermore, unexpected bubbles, such as small amounts of bubbles remaining in stagnant ink flow areas during initial filling, flow through the flow path due to the ejection and circulation operations. As shown in Figure 31(c), bubbles can be collected through the first communication port 751 (see Figure 27(a)) of the bubble removal unit 770 due to the buoyancy of the bubbles. By reducing the pressure in the decompression chamber 760 and performing the decompression operation, bubbles can be removed from the ink. Repeating this decompression operation prevents new bubbles generated during normal use from flowing into the pressure chamber 12, thereby reducing the possibility of ejection failure. When the decompression chamber 760 is maintained in a decompressed state by the third check valve 213, performing the decompression operation causes bubbles to permeate the decompression chamber 760, reducing the degree of decompression in the decompression chamber 760 and reducing the efficiency of decompression. The amount of reduction in the degree of decompression is expressed by the following equation (6).

[0152] (p2×Q+p1×Q1) / v (6) p1: atmospheric pressure (absolute pressure) p2: Internal pressure of the bubble (absolute pressure) v: Volume of the decompression chamber 760 Q1: Amount of transmission from the outside

[0153] The internal bubble pressure, represented by p2, is the same as the ink pressure. The larger the volume of the decompression chamber 760, represented by v, the smaller the decrease in the degree of decompression due to the decompression operation, and the more effectively the decompression efficiency can be suppressed. The amount of permeation from the outside, represented by Q1, is the amount of gas that permeates into the decompression chamber 760 from the outside, and is determined by the material of the unit housing that forms the decompression chamber 760, the surface area of ​​the portion of the unit housing that is in contact with the outside air, and the thickness of the unit housing.

[0154] When the degree of decompression in the decompression chamber 760 decreases, the third check valve 213 and the ink supply unit 400 are operated to increase the degree of decompression in the decompression chamber 760, thereby maintaining bubble removal efficiency. The operation of increasing the degree of decompression (for example, the aforementioned decompression operation for decompressing bubbles) may be performed periodically using a timer. The operation of increasing the degree of decompression may be performed by detecting the degree of decompression in the decompression chamber 760 with a sensor and triggered by a decrease in a predetermined degree of decompression. When the decompression chamber 760 is in a decompressed state and the gas-permeable membrane 710 deforms toward the decompression chamber 760, the deformation suppression member 720 comes into contact with the gas-permeable membrane 710 from the decompression chamber 760 side. The deformation suppression member 720 suppresses deformation of the gas-permeable membrane 710 by pressing the gas-permeable membrane 710 in a direction that suppresses deformation of the gas-permeable membrane 710. By suppressing deformation of gas-permeable membrane 710, the load applied to the welded portion of gas-permeable membrane 710 can be reduced, and the possibility of gas-permeable membrane 710 peeling off can be reduced.

[0155] In this embodiment, the operation of the bubble removal unit has been described using an example of a configuration in which the bubble removal unit 770 (first bubble removal unit 770A and second bubble removal unit 770B) has the bubble reservoir chamber 520 (first bubble reservoir chamber 520A and second bubble reservoir chamber 520B), but this is not limited to this. If the space between the pressure chamber 12 and the decompression chamber 760 is used as a liquid reservoir chamber that stores liquid for supplying liquid (ink) to the pressure chamber 12, bubbles may be stored in part of the liquid reservoir chamber. In this case, a gas-permeable membrane is formed at a position in contact with the liquid reservoir chamber, and the decompression chamber is adjacent to the liquid reservoir chamber via the gas-permeable membrane.

[0156] <Flow path opening position> Next, the position of the opening connected to the flow path in the second pressure control chamber 152 will be described with reference to Figure 50. Figure 50(a) is a cross-sectional view that schematically shows the backflow of ink from the first recovery flow path 140 to the pressure chamber 12, and Figure 50(b) is a cross-sectional view that schematically shows the flow of ink during a recording operation.

[0157] The second pressure control chamber 152 is connected to the pump inlet flow path 170 via a pump inlet opening 1001. This pump inlet opening 1001 is disposed vertically below the second foam reservoir chamber 520B in the second pressure adjustment means 150. In this embodiment, the pump inlet opening 1001 is provided vertically below the communication port 191B in the second pressure control chamber 152, and is preferably provided, for example, near the bottom of the second pressure control chamber 152 in the vertical direction.

[0158] Furthermore, the second pressure control chamber 152 is connected to the first recovery channel 140 via a first recovery channel opening 1002. The first recovery channel opening 1002 is preferably located vertically below the second foam reservoir chamber 520B, and more preferably located vertically above the second pressure adjustment means 150. In this embodiment, the first recovery channel opening 1002 is located vertically above the second pressure control chamber 152 and vertically below the second foam reservoir chamber 520B. Note that the "vertical upper part of the second pressure control chamber 152" refers to the "vertical upper part of the second pressure control chamber 152 (including the vicinity of the top)."

[0159] Bubbles that flow into the second pressure control chamber 152 move vertically upward due to buoyancy or the flow of ink, and move to the top of the second pressure control chamber 152. Bubbles that reach the top of the second pressure control chamber 152 flow into the first recovery channel 140 via the first recovery channel opening 1002 provided vertically above the second pressure control chamber 152, and then flow into the second bubble reservoir chamber 520B, which is located vertically above the first recovery channel opening 1002. In this way, by providing the first recovery channel opening 1002, bubbles that flow into the second pressure control chamber 152 move efficiently to the second bubble reservoir chamber 520B, and movement of the bubbles toward the pressure chamber 12 is suppressed.

[0160] Furthermore, in the second pressure control chamber 152, the pump inlet opening 1001 is provided vertically below the second pressure control chamber 152. Therefore, bubbles that flow into the second pressure control chamber 152 and move vertically upward due to buoyancy or the flow of ink are prevented from flowing into the pump inlet flow path 170 and the circulation pump 500 via the pump inlet opening 1001. As a result, when a piezoelectric diaphragm pump, for example, is used as the circulation pump 500, the flow of bubbles into the pump chamber is prevented, and malfunctions of the circulation pump 500 are prevented.

[0161] <Size of the defoaming unit> Next, the sizes of the first bubble removal unit 770A and the second bubble removal unit 770B will be described. The first bubble removal unit 770A and the second bubble removal unit 770B may be approximately the same size. However, for example, the first bubble removal unit 770A may be configured larger than the second bubble removal unit 770B. A case in which the first bubble removal unit 770A is configured larger than the second bubble removal unit 770B will be described below with reference to FIGS. 51 and 52. FIG. 51 is a vertical cross-sectional view schematically illustrating a circulation path in which the first bubble removal unit 770A is configured larger than the second bubble removal unit 770B. FIGS. 52(a) and 52(b) illustrate modified examples of the connection of the third air flow path 113 to the first bubble removal unit 770A and the second bubble removal unit 770B.

[0162] When the first bubble removal unit 770A is formed larger than the second bubble removal unit 770B, the first decompression chamber 760A is formed to have a larger volume than the second decompression chamber 760B, and the first bubble storage chamber 520A is formed to have a larger volume than the second bubble storage chamber 520B. In this case, the first gas-permeable membrane 710A is formed to have a larger area than the second gas-permeable membrane 710B. The first decompression chamber 760A is the decompression chamber 760 provided in the first bubble removal unit 770A, and the first gas-permeable membrane 710A is the gas-permeable membrane 710 provided in the first bubble removal unit 770A. The second decompression chamber 760B is the decompression chamber 760 provided in the second bubble removal unit 770B, and the second gas-permeable membrane 710B is the gas-permeable membrane 710 provided in the second bubble removal unit 770B.

[0163] Here, bubbles remaining in the second pressure control chamber 152, bubbles generated within the liquid ejection head 1, and bubbles that have permeated into the liquid ejection head 1 from the outside flow into the second bubble reservoir chamber 520B. On the other hand, bubbles remaining in the first pressure control chamber 122, bubbles generated within the liquid ejection head 1, and bubbles that have permeated into the liquid ejection head 1 from the outside flow into the first bubble reservoir chamber 520A, as well as bubbles flowing in via the second supply path 112. Examples of bubbles that flow in via the second supply path 112 include bubbles that are mixed in when the ink tank 2 is attached or detached, bubbles that remain in the flow path from the ink tank 2 to the second supply path 112, and bubbles that have permeated into the flow path from the outside.

[0164] Furthermore, the bypass inlet opening 1003, which is an opening through which the first pressure control chamber 122 communicates with the bypass flow path 160, is provided in the vertically lower part of the first pressure control chamber 122. Note that the "vertically lower part of the first pressure control chamber 122" refers to the "vertically lower part of the first pressure control chamber 122 (including the bottom part and its vicinity)." Therefore, the configuration is such that bubbles that have flowed into the first pressure control chamber 122 are unlikely to flow out to the second pressure adjustment means 150 via the bypass inlet opening 1003 and the bypass flow path 160.

[0165] Therefore, there is a high possibility that more bubbles will exist in the first pressure control chamber 122 than in the second pressure control chamber 152. Therefore, by making the first bubble reservoir 520A, which can collect bubbles in the first pressure control chamber 122, larger than the second bubble reservoir 520B, which can collect bubbles in the second pressure control chamber 152, it is possible to more reliably prevent bubbles from flowing into the pressure chamber 12. That is, by making it possible to collect bubbles in the first pressure control chamber 122, which contains more bubbles, in the larger-capacity first bubble reservoir 520A, it is possible to prevent bubbles from circulating in the circulation path. Furthermore, by making the area of ​​the first gas-permeable membrane 710A that can come into contact with bubbles collected in the first bubble reservoir 520A larger than the area of ​​the second gas-permeable membrane 710B that can come into contact with bubbles collected in the second bubble reservoir 520B, the bubble removal speed in the first bubble removal unit 770A is improved. This makes it possible to maintain a good collection effect in the first bubble reservoir chamber 520A and to suppress the circulation of bubbles in the circulation path.

[0166] Both first decompression chamber 760A and second decompression chamber 760B are connected to third air flow path 113. First decompression chamber 760A and second decompression chamber 760B are connected to one-way pump 404 via third air flow path 113, and the interiors of first decompression chamber 760A are decompressed by the operation of one-way pump 404. When first decompression chamber 760A is decompressed, a pressure difference generated between first decompression chamber 760A and first foam reservoir chamber 520A causes first gas permeable membrane 710A, located between first decompression chamber 760A and first foam reservoir chamber 520A, to receive a force toward first decompression chamber 760A. Furthermore, when second decompression chamber 760B is decompressed, the pressure difference between second decompression chamber 760B and second bubble reservoir chamber 520B causes second gas-permeable membrane 710B, located between second decompression chamber 760B and second bubble reservoir chamber 520B, to be subjected to a force toward second decompression chamber 760B. Therefore, if, for some reason, first decompression chamber 760A and second decompression chamber 760B are decompressed more than expected, first gas-permeable membrane 710A and second gas-permeable membrane 710B may be damaged.

[0167] If the first gas-permeable membrane 710A is damaged, there is a possibility that ink in the first foam reservoir chamber 520A or the supply channel 130 will flow into the first decompression chamber 760A. If the second gas-permeable membrane 710B is damaged, there is a possibility that ink in the second foam reservoir chamber 520B or the first recovery channel 140 will flow into the second decompression chamber 760B. Note that when the first decompression chamber 760A and the second decompression chamber 760B are decompressed, the first gas-permeable membrane 710A, which is larger than the second gas-permeable membrane 710B, will be subjected to a greater force than the second gas-permeable membrane 710B, and will be more likely to be damaged.

[0168] Therefore, the third air flow path 113 is designed so that the length from the first gas permeable membrane 710A to the third check valve 213 in the third air flow path 113 is longer than the length from the second gas permeable membrane 710B to the third check valve 213. This makes it difficult for ink that has flowed into the first decompression chamber 760A due to damage to the first gas permeable membrane 710A to flow into the one-way pump 404 via the third air flow path 113. Specifically, for example, the third air flow path 113 is connected to the first decompression chamber 760A via the second decompression chamber 760B (see FIG. 52(a)). In other words, in this case, the third check valve 213, the second decompression chamber 760B, and the first decompression chamber 760A are located in series in this order from the one-way pump 404 side in the third air flow path 113. Alternatively, for example, the third air flow path 113 branches off near the connection point of the second decompression chamber 760B and extends from this branch point to connect to the first decompression chamber 760A (see Figure 52(b)). In other words, in this case, the third air flow path 113 connects to the first decompression chamber 760A and the second decompression chamber 760B so that the flow path from the third check valve 213 to the first decompression chamber 760A is longer than the flow path from the third check valve 213 to the second decompression chamber 760B.

[0169] In the above description, first bubble removal unit 770A is larger than second bubble removal unit 770B, but the present invention is not limited to this. For example, in first bubble removal unit 770A, first decompression chamber 760A may be the same size as second decompression chamber 760B, while first bubble reservoir chamber 520A may be larger than second bubble reservoir chamber 520B.

[0170] In the above description, the first bubble removal unit 770A is provided in the supply flow path 130 near the first pressure adjustment means 120, but this is not limiting. The first bubble removal unit 770A may be provided in the first pressure adjustment means 120. In this case, the first bubble removal unit 770A is provided above the first pressure adjustment means 120 in the vertical direction, including the top of the first pressure adjustment means 120 and its vicinity. Furthermore, in the above description, the second bubble removal unit 770B is provided in the first recovery flow path 140 near the second pressure adjustment means 150, but this is not limiting. The second bubble removal unit 770B may be provided in the second pressure adjustment means 150. In this case, the second bubble removal unit 770B is provided above the second pressure adjustment means 150 in the vertical direction, including the top of the second pressure adjustment means 150 and its vicinity.

[0171] In the above description, first bubble removal unit 770A is described as including first bubble storage chamber 520A, but this is not limiting. As long as the configuration allows bubbles to be positioned adjacent to first gas-permeable membrane 710A, first bubble storage chamber 520A may be omitted. Furthermore, in the above description, second bubble removal unit 770B is described as including second bubble storage chamber 520B, but this is not limiting. As long as the configuration allows bubbles to be positioned adjacent to second gas-permeable membrane 710B, second bubble storage chamber 520B may be omitted.

[0172] As described above, in the liquid ejection head 1, the bubble removal units 770 are provided upstream of the pressure chambers 12 that supply ink and downstream of the pressure chambers 12 that can recover ink. Specifically, the first decompression chamber 760A, the interior of which can be decompressed, is provided adjacent to the first liquid storage section, which includes the first pressure adjustment means 120, the supply flow path 130, and the first foam storage chamber 520A, via the first gas-permeable membrane 710A. The second decompression chamber 760B, the interior of which can be decompressed, is provided adjacent to the second liquid storage section, which includes the second pressure adjustment means 150, the first recovery flow path 140, and the second foam storage chamber 520B, via the second gas-permeable membrane 710B. This makes it possible to collect bubbles generated between the bubble removal unit 770 (gas permeable membrane 710) and the pressure chamber 12, or bubbles generated in the pressure chamber 12, from the second decompression chamber 760B, thereby making it possible to more reliably suppress the effects of bubbles than, for example, the technology disclosed in Patent Document 1.

[0173] <Other configurations> The configuration of the circulation path in this embodiment is not limited to the above-described configuration. Therefore, as other configurations of the circulation path, a first configuration example and a second configuration example of the ink path, as well as various modified examples of the circulation path, will be described.

[0174] <First configuration example of ink path> 32 is a diagram schematically illustrating a first configuration example of the ink path. The first configuration example of the ink path illustrates an example in which the second pressure adjustment means 150, second foam reservoir chamber 520B, circulation pump 500, bypass flow path 160, and first recovery flow path 140 are not arranged. In the first configuration example of the ink path, ink is not circulated, and ink supplied from the second supply path 112 flows through the first pressure adjustment means 120, supply flow path 130, and pressure chamber 12 in that order, and is ejected from the ejection port 13. The pressures of the first pressure control chamber 122, supply flow path 130, and pressure chamber 12 are controlled by the first pressure adjustment means 120, thereby achieving stable ink ejection.

[0175] The first bubble reservoir 520A is provided vertically above the supply flow path 130 so as to be in fluid communication with the supply flow path 130, and the first bubble removal unit 770A is formed to extend vertically above the first bubble reservoir 520A. This allows bubbles that have become mixed into the ink in the first pressure adjustment means 120 or the supply flow path 130 due to circulation or ejection operations to be collected in the first bubble reservoir 520A and then removed from the ink by the bubble removal operation. Bubbles that may become mixed into the ink include, but are not limited to, the aforementioned upstream bubbles, eluted bubbles, and unexpected bubbles. It is possible to remove from the ink a quantity of bubbles that can be collected in the bubble reservoir 520 and that can achieve a sufficient bubble removal speed. This greatly reduces the possibility of bubbles entering the ejection port 13.

[0176] The first bubble removal unit 770A communicates with the ink supply unit 400 in the main body of the liquid ejection device 50, and is depressurized by the operation of the ink supply unit 400. Furthermore, a third check valve 213 is provided between the bubble removal unit 770 and the ink supply unit 400, and the depressurized state is maintained even if the main body of the liquid ejection device 50 is not constantly operating, thereby enabling the bubble removal operation. The third check valve 213 may also be provided in the third air flow path 113 between the first bubble removal unit 770A and the ink supply unit 400.

[0177] Two or more foam reservoir chambers 520 and two or more bubble removal units 770 may be provided. Furthermore, the foam reservoir chambers 520 and the bubble removal units 770 do not need to be provided in the supply flow path 130. For example, the foam reservoir chambers 520 and the bubble removal units 770 may be provided vertically above the ink tank 2, the first supply path 111, the second supply path 112, the third supply path 910, the filter 110, the pressure chamber 12, or the like. Furthermore, the foam reservoir chambers 520 and the bubble removal units 770 do not necessarily need to be provided vertically above the fluid communication parts, such as the supply flow path 130. As long as the foam reservoir chambers 520 are configured to be able to capture bubbles and bring them into contact with the gas-permeable membrane, the foam reservoir chambers 520 may be connected to the side of the fluid communication parts, and the bubble removal units 770 may be formed to extend laterally from the foam reservoir chambers 520. This also applies to the case where the foam reservoir 520 and the foam removal unit 770 are provided in multiple portions of the fluid communication part other than the supply flow path 130 and the first recovery flow path 140.

[0178] <First modified example of circulation route> Figures 33 and 35 are diagrams schematically showing a first modified example of the circulation path. Figure 33 shows the circulation path when circulation is performed without ejection. Figure 35 shows the circulation path when high-duty printing is performed. Also, Figure 34 is a diagram schematically showing the vicinity of the heated circulation pump 904. Figures 34(a), 34(b), 34(c), and 34(d) show an overview of liquid delivery by the heated circulation pump 904.

[0179] The first modified example of the circulation path shows an example in which the second pressure adjustment means 150, the second foam reservoir chamber 520B, the circulation pump 500, the bypass flow path 160, and the first recovery flow path 140 are not provided. The first modified example of the circulation path shows an example in which, instead of the circulation pump 500, etc., a heated circulation pump 904 is provided between the supply flow path 130 and the pressure chamber 12, and a second recovery flow path 905 that connects the pressure chamber 12 and the supply flow path 130 is provided. In the first modified example of the circulation path, during circulation as shown in FIG. 33 , the heated circulation pump 904 circulates ink within the ejection module 300. During an ejection operation as shown in FIG. 35 , ink supplied from the second supply path 112 flows in the order of the first pressure adjustment means 120, the supply flow path 130 or the second recovery flow path 905, and the pressure chamber 12, and is ejected from the ejection port 13. When high-duty printing is performed, the ink in the second recovery flow path 905 flows in the opposite direction to when circulating, so that ink is supplied to the pressure chamber 12 and the ejection port 13 from both the supply flow path 130 and the second recovery flow path 905. The pressures of the first pressure control chamber 122, the supply flow path 130, and the pressure chamber 12 are controlled by the first pressure adjustment means 120, so stable ink ejection is achieved.

[0180] The first bubble reservoir chamber 520A is provided vertically above the supply flow path 130 so as to be in fluid communication with the supply flow path 130, and the first bubble removal unit 770A is formed to extend vertically above the first bubble reservoir chamber 520A. This allows bubbles that have become mixed into the ink in the first pressure adjustment means 120, the supply flow path 130, the second recovery flow path 905, etc., due to circulation and ejection operations to be collected in the bubble reservoir chamber 520 and then removed from the ink by the bubble removal operation. Bubbles that may become mixed into the ink include, but are not limited to, the aforementioned upstream bubbles, eluted bubbles, and unexpected bubbles. It is possible to remove from the ink an amount of bubbles that can be collected in the bubble reservoir chamber 520 and that can provide a sufficient bubble removal speed. This greatly reduces the possibility of bubbles entering the ejection port 13.

[0181] The first bubble removal unit 770A communicates with the ink supply unit 400 in the main body of the liquid ejection device 50, and is depressurized by the operation of the ink supply unit 400. Furthermore, a third check valve 213 is provided between the bubble removal unit 770 and the ink supply unit 400, and the depressurized state is maintained even if the main body of the liquid ejection device 50 is not constantly operating, thereby enabling the bubble removal operation. The third check valve 213 may also be provided in the third air flow path 113 between the first bubble removal unit 770A and the ink supply unit 400.

[0182] Two or more foam reservoir chambers 520 and two or more bubble removal units 770 may be provided. Furthermore, the foam reservoir chambers 520 and the bubble removal units 770 do not need to be provided in the supply flow path 130. For example, the foam reservoir chambers 520 and the bubble removal units 770 may be provided vertically above the ink tank 2, the first supply path 111, the second supply path 112, the third supply path 910, the filter 110, the pressure chamber 12, the second recovery path 905, or the like. Furthermore, the foam reservoir chambers 520 and the bubble removal units 770 do not necessarily need to be provided vertically above fluid communication sections such as the supply flow path 130. As long as the foam reservoir chambers 520 are configured to be able to collect bubbles and bring them into contact with the gas-permeable membrane, the foam reservoir chambers 520 may be connected to the side of the fluid communication section, and the bubble removal unit 770 may be formed to extend laterally from the foam reservoir chamber 520. This also applies to the case where the foam reservoir 520 and the foam removal unit 770 are provided in multiple portions of the fluid communication part other than the supply flow path 130 and the first recovery flow path 140.

[0183] The heated circulation pump 904 is composed of a heater element capable of heating ink. Heating the ink generates bubbles from the heater element, thereby pumping the ink. First, as shown in FIG. 34(a), the ink is rapidly heated by the heater element constituting the heated circulation pump 904, causing bubbles to form and expand due to film boiling. The amount of expansion of the bubbles differs between the upstream and downstream sides of the ink. Next, as shown in FIG. 34(b), the heater is turned off when the bubbles expand to a certain amount. Next, as shown in FIG. 34(c), the heating is stopped, causing the bubbles to contract. The amount of contraction of the bubbles differs between the upstream and downstream sides of the ink. Finally, as shown in FIG. 34(d), the bubbles completely contract and collapse, generating an ink flow from the upstream side to the downstream side. Repeating the processes shown in FIGS. 34(a), 34(b), 34(c), and 34(d) generates a steady ink flow from the supply channel 130 through the pressure chamber 12 to the second recovery channel 905. The heating circulation pump 904 does not need to be provided between the supply flow path 130 and the pressure chamber 12, but may be provided between the pressure chamber 12 and the second recovery flow path 905.

[0184] <Second modified example of circulation route> 36 and 37 are diagrams schematically showing a second modified example of the circulation path. Fig. 36 shows the circulation path when circulation is performed without ejection. Fig. 37 shows the circulation path when high-duty recording is performed. The second modified example of the circulation path shows an example in which the second pressure adjustment means 150 is not provided, and the bypass flow path 160 and the first recovery flow path 140 are directly connected.

[0185] In the second variation of the circulation path, the flow path resistance of the ink flow path through the bypass flow path 160 to the first recovery flow path 140 is R1, and the flow path resistance of the ink flow path from the supply flow path 130 to the first recovery flow path 140 through the ejection module 300 is R2. Since the flow rate of ink flowing through each flow path is inversely proportional to the flow path resistance, the ratio of the ink flow rate through the bypass flow path 160 to the ink flow rate through the ejection module 300 is R2 to R1. In accordance with this relationship, the flow path resistances are set to achieve a circulation amount that can suppress ink thickening near the ejection ports 13 in the ejection module 300. In other words, the flow path resistances are set so that the flow velocity of ink in the pressure chamber 12 is equal to or greater than a predetermined flow velocity. The flow path resistance R1 of the flow path through the bypass flow path 160 is controlled by changing the cross-sectional area or length of the flow path, providing a throttle in the flow path, or the like.

[0186] 37, when a printing operation is performed at a high duty, ink is supplied from both sides to the pressure chamber 12. That is, ink supplied from the first pressure control chamber 122 to the supply flow path 130 is supplied to the ejection port 13 via the common supply flow path 18 of the ejection module 300. Meanwhile, a portion of the ink supplied from the first pressure control chamber 122 to the bypass flow path 160 is supplied to the first pressure control chamber 122 via the circulation pump 500 and the pump outlet flow path 180. Furthermore, a portion of the ink supplied to the bypass flow path 160 is supplied to the first recovery flow path 140, and then to the ejection port 13 via the common recovery flow path 19 of the ejection module 300. Therefore, ink ejected from the ejection port 13 is supplied from both the supply flow path 130 and the first recovery flow path 140.

[0187] The first foam reservoir chamber 520A is provided vertically above the supply flow channel 130 so as to be in fluid communication with the supply flow channel 130, and the first bubble removal unit 770A is formed to extend vertically above the first foam reservoir chamber 520A. The second foam reservoir chamber 520B is provided vertically above the first recovery flow channel 140 so as to be in fluid communication with the first recovery flow channel 140, and the second bubble removal unit 770B is formed to extend vertically above the second foam reservoir chamber 520B. Although not shown in FIGS. 36 and 37 , the first recovery flow channel 140 that communicates with the second foam reservoir chamber 520B may further include a space capable of storing liquid (ink). This space is formed, for example, vertically below the second foam reservoir chamber 520B. In this case, this space, the first recovery channel 140, the second bubble chamber 520B, etc. correspond to the second liquid storage section. As a result, bubbles that have become mixed into the ink in the first pressure adjustment means 120 (and the above-mentioned space capable of storing liquid), the supply channel 130, the first recovery channel 140, etc. due to the circulation and discharge operations can be collected in the bubble chamber 520 and removed from the ink by the bubble removal operation. Bubbles that become mixed into the ink include, but are not limited to, the aforementioned upstream bubbles, eluted bubbles, and unexpected bubbles. It is possible to remove from the ink an amount of bubbles that can be collected in the bubble chamber 520 and that can provide a sufficient bubble removal speed. This greatly reduces the possibility of bubbles entering the discharge port 13.

[0188] The first bubble removal unit 770A and the second bubble removal unit 770B are connected to the ink supply unit 400 of the main body of the liquid ejection device 50, and are depressurized by the operation of the ink supply unit 400. Furthermore, a third check valve 213 is provided between the bubble removal unit 770 and the ink supply unit 400, and the depressurized state is maintained, allowing the bubble removal operation to be performed even when the main body of the liquid ejection device 50 is not constantly operating. The third check valve 213 may be provided in each branched portion of the third air flow path 113 between the ink supply unit 400 and the first bubble removal unit 770A and the second bubble removal unit 770B. The third check valve 213 may also be provided in a combined portion of the third air flow path 113 between the ink supply unit 400 and the first bubble removal unit 770A and the second bubble removal unit 770B.

[0189] The foam reservoir chamber 520 and the bubble removal unit 770 do not have to be provided in both the supply flow path 130 and the first recovery flow path 140; they may be provided only in the supply flow path 130 or only in the first recovery flow path 140. Furthermore, three or more foam reservoir chambers 520 and bubble removal units 770 may be provided. The foam reservoir chambers 520 and bubble removal units 770 do not have to be provided in the supply flow path 130 and the first recovery flow path 140. For example, the foam reservoir chamber 520 and the bubble removal unit 770 may be provided vertically above the ink tank 2, the first supply path 111, the second supply path 112, the third supply path 910, etc. The foam reservoir chamber 520 and the bubble removal unit 770 may be provided vertically above the filter 110, the pump outlet flow path 180, the bypass flow path 160, the pressure chamber 12, etc. Furthermore, the foam reservoir chamber 520 and the bubble removal unit 770 do not necessarily have to be provided vertically above a fluid communication part such as the supply flow path 130. As long as the configuration allows bubbles to be collected and brought into contact with the gas-permeable membrane, the foam reservoir chamber 520 may be connected to a side surface of the fluid communication part, and the bubble removal unit 770 may be formed to extend to the side of the foam reservoir chamber 520. This also applies when the foam reservoir chamber 520 and the bubble removal unit 770 are provided in multiple parts of the fluid communication part other than the supply flow path 130 and the first recovery flow path 140.

[0190] <Third modified example of circulation route> 38 and 39 are diagrams schematically showing a third modified example of the circulation path. Fig. 38 shows the circulation path when circulation is performed without ejection. Fig. 39 shows the circulation path when high-duty recording is performed. The third modified example of the circulation path shows an example in which the second pressure adjustment means 150 is not provided, the bypass flow path 160 and the first recovery flow path 140 are directly connected, and a relief valve 2301 is provided in the bypass flow path 160.

[0191] The relief valve 2301 is configured so that ink flows from the upstream side to the downstream side of the relief valve 2301 when the ink pressure downstream of the relief valve 2301 falls below a certain value. That is, the relief valve 2301 is configured to open when the ink pressure on the recovery channel side of the relief valve 2301 falls below a certain value relative to the ink pressure on the supply channel side. The ink flow in the third modified example of the circulation path is basically the same as when the second pressure adjustment means 150 is provided, as shown in FIGS. 38 and 39 . The amount of ink circulating in the ejection module 300 is determined by the differential pressure between the control pressure of the first pressure control chamber 122 and the control pressure of the relief valve 2301. The control pressure of the relief valve 2301 is set to a circulation amount that can suppress thickening of the ink near the ejection ports 13 in the ejection module 300.

[0192] In the third modified example of the circulation path, when a printing operation is performed at a high duty, as shown in Fig. 39, the pressure chamber 12 is supplied from both sides. That is, ink supplied from the first pressure control chamber 122 to the supply channel 130 is supplied to the ejection port 13 via the common supply channel 18 of the ejection module 300. Meanwhile, a portion of the ink supplied from the first pressure control chamber 122 to the bypass channel 160 passes through the relief valve 2301 and is supplied to the first pressure control chamber 122 via the circulation pump 500 and the pump outlet channel 180. Furthermore, a portion of the ink supplied to the bypass channel 160 passes through the relief valve 2301 and is supplied to the first recovery channel 140, and is then supplied to the ejection port 13 via the common recovery channel 19 of the ejection module 300. Therefore, the ink ejected from the ejection port 13 is supplied from both the supply channel 130 and the first recovery channel 140.

[0193] The first foam reservoir chamber 520A is provided vertically above the supply flow channel 130 so as to be in fluid communication with the supply flow channel 130, and the first bubble removal unit 770A is formed to extend vertically above the first foam reservoir chamber 520A. The second foam reservoir chamber 520B is provided vertically above the first recovery flow channel 140 so as to be in fluid communication with the first recovery flow channel 140, and the second bubble removal unit 770B is formed to extend vertically above the second foam reservoir chamber 520B. Although not shown in FIGS. 38 and 39 , the first recovery flow channel 140 that communicates with the second foam reservoir chamber 520B may further include a space capable of storing liquid (ink). This space is formed, for example, vertically below the second foam reservoir chamber 520B. In this case, this space, the first recovery channel 140, the second bubble chamber 520B, etc. correspond to the second liquid storage section. As a result, bubbles that have become mixed into the ink in the first pressure adjustment means 120 (and the above-mentioned space capable of storing liquid), the supply channel 130, the first recovery channel 140, etc. due to the circulation and discharge operations can be collected in the bubble chamber 520 and removed from the ink by the bubble removal operation. Bubbles that become mixed into the ink include, but are not limited to, the aforementioned upstream bubbles, eluted bubbles, and unexpected bubbles. It is possible to remove from the ink an amount of bubbles that can be collected in the bubble chamber 520 and that can provide a sufficient bubble removal speed. This greatly reduces the possibility of bubbles entering the discharge port 13.

[0194] The first bubble removal unit 770A and the second bubble removal unit 770B are connected to the ink supply unit 400 of the main body of the liquid ejection device 50, and are depressurized by the operation of the ink supply unit 400. Furthermore, a third check valve 213 is provided between the bubble removal unit 770 and the ink supply unit 400, and the depressurized state is maintained, allowing the bubble removal operation to be performed even when the main body of the liquid ejection device 50 is not constantly operating. The third check valve 213 may be provided in each branched portion of the third air flow path 113 between the ink supply unit 400 and the first bubble removal unit 770A and the second bubble removal unit 770B. The third check valve 213 may also be provided in a combined portion of the third air flow path 113 between the ink supply unit 400 and the first bubble removal unit 770A and the second bubble removal unit 770B.

[0195] The foam reservoir chamber 520 and the bubble removal unit 770 do not have to be provided in both the supply flow path 130 and the first recovery flow path 140; they may be provided only in the supply flow path 130 or only in the first recovery flow path 140. Furthermore, three or more foam reservoir chambers 520 and bubble removal units 770 may be provided. The foam reservoir chambers 520 and bubble removal units 770 do not have to be provided in the supply flow path 130 and the first recovery flow path 140. For example, the foam reservoir chamber 520 and the bubble removal unit 770 may be provided vertically above the ink tank 2, the first supply path 111, the second supply path 112, the third supply path 910, etc. The foam reservoir chamber 520 and the bubble removal unit 770 may be provided vertically above the filter 110, the pump outlet flow path 180, the bypass flow path 160, the pressure chamber 12, etc. Furthermore, the foam reservoir chamber 520 and the bubble removal unit 770 do not necessarily have to be provided vertically above a fluid communication part such as the supply flow path 130. As long as the configuration allows bubbles to be collected and brought into contact with the gas-permeable membrane, the foam reservoir chamber 520 may be connected to a side surface of the fluid communication part, and the bubble removal unit 770 may be formed to extend to the side of the foam reservoir chamber 520. This also applies when the foam reservoir chamber 520 and the bubble removal unit 770 are provided in multiple parts of the fluid communication part other than the supply flow path 130 and the first recovery flow path 140.

[0196] <Second configuration example of ink path> FIG. 40 is a schematic diagram illustrating a second configuration example of the ink path. The second configuration example of the ink path does not include the first pressure adjustment unit 120, the second pressure adjustment unit 150, the second foam reservoir chamber 520B, the circulation pump 500, the bypass flow path 160, and the first recovery flow path 140. The second configuration example of the ink path also includes a third pressure adjustment unit 902 that communicates with the second supply path 112, instead of the first pressure adjustment unit 120 and the second pressure adjustment unit 150. In the second configuration example of the ink path, ink is not circulated, and ink supplied from the second supply path 112 flows through the supply flow path 130 and the pressure chamber 12, and is then ejected from the ejection port 13. The pressures of the second supply path 112, the third supply path 910, the supply flow path 130, and the pressure chamber 12 are controlled by the third pressure adjustment unit 902, thereby achieving stable ink ejection.

[0197] The third pressure adjustment means 902 is disposed outside the liquid ejection head 1 and communicates with the third supply path 910 of the liquid ejection head 1 via the second supply path 112. The third pressure adjustment means 902 may be, for example, a water head type that utilizes a water head difference, but either type is applicable. This modified example is applicable to both ink cartridge types and ink supply types such as CISS types.

[0198] The first bubble reservoir chamber 520A is provided vertically above the supply flow path 130 so as to be in fluid communication with the supply flow path 130, and the first bubble removal unit 770A is formed to extend vertically above the first bubble reservoir chamber 520A. This allows bubbles that have become mixed into the ink in the supply flow path 130 or elsewhere due to circulation or ejection operations to be collected in the bubble reservoir chamber 520A and then removed from the ink by the bubble removal operation. Bubbles that may become mixed into the ink include, but are not limited to, the aforementioned upstream bubbles, eluted bubbles, and unexpected bubbles. It is possible to remove from the ink a quantity of bubbles that can be collected in the bubble reservoir chamber 520 and that can provide a sufficient bubble removal speed. This greatly reduces the possibility of bubbles entering the ejection port 13.

[0199] The first bubble removal unit 770A communicates with the ink supply unit 400 in the main body of the liquid ejection device 50, and is depressurized by the operation of the ink supply unit 400. Furthermore, a third check valve 213 is provided between the bubble removal unit 770 and the ink supply unit 400, and the depressurized state is maintained even if the main body of the liquid ejection device 50 is not constantly operating, thereby enabling the bubble removal operation. The third check valve 213 may also be provided in the third air flow path 113 between the first bubble removal unit 770A and the ink supply unit 400.

[0200] Two or more foam reservoir chambers 520 and two or more bubble removal units 770 may be provided. Furthermore, the foam reservoir chambers 520 and the bubble removal units 770 do not need to be provided in the supply flow path 130. For example, the foam reservoir chambers 520 and the bubble removal units 770 may be provided vertically above the ink tank 2, the first supply path 111, the second supply path 112, the third supply path 910, the filter 110, the pressure chamber 12, or the like. Furthermore, the foam reservoir chambers 520 and the bubble removal units 770 do not necessarily need to be provided vertically above the fluid communication parts, such as the supply flow path 130. As long as the foam reservoir chambers 520 are configured to be able to capture bubbles and bring them into contact with the gas-permeable membrane, the foam reservoir chambers 520 may be connected to the side of the fluid communication parts, and the bubble removal units 770 may be formed to extend laterally from the foam reservoir chambers 520. This also applies to the case where the foam reservoir 520 and the foam removal unit 770 are provided in multiple portions of the fluid communication part other than the supply flow path 130 and the first recovery flow path 140.

[0201] <Fourth modified example of circulation route> 41 and 42 are schematic diagrams illustrating a fourth variation of the circulation path. FIG. 41 illustrates the circulation path when circulation is performed without ejection. FIG. 42 illustrates the circulation path when high-duty printing is performed. The fourth variation of the circulation path illustrates an example in which the first pressure adjustment unit 120, the second pressure adjustment unit 150, the second bubble reservoir chamber 520B, the circulation pump 500, the bypass flow path 160, and the first recovery flow path 140 are not provided. The fourth variation of the circulation path also illustrates an example in which a third pressure adjustment unit 902 communicating with the second supply path 112, a heated circulation pump 904 provided between the supply flow path 130 and the pressure chamber 12, and a second recovery flow path 905 communicating between the pressure chamber 12 and the supply flow path 130 are provided. In the fourth variation of the circulation path, ink flows similar to those illustrated in FIGS. 33 and 35 . The pressures of the second supply path 112, the third supply path 910, the supply flow path 130, and the pressure chamber 12 are controlled by the third pressure adjusting means 902, thereby realizing stable ink ejection.

[0202] The third pressure adjustment means 902 is disposed outside the liquid ejection head 1 and communicates with the third supply path 910 of the liquid ejection head 1 via the second supply path 112. The third pressure adjustment means 902 may be, for example, a water head type that utilizes a water head difference, but either type is applicable. This modified example is applicable to both ink cartridge types and ink supply types such as CISS types.

[0203] The first bubble reservoir chamber 520A is provided vertically above the supply flow path 130 so as to be in fluid communication with the supply flow path 130, and the first bubble removal unit 770A is formed to extend vertically above the first bubble reservoir chamber 520A. This allows bubbles that have become mixed into the ink in the first pressure adjustment means 120, the supply flow path 130, the second recovery flow path 905, etc., due to circulation and ejection operations to be collected in the bubble reservoir chamber 520 and then removed from the ink by the bubble removal operation. Bubbles that may become mixed into the ink include, but are not limited to, the aforementioned upstream bubbles, eluted bubbles, and unexpected bubbles. It is possible to remove from the ink an amount of bubbles that can be collected in the bubble reservoir chamber 520 and that can provide a sufficient bubble removal speed. This greatly reduces the possibility of bubbles entering the ejection port 13.

[0204] The first bubble removal unit 770A communicates with the ink supply unit 400 in the main body of the liquid ejection device 50, and is depressurized by the operation of the ink supply unit 400. Furthermore, a third check valve 213 is provided between the bubble removal unit 770 and the ink supply unit 400, and the depressurized state is maintained even if the main body of the liquid ejection device 50 is not constantly operating, thereby enabling the bubble removal operation. The third check valve 213 may also be provided in the third air flow path 113 between the first bubble removal unit 770A and the ink supply unit 400.

[0205] Two or more foam reservoir chambers 520 and two or more bubble removal units 770 may be provided. Furthermore, the foam reservoir chambers 520 and the bubble removal units 770 do not need to be provided in the supply flow path 130. For example, the foam reservoir chambers 520 and the bubble removal units 770 may be provided vertically above the ink tank 2, the first supply path 111, the second supply path 112, the third supply path 910, the filter 110, the pressure chamber 12, the second recovery path 905, or the like. Furthermore, the foam reservoir chambers 520 and the bubble removal units 770 do not necessarily need to be provided vertically above fluid communication sections such as the supply flow path 130. As long as the foam reservoir chambers 520 are configured to be able to collect bubbles and bring them into contact with the gas-permeable membrane, the foam reservoir chambers 520 may be connected to the side of the fluid communication section, and the bubble removal unit 770 may be formed to extend laterally from the foam reservoir chamber 520. This also applies to the case where the foam reservoir 520 and the foam removal unit 770 are provided in multiple portions of the fluid communication part other than the supply flow path 130 and the first recovery flow path 140.

[0206] The heated circulation pump 904 sends ink by performing the same operation as in Fig. 34. The heated circulation pump 904 does not need to be provided between the supply flow path 130 and the pressure chamber 12, and may be provided between the pressure chamber 12 and the second recovery flow path 905.

[0207] <Fifth modified example of circulation route> 43 and 44 are diagrams schematically showing a fifth modified example of the circulation path. Fig. 43 shows the circulation path when circulation is performed without ejection. Fig. 44 shows the circulation path when high-duty recording is performed. The fifth modified example of the circulation path shows an example in which the first pressure adjustment means 120 and the second pressure adjustment means 150 are not provided, and the bypass flow path 160 and the first recovery flow path 140 are directly connected.

[0208] In the fifth variation of the circulation path, the flow path resistance of the ink flow path through the bypass flow path 160 to the first recovery flow path 140 is R1, and the flow path resistance of the ink flow path from the supply flow path 130 to the first recovery flow path 140 through the ejection module 300 is R2. Since the flow rate of ink flowing through each flow path is inversely proportional to the flow path resistance, the ratio of the ink flow rate through the bypass flow path 160 to the ink flow rate through the ejection module 300 is R2 to R1. In accordance with this relationship, the flow path resistances are set to achieve a circulation amount that can suppress ink thickening near the ejection ports 13 in the ejection module 300. In other words, the flow path resistances are set so that the flow velocity of ink in the pressure chamber 12 is equal to or greater than a predetermined flow velocity. The flow path resistance R1 of the flow path through the bypass flow path 160 is controlled by changing the cross-sectional area or length of the flow path, providing a throttle in the flow path, or the like.

[0209] In the fifth modified example of the circulation path, when a printing operation is performed at a high duty, as shown in Fig. 44, the pressure chamber 12 is supplied from both sides. That is, ink supplied from the third supply path 910 to the supply flow path 130 is supplied to the ejection port 13 of the ejection module 300. Meanwhile, a portion of the ink supplied from the third supply path 910 to the bypass flow path 160 is supplied to the third supply path 910 via the circulation pump 500. Furthermore, a portion of the ink supplied from the third supply path 910 to the bypass flow path 160 is supplied to the first recovery flow path 140, and then to the ejection port 13 of the ejection module 300. Therefore, the ink ejected from the ejection port 13 is supplied from both the supply flow path 130 and the first recovery flow path 140.

[0210] The third pressure adjustment means 902 is disposed outside the liquid ejection head 1 and communicates with the third supply path 910 of the liquid ejection head 1 via the second supply path 112. The third pressure adjustment means 902 may be, for example, a water head type that utilizes a water head difference, but either type is applicable. This modified example is applicable to both ink cartridge types and ink supply types such as CISS types.

[0211] The first foam reservoir chamber 520A is provided vertically above the supply flow channel 130 so as to be in fluid communication with the supply flow channel 130, and the first bubble removal unit 770A is formed to extend vertically above the first foam reservoir chamber 520A. The second foam reservoir chamber 520B is provided vertically above the first recovery flow channel 140 so as to be in fluid communication with the first recovery flow channel 140, and the second bubble removal unit 770B is formed to extend vertically above the second foam reservoir chamber 520B. Although not shown in FIGS. 43 and 44 , the supply flow channel 130 communicating with the first foam reservoir chamber 520A may further include a space capable of storing liquid (ink). This space is formed, for example, vertically below the first foam reservoir chamber 520A. In this case, this space, the supply flow channel 130, and the first foam reservoir chamber 520A correspond to the first liquid reservoir. 43 and 44, the first recovery channel 140, which communicates with the second foam reservoir chamber 520B, may further include a space capable of storing liquid (ink). This space is formed, for example, below the second foam reservoir chamber 520B in the vertical direction. In this case, this space, the first recovery channel 140, and the second foam reservoir chamber 520B correspond to the second liquid reservoir.

[0212] As a result, bubbles that have become mixed into the ink in the supply flow path 130, the first recovery flow path 140, the pump inlet flow path 170, the pump outlet flow path 180, etc. due to the circulation and discharge operations can be collected in the bubble reservoir chamber 520 and removed from the ink by the bubble removal operation. Bubbles that become mixed into the ink include, but are not limited to, the aforementioned upstream bubbles, eluted bubbles, and unexpected bubbles. It is possible to remove from the ink an amount of bubbles that can be collected in the bubble reservoir chamber 520 and that can provide a sufficient bubble removal speed. This greatly reduces the possibility of bubbles entering the discharge port 13.

[0213] The first bubble removal unit 770A and the second bubble removal unit 770B are connected to the ink supply unit 400 of the main body of the liquid ejection device 50, and are depressurized by the operation of the ink supply unit 400. Furthermore, a third check valve 213 is provided between the bubble removal unit 770 and the ink supply unit 400, and the depressurized state is maintained, allowing the bubble removal operation to be performed even when the main body of the liquid ejection device 50 is not constantly operating. The third check valve 213 may be provided in each branched portion of the third air flow path 113 between the ink supply unit 400 and the first bubble removal unit 770A and the second bubble removal unit 770B. The third check valve 213 may also be provided in a combined portion of the third air flow path 113 between the ink supply unit 400 and the first bubble removal unit 770A and the second bubble removal unit 770B.

[0214] The foam reservoir chamber 520 and the bubble removal unit 770 do not have to be provided in both the supply flow path 130 and the first recovery flow path 140; they may be provided only in the supply flow path 130 or only in the first recovery flow path 140. Furthermore, three or more foam reservoir chambers 520 and bubble removal units 770 may be provided. The foam reservoir chambers 520 and bubble removal units 770 do not have to be provided in the supply flow path 130 and the first recovery flow path 140. For example, the foam reservoir chamber 520 and the bubble removal unit 770 may be provided vertically above the ink tank 2, the first supply path 111, the second supply path 112, the third supply path 910, etc. The foam reservoir chamber 520 and the bubble removal unit 770 may be provided vertically above the filter 110, the pump inlet flow path 170, the pump outlet flow path 180, the bypass flow path 160, the pressure chamber 12, etc. Furthermore, the foam reservoir chamber 520 and the bubble removal unit 770 do not necessarily have to be provided vertically above a fluid communication part such as the supply flow path 130. As long as the configuration allows bubbles to be collected and brought into contact with the gas-permeable membrane, the foam reservoir chamber 520 may be connected to a side surface of the fluid communication part, and the bubble removal unit 770 may be formed to extend to the side of the foam reservoir chamber 520. This also applies when the foam reservoir chamber 520 and the bubble removal unit 770 are provided in multiple parts of the fluid communication part other than the supply flow path 130 and the first recovery flow path 140.

[0215] <Sixth modified example of circulation route> Figures 45 and 46 are diagrams schematically showing a sixth modified example of the circulation path. Figure 45 shows the circulation path when circulation is performed without ejection. Figure 46 shows the circulation path when high-duty printing is performed. The sixth modified example of the circulation path shows an example in which the first pressure adjustment means 120 is not provided, and a third pressure adjustment means 902 communicating with the second supply path 112 is provided.

[0216] In the sixth modified example of the circulation path, when a printing operation is performed at a high duty, as shown in FIG. 46 , the pressure chamber 12 is supplied from both sides. That is, ink supplied from the third supply path 910 to the supply flow path 130 is supplied to the ejection port 13 of the ejection module 300. Meanwhile, a portion of the ink supplied from the third supply path 910 to the bypass flow path 160 is supplied to the third supply path 910 via the second pressure adjustment means 150, the pump inlet flow path 170, the circulation pump 500, and the pump outlet flow path 180. Furthermore, a portion of the ink supplied to the bypass flow path 160 is supplied to the first recovery flow path 140 via the second pressure adjustment means 150, and then to the ejection port 13 of the ejection module 300. Therefore, ink ejected from the ejection port 13 is supplied from both the supply flow path 130 and the first recovery flow path 140.

[0217] The third pressure adjustment means 902 is disposed outside the liquid ejection head 1 and communicates with the third supply path 910 of the liquid ejection head 1 via the second supply path 112. The third pressure adjustment means 902 may be, for example, a water head type that utilizes a water head difference, but either type is applicable. This modified example is applicable to both ink cartridge types and ink supply types such as CISS types.

[0218] The first foam reservoir chamber 520A is provided vertically above the supply flow channel 130 so as to be in fluid communication with the supply flow channel 130, and the first bubble removal unit 770A is formed to extend vertically above the first foam reservoir chamber 520A. The second foam reservoir chamber 520B is provided vertically above the first recovery flow channel 140 so as to be in fluid communication with the first recovery flow channel 140, and the second bubble removal unit 770B is formed to extend vertically above the second foam reservoir chamber 520B. Although not shown in FIGS. 45 and 46 , the supply flow channel 130 communicating with the first foam reservoir chamber 520A may further include a space capable of storing liquid (ink). This space is formed, for example, vertically below the first foam reservoir chamber 520A. In this case, this space, the supply flow channel 130, and the first foam reservoir chamber 520A correspond to the first liquid reservoir. The first recovery passage opening 1002 in the second pressure control chamber 152 is disposed vertically above the second pressure control chamber 152 and vertically below the second foam reservoir chamber 520B. The pump inlet opening 1001 in the second pressure control chamber 152 is disposed vertically below the second pressure control chamber 152.

[0219] As a result, bubbles that have become mixed into the ink in the second pressure adjustment means 150, the supply flow path 130, the first recovery flow path 140, the pump outlet flow path 180, etc., due to the circulation and discharge operations can be collected in the bubble reservoir chamber 520 and removed from the ink by the bubble removal operation. Bubbles that become mixed into the ink include, but are not limited to, the aforementioned upstream bubbles, eluted bubbles, and unexpected bubbles. It is possible to remove from the ink an amount of bubbles that can be collected in the bubble reservoir chamber 520 and that can provide a sufficient bubble removal speed. This greatly reduces the possibility of bubbles entering the discharge port 13.

[0220] The first bubble removal unit 770A and the second bubble removal unit 770B are connected to the ink supply unit 400 of the main body of the liquid ejection device 50, and are depressurized by the operation of the ink supply unit 400. Furthermore, a third check valve 213 is provided between the bubble removal unit 770 and the ink supply unit 400, and the depressurized state is maintained, allowing the bubble removal operation to be performed even when the main body of the liquid ejection device 50 is not constantly operating. The third check valve 213 may be provided in each branched portion of the third air flow path 113 between the ink supply unit 400 and the first bubble removal unit 770A and the second bubble removal unit 770B. The third check valve 213 may also be provided in a combined portion of the third air flow path 113 between the ink supply unit 400 and the first bubble removal unit 770A and the second bubble removal unit 770B.

[0221] The foam reservoir chamber 520 and the bubble removal unit 770 do not have to be provided in both the supply flow path 130 and the first recovery flow path 140; they may be provided only in the supply flow path 130 or only in the first recovery flow path 140. Furthermore, three or more foam reservoir chambers 520 and bubble removal units 770 may be provided. The foam reservoir chambers 520 and bubble removal units 770 do not have to be provided in the supply flow path 130 and the first recovery flow path 140. For example, the foam reservoir chamber 520 and the bubble removal unit 770 may be provided vertically above the ink tank 2, the first supply path 111, the second supply path 112, the third supply path 910, etc. The foam reservoir chamber 520 and the bubble removal unit 770 may be provided vertically above the filter 110, the pump inlet flow path 170, the pump outlet flow path 180, the bypass flow path 160, the pressure chamber 12, etc. Furthermore, the foam reservoir chamber 520 and the bubble removal unit 770 do not necessarily have to be provided vertically above a fluid communication part such as the supply flow path 130. As long as the configuration allows bubbles to be collected and brought into contact with the gas-permeable membrane, the foam reservoir chamber 520 may be connected to a side surface of the fluid communication part, and the bubble removal unit 770 may be formed to extend to the side of the foam reservoir chamber 520. This also applies when the foam reservoir chamber 520 and the bubble removal unit 770 are provided in multiple parts of the fluid communication part other than the supply flow path 130 and the first recovery flow path 140.

[0222] <Other variations of the circulation route> Next, other modified examples of the circulation flow path will be described. As described above, the configuration in which ink flows back from the first recovery flow path 140 toward the pressure chamber 12 only needs to include the bypass flow path 160. Furthermore, the configuration in which ink flows back from the first recovery flow path 140 toward the pressure chamber 12 only needs to include no mechanism that functions as a check valve between the junction of the bypass flow path 160 and the pressure chamber 12. Therefore, if the circulation flow path can maintain this relationship, ink can be supplied to both sides of the pressure chamber 12, thereby improving ejection stability.

[0223] Figures 47, 48, and 49 are block diagrams schematically showing other modified examples of the circulation path. In Figures 47, 48, and 49, the bubble removal unit 770 and the gas flow path connected to the bubble removal unit 770 (for example, the third air flow path 113) are not shown.

[0224] 47 shows an example in which the pump outlet flow path 180 located downstream of the circulation pump 500 is configured to be connected to the ink tank 2 instead of the first pressure control chamber 122. In this configuration as well, ejection stability can be improved, similar to the configurations described so far.

[0225] 48 shows an example in which the circulation pump 500 that was previously mounted inside the liquid ejection head 1 is installed on the main body side of the liquid ejection device 50. A portion of the pump inlet flow path 170 and the pump outlet flow path 180 are also arranged outside the liquid ejection head 1. In this configuration as well, ejection stability can be improved, similar to the configurations described so far.

[0226] 49 shows an example in which the circulation pump 500 that was mounted inside the liquid ejection head 1 is installed on the main body side of the liquid ejection device 50, and the pump outlet flow path 180 is connected to the ink tank 2. In this configuration as well, ejection stability can be improved, similar to the configurations described so far.

[0227] <Other variations> 1(a) is a so-called serial type liquid ejection head that ejects ink while moving in the main scanning direction, but is not limited to this. It may also be a so-called full-line type liquid ejection head that has ejection ports formed across the entire width of the recording medium P and is capable of ejecting ink across the entire width of the recording medium P without moving in the main scanning direction.

[0228] The disclosure of the above embodiment includes the following configurations and methods. (Configuration 1) a discharge port for discharging a liquid; a pressure chamber provided with an energy generating element that generates energy for ejecting liquid from the ejection port; a first liquid storage section that communicates with one end of the pressure chamber and is capable of storing liquid to be supplied to the pressure chamber; a first decompression chamber adjacent to the first liquid storage portion via a first gas permeable membrane and configured to be capable of decompressing the interior thereof; a second liquid storage section that communicates with the other end of the pressure chamber and is capable of storing the liquid recovered from the pressure chamber; a second decompression chamber that is adjacent to the second liquid storage section via a second gas-permeable membrane and is configured so that the pressure inside can be reduced; (Configuration 2) The liquid ejection head according to Configuration 1, wherein the liquid is circulatable from the second liquid storage section to the first liquid storage section. (Configuration 3) further comprising a pump connected to the first liquid reservoir and the second liquid reservoir; 3. The liquid ejection head according to claim 1, wherein the pump is configured to be able to cause the liquid in the second liquid storage portion to flow into the first liquid storage portion. (Configuration 4) the first liquid storage section includes a first flow path for supplying liquid to the pressure chamber; 4. The liquid ejection head according to any one of configurations 1 to 3, wherein the second liquid storage section includes a second flow path for recovering liquid from the pressure chamber. (Configuration 5) 5. The liquid ejection head according to configuration 4, wherein the first liquid storage section includes a first pressure adjusting means for adjusting the pressure of the liquid in the first flow path. (Configuration 6) The liquid ejection head according to configuration 4 or 5, wherein the second liquid storage section includes a second pressure adjusting means that adjusts the pressure of the liquid in the second flow path. (Configuration 7) 7. The liquid ejection head according to any one of configurations 1 to 6, further comprising a bypass flow path that connects the first liquid storage section and the second liquid storage section without passing through the pressure chamber. (Configuration 8) the first decompression chamber is provided above the first liquid storage portion in the vertical direction, 8. The liquid ejection head according to any one of configurations 1 to 7, wherein the second decompression chamber is provided above the second liquid storage section in the vertical direction. (Configuration 9) the first liquid storage section includes a first foam storage chamber capable of storing foam therein; the first bubble reservoir chamber is adjacent to the first decompression chamber via the first gas permeable membrane; the second liquid storage section includes a second foam storage chamber capable of storing foam therein; 9. The liquid ejection head according to any one of configurations 1 to 8, wherein the second bubble reservoir chamber is adjacent to the second decompression chamber via the second gas-permeable membrane. (Configuration 10) the first liquid storage section includes a first flow path for supplying liquid to the pressure chamber; the second liquid storage section includes a second flow path for recovering liquid from the pressure chamber, and a second pressure adjustment means for adjusting the pressure of the liquid in the second flow path; 10. The liquid ejection head according to claim 9, wherein the second pressure adjusting means is connected to the second flow path at a position vertically below the second bubble reservoir chamber. (Configuration 11) further comprising a pump that causes the liquid in the second liquid storage portion to flow into the first liquid storage portion; the second liquid storage section includes a second flow path for recovering liquid from the pressure chamber, and a second pressure adjustment means provided vertically below the second bubble reservoir chamber and for adjusting the pressure of the liquid in the second flow path, the first liquid storage section and the pump are connected via a third flow path; the second pressure adjusting means and the pump are connected via a fourth flow path; 11. The liquid ejection head according to configuration 9 or 10, wherein the position to which the fourth flow path is connected in the second pressure adjustment means is located vertically below the second bubble reservoir chamber. (Configuration 12) 12. The liquid ejection head according to any one of configurations 9 to 11, wherein the volume of the first bubble reservoir is larger than the volume of the second bubble reservoir. (Configuration 13) 13. The liquid ejection head according to configuration 12, wherein the first decompression chamber and the second decompression chamber are in communication with each other. (Configuration 14) 14. The liquid ejection head according to configuration 12 or 13, wherein the area of ​​the first gas permeable membrane that can come into contact with bubbles is larger than the area of ​​the second gas permeable membrane that can come into contact with bubbles. (Configuration 15) 15. The liquid ejection head according to any one of configurations 1 to 14, wherein the first decompression chamber and the second decompression chamber are decompressed by a decompression means provided outside the liquid ejection head. (Configuration 16) 16. The liquid ejection head of Configuration 15, wherein the first decompression chamber is disposed at a position where a flow path from the decompression means is longer than that of the second decompression chamber. (Configuration 17) 17. The liquid ejection head according to configuration 15 or 16, further comprising a check valve that regulates the flow of air from the pressure reducing means toward the first pressure reducing chamber and the second pressure reducing chamber. (Configuration 18) A liquid ejection head according to any one of claims 1 to 17; a pressure reducing means for reducing the pressure in the first pressure reducing chamber and the second pressure reducing chamber in the liquid ejection head. (Configuration 19) a discharge port for discharging a liquid; a pressure chamber provided with an energy generating element that generates energy for ejecting liquid from the ejection port; a first liquid reservoir that is fluidly connected to one end of the pressure chamber and that is capable of storing liquid to be supplied to the pressure chamber; a first bubble removal means capable of discharging bubbles accumulated in the first liquid storage portion to the outside; a second liquid reservoir that is in fluid communication with the other end of the pressure chamber and that is capable of storing liquid recovered from the pressure chamber; a second bubble removal means capable of discharging bubbles accumulated in the second liquid storage portion to the outside; [Explanation of symbols]

[0229] 1 Liquid ejection head 12 Pressure Chamber 120 First pressure adjusting means 130 supply channel 140 First recovery channel 150 Second pressure adjusting means 520 Bubble Chamber 710 Gas-permeable membrane 760 Decompression Chamber

Claims

1. a discharge port for discharging a liquid; a pressure chamber provided with an energy generating element that generates energy for ejecting liquid from the ejection port; a first liquid storage portion that communicates with one end of the pressure chamber and is capable of storing liquid to be supplied to the pressure chamber; a first decompression chamber adjacent to the first liquid storage portion via a first gas permeable membrane and configured to be capable of decompressing the interior thereof; a second liquid storage section that communicates with the other end of the pressure chamber and is capable of storing the liquid recovered from the pressure chamber; a second decompression chamber adjacent to the second liquid storage section via a second gas-permeable membrane, the second decompression chamber being configured so that the pressure inside can be reduced;

2. The liquid ejection head according to claim 1 , wherein the liquid is circulatable from the second liquid storage section to the first liquid storage section.

3. further comprising a pump connected to the first liquid reservoir and the second liquid reservoir; The liquid ejection head according to claim 1 , wherein the pump is configured to be able to cause the liquid in the second liquid storage portion to flow into the first liquid storage portion.

4. the first liquid storage portion includes a first flow path for supplying liquid to the pressure chamber; The liquid ejection head according to claim 1 , wherein the second liquid storage section includes a second flow path for recovering the liquid from the pressure chamber.

5. The liquid ejection head according to claim 4 , wherein the first liquid storage section includes a first pressure adjusting means for adjusting the pressure of the liquid in the first flow path.

6. The liquid ejection head according to claim 4 , wherein the second liquid storage section includes a second pressure adjusting means for adjusting the pressure of the liquid in the second flow path.

7. 2. The liquid ejection head according to claim 1, further comprising a bypass flow path that connects the first liquid storage portion and the second liquid storage portion without passing through the pressure chamber.

8. the first decompression chamber is provided above the first liquid storage portion in the vertical direction, The liquid ejection head according to claim 1 , wherein the second decompression chamber is provided above the second liquid storage portion in the vertical direction.

9. the first liquid storage section includes a first foam storage chamber capable of storing foam therein; the first bubble reservoir chamber is adjacent to the first decompression chamber via the first gas permeable membrane; the second liquid storage section includes a second foam storage chamber capable of storing foam therein; The liquid ejection head according to claim 1 , wherein the second bubble reservoir chamber is adjacent to the second decompression chamber via the second gas-permeable membrane.

10. the first liquid storage portion includes a first flow path for supplying liquid to the pressure chamber; the second liquid storage section includes a second flow path for recovering liquid from the pressure chamber, and a second pressure adjusting means for adjusting the pressure of the liquid in the second flow path, 10. The liquid ejection head according to claim 9, wherein the position where the second flow path is connected to the second pressure adjusting means is located vertically below the second bubble reservoir chamber.

11. a pump that causes the liquid in the second liquid storage portion to flow into the first liquid storage portion; the second liquid reservoir includes a second flow path for recovering liquid from the pressure chamber, and a second pressure adjusting means provided vertically below the second bubble reservoir chamber and for adjusting the pressure of the liquid in the second flow path, the first liquid storage portion and the pump are connected via a third flow path; the second pressure adjusting means and the pump are connected via a fourth flow path; 10. The liquid ejection head according to claim 9, wherein the position where the fourth flow path is connected to the second pressure adjusting means is located vertically below the second bubble reservoir chamber.

12. The liquid ejection head according to claim 9 , wherein the volume of the first bubble reservoir chamber is larger than the volume of the second bubble reservoir chamber.

13. The liquid ejection head according to claim 12, wherein the first decompression chamber and the second decompression chamber communicate with each other.

14. 13. The liquid ejection head according to claim 12, wherein an area of ​​the first gas-permeable membrane that can come into contact with the bubbles is larger than an area of ​​the second gas-permeable membrane that can come into contact with the bubbles.

15. 2. The liquid ejection head according to claim 1, wherein the first decompression chamber and the second decompression chamber are decompressed by a decompression means provided outside the liquid ejection head.

16. 16. The liquid ejection head according to claim 15, wherein the first pressure reduction chamber is disposed at a position where a flow path from the pressure reduction means is longer than that of the second pressure reduction chamber.

17. 16. The liquid ejection head according to claim 15, further comprising a check valve that regulates the flow of air from the pressure reducing means toward the first pressure reducing chamber and the second pressure reducing chamber.

18. A liquid ejection head according to any one of claims 1 to 17; a pressure reducing means for reducing the pressure in the first pressure reducing chamber and the second pressure reducing chamber in the liquid ejection head.

19. a discharge port for discharging a liquid; a pressure chamber provided with an energy generating element that generates energy for ejecting liquid from the ejection port; a first liquid reservoir that is in fluid communication with one end of the pressure chamber and that is capable of storing liquid to be supplied to the pressure chamber; a first bubble removal means capable of discharging bubbles accumulated in the first liquid storage portion to the outside; a second liquid reservoir that is in fluid communication with the other end of the pressure chamber and that is capable of storing liquid recovered from the pressure chamber; a second bubble removal means capable of discharging bubbles accumulated in the second liquid storage portion to the outside.

Images