Liquid discharge head and liquid discharge device

Abstract

This invention provides a liquid discharge head that can improve circulation efficiency while maintaining an appropriate flow velocity near the discharge port and suppressing the evaporation rate from the discharge port. [Solution] The liquid discharge head of the present disclosure is a liquid discharge head that discharges liquid from a discharge port while moving in a predetermined direction, and is characterized by comprising: a discharge element that generates energy for discharging liquid from a discharge port; a pressure chamber communicating with the discharge port; a nozzle that communicates with the discharge port at one end and with the pressure chamber at the other end; an individual supply channel that supplies liquid to the pressure chamber; an individual recovery channel that recovers liquid from the pressure chamber; a liquid delivery element disposed between the pressure chamber and the individual supply channel and delivers liquid from the individual supply channel to the individual recovery channel; and a circulation unit that circulates liquid from a common recovery channel that recovers liquid from a plurality of individual recovery channels to a common supply channel that supplies liquid to a plurality of individual supply channels.

Description

Technical Field

[0001] The present invention relates to a liquid ejection head and a liquid ejection apparatus including the liquid ejection head.

Background Art

[0002] Conventionally, in a liquid ejection head, one of the factors that deteriorates image quality is the concentration of ink (liquid). In ejection ports where ejection is not performed for a while, evaporation of ink proceeds from the ejection ports, and the ink thickens. When the ink thickens, the ejection amount and ejection direction may vary. In this case, streaks and density unevenness appear in the image, and the image quality deteriorates.

[0003] In Patent Document 1, in addition to a configuration in which ink is circulated by individual pumps disposed in a pressure chamber, a configuration is disclosed in which ink is circulated between the liquid ejection head and the main body using a main body side pump outside the liquid ejection head.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in Patent Document 1, when the main body mechanism becomes large, the flow rate of the main body side pump increases accordingly, and this flow rate also affects the vicinity of the ejection port, and there is a risk that the evaporation rate from the ejection port increases.

[0006] In view of the above problems, an object of the present disclosure is to provide a liquid ejection head capable of improving circulation efficiency while appropriately maintaining the flow rate in the vicinity of the ejection port and suppressing the evaporation rate from the ejection port.

Means for Solving the Problems

[0007] The liquid discharge head of this disclosure is a liquid discharge head that discharges liquid from a discharge port while moving in a predetermined direction, and is characterized by comprising: a discharge element that generates energy for discharging liquid from a discharge port; a pressure chamber communicating with the discharge port; a nozzle that communicates with the discharge port at one end and with the pressure chamber at the other end; an individual supply channel for supplying liquid to the pressure chamber; an individual recovery channel for recovering liquid from the pressure chamber; a liquid delivery element disposed between the pressure chamber and the individual supply channel for delivering liquid from the individual supply channel to the individual recovery channel; and a circulation unit that circulates liquid from a common recovery channel that recovers liquid from a plurality of individual recovery channels to a common supply channel that supplies liquid to a plurality of individual supply channels. [Effects of the Invention]

[0008] According to this disclosure, it is possible to improve circulation efficiency while appropriately maintaining the flow velocity near the discharge port and suppressing the evaporation rate from the discharge port. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram illustrating a liquid dispensing device. [Figure 2] This is a disassembled perspective view of the liquid dispensing head. [Figure 3] These are longitudinal cross-sections of the liquid dispensing head and enlarged cross-sectional views of the dispensing module. [Figure 4] This is a schematic diagram of the external appearance of the circulation unit. [Figure 5] This is a longitudinal cross-sectional view showing the circulation path. [Figure 6] This is a block diagram schematically showing the circulation path. [Figure 7] This is a cross-sectional view showing an example of a pressure regulating means. [Figure 8] This is a perspective view of the circulation pump. [Figure 9] This is a cross-sectional view of the circulation pump shown in Figure 8(a) along the line IX-IX. [Figure 10] This diagram illustrates the flow of ink within the liquid ejection head. [Figure 11]It is a schematic diagram showing a circulation path in a discharge unit. [Figure 12] It is a diagram showing an opening plate 330. [Figure 13] It is a diagram showing a discharge element substrate. [Figure 14] It is a cross-sectional view showing the ink flow in a discharge unit. [Figure 15] It is a cross-sectional view showing the vicinity of a discharge port. [Figure 16] It is a cross-sectional view showing a comparative example in the vicinity of a discharge port. [Figure 17] It is a diagram showing a comparative example of a discharge element substrate. [Figure 18] It is a diagram showing the flow path configuration of a liquid discharge head. [Figure 19] It is a diagram showing the connection state between the main body of a liquid discharge device and a liquid discharge head. [Figure 20] It is a diagram showing a part of a discharge module. [Figure 21] It is a diagram showing a discharge pulse and a drive pulse of a liquid feeding element.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but it can be implemented in any form and is not limited to other forms.

[0011] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the present disclosure, and not all combinations of features described in these embodiments are essential for the solution of the present disclosure. The same reference numerals are assigned to the same components. In this embodiment, as a discharge element for discharging a liquid, an example using a thermal method in which bubbles are generated by an electrothermal conversion element to discharge the liquid will be described, but the present disclosure is not limited thereto. The present disclosure can also be applied to a liquid discharge head that discharges a liquid using a piezoelectric element (piezo) or other discharge methods. Further, the pumps, pressure adjustment means, etc. described below are not limited to the configurations themselves described in the embodiments and the drawings. In the following description, first, the basic configuration of the present disclosure will be described, and then the characteristic parts of the present disclosure will be described.

[0012] <Liquid discharge device> FIG. 1 is a diagram for explaining a liquid discharge device, and is an enlarged view of a liquid discharge head of the liquid discharge device and its periphery. First, the schematic configuration of the liquid discharge device 50 in the present embodiment will be described with reference to FIG. 1. FIG. 1(a) is a perspective view schematically showing a liquid discharge device using a liquid discharge head 1. The liquid discharge device 50 of the present embodiment constitutes a serial inkjet recording device that discharges ink as a liquid while scanning the liquid discharge head 1 to perform recording on a recording medium P.

[0013] The liquid discharge head 1 is mounted on a carriage 60. The carriage 60 reciprocates along a guide shaft 51 in the main scanning direction (X direction). The sheet-shaped recording medium P is conveyed in the sub-scanning direction (Y direction) intersecting (in this example, orthogonal) to the main scanning direction by conveyance rollers 55, 56, 57, 58. In each figure referred to below, the Z direction indicates the vertical direction and intersects (in this example, is orthogonal) to the X-Y plane defined by the X direction and the Y direction. The liquid discharge head 1 is configured to be removable and attachable to the carriage 60 by the user.

[0014] The liquid discharge head 1 includes a circulation unit 54 and a discharge unit 3 (see Figure 2), which will be described later. The specific configuration will be described later, but the discharge unit 3 is provided with multiple discharge ports and an energy generating element (hereinafter referred to as a discharge element) that emits discharge energy for discharging liquid from each discharge port.

[0015] Furthermore, the liquid dispensing device 50 is equipped with an ink tank 2, which is the source of ink, and an external pump 21. The ink stored in the ink tank 2 is supplied to the circulation unit 54 via an ink supply tube 59 by the driving force of the external pump 21.

[0016] The liquid ejection device 50 forms a predetermined image on the recording medium P by repeatedly performing a recording scan, in which the liquid ejection head 1 mounted on the carriage 60 moves in the main scanning direction and ejects ink for recording, and a transport operation, in which the recording medium P is transported in the sub-scanning direction. In this embodiment, the liquid ejection head 1 is capable of ejecting four types of ink: black (K), cyan (C), magenta (M), and yellow (Y), and it is possible to record 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. This disclosure is also applicable to liquid ejection heads for ejecting other types of ink. In other words, the type and number of inks ejected from the liquid ejection head are not limited.

[0017] Furthermore, the liquid ejection device 50 is provided with a cap member (not shown) that can cover the ejection port surface of the liquid ejection head, located at a position offset in the X direction from the transport path of the recording medium P. The cap member covers the ejection port surface of the liquid ejection head 1 during non-recording operations and is used to prevent drying of the ejection port, protect it, and perform ink suction operations from the ejection port.

[0018] The liquid ejection head 1 shown in Figure 1(a) is an example in which four circulation units 54 corresponding to four types of ink are provided on the liquid ejection head 1, but it is sufficient to provide circulation units 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 can be configured to have one or more circulation units. It is also possible to configure it to circulate only at least one ink, rather than circulating all four types of ink.

[0019] Figure 1(b) is a block diagram showing the control system of the liquid dispensing device 50. The CPU 103 functions as a control means that controls the operation of each part of the liquid dispensing device 50 based on a program such as a processing procedure 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 an external host device 400 of the liquid dispensing device 50 and controls the head driver 1A, and controls the driving of the dispensing element 15 and the liquid delivery element 1001 provided in the dispensing unit 3. The CPU 103 also controls various drivers provided in the liquid dispensing device. For example, the CPU 103 controls the motor driver 105A of the carriage motor 105 for moving the carriage 60, and the motor driver 104A of the transport motor 104 for transporting the recording medium P. Furthermore, the CPU 103 controls the pump driver 500A that drives the circulation pump 500 (described later), and the pump driver 21A of the external pump 21. Although Figure 1(b) shows a configuration in which image data received from the host device 400 is processed, processing may also be performed in the liquid dispensing device 50 without relying on data from the host device 400.

[0020] <Basic configuration of a liquid dispensing head> Figure 2 is an exploded perspective view of the liquid discharge head 1 of this embodiment. Figure 3 is a cross-sectional view of the liquid discharge head 1 shown in Figure 2 along the line IIIA-IIIA. Figure 3(a) is an overall longitudinal cross-sectional view of the liquid discharge head 1, and Figure 3(b) is an enlarged view of the discharge module shown in Figure 3(a). Hereinafter, the basic configuration of the liquid discharge head 1 in this embodiment will be described, mainly focusing on Figures 2 and 3, with appropriate reference to Figure 1.

[0021] As shown in Figure 2, the liquid ejection head 1 comprises a circulation unit 54 and an ejection unit 3 for ejecting ink supplied from the circulation unit 54 onto the recording medium P. In this embodiment, the liquid ejection head 1 is fixedly supported on the carriage 60 of the liquid ejection device 50 by positioning means (not shown) and electrical contacts 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 Figure 1, and records onto the recording medium P.

[0022] An external pump 21, connected to an ink tank 2 which serves as the ink supply source, is equipped with an ink supply tube 59 (see Figure 1). A liquid connector (not shown) is provided at the tip of this ink supply tube 59. When the liquid ejection head 1 is mounted on the liquid ejection device 50, the liquid connector at the tip of the ink supply tube 59 is hermetically connected to a liquid connector insertion port 53a, which is a liquid inlet provided on the head housing 53 of the liquid ejection head 1. This forms an ink supply path from the ink tank 2 through the external pump 21 to the liquid ejection head 1. In this embodiment, since four types of ink are used, four sets of ink tanks 2, external pumps 21, ink supply tubes 59, and circulation units 54 are provided, corresponding to each ink, and four independent ink supply paths corresponding to each ink are formed. Thus, the liquid ejection device 50 of this embodiment is equipped with an ink supply system that supplies ink from an ink tank 2 located outside the liquid ejection head 1. Note that the liquid ejection device 50 of this embodiment is not equipped with an ink recovery system that recovers the ink in the liquid ejection head 1 into the ink tank 2. Therefore, the liquid ejection head 1 is provided with a liquid connector inlet 53a for connecting the ink supply tube 59 of the ink tank 2, but it is not provided with a connector inlet for connecting a tube to collect the ink from the liquid ejection head 1 back into the ink tank 2. Note that a separate liquid connector inlet 53a is provided for each ink cartridge.

[0023] In Figure 3, 54B represents the circulation unit for black ink, 54C represents the circulation unit for cyan ink, 54M represents the circulation unit for magenta ink, and 54Y represents the ink circulation unit for yellow ink. Each circulation unit has substantially the same configuration, and in this embodiment, unless otherwise specified, each circulation unit is referred to as circulation unit 54.

[0024] In Figures 2 and 3(a), the dispensing unit 3 comprises two dispensing modules 300, a first support member 4, a second support member 7, an electrical wiring member (electrical wiring tape) 5, and an electrical contact substrate 6. As shown in Figure 3(b), the dispensing module 300 comprises a silicon substrate 310 with a thickness of 0.5 to 1 mm and a plurality of dispensing elements 15 provided on one side of the silicon substrate 310. Although not shown in Figure 3, the silicon substrate 310 also comprises a plurality of liquid delivery elements 1001 (see Figure 20), which will be described later. In this embodiment, the dispensing elements 15 are composed of electric thermal conversion elements (heaters) that generate thermal energy as dispensing energy for dispensing liquid. Power is supplied to each dispensing element 15 via electrical wiring formed on the silicon substrate 310 by film deposition technology.

[0025] Furthermore, an ejection port forming member 320 is formed on the surface of the silicon substrate 310 (the bottom surface in Figure 3(b)). The ejection port forming member 320 has multiple pressure chambers 12 corresponding to multiple ejection elements 15 and multiple ejection ports 13 for ejecting ink, each formed by photolithography technology. In addition, a common supply channel 18 and a common recovery channel 19 are formed on the silicon substrate 310. The silicon substrate 310 also has a supply connection channel 323 connecting the common supply channel 18 to each pressure chamber 12 and a recovery connection channel 324 connecting the common recovery channel 19 to each pressure chamber 12. In this embodiment, one ejection module 300 is configured to eject two types of ink. That is, of the two ejection modules shown in Figure 3(a), the ejection module 300 located on the left side of the figure ejects black ink and cyan ink, and the ejection module 300 located on the right side of the figure ejects magenta ink and yellow ink. Note that this combination is just one example, and any combination of inks is acceptable. One ejection module may eject one type of ink, or it may eject three or more types of ink. The two ejection modules 300 do not have to eject the same number of types of ink. The system may consist of one ejection module 300, or it may consist of three or more ejection modules 300. Furthermore, in the example shown in Figure 3, two rows of ejection ports extending in the Y direction are formed for one color of ink. A pressure chamber 12, a common supply channel 18, and a common recovery channel 19 are formed for each of the multiple ejection ports 13 constituting each row of ejection ports.

[0026] On the back side (top side in Figure 3(b)) of the silicon substrate 310, an ink supply port and an ink recovery port, which will be described later, are formed. The ink supply port supplies ink from the ink supply channel 48 to a plurality of common supply channels 18, and the ink recovery port recovers ink from a plurality of common recovery channels 19 to the ink recovery channel 49.

[0027] The ink supply port and ink recovery port referred to here refer to the openings that supply and recover ink during forward ink circulation, as described later. That is, during forward ink circulation, ink is supplied from the ink supply port to each common supply channel 18, and ink is recovered from each common recovery channel 19 to the ink recovery port. However, there are also cases where ink circulation is performed in the reverse direction. In this case, ink is supplied from the ink recovery port described above to the common recovery channel 19, and ink is recovered from the common supply channel 18 to the ink supply port.

[0028] As shown in Figure 3(a), the ejection module 300 is bonded and fixed to one side of the first support member 4 (the bottom side in Figure 3(a)) on its back surface (the top surface in Figure 3(a)). The first support member 4 has an ink supply channel 48 and an ink recovery channel 49 that penetrate from one side to the other. One opening of the ink supply channel 48 communicates with the aforementioned ink supply port in the silicon substrate 310, and one opening of the ink recovery channel 49 communicates with the aforementioned ink recovery port in the silicon substrate 310. The ink supply channel 48 and the ink recovery channel 49 are provided independently for each type of ink.

[0029] Furthermore, a second support member 7, which has an opening 7a (see Figure 2) through which the ejection module 300 is inserted, is adhesively fixed to one side of the first support member 4 (the upper surface in Figure 3(a)). 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 component that applies an electrical signal to the ejection module 300 for ejecting ink. The electrical connection between the ejection module 300 and the electrical wiring member 5 is sealed with a sealing material (not shown) to protect it from corrosion by ink and external impacts.

[0030] Furthermore, an electrical contact substrate 6 is thermocompressed to the end 5a (see Figure 2) 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 electrical signals from the liquid dispensing device 50.

[0031] Furthermore, a joint member 8 (Figure 3(a)) is provided between the first support member 4 and the circulation unit 54. The joint member 8 has supply ports 88 and recovery ports 89 formed for each type of ink. The supply ports 88 and recovery ports 89 connect the ink supply channel 48 and ink recovery channel 49 of the first support member 4 with the channels formed in the circulation unit 54. In Figure 3(a), supply ports 88B and recovery ports 89B correspond to black ink, and supply ports 88C and recovery ports 89C correspond to cyan ink. Also, supply ports 88M and recovery ports 89M correspond to magenta ink, and supply ports 88Y and recovery ports 89Y correspond to yellow ink.

[0032] Furthermore, the openings at one end of the ink supply channel 48 and ink recovery channel 49 of the first support member 4 have small opening areas that match the ink supply port and ink recovery port of the silicon substrate 310. In contrast, the openings at the other ends of the ink supply channel 48 and 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 formed to match the flow path of the circulation unit 54. By adopting such a configuration, it is possible to suppress the increase in flow resistance for the ink collected from each recovery channel. However, the shapes of the openings at one end and the other end of the ink supply channel 48 and ink recovery channel 49 are not limited to the above example.

[0033] In the liquid discharge head 1 having the above configuration, the ink supplied to the circulation unit 54 flows through the supply port 88 of the joint member 8 and the ink supply channel 48 of the first support member 4, and then into the common supply channel 18 from the ink supply port of the discharge module 300. Subsequently, the ink flows from the common supply channel 18 into the pressure chamber 12 via the supply connection channel 323, and a portion of the ink that has flowed into the pressure chamber is discharged from the discharge port 13 by the drive of the discharge element 15. The remaining ink that has not been discharged flows from the pressure chamber 12 through the recovery connection channel 324 and the common recovery channel 19, and then 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 back into the circulation unit 54 via the recovery port 89 of the joint member 8 and is recovered.

[0034] <Components of the circulation unit> Figure 4 is a schematic diagram of the external appearance of one circulation unit 54 corresponding to one type of ink applied to the recording device of this embodiment. The circulation unit 54 includes a filter 110, a first pressure regulating means 120, a second pressure regulating means 150, and a circulation pump 500. These components are connected by flow paths as shown in Figures 5 and 6, forming a circulation path within the liquid discharge head 1 for supplying and recovering ink to the discharge module 300.

[0035] <Circulation path within the liquid dispensing head> Figure 5 is a schematic longitudinal cross-sectional view showing the circulation path of one type of ink (one color ink) configured within the liquid discharge head 1. To explain the circulation path more clearly, the relative positions of each component (first pressure adjustment means 120, second pressure adjustment means 150, circulation pump 500, etc.) in Figure 5 are simplified. Therefore, the relative positions of each component differ from those in Figure 19, which will be described later. Figure 6 is a schematic block diagram showing the circulation path shown in Figure 5. As shown in Figures 5 and 6, the first pressure adjustment means 120 includes a first valve chamber 121 and a first pressure control chamber 122. The second pressure adjustment means 150 includes a second valve chamber 151 and a second pressure control chamber 152. The first pressure adjustment means 120 is configured to have a relatively higher control pressure than the second pressure adjustment means 150. In this embodiment, by using these two pressure adjustment means 120 and 150, circulation within a constant pressure range is achieved within the circulation path. Furthermore, the system is configured so that ink flows through the pressure chamber 12 (discharge element 15) at a flow rate corresponding to the pressure difference between the first pressure adjustment means 120 and the second pressure adjustment means 150. The circulation path in the liquid discharge head 1 and the flow of ink within the circulation path will be explained below with reference to Figures 5 and 6. The arrows in each figure indicate the direction of ink flow.

[0036] First, we will explain the connection status of each component in the liquid dispensing head 1.

[0037] An external pump 21, which sends ink contained in an ink tank 2 (Figure 6) located outside the liquid ejection head 1 to the liquid ejection head 1, is connected to a circulation unit 54 via an ink supply tube 59 (Figure 1). A filter 110 is provided in the ink flow path located upstream of the circulation unit 54. The ink supply path located downstream of the filter 110 is connected to the first valve chamber 121 of the first pressure adjustment means 120. The first valve chamber 121 communicates with the first pressure control chamber 122 via a communication port 191A that can be opened and closed by a valve 190A shown in Figure 5.

[0038] The first pressure control chamber 122 is connected to the supply channel 130, the bypass channel 160, and the pump outlet channel 180 of the circulation pump 500. The supply channel 130 is connected to the common supply channel 18 via the aforementioned ink supply port provided in the discharge module 300. The bypass channel 160 is connected to the second valve chamber 151 provided in the second pressure adjustment means 150. The second valve chamber 151 communicates with the second pressure control chamber 152 via a communication port 191B that is opened and closed by the valve 190B shown in Figure 5. Figures 5 and 6 show an example in which one end of the bypass channel 160 is connected to the first pressure control chamber 122 of the first pressure adjustment means 120, and the other end of the bypass channel 160 is connected to the second valve chamber 151 of the second pressure adjustment means 150. However, one end of the bypass channel 160 may be connected to the supply channel 130, and the other end of the bypass channel may be connected to the second valve chamber 151.

[0039] The second pressure control chamber 152 is connected to the recovery channel 140. The recovery channel 140 is connected to the common recovery channel 19 via the aforementioned ink recovery port provided in the discharge module 300. Furthermore, the second pressure control chamber 152 is connected to the circulation pump 500 via the pump inlet channel 170. In Figure 5, 170a indicates the inlet of the pump inlet channel 170.

[0040] Next, the flow of ink in the liquid ejection head 1 having the above configuration will be described. As shown in Figure 6, the ink contained in the ink tank 2 is pressurized by an external pump 21 provided in the liquid ejection device 50 and supplied to the circulation unit 54 of the liquid ejection head 1 as a positive pressure ink flow.

[0041] 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 pressure of the ink decreases due to the pressure loss when passing through the filter 110, but the pressure of the ink at this stage is positive. Subsequently, when the valve 190A is open, 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. Due to the pressure loss when passing through the communication port 191A, the pressure of the ink that has flowed into the first pressure control chamber 122 switches from positive to negative.

[0042] Next, the flow of ink within the circulation path will be explained. The circulation pump 500 operates to send ink drawn in from the pump inlet passage 170, which is on its upstream side, to the pump outlet passage 180, which is on its downstream side. Therefore, when the pump is driven, the ink supplied to the first pressure control chamber 122 flows into the supply passage 130 and the bypass passage 160 together with the ink sent from the pump outlet passage 180. As will be described in detail later, in this embodiment, a piezoelectric diaphragm pump is used as the circulation pump capable of pumping liquid, with a piezoelectric element attached to the diaphragm as the driving source. A piezoelectric diaphragm pump is a pump that pumps liquid by changing the volume inside the pump chamber by inputting a driving voltage to the piezoelectric element, and by the alternating movement of two check valves due to pressure fluctuations.

[0043] The ink flowing into the supply channel 130 flows from the ink supply port of the ejection module 300 through the common supply channel 18 into the pressure chamber 12, and some of the ink is ejected from the ejection port 13 by the drive (heat generation) of the ejection element 15. The remaining ink that is not used for ejection flows through the pressure chamber 12, passes through the common recovery channel 19, and then flows into the recovery channel 140 connected to the ejection module 300. The ink that flows into the recovery channel 140 flows into the second pressure control chamber 152 of the second pressure adjustment means 150.

[0044] Meanwhile, ink flowing from the first pressure control chamber 122 into the bypass channel 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 has flowed into the second pressure control chamber 152 via the bypass channel 160 and the ink recovered from the recovery channel 140 are drawn into the circulation pump 500 via the pump inlet channel 170 by the drive of the circulation pump 500. The ink drawn into the circulation pump 500 is then sent to the pump outlet channel 180 and flows back into the first pressure control chamber 122. Subsequently, the ink that has flowed from the first pressure control chamber 122 to the second pressure control chamber 152 via the supply channel 130 and the discharge module 300, and the ink that has flowed into the second pressure control chamber 152 via the bypass channel 160, both flow into the circulation pump 500. Then, they are sent from the circulation pump 500 back into the first pressure control chamber 122. In this way, ink is circulated within the circulation path.

[0045] As described above, in this embodiment, the circulation pump 500 makes it possible to circulate the liquid along the circulation path formed in the liquid discharge head 1. This makes it possible to suppress the thickening of the ink and the accumulation of sedimentary components of the colorant ink within the discharge module 300, and to maintain good ink fluidity in the discharge module 300 and good discharge characteristics at the discharge port.

[0046] Furthermore, since the circulation path in this embodiment is completed within the liquid ejection head 1, the length of the circulation path can be significantly shortened compared to the case where ink is circulated between the ink tank 2 located outside the liquid ejection head and the liquid ejection head 1. As a result, ink circulation can be performed with a small circulation pump.

[0047] Furthermore, the connection channel between the liquid ejection head 1 and the ink tank 2 is configured to include only a channel for supplying ink. In other words, a channel for recovering ink from the liquid ejection head 1 to the ink tank 2 is not required. Therefore, only an ink supply tube is needed to connect the ink tank 2 and the liquid ejection head 1, and there is no need for an ink recovery tube. Consequently, the internal structure of the liquid ejection device 50 can be simplified by reducing the number of tubes, enabling miniaturization of the entire device. Furthermore, by reducing the number of tubes, it is possible to reduce ink pressure fluctuations caused by the oscillation of the tubes during the main scanning of the liquid ejection head 1. In addition, the oscillation of the tubes during the main scanning of the liquid ejection head 1 becomes a driving load for the carriage motor that drives the carriage 60. Therefore, by reducing the number of tubes, the driving load of the carriage motor is reduced, making it possible to simplify the main scanning mechanism including the carriage motor. Furthermore, since it is not necessary to recover ink from the liquid ejection head to the ink tank, it is also possible to miniaturize the external pump 21. Thus, according to this embodiment, it is possible to miniaturize the liquid dispensing device 50 and reduce its cost.

[0048] <Pressure adjustment means> Figure 7 shows an example of a pressure regulating means. Referring to Figure 7, the configuration and operation of the pressure regulating means (first pressure regulating means 120, second pressure regulating means 150) built into the liquid discharge head 1 described above will be explained in more detail. Note that the first pressure regulating means 120 and the second pressure regulating means 150 have substantially the same configuration. For this reason, the first pressure regulating means 120 will be used as an example in the following explanation, and for the second pressure regulating means 150, only the reference numerals for the parts corresponding to the first pressure regulating means in Figure 7 will be added. In the case of the second pressure regulating 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.

[0049] The first pressure regulating means 120 has a first valve chamber 121 and a first pressure control chamber 122 formed within a cylindrical housing 125. The first valve chamber 121 and the first pressure control chamber 122 are separated by a partition wall 123 provided within 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 the communication 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 at the communication port 191 is blocked. Furthermore, in order to improve the close contact with the partition wall 123, it is preferable that the contact portion of the valve 190 with the partition wall 123 be formed of an elastic material. In addition, a valve shaft 190a is provided protruding from the center of the valve 190, which is inserted into the communication port 191. By pressing this valve shaft 190a against the biasing force of the valve spring 200, the valve 190 is separated from the partition wall 123, and ink flow becomes possible through the communication port 191. Hereinafter, the state in which the flow of ink through the communication port 191 is blocked by the valve 190 will be referred to as the "closed state," and the state in which ink flow is possible through the communication port 191 will be referred to as the "open state."

[0050] The opening of the cylindrical housing 125 is closed by a flexible member 230 and a pressure plate 210. The flexible member 230, the pressure plate 210, the peripheral wall of the housing 125, and the partition wall 123 form the first pressure control chamber 122. 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 made of a resin molded part and the flexible member 230 can be made of a resin film. In this case, the pressure plate 210 can be fixed to the flexible member 230 by heat welding.

[0051] A pressure adjustment spring 220 (biasing member) is provided between the pressure plate 210 and the partition wall 123. Due to the biasing force of the pressure adjustment spring 220, the pressure plate 210 and the flexible member 230 are biased in a direction that expands the internal volume of the first pressure control chamber 122, as shown in Figure 7(a). Furthermore, when the pressure in the first pressure control chamber 122 decreases, the pressure plate 210 and the flexible member 230 are displaced against the pressure of the pressure adjustment spring 220 in a direction that decreases the internal volume of the first pressure control chamber 122. When the internal volume of the first pressure control chamber 122 decreases to a certain amount, the pressure plate 210 comes into contact with the valve shaft 190a of the valve 190. Subsequently, as the internal volume of the first pressure control chamber 122 decreases further, the valve 190 moves together with the valve shaft 190a against the biasing force of the valve spring 200 and moves away from the partition wall 123. As a result, the communication port 191 is in the open state (state shown in Figure 7(b)).

[0052] In this embodiment, the connection settings within the circulation path are configured such that the pressure in the first valve chamber 121 is higher than the pressure in the first pressure control chamber 122 when the communication port 191 is open. As a result, when the communication port 191 is open, ink flows from the first valve chamber 121 into the first pressure control chamber 122. This ink inflow causes the flexible member 230 and the pressure plate 210 to displace in a direction that increases the internal volume of the first pressure control chamber 122. Consequently, the pressure plate 210 separates from the valve shaft 190a of the valve 190, the valve 190 comes into close contact with the partition wall 123 due to the biasing force of the valve spring 200, and the communication port 191 is closed (the state shown in Figure 7(c)).

[0053] Thus, in the first pressure adjustment means 120 of this embodiment, when the pressure in the first pressure control chamber 122 decreases to below a certain pressure (for example, when the negative pressure becomes strong), ink flows in from the first valve chamber 121 through the communication port 191. This prevents the pressure in the first pressure control chamber 122 from decreasing further. Therefore, the first pressure control chamber 122 is controlled to maintain a pressure within a certain range.

[0054] Next, we will explain the pressure in the first pressure control chamber 122 in more detail.

[0055] As described above, consider the 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, and the pressure plate 210 comes into contact with the valve shaft 190a, causing the communication port 191 to open (the state shown in Figure 7(b)). At this time, the relationship of the forces acting on the pressure plate 210 is expressed by the following equation 1.

[0056] P2×S2+F2+(P1-P2)×S1+F1=0...Equation 1 Furthermore, rearranging equation 1 for P2, P2=-(F1+F2+P1×S1) / (S2-S1)...Equation 2 This is the result.

[0057] P1: Pressure (gauge pressure) in the first valve chamber 121 P2: Pressure (gauge pressure) in the first pressure control chamber 122 F1: Spring force of valve spring 200 F2: Spring force of pressure regulating spring 220 S1: Pressure-receiving area of ​​valve 190 S2: Pressure receiving area of ​​pressure plate 210 Here, the spring force F1 of the valve spring 200 and the spring force F2 of the pressure regulating spring 220 are considered positive (rightward in Figure 7) when pushing the valve 190 and the pressure plate 210. Furthermore, with respect to the pressure P1 in the first valve chamber 121 and the pressure P2 in the first pressure control chamber 122, the relationship P1 ≥ P2 is satisfied.

[0058] The pressure P2 in the first pressure control chamber 122 when the communication port 191 is open is determined by equation 2. When the communication port 191 is open, ink flows from the first valve chamber 121 into the first pressure control chamber 122 because the relationship P1 ≥ P2 is configured. As a result, the pressure P2 in the first pressure control chamber 122 does not decrease further, and P2 is maintained within a certain pressure range.

[0059] On the other hand, as shown in Figure 7(c), when the pressure plate 210 is not in contact with the valve shaft 190a and the communication port 191 is closed, the relationship of the forces acting on the pressure plate 210 is given by Equation 3.

[0060] P3×S3+F3=0...Equation 3 Now, if we rearrange equation 3 for P3, P3 = -F3 / S3 ... Equation 4 This is the result.

[0061] F3: Spring force of the pressure regulating spring 220 when the pressure plate 210 and the valve shaft 190a are not in contact. P3: Pressure (gauge pressure) in the first pressure control chamber 122 when the pressure plate 210 and the valve shaft 190a are not in contact. S3: Pressure receiving area of ​​pressure plate 210 when pressure plate 210 and valve 190 are not in contact. In Figure 7(c), the pressure plate 210 and the flexible member 230 are shown displaced to the right as far as they can go. 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 as the pressure plate 210 and the flexible member 230 move to the state shown in Figure 7(c). Specifically, when the pressure plate 210 and the flexible member 230 are to the left in Figure 7 compared to Figure 7(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, according to the relationship in Equation 4, the pressure P3 in the first pressure control chamber 122 decreases. Therefore, according to Equations 2 and 4, the pressure in the first pressure control chamber 122 gradually increases from the state shown in Figure 7(b) to the state shown in Figure 7(c) (that is, the negative pressure weakens and approaches the positive pressure). In other words, starting from the state where the communication port 191 is open, the pressure plate 210 and the flexible member 230 are gradually displaced to the right, and the pressure in the first pressure control chamber gradually increases until the internal volume of the first pressure control chamber 122 reaches the limit of its displacement. In other words, the negative pressure weakens.

[0062] <Circulation pump> Next, with reference to Figures 8 and 9, the configuration and operation of the circulation pump 500 built into the liquid discharge head 1 described above will be explained in detail.

[0063] Figure 8 is an external perspective view of the circulation pump 500. Figure 8(a) is an external perspective view showing the front side of the circulation pump 500, and Figure 8(b) is an external perspective view showing the rear side of the circulation pump 500. The outer shell of the circulation pump 500 consists of a pump housing 505 and a cover 507 fixed to the pump housing 505. The pump housing 505 consists of a housing body 505a and a flow path connecting member 505b that is adhesively fixed to the outer surface of the housing body 505a. Each of the housing body 505a and the flow path connecting member 505b is provided with a pair of through holes communicating with each other at two different positions. The pair of through holes provided at one position form a pump supply hole 501, and the pair of through holes provided at the other position form a pump discharge hole 502. The pump supply hole 501 is connected to a pump inlet flow path 170 connected to a second pressure control chamber 152, and the pump discharge hole 502 is connected to a pump outlet flow path 180 connected to a first pressure control chamber 122. The ink supplied from the pump supply port 501 passes through the pump chamber 503 (see Figure 9), which will be described later, and is discharged from the pump discharge port 502.

[0064] Figure 9 is a cross-sectional view of the circulation pump 500 shown in Figure 8(a) along the line IX-IX. A diaphragm 506 is joined to the inner surface of the pump housing 505, and a pump chamber 503 is formed between the diaphragm 506 and a recess formed on the inner surface of the pump housing 505. The pump chamber 503 communicates with 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 portion of the pump supply hole 501, and a check valve 504b is provided in the middle portion of the pump discharge hole 502. Specifically, the check valve 504a is positioned so that a part of it can move to the left in the figure within the space 512a formed in the middle portion of the pump supply hole 501. The check valve 504b is positioned so that a part of it can move to the right in the figure within the space 512b formed in the middle portion of the pump discharge hole 502.

[0065] When the diaphragm 506 is displaced and the volume of the pump chamber 503 increases, causing the pump chamber 503 to be depressurized, the check valve 504a moves away from the opening of the pump supply hole 501 in space 512a (i.e., moves to the left in the figure). When the check valve 504a moves away from the opening of the pump supply hole 501 in space 512a, it becomes an open state that allows ink to flow through the pump supply hole 501. Conversely, when the diaphragm 506 is displaced and the volume of the pump chamber 503 decreases, causing the pump chamber 503 to be pressurized, the check valve 504a comes into close contact with the wall surface surrounding the opening of the pump supply hole 501. As a result, it becomes a closed state that blocks the flow of ink through the pump supply hole 501.

[0066] On the other hand, when the pump chamber 503 is depressurized, the check valve 504b closes to the wall surrounding the opening of the pump housing 505, blocking 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 towards the space 512b (i.e., to the right in the figure), allowing the flow of ink through the pump discharge hole 502.

[0067] Furthermore, the material of each check valve 504a and 504b may be any material that can deform in accordance with the pressure in the pump chamber 503, and can be formed from elastic materials such as EPDM or elastomer, or from films or thin sheets of polypropylene, etc. However, it is not limited to these.

[0068] As mentioned above, the pump chamber 503 is formed by the joint between the pump housing 505 and the diaphragm 506. Therefore, the pressure in the pump chamber 503 changes as the diaphragm 506 deforms. For example, when the diaphragm 506 is displaced toward the pump housing 505 (displaced to the right in the figure) and the volume of the pump chamber 503 decreases, the pressure inside the pump chamber 503 increases. This causes the check valve 504b, which is positioned opposite the pump discharge hole 502, to open, and the ink in the pump chamber 503 is discharged. At this time, the check valve 504a, which is positioned opposite the pump supply hole 501, is in close contact with the wall surface surrounding the pump supply hole 501, so backflow of ink from the pump chamber 503 to the pump supply hole 501 is suppressed.

[0069] Conversely, if the diaphragm 506 is displaced in a direction that expands the pump chamber 503, the pressure in the pump chamber 503 decreases. As a result, the check valve 504a, which is positioned opposite the pump supply hole 501, opens, and ink is supplied to the pump chamber 503. At this time, the check valve 504b, which is positioned at the pump discharge hole 502, comes into close contact with the surrounding wall surface of the opening formed in the pump housing 505, closing the opening. Therefore, backflow of ink from the pump discharge hole 502 to the pump chamber 503 is suppressed.

[0070] In this way, the circulating pump 500 performs ink suction and discharge by deforming the diaphragm 506 and changing the pressure inside the pump chamber 503. However, if bubbles are mixed into the pump chamber 503, even if the diaphragm 506 is displaced, the expansion and contraction of the bubbles will reduce the pressure change inside the pump chamber 503, and the amount of liquid delivered will decrease. Therefore, the pump chamber 503 is positioned parallel to gravity to make it easier for bubbles mixed into the pump chamber 503 to collect at the top of the pump chamber 503, and the pump discharge hole 502 is positioned above the center of the pump chamber 503. This makes it possible to improve the discharge of bubbles inside the pump and stabilize the flow rate.

[0071] <Ink flow within the liquid ejection head> Figure 10 is a diagram illustrating the flow of ink within the liquid ejection head. The circulation of ink within the liquid ejection head 1 will be explained with reference to Figure 10. In order to more clearly explain the ink circulation path, the relative positions of each component (first pressure adjustment means 120, second pressure adjustment means 150, circulation pump 500, etc.) in Figure 10 have been simplified. Therefore, the relative positions of each component differ from those in Figure 19, which will be described later. Figure 10(a) schematically shows the flow of ink when a recording operation is performed, in which ink is ejected from the ejection port 13 to record. The arrows in the figure indicate the flow of ink. In this embodiment, both the external pump 21 and the circulation pump 500 start to drive when a recording operation is performed. Note that the external pump 21 and the circulation pump 500 may be driven regardless of the recording operation. Also, the external pump 21 and the circulation pump 500 do not have to be driven in conjunction, but may be driven separately and independently.

[0072] During recording, the circulation pump 500 is ON (operating), and the ink flowing out from the first pressure control chamber 122 flows into the supply channel 130 and the bypass channel 160. The ink that flows into the supply channel 130 passes through the discharge module 300, then flows into the recovery channel 140, and is subsequently supplied to the second pressure control chamber 152.

[0073] Meanwhile, the ink that flows from the first pressure control chamber 122 into the bypass channel 160 flows into the second pressure control chamber 152 via the second valve chamber 151. The ink that flows into the second pressure control chamber 152 passes through the pump inlet channel 170, the circulation pump 500, and the pump outlet channel 180, and then flows back into the first pressure control chamber 122. At this time, the control pressure by the first valve chamber 121 is set higher than the control pressure of the first pressure control chamber 122, based on the relationship in Equation 2 described above. Therefore, the ink in the first pressure control chamber 122 does not flow into the first valve chamber 121 but is supplied again to the discharge module 300 via the supply channel 130. The ink that flows into the discharge module 300 flows back into the first pressure control chamber 122 via the recovery channel 140, the second pressure control chamber 152, the pump inlet channel 170, the circulation pump 500, and the pump outlet channel 180. Thus, ink circulation that is completed within the liquid discharge head 1 is performed.

[0074] In the ink circulation described above, the amount of ink circulated (flow rate) within the ejection module 300 is determined by the differential pressure of the control pressures between the first pressure control chamber 122 and the second pressure control chamber 152. This differential pressure is set to a circulation amount that suppresses the thickening of the ink near the ejection port within the ejection module 300. In addition, the amount of ink consumed by recording 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 consumed ink is supplied will be explained in detail. As the amount of ink consumed by recording decreases in the circulation path, the pressure in the first pressure control chamber decreases, and as a result, the amount of ink in the first pressure control chamber 122 also decreases. As the amount of ink in the first pressure control chamber 122 decreases, the internal volume of the first pressure control chamber 122 decreases. Due to this decrease in the internal volume of the first pressure control chamber 122, the communication port 191A opens, and ink is supplied from the first valve chamber 121 to the first pressure control chamber 122. As the supplied ink passes from the first valve chamber 121 to the communication port 191A, a pressure loss occurs, and upon flowing into the first pressure control chamber 122, the positive pressure ink switches to a negative pressure state. As ink flows from the first valve chamber 121 into the 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 the communication port 191A closes. In this way, the communication port 191A repeatedly switches between open and closed states depending on the ink consumption. If no ink is consumed, the communication port 191A remains closed.

[0075] Figure 10(b) schematically shows the ink flow immediately after the recording operation is completed and the circulation pump 500 is turned OFF (stopped). At the time 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 pressure during the recording operation. Therefore, ink movement occurs as shown in Figure 10(b) in accordance with 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 discharge module 300 via the supply channel 130, and then through the recovery channel 140 to the second pressure control chamber 152. In addition, ink continues to flow from the first pressure control chamber 122 to the second pressure control chamber 152 via the bypass channel 160 and the second valve chamber 151.

[0076] The amount of ink that moves from the first pressure control chamber 122 to the second pressure control chamber 152 due to the flow of ink is supplied from the ink tank 2 to the first pressure control chamber 122 via the filter 110 and the first valve chamber 121. Therefore, the volume inside the first pressure control chamber 122 is kept constant. From the relationship in Equation 2 described above, when the volume inside 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 kept constant. Therefore, the pressure in the first pressure control chamber 122 is determined according to the change in the pressure (gauge pressure) P1 in the first valve chamber 121. Thus, if 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 kept at the same pressure as the control pressure during recording.

[0077] On the other hand, the pressure in the second pressure control chamber 152 changes over time in accordance with the change in volume due to the inflow of ink from the first pressure control chamber 122. Specifically, from the state shown in Figure 10(b) until the communication port 191 closes and the second valve chamber 151 and the second pressure control chamber 152 become disconnected, as shown in Figure 10(c), the pressure in the second pressure control chamber 152 changes according to Equation 2. After that, the pressure plate 210 and the valve shaft 190a become non-contacting, and the communication port 191 closes. Then, as shown in Figure 10(d), ink flows from the recovery channel 140 into the second pressure control chamber 152. This inflow of ink 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 internal volume of the second pressure control chamber 152 reaches its maximum. That is, it rises.

[0078] Furthermore, in the state shown in Figure 10(c), no ink flow occurs from the first pressure control chamber 122 through the bypass channel 160 and the second valve chamber 151 to the second pressure control chamber 152. Therefore, only the flow of ink from the first pressure control chamber 122 to the second pressure control chamber 152 occurs, after it is supplied to the discharge module 300 via the supply channel 130 and then through the recovery channel 140. As mentioned above, the movement of ink from the first pressure control chamber 122 to the second pressure control chamber 152 occurs in accordance with the pressure difference between the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152. For this reason, 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.

[0079] 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 Figure 10(d). When the second pressure control chamber 152 expands as shown in Figure 10(d), a storage section capable of storing ink is formed in the second pressure control chamber 152. The time from stopping the circulation pump 500 to transitioning to the state shown in Figure 10(d) may vary depending on the shape and size of the flow path and the properties of the ink, but it generally takes about 1 to 2 minutes. When the circulation pump 500 is driven from the state shown in Figure 10(d) with ink 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, as shown in Figure 10(e), the amount of ink in the first pressure control chamber 122 increases, and the flexible member 230 and the pressure plate 210 are displaced in the expansion direction. Then, as the circulation pump 500 continues to operate, the conditions within the circulation path will change, as shown in Figure 10(a).

[0080] In the above explanation, Figure 10(a) was used as an example during recording, but as mentioned above, ink circulation may occur without recording. Even in this case, the ink flow shown in Figures 10(a) to (e) will occur in response to the driving and stopping of the circulation pump 500.

[0081] As mentioned above, in this embodiment, the communication port 191B in the second pressure adjustment means 150 is shown as being open when the circulation pump 500 is driven and ink is circulated, and closed when ink circulation stops, but it is not limited to this. The control pressure may be set so that the communication port 191B in the second pressure adjustment means 150 is closed even when the circulation pump 500 is driven and ink is circulated. The role of the bypass passage 160 will be explained in detail below.

[0082] The bypass channel 160 connecting the first pressure adjustment means 120 and the second pressure adjustment means 150 is provided to prevent the discharge module 300 from being affected, for example, when the negative pressure generated in the circulation path becomes stronger than a predetermined value. The bypass channel 160 is also provided to supply ink to the pressure chamber 12 from both sides of the supply channel 130 and the recovery channel 140.

[0083] First, we will explain an example in which a bypass channel 160 is provided to prevent the negative pressure from affecting the discharge module 300 when the negative pressure exceeds a predetermined value. For example, the properties of the ink (e.g., viscosity) may change due to changes in ambient temperature. When the viscosity of the ink changes, the pressure loss in the circulation path also changes. For example, if the viscosity of the ink 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 amount, increases, and the flow rate through the discharge module 300 increases. On the other hand, since the discharge module 300 is kept at a constant temperature by a temperature control mechanism (not shown), the viscosity of the ink in the discharge module 300 is kept constant even if the ambient temperature changes. As the flow rate of the ink flowing through the discharge module 300 increases while the viscosity of the ink in the discharge module 300 does not change, the negative pressure in the discharge module 300 increases due to flow resistance. In this way, if the negative pressure in the discharge module 300 exceeds a predetermined value, the meniscus of the discharge port 13 may be destroyed, drawing in outside air into the circulation path and potentially preventing normal discharge. Even if the meniscus is not destroyed, the negative pressure in the pressure chamber 12 may exceed a predetermined value, potentially affecting the discharge.

[0084] Therefore, in this embodiment, a bypass channel 160 is formed within the circulation path. By providing the bypass channel 160, ink flows through the bypass channel 160 when the negative pressure exceeds a predetermined value, thus maintaining a constant pressure in the discharge module 300. Accordingly, for example, the communication port 191B in the second pressure adjustment means 150 may be configured with a control pressure that maintains a closed state even when the circulation pump 500 is running. Furthermore, the control pressure in the second pressure adjustment means may be set so that the communication port 191 in the second pressure adjustment means 150 opens when the negative pressure exceeds a predetermined value. In other words, as long as the meniscus does not collapse due to changes in the flow rate of the pump caused by viscosity changes such as environmental changes, or as long as a predetermined negative pressure is maintained, the communication port 191B may be in a closed state when the circulation pump 500 is running.

[0085] Next, we will describe an example in which a bypass channel 160 is provided to supply ink to the pressure chamber 12 from both sides of the supply channel 130 and the recovery channel 140. Pressure fluctuations in the circulation path can also be caused by the ejection operation of the ejection element 15, because the ejection operation generates a force that draws ink into the pressure chamber.

[0086] The following explains that when recording at a high duty cycle, the ink supplied to the pressure chamber 12 is supplied from both the supply channel 130 and the recovery channel 140. Note that the definition of duty cycle can vary depending on various conditions, but here, we will treat the state where a single 4pl ink droplet is recorded on a 1200dpi grid as 100%. Recording at a high duty cycle means, for example, recording at a 100% duty cycle.

[0087] If a high duty cycle is maintained, the amount of ink flowing from the pressure chamber 12 into the second pressure control chamber 152 through the recovery channel 140 decreases. On the other hand, the circulation pump 500 discharges ink at a constant rate, disrupting the balance between inflow and outflow within the second pressure control chamber 152. This reduces the amount of ink in the second pressure control chamber 152, increasing the negative pressure within it and causing it to shrink. As the negative pressure within the second pressure control chamber 152 increases, the amount of ink flowing into the second pressure control chamber 152 via the bypass channel 160 increases, and the second pressure control chamber 152 stabilizes with a balance between inflow and outflow. Thus, as a result, the negative pressure within the second pressure control chamber 152 increases in accordance with the duty cycle. Furthermore, as described above, in a configuration where the communication port 191B is closed when the circulation pump 500 is running, the communication port 191B will open according to the duty cycle, and ink will flow from the bypass flow path 160 into the second pressure control chamber 152.

[0088] As the duty cycle continues to be higher, the amount of ink flowing from the pressure chamber 12 to the second pressure control chamber 152 through the recovery channel 140 decreases, while the amount of ink flowing into the second pressure control chamber 152 through the bypass channel 160 and the communication port 191B increases. If this condition progresses further, the amount of ink flowing from the pressure chamber 12 to the second pressure control chamber 152 through the recovery channel 140 becomes zero, and all the ink flowing out to the circulation pump 500 becomes ink flowing in from the communication port 191B. If this condition progresses further, ink now flows back from the second pressure control chamber 152 to the pressure chamber 12 through the recovery channel 140. In this state, the ink flowing out of 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 through the bypass channel 160 and the communication port 191B. In this case, the pressure chamber 12 will be filled with ink from the supply channel 130 and ink from the recovery channel 140, and then discharged.

[0089] Furthermore, the ink backflow that occurs when the recording duty cycle is high is a phenomenon caused by the provision of the bypass channel 160. In addition, although the above describes an example in which the communication port 191B in the second pressure adjustment means opens in response to ink backflow, ink backflow can also occur when the communication port 191B in the second pressure adjustment means is open. Moreover, even in a configuration without the second pressure adjustment means, the above-mentioned ink backflow can occur due to the provision of the bypass channel 160.

[0090] <Discharge Unit Configuration> Figure 11 is a schematic diagram showing the circulation path for one ink color in the ejection unit 3 of this embodiment. Figure 11(a) is an exploded perspective view of the ejection unit 3 as seen from the first support member 4 side, and Figure 11(b) is an exploded perspective view of the ejection unit 3 as seen from the ejection module 300 side. The arrows labeled IN and OUT in the figures indicate the flow of ink. Only the flow of one color is explained here, but the flow for other colors is similar. In addition, the second support member 7 and the electrical wiring member 5 are omitted from Figure 11, and are also omitted in the following explanation of the ejection unit configuration. Furthermore, the first support member 4 in Figure 11(a) is shown in the cross-section at XI-XI in Figure 3. The ejection module 300 comprises an ejection element substrate 340 and an opening plate 330. Figure 12 shows the opening plate 330, and Figure 13 shows the ejection element substrate 340.

[0091] Ink is supplied to the discharge unit 3 from the circulation unit 54 via the joint member 8 (see Figure 3). The ink path from when the ink passes through the joint member 8 until it returns to the joint member 8 will be described below. Note that the joint member 8 is not shown in the following drawings.

[0092] The ejection module 300 comprises an ejection element substrate 340, which is a silicon substrate 310, an opening plate 330, and an ejection port forming member 320. The ejection element substrate 340, the opening plate 330, and the ejection port forming member 320 are joined together by overlapping so that the flow paths of each ink are in communication, forming the ejection module 300, which is supported by the first support member 4. The ejection module 300 is supported by the first support member 4, forming the ejection unit 3. The ejection element substrate 340 comprises an ejection port forming member 320, which comprises multiple rows of ejection ports 13 arranged in a row, and ejects a portion of the ink supplied through the ink flow paths in the ejection module 300 from the ejection ports 13. The ink that is not ejected is recovered through the ink flow paths in the ejection module 300.

[0093] As shown in Figures 11 and 12, the opening plate 330 is provided with a plurality of arranged ink supply ports 311 and a plurality of arranged ink recovery ports 312. As shown in Figures 13 and 14, the ejection element substrate 340 is provided with a plurality of arranged supply connection channels 323 and a plurality of arranged recovery connection channels 324. Furthermore, the ejection element substrate 340 is provided with 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 channels within the ejection unit 3 are formed by connecting the ink supply channels 48 and ink recovery channels 49 (see Figure 3) provided in the first support member 4 with the 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.

[0094] The ink supplied to the discharge unit 3 is supplied from the circulation unit 54 (see Figure 3(a)) to the ink supply channel 48 (see Figure 3(a)) of the first support member 4. The ink that flows through the support member supply port 211 in the ink supply channel 48 is supplied to the common supply channel 18 of the discharge element substrate 340 via the ink supply channel 48 (see Figure 3(a)) and the ink supply port 311 of the opening plate 330, and enters the supply connection channel 323. This is the end of the supply side channel. After that, the ink flows through the pressure chamber 12 (see Figure 3(b)) of the discharge port forming member 320 to the recovery connection channel 324 of the recovery side channel. Details of the ink flow in the pressure chamber 12 will be described later.

[0095] In the recovery channel, ink that enters the recovery connection channel 324 flows into the common recovery channel 19. Subsequently, the ink flows from the common recovery channel 19 through the ink recovery port 312 of the opening plate 330 to the ink recovery channel 49 of the first support member 4, and is recovered in the circulation unit 54 via the support member recovery port 212.

[0096] The area of ​​the opening plate 330 that does not have an ink supply port 311 or an ink recovery port 312 corresponds to the area of ​​the first support member 4 that partitions the support member supply port 211 and the support member recovery port 212. Furthermore, the first support member 4 also does not have an opening in this area. Such an area is used as the bonding area when bonding the discharge module 300 and the first support member 4.

[0097] In Figure 12, the opening plate 330 has multiple rows of openings arranged in the X direction, and multiple rows of openings arranged in the Y direction, with supply (IN) openings and recovery (OUT) openings arranged alternately in the Y direction with a half-pitch offset in the X direction. In Figure 13, the ejection element substrate 340 has a common supply channel 18 that communicates with multiple supply connection channels 323 arranged in the Y direction, and a common recovery channel 19 that communicates with multiple recovery connection channels 324 arranged in the Y direction, arranged alternately in the X direction. The common supply channels 18 and 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. In addition, the supply connection channels 323 and recovery connection channels 324 are arranged in a number corresponding to the number of ejection ports 13. Note that there does not necessarily have to be a one-to-one correspondence, and one supply connection channel 323 and one recovery connection channel 324 may correspond to multiple ejection ports 13.

[0098] When the opening plate 330 and the ejection element substrate 340 are joined together so that the flow paths of each ink are in communication, they form an ejection module 300, which is then supported by the first support member 4, thereby forming an ink flow path with the supply flow path and recovery flow path described above.

[0099] Figures 14(a) to (c) are cross-sectional views showing the ink flow in different parts of the ejection unit 3. Figure 14(a) is the cross-section shown from XIVa to XIVa in Figure 11(a), showing the cross-section of the part of the ejection unit 3 where the ink supply channel 48 and the ink supply port 311 are in communication. Figure 14(b) is the cross-section shown from XIVb to XIVb in Figure 11(a), showing the cross-section of the part of the ejection unit 3 where the ink recovery channel 49 and the ink recovery port 312 are in communication. Figure 14(c) is the cross-section shown from XIVc to XIVc in Figure 11(a), showing the cross-section of the part where the ink supply port 311 and the ink recovery port 312 are not in communication with the channel of the first support member 4. Note that the liquid delivery element 1001 is omitted in Figures 14(a) to (c).

[0100] In the ink supply channel, as shown in Figure 14(a), ink is supplied from the portion where the ink supply channel 48 of the first support member 4 and the ink supply port 311 of the opening plate 330 overlap and communicate. In the ink recovery channel, as shown in Figure 14(b), ink is recovered from the portion where the ink recovery channel 49 of the first support member 4 and the ink recovery port 312 of the opening plate 330 overlap and communicate. Also, as shown in Figure 14(c), in the ejection unit 3, there are areas where the opening plate 330 does not have an opening. In such areas, ink is not supplied or recovered between the ejection element substrate 340 and the first support member 4. Ink is supplied in the area where the ink supply port 311 is provided, as shown in Figure 14(a), and ink is recovered in the area where the ink recovery port 312 is provided, as shown in Figure 14(b). In this embodiment, a configuration using the opening plate 330 has been described as an example, but a configuration without the opening plate 330 may also be used. For example, the first support member 4 may have channels corresponding to the ink supply channel 48 and the ink recovery channel 49, and the ejection element substrate 340 may be bonded to the first support member 4.

[0101] Figures 15(a) and (b) are cross-sectional views showing the vicinity of the discharge port 13 in the discharge module 300, and Figure 16 is a cross-sectional view showing a discharge module with a configuration in which the common supply channel 18 and common recovery channel 19 are extended in the X direction as a comparative example. The thick arrows shown in the common supply channel 18 and common recovery channel 19 in Figures 15 and 16 indicate the oscillation of ink in a configuration using a serial type liquid discharge device 50. Ink supplied to the pressure chamber 12 via the common supply channel 18 and the supply connection channel 323 is discharged from the discharge port 13 when the discharge element 15 is driven. If the discharge element 15 is not driven, the ink is recovered from the pressure chamber 12 through the recovery connection channel 324, which is a recovery channel, to the common recovery channel 19.

[0102] In a configuration using a serial-type liquid ejection device 50, when ejection is performed from circulating ink in this manner, the ejection of ink is inevitably affected to some extent by the oscillation of the ink in the ink flow path due to the main scanning of the liquid ejection head 1. Specifically, the effect of the oscillation of the ink in the ink flow path may manifest as differences in the amount of ink ejected or deviations in the ejection direction. As shown in Figure 16, if the common supply flow path 18 and the common recovery flow path 19 have a wide cross-sectional shape 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 becomes more susceptible to inertial force in the main scanning direction, causing large oscillations in the ink. As a result, there is a risk that the oscillation of the ink may affect the ejection of ink from the ejection port 13. Furthermore, if the common supply flow path 18 and the common recovery flow path 19 are widened in the X direction, the distance between colors will increase, which may reduce printing efficiency.

[0103] Therefore, in this embodiment, the common supply channel 18 and the common recovery channel 19 both extend in the Y direction in the cross-section shown in Figure 15, but are also configured to extend in the Z direction, which is perpendicular to the X direction, which is the main scanning direction. This configuration makes it possible to reduce the width of each channel in the common supply channel 18 and the common recovery channel 19 in the main scanning direction. By reducing the width of each channel in the common supply channel 18 and the common recovery channel 19 in the main scanning direction, the oscillation of the ink due to the inertial force (thick black arrow in the figure) acting on the ink in the common supply channel 18 and the common recovery channel 19 acting on the opposite side of the main scanning direction during main scanning is reduced. This makes it possible to suppress the effect of ink oscillation on ink discharge. In addition, by extending the common supply channel 18 and the common recovery channel 19 in the Z direction, the cross-sectional area is increased, and flow pressure loss is reduced.

[0104] As described above, the common supply channel 18 and the common recovery channel 19 are configured to reduce the oscillation of ink in the common supply channel 18 and the common recovery channel 19 during main scanning by reducing the width of each channel in the main scanning direction, but the oscillation is not eliminated. Therefore, in order to suppress differences in the ejection of each ink type that may still occur even with reduced oscillation, in this embodiment the common supply channel 18 and the common recovery channel 19 are configured to be positioned in a position that overlaps with respect to the X direction.

[0105] As described above, in this embodiment, the supply connection channel 323 and the recovery connection channel 324 are provided corresponding to the discharge port 13, and the supply connection channel 323 and the recovery connection channel 324 are arranged side by side in the X direction with the discharge port 13 in between. Therefore, there is a portion where the common supply channel 18 and the common recovery channel 19 do not overlap in the X direction, and if the correspondence between the supply connection channel 323 and the recovery connection channel 324 in the X direction is disrupted, it will affect the flow and discharge of ink in the X direction in the pressure chamber 12. If the effect of ink oscillation is added to this, it may further affect the discharge of ink at each discharge port.

[0106] Therefore, by arranging the common supply channel 18 and the common recovery channel 19 in positions that overlap with respect to the X direction, the ink oscillation during main scanning in the common supply channel 18 and the common recovery channel 19 becomes almost the same at any position in the Y direction where the discharge ports 13 are arranged. As a result, the pressure difference between the common supply channel 18 side and the common recovery channel 19 side that occurs in the pressure chamber 12 does not fluctuate significantly, and stable discharge can be achieved.

[0107] Furthermore, in some liquid ejection heads that circulate ink, the flow path for supplying ink to the liquid ejection head and the flow path for recovering ink are configured as the same flow path. However, 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 in communication, and the pressure chamber 12 and the recovery connection flow path 324 are in communication, and ink is ejected from the discharge port 13 of the pressure chamber 12. In other words, the pressure chamber 12, which is the path connecting the supply connection flow path 323 and the recovery connection flow path 324, is configured to have a discharge port 13. Therefore, an ink flow occurs in the pressure chamber 12 from the supply connection flow path 323 side to the recovery connection flow path 324 side, 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 susceptible to the effects of ink evaporation from the discharge port 13, can be kept in a fresh state.

[0108] Furthermore, since both the common supply channel 18 and the common recovery channel 19 are connected to the pressure chamber 12, if it becomes necessary to discharge at a high flow rate, it is possible to supply ink from both channels. In other words, compared to a configuration in which ink supply and recovery are handled by only one channel, the configuration in this embodiment has the advantage of not only enabling efficient circulation but also being able to handle high flow rate discharge.

[0109] Furthermore, the common supply channel 18 and the common recovery channel 19 should be located closer together in the X direction to minimize the effects of ink sloshing. Preferably, the distance between the channels should be 75 μm to 100 μm.

[0110] Figure 17 shows a comparative example of an ink ejection element substrate 340. Note that the supply connection channel 323 and the recovery connection channel 324 are omitted in Figure 17. Ink that has received thermal energy from the ejection element 15 in the pressure chamber 12 flows into the common recovery channel 19, so ink that is relatively hotter than the ink in the common supply channel 18 flows through it. In this case, as shown in part α enclosed by the dashed line in Figure 17, there is a part of the ejection element substrate 340 in the X direction where only the common recovery channel 19 exists. In this case, the temperature rises locally in that part, causing temperature unevenness within the ejection module 300, which may affect the ejection process.

[0111] Ink at a relatively lower temperature flows through the common supply channel 18 compared to the common recovery channel 19. Therefore, if the common supply channel 18 and the common recovery channel 19 are adjacent to each other, some of the temperatures in the vicinity cancel each other out, thus suppressing the temperature rise. For this reason, it is preferable that the common supply channel 18 and the common recovery channel 19 are adjacent to each other, overlapping in the X direction with approximately the same length.

[0112] Figures 18(a) and (b) show the flow path configuration of the liquid ejection head 1 corresponding to three ink colors: cyan (C), magenta (M), and yellow (Y). As shown in Figure 18(a), the liquid ejection head 1 is provided with circulation channels for each type of ink. The pressure chamber 12 is located along the X direction, which is the main scanning direction of the liquid ejection head 1. Also, as shown in Figure 18(b), the common supply channel 18 and the common recovery channel 19 are located along the row of ejection ports 13, and extend in the Y direction so as to sandwich the row of ejection ports between the common supply channel 18 and the common recovery channel 19.

[0113] <Connection between the main unit and the liquid dispensing head> Figure 19 is a schematic diagram showing in more detail the connection state between the ink tank 2 and external pump 21 and the liquid ejection head 1, as well as the arrangement of the circulation pump and other components, provided in the main body of the liquid ejection device 50 of this embodiment. The liquid ejection device 50 in this embodiment is configured to allow for easy replacement of only the liquid ejection head 1 in the event of a malfunction in the liquid ejection head 1. Specifically, it has a liquid connection part 700 that allows for easy connection and disconnection of the ink supply tube 59 connected to the external pump 21 and the liquid ejection head 1. This makes it possible to easily attach and detach only the liquid ejection head 1 from the liquid ejection device 50.

[0114] As shown in Figure 19, the liquid connection section 700 has a liquid connector insertion port 53a protruding from the head housing 53 of the liquid discharge head 1, and a cylindrical liquid connector 59a into which the liquid connector insertion port 53a can be inserted. The liquid connector insertion port 53a is fluidly connected to an ink supply channel formed inside the liquid discharge head 1 and is connected to the first pressure adjustment means 120 via the aforementioned filter 110. The liquid connector 59a is provided at the tip of an ink supply tube 59 connected to an external pump 21 that pressurizes and supplies ink from the ink tank 2 to the liquid discharge head 1.

[0115] As described above, the liquid discharge head 1 shown in Figure 19 can be easily attached, detached, and replaced by the liquid connection part 700. However, if the sealing performance between the liquid connector insertion port 53a and the liquid connector 59a deteriorates, there is a risk that the ink supplied under pressure by the external pump 21 may leak from the liquid connection part 700. If the leaked ink adheres to the circulation pump 500, etc., it may cause a malfunction in the electrical system. Therefore, in this embodiment, the circulation pump, etc. are arranged as follows.

[0116] <Placement of circulation pumps, etc.> As shown in Figure 19, in this embodiment, in order to prevent ink leaking from the liquid connection part 700 from adhering to the circulation pump 500, the circulation pump 500 is positioned above the liquid connection part 700 in the direction of gravity. In other words, the circulation pump 500 is positioned above the liquid connector insertion port 53a, which is the liquid inlet of the liquid discharge head 1, in the direction of gravity. Furthermore, the circulation pump 500 is positioned in a location that does not come into contact with the components constituting the liquid connection part 700. As a result, even if ink leaks from the liquid connection part 700, the ink will flow horizontally, which is the opening direction of the liquid connector 59a, or downward in the direction of gravity, thus preventing the ink from reaching the circulation pump 500, which is located above in the direction of gravity. In addition, because the circulation pump 500 is positioned away from the liquid connection part 700, the possibility of ink traveling along the components and reaching the circulation pump 500 is also reduced.

[0117] Furthermore, an electrical connection section 515, which electrically connects the circulation pump 500 and the electrical contact substrate 6 via a flexible wiring member 514, is provided above the liquid connection section 700 in the direction of gravity. This reduces the possibility of electrical problems caused by ink originating from the liquid connection section 700.

[0118] Furthermore, in this embodiment, since the wall portion 53b of the head housing 53 is provided, even if ink is ejected from the opening 59b of the liquid connection portion 700, the ink can be blocked, reducing the possibility of it reaching the circulation pump 500 or the electrical connection portion 515.

[0119] <Circulation channel within the discharge module> The features of this disclosure will be described below. Figure 20(a) is a partially enlarged view of the discharge module 300 of this embodiment, viewed along the discharge direction. Figure 20(b) is a schematic cross-sectional view of the discharge module 300 of this embodiment. The discharge module 300 of this embodiment has a configuration in which a discharge substrate 1006 that forms the discharge port 13, a flow channel member 1007 that forms the flow channel, a first substrate 1008, and a second substrate 1009 are stacked in the Z direction in order. The structure of the discharge module 300 and the flow of ink in the circulating flow channel will be described below. The arrows in the figures indicate the direction of ink flow.

[0120] The discharge substrate 1006 has a plurality of discharge ports 13 for discharging ink, and a nozzle that communicates with the discharge ports at one end and with a pressure chamber described later at the other end. The flow path member 1007 is provided with a plurality of individual flow paths 1002, a plurality of pressure chambers 12, and a plurality of filters 1003 provided on the ink supply side and the ink recovery side, respectively. The first substrate 1008 is provided with a discharge element 15 for discharging ink, a liquid delivery element 1001 for circulating ink, a supply connection flow path 323, and a recovery connection flow path 324. The second substrate 1009 has a common supply flow path 18 that communicates with the supply connection flow path 323 and a common recovery flow path 19 that communicates with the recovery connection flow path 324.

[0121] Multiple individual flow paths 1002 are flow paths formed by the ejection substrate 1006, the flow path member 1007, and the first substrate 1008, and are formed to extend in the X direction of the flow path member 1007. The individual flow paths 1002 include an individual supply flow path 1004 on the ink supply side and an individual recovery flow path 1005 on the ink recovery side. The individual supply flow path 1004 is in communication with the supply connection flow path 323. The individual recovery flow path 1005 is in communication with the recovery connection flow path 324. As a result, the individual flow paths 1002 become paths that can supply and circulate ink.

[0122] The multiple pressure chambers 12 are regions that generate energy for discharging liquid, and do not necessarily have to be chambers with clearly defined boundaries. Discharge elements 15 are provided within the multiple pressure chambers 12.

[0123] Filter 1003 is installed between the supply connection channel 323 and the individual supply channel 1004. Filter 1003 is also installed between the individual recovery channel 1005 and the recovery connection channel 324. This prevents foreign matter, air bubbles, and other contaminants from entering the individual channel 1002.

[0124] Multiple ejection elements 15 are provided at positions facing the ejection port 13, and a row of energy generating elements arranged in a line in the Y direction at predetermined intervals is provided within the individual flow path 1002. The ejection elements 15 generate ejection energy to eject ink from the ejection port 13. In this embodiment, the ejection elements 15 use electrothermal conversion elements (heaters) as described above, but piezoelectric actuators (piezo elements) may also be used.

[0125] The liquid delivery element 1001 is positioned on the individual supply channel 1004 side, at a predetermined distance in the X direction from the discharge element 15. The liquid delivery element 1001 generates thermal energy to circulate ink within the individual channel 1002. When the liquid delivery element 1001 is driven, the ink is heated, and the ink is discharged due to the boiling of the ink film. In this embodiment, the liquid delivery element 1001 uses an electrothermal conversion element (heater), but a piezoelectric actuator (piezo element) or the like may also be used. In this disclosure, the circulation of ink delivered by the liquid delivery element 1001 is called microcirculation 1011. This allows the ink in the individual channel 1002 to be sent from the individual supply channel 1004 to the individual recovery channel 1005 via the pressure chamber 12. The liquid delivery element 1001 may be configured to deliver liquid when the liquid discharge device 50 is stopped. The ink supplied from the circulation unit 54 passes through the common supply channel 18 and flows into the individual channels 1002 and the pressure chamber 12 via the supply connection channel 323. The ink supplied from the circulation unit 54 also passes through the other end of the nozzle. The ink that flows into the pressure chamber 12 flows out from the common recovery channel 19 via the recovery connection channel 324. In this disclosure, the circulation of ink that is constantly supplied into the discharge module 300 by the circulation unit 54 is referred to as macro circulation 1012.

[0126] Here, let R1 be the flow resistance between the liquid delivery element 1001 and the individual supply channel 1004, and let R2 be the flow resistance between the liquid delivery element 1001 and the individual recovery channel 1005. Since the liquid delivery element 1001 is located closer to the individual supply channel 1004 than to the individual recovery channel 1005, the flow resistance R1 is smaller than the flow resistance R2. For this reason, bubbles generated by the driving of the liquid delivery element 1001 tend to grow towards the individual supply channel 1004. When the bubbles contract, ink flows in to compensate for the volume, so the amount of ink flowing from the individual supply channel 1004 becomes greater than the amount of ink flowing from the individual recovery channel 1005, and as a result, ink flows from the individual supply channel 1004 to the individual recovery channel 1005. That is, a microcirculation 1011 occurs. The ratio of flow resistance R1 to flow resistance R2 affects the left-right ratio of the bubbles, and as a result, affects the magnitude of the microcirculation flow. In this embodiment, the flow resistance ratio R1 / R2 is preferably set to a range of 0.05 to 0.4. By setting the flow resistance ratio R1 / R2 within this range, the circulating flow within the individual flow channels 1002 can be kept within a suitable range. As mentioned above, the circulation unit 54 in this embodiment has a circulation pump 500 for circulating the liquid. The circulation pump 500 is a piezoelectric diaphragm pump.

[0127] Thus, in this embodiment, when ink is consumed, new ink can be supplied into the individual channel 1002. Furthermore, even when ink is not being consumed, new ink can be circulated within the individual channel 1002.

[0128] (Explanation of the drive signal for the liquid delivery element) Figure 21 is a diagram showing the ejection pulse and the drive pulse for the liquid delivery element. When the head driver 1A (see Figure 1(b)) applies the ejection pulse 1020 to the ejection element 15, ink is ejected from the ejection port 13, and there is an ejection pulse pause time 1021 until the next ejection pulse 1020 is applied to the ejection element 15. During the ejection pulse pause time 1021, when the head driver 1A applies the liquid delivery element drive pulse 1022 to the liquid delivery element 1001, the liquid delivery element 1001 is driven, and microcirculation 1011 is generated in the individual flow path 1002. In this embodiment, a liquid delivery element drive pulse pause time 1023 is provided between the period from the ejection pulse 1020 to the liquid delivery element drive pulse 1022, and between the period from the liquid delivery element drive pulse 1022 to the next liquid delivery element drive pulse 1022. The liquid delivery element drive pulse 1022 is applied to the liquid delivery element 1001 after the liquid delivery element drive pulse pause time 1023 has elapsed. In this embodiment, the liquid delivery element drive pulse pause time 1023 and the liquid delivery element drive pulse 1022 are repeated three times during the discharge pulse pause time 1021. By intermittently applying the liquid delivery element drive pulse 1022 in this way, the liquid in the individual flow path 1002 is delivered intermittently. Subsequently, the head driver 1A (see Figure 1(b)) applies the discharge pulse 1020 to the discharge element 15, and ink is discharged from the discharge port 13. In this embodiment, the liquid delivery element drive pulse pause time 1023 and the liquid delivery element drive pulse 1022 are repeated three times during the discharge pulse pause time 1021, but this is not limited to this. It is preferable that the liquid delivery element drive pulse 1022 is applied to the liquid delivery element 1001 at least once before the discharge pulse 1020 is applied to the discharge element 15.

[0129] According to this disclosure, by driving the liquid delivery element 1001, microcirculation 1011 is generated within the individual flow path 1002, enabling the circulation of ink near the discharge port at a high flow rate only at the necessary timing. On the other hand, by driving the circulation pump of the circulation unit 54, ink concentration and sedimentation of the entire liquid discharge head can be suppressed at an appropriate flow rate. That is, ink concentration and sedimentation of the entire liquid discharge head can be suppressed while suppressing the evaporation rate of ink evaporating from the discharge port 13.

[0130] <Other Embodiments> This disclosure includes configurations represented by the following example of a liquid dispensing head.

[0131] <Configuration 1> A liquid dispensing head that discharges liquid from a discharge port while moving in a predetermined direction, A discharge element that generates energy for discharging liquid from the aforementioned discharge port, A pressure chamber communicating with the aforementioned discharge port, A nozzle that communicates with the discharge port at one end and with the pressure chamber at the other end, A separate supply channel for supplying liquid to the pressure chamber, A separate recovery channel for recovering liquid from the pressure chamber, A liquid delivery element is positioned between the pressure chamber and the individual supply channel, and delivers liquid from the individual supply channel to the individual recovery channel. A circulation unit that circulates liquid from a common recovery channel that recovers liquid from multiple individual recovery channels to a common supply channel that supplies liquid to multiple individual supply channels, A liquid dispensing head characterized by having the following features.

[0132] <Configuration 2> The circulation unit is a liquid discharge head according to configuration 1, which circulates the liquid only within the liquid discharge head. <Structure 3> The circulation unit is a liquid discharge head according to configuration 1 or 2, having a pump for circulating the liquid. <Structure 4> The pump is a piezoelectric diaphragm pump, as described in configuration 3, for the liquid discharge head.

[0133] <Composition 5> The liquid dispensing head according to any one of configurations 1 to 4, wherein the liquid dispensing element is an electrothermal conversion element.

[0134] <Composition 6> The liquid dispensing head according to any one of configurations 1 to 4, wherein the liquid dispensing element is a piezoelectric actuator.

[0135] <Composition 7> The liquid discharge head according to any one of configurations 1 to 6, wherein the liquid delivery element is driven intermittently to generate a continuous flow of liquid from the individual supply channel to the individual recovery channel.

[0136] <Structure 8> The liquid delivery element is a liquid discharge head according to any one of configurations 1 to 7, which is driven during the period when the discharge element is not driven.

[0137] <Composition 9> The liquid discharge head according to any one of configurations 1 to 8, wherein the individual supply channels, the liquid delivery elements, the pressure chamber, and the individual recovery channels are arranged along the predetermined direction.

[0138] <Composition 10> The liquid dispensing head according to any one of configurations 1 to 9, wherein the dispensing element is an electrothermal conversion element.

[0139] <Composition 11> The liquid dispensing head according to any one of configurations 1 to 10, wherein the dispensing element is a piezoelectric actuator.

[0140] <Composition 12> A scanning means for scanning a carriage to which a liquid discharge head described in any one of configurations 1 to 11 is attached in the predetermined direction, A conveying means for conveying the sheet to which the liquid droplets discharged by the liquid discharge head are applied in a direction intersecting the predetermined direction, A control means for controlling the discharge scanning means, the transport means, the circulation unit, the discharge element, and the liquid delivery element. A liquid dispensing device characterized by comprising the following features. [Explanation of Symbols]

[0141] 12 Pressure chamber 13 Outlet 15 Discharge element 18 Common supply channels 19 Common recovery channel 54 Circulation Unit 1001 Liquid delivery element 1004 Individual supply channel 1005 Individual recovery channel

Claims

1. A liquid dispensing head that discharges liquid from a discharge port while moving in a predetermined direction, A discharge element that generates energy for discharging liquid from the aforementioned discharge port, A pressure chamber communicating with the aforementioned discharge port, A nozzle that communicates with the discharge port at one end and with the pressure chamber at the other end, A separate supply channel for supplying liquid to the pressure chamber, A separate recovery channel for recovering liquid from the pressure chamber, A liquid delivery element is positioned between the pressure chamber and the individual supply channel, and delivers liquid from the individual supply channel to the individual recovery channel. A circulation unit that circulates liquid from a common recovery channel that recovers liquid from multiple individual recovery channels to a common supply channel that supplies liquid to multiple individual supply channels, Equipped with, A liquid discharge head characterized in that the liquid circulation path formed by the circulation unit passes through the other end of the nozzle.

2. The liquid discharge head according to claim 1, wherein the circulation unit circulates the liquid only within the liquid discharge head.

3. The liquid discharge head according to claim 1, wherein the circulation unit has a pump for circulating the liquid.

4. The liquid discharge head according to claim 3, wherein the pump is a piezoelectric diaphragm pump.

5. The liquid discharge head according to claim 1, wherein the liquid delivery element is an electrothermal conversion element.

6. The liquid discharge head according to claim 1, wherein the liquid delivery element is a piezoelectric actuator.

7. The liquid discharge head according to claim 1, wherein the liquid delivery element is driven intermittently to generate an intermittent flow of liquid from the individual supply channel to the individual recovery channel.

8. The liquid dispensing head according to claim 1, wherein the liquid delivery element is driven during the period when the dispensing element is not driven.

9. The liquid discharge head according to claim 1, wherein the individual supply channels, the liquid delivery elements, the pressure chambers, and the individual recovery channels are arranged along the predetermined direction.

10. The liquid dispensing head according to claim 1, wherein the dispensing element is an electrothermal conversion element.

11. The liquid dispensing head according to claim 1, wherein the dispensing element is a piezoelectric actuator.

12. A scanning means for scanning a carriage to which the liquid discharge head described in claim 1 is attached in the predetermined direction, A conveying means for conveying the sheet to which the liquid droplets discharged by the liquid discharge head are applied in a direction intersecting the predetermined direction, A control means for controlling the discharge scanning means, the transport means, the circulation unit, the discharge element, and the liquid delivery element. A liquid dispensing device characterized by comprising the following features.

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