Liquid dispensing head and liquid dispensing device

Abstract

To provide a liquid discharge head and a liquid discharge device which can make liquid concentration uniform by liquid circulation in a short time, and can reduce downtime.SOLUTION: A liquid discharge head 1 includes a pressure chamber 12 communicating with a discharge port 13, a discharge element 15 for discharging liquid from the discharge port, and a circulation path of the liquid including the pressure chamber. The circulation path includes a supply passage 130 for supplying the liquid to the pressure chamber 12, a recovery flow passage 140 for recovering the liquid from the pressure chamber 12, a circulation pump 500 for supplying the liquid recovered from the recovery flow passage to the supply flow passage, and pressure adjustment means 120 for adjusting a pressure of the liquid supplied to the supply flow passage. A pressure P21 of the liquid supplied to the pressure chamber in a stop state of the circulation pump, a pressure P22 of the liquid supplied to the pressure chamber in a driving state of the circulation pump, and a pressure loss ΔP from the pressure adjustment means to the pressure chamber in the driving state of the circulation pump have a relation of P22>P21 and P22-ΔP<0.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure relates to a liquid ejection head having a liquid circulation path and a liquid ejection apparatus including the liquid ejection head.

Background Art

[0002] Some liquid ejection apparatuses circulate a liquid for the purpose of preventing sedimentation of coloring materials and ink thickening. Patent Document 1 discloses a liquid ejection apparatus that circulates a liquid between a liquid ejection head that ejects a liquid and a liquid storage unit that stores the liquid supplied to the liquid ejection head. In this liquid ejection apparatus, ink in the liquid storage unit is supplied to the liquid ejection head via a supply flow path, and the liquid that has not been ejected by the liquid ejection head is returned to the liquid storage unit again via a recovery flow path, thereby constituting a circulation path for recovery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a liquid ejection apparatus, when performing a liquid ejection operation, it is preferable to redisperse sediment components such as coloring materials and ink aggregates sedimented in the path and to suppress ink thickening. Therefore, in a liquid ejection apparatus having a liquid circulation path, liquid circulation is performed prior to the ejection operation. However, in the liquid ejection apparatus disclosed in Patent Document 1, a long circulation path that returns from the liquid storage unit through the liquid ejection head and back to the liquid storage unit again is configured. For this reason, when redispersing sediment components and suppressing ink thickening, it is necessary to circulate the liquid through a long circulation path prior to the ejection operation, resulting in a long downtime and a decrease in productivity.

[0005] The present invention aims to provide a liquid dispensing head and liquid dispensing device that can redisperse settled components and suppress ink viscosity increase through short-time circulation, thereby reducing downtime. [Means for solving the problem]

[0006] The present invention relates to a liquid discharge head comprising: a pressure chamber communicating with a discharge port for discharging liquid; a discharge element for discharging the liquid supplied to the pressure chamber from the discharge port; and a liquid circulation path including the pressure chamber, wherein the circulation path comprises: a supply channel for supplying liquid to the pressure chamber; a recovery channel for recovering liquid from the pressure chamber; a circulation pump for supplying the liquid recovered from the recovery channel to the supply channel; and a mechanism for adjusting the pressure of the liquid supplied to the supply channel. 1 A pressure adjustment means is provided, The first pressure regulating means includes a first liquid chamber for containing liquid, and a first valve chamber which is connected to the first liquid chamber via a first communication port and includes a first valve for switching the first communication port between an open state and a closed state. When the aforementioned circulation pump is stopped Inside the first liquid chamber The liquid pressure P21 and the driving state of the circulation pump Inside the first liquid chamber The liquid pressure P22 and the driving state of the circulation pump The first liquid chamber in from The aforementioned The pressure loss ΔP to the pressure chamber is characterized by the relationship P22 > P21 and P22 - ΔP < 0. [Effects of the Invention]

[0007] According to the present invention, a liquid dispensing head and liquid dispensing device can be provided that can redisperse settled components and suppress ink viscosity increase through short-time circulation, thereby reducing downtime. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram illustrating a liquid dispensing device. [Figure 2] 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 circulation unit's appearance. [Figure 5] This is a longitudinal cross-sectional view showing the circulation path. [Figure 6] It is a block diagram schematically showing a circulation path. [Figure 7] It is a cross-sectional view showing an example of a pressure adjusting means. [Figure 8] It is an external perspective view of a circulation pump. [Figure 9] It is a cross-sectional view taken along line IX-IX of the circulation pump shown in Fig. 8(a). [Figure 10] It is an exploded perspective view of a circulation pump. [Figure 11] It is a diagram showing an electrical connection portion of a piezoelectric ceramic. [Figure 12] It is a diagram for explaining the flow of ink in a liquid discharge head. [Figure 13] It is a schematic diagram showing a circulation path in a discharge unit. [Figure 14] It is a diagram showing an opening plate 330. [Figure 15] It is a diagram showing a discharge element substrate. [Figure 16] It is a cross-sectional view showing the ink flow in a discharge unit. [Figure 17] It is a cross-sectional view showing the vicinity of the discharge port. [Figure 18] It is a cross-sectional view showing a comparative example in the vicinity of the discharge port. [Figure 19] It is a diagram showing a comparative example of a discharge element substrate. [Figure 20] It is a diagram showing the flow path configuration of a liquid discharge head. [Figure 21] It is a diagram showing the connection state between the main body portion of a liquid discharge device and a liquid discharge head. [Figure 22] It is a longitudinal sectional view of a liquid discharge head in a second embodiment.

Mode for Carrying Out the Invention

[0009] Preferred embodiments of this disclosure will be described in detail below with reference to the attached drawings. Note that the following embodiments are not limiting to the scope of this disclosure, and not all combinations of features described in these embodiments are necessarily essential to the solutions of this disclosure. The same reference numerals are used for identical components. In these embodiments, a thermal method is used as the liquid dispensing element, where bubbles are generated by an electrothermal conversion element to dispense the liquid; however, the invention is not limited to this. It can also be applied to liquid dispensing heads employing a piezoelectric element (piezoelectric element) to dispense the liquid, or other dispensing methods. Furthermore, the pumps and pressure regulating means described below are not limited to the configurations shown in the embodiments and drawings.

[0010] (First Embodiment) <Liquid discharge device> Figure 1 is a diagram illustrating a liquid ejection device, and is an enlarged view of the liquid ejection head and its surroundings. First, the general configuration of the liquid ejection device 50 in this embodiment will be explained with reference to Figure 1. Figure 1(a) is a schematic perspective view showing a liquid ejection device using the liquid ejection head 1. The liquid ejection device 50 in this embodiment constitutes a serial type inkjet recording device that ejects ink as a liquid while scanning the liquid ejection head 1 to record onto a recording medium P.

[0011] The liquid discharge head 1 is mounted on the carriage 60. The carriage 60 reciprocates along the guide axis 51 in the main scanning direction (X direction). The recording medium P is transported by transport rollers (transport means) 55, 56, 57, and 58 in the sub-scanning direction (Y direction) which intersects (in this example, is perpendicular to) the main scanning direction. In the figures referenced below, the Z direction represents the vertical direction and intersects (in this example, is perpendicular to) the XY plane defined by the X and Y directions. The liquid discharge head 1 is configured to be detachable from the carriage 60 by the user.

[0012] 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.

[0013] Furthermore, the liquid dispensing device 50 is equipped with an ink tank 2, which is an ink supply source (liquid supply source), 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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 provided in the dispensing unit 3. The CPU 103 also controls the drivers of various actuators 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.

[0018] <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, taken along 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.

[0019] 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.

[0020] 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 discharge head 1 is mounted on the liquid discharge 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 an inlet for introducing ink and is provided on the head housing 53 of the liquid discharge head 1. This forms an ink supply path from the ink tank 2 through the external pump 21 to the liquid discharge 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 discharge device 50 of this embodiment is equipped with an ink supply system that supplies ink from an ink tank 2 located outside the liquid discharge head 1. Furthermore, the liquid ejection device 50 of this embodiment does not include an ink recovery system for recovering the ink in the liquid ejection head 1 into the ink tank 2. Therefore, although the liquid ejection head 1 is provided with a liquid connector insertion port 53a for connecting the ink supply tube 59 of the ink tank 2, it is not provided with a connector insertion port for connecting a tube for recovering the ink from the liquid ejection head 1 into the ink tank 2. Note that a liquid connector insertion port 53a is provided for each ink.

[0021] 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.

[0022] 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. In this embodiment, the dispensing elements 15 are composed of electrothermal 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] Also, on one side of the first support member 4 (in Figure 3(a)) under A second support member 7, having an opening 7a (see Figure 2) through which the ejection module 300 is inserted, is adhesively fixed to the surface. An electrical wiring member 5, which is electrically connected to the ejection module 300, is held in the second support member 7. The electrical wiring member 5 is a component for applying 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] <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.

[0033] <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 21, 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.

[0034] First, we will explain the connection status of each component in the liquid dispensing head 1.

[0035] 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 (first communication port) which can be opened and closed by a valve 190A (first valve) shown in Figure 5.

[0036] 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 (second communication port) which is opened and closed by the second 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] <Pressure regulating 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.

[0047] 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."

[0048] 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.

[0049] A pressure adjustment spring 220 (biasing means) is provided between the pressure plate 210 and the partition wall 123. The biasing force of the pressure adjustment spring 220 biases the pressure plate 210 and the flexible member 230 in a direction 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)).

[0050] 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)).

[0051] 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.

[0052] As described above, the first pressure adjustment means 120 includes a first pressure control chamber (first liquid chamber) 122 that houses liquid supplied from a liquid supply source (ink tank 2) and a circulation pump 500, and a first adjustment mechanism that adjusts the pressure of the liquid in the first pressure control chamber 122. The first adjustment mechanism comprises the aforementioned pressure plate 210, pressure adjustment spring 220, valve 190, valve spring 200, and first valve chamber 121, and is configured to adjust the pressure of the liquid housed in the first pressure control chamber 122 in conjunction with the volume of the first pressure control chamber 122. The second pressure adjustment means 150 includes a second pressure control chamber (second liquid chamber) 152 connected to the pump inlet passage 170, and a second adjustment mechanism that adjusts the pressure of the liquid housed in the second pressure control chamber 152. The second adjustment mechanism comprises the aforementioned pressure plate 210, pressure adjustment spring 220, second valve 190B, second valve spring 200, and second valve chamber 151, and is configured to adjust the pressure of the liquid contained in the second pressure control chamber 152 in conjunction with the volume of the second pressure control chamber 152.

[0053] Next, we will explain the pressure in the first pressure control chamber 122 in more detail.

[0054] 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.

[0055] 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. 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

[0056] Here, the spring force F1 of the valve spring 200 and the spring force F2 of the pressure regulating spring 220 are positive in the direction that pushes the valve 190 and the pressure plate 210 (in Figure 7). left The direction is set as follows. 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 configuration is such that P1 ≥ P2.

[0057] 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.

[0058] 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.

[0059] P3×S3+F3=0...Equation 3

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

[0061] In Figure 7(c), the pressure plate 210 and the flexible member 230 are shown as being displaced to their limits. leftThis represents a state of displacement in the direction shown. Depending on the amount of displacement while the pressure plate 210 and the flexible member 230 are displaced to the state shown in Figure 7(c), 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. Specifically, the pressure plate 210 and the flexible member 230 are displaced in the state shown in Figure 7(c). right When in this direction, the pressure-receiving area S3 of the pressure plate 210 decreases, and the spring force F3 of the pressure adjustment spring 220 increases. 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 in Figure 7(b) to the state in Figure 7(c) (that is, the negative pressure weakens and approaches the positive pressure side). That is, from the state in which the communication port 191 is open, the pressure plate 210 and the flexible member 230 left As the displacement gradually increases in the direction, the pressure in the first pressure control chamber 122 gradually rises until the internal volume of the first pressure control chamber 122 reaches its limit of 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] Here, with reference to Figures 10 and 11, the specific configuration of the components of the circulation pump 500 will be described. Figure 10 is an exploded perspective view of the circulation pump 500, where Figure 10(a) is an exploded perspective view of each component of the circulation pump 500 viewed from the rear, and Figure 10(b) is an exploded perspective view of each component of the circulation pump 500 viewed from the front. The circulation pump 500 in this embodiment is a piezoelectric pump driven by applying voltage to a piezoelectric ceramic. As shown in Figure 10, a circular vibrating plate 509 is bonded to the diaphragm 506 with adhesive 508. A circular piezoelectric ceramic 510 is fixed to the vibrating plate 509 by adhesive. The diaphragm 506 uses injection-molded materials such as PPE+PS (modified polyphenylene ether) or polypropylene, but it is also possible to use a film or a punched resin plate, and is not limited to these. The vibrating plate 509 is made of brass, stainless steel, iron-nickel alloy, etc., but is not limited to these.

[0072] A drive circuit board 513 is provided on the surface facing the piezoelectric ceramic 510. The drive circuit board 513 is connected to a power supply unit provided in the main body of the liquid dispensing device 50 and applies a predetermined drive voltage (AC voltage) to the piezoelectric ceramic 510 and the diaphragm 509.

[0073] Figure 11 shows the electrical connection of the piezoelectric ceramic 510 as seen through the drive circuit board 513 from the cover 507 side. The drive circuit board 513 and the piezoelectric ceramic 510 are connected by an electrical connection cable 518a, and the drive circuit board 513 and the diaphragm 509 are electrically connected by an electrical connection cable 518b. The electrical connections between the electrical connection cable 518a and the drive circuit board 513, and between the electrical connection cable 518b and the drive circuit board 513, are made by solder 520. In addition, the electrical connections between the electrical connection cable 518a and the piezoelectric ceramic 510, and between the electrical connection cable 518b and the diaphragm 509, are made by solder 521.

[0074] The diaphragm 509 is connected to the GND wiring of the drive circuit board 513 via an electrical connection cable 518b, and the piezoelectric ceramic 510 is connected to the AC voltage output section of the drive circuit board 513 via an electrical connection cable 518a. By connecting the diaphragm 509 to GND and applying an AC voltage with a phase difference to the piezoelectric ceramic 510, the piezoelectric ceramic 510 expands and contracts, deforming the diaphragm. This changes the pressure inside the pump chamber, allowing ink to be drawn in and discharged.

[0075] The drive circuit board 513 is electrically connected to the electrical contact board 6 by a cable, and the electrical contact board 6 is provided with electrical connection terminals for driving the pump. When the circulation unit 54 is attached to the carriage 60, an electrical signal output from an electrical contact part (first electrical connection part) not shown on the carriage 60 side is input to the drive circuit board 513 via an electrical connection terminal (second electrical connection part) not shown on the electrical contact board 6.

[0076] By providing electrical connection terminals for pump drive on the electrical contact board 6 in this manner, it is possible to drive the circulation pump 500 by applying a predetermined drive voltage to the electrical connection terminals, even when the pump is detached from the carriage 60.

[0077] <Ink flow within the liquid ejection head> Figure 12 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 12. 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 12 have been simplified. Therefore, the relative positions of each component differ from those in Figure 21, which will be described later. Figure 12(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.

[0078] During recording, the circulation pump 500 is ON (operated), and ink flowing out from the first pressure control chamber 122 (first liquid chamber) flows into the supply channel 130 and the bypass channel 160. The ink flowing 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.

[0079] 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.

[0080] In the ink circulation described above, the amount (flow rate) of ink circulating in the ejection module 300 is determined by the differential pressure of the control pressures in the first pressure control chamber 122 and the second pressure control chamber 152. This differential pressure is set to a circulation amount that can suppress the thickening of the ink near the ejection port in 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. When the internal volume of the first pressure control chamber 122 decreases to below a predetermined volume, the communication port 191A (first communication port) switches to an open state, and ink is supplied from the first valve chamber 121 to the first pressure control chamber 122. As this 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 into the first pressure control chamber 122 from the first valve chamber 121, the pressure inside the first pressure control chamber increases, and when the internal volume of the first pressure control chamber increases to above a predetermined volume, 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.

[0081] Figure 12(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 12(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.

[0082] 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.

[0083] 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 12(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 12(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 12(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.

[0084] Furthermore, in the state shown in Figure 12(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.

[0085] 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 12(d). When the second pressure control chamber 152 expands as shown in Figure 12(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 12(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 12(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 12(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 12(a).

[0086] In the above liquid circulation operation, the characteristic pressure relationships shown in Equations 5 and 6 below are maintained.

[0087] P22>P21...Formula 5 P21: Pressure (gauge pressure) in the first pressure control chamber 122 when the circulation pump 500 is stopped. P22: Pressure (gauge pressure) in the first pressure control chamber 122 when the circulation pump 500 is in operation. Furthermore, the pressure in the first pressure control chamber 122 weakens when the circulation pump 500 is driven, P22-ΔP<0...Equation 6 ΔP: Pressure loss from the first pressure control chamber 122 to the pressure chamber 12 when the circulation pump is running. This prevents ink leakage from the discharge port 13 when the circulation pump 500 is driven.

[0088] With the above configuration, it becomes possible to circulate the ink through a circulation path that is completed within the liquid ejection head 1. Therefore, even if ink concentration or colorant sedimentation temporarily occurs in the pressure chamber 12, the circulation of ink in the circulation path can quickly resolve the colorant sedimentation and liquid viscosity increase, thereby reducing downtime during recording.

[0089] Furthermore, in this embodiment, the filter 110 is located outside the ink circulation path, and the ink that has passed through the filter then circulates within the circulation path without passing through the filter 110 again. This prevents ink aggregates and other debris from clogging the filter 110 due to repeated ink circulation. In addition, a relatively short circulation path can be created that is completed within the liquid discharge head 1, and pressure loss in the circulation path can be reduced by placing the filter outside the circulation path. This makes it possible to perform circulation with the relatively small circulation pump 500 described in this embodiment. Moreover, the pressure of the liquid supplied from the external pump via the filter 110 can be appropriately controlled by the first pressure adjustment means 120 to control the pressure toward the supply channel 130. This makes it possible to supply ink to the filter 110 under pressure using the external pump, allowing the filtration area of ​​the filter to be set smaller, and enabling miniaturization of the liquid discharge head.

[0090] Furthermore, in this embodiment, as shown in Figure 12, the filtration surface of the filter 110 is positioned along the direction of gravity, more preferably parallel to the direction of gravity, and the inlet side flow path 270 and the outlet side flow path 290 of the filter 110 are positioned below the filter. This makes it easier for the settled colorant to flow downstream, and makes it possible to suppress clogging of the filter 110.

[0091] Furthermore, the first pressure control chamber 122 and the second pressure control chamber 152 are provided with liquid outlets 240 and 250 for discharging the liquid contained inside, located below each pressure control chamber 122 and 152 in the direction of gravity (below the midpoint of each pressure control chamber in the direction of gravity). As a result, even if the ink composition settles, these settled materials can be easily discharged from each pressure control chamber 122 and 152, thereby shortening the ink agitation time due to circulation.

[0092] Furthermore, when using inks with a fast settling rate of colorants, such as white ink, it is necessary to circulate and agitate the ink even when recording is not being performed. However, in this embodiment, ink circulation can be performed in the liquid ejection head 1 even when the circulation unit 54 is not mounted on the main body of the liquid ejection device 50, such as the carriage. That is, even when the liquid ejection head 1 is removed from the carriage 60 provided on the main body of the liquid ejection device 50, the circulation pump 500 can be driven by applying an AC voltage to the electrical connection terminals of the electrical contact board 6 to circulate the ink. This makes it possible to eliminate the settling of the colorants in the ink inside the liquid ejection head 1 in advance before use, and the recording operation can be started efficiently. In addition, when circulating ink without mounting the liquid ejection head 1 on the main body of the liquid ejection device, power consumption can be reduced compared to when circulating with the liquid ejection head 1 mounted on the liquid ejection body.

[0093] In the above explanation, Figure 12(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 12(a) to (e) will occur in response to the driving and stopping of the circulation pump 500.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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 150 may be set such that the communication port 191B 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] <Discharge Unit Configuration> Figure 13 is a schematic diagram showing the circulation path for one ink color in the ejection unit 3 of this embodiment. Figure 13(a) is an exploded perspective view of the ejection unit 3 as seen from the first support member 4 side, and Figure 13(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 for one color is explained, 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 13, and are also omitted in the following explanation of the ejection unit configuration. Furthermore, the first support member 4 in Figure 13(a) is shown as a cross-section at XI-XI in Figure 3. The ejection module 300 comprises an ejection element substrate 340 and an opening plate 330. Figure 14 shows the opening plate 330, and Figure 15 shows the ejection element substrate 340.

[0104] 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.

[0105] 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.

[0106] As shown in Figures 13 and 14, 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 15 and 16, 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] In Figure 14, 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 15, 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 also 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.

[0111] 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.

[0112] Figures 16(a) to (c) are cross-sectional views showing the ink flow in different parts of the ejection unit 3. Figure 16(a) is the cross-section shown as XIVa-XIVa in Figure 13(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 16(b) is the cross-section shown as XIVb-XIVb in Figure 13(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 16(c) is the cross-section shown as XIVc-XIVc in Figure 13(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.

[0113] In the ink supply channel, as shown in Figure 16(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 16(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 16(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 16(a), and ink is recovered in the area where the ink recovery port 312 is provided, as shown in Figure 16(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.

[0114] Figures 17(a) and (b) are cross-sectional views showing the vicinity of the discharge port 13 in the discharge module 300, and Figure 18 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 17 and 18 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 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 via the recovery connection channel 324, which is a recovery channel, to the common recovery channel 19.

[0115] 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 caused by 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 18, 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.

[0116] 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 17, 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] Figure 19 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 19. 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 19, 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.

[0124] 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.

[0125] Figures 20(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 20(a), the liquid ejection head 1 is provided with separate circulation channels for each ink type. 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 20(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.

[0126] <Connection between the main unit and the liquid dispensing head> Figure 21 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.

[0127] As shown in Figure 21, 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.

[0128] As described above, the liquid discharge head 1 shown in Figure 21 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.

[0129] <Placement of circulation pumps, etc.> As shown in Figure 21, 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.

[0130] 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.

[0131] Furthermore, in this embodiment, since the wall portion 52b 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.

[0132] (Second Embodiment) Next, a second embodiment of the present invention will be described. Figure 22 is a longitudinal cross-sectional view of the liquid discharge head in the second embodiment. This embodiment includes a second supply channel 600 that connects the first pressure control chamber 122 of the first pressure adjustment means 120 in the first embodiment with the supply channel 130. One end of the second supply channel 600 communicates with the upper end of the first pressure control chamber 122 in the direction of gravity, and the other end communicates with the upper end of the supply channel 130 in the direction of gravity. By providing this second supply channel 600, it becomes possible to efficiently discharge bubbles that have flowed in from the upstream side of the first pressure adjustment means 120 or bubbles that have been generated in the circulation channel to the outside.

[0133] In other words, the first pressure control chamber 122 of the first pressure adjustment means 120 is positioned above the liquid discharge head 1 in the direction of gravity. Therefore, bubbles BL that flow into the first pressure adjustment means 120 along with the ink from the upstream side of the liquid discharge head 1, or bubbles BL that flow into the first pressure control chamber 122 from the circulation channel, both float to the top of the first pressure control chamber 122 or the top of the second supply channel 600 and are collected. Furthermore, the collected bubbles BL are prevented from moving to the discharge module 300 at the flow velocity of the liquid flowing in the supply channel 130 and the second supply channel 600 during the ink discharge operation.

[0134] The bubbles BL collected in the upper part of the first pressure control chamber 122 and the second supply channel 600 can be discharged together with the ink by performing a suction process that forcibly sucks the ink from the discharge port when the discharge operation is not taking place. The suction process is performed by closely pressing a cap member against the discharge port surface where the discharge port of the liquid discharge head 1 is formed, and applying negative pressure from a negative pressure source connected to the cap member to the discharge port, thereby forcibly sucking the ink from the discharge port. The flow velocity of the ink generated in the channel during this suction is greater than the flow velocity of the ink generated by the normal ink discharge operation. Therefore, the bubbles BL collected in the upper part of the first pressure control chamber 122 and the second supply channel 600, together with the ink, pass through the second supply channel 600 and the supply channel 130 to the pressure chamber 12, and are then discharged together with the ink from the discharge port 13. This suction process is generally performed in suction recovery processes to restore discharge performance by discharging thickened ink, etc., generated in the discharge port or pressure chamber, or in initial filling processes to fill the channel with ink.

[0135] In this way, by forming a second supply channel, air bubbles mixed in the ink within the liquid ejection head 1 can be collected and discharged all at once by suction, enabling efficient air bubble discharge.

[0136] (Other embodiments) In the above embodiment, an example was shown in which a bypass passage is provided to prevent the discharge module 300 from being affected when the pressure generated by the circulation pump 500 exceeds a predetermined value. However, if the pressure fluctuation caused by the circulation pump 500 is small and the pressure is maintained within the predetermined value, the bypass passage 160 and the second pressure adjustment means 150 can be omitted. [Explanation of symbols]

[0137] 12 Pressure Chamber 13 Outlet 15 Discharge element 120 First pressure regulating means 122 First Pressure Control Room 130 Supply channel 140 Recovery channel 150 Second pressure regulating means 500 Circulation Pump

Claims

1. A liquid discharge head comprising: a pressure chamber communicating with a discharge port for discharging liquid; a discharge element for discharging the liquid supplied to the pressure chamber from the discharge port; and a liquid circulation path including the pressure chamber, The aforementioned circulation path is A supply channel for supplying liquid to the pressure chamber, A recovery channel for recovering liquid from the pressure chamber, A circulation pump that supplies the liquid recovered from the recovery channel to the supply channel, The system includes a first pressure adjusting means for adjusting the pressure of the liquid supplied to the supply channel, The first pressure regulating means includes a first liquid chamber for containing liquid, and a first valve chamber which is connected to the first liquid chamber via a first communication port and includes a first valve for switching the first communication port between an open state and a closed state. The pressure P21 of the liquid inside the first liquid chamber when the circulation pump is stopped, The pressure P22 of the liquid inside the first liquid chamber when the circulation pump is in operation, The pressure loss ΔP from the first liquid chamber to the pressure chamber in the operating state of the circulation pump is P22 > P21, and P22 - ΔP < 0, A liquid dispensing head characterized by having a specific relationship.

2. The first pressure regulating means is connected between the inlet into which the liquid supplied from the liquid supply source is introduced and the supply channel, The liquid discharge head according to claim 1, wherein the first liquid chamber contains liquid supplied from the liquid supply source and the circulation pump, and the first pressure adjusting means has a first adjustment mechanism for adjusting the pressure of the liquid supplied from the first liquid chamber to the supply channel.

3. The volume of the first liquid chamber changes according to the amount of liquid supplied from the liquid supply source and the circulation pump. The liquid discharge head according to claim 2, wherein the first adjustment mechanism adjusts the pressure of the liquid contained in the first liquid chamber in conjunction with the volume of the first liquid chamber.

4. The first adjustment mechanism is, The first valve chamber is connected to the first liquid chamber via the first communication port and supplies liquid supplied from the liquid supply source to the first liquid chamber via the first communication port, A liquid discharge head according to claim 2 or 3, comprising: a first valve that switches the first communication port between an open state and a closed state according to the volume of the first liquid chamber.

5. The liquid discharge head according to claim 4, wherein the first valve opens the first communication port when the volume of the first liquid chamber containing the liquid is less than a predetermined volume, and closes the first communication port when the volume of the first liquid chamber is equal to or greater than the predetermined volume.

6. The volume of the first liquid chamber changes due to the displacement of a flexible member formed in at least a part of the first liquid chamber. The first adjustment mechanism is, A biasing means for biasing the flexible member in a direction that expands the volume of the first liquid chamber, The first valve is displaced in accordance with the displacement of the flexible member, The liquid discharge head according to any one of claims 4 or 5, wherein the first valve is displaced to a position that opens the first communication port when the flexible member is displaced to a position where the volume of the first liquid chamber is less than a predetermined volume, and the first communication port is closed when the flexible member is displaced to a position where the volume of the first liquid chamber is greater than or equal to a predetermined volume.

7. The circulation path further comprises a second pressure regulating means fluidly connected to the first liquid chamber, the recovery channel, and the circulation pump, The liquid discharge head according to any one of claims 2 to 6, wherein the second pressure adjusting means comprises a second liquid chamber for containing liquid supplied from the first liquid chamber and the recovery channel, and a second adjusting mechanism for adjusting the pressure of the liquid supplied to the second liquid chamber.

8. The volume of the second liquid chamber changes according to the amount of liquid supplied from the liquid supply source and the circulation pump. The liquid discharge head according to claim 7, wherein the second adjustment mechanism adjusts the pressure of the liquid contained in the second liquid chamber in conjunction with the volume of the second liquid chamber.

9. The second adjustment mechanism is, A second valve chamber is connected to the second liquid chamber via a second communication port, and supplies liquid from the first liquid chamber and the recovery channel to the second liquid chamber via the second communication port, The system includes a second valve that switches the second communication port between an open state and a closed state according to the volume of the second liquid chamber, The liquid discharge head according to claim 8, wherein the second valve opens the second communication port when the volume of the second liquid chamber containing the liquid is less than a predetermined volume, and closes the second communication port when the volume of the second liquid chamber is equal to or greater than the predetermined volume.

10. The liquid discharge head according to any one of claims 7 to 9, wherein each of the first liquid chamber and the second liquid chamber has a discharge port for discharging the liquid contained therein, located below the first liquid chamber and the second liquid chamber in the direction of gravity.

11. The liquid discharge head according to any one of claims 2 to 10, further comprising a second supply channel that connects the upper part of the first liquid chamber with the supply channel.

12. A liquid discharge head according to any one of claims 1 to 11, having an electrical connection terminal capable of applying at least the drive voltage of the circulation pump from an external power source.

13. The liquid discharge head according to any one of claims 1 to 12, wherein the circulation pump is a piezoelectric pump having a pump chamber to which liquid is supplied and a piezoelectric element that is displaced so as to change the volume of the pump chamber when a driving voltage is applied.

14. The liquid discharge head according to claim 13, wherein an AC voltage having a phase difference is applied to the piezoelectric element as a driving voltage.

15. A liquid discharge head according to any one of claims 1 to 14, comprising a filter provided between the circulation path and the liquid supply source for filtering the liquid supplied from the liquid supply source.

16. The liquid dispensing head according to claim 15, wherein the filter is arranged along the direction of gravity.

17. A liquid dispensing device comprising: a liquid dispensing head according to any one of claims 1 to 16; a liquid supply source for supplying liquid to the liquid dispensing head; and a transport means for transporting a recording medium at a position opposite the discharge port of the liquid dispensing head.

18. The liquid dispensing device according to claim 17, wherein the liquid dispensing head is detachably mounted on a carriage that moves along a main scanning direction intersecting the direction in which the recording medium is transported by the transport means, and dispensing liquid from the dispensing port while moving together with the carriage in the main scanning direction to perform recording.

19. The carriage has a first electrical connection part that is electrically connected to a power supply, The liquid dispensing device according to claim 18, wherein the liquid dispensing head has a second electrical connection that is connected to the first electrical connection by being mounted on the carriage.

20. The liquid dispensing device according to claim 19, wherein the liquid dispensing head is supplied with power to generate liquid dispensing energy by the dispensing element and the driving voltage for the circulation pump from the power supply via the first electrical connection and the second electrical connection.

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