Recording device and control method for the same, program, and storage medium

Abstract

To suppress an influence given by ink concentration to ink discharge.SOLUTION: A recorder includes: an ink discharge head including a plurality of discharge ports discharging a plurality of kinds of ink respectively and a plurality of circulation paths for circulating the ink between the plurality of discharge ports and a plurality of liquid chambers housing the plurality of kinds of ink; and circulating means circulating the ink in the plurality of circulation paths. The circulating means controls in which of the plurality of circulation paths the ink should be circulated by the circulating means on the basis of recording data.SELECTED DRAWING: Figure 25

Description

[Technical field]

[0001] The present invention relates to a printing apparatus that circulates ink in a circulation path that includes a print head. [Background technology]

[0002] In inkjet recording devices that use aqueous ink, when the water in the ink evaporates from the nozzles of the print head, the viscosity of the ink near the ejection ports increases, causing various problems when ejecting the ink from the nozzles.

[0003] To address this issue, a method has been known in which two flow paths are formed in the nozzle, and ink is circulated between the liquid chamber in the head and the nozzle, removing ink that has thickened due to evaporation of water near the nozzle and replacing it with ink that has not evaporated. However, when considering the entire circulation flow path, evaporation of water from the nozzle progresses, so the amount of water in the circulation flow path gradually decreases, resulting in the problem of ink concentration.

[0004] Therefore, Patent Document 1 describes a technology for circulating ink only for the colors that are ejected in image formation. Specifically, during monochrome mode recording, only black ink is circulated, and color inks are not circulated, thereby suppressing concentration of color inks due to evaporation of moisture. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-121784 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when controlling ink not used in image formation so as not to circulate, the viscosity of the ink increases due to the progress of water evaporation in the vicinity of the nozzles, and even if an attempt is made to circulate the ink again, the thickened ink may not flow from the nozzles. In particular, in unused nozzle rows in the same chip as the nozzle rows used in image formation, the temperature of the ink increases due to heat retention control and temperature rise caused by ejection. This promotes water evaporation and causes an early increase in viscosity. In such cases, not only will ink ejection problems occur, but even if an attempt is made to circulate the ink, it may not be possible to recirculate the thickened ink in the nozzles.

[0007] The present invention has been made in view of the above-mentioned problems, and has an object to suppress the effect of ink concentration on ink ejection. [Means for solving the problem]

[0008] The recording device of the present invention is characterized in that it comprises an ink ejection head having a plurality of ejection ports each ejecting a plurality of types of ink, and a plurality of circulation paths for circulating ink between the plurality of ejection ports and a plurality of liquid chambers each containing the plurality of types of ink, a circulation means for circulating ink in the plurality of circulation paths, and a control means for controlling, based on recording data, which of the plurality of circulation paths the ink is circulated through by the circulation means. Effect of the Invention

[0009] According to the present invention, it is possible to suppress the influence of ink concentration on ink ejection. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a liquid ejection device. [Diagram 2] FIG. [Diagram 3] FIG. 2 is a perspective view of a liquid ejection head. [Figure 4]FIG. 1 is an exploded perspective view showing a liquid ejection head; [Diagram 5] 2A and 2B are a longitudinal section of a liquid ejection head and an enlarged cross-sectional view of an ejection module [Figure 6] FIG. 1 is a schematic view showing the appearance of a circulation unit; [Figure 7] FIG. [Figure 8] FIG. 2 is a block diagram showing a schematic diagram of a circulation path. [Figure 9] FIG. 4 is a cross-sectional view showing an example of a pressure adjusting means. [Figure 10] FIG. 2 is an external perspective view of a circulation pump. [Figure 11] 9 is a cross-sectional view of the circulating pump shown in FIG. 8(a) taken along line IX-IX. [Figure 12] 3A and 3B are diagrams illustrating the flow of ink in a liquid ejection head. [Figure 13] FIG. 4 is a schematic diagram showing a circulation path in the discharge unit. [Figure 14] FIG. 3 shows an aperture plate 330. [Figure 15] FIG. 2 is a diagram showing a discharge element substrate. [Figure 16] 5A and 5B are cross-sectional views showing the ink flow in the ejection unit. [Figure 17] FIG. 4 is a cross-sectional view showing the vicinity of a discharge port. [Figure 18] FIG. 11 is a cross-sectional view showing a comparative example near the ejection port. [Figure 19] 11A and 11B are diagrams showing a comparative example of a discharge element substrate. [Figure 20] FIG. 2 is a diagram showing a flow path configuration of a liquid ejection head. [Figure 21] FIG. 4 is a schematic diagram showing a state of ink concentration in the vicinity of a nozzle. [Figure 22] 11 is a graph showing ink concentration in a circulation flow path versus elapsed time during a printing operation. [Figure 23] 1 is a graph of the discharge rate of concentrated ink. [Figure 24] 2 is a table showing the correspondence between recording conditions and inks to be used. [Figure 25] 13 is a flowchart showing a circulation determination process during a recording operation. [Figure 26] 11 is a flowchart of recovery determination before the start of a recording operation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A preferred embodiment of the present disclosure will be described in detail below with reference to the accompanying drawings. The following embodiments do not limit the disclosed matters, and not all combinations of features described in the present embodiment are necessarily essential to the solving means of the present disclosure. The same components are given the same reference numbers. In this embodiment, an example is described in which a thermal method is adopted in which an electrothermal conversion element generates bubbles to eject liquid as an ejection element for ejecting liquid, but this is not limited thereto. The present invention can also be applied to a liquid ejection head that employs an ejection method that ejects liquid using a piezoelectric element (piezo) or another ejection method. Furthermore, the pump and pressure adjustment means described below are not limited to the configurations described in the embodiments and drawings, and it is also possible to apply those having equivalent functions.

[0012] <Liquid discharge device> Fig. 1 is a diagram illustrating a liquid ejection device. First, a schematic configuration of a liquid ejection device 50 in this embodiment will be described with reference to Fig. 1. Fig. 1(a) is a perspective view that shows a liquid ejection device that uses a liquid ejection head 1. The liquid ejection device 50 in this embodiment constitutes a serial type inkjet recording device that performs recording on a recording medium P by ejecting ink as a liquid while scanning the liquid ejection head 1.

[0013] The configuration of this inkjet recording device and its operation during recording will be described with reference to Fig. 1. First, a recording medium P is conveyed in the Y direction from a spool 106 holding the recording medium P by a conveying roller driven via gears by a conveying motor 104. Meanwhile, at a predetermined conveying position, a carriage motor 103 (see Fig. 1(b)) causes a carriage 60 to perform reciprocating scanning (reciprocating movement) in the X direction along a guide shaft 108 extending in the X direction.

[0014] The recording medium P is transported by a transport roller in a sub-scanning direction (Y direction) that intersects (orthogonal in this example) the main scanning direction. In each of the figures referred to below, the Z direction indicates the vertical direction, and intersects (orthogonal in this example) the XY plane defined by the X and Y directions. The liquid ejection head 1 is configured so that it can be removed from and attached to the carriage 60 by the user.

[0015] During the scanning process of the carriage 60, the nozzles of the liquid ejection head 1 are ejected at a timing based on a position signal obtained by the encoder 107, and a certain bandwidth corresponding to the nozzle arrangement range is recorded. After that, the recording medium P is transported, and the next bandwidth is recorded.

[0016] The fed recording medium P is sandwiched between a feed roller and a pinch roller and guided to a recording position (scanning area of ​​the liquid ejection head 1) on the platen 57. Normally, in a resting state, the face of the liquid ejection head 1 is capped by a cap 61 provided in the recovery unit 23 (see FIG. 2), so prior to recording, the cap is opened to make the liquid ejection head 1 or carriage 60 ready for scanning. Thereafter, when data for one scan is accumulated in the buffer, the carriage 60 is scanned by the carriage motor 103, and recording is performed as described above.

[0017] A carriage belt (not shown) can be used to transmit the driving force from the carriage motor 103 to the carriage 60. However, instead of the carriage belt, it is also possible to use other driving methods, such as a method including a lead screw that is rotationally driven by the carriage motor 103 and extends in the X direction, and an engagement portion that is provided on the carriage 60 and engages with a groove in the lead screw.

[0018] Furthermore, ink is supplied to the liquid ejection head 1 from an ink tank 2 (see FIG. 8) mounted inside the main body or on an external unit through an ink supply tube 59 via a carriage 60. Ink may be supplied from the ink tank 2 to the liquid ejection head 1 using a pressurizing unit, or ink may be supplied by capping the nozzle surface of the liquid ejection head 1 with a cap of the recovery unit 23 and applying negative pressure to the inside of the cap with a suction pump to suck the ink.

[0019] Furthermore, the carriage may be equipped with one liquid ejection head 1 or multiple liquid ejection heads capable of ejecting ink of multiple colors, or a single liquid ejection head 1 capable of ejecting ink of multiple colors may be mounted on the carriage.

[0020] In the description of this embodiment, the position in the X direction where the liquid ejection head 1 is capped during non-printing operation is called the reference side, and the direction in which it moves from the cap position during printing operation is called the non-reference side.

[0021] The liquid ejection head 1 includes a circulation unit 54 and an ejection unit 3 (see FIG. 4) described later. The specific configuration will be described later, but the ejection unit 3 is provided with a plurality of ejection ports and energy generating elements (hereinafter referred to as ejection elements) that generate ejection energy for ejecting liquid from each ejection port.

[0022] The liquid ejection device 50 is also provided with an ink tank 2, which is an ink supply source, and an external pump 21, and 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.

[0023] The liquid ejection head 1 is provided with a circulation unit 54 according to the type of liquid to be ejected. A plurality of circulation units 54 may be provided for the same type of liquid. That is, the liquid ejection head 1 can be configured to include one or more circulation units. The liquid ejection head 1 shown in FIG. 1(a) is a so-called serial type liquid ejection head that ejects ink while moving in the main scanning direction, but is not limited to this. The liquid ejection head may be a so-called full-line type liquid ejection head in which ejection ports are formed over the entire width of the recording medium P and ejection is possible over the entire width of the recording medium P without movement in the main scanning direction.

[0024] FIG. 1B is a block diagram showing a control system of the liquid ejection device 50. The CPU 100 functions as a control means for controlling the operation of each part of the liquid ejection device 50 based on a program such as a processing procedure stored in the ROM 101. The ROM 101 also stores multi-value gradation data of an intermediate product and a multi-pass mask. The RAM 102 is used as a work area when the CPU 100 executes processing. The CPU 100 receives image data from a host device 400 outside the liquid ejection device 50, controls a head driver 1A, and controls the driving of ejection elements provided in the liquid ejection head 1. The CPU 100 also controls drivers of various actuators provided in the liquid ejection device 50. For example, the CPU 100 controls a motor driver 103A of a carriage motor 103 for moving the carriage 60, a motor driver 104A of a conveyance motor 104 for conveying the recording medium P, and the like. Furthermore, the CPU 100 controls a pump driver 500A that drives the circulation pump 500 described below, a pump driver 21A for the external pump 21, a motor driver 22A for the recovery unit motor 22, etc. The recovery unit motor 22 is a motor mounted on the recovery unit 23, and switches the units to be driven by a camshaft to operate the wiper guide 223 and the suction pump 213. Note that, although Fig. 1(b) shows a form in which processing is performed upon receiving image data from the host device 400, processing may also be performed by the liquid ejection device 50 without relying on data from the host device 400.

[0025] <Recovery Unit> FIG. 2 is a schematic diagram of the recovery unit 23 in this embodiment. The cap 61 is supported by a lifting mechanism (not shown) so that it can be raised and lowered, and moves between a raised position and a lowered position. At the raised position, the cap 61 comes into contact with the liquid ejection head 1 and covers (caps) the nozzle surface of the liquid ejection head 1. By covering the nozzle surface of the liquid ejection head 1, the cap 61 prevents the nozzles of the liquid ejection head 1 from drying and the ink from evaporating during non-recording operations. Alternatively, the cap 61 is used when ink is sucked from the liquid ejection head 1 by driving a suction pump 213 (described later). In addition, the cap 61 is located at a lowered position during recording operations to avoid interference with the liquid ejection head 1 that moves together with the carriage 60. When the cap 61 is located at the lowered position, the liquid ejection head 1 can perform preliminary ejection to the cap 61 when it moves to a position facing the cap 61.

[0026] The wipers (wiper blades) 221 and 222 are made of an elastic material such as rubber. In this embodiment, two wipers 221 each for wiping the nozzle surfaces of two chips, and a wiper 222 for wiping the entire nozzle orifice surface including the nozzle row are provided. The wipers 221 and 222 are fixed to a wiper holder 220. The wiper holder 220 can move in the front-rear direction (the direction in which the nozzles are arranged in the liquid ejection head 1) in the figure indicated by an arrow W along a wiper guide 223. When the liquid ejection head 1 is positioned at the standby position, the wiper holder 220 moves in the direction of the arrow W (one direction), so that the wipers 221 and 222 can perform a wiping operation in which the wipers wipe the nozzle surface while contacting the nozzle surface. When the wiping operation is completed, the carriage 60 is moved and withdrawn from the area where the wiping operation is performed, and then the wiper holder 220 is moved to return the wipers 221 and 222 to their original positions (the positions before the wiping operation).

[0027] In this embodiment, the wiper is made of an elastic material such as rubber, but may be made of a porous material that absorbs ink. A vacuum wiper configuration capable of sucking the nozzle surface may also be used. In this embodiment, wiping is performed only when the wiper moves in one direction, but the wiper may be configured to perform wiping when it moves back and forth in both directions. In this embodiment, the wiping direction is the direction in which the nozzles are arranged in the liquid ejection head 1, but the wiper may be configured to move in a direction intersecting (orthogonal to) that direction (a direction intersecting with the arrangement direction of the nozzle rows). In this configuration, the wiper may be fixed and the carriage 60 may move in the scanning direction to wipe the nozzle surface. In addition, in a configuration in which multiple wiping members or wiping in different wiping directions are used, the positions of the recovery units may be arranged separately. In that case, the recovery unit may be arranged separately near the standby position of the carriage unit and on the opposite side across the recording medium.

[0028] The suction pump 213 is driven with the cap 61 covering the nozzle surface of the liquid ejection head 1 to make the inside a substantially sealed space, and generates a negative pressure inside to perform a suction operation to suck ink from the liquid ejection head 1. This suction operation is performed when filling the liquid ejection head 1 with ink from the ink tank 2 (initial filling) and when sucking and removing dust, stuck matter, air bubbles, etc. from inside the nozzles (suction recovery). The cap 61 is connected to a waste ink absorber (not shown) via a flexible tube 58.

[0029] In this embodiment, a tube pump is used as the suction pump 213. The tube pump has a holding section formed with a curved surface section along which the tube 58 (at least a part of the tube 58) is held, a roller capable of pressing the held tube 58, and a roller support section rotatably supporting the roller. The tube pump rotates the roller support section in a predetermined direction to rotate the roller while squashing the tube 58. This generates negative pressure inside the cap 61, and ink is sucked from the liquid ejection head 1. The sucked ink is discharged to the waste ink absorber through the tube 58. The suction operation is also performed when preliminary ejection is performed on the cap 61 by the liquid ejection head 1, and ink received in the cap 61 by the preliminary ejection is discharged. That is, when the ink held in the cap 61 after preliminary ejection reaches a predetermined amount, the suction pump 213 is driven to discharge the ink held in the cap 61 through the tube 58 to the waste ink absorber.

[0030] <Basic configuration of liquid ejection head> 3 is a diagram showing the configuration of the liquid ejection head 1 in this embodiment. In this embodiment, the liquid ejection head is configured with one liquid ejection head 110 capable of recording six colors of ink (multiple types of ink) and two liquid ejection heads 111 capable of recording three colors of ink (multiple types of ink), for a total of three liquid ejection heads. The liquid ejection heads in this embodiment are arranged as follows, from the reference side in the scanning direction: liquid ejection heads 111, 110, 111. For the sake of distinction, the liquid ejection head on the reference side in the scanning direction will be referred to as 111R, and the liquid ejection head on the non-reference side will be referred to as 111L.

[0031] As for the arrangement of the inks, the liquid ejection head 111L has primers arranged for all three colors, and three buffer tanks 401PR are provided. The central liquid ejection head 110 has color inks arranged in the order of light magenta, light cyan, yellow, magenta, cyan, and black from the reference side, and independent buffer tanks 401LM, 401LC, 401Y, 401M, 401C, and 401BK are provided for the six colors of ink. The liquid ejection head 111R has buffer tanks 401GY, 401GR, and 401OR for the three colors of ink, gray, green, and orange from the reference side. Note that, for the sake of explanation, the buffer tanks are shown in FIG. 3 so that they can be seen, but the buffer tanks are stored inside the liquid ejection head. The arrangement of the liquid ejection heads and the inks is not limited, and the number of ink colors arranged in one liquid ejection head does not have to be three, and the color arrangement does not have to be as shown in the example of this embodiment.

[0032] On the underside of the liquid ejection heads 110 and 111, chips 403 are arranged on which nozzle rows corresponding to the respective inks are formed. The chip 403 has two rows of 1024 nozzles 402 arranged at intervals of 1200 dpi per color, making it possible to eject three colors with one chip. The liquid ejection head 110 is capable of recording six colors by arranging two chips 403, while the liquid ejection head 111 is capable of recording three colors by arranging one chip 403. Note that the nozzle rows for one color do not need to be arranged on the same line, and may be arranged alternately one by one, with a total of four rows of 512 nozzle rows arranged at intervals of 600 dpi.

[0033] Fig. 4 is an exploded perspective view showing the liquid ejection head 1 of this embodiment. Fig. 5 is a vertical cross-sectional view of the liquid ejection head 1. Fig. 5(a) is an overall vertical cross-sectional view of the liquid ejection head 1, and Fig. 5(b) is an enlarged view of the ejection module shown in Fig. 5(a). The liquid ejection head 1 of this embodiment will be described below mainly with reference to Fig. 4 and Fig. 5, and also with reference to Fig. 1 as appropriate.

[0034] 4, the liquid ejection head 1 includes a circulation unit 54 and an ejection unit 3 for ejecting ink supplied from the circulation unit 54 onto a recording medium P. The liquid ejection head 1 in this embodiment is fixedly supported on a carriage 60 of the liquid ejection device 50 by positioning means and electrical contacts (not shown) provided on the carriage 60. The liquid ejection head 1 ejects ink while moving together with the carriage 60 in the main scanning direction (X direction) shown in FIG. 1, and performs recording on the recording medium P.

[0035] An ink supply tube 59 is provided on the external pump 21 connected to the ink tank 2 serving as the ink supply source (see FIG. 1). A liquid connector (not shown) is provided on the tip of the ink supply tube 59. When the liquid ejection head 1 is mounted on the liquid ejection device 50, the liquid connector provided on the tip of the ink supply tube 59 is airtightly connected to a liquid connector insertion port (not shown) provided on the head housing 53 of the liquid ejection head 1. This forms an ink supply path from the ink tank 2 to the liquid ejection head 1 via the external pump 21. In this embodiment, since four types of ink are used, four sets of the ink tank 2, the external pump 21, the ink supply tube 59, and the circulation unit 54 are provided corresponding to each ink, and four ink supply paths corresponding to each ink are independently formed. In this way, the liquid ejection device 50 of this embodiment is provided with an ink supply system to which ink is supplied from the ink tank 2 provided outside the liquid ejection head 1. Note that the liquid ejection device 50 of this embodiment is not provided with an ink recovery system that recovers the ink in the liquid ejection head 1 to the ink tank 2.

[0036] 5, 54B indicates a circulation unit for black ink, 54C indicates a circulation unit for cyan ink, 54M indicates a circulation unit for magenta ink, and 54Y indicates an ink circulation unit for yellow ink. Each circulation unit has substantially the same configuration, and in this embodiment, when there is no need to distinguish between the circulation units, they will be referred to as circulation unit 54.

[0037] In Fig. 4 and Fig. 5(a), the discharge unit 3 includes two discharge modules 300, a first support member 4, a second support member 7, an electric wiring member (electric wiring tape) 5, and an electric contact substrate 6. As shown in Fig. 5(b), the discharge module 300 includes a silicon substrate 310 having a thickness of 0.5 to 1 mm, and a plurality of discharge elements 15 provided on one side of the silicon substrate 310. In this embodiment, the discharge elements 15 are configured by electrothermal conversion elements (heaters) that generate thermal energy as discharge energy for discharging liquid. Electric power is supplied to each discharge element 15 via electric wiring formed on the silicon substrate 310 by a film formation technique.

[0038] Further, an ejection port forming member 320 is formed on the surface (lower surface in FIG. 5(b)) of the silicon substrate 310. In the ejection port forming member 320, a plurality of pressure chambers 12 corresponding to a plurality of ejection elements 15 and a plurality of ejection ports 13 for ejecting ink are formed by photolithography. Furthermore, in the silicon substrate 310, an individual supply flow path 18 and an individual recovery flow path 19 communicating with each pressure chamber 12 are formed. In this embodiment, one ejection module 300 is configured to eject two types of ink. That is, of the two ejection modules shown in FIG. 5(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. Furthermore, in the example shown in FIG. 5, two ejection port rows extending in the Y direction are formed for one color of ink. For each of the plurality of ejection ports 13 constituting each ejection port row, a pressure chamber 12, an individual supply flow path 18, and an individual recovery flow path 19 are formed.

[0039] An ink supply port and an ink recovery port, which will be described later, are formed on the back surface (upper surface in FIG. 5(b)) of the silicon substrate 310. The ink supply port supplies ink from an ink supply flow path 48 to the multiple individual supply flow paths 18, and the ink recovery port recovers ink from the multiple individual recovery flow paths 19 to an ink recovery flow path 49.

[0040] The ink supply port and ink recovery port referred to here refer to openings that supply and recover ink during forward ink circulation, which will be described later. That is, during forward ink circulation, ink is supplied from the ink supply port to each individual supply flow path 18, and ink is recovered from each individual recovery flow path 19 to the ink recovery port. However, during ink circulation in a direction opposite to the forward direction, ink is supplied from the ink recovery port described above to the individual recovery flow path 19, and ink is recovered from the individual supply flow path 18 to the ink supply port.

[0041] As shown in FIG. 5(a), the back surface (upper surface in FIG. 5(a)) of the ejection module 300 is adhesively fixed to one surface (lower surface in FIG. 5(a)) of the first support member 4. An ink supply flow path 48 and an ink recovery flow path 49 are formed in the first support member 4, penetrating from one surface to the other surface. One opening of the ink supply flow path 48 is connected to the aforementioned ink supply port in the silicon substrate 310, and one opening of the ink recovery flow path 49 is connected to the aforementioned ink recovery port in the silicon substrate 310. The ink supply flow path 48 and the ink recovery flow path 49 are provided independently for each type of ink.

[0042] A second support member 7 having an opening 7a (see FIG. 4) through which the ejection module 300 is inserted is adhesively fixed to the other surface (upper surface in FIG. 5(a)) of the first support member 4. The second support member 7 holds an electrical wiring member 5 that is electrically connected to the ejection module 300. The electrical wiring member 5 is a member for applying an electrical signal to the ejection module 300 to eject ink. The electrical connection portion between the ejection module 300 and the electrical wiring member 5 is sealed with a sealant and is protected from corrosion by ink and external impacts.

[0043] Furthermore, an electrical contact board 6 is thermocompression bonded to an end 5a (see FIG. 4) of the electrical wiring member 5 using an anisotropic conductive film (not shown), and the electrical wiring member 5 and the electrical contact board 6 are electrically connected to each other. The electrical contact board 6 has an external signal input terminal (not shown) for receiving an electrical signal from the liquid ejection device 50.

[0044] Furthermore, a joint member 8 (FIG. 5(a)) is provided between the first support member 4 and the circulation unit 54. A supply port 88 and a recovery port 89 are formed in the joint member 8 for each type of ink. The supply port 88 and the recovery port 89 serve to communicate the ink supply flow path 48 and the ink recovery flow path 49 of the first support member 4 with the flow paths formed in the circulation unit 54. In FIG. 5(a), the supply port 88B and the recovery port 89B correspond to black ink, and the supply port 88C and the recovery port 89C correspond to cyan ink. Furthermore, the supply port 88M and the recovery port 89M correspond to magenta ink, and the supply port 88Y and the recovery port 89Y correspond to yellow ink.

[0045] The openings at one end of the ink supply flow path 48 and the ink recovery flow path 49 of the first support member 4 have a small opening area that matches the ink supply port and ink recovery port in the silicon substrate 310. In contrast, the opening areas of the openings at the other end of the ink supply flow path 48 and the ink recovery flow path 49 of the first support member 4 have a shape that is expanded 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 an increase in flow path resistance for the ink collected from each recovery flow path.

[0046] In the liquid ejection head 1 having the above configuration, ink supplied to the circulation unit 54 passes through the supply port 88 of the joint member 8 and the supply flow path 48 of the first support member 4, and flows from the ink supply port of the ejection module 300 into the individual supply flow path 18. The ink then flows from the individual supply flow path 18 into the pressure chamber 12, and a portion of the ink that has flowed into the pressure chamber 12 is ejected from the ejection port 13 by driving the ejection element 15. The remaining ink that has not been ejected passes from the pressure chamber 12 through the individual recovery flow path 19 and flows from the ink recovery port into the recovery flow path 49 of the first support member 4. The ink that has flowed into the recovery flow path 49 then flows into the circulation unit 54 through the recovery port 89 of the joint member 8 and is recovered.

[0047] <Components of the circulation unit> 6 is a schematic external view of one circulation unit 54 corresponding to one type of ink applied to the recording apparatus of this embodiment. The circulation unit 54 includes a filter 110, a first pressure adjustment means 120, a second pressure adjustment means 150, and a circulation pump 500. These components are connected by respective flow paths as shown in FIGS. 7 and 8, and form a circulation path in the liquid ejection head 1 for supplying and recovering ink to and from the ejection module 300.

[0048] <Circulation path inside the liquid ejection head> FIG. 7 is a vertical cross-sectional view showing a circulation path of one type of ink (ink of one color) formed in the liquid ejection head 1. FIG. 8 is a block diagram showing the circulation path shown in FIG. 7. As shown in FIGS. 7 and 8, 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 certain pressure range is realized in the circulation path. In addition, the ink is configured to flow near the pressure chamber 12 (ejection element 15) at a flow rate according to the pressure difference between the first pressure adjustment means 120 and the second pressure adjustment means 150. Hereinafter, the circulation path in the liquid ejection head 1 and the flow of ink in the circulation path will be described with reference to FIGS. 7 and 8. The arrows in each figure indicate the direction of ink flow.

[0049] First, the connection state of each component of the liquid ejection head 1 will be described. An external pump 21 that sends ink contained in an ink tank 2 (FIG. 8) provided 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 (FIG. 1). A filter 110 is provided in the ink flow path located upstream of the circulation unit 54. An ink supply path located downstream of the filter 110 is connected to a first valve chamber 121 of a first pressure adjustment means 120. The first valve chamber 121 communicates with a first pressure control chamber 122 via a communication port 191A that is opened and closed by a valve 190A shown in FIG.

[0050] The first pressure control chamber 122 is connected to the supply flow path 130, the bypass flow path 160, and the pump outlet flow path 180 of the circulation pump 500. The supply flow path 130 is connected to the individual supply flow paths 18 via the ink supply port provided in the ejection module 300. In addition, the bypass flow path 160 is connected to a second valve chamber 151 provided in the second pressure adjustment means 150. The second valve chamber 151 is connected to the second pressure control chamber 152 via a communication port 191B that is opened and closed by a valve 190B shown in FIG.

[0051] The second pressure control chamber 152 is connected to the recovery passage 140. The recovery passage 140 is connected to the individual recovery passage 19 via the ink recovery port provided in the ejection module 300. Furthermore, the second pressure control chamber 152 is connected to the circulation pump 500 via a pump inlet passage 170. In addition, in FIG. 7, 170a indicates the inlet of the pump inlet passage 170.

[0052] Next, a description will be given of the flow of ink in the liquid ejection head 1 having the above configuration. As shown in Fig. 8, the ink stored in the ink tank 2 is pressurized by an external pump 21 provided in the liquid ejection device 50, and is supplied to the circulation unit 54 of the liquid ejection head 1 as a positive pressure ink flow.

[0053] The ink supplied to the circulation unit 54 passes through a filter 110 to remove foreign matter such as dust, and then flows into a first valve chamber 121 provided in a first pressure adjustment means 120. At this time, the ink is depressurized from a positive pressure to a negative pressure.

[0054] Next, the flow of ink in the circulation path will be described. The circulation pump 500 operates to send ink sucked from the pump inlet flow path 170 on the upstream side to the pump outlet flow path 180 on the downstream side. Therefore, when the pump is driven, the ink supplied to the first pressure control chamber 122 flows into the supply flow path 130 and the bypass flow path 160 together with the ink sent from the pump outlet flow path 180. Note that, although details will be described later, in this embodiment, a piezoelectric diaphragm pump using a piezoelectric element attached to a diaphragm as a driving source is used as the circulation pump. The piezoelectric diaphragm pump is a pump that changes the volume of the pump chamber by inputting a driving voltage to the piezoelectric element, and sends liquid by alternately moving two check valves due to pressure fluctuations.

[0055] The ink that has flowed into the supply flow path 130 flows from the ink supply port of the ejection module 300 through the individual supply flow path 18 into the pressure chamber 12, and some of the ink is supplied to the ejection port 13 and ejected from the ejection port 13 by driving (heat generation) the ejection element 15. The remaining ink that is not used for ejection flows through the pressure chamber 12, passes through the individual recovery flow path 19, and then flows into the recovery flow path 140 connected to the ejection module 300. The ink that has flowed into the recovery flow path 140 flows into the second pressure control chamber 152 of the second pressure adjustment means 150.

[0056] On the other hand, the ink that has flowed into the bypass flow path 160 flows into the second valve chamber 151, and 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 flow path 160 and the ink that has been recovered from the recovery flow path 140 are sucked into the circulation pump 500 via the pump inlet flow path 170 by the operation of the circulation pump 500. Then, the ink that has been sucked into the circulation pump 500 is sent to the pump outlet flow path 180 and flows into the first pressure control chamber 122 again. Thereafter, the ink that has flowed into the second pressure control chamber 152 from the first pressure control chamber 122 via the supply flow path 130 via the ejection module 300 and the ink that has flowed into the second pressure control chamber 152 via the bypass flow path 160 flows into the circulation pump 500. Then, the ink is sent from the circulation pump 500 to the first pressure control chamber 122. In this manner, the ink is circulated in the circulation path.

[0057] As described above, the circulation pump 500 provided in the liquid ejection head 1 makes it possible to circulate the liquid along a circulation path including the ejection module 300. This makes it possible to suppress thickening of the ink and deposition of the ink sedimentation components of the coloring material in the ejection module 300, and makes it possible to maintain good ink fluidity in the ejection module 300 and ejection characteristics at the ejection ports. In addition, since there is no need to circulate outside the liquid ejection head 1, a small pump can be used as the circulation pump 500, making it possible to miniaturize the device.

[0058] <Pressure Adjustment Means> 9 is a diagram showing an example of pressure adjustment means. The configuration and operation of the pressure adjustment means (first pressure adjustment means 120, second pressure adjustment means 150) built into the liquid ejection head 1 described above will be described in more detail with reference to FIG. 9. Since the first pressure adjustment means 120 and the second pressure adjustment means 150 have the same configuration, the first pressure adjustment means 120 will be taken as an example for description below, and the second pressure adjustment means 150 will only be described with reference numerals corresponding to the first pressure adjustment means in FIG. 9. In the case of the second pressure adjustment means 150, the first valve chamber 121 described below will be read as the second valve chamber 151, and the first pressure control chamber 122 will be read as the second pressure control chamber 152.

[0059] The first pressure adjustment means 120 has a first valve chamber 121 and a first pressure control chamber 122 formed in a cylindrical housing 125. The first valve chamber 121 and the first pressure control chamber 122 are separated by a partition wall 123 provided in the cylindrical housing 125. However, the first valve chamber 121 communicates with the first pressure control chamber 122 through a communication port 191 formed in the partition wall 123. The first valve chamber 121 is provided with a valve 190 that switches between communication and blocking between the first valve chamber 121 and the first pressure control chamber 122 at the communication port 191. The valve 190 is held at a position facing the communication port 191 by a valve spring 200, and has a configuration that allows it to come into close contact with the partition wall 123 by the biasing force of the valve spring 200. When the valve 190 comes into close contact with the partition wall 123, the flow of ink through the communication port 191 is blocked. In order to increase the close contact with the partition 123, it is preferable that the portion of the valve 190 that comes into contact with the partition 123 is made of an elastic material. A valve shaft 190a that is inserted into the communication port 191 protrudes from the center of the valve 190. By pressing this valve shaft 190a against the biasing force of a valve spring 200, the valve 190 moves away from the partition 123, allowing ink to flow through the communication port 191. Hereinafter, the state in which the valve 190 blocks the flow of ink through the communication port 191 is referred to as the "closed state," and the state in which ink can flow through the communication port 191 is referred to as the "open state."

[0060] The opening of the cylindrical housing 125 is closed by the flexible member 230 and the pressure plate 210. The first pressure control chamber 122 is formed by the flexible member 230, the pressure plate 210, the peripheral wall of the housing 125, and the partition wall 123. The pressure plate 210 is configured to be displaceable in accordance with the displacement of the flexible member 230. The materials of the pressure plate 210 and the flexible member 230 are not particularly limited, but for example, the pressure plate 210 can be configured from a resin molded part, and the flexible member 230 can be configured from a resin film. In this case, the pressure plate 210 can be fixed to the flexible member 230 by thermal welding.

[0061] A pressure adjustment spring 220 is provided between the pressure plate 210 and the partition wall 123. The pressure plate 210 and the flexible member 230 are biased by the biasing force of the pressure adjustment spring 220 in a direction in which the internal volume of the first pressure control chamber 122 expands. 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 in which the internal volume of the first pressure control chamber 122 decreases. When the internal volume of the first pressure control chamber 122 decreases to a certain amount, the pressure plate 210 abuts against the valve shaft 190a of the valve 190. When the internal volume of the first pressure control chamber 122 further decreases thereafter, 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 opened.

[0062] In this embodiment, the connection in the circulation path is set so that the pressure in the first valve chamber 121 when the communication port 191 is in the open state is higher than the pressure in the first pressure control chamber 122. As a result, when the communication port 191 is in the open state, ink flows from the first valve chamber 121 to the first pressure control chamber 122. This ink inflow displaces the flexible member 230 and the pressure plate 210 in a direction in which the internal volume of the first pressure control chamber 122 increases. As a result, the pressure plate 210 moves away from the valve shaft 190a of the valve 190, and the communication port 191 is brought into close contact with the partition wall 123 by the biasing force of the valve spring 200, and the communication port 191 is in a closed state.

[0063] In this manner, in the first pressure adjustment means 120 of this embodiment, when the pressure in the first pressure control chamber 122 decreases to a certain pressure or below (for example, when the negative pressure becomes stronger), ink flows in from the first valve chamber 121 via the communication port 191. This prevents the pressure in the first pressure control chamber 122 from decreasing any further. Therefore, the pressure in the first pressure control chamber 122 is controlled to be kept within a certain range.

[0064] Next, the pressure in the first pressure control chamber 122 will be described in more detail. Consider a state in which the flexible member 230 and the pressure plate 210 are displaced in response to the pressure in the first pressure control chamber 122 as described above, and the pressure plate 210 comes into contact with the valve shaft 190a, opening the communication port 191 (the state shown in FIG. 9(b)). At this time, the relationship of the forces acting on the pressure plate 210 is expressed by the following equation 1.

[0065] P2×S2+F2+(P1-P2)×S1+F1=0...Equation 1 Furthermore, rearranging Equation 1 for P2 gives P2=-(F1+F2+P1×S1) / (S2-S1)...Equation 2 It becomes.

[0066] P1: Pressure (gauge pressure) of the first valve chamber 121 P2: Pressure (gauge pressure) of the first pressure control chamber 122 F1: Valve spring force 200 F2: Spring force of the pressure adjusting spring 220 S1: Pressure receiving area of ​​valve 190 S2: Pressure receiving area of ​​the pressure plate 210 Here, the spring force F1 of the valve spring 200 and the spring force F2 of the pressure adjustment spring 220 are positive (rightward in FIG. 9) in the direction pressing the valve 190 and the pressure plate 210. In addition, the pressure P1 in the first valve chamber 121 and the pressure P2 in the first pressure control chamber 122 are configured so that P1 satisfies the relationship P1≧P2.

[0067] The pressure P2 in the first pressure control chamber 122 when the communication port 191 is open is determined by formula 2, and when the communication port 191 is open, due to the relationship P1≧P2, ink flows from the first valve chamber 121 into the first pressure control chamber 122. As a result, the pressure P2 in the first pressure control chamber 122 does not decrease any further, and P2 is maintained within a certain pressure range.

[0068] On the other hand, as shown in FIG. 9(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 expressed by Equation 3.

[0069] P3×S3+F3=0...Equation 3 Now, rearrange Equation 3 for P3 as follows: P3 = -F3 / S3 Equation 4 It becomes.

[0070] F3: The spring force of the pressure adjusting spring 220 when the pressure plate 210 and the valve shaft 190a are not in contact with each other P3: pressure (gauge pressure) in the first pressure control chamber 122 when the pressure plate 210 and the valve shaft 190a are not in contact with each other S3: The pressure-receiving area of ​​the pressure plate 210 when the pressure plate 210 and the valve 190 are not in contact with each other Here, FIG. 9(c) shows a state in which the pressure plate 210 and the flexible member 230 are displaced to the right side of the figure to the limit of their displacement. The pressure P3 in the first pressure control chamber 122, the spring force F3 of the pressure adjustment spring 220, and the pressure receiving area S3 of the pressure plate 210 change according to the amount of displacement while the pressure plate 210 and the flexible member 230 are displaced to the state of FIG. 9(c). Specifically, when the pressure plate 210 and the flexible member 230 are in the left direction in FIG. 9 compared to FIG. 9(c), the pressure receiving area S3 of the pressure plate 210 becomes smaller, and the spring force F3 of the pressure adjustment spring 220 becomes larger. As a result, the pressure P3 in the first pressure control chamber 122 becomes smaller according to the relationship of Equation 4. Therefore, according to Equation 2 and Equation 4, the pressure in the first pressure control chamber 122 gradually increases from the state of FIG. 9(b) to the state of FIG. 9(c) (i.e., the negative pressure becomes weaker and approaches the positive pressure side). That is, from a state in which the communication port 191 is open, the pressure plate 210 and the flexible member 230 gradually displace to the right, and the pressure in the first pressure control chamber 122 gradually increases until the internal volume of the first pressure control chamber 122 finally reaches its limit of displacement. In other words, the negative pressure weakens.

[0071] <Circulation pump> Next, the configuration and operation of the circulation pump 500 built into the above-mentioned liquid ejection head 1 will be described in detail with reference to FIGS.

[0072] FIG. 10 is an external perspective view of the circulation pump 500. FIG. 10(a) is an external perspective view showing the front side of the circulation pump 500, and FIG. 10(b) is an external perspective view showing the rear side of the circulation pump 500. The outer shell of the circulation pump 500 is composed of a pump housing 505 and a cover 507 fixed to the pump housing 505. The pump housing 505 is composed of a housing body 505a and a flow path connecting member 505b 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 forms the pump supply hole 501, and the pair of through holes provided at the other position forms the pump discharge hole 502. The pump supply hole 501 is connected to a pump inlet flow path 170 which is connected to the second pressure control chamber 152, and the pump discharge hole 502 is connected to a pump outlet flow path 180 which is connected to the first pressure control chamber 122. Ink supplied from the pump supply hole 501 passes through a pump chamber 503 (see FIG. 11) which will be described later, and is discharged from the pump discharge hole 502.

[0073] FIG. 11 is a cross-sectional view of the circulation pump 500 shown in FIG. 10(a) taken along line IX-IX. A diaphragm 506 is joined to the inner surface of a 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 is connected to a pump supply hole 501 and a pump discharge hole 502 formed in the pump housing 505. A check valve 504a is provided in the middle of the pump supply hole 501, and a check valve 504b is provided in the middle of the pump discharge hole 502. Specifically, the check valve 504a is disposed in a space 512a formed in the middle of the pump supply hole 501 such that a part of the check valve 504a can move leftward in the figure. The check valve 504b is disposed in a space 512b formed in the middle of the pump discharge hole 502 such that a part of the check valve 504b can move rightward in the figure.

[0074] When diaphragm 506 is displaced to increase the volume of pump chamber 503 and reduce the pressure in pump chamber 503, check valve 504a moves away from the opening of pump supply hole 501 in space 512a (i.e., moves to the left in the figure). When valve 504a moves away from the opening of pump supply hole 501 in space 512a, it enters an open state that allows the flow of ink through pump supply hole 501. When diaphragm 506 is displaced to reduce the volume of pump chamber 503 and reduce the pressure in pump chamber 503, check valve 504a comes into close contact with the wall surface surrounding the opening of pump supply hole 501 and enters a closed state that blocks the flow of ink through pump supply hole 501.

[0075] On the other hand, when the pump chamber 503 is depressurized, the check valve 504b comes into close contact with the wall surface surrounding the opening of the pump housing 505 and enters a closed state in which it blocks the flow of ink through the pump discharge hole 502. When the pump chamber 503 is pressurized, the check valve 504b moves away from the opening of the pump housing 505 toward the space 512b (i.e., moves to the right in the figure), allowing the flow of ink through the pump discharge hole 502.

[0076] The material of each of the check valves 504a and 504b may be any material that can deform in response to the pressure in the pump chamber 503, and may be, for example, an elastic material such as EPDM or elastomer, or a film or thin plate such as polypropylene, but is not limited to these.

[0077] As described above, pump chamber 503 is formed by joining pump housing 505 and diaphragm 506. Therefore, the pressure in pump chamber 503 changes as diaphragm 506 deforms. For example, when diaphragm 506 is displaced toward pump housing 505 (displaced to the right in the figure) and the volume of pump chamber 503 decreases, the pressure in pump chamber 503 increases. As a result, check valve 504b arranged opposite pump discharge hole 502 opens, and ink in pump chamber 503 is discharged. At this time, check valve 504a arranged opposite pump supply hole 501 is in close contact with the wall surface surrounding pump supply hole 501, so that the backflow of ink from pump chamber 503 to pump supply hole 501 is suppressed.

[0078] Conversely, when the diaphragm 506 is displaced in the direction in which the pump chamber 503 expands, the pressure in the pump chamber 503 decreases. As a result, the check valve 504a arranged opposite the pump supply hole 501 opens, and ink is supplied to the pump chamber 503. At this time, the check valve 504b arranged in the pump discharge hole 502 comes into close contact with the wall surface surrounding the opening formed in the pump housing 505 to close the opening, thereby suppressing the backflow of ink from the pump discharge hole 502 to the pump chamber 503.

[0079] In this way, in the circulation pump 500, the diaphragm 506 deforms, changing the pressure in the pump chamber 503, thereby sucking in and discharging ink. At this time, if bubbles get into the pump chamber 503, even if the diaphragm 506 is displaced, the bubbles expand and contract, reducing the pressure change in the pump chamber 503 and decreasing the amount of liquid delivered. Therefore, the pump chamber 503 is arranged parallel to gravity to make it easier for bubbles that get into the pump chamber 503 to gather above the pump chamber 503, and the pump discharge hole 502 is arranged above the center of the pump chamber 503. This makes it possible to improve the discharge of bubbles in the pump and stabilize the flow rate.

[0080] <Ink flow inside the liquid ejection head> FIG. 12 is a diagram for explaining the flow of ink in the liquid ejection head. The circulation of ink in the liquid ejection head 1 will be explained with reference to FIG. 12. FIG. 12(a) is a schematic diagram showing the flow of ink when a recording operation is performed. The arrows in the figure indicate the flow of ink. In this embodiment, when a recording operation is performed, both the external pump 21 and the circulation pump 500 start to operate. The external pump 21 and the circulation pump 500 may be operated regardless of the recording operation. The external pump 21 and the circulation pump 500 do not have to be driven in conjunction with each other, and may be driven independently.

[0081] During the recording operation, the circulation pump 500 is ON (driven), and the ink flowing out from the first pressure control chamber 122 flows into the supply flow path 130 and the bypass flow path 160. The ink that flows into the supply flow path 130 passes through the ejection module 300, then flows into the recovery flow path 140, and is then supplied to the second pressure control chamber 152.

[0082] On the other hand, the ink that has flowed into the bypass flow path 160 from the first pressure control chamber 122 flows into the second pressure control chamber 152 via the second valve chamber 151. The ink that has flowed into the second pressure control chamber 152 passes through the pump inlet flow path 170, the circulation pump 500, and the pump outlet flow path 180, and then flows into the first pressure control chamber 122 again. 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 of the above-mentioned formula 2. Therefore, the ink in the first pressure control chamber 122 is supplied to the ejection module 300 again via the supply flow path 130 without flowing into the first valve chamber 121. The ink that has flowed into the ejection module 300 flows into the first pressure control chamber 122 again via the recovery flow path 140, the second pressure control chamber 152, the pump inlet flow path 170, the circulation pump 500, and the pump outlet flow path 180. In this manner, the ink circulation that is completed within the liquid ejection head 1 is performed.

[0083] In the above ink circulation, the amount of ink circulating (flow rate) in the ejection module 300 is determined by the difference in the control pressure between the first pressure control chamber 122 and the second pressure control chamber 152. This pressure difference is set so as to be a circulation amount capable of suppressing thickening of ink near the ejection port in the ejection module 300. In addition, the ink consumed by the 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 the consumed ink is supplied will be described in detail. The ink in the first pressure control chamber 122 is also reduced by reducing the ink from the circulation path by the amount of ink consumed by the recording. As the ink in the first pressure control chamber 122 is reduced, the internal volume of the first pressure control chamber 122 is reduced. Due to this reduction in the internal volume of the first pressure control chamber 122, the communication port 191A is opened, and ink is supplied from the first valve chamber 121 to the first pressure control chamber 122. This supplied ink experiences a pressure loss when passing through communication port 191A from first valve chamber 121, and as it flows into first pressure control chamber 122, the ink changes from a positive pressure state to a negative pressure state. As ink flows into first pressure control chamber 122 from first valve chamber 121, the internal volume of the first pressure control chamber increases, and communication port 191A closes. In this way, communication port 191A alternates between an open state and a closed state depending on the consumption of ink. Furthermore, if ink is not consumed, communication port 191A remains closed.

[0084] FIG. 12B is a schematic diagram showing the flow of ink immediately after the recording operation is completed and the circulation pump 500 is turned off (stopped). When the recording operation is completed and the circulation pump 500 is turned off, the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152 are both at the control pressure during the recording operation. Therefore, the ink moves as shown in FIG. 12B according to the pressure difference between the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152. Specifically, the ink continues to flow from the first pressure control chamber 122 to the ejection module 300 via the supply flow path 130, and then to the second pressure control chamber 152 via the recovery flow path 140. The ink also continues to flow from the first pressure control chamber 122 to the second pressure control chamber 152 via the bypass flow path 160 and the second valve chamber 151.

[0085] The amount of ink that has moved from the first pressure control chamber 122 to the second pressure control chamber 152 by these ink flows is supplied to the first pressure control chamber 122 from the ink tank 2 via the filter 110 and the first valve chamber 121. Therefore, the content volume in the first pressure control chamber 122 is kept constant. From the relationship of the above-mentioned formula 2, when the content volume in 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. Therefore, when there is no change in the pressure P1 in the first valve chamber 121, the pressure P2 in the first pressure control chamber 122 is kept at the same pressure as the control pressure during the recording operation.

[0086] On the other hand, the pressure of the second pressure control chamber 152 changes over time according to the change in the content volume caused by the inflow of ink from the first pressure control chamber 122. Specifically, from the state of FIG. 12(b) until the communication port 191 is closed and the second valve chamber 151 and the second pressure control chamber 152 are not in communication with each other as shown in FIG. 12(c), the pressure of the second pressure control chamber 152 changes according to Equation 2. Thereafter, the pressure plate 210 and the valve shaft 190a are not in contact with each other and the communication port 191 is closed. Then, as shown in FIG. 12(d), ink flows from the recovery passage 140 into the second pressure control chamber 152. This ink inflow displaces the pressure plate 210 and the flexible member 230, and the pressure of 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.

[0087] 12(c), no ink flow occurs from the first pressure control chamber 122 to the second pressure control chamber 152 via the bypass flow path 160 and the second valve chamber 151. Therefore, after the ink in the first pressure control chamber 122 is supplied to the ejection module 300 via the supply flow path 130, only a flow occurs to the second pressure control chamber 152 via the recovery flow path 140. As described above, the movement of ink from the first pressure control chamber 122 to the second pressure control chamber 152 occurs according to the pressure difference between the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152. Therefore, when the pressure in the second pressure control chamber 152 becomes equal to the pressure in the first pressure control chamber 122, the movement of ink stops.

[0088] In addition, in a state where the pressure in the second pressure control chamber 152 is equal to the pressure in the first pressure control chamber 122, the second pressure control chamber 152 expands to a state shown in FIG. 12(d). When the second pressure control chamber 152 expands as shown in FIG. 12(d), a storage portion capable of storing ink is formed in the second pressure control chamber 152. The time from when the circulation pump 500 is stopped to when the state shown in FIG. 12(d) is transitioned to is about 1 to 2 minutes, which may vary depending on the shape and size of the flow path and the properties of the ink. When the circulation pump 500 is driven from the state shown in FIG. 12(d) where ink is stored in the storage portion, the ink in the storage portion is supplied to the first pressure control chamber 122 by the circulation pump 500. As a result, the amount of ink in the first pressure control chamber 122 increases as shown in FIG. 12(e), and the flexible member 230 and the pressure plate 210 are displaced in the expansion direction. Then, when the circulation pump 500 continues to be driven, the state inside the circulation path changes as shown in FIG. 12(a).

[0089] 12(a) is an example of a recording operation, but as described above, ink may be circulated without a recording operation. Even in this case, ink flows as shown in FIGS. 12(a) to 12(e) occur depending on whether the circulating pump 500 is driven or stopped.

[0090] As described above, in this embodiment, the communication port 191B in the second pressure adjustment means 150 is in an open state when the circulation pump 500 is driven to circulate the ink, and is in a closed state when the circulation of the ink stops, but the present invention 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 in a closed state even when the circulation pump 500 is driven to circulate the ink. A specific description will be given below. The bypass flow path 160 connecting the first pressure adjustment means 120 and the second pressure adjustment means is provided to prevent the negative pressure generated in the circulation path from being affected by the negative pressure, for example, when the negative pressure is stronger than a preset value, from being exerted on the ejection module 300. When the ink characteristics (for example, viscosity) change due to a change in the environmental temperature, the pressure loss in the circulation path also changes. For example, when the viscosity of the ink decreases, the pressure loss in the circulation path decreases, and the negative pressure in the circulation path may become stronger than a preset value. When the negative pressure in the ejection module 300 becomes stronger than the preset value, external air is drawn into the circulation path from the ejection port 13, destroying the meniscus of the ejection port 13, and there is a risk that normal ejection cannot be performed. For this reason, in this embodiment, a bypass flow path 160 is formed in the circulation path. By providing the bypass flow path 160, when the negative pressure becomes stronger than the preset value, ink also flows through the bypass flow path 160, so that the pressure in the ejection module 300 can be kept constant. Therefore, for example, the communication port 191 in the second pressure adjustment means 150 may be configured with a control pressure that maintains the closed state even when the circulation pump 500 is being driven. Then, the control pressure in the second pressure adjustment means may be set so that the communication port 191 in the second pressure adjustment means 150 is in an open state when the negative pressure becomes stronger than the preset value.

[0091] The pressure fluctuation in the circulation path may also be caused by the ejection operation of the ejection element 15. This is because the ejection operation generates a force that draws ink into the pressure chamber. Therefore, for example, even if the communication port 191 in the second pressure adjustment means 150 is configured to be in a closed state when the circulation pump 500 is driven, the communication port 191 may be in an open state due to the ejection operation. For example, when recording with a high duty is continued, the negative pressure in the pressure chamber increases. When the negative pressure in the pressure chamber increases, ink also flows back into the pressure chamber (ejection port 13) from the recovery flow path 140 side. This backflow reduces the ink in the second pressure control chamber 152, and the second pressure control chamber 152 shrinks. As a result, the communication port 191 in the second pressure adjustment means 150 opens. In this case, the pressure chamber is filled with ink in the supply flow path 130 and ink in the recovery flow path 140, and is ejected. Incidentally, the backflow of ink that occurs when the printing duty is high is a phenomenon that occurs due to the provision of the bypass flow path 160. Also, in the above, an example has been described in which the communication port 191 in the second pressure adjustment means is opened in response to the backflow of ink, but backflow of ink may also occur when the communication port 191 in the second pressure adjustment means is open. Even in a configuration that does not include the second pressure adjustment means, the provision of the bypass flow path 160 may cause the above-mentioned backflow of ink.

[0092] <Configuration of the discharge unit> FIG. 13 is a schematic diagram showing a circulation path for one color of ink in the discharge unit 3 of this embodiment. FIG. 13(a) is an exploded perspective view of the discharge unit 3 seen from the first support member 4 side, and FIG. 13(b) is an exploded perspective view of the discharge unit 3 seen from the discharge module 300 side. The arrows indicated by IN and OUT in the figure indicate the flow of ink, and the flow of ink for only one color will be described, but the other colors flow in the same manner. In addition, in FIG. 13, the second support member 7 and the electric wiring member 5 are omitted for ease of viewing, and are also omitted in the following description of the configuration of the discharge unit. In addition, the first support member 4 in FIG. 13(a) shows a cross section taken along line XI-XI in FIG. 5. The discharge module 300 includes a discharge element substrate 340 and an aperture plate 330. FIG. 14 is a diagram showing the aperture plate 330, and FIG. 15 is a diagram showing the discharge element substrate 340.

[0093] Ink is supplied to the discharge unit 3 from the circulation unit 54 via a joint member 8 (see FIG. 5). The ink path from when the ink passes through the joint member 8 until when the ink returns to the joint member 8 will be described. Note that the joint member 8 will be omitted from the following drawings.

[0094] The ejection module 300 includes an ejection element substrate 340 and an aperture plate 330, which are overlapped and joined together so that the ink flow paths communicate with each other to form the ejection module 300, and are supported by a first support member 4. The ejection module 300 is supported by the first support member 4 to form an ejection unit 3. The ejection element substrate 340 includes an ejection port forming member 320, which includes a plurality of ejection port rows in which a plurality of ejection ports 13 are arranged in rows, and ejects a portion of the ink supplied via the ink flow path in the ejection module 300 from the ejection port 13. Ink that is not ejected is collected via the ink flow path in the ejection module 300.

[0095] As shown in Figs. 13 and 14, the opening plate 330 has a plurality of arranged ink supply ports 311 and a plurality of arranged ink recovery ports 312. As shown in Figs. 15 and 16, the ejection element substrate 340 has a plurality of arranged supply connection channels 323 and a plurality of arranged recovery connection channels 324. The ejection element substrate 340 further has an individual supply channel 18 communicating with the plurality of supply connection channels 323 and an individual recovery channel 19 communicating with the plurality of recovery connection channels 324. The ink flow channel in the ejection unit 3 is formed by communicating an ink supply channel 48 and an ink recovery channel 49 (see Fig. 5) provided in the first support member 4 with a channel 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.

[0096] Ink supplied to the ejection unit 3 is supplied from the circulation unit 54 (see FIG. 5(a)) side to the ink supply flow path 48 (see FIG. 5(a)) of the first support member 4. The ink flowing through the support member supply port 211 in the ink supply flow path 48 is supplied to the individual supply flow path 18 of the ejection element substrate 340 via the ink supply flow path 48 (see FIG. 5(a)) and the ink supply port 311 of the opening plate 330, and enters the supply connection flow path 323. This is the supply side flow path. After that, the ink flows through the pressure chamber 12 (see FIG. 5(b)) of the ejection port forming member 320 to the recovery connection flow path 324 of the recovery side flow path. The flow of ink in the pressure chamber 12 will be described in detail later.

[0097] In the recovery side flow path, the ink that has entered the recovery connection flow path 324 flows into the individual recovery flow path 19. After that, the ink flows from the individual recovery flow path 19 through the ink recovery port 312 of the opening plate 330 to the ink recovery flow path 49 of the first support member 4, and is recovered into the circulation unit 54 via the support member recovery port 212.

[0098] The area of ​​the opening plate 330 without the ink supply port 311 or the ink recovery port 312 corresponds to the area for separating the support member supply port 211 and the support member recovery port 212 in the first support member 4. Moreover, this area does not have an opening in the first support member 4 either. Such an area is used as an adhesion area when the ejection module 300 and the first support member 4 are adhered to each other.

[0099] In FIG. 14, the aperture plate 330 has a plurality of rows of apertures arranged in the X direction, and the supply (IN) apertures and the recovery (OUT) apertures are arranged alternately in the Y direction so as to be shifted by half a pitch in the X direction. In FIG. 15, the ejection element substrate 340 has individual supply flow paths 18 communicating with a plurality of supply connection flow paths 323 arranged in the Y direction, and individual recovery flow paths 19 communicating with a plurality of recovery connection flow paths 324 arranged in the Y direction, arranged alternately in the X direction. The individual supply flow paths 18 and the individual recovery flow paths 19 are divided according to the type of ink, and further, the number of the individual supply flow paths 18 and the individual recovery flow paths 19 is determined according to the number of ejection port rows of each color. In addition, the supply connection flow paths 323 and the recovery connection flow paths 324 are also arranged in the number corresponding to the ejection ports 13. It is not necessarily required that they correspond one-to-one, and one supply connection flow path 323 and one recovery connection flow path 324 may correspond to a plurality of ejection ports 13.

[0100] Such an opening plate 330 and an ejection element substrate 340 are overlapped and joined so that the flow paths of each ink are connected to form an ejection module 300, and by being supported by the first support member 4, an ink flow path having a supply flow path and a recovery flow path as described above is formed.

[0101] Figures 16(a) to (c) are cross-sectional views showing ink flows in different parts of the discharge unit 3. Figure 16(a) shows a cross-section of a part in the discharge unit 3 where the ink supply flow path 48 and the ink supply port 311 communicate with each other, and Figure 16(b) shows a cross-section of a part in the discharge unit 3 where the ink recovery flow path 49 and the ink recovery port 312 communicate with each other. Also, Figure 16(c) shows a cross-section of a part where the ink supply port 311 and the ink recovery port 312 do not communicate with the flow path of the first support member 4.

[0102] In the supply flow path for supplying ink, as shown in FIG. 16(a), ink is supplied from a portion where the ink supply flow path 48 of the first support member 4 and the ink supply port 311 of the opening plate 330 overlap and communicate with each other. In the recovery flow path for recovering ink, as shown in FIG. 16(b), ink is recovered from a portion where the ink recovery flow path 49 of the first support member 4 and the ink recovery port 312 of the opening plate 330 overlap and communicate with each other. In addition, as shown in FIG. 16(c), in the ejection unit 3, there are also regions where the opening plate 330 does not have an opening. In such regions, ink is not supplied or recovered, and ink is supplied in the region where the ink supply port 311 is provided as shown in FIG. 16(a), and ink is recovered in the region where the ink recovery port 312 is provided as shown in FIG. 16(b). In the present embodiment, the configuration using the opening plate 330 has been described as an example, but a configuration without the opening plate 330 may be used. For example, a configuration may be used in which flow paths corresponding to the ink supply flow path 48 and the ink recovery flow path 49 are formed in the first support member 4, and the ejection element substrate 340 is joined to the first support member 4.

[0103] 17(a) and (b) are cross-sectional views showing the vicinity of the ejection port 13 in the ejection module 300, and FIG. 18 is a cross-sectional view showing an ejection module having an individual supply flow path 18 and an individual recovery flow path 19 expanded in the X direction as a comparative example. Note that the thick arrows shown in the individual supply flow path 18 and the individual recovery flow path 19 in FIG. 17 and FIG. 18 indicate the oscillation of ink in a configuration using a serial type liquid ejection device 50. The ink supplied to the pressure chamber 12 via the individual supply flow path 18 and the supply connection flow path 323 is ejected from the ejection port 13 by driving the ejection element 15. When the ejection element 15 is not driven, the ink is recovered from the pressure chamber 12 to the individual recovery flow path 19 via the recovery connection flow path 324, which is a recovery flow path.

[0104] In the case of using the serial type liquid ejection device 50, when ejection is performed from the circulating ink, the ejection of the ink is influenced by the ink oscillation in the ink flow path due to the scanning of the liquid ejection head 1. Specifically, the influence of the ink oscillation in the ink flow path may appear as a difference in the amount of ink ejected or a deviation in the ejection direction. As shown in FIG. 18, when the individual supply flow path 18 and the individual recovery flow path 19 have a cross-sectional shape that is wide in the X direction, which is the scanning direction, the ink in the individual supply flow path 18 and the individual recovery flow path 19 is easily subjected to an inertial force in the scanning direction, and the ink is greatly oscillated. As a result, there is a risk that the ink oscillation will affect the ejection of the ink from the ejection port 13. Furthermore, if the individual supply flow path 18 and the individual recovery flow path 19 are widened in the X direction, the distance between the colors will be increased, which may reduce the printing efficiency.

[0105] Therefore, the individual supply flow paths 18 and the individual recovery flow paths 19 of this embodiment extend in the Y direction in the cross section shown in FIG. 17, but are also configured to extend in the Z direction perpendicular to the X direction, which is the scanning direction. With this configuration, the width of each of the individual supply flow paths 18 and the individual recovery flow paths 19 in the scanning direction can be reduced. By reducing the width of each of the individual supply flow paths 18 and the individual recovery flow paths 19 in the scanning direction, the ink oscillation caused by the inertial force (indicated by the thick black arrow in the figure) acting on the ink in the individual supply flow paths 18 and the individual recovery flow paths 19 in the opposite direction to the scanning direction during scanning is reduced. This makes it possible to suppress the effect of the ink oscillation on the ink ejection. In addition, the cross-sectional area is increased by extending the individual supply flow paths 18 and the individual recovery flow paths 19 in the Z direction, thereby reducing the flow path pressure loss.

[0106] As described above, by reducing the width of each of the individual supply flow paths 18 and the individual recovery flow paths 19 in the scanning direction, the oscillation of ink in the individual supply flow paths 18 and the individual recovery flow paths 19 during scanning is reduced, but the oscillation is not eliminated. Therefore, in order to suppress differences in ejection for each ink type that may still occur even with the reduced oscillation, in this embodiment, the individual supply flow paths 18 and the individual recovery flow paths 19 are configured to be disposed at positions that overlap with each other in the X direction.

[0107] As described above, in this embodiment, the supply connection flow path 323 and the recovery connection flow path 324 are provided corresponding to the ejection port 13, and the supply connection flow path 323 and the recovery connection flow path 324 are arranged side by side in the X direction with the ejection port 13 in between. Therefore, there are portions where the individual supply flow paths 18 and the individual recovery flow paths 19 do not overlap in the X direction, and if the corresponding relationship in the X direction between the supply connection flow path 323 and the recovery connection flow path 324 is lost, it will affect the flow and ejection of ink in the X direction in the pressure chamber 12. If the influence of ink fluctuation is added to this, it may further affect the ejection of ink from each ejection port.

[0108] Therefore, by arranging the individual supply flow paths 18 and the individual recovery flow paths 19 at positions where they overlap in the X direction, the ink oscillation during scanning in the individual supply flow paths 18 and the individual recovery flow paths 19 becomes approximately equal at any position in the Y direction where the ejection ports 13 are arranged. As a result, the pressure difference between the individual supply flow path 18 side and the individual recovery flow path 19 side generated in the pressure chamber 12 does not vary greatly, and stable ejection can be performed.

[0109] In addition, in some liquid ejection heads that circulate ink, the flow path that supplies ink to the liquid ejection head and the flow path that recovers ink are configured as the same flow path, but in this embodiment, the individual supply flow paths 18 and the individual recovery flow paths 19 are configured as separate flow paths. The supply connection flow path 323 and the pressure chamber 12 are connected to each other, and the pressure chamber 12 and the recovery connection flow path 324 are connected to each other, and ink is ejected from the ejection port 13 of the pressure chamber 12. In other words, the pressure chamber 12, which is a path that connects the supply connection flow path 323 and the recovery connection flow path 324, is configured to have the ejection port 13. Therefore, an ink flow that flows from the supply connection flow path 323 side to the recovery connection flow path 324 side is generated in the pressure chamber 12, and the ink in the pressure chamber 12 is efficiently circulated. By efficiently circulating the ink in the pressure chamber 12, the ink in the pressure chamber 12, which is easily affected by the evaporation of ink from the ejection port 13, can be kept fresh.

[0110] Furthermore, since the two flow paths, the individual supply flow path 18 and the individual recovery flow path 19, are connected to the pressure chamber 12, if it becomes necessary to eject ink at a high flow rate, it is possible to supply ink from both flow paths. In other words, compared to a configuration in which ink supply and recovery are configured using only one flow path, the configuration of this embodiment has the advantage of not only being able to circulate ink efficiently, but also being able to handle ejection at a high flow rate.

[0111] Furthermore, the individual supply flow paths 18 and the individual recovery flow paths 19 are less susceptible to the influence of ink fluctuations when they are disposed close to each other in the X direction. It is preferable that the distance between the flow paths is 75 μm to 100 μm.

[0112] Fig. 19 is a diagram showing an ejection element substrate 340 as a comparative example. Note that in Fig. 19, the supply connection flow path 323 and the recovery connection flow path 324 are omitted. Since ink that has received thermal energy from the ejection elements 15 in the pressure chambers 12 flows into the individual recovery flow path 19, ink with a relatively high temperature flows compared to the temperature of the ink in the individual supply flow path 18. At this time, in the comparative example, there is a portion in the X direction of the ejection element substrate 340 where only the individual recovery flow path 19 exists, such as the α portion surrounded by the dashed line in Fig. 19. In this case, the temperature locally increases in that portion, causing temperature unevenness in the ejection module 300, which may affect ejection.

[0113] In the individual supply flow paths 18, ink flows that is at a relatively low temperature relative to the individual recovery flow paths 19. Therefore, when the individual supply flow paths 18 and the individual recovery flow paths 19 are adjacent to each other, the temperatures in the individual supply flow paths 18 and the individual recovery flow paths 19 are partially offset in the vicinity thereof, suppressing a temperature rise. Therefore, it is preferable that the individual supply flow paths 18 and the individual recovery flow paths 19 are adjacent to each other and have approximately the same length, and are positioned so as to overlap each other in the X direction.

[0114] 20(a) and (b) are diagrams showing the flow path configuration of the liquid ejection head 1 corresponding to three colors of ink: cyan (C), magenta (M), and yellow (Y). As shown in FIG. 20(a), the liquid ejection head 1 is provided with a circulation flow path for each type of ink. The pressure chambers 12 are provided along the X direction, which is the scanning direction of the liquid ejection head 1. As shown in FIG. 20(b), the individual supply flow paths 18 and the individual recovery flow paths 19 are provided along the ejection port row in which the ejection ports 13 are arranged, and are provided extending in the Y direction so as to sandwich the ejection port row between the individual supply flow paths 18 and the individual recovery flow paths 19.

[0115] Next, a method for determining which inks are to be used for image formation and which inks are not to be used, based on the input image and printing conditions, and a method for determining whether or not to circulate ink during printing operation, in this embodiment, will be described. This makes it possible to prevent the ink from thickening in the nozzles of ink that is not used in image formation, and to prevent ejection defects when the ink is used again for image printing.

[0116] First, the concentration of ink in the nozzles during a recording operation will be described. When a recording operation begins, the cap 61 that was in contact with the ink ejection head 1 is removed, and the nozzles 402 (see FIG. 3) are opened to the atmosphere. Therefore, during image formation, the water in the ink in the nozzles gradually evaporates into the atmosphere, and the ink becomes concentrated. In the ink that has been concentrated by the evaporation of water, the ratio of the coloring material, resin, and solvent, which are contents other than water, increases relatively from the initial state, and the viscosity of the ink in the vicinity of the nozzles increases.

[0117] FIG. 21(a) is a schematic diagram showing concentration in a state where the nozzle 402 is open to the atmosphere and circulating. The flow of ink is indicated by arrows, and the concentration of the ink is indicated by the density. When the ink in the nozzle is circulated during a printing operation, as the water evaporates from the ink liquid surface (meniscus) of the nozzle, the ink in the surface layer becomes concentrated. However, the ink flows due to circulation in the back, so that ink in a non-concentrated state continues to be supplied. Since the circulation flow rate is low in the surface layer and ink remains there, the concentrated ink in the surface layer evaporates further over time. However, since water is supplied while mixing with the non-concentrated ink flowing in the lower layer at the boundary, the water is not completely lost from the ink in the surface layer. Therefore, when the non-concentrated ink in the lower layer bubbles due to the heater drive of the nozzle, the concentrated ink in the surface layer is ejected out of the nozzle by the energy of the bubbles. If the ink is only circulated in a non-ejecting state for a long time, it will be ejected in a state where the ink in the surface layer is highly concentrated, and the increased viscosity can cause ejection problems such as a decrease in ejection speed and bending of the ejection direction. In such cases, it is possible to recover the ejection performance by ejecting a small amount of preliminary ink outside the image formation area, which expels the concentrated ink in the surface layer.

[0118] The ink in the circulation flow path is homogenized as it flows through the circulation flow path, partially mixing with the ink concentrated near the nozzle, and the moisture ratio gradually decreases and the ink becomes more concentrated. Figure 22 is a graph showing the change in the moisture evaporation rate of the ink in the circulation flow path during printing. The higher the moisture evaporation rate, the more concentrated the ink is. The rate of concentration depends not only on the rate at which moisture evaporates from the nozzle, but also on the nozzle opening area, the number of nozzles, the circulation flow rate, and the ink volume in the circulation flow path. In particular, during printing, the area near the nozzle is heated to a constant temperature by a heater to reduce the ink viscosity and stabilize the ejection characteristics, so the evaporation rate of the heated ink in the nozzle is faster than when this is not the case.

[0119] When ink is used in image formation, the amount of ink ejected from the nozzles is newly supplied to the liquid ejection head 1, and the ink concentration saturates at the point where the ink consumption rate and the water evaporation rate in the circulation flow path are balanced, as shown in the graph shown by the dotted line in Fig. 22. However, when ink is unused in image formation, the concentration rate of ink in the circulation flow path cannot be suppressed by merely ejecting a small amount of ink in advance, and the ink concentration in the circulation flow path increases significantly over time, as shown in the graph shown by the solid line in Fig. 22.

[0120] As the ink concentration in the circulation flow path increases, the ink ejection characteristics deteriorate due to increased viscosity, and the color fluctuation due to increased colorant concentration affects image formation. In such cases, it is necessary to lower the ink concentration in the circulation flow path by discharging the concentrated ink and supplying new ink to homogenize the ink in the circulation flow path. Therefore, when the ink concentration exceeds the allowable range, the ink is sucked from the nozzle of the corresponding ink using the cap 61, or new ink is injected into the circulation flow path by ejecting ink from the nozzle, thereby lowering the concentration.

[0121] In the example of ink not used in image formation shown by the solid line in Fig. 22, when the water evaporation rate becomes 10% or more, a discharge operation is performed to lower the ink concentration. Note that it is not necessary to discharge all of the concentrated ink in this operation, and it is sufficient that the discharge amount is sufficient to lower the concentration to a range that does not affect the discharge characteristics or image formation. In the liquid discharge head 1 of this embodiment, the circulation flow path internal volume is about 10 ml, so 5 ml or more is set as the amount to be discharged when the concentration decreases. The consumption amount is shown in the graph of Fig. 23 (a).

[0122] On the other hand, if the ink in the nozzle is not circulated during the printing operation, the water gradually evaporates from the ink in the nozzle during the printing operation, but the ink in the circulation flow path does not move, so the closer to the nozzle, the more concentrated the ink becomes. Figure 21(b) is a schematic diagram showing the ink concentration state when the nozzle is open to the atmosphere and not circulated. If the time open to the atmosphere is short and the concentration of the ink in the nozzle is low, it is possible to discharge the concentrated ink by ejection. However, if the ink is open to the atmosphere for a long time and the concentration of the ink in the nozzle is high, the viscosity of the entire ink in the nozzle increases, and even if the heater is driven to eject it, it may not be possible to generate enough bubbling energy to discharge the concentrated ink. However, for ink located away from the nozzle, the effect of evaporation near the nozzle is small, and the water evaporation rate is small when viewed in the entire circulation flow path.

[0123] 21(b), the ink is concentrated only up to the inlet 421 and the outlet 422, and is not concentrated in the ink behind the common flow path 431. Therefore, when unused ink becomes too concentrated to be ejected, the ejection performance can be restored by consuming only a small amount of ink by sucking out the concentrated ink near the nozzles using the suction action of the cap 61.

[0124] The volume of the flow paths around the nozzles and the common flow path 431 is approximately 20 μl, but in this embodiment, in order to ensure stable suction with the cap, the suction volume is set to approximately 0.5 ml, and the consumption amount is shown in FIG. 23(b). In addition, the concentration level in the circulation flow path is maintained at a low level. Even if the suction operation is unable to completely remove the concentrated ink, if the ink is restored to a state where it can be circulated, the remaining minute particles of concentrated ink are uniformly mixed into the ink in the circulation flow path. Therefore, the effect of the concentration level on the ink in the circulation flow path is small, and the effect on the ejection characteristics and image formation is also suppressed.

[0125] However, if the ink in the nozzle is not circulated when the temperature rises, not only will the moisture evaporate quickly and concentration will progress, but the ink properties may change due to the influence of temperature. For example, as the pigment or resin in the concentrated ink aggregates, the solid content in the nozzle may separate, and the mass may grow and block the nozzle. To prevent this, it is necessary to either discharge the ink in the nozzle before the solid content begins to aggregate, or to suppress concentration in the nozzle by circulation. It is difficult to discharge ink by ejection when the ink is in an advanced concentrated state, and suction by a cap will also discharge ink from other nozzles, resulting in a large amount of ink consumption. Therefore, in the configuration of this embodiment in which the ink in the nozzle can be circulated, it is preferable to circulate the ink under conditions in which the temperature rises during the printing operation.

[0126] For the above reasons, it is necessary to continue circulating ink within the nozzles for ink that may increase in temperature during printing. Therefore, by circulating not only the ink used during printing, but also the ink in the same chip, the adverse effects of changes in ink properties can be suppressed. In addition, ink that is not likely to increase in temperature is not circulated as much as possible, and by sucking out the concentrated ink in the nozzles when use is resumed, it is possible to suppress the amount of ink to be discarded and suppress the concentration of ink in the circulation flow path.

[0127] In this embodiment, an example is shown in which whether or not to perform circulation for each ink during a printing operation is determined based on the printing conditions.

[0128] Figure 24 is a table showing the correspondence between the inks used in image formation and the recording conditions of the input image data. In the table, the inks with a recording quality marked with a "●" are used in image formation, and the rest are not used. In addition, the inks with a "△" are not used in image formation, but need to be circulated.

[0129] As shown in Figure 24, in the case of non-absorbent recording media such as tack sheets and films, the moisture and solvents in the color ink that lands on the recording medium are not absorbed into the recording medium. Therefore, when a large amount of ink is applied, the surface tension between the recording medium and the ink is not enough to suppress the movement, resulting in bleeding. For this reason, in the case of non-absorbent recording media, a primer is used, which reacts with the ink to increase the viscosity and suppress the movement. On the other hand, in the case of recording media such as inkjet paper, where an ink-receiving layer is formed on the surface of the recording medium, the moisture and solvents are absorbed into the receiving layer, so there is no need to use a primer.

[0130] In addition, in a printing mode that prioritizes image printing speed, only the four basic colors of cyan, magenta, yellow, and black are used to prevent a drop in printing speed by suppressing the amount of processing required to generate printing data for each ink color from input image data. On the other hand, in a printing mode that prioritizes image quality, the light inks light cyan, light magenta, and gray, as well as the special colors green and orange, are used to improve color development and reduce graininess. In an intermediate printing mode, for example, the basic colors, light cyan, and light magenta are selected as the inks to be used.

[0131] In the ink configuration of this embodiment, a light gray and special colors such as green and orange are used. However, red, blue, and violet may be used as other special colors, and clear ink used for gloss control and white ink used for expressing white in transparent films may be used. In addition, the allocation and order of ink colors for each head are not limited to those shown in this embodiment. In addition, in this embodiment, an example is given of a configuration in which ink to be used is selected according to the print mode, but if image data is input as data corresponding to the ink, the ink to be used may be determined according to the presence or absence of that data.

[0132] For the inks selected for use as described above, a determination is made as to whether or not ink is to be used for each chip 403. Since the basic colors are used under all printing conditions, the two chips 403 of the liquid ejection head 110 are always used. The chip 403 of the liquid ejection head 111L, which uses only the primer, is not used for inkjet paper, but is used for other printing media. The liquid ejection head 111R is used only in the high-quality printing mode.

[0133] This is shown in the flow chart in FIG.

[0134] In FIG. 25, first, in step S1101, it is determined whether the ink is to be used for image formation, and in step S1102, it is determined whether there is any ink to be used in the same chip among the inks determined to be unused. For the inks determined to be used in steps S1101 and S1102, a circulation pump is driven in step S1105. In addition, in this embodiment, a timer Tc is prepared to measure the time during which the ink in the nozzle is concentrated by opening the cap without circulating. Note that while the circulation pump is driven, the timer Tc is set to 0. For example, for ink that has not been used in a previous printing operation and has not been circulated, there may be cases where the timer is not 0 at the start of the printing operation. In that case, when the ink is used again in image formation, it is circulated and the concentrated ink in the nozzle is removed, so the timer Tc is reset in step S1106.

[0135] On the other hand, for ink that is not used in image formation and has no color used in the same chip, the circulation pump is not driven, and in step S1103, timer Tc is not initialized and is added cumulatively to the current count value. This is because if circulation is not selected for all printing operations when multiple printing operations are performed, the ink in the nozzles remains concentrated without being circulated. Note that timer Tc is also reset when a recovery operation is performed by cap suction and the thickened ink in the nozzles is discharged.

[0136] Whether or not to perform circulation during a recording operation is determined as described above, and flag processing for recovery processing required before the start of the next recording operation is performed based on whether or not circulation was performed during the last recording operation.

[0137] If the ink is not circulating during a printing operation, and if the ink has not circulated for a long time and has become concentrated inside the nozzle, it is necessary to discharge the concentrated ink by suction. Therefore, in step S1104, a flag for determining whether a suction operation is to be performed is turned ON. On the other hand, if the ink is circulating during a printing operation, and the ink inside the circulation flow path has become concentrated, it is necessary to perform a discharge operation to discharge the concentrated ink. Therefore, in step S1107, a concentration resolution flag is turned ON.

[0138] After the circulation during the printing operation and the recovery operation flag are set as described above, the printing operation is performed. After the printing operation is completed, the nozzles are covered with caps again to prevent the ink in the nozzles from drying, and the main body operation is paused.

[0139] During printing, the ink in the circulation flow path and the nozzles becomes concentrated, but since the color to be used varies depending on the next print image data and printing conditions, in this embodiment, recovery processing of the concentrated ink is performed at the start of printing. If only the same ink is used, there is a possibility that the recovery processing of the ink not used in image formation can be skipped, which has the effect of shortening the recovery operation time between printing operations.

[0140] Next, FIG. 26 is a flowchart showing the recovery process determination before the start of a recording operation and the recovery operation in this embodiment.

[0141] First, in step S1201, it is determined whether or not the color is to be used in image formation. The determination method is as described above. Here, for ink determined not to be used, it is not used in image formation, so even if the ink in the circulation flow path is concentrated, or the concentrated ink cannot be circulated, it does not affect the image. However, it is necessary to prevent the ink in the nozzle from being concentrated so that the solid content of the ink aggregates and cannot be removed by suction. Therefore, in step S1202, if the count time of the timer Tc is longer than the threshold value T0 of the time required for recovery by suction, a suction operation is performed to remove the concentrated ink in the nozzle. Note that since the increase in viscosity during concentration differs depending on the ink, T0 may be set to a different threshold value depending on the ink. After the suction operation is performed, the concentrated ink in the nozzle is removed, so the timer Tc is reset.

[0142] If it is determined in step S1201 that the color is to be used in image formation, then in step S1211, the suction determination flag is checked. If the suction determination flag was ON in the previous printing operation, it is possible that the ink in the nozzles has not been circulated and has become concentrated. Therefore, if it is predicted that the ink has become concentrated to a degree that will affect image formation based on the time that has passed while the nozzles were open to the atmosphere, the concentrated ink is removed by suction. Specifically, in step S1212, a comparison is made to see whether the timer Tc is longer than a threshold value T1, and if the threshold value is exceeded, a suction operation is performed.

[0143] The threshold T1 is a threshold for the concentration that affects the image, i.e., the ink density and ejection performance, so a time shorter than the threshold T0 for determining whether solid aggregates will occur is set. Also, since the degree of image effect due to concentration differs depending on the ink, T1 may be set to a different threshold for each ink. After the suction operation is performed, the timer Tc is reset in step S1214.

[0144] If it is determined in step S1212 that the threshold has not been exceeded, the ink concentration in the nozzles has not progressed and there is no effect on image formation, so the suction operation is not performed. Note that when the suction determination flag is ON, the ink in the nozzles has not been circulated in the previous recording operation, so the ink in the entire circulation flow path has not become concentrated and there is no need to eliminate the concentration of the ink in the circulation flow path. Therefore, the concentration elimination operation is not performed.

[0145] If the suction determination flag is OFF in step S1211, the concentration resolution flag is checked in step S1221. If the concentration resolution flag is ON in the previous printing operation, the ink in the nozzle is circulated, so there is a possibility that the concentration of the entire circulation flow path has progressed. Therefore, in step S1222, it is determined whether the ink concentration exceeds the concentration threshold Dth that affects image formation. Specifically, the concentration Dh predicted from the concentration due to evaporation of water from the nozzle and the concentration resolution due to mixing with new ink as the ink is consumed is compared with the threshold Dth. In this embodiment, for example, Dth=10% is set. If the concentration Dh>threshold Dth, a discharge operation is performed to discharge the concentrated ink in step S1223. If the concentration Dh≦threshold Dth, there is no need to resolve the concentration, so the concentration resolution operation is not performed and the recovery process before the printing operation is terminated.

[0146] As described above, in this embodiment, the necessity of circulating ink that is not used in image formation during a recording operation is determined, and the ink is appropriately discharged based on the concentration state in the nozzles and the circulation flow path. This makes it possible to maintain a state in which concentration fluctuations and ejection defects that cause deterioration of image quality do not occur, even when unused ink is used again for image formation.

[0147] The disclosure of this specification includes the following recording device, method, program, and storage medium.

[0148] (Item 1) an ink ejection head including a plurality of ejection ports that eject a plurality of types of ink, and a plurality of circulation paths for circulating ink between the plurality of ejection ports and a plurality of liquid chambers that respectively accommodate the plurality of types of ink; a circulation unit that circulates ink in the plurality of circulation paths; a control means for controlling which of the plurality of circulation paths the ink is to be circulated through by the circulation means based on recording data; A recording device comprising:

[0149] (Item 2) The recording device described in item 1 is further provided with a selection means for selecting an ink to be used for recording based on the recording data, and the control means controls which of the multiple circulation paths the ink is circulated through, depending on the ink selected by the selection means.

[0150] (Item 3) 3. The recording apparatus according to item 2, wherein the control means controls the circulation means so as to circulate the ink in a circulation path corresponding to the ink selected by the selection means.

[0151] (Item 4) The recording device described in item 3, characterized in that the ink ejection head has a plurality of chips in which the plurality of ejection ports are arranged separately, and the control means controls the circulation means to circulate ink in a circulation path corresponding to the ink whose ejection ports are arranged on the same chip as the ejection ports of the ink used for recording.

[0152] (Item 5) 5. The recording apparatus according to any one of items 1 to 4, further comprising a measuring unit that measures an elapsed time in a circulation path where ink is not circulated during a recording operation of the recording apparatus.

[0153] (Item 6) The recording device described in item 5 is further provided with a suction means for suctioning ink from the ejection port, and the control means controls the suction means to suction ink from the ejection port corresponding to a circulation path in which the ink is not circulating when the elapsed time exceeds a first threshold value.

[0154] (Item 7) 7. The recording apparatus according to item 6, wherein the suction by the suction means is performed before a next recording operation is started.

[0155] (Item 8) 8. The recording apparatus according to item 6 or 7, wherein the suction means comprises a cap that covers the discharge port and a pump that creates a negative pressure inside the cap.

[0156] (Item 9) 9. The recording apparatus according to any one of items 1 to 8, further comprising a prediction unit for predicting a concentration level of the ink in the circulation path circulated by the circulation unit.

[0157] (Item 10) 10. The recording apparatus according to item 9, wherein the control means controls the ink to be ejected from the ejection port when the concentration level becomes greater than a second threshold value.

[0158] (Item 11) 11. The recording apparatus according to item 10, wherein the ejection of ink from the ejection port is performed before a next recording operation is started.

[0159] (Item 12) The recording device described in any one of items 1 to 11, characterized in that the control means controls the ink to be discharged before the next recording operation is started for ink that was not used in the previous recording operation and for which the time during which it has not been circulated during the recording operation exceeds a third threshold value.

[0160] (Item 13) A method for controlling a recording device including an ink ejection head having a plurality of ejection ports that eject a plurality of types of ink, and a plurality of circulation paths for circulating ink between the plurality of ejection ports and a plurality of liquid chambers that respectively accommodate the plurality of types of ink, comprising: a circulating step of circulating ink in the plurality of circulation paths; a control step of controlling which of the plurality of circulation paths the ink is to be circulated through in the circulation step based on recording data; 13. A method for controlling a recording apparatus comprising the steps of:

[0161] (Item 14) Item 14. A program for causing a computer to execute each step of the control method according to item 13.

[0162] (Item 15) A computer-readable storage medium storing a program for causing a computer to execute each step of the control method described in item 13.

[0163] (Other embodiments) The present invention can also be realized by a process in which a program for realizing one or more functions of the above-mentioned embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) for realizing one or more functions.

[0164] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0165] 110: liquid ejection head, 23: recovery unit, 54: circulation unit, 61: cap, 402: nozzle

Claims

1. an ink ejection head including a plurality of ejection ports that eject a plurality of types of ink, and a plurality of circulation paths for circulating ink between the plurality of ejection ports and a plurality of liquid chambers that respectively accommodate the plurality of types of ink; a circulation unit that circulates ink in the plurality of circulation paths; a control means for controlling which of the plurality of circulation paths the ink is to be circulated through by the circulation means based on recording data; A recording device comprising:

2. 2. The recording apparatus according to claim 1, further comprising a selection unit that selects an ink to be used for recording based on the recording data, and the control unit controls which of the plurality of circulation paths the ink is circulated through, depending on the ink selected by the selection unit.

3. 3. The recording apparatus according to claim 2, wherein the control means controls the circulating means so as to circulate the ink in a circulation path corresponding to the ink selected by the selection means.

4. The recording apparatus according to claim 3, characterized in that the ink ejection head has a plurality of chips in which the plurality of ejection ports are arranged separately, and the control means controls the circulation means so as to circulate the ink in a circulation path corresponding to the ink whose ejection ports are arranged in the same chip as the ejection ports of the ink used for recording.

5. 2. The recording apparatus according to claim 1, further comprising a measuring device for measuring an elapsed time in a circulation path where no ink circulation occurs during a recording operation of the recording apparatus.

6. The recording device according to claim 5, further comprising a suction means for suctioning ink from the ejection port, and the control means controls the suction means to suction ink from the ejection port corresponding to a circulation path in which the ink is not circulating when the elapsed time exceeds a first threshold value.

7. 7. The recording apparatus according to claim 6, wherein the suction by the suction means is performed before a next recording operation is started.

8. 7. The recording apparatus according to claim 6, wherein the suction means comprises a cap for covering the ejection port, and a pump for creating a negative pressure inside the cap.

9. 2. The recording apparatus according to claim 1, further comprising a prediction unit for predicting a concentration level of the ink in the circulation path circulated by the circulation unit.

10. 10. The recording apparatus according to claim 9, wherein the control means controls the ink to be ejected from the ejection port when the concentration level becomes greater than a second threshold value.

11. 11. The printing apparatus according to claim 10, wherein the ejection of ink from the ejection openings is performed before a next printing operation is started.

12. The recording apparatus according to claim 1, wherein the control means controls to perform an ink drainage operation for ink that was not used in the previous recording operation and for which the time during which it has not been circulated during the recording operation exceeds a third threshold value before the next recording operation is started.

13. A method for controlling a recording device including an ink ejection head having a plurality of ejection ports that eject a plurality of types of ink, and a plurality of circulation paths for circulating ink between the plurality of ejection ports and a plurality of liquid chambers that respectively accommodate the plurality of types of ink, comprising: a circulating step of circulating ink in the plurality of circulation paths; a control step of controlling which of the plurality of circulation paths the ink is to be circulated through in the circulation step based on recording data; 13. A method for controlling a recording apparatus comprising the steps of:

14. A program for causing a computer to execute each step of the control method according to claim 13.

15. A computer-readable storage medium storing a program for causing a computer to execute each step of the control method according to claim 13.

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