Liquid ejection device and control method

Abstract

To provide a liquid ejection device capable of stably ejecting liquid by removing burnt residue at an appropriate timing without impairing the life of a head. The timing for performing a kogation removal operation, which involves dissolving metal from a protective layer through an electrochemical reaction with the liquid, is determined based on information relating to the ejection characteristics of the liquid.

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection apparatus and a control method. [Background technology]

[0002] In a liquid ejection device that performs recording by ejecting a liquid such as ink, one method of generating energy for ejecting the liquid is to heat the ink with an electrothermal conversion element (hereinafter also referred to as a "heater") having a heating resistor, thereby causing the ink to bubble and be ejected. In such a method of ejecting ink by heating with a heater, the ink may be scorched on the surface when heated by the heater, which may cause a change in the ejection speed. When the liquid ejection device is a recording device, a change in the ejection speed of some heaters may cause thinning of lines due to deviation in the landing position, distorted characters, changes in color, etc., which may result in a decrease in recording quality.

[0003] Patent Document 1 discloses a technology in which a protective layer is placed in the heat action area as an electrode to cause an electrochemical reaction with the ink, and when the number of recorded dots exceeds a threshold, an electrochemical reaction with the ink occurs, dissolving the surface layer of the protective layer and removing the kogation on the heat action area. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-105364 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the adhesion of kogation varies depending on the type of ink, the ink production lot, the material lot, and in the case of pigment ink, the average particle size of the pigment, etc. Therefore, if kogation removal is performed at a uniform timing as in Patent Document 1, depending on the ink used, the protective layer may be eluted in a state where there is no kogation adhesion, shortening the heater lifespan.

[0006] Therefore, the present invention provides a liquid ejection device that can perform kogation removal processing at an appropriate timing and eject liquid stably without shortening the life of the head. [Means for solving the problem]

[0007] Therefore, the liquid ejection device of the present invention is a liquid ejection device that comprises an ejection means having a heating resistor that generates energy for ejecting liquid by generating heat when electricity is applied, a protective part that covers and protects the heating resistor, and an electrode part that can be electrically connected to the protective part via liquid, and a control means that controls a kogation removal operation that removes kogation by dissolving the protective part into liquid by applying a voltage between the protective part and the electrode part, and is characterized in that the control means determines the timing of executing the kogation removal operation in the ejection means that ejects the liquid based on information regarding the ejection characteristics of the liquid. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a technique for suppressing a decrease in recording quality and a shortened life of an electrothermal conversion element. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a liquid ejection device. [Figure 2] FIG. 1 is a block diagram showing the configuration of a recording device. [Figure 3] FIG. 2 is a schematic diagram showing a first circulation path as one form of a circulation path. [Figure 4] FIG. 4 is a schematic diagram showing a second circulation path. [Figure 5] FIG. 2 is a perspective view of a liquid ejection head. [Figure 6] FIG. 2 is an exploded perspective view of each component or unit that constitutes the liquid ejection head. [Figure 7] 3 is a diagram showing the front and back surfaces of the first to third flow path members. FIG. [Figure 8] 10 is a perspective view of the first flow path member as seen from the surface on which the discharge module is mounted. FIG. [Figure 9] FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 8. [Figure 10] FIG. 2 is a perspective view showing a discharge module. [Figure 11] FIG. 2 is a plan view of a recording element substrate. [Figure 12] FIG. 2 is a perspective view showing a cross section of a recording element substrate and a cover member. [Figure 13] FIG. 4 is a partially enlarged plan view showing an adjacent portion of the recording element substrate. [Figure 14] FIG. 3 is a diagram showing the vicinity of a heat application portion on a recording element substrate. [Figure 15] 10 is a graph showing the relationship between the ejection speed and the number of ejections. [Figure 16] FIG. 2 is a diagram showing communication between the liquid ejection head, the ink cartridge, and the main body. [Figure 17] FIG. 10 is a diagram showing an example of a table for calculating the period of kogation removal. [Figure 18] 10 is a flowchart showing an example of a flow of a recording process and a kogation removal process. [Figure 19] 10 is a flowchart showing a recording process. [Figure 20] 10 is a flowchart showing a recording process. [Figure 21] FIG. 10 is a diagram showing an example of a discharge speed detection pattern. DETAILED DESCRIPTION OF THE INVENTION

[0010] A first embodiment of the present invention will be described below with reference to the drawings.

[0011] FIG. 1 is a diagram showing the schematic configuration of a liquid ejection apparatus (hereinafter also referred to as a recording apparatus) 1000 according to this embodiment. The recording apparatus 1000 is a line-type recording apparatus having a conveying unit 1 that conveys a recording medium 2 and a line-type liquid ejection head 3 arranged approximately perpendicular to the conveying direction of the recording medium. The recording medium 2 is a continuous or intermittent recording medium that is conveyed continuously or intermittently in one pass. The recording medium 2 is not limited to cut paper, but may also be continuous roll paper. The liquid ejection head 3 is capable of full-color printing using CMYK (cyan, magenta, yellow, and black) inks as liquids. Each liquid ejection head 3 may correspond to one color or multiple colors. As described below, the liquid ejection head 3 is fluidly connected to a liquid supply unit that constitutes a supply path that supplies ink to the liquid ejection head 3, an ink cartridge 1006 serving as a main tank, and a buffer tank 1003 (see FIG. 3). The liquid ejection head 3 is also electrically connected to an electrical control unit that transmits power and ejection control signals to the liquid ejection head 3. The liquid paths and electrical signal paths within the liquid ejection head 3 will be described later. The recording apparatus 1000 circulates ink through the liquid ejection head 3.

[0012] 2 is a block diagram showing the configuration of a recording apparatus 1000. The recording apparatus 1000 includes a control unit 30 having a CPU 30a such as a microprocessor and a RAM 30b that is used as a work area for the CPU 30a and stores various data such as recording data and registration adjustment values. The control unit 30 includes a ROM 30c that stores the control program for the CPU 30a and various data. The recording apparatus 1100 also includes an interface 31, an operation panel 32, and drivers 35 and 36. The driver 35 drives and controls a motor 34 for driving the transport rollers, circulation pumps 1001, 1002, and 1004 of the ink supply flow path, and a refill pump 1005, while the driver 36 drives the liquid ejection head 3.

[0013] The recording data received by the recording device 1000 is stored in RAM 30b of the control unit 30. In accordance with the recording data stored in RAM 30b, the control unit 30 outputs ON / OFF signals to the driver 35 for driving the motor 34 and outputs ejection signals and the like to the driver 36, thereby forming an image on the recording medium. The control unit 30 also outputs a signal to the driver 35 for driving the circulation pump 1002 in accordance with a control sequence described below, thereby controlling the circulation pump 1002.

[0014] Fig. 3 is a schematic diagram showing a first circulation path as one form of circulation path applied to the recording apparatus according to this embodiment. As shown in Fig. 3, the liquid ejection head 3 is fluidly connected to two first circulation pumps 1001 (high pressure side) and 1002 (low pressure side), a buffer tank 1003, etc. Note that, for the sake of simplicity, Fig. 3 shows only the path through which one color of ink out of CMYK ink flows, but in reality, circulation paths for all four colors are provided in the liquid ejection head 3 and the recording apparatus main body.

[0015] The recording device 1000 is mountable with an ink cartridge 1006 that contains ink, and has a buffer tank 1003 that serves as a sub-tank connected to the ink cartridge 1006. The buffer tank 1003 has an air vent (not shown) that connects the inside of the tank to the outside, and is capable of discharging air bubbles in the ink to the outside. The buffer tank 1003 is also connected to a replenishment pump 1005. When ink is consumed in the liquid ejection head 3, the replenishment pump 1005 transfers the consumed ink from the ink cartridge 1006 to the buffer tank 1003. Ink is consumed in the liquid ejection head 3, for example, when ink is ejected (discharged) from the ejection ports of the liquid ejection head, such as for recording by ejecting ink or for suction recovery.

[0016] The two first circulation pumps 1001 and 1002 draw ink from the liquid connection 111 of the liquid ejection head 3 and send it to the buffer tank 1003. The first circulation pumps 1001 and 1002 are preferably positive displacement pumps with a constant liquid delivery capacity. Specific examples include tube pumps, gear pumps, diaphragm pumps, and syringe pumps. However, pumps that ensure a constant flow rate by arranging a general constant flow valve or relief valve at the pump outlet can also be used. When the liquid ejection head 3 is driven, the first circulation pump (high-pressure side) 1001 and the first circulation pump (low-pressure side) 1002 cause a certain amount of ink to flow through the common supply flow path 211 and the common recovery flow path 212, respectively. This flow rate is preferably set to a level at which the temperature difference between the recording element substrates 10 in the liquid ejection head 3 does not affect the image quality of the recording. However, if the flow rate is set too high, the negative pressure difference between the recording element substrates 10 will become too large due to the influence of pressure loss in the flow paths within the liquid ejection unit 300, resulting in uneven density in the image. For this reason, it is preferable to set the flow rate while taking into consideration the temperature difference and negative pressure difference between the recording element substrates 10.

[0017] The negative pressure control unit 230 is provided in the path connecting the second circulation pump 1004 and the liquid ejection unit 300. Therefore, the negative pressure control unit 230 has the function of maintaining the pressure downstream of the negative pressure control unit 230 (i.e., the liquid ejection unit 300 side) at a preset constant pressure even when the flow rate in the circulation system fluctuates due to differences in printing duties. The two pressure adjustment mechanisms constituting the negative pressure control unit 230 may be any mechanism capable of controlling the pressure downstream of the negative pressure control unit 230 within a certain range centered on a desired set pressure. As an example, a mechanism similar to a so-called "pressure reducing regulator" may be employed. When a pressure reducing regulator is used, it is preferable to pressurize the upstream side of the negative pressure control unit 230 via the liquid supply unit 220 using the second circulation pump 1004, as shown in FIG. 3 . This configuration suppresses the effect of head pressure on the liquid ejection head 3 in the buffer tank 1003, thereby increasing the flexibility of the layout of the buffer tank 1003 in the recording apparatus 1000. The second circulation pump 1004 may be any pump having a head pressure equal to or greater than a certain pressure within the range of ink circulation flow rate used when driving the liquid ejection head 3, such as a turbo pump or a positive displacement pump. Specifically, a diaphragm pump or the like may be used. Also, instead of the second circulation pump 1004, for example, a head tank disposed with a certain head difference relative to the negative pressure control unit 230 may be used.

[0018] 3, the negative pressure control unit 230 has two pressure adjustment mechanisms, each set to a different control pressure. Of the two negative pressure adjustment mechanisms, the one set to a relatively high pressure (indicated as H in FIG. 3) is connected to a common supply flow path 211 in the liquid ejection unit 300 via the liquid supply unit 220. Furthermore, the one set to a relatively low pressure (indicated as L in FIG. 3) is connected to a common recovery flow path 212 via the liquid supply unit 220.

[0019] The liquid ejection unit 300 is provided with a common supply flow path 211, a common recovery flow path 212, and individual supply flow paths 213a and individual recovery flow paths 214b that communicate with each recording element substrate 10. Because the individual supply flow paths 213a and individual recovery flow paths 214b communicate with the common supply flow path 211 and the common recovery flow path 212, a flow (arrow in FIG. 3) occurs in which a portion of the ink flows from the common supply flow path 211 through the internal flow paths of the recording element substrate 10 to the common recovery flow path 212. The reason for this is that a pressure adjustment mechanism H is connected to the common supply flow path 211, and a pressure adjustment mechanism L is connected to the common recovery flow path 212, causing a pressure difference between the two common flow paths.

[0020] In this way, in the liquid ejection unit 300, ink flows through the common supply flow path 211 and the common recovery flow path 212, while a portion of the ink flows through each recording element substrate 10. This allows heat generated in each recording element substrate 10 to be discharged to the outside of the recording element substrate 10 via the flow through the common supply flow path 211 and the common recovery flow path 212. Furthermore, with this configuration, while recording is being performed using the liquid ejection head 3, ink can also flow through ejection ports and pressure chambers that are not performing recording, thereby suppressing thickening of the ink in those areas. Furthermore, thickened ink and foreign matter in the ink can be discharged to the common recovery flow path 212. This allows the liquid ejection head 3 of this embodiment to perform high-speed, high-quality recording.

[0021] 4 is a schematic diagram showing a second circulation path, which is different from the first circulation path described above, among the circulation paths applied to the recording apparatus 1000 according to this embodiment. The main differences from the first circulation path are as follows.

[0022] First, each of the two pressure adjustment mechanisms constituting the negative pressure control unit 230 has a mechanism (a mechanical component having the same function as a so-called "back pressure regulator") that controls the pressure upstream of the negative pressure control unit 230 within a certain range centered on a desired set pressure. Also, the second circulation pump 1004 acts as a negative pressure source that reduces the pressure downstream of the negative pressure control unit 230. Furthermore, the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 are disposed upstream of the liquid ejection head 3, and the negative pressure control unit 230 is disposed downstream of the liquid ejection head 3.

[0023] The negative pressure control unit 230 in the second circulation path operates to keep pressure fluctuations upstream of itself (i.e., the liquid ejection unit 300 side) within a certain range, even if fluctuations in flow rate occur due to changes in the printing duty when printing is performed by the liquid ejection head 3. The pressure fluctuations are kept within a certain range, for example, centered around a preset pressure. As shown in FIG. 4, it is preferable to use the second circulation pump 1004 to pressurize the downstream side of the negative pressure control unit 230 via the liquid supply unit 220. This reduces the effect of the head pressure of the buffer tank 1003 on the liquid ejection head 3, thereby increasing the flexibility in layout of the buffer tank 1003 in the printing apparatus 1000. Note that instead of the second circulation pump 1004, for example, a head tank arranged with a predetermined head difference relative to the negative pressure control unit 230 may be used.

[0024] 4 includes two pressure adjustment mechanisms, each set to a different control pressure. Of the two negative pressure adjustment mechanisms, the one set to a relatively high pressure (indicated as H in FIG. 4) is connected to the common supply flow path 211 in the liquid ejection unit 300 via the liquid supply unit 220. The one set to a relatively low pressure (indicated as L in FIG. 4) is connected to the common recovery flow path 212 via the liquid supply unit 220.

[0025] The two negative pressure adjustment mechanisms make the pressure in the common supply flow path 211 relatively higher than the pressure in the common recovery flow path 212. With this configuration, an ink flow occurs from the common supply flow path 211 through the individual supply flow paths 213 and the internal flow paths of each recording element substrate 10 to the common recovery flow path 212 (arrows in FIG. 4). In this way, the second circulation path achieves an ink flow state similar to that of the first circulation path within the liquid ejection unit 300, but has two advantages different from the first circulation path.

[0026] The first advantage is that, in the second circulation path, the negative pressure control unit 230 is disposed downstream of the liquid ejection head 3, so there is less concern about dust or foreign matter generated by the negative pressure control unit 230 flowing into the liquid ejection head 3. The second advantage is that, in the second circulation path, the maximum flow rate required to supply liquid from the buffer tank 1003 to the liquid ejection head 3 is lower than in the case of the first circulation path. The reason for this is as follows. The sum of the flow rates in the common supply flow path 211 and the common recovery flow path 212 when circulating during standby for recording is defined as A. The value of A is defined as the minimum flow rate required to keep the temperature difference within the liquid ejection unit 300 within a desired range when adjusting the temperature of the liquid ejection head 3 during standby for recording. The ejection flow rate when ink is ejected from all of the ejection ports of the liquid ejection unit 300 (during full ejection) is defined as F. In this case, in the case of the first circulation path (see Figure 3), the set flow rate of the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 is A, so the maximum amount of liquid supplied to the liquid ejection head 3 required for full ejection is A + F.

[0027] On the other hand, in the case of the second circulation path (see FIG. 4), the amount of liquid required to be supplied to the liquid ejection head 3 during standby for printing is flow rate A. The amount of liquid required to be supplied to the liquid ejection head 3 during full ejection is flow rate F. Therefore, in the case of the second circulation path, the sum of the set flow rates of the first circulation pump (high-pressure side) 1001 and the first circulation pump (low-pressure side) 1002, i.e., the maximum required supply flow rate, is the larger of A or F. Therefore, as long as the same liquid ejection unit 300 is used, the maximum required supply flow rate (A or F) in the second circulation path is always smaller than the maximum required supply flow rate (A + F) in the first circulation path. Therefore, the second circulation path offers greater flexibility in the type of circulation pump that can be applied. This allows, for example, the use of a simple, low-cost circulation pump and the reduction of the load on a cooler (not shown) installed in the main body path, resulting in the advantage of reducing the cost of the recording apparatus main body. This advantage is greater for line heads with a relatively large value of A or F, and is more beneficial for line heads with a longer longitudinal length.

[0028] However, the first circulation path has some advantages over the second circulation path. Specifically, in the second circulation path, the flow rate through the liquid ejection unit 300 is at its maximum during standby for printing. Therefore, the lower the printing duty, the higher the negative pressure applied to each ejection port. Therefore, particularly when the flow path widths (lengths perpendicular to the ink flow direction) of the common supply flow path 211 and the common recovery flow path 212 are reduced and the head width (lengths in the shorter direction of the liquid ejection head) is reduced, high negative pressures are applied to the ejection ports in low-duty images where unevenness is easily visible. The application of such high negative pressures may increase the impact of satellite droplets. On the other hand, in the case of the first circulation path, high negative pressures are applied to the ejection ports during high-duty image formation. Therefore, even if satellite droplets are generated, they are less visible, and the impact on the printed image is minimal. A preferable selection can be made between the two circulation paths in light of the specifications of the liquid ejection head and the recording apparatus main body (ejection flow rate F, minimum circulation flow rate A, and flow path resistance within the head).

[0029] Figures 5(a) and 5(b) are perspective views of the liquid ejection head 3. Below, in Figures 5 to 13, a configuration in which one liquid ejection head ejects four colors of ink will be described. As shown in Figure 5(a), the liquid ejection head 3 has a signal input terminal 91 and a power supply terminal 92 electrically connected to each recording element substrate 10 via a flexible wiring substrate 40 and an electrical wiring substrate 90. The signal input terminal 91 and the power supply terminal 92 are electrically connected to a control unit of the recording apparatus 1000, and an ejection drive signal is supplied to the recording element substrate 10 via the signal input terminal 91, and power required for ejection is supplied to the recording element substrate 10 via the power supply terminal 92.

[0030] By consolidating the wiring using the electrical circuit within the electrical wiring board 90, the number of signal input terminals 91 and power supply terminals 92 can be made smaller than the number of printing element substrates 10. This reduces the number of electrical connections that need to be removed when assembling the liquid ejection head 3 to the printing apparatus 1000 or when replacing the liquid ejection head 3. As shown in FIG. 5(b), liquid connections 111 provided at both ends of the liquid ejection head 3 are connected to the liquid supply system of the printing apparatus 1000. This allows ink to be supplied from the supply system of the printing apparatus 1000 to the liquid ejection head 3, and ink that has passed through the liquid ejection head 3 is collected by the supply system of the printing apparatus 1000. In this way, each color of ink can circulate via the paths in the printing apparatus 1000 and the paths in the liquid ejection head 3.

[0031] FIG. 6 is an exploded perspective view of each component or unit that constitutes the liquid ejection head 3. A liquid ejection unit 300, a liquid supply unit 220, and an electric wiring board 90 are attached to a housing 80. A liquid connection part 111 (see FIGS. 3 and 4) is provided in the liquid supply unit 220, and filters 221 (see FIG. 4) for each color are provided inside the liquid supply unit 220 and communicate with the openings of the liquid connection part 111 to remove foreign matter from the ink being supplied. Each of the two liquid supply units 220 is provided with filters 221 for two colors. The ink that passes through the filters 221 is supplied to negative pressure control units 230 that are arranged on the liquid supply unit 220 corresponding to each color.

[0032] The negative pressure control unit 230 is a unit consisting of pressure adjustment valves for each color. The negative pressure control unit 230 significantly attenuates changes in pressure loss within the supply system of the recording apparatus 1000 (the supply system upstream of the liquid ejection head 3) that occur due to fluctuations in the ink flow rate through the action of valves, spring members, and the like provided within each unit. Therefore, the negative pressure control unit 230 can stabilize negative pressure changes downstream of the pressure control unit (the liquid ejection unit 300 side) within a certain range. As shown in FIG. 3, each negative pressure control unit 230 for each color contains two pressure adjustment valves. These pressure adjustment valves are set to different control pressures, and their high-pressure sides communicate with the common supply flow path 211 in the liquid ejection unit 300, and their low-pressure sides communicate with the common recovery flow path 212 via the liquid supply unit 220.

[0033] The housing 80 is composed of a liquid ejection unit support portion 81 and an electric wiring board support portion 82. It supports the liquid ejection unit 300 and the electric wiring board 90 while ensuring the rigidity of the liquid ejection head 3. The electric wiring board support portion 82 supports the electric wiring board 90 and is fixed to the liquid ejection unit support portion 81 with screws. The liquid ejection unit support portion 81 corrects warping and deformation of the liquid ejection unit 300 and ensures the relative positional accuracy of the multiple recording element substrates 10, thereby suppressing streaks and unevenness in printed materials. Therefore, the liquid ejection unit support portion 81 preferably has sufficient rigidity and is preferably made of a metal material such as stainless steel or aluminum, or a ceramic such as alumina. The liquid ejection unit support portion 81 has openings 83 and 84 through which the joint rubber 100 is inserted. Ink supplied from the liquid supply unit 220 is guided via the joint rubber to the third flow path member 70 constituting the liquid ejection unit 300.

[0034] The liquid ejection unit 300 has a plurality of ejection modules 200 and a flow path member 210, and a cover member 130 is attached to the recording medium side surface of the liquid ejection unit 300. Here, as shown in FIG. 6, the cover member 130 is a member having a frame-like surface with a long opening 131 provided therein, and the recording element substrate 10 and sealant 110 (see FIG. 10) included in the ejection module 200 are exposed through the opening 131. The frame portion around the opening 131 functions as an abutment surface for a cap member that caps the liquid ejection head 3 when the liquid ejection unit 300 is on standby for recording. For this reason, it is preferable to apply an adhesive, sealant, filler, or the like around the periphery of the opening 131 to fill in any irregularities or gaps on the ejection port surface of the liquid ejection unit 300, thereby forming a closed space when the liquid ejection unit 300 is capped.

[0035] Next, the configuration of the flow path member 210 included in the liquid ejection unit 300 will be described. As shown in Fig. 6, the flow path member 210 is formed by laminating a first flow path member 50, a second flow path member 60, and a third flow path member 70. The flow path member 210 distributes ink supplied from the liquid supply unit 220 to each ejection module 200, and returns ink circulating from the ejection modules 200 to the liquid supply unit 220. The flow path member 210 is fixed to the liquid ejection unit support part 81 with screws, which prevents the flow path member 210 from warping or deforming.

[0036] 7(a) to 7(f) are diagrams showing the front and back surfaces of the first to third flow path members. FIG. 7(a) shows the surface of the first flow path member 50 on which the discharge module 200 is mounted, and FIG. 7(f) shows the surface of the third flow path member 70 that abuts against the liquid discharge unit support 81. The first flow path member 50 and the second flow path member 60 are joined so that the abutting surfaces of the respective flow path members, that is, the surface shown in FIG. 7(b), and the surface shown in FIG. 7(c), face each other. The second flow path member and the third flow path member are joined so that the abutting surfaces of the respective flow path members, that is, the surface shown in FIG. 7(d), and the surface shown in FIG. 7(e), face each other. By joining the second flow path member 60 and the third flow path member 70, eight common flow paths extending in the longitudinal direction of the flow path members are formed by the common flow path grooves 62 and the common flow path grooves 71 formed in the respective flow path members. 7, a set of a common supply flow path 211 and a common recovery flow path 212 is formed for each color within the flow path member 210. The communication ports 72 of the third flow path member 70 communicate with each hole of the joint rubber 100, and are fluidly connected to the liquid supply unit 220. A plurality of communication ports 61 are formed in the bottom surface of the common flow path groove 62 of the second flow path member 60, and are fluidly connected to one end of the individual flow path grooves 52 of the first flow path member 50. A communication port 51 is formed in the other end of the individual flow path groove 52 of the first flow path member 50, and is fluidly connected to a plurality of discharge modules 200 via the communication ports 51. The individual flow path grooves 52 make it possible to aggregate the flow paths toward the center of the flow path member.

[0037] The first to third flow path members are preferably made of a material that is resistant to corrosion by liquids and has a low linear expansion coefficient. Suitable materials include alumina, LCP (liquid crystal polymer), PPS (polyphenyl sulfide), and PSF (polysulfone) as a base material, and a composite material (resin material) containing inorganic fillers such as silica particles and fibers. The flow path member 210 may be formed by laminating three flow path members and bonding them together, or by welding when a resin composite resin material is selected as the material.

[0038] 8 is a partially enlarged perspective view of the flow paths in a flow path member 210 formed by joining the first to third flow path members, viewed from the side of the first flow path member 50 on which the ejection module 200 is mounted. The connection relationship of each flow path in the flow path member 210 will be described below. The flow path member 210 is provided with common supply flow paths 211 (211a, 211b, 211c, 211d) and common recovery flow paths 212 (212a, 212b, 212c, 212d) that extend in the longitudinal direction of the liquid ejection head 3 for each color. A plurality of individual supply flow paths (213a, 213b, 213c, 213d) formed by individual flow path grooves 52 are connected to the common supply flow path 211 for each color via communication ports 61. Furthermore, a plurality of individual recovery flow paths (214a, 214b, 214c, 214d) formed by the individual flow path grooves 52 are connected to the common recovery flow path 212 for each color via the communication ports 61. With this flow path configuration, ink can be collected from each common supply flow path 211 via the individual supply flow paths 213 to the recording element substrate 10 located in the center of the flow path member 210. Furthermore, ink can be recovered from the recording element substrate 10 via the individual recovery flow paths 214 to each common recovery flow path 212.

[0039] 9 is a cross-sectional view taken along line IX-IX in FIG. 8. As shown in this figure, each of the individual recovery channels (214a, 214c) communicates with the ejection module 200 via the communication port 51. While only the individual recovery channels (214a, 214c) are shown in FIG. 9, in another cross-section, the individual supply channels 213 communicate with the ejection module 200 as shown in FIG. 8. A channel is formed in the support member 33 and the recording element substrate 10 included in each ejection module 200 to supply ink from the first channel member 50 to the recording elements 15 (see FIG. 11(b)) provided on the recording element substrate 10. A channel is also formed in the support member 33 and the recording element substrate 10 to recover (return) some or all of the ink supplied to the recording elements 15 to the first channel member 50. Here, the common supply flow path 211 for each color is connected to the negative pressure control unit 230 (high pressure side) of the corresponding color via the liquid supply unit 220, and the common recovery flow path 212 is connected to the negative pressure control unit 230 (low pressure side) via the liquid supply unit 220. This negative pressure control unit 230 generates a differential pressure (pressure difference) between the common supply flow path 211 and the common recovery flow path 212. For this reason, within the liquid ejection head in which the flow paths are connected as shown in Figures 8 and 9, a flow is generated for each color that flows in the order of the common supply flow path 211 -> individual supply flow path 213a -> recording element substrate 10 -> individual recovery flow path 214b -> common recovery flow path 212.

[0040] FIG. 10(a) is a perspective view showing one ejection module 200, and FIG. 10(b) is an exploded view of the ejection module 200. The manufacturing method of the ejection module 200 involves first adhering the recording element substrate 10 and the flexible wiring substrate 40 to a support member 33, which is provided with a liquid communication port 37. Then, the terminals 16 on the recording element substrate 10 are electrically connected to the terminals 41 on the flexible wiring substrate 40 by wire bonding, and then the wire-bonded portion (electrical connection portion) is covered and sealed with a sealant 110. The terminals 42 on the flexible wiring substrate 40 on the side opposite the recording element substrate 10 are electrically connected to the connection terminals 93 (see FIG. 6) on the electrical wiring substrate 90. The support member 33 is a support that supports the recording element substrate 10 and also a flow path member that fluidly connects the recording element substrate 10 and the flow path member 210. Therefore, it is preferable that the support member 33 has high flatness and can be bonded to the recording element substrate with sufficiently high reliability. Examples of the material for the support member 33 include alumina and resin.

[0041] Fig. 11(a) is a plan view of the surface of the recording element substrate 10 on which the ejection ports 13 are formed, Fig. 11(b) is an enlarged view of the portion indicated by Xb in Fig. 11(a), and Fig. 11(c) is a plan view of the back surface of Fig. 10(a). Fig. 12 is a perspective view showing a cross section of the recording element substrate 10 and the cover member 20 taken along the cross-sectional line XII-XII shown in Fig. 11(a). The configuration of the recording element substrate 10 will be described below.

[0042] 11(a), four ejection port arrays corresponding to the respective ink colors are formed in the ejection port forming member 12 of the recording element substrate 10. Note that hereinafter, the direction in which the ejection port arrays in which the multiple ejection ports 13 are arranged extend will be referred to as the "ejection port array direction."

[0043] As shown in FIG. 11(b), a recording element 15, which is a heating element for causing bubbles in the ink using thermal energy, is disposed at a position corresponding to each ejection port 13. A partition 22 defines a pressure chamber 23, inside which the recording element 15 is disposed. The recording element 15 is electrically connected to the terminal 16 shown in FIG. 11(a) by electrical wiring (not shown) provided on the recording element substrate 10. The recording element 15 generates heat and boils the ink based on a pulse signal input from the control circuit of the recording device 1000 via the electrical wiring substrate 90 (FIG. 5) and the flexible wiring substrate 40 (see FIG. 10(b)). The bubbling force caused by this boiling causes the ink to be ejected from the ejection port 13. As shown in FIG. 12(b), a liquid supply path 18 extends on one side along each ejection port row, and a liquid recovery path 19 extends on the other side. The liquid supply path 18 and the liquid recovery path 19 are flow paths that extend in the direction of the ejection port array provided on the recording element substrate 10, and communicate with the ejection ports 13 via the supply path 17a and the recovery path 17b, respectively.

[0044] As shown in FIGS. 11(b) and 12, a sheet-like lid member 20 is laminated on the back surface of the recording element substrate 10 opposite the surface on which the ejection ports 13 are formed. The lid member 20 is provided with a plurality of openings 21 that communicate with the liquid supply channels 18 and liquid recovery channels 19, which will be described later. Three openings 21 are provided in the lid member 20 for each liquid supply channel 18, and two openings 21 are provided in the lid member 20 for each liquid recovery channel 19. As shown in FIG. 11(c), each opening 21 in the lid member 20 communicates with a plurality of communication ports 51 shown in FIG. 8 and other figures. As shown in FIG. 12, the lid member 20 functions as a lid that forms part of the walls of the liquid supply channels 18 and liquid recovery channels 19 formed in the substrate 11 of the recording element substrate 10. The lid member 20 is preferably made of a material that has sufficient corrosion resistance to ink, and from the standpoint of preventing color mixing, high precision is required for the shape and position of the openings 21. For this reason, it is preferable to use a photosensitive resin material or a silicon plate as the material for the lid member 20, and to form the openings 21 by a photolithography process. In this way, the lid member changes the pitch of the flow paths by the openings 21, and in consideration of pressure loss, it is desirable that the lid member be thin and made of a film-like material.

[0045] Next, the flow of ink within the recording element substrate 10 will be described. As shown in Figure 12, the recording element substrate 10 is formed by laminating a substrate 11 made of Si and an ejection port forming member 12 made of photosensitive resin, and a lid member 20 is bonded to the back surface of the substrate 11. Recording elements 15 are formed on one surface of the substrate 11 (see Figure 11(b)), and grooves that form liquid supply paths 18 and liquid recovery paths 19 that extend along the ejection port array are formed on the back surface. The liquid supply paths 18 and liquid recovery paths 19 formed by the substrate 11 and the lid member 20 are connected to a common supply path 211 and a common recovery path 212 in a path member 210, respectively, and a pressure difference is generated between the liquid supply path 18 and the liquid recovery path 19.

[0046] When ink is ejected from the multiple ejection ports 13 of the liquid ejection head 3 to perform printing, the differential pressure causes the ink flow in the liquid supply path 18 provided in the substrate 11 to follow the flow indicated by arrow C in FIG. 12 at ejection ports that are not performing the ejection operation. That is, the ink flows to the liquid recovery path 19 via the supply port 17a, the pressure chamber 23, and the recovery port 17b. This flow allows the ink, which has increased in viscosity due to evaporation from the ejection ports 13 and the pressure chamber 23 that are not performing printing, as well as bubbles and foreign matter, to be recovered to the liquid recovery path 19. This flow also makes it possible to suppress the increase in viscosity of the ink in the ejection ports 13 and the pressure chamber 23. The ink recovered to the liquid recovery path 19 passes through the opening 21 of the cover member 20 and the liquid communication port 37 of the support member 33 (see FIG. 10(b)), and is then recovered to the communication port 51 in the flow path member 210, the individual recovery path 214, and the common recovery path 212 in that order. This ink is ultimately recovered to the supply path of the recording device 1000.

[0047] In other words, ink supplied from the recording apparatus main body to the liquid ejection head 3 flows, and is supplied and recovered in the following order: The ink first flows into the liquid ejection head 3 from the liquid connection portion 111 of the liquid supply unit 220. The ink is then supplied, in this order, to the joint rubber 100, the communication port 72 and common flow path groove 71 provided in the third flow path member, the common flow path groove 62 and communication port 61 provided in the second flow path member, and the individual flow path grooves 52 and communication port 51 provided in the first flow path member. The ink is then supplied to the pressure chambers 23 via the liquid communication port 37 provided in the support member 33, the opening 21 provided in the cover member, and the liquid supply path 18 and supply port 17a provided in the substrate 11. Of the ink supplied to the pressure chambers 23, the ink that is not ejected from the ejection port 13 flows, in this order, through the recovery port 17b and liquid recovery path 19 provided in the substrate 11, the opening 21 provided in the cover member, and the liquid communication port 37 provided in the support member 33. The ink then flows sequentially through the communication ports 51 and individual flow channel grooves 52 provided in the first flow channel member, the communication ports 61 and common flow channel groove 62 provided in the second flow channel member, the common flow channel groove 71 and communication ports 72 provided in the third flow channel member 70, and the joint rubber 100. The ink then flows from the liquid connection portion 111 provided in the liquid supply unit to the outside of the liquid ejection head 3. In the configuration of the first circulation path shown in FIG. 3, the ink that flows in from the liquid connection portion 111 passes through the negative pressure control unit 230 and is then supplied to the joint rubber 100. In the configuration of the second circulation path shown in FIG. 3, the ink recovered from the pressure chamber 23 passes through the joint rubber 100, and then flows from the liquid connection portion 111 to the outside of the liquid ejection head via the negative pressure control unit 230.

[0048] 3 and 4, not all of the ink that flows in from one end of the common supply flow path 211 of the liquid ejection unit 300 is supplied to the pressure chambers 23 via the individual supply flow paths 213a. Some ink flows from the other end of the common supply flow path 211 to the liquid supply unit 220 without flowing into the individual supply flow paths 213a. In this way, by providing a flow path that does not pass through the recording element substrate 10, it is possible to prevent backflow of the circulating flow of ink, even in the case of a recording element substrate 10 that has fine flow paths with high flow resistance. In this way, the liquid ejection head 3 can prevent the viscosity of the ink in the pressure chambers and in the vicinity of the ejection ports from increasing, thereby preventing deviations from the normal ejection direction and ejection failures, thereby enabling high-quality printing.

[0049] FIG. 13 is a partially enlarged plan view showing the adjacent portions of the recording element substrates 10 in two adjacent ejection modules. As shown in FIG. 11(a) and other figures, the recording element substrates 10 are generally parallelogram-shaped. As shown in FIG. 13, each of the ejection port arrays (14a-14d) in which the ejection ports 13 are arranged in each of the recording element substrates 10 is arranged at a fixed angle with respect to the recording medium transport direction. As a result, the ejection port arrays in the adjacent portions of the recording element substrates 10 overlap in the recording medium transport direction, with at least one ejection port overlapping with the recording medium transport direction. In FIG. 13, two ejection ports on line D overlap with each other. With this arrangement, even if the position of the recording element substrate 10 is slightly shifted from the predetermined position, drive control of the overlapping ejection ports can make black stripes and white gaps in the recorded image less noticeable. The configuration shown in FIG. 13 can also be achieved when multiple recording element substrates 10 are arranged in a straight line (inline) rather than in a staggered arrangement. This makes it possible to prevent black streaks and white spots at the joints between the recording element substrates 10 while suppressing an increase in the length of the liquid ejection head 3 in the recording medium transport direction. Note that although the main plane of the recording element substrate 10 is a parallelogram here, this is not limited to this, and the present invention can also be preferably applied to recording element substrates of, for example, a rectangle, a trapezoid, or other shapes.

[0050] Fig. 14(a) is an enlarged plan view schematically showing the vicinity of the thermal application portion in the recording element substrate 10, and Fig. 14(b) is a cross-sectional view taken along the dashed dotted line XIVb-XIVb in Fig. 14(a). The structure of the thermal application portion in the recording element substrate according to this embodiment will be described below.

[0051] In the liquid ejection head 3, a liquid ejection recording substrate is formed by stacking multiple layers on a base (not shown) made of silicon. In this embodiment, a heat storage layer (not shown) made of a thermal oxide film, SiO film, SiN film, or the like is disposed on the base. A heating resistor 126 is disposed on the heat storage layer, and a wiring layer (not shown) made of a metal material such as Al, Al-Si, or Al-Cu (formed below the insulating layer 127 in FIG. 4(b)) is connected to the heating resistor 126 via a tungsten plug 128. The heating resistor 126 generates heat when current is applied via the electrode wiring layer (not shown).

[0052] 14(b), the heating resistor 126 is covered with an insulating protective layer 127. The insulating protective layer 127 is an insulating layer that is also provided on the upper side of the heating resistor 126 so as to cover the heating resistor 126. The insulating protective layer 127 is formed of an SiO film, a SiN film, or the like.

[0053] Three protective layers are disposed on the insulating protective layer 127 to prevent the insulating protective layer 127 from coming into contact with liquid. The three protective layers include a lower protective layer 125, an upper protective layer 124, and an adhesive protective layer 123, and protect the surface of the heating resistor 126 from chemical and physical shocks caused by heat generation by the heating resistor 126.

[0054] In this embodiment, the lower protective layer 125 is made of tantalum (Ta), the upper protective layer 124 is made of iridium (Ir), and the adhesive protective layer 123 is made of tantalum (Ta). Protective layers made of these materials are electrically conductive. An adhesive protective layer 122 is disposed on the adhesive protective layer 123 to provide liquid resistance and improve adhesion to the ejection port forming member 12. The adhesive protective layer 122 is formed of SiC. The adhesive protective layer 122 is not disposed in the position corresponding to the heating resistor 126, and the upper protective layer 124 is exposed within the pressure chamber 23, providing a protective portion for the heating resistor 126. This region is the thermally active portion during ejection. The upper protective layer 124 is formed of a material that contains a metal that dissolves due to an electrochemical reaction and does not form an oxide film that prevents dissolution when heated.

[0055] The upper protective layer 124 of the heat application part is in contact with the liquid, and when the liquid is discharged, the temperature of the liquid rises instantaneously, causing bubbles to form, which then disappear, resulting in cavitation. For this reason, in this embodiment, the upper protective layer 124, which is made of a highly corrosion-resistant and reliable iridium material, is arranged in a position that comes into contact with the liquid.

[0056] In this embodiment, an ink circulation configuration is adopted in which liquid is supplied from the supply port 17a and recovered to the recovery port 17b inside the pressure chamber 23. Therefore, during printing, the liquid flows over the heating resistor 126 in a direction from the supply port 17a on the upstream side to the recovery port 17b on the downstream side.

[0057] In the case of a method in which ink is ejected by heating the heating resistor 126, the ink may be scorched on the surface of the upper protective layer 124 due to the heating of the ink by the heating resistor 126, which may change the ejection speed.

[0058] Therefore, an electrode (electrode portion) 129 is formed in the pressure chamber 132, which is electrically connected to the upper protective layer 124 (protective portion) of the heat application portion via ink. By applying a voltage between the electrode 129 and the upper protective layer 124, an electrical connection is established between them via the ink, and the upper protective layer 124, made of iridium, is dissolved into the ink (liquid). This dissolution removes kogation that has accumulated on the upper protective layer 124. More specifically, the portion of the upper protective layer 124 directly above the heating resistor 126 serves as one electrode (anode) 121, and the electrode 129 serves as the other electrode (cathode). This causes an electrochemical reaction (metal dissolution reaction) to occur, dissolving the metal of the upper protective layer 124 into the ink. By dissolving the metal of the upper protective layer 124 into the ink in this way, the kogation that has accumulated on the upper protective layer 124 is removed along with the dissolution of the metal.

[0059] In addition, the portion of the upper protective layer 124 directly above the heating resistor 126 (in the direction of ink ejection relative to the heating resistor 126) may be used as one electrode 121, and the other may be used as a ground wiring (not shown), or an electrode opposite to the electrode 121 may be provided.

[0060] In this way, by removing the kogation accumulated on the upper protective layer 124 (hereinafter referred to as the kogation removal operation), the surface of the heat application portion can be made to have no kogation or a state with little kogation. Conventionally, the kogation removal operation is performed, for example, when the number of drive pulses applied to the plurality of heating resistors 126 arranged in the liquid ejection head 3 is set to a predetermined value (for example, 5×10 8 ) was implemented uniformly at the timing of the above.

[0061] However, the degree of kogation varies depending on the type of ink and changes in ink properties due to shipping of the ink cartridge. Therefore, if a certain number of drive pulses is set as a threshold and the kogation removal operation is performed uniformly, it is possible that the kogation removal operation will be performed in a situation where the kogation adhesion is not severe enough to affect the ejection characteristics. In this way, performing the kogation removal operation before the kogation adhesion affects the ejection characteristics may shorten the life of the heating resistor.

[0062] Therefore, in this embodiment, the timing for performing the kogation removal operation is determined based on the type of ink, the ink distribution time, the elapsed time since the ink cartridge 1006 was mounted in the mounting portion of the recording device 1000, and the number of drive pulses for the corresponding electrothermal conversion element.

[0063] Kogane removal is preferably performed when ejection characteristics, such as ejection speed, change to a degree that affects the image. For example, it is known that a 2 m / s slower ejection speed results in image degradation, such as uneven density and misaligned lines. It is also known that the number of drive pulses required to slow the ejection speed by 2 m / s varies depending on conditions such as the type of ink, the ink flow time, and the time elapsed since installation. Therefore, in this embodiment, the number of drive pulses required to slow the ejection speed by 2 m / s from a kogane-free state is obtained in advance through experiments for various conditions and stored as a threshold value associated with each condition. The kogane removal operation is then performed when the total number of drive pulses since the liquid ejection head was first used or since the previous kogane removal operation exceeded this threshold.

[0064] The speed to be slowed down is not limited to 2 m / s, and it is desirable to set it appropriately according to the device.

[0065] Here, let us consider an ink that requires twice as many drive pulses to reduce the ejection speed by 2 m / s compared to other inks. 8 15(b) is a graph showing the relationship between the ejection speed and the number of ejections (number of drive pulses) for the ink when the kogation removal operation is performed when the ink density reaches or exceeds 1 / 200 of the ink density. Fig. 15(b) is a graph showing the relationship between the ejection speed and the number of ejections for the ink when the kogation removal operation is performed in accordance with the ink type, distribution time, and elapsed time since installation in this embodiment.

[0066] As shown in FIG. 15(b), the number of drive pulses until the next kogation removal operation is set to a predetermined number (e.g., 5×10 8 ) than (for example, 10 × 10 8 =1.0×10 9 ) and the period until the kogation removal operation is performed is longer than before. In other words, it is possible to avoid performing the kogation removal operation more than necessary when the ejection characteristics have not changed significantly. As a result, the life of the liquid ejection head can be extended compared to before.

[0067] On the other hand, for inks that require half the number of drive cycles to reduce the ejection speed by 2 m / s, the number of drive pulses required until the next kogation removal operation is a predetermined number of drive pulses (for example, 5 × 10 8 ) (e.g., 2.5 × 10 8 ) As a result, the time required to perform the kogation removal operation is shorter than before. In other words, the kogation removal operation can be performed at the appropriate timing when the ejection characteristics change. As a result, it is possible to prevent a decrease in image quality.

[0068] The threshold value is the number of driving pulses of the electrothermal conversion element, which is 5×10 8 ~6×10 9 It is desirable that the range is within the range.

[0069] 5 to 13, for the sake of convenience, one liquid ejection head 3 is described as ejecting ink of four colors. However, in the present embodiment described below, the liquid ejection head 3 is described as ejecting only one color of ink (one type of liquid). The liquid ejection device has detachable liquid ejection heads 3 in a number corresponding to the ink colors to be used, and ink cartridges 1006 that contain ink to be supplied to each liquid ejection head 3.

[0070] FIG. 16 is a diagram showing an example of a model of communication between the liquid ejection head 3, the main body of the recording apparatus 1000, and the ink cartridge 1006. The main body circuit board 1500 built into the main body of the recording apparatus 1000 has a CPU 30a, a ROM 30c, a RAM 30b, etc. (see FIG. 2). The CPU 30a of the main body circuit board 1500 receives information from the ROM 151 of the ink cartridge 1006, such as the manufacturing date and time of the ink cartridge 1006, the ink type, the amount of ink filled, and installation information for the ink cartridge 1006 in the main body. Then, by referencing tables and the like stored in advance in the ROM 30c of the main body circuit board 1500, the CPU 30a transmits threshold values ​​associated with each condition as information related to the ejection characteristics of the ink cartridge 1006 to the electrical wiring board 90 of the liquid ejection head 3. The CPU 30a also writes installation information for the ink cartridge 1006 in the main body to the ROM 30c.

[0071] Furthermore, the CPU 30a of the main substrate 1500 receives temperature information on each recording element substrate 10 from the liquid ejection head 3, and transmits control signals to the electrical wiring substrate 90 of the liquid ejection head 3 to drive each recording element substrate 10 based on the received temperature information.

[0072] FIG. 17 shows an example of a table referenced by the CPU 30a to determine whether to perform a kogation removal operation. The table associates the ink type of the ink cartridge 1006, its distribution time (current time minus the manufacturing date), and its installation time with the number of drive pulses since the previous kogation removal operation, which is appropriate for performing the kogation removal operation. Based on this table, the CPU 30a determines the timing for performing the kogation removal operation using the liquid ejection head 3 that ejects ink supplied from the installed ink cartridge 1006. While the example in FIG. 17 illustrates a configuration in which the number of drive pulses is set based on three conditions: ink type, distribution time, and elapsed time since installation, the table may also be configured to set the number of drive pulses based on at least one condition. For example, the threshold number of drive pulses may be associated one-to-one with the ink type. Furthermore, the threshold number of drive pulses may be associated one-to-one with the sum of the distribution time and the elapsed time since installation. In FIG. 17, the "W" in the table represents "Week."

[0073] FIG. 18 is a flowchart showing an example of the sequence of a series of recording processes and kogation removal processes in this embodiment. The series of processes shown in FIG. 18 is performed by the CPU 30a of the recording device 1000 expanding program code stored in program memory into data memory and executing it. Alternatively, some or all of the functions of the steps in FIG. 18 may be realized by hardware such as an ASIC or electronic circuit. Note that the symbol "S" in the description of each process indicates a step in the flowchart. The recording processes and kogation removal processes in this embodiment will be described below using the flowchart in FIG. 18.

[0074] When a print job is input, the CPU 30a reads the cartridge information from the ROM 151 of the ink cartridge 1006 in S1801. The cartridge information includes the cartridge number, ink type, manufacturing date, amount of ink filled, and time of installation in the main body. In S1802, the CPU 30a refers to the table stored in the ROM 30c, and determines the threshold value (predetermined threshold value) for the number of drive pulses based on the information read in S1801. For example, suppose the ink type contained in the target ink cartridge 1006 is "ink A," the transportation time of the cartridge is "2W," and the installation time of the cartridge is "1W." In this case, the CPU 30a determines "6 x 10 9 " is set as the threshold value of the liquid ejection head 3 corresponding to the ink cartridge.

[0075] In S1803, the CPU 30a performs recording processing according to the input recording job. After the recording processing is completed, in S1804, the CPU 30a writes the installation time of the ink cartridge 1006 stored in the ROM 30c of the recording device 1000 to the ROM 151 of the ink cartridge 1006. In other words, the installation time of the ink cartridge 1006 stored in the ROM 151 of the ink cartridge 1006 is updated.

[0076] Thereafter, in S1805, the CPU 30a determines whether the number of drive pulses exceeds the threshold determined in S1802. If it exceeds the threshold (Yes), the process proceeds to S1806; if it does not exceed the threshold (No), the process proceeds to S1807. If the process proceeds to S1806, the CPU 30a performs a kogation removal operation (removal of kogation) by dissolving the upper protective layer 124 into the ink through an electrochemical reaction. In S1807, the CPU 30a determines whether the next job has been received. If it has been received (No), the process returns to S1801 and repeats. If the next job has not been received, the process ends.

[0077] In this way, the kogation removal operation is performed by dissolving the metal of the protective layer through an electrochemical reaction with the ink based on information about the ink ejection characteristics. This allows the kogation removal operation to be performed at the appropriate time, enabling stable liquid ejection without shortening the life of the liquid ejection head.

[0078] In this embodiment, the recording apparatus 1000 is described as circulating ink through the liquid ejection head 3, but the present invention is not limited to this and can be applied to a recording apparatus that does not circulate ink. Also, in this embodiment, the line-type liquid ejection head is described as an example, but the present invention is not limited to this and can be applied to a serial-type liquid ejection head that performs recording by alternately moving the liquid ejection head and the recording medium relative to each other.

[0079] (Second embodiment) The second embodiment of the present invention will be described below with reference to the drawings. Note that the basic configuration of this embodiment is the same as that of the first embodiment, so only the characteristic configuration will be described below.

[0080] In this embodiment, a test image for density detection is printed, the printed image is read by a scanner, and the burnt removal process is performed based on whether the density of the read image is within a predetermined target density range.

[0081] If kogation occurs on the upper protective layer 124 and the ejection speed decreases, the ejection speed differs between the ejection ports corresponding to the kogated upper protective layer 124 and the ejection ports corresponding to the non-kogated upper protective layer 124, resulting in density unevenness in the image even when an image of uniform density is recorded. Whether or not to perform kogation removal processing is determined depending on whether or not the density unevenness in the image is within a preset target density range.

[0082] FIG. 19 is a flowchart showing the recording process in this embodiment. The series of processes shown in FIG. 19 is performed by the CPU 30a of the recording device 1000 expanding program code stored in program memory into data memory and executing it. Alternatively, some or all of the functions of the steps in FIG. 19 may be realized by hardware such as an ASIC or electronic circuit. Note that the symbol "S" in the description of each process indicates a step in the flowchart. The recording process and kogation removal process in this embodiment will be described below using the flowchart in FIG. 19.

[0083] When a print job is input, the CPU 30a performs test printing of an image of uniform density in S1901. In S1902, the CPU 30a reads the printed image of uniform density using a scanner, which is an optical sensor. Thereafter, in S1903, the CPU 30a determines whether the density of the read image (information related to ejection characteristics) is within a preset target density range. If it is within the set target density range, the process proceeds to S1905; if it is not within the set target density range, the process proceeds to S1904. In S1904, the CPU 30a performs a kogation removal operation (removal of kogation) by dissolving the upper protective layer 124 into the ink through an electrochemical reaction. In S1905, the CPU 30a performs printing processing in accordance with the print job and then ends this process.

[0084] In this way, according to this embodiment, the kogation removal operation is performed based on information about the ejection characteristics, which is the density of the read image. This allows the kogation removal operation to be performed at the appropriate time, making it possible to eject liquid stably without shortening the life of the liquid ejection head.

[0085] (Third embodiment) The third embodiment of the present invention will be described below with reference to the drawings. Note that the basic configuration of this embodiment is the same as that of the first embodiment, so only the characteristic configuration will be described below.

[0086] In this embodiment, a discharge speed detection pattern is recorded, the recorded pattern is read by a scanner, which is an optical sensor, and the kogation removal process is carried out based on the discharge speed rank determined from the read discharge speed detection pattern.

[0087] FIG. 20 is a flowchart showing the recording process in this embodiment. The series of processes shown in FIG. 20 is performed by the CPU 30a of the recording device 1000 by loading program code stored in program memory into data memory and executing it. Alternatively, some or all of the functions of the steps in FIG. 20 may be realized by hardware such as an ASIC or electronic circuit. Note that the symbol "S" in the description of each process indicates a step in the flowchart. The recording process and kogation removal process in this embodiment will be described below using the flowchart in FIG. 20.

[0088] When a print job is input, the CPU 30a records a discharge speed detection pattern in S2001. In S2002, the CPU 30a reads the recorded discharge speed detection pattern with a scanner and selects a discharge speed rank. Thereafter, in S2003, the CPU 30a determines whether the selected discharge speed rank (information on the discharge characteristics) is within a preset target range. If it is within the set target range, the process proceeds to S2005; if it is not within the set target range, the process proceeds to S2004. When the process proceeds to S2004, the CPU 30a performs a kogation removal operation (removal of kogation) by dissolving the upper protective layer 124 into the ink through an electrochemical reaction. When the CPU 30a proceeds to S2005, it performs printing processing in accordance with the print job and ends this process.

[0089] Figure 21 is a diagram showing an example of a discharge speed detection pattern. In the figure, dots printed while moving the recording medium in the forward direction are shown as black circles (forward printing), and dots printed while moving the recording medium in the backward direction are shown as diagonal circles (backward printing). For ease of explanation, dots printed by six discharge elements are shown here. Note that when a serial type liquid discharge head is used, a similar pattern can be printed while moving the liquid discharge head back and forth relative to the recording medium.

[0090] In the ejection speed detection pattern, the first column 311 of forward recording and the second column 312 of forward recording are ejected so that they land with a 300 dpi pixel offset from each other. The ejection timing is also adjusted so that the first column 313 of backward recording and the second column 314 of backward recording are offset by a 300 dpi pixel, and so that they land with a 1200 dpi pixel offset from the first column 311 and the second column 312 of forward recording. When there is no scorching on the heated area and ink is ejected at a standard speed, a dot pattern like the one shown in rank 0 is obtained. On the other hand, when scorching occurs on the heated area and ink is ejected at a speed slower than the standard, a dot pattern like the one shown in rank 1 is formed. Conversely, when ink is ejected at a speed faster than the standard, a dot pattern like the one shown in rank -1 is formed. By reading the ejection speed detection pattern recorded in this way with the scanner of the recording apparatus 1000 in S2002 of FIG. 20, the ejection speed rank can be selected from the reading result (the amount of deviation of the landing position between forward recording and backward recording).

[0091] For example, if the selected rank is within ±1, the CPU 30a determines YES in S2003 and does not perform the kogation removal operation, but if the selected rank exceeds ±1, the CPU 30a determines NO in S2003 and performs the kogation removal operation.

[0092] In this way, the kogation removal operation is performed based on information about the ejection characteristics, which is the ejection speed rank selected from the read ejection speed pattern. This allows the kogation removal operation to be performed at the appropriate time, making it possible to eject liquid stably without shortening the life of the liquid ejection head.

[0093] (Other embodiments) In the above, we have explained how the burnt removal operation is performed when a recording job is input, but the burnt removal determination process may also be performed periodically regardless of the recording job, or may be performed in response to a user instruction.

[0094] In the above embodiment, one liquid ejection head 3 ejects ink of one color, and the kogation removal operation is performed for each liquid ejection head 3 corresponding to each color, but the present disclosure is not limited to this. One liquid ejection head 3 may also eject multiple inks. In this case, the kogation removal operation may be performed for each ejection element array corresponding to each color. Also, the ink cartridge may be integrated with the recording head.

[0095] The disclosure of this embodiment includes the following configurations and methods.

[0096] (Configuration 1) a heating resistor that generates heat when energized to generate energy for ejecting liquid; a protective portion that covers and protects the heating resistor; an electrode portion that is electrically conductive with the protective portion via a liquid; a discharge means having a control unit that controls a kogation removal operation by applying a voltage between the protective unit and the electrode unit to dissolve the protective unit in a liquid and remove the kogation; A liquid ejection device comprising: The liquid ejection device is characterized in that the control means determines the timing for executing the kogation removal operation in the ejection means that ejects the liquid, based on information related to the ejection characteristics of the liquid.

[0097] (Configuration 2) 2. The liquid ejection device according to configuration 1, wherein the information regarding the ejection characteristics is a threshold value of the total number of drive pulses applied to the heating resistor of the ejection means after the previous kogation removal operation of the ejection means is performed.

[0098] (Configuration 3) a mounting portion capable of mounting a plurality of cartridges for supplying liquid to each of the plurality of discharge means, each of the plurality of cartridges has a storage means for storing at least one piece of information on the type of liquid contained therein, the time of distribution, and the time elapsed since the cartridge was attached to the liquid ejection device; 3. The liquid ejection device according to configuration 2, wherein the control means sets the threshold value for each of the ejection means based on the information read from the storage means.

[0099] (Configuration 4) The threshold is 5×10 8 ~6×10 9 4. The liquid ejection device according to configuration 2 or 3, which is within the range of (a) to (c).

[0100] (Configuration 5) 2. The liquid ejection device according to configuration 1, wherein the information about the ejection characteristics is the density of an image formed by ejection by the ejection means.

[0101] (Configuration 6) 6. The liquid ejection apparatus according to configuration 5, wherein the control unit executes the kogation removal operation when the density of the image is not within a preset target density range.

[0102] (Configuration 7) 2. The liquid ejection device according to configuration 1, wherein the information regarding the ejection characteristics is the ejection speed of the ejection means.

[0103] (Configuration 8) 8. The liquid ejection device according to configuration 7, wherein the control means executes the kogation removal operation when the ejection speed is not within a preset target range.

[0104] (Configuration 9) 9. The liquid ejection device according to configuration 7 or 8, wherein the ejection speed is acquired based on the amount of deviation of the landing position of the ejection means between forward printing and backward printing on the recording medium.

[0105] (Configuration 10) 10. The liquid ejection device according to any one of configurations 1 to 9, wherein the protective portion and the electrode portion are made of the same metal material.

[0106] (Configuration 11) 10. The liquid ejection device according to any one of configurations 1 to 9, wherein the electrode portion is grounded during the kogation removal operation.

[0107] (Method 1) a discharge step of discharging liquid by the action of a heating resistor; an acquisition step of acquiring information about the ejection characteristics of the liquid; an elution step of eluting the metal of the protective layer provided on the portion of the heating resistor that is subjected to heat by an electrochemical reaction with a liquid; A method for controlling a liquid ejection device, comprising: A method for controlling a liquid ejection device, wherein the elution step is performed based on information about the ejection characteristics of the liquid acquired in the acquisition step.

[0108] (Method 2) The method for controlling a liquid ejection device according to Method 1, wherein the information regarding the ejection characteristics is a threshold value for the total number of drive pulses applied to the heating resistor after the previous kogation removal operation in the ejection process is performed.

[0109] (Method 3) a mounting step of mounting a plurality of cartridges for supplying liquid to each of the plurality of discharge means, a storing step of storing at least one piece of information of the type of liquid contained therein, the distribution time, and the elapsed time since the cartridge was attached to the liquid ejection device in a storing means of the cartridges, The method for controlling a liquid ejection device according to Method 2, wherein the threshold value is set for each of the ejection means based on the information read out from the storage means.

[0110] (Method 4) The method for controlling a liquid ejection device according to Method 1, wherein the information regarding the ejection characteristics is the density of an image formed by ejection in the ejection step.

[0111] (Method 5) The liquid ejection device control method according to Method 4, wherein the kogation removal operation is executed when the density of the image is not within a preset target density range.

[0112] (Method 6) The method for controlling a liquid ejection device according to Method 1, wherein the information regarding the ejection characteristics is the ejection speed of the ejection means.

[0113] (Method 7) The method for controlling a liquid ejection device according to Method 6, wherein the kogation removal operation is executed when the ejection speed is not within a preset target range.

[0114] (Method 8) 8. The method for controlling a liquid ejection device according to Method 6 or 7, wherein the ejection speed is acquired based on the amount of deviation of the landing position of the ejection means between forward printing and backward printing on the recording medium. [Explanation of symbols]

[0115] 3 Liquid ejection head 10. Recording element board 13 Outlet 124 Upper protective layer 125 Lower protective layer 126 Heating resistor 200 Dispensing Module 1000 Recording Device

Claims

1. a heating resistor that generates heat when energized to generate energy for ejecting liquid; a protective portion that covers and protects the heating resistor; an electrode portion that is electrically conductive with the protective portion via a liquid; a discharge means having a control unit that controls a kogation removal operation by applying a voltage between the protective unit and the electrode unit to dissolve the protective unit in a liquid and remove the kogation; A liquid ejection device comprising: The liquid ejection device is characterized in that the control means determines the timing for executing the kogation removal operation in the ejection means that ejects the liquid, based on information related to the ejection characteristics of the liquid.

2. 2. The liquid ejection device according to claim 1, wherein the information about the ejection characteristics is a threshold value for the total number of drive pulses applied to the heating resistor of the ejection means after the previous kogation removal operation of the ejection means is performed.

3. a mounting portion capable of mounting a plurality of cartridges for supplying liquid to each of the plurality of discharge means, each of the plurality of cartridges has a storage means for storing at least one piece of information on the type of liquid contained therein, the time of distribution, and the time elapsed since the cartridge was attached to the liquid ejection device; The liquid ejection device according to claim 2 , wherein the control means sets the threshold value for each of the ejection means based on the information read from the storage means.

4. The threshold is 5×10 8 ~6 x 10 9 3. The liquid ejection device according to claim 2, wherein the liquid ejection amount is within the range of .

5. 2. The liquid ejection device according to claim 1, wherein the information about the ejection characteristics is the density of an image formed by ejection by the ejection means.

6. 6. The liquid ejection apparatus according to claim 5, wherein the control means executes the kogation removal operation when the density of the image is not within a preset target density range.

7. 2. The liquid ejection device according to claim 1, wherein the information about the ejection characteristics is the ejection speed of the ejection means.

8. 8. The liquid ejection device according to claim 7, wherein the control means executes the kogation removal operation when the ejection speed is not within a preset target range.

9. 8. The liquid ejection apparatus according to claim 7, wherein the ejection speed is acquired based on a deviation amount of a landing position of the ejection means between forward printing and backward printing on the recording medium.

10. The liquid ejection device according to claim 1, wherein the protective portion and the electrode portion are made of the same metal material.

11. The liquid ejection device according to claim 1 , wherein the electrode portion is grounded during the kogation removal operation.

12. a discharge step of discharging the liquid from the discharge means by the action of the heating resistor; an acquisition step of acquiring information about the ejection characteristics of the liquid; an elution step of eluting the metal of the protective layer provided on the portion of the heating resistor that is subjected to heat by an electrochemical reaction with a liquid; A method for controlling a liquid ejection device, comprising: A method for controlling a liquid ejection device, wherein the elution step, which is a kogation removal operation, is performed based on information about the ejection characteristics of the liquid acquired in the acquisition step.

13. 13. The method for controlling a liquid ejection device according to claim 12, wherein the information about the ejection characteristics is a threshold value for the total number of drive pulses applied to the heating resistor after the previous kogation removal operation in the ejection process is performed.

14. a mounting step of mounting a plurality of cartridges for supplying liquid to each of the plurality of discharge means, a storing step of storing at least one piece of information on the type of liquid contained therein, the time of distribution, and the time elapsed since the cartridge was attached to the liquid ejection device in a storing means of the cartridges, The method for controlling a liquid ejection device according to claim 13, wherein the threshold value is set for each of the ejection units based on the information read from the storage unit.

15. The method for controlling a liquid ejection device according to claim 12, wherein the information regarding the ejection characteristics is the density of an image formed by ejection in the ejection step.

16. The method for controlling a liquid ejection device according to claim 15, wherein the kogation removal operation is executed when the density of the image is not within a preset target density range.

17. 13. The method for controlling a liquid ejection device according to claim 12, wherein the information regarding the ejection characteristics is the ejection speed of the ejection means.

18. The method for controlling a liquid ejection device according to claim 17, wherein the kogation removal operation is executed when the ejection speed is not within a preset target range.

19. 18. The method for controlling a liquid ejection device according to claim 17, wherein the ejection speed is acquired based on a deviation amount of a landing position of the ejection means between forward printing and backward printing on the recording medium.

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