Liquid ejection apparatus and adjustment method for liquid ejection apparatus

Abstract

To achieve downsizing of a liquid ejection head and enable proper liquid circulation.SOLUTION: A liquid ejection apparatus includes: a liquid ejection head 3 having an ejection port and an ejection element configured to eject a liquid from the ejection port; a circulation pump 1002 configured to circulate the liquid to be supplied to the ejection port; evaluation means configured to change an output of the circulation pump 1002 and evaluate an ejection state in which the liquid is ejected from the ejection port by the ejection element; and setting means configured to set the output of the circulation pump 1002 based on a result of the evaluation of the ejection state by the evaluation means.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejection device and a method for adjusting a liquid ejection device. [Background technology]

[0002] An inkjet recording apparatus, which is one example of a liquid ejection apparatus, is equipped with a liquid ejection head that ejects liquid such as ink from ejection ports. Some liquid ejection heads have a circulation flow path for circulating the ink supplied to the ejection ports. By circulating the ink supplied to the ejection ports using a pump or the like, it is possible to prevent the ink from becoming viscous due to foreign matter contamination, evaporation, or the like, and therefore the ejection ports are less likely to become clogged with highly viscous ink.

[0003] Patent Document 1 discloses a liquid ejection device that includes a circulation flow path for circulating liquid (ink) supplied to a liquid ejection head, a pump for circulating the liquid in the circulation flow path, and a pressure sensor for detecting the pressure in the circulation flow path. By controlling the pump based on the pressure detected by the pressure sensor, stable liquid circulation can be achieved. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-196164 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with a configuration in which a pressure sensor is installed in a liquid circulation flow path, it is difficult to reduce the size of the liquid ejection head.

[0006] An object of the present disclosure is to make it possible to reduce the size of a liquid ejection head while still allowing appropriate circulation of liquid. [Means for solving the problem]

[0007] A liquid ejection device according to one aspect of the present disclosure is characterized by comprising: a liquid ejection head having an ejection port and an ejection element for ejecting liquid from the ejection port; a circulation pump for circulating the liquid supplied to the ejection port; an evaluation means for changing the output of the circulation pump to evaluate the ejection state in which the liquid is ejected from the ejection port by the ejection element; and a setting means for setting the output of the circulation pump based on the evaluation result of the ejection state by the evaluation means. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to reduce the size of the liquid ejection head while ensuring appropriate circulation of the liquid. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram illustrating an inkjet recording apparatus. [Figure 2] FIG. 2 is a plan view showing a surface of a recording element substrate on which ejection ports are formed. [Figure 3] FIG. 3 is an enlarged view of the area surrounded by the frame A in FIG. 2. [Figure 4] FIG. 2 is a plan view showing the surface of the recording element substrate opposite to the side where the ejection ports are formed. [Figure 5] FIG. 2 is a block diagram illustrating a hardware configuration of the inkjet printing apparatus. [Figure 6] FIG. 2 is a block diagram illustrating a functional configuration of the inkjet printing apparatus. [Figure 7] 10 is a flowchart showing each step of a pump adjustment mode. [Figure 8] FIG. 1 is a schematic diagram of an evaluation pattern. [Figure 9] 10 is a graph showing the relationship between the output of a circulation pump and the circulation flow rate of ink. [Figure 10] FIG. 10 is a schematic diagram illustrating a modified example of an inkjet recording apparatus. [Figure 11] 10 is a flowchart showing each step of a pump adjustment mode. [Figure 12] FIG. 2 is a schematic diagram of a light source and an optical sensor. [Figure 13] FIG. 2 is a plan view showing the positional relationship between a temperature detection element and a heater. [Figure 14] FIG. 14 is a cross-sectional view taken along line XIV-XIV in FIG. [Figure 15] 10 is a graph showing temperature profiles during normal ejection and non-ejection. [Figure 16] 10 is a flowchart showing each step of a pump adjustment mode. [Figure 17] 10 is a flowchart showing each step of a pump adjustment mode. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In the following description, an inkjet recording apparatus will be used as an example of a liquid ejection apparatus. The inkjet recording apparatus may be, for example, a single-function printer having only a recording function, or a multi-function printer having multiple functions such as a recording function, a fax function, and a scanner function. Furthermore, the liquid ejection apparatus is not limited to an inkjet recording apparatus, and may also be a manufacturing apparatus for manufacturing color filters, electronic devices, optical devices, microstructures, and the like using an inkjet recording method.

[0011] In the following explanation, "recording" refers not only to the formation of meaningful information such as characters and figures, but also to the formation of images, patterns, structures, etc. on a recording medium, or the processing of a recording medium, regardless of whether the information is visible to humans or not.

[0012] "Recording media" refers not only to paper used in general recording devices, but also to anything that can accept ink, such as cloth, plastic film, metal plate, glass, ceramics, resin, wood, and leather.

[0013] The term "ink" should be interpreted broadly in the same manner as the definition of "recording" above. Therefore, "ink" refers to a liquid that can be applied to a recording medium to form an image, design, pattern, etc., to process the recording medium, or to process the ink (for example, to solidify or insolubilize the coloring material in the ink applied to the recording medium).

[0014] Unless otherwise specified, the term "printing element" refers collectively to the ink ejection orifices, the liquid paths communicating with the ejection orifices, and the ejection elements that generate the energy used to eject ink. The "printing element" may also be called a "nozzle."

[0015] <<First Embodiment>> <Configuration of Inkjet Recording Apparatus> Inkjet recording devices include serial type recording devices that perform recording by alternately moving a liquid ejection head and transporting a recording medium, and line type recording devices that perform recording by transporting a recording medium while the liquid ejection head is fixed. This embodiment can be applied to both serial type recording devices and line type recording devices.

[0016] FIG. 1 is a schematic diagram showing an inkjet recording apparatus 1 equipped with a serial type head. FIG. 1 shows an ink supply flow path Fw1 and a circulation flow path Fw2 in the inkjet recording apparatus 1. Note that a supply flow path and a circulation flow path are provided for each of the four colors of ink so that full color printing is possible using four colors of ink: cyan (C), magenta (M), yellow (Y), and black (K). In this embodiment, for the sake of simplicity, only a supply flow path and a circulation flow path corresponding to one of the four colors of ink will be described.

[0017] 1, the inkjet recording apparatus 1 according to the first embodiment includes a main tank 1006, a liquid ejection head 3, a supply pump 1001 (P1), and a circulation pump 1002 (P2). The supply pump 1001 is provided on an ink supply tube 112 that connects the main tank 1006 to a liquid connection part 111 of the liquid ejection head 3. The supply pump 1001 supplies ink stored in the main tank 1006 to the liquid ejection head 3 via the ink supply tube 112 and the liquid connection part 111.

[0018] The liquid ejection head 3 is detachably mounted on a carriage (not shown). The carriage on which the liquid ejection head 3 is mounted moves back and forth in the main scanning direction (for example, the width direction of the recording medium MD) by a carriage motor 68 (see FIG. 5) and a guide shaft (not shown). The recording medium MD is transported in a sub-scanning direction that intersects with the main scanning direction, specifically, is perpendicular to the main scanning direction, by a transport motor 69 (see FIG. 5) and a transport roller (not shown). The inkjet recording apparatus 1 performs recording on the recording medium MD by having the liquid ejection head 3 eject ink while alternately moving the liquid ejection head 3 (carriage) and transporting the recording medium.

[0019] The liquid ejection head 3 has a filter 211, a first negative pressure control unit 230 on the high-pressure side, a second negative pressure control unit 231 on the low-pressure side, a liquid supply unit 220, and a recording element substrate 10. The filter 211 is disposed between the liquid connection portion 111 and the first negative pressure control unit 230. The first negative pressure control unit 230 has a first pressure control chamber 230H on the high-pressure side and a pressure adjustment mechanism (not shown). The first pressure control chamber 230H is connected to the liquid connection portion 111 (filter 211) and a common supply flow path 221 formed in the liquid supply unit 220. The first negative pressure control unit 230 uses the pressure adjustment mechanism to control the pressure of ink flowing through the first pressure control chamber 230H to a pressure lower than the pressure of ink flowing upstream of the first pressure control chamber 230H.

[0020] The second negative pressure control unit 231 has a second pressure control chamber 231L on the low-pressure side and a pressure adjustment mechanism (not shown). The second pressure control chamber 231L is connected to the circulation pump 1002 and a common recovery flow path 222 formed in the liquid supply unit 220. The second negative pressure control unit 231 uses the pressure adjustment mechanism to control the pressure of the ink flowing through the second pressure control chamber 231L to a pressure lower than the pressure of the ink flowing through the first pressure control chamber 230H.

[0021] The circulation pump 1002 sends ink that has flowed into the second negative pressure control unit 231 (second pressure control chamber 231L) to the first negative pressure control unit 230 (first pressure control chamber 230H). The circulation pump 1002 is provided in the liquid ejection head 3. To ensure smooth movement of the liquid ejection head 3 (carriage), it is desirable that the circulation pump 1002 be small and lightweight. For example, the circulation pump 1002 may be configured using a piezoelectric pump, a tube pump, or a small diaphragm pump.

[0022] Ink stored in the main tank 1006 is supplied to the liquid ejection head 3 by the supply pump 1001 via the ink supply tube 112 and the liquid connection part 111. The ink that passes through the liquid connection part 111 passes through the filter 211 and the first negative pressure control unit 230 (first pressure control chamber 230H), flows into the common supply flow path 221 of the liquid supply unit 220, and is supplied to the recording element substrate 10 having the ejection ports 13 (see FIG. 2). In this way, a supply flow path Fw1 is formed that connects the main tank 1006 and the recording element substrate 10 of the liquid ejection head 3 and through which ink flows to be supplied to the ejection ports 13 of the recording element substrate 10. The supply flow path Fw1 includes the ink supply tube 112, the liquid connection part 111, the filter 211, the first pressure control chamber 230H, and the common supply flow path 221 of the liquid supply unit 220.

[0023] A portion of the ink supplied to the ejection ports 13 of the recording element substrate 10 is ejected from the ejection ports 13. Due to the pressure difference between the first negative pressure control unit 230 and the second negative pressure control unit 231, the ink that is not ejected from the ejection ports 13 flows through the common recovery channel 222 of the liquid supply unit 220 into the second negative pressure control unit 231 (second pressure control chamber 231L). The ink that has flowed into the second negative pressure control unit 231 (second pressure control chamber 231L) is returned to the first negative pressure control unit 230 (first pressure control chamber 230H) by the circulation pump 1002. In this way, the liquid ejection head 3 is formed with a circulation channel Fw2 through which ink circulated by the circulation pump 1002 flows. The circulation channel Fw2 includes the common supply channel 221 and common recovery channel 222 of the liquid supply unit 220, the first negative pressure control unit 230, and the first pressure control chamber 230H.

[0024] Furthermore, a bypass flow path Fw3 connecting the first negative pressure control unit 230 and the second negative pressure control unit 231 is formed in the circulation flow path Fw2 of the liquid ejection head 3. A portion of the ink returned to the first negative pressure control unit 230 flows through the bypass flow path Fw3 into the second negative pressure control unit 231 without passing through the liquid supply unit 220 and the recording element substrate 10. This allows the second negative pressure control unit 231 to compensate for the ink shortage when the output of the circulation pump 1002 is high and the amount of ink returned to the first negative pressure control unit 230 is greater than the amount of ink flowing to the recording element substrate 10. A check valve (not shown) is provided in the bypass flow path Fw3. The check valve allows ink to flow in the bypass flow path Fw3 only in the direction from the first negative pressure control unit 230 to the second negative pressure control unit 231.

[0025] <Configuration of the recording element substrate> Fig. 2 is a plan view showing the surface of the recording element substrate 10 on which the ejection ports 13 are formed. Fig. 3 is an enlarged view of the part surrounded by frame A in Fig. 2. Fig. 4 is a plan view showing the surface of the recording element substrate 10 opposite to the side on which the ejection ports 13 are formed. As shown in Figs. 2 to 4, the recording element substrate 10 is made of a substrate 11, an ejection port forming member 12, and a cover member 20. As shown in Fig. 2, the substrate 11 is formed in the shape of a rectangular plate using silicon (Si).

[0026] 2, the ejection port forming member 12 is formed on one surface of the substrate 11 using a photosensitive resin material or the like. Four ejection port arrays 14 corresponding to the four colors of ink are formed in the ejection port forming member 12. Each ejection port array 14 includes a plurality of ejection ports 13 arranged in the longitudinal direction of the ejection port forming member 12. Hereinafter, the direction in which the ejection port array 14 in which the plurality of ejection ports 13 are arranged extends will be referred to as the "ejection port array direction."

[0027] As shown in FIG. 3, heaters 15 are disposed on the substrate 11 at locations corresponding to the respective ejection ports 13. The heaters 15 are heat-generating elements that use thermal energy to generate bubbles in ink. In other words, the heaters 15 are ejection elements that eject ink from the ejection ports 13. A partition wall 22 formed between the ejection port forming member 12 and the substrate 11 defines pressure chambers 23 that communicate with the ejection ports 13 and contact the heaters 15. The heaters 15 are electrically connected to terminals 16 shown in FIG. 2 by electrical wiring (not shown) provided on the recording element substrate 10. The heaters 15 generate heat based on pulse signals input from the control unit 50 (see FIG. 5) of the inkjet recording apparatus 1 via an electrical wiring board (not shown) or a flexible wiring board (not shown), thereby boiling the ink. The heaters 15 eject ink from the ejection ports 13 by the bubbling force caused by this boiling.

[0028] Furthermore, a supply-side common liquid chamber 24 and a recovery-side common liquid chamber 25 are formed between the ejection port forming member 12 and the substrate 11. The supply-side common liquid chamber 24 and the recovery-side common liquid chamber 25 extend in the ejection port array direction, sandwiching each ejection port array 14 therebetween. The ejection ports 13 communicate with the supply-side common liquid chamber 24 and the recovery-side common liquid chamber 25 via a pressure chamber 23. The supply-side common liquid chamber 24 communicates with a liquid supply path 18 on the cover member 20 side via a supply port 17a formed in the substrate 11. The recovery-side common liquid chamber 25 communicates with a liquid recovery path 19 on the cover member 20 side via a recovery port 17b formed in the substrate 11.

[0029] As shown in FIG. 4, the lid member 20 is made of silicon (Si) and is formed in the shape of a rectangular thin plate that matches the outer periphery of the substrate 11. The lid member 20 is bonded to the surface of the substrate 11 opposite the ejection port forming member 12. A liquid supply channel 18 and a liquid recovery channel 19 are formed between the lid member 20 and the substrate 11 (see FIG. 3). As shown in FIG. 3, the liquid supply channel 18 and the liquid recovery channel 19 extend in the ejection port array direction, aligned with the supply-side common liquid chamber 24 and the recovery-side common liquid chamber 25. The lid member 20 functions as a lid that forms part of the walls of the liquid supply channel 18 and the liquid recovery channel 19. Grooves that form the liquid supply channel 18 and the liquid recovery channel 19 are formed on the surface of the substrate 11 that faces the lid member 20.

[0030] As shown in FIG. 4, the lid member 20 has a plurality of openings 21 formed therein that communicate with the liquid supply channels 18 or the liquid recovery channels 19. In this embodiment, three openings 21 are provided for one liquid supply channel 18, and two openings 21 are provided for one liquid recovery channel 19. It is desirable that the lid member 20 have sufficient corrosion resistance against ink. Furthermore, to prevent color mixing, high precision is required for the shape and position of the openings 21. For this reason, it is desirable that the plurality of openings 21 be formed in the lid member 20 by a photolithography process using a photosensitive resin material. Furthermore, in consideration of pressure loss, it is desirable that the lid member 20 be thin. Therefore, it is desirable that the lid member 20 be formed in a film-like shape.

[0031] Next, the flow of ink within the recording element substrate 10 will be described. Ink that flows through the common supply flow path 221 of the liquid supply unit 220 flows into the liquid supply path 18 through the opening 21 of the lid member 20 of the recording element substrate 10. The ink that flows into the liquid supply path 18 flows into the pressure chamber 23 through the supply port 17a and the supply-side common liquid chamber 24. A portion of the ink that flows into the pressure chamber 23 is ejected from the ejection port 13 by activation of the heater 15. Ink that has flowed into the pressure chamber 23 but is not ejected from the ejection port 13 flows into the liquid recovery path 19 through the recovery-side common liquid chamber 25 and the recovery port 17b. The ink that has flowed into the liquid recovery path 19 flows through the opening 21 of the lid member 20 and into the common recovery flow path 222 of the liquid supply unit 220.

[0032] In the inkjet recording apparatus 1 according to the first embodiment, by driving the circulation pump 1002, it is possible to circulate ink so that it passes through the pressure chambers 23 of the liquid ejection head 3. As a result, when ink is ejected from the ejection ports 13 of the liquid ejection head 3 to perform recording on the recording medium MD, it is possible to cause ink to flow even in the ejection ports 13 and pressure chambers 23 from which ink is not ejected. This makes it possible to prevent the viscosity of the ink from increasing in the ejection ports 13 and pressure chambers 23 from which ink is not ejected. Therefore, the liquid ejection head 3 is able to perform high-quality recording on the recording medium MD at high speed.

[0033] If the ink passing through the pressure chamber 23 does not circulate normally through the circulation flow path Fw2, insufficient ink flow occurs in the ejection port 13 and the pressure chamber 23, causing the viscosity of the ink to increase in the ejection port 13 and the pressure chamber 23. If the ink viscosity increases, it becomes difficult for the ink to be ejected from the ejection port 13 even when the heater 15 is activated, and the ejection speed and volume of the droplets ejected from the ejection port 13 may change. Furthermore, if the ink viscosity increases, there is a possibility that the ink will not be ejected from the ejection port 13 even when the heater 15 is activated. As a result, for example, when printing on the recording medium MD, problems such as a decrease in print density on the recording medium MD and misalignment of the print position on the recording medium MD may occur.

[0034] Causes of ink passing through the pressure chamber 23 not circulating normally through the circulation flow path Fw2 include, for example, deterioration of the circulation pump 1002, clogging of the circulation flow path Fw2 by bubbles or foreign matter, and an abnormal increase in ink viscosity. The circulation pump 1002 is configured using a piezoelectric pump, a tube pump, a diaphragm pump, or the like, and the circulation pump 1002 gradually deteriorates with continued use. When the circulation pump 1002 deteriorates, the amount of ink circulating through the circulation flow path Fw2 decreases, preventing sufficient ink flow through the ejection openings 13 and the pressure chamber 23, and increasing the viscosity of the ink at the ejection openings 13 and the pressure chamber 23. As a result, the above-mentioned problems can occur, for example, when printing on a recording medium MD.

[0035] Furthermore, if the ambient environment of the inkjet recording apparatus 1 changes, for example, if the ambient temperature drops, the viscosity of the ink increases. Therefore, even if the ambient environment of the inkjet recording apparatus 1 changes, the flow rate of the ink circulating through the circulation flow path Fw2 may be insufficient with the output of the circulation pump 1002 in the conventional environment, and the above-mentioned problems may occur, for example, when printing on the recording medium MD. Therefore, in the inkjet recording apparatus 1, it is necessary to set the output of the circulation pump 1002 so that the ink circulates normally before recording on the recording medium MD. In this embodiment, a configuration is described that allows for appropriate ink circulation while miniaturizing the liquid ejection head 3.

[0036] <Controller configuration> FIG. 5 is a block diagram showing the hardware configuration of the inkjet recording apparatus 1. As shown in FIG. 5, the inkjet recording apparatus 1 according to the first embodiment further includes a control unit 50, an interface 61, an operation panel 62, a scanner 63, a head driver 65, a pump driver 66, and a motor driver 67. The control unit 50 includes a CPU 51, a RAM 52, and a ROM 53. The CPU (Central Processing Unit) 51 functions as a control unit that controls the operation of each unit of the inkjet recording apparatus 1 based on programs such as processing procedures stored in the ROM 53. The RAM (Random Access Memory) 52 is used as a work area when the CPU 51 executes processing. The ROM (Read Only Memory) 53 stores programs executed by the CPU 51 and various data necessary for the operation of the inkjet recording apparatus 1.

[0037] The control unit 50 is electrically connected to an operation panel 62, a scanner 63, a head driver 65, a pump driver 66, and a motor driver 67 via an interface 61. The interface 61 receives image data transmitted from an external host device (not shown) and sends the image data to the control unit 50. The CPU 51 controls the head driver 65 based on the image data transmitted from the external host device, and controls the operation of the heaters 15 (discharge elements) provided in the liquid discharge head 3. The CPU 51 also controls the pump driver 66 to control the operation of the supply pump 1001 and the circulation pump 1002. The CPU 51 controls the motor driver 67 to control the operation of the carriage motor 68 and the transport motor 69.

[0038] Furthermore, the operation panel 62 transmits input data input by operating the operation panel 62 to the control unit 50 via the interface 61. The scanner 63 is disposed near the downstream side of the liquid ejection head 3 in the transport direction (sub-scanning direction) of the recording medium MD. The scanner 63 reads the surface of the recording medium MD recorded by the liquid ejection head 3 and acquires the data as electronic image data. The scanner 63 transmits the acquired image data to the control unit 50 via the interface 61.

[0039] FIG. 6 is a block diagram showing the functional configuration of the control unit 50 in the inkjet recording apparatus 1. The control unit 50 has an evaluation unit 151 and a setting unit 152. These functions are realized by the CPU 51 of the control unit 50 executing a program stored in the ROM 53. For this reason, it can be said that the CPU 51 has each of the functions of the control unit 50 shown in FIG. 6, but it is not necessary for the CPU 51 to have all of these functions. For example, the control unit 50 may be provided with a dedicated processing circuit that performs processing corresponding to at least one of the functions of the control unit 50. Furthermore, in this embodiment, information may be exchanged between the functions of the control unit 50 via the RAM 52.

[0040] The evaluation means 151 changes the output of the circulation pump 1002 and evaluates the state in which ink is ejected from the ejection ports 13 by the heaters 15 (ejection elements). In this embodiment, the state in which ink is ejected from the ejection ports 13 by the heaters 15 is referred to as the ink ejection state. In this embodiment, the evaluation means 151 evaluates the ink ejection state based on an evaluation pattern PTN (see FIG. 8) recorded on the recording medium MD by ink being ejected from the ejection ports 13. For example, the evaluation means 151 evaluates the ink ejection state based on image data of the evaluation pattern PTN read by the scanner 63.

[0041] The evaluation unit 151 changes the output of the circulation pump 1002 by changing a parameter that can change the flow rate of ink delivered by the circulation pump 1002. For example, if the circulation pump 1002 is configured using a piezoelectric pump, the evaluation unit 151 changes the output of the circulation pump 1002 by changing the drive voltage or drive frequency of a piezoelectric element that makes up the piezoelectric pump. If the circulation pump 1002 is configured using a tube pump, the evaluation unit 151 changes the output of the circulation pump 1002 by changing the rotation speed of a roller that makes up the tube pump. The roller of the tube pump delivers ink by squeezing the tube of the tube pump.

[0042] The setting means 152 sets the output of the circulation pump 1002 based on the evaluation result of the ink ejection state by the evaluation means 151. For example, based on the evaluation result of the ink ejection state by the evaluation means 151, the setting means 152 sets the output of the circulation pump 1002 to an output that allows ink to be ejected normally from the ejection ports 13. If the circulation pump 1002 is configured using a piezoelectric pump, the setting means 152 sets the output of the circulation pump 1002 by setting the drive voltage or drive frequency of a piezoelectric element that constitutes the piezoelectric pump. If the circulation pump 1002 is configured using a tube pump, the setting means 152 sets the output of the circulation pump 1002 by setting the rotation speed of a roller that constitutes the tube pump.

[0043] <Method for adjusting an inkjet recording device> Next, as a method for adjusting a liquid ejection device, a method for adjusting the inkjet recording apparatus 1 according to the first embodiment will be described. In this embodiment, a mode in which the output of the circulation pump 1002 is set so that ink circulates normally before recording on a recording medium MD is referred to as a "pump adjustment mode." After recording on a certain number of recording media MD has been performed, or after a certain amount of time has elapsed, the control unit 50 performs control to transition to the pump adjustment mode.

[0044] It should be noted that the control unit 50 may be configured to perform control to transition to the pump adjustment mode when the user operates the operation panel 62. In this case, the operation panel 62 may transmit input data corresponding to the operation for transitioning to the pump adjustment mode to the control unit 50. In this case, the pump adjustment mode may also be part of a head diagnosis mode that detects abnormalities in the liquid ejection head 3.

[0045] Fig. 7 is a flowchart showing each step of the pump adjustment mode according to the first embodiment. Note that each step (process) of the flowchart shown in Fig. 7 is executed by the CPU 51 executing a control program stored in the ROM 53 of the control unit 50.

[0046] First, in step S101, the evaluation means 151 of the control unit 50 performs a process of setting the output of the circulation pump 1002 to an arbitrary value Pa1. At this time, the evaluation means 151 controls the pump driver 66 to set the output of the circulation pump 1002 to Pa1. As a result, ink is circulated through the circulation flow path Fw2 by the circulation pump 1002 whose output has been set to Pa1.

[0047] In step S102, the control unit 50 performs a process of recording the evaluation pattern PTN (see FIG. 8) on the recording medium MD. At this time, the CPU 51 of the control unit 50 controls the head driver 65 based on image data of the evaluation pattern PTN stored in, for example, the ROM 53, and controls the operation of the heaters 15 (ejection elements) provided in the liquid ejection head 3. As a result, the liquid ejection head 3 ejects ink from the ejection ports 13 by operating the heaters 15, and records the evaluation pattern PTN, for example, on the recording medium MD. At this time, the scanner 63 also reads the evaluation pattern PTN recorded on the recording medium MD by the liquid ejection head 3, and acquires it as electronic image data. The scanner 63 transmits the acquired image data of the evaluation pattern PTN to the control unit 50.

[0048] FIG. 8 is a schematic diagram of an evaluation pattern PTN. FIG. 8(a) is a schematic diagram of an evaluation pattern PTN that is printed when ink circulates normally through the circulation flow path Fw2. FIG. 8(b) is a schematic diagram of an evaluation pattern PTN that is printed when ink does not circulate normally through the circulation flow path Fw2. Note that the black circles in FIGS. 8(a) and 8(b) indicate dots formed on the recording medium by droplets ejected from each ejection port 13 of the liquid ejection head 3. The thick arrows in FIGS. 8(a) and 8(b) indicate the printing direction (main scanning direction) of the evaluation pattern PTN.

[0049] As shown in Figure 8(a), if ink circulates normally through the circulation flow path Fw2, an evaluation pattern PTN is printed at a predetermined printing position on the printing medium MD during the first printing operation after the inkjet recording apparatus 1 has been idle for a long period of time. As shown in Figure 8(b), if ink does not circulate normally through the circulation flow path Fw2, the printing position of the evaluation pattern PTN will be shifted relative to the printing medium MD during the first printing operation after the inkjet recording apparatus 1 has been idle for a long period of time. By determining whether the evaluation pattern PTN printed on the printing medium MD is normal, it is possible to evaluate whether the ink is being ejected normally from the ejection ports 13.

[0050] Returning to FIG. 7 , in step S103, the evaluation means 151 of the control unit 50 determines whether the evaluation pattern PTN recorded on the recording medium MD is normal. For example, the evaluation means 151 determines whether the evaluation pattern PTN is recorded at a predetermined recording position on the recording medium MD by image processing based on image data of the evaluation pattern PTN transmitted from the scanner 63. The evaluation means 151 may also determine whether the evaluation pattern PTN is recorded at a predetermined recording position on the recording medium MD by comparing the image data transmitted from the scanner 63 with image data of a reference evaluation pattern PTN. The evaluation means 151 determines that the evaluation pattern PTN recorded on the recording medium MD is normal if the evaluation pattern PTN is recorded at the predetermined recording position on the recording medium MD. In other words, if the evaluation pattern PTN is recorded at the predetermined recording position on the recording medium MD, the evaluation means 151 evaluates that the ink ejection state is a state in which ink is ejected normally from the ejection ports 13. Furthermore, if the evaluation pattern PTN is not recorded at a predetermined recording position on the recording medium MD, the evaluation means 151 evaluates that the ink ejection state is not a state in which ink is ejected normally from the ejection openings 13.

[0051] If the evaluation means 151 determines that the evaluation pattern PTN recorded on the recording medium MD is normal, that is, if the determination in step S103 is YES, the process proceeds to step S104. If the evaluation means 151 determines that the evaluation pattern PTN recorded on the recording medium MD is not normal, that is, if the determination in step S103 is NO, the process proceeds to step S109.

[0052] In step S104, the evaluation means 151 of the control unit 50 performs processing to change the output of the circulation pump 1002 to Pa0, which is lower than Pa1. At this time, the evaluation means 151 controls the pump driver 66 to change the output of the circulation pump 1002 to Pa0. As a result, the ink is circulated through the circulation flow path Fw2 by the circulation pump 1002, whose output has been changed from Pa1 to Pa0.

[0053] In step S105, the control unit 50 performs a process of recording the evaluation pattern PTN on the recording medium MD, similar to step S102. At this time, the scanner 63 reads the evaluation pattern PTN recorded on the recording medium MD by the liquid ejection head 3 and acquires it as electronic image data. The scanner 63 transmits the acquired image data of the evaluation pattern PTN to the control unit 50.

[0054] In step S106, the evaluation means 151 of the control unit 50 determines whether the evaluation pattern PTN recorded on the recording medium MD is normal, as in step S103. If the evaluation means 151 determines that the evaluation pattern PTN recorded on the recording medium MD is normal, that is, if the determination in step S106 is YES, the process proceeds to step S107. If the evaluation means 151 determines that the evaluation pattern PTN recorded on the recording medium MD is not normal, that is, if the determination in step S106 is NO, the process proceeds to step S108.

[0055] In step S107, the setting means 152 of the control unit 50 performs processing to set the output of the circulation pump 1002 to Pa0 or higher, and then ends the processing. Because the determination in the previous step S106 is YES, the circulation pump 1002, whose output is set to Pa0 or higher, allows ink to circulate normally through the circulation flow path Fw2. This allows ink to be ejected normally from the ejection ports 13 of the liquid ejection head 3, making it possible to perform high-speed, high-quality recording on the recording medium MD. Therefore, based on the evaluation result of the ink ejection state by the evaluation means 151, the setting means 152 sets the output of the circulation pump 1002 to Pa0 or higher, at which ink can be ejected normally from the ejection ports 13.

[0056] In step S108, the setting means 152 of the control unit 50 performs processing to set the output of the circulation pump 1002 to Pa1 or higher, and then ends the processing. Because the determination in the previous step S106 is NO, the circulation pump 1002, whose output is set to Pa1 or higher, allows ink to circulate normally through the circulation flow path Fw2. This allows ink to be ejected normally from the ejection ports 13 of the liquid ejection head 3, making it possible to perform high-speed, high-quality recording on the recording medium MD. Therefore, based on the evaluation result of the ink ejection state by the evaluation means 151, the setting means 152 sets the output of the circulation pump 1002 to Pa1 or higher, at which ink can be ejected normally from the ejection ports 13.

[0057] In step S109, the evaluation means 151 of the control unit 50 performs processing to change the output of the circulation pump 1002 to Pa2, which is higher than Pa1. At this time, the evaluation means 151 controls the pump driver 66 to change the output of the circulation pump 1002 to Pa2. As a result, the circulation pump 1002, whose output has been changed from Pa1 to Pa2, circulates ink through the circulation flow path Fw2.

[0058] In step S110, the control unit 50 performs a process of recording the evaluation pattern PTN on the recording medium MD, similar to step S102. At this time, the scanner 63 reads the evaluation pattern PTN recorded on the recording medium MD by the liquid ejection head 3, and acquires it as electronic image data. The scanner 63 transmits the acquired image data of the evaluation pattern PTN to the control unit 50.

[0059] In step S111, the evaluation means 151 of the control unit 50 determines whether the evaluation pattern PTN recorded on the recording medium MD is normal, as in step S103. If the evaluation means 151 determines that the evaluation pattern PTN recorded on the recording medium MD is normal, that is, if the determination in step S111 is YES, the process proceeds to step S112. If the evaluation means 151 determines that the evaluation pattern PTN recorded on the recording medium MD is not normal, that is, if the determination in step S111 is NO, the process proceeds to step S113.

[0060] In step S112, the setting means 152 of the control unit 50 performs processing to set the output of the circulation pump 1002 to Pa2 or higher, and then ends the processing. Because the determination in the previous step S111 is YES, the circulation pump 1002, whose output is set to Pa2 or higher, allows ink to circulate normally through the circulation flow path Fw2. This allows ink to be ejected normally from the ejection ports 13 of the liquid ejection head 3, making it possible to perform high-speed, high-quality recording on the recording medium MD. Therefore, based on the evaluation result of the ink ejection state by the evaluation means 151, the setting means 152 sets the output of the circulation pump 1002 to Pa2 or higher, at which ink can be ejected normally from the ejection ports 13.

[0061] In step S113, the evaluation means 151 of the control unit 50 performs processing to change the output of the circulation pump 1002 to Pa3, which is higher than Pa2. At this time, the evaluation means 151 controls the pump driver 66 to change the output of the circulation pump 1002 to Pa3. As a result, the ink is circulated through the circulation flow path Fw2 by the circulation pump 1002, whose output has been changed from Pa2 to Pa3.

[0062] In step S114, the control unit 50 performs a process of recording the evaluation pattern PTN on the recording medium MD, similar to step S102. At this time, the scanner 63 reads the evaluation pattern PTN recorded on the recording medium MD by the liquid ejection head 3, and acquires it as electronic image data. The scanner 63 transmits the acquired image data of the evaluation pattern PTN to the control unit 50.

[0063] In step S115, the evaluation means 151 of the control unit 50 determines whether the evaluation pattern PTN recorded on the recording medium MD is normal, as in step S103. If the evaluation means 151 determines that the evaluation pattern PTN recorded on the recording medium MD is normal, that is, if the determination in step S115 is YES, the process proceeds to step S116. If the evaluation means 151 determines that the evaluation pattern PTN recorded on the recording medium MD is not normal, that is, if the determination in step S115 is NO, an abnormality is notified and the process ends.

[0064] As a notification of an abnormality, a process of displaying a message to the effect that an abnormality has occurred on a display device or the like (not shown) may be performed. As a notification of an abnormality, a process of displaying a message to the effect that replacement of the liquid ejection head 3 is recommended on a display device or the like may be performed.

[0065] In step S116, the setting means 152 of the control unit 50 performs processing to set the output of the circulation pump 1002 to Pa3 or higher, and then ends the processing. Because the determination in the previous step S115 is YES, the circulation pump 1002, whose output is set to Pa3 or higher, allows ink to circulate normally through the circulation flow path Fw2. This allows ink to be ejected normally from the ejection ports 13 of the liquid ejection head 3, making it possible to perform high-speed, high-quality recording on the recording medium MD. Therefore, based on the evaluation result of the ink ejection state by the evaluation means 151, the setting means 152 sets the output of the circulation pump 1002 to Pa3 or higher, at which ink can be ejected normally from the ejection ports 13.

[0066] FIG. 9 is a graph showing the relationship between the output of the circulation pump 1002 and the circulation flow velocity of ink within the pressure chamber 23. The circulation flow velocity of ink refers to the flow velocity of ink circulating through the circulation flow path Fw2. The graph in FIG. 9 also shows a case where the evaluation pattern PTN is determined to be abnormal when the output of the circulation pump 1002 is set to Pa1 or Pa2, and is determined to be normal when the output of the circulation pump 1002 is set to Pa3. As shown in FIG. 9, the circulation flow velocity of ink within the pressure chamber 23 when the output of the circulation pump 1002 is Pa1 is defined as Vp1. The circulation flow velocity of ink within the pressure chamber 23 when the output of the circulation pump 1002 is Pa2 is defined as Vp2. The circulation flow velocity of ink within the pressure chamber 23 when the output of the circulation pump 1002 is Pa3 is defined as Vp3.

[0067] 9, the minimum ink circulation flow velocity Vth at which the evaluation pattern PTN can be normally printed, in other words, at which ink can be normally ejected from the ejection ports 13, is considered to be between Vp2 and Vp3. If the minimum ink circulation flow velocity Vth at which ink can be normally ejected from the ejection ports 13 can be detected, high-speed, high-quality printing on the recording medium MD can be performed by setting the output of the circulation pump 1002 so that the ink circulation flow velocity is equal to or greater than Vth. According to this embodiment, by setting the output of the circulation pump 1002 to equal to or greater than the minimum output Pth at which ink can be normally ejected from the ejection ports 13, which corresponds to Vth, the ink circulation flow velocity can be made greater than Vth, thereby enabling appropriate ink circulation.

[0068] As described above, the inkjet recording apparatus 1 (liquid ejection apparatus) and the method for adjusting the inkjet recording apparatus 1 according to the first embodiment can appropriately circulate ink (liquid) while miniaturizing the liquid ejection head 3. That is, in this embodiment, the output of the circulation pump 1002 is changed to evaluate the ink ejection state, and the output of the circulation pump 1002 is set based on the evaluation result of the ink ejection state. For example, in the step of evaluating the ink ejection state, it is evaluated whether the ink ejection state is such that ink is normally ejected from the ejection ports 13 of the liquid ejection head 3. If the ink ejection state is such that ink is not normally ejected from the ejection ports 13, the output of the circulation pump 1002 is increased, and then the ink ejection state is evaluated again to determine whether the ink is normally ejected from the ejection ports 13. If the ink ejection state is such that ink is normally ejected from the ejection ports 13, the output of the circulation pump 1002 may be decreased, and then the ink ejection state is evaluated again to determine whether the ink is normally ejected from the ejection ports 13. By changing the output of the circulation pump 1002 and evaluating the ink ejection state, it is possible to appropriately set the output of the circulation pump 1002 without providing a pressure sensor or the like in the circulation flow path Fw2 of the ink flowing inside the liquid ejection head 3. In this case, by setting the output of the circulation pump 1002 to an output that allows ink to be ejected normally from the ejection ports 13 (for example, an output Pth or higher), appropriate ink circulation can be achieved. In this way, appropriate ink circulation can be achieved while miniaturizing the liquid ejection head 3.

[0069] Furthermore, by determining whether the evaluation pattern PTN is normal or not based on the evaluation pattern PTN read by the scanner 63, it is possible to evaluate whether the ink ejection state is such that ink is ejected normally from the ejection openings 13 of the liquid ejection head 3. This makes it possible to more easily evaluate the ink ejection state.

[0070] In the first embodiment described above, the output of the circulation pump 1002 is changed up to Pa3, but this is not limiting. For example, the output of the circulation pump 1002 may be changed up to Pa4, which is greater than Pa3, or may be changed up to Pa5, which is greater than Pa4.

[0071] In the first embodiment described above, the evaluation means 151 of the control unit 50 determines whether the evaluation pattern PTN recorded on the recording medium MD is normal by image processing, but the present invention is not limited to this. For example, a user may visually determine whether the evaluation pattern PTN recorded on the recording medium MD is normal. In this case, the operation panel 62 may transmit input data corresponding to an operation to input a determination result as to whether the evaluation pattern PTN is normal to the control unit 50. Based on the input data related to the determination result transmitted from the operation panel 62, the evaluation means 151 can evaluate whether the ink ejection state is a state in which ink is ejected normally from the ejection ports 13 of the liquid ejection head 3.

[0072] <Modification> As mentioned above, this embodiment can be applied not only to serial-type recording devices but also to line-type recording devices. Therefore, a modification of the first embodiment will be described. In this modification of the first embodiment, components having the same configuration as those in the first embodiment are given the same reference numerals as those in the first embodiment.

[0073] Fig. 10 is a schematic diagram showing an inkjet recording apparatus 2 equipped with a line-type head. As shown in Fig. 10, the inkjet recording apparatus 2 according to the modified example includes a main tank 1006, a buffer tank 1007, a liquid ejection head 3, a refill pump 1003 (P3), a first circulation pump 1004 (P4), and a second circulation pump 1005 (P5). The main tank 1006 is connected to the buffer tank 1007 via the refill pump 1003. The main tank 1006 has an atmosphere communication port (not shown) that communicates between the inside and outside of the main tank 1006, and is capable of discharging air bubbles in the ink to the outside.

[0074] The refill pump 1003 sends ink stored in the main tank 1006 to the buffer tank 1007. When ink is consumed by ejecting ink from the ejection ports 13 (not shown in FIG. 10) of the liquid ejection head 3 for recording on a recording medium, suction recovery, or the like, the refill pump 1003 sends the consumed ink from the main tank 1006 to the buffer tank 1007. In the modified example, a supply flow path Fw1 is formed that connects the main tank 1006 and the buffer tank 1007 to the liquid ejection head 3 and through which ink flows that is supplied to the ejection ports 13 of the liquid ejection head 3. In the modified example, a circulation flow path Fw2 is formed through which ink circulated by the first circulation pump 1004 and the second circulation pump 1005 flows.

[0075] The liquid ejection head 3 has a filter 211, a first negative pressure control unit 230 on the high-pressure side, a second negative pressure control unit 231 on the low-pressure side, a liquid supply unit 220, and a liquid ejection unit 300. The filter 211 is disposed in the liquid supply unit 220 between an upstream liquid connection part 111 and the first and second negative pressure control units 230 and 231. The first negative pressure control unit 230 has a first pressure control chamber 230H on the high-pressure side and a pressure adjustment mechanism (not shown). An upstream portion of the first pressure control chamber 230H is connected to the upstream liquid connection part 111 via the filter 211. A downstream portion of the first pressure control chamber 230H is connected to a common supply flow path 221 formed in the liquid ejection unit 300 via the liquid supply unit 220. The first negative pressure control unit 230 uses a pressure adjustment mechanism to control the pressure of the ink flowing through the first pressure control chamber 230H to a pressure lower than the pressure of the ink flowing upstream of the first pressure control chamber 230H.

[0076] The second negative pressure control unit 231 has a second pressure control chamber 231L on the low-pressure side and a pressure adjustment mechanism (not shown). An upstream portion of the second pressure control chamber 231L is connected to the upstream liquid connection portion 111 via a filter 211. A downstream portion of the second pressure control chamber 231L is connected to a common recovery channel 222 formed in the liquid ejection unit 300 via a liquid supply unit 220. The second negative pressure control unit 231 uses the pressure adjustment mechanism to control the pressure of ink flowing through the second pressure control chamber 231L to a pressure lower than the pressure of ink flowing through the first pressure control chamber 230H.

[0077] The first negative pressure control unit 230 and the second negative pressure control unit 231 function to maintain the pressure in each flow path in the liquid ejection unit 300 at a constant set pressure even when the ink circulation flow rate fluctuates due to differences in so-called printing rate (duty). The pressure adjustment mechanisms of the first negative pressure control unit 230 and the second negative pressure control unit 231 are configured using, for example, a mechanism similar to a so-called pressure-reducing regulator. This allows the pressure adjustment mechanisms to control the pressure in each flow path in the liquid ejection unit 300 within a certain range centered on the set pressure. When the pressure adjustment mechanism is configured using a mechanism similar to a pressure-reducing regulator, it is desirable to pressurize the upstream side of the first negative pressure control unit 230 and the second negative pressure control unit 231 via the liquid supply unit 220 using the second circulation pump 1005. This suppresses the effect of head pressure on the liquid ejection head 3 in the buffer tank 1007, thereby increasing the degree of freedom in the layout of the buffer tank 1007.

[0078] The liquid ejection unit 300 has a plurality of recording element substrates 10, a common supply channel 221, a common recovery channel 222, and a plurality of individual supply channels 223 and individual recovery channels 224 connected to the plurality of recording element substrates 10. The plurality of recording element substrates 10 are arranged side by side, for example, in the width direction of the recording medium. The common supply channel 221 is connected to a first pressure control chamber 230H and the plurality of individual supply channels 223. The common recovery channel 222 is connected to a second pressure control chamber 231L and the plurality of individual recovery channels 224. Furthermore, the common supply channel 221 and the common recovery channel 222 are connected to the first circulation pump 1004 via the liquid supply unit 220 and a downstream liquid connection part 111. A pressure difference between the first negative pressure control unit 230 and the second negative pressure control unit 231 generates a pressure difference between the ink flowing through the common supply channel 221 and the ink flowing through the common recovery channel 222. Therefore, as shown by the thick arrows in FIG. 10, a part of the ink flowing through the common supply flow path 221 passes through the internal flow paths of each recording element substrate 10 and flows toward the common recovery flow path 222.

[0079] In the liquid ejection unit 300, ink flows through the common supply flow path 221 and the common recovery flow path 222, and part of the ink flowing through the common supply flow path 221 passes through the internal flow paths of each recording element substrate 10 and heads toward the common recovery flow path 222. Therefore, heat generated in each recording element substrate 10 can be discharged to the outside of the liquid ejection head 3 (liquid ejection unit 300) by the ink flowing through the common supply flow path 221 and the common recovery flow path 222. The supply flow path Fw1 includes an upstream liquid connection part 111, a filter 211, a first pressure control chamber 230H, the common supply flow path 221, and a plurality of individual supply flow paths 223. The circulation flow path Fw2 includes upstream and downstream liquid connection parts 111, a filter 211, a first pressure control chamber 230H, a second pressure control chamber 231L, a common supply flow path 221, a common recovery flow path 222, and a plurality of individual supply flow paths 223 and individual recovery flow paths 224.

[0080] The first circulation pump 1004 draws ink from the liquid connection portion 111 downstream of the liquid ejection head 3 and sends it to the buffer tank 1007. The first circulation pump 1004 is preferably configured using a positive displacement pump with a constant liquid delivery capacity. Examples of the positive displacement pump include a tube pump, a gear pump, a diaphragm pump, and a syringe pump. The first circulation pump 1004 may be configured to ensure a constant flow rate by including a general constant flow valve or a relief valve at the outlet of the first circulation pump 1004. When the liquid ejection head 3 is in operation, the first circulation pump 1004 causes a certain constant flow rate of ink to flow through the common supply flow path 221 and the common recovery flow path 222 in the liquid ejection unit 300. The flow rates of the ink flowing through the common supply flow path 221 and the common recovery flow path 222 are preferably set to a flow rate or higher that does not affect the print quality due to temperature differences between the multiple printing element substrates 10. Furthermore, if the flow rate of ink flowing through the common supply flow path 221 and the common recovery flow path 222 is set to an excessively large flow rate, the negative pressure difference between the multiple 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. This will result in uneven density in the image recorded on the recording medium. Therefore, it is desirable to set the flow rate of ink flowing through the common supply flow path 221 and the common recovery flow path 222 taking into consideration the temperature difference and negative pressure difference between the multiple recording element substrates 10.

[0081] The second circulation pump 1005 sends ink stored in the buffer tank 1007 to the first negative pressure control unit 230 and the second negative pressure control unit 231 via the upstream liquid connection part 111 and the filter 211. The second circulation pump 1005 may be any pump that has an output that generates a flow of ink when the liquid ejection head 3 is operated. The second circulation pump 1005 is configured using a turbo pump, a positive displacement pump, or the like. For example, a diaphragm pump or the like is used as the positive displacement pump. Note that instead of the second circulation pump 1005, a tank may be provided that is disposed with a certain head difference relative to the first negative pressure control unit 230.

[0082] The ink stored in the buffer tank 1007 is caused to flow to the liquid ejection head 3 via the upstream liquid connection part 111 by the second circulation pump 1005. A portion of the ink that passes through the upstream liquid connection part 111 passes through the filter 211 and the first negative pressure control unit 230 (first pressure control chamber 230H) and flows to the common supply flow path 221 of the liquid ejection unit 300. The other ink that passes through the upstream liquid connection part 111 passes through the filter 211 and the second negative pressure control unit 231 (second pressure control chamber 231L) and flows to the common recovery flow path 222 of the liquid ejection unit 300. A portion of the ink flowing through the common supply flow path 221 is supplied to the recording element substrate 10 having the ejection ports 13. A portion of the ink supplied to the ejection ports 13 of the recording element substrate 10 is ejected from the ejection ports 13. Ink that is not ejected from the ejection ports 13 flows into the common recovery flow path 222 due to the pressure difference between the common supply flow path 221 and the common recovery flow path 222. The ink flowing through the common supply flow path 221 and the ink flowing through the common recovery flow path 222 are returned to the buffer tank 1007 by the first circulation pump 1004 via the downstream liquid connection part 111.

[0083] In this modification, the output of the first circulation pump 1004 and the second circulation pump 1005 is changed to evaluate the ink ejection state, and the output of the first circulation pump 1004 and the second circulation pump 1005 is set based on the evaluation result of the ink ejection state. For example, if the ink ejection state is not such that ink is being ejected normally from the ejection ports 13, the output of each circulation pump 1004, 1005 is increased, and then the ink ejection state is evaluated again to determine whether ink is being ejected normally from the ejection ports 13. If the ink ejection state is such that ink is being ejected normally from the ejection ports 13, the output of each circulation pump 1004, 1005 may be decreased, and then the ink ejection state is evaluated again to determine whether ink is being ejected normally from the ejection ports 13. In this way, by performing the same processing as in the first embodiment, it is possible to appropriately set the output of the first circulation pump 1004 and the second circulation pump 1005 without providing a pressure sensor or the like in the circulation flow path Fw2 of ink flowing inside the liquid ejection head 3. Therefore, the liquid ejection head 3 can be made smaller, and the ink can be circulated appropriately.

[0084] <<Second embodiment>> Next, a second embodiment will be described. Since the individual components in the second embodiment have the same configuration as those in the first embodiment, they will be described using the same reference numerals as those in the first embodiment. The inkjet recording apparatus 1 according to the second embodiment is provided with a light source 401 and an optical sensor 402 (see FIG. 12) instead of the scanner 63.

[0085] <Method for adjusting an inkjet recording device> As an adjustment method for a liquid ejection device, an adjustment method for an inkjet recording device 1 according to a second embodiment will be described. As in the first embodiment, when a certain number of recording media MD have been recorded or a certain amount of time has elapsed, the control unit 50 performs control to transition to pump adjustment mode. Note that, as in the first embodiment, the control unit 50 may also perform control to transition to pump adjustment mode when the user operates the operation panel 62.

[0086] Fig. 11 is a flowchart showing each step of the pump adjustment mode according to the second embodiment. Note that each step (process) of the flowchart shown in Fig. 11 is executed by the CPU 51 executing a control program stored in the ROM 53 of the control unit 50.

[0087] First, in step S201, the evaluation means 151 of the control unit 50 performs processing to set the output of the circulation pump 1002 to an arbitrary value Pa1, as in the first embodiment.

[0088] In step S202, the control unit 50 performs a process of activating the heaters 15 (ejection elements) of the liquid ejection head 3 to eject ink from the ejection ports 13. At this time, the CPU 51 controls the head driver 65 based on adjustment data stored in, for example, the ROM 53, and controls the operation of the heaters 15 provided in the liquid ejection head 3. As a result, the liquid ejection head 3 ejects ink from the ejection ports 13 by operating the heaters 15. Note that the evaluation pattern PTN is not recorded on the recording medium MD. At this time, the optical sensor 402 (see FIG. 12) detects the liquid droplets DP (see FIG. 12) ejected from the ejection ports 13.

[0089] FIG. 12 is a schematic diagram of a light source 401 and an optical sensor 402. The light source 401 and the optical sensor 402 are disposed at positions spaced apart from each other in the direction in which ink is ejected from the liquid ejection head 3. The optical sensor 402 receives light LT emitted from the light source 401. When a droplet DP ejected from the ejection orifice 13 passes between the light source 401 and the optical sensor 402, the light LT received by the optical sensor 402 is blocked. The optical sensor 402 can detect the droplet DP ejected from the ejection orifice 13 by detecting the light blocking by the droplet DP. For example, the light source 401 and the optical sensor 402 can be used to detect the time during which the droplet DP blocks light. Multiple light sources 401 and optical sensors 402 can also be used to detect the speed, volume, etc. of the droplet DP ejected from the ejection orifice 13. This makes it possible to accurately determine whether ink is ejected normally from the ejection orifice 13. The optical sensor 402 transmits a detection signal to the control unit 50 according to the result of detecting the droplet DP.

[0090] 11 , in step S203, the evaluation means 151 of the control unit 50 determines whether or not ink has been normally ejected from the ejection port 13, based on the detection signal transmitted from the optical sensor 402. In other words, the evaluation means 151 evaluates, based on the detection signal transmitted from the optical sensor 402, whether or not the ink ejection state is a state in which ink is normally ejected from the ejection port 13.

[0091] If the evaluation means 151 determines that ink has been normally ejected from the ejection opening 13, that is, if the determination in step S203 is YES, the process proceeds to step S204. If the evaluation means 151 determines that ink has not been normally ejected from the ejection opening 13, that is, if the determination in step S203 is NO, the process proceeds to step S209.

[0092] In step S204, the evaluation means 151 of the control unit 50 performs processing to set the output of the circulation pump 1002 to Pa0, which is lower than Pa1, in the same manner as in the first embodiment.

[0093] In step S205, similar to step S202, the control unit 50 operates the heater 15 of the liquid ejection head 3 to eject ink from the ejection ports 13. At this time, the optical sensor 402 detects the droplets DP ejected from the ejection ports 13. The optical sensor 402 transmits a detection signal to the control unit 50 according to the result of the detection of the droplets DP.

[0094] In step S206, similarly to step S203, the evaluation means 151 of the control unit 50 determines whether or not ink has been normally ejected from the ejection port 13 based on the detection signal transmitted from the optical sensor 402. If the evaluation means 151 determines that ink has been normally ejected from the ejection port 13, that is, if the determination in step S206 is YES, the process proceeds to step S207. If the evaluation means 151 determines that ink has not been normally ejected from the ejection port 13, that is, if the determination in step S206 is NO, the process proceeds to step S208.

[0095] In step S207, the setting means 152 of the control unit 50 performs processing to set the output of the circulation pump 1002 to Pa0 or more, and then ends the processing. As in the first embodiment, the setting means 152 sets the output of the circulation pump 1002 to Pa0 or more at which ink can be normally ejected from the ejection ports 13, based on the evaluation result of the ink ejection state by the evaluation means 151.

[0096] In step S208, the setting means 152 of the control unit 50 performs processing to set the output of the circulation pump 1002 to Pa1 or more, and then ends the processing. As in the first embodiment, the setting means 152 sets the output of the circulation pump 1002 to Pa1 or more at which ink can be normally ejected from the ejection ports 13, based on the evaluation result of the ink ejection state by the evaluation means 151.

[0097] In step S209, the evaluation means 151 of the control unit 50 performs processing to set the output of the circulation pump 1002 to Pa2, which is higher than Pa1, in the same manner as in the first embodiment.

[0098] In step S210, similar to step S202, the control unit 50 operates the heater 15 of the liquid ejection head 3 to eject ink from the ejection ports 13. At this time, the optical sensor 402 detects the droplets DP ejected from the ejection ports 13. The optical sensor 402 transmits a detection signal to the control unit 50 according to the result of the detection of the droplets DP.

[0099] In step S211, similar to step S203, the evaluation means 151 of the control unit 50 determines whether or not ink has been normally ejected from the ejection port 13 based on the detection signal transmitted from the optical sensor 402. If the evaluation means 151 determines that ink has been normally ejected from the ejection port 13, that is, if the determination in step S211 is YES, the process proceeds to step S212. If the evaluation means 151 determines that ink has not been normally ejected from the ejection port 13, that is, if the determination in step S211 is NO, the process proceeds to step S213.

[0100] In step S212, the setting means 152 of the control unit 50 performs processing to set the output of the circulation pump 1002 to Pa2 or more, and then ends the processing. As in the first embodiment, the setting means 152 sets the output of the circulation pump 1002 to Pa2 or more at which ink can be normally ejected from the ejection ports 13, based on the evaluation result of the ink ejection state by the evaluation means 151.

[0101] In step S213, the evaluation means 151 of the control unit 50 performs processing to set the output of the circulation pump 1002 to Pa3, which is higher than Pa2, in the same manner as in the first embodiment.

[0102] In step S214, similar to step S202, the control unit 50 operates the heater 15 of the liquid ejection head 3 to eject ink from the ejection ports 13. At this time, the optical sensor 402 detects the droplets DP ejected from the ejection ports 13. The optical sensor 402 transmits a detection signal to the control unit 50 according to the result of the detection of the droplets DP.

[0103] In step S215, similar to step S203, the evaluation means 151 of the control unit 50 determines whether ink has been normally ejected from the ejection port 13 based on the detection signal transmitted from the optical sensor 402. If the evaluation means 151 determines that ink has been normally ejected from the ejection port 13, that is, if the determination in step S215 is YES, the process proceeds to step S216. If the evaluation means 151 determines that ink has not been normally ejected from the ejection port 13, that is, if the determination in step S215 is NO, an abnormality is reported and the process ends.

[0104] As a notification of an abnormality, a process of displaying a message to the effect that an abnormality has occurred on a display device or the like (not shown) may be performed. As a notification of an abnormality, a process of displaying a message to the effect that replacement of the liquid ejection head 3 is recommended on a display device or the like may be performed.

[0105] In step S216, the setting means 152 of the control unit 50 performs processing to set the output of the circulation pump 1002 to Pa3 or more, and then ends the processing. As in the first embodiment, the setting means 152 sets the output of the circulation pump 1002 to Pa3 or more at which ink can be normally ejected from the ejection ports 13, based on the evaluation result of the ink ejection state by the evaluation means 151.

[0106] As described above, according to the second embodiment, similar to the first embodiment, it is possible to reduce the size of the liquid ejection head 3 while still achieving appropriate circulation of ink (liquid).

[0107] Furthermore, the evaluation means 151 evaluates whether the ink ejection state is a state in which ink is normally ejected from the ejection ports 13, based on the detection signal sent from the optical sensor 402. This makes it possible to more easily evaluate the ink ejection state, since a recording medium is not required. When evaluating the ink ejection state, since the liquid ejection head 3 does not need to record on a recording medium, ink may be ejected into a cap (not shown) covering the tip of the liquid ejection head 3 to prevent the ink from drying out from the ejection ports 13.

[0108] As with the first embodiment, this embodiment is not limited to serial type recording apparatuses, but can also be applied to line type recording apparatuses.

[0109] In the second embodiment described above, the output of the circulation pump 1002 is changed up to Pa3, but this is not limiting. For example, the output of the circulation pump 1002 may be changed up to Pa4, which is greater than Pa3, or may be changed up to Pa5, which is greater than Pa4.

[0110] <Modification> In the second embodiment described above, the evaluation unit 151 evaluates whether the ink ejection state is such that ink is normally ejected from the ejection openings 13 based on the detection signal transmitted from the optical sensor 402. However, this is not limiting. For example, the evaluation unit 151 may evaluate whether the ink ejection state is such that ink is normally ejected from the ejection openings 13 based on the detection signal transmitted from a temperature detection element 905 (see FIGS. 13 and 14). Therefore, a modification of the second embodiment will be described. In the modification of the second embodiment, components having the same configuration as those in the first embodiment described above are denoted by the same reference numerals as in the first embodiment. In the inkjet recording apparatus 1 according to the modification of the second embodiment, a temperature detection element 905 is provided instead of the light source 401 and the optical sensor 402.

[0111] FIG. 13 is a plan view showing the positional relationship between the temperature detection element 905 and the heater 15. FIG. 14 is a cross-sectional view taken along line XIV-XIV in FIG. 13. As shown in FIGS. 13 and 14, the temperature detection element 905 is provided near the heater 15 on the recording element substrate 10 to detect the temperature. Note that some of the films that make up the recording element substrate 10 are not shown in FIG. 13. FIG. 13 is a perspective view seen from the silicon substrate 901 side, showing the positional relationship between the temperature detection element 905 and the heater 15.

[0112] In the recording element substrate 10 according to the modified example, as shown in FIG. 14, a plurality of films are formed on a silicon substrate 901 constituting the aforementioned substrate 11. Specifically, an insulating film 903 (PSG film) is formed on the silicon substrate 901 via a field oxide film 902. The field oxide film 902 is formed using silicon dioxide (SiO2) or the like. A temperature detection element 905 and a first wiring 904 made of aluminum are formed on the insulating film 903. The temperature detection element 905 is formed using a resistance temperature sensor made of aluminum (Al), platinum (Pt), titanium (Ti), tantalum (Ta), or the like. The first wiring 904 is electrically connected to the temperature detection element 905.

[0113] An interlayer insulating film 906 is formed on the temperature detection element 905 (and on the insulating film 903) using silicon monoxide (SiO) or the like. A heater 15 and a second wiring 908 made of aluminum are formed on the interlayer insulating film 906. The heater 15 is formed using TaSiN or the like. The heater 15 is electrically connected to the second wiring 908 and converts electrical energy into thermal energy. The second wiring 908 is electrically connected to a drive circuit (not shown) formed on the silicon substrate 901 and the heater 15.

[0114] A passivation film 909 is formed on the heater 15 (and on the second wiring 908) using silicon monoxide (SiO) or the like. A cavitation-resistant film 910 is formed on the passivation film 909 using tantalum (Ta), iridium (Ir), or the like. The cavitation-resistant film 910 improves the cavitation resistance of the heater 15.

[0115] The multiple films on the silicon substrate 901 are formed using a semiconductor manufacturing process. For example, by performing film formation, patterning, etc. on the insulating film 903, it is possible to form the temperature detection element 905 without significantly changing the structure of a conventional printing element substrate.

[0116] FIG. 13 shows a region 911 of the heater 15, a region 912 of the second wiring 908, and a region 914 of the first wiring 904 as viewed from the silicon substrate 901 side. As shown in FIG. 13, the temperature detection element 905 is formed in a zigzag shape at a position overlapping the region 911 of the heater 15. The zigzag shape of the temperature detection element 905 increases the length of the temperature detection element 905, thereby increasing the resistance value of the temperature detection element 905. The higher the resistance value of the temperature detection element 905, the larger the temperature detection signal output from the temperature detection element 905, allowing for more accurate detection of temperature changes. In the example shown in FIG. 13, the temperature detection element 905 is formed in a zigzag shape, but this is not limiting. For example, the temperature detection element 905 may be formed in a rectangular shape.

[0117] FIG. 15 is a graph showing the temperature profiles detected by the temperature detection element 905 during normal ejection and during non-ejection. Normal ejection refers to when ink is ejected normally from the ejection port 13. Non-ejection refers to when ink is not ejected from the ejection port 13. In the graph shown in FIG. 15, the temperature profile during normal ejection is represented by a solid line, and the temperature profile during non-ejection is represented by a dashed line. The vertical axis of the graph shown in FIG. 15 represents the temperature (unit: °C) detected by the temperature detection element 905. The horizontal axis of the graph shown in FIG. 15 represents the time (unit: μs). Here, it is assumed that a drive voltage is applied to the heater 15 at time T1, and the temperature detected by the temperature detection element 905 reaches the maximum temperature at time T2.

[0118] As shown by the solid line in FIG. 15 , during normal ejection, the temperature detected by the temperature detection element 905 reaches its maximum temperature, and then a characteristic point where the temperature drops suddenly appears, for example, at time T3. As shown by the dashed line in FIG. 15 , during non-ejection, the temperature detected by the temperature detection element 905 reaches its maximum temperature, and then a characteristic point where the temperature drops suddenly does not appear. When the heater 15 is activated to eject ink from the ejection port 13, the bubbles generated by film boiling caused by the heater 15 reach their maximum size and then shrink. As the bubbles shrink, a force acts to pull the droplets ejected from the ejection port 13 into the pressure chamber 23, causing some of the droplets ejected from the ejection port 13 to return to the heater 15. This causes some of the droplets, which have cooled after being ejected from the ejection port 13, to return to the heater 15, resulting in a characteristic point where the temperature drops suddenly. By detecting the presence or absence of this characteristic point using the temperature detection element 905, it is possible to evaluate whether the ink is being ejected normally from the ejection port 13.

[0119] Therefore, by performing the same process as in the second embodiment, it is possible to reduce the size of the liquid ejection head 3 and to circulate ink (liquid) appropriately, as in the first embodiment.

[0120] Furthermore, the evaluation means 151 evaluates whether the ink ejection state is such that ink is normally ejected from the ejection ports 13, based on the detection signal sent from the temperature detection element 905. This eliminates the need for a recording medium, making it possible to more easily evaluate the ink ejection state. When evaluating the ink ejection state, since the liquid ejection head 3 does not need to record on a recording medium, ink may be ejected into a cap (not shown) that covers the tip of the liquid ejection head 3 to prevent the ink from drying out from the ejection ports 13. Furthermore, according to the modified example, there is no need to provide a separate sensor unit in the inkjet recording apparatus 1, making it possible to reduce the size of the inkjet recording apparatus 1.

[0121] <<Third Embodiment>> Next, a third embodiment will be described. Since the individual components in the third embodiment have the same configuration as those in the first embodiment, they will be described using the same reference numerals as those in the first embodiment. The inkjet recording apparatus 1 according to the third embodiment is provided with a light source 401 and an optical sensor 402 similar to those in the second embodiment, instead of the scanner 63.

[0122] <Method for adjusting an inkjet recording device> As an adjustment method for a liquid ejection device, an adjustment method for an inkjet recording device 1 according to a third embodiment will be described. As in the first embodiment, when a certain number of recording media MD have been recorded or a certain amount of time has elapsed, the control unit 50 performs control to transition to pump adjustment mode. Note that, as in the first embodiment, the control unit 50 may also perform control to transition to pump adjustment mode when the user operates the operation panel 62.

[0123] Fig. 16 is a flowchart showing each step of the pump adjustment mode according to the third embodiment. In the third embodiment, the flow detects the minimum ink circulation flow velocity Vth at which ink can be normally ejected from the ejection ports 13, and sets the output Pp of the circulation pump 1002 so that the ink circulation flow velocity is greater than Vth. Note that the CPU 51 executes a control program stored in the ROM 53 of the control unit 50, thereby executing each step (process) of the flowchart shown in Fig. 16.

[0124] First, in step S301, the evaluation means 151 of the control unit 50 performs processing to set the output Pa of the circulation pump 1002 to the minimum output Pmin that can be set in the circulation pump 1002. At this time, the evaluation means 151 controls the pump driver 66 to set the output Pa of the circulation pump 1002 to Pmin. As a result, ink is circulated through the circulation flow path Fw2 by the circulation pump 1002, whose output Pa is set to Pmin.

[0125] In step S302, similarly to the second embodiment, the control unit 50 operates the heaters 15 (discharge elements) of the liquid discharge head 3 to discharge ink from the discharge ports 13. At this time, the optical sensor 402 detects the droplets DP discharged from the discharge ports 13. The optical sensor 402 transmits a detection signal to the control unit 50 according to the result of the detection of the droplets DP.

[0126] In step S303, similarly to the second embodiment, the evaluation means 151 of the control unit 50 determines whether or not ink has been normally ejected from the ejection port 13 based on the detection signal transmitted from the optical sensor 402. If the evaluation means 151 determines that ink has not been normally ejected from the ejection port 13, that is, if the determination in step S303 is NO, the process proceeds to step S304. If the evaluation means 151 determines that ink has been normally ejected from the ejection port 13, that is, if the determination in step S303 is YES, the process proceeds to step S306.

[0127] In step S304, the evaluation means 151 of the control unit 50 determines whether the output Pa of the circulation pump 1002 is the maximum output Pmax that can be set in the circulation pump 1002. In other words, the evaluation means 151 determines whether the output Pa of the circulation pump 1002 is equal to Pmax. If the evaluation means 151 determines that the output Pa of the circulation pump 1002 is not equal to Pmax, that is, if the determination in step S304 is NO, the process proceeds to step S305. If the evaluation means 151 determines that the output Pa of the circulation pump 1002 is equal to Pmax, that is, if the determination in step S304 is YES, an abnormality is reported and the process ends.

[0128] As a notification of an abnormality, a process of displaying a message to the effect that an abnormality has occurred on a display device or the like (not shown) may be performed. As a notification of an abnormality, a process of displaying a message to the effect that replacement of the liquid ejection head 3 is recommended on a display device or the like may be performed.

[0129] In step S305, the evaluation means 151 of the control unit 50 performs processing to increase the output Pa of the circulation pump 1002 by a fixed value n. At this time, the evaluation means 151 controls the pump driver 66 to set the output Pa of the circulation pump 1002 to Pa+n. As a result, ink is circulated through the circulation flow path Fw2 by the circulation pump 1002, whose output Pa is set to Pa=Pa+n. After performing processing to increase the output Pa of the circulation pump 1002 by the fixed value n, the evaluation means 151 returns to step S302.

[0130] In step S306, the setting means 152 of the control unit 50 performs processing to set Pa to the minimum output Pth at which ink can be normally ejected from the ejection ports 13. Because the determination in the previous step S303 is YES, the ink can be normally circulated through the circulation flow path Fw2 by the circulation pump 1002, whose output is set to Pa. This allows ink to be normally ejected from the ejection ports 13 of the liquid ejection head 3, making it possible to perform high-quality printing on the recording medium MD at high speed.

[0131] In step S307, the setting means 152 of the control unit 50 sets the output Pp of the circulation pump 1002 to be actually used to Pth × k, and then ends the process. The coefficient k is a constant coefficient set in the range of 1.05 to 5. The output Pp of the circulation pump 1002 to be actually used is calculated by multiplying the minimum output Pth of the circulation pump 1002 at which ink can be normally ejected from the ejection ports 13 by the constant coefficient k. This prevents ink from being normally ejected from the ejection ports 13 due to slight environmental changes, variations in the ink ejection state, etc. Furthermore, by setting the constant coefficient k in the range of 1.05 to 5, the output of the circulation pump 1002 does not become too high, thereby extending the life of the circulation pump 1002.

[0132] As described above, according to the third embodiment, similar to the first embodiment, it is possible to reduce the size of the liquid ejection head 3 while still achieving appropriate circulation of ink (liquid).

[0133] Furthermore, the evaluation means 151 evaluates whether the ink ejection state is a state in which ink is normally ejected from the ejection ports 13, based on the detection signal sent from the optical sensor 402. This makes it possible to more easily evaluate the ink ejection state, since a recording medium is not required. When evaluating the ink ejection state, since the liquid ejection head 3 does not need to record on a recording medium, ink may be ejected into a cap (not shown) covering the tip of the liquid ejection head 3 to prevent the ink from drying out from the ejection ports 13.

[0134] As with the first embodiment, this embodiment is not limited to serial type recording apparatuses, but can also be applied to line type recording apparatuses.

[0135] In the third embodiment described above, the evaluation unit 151 evaluates whether the ink ejection state is a state in which ink is ejected normally from the ejection ports 13 based on the detection signal transmitted from the optical sensor 402. However, this is not limiting. For example, similar to the modified example of the second embodiment, the evaluation unit 151 may evaluate whether the ink ejection state is a state in which ink is ejected normally from the ejection ports 13 based on the detection signal transmitted from the temperature detection element 905. Similarly to the first embodiment, the evaluation unit 151 may evaluate whether the ink ejection state is a state in which ink is ejected normally from the ejection ports 13 of the liquid ejection head 3 based on the evaluation pattern PTN read by the scanner 63. In this case, the ink ejection state may be evaluated after printing all evaluation patterns PTN with the output of the circulation pump 1002 changed. This makes it possible to evaluate the ink ejection state in a short time.

[0136] In the third embodiment described above, the evaluation unit 151 increases the output Pa of the circulation pump 1002 by a constant value n from the minimum output Pmin that can be set in the circulation pump 1002, but this is not limited to this. For example, the evaluation unit 151 may decrease the output Pa of the circulation pump 1002 by a constant value n from the maximum output Pmax that can be set in the circulation pump 1002. This makes it possible to set the ink ejection state to a state in which ink is ejected normally from the ejection port 13 from the beginning. Therefore, until the minimum ink circulation flow velocity Vth (and Pth) at which ink can be ejected normally from the ejection port 13 is detected, it is possible to prevent the viscosity of the ink in the ejection port 13 from increasing, and fluctuations in the detection results of Vth and Pth are less likely to occur.

[0137] Next, a fourth embodiment will be described. Since the individual components in the fourth embodiment have the same configuration as those in the first embodiment, they will be described using the same reference numerals as those in the first embodiment. The inkjet recording apparatus 1 according to the fourth embodiment is provided with a light source 401 and an optical sensor 402 similar to those in the second embodiment, instead of the scanner 63.

[0138] <Method for adjusting an inkjet recording device> As an adjustment method for a liquid ejection device, an adjustment method for an inkjet recording device 1 according to a fourth embodiment will be described. As in the first embodiment, when a certain number of recording media MD have been recorded or a certain amount of time has elapsed, the control unit 50 performs control to transition to pump adjustment mode. Note that, as in the first embodiment, the control unit 50 may also perform control to transition to pump adjustment mode when the user operates the operation panel 62.

[0139] 17 is a flowchart showing each step of the pump adjustment mode according to the fourth embodiment. In the fourth embodiment, the flow is to set the output Pp of the circulation pump 1002 based on the output Pr of the circulation pump 1002 stored in a storage element (for example, a ROM or the like) provided in the liquid ejection head 3. Note that the CPU 51 executes a control program stored in the ROM 53 of the control unit 50, thereby executing each step (process) of the flowchart shown in FIG.

[0140] First, in step S 401 , the evaluation means 151 of the control unit 50 reads information about the output Pr of the circulation pump 1002 stored in the memory element of the liquid ejection head 3 .

[0141] In step S402, the evaluation means 151 of the control unit 50 performs processing to set the output Pa of the circulation pump 1002 to Pr-m. At this time, the evaluation means 151 controls the pump driver 66 to set the output Pa of the circulation pump 1002 to Pr-m. As a result, ink is circulated through the circulation flow path Fw2 by the circulation pump 1002, whose output Pa is set to Pa=Pr-m.

[0142] The output Pr of the circulation pump 1002 stored in the memory element of the liquid ejection head 3 is the minimum output Pth obtained during the previous adjustment, at which ink can be ejected normally from the ejection ports 13. In the current adjustment, since Pth may have changed since the previous adjustment, the output Pa of the circulation pump 1002 is set to an output that is smaller by a constant value m than the output Pr (Pth) of the circulation pump 1002 stored in the memory element. For example, if the circulation pump 1002 is configured using a piezoelectric pump, when the drive voltage of the piezoelectric element corresponding to Pth is 80 V, the constant value m is set to 10 V. In this case, the drive voltage of the piezoelectric element corresponding to Pa is 70 V.

[0143] In step S403, similarly to the second embodiment, the control unit 50 operates the heaters 15 (discharge elements) of the liquid discharge head 3 to discharge ink from the discharge ports 13. At this time, the optical sensor 402 detects the droplets DP discharged from the discharge ports 13. The optical sensor 402 transmits a detection signal to the control unit 50 according to the result of the detection of the droplets DP.

[0144] In step S404, similarly to the second embodiment, the evaluation means 151 of the control unit 50 determines whether or not ink has been normally ejected from the ejection port 13 based on the detection signal transmitted from the optical sensor 402. If the evaluation means 151 determines that ink has not been normally ejected from the ejection port 13, that is, if the determination in step S404 is NO, the process proceeds to step S405. If the evaluation means 151 determines that ink has been normally ejected from the ejection port 13, that is, if the determination in step S404 is YES, the process proceeds to step S407.

[0145] In step S405, the evaluation means 151 of the control unit 50 determines whether the output Pa of the circulation pump 1002 is the maximum output Pmax that can be set in the circulation pump 1002. In other words, the evaluation means 151 determines whether the output Pa of the circulation pump 1002 is equal to Pmax. If the evaluation means 151 determines that the output Pa of the circulation pump 1002 is not equal to Pmax, that is, if the determination in step S405 is NO, the process proceeds to step S406. If the evaluation means 151 determines that the output Pa of the circulation pump 1002 is equal to Pmax, that is, if the determination in step S405 is YES, an abnormality is reported and the process ends.

[0146] As a notification of an abnormality, a process of displaying a message to the effect that an abnormality has occurred on a display device or the like (not shown) may be performed. As a notification of an abnormality, a process of displaying a message to the effect that replacement of the liquid ejection head 3 is recommended on a display device or the like may be performed.

[0147] In step S406, the evaluation means 151 of the control unit 50 performs processing to increase the output Pa of the circulation pump 1002 by a fixed value n. At this time, the evaluation means 151 controls the pump driver 66 to set the output Pa of the circulation pump 1002 to Pa+n. As a result, ink is circulated through the circulation flow path Fw2 by the circulation pump 1002, whose output Pa is set to Pa=Pa+n. After performing processing to increase the output Pa of the circulation pump 1002 by the fixed value n, the evaluation means 151 returns to step S403.

[0148] In step S407, the setting means 152 of the control unit 50 performs processing to set Pa to the minimum output Pth at which ink can be normally ejected from the ejection ports 13. Because the determination in the previous step S404 is YES, the ink can be normally circulated through the circulation flow path Fw2 by the circulation pump 1002, whose output is set to Pa. This allows ink to be normally ejected from the ejection ports 13 of the liquid ejection head 3, making it possible to perform high-quality printing on the recording medium MD at high speed.

[0149] In step S408, the setting means 152 of the control unit 50 performs processing to set the output Pp of the circulation pump 1002 to be actually used to Pth × k. The coefficient k is a constant coefficient set in the range of 1.05 to 5. The output Pp of the circulation pump 1002 to be actually used is calculated by multiplying the minimum output Pth of the circulation pump 1002 at which ink can be normally ejected from the ejection ports 13 by the constant coefficient k. This makes it possible to prevent ink from being normally ejected from the ejection ports 13 due to slight environmental changes, variations in the ink ejection state, etc. Furthermore, by setting the constant coefficient k in the range of 1.05 to 5, the output of the circulation pump 1002 does not become too high, thereby extending the life of the circulation pump 1002.

[0150] In step S409, the setting means 152 of the control unit 50 performs processing to write information regarding the minimum output power Pth at which ink can be normally ejected from the ejection ports 13 to the memory element of the liquid ejection head 3, and then ends the processing. Note that the output power Pr of the circulation pump 1002 stored in the memory element of the liquid ejection head 3 is rewritten to the minimum output power Pth at which ink can be normally ejected from the ejection ports 13, which was determined during the current adjustment. Alternatively, the setting means 152 may store the information regarding Pth in a separate memory area of ​​the memory element without rewriting it. This makes it possible to predict the latest Pth by analyzing the transition of Pth, thereby shortening the adjustment time of the inkjet recording apparatus 1.

[0151] As described above, according to the fourth embodiment, similar to the first embodiment, it is possible to reduce the size of the liquid ejection head 3 while ensuring appropriate circulation of ink (liquid).

[0152] Furthermore, the evaluation means 151 evaluates whether the ink ejection state is a state in which ink is normally ejected from the ejection ports 13, based on the detection signal sent from the optical sensor 402. This makes it possible to more easily evaluate the ink ejection state, since a recording medium is not required. When evaluating the ink ejection state, since the liquid ejection head 3 does not need to record on a recording medium, ink may be ejected into a cap (not shown) covering the tip of the liquid ejection head 3 to prevent the ink from drying out from the ejection ports 13.

[0153] Furthermore, the evaluation means 151 can quickly detect the minimum output Pth of the circulation pump 1002 that allows ink to be normally ejected from the ejection ports 13, based on information about the output Pr of the circulation pump 1002 stored in the memory element of the liquid ejection head 3. This makes it possible to shorten the adjustment time for the inkjet recording apparatus 1.

[0154] As with the first embodiment, this embodiment is not limited to serial type recording apparatuses, but can also be applied to line type recording apparatuses.

[0155] In the fourth embodiment described above, the evaluation unit 151 evaluates whether the ink ejection state is a state in which ink is ejected normally from the ejection ports 13 based on the detection signal transmitted from the optical sensor 402. However, this is not limiting. For example, similar to the modified example of the second embodiment, the evaluation unit 151 may evaluate whether the ink ejection state is a state in which ink is ejected normally from the ejection ports 13 based on the detection signal transmitted from the temperature detection element 905. Similarly to the first embodiment, the evaluation unit 151 may evaluate whether the ink ejection state is a state in which ink is ejected normally from the ejection ports 13 of the liquid ejection head 3 based on the evaluation pattern PTN read by the scanner 63. In this case, the ink ejection state may be evaluated after printing all evaluation patterns PTN with the output of the circulation pump 1002 changed. This makes it possible to evaluate the ink ejection state in a short time.

[0156] In the fourth embodiment described above, the evaluation unit 151 increases the output Pa of the circulation pump 1002 from Pr-m by a fixed value n, but this is not limited to this. For example, the evaluation unit 151 may decrease the output Pa of the circulation pump 1002 by a fixed value n from the maximum output Pmax that can be set in the circulation pump 1002. This makes it possible to set the ink ejection state to a state in which ink is ejected normally from the ejection port 13 from the beginning. Therefore, until the minimum ink circulation flow velocity Vth (and Pth) at which ink can be ejected normally from the ejection port 13 is detected, it is possible to prevent the viscosity of the ink in the ejection port 13 from increasing, and fluctuations in the detection results of Vth and Pth are less likely to occur.

[0157] In each of the above-described embodiments, the inkjet recording apparatus is provided with a thermal liquid ejection head 3 having heaters 15 as ejection elements, but this is not limiting. For example, the inkjet recording apparatus may be provided with a piezo liquid ejection head having piezo elements as ejection elements.

[0158] <<Other embodiments>> The disclosure of this embodiment includes configurations typified by the following examples of a liquid ejection device and an example of a method for adjusting a liquid ejection device.

[0159] <Configuration 1> a liquid ejection head having an ejection port and an ejection element for ejecting liquid from the ejection port; a circulation pump for circulating the liquid supplied to the discharge port; an evaluation means for evaluating a discharge state in which the liquid is discharged from the discharge port by the discharge element by changing an output of the circulation pump; a setting means for setting the output of the circulation pump based on the evaluation result of the discharge state by the evaluation means; A liquid ejection device comprising:

[0160] <Configuration 2> 2. The liquid ejection device according to configuration 1, wherein the evaluation means evaluates the ejection state based on an evaluation pattern formed by ejecting liquid from the ejection port and recording it on a recording medium.

[0161] <Configuration 3> a scanner that reads the evaluation pattern recorded on the recording medium; 3. The liquid ejection device according to configuration 2, wherein the evaluation means evaluates the ejection state based on the evaluation pattern read by the scanner.

[0162] <Configuration 4> further comprising an optical sensor for detecting droplets ejected from the ejection port; 2. The liquid ejection device according to configuration 1, wherein the evaluation means evaluates the ejection state based on a result of droplet detection by the optical sensor.

[0163] <Configuration 5> the liquid ejection head has a temperature detection element provided in the ejection element, 2. The liquid ejection device according to configuration 1, wherein the evaluation means evaluates the ejection state based on the temperature detected by the temperature detection element.

[0164] <Configuration 6> 6. The liquid ejection device according to any one of configurations 1 to 5, wherein the evaluation means evaluates whether the ejection state is a state in which liquid is normally ejected from the ejection port.

[0165] <Configuration 7> The liquid ejection device according to configuration 6, wherein the setting means sets the output of the circulation pump to an output that enables normal ejection of liquid from the ejection port based on the evaluation result of the ejection state by the evaluation means.

[0166] <Configuration 8> The liquid ejection device according to configuration 7, wherein the output capable of ejecting liquid normally from the ejection port is calculated by multiplying the minimum output of the circulation pump capable of ejecting liquid normally from the ejection port by a certain coefficient.

[0167] <Configuration 9> 9. The liquid ejection device according to configuration 8, wherein the constant coefficient is set in the range of 1.05 to 5.

[0168] <Configuration 10> 10. The liquid ejection device according to any one of configurations 1 to 9, wherein the evaluation means changes the output of the circulation pump based on information about the output of the circulation pump stored in a memory element.

[0169] <Configuration 11> A method for adjusting a liquid ejection device including a liquid ejection head having ejection ports and ejection elements for ejecting liquid from the ejection ports, and a circulation pump for circulating liquid supplied to the ejection ports, the method comprising: a step of evaluating a discharge state in which the liquid is discharged from the discharge port by the discharge element while changing the output of the circulation pump; setting the output of the circulation pump based on the evaluation result of the discharge state; A method for adjusting a liquid ejection device, comprising:

[0170] <Configuration 12> 12. The method for adjusting a liquid ejection device according to Configuration 11, wherein in the step of evaluating the ejection state, it is evaluated whether the ejection state is a state in which liquid is normally ejected from the ejection port.

[0171] <Configuration 13> A method for adjusting a liquid ejection device according to configuration 12, wherein, in the step of evaluating the ejection state, if it is evaluated that the ejection state is not a state in which liquid is being ejected normally from the ejection port, the output of the circulation pump is changed to be higher, and then it is again evaluated whether the ejection state is a state in which liquid is being ejected normally from the ejection port.

[0172] <Configuration 14> A method for adjusting a liquid ejection device according to configuration 12 or 13, wherein, in the step of evaluating the ejection state, if the ejection state is evaluated as being a state in which liquid is normally ejected from the ejection port, the output of the circulation pump is changed to be lower, and then it is again evaluated whether the ejection state is a state in which liquid is normally ejected from the ejection port. [Explanation of symbols]

[0173] 1. Inkjet recording device 3 Liquid ejection head 13 Outlet 15 Heater 50 control section 151 Evaluation tools 152 Setting Method 1002 Circulation pump

Claims

1. a liquid ejection head having an ejection port and an ejection element for ejecting liquid from the ejection port; a circulation pump for circulating the liquid supplied to the discharge port; an evaluation means for evaluating a discharge state in which the liquid is discharged from the discharge port by the discharge element by changing an output of the circulation pump; a setting means for setting the output of the circulation pump based on the evaluation result of the discharge state by the evaluation means; A liquid ejection device comprising:

2. 2. The liquid ejection apparatus according to claim 1, wherein the evaluation means evaluates the ejection state based on an evaluation pattern recorded on a recording medium by ejecting liquid from the ejection openings.

3. a scanner that reads the evaluation pattern recorded on the recording medium; 3. The liquid ejection device according to claim 2, wherein the evaluation means evaluates the ejection state based on the evaluation pattern read by the scanner.

4. further comprising an optical sensor for detecting droplets ejected from the ejection port; 2. The liquid ejection apparatus according to claim 1, wherein the evaluation means evaluates the ejection state based on a result of droplet detection by the optical sensor.

5. the liquid ejection head has a temperature detection element provided in the ejection element, The liquid ejection device according to claim 1 , wherein the evaluation means evaluates the ejection state based on the temperature detected by the temperature detection element.

6. The liquid ejection device according to claim 1 , wherein the evaluation means evaluates whether the ejection state is a state in which liquid is ejected normally from the ejection port.

7. The liquid ejection device according to claim 6 , wherein the setting means sets the output of the circulation pump to an output that allows liquid to be ejected normally from the ejection port based on the evaluation result of the ejection state by the evaluation means.

8. 8. The liquid ejection device according to claim 7, wherein the output capable of ejecting liquid normally from the ejection port is calculated by multiplying the minimum output of the circulation pump capable of ejecting liquid normally from the ejection port by a constant coefficient.

9. The liquid ejection device according to claim 8 , wherein the constant coefficient is set in the range of 1.05 to 5.

10. 2. The liquid ejection device according to claim 1, wherein the evaluation means changes the output of the circulation pump based on information about the output of the circulation pump stored in a memory element.

11. A method for adjusting a liquid ejection device including a liquid ejection head having ejection ports and ejection elements for ejecting liquid from the ejection ports, and a circulation pump for circulating liquid supplied to the ejection ports, the method comprising: a step of evaluating a discharge state in which the liquid is discharged from the discharge port by the discharge element while changing the output of the circulation pump; setting the output of the circulation pump based on the evaluation result of the discharge state; A method for adjusting a liquid ejection device, comprising:

12. The method for adjusting a liquid ejection device according to claim 11 , wherein in the step of evaluating the ejection state, the ejection state is evaluated as to whether or not the liquid is being ejected normally from the ejection port.

13. 13. The method for adjusting a liquid ejection device according to claim 12, wherein, if, in the step of evaluating the ejection state, it is evaluated that the ejection state is not a state in which liquid is ejected normally from the ejection port, the output of the circulation pump is changed to be higher, and then it is again evaluated whether the ejection state is a state in which liquid is ejected normally from the ejection port.

14. 14. A method for adjusting a liquid ejection device according to claim 12 or 13, wherein, in the step of evaluating the ejection state, if the ejection state is evaluated as a state in which liquid is ejected normally from the ejection port, the output of the circulation pump is changed to be lower, and then the method again evaluates whether the ejection state is a state in which liquid is ejected normally from the ejection port.

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