Recording device and control method

Abstract

To provide a technique that can suppress occurrence of wasted ink that is generated by discharge of ink for adjusting ink density in a circulation path.SOLUTION: A recording device comprises: a circulation path which allows for supplying recording agent to a recording element substrate provided with a nozzle capable of discharging the recording agent, as well as, allows for collecting the recording agents not discharged from the recording element substrate; acquisition means that acquires information on density of the recording agent circulating in the circulation path; and discharge-control means that executes ink discharge-control for discharging the recording agent through the circulation path in accordance with the information on the density, and then, supplying an amount corresponding to a discharge amount, of the recording agent to the circulation path. When executing the discharge-control, the discharge-control means selectively executes either of first discharge-control of making the discharge amount of ink a first discharge amount and second discharge-control of making the discharge amount a second discharge amount more than the first discharge amount.SELECTED DRAWING: Figure 11

Description

[Technical Field]

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

[0002] Inkjet recording devices have been known in the past that circulate ink in an ink circulation path that includes a recording head, thereby suppressing thickening of the ink in the nozzles and suppressing deterioration of the ink ejection characteristics from the nozzles. However, in such recording devices, evaporation of ink from the nozzles during circulation causes thickening of the ink in the circulation path, i.e., an increase in the ink concentration.

[0003] Patent Documents 1 and 2 disclose a technique for obtaining the ink concentration in a circulation path based on the amount of ink evaporated during circulation and the amount of ink consumed during printing, and for discharging a portion of the thickened ink from the circulation path based on the obtained concentration. Note that with the techniques of Patent Documents 1 and 2, as ink is discharged from the circulation path, new ink is supplied to the circulation path, thereby adjusting the ink concentration in the circulation path to a constant level. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-121788 [Patent Document 2] Japanese Patent Application Publication No. 2018-008513 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the techniques disclosed in Patent Documents 1 and 2, the ink concentration obtained to determine whether to discharge ink is an estimated value, which may result in an error between the ink concentration used to determine whether to discharge ink and the actual ink concentration in the circulation path, making it impossible to discharge ink appropriately and increasing the amount of waste ink generated.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a technology that can suppress the increase in waste ink caused by discharging ink to adjust the ink concentration in the circulation path. [Means for solving the problem]

[0007] In order to achieve the above object, one embodiment of a printing apparatus according to the present invention includes a printing element substrate having nozzles capable of ejecting printing agent; a circulation path including the printing element substrate, which circulates the printing agent, supplies the printing agent to the printing element substrate, and recovers printing agent that has not been ejected from the printing element substrate; acquisition means for acquiring information regarding the concentration of the printing agent circulating through the circulation path; and a device for discharging printing agent from the circulation path in accordance with the information regarding the concentration, and supplying an amount of printing agent corresponding to the amount discharged to the circulation path. recording agent an emission control means for executing the emission control; an image processing unit capable of executing image density correction based on the density of the recording material in image processing when generating recording data to be recorded on a recording medium; When the discharge control is performed, the discharge control means recording agent a first emission control in which the amount of emission becomes a first emission amount, and a second emission control in which the amount of emission becomes a second emission amount that is greater than the first emission amount; The information about the density includes a density estimate value that is an estimate of the density of the recording material and an estimation error that is an error that may occur in the density estimate value, and the image processing unit executes the image density correction as the process when a difference between the density estimate value acquired by the acquisition unit and the density estimate value when the process related to the image density correction was most recently executed is equal to or greater than a threshold value. It is characterized by: [Effects of the Invention]

[0008] According to the present invention, it is possible to suppress an increase in waste ink that occurs when ink is discharged to adjust the ink concentration in the circulation path. [Brief explanation of the drawings]

[0009] [Figure 1] Schematic diagram of the recording device [Figure 2] Block diagram showing the configuration of the control system of the recording device [Figure 3] 1 is a flowchart showing detailed image processing. [Figure 4] A perspective view of the nozzle surface of the recording head [Figure 5] FIG. 1 is a diagram illustrating the configuration of a printing element substrate. [Figure 6] Schematic diagram showing the ink circulation path in a recording device [Figure 7] Timing chart of each process executed during recording [Figure 8] Block diagram showing the functional configuration of the engine controller [Figure 9] 10 is a flowchart showing detailed processing contents of the acquisition process. [Figure 10] Table for obtaining the amount of ink evaporation [Figure 11] 10 is a flowchart showing the detailed processing contents of the adjustment processing. [Figure 12] Graph showing the relationship between nozzle circulation flow rate and evaporation amount [Figure 13] Graph showing the transition of estimated error at 0% recording duty [Figure 14] Graph showing the change in estimation error when ink with an evaporation rate of 2% is supplied [Figure 15] A graph showing the change in density estimation value and estimation error due to ink discharge control. [Figure 16] 10 is a flowchart showing the detailed processing contents of the decision processing. [Figure 17] Block diagram showing the functional configuration of the image processing unit [Figure 18] Flowchart showing detailed processing contents of HS processing [Figure 19] Flowchart showing an example of a measurement image [Figure 20] Measurement curve diagram [Figure 21] FIG. 1 shows measurements in an area corresponding to a given patch in a scanned image. [Figure 22]Flowchart showing detailed processing contents of CS processing [Figure 23] A diagram showing a three-dimensional space with the RGB values ​​of the scanned image as the axes. [Figure 24] Graph showing the transition of estimated error at a recording duty of 2% [Figure 25] A graph showing the change in density estimation value and estimation error due to ink discharge control. DETAILED DESCRIPTION OF THE INVENTION

[0010] An example of a recording device and a control method will be described below with reference to the accompanying drawings. Note that the following embodiments do not limit the present invention, and not all of the combinations of features described in the embodiments are necessarily essential to the solutions of the present invention. Furthermore, the positions, shapes, etc. of the components described in the embodiments are merely examples, and are not intended to limit the present invention to those alone.

[0011] (First embodiment) First, a recording apparatus according to a first embodiment will be described with reference to FIGS.

[0012] <Configuration of recording device> FIG. 1 is a schematic diagram of a recording device. The recording device 10 in FIG. 1 includes a feeding module 12 that feeds cut-sheet recording media and a recording module 14 that records on the recording media fed by the feeding module 12. The recording device 10 also includes a first fixing module 16 that uses non-contact heating to fix the recording agent to the recording medium after recording, and a second fixing module 18 that uses contact heating to fix the recording agent to the recording medium. The recording device 10 also includes a cooling and reversing module 20 that cools the recording medium and reverses it during double-sided recording, and a stacking module 22 that discharges and stacks the resulting product. The recording device 10 also includes a control unit 200 (described below) that controls the overall operation of the recording device 10.

[0013] The recording module 14 includes a conveyor belt 24 that conveys the recording medium fed from the feeding module 12. The conveyor belt 24 conveys the recording medium while holding it in place by air suction. The recording module 14 also includes a recording head 26 that is positioned opposite the conveyor belt 24 and ejects a recording agent onto the recording medium conveyed by the conveyor belt 24 to perform recording. A plurality of recording heads 26 are arranged in parallel along the recording medium transport direction. In this embodiment, four colors of pigment ink—yellow (Y), magenta (M), cyan (C), and black (K)—are used as the recording agent, as well as a treatment liquid (P) that performs a predetermined process on the ink ejected onto the recording medium. Therefore, in this embodiment, the recording head 26 includes five line-type recording heads corresponding to the treatment liquids in addition to the four colors of ink—Y, M, C, and K. Note that the number of colors of the recording heads 26 in the recording module 14 is not limited to the four colors described above, and the number of recording heads is not limited to five. The ink is not limited to ink containing a pigment, and various known inks such as ink containing a dye can be used.

[0014] The recording head 26 is configured to be able to eject ink by, for example, an inkjet method. Various known inkjet techniques can be used, such as a method using a heat generating element, a method using a piezoelectric element, a method using an electrostatic element, or a method using a MEMS element. The recording head 26 receives a corresponding type of ink from a main tank 606 (see FIG. 6) provided in the recording device 10 via a tube or the like.

[0015] The recording module 14 includes a maintenance unit 28 for maintaining and restoring good ink ejection performance in the recording head 26. The maintenance unit 28 includes, for example, a cap unit (not shown) that protects the nozzle surface of the recording head 26 on which nozzles that eject ink are formed, a wiping unit that wipes the nozzle surface, and a suction unit that sucks ink from the recording head 26 through the nozzles. The recording head 26 and the maintenance unit 28 are configured to be movable relative to each other; for example, when using the maintenance unit 28, the maintenance unit 28 is located below the recording head 26 in a position facing the nozzle surface. Note that the maintenance unit 28 may be configured so that only the components thereof move.

[0016] <Configuration of the control system of the recording device> Next, the configuration of the control system of the recording device 10 will be described. FIG. 2 is a block diagram showing the configuration of the control system of the recording device 10. The recording device 10 is communicably connected to a higher-level device (DFE) HC2, which is communicatively connected to a host device HC1. The host device HC1 generates or stores manuscript data that is the source of the recorded image. Here, the manuscript data is generated in the form of an electronic file such as a document file or an image file. The manuscript data is transmitted from the host device HC1 to the higher-level device HC2. The higher-level device HC2 converts the received manuscript data into a data format usable by the recording device 10, for example, RGB data that expresses an image in RGB. The converted data is transmitted from the device HC2 to the recording device 10.

[0017] The control unit 200, which controls the overall operation of the recording device 10, includes a main controller 202 and an engine controller 204. The main controller 202 includes a processing unit 206, a storage unit 208, an operation unit 210, an image processing unit 212, communication interfaces (I / F) 214 and 216, and a buffer 218.

[0018] The processing unit 206 is realized by a processor such as a CPU, executes programs stored in the storage unit 208, and performs overall control of the main controller 202. The storage unit 208 is realized by a storage device such as a ROM, RAM, hard disk, or SSD, and stores programs and data executed by the processing unit 206, as well as providing a work area for the processing unit 206. The operation unit 210 is an input device such as a touch panel, keyboard, or mouse, and receives instructions from a user.

[0019] The buffer 218 is realized by, for example, a RAM, a hard disk, or an SSD, and is a storage area for storing various types of information. The image processing unit 212 is realized by, for example, an electronic circuit having an image processing processor, and is configured to be able to perform image processing on image data (RGB data) input from the higher-level device HC2. The communication I / F 214 communicates with the higher-level device HC, and the communication I / F 216 communicates with the engine controller 204. Note that, although the control unit 200 has been described as including one each of the processing unit 206, the storage unit 208, and the image processing unit 212, a plurality of these components may be provided. The configuration of the engine controller 204 will be described later.

[0020] The dashed arrows in Figure 2 indicate an example of the flow of data input to the control unit 200. Image data (RGB data) received from the higher-level device HC2 via the communication I / F 214 is accumulated in the buffer 218. The image processing unit 212 reads the image data from the buffer 218, performs predetermined image processing on the read image data, generates print data to be used by the engine controller 204, and stores the data again in the buffer 218. The print data stored in the buffer 218 is then transmitted from the communication I / F 216 to the engine controller 204. Thereafter, the engine controller 204 drives the print head 26 based on the print data, and a print operation is performed to execute printing on the print medium.

[0021] <Image processing> Next, the image processing executed by the image processing unit 212 will be described. Fig. 3 is a flowchart showing the detailed processing contents of the image processing executed by the image processing unit 212. The series of processes shown in the flowchart in Fig. 3 are performed by the CPU of the main controller 202 by expanding program code stored in the ROM of the main controller 202 into the RAM of the main controller 202 and executing the program code. Alternatively, some or all of the functions of the steps in Fig. 4 may be executed by hardware such as an ASIC or an electric circuit. In this specification, the symbol S in the description of each process indicates a step in the flowchart.

[0022] When image processing starts, first, in S302, the image processing unit 212 acquires RGB data (image data) stored in the buffer 218. In this embodiment, the RGB data is assumed to be composed of 8 bits for each RGB value. The RGB data also has a data resolution of 600 dpi x 600 dpi. Next, in S304, the image processing unit 212 executes color conversion processing to convert the RGB data into CMYK data corresponding to ink colors that can be printed by the printing device 10. This color conversion processing generates CMYK data composed of 12 bits for each CMYK value.

[0023] Thereafter, in S306, the image processing unit 212 performs a quantization process on the CMYK data to generate quantized data consisting of 3 bits for each of CMYK. For example, dithering or error diffusion can be used as this quantization process. In this embodiment, quantized data having a data resolution of 600 dpi is generated by the quantization process. Then, in S308, the image processing unit 212 acquires attribute information. The attribute information is information that indicates whether the attribute of the image to be recorded for that pixel is a character attribute, a thin line attribute, or another attribute (such as an image attribute), and is composed of 1 bit. More specifically, if a character or a thin line is recorded in a certain pixel, a "1" is acquired as the attribute information. On the other hand, if something other than a character or a thin line is recorded, a "0" is acquired as the attribute information.

[0024] Note that S306 may be executed in parallel with the processes of S302 to S306. In addition, in this embodiment, the attribute information is acquired separately from the RGB data, but this is not limiting, and the image processing unit 212 may acquire the RGB data and the attribute information in a combined state.

[0025] After acquiring the quantized data and attribute information, the image processing unit 212 then combines the 3-bit quantized data for each CMYK value with the 1-bit attribute information in S310 to generate combined data consisting of 4 bits for each CMYK value. The data resolution of the generated combined data is the same as that of the quantized data, 600 dpi x 600 dpi. Then, in S312, the image processing unit 212 performs index expansion processing on the combined data to generate two planes of data consisting of 1-bit information for each CMYK value and attribute information. In this index expansion, the 600 dpi x 600 dpi quantized data for each CMYK value in the combined data is expanded to 1-bit data for each CMYK value at a resolution of 1200 dpi x 1200 dpi using an index pattern.

[0026] Then, in S314, the image processing unit 212 performs a distribution process to distribute the expanded data to each print head 26 that ejects different inks, and generates print data to be used for printing. The generated print data is 1-bit data with a resolution of 1200 dpi x 1200 dpi for each color of CMYK, and indicates whether or not to eject ink. Then, in S316, the image processing unit 212 sends the generated print data to the buffer 218, and this image processing ends.

[0027] <Recording head configuration> Next, we will explain the configuration of the recording head 26. Figures 4(a), (b), and (c) are diagrams showing the configuration of the surface of the recording head 26 on which nozzles are formed.

[0028] The recording head 26 has a surface (nozzle surface) 400 facing the conveyed recording medium, on which multiple recording element substrates 402 are provided. The recording element substrates 402 may be arranged in a line along the extension direction of the recording head 26 (see FIG. 4(a)), or may be arranged in a staggered pattern along the extension direction of the recording head 26 (see FIG. 4(b)). Alternatively, the recording head 26 may be configured to include only one recording element substrate 402 (see FIG. 4(a)).

[0029] The recording head 26 also includes a negative pressure control unit 616 that controls the pressure (negative pressure) in an ink circulation path (described later) in the recording device 10 including the recording head 26, and an ink supply unit 614 that is fluidly connected to the negative pressure control unit 616 (see FIG. 5). The recording head 26 also includes a liquid connection part 612 that serves as an ink supply port and an ink discharge port for the ink supply unit 614 (see FIG. 5).

[0030] <Configuration of the recording element substrate> Next, we will explain the configuration of the recording element substrate 402. Figures 5(a) to 5(c) are diagrams for explaining the outline of the configuration of the recording element substrate, where (a) is an overall perspective view, (b) is a partially enlarged plan view showing the internal configuration in a transparent state, and (c) is a cross-sectional view taken along line Vc-Vc in (b).

[0031] The recording element substrate 402 includes a substrate 502 and an orifice plate 504 formed on one surface of the substrate 502. The substrate 502 is preferably formed from a material such as a processable semiconductor substrate. Using this material allows multiple electronic devices, such as energy generating elements, electrical circuits, electrical wiring, and temperature sensors, to be arranged on the surface of the substrate 502. The orifice plate 504 is formed from a material such as a resin substrate on which the nozzles 500 can be formed by laser processing, or an inorganic plate on which the nozzles 500 can be formed by dicing. The orifice plate 504 may also be formed from a material such as a photosensitive resin material on which the nozzles 500 and ink flow paths can be formed by photocuring. Alternatively, various known materials may be used, such as a semiconductor substrate similar to the substrate 502, on which the nozzles 500 and ink flow paths can be formed by MEMS processing.

[0032] The orifice plate 504 has a nozzle row 506 formed therein, in which a plurality of nozzles 500 for ejecting ink are arranged along the extension direction of the substrate 502. The orifice plate 504, together with one surface of the substrate 502, forms a plurality of pressure chambers 508 (see FIGS. 5(b) and 5(c)). Each pressure chamber 508 is connected to a nozzle 500. Each pressure chamber 508 is provided with an energy generating element 510 that generates energy for ejecting liquid (see FIG. 5(c)). The energy generating element 510 is provided on the substrate 502, and the nozzles 500 formed in the orifice plate 504 are formed at positions facing the energy generating elements 510.

[0033] Various known elements such as a heat generating element (electrothermal conversion element) or a piezoelectric element can be used as the energy generating element 510. When a heat generating element is used as the energy generating element 510, the ink in the pressure chamber 508 is boiled by the heat generating element, and the ink is ejected from the nozzle 500 by the bubbling energy generated when boiling.

[0034] On one side of the pressure chamber 508 in a direction intersecting the extension direction of the nozzle row 506, an inflow channel 512 is formed, which allows ink to flow into the pressure chamber 508, and on the other side of the direction, an outflow channel 514 is formed, which allows ink to flow out of the pressure chamber 508.

[0035] On one side of the substrate 502 in a direction intersecting the extension direction of the nozzle arrays 506, a plurality of supply ports 516 that supply ink to the inflow channels 512 are arranged along the extension direction (see FIG. 5(c)). Furthermore, on the other side of the direction intersecting the extension direction of the nozzle arrays 506, a plurality of recovery ports 518 that recover ink from the outflow channels 514 are arranged along the extension direction. The supply ports 516 and the recovery ports 518 are through-holes that penetrate from one surface of the substrate to the other. The substrate 502 is also provided with a temperature detection unit 520 between the two nozzle arrays 506 that can detect temperature. The temperature detection unit 520 detects the temperature of the ink on the recording element substrate 402. Although not shown, the recording element substrate 402 is also provided with a temperature adjustment heater that can adjust the surface temperature of the nozzle surface 400 of the recording head 26 to a set temperature.

[0036] <Circulation route> Next, we will explain the ink circulation path in the recording apparatus 10. Figure 6 is a schematic diagram of the ink circulation path in the recording apparatus 10.

[0037] In the ink circulation path 600 provided in the recording device 10, the recording head 26 is fluidly connected to a first circulation pump 602, a buffer tank 604, and the like. In other words, a circulation path 600 is formed independently for each type of ink (treatment liquid). Since the circulation paths 600 corresponding to each ink have the same configuration, the following description will focus on the circulation path 600 including the recording head 26 that ejects K ink.

[0038] The buffer tank 604 is equipped with an atmosphere communication port (not shown) that connects the inside of the buffer tank 604 with the outside, allowing air bubbles in the ink in the buffer tank 604 to be discharged to the outside. The buffer tank 604 is connected to a main tank 606, and a refill pump 608 is provided between the buffer tank 604 and the main tank 606. The refill pump 608 supplies ink from the main tank 606 to the buffer tank 604. For example, when the amount of ink circulating in the circulation path 600 decreases due to a printing operation on a printing medium or a maintenance operation on the print head 26, the refill pump 608 is controlled to transfer the reduced amount of ink from the main tank 606 to the buffer tank 604.

[0039] The ink in the buffer tank 604 is supplied by a second circulation pump 610 to an ink supply unit 614 of the recording head 26 via a liquid connection part 612. The ink supplied to the ink supply unit 614 is adjusted to two different negative pressures (high pressure and low pressure) by a negative pressure control unit 616 connected to the ink supply unit 614 via a filter 615, and is then split into two flow paths, one on the high pressure side and one on the low pressure side, and supplied to the recording element substrate 402.

[0040] Ink flowing through the high-pressure flow path is supplied to a common supply flow path 618 that supplies ink to each recording element substrate 402. Ink flowing through the low-pressure flow path is supplied to a common recovery flow path 620 into which ink recovered from the recording element substrate 402 flows. Due to the pressure difference between the common supply flow path 618 and the common recovery flow path 620, some of the ink supplied to the common supply flow path 618 flows into the recording element substrate 402 via individual supply flow paths 619. The ink that has flowed into the recording element substrate 402 then flows in order to the supply port 516, the inflow flow path 512, the pressure chamber 508, the outflow flow path 514, and the recovery port 518, and then flows out into the common recovery flow path 620 via an individual recovery flow path 621.

[0041] Here, the first circulation pump 602 includes a first pump 602a on the high-pressure side and a second pump 602b on the low-pressure side. The first pump 602a is connected to the common supply flow path 618 via an ink supply unit 614, and the second pump 602b is connected to the common recovery flow path 620 via the ink supply unit 614. As a result, ink recovered from the print head 26 is recovered into the buffer tank 604 via the first circulation pump 602. That is, ink that does not flow to the printing element substrate 402 in the common supply flow path 618 is recovered into the buffer tank 604 by the first pump 602a via the ink supply unit 614 and the liquid connection part 612. Furthermore, ink flowing out from the common recovery flow path 620 is recovered into the buffer tank 604 by the second pump 602b via the ink supply unit 614 and the liquid connection part 612.

[0042] The first circulation pump 602 (i.e., the first pump 602a and the second pump 602b) is preferably a positive displacement pump having a constant liquid delivery capacity. Specifically, it is preferable to use a tube pump, a gear pump, a diaphragm pump, a syringe pump, or the like as the first circulation pump 602. Note that the first circulation pump 602 may be configured to ensure a constant flow rate by, for example, arranging a general constant flow valve or a relief valve at the pump outlet.

[0043] When the print head 26 is driven, the first circulation pump 602 is driven to cause ink to flow at a predetermined flow rate through the common supply flow path 618 and the common recovery flow path 620. By flowing ink in this manner, the temperature of the print head 26 is maintained at an optimum temperature during printing. The predetermined flow rate is set to a flow rate that allows the temperature difference between each print element substrate 402 in the print head 26 to be maintained at a temperature difference that does not affect the print image quality. Note that if the flow rate is set too high, the negative pressure difference between each print element substrate 402 will increase due to the influence of pressure loss in the common supply flow path 618 and the common recovery flow path 620, etc., resulting in density unevenness in the printed image. For this reason, the predetermined flow rate is set taking into consideration the temperature difference and negative pressure difference between each print element substrate 402.

[0044] The buffer tank 604 may be provided with a heating unit for controlling the temperature of the ink circulating through the circulation path 600, or may be provided with a degassing unit for removing gas dissolved in the ink. The amount of ink circulating through the circulation path 600 including the buffer tank 604 is set to, for example, 2180 g.

[0045] The negative pressure control unit 616 is provided in the path between the second circulation pump 610 and the recording element substrate 402. The negative pressure control unit 616 operates to maintain the pressure downstream of the negative pressure control unit 616 (the recording element substrate 402 side) at a preset constant pressure even when the flow rate of ink in the circulation path 600 fluctuates due to differences in the ejection amount per unit area, etc. The upstream side of the negative pressure control unit 616 is pressurized by the second circulation pump 610. This configuration can suppress the effect of the head pressure of the buffer tank 604 on the recording head 26, thereby increasing the degree of freedom in the layout of the buffer tank 604 in the recording apparatus 10.

[0046] The second circulation pump 610 may be a turbo pump, a positive displacement pump, or the like, as long as it has a head pressure equal to or greater than a certain pressure within the range of the ink circulation flow rate used when driving the recording head 26. Specifically, the second circulation pump 610 may be a diaphragm pump, or the like.

[0047] In this way, the circulation path 600 is configured so that the circulating ink passes through each recording element substrate 402. Therefore, heat generated in each recording element substrate 402 can be discharged to the outside of the recording element substrate 402 by the ink flowing through the common supply flow path 618 and the common recovery flow path 620. Furthermore, with this configuration, while the recording head 26 is performing recording, ink flow can be generated even in the nozzles 500 that are not ejecting ink. Therefore, this ink flow can suppress the viscosity of the ink in the nozzles 500, and the ink ejection performance of the recording head 26 can be maintained at a good level.

[0048] <Processing during recording> Next, the processes executed during printing in the printing apparatus 10 will be described. Figure 7 is a timing chart of multiple processes executed during printing in the printing apparatus 10. In the following description, the state of the printing apparatus 10 before executing a printing operation based on a job will be referred to as a standby state as appropriate. When the printing apparatus 10 is in a standby state, the first circulation pump 602 and the second circulation pump 610 are stopped, and ink is not circulating in the circulation path 600. Furthermore, the temperature of the print head 26 in the standby state is set to T0°C, and the humidity at the nozzles 500 is set to RH1.

[0049] When a printing operation based on a job is started in the printing apparatus 10, the engine controller 204 drives the first circulation pump 602 to circulate ink in the circulation path 600. Next, a cap portion (not shown) of the maintenance unit 28 moves away from the nozzle surface 400 of the print head 26, exposing the nozzles 500 to the outside. As a result, the humidity around the nozzles 500 becomes equal to the humidity (RH0) of the installation environment of the printing apparatus 10, causing the ink to evaporate from the nozzles 500. Thereafter, a temperature-control heater (not shown) provided on the printing element substrate 402 is driven to raise the temperature of the printing element substrate 402 to a temperature required for the printing operation. Then, when the flow velocity of the ink in the circulation path 600 (circulation flow velocity) reaches a predetermined velocity V and the temperature of the printing element substrate 402 reaches a predetermined temperature Top°C, the printing operation is performed to print on the printing medium.

[0050] The evaporation rate of ink from the nozzles 500 increases sharply when the cap is released. Furthermore, during a printing operation, ink evaporation mainly progresses from non-ejecting nozzles that do not eject ink. Evaporation of ink from non-ejecting nozzles increases the ink concentration in the circulation path 600. Because the circulation flow rate cannot be controlled individually for each nozzle 500, the evaporation rate of ink from each non-ejecting nozzle during a printing operation is constant. Note that while the evaporation component from non-ejecting nozzles is dominant in ink evaporation from nozzles during a printing operation, in this embodiment, when calculating the amount of ink evaporation, it is assumed that evaporation progresses uniformly across all nozzles, regardless of the ejection state, for simplicity of calculation.

[0051] After the printing operation is completed, the first circulation pump 602 is stopped, stopping the circulation of ink in the circulation path 600. After a predetermined time has elapsed since the first circulation pump 602 was stopped, the circulation flow in the nozzles 500 completely stops. Therefore, when the first circulation pump 602 is stopped, the evaporation rate from the non-ejecting nozzles drops sharply. After that, the cap portion is brought into contact with the nozzle surface 400 of the print head 26. This increases the humidity around the nozzles 500, recovering it to the humidity RH1 before the printing operation for the job was performed, and the evaporation rate from the non-ejecting nozzles converges to zero.

[0052] <Adjustment processing> In the above configuration, the recording device 10 executes an adjustment process to adjust the ink density (for example, pigment density) in the circulation path that has increased due to the recording operation to a density that does not cause a deterioration in the recorded image quality.

[0053] Specifically, the recording device 10 first executes an acquisition process to acquire an estimated value of the ink density in the circulation path 600 that has thickened during the job-based recording operation, before or after the execution of the job-based recording operation. Then, based on the acquired estimated value of the ink density, the recording device 10 executes an adjustment process to adjust the ink density in the circulation path 600 by discharging a portion of the thickened ink from the circulation path 600 and supplying new ink from the main tank 606. In the following description, the process of discharging a portion of the ink from the circulation path 600 and supplying new ink to the circulation path 600 is appropriately referred to as ink discharge control. This adjustment process adjusts the ink density in the circulation path 600 to within a predetermined temperature range that is unlikely to cause a deterioration in the recorded image quality. The timing of executing the adjustment process (and acquisition process) is not limited to before or after the execution of the job-based recording operation, and may be executed, for example, when a user instructs it to do so. The adjustment process is executed for each type of ink.

[0054] Functional Configuration of Engine Controller 204 The acquisition process and adjustment process are executed by the engine controller 204. Fig. 8 is a block diagram showing the functional configuration of the engine controller 204. Note that each component of the engine controller 204 shown in Fig. 8 is realized by a known hardware configuration such as a CPU, a ROM, and a RAM provided in the engine controller 204.

[0055] The engine controller 204 includes a printhead temperature adjustment control unit 802 that controls temperature adjustment of the printhead 26 using a temperature adjustment heater (not shown) provided on the printelement substrate 402 based on the detection results of a temperature detection unit 520 provided on the printelement substrate 402. The engine controller 204 also includes an evaporation amount acquisition unit 804 that acquires the amount of evaporation per unit time from the nozzles 500. The engine controller 204 also includes a dew-point temperature calculation unit 806 that calculates the dew-point temperature around the nozzle surface 400 of the printhead 26 based on the detection results of a temperature and humidity sensor 800 provided in the recording device 10. The temperature and humidity sensor 800 is configured to be able to detect the temperature and humidity (relative humidity) of the space between the printhead 26 and the print medium.

[0056] The engine controller 204 includes an ink discharge control unit 808 that controls the discharge of ink from the circulation path 600 and the supply of ink to the circulation path 600 associated with the discharge. The engine controller 204 also includes a density estimate calculation unit 810 that calculates an estimate of the density of ink in the circulation path 600, and an image density correction unit 812 that performs image density correction. The engine controller 204 also includes a print duty calculation unit 814 that calculates a print duty based on the calculation results of a dot number calculation unit 816 (described later). The engine controller 204 also includes a dot number calculation unit 816 that calculates the number of ink droplets to be ejected from the nozzles of the print head 26 based on print data.

[0057] = Acquisition process = In the recording device 10, an acquisition process is executed before a recording operation is performed after a job is input, or after the recording operation of the job is completed, and an adjustment process is performed using the information acquired in the acquisition process. First, the acquisition process will be described. FIG. 9 is a flowchart showing the detailed processing content of the acquisition process. The series of processes shown in the flowchart in FIG. 9 are performed by the CPU of the engine controller 204 expanding program code stored in the ROM of the engine controller 204 into the RAM of the engine controller 204 and executing it. Alternatively, some or all of the functions of the steps in FIG. 9 may be performed by hardware such as an ASIC or an electric circuit.

[0058] When the acquisition process begins, first, in S902, the printhead temperature adjustment controller 802 acquires the temperature of each printing element substrate 402. Specifically, the detection results of the temperature detection units 520 provided on each printing element substrate 402 are acquired. The acquisition timing is, for example, every 200 msec. In this case, for example, the temperature can be acquired approximately four times per A4 sheet of printing medium transported at a transport speed of 0.6765 mm / sec. Then, in S904, the printhead temperature adjustment controller 802 acquires a target temperature for temperature control of the printing element substrate 402 in the printhead 26. In this embodiment, the highest temperature among the temperatures detected by the temperature detection units 520 acquired in S902 is acquired as the target temperature. Note that the target temperature may be the average value of the detection results of the temperature detection units 520, or the lowest temperature.

[0059] Next, in S906, the dew-point temperature calculation unit 806 acquires the temperature and relative humidity detected by the temperature and humidity sensor 800 and calculates the dew-point temperature using the acquired temperature and relative humidity. Then, in S908, the evaporation amount acquisition unit 804 acquires the amount of ink evaporation per unit time from the nozzles based on the dew-point temperature acquired in S906 and the target temperature acquired in S904. A table showing the amount of ink evaporation per unit time corresponding to combinations of the temperature and dew-point temperature of the recording element substrate 402 is stored in a storage area such as ROM or RAM of the engine controller 204 (see FIG. 10). FIG. 10 is a diagram showing an example of a table showing the amount of ink evaporation per unit time corresponding to combinations of the temperature and dew-point temperature of the recording element substrate 402. Note that although FIG. 10 uses symbols V1 to V40 to represent the amount of ink evaporation per unit time, in reality, numerical values ​​corresponding to the amount of ink evaporation per unit time are input. Therefore, in S908, the evaporation amount of ink per unit time is obtained using the table in FIG.

[0060] In S910, the dot number calculation unit 816 counts the number of ink droplets ejected from all nozzles 500 of the print head 26. In S912, the print duty calculation unit 814 calculates the print duty per predetermined time and obtains the amount of ink consumed in the printing operation of the job. That is, if the acquisition process is performed before the execution of a job, in S910, the number of ink droplets ejected from the print head 26 is calculated based on the print data used in the printing operation performed in the job immediately before the job to be executed. In S912, the amount of ink consumed in the printing operation performed in the job immediately before the job to be executed is obtained. On the other hand, if the acquisition process is performed after the execution of a job, in S910, the number of ink droplets ejected from the print head 26 is calculated based on the print data used in the printing operation of the executed job. In S912, the amount of ink consumed in the printing operation of the executed job is obtained.

[0061] Then, in S914, the concentration estimate calculation unit 810 calculates an estimated concentration of the ink in the circulation path 600 based on the evaporation amount acquired in S908 and the consumption amount acquired in S912, and the process ends. The technology for acquiring an estimated concentration of the ink in the circulation path based on the evaporation amount of ink per unit time and the amount of ink consumed in a printing operation is well known, and therefore a detailed description thereof will be omitted. For example, to simplify the calculation, the calculated estimated concentration is assumed to be the state after the ink in the circulation path, which has been thickened due to evaporation, mixes with non-thickened ink and becomes uniform after a certain period of time. In this case, although it actually takes some time for the thickened ink evaporated from the nozzles to become uniform within the circulation path, the calculation is performed under strict evaporation conditions.

[0062] =Adjustment processing= Once the acquisition process is complete, an adjustment process is then executed to adjust the concentration of ink in the circulation path 600. This adjustment process is executed by the ink discharge control unit 808 of the engine controller 204. FIG. 11 is a flowchart showing the detailed processing content of the adjustment process. The series of processes shown in the flowchart of FIG. 11 are performed by the CPU of the engine controller 204 expanding program code stored in the ROM of the engine controller 204 into the RAM of the engine controller 204 and executing it. Alternatively, some or all of the functions of the steps in FIG. 11 may be executed by hardware such as an ASIC or an electric circuit.

[0063] When the adjustment process starts, first, in S1102, the ink discharge control unit 808 acquires the density estimation value N acquired in the acquisition process. Then, in S1104, the ink discharge control unit 808 acquires the estimated error Er stored in a storage area such as the ROM or RAM of the engine controller 204. The estimated error Er is an error that may occur in the ink density estimation value acquired in the acquisition process, and the value determined and acquired experimentally is stored in the storage area. This estimated error Er will be described later.

[0064] Next, in S1106, the ink discharge control unit 808 determines whether the threshold value Th is "0 (initial value)." If it is determined in S1106 that the threshold value Th is "0," the process proceeds to S1108, where the ink discharge control unit 808 determines whether the sum of the density estimation value N and the estimation error Er is equal to or greater than a limit value (greater than or equal to limit value Th_1). If it is determined in S1108 that N+Er≧Th_1 is not true, that is, that the sum of the density estimation value N and the estimation error Er is less than limit value Th_1, the adjustment process ends. If it is determined in S1108 that N+Er≧Th_1 is true, the process proceeds to S1110, where the ink discharge control unit 808 executes a first discharge control to discharge a small amount of ink from the circulation path 600. The limit value Th_1 is a threshold for determining whether or not it is necessary to discharge ink. The limit value Th_1 is set by experimentally determining the lower limit of the ink concentration at which ink discharge control must be implemented due to an increase in ink concentration in the circulation path 600, and setting this value or a value that is a specified amount smaller than this value as the limit value. The ink concentration at which ink discharge control must be implemented is, for example, the ink concentration at which at least one of the following occurs: uneven density in the printed image, the ink discharge characteristics from the nozzles deteriorate, and the reliability of the ink circulation function in the circulation path deteriorates.

[0065] Specifically, in S1110, as the first discharge control, the ink discharge control unit 808 discharges a small amount of ink from the circulation path 600 and supplies an amount of ink corresponding to the discharged amount to the circulation path 600. The small amount is, for example, 200 g. To discharge ink from the circulation path 600, for example, a preliminary discharge is performed, in which ink that does not contribute to printing is discharged from each nozzle of the print head 26 onto the cap portion of the maintenance unit 28. Alternatively, a suction discharge is performed, in which the pressure inside the cap portion is reduced by suction and ink is forcibly sucked from each nozzle of the print head 26. Note that the method of discharging ink from the circulation path 600 is not limited to this, and various known techniques, such as discharging ink from the buffer tank 604, can be applied. In this case, depending on the discharge method, the printing apparatus 10 maintains a configuration that can stably discharge ink from the circulation path 600. Also, in S1110, the ratio R0 (Er0 / N0) of the estimated density value N0 to the estimated error Er0 at this time is acquired. Thereafter, in S1112, the ink discharge control unit 808 sets the threshold value Th to the density estimation value N, and this adjustment process ends.

[0066] On the other hand, if it is determined in S1106 that the threshold value Th is not "0", the process proceeds to S1116, where the ink discharge control unit 808 determines whether or not at least one of the following two conditions is satisfied: Condition 1: N+Er≧Th1; Condition 2: R≧R0, where R is the density estimation value N at this time point t. t and the estimated error Er t Ratio to (Er t / N t )

[0067] If it is determined in S1116 that neither Condition 1 nor Condition 2 is satisfied, the process proceeds to S1118, where the ink discharge control unit 808 executes a first discharge control to discharge a small amount of ink from the circulation path 600, and then ends the adjustment process. The specific processing content of S1118 is the same as S1110. Furthermore, if it is determined in S1116 that at least one of Condition 1 and Condition 2 is satisfied, the process proceeds to S1120, where the ink discharge control unit 808 executes a second discharge control to discharge a large amount of ink from the circulation path 600.

[0068] Specifically, in S1120, as the second discharge control, the ink discharge control unit 808 discharges a large amount of ink from the circulation path 600 and supplies an amount of ink corresponding to the discharged amount to the circulation path 600. The large amount is set to, for example, 1280 g, taking into consideration the capacity of the buffer tank 604 and the operation of supplying ink to the print head 26. This amount is set, for example, to be equal to the upper limit of the amount of ink that can fill the circulation path 600 with ink, or a certain amount less than the upper limit, without performing additional processing, even if ink is supplied after being discharged from the circulation path 600.

[0069] Thereafter, in S1122, the ink discharge control unit 808 initializes the threshold value Th to "0" and then terminates the adjustment process. The density estimation value N that satisfies N+Er≧Th_1 may vary within the range of the estimation error Er. For this reason, in this embodiment, after the second discharge control in which a large amount of ink is discharged, the threshold value Th set corresponding to the above-mentioned density estimation value N is initialized, so that the density estimation value N that satisfies N+Er≧Th_1 is again set as the threshold value Th.

[0070] <Estimation error> Next, the estimated error Er obtained in S1104 will be described.

[0071] The following are examples of causes of errors in concentration estimates:

[0072] Ink flow velocity near the nozzle (nozzle circulation velocity) The position of the recording head 26 in the conveyance direction of the recording medium - Moisture absorption to recording media The estimation error has positive and negative components, and the positive component increases the density estimation value. At the position where the print head 26 is arranged, the component is basically positive, but it can also become negative depending on the position in the transport direction. The higher the nozzle circulation flow rate, the more fresh ink is supplied to the vicinity of the nozzles, which promotes evaporation from the nozzles. The higher the moisture absorption by the print medium, the more moisture in the space between the print head 26 and the print medium is taken by the print medium, which promotes evaporation of ink from the nozzles.

[0073] Figure 12 is a graph showing the relationship between the nozzle circulation flow rate and the evaporation rate when the temperature of the recording element substrate 402 is 35°C and the dew point temperature is 10°C (temperature: 25°C, relative humidity: 40%). The center tolerance value of the nozzle circulation flow rate is 45 mm / sec, and the maximum tolerance value is 60 mm / sec. From the relationship between the nozzle circulation flow rate and the evaporation rate shown in Figure 12, when the nozzle circulation flow rate is 45 mm / sec, the evaporation rate is 6.83 g / hour, and when the nozzle circulation flow rate is 60 mm / sec, the evaporation rate is 8.29 g / hour.

[0074] Experimental results have shown that moisture absorption into the recording medium causes a 2°C drop in dew point temperature under the worst-case conditions (0% print duty). When the increase in evaporation rate due to a 2°C dew point is added to the evaporation rate at a nozzle circulation flow rate of 60 mm / sec, the evaporation rate becomes 8.55 g / hour.

[0075] Then, the recording device 10 is driven under the following conditions to calculate the error in the density estimate due to the nozzle circulation flow velocity when the nozzle circulation flow velocity has a central tolerance value of 45 mm / sec and a maximum tolerance value of 60 mm / sec. Hereinafter, the case when the nozzle circulation flow velocity has a central tolerance value of 45 mm / sec will be referred to as the "center tolerance" and the case when the nozzle circulation flow velocity has a maximum tolerance value of 60 mm / sec will be referred to as the "maximum tolerance."

[0076] Conveying speed: 0.6765mm / sec Paper size (recording medium): A4 (297mm x 210mm) Recording duty: 0% Recording time: 1000 hours Ink discharge control: When evaporation rate (evaporation amount / ink amount in circulation path 600) reaches 10% Ink volume at 600 circulation paths: 2180g The timing for executing ink discharge control when the tolerance is at its center and at its maximum is the same as the timing for executing ink discharge control when the tolerance is at its maximum. In other words, when the evaporation rate reaches 10% at the maximum tolerance, ink discharge control is also executed when the tolerance is at its center. Note that because the evaporation rate at the maximum tolerance (8.55 g / hour) is greater than at the tolerance center (6.83 b / hour), the timing for executing ink discharge control is reached earlier when the tolerance is at its maximum.

[0077] When the recording device 10 is operated under these conditions, the difference in the ink evaporation rate over time between when the tolerance is maximum and when the tolerance is centered is as shown in Figure 13. Figure 13 is a graph showing the transition of the estimation error, which is the difference in the ink evaporation rate between when the tolerance is maximum and when the tolerance is centered, obtained through an experiment. As is clear from the graph in Figure 13, the upper limit of the difference in evaporation rate between the two is 3%. Therefore, based on the results of this experiment, the density value corresponding to the upper limit of the evaporation rate difference (density error) of 3% is set as the estimation error.

[0078] If the ink discharge amount, supply amount, and concentration of the supplied ink are all precisely constant during discharge control, the upper limit of the evaporation rate difference obtained in the above experiment will not exceed 3%. However, there is a risk that the above value will not be constant due to variations in product form.

[0079] For example, when ink with an evaporation rate of 2% is supplied from the main tank 606 under the same conditions as in the above experiment, the transition of the estimation error is as shown in Figure 14, and the upper limit of the difference in evaporation rate rises. Figure 14 is a graph showing the transition of the concentration error when ink with an evaporation rate of 2% is supplied during ink discharge control.

[0080] In addition, if a threshold value (limit value Th_1) is set to compare with the estimated ink concentration value when determining whether to perform ink discharge control, taking into account variations in the above values ​​due to product configuration, the threshold value will be set low, which will increase the frequency of ink discharge control and increase the amount of waste ink generated.

[0081] In this embodiment, ink discharge control is performed taking into account the error component of the density estimation value used when determining whether to perform ink discharge control. Specifically, if the density estimation value exceeds the value at the time of the first ink discharge control (discharge control in S1110), subsequent ink discharge control is performed. Then, in the subsequent ink discharge control, discharge control of inks with different ink discharge amounts is selectively performed taking into account the estimation error.

[0082] FIG. 15 is a conceptual diagram showing the change in density estimation value and estimation error due to ink discharge control. The solid line represents the change in the ink density estimation value, and the error bar represents the actual estimation error at that density estimation value. The error bar, or estimation error, increases over time. For this reason, in this embodiment, in the second and subsequent ink discharge controls (after setting the threshold value Th), a second discharge control is executed when the upper limit of the estimation error is reached.

[0083] 25 is a conceptual diagram showing the change in the density estimation value and estimation error due to ink discharge control, in which the second discharge control is executed when R≧R0. After time k when the value resulting from the density estimation value N and the estimation error Er reaches the limit value Th_1, some abnormal operation may occur and the estimation error Er may be recorded as large at time k+n (Er k+n / D)≧(Erk / N), and the second discharge control is executed. Note that "D" is the concentration estimate value at time k+n. Furthermore, abnormal operation is, for example, a temperature control temperature abnormality, an operational error of the cap part, etc.

[0084] <Action and effect> As described above, in the recording device 10 having a configuration for circulating ink during a recording operation, ink discharge control is performed before or after execution of a job in order to adjust the ink concentration in the circulation path that has increased due to the recording operation of the most recent job. Specifically, whether or not to perform ink discharge control and the amount of ink to be discharged during ink discharge control are determined using information about the ink concentration in the circulation path, such as an estimated value of the ink concentration in the circulation path and an estimation error, which is a possible error in the estimated value.

[0085] As a result, in this embodiment, the amount of ink discharged during ink discharge control can be reduced compared to known techniques that use an estimated concentration value without taking into account errors in the estimated concentration value, which reduces the amount of waste ink generated by ink discharge control and contributes to cost reduction.

[0086] (Second embodiment) Next, a recording device according to a second embodiment will be described with reference to Figures 16 to 23. In the following description, the same or corresponding components as those in the recording device described in the first embodiment will be denoted by the same reference numerals as those used in the first embodiment, and detailed description thereof will be omitted.

[0087] Ink discharge control in response to an increase in ink concentration within the circulation path 600 is performed based on thresholds set in response to the occurrence of density unevenness in the printed image, a deterioration in ink ejection characteristics, and a decrease in the reliability of the circulation function. However, the inventors of the present application have discovered that density unevenness occurs more due to a relatively small increase in ink concentration than due to a decrease in ink ejection characteristics or a decrease in the reliability of the circulation function.

[0088] The visibility of density unevenness can be reduced by performing image density correction, which controls the number of ink droplets (number of dots) applied to the recording medium in response to variations in the ejection amount of the recording head 26. Note that if the ink density fluctuates, and if the correction information acquired during image density correction in the initial adjustment performed when the device is installed is continued to be used as is, the correction will no longer be appropriate, and density unevenness may occur.

[0089] The inventors of this application have found that density unevenness may become visible when the ink concentration increases by 2.5% to 3.0%. Meanwhile, the increase in ink concentration did not result in any decrease in the ink ejection characteristics or the reliability of the circulation function. Therefore, by performing image density correction, it is possible to set a threshold value that corresponds to the relatively high concentration at which ink discharge control is required, the deterioration of ink ejection characteristics, and the deterioration of the circulation function reliability. This makes it possible to reduce the number of times ink discharge control is performed, thereby reducing the amount of waste ink generated.

[0090] Therefore, in the second embodiment, a determination process is executed in parallel with the adjustment process to determine whether or not to execute image density correction (hereinafter referred to as "image density correction based on ink density"), which corrects density unevenness that occurs based on changes in ink density. That is, in the second embodiment, before or after execution of a job, processing for ink discharge control and processing for image density correction are executed, and based on the results of this processing, ink discharge control and image density correction are executed.

[0091] In this embodiment, a determination process is performed to determine whether or not image density correction is required when print data is generated, in parallel with an adjustment process that adjusts the density of ink in the circulation path 600 using the density estimated value obtained in the acquisition process. That is, in this embodiment, the determination process is performed in parallel with the adjustment process after the acquisition process. In the following explanation, since the acquisition process and the adjustment process are the same as those in the first embodiment, detailed explanations of those processes will be omitted, and only the determination process will be explained in detail.

[0092] <Decision process> Fig. 16 is a flowchart showing detailed processing contents of the decision processing for determining whether or not to execute image density correction based on ink density. This decision processing is executed by the image density correction unit 812 of the engine controller 204. The series of processing shown in the flowchart of Fig. 16 is performed by the CPU of the engine controller 204 expanding program code stored in the ROM of the engine controller 204 into the RAM of the engine controller 204 and executing it. Alternatively, some or all of the functions of the steps in Fig. 16 may be executed by hardware such as an ASIC or an electric circuit.

[0093] When the determination process starts, first, in S1602, the image density correction unit 812 acquires the density estimate value Nc when image density correction was most recently performed. As will be described later, the density estimate value Nc when image density correction was most recently performed is stored in a storage area such as the ROM or RAM of the engine controller 204. Note that when the circulation path 600 is first filled with ink or when the circulation path 600 is refilled with ink, for example, the density of the ink stored in the main tank 606 is acquired. Note that the ink density in the main tank 606 is assumed to be held in a storage area.

[0094] Next, in S1604, the image density correction unit 812 acquires the ink density estimation value N acquired in the most recent acquisition process. Then, in S1606, the image density correction unit 812 It is determined whether the difference between the concentration estimated value Nc obtained in S1602 and the concentration estimated value N obtained in S1604 is 2% or more (that is, |N-Nc|≧2).

[0095] The threshold value of 2% was obtained based on the following experiment conducted by the inventors. The inventors performed image density correction at a resolution of 16 pixels (0.677 m) at 600 dpi in the extension direction of the nozzle array, and conducted a sensory evaluation to determine the level of color difference required at this frequency before it was visually recognized as density unevenness. As a result, a ΔE2000 of 1 or greater was found to be the most visually acceptable. Therefore, the standard (proximity ΔE) was set to within 0.8, and experimental results showed that the ink density change amount that satisfied this standard was 2%. Therefore, the threshold value used in S1606 is a value obtained by conducting the above-mentioned experiment in accordance with various conditions. In other words, the threshold value is set appropriately.

[0096] If it is determined in S1606 that |N-Nc| is 2, the process proceeds to S1608, where the image density correction unit 812 determines to perform image density correction. Thereafter, the process proceeds to S1610, where the image density correction unit 812 updates the density estimated value Nc, which is stored in the storage area when image density correction is performed, to the density correction value N acquired in S1604, and ends this determination process. If it is determined in S1606 that |N-Nc| is not 2, the process proceeds to S1612, where the image density correction unit 812 determines not to perform image density correction, and ends this determination process. After the determination process is completed, the image density correction unit 812 performs image density correction when generating print data to be used in the printing operation of the job after this determination process, depending on whether or not image density correction is required.

[0097] <Image density correction> Next, image density correction based on ink density will be described. In the recording apparatus 10, image density correction based on ink density is performed by head shading (HS) processing and color shading (CS) processing. Figure 17 shows the functional configuration of the image processing unit 212 that executes image density correction, where (a) shows the configuration corresponding to HS processing, and (b) shows the configuration corresponding to HS processing and CS processing. Each component shown in Figure 17 is realized by the CPU, ROM, and RAM in the main controller 202.

[0098] =HS Processing= The HS processing is performed by the image processing unit 212. First, the functional configuration of the image processing unit 212 that performs the HS processing will be described with reference to Fig. 17(a).

[0099] The image processing unit 212 includes an input color conversion processing unit 1702 that converts image data input from the buffer 218 into image data that corresponds to the color gamut of the recording device 10. In this embodiment, the input image data is data that indicates color coordinates (R, G, B) in a color space coordinate system such as sRGB, which is the representation color of a monitor. The input color conversion processing unit 1702 converts each of the 8-bit input image data R, G, B into image data (R', G', B') that corresponds to the color gamut of the recording device 10. This conversion can be performed using known techniques such as matrix calculation processing or processing using a three-dimensional lookup table (LUT). In this embodiment, a three-dimensional LUT is used, and interpolation calculations are used in combination to perform the conversion.

[0100] The image processing unit 212 also includes an ink color conversion processing unit 1704 that performs conversion processing on the image data converted by the input color conversion processing unit 1702 to convert the image data into color signals corresponding to the multiple inks used in the printing device 10. In this embodiment, since the printing device 10 uses K ink, C ink, M ink, and Y ink, the image data as RGB signals is converted into image data consisting of 8-bit color signals for each of K, C, M, and Y. For example, this color conversion is performed using a three-dimensional LUT in combination with interpolation calculations, just like the input color conversion processing unit 1702. Note that other known conversion methods, such as matrix calculation processing, can also be used.

[0101] Furthermore, the image processing unit 212 includes an HS processing unit 1706 that performs corrections according to the ink ejection characteristics of the nozzles 500 that make up the recording head 26 on the image data of the ink color signals that have been ink color converted by the ink color conversion processing unit 1704. The HS processing performed by the HS processing unit 1706 will be described in detail later.

[0102] Furthermore, the image processing unit 212 includes a TRC processing unit 1708 that adjusts the number of dots to be printed for each ink color for image data made up of 8-bit ink color signals that have been HS processed by the HS processing unit 1706. More specifically, the number of dots to be printed on the recording medium is adjusted by correcting the image data so that the relationship between the number of dots printed on the recording medium and the brightness achieved by that number of dots is linear.

[0103] The image processing unit 212 also includes a quantization processing unit 1710 that performs quantization processing on the 8-bit, 256-value ink color image data processed by the TRC processing unit 1708 to obtain 1-bit binary data for print data. Various known techniques, such as dithering and error diffusion, can be used as the quantization processing method. After the quantization processing, the process from the acquisition of attribute information (S308) onwards, as described in the image processing shown in the flowchart of FIG. 3, is performed to generate print data, which is then stored in the buffer 218.

[0104] Next, the HS processing based on ink density executed by the HS processing unit 1706 will be described. FIG. 18 is a flowchart showing the detailed processing contents of the HS processing. FIG. 19 is a diagram showing an example of a measurement image for acquiring density characteristics of each nozzle 500 in the print head 26. FIG. 20 is a diagram showing measurement curves, where (a) is a measurement curve acquired from a scanned image and (b) is a measurement curve after correction. The HS processing of FIG. 18 is executed by the HS processing unit 1706 of the image processing unit 212 in the main controller 202. The series of processes shown in the flowchart of FIG. 18 are performed by the CPU of the main controller 202 by loading program code stored in the ROM of the main controller 202 into the RAM of the main controller 202 and executing it. Alternatively, some or all of the functions of the steps in FIG. 18 may be executed by hardware such as an ASIC or electrical circuit.

[0105] When the HS processing starts, first, in S1802, the HS processing unit 1706 acquires, as an input image, image data of the ink color signals output from the ink color conversion processing unit 1704. Next, in S1804, the HS processing unit 1706 acquires a measurement curve at a position corresponding to the pixel of interest.

[0106] Here, the measurement curve will be described. The measurement curve is created by recording a measurement image on a recording medium and reading the recorded measurement image. A measurement image 1900 is composed of nine patches with different gradations, from patch 1902 to patch 1918, as shown in FIG. 19, for example. Each patch is recorded using only a single ink color. In this embodiment, it is assumed that the patches are recorded using only K ink.

[0107] In order to record the measurement image 1900 in a single ink color, the image data of the measurement image 1900 is input to the image processing unit 212 and then input to the TRC processing unit 1708. This allows the image data of the measurement image 1900 to be directly input to the TRC processing unit 1708 without passing through the input color conversion processing unit 1702, ink color conversion processing unit 1704, and HS processing unit 1706 (see the dashed arrow in FIG. 17(a)). Thereafter, the measurement image 1900 is recorded on a recording medium based on the recording data of the measurement image 1900 created through processing in the quantization processing unit 1710.

[0108] The measurement image 1900 recorded on the recording medium is scanned by a scanner (not shown) provided in the recording device 10, resulting in a scanned image. Known technologies can be used for the scanner that scans the measurement image 1900 recorded on the recording medium, and a detailed description of its placement will be omitted. The scanned image is acquired in three channels (RGB), and then converted into a single-channel scanned image using a color conversion table prepared in advance to match the color characteristics of the scanner. For example, this color conversion table converts Y in the CIEXYZ color space into a linear 16-bit value.

[0109] The color space of the scanned image may be any, such as CIELab* L* or density. Furthermore, if the measurement image is recorded using color inks such as C, M, and Y, values ​​corresponding to saturation may be used instead of values ​​corresponding to brightness. For example, values ​​of the R, G, and B channels may be used as values ​​corresponding to the complementary colors of C, M, and Y, respectively. Furthermore, a scanned image of the measurement image 1900 for obtaining the measurement curve may be obtained, for example, before executing this HS processing. In this case, in S1804, the scanned image stored in the memory area is obtained.

[0110] A measurement curve is obtained by interpolation from the signal values ​​of the scanned image thus obtained (see FIG. 20(a)). In the measurement curve of FIG. 20(a), the horizontal axis represents the input signal values ​​of patches 1902 to 1918 of the measurement image 1900, and the vertical axis represents the signal values ​​of the scanned image. Point P in FIG. 20(a) is the upper limit of the input signal value of each patch, which is 255 in this embodiment because the input signal value is 8 bits.

[0111] The measurement curve obtained by interpolation from the scanned image signal values ​​of patches 1902 to 1918 is measurement curve 2004. In this embodiment, piecewise linear interpolation is used as the interpolation method. Any interpolation method can be used, and various known methods such as a method using a spline curve can be used. The measurement curve 2004 represents the density characteristics of the nozzle corresponding to pixel position x, and is obtained for each nozzle 500 used to record the measurement image 1900. A different measurement curve is obtained for each ejection characteristic of the nozzle 500; for example, for a nozzle 500 with a small ejection volume, the measurement curve 2004 shifts upward (toward brighter).

[0112] Returning to FIG. 18 , once the measurement curve has been acquired, in S1806, the HS processing unit 1706 corrects errors in the measurement values ​​in the acquired measurement curve to acquire a corrected measurement curve 2014 (see FIG. 21( b)). FIG. 21 shows the measurement values ​​in the region corresponding to patch 1918 in the scanned image, where (a) is the measurement value when the recording medium is not distorted, and (b) is the measurement value when the recording medium is distorted. In each diagram in FIG. 21 , the horizontal axis represents the nozzle number, and the vertical axis represents the signal value of the scanned image. The nozzle number represents the number assigned to each nozzle provided in the print head 26. If the recording medium is not distorted and the print head 26 and the scanner are installed sufficiently close to each other, the measurement result shown in FIG. 21( a) will be obtained. If the recording medium is distorted and the print head 26 and the scanner are installed far apart, or if the scanning is performed after printing via a drying process, the measurement result shown in FIG. 21( b) will be obtained. Comparing the two measurement results, it can be seen that the measurement results in Figure 21(b) did not correctly acquire measurements near the edges due to distortion of the recording medium. In the measurement results in Figure 21(b), the waveform intervals are narrower near the edges, which is because the edges of the recording medium are raised and tilted relative to the scanner. The correction process performed on the measurement curve is a process in which the measurement values ​​of normal areas other than the edges are used to correct the measurement values ​​of abnormal areas at the edges. Note that publicly known techniques can be used for this type of correction process on the measurement curve.

[0113] Then, in S1808, the HS processing unit 1706 acquires a target characteristic 2006. The target characteristic 2006 is a target characteristic that is predetermined in accordance with the measurement curve of each nozzle 500. In this embodiment, as shown in FIG. 20A, a measurement value that is linear with respect to gradation is set as the target characteristic. Then, in S1810, the HS processing unit 1706 acquires a corrected input value. Specifically, it acquires a target value 2022, which is a value corresponding to the target characteristic 2006 that corresponds to the input value 2020 acquired in S1802 (see FIG. 20B). Then, it acquires a gradation value corresponding to the target value 2022 from the corrected measurement curve 2014, and acquires the acquired value as the corrected input value 2024. Note that in subsequent jobs, the corrected measurement curve 2014 acquired in S1806 will be used in the HS processing when creating print data, for example, until it is determined again in the determination processing to perform image density correction.

[0114] =CS Processing= The CS processing is performed by the image processing unit 212. First, the functional configuration of the image processing unit 212 that performs the HS processing and CS processing will be described with reference to Fig. 17(b).

[0115] In addition to the various components used in the HS process, the image processing unit 212 also includes an MCS processing unit 1712 that executes CS processing to perform corrections on image data of RGB signals according to the ejection characteristics of the nozzles in the print head 26. The measurement image used in the CS process is a recording of multiple patches in which the input signal values ​​R, G, and B are changed independently. For example, five gradations of 0, 64, 128, 192, and 255 are used for each of R, G, and B, and the five 3 = 125 different multi-color patches are recorded. Note that the combination of the above patches is not limited and can be any combination.

[0116] Image data of the measurement image used in CS processing is input to the image processing unit 212, and then input to the ink color conversion processing unit 1704. This allows the image data of the measurement image to be directly input to the TRC processing unit 1708 without passing through the input color conversion processing unit 1702 and the MCS processing unit 1712 (see the dashed-dotted arrow in Figure 17(b)). The measurement image is then recorded on a recording medium based on the recording data of the measurement image created through HS processing and the like. The recorded measurement image is scanned by a scanner to obtain a scanned image. The scanned image is not converted to one channel, but is retained as three RGB channels.

[0117] Next, the specific processing contents of the CS processing based on ink density will be described. FIG. 22 is a flowchart showing the detailed processing contents of the CS processing. The main differences between CH processing and HS processing are that the measurement image is multi-color and the measurement values ​​are in three RGB channels. The CS processing of FIG. 22 is executed by the MCS processing unit 1712 of the image processing unit 212 in the main controller 202. The series of processes shown in the flowchart of FIG. 22 are performed by the CPU of the main controller 202 expanding program code stored in the ROM of the main controller 202 into the RAM of the main controller 202 and executing it. Alternatively, some or all of the functions of the steps in FIG. 22 may be executed by hardware such as an ASIC or electrical circuit.

[0118] When the CS process starts, first, in S2202, the MCS processing unit 1712 acquires input values ​​using image data output from the input color conversion processing unit 1702 and corresponding to the color gamut of the recording device 10 as an input image. Next, in S2204, the MCS processing unit 1712 acquires measured RGB values ​​of the nozzle position corresponding to the pixel of interest from the scanned image obtained by the scanner. In this embodiment, 125 measured RGB values ​​are acquired as the measurement values ​​of the 125 patches. Note that the scanned image may be acquired, for example, before the CS process is executed. In this case, in S2204, the scanned image stored in the memory area is acquired.

[0119] Thereafter, in S2206, the MCS processing unit 1712 corrects the measured RGB values. This correction can be performed using known techniques. Note that the difference from HS processing is that a representative value of the normal region is determined for each of the three RGB channels and applied to the abnormal region. Then, in S2208, target RGB values ​​are acquired. For example, the target RGB values ​​are acquired by referencing an LUT (not shown) that holds the correspondence between the input RGB and the target RGB of the scanned image. Thereafter, in S2210, the MCS processing unit 1712 acquires the corrected input values.

[0120] Here, the method for obtaining the corrected input values ​​in S2210 will be described. FIG. 23 is a diagram showing a three-dimensional space with the RGB values ​​of the scanned image as its axes. Point 2302 in FIG. 23 represents the target RGB value obtained in S2208. Points 2304, 2306, 2308, and 2310 in FIG. 23 represent the corrected measured RGB values ​​of four points selected from the 125 corrected measured RGB values ​​obtained in S2206 to form the smallest tetrahedron containing point 2302. The distances between point 2302 and points 2304, 2306, 2308, and 2310 are calculated, and the corrected input values ​​are obtained by interpolating the input RGB values ​​of the four points according to the distance ratio. Note that in subsequent jobs, the correction information obtained in S2206 is used in the CS process when creating print data, for example, until the execution of image density correction is again determined in the determination process.

[0121] <Action and effect> As described above, the recording device 10 of the second embodiment executes ink discharge control similar to that of the first embodiment, and also executes image density correction based on the ink density when generating print data, based on the estimated density value of the ink in the circulation path 600. As a result, in this embodiment, in addition to the effects of the first embodiment, it is possible to increase the threshold value for determining whether or not to execute ink discharge control while suppressing the occurrence of density unevenness, thereby reducing the number of times ink discharge control is executed and reducing the amount of waste ink generated.

[0122] That is, by performing image density correction based on ink density, it becomes possible to perform ink discharge control at a timing when the estimated ink density value is relatively high, thereby suppressing an increase in the amount of waste ink caused by ink discharge control. Note that, for example, the first discharge control is performed so that the estimated ink density value in the circulation path 600 after ink discharge control changes by less than 2% from the estimated density value at the time of the previous image density correction. As a result, after the first discharge control, it becomes possible to perform printing without density unevenness in the printed image, even without performing image density correction.

[0123] (Other embodiments) The above embodiment may be modified as shown in the following (1) to (7).

[0124] (1) In the first embodiment, the upper limit of the estimated error when the print duty is 0% is retained as the estimated error, but this is not limited to this. The estimated error decreases as the print duty increases. FIG. 24 is a diagram showing the transition of the estimated error when the print duty is changed to 2% among the conditions of the experiment that obtained the experimental results of FIG. 13. In FIG. 24, the upper limit of the estimated error is approximately 2%. Therefore, the upper limit of the estimated error corresponding to the print duty may be retained. In this case, the adjustment process uses the estimated error corresponding to the print duty in the printing operation of the job. Furthermore, instead of the upper limit of the estimated error, for example, the median between the upper limit and the lower limit of the estimated error may be used, or a predetermined value such as a value between the median and the upper limit may be used.

[0125] (2) In the first embodiment, two types of discharge control, the first discharge control or the second discharge control, are executed based on the concentration estimate value and the estimation error. However, this is not limited to this. The second discharge process may be executed when the number of consecutive executions of the first discharge process reaches a predetermined number, and the first discharge control may be executed if the number of executions is less than the predetermined number. In this case, when the second discharge control is executed, the count value of the number of executions of the first discharge control is initialized.

[0126] Specifically, in a configuration in which emission control is performed based on the concentration estimate value and the estimation error, after obtaining the concentration estimate value N and the estimation error Er, it is determined whether the condition N+Er≧Th_1 is met, and if not, emission control is not performed. Furthermore, if the above condition is met, the count value of the number of times the first emission process has been performed is referenced. If the count value is less than a predetermined value, the first emission control is performed, and "1" is added to the count value. On the other hand, if the count value is equal to or greater than the predetermined value, the second emission control is performed, and the count value is initialized to "0."

[0127] Alternatively, in a configuration in which discharge control is performed based only on the concentration estimated value, it is determined whether or not the condition that the concentration estimated value N is equal to or greater than the limit value Th_1 is met, and if not, discharge control is not performed. Also, if the above condition is met, the count value of the number of times the first discharge process has been performed is referenced. Then, if the count value is less than a predetermined value, the first discharge control is performed and "1" is added to the count value. On the other hand, if the count value is equal to or greater than the predetermined value, the second discharge control is performed and the count value is initialized to "0."

[0128] (3) In the first embodiment, the necessity for ink discharge control and the amount of ink discharged during ink discharge control are determined based on the density estimate value and the estimation error. However, this is not limited to this. For example, image density correction such as HS processing and CS processing may be performed after discharge control with a large ink discharge amount (second discharge control). Furthermore, although not specifically described in the above embodiment, the recording device 10 may also perform image density correction based on the nozzle ejection characteristics. In other words, in this case, in the second embodiment, if image density correction based on ink density has not been performed even once, image density correction based on the nozzle ejection characteristics is performed, and after image density correction has been performed, image density correction based on ink density is performed. Note that, as described in the above embodiment, image density correction based on ink density acquires correction information using information obtained by printing and scanning a measurement image, and therefore also addresses density unevenness based on the nozzle ejection characteristics.

[0129] (4) Although not specifically mentioned in the second embodiment, the recording device 10 may store multiple sets of correction information for the HS process and the CS process in a storage area according to ink density. In this case, when the execution of image density correction based on ink density is determined in the determination process, correction information associated with an ink density that approximates the density estimate is acquired, and the HS process and the CS process are executed using this correction information. Furthermore, in subsequent jobs, print data is generated using the acquired correction information until the execution of image correction processing based on ink density is again determined in the determination process.

[0130] (5) In the second embodiment, the adjustment process and the determination process are executed in parallel after the acquisition process, but this is not limited to this. The determination process may be executed after the acquisition process and the adjustment process. Also, although not specifically mentioned in the second embodiment, even if the execution of image density correction is determined in the determination process, if ink discharge control is executed in the adjustment process, the image density correction may not be executed. Therefore, in a configuration in which the determination process is executed after the adjustment process, if ink discharge control is executed in the adjustment process, the determination process may not be executed.

[0131] (6) Although not specifically mentioned in the first embodiment, the threshold value Th is also initialized and set to "0" at a predetermined timing, such as when the circulation path 600 is refilled with ink. In the above embodiment, one of two types of discharge control, namely, the first discharge control and the second discharge control, which discharges a larger amount of ink than the first discharge control, is selectively executed, but this is not limited to this. It is also possible to selectively execute a specific discharge control from three or more types of discharge control with different ink discharge amounts by setting multiple limit values, for example.

[0132] (7) The above embodiment and the various forms shown in (1) and (6) above may be combined as appropriate.

[0133] The disclosure of the above embodiment includes the following configurations and methods. (Configuration 1) a printing element substrate having nozzles capable of ejecting a printing material; a circulation path including the recording element substrate, which circulates the recording agent, supplies the recording agent to the recording element substrate, and recovers the recording agent that has not been ejected from the recording element substrate; an acquisition unit for acquiring information about the concentration of the printing agent circulating through the circulation path; a discharge control unit that controls the discharge of ink by discharging the recording material from the circulation path in accordance with the information about the concentration and supplying the amount of recording material corresponding to the discharge amount to the circulation path, The recording device is characterized in that, when executing the discharge control, the discharge control means selectively executes one of a first discharge control in which the ink discharge amount is a first discharge amount and a second discharge control in which the discharge amount is a second discharge amount that is greater than the first discharge amount. (Configuration 2) The information about the concentration is a concentration estimate value that is an estimate of the concentration of the recording material; and an estimation error, which is an error that may occur in the density estimation value. (Configuration 3) 3. The recording apparatus according to configuration 2, wherein the estimated error differs depending on the recording duty. (Configuration 4) The recording device described in configuration 2 or 3 is characterized in that the discharge control means executes first control to perform the first discharge control when the sum of the density estimation value and the estimation error is equal to or greater than a limit value of ink density at which at least one of the following occurs: density unevenness in the recorded image, the ejection characteristics of the recording agent from the nozzles deteriorate, and the reliability of the circulation function of the recording agent in the circulation path deteriorates. (Configuration 5) The recording device described in any one of configurations 3 or 4 is characterized in that the discharge control means performs the second discharge control when at least one of a first condition that the sum of the concentration estimated value and the estimated error is greater than or equal to the limit value and a second condition that the ratio of the concentration estimated value to the estimated error is greater than or equal to the ratio of the concentration estimated value to the estimated error when the first discharge control was performed in the most recent first control is satisfied, and performs the second control that performs the first discharge control when neither the first condition nor the second condition is satisfied. (Configuration 6) The discharge control means Execute the first control when the threshold is an initial value, and execute the second control when the threshold is set to a value different from the initial value; In the first control, when the first discharge control is performed, the threshold value is set to the concentration estimation value; 6. The recording apparatus according to configuration 5, wherein, in the second control, when the second discharge control is performed, the threshold value is set to an initial value. (Configuration 7) The discharge control means When the number of consecutive executions of the first discharge control is less than a predetermined number of times, the first discharge control is executed; 4. The recording apparatus according to any one of configurations 1 to 3, wherein when the number of consecutive executions of the first discharge control has reached the predetermined number, the recording apparatus executes the second discharge control. (Configuration 8) The image processing device further includes an image processing unit capable of executing image density correction based on ink density in image processing when generating print data for printing on a print medium, The recording device according to any one of configurations 2 to 5, wherein the image processing means executes the image density correction as the process when a difference between the density estimation value acquired by the acquisition means and the density estimation value when the most recent process related to the image density correction is executed is equal to or greater than a threshold value. (Configuration 9) The image processing device further includes an image processing unit capable of executing image density correction based on ink density in image processing when generating print data for printing on a print medium, The recording device according to any one of configurations 2 to 5, wherein the image processing means acquires correction information to be used for the image density correction as the processing when a difference between the density estimation value acquired by the acquisition means and the density estimation value when the most recent processing related to image density correction is executed is equal to or greater than a threshold value. (Configuration 10) 10. The recording apparatus according to configuration 8 or 9, wherein the threshold value corresponds to a change in density of the recording material that causes density unevenness in the recorded image. (Configuration 11) The recording device according to any one of configurations 1 to 10, wherein the discharge control means discharges the recording agent from the circulation path by preliminary discharge, which discharges recording agent that does not contribute to recording from the nozzles of the recording element substrate, or by suction discharge, which forcibly sucks and discharges the recording agent from the nozzles. (Configuration 12) 12. The recording device according to any one of configurations 1 to 11, wherein the recording material includes ink containing a pigment and a treatment liquid that performs a predetermined treatment on the ink ejected onto the recording medium. (Configuration 13) A control method for a recording device capable of performing ink discharge control, which discharges recording material from a circulation path including a recording element substrate having nozzles capable of ejecting recording material in accordance with a concentration of the recording material circulating through the circulation path, and supplies an amount of recording material to the circulation path in accordance with the discharge amount, acquiring information about the concentration of the printing agent circulating through the circulation path; A control method characterized by selectively executing one of a first discharge control in which the ink discharge amount is a first discharge amount and a second discharge control in which the discharge amount is a second discharge amount greater than the first discharge amount, depending on the information regarding the concentration. [Explanation of symbols]

[0134] 10 Recording Device 204 Engine Controller 402 Printing element substrate 500 nozzles 600 Circulation Route

Claims

1. a printing element substrate having nozzles capable of ejecting a printing material; a circulation path including the recording element substrate, which circulates the recording agent, supplies the recording agent to the recording element substrate, and recovers the recording agent that has not been ejected from the recording element substrate; an acquisition unit for acquiring information about the concentration of the printing agent circulating through the circulation path; a discharge control unit that controls the discharge of the recording material by discharging the recording material from the circulation path in accordance with the information about the concentration and supplying the amount of recording material corresponding to the discharge amount to the circulation path; an image processing unit capable of executing image density correction based on the density of the recording material in image processing when generating recording data for recording on a recording medium; the discharge control means, when executing the discharge control, selectively executes one of a first discharge control in which the discharge amount of the recording agent is a first discharge amount and a second discharge control in which the discharge amount is a second discharge amount greater than the first discharge amount; the information about the concentration includes a concentration estimate value that is an estimate of the concentration of the recording material, and an estimation error that is an error that may occur in the concentration estimate value; The image processing means performs the image density correction as the processing when the difference between the density estimated value acquired by the acquisition means and the density estimated value when the most recent processing related to the image density correction is performed is greater than or equal to a threshold value.

2. 2. The recording apparatus according to claim 1, wherein the estimated error varies depending on the recording duty.

3. The recording device described in claim 1, characterized in that when the predetermined threshold is an initial value, the discharge control means executes first control to perform the first discharge control when the sum of the concentration estimation value and the estimation error is equal to or greater than a limit value of the recording material concentration at which at least one of the following occurs: the occurrence of density unevenness in the recorded image, a deterioration in the ejection characteristics of the recording material from the nozzle, and a deterioration in the reliability of the circulation function of the recording material in the circulation path.

4. The recording device described in claim 3, characterized in that when the specified threshold is a value different from the initial value, the discharge control means performs the second discharge control when at least one of the following conditions is met: a first condition that the sum of the concentration estimated value and the estimated error is greater than or equal to the limit value; and a second condition that the ratio of the concentration estimated value to the estimated error is greater than or equal to the ratio of the concentration estimated value to the estimated error when the first discharge control was performed in the most recent first control, and performs the second control that performs the first discharge control when neither the first condition nor the second condition is met.

5. The discharge control means In the first control, when the first discharge control is performed, the predetermined threshold value is set to the concentration estimation value; 5. The recording apparatus according to claim 4, wherein, in the second control, when the second discharge control is performed, the predetermined threshold value is set to the initial value.

6. The discharge control means When the number of consecutive executions of the first discharge control is less than a predetermined number of times, the first discharge control is executed; 2. The recording apparatus according to claim 1, wherein when the number of consecutive executions of the first discharge control has reached the predetermined number, the second discharge control is executed.

7. 7. The printing apparatus according to claim 1, wherein the threshold value corresponds to a change in density of the printing material that causes density unevenness in the printed image.

8. The recording device according to any one of claims 1 to 6, characterized in that the discharge control means discharges the recording agent from the circulation path by preliminary discharge, which discharges recording agent that does not contribute to recording from the nozzles of the recording element substrate, or by suction discharge, which forcibly sucks and discharges the recording agent from the nozzles.

9. 7. The recording apparatus according to claim 1, wherein the recording material includes ink containing a pigment and a processing liquid that performs a predetermined process on the ink ejected onto the recording medium.

10. a printing element substrate having nozzles capable of ejecting a printing material; a circulation path including the recording element substrate, which circulates the recording agent, supplies the recording agent to the recording element substrate, and recovers the recording agent that has not been ejected from the recording element substrate; an acquisition unit for acquiring information about the concentration of the printing agent circulating through the circulation path; a discharge control unit that controls the discharge of the recording material by discharging the recording material from the circulation path in accordance with the information about the concentration and supplying the amount of recording material corresponding to the discharge amount to the circulation path; an image processing unit capable of executing image density correction based on the density of the recording material in image processing when generating recording data for recording on a recording medium; the discharge control means, when executing the discharge control, selectively executes one of a first discharge control in which the discharge amount of the recording agent is a first discharge amount and a second discharge control in which the discharge amount is a second discharge amount greater than the first discharge amount; the information about the concentration includes a concentration estimate value that is an estimate of the concentration of the recording material, and an estimation error that is an error that may occur in the concentration estimate value; The image processing means acquires correction information to be used for the image density correction as the processing when the difference between the density estimated value acquired by the acquisition means and the density estimated value when the most recent processing related to the image density correction is performed is greater than or equal to a threshold value.

11. A control method for a recording device capable of performing discharge control of a recording material, the control method comprising: discharging a recording material from a circulation path including a recording element substrate having nozzles capable of ejecting the recording material in accordance with a concentration of the recording material circulating through the circulation path; and supplying the amount of recording material to the circulation path in accordance with the discharge amount, the method comprising: an acquisition step of acquiring information about the concentration of the printing material circulating through the circulation path; a discharge control step of selectively executing one of a first discharge control step of discharging the printing material from the circulation path by a first discharge amount and supplying the printing material to the circulation path in an amount corresponding to the first discharge amount, and a second discharge control step of discharging the printing material from the circulation path by a second discharge amount greater than the first discharge amount and supplying the printing material to the circulation path in an amount corresponding to the second discharge amount, according to the information on the concentration; an image processing step of performing image density correction based on the density of the recording material in image processing when generating recording data to be recorded on a recording medium, the information about the concentration includes a concentration estimate value that is an estimate of the concentration of the recording material, and an estimation error that is an error that may occur in the concentration estimate value; A control method characterized in that, in the image processing step, if the difference between the density estimated value acquired in the acquisition step and the density estimated value when the most recent processing related to the image density correction was performed is greater than or equal to a threshold value, the image density correction is performed as the processing.

Images