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] Conventionally, there is known an inkjet recording device that circulates ink in an ink circulation path including a recording head, thereby suppressing thickening of the ink in the nozzles and suppressing deterioration of the ink ejection characteristics from the nozzles. Note that in such a recording device, the ink in the circulation path thickens, that is, the ink concentration increases, due to evaporation of the ink from the nozzles during circulation.

[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 discharging a portion of the thickened ink from the circulation path based on the concentration. Note that in 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] JP 2017-121788 A [Patent Document 2] JP 2018-008513 A 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 or not to discharge ink is an estimated value, which may result in an error between the ink concentration used to determine whether or not to discharge ink and the actual ink concentration in the circulation path, which may prevent ink from being discharged appropriately and may increase 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 the discharge of ink to adjust the ink concentration in the circulation path. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, one embodiment of a recording device according to the present invention comprises a recording element substrate having nozzles capable of ejecting a recording agent, a circulation path including the recording element substrate and capable of circulating the recording agent to supply the recording agent to the recording element substrate and recovering the recording agent not ejected from the recording element substrate, an acquisition means for acquiring information regarding the concentration of the recording agent circulating through the circulation path, and a discharge control means for executing ink discharge control in accordance with the information regarding the concentration, which discharges the recording agent from the circulation path and supplies an amount of recording agent corresponding to the discharge amount to the circulation path, and is characterized in that, when executing the discharge control, the discharge control means selectively executes one of a first discharge control in which the discharge amount of ink 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. Effect of the Invention

[0008] According to the present invention, it is possible to suppress an increase in waste ink caused by discharging ink to adjust the ink concentration in the circulation path. [Brief description of the drawings]

[0009] [Figure 1] Schematic diagram of the recording device [Diagram 2]A block diagram showing the configuration of a control system of a printing apparatus. [Diagram 3] 1 is a flowchart showing detailed image processing. [Figure 4] A perspective view of a nozzle surface of a recording head [Diagram 5] FIG. 1 is a diagram illustrating the configuration of a recording element substrate. [Figure 6] FIG. 1 is a schematic diagram showing the circulation path of ink 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] 11 is a flowchart showing detailed processing contents of the acquisition process. [Figure 10] Table for obtaining the amount of ink evaporation [Figure 11] 11 is a flowchart showing the detailed processing contents of the adjustment processing [Figure 12] Graph showing the relationship between nozzle circulation speed and evaporation rate [Figure 13] Graph showing the transition of the estimated error at 0% recording duty [Figure 14] A graph showing the change in estimation error when ink with an evaporation rate of 2% is supplied [Figure 15] FIG. 13 shows changes in density estimation value and estimation error due to ink discharge control. [Figure 16] 11 is a flowchart showing the detailed process of the decision process. [Figure 17] A block diagram showing the functional configuration of an 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 [Diagram 23]A diagram showing a three-dimensional space with the RGB values ​​of a scanned image as its axis. [Figure 24] Graph showing the transition of the estimated error at a recording duty of 2% [Diagram 25] FIG. 13 shows changes in density estimation value and estimation error due to ink discharge control. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 embodiment does not limit the present invention, and not all of the combinations of features described in the present embodiment are essential to the solution of the present invention. Also, the positions and shapes of the components described in the embodiment are merely examples, and are not intended to limit the present invention to only those.

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

[0012] <Recording device configuration> FIG. 1 is a schematic diagram of a recording device. The recording device 10 in FIG. 1 includes a feed module 12 that feeds a cut sheet-like recording medium, and a recording module 14 that records on the recording medium fed by the feed module 12. The recording device 10 also includes a first fixing module 16 that promotes the fixing of the recording agent to the recording medium by non-contact heating after recording, and a second fixing module 18 that promotes the fixing of the recording agent to the recording medium by contact heating. The recording device 10 also includes a cooling / reversing module 20 that cools the recording medium and performs a reversing operation when recording on both sides, and a loading module 22 to which the product is discharged and on which the discharged product is loaded. The recording device 10 also includes a control unit 200 (described later) 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 fixing it by air suction. The recording module 14 also includes a recording head 26 that is disposed at a position opposite to 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 conveying direction of the recording medium. In this embodiment, in addition to four pigment inks of yellow (Y) ink, magenta (M) ink, cyan (C) ink, and black (K) ink as the recording agent, a processing liquid (P) that performs a predetermined process on the ink ejected onto the recording medium is used. Therefore, in this embodiment, the recording head 26 includes five line-type recording heads corresponding to the processing liquid in addition to the four inks of Y ink, M ink, C ink, and K ink. Note that the number of colors of the recording heads 26 in the recording module 14 is not limited to the above four colors, and the number of recording heads is not limited to five. Furthermore, 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 capable of ejecting ink by, for example, an inkjet method. As the inkjet method, various known techniques can be used, such as a method using a heat element, a method using a piezoelectric element, a method using an electrostatic element, a method using a MEMS element, etc. The recording head 26 is supplied with the 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) for protecting the nozzle surface of the recording head 26 on which nozzles for ejecting ink are formed, a wiping unit for wiping the nozzle surface, and a suction unit for sucking ink in 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, and for example, when the maintenance unit 28 is used, the maintenance unit 28 is located at a position facing the nozzle surface on the lower side of the recording head 26. Note that only the components of the maintenance unit 28 may be configured to 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 communicably connected to a host device HC1. In the host device HC1, manuscript data that is the source of a recorded image is generated or stored. 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. In the higher-level device HC2, the received manuscript data is converted into a data format that can be used 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, 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, a RAM, a hard disk, or an 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, a keyboard, or a mouse, and receives instructions from a user.

[0019] The buffer 218 is realized by, for example, a RAM, a hard disk, and an SSD, and is a storage area for storing various information. The image processing unit 212 is realized by, for example, an electronic circuit having an image processor, and is configured to be able to execute 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 having 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 Fig. 2 show 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 recording data to be used by the engine controller 204, and stores the data in the buffer 218 again. The recording 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 recording head 26 based on the recording data, and a recording operation is performed to execute recording on the recording 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 processing shown in the flowchart in Fig. 3 is 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. 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 means 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 is also assumed to have 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 recorded by the recording 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, a dither method or an error diffusion method can be used as the 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 indicating whether the attribute of the image recorded on the pixel is a character attribute or a thin line attribute, or another attribute (such as an image image attribute), and is composed of 1 bit. More specifically, when a character or a thin line is recorded on a certain pixel, "1" is acquired as the attribute information. On the other hand, when something other than a character or a thin line is recorded, "0" is acquired as the attribute information.

[0024] Note that S306 may be executed in parallel with the processes from 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 the attribute information, in S310, the image processing unit 212 combines the quantized data of 3 bits for each CMYK value with the 1-bit attribute information 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. In S312, the image processing unit 212 performs index expansion processing on the combined data to generate data consisting of 1-bit information for each CMYK value and the attribute information for two planes. In this index expansion, the quantized data of 3 bits for each CMYK value, which has a resolution of 600 dpi x 600 dpi, among the combined data, is expanded to 1-bit for each CMYK value at a resolution of 1200 dpi x 1200 dpi using an index pattern.

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

[0027] <Recording head configuration> Next, a description will be given of 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 is provided with a plurality of recording element substrates 402 on a surface (nozzle surface) 400 facing the conveyed recording medium. 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 manner 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 in fluid communication with the negative pressure control unit 616 (see FIG. 5). The recording head 26 also includes a liquid connection portion 612 that serves as a supply port and a discharge port for ink to the ink supply unit 614 (see FIG. 5).

[0030] <Configuration of the recording element substrate> Next, the configuration of the recording element substrate 402 will be described. Figures 5(a) to (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 see-through 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, and by using this material, a plurality of electronic devices such as energy generating elements, electric circuits, electric wiring, and temperature sensors can 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 nozzle 500 can be formed by laser processing, or an inorganic plate on which the nozzle 500 can be formed by dicing. The orifice plate 504 may be formed from a material such as a photosensitive resin material on which the nozzle 500 and the ink flow path can be formed by photocuring. Alternatively, a semiconductor substrate may be used like the substrate 502, and various known materials may be used to form the nozzle 500 and the ink flow path by MEMS processing.

[0032] In the orifice plate 504, a nozzle row 506 is formed in which a plurality of nozzles 500 for ejecting ink are arranged along the extending direction of the substrate 502. The orifice plate 504 forms a plurality of pressure chambers 508 together with one surface of the substrate 502 (see FIGS. 5(b) and 5(c)). Each pressure chamber 508 is connected to a nozzle 500. In addition, 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 nozzle 500 formed in the orifice plate 504 is formed at a position facing the energy generating element 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 by the boiling.

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

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

[0036] <Circulation route> Next, there will be described the ink circulation path in the recording apparatus 10. FIG.

[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 has an air communication port (not shown) that communicates between the inside and the outside, and is configured to be able to discharge air bubbles in the ink in the buffer tank 604 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 the ink in 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 recording operation on a recording medium or a maintenance operation on the recording 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 to an ink supply unit 614 of the recording head 26 via a liquid connection part 612 by a second circulation pump 610. 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, a high pressure side and a low pressure side, and supplied to the recording element substrate 402.

[0040] Ink flowing through the high pressure side 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 side 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, a part of the ink supplied to the common supply flow path 618 flows into the recording element substrate 402 via the individual supply flow paths 619. Then, the ink that flows into the recording element substrate 402 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 the individual recovery flow paths 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 the 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, the ink recovered from the print head 26 is recovered to the buffer tank 604 via the first circulation pump 602. That is, the ink that does not flow to the printing element substrate 402 in the common supply flow path 618 is recovered to the buffer tank 604 by the first pump 602a via the ink supply unit 614 and the liquid connection part 612. Also, the ink flowing out from the common recovery flow path 620 is recovered to 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 quantitative liquid delivery capability. Specifically, the first circulation pump 602 is preferably a tube pump, a gear pump, a diaphragm pump, a syringe pump, or the like. Note that the first circulation pump 602 may be configured to ensure a constant flow rate by arranging a general constant flow valve or a relief valve at the pump outlet, for example.

[0043] When the recording head 26 is driven, the first circulation pump 602 is driven to cause ink to flow at a predetermined flow rate in the common supply flow path 618 and the common recovery flow path 620. By flowing ink in this manner, the temperature of the recording head 26 during recording is maintained at an optimal temperature. The predetermined flow rate is set to a flow rate that allows the temperature difference between the recording element substrates 402 in the recording head 26 to be maintained at a temperature difference that does not affect the recorded image quality. If the flow rate is set too high, the negative pressure difference between the recording element substrates 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 uneven density in the recorded image. For this reason, the predetermined flow rate is set while taking into consideration the temperature difference and negative pressure difference between the recording element substrates 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 dissolved gases in the ink. The amount of ink circulating through the circulation path 600 including the buffer tank 604 is, 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 if the flow rate of ink in the circulation path 600 varies due to differences in the ejection amount per unit area or the like. The upstream side of the negative pressure control unit 616 is pressurized by the second circulation pump 610. With this configuration, the effect of the head pressure of the buffer tank 604 on the recording head 26 can be suppressed, 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 or a positive displacement pump, 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.

[0047] In this manner, 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, when recording is being performed by the recording head 26, a flow of ink can be generated even in the nozzles 500 that are not ejecting ink. Therefore, this flow of ink 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 recording in the recording device 10 will be described. Fig. 7 is a timing chart of a number of processes executed during recording in the recording device 10. In the following description, the state of the recording device 10 before executing a recording operation based on a job will be appropriately referred to as a standby state. When the recording device 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. Also, the temperature of the recording head 26 in the standby state is T0°C, and the humidity at the nozzle 500 is 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 the ink in the circulation path 600. Next, the cap portion (not shown) in the maintenance unit 28 moves away from the nozzle surface 400 of the printing head 26, and the nozzle 500 is exposed to the outside. As a result, the humidity around the nozzle 500 becomes equal to the humidity (RH0) of the installation environment of the printing apparatus 10, and the ink evaporates from the nozzle 500. Thereafter, the 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 rate of the ink in the circulation path 600 (circulation flow rate) reaches a predetermined speed 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 portion is separated. Furthermore, during a recording operation, the ink mainly evaporates from non-ejecting nozzles that do not eject ink. The evaporation of ink from non-ejecting nozzles increases the ink concentration in the circulation path 600. Since the circulation flow rate cannot be controlled individually for each nozzle 500, the evaporation rate of ink from each non-ejecting nozzle during a recording operation is constant. Note that, although the evaporation component from non-ejecting nozzles is dominant in the evaporation of ink from nozzles during a recording operation, in this embodiment, when calculating the amount of ink evaporation, in order to simplify the calculation, it is assumed that the evaporation proceeds uniformly for all nozzles regardless of the ejection state.

[0051] After the recording operation is completed, the first circulation pump 602 is stopped to stop the circulation of ink in the circulation path 600. After the first circulation pump 602 is stopped, the circulation flow in the nozzle 500 completely stops after a predetermined time has elapsed. Therefore, when the first circulation pump 602 is stopped, the evaporation rate from the non-ejecting nozzles drops sharply. Then, the cap portion is brought into contact with the nozzle surface 400 of the recording head 26. As a result, the humidity around the nozzle 500 increases and recovers to the humidity RH1 before the recording operation of the job is performed, and the evaporation rate from the non-ejecting nozzles converges to 0.

[0052] <Adjustment process> In the above configuration, the recording device 10 executes an adjustment process to adjust the ink concentration (for example, pigment concentration) in the circulation path that has increased due to the recording operation to a concentration 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 due to the printing operation of the job, at a timing such as before or after the printing operation based on the job is executed. Then, based on the acquired estimated value of the ink density, an adjustment process is executed to adjust the ink density in the circulation path 600 by discharging a part of the ink that has thickened from the circulation path 600 and supplying new ink from the main tank 606. In the following description, discharging a part 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. By this adjustment process, the ink density in the circulation path 600 is adjusted to within a predetermined temperature range in which deterioration of the recorded image quality is unlikely to occur. The timing to execute the adjustment process (and the acquisition process) is not limited to before or after the printing operation based on the job is executed, and may be executed, for example, at a timing instructed by a user. The adjustment process is executed for each type of ink.

[0054] Functional configuration of engine controller 204 The acquisition process and the 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 control unit 802 that controls temperature adjustment of the printhead 26 by a temperature control heater (not shown) provided on the printhead substrate 402 based on the detection result of the temperature detection unit 520 provided on the printhead 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 nozzle 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 result of a temperature and humidity sensor 800 provided in the printing apparatus 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 printing 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 a calculation result in a dot number calculation unit 816, which will be described later. The engine controller 204 also includes a dot number calculation unit 816 that calculates the number of ink droplets 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 a recording operation by the job is completed, and an adjustment process is executed using the information acquired in the acquisition process. First, the acquisition process will be described. FIG. 9 is a flowchart showing the detailed processing contents of the acquisition process. A series of processes shown in the flowchart of FIG. 9 is performed by the CPU of the engine controller 204 expanding program codes stored in the ROM of the engine controller 204 into the RAM of the engine controller 204 and executing them. Alternatively, some or all of the functions of the steps in FIG. 9 may be executed by hardware such as an ASIC or an electric circuit.

[0058] When the acquisition process is started, first, in S902, the printhead temperature control unit 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, a 200 msec cycle. In this case, for example, the temperature can be acquired approximately four times per A4 printing medium conveyed at a conveying speed of 0.6765 mm / sec. In addition, in S904, the printhead temperature control unit 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 at each temperature detection unit 520 acquired in S902 is acquired as the target temperature. The target temperature may be the average value of the detection results of each temperature detection unit 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 nozzle 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 the combination of the temperature and dew point temperature of the recording element substrate 402 is stored in a storage area such as a 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 the combination of the temperature and dew point temperature of the recording element substrate 402. Note that, in FIG. 10, symbols V1 to V40 are written as the amount of ink evaporation per unit time, but in reality, a numerical value corresponding to the amount of ink evaporation per unit time is input. Therefore, in S908, the amount of ink evaporation per unit time is obtained using the table in FIG.

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

[0061] Thereafter, in S914, the concentration estimate calculation unit 810 calculates the concentration estimate of the ink in the circulation path 600 based on the evaporation amount acquired in S908 and the consumption amount acquired in S912, and ends this acquisition process. The technology for acquiring the concentration estimate of the ink in the circulation path based on the evaporation amount of ink per unit time and the consumption amount of ink consumed in the printing operation is a known technology, so a detailed description thereof will be omitted. For example, in order to simplify the calculation, the calculated concentration estimate is assumed to be a state after the ink in the circulation path that has been thickened by the evaporation amount is mixed with ink that has not been thickened and has become uniform after a certain period of time. In this case, it actually takes some time for the ink that has evaporated from the nozzle and thickened to become uniform in the circulation path, but the calculation is deliberately performed under strict conditions for evaporation.

[0062] =Adjustment process= When the acquisition process is completed, next, an adjustment process is 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 contents of the adjustment process. A series of processes shown in the flowchart of Fig. 11 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. 11 may be executed by hardware such as an ASIC or an electric circuit.

[0063] When the adjustment process is started, 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 an experimentally determined value is stored in the storage area. This estimated error Er will be described later.

[0064] Next, in S1106, the ink discharge control unit 808 judges whether the threshold value Th is "0 (initial value)". If it is judged in S1106 that the threshold value Th is "0", the process proceeds to S1108, where the ink discharge control unit 808 judges whether the sum of the concentration estimation value N and the estimated error Er is equal to or greater than the limit value (equal to or greater than the limit value Th_1). If it is judged in S1108 that N+Er≧Th_1 is not satisfied, that is, that the sum of the concentration estimation value N and the estimated error Er is less than the limit value Th_1, the adjustment process is terminated. If it is judged in S1108 that N+Er≧Th_1, the process proceeds to S1110, where the ink discharge control unit 808 executes a first discharge control for discharging a small amount of ink from the circulation path 600. The limit value Th_1 is a threshold value for judging whether it is necessary to execute the discharge of 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 performed due to an increase in the 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. An ink concentration at which ink discharge control must be performed is, for example, an 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. For example, the ink is discharged from the circulation path 600 by performing a preliminary discharge in which ink that does not contribute to recording is discharged from each nozzle of the recording head 26 to the cap part of the maintenance part 28. Alternatively, the ink is discharged by suction to reduce the pressure inside the cap part and forcibly sucking the ink from each nozzle of the recording head 26. Note that the method of discharging the ink from the circulation path 600 is not limited to this, and various known techniques such as discharging the ink from the buffer tank 604 can be applied. In this case, depending on the discharge method, the recording device 10 holds a configuration capable of stably discharging the ink from the circulation path 600. In addition, in S1110, the ratio R0 (Er0 / N0) of the estimated density value N0 and 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 ends this adjustment process.

[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. 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 to discharge a small amount of ink from the circulation path 600, and then ends the adjustment process. The specific process content of S1118 is the same as S1110. Also, 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 ink supply operation to the print head 26. This amount is set to, for example, the upper limit of the amount of ink that can fill the circulation path 600 with ink without executing additional processing, even if ink is supplied after being discharged from the circulation path 600, or a certain amount less than the upper limit.

[0069] Thereafter, in S1122, the ink discharge control unit 808 initializes the threshold value Th to "0", and then ends the adjustment process. The concentration 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 concentration estimation value N is initialized, so that the concentration estimation value N that satisfies N+Er≧Th_1 is set as the threshold value Th again.

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

[0071] Examples of causes of errors in concentration estimates include the following:

[0072] - Ink flow velocity near the nozzle (nozzle circulation velocity) Position of the recording head 26 in the conveying direction of the recording medium Moisture absorption in recording media The estimation error has positive and negative components, and the positive components increase the estimated concentration value. At the position where the recording head 26 is arranged, the component is basically positive, but it can also be negative depending on the position in the transport direction. The higher the nozzle circulation flow speed, the more fresh ink is supplied to the vicinity of the nozzles, promoting evaporation from the nozzles. The higher the moisture absorption into the recording medium, the more moisture in the space between the recording head 26 and the recording medium is taken by the recording medium, promoting evaporation of ink from the nozzles.

[0073] Fig. 12 is a graph showing the relationship between the nozzle circulation flow speed and the evaporation amount 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 speed is 45mm / sec and the maximum tolerance value is 60mm / sec. From the relationship between the nozzle circulation flow speed and the evaporation amount shown in Fig. 12, when the nozzle circulation flow speed is 45mm / sec, the evaporation amount is 6.83g / hour, and when the nozzle circulation flow speed is 60mm / sec, the evaporation amount is 8.29g / hour.

[0074] Experimental results show that moisture absorption into the recording medium causes the dew point temperature to drop by 2°C under the worst conditions (0% recording duty). If the increase in evaporation rate due to a 2°C dew point is added to the evaporation rate at a nozzle circulation speed of 60mm / sec, the evaporation rate becomes 8.55g / 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 appropriately referred to as the "center of tolerance", and the case when the nozzle circulation flow velocity has a maximum tolerance value of 60 mm / sec will be appropriately referred to as the "maximum tolerance".

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

[0077] When the recording device 10 is operated under these conditions, the difference in the ink evaporation rate at the maximum tolerance and the center tolerance with respect to the elapsed time is as shown in Figure 13. Figure 13 is a graph showing the transition of the estimated error, which is the difference in the ink evaporation rate at the maximum tolerance and the center tolerance obtained by experiment. As is clear from the graph in Figure 13, the upper limit of the difference in the evaporation rates between the two is 3%. Therefore, based on the results of this experiment, the concentration value corresponding to the upper limit of the evaporation rate difference (concentration error) of 3% is set as the estimated error.

[0078] If the values ​​of the ink discharge amount, supply amount, and concentration of the ink supplied during discharge control are precisely constant, the upper limit of the difference in evaporation rate obtained in the above experiment will not be greater than 3%. However, the above value may vary depending on the product form and may not be constant.

[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 estimated error is as shown in Fig. 14, and the upper limit of the difference in evaporation rate increases. Fig. 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 be compared with the ink concentration estimate value when determining whether to execute the ink discharge control, taking into account the variation in the above-mentioned value due to the product form. In this case, the threshold value is set to a low value, which increases the frequency of execution of the ink discharge control and increases the amount of waste ink generated.

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

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

[0083] FIG. 25 is a conceptual diagram showing the change in the concentration estimation value and the estimation error due to the ink discharge control, in which the second discharge control is executed when R≧R0. After time k, when the concentration estimation value N and the estimation error Er reach the limit value Th_1, some abnormal operation causes the estimation error Er to be large at time k+n (Er k+n / D)≧(Erk / N), and the second discharge control is executed. Here, "D" is the concentration estimate value at time k+n. Also, the abnormal operation is, for example, a temperature control abnormality, an operation 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 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 discharged during ink discharge control are determined using information on 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 an error that the estimated value may take.

[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 can reduce the amount of waste ink generated by ink discharge control, thereby contributing 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 reference numerals as those used in the first embodiment are used for the same or corresponding configurations as those of the recording device described in the first embodiment, and detailed description thereof will be omitted.

[0087] Ink discharge control in response to an increase in ink concentration in the circulation path 600 is performed based on a threshold value set according to the occurrence of uneven concentration in a printed image, a deterioration in ink ejection characteristics, and a deterioration in the reliability of the circulation function. However, the inventors of the present application have found that uneven concentration occurs due to a relatively small increase in ink concentration, rather than a deterioration in ink ejection characteristics and a deterioration in the reliability of the circulation function.

[0088] The visibility of density unevenness can be reduced by performing image density correction that controls the number of ink droplets (number of dots) applied onto the recording medium in response to variations in the ejection amount of the recording head 26. Note that if the ink density fluctuates, for example, 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] According to the findings of the present inventors, it has been found that density unevenness may be visible when the ink concentration increases by 2.5% to 3.0%. On the other hand, no decrease in the ink ejection characteristics and the reliability of the circulation function was observed with the above-mentioned increase in ink concentration. From this, by performing image density correction, it becomes possible to set a threshold value in accordance with the relatively high concentration at which ink discharge control is required, the decrease in ink ejection characteristics, and the decrease in the reliability of the circulation function. This makes it possible to reduce the number of times ink discharge control is performed, and thus the amount of waste ink generated.

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

[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 ink density of the circulation path 600 using the density estimate 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 description, since the acquisition process and the adjustment process are the same processes as those in the first embodiment described above, detailed description thereof will be omitted, and the determination process will be described in detail.

[0092] <Decision process> Fig. 16 is a flowchart showing detailed processing contents of the decision processing for deciding 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 is started, first, in S1602, the image density correction unit 812 acquires a density estimate value Nc when image density correction was most recently performed. As 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 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 estimate value Nc obtained in S1602 and the concentration estimate 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 by the inventor of the present application. The inventor of the present application performed image density correction with a resolution of 16 pixels (0.677 m) at 600 dpi in the extension direction of the nozzle row, and performed a sensory evaluation to see how much color difference was required at this frequency to be visually recognized as density unevenness. As a result, the majority of cases had a visually acceptable value of 1 or more for ΔE2000. Therefore, the standard (proximity ΔE) was set to within 0.8, and an experimental result was obtained in which the amount of change in ink density that satisfied this was 2%. Therefore, the threshold value used in S1606 is a value obtained by performing the above-mentioned experiment according to various conditions. In other words, the threshold value is a value that is set appropriately.

[0096] If it is determined in S1606 that |N-Nc|≧2, the process proceeds to S1608, where the image density correction unit 812 determines to execute image density correction. Thereafter, the process proceeds to S1610, where the image density correction unit 812 updates the density estimation value Nc stored in the storage area when the image density correction is executed to the density correction value N acquired in S1604, and ends this determination process. Also, if it is determined in S1606 that |N-Nc|≧2 is not satisfied, the process proceeds to S1612, where the image density correction unit 812 determines not to execute image density correction, and ends this determination process. When the determination process ends, the image density correction unit 812 executes image density correction when generating recording data used in the recording operation of the job after this determination process, depending on whether or not image density correction is to be executed as determined in the determination process.

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

[0098] =HS Processing= The HS processing is executed by the image processing unit 212. First, the functional configuration of the image processing unit 212 that executes 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 corresponding to the color reproduction range of the recording device 10. In this embodiment, the input image data is data indicating color coordinates (R, G, B) in a color space coordinate system such as sRGB, which is the representation color of the 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') in the color reproduction range of the recording device 10. This conversion can be performed using known methods such as matrix calculation processing or processing using a three-dimensional lookup table (LUT). In this embodiment, a three-dimensional LUT is used, and an interpolation calculation is 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 recording device 10. In this embodiment, since the recording device 10 uses K ink, C ink, M ink, and Y ink, the image data of 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 also performed by using a three-dimensional LUT in combination with an interpolation operation, as in the input color conversion processing unit 1702. Note that other known conversion methods such as matrix operation processing can be used.

[0101] Furthermore, the image processing unit 212 includes an HS processing unit 1706 that performs corrections on the image data of the ink color signals that have been ink color converted by the ink color conversion processing unit 1704 in accordance with the ink ejection characteristics of the nozzles 500 that constitute the recording head 26. Details of the HS processing performed by the HS processing unit 1706 will be described 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 consisting 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 printing medium is adjusted by correcting the image data so that the relationship between the number of dots printed on the printing medium and the brightness achieved by that number of dots becomes 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 printing data. As a quantization processing method, various known techniques such as dithering and error diffusion can be used. After the quantization processing, the processing from the acquisition of attribute information (S308) onwards described in the image processing shown in the flowchart of FIG. 3 is performed to generate printing data, and the generated printing data is stored in the buffer 218.

[0104] Next, the HS process based on the 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 process. FIG. 19 is a diagram showing an example of a measurement image for acquiring density characteristics at each nozzle 500 in the recording 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 process of FIG. 18 is executed by the HS processing unit 1706 of the image processing unit 212 in the main controller 202. A series of processes shown in the flowchart of FIG. 18 is performed by the CPU of the main controller 202 expanding the 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 an electric 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 a 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 with only a single ink color. In this embodiment, it is assumed that the patches are recorded with 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, the ink color conversion processing unit 1704, and the HS processing unit 1706 (see the dashed arrow in FIG. 17(a)). After that, 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 to obtain a scanned image. A known technique can be used for the scanner that scans the measurement image 1900 recorded on the recording medium and its arrangement position, so detailed explanations are omitted. The scanned image is acquired in three channels, RGB, and then converted into a one-channel scanned image by a color conversion table prepared in advance in accordance with the color characteristics of the scanner. For example, a color conversion table that converts Y in the CIEXYZ color space into a linear 16-bit value is used as this color conversion table.

[0109] The color space of the scanned image is arbitrary, and may be L* of CIELab* or density. In addition, when the measurement image is recorded with color inks such as C, M, and Y, a value corresponding to saturation may be used instead of a value corresponding to brightness. For example, values ​​of R, G, and B channels may be used as values ​​corresponding to the complementary colors of C, M, and Y, respectively. In addition, a scanned image of the measurement image 1900 for acquiring the measurement curve may be acquired, for example, before executing this HS process. In this case, in S1804, the scanned image stored in the storage area is acquired.

[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 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 since the input signal value is 8 bits.

[0111] A measurement curve obtained by an interpolation calculation from the scanned image signal values ​​of patches 1902 to 1918 becomes a 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 the pixel position x, and is obtained as many times as the number of nozzles 500 used when recording the measurement image 1900. A different measurement curve is obtained for each ejection characteristic of the nozzle 500, and for example, for a nozzle 500 with a small ejection amount, the measurement curve 2004 shifts upward (in the brighter direction).

[0112] Return to FIG. 18. When the measurement curve is acquired, in S1806, the HS processing unit 1706 corrects the error of the measurement value in the acquired measurement curve to acquire a corrected measurement curve 2014 (see FIG. 21(b)). FIG. 21 is a diagram showing the measurement value in the area corresponding to the 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 is the nozzle number, and the vertical axis is the signal value of the scanned image. The nozzle number represents the number given to each nozzle provided in the recording head 26. In a main body configuration in which the recording medium is not distorted and the recording head 26 and the scanner are installed sufficiently close to each other, the measurement result is as shown in FIG. 21(a). In addition, in a main body configuration in which the recording medium is distorted and the recording head 26 and the scanner are installed far from each other, or in which the main body configuration in which the recording medium is scanned after a drying process is performed after recording, the measurement result is as shown in FIG. 21(b). Comparing the two measurement results, it can be seen that the measurement results in Figure 21(b) did not obtain the correct measurement values ​​on the edge side due to distortion of the recording medium. In the measurement results in Figure 21(b), the waveform intervals are narrower on the edge side, which is because the edge of the recording medium is lifted and tilted relative to the scanner. The correction process applied to the measurement curve is a process in which the measurement values ​​of normal areas other than the edge are used to correct the measurement values ​​of abnormal areas at the edge. It should be noted 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 the target characteristic 2006. The target characteristic 2006 is a target characteristic that is determined in advance according to the measurement curve of each nozzle 500. In this embodiment, as shown in FIG. 20(a), 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, a target value 2022 that is a value corresponding to the target characteristic 2006 that corresponds to the input value 2020 acquired in S1802 is acquired (see FIG. 20(b)). Then, a gradation value corresponding to the target value 2022 is acquired from the corrected measurement curve 2014, and the acquired value is acquired as the corrected input value 2024. Note that in subsequent jobs, for example, the corrected measurement curve 2014 acquired in S1806 is used in the HS processing when creating print data until the execution of image density correction is determined again in the determination processing.

[0114] =CS Processing= The CS processing is executed by the image processing unit 212. First, the functional configuration of the image processing unit 212 that executes 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 five 3 = 125 different multi-color patches are recorded. Note that the combination of the above patches is not limited and may 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 FIG. 17(b)). After that, the measurement image is 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 held as three RGB channels.

[0117] Next, the specific processing contents of the CS processing based on the ink density will be described. Fig. 22 is a flowchart showing the detailed processing contents of the CS processing. The main difference between the CH processing and the HS processing is that the measurement image is multi-color and the measurement value is RGB three-channel. 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 processing shown in the flowchart of Fig. 22 is performed by the CPU of the main controller 202 expanding the 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 an electric circuit.

[0118] When the CS process is started, first, in S2202, the MCS processing unit 1712 acquires input values ​​using image data corresponding to the color reproduction range of the recording device 10 output from the input color conversion processing unit 1702 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 scanned by the scanner. In this embodiment, 125 measured RGB values ​​are acquired as the measured 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 storage area is acquired.

[0119] Thereafter, in S2206, the MCS processing unit 1712 corrects the measured RGB values. The correction here can be performed using known techniques. 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, the target RGB values ​​are acquired. For example, the target RGB values ​​are acquired by referring to 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, a method of acquiring the corrected input value in S2210 will be described. FIG. 23 is a diagram showing a three-dimensional space with the RGB values ​​of the scanned image as axes. A point 2302 in FIG. 23 represents the target RGB value acquired in S2208. Points 2304, 2306, 2308, and 2310 in FIG. 23 represent the four corrected measured RGB values ​​selected to form the smallest tetrahedron containing the point 2302 among the 125 corrected measured RGB values ​​acquired in S2206. The distances between the point 2302 and the points 2304, 2306, 2308, and 2310 are calculated, and the four input RGB values ​​are interpolated according to the ratio of the distances to acquire the corrected input value. Note that in subsequent jobs, for example, the correction information acquired in S2206 is used in the CS process when creating print data until the execution of image density correction is determined again in the determination process.

[0121] <Action and effect> As described above, in the recording device 10 of the second embodiment, the same ink discharge control as in the first embodiment is executed, and image density correction based on the ink density is executed when recording data is generated, based on the estimated value of the density 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, and it is possible to suppress the number of times ink discharge control is executed, thereby suppressing the amount of waste ink generated.

[0122] That is, by executing image density correction based on ink density, it becomes possible to execute ink discharge control at a timing when the ink density estimate value is relatively high, and it is possible to suppress an increase in the amount of waste ink caused by ink discharge control. Note that, for example, the first discharge control is executed so that the ink density estimate value in the circulation path 600 after the ink discharge control changes by less than 2% from the density estimate value at the time of the previous image density correction. As a result, after the first discharge control, it becomes possible to perform recording without causing density unevenness in the recorded image, even without 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 held as the estimated error, but this is not limited to the above. The estimated error becomes smaller as the print duty becomes higher. 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 result of FIG. 13. In FIG. 24, the upper limit of the estimated error is about 2%. Therefore, the upper limit of the estimated error according to the print duty may be held. In this case, the adjustment process uses the estimated error corresponding to the print duty in the print operation by the job. Also, instead of the upper limit of the estimated error, for example, the median value between the upper limit of the estimated error and the lower limit of the estimated error may be set, or a predetermined value such as a value between the median value and the upper limit may be set.

[0125] (2) In the first embodiment, two types of discharge control, the first discharge control and the second discharge control, are executed based on the concentration estimation value and the estimation error, but the present invention 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 form in which discharge control is performed based on a concentration estimate value and an estimation error, after acquiring the concentration estimate value N and the estimation error Er, it is determined whether or not the condition N+Er≧Th_1 is satisfied, and if not, discharge control is not performed. If the above condition is satisfied, the count value of the number of times the first discharge process has been performed is referred to. 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."

[0127] Alternatively, in the case of 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 satisfied, and if not, discharge control is not performed. If the above condition is satisfied, 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 of ink discharge control and the amount of ink discharged during ink discharge control are determined based on the density estimation value and the estimation error, but the present invention is not limited to this. For example, image density correction such as HS processing and CS processing may be performed after discharge control in which the amount of ink discharged is increased (second discharge control). In addition, although not specifically described in the above embodiment, the recording device 10 may perform image density correction based on the nozzle discharge characteristics. That is, in this case, in the second embodiment, when image density correction based on ink density has not been performed even once, image density correction based on nozzle discharge characteristics is performed, and after image density correction is 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 recording and scanning a measurement image, so that it also deals with density unevenness based on nozzle discharge characteristics.

[0129] (4) Although not specifically mentioned in the second embodiment, the recording device 10 may store multiple pieces of correction information for the HS process and the CS process in a storage area according to the ink density. In this case, when the execution of image density correction based on ink density is decided in the decision process, correction information associated with an ink density that is close to the density estimate value is obtained, and the HS process and the CS process are executed using this correction information. Furthermore, in subsequent jobs, recording data is generated using the obtained correction information until the execution of image correction processing based on ink density is decided again in the decision 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, when ink discharge control is executed in the adjustment process, the image density correction may not be executed. Therefore, in the case of a form in which the determination process is executed after the adjustment process, when 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 the timing when the circulation path 600 is refilled with ink. In the above embodiment, one of two types of discharge control, the first discharge control and the second discharge control in which the amount of ink discharged is greater than that of the first discharge control, is selectively executed, but this is not limited to this. A specific discharge control may be selectively executed from three or more types of discharge control with different ink discharge amounts, for example, by setting multiple limit values.

[0132] (7) The above embodiment and the various configurations 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 recording element substrate having nozzles capable of ejecting a recording material; a circulation path including the recording element substrate, the circulation path being capable of circulating the recording agent to supply the recording agent to the recording element substrate and recovering the recording agent not ejected from the recording element substrate; an acquisition unit for acquiring information regarding the concentration of the recording material circulating through the circulation path; a discharge control unit that executes ink discharge control to discharge the recording material from the circulation path in response to the information about the concentration, and to supply 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 discharge amount of ink 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 regarding 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, characterized in that the discharge control means executes a 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 ink concentration at which at least one of the following occurs: the occurrence of concentration unevenness in the recorded image, a deterioration in the ejection characteristics of the recording agent from the nozzles, and a deterioration in reliability of the circulation function of the recording agent in the circulation path. (Configuration 5) The recording device described in any one of configurations 3 or 4, 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 executes a 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 is executes the first control when a threshold is an initial value, and executes the second control when the threshold is set to a value different from the initial value; In the first control, when the first emission 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 is 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 for generating recording data for recording on a recording 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 processing when a difference between the density estimated value acquired by the acquisition means and the density estimated value when the processing related to the image density correction was most recently 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 for generating recording data for recording on a recording 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 estimated value acquired by the acquisition means and the density estimated 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 an amount of change in density of the recording material that causes density unevenness in a recorded image. (Configuration 11) The recording device according to any one of configurations 1 to 10, characterized in that the discharge control means discharges the recording agent from the circulation path by a preliminary discharge that discharges recording agent that does not contribute to recording from the nozzles of the recording element substrate, or by a suction discharge that forcibly sucks and discharges the recording agent from the nozzles. (Configuration 12) 12. The recording apparatus according to any one of configurations 1 to 11, wherein the recording material includes an ink containing a pigment and a processing liquid that performs a predetermined processing 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 a recording material from a circulation path including a recording element substrate having nozzles capable of ejecting a recording material in accordance with a concentration of the recording material circulating through the circulation path, and supplies an amount of the recording material to the circulation path in accordance with an amount of the discharged recording material, comprising: acquiring information regarding the concentration of the printing material circulating through the circulation path; A control method characterized by selectively executing one of a first discharge control in which an 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 recording element substrate having nozzles capable of ejecting a recording material; a circulation path including the recording element substrate, the circulation path being capable of circulating the recording agent to supply the recording agent to the recording element substrate and recovering the recording agent not ejected from the recording element substrate; an acquisition unit for acquiring information regarding the concentration of the recording material circulating through the circulation path; a discharge control unit that executes ink discharge control to discharge the recording material from the circulation path in response to the information about the concentration, and to supply 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.

2. The information regarding the concentration is a concentration estimate value that is an estimate of the concentration of the recording material; 2. The recording apparatus according to claim 1, further comprising an estimation error which is an error that may occur in the density estimation value.

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

4. The recording device described in claim 2, characterized in that the discharge control means executes a 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 ink concentration at which at least one of the following occurs: the occurrence of concentration unevenness in the recorded image, a deterioration in the ejection characteristics of the recording agent from the nozzles, and a deterioration in the reliability of the circulation function of the recording agent in the circulation path.

5. The recording device described in claim 4, 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 executes a second control that performs the first discharge control when neither the first condition nor the second condition is satisfied.

6. The discharge control means is executes the first control when a threshold value is an initial value, and executes the second control when the threshold value 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 claim 5, wherein, in the second control, when the second discharge control is performed, the threshold value is set to an initial value.

7. The discharge control means is 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.

8. The image processing device further includes an image processing unit capable of executing image density correction based on ink density in image processing for generating recording data for recording on a recording medium, The recording device according to claim 2, characterized in that 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 was performed is equal to or greater than a threshold value.

9. The image processing device further includes an image processing unit capable of executing image density correction based on ink density in image processing for generating recording data for recording on a recording medium, The recording device described in claim 2, characterized in that 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 image density correction was performed is equal to or greater than a threshold value.

10. 10. The printing apparatus according to claim 8, wherein the threshold value corresponds to an amount of change in density of the printing material that causes density unevenness in a printed image.

11. The recording device according to any one of claims 1 to 9, wherein the discharge control means discharges the recording agent from the circulation path by a preliminary discharge that discharges recording agent that does not contribute to recording from the nozzles of the recording element substrate, or by a suction discharge that forcibly sucks and discharges the recording agent from the nozzles.

12. 10. The recording apparatus according to claim 1, wherein the recording material includes ink containing a pigment and a processing liquid for performing a predetermined process on the ink ejected onto the recording medium.

13. A control method for a recording device capable of performing ink discharge control, which discharges a recording material from a circulation path including a recording element substrate having nozzles capable of ejecting a recording material in accordance with a concentration of the recording material circulating through the circulation path, and supplies an amount of the recording material to the circulation path in accordance with an amount of the discharged recording material, comprising: acquiring information regarding the concentration of the printing material 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.

Images