JP2014024211A - Inkjet recording apparatus and method for setting driving condition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording apparatus capable of preventing deterioration in an image quality by setting a driving condition for a recording head to a suitable driving condition in response to a temporal change of the recording head, and a method for setting the driving condition.SOLUTION: An inkjet recording apparatus (20), which records an image on a recording medium using a recording head (14) having a discharge port for discharging ink, includes acquisition means for acquiring information on use history of the recording head (14), prediction means for predicting a driving condition suitable for driving of the recording head (14) from a driving parameter in response to the information, formation means for forming a pattern under the predicted driving condition and a driving condition in its large-small range, and setting means for setting a driving condition for the recording head (14) by reading and analyzing the pattern and calculating the driving condition suitable for driving of the recording head (14) during recording.

Description

  The present invention relates to an ink jet recording apparatus and a driving condition setting method thereof, and more particularly to a method of setting a driving condition of a recording head used in the ink jet recording apparatus.

  In an ink jet recording apparatus that uses a recording head that discharges ink from an ejection port, the amount of ink discharged and the timing of ink discharge may be shifted due to changes in the recording head over time, and image quality may deteriorate.

  On the other hand, in Patent Document 1, a correction pattern is formed on a recording medium for each of a plurality of stages of a driving voltage serving as a reference and a driving voltage in a large or small range. Then, the most appropriate density pattern is selected from the pattern reading results, and the driving voltage of the driving element provided corresponding to the ejection port is corrected based on the driving voltage when the pattern is formed. The ink discharge amount is adjusted.

JP 2004-358965 A

  However, the configuration of Patent Document 1 basically has a fixed driving voltage as a reference when recording the plurality of correction patterns. For this reason, the correction pattern is formed with a relatively wide driving voltage so that an appropriate driving voltage changed at that time can be selected. As a result, it may take time to form a correction pattern, read it, and analyze it. On the other hand, it is conceivable to reduce the resolution of the drive voltage. However, if the resolution of the drive voltage is lowered, the formation accuracy of the correction pattern also decreases, and the drive voltage of the drive element can be corrected appropriately. It may disappear.

  The present invention has been made in view of the above problems. An object of the invention is to provide an ink jet recording apparatus capable of preventing a reduction in image quality by setting a driving condition of the recording head to an appropriate driving condition in accordance with a change with time of the recording head, and a method of setting the driving condition Is to provide.

  In order to solve the above-described problems, an ink jet recording apparatus according to the present invention is an ink jet recording apparatus that records an image on a recording medium using a recording head having an ejection port for ejecting ink, wherein the recording history of the recording head is used. An acquisition unit that acquires information on, a prediction unit that predicts a driving condition suitable for driving the recording head from a driving parameter according to the information, and the predicted driving condition and a driving condition in a range of the size A forming unit that forms a pattern; and a setting unit that reads and analyzes the pattern, calculates a driving condition suitable for driving the recording head during recording, and sets the driving condition of the recording head. It is characterized by that.

  According to the above-described configuration, the information regarding the print head usage history is acquired, and the drive condition is predicted according to this information. As a result, it is possible to predict an appropriate driving condition according to the change with time of the recording head.

  Further, according to the above configuration, since the pattern is formed under the predicted driving condition and the driving condition in a range of the predicted driving condition, the pattern is comparatively narrower than the conventional example in which the basic driving condition is basically fixed. A pattern can be formed under a range of driving conditions. Therefore, time is not required for pattern formation, reading and analysis processing. Further, since the resolution is not lowered, the pattern formation accuracy is not lowered, and the drive conditions of the drive element can be appropriately set based on the reading analysis result.

  Therefore, according to the present invention, it is possible to prevent the image quality from deteriorating by setting the driving condition of the recording head to an appropriate driving condition in accordance with the change with time of the recording head.

It is sectional drawing which shows the internal structure of an inkjet recording device. It is a schematic diagram which shows a recording head. It is a block diagram which shows the control structure of an inkjet recording device. It is a figure which shows an example of a control command. (A) And (b) is a graph which shows the change of the film thickness of a protective film. It is a graph which shows the relationship between an optimal drive pulse width and a dot count value. It is a flowchart which shows an example of operation | movement until the optimization process start of a drive condition. It is a flowchart which shows an example of the operation | movement which updates a dot count value. It is a flowchart which shows an example of operation | movement of the optimization process of a drive condition. It is a figure which shows the pattern for a correction | amendment. It is a graph which shows contrast with embodiment and a prior art example.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing the internal configuration of the inkjet recording apparatus 20. As shown in the figure, an inkjet recording apparatus 20 (hereinafter referred to as “recording apparatus 20”) is connected to a computer 30. The computer 30 supplies image data to the recording device 20. In the present embodiment, the recording device 20 records an image on a roll-shaped recording medium based on image data received from the computer 30.

  The recording device 20 includes a supply unit 1, a decurling unit 2, a skew feeding correction unit 3, a recording unit 4, a scanner unit 5 (reading unit), a cutter unit 6, an information recording unit 7, a drying unit 8, a winding unit 9, and a discharge unit. A transport unit 10, a sorter unit 11, a discharge tray 12, and a control unit 13 are provided. The control unit 13 includes a controller unit 15 (drive control unit) and a power supply unit 16. The control unit 13 controls each unit in the recording apparatus 20. The controller unit 15 receives image data from the computer 30. The power supply unit 16 supplies a voltage to each component in the recording apparatus 20.

  The supply unit 1 accommodates a roll-shaped recording medium wound around the rolls R1 and R2, and supplies the recording medium to the decurling unit 2. The decurling unit 2 reduces curling (warping) of the recording medium supplied from the supply unit 1. The skew correction unit 3 corrects the skew (tilt with respect to the original traveling direction) of the recording medium that has passed through the decurling unit 2. The recording medium whose skew has been corrected by the skew correction unit 3 is conveyed to the recording unit 4.

  The recording unit 4 forms an image on a recording medium and performs recording. In the present embodiment, the recording unit 4 records a correction pattern. The recording unit 4 is provided with a plurality of inkjet recording heads 14 (hereinafter referred to as “recording heads 14”). Each recording head 14 is a full-line type recording head, and has a length corresponding to the width of the recording medium of the maximum size expected to be used. Although details will be described later, the scanner unit 5 reads a correction pattern or the like recorded by the recording unit 4.

  The cutter unit 6 cuts the recording medium on which the image is recorded by the recording unit 4 into a predetermined length. The information recording unit 7 records information such as a serial number and date on a recording medium cut to a predetermined length by the cutter unit 6 as necessary. The drying unit 8 heats the recording medium and dries the ink or the like applied to the recording medium. When performing double-sided recording on the recording medium, the winding unit 9 temporarily winds the recording medium on which recording has been completed on one side. The wound recording medium is conveyed again to the recording unit 4 so that ink is applied to a surface different from the surface on which recording is completed.

  The discharge conveyance unit 10 conveys the recording medium dried by the drying unit 8 to the sorter unit 11. The sorter unit 11 discharges the recording medium to the discharge tray 12. The discharge tray 12 has a plurality of trays, and the recording medium sorted and discharged from the sorter unit 11 is placed on the tray. The recording apparatus 20 is provided with a transport mechanism having a plurality of roller pairs 17 and a belt, and the recording medium is transported along the transport path 18 by the transport mechanism.

  In the present embodiment, the recording unit 4 and the scanner unit 5 are disposed adjacent to each other. Therefore, after the image is recorded by the recording unit 4, the recording medium is conveyed to the scanner unit 5 disposed adjacent to the recording medium. However, the arrangement of the recording unit 4 and the scanner unit 5 in the present invention is not limited to this. As long as the correction pattern recorded on the recording medium can be read by the recording unit 4, the recording unit 4 and the scanner unit 5 are not necessarily arranged adjacent to each other.

  In the present embodiment, the recording unit 4 uses four recording heads. An ink tank (not shown) is connected to each of the four recording heads so that the corresponding ink can be supplied. Corresponding ink is supplied from the ink tank to each recording head via an ink tube (not shown). In the present embodiment, the ink tank contains cyan (C), magenta (M), yellow (Y), and black (K) inks, respectively.

  FIG. 2 is a schematic diagram showing the configuration of the recording head 14. In the drawing, one of the four recording heads is shown, but the other three recording heads have the same configuration. Each recording head is disposed substantially perpendicular to the recording medium conveyance direction (Y direction shown in the figure), and each of the four recording heads is disposed substantially parallel to each other.

  As shown in FIG. 2, eight chips 60 are arranged on the recording head 14 in a staggered pattern. A plurality of discharge port arrays 61 including a plurality of discharge ports are arranged on the chip 60. The plurality of discharge ports constituting the discharge port array 61 are arranged along a direction intersecting the Y direction (X direction shown in the figure). Each ejection port is provided with a driving element.

  The drive element includes, for example, a heating resistor element (heater) and a protective film that protects the heating resistor element. The heat generating resistor element generates heat when energized, causes the liquid (ink) to foam by the generated heat, and discharges the liquid (ink) from the discharge port by the foaming energy. The ejected ink droplets are applied to the recording medium to form dots on the recording medium, and the dots form an image, thereby recording on the recording medium. The protective film is used to protect the heating resistor element from an oxidation phenomenon caused by direct contact with ink. In the present embodiment, a case where a driving element composed of a heating resistor element and a protective film is used will be described.

  The recording head 14 includes electrode portions (not shown) at both ends in the discharge port arrangement direction (X direction shown in the drawing). This electrode part and the flexible wiring board (not shown) on the recording apparatus 20 side are electrically connected.

  The voltage is supplied to each drive element from the power supply unit 16 shown in FIG. In the present embodiment, a case will be described in which a plurality of chips 60 in the recording head 14 are used as a unit to uniformly supply a voltage. The voltage supply to the drive element of the recording head 14 can be switched on / off of voltage supply for each ejection port unit constituting the ejection port array 61 in each chip 60 by a DC-DC converter or the like. . However, from the viewpoint of the configuration of the recording apparatus 20, it is desirable to supply voltage uniformly to a plurality of chips.

  In the present embodiment, a configuration including a recording head that supplies ink of four colors C, M, Y, and K will be described. However, the type of ink color in the present invention is not limited to this. For example, a recording head that supplies ink such as light cyan ink, light magenta ink, red ink, and green ink may be provided. Further, the liquid supplied from the recording head is not limited to ink, and liquid that can be used for processing the recording medium and processing the ink (for example, solidification or insolubilization of the colorant contained in the ink applied to the recording medium). included.

  Further, the recording head 14 incorporates, for example, a nonvolatile memory (ROM 140 in the present embodiment). This nonvolatile memory is electrically connected to the flexible wiring substrate on the recording device 20 side.

  The recording head 14 has an effective ejection width of about 8 inches, and is substantially the same as the length (width) of the A4 size recording medium in the short side direction. Therefore, when the A4 size recording medium is conveyed in a portrait orientation, the liquid ejecting head has a length that allows continuous recording by one scanning of each recording head. In the present embodiment, the four recording heads 14 that respectively eject four colors of ink are the same liquid ejecting head, and these constitute a liquid ejecting recording apparatus capable of full color recording.

  The ROM 140 incorporated in the recording head 14 stores information on the recording head 14 at the time of shipment of the recording apparatus 20. Specifically, information on the optimum driving conditions at the time of shipment of the recording head 14 from the factory, and a use history (dot count value (total number of ink ejections)) for each ejection port in the recording head 14 by inspection at the factory, etc. And information about. Further, the ROM 140 has an area enough to write the optimum driving conditions measured after the recording head 14 is mounted on the recording device 20. The ROM 140 may store other information specific to the recording head other than the above information.

  Here, the optimum drive condition of the print head means that when the print head is used, the amount of ink discharged from the discharge port and the discharge timing are stable, and the durability (performance) of the drive element is sufficiently secured. It is a condition. This optimum driving condition is determined based on the threshold value of electric energy applied to the driving element when ink is ejected. That is, the optimum driving condition is calculated from a threshold value electric energy calculated from a fixed value in consideration of the stability of the ink ejection amount, the stability of the ejection timing, and the durability of the driving element.

  Here, the threshold electric energy is the lowest electric energy at which ink can be discharged from the discharge port. Therefore, there are cases where ink cannot be ejected with the threshold electric energy due to a variation in voltage due to external factors or a difference in the fine size of the ejection port. For this reason, the optimum driving condition is determined from a value that is equal to or greater than the threshold electric energy and that does not place an excessive burden on the driving element due to the supply of the electric energy. The method for determining the optimum drive condition will be described later in detail.

  In addition, the electric energy varies depending on the voltage applied to the driving element (applied voltage) and the time for applying the voltage (application time / driving pulse width). Therefore, the adjustment of the optimum driving condition can be performed by changing the applied voltage and / or the driving pulse width. In the present embodiment, a method for optimizing the driving condition by changing the driving pulse width will be described. However, by adjusting the applied voltage or both the driving pulse width and the applied voltage, The driving conditions may be optimized.

  In the present embodiment, the driving conditions are optimized with a predetermined number of chips 60 of the recording head 14 as a minimum unit. However, the driving conditions may be optimized in units of discharge ports or recording heads.

  FIG. 3 is a block diagram showing a control configuration of the recording apparatus 20. As shown in the figure, the controller unit 15 acquires information from the recording head 14 and the scanner unit 5.

  As shown in FIG. 3, the controller unit 15 includes a CPU 40, a ROM 51, a RAM 52, an interface (I / F) 53, and a timer 54. The CPU 40 comprehensively controls processing in the recording device 20. The ROM 51 records various programs and the like. The RAM 52 is used not only as a work area for the CPU 40 but also as a memory area for storing a dot count value, which will be described later. The I / F 53 is a communication interface that connects the recording device 20 and an external device (in this embodiment, the computer 30). The timer 54 counts down the timer value.

  Here, an example of a functional configuration realized by the CPU 40 will be described. As shown in FIG. 3, the CPU 40 includes a voltage supply control unit 41, an information acquisition unit 42, a dot count unit 43, a measurement unit 44, an update processing unit 45, an update unit 46, and a determination unit 47. The voltage supply control unit 41 performs control to apply the voltage supplied from the power supply unit 16 to the drive elements of the respective discharge ports. This control is performed with a predetermined number of chips 60 of the recording head 14 as one unit. Thereby, in the recording head 14, on / off of voltage supply is controlled in units of a predetermined number of chips 60.

  The information acquisition unit 42 acquires information on the optimum driving condition of the recording head 14 and usage history (dot count value) from the ROM 140 of the recording head 14. Further, the information acquisition unit 42 acquires the information of the scanned image of the recording medium from the scanner unit 5. The dot count unit 43 performs dot count control described later. The measuring unit 44 detects the gradation value of each band pattern of the correction pattern.

  The update processing unit 45 writes the dot count value obtained by the dot count unit 43 in the ROM 140. The update unit 46 updates the optimum drive condition measured by the measurement unit 44 to the set value in the RAM 52. The determination unit 47 determines whether or not to perform the measurement of the optimum driving condition on the basis of the dot count value obtained by the dot count unit 43. Although details will be described later, the update process is performed at regular time intervals according to the count-down of the timer value of the timer 54. Each of these configurations is realized by the CPU 40 reading and executing a program recorded in the ROM 51 using the RAM 52 as a work area.

  The scanner unit 5 includes an exposure lamp and a CCD (Charge Coupled Devices) sensor unit. The exposure lamp is used as a light source for irradiating the recording medium recorded by the recording unit 4 with light. The CCD sensor unit is composed of a CCD sensor (imaging device) and an optical system. The CCD sensor receives light irradiated from the exposure lamp and reflected from the recording medium. The optical system is for condensing all reflected light in the recording range of the recording medium on the CCD sensor, and a mirror, a lens, or the like is used. The scanner unit 5 irradiates a recording medium with light from an exposure lamp, and forms an image of the reflected light with a CCD sensor.

  The CCD sensor is composed of three linear sensors in which photodiodes that convert optical signals into electric signals are arranged in a line. The three linear sensors are arranged in parallel to each other.

  The CCD sensor includes three filters of R (red), G (green), and B (blue), and different color filters are provided for each linear sensor. Each linear sensor detects light of a component corresponding to the color of the filter. For example, a linear sensor including an R filter detects the intensity of red component light. The three linear sensors are arranged along a direction (X direction in FIG. 2) that intersects the recording medium conveyance direction (Y direction in FIG. 2).

  The recording medium is transported at a constant speed by the transport mechanism. At this time, the controller unit 15 reads the amount of light received by the CCD sensor at a predetermined cycle, thereby obtaining an image corresponding to the distance the recording medium has moved during one cycle as data for one line of the output image. Take in. At this time, three data of R component, G component, and B component are taken into the controller unit 15 as data for one line.

  FIG. 4 is a diagram illustrating an example of a control command. This control command is transmitted from the computer 30 shown in FIG. As shown in FIG. 4, for example, there are a format command 71, an image data command 75, a dot count command 78, and a job start command 80 as control commands. Each command 71, 75, 78, 80 is added with an identification code for the recording device 20 to identify.

  The format command 71 indicates the start of image data to be recorded. The format command 71 includes data 72 in the horizontal direction (discharge port array direction, X direction shown in FIG. 2) size of the recording area to be recorded on the recording medium, and the vertical direction (printing medium transport direction, Y direction shown in FIG. 2). ) Size data 73 and recording number data 74 are included.

  The image data command 75 includes a data length 76 indicating the length of the data, and image data (bitmap data) 77 in a bitmap format. The dot count command 78 includes dot count data 79. The dot count data 79 indicates a total value (dot count value) of the number of ejection dots ejected when each ejection port of the recording head 14 records the bitmap data 77.

  The job start command 80 includes only the identification code, thereby instructing the end of the recording data and the start of the recording job. The dot count command 78 counts the number of recording dots in the chip 60 unit or ejection port unit of the recording head 14. The counted value is stored in the RAM 52.

  Next, a driving parameter determination method in the present embodiment will be described. 5A and 5B are graphs showing changes in the thickness of the protective film of the drive element. FIG. 4A is a graph showing the relationship between the optimum drive pulse width and the protective film thickness, and FIG. 4B is a graph showing the relationship between the protective film thickness and the dot count value.

  In FIG. 5A, the horizontal axis indicates the thickness of the protective film, and the vertical axis indicates the optimum drive pulse width. As shown in FIG. 5A, the optimum drive pulse width is 0.75 μsec when the protective film thickness is 0.10 μm, and the optimum drive pulse width is 0.80 μsec when the protective film thickness is 0.20 μm. When the thickness of the protective film is about 0.26 μm, the optimum drive pulse width is 0.83 μsec. When the thickness of the protective film changes by 0.10 μm, the optimum driving pulse width changes by about 0.10 μsec.

  That is, when the thickness of the protective film is reduced from 0.20 μm to 0.10 μm, the optimum drive pulse width is shortened by about 0.10 μsec. It can be seen that, in order to transmit energy to the ink, it is sufficient to apply the voltage in a shorter time as the film thickness is smaller than in the case where the film thickness is larger. On the other hand, it is desirable to apply a voltage for a longer time as the protective film is thicker than when the protective film is thin.

  Therefore, the optimum driving pulse width increases as the thickness of the protective film of the driving element increases. On the other hand, the optimum driving pulse width decreases as the thickness of the protective film of the driving element decreases.

  In FIG. 5B, the horizontal axis indicates the dot count value, and the vertical axis indicates the thickness of the protective film. Ink A and ink B shown in FIG. 5B are different in ink type (coloring material and material).

As shown in FIG. 5B, when the dot count value is 2 × 10 ⁸ , the film thickness of the protective film of the drive element for the ejection port that ejects ink A is 0.20 μm, whereas the ink The film thickness of the protective film of the drive element of the discharge port for discharging B is about 0.22 μm. When the dot count value is 6 × 10 ⁸ , the thickness of the protective film of the ejection port driving element that ejects ink A is 0.15 μm, whereas the thickness of the ejection port driving element that ejects ink B is 0.15 μm. The thickness of the protective film is 0.20 μm.

  In both ink A and ink B, the film thickness of the protective film decreases as the dot count value increases, but the film thickness of ink A tends to decrease relative to ink B, and the film thickness of ink B decreases relative to ink A. I find it difficult. Thus, even if the dot count value is the same, the amount of change in the thickness of the protective film differs for each ink. Therefore, in order to accurately predict the optimum drive pulse width from the dot count value, it is desirable to grasp the relationship between the dot count value, the film thickness of the protective film, and the optimum drive pulse width for each ink type.

FIG. 6 is a graph showing the relationship between the optimum drive pulse width of ink A and the dot count value shown in FIG. In FIG. 6, the horizontal axis represents the dot count value, and the vertical axis represents the predicted optimum drive pulse width. As shown in the figure, when the dot count value is 2 × 10 ⁸ , the optimum drive pulse width is 0.80 μsec, and when the dot count value is 6 × 10 ⁸ , the optimum drive pulse width is 0.70 μsec. It is.

  As shown in FIG. 5B, the protective film thickness decreases as the dot count value increases. As shown in FIG. 5A, the optimum drive pulse width decreases as the protective film thickness decreases. . Therefore, as shown in FIG. 6, as the dot count value increases, the optimum drive pulse width becomes shorter. As described above, by deriving the relationship shown in FIG. 6 from the relationships shown in FIGS. 5A and 5B, the predicted optimum drive pulse width corresponding to the dot count value can be derived. In the present embodiment, the value derived in this way is used as a drive parameter.

  As described above, since the relationship between the dot count value and the film thickness of the protective film is different for each ink type, it is desirable to obtain the optimum drive pulse width corresponding to the dot count value for each ink type. Therefore, in order to calculate the predicted value of the optimum driving pulse, a relational expression representing these relations or a table of these correspondence relations is recorded or stored in a predetermined memory for each ink. In the present embodiment, the predicted value of the optimum drive pulse width of the drive element is calculated from the above relationship, and the optimum drive condition is set.

  Note that since one of the changes over time of the recording head can be a change in the thickness of the protective film, in this embodiment, the predicted value of the optimum drive pulse is calculated in consideration of the change in the thickness of the protective film. The method was explained. However, the predicted value of the optimum drive pulse may be calculated in consideration of other points as long as it is due to a change with time of the recording head.

  Next, the operation until the drive condition optimization process is started will be described. The drive condition optimization process in the present embodiment is executed when the recording head is first mounted on the recording apparatus and when the count value by the dot count control exceeds a predetermined value. The start timing of the optimization process is determined by the determination unit 47. FIG. 7 is a flowchart showing an example of the operation until the drive condition optimization process is started. The operation up to the start of the optimization process will be described with reference to FIG.

  The user turns on the power of the recording apparatus 20 (S700). Then, the CPU 40 confirms whether the drive pulse information measured by the recording apparatus 20 is present in the ROM 140 of the recording head 14 in addition to the optimum driving pulse information at the time of shipment (S701).

  When the optimum drive pulse information measured by the recording apparatus 20 does not exist (NO in S701), the CPU 40 determines that the recording head is attached to the recording apparatus 20 for the first time after shipment, and relates to the dot count value. First, drive condition optimization processing is executed (S706). This is because there is a possibility that the optimum driving conditions may change before the recording head mounted on the recording apparatus 20 for the first time after shipment.

  When the optimum drive pulse information measured by the recording apparatus 20 exists (YES in S701), the information acquisition unit 42 reads the dot count value from the ROM 140 of the recording head 14 (S702). Here, the CPU 40 starts dot count control at the dot count unit 43 (S703). At this time, the initial value of the dot count value is the value read in S702. The usage status of the recording head 14 is measured from this timing.

  Next, the CPU 40 starts update processing of the dot count value measured by the dot count unit 43 by the update processing unit 45 (S704). Details of the operation in S704 will be described later. If the dot count value is equal to or greater than the predetermined value (YES in S705), the drive condition optimization process is executed (S706). If the dot count value is not equal to or greater than the predetermined value (NO in S705), the dot count value is measured until the dot count value becomes equal to or greater than the predetermined value.

  The dot count value update processing is executed by overwriting the ROM 140 of the recording head 14 with the dot count value updated in the RAM 52 of the recording apparatus 20 at regular time intervals. The CPU 40 constantly monitors the dot count value counted according to the usage status of the printing apparatus 20, and executes the drive condition optimization process every time the dot count value exceeds a predetermined value (S706). The CPU 40 uses the determination unit 47 to determine whether or not to execute this optimization process.

  Further, it is desirable that the method for defining the predetermined value of the count value is determined by the degree of change in the optimum value of the driving condition of the recording head 14 due to use.

  Next, the operation of updating the dot count value in the ROM 140 of the recording head 14 will be described with reference to FIG. FIG. 8 is a flowchart showing an example of an operation for updating the dot count value. FIG. 8 shows an operation flow in S704 shown in FIG.

  When the update processing operation of the ROM 140 of the recording head 14 shown in S704 of FIG. 7 is started, the CPU 40 initializes the timer value by the timer 54 as shown in FIG. 8 (S800). Timer value countdown is started (S801). If CPU 40 determines that the timer value is not 0 (NO in S802), the countdown continues until the timer value becomes 0.

  If the CPU 40 determines that the timer value has become 0 (YES in S802), the CPU 40 acquires the dot count value stored in the RAM 52, and uses the update processing unit 45 to store the information in the ROM 140 of the recording head 14. Write (S803). As a result, the dot count value stored in the ROM 140 of the recording head 14 is updated. Thereafter, the process returns to S800 again, and the above-described process is repeatedly executed.

  As the timer value, for example, even when the update to the ROM 140 cannot be performed due to unexpected power OFF or the like, the amount of change in the optimum driving condition of the recording head 14 with respect to the dot count value of the recording head 14 It is desirable to set the value so that the estimation can be performed appropriately. The timer value is preferably set in consideration of the communication load due to writing to the ROM 140 of the recording head 14.

  With the above operation, the execution timing of the optimization process for the drive condition of the recording head 14 is determined.

  The drive condition optimization process executed in accordance with the start determination of the drive condition optimization process in S706 shown in FIG. 7 will be described with reference to FIG. FIG. 9 is a flowchart showing an example of the operation of the drive condition optimization process. If the optimum pulse information measured by the recording apparatus 20 in S701 shown in FIG. 7 does not exist, and if the dot count value is equal to or larger than the predetermined value in S705 shown in FIG. 7, the drive condition optimization process starts. (S706).

  Then, as shown in FIG. 9, the CPU 40 reads information on the current drive condition acquired from the ROM 140 of the recording head 14 using the information acquisition unit 42 (acquisition means / acquisition process) (S900). Further, the CPU 40 reads the dot count value of the target chip and the information (for example, ink type) of the filled chip from the ROM 140 using the information acquisition unit 42 (S901).

  Here, when the optimization process is not executed before the current optimization process (NO in S902), the CPU 40 shows an example in FIG. 6 based on the read dot count value and ink information. Referring to the table, the current predicted optimum drive condition is calculated (S903). Then, a predicted drive threshold value is calculated from the predicted optimum drive condition (S903 / prediction means / prediction process). Further, even when the optimization process has already been executed, when the previously updated optimum driving condition and the predicted optimum driving condition (FIG. 6) match (in the case of YES in S904), the same as above. Then, the current predicted drive threshold value is calculated (S903).

  On the other hand, when the optimization process has already been executed (YES in S902), the previously updated optimum drive condition does not match the previously predicted predicted optimum drive condition (FIG. 6) ( In the case of NO in S904), the fluctuation amount is calculated (S905).

  Based on the dot count value and the ink information read in S901, the CPU 40 adds or subtracts the above-mentioned variation to the optimum drive condition referring to the table of FIG. 6, thereby predicting the optimum optimum drive condition suitable for the current drive. Is calculated (S906 / prediction means / prediction step). Then, a current predicted drive threshold value (predicted drive threshold pulse width) is calculated from the predicted optimal drive condition (S906).

  Next, with the predicted drive threshold as the center value, the predicted drive threshold and its magnitude are set, and the correction pattern is recorded by the recording unit 4 (S907 / formation unit / formation step). Details of the correction pattern will be described later. The recording medium on which the correction pattern is recorded is transported to the scanner unit 5 by the transport mechanism.

  The scanner unit 5 reads the correction pattern recorded on the conveyed recording medium (S908). The RGB data read by the scanner unit 5 is read by the information acquisition unit 42 and stored in the RAM 52 (S908).

  Further, the measurement unit 44 analyzes the RGB data and detects the gradation value of each band pattern of the correction pattern (S908). The CPU 40 compares the detected gradation values of the respective band patterns, and detects the driving pulse width in which the ejection becomes unstable due to the change of the driving pulse width and the gradation value has changed (S908). The detected drive pulse width is the current drive threshold pulse width, and the optimum drive pulse width is calculated from this value (S908). That is, the optimum drive pulse width, which is the optimum drive condition suitable for actual recording, is calculated from the drive threshold pulse width.

  Next, the update unit 46 feeds back the calculated optimum drive condition (optimum drive pulse width) to the recording unit 4 and updates the drive condition (S909 / setting means / setting step). The update processing unit 45 updates the optimum driving condition by overwriting the ROM 140 of the recording head 14 (S910). Then, the optimization process ends. This overwritten information is used at the next update. By performing such a series of processes, the print head drive condition optimization process is executed.

  FIG. 10 is a diagram showing the correction pattern 100. The correction pattern 100 is composed of a plurality of band patterns. Each band pattern has a length corresponding to the effective ejection width of the recording head 14 and is a rectangular pattern that is long in the X direction. The correction pattern 100 shown in the figure is an example of a band pattern recorded in S907 in FIG. As shown in the figure, the band pattern 200 and the band pattern 201 have different densities.

  Each band pattern is formed in accordance with pattern data having the same gradation value, but the drive pulse width set for each band is different as described above. As a result, the ejection becomes unstable, and the drive pulse width in which the gradation value has changed becomes the drive threshold pulse width. Therefore, as shown in FIG. 10, in the correction pattern 100, since the gradation value is changed in the band pattern 201, the drive pulse width applied to the drive element used for recording the band pattern 201 is This is the drive threshold pulse width.

  The correction pattern 100 is intended to confirm ejection failure due to a difference in drive pulse width. Therefore, the pattern layout is not limited to the above. In addition to the band pattern, a preliminary discharge pattern for confirming the state of the recording head may be recorded on the recording medium.

  The effect of this embodiment will be described as follows in comparison with the conventional example. FIG. 11 is a graph comparing the range of drive pulse conditions for recording a correction pattern in this embodiment with that according to the conventional example. In the figure, the horizontal axis indicates the dot count value, and the vertical axis indicates the predicted optimum drive pulse width.

  In this embodiment, when the recording head is mounted on the recording apparatus for the first time after shipment, and when the dot count value exceeds a predetermined value, the drive condition optimization process is executed. In FIG. Only the optimization process when the value exceeds the predetermined value will be described. Dotted lines L1 to L4 in the figure indicate the timing of optimization processing that is executed each time the dot count value exceeds a predetermined value, and the optimization processing is executed in the order of dotted lines L1 to L4. A dotted line L3 indicates the execution timing of the current optimization process.

  FIG. 11 is also a graph for the ink A shown in FIG. Near the dotted line L3 indicating the current processing timing, the range of the drive pulse width when the pattern is recorded in the present embodiment and the range of the drive pulse width when the pattern is recorded in the conventional example are shown. In the present embodiment, the center value C1 of the drive pulse width range is the predicted drive threshold value.

  The center value C2 of the drive pulse width at the current processing timing in the conventional example is the same value as the center value C3 of the drive pulse width at the previous processing timing in the conventional example. This is because, in the conventional example, the drive condition (drive voltage in the conventional example) is changed according to the temperature in the recording apparatus. It is to become.

  Therefore, in the conventional example, in any dot count value, in order to record a pattern with a value including the predicted drive threshold value, the pattern must be recorded for each drive pulse width belonging to a relatively wide range. Even if the temperature changes, in the conventional example, the reference drive voltage is basically fixed, so that a pattern for each drive pulse width belonging to a relatively wide range is included in order to include the predicted drive threshold. There is no change in having to record.

  For this reason, it takes time to record the pattern, and it also takes time to analyze the pattern in the scanner unit. Further, since the range of the drive pulse width for recording the pattern is wide and the pattern is recorded for each drive pulse width belonging to the range, a large amount of recording medium is consumed.

  In contrast, in the present embodiment, the relationship between the dot count value and the drive pulse width is grasped in advance, and the optimum drive condition is predicted. Therefore, as shown in FIG. 11, when the range of the drive pulse width for recording the correction pattern 100 in the present embodiment and the range of the drive pulse width for recording the correction pattern in the conventional example are compared, The range is narrower.

  Therefore, in this embodiment, by recording a pattern for each drive pulse width belonging to a relatively narrow range, a drive pulse width suitable for the recording can be selected. By doing so, it is possible to set the driving condition of the driving element (driving pulse width in the present embodiment) to the optimum driving condition corresponding to the change in the print head without reducing the resolution in the conventional example.

  Further, in the present embodiment, since the pattern is recorded only for each drive pulse width belonging to a relatively narrow range, the time for recording the pattern can be shortened as compared with the conventional example. The time for analysis can also be shortened. In addition, since the number of patterns to be recorded can be reduced as compared with the conventional example, the consumption of the recording medium can be minimized.

  As described above, in the present embodiment, the pattern is recorded without reducing the resolution as compared with the conventional case. Therefore, the pattern can be formed without reducing the pattern formation accuracy. As a result, the drive conditions set by reading and analyzing this pattern can also be appropriately set.

  Therefore, in the present embodiment, since it is possible to set an optimum driving condition according to the change with time of the recording head, it is possible to prevent a decrease in image quality due to a change in ink ejection amount or a deviation in ink ejection timing. be able to.

14 Recording head 20 Inkjet recording apparatus

Claims (6)

An inkjet recording apparatus that records an image on a recording medium using a recording head having an ejection port for ejecting ink,
Obtaining means for obtaining information relating to the use history of the recording head;
Predicting means for predicting a driving condition suitable for driving the recording head from a driving parameter in accordance with the information;
Forming means for forming a pattern under the predicted driving condition and a driving condition in a range of the size;
An inkjet recording apparatus comprising: setting means for reading and analyzing the pattern, calculating a driving condition suitable for driving the recording head during recording, and setting the driving condition of the recording head .   2. The ink jet recording apparatus according to claim 1, wherein the driving condition is a voltage applied to the recording head, a time during which a voltage is applied to the recording head, or both.   3. The ink jet recording apparatus according to claim 1, wherein the use history of the recording head is a total number of ink ejections.   4. The ink jet recording apparatus according to claim 1, wherein the information about the usage history of the recording head includes information about a type of ink ejected from the recording head. 5. A reading unit for reading the pattern;
The ink jet recording apparatus according to claim 1, wherein the reading unit is a scanner having a light source and an image sensor. A method for setting driving conditions of an ink jet recording apparatus that records an image on a recording medium using a recording head having an ejection port for ejecting ink,
An acquisition step of acquiring information relating to the usage history of the recording head;
A predicting step of predicting a driving condition suitable for driving the recording head from a driving parameter according to the information;
A forming step of forming a pattern under the predicted driving condition and a driving condition within a range of the driving condition,
A setting step of reading and analyzing the pattern, calculating a driving condition suitable for driving the recording head at the time of recording, and setting the driving condition of the recording head. Setting method.

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