JP2006168074A - Inkjet recording apparatus and preliminary delivery controlling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording apparatus and a preliminary delivery controlling method capable of sufficiently drawing out delivery restoring effects of respective nozzles and suppressing unnecessary discharging of ink accompanied with preliminary delivery as much as possible. <P>SOLUTION: The number of the next preliminary delivery during recording operation is set on every nozzle in accordance with the delivery downtime for an individual nozzle. As it is possible thereby to practice the preliminary delivery in use by an appropriate number to the individual nozzle even when a deviation on delivery frequency among a plurality of the nozzles during recording, it becomes possible to keep a stable delivering condition of a recording head under a condition that consumption of the ink is decreased as much as possible. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink jet recording apparatus and a discharge control method, and more particularly to an ink jet recording apparatus and a preliminary discharge control method for efficiently performing preliminary discharge for performing discharge recovery processing of an ink jet recording head.

  Inkjet recording apparatuses have many advantages such as being easy to downsize, low noise, and being inexpensive, and are widely used as various printing apparatuses including computer output apparatuses. Such an ink jet recording apparatus is generally equipped with an ink jet recording head having a nozzle group composed of a plurality of nozzles. A pulse voltage as a drive signal is selectively applied to each nozzle according to the image data, and the drive element in the nozzle operates thereby to eject ink as droplets. ing. The ejected ink droplets land on a desired position on the recording medium to form dots. In the recording medium, a desired image is expressed by an array of a plurality of dots landed according to image data.

  In general, a plurality of ejection openings for ejecting ink droplets are arranged on the same plane of an ink jet recording head and are exposed to the outside air under similar conditions. On the ink surface exposed to the outside air, a volatile solvent component such as water or alcohol contained in the ink evaporates, and the concentration of the nonvolatile component becomes relatively high. As a result, the viscosity of the ink increases, which may adversely affect the discharge state of the recording head. Therefore, in a general ink jet recording apparatus, when the recording head is in a standby state, a capping unit that covers all the ejection openings of the nozzle group with a cap member formed of rubber or the like and suppresses ink evaporation from the ejection openings. Is provided.

  However, even in a recording apparatus having such a capping unit, it is difficult to eliminate the gas that permeates the cap member. As the waiting time becomes longer, the concern about ejection failure due to evaporation gradually increases. Therefore, in order to avoid such a concern, a so-called preliminary ejection operation in which ejection unrelated to an image is preliminarily performed is generally employed. Such a preliminary ejection operation is performed by applying several to several thousand drive pulses to all the nozzles with respect to the print head immediately before printing.

  The preliminary ejection operation can exert its effect not only immediately before the recording operation but also during the recording. In the process of executing recording according to image data, the discharge frequency is inevitably biased among the plurality of nozzles. For example, in a nozzle in which ink is frequently ejected from the ejection port in accordance with the recording signal, ink near the ejection port is newly filled one after another, so that some ink evaporation is unlikely to be a problem. However, on the other hand, in the nozzles that have not been ejected for a certain period of time, the evaporation of the ink and the increase in viscosity are promoted compared to other nozzles. That is, the recording head partially includes nozzles having increased ink viscosity, and thus includes a cause of ejection failure.

  Even in such a case, it is possible to suppress the concern about ejection failure by executing the preliminary ejection operation at an appropriate timing during the recording operation. At this time, even if the nozzles are frequently ejected during recording, the image quality is not deteriorated by further adding the number of ejections. Therefore, the timing and number of pre-ejections during recording are generally determined for nozzles that have not ejected within the elapsed time from the previous pre-ejection operation. That is, assuming such a state of viscosity in the nozzles, the number of shots sufficient to discharge ink whose viscosity has been increased is determined, and this number of shots is applied to all nozzles. Determining the number of preliminary ejections common to all nozzles based on the nozzle with the least ejection frequency is a suitable control method for maintaining the reliability of the recording head without performing complicated drive control. It is.

  In the preliminary ejection operation, several methods have already been proposed for determining the appropriate number of preliminary ejections as much as possible while avoiding unnecessary ejection. For example, Patent Document 1 discloses the content of measuring the interval time between the previous ink discharge and the next ink discharge and executing the preliminary discharge the number of times corresponding to the measured value before recording. Japanese Patent Application Laid-Open No. 2004-228561 discloses contents for adjusting the total ink amount discharged by the spit operation (preliminary ejection) during the recording operation based on the image data. According to this document, an appropriate number of ejections (number of dots) in the current spit operation is determined according to the presence / absence of ejection from the previous spit operation and the presence / absence of ejection until the next spit operation. Further, according to Patent Document 3, in an inkjet recording apparatus having a recording head composed of a plurality of discharge ports having a heat source, a preliminary recording is performed according to past printing history such as the number of printing pulses, printing time, and printing area. The contents for controlling the discharge operation are disclosed. According to this document, the number of drive pulses per unit time is calculated, and when this value exceeds the allowable value, the ejection recovery process (preliminary ejection or the like) of the recording head is performed.

JP 10-34974 A JP 2003-231272 A JP 2000-127443 A

  By the way, in recent years, while the demand for higher image density and higher robustness has been increasing, improvement of highly functional inks in response to these demands has also been promoted. In many cases, the amount of water is reduced as compared with conventional materials. Therefore, in the ink jet recording head, the increase in viscosity accompanying ink evaporation from the ejection port has become more conspicuous than in the past. On the other hand, in order to increase the recording resolution and recording speed of an image, the number of nozzles provided in the recording head and the density of the nozzles are increased, and the technology for reducing the droplet size of each nozzle has been promoted. Along with this, the surface area of the ink exposed to the outside air in one recording head also increases, and the amount of ink evaporation per unit time tends to increase compared to the conventional case.

  That is, in recent ink jet recording apparatuses, the amount of ink evaporated from the recording head, the viscosity increase due to evaporation, and the discharge failure associated therewith appear more conspicuous than before, and the preliminary discharge operation as described above is more frequent. Is needed. In addition, the amount of ink discharged by such frequent preliminary ejection operations is newly regarded as a problem.

  As described above, in a nozzle that ejects ink relatively frequently during a recording operation, ink in the vicinity of the ejection opening is newly filled one after another, and the problem due to thickening in particular is unlikely to occur. That is, it can be said that the necessity for executing the preliminary ejection is low compared to the others. However, in the case where the preliminary ejection that is frequently required as in recent years is performed for all the nozzles in the same manner as in the past, the amount of ink that is wasted is increased due to the number of preliminary ejections more than necessary. This is a quantity that cannot be ignored. This is because excessive consumption of ink invites an increase in running cost.

  According to the patent documents already described, it was possible to adjust the number of preliminary ejections according to the situation in order to prevent unnecessary preliminary ejection as much as possible. However, the number of preliminary discharges determined here is set in a state where the number of preliminary ejections is uniformly or uniformly distributed with respect to all the nozzles arranged in the recording head. That is, the number of discharges of all nozzles is determined according to the nozzle with the lowest discharge frequency, and the above problem cannot be solved sufficiently.

  The present invention has been made to solve the above-described problems, and the object of the present invention is to sufficiently bring out the discharge recovery effect of each nozzle and to suppress unnecessary ink discharge associated with preliminary discharge as much as possible. It is an object of the present invention to provide an ink jet recording apparatus and a preliminary discharge control method that can be used.

Therefore, in the present invention, an inkjet recording apparatus that forms an image on a recording medium using an inkjet recording head having a plurality of nozzles that eject ink in accordance with image information, the preliminary recording is independent of the image formation. For each of the plurality of nozzles, the time elapsed since the previous discharge was performed is counted as a discharge pause time, and the count value is obtained each time a new discharge is performed. Discharge rest time measuring means for resetting, and setting means for setting the number of preliminary discharges for the preliminary discharge for each individual nozzle according to the discharge pause time of each nozzle obtained by the discharge pause means The preliminary ejection unit is configured to set the individual ejection unit set by the setting unit at a predetermined timing in the image forming process. And executes a preliminary discharge in accordance with the preliminary ejection number of nozzle.

  Also, a preliminary ejection control method for performing preliminary ejection regardless of formation of an image on a recording medium using an inkjet recording head having a plurality of nozzles that eject ink according to image information, For each of the plurality of nozzles, a discharge pause time measuring step of counting an elapsed time since the last discharge is executed as a discharge pause time, and resetting the count value each time a new discharge is executed, A setting step for setting the number of preliminary ejections for the preliminary ejection for each of the individual nozzles according to the ejection pause time of the individual nozzles obtained by the ejection pause step, and the image forming process. Preliminary ejection corresponding to the number of preliminary ejections of the individual nozzles set in the setting step is executed at a predetermined timing in step (b).

  According to the present invention, it is possible to realize reliable preliminary discharge with a smaller number of shots than in the prior art. Therefore, it is possible to maintain a stable ejection state of the recording head while reducing ink consumption as much as possible. In addition, since it is not necessary to perform a new carriage movement scan for the preliminary ejection operation, it is possible to reduce the running cost without extending the recording time.

(First embodiment)
The first embodiment of the present invention will be described below in detail with reference to the drawings.

(Configuration of inkjet recording apparatus)
FIG. 1 is an outer shell configuration diagram of an ink jet recording apparatus applied to an embodiment of the present invention. The outer shell of the ink jet recording apparatus main body M1000 in this embodiment includes an outer member including a lower case M1001, an upper case M1002, an access cover M1003, and a paper discharge tray M1004, and a chassis M3019 housed in the outer member (see FIG. 2). ).

  The chassis M3019 is composed of a plurality of plate-like metal members having a predetermined rigidity, forms a skeleton of the recording apparatus, and holds each recording operation mechanism described later. The lower case M1001 forms a substantially lower half of the outer shell of the recording apparatus main body M1000, and the upper case M1002 forms a substantially upper half of the outer shell of the recording apparatus main body M1000. The combination of both cases will be described later. It has a hollow body structure having a storage space for storing each mechanism. An opening is formed in each of the upper surface portion and the front surface portion of the recording apparatus main body M1000.

  One end of the discharge tray M1004 is rotatably held by the lower case M1001, and the opening formed on the front surface of the lower case M1001 can be opened and closed by the rotation. Therefore, when executing the recording operation, the discharge tray M1004 is rotated to the front side to form the opening, so that the recording medium can be discharged from the recording medium and the discharged recording media are sequentially stacked. To get. The paper discharge tray M1004 stores two auxiliary trays M1004a and M1004b, and the support area of the recording medium can be expanded or reduced in three stages by pulling each tray forward as necessary. It is like that.

  One end of the access cover M1003 is rotatably held by the upper case M1002, and an opening formed on the upper surface can be opened and closed. By opening the access cover M1003, the print head cartridge H1000 (see FIG. 3) or the ink tank H1900 (see FIG. 4) housed in the main body can be replaced. Although not specifically shown here, when the access cover M1003 is opened and closed, the protrusion formed on the back surface rotates the cover opening and closing lever, and the rotation position of the lever is detected by a micro switch or the like. Thus, the open / closed state of the access cover can be detected.

  On the upper surface of the rear portion of the upper case M1002, a power key E0018 and a resume key E0019 are provided so that they can be pressed, and a display lamp E0020 is provided. This is to inform the user of the recording apparatus. Further, the display lamp E0020 has various display functions such as notifying the user of troubles of the recording apparatus or the like by the manner of blinking or color change. It is also possible to make a buzzer. If the trouble is solved, the recording operation is resumed by pressing the resume key E0019.

(Operation mechanism of inkjet recording apparatus)
FIG. 2 is a configuration diagram for explaining the internal mechanism of the inkjet recording apparatus H1000. As a recording operation mechanism in the present embodiment, an automatic feeding unit M3022 that automatically feeds a recording medium into the apparatus main body, and a recording medium that is sent one by one from the automatic feeding unit M3022 are set at predetermined recording positions. A conveyance unit M3029 for guiding the recording medium from the recording position to the discharge unit M3030, a recording unit for performing desired recording on the recording medium conveyed to the recording position, and suction and wiping for the recording unit, etc. The recovery unit M5000 performs the recovery process.

  The recording unit includes a carriage M4001 that is movably supported by a carriage shaft M4021, and a recording head cartridge H1000 (see FIG. 3) that is detachably mounted on the carriage M4001, and ejects ink into the recording head cartridge H1000. There are six colors of discharge sections composed of a plurality of nozzles.

  The recovery unit M5000 includes a suction pump for removing ink and air bubbles whose viscosity has greatly increased in the nozzle and the flow path of the recording head cartridge H1000, a wiper for wiping off ink and dust adhering to the discharge unit, Caps are provided for protecting the ejection openings during the standby of the recording head cartridge H1000 and suppressing the evaporation of ink existing in the nozzles, as well as a preliminary ejection receiver for receiving ink discharged by preliminary ejection. The preliminary ejection operation that is a feature of the present invention will be described in detail later.

(Inkjet recording head)
FIG. 3 is a schematic perspective view of an ink jet recording cartridge applied to this embodiment.
As shown in the drawing, the recording head cartridge H1000 in this embodiment includes an ink tank H1900 that stores ink, and an ink jet recording head H1001 that discharges ink supplied from the ink tank H1900 from a nozzle group in accordance with recording information (hereinafter, “ Recording head ”). The recording head H1001 is detachably mounted on the carriage M4001 described above.

  FIG. 4 is a configuration diagram for explaining a state in which an ink tank is attached to and detached from the recording head H1001. The recording head cartridge H1000 of this embodiment is provided with independent ink tanks H1900 for each color of black, light cyan, light magenta, cyan, magenta, and yellow in order to enable the formation of a photographic image with high quality. Each ink tank H1900 is detachable independently from the recording head H1001, as shown in the figure. Below the recording head H1001, there is formed an ejection port array in which 300 ejection ports are arranged in a row at an arrangement pitch of 600 dpi for each color. Since six color ink tanks are used in this example, six rows of ejection port arrays are arranged, and nozzles each including an electrothermal converter are arranged in these ejection ports.

(carriage)
Returning again to FIG. The carriage M4001 includes a carriage cover M4002 for guiding the recording head H1001 to a predetermined mounting position on the carriage M4001, and a head set lever M4007 that presses the recording head H1001 so as to be engaged with the recording head H1001 and set to the predetermined mounting position. Is provided. That is, the head set lever M4007 is provided on the upper part of the carriage M4001 so as to be rotatable with respect to the head set lever shaft, and a head set plate (not shown) is provided via a spring at the engaging portion with the recording head H1001. Thus, the recording head H1001 is pressed by the spring force and is mounted on the carriage M4001.

  A contact flexible cable E0011 is provided at another engagement portion of the carriage M4001 with the recording head H1001, and a contact portion on the contact flexible cable E0011 and a contact portion provided on the recording head H1001 (external signal input terminal, not shown). Are in electrical contact with each other to exchange information for recording and supply power to the recording head H1001.

  An elastic member such as rubber (not shown) is provided between the contact portion of the contact flexible cable E0011 and the carriage M4001, and the contact portion and the carriage M4001 are connected by the elastic force of the elastic member and the pressing force of the headset lever spring. A reliable contact is made possible. Further, the contact flexible cable E0011 is connected to a carriage substrate (not shown) mounted on the back surface of the carriage M4001.

(Discharge control)
FIG. 5 is a block diagram for explaining a control configuration in the ink jet recording apparatus of the present embodiment. In the figure, a CPU 400 executes control of each part of the apparatus and data processing via a main bus line 405. The CPU 400 controls data processing, head driving, and carriage driving via each unit described below by executing a program stored in the ROM 401 (including a program for performing preliminary ejection control described in the following embodiment). . At this time, the RAM 402 is used as a work area for data processing by the CPU 400. As a storage device used as a memory, a hard disk or the like may be used in addition to the RAM.

  The image input unit 403 has an interface with a host device connected to the outside, and temporarily holds image data input from the host. The image signal processing unit 404 executes data processing such as color conversion and binarization.

  The operation unit 406 includes the power key E0018 and the resume key E0019 described above, and allows an operator to input instructions.

  The recovery system control circuit 407 controls recovery operations such as suction, wiping, and preliminary ejection in accordance with a recovery processing program stored in the ROM 401. The recovery system motor 408 drives the recording head H1001 and the cleaning wiper 409, the cap 410, and the suction pump 411 facing and separating from the recording head H1001.

  The head drive control circuit 416 controls the drive of the electrothermal transducer for causing ink to be ejected from the ejection port array below the recording head H1001, thereby executing ink ejection and preliminary ejection for image formation.

  Similarly, the carriage drive control circuit 417 and the paper feed control circuit 418 are driven by the CPU 400 executing a program, and control carriage movement and paper feed, respectively.

  With these two control circuits, the recording head H1001 mounted on the carriage M4001 can be driven and controlled with an accuracy of 1200 dpi in the scanning direction, and ink can be ejected with the same accuracy. Obtainable.

  The preliminary ejection control unit 100 is provided in a form linked to the head driving circuit 416, and includes a clock 415 for measuring the ejection pause time of each nozzle in the recording head H1001, and an ejection pause time measurement for measuring the ejection pause time. A circuit 413, a discharge pause time storage circuit 412 for updating and storing the measured discharge pause time, and a discharge count storage circuit 414 for accumulating and storing the number of discharges at the nozzle each time the discharge pause time is updated are provided. Further, the discharge pause time storage circuit 412 and the discharge count storage circuit 414 are provided with RAMs for storing nozzle unit data.

(Preliminary discharge)
Hereinafter, the recording operation in the present embodiment and the preliminary ejection operation performed during the recording operation will be described.

  Since the recording apparatus of the present embodiment is a serial type ink jet recording apparatus, the recording head H1001 mounted on the carriage M4001 is arranged substantially parallel to the paper feed direction for each color 300 while moving as the carriage M4001 scans. Ink is ejected from the nozzles. In order to execute this ejection, the head drive circuit 416 applies a pulsed electrical signal at a frequency of 10 kHz to each electrothermal transducer of the recording head H1001, and ink is ejected from one nozzle at intervals of 100 μs. Can be continuously discharged. However, the actual ejection is configured such that the pulse is selectively applied by a recording signal based on image data.

  Here, if the recording width of the recording medium is 8 inches, the recording density in the main scanning direction is 1200 dpi, so the maximum number of recording dots in the main scanning direction is 9600 dots. That is, the time required for printing in one printing scan is 0.96 seconds. Further, considering the acceleration / deceleration time of the carriage drive motor and the reversal switching time in the moving scanning direction, the maximum required time for one printing scan can be determined to be approximately 1 second.

  In the recording apparatus of the present embodiment, the preliminary ejection operation is set to be performed at intervals of 5 seconds even during the recording operation. At the time of implementation, interrupt control from the preliminary ejection control unit 100 is performed on the head drive control circuit 416 by using ejection pulse generation timing.

  Hereinafter, a recording operation after an image signal is input and a preliminary ejection operation performed in accordance with the recording operation will be described.

  In the standby state before the image signal is input, the cap provided in the recovery unit M5000 is in contact with the ejection port array of the recording head H1001. Therefore, when an image signal is input from the host device, first, the cap covering the ejection port array of the recording head H1001 is opened. Thereafter, after performing preliminary discharge from all nozzles in accordance with the standby time and predetermined initialization processing such as wiping operation, ink discharge according to the image data is started from the necessary nozzles for each discharge cycle. . The process is transferred to the preliminary discharge control unit 100 in FIG. 5 at each discharge timing.

  FIG. 6 is a flowchart for explaining a preliminary discharge operation process in the preliminary discharge control unit 100. Here, for the sake of simplicity, the description is given using eight nozzles for convenience. Further, although this flowchart is applied to ink for one color, in the present embodiment, the same flowchart can be assigned to nozzles for other five colors. The six colors of ink filled in the ink tank H1900 of this embodiment have different color materials, but the other components are prepared with substantially the same, and the types and amounts of volatile components are also six colors. This is because they can be regarded as almost the same.

  In the preliminary discharge control unit 100, first, a time t that has elapsed since the previous preliminary discharge operation is acquired (step S501). If this time is immediately before the start of the recording operation and immediately after the cap is opened, the preliminary ejection performed in the initialization process corresponds to the previous preliminary ejection here.

  In step S502, it is determined whether or not the acquired elapsed time t is 5 seconds or more. If the determination result is less than 5 seconds, the process in the preliminary ejection control unit 100 ends, and the process proceeds to ejection control for the next dot. On the other hand, if the elapsed time t is 5 seconds or more, it is determined that the timing corresponds to the timing for performing preliminary ejection during recording, and the process proceeds to step S503.

  In step S503, it is determined whether the carriage M4001 is positioned at the end of the recording area. If the carriage M4001 is not positioned at the end of the recording area, it is determined that it is not yet time to execute preliminary ejection, and the processing in the preliminary ejection control unit 100 is terminated. On the other hand, if it is determined that the carriage M4001 is positioned at the end of the recording area, the process proceeds to step S504.

  As described with reference to FIG. 2, the ink jet recording apparatus according to the present embodiment is configured such that the preliminary ejection operation is performed at the position of the recovery unit M5000. Therefore, even if it is determined in step S502 that t is 5 seconds or more, if the recording head is in the middle of recording scanning, the preliminary ejection cannot be executed here. At this time, the ink ejection is interrupted even during the recording, the preliminary ejection is performed after the carriage M4001 is moved to the position of the recovery unit M5000, and the carriage M4001 is returned to the recording interruption position again. You can also In this case, however, the ink landing position is deviated before and after the recording is interrupted, and the entire recording time is increased due to the extra time associated with the movement of the carriage M4001. Connected. In the present exemplary embodiment, when the preliminary ejection operation during recording has been performed for 5 seconds or more from the previous preliminary ejection and the carriage M4001 is at the end of the recording area, according to the determination process in steps S502 and S503. Try to run into. That is, the preliminary ejection operation during recording in the present embodiment is configured to be performed at a predetermined position without increasing the recording time as much as possible.

  In step S504, the carriage M4001 is positioned at the recovery unit M5000, and preparations for performing preliminary discharge are made.

  In subsequent step S505, the ejection pause time of each nozzle is acquired from the pause time storage circuit 412 in the preliminary ejection control unit 100. In this example, since there are eight nozzles, the discharge pause time of each nozzle is s (1) to s (8) in the order of arrangement here.

  In step S506, the number of preliminary ejections e (1) to e (8) to be applied to each nozzle is set with reference to a lookup table (LUT) prepared in advance.

  FIG. 7 is a diagram showing the LUT. This table applied to the present embodiment has been experimentally obtained by the inventor after earnest examination, and the accompanying change in the amount of ink evaporated from the ejection port according to the standing time of 5 seconds or less. In consideration of the thickened state of ink, the number of preliminary ejections sufficient to recover one nozzle from this thickened state is determined.

  In subsequent step S507, the number of ejections of the nozzle adjacent to each nozzle is obtained from the ejection number storage circuit 414 for each nozzle. Here, for the nozzle of interest, the total value of the number of ejections of the two nozzles located on both sides thereof is obtained as the adjacent nozzle total number of ejections p. For example, when the target nozzle is the fourth nozzle in the group of eight nozzles, the adjacent nozzles are the third nozzle and the fifth nozzle. Therefore, the number of ejections of these two nozzles is summed, and the result is the total number of ejections of adjacent nozzles p (4) of the fourth nozzle. In this way, after obtaining the total number of adjacent nozzle discharges p (1) to p (8) for all nozzles, the process proceeds to step S508.

  FIG. 8 is an LUT for installing a preliminary discharge number reduction coefficient with respect to the total number of adjacent nozzle discharges. In step S508, referring to the LUT shown in FIG. 8, the preliminary discharge reduction coefficient corresponding to p (1) to p (8) of the total number of adjacent nozzle discharges acquired in step S507 is set for each nozzle. Ask. Subsequently, the preliminary ejection number e (1) to e (8) once set in step S506 is multiplied by the respective preliminary ejection number reduction coefficient, and the result is the final preliminary ejection number e (1) to e ( 8) is newly set.

  Steps S507 and S508 described above are steps for taking into account not only the discharge history of individual nozzles but also the effect of meniscus vibration that is affected by the discharge of adjacent nozzles. The “meniscus vibration” and the effect on the thickened ink will be described below.

  Depending on the actual image data, even if the nozzle does not perform the ejection operation and has a long pause time, if the neighboring nozzles, especially the neighboring nozzles, are driven, the influence of vibration associated with the ink ejection of the neighboring nozzles will be affected. In response, a phenomenon in which the meniscus in the nozzle vibrates is known. Such a phenomenon is called “meniscus vibration”. When the “meniscus vibration” occurs, the ink in the nozzle flows to some extent, so that even if the volatile component evaporates at the tip of the nozzle, the viscosity distribution is diffused in the nozzle. In other words, in each nozzle, it may be possible to stabilize the ejection state with a smaller number of preliminary ejections than the number of preliminary ejections required based on the ejection pause time.

  Such “meniscus vibration” has a greater influence from adjacent nozzles as the nozzle arrangement density is higher, so that the degree of vibration and the effect of ink diffusion are also greater. In the case of applying a recording head having an arrangement density of 600 dpi as in the present embodiment, the amount of ink consumed more wastefully for preliminary ejection can be further increased by taking into account the influence of “meniscus vibration”. Can be reduced.

  Therefore, it is possible to further reduce the number of wasteful preliminary discharges by suppressing the number of preliminary discharges according to the state of meniscus vibration. The preliminary discharge number reduction coefficient shown in FIG. 8 is obtained experimentally by the inventors by estimating the ink diffusion state in the nozzle from the state of meniscus vibration that fluctuates according to the number of discharges of adjacent nozzles. ing.

  In step S509, the preliminary discharge of each nozzle is executed according to the number determined in step S508.

  After the preliminary discharge operation, in step S510, the currently set discharge pause times s (1) to s (8) and the adjacent nozzle total discharge times p (1) to p (8) are set. Reset everything. This is because, at the time when the preliminary discharge is executed in step S509, the previous discharge pause time becomes unnecessary.

  Thus, a series of control steps in the preliminary discharge control unit 100 is completed. When the preliminary ejection operation is completed, the carriage M4001 moves from the position of the recovery unit M5000 into the image forming area, and starts the next recording scan according to the image data. And the preliminary discharge control for every drive pulse period demonstrated with the said flowchart is restarted.

  In step S508, the number of preliminary discharges calculated by multiplying the preliminary discharge reduction coefficient may not be an integer. For example, it is assumed that the discharge pause time t of the nozzle of interest is 4.7 seconds and the total discharge count p of adjacent nozzles is 35000 times. In this case, in step 506, the number of preliminary ejections is selected as 12, and in subsequent step S508, 0.9 is selected as the preliminary ejection number reduction coefficient. Therefore, the final number of preliminary discharges is 12 × 0.9 = 10.8, and there is a value after the decimal point. In such a case, in the present embodiment, the number of preliminary ejections is rounded up to the nearest decimal point. That is, the final preliminary ejection number is set as 11 shots. However, such rounding up does not characterize the present invention or the present embodiment. If it is desired to further reduce ink consumption, the value after integration may be rounded off to obtain the final preliminary ejection number.

  Also, the specific numerical contents shown in FIGS. 7 and 8 do not characterize the present embodiment. As described above, the values shown here are values obtained and set experimentally by the inventor under predetermined conditions. It goes without saying that the value can be changed depending on the form of the recording head to be applied and the composition of the ink.

  This embodiment is characterized in that the number of preliminary ejections is set in consideration of “meniscus vibration” from nozzles in the vicinity of the nozzle of interest. At this time, in the above description, the ink flow state is determined based on the sum of the number of ejections from two nozzles adjacent to the target nozzle. However, the present embodiment is not limited to this. A situation where not only the adjacent nozzles but also a wider range of nozzles centering on the nozzle of interest is also affected by the “meniscus vibration”. In such a case, for example, a mode in which a wider range of discharge counts are taken into account may be employed, such as counting the sum of the discharge counts of neighboring nozzles while applying a weighting coefficient.

(Second Embodiment)
The second embodiment of the present invention will be described below. Also in this embodiment, the configuration of the ink jet recording apparatus described with reference to FIGS. 1 to 5 is the same as that of the first embodiment. However, in the present embodiment, in order to obtain a higher-quality and high-fastness image, the composition of the solvent contained is different in accordance with the characteristics of the respective color materials of the six colors of ink used. And In such a case, since the content of volatile components such as water and alcohol is different for each ink, the progress of ink evaporation in the vicinity of the ejection port is also different. In the present embodiment, in order to cope with such a situation, different preliminary ejection control is performed for each type of ink.

  Hereinafter, a recording operation after an image signal is input in the present embodiment and a preliminary ejection operation performed in accordance with the recording operation will be described. The process from the input of the image signal to the transition of the process to the preliminary ejection control unit 100 in FIG. 5 at each ejection timing is the same as in the first embodiment.

  FIG. 9 is a flowchart for explaining the preliminary discharge operation in the preliminary discharge control unit 100 of the present embodiment. Here, as in the first embodiment, the description is made using eight nozzles for convenience.

  In the preliminary ejection control unit 100, first, the time t that has elapsed since the previous preliminary ejection operation is acquired (step S511). If this time is immediately before the start of the recording operation and immediately after the cap is opened, the preliminary ejection performed in the initialization process corresponds to the previous preliminary ejection here.

  In step S512, it is determined whether or not the acquired elapsed time t is 5 seconds or longer. If the determination result is less than 5 seconds, the process in the preliminary ejection control unit 100 ends, and the process proceeds to ejection control for the next dot. On the other hand, when the elapsed time t is 5 seconds or more, it is determined that the timing corresponds to the timing for performing preliminary ejection during recording, and the process proceeds to step S513.

  In step S513, it is determined whether the carriage M4001 is located at the end of the recording area. If the carriage M4001 is not positioned at the end of the recording area, it is determined that it is not yet time to execute preliminary ejection, and the processing in the preliminary ejection control unit 100 is terminated. On the other hand, if it is determined that the carriage M4001 is positioned at the end of the recording area, the process proceeds to step S514.

  Also in the present embodiment, as in the first embodiment, the preliminary ejection operation can be performed at a predetermined position without increasing the recording time as much as possible by the determination process in steps S512 and S513. It has become.

  In step S514, the carriage M4001 is moved to the recovery unit M5000, and preparations for performing preliminary discharge are made.

  In step S515, in order to sequentially perform the subsequent processing for each of the six colors of ink, it is determined that attention is first given to the black ink that is the first color. Hereinafter, Steps S516 to S519 are steps performed individually for one color of interest.

  In step S516, the discharge pause times s (1) to s (8) at each nozzle are read from the pause time storage circuit 412 in the preliminary discharge control unit 100.

  In step S517, the number of preliminary ejections e (1) to e (8) to be applied to each nozzle is set with reference to a lookup table (LUT) prepared in advance.

  FIG. 10 is a diagram showing an LUT applied in the present embodiment. This table has been experimentally obtained by the inventor after intensive studies. In other words, taking into account the change in the amount of ink that evaporates from the discharge port according to the standing time of 5 seconds or less and the accompanying ink thickening state for each ink color, one nozzle is recovered from this thickening state The number of preliminary discharges sufficient for the purpose is also determined for each ink color. In the figure, the symbols Bk, LC, LM, C, M, and Y represent black, light cyan, light magenta, cyan, magenta, and yellow, respectively. The nozzle rows that discharge these six colors are arranged in parallel on the recording head in the above order, and the series of steps from Step S516 to Step S519 are also performed in the order described above, so that it is the most time-consuming. This is a configuration that realizes a preliminary discharge operation without any trouble. In the following description, for the sake of simplicity, numbers 1 to 6 are assigned to the respective colors in the above order. When the ink color of interest is black, in step S517, the number of preliminary ejections is selected from e (1) to e (8) in the column where “[1] Bk” is displayed. The

  In step S518, preliminary ejection is executed in accordance with the number of preliminary ejections set in step S517.

  After the preliminary ejection operation is completed, in step S519, the currently set ejection pause times s (1) to s (8) are reset. Thus, the preliminary ejection operation for one color is completed.

  In step S520, it is determined whether or not preliminary discharge operations for all six colors have been completed. If it is determined that the preparatory ejection operations for all six colors have not yet been completed, the process proceeds to step S521, and the ink color to be subjected to the preliminary ejection operation is shifted to the next ink color. That is, the ink color of interest is changed in the order of [1] to [6]. Thereafter, the processing in steps S516 to S519 is repeated for the changed ink color. Of course, the LUT column referenced in step S517 is changed according to the ink color of interest.

  After the processing from the first color, black, to the sixth color, yellow, is completed as described above, if it is determined in step S520 that the preliminary ejection operations for all six colors have been completed, the present embodiment A series of control steps in the preliminary ejection control unit 100 is completed.

  When the preliminary ejection operation is completed, the carriage M4001 moves from the position of the recovery unit M5000 into the image forming area, and starts the next recording scan according to the image data. And the preliminary discharge control for every drive pulse period demonstrated with the said flowchart is restarted.

  In this embodiment, when determining the number of preliminary discharges of the target nozzle, the number of preliminary discharges is not reduced according to the total number of discharges of adjacent nozzles as in the first embodiment. As shown also in FIG. 10, in the recording head applied in the present embodiment, the number of necessary preliminary ejections is small as a whole. This is because it can be determined that there is no significant difference in the total ink discharge amount due to ejection. However, such a configuration does not characterize the present embodiment. Also in the present embodiment, as in the first embodiment, a process of counting the total number of ejections of adjacent nozzles and reducing the number of preliminary ejections according to the degree of meniscus vibration may be incorporated. It will be easily understood that such a configuration does not hinder the present embodiment, and more accurate preliminary discharge control can be expected.

  In the above-described two embodiments, the description has been made using the recording head configured to eject ink by disposing an electrothermal converter inside each nozzle and applying a voltage pulse to the electrothermal converter. However, the present invention is not limited to such a recording head. Whatever the discharge method from the nozzles, the effect of the present invention is exhibited as long as the ink is selectively discharged from a plurality of nozzles according to the image data. For example, even if the configuration is such that ink is ejected by disposing a piezoelectric element inside the nozzle, the effect of the present invention is not affected at all.

  In the above two embodiments, the preliminary discharge operation can be executed when 5 seconds have elapsed from the previous preliminary discharge. However, the present invention is not limited to such a configuration. The threshold value of the elapsed time may not be 5 seconds, and may not be a configuration in which execution of the preliminary discharge is determined based on a predetermined elapsed time. For example, any parameter may be adopted as long as it is determined based on parameters that can be used as a guideline for increasing the viscosity of ink, such as the number of times of recording scanning and the number of recording dots. The most basic feature of the present invention is that an appropriate number of preliminary ejections is set for each nozzle. Therefore, no matter what triggers the preliminary ejection, the gist of the present invention is not affected.

  Further, in the above two embodiments, the recovery unit M5000 is installed on one side of the recording area and the preliminary ejection operation is executed here. However, the present invention is not limited to such a configuration. Absent. For example, in an ink jet recording apparatus that performs a bidirectional recording operation, a member for receiving preliminary ejection is provided on both sides of the recording area so that preliminary ejection can be performed from either end of the recording area. In this case, the preliminary discharge operation can be realized more efficiently.

1 is a configuration diagram of an outer shell of an ink jet recording apparatus applied to an embodiment of the present invention. It is a block diagram for demonstrating the internal mechanism of the inkjet recording device applicable to this invention. 1 is a schematic perspective view of an inkjet recording cartridge applicable to an embodiment of the present invention. FIG. 4 is a configuration diagram for explaining a state in which an ink tank is attached to and detached from a recording head. It is a block diagram for demonstrating the structure of control in the inkjet recording device of embodiment of this invention. It is a flowchart for demonstrating the preliminary discharge operation process in the 1st Embodiment of this invention. It is a figure which shows LUT for setting the number of preliminary discharge applied to each nozzle. It is a figure which shows LUT for installing the preliminary discharge number reduction coefficient with respect to the adjacent nozzle total discharge frequency. It is a flowchart for demonstrating the preliminary discharge operation | movement in the preliminary discharge control part of 1st Embodiment. It is a figure which shows LUT for setting the number of preliminary discharge applied to each nozzle.

Explanation of symbols

100 Pre-discharge controller 400 CPU
401 ROM
402 RAM
403 Image input unit 404 Image signal processing unit 405 Main bus line 406 Operation unit 407 Recovery system control circuit 408 Recovery system motor 409 Wiper 410 Cap 411 Suction pump 412 Discharge pause time storage circuit 413 Discharge storage time measurement circuit 415 Clock 416 Head drive control Circuit 417 Carriage drive circuit 418 Paper feed control circuit H1000 Inkjet recording head cartridge H1001 Inkjet recording head H1900 Ink tank M1000 Inkjet recording apparatus M4001 Carriage M5000 Recovery unit

Claims (11)

An inkjet recording apparatus that forms an image on a recording medium using an inkjet recording head having a plurality of nozzles that eject ink according to image information,
Preliminary ejection means for performing preliminary ejection independently of the formation of the image;
For each of the plurality of nozzles, a discharge pause time measuring unit that counts an elapsed time since the previous discharge is executed as a discharge pause time, and resets the count value each time a new discharge is executed,
Setting means for setting the number of preliminary discharges for the preliminary discharge for each individual nozzle according to the discharge pause time of the individual nozzles obtained by the discharge pause means, the preliminary discharge means, An ink jet recording apparatus that performs preliminary ejection corresponding to the number of preliminary ejections of the individual nozzles set by the setting unit at a predetermined timing in the image forming process.   The setting means refers to a lookup table showing a correspondence relationship between the discharge pause time and the number of preliminary discharges for the preliminary discharge, thereby determining the number of preliminary discharges for the preliminary discharge. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is set for each of the nozzles.   The inkjet recording apparatus according to claim 2, wherein the inkjet recording head is capable of ejecting a plurality of types of ink, and the look-up table is prepared for each of the plurality of types of ink.   The ink jet recording apparatus according to claim 3, wherein the plurality of types of inks have different types of color materials.   5. The ink jet recording apparatus according to claim 3, wherein the plurality of types of inks have different volatile component contents.   Each time the discharge pause time measurement means resets the count value for each of the plurality of nozzles, the discharge pause time measurement means further includes an integration means for integrating the number of resets as the number of discharges of the individual nozzles. The number of preliminary ejections of the individual nozzles set by the setting unit is changed according to the number of ejections of the individual nozzles obtained by the integrating unit, and then the predetermined number during the image formation is changed. 6. The ink jet recording apparatus according to claim 1, wherein the preliminary ejection is executed at a timing.   The preliminary ejection unit refers to a lookup table showing a correspondence relationship between the number of ejections and a correction parameter for making a change to the preliminary ejection number. The inkjet recording apparatus according to claim 6, wherein the number of ejections is changed in accordance with the correction parameter.   8. The predetermined timing is a timing at which a predetermined time has elapsed from a time of the preliminary ejection performed immediately before by the preliminary ejection unit. Inkjet recording device.   The discharge pause time measuring means updates a clock for executing the count, a discharge pause time measuring circuit that detects an output value of the clock and measures the discharge pause time, and updates and stores the discharge pause time. An ink jet recording apparatus according to claim 1, further comprising an ejection pause time storage circuit for the purpose. A preliminary ejection control method for performing preliminary ejection regardless of formation of an image on a recording medium using an inkjet recording head having a plurality of nozzles that eject ink according to image information,
For each of the plurality of nozzles, a discharge pause time measuring step of counting an elapsed time since the previous discharge was executed as a discharge pause time, and resetting the count value each time a new discharge is executed,
A setting step for setting the number of preliminary discharges for the preliminary discharge for each individual nozzle according to the discharge pause time of each nozzle obtained by the discharge pause step;
And a preliminary ejection according to the number of preliminary ejections of the individual nozzles set in the setting step is performed at a predetermined timing in the image forming process. . Each time the discharge pause time measurement step resets the count value for each of the plurality of nozzles, the discharge pause time measurement step further includes an integration step of integrating the reset count as the discharge count of the individual nozzles. In accordance with the number of discharges of the individual nozzles, the preliminary number of discharges of the individual nozzles set in the setting step is changed, and then the preliminary operation is performed at a predetermined timing during the image formation. The preliminary discharge control method according to claim 10, wherein a proper discharge is performed.

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