JP2006168098A - Ink jet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate uneven density resulting from temporary interruption in the way of image formation by multipass system which occurs especially when long output printing is performed in so-called multipass recording system. <P>SOLUTION: With regard to uneven density resulting from temporary interruption, a place where uneven density has little or no effect is searched on a recording image when a band position is selected, and recovery operation of a head is performed at that band position, if possible, in the way of recording a page thus avoiding occurrence of uneven density. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a so-called multipass recording type inkjet recording apparatus.

  In recent years, with the progress of office automation and the spread of personal computers and the like, as an apparatus for recording a digital image handled on a personal computer on a recording material, an ink jet recording apparatus using an ink jet recording head has been rapidly used. It is popular. Ink jet recording heads are generally provided with a plurality of liquid discharge ports for discharging a liquid and a plurality of liquid flow channels communicating therewith, in order to discharge liquid from each liquid discharge port in each liquid flow channel. Is provided with a recording element that gives the liquid energy.

  As a method for ejecting liquid in an ink jet recording apparatus, a heating element (electrical / thermal energy converter) is provided as a recording element in the vicinity of the ejection port, and an electric signal is applied to the heating element to locally heat the liquid. There are a method using an electric / thermal energy converter that causes a pressure change to discharge a liquid from an outlet, and a method using an electric / mechanical converter such as a piezoelectric element as a recording element. Further, a configuration in which an electric pressure converting means such as a piezo element is used as a recording element and a liquid is mechanically applied to discharge the liquid has been conventionally known.

  In this ink jet recording apparatus, the digital image recording time is shortened and the output image quality is improved. Therefore, as a recording head mounted in an ink jet recording apparatus, a recording head (hereinafter referred to as a multi-head) in which a plurality of recording elements are integrated and liquid discharge ports and liquid flow paths are integrated with high density is the mainstream. It has become.

  In general, an ink jet recording apparatus includes a recording unit having a carriage on which a recording head and a liquid tank for storing a liquid to be supplied are mounted, a conveying unit that conveys a recording material, and a control unit that controls them. A recording head that discharges liquid droplets from a plurality of liquid discharge ports is serially scanned in a direction (hereinafter, referred to as a main scanning direction) that intersects (for example, orthogonally) with a recording paper conveyance direction (hereinafter, referred to as a sub scanning direction). On the other hand, the recording material is intermittently conveyed by an amount equal to the recording width in one serial scan at the time of non-recording.

  In addition, a color ink jet recording apparatus capable of recording a color image is also widely used. In this apparatus, ink droplets ejected from a plurality of recording heads corresponding to each of a plurality of colors of ink are superimposed on a recording material. Together, a color image is formed.

  In the ink jet recording method, characters, figures, and the like are recorded by selectively discharging liquid as fine droplets from a liquid discharge port onto a recording material in accordance with recording data. The ink jet recording method has advantages such as low noise, low running cost, easy downsizing of the apparatus, and relatively easy colorization because it is non-impact. For this reason, an ink jet recording apparatus is widely used as a recording apparatus used in combination with a computer, a word processor, or the like, or as a recording apparatus mounted on a copying machine, a printer, a facsimile, or the like used alone.

  As described above, the demand for inkjet recording apparatuses is increasing as an excellent recording means in a wide range of industrial fields, and it is required to be able to record higher quality images, and the demand for higher speed is further increased. ing.

  In the conventional ink jet recording method, it is necessary to use a special coated paper having an ink absorbing layer in order to obtain a color image with high color development without ink bleeding on a recording material. However, in recent years, a method has been put into practical use that has the ability to record on plain paper that is used in large quantities in general printers and copiers by improving ink. In addition, it is desired to cope with various recording materials having different ink absorption characteristics such as an OHP sheet, cloth, and plastic sheet. In order to meet these demands, development and commercialization of a recording apparatus capable of performing the best recording irrespective of the type of recording material have been promoted.

  Furthermore, regarding the size of the recording material, it is possible to record on a large-sized recording material that is required for recording on posters and woven fabrics such as clothing for event display and advertising purposes. It has also been requested. Therefore, recently, as a printing system configured for business use, for example, a printing system capable of recording on a large size recording paper such as A0 or B0 size has been configured, and a large inkjet printer is used. It is becoming.

  In such a commercial printing system for recording on A0 or B0 size or larger recording materials, a paper receiving tray is prepared and the printed recording material is discharged to this tray. In addition to the method described above, a method including a mechanism for winding a large recording material that has been printed out has already begun to become popular.

  This is because in recent years, it has been required to perform recording even on extremely large recording materials having a length of several meters to several tens of meters.

  By the way, in the ink jet recording apparatus, in order to perform a recovery process for maintaining a good ink discharge state of the recording head, particularly when the recording operation is paused during page recording for a large recording material. There is. For example, the recording head may generate ink mist as ink is discharged from the discharge port, or may generate splash due to an impact when the discharged ink lands on the recording medium. These mist, splash, and the like adhere to the ejection port surface of the recording head in which the ejection ports are arranged, and cause the ejection failure of the ink by closing the ejection port. The recovery process is a process for maintaining a good ink discharge state of the recording head in order to prevent the occurrence of ink discharge failure due to such factors.

  As one of the recovery processes, a blade made of an elastic material such as rubber is brought into contact with the ejection port surface of the recording head, and the blade and the recording head are moved relative to each other (usually, the recording head is moved). Thus, there is a so-called wiping in which ink adhering to the periphery of the discharge port is wiped off and removed. As another recovery process, there is so-called preliminary ejection in which ink that does not contribute to image recording is ejected from an ejection port. When an image is recorded by selectively ejecting ink from a plurality of ejection ports of the recording head according to recording data, there are ejection ports that do not eject ink for a certain period of time. Since the ink in the vicinity of the discharge port remains exposed to the outside air, the viscosity increases. When ink is discharged from the discharge port, the ink discharge amount and discharge speed are reduced, and the ink discharge direction is reduced. There is a risk of causing an ejection failure of the ink due to deflection or the like. Therefore, in order to remove such thickened ink, preliminary ejection is performed in which ink that does not contribute to image recording is ejected toward a predetermined portion of the recording apparatus.

  As another form of the recovery process, suction recovery is known. If air bubbles are mixed or generated in the liquid path of the recording head or in the common liquid chamber due to, for example, continuous ejection of ink or long-term non-use of the recording apparatus, the bubbles will enter the liquid path. This may hinder ink supply and ink discharge operation and may cause ink discharge failure. Mainly, in order to prevent such discharge failure, a cap made of a material such as rubber is brought into contact with the discharge port surface of the recording head, and then negative pressure is introduced into the cap. Then, suction recovery is performed in which the ink is forcibly sucked and discharged from the ejection port into the cap.

  The various recovery processes as described above are executed before image recording, after image recording ends, or between recording scans during image recording. By such a recovery process, it is possible to always maintain an appropriate ink discharge state of the recording head, and to perform high-quality recording while preventing deterioration in image quality. In particular, when recording is performed continuously on a relatively large recording surface, such as when poster output is performed by the above-described business printer, recovery processing is performed between recording scans in the recording operation. It is important to do.

  Here, the image quality of the ink jet recording apparatus will be further described. While color image output using multi-color ink is generalized in this way, in addition to the evaluation of image quality when printing only in monochrome, color developability Elements such as reproducibility, gradation, and uniformity are also important elements related to image quality.

  In particular, with regard to the uniformity of image recording, there is a slight variation in the production of nozzles in the multi-head manufacturing process, which affects the printing accuracy of each nozzle and causes uneven ink discharge during printing and the discharge direction. Misalignment occurs. The variation in the nozzle unit in the manufacturing process finally becomes the density unevenness of the output image, which causes the image quality to deteriorate.

  On the other hand, in recent inkjet recording apparatuses, for the purpose of improving image quality, a method for completing image recording by scanning a recording head a plurality of times in the main scanning direction with respect to the same recording area on a recording medium, so-called A multi-pass recording method is adopted.

  FIG. 7 is an explanatory diagram of the two-pass recording method in which the image recording is completed by scanning the recording head twice in the main scanning direction with respect to the same recording area on the recording medium as the multi-pass recording method. Here, the relationship between the position of the recording head H and the recording area of the image recorded on the recording medium P is shown.

  An image is recorded on the recording medium P by ejecting ink based on image data while the recording head H moves in the main scanning direction (arrow X1 direction), and the recording head H scans once in this way. Each time the printer operates, the recording medium P is conveyed in the sub-scanning direction (arrow Y direction) by a width corresponding to ½ of the width of the recording head H (hereinafter referred to as ½ band width). In FIG. 7, the position of the recording medium P is fixed, and the recording head H is expressed as moving in the direction opposite to the sub-scanning direction with respect to the recording medium P. In the first scanning operation, the image data thinned out for the neighboring pixels in the image data of one bandwidth corresponding to the width of the recording head H is recorded, and in the second scanning operation, the image of the one bandwidth is recorded. Of the data, image data that was not thinned out in the first scanning operation is recorded.

  Accordingly, the recording of the image on the recording medium P is completed by the ½ bandwidth by the scanning operation of the recording head H twice. That is, the image data thinned out for the adjacent pixels is recorded in the first scanning operation, and the first scanning is performed in the second scanning operation. The image data not thinned out in the operation is recorded. Hereinafter, the first scan operation is referred to as the ½ pass, the second scan operation is referred to as the ½ pass, and the ½ pass for the recording area corresponding to the ½ band width on the recording medium P. The area where only the recording is performed is called a 1/2 pass recording area, and the area where the recording of the 2/2 pass is also performed and the image is completed is called a 2/2 pass recording area.

  FIG. 2 is a schematic diagram showing an image recorded during the recording operation when two-pass recording is performed. During the recording operation, the recording area corresponding to the ½ bandwidth at the rear end in the sub-scanning direction is a ½ pass recording area, and only the thinned image data is recorded by the ½ pass recording. The For this reason, the image is not completed in the half-pass recording area at the rear end, and the density of the area is approximately ½ that when the image is completed.

For example, Patent Document 1 discloses a configuration for performing multi-pass printing for an ink jet recording apparatus. This patent document 1 discloses a configuration in which printing is paused after a multi-pass printing up to halfway is completed before the printing operation is temporarily paused during the printing operation.
JP 2000-15868 A

  However, in the multi-pass recording method as described above, when the recording operation is temporarily stopped in the middle of the recording operation, the time between the first scanning operation and the second scanning operation for the same recording area. An interval (hereinafter referred to as a recording time difference) changes with a pause, and the recording density may change due to the suspension, resulting in density unevenness.

  FIG. 3 and FIG. 4 are explanatory diagrams of the unevenness caused by such a change in the recording time difference.

  FIG. 3 shows ink penetration and fixing of the recording medium 202 when the time between the first and second scan operations (1/2 pass and 2/2 pass) in the 2-pass printing method is short. It is the figure which represented a mode typically. The ink droplet 201a ejected in the ½ pass as shown in FIG. 11A penetrates in the direction perpendicular to the surface of the recording medium 202 and the direction spreading on the surface as shown in FIG. A pigment such as a dye as a component physically and chemically binds to the recording medium 202. Although the ink droplet 201b ejected in the 2/2 pass also penetrates in the direction perpendicular to the surface of the recording medium 202 and the direction spreading on the surface as shown in FIG. The ink droplet 201a that has landed first does not penetrate or fix much in the fixed area. The cause is considered to be that the ink droplet 201a that has landed earlier is still penetrating. Therefore, the ink droplet 201b that has landed later penetrates and is fixed further below the region where the ink droplet 201a that has landed first penetrates, as shown in FIG.

  FIG. 4 is a diagram schematically showing the state of ink permeation and fixing with respect to the recording medium 202 when the time between the 1/2 pass and the 2/2 pass in the 2-pass printing method is long. . The ink droplet 201a ejected in the ½ pass as shown in FIG. 11A penetrates in the direction perpendicular to the surface of the recording medium 202 and the direction spreading on the surface as shown in FIG. A pigment such as a dye as a component physically and chemically binds to the recording medium 202. As shown in FIG. 5C, the ink droplet 201b ejected in the 2/2 pass and subsequently landed penetrates a relatively large amount in the region where the first landed 201a has penetrated and fixed. This is because the ink droplet 201a that has landed first sufficiently penetrates and spreads, or the volatile component thereof evaporates, so the amount of ink droplet 201a per unit volume of the recording medium 202 decreases, and the ink droplet 201b that landed later It may be because it has become possible to penetrate.

  As described above, the amount of ink fixed near the surface of the recording medium, that is, the amount of a pigment such as a dye differs depending on the change in the time interval between the 1/2 pass and the 2/2 pass. Further, since the recording density corresponds to the absorption of light of the dye fixed near the surface of the recording medium, the recording density varies depending on the change in the time interval between the 1/2 pass and the 2/2 pass.

  Therefore, when an image is recorded by the multi-pass recording method, if the recording is interrupted due to the temporary stop, the recording image before and after the interruption is left ununiformly.

  Therefore, in Japanese Patent Laid-Open No. 2000-15868, ink is interrupted during a printing operation by performing a printing pause after completing a multi-pass printing up to a middle before temporarily stopping the printing operation during the printing operation. An apparatus that can avoid uneven printing even when a supply operation or a recovery process is performed is disclosed. As a result, there is no multipass incomplete area at the time of transition from the printing operation state to the resting state, and therefore density unevenness is considerably improved.

  However, according to this method, with respect to the image formation for completing the pass before the suspension of printing, a plurality of reciprocal printing scans are executed while the conveyance of the recording material is stopped. It is understood that density unevenness that may be caused by nozzle unit variation that occurs in the head manufacturing process will occur due to ink ejection from only a predetermined nozzle of the head, Currently, further improvements are desired.

  In addition to the above, there are JP-A-11-245393, JP-A-2001-171147, and the like that have been proposed as methods for reducing the influence of density unevenness. However, considering from our experience the degree of influence of the density unevenness that we are interested in, none of these proposals have already been proposed, even though the effect of density unevenness is large in the image area where the print density of the recorded image is high. The execution of the head recovery process is started based on the determination based on the number of recorded pixels in the area where image formation has been completed and the print length parameter recorded so far. That is, there has been no function for selecting the timing for executing the recording pause according to the original image itself.

  By the way, it is actually possible to execute the head recovery process at a timing before printing reaches the execution determination threshold value for shifting to the print pause for the head recovery process during the page recording operation. Further, the threshold value set for timing determination is not a true limit value, but is set with a certain margin such as 10% to 30%, for example, so even after the set threshold value is exceeded. It is actually possible to give priority to the continuation of printing without performing the head recovery process for a short time.

  Therefore, an object of the present invention is a density unevenness caused by a temporary stop in the middle of image formation by a multi-pass method, which often occurs when a long output printing is performed in a so-called multi-pass recording method. The selection of the generated band position automatically searches for a place where there is little or no influence of density unevenness on the recorded image, and if possible, the head recovery operation is performed during page recording at the band position. An object of the present invention is to provide an ink jet recording apparatus capable of avoiding occurrence of unevenness.

  In order to achieve the above object, in the apparatus of the present invention described in claim 1, the recording head is used for the same recording area on a recording medium using a recording head capable of discharging ink from a plurality of discharge ports. In an ink jet recording apparatus that records an image by scanning a plurality of times and performs image formation by a multipass recording method capable of temporarily stopping image recording, the first related to the cumulative image recording length formed during page recording operation Determination means for determining whether to permit execution of a pause in a recording operation for shifting to a head recovery process during a page recording operation by performing a threshold determination based on the threshold D1 and a threshold determination regarding the cumulative number of recorded pixels on which an image is formed; Search means for searching for a blank band region in a recorded image to be imaged by counting the number of recorded pixels in the image memory; and the cumulative image A second threshold value D2 relating to the recording length is provided, a blank band region is searched for in a recorded image to be formed, and the cumulative image recording length has reached the second threshold value D2 and a recording to be imaged from now on When the search for the blank band region is successful in the image, the head recovery process is performed when the blank band region is formed. On the other hand, when the blank band region is not found, It is possible to shift to head recovery processing in the middle of page recording by threshold determination based on the first threshold D1 regarding the cumulative image recording length and threshold determination regarding the cumulative recording pixel number.

  Further, in the ink jet recording apparatus of the present invention, the page recording operation is set with respect to the cumulative image recording length by setting the second threshold with respect to the cumulative image recording length smaller than the first threshold. It is characterized in that the head recovery processing can be performed in the searched blank band area before reaching the original image recording length.

  As described above, according to the present invention, in a recording apparatus that performs a page recording operation by a so-called multi-pass recording method, an image region in which image formation is to be performed during an image recording operation as a temporary stop position when the recording operation is paused A means for searching for a blank band area in the image memory from the inside, and a control for stopping printing in the blank band area when the search is successful are provided. As a result, for example, when there is a blank band area in the image area, it is possible to avoid the occurrence of density unevenness related to the printing pause.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Basic configuration of recording device)
FIG. 5 is a front view showing an ink jet recording apparatus according to an embodiment of the present invention.

  In FIG. 5, reference numeral 2 denotes a recording apparatus main body including a paper transport system unit. This recording apparatus performs recording on a relatively large recording sheet (recording medium). Reference numeral 1 denotes a carriage. By mounting 12 recording heads 5 and moving in the main scanning direction indicated by arrows X (X1, X2), recording scanning of the recording paper (recording medium) of the recording head 5 is possible. Become. That is, the carriage 1 is guided and supported by the guide shaft 11 so as to be movable in the main scanning direction along the guide shaft 11, and is reciprocated in the main scanning direction by the driving force transmitted through the belt 13. In addition to the cyan, magenta, yellow, and black inks used from the recording head 5, a total of six colors including light cyan and light magenta for the purpose of reducing graininess are employed. For the purpose of improving the recording speed, two recording heads 5 are used for one color ink. That is, two sets of recording heads 5 in total for six inks of six colors, one X1 direction in the main scanning direction (hereinafter referred to as the forward scanning direction) and the other X2 direction (hereinafter referred to as the backward scanning direction). (Referred to as “direction”). As a result, recording is performed by the reciprocal recording of the forward scanning and the backward scanning of the recording head 5 with the same ink ejection order from the 12 recording heads 5 during the forward scanning in the X1 direction and the sub-scanning in the X2 direction. High-quality images can be recorded while increasing the speed.

  In addition, ejection openings capable of ejecting ink are formed in two recording heads 5 for each color of ink in a line with the same pitch along the conveyance direction of the recording paper. The recording heads 5 may be arranged so that the outlet row and the ejection port row of the other recording head 5 are shifted by a half pitch in the recording sheet conveyance direction. In this case, the recording density in the conveyance direction of the recording paper can be doubled as compared with the case where one recording head 5 is used for one color ink. The recording apparatus is not necessarily limited to a configuration in which reciprocal recording is performed by forward scanning and backward scanning of the recording head 5, and may be configured to perform unidirectional recording in which recording is performed by only one reciprocal scanning.

  Reference numerals 30A, 30B, 30C, and 30D denote recovery mechanisms that perform a suction recovery process as a recovery process for maintaining a good ink discharge state of the recording head 5 and protect the recording head 5 when the recording head 5 is not used. . That is, these recovery mechanisms 30A, 30B, 30C, and 30D each include a cap that can come into contact with the discharge port surface of the recording head 5 on which the ink discharge port is formed. By introducing a negative pressure from a pump (not shown) into the cap after being brought into contact with the surface, ink that does not contribute to image recording is forcibly sucked and discharged from the ejection port of the recording head 5 into the cap. . The cap protects the ejection port of the recording head 5 by contacting the ejection port surface when the recording head 5 is not used.

  Reference numeral 31 denotes a preliminary ejection ink receiving box that receives ink ejected by the preliminary ejection operation of each recording head 5. Preliminary ejection is another recovery process for the recording head 5, and ink that does not contribute to image recording is ejected from the ejection port toward the preliminary ejection ink receiving box 31. Reference numeral 32 denotes a wiping mechanism for performing a wiping operation on the discharge port surface of each recording head 5. The wiping is another one of the recovery processing for the recording head 5, and a blade made of an elastic material such as rubber is brought into contact with the discharge port surface of the recording head 5 so that the blade and the recording head 5 are relatively moved. By moving (in the case of this example, the recording head 5 is moved), ink adhering to the periphery of the ejection port is wiped off and removed.

  When the recording apparatus configured as described above receives recording data from the host apparatus, the carriage 1 is moved along the guide shaft 11 in the main scanning direction (in the main scanning direction) (in order to record an image on a recording sheet sent by a paper transport unit (not shown)). An image for one band is recorded on the recording paper by ejecting ink from the recording head 5 while moving in the X1 or X2 direction. Then, the recording sheet is conveyed in the sub-scanning direction intersecting with the carriage 1 (orthogonal in this example) by the paper conveying unit. In order to detect the movement position of the carriage 1, an encoder film 12 is disposed along the movement path of the carriage 1. That is, the encoder sensor mounted on the carriage 1 can detect the encoder film 12, and the movement position of the carriage 1 can be detected based on the detection signal. Further, based on the detection signal of the encoder sensor, the carriage 1 is controlled to move to a predetermined home position (in this example, positions corresponding to the recovery mechanisms 30A, 30B, 30C, and 30D).

  In each recording head 5, for example, 256 ejection openings are arranged at a density of 600 dpi (dots / inch) so as to be aligned in the sub-scanning direction, and ink can be ejected from each ejection opening. The method of discharging ink from the discharge port is arbitrary, and for example, a method of discharging using a piezo element or a method of discharging using heat generated by an electrothermal transducer (heater) may be used. The recording head 5 of this example is configured to eject ink using the heat generated by the electrothermal transducer. In other words, an electrothermal converter is provided in each ink liquid path communicating with each ejection port, and the ink in the ink liquid path is locally heated by the heat energy generated from the electrothermal converter to cause film boiling. The ink is ejected from the ejection port corresponding to the ink liquid path by the pressure at that time.

(Recording device control system)
FIG. 6 is a diagram showing the configuration of an image recording apparatus equipped with an ink jet recording head according to a typical embodiment of the present invention.

  As shown in FIG. 6, reference numeral 601 denotes a CPU, and a ROM 602 and a RAM 603 are connected to its internal bus. The CPU 601 reads the program from the ROM 602 and executes the program by repeating read / write to the RAM 603. Reference numeral 604 denotes an interface that is connected to an external host device (not shown) and transfers a print command and image data to be printed by the main body, and is connected to the CPU 601 and a band memory 610 described later. Reference numeral 605 denotes an operation / display unit that displays various key input operations and operation states on the apparatus, and is connected to the CPU 601. Further, when the operation setting of the recording apparatus main body is changed from the host via the interface 604, the memory contents at a predetermined position in the RAM 603 are changed via the CPU 601. Reference numeral 606 denotes a motor driver that controls a carriage driving motor, which is connected to the CPU 601 and controlled, and a motor driving signal is output to the connected motor 607. Reference numeral 608 denotes a motor driver that controls the conveyance system driving motor, which is connected to the CPU 601 and controlled, and a motor driving signal is output to the connected motor 609. Reference numeral 610 denotes a band memory, and image data transferred from a host (not shown) is temporarily stored in the page recording. Image data for printing is received via the interface 604, and image data necessary for printing an area divided in accordance with a predetermined width output for each scan of the carriage is controlled by the CPU 601. Stored. Further, the number of recording pixels for each predetermined image height at the timing when the image data is stored is counted here. As the memory capacity of the band memory 610, it is usually possible to store at least two bands of image data, and not only the most recent image data to be imaged from now on, but also several recording scans ahead. In practice, it is possible to hold in advance the image data for image formation. Further, the band memory 610 outputs image data in bandwidth units to the multi-pass data processing unit 611 in accordance with the drive timing of the carriage. The multipass data processing unit 611 performs thinning processing by causing the data thinning mask data for multipass printing to act on the image data. Reference numeral 612 denotes a head controller whose output is input to the multi-head 613. The head controller 612 drives the multi-head 613 so that printing of an area divided into a predetermined width is executed while the carriage performs one scan operation under the control of the CPU 601. The multi-head 613 is controlled by the head controller 612, and ejects ink from a plurality of ink ejection ports formed on the recording head, and executes printing for one scan while synchronizing with the carriage operation.

  Next, the operation of the present invention will be described with reference to FIGS. Here, FIG. 8 is an example of print parameters received from the host device during the page recording operation. FIG. 9 is an operation flowchart showing the image forming operation of the present invention.

  First, from the host side, receive operation parameters related to the printing operation, such as the print start command, image size, leading and trailing margins, and parameters for specifying the paper feed stage and paper type used for printing. The data is stored in the RAM 603 (step 901).

  Next, the CPU 601 reads out the parameters received in step 901 and initializes internal variables such as the total number of recording scans and the total number of recorded pixels at the time of page recording. In addition, a data thinning mask for multi-pass printing can be selected based on the printing mode designated by the host device or the set paper type, or an area setting for storing an image in the memory on the main body side or for one page. Operation parameters related to printing in units of pages are set on the main body side, such as calculation of the total number of scheduled scans for recording. (Step 902).

  Note that the mask data for data thinning is random mask data stored in advance in the ROM 602 and RAM 603, but this mask data is not limited to a method stored in advance. For example, it may be received from the host device following the reception of the print parameter in step 901.

  Subsequently, the CPU 601 instructs the motor driver 608 on the number of drive steps based on the paper cassette designation and the leading edge margin designation received in step 901. Then, the LF motor driver 608 drives the LF motor 609 and conveys the paper to the print start position (step 903).

  Then, the CPU 601 instructs the CR motor driver 606 to move the carriage to a predetermined position for starting printing. Then, the CR motor driver 606 drives the CR motor 607 to move the carriage to the print scan start position. Further, the CPU 601 performs data processing operation settings in the multi-pass data processing unit 611 and performs operation settings related to head drive control in the head controller 612 in order to execute print scanning. Set the operation related to. (Step 904).

  Subsequently, the CPU 601 instructs the host interface 604 to start data reception. As a result, image data transfer from the host to the band memory 610 via the host interface 604 is started. Further, the CPU 601 reads out from the band memory 610 to calculate the number of pixels (dot count) actually printed in the printing scan to be performed for each ink color, counts the total number of print pixels up to the present, and stores this in the RAM 603. Store (step 905).

  The CPU 601 executes a recovery process transition determination which will be described in detail later in order to temporarily interrupt the page recording operation and shift to the multi-head suction recovery process (step 906).

  The CPU 601 then instructs the CR motor driver 606 to drive the CR motor 607 in order to execute a print scan. In the carriage scan operation for printing, an encoder signal (not shown) changes in accordance with the driving of the carriage. In accordance with the change, the image data is output from the band memory 610 to the multipass data processing unit. The multi-pass data processing unit 611 performs image data thinning processing for multi-pass printing, and the output image data is output to the head controller 612. The image data input to the head controller 612 is further output to the multi-head 613 in accordance with the drive control set for the multi-head 613. As described above, the encoder output value is changed by driving the carriage, whereby the image data stored in the band memory 610 is output from the multi-head 613, and the image recording operation on the recording paper is executed. Then, the recording scan count counter is incremented by one. (Step 907).

  When the recording scan is completed in step 907, the CPU 601 next causes the motor driver 608 to set a predetermined motor speed in accordance with the set number of printing passes in order to execute conveyance of recording paper for multi-pass printing. Indicate the number of drive steps. Then, the LF motor driver 608 drives the LF motor 609 and conveys the sheet by a predetermined amount for multi-pass printing (step 908).

  In this way, the CPU 601 executes one print scan for multi-pass printing.

  Here, the CPU 601 determines whether or not a predetermined recording scan for one page has been completed. Then, when the execution of the printing scan of the predetermined number of scans set at the start of the page recording operation has been completed (step 909), the CPU 601 first feeds the paper to the cutter operation position, and then continues (not shown). The paper cutting operation is executed by operating the paper cutter (step 910), and then the printing operation is terminated. However, if all the print scans have not been executed in step 909, the process proceeds to step 905, and the second and subsequent print scans are executed to perform the page recording operation.

The shift to the head recovery process in the middle of page recording in the ink jet recording apparatus of the present invention is started by completing the multipass recording in the middle of image formation.
Here, a recording scan for completing a multi-pass recording pass will be described with reference to FIG. FIG. 10 is a diagram ((a) to (d)) showing a state of a recording scan for completing a multi-pass recording in the middle of recording in order to shift to a head recovery process in the middle of page recording by the 4-pass recording method; FIG. 11 is a diagram ((e) to (f)) illustrating a recording scan state in which multipass recording is resumed after the head recovery process is completed. Here, the four-pass recording is a recording method in which image formation is performed by performing recording scanning four times on a recording area. The light black portion in each recording scan indicates an ejection port array used for image formation in each recording scan. The four-pass printing indicates that the ejection port array is vertically divided into four in the recording head, and the white blank portion indicates the ejection port array in which image formation is not performed in the recording scan. . By the way, the size of a recording area where an image is formed on a recording material by one recording scan is called one band. In the four-pass recording method, a recording material is usually conveyed by a size of a quarter of one band every time one recording scan is performed, so that a region that is divided into four parts vertically is four times. A recording scan is performed to complete 100% image formation.

  With reference to this figure, a description will be given of multi-pass printing that is performed in order that the inkjet printing apparatus of the present invention shifts to the head recovery process during the page printing operation.

  (A) is a recording scan immediately before shifting to the completion of a pass for printing suspension. A pass for transition is completed from the next recording scan.

  The ink jet recording apparatus of the present invention completes a pass in the middle of page recording by performing image formation without performing paper transport for three recording scans in the case of four-pass recording.

  (B) is a recording scan in which the paper is transported by a quarter of the scan of (a) and image formation is performed using the recording nozzle rows of only three quarters.

  (C) is a recording scan in which image formation is performed using only two-quarters of the recording nozzle rows without performing paper conveyance for the completion of the pass.

  (D) is a recording scan in which image formation is performed by using only one-fourth recording nozzle rows without performing paper conveyance for the completion of a pass. With the recording scan of (d), the completion of the pass for shifting to the recording pause in the middle of page recording is completed.

  (E)-(h) is the figure which showed each recording scan when returning from the print halt state for the head recovery process in the middle of page recording, and restarting the page recording operation by a multipass recording system. .

  (E) is a recording scan in which image formation is performed using only one-fourth of the recording nozzle rows. Since this recording scan is performed without changing the position of the recording head from the recording scan (d) immediately before entering the printing pause, the recording area completed before the printing pause and the recording completed after the printing pause. This is a page recording operation in which the occurrence of white streaks due to the print position deviation that easily occurs between the areas is suppressed.

  (F) is a recording in which paper is conveyed by a quarter of the bandwidth from the position of the previous recording head (e) for multi-pass, and image formation is performed by using a recording nozzle row by two-fourths. It is a scan.

  (G) is a recording in which the paper is conveyed by a quarter of the bandwidth from the position of the previous recording head (f) for multi-pass, and image formation is performed by using the recording nozzle row by a third. It is a scan.

  (H) is an original recording scan of the multipass recording method. A recording scan that transports paper by a quarter of the bandwidth from the previous recording head position (g) for multi-pass, and forms an image using all four recording nozzle rows of the recording head. It is. Thereafter, the page recording is completed by performing the recording scan of (h) and paper conveyance of only a quarter of the bandwidth.

  Next, start determination for starting the page recording pause of the inkjet recording apparatus will be described. This is actually a start determination for entering a transition process performed to complete multi-pass recording up to that point in order to enter page recording pause in the middle of page recording.

  First, the ink jet recording apparatus automatically performs head recovery processing during page recording as a normal determination operation. This is a determination that is made based on the cumulative print length and the cumulative number of recorded pixels that have been recorded up to that point. Is performed automatically. Further, the present ink jet recording apparatus is configured such that when a blank band area is found, head recovery processing can be executed in the blank band area.

  Hereinafter, the start determination operation for the transfer process of the inkjet recording apparatus will be described in detail with reference to FIG. FIG. 1 is an operation flowchart for explaining the start determination operation for the transition processing.

  The ink jet recording apparatus performs the transition process determination immediately before starting each recording scan during the page recording. Further, in addition to the original transition processing determination, when the accumulated image recording length has reached a predetermined amount, the blank band region is searched for in the image memory for the recorded image to be recorded from now on in this blank band region. Control is performed so that the head recovery process is executed.

  Therefore, if the accumulated image recording length has already exceeded the predetermined amount D2 during the page recording operation (step 1001), the number of recording pixels in the band memory 610 is counted to perform the recording scan to be executed from now on. A search is made for a blank band region extending over the next recording scan region.

Here, if a blank band region that is equal to or larger than the two-fourth band is found across the recording scan to be executed and the next recording scan region (step 1002),
In order to complete the multi-pass recording in the middle of the page recording so far, the recording scan of FIG. 10B for starting the recording scan of the transition process from the current recording scan is executed (step 1003). On the other hand, if a blank band area is not found in step 1002, further, if the cumulative print length in which image formation has been completed by the page recording operation has reached a predetermined length D1 (step 1004), Further, if the cumulative number of pixels for which image formation has been completed by the page recording operation has reached a predetermined number of pixels (step 1005), even if the blank band region cannot be searched for, The CPU advances the processing to step 1003, and the recording shown in FIG. 10B for starting the recording scan of the transition processing from the current recording scan so as to complete the pass of the multi-pass recording in the middle of the page recording so far. Run a scan.

  In step 1001, if the cumulative print length has not yet reached the predetermined amount D2 during the page recording operation, the page recording operation by the normal multipass recording method is continued.

  The ink jet recording apparatus according to the present invention determines the start of transition for the head recovery process in this manner, so that if the search is successful after the search for the blank band area, the head recovery process in the blank band area is performed. Control to do.

  In the recorded image, the printing pause is executed in the blank area where the image formation is not actually performed. Therefore, the density unevenness due to the temporary pause of the image formation during the page recording is avoided.

  When no blank band area is found, control is performed so that the head recovery process can be performed by the original threshold determination based on the cumulative recording image length and the cumulative recording pixel number.

  Here, with reference to FIG. 11, a detailed description will be given of image formation when a print pause for head recovery is executed in a blank band region. FIG. 11 is a diagram showing a state of a recording scan in which multi-pass recording in the middle of recording is completed in an area including a blank band area in order to shift to head recovery processing in the middle of page recording by the 4-pass recording method ((a)). (D)) and (e) to (f) are diagrams showing a recording scan state in which multi-pass recording is resumed after the head recovery process is completed. With reference to this figure, a description will be given of multi-pass printing performed by the ink jet printing apparatus of the present invention in order to shift to head recovery processing in an area including a blank band area during a page printing operation. The quarter band after the recording scan immediately before the transition to the print pause for the head recovery process and the first quarter band after the pause and restarting the recording operation are blank band areas. Therefore, image formation is not performed for the two-quarter band.

  (A) is a recording scan immediately before shifting to the completion of a pass for printing suspension. Since there is no image data to be recorded in this area in the ¼ recording nozzle array at the rear end of the recording head, image formation is not performed. A pass for transition is completed from the next recording scan.

  The ink jet recording apparatus of the present invention completes a pass in the middle of page recording by performing image formation without performing paper transport for two more recording scans in the case of four-pass recording.

  (B) is a recording scan in which the paper is conveyed by a quarter for the completion of the pass from the recording scan in (a), and image formation is performed using a recording nozzle array of only two-fourths. Since there is no image data to be recorded in this area in the two-fourth recording nozzle rows at the rear end of the recording head, image formation is not performed.

  (C) is a recording scan in which image formation is performed by using only one-fourth recording nozzle rows without carrying a sheet for completing a pass. Since there is no image data to be recorded in this area in the two-fourth recording nozzle rows at the rear end of the recording head, image formation is not performed. By the recording scan of (c), the completion of the pass for shifting to the recording pause in the middle of the page recording is completed.

  In (d), image formation is not performed in this recording scan because there is no image data to be recorded in this area in the recording nozzle array of the recording head. Therefore, the recording scan itself does not have to be performed.

  (E)-(h) is the figure which showed each recording scan when returning from the print halt state for the head recovery process in the middle of page recording, and restarting the page recording operation by a multipass recording system. .

  In (e), image formation is not performed in this recording scan because there is no image data to be recorded in this area in the recording nozzle array of the recording head. For this reason, the recording scan itself need not be performed. This recording scan is performed without changing the position of the recording head from the recording scan (d) immediately before the printing pause.

  In (f), paper is conveyed by a quarter of the bandwidth from the position of the previous recording head (e) for multi-pass, and image formation is performed using a recording nozzle array of only a quarter. It is a recording scan.

  In (g), paper is conveyed by a quarter of the bandwidth from the position of the previous recording head (f) for multi-pass, and image formation is performed using only two-fourths of the recording nozzle rows. It is a recording scan.

  In (h), for multi-pass, paper is conveyed by a quarter of the bandwidth from the previous recording head position of (g), and image formation is performed using the recording nozzle array of three-fourths of the recording head. Is a recording scan. After this, page recording is completed by performing the recording scan of (h) and paper conveyance by a quarter of the bandwidth. In the recording nozzle row at the upper end of the recording head, since there is no image data to be imaged, image formation is not performed on that portion.

(Other embodiments)
The present invention can be applied to various ink jet recording apparatuses capable of recording an image using a recording head having a plurality of ink discharge ports. For example, a recording apparatus that records color images using inks of the same or different colors, a recording apparatus that records multi-tone images using inks of the same color and different densities, and a combination of these functions Similar effects can be achieved by similarly applying the present invention to the apparatus.

  Further, the present invention uses a replaceable ink jet cartridge in which a recording head and an ink tank as recording means are integrated, a recording head and an ink tank as recording means are separated, and an ink is provided between them. The same effect can be obtained by applying the present invention in the same manner regardless of the arrangement of the recording means and the ink tank, such as a configuration of connecting with a supply tube or the like.

It is an operation | movement flowchart which shows the operation | movement of the transfer process start determination performed to the recovery process performed during page recording operation | movement of the inkjet recording device of this invention. It is explanatory drawing of the recorded image in the middle of the recording operation at the time of performing two-pass recording. FIG. 6 is an explanatory diagram showing how ink permeates and fixes when the time interval between the 1/2 pass and the 2/2 pass is short in 2-pass printing. FIG. 5 is an explanatory diagram of ink penetration and fixing when the time interval between the 1/2 pass and the 2/2 pass is long in 2-pass printing. 1 is a front view of an ink jet recording apparatus according to an embodiment of the present invention. It is a block block diagram of the control system in the inkjet recording device of this invention. FIG. 6 is an explanatory diagram of a relationship between a recording head position and a recording area when performing two-pass recording as multi-pass recording. It is an example of the printing parameter received from the host device during the page recording operation. It is an operation | movement flowchart shown about recording operation | movement of the inkjet recording device of this invention. Recording scan to complete multi-pass printing during recording in order to shift to head recovery processing in the middle of page recording operation by multi-pass recording method, and when multi-pass recording is restarted after recovery processing is completed It is a figure which shows the mode of the recording scan of. In order to shift to the head recovery process in the middle of the page recording operation by the multipass recording method, the state of the recording scan for completing the multipass recording in the middle of the recording in the blank band area in the image area, and after the recovery process is completed It is a figure which shows the mode of the recording scan when multipass recording is started again.

Explanation of symbols

1 Carriage 2 Device body (including transport system unit)
5 Recording head 11 Guide shaft 12 Encoder film 13 Belt 30A, 30B, 30C, 30D Recovery mechanism 31 Preliminary ejection ink receiving box 32 Wiping mechanism 101a, 101b Ink droplet 102 Recording medium 601 CPU
602 ROM
603 RAM
604 interface 605 operation / display unit 606 CR motor driver 607 CR motor 608 LF motor driver 609 LF motor 610 band memory 611 multipath data processing unit 612 head controller 613 multi head

Claims (2)

Using a recording head capable of ejecting ink from a plurality of ejection openings, an image is recorded by scanning the recording head a plurality of times with respect to the same recording area on the recording medium, and image recording can be temporarily stopped. In an inkjet recording apparatus that performs image formation by a multipass recording method,
Transition to the head recovery process during the page recording operation by performing the threshold determination based on the first threshold D1 regarding the accumulated image recording length of the image formed during the page recording operation and the threshold determination regarding the accumulated recording pixel number formed by the image. Determining means for determining permission for execution of recording operation suspension for
Search means for searching for a blank band area in a recorded image to be imaged by counting the number of recorded pixels in the image memory;
A second threshold D2 relating to the cumulative image recording length,
A blank band region is searched for in the recorded image to be formed, and the accumulated image recording length has reached the second threshold value D2, and the search for the blank band region in the recorded image to be imaged has succeeded. Control to perform a head recovery process when the blank band region is formed,
On the other hand, if the blank band area is not found, the process proceeds to the head recovery process in the middle of page recording by the threshold determination based on the first threshold D1 regarding the cumulative image recording length and the threshold determination regarding the cumulative recording pixel number. To
An ink jet recording apparatus.   The threshold value relating to the cumulative image recording length according to claim 1, wherein the magnitude of the second threshold value D2 relating to the cumulative image recording length is an amount set smaller than the first threshold value D1.

Images