JP2007253407A - Image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a preliminarily-discharged liquid from reacting and consolidating inside a receiving opening while suppressing a cost increase. <P>SOLUTION: An image formation device performs an image recording while carrying out a both-ways scanning on a liquid discharge means, which has two or more nozzle groups for discharging a different kind of liquid, in the direction perpendicular to the conveying direction of a recording medium. The problem concerned is solved by composing the image formation device which is equipped with a preliminary discharge control means for making a control so as to perform the preliminary discharge at a different scan timing for every nozzle group. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that performs image recording by discharging droplets from a nozzle toward a recording medium.

  2. Description of the Related Art In recent years, ink jet recording apparatuses have become widespread as output devices such as computers. Features of this apparatus include low noise during recording operations, low running costs, and the ability to record high-quality images on various types of recording media.

  An ink jet recording apparatus includes a recording head (hereinafter simply referred to as a “head”) having a large number of ejection openings (nozzles), and ejects ink droplets from the nozzles toward the recording medium, thereby forming a desired recording medium. Record images. In such an apparatus, if the state where ink droplets are not ejected from a specific nozzle continues, the ink in the nozzles thickens due to evaporation or the like, and the flying direction of the ink droplets shifts, or ink with high density immediately after ejection starts. Drops may be ejected, and white streaks and density unevenness may be visually recognized in the recorded image. For this reason, in an ink jet recording apparatus, an ink discharge operation (preliminary discharge operation) that is unrelated to image recording is generally performed within a time when no discharge failure occurs.

  In a so-called serial type ink jet recording apparatus that performs recording while reciprocally scanning the head in the direction (main scanning direction) perpendicular to the conveyance direction (sub-scanning direction) of the recording medium, It is determined whether or not a predetermined time or more has elapsed since the preliminary ejection. If the predetermined time or more has elapsed, the head is moved to the preliminary ejection position outside the recording medium to perform the preliminary ejection. Yes. However, if preliminary ejection is frequently performed, not only the recording speed is reduced, but also wasteful ink consumption is performed, which causes an increase in running cost. In order to solve such a problem, for example, in Patent Document 1, the number of ink ejections from each of a plurality of nozzles is measured during a recording scan by reciprocal scanning of the head, and the ink from each of the measured plurality of nozzles is measured. Whether or not the number of ejections has reached a predetermined number is determined at predetermined time intervals, the recordable time is adjusted according to the determination result, and the adjusted recording is possible each time one recording scan by the reciprocating scan ends. A method has been proposed in which the time is compared with the time required for the next recording scan, and control is performed so that preliminary ejection from the recording head is performed according to the comparison result.

Some ink jet recording apparatuses use a head for discharging a processing liquid (a head for processing liquid) in combination with the recording medium in order to promote ink fixability on the recording medium. In such an apparatus, when the ink and the processing liquid are preliminarily discharged toward the absorber (for example, a sponge) serving as the receiving port, the ink and the processing liquid are mixed and absorbed by the inside of the absorber to be reacted and solidified. In addition, the absorption performance of the absorber during long-term use deteriorates. In order to solve such a problem, for example, in Patent Document 2, a partition plate is provided so as to separate the receiving port for ink and processing liquid, and the absorber is separately used for ink and processing liquid. By providing it, it is possible to prevent the preliminarily ejected ink and the treatment liquid from being solidified and to prevent the absorption performance of the absorber from deteriorating.
JP 2004-82629 A JP 2004-74640 A

  However, when performing preliminary ejection by the control method described in Patent Document 1 described above, there are the following problems. That is, when a plurality of color inks, in particular, black ink and other color inks are simultaneously preliminarily ejected, the color inks are mixed together and dispersed in the ink by the absorber disposed at the preliminary ejection receptacle. The color material may become insoluble and precipitate. As a result, as in the case of the ink and the treatment liquid, the absorber is solidified and the absorption performance is deteriorated.

  On the other hand, the method using a receptacle as described in Patent Document 2 has the following problems. That is, the pre-discharged absorber for absorbing ink and the absorber for absorbing processing liquid are separately arranged in each part of the receiving port that is individualized by the partition plate. Since the ink suction pump and the processing liquid suction pump for individually sucking and discharging the ink and the processing liquid are connected to each other, the complexity of the receiving port structure and the increase in the number of parts cause a cost increase.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an image forming apparatus capable of preventing the pre-discharged liquids from reacting and solidifying inside the receiving port while suppressing an increase in cost. And

  In order to achieve the above object, according to the first aspect of the present invention, an image is scanned while reciprocally scanning a liquid ejecting means having a plurality of nozzle groups for ejecting different types of liquid in a direction perpendicular to the conveyance direction of the recording medium. Provided is an image forming apparatus that performs recording, and is provided with a preliminary discharge control unit that controls to perform preliminary discharge at different scanning timings for each nozzle group.

  According to the present invention, since the preliminary ejection timing can be changed for each nozzle group that ejects different types of liquid, the liquid preliminarily ejected from each nozzle group reacts and solidifies inside the preliminary ejection receptacle. Can be prevented. As a result, a simple structure can be achieved without partitioning the preliminary discharge receiving port for each nozzle group, so that the cost can be reduced.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, every time one reciprocating scan of the liquid ejection unit is completed, the previous ejection is performed until the time point. First acquisition means for acquiring the first elapsed time for each nozzle, and first comparison means for comparing the first elapsed time of each nozzle acquired by the first acquisition means with a predetermined first discharge compensation time. Further, the preliminary ejection control means performs preliminary ejection for each nozzle according to the comparison result by the first comparison means.

  According to the aspect of the second aspect, not only the preliminary ejection timing can be changed for each nozzle group, but also only the nozzles (abnormal nozzles) that are likely to cause ejection failure among the nozzle groups are reserved. Since discharge is performed, wasteful liquid consumption can be prevented and an increase in running cost can be prevented.

  According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, every time when one reciprocating scan of the liquid ejection unit is completed, from that time until the next ejection is performed. Second acquisition means for acquiring a second elapsed time for each nozzle; and second comparison means for comparing the second elapsed time of each nozzle acquired by the second acquisition means with a predetermined second discharge compensation time. Further, the preliminary discharge control means performs preliminary discharge for each nozzle according to the comparison result by the second comparison means.

  According to the aspect of claim 3, since the number of preliminary ejections can be reduced, it is possible to prevent a decrease in recording speed and an increase in running cost.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect of the present invention, the number of ejections acquisition unit that acquires the number of ejections per unit time of each nozzle, Adjusting means for adjusting the second discharge compensation time in accordance with the number of nozzle discharges, wherein the second comparison means includes the second elapsed time of each nozzle acquired by the second acquisition means and the The second discharge compensation time adjusted by the adjusting means is compared.

  A fifth aspect of the present invention is the image forming apparatus according to any one of the first to fourth aspects, wherein the liquid ejection unit ejects at least one kind of color ink. And a second nozzle group for discharging a processing liquid for promoting the fixing property of the color ink.

  The present invention is suitable for an embodiment in which a treatment liquid that promotes the fixability of the color ink is used, and the color ink and the treatment liquid can be prevented from reacting and solidifying inside the preliminary ejection receptacle.

  A sixth aspect of the present invention is the image forming apparatus according to any one of the first to fourth aspects, wherein the liquid ejecting means includes a first nozzle group that ejects black ink, and at least one. It has the 2nd nozzle group which discharges color inks other than the said kind of black ink, It is characterized by the above-mentioned.

  The present invention is suitable for an embodiment in which black ink and other color inks are used, and the black ink and other color inks can be prevented from reacting and solidifying inside the preliminary ejection receptacle.

  According to the present invention, since the preliminary ejection timing can be changed for each nozzle group that ejects different types of liquid, the liquid preliminarily ejected from each nozzle group reacts and solidifies inside the preliminary ejection receptacle. Can be prevented. As a result, a simple structure can be achieved without partitioning the preliminary discharge receiving port for each nozzle group, so that the cost can be reduced.

  Hereinafter, preferred embodiments (first to third embodiments) of the present invention will be described in detail with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is an overall configuration diagram of an ink jet recording apparatus as a first embodiment of the present invention. As shown in the figure, the ink jet recording apparatus 10 of the present embodiment ejects cyan (C), magenta (M), and yellow (Y) color inks and a processing liquid (S) that promotes fixing of these color inks. A printing unit 12 having a head (not shown in FIG. 1; described as reference numeral 50 in FIG. 2), and color ink (C, M, Y) and processing liquid (S) supplied to the printing unit 12 are stored. A liquid storage / loading unit 14, a paper feeding unit 18 that supplies the recording paper 16, a decurling unit 20 that removes curling of the recording paper 16, and an ejection surface (nozzle surface) of the printing unit 12 are arranged to face each other. The suction belt conveyance unit 22 that conveys the recording paper 16 while maintaining the flatness of the recording paper 16, the print detection unit 24 that reads the printing result by the printing unit 12, and the printed recording paper (printed matter) A paper discharge unit 26 for discharging the paper to It is provided.

  In FIG. 1, a magazine for rolled paper (continuous paper) is shown as an example of the paper supply unit 18, but a plurality of magazines having different paper widths, paper quality, and the like may be provided side by side. Further, instead of the roll paper magazine or in combination therewith, the paper may be supplied by a cassette in which cut papers are stacked and loaded.

  In the case of an apparatus configuration using roll paper, a cutter 28 is provided as shown in FIG. 1, and the roll paper is cut into a desired size by the cutter 28. The cutter 28 includes a fixed blade 28A having a length equal to or greater than the conveyance path width of the recording paper 16, and a round blade 28B that moves along the fixed blade 28A. The fixed blade 28A is provided on the back side of the print. The round blade 28B is arranged on the print surface side with the conveyance path interposed therebetween. Note that the cutter 28 is not necessary when cut paper is used.

  When multiple types of recording paper are used, an information recording body such as a barcode or wireless tag that records paper type information is attached to the magazine, and the information on the information recording body is read by a predetermined reader. Therefore, it is preferable to automatically determine the type of paper to be used and perform ink ejection control so as to realize appropriate ink ejection according to the type of paper.

  The recording paper 16 delivered from the paper supply unit 18 retains curl due to having been loaded in the magazine. In order to remove this curl, heat is applied to the recording paper 16 by the heating drum 30 in the direction opposite to the curl direction of the magazine in the decurling unit 20. At this time, it is more preferable to control the heating temperature so that the printed surface is slightly curled outward.

  After the decurling process, the cut recording paper 16 is sent to the suction belt conveyance unit 22. The suction belt conveyance unit 22 has a structure in which an endless belt 33 is wound between rollers 31 and 32, and at least a portion facing the ejection surface of the printing unit 12 and the sensor surface of the printing detection unit 24 is flat. It is configured to make.

  The belt 33 has a width that is wider than the width of the recording paper 16, and a plurality of suction holes (not shown) are formed on the belt surface. As shown in FIG. 1, an adsorption chamber 34 is provided at a position facing the discharge surface of the printing unit 12 and the sensor surface of the print detection unit 24 inside the belt 33 spanned between the rollers 31 and 32. Then, the suction chamber 34 is sucked by the fan 35 to be a negative pressure, whereby the recording paper 16 on the belt 33 is sucked and held.

  The power of a motor (not shown) is transmitted to at least one of the rollers 31 and 32 around which the belt 33 is wound, so that the belt 33 is driven in the clockwise direction in FIG. The recording paper 16 is conveyed in the sub-scanning direction (paper conveying direction; right direction in FIG. 1).

  Since ink adheres to the belt 33 when a borderless print or the like is printed, the belt cleaning unit 36 is provided at a predetermined position outside the belt 33 (an appropriate position other than the print area). Although details of the configuration of the belt cleaning unit 36 are not shown, for example, there are a method of niping a brush roll, a water absorbing roll, etc., an air blowing method of spraying clean air, or a combination thereof. In the case where the cleaning roll is nipped, the cleaning effect is great if the belt linear velocity and the roller linear velocity are changed.

  Although a mode using a roller / nip transport mechanism instead of the suction belt transport unit 22 is also conceivable, when the print area is transported by a roller / nip, the roller comes into contact with the print surface of the paper immediately after printing, so that the image blurs. There is a problem that it is easy. Therefore, as in this example, suction belt conveyance that does not contact the image surface in the printing region is preferable.

  A heating fan 40 is provided on the upstream side of the printing unit 12 on the paper conveyance path formed by the suction belt conveyance unit 22. The heating fan 40 heats the recording paper 16 by blowing heated air onto the recording paper 16 before printing. Heating the recording paper 16 immediately before printing makes it easier for the ink to dry after landing.

  The liquid storage / loading unit 14 includes tanks for storing the respective color inks and processing liquids to be supplied to the printing unit 12, and each tank communicates with the head via a pipe line (not shown). In addition, the liquid storage / loading unit 14 includes notifying means (display means, warning sound generating means, etc.) for notifying that when the remaining amount of liquid (ink or processing liquid) in each tank decreases, and between the liquids A mechanism for preventing erroneous loading is provided.

  The print detection unit 24 includes an image sensor (line sensor or the like) for imaging the droplet ejection result of the print unit 12, and means for checking nozzle clogging and other ejection defects from the droplet ejection image read by the image sensor. Function as.

  The print detection unit 24 of this example is composed of a line sensor having a light receiving element array wider than the image recording width of the recording paper 16. The line sensor includes an R sensor row in which photoelectric conversion elements (pixels) provided with red (R) color filters are arranged in a line, a G sensor row provided with green (G) color filters, The color separation line CCD sensor includes a B sensor array provided with a blue (B) color filter. Instead of the line sensor, an area sensor in which the light receiving elements are two-dimensionally arranged can be used.

  The print detection unit 24 reads the test pattern ejected by the print unit 12 and detects the ejection of each nozzle. The ejection determination includes the presence / absence of ejection, measurement of dot size, measurement of dot landing position, and the like.

  A post-drying unit 42 is provided following the print detection unit 24. The post-drying unit 42 is means for drying the printed image surface, and for example, a heating fan is used. Since it is preferable to avoid contact with the printing surface until the ink after printing is dried, a method of blowing hot air is preferred.

  When printing on porous paper with dye-based ink, the weather resistance of the image is improved by preventing contact with ozone or other things that cause dye molecules to break by blocking the paper holes by pressurization. There is an effect to.

  A heating / pressurizing unit 44 is provided following the post-drying unit 42. The heating / pressurizing unit 44 is a means for controlling the glossiness of the image surface, and pressurizes with a pressure roller 45 having a predetermined uneven surface shape while heating the image surface to transfer the uneven shape to the image surface. To do.

  The printed matter generated in this manner is outputted from the paper output unit 26. It is preferable that the original image to be printed (printed target image) and the test print are discharged separately. The ink jet recording apparatus 10 is provided with sorting means (not shown) for switching the paper discharge path in order to select the print product of the main image and the print product of the test print and send them to the discharge units 26A and 26B. ing. Note that when the main image and the test print are simultaneously formed in parallel on a large sheet, the test print portion is separated by a cutter (second cutter) 48. The cutter 48 is provided immediately before the paper discharge unit 26, and cuts the main image and the test print unit when the test print is performed on the image margin. The structure of the cutter 48 is the same as that of the first cutter 28 described above, and includes a fixed blade 48A and a round blade 48B. Although not shown, the paper output unit 26A for the target prints is provided with a sorter for collecting prints according to print orders.

  FIG. 2 is a view showing the periphery of the printing unit 12 as a main configuration of the inkjet recording apparatus 10 of the present embodiment, where (a) is a plan view and (b) is a front view. In addition, illustration of the suction belt conveyance part 22 (refer FIG. 1) which conveys the recording paper 16 is abbreviate | omitted.

  As shown in the drawing, a head 50 that discharges cyan (C), magenta (M), yellow (Y) ink and processing liquid (S) is mounted on a carriage 60. The carriage 60 is configured to be reciprocally movable along a guide rail 62 extending in the width direction (main scanning direction) of the recording paper 16 by a carriage motor (not shown), and the head 50 is moved in the main scanning direction as the carriage 62 moves. A reciprocating scan is performed along.

  While repeating the paper feeding operation for transporting the recording paper 16 by a predetermined amount in the sub-scanning direction and the head scanning by the reciprocating scanning of the head 50 along the main scanning direction, a predetermined liquid (color ink or processing liquid) is respectively output from the head 50. ) Is ejected toward the recording paper 16 to record a desired image on the recording paper 16.

  FIG. 3 is a plan view showing the ejection surface of the head 50. As shown in the drawing, a plurality of nozzle rows 151 in the sub-scanning direction (five rows in this example) are provided on the ejection surface of the head 50. Nozzle columns 151C, 151M, and 151Y corresponding to cyan (C), magenta (M), and yellow (Y) color inks are sequentially arranged along the main scanning direction, and the main nozzle arrays 151C, 151M, and 151Y Two nozzle rows 151S and 151S corresponding to the processing liquid (S) are arranged on both sides in the scanning direction. The plurality of nozzles 51 constituting each nozzle row 151 each discharge a corresponding liquid (color ink or processing liquid).

  When the head 50 is reciprocally scanned along the main scanning direction, the processing liquid is discharged from the processing liquid nozzles 51s belonging to the nozzle row 151S on the upstream side in the scanning direction, and subsequently, the respective nozzles 151C, 151M, and 151Y The corresponding color ink is ejected from the ink nozzles 51i. At this time, the processing liquid is not discharged from the processing liquid nozzles 51s belonging to the nozzle row 151S on the downstream side in the scanning direction. The same operation is performed when the scanning direction of the head 50 is reversed. As described above, since the processing liquid is ejected to the recording paper 16 before each color ink, each color ink ejected later is mixed with the processing liquid substantially at the same time as landing on the recording paper 16 and dispersed in each color ink. Alternatively, the dissolved color material is solidified or insolubilized. As a result, each color ink landed on the recording paper 16 is immediately fixed without breaking the dot shape, and high-quality image recording is possible.

  4 is a partial cross-sectional view of the head 50 (cross-sectional view taken along line 4-4 in FIG. 3). As illustrated, an individual flow path 52 communicating with the nozzle 51 is provided in the head 50. The individual flow path 52 is provided for each nozzle 51. One end of the individual flow path 52 communicates with a common flow path (not shown), and a predetermined liquid (color ink or processing liquid) is supplied to the individual flow path 52 from the liquid storage / loading unit 14 of FIG. ) Is supplied. The common flow path is provided for each predetermined liquid (color ink or processing liquid).

  In addition, an electrothermal converter (for example, a heater) 54 that generates thermal energy is provided on the inner wall surface of the individual flow path 52. The electrothermal converter 54 is provided for each nozzle 51. By applying a predetermined driving voltage to the electrothermal transducer 54, bubbles are generated in the liquid (color ink or processing liquid) in the individual flow path 52, and droplets are ejected from the corresponding nozzles 51 by the pressure of the bubbles. To do.

  Note that the embodiment of the present invention is not limited to the thermal method in which the discharge is performed using the electrothermal transducer 54 as in the present embodiment, and for example, the discharge is performed using a piezoelectric element typified by a piezo. A piezoelectric system or other various systems may be used.

  In the ink jet recording apparatus 10 of the present embodiment, in order to prevent a discharge failure due to an increase in viscosity (thickening) of ink in the nozzle 51, discharge (preliminary discharge) unrelated to image recording is performed from each nozzle 51. Done. As shown in FIG. 2, the preliminary ejection is performed by moving the head 50 to a predetermined position (preliminary ejection position) outside the recording paper 16, that is, outside the recording area by the head 50. At the preliminary discharge position, an absorber 64 made of, for example, a sponge is disposed as a receiving port for liquid (color ink or processing liquid) preliminary discharged from each nozzle 51. The absorber 64 directly receives and absorbs the liquid preliminarily discharged from each nozzle 51 and absorbs the liquid preliminarily discharged from each nozzle 51 to the first absorber (temporary receiving port). ) And a second absorbent body (main receiving port) 64b that is indirectly absorbed through 64a.

  Preliminary ejection control, which is a feature of the present invention, will be described in detail later. In this embodiment, two nozzle arrays 151S and 151S corresponding to the processing liquid are replaced with a first nozzle group 152A, and nozzle arrays 151C corresponding to each color ink. 151M and 151Y are set as the second nozzle group 152B, and preliminary ejection is performed at different scanning timings for each nozzle group.

  FIG. 5 is a principal block diagram showing the system configuration of the inkjet recording apparatus 10. The inkjet recording apparatus 10 includes a communication interface 70, a system controller 72, an image memory 74, a motor driver 76, a heater driver 78, a print control unit 80, an image buffer memory 82, a head driver 84, and the like.

  The communication interface 70 is an interface unit that receives image data sent from the host computer 86. A serial interface or a parallel interface can be applied to the communication interface 70. In this part, a buffer memory (not shown) for speeding up communication may be mounted.

  Image data sent from the host computer 86 is taken into the inkjet recording apparatus 10 via the communication interface 70 and temporarily stored in the image memory 74. The image memory 74 is a storage unit that temporarily stores an image input via the communication interface 70, and data is read and written through the system controller 72. The image memory 74 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The system controller 72 is a control unit that controls each unit such as the communication interface 70, the image memory 74, the motor driver 76, and the heater driver 78. The system controller 72 includes a central processing unit (CPU) and its peripheral circuits, and performs communication control with the host computer 86, read / write control of the image memory 74, and the like, as well as a transport system motor 88 and heater 89. A control signal for controlling is generated.

  The motor driver 76 is a driver (drive circuit) that drives the motor 88 in accordance with an instruction from the system controller 72. The heater driver 78 is a driver that drives the heaters 89 of the post-drying unit 42 and other units in accordance with instructions from the system controller 72.

  The print control unit 80 has a signal processing function for performing various processing and correction processing for generating a print control signal from the image data in the image memory 74 according to the control of the system controller 72, and the generated print A control unit that supplies a control signal (dot data) to the head driver 84. Necessary signal processing is performed in the print controller 80, and the ejection amount and ejection timing of the ink droplets of the head 50 are controlled via the head driver 84 based on the image data. Thereby, a desired dot size and dot arrangement are realized. Note that preliminary discharge control, which will be described later, is executed in the print control unit 80.

  The print control unit 80 includes an image buffer memory 82, and image data, parameters, and other data are temporarily stored in the image buffer memory 82 when image data is processed in the print control unit 80. In FIG. 5, the image buffer memory 82 is shown in a form associated with the print control unit 80, but it can also be used as the image memory 74. Also possible is an aspect in which the print controller 80 and the system controller 72 are integrated and configured with one processor.

  The head driver 84 generates a drive signal for driving the electrothermal transducer 54 (see FIG. 4) corresponding to each nozzle 51 of the head 50 based on the print data given from the print controller 80, and performs electrothermal conversion. The generated drive signal is supplied to the body 54. The head driver 84 may include a feedback control system for keeping the driving condition of the head 50 constant.

  The print detection unit 24 reads the test pattern recorded by the head 50, performs necessary signal processing and the like, and detects the discharge status (existence of discharge, dot size, dot landing position, etc.) of each nozzle 51 (ie, The variation of each nozzle 51 is detected), and the detection result is provided to the print controller 80. The print controller 80 performs various corrections on the head 50 based on information obtained from the print detector 24 as necessary.

  Next, preliminary discharge control, which is a characteristic part of the present invention, will be described.

  FIG. 6 is a flowchart showing an example of preliminary discharge control performed in the inkjet recording apparatus 10 of the present embodiment. It is assumed that the head 50 is at the preliminary ejection position at the start of the recording operation.

  First, when the recording operation is started, a scan counter N indicating the number of reciprocating scans of the head 50 is reset to 0 (step S100). Next, a paper feeding operation for transporting the recording paper 16 by a predetermined amount in the sub-scanning direction is performed, and the recording paper 16 is set at a predetermined position (recording start position) (step S102). Subsequently, head scanning is performed in which the head 50 is reciprocally scanned along the main scanning direction (step S104). At this time, the corresponding color ink or processing liquid is ejected from each nozzle 51 according to the dot data. At the end of head scanning, the scanning counter N is incremented by 1 (step S106).

Here, X ₀ , X ₁ , k are arbitrary positive integers (1, 2, 3,...), And the relationship of X ₀ , X ₁ <k and X ₀ ≠ X ₁ is established. To do. Further, m is 0 or any positive integer (1, 2, 3,...).

  In the next step S108, it is determined whether or not the relationship of the following equation is established.

N−X ₀ = k × m (1)
When the relationship of Formula (1) is satisfied (in the case of Yes), the head 50 is moved to the preliminary discharge position (step S110), and the processing liquid is preliminary discharged from all the processing liquid nozzles 51s of the first nozzle group 152A. (Step S112). After preliminary ejection, the process proceeds to step S120. On the other hand, when the relationship of Formula (1) is not satisfied (in the case of No), the process proceeds to step S114 as it is.

  In the next step S114, it is determined whether or not the relationship of the following equation is established.

N−X ₁ = k × m (2)
When the relationship of Expression (2) is satisfied (in the case of Yes), the head 50 is moved to the preliminary ejection position (step S116), and the corresponding color ink is preliminary reserved from all the ink nozzles 51i of the second nozzle group 152B. Discharge (step S118). After preliminary ejection, the process proceeds to step S120. On the other hand, when the relationship of Formula (2) is not satisfied (in the case of No), the process proceeds to step S120 as it is.

  When the processing liquid is preliminarily ejected in step S112, when ink is preliminarily ejected in step S118, or in the case of No in step S114 (that is, when neither of the relations of the expressions (1) and (2) is established). Determines whether the recording data has ended (step S120). If the recording data has not ended (No), the process returns to step S102. On the other hand, when the recording data is finished (in the case of Yes), the recording operation is finished.

In this flowchart, the constant k defines the frequency with which each nozzle 51 performs preliminary ejection, and X ₀ and X ₁ define the preliminary ejection timing of the processing liquid and color ink, respectively. For example, when k = 3, X ₀ = 1, and X ₁ = 2, the processing liquid is preliminarily ejected from the first nozzle group 152A at the end of the first head scan (N = 1), and the second time. At the end of head scanning (N = 2), color ink is preliminarily ejected from the second nozzle group 152B. Preliminary ejection is not performed at the end of the third head scan (N = 3). From the fourth time on, processing is performed in the same order. As described above, each nozzle group 152A, 152B performs preliminary ejection once in k times of head scanning, and further, preliminary ejection is performed at the end of different head scanning for each nozzle group (that is, at different scanning timings). Control is done.

  In the first embodiment, the first nozzle group 152A that discharges the processing liquid and the second nozzle group 152B that discharges each color ink perform preliminary discharge at different scanning timings. Thus, the treatment liquid and the color ink do not react and solidify, and deterioration of the absorption performance of the absorber 66 can be prevented. As a result, a simple structure can be achieved without partitioning the preliminary discharge receiving port for each nozzle group, so that the cost can be reduced.

  In the present embodiment, the configuration in which each color ink of cyan, magenta, and yellow is used is exemplified, but the combination of the ink color and the number of colors is not limited to this embodiment. For example, a configuration in which black ink is added is also possible.

  In this embodiment, each color ink is preliminarily ejected at the same scanning timing. However, a predetermined color ink may be preliminarily ejected at a scanning timing different from that of other color inks. In particular, in the case where the black ink is added as described above, the nozzles are classified into a nozzle group for discharging the processing liquid, a nozzle group for discharging the black ink, and a nozzle group for discharging other color inks. Preliminary ejection is preferably performed at different scanning timings for each group. Furthermore, preliminary ejection may be performed with different scanning timing for each color ink. However, if the scanning timing for performing preliminary ejection is increased, the recording speed is reduced. Therefore, it is preferable to perform preliminary ejection at the same scanning timing for color inks that are difficult to react and solidify even when mixed.

  FIG. 7 is a plan view showing an ejection surface of a head 50 ′ as a modified example of the first embodiment. As shown in the figure, on the ejection surface of the head 50 ', nozzle rows 151K' and 151C in the sub-scanning direction corresponding to black (K), cyan (C), magenta (M), and yellow (Y) inks, respectively. ', 151M', 151Y 'are provided. Note that this modification is an aspect in which the processing liquid (S) is not used, unlike the head 50 of the first embodiment.

  In this modification, the nozzle row 151K ′ corresponding to the black ink is the first nozzle group 152A ′, and the nozzle rows 151C ′, 151M ′, 151Y ′ corresponding to the other color inks are the second nozzle group 152B ′. Similarly to the head 50 of the embodiment, preliminary ejection is performed at different scanning timings for each nozzle group. That is, in the flowchart of FIG. 6, black ink is preliminarily ejected from the first nozzle group 152A ′ in step S112, and cyan, magenta, and yellow color inks are preliminarily ejected from the second nozzle group 152B ′ in step S118. Other processes are the same as those in the first embodiment.

  It is generally known that the color material may solidify or become insoluble when black ink and other color inks are mixed. In this way, black ink and other color inks are preliminarily ejected at different scanning timings. Accordingly, it is possible to prevent these inks from reacting and solidifying inside the absorber 64 serving as a receiving port for preliminary ejection, and it is possible to prevent the absorption performance of the absorber 64 from being deteriorated.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the following description, description of parts common to the first embodiment described above will be omitted, and description will be made focusing on characteristic parts of the present embodiment.

  In the second embodiment, every time one reciprocating scan of the head 50 is completed, an interval time (first elapsed time) T from the previous ejection to the time is measured for each nozzle 51. The interval time T of each nozzle 51 is compared with a predetermined discharge compensation time (first discharge compensation time) H, and preliminary discharge is performed for abnormal nozzles that are likely to cause discharge failure according to the comparison result. . At this time, if any of the nozzle groups 152A and 152B includes an abnormal nozzle, the nozzle group including the nozzle having the largest difference between the interval time T and the discharge compensation time H is preferentially reserved. Discharge.

  In the following, in particular, the interval time of the treatment liquid nozzle 51s belonging to the first nozzle group 152A is represented as Ts, and the interval time of the ink nozzle 51i belonging to the second nozzle group 152B is represented as Ti. Also, a value obtained by subtracting the time required for one reciprocating scanning from the time for compensating good ejection is taken as ejection compensation time H, the ejection compensation time for the processing liquid nozzle 51s is taken as Hs, and the ejection compensation time for the ink nozzle 51i is taken as Hi. To express. The ejection compensation times Hs and Hi are determined according to the head design value, the type and combination of ink and processing liquid, and the like.

  FIG. 8 is a flowchart illustrating an example of preliminary discharge control according to the second embodiment.

  First, when the recording operation is started, preliminary ejection is performed from all the nozzles 51 at the preliminary ejection position (step S200), and the interval time T of all the nozzles 51 is reset to 0 (step S201). Next, a paper feeding operation for conveying the recording paper 16 by a predetermined amount in the sub-scanning direction is performed (step S202), and head scanning is performed in which the head 50 is reciprocally scanned along the main scanning direction (step S204). Subsequently, the interval time T of all the nozzles 51 is acquired (step S206).

  In the next step S208, it is determined whether or not there is a processing liquid nozzle 51s in which the interval time Ts is equal to or longer than the discharge compensation time Hs, that is, an abnormal nozzle that is likely to cause a discharge failure in the first nozzle group 152A. To do. If there is an abnormal nozzle in the first nozzle group 152A (Yes), the process proceeds to step S210. On the other hand, if there is no abnormal nozzle (No), the process proceeds to step S214.

  In step S210, it is determined whether or not the second nozzle group 152B includes an ink nozzle 51i whose interval time Ti is equal to or longer than the ejection compensation time Hi, that is, an abnormal nozzle that is likely to cause ejection failure. If an abnormal nozzle exists in the second nozzle group 152B (Yes), the process proceeds to step S212. On the other hand, when there is no abnormal nozzle (in the case of No), the process proceeds to step S216.

  If Yes in step 210, that is, if both the first nozzle group 152A and the second nozzle group 152B include an abnormal nozzle, the interval time Ts of the abnormal nozzle included in the first nozzle group 152A and the discharge compensation The maximum value (Max [Ts−Hs]) of the difference in time Hs is from the maximum value (Max [Ti−Hi]) of the difference between the interval time Ti of the abnormal nozzles included in the second nozzle group 152B and the discharge compensation time Hi. It is determined whether it is larger (step S212). When the first nozzle group 152A is larger (in the case of Yes), the process proceeds to step S216. On the other hand, if the second nozzle group 152B is larger or the maximum values of the first nozzle group 152A and the second nozzle group 152B are equal (in the case of No), the process proceeds to step S222.

  If No in step S208, that is, if there is no abnormal nozzle in the first nozzle group 152A, the same determination as in step S210 is performed (step S214). When there is an abnormal nozzle in the second nozzle group 152B (Yes), the process proceeds to step S222. On the other hand, when there is no abnormal nozzle (in the case of No), the process proceeds to step S228.

  In the case of No in step S210 (that is, when an abnormal nozzle exists only in the first nozzle group 152A), or in the case of Yes in step S212 (that is, there is an abnormal nozzle group in each of the nozzle groups 152A and 152B, If the maximum value (Max [Ts−Hs]) of the one nozzle group 152A is larger, the head 50 is moved to the preliminary ejection position (step S216), and processing is performed from the abnormal nozzles included in the first nozzle group 152A. The liquid is preliminarily discharged (step S218). Thereafter, the interval time Ts of the abnormal nozzle that has performed preliminary ejection is reset to 0 (step S220), and the process returns to step S202.

  In the case of No in step S212 (that is, each nozzle group 152A, 152B has an abnormal nozzle, the maximum value (Max [Ts−Hs]) of the second nozzle group 152B is larger, or the first nozzle group. If the maximum value of 152A (Max [Ts−Hs]) is equal to the maximum value of the second nozzle group 152B (Max [Ti−Hi]), or if Yes in step S214 (ie, the second nozzle group 152B). In the case where an abnormal nozzle exists only in step S2), the head 50 is moved to the preliminary ejection position (step S222), and the corresponding color ink is preliminarily ejected from the abnormal nozzle included in the second nozzle group 152B (step S224). Thereafter, the interval time Ti of the abnormal nozzle that has performed preliminary ejection is reset to 0 (step S226), and the process returns to step S202.

  In the case of No in step S214, that is, if there is no abnormal nozzle in either the first nozzle group 152A or the second nozzle group 152B, it is determined whether or not the recording data has ended (step S228). If the recording data is not finished (No), the process returns to step S202. On the other hand, when the recording data is finished (in the case of Yes), the recording operation is finished.

  In the second embodiment, not only the same effects as in the first embodiment can be obtained, but also a discharge failure may be caused by comparing the interval time T indicating the elapsed time from the previous discharge and the discharge compensation time H. Preliminary ejection can be performed only for abnormal nozzles having high characteristics, and wasteful ink consumption due to preliminary ejection can be suppressed, and an increase in running cost can be prevented.

(Third embodiment)
Next, a third embodiment of the present invention will be described. In the following description, the description of the parts common to the first and second embodiments described above will be omitted, and the characteristic parts of the present embodiment will be mainly described.

  In the second embodiment, since the future discharge situation is not taken into consideration, for example, preliminary discharge may be performed even when discharge data exists immediately after determination of preliminary discharge. On the other hand, in the third embodiment, preliminary ejection control in consideration of future ejection conditions is performed to reduce unnecessary preliminary ejection and prevent a decrease in recording speed and an increase in running cost.

  Specifically, every time one reciprocating scan of the head 50 is completed, an interval time (second elapsed time) T ′ from that point to the next discharge is measured for each nozzle 51, The interval time T ′ of the nozzle 51 is compared with a predetermined ejection compensation time (second ejection compensation time) H ′, and preliminary ejection is performed for abnormal nozzles that are likely to cause ejection failure according to the comparison result. . At this time, as in the second embodiment, if any of the nozzle groups 152A and 152B includes an abnormal nozzle, the nozzle having the largest difference between the interval time T ′ and the discharge compensation time H ′ is included. Preliminary discharge is performed with priority given to the nozzle group.

  In the following, in particular, the number of discharges, the interval time, and the discharge compensation time of the processing liquid nozzle 51s belonging to the first nozzle group 152A are represented as Ms, Ts ′, and Hs ′, respectively, and the ink nozzles 51i belonging to the second nozzle group. The number of discharges, the interval time, and the discharge compensation time are represented as Mi, Ti ′, and Hi ′, respectively.

  FIG. 9 is a flowchart illustrating an example of preliminary discharge control according to the third embodiment.

  First, when the recording operation is started, a paper feeding operation for conveying the recording paper 16 by a predetermined amount in the sub-scanning direction is performed (step S300), and head scanning is performed in which each head 50 is reciprocally scanned along the main scanning direction (step S300). S302). Subsequently, an interval time (second elapsed time) T ′ from the time when the head scanning is completed until the next ejection is obtained for each nozzle 51, and the unit time per unit time that each nozzle 51 performs immediately before is obtained. The number of ejections M is acquired (step S304). The interval time T ′ and the number of ejections M can be obtained based on dot data generated by the print control unit in FIG.

  Next, the discharge compensation time H ′ is adjusted according to the number of discharges M acquired in the previous step S304 (step S306). Since the ink in the nozzle 51 having a large number of ejections M is kept fresh, the ejection compensation time T ′ of the nozzle 51 can be lengthened. On the other hand, in the case of the nozzle 51 having a small number of discharges M, it is necessary to shorten the discharge compensation time T ′ of the nozzle 51. For example, data indicating the relationship between the number M of discharges and the discharge compensation time H ′ is stored as a table in a storage means (not shown), and the discharge compensation time H ′ is adjusted by referring to this table. May be.

  As a method for adjusting the discharge compensation time H ′ according to the number M of discharges, the following equation may be used.

H ′ = {1 + a (M−M ₀ )} H ₀ ′ (3)
M ₀ is the average number of discharges, H ₀ ′ is the discharge compensation time when the average number of discharges M ₀ , and a is an arbitrary coefficient (> 0). For example, when M> M ₀ , H ′> H ₀ ′. On the other hand, when M <M ₀ , H ′ <H ₀ ′. As described above, by using the expression (3), the discharge compensation time H ′ can be increased or decreased according to the number M of discharges.

  In the next step S308, whether or not there is a treatment liquid nozzle 51s in which the interval time Ts ′ is equal to or longer than the discharge compensation time Hs ′, that is, whether there is an abnormal nozzle that is likely to cause a discharge failure in the first nozzle group 152A. Judge. If there is an abnormal nozzle in the first nozzle group 152A (Yes), the process proceeds to step S310. On the other hand, if there is no abnormal nozzle (No), the process proceeds to step S314.

  In step S310, it is determined whether or not there is an ink nozzle 51i in which the interval time Ti ′ is equal to or longer than the ejection compensation time Hi ′, that is, an abnormal nozzle that is likely to cause ejection failure in the second nozzle group 152B. . If there is an abnormal nozzle in the second nozzle group 152B (Yes), the process proceeds to step S312. On the other hand, when there is no abnormal nozzle (in the case of No), the process proceeds to step S316.

  If Yes in step 310, that is, if both the first nozzle group 152A and the second nozzle group 152B include an abnormal nozzle, the interval time Ts ′ and the discharge compensation time of the abnormal nozzle included in the first nozzle group 152A The maximum value of the difference between Hs '(Max [Ts'-Hs']) is the maximum value of the difference between the interval time Ti 'of the abnormal nozzles included in the second nozzle group 152B and the next discharge compensation time Hi' (Max [Ti '-Hi']) is determined (step S312). When the first nozzle group 152A is larger (in the case of Yes), the process proceeds to step S316. On the other hand, if the second nozzle group 152B is larger, or if the maximum values of the first nozzle group 152A and the second nozzle group 152 are equal (No), the process proceeds to step S320.

  If No in step S308, that is, if there is no abnormal nozzle in the first nozzle group 152A, the same determination as in step 310 is performed (step 314). If an abnormal nozzle exists in the second nozzle group 152B (Yes), the process proceeds to step S320. On the other hand, when there is no abnormal nozzle (in the case of No), the process proceeds to step S324.

  In the case of No in step S310 (that is, when an abnormal nozzle exists only in the first nozzle group 152A), or in the case of Yes in step 312 (that is, an abnormal nozzle group exists in each of the nozzle groups 152A and 152B, When the maximum value of one nozzle group 152A (Max [Ts′−Hs ′]) is larger), the head 50 is moved to the preliminary ejection position (step S316), and processing is performed from the abnormal nozzles included in the first nozzle group 152A. The liquid is preliminarily discharged (step S318). After the preliminary discharge, the process returns to step S300.

  In the case of No in step S312, (that is, there is an abnormal nozzle group in each of the nozzle groups 152A and 152B, and the maximum value (Max [Ti′−Hi ′]) of the second nozzle group 152B is larger, or If the maximum value of the first nozzle group 152A (Max [Ts′−Hs ′]) is equal to the maximum value of the second nozzle group 152B (Max [Ti′−Hi ′])), or if “Yes” in step 314 ( That is, when an abnormal nozzle exists only in the second nozzle group 152B, the head 50 is moved to the preliminary ejection position (step S320), and the corresponding color ink is preliminarily reserved from the abnormal nozzle included in the second nozzle group 152B. Discharge (step S322). After the preliminary discharge, the process returns to step S300.

  If No in step S314, that is, if there is no abnormal nozzle in either the first nozzle group 152A or the second nozzle group 152B, it is determined whether or not the recording data has been completed (step S324). If the recording data has not ended (No), the process returns to step S300. On the other hand, when the recording data is finished (in the case of Yes), the recording operation is finished.

  In the third embodiment, not only the preliminary discharge control is performed in consideration of the future discharge situation, but also the discharge compensation time H ′ is adjusted according to the number of discharges M per unit time immediately before. Compared to the second embodiment, the number of preliminary ejections can be reduced, and a decrease in recording speed and an increase in running cost can be prevented.

  Although the image forming apparatus of the present invention has been described in detail above, the present invention is not limited to the above examples, and various improvements and modifications may be made without departing from the spirit of the present invention. Of course.

Overall configuration diagram of inkjet recording apparatus Main part configuration diagram showing the periphery of the printing unit of the inkjet recording apparatus Plan view showing the ejection surface of the head Partial sectional view of the head (sectional view taken along line 4-4 in FIG. 3) Main block diagram showing the system configuration of the inkjet recording apparatus The flowchart figure which showed an example of the preliminary discharge control of 1st Embodiment The top view which showed the discharge surface of the head as a modification of 1st Embodiment The flowchart figure which showed an example of the preliminary discharge control of 2nd Embodiment The flowchart figure which showed an example of the preliminary discharge control of 3rd Embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Inkjet recording apparatus, 12 ... Printing part, 16 ... Recording paper, 50 ... Head, 51 ... Nozzle, 52 ... Individual flow path, 54 ... Electrothermal converter, 80 ... Print control part, 151 ... Nozzle row, 152A ... 1st nozzle group, 152B ... 2nd nozzle group

Claims (6)

An image forming apparatus that performs image recording while reciprocally scanning a liquid ejection unit having a plurality of nozzle groups that eject different types of liquids in a direction perpendicular to a conveyance direction of a recording medium,
An image forming apparatus comprising: a preliminary discharge control unit that controls to perform preliminary discharge at different scanning timings for each nozzle group. A first acquisition unit that acquires, for each nozzle, a first elapsed time from the previous discharge to the time point each time one reciprocating scan of the liquid discharge unit is completed;
First comparison means for comparing the first elapsed time of each nozzle acquired by the first acquisition means with a predetermined first discharge compensation time;
The image forming apparatus according to claim 1, wherein the preliminary ejection control unit performs preliminary ejection for each nozzle according to a comparison result by the first comparison unit. A second acquisition unit that acquires, for each nozzle, a second elapsed time from the time point until the next discharge is performed each time one reciprocating scan of the liquid discharge unit is completed;
A second comparison means for comparing the second elapsed time of each nozzle acquired by the second acquisition means with a predetermined second discharge compensation time;
The image forming apparatus according to claim 1, wherein the preliminary ejection control unit performs preliminary ejection for each nozzle according to a comparison result by the second comparison unit. A discharge number acquisition means for acquiring the number of discharges per unit time of each nozzle;
Adjusting means for adjusting the second discharge compensation time according to the number of discharges of each nozzle acquired by the discharge number acquisition unit;
The said 2nd comparison means compares the 2nd elapsed time of each nozzle acquired by the said 2nd acquisition means with the said 2nd discharge compensation time adjusted by the said adjustment means. Image forming apparatus.   2. The liquid ejection unit includes a first nozzle group that ejects at least one kind of color ink and a second nozzle group that ejects a treatment liquid that promotes fixing of the color ink. The image forming apparatus according to claim 4. 5. The liquid ejection unit includes a first nozzle group that ejects black ink and a second nozzle group that ejects at least one kind of color ink other than the black ink. The image forming apparatus according to claim 1.

Images