JP4259965B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus and an image forming method.

  A droplet discharge device that discharges droplets is applied in various fields. In particular, an inkjet recording device that performs recording by discharging a liquid (ink) containing a colorant such as a dye or a pigment is a printer or a facsimile. It is applied as an image forming apparatus such as a copying machine or a plotter.

  Inkjet recording is performed by discharging liquid from a so-called recording head onto a recording material, making it easy to make the recording head compact, recording high-definition images at high speed, and special printing on plain paper. Recording without the need for processing, low running costs, low noise due to the non-impact method, and the ease of forming a color image using color liquid. Have.

  In recent years, recording heads used in such ink jet recording apparatuses have been actively applied to the formation of electronic components and wiring of electronic components, the manufacture of displays such as organic EL panels, and the processing of microlenses. .

  In particular, a full line type ink jet recording apparatus using a line type recording head in which a large number of ejection openings (nozzles) are arranged along the entire width in the recording width direction of the recording area is markedly more effective than a serial type ink jet recording apparatus. Can be speeded up. In such a full-line type inkjet recording apparatus, a plurality of recording media (also referred to as recording medium, paper, transfer paper, recording paper, recording paper, etc.) are arranged in the transport direction from the viewpoint of high-speed recording. So-called one-pass recording is performed in which a recording medium is conveyed at a constant speed directly under a line type recording head, and droplets are ejected for recording.

  However, when the line type droplet discharge head is intended to print at 600 dpi with a paper width of A4 horizontal size, when the line type recording head is a fixed type, there are nozzles that discharge about 7000 ink droplets per color. In order to form a color image, a head for at least four colors of cyan, magenta, yellow, and black is necessary. Therefore, the total number of nozzles is 7000 × 4 colors = 28000 nozzles. . If even one of these has defects such as non-ejection, defects such as white stripes and discoloration occur, resulting in an incomplete image.

Therefore, as a method of complementing defective nozzles such as non-ejection nozzles, there is a method including a line type recording head and a serial type recording head that can move in the arrangement direction of the ejection ports of the line type recording head.
JP-A-2-276647

In addition, there is a type in which an auxiliary recording head having a recording width smaller than that of the line type recording head is attached to the defective nozzle position of the line type recording head, and the defective nozzle of the line type recording head is replaced with the auxiliary recording head to complement the defective type.
JP-A-3-24752

In addition, there are some which supplement two line type recording heads.
Japanese Patent Laid-Open No. 10-6488 JP-A-10-258510

In addition, there is an apparatus in which ink droplets ejected from other normal nozzles are deflected at positions where defective nozzles are to be printed and are printed at positions where non-ejection nozzles are to be shot.
Japanese Patent Laid-Open No. 10-7665

Further, there is a defective nozzle that is used as a black ink recording head, and the defective nozzle complements the black ink color of the defective nozzle by mixing color inks.
Japanese Patent Laid-Open No. 200019-191510

  However, since the one described in Patent Document 1 only includes a plurality of line type recording heads and one serial type recording head, it corresponds to a case where defective nozzles exist in two or more line type recording heads. Can not do it.

  The ones described in Patent Documents 2, 3, and 6 are useful as a method of complementing nozzles whose defects are known in advance as means for compensating for defects in the manufacturing process of the line type recording head. It is not possible to compensate for defective nozzles that occur during use on the side.

  In the device described in Patent Document 5, the adjustment of the deflection amount of the ink droplet deflected by the nozzle that complements the defective nozzle requires a fine position adjustment and has a drawback that it takes a lot of time for the adjustment.

  In the case of the one described in Patent Document 4, since a color mixture of each color is used instead of the black ink, the color tone is different from that of the black ink, and the image quality is deteriorated.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and an image forming method capable of easily complementing non-ejection nozzles of a plurality of line-type recording heads.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
In an image forming apparatus provided with a plurality of line-type recording heads in which the arrangement direction of nozzles for discharging droplets is a direction orthogonal to the conveyance direction of the recording medium,
A second recording head having a plurality of nozzles that can reciprocate in a direction orthogonal to the recording medium conveyance direction in correspondence with each line type recording head, and that is arranged in the recording medium conveyance direction;
The second recording head performs printing to complement a portion corresponding to the defective nozzle of the line type recording head,
The at least one defective nozzle is complemented by switching nozzles used for complementing among the plurality of nozzles of the second recording head.

  Further, the line type recording head preferably includes a guide member for guiding the reciprocating motion of the second recording head. In this case, the guide member is provided with reference to the nozzle hole of the line type recording head. Is preferred. Further, it is preferable that the line-type recording head is provided with a driving unit for performing the reciprocating operation of the second recording head.

Further, when the defective nozzle of the line-type recording head is one, the second recording head is moved, not preferable be supplemented stop defective nozzle position.

  When switching the nozzles used for complementation, when one nozzle among the plurality of nozzles of the second recording head is Nm and the upstream nozzle in the transport direction of the recording medium adjacent to this nozzle Nm is Nm-1. The nozzle Nm is used for complementation one or more times, then the nozzle Nm and the nozzle Nm-1 are used for complementation simultaneously, and further, the nozzle Nm-1 is used for complementation.

  Further, when one nozzle among the plurality of nozzles of the second recording head is Nm and the nozzle on the downstream side in the conveyance direction of the recording medium adjacent to the nozzle Nm is Nm + 1, the nozzle Nm is used for 1 or It is possible to perform complementation a plurality of times, then complement simultaneously using the nozzle Nm and the nozzle Nm + 1, then stop the printing timing, and further complement using the nozzle Nm + 1.

  Further, when one of the plurality of nozzles of the second recording head is Nm, the upstream nozzle in the conveyance direction of the recording medium adjacent to this nozzle Nm is Nm-1, and the downstream nozzle is Nm + 1. The nozzle Nm is used for complementing one or more times, then the nozzle Nm and the nozzle Nm-1 are used for complementation simultaneously, and then the printing timing is paused, and further, the nozzle Nm-1 is used. A first mode in which complementation is performed, and complementation is performed one or more times using the nozzle Nm, then complementation is performed simultaneously using the nozzle Nm and the nozzle Nm + 1, and further complementation is performed using the nozzle Nm + 1. Mode, and complementation in the second mode can be performed after complementation in the first mode.

  Furthermore, one of the plurality of nozzles of the second recording head is Nm, the upstream nozzle in the conveyance direction of the recording medium adjacent to this nozzle Nm is Nm-1, and the downstream nozzle is Nm + 1. When the nozzle Nm is used for complementation one or more times, then the nozzle Nm and the nozzle Nm-1 are used for complementation at the same time, then the printing timing is paused, and the nozzle Nm-1 is used. The first mode in which the nozzle Nm is used, and the nozzle Nm is used for the completion one or more times, then the nozzle Nm and the nozzle Nm + 1 are used for the completion simultaneously, and further the nozzle Nm + 1 is used for the completion. 2 modes, and complementation in the first mode can be performed after complementation in the second mode.

  In addition, when the nozzle used for complementing among the plurality of nozzles of the second recording head is switched, the nozzles that perform complementation using a plurality of nozzles of the nozzles of the second recording head and that are used sequentially Is preferably switched.

  In this case, the nozzle to be used can be switched from the downstream side in the conveyance direction of the recording medium to the upstream side. Alternatively, the nozzles used can be switched from the upstream side to the downstream side in the conveyance direction of the recording medium. Furthermore, after supplementing by switching the nozzles used from the downstream side to the upstream side in the conveyance direction of the recording medium, it is possible to supplement by switching the nozzles used from the upstream side to the downstream side in the conveyance direction of the recording medium. . Furthermore, after supplementing by switching the nozzles used from the upstream side to the downstream side in the conveyance direction of the recording medium, it is possible to supplement by switching the nozzles used from the downstream side to the upstream side in the conveyance direction of the recording medium. it can.

Further, when the number of defective nozzles in the line type recording head is plural, the second recording head can be complemented while scanning. In this case, it is preferable to set the home position of the second recording head to the position of the defective nozzle that complements the first of the line type recording head .

  An image forming apparatus according to the present invention scans a second recording head having a plurality of nozzles arranged in a direction orthogonal to the conveyance direction of the recording medium to complement defective nozzles of the line type recording head. The forming apparatus is configured to determine whether or not the second recording head can be complemented.

  Here, it is possible to calculate the number of nozzles necessary for complementing the second recording head, and determine whether or not complementation is possible by comparing with the number of nozzles that can be printed by the second recording head. In this case, the number of nozzles necessary for complementation can be calculated based on the time required for the second recording head to reciprocate once for complementation from the position of the defective nozzle of the line type recording head.

  Further, when there is no image information to be printed at the position of the defective nozzle of the line type recording head, the number of nozzles necessary for complementing the second recording head is calculated, and the number of nozzles that can be printed by the second recording head It is preferable not to compare.

The image forming apparatus according to the present invention is orthogonal to the conveyance direction of the recording medium corresponding to the plurality of line-type recording heads in which the direction in which the nozzles for discharging droplets are arranged is orthogonal to the conveyance direction of the recording medium. a second recording head capable reciprocally in the direction, the second recording head performs Shirushiutsushi to complement a portion corresponding to the defective nozzle of the line-type recording head, for at least one defective nozzle, the second Since the nozzles used for complementation are switched and complemented among the plurality of nozzles of the recording head, the second recording head can complement the defective nozzles of each line type recording head.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a configuration diagram of an image forming unit of an image forming apparatus according to the present invention, and FIG. 2 is an explanatory plan view of the image forming unit.

  In this image forming apparatus, four line-type recording heads (hereinafter referred to as “line-type heads”) that discharge ink droplets 11K, 11C, 11M, and 11Y of different colors, which are unitized as a line-type recording head unit 1, are used. 10K, 10C, 10M, 10Y and a second recording head (hereinafter referred to as “complementary head”) having nozzles 56 for discharging a plurality of droplets provided corresponding to the respective line-type heads 10K, 10C, 10M, 10Y. 50K, 50C, 50M, 50Y.

  When a specific color is indicated, “Y” is added to the end of the code, “M” is added to the magenta color, “C” is added to the cyan color, and “K” is added to the black color. In the case of applying in common without specifying a color, only the reference numerals with Y, M, C, and K are omitted at the end.

  Here, the line-type heads 10K, 10C, 10M, and 10Y include nozzles 13 that eject a large number of droplets corresponding to the entire width of the image forming area, and record the arrangement direction of the nozzles 13 (nozzle row direction). The medium (hereinafter referred to as “paper”, but is not limited to paper) 2 is arranged as a direction (arrow BC direction) orthogonal to the conveyance direction A of the medium 2. Further, the complementary heads 50K, 50C, 50M, and 50Y are arranged so that the alignment direction of the nozzles 56 is the same as the conveyance direction A of the paper 2.

  The nozzle array of the line recording head 10K is shown on a straight line. However, due to the structure of the head, as shown in FIG. 4, two nozzles are divided into an odd nozzle row 13O and an even nozzle row 13E, and adjacent nozzles are arranged. It is also possible to adopt a configuration in which the interval is set to 1/2 of the image resolution (for example, in the case of 600 dpi, the interval between adjacent nozzles is 0.0846 mm).

  The line-type heads 10K, 10C, 10M, and 10Y are each formed with a guide groove 55, while the complementary heads 50K, 50C, 50M, and 50Y are slidably fitted into the guide groove 55. 56 is provided so that the complementary heads 50K, 50C, 50M, and 50Y can be moved to the line-type heads 10K, 10C, 10M, and 10Y in the direction of the arrow BC, that is, in the direction orthogonal to the conveyance direction of the sheet 2, respectively.

  In this case, the line-type heads 10K, 10C, 10M, and 10Y are formed with holes and nozzle surfaces joined so that the rows of nozzles 13 are parallel and equidistant with respect to the guide groove 55. Accordingly, the gap between the nozzle surfaces of the complementary heads 50K, 50C, 50M, and 50Y and the paper 2 is not only uniform because it is arranged in parallel with the paper 2, but also in parallel with the nozzle 13 of the line type head 10. The complementary head 50 is operable.

  As driving means for moving the complementary heads 50K, 50C, 50M, and 50Y in the direction of the arrow BC, the complementary heads 50K, 50C, 50M, and 50Y are fixed to the head wires 54K, 54C, 54M, and 54Y, and the head wire 54K is used. , 54C, 54M, 54Y are routed to side pulleys 52K, 52C, 52M, 52Y and side pulleys 53K, 53C, 53M, 53Y attached to both ends of the line type heads 10K, 10C, 10M, 10Y.

  Both ends of the head wires 54K, 54C, 54M, and 54Y are fixed to head motors (not shown) arranged in the line type heads 10K, 10C, 10M, and 10Y, and the head wires 54K, The complementary heads 50K, 50C, 50M, and 50Y are moved in the direction of the arrow BC via 54C, 54M, and 54Y.

  Thus, by providing the guide for operating the second recording head in the line type recording head, the positional accuracy with the nozzle row of the line type recording head is high, the dot deviation of the image after printing is reduced, and the image Quality can be maintained. Moreover, it can be unitized as a head unit, and efficiency in production processes such as inspection as a head unit can be achieved.

  In this case, by providing the guide with reference to the nozzle position of the line type recording head, the positional accuracy with the nozzle row of the line type recording head is high, and the dot deviation of the image after printing is reduced. Further, by providing a drive mechanism for the second recording head in the line-type recording head, the head unit can be unitized, the head unit can be inspected as a single product, and the efficiency in the production process can be improved. .

  The line-type head 10 mainly forms an image on the paper 2, and the complementary head 50 is substituted for a defective nozzle of the line-type head 10. Therefore, the number of nozzles of the complementary head 50 is determined based on the ratio of the number of defective nozzles of the line type head 10. Therefore, the number of nozzles of the complementary head 50 can be set to be considerably smaller than that of the line type head 10.

  On the other hand, a transport roller 21 and a pressure roller 22 are disposed on the entrance side, and a discharge roller 23 and a spur roller 24 are disposed on the exit side to transport the sheet 2 to the image forming area below the head unit 1. A guide member 25 for guiding the paper 2 is provided below the unit 1.

  Further, line type head caps 31K, 31C, 31M, 31Y for capping the nozzle surfaces of the line type heads 10K, 10C, 10M, 10Y of the head unit 1 are arranged so as to be movable in the transport direction, and complementary heads 50K, 50C, Complementary head caps 51K, 51C, 51M and 51Y for capping the nozzle surfaces of 50M and 50Y are arranged so as to be movable up and down outside the recording area (side pulley 53 side).

The operation up to the preparation when the defective nozzle of the line-type head 10 in the embodiment configured as described above is complemented by the complementing head 50 will be described with reference to FIG.
First, as shown in FIG. 3A, in the standby state, the line-type head 10 and the complementary head 50 are in a state where the nozzle surfaces are sealed by the line-type head cap 31 and the complementary head cap 51, respectively.

  Then, when the printing operation (image forming operation) is started, as shown in FIG. 3B, the line-type head 10, the supplementary head 50, and the supplementary head cap 51 rise together in the arrow D direction. Then, as shown in FIG. 3C, the line-type head cap 31 moves backward in the direction indicated by the arrow E (moves upstream in the paper transport direction).

  Thereafter, as shown in FIG. 3 (d), the line-type head 10, the complementary head 50, and the complementary head cap 51 are integrally lowered in the direction indicated by the arrow F and stopped at a predetermined position. Next, as shown in FIG. 3E, the complementary head cap 51 is lowered in the direction indicated by the arrow G, and the line-type head 10 and the complementary head 50 are ready for printing.

  Next, the operation of the image forming apparatus configured as described above will be described. Prior to this, problems in the image forming apparatus not including the complementary head will be described with reference to FIGS. 16 is a schematic side view of a general line printer during non-printing, FIG. 17 is a schematic side view during printing, FIG. 18 is a schematic plan view during printing, and FIG. 19 is its operation. It is explanatory drawing with which it uses for description.

  Here, the line-type head unit 1001 includes line-type heads 1010Y, 1010M, 1010C, and a head 1010K corresponding to the inks 1011Y, 1011M, 1011C, and 1011K of each color, and can eject the inks 1011Y, 1011M, 1011C, and 1011K of each color. is there.

  In addition, line type head caps 1012Y, 1012M, 1012C, and 1012K are provided to protect the nozzle surfaces of the line type heads 1010Y, 1010M, 1010C, and 1010K when the discharge operations of the respective color inks 1011Y, 1011M, 1011C, and 1011K are not performed. Has been placed. Further, the paper 1018 feeding mechanism includes a conveyance roller 1013, a pressure roller 1014, a paper discharge roller 1015, a spur 1016, a guide plate 1017, and the like.

  At the time of the printing operation, the line type heads 1010Y, 1010M, 1010C, and 1010K are moved up in the direction indicated by the arrow H in FIG. Each of the line type heads 1010Y, 1010M, 1010C, and 1010K descends again in the direction of arrow I and stops at a predetermined position.

  Next, when the printing operation is started, the line heads 1010Y, 1010M, 1010C, and 1010K are based on the image information on the paper 1018 fed by the conveying roller 1013 and the pressure roller 1014 as shown in FIG. The inks 1011Y, 1011M, 1011C, and 1011K of the respective colors are ejected to form an image 1002 as shown in FIG.

  Here, as shown in FIG. 19, the line-type heads 1010Y, 1010M, 1010C, and 1010K cover the entire print width of the paper 1018. If the print width of the paper 1018 is A4 size side, each line-type head 1010Y. In 1010M, 1010C, and 1010K, when the image resolution is 600 dpi, nozzles that eject about 7,000 inks are arranged. The recording paper 1018 is continuously conveyed in the K direction during printing. The speed corresponds to the response frequency time of the head at a desired image resolution of 600 dpi. In this way, an image is formed by the line type head 1010.

  As an example, FIG. 19 shows an example of an image 1002 formed by printing ink 1011K from all nozzles of the line-type head 1010K. It goes without saying that the same applies to the line type heads of other colors. The paper 1018 is continuously conveyed in the arrow K direction. The line type head 1010K is arranged in a direction orthogonal to the conveyance direction of the paper 1018.

  In this case, the nozzle positions for discharging the ink 1011K of the line type head 1010K are N1, N2... Nn-3, Nn-2, Nn-1, and Nn from the left end in FIG. The interval between adjacent nozzles is set to 0.0423 mm corresponding to 600 dpi which is the resolution of the image.

  In FIG. 19, x marks are marked at the nozzle positions of defective ejection nozzles. In this example, the nozzle number N11 is a nozzle that has an ejection curve on the nozzle number N10 side, and dots are formed on the paper 1018 near the dot side ejected by the nozzle of the nozzle number N10. Further, the nozzle of nozzle number N19 is a nozzle that cannot be ejected, and appears on the paper 1018 as a white stripe. In addition to this, there is a defect that a predetermined ink discharge amount is insufficient and a dot diameter smaller than a predetermined size is formed.

  Thus, the line-type head 1010 has a high possibility of causing various problems and defects due to the large number of nozzles. In addition to the manufacturing process of the head, such troubles are caused by various causes such as clogging due to adhesion of paper dust or dust, nozzle clogging due to an increase in ink viscosity, even if machines are used in the market. Occurs.

  In this case, even if a maintenance / recovery function such as suction from the nozzle surface of the head, empty ejection, or wiping off the nozzle surface is used, the above-mentioned nozzle failure is not completely recovered, and the line type is used for image deterioration. The head 1010 has been replaced, which causes a reduction in the reliability of the apparatus.

  On the other hand, in the image forming apparatus according to the present embodiment, the defective nozzle of the line type head 10 is complemented by the complementing head 50 so that an image having a required image quality can be formed. Therefore, a specific example of the complementing method will be described.

First, a complementing method for complementing one defective nozzle of the line type head 10 and making the complementing head 50 stationary at the defective nozzle position of the line type head 10 will be described with reference to FIG.
In the example shown in FIG. 5, it is assumed that only the nozzle number N7 marked with Δ among the nozzles of the line type head 10 is a defective nozzle. At this time, a head motor (not shown) is driven to move the complementary head 50 in the direction of the arrow S, and the nozzle number N7 (hereinafter simply referred to as “N7 nozzle”) marked with Δ among the nozzles of the line type head 10. The same applies to the description of other nozzles.), And a droplet is ejected from the nozzle of the Na nozzle (marked with ◎) of the supplementary head 50 for printing. Note that printing using the nozzles of the complementing head 50 is referred to as “complementing”.

  The nozzles used for complementing among the nozzles of the supplementary head 50 (hereinafter referred to as “complementary nozzles”) are not limited to Na nozzles, and any nozzle in the supplementary head 50 is used. However, it is possible to complement.

  In this case, since the complementary heads 50K, 50C, 50M, and 50Y are provided corresponding to the line-type heads 10K, 10C, 10M, and 10Y of the respective colors, the line-type heads 10K, 10C, 10M, and 10Y of any color are provided. Even when a defective nozzle is generated, the defective nozzle can be supplemented.

  As described above, the second recording head that can reciprocate in the direction orthogonal to the conveyance direction of the recording medium corresponding to each line type recording head is provided. Can be supplemented by the recording head.

  In this case, since the second recording head has a plurality of nozzles arranged in the conveyance direction of the recording medium, the nozzles at any position of the line type recording head can be complemented.

  The second recording head is driven so as to complement and print the portion corresponding to the defective nozzle of the line type recording head, thereby preventing the generation of a defective image and forming an image with high image quality. .

  Furthermore, the defective nozzle at any position of the line type recording head can be complemented by moving the second recording head to the position of the defective nozzle of the line type recording head.

  When the nozzles (complementary nozzles) used for complementing among the nozzles of the supplementary head 50 are limited as in the first embodiment described above, the ink 11 in the unused nozzles is dried and the viscosity is increased, so that the supplementary nozzles are used. Since the nozzle of the head 50 itself may lead to problems such as non-ejection and bending in the ejection direction, it is preferable to use the nozzle uniformly.

  Therefore, the complementary nozzles of the complementary head 50 are switched using switching determination criteria such as the number of times of printing and the printing time. That is, referring to FIG. 6, when only the N7 nozzle marked with Δ among the nozzles of the line type head 10 is a defective nozzle, the head motor (not shown) is driven to move the complementary head 50 to the arrow S. It is the same as in the first embodiment to move in the direction and stop at the position of the N7 nozzle marked with Δ among the nozzles of the line type head 10.

  Thereafter, in FIG. 6, first, the Nz nozzle on the lower side (downstream side in the transport direction) of the paper 2 in the transport direction A of the complementary head 50 is printed a predetermined number of times, and then the complementary nozzle is printed on the upstream side in the transport direction Ny. Switching to the nozzle, printing is performed in the same manner with the Ny nozzle, and printing is performed while sequentially switching to the Na nozzle.

  Here, when the complementary nozzles are switched, the paper 2 is sent by the dot interval d to be printed, and therefore, in order to prevent missing printing, the complementary nozzles to be switched with the complementary nozzles before the switching are used for printing. For example, when printing with the Nz nozzle and switching to the Ny nozzle, the last printing of the Nz nozzle and the first printing of the Ny nozzle are performed simultaneously.

  That is, when one nozzle among the plurality of nozzles of the second recording head (complementary nozzle 50) is the nozzle Nm, and the upstream nozzle in the transport direction of the recording medium adjacent to the nozzle Nm is Nm-1. The nozzle Nm is used for complementation one or more times, then the nozzle Nm and the nozzle Nm-1 are used for complementation simultaneously, and further, the nozzle Nm-1 is used for complementation.

  When the printing of the Na nozzle is completed, the sheet 2 is sent to the Nz nozzle position, and when the Nz nozzle corresponds to the position to be hit next, the reprinting is repeatedly performed again from the Nz nozzle. .

  Thus, by switching the complementary nozzles of the second recording head, the complementary nozzles are limited, and clogging of nozzles that are not used for complementation can be prevented. Further, by using each nozzle equally as a complementary nozzle, the frequency of use of the complementary nozzle is not biased, and the life of the entire second recording head is improved.

  In this case, the supplementary nozzles are switched in order from the downstream side in the recording medium conveyance direction so that the printing by the complementary nozzles can be made regular and the supplementary control can be easily performed. Become.

Next, an embodiment in which the complementary nozzles of the complementary head 50 are used from the Na nozzle on the upper side (upstream side) in the paper transport direction will be described with reference to FIG.
First, printing is performed a predetermined number of times by the Na nozzle on the upstream side in the paper transport direction A of the supplementary head 50, and thereafter, printing is similarly performed by the Nb nozzle, and sequentially switched to the Nz nozzle.

  Here, when the complementary nozzle is switched, the recording paper 2 is sent by the dot interval d to be printed, but since the nozzle after the switching is on the lower side (downstream side) of the paper 2, it is already printed at the position to be printed. Therefore, printing is not performed (printing timing is paused), and the next printing is started when the sheet 2 reaches a position to be printed next. Specifically, when printing with the Na nozzle and switching to the Nb nozzle, after the last printing of the Na nozzle, one dot printing is not performed (the printing timing is paused), and the printing with the next Nb nozzle is performed. Start.

  Then, when the printing of the Nz nozzle is completed, the supplementary printing is performed from the Na nozzle to the Nz nozzle in order to switch to the position of the Na nozzle, and the printing is repeated again from the Na nozzle.

  That is, when one nozzle among the plurality of nozzles of the second recording head (complementary head 50) is Nm and the nozzle on the downstream side in the transport direction of the recording medium adjacent to the nozzle Nm is Nm + 1, the nozzle Completion is performed one or more times using Nm, then complementation is simultaneously performed using nozzle Nm and nozzle Nm + 1, then the printing timing is paused, and further complementation is performed using nozzle Nm + 1.

  In this way, by sequentially switching the complementary nozzles of the second recording head from the upstream side in the conveyance direction of the recording medium, the printing of the complementary nozzles can be made regular, and the complementary control becomes easy.

  Next, an example in which Example 2 and Example 3 are combined will be described. That is, complementary printing is performed by sequentially switching from the Nz nozzle to the Na nozzle of the complementing head 50, and after completing the complementary printing of the Na nozzle, the printing is sequentially switched from the Na nozzle to the Nz nozzle. Thus, the line-type head 10 can be complemented. Alternatively, it is possible to perform the complementary printing by sequentially switching from the Na nozzle to the Nz nozzle, and after completing the complementary printing of the Nz nozzle, conversely, by sequentially switching and printing from the Nz nozzle to the Na nozzle, the line type is repeated. The head 10 can be complemented.

  At this time, troublesome control of stopping printing when switching from the Na nozzle to the Nz nozzle described in the second embodiment and printing of all nozzles when switching from the Nz nozzle to the Na nozzle described in the third embodiment is required. do not do.

  That is, one of the plurality of nozzles of the second recording head (complementary head 50) is Nm, the upstream nozzle in the transport direction of the recording medium adjacent to this nozzle Nm is Nm-1, and the downstream nozzle is Nm-1. When the nozzle is set to Nm + 1, the nozzle Nm is used for complementation one or more times, then the nozzle Nm and the nozzle Nm-1 are used for complementation at the same time, and then the printing timing is paused. -1 is used for complementation, nozzle Nm is used for complementation one or more times, nozzle Nm and nozzle Nm + 1 are used for complementation at the same time, and nozzle Nm + 1 is used. And the second mode for performing complementation, and after performing complementation in the first mode, complementation in the second mode is performed.

  Alternatively, one of the plurality of nozzles of the second recording head (complementary head 50) is Nm, the upstream nozzle in the transport direction of the recording medium adjacent to this nozzle Nm is Nm-1, and the downstream nozzle When the nozzle is set to Nm + 1, the nozzle Nm is used for complementation one or more times, then the nozzle Nm and the nozzle Nm-1 are used for complementation at the same time, and then the printing timing is paused. -1 is used for complementation, nozzle Nm is used for complementation one or more times, nozzle Nm and nozzle Nm + 1 are used for complementation at the same time, and nozzle Nm + 1 is used. And the second mode for performing complementation, and after performing complementation in the second mode, complementation in the first mode is performed.

  In this way, by switching the complementary nozzle of the second recording head from the upstream side in the paper transport direction and from the downstream side alternately, the nozzles located on one end face of the complementary nozzle are reversed. It is not necessary to perform an operation for adjusting the complement for connection when switching to the nozzle located on the side end face, and the control becomes easier.

  In the above-described first to fourth embodiments, an example has been described in which complementation is basically performed with one complementary nozzle of the supplementary head 50, but all the nozzles of the supplementary head 50 are used or divided into a plurality of blocks and divided into a plurality of nozzles. Even if it complements, the same operation effect can be obtained only by extending the interval of the printing cycle of the same nozzle.

In the above-described first to fourth embodiments, the example in which the same nozzle is continuously supplemented has been described. Next, an example in which the printing of a plurality of nozzles is sequentially shifted and complemented will be described with reference to FIG.
In FIG. 8, the nozzles Na to Nz of the supplementary head 50 are set in the same manner as described above, and the transport direction of the paper 2 is the arrow A direction. The complementary head 50 is shown fixed, and the positional relationship of the printed dots at each printing timing is shown in the horizontal axis direction. Therefore, this figure shows the printing situation by the complementary head 50 for each time series at the defective nozzle position of the line type head 10.

  First, at the printing timing t1, printing is performed by the Nz nozzle and the Ny nozzle on the downstream side in the transport direction A on the paper 2 (y and z are indicated in circles, and the same applies hereinafter). Next, at the next printing timing t2, printing is performed using the Ny nozzle and the Nx nozzle, and the Nb nozzle and the Na nozzle are sequentially switched. In FIG. 12, dots printed at the previous timing are simply circled.

  When printing from the Nb nozzle and Na nozzle is completed at the printing timing tk, the printing is repeated at the printing timing tk + 1 when the position to be printed next to the position of the paper 2 comes to the position of the Nz nozzle, and printing is performed with the Nz nozzle and Ny nozzle. Copy. By repeating printing in this way, the printing interval of the same nozzle can be doubled and the load on the head can be reduced.

  In the example of FIG. 8, an example in which the number of complementary nozzles to be used is two is shown, but the same applies when using a plurality of nozzles of three or more. The load will be reduced.

  Thus, by using the plurality of nozzles of the second recording head as complementary nozzles and switching the complementary nozzles in units of a plurality of nozzles, clogging of nozzles not used for complementation can be prevented. Further, by using the complementary nozzles evenly, the usage frequency of the complementary nozzles is not biased and the life of the entire second recording head is improved.

  In this case, by sequentially switching the complementary nozzles of the second recording head from the downstream side in the paper transport direction, the printing of the complementary nozzles can be made regular, and the complementary control becomes easy.

Next, an example of complementing from the upper (upstream) Na nozzle side in the paper transport direction A will be described with reference to FIG.
At the printing timing t1, printing is performed with all the nozzles complemented by the complementary head 50. (Indicated by adding a to z to the letter O.) Next, at the printing timing t2, printing is performed with the Nb nozzle and the Nc nozzle, printing is performed sequentially, and printing is performed with the Nx nozzle and the Ny nozzle at the printing timing tk. In FIG. 9, the dots printed at the previous timing are simply circled.

  Then, at the printing timing tk + 1, all the nozzles of the complementary head 50 are printed as complementary nozzles. By repeating printing in this way, the printing interval of the same nozzle is extended and the load on the head can be reduced.

  In the example of FIG. 12, an example in which the number of complementary nozzles to be used is two is shown, but the same is true when a plurality of nozzles of three or more are used. The load will be reduced.

  Thus, by using the plurality of nozzles of the second recording head as complementary nozzles and switching the complementary nozzles in units of a plurality of nozzles, clogging of nozzles not used for complementation can be prevented. Further, by using the complementary nozzles evenly, the usage frequency of the complementary nozzles is not biased and the life of the entire second recording head is improved.

  In this case, by sequentially switching the complementary nozzles of the second recording head from the upstream side in the paper transport direction, the printing of the complementary nozzles can be regularized and the complementary control can be facilitated.

  In addition, after the sixth embodiment and the seventh embodiment described above are combined and the complementary nozzle of the second recording head is switched from the downstream side in the paper transport direction, the complementary nozzle is switched upstream in the paper transport direction. Alternatively, after the complementary nozzles of the second recording head are switched from the upstream side in the paper transport direction, the complementary nozzles can be switched from the downstream side in the paper transport direction.

  In this way, the switching of the complementary nozzle of the second recording head is performed alternately from the upstream side and the downstream side in the recording medium conveyance direction, so that the nozzle located on one end face of the complementary nozzle can be switched. There is no need to perform an operation of adjusting the complement for connection when switching to the nozzle located on the opposite end face, and the control becomes easier.

Next, an example in which a plurality of defective nozzles including one of the line type heads 10 are complemented and the complementing head 50 is scanned and complemented will be described with reference to FIG.
In FIG. 10, the preparatory operation for retracting the line-type head cap 31 before actual printing from the line-type head 10 is the same as that in the first embodiment.

  In FIG. 10, there are five nozzle numbers Nk (marked with Δ), Nk + 7 (marked with x), Nk + 8 (marked with o), Nk + 9 (marked with □), and Nk + 11 (marked with D). It shows that the nozzle is a defective nozzle of the line type head 10.

  Here, when all of the nozzles from the Na nozzle to the Nz nozzle are used as the complementary head 50, the complementary head 50 can reciprocate in a direction (arrow BC direction) perpendicular to the conveyance direction A of the paper 2. .

  Note that FIG. 10 shows the paper 2 fixed and the complementary head 50 relatively moving so that the scanning direction can be easily understood. Therefore, the movement of the complementary head 50 in the direction of arrow BC is expressed by the relative synthesis direction with the traveling component (arrow A direction) of the recording medium, that is, the arrows S (S1, S2,...). Further, the nozzle on the downstream side in the conveyance direction of the paper 2 is an Nz nozzle, and the nozzle on the upstream side in the conveyance direction of the paper 2 is an Na nozzle.

  When the sheet 2 is conveyed, the Na nozzle of the supplementary head 50 moves in the C direction in view of the position and timing at which the defective nozzle (Nk + 7 nozzle) of the line type head 10 should be hit (indicated by arrow S1 in FIG. 10). Direction) and defective nozzles (Nk + 7 nozzle, Nk + 8 nozzle, Nk + 9 nozzle, Nk + 11 nozzle) of the line type head 10 are printed. When the printing is finished, the direction returns to the arrow B direction.

  Next, printing is performed at each position of defective nozzles (Nk nozzle, Nk + 7 nozzle, Nk + 8 nozzle, Nk + 9 nozzle, Nk + 11 nozzle) of the line-type head 10 by the operation of the complementary head 50 in the arrow S2 direction. The defective nozzle of the line type head 10 is complemented.

  Similarly, the operation in the directions indicated by arrows S3, S4,... Is repeated, and printing is performed by the supplementary head 50, so that the position where the defective nozzle of the line type head 10 is to be printed is printed to form a complete image. Go.

  In FIG. 10, the nozzle position of the line type head 10 to be complemented first is set to the position of Nk + 7 nozzles. However, when the line LK is the leading edge of the sheet, the position to be complemented first is the Nk nozzle of the line type head. Nk + 7 nozzles, Nk + 8 nozzles, Nk + 9 nozzles, and NK + 11 nozzles may be complemented.

  Further, although an example of complementing using all the nozzles of the complementing head 50 has been described, it is not always necessary to use all the nozzles, and the same effect can be obtained even if some of the nozzles are used. Further, the nozzles of the complementing head 50 may be divided into blocks, and the nozzle blocks to be complemented may be switched as necessary.

  As described above, the plurality of defective nozzles of the line-type head can be complemented by complementing the second recording head while scanning.

Here, determination of whether or not complementation by the complementing head 50 is possible will be described.
Whether or not complementing by the supplementing head 50 is possible is determined by the relationship between the operation time in which the supplementing head 50 reciprocates for complementing and the traveling time of the paper 18 to the next printing position to be complemented.

  11, the defective nozzles of the line type head 10 are Nk, Nk + 7, Nk + 8, Nk + 9, and Nk + 11 nozzles as in the example of FIG. 14, and the conveyance direction of the paper 2 is the arrow A direction. Also, the printed dot interval is the interval d in both the transport direction of the paper 2 and the arrangement direction of the line type head 10.

  Therefore, if the speed in the transport direction of the paper 2 is vd, the scanning speed required for printing of the complementary head 50 is similarly vd. If the home position of the complementary head 50 is HP, the operation of the complementary head 50 reciprocates with respect to the home position HP. The distance from the home position HP to the nozzle of the nozzle number N1 of the line type head 10 is ls, and the forward speed is variable because it includes the acceleration time, and the time (forward time) is ts.

  The distance from the nozzle of the nozzle number N1 of the line type head 10 to the nozzle of the nozzle number Nk + 1 to be complemented is (k + 10) × d. During this time, printing for complementation is performed, so the forward speed (scanning speed) is vd. Therefore, the forward time (scanning time) from the nozzle position of nozzle number N1 to the nozzle position of nozzle number Nk + 1 is (k + 10) × d / vd.

  Further, the distance from the nozzle of nozzle number k + 11 to the last position LP to be stopped is ll, the forward speed is variable, and the forward time is tl.

  Therefore, the forward time from the home position HP to the last position LP is ts + (k + 10) × d / vd + tl. Similarly, with respect to the return, the return time from the last position LP to the home position HP is th1 + ((k + 10) × d−, where vh is the constant return speed, acceleration distance lh2 + lh3, acceleration time th2, deceleration distance ls + 1h1, and deceleration time th1. (Lh1 + lh2)) / vh.

  Assuming that the number of nozzles necessary for the complementing head 50 to complement at a time is m, (m−1) × d / vd time is a round-trip time for complementation {ts + (k + 10) × d / vd + tl + th1 + ((k + 10) × d- (lh1 + lh2)) / vh} must be at least as long or longer.

  Here, (ts + tl + th1 + th2) × vd / d and (lh1 + lh2) × vd / (vh × d) are the number of time components necessary to operate the complementary head 50, and therefore, if this is defined as mh, (1 ) Can be expressed by the following equation (2).

  Accordingly, the number m of nozzles of the supplementary head 50 needs to satisfy the relational expression defined by the above expression (2). Equation (2) represents the case where the home position HP of the complementary head 50 is fixed. However, the home position HP is set by software based on the output of an encoder or the like (not shown), and the position can be changed. It may be changed by software to the vicinity where a constant speed vd can be secured at the position of the nozzle (k nozzle).

  Further, if the position near the defective nozzle (k nozzle) is set as the home position HP2 and the complementary head 50 is scanned, the positions from the nozzles N1 to Nk can be shortened, and the number m of complementary nozzles in the complementary head 50 can be saved. ) Becomes the following expression (3).

  In this way, by moving the home position HP to the vicinity of the defective nozzle position closest to the home position HP, it is possible to reduce the number of nozzles necessary for complementing without needless scanning, or a line type recording head that can be complemented The number of defective nozzles can be increased.

Next, an example of complementation when defective nozzles are dispersed at a plurality of locations will be described with reference to FIG.
In this example, defective nozzles of the line-type head 10 do not concentrate at one place, but are generated in two groups (two places) of N3 nozzle, Nk nozzle, Nk + 1 nozzle, and Nk + 2 nozzle.

  In this case, the home position of the complementary head 50 is moved from HP to the home position HP2, the N3 nozzle that is a defective nozzle is complementarily printed at the scanning speed vd, and the speed vd is reached to the vicinity of the next defective nozzle Nk nozzle. The complementary head 50 is moved at the higher speed vs, and the defective nozzles Nk, Nk + 1, and Nk + 2 are complemented at the scanning speed vd, stopped at the last position LP, and returned to the return speed vh. Returning to the home position HP2, the second scan is performed again to complete the image.

  By doing in this way, the time which moves from the defective nozzle N3 to the next defective nozzle Nk can be reduced, and it becomes possible to keep it within the number m of complementary nozzles. In this case, it is preferable to set a plurality of speeds vs depending on the amount of movement between the defective nozzles so that they can be selected based on the distance between the defective nozzles.

  In this way, by adopting a configuration in which the moving speed of the second recording head between the defective nozzle to be complemented by the line type recording head and the next defective nozzle to be complemented is higher than the scanning speed for complementation, the second The number of defective nozzles of the line-type recording head that can be complemented by the recording head increases, and further, the defective nozzle of the line-type recording head that can be complemented by the second recording head by combining with the configuration for moving the home position described above. The number increases further.

Next, an example of the control unit and the complementary control process of the image forming apparatus in the above-described embodiment will be described with reference to FIGS.
The control unit of the image forming apparatus includes a main control unit 71 that controls the entire apparatus, a storage unit 72 that stores various data, and a determination setting unit 73 that performs various determinations and settings.

  The judgment setting unit 73 detects nozzle defects in various data processing apparatuses such as an external personal computer (not shown), image data 74 from external devices such as image scanners and digital cameras, and line type heads 10K, 10C, 10M, and 10Y. Detection signal from the line-type head defective nozzle detecting unit 75, detection signal from the complementary head defective nozzle detecting unit 76 for detecting defective nozzles in the complementary heads 50K, 50C, 50M, and 50Y, and HP detection for detecting the home position A detection signal from the unit 77 is input, and a speed table storage unit 78 storing a speed table is connected.

  The line-type head defective nozzle detection unit 75 has, for example, a means for optically detecting the ink droplets 11 ejected from the line-type head 10, and performs printing using all the nozzles of each line-type head 10. The presence or absence of a defective nozzle is detected from the result. Similarly, the complementary head defective nozzle detection unit 76 has means for optically detecting the ink droplets 11 ejected from the complementary head 50, for example, and prints using all the nozzles of each complementary head 50. The presence or absence of a defective nozzle is detected from the result.

  The main control unit 71 inputs information stored in the storage unit 72, a detection signal from the above-described line type head defective nozzle detection unit 75, a detection signal from the complementary head defective nozzle detection unit 76, and the like. The main control unit 71 sends data to be printed to the line type head driving unit 81 to drive and control the line type head 10, and sends data to be printed to the complementary head driving unit 82 to give the complementary head. 50 is driven and controlled. Further, the main control unit 71 controls driving of the complementary head motor 84 that moves the complementary head 50 that has sent drive data to the head motor driving unit 83.

  Further, the main control unit 71 controls the movement of the line type head cap 31 by driving the line type head maintenance and recovery operation driving unit 86 by the line type head maintenance and recovery operation control unit 85 to control the movement of the line type head cap 31. The controller 87 controls the driving of the complementary head maintenance / recovery operation driving unit 88 to drive and control the movement of the complementary head cap 51. Further, the main control unit 71 displays necessary information on a display unit 89 provided on an operation panel or the like.

  In this image forming apparatus, when the power is turned on or when printing is started, a detection signal from the line type head defective nozzle detection unit 75 and a detection signal from the complementary head defective nozzle detection unit 76 are received. The presence or absence of defective nozzles in the line type head 10 and the presence or absence of defective nozzles in the supplementary head 50 are determined.

  At this time, if a defective nozzle is detected for the line-type head 10 and / or the supplementary head 50, it is transmitted to the main control unit 71, and the main control unit 71 performs the line-type head drive unit 81 and / or the complement. The ink droplets 11 are purged from the defective nozzles of the line-type head 10 and the complementary head 50 through the head driving unit 82, and air bubbles and high-viscosity ink are discharged.

  Further, the information is given from the main control unit 71 to the line-type head maintenance / recovery operation control unit 85 and the supplementary head maintenance / recovery operation control unit 87, and the line-type head maintenance / recovery operation control unit 85, the supplemental head maintenance / recovery operation control. The unit 87 drives the line type head maintaining operation driving unit 86 and the complementary head maintaining operation driving unit 88 to perform forced suction of the ink 11 and wiping of the nozzle surface in the line type head cap 31 and the complementary head cap 51. The maintenance operation of the line-type head 10 and the supplementary head 50 is performed.

  However, when the defective nozzle cannot be returned to the normal state, the defective nozzle positions of the line-type head 10 and the complementary head 50 are detected and determined by the line-type defective head nozzle detection unit 75 and the complementary head defective nozzle detection unit 76. Information is input to the setting unit 73 in advance.

  Therefore, with reference to FIG. 14, the presence / absence of a defective nozzle of the line type head 10 is determined based on the detection signal from the line type defective head nozzle detection unit 75, and if there is no defective nozzle, the determination setting unit 73 Data 74 is associated with each nozzle of the line-type head 10 as printing information and stored in the storage unit 72. The information stored in the storage unit 72 is sent to the control unit 71 and transmitted to the line-type head drive unit 81 as a printing command, and ink droplets are ejected by the line-type head 10 in synchronization with the conveyance operation of the paper 2. Then, printing is performed to form an image.

  On the other hand, when the line type head 10 has a defective nozzle, the determination setting unit 72 determines whether the line type head 10 can print from the image data 74 and the defective nozzle position. For example, for monochromatic printing, no other ink 11 is necessary, or there is no information to be printed at the position of the defective nozzle as it is, and image formation is not affected even if there is a defective nozzle. There is.

  Therefore, as a result of this determination, when it is determined that the defective nozzle is not necessary for image formation, the determination setting unit 73 stores the image data 74 in each line type head 10 as in the case where there is no defective nozzle. The information is stored in the storage unit 72 in association with the nozzle as printing information. The information stored in the storage unit 72 is sent to the control unit 71 and transmitted to the line-type head drive unit 81 as a printing command, and ink droplets are ejected by the line-type head 10 in synchronization with the conveyance operation of the paper 2. Then, printing is performed to form an image.

  In this way, when it is not necessary to compensate for defective nozzles, even if impossibility is impossible, by skipping the discrimination process, unnecessary processing is eliminated, processing speed can be increased, and the desired image can be obtained. Can do.

  On the other hand, when it is determined that a defective nozzle of the line type head 10 is necessary to form the image data 74, the determination setting unit 73 determines the movement amount of the home position HP from the information from the HP detection unit 77. The speed table between the defective nozzles is selected and read out from the speed table storage unit 78, and the required number of nozzles m of the complementary head 50 required for the complement is calculated as shown in the above-described equation (3). It is determined whether or not it is possible to complement.

  In this way, by determining whether or not complementation is possible, it is not necessary to move the complementing head to perform the complementing operation until it is impossible to complement, and the processing can be simplified.

  In this case, the determination can be made accurately by determining whether or not complementation is possible by comparing the number of nozzles necessary to complement the defective nozzle and the number of nozzles that can be complemented by the second recording head. . Further, the number of nozzles necessary for complementation can be easily calculated by calculating based on the time during which the second recording head reciprocates for complementation.

  If it can be complemented, new home position HP position information, speed table information between defective nozzles, and image data 74 other than the defective nozzles of the line type head 10 are marked on the nozzles other than the defective nozzles of the line type head 10. The image data 74 of the defective nozzle part of the line-type head 10 is stored in the storage unit 72 in association with the non-defective nozzle of the complementing head 50 as the printing information. Store.

  As a result, the information stored in the storage unit 72 is sent to the main control unit 71, and the main control unit 71 transmits the information to the line type head drive unit 81, the head motor drive unit 83, and the complementary head moving unit 82 as a printing command. Then, the head motor 84, the complementary head 50, and the line type head 10 are operated, and printing is performed in synchronization with the conveyance operation of the paper 2 to form an image.

  At this time, as a result of calculating the required number of nozzles m of the supplementary head 50 by the judgment setting unit 73, when it is judged that complementation is impossible, as shown in FIG. The estimated printing time is calculated and stored in the storage unit 72 together with input information indicating whether printing is possible on the display unit 89 and displayed on the display unit 89 of the image forming apparatus through the main control unit 71. This information is also output to the external device that has issued a printing instruction such as a computer through the main controller 75.

  When an instruction for printing is input from an operation panel including the display unit 89 of the image forming apparatus or an external device (host) such as a computer, the image data 74 is transferred to nozzles other than the defective nozzles of the complementary head 50. The printing information is associated and stored in the storage unit 72, and the information is sent to the main control unit 71 and transmitted to the head motor driving unit 83 and the complementary head driving unit 82 as a printing command. The transport operation of the paper 2 is an intermittent feed operation of a feed amount corresponding to the number of nozzles that can be printed by the supplementary head 50, and is printed by nozzles other than the defective one of the supplementary head 50 in synchronization with the intermittent feed operation. Copy to form an image.

  On the other hand, when instruction information indicating that printing is not performed is given from the outside such as an operation panel including the display unit 89 of the image forming apparatus or a computer, information regarding the necessity of replacement of the line-type head 10, information regarding necessity of repair, and defective nozzles The number and the like are displayed on the display unit 89 of the image forming apparatus and transferred to an external device such as a computer.

  As described above, when the defective nozzle of the line type recording head cannot be complemented, information for prompting the determination as to whether or not to print with the second recording head is output, and the judgment of the user of the image forming apparatus is requested. Will be able to.

  Then, when information indicating that the printing by the second recording head is performed is given, the printing operation by the second recording head is performed, so that an emergency response until repair such as head replacement is performed. Image formation can be performed. In addition, when information indicating that printing by the second recording head is not performed or when the information is given, the information on the defective nozzle is output, thereby facilitating maintenance and repair. .

  In this way, even if a defective nozzle exists in the line type head, an expected image can be formed, and the reliability of the image forming apparatus using the droplet discharge method is dramatically improved.

FIG. 2 is a configuration diagram of an image forming unit of the image forming apparatus according to the present invention. FIG. 2 is an explanatory plan view of the image forming unit. FIG. 6 is an explanatory diagram for explaining a preparation operation for a complementary operation in the image forming apparatus. It is explanatory drawing of the state similarly following Fig.3 (a). It is explanatory drawing of the state similarly following FIG.3 (b). It is explanatory drawing of the state similarly following FIG.3 (c). It is explanatory drawing of the state which similarly follows FIG.3 (d). It is a plane explanatory view explaining other examples of composition of a line type head. It is a plane explanatory view used for description of Example 1 of the complementary operation. It is plane explanatory drawing with which it uses for description of Example 2 of a complementation operation | movement. It is a plane explanatory view used for description of Example 3 of the complementary operation. It is plane explanatory drawing provided to description of Example 6 of a complementation operation | movement. It is plane explanatory drawing provided to description of Example 7 of a complementation operation | movement. It is plane explanatory drawing with which it uses for description of Example 8 of a complementation operation | movement. It is explanatory drawing which shows the velocity diagram at the time of defective nozzle complementation. It is explanatory drawing which shows the other example of the velocity diagram at the time of defective nozzle complementation. 2 is a schematic block diagram illustrating an example of a control unit of the image forming apparatus. FIG. It is a flowchart with which it uses for description of a complementation process. It is a flowchart with which it uses for description of a complementary process similarly. FIG. 3 is a configuration diagram of an image forming unit of an image forming apparatus that does not have a complementary head. FIG. 2 is an explanatory plan view of the image forming unit. FIG. 6 is an explanatory plan view of an image forming operation performed by the image forming unit. FIG. 6 is an explanatory plan view illustrating a relationship between an image formed by the image forming unit and a nozzle defect.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Line type recording head unit 2 ... Recording medium (paper)
DESCRIPTION OF SYMBOLS 10 ... Line type recording head 11 ... Ink droplet 13 ... Nozzle 31 ... Line type recording head cap 50 ... Complementary recording head 51 ... Complementary recording head cap 71 ... Main control part 73 ... Judgment setting part 75 ... Line type head defective nozzle Detecting unit 76 ... complementary head defective nozzle detecting unit 84 ... head motor 89 ... display unit

Claims (20)

In an image forming apparatus provided with a plurality of line-type recording heads in which the arrangement direction of nozzles for discharging droplets is a direction orthogonal to the conveyance direction of the recording medium,
A second recording head having a plurality of nozzles that can reciprocate in a direction orthogonal to the recording medium conveyance direction in correspondence with each line type recording head, and that is arranged in the recording medium conveyance direction;
The second recording head performs printing to complement a portion corresponding to the defective nozzle of the line type recording head,
An image forming apparatus, wherein at least one defective nozzle is complemented by switching nozzles used for complementing among a plurality of nozzles of the second recording head.   The image forming apparatus according to claim 1, wherein the line type recording head includes a guide member for guiding a reciprocating operation of the second recording head.   3. The image forming apparatus according to claim 2, wherein the guide member is provided with reference to a nozzle hole of the line type recording head.   4. The image forming apparatus according to claim 1, wherein the line-type recording head is provided with a driving unit for reciprocating the second recording head.   5. The image forming apparatus according to claim 1, wherein when the number of defective nozzles in the line type recording head is one, the second recording head moves and stops at the position of the defective nozzle to compensate. An image forming apparatus.   6. The image forming apparatus according to claim 5, wherein one of the plurality of nozzles of the second recording head is Nm, and an upstream nozzle in the transport direction of the recording medium adjacent to the nozzle Nm is Nm-1. When using the nozzle Nm, complement one or more times, then using the nozzle Nm and the nozzle Nm-1 at the same time, and further complementing using the nozzle Nm-1. An image forming apparatus.   6. The image forming apparatus according to claim 5, wherein one of the plurality of nozzles of the second recording head is set to Nm, and a nozzle on the downstream side in the transport direction of the recording medium adjacent to the nozzle Nm is set to Nm + 1. At this time, the nozzle Nm is used for complementation one or more times, then the nozzle Nm and the nozzle Nm + 1 are used for complementation at the same time, and then the printing timing is paused. An image forming apparatus.   6. The image forming apparatus according to claim 5, wherein one of the plurality of nozzles of the second recording head is Nm, and an upstream nozzle in the transport direction of the recording medium adjacent to the nozzle Nm is Nm-1. When the downstream nozzle is set to Nm + 1, the nozzle Nm is used to complement one or more times, then the nozzle Nm and the nozzle Nm-1 are used to complement simultaneously, and then the printing timing is paused. Furthermore, the first mode in which complementation is performed using the nozzle Nm-1, the complementation is performed one or more times using the nozzle Nm, and then complementation is performed simultaneously using the nozzle Nm and the nozzle Nm + 1. , And a second mode for performing complementation using the nozzle Nm + 1, and performing complementation in the second mode after performing complementation in the first mode.   6. The image forming apparatus according to claim 5, wherein one of the plurality of nozzles of the second recording head is Nm, and an upstream nozzle in the transport direction of the recording medium adjacent to the nozzle Nm is Nm-1. When the downstream nozzle is set to Nm + 1, the nozzle Nm is used to complement one or more times, then the nozzle Nm and the nozzle Nm-1 are used to complement simultaneously, and then the printing timing is paused. Furthermore, the first mode in which complementation is performed using the nozzle Nm-1, the complementation is performed one or more times using the nozzle Nm, and then the complementation is performed simultaneously using the nozzle Nm and the nozzle Nm + 1. , And a second mode in which complementation is performed using the nozzle Nm + 1, and after completion in the second mode, complementation in the first mode is performed.   6. The image forming apparatus according to claim 5, wherein complementation is performed using a plurality of nozzles of the nozzles of the second recording head, and the nozzles to be sequentially used are switched.   The image forming apparatus according to claim 10, wherein the nozzles used are switched from the downstream side to the upstream side in the conveyance direction of the recording medium.   11. The image forming apparatus according to claim 10, wherein the nozzles used are switched from the upstream side to the downstream side in the conveyance direction of the recording medium.   The image forming apparatus according to claim 10, wherein the nozzle used from the downstream side to the upstream side in the conveyance direction of the recording medium is complemented and then used from the upstream side to the downstream side in the conveyance direction of the recording medium. An image forming apparatus that performs complementation by switching nozzles.   The image forming apparatus according to claim 10, wherein the nozzle used from the upstream side to the downstream side in the transport direction of the recording medium is switched and complemented, and then used from the downstream side to the upstream side in the transport direction of the recording medium. An image forming apparatus that performs complementation by switching nozzles.   5. The image forming apparatus according to claim 1, wherein when the number of defective nozzles of the line type recording head is plural, the second recording head is complemented while scanning. .   16. The image forming apparatus according to claim 15, wherein the home position of the second recording head is set to a position of a defective nozzle that complements the first of the line type recording head.   16. The image forming apparatus according to claim 15, further comprising a determining unit that determines whether or not the second recording head can be complemented.   18. The image forming apparatus according to claim 17, wherein the number of nozzles of the second recording head necessary for complementing the first recording head is calculated and compared with the number of nozzles that can be printed by the second recording head. And determining whether or not complementation is possible.   19. The image forming apparatus according to claim 18, wherein the number of nozzles necessary for complementation is calculated based on a time required for the second recording head to make one reciprocation for complementation from a position of a defective nozzle of the line type recording head. An image forming apparatus.   18. The image forming apparatus according to claim 17, wherein when there is no image information to be printed at a position of a defective nozzle of the line type recording head, the nozzle of the second recording head necessary for complementing the first recording head. The image forming apparatus is characterized in that the number is not calculated and compared with the number of printable nozzles of the second recording head.

Images