JP5488340B2 - Image forming apparatus and program - Google Patents

Description

  The present invention relates to an image forming apparatus and a program, and more particularly to an image forming apparatus and a program for forming an image by ejecting droplets in a horizontal direction or a direction inclined with respect to the horizontal direction.

  As an image forming apparatus such as a printer, a facsimile machine, a copying apparatus, a plotter, and a complex machine of these, for example, an ink jet recording apparatus is known as an image forming apparatus of a liquid discharge recording method using a recording head for discharging ink droplets. . This liquid discharge recording type image forming apparatus ejects ink droplets from a recording head onto a conveyed paper to form an image (recording, printing, printing, and printing are also used synonymously). Serial type image forming device that forms an image by ejecting droplets while the recording head moves in the main scanning direction, and a line type that forms images by ejecting droplets without the recording head moving There is a line type image forming apparatus using a head.

  In the present application, “image forming apparatus” means an apparatus for forming an image by landing ink on a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc. "Image formation" is not only the application of images with meanings such as characters and figures to the medium, but also the addition of images with no meaning such as patterns to the medium (simply applying droplets to the medium) Also means landing). The term “ink” is not limited to what is referred to as ink, but is used as a general term for all liquids that can perform image formation, such as recording liquid, fixing processing liquid, liquid, and resin. . The term “paper” is not limited to paper, but includes the above-described OHP sheet, cloth, and the like, and means that ink droplets adhere to the recording medium, recording medium, recording paper, recording It is used as a general term for what includes what is called paper. In addition, the “image” is not limited to a planar one, but includes an image given to a three-dimensionally formed image, and an image formed by three-dimensionally modeling a solid itself.

  By the way, as a liquid ejection type image forming apparatus, a recording medium is conveyed in a direction along the vertical direction or in a direction inclined with respect to a direction along the vertical direction, and in a horizontal direction or a horizontal direction with respect to the recording medium. In general, a configuration in which an image is formed on a recording medium by ejecting liquid droplets from a recording head while reciprocating a recording head that ejects liquid droplets in a direction inclined with respect to the recording head (Patent Document). 1 to 3).

  Recently, a configuration has been adopted in which an image is formed by ejecting liquid droplets from a recording head toward a lower direction along the vertical direction while conveying a recording medium in the horizontal direction.

JP 05-338175 A Japanese Patent Laid-Open No. 06-071897 JP-A-11-204288

  By the way, as described above, the recording medium is transported in the direction along the vertical direction or the direction inclined with respect to the direction along the vertical direction, and the horizontal direction or the direction inclined with respect to the horizontal direction with respect to the recording medium. When a method of ejecting droplets toward the head (hereinafter referred to as “horizontal strike method”) is used and an image is formed by a so-called interlace method, the bleeding of the droplets that have landed on the recording medium affects the influence of gravity. There is a problem that the image quality is deteriorated due to the increase in the gravity direction.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to improve the image quality in the horizontal driving method.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A recording head that ejects liquid droplets in a horizontal direction or a direction inclined with respect to the horizontal direction;
Means for conveying the recording medium facing the recording head in a direction along the vertical direction or in a direction inclined with respect to the direction along the vertical direction;
Means for controlling the formation of an image on the recording medium by discharging droplets from the recording head while reciprocating the recording head,
The means for controlling is as follows:
Liquid ejected in the second scan when droplets are ejected in the second scan of the recording head between at least two droplets in the medium transport direction ejected in the first scan of the recording head The control is performed so that the droplet amount is smaller than the droplet amount ejected in the first scanning.

  Here, the feeding amount of the recording medium can be corrected according to the landing position of the droplets ejected in the second scanning.

  Further, the feeding amount of the recording medium can be corrected according to the type of the image.

  Further, the number of droplets ejected in the second scan may be larger than the number of droplets ejected in the first scan.

The program according to the present invention is:
While transporting the recording medium in a direction along the vertical direction or in a direction inclined with respect to the direction along the vertical direction, the recording medium is horizontally or in a direction inclined with respect to the horizontal direction with respect to the recording medium. A program for causing a computer to perform a process of ejecting liquid droplets toward the recording medium to form an image on the recording medium,
Liquid ejected in the second scan when droplets are ejected in the second scan of the recording head between at least two droplets in the medium transport direction ejected in the first scan of the recording head The computer is configured to perform a process of making the droplet amount smaller than the droplet amount ejected in the first scanning.

  According to the image forming apparatus and the program according to the present invention, the recording medium is transported in a direction along the vertical direction or in a direction inclined with respect to the direction along the vertical direction, and is horizontal to the recording medium from the recording head. At least two droplets ejected in the first scan of the recording head when the droplets are ejected in the direction or the direction inclined with respect to the horizontal direction to form an image on the recording medium. During this period, when droplets are ejected in the second scan of the recording head, the droplet amount ejected in the second scan is less than the droplet amount ejected in the first scan Therefore, it is possible to improve the image quality in the horizontal placing method.

FIG. 3 is a side explanatory view of a mechanism unit of the image forming apparatus according to the present invention. It is side surface explanatory drawing of a conveyance path open state similarly. It is an elevation explanatory drawing similarly. It is block explanatory drawing which shows the outline | summary of the control part of the apparatus. It is explanatory drawing with which it uses for description of the blur of the dot of a horizontal hitting method and a vertical hitting method. It is explanatory drawing with which it uses for description of interlace system printing. It is explanatory drawing with which it uses for description of 1st Embodiment of this invention. It is explanatory drawing with which it uses for description of 2nd Embodiment of this invention. It is explanatory drawing with which it uses for description of the landing position correction | amendment of a return pass dot similarly. It is explanatory drawing with which it uses for description of 3rd Embodiment of this invention. It is explanatory drawing with which it uses for description of 4th Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an image forming apparatus according to the present invention will be described with reference to FIGS. 1 is an explanatory side view of the mechanism portion of the image forming apparatus, FIG. 2 is an explanatory side view of the state where the conveyance path is opened, and FIG.

  This image forming apparatus is a serial type image forming apparatus, and has an image forming unit 2, a transport mechanism unit 5 and the like inside the apparatus main body, and can stack sheets 10 as recording media on the lower side of the apparatus main body. The image forming unit 2 includes a paper feed tray 4 and takes in the paper 10 fed from the paper feed tray 4 and intermittently transports the paper 10 in the vertical direction (direction along the vertical direction) by the transport mechanism 5. After a desired image is recorded by ejecting liquid droplets in the horizontal direction, the paper 10 on which the image is formed is further conveyed upward through the paper discharge unit 6 to be discharged on the upper side of the apparatus main body. The paper 10 is discharged to the tray 7.

  Further, when performing duplex printing, after completion of one-side (front) printing, the sheet 10 partially discharged to the sheet discharge tray 7 is taken into the reversing unit 8 and reversed, and the sheet 10 is reversed by the transport mechanism unit 5. While transporting, the other surface (back surface) is sent to the transport mechanism 5 again as a printable surface, and the paper 10 is discharged to the paper discharge tray 7 after the other surface (back surface) is printed.

  Here, the image forming unit 2 slidably holds a carriage 23 on which a recording head 24 is mounted with a main guide member 21 and a sub guide member 22 that are horizontally mounted between the left and right side plates 11L and 11R, and a main scanning motor. 25, the moving scanning is performed in the main scanning direction via the timing belt 28 passed between the driving pulley 26 and the driven pulley 27.

  The carriage 23 has recording heads 24a and 24b composed of liquid ejection heads for ejecting ink droplets of each color of yellow (Y), magenta (M), cyan (C), and black (K). As shown, the recording head 24 is arranged in a sub-scanning direction perpendicular to the main scanning direction, and the droplet discharge direction is mounted in the horizontal direction.

  Each of the recording heads 24 has two nozzle rows. One nozzle row of the recording head 24a has black (K) droplets, the other nozzle row has cyan (C) droplets, and the recording head 24b has one nozzle row. One nozzle row ejects magenta (M) droplets, and the other nozzle row ejects yellow (Y) droplets. As the recording head 24, a recording head having a nozzle row of each color in which a plurality of nozzles are arranged on one nozzle surface may be used.

  The liquid discharge head constituting the recording head 24 includes a piezoelectric actuator such as a piezoelectric element, a thermal actuator that utilizes a phase change due to liquid film boiling using an electrothermal conversion element such as a heating resistor, and a metal due to a temperature change. A shape memory alloy actuator using a phase change, an electrostatic actuator using an electrostatic force, or the like provided as pressure generating means for generating a pressure for discharging a droplet can be used. The carriage 23 can also be mounted with a liquid discharge head that discharges a fixing liquid that reacts with the ink to enhance the fixability of the ink.

  Although not shown, the carriage 23 is provided with a head tank (not shown) for supplying ink of each color corresponding to the nozzle row of the recording head 24. The head tank is detachably attached to the apparatus main body. Ink is supplied from each color ink cartridge (main tank).

  Further, an encoder scale 121 having a predetermined pattern is stretched between the both side plates 21L and 21R along the main scanning direction of the carriage 23, and the carriage 23 is composed of a transmission type photosensor that reads the pattern of the encoder scale 121. An encoder sensor 122 is provided, and the encoder scale 121 and the encoder sensor 122 constitute a linear encoder (main scanning encoder) 123 that detects the movement of the carriage 23.

  A maintenance / recovery mechanism 9 for maintaining and recovering the state of the nozzles of the recording head 24 is disposed in a non-printing area on one side in the scanning direction of the carriage 23. The maintenance / recovery mechanism 9 includes caps 92a and 92b for capping each nozzle surface of the recording head 24 (referred to as “cap 92” when not distinguished) and wiping by moving the nozzle surface in the direction of the arrow. A wiper member (wiper blade) 93 that performs the discharge, and an empty discharge receiver 94 that receives liquid droplets for discharging the liquid droplets that do not contribute to recording in order to discharge the thickened recording liquid.

  The sheets 10 in the sheet feeding tray 4 are stacked on a sheet stacking unit (pressure plate) 41, separated one by one by a sheet feeding roller (half moon roller) 43 and a separation pad (not shown), fed into the apparatus main body, and conveyed. Along the guide surfaces of the guide members 45 and 46 and the pressing member 47, the sheet is fed between the conveying belt 51 and the pressing roller 48 of the conveying mechanism unit 5 and conveyed while being pressed against the conveying belt 51 by the tip pressure roller 47. Is done.

  The conveyance mechanism unit 5 includes an endless conveyance belt 51 that is stretched between a conveyance roller 52 that is a driving roller and a driven roller 53, a charging roller 54 that charges the conveyance belt 51, and the image forming unit 2. A platen member 55 that maintains the flatness of the conveyor belt 51 at a portion facing the conveyor belt 51, a conveyor roller 56, a driven roller 53, and a spur unit 57 having a spur 58 that opposes the conveyor roller 56, and the like.

  The conveyance belt 51 rotates in the belt conveyance direction (sub-scanning direction, paper conveyance direction) when the conveyance roller 52 is rotationally driven by the sub-scanning motor 151 via the timing belt 152 and the timing pulley 153.

  Further, a high-resolution code wheel 154 is attached to the shaft 52a of the transport roller 52, and an encoder sensor 155 including a transmissive photosensor for detecting a pattern formed on the code wheel 154 is provided. These code wheel 154 and the encoder A rotary encoder (sub-scanning encoder) 156 that detects the amount and position of movement of the conveyor belt 51 by the sensor 155 is configured.

  The paper discharge unit 6 includes a conveyance guide member 61, a paper discharge roller 62A and a spur 62B, and a paper discharge roller 63A and a spur 63B. The paper 10 on which an image is formed is disposed between the paper discharge roller 63A and the spur 63B. Paper is discharged face down on the paper discharge tray 7.

  Further, the reversing unit 8 has continuous reversing paths 81a to 81c for reversing the paper 10 partially ejected to the paper discharge tray 7, and switching for switching the transport path in order to send the paper 10 to the reversing path 81a. It has a nail 83 and the like. The reverse path 81a is formed by the conveyance guide member 61 and the guide member 83a, the reverse path 81b is formed by the conveyance belt 51 and the guide member 84, and the reverse path 81c is formed by the conveyance guide members 45 and 46. The reverse path 81a is provided with a transport roller 85 and a required number of spurs 88, and the reverse path 81b is provided with transport auxiliary rollers 86 and 87 facing the driven roller 53 and the transport roller 52, respectively.

  Here, as shown in FIG. 2, a front cover 101 is provided on the front side of the apparatus main body so as to be openable and closable with a support shaft 102 at the lower end as a fulcrum. 85, conveyance auxiliary rollers 86 and 87 are attached. Further, the conveyance belt 51, the conveyance roller 52, the driven roller 53, and the conveyance roller 56 are integrated as a conveyance belt unit 50, and are provided so as to be openable and closable (swingable) with the shaft 52a of the conveyance roller 52 as a fulcrum. Further, the conveyance guide member 61 is also provided so as to be openable and closable (swingable) with the switching claw 82 side as a fulcrum.

  Thereby, by opening the front cover 101, the reversal paths 81a to 81c can be opened, and the jam processing at the time of duplex printing can be easily performed. Further, by opening the front cover 101, the conveyance belt unit 50 can be opened to separate the recording head 24 and the conveyance belt 51, and the conveyance guide member 61 can be opened to open the paper discharge path 60. Therefore, the jam processing becomes easy.

  In this image forming apparatus configured as described above, the paper 10 is separated and fed from the paper feed tray 4 one by one, and the paper 10 is electrostatically attracted to the charged transport belt 51, and the transport belt 51 is moved by the circular movement. The paper 10 is conveyed in the vertical direction. Therefore, by driving the recording head 24 according to the image signal while moving the carriage 23, ink droplets are ejected onto the stopped paper 10 to record one line, and after the paper 10 is conveyed by a predetermined amount, The next line is recorded, and the sheet 10 for which recording has been completed is discharged to the discharge tray 7.

  When performing the maintenance and recovery of the nozzles of the recording head 24, the nozzle 23 is moved to a position facing the maintenance and recovery mechanism 9 that is the home position, and is capped by the cap 92 to perform suction from the nozzles. By performing a maintenance and recovery operation such as idle ejection for ejecting droplets that do not contribute to image formation, image formation by stable droplet ejection can be performed.

Next, an outline of the control unit of the image forming apparatus will be described with reference to FIG. In addition, the figure is a block explanatory drawing of the control part.
The control unit 500 temporarily stores a CPU 501 that controls the entire apparatus, various programs including a program that causes the CPU 501 to execute control (processing) according to the present invention, a ROM 502 that stores other fixed data, image data, and the like. RAM 503 for storing, rewritable nonvolatile memory 504 for holding data even while the power of the apparatus is shut off, image processing for performing various signal processing and rearrangement on image data, and other control of the entire apparatus An ASIC 505 for processing input / output signals for the purpose is provided.

  Also, a print control unit 508 including a data transfer unit for driving and controlling the recording head 24 and a driving signal generating unit, a head driver (driver IC) 509 for driving the recording head 24 provided on the carriage 23 side, A main scanning motor 25 that moves and scans the carriage 23, motor driving units 510 and 511 for driving a sub-scanning motor 151 that moves the conveyor belt 51 in a circular manner, an AC bias supply unit 512 that supplies an AC bias to the charging roller 54, and the like It has.

  The control unit 500 is connected to an operation panel 514 for inputting and displaying information necessary for the apparatus.

  The control unit 500 has an I / F 506 for transmitting and receiving data and signals to and from the host side, an information processing device such as a personal computer, an image reading device such as an image scanner, an imaging device such as a digital camera, and the like. From the host 600 side via the cable or network via the I / F 506.

  Then, the CPU 501 of the control unit 500 reads and analyzes the print data in the reception buffer included in the I / F 506, performs necessary image processing, data rearrangement processing, and the like in the ASIC 505, and prints the image data. The data is transferred from the unit 508 to the head driver 509. Note that the generation of dot pattern data for image output is performed by the printer driver 601 on the host 600 side.

  The print control unit 508 transfers the above-described image data as serial data, and outputs a transfer clock, a latch signal, a control signal, and the like necessary for transferring the image data and confirming the transfer to the head driver 509. Including a D / A converter for D / A converting D / A conversion of drive pulse pattern data stored in the ROM, a voltage signal amplifier, a current amplifier, and the like, and a drive signal or a plurality of drive pulses Is output to the head driver 509.

  The head driver 509 selectively selects a drive pulse that constitutes a drive signal provided from the print control unit 508 based on image data corresponding to one line of the print head 24 that is input serially, and drops droplets of the print head 24. The recording head 24 is driven by applying it to a driving element (for example, a piezoelectric element) that generates energy to be discharged. At this time, by selecting a drive pulse that constitutes a drive signal, for example, droplets having different droplet sizes, such as large droplets, medium droplets, and small droplets, can be ejected and dots having different sizes can be sorted.

  The I / O unit 513 acquires information from the main scanning encoder 123, the sub-scanning encoder 156, and various sensor groups 515 mounted on the apparatus, extracts information necessary for controlling the printer, and print control unit 508. Also used to control the motor drive units 510 and 511 and the AC bias supply unit 511. The sensor group 515 includes an optical sensor for detecting the position of the paper, a thermistor for monitoring the temperature and humidity in the machine, a sensor for monitoring the voltage of the charging belt, an interlock switch for detecting opening and closing of the cover, and the like. The I / O unit 513 can process various sensor information.

  The CPU 501 also detects a speed detection value and a position detection value obtained by sampling a detection pulse from the encoder sensor 122 constituting the main scanning encoder 123, and a speed target value and a position target obtained from a previously stored speed / position profile. The drive output value (control value) for the main scanning motor 25 is calculated based on the value and the main scanning motor 25 is driven via the motor driving unit 210. Similarly, a speed detection value and a position detection value obtained by sampling a detection pulse from the encoder sensor 155 constituting the sub-scanning encoder 156, a speed target value and a position target value obtained from a previously stored speed / position profile, and Based on this, a drive output value (control value) for the sub-scanning motor 151 is calculated, and the sub-scanning motor 151 is driven via the motor driving unit 211.

Next, a horizontal strike as in the image forming apparatus and a method of forming an image by ejecting droplets in a vertical direction while conveying a paper in the horizontal direction (this method is referred to as a “vertical strike method”). The bleeding of landing droplets will be described with reference to FIGS.
First, in the case of the vertical hitting method, as shown in FIG. 5B, since the printing surface is horizontal, droplets If and Ib on the paper (medium) 10 (referred to as “droplet I” when not distinguished). .)), The bleeding portion Ia is generated almost uniformly around the droplet I. On the other hand, in the case of the horizontal hitting method, as shown in FIG. 5A, since the printing surface is vertical, when the droplet I lands on the paper (medium) 10, Since gravity acts, the bleeding part Ia spreads in the direction of gravity. The degree of dot enlargement due to bleeding of the droplet I after landing varies depending on the mass of the droplet, the velocity of the droplet, the environmental temperature, the environmental humidity, the image to be formed, and the like.

  Here, for example, when an image is formed by the ½ interlace method, as shown in FIG. 6, half of the dots of the image are formed on the paper in the forward path (first scan of the head). Next, the remaining half of the dots are formed in the middle of the dots formed in the forward path in the backward path (second scan of the head). Thereby, the dot interval can be narrowed to a distance shorter than the nozzle interval of the head, and a high-resolution image can be formed.

  When such an interlaced image formation is performed by a horizontal image forming apparatus, as shown in FIG. 5 (a) described above, it is formed by the forward dot Df (the landed droplet If and its bleeding portion Ia). The dot Db of the return path (formed by the landed droplet Ib and its bleeding portion Ia) is greatly covered. As a result, the image quality is adversely affected, such as a change in color tone or a decrease in resolution, with respect to the image quality.

A first embodiment of the present invention will be described with reference to the explanatory diagram of FIG.
In the present embodiment, the droplet amount of the droplet Ib ejected in the return path, which is driven between the droplets If and If, is decreased with respect to the droplet amount of the droplets If and If ejected in the forward path. By reducing the amount of droplets, the influence of gravity is reduced, so that bleeding in the direction of gravity after droplet landing is less than when the amount of droplets is large. As a result, the influence of the dots Db formed in the return path on the dots Df formed in the forward path is reduced.

  In order to perform such control (processing), for example, the amount of droplets discharged in the backward path or the correction amount of the droplet amount discharged in the backward path relative to the droplet volume discharged in the forward path (these are referred to as “drop volume information”). Is stored and held in the NVRAM 504 or the like, and before starting printing in the backward path, the droplet volume information is read from the NVRAM 504, and the ejection volume of the ejection path in the backward path is compared with the droplet volume of the ejection path in the forward path. Image formation is performed by controlling the drop volume to a small drop volume. For example, control (processing) is performed so that the droplet size of the ejected droplet in the return path is one step smaller than the droplet size of the droplet ejected in the outbound route.

  Note that if the amount of droplets that form the dots on the return path is reduced, the image formed on the return path may become brighter than usual. However, ink bleeding occurs from the dots originally formed in the forward path to the dot areas formed in the backward path. That is, the color is placed on the return path formation area before the return path dot is formed. Since the color is added to the dot area where the drop amount is reduced in the return path, the brightness of the dot area where the drop amount is reduced becomes darker than the brightness of the dot alone where the drop amount is reduced. Therefore, image quality deterioration due to a change in brightness can be prevented by setting the drop amount in the return path to a drop amount that does not cause deterioration in image quality, which is obtained in advance through experiments or the like.

  As described above, when an image is formed on a recording medium by ejecting droplets from the recording head toward the horizontal direction with respect to the recording medium while conveying the recording medium in a direction along the vertical direction, When droplets are ejected in the second scan of the recording head between at least two droplets ejected in the first scan of the recording head, droplets ejected in the second scan By adopting a configuration in which the amount is made smaller than the amount of droplets ejected in the first scan, it is possible to improve the image quality in the horizontal hitting method (suppress deterioration in image quality).

  In the above embodiment, the control according to the present invention is performed by the program of the image forming apparatus. However, when print data (image data) is generated by a program such as a printer driver on the host side, printing is performed in advance on the return path. The dots can be corrected (converted) to dots smaller than the dots printed in the forward path, and the corrected print data can be given to the image forming apparatus.

Next, a second embodiment of the present invention will be described with reference to the explanatory diagrams of FIGS.
First, the bleeding of the droplets in the direction of gravity is asymmetric in the vertical direction under the influence of gravity. Therefore, as shown in FIG. 8A, when only the droplet amount adjustment is performed as in the first embodiment, when the dot Db in the return path is viewed, the upper region (point da) of the droplet Ib is Compared with the lower side (db point) of the droplet Ib, the dot Df in the forward path is more affected, and this phenomenon may cause deterioration in image quality.

  Therefore, in this embodiment, as shown in FIG. 8B, the landing point of the droplet Ib that forms the return dot Db is shifted in the direction of gravity. Thereby, it is possible to average the influence from above and below from the dot Df in the forward path, and to reduce the deterioration of the image quality.

  Here, the landing position of the droplet Ib that forms the backward dot Db will be described. As shown in FIG. 9, the landing position of the droplet Ib that forms the backward dot Db is the position of the two forward dots Df. It is set as the middle position of the boundary line including the blur (in order to average the influence from two dots). When the radius of the droplet If of the forward dot Df is a, the coefficient of the amount of bleeding in the downward direction is k, the coefficient of the amount of bleeding in the upward direction is l, and the distance between the dots is D, the distance d to be obtained (forward dot printing) The sheet feed amount before the backward dot printing is expressed by the following equation (1).

  d = (D + a (k + 1)) / 2 (1)

  The counts k and l are coefficients that vary depending on the environment such as the mass of the droplet, the droplet velocity, the paper quality, the temperature, the humidity, and the print image.

  In order to perform such landing position correction control, the values of a, k, and l obtained in advance through experiments or the like are stored in the NVRAM 504 or the like, and stored in the NVRAM 504 when the forward printing is finished and the paper is fed. The values of a, k, and l are read out, and the value of the feed amount d is calculated using the above equation (1) from this value and the value of the inter-dot distance D that has already been set. Then, the paper 10 is moved relative to the recording head 24 by a distance of the calculated feed amount d (a minute section feed), and then the backward printing is performed.

Next, a third embodiment of the present invention will be described with reference to the explanatory diagram of FIG.
In the present embodiment, the control to be applied is varied depending on the type of image. That is, the amount of bleeding due to the gravity of the droplet changes depending on the object to be printed. As a typical example, a character and an image other than a character such as a photograph will be described. Characters use a small amount of ink and the spacing between dots is sparse, whereas photographs and graphics use a large amount of ink. In most cases, the spacing between dots is close to the entire area. In addition, when a photograph or graphic is formed, an increase in the amount of bleeding due to gravity is conceivable due to the influence of a large amount of ink mist scattered or the combination of droplets. Therefore, the image quality of the entire document can be improved by switching the control to be applied depending on whether the print image is a character or non-character.

  For example, as an example, normal printing is performed for characters, and the landing position of droplets is corrected for images other than characters, thereby affecting the image quality due to droplet bleeding after landing. Reduce.

  In this case, if the print target in one scan (one scan) of the carriage 23 is only a character or only an image other than a character, printing can be performed in one scan, but other than characters and characters in one scan. When images are mixed, it is necessary to scan several times. That is, in the interlace process, when the return position correction is performed as in the second embodiment, it is necessary to change the sheet feed amount according to the type of image.

This will be described with reference to an example in which a character area A and an image area B other than characters are mixed in one scan as shown in FIG.
First, dots of both characters and non-character images are formed on the forward path (circled number 1 in the figure). Next, the paper is fed by a normal inter-dot distance d (circled number 2 in the figure) to form a return path dot in the character area (circled number 3 in the figure). For the image area other than characters, printing is not performed on the return path, but only the carriage 23 is moved (circled number 4 in the figure). Paper is fed (circled number 5 in the figure). Then, dots in the image area other than the characters that should have been formed in the return path are formed on the forward path (circled number 6 in the figure).

  Of print data, information indicating character data (or image data other than characters) is included in the print data by the function of the OS on the host 600 side connected to the image forming apparatus. Passed. Based on this information, as described above, the control may be switched depending on the type of image.

Next, a fourth embodiment of the present invention will be described with reference to the explanatory diagram of FIG.
In the present embodiment, the total droplet amount is secured by reducing the droplet amount of the droplets in the return path and increasing the number of droplets. In other words, as described in each of the above embodiments, when the drop amount of the drop in the return path is reduced, the shortage of the drop is alleviated to some extent by the bleeding of the dots, but as shown in FIG. An area c that cannot be covered by the small droplets of printing occurs, and the image quality may deteriorate.

  Therefore, as shown in FIG. 11B, dots are formed in the region c by hitting a larger number of droplets (dots) in the return path than in the forward path. The number of dots in the return pass is set to “2” or more when the dot cycle of the forward pass is “1”.

  Note that the above-described drop amount adjustment (decrease, correction) processing on the return path can be performed by a computer by a program stored in a ROM or the like, and this program can be provided by being stored in a storage medium, or Is provided by downloading through a network such as the Internet. The image forming system can also be configured by combining the image forming apparatus described in the above embodiment and the host side (information processing apparatus).

  In the above embodiment, the paper is conveyed in the direction along the vertical direction (vertical direction) and the liquid droplets are ejected in the horizontal direction. However, the paper is moved in the direction along the vertical direction (vertical direction). Even if the liquid droplets are transported in an inclined direction and the liquid droplets are discharged in a horizontal direction or a direction inclined with respect to the horizontal direction, the bleeding of the landed liquid droplets is different in the vertical direction of the gravity direction. Can be applied as well.

2 Paper feed tray 10 Paper (recording medium)
23 Carriage 24 Recording Head 51 Conveying Belt 500 Control Unit

Claims (5)

A recording head that ejects liquid droplets in a horizontal direction or a direction inclined with respect to the horizontal direction;
Means for conveying the recording medium facing the recording head in a direction along the vertical direction or in a direction inclined with respect to the direction along the vertical direction;
Means for controlling the formation of an image on the recording medium by discharging droplets from the recording head while reciprocating the recording head,
The means for controlling is as follows:
Liquid ejected in the second scan when droplets are ejected in the second scan of the recording head between at least two droplets in the medium transport direction ejected in the first scan of the recording head An image forming apparatus that performs control so that a droplet amount is smaller than a droplet amount discharged in the first scan.   The image forming apparatus according to claim 1, wherein the feeding amount of the recording medium is corrected according to a landing position of a droplet ejected in the second scanning.   The image forming apparatus according to claim 1, wherein the feeding amount of the recording medium is corrected according to the type of the image.   4. The image formation according to claim 1, wherein the number of droplets ejected in the second scan is larger than the number of droplets ejected in the first scan. 5. apparatus. While transporting the recording medium in a direction along the vertical direction or in a direction inclined with respect to the direction along the vertical direction, the recording medium is horizontally or in a direction inclined with respect to the horizontal direction with respect to the recording medium. A program for causing a computer to perform a process of ejecting liquid droplets toward the recording medium to form an image on the recording medium,
Liquid ejected in the second scan when droplets are ejected in the second scan of the recording head between at least two droplets in the medium transport direction ejected in the first scan of the recording head A program that causes a computer to perform a process of reducing the droplet amount of the droplets less than the droplet amount discharged in the first scan.

Images