JP2016159542A - Print control device and print control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress image quality degradation due to the difference in the conveyance errors of print media between the right side and the left side.SOLUTION: A print control device which achieves printing of an image on a print medium by moving a nozzle array in which a plurality of nozzles are arrayed with a prescribed interval along a first direction intersecting the nozzle array direction and discharging from one or more nozzles ink to the print medium conveyed in a second direction intersecting the first direction, comprises: a detection part which detects errors of conveyance in the second direction on one end side and the other end side of the print medium in the first direction; and a discharge control part which performs used nozzle deviating processing for deviating the range of the nozzles in the nozzle array used in ink discharge in accordance with the errors of conveyance on the one end side and the other end side between respective image regions obtained by dividing the image in the first direction.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a print control apparatus and a print control method.

  2. Related Art Inkjet printers that realize printing by ejecting ink from nozzles onto a print medium while moving a print head having a plurality of nozzles capable of ejecting ink in a predetermined main scanning direction are known. The print medium is generally transported along a transport direction (also referred to as a sub-scan direction) orthogonal to the main scanning direction. However, due to various errors in the mechanisms (rollers, gears, motors, etc.) for transporting the print media that the printer has, errors between the rollers and the print media, slippage between the rollers and the print media, etc. However, the print medium is actually transported under the print head with some error relative to ideal transport.

  The “error” mentioned here is roughly divided into an error in the main scanning direction and an error in the transport direction. That is, when the print medium is based on a certain ideal position with respect to the print head, the print medium is close to one end side or the other end side in the main scanning direction (there is an error in the main scanning direction). Can be conveyed under the print head. In addition, the print medium should be transported by a certain distance. Actually, the print medium is transported slightly or slightly more than the distance. It is possible to stop under the print head in a state close to either the upstream side or the downstream side (a state in which there is an error in the transport direction).

In addition, by calculating the drawing area as needed from the left and right edges of the recording medium detected during printing, even if the recording medium has a skew in the horizontal direction (main scanning direction), it is possible to draw in a predetermined area of the recording medium. A recording apparatus is known (see Patent Document 1).
The ink jet recording head also has an effective nozzle for printing in the sub-scanning direction and an adjustment nozzle for pausing for one nozzle row, and the target moving amount of the print medium in the sub-scanning direction and the actual amount for each main scanning unit. There is known an ink jet recording apparatus that performs a print control by comparing an amount of movement and determining an effective nozzle and an adjustment nozzle based on the result (see Patent Document 2).

JP 2012-71575 A Japanese Patent Laid-Open No. 2004-175012

  The print medium may be transported while being slightly inclined with respect to the transport direction. This means that the error in the transport direction differs between the right and left print media when the transport direction is the front. When the error in the transport direction differs between the right and left of the print medium, for example, as described in Reference 2, the target movement amount in the sub-scanning direction of the print medium is compared with the actual movement amount, and the effective nozzle is determined based on the result. It is difficult to print an image at an ideal position on the print medium even if the print is controlled by determining the adjustment nozzle.

  The present invention has been made in view of at least such problems, and can print an image at an accurate position with respect to a print medium when an error in conveyance of the print medium differs between right and left of the print medium. A print control apparatus and a print control method are provided.

  According to one aspect of the present invention, a nozzle row in which a plurality of nozzles capable of ejecting ink are arranged at a predetermined interval is moved along a first direction that intersects a nozzle row direction in which the nozzle row faces. A print control apparatus that realizes printing of an image on a print medium by ejecting ink from a nozzle to a print medium conveyed in a second direction that intersects the first direction, A detection unit that detects the conveyance error in the second direction on each of the one end side and the other end side of the print medium, and the one end side and the other end side between the image areas obtained by dividing the image in the first direction. A discharge control unit that performs a use nozzle shift process for shifting the range of nozzles in the nozzle row used for ink discharge according to each transport error.

  According to this configuration, the transport error in the second direction on each of the one end side and the other end side of the print medium in the first direction (that is, the transport error on the left and right sides of the print medium when the second direction is the front). Accordingly, the range of nozzles used in the nozzle row is shifted between the image areas in the first direction. For this reason, a print result in which the positional relationship between the print medium and the image in the second direction is in an ideal state can be obtained at any position in the first direction.

One aspect of the present invention is that the ejection control unit increases the number of divisions of the image in the first direction as the difference between the transport error on the one end side and the transport error on the other end side increases. It is good.
According to this configuration, even when the inclination of the print medium is large, the positional relationship between the print medium and the image in the second direction can be in an ideal state at any position in the first direction.

One of the aspects of the present invention may be configured such that the ejection control unit changes the aspect of shifting the nozzle range to be used in accordance with the inclination of the nozzle row direction with respect to the second direction.
According to this configuration, the used nozzle shifting process can be performed in consideration of the inclination of the nozzle row itself.

In one aspect of the present invention, the detection unit detects an inclination of the print medium with respect to the second direction, and the discharge control unit determines a nozzle within the range of the nozzles to be used in the nozzle row direction. For each predetermined number of nozzles divided for each number, an ejection timing shifting process for shifting the ink ejection timing according to the inclination may be performed.
According to this configuration, in addition to the used nozzle shifting process, the ejection timing shifting process is performed. Therefore, in addition to the effect of the used nozzle shifting process, the positional relationship between the print medium and the image in the first direction can be in an ideal state at any position in the second direction.

In one aspect of the present invention, the discharge control unit may reduce the predetermined number as the inclination of the print medium with respect to the second direction is larger.
According to this configuration, even when the inclination of the print medium is large, the positional relationship between the print medium and the image in the first direction can be in an ideal state at any position in the second direction.

In one aspect of the present invention, the ejection control unit may adjust the degree of shifting the ink ejection timing in accordance with the inclination of the nozzle row direction with respect to the second direction.
According to this configuration, it is possible to perform the discharge timing shifting process in consideration of the inclination of the nozzle row itself.

One aspect of the present invention is such that when the amount of conveyance performed between movement (pass) and movement (pass) of the nozzle row accompanied by ink ejection from the nozzle is larger than a predetermined amount, The discharge control unit may perform the used nozzle shifting process.
According to this configuration, when the image quality deterioration due to the conveyance error in the second direction is substantially conspicuous, the used nozzle shifting process is executed to improve the image quality.

  The technical idea of the present invention is also realized by a device other than a printing control device. For example, the present invention relates to a method (printing control method) including a step executed by each unit of the printing control apparatus, a computer program that causes a computer to execute the method, and a computer-readable storage medium that stores the program, It may be realized in various categories.

1 is a block diagram illustrating a schematic configuration of a print control apparatus. The figure which illustrates a printing head etc. simply. 6 is a flowchart showing print control processing. The figure which shows an example of the correspondence of a nozzle and the pixel allocated to a nozzle. The flowchart which shows the detail of the process included in step S300. The figure which illustrates right and left accumulated conveyance error. The figure which illustrates an image area number determination table and a nozzle group number determination table. The figure for demonstrating an example of step S340. The figure which illustrates the printing result reflecting the use nozzle shift process. The flowchart which shows the detail of the process included in step S300 in 2nd Embodiment. The figure for demonstrating an example of step S360. The figure for demonstrating the process which shifts the timing of ink discharge. The figure which illustrates the printing result reflecting the use nozzle shift process and the discharge timing shift process. The figure which illustrates a nozzle row in the case where there is no nozzle row inclination and it exists. The figure for demonstrating an example of microweave printing.

Embodiments of the present invention will be described in the following order with reference to the drawings. Each figure is only an example for explaining an embodiment, and may not be consistent with each other.
1. Outline of the apparatus 1. First embodiment Second Embodiment 4. Modified example

1. Outline of the device:
FIG. 1 is a block diagram illustrating functions of the print control apparatus 10 and the like according to the present embodiment. The print control apparatus 10 is grasped as a product such as a printer or a multifunction peripheral including a printer function. When the print control apparatus 10 is configured to include a printing unit 70 that actually performs printing on the printing medium G and a unit (for example, a control unit 11 described later) for controlling the behavior of the printing unit 70 A part thereof may be referred to as a print control apparatus. The print control apparatus 10 may be called a printing apparatus from the viewpoint of including the printing unit 70, or may be called an image processing apparatus or the like because various image processing can be executed. Each configuration shown in FIG. 1 is not limited to a single location or a case where the configurations are aggregated in a single case, but a single system is constructed by the presence of these configurations in locations away from each other and being communicable. It may be. For example, the print control apparatus (or printing apparatus) 10 controls the printer by mounting a printer that actually performs printing on the print medium G and a computer program (printer driver) for controlling the behavior of the printer. And a device (such as a personal computer).

  In FIG. 1, the printing control apparatus 10 is illustrated as a configuration including a control unit 11, an operation input unit 16, a display unit 17, a communication interface (I / F) 18, a slot unit 19, a printing unit 70, a sensor 80, and the like. Yes. The control unit 11 includes, for example, an IC having a CPU, a ROM, a RAM, and other storage media. In the control unit 11, various functions (for example, the detection unit 12, the discharge control unit 13, and the like) are performed by the CPU executing arithmetic processing according to a program stored in the ROM using the RAM as a work area. Realize.

  The operation input unit 16 includes various buttons and keys for accepting an operation by the user. The display unit 17 is a part for displaying various information related to the print control apparatus 10 and is configured by, for example, a liquid crystal display (LCD). A part of the operation input unit 16 may be realized as a touch panel displayed on the display unit 17.

  The printing unit 70 is a mechanism for printing an image on the printing medium G under the control of the control unit 11. When the printing method employed by the printing unit 70 is an inkjet method, the printing unit 70 intersects the print head 40, the carriage 30 that moves the print head 40 along the first direction (main scanning direction), and the first direction. It has a configuration of a transport unit 20 or the like that transports the print medium G in the second direction (transport direction). In the following, the main scanning direction is represented by reference numeral D1, and the transport direction is represented by reference numeral D2.

  The print head 40 supplies various inks from ink cartridges (not shown) for each of a plurality of types of ink (for example, cyan (C) ink, magenta (M) ink, yellow (Y) ink, black (K) ink, etc.)). Receive. The print head 40 can eject ink droplets from a plurality of nozzles Nz provided corresponding to various inks. As the ejected ink droplets land on the printing medium G, dots are formed on the printing medium G. “Dot” basically refers to an ink droplet that has landed on the print medium G, but the expression “dot” may be used for convenience in the description of the process before the ink droplet has landed on the print medium G. The specific types and number of liquids used by the printing unit 70 are not limited to those described above. For example, various inks and liquids such as light cyan, light magenta, orange, green, gray, light gray, white, metallic ... It can be used.

  The carriage 30 on which the print head 40 is mounted receives power from a carriage motor (not shown) and moves in parallel with the main scanning direction D1. The print head 40 implements printing by ejecting ink onto the print medium G while moving with the carriage 30. The print head 40 moves with the movement from one end side (for example, the left side LS) to the other end side (for example, the right side RS) in the main scanning direction D1 or the movement from the other end side to the one end side in the main scanning direction D1. The process of ejecting ink is also referred to as a single “main scan” or “pass”.

  The transport unit 20 includes a roller for supporting and transporting the print medium G, a gear for rotating the roller, a motor, and the like. The print medium G is typically paper. However, in the present embodiment, materials other than paper are included in the concept of the print medium G as long as the material can record liquid and can be transported by the transport unit 20.

The communication I / F 18 is a generic name for interfaces for connecting the print control apparatus 10 to the external device 100 by wire or wirelessly. Examples of the external device 100 include various devices that are input sources of image data for the print control apparatus 10 such as a smartphone, a tablet terminal, a digital still camera, and a personal computer (PC). The print control apparatus 10 can be connected to the external device 100 via the communication I / F 18 by various means and communication standards such as a USB cable, a wired network, a wireless LAN, and e-mail communication.
The slot part 19 is a part for inserting an external storage medium such as a memory card. That is, the print control apparatus 10 can also input image data stored in the storage medium from an external storage medium such as a memory card inserted in the slot unit 19.

  FIG. 2 simply illustrates the print head 40 and the print medium G. The left side of FIG. 2 illustrates the arrangement of the nozzles Nz on the ink ejection surface 41a of the print head 40. The ink discharge surface 41a is a surface on which the nozzle Nz is opened, and is a surface that faces the print medium G when the print head 40 moves in the main scanning direction D1. The print head 40 has a nozzle row NL for each ink to be ejected (for example, CMYK ink). The nozzle row NL is a row in which a plurality of nozzles Nz are arranged at a predetermined interval (a constant nozzle pitch). In the example of FIG. 2, four nozzle rows NL are provided in parallel. In this specification, even when expressions that are strictly understood as constant, parallel, etc. are used, they do not mean only strictly constant, parallel, but are allowed in terms of product performance. It also includes the error of the degree and the error that can occur at the time of manufacturing the product.

  The direction in which the nozzle row NL faces is referred to as a nozzle row direction D3. The nozzle row direction D3 intersects the main scanning direction D1. Although depending on the design of the printing unit 70, the nozzle row direction D3 is orthogonal to the main scanning direction D1 or intersects at an oblique angle that is not orthogonal (90 degrees). In the example of FIG. 2, the nozzle row direction D3 is orthogonal to the main scanning direction D1. In addition to being ejected by one nozzle row NL, one color ink may be ejected by, for example, a plurality of nozzle rows NL arranged so as to be shifted from each other in the nozzle row direction D3.

  As shown in FIG. 2, the transport direction D2 is orthogonal to the main scanning direction D1. That is, in the example of FIG. 2, the nozzle row direction D3 and the transport direction D2 are parallel. However, the transport direction D2 orthogonal to the main scanning direction D1 is “ideal” in the direction in which the transport unit 20 transports the print medium G. As described in the background art, an error may occur in the actual conveyance of the print medium G. Therefore, when the transport unit 20 transports the print medium G from the upstream US in the transport direction D2 to the downstream BS, the direction in which the print medium G actually travels may be inclined with respect to the transport direction D2. Therefore, it can be said that the print medium G is conveyed in a direction crossing the main scanning direction D1.

  In FIG. 2, one print target area GPA in the print medium G is illustrated by hatching. The print target area GPA is an area that receives ink ejection from the print head 40 by one or more passes during a period from the end of the previous conveyance (paper feed) of the print medium G to the start of the next paper feed. is there. In FIG. 2, the “ideal position” in the printing unit 70 where the print target area GPA should be present when ink ejection is received from the print head 40 is illustrated as an area partitioned by four position marks PM. . The position mark PM does not actually exist, but is merely shown for convenience of explanation. The transport unit 20 feeds the paper so that the next print target area GPA stops at the ideal position. In the example of FIG. 2, since the print target area GPA completely coincides with the ideal position, the ideal paper feed for the print target area GPA, that is, as designed, is realized. However, such ideal paper feeding is not always realized, and the printing target area GPA is stationary at a position shifted from the ideal position to the left LS or the right RS, and to the upstream US or the downstream BS. Or stand still in a tilted state as described above.

  FIG. 2 illustrates the sensors 81L, 81R, and 82. The sensors 81L, 81R, and 82 are included in the sensor 80 (see FIG. 1). Although not shown, the printing unit 70 has a so-called platen as a table for supporting the printing medium G. The print medium G is conveyed on the platen. The ideal position surrounded by the four position marks PM is a partial range of the platen. The left sensor 81L and the right sensor 81R are two sensors arranged in a predetermined range where the end of the left side LS and the end of the right side RS of the transported print medium G are expected to pass, respectively. For example, the sensors 81L and 81R are embedded in the platen so as to be exposed upward, and the positions in the transport direction D2 are the same. The sensor 82 is a sensor mounted on the carriage 30 together with the print head 40. That is, the sensor 82 can be moved along the main scanning direction D <b> 1 by the carriage 30 similarly to the print head 40. The role of the sensors 81L, 81R, 82 will be described later.

2. First embodiment:
A first embodiment according to the present invention will be described.
FIG. 3 is a flowchart showing print control processing executed by the control unit 11. When the image data representing the image to be printed is input (step S100), the control unit 11 executes image processing for generating print data from the image data (step S200). Various formats of image data can be considered. For example, the image data is data expressed by gradation in RGB (red, green, blue) for each pixel. The control unit 11 appropriately performs known image processing such as resolution conversion processing, color (color system) conversion processing, and halftone processing on the image data, so that an image to be printed is a dot pattern with a plurality of pixels. Print data expressed by the above is generated.

A dot pattern (dot pattern) is an array of dots on (dot formation or ink ejection) and off (dot non-formation or ink non-ejection). It also defines dot on / off for each pixel. I can say that. For example, when the print head 40 ejects CMYK ink, the print data includes data defining dot on / off for each pixel for each CMYK ink.
Each nozzle Nz included in the print head 40 may eject ink droplets of a plurality of sizes. As an example, the nozzle Nz can eject ink droplets of three different sizes (ink droplets referred to as large dots, medium dots, small dots, etc.). In this case, the print data generated in step S200 is not simply binary data indicating dot on / off, but multivalue (four values) indicating either large dot, medium dot, or small dot on or dot off. ) Data.

  The control unit 11 determines an assignment destination nozzle Nz for each pixel constituting such print data, transfers the data to the print head 40 in accordance with the determination, and transfers them to the print head 40 after rearranging them. The output process is performed (step S300). By assigning each pixel to the nozzle Nz in this way, the dot of each pixel constituting the print data is scanned by any nozzle Nz in the print head 40 according to the ink color and the pixel position. In (Pass), it is determined at which timing during the pass the ejection is performed. In the first embodiment, the allocation corresponding to the “used nozzle shifting process” is performed in step S300. The used nozzle shifting process is roughly used for ink ejection between image areas obtained by dividing an image in the main scanning direction D1, depending on the transport errors on one end side and the other end side in the main scanning direction D1. This refers to shifting the range of nozzles Nz (used nozzle range) within the nozzle row to be used. Step S300 will be described later in detail (FIG. 5 and the like).

  The print head 40 drives each nozzle Nz based on the transferred print data. For example, a drive signal (a kind of pulse) for driving each nozzle Nz is given to the print head 40. Although detailed description is omitted, in the print head 40, according to dot on / off information for each pixel represented by print data (or information on large dot on, medium dot on, small dot on, dot off). Thus, the application of the drive signal to the drive element provided for each nozzle Nz is switched. As a result, each nozzle Nz performs ink ejection / non-ejection (dot formation / non-formation, or formation / non-formation of any one of large dots, medium dots, and small dots) based on the information of the pixels assigned to itself. Realize.

  FIG. 4 shows an example of the correspondence between the nozzles Nz and the pixels assigned to the nozzles Nz. FIG. 4 shows a nozzle array NL (nozzle array KNL) corresponding to one color ink (for example, K ink) and print data KDP representing a dot pattern of K ink among the print data obtained in step S200. Some are shown. The print data (for example, print data KDP) is composed of a plurality of pixels PX arranged corresponding to the main scanning direction D1 and the conveyance direction D2, respectively. For convenience of explanation, the direction of arrangement of pixels constituting data may be expressed by directions D1 and D2, but this is only a correspondence relationship between the direction of the image and the directions D1 and D2 when the printing unit 70 executes printing. Based on. FIG. 4 shows an example in which the nozzle array NL corresponding to one color ink is composed of 18 nozzles Nz for simplicity, but the nozzle array NL corresponding to one color ink is actually shown in FIG. More nozzles Nz (for example, about 180 nozzles) are formed.

  The nozzle row NL corresponding to one color ink is divided into nozzles Nz (used nozzles) used for printing and nozzles Nz (unused nozzles) not used for printing. The unused nozzle is also called a spare nozzle. In FIG. 4, for easy understanding, the unused nozzles are marked with x. That is, the print target area GPA (see FIG. 2) of the print medium G receives ink ejection from the used nozzles in the nozzle array NL. The number of used nozzles q in the nozzle row NL is basically constant. If the number of nozzles constituting the nozzle array NL is p (where p> q), the number of unused nozzles in the nozzle array NL is (p−q). Further, normally, as shown in FIG. 4, (p−q) / 2 unused nozzles are positioned on both sides of the used nozzle range (q used nozzles) in the nozzle row direction D3.

  In FIG. 4, when the printing unit 70 adopts so-called band printing as a printing method, a group of pixels PX assigned to each nozzle Nz as a use nozzle is indicated by hatching. In general, the band printing prints a bundle (band image) of raster lines corresponding to the number of used nozzles in the nozzle array NL onto one print target area GPA by one pass of the print head 40. This is a printing method in which such a pass and conveyance (paper feed) of the print medium G for a length in the conveyance direction D2 of the band image are alternately repeated. The raster line is an area formed by a plurality of pixels PX that are continuous along the main scanning direction D1, and in raster printing, one raster line is printed in one-to-one correspondence with one used nozzle. Of course, the printing method that can be adopted by the printing unit 70 is not limited to band printing. However, if the printing method is determined by any printing method, the control unit 11 selects which pixel that constitutes the print data. It can be determined whether it should be assigned to the nozzle used.

  The positional relationship between the used nozzles and the unused nozzles in the nozzle row NL illustrated in FIG. 4 is a normal positional relationship as described above. That is, such a normal positional relationship is adopted when the print target area GPA on which the band image is to be printed exists at the ideal position. On the other hand, when the print target area GPA on which the band image is to be printed is shifted from the ideal position, the positional relationship between the used nozzles and the unused nozzles in the nozzle row NL is expressed as follows: Such a normal positional relationship is changed (use nozzle shift processing is performed).

FIG. 5 is a flowchart showing details of the process included in step S300 (FIG. 3). Here, the description will be given on the assumption that the printing unit 70 performs band printing. The processing shown in FIG. 5 is repeatedly performed with one paper feed and subsequent passes as one set.
After one paper feed (step 310) by the transport unit 20 is executed, the detection unit 12 acquires the left and right cumulative transport errors (step S320). First, the detection unit 12 determines the amount of movement in the transport direction D2 of the end portion of the left side LS and the end portion of the right side RS of the printing medium G from the left and right sensors 81L and 81R by the latest paper feed (step S310). get. The left and right sensors 81L and 81R that can detect the amount of movement of the object have the same configuration, and include, for example, a light emitter, a light receiver, and the like. Light (laser light or the like) emitted from the light emitter is reflected by the print medium G passing over the sensor, and the amount of movement of the print medium G passing through is detected by the light receiver reading the reflected light. That is, when one paper feed is executed, the left sensor 81L detects the movement amount (left end portion movement amount) of the end portion of the left side LS of the printing medium G in the transport direction D2, and the right sensor 81R The movement amount (right end portion movement amount) in the transport direction D2 of the end portion of the right side RS of the print medium G is detected.

  The detection unit 12 updates the accumulated left end portion movement amount by adding the latest left end portion movement amount acquired from the left sensor 81L to the current accumulated left end portion movement amount. Similarly, the detection unit 12 updates the accumulated right end portion movement amount by adding the latest right end portion movement amount acquired from the right sensor 81R to the current accumulated right end portion movement amount. The current cumulative left edge movement is the sum of the left edge movements from the first paper feed to the paper feed immediately before the most recent paper feed, and the current cumulative right edge movement is the first paper feed. This is the total amount of movement of the right end portion from the feed to the paper feed immediately before the latest paper feed. Of course, if the most recent paper feed is the first paper feed, the current accumulated left end movement amount and accumulated right end portion movement amount are both zero.

  Next, the detection unit 12 sets a value obtained by subtracting the accumulated standard movement amount from the updated accumulated left end portion movement amount as the left accumulated conveyance error ΔFL. Similarly, a value obtained by subtracting the same cumulative standard movement amount from the updated cumulative right end portion movement amount is set as a right cumulative conveyance error ΔFR. As described above, the left and right cumulative conveyance errors ΔFL and ΔFR are acquired. The cumulative standard movement amount is an ideal design value of the cumulative left end portion movement amount and the cumulative right end portion movement amount. The accumulated standard movement amount used in step S320 immediately after the first paper feed of the print medium G (step S310) is, for example, from the sensors 81L and 81R in the transport direction D2 to the tip of the ideal position (end of the downstream BS). This is a value obtained by adding the predetermined distance W to the distance F1 (see FIG. 2). The predetermined distance W is the width of a margin (edge) to be provided at the end of the print medium G.

  When the printing medium G moves in the transport direction D2 by F1 + W after the leading edge of the printing medium G reaches the sensors 81L and 81R, the printing target area GPA closest to the leading edge of the printing medium G is accurately arranged at the ideal position. Because it can be said that. That is, if both the left end movement amount and the right end movement amount due to the first paper feed are equal to the F1 + W, it can be said that the first paper feed has been executed accurately. The accumulated standard movement amount used in step S320 after the second and subsequent paper feeds (step S310) is the length of the print target area GPA in the transport direction D2 (distance F2 as a default value, FIG. 2) for each paper feed. Value). It can be said that the distance F2 is the length of the band image in the transport direction D2.

  FIG. 6 illustrates the left cumulative transport error ΔFL and the right cumulative transport error ΔFR acquired by the detection unit 12 as a result of step S320. In FIG. 6 (and FIG. 9), the left and right accumulated transport errors ΔFL and ΔFR are shown in a large manner in consideration of easy viewing. In FIG. 6, the position of the tip of the ideal position (the end of the downstream BS) is indicated by a standard line SL, and is conveyed so as to be arranged at the ideal position by the latest paper feed (step S310) (but actually The printing target area GPA that has not been accurately arranged at the ideal position is indicated by a rectangle. If the left and right cumulative conveyance errors ΔFL and ΔFR are positive values, it means that the printing medium G is conveyed more than ideal, and if the values are negative, the printing medium G is conveyed less than ideal. Means that FIG. 6 illustrates a case where the left and right cumulative transport errors ΔFL and ΔFR are both negative values and there is a difference between the left and right cumulative transport errors ΔFL and ΔFR. Of course, one of the left and right accumulated transport errors ΔFL and ΔFR may be negative and the other may be positive. Although it is possible that both the left and right accumulated transport errors ΔFL and ΔFR are both 0, in the following, the left and right accumulated transport errors ΔFL and ΔFR are not both 0 and there is a difference between them. Continue the explanation.

  In step S330, the ejection control unit 13 determines the number of image areas in which the used nozzle ranges are shifted from each other, and an image to be printed on the print target area GPA according to the determined number of image areas (in the case of performing band printing). Is a band image) in the main scanning direction D1. The ejection control unit 13 increases the number of image regions, that is, the number of divisions, as the absolute value of the difference between the left cumulative conveyance error ΔFL and the right cumulative conveyance error ΔFR acquired in step S320 (hereinafter, left-right conveyance error) increases. Increase. The division referred to in step S330 (and step S370 described later) is basically equally divided.

  FIG. 7A illustrates an image area number determination table T1 in which the correspondence between the left-right conveyance error and the number of image areas is defined in advance. The ejection control unit 13 can determine the number of image areas according to the left-right conveyance error by referring to such a table T1 by reading it from a predetermined memory. In the table T1, the number of image areas = 1 means that an image to be printed on the print target area GPA is not divided, and the number of image areas = 2 means that the image is divided into two.

In step S340, the ejection control unit 13 sets the range of used nozzles (used nozzle range) in the nozzle row NL to be different for each image area divided in step S330, and uses that belong to the set used nozzle range. Assign pixels to nozzles.
The table T1 referred to in step S330 is defined on the assumption that the amount (shift amount) of shifting the used nozzle range between adjacent image regions in the main scanning direction D1 is set in advance. For example, the table T1 defines the required number of image areas corresponding to the left-right conveyance error on the assumption that the amount of deviation is one nozzle.

  FIG. 8 is a diagram for explaining an example of step S340. FIG. 8 shows the correspondence between the nozzle row NL (nozzle row KNL) corresponding to one color ink (for example, K ink) and the image areas IA1, IA2, IA3, IA4, and IA5 assigned to the used nozzles. Show. In FIG. 8, for convenience of description, the p nozzles Nz constituting the nozzle row NL are changed from one end side in the nozzle row direction D3 (downstream BS in the transport direction D2) to the other end side (upstream US in the transport direction D2). Nozzles numbered from # 1 to #p are given toward the end. Here, the number of unused nozzles is, for example, ten. When the normal positional relationship described above with reference to FIG. 4 (normal positional relationship between used nozzles and non-used nozzles) is followed, a total of 10 nozzle numbers = # 1 to # 5, # p−4 to #p. No. Nz corresponds to an unused nozzle, and q nozzles Nz of nozzle numbers = # 6 to # p-5 correspond to used nozzles. That is, nozzle numbers = # 6 to # p-5 are the normal used nozzle range.

  The image areas IA1, IA2, IA3, IA4, and IA5 are, for example, image areas when one band image indicated by hatching in FIG. 4 is divided into five in the main scanning direction D1 in step S330 (divided into five equal parts). is there. In step S340, different use nozzle ranges are set for each of such image areas IA1, IA2, IA3, IA4, and IA5 as illustrated in FIG.

  The ejection control unit 13 sets the use nozzle range according to the left cumulative conveyance error ΔFL (see FIG. 6) for the image area IA1 closest to the left LS in the main scanning direction D1 among the image areas. For example, the number of nozzles corresponding to the number obtained by dividing ΔFL by the nozzle pitch in the nozzle row NL (conveying direction nozzle pitch; see Modification 1 below for the meaning of the conveying direction nozzle pitch). Is an offset value of the used nozzle range. The offset value is a value for shifting the used nozzle range to the smaller nozzle number if the cumulative transport error (here, the left cumulative transport error ΔFL) to be divided by the nozzle pitch is a positive value. If the target cumulative transport error is a negative value, a value for shifting the used nozzle range to the larger nozzle number is set. Here, it is assumed that an offset value of 5 is obtained from the left cumulative conveyance error ΔFL. In such a case, for the image area IA1, the normal use nozzle range is shifted to the larger nozzle number by the offset value = 5, that is, the nozzle numbers = # 11 to #p become the use nozzle range. .

  For the image area IA5 closest to the right side RS in the main scanning direction D1 among the image areas, the discharge control unit 13 sets the used nozzle range by the same method according to the right cumulative conveyance error ΔFR (see FIG. 6). Set. Here, it is assumed that an offset value of 1 is obtained from the right cumulative conveyance error ΔFR. In such a case, for the image area IA5, the normal use nozzle range is shifted to the larger nozzle number by the offset value = 1, that is, the nozzle numbers = # 7 to # p-4 are used nozzle ranges. It becomes.

  The offset values for the image areas IA2, IA3, IA4 other than the left and right image areas IA1, IA5 can be linearly interpolated using the offset values of the image areas IA1, IA5. In the above example, since the offset value of the image area IA1 = 5 and the offset value of the image area IA1 = 1, the offset value for each of the image areas IA2, IA3, and IA4 is the corresponding image in the main scanning direction D1. Interpolation is performed according to the distance between the area and the image areas IA1 and IA5, and values such as 4, 3, and 2 are obtained.

  Therefore, for the image area IA2, the range in which the normal use nozzle range is shifted toward the larger nozzle number by the offset value = 4 (nozzle number = # 10 to # p-1) is the use nozzle range. For the image area IA3, a range (nozzle number = # 9 to # p-2) in which the normal use nozzle range is shifted toward the larger nozzle number by the offset value = 3 is the use nozzle range. For the image area IA4, a range (nozzle number = # 8 to # p-3) obtained by shifting the normal use nozzle range toward the larger nozzle number by the offset value = 2 is the use nozzle range. As described above, the number of image areas is determined on the assumption that the amount (shift amount) of shifting the used nozzle range between adjacent image areas in the main scanning direction D1 is one nozzle. For this reason, if the use nozzle range of either one of the left and right image areas IA1 and IA5 is determined, the use nozzle ranges for the other image areas are only shifted by one nozzle, so it can be said that they are determined automatically. For reference, in FIG. 8, an image including the image areas IA1, IA2, IA3, IA4, and IA5 when the used nozzle range remains the normal used nozzle range is indicated by a broken-line rectangle.

  The ejection control unit 13 determines a nozzle Nz to which a pixel is assigned for each image region. That is, each pixel included in the image area IA1 is assigned to any nozzle Nz in the used nozzle range (nozzle numbers = # 11 to #p) according to the position. Similarly, each pixel included in the image area IA2 is assigned to any nozzle Nz in the used nozzle range (nozzle number = # 10 to # p-1) according to the position, and each pixel included in the image area IA3 is assigned. A pixel is assigned to any nozzle Nz in the used nozzle range (nozzle number = # 9 to # p-2) according to its position, and for each pixel included in the image area IA4, the used nozzle is selected according to its position. Assigned to any nozzle Nz in the range (nozzle number = # 8 to # p-3), and for each pixel included in the image area IA5, the used nozzle range (nozzle number = # 7 to #p) according to its position -4) is assigned to one of the nozzles Nz.

  FIG. 9 exemplifies the print result executed by the print head 40 through such step S340 (step S300). FIG. 9 shows a state in which images (band images) of the image areas IA1, IA2, IA3, IA4, and IA5 are printed on the print target area GPA shown in FIG. In other words, as a result of the used nozzle shifting process, the image areas IA1, IA2, IA3, IA4, and IA5 are printed out of alignment in the transport direction D2 with respect to the left and right cumulative transport errors ΔFL and ΔFR of the print target area GPA. That is, according to the present embodiment, the positional relationship between the print medium G and the image in the transport direction D2 is optimized at any position in the main scanning direction D1 in a situation where the left and right cumulative transport errors ΔFL and ΔFR are different. . For this reason, the width of the margin secured at each of the front end (end of the downstream BS) and the rear end (end of the upstream US) of the print medium G is also substantially constant at any position in the main scanning direction D1 (image quality). Improvement), the user satisfaction with the printing result is improved. In addition, since the gap and overlap in the transport direction D2 between images printed in each print target area GPA (band image in the above example) are eliminated, the image quality is further improved. In a printer that conveys and prints a relatively large print medium G (so-called large format printer (LFP)), the width of the print medium G in the main scanning direction D1 is large, so that the left-right transport error also increases. The image quality deterioration due to the left-right conveyance error was easily noticeable. According to the present embodiment, image quality deterioration due to such a left-right conveyance error can be eliminated, and it can be said that a great effect can be obtained by adopting it in LFP.

3. Second embodiment:
A second embodiment according to the present invention will be described. In the second embodiment, the “ejection timing shifting process” is further added to the first embodiment. In the following, description of matters common to the first embodiment will be omitted as appropriate.
In the ejection timing shifting process according to the second embodiment, the inclination of the print medium G with respect to the transport direction D2 is detected. Then, the ink ejection timing is shifted in accordance with the inclination for each predetermined number of used nozzles when the used nozzles in the used nozzle range are divided by a predetermined number in the nozzle row direction D3 (conveying direction D2).

  FIG. 10 is a flowchart showing details of the process included in step S300 (FIG. 3) in the second embodiment. Here, the description will be given on the assumption that the printing unit 70 performs band printing. The processing shown in FIG. 10 is repeatedly performed with one paper feed and subsequent passes as one set. In FIG. 10, steps S350 to S380 are added when compared with FIG. FIG. 5 is a flowchart that basically shows the processing performed by the control unit 11 (except for step S310). As described above, it goes without saying that printing is realized by the cooperation of the control unit 11, the printing unit 70, and the like. In FIG. 10, the processing performed by the printing unit 70 (step S <b> 350 and the like) is described in addition to step S <b> 310, but the processing performed by such a printing unit 70 is not shown in the flowchart of FIG. 5. Thus, FIG. 5 is not an insufficient figure. In particular, step S380 in FIG. 10 is realized by the cooperation of the control unit 11 (ejection control unit 13) and the print head 40 (that is, a part of the printing unit 70).

Further, the execution order of each step S shown in FIG. 10 is not necessarily the same as that shown in FIG. For example, steps S320 to S340 may be started after step S350 (start of movement of the carriage 30), and steps S320 to S340 and steps S360 and S370 may be processed in parallel.
When the movement of the carriage 30 along the main scanning direction D1 is started (Step S350) after the paper feeding by the transport unit 20 is performed once (Step 310), the detection unit 12 detects the end of the print medium G. The part position and the inclination are acquired (step S360).

  FIG. 11 is a diagram for explaining step S360. FIG. 11 shows a part of the print medium G conveyed by the paper feed in step S310 (for example, the print target area GPA). When the movement of the carriage 30 is started, a sensor 82 (see FIG. 2) mounted on the carriage 30 together with the print head 40 detects an end portion (hereinafter, a paper end) of the print medium G. The position at which the carriage 30 starts to move to start one pass (carriage start position ST) is the left LS or the right RS from the area where the print medium G on the platen is conveyed. Here, it is assumed that the carriage start position ST is a predetermined position on the left side LS from the area where the printing medium G on the platen is conveyed. The movement amount of the carriage 30 in the main scanning direction D1 is specified using the carriage start position ST as a reference (movement amount 0).

  It is assumed that the sensor 82 has at least two paper edge sensors for detecting the paper edge. It is assumed that the two paper edge sensors are separated by a predetermined distance V in the transport direction D2 and are disposed at the same position in the main scanning direction D1. Of the two paper edge sensors, a sensor on the downstream BS in the transport direction D2 is referred to as a first paper edge sensor, and a sensor on the upstream US in the transport direction D2 is referred to as a second paper edge sensor. When the first paper edge sensor and the second paper edge center simultaneously detect the paper edge, it can be said that the print medium G has been fed without inclination with respect to the transport direction D2. Conversely, if the timing at which the first paper edge sensor and the second paper edge center detect the paper edge is different, it can be said that the printing medium G is fed in a state inclined with respect to the transport direction D2. FIG. 11 illustrates the paper edge E1 of the print medium G detected by the first paper edge sensor and the paper edge E2 of the print medium G detected by the second paper edge sensor.

  The first paper edge sensor outputs a detection signal to the detection unit 12 when the paper edge E1 is detected. The second paper edge sensor outputs a detection signal to the detection unit 12 when the paper edge E2 is detected. Therefore, the detection unit 12 can acquire the position of the paper edge E1 in the main scanning direction D1 based on the detection signal from the first paper edge sensor and the movement amount of the carriage 30 at that time. Similarly, the detection unit 12 can acquire the position of the paper edge E2 in the main scanning direction D1 based on the detection signal from the second paper edge sensor and the movement amount of the carriage 30 at that time. Further, the detection unit 12 can specify the inclination θ of the print medium G with respect to the transport direction D2 according to the ratio of the distance between the paper edge E1 and the paper edge E2 (distance H shown in FIG. 11) to the predetermined distance V. . As described above, the detection unit 12 can acquire the edge position (position of the paper edges E1 and E2) and the inclination θ of the print medium G.

  In step S370, the ejection control unit 13 determines the number of nozzle groups for shifting the ink ejection timing from each other in the used nozzle range according to the inclination θ acquired in step S360. The discharge control unit 13 increases the number of nozzle groups as the absolute value of the inclination θ is larger. FIG. 7B illustrates a nozzle group number determination table T2 that predefines the correspondence between the inclination θ and the number of nozzle groups. The discharge control unit 13 can determine the number of nozzle groups according to the inclination θ by referring to such a table T2 by reading it from a predetermined memory. In the table T2, the number of nozzle groups = 1 means that all the used nozzles in the used nozzle range are one nozzle group, that is, the ink ejection timing is not shifted within the used nozzle range. In the table T2, the number of nozzle groups = 2 means that the used nozzles in the used nozzle range are divided into two (ie, equally divided), that is, the used nozzles in the used nozzle range are divided into two nozzle groups, and each ink This means that the discharge timing is shifted. Naturally, the larger the inclination θ, the smaller the number (predetermined number) of nozzles used per nozzle group. The minimum value that the predetermined number can take is 1. When the predetermined number is 1, it means that the ink ejection timings of all the used nozzles in the used nozzle range are shifted.

In step S380, the ejection control unit 13 drives the used nozzles in the used nozzle range while shifting the ink ejection timing for each nozzle group corresponding to the number of nozzle groups determined in step S370.
FIG. 12 is a diagram for explaining processing for shifting the timing of ink ejection when printing an image region assigned to a used nozzle in a certain used nozzle range. The left side of FIG. 12 shows, as an example, an image area IA1 that is printed first with respect to the print target area GPA among the image areas having different use nozzle ranges. As described with reference to FIG. 8, the used nozzle range for printing the image area IA1 is nozzle number = # 11 to #p. The right side of FIG. 12 schematically shows that the ink ejection timings of the nozzle group corresponding areas IA11, IA12, IA13, IA14, and IA15 constituting the image area IA1 are shifted.

  The nozzle group corresponding areas IA11, IA12, IA13, IA14, and IA15 are areas that correspond one-to-one with the nozzle groups corresponding to the determined number of nozzle groups. That is, when the determined number of nozzle groups is 5, the image area IA1 is divided into five nozzle group corresponding areas IA11, IA12, IA13, IA14, and IA15. As described above, since the number of used nozzles in the used nozzle range is q, when the number of nozzle groups is 5, the number (predetermined number) of used nozzles per nozzle group is q / 5. Accordingly, the nozzle group corresponding areas IA11, IA12, IA13, IA14, and IA15 are areas printed by q / 5 used nozzles. Although it can be seen from FIG. 12 that the number of nozzles used per nozzle group is five, there is no significant meaning because the number of nozzles is only such for convenience of paper.

  The ejection control unit 13 calculates the shift amount (distance Δx) in the main scanning direction D1 between the adjacent nozzle group corresponding regions. In the second embodiment, the ink ejection timing is shifted so that the left and right edges of the image printed in the print target area GPA are inclined to be equal to the inclination θ of the printing medium G at that time. Therefore, the ratio between the length (distance F2 / 5 in the example of FIG. 12) of one nozzle group corresponding region in the conveyance direction D2 and the distance Δx should be equal to the ratio between the distance V and the distance H. The discharge controller 13 can calculate the distance Δx based on this relationship. Since the ratio between the distance V and the distance H is equal to the inclination θ, it can be said that such a shift amount (distance Δx) is obtained based on the inclination θ. Refer to FIG. 2 for the distance F2.

  The discharge controller 13 obtains a shift amount in the main scanning direction D1 for each of the nozzle group corresponding areas IA11, IA12, IA13, IA14, and IA15. In this case, among the nozzle group corresponding regions IA11, IA12, IA13, IA14, and IA15, the shift amount for the region where printing should be started first is 0, and the shift amount based on the region where printing should be started first is used. Find for other areas. According to the example of FIG. 11, the first paper edge sensor on the downstream side BS in the transport direction D2 detects the paper edge before the second paper edge sensor on the upstream side US (the paper edge E1 is the paper edge). Therefore, the area where printing should start first among the nozzle group corresponding areas IA11, IA12, IA13, IA14, and IA15 is the nozzle group corresponding area of the most downstream BS among them. IA11. Therefore, the shift amount for each nozzle group corresponding area IA12, IA13, IA14, IA15 is obtained with reference to the nozzle group corresponding area IA11. As described above, since the shift amount between the adjacent nozzle group corresponding regions is the distance Δx, when the nozzle group corresponding region IA11 is used as a reference, the shift amount of the nozzle group corresponding region IA12 is the distance Δx, corresponding to the nozzle group. The shift amount of the area IA13 is 2 × distance Δx, the shift amount of the nozzle group corresponding area IA14 is distance 3 × distance Δx, and the shift amount of the nozzle group corresponding area IA15 is 4 × distance Δx.

  The ejection control unit 13 is driven by shifting the timing of ink ejection for each nozzle group in accordance with each shift amount obtained in this way. According to the example of FIG. 12, a nozzle group for printing a nozzle group corresponding area IA11 with a shift amount of 0 (also referred to as a first nozzle group for the sake of convenience. According to one nozzle Nz in the used nozzle range corresponding to the image area IA1). Nozzle group (nozzle number = nozzles Nz of # 11 to # 15 in the example of FIG. 12), the ink ejection timing is not shifted. In normal printing, it is common to secure margins of a predetermined width (for example, the distance W) on the top, bottom, left, and right of an image. For this reason, the discharge control unit 13 first detects the paper edge after the sensor 82 detects the paper edge (either the first paper edge sensor or the second paper edge sensor after the carriage 30 starts moving). From) Immediately after the period until the carriage 30 moves in the predetermined width (margin securing period), the driving of the first nozzle group is started. As a result, with respect to the first nozzle group, a normal operation of starting driving after securing a margin of a predetermined width at the paper edge, that is, control not correcting (not shifting) the ink ejection timing is performed.

  The discharge control unit 13 prints the nozzle group corresponding area IA12 whose shift amount is the distance Δx (also referred to as a second nozzle group for convenience. One nozzle Nz in the used nozzle range corresponding to the image area IA1). 12. For the example of FIG. 12, in the example of FIG. 12, for q / 5 nozzles Nz following # 15, the driving start timing is set to the distance Δx with reference to the timing at which the first nozzle group starts driving. Shift (delay) by the appropriate time (timing adjustment time). The timing adjustment time is obtained by dividing the shift amount (distance Δx) by the moving speed of the carriage 30 as a default value. That is, the second nozzle group starts driving after the margin ensuring period + timing adjustment time has elapsed. For example, the ejection control unit 13 delays / accelerates the timing for generating the drive signal for the first pixel assigned to one nozzle Nz within one pass from the “normal operation”. Thus, the timing at which the nozzle Nz starts to be driven in the pass can be shifted.

  The ejection controller 13 prints a nozzle group corresponding area IA13 having a shift amount of 2 × distance Δx (also referred to as a third nozzle group for convenience), and a nozzle group having a shift amount of 3 × distance Δx. Nozzle group for printing the corresponding area IA14 (also referred to as a fourth nozzle group for convenience), Nozzle group for printing the nozzle group corresponding area IA15 whose shift amount is 4 × distance Δx (for convenience, the fifth nozzle group) In each case, each timing adjustment time is calculated by the same method, and control is performed so that driving is started after the margin ensuring period + timing adjustment time elapses.

  An image (raster line) printed by one nozzle Nz is drawn in the same manner in the main scanning direction D1 because the drive timing for the first pixel is shifted as described above. Many of the used nozzle ranges of the image areas IA2, IA3, IA4, and IA5 (see FIG. 8) overlap each other. Therefore, by shifting the ink ejection timing as described above for each of the second nozzle group, the third nozzle group, the fourth nozzle group, and the fifth nozzle group constituting the use nozzle range of the image area IA1, the image area The pixels in the image areas IA2, IA3, IA4, and IA5 other than IA1 are pixels that are assigned to the nozzles Nz belonging to any of the second nozzle group, the third nozzle group, the fourth nozzle group, and the fifth nozzle group. The dot ejection timing is shifted under the influence of the timing adjustment time applied to the allocation destination nozzle Nz.

  However, in this case, among the pixels of the image areas IA2, IA3, IA4, and IA5 other than the image area IA1, the nozzles Nz that are not included in the used nozzle range of the image area IA1 (the nozzle number is # 10 according to the example of FIG. 8). For the pixels assigned to any of the following nozzles Nz), the ink ejection timing remains unadjusted. Accordingly, the ejection control unit 13 uses a predetermined number of nozzles Nz that are not included in the use nozzle range of the image area IA1 and are used nozzles for the other image areas IA2, IA3, IA4, and IA5. Timing adjustment time is calculated for each group, and ink ejection timing is adjusted according to the calculated timing adjustment time. In this case, the discharge control unit 13 steps to each nozzle group located on the downstream side BS with respect to the first nozzle group, such as −1 × distance Δx, −2 × distance Δx. By applying a timing adjustment time (in this case, a negative timing adjustment time) according to the different shift amounts, the ink ejection timings are shifted (accelerated).

  FIG. 13 exemplifies the printing result executed by the print head 40 through such step S380 (step S300). FIG. 13 shows a state in which images (band images) of the image areas IA1, IA2, IA3, IA4, and IA5 are printed on the print target area GPA shown in FIG. That is, as a result of the used nozzle shifting process and the ejection timing shifting process, the image areas IA1, IA2, IA3, IA4, and IA5 are mutually in the transport direction D2 according to the cumulative transport errors ΔFL and ΔFR on the left and right of the print target area GPA. Printing was performed at a discharge timing shifted for each nozzle group in accordance with the inclination θ of the print medium G. That is, according to the second embodiment, as in the first embodiment, the positional relationship between the print medium G and the image in the transport direction D2 is the main scanning direction D1 in the situation where the left and right cumulative transport errors ΔFL and ΔFR are different. It is optimized at any position. In addition, according to the second embodiment, as can be seen from the comparison between FIG. 13 and FIG. 9, the angle of the left and right edges of the image (the set of image areas IA1, IA2, IA3, IA4, and IA5) It is almost parallel to the inclination of the paper edge. That is, the margin width secured at each of the left end (end of the left LS) and the right end (end of the right RS) of the print medium G is substantially constant at any position in the transport direction D2, and the user's print result is printed. Satisfaction is further improved.

  Although not shown in FIG. 13 in a simplified manner, nozzle groups corresponding regions IA11, IA11, as shown in FIG. 12 are formed on the left and right edges of the image (a set of image regions IA1, IA2, IA3, IA4, and IA5). A step corresponding to the steps of IA12, IA13, IA14, and IA15 appears. However, as described above, since the number of such nozzle group corresponding regions increases as the inclination θ increases, the shift amount (distance Δx) in the main scanning direction D1 between the adjacent nozzle group corresponding regions becomes the inclination θ. Regardless, it is almost constant. Therefore, such a level difference is of little concern for the user.

  In the description of the second embodiment so far, the ink ejection timing is shifted by delaying / accelerating the timing of generating the drive signal. However, the ejection control unit 13 does not adjust the generation timing of the drive signal, but instead adjusts the coordinate position of the pixel in the print data given to the print head 40 according to the shift amount for each nozzle group corresponding region. As a result, the ejection timing may be shifted by performing a process of shifting in the main scanning direction D1.

4). Variations:
The present invention is not limited to the first embodiment and the second embodiment described above, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications may be adopted. It is. A configuration in which each modified example is appropriately combined with each embodiment also falls within the disclosure scope of the present invention.

First modification:
The ejection control unit may adjust the mode of shifting the used nozzle range and the extent of shifting the timing of ink ejection according to the inclination of the nozzle array direction D3 (nozzle array inclination) with respect to the transport direction D2.
Until now, the transport direction D2 and the nozzle row direction D3 are basically parallel (no nozzle row tilt), but in the first modification, the nozzle row direction D3 is inclined with respect to the transport direction D2. think of. As the case where the nozzle row is inclined, there are a case where it is intentionally inclined as a design of the printing unit 70 (first case) and a case where it is inclined due to an attachment error (second case). Here, the second case is assumed here. In the product in which the nozzle row direction D3 is intentionally tilted as the design of the printing unit 70, the operation and processing for preventing such nozzle row tilt from being reflected in the printing result are incorporated. Will not be a problem.

  In FIG. 14, a part of the nozzle array NL having no nozzle array inclination is illustrated on the left side, and a part of the nozzle array NL having the nozzle array inclination is illustrated on the right side. The nozzle pitch NP in the nozzle row direction D3 is constant regardless of whether or not the nozzle row is inclined. On the other hand, when there is no nozzle row tilt, the nozzle pitch in the transport direction D2 (transport direction nozzle pitch) is equal to the nozzle pitch NP, but when there is a nozzle row tilt, the transport direction nozzle pitch is smaller than the nozzle pitch NP. Become.

  In consideration of such a situation, when determining the number of image areas in step S330 (see FIG. 5 and FIG. 10), the ejection control unit 13 corrects the number of image areas according to the nozzle row inclination. In addition, the discharge control part 13 presupposes that it has the grade of the nozzle row inclination as information beforehand. The degree of nozzle row inclination can be acquired in advance by, for example, a method of evaluating a test pattern in which ruled lines are printed on the print medium G by the print head 40. When the ejection control unit 13 refers to the image area number determination table T1 as described above and determines the number of image areas in accordance with the left-right conveyance error, the degree of nozzle array inclination is 0, that is, there is no nozzle array inclination. In this case, the determined number of image areas is used as it is (used for dividing the image to be printed on the print target area GPA in the main scanning direction D1). On the other hand, when the degree of nozzle row inclination is not 0, the number of image areas obtained by correcting the determined number of image areas with a predetermined correction coefficient is employed instead.

  The correction coefficient used here is a correction coefficient for increasing the number of image areas. This is because the transport direction nozzle pitch is smaller than the transport direction nozzle pitch (= NP) that should originally exist, and in order to appropriately fill the transport error between the left and right, the number of image areas is increased (the image to be printed in the print target area GPA). This is because it is necessary to increase the number of divisions in the main scanning direction D1. It is assumed that several values are prepared in advance according to the degree of nozzle row inclination.

  Further, when the discharge control unit 13 acquires the inclination θ of the print medium G in step S360, the discharge control unit 13 corrects the acquired inclination θ according to the nozzle row inclination. When the degree of nozzle row inclination is 0, that is, when there is no nozzle row inclination, the ejection control unit 13 adopts the obtained inclination θ as it is (used to determine the number of nozzle groups and the distance Δx). On the other hand, when the degree of nozzle row inclination is not 0, the inclination θ ′ obtained by correcting the acquired inclination θ is used instead. That is, the inclination θ acquired in accordance with the output from the sensor 80 in step S360 is the inclination of the print medium G with reference to the transport direction D2, and this inclination θ is the nozzle array direction D3 (nozzle array inclination). The inclination is corrected to the reference inclination θ ′. For example, in the nozzle row direction D3, the downstream BS in the transport direction D2 is inclined to the right side RS as in the nozzle row NL on the right side in FIG. 14, and the downstream BS in the transport direction D2 is left on the print medium G in FIG. When inclined to LS, the inclination θ ′ of the printing medium G with respect to the nozzle row direction D3 is larger than the inclination θ. On the contrary, when the nozzle row direction D3 is inclined substantially parallel to the print medium G, the inclination θ ′ of the print medium G with respect to the nozzle row direction D3 is a considerably smaller angle than the inclination θ.

  According to the first modification, the mode (in this case, the number of image areas) of shifting the used nozzle range is adjusted in consideration of the nozzle row inclination. Further, taking into account the inclination of the nozzle row, the number of nozzle groups and the extent to which the ink ejection timing is shifted (distance Δx) are adjusted. Therefore, even if there is a nozzle row inclination, the image printing position on the print medium G is appropriate as in the case where there is no nozzle row inclination.

Second modification:
When the amount of conveyance (paper feed) executed between the movement (pass) and movement (pass) of the nozzle row accompanied by ink ejection from the nozzles Nz is greater than a predetermined amount, the ejection control unit 13 shifts the used nozzles. Process. The case where the paper feed amount between passes is larger / smaller than the predetermined amount is caused by a difference in print mode adopted by the print control apparatus 10 in accordance with a user instruction. For example, the band printing described above is a representative example of a printing mode in which the paper feed amount between passes is greater than a predetermined amount. In band printing, since a large distance of the length of the band image (distance F2) in the conveyance direction D2 is conveyed by one paper conveyance, a conveyance error that occurs every paper conveyance tends to be large. Accordingly, the ejection control unit 13 performs a nozzle feeding process to perform paper feeding when it is instructed to perform printing in a printing mode in which a single paper feeding amount is relatively large, such as band printing. Image quality degradation (gap between band images and unnecessary overlap) due to each transport error is prevented. Note that the specific example of the print mode to which the used nozzle shifting process and the ejection timing shifting process are applied is not limited to band printing, for example, overlapping printing that prints the same raster line in multiple passes is also applicable. obtain.

On the other hand, microweave (MW) printing as described in FIG. 15 is a representative example of a printing mode in which the paper feed amount between passes is less than a predetermined amount.
FIG. 15 is a diagram for explaining a correspondence relationship between the nozzles Nz constituting the nozzle row NL and the dots formed on the print medium G by ink ejection from the nozzles Nz by MW printing. The left side of FIG. 15 shows an example in which the nozzle row NL corresponding to one ink color is composed of five nozzles Nz (circles) for the sake of simplicity. Numbers 1 to 5 given in circles representing the nozzles Nz from one end side to the other end side of the nozzle row NL are nozzle numbers. In FIG. 15, the position of one nozzle row NL (the relative position with respect to the print medium G in the transport direction D2) changes for each pass (first pass, second pass,...) By the print head 40. Show. Of course, the print head 40 does not actually move along the transport direction D2, but the print medium G is transported in the transport direction by a predetermined paper feed amount determined according to the print mode by the transport unit 20 every time a pass is completed. It is moved to D2.

  The right side of FIG. 15 illustrates a plurality of dots Dc formed on the print medium G by each nozzle Nz. The numbers 1 to 5 given in the circles representing the dots Dc indicate the nozzle numbers of the nozzles Nz used for forming the dots Dc. A row in which dots Dc corresponding to the same nozzle number are arranged in the main scanning direction D1 corresponds to one raster line. As can be seen from FIG. 15, according to the MW printing mode, each time a pass is completed, the nozzle density is increased in the transport direction D2 by feeding paper at a constant distance that is longer than the nozzle pitch and shorter than twice the nozzle pitch. A plurality of raster lines arranged at a higher resolution (4 times in the example of FIG. 15) are printed. Further, as can be seen from FIG. 15, according to the MW printing, the raster line printed by the common nozzle Nz is not adjacent to the transport direction D2. That is, each of the plurality of raster lines arranged adjacent to each other in the transport direction D2 is printed by a different nozzle Nz among the plurality of nozzles Nz in the nozzle row NL.

  The paper feed amount between passes in such MW printing is overwhelmingly small when compared with, for example, band printing. In the case of band printing, for example, an area filled with the number of dots Dc as shown in FIG. 15 is filled in one pass (although the resolution is different). When the ejection control unit 13 is instructed to execute printing in a printing mode in which the amount of paper transported at one time is relatively small as in MW printing, the transport error for each paper transport is very small in the first place. Since it is not visually recognized, the used nozzle shifting process is not executed (the normal used nozzle range is used).

DESCRIPTION OF SYMBOLS 10 ... Print control apparatus, 11 ... Control part, 12 ... Detection part, 13 ... Discharge control part, 16 ... Operation input part, 17 ... Display part, 18 ... Communication I / F, 20 ... Conveyance unit, 30 ... Carriage, 40 ... Print head, 70 ... Print section, 80, 81L, 81R, 82 ... Sensor, 100 ... External device, G ... Print medium, NL ... Nozzle array, Nz ... Nozzle

Claims (8)

A nozzle row in which a plurality of nozzles capable of ejecting ink are arranged at predetermined intervals is moved along a first direction intersecting a nozzle row direction toward the nozzle row, and intersects the first direction from one or more nozzles. A print control apparatus that realizes printing of an image on a print medium by ejecting ink onto the print medium conveyed in a second direction,
A detection unit for detecting an error in the conveyance in the second direction on each of the one end side and the other end side of the print medium in the first direction;
Use nozzle shift that shifts the range of nozzles in the nozzle row used for ink ejection in accordance with the error in transport on each of the one end side and the other end side between image areas obtained by dividing the image in the first direction. A printing control apparatus comprising: an ejection control unit that performs processing.   The discharge control unit increases the number of divisions of the image in the first direction as the difference between the conveyance error on the one end side and the conveyance error on the other end side is larger. The printing control apparatus described.   3. The print control according to claim 1, wherein the ejection control unit changes a mode of shifting a range of the nozzles to be used in accordance with an inclination of the nozzle row direction with respect to the second direction. apparatus. The detection unit detects an inclination of the print medium with respect to the second direction;
The discharge control unit shifts the ink discharge timing in accordance with the inclination for each predetermined number of nozzles when the nozzles in the range of nozzles to be used are divided into a predetermined number in the nozzle row direction. The printing control apparatus according to claim 1, wherein a shift process is performed.   The print control apparatus according to claim 4, wherein the ejection control unit reduces the predetermined number as the inclination of the print medium with respect to the second direction is larger.   6. The print control apparatus according to claim 4, wherein the ejection control unit adjusts a degree of shifting the ink ejection timing according to an inclination of the nozzle row direction with respect to the second direction. .   The ejection control unit performs the used nozzle shifting process when the amount of conveyance performed between movements of the nozzle row accompanied by ink ejection from the nozzles is larger than a predetermined amount. The print control apparatus according to any one of claims 1 to 6. A nozzle row in which a plurality of nozzles capable of ejecting ink are arranged at predetermined intervals is moved along a first direction intersecting a nozzle row direction toward the nozzle row, and intersects the first direction from one or more nozzles. A print control method for realizing printing of an image on a print medium by ejecting ink onto the print medium conveyed in a second direction,
A detection step of detecting an error in the conveyance in the second direction on each of the one end side and the other end side of the print medium in the first direction;
Use nozzle shift that shifts the range of nozzles in the nozzle row used for ink ejection in accordance with the error in transport on each of the one end side and the other end side between image areas obtained by dividing the image in the first direction. A printing control method comprising: an ejection control step of performing processing.