JP2017193099A - Printing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress curling of a sheet, and to improve printing efficiency.SOLUTION: A printer can execute double-sided printing for performing printing onto a second surface being a back surface of a first surface after printing onto the first surface of a printing medium. The printer comprises: a transportation section transporting the printing medium; a print head having a plurality of nozzles, and discharging ink onto the printing medium from the plurality of nozzles; a humidity detection section detecting humidity; and a control section controlling printing related operation including operation of the transportation section and operation of the print head. The control section controls the printing related operation after the printing onto the first surface based on printing density and humidity of the first surface.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a printing apparatus.

  In the field of printers, products capable of performing double-sided printing are known in which after printing on the front side of a sheet, the sheet is reversed and printed on the back side of the sheet.

  Further, in an inkjet recording apparatus having a double-sided printing mechanism, a means for determining whether or not the ink placement Duty on the front and back sides is excessive with respect to the printing target medium, and a plurality of printing modes (double-sided printing / single-sided printing mode, high A configuration is disclosed that includes means for automatically selecting a printing mode suitable for a situation from a duty / low duty printing mode and a printing mode using / not using a colorless printability improving processing liquid (Patent Document). 1).

JP 2003-341033 A

  When performing duplex printing, when ink is ejected onto the surface of the paper, the paper may swell and bend (curl) due to the moisture of the ink. When printing is performed on the back side of the curled paper in this way, a part of the paper is too close to the print head for ejecting ink or is in contact with the print head. May decrease or the paper may become dirty. Further, when the curled paper is transported, there is a risk of transport error such as paper jam. On the other hand, the degree of curling of the paper subjected to ink ejection varies depending on various conditions. For this reason, even if processing for suppressing such curling is performed in the process of double-sided printing, it can be said that it is necessary to perform processing according to the degree of curling.

  The present invention has been made in view of the above-described problems, and provides a printing apparatus that contributes to curling suppression and printing efficiency improvement.

  One aspect of the present invention is a printing apparatus capable of performing double-sided printing for performing printing on a second surface, which is the back surface of the first surface, after printing on the first surface of the print medium, A transport unit that transports the ink, a print head that has a plurality of nozzles and ejects ink from the nozzles to the print medium, a humidity detection unit that detects humidity, an operation of the transport unit, and an operation of the print head A control unit that controls a printing-related operation, and the control unit controls the printing-related operation after printing on the first surface based on the printing density and the humidity of the first surface.

  According to this configuration, printing-related operations after printing on the first surface, that is, printing on the second surface, based on factors that affect the degree of curl of the print medium, such as print density and humidity on the first surface. For controlling the operation of the conveying section and the operation of the print head. As a result, it is possible to realize a printing-related operation suitable for the degree of curl generated on the print medium, and to achieve both curl suppression and print efficiency improvement.

In one aspect of the present invention, the control unit is configured such that the print density at the end of the first surface in the transport direction of the print medium by the transport unit is equal to or greater than a predetermined threshold value regarding the density. End processing that restricts the nozzles that are driven for printing on the end of the second surface in the transport direction may be executed.
According to this configuration, when the printing density at the edge of the first surface is equal to or higher than the threshold value and the curl is predicted to occur, the edge processing is performed when printing on the edge of the second surface. Thus, the degree of curling can be suppressed.

One of the aspects of the present invention is that the end treatment includes a part of the second surface including a nozzle on the downstream side in the transport direction including a nozzle on the most upstream side in the transport direction among the nozzles. Downstream end processing for driving and printing, and upstream end for printing the upstream end of the second surface by driving some of the nozzles including the most downstream nozzle among the nozzles And at least one of the processes may be included.
According to this configuration, it is possible to avoid excessive approach and contact between the print medium and the print head when printing on the second surface by performing the downstream end processing and the upstream end processing.

One aspect of the present invention is that, as the humidity increases, the control unit performs a process of transporting the print medium by the transport unit after printing on the first surface and before starting printing on the second surface. The stop time for temporarily stopping the conveyance may be shortened.
According to this configuration, the curling can be suppressed and the printing efficiency can be improved by controlling the stop time, that is, the drying time of the print medium according to the humidity level.

In one aspect of the present invention, the control unit may set the stop time to 0 when the humidity is equal to or higher than a predetermined threshold related to the humidity.
According to this configuration, when it is predicted that the curl will hardly occur because the humidity is equal to or higher than the threshold value, the printing efficiency can be improved by setting the stop time to zero.

  The technical idea of the present invention is also realized by a device other than a printing device. For example, a method (printing method) including each process executed by each component of the printing apparatus can be regarded as an invention. In addition, a program that causes a computer to execute such a method and a computer-readable storage medium that stores the program are also established as inventions.

FIG. 2 is a block diagram illustrating a configuration of a printing apparatus. FIG. 6 is a diagram simply illustrating a configuration related to sheet conveyance and a change in sheet position. FIG. 3A and FIG. 3B are diagrams for explaining details of the sheet and the like. The flowchart which shows the process in connection with control of the printing related operation | movement after 1st surface printing. The figure which shows the mode selection table concerning 1st Example. The figure which shows a drying time table. The figure which shows the mode selection table concerning 2nd Example. The figure which shows the positional relationship of the paper and print head in the case of 2nd surface printing. 9A is a diagram simply showing the positional relationship between the paper and the print head when the normal printing process is performed on the downstream edge of the paper, and FIG. 9B is the paper when the edge processing is performed on the downstream edge of the paper. FIG. 6 is a diagram simply showing the positional relationship between the printer and the print head. FIG. 10A is a diagram simply showing the positional relationship between the paper and the print head when the normal printing process is performed on the upstream edge of the paper, and FIG. 10B is the paper when the edge processing is performed on the upstream edge of the paper. FIG. 6 is a diagram simply showing the positional relationship between the printer and the print head. The figure for demonstrating the detail of the paper concerning a modification.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Each figure is only an example for explaining the present embodiment. Also, the figures and dimensions may not match each other.

1. Schematic description of the device:
FIG. 1 is a block diagram illustrating the configuration of the printing apparatus 10 according to the present embodiment. The printing apparatus 10 can execute double-sided printing in which printing is performed on the second surface, which is the back surface of the first surface, after printing on the first surface of the print medium. The printing apparatus 10 is grasped as a product such as a printer, a multifunction machine including a plurality of functions such as a printer, a scanner, and a facsimile. The printing apparatus may be referred to as a recording apparatus, a liquid ejection (ejection) apparatus, or the like. Further, the whole or part of the printing apparatus may be referred to as a printing control apparatus. In FIG. 1, the printing apparatus 10 includes a control unit 11, an operation input unit 12, a display unit 13, a communication interface (I / F) 14, a slot unit 15, a printing unit 16, a conveyance unit 17, a humidity detection unit 18, and the like. It is illustrated as a configuration.

  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, the CPU controls the behavior of each component of the printing apparatus 10 by executing arithmetic processing according to a program stored in the ROM or the like using the RAM or the like as a work area.

  The operation input unit 12 includes various buttons and keys for accepting an operation by the user. The display unit 13 is a part for displaying various information related to the printing apparatus 10 and is configured by, for example, a liquid crystal display (LCD). A part of the operation input unit 12 may be realized as a touch panel displayed on the display unit 13.

  The printing unit 16 is a mechanism for printing an image on a printing medium (paper) under the control of the control unit 11. In the present embodiment, the description will be continued assuming that the print medium is paper, but the use of materials other than paper as the print medium is not excluded. When the printing method employed by the printing unit 16 is an inkjet method, the printing unit 16 includes a plurality of nozzles and a print head 16a or a print head 16a that discharges liquid (ink) from the nozzles. The carriage 16b moves along the scanning direction. The print head may be called a print head, a recording head, a liquid ejection (ejection) head, or the like. Although not shown, the print head 16a receives ink supplied from an ink cartridge or the like that holds ink, and discharges the supplied ink from each nozzle. When ink ejected from each nozzle lands on the paper, ink dots are formed on the paper.

  The transport unit 17 transports paper under the control of the control unit 11. The transport unit 17 includes rollers that rotate to transport the paper in a predetermined transport path (for example, the rollers 23, 24, 25, and 26 shown in FIG. 2), motors that generate power to rotate the rollers, It includes a gear train for transmitting the power generated by the motor to the rollers. The print head 16a performs printing by ejecting ink onto the paper transported along the transport path by the transport unit 17. There are various types of ink ejected by the print head 16a. For example, the print head 16a ejects ink of a plurality of colors such as cyan (C), magenta (M), yellow (Y), and black (K).

  The communication I / F 14 is a general term for interfaces for connecting the printing 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 information necessary for printing for the printing apparatus 10 such as a smartphone, a tablet terminal, a digital still camera, and a personal computer (PC). The printing apparatus 10 can be connected to the external device 100 via the communication I / F 14 by various means and communication standards such as a USB cable, a wired network, a wireless LAN, and e-mail communication. The slot 15 is a part for inserting an external storage medium such as a memory card. That is, the printing apparatus 10 can also input information necessary for printing from an external storage medium such as a memory card inserted into the slot unit 15.

  The humidity detector 18 is a humidity sensor that can detect the humidity of the environment in which the printing apparatus 10 is placed. The humidity detection unit 18 may detect humidity in the casing of the printing apparatus 10 or may detect humidity near the surface of the casing. The detection result by the humidity detector 18 is input by the controller 11.

  It can be said that the control unit 11 controls “print-related operations” including the operation of the transport unit 17 and the operation of the print head 16a. The printing-related operation is a concept that can include all operations and processes performed by each component in the printing apparatus 10 until printing on a sheet is completed. In addition to the operation of the transport unit 17 and the operation of the print head 16a, the carriage-related operation This includes the operation of 16b and the operation of the control unit 11 itself (for example, image processing and data processing necessary for printing).

  FIG. 2 simply shows a configuration mainly related to the conveyance of the paper P in the printing apparatus 10 from the viewpoint of facing the main scanning direction of the carriage 16b. Reference sign Df illustrates the transport direction in which the transport unit 17 transports the paper P. The transport direction Df is basically orthogonal to the main scanning direction. In FIG. 2, the main scanning direction is a direction perpendicular to the drawing. The transport unit 17 changes the position of the paper P to be transported as shown in the upper, middle, and lower stages of FIG. The printing apparatus 10 includes, for example, a paper feed cassette 31 that can store a plurality of sheets P, and a discharge port 32 that discharges the sheets P to the outside of the casing 30 of the printing apparatus 10. In the example of FIG. 2, the paper feed cassette 31 is accommodated in the lower part of the housing 30. Needless to say, the user can attach the paper feed cassette 31 to the housing 30 and pull the paper feed cassette 31 from the housing 30.

  2, the printing apparatus 10 includes a conveyance path 40 toward the discharge port 32 with the paper feed cassette 31 as a supply source, and a reverse conveyance that connects two predetermined points in the conveyance path 40, as indicated by two-dot chain arrows in FIG. And a path 41. The paper feed cassette 31 is on the most upstream side of the transport path 40. The discharge port 32 is on the most downstream side of the transport path 40. A pickup (PU) roller 24 is disposed in the vicinity of the paper feed cassette 31. The PU roller 24 contacts the uppermost paper P stored in the paper feed cassette 31, thereby feeding the paper P from the paper feed cassette 31 into the transport path 40 one by one. Corresponding to the conveyance path 40, intermediate rollers 23 and driven rollers 23a and 23b respectively opposed to the intermediate rollers 23 are arranged. The paper P transported from the paper cassette 31 is transported according to the rotation of the intermediate roller 23 while being sandwiched between the intermediate roller 23 and the driven roller 23a and / or sandwiched between the intermediate roller 23 and the driven roller 23b. The path 40 is conveyed downstream.

  Corresponding to the transport path 40, a transport (PF) roller 25 and a discharge (EJ) roller 26 are disposed downstream of the intermediate roller 23. Specifically, a part of the transport path 40 is the platen 16c. A PF roller 25 and a driven roller 25a facing the PF roller 25 are disposed upstream of the platen 16c in the transport direction Df, and the EJ roller 26 and EJ are disposed downstream of the platen 16c in the transport direction Df. A driven roller 26 a facing the roller 26 is provided. The print head 16a is disposed so as to face the platen 16c at a position above the platen 16c. The print head 16a is moved along the main scanning direction by the carriage 16b in a state where the nozzle surface 16a1, which is a surface on which each nozzle opens, faces the platen 16c.

  The paper P transported along the transport path 40 according to the rotation of the intermediate roller 23 is eventually sandwiched between the PF roller 25 and the driven roller 25a and / or sandwiched between the EJ roller 26 and the driven roller 26a. It is transported to the downstream side DS according to the rotation (forward rotation) of 25 and 26. The paper P is intermittently transported (paper fed) during the period of passing under the nozzle surface 16a1. That is, the conveyance (paper feed) of the paper P from the upstream US to the downstream DS for a predetermined distance and the ink ejection by the print head 16a accompanying the movement of the carriage 16b along the main scanning direction (the path of the print head 16a) Are alternately repeated, the surface of the paper P facing the nozzle surface 16a1 receives ink ejection on the platen 16c.

  FIG. 3 is an example for explaining the details of the sheet P. FIG. 3A shows one sheet P from the same viewpoint as FIG. 2, and FIG. 3B shows the one sheet P on the first surface. Shown from the F1 side. The paper P has a first surface F1 and a second surface F2. The first surface F1 is a surface that is first opposed to the nozzle surface 16a1 after being conveyed from a supply source such as the paper feed cassette 31, and is also referred to as a surface. The second surface F2 is a surface that faces the nozzle surface 16a1 when the paper P is reversed after printing on the first surface F1 during double-sided printing on the paper P, and is also referred to as a back surface. 3A and 3B, it is assumed that the sheet P is in a state where the first surface F1 is opposed to the nozzle surface 16a1. The end of the paper P facing the downstream DS with the first surface F1 facing the nozzle surface 16a1 is referred to as a paper edge E1 for convenience, and the end of the paper P facing the upstream US in this state is referred to as the paper edge for convenience. Called E2. In a state where the second surface F2 faces the nozzle surface 16a1, the paper end E1 faces the upstream side US, and the paper end E2 faces the downstream side DS.

  3A and 3B indicate the end portions of the first surface F1 in the transport direction Df of the paper P. That is, the end portion R1 is a predetermined region on the downstream side DS included in the first surface F1, and the end portion R2 is a predetermined region on the upstream side US included in the first surface F1. Reference symbol R3 indicates a central portion of the first surface F1. The center portion R3 is a region excluding the end portions R1 and R2 of the first surface F1.

  The upper part of FIG. 2 shows a state where printing on the first surface F1 of the paper P has been completed. In such a state, the sheet end E2 is located on the downstream side DS with respect to the PF roller 25, and is located at a position substantially corresponding to the position of the most downstream side DS of the print head 16a. When double-sided printing is set as the printing condition, the control unit 11 controls the transport unit 17 to transport the paper P by the reverse rotation of the rollers 25 and 26 from the state shown in the upper part of FIG. Back feed) is started, and the paper P is sent to the upstream side US. Of course, when the double-sided printing is not set as the printing condition (single-sided printing is set), the control unit 11 does not cause the transport unit 17 to perform such backfeeding, and continues the rollers 25 and 26. The paper P that has been normally rotated and has finished printing on the first surface F <b> 1 is discharged from the discharge port 32.

  The transport unit 17 can temporarily stop the back feed when the paper end E2 of the paper P comes to the upstream side US from the PF roller 25 by the back feed. The middle part of FIG. 2 shows a state where the back feed is temporarily stopped in this way. By temporarily stopping the back feed, it is possible to secure time for naturally drying the paper P on which the printing on the first surface F1 has been completed. As shown in the middle part of FIG. 2, as a result of the temporary stop of the back feed, the paper P is sandwiched between the PF roller 25 and the driven roller 25a and is sandwiched between the EJ roller 26 and the driven roller 26a. Is also referred to as a first stop position. The stop time at the first stop position is referred to as a first drying time.

  After the first drying time has elapsed since the paper P was stopped at the first stop position, the transport unit 17 resumes the back feed of the paper P. The sheet end E2 of the sheet P that further proceeds to the upstream side US by resuming the back feed enters the reverse conveyance path 41. The reverse conveyance path 41 connects from a predetermined point between the intermediate roller 23 and the PF roller 25 in the conveyance path 40 to a predetermined point between the PU roller 24 and the intermediate roller 23 in the conveyance path 40. By continuing the back feed, the paper P proceeds on the reversing conveyance path 41 and eventually joins the conveyance path 40 with the paper edge E2 at the head. Thus, the paper P entering the transport path 40 is transported along the transport path 40 again according to the rotation of the intermediate roller 23.

  The conveyance unit 17 is configured such that the sheet end E2 of the sheet P entering the conveyance path 40 via the reverse conveyance path 41 has a predetermined driven roller corresponding to the intermediate roller 23 (for example, downstream of the driven rollers 23a and 23b). It is possible to temporarily stop the back feed and the rotation of the intermediate roller 23 at the timing of passing the driven roller 23b). The lower part of FIG. 2 shows a state in which the back feed and the rotation of the intermediate roller 23 are temporarily stopped in this way. Thereby, it is possible to further ensure the time for naturally drying the paper P on which the printing of the first surface F1 has been completed. As shown in the lower part of FIG. 2, the position of the sheet P in which the vicinity of the sheet end E2 is sandwiched between the intermediate roller 23 and a predetermined driven roller (for example, the driven roller 23b) is also referred to as a second stop position. . The stop time at the second stop position is referred to as a second drying time.

  After the second drying time has elapsed since the sheet P was stopped at the second stop position, the transport unit 17 resumes transport of the sheet P in the transport path 40 by the rotation of the intermediate roller 23. The transport unit 17 ends the back feed when the paper end E1 of the paper P passes the PF roller 25 to the upstream side US by the back feed. The paper P traveling from the paper edge E2 to the top, that is, the paper P after reversal, is eventually sandwiched between the PF roller 25 and the driven roller 25a and / or sandwiched between the EJ roller 26 and the driven roller 26a. In a state where the surface F2 is opposed to the nozzle surface 16a1, it is conveyed to the downstream side DS according to the rotation (forward rotation) of the rollers 25 and 26. Of course, ink discharge, that is, printing is performed by the print head 16a on the second surface F2. And the conveyance part 17 discharges | emits the paper by which the printing to the 2nd surface F2 was complete | finished from the discharge port 32 according to the normal rotation of the rollers 25 and 26 continuously.

Thus, in the process of transporting the paper P by the transport unit 17 after printing on the first surface F1 and before starting printing on the second surface F2, the transport is temporarily performed at the first stop position or the second stop position. The process that stops at this point is called a drying process.
The paper P that has received ink discharged onto the first surface F1 is easily swollen by the moisture of the ink and easily curls. At this time, the first surface F1 is curled so as to rise upward (convex). The drying of the paper P at the first stop position described above produces an effect of correcting such a curl. Further, by drying the paper P at the first stop position, after that, when the first surface F1 of the paper P comes into contact with the intermediate roller 23, the ink attached to the first surface F1 is transferred to the intermediate roller 23 side. Can be prevented.

  In addition, the drying of the paper P at the second stop position described above has the effect of curling the paper P in the direction opposite to the curl direction, resulting in flattening (decurling). That is, by curling the paper P along the curved surface of the intermediate roller 23 as shown in the lower part of FIG. 2, it is possible to cancel the curling of the paper P caused by the ink ejection onto the first surface F1. In particular, the vicinity (edge R2) of the paper P near the paper edge E2 is a portion that is printed most slowly when printing on the first surface F1, so that the drying does not progress most in the first surface F1, The degree of curling is also relatively large. At the second stop position, a certain range of the paper P including the vicinity of the paper edge E2 where the degree of curling is large is decurled using the curved surface of the intermediate roller 23, so that the warp of the paper P, that is, curl can be accurately detected. Can be removed.

2. Examples relating to control of printing-related operations:
In the present embodiment, the control unit 11 controls printing-related operations after printing on the first surface F1 based on the print density of the first surface F1 and the humidity detected by the humidity detection unit 18. In the following, some embodiments relating to printing-related operations after printing on the first surface F1 will be described.

First embodiment:
FIG. 4 is a flowchart showing processing related to control of printing-related operations after printing on the first surface F1. As a premise for explaining the flowchart, it is assumed that double-sided printing is set as one of the printing conditions. Setting of printing conditions employed by the printing apparatus 10 can be performed, for example, by a user operating the operation input unit 12 in advance. Alternatively, the printing apparatus 10 sets printing conditions according to a command from the external device 100 via the communication I / F 14.

  The control unit 11 acquires the print density of the first surface F1 of the paper P (step S100). The print density of the first surface F1 can also be expressed as the amount of ink ejected on the first surface F1, the coverage with ink on the first surface F1, or the like. Such a print density can be acquired based on print data for printing on the first surface F1. From the input data representing the image to be printed (an image that can include various objects such as photographs, CG, and characters) arbitrarily designated by the user who operates the operation input unit 12 or the external device 100, the control unit 11 Print data can be generated. There are various formats of input data. For example, it is bitmap data having gradation values of red (R), green (G), and blue (B) for each pixel. The control unit 11 generates print data from input data by appropriately executing known image processing such as format conversion processing, resolution conversion processing, color (color system) conversion processing, and halftone processing. The print data is, for example, data after the halftone process that defines dot-on (ink ejection) or dot-off (ink non-ejection) of each CMYK ink for each pixel.

  The control unit 11 causes the print head 16a to execute ink ejection from each nozzle based on such print data. Naturally, the control unit 11 sequentially print data for printing on the first surface F1 (first surface print data) and print data for printing on the second surface F2 (second surface print data). Generate. Alternatively, the control unit 11 inputs such print data from the external device 100 via the communication I / F 14. The control unit 11 may acquire the print density from the entire first-surface print data for one sheet of paper P, or acquire the print density limited to data in a range that strongly affects the curl of the paper P. May be. As a specific example of the latter, the control unit 11 prints from data (edge-corresponding print data) within a range corresponding to the edges R1, R2 (see FIGS. 3A and 3B) of the paper P in the first-side print data. Get the concentration.

  Assume that the positions and sizes of the end portions R1 and R2 on the paper P are fixed for each size of the paper P. The size of the paper P is also set as one of the printing conditions (for example, the size of the paper P is set to A4). Since the control unit 11 generates the first side print data and the second side print data in accordance with the size of the paper P, the control unit 11 has a predetermined arrangement of the first side print data on the paper P (with a predetermined width in the vertical and horizontal directions). The edge-corresponding print data can also be specified based on the arrangement considering the edge.

  For example, the control unit 11 can capture the number of dots in the edge-corresponding print data as the print density of the first surface F1. The number of dots may be counted as one dot for each CMYK dot-on. Alternatively, the control unit 11 may capture the dot-on rate in the edge corresponding print data as the print density of the first surface F1. Since the number of pixels constituting the edge-corresponding print data is a value that is naturally determined from the resolution of the print data and the size of the paper P, the edge-corresponding print data in such an edge-corresponding print data number (here 4) The dot number ratio is defined as the dot-on rate. In any case, the control unit 11 directly or indirectly indicates the amount of ink ejected to a limited area such as the end portions R1 and R2 of the entire first surface F1 or the first surface F1 (for example, The number of dots and the dot-on rate in the edge-corresponding print data described above are acquired as the print density of the first surface F1.

  The control part 11 acquires the humidity detection result by the humidity detection part 18 from the humidity detection part 18 (step S110). The processing order of step S100 and step S110 may be reversed. Alternatively, the control unit 11 may perform step S100 and step S110 in parallel.

  Next, the control unit 11 selects a mode of printing-related operation after printing on the first surface F1 based on the print density of the first surface F1 acquired in step S100 and the humidity acquired in step S110. (Step S120). Specifically, the control unit 11 compares the print density of the first surface F1 with a plurality of threshold values (threshold values THd1, THd2,...) Relating to the predetermined print density, and the humidity is It is compared with a plurality of threshold values (threshold values THh1, THh2,...) Relating to the predetermined humidity. In the first embodiment, the control unit 11 selects a drying process mode based on the comparison result and the mode selection table 50. The drying process is a kind of printing-related operation after printing on the first surface F1.

  FIG. 5 illustrates the mode selection table 50. The control unit 11 stores such a table in advance and can refer to it appropriately. In the mode selection table 50, “Duty” indicates the print density of the first surface F1. The controller 11 further determines the humidity depending on whether the duty is less than the threshold value THd1, the duty is greater than or equal to the threshold value THd1 and less than the threshold value THd2, and the duty is greater than or equal to the threshold value THd2. The drying process mode is selected according to whether the value is less than the value THh1, the humidity is greater than or equal to the threshold value THh1, and less than the threshold value THh2, and the humidity is greater than or equal to the threshold value THh2. The drying process mode is divided into a plurality of modes, for example, a long-time drying mode, a standard drying mode, a short-time drying mode, and a drying time 0 mode. Note that THd1 <THd2 and THh1 <THh2.

  For convenience, a duty less than the threshold THd1 is also expressed as a low density, a duty greater than or equal to the threshold THd1 and less than the threshold THd2 is expressed as a medium density, and a duty greater than the threshold THd2 is expressed as a high density. For convenience, the humidity below the threshold THh1 is also expressed as low humidity, the humidity above the threshold THh1 and below the threshold THh2, and the humidity above the threshold THh2 as high humidity.

  FIG. 6 illustrates the drying time table 60. The control unit 11 stores such a table in advance, and can refer to it appropriately when executing the drying process. The drying time table 60 defines the length of the drying time that should be adopted in each of the long-time drying mode, the standard drying mode, the short-time drying mode, and the drying time 0 mode. In FIG. 6, symbol T1 means the first drying time, and symbol T2 means the second drying time. The drying time 0 mode is a mode in which the first drying time T1 and the second drying time T2 are both 0, so that the drying process is not actually executed. The seconds shown in FIG. 6 for the long-time drying mode, the standard drying mode, and the short-time drying mode are merely examples, but in any case, the drying is performed in the order of the long-time drying mode, the standard drying mode, and the short-time drying mode. The time is set longer.

  According to FIG. 5, the control unit 11 selects a drying process mode in which the drying time (T1, T2) is longer as the duty, that is, the printing density of the first surface F1 is higher. This is because as the duty is higher, the curl of the paper P is likely to increase, and a longer drying time is required to suppress the curl. Further, according to FIG. 5, it can be said that the control unit 11 tends to select a drying process mode having a shorter drying time (T 1, T 2) as the humidity detected by the humidity detection unit 18 is higher. This is because even if the duty is the same, if the ambient humidity is high, the degree of curling of the paper P when ink is ejected becomes small. According to FIG. 5, the control unit 11 selects the long-time drying mode with the longest drying time when the concentration is high and the humidity is low, and selects the short-time drying mode when the concentration is high and the humidity is high. . Further, the control unit 11 selects the standard drying mode when the medium concentration is low and the humidity is low, while selecting the drying time 0 mode when the medium concentration is high and the humidity is high. However, since the curling of the paper P hardly occurs regardless of the humidity when the density is low, the control unit 11 selects the drying time 0 mode.

  The control unit 11 controls the printing-related operation after printing on the first surface F1 in the mode selected in step S120 (step S130). Although not specifically described in the flowchart of FIG. 4, the controller 11 naturally controls the conveyance unit 17, the carriage 16 b, and the print head 16 a before starting Step S <b> 130. Printing on the first surface F1 of the paper P based on the data is finished. That is, step S130 is a process that starts after the state of printing on the first surface F1 (the state shown in the upper part of FIG. 2), and the control unit 11 does not finish printing on the first surface F1. The mode selection in step S120 is finished.

  In the first embodiment, the control unit 11 controls the transport unit 17 according to the drying process mode selected in step S120, thereby causing the drying process to be performed or not causing the drying process to be performed (step S130). ). That is, when the controller 11 selects any one of the long-time drying mode, the standard drying mode, and the short-time drying mode, the control unit 11 prints the paper P after the printing on the first surface F1 on the second surface F2. In the process of transporting for the first time, the first drying time T1 and the second drying time T2 defined in the drying time table 60 corresponding to the selected mode are respectively adopted, and the first stop position and the second stop position are adopted. In each case, the conveyance of the paper P is temporarily stopped. On the other hand, when the drying time 0 mode is selected, the printing of the second surface F2 is performed without stopping the paper P after the printing of the first surface F1 at either the first stop position or the second stop position. For transport.

  As described above, according to the present embodiment, when the printing apparatus 10 performs double-sided printing on the paper P, the printing apparatus 10 affects each element that affects the degree of curling of the paper P, such as the print density and humidity of the first surface F1 of the paper P. Based on this, the printing-related operation after printing on the first surface F1 is controlled. As a result, a printing-related operation suitable for the degree of curling occurring on the paper P can be realized, and both curling suppression and printing efficiency can be achieved. In particular, in the first embodiment, the drying time in the drying process (first drying time T1, second drying time T2) is varied according to the difference in humidity. Thereby, when the humidity is low, a relatively long drying time can be secured, and the curl generated according to the printing density of the first surface F1 can be surely suppressed before printing on the second surface F2. . In addition, when the humidity is high, the curl generated depending on the printing density of the first surface F1 is small or hardly, so the drying time is shortened or zero, and printing on the second surface F2 is performed. It is possible to start earlier and increase printing efficiency.

Second embodiment:
The second embodiment will be described using the flowchart of FIG. Further, in the second embodiment, the description common to the above description is omitted as appropriate.
When the control unit 11 selects a mode of printing-related operation after printing on the first surface F1 based on the print density of the first surface F1 acquired in step S100 and the humidity acquired in step S110, the mode The mode may be selected with reference to the selection table 51 (step S120).

  FIG. 7 illustrates the mode selection table 51. The control unit 11 stores such a table in advance and can refer to it appropriately. Similarly to the mode selection table 50 (see FIG. 5), the mode selection table 51 also defines the drying processing mode to be selected according to the combination of Duty (print density of the first surface F1) and humidity. The mode selection table 51 further defines which end processing mode or normal mode should be selected according to the combination of Duty and Humidity. The edge processing mode is a mode in which the following edge processing is executed, and the normal mode means a mode in which the following normal printing processing is executed without executing the edge processing. The edge processing is a kind of printing-related operation after printing on the first surface F1.

  That is, in the second embodiment, the control unit 11 selects the drying process mode based on the comparison result between the duty and the threshold values THd1 and THd2, the comparison result between the humidity and the threshold values THh1 and THh2, and the mode selection table 51. Then, the edge processing mode is selected or not selected (step S120). The basic tendency of the correspondence relationship between the duty and humidity in the mode selection table 51 and the mode of the drying process is the same as that of the mode selection table 50. That is, there is a tendency that the higher the Duty is, the longer the drying process mode (T1, T2) is selected, and the higher the humidity is, the shorter the drying process (T1, T2) is. It can be said that there is.

  However, as compared with the mode selection table 51 and the mode selection table 50, when the combination of Duty and Humidity is the same, the mode selection table 51 selects a drying process mode with a shorter drying time (T1, T2). It can be said that it has a tendency. This is because the edge processing is effective for suppressing curling of the paper P. The mode selection table 51 tends to select the edge processing mode as the duty is higher, and tends to not select the edge processing mode as the humidity is higher. That is, in the second embodiment, curling of the paper P can be suppressed by the drying process and the edge processing, and therefore, the curling suppression effect by the drying process is reduced when compared with the first embodiment (the drying time is shortened). )be able to.

  The control unit 11 controls the printing-related operation after printing on the first surface F1 in the mode selected in step S120 (step S130). In other words, in the second embodiment, the control unit 11 controls the transport unit 17 and the like to cause the drying process to be performed according to the drying process mode selected in step S120 or not to perform the drying process. If the edge processing mode is selected in S120, the edge processing is executed when printing on the second surface F2, and if the normal mode is selected, the edge processing is not executed when printing on the second surface F2. The normal printing process is executed.

An example of edge processing and normal printing processing executed under the control of the control unit 11 will be described.
FIG. 8 illustrates the positional relationship between the paper P and the print head 16a when printing on the second surface F2 from the viewpoint from above. Since the paper P shown in FIG. 8 is in a state after reversal, the paper edge E2 faces the downstream DS in the transport direction Df and the paper edge E1 is upstream, contrary to the paper P shown in FIGS. 3A and 3B. Facing the side US. Reference sign Dm in FIG. 8 indicates the main scanning direction of the carriage 16b.

  The print head 16a according to the present embodiment has a nozzle row NL (NLc, NLm, NLy, NLk) for each ink (for example, CMYK ink). Each nozzle row NL included in the print head 16a is configured by a total of N nozzles Nz of nozzle numbers # 1 to #N arranged at a predetermined interval from the upstream US in the transport direction Df to the downstream DS. The specific value of N is not limited, but as an example, N = 400. In FIG. 8, individual nozzles Nz constituting the nozzle row NL are indicated by dots. In FIG. 8, the nozzle row NL is expressed very simply. For example, the nozzle row NL corresponding to one ink color is composed of a plurality of nozzle rows, or the direction in which the nozzle row NL faces is the transport direction Df. Or the positions of the individual nozzles Nz in the main scanning direction Dm may be shifted.

  A symbol H shown for the paper P illustrates a width corresponding to a distance in the transport direction Df that is sent by one paper feed by the transport unit 17 in the normal printing process. Regions having a width H on the paper P (for example, individual regions separated by a broken line on the paper P in FIG. 8) are referred to as unit regions here. The width H is the length of the nozzle row NL in the transport direction Df, that is, the distance in the transport direction Df from the most upstream US nozzle Nz (nozzle number # 1) to the most downstream DS nozzle Nz (nozzle number #N). It can be said that it corresponds to. In the normal printing process, the transport unit 17 causes the image at the position of the most downstream DS in the unit area to be the most downstream DS nozzle Nz in the paper feed for causing the print head 16a to print the unit area of the most downstream DS. It is conveyed so as to be printed at (nozzle number #N). After the paper feeding, printing is performed on the unit area of the most downstream DS by the pass of the print head 16a. In the normal printing process, the printing on the entire surface of the paper P is finished by repeating the paper feeding for the width H and the pass of the print head 16a.

  FIG. 9A simply shows the positional relationship between the paper P and the print head 16a when performing normal printing processing on the downstream end of the paper P from the viewpoint of facing the main scanning direction. The positional relationship between the paper P and the print head 16a in the case where the edge processing is performed on the edge of the downstream side DS of the paper P is simply shown from the viewpoint of facing the main scanning direction. The edge processing performed on the downstream DS end of the paper P is also expressed as “downstream edge processing”. Note that the edge processing (see FIG. 10B) performed on the upstream US edge of the paper P is also expressed as “upstream edge processing”. In FIGS. 9A and 9B, since the paper end E2 of the paper P faces the downstream DS, it can be said that the printing is performed on the end of the second surface F2 on the downstream DS.

  FIG. 9A may be understood as showing the same scene as FIG. 8 from a different viewpoint from FIG. That is, in the normal printing process as illustrated in FIG. 9A, the control unit 11 causes the transport unit 17 to make the most downstream side on the second surface F2 before executing the first pass to the second surface F2 by the print head 16a. The paper P is fed to a position where an image at the position of the most downstream DS in the unit area of the DS is printed by the nozzle Nz (nozzle number #N) of the most downstream DS. In the normal printing process, the control unit 11 does not limit the nozzles Nz that are driven for printing. That is, in the example of FIG. 9A, basically, the nozzles Nz from the nozzle numbers # 1 to #N can be driven based on the print data for the second surface.

  On the other hand, in the edge processing, the control unit 11 limits the nozzles Nz that are driven for printing. Specifically, as shown in FIG. 9B, in the downstream end portion processing, the upstream US including the nozzle Nz (nozzle number # 1) of the most upstream US among the nozzle numbers # 1 to #N. Printing is performed by driving the nozzles Nz belonging to the fixed range X1. That is, in the downstream side end processing, the control unit 11 causes the transport unit 17 to make the unit area of the most downstream DS on the second surface F2 before executing the first pass to the second surface F2 by the print head 16a. The paper P is fed to the position where the image at the position of the most downstream DS is printed by the nozzle Nz of the most downstream DS in the range X1. Then, after the paper feed, the print head 16a drives the nozzles Nz in the range X1 based on the second surface print data in the first pass to the second surface F2.

  As shown in FIGS. 9A and 9B, in the scene where printing is performed on the downstream DS end of the second surface F2, the paper end E2 on the downstream DS of the paper P basically does not reach the EJ roller 26. . As described above, in a situation where the paper end E2 side is not sandwiched between the EJ roller 26 and the driven roller 26a, the paper end E2 side is placed on the platen 16c due to the effect of curling of the paper P that occurs after printing on the first surface F1. From the top to the top (nozzle surface 16a1 side). Further, the height of the curl on the paper edge E2 side (the height from the platen 16c to the paper edge E2) is such that the distance between the paper edge E2 and the PF roller 25 and the driven roller 25a sandwiching the paper P is the same. There is a tendency to increase as the distance increases. 9A and 9B, a two-dot chain line shows that the portion of the downstream side DS of the sheet P sandwiched by the PF roller 25 and the driven roller 25a, that is, the sheet end E2 side of the sheet P is curled upward. This is illustrated in When printing on the second surface F2, the paper P may actually be in a posture as indicated by the two-dot chain line on the paper edge E2 side.

  As is clear from a comparison between FIG. 9A and FIG. 9B, when printing is performed on the downstream DS end of the second surface F2, the downstream edge processing is performed more than when the normal printing process is performed (FIG. 9A). In the case of carrying out (FIG. 9B), since the distance between the paper edge E2 and the PF roller 25 and the driven roller 25a holding the paper P is shorter, the curl height on the paper edge E2 side is also lower. In other words, the control unit 11 controls the print head 16a and the conveyance unit 17 to execute the downstream end processing, thereby appropriately curling the vicinity of the paper end E2 facing the downstream DS when printing on the second surface F2. Can be suppressed. After selecting the edge processing mode, the control unit 11 performs the normal printing process (paper feeding for the width H and the print head 16a) on the second surface F2 after the downstream edge processing on the second surface F2 of the paper P. (Pass repetition) is executed, and upstream edge processing is executed at the end of printing on the second surface F2.

  FIG. 10A simply shows the positional relationship between the paper P and the print head 16a when the normal printing process is performed on the end portion of the upstream US of the paper P from the viewpoint of facing the main scanning direction. The positional relationship between the paper P and the print head 16a when performing edge processing (upstream edge processing) on the upstream US edge of the paper P is simply shown from the viewpoint of facing the main scanning direction. ing. 10A and 10B, since the paper edge E1 of the paper P faces the upstream side US, it can be said that the printing is performed on the upstream side US edge of the second surface F2. However, FIG. 10B shows a change in the positional relationship between the paper P and the print head 16a before and after execution of the final paper feed for printing on the second surface F2.

  In the normal printing process as illustrated in FIG. 10A, the control unit 11 causes the transport unit 17 to make the most upstream US on the second surface F2 before executing the final pass to the second surface F2 by the print head 16a. The paper P is fed to the position where the image at the position of the most downstream DS in the unit area is printed by the nozzle Nz (nozzle number #N) of the most downstream DS (last paper feed). In the example of FIG. 10A, as in the example of FIG. 9A, the control unit 11 does not limit the nozzles Nz to be driven for printing, and the nozzles Nz from the nozzle numbers # 1 to #N are for the second surface. It can be driven based on the print data.

  On the other hand, in the edge processing, the control unit 11 limits the nozzles Nz that are driven for printing. Specifically, as shown in the lower part of FIG. 10B, in the upstream end processing, the downstream side including the nozzle Nz (nozzle number #N) of the most downstream DS among the nozzle numbers # 1 to #N. Printing is performed by driving the nozzles Nz belonging to the DS fixed range X2. In order to realize such upstream edge processing, the control unit 11 adds, for example, an image that can be printed in the last one paper feed and the last one pass in the case of normal printing processing. Print in two passes with paper feed in between. For example, the control unit 11 controls the transport unit 17 before executing the second pass from the end to the second surface F2 by the print head 16a, and the end of the sheet P of the sheet P as shown in the upper part of FIG. 10B. The paper P is fed within a range where E1 does not pass through the PF roller 25 (second paper feed from the end). In this situation, in the second pass from the last, the control unit 11 performs the nozzle Nz (nozzle number # 1) from the position of the most downstream DS to the most upstream US of the unprinted area in the area on the second surface F2. ) Is printed based on the second surface print data by driving the nozzle Nz corresponding to the range Y1.

  Next, the control unit 11 controls the transport unit 17 so that the unprinted most downstream DS position image is the most downstream DS nozzle Nz (nozzle number #N) as shown in the lower part of FIG. 10B. The paper P is fed to the position where printing is performed at (the last paper feed). After the paper feed, the print head 16a drives the nozzles Nz in the range X2 based on the second surface print data in the final pass to the second surface F2. As described above, the number of nozzles Nz belonging to the range X2 is fixed. Accordingly, the control unit 11 determines the size of the range Y1 (= second paper feed amount from the end) among the images that have not been printed on the second surface F2 immediately before the second pass from the end. The number of nozzles Nz in the range X2 is determined according to the amount of the image portion excluding the upstream US image portion that can be printed in the last pass.

  10A and 10B, in the scene where printing is performed on the upstream US end of the second surface F2, the paper end E1 on the upstream US side of the paper P is basically the PF roller 25. It is in the downstream US. As described above, in a situation where the paper edge E1 side is not sandwiched between the PF roller 25 and the driven roller 25a, the paper edge E1 side is placed on the platen 16c under the influence of the curl of the paper P that occurs after printing on the first surface F1. From the top to the top (nozzle surface 16a1 side). Further, the height of the curl on the paper edge E1 side (the height from the platen 16c to the paper edge E1) is such that the distance between the paper edge E1 and the EJ roller 26 and the driven roller 26a sandwiching the paper P is the same. There is a tendency to increase as the distance increases. 10A and 10B, the two-dot chain line shows that the portion of the paper P upstream of the portion sandwiched between the EJ roller 26 and the driven roller 26a, that is, the paper edge E1 side is curled upward. Illustrated. That is, at the time of printing on the second surface F2, the paper P may actually have a posture as indicated by the two-dot chain line on the paper edge E1 side.

  As is clear from the comparison between the lower part of FIG. 10A and FIG. 10B, when printing is performed on the end portion on the upstream side US of the second surface F <b> 2, the upstream end portion is more than the case where the normal printing process is performed (FIG. 10A). When the processing is performed (the lower stage in FIG. 10B), the distance between the paper edge E1 and the EJ roller 26 and the driven roller 26a sandwiching the paper P is shorter, so the curl height on the paper edge E1 side is also lower. That is, the control unit 11 controls the print head 16a and the conveyance unit 17 to execute the upstream side end process, thereby appropriately curling the vicinity of the paper end E1 facing the upstream side US when printing on the second surface F2. Can be suppressed.

  As described above, according to the present embodiment, when the printing apparatus 10 performs double-sided printing on the paper P, the printing apparatus 10 affects each element that affects the degree of curling of the paper P, such as the print density and humidity of the first surface F1 of the paper P. Based on this, the printing-related operation after printing on the first surface F1 is controlled. In particular, in the second embodiment, in addition to the drying process corresponding to each element, the edge process is performed or not performed when printing on the second surface F2 according to each element. As is clear from the above description, the edge processing is effective in curling at the downstream DS or upstream US edge of the second surface F2, but paper feeding is more effective than the normal printing processing. Efficiency will decrease. Therefore, the control unit 11 selects the edge processing mode on the condition that the printing density of the first surface F1 is, for example, a predetermined threshold THd1 (see FIG. 7) or more relating to the density. . According to such a configuration, the curling is appropriately suppressed by executing the edge processing when printing the second surface F2 in a situation where the curl is likely to be relatively large, and the second curling is not likely to occur. Printing efficiency can be improved without performing edge processing when printing the surface F2.

Further, according to the example of FIG. 7, the control unit 11 selects the drying time 0 mode when the humidity is equal to or higher than a predetermined threshold value THh2 related to humidity. According to such a configuration, when it is predicted that the curl will hardly occur due to high humidity, the printing efficiency can be improved by setting the drying time (T1, T2) to zero.
Note that FIG. 7 suggests that both the selection of the drying process mode and the selection of the edge processing mode or the normal mode are performed based on the print density (Duty) and humidity of the first surface F1. As a “third embodiment”, the controller 11 may only select the edge processing mode or the normal mode based on the print density (Duty) and humidity of the first surface F1 in step S120.

3. Variations:
In the present embodiment, it is possible to employ modifications as described later. Of course, each modification can be combined as appropriate.

First modification:
The end portion R2 (see FIGS. 3A and 3B) of the first surface F1 is a portion that is printed the latest in the first surface F1, and the back side is printed earliest when the second surface F2 is printed. is there. Therefore, it can be said that the drying time (T1, T2) is a time required for drying the ink ejected to the end portion R2. Therefore, in step S100, the control unit 11 obtains the print density acquired from the data within the range corresponding to the end portion R2 of the first surface F1 among the print data for the first surface, and the print density (Duty of the first surface F1). ). According to such a configuration, in step S120, the control unit 11 can select a drying process mode according to the print density (and humidity) of the end portion R2 of the first surface F1.

Second modification:
As described above, the edge processing at the time of printing on the second surface F2 is the most upstream US nozzle Nz (nozzle number # 1) among the nozzles of the print head 16a having the downstream DS end of the second surface F2. ) Including the nozzle Nz (nozzle number #N) of the most downstream DS at the upstream US end of the second surface F2. And upstream end processing for printing by driving the nozzle Nz. The control unit 11 may execute both of the downstream end processing and the upstream end processing, or may execute only one of them.

  For example, in step S100, the control unit 11 obtains the print density acquired from the data within the range corresponding to the end portion R1 of the first surface F1 among the print data for the first surface, as the first print density ( First print), and the print density acquired from the data within the range corresponding to the end portion R2 of the first face F1 among the print data for the first face is set as the second print density (second duty) of the first face F1. . In step S120, when the control unit 11 selects one of the edge processing mode and the normal mode, the control unit 11 makes a finer selection according to each of the first print density and the second print density. That is, it is selected whether or not to execute the upstream side edge processing according to the first printing density (and humidity), and the downstream side edge processing is executed according to the second printing density (and humidity). Select whether or not. Although depending on the humidity condition, the control unit 11 basically tends to select the upstream end processing as the first print density is higher, and the higher the second print density is, the lower the downstream side is. Choose to run edge processing and win.

  In other words, in the end processing mode, both the end processing mode for executing both the downstream end processing and the upstream end processing, and the downstream end processing are executed and the upstream end processing is not executed. It can be said that there are a downstream end processing mode and an upstream end processing mode in which upstream end processing is performed and downstream end processing is not performed. The control unit 11 selects any one of the both end processing mode, the downstream end processing mode, the upstream end processing mode, and the normal mode. According to the second modified example, when the second surface F2 is printed, the necessary processing is performed from the downstream side edge processing and the upstream side edge processing as viewed from the print density of the first surface F1. , A decrease in printing efficiency can be suppressed.

Other variations:
FIG. 11 shows one sheet P from the first surface F1 side from the same viewpoint as FIG. 3B. Reference numerals R4 and R5 indicate end portions of the first surface F1 in a direction (main scanning direction of the carriage 16b) orthogonal to the transport direction Df of the paper P. That is, the end portions R4 and R5 are predetermined regions on both ends in the main scanning direction included in the first surface F1. In step S100, the control unit 11 obtains the print density acquired from the data within the range corresponding to the end portions R4 and R5 of the first surface F1 among the print data for the first surface, and the print density (Duty of the first surface F1). ). This is because the data in the range corresponding to the end portions R4 and R5 in the first side print data corresponds to an example of data in a range that strongly affects the curling of the paper P. In particular, the range illustrated with hatching in FIG. 11 (four corners of the first surface F1) is likely to curl when ink is discharged. Therefore, by acquiring the print density of the edges R4 and R5 including these four corners as the print density (Duty) of the first surface F1, curling of the paper P after the first surface F1 printing can be accurately suppressed. it can. Assume that the positions and sizes of the end portions R4 and R5 on the paper P are also fixed for each size of the paper P in the same manner as the end portions R1 and R2.

  The user may be able to select in advance a mode selection table to be referred to when selecting a mode in step S120. That is, the user can select which of the mode selection tables 50 and 51 is to be referred to by the control unit 11 in step S120 by arbitrarily operating the operation input unit 12. In addition to the mode selection tables 50 and 51, a plurality of patterns may exist in the mode selection table. For example, the control unit 11 may automatically switch the mode selection table to be referred to according to the printing condition selected by the user arbitrarily operating the operation input unit 12. Specifically, the control unit 11 switches the mode selection table to be referred to according to whether the print target selected by the user is a photograph or a document, or the user can select a rubbing avoidance mode (printing with paper P). The mode selection table to be referred to is switched according to whether or not a mode in which contact avoidance with the head 16a is emphasized is selected.

  The control unit 11 may adjust a platen gap (PG) that is a height from the platen 16c to the print head 16a (nozzle surface 16a1). The PG can be adjusted by changing the position of the carriage 16b in the vertical direction (vertical direction) in the printing apparatus 10. When the curl of the paper P is predicted to be relatively large according to the conditions such as the print density and humidity described so far, the control unit 11 sets the PG higher than the reference height to the second surface F2. It is possible to avoid the paper edges E2 and E1 of the paper P from contacting the print head 16a during printing. The process of adjusting PG is also a kind of printing related operation.

  The control unit 11 can improve the alignment of the paper P discharged out of the discharge port 32 by switching the transport speed when the printed paper P is discharged to the transport unit 17. The paper P that has been printed on the second surface F2 is discharged from the discharge port 32 as the EJ roller 26 rotates. If the printing density of the second surface F2 is relatively high, the paper P is moved to the second surface F2. The paper P may be curled due to the printing. Therefore, the control unit 11 determines the print density of the second surface F2 based on the print data for the second surface, and when the print density is higher than a predetermined threshold, the discharge conveyance speed (EJ roller) 26) or the discharge is temporarily stopped. Due to the reduction or temporary stop of the discharge, the curl generated on the paper P due to the printing on the second surface F2 is settled and sequentially discharged out of the discharge port 32. The alignment of the sheets P accumulated on the tray is improved.

  The most upstream US nozzle Nz (nozzle number # 1) and the most downstream DS nozzle Nz (nozzle number #N) described so far refer to the actual endmost nozzle Nz in the nozzle row NL. Not exclusively. For example, the nozzle row NL may have nozzles (dummy nozzles) that are not used for printing at the ends of the upstream side US and the downstream side DS. When such a dummy nozzle exists, the nozzles Nz of the upstream side US and the downstream side DS are specified among the nozzles Nz excluding the dummy nozzles among the nozzles Nz constituting the nozzle row NL. .

DESCRIPTION OF SYMBOLS 10 ... Printing apparatus, 11 ... Control part, 12 ... Operation input part, 13 ... Display part, 16 ... Printing part, 16a ... Print head, 16a1 ... Nozzle surface, 16b ... Carriage, 17 ... Conveyance part, 18 ... Humidity detection part , 23 ... Intermediate roller, 24 ... PU roller, 25 ... PF roller, 26 ... EJ roller, 30 ... Housing, 31 ... Paper feed cassette, 32 ... Discharge port, 40 ... Transport path, 41 ... Reverse transport path, 50 , 51 ... Mode selection table, 60 ... Drying time table, Df ... Transport direction, US ... Upstream side, DS ... Downstream side, Dm ... Main scanning direction, E1, E2 ... Paper end, F1 ... First side, F2 ... First 2 sides, NL ... nozzle row, Nz ... nozzle, P ... paper, R1, R2, R4, R5 ... end

Claims (5)

A printing apparatus capable of performing double-sided printing that performs printing on a second surface that is the back surface of the first surface after printing on the first surface of the print medium,
A transport unit for transporting the print medium;
A print head having a plurality of nozzles and discharging ink from the nozzles to the print medium;
A humidity detector for detecting humidity;
A control unit that controls a printing-related operation including an operation of the transport unit and an operation of the print head,
The control unit controls the printing-related operation after printing on the first surface based on the print density of the first surface and the humidity.   When the printing density at the end of the first surface in the conveyance direction of the print medium by the conveyance unit is equal to or greater than a predetermined threshold value related to the density, the control unit The printing apparatus according to claim 1, wherein an edge process is performed to limit the nozzles to be driven for printing on the edge part.   In the end portion processing, the downstream end portion that prints the downstream end portion of the second surface in the transport direction by driving some of the nozzles including the most upstream nozzle in the transport direction. At least one of processing and upstream end processing for printing the upstream end of the second surface by driving some of the nozzles including the most downstream nozzle. The printing apparatus according to claim 2.   The controller temporarily stops the conveyance in the course of conveyance of the print medium by the conveyance unit after printing on the first surface and before printing on the second surface as the humidity is higher. The printing apparatus according to claim 1, wherein the stop time is shortened.   The printing apparatus according to claim 4, wherein the control unit sets the stop time to 0 when the humidity is equal to or higher than a predetermined threshold related to the humidity.

Images