JP2008173835A - Liquid ejection device - Google Patents

Abstract

In a nozzle group having a larger number of nozzles than other nozzle groups, the use frequency of some nozzles is prevented from becoming very high.
A liquid ejecting apparatus includes a transport unit that transports a medium along a predetermined direction, a first nozzle group having a plurality of nozzles that eject a first liquid, and a type different from the first liquid. A second nozzle group 211K2 having more nozzles for discharging the second liquid than the first nozzle group, and a controller. The controller includes a first liquid ejection operation for ejecting the first liquid and the second liquid using a part of the nozzles of the first nozzle group and the nozzles of the second nozzle group, and the first nozzle group. The second liquid ejection operation for ejecting the first liquid and the second liquid is performed using another nozzle different from some of the nozzles in the second nozzle group and the nozzles in the second nozzle group.
[Selection] Figure 7

Description

  The present invention relates to a liquid ejecting apparatus that has two or more nozzle groups that eject different types of liquids and have different numbers of nozzles.

  An ink jet printer is known as a liquid ejecting apparatus. This ink jet printer prints on a medium by ejecting ink such as cyan (C), magenta (M), yellow (Y), and black (K) toward a medium such as paper. In such an ink jet printer, in order to eject each color ink such as cyan (C), magenta (M), yellow (Y), black (K), etc., a plurality of different color inks are ejected. Nozzle group.

By the way, in such an ink jet printer, in order to execute monochrome printing at high speed, a black nozzle group that ejects black (K) ink is a nozzle group that ejects ink of other colors, that is, for example, yellow. Those having more nozzles than the yellow nozzle group for ejecting (Y) ink, the magenta nozzle group for ejecting magenta (M) ink, the cyan nozzle group for ejecting cyan (C) ink, etc. There is. Specifically, for example, the black nozzle group may include twice or three times as many nozzles as the yellow nozzle group, magenta nozzle group, cyan nozzle group, or the like (see Patent Document 1).
JP-A-8-238805

  However, when color printing is performed in an inkjet printer in which the number of nozzles of the black nozzle group is larger than that of the yellow nozzle group, magenta nozzle group, cyan nozzle group, etc., the black nozzle group matches the nozzle group of other colors. Only some of the nozzles were used. That is, only a part of the nozzles of the same number as the nozzle groups of the other colors are used among the nozzles of twice or three times the number of nozzle groups of the other colors. For this reason, in the nozzles of the black nozzle group, there is a problem that a difference occurs in the frequency of use, and the degree of consumption of some of the nozzles is remarkably increased. In particular, in the case of the black nozzle group, since it is used for monochrome printing in addition to color printing, there is a possibility that exhaustion of some of the nozzles may become severe.

  The present invention has been made in view of such circumstances, and its purpose is to prevent the frequency of use of some nozzles from becoming very high in a nozzle group having a larger number of nozzles than other nozzle groups. There is to do.

The main invention for achieving the object is as follows:
(A) a transport unit that performs a transport operation of transporting the medium along a predetermined direction;
(B) a first nozzle group having a plurality of nozzles that are arranged along the predetermined direction and that discharge a first liquid toward the medium when moved relative to the medium;
(C) A type different from the first liquid toward the medium when it is arranged along the predetermined direction and moves relative to the medium integrally with the first nozzle group. A second nozzle group having more nozzles for discharging the second liquid than the first nozzle group;
(D) the transport operation by the transport unit;
When the first nozzle group and the second nozzle group are moving relative to the medium, at least one of the first liquid and the second liquid is directed toward the medium. A controller that alternately performs a liquid discharge operation to be discharged,
When both the first liquid and the second liquid are discharged onto one medium, the liquid discharge operation is performed by either of the nozzles of the first nozzle group and the nozzles of the second nozzle group. A first liquid ejection operation for ejecting the first liquid and the second liquid toward the medium using a part of the nozzles; and a nozzle of the first nozzle group and a nozzle of the second nozzle group A controller that performs a second liquid ejection operation for ejecting the first liquid and the second liquid toward the medium using another nozzle different from the some of the nozzles;
A liquid ejecting apparatus comprising (E).

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  At least the following matters will become apparent from the description of the present specification and the accompanying drawings.

(A) a transport unit that performs a transport operation of transporting the medium along a predetermined direction;
(B) a first nozzle group having a plurality of nozzles that are arranged along the predetermined direction and that discharge a first liquid toward the medium when moved relative to the medium;
(C) Different from the first liquid toward the medium when arranged along the predetermined direction and moved relative to the medium integrally with the first nozzle group. A second nozzle group having more nozzles for discharging the second liquid of the type than the first nozzle group;
(D) the transport operation by the transport unit;
When the first nozzle group and the second nozzle group are moving relative to the medium, at least one of the first liquid and the second liquid is directed toward the medium. A controller that alternately performs a liquid discharge operation to be discharged,
When both the first liquid and the second liquid are discharged onto one medium, the liquid discharge operation is performed by either of the nozzles of the first nozzle group and the nozzles of the second nozzle group. A first liquid ejection operation for ejecting the first liquid and the second liquid toward the medium using a part of the nozzles; and a nozzle of the first nozzle group and a nozzle of the second nozzle group A controller that performs a second liquid ejection operation for ejecting the first liquid and the second liquid toward the medium using another nozzle different from the some of the nozzles;
A liquid discharge apparatus comprising (E).

  In such a liquid ejecting apparatus, when both the first liquid and the second liquid are ejected to one medium, the liquid ejecting operation is performed alternately with the transporting operation by the transporting unit. , A first liquid ejection operation using some of the nozzles of the first nozzle group and the nozzles of the second nozzle group, and the one of the nozzles of the first nozzle group and the nozzles of the second nozzle group. Even when the number of nozzles in the second nozzle group is greater than the number of nozzles in the first nozzle group, by performing the second liquid ejection operation using another nozzle different from the nozzles of the part, It is possible to prevent the use frequency of some nozzles of the second nozzle group from increasing.

  In such a liquid ejecting apparatus, the some nozzles are located downstream of the other nozzles in the predetermined direction, and are located at the downstream end of the medium in the predetermined direction. When the second liquid is discharged in the direction, the second liquid may be discharged from the part of the nozzles. Thereby, the image quality at the front end of the medium is improved.

  In such a liquid ejection device, the some nozzles are located downstream of the other nozzles in the predetermined direction, and are located at an upstream end of the medium in the predetermined direction. When the second liquid is discharged in the direction, the second liquid may be discharged from the other nozzle. This improves the image quality at the trailing edge of the medium.

  In such a liquid ejection apparatus, the number of nozzles of the second nozzle group may be an integer multiple of the number of nozzles of the first nozzle group. Thus, when the number of nozzles of the second nozzle group is an integral multiple of the number of nozzles of the first nozzle group, it is possible to prevent the frequency of use of some of the nozzles of the second nozzle group from increasing.

  In such a liquid ejection apparatus, the first nozzle group and the second nozzle group may be arranged in parallel to each other. Thus, when the 1st nozzle group and the 2nd nozzle group are arrange | positioned mutually parallel, it can prevent that the usage frequency of a part of nozzle of a 2nd nozzle group becomes high.

  In the liquid ejecting apparatus, the first liquid and the second liquid are disposed toward the medium when the liquid ejecting apparatus is disposed along the predetermined direction and moves relative to the medium. You may provide the 3rd nozzle group which has fewer nozzles than the said 2nd nozzle group which discharges the 3rd type of liquid different from a liquid. When such a third nozzle group is provided, it is possible to prevent the use frequency of some nozzles of the second nozzle group from increasing.

  Further, in this liquid discharge apparatus, the number of the partial nozzles of the second nozzle group used in the first liquid discharge operation and the second nozzle used in the second liquid discharge operation The number of other nozzles different from the some nozzles in the group may be equal. In this way, the number of some nozzles in the second nozzle group used in the first liquid ejection operation and other nozzles different from the some nozzles in the second nozzle group used in the second liquid ejection operation. If the number is equal, it is possible to further prevent the frequency of use of some nozzles of the second nozzle group from becoming higher.

  In the liquid ejecting apparatus, the first liquid and the second liquid may be ink. Thus, if the first liquid and the second liquid are inks, it is possible to prevent the frequency of use of some of the nozzles of the second nozzle group from increasing in the liquid ejection apparatus serving as the printing apparatus.

  In the liquid ejecting apparatus, the first liquid and the second liquid may be inks having different colors. As described above, when the first liquid and the second liquid are inks having different colors, it is possible to prevent the use frequency of some nozzles of the second nozzle group from increasing.

=== Overview of Liquid Discharge Device ===
Hereinafter, an embodiment of the liquid ejection apparatus according to the present embodiment will be described. Here, as an example of the liquid ejecting apparatus, an ink jet printer 1 which is a printing apparatus that performs printing by ejecting ink toward a medium will be described. 1 to 3 describe the ink jet printer 1. FIG. 1 shows the appearance of the inkjet printer 1. FIG. 2 shows the internal configuration of the inkjet printer 1. FIG. 3 illustrates the configuration of the transport unit of the inkjet printer 1. FIG. 4 shows the nozzles of the ink jet printer 1. FIG. 5 illustrates the system configuration of the inkjet printer 1.

  As shown in FIG. 1, the ink jet printer 1 has a structure for discharging a medium such as printing paper supplied from the back surface from the front surface, and an operation panel 2 and a paper discharge portion 3 are provided on the front surface portion. ing. In addition, a paper feeding unit 4 is provided on the back side. Various operation buttons 5 and display lamps 6 are provided on the operation panel 2. The paper discharge unit 3 is provided with a paper discharge tray 7 that closes the paper discharge port when not in use. The paper feed unit 4 is provided with a paper feed tray 8 for holding a medium such as cut paper.

  Inside the ink jet printer 1, a carriage 41 is provided as shown in FIG. The carriage 41 is provided to be relatively movable along the left-right direction. Around the carriage 41, a carriage motor 42, a pulley 44, a timing belt 45, and a guide rail 46 are provided. The carriage motor 42 is constituted by a DC motor or the like, and is a drive source for relatively moving the carriage 41 in the left-right direction (hereinafter also referred to as the carriage movement direction). The timing belt 45 is connected to the carriage motor 42 via the pulley 44, and a part of the timing belt 45 is connected to the carriage 41. The carriage 41 is moved relative to the carriage 41 in the carriage movement direction (left-right direction) by the rotation of the carriage motor 42. Move. The guide rail 46 guides the carriage 41 along the carriage movement direction (left-right direction).

  In addition, in the periphery of the carriage 41, a linear encoder 51 that detects the position of the carriage 41 and a direction in which the medium S intersects the moving direction of the carriage 41 (the front-rear direction in the figure, hereinafter also referred to as the transport direction). A transport roller 17A for transporting along the transport path 17 and a transport motor 15 for rotationally driving the transport roller 17A are provided.

  On the other hand, the carriage 41 is provided with an ink cartridge 48 that stores various inks, and a head 21 that performs printing on the medium S. The ink cartridge 48 contains, for example, each color ink such as yellow (Y), magenta (M), cyan (C), black (K), and is detachable from a cartridge mounting portion 49 provided on the carriage 41. It is attached to. In the present embodiment, the head 21 performs printing by ejecting ink onto the medium S. For this purpose, the head 21 is provided with a number of nozzles for ejecting ink.

  In addition to this, in the inkjet printer 1, printing is performed in order to prevent clogging of the nozzles of the head 21 and the pump device 31 that sucks out ink from the nozzles in order to eliminate clogging of the nozzles of the head 21. A capping device 35 that seals the nozzles of the head 21 when not in use (such as during standby) is provided.

  Next, the conveyance unit of the inkjet printer 1 will be described. As shown in FIG. 3, the transport unit includes a paper feed roller 13, a paper detection sensor 53, a transport roller 17A, a paper discharge roller 17B, a platen 14, and free rollers 18A and 18B. Yes.

  The medium S to be printed is set in the paper feed tray 8. The medium S set in the paper feed tray 8 is conveyed along the direction of arrow A in the drawing by the paper feed roller 13 having a substantially D-shaped cross section, and is sent into the ink jet printer 1. The medium S sent to the inside of the ink jet printer 1 comes into contact with the paper detection sensor 53. The paper detection sensor 53 is installed between the paper feed roller 13 and the transport roller 17A, and detects the medium S fed by the paper feed roller 13.

  The medium S detected by the paper detection sensor 53 is sequentially transported to the platen 14 on which printing is performed by the transport roller 17A. A free roller 18A is provided at a position facing the conveying roller 17A. The medium S is smoothly transported by sandwiching the medium S between the free roller 18A and the transport roller 17A.

  The medium S sent to the platen 14 is sequentially printed by the ink ejected from the head 21. The platen 14 is provided to face the head 21 and supports the medium S to be printed from below.

  The medium S on which printing has been performed is sequentially discharged out of the printer by the paper discharge roller 17B. The paper discharge roller 17B is driven in synchronism with the transport motor 15, and sandwiches the medium S with the free roller 18B provided facing the paper discharge roller 17B, and discharges the medium S to the outside of the printer. To do.

<Head>
FIG. 4 is a diagram showing an arrangement of ink nozzles provided on the lower surface of the head 21. On the lower surface of the head 21, as shown in the figure, a yellow nozzle group 211Y composed of nozzles that eject yellow (Y) ink, a magenta nozzle group 211M composed of nozzles that eject magenta (M) ink, A cyan nozzle group 211C composed of nozzles that eject cyan (C) ink and a black nozzle group 211K composed of nozzles that eject black (K) ink are provided.

  Here, each of the yellow nozzle group 211Y, the magenta nozzle group 211M, and the cyan nozzle group 211C includes 60 nozzles # 1 to # 60. The yellow nozzle group 211Y, the magenta nozzle group 211M, and the cyan nozzle group 211C have nozzles # 1 to # 60 spaced apart from each other along the transport direction (corresponding to a predetermined direction) as shown in FIG. Open and arranged in a straight line. The yellow nozzle group 211Y, the magenta nozzle group 211M, and the cyan nozzle group 211C are also arranged side by side along the transport direction (corresponding to a predetermined direction).

  On the other hand, the black nozzle group 211K is arranged in parallel to the yellow nozzle group 211Y, the magenta nozzle group 211M, and the cyan nozzle group 211C. The black nozzle group 211K is composed of 180 nozzles # 1 to # 180, and these nozzles # 1 to # 180 are linearly spaced apart from each other along the transport direction (corresponding to a predetermined direction). It is arranged.

  Thus, the number of nozzles (180) of the black nozzle group 211K is larger than the number of nozzles (60) of the other nozzle groups, that is, here, the yellow nozzle group 211Y, the magenta nozzle group 211M, and the cyan nozzle group 211C. This is because monochrome printing is executed at a higher processing speed. That is, at the time of monochrome printing, only the black nozzle group 211K that discharges black (K) ink is used. For this reason, if the number of nozzles of the black nozzle group 211K that discharges black (K) ink is increased, the monochrome printing process can be performed at a higher speed.

  In the present embodiment, among the nozzles # 1 to # 180 of the black nozzle group 211K, the nozzles # 1 to # 60 are referred to as a first nozzle group 211K1 as shown in FIG. The nozzles # 61 to # 120 are referred to as a second nozzle group 211K2. The nozzles # 121 to # 180 are referred to as a third nozzle group 211K3.

  Here, the black nozzle group 211K corresponds to a “second nozzle group”. Further, the yellow nozzle group 211Y, the magenta nozzle group 211M, or the cyan nozzle group 211C corresponds to a “first nozzle group”. The black (K) ink ejected from the nozzles # 1 to # 180 of the black nozzle group 211K corresponds to a “second liquid”. The yellow (Y), magenta (M), or cyan (C) ink ejected from the nozzles # 1 to # 60 of the yellow nozzle group 211Y, magenta nozzle group 211M, or cyan nozzle group 211C is “first liquid. Is equivalent to.

  The nozzles # 1 to # 60 of the yellow nozzle group 211Y, the magenta nozzle group 211M, and the cyan nozzle group 211C and the nozzles # 1 to # 180 of the black nozzle group 211K are piezoelectric elements as drive elements for ejecting ink. An element (not shown) is provided. When a voltage having a predetermined time width is applied between the electrodes provided at both ends of the piezo element, the piezo element expands according to the voltage application time and deforms the side wall of the ink flow path. As a result, the volume of the ink flow path contracts according to the expansion and contraction of the piezo element, and the ink corresponding to this contraction becomes ink droplets, and the yellow nozzle group 211Y, the magenta nozzle group 211M, and the cyan nozzle group 211C. The nozzles # 1 to # 60 and the nozzles # 1 to # 180 of the black nozzle group 211K are discharged.

<System configuration>
FIG. 5 is a diagram illustrating an example of the system configuration of the inkjet printer 1. As shown in the figure, the inkjet printer 1 includes a buffer memory 122, an image buffer 124, a controller 126, a main memory 127, a communication interface 129, a carriage motor control unit 128, and a conveyance motor control unit 130. The head driving unit 132 is provided.

  The communication interface 129 is for the inkjet printer 1 to exchange data with an external computer 140 such as a personal computer. The communication interface 129 is communicably connected to the external computer 140 by wire or wireless, and receives various data such as print data transmitted from the computer 140.

  Various data such as print data received by the communication interface 129 are temporarily stored in the buffer memory 122. In the image buffer 124, the print data stored in the buffer memory 122 is sequentially stored. The print data stored in the image buffer 124 is sequentially sent to the head driving unit 132.

  The main memory 127 is composed of ROM, RAM, EEPROM, and the like. The main memory 127 stores various programs for controlling the inkjet printer 1 and various setting data.

  The controller 126 reads a control program, each setting data, and the like from the main memory 127, and controls the entire inkjet printer 1 according to the control program and various setting data. The controller 126 receives detection signals from various sensors such as the rotary encoder 134 and the linear encoder 51.

  When various data such as print data sent from the external computer 140 is received by the communication interface 129 and stored in the buffer memory 122, the controller 126 stores necessary information from the stored data in the buffer memory. Read from 122. Then, the controller 126 refers to the output from the linear encoder 51 and the rotary encoder 134 based on the read information, and according to the control program, the carriage motor control unit 128, the conveyance motor control unit 130, and the head drive unit. 132 and the like are controlled.

  The carriage motor control unit 128 controls the carriage motor 42 in accordance with a command from the controller 126. The carry motor control unit 130 controls the carry motor 15 in accordance with a command from the controller 126.

  The head drive unit 132 drives and controls the nozzles of each color provided in the head 21 based on the print data stored in the image buffer 124 in accordance with a command from the controller 126.

=== Conventional Problems and Solutions ===
<Conventional problems>
In such an ink jet printer 1, when monochrome printing is performed, all the nozzles # 1 to # 180 of the black nozzle group 211K are used in order to perform processing at high speed. However, when color printing is performed, some of the nozzles of the black nozzle group 211K are matched with the number of nozzles of other colors, that is, the yellow nozzle group 211Y, the magenta nozzle group 211M, and the cyan nozzle group 211C. Only nozzles were used. That is, in this embodiment, the black nozzle group 211K has 180 nozzles # 1 to # 180, but when color printing is performed, nozzles of nozzle groups 211Y, 211M, and 211C of other colors. In accordance with the number (60), only 60 nozzles were used. For this reason, in the nozzles of the black nozzle group, there is a problem that a difference occurs in the frequency of use, and the degree of consumption of some of the nozzles is remarkably increased.

<Solution>
Therefore, in the present embodiment, when color printing is performed, by switching the nozzles to be used in a nozzle group having a larger number of nozzles than other nozzle groups such as the black nozzle group 211K, some of the nozzles are changed. Prevents frequent use. The specific method will be described in detail below.

=== Printing operation ===
Here, the printing operation of the inkjet printer 1 will be described. Here, the case of “bidirectional printing” will be described as an example. FIG. 6 is a flowchart showing an example of the processing procedure of the printing operation of the inkjet printer 1. Each process described below is executed by the controller 126 reading a program from the main memory 127 and controlling the carriage motor control unit 128, the conveyance motor control unit 130, the head driving unit 132, and the like according to the program. Is done.

  Upon receiving print data from the computer 140, the controller 126 first performs a paper feed process to execute printing based on the print data (S102). The paper feed process is a process of supplying the medium S to be printed into the ink jet printer 1 and transporting it to a print start position (also referred to as a cue position). The controller 126 rotates the paper feed roller 13 to send the medium S to be printed to the transport roller 17A. The controller 126 rotates the transport roller 17A to position the medium S sent from the paper feed roller 13 at the print start position (near the upper side of the platen 14).

  Next, the controller 126 drives the carriage motor 42 through the carriage motor control unit 128 and moves the carriage 41 relative to the medium S to execute a printing process for printing on the medium S. Here, first, forward printing is performed to eject ink from the head 21 while moving the carriage 41 in one direction along the guide rail 46 (S104). The controller 126 drives the carriage motor 42 to move the carriage 41 and drives the head 21 based on the print data to eject ink. The ink ejected from the head 21 reaches the medium S and is formed as dots.

  After printing in this way, the controller 126 next executes a transport process for transporting the medium S by a predetermined amount (S106). Here, the controller 126 drives the conveyance motor 15 through the conveyance motor control unit 130 to rotate the conveyance roller 17A, and conveys the medium S by a predetermined amount relative to the head 21 in the conveyance direction. By this carrying process, the head 21 can print in an area different from the previously printed area.

  After performing the carrying process in this manner, the controller 126 determines whether or not to discharge paper (S108). Here, if there is no other data to be printed on the medium S being printed, the controller 126 executes a paper discharge process (S116). On the other hand, if there is other data to be printed on the medium S being printed, the controller 126 performs the backward printing without performing the paper discharge process (S110). In this backward printing, printing is performed by moving the carriage 41 along the guide rail 46 in the direction opposite to the previous forward printing. Again, the controller 126 rotates the carriage motor 42 through the carriage motor control unit 128 to move the carriage 41 in the reverse direction, and also drives the head 21 based on the print data to eject ink and print. Apply.

  After performing the return pass printing, a carrying process is executed (S112), and then a paper discharge determination is made (S114). Here, if there is other data to be printed on the medium S being printed, the paper discharge process is not performed, the process returns to step S104, and the forward printing is executed again (S104). On the other hand, if there is no other data to be printed on the medium S being printed, a paper discharge process is executed (S116).

  After the paper discharge process is performed, next, a print end determination is performed to determine whether or not to end printing (S118). Here, based on the print data from the computer 140, it is checked whether there is a medium S to be printed next. If there is a medium S to be printed next, the process returns to step S102, the paper feed process is executed again, and printing is started. On the other hand, if there is no medium S to be printed next, the printing process is terminated.

=== How to use the nozzle ===
Next, a method of using the nozzles of the black nozzle group 211K when performing color printing in the inkjet printer 1 according to the present embodiment will be described. In the present embodiment, the black nozzle group 211K has a larger number of nozzles than the other color nozzle groups, that is, the yellow nozzle group 211Y, the magenta nozzle group 211M, and the cyan nozzle group 211C. In printing or return pass printing, the nozzle to be used is switched. Hereinafter, an example of a method for switching the used nozzles of the black nozzle group at the time of color printing will be described with reference to three examples of the first to third embodiments. Note that the method of using the nozzles of the black nozzle group 211K when performing color printing is not limited to these first to third embodiments.

<First Embodiment>
FIG. 7 illustrates a first embodiment of a method of using the nozzles # 1 to # 180 of the black nozzle group 211K when performing color printing. Here, the 180 nozzles # 1 to # 180 of the black nozzle group 211K are divided into the three groups described in FIG. 4, that is, the first nozzle group 211K1, the second nozzle group 211K2, and the third nozzle group 211K3. To use.

  First, it is assumed that the positional relationship between the medium S and the head 21 is a positional relationship corresponding to “pass 1” as shown in FIG. At this time, it is assumed that the third nozzle group 211K3 is used in the black nozzle group 211K. As a result, the black (K) ink ejected from the nozzles # 121 to # 180 of the third nozzle group 211K3 by using the third nozzle group 211K3, as shown on the right side in FIG. A black (K) pattern is formed corresponding to the region P1. At this time, a cyan (C) pattern is also formed corresponding to the region P1 on the medium S using the cyan nozzle group 211C.

  After the pattern is formed in this way, the medium S is conveyed by a predetermined amount. It is assumed that the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 2” by this conveyance. At this time, again using the third nozzle group 211K3, the medium S as shown on the right side in the drawing by the black (K) ink ejected from the nozzles # 121 to # 180 of the third nozzle group 211K3. A black (K) pattern is formed corresponding to the upper region P2. At this time, a magenta (M) pattern is formed corresponding to the region P1 on the medium S using the magenta nozzle group 211M. Further, a cyan (C) pattern is formed corresponding to the region P2 on the medium S using the cyan nozzle group 211C.

  After the pattern is formed in this way, the medium S is conveyed by a predetermined amount. It is assumed that the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 3” by this conveyance. At this time, again using the third nozzle group 211K3, the medium S as shown on the right side in the drawing by the black (K) ink ejected from the nozzles # 121 to # 180 of the third nozzle group 211K3. A black (K) pattern is formed corresponding to the upper region P3. At this time, a yellow (Y) pattern is formed corresponding to the region P1 on the medium S using the yellow nozzle group 211Y. Further, a magenta (M) pattern is formed corresponding to the region P2 on the medium S using the magenta nozzle group 211M. Further, a cyan (C) pattern is also formed corresponding to the region P3 on the medium S using the cyan nozzle group 211C.

  Then, after the pattern is formed in this way, the medium S is conveyed by a predetermined amount. It is assumed that the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 4” by this conveyance. Here, the black nozzle group 211K is not used, and a black (K) pattern is not formed. On the other hand, here, a yellow (Y) pattern is formed corresponding to the region P2 on the medium S using the yellow nozzle group 211Y. Further, a magenta (M) pattern is formed corresponding to the region P3 on the medium S using the magenta nozzle group 211M. Further, a cyan (C) pattern is formed corresponding to the region P4 on the medium S using the cyan nozzle group 211C.

  Thereafter, the medium S is transported by a predetermined amount, and the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 5”. At this time, black (K) ink ejected from the nozzles # 61 to # 120 of the second nozzle group 211K2 by using the second nozzle group 211K2 in the black nozzle group 211K, on the right side in FIG. As shown, a black (K) pattern is formed corresponding to the region P4 on the medium S. At this time, a yellow (Y) pattern is formed corresponding to the region P3 on the medium S using the yellow nozzle group 211Y. Further, a magenta (M) pattern is formed corresponding to the region P4 on the medium S using the magenta nozzle group 211M. A cyan (C) pattern is also formed corresponding to the region P5 on the medium S using the cyan nozzle group 211C.

  After the pattern is formed in this way, the medium S is conveyed by a predetermined amount. It is assumed that the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 6” by this conveyance. At this time, again using the second nozzle group 211K2, the medium S as shown on the right side in the drawing by the black (K) ink ejected from the nozzles # 61 to # 120 of the second nozzle group 211K2 respectively. A black (K) pattern is formed corresponding to the upper region P5. At this time, a yellow (Y) pattern is formed corresponding to the region P4 on the medium S using the yellow nozzle group 211Y. Further, a magenta (M) pattern is formed corresponding to the region P5 on the medium S using the magenta nozzle group 211M. Further, a cyan (C) pattern is also formed corresponding to the region P6 on the medium S using the cyan nozzle group 211C.

  Then, after the pattern is formed in this way, the medium S is conveyed by a predetermined amount. It is assumed that the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 7” by this conveyance. At this time, again using the second nozzle group 211K2, the medium S as shown on the right side in the drawing by the black (K) ink ejected from the nozzles # 61 to # 120 of the second nozzle group 211K2 respectively. A black (K) pattern is formed corresponding to the upper region P6. At this time, a yellow (Y) pattern is formed corresponding to the region P5 on the medium S using the yellow nozzle group 211Y. Further, a magenta (M) pattern is formed corresponding to the region P6 on the medium S by using the magenta nozzle group 211M. Further, a cyan (C) pattern is also formed corresponding to the area P7 on the medium S using the cyan nozzle group 211C.

  After the pattern is formed in this way, the medium S is conveyed by a predetermined amount. It is assumed that the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 8” by this conveyance. Here, the black nozzle group 211K is not used, and a black (K) pattern is not formed. On the other hand, here, a yellow (Y) pattern is formed corresponding to the region P6 on the medium S using the yellow nozzle group 211Y. Further, a magenta (M) pattern is formed corresponding to the region P7 on the medium S using the magenta nozzle group 211M. Further, a cyan (C) pattern is formed corresponding to the region P8 on the medium S using the cyan nozzle group 211C.

  Thereafter, the medium S is transported by a predetermined amount, and the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 9”. At this time, black (K) ink ejected from the nozzles # 1 to # 60 of the first nozzle group 211K1 by using the first nozzle group 211K1 in the black nozzle group 211K on the right side in FIG. As shown, a black (K) pattern is formed corresponding to the region P7 on the medium S. At this time, a yellow (Y) pattern is formed corresponding to the region P7 on the medium S using the yellow nozzle group 211Y. Further, a magenta (M) pattern is formed corresponding to the region P8 on the medium S using the magenta nozzle group 211M. Further, a cyan (C) pattern is also formed corresponding to the region P9 on the medium S using the cyan nozzle group 211C.

  After the pattern is formed in this way, the medium S is conveyed by a predetermined amount. It is assumed that the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 10” by this conveyance. At this time, again using the first nozzle group 211K1, the medium S as shown on the right side in the drawing by black (K) ink ejected from the nozzles # 1 to # 60 of the first nozzle group 211K1. A black (K) pattern is formed corresponding to the upper region P8. At this time, a yellow (Y) pattern is formed corresponding to the region P8 on the medium S using the yellow nozzle group 211Y. Further, a magenta (M) pattern is formed corresponding to the region P9 on the medium S using the magenta nozzle group 211M. A cyan (C) pattern is also formed corresponding to the region P10 on the medium S using the cyan nozzle group 211C.

  Then, after the pattern is formed in this way, the medium S is conveyed by a predetermined amount. It is assumed that the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 11” by this conveyance. At this time, again using the first nozzle group 211K1, the medium S as shown on the right side in the drawing by black (K) ink ejected from the nozzles # 1 to # 60 of the first nozzle group 211K1. A black (K) pattern is formed corresponding to the upper region P9. At this time, a yellow (Y) pattern is formed corresponding to the region P9 on the medium S using the yellow nozzle group 211Y. Further, a magenta (M) pattern is formed corresponding to the area P10 on the medium S using the magenta nozzle group 211M. Further, a cyan (C) pattern is also formed corresponding to the area P11 on the medium S using the cyan nozzle group 211C.

  By performing color printing while switching the nozzles (here, the first nozzle group 211K1 to the third nozzle group 211K3) to be used for the nozzles # 1 to # 180 of the 180 black nozzle groups 211K in this way. Even if the black nozzle group 211K has a larger number of nozzles than the other color nozzle groups, that is, the yellow nozzle group 211Y, the magenta nozzle group 211M, and the cyan nozzle group 211C, the frequency of use of some nozzles Can be prevented from becoming very high.

  Here, the operation of ejecting black (K) ink toward the medium S using the nozzles # 1 to # 60 of the first nozzle group 211K1 of the black nozzle group 211K is referred to as “first liquid ejection operation”. Is directed toward the medium S using the other nozzle groups of the black nozzle group 211K, that is, the nozzles # 61 to # 120 of the second nozzle group 211K2 and the nozzles # 121 to # 180 of the third nozzle group 211K3. The operation of ejecting black (K) ink corresponds to a “second liquid ejection operation”.

Second Embodiment
8A to 8D are explanatory diagrams of the posture of the medium S during printing. FIG. 8A is an explanatory diagram for pass 1. FIG. FIG. 8B is an explanatory diagram for pass 3. FIG. 8C is an explanatory diagram for the path 4 and later. FIG. 8D is an explanatory diagram when the trailing edge of the medium S is printed.

  As shown in FIGS. 8A and 8B, in pass 1 to pass 3, the leading edge of the medium S (the end on the downstream side in the transport direction of the medium S) does not reach the paper discharge roller 17B. It is conveyed only by the conveyance roller 17A. For this reason, the leading edge of the medium S is lifted from the platen 14 as shown in FIGS. 8A and 8B.

  If the pattern is formed in a state where the medium S is lifted from the platen 14, the pattern is formed in a shifted manner, so that the image quality is deteriorated. In the first embodiment described above, the pattern is formed using the third nozzle group 211K3 of the black nozzle group 211K for the areas P1 to P3 on the leading end side of the medium S. As a result, in the wide area (area P1 to area P3) on the leading end side of the medium S, a pattern is formed with the medium S floating from the platen 14, and the image quality of black is deteriorated. Similarly, in the first embodiment described above, of the black nozzle group 211K, the first nozzle group 211K1 is used with respect to the region on the rear end (end on the upstream side in the transport direction of the medium S) side of the medium S. A pattern is formed. As a result, a pattern is formed in a state where the medium S is lifted from the platen 14 in a wide area on the rear end side of the medium S, and the image quality of black is deteriorated.

  On the other hand, in the second embodiment described below, a pattern is formed in a region on the leading end side of the medium S using the first nozzle group 211K1 that is the nozzle group on the downstream side in the transport direction of the black nozzle group 211K. Thereby, when forming the pattern in the area P2 and the area P3, since the leading edge of the medium S reaches the paper discharge roller 17B, the pattern can be formed in a state in which the medium S does not float from the platen 14, and therefore the area P2 and The image quality of black in the region P3 is improved. In the second embodiment described below, a pattern is formed in the area on the rear end side of the medium S using the third nozzle group 211K3 that is the nozzle group upstream of the black nozzle group 211K in the transport direction. Thereby, on the rear end side of the medium S, the region where the image quality of black is deteriorated is narrower than that in the first embodiment.

  FIG. 9 illustrates a second embodiment of a method of using the nozzles # 1 to # 180 of the black nozzle group 211K when performing color printing. Here, as in the first embodiment described above, the 180 nozzles # 1 to # 180 of the black nozzle group 211K are replaced with the three groups described in FIG. 4, that is, the first nozzle group 211K1 and the second nozzle. The group 211K2 and the third nozzle group 211K3 are used separately. In the following description of the second embodiment, description of the method of using the color nozzle group other than the black nozzle group is omitted.

  First, it is assumed that the positional relationship between the medium S and the head 21 is a positional relationship corresponding to “pass 1” as shown in FIG. Here, the black nozzle group 211K is not used, and a black (K) pattern is not formed.

  After pass 1, the medium S is conveyed by a predetermined amount. It is assumed that the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 2” by this conveyance. Also at this time, the black nozzle group 211K is not used, and a black (K) pattern is not formed.

  After pass 2, the medium S is conveyed by a predetermined amount. It is assumed that the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 3” by this conveyance. At this time, it is assumed that the first nozzle group 211K1, which is the nozzle group on the downstream side in the transport direction, of the black nozzle group 211K is used. As a result, the black (K) ink ejected from the nozzles # 1 to # 60 of the first nozzle group 211K1 using the first nozzle group 211K1 is applied to the medium S as shown on the right side in the drawing. A black (K) pattern is formed corresponding to the region P1. In pass 1 to pass 3, since the leading edge of the medium S does not reach the paper discharge roller 17B, the image quality of the patterns formed up to this time may not be good.

  Then, after the pattern is formed in this way, the medium is conveyed by a predetermined amount. It is assumed that the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 4” by this conveyance. At this time, again using the first nozzle group 211K1, the medium S as shown on the right side in the drawing by black (K) ink ejected from the nozzles # 1 to # 60 of the first nozzle group 211K1. A black (K) pattern is formed corresponding to the upper region P2. At this time, since the leading end of the medium S passes through the paper discharge roller 17B, the medium S does not float from the platen 14. For this reason, the pattern formed in the region P2 has better image quality than the pattern formed in the region P2 of the first embodiment.

  Thereafter, the medium S is transported by a predetermined amount, and the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 5”. At this time, not only the first nozzle group 211K1 but also the second nozzle group 211K2 is used in the black nozzle group 211K. That is, the area on the medium S as shown on the right side in the drawing by the black (K) ink ejected from the nozzles # 1 to # 60 of the first nozzle group 211K1 using the first nozzle group 211K1. A black (K) pattern is formed corresponding to P3, and the second nozzle group 211K2 is used to eject black (K) ink from each nozzle # 61 to # 120 of the second nozzle group 211K2. As shown on the right side of the figure, a black (K) pattern is formed corresponding to the area P4 on the medium S. As described above, the two groups, the first nozzle group 211K1 and the second nozzle group 211K2, are used because the nozzle group to be used is switched from the first nozzle group 211K1 to the second nozzle group 211K2 in the next pass. is there.

  After the pattern is formed in this way, the medium S is transported by a predetermined amount, and the positional relationship between the medium S and the head 21 becomes the positional relationship corresponding to “pass 6”. At this time, the black (K) ink ejected from the nozzles # 61 to # 120 of the second nozzle group 211K2 using the second nozzle group 211K2, as shown on the right side in FIG. A black (K) pattern is formed corresponding to the region P5.

  After the pattern is formed in this way, the medium S is transported by a predetermined amount, and the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 7”. At this time, the black (K) ink ejected from the nozzles # 61 to # 120 of the second nozzle group 211K2 using the second nozzle group 211K2, as shown on the right side in FIG. A black (K) pattern is formed corresponding to the region P6.

  Thereafter, the medium S is conveyed by a predetermined amount, and the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 8”. At this time, not only the second nozzle group 211K2 but also the third nozzle group 211K3 is used in the black nozzle group 211K. That is, the area on the medium S as shown on the right side of the drawing by the black (K) ink ejected from the nozzles # 61 to # 120 of the second nozzle group 211K2 using the second nozzle group 211K2. A black (K) pattern is formed corresponding to P7, and the third nozzle group 211K3 is used to eject black (K) ink from the nozzles # 121 to # 180 of the third nozzle group 211K3. As shown on the right side of the figure, a black (K) pattern is formed corresponding to the region P8 on the medium S. In this way, the second nozzle group 211K2 and the third nozzle group 211K3, which are two groups, are used because the nozzle group to be used is switched from the second nozzle group 211K2 to the third nozzle group 211K3 in the next pass. is there.

  After the pattern is formed in this manner, the medium S is transported by a predetermined amount, and the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 9”. At this time, the black (K) ink ejected from the nozzles # 121 to # 180 of the third nozzle group 211K3 using the third nozzle group 211K3, as shown on the right side in FIG. A black (K) pattern is formed corresponding to the region P9.

  After the pattern is formed in this manner, the medium S is conveyed by a predetermined amount, and the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 10”. At this time, the rear end of the medium S passes through the transport roller 17A, and the medium S is lifted from the platen 14 as shown in FIG. 8D. At this time, the black (K) ink ejected from the nozzles # 121 to # 180 of the third nozzle group 211K3 using the third nozzle group 211K3, as shown on the right side in FIG. A black (K) pattern is formed corresponding to the region P10. Thereby, the printing of the black pattern is completed.

  In pass 11 and pass 12, the black nozzle group 211K is not used, and a black (K) pattern is not formed. Therefore, the pattern is formed only in the region P10 in a state where the rear end of the medium S is lifted from the platen 14. If the first nozzle group 211K1 on the downstream side in the transport direction is used when printing the rear end of the medium S, a pattern is formed in the regions P8 to P10 in pass 10 to pass 12, and the second Compared with the embodiment, the area with poor image quality is widened.

  As described above, also in the second embodiment, it is possible to prevent the usage frequency of some nozzles from becoming very high by switching the nozzles to be used. The first nozzle group 211K1 on the downstream side in the transport direction is used when forming a pattern at the leading edge of the medium S, and the third nozzle group 211K3 on the upstream side in the transport direction is used when forming a pattern on the rear end of the medium S. The image quality can be improved by switching the nozzles.

<Third Embodiment>
FIG. 10 illustrates a third embodiment of a method of using the nozzles # 1 to # 180 of the black nozzle group 211K when performing color printing. Here, as in the first embodiment described above, the 180 nozzles # 1 to # 180 of the black nozzle group 211K are replaced with the three groups described in FIG. 4, that is, the first nozzle group 211K1 and the second nozzle. The group 211K2 and the third nozzle group 211K3 are used separately.

  First, it is assumed that the positional relationship between the medium S and the head 21 is a positional relationship corresponding to “pass 1” as shown in FIG. At this time, it is assumed that the third nozzle group 211K3 is used in the black nozzle group 211K. As a result, the black (K) ink ejected from the nozzles # 121 to # 180 of the third nozzle group 211K3 by using the third nozzle group 211K3, as shown on the right side in FIG. A black (K) pattern is formed corresponding to the region P1. At this time, a cyan (C) pattern is also formed using the cyan nozzle group 211C corresponding to the region P1 on the medium S.

  After the pattern is formed in this way, the medium S is conveyed by a predetermined amount. It is assumed that the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 2” by this conveyance. Here, the black nozzle group 211K is not used, and a black (K) pattern is not formed. On the other hand, here, a magenta (M) pattern is formed in the area P1 on the medium S using the magenta nozzle group 211M. Further, a cyan (C) pattern is formed in the area P2 on the medium S using the cyan nozzle group 211C.

  Thereafter, the medium S is transported by a predetermined amount, and the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 3”. At this time, the second nozzle group 211K2 is used in the black nozzle group 211K. As a result, the black (K) ink ejected from the nozzles # 61 to # 120 of the second nozzle group 211K2 by using the second nozzle group 211K2 on the medium S as shown on the right side in FIG. A black (K) pattern is formed corresponding to the region P2. At this time, a yellow (Y) pattern is formed in the region P1 on the medium S using the yellow nozzle group 211Y. Further, a magenta (M) pattern is formed in the area P2 on the medium S using the magenta nozzle group 211M. Further, a cyan (C) pattern is also formed in the area P3 on the medium S using the cyan nozzle group 211C.

  Then, after the pattern is formed in this way, the medium S is conveyed by a predetermined amount. By this conveyance, the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 4”. Here, the black nozzle group 211K is not used, and a black (K) pattern is not formed. On the other hand, here, a yellow (Y) pattern is formed in the region P2 on the medium S using the yellow nozzle group 211Y. Further, a magenta (M) pattern is formed in the region P3 on the medium S using the magenta nozzle group 211M. Further, a cyan (C) pattern is formed in the region P4 on the medium S using the cyan nozzle group 211C.

  Thereafter, the medium S is transported by a predetermined amount, and the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 5”. At this time, among the black nozzle group 211K, the first nozzle group 211K1 is used. As a result, the black (K) ink ejected from the nozzles # 1 to # 60 of the first nozzle group 211K1 by using the first nozzle group 211K1 on the medium S as shown on the right side in FIG. A black (K) pattern is formed corresponding to the region P3. At this time, a yellow (Y) pattern is formed in the region P3 on the medium S using the yellow nozzle group 211Y. Further, a magenta (M) pattern is formed in a region P4 on the medium S using the magenta nozzle group 211M. Further, a cyan (C) pattern is also formed in the area P5 on the medium S using the cyan nozzle group 211C.

  After the pattern is formed in this way, the medium S is conveyed by a predetermined amount. By this conveyance, the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 6”. At this time, among the black nozzle group 211K, the first nozzle group 211K1 and the second nozzle group 211K2 are used. As a result, the black (K) ink ejected from the nozzles # 1 to # 60 of the first nozzle group 211K1 by using the first nozzle group 211K1 on the medium S as shown on the right side in FIG. A black (K) pattern is formed corresponding to the region P4. At this time, the second nozzle group 211K2 is used to cause the medium to be ejected from the nozzles # 61 to # 120 of the second nozzle group 211K2 by the black (K) ink as shown on the right side of the drawing. A black (K) pattern is formed corresponding to the region P5 on S. At this time, a yellow (Y) pattern is formed in the region P4 on the medium S using the yellow nozzle group 211Y. Further, a magenta (M) pattern is formed in the region P5 on the medium S using the magenta nozzle group 211M. Further, a cyan (C) pattern is also formed in a region P6 on the medium S using the cyan nozzle group 211C.

  Then, the medium S is transported by a predetermined amount, and the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 7”. At this time, among the black nozzle group 211K, the third nozzle group 211K3 is used. As a result, the black (K) ink ejected from the nozzles # 121 to # 180 of the third nozzle group 211K3 by using the third nozzle group 211K3, as shown on the right side in FIG. A black (K) pattern is formed corresponding to the region P7. At this time, a yellow (Y) pattern is formed in the region P5 on the medium S using the yellow nozzle group 211Y. Further, a magenta (M) pattern is formed in the region P6 on the medium S using the magenta nozzle group 211M. Further, a cyan (C) pattern is also formed in the region P7 on the medium S using the cyan nozzle group 211C.

  Then, after the pattern is formed in this way, the medium S is conveyed by a predetermined amount. It is assumed that the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 8” by this conveyance. At this time, among the black nozzle group 211K, the first nozzle group 211K1 is used. As a result, the black (K) ink ejected from the nozzles # 1 to # 60 of the first nozzle group 211K1 by using the first nozzle group 211K1 on the medium S as shown on the right side in FIG. A black (K) pattern is formed corresponding to the region P6. At this time, a yellow (Y) pattern is formed in the region P6 on the medium S using the yellow nozzle group 211Y. Further, a magenta (M) pattern is formed in the region P7 on the medium S using the magenta nozzle group 211M. Further, a cyan (C) pattern is also formed in the region P8 on the medium S using the cyan nozzle group 211C.

  Thereafter, the medium S is transported by a predetermined amount, and the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 9”. At this time, among the black nozzle group 211K, the second nozzle group 211K2 and the third nozzle group 211K3 are used. As a result, the black (K) ink ejected from the nozzles # 61 to # 120 of the second nozzle group 211K2 by using the second nozzle group 211K2 on the medium S as shown on the right side in FIG. A black (K) pattern is formed corresponding to the region P8. At this time, as shown on the right side of the drawing, black (K) ink is ejected from the nozzles # 121 to # 180 of the third nozzle group 211K3 using the third nozzle group 211K3. A black (K) pattern is formed corresponding to the region P9 on S. At this time, a yellow (Y) pattern is formed in the region P7 on the medium S using the yellow nozzle group 211Y. Further, a magenta (M) pattern is formed in the region P8 on the medium S using the magenta nozzle group 211M. Further, a cyan (C) pattern is also formed in a region P9 on the medium S using the cyan nozzle group 211C.

  Then, after the pattern is formed in this way, the medium S is conveyed by a predetermined amount. It is assumed that the positional relationship between the medium S and the head 21 becomes a positional relationship corresponding to “pass 10” by this conveyance. Here, the black nozzle group 211K is not used, and a black (K) pattern is not formed. On the other hand, here, a yellow (Y) pattern is formed in the region P8 on the medium S using the yellow nozzle group 211Y. Further, a magenta (M) pattern is formed in the region P9 on the medium S using the magenta nozzle group 211M. Further, a cyan (C) pattern is formed in the region P10 on the medium S using the cyan nozzle group 211C.

  By sequentially switching the 180 nozzles # 1 to # 180 of the black nozzle group 211K for each pass in this way, the usage frequency of some of the nozzles in the black nozzle group 211K becomes very high. Can be prevented.

  Here, the operation of ejecting black (K) ink toward the medium S using the nozzles # 1 to # 60 of the first nozzle group 211K1 of the black nozzle group 211K is referred to as “first liquid ejection operation”. Is directed toward the medium S using the other nozzle groups of the black nozzle group 211K, that is, the nozzles # 61 to # 120 of the second nozzle group 211K2 and the nozzles # 121 to # 180 of the third nozzle group 211K3. The operation of ejecting black (K) ink corresponds to a “second liquid ejection operation”.

=== Summary ===
As described above, in the present embodiment, even when the number of nozzles of the black nozzle group 211K is larger than that of the other nozzle groups, that is, the yellow nozzle group 211Y, the magenta nozzle group 211M, and the cyan nozzle group 211C, By performing color printing while switching the nozzles used for each pass (here, the first nozzle group 211K1 to the third nozzle group 211K3), it is possible to prevent the usage frequency of some nozzles from becoming very high. Can do.

=== Other Embodiments ===
As described above, the embodiment has been described. However, the above-described embodiment is for facilitating the understanding of the present invention, and is not intended to limit the present invention. The present invention can be changed or improved without departing from the gist thereof, and needless to say, the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About liquid>
In the embodiment described above, the case of ink has been described as an example of “liquid” (“first liquid” and “second liquid”), but “liquid” (“first liquid” here) "And" second liquid "), any type of liquid may be used.

<About liquid ejection device>
In the above-described embodiment, the “liquid ejecting apparatus” has been described by taking an example of an apparatus that ejects ink as a liquid toward a medium. However, in the “liquid ejecting apparatus” described here, liquid is ejected. Any type of device may be used as long as it is a device. Specifically, a textile printing apparatus (method) for patterning a fabric, a circuit board manufacturing apparatus (method) for forming a circuit pattern on a circuit board, and a DNA chip by applying a solution of DNA to a chip. It may be a DNA chip manufacturing apparatus (method) for manufacturing the display device, a display manufacturing apparatus (method) such as an organic EL (Organic Light Emitting Diode) display, or the like.

<About the first nozzle group and the second nozzle group>
In the above-described embodiment, the black nozzle group 211K is taken as an example of the “second nozzle group”, and other nozzle groups excluding the black nozzle group 211K, ie, here, the yellow nozzle group is used as the “first nozzle group”. The 211Y, the magenta nozzle group 211M, or the cyan nozzle group 211C has been described as an example. However, the “first nozzle group” and the “second nozzle group” here are not necessarily limited to such nozzle groups. Absent. That is, any type of nozzle group may be used as long as the number of nozzles in the “second nozzle group” is larger than the number of nozzles in the “first nozzle group”.

<About the first liquid and the second liquid>
In the embodiment described above, yellow (Y), magenta (M), and cyan (C) inks are used as examples of the “first liquid”, and black (K) is used as the “second liquid”. Although the ink has been described as an example, the “first liquid” and the “second liquid” here are not necessarily limited to such a combination. In other words, the “first liquid” and the “second liquid” may be any liquid as long as they are of different types. That is, if the “first liquid” and the “second liquid” are inks, inks of other colors except black (K), yellow (Y), magenta (M), and cyan (C) are used. It does not matter.

1 is an external view of an ink jet printer. The internal block diagram of an inkjet printer. Explanatory drawing of the conveyance part of an inkjet printer. Explanatory drawing of the nozzle of an inkjet printer. 1 is an explanatory diagram of a system configuration of an inkjet printer. FIG. 6 is a flowchart for explaining a printing operation. Explanatory drawing explaining 1st Embodiment of the usage method of a nozzle. 8A to 8D are explanatory views of the posture of the medium S during printing. FIG. 8A is an explanatory diagram for pass 1. FIG. FIG. 8B is an explanatory diagram for pass 3. FIG. 8C is an explanatory diagram in the case of pass 4 and after. FIG. 8D is an explanatory diagram when the trailing edge of the medium S is printed. Explanatory drawing explaining 2nd Embodiment of the usage method of a nozzle. Explanatory drawing explaining 3rd Embodiment of the usage method of a nozzle.

Explanation of symbols

1 Inkjet printer, 2 operation panel, 3 paper discharge unit, 4 paper supply unit,
5 operation buttons, 6 indicator lamps, 7 paper discharge tray, 8 paper feed tray,
15 transport motor, 17A transport roller, 21 head, 31 pump device,
35 capping device, 41 carriage, 42 carriage motor,
44 pulley, 45 timing belt, 46 guide rail,
48 ink cartridges, 49 cartridge mounting parts,
51 linear encoder, 122 buffer memory, 124 image buffer,
126 controller, 127 main memory, 128 carriage motor control unit,
129 communication interface, 130 transport motor controller,
132 head drive unit, 134 rotary encoder, 140 computer,
211C cyan nozzle group, 211M magenta nozzle group,
211Y yellow nozzle group, 211K black nozzle group,
211K1 first nozzle group, 211K2 second nozzle group, 211K3 third nozzle group

Claims (9)

(A) a transport unit that performs a transport operation of transporting the medium along a predetermined direction;
(B) a first nozzle group having a plurality of nozzles that are arranged along the predetermined direction and that discharge a first liquid toward the medium when moved relative to the medium;
(C) A type different from the first liquid toward the medium when it is arranged along the predetermined direction and moves relative to the medium integrally with the first nozzle group. A second nozzle group having more nozzles for discharging the second liquid than the first nozzle group;
(D) the transport operation by the transport unit;
When the first nozzle group and the second nozzle group are moving relative to the medium, at least one of the first liquid and the second liquid is directed toward the medium. A controller that alternately performs a liquid discharge operation to be discharged,
When both the first liquid and the second liquid are discharged onto one medium, the liquid discharge operation is performed by either of the nozzles of the first nozzle group and the nozzles of the second nozzle group. A first liquid ejection operation for ejecting the first liquid and the second liquid toward the medium using a part of the nozzles; and a nozzle of the first nozzle group and a nozzle of the second nozzle group A controller that performs a second liquid ejection operation for ejecting the first liquid and the second liquid toward the medium using another nozzle different from the some of the nozzles;
A liquid discharge apparatus comprising (E). The some nozzles are located downstream of the other nozzles in the predetermined direction,
2. The second liquid is discharged from the partial nozzles when the second liquid is discharged toward the downstream end of the medium in the predetermined direction. The liquid discharge apparatus as described. The some nozzles are located downstream of the other nozzles in the predetermined direction,
The second liquid is discharged from the other nozzle when the second liquid is discharged toward the upstream end of the medium in the predetermined direction. The liquid discharge apparatus according to 1.   The liquid ejection apparatus according to claim 1, wherein the number of nozzles of the second nozzle group is an integral multiple of the number of nozzles of the first nozzle group.   The liquid discharge apparatus according to claim 1, wherein the first nozzle group and the second nozzle group are arranged in parallel to each other.   When the liquid is disposed along the predetermined direction and moves relative to the medium, a third liquid of a type different from the first liquid and the second liquid is directed toward the medium. The liquid ejection apparatus according to claim 1, further comprising a third nozzle group having a smaller number of nozzles to be ejected than the second nozzle group.   The number of the partial nozzles of the second nozzle group used in the first liquid discharge operation is different from the partial nozzles of the second nozzle group used in the second liquid discharge operation. The liquid discharge apparatus according to claim 1, wherein the number of the nozzles is equal.   The liquid ejecting apparatus according to claim 1, wherein the first liquid and the second liquid are inks.   The liquid ejecting apparatus according to claim 8, wherein the first liquid and the second liquid are inks having different colors.