Inkjet printer, cleaning method and program

Abstract

To provide a technology that improves the cleaning performance of the nozzle surface of a head while suppressing increases in size and ink consumption.SOLUTION: An inkjet printer includes: a plurality of heads each having a nozzle surface 322 that ejects ink; a cleaning device 80 having a wiping member 81 capable of absorbing ink and cleaning the nozzle surface 322 by pressing the wiping member 81 against the nozzle surface 322; and a controller that controls the cleaning device 80. The controller selects a head 320_1 to be cleaned from among the plurality of heads. The controller controls the cleaning device 80 so that a used region 811 of the wiping member 81 that was used to clean the nozzle surface of the head selected before the head 320_1 to be cleaned is also used to clean the nozzle surface 322 of the head 320_1 to be cleaned.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to an inkjet printer, a cleaning method, and a program. [Background technology]

[0002] Inkjet printers have ink heads (hereinafter referred to as "heads") that eject ink. Ink mist or droplets adhere to the nozzle surface of the head due to ink ejection (printing), purging, etc. Japanese Patent Application Laid-Open No. 2021-192967 (Patent Document 1) discloses an inkjet recording device that uses a wiping member that absorbs ink to wipe away ink that has adhered to the nozzle surface. By wiping off the ink that has adhered to the nozzle surface, the nozzle surface is cleaned.

[0003] Ink adhering to the nozzle surface dries and thickens over time. As the ink thickens, its ability to be cleaned by the wiping member may decrease. As a result, ink that could not be wiped away by the wiping member remains around the nozzles. If this ink accumulates on the nozzle surface, the ink may be ejected in an unintended direction. This can result in a decrease in image quality.

[0004] Increasing the pressing force of the wiping member against the nozzle surface improves the cleaning ability of the wiping member. However, increasing the pressing force of the wiping member against the nozzle surface increases wear on the nozzle surface. As a result, the durability of the head decreases. Furthermore, when wiping the nozzle surface by moving the wiping member relative to the nozzle surface, slowing the relative speed increases the contact time between the nozzle surface and the wiping member, improving cleaning ability. However, increasing the contact time between the nozzle surface and the wiping member increases the time required for maintenance (i.e., downtime of the inkjet printer). Therefore, there is a need for technology that improves cleaning ability while maintaining the durability of the head and suppressing increases in downtime.

[0005] Japanese Patent Laid-Open Publication No. 2005-161129 (Patent Document 2) discloses a device that sprays cleaning liquid onto a wiping member. Supplying cleaning liquid to the wiping member (wetting it) improves the liquid absorption of the wiping member, lowers the viscosity of the ink, allows the cleaning liquid to penetrate into the interface between the adhering ink and the nozzle surface, and increases the contact area between the wiping member and the nozzle surface. This improves cleaning performance.

[0006] Japanese Patent Laid-Open Publication No. 2006-297651 (Patent Document 3) discloses an inkjet printer that ejects ink from the nozzles when a wiping member is in contact with the nozzle surface. Wetting the wiping member with ink also improves the liquid absorption of the wiping member, reduces the viscosity of the ink, allows low-viscosity ink to penetrate the interface between the adhering ink and the nozzle surface, and increases the contact area between the wiping member and the nozzle surface. This improves cleaning performance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2021-192967 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-161129 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-297651 Summary of the Invention [Problem to be solved by the invention]

[0008] The device disclosed in Patent Document 2 requires a member for spraying the cleaning liquid, which increases the size of the device. Also, it is technically difficult to spray the cleaning liquid uniformly onto the wiping member.

[0009] The inkjet printer disclosed in Patent Document 3 intentionally ejects ink onto the wiping member to wet the wiping member, which increases ink consumption.

[0010] In order to solve these problems, one object of the present disclosure is to improve the cleaning performance of the nozzle surface of the head while suppressing increases in size and ink consumption. [Means for solving the problem]

[0011] An inkjet printer according to one aspect of the present disclosure includes a plurality of heads each having a nozzle surface that ejects ink, a cleaning device having a wiping member capable of absorbing ink and cleaning the nozzle surface by pressing the wiping member against the nozzle surface, and a controller that controls the cleaning device. The controller selects a head to be cleaned from the plurality of heads. The controller controls the cleaning device so that a first region of the wiping member used to clean the nozzle surface of the head selected before the head to be cleaned is also used to clean the nozzle surface of the head to be cleaned.

[0012] Preferably, the wiping member is a web. Preferably, the ink is a UV ink that is cured by ultraviolet light.

[0013] Preferably, when a predetermined condition is satisfied, the controller controls the cleaning device so that the first area is also used to clean the nozzle surface of the head to be cleaned. When the predetermined condition is not satisfied, the controller controls the cleaning device so that the second area of ​​the wiping member that is not used to clean the nozzle surface is used to clean the nozzle surface of the head to be cleaned.

[0014] Preferably, the predetermined conditions include a first condition that the head to be cleaned and the head selected before the head to be cleaned eject ink of the same color.

[0015] Preferably, each of the multiple heads is mounted on one of multiple head units. Each of the multiple head units is mounted with two or more heads among the multiple heads that eject ink of the same color. The controller sequentially selects a target head unit from the multiple head units. After selecting all of the two or more heads mounted on the target head unit as heads to be cleaned, the controller selects an unselected head unit from the multiple head units as the target head unit.

[0016] Preferably, the predetermined condition includes a second condition that the time elapsed since the most recent cleaning using the first area is less than a first threshold.

[0017] Preferably, the predetermined condition includes a third condition that the number of heads cleaned using the first region is equal to or less than a second threshold.

[0018] Preferably, the predetermined condition includes a fourth condition that an estimated amount of ink absorbed by the first region is less than a third threshold, the estimated amount being estimated based on the coverage of each of the one or more heads cleaned using the first region and the print volume since the last cleaning of each of the one or more heads.

[0019] Preferably, the plurality of heads are repeatedly cleaned. If the predetermined condition is not satisfied, the controller selects, as the head to be cleaned, a head that has been cleaned using the second region the fewest number of times in past cleanings among the plurality of heads.

[0020] Preferably, the plurality of heads are repeatedly cleaned. If the predetermined condition is not satisfied, the controller selects, from the plurality of heads, the head that has the lowest average coverage since the previous cleaning as the head to be cleaned.

[0021] Preferably, when the first region is used to clean the head to be cleaned, the controller operates at least one of the head to be cleaned and the cleaning device under a first operating condition, and when the second region is used to clean the head to be cleaned, the controller operates at least one of the head to be cleaned and the cleaning device under a second operating condition that has better cleaning ability than the first operating condition.

[0022] Preferably, the relative speed between the wiping member and the head to be cleaned is slower under the second operating condition than under the first operating condition.

[0023] Preferably, the pressing force of the wiping member against the head to be cleaned is stronger under the second operating condition than under the first operating condition.

[0024] A cleaning method according to another aspect of the present disclosure is a method for cleaning the nozzle surface of an inkjet printer that includes multiple heads each having a nozzle surface that ejects ink, and a cleaning device that has a wiping member capable of absorbing ink and cleans the nozzle surface by pressing the wiping member against the nozzle surface. The cleaning method includes selecting a head to be cleaned from the multiple heads, and controlling the cleaning device so that a first region of the wiping member that was used to clean the nozzle surface of the head selected before the head to be cleaned is also used to clean the nozzle surface of the head to be cleaned.

[0025] A program according to another aspect of the present disclosure causes a computer to execute the cleaning method described above. [Effects of the Invention]

[0026] According to the present disclosure, the inkjet printer, cleaning method, and program improve the cleanability of the nozzle surface of the head while suppressing increases in size and ink consumption. Furthermore, the first area used to clean the nozzle surface of one head is reused to clean the nozzle surface of another head, reducing the consumption of wiping members. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a cross-sectional view illustrating an example of an inkjet printer according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram illustrating an example of a hardware configuration of an inkjet printer according to an embodiment of the present invention. [Figure 3] FIG. 2 is a diagram illustrating an example of the bottom surface of the head unit. [Figure 4] FIG. 2 is a diagram illustrating an example of a head. [Figure 5] FIG. 2 is a diagram illustrating an example of the configuration of a cleaning device. [Figure 6] 10 is a flowchart showing the flow of a first embodiment of cleaning control. [Figure 7] FIG. 7 is a schematic diagram showing the operation of the head and cleaning device in steps S1 to S7 of the flow shown in FIG. [Figure 8] 7 is a schematic diagram showing the operation of the head and cleaning device in steps S8 to S13 of the flow shown in FIG. 6. FIG. [Figure 9] 10A and 10B are diagrams showing an example of the order in which heads to be cleaned are selected and an example of the area of ​​the wiping member used to clean each head in the first embodiment. [Figure 10] 10 is a flowchart showing the flow of a second embodiment of cleaning control. [Figure 11] FIG. 10 is a diagram showing an example of the order in which heads 320 to be cleaned are selected and an example of the area of ​​the wiping member used to clean each head in the second embodiment. [Figure 12] 10 is a flowchart showing the flow of a third embodiment of cleaning control. [Figure 13] FIG. 10 is a diagram showing the evaluation results of image quality in a comparative example and first to third examples. [Figure 14] FIG. 10 is a diagram illustrating another example of the configuration of the cleaning device. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, embodiments and modifications according to the present disclosure will be described while referring to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated. Note that the embodiments and modifications described below may be selectively combined as appropriate.

[0029] <A. Overall Configuration of Inkjet Printer> Referring to FIGS. 1 and 2, the overall configuration of the inkjet printer in the present embodiment will be described. FIG. 1 is a cross-sectional view showing an example of the inkjet printer in the present embodiment. FIG. 2 is a diagram showing an example of the hardware configuration of the inkjet printer in the present embodiment.

[0030] Referring to FIGS. 1 and 2, the inkjet printer 1 prints an image on the sheet 2 using ink. The ink may be aqueous ink or UV (ultraviolet) ink that cures by ultraviolet rays. The sheet 2 is, for example, paper.

[0031] The inkjet printer 1 includes a controller 10, a paper feeding unit 20, a printing unit 30, a fixing unit 40, a paper discharging unit 50, a cleaning device 80, an operation panel 90, and a communication interface 95. The controller 10, the paper feeding unit 20, the printing unit 30, the fixing unit 40, the paper discharging unit 50, the cleaning device 80, the operation panel 90, and the communication interface 95 are connected by a bus 99.

[0032] The controller 10 includes a hardware processor (hereinafter referred to as "processor 11"), memory 12, and storage 13. The processor 11 is configured, for example, by a central processing unit (CPU) or a micro-processing unit (MPU). The memory 12 is configured, for example, by a volatile storage device such as a dynamic random access memory (DRAM) or a static random access memory (SRAM). The storage 13 is configured, for example, by a non-volatile storage device such as a hard disk drive (HDD), a solid state drive (SSD), or a flash memory.

[0033] The storage 13 stores a program 131. The program 131 includes computer-readable instructions for controlling the inkjet printer 1. By executing the program 131, the processor 11 controls each part of the inkjet printer 1 and realizes various processes according to this embodiment.

[0034] Program 131 may be provided not as a standalone program, but as part of an arbitrary program. In this case, it cooperates with the arbitrary program to realize the processing according to this embodiment. Even if the program does not include some of these modules, it does not deviate from the spirit of inkjet printer 1 according to this embodiment. Furthermore, some or all of the functions provided by program 131 may be realized by dedicated hardware.

[0035] The paper feed unit 20 supplies the sheets 2 one by one to the printing unit 30. The printing unit 30 uses ink to form (print) an image based on image data on the conveyed sheets 2. The printing unit 30 includes a conveying drum 31, a plurality of head units 32, the conveying drum 31, and a scanning mechanism 33.

[0036] The transport drum 31 is a member that transports the sheet 2. The transport drum 31 is cylindrical. The transport drum 31 transports the sheet 2 by rotating in the direction of arrow 312 while holding the sheet 2 on its outer circumferential surface, which is a transport surface 311. The transport drum 31 is connected to a motor that rotates the transport drum 31, and rotates by an angle proportional to the amount of rotation of the motor.

[0037] The multiple head units 32 are arranged along the circumferential direction of the transport drum 31. The multiple head units 32 include, for example, head units 32_1, 32_2, 32_3, and 32_4 corresponding to yellow (Y), magenta (M), cyan (C), and black (K), respectively. The multiple head units 32 may further include a head unit corresponding to another color (for example, white). Head unit 32_1 is a line head that ejects yellow ink along the width direction of the sheet 2 held on the transport drum 31. Head unit 32_2 is a line head that ejects magenta ink along the width direction of the sheet 2 held on the transport drum 31. Head unit 32_3 is a line head that ejects cyan ink along the width direction of the sheet 2 held on the transport drum 31. Head unit 32_4 is a line head that ejects black ink along the width direction of the sheet 2 held on the transport drum 31. The width direction of the sheet 2 is a direction perpendicular to the transport direction of the sheet 2. The width direction of the sheet 2 corresponds to the Y direction in Figure 1. The head unit 32 holds a plurality of nozzles. The nozzles eject ink onto the sheet 2 according to instructions from the controller 10.

[0038] The scanning mechanism 33 causes the plurality of head units 32 to scan in response to a command from the controller 10 .

[0039] The fixing unit 40 fixes the ink to the sheet 2. For example, when UV ink is used, the fixing unit 40 irradiates the sheet 2 with ultraviolet light to fix the ink to the sheet 2.

[0040] The paper discharge section 50 includes a paper discharge tray 51 on which the printed sheet 2 conveyed from the printing section 30 is placed.

[0041] The cleaning device 80 cleans the head unit 32. The detailed configuration of the cleaning device 80 will be described later.

[0042] The operation panel 90 accepts user operations, converts the operations into operation signals, and outputs them to the processor 11. Furthermore, the operation panel 90 displays various information such as the operating status of the inkjet printer 1 and processing results.

[0043] The communication interface 95 transmits and receives information to and from the external device 500. As an example, the processor 11 receives image data from the external device 500 via the communication interface 95.

[0044] <B.ヘッドユニット> 3 is a diagram showing an example of the bottom surface of a head unit. The bottom surface of the head unit 32 is the surface from which ink is ejected, and is typically rectangular. When forming an image on the sheet 2, the head unit 32 is arranged so that the longitudinal direction of the bottom surface (the Y direction in the figure) coincides with the width direction of the sheet 2. As shown in FIG. 3, the head unit 32 includes two or more heads 320.

[0045] FIG. 4 is a diagram showing an example of a head. The head 320 has a nozzle surface 322 that ejects ink. The nozzle surface 322 is rectangular. The longitudinal direction of the rectangular nozzle surface 322 is parallel to the longitudinal direction of the bottom surface of the head unit 32 (the Y direction in the figure). The nozzle surface 322 has a plurality of nozzles 330 that eject ink droplets arranged in a staggered pattern. For example, the head 320 has a plurality of nozzle rows in which the plurality of nozzles 330 are arranged at predetermined intervals along the longitudinal direction (Y direction) of the nozzle surface 322. The plurality of nozzle rows are arranged at predetermined intervals along the lateral direction (X direction) of the nozzle surface 322. In the example of FIG. 4, six nozzle rows are provided on the nozzle surface 322 of the head 320.

[0046] Returning to the description of FIG. 3, on the bottom surface of the head unit 32, the plurality of heads 320 are arranged in a staggered pattern such that they partially overlap each other along the longitudinal direction (Y direction) of the bottom surface of the head unit 32. With this arrangement, the arrangement intervals of the plurality of nozzles 330 in the longitudinal direction (Y direction) of the bottom surface of the head unit 32 become uniform. As a result, the head unit 32 can discharge ink over the entire width direction (Y direction) of the sheet 2 conveyed by the conveyance drum 31 to form an image.

[0047] <C. Cleaning Device> FIG. 5 is a diagram showing an example of the configuration of the cleaning device. As shown in FIG. 5, the cleaning device 80 includes a wiping member 81, rollers 82 and 83, and a pressing portion 84.

[0048] The wiping member 81 is capable of absorbing ink. The wiping member 81 has an elongated shape (sheet-like). The wiping member 81 is typically a web. The web is a sheet made of fibers, such as a woven fabric of fibers such as polyester, acrylic, nylon, polyethylene, etc. The length in the width direction (X direction) of the elongated wiping member 81 is the same as or slightly longer than the length in the short side direction (X direction) of the nozzle surface 322 (see FIG. 4) of the head 320.

[0049] The roller 82 is a roller for winding the unused area of the wiping member 81 that has not been used for cleaning. The one with the wiping member 81 wound around the roller 82 may also be called a web roll.

[0050] The roller 83 is a roller for winding up the used area of the wiping member 81 that has been used for cleaning.

[0051] Each of the rollers 82 and 83 is rotated by a drive unit (not shown). Thereby, the conveyance direction of the wiping member 81 can be switched. Specifically, when the wiping member 81 is conveyed from the roller 82 to the roller 83, the roller 83 is driven to rotate in the direction of winding up the wiping member 81 (counterclockwise in the example shown in FIG. 5). When the wiping member 81 is conveyed from the roller 83 to the roller 82, the roller 82 is driven to rotate in the direction of winding up the wiping member 81 (clockwise in the example shown in FIG. 5).

[0052] The pressing portion 84 presses the wiping member 81 against the nozzle surface 322 of the head 320 to be cleaned between the rollers 82 and 83. Thereby, the wiping member 81 absorbs the ink adhering to the nozzle surface 322 and cleans the nozzle surface 322.

[0053] The pressing portion 84 has a roller shape and is rotatable. The pressing portion 84 rotates as the wiping member 81 is conveyed. When the pressing portion 84 presses the wiping member 81 against the nozzle surface 322 of the head 320, friction occurs between the wiping member 81 and the nozzle surface 322. The friction causes wear of the head 320. Therefore, in order to reduce the friction, the pressing portion 84 may be realized by a porous material such as a low-hardness sponge.

[0054] When the nozzle surface 322 is cleaned, the head 320 is arranged such that the short-side direction of the nozzle surface 322 coincides with the width direction (X direction) of the long wiping member 81. When cleaning the nozzle surface 3 of the head 320, the wiping member 81 is conveyed from the roller 82 to the roller 83. Further, when cleaning the nozzle surface 322 of the head 320, the head 320 is scanned in the direction opposite to the conveyance direction (Y direction) of the wiping member 81. Thereby, the nozzle surface 322 of the head 320 and the wiping member 81 move relative to each other.

[0055] <D. Cleaning Control by the Controller> When a maintenance start condition is met, the controller 10 performs cleaning control to clean the nozzle surfaces 322 of the multiple heads 320 included in the inkjet printer 1. The maintenance start condition may include, for example, a condition that the number of printed sheets since the previous maintenance has reached a specified number, or a condition that the elapsed time since the previous maintenance has reached a specified time.

[0056] Cleaning control includes control of the scanning of the multiple heads 320 and control of the operation of the cleaning device 80. Specifically, the controller 10 sequentially selects a head 320 to be cleaned from the multiple heads 320 included in the inkjet printer 1. The controller 10 can control the cleaning device 80 so that a used area of ​​the wiping member 81 that was used to clean the nozzle surface 322 of the head 320 selected before the head 320 to be cleaned is also used to clean the nozzle surface 322 of the head 320 to be cleaned. The used area corresponds to the "first area" in this disclosure.

[0057] When the wiping member 81 contacts the nozzle surface 322 of the head 320, some of the ink in the nozzles 330 is naturally drawn to the wiping member 81 by capillary action. The amount of ink naturally drawn from the nozzles 330 to the wiping member 81 is usually greater than the amount of ink adhering to the nozzle surface 322. Therefore, the used area of ​​the wiping member 81 contains ink that has not increased in viscosity and is wetted. By using the used area to clean the nozzle surface 322, the ink adhering to the nozzle surface 322 is made less viscous (i.e., diluted) by the ink absorbed in the used area. Furthermore, using the wetted used area can improve the liquid absorption of the wiping member 81, allow low-viscosity ink to penetrate to the interface between the adhering ink and the head 320, and increase the contact area between the wiping member 81 and the nozzle surface. As a result, cleaning performance is improved.

[0058] With the above control, the inkjet printer 1 does not require a member for spraying cleaning liquid, as disclosed in Patent Document 2, to wet the wiping member 81. Furthermore, the inkjet printer 1 uses the used area, which has been wetted by ink naturally drawn from the nozzles 330 by capillary action, to clean the nozzle surface 322 of the next head 320. Therefore, as disclosed in Patent Document 3, when cleaning the nozzle surface, it is not necessary to intentionally eject ink from the nozzles to wet the wiping member. Therefore, the inkjet printer 1 can improve the cleanability of the nozzle surface 322 of the head 320 while suppressing increases in size and ink consumption. Furthermore, the first area used to clean the nozzle surface 3200 of one head 320 is reused to clean the nozzle surface 322 of another head 320, thereby reducing the consumption of the wiping member 81.

[0059] Note that when the used region is used to clean the nozzle surface 322, the following problems may occur. Therefore, when a predetermined condition is met, the controller 10 may control the cleaning device 80 so that the used region is used to clean the nozzle surface 322 of the head 320 to be cleaned. When the predetermined condition is not met, the controller 10 may control the cleaning device so that an unused region of the wiping member 81 that has not been used to clean the nozzle surface 322 is used to clean the nozzle surface 322 of the head 320 to be cleaned. The unused region corresponds to the "second region" in this disclosure.

[0060] Cleaning the nozzle surface 322 of the head 320 that ejects ink of a second color using a used area that has absorbed ink of a first color may cause color mixing. Therefore, the predetermined condition may include a first condition that the head 320 to be cleaned and the head 320 selected before the head 320 to be cleaned eject ink of the same color.

[0061] Ink thickens (hardens) over time. Cleaning the nozzle surface 322 using a used area containing thickened (hardened) ink can reduce cleaning performance. Therefore, the predetermined condition may include a second condition that the time elapsed since the most recent cleaning using a used area is less than a first threshold. The first threshold is set in advance depending on the type of ink. Generally, UV ink is more difficult to harden than water-based ink. Therefore, UV ink has the advantage that the first threshold can be set longer than water-based ink.

[0062] The long wiping member 81 cannot absorb ink beyond its absorption capacity. In other words, even if an attempt is made to clean the nozzle surface 322 using a used area that has already absorbed the ink up to its absorption capacity, the used area cannot absorb ink from the nozzle surface 322. The amount of ink absorbed in the used area depends on the number of heads 320 cleaned using the used area. Therefore, the predetermined condition may include a third condition that the number of heads cleaned using the used area is equal to or less than a second threshold. The second threshold is set in advance based on the absorption capacity of the wiping member 81 and the amount of ink absorbed by the wiping member 81 when cleaning the nozzle surface 322 of one head 320 (hereinafter referred to as the "absorption amount per head"). Specifically, the second threshold is the quotient (integer) obtained by dividing the absorption capacity by the absorption amount per head, minus 1.

[0063] The liquid absorption capacity depends on the material and thickness of the wiping member 81. The liquid absorption capacity is calculated, for example, from the difference between the weight of an unused wiping member 81 and the weight of the wiping member 81 after it has been immersed in ink.

[0064] The amount of ink drawn from the nozzles 330 to the wiping member 81 during cleaning remains almost constant under the same cleaning conditions. However, the level of ink adhesion to the head 320 varies depending on the print image density (coverage). In other words, the amount of ink absorbed per head depends on the amount of ink adhering to the nozzle surface 322. The amount of ink adhering to the nozzle surface 322 depends on the print image density (coverage) and the amount of ink printed since the previous maintenance. Therefore, the amount of ink absorbed per head is determined in advance, for example, through an experiment in which the inkjet printer 1 is operated under standard conditions. The standard conditions are conditions in which, after printing a standard image density (hereinafter referred to as "standard coverage") and a standard maintenance interval, all nozzle surfaces 322 of the multiple heads 320 are cleaned using unused areas of the wiping member 81. The amount of ink absorbed per head is calculated from the change in weight of the wiping member 81 before and after the experiment. Specifically, the absorption amount per head is a value obtained by dividing the increase in the number of wiping members 81 before and after the experiment by the number of heads 320.

[0065] (D1. First Example of Cleaning Control) A first embodiment of cleaning control will be described with reference to Figs. 6 to 9. Fig. 6 is a flowchart showing the flow of the first embodiment of cleaning control. The flow shown in Fig. 6 is carried out when the maintenance start conditions are met. Fig. 7 is a schematic diagram showing the operation of the head and cleaning device in steps S1 to S7 of the flow shown in Fig. 6. Fig. 8 is a schematic diagram showing the operation of the head and cleaning device in steps S8 to S13 of the flow shown in Fig. 6. Fig. 9 is a diagram showing an example of the order in which heads to be cleaned are selected and an example of the area of ​​the wiping member used to clean each head in the first embodiment.

[0066] First, in step S1, the controller 10 controls the scanning mechanism 33 to move the head 320 to be cleaned to a standby position.

[0067] The head 320 to be cleaned is selected one by one in order from the plurality of heads 320 included in the plurality of head units 32. In the first embodiment, the order in which the head 320 to be cleaned is selected from the plurality of heads 320 is fixed. In the example shown in the upper part of Fig. 7, the head 320_1 is selected as the head to be cleaned.

[0068] As described above, cleaning the nozzle surface 322 of the head 320 that ejects ink of a second color using an unused area that has absorbed ink of a first color can cause color mixing. Therefore, in order to maximize the number of times cleaning is performed using used areas, the controller 10 sequentially selects target head units from the multiple head units 32. After selecting all of the two or more heads 320 mounted on the target head unit as heads to be cleaned, the controller 10 selects an unselected head unit from the multiple head units 32 as the target head unit.

[0069] For example, if each of the head units 32_1, 32_2, 32_3, and 32_4 includes six heads 320, Nos. 1 to 6, the heads 320 to be cleaned are selected according to the selection order shown in FIG. 9. The selection order is described in the fields of the table shown in FIG. 9. As shown in FIG. 9, the controller 10 first selects the head 320, No. 1, of the yellow (Y) head unit 32_1 as the cleaning target, and then selects the heads 320, Nos. 2 to 6, of the head unit 32_1 in this order. Next, the controller 10 selects the heads 320, Nos. 1 to 6, of the magenta (M) head unit 32_2 in this order. Next, the controller 10 selects the heads 320, Nos. 1 to 6, of the cyan (C) head unit 32_3 in this order. Finally, the controller 10 selects the heads 320, Nos. 1 to 6, of the black (K) head unit 32_4 in this order. In the plurality of head units 32, the selection order of the heads 320 Nos. 1 to 6 may be the same or different from one another.

[0070] In the first embodiment, the selection order of the heads 320 to be cleaned from the multiple heads 320 is fixed. That is, the controller 10 selects the heads 320 to be cleaned according to the same selection order (for example, the selection order shown in FIG. 9) every time maintenance is performed.

[0071] As shown in the upper part of FIG. 7, the standby position is the position of the head 320 when the tip of the nozzle surface 322 in the longitudinal direction (Y direction) is above the pressing portion 84 of the cleaning device 80.

[0072] 7, in step S1, wiping member 81 is stopped. At this time, wiping member 81 includes a used area 811 that was used in the most recent cleaning between pressing portion 84 and roller 83. The area of ​​wiping member 81 that is closer to roller 82 than pressing portion 84 is an unused area 812 that has not been used for cleaning.

[0073] Note that if a portion of the used region 811 is taken up by the roller 83, color mixing may occur in that portion. If the used region 811 in which color mixing has occurred is used to clean the nozzle surface 322, an unintended color will be mixed into the printed image. For this reason, the distance between the pressing unit 84 and the roller 83 is designed so that the used region 811 used when cleaning a certain nozzle surface 322 is not taken up by the roller 83. Furthermore, the transport of the wiping member 81 is stopped before the used region 811 is taken up by the roller 83. In other words, the transport of the wiping member 81 is stopped at a position where the used region 811 is close to the pressing unit 84.

[0074] In the next step S2, the controller 10 determines whether a first condition is met, that is, the head 320 to be cleaned and the head 320 selected before the head 320 to be cleaned eject ink of the same color. If the first condition is met (YES in step S2), cleaning control proceeds to step S3.

[0075] In step S3, the controller 10 determines whether a second condition is met, that is, the time elapsed since the most recent cleaning is less than a first threshold value. If the second condition is met (YES in step S3), the cleaning control proceeds to step S4.

[0076] In step S4, the controller 10 determines whether a third condition is met, that is, the number of heads cleaned using the used area is equal to or less than a second threshold value. If the third condition is met (YES in step S3), the cleaning control proceeds to step S5.

[0077] In step S5, controller 10 controls cleaning device 80 to transport wiping member 81 so that the tip of used region 811 on the roller 83 side is positioned at pressing portion 84. As shown in the upper part of FIG. 7, in step S1, used region 811 is positioned between pressing portion 84 and roller 83. Therefore, controller 10 rotates roller 82 in the direction of winding up wiping member 81, as shown on the left side of the middle part of FIG. 7. Then, wiping member 81 is transported until the tip of used region 811 on the roller 83 side reaches pressing portion 84. Note that, as described above, used region 811 is positioned close to pressing portion 84. Therefore, it takes a short time to rewind wiping member 81 so that the tip of used region 811 on the roller 83 side is positioned at pressing portion 84.

[0078] If any of the first to third conditions is not satisfied (NO in any of steps S2 to S4), cleaning control proceeds to step S6. In step S6, controller 10 controls cleaning device 80 to transport wiping member 81 so that the tip of unused region 812 on the roller 83 side is positioned at pressing portion 84. As shown in the upper part of FIG. 7, in step S1, unused region 812 is an area closer to roller 82 than pressing portion 84. Therefore, controller 10 slightly rotates roller 83 in the direction of winding up wiping member 81, as shown on the right side of the middle part of FIG. 7. As a result, the tip of unused region 812 on the roller 83 side reaches pressing portion 84.

[0079] After step S5 or step S6, cleaning control proceeds to step S7. In step S7, the controller 10 controls the scanning mechanism 33 to press the head 320 to be cleaned against the wiping member 81. Specifically, as shown in the lower part of FIG. 7, the head 320_1 to be cleaned moves downward (in the -Z direction) so as to be pressed against the wiping member 81. At this time, the wiping member 81 is pressed against the nozzle surface 322 of the head 320 to be cleaned with a first pressing force. The first pressing force is set to a low pressure that can sufficiently ensure the durability of the head 320.

[0080] In the next step S8, the controller 10 controls the cleaning device 80 to start conveying the wiping member 81 from roller 82 to roller 83 (see the upper part of FIG. 8). Furthermore, in step S9, the controller 10 controls the scanning mechanism 33 to start scanning the head 320 of the cleaning target in the direction opposite to the conveying direction of the wiping member 81 (Y direction) (see the upper part of FIG. 8). At this time, the controller 10 causes the head 320 to scan at a first speed. The first speed is determined in advance in consideration of cleaning performance. Note that steps S8 and S9 are typically performed simultaneously.

[0081] In the next step S10, the controller 10 determines whether a first predetermined time has elapsed since step S9. The first predetermined time is the time required to clean the entire nozzle surface 322 of the head 320 to be cleaned. The first predetermined time is determined in advance according to the scanning speed (first speed) of the head 320 to be cleaned. Specifically, the value obtained by dividing the longitudinal length of the nozzle surface 322 of the head 320 by the first speed is set as the first predetermined time.

[0082] By carrying out steps S8 to S10, the nozzle surface 322 of the head 320 to be cleaned (head 320_1 in the example shown in FIG. 8) is cleaned by the wiping member 81, as shown in the upper part of FIG.

[0083] If the first predetermined time has not elapsed since step S9 (NO in step S10), the cleaning control returns to step S10 again. If the first predetermined time has elapsed since step S9 (YES in step S10), the cleaning control proceeds to step S11.

[0084] In step S11, the controller 10 controls the scanning mechanism 33 and the cleaning device 80 to stop the scanning of the head 320 to be cleaned and the transportation of the wiping member 81.

[0085] In the next step S12, the controller 10 controls the scanning mechanism 33 to move the head 320 to be cleaned away from the wiping member 81. Specifically, as shown in the middle part of FIG. 8, the head 320 to be cleaned (head 320_1 in the example shown in FIG. 8) moves upward (in the Z direction) so as to move away from the wiping member 81.

[0086] In the next step S13, the controller 10 controls the scanning mechanism 33 to retract the head 320 to be cleaned from the cleaning device 80. If an unselected head 320 remains after step S13, the cleaning control returns to step S1. This causes the next head 320 to be cleaned to move to the standby position. Note that steps S13 and S1 may be performed in parallel. That is, as shown in the lower part of FIG. 8 , the head 320_1, which has completed cleaning, may be retracted from the cleaning device 80, and simultaneously the head 320_2, which is the next head to be cleaned, may move to the standby position. Furthermore, steps S2 to S6 may be performed on the head 320_2, which is the next head to be cleaned, in parallel with step S13. For example, while the head 320_1, which has completed cleaning, is retracted from the cleaning device 80, the controller 10 may control the cleaning device 80 to transport the wiping member 81 so that the tip of the used region 811 on the roller 83 side is positioned at the pressing portion 84. This reduces the time required for cleaning control for multiple heads 320.

[0087] When each of the head units 32_1, 32_2, 32_3, and 32_4 includes six heads 320, Nos. 1 to 6, and the second threshold is 5, the area of ​​the wiping member 81 used to clean each head 320 is shown in FIG. 9. In FIG. 9, the field representing cleaning using the unused area 812 is hatched. As shown in FIG. 9, the No. 1 head 320 of the yellow head unit 32_1 is cleaned using the unused area of ​​the wiping member 81. Thereafter, the No. 2 to No. 6 heads 320 of the head unit 32_1 are cleaned using the used area that was used to clean the No. 1 head 320 of the head unit 32_1. Next, the No. 1 head 320 of the magenta head unit 32_2 is cleaned using the unused area of ​​the wiping member 81. Thereafter, the No. 2 to No. 6 heads 320 of the head unit 32_2 are cleaned using the used area that was used to clean the No. 1 head 320 of the head unit 32_2. Next, the No. 1 head 320 of the cyan head unit 32_3 is cleaned using an unused area of ​​the wiping member 81. Thereafter, the No. 2 to No. 6 heads 320 of the head unit 32_3 are cleaned using the used area that was used to clean the No. 1 head 320 of the head unit 32_3. Next, the No. 1 head 320 of the black head unit 32_4 is cleaned using an unused area of ​​the wiping member 81. Thereafter, the No. 2 to No. 6 heads 320 of the head unit 32_4 are cleaned using the used area that was used to clean the No. 1 head 320 of the head unit 32_4.

[0088] In this way, the heads 320 Nos. 2 to 6 of each head unit 32 are cleaned using the used area of ​​the wiping member 81. This improves the cleaning performance of the heads 320 Nos. 2 to 6 of each head unit 32.

[0089] (D2. Second Example of Cleaning Control) In the first embodiment, in each head unit 32, a head 320 that is cleaned using an unused area of ​​the wiping member 81 is fixed. For example, in the example shown in FIG. 9, the No. 1 head 320 in each head unit 32 is always cleaned using an unused area of ​​the wiping member 81. The cleaning performance of cleaning using an unused area may be lower than the cleaning performance of cleaning using a used area, depending on the state of ink adhering to the nozzle surface 322. As a result, in each head unit 32, more ink remains on the nozzle surface 322 of a particular head 320 without being completely cleaned. The second embodiment can improve this situation.

[0090] A second embodiment of cleaning control will be described with reference to Figures 10 and 11. Figure 10 is a flowchart showing the flow of the second embodiment of cleaning control.

[0091] As shown in Fig. 10, the flow of the second embodiment of cleaning control differs from the flow shown in Fig. 6 in that it includes step S14. Step S14 is performed between step S6 and step S7.

[0092] In step S14, the controller 10 reselects as the head 320 to be cleaned the head 320 that has been cleaned using unused areas the fewest times in past cleanings from among the multiple heads 320. Then, the controller 10 controls the scanning mechanism 33 to move the head 320 to be cleaned to the standby position.

[0093] Fig. 11 is a diagram showing an example of the selection order of heads 320 to be cleaned in the second embodiment. Fig. 11 shows a table showing the selection order of heads 320 to be cleaned in each of the Nth to N+3th maintenances. In the table shown in Fig. 11, fields indicating cleaning using unused area 812 are hatched.

[0094] 11 shows an example of the selection order when four head units 32_1, 32_2, 32_3, and 32_4 corresponding to yellow, magenta, cyan, and black, respectively, each include six heads 320, No. 1 to 6, and the second threshold value is 5. In each head unit 32, the head 320 that is first selected as the cleaning target is cleaned using an unused area.

[0095] As shown in FIG. 11 , the controller 10 selects the heads 320 to be cleaned using unused areas in each head unit 32, in the order of No. 1 to No. 6. Specifically, during the Nth maintenance, the controller 10 controls the scanning mechanism 33 and the cleaning device 80 so that the No. 1 head 320 of each head unit 32 is cleaned using the unused area of ​​the wiping member 81. During the next (N+1)th maintenance, the controller 10 controls the scanning mechanism 33 and the cleaning device 80 so that the No. 2 head 320 of each head unit 32 is cleaned using the unused area of ​​the wiping member 81. During the next (N+2)th maintenance, the controller 10 controls the scanning mechanism 33 and the cleaning device 80 so that the No. 3 head 320 of each head unit 32 is cleaned using the unused area of ​​the wiping member 81. During the next (N+3)th maintenance, the controller 10 controls the scanning mechanism 33 and the cleaning device 80 so that the No. 4 head 320 of each head unit 32 is cleaned using the unused area of ​​the wiping member 81. In this way, in the (N+k)th maintenance, the controller 10 controls the scanning mechanism 33 and the cleaning device 80 so that the head 320 No. i (i represents the remainder when (k+1) is divided by 6) of each head unit 32 is cleaned using an unused area of ​​the wiping member 81. As a result, the head 320 that has been cleaned using an unused area the fewest times in past cleanings is selected as the head to be cleaned using an unused area.

[0096] It should be noted that the selection order of the heads 320 to be cleaned using unused areas in the multiple head units 32 may be the same or different from one another.

[0097] According to the second embodiment, the heads 320 that are cleaned using unused areas are distributed. That is, cleaning using unused areas is not concentrated on a specific head 320. This makes the state of the nozzle surfaces 322 of the multiple heads 320 uniform.

[0098] (D3. Third Example of Cleaning Control) As described above, the cleaning performance of cleaning using an unused area of ​​the wiping member 81 may be lower than the cleaning performance of cleaning using a used area, depending on the state of ink adhering to the nozzle surface 322. Therefore, the controller 10 sets different operating conditions for at least one of the head 320 to be cleaned and the cleaning device 80 when cleaning using an unused area and when cleaning using a used area. Specifically, when cleaning the head 320 to be cleaned using a used area, the controller 10 operates at least one of the head 320 to be cleaned and the cleaning device 80 under first operating conditions. When cleaning the head 320 to be cleaned using an unused area, the controller 10 operates at least one of the head 320 to be cleaned and the cleaning device 80 under second operating conditions that provide better cleaning performance than the first operating conditions. The operating conditions include, for example, the relative speed between the wiping member 81 and the head 320 to be cleaned, or the pressing force of the wiping member 81 against the head 320.

[0099] Specifically, the controller 10 slows the scanning speed of the head 320 when cleaning using an unused area compared to when cleaning using a used area. This slows the relative speed between the wiping member 81 and the head 320 to be cleaned. When the relative speed between the wiping member 81 and the head 320 to be cleaned is slowed, the contact time between the nozzle surface 322 and the wiping member 81 becomes longer. As a result, cleaning performance improves.

[0100] Alternatively, the controller 10 strengthens the pressing force of the wiping member 81 against the head 320 when cleaning using an unused area compared to when cleaning using a used area, resulting in improved cleaning performance.

[0101] A third embodiment of cleaning control will be described with reference to Fig. 12. Fig. 12 is a flowchart showing the flow of the third embodiment of cleaning control.

[0102] As shown in Fig. 12, the flow of the third embodiment of cleaning control differs from the flow shown in Fig. 10 in that it includes steps S15 to S18. Steps S15 to S18 are performed in order after step S14.

[0103] In step S15, the controller 10 controls the scanning mechanism 33 to bring the head 320 to be cleaned into pressure contact with the wiping member 81. Step S15 is the same as step S7.

[0104] In the next step S16, the controller 10 controls the cleaning device 80 to start conveying the wiping member 81 from the roller 82 to the roller 83. Step S16 is the same as step S8.

[0105] In the next step S17, the controller 10 controls the scanning mechanism 33 to start scanning the head 320 of the cleaning target in the direction (Y direction) opposite to the transport direction of the wiping member 81. At this time, the controller 10 causes the head 320 to scan at a second speed that is slower than the first speed in step S9.

[0106] In the next step S18, the controller 10 determines whether a second predetermined time has elapsed since step S17. The second predetermined time is the time required to clean the entire nozzle surface 322 of the head 320 to be cleaned. The second predetermined time is determined in advance according to the scanning speed (second speed) of the head 320 to be cleaned. Specifically, the second predetermined time is set to a value obtained by dividing the longitudinal length of the nozzle surface 322 of the head 320 by the second speed. Because the second speed is slower than the first speed, the second predetermined time is longer than the first predetermined time.

[0107] If the second predetermined time has not elapsed since step S17 (NO in step S18), the cleaning control returns to step S18 again. If the second predetermined time has elapsed since step S17 (YES in step S18), the cleaning control proceeds to step S11.

[0108] According to the flow shown in FIG. 12 , the scanning speed of the head 320 cleaned using the unused area of ​​the wiping member 81 is slower than the scanning speed of the head 320 cleaned using the used area. The slow scanning speed of the head 320 increases the contact time between the nozzle surface 322 and the wiping member 81. As a result, cleaning performance improves. As a result, the state of the nozzle surface 322 cleaned using the unused area approaches the state of the nozzle surface 322 cleaned using the used area. In other words, the state of the nozzle surfaces 322 of the multiple heads 320 becomes more uniform.

[0109] Note that slowing down the scanning speed of the head 320 increases the time required for cleaning. However, because the scanning speed is controlled to be slow only when cleaning the head 320 using unused areas, the total time required for cleaning control of the multiple heads 320 is sufficiently short compared to when slowing down the scanning speed for all heads 320.

[0110] Instead of causing the head 320 to scan at the same first speed as in step S9 in step S17, the controller 10 may perform the following process. That is, in step S7, the controller 10 causes the pressing portion 84 to press the head 320 with a first pressing force, and in step S15, the controller 10 causes the pressing portion 84 to press the head 320 with a second pressing force. The second pressing force is stronger than the first pressing force. Also by this, the cleaning property during cleaning using the unused area is improved. As a result, the state of the nozzle surface 322 cleaned using the unused area approaches the state of the nozzle surface 322 cleaned using the used area. That is, the states of the nozzle surfaces 322 of the plurality of heads 320 become more uniform.

[0111] <E. Verification of cleaning property> The inventor conducted the following verification tests to verify the image quality in the first to third embodiments of the cleaning control. As a verification test, the inventor evaluated the image quality when performing the cleaning control of the comparative example and the first to third embodiments. The common conditions and individual conditions in the comparative example and the first to third embodiments are as follows.

[0112] (E1. Common conditions) For the ink of the inkjet printer 1, aqueous ink was used. Each head unit 32 was equipped with six heads 320. As the wiping member 81, a woven fabric of a mixed fiber of polyester and nylon was used. The thickness of the wiping member 81 was 0.35 mm. As the pressing portion 84, a silicon sponge was used. The pressing force of the wiping member 81 (pressing portion 84) against the head 320 was 1 kPa. By setting the pressing force to 1 kPa, the durability of the head 320 was sufficiently ensured. The conveyance speed of the wiping member 81 during cleaning was 10 mm / s.

[0113] (E2. Individual conditions) (Comparative example) The controller 10 controlled the scanning mechanism 33 and the cleaning device 80 so that cleaning was always performed using unused areas of the wiping member 81 for each of the multiple heads 320 included in the inkjet printer 1. In other words, the controller 10 controlled the scanning mechanism 33 and the cleaning device 80 according to a flow that omitted steps S2 to S5 from the flow shown in Fig. 6 and executed step S6 before step S7. The scanning speed of the heads 320 during cleaning was 20 mm / s.

[0114] (First Example) The controller 10 controlled the scanning mechanism 33 and the cleaning device 80 according to the flow shown in Fig. 6. However, the first threshold was set to 10 minutes, and the second threshold was set to 5. In step S9, the controller 10 set the scanning speed of the head 320 during cleaning to 20 mm / s.

[0115] (Second Example) The controller 10 controlled the scanning mechanism 33 and the cleaning device 80 according to the flow shown in Fig. 10. However, the first threshold was set to 10 minutes, and the second threshold was set to 5 minutes. In step S9, the controller 10 set the scanning speed of the head 320 during cleaning to 20 mm / s.

[0116] (Third Example) The controller 10 controlled the scanning mechanism 33 and the cleaning device 80 according to the flow shown in Fig. 12. However, the first threshold was set to 10 minutes, and the second threshold was set to 5. In step S9, the controller 10 set the scanning speed of the head 320 during cleaning to 20 mm / s, and in step S17, the controller 10 set the scanning speed of the head 320 during cleaning to 10 mm / s.

[0117] (E3. Evaluation Method) After purging and cleaning the nozzle surface 322 of each head 320, the controller 10 performed continuous printing and performed cleaning control for multiple heads 320 every hour. The inventor evaluated the quality (image quality) of the printed image after the cleaning control.

[0118] As mentioned above, image quality depends on the cleanability of the nozzle surface 322. If the cleanability is insufficient, thickened ink accumulates around the nozzles 330 on the nozzle surface 322. This can cause the ink to bend and be ejected in an unintended direction, resulting in a decrease in image quality. In the verification test, a high-coverage image with approximately three times the expected coverage in the market was used as the image to be used for continuous printing in order to accelerate the accumulation of ink on the nozzle surface 322.

[0119] (E4. Verification Results) 13 is a diagram showing the evaluation results of image quality for the comparative example and the first to third examples. In the comparative example, the image quality became poor (NG) after cleaning control was performed three times. At this time, a large amount of ink was found adhering around the nozzles 330 on the nozzle surface 322.

[0120] In the first embodiment, the image quality became poor (NG) after cleaning control was performed five times. It was confirmed that the image quality stability in the first embodiment was improved to twice that of the comparative example. The reason for the improvement in image quality stability is thought to be that the frequency of cleaning using unused areas of the wiping member 81 was one-sixth that of the comparative example, thereby reducing the probability of ink accumulation on the nozzle surface 322.

[0121] In the second embodiment, when the cleaning control was performed 12 times, the image quality became poor (NG). It was confirmed that the image quality stability in the second embodiment was improved 5.5 times compared to the image quality stability in the comparative example and 2.75 times compared to the image quality stability in the first embodiment. The reason for the further improvement in image quality stability is considered to be that the accumulation rate of ink for a specific head 320 decreased due to the dispersion of the heads 320 cleaned using the unused area of the wiping member 81. In the case of the second embodiment, the higher the number of heads 320 mounted on each head unit 32, the more the image quality stability can be improved.

[0122] In the third embodiment, when the cleaning control was performed 17 times, the image quality became poor (NG). It was confirmed that the image quality stability in the third embodiment was improved 8 times compared to the image quality stability in the comparative example and 1.45 times compared to the image quality stability in the second embodiment. The reason for the further improvement in image quality stability is considered to be that the cleaning performance of the head 320 improved by reducing the scanning speed of the head 320 cleaned using the unused area of the wiping member 81.

[0123] <F. Variation> (F1. Variation 1) In step S14 of the flow shown in FIG. 10 or FIG. 12, the controller 10 may select, as the head 320 to be cleaned, the head with the lowest coverage after the previous cleaning among the plurality of heads 320. The controller 10 records the coverage (image density) of each head 320 for each print. The controller 10 calculates the average (hereinafter referred to as "average coverage") of the coverage in a plurality of prints after the previous cleaning for each of the two or more heads 320 included in each head unit 32. The controller 10 may select, in each head unit 32, the head 320 with the lowest average coverage as the target for cleaning using the unused area.

[0124] The head 320 with the lowest average coverage is assumed to be the head with the least amount of ink adhering to the nozzle surface 322. Therefore, even if the head 320 with the lowest average coverage is cleaned using an unused area that is inferior in cleaning ability compared to a used area, the ink adhering to the nozzle surface 322 can be wiped away.

[0125] (F2. Variation 2) In step S4 of the flow shown in FIG. 6, 10, or 12, the controller 10 may determine whether a fourth condition is satisfied instead of the third condition. The fourth condition is that the estimated amount of ink absorbed by the used area is less than a third threshold. The estimated amount is estimated based on the coverage of each of the one or more heads cleaned using the used area and the print volume of each of the one or more heads since the previous cleaning. For example, the estimated amount is expressed as the product of the standard coverage, the print volume, and a coefficient. Alternatively, the estimated amount is expressed as the product of the average coverage, the print volume, and a coefficient. The coefficient is determined in advance through an experiment in which the inkjet printer 1 is operated under standard conditions. Specifically, the coefficient is the value obtained by dividing the above-mentioned "absorption amount per head" by the standard coverage and the print volume at a standard maintenance interval.

[0126] By using the fourth condition, it is also determined in step S4 whether the amount of ink absorbed in the used area has reached the liquid absorption capacity.

[0127] (F3. Variation 3) In the above description, the inkjet printer 1 cleans the nozzle surface 322 by moving the wiping member 81 relative to the nozzle surface 322 of the head 320. However, the cleaning method is not limited to this.

[0128] Fig. 14 is a diagram showing another example of the configuration of the cleaning device. As shown in Fig. 14, a cleaning device 80_1 differs from the cleaning device 80 shown in Fig. 5 in that it includes a pressing portion 84_1 instead of the pressing portion 84.

[0129] The pressing portion 84_1 is pad-shaped. The pressing portion 84_1 has an upper surface having the same shape as the nozzle surface 322 of the head 320 or a shape slightly smaller than the nozzle surface 322. The pressing portion 84_1 presses the wiping member 81 against the nozzle surface 322 of the head 320. At this time, substantially the entire area of the nozzle surface 322 comes into contact with the wiping member 81. As a result, the ink adhering to the nozzle surface 322 is absorbed by the wiping member 81. As a result, the nozzle surface 322 is cleaned. When cleaning the nozzle surface 322, the controller 10 does not convey the wiping member 81 and does not scan the head 320. Therefore, when using the cleaning device 80_1 shown in FIG. 14, steps S8, S9, S11, S16, and S17 are omitted in the flow shown in FIGS. 6, 10, or 12. Further, in step S5, the controller 10 may convey the wiping member 81 so that the used area of the wiping member 81 is located on the upper surface of the pressing portion 84_1. In step S6, the controller 10 may convey the wiping member 81 so that the unused area of the wiping member 81 is located on the upper surface of the pressing portion 84_1.

[0130] <G. Addendum> The above-described embodiments and modifications include the following technical ideas.

[0131] [Configuration 1] A plurality of heads having nozzle surfaces for discharging ink, A cleaning device having a wiping member capable of absorbing the ink, and cleaning the nozzle surface by pressing the wiping member against the nozzle surface, A controller for controlling the cleaning device, The controller, Selects a head to be cleaned from the plurality of heads, An inkjet printer that controls the cleaning device so that a first area used for cleaning the nozzle surface of a head selected before the head to be cleaned among the wiping members is also used for cleaning the nozzle surface of the head to be cleaned.

[0132] [Configuration 2] 2. The inkjet printer according to claim 1, wherein the wiping member is a web.

[0133] [Configuration 3] The controller When a predetermined condition is satisfied, the cleaning device is controlled so that the first area is also used to clean the nozzle surface of the head to be cleaned; An inkjet printer according to configuration 1 or 2, wherein, if the specified condition is not satisfied, the cleaning device is controlled so that a second area of ​​the wiping member that is not being used to clean the nozzle surface is used to clean the nozzle surface of the head to be cleaned.

[0134] [Configuration 4] 4. The inkjet printer according to claim 3, wherein the predetermined conditions include a first condition that the head to be cleaned and a head selected before the head to be cleaned eject ink of the same color.

[0135] [Configuration 5] each of the plurality of heads is mounted on one of a plurality of head units, and each of the plurality of head units is mounted with two or more heads among the plurality of heads that eject ink of the same color; The controller Selecting a target head unit from the plurality of head units in order; An inkjet printer according to configuration 4, wherein after all of the two or more heads mounted on the target head unit are selected as the heads to be cleaned, an unselected head unit from among the plurality of head units is selected as the target head unit.

[0136] [Configuration 6] 6. The inkjet printer according to any one of configurations 3 to 5, wherein the predetermined condition includes a second condition that the time elapsed since the most recent cleaning using the first area is less than a first threshold value.

[0137] [Configuration 7] 7. The inkjet printer according to any one of configurations 3 to 6, wherein the predetermined conditions include a third condition that the number of heads cleaned using the first area is equal to or less than a second threshold.

[0138] [Configuration 8] An inkjet printer according to any one of configurations 3 to 6, wherein the predetermined condition includes a fourth condition that an estimated amount of ink absorbed by the first area is less than a third threshold, the estimated amount being estimated based on the coverage of each of one or more heads cleaned using the first area and the amount of printing since the previous cleaning of each of the one or more heads.

[0139] [Configuration 9] The plurality of heads are repeatedly cleaned; An inkjet printer according to any one of configurations 3 to 8, wherein if the specified condition is not met, the controller selects, from among the plurality of heads, the head that has been cleaned using the second area the fewest number of times in past cleanings as the head to be cleaned.

[0140] [Configuration 10] The plurality of heads are repeatedly cleaned; 9. The inkjet printer according to any one of configurations 3 to 8, wherein if the predetermined condition is not met, the controller selects, from among the plurality of heads, the head with the lowest average coverage since the previous cleaning as the head to be cleaned.

[0141] [Configuration 11] The controller When cleaning the head to be cleaned using the first area, operating at least one of the head to be cleaned and the cleaning device under a first operating condition; An inkjet printer according to any one of configurations 3 to 10, wherein when the second area is used to clean the head to be cleaned, at least one of the head to be cleaned and the cleaning device is operated under second operating conditions that have better cleaning ability than the first operating conditions.

[0142] [Configuration 12] 12. The inkjet printer according to claim 11, wherein the relative speed between the wiping member and the head to be cleaned is faster under the second operating condition than under the first operating condition.

[0143] [Configuration 13] 12. The inkjet printer according to claim 11, wherein the pressing force of the wiping member against the head to be cleaned is stronger under the second operating condition than under the first operating condition.

[0144] [Configuration 14] 14. The inkjet printer according to any one of configurations 1 to 13, wherein the ink is a UV ink that is cured by ultraviolet light.

[0145] [Configuration 15] A method for cleaning a nozzle surface in an inkjet printer including a plurality of heads each having a nozzle surface that ejects ink, and a cleaning device having a wiping member capable of absorbing the ink, the cleaning device cleaning the nozzle surface by pressing the wiping member against the nozzle surface, selecting a head to be cleaned from the plurality of heads; and controlling the cleaning device so that a first region of the wiping member that was used to clean the nozzle surface of a head selected before the head to be cleaned is also used to clean the nozzle surface of the head to be cleaned.

[0146] [Configuration 16] A program for causing a computer to execute a method for cleaning a nozzle surface in an inkjet printer including a plurality of heads each having a nozzle surface that ejects ink, and a cleaning device having a wiping member capable of absorbing the ink and that cleans the nozzle surface by pressing the wiping member against the nozzle surface, the cleaning method comprising: selecting a head to be cleaned from the plurality of heads; and controlling the cleaning device so that a first region of the wiping member that was used to clean the nozzle surface of a head selected before the head to be cleaned is also used to clean the nozzle surface of the head to be cleaned.

[0147] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0148] 1 inkjet printer, 2 sheet, 10 controller, 11 processor, 12 memory, 13 storage, 20 paper feed unit, 30 printing unit, 31 transport drum, 32 head unit, 33 scanning mechanism, 40 fixing unit, 50 paper discharge unit, 51 paper discharge tray, 80 cleaning device, 81 wiping member, 82, 83 roller, 84 pressing unit, 90 operation panel, 95 communication interface, 99 bus, 131 program, 311 transport surface, 320 head, 322 nozzle surface, 330 nozzle, 500 external device, 811 used area, 812 unused area.

Claims

1. a plurality of heads each having a nozzle surface for ejecting ink; a cleaning device that has a wiping member capable of absorbing the ink and cleans the nozzle surface by pressing the wiping member against the nozzle surface; a controller for controlling the cleaning device, The controller selecting a head to be cleaned from the plurality of heads; an inkjet printer that controls the cleaning device so that a first region of the wiping member that was used to clean the nozzle surface of a head selected before the head to be cleaned is also used to clean the nozzle surface of the head to be cleaned.

2. The inkjet printer according to claim 1 , wherein the wiping member is a web.

3. The controller When a predetermined condition is satisfied, the cleaning device is controlled so that the first area is also used to clean the nozzle surface of the head to be cleaned; 3. The inkjet printer according to claim 1, wherein, when the predetermined condition is not satisfied, the cleaning device is controlled so that a second area of ​​the wiping member that is not used for cleaning the nozzle surface is used to clean the nozzle surface of the head to be cleaned.

4. The inkjet printer according to claim 3 , wherein the predetermined conditions include a first condition that the head to be cleaned and a head selected before the head to be cleaned eject ink of the same color.

5. each of the plurality of heads is mounted on one of a plurality of head units, and each of the plurality of head units is mounted with two or more heads among the plurality of heads that eject ink of the same color; The controller Selecting a target head unit from the plurality of head units in order; The inkjet printer according to claim 4 , wherein after all of the two or more heads mounted in the target head unit are selected as the heads to be cleaned, an unselected head unit from among the plurality of head units is selected as the target head unit.

6. The inkjet printer according to claim 3 , wherein the predetermined condition includes a second condition that the time elapsed since the most recent cleaning using the first area is less than a first threshold value.

7. The inkjet printer according to claim 3 , wherein the predetermined conditions include a third condition that the number of heads cleaned using the first area is equal to or less than a second threshold.

8. 4. The inkjet printer according to claim 3, wherein the predetermined condition includes a fourth condition that an estimated amount of ink absorbed by the first region is less than a third threshold, the estimated amount being estimated based on the coverage of each of one or more heads cleaned using the first region and the amount of printing since the last cleaning of each of the one or more heads.

9. The plurality of heads are repeatedly cleaned; The inkjet printer according to claim 3 , wherein if the predetermined condition is not satisfied, the controller selects, from among the plurality of heads, the head that has been cleaned using the second area the fewest number of times in past cleanings as the head to be cleaned.

10. The plurality of heads are repeatedly cleaned; The inkjet printer according to claim 3 , wherein if the predetermined condition is not satisfied, the controller selects, from among the plurality of heads, the head that has the lowest average coverage since the previous cleaning as the head to be cleaned.

11. The controller When cleaning the head to be cleaned using the first area, at least one of the head to be cleaned and the cleaning device is operated under a first operating condition; 4. The inkjet printer according to claim 3, wherein when the second area is used to clean the head to be cleaned, the at least one of the head to be cleaned and the cleaning device is operated under second operating conditions that provide better cleaning than the first operating conditions.

12. The inkjet printer according to claim 11 , wherein the relative speed between the wiping member and the head to be cleaned is slower under the second operating condition than under the first operating condition.

13. The inkjet printer according to claim 11 , wherein the pressing force of the wiping member against the head to be cleaned is stronger under the second operating condition than under the first operating condition.

14. The inkjet printer according to claim 1 , wherein the ink is a UV ink that is cured by ultraviolet light.

15. A method for cleaning a nozzle surface in an inkjet printer including a plurality of heads each having a nozzle surface that ejects ink, and a cleaning device having a wiping member capable of absorbing the ink, the cleaning device cleaning the nozzle surface by pressing the wiping member against the nozzle surface, selecting a head to be cleaned from the plurality of heads; and controlling the cleaning device so that a first region of the wiping member used to clean the nozzle surface of a head selected before the head to be cleaned is also used to clean the nozzle surface of the head to be cleaned.

16. A program for causing a computer to execute a method for cleaning a nozzle surface in an inkjet printer including a plurality of heads each having a nozzle surface that ejects ink, and a cleaning device having a wiping member capable of absorbing the ink and that cleans the nozzle surface by pressing the wiping member against the nozzle surface, the cleaning method comprising: selecting a head to be cleaned from the plurality of heads; and controlling the cleaning device so that a first region of the wiping member that was used to clean the nozzle surface of a head selected before the head to be cleaned is also used to clean the nozzle surface of the head to be cleaned.

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